The original state of steel, i.e. the delivery state of steel pipe, can be divided into (code in brackets): cold working / hard (BK), cold working / soft (BKW), stress relief annealing after cold working (BKS), tempering (GBK) and normalizing (NBK). The commonly used state is annealing state, which is convenient for subsequent processing.
The performance and general applicability of steel pipes in various states are as follows:
Cold worked / hard (BK) steel pipes are produced by cold working of finished products with normal or maximum deformation, without heat treatment, and have the highest dimensional accuracy, the highest tensile strength and the lowest elongation coefficient. It is generally used to manufacture motorcycle parts, such as shock absorber and sliding column.
Cold worked / soft (BKW) steel pipes are produced by cold working of finished products with small deformation without heat treatment. They have the highest dimensional accuracy, high tensile strength and certain elongation coefficient (10-15%). It is generally used to manufacture automobile parts.
The steel pipe of stress relief annealing (BKS) after cold working is subject to low temperature and rapid heat treatment after cold working, with high dimensional accuracy, slightly higher tensile strength and certain elongation coefficient (more than 15%). It is generally used to manufacture various mechanical parts.
Annealed (GBK) steel pipe is subject to normal and complete heat treatment after cold working, with normal dimensional accuracy, normal tensile strength and elongation coefficient (more than 20%). It is the most commonly used state and has the widest range of application.
Normalizing (NBK) is controlled cooling after complete heat treatment after cold working. It has normal dimensional accuracy and slightly higher tensile strength and elongation coefficient (more than 20%). Well pipe is in this state.
In addition, the steel pipe price of the steel pipe factory has little correlation with the delivery status, mainly depending on the requirements of specification, precision and length.
