How to distinguish electric resistance welded tube from other steel pipes?

Electric resistance welded tube is an acronym for Electric Resistance Welded. The welding method of ERW welded pipe is obviously different from that of submerged arc welded pipe.

Unfilled metal is used for pressure welding without other components in the weld. The skin effect and proximity effect of the high-frequency current make the edge of the plate instantly heated to the welding temperature, and the weld seam is formed by the squeeze roller. High-quality seamless pipe requires on-line or off-line heat treatment of the weld to refine the weld area.

High-quality electric resistance welded tube welds can achieve the same level of toughness as the parent metal, which is not possible with the submerged arc welding process. EFW is an abbreviation for Electric Saw Welding (EFW). It is a metal bonding process between the metal heated workpiece and the metal passing through one or more consumable electrodes, the metal arc and the filling material are completely melted, without pressure, and all hard metal parts are filled from the electrodes. GMAW - Electrofusion Welding (EFW), similar to submerged arc welding, except that it has an inert gas shield and the effect is better. Spiral Welding – This is also submerged arc welding, using a spiral weld.

According to different manufacturing processes, steel pipes can be divided into (SML). As the main oil-gathering pipelines and small-diameter high-pressure natural gas pipelines, the number of long-distance oil pipelines is very small. Most pipes fall into three categories: High Frequency Straight Seam (ERW), Spiral Submerged Arc (SSAW) and Submerged Arc (LSAW). The following is a comparison of several technical characteristics and quality performance of steel pipes:

Longitudinal high frequency (ERW) can be divided into induction welding and contact welding according to different welding methods. Using hot-rolled wide coils as raw materials, after pre-bending, continuous forming, welding, heat treatment, sizing, straightening, cutting and other processes, compared with spiral welding, the welding seam is shorter, the precision is high, the thickness is large and uniform, and the surface quality is good. High pressure resistance, but the disadvantage is that it can only produce small-diameter thin-walled pipes, and the welds are prone to defects such as gray spots, lack of fusion, and groove corrosion. At present, they are widely used in urban gas and crude oil transportation.

SSAW is the forming angle (adjustable) between the rolling direction and the centerline of the formed tube. When forming and welding on the side, the weld seam of the helix has the advantage of producing steel pipes of different specifications of the same specification. Diameter specification, wide range of raw materials, weld avoidable stress, good stress, disadvantage is poor geometry, weld length, weld length, cracks, porosity, slag inclusion, weld offset, weld defect, bad Weld stress is tensile stress. According to general oil and gas pipeline design specifications, spiral submerged arc can only be used in the third and fourth categories. The improved foreign raw materials will be transformed into steel. Through pre-welding and lean separation forming welding, cold expansion after welding, the welding quality is close to UOE. Currently, there is no such process. Our factory is moving in the direction of improvement. The "West-East Gas Pipeline" still uses the traditional method, but the end of the pipeline has been expanded.

Longitudinal submerged arc welding (LSAW) uses a single thick plate as raw material, pressurizes the steel plate in a mold or forming machine (coil), and uses double-sided submerged arc welding to expand production. Its finished products have various specifications. The toughness, plasticity, uniformity and compactness of the weld are good. The utility model has the advantages of large diameter, thick wall, high pressure resistance, low temperature resistance, strong corrosion resistance and the like.

In the construction of high-strength, high-toughness, and high-quality long-distance oil and gas pipelines, most steel pipes are welded by large-diameter, thick-walled straight seam arc welding. According to API standards, in large oil and gas pipelines, longitudinal submerged arc pipelines are the only specified pipeline type when passing through one or two areas such as mountainous areas, seabeds and densely populated urban areas. According to different forming methods, it can be divided into: UOE: single steel plate edge pre-bending, U-shaped forming, O-shaped forming, welding, welding, mechanical cold expansion process; JCOE: pre-welding, forming, post-processing - according to "j-c-o-e" welding cold expansion Process; HME: roll forming and welding after cold expansion by the "C-C-O" method through the mandrel

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