Because of the skin effect and proximity effect by high frequency current, before the material goes to squeeze rolls, the induction coil heat up the material on weld seam to a molten state, and the squeeze roller press the melt edge together. Excess metal and oxide accumulate on the upper part of the weld to form an outer surface burr while accumulate inside of steel pipe welding line form the inside surface burr.
External burrs are generally eliminated by gouging, but because of the small space inside of pipe, it is more difficult to remove the inside weld burr. Due to the existence of internal burrs, cracks or scratches can be formed on the inner surface of the steel pipe when the tube is subjected to cold drawing or cold rolling. For the precision welded pipe, no inner burr removing cannot reach the surface quality requirements; so that the following process can not be processed.
Inside burr removing is usually done on continuous welded tube production line, also can be done off the production line.
Cutting method: This method is to cut the burr by using a fixed blade or a rotating cutting head in the pipe
Oxidation process: When welding, the jet injects oxygen air into the pipe, with the heat of welding, the oxidation will be accelerated on inner burr and oxide fall off under the air flow.
Drawing method: When the steel pipe passes through the die, the burr in the steel pipe is removed under the action of the annular blade of the floating plug.