There are three tempering processes for seamless pipes
(1) Low temperature tempering (heating temperature is usually 150 ℃ ~ 250 ℃) can reduce the quenching stress of seamless pipes, reduce brittleness and maintain high hardness. For workpieces requiring high hardness and good wear resistance
(2) Medium temperature tempering (heating temperature is 350°C to 500°C) can significantly reduce quenching stress and improve elasticity.
(3) High temperature tempering (heating temperature is 500 ℃ ~ 650 ℃) can eliminate the quenching stress, so that the parts can obtain excellent comprehensive mechanical properties. Usually "quenching and high temperature tempering" is called quenching and tempering. Quenching and tempering is widely used to process all kinds of important medium carbon steel seamless pipes.
Low temperature tempering is also known as "stress relief tempering". The structure after tempering is tempered martensite. Steel has high hardness and high wear resistance, but reduced internal stress and brittleness. Mainly used in tool dies and rolling bearings made of high carbon steel and high carbon alloy steel, as well as carburized and surface quenched parts, the hardness after tempering is generally 58-64HRC.
The purpose of low temperature tempering of seamless pipe
1. Eliminate the residual stress generated when the seamless tube is quenched, and prevent deformation and cracking;
2. Adjust the hardness, strength, plasticity and toughness of the seamless pipe to meet the performance requirements;
3. Stable organization and size to ensure accuracy;
4. Improve and enhance the processing performance of seamless pipes.
Low temperature temper brittleness of seamless pipes
The embrittlement phenomenon that occurs in the tempering at 250~400℃ after the seamless tube is quenched into martensite. The embrittlement that has occurred cannot be eliminated by reheating, so it is also called irreversible temper embrittlement. Much research has been done on the causes of low temperature temper brittleness.It is generally believed that when the quenched steel is tempered in the range of 250~400 ℃, cementite precipitates on the prior austenite grain boundary or on the martensite interface to form a thin shell, which is the main reason for the brittleness of the seamless tube caused by low temperature tempering.Adding a certain amount of silicon to the steel delays the formation of cementite during tempering, which can increase the temperature at which low temperature tempering brittleness occurs.Therefore, the ultra-high strength steel containing silicon can be tempered at 300~320 ℃ without embrittlement, which is beneficial to improve the comprehensive mechanical properties.
(1) Low temperature tempering (heating temperature is usually 150 ℃ ~ 250 ℃) can reduce the quenching stress of seamless pipes, reduce brittleness and maintain high hardness. For workpieces requiring high hardness and good wear resistance
(2) Medium temperature tempering (heating temperature is 350°C to 500°C) can significantly reduce quenching stress and improve elasticity.
(3) High temperature tempering (heating temperature is 500 ℃ ~ 650 ℃) can eliminate the quenching stress, so that the parts can obtain excellent comprehensive mechanical properties. Usually "quenching and high temperature tempering" is called quenching and tempering. Quenching and tempering is widely used to process all kinds of important medium carbon steel seamless pipes.
Low temperature tempering is also known as "stress relief tempering". The structure after tempering is tempered martensite. Steel has high hardness and high wear resistance, but reduced internal stress and brittleness. Mainly used in tool dies and rolling bearings made of high carbon steel and high carbon alloy steel, as well as carburized and surface quenched parts, the hardness after tempering is generally 58-64HRC.
The purpose of low temperature tempering of seamless pipe
1. Eliminate the residual stress generated when the seamless tube is quenched, and prevent deformation and cracking;
2. Adjust the hardness, strength, plasticity and toughness of the seamless pipe to meet the performance requirements;
3. Stable organization and size to ensure accuracy;
4. Improve and enhance the processing performance of seamless pipes.
Low temperature temper brittleness of seamless pipes
The embrittlement phenomenon that occurs in the tempering at 250~400℃ after the seamless tube is quenched into martensite. The embrittlement that has occurred cannot be eliminated by reheating, so it is also called irreversible temper embrittlement. Much research has been done on the causes of low temperature temper brittleness.It is generally believed that when the quenched steel is tempered in the range of 250~400 ℃, cementite precipitates on the prior austenite grain boundary or on the martensite interface to form a thin shell, which is the main reason for the brittleness of the seamless tube caused by low temperature tempering.Adding a certain amount of silicon to the steel delays the formation of cementite during tempering, which can increase the temperature at which low temperature tempering brittleness occurs.Therefore, the ultra-high strength steel containing silicon can be tempered at 300~320 ℃ without embrittlement, which is beneficial to improve the comprehensive mechanical properties.
