ERW pipe welding defects

ERW pipe is the fastest and most efficient tube method, but when produced, there are a variety of high frequency tube welding defects. Analysis of the frequency of inclusions in steel production, the pre-arc fusion inadequate inadequate edge fusion, central fusion deficiencies, stick welding, casting welding, porosity, skip welding and other welding defects nine common causes and preventive measures.

ERW welding process
ERW is fed into the forming machine steel strip into a cylindrical tube through an induction loop or contact welding angle, induction coil induces a magnetic field near the edge of the current through the strip, strip edge due to its resistance to heat generated by resistance is heated, the heated press roll strip edges are extruded into the weld. High frequency welding without adding metal, is actually a forge welding. If the generation control is better, fusion faces no residual molten metal or oxide. If the machine a weld specimens were polished, etched and observed under the optical microscope, the heat-affected zone is shaped like a drum, it is because a high frequency current into the strip from the edge of the strip end portion and the side edge portion into the steel with heat. HAZ color slightly darker than the base metal, because the welding of carbon diffusion to the heating of the strip edges, weld cooling is absorbed in the strip edges. Particularly near the strip edge carbon to CO or carbon dioxide, the remaining iron no carbon, lighter color.

ERW pipe welding defects
ERW may be a variety of high-frequency welding defects. Each defect has many different names, there is no generally accepted terminology. Here are the names defects, defects in parentheses Another common name: inclusions (black burnt oxide); pre-arc (white burnt oxide); fusion deficiency (slit); edge fusion inadequate (edge waves); central fusion inadequate (central cold welding); stick welding (cold welding); cast welding (brittle weld); stomata (pinhole); jump welding.