Small-diameter precision seamless steel pipes are produced with strict control over delivery conditions to achieve the required mechanical properties and dimensional accuracy. Different delivery states determine their performance and suitability for various industrial applications.
Delivery States of Steel Pipes
The delivery conditions of small-diameter precision seamless steel pipes include:
Cold-Worked / Hard (BK)
Cold-Worked / Soft (BKW)
Cold-Worked, Stress-Relieved Annealed (BKS)
Annealed (GBK)
Normalized (NBK)
Among these, the annealed condition is most commonly used, as it facilitates subsequent machining and forming. Different states offer distinct performance characteristics and application scopes as outlined below:
Cold-Worked / Hard (BK)
Produced through normal or heavy cold deformation without heat treatment, BK pipes feature:
High dimensional accuracy
High tensile strength
Low elongation
Application: Commonly used for motorcycle components such as shock absorber tubes.
Cold-Worked / Soft (BKW)
Manufactured using small-deformation cold working without heat treatment, BKW pipes offer:
High dimensional accuracy
Relatively high tensile strength
Moderate elongation (10–15%)
Application: Suitable for automotive parts manufacturing.
Cold-Worked, Stress-Relieved Annealed (BKS)
After cold working, the pipes undergo rapid low-temperature annealing. They provide:
Good dimensional accuracy
Slightly higher tensile strength
Elongation above 15%
Application: Widely used in general mechanical components.
Annealed (GBK)
Fully annealed after cold working, GBK pipes have:
Standard dimensional accuracy
Standard tensile strength
Elongation above 20%
Application: Most common condition for broad engineering uses.
Normalized (NBK)
After full heat treatment and controlled cooling, NBK pipes offer:
Standard dimensional accuracy
Slightly higher tensile strength
Elongation above 20%
Application: Typical for oil well tubing and components requiring enhanced strength.
Note: The delivery state has limited influence on pricing. Cost primarily depends on pipe specifications, required precision, and length.
United Steel Industry As the most important steel pipe manufacturer and exporter in China, in the past 20 years, we have completed more than 100 projects, with partners in more than 100 countries, and established relationships with oil and gas and EPC companies in many countries business relationship.
For more information about the product price, catalog and rolling mill inspection certificate,
please consult:Email:Sales@usisteels.com
