What is the hot forming ?
Direct method: Form is heated in unsprung steel sheet, form is given in hot condition and hardened in cast to obtain desired properties.
Indirect method: Saca forming, cutting and punching are completed in cold conditions. The piece is then heated and hardened in the mold to increase its strength. The choice of method is chosen depending on the complexity of the part and the coating of the sheet (eg zinc-based coatings usually require an indirect method). In both methods, the sheet is shaped softer and formable, then the cooling channels are hardened into the punched mold. Hot-formed steels generally have ~ 1000 MPa flow and ~ 1500 MPa breaking strength.
In hot forming, the temperature of the sheet at the oven outlet is about 950 ° C. The transfer of the sheet is usually carried out using robotic applications. In the case of the sheet heated to the minimum austenitic temperature, the waiting time in the air during the die loading is important for the quality of the process. The heating oven is located in a region near the prase where the forming process takes place so that this process is as small as possible. The use of a robotic application is also an advantage for a fast transport and die loading operation.
Thanks to the use of high strength steel, lower sheet metal can be used for weight saving by providing the same crash performance.
However, as steels become less resistant to form deformation, spring back also increases. So it is a problem to be able to produce a complex geometry, or to tolerate tolerances.
The most important disadvantage of the process is the high investment cost. The hot forming can not be done in the conventional press lines and press molds. High cost press lines specially designed for hot forming and press molds with special cooling mechanisms are required. In Turkey, automotive, etc. there are dozens of conventional lines (suitable for cold forming operations) that are installed to serve the sectors. But the number of facilities specially designed and installed for hot forming is less than five in our country.
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