高碳微合金非调质钢C70S6的开发和工艺实践

Development of High Carbon Microalloying Non-Quenched-Tempered Steel C70S6 and Process Practice

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,0.0120~0.0140N)的生产流程为120 t顶底复吹转炉-LF-RH-240 mm×240 mm方坯连铸-Φ39 mm棒材轧制。生产结果表明,通过控制Mn/S≥3,采用碱度[(CaO)/(SiO_2)]4.32的LF精炼渣(/%:59.87CaO,13.86SiO_2,5.55MgO,16.34Al_2O_3,0.64S,0.072MnO),钢水过热度15~30℃连铸拉速0.65 m/min,弱二冷比水量0.5 L/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。

The production flowsheet of developed high carbon microalloying non-quenched-tempered steel C70S6 （/%： 0.68N0.73C, 0.15-0.25Si, 0.45-0.55Mn, ≤0.030P, 0.055-0.070S, 0. 10~0.15Cr, 0. 04 - 0. 08Ni, O. 03 - 0.04V, 0. 012 0 - 0. 014 ON） is 120 t top and bottom combined blowing eonverter-LF-RH-240 mm x 240 mm bloom casting-Φ39 mm bar rolling. Production results show that with process measures including controlling Mn/S≥3, using basicity [（ CaO）/（ SiO2 ）] 4.32 LF refining slag （/% ： 59.87CAO, 13.86SIO2, 5.55MGO, 16.34Al2O3, 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 Ⅲ section of secondary water cooling and finishing rolling temperature at ≤880 ℃, 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.