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2 features of ERW erw welded pipe

Views: 0     Author: Site Editor     Publish Time: 2020-10-19      Origin: Site

1. 1 Technical advantages of ERW casing (compared to seamless casing) 

(1) High dimensional accuracy

The ERW casing adopts a mechanical sizing process after forming, so that the accuracy of its dimensions (outer diameter, wall thickness, roundness, etc.) is improved compared with that of the jointed casing, and its outer diameter deviation generally does not exceed ±0.5%. Such as those produced by Nippon Steel Corporation. The standard deviation of the wall thickness of 244.5 mm ERW casing is <0.10 mm, while the standard deviation of the corresponding seamless casing is 0.41 mm.

(2) Good weld toughness

The manufacturing process of ERW casing can ensure high-strength and high-toughness welds. The composition of the welds and the lower C, S and P content in the matrix material make the casing tougher than seamless casings.

(3) Good anti-extrusion and anti-explosion performance

Compared with similar API seamless casing, ERW casing has 30%-40% higher anti-extrusion strength, and anti-explosion performance (internal pressure) is about 50% higher.

(4) Advanced technology, good product quality control

The base material of ERW casing is controlled-rolled coil, which is isotropic and can be 100% non-destructive inspection.

(5) Low cost

Compared with similar seamless casing, the cost of ERW casing is 5%-10% lower, the production efficiency is high, the degree of mechanization and automation is high, and the production energy consumption is low; the yield rate of ERW casing is 939-98%, while The yield rate of seam casing is 85%-90%; the investment of ERW casing is 40% lower than that of seamless casing project.

The geometric dimensions of ERW steel pipes and seamless steel pipes required by the standard are compared in Table 1.

1. 2 Technical characteristics of ERW casing

(1) Controlled rolled coils are selected as raw materials, S and P content and carbon equivalent are strictly controlled, usually ω(S) is less than 0.015%, and carbon equivalent is less than 0.25%. And use elements such as Nb, V, Ti and Cu to improve the toughness of steel by microalloying, and improve its weldability and corrosion resistance.

(2) Thicker coils are mirror-edged, which can reduce local overheating and oxidation caused by burrs during welding.

(3) Spiral loopers are widely used for continuous production, and there is no welding pause caused by roll-to-roll intermittent production, resulting in product quality defects due to unstable welding current and voltage when re-starting welding.

(4) Advanced hydraulic deburring technology is generally used, and the inner burr height of the casing is controlled within 1.14 mm.

(5) The welding parameters are strict, including the control of power input power, welding V-angle, welding speed, and welding temperature. The welding temperature is controlled by the speed-power closed loop of the high frequency welder, and the fluctuation is controlled within ±5 degrees Celsius.

{6) Pay attention to post-weld heat treatment, and improve the structure and internal stress of the weld zone through post-weld heat treatment.

(7) Adopting high-strength sizing unit, large reduction amount and good precision of finished product.

(8) On-line or off-line non-destructive testing of welds and steel pipes as a whole, to find defects in time and accurately, so as to adjust the production process in time to ensure product quality.

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