【作者】 张国兴；

【导师】 王谦；

【作者基本信息】 重庆大学 ， 冶金工程， 2010， 硕士

【摘要】 电工钢等部分超低碳钢在转炉出钢采用弱脱氧工艺,从出钢到RH工位之前钢水氧活度较高,LF精炼过程中不仅无法实行有效的脱硫,甚至有回硫现象的发生,脱硫主要是在RH脱氧合金化之后进行,但RH脱硫时间较短,脱硫比较困难。本文主要针对攀钢超低碳电工钢冶炼工程中,由于转炉出钢采用弱脱氧工艺,RH冶炼过程中回硫严重,RH脱硫时间短、加入RH脱硫剂后浸渍管侵蚀严重等问题,通过热力学计算和实验研究,得到了高效的RH脱硫剂各组分的控制范围和顶渣成分的控制范围,同时提出了减缓RH浸渍管侵蚀的措施,研究结果如下:利用FACTSage热力学软件计算了顶渣中各组分对硫分配比Ls的影响,结果表明:①过高的（FeO+MnO）含量是造成回硫现象的主要原因,随着FeO含量的降低,钢水氧活度迅速降低,Ls增大,（FeO+MnO）含量必须控制在15%以下,RH脱硫之后需控制在10%以下;②CaO/Al₂O₃比值的增加不仅提高炉渣的硫容量,还可降低顶渣FeO的活度,应该控制在2.5⁴;③MgO含量对Ls的影响不大,基本趋于稳定,但一定的MgO含量有助于缓解侵蚀,应控制在9%左右;④SiO₂不仅会降低炉渣的硫容量,而且还会增加顶渣中FeO的活度,因此要严格控制顶渣中的SiO₂含量。通过在硅钼棒为发热体的高温炉上（以下称为硅钼棒炉）进行钢渣接触实验,分析了CaO-Al₂O₃-CaF₂系脱硫剂中不同CaO/Al₂O₃、不同CaF₂含量对脱硫剂脱硫能力的影响,结果表明:①CaO/Al₂O₃的增加可以提高Ls,提高炉渣的脱硫能力;②渣中添加CaF₂可以有效的提高炉渣的脱硫能力,但当CaF₂含量大于15%,Ls不再增加;③考虑了脱氧产物的上浮对炉渣成分的影响,得到了最佳的脱硫剂配比%CaO/%Al₂O₃=2.5-4;SiO₂<5%;F-控制在8%左右,熔点不大于1350℃。实验室条件采用二次回归正交设计的方法,研究了含BaO和Na₂O的脱硫剂中各组分对Ls的影响,结果表明:①CaO/Al₂O₃比值的增加,Ls先增大后减小,在CaO/Al₂O₃为1.9时达到最小;②随着MgO含量的增加,Ls先增大后减小,当MgO=6%时,Ls最大;③随着BaO含量的增加,Ls减小,大于10%以后趋于平缓,随着Na₂O含量的增加,Ls呈线性增加;④随着CaF₂含量的增加,Ls将减小;⑤BaO、Na₂O和CaF₂含量的增加,均可以有效的降低渣系的熔点;⑥最终确定了脱硫剂中不添加BaO和Na₂O,而采用上述确定的CaO-Al₂O₃-CaF₂系脱硫剂。利用FACTSage热力学软件计算分析了RH脱硫剂对采用高铝浇注料的RH浸渍管的侵蚀机理,并通过实验进行了验证,结果表明:①RH脱硫剂在与浇注料接触后,主要生成的相为CaO·6Al₂O₃（CA6）和CaO·2Al₂O₃（CA2）,继而继续与CaO结合成低熔点物质进入渣中;②CaF₂会与渣中的CaO和Al₂O₃结合成低熔点物质11CaO·7Al₂O₃·CaF₂,加快炉渣的渗透,加重侵蚀;③脱硫剂中添加5%的MgO,不仅可以生成高熔点的MgO·Al₂O₃（MA）尖晶石相,而且可以降低Al₂O₃在渣中的溶解度,从而缓解侵蚀,同时在耐火材料中添加一定量的MgO含量之后,也可以生成高熔点的MA相;④实验验证了热力学计算结果,表明在脱硫剂中添加5%MgO之后,脱硫剂对刚玉坩埚的侵蚀减轻。本文分析了RH冶炼条件下脱硫动力学的影响因素,建立了RH投入法脱硫的动力学模型,结果表明RH脱硫的主要影响因素为反应的容积系数,增大RH吹氩流量,提高真空度,提高炉渣的硫容量,均可以提高RH脱硫速率。工业试验结果表明,通过顶渣改质工艺,将顶渣中的FeO含量控制在15%以下,RH冶炼结束在10%以下之后,钢水氧活度有了很大程度的下降,硫分配比Ls增大,避免了RH回硫现象的发生,RH的脱硫效率达到了30%,成品硫含量小于0.005%,达到了钢种的要求。更多还原

【Abstract】 Soft-killed process is adopted after tapping for some ultra-low carbon steel, oxygen activity in steel was very so high that effective desulfurization cannot be performed in LF furnace, even that resulfurization would be happened. So desulfurization was carrried out after RH deoxidation alloying, but left time for desulfurization was short and difficult to remove sulfur from steel in soft killed process.In the present study, based on the severe problem that resulfurization during RH melting, short time for RH desulfurization in soft-killed process and corrosion of RH submerged tube after RH desulfurizer input for the melting of ultra-low carbon electric steel, high efficient desulfurizer and control range of every component in top slag were obtained through thermodynamic calculation and experimental study in laboratory, improvement measures for the corrosion of RH submerged tube were also put forward, the research results were gotten as following:The effects of components on Ls were calculated using FACTSage thermodynamic software and the results show that:①overhigh content of （FeO+MnO） was the main reason for resulfurization, Ls would be increased and oxygen activity in steel decreased with the decrease of FeOcontent. For the avoiding of resulfurization, （FeO+MnO） content in top slag should be controlled below 15% and after RH desulfurization should be controlled below 10% at least;②the increase of （%CaO）/（%Al₂O₃） increases the sulfur distribution. The component of CaO in slag can increase sulphide capacity of top-slag, and decrease FeO activity, and （%CaO）/（%Al₂O₃） should be controlled 2.5⁴;③no substantial effect of MgO on the sulphide distribtution when it increases from 7 to 13 mass%, and a certain amount of MgO in slag helps to alleviate corrosion and should be controlled around 9%;④SiO₂ can decrease the sulphide capacity and increase the activity of FeO in slag so SiO₂ concentration in top slag should be controlld strictly.The effect of the ratio of CaO/Al₂O₃ and the content CaF₂ on desulfurizing ability of desulfurizer based on CaO-Al₂O₃-CaF₂ slag system was analyzed through desulfurization experiment performed in MoSi2 furnace. The results show that:①the sulfur distribution and desulfurizing ability of desulfurizer is found to increase with the increase of （%CaO）/（%Al₂O₃）;②the addition of CaF₂ can effectively increase the desulfurizing ability of desulfurizer but when CaF₂ content is in the range 15%²0%, sulfur distribution goes near to steadiness;③Considering that large amount of Al₂O₃ produced by deoxidizing may reduced the ratio of CaO/Al₂O₃ of desulfurizer, the optimum desulfurizer composition was obtained as follows: %CaO/%Al₂O₃=2.5-4;SiO₂<5%;F-<8%,the melting point should be controlled lower than 1350℃.As for the influence of various components in desulfurizer containing BaO and Na₂O on Ls based on CaO-SiO₂-Al₂O₃-MgO-BaO-Na₂O-CaF₂ slag system, the quadratic regression orthogonal method was used for the experimental study and the results show that:①with the increase of the ratio of CaO/Al₂O₃, Ls increases at first, then decreases and the least Ls was obtained when CaO/Al₂O₃ was 1.9;②with the increase of the content of MgO, Ls increases at first, then decreases and the largest Ls was obtained when MgO content was 6%;③Ls decreased with the increase of BaO content and goes near to steadiness when BaO content was larger than 10%;④Ls decreased with the increase of CaF₂ content;⑤the melting point of slag can be effectively decreased with the addition of BaO、Na₂O and CaF₂;⑥no addition of BaO and Na₂O in desulfurizer was decided to be used in industrial test, and desulfurizer composition was obtained as follows: %CaO/%Al₂O₃=2.5-4;SiO₂<5%;F-<8%,the melting point should be controlled lower than 1350℃.The reaction between RH desulfurizer and high alumina refractory castable for RH submerged tube was thermodynamic analyzed using FACTSage software and the impact on corrosion of CaF₂ and MgO in desulfurier and castable was also analyzed. The verification test was also carried out, the results indicate that:①CaO·6Al2O（3CA6） and CaO·2Al2O（3CA2）are the main phase produced by the reaction between castable and by RH desulfurizer, and the reactants with low melting point dissolved into slag;②CaF₂ reacts with CaO and Al₂O₃ to produce 11CaO·7Al₂O₃·CaF₂ which may quicken the penetration and sharpen the erosion;③the saturation solubility of Al₂O₃ in RH desulfurizer is lower after addition of 5% MgO, Meanwhile, compacted MgO·Al₂O₃（MA） spinel with high melting point can be produced, which can effectively reduce corrosion and extend RH submerged tube utility longevity;④thermodynamic calculation was demonstrated by experiments and the results indicate that after addition of 5% MgO in desulfurizer, corrosion of desulfurizer to corundum crucible was reduced.The influence factors of desulfurization process kinetics in RH process were analyzed in this paper and a model for RH desulfurization using the method of top addition was also established, the results show that the main influence factor of RH desulfurization is the reaction volumetric coefficient, increasing Ar gas flow rate, improving vaccum degree and sulfuide capacity of slag can effectively increase the rate of RH desulfurization.Industrial test shows that after the content of （FeO+MnO） was controlled below 15% and 10% after RH through the slag property changing treatment, oxygen activity in steel decreased and Ls increased obviously, resulfurization can be avoidable. Combined with the process of slag modification and application of RH desulphurizer, the efficient rate of RH desulfurization can be close to 30%, sulphur content in products is lower than 0.005%, and meets the needs of steel grade.更多还原