The galvanized steel pipe is defined by its excellent benefits such as corrosion resistance, long life, low first price and upkeep prices, has actually been wieldy utilized in exterior and interior, aquatic as well as below ground applications
Galvanized steel pipe is a 20um thick zinc finish on the outside of the low carbon steel pipeline. The melting factor of zinc is at 419 ° C and also the boiling point is around 908 ° ℃. In welding, zinc is thawed on the surface of the molten pool or at the origin of the weld. Because zinc has a reasonably high strong solubility in iron, the zinc liquid will deeply erode the weld metal along the grain border, developing "liquid metal embrittlement". At the exact same time, zinc and iron can develop an intermetallic breakable compound, which minimizes the plasticity of the weld metal and also leads to fractures under the activity of tensile stress and anxiety.
When welding galvanized steel, the surface area of groove and the edge of the zinc layer under the action of arc warm, oxidation, melting and also evaporation of white smoke and also steam conveniently bring about bond porosity. ZnO formed by wldsteel.com oxidation has a high melting factor, above 1800 ° C. If the parameters are also little in the welding process, ZnO slag addition will be triggered. At the same time, as Zn becomes a deoxidizer, FeO-MnO or Feo-Mno-Sio2 oxide slag inclusion with low melting point will be created. It has to be noted that the white dirt of zinc volatilization is hazardous to body and the galvanized layer at welding need to be polished off.
Action 1: Sprucing up
The galvanized layer must be polished off at the welding part, otherwise will certainly occur bubbles, trachoma, incorrect welding as well as other problems, which leads to weak welding joint and rigidity declines.
Step 2: Weld groove
The prep work of galvanized steel prior to welding is similar to the general reduced carbon steel, it is required to take notice of the groove size as well as galvanized layer. The groove size is normally 60 ~ 65 ° as well as there is a particular void, generally 1.5 ~ 2.5 mm; In order to reduce the infiltration of zinc into the weld, the galvanized layer in the groove can be eliminated prior to welding and after that bonded. In sensible welding, the groove is normally focused and also no blunt side is left. Two-layer welding lowers the opportunity of incomplete welding. The welding pole should be picked according to the base product of galvanized steel tube. Usually speaking, J422 is an optimal selection.
GL bonded groove
Action 3: Welding
In the very first layer of multilayer welding weld, attempt to melt the zinc layer and make it evaporated, dissipation, this can considerably lower the zinc liquid continued to be in the weld. The exact same approach is made use of for fillet welds. First move the electrode tail onward concerning 5 ~ 7mm, and then return to the original placement to proceed welding after thawing the zinc layer. If the option of short slag electrode such as J427, there will be an extremely tiny bite side propensity; To and fro input electrode can get the welding top quality without flaws