Bhat Metals Rajajinagar, Bangalore, Karnataka

It is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the re-crystallization temperature and maintaining a suitable temperature, and then cooling. Annealing is used to induce ductility, soften material, relieve internal stresses, refine the structure by making it homogeneous, and improve cold working properties. Machining induces stresses in parts. The bigger and more complex the part, the more the stresses. These stresses can cause distortions in the part long term. If the parts are clamped in service, then cracking could occur. Also hole locations can change causing them to go out of tolerance. For these reasons, stress relieving is often necessary. Tempering is a process done subsequent to quench hardening. Quench-hardened parts are often too brittle. This brittleness is caused by a predominance of Martensite. This brittleness is removed by tempering. Tempering results in a desired combination of hardness, ductility, toughness, strength, and structural stability. Tempering is done immediately after quench hardening. When the steel cools to about 40 ºC (104 ºF) after quenching, it is ready to be tempered. The part is reheated to a temperature of 150 to 400 ºC (302 to 752 ºF).

Glow discharge that envelopes the entire surface achieves a consistent hardness and case depth. This is specially noticeable on complex geometries where gas nitriding case depths can be non-uniform. Plasma nitriding (H2+N2) least affects the surface finish of the product. Salt bath and gas nitriding, which uses ammonia (NH3) and phosphate for activa- tion , will roughen a ground or polished surface. Higher surface hardness is achieved at lower processing temperatures (500 ºC). Thus distortion is almost zero and no changes in the properties at the core of the material