Hydrogen related risks for automotive steels

Purpose and goal

The results provide understanding of the factors which govern the risk to HE: steel properties, hydrogen levels, residual stresses, and their performance in laboratory as well in service environment. The risk to HE is proportional to the strength increase of the steel but can be mitigated. The recommendations include avoiding severe laboratory testing conditions and mechanically sheared edges as well as recommendations for sample handling and their preparation regarding hydrogen analysis of hot stamped steels. All project goals were fulfilled.

Expected results and effects

The results contributed to better knowledge of HE in cold rolled and press-hardened UHSS for automotive applications. The main deliverable is recommendations/guidelines on how to mitigate HE, and the respective risks such as environments, material, deformation levels, and steps in the manufacturing processes. This project contributed to industrial partners in achievement their goal for designing better products and recommendations to costumers on how to handle and use safely UHSS.

Planned approach and implementation

1)The source of hydrogen and its content at the different stages of the manufacturing process was identified 2)The residual stresses, inherent and induced by forming and cutting and their impact on the HE sensitivity/resistivity were evaluated 3) The effect of different protective coatings (zinc and AlSi) on HE sensitivity was evaluated 4) Advanced instrumental techniques (TDMS, SKPFM, LSI) were used to increase the knowledge and understanding of H trapping in UHSSs 5) A guideline concerned with HE mitigation of automotive cold formed and hot stamped UHSSs was established