Outer diameter toleranceERW steel pipe: It is cold-formed, and the sizing is completed by 0.6% reduction.

The process temperature is basically constant at room temperature, so the outer diameter control is accurate and the fluctuation range is small, which is helpful to eliminate black leather buckles;Seamless steel pipe: hot-rolled forming process is adopted, and its sizing is completed at about 8000C.

Wall thickness toleranceERW steel pipe: using hot-rolled coil as raw material, modern hot-rolling thickness tolerance can be controlled within 0.05mm, while seamless steel pipe is produced by round steel perforation method, the wall thickness deviation is large, and the subsequent hot rolling can partially eliminate the wall Thickness unevenness, but the most advanced unit can only be controlled within +5~10%t, which corresponds to 8.94mm thick steel pipe.Seamless steel pipe: The limit of wall thickness control accuracy is 0.9mm.4.

OvalityERW steel pipe: adopts cold bending forming, so the outer diameter control is accurate and the fluctuation range is small.Seamless steel pipe: Hot-rolled forming process is adopted.

Tensile testThe tensile properties of seamless steel pipes and ERW steel pipes conform to API standards, but the strength of seamless steel pipes is generally at the upper limit and the plasticity is at the lower limit.

In comparison, the strength index of ERW steel pipes is in the best state, and the plasticity index is 33.3% higher than the standard.