API 5L Line Pipe Heat Treatment Process

According to the different performance requirements and different tempering temperatures of API 5L line pipe, tempering can be divided into the following types:
Low temperature tempering (150-250℃)
The structure obtained by low temperature tempering is tempered martensite. Its purpose is to reduce the internal stress and brittleness of quenched steel while maintaining the high hardness and high wear resistance of quenched steel to avoid cracking or premature damage during use. Mainly used in various high-carbon cutting tools, measuring tools, rolling bearings and carburized parts, etc. The hardness after tempering is generally HRC58-64.
Medium temperature tempering (250-500℃)
The structure obtained by tempering at medium temperature is tempered troostite. The purpose is to obtain high yield strength, elastic limit and high toughness. Therefore, it is mainly used for the treatment of various hot working molds. The hardness after tempering is generally HRC35-50.
High temperature tempering (500-650℃)
The structure obtained by high temperature tempering is tempered sorbite. Traditionally, the heat treatment that combines quenching and high-temperature tempering is called quenching and tempering treatment. Its purpose is to obtain comprehensive mechanical properties with good strength, hardness, plasticity and toughness. Therefore, it is widely used in important structural parts of automobiles and machine tools, such as connecting rods, bolts, gears, shafts, etc. The hardness after tempering is generally HB200-330.
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