The Q235b SSAW steel pipe for water supply uses the welding technology of double-sided submerged arc welding widely, which is similar to the LSAW steel pipe. The formation process and characteristics of the submerged arc automatic welding are briefly discussed below.
The principle of submerged arc welding: submerged arc welding is the use of arc thermal energy welding, and manual welding rod arc welding is different, submerged arc welding wire above no coating, submerged arc welding flux is pre-paste in the place to be welded, buried The arc welding wire extends into the flux, and the arc is formed under the flux. The formation of the submerged arc welding is such that the welding wire is in contact with the workpiece. After pressing the start button, the welding wire and the workpiece are energized. The wire is drawn back and the arc is drawn. Combustion, welding car forward, continuous downward welding wire, maintaining the arc burning under the flux layer, forming a weld pool below the arc.
Around the arc, the flux melts to form a cavity. The cavity and the pool continue to advance, and the metal behind the bath solidifies to form a continuous weld. This process is performed under the flux, so we can’t see it with the naked eye. With the help of X-ray photography, we can see that the spiral steel pipe adopts the welding technology of submerged arc welding, in addition to this kind of high production efficiency; the production of auxiliary time is less, save the time for changing the welding rod; the welding conditions are clean and no spatter, saving the cleaning Time; high weld quality. Also provides the necessary conditions for the delivery of spiral welded pipe plant, so that a large amount of spiral steel pipe production time is guaranteed, so it is still widely used.
After the two edges of the tube are heated to the welding temperature, under the extrusion of the squeezing roll, common metal crystal grains are formed to infiltrate and crystallize with each other, finally forming a firm weld. If the squeezing force of the spiral steel pipe is too small, the number of common crystals formed is small, the strength of the weld metal is decreased, cracking will occur after stress, and if the squeezing force is too large, the molten metal will be extruded out of the weld seam. Not only reduces the weld strength, but also produces a large number of internal and external burrs, and even lead to welding gaps and other defects.