【摘要】 将Mn-B系高强度贝氏体钢板轧成25 mm规格采用超快冷系统进行加速冷却。冷却后钢板可以获得710~850 MPa的高抗拉强度,但断后伸长率仅12.0%~13.0%。通过光学显微镜、扫描电镜、透射电镜等对钢板及单向拉伸断口的显微组织、析出物等进行分析。结果表明,在超快冷条件下钢板表层可以获得广泛的板条贝氏体组织,板条贝氏体中的渗碳体分布于板条及板条束间的界面上,形成类似珠光体的片层结构,明显提高钢板强度。在变形过程中,渗碳体内易生成微裂纹,降低基体组织的加工硬化能力,导致断后伸长率偏低、钢板塑性下降。更多还原

【Abstract】 High strength bainite steel plates with the Mn-B component system were rolled into 25 mm thickness and then cooled by ultra-rapid cooling system( UFC). Consequentially,the high tensile strength of plates was between 710 MPa and 850 MPa and the elongation was in the range of 12. 0% and 13. 0%. The microstructure and precipitations of samples for each plates were observed by optical microscope,scanning electron microscope and transmission electron microscopy. The results show that microstructure at the surface of plates are almost lath bainite,with cementite distributing along the boundaries between adjacent laths and pockets,which is similar to lamellar structure of pearlite and greatly increase the tensile strength of plates. During deformation,micro-crack is easy to generated in the cementite and reduces the work hardening capacity and results in the elongation and plasticity reducing.更多还原