Multi-wire submerged arc welding for LSAW pipes

Welding current

In LSAW pipe multi-wire submerged arc welding, all the wire welding current increases, the height of the weld will increase, but different wires increase to different degrees. Usually the first wire of the welding current in all the wire in the largest, it changes relative to other wires will cause a large change in the height of the residual, and the middle of the wire relative to the last wire to be a little stronger. Similarly, the first wire welding current on the weld depth of fusion also has the greatest impact, the middle wire as a weld filler on the weld depth of fusion is relatively small, the last wire has almost no effect on this. This point in the automation forum has also seen related reports. Therefore, in the preparation of multi-wire submerged arc welding welding process, should be the first wire welding current is the largest, followed by the middle, the last one is the smallest.

Arc voltage

In the LSAW pipe multi-wire submerged arc welding, all the wire voltage on the weld height and width of the melt have a certain impact, especially with the AC wire voltage on the weld and the transition of the base material has a greater impact on the transition conditions, the voltage is too low will not be able to form a smooth transition.

Due to the arc voltage size is basically proportional to the width of the weld, that is, the arc arc voltage size determines the width of the molten pool, the larger the arc arc voltage the larger the width of the molten pool. If the wire arc voltage is less than the former wire arc voltage, after the wire melt pool width is less than the former wire melt pool width, resulting in the melt pool cross-section is “gourd” type. Therefore, in the preparation of multi-wire submerged arc welding welding process, it should be the first wire arc voltage is the smallest, followed by the middle, the last one is the largest.

elding speed

In the LSAW pipe multi-wire submerged arc welding, welding speed on the weld depth and width of the melt has a greater impact, the impact of residual height is relatively small. The faster the speed, the smaller the depth and width of the melt, and vice versa. Generally, under the premise of ensuring the welding quality, the welding speed should be increased to improve the production efficiency of LSAW pipe.

Power supply DC - AC mixed configuration, DC reverse connection. Flux using fine particles, high melting point, moderate viscosity, good arc stabilization of high alkali type flux. Welding wire into a longitudinal straight line arrangement; equal spacing arrangement; the first wire tilted forward, behind the wire set to transition to the back of the tilt, and sequentially increase the angle of the back of the tilt; wire dry elongation to 35 ~ 45mm is appropriate. In order to ensure the depth of fusion and the selection of appropriate welding line energy conditions, the welding current is sequentially reduced, and the arc voltage is sequentially increased.