ERW steel pipe

ERW(Electric Resistance Welding) steel pipe refers to the hot-rolled coil heats the edge to melt through the high-frequency current, and is welded under the extrusion effect of the extrusion roller.

ERW welding pipe has the following characteristics: High-frequency resistance welding is a kind of pressure welding without filling metal; The current energy is highly concentrated in the welding area, the heating speed is fast, the welding speed is high; The impact energy of weld is low and the dispersion is large.

ERW welded pipe has advantages of excellent dimensional precision, good surface quality, high production efficiency, less investment, short construction period, low production cost, quick effect, etc., but it has higher requirements on forming quality.

ERW steel pipe specification

Diameter114-Φ356mm (4"-14") 
Wall thickness3.0-12.7mm (1/8"-1/2")
Length3-12.2m (10'-40') 
MaterialGB/T9711 L190-L555 (API 5L A-X80)

Making processing

ERW process does not add any welding material in the welding process, weld forming without a hot melting state, just weld metal after the recrystallization process, so the formation of weld in exact accordance with the chemical composition of the parent metal, steel pipe after annealing treatment after welding, manufacturing molding cold stress, welding stress were improved, so the ERW steel tube has good comprehensive mechanical properties. The welded pipe production line can produce high-frequency resistance straight seam welded pipe, square pipe, rectangular pipe, and steel sheet pile products.

The production line is equipped with a solid-state high-frequency welder and 500KW intermediate frequency heat processor, double-channel on-line UT flaw detection machine, hydraulic testing machine, shear pair welder and super spiral looper, microcomputer controlled flying saw machine, roller wheel. with a high degree of automation, stable, and reliable process control.

SML vs ERW steel pipe

  1. Outside diameter tolerance

ERW steel tube: it is formed by cold bending and determined by 0.6% reduction. The process temperature is basically constant at room temperature, so the outside diameter is controlled accurately and the fluctuation range is small, which is conducive to the elimination of black leather buckle.

Seamless steel tube: Adopting the hot rolling forming procedure, its sizing is completed around 8000C. The composition of steel tube raw materials, cooling conditions, and the cooling state of the roll has a great impact on its outside diameter, so the outside diameter control is difficult to be accurate, and the fluctuation range is large.

  1. 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 tube: limit of wall thickness control accuracy is 0.9mm.

  1. Ellipticity

ERW steel tube: cold bending forming, so the outside diameter control is accurate and the fluctuation range is small.

Seamless steel tube: adopting the hot rolling forming process, the composition of steel tube raw materials, cooling conditions, and the cooling state of the roll have a great impact on its outside diameter, so the outside diameter control is difficult to be accurate, and the fluctuation range is large.

HFW vs ERW steel pipe

The principle is different. ERW is a welding method in which pressure is applied through electrodes after the weldment is assembled, and the resistance heat generated by the current passing through the contact surface of the joint and the adjacent area is used for welding. HFW uses solid resistance heat as an energy source. In the process of steel pipe welding, the surface of the welded area is heated to a molten, lively, and sealed plastic state by the resistance heat generated by the high-frequency current. Then the upsetting force is used(or not) to realize the metal bonding.

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