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利用热膨胀仪研究了合金元素硅和铬对C-Si-Mn-Nb系与C-Cr-Mn-Nb系超高强双相钢连续冷却相变规律的影响;采用单向拉伸试验,以及OM、SEM和TEM等方法对比研究了2种DP钢的组织性能与断口形貌。结果表明:硅元素能够提高Ac1和Ac3点温度,扩大两相区,促进铁素体相变,并能提高马氏体的回火稳定性,改善其形貌和分布;铬元素的添加导致了奥氏体中碳的分布不均匀,使得马氏体内部同时出现了孪晶与板条状精细结构,而且快冷过程中出现了残余奥氏体和马奥岛组织,部分马氏体会在时效过程中发生分解;两钢的抗拉强度均超过1 000 MPa,伸长率超过15%,且含硅的双相钢各项力学性能均要优于含铬的双相钢。
The effects of alloying elements, such as silicon and chromium, on the continuous cooling transformation of C-Si-Mn-Nb and C-Cr-Mn-Nb superhigh strength duplex steels were investigated by means of thermal dilatometer. Uniaxial tensile tests and OM SEM and TEM were used to study the microstructure and fracture morphology of two DP steels. The results show that silicon can increase the temperature of Ac1 and Ac3, expand the two-phase region, promote the ferrite transformation and improve the tempering stability and the morphology and distribution of martensite. The addition of chromium causes The distribution of carbon in austenite is not uniform, making twin and strip-like fine structure appear in the martensite at the same time, and the residual austenite and the island tissue appear in the process of rapid cooling. Some of the martensite will be aged During the process of decomposition, the tensile strengths of both steels exceed 1 000 MPa and the elongation exceeds 15%. The mechanical properties of the dual phase steels containing silicon are better than that of the dual phase steels containing chromium.