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设计了一种超低碳Fe-Mn-Nb-Cu-B系屈服强度为690 MPa级工程机械结构用钢,利用扫描电镜(SEM)和透射电镜(TEM)等仪器研究了不同终冷温度对钢组织和性能的影响。结果表明:终冷温度对实验钢组织和力学性能具有较大影响,终冷温度较高时以粒状贝氏体为主,终冷温度较低时以板条贝氏体为主,在其它工艺相同的情况下,随着终冷温度的降低,屈服强度、抗拉强度和屈强比都呈升高的趋势,延伸率呈下降的趋势。终轧后经弛豫处理、终冷温度为350℃的实验钢的综合力学性能最优,屈服强度和抗拉强度分别达到715 MPa与860 MPa,伸长率达到20.6%。分析认为:实验钢的微观组织对其力学性能的变化起着主要的作用,这主要与其贝氏体的类型,组织中M-A岛的数量、大小和形态,还有组织中位错的密度和状态有关。
An ultra-low-carbon Fe-Mn-Nb-Cu-B system steel with a yield strength of 690 MPa was designed for construction machinery. The effects of different final cooling temperature pairs Effect of Steel Structure and Properties. The results show that the final cooling temperature has a great influence on the microstructure and mechanical properties of the experimental steel. When the final cooling temperature is high, the granular bainite is the main part. When the final cooling temperature is low, the lath bainite is the main part. In other processes Under the same conditions, the yield strength, tensile strength and yield ratio all showed an increasing tendency with the decreasing of the final cooling temperature, and the elongation rate showed a decreasing trend. After finishing rolling and relaxation treatment, the experimental steel with the final cooling temperature of 350 ℃ has the best mechanical properties, yield strength and tensile strength reach 715 MPa and 860 MPa respectively, and the elongation reaches 20.6%. The analysis shows that the microstructure of the experimental steel plays a major role in the change of its mechanical properties, which is mainly related to the type of bainite, the number, size and shape of MA islands in the tissue, as well as the density and state of dislocation in the tissue related.