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10 Important differences between Cold working and Hot working

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Following are the 10 important differences between cold working and hot working Working of metal and alloy below their recrystallization temperature is known as cold working , and working of metal and alloy above their recrystallization temperature is known as hot working . During cold working strain hardening occurs and due to this tensile strength, hardness increases while the impact strength and ductility decreases, whereas, due to hot working strain hardening is removed by recrystallization. Microstructure of cold worked component shows distorted grains, whereas, microstructure of hot worked components shows equiaxed and usually refined grains. Due to cold working defect density increases i.e. vacancies, dislocations, etc. increases and hence the density of material slightly decreases, whereas, due to hot working there is almost no change in defect density of material. Cold working cannot be done indefinitely without cracking of material due to strain hardening, whereas, ho
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CONSTITUTIONAL SUPERCOOLING

ABOUT CONSTITUTIONAL SUPERCOOLING Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid. Some of its applications involve refrigeration, organ preservation etc. Constitutional supercooling, is a type of supercooling which occurs during solidification due to compositional changes, and results in cooling a liquid below the freezing point ahead of the solid–liquid interface. This effect occurs when the temperature gradient in the liquid ahead of the interface is small or when interface velocity is large. Constitutional supercooling leads to the formation of dendritic structure during solidification of casting. Fig 1.1 Typical casting grain structure Order of supercooling : Chill Zone > Columnar Grains Zone > Central Equiaxed Chill zone has greater supercooling effect because it is formed when molten metal comes in contact with the cold mould walls. Fig 1.2 The origin of c
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