MnS偏析对440 MPa级冷轧低合金高强钢塑性影响浅析

Analysis on the Effect of MnS Segregation on Plasticity of 440 MPa Cold Rolled High Strength Low Alloy Steel

针对CSP流程生产的440 MPa级冷轧低合金高强钢屈服强度异常升高问题,通过金相显微镜、SEM对比,分析了正常(A)试样和异常(B)试样拉伸断口显微形貌及金相组织。结果表明,B试样中存在大量MnS析出物并聚集偏析,MnS偏析导致440 MPa级冷轧低合金高强钢塑性指标偏低,材料冲压成形性能较差。工业化生产440MPa级冷轧低合金高强钢过程中针对塑性较差问题,可以通过降低C含量至0.055%、降低S含量至50 ppm和适当提高连铸机拉速至4.6 m/min的措施有效降低MnS偏析,从而提高了材料的冲压成形性能,大大降低了产品在市场质量异议风险。

Aiming at the problem of abnormal rise in yield strength of 440 MPa grade cold rolled high strength low alloy steel produced by CSP process, the microstructure and microstructure of tensile fracture of normal specimen A and abnormal specimen B were analyzed by metallographic microscope and SEM. The results show that there are a lot of MnS precipitates and segregation in specimen B. MnS segregation results in low plasticity index of 440 MPa grade cold rolled high strength low alloy steel, and poor stamping performance. In order to solve the problem of poor plasticity during the industrial produc- tion of 440 MPa grade cold rolled high strength low alloy steel, the MnS segregation can be effectively reduced by reducing the C content to 0.055%, reducing the S content to 50 ppm and properly increasing the drawing speed of the continuous caster to 4.6 m/rain. Thus, the stamping property of the material is improved, and the risk of product quality objection in the market is greatly reduced.