The quenching and tempering of seamless steel pipe is a comprehensive heat treatment process of quenching and high temperature tempering. Most of the quenched and tempered parts work under relatively large dynamic loads. They are subjected to tension, compression, bending, torsion or shearing. Some surfaces also have friction, requiring a certain degree of wear resistance and so on. In short, the parts work under various compound stresses. Such parts are mainly structural parts of various machines and mechanisms, such as shafts, connecting rods, bolts, gears, etc., which are commonly used in manufacturing industries such as machine tools, automobiles, and tractors. Especially for large parts in heavy machine manufacturing, quenching and tempering treatment is used more. Therefore, the quenching and tempering treatment occupies a very important position in the heat treatment.
In mechanical products, quenched and tempered parts, because of their different stress conditions, the required performance is not exactly the same. Generally speaking, all kinds of quenched and tempered parts should have excellent comprehensive mechanical properties, that is, the appropriate combination of high strength and high toughness to ensure the long-term smooth operation of the parts.
The heat treatment process of steel pipe includes annealing, normalizing, quenching, tempering and surface heat treatment. The tempering includes quenching and tempering treatment and aging treatment.
Steel pipe tempering: reheating the quenched steel to a certain temperature and then cooling it by a certain method is called tempering. Its purpose is to eliminate the internal stress caused by quenching, reduce the hardness and brittleness, in order to obtain the expected mechanical properties.
Quenching and tempering usually refers to the heat treatment process of quenching + high temperature tempering to obtain tempered sorbite. The method is to quench first, and the quenching temperature is: Ac3+30~50℃ for hypoeutectoid steel; Ac1+30~50℃ for hypereutectoid steel; alloy steel can be slightly higher than carbon steel. After quenching, it can be tempered at 500~650℃. The main purpose of modulation is to obtain comprehensive mechanical properties with relatively good strength, plasticity and toughness.
However, at the same time, it should be noted that there is also the saying of quenched and tempered steel. Quenched and tempered steel is the process of adding manganese and silicon when smelting steel. Pay attention to the difference.