What is the purpose of heat treatment for cold drawn precision seamless steel tubes?
The heat treatment of cold drawn tubes is a crucial step in the cold drawing process. Whether it's the heat treatment between operations in the cold drawing process of uncold-drawn blanks or the heat treatment of finished tubes after cold drawing, it significantly impacts the drawing effect and the microstructure or physical property indices of the finished tubes. If the billet of the cold drawn tube is not in the normalizing and annealing state, it has a high hardness, which requires heat treatment to reduce hardness and improve the structure to enhance its cold drawing effect. After cold drawing, the steel tubes undergo plastic deformation, causing lattice distortion and grain fragmentation, leading to work hardening. This results in an unstable microstructure with a marked increase in hardness and strength indices, while plasticity significantly decreases.
The purpose of the heat treatment between the cold drawing process is to eliminate internal stresses, reduce hardness, improve the plasticity of the material, and enhance the effect of subsequent cold drawing. Otherwise, due to the decrease in material plasticity during the re-drawing process, phenomena such as broken tubes and mold damage may occur. The heat treatment of the finished cold-drawn tubes is mainly to eliminate internal stresses, ensure their strength, hardness, and other physical property indicators, meeting the requirements for use.
