Black ERW steel pipe is produced by hot rolling coil of forming machine, using skin effect and proximity effect of high frequency current to melt the edge of the pipe and realize production under the action of extrusion roll press welding.


The black ERW steel pipe is different from the common welding technology. The weld is made of the basic material melted by the steel body, and its mechanical strength is better than that of the common pipe. Smooth appearance, high precision and low weld height are good for 3PE anticorrosive coating. There are obvious differences in welding methods between high frequency welded pipe and submerged arc welded pipe. It is more difficult to ensure the welding quality than submerged arc welding because of the high-speed completion in the instant of welding.