基于铸坯的25Mn钢环件热辗扩成形力学性能分析

Analysis of mechanical properties of hot rolling process for as-cast 25Mn steel ring

环形铸坯辗扩成形是一个多场耦合、局部加载和连续成形过程,与传统辗扩工艺相比,缩短工艺流程,减少加热次数,节材、降能耗,具有重要的研究价值与推广应用前景。辗扩过程中,不仅要控制环形铸坯辗扩后的成形精度,还应通过高温塑性变形获得所需微观组织,提高综合力学性能,实现成形/成性一体化调控。根据环件轧制技术及基于铸坯的辗扩成形基础理论,通过对25Mn钢环形铸坯进行辗扩,分析辗扩成形环件不同部位微观组织的变化及力学性能,并借助扫描电镜观察,揭示其拉伸与冲击断口的断裂机理。结果表明:辗扩后环件的外形好,宽展小,椭圆度为0.4;组织内部平均晶粒尺寸小,环件各个区域的力学性能均较高,且中层的略低于内层和外层;拉伸与冲击断裂形式主要为准解理,并伴有韧窝断裂。可见,基于铸坯的25Mn钢环件热辗扩"成形"/"成性"质量较高,为其进一步研究以及实际生产提供了理论指导价值。

The ring rolling of casting blank is a process of multi-field coupling, local loading and continuous forming. It have important research value and application prospect due to its numerous merits such as shortening process, reducing heating time, saving materials and energy comparing with traditional ring rolling process. During ring rolling process, not only the forming precision of rolled ring has to be controlled, but also micro-structure has to be gained by elevated temperature plastic deformation, which can improve the comprehensive mechanical properties and realize the integrated control of forming and performance for rings. According to the ring rolling technology and the basic theory of rolling for casting blank, the 25Mn steel casting ring has been rolled and its micro-structure and mechanical properties of different parts of ring have been analyzed. The fracture mechanism of tensile and impact have been revealed by scanning electron microscope.The results show that the good shape and small broadsiding have been obtained after ring rolling process. The ovality of the rolled ring is 0.4. The average grain size inside is small. The mechanical properties are high in different areas, and the middle is slightly lower than the inner and outer of 25Mn steel ring. The fracture mechanism of tensile and impact mainly are quasi cleavage and toughness nest fracture has been accompanied. Therefore, the quality of forming and performance are splendid after hot roiling process for 25Mn steel casting ring. It provides theoretical value for further research and practical production.