1. The original state of steel, that is, the delivery state of seamless steel pipes, can be divided into (codes in brackets): cold working/hard (BK), cold working/soft (BKW), stress relief annealing after cold working (BKS), tempering (GBK), normalizing (NBK). The commonly used state is the annealing state, which is convenient for subsequent processing. The performance and general applicability of seamless steel pipes in various states are as follows:
2. Cold working/hard (BK) steel pipes are produced by cold working of finished products with normal or large deformation, without heat treatment, with high dimensional accuracy, high tensile strength, and low elongation coefficient. Generally used to manufacture motorcycle parts, such as shock absorber sliding columns.
3. Cold working/soft (BKW) steel pipes are produced by cold working of finished products with small deformation, without heat treatment, with high dimensional accuracy, high tensile strength, and a certain elongation coefficient (10-15%). Generally used to manufacture automotive parts.
4. The steel pipes that are stress-relieved and annealed (BKS) after cold working are subjected to low-temperature and rapid heat treatment after cold working, and have higher dimensional accuracy, slightly higher tensile strength, and a certain elongation coefficient (more than 15%). They are generally used to manufacture various mechanical parts.
5. The steel pipes that are annealed (GBK) are subjected to normal and complete heat treatment after cold working and have normal dimensional accuracy, normal tensile strength, and elongation coefficient (more than 20%). It is a commonly used state with a wide range of applications.
6. Normalizing (NBK) is controlled cooling after complete heat treatment after cold working, and has normal dimensional accuracy, slightly higher tensile strength, and elongation coefficient (more than 20%). Oil well pipes are in this state.
Post time: May-20-2025