Applications of press hardening steel in car body and its resistance spot welding
Press hardening steel reaches the strength up to 2000 MPa and it finds applications mostly as safety components in a car body with high impact resistance. The steel increases the safety of the passengers while at the same time reducing the thickness of the sheets and thus reducing the weight of the entire car body. Hence, the part of the press hardening steel in the car body is incessantly increasing. Currently, 22MnB5 steel with Al-Si coating is most commonly used. The main role of the coating is to protect and hinder the oxidation and decarburization of the steel during heat treatment. During hot stamping, however, the chemical and phase composition of the coating change and strongly depend on the process conditions. This variable distribution of the phases and inhomogeneities have a negative impact on joining technologies, particularly resistance spot welding. Therefore, there is an effort to replace the Al-Si coating by zinc-based coatings, which are predominantly used in car bodies as corrosion protection.
The authors wish to thank the Financial support from specific university research (MSMT No 21-SVV/2019) for its financial support of this research.