Bulk Processing of Metals - Assignment Example

BULK PROCESSING OF METALS By Name Course Instructor Institution City/State Date Bulk processing of metals Question One The casting properties, as pointed out by Ayoola et al. (2012) are influenced by the process of utilised and the moulding materials’ properties employed. More importantly, the mould utilised in the metal casting is reliant on the produced casting, the involved alloy as well as the shape complexity to be cast. The transfer of heat between the mould and solidifying casting is critical for ensuring that the casting is of high quality. Besides that, the transfer of heat between the mould and the casting is controlled primarily by the mould-metal interface conditions. Ayoola et al. (2012) posit that the equi-axed grain structures of the CO2 moulds and metal castings’ precipitates are fine than the natural sand moulds as well as cement castings. Still, the hardness of the CO2 mould’s casting is very high thanks to the hardened silica gel formation through the mould that facilitates its chilling effect. According to Kundu (2011), the ferrite grain structure strongly influences the microalloyed steels’ mechanical properties. The author posits that a uniform and fine ferrite grains distribution lead to a high toughness and high strength. Normally, the casting yield is improved by continuous casting; thus, reducing the amount of hot working needed to manufacture the products and leading to cost, time and energy savings. In Datau et al. (2012) study, they established that the mould, as well as pouring temperatures, enormously influences the sand casted aluminium alloy’s mechanical properties. For instance, there was an increase in hardness, ultimate strength, and also elongation after the pouring and pouring temperatures were increased. Datau et al. (2012) observed that the ultimate strength increased more than elongation and harness (see table one). The authors further observed that reducing the runner size led to improved solidification time, elongation, hardness as well as ultimate strength. When the size of the runner towards the mould cavity was reduced to the extent that it was smaller as compared to runner’s size towards the sprue, both the mechanical properties and solidification time of the alloy increased. At the time of solidification, the strength of a hot metal is very low but it must shrink while cooling. Because of temperature differences, the cooling part will have strain mismatches. The coefficient of thermal conductivity affects the rate of cooling and also defines the internal stresses and temperature gradient because of temperature difference. Table One: Mechanical Properties and Solidification Time at Different Pouring Temperatures (Datau et al., 2012, p.40) In Akhil et al. (2014) study, they observed that the ultimate tensile stress of the as-cast increases when the section size of the cast component section size is reduced (see figure one). This was attributed to the smaller section size’s grain refinement caused by the fast rate of cooling. There was an improvement in the ultimate tensile strength at aged as well as heat treated condition but remained nearly constant with section size variation. This was because the grain refinement increased in aged and heat treated condition regardless of the section size. When the section size was reduced, Akhil et al. (2014) posit that the mechanical properties like ultimate tensile stress, impact strength, and hardness increased because of grain refinement. Fig One; Impact Strength Variation with Section Size (Akhil Et Al., 2014, P.1680) Word Count – 508 Question Two Engine blocks manufacturing is normally performed through utilisation of sand casting. Importantly, sand casting is considered more suitable than die casting because it is more cost effective and does not easily wear because of the molten metal high temperature. Manufacturing the engine block through Sand casting improved the machinability property; thus, making it easy for automakers to achieve the desired surface finish. Green sand mould casting, as mentioned by Barbezat (2005), is a type of the sand casting technique normally utilised for the production of the engine block. In this case, the term green symbolises the existence of moisture inside the sand mould. For many years, cast iron has been utilised as the main material for making engine blocks, mainly because of its various properties such cheap production through sand casting and improved machinability. Actually, sand casting is a suitable process for metals that have high melting temperatures like titanium, nickel, and steel. The collapsibility property of sand casts make it suitable for manufacturing the engine blocks since this property allows for the metal casting to freely shrink during the solidification stage. This property enables the mould to collapse sufficiently for the shrinkage of the casting; thus, cracking or hot tearing cannot develop in the engine blocks. Other properties that make sand casting suitable for making engine blocks is flowability and refractory strength; a more flowability makes it possible to produce a detailed casting and the refractory strength demonstrates the ability of the sand mixture to withstand extreme temperature levels. Sand casting has started becoming popular in the prosthetic hip replacements because of its ability to manufacture components with different shape; thus, offering tight tolerances for hip replacement components. Therefore, sand casting is suitable for manufacturing prosthetic hip replacements considering that the majority of contemporary orthopaedic implants are manufactured through sand casting. Sand casting is considered a suitable approach because it offers competes with high precision as well as improved surface finish. In McCormack Et Al. (1999) study, they manufactured a ‘bone’ tube from aluminium through the green-sand casting technique. According to the authors, the sand casting technique allowed for repeatable dimensions between the specimens and also an aluminium wall with a consistent surface roughness that was the same as the reamed intramedullary cavity’s bone. The ability of sand casting technique to produce bearing surfaces makes it suitable for increasing the total hip replacement longevity. Sand casting can be utilised to manufacture the metal-on-metal bearings and aluminium oxide ceramic bearings, which are commonly utilised for Prosthetic hip replacements. Sand casting makes it possible to achieve complex shapes and angles and for small and large series. The products manufactured through sand casting normally have reduced machining cycles, improved corrosion resistance, and are cost effective as compared component manufactured through forging or welding. Sand casting is suitable for manufacturing prosthetic hip replacements because of its ability to produce small components and improved performance as well as durability. Furthermore, sand casting allows for the production of metal-on-Polyethylene, which is the most preferred material for hip replacements amongst the surgeons. Word Count – 506 Question Three According to Ugwekar and Lakhawat (2012), Aluminium is widely utilised for manufacturing various products due to its high tensile strength, low density, as well as corrosion resistance. Aluminium is a good conductor of electrical energy; therefore, it is normally utilised for transmission of electricity. Aluminium is considered to be amongst the plentiful elements that exist in the earth's surface. Still, aluminium is always present as hydrated aluminium oxide rather than metallic and pure form. The hydrated aluminium oxide has some impurities such as Titania, iron oxide, as well as silica. Bauxite is considered to be aluminium ore and contains hydrated aluminium oxide and iron, with the former accounting for the biggest constituent material. Currently, there are plentiful bauxite deposits across the globe. Extraction of pure aluminium from bauxite normally involves two processes; at first, impurities like silica, water, iron oxide, and Titania are eliminated by refining the ore. After that, the resultant Al2O3 is smelted with the aim of producing pure aluminium. Then, through the rolling process, aluminium foil is produced. The process used to refine bauxite is the Bayer process, which normally involves four stages; the first stage is digestion, whereby the aluminium ore is ground as well as mixed with NaOH and then pumped to huge tanks that have been pressurised. The tanks are known as digesters, and it is where heat, sodium hydroxide (NaOH), and pressure breaks down Bauxite into a saturated sodium aluminate solution as well as insoluble impurities. The second phase is clarification, whereby the sodium aluminate solution together with the impurities passes through numerous presses and tanks. In this stage, the contaminants are trapped using cloth filters and are then discarded. The remaining solution is then conveyed into the cooling tower. Precipitation is the third stage; it is where the Al2O3 solution is moved into a large silo, whereby the hydrated aluminium crystals are seeded with the fluid with the aim of facilitating the formation of aluminium particles. When the other solution’s crystals are attracted by the seed crystals, large aluminium hydrate clumps start forming. They are filtered as well as rinsed. The final stage of the Bayer process is Calcination, the whereby the aluminium hydrate is exposed to high temperatures with the aim of dehydrating the material; thus, leaving behind a fine white powder residue, aluminium oxide. The aluminium oxide is then smelted so as to achieve pure, metallic aluminium through the electrolytic method. The final product is then annealed before they are rolled into tin foil. Some properties of aluminium tin alloy high strength as well as low weight; thus, leading to greater load capacity. Furthermore, aluminium foils are corrosion resistant since a protective oxide coating is formed almost instantly when aluminium is exposed to air. Aluminium foil is a good conductor of electricity and heat and is a good reflector of both heat and visible light; thus, they are considered suitable for architectural insulation as well as thermal rescue blankets. The aluminium foil has high ductility and its strength could be increased through cold working. Word Count – 504 References Akhil, K.T., SanjiviArul & R.Sellamuthu, 2014. The Effect of Heat Treatment and Aging Process on Microstructure and Mechanical Properties of A356 Aluminium Alloy Sections in Casting. Procedia Engineering , vol. 97, pp.1676 – 1682. Ayoola, W.A., Adeosun, S.O., Sanni, O.S. & Oyetunji, A., 2012. Effect of Casting Mould on Mechanical Properties of 6063 Aluminium alloy. Journal of Engineering Science and Technology , vol. 7, no. 1, pp.89 - 96. Barbezat, G., 2005. Advanced thermal spray technology and coating for lightweight engine blocks for the automotive industry. Surface & Coatings Technology, vol. 200, no. 5-6, pp.1990 – 1993. Datau, S.G., Oji, J.I.R. & N., D., 2012. The Effect of Sand Casting Process Parameters On Mechanical Properties of Aluminum Alloy Casting. nternational Journal of Metallurgical & Materials Science and Engineering , vol. 2, no. 3, pp. 32-41. Kundu, A., 2011. Grain Structure Development During Casting, Reheating and Deformation of Nb-Microalloyed Steel. Thesis. Birmingham: The University of Birmingham. Mccormack, B., Prendergast, P.J. & O’Dwyer, B., 1999. Fatigue of cemented hip replacements under torsional loads. Fatigue & Fracture of Engineering Materials & Structures , vol. 22, no. 1, pp.33 - 40. Ugwekar, R.P. & Lakhawat, G.P., 2012. Potash Alum from Waste Aluminum Cans and Medicinal Foil. IOSR Journal of Engineering, vol. 2, no. 7, pp.62-64. Read More