Method for preventing cracks in galvanized sheets

(1)Before welding, V, Y or X groove is opened at the welding place of galvanized plate. The galvanized layer near the groove is removed by oxyacetylene or sandblasting, and the clearance should not be too large, generally about 1.5mm.

(2) Choose welding materials with low Si content. Welding wire with low Si content should be used in gas shielded welding, and titanium and titanium-calcium electrode should be used in manual welding.

The zinc layer near the groove produces oxidation (forming ZnO) and evaporation under the action of arc heat, and volatilizes white dust and vapor, so it is easy to cause porosity in the weld. The greater the welding current, the more serious the zinc evaporation and the greater the stomatal sensitivity. It is not easy to produce porosity in the medium current range when welding with titanium and titanium-calcium electrode. When using cellulose type and low hydrogen type welding electrode, small current and large current are easy to produce porosity. In addition, the Angle of the electrode should be controlled within the range of 30°~70°.

(3) zinc evaporation and soot

When the galvanized steel plate is welded by arc welding, the zinc layer near the molten pool is oxidized into ZnO and evaporates under the action of arc heat, forming a large soot. The main component of this smoke is ZnO, which has a great stimulating effect on workers' respiratory organs. Therefore, good ventilation measures must be taken during welding. Under the same welding specification, the amount of smoke produced by titanium oxide electrode is lower, while the amount of smoke produced by low hydrogen electrode is larger.