| Hot stamping is an advanced forming technique to manufacture automobile parts with ultra high strength. During the process, the blank is firstly heated to obtain full austenite microstructure, later transferred to the mold with inner cooling system then formed and quenched at the same time by mold closing. The product from hot stamping promises good configurational quality and mechanical properties thus calling for less weight as to vehicle security. The research was focused on process analysis.Driven by the part’s final properties, the whole process analysis was crystallized by parameters analysis. Mathematical calculations and numerical simulation were used to define process method, and the mold of U-shaped part was designed for a hot stamping experiment which proves the method. The parameter method with a general form was made out of logical deduction rather than empirical data of 22MnB5. The process applicability of 22MnB5 and the experimental blank of 22Mn2Cr1 were also compared. A thermal recycle analysis was used to simulate the mold’s temperature history in continuous hot stamping, orthogonal design and function fitting were used to define parameters during quenching phase, the result suggested that higher conductance of mold and convective coefficient of cooling water were always favorable, however the contact conductance between mold and blank should be limited into a reasonable range. The mold’s cooling system design was an improvement based on traditional solutions; some parameters in the mold were defined through calculations based on a fast heat transfer requirement. The experiment has also covered transient temperature measuring of the middle point on one of the blank’s edges to obtain the experimental cooling rate, which showed good agreement with rate from simulation. Through tests and observation, the final U-shaped part was proved to get full martensite microstructure which indicates a success in the process method and accuracy of modeling. |
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