汽車高強度安全部件降氫脆敏感性製程技術開發

Development of Technology for Reducing Hydrogen Embrittlement Sensitivity of High-Strength Safety Components for Automobiles

汽車車體考量安全性的提升，於外部結構（如側門環A、B、C柱，防撞樑等）及內部駕乘室（座椅、安全帶舌片）等汽車安全部件，採用高強度鋼之比例日漸提升。由於，車身於銲接組立過程中，熱影響及環境水氣反應可能造成氫滲入鋼材，且高強度鋼因金相組織因素，其對氫脆敏感性遠高於一般軟鋼，造成安全部件發生氫脆的敏感性增加。但是，車體外部結構與乘用座椅經組裝為白車身後，會進行磷化與塗裝烘烤的表面處理程序，高強度鋼可藉由烘烤製程進行除氫已消除氫脆風險。然而，作為確保駕乘人員安全之安全帶舌片高強度鋼，其製程為酸洗＋電鍍，相較於白車身的表面處理製程，其吸氫程度更為顯著，使得安全帶舌片的氫脆敏感性提升。本研究藉由調整安全帶舌片之酸洗處理程序，使舌片之含氫量較原製程下降約67%；並於不影響安全部件管制強度之前題，建立電鍍後去氫熱處理技術，使最終產品之含氫量僅約為原有串製程的25%。

To enhance the safety of vehicle body, the proportion of high strength steels used in either structural parts as door ring constructions or cabin parts as seat and seat belt buckle is increasing. Due to welding procedures of vehicle white-body assembling, the reaction of heating affect and ambient moisture might cause hydrogen adsorption on and migration inward high strength steels, might increase hydrogen-induce-cracking sensitive especially in high strength steel than soft steels. However, the assembling vehicle construction body would proceed phosphating and electro-deposited painting processes, and the hydrogen-induced-cracking sensitive of high strength steels would decrease during heat-curing after electro-deposited painting. On the contrary, the manufacturing processes of high-strength seat belt buckle were heat-treatment, blanking, pickling and electro-plating. The phenomenon of hydrogen adsorption and migration of high-strength steels was more aggressive than white-body surface treatments, especially in pickling and electro-plating process. The pickling technique was improved to reduce the hydrogen-induced cracking sensitivity of high-strength seat belt buckles, achieving a 67% drop in hydrogen adsorption compared to the original process. Meanwhile, post-heat-treatment was carried to de-hydrogen after electro-plating, resulting in a reduction in hydrogen adsorption to 25% compared to the original manufacturing process, while the strength of the seat belt buckle was maintained within engineering safety specifications.