Dynamic mass variation and multiphase interaction among steel, slag, lining refractory and nonmetallic inclusions: Laboratory experiments and mathematical prediction

The mass transfer among the multiphase interactions among the steel, slag, lining refractory, and nonmetallic inclusions during the refining process of a bearing steel was studied using laboratory experiments and numerical kinetic prediction. Experiments on the system with and without the slag phase were carried out to evaluate the influence of the refractory and the slag on the mass transfer. A mathematical model coupled the ion and molecule coexistence theory, coupled-reaction model, and the surface renewal theory was established to predict the dynamic mass transfer and composition transformation of the steel, the slag, and nonmetallic inclusions in the steel. During the refining process,Al_(2)O_(3) inclusions transformed into Mg O inclusions owing to the mass transfer of [Mg] at the steel/refractory interface and(Mg O) at the slag/refractory interface. Most of the aluminum involved in the transport entered the slag and a small part of the aluminum transferred to lining refractory, forming the Al_(2)O_(3) or Mg O·Al_(2)O_(3). The slag had a significant acceleration effect on the mass transfer. The mass transfer rate(or the reaction rate) of the system with the slag was approximately 5 times larger than that of the system without the slag. In the first 20 min of the refining, rates of magnesium mass transfer at the steel/inclusion interface, steel/refractory interface, and steel/slag interface were x, 1.1 x, and 2.2 x,respectively. The composition transformation of inclusions and the mass transfer of magnesium and aluminum in the steel were predicted with an acceptable accuracy using the established kinetic model.

42CrMo钢中非金属夹杂物的研究

本文通过电炉冶炼的42CrMo钢冶炼过程的不同阶段钢样、渣样及耐火材料的系统分析,对该钢中夹杂物的性质和来源进行了研究。实验片果表明:42CrMo钢中夹杂物的生成与渣和耐火材料有密切的关系;出钢过程中钢渣混出能去除硫化物夹杂,但会使钢渣卷入钢液生成大尺寸夹杂物;浇注过程中使用的耐火材料会被钢水浸蚀进入钢液,它是42CrMo纲中外来夹杂物的一个重要来源。

LD→LF→CC工艺生产82B钢的洁净度研究

采用加入示踪剂、全流程系统取样与实验室综合分析相结合的方法,对82B钢生产过程中各工序钢中T.O和N含量、显微夹杂物和大型夹杂物数量和粒径分布以及成分类型进行了系统研究。结果表明:LF精炼后钢中w(T.O)和显微夹杂物数量显著下降,分别降低62.06%和43.57%;铸坯中w(T.O)和显微夹杂物数量的平均值分别为28.42×10-6和17.78个/mm2,铸坯中小于4μm的显微夹杂物数量占87.21%;LF精炼时钢包包衬侵蚀严重,软吹前的精炼过程和中间包浇铸时钢液因吸气造成的二次氧化较严重;中间包内钢液浇铸不稳定,存在严重的卷渣现象。

坩埚材质及顶渣成分对帘线钢夹杂物成分的影响

使用碳管炉熔炼帘线钢72A,研究不同材质坩埚及不同成分顶渣对钢中夹杂物的影响。结果表明,MgO坩埚冶炼的帘线钢中夹杂物变形率高于ZrO2、SiO2、Al2O3坩埚。采用SiO2坩埚冶炼时,钢中夹杂物几乎不变形,其SiO2含量大于90%(质量分数,下同)。采用Al2O3坩埚,个别夹杂物Al2O3的含量达到40%左右,不适合冶炼帘线钢。钢中夹杂物成分进入较低熔点区(即不大于1 500℃的区域)的条件为:采用MgO坩埚,顶渣碱度为1.0时,wAl2O3≤3%,或顶渣碱度为0.9时,wAl2O3为9%;采用ZrO2坩埚时,顶渣碱度为1.1～1.2时,wAl2O3为3%。

LD-LF-CC工艺生产的82B钢铸坯洁净度研究

采用加入示踪剂、对铸坯进行系统取样与实验室综合分析相结合的方法,对LD—LF—CC工艺生产的82B钢铸坯中T[O]、显微夹杂物和大型夹杂物数量和粒径分布以及成分类型进行了系统研究。结果表明:铸坯中T[O]和显微夹杂物数量的平均值分别为28.42×10-6和17.78个/mm2,铸坯中0～4μm和4～10μm的夹杂物分别占显微夹杂物总数的87.21%和12.22%,显微夹杂物的类型主要为复合氧化物类和由复合氧化物和硫化钙构成的复合夹杂物。铸坯中大型夹杂物含量差别很大,大于300μm的夹杂物占大多数,大型夹杂物的形成与钢包耐火材料侵蚀和中间包卷渣有关。