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The production process of the galvanizing line is as follows: cold roll → degrease → continuous annealing → galvanizing → finishing → tension and leveling → roller coating → induction heating → air cooling → quality inspection → coating, weighing and packaging. In its production, it is easy to have stamping cracking defects, which affect the production of users. The causes are
1. Annealing temperature
The very hot 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 size is small, the strength is high, and the elongation is low; If the annealing temperature is high, it is easy to cause the grain size to be unusually coarse and the strength of urine clothes to be reduced
At the same time, the tensile strength has dropped more severely, and the product is prone to direct fracture during the stamping and stretching process of customers.
2. Machining lubrication
The surface roughness of the material will affect the oil storage capacity of its surface. The proper surface roughness of the steel coil is also very important for the stamping performance of the material. At the same time, the selection of the amount of oil applied is very important. If the amount of oil applied is too small, the material will not be sufficiently lubricated during the stamping process, which will lead to the material stamping
Crack; If too much oil is applied, it is easy to slip during slitting and forming, affecting the production rhythm.
3. Material thickness and die clearance fit
In the process of material stamping, the matching of die clearance and material thickness is also an important factor leading to material cracking.
4. Control of defects such as inclusions
Defects such as inclusion and foreign matter pressing are very unfavorable to the stamping forming of stamping products. Because the local elongation of the inclusion 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 shall set a reasonable galvanizing annealing temperature, and the target value shall be controlled at about 850 ℃, and the stability of temperature control shall be guaranteed;
2. Select the correct stamping antirust oil and give a reasonable amount of oil;
3. The rolling force of the finishing machine shall be controlled above 1200kN;
4. The inclusion shall be controlled in the steelmaking process to ensure the cleanliness of molten steel;
5. Fully understand the mold used and ensure the matching of mold clearance, material deformation capacity and material thickness