Experimental and Numerical Studies on the Roll Bonding of Manganese/stainless Steel for Press Hardening

For the press hardening process an Al-Si coating is usually applied on the surface of typical boron-manganese steels (22MnB5), to form a diffusion layer for protection against scaling. However, the diffusion layer requires long heating times and is environmentally questionable. This paper describes a new approach to substitute the Al-Si coating by a stainless steel (X5CrNi18–10) to provide an environmentally friendly alternative, save heating energy and raise the production efficiency. For this, the hot roll bonding of 22MnB5 and two protective layers of X5CrNi18-10 to produce laminated composites are investigated by experiments and FE-simulations. The aim is to set up a computer-aided design of the hot roll bonding using a calibrated isothermal bond strength model and to validate it by hot roll bonding experiments. Firstly, the bonding properties of the material combination 22MnB5/X5CrNi18-10 are characterized at 1000 ℃ in a lab scale experiment. With those truncated cone tests an isothermal bond strength model is parametrized by bond strength measurements at different height reductions and stress states. Secondly, the contact parameters are calibrated by the simulations of the truncated cone tests. With the calibrated contact parameters, the experimental compression and de-bonding forces are reproduced by the simulations with a general deviation of 15%. Finally, the calibrated contact parameters and the bond strength model are implemented into the hot roll bonding process model of the first two rolling passes. According lab-scale roll bonding experiments are performed to validate the simulations. A comparison of the rolling forces as well as layer thicknesses after each pass show a good agreement between the simulations and experiments.