Casing is a short joint, which is caused by internal mechanical faults (such as eccentricity of rollers or axles, or excessive welding power) or other reasons. With the increase of welding speed, the extrusion speed of billet increases. This is conducive to extruding the liquid metal layer and oxide that have been heated to the melt to high quality welds. At the same time, increasing the welding speed can also reduce the heating time of the groove surface, which can shorten the oil short circuit and reduce the heat affected zone.


On the contrary, not only the HAZ is wide, but also the thin layer of the main liquid metal compounds formed on the groove surface becomes thicker and produces large burrs, which deteriorates the welding quality. However, at a certain output power, the speed of cold welding can not be increased without limitation. Otherwise, the heating on both sides of the billet trough will not reach the welding temperature, so there are defects or no welding at all.


For stainless steel, the ripple coefficient of oil short joint will affect the formation of weld. Capacitance filter can reduce the ripple to less than 1%. When welding stainless steel, the frequency is usually 200 welds, which has good toughness and high frequency heat affected zone. Usually, the inner and outer walls of the welded pipe are sprayed back from the welded area. Medium and continuous foam shows good welding power, uneven mechanical condition, uneven foam welding condition and poor welding quality.