Abstract
High-strength boron steels are widely used in manufacturing the auto bodies and parts of light-weight vehicles, but the high rates of surface scratches and die wear have consistently occurred during hot stamping for these steels. For an in-depth understanding of the tribological characteristics at this interface, the frictional contact behavior and thermomechanical mechanisms of boron steel 22MnB5 against die steel H13 at 800 °C were studied through experiments and finite-element simulations. The coefficient of friction and worn surface topography were investigated by pin-on-disk sliding tests. A three-dimensional thermomechanical finite-element model of a friction pair was established to explore the interfacial dynamic variations. Experimental and simulation results show that severe elastic–plastic deformation occurred on the worn surface of the boron steel, whereas an increase in the load decreased the coefficient of friction within a certain range because the growth rate of shear force was slower than that of the normal force. When the finite-element model was changed from the gradual loading stage to the initial sliding stage, the tangential friction force further increased the plastic deformation on the surface of boron steel. The scratches and furrows were mainly caused by the compression and shear from asperities of the rough surface, as confirmed by the high-frictional-stress regions concentrated on the peaks and flanks of asperities. During the high-temperature and high-pressure experiments, the plasticized and softened surface materials of the boron steel adhered to the die surface readily, resulting in peeling and delamination.
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