In order to improve the bending property of higher strength grade hot stamping steel, the traditional manganese-boron steel should be modified by an adjustment of alloy elements, such as niobium, molybdenum…etc., to refine its grain and to eliminate its inclusions. In this study, the effects of niobium and molybdenum additions on the microstructure and the mechanical property of hot stamping steels have been investigated by using OM, SEM, TEM and VDA238-100 bending test. The results indicated that the bending energy of steel with niobium and molybdenum additions could be greatly improved due to its refined grain and the inhibition of crack origins, such as nitrides and sulphides, which are harmful to bending crack propagation. These analytic results are useful in developing ultra-high grade hot stamping steels in future.
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