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本研究曾经试验性地测定了两种含硅贝氏体钢的断裂韧性,并阐明了断裂韧性和钢的显微结构的关系。具有高强度和高韧性相结合的最佳贝氏体显微组织由贝氏体铁素体和取代渗碳体的残余奥氏体交织状薄板条构成。这种组织可以用往钢中加硅的方法加以获得。残余奥氏体薄膜具有热稳定和机械稳定性,其作用在于减小实际断裂晶粒尺寸,并可能使扩展的微裂纹钝化。块状残余奥氏体则是不稳定的,因此,不利于提高韧性。这两种试验性钢的强度和韧性值相当于或高于某些工业用马氏体钢。
This study has tentatively measured the fracture toughness of two silicon-containing bainitic steels and clarified the relationship between fracture toughness and the microstructure of the steel. The best bainitic microstructure with a combination of high strength and high toughness is composed of interlaminar, thin retained austenite strips of bainitic ferrite and substituting cementite. This organization can be obtained by adding silicon to the steel. Retained austenite films have thermal stability and mechanical stability, their role is to reduce the actual fracture grain size, and may extend the micro-crack passivation. Blocky retained austenite is unstable, therefore, not conducive to improving toughness. The strength and toughness of these two experimental steels equals or exceeds that of some industrial martensitic steels.