The galvanized steel pipeline is defined by its outstanding benefits such as corrosion resistance, long life, low preliminary price as well as upkeep expenses, has been wieldy used in outdoor and interior, aquatic as well as underground applications

Galvanized steel pipe is a 20um thick zinc covering outside of the reduced carbon steel pipeline. The melting point of zinc goes to 419 ° C as well as the boiling point is around 908 ° ℃. In welding, zinc is melted on the surface of the molten pool or at the origin of the weld. Because zinc has a reasonably high solid solubility in iron, the zinc fluid will deeply deteriorate the weld metal along the grain limit, creating "liquid steel embrittlement". At the very same time, zinc as well as iron can develop an intermetallic brittle compound, which lowers the plasticity of the weld metal as well as brings about fractures under the action of tensile stress.

When welding galvanized steel, the surface area of groove and also the edge of the zinc layer under the action of arc heat, oxidation, melting as well as dissipation of white smoke and vapor conveniently lead to bond porosity. ZnO formed by oxidation has a high melting factor, over 1800 ° C. If the specifications are also tiny in the welding process, ZnO slag incorporation will certainly be triggered. At the same time, as Zn ends up being a deoxidizer, FeO-MnO or Feo-Mno-Sio2 oxide slag inclusion with reduced melting point will certainly be generated. It has to be kept in mind that the white dirt of zinc volatilization is damaging to human body and the galvanized layer at welding should be polished off.

Action 1: Polishing

The galvanized layer has to be gotten rid of at the welding part, or else will certainly happen bubbles, trachoma, false welding and various other issues, which causes breakable welding seam and rigidness reductions.

Action 2: Weld groove

The prep work of galvanized steel before welding resembles the general low carbon steel, it is necessary to pay attention to the groove dimension as well as galvanized layer. The groove size is generally 60 ~ 65 ° and also there is a specific space, generally 1.5 ~ 2.5 mm; In order to decrease the infiltration of zinc into the weld, the galvanized layer in the groove can be gotten rid of before welding and afterwards bonded. In practical welding, the groove is typically focused as well as no blunt side is left. Two-layer welding minimizes the possibility of incomplete welding. The welding pole need to be picked according to the base material of galvanized steel tube. Normally speaking, J422 is a suitable selection.

GL bonded groove

Action 3: Welding

In the first layer of multilayer welding weld, attempt to wldsteel co.,ltd thaw the zinc layer and make it evaporated, evaporation, this can significantly decrease the zinc liquid remained in the weld. The exact same method is made use of for fillet welds. First move the electrode tail forward concerning 5 ~ 7mm, and then go back to the original setting to continue welding after thawing the zinc layer. If the selection of short slag electrode such as J427, there will certainly be a very tiny bite edge propensity; Back and forth input electrode can obtain the welding top quality without defects