Performance and Processing of Small-Diameter Precision Seamless Steel Pipes:


1. The original state of the steel used in small-diameter precision seamless steel pipes, i.e., the delivery state of the pipes, can be divided into (codes in parentheses): Cold-worked/Hard (BK), Cold-worked/Soft (BKW), Cold-worked Stress-Relieved Annealed (BKS), Tempered (GBK), and Normalized (NBK). The most commonly used state is annealed, which facilitates subsequent processing. The performance and general applications of steel pipes in various states are as follows:


2. Cold-worked/Hard (BK) small-diameter precision seamless steel pipes are produced through normal or large deformation cold working passes without heat treatment. They possess high-dimensional accuracy, high tensile strength, and a low elongation coefficient. They are generally used in the manufacture of motorcycle parts, such as shock absorber slides.


3. Cold-worked/soft (BKW) small-diameter precision seamless steel pipes are produced through cold working with minimal deformation in a few passes, without heat treatment. They possess high-dimensional accuracy, relatively high tensile strength, and a certain elongation (10-15%). They are generally used in the manufacture of automotive parts.


4. Cold-worked stress-relieved annealed (BKS) small-diameter precision seamless steel pipes undergo low-temperature, rapid heat treatment after cold working. They possess relatively high dimensional accuracy, slightly higher tensile strength, and a certain elongation (above 15%). They are generally used in the manufacture of various mechanical parts.


5. Annealed (GBK) small-diameter precision seamless steel pipes undergo normal and complete heat treatment after cold working. They possess normal dimensional accuracy, normal tensile strength, and an elongation (above 20%. This is a commonly used state with a wide range of applications.


6. Normalized (NBK) small-diameter precision seamless steel pipes undergo complete heat treatment after cold working, followed by controlled cooling. They possess normal dimensional accuracy, slightly higher tensile strength, and an elongation of above 20%. Oil well tubing is an example of this state. In addition, the price of steel pipes from steel pipe manufacturers is not closely related to the delivery status; it mainly depends on the specifications, precision, and length requirements.