Causes of Cracks in prepainted galvanized sheet
The pre-painted galvanized sheet may have cracks during processing, resulting in incomplete products.
So what is the reason for this phenomenon? Many friends have questions in this regard, and it is particularly important for us to prevent this phenomenon from happening.
Let me teach you all.
Reasons for cracks in prepainted galvanized sheet (1)
The zinc layer near the groove of the color-coated galvanized sheet oxidize (formed ZnO)
and evaporated under the action of the arc heat, emitting white smoke and vapor, and easily causing pores in the weld.
The greater the welding current, the more severe the zinc evaporation and the greater the pore sensitivity.
When welding with titanium and titanium calcium electrodes, it is not easy to produce pores in the medium current range.
When using cellulose electrodes and low-hydrogen electrodes for welding, pores are prone to occur under low and high currents. In addition,
the angle of the electrode should control within 30° ~ 70° as much as possible.
Reasons for cracks in prepainted galvanized sheet (2)
Secondly, during arc welding of color-coated galvanized sheet, the zinc layer near the molten pool oxidizes to ZnO under the action of arc heat and evaporates, forming a large amount of smoke and dust.
Therefore, ventilation measures must be taken.
Under the same welding specifications, welding with titanium oxide electrodes produces a lower amount of smoke,
while welding with low hydrogen electrodes produces a larger amount of smoke.
When the welding current of the color-coated galvanized sheet is low, the ZnO formed during heating is not easy to escape, and it is easy to cause ZnO slag inclusion.
Zinc oxide is relatively stable, with a melting point of 1800°C.
Lumpy zinc oxide slag inclusions have a very adverse effect on weld plasticity.
When using titanium oxide electrodes, ZnO fine and evenly distribute, and has little effect on plasticity and tensile strength.
However, when cellulose or hydrogen electrodes are used, the ZnO in the weld is getting larger and larger, and the welding performance is poor.
The above is the analysis of the causes of cracks in the color-coated board.
I believe everyone knows that in the future, we must prevent the occurrence of the above situation in practice so that we can produce plates.
Cracks will cause the board to be unsightly and incomplete, affecting our normal use, so be careful.