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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.

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Hot stamping is an innovative technology that enables the production of high-strength automotive body parts by heating the material to a high temperature and simultaneously forming and quenching it in-die. The process results in parts with excellent strength-to-weight ratios, which are essential for the automotive industry. The widely used 22MnB5 material is heated to temperatures above 900°C, and an Al-Si coating is applied to prevent the formation of oxide scale on the sheet surface. The distinctive color on the sheet surface after hot stamping is produced by the Al-Si coating. This phenomenon is attributed to the formation of Al2O3 on the surface of the Al-Si coating layer and the diffusion of Fe from the substrate into the Al-Si coating layer, both of which are significantly influenced by the heating time and temperature. In this study, the neural network was investigated to predict the hot stamping heating temperature and time conditions based on the color exhibited on the sheet surface after the process. Additionally, the neural network was combined with numerical models to predict the inter-diffusion layer thickness in the Al-Si coating layer, which affects the weldability of the vehicle part, and the amount of hydrogen uptake that directly influences hydrogen embrittlement.