Cold-rolled steel sheet is prone to cracks before welding. Why is this happening? So we must first understand the causes of cracks in order to find the cause and prevent accidents. So how did the history of cold-rolled steel sheets crack? The following Galvanized Steel Sheet Manufacturer will come to tell you.
The zinc layer near the groove of the cold-rolled steel plate is oxidized and evaporated under the action of arc heat, and white smoke and vapor are volatilized, so it is easy to cause porosity in the weld. The larger the welding current, the more severe the evaporation of zinc, and the more sensitive the pores. When welding with titanium-type, titanium-calcium-type electrodes, it is not easy to generate pores in the medium current range. However, when welding with cellulose and low hydrogen electrodes, pores are easily generated at low and large currents. In addition, the electrode angle should be controlled within the range of 30-70 degrees.
Next, when cold-rolled steel plates are welded by arc welding, the zinc layer near the molten pool is oxidized to ZnO and evaporated by the heat of the arc, forming a large amount of smoke. Therefore, good ventilation measures must be taken. Under the same welding specifications, the amount of soot generated when welding with titanium oxide electrodes is low, while the amount of soot generated when welding with low hydrogen electrodes is large.
Finally, when the welding current of Cold Rolled Steel Sheet is small, the ZnO formed during heating is not easy to escape, and it is easy to cause ZnO slag inclusion. ZnO is relatively stable and its melting point is 1800 ° C. Large ZnO slag inclusions have a very adverse effect on weld plasticity. When a titanium oxide electrode is used, ZnO is finely and uniformly distributed, and has little effect on plasticity and tensile strength. When using cellulose or hydrogen electrodes, the ZnO in the weld is larger and more, and the weld performance is poor.
Cold Rolled Steel Sheet
1. Can withstand a temperature of 225° C, after which zinc is oxidized violently, showing white zinc oxide.
2. When the temperature reaches 225° C, zinc is oxidized violently, showing white zinc oxide. After grilling at high temperature, the anticorrosive material on the surface of galvanized sheet is oxidized, so the galvanized sheet cannot withstand high temperature, the heated surface will change color, or other substances with protective surface on the surface will easily turn yellow after oxidation.
3. Zinc has a melting point of 419.5° C and is chemically active. In the air at normal temperature, a thin and dense layer of basic zinc carbonate film is formed on the surface, which prevents further oxidation.
4. Galvanized generally refers to galvanized steel. The main purpose is to prevent the surface of the steel plate from suffering corrosion and prolong its service life. The surface of the steel plate is coated with a layer of metal zinc. This zinc-coated steel plate is called Galvanized Steel Sheet.
The above is the reason for the cracks in the cold rolled steel sheet, I hope to help everyone.