Heat treatment is a seamless steel pipe thermal processing technology that heats, heats, and cools seamless steel pipe in a certain medium, and controls its performance by changing the surface or internal crystalline structure of the material. In addition to annealing and tempering, there are three types of normal heat treatment processes:

1. Normalization

Normalization processing, also called normalization processing. The normalizing treatment in the heat treatment process of seamless steel pipes is actually normalizing treatment. Usually in the hot working process, the structure of the seamless steel pipe material changes, and the performance also changes accordingly. In order to restore the structure to normal, normalizing treatment is often used, so normalizing treatment is also called normalization treatment.
Normalization treatment can be used as a final heat treatment, or as a pre-heat treatment, and can also improve processing performance. In general, carbon steel normalizing treatment is a heat treatment process that heats a carbon steel workpiece that has been heated to a high temperature and completes austenitization, and is directly cooled in the air to obtain a fine pearlite structure. The structure of normalizing heat treatment has better comprehensive mechanical properties.

2. Quenching

Quenching is to heat the seamless steel pipe to a temperature above the austenitizing temperature, namely the critical temperature AC3 (hypoeutectoid steel) or AC1 (hypereutectoid steel), and hold it for a period of time to make it fully or partially austenitized Then, the heat treatment process of martensite (or bainite) transformation is performed by cooling faster than the critical cooling rate to below Ms (or near isothermal temperature).
In addition, the solid solution treatment of aluminum alloy, copper alloy, titanium alloy, tempered glass and other materials or the heat treatment process with rapid cooling process is usually called quenching.

3. Tempering

Quenching and tempering is a double heat treatment of quenching and high temperature tempering. Quenching and tempering can adjust the performance and material of seamless steel pipe to a large extent, and its strength, plasticity and toughness are good, and it has good comprehensive mechanical properties.
During quenching and tempering, the quenched part of the seamless steel pipe obtains a microstructure dominated by fine needle-shaped quenched martensite. However, high-temperature tempering refers to tempering between 500-650℃, and tempered sorbite is obtained after high-temperature tempering. This is a mixture of ferrite and granular carbide.