What is Heat Treatment

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What is Heat Treatment

Metal heat treatment is one of the important processes in mechanical manufacturing. Compared with other processing techniques, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but changing the workpiece inside microstructure or changing the chemical composition on the surface of the workpiece , improve the performance of the workpiece.

Its characteristic is to improve the inherent quality of the workpiece, which is generally not visible to the eye. In order to make the metal workpiece have the required mechanical properties, physical properties and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment processes are often essential. Annealing, normalizing, quenching and tempering are the four basic processes in the overall heat treatment.

Four Basic Heat Treatment Processes

Annealing

Annealing is to heat the workpiece to an appropriate temperature, use different holding times according to the material and the size of the workpiece, and then slowly cool down, the purpose is to make the internal structure of the metal reach or near the equilibrium state, to obtain good process performance and performance, or Further quenching for organizational preparation.

Normalizing

Normalizing is to heat the workpiece to a suitable temperature and cool it in the air. The effect of normalizing is similar to annealing, except that the resulting structure is finer. It is often used to improve the cutting performance of the material, and sometimes it is used for low requirements parts as the final heat treatment.

Quenching

Quenching is to quickly cool the workpiece in the quenching medium such as water, oil or other inorganic salts, organic aqueous solution after heating and heat preservation. After quenching, the steel parts become hard, but at the same time they become brittle.

Tempering

Tempering is to keep the quenched steel parts at an appropriate temperature higher than room temperature and lower than 710 ℃ for a long time, and then cool them, which can reduce the brittleness of the steel parts