The color galvanized sheet is prone to crack before welding. Why does this happen? So we need to understand the causes of cracks before we can find out the causes, so as to prevent accidents. The zinc layer near the groove of color-coated galvanized sheet
produces oxidation (forming zinc oxide) and evaporation under the action of arc heat, and evaporates white dust and vapor, so it is very easy to cause Blowhole in the weld.
The higher the welding current, the more serious the evaporation of zinc and the greater the pore sensitivity. It is not easy to produce Blowhole in medium current range when welding with Ti-type and Ti-Ca-type electrodes. When using cellulose type and low hydrogen type electrodes to weld, gas holes are easily produced under low current and high current. In addition, the angle of electrode should be controlled in the range of 30 ~70.
Secondly, when the color-coated galvanized sheet is welded by arc welding, the zinc layer near the molten pool oxidizes into zinc oxide and evaporates under the action of arc heat, forming a large amount of smoke and dust. Therefore, good ventilation measures must be taken. Under the same welding specifications, the amount of fume produced by titanium oxide electrode welding is lower, while that produced by low hydrogen electrode welding is larger.
Finally, when the welding current of color-coated galvanized sheet is small, the formation of zinc oxide during heating process is not easy to escape, resulting in zinc oxide slag inclusion. The melting point of ZnO is 1800 C. Bulk ZnO slag has a very adverse effect on weld plasticity. When using titanium oxide electrode, the distribution of zinc oxide is fine and uniform, which has little effect on the plasticity and tensile strength. When using cellulose or hydrogen electrodes, the zinc oxide in the weld is larger and more, and the performance of the weld is poor.