Why does galvanized plate produce fume and black change?

                                    
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14/11/22
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#1
The zinc layer near the bevel of a galvanized plate is oxidized and evaporated by the heat of the arc and emits white soot and vapor, thus causing porosity in the weld seam. The higher the welding current, the more serious the evaporation of zinc, and the greater the susceptibility to porosity. When welding with titanium type and titanium-calcium-type welding rods, it is not easy to produce pores in the medium current range. While welding with cellulose and low hydrogen type welding rod, small and large current are prone to pores. In addition, the angle of the electrode should be controlled within the range of 30°-70° as far as possible.

Secondly, when welding galvanized plates by the electric arc, the zinc layer near the molten pool oxidizes and evaporates under the action of arc heat, forming a large amount of fume and dust. Therefore, good ventilation measures must be taken. Under the same welding specification, the amount of fume generated when welding with titanium oxide electrodes is lower, while the amount of fume generated when welding with low-hydrogen electrodes is higher.

There is also a special corrosion condition for galvanized plate called blackening.
After a certain period, due to the influence of lead and other elements in the galvanized plate, the lusterless part of the zinc flower will be blackened. This situation has improved considerably since the use of antimony to promote the formation of zinc bloom instead of lead. Another situation is that galvanized plate in transport, because of the low winding tension, the steel strip layer between the loose, steel coil contact with the pad wood parts will be friction and oxidation, the white oxide is friction off, galvanized plate surface black spots, this situation will make the passivation film is destroyed, galvanized layer thinning, galvanized plate life The life of the galvanized plate is greatly reduced, and the appearance is also affected.