Effect of Si and Cr on microstructure and properties of high strength wear-resistant plate
In recent years, in order to meet the requirements of automotive lightweight, the proportion of high-strength wear-resistant steel used in automotive steel has gradually increased. DP steel with phase transformation strengthening as the main mechanism, give full play to the hard phase (martensite) and soft phase (ferrite) deformation coordination, so that it has a high initial work hardening rate, low yield to strength ratio and good strength and plastic coordination, has developed into a high-performance advanced high strength steel (AHSS). In order to obtain ultra-high strength cold-rolled DP steel, a certain amount of silicon is often added on the basis of traditional C-Mn system to play its role of solid solution strengthening, and as a non-carbide forming element.
The effect of alloying elements Si and Cr on the phase transformation of C-Si-Mn-Nb and C-Cr-Mn-Nb high strength wear-resistant plates under continuous cooling was studied by thermal dilatometer. The microstructure and fracture morphology of two DP steels were studied by unidirectional tensile test, OM, SEM and TEM.
The results show that silicon can increase the temperature of Ac1 and Ac3, enlarge the two-phase region, promote the ferrite transformation, and improve the tempering stability, morphology and distribution of martensitic wear-resistant plates. The addition of chromium element leads to uneven distribution of carbon in austenite, resulting in twin and strip fine structure in martensite, residual austenite and Mao-island structure in the rapid cooling process, and some of the martensite will decompose in the aging process. The tensile strength of the two steels exceeds 1000MPa, the elongation exceeds 15%, and the mechanical properties of the wear-resisting plate containing silicon are better than those of the biphase steel containing chromium.
