In order to effectively reduce and control the non-metallic inclusions in a GCr15 bearing steel produced by BOF→LF→VD→CC process and improve its product quality， the characteristics and evolution mechanism of inclusions in bearing steel produced by the whole process were analyzed firstly by methods of systematic sampling， automatic analysis and scanning of inclusions and thermodynamic calculation in the present study. The results show that the inclusions in molten steel are mainly MgO-Al2O3 and Al2O3 after the slag melting during LF stage， and they are transformed into CaO-MgO-Al2O3 and CaO-Al2O3 with the size of 1-5 μm in the end of the LF stage. The type of inclusions remains unchanged after VD soft blowing. However， the inclusion density decreases from 16.53 pcs/mm2 in the end of the LF stage to 14.02 pcs/mm2， resulting in an inclusion removal rate of approximately 15.2%. The number density of inclusions in the tundish increases to 16.39 pcs/mm2. The types of inclusions are still mainly CaO-MgO-Al2O3 and CaO-Al2O3， of which 1-2 μm and ＞ 2-5 μm size accounted for 62.8% and 35.6%， respectively. The number of CaS-containing compound inclusions in the billet increases significantly. Thermodynamic calculation explains the evolution causes of the above inclusions. It is found that when the w［Al］s is at 0.02%， the stable existence of MgO-Al2O3 is associated with a significant variation in Mg content， ranging from 0.000 3% to 0.01%， which facilitates the formation of MgO-Al2O3 or CaO-MgO-Al2O3 type inclusions during the production of GCr15 bearing steel. The T.Ca/T.O ratios of the molten steel in LF ending， VD soft blowing process， and tundish were observed to be 0.39， 1.0， and 0.62， respectively； these values align with the theoretical （T.Ca）/（T.O） ratio range （0.13 to 1.25） conducive to the formation of five distinct types of calcium aluminate. As a result， a substantial quantity of calcium aluminate inclusions was detected. During the cooling process of the molten steel， a transformation of inclusions occurs. The liquid calcium aluminate inclusions diminishes， while the quantities of MgO·Al2O3 and CaS inclusions markedly increases.
针对通过RTD曲线结合水模型流场可视化分析中间包内流体运动形态的方法较为复杂,且无法精确地给出死区区域分布的问题,提出了连铸中间包内流体运动形态模型分析方法.基于物理模拟所得RTD曲线分析结果,通过数值模拟判定死区,并确定了死区临界速度值与入口速度值的关系.以死区临界速度为基础,通过数值模拟可实时在线确定死区的占比和区域分布结果,进而评估单流和多流中间包内流体运动形态,并探究了连铸拉速及中间包构造对中间包内死区的占比和区域分布的影响.结果表明,采用流体运动形态模型能快速判定中间包死区,实现了死区的定量化和可视化.同时对比同一构造单流中间包时,死区临界速度随连铸拉速的提高而增大,死区体积分数则相反,而死区分布模式不发生改变.此外,可直观对比多流中间包内不同挡墙导流孔孔径和仰角下死区的大小和区域分布.当多流中间包内挡墙导流孔的孔径为 70mm,开孔仰角为 19°时,多流中间包内死区体积分数仅为7.64%,且死区集中在中部水口和侧壁附近.
通过凝固仿真模拟计算结合现场试验得出了非调质钢最优的连铸轻压下工艺参数:1～5 号拉矫辊执行 3 mm-4 mm-5 mm-5 mm-3 mm的压下量,对应连铸拉速0.85 m/min,在提高铸坯低倍质量的同时,避免了压下裂纹的出现.在最优轻压下、拉速工艺参数的基础上研究了电磁搅拌对偏析等的影响,结合设备实际采用极值法试验得出了最佳的电磁搅拌参数:结晶器电磁搅拌电流 350 A,频率2.0 Hz;末端电磁搅拌电流 200 A,频率 6 Hz.最终通过对连铸工艺参数的多元耦合研究,可以控制铸坯中心碳偏析指数不大于1.10.
为探究 37Mn5 钢精炼过程尺寸在 10μm以上的大尺寸Al2 O3-SiO2-MnO类夹杂物的形成与演变机理,在实际"EAF→LF→VD→钙处理→CC"工艺生产 37Mn5 钢的精炼全流程进行系统取样,检测了钢液成分并重点分析了不同冶炼阶段大尺寸Al2 O3-SiO2-MnO 类夹杂物的形貌和成分特征,结合实际生产工艺与热力学计算,揭示了这类夹杂物的演变规律.研究结果表明:由于出钢过程局部钢液 Al 含量低而O含量高,大尺寸Al2 O3-SiO2-MnO夹杂物形成;LF精炼初期,局部 Ca 含量增加形成Al2 O3-SiO2-MnO-CaO夹杂物;LF 精炼中期以后 Ti 含量增加会变性前期形成的这两类夹杂物,形成含TiOx的夹杂物,随着冶炼的进行,Ti元素在夹杂物中分布逐渐均匀;VD 后钙处理量不足导致夹杂物变性效果不理想,对大尺寸夹杂物的影响不大.出钢过程合理的脱氧、合金化和造渣制度可以减少Al2 O3-SiO2-MnO 类夹杂物的形成,从而减少夹杂物数量,改善钢材质量.
为降低全废钢量子电弧炉出钢氮含量、优化电弧炉冶炼性能、减少电弧炉冶炼碳排放量,通过对量子电弧炉喷吹工艺进行优化改进,采用CO2 喷吹工艺替代原始喷吹工艺以实现上述目标.在 150 t量子电弧炉上进行了大量CO2 喷吹工艺试验,分别对比了改进工艺前后的电弧炉出钢氮含量、冶炼电耗、冶炼周期、碳排放等性能指标的变化趋势.试验结果表明:使用CO2 喷吹工艺后,电弧炉出钢氮质量分数降低30.6×10-6、冶炼电耗降低5.6 kWh/t、冶炼周期缩短3.2 min、平均出钢碳氧积降低了4.4×10-4、渣中 FeO质量分数降低了4.5百分点、碳排放降低8.4%.通过将 CO2 载气喷吹碳粉工艺与Ar+ CO2 动态混合底吹工艺结合应用于电弧炉炼钢中能够有效降低钢水出钢氮含量、冶炼电耗、碳排放量等性能指标,优化量子电弧炉喷吹工艺.
