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针对昆钢400MPa盘条钢筋生产过程中出现的屈服强度及断后伸长率偏低、同卷盘条力学性能不稳定等问题,取样进行了化学成分、金相显微组织、断口形貌及夹杂物检验分析。结果表明:屈服强度及断后伸长率偏低的主要原因为试样金相显微组织出现8%～30%的粒状贝氏体,粒状贝氏体质量分数30%的试样断口形貌表现为脆性断裂,钢筋塑韧性差;同卷盘条力学性能不稳定的主要原因为冷却速度不同造成金相组织中贝氏体质量分数不同。针对上述情况,炼钢采取出钢全程底吹氩及渣洗工艺,轧钢采取降低精轧及吐丝温度(精轧入口温度控制为870～890℃、吐丝温度控制为840～870℃)、减弱斯太尔摩控冷强度、增加辊道速度等措施,消除了400MPa盘条钢筋性能异常情况。
In view of the problems of yield strength and elongation at break after the production of 400MPa steel bar of Kunming Iron and Steel Co., Ltd., as well as instability of the mechanical properties of the coil, samples were taken for chemical composition, metallographic microstructure, fracture morphology and inclusions inspection analysis. The results show that the main reason for the low yield strength and elongation at break is that the microstructure of the sample shows granular bainite with 8% ~ 30%, and the fracture morphology of the sample with the granular bainite content of 30% Fracture, poor plasticity and toughness of steel. The main reason for the unstable mechanical properties of the wire rod is the different bainite content in the microstructure caused by the different cooling rates. In view of the above situation, the steelmaking process of argon blowing and slag washing at the bottom of the steelmaking process is taken. The rolling temperature is controlled to be lower at finish rolling and spinning (finishing inlet temperature is controlled at 870-890 ℃ and spinning temperature is at 840-870 ℃) Weakened the Stelmor control cold strength, increase the roller speed and other measures to eliminate the abnormal performance of 400MPa wire rod.