Seamless precision steel pipe heat treatment process

1. Quenching + high temperature tempering (also called quenching and tempering treatment)
The steel pipe is heated to the quenching temperature to transform the internal structure of the steel pipe into austenite, and then rapidly cooled at a speed greater than the critical quenching speed to transform the internal structure of the steel pipe into martensite. This is combined with high-temperature tempering to finally transform the steel pipe structure into a uniform Tempered sorbite structure. This process can not only improve the strength and hardness of the steel pipe, but also organically combine the strength, plasticity and toughness of the steel pipe.

2. Normalizing (also called normalizing)
It is a heat treatment process that uses air as the medium for cooling after the steel pipe is heated to the normalizing temperature to completely transform the internal structure of the steel pipe into an austenite structure. After normalizing, different metal structures can be obtained, such as pearlite, bainite, martensite or their mixed structures. This process can not only refine the grains, uniform composition, and eliminate stress, but also increase the hardness of the steel pipe and improve its cutting performance.

3. Normalizing + tempering
The steel pipe is heated to the normalizing temperature to completely transform the internal structure of the steel pipe into an austenite structure, then cooled in the air, and then combined with the tempering process. The structure of the steel pipe is tempered ferrite + pearlite, or ferrite + bainite, or tempered bainite, or tempered martensite, or tempered sorbite. This process can stabilize the internal structure of the steel pipe and improve the plasticity and toughness of the steel pipe.

4. Annealing
A heat treatment process in which the steel pipe is heated to the annealing temperature and kept warm for a certain period of time, then slowly cooled to a certain temperature in the furnace and then cooled out of the furnace. Reduce the hardness of the steel pipe and improve its plasticity to facilitate subsequent cutting or cold deformation processing; refine the grains, eliminate structural defects, uniform the internal structure and composition, improve the performance of the steel pipe or prepare for subsequent processes; eliminate the internal structure of the steel pipe stress to prevent deformation or cracking.

5. Solid solution treatment
It is a heat treatment process that heats the steel pipe to the solid solution temperature so that carbides and various alloying elements are fully and evenly dissolved in austenite, and then cools it rapidly so that carbon and alloying elements have no time to precipitate and obtain a single austenite structure. The functions of this process: Uniform the internal structure of the steel pipe and the composition of the steel pipe; Eliminate hardening during processing to facilitate subsequent cold deformation processing; Restore the corrosion resistance of stainless steel.