What is the tempering process of black steel pipe?
The tempering process of seamless black steel pipe is used in conjunction with the quenching of black steel seamless pipe. Reheat the quenched black steel seamless pipe to the critical temperature, keep it warm for a period of time, and then cool it in air, water or oil.
The purpose of tempering is to eliminate the internal stress of the black steel seamless steel pipe during quenching, improve the elongation toughness, and reduce the hardness and strength. The higher the tempering temperature, the lower the hardness and strength, and the higher the elongation toughness. In addition, black steel seamless pipes are tempered to improve the stability of the internal structure and maintain its specifications and performance.
According to the different performance requirements of black steel seamless steel pipes, according to the different tempering temperature, tempering can be divided into the following types:
1) Low temperature tempering (150-250 degrees)
The microstructure obtained by low temperature tempering of black steel seamless steel pipe is tempered martensite. Its purpose is to reduce the quenching internal stress and brittleness of the quenched black steel seamless steel pipe on the premise of maintaining high hardness and high wear resistance, so as to avoid cracking or premature damage during use. It is mainly used for various high-carbon cutting tools, measuring tools, cold stamping dies, rolling bearings and carburized parts, etc. The hardness after tempering is generally HRC58-64.
2) Medium temperature tempering (250-500 degrees)
The microstructure of black steel seamless steel pipe tempered at medium temperature is tempered troostite. Its purpose is to obtain the yield strength, elastic limit and high toughness of black steel seamless steel pipe. Therefore, it is mainly used for the treatment of various springs and hot work molds, and the hardness after tempering is generally HRC35-50.
3) High temperature tempering (500-650 degrees)
The microstructure obtained by high temperature tempering of black steel seamless steel pipe is tempered sorbite. Customarily, the heat treatment combining quenching and high-temperature tempering is called quenching and tempering treatment, and its purpose is to obtain comprehensive mechanical properties with good strength, hardness, plasticity and toughness. Therefore, it is widely used in important structures such as automobiles, tractors, and machine tools.
