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为了提高热成形钢的综合性能,设计了一种C-Si-Mn-Cr-B系热成形钢,采用热膨胀仪测定并研究了30Si Mn Cr B5热成形钢的连续冷却转变曲线和相变规律.分析了经轧制、退火及热成形模拟后钢板的微观组织形貌和力学性能,结合等密度线极图的方法,判定了热成形模拟后钢板中马氏体变体与母相的取向关系.30Si Mn Cr B5热成形钢具有较好的淬透性,临界冷速为5℃·s-1,有效抑制了珠光体和贝氏体的形成,完全马氏体组织的硬度可达600 HV以上.热成形模拟后的微观组织由板条马氏体和残余奥氏体构成,残余奥氏体主要以薄膜状分布在马氏体板条间,质量分数为6%~8%,抗拉强度为1800 MPa左右,总伸长率可达10%以上,强度和塑性的匹配较好.热成形模拟后30Si Mn Cr B5热成形钢板中马氏体变体与母相的取向关系更接近N-W关系,12种变体没有都出现在原始奥氏体内.
In order to improve the overall performance of thermoformed steel, a C-Si-Mn-Cr-B thermoformed steel was designed. The continuous cooling transformation curve and phase transformation of 30Si Mn Cr B5 thermoformed steel The microstructure and mechanical properties of the steel after the rolling, annealing and thermoforming simulation were analyzed, and the orientation of the martensite and the parent phase in the steel after hot forming simulation Relationship.30Si Mn Cr B5 thermoformed steel has good hardenability, critical cooling rate of 5 ℃ · s-1, effectively inhibiting the formation of pearlite and bainite, the hardness of complete martensite up to 600 HV.The above microstructure after thermoforming is composed of lath martensite and retained austenite, the residual austenite is mainly distributed in thin film between martensite laths, the mass fraction is 6% ~ 8% The tensile strength is about 1800 MPa, the total elongation is up to 10%, and the matching of strength and plasticity is better.Most orientation of martensite in 30Si Mn Cr B5 thermoformed steel after thermoforming is closer to the parent phase NW relationship, 12 variants did not appear in the original austenite.