Blanking immediately after heating and ultrasonic cleaning for compact hot-stamping systems using rapid resistance heating

摘要

To produce ultra-high-strength steel parts for improving fuel consumption and collision safety of automobiles, a compact hot-stamping process having resistance heating was developed. In this process, a blanking operation was introduced immediately after heating to deal with non-rectangular blanks in resistance heating. By blanking, not only were the blank shapes optimised for stamping but the formability was also improved by removing both non-heating edges in contact with the electrode. A rectangular quenchable steel sheet was resistance-heated; the sheet was immediately blanked into the desired shape, and the blank was hot-stamped. In addition, reinforcements used for a body-in-white were hot-stamped using the proposed process to examine the applicability. The reduction in thickness of the hot-stamped reinforcement using a hot-blanked sheet was reduced compared with that using a rectangular blank. The formability was improved by blanking immediately after heating. Moreover, ultrasonic cleaning with diluted hydrochloric acid removed the thin oxide scale caused by resistance heating, and the spot-resistance weldability and electrodeposition paintability were improved. Blanking immediately after heating and ultrasonic cleaning are useful for practical hot-stamping processes using resistance heating.