冷却模式对热轧双相钢组织及断裂机制的影响

为研究冷却模式对热轧双相钢显微组织及断裂机制的影响,采用两段式(空冷+水冷)、连续式两种冷却方式,得到不同相比例和力学性能的热轧双相钢,轧后取样并在扫描电镜上进行原位拉伸实验.结果表明,两段式冷却模式得到的马氏体呈小岛状,而连续式冷却模式得到的马氏体呈块状,马氏体含量和形貌的不同导致两种冷却方式得到的双相钢力学性能存在差异.原位拉伸过程中,裂纹首先萌生于铁素体与夹杂物界面处,随着变形继续进行,在铁素体与马氏体界面处开始出现裂纹,当变形量进一步增大时,细小岛状马氏体始终不发生断裂,而块状马氏体在颈缩阶段发生断裂.

Effect of cooling mode on microstructure and fracture mechanism of hot-rolled

In order to investigate the effect of cooling mode on microstructure and fracture mechanism of hot-rolled dual-phase steel,in the present paper,two cooling modes including continuous water cooling and two-section cooling(air cooling plus water cooling) were employed to produce hot-rolled dual-phase steels with different phase fractions and mechanical properties.Situ-tensile test conducted on SEM shows that fine martensite island and massive martensite can be obtained under these two cooling modes respectively.Differences in the content and shape of martensite result in different mechanical properties of the two types of steel.The cracks appear firstly at the interface between ferrite and inclusion,and then occur at the interface between ferrite and martensite during the tensile test.With the deformation going on,massive martensite begins to fracture in the stage of necking during deformation,however,no cracks occur in the fine martensite island.