STKR400 Japanese standard square tube

STKR400 material characteristics analysis

• Yield strength ≥ 235MPa, tensile strength 400-510MPa
• Elongation ≥ 17%, with good plastic deformation ability
• Carbon content below 0.30%, sulfur and phosphorus content strictly controlled
• Excellent weldability, suitable for various steel structure connections
• Compared with ordinary Q235B material, STKR400 performs better in low-temperature impact toughness and can still maintain stable performance under -20°C environment.

Critical control points of production process 

GNEE Group uses high-frequency resistance welding (ERW) technology, combined with an online eddy current flaw detection system, to ensure the welding quality of each linear meter of pipe. The Japanese standard has strict requirements for the treatment of burrs in pipes, and the residual height shall not exceed 10% of the wall thickness.

Comparison of dimensional tolerance systems

There are significant differences between the JIS standard and the national standard GB/T6728 in terms of dimensional tolerance:

• Side length tolerance: The Japanese standard requires ±0.5mm, which is stricter than the national standard of ±1.0mm
• Wall thickness deviation: The Japanese standard is controlled at ±10%, and the national standard allows ±12.5%
• Curvature: No more than 1.5mm per meter, which is 75% of the national standard
• This strict tolerance system makes STKR400 pipes particularly suitable for precision steel structure assembly, and has advantages in the fields of automobile production lines, semiconductor equipment frames, etc.

Applications

• Automation equipment frame: take advantage of its high dimensional stability
• Building curtain wall support system: take advantage of weather resistance
• Logistics storage shelves: reflect high strength-to-weight ratio characteristics
• Engineering machinery protection structure: rely on its impact resistance