1.Outer Diameter Tolerance
ERW steel pipe: Cold-formed and sizing by reducing the diameter by 0.6%. The outer diameter is controlled accurately and the fluctuation range is small, which is helpful to eliminate black leather buckles.
Seamless steel pipe: Hot-rolling forming process and sizing completed at about 8000C. The raw material composition, cooling conditions, and cooling conditions of the rolls of the steel pipe have a large impact on outer diameter, so it is difficult to control the outer diameter accurately and fluctuate.
2.Wall Thickness Tolerance
ERW steel pipe: using hot-rolled strip as the raw material, the thickness tolerance of modern hot-rolled strips can be controlled within 0.05mm, and seamless steel pipes are produced by round steel perforation, with large wall thickness deviations. The subsequent hot rolling can partially eliminate the wall thickness. Thickness non-uniformity, but currently the most advanced units can only be controlled within ± 5 to 10% t, corresponding to steel tubes with a thickness of 8.94mm.
Seamless steel tube: The limit of the wall thickness control accuracy is 0.9mm.
3.Tensile Test
The tensile properties of seamless steel pipes and ERW steel pipes are meet API standards, but the strength of seamless steel pipes are at the upper limit and the plasticity are at the lower limit. In comparison, the plasticity index of ERW steel pipes is 33.3% higher than the standard. Because the raw material of ERW steel pipe—hot-rolled coils is ensured by means of microalloying smelting, refining outside the furnace, and controlled cold and controlled rolling; seamless steel pipes mainly rely on means of increasing carbon content, and it is difficult to ensure strength and plasticity.
4. Anti-crush Test
Because of raw materials and pipe manufacturing process of ERW steel pipe. Its wall thickness uniformity and ovality are far superior to seamless steel pipes, which makes it the crush resistance higher than seamless steel pipes.
5.The Amount of Steel Pipe Used for the 10,000-meter
The wall thickness of the ERW steel pipe is uniform, and its wall thickness tolerance is negligible. The control accuracy limit of the difference in wall thickness of the seamless steel pipe is ± 5% t, and generally controlled within ± 5 ~ 10% t. In order to ensure that its minimum wall thickness can meet the standard requirements and use performance, it can only be solved by appropriately increasing the wall thickness. Therefore, with the same specifications and the same weight of casing, ERW steel pipe is 5-10% longer or even more than the seamless steel pipe, which reduces the amount of steel used for 10,000 meters of casing steel 5-10%. Even at the same price, ERW bushings virtually save users 5 to 10% of their purchase costs.
