Thursday, June 13, 2019
Melting and SOLIDIFICATION
LABORATORY REPORT ON MELTING AND SOLIDIFICATION
ABSTRACT
The quality of final casting mainly depends on the rate of solidification as rapid of solidification produce fine grains structures with better mechanical properties. The quality of casting in the foundry can be measured by the rate at which solidification of the molten metal takes place, which is consequent upon the rate the mould, is able to dissipate the heat of solidification to the surroundings. The faster or slower the heat removal process during solidification the structure of the grains formed by the casting is either finer of coarser. An experimental investigation was carried out to compare the rate of solidification of commercially pure aluminium in metallic moulds. The rate at which solidification occurred was compared with the rate at which the mould absorbed and dissipates heat. The experiments conducted recorded the temperature fields at different casting location and that of the moulds respectively. The results showed that there is a direct relation of the rate of heat absorption by the mould and the rate of solidification in metallic moulds.
INTRODUCTION
Problems involing the solidification and melting of materials frequently arise in industrial process such as casting The casting process is more economical than any other process of metal manufacture, provided that the melting point is lower than 1800ºC1. Although the manufacturing path from the liquid to the finished shape is the most direct, this involves a simultaneous control of the processes parts, including melting, alloying, molding, pouring, solidification process and finishing. Therefore, it is not surprising that the production of castings is a challenging technology1,2. Solidification involves extraction of heat from the molten metal thereby transforming it to solid state at the solid-liquid interface. The rate of solidification is determined mainly by rate of heat extraction through conduction and convection and can be represented using cooling curves This research was to study the temperature distribution in aluminium cast as well as that in the metallic mould during the process of solidification. Solidification phenomenon was investigated from heat transfer perspective in order to contribute to a better understanding of the solidification process in the casting of aluminium in permanent moulds. Permanent mould casting is the casting of metals by continually using a reuseable mould, thus making casting time much shorter than in temporary sand casting. Permanent mould casting can be gravity die casting; centrifugal casting; and die casting
PROCEDURE
We are provided with an aluminum metal, crucible, metal mould and other tools to facilitate handling of the heated metal
Place crucible containing the aluminum metal in the furnace with the lid covered. heat strongly to ensure then metal becomes completely molten, carefully transfer the crucible containing the molten metal out of the furnace and pour the molten metal into a well prepared metal mold
On complete cooling to solid state dismantle the mould and cool the solidified metal under a running tap
Repeat the above steps and cast the molten metal into a preheated mould at 2000c and 6000c respectively. with the use of a hacksaw, cut off specimen of about 2cm long in a transverse and longitudinal direction(slightly off the center) of the cast samples
Prepare the sample s for metallographic investigation using a given mixed acid etchant. Care must be exercised to ensure that etchant does not come in contact with the skin or eyes
Examine and sketch the structure observe under microscope paying particular attention to the relative size and shape of the grain
DATA AND RESULTS
GROUP A
GROUP B
GROUP C
GROUP D
QUESTIONS AND ANSWERS
Safety precautions when pouring the molten metals
1. Personal Protective Equipment - Clothing covering all skin, purpose built or made of natural materials like leather, heavy wool or heavy cotton. No Polyester or nylons. Boots to be Class 1 safety. Full face shield and leather gauntlets. 2. Tidy foundry area - Pouring area to be free from all items not involved in pouring process. Floor to be clear of trip hazards and concrete slabs and pavers covered with minimum 1" layer of sand 3. Clamp or Weight Flasks - Hydrostatic pressure of liquid metal can lift a lot of weight - once the cope and drag have separated due to this pressure the uncontrolled flow of metal is extremely hazardous. 4. Use Dry Clean Metal - Impurities on the surface of the melt metal may become an airborne breathing hazard e.g.. lead paint etc. in the melt these impurities often increase the dross to be removed from the melt. 5. Preheat all metal and furnace tools - This reduces the risk of condensation an tools and furnace recharge metal from steam explosions occurring in the melt. 6. Move the melt slowly & a short distance furnace to flask - It is said that liquid metal is runnier than water and splashes further - minimise the possibility of spills and splashes. 7. Know what you're melting - The characteristics like melting temperature of the metal is good to know before you start and more importantly know the adverse health affects of hazardous alloy elements like Lead, Zinc, mercury or Berilium. 8. Inspections before use - knowing the condition of the crucible the furnace walls the fuel lines burners and pouring tools is critical. Failure of any of these items during a melt or pour can be extremely undesirable. 9. Watch for a bubbling sprue - low permeability sand or excess moisture in the mould can result in a steam build up or blow back out the sprue - if your lucky you'll see the bubbling before it builds up pressure. Quickly execute safety rule 10. 10. Plan emergency exit route - Identify before you start to pour what your escape routes are if the unexpected eventuates. like a flask failure leading to metal leak, Bubbling sprue, cracked crucible, faulty pouring hardware etc.
Defect observed in cast specimen
Casting defects can be categorized into 5 types
1. Gas Porosity: Blowholes, open holes, pinholes 2. Shrinkage defects: shrinkage cavity 3. Mold material defects: Cut and washes, swell, drops, metal penetration, rat tail 4. Pouring metal defects: Cold shut, misrun, slag inclusion 5. Metallurgical defects: Hot tears, hot spot.
Blow holes When gases entrapped on the surface of the casting due to solidifying metal, a rounded or oval cavity is formed called as blowholes. These defects are always present in the cope part of the mold.
Causes
(i) Excessive moisture in the sand. (ii) Low Permeability of the sand. (iii) Sand grains are too fine. (iv) Too hard rammed sand. (v) Insufficient venting is provided.
Ways of minimizing
(i) The moisture content in the sand must be controlled and kept at desired level. (ii) High permeability sand should be used. (iii) Sand of appropriate grain size should be used. (iv) Sufficient ramming should be done. (v) Adequate venting facility should be provided.
Shrinkage The formation of cavity in the casting due to volumetric contraction is called as shrinkage cavity.
Causes
(i) Uneven or uncontrolled solidification of molten metal. (ii) Pouring temperature is too high.
Ways of minimizing
(i) This defect can be removed by applying principle of directional solidification in molddesign. (ii) Wise use of chills (a chill is an object which is used to promote solidification in a specific portion of a metal casting) and padding
CONCLUSSIONS
A commercially pure aluminium casting experiment was carried out in order to investigate the rate of solidification as well as the rate of heat transfer between the metallic mould and the cast. It is observed that as soon as the aluminium metal was poured into the moulds, the temperature falls rapidly for several degrees and thereafter relatively slowly. The sudden change in the rate of fall in temperature indicates undercooling at the interface. This undercooling is attributed to the latent heat of fusion released when solidification began at the mould wall and was completed at the interface almost instantaneously. Temperature rises rapidly in thick mould from the beginning of solidification until it reached a maximum value, it then start decreasing. Whereas a progressive rise in temperature is observed for the thi the temperature increase to a maximum point and then remain slightly constant indicating slow extraction of heat. The investigation showed that thinner moulds had higher rate of heat extraction and therefore higher rate of solidification.
ABSTRACT
The quality of final casting mainly depends on the rate of solidification as rapid of solidification produce fine grains structures with better mechanical properties. The quality of casting in the foundry can be measured by the rate at which solidification of the molten metal takes place, which is consequent upon the rate the mould, is able to dissipate the heat of solidification to the surroundings. The faster or slower the heat removal process during solidification the structure of the grains formed by the casting is either finer of coarser. An experimental investigation was carried out to compare the rate of solidification of commercially pure aluminium in metallic moulds. The rate at which solidification occurred was compared with the rate at which the mould absorbed and dissipates heat. The experiments conducted recorded the temperature fields at different casting location and that of the moulds respectively. The results showed that there is a direct relation of the rate of heat absorption by the mould and the rate of solidification in metallic moulds.
INTRODUCTION
Problems involing the solidification and melting of materials frequently arise in industrial process such as casting The casting process is more economical than any other process of metal manufacture, provided that the melting point is lower than 1800ºC1. Although the manufacturing path from the liquid to the finished shape is the most direct, this involves a simultaneous control of the processes parts, including melting, alloying, molding, pouring, solidification process and finishing. Therefore, it is not surprising that the production of castings is a challenging technology1,2. Solidification involves extraction of heat from the molten metal thereby transforming it to solid state at the solid-liquid interface. The rate of solidification is determined mainly by rate of heat extraction through conduction and convection and can be represented using cooling curves This research was to study the temperature distribution in aluminium cast as well as that in the metallic mould during the process of solidification. Solidification phenomenon was investigated from heat transfer perspective in order to contribute to a better understanding of the solidification process in the casting of aluminium in permanent moulds. Permanent mould casting is the casting of metals by continually using a reuseable mould, thus making casting time much shorter than in temporary sand casting. Permanent mould casting can be gravity die casting; centrifugal casting; and die casting
PROCEDURE
We are provided with an aluminum metal, crucible, metal mould and other tools to facilitate handling of the heated metal
Place crucible containing the aluminum metal in the furnace with the lid covered. heat strongly to ensure then metal becomes completely molten, carefully transfer the crucible containing the molten metal out of the furnace and pour the molten metal into a well prepared metal mold
On complete cooling to solid state dismantle the mould and cool the solidified metal under a running tap
Repeat the above steps and cast the molten metal into a preheated mould at 2000c and 6000c respectively. with the use of a hacksaw, cut off specimen of about 2cm long in a transverse and longitudinal direction(slightly off the center) of the cast samples
Prepare the sample s for metallographic investigation using a given mixed acid etchant. Care must be exercised to ensure that etchant does not come in contact with the skin or eyes
Examine and sketch the structure observe under microscope paying particular attention to the relative size and shape of the grain
DATA AND RESULTS
GROUP A
GROUP B
GROUP C
GROUP D
QUESTIONS AND ANSWERS
Safety precautions when pouring the molten metals
1. Personal Protective Equipment - Clothing covering all skin, purpose built or made of natural materials like leather, heavy wool or heavy cotton. No Polyester or nylons. Boots to be Class 1 safety. Full face shield and leather gauntlets. 2. Tidy foundry area - Pouring area to be free from all items not involved in pouring process. Floor to be clear of trip hazards and concrete slabs and pavers covered with minimum 1" layer of sand 3. Clamp or Weight Flasks - Hydrostatic pressure of liquid metal can lift a lot of weight - once the cope and drag have separated due to this pressure the uncontrolled flow of metal is extremely hazardous. 4. Use Dry Clean Metal - Impurities on the surface of the melt metal may become an airborne breathing hazard e.g.. lead paint etc. in the melt these impurities often increase the dross to be removed from the melt. 5. Preheat all metal and furnace tools - This reduces the risk of condensation an tools and furnace recharge metal from steam explosions occurring in the melt. 6. Move the melt slowly & a short distance furnace to flask - It is said that liquid metal is runnier than water and splashes further - minimise the possibility of spills and splashes. 7. Know what you're melting - The characteristics like melting temperature of the metal is good to know before you start and more importantly know the adverse health affects of hazardous alloy elements like Lead, Zinc, mercury or Berilium. 8. Inspections before use - knowing the condition of the crucible the furnace walls the fuel lines burners and pouring tools is critical. Failure of any of these items during a melt or pour can be extremely undesirable. 9. Watch for a bubbling sprue - low permeability sand or excess moisture in the mould can result in a steam build up or blow back out the sprue - if your lucky you'll see the bubbling before it builds up pressure. Quickly execute safety rule 10. 10. Plan emergency exit route - Identify before you start to pour what your escape routes are if the unexpected eventuates. like a flask failure leading to metal leak, Bubbling sprue, cracked crucible, faulty pouring hardware etc.
Defect observed in cast specimen
Casting defects can be categorized into 5 types
1. Gas Porosity: Blowholes, open holes, pinholes 2. Shrinkage defects: shrinkage cavity 3. Mold material defects: Cut and washes, swell, drops, metal penetration, rat tail 4. Pouring metal defects: Cold shut, misrun, slag inclusion 5. Metallurgical defects: Hot tears, hot spot.
Blow holes When gases entrapped on the surface of the casting due to solidifying metal, a rounded or oval cavity is formed called as blowholes. These defects are always present in the cope part of the mold.
Causes
(i) Excessive moisture in the sand. (ii) Low Permeability of the sand. (iii) Sand grains are too fine. (iv) Too hard rammed sand. (v) Insufficient venting is provided.
Ways of minimizing
(i) The moisture content in the sand must be controlled and kept at desired level. (ii) High permeability sand should be used. (iii) Sand of appropriate grain size should be used. (iv) Sufficient ramming should be done. (v) Adequate venting facility should be provided.
Shrinkage The formation of cavity in the casting due to volumetric contraction is called as shrinkage cavity.
Causes
(i) Uneven or uncontrolled solidification of molten metal. (ii) Pouring temperature is too high.
Ways of minimizing
(i) This defect can be removed by applying principle of directional solidification in molddesign. (ii) Wise use of chills (a chill is an object which is used to promote solidification in a specific portion of a metal casting) and padding
CONCLUSSIONS
A commercially pure aluminium casting experiment was carried out in order to investigate the rate of solidification as well as the rate of heat transfer between the metallic mould and the cast. It is observed that as soon as the aluminium metal was poured into the moulds, the temperature falls rapidly for several degrees and thereafter relatively slowly. The sudden change in the rate of fall in temperature indicates undercooling at the interface. This undercooling is attributed to the latent heat of fusion released when solidification began at the mould wall and was completed at the interface almost instantaneously. Temperature rises rapidly in thick mould from the beginning of solidification until it reached a maximum value, it then start decreasing. Whereas a progressive rise in temperature is observed for the thi the temperature increase to a maximum point and then remain slightly constant indicating slow extraction of heat. The investigation showed that thinner moulds had higher rate of heat extraction and therefore higher rate of solidification.
Manganese
OCCURRENCE OF MANGANESE
Manganese is a chemical element with symbol Mn and atomic number 25. Manganese comprises about 1000 ppm (0.1%) of the Earth's crust, the 12th most abundant of the crust's elements. It is not found as a free element in nature; it is often found in minerals in combination with iron. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.
Manganese is widely distributed in the terrestrial crust. It is usually associated with the iron ores, in relatively small concentrations. The principal manganese ores are:
pyrolusite (MnO2), psilomelane, manganite (MnO(OH)), braunite (3Mn2O3.MnSiO3) and hausmannite (Mn3O4), that can be found in Brazil, Gabon, India, Ghana, Congo and South Africa. Other manganese ores, although less important, are: rhodochrosite (MnCO3) and rhodonite (MnSiO3).
Historically, manganese is named for pyrolusite and other black minerals from the region of Magnesia in Greece, which also gave its name to magnesium and the iron ore magnetite . By the mid-18th century, Swedish-German chemist Carl Wilhelm Scheele had used pyrolusite to produce chlorine . Scheele and others were aware that pyrolusite (now known to be manganese dioxide ) contained a new element, but they were unable to isolate it. Johan Gottlieb Gahn was the first to isolate an impure sample of manganese metal in 1774, which he did by reducing the dioxide with carbon .
Manganese phosphating is used for rust and corrosion prevention on steel. Ionized manganese is used industrially as pigments of various colors, which depend on the oxidation state of the ions. The permanganates of alkali and alkaline earth metals are powerful oxidizers. Manganese dioxide is used as the cathode (electron acceptor) material in zinc-carbon and alkaline batteries.
In biology, manganese(II) ions function as cofactors for a large variety of enzymes with many functions. Manganese enzymes are particularly essential in detoxification of superoxide free radicals in organisms that must deal with elemental oxygen. Manganese also functions in the oxygen-evolving complex of photosynthetic plants. While the element is a required trace mineral for all known living organisms, it also acts as a neurotoxin in larger amounts. Especially through inhalation, it can cause manganism , a condition in mammals leading to neurological damage that is sometimes irreversible.
MINING METHOD OF MANGANESE
Mining is the extraction of valuable minerals or other geological materials from the earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. These deposits form a mineralized package that is of economic interest to the miner. Ores recovered by mining include metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay. Mining is required to obtain any material that cannot be grown through agricultural processes, or feasibly created artificially in a laboratory or factory. Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water.
Modern mining processes involve prospecting for ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials, and final reclamation of the land after the mine is closed.
Mining is the process of taking out the ores from the mines, when an ore occurs near the surface of the earth and can be directly dug out. Such mining is termed as open-pit mining. When an ore is taken out form greater depths, then the mining is termed deep mining and these are the two basic method of mining manganese.
BENEFICIATION ROUTES FOR MANGANESE ORE
MATERALS AND METHODS
The materials employed for this work include: a composite sample of Wasagu manganese ore. The equipment used were small size laboratory jaw crusher, cone crusher, pulverizing machine,
standard sieve shakers, Wifley shaking table, spiral concentrator, high intensity magnetic separator, XRF spectrometer.
Sample preparation
Composite sample of Wasagu manganese ore weighing 50 kg were collected from four (4) pits at 5 m interval and a depth of 6 m. The pits were dug by local artisanal miners. The average size of a sample is about 8 cm. The sample was dried, crushed, using the cone crushers to sizes
ranging from 0.2 cm to 0.5 cm and was finally pulverized and sieved through the mesh sizes -710+500 μm, -500+355 μm, -355+250 μm, -250+180 μm,-180+125 μm,-125+90 μm,-90+63 μm.
Methods
Size-assay analysis of the composite sample was carried out in order to determine the 80 % passing and the distribution of manganese within the size fractions. The various size fractions
retained on each sieve was weighed and assayed for %Mn content using the XRF spectrometer.
Concentration Test was carried out using laboratory scale shaking table, on some samples of manganese ore ground to the following particle sizes -710+500 μm, -500+355 μm, -355+250μm, -250+180μm,-180+125 μm,-125+90 μm,-90+63 μm.
Each particle size fraction was prepared using 25 % solid by weight and was used for each batch of concentration test.
Concentration Test was also carried out on representative samples of manganese ore ground to the following particle sizes using spiral concentration with -710+500μm, -500+355 μm, -355+250 μm, -250+180 μm, -180+125 μm, -125+90 μm, -90+63 μm.
Each particle size fraction was prepared using 25 % solid by weight and was used for each batch of concentration test.
Magnetic Separator was also used to separate the magnetic from the nonmagnetic minerals. A representative sample of the ground ore was used, which was sized into various size fractions
ranging -710+500 μm, -500+355 μm, -355+250 μm, -250+180. μm,-180+125μm,-125+90 μm,-90+63 μm. These various size fractions were subjected to magnetic separation, using a dry belt high intensity magnetic separator. After which two products (concentrate and tailings) were produced for analysis.
EXTRACTIVE METALLURGY OF MANGANESE
HYDROMETALLURGY
Hydrometallurgical processes involve the removal of metals from different types of ores, concentrates and waste products by aqueous solutions containing different chemical reagents. These processes generally include the following unit operations: roasting (not always), leaching by acids, bases or water, removal of impurities such as iron, separation and recovery processes and refining of recovered metals.
Basic Steps in Hydrometallurgy
The actual process of extraction of a metal from its ore depends upon the nature of the ore and the metal. There is no universally operational method for the extraction of metals including manganese. Certain common steps, however, are involved in all metallurgical processes. These steps are:
Mining: Mining is the process of taking out the ores from the mines, when an ore occurs near the surface of the earth and can be directly dug out. Such mining is termed as open-pit mining. When an ore is taken out form greater depths, then the mining is termed deep mining.
Crushing: Extracted ore often occurs in big lumps. It is essential to break it into smaller pieces. The lumps are crushed to smaller pieces by hammering in a hammer mill or by help of a jaw crusher.
Grinding: The crushed ore is then finally grinded to fine powder state in a stamp mill or a pulveriser.
Ore Dressing: The removal of the undesired foreign impurities from the roe is called ore-dressing (beneficiation).
Any of the following methods is used for concentrating the ores, the various methods used in ore dressing include:
a) Hand picking: If the impurities present are quite different from the ore and are of large size, these may be removed by hand picking. This method is slow and is generally adopted in the initial stages of concentration.
b) Gravity or levigation separation: When the ore particles are heavier than the gangue particles, the ore is fed into a running stream of water and impurities are washed away and in order to concentrate the ore in bulk, a slanting vibrating wooden table with wooden strips called riffles is introduced in the process, such tables are termed Wilfley tables. Sometimes in the gravity method, a hydraulic classifier based on the gravity method is used. Ore is agitated by a powerful current of water pushing upwards through the bottom of a conical reservoir. The heavier ore particles settle down and are continuously removed from another opening near the bottom, while the lighter particles are washed away by water.
c) Magnetic separation: This is done especially in the case of hematite ore, were by the powdered ore is dropped on to leather or brass conveyer belt, which moves over two rollers one of these rollers, is magnetic. When the ore passes over the magnetic roller, it sticks to the belt due to the force of attraction and falls nearer due to the force of attraction of the magnetized roller. The gangue falls over readily further away.
d) Froth flotation process: This process is used for concentrating sulphide ores and the ores are preferentially wetted by oil while the gangue particles are wetted by water. Powdered ore is mixed with water and a little pine oil and the mixture is vigorously stirred by passing compressed air. The froth, which is produced rises to the surface and carries the ore particles along with it. The gangue is left behind.
Leaching: This is the most important starting point of hydrometallurgical processes. It involves the use of aqueous solutions containing a lixiviant which is brought into contact with a material containing a valuable metal. The lixiviant in solution may be acidic or basic in nature. The type and concentration of the leachant is normally controlled to allow some degree of selectivity for the metal or metals that are to be recovered. In the leaching process, oxidation potential, temperature and pH of the solution are important parameters and are often manipulated to optimize dissolution of the desired metal component into the aqueous phase.
Other methods of extracting manganese include the following:
PYROMETALLURGY
This metallurgical process includes smelting and roasting. It involves heating in a blast furnace at temperature above 1500˚C to convert waste to a form that can be refined. The oxide (waste) is heated with a reducing agent such as carbon in the form of coke or coal, the oxygen of the metal combines with the carbon and is removed as carbon dioxide gas. The waste material in non-metallic part is called gangue. It is removed by means of a flux which, when heated combines with it to form a molten mass called slag. Being lighter than the metal, the slag floats on it and can be skimmed or drawn off.
BIOMETALLURGY/BIOLEACHING
Bioleaching is a technology in which metal ions are extracted from low-grade ores and nodules by direct or indirect actions of micro-organisms. The advantages of bioleaching include the absence of noxious of gases or toxic effluent, simplicity of plant operation and maintenance, economic and simple process requiring low capital and low-operating costs and applicability to various metals. The principal bacterium in ore leaching is Thiobacillus ferrooxidans, which is capable of oxidizing ferrous iron as well as sulphur compounds. The thermophilic sulfolobus plays a role in leaching at elevated temperature. Most of the biotechnical processes for leaching of metals have been developed using aerobic microorganisms.
However, the highly oxidized metal compounds such as MnO2 and Fe2O3 can be solubilized by reduction processes. Hence, Mn and Fe from MnO2 and Fe2O3 can be recovered by the direct or indirect actions of heterotrophic microorganisms that thrive under micro-aerobic or anaerobic conditions. In the former case, the microorganisms are capable of utilizing MnO2 as a final acceptor of electrons in the respiratory chain of their metabolism, instead of oxygen. That is, anaerobic heterotrophs such as iron-reducing bacteria, manganese-reducing bacteria, and sulphur-reducing bacteria donate electrons, which are produced by the oxidation of organic substrates to Fe2O3, MgO, MnO2, SeO4 and V2O3, and leach the reduced metal ions into the medium. In the second case, the reduction process is associated with the formation of reducing compounds, which are products of their metabolism. The anaerobic bioleaching technology of metals has not been commercialized. This is because it has to be adapted according to each type of metals. Moreover, there is a demand for a less expensive and more environmentally friendly anaerobic bioleaching process.
SOLUTION CONCENTRATION AND PURIFICATION
After leaching, the leach liquor must normally undergo concentration of the metal ions that are to be recovered. Additionally, some undesirable metals may have also been taken into solution during the leach process. The solution is often purified to eliminate the undesirable components. The processes employed for solution concentration and purification include: precipitation, cementation, solvent extraction, electrolysis, ion exchange etc.
REFINING PROCESSES FOR MANGANESE
In pyrometallurgy, heating and refining of manganeses are made in blast furnaces using only coke as reductant and as energy source or in electric smelting furnaces. Depending on the ore quality the efficient electric furnaces consume about 2100 - 2800 kWh electric power per 1 t of ferromanganese alloy (Kroschwitz and Howe-Grant, 1982) and (Elvers et al, 1990).
PROPERTIES AND APPLICATIONS OF MANGANESE
PROPERTIES
Manganese is black manganese dioxide. Manganese can be welded, machined, and coldworked because they are less ductile and malleable. They have high strength and hardness
APPLICATIONS
Mn is necessary for a variety of metabolic functions including those involved in skeletal system development, energy metabolism, activation of certain enzymes, nervous system function, immunological system function, and reproductive hormone function, and is an antioxidant that protects cells from damage due to free radicals.
Mn also plays an essential role in regulation of cellular energy, bone and connective tissue growth and blood clotting.
In the brain, Mn is an important cofactor for a variety of enzymes, including the antioxidant enzyme superoxide dismutase, as well as enzymes involved in neurotransmitter synthesis and metabolism.
Manganese has three primary metabolic functions:
(i) it acts as an activator of the gluconeogenic enzymes pyruvate carboxylase and isocitrate dehydrogenase,
(ii) it is involved in protecting mitochondria1 membranes through superoxide
dismutase; and
(iii) it activates glycosyl transferase, which is involved in mucopolysaccharide synthesis.
The most important source of Mn for the general population is diet, and the average intake of Mn from food ranges from 2 to 9 mg/day.
In addition, vitamin and mineral supplements may contain 1 to 20 mg Mn/tablet.
Manganese is mainly used as an alloying agent in the manufacture of steel to increase its tensile strength. It is also added during the steelmaking process to remove sulfur as a slag.
Austenitic manganese steels are used for railroad trackwork, power shovel buckets, and rock crushers. Mediumcarbon manganese steels are used in the manufacture of car axles and gears
Manganese is a chemical element with symbol Mn and atomic number 25. Manganese comprises about 1000 ppm (0.1%) of the Earth's crust, the 12th most abundant of the crust's elements. It is not found as a free element in nature; it is often found in minerals in combination with iron. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.
Manganese is widely distributed in the terrestrial crust. It is usually associated with the iron ores, in relatively small concentrations. The principal manganese ores are:
pyrolusite (MnO2), psilomelane, manganite (MnO(OH)), braunite (3Mn2O3.MnSiO3) and hausmannite (Mn3O4), that can be found in Brazil, Gabon, India, Ghana, Congo and South Africa. Other manganese ores, although less important, are: rhodochrosite (MnCO3) and rhodonite (MnSiO3).
Historically, manganese is named for pyrolusite and other black minerals from the region of Magnesia in Greece, which also gave its name to magnesium and the iron ore magnetite . By the mid-18th century, Swedish-German chemist Carl Wilhelm Scheele had used pyrolusite to produce chlorine . Scheele and others were aware that pyrolusite (now known to be manganese dioxide ) contained a new element, but they were unable to isolate it. Johan Gottlieb Gahn was the first to isolate an impure sample of manganese metal in 1774, which he did by reducing the dioxide with carbon .
Manganese phosphating is used for rust and corrosion prevention on steel. Ionized manganese is used industrially as pigments of various colors, which depend on the oxidation state of the ions. The permanganates of alkali and alkaline earth metals are powerful oxidizers. Manganese dioxide is used as the cathode (electron acceptor) material in zinc-carbon and alkaline batteries.
In biology, manganese(II) ions function as cofactors for a large variety of enzymes with many functions. Manganese enzymes are particularly essential in detoxification of superoxide free radicals in organisms that must deal with elemental oxygen. Manganese also functions in the oxygen-evolving complex of photosynthetic plants. While the element is a required trace mineral for all known living organisms, it also acts as a neurotoxin in larger amounts. Especially through inhalation, it can cause manganism , a condition in mammals leading to neurological damage that is sometimes irreversible.
MINING METHOD OF MANGANESE
Mining is the extraction of valuable minerals or other geological materials from the earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. These deposits form a mineralized package that is of economic interest to the miner. Ores recovered by mining include metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay. Mining is required to obtain any material that cannot be grown through agricultural processes, or feasibly created artificially in a laboratory or factory. Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water.
Modern mining processes involve prospecting for ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials, and final reclamation of the land after the mine is closed.
Mining is the process of taking out the ores from the mines, when an ore occurs near the surface of the earth and can be directly dug out. Such mining is termed as open-pit mining. When an ore is taken out form greater depths, then the mining is termed deep mining and these are the two basic method of mining manganese.
BENEFICIATION ROUTES FOR MANGANESE ORE
MATERALS AND METHODS
The materials employed for this work include: a composite sample of Wasagu manganese ore. The equipment used were small size laboratory jaw crusher, cone crusher, pulverizing machine,
standard sieve shakers, Wifley shaking table, spiral concentrator, high intensity magnetic separator, XRF spectrometer.
Sample preparation
Composite sample of Wasagu manganese ore weighing 50 kg were collected from four (4) pits at 5 m interval and a depth of 6 m. The pits were dug by local artisanal miners. The average size of a sample is about 8 cm. The sample was dried, crushed, using the cone crushers to sizes
ranging from 0.2 cm to 0.5 cm and was finally pulverized and sieved through the mesh sizes -710+500 μm, -500+355 μm, -355+250 μm, -250+180 μm,-180+125 μm,-125+90 μm,-90+63 μm.
Methods
Size-assay analysis of the composite sample was carried out in order to determine the 80 % passing and the distribution of manganese within the size fractions. The various size fractions
retained on each sieve was weighed and assayed for %Mn content using the XRF spectrometer.
Concentration Test was carried out using laboratory scale shaking table, on some samples of manganese ore ground to the following particle sizes -710+500 μm, -500+355 μm, -355+250μm, -250+180μm,-180+125 μm,-125+90 μm,-90+63 μm.
Each particle size fraction was prepared using 25 % solid by weight and was used for each batch of concentration test.
Concentration Test was also carried out on representative samples of manganese ore ground to the following particle sizes using spiral concentration with -710+500μm, -500+355 μm, -355+250 μm, -250+180 μm, -180+125 μm, -125+90 μm, -90+63 μm.
Each particle size fraction was prepared using 25 % solid by weight and was used for each batch of concentration test.
Magnetic Separator was also used to separate the magnetic from the nonmagnetic minerals. A representative sample of the ground ore was used, which was sized into various size fractions
ranging -710+500 μm, -500+355 μm, -355+250 μm, -250+180. μm,-180+125μm,-125+90 μm,-90+63 μm. These various size fractions were subjected to magnetic separation, using a dry belt high intensity magnetic separator. After which two products (concentrate and tailings) were produced for analysis.
EXTRACTIVE METALLURGY OF MANGANESE
HYDROMETALLURGY
Hydrometallurgical processes involve the removal of metals from different types of ores, concentrates and waste products by aqueous solutions containing different chemical reagents. These processes generally include the following unit operations: roasting (not always), leaching by acids, bases or water, removal of impurities such as iron, separation and recovery processes and refining of recovered metals.
Basic Steps in Hydrometallurgy
The actual process of extraction of a metal from its ore depends upon the nature of the ore and the metal. There is no universally operational method for the extraction of metals including manganese. Certain common steps, however, are involved in all metallurgical processes. These steps are:
Mining: Mining is the process of taking out the ores from the mines, when an ore occurs near the surface of the earth and can be directly dug out. Such mining is termed as open-pit mining. When an ore is taken out form greater depths, then the mining is termed deep mining.
Crushing: Extracted ore often occurs in big lumps. It is essential to break it into smaller pieces. The lumps are crushed to smaller pieces by hammering in a hammer mill or by help of a jaw crusher.
Grinding: The crushed ore is then finally grinded to fine powder state in a stamp mill or a pulveriser.
Ore Dressing: The removal of the undesired foreign impurities from the roe is called ore-dressing (beneficiation).
Any of the following methods is used for concentrating the ores, the various methods used in ore dressing include:
a) Hand picking: If the impurities present are quite different from the ore and are of large size, these may be removed by hand picking. This method is slow and is generally adopted in the initial stages of concentration.
b) Gravity or levigation separation: When the ore particles are heavier than the gangue particles, the ore is fed into a running stream of water and impurities are washed away and in order to concentrate the ore in bulk, a slanting vibrating wooden table with wooden strips called riffles is introduced in the process, such tables are termed Wilfley tables. Sometimes in the gravity method, a hydraulic classifier based on the gravity method is used. Ore is agitated by a powerful current of water pushing upwards through the bottom of a conical reservoir. The heavier ore particles settle down and are continuously removed from another opening near the bottom, while the lighter particles are washed away by water.
c) Magnetic separation: This is done especially in the case of hematite ore, were by the powdered ore is dropped on to leather or brass conveyer belt, which moves over two rollers one of these rollers, is magnetic. When the ore passes over the magnetic roller, it sticks to the belt due to the force of attraction and falls nearer due to the force of attraction of the magnetized roller. The gangue falls over readily further away.
d) Froth flotation process: This process is used for concentrating sulphide ores and the ores are preferentially wetted by oil while the gangue particles are wetted by water. Powdered ore is mixed with water and a little pine oil and the mixture is vigorously stirred by passing compressed air. The froth, which is produced rises to the surface and carries the ore particles along with it. The gangue is left behind.
Leaching: This is the most important starting point of hydrometallurgical processes. It involves the use of aqueous solutions containing a lixiviant which is brought into contact with a material containing a valuable metal. The lixiviant in solution may be acidic or basic in nature. The type and concentration of the leachant is normally controlled to allow some degree of selectivity for the metal or metals that are to be recovered. In the leaching process, oxidation potential, temperature and pH of the solution are important parameters and are often manipulated to optimize dissolution of the desired metal component into the aqueous phase.
Other methods of extracting manganese include the following:
PYROMETALLURGY
This metallurgical process includes smelting and roasting. It involves heating in a blast furnace at temperature above 1500˚C to convert waste to a form that can be refined. The oxide (waste) is heated with a reducing agent such as carbon in the form of coke or coal, the oxygen of the metal combines with the carbon and is removed as carbon dioxide gas. The waste material in non-metallic part is called gangue. It is removed by means of a flux which, when heated combines with it to form a molten mass called slag. Being lighter than the metal, the slag floats on it and can be skimmed or drawn off.
BIOMETALLURGY/BIOLEACHING
Bioleaching is a technology in which metal ions are extracted from low-grade ores and nodules by direct or indirect actions of micro-organisms. The advantages of bioleaching include the absence of noxious of gases or toxic effluent, simplicity of plant operation and maintenance, economic and simple process requiring low capital and low-operating costs and applicability to various metals. The principal bacterium in ore leaching is Thiobacillus ferrooxidans, which is capable of oxidizing ferrous iron as well as sulphur compounds. The thermophilic sulfolobus plays a role in leaching at elevated temperature. Most of the biotechnical processes for leaching of metals have been developed using aerobic microorganisms.
However, the highly oxidized metal compounds such as MnO2 and Fe2O3 can be solubilized by reduction processes. Hence, Mn and Fe from MnO2 and Fe2O3 can be recovered by the direct or indirect actions of heterotrophic microorganisms that thrive under micro-aerobic or anaerobic conditions. In the former case, the microorganisms are capable of utilizing MnO2 as a final acceptor of electrons in the respiratory chain of their metabolism, instead of oxygen. That is, anaerobic heterotrophs such as iron-reducing bacteria, manganese-reducing bacteria, and sulphur-reducing bacteria donate electrons, which are produced by the oxidation of organic substrates to Fe2O3, MgO, MnO2, SeO4 and V2O3, and leach the reduced metal ions into the medium. In the second case, the reduction process is associated with the formation of reducing compounds, which are products of their metabolism. The anaerobic bioleaching technology of metals has not been commercialized. This is because it has to be adapted according to each type of metals. Moreover, there is a demand for a less expensive and more environmentally friendly anaerobic bioleaching process.
SOLUTION CONCENTRATION AND PURIFICATION
After leaching, the leach liquor must normally undergo concentration of the metal ions that are to be recovered. Additionally, some undesirable metals may have also been taken into solution during the leach process. The solution is often purified to eliminate the undesirable components. The processes employed for solution concentration and purification include: precipitation, cementation, solvent extraction, electrolysis, ion exchange etc.
REFINING PROCESSES FOR MANGANESE
In pyrometallurgy, heating and refining of manganeses are made in blast furnaces using only coke as reductant and as energy source or in electric smelting furnaces. Depending on the ore quality the efficient electric furnaces consume about 2100 - 2800 kWh electric power per 1 t of ferromanganese alloy (Kroschwitz and Howe-Grant, 1982) and (Elvers et al, 1990).
PROPERTIES AND APPLICATIONS OF MANGANESE
PROPERTIES
Manganese is black manganese dioxide. Manganese can be welded, machined, and coldworked because they are less ductile and malleable. They have high strength and hardness
APPLICATIONS
Mn is necessary for a variety of metabolic functions including those involved in skeletal system development, energy metabolism, activation of certain enzymes, nervous system function, immunological system function, and reproductive hormone function, and is an antioxidant that protects cells from damage due to free radicals.
Mn also plays an essential role in regulation of cellular energy, bone and connective tissue growth and blood clotting.
In the brain, Mn is an important cofactor for a variety of enzymes, including the antioxidant enzyme superoxide dismutase, as well as enzymes involved in neurotransmitter synthesis and metabolism.
Manganese has three primary metabolic functions:
(i) it acts as an activator of the gluconeogenic enzymes pyruvate carboxylase and isocitrate dehydrogenase,
(ii) it is involved in protecting mitochondria1 membranes through superoxide
dismutase; and
(iii) it activates glycosyl transferase, which is involved in mucopolysaccharide synthesis.
The most important source of Mn for the general population is diet, and the average intake of Mn from food ranges from 2 to 9 mg/day.
In addition, vitamin and mineral supplements may contain 1 to 20 mg Mn/tablet.
Manganese is mainly used as an alloying agent in the manufacture of steel to increase its tensile strength. It is also added during the steelmaking process to remove sulfur as a slag.
Austenitic manganese steels are used for railroad trackwork, power shovel buckets, and rock crushers. Mediumcarbon manganese steels are used in the manufacture of car axles and gears
Clay and moisture content
LABORATORY REPORT ON THE DETERMINATION OF THE MOISURE AND CLAY CONTENT OF GREEN SAND
ABSTRACT
The quality of castings in a green sand mould is influenced significantly by its properties, such as green compression strength, permeability, mould hardness, and others, which depend on input parameters. The relationships of these properties with the input parameters, like sand grain size and shape, binder, water, clay, etc. are complex in nature.
The goal of this paper is to determine the green sand mould compressive strength in case of input parameters.
A good moulding sand however, must possess the following properties. The properties are determined by the amount of clay, moisture content and by the shape and size of the silica grain in the sand;
PERMEABILITY
COHESIVENESS OR STRENGTH
ADHESIVENESS
PLASTICITY
REFRACTORINESS
BINDING
CHEMICAL RESISTIVITY
FLOWBILITY
However, all this properties at the end of the experiment were achieved as a result of taken important consideration to controlling the amount of clay and moisture content of the sand during sand preparation.
INTRODUCTION
Sand moulding processes are the oldest moulding methods and still remain the most popular world-wide. Sand mould, into which molten metal is poured to produce a casting of desired shape can be made from either dry or green sand. In each case, the moulding sand consist essentially of base material such as silica, zircon, olivine, chromite or any other which imparts refractoriness to the moulding sand; the clay and or other binders which bind the refractory- based particles together and the additives which are often organic whose primary function is to impart special properties to the moulding sand.
However this report will give the account of detail steps involves in maintaining the strength, plasticity, flowability and other properties of a good moulding sand. An important parameter here in that will be discussed are the clay and moisture contents.
At present, there are many methods for measuring the moisture content of green sand, and they can be divided into two categories of direct method and indirect method. In the direct method, the absolute moisture content can be measured by heat or chemical reaction. For the indirect method, the moisture content is obtained by measuring the physical parameters or performance indexes related to the moisture. In general, the direct method has high precision but long measurement period, so it is only suitable for laboratory while unsuitable for the production line. Although the precision of the indirect method is not as high as the direct method, it can be used for online measuring the moisture content of green sand due to the fast speed.
OBJECTIVES:
To stress the importance of water in moulding sand
MATERIALS ROVIDED:
A sample of the green sand
Crucible
An oven
A weighing balance
Distil water
1 litre capacity jar
Dry moulding sand
Rotating machine
Weighing machine
1% aqueous solution of NaOH
PROCEDURE I
The following are the step taken for the determination of moisture content:
I weighed he green sand sample of about 100g into the crucible of known mass M0.
I then placed the crucible and its content inside the oven, in which the temperature
was then maintained between 105 – 110oC.
The crucible was brought out and weighed at an intervals of ten minutes.
I repeated the experiment for the same sample until a constant mass was obtained
(i.e. for about five(5) times continually.
After the fifth time the sample was brought out.
DATA AND RESULTS
If:
The mass of the crucible = M0
The mass of given Sand + crucible = M1
And the mass of the sand + crucible = M2
Then:
The mass of the green sand = M1 – M0
The final mass of sand = M2 – M0
And the mass of sand the moisture in the sand is = (M1 – M0) – (M2 – M0) = M1 - M2
TABLE OF RESULTS
S/N
WEIGHT OF GREEN SAND
1.0
104.66g
2.0
96.73g
3.0
96.40g
4.0
96.38g
5.0
96.40g
Table 1
Initial Weight of sand = 100.51g
Mass of crucible = 7.51g
Calculations
M0 = 7.51g
M1 = (100.51 + 7.51) g = 108.02g
Final mass of the sand = 96.40g
M2 = (96.40 + 7.51) g = 103.91g
And the mass of sand the moisture in the sand is
(M1 – M0) – (M2 – M0) = M1 - M2
108.02g – 103.91g = 4.11g
Moisture content =
= x 100
=
= 4.089g
PROCEDURES II
The following are the step taken for the determination of clay content:
I weight of 50g out of the dry moulding sand out of the previously processed sand.
This is poured into a jar of 1litre capacity with diameter 90mm,
A 450mL of distilled water is poured into the jar with the content
Then I added 25mL of 1% aqueous solution of NaOH to the jar.
Having securely closed jar, I keep on shaking the jar gently for sufficient time to allow the content to settle
Then additional water is added to a level of 150mm.
After 10mins the excess water is siphoned away and the operation is repeated all over
After the end of the 3rd time the system is allowed to stand for about 5mins and this continuous for as long as the water remaining under the stand.
However the left over could not be filtered, dried nor weighed because the clay could not be emptied from the used jar (see the figures below). Hence the clay content cannot be calculated.
Before settling after settling
DISCUSSION OF RESULTS
A noticeable decrease in the moisture content is observed as shown in the table 1 above. This decrease is as a result of the repeated addition of water to the sand sample and particularly because of the sample duration in the oven.
Hence it can be realised that the heat or dryness play an important role to the estimation of the moisture content.
Haven poke nosed into other group values, differences were observed in the various moisture contents. The various are as a result of; (i) systematic error that might have occur during weighing (ii) random errors that are caused by the air during measurement.
QUESTIONS AND ANSWERS
(1) Observation precaution taken to ensure successful result
I avoided systematic error during my measurement.
I ensure the temperature range is not exceeded.
I avoided extra time limit.
(2) The determined moisture content of the green sand from the experiment is 4.089g
(3) Importance of moisture in the moulding and core sand are;
Moisture increases the compartment of the moulding and core sand.
Moisture also helps to keep the nutrient content in the sands from being loosed away easily.
Moisture increases moulding sand flowability
Moisture improves the strength of the moulding and core sand
(4) Some differences:
i. Differences between the dry sand and green sand
a. Dry sand is basically the sands that has loses some certain percentage of their moisture content. They are mostly sands that have being used one or more times for moulding while green sands are sands that still retain most of their moisture content. And they contain more good moulding sand properties compare to dry sands.
b. Green sand is a mixture of sand with 20-30% clay having total amount of water from 6-10%.green sand mould is used for small size casting of ferrous and non ferrous metals. Dry sand is a green sand moulds when baked or dried before pouring the molten metals.
ii. Difference between the moisture and water of crystallization of the sand
Moisture content is the quantity of water contained in a material measured through weight loss on drying while water of crystallization of sand is a measure of free water in a sample and ranged between 0 and 1.
(5) Determine the clay content of the sample you are given:
Clay content could not be determined. The experiment was inconclusive.
(6) In what way does clay content affect the moulding and core sands:
Clay reduces permeability of sand and increases the strength of the sand. An adequate percentage of clay content will increase the flowability of the moulding and core sand. Adding it into sand can increase its ability to stick together but reduces the ability of the metal to outgas.
CONCLUSION
It can be concluded that, water is very crucial in the moulding sand as it helps to keep the sand weigh constant and also to improve many moulding sand properties.
Hence one must be accurate in take appropriate volume of water to be used during moulding and core sand preparation.
ABSTRACT
The quality of castings in a green sand mould is influenced significantly by its properties, such as green compression strength, permeability, mould hardness, and others, which depend on input parameters. The relationships of these properties with the input parameters, like sand grain size and shape, binder, water, clay, etc. are complex in nature.
The goal of this paper is to determine the green sand mould compressive strength in case of input parameters.
A good moulding sand however, must possess the following properties. The properties are determined by the amount of clay, moisture content and by the shape and size of the silica grain in the sand;
PERMEABILITY
COHESIVENESS OR STRENGTH
ADHESIVENESS
PLASTICITY
REFRACTORINESS
BINDING
CHEMICAL RESISTIVITY
FLOWBILITY
However, all this properties at the end of the experiment were achieved as a result of taken important consideration to controlling the amount of clay and moisture content of the sand during sand preparation.
INTRODUCTION
Sand moulding processes are the oldest moulding methods and still remain the most popular world-wide. Sand mould, into which molten metal is poured to produce a casting of desired shape can be made from either dry or green sand. In each case, the moulding sand consist essentially of base material such as silica, zircon, olivine, chromite or any other which imparts refractoriness to the moulding sand; the clay and or other binders which bind the refractory- based particles together and the additives which are often organic whose primary function is to impart special properties to the moulding sand.
However this report will give the account of detail steps involves in maintaining the strength, plasticity, flowability and other properties of a good moulding sand. An important parameter here in that will be discussed are the clay and moisture contents.
At present, there are many methods for measuring the moisture content of green sand, and they can be divided into two categories of direct method and indirect method. In the direct method, the absolute moisture content can be measured by heat or chemical reaction. For the indirect method, the moisture content is obtained by measuring the physical parameters or performance indexes related to the moisture. In general, the direct method has high precision but long measurement period, so it is only suitable for laboratory while unsuitable for the production line. Although the precision of the indirect method is not as high as the direct method, it can be used for online measuring the moisture content of green sand due to the fast speed.
OBJECTIVES:
To stress the importance of water in moulding sand
MATERIALS ROVIDED:
A sample of the green sand
Crucible
An oven
A weighing balance
Distil water
1 litre capacity jar
Dry moulding sand
Rotating machine
Weighing machine
1% aqueous solution of NaOH
PROCEDURE I
The following are the step taken for the determination of moisture content:
I weighed he green sand sample of about 100g into the crucible of known mass M0.
I then placed the crucible and its content inside the oven, in which the temperature
was then maintained between 105 – 110oC.
The crucible was brought out and weighed at an intervals of ten minutes.
I repeated the experiment for the same sample until a constant mass was obtained
(i.e. for about five(5) times continually.
After the fifth time the sample was brought out.
DATA AND RESULTS
If:
The mass of the crucible = M0
The mass of given Sand + crucible = M1
And the mass of the sand + crucible = M2
Then:
The mass of the green sand = M1 – M0
The final mass of sand = M2 – M0
And the mass of sand the moisture in the sand is = (M1 – M0) – (M2 – M0) = M1 - M2
TABLE OF RESULTS
S/N
WEIGHT OF GREEN SAND
1.0
104.66g
2.0
96.73g
3.0
96.40g
4.0
96.38g
5.0
96.40g
Table 1
Initial Weight of sand = 100.51g
Mass of crucible = 7.51g
Calculations
M0 = 7.51g
M1 = (100.51 + 7.51) g = 108.02g
Final mass of the sand = 96.40g
M2 = (96.40 + 7.51) g = 103.91g
And the mass of sand the moisture in the sand is
(M1 – M0) – (M2 – M0) = M1 - M2
108.02g – 103.91g = 4.11g
Moisture content =
= x 100
=
= 4.089g
PROCEDURES II
The following are the step taken for the determination of clay content:
I weight of 50g out of the dry moulding sand out of the previously processed sand.
This is poured into a jar of 1litre capacity with diameter 90mm,
A 450mL of distilled water is poured into the jar with the content
Then I added 25mL of 1% aqueous solution of NaOH to the jar.
Having securely closed jar, I keep on shaking the jar gently for sufficient time to allow the content to settle
Then additional water is added to a level of 150mm.
After 10mins the excess water is siphoned away and the operation is repeated all over
After the end of the 3rd time the system is allowed to stand for about 5mins and this continuous for as long as the water remaining under the stand.
However the left over could not be filtered, dried nor weighed because the clay could not be emptied from the used jar (see the figures below). Hence the clay content cannot be calculated.
Before settling after settling
DISCUSSION OF RESULTS
A noticeable decrease in the moisture content is observed as shown in the table 1 above. This decrease is as a result of the repeated addition of water to the sand sample and particularly because of the sample duration in the oven.
Hence it can be realised that the heat or dryness play an important role to the estimation of the moisture content.
Haven poke nosed into other group values, differences were observed in the various moisture contents. The various are as a result of; (i) systematic error that might have occur during weighing (ii) random errors that are caused by the air during measurement.
QUESTIONS AND ANSWERS
(1) Observation precaution taken to ensure successful result
I avoided systematic error during my measurement.
I ensure the temperature range is not exceeded.
I avoided extra time limit.
(2) The determined moisture content of the green sand from the experiment is 4.089g
(3) Importance of moisture in the moulding and core sand are;
Moisture increases the compartment of the moulding and core sand.
Moisture also helps to keep the nutrient content in the sands from being loosed away easily.
Moisture increases moulding sand flowability
Moisture improves the strength of the moulding and core sand
(4) Some differences:
i. Differences between the dry sand and green sand
a. Dry sand is basically the sands that has loses some certain percentage of their moisture content. They are mostly sands that have being used one or more times for moulding while green sands are sands that still retain most of their moisture content. And they contain more good moulding sand properties compare to dry sands.
b. Green sand is a mixture of sand with 20-30% clay having total amount of water from 6-10%.green sand mould is used for small size casting of ferrous and non ferrous metals. Dry sand is a green sand moulds when baked or dried before pouring the molten metals.
ii. Difference between the moisture and water of crystallization of the sand
Moisture content is the quantity of water contained in a material measured through weight loss on drying while water of crystallization of sand is a measure of free water in a sample and ranged between 0 and 1.
(5) Determine the clay content of the sample you are given:
Clay content could not be determined. The experiment was inconclusive.
(6) In what way does clay content affect the moulding and core sands:
Clay reduces permeability of sand and increases the strength of the sand. An adequate percentage of clay content will increase the flowability of the moulding and core sand. Adding it into sand can increase its ability to stick together but reduces the ability of the metal to outgas.
CONCLUSION
It can be concluded that, water is very crucial in the moulding sand as it helps to keep the sand weigh constant and also to improve many moulding sand properties.
Hence one must be accurate in take appropriate volume of water to be used during moulding and core sand preparation.
Green sand moulding
LABORATORY REPORT ON THE PRINCIPLES OF GREEN SAND MOULDING
ABSTRACT
This report gives the account of the principles involve in the green sand moulding. It entails the step by step procedures to be taken in making moulding. Here in this report, some foundry terms like; the cope and the drag, the runner, ingate, etc. will be discussed.
Moulding however is important in the casting as it dictate the shape or form to which the cast is going to assumed. It necessary that fine green sand should be used for a better output.
INTRODUCTION
The main objective of this report is to give the account of my familiarity with the principles of the green sand moulding and some foundry terminologies.
There are several moulding methods that could be employed to moulding. But each method is depend on the type of metal or alloy to be cast.
Sand casting is however one of the most popularly available casting technique and it involves moulding with green sands. Green sands are the mixture of sand grains (e.g silica sand), clay, water and other special additives to develop specific mould properties needed for the production of the premium castings.
The following are the materials needed for moulding:
The pattern to be mould
The green sand
The moulding boxes
The rammer
Sand muller
Sprue cutter
Riddle and bottom board
Parting sand and strike-off bar
However the under listed flow is the step by step procedure in making moulding:
Sand preparation→Pattern making→Core making→Moulding→Closing
Finally, in this report details will be given on some specific characteristics a moulding sand most have.
PROCEDURE
The following are the step taken during the experiment:
At first, I made the green sand from the mixture of silica sand, clay (which was
used as a binder), water and additives.
I allow mulling to occur up to 3minutes and the open the bottom of the muller to
allow the sand to dump out.
I took a handful of the sand and squeeze it to affirm that it the strength is sufficient
for the moulding.
I did not use the cope because floor moulding was done
I leveled the floor with the sand about 3cm high and then compact it to give a fine
smooth surface.
I placed the pattern diagonally on the sand and make it sink about 0.5cm down
I dusted the surface with the parting sand and then placed the drag on the top of the
pattern.
Then I put a rod very close to the pattern before I filled the drag up it sand and
thereafter ram the sand around the pattern using the rammer until a rigid and
strength-full state is observed within the moulding flask.
More sand is added to until the drag is filled to overflowing and the ram again, the
excess sands were leveled using the strike-off bar.
Then I remove the rod I had put when filling the drag to create a cavity for the
sprue and the riser.
Now I separate the drag from the floor cope and removed out the pattern.
I realign the drag and floor cope back haven demarcated the pin holes before.
Cut the sprue and the riser to make a very complete moulding
Then I blow off the sands from the mould and I ensured that the sprue holes is
clearn.
I realign the mould back properly and cover the riser up to avoid particle and air
with the mould cavity till the molten metal will be ready for pouring.
DEFINITION OF TERMS
DRAG: drag is the top part of a moulding flask. The drag aligns the cope. A typical drag is illustrated in the fig2 above.
RAMMER: it is the tool use to compress the moulding sand. The hand off a rammer is made of tool and resembles like handless mallet with one end flat and the other end blunt edge. A typical rammer is shown in the figure below.
MOULDING FLASK: it is tooling use to contain a mould in metal casting. It has only sides and there is no top or bottom. It is use to form frame around the mould. But in actual sence moulding flask is the cope and grad pulled together. See the figure bellow:
SPRUE: a sprue is the passage through which the liquid material is introduced into a mold. In many cases it is controls the flow of material into the mould. Sprue is however the passage through which a molten material is introduce into a mld and the term also refers to the excess material which solidifies as in the sprue passage
RISERS: risers are also known as the feeders. They are reservoirs built into a metal casting mould to prevent cavities due to shrinkage. See figure7 below.
GATING SYSTEM: this particular term is referred to all passageways through which the molten metal passes to enter the mould cavity. The gating system is made up of; pouring basin, sprue, runner, gates and risers.
ADVANTAGES OF SAND CASTING
Nearly any alloy: Sand castings can be readily produced in nearly any ferrous or non-ferrous alloy. Some other casting processes will melt and pour super-alloys in vacuum, but that is not typically done as a sand casting. Some materials cannot be “worked”, and must be produced as a casting.
Low tooling cost: The relatively low cost of tooling makes sand casting a process of choice for lower volume needs. Patterns do wear so the material selected for the pattern (typically wood, plastic, or metal) will depend on the expected usage quantity of the part being produced. Though not necessarily cheaper in the short run, the use of machined (or “patternless”) moulds may be a cost effective option for components with expected lower usage over a longer period of time.
Versatile – Size, Weight, Shape: Sand castings can be produced in weights from ounces to 200+ tons. Through the use of cores, internal structures can be cast in place. Shaped parts rely mainly on the imagination of the designer. Most sand castings, however, will need at least some machined surfaces, either because of innate tolerance limits of the process, or the need to mate with other components.
Any Quantity : Because the tooling cost can be minimal, sand casting may be appropriate for a single piece run. Alternatively, there are automotive components that are produced using this process, so it may also be used in high volume applications. Other elements of design and tolerance are often more important than quantity when selecting this as the preferred casting process.
Timing: The casting process itself may be quicker than some others, like investment casting, but it is important to consider the post-casting processes like machining that may be required when computing total lead times.
DISADVANTAGES OF SAND CASTING
Lower Dimensional Accuracy : No-bake molding can deliver better dimensional accuracy and repeatability than green sand molding, but this process will, on average, provide less precision than other common casting processes.
Pattern Maintenance : While of lower cost than tooling for other casting processes, there is still an art to pattern creation. Patterns can be bulky so storage must be managed; this is especially significant if the casting is produced infrequently. Patternless molding can relieve some challenges of pattern storage and maintenance.
Surface Finish : Sand castings tend to deliver a rougher surface finish than other casting processes. That point may be moot if certain surfaces are machined anyway, or if surfaces in the as-cast condition are acceptable.
CASTING DEFECTS ASSOCIATED WITH MOULDING
The following are the casting defects associated with moulding:
Shrinkage defect
Gas porosity defect
Blow holes
Sand burning
Inclusion
Pouring metal defect
Metallurgical defect and etc
COURSES AND PREVENTION
The following are the possible course of the aforementioned defects ;
Inadequate core venting
Excessive release of gas from core
Excessive moisture absorption by the cores
Low gas permeability of the core sand
Moisture content of sand too high, or water released too quickly
Gas permeability of the sand too low
Sand temperature too high
Bentonite content too high
Too much gas released from lustrous carbon producer
The following are the possible prevention measures;
Improve core venting, provide venting channels, ensure core prints are free of
dressing
Reduce amounts of gas. Use slow-reacting binder. Reduce quantity of binder. Use a
coarser sand if necessary.
apply dressing to cores, thus slowing down the rate of heating and reducing gas
pressure.
Dry out cores and store dry, thus reducing absorption of water and reducing gas
pressure.
Reduce moisture content of sand. Improve conditioning of the sand. Reduce inert dust content.
Improve gas permeability. Endeavour to use coarser sand. Reduce bentonite and carbon carrier content.
Reduce sand temperature. Install a sand cooler if necessary. Increase sand quantity.
Reduce bentonite content. Use bentonite with a high montmorillonite content, high specific binding capacity and good thermal stability.
Use slow-reacting lustrous carbon producers or carbon carriers with higher capacity for producing lustrous carbon. In the last instance, the content of carbon carriers in the moulding sand can be reduced.
CONCLUSION
However at the end of the experiment I was able to understand the techniques involved in sand moulding. Also so many foundry terms are no longer a strange words to me again.
ABSTRACT
This report gives the account of the principles involve in the green sand moulding. It entails the step by step procedures to be taken in making moulding. Here in this report, some foundry terms like; the cope and the drag, the runner, ingate, etc. will be discussed.
Moulding however is important in the casting as it dictate the shape or form to which the cast is going to assumed. It necessary that fine green sand should be used for a better output.
INTRODUCTION
The main objective of this report is to give the account of my familiarity with the principles of the green sand moulding and some foundry terminologies.
There are several moulding methods that could be employed to moulding. But each method is depend on the type of metal or alloy to be cast.
Sand casting is however one of the most popularly available casting technique and it involves moulding with green sands. Green sands are the mixture of sand grains (e.g silica sand), clay, water and other special additives to develop specific mould properties needed for the production of the premium castings.
The following are the materials needed for moulding:
The pattern to be mould
The green sand
The moulding boxes
The rammer
Sand muller
Sprue cutter
Riddle and bottom board
Parting sand and strike-off bar
However the under listed flow is the step by step procedure in making moulding:
Sand preparation→Pattern making→Core making→Moulding→Closing
Finally, in this report details will be given on some specific characteristics a moulding sand most have.
PROCEDURE
The following are the step taken during the experiment:
At first, I made the green sand from the mixture of silica sand, clay (which was
used as a binder), water and additives.
I allow mulling to occur up to 3minutes and the open the bottom of the muller to
allow the sand to dump out.
I took a handful of the sand and squeeze it to affirm that it the strength is sufficient
for the moulding.
I did not use the cope because floor moulding was done
I leveled the floor with the sand about 3cm high and then compact it to give a fine
smooth surface.
I placed the pattern diagonally on the sand and make it sink about 0.5cm down
I dusted the surface with the parting sand and then placed the drag on the top of the
pattern.
Then I put a rod very close to the pattern before I filled the drag up it sand and
thereafter ram the sand around the pattern using the rammer until a rigid and
strength-full state is observed within the moulding flask.
More sand is added to until the drag is filled to overflowing and the ram again, the
excess sands were leveled using the strike-off bar.
Then I remove the rod I had put when filling the drag to create a cavity for the
sprue and the riser.
Now I separate the drag from the floor cope and removed out the pattern.
I realign the drag and floor cope back haven demarcated the pin holes before.
Cut the sprue and the riser to make a very complete moulding
Then I blow off the sands from the mould and I ensured that the sprue holes is
clearn.
I realign the mould back properly and cover the riser up to avoid particle and air
with the mould cavity till the molten metal will be ready for pouring.
DEFINITION OF TERMS
DRAG: drag is the top part of a moulding flask. The drag aligns the cope. A typical drag is illustrated in the fig2 above.
RAMMER: it is the tool use to compress the moulding sand. The hand off a rammer is made of tool and resembles like handless mallet with one end flat and the other end blunt edge. A typical rammer is shown in the figure below.
MOULDING FLASK: it is tooling use to contain a mould in metal casting. It has only sides and there is no top or bottom. It is use to form frame around the mould. But in actual sence moulding flask is the cope and grad pulled together. See the figure bellow:
SPRUE: a sprue is the passage through which the liquid material is introduced into a mold. In many cases it is controls the flow of material into the mould. Sprue is however the passage through which a molten material is introduce into a mld and the term also refers to the excess material which solidifies as in the sprue passage
RISERS: risers are also known as the feeders. They are reservoirs built into a metal casting mould to prevent cavities due to shrinkage. See figure7 below.
GATING SYSTEM: this particular term is referred to all passageways through which the molten metal passes to enter the mould cavity. The gating system is made up of; pouring basin, sprue, runner, gates and risers.
ADVANTAGES OF SAND CASTING
Nearly any alloy: Sand castings can be readily produced in nearly any ferrous or non-ferrous alloy. Some other casting processes will melt and pour super-alloys in vacuum, but that is not typically done as a sand casting. Some materials cannot be “worked”, and must be produced as a casting.
Low tooling cost: The relatively low cost of tooling makes sand casting a process of choice for lower volume needs. Patterns do wear so the material selected for the pattern (typically wood, plastic, or metal) will depend on the expected usage quantity of the part being produced. Though not necessarily cheaper in the short run, the use of machined (or “patternless”) moulds may be a cost effective option for components with expected lower usage over a longer period of time.
Versatile – Size, Weight, Shape: Sand castings can be produced in weights from ounces to 200+ tons. Through the use of cores, internal structures can be cast in place. Shaped parts rely mainly on the imagination of the designer. Most sand castings, however, will need at least some machined surfaces, either because of innate tolerance limits of the process, or the need to mate with other components.
Any Quantity : Because the tooling cost can be minimal, sand casting may be appropriate for a single piece run. Alternatively, there are automotive components that are produced using this process, so it may also be used in high volume applications. Other elements of design and tolerance are often more important than quantity when selecting this as the preferred casting process.
Timing: The casting process itself may be quicker than some others, like investment casting, but it is important to consider the post-casting processes like machining that may be required when computing total lead times.
DISADVANTAGES OF SAND CASTING
Lower Dimensional Accuracy : No-bake molding can deliver better dimensional accuracy and repeatability than green sand molding, but this process will, on average, provide less precision than other common casting processes.
Pattern Maintenance : While of lower cost than tooling for other casting processes, there is still an art to pattern creation. Patterns can be bulky so storage must be managed; this is especially significant if the casting is produced infrequently. Patternless molding can relieve some challenges of pattern storage and maintenance.
Surface Finish : Sand castings tend to deliver a rougher surface finish than other casting processes. That point may be moot if certain surfaces are machined anyway, or if surfaces in the as-cast condition are acceptable.
CASTING DEFECTS ASSOCIATED WITH MOULDING
The following are the casting defects associated with moulding:
Shrinkage defect
Gas porosity defect
Blow holes
Sand burning
Inclusion
Pouring metal defect
Metallurgical defect and etc
COURSES AND PREVENTION
The following are the possible course of the aforementioned defects ;
Inadequate core venting
Excessive release of gas from core
Excessive moisture absorption by the cores
Low gas permeability of the core sand
Moisture content of sand too high, or water released too quickly
Gas permeability of the sand too low
Sand temperature too high
Bentonite content too high
Too much gas released from lustrous carbon producer
The following are the possible prevention measures;
Improve core venting, provide venting channels, ensure core prints are free of
dressing
Reduce amounts of gas. Use slow-reacting binder. Reduce quantity of binder. Use a
coarser sand if necessary.
apply dressing to cores, thus slowing down the rate of heating and reducing gas
pressure.
Dry out cores and store dry, thus reducing absorption of water and reducing gas
pressure.
Reduce moisture content of sand. Improve conditioning of the sand. Reduce inert dust content.
Improve gas permeability. Endeavour to use coarser sand. Reduce bentonite and carbon carrier content.
Reduce sand temperature. Install a sand cooler if necessary. Increase sand quantity.
Reduce bentonite content. Use bentonite with a high montmorillonite content, high specific binding capacity and good thermal stability.
Use slow-reacting lustrous carbon producers or carbon carriers with higher capacity for producing lustrous carbon. In the last instance, the content of carbon carriers in the moulding sand can be reduced.
CONCLUSION
However at the end of the experiment I was able to understand the techniques involved in sand moulding. Also so many foundry terms are no longer a strange words to me again.
AGGLOMERATION
A SHORT NOTE ON AGGLOMERATION
Agglomerates are particulate materials consisting of large particles formed by the joining or binding together of primary particles whose original identity can still be visible in the final agglomerate form. The term can refer to: Cluster of primary particles held together by weak physical interactions Cluster of molecules or particles that results from agglomeration Scrambled auto-assembly of otherwise isolated single molecules or particles Cluster of primary particles interconnected by chemical bonds.
Agglomeration of corrosion products in boilers increases scale buildup, which leads to corroded boiler walls and heat loss. Agglomerate is also known as flocculate, aggregation, coagulation and coalescence.
An agglomerate is a material formed by objects sticking together and forming clumps. A common example is when mixing powders into liquid, the powders often form clumps, requiring some mechanical effort to break apart.
In surface chemistry, agglomerate is the process by which fine particulates are caused to clump together into a floc. The floc may then float to the top of the liquid (creaming), settle to the bottom of the liquid (sedimentation), or be readily filtered from the liquid.
Agglomerates are affected by several parameters, including:
Mixing speeds
Mixing intensity
Mixing time
Agglomeration and sedimentation are widely employed in:
Purification of drinking water
Sewage treatment
Storm-water treatment
Treatment of other industrial wastewater streams
Agglomerates can cause corrosion. For example, in process water systems, corrosion products agglomerate significantly in certain locations. Significant agglomerations (or deposits) can occur in copper cooling passages and where heat is removed by water cooling. Such agglomerations also occur at restrictions found in non-copper system components like valve seats, fixed orifices, pump seal faces, etc. Agglomerations causes component clogging and malfunction, which leads to increased corrosion rate.
Agglomerates also cause sedimentation in water treatment plants and scale formation in boilers, which ultimately leads to process inefficiency, corrosion and boiler failure.
As in the case of metallurgy, generally, the success of metallurgical processes depends on the particle size and uniformity of the raw materials used. In the light of beneficiation of low grade ores, the particle size of the concentrates had consistently reduced and hence not suitable directly for metallurgical operations. Thus it become necessary to agglomerate the fine concentrates to make them suitable for subsequent metallurgical operations.
The type of agglomeration process depends on the quality of raw materials used and the quality of agglomerate needed for subsequent operation.
Agglomeration plays an important role in industrial applications as is the case with ferro alloy industry. Since the power consumption in the electric furnace is a major contributor for the cost of ferro alloy production, pre reduction before the ore is charged into the electric furnace reduces the cost of net product made, by lowering of the power consumption in the arc furnace.
Agglomerates are particulate materials consisting of large particles formed by the joining or binding together of primary particles whose original identity can still be visible in the final agglomerate form. The term can refer to: Cluster of primary particles held together by weak physical interactions Cluster of molecules or particles that results from agglomeration Scrambled auto-assembly of otherwise isolated single molecules or particles Cluster of primary particles interconnected by chemical bonds.
Agglomeration of corrosion products in boilers increases scale buildup, which leads to corroded boiler walls and heat loss. Agglomerate is also known as flocculate, aggregation, coagulation and coalescence.
An agglomerate is a material formed by objects sticking together and forming clumps. A common example is when mixing powders into liquid, the powders often form clumps, requiring some mechanical effort to break apart.
In surface chemistry, agglomerate is the process by which fine particulates are caused to clump together into a floc. The floc may then float to the top of the liquid (creaming), settle to the bottom of the liquid (sedimentation), or be readily filtered from the liquid.
Agglomerates are affected by several parameters, including:
Mixing speeds
Mixing intensity
Mixing time
Agglomeration and sedimentation are widely employed in:
Purification of drinking water
Sewage treatment
Storm-water treatment
Treatment of other industrial wastewater streams
Agglomerates can cause corrosion. For example, in process water systems, corrosion products agglomerate significantly in certain locations. Significant agglomerations (or deposits) can occur in copper cooling passages and where heat is removed by water cooling. Such agglomerations also occur at restrictions found in non-copper system components like valve seats, fixed orifices, pump seal faces, etc. Agglomerations causes component clogging and malfunction, which leads to increased corrosion rate.
Agglomerates also cause sedimentation in water treatment plants and scale formation in boilers, which ultimately leads to process inefficiency, corrosion and boiler failure.
As in the case of metallurgy, generally, the success of metallurgical processes depends on the particle size and uniformity of the raw materials used. In the light of beneficiation of low grade ores, the particle size of the concentrates had consistently reduced and hence not suitable directly for metallurgical operations. Thus it become necessary to agglomerate the fine concentrates to make them suitable for subsequent metallurgical operations.
The type of agglomeration process depends on the quality of raw materials used and the quality of agglomerate needed for subsequent operation.
Agglomeration plays an important role in industrial applications as is the case with ferro alloy industry. Since the power consumption in the electric furnace is a major contributor for the cost of ferro alloy production, pre reduction before the ore is charged into the electric furnace reduces the cost of net product made, by lowering of the power consumption in the arc furnace.
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