Compared of seamless steel pipe and ERW steel pipe

1, the outer diameter of tolerance

ERW steel pipe, is made of cold bending forming, by reducing 0.6% complete sizing, the basic technological process temperature constant at room temperature, and outside diameter control accuracy and small range, which is conducive to eliminate black buckle;

Seamless steel pipe: the hot rolling molding process, the sizing was completed in about 8000 c, steel tube raw material component, cooling condition and roll cooling condition has great influence on its outer diameter, and outside diameter control is difficult to accurately, and the fluctuation range is larger.

2, the wall thickness tolerance

ERW steel pipe: the hot rolled strip coil as raw materials, modern hot even thickness tolerance can control within 0.05 mm, and seamless steel tube production adopts the round steel perforated way, wall thickness deviation is bigger, then the hot rolling can partly eliminate wall thickness nonuniformity, but at present the most advanced unit can only control within + / - 5 ~ 10% t, corresponding to the 8.94 mm thickness of steel pipe.

Seamless steel pipe: the limit of the wall thickness control precision is 0.9 mm.

3, ovality

ERW steel pipe, is made of cold bending forming, and outside diameter control accurately, small range.

Seamless steel pipe: the hot rolling molding process, the steel tube raw material component, cooling condition and roll cooling condition has great influence on its outer diameter, and outside diameter control is difficult to accurately, and the fluctuation range is larger.

4, tensile test,

Seamless steel pipe and ERW pipe tensile performance indexes accord with standard of API, but the strength of the seamless steel tube is generally in the ceiling, the plastic is in lower limit, by comparison, ERW steel pipe strength index in the best state, plasticity index is higher than the standard 33.3%, the reason for the ERW welded steel pipe of raw materials - hot rolled coil is depend on the performance of micro alloying of smelting, refining outside the furnace and controlled rolling of cooling means to guarantee; Seamless steel pipe mainly, by the means of increasing carbon content is difficult to ensure the reasonable match of strength and plasticity.

5, hardness

ERW steel tube of raw materials - hot rolled coil in central controlled rolling high precision cold rolling process, to ensure uniform coil parts performance.

6, the grain body

ERW steel tube of raw materials - casting billet, hot rolled coil USES is generous with thicker fine crystal surface solidification layer, no columnar crystal zone and shrinkage cavity and osteoporosis, composition deviation is small, compact structure; Later in the rolling process, the application of controlled rolling technology of controlled cooling further ensures that the grain size of raw materials.

7, collapse resistance test

ERW steel pipe because of its raw materials, the characteristics of the pipe technology. The wall thickness uniformity, ovality is much better than the seamless steel tube, is the main reason for the collapse resistance higher than that of seamless steel tube.

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