In the field of oil drilling and oil well, high-frequency electric resistance welded casing (referred to as ERW casing) compared with seamless casing is high dimensional accuracy, weld toughness, anti-extrusion of high-performance, and low cost advantages, which has been widely used in foreign countries, and achieved good results.


Characteristics of ERW casing (compared with seamless casing)
High dimensional accuracy: ERW casing using a mechanical sizing process after molding, precision seamless casing has increased its size (outside diameter, wall thickness, roundness, etc.), and its outer diameter deviation not exceeding ± 0 Average .5%. Such as produced by Nippon Steel 6244.5 n'un ERW casing thickness standard deviation of <0.10 mill corresponding seamless casing standard deviation was 0.41 mill.


Good weld toughness: ERW casing manufacturing process can be guaranteed to get the C, S and P content is low in the component organization and the base material of high strength, high toughness of the weld, the weld toughness seamless sleeve so that the sleeve tube.


Anti-extrusion the antiknock properties: high strength 30% to 40% compared with the similar API seamless casing, ERW casing anti-extrusion, anti-knock properties (internal pressure) about 50% higher.


Advanced technology, product quality control: ERW sleeve base metal control rolled coil, isotropic, 100% non-destructive testing.


Low cost: compared with similar seamless casing, ERW casing 5% to 10% low cost, high efficiency, high degree of mechanization and automation, low energy consumption and production; ERW casing finished product rate of 93% to 98% , and seamless casing finished product rate of 85% to 90%; ERW casing the entire project investment is 40% lower than the seamless casing project.


The technical characteristics of the ERW casing
(1) Selection of raw materials controlled rolling coil, the strict control of the content of S and P, and the carbon equivalent, usually W (S) ≤ 0.015%, the carbon equivalent ≤ O. 25%. And the use of micro-alloying element such as Nb, V, Ti, and cu improve the toughness of steel to improve weldability and corrosion resistance.


(2) Thick coil after the edge milling treatment, can reduce the welding burrs caused by local overheating and oxidation.


(3) Widely used spiral looper for continuous production, there is no roll-to-volume batch production caused by welding standstill, resulting in re-starting welding, welding current, voltage instability due to product quality defects.


(4) Commonly used in state-of-the-art hydraulic removal of burrs process, casing inner burr height control 1.14 NLNL.


(5) Strict welding parameters, including the input power, welding V-shaped angle, welding speed, welding temperature control. Welding temperature by high-frequency welding speed of a closed loop power control, controlling the fluctuation of less than ± 5 ℃.


(6) Emphasis on post-weld heat treatment, through post-weld heat treatment to improve the organization and the internal stress of the weld zone.


(7) Making of high strength and sizing unit, reducing large precision finished.


(8) For the weld and steel as a whole-line or off-line non-destructive testing, timely and accurate detection of defects, in order to timely adjust the production process to ensure product quality.