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利用 EM,对45Cr2NiMoVSi 钢模拟500×500mm大模块油淬时心部组织中的残余奥氏体(以下简称 A1)进行了研究,特别是就 Ar 对裂纹扩展的阻碍作用进行了二次电子像扫描的动态观察。结果表明:上述模拟组织中的 Ar 绝大部分以薄膜状(film)存在于α-Fe 板条问:裂纹总是试图沿着晶界或α-Fe 板条界扩展,但若遇到 Ar,裂纹将先钝化而后改向扩展,也就是说 Ar 对裂纹的扩展有着明显的阻碍作用;我们认为这种阻碍作用正是 Ar 提高钢的韧性的主要原因。
Using EM, the residual austenite (hereinafter referred to as A1) in the heart tissue of 45Cr2NiMoVSi steel simulating 500 × 500mm large module was oil-quenched. Especially, the secondary electron image scanning was performed on the impeding effect of Ar on crack propagation Dynamic observation. The results show that most of Ar in the above simulated structure exists as a film on the α-Fe slab. Q: Cracks always attempt to propagate along grain boundaries or α-Fe slab boundaries. However, if Ar is encountered, The crack will be passivated and then redirected. That is to say, Ar has a significant hindrance to the crack growth. This obstacle, we think, is the main reason that Ar improves the toughness of the steel.