根据部分轮辐用热轧双相钢在模拟服役过程中多处发生开裂的问题，利用金相显微镜、扫描电镜等相关实验手段，对失效部位及原材料进行了深入研究。结果表明，造成轮辐用热轧双相钢疲劳失效的主要原因是：①样品心部马氏体粒子尺寸较大，数目较少，呈块状，宽度介于2～10μm，长度介于5～15μm，5μm以内的马氏体第二相粒子较少，不能为位错移动提供足够的有效障碍，导致开裂。②样品中存在一定量大尺寸夹杂物，复合Al2 O3类夹杂物沿轧制方向排成一排，单个夹杂物尺寸介于3～30μm之间。③板材中存在轻微的混晶现象，最大的晶粒尺寸为20μm，最小的晶粒尺寸只有2μm，由于服役过程中变形不协调而引起晶间应力集中加剧，使得粗晶粒提早产生裂纹。%In view of problems of several cracks formed in the hot rolled dual phase steel for spokes during the simulated service, deep investigations on cracking parts and materials were made by means of OM, SEM and so on. The results showed that reasons are as follows:①The martensite particles in the core of the specimen with larger size is in a smaller number, forming lumps with width between 2~10 μm and length between 5~15 μm. There are few second-phase martensite particles of less than 5 μm so that they can′t provide enough and effective barriers against dislocation movement, resulting in cracking. ② There are a certain amount of large inclusions in the specimen. Compound Al2 O3 inclusions are in a row along the rolling direction, with size between 3~30 μm for single inclusion. ③ Minor mischcrystal phenomenon exists in the plates. The grain size is between 20 μm and 2 μm. Because the deformation and incoordination intensify the intergranular stress concentration during the service, cracks occur early in the coarse grains.
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