Correct option is A
Carburising is the process used to increase the carbon content of the surface layer of mild steel, effectively converting it to
high-carbon steel at the surface. Carburising is a heat treatment process in which the steel is exposed to a carbon-rich atmosphere at high temperatures, typically around 900–950°C. This allows carbon atoms to diffuse into the surface layer of the steel, increasing its carbon content and improving hardness and wear resistance.
Purpose of Carburising: To increase the surface hardness of mild steel while maintaining a tough and ductile core.
Types of Carburising:
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Pack Carburising: Steel is packed in a carbonaceous material and heated.
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Gas Carburising: Carbon-rich gases like methane are used for diffusion.
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Liquid Carburising: Steel is immersed in a molten carbon-containing bath.
Typical Applications: Carburised steels are used in gears, cams, shafts, and other components requiring a hard surface for wear resistance.
Post-Carburising Processes: After carburising, parts may be quenched to lock in hardness and sometimes tempered to relieve internal stresses.
