A study of annealing time to surface characteristics and hydrogen embrittlement on AlSi coated 22MnB5 during hot stamping process

Abstract

Hydrogen embrittlement is influenced by material sensitivity, residual stress and hydrogen uptake. During hot stamping process, there are various factors that affect hydrogen embrittlement, such as annealing time during the heating process. As the annealing time increases, the color of the metallic coating gradually turns from blue to red and microstructure becomes larger. When the surface properties of automotive steel are changed, it is necessary to check whether there is any problem in electro-coating process and corrosion resistance. In this study, we investigated the effect of the metallic layers by diffusion of Fe and defect sensitivity resulting of the electrocoating process such as pinhole, corrosion resistance and hydrogen embrittlement sensitivity of steel, with annealing time in the hot stamping heating furnace. Coating workability shows similar results regardless of annealing time, but the sensitivity of hydrogen embrittlement is greatly influenced by annealing time in the hot-stamping furnace. And we have found a way to manage optimal annealing time to reduce of hydrogen embrittlement sensitivity on hot stamping steel by chroma- meter.