Seamless steel tube heat treatment is divided into three categories:
(1) Final heat treatment to meet the performance requirements of seamless steel products; (2) heat treatment in the heat treatment state required by users and standards; (3) heat treatment between processes in the steel pipe manufacturing process.
The commonly used heat treatment processes for seamless steel tubes mainly include quenching, tempering, normalizing and annealing. For example: casings, oil pipes, drill pipes, line pipes, etc. in oil special pipes, according to the level of steel grade, the normalizing, normalizing and tempering, quenching and tempering processes are adopted accordingly;
High-pressure boiler tubes and high-pressure fertilizer pipes often use normalizing, normalizing and tempering, quenching and tempering (thick-walled pipes) and solid solution treatment of austenitic stainless steel pipes; spheroidizing annealing of steel pipes for bearings.
Some alloy steel pipes with high alloy content, in order to prevent users from cracking and deformation before use, users and standards usually require the manufacturer to deliver in heat treatment state, and seamless steel production plants need to perform heat treatment such as annealing and normalizing. The heat treatment between the processes is used in the production process of cold-rolled and cold-drawn steel pipes, and recrystallization annealing and softening annealing are usually employed. The purpose is to eliminate the cold work hardening effect, reduce the hardness and improve the toughness to facilitate further cold working.
