time to that in thermodynamic equilibrium at room temperature.To analyze the effect of cooling rate on inclusion composition during solidification and cooling of liquid steel,the continuous cooling transformation curve of inclusion composition in the bearing steel was discussed.At a fixed cooling rate,the transformation fraction of inclusion composition increased with the reaction time.Simultaneously,the critical cooling rate of different types of steels could be obtained intuitively using these curves.Besides,in order to estimate the effect of heating temperature and holding time on inclusions composition in solid steels,the isothermal transformation curve of inclusion composition in the heavy rail steel was studied. With the increase of holding time and heating temperature,the transformation fraction of inclusion composition had an apparent increase.Moreover,the influence of steel composition and inclusion size on the transformation of inclusion composition could be determined using the equal diameter transformation curve in a pipeline steel at 1473 K.Inclusions with small size almost transformed completely within 60 min,while the larger inclusions changed little even after heating for several hours.These concepts and characteristic curves can intuitively show the composition transformation of non-metallic inclusions in steels during solidification and cooling of liquid steel and heating of solid steel,expanding the control strategy of inclusions in steels from liquid steel to solid steel. KEY WORDS Non-metallic Inclusions:Kinetic model:Transformation fraction: Cooling rate,Time-Temperature Transformation(TTT);Continuous-Cooling-Transformation(CCT);Time-Diameter Transformation(TDT) 钢中非金属夹杂物对钢的延展性、韧性、疲劳性能、抗腐蚀能和使用寿命等都有极大的影响， 也会导致最终产品的质量缺陷，因此，必须严格控制钢中非金属夹杂物的多少、大小、成分、形貌和 夹杂物在钢中的具体位置。在钢的精炼→连铸→轧制过程中，钢中非金属夹杂物的这些特征，特 别是成分上，都发生变化。 过去的几十年中，大多数是研究钢液中非金属夹杂物的演变过程14，通过脱氧51对夹杂物进 行控制，利用合金处理0,18，和渣改性20,2川夹杂物，通过吹氩2去除夹杂物等操作，尽量降低钢中 的有害夹杂物，提高钢液的洁净度。例如，研究炉精除过程钢液中夹杂物的演变、中间包钢液或者 结晶器钢液中夹杂物的去除等现象。近年来，相关研究发现在钢液凝固和冷却过程中，随着温度的 降低，钢和夹杂物之间化学反应的平衡也会随之变化从而导致夹杂物的成分发生转变。如图 1所示，在管线钢连铸过程中取样发现，中间包钢液中夹杂物成分和连铸坯中夹杂物成分差别很 大，而在浇铸过程中并没有发生二次氧化，夹杂物缄分的变化只能是因为钢液凝固和冷却过程中， 钢基体和夹杂物继续发生化学反应而导致。 Cao 0 25 50 75 100 Mgo ★Average composition 0 -1873K liquidus 1873K 50%liquid Number density:4 25 Average diamet Area fraction:2g 50 00 。0 8 0 75 务 响 方 100Al,0 (a)中间包钢液中非金属夹杂物成分time to that in thermodynamic equilibrium at room temperature. To analyze the effect of cooling rate on inclusion composition during solidification and cooling of liquid steel, the continuous cooling transformation curve of inclusion composition in the bearing steel was discussed. At a fixed cooling rate, the transformation fraction of inclusion composition increased with the reaction time. Simultaneously, the critical cooling rate of different types of steels could be obtained intuitively using these curves. Besides, in order to estimate the effect of heating temperature and holding time on inclusions composition in solid steels, the isothermal transformation curve of inclusion composition in the heavy rail steel was studied. With the increase of holding time and heating temperature, the transformation fraction of inclusion composition had an apparent increase. Moreover, the influence of steel composition and inclusion size on the transformation of inclusion composition could be determined using the equal diameter transformation curve in a pipeline steel at 1473 K. Inclusions with small size almost transformed completely within 60 min, while the larger inclusions changed little even after heating for several hours. These concepts and characteristic curves can intuitively show the composition transformation of non-metallic inclusions in steels during solidification and cooling of liquid steel and heating of solid steel, expanding the control strategy of inclusions in steels from liquid steel to solid steel. KEY WORDS Non-metallic Inclusions; Kinetic model; Transformation fraction; Cooling rate; Time-Temperature￾Transformation (TTT); Continuous-Cooling-Transformation (CCT); Time-Diameter-Transformation (TDT) 钢中非金属夹杂物对钢的延展性、韧性、疲劳性能、抗腐蚀能力和使用寿命等都有极大的影响， 也会导致最终产品的质量缺陷，因此，必须严格控制钢中非金属夹杂物的多少、大小、成分、形貌和 夹杂物在钢中的具体位置[1-6]。在钢的精炼连铸轧制过程中，钢中非金属夹杂物的这些特征，特 别是成分上，都发生变化。 过去的几十年中，大多数是研究钢液中非金属夹杂物的演变过程[7-14]，通过脱氧[15-17]对夹杂物进 行控制，利用合金处理[10, 18, 19]和渣改性[20, 21]夹杂物，通过吹氩[22]去除夹杂物等操作，尽量降低钢中 的有害夹杂物，提高钢液的洁净度。例如，研究炉外精炼过程钢液中夹杂物的演变、中间包钢液或者 结晶器钢液中夹杂物的去除等现象。近年来，相关研究发现在钢液凝固和冷却过程中，随着温度的 降低，钢和夹杂物之间化学反应的平衡也会随之变化，从而导致夹杂物的成分发生转变[23-26]。如图 1 [27]所示，在管线钢连铸过程中取样发现，中间包钢液中夹杂物成分和连铸坯中夹杂物成分差别很 大，而在浇铸过程中并没有发生二次氧化，夹杂物成分的变化只能是因为钢液凝固和冷却过程中， 钢基体和夹杂物继续发生化学反应而导致。 录用稿件，非最终出版稿 (a)中间包钢液中非金属夹杂物成分