The difference between annealed and non-annealed steel pipes

The difference between annealed steel pipe and non-annealed steel pipe is that after annealing treatment, the structure of the steel pipe will change, which will affect its performance and use. Annealing can reduce the hardness of the steel pipe, increase the plasticity, improve the machinability and corrosion resistance. The non-annealed steel pipe may have higher hardness and strength, but it is difficult to process and treat. Therefore, in the production and application of steel pipes, it is necessary to choose whether to anneal according to the specific needs. The steel pipe metal or alloy is heated to the appropriate temperature, held for a certain time, and then slowly cooled (generally cooling with the furnace), the heat treatment process is called annealing. 

The role of steel pipe annealing:
1) Reduce the hardness of steel pipe, improve plasticity, easy machining and cold deformation processing;
2) Uniform the chemical composition and structure of steel pipe, refine the grain, improve the performance of steel or prepare for quenching;
3) Eliminate the internal stress and work hardening of the steel pipe to prevent deformation and cracking.

The selection of annealing method of steel pipe generally has the following principles:
1) All kinds of steel with sub-eutectoid structure are generally fully annealed, and isothermal annealing can be selected in order to shorten the annealing time;
2) Spheroidizing annealing is generally selected for hypereutectoid steel, and incomplete annealing can be selected when the requirements are not high. Tool steel and bearing steel are often used for spheroidizing annealing. Cold extrusions and cold heading parts of low or medium carbon steel are sometimes also nodulated annealed