Abstract: Experimental results obtained that the main causes of low plasticity indexes of Φ12 mm hot rolled coil of steel SCM435 (/% : 0. 34 〜0. 35C, 0. 98 〜1.00Cr, 0. 19 ~0. 21 Mo) are size 50 -60 μm large calcium aluminate inclusion formed by slag entrapment in tundish and mold, and formed 8% ~ 10% martensite due to lack of enough time for bainite phase transformation. With (a) extending LF refining soft stirring time, using shielding casting and slag detecting system ,stabilizing cast speed to reduce slag entrapment and larger inclusions； and ( b) improving control cooling process to reduce martensite content in structure, the elongation and reduction of area of hot rolled coil increase respectively from original 3. 9% 〜10.0% and 4.7% -39.3% to 10.6% -11.0% and 39. 9% 〜43. 6%.

摘要： 试验结果得出中间包和结晶器卷渣形成的尺寸50～60μm大型铝酸钙夹杂物和贝氏体相变时间不足形成的8%～10%马氏体是SCM435钢(/%:0.34～0.35C、0.98～1.00Cr、0.19～0.21Mo)Φ12 mm热轧盘条塑性指标低的主要原因。通过(1)延长LF精炼软搅拌时间,采用保护式浇铸和钢包下渣检测控制系统,稳定拉速以减少卷渣和大型夹杂物;(2)改善控冷工艺,减少了马氏体含量,使热轧盘条的伸长率和断面收缩率分别从原先的3.9%～10.0%和4.7%～39.3%提高到10.6%～11.0%和39.9%～43.6%。

关键词: 冷镦钢SCM435, 热轧盘条, 洁净度, 马氏体, 塑性