Causes and Control of Stamping Cracking of Galvanized Sheet

The production process of galvanizing is: uncoiling → cleaning → continuous annealing → galvanizing → finishing → straightening → passivation/oiling → coiling → packaging. In its production prone to stamping cracking, analysis of its causes:
1. Annealing temperature
Annealing temperature is an important process parameter in the galvanizing process, and the annealing temperature has a great influence on the yield strength of the product. When the annealing temperature is low, the annealing is not sufficient, the grain is small, the strength is high, and the elongation is low; the annealing temperature is too high, it is easy to cause the grain to be abnormally coarse, and the yield strength decreases while the tensile strength decreases even more. The product is prone to direct fracture during stamping and stretching.
2. Processing and lubrication
The surface roughness of the material will affect the oil storage capacity of the surface, and the appropriate surface roughness of the steel coil is also very important to the stamping performance of the material. At the same time, the selection of the amount of coating oil is very important. If the amount of coating oil is too small, the material will not be sufficiently lubricated in the stamping process, which will lead to cracking in the stamping of the material. If the amount of oil is too much, it will slip easily during the slitting and forming process, affecting the production rhythm.
3. Material thickness and die clearance fit
During the stamping process, the matching between the die gap and the material thickness is also an important factor leading to the cracking of the material.
4. Control of defects such as inclusions
Defects such as inclusions and foreign matter pressure-in are very unfavorable to the stamping forming of stamping products. Due to the insufficient local elongation of the inclusions, stamping and tensile cracking are easy to occur.
According to the above analysis, the following measures can be taken to avoid stamping cracking of galvanized sheet:
1. Set a reasonable galvanizing annealing temperature and ensure the stability of temperature control;
2, choose the correct stamping anti-rust oil, given a reasonable amount of oil;
3. The rolling force of the finishing machine should be controlled above 1200kN;
4, steelmaking process to control inclusions, to ensure the cleanliness of molten steel;
5, fully understand the use of the mold, to ensure that the mold gap, material deformation capacity, material thickness matching.