Welded steel pipes can be roughly divided into three categories according to the molding process:
First, electric resistance welded steel pipe
ERW (Electric resistance welded Pipe), the weld type is straight seam. Resistance welding uses a pressure-welding method without filler metal. The weld is not filled with other components. The skin effect and the proximity effect of the high-frequency current cause the edge of the plate to be instantaneously heated to the welding temperature, and extruded by a squeeze roll to form a forging. The weld of the tissue.
Electric resistance welded steel pipes can be further divided into two types: HFW (High Frequency Welding Pipe) and LFW (Low frequency welding).
ERW steel pipe is mainly used to transport vapor and liquid objects such as oil and natural gas, and can meet various requirements of high and low pressure. At present, it plays an important role in the world of transportation pipes.
Second, spiral welded steel pipe
SSAW (Spiral submerged-arc welding pipe), the weld type is a spiral seam. Submerged arc welding method, double-layer welding inside and outside. Submerged arc welding (including submerged arc surfacing and electroslag surfacing) is an important welding method, which has the advantages of stable welding quality, high welding productivity, no arcing and little smoke.
Spiral welded pipe has a large caliber and can reach more than 3000mm, which is suitable for large-diameter pipe transportation and building structure.
Third, straight seam welded steel pipe
LSAW (Longitudinally Submerged Arc Welded Pipe), the weld type is straight seam. The same method of submerged arc welding is used, and the inner and outer layers are welded. Straight seam steel pipe has a large wall thickness and is similar to spiral welded steel pipe.
Straight seam welded steel pipes can be divided into two categories according to the molding process: UOE (Uing and Oing forming pipe) and JCO (J-ing, C-ing and O-ing pipe). UOE molding method (U molding, O molding, E expansion), JCOE molding method (steel sheet is pressed into J type, and then pressed into C type and O type, and then expanded).
It should be specially noted that SAW belongs to EFW Electric Fusion Welded Pipe, which is a process of combining metal between one or several consumable electrodes and workpieces to heat the metal. The material is fully melted and does not require pressurization. The part of the filling metal is all from the electrode.