Quenching and tempering treatment of cold-drawn seamless pipe

Cold drawn seamless tubing refer to seamless steel pipes with high dimensional accuracy and good surface finish for mechanical structures and hydraulic equipment. The quenching and tempering of cold drawn seamless steel pipe refers to the double heat treatment of quenching and high temperature tempering.

Process: Temper the quenched steel at high temperature (500-600°C). It is mostly used for important structural parts, such as shafts, gears, connecting rods, etc. Quenching and tempering is generally carried out after rough machining.

Purpose: to refine the grains, so that the steel parts can obtain high toughness and sufficient strength, that is, have good comprehensive mechanical properties.

There are two types of quenched and tempered steel for cold drawn seamless pipes: carbon quenched and tempered steel and alloy quenched and tempered steel. Whether it is carbon steel or alloy steel, the carbon content is strictly controlled. If the carbon content is too high, although the strength of the quenched and tempered workpiece is high, the toughness is not enough. If the carbon content is too low, the toughness is increased but the strength is insufficient.

In order to obtain good comprehensive performance of the quenched and tempered parts, the carbon content is generally controlled at 0.30~0.50%. When tempering and quenching cold-drawn seamless pipes, the entire cross-section of the workpiece is required to be hardened, so that the workpiece can obtain a microstructure dominated by fine acicular quenched martensite. Through high-temperature tempering, a microstructure dominated by uniformly tempered sorbite is obtained.

Cold-drawn seamless steel pipe quenched and tempered parts have good comprehensive mechanical properties and are widely used in various important structural parts, especially those connecting rods, bolts, gears and shafts that work under alternating loads. But the surface hardness is low and not wear-resistant. Tempering + surface quenching can be used to improve the surface hardness of parts.

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