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对普通Q235钢进行55%的冷变形,然后加热至750℃并保温不同时间,水冷后获得了平均晶粒尺寸在5~8μm,且具有双峰尺度分布的铁素体组织,讨论了此类组织的形成过程及其对性能的影响。结果表明:试验钢的屈服强度和抗拉强度分别达到825 MPa和970 MPa,此时仍具有11.4%的均匀伸长率。分析认为临界区保温期间同时存在变形铁素体的再结晶以及奥氏体晶粒的形核长大,再结晶得到多边形铁素体,且其随保温时间的延长快速长大,粗大的多边形铁素体限制了奥氏体晶粒的合并长大,因此冷却后生成的准多边形铁素体更加细小,促进了双峰尺度分布的形成。试验钢应力应变曲线表现为连续屈服,证明细小的准多边形铁素体可以起到与双相钢中硬相相同的作用。
55% cold deformation of ordinary Q235 steel was carried out, and then heated to 750 ℃ for different time. After cooling, the ferrite structure with average grain size of 5 ~ 8μm and bimodal size distribution was obtained. Formation of the organization and its impact on performance. The results show that the yield strength and tensile strength of the test steel reach 825 MPa and 970 MPa, respectively, and still have a uniform elongation of 11.4%. The analysis shows that there exist both the recrystallization of deformed ferrite and the nucleation and growth of austenite grains during the heat preservation in the critical region, and the polygonal ferrite is recrystallized and grows rapidly with the prolongation of holding time. The thick polygonal iron The austenite limits the coalescence and growth of austenite grains, so the quasi-polygonal ferrite produced after cooling is finer and promotes the formation of bimodal scale distribution. The stress-strain curve of the test steel shows continuous yielding, demonstrating that the fine quasi-polygonal ferrite can perform the same function as the hard phase in duplex steel.