The production process of galvanizing line is as follows: cold hard roll → degreasing → continuous annealing → galvanizing → finishing → straightening → roller coating → induction heating → air cooling → quality inspection → oiling, weighing and packing.
In its production, stamping cracks are easy to appear, which affects the production of users. The causes are as follows:
1. Annealing temperature
Annealing temperature is an important parameter in galvanizing process, which has a great influence on yield strength of products. When the annealing temperature is low, the annealing is not sufficient, the grains are small,
the strength is high, and the elongation is low; when the annealing temperature is too high, the grains are easy to be abnormally coarse, the yield strength is reduced, and the tensile strength is decreased more severely, and the products are easy to
break directly in the stamping and drawing process of customers.
2. Machining lubrication
The surface roughness of the material will affect the oil storage capacity of its surface. The appropriate surface roughness of the steel coil is also very important for the stamping performance of the material. At the same time, the choice of
the amount of oil is very important. If the amount of oil is too small, the material will not be sufficiently lubricated in the stamping process, which will lead to the material stamping cracking; if the amount of oil is too large, it will easily slip
in the process of slitting and forming, which will affect the production rhythm.
3. Material thickness and die clearance fit
In the stamping process, the matching of die gap and material thickness is also an important factor that leads to
4. Control of inclusions and other defects
The defects such as inclusion and foreign matter press in are very unfavorable to the stamping forming of stamping products. Because the local elongation of the inclusion part is
not enough, it is easy to produce stamping and tensile cracking.
According to the above analysis, the following measures can be taken to avoid stamping cracking of galvanized sheet:
1. The steel plant should set reasonable annealing temperature
for galvanizing, the target value should be controlled at about 850 ℃, and the stability of temperature control should be ensured;
2. Select the right anti rust oil for stamping and give a reasonable amount of oil;
3. The rolling force of
the polishing machine shall be controlled above 1200kN;
4. Inclusions shall be controlled in the steel-making process to ensure the cleanliness of the molten steel;
5. Fully understand the mold used to ensure the matching of mold clearance,
material deformation ability and material thickness.