The manufacturing process involves cold forming operations followed by dedicated stress-relieving annealing at temperatures typically between 450-650°C, higher than BKW low-temperature annealing but lower than complete annealing temperatures. This precise thermal treatment focuses exclusively on stress elimination without altering the cold-worked microstructure, maintaining the strength advantages of cold processing while preventing stress-induced deformation or cracking during subsequent operations.

These BKS condition pipes achieve exceptional stress reduction, eliminating 70%-90% of residual internal stresses from cold working. This significant stress relief ensures superior dimensional stability during subsequent processing and end-use applications, substantially outperforming hard condition (BK) tubes in resistance to deformation and cracking. The maintained dimensional precision matches hard condition tubes with outer diameter/wall thickness tolerances typically within ±0.05mm and surface roughness Ra≤1.6μm, enabling direct assembly without additional machining.

The balanced mechanical properties of Cold Finished and Stress-Relieved Steel Pipes preserve most cold-working strengthening effects while significantly improving plasticity compared to BK condition. Typical St45 material BKS tubes demonstrate tensile strength of 400-520MPa with elongation rates of 18%-24%, offering an optimal combination for applications requiring both strength and moderate formability. The excellent surface quality remains unaffected by protective atmosphere stress relief annealing, presenting clean, smooth surfaces without oxide scale.

Technical Advantages:

  • Exceptional stress elimination (70%-90% reduction)

  • Maintained dimensional accuracy comparable to hard condition

  • Balanced mechanical properties between strength and formability

  • Preserved cold-working strengthening effects

  • Superior surface quality without oxide formation

  • Enhanced resistance to deformation and cracking

These stress-relieved precision tubes serve critical applications in hydraulic and pneumatic systems for high-pressure hydraulic lines, precision cylinder barrels, and piston rods where both high accuracy and pressure cycle resistance are essential. The mechanical manufacturing industry utilizes these pipes for shaft and sleeve components requiring subsequent machining, grinding, or welding operations, preventing dimensional inaccuracies from stress redistribution during processing.

The automotive sector employs these BKS/+SR condition tubes for engine high-pressure fuel lines and transmission oil pipes where stable performance under high-temperature, high-pressure conditions is paramount. Precision instruments and electronic equipment benefit from these tubes for sensor housings and small transmission conduits requiring both high-precision assembly and minor forming capabilities such as bending or flaring.

Supported by Tianzhan's 21 years of seamless tube expertise and advanced manufacturing capabilities, we provide customized BKS/+SR solutions tailored to your specific application requirements. Our technical team ensures each Cold Finished and Stress-Relieved Steel Pipe (BKS/+SR Condition) meets exact specifications for materials, dimensions, surface quality, and mechanical properties, delivering reliable performance for applications demanding precision, stability, and stress-resistant characteristics.