Hyundai Steel (South Korea)

The demand for hot stamping parts in the automobile industry is increasing due to the growth of eco-friendly vehicles with improved crash safety performance and lighter weight. However, the use of ultra-high-strength steel in cold stamping is challenging due to its high yield strength and low elongation. Hot stamping is a widely used process to overcome this challenge, but the long die quenching time reduces its productivity. In order to address this issue, a Groove Pressing method was applied to the sidewall of the die to improve cooling performance without requiring additional devices within the die. The study investigated the required contact pressure between the sheet and the die for the implementation of the groove shape on the sidewall. Computational analysis was performed to design optimal groove shape for the sidewall, and the results showed that Case 3 was the most suitable in terms of cooling performance and contact pressure. The groove shape was incorporated into the die making, and experiments were conducted on aluminized coated 22MnB5 1.2 mm sheet. The results showed that the implementation of the groove shape on the sidewall improved cooling performance, dimensional quality, and mechanical properties without affecting the corrosion resistance of the component. The study demonstrates the potential of the Groove Pressing method as a practical solution for improving the productivity of the hot stamping process in the automobile industry.

Abstract This paper aims to improve the accuracy of the finite element analysis for the preform shape transformation according to the difference in the type of carbon fiber and friction force. The carbon fiber type (Toray T700, Zoltek), the fiber direction (0°/90°, ± 45°), and the frictional force were measured, which occurred between the fiber and the mold and between the fiber and the fiber. A comparative experiment was conducted through actual preform production by designating it as a variable for element analysis. The analysis was conducted according to the difference between the static friction coefficient and the dynamic friction coefficient in the molding analysis. Within the range of the Coulomb equation, the shear angle changing was compared with the actual preform shape to show similar results.