Experimental Study on Developing Widely Applicable Rare Earth Press Hardening Steel Based on Data Optimization

In order to expand the process window of press hardening steel 1500HS, an experimental study was conducted on the addition of rare earth elements to this alloy, based on prior statistical analysis of literature regarding rare earth applications in steel. In this study, a vacuum induction furnace was used to melt hot-formed steels with and without a specific Ce content. Subsequently, phase transformations of the specimens were comparatively analyzed using a Gleeble-3800 thermomechanical simulator and metallographic analysis techniques. The results show that Ce can effectively improve the stability of austenite, inhibitive the ferrite transformation, and reduce the ferrite transformation temperature by 28 ℃~34 ℃. The influence of Ce on the bainite and martensite transformation temperatures in press hardening steel is not significant. However, it reduces the martensite critical cooling rate from 30 ℃/s to 20 ℃/s. The addition of Ce can effectively increase the process window press hardening stamping process. Under the experimental conditions, the processing window for stamping and mold closure of press hardening steel can be reduced by 45 ℃, which is beneficial for production in lower ambient temperatures or for thin-gauge products.