Small diameter seamless steel pipe is hardened and reheated to a certain temperature, then some cooling methods are called pipeline tempering. Its purpose is to eliminate the internal stress produced by quenching, reduce hardness and brittleness, and obtain the required mechanical properties. Tempering is divided into high temperature tempering, medium temperature tempering and low temperature tempering.


After quenching, the seamless steel pipe is tempered and heated to below the critical temperature, holding time, and then cooled in air or oil. Quenching and tempering immediately after, but also the last step in heat treatment.
(1) Obtain the required mechanical properties. Usually, the strength and hardness of quenched parts are greatly improved, but the ductility and toughness are obviously reduced, and the actual working conditions of components require good strength and toughness. The required mechanical properties can be obtained by choosing appropriate tempering temperature after tempering.
(2) stable organization and scale;
3. Eliminate pressure.


Tempering category
(1) The hardened steel is heated to 150-50 C and kept warm for a certain time at this temperature, then cooled in air, tempered for cutting tools, measuring tools, dies, rolling and carburizing parts, etc. Steel produced by stress relief quenching.
(2) Tempered quenched steel is heated to 350-450% and cooled after holding for a period of time. It is generally used in various parts such as hot springs. In order to obtain higher elastic components, steel has certain toughness and hardness.
(3) After quenching, the heating steel is tempered to 500-650oC at high temperature. After heating and cooling, it is mainly used for important structural parts with high strength and toughness, such as spindle, crankshaft, cam, gear and connecting rod.