TB-P无碳预熔中空型碱性中间包覆盖剂的开发应用

TB-P中间包覆盖剂集无碳、预熔、中空、碱性于一体,选择CaO-MgO-Al2O3-SiO2渣系,CaO/SiO2＞2,(MgO)为(14±4.5)%,(Al2O3)为(12±4.5)%,(Fe2O3)＜2%、F.C≤0.1%.在工作层采用镁质喷涂料的60 t中间包使用时,铺展性、均一性、保温性等工艺性能良好,不结壳,无增碳隐患,Al2O3吸附率达30%左右.无碳预熔中空型碱性中间包覆盖剂较好地发挥了"中间包冶金"--"中间包全碱性技术"的精炼功能.     

中间包碱性覆盖剂的研制

根据CaO-SiO2-Al2O3三元相图研制开发了一种中间包碱性覆盖剂,研究了其与酸性和中性覆盖剂吸收Al2O3夹杂的能力,指出碱性覆盖剂吸收Al2O3夹杂的能力优于酸性和中性覆盖剂,并通过工业试验验证了所研制的碱性覆盖剂具有较好的冶金效果．     

碱性中间包覆盖剂吸附夹杂能力的研究

根据CaO-SiO2-Al2O3三元相图研制开发了一种碱性中间包覆盖剂,研究了其与酸性和中性覆盖剂吸附Al2O3夹杂的能力,指出碱性覆盖剂具有优于酸性和中性覆盖剂吸附Al2O3夹杂的能力,并通过工业试验验证了所研制的碱性覆盖剂具有优良的冶金效果.     

中间包覆盖剂开发状况分析

对中间包覆盖剂的发展历程进行了简要介绍,在此基础上对中间包覆盖剂的绝热保温、防止氧化和吸收夹杂物等冶金功能进行了论述,并对酸性、中性、碱性三种类型的覆盖剂的划分标准、原料组成、使用效果及优缺点进行了分析,最后对无碳中间包覆盖剂、高碱度中间包覆盖剂及双层中间包覆盖剂的开发现状进行了简要介绍。     

中间包覆盖剂及内衬材料对钢水清洁度的影响

阐述近年国内外中间包覆盖剂内衬材料的发展情况，研究中间包覆盖剂地夹杂物的吸附、钢水的氧化和对钢卷渣及钢水脱硫的影响；讨论酸性内衬及碱性内衬对钢水清洁度的不同效果。结论：高碱性、成分、结构合适的中间包覆盖剂及内衬材料是生产高洁净钢的重要条件。．     

IF钢顶渣控制分析

本文详细论述了IF钢顶渣改质和中包覆盖剂对钢液洁净度的作用机理,试验研究了顶渣改质和中包覆盖剂对IF钢线性缺陷的影响。理论显示RH顶渣的C/A比应在1.5～2.0之间,顶渣改质的T.Fe含量低于5%最好,其次是在5%～10%之间。然而现场试验结果表明DR07外板2、3级线性缺陷指数和渣的C/A比有明显对应关系,但是和渣中T.Fe的对应关系不明显。浇铸IF钢中间包使用碱性覆盖剂时,冷轧卷线性缺陷发生率显著低于使用酸性覆盖剂和双层覆盖剂的工艺。     

连铸中间包碱性覆盖剂及其冶金效果

连铸中间包覆盖剂对钢的清洁度有很大影响，碱性覆盖剂与酸性覆盖剂相比具有绝热保温，防止钢水二次氧化，有效地吸收钢水中的非金属夹杂（主要是Ａｌ２Ｏ３）防止碱性中间包材材料侵蚀等优点。     

RH精炼终点-中间包浇铸过程超低碳钢水增碳的影响因素

通过数据统计,分析了钢厂180 t RH精炼结束到45 t中间包浇铸过程中钢包衬、中间包涂料和覆盖剂等对MA超低碳钢水(≤0.005%C)增碳的影响。结果表明,连续浇铸第1炉增碳较大,增碳量5×10^-6~10×10^-6,其余炉次增碳量≤3×10^-6。通过第1炉缓缓加入覆盖剂控制中间包液面波动,加Al₂O₃减少钢包渣线侵蚀,减少钢包砖衬、中间包涂料和覆盖剂游离碳含量,可使RH精炼终点-中间包浇铸过程中钢水增碳量≤3×10^-6。     

中间包覆盖剂的碱度对铁素体不锈钢冶金质量的影响

针对出现的430、0Cr13R、409等铁素体不锈钢冷轧板夹杂缺陷,研究了中间包覆盖剂的碱度(1.10～5.98)对钢的洁净度的影响,分析了R=5.98高碱度中间包覆盖剂在浇铸过程中碱度、Al₂O₃和SiO₂含量的变化。结果表明,在连铸过程中R=5.98高碱度中间包覆盖剂用原渣的R=5.98降至R=3.0,高碱度中间包覆盖剂具有良好的吸收钢中夹杂能力,对钢液的供氧能力弱,能够显著改善钢的洁净度。     

高碱度中间包覆盖剂对改善0Cr18Ni9不锈钢洁净度的影响

0Cr18Ni9奥氏体不锈钢的生产流程为铁水脱磷预处理-75 t转炉-VOD-LF-200 mm×1 200 mm坯连铸工艺。分析了连铸过程20 t中间包覆盖剂(/%:40.54CaO,28.89Al₂O₃,7.8SiO₂,6.32MgO,1.84C,碱度5.2)组分变化,及钢中氧、夹杂物去除效果。结果表明,采用高碱度中间包覆盖剂时,多炉连浇后覆盖剂吸收钢中硅酸类夹杂物效果明显,0Cr18Ni9不锈钢中平均氧含量由LF钢水中的56.5×10^-6,降低到中间包钢水中的37.5×10^-6和铸坯的33.3×10^-6,铸坯中夹杂物数量及大小较LF后有明显降低,高碱度中间包覆盖剂对去除20μm以上的大颗粒夹杂效果明显。     

降低转炉出钢温度的实践

钢水过程热损失主要为钢水的辐射散热,对流传热和钢包、中间包耐火材料的吸热。为了减少钢水的过程温降,相应采取了一系列措施：优化钢包保温层,降低包衬的导热系数,减轻包衬的热损失;对脱氧合金化用合金进行烘烤,提高合金加入钢水前的温度;大包加保温盖,实施全程保护浇注等。改进后,平均出钢温度降低20℃以上。     

中间包覆盖剂对430不锈钢钢水洁净度的影响

为了提高430铁素体不锈钢钢水洁净度,采用光学显微镜、扫描电镜和电子探针对比分析了不同熔点中间包覆盖剂对430钢水洁净度的影响。结果表明,采用两类中间包覆盖剂生产的430不锈钢夹杂物成分都以CaOSiO2-Al2O3-MgO类为主,中间包覆盖剂对钢水中已经形成的夹杂物影响较小,不会改变夹杂物类型。使用低熔点中间包覆盖剂,板坯中夹杂物数量要明显少于使用高熔点中间包覆盖剂的炉次。     

Characteristic Analysis of Solidified Crust for Basic Tundish Flux With AlKilled Steel Casting

This present paper focused on the formation reasons of solidified crust when a basic tundish flux was used to cast the Al-killed steel. Crust samples were taken in an actual tundish, and analyzed by the methods of XRD, SEM and EDX. It was found that the main compositions of crystallization phases existing in tundish crust are Ca12Al4O33, Ca2SiO4 and a little spinel. Spinel and Ca2SiO4 distributed at grain boundaries of Ca12Al4O33, which increased the connection strength of crystallization phases by pinning the grain boundary, density or hardness of tundish crust will also significantly increased. When an initial composition of tundish flux was in spinel region of CaO-SiO2-Al2O3-10%MgO phase diagram, it was easier to form spinel in crust. Three approaches for spinel formation in crust were summarized. When flux is nearly saturated with magnesia, on the metal/flux interface, MgO in flux reduced by dissolved Al and formed the spinel. Inside molten steel and on the interface of steel/refractory, with a feasible Al content it is also easy to form spinel and spinel inclusions will float and captured by flux.     

Characteristic Analysis of Solidified Crust for Basic Tundish Flux With Al-Killed Steel Casting

The solidified crust was harmful to Al-killed steel casting using a basic tundish flux. After sampling from an actual tundish, XRD, SEM and EDX examinations were carried out to analyze the microstructure of solidified crusts. The conclusions were obtained as follows: main crystallization phases existing in tundish crust were Ca12A14 O33, Ca2SiO4 and a little spinel; spinel and Ca2SiO4 distributed between the grain boundaries of Ca12A14O33,which increased the connection strength of crystallization phases by pinning grain boundary, density or hardness of solidified crust maybe also significantly increases; when initial composition of tundish flux was located in spinel region of CaO-SiO2-Al2O3-10%MgO phase diagram, it was easier to precipitate spinel from molten slag; three approaches of spinel formation in flux were summarized. When flux was saturated with magnesia on the metal/flux interface, MgO in flux was reduced by dissolved aluminum and then formed spinel. On the interface of steel/refractory,with feasible aluminum content, it was also easy to form spinel, and spinel inclusions will be floated and captured bytundish flux.     

稀土氧化物对中间包覆盖剂粘性特征的影响

稀土氧化物对中间包覆盖剂和实验室合成渣粘度的影响的试验表明，当稀土氧化物含量不大于10％时，具有降低覆盖剂高温粘度的功能，当稀土氧化物含量接近20％时，会显著增大覆盖剂粘度。     

八流中间包耐材蓄热对中间包钢液温度的影响

对八流40 t中间包烘烤及浇钢过程的包壁与钢液温度进行了数值模拟计算与20CrMnTiH钢200 mm×200 mm坯连铸现场实测。结果表明,模拟计算烘烤期间中间包耐材升温缓慢,浇钢后中间包内衬耐材升温加快,第3炉外壁温度397℃,达到热平衡;第2炉结束时,计算两侧与中部钢液温度较第1炉对应位置分别升高5.2、1.5℃,计算边流与中部流钢液温差4.8℃,实测第2炉边流间与中部流间钢液温度相差4℃,中间包钢液温度均匀稳定,计算值与实测值趋势一致;烘烤包温度由900℃提高至1000℃时,第1炉中间包钢液温降减慢,水口出钢温度略增,各流间温差减少。