Abstract: The production flowsheet of developed high carbon microalloying non-quenched-tempered steel C70S6 (/% : 0. 68~0.73C, 0.15~0.25Si, 0.45~0.55Mn, ≤0.030P, 0.055~0.070S, 0.10~0.15Cr, 0.04~0.08Ni, 0.03~0.04V, 0.0120~0.0140N) is 120 t top and bottom combined blowing converter-LF-RH-240mmx240mm bloom casting-φ39 mm bar rolling. Production results show that with process measures including controlling Mn/S≥3, using basicity [(CaO )/( SiO₂ ) ] 4.32LF refining slag (/% : 59.87CaO, 13.86SiO₂, 5.55MgO, 16.34A1₂O₃, 0.64S, 0.072MnO) , liquid superheating extent 15~30℃，casting speed 0.65 m/min, weak secondary water rate 0.5 L/t, using air mist spray cooling at M section of secondary water cooling and finishing rolling temperature at ≤880°C , the mechanical properties of high carbon microalloying non-quenched-tempered steel C70S6 are tensile strength ≥950 MPa, yield strength ≥550 MPa, elongation ≥10% , reduction of area ≥20% and HB hardness value 240~290, and each index all meets the requirement for fracture splitting connecting rod.

摘要： 开发的高碳微合金非调质钢C70S6（/%:0.68~0.73C，0.15~0.25Si，0.45~0.55Mn，≤0.030P，0.055~0.070S，0.10~0.15Cr，0.04~0.08Ni，0.03~0.04V，0.012~00.0140N）的生产流程为120t顶底复吹转炉-LF-RH-240mm×240mm方坯连铸-Φ39mm棒材轧制。生产结果表明，通过控制Mn/S≥3，采用碱度[（CaO）/（SiO₂）]4.32的LF精炼渣（/%:59.87CaO，13.86SiO₂，5.55MgO，16.34Al₂O₃，0.64S，0.072MnO）,钢水过热度1530℃连铸拉速0.65m/min，弱二冷比水量0.5L/t；二冷Ⅲ段采用气雾冷却，终轧温度≤880℃等工艺措施，高碳微合金非调质钢C70S6抗拉强度≥950 MPa，屈服强度≥550 MPa，伸长率≥10%，断面收缩率≥20%，硬度HB值为240~290，其各项指标均满足胀断连杆要求。

关键词: 120t BOF-LF-RH-CC流程, 高碳微合金非调质钢, 胀断连杆, C70S6, 开发, 工艺实践