顶渣对帘线钢中夹杂物塑性化的控制

以某钢厂生产的帘线钢铸坯试样为原料,使用硅钼棒炉对其进行顶渣熔炼实验,研究顶渣成分对CaO-Al2O3-SiO2 类夹杂物塑性化的影响。结果表明, 在顶渣碱度为0.8～1.2时,随着顶渣中Al2O3 质量分数的增加夹杂物中的Al2O3 质量分数也随之增加。当顶渣中Al2O3质量分数低于10%时,CaO-Al2O3-SiO2 类夹杂物的成分在塑性区范围,对应的此时钢液中的w［Al］s低于8×10-6。通过控制顶渣的成分可以把CaO-Al2O3-SiO2 类夹杂物的成分控制在塑性区内。     

帘线钢中非金属夹杂物的控制技术研究

采用转炉、LF精炼、真空处理、软吹、连铸工艺生产帘线钢,将钢水中S、P、Ti、As等残余元素的含量尽可能降低,出钢采用含超低铝和钛的合金,使用低碱度的酸性渣进行炉外精炼,严格控制钢中酸溶铝含量,同时控制渣中MgO、Al2O3含量,将帘线钢中的非金属夹杂物控制在锰铝榴石(3MnO-Al2O3-3SiO2)和位于钙斜长石(CaO-Al2O3-2SiO2)和假硅灰石(CaO-SiO2)共晶线周边的玻璃态塑性夹杂区域内,尽可能降低钢中不可变形夹杂物,如Al2O3和(Mg、Mn)O.Al2O3的数量和大小,通过控制钢中钛、氮含量来消除TiN(TiCN)夹杂。     

精炼渣碱度对304不锈钢夹杂物的影响

结合生产实际,采用定量金相和SEM+EDS统计分析方法,研究了硅脱氧条件下,精炼渣碱度对304奥氏体不锈钢在LF精炼、连铸过程夹杂物变化规律的影响。结果表明:钢水中主要形成球状CaO-Al2O3-SiO2类复合夹杂,适当高的精炼渣碱度有利于钢中细小夹杂物的形成。随精炼渣碱度的提高,复合夹杂物中CaO含量增加,SiO2含量减小,Al2O3含量变化不大。现场条件下,由FeSi合金带入钢中的Al形成的Al2O3对复合夹杂物的塑性变形影响较大。在精炼渣碱度分别为1.0和1.5时,铸坯复合夹杂物中Al2O3质量分数为25%左右,夹杂物的变形能力稍弱。     

小方坯流程高品质轴承钢工艺

相比于电炉冶炼和大方坯流程,采用转炉冶炼加小方坯流程具有更低的生产成本。根据天钢的实际生产情况,对采用“铁水脱硫扒渣→转炉冶炼→LF造渣精炼→VD真空精炼→小方坯连铸”流程生产高品质轴承钢的关键技术进行研究。分析冶炼过程钢水及连铸坯中夹杂物可知：随着LF炉炉渣碱度的升高,钢液中wT［O］大幅降低,控制炉渣碱度R在一个较高范围（7.0~9.0）对于控制钢液中wT［O］很重要;LF精炼初期,夹杂物中Al2O3含量较高,随着精炼的进行夹杂物向着CaO-Al2O3-MgO系和Al2O3-MgO系方向夹杂物发展;VD真空处理促进钢-渣-夹杂物间反应向平衡方向移动,夹杂物接着向CaO-Al2O3-MgO系方向发展,夹杂物中CaO含量增加;在小方坯连铸过程中,采用两级电磁搅拌加低拉速、低比水量的模式获得了较小的碳偏析度。     

VD低碱度渣对GCr15轴承钢夹杂物的影响

为了减轻铝脱氧GCr15轴承钢中B类和D类夹杂物的危害,开展了VD低碱度渣和正常碱度渣精炼的对比工业试验研究。结果显示,与正常碱度精炼渣相比,碱度为1.96的精炼渣可使连铸坯中塑性夹杂物比例由14.81%上升为40.65%;同时,全氧(T. O)含量由7.7×10^-6下降至4.9×10^-6,全铝(T. Al)和酸溶铝(AlS)含量由279×10^-6、210×10^-6分别下降至80×10^-6、75×10^-6。热力学计算表明,低碱度精炼渣引起钢液中[Si]活度增大使复合夹杂中Al2O3(inc)含量下降,钢中酸溶铝(AlS)含量落在与塑性夹杂物平衡对应的等铝浓度线范围内,理论计算与试验结果吻合。VD低碱度渣精炼有利于实现轴承钢夹杂物塑性化控制。     

精炼渣控制82B帘线钢中夹杂物形态的实验室研究

在实验室条件下,采用高温钼丝炉对用45钢和重轨钢熔炼成的帘线钢进行脱氧和渣钢平衡试验,研究了精炼渣组分对夹杂物形态的影响。结果表明:在精炼渣碱度为0.8～1.2时,夹杂物中Al2O3含量和钢中Als随精炼渣中Al2O3含量的增加而增加。把精炼渣Al2O3质量分数控制在10%以下时,能够使CaO-SiO2-Al2O3夹杂物处于塑性范围内。因此,在低碱度条件下,通过Si、Mn脱氧和调整精炼渣中Al2O3含量来控制夹杂物的形态是可行的。     

齿轮钢（8620H）精炼渣优化及工业试验

利用FactSage热力学软件计算了CaO-Al2O3-SiO2-5%MgO四元系的CaO、Al2O3等活度线,通过等活度线图着重探讨精炼渣碱度、w(CaO)/w（Al2O3）、MI指数（曼内斯曼指数）与Al2O3夹杂吸附能力的影响关系,最终得到适用于杭钢生产齿轮钢（8620H）的LF精炼渣系范围为：CaO质量分数为50%~55%,Al2O3质量分数为25%~30%,SiO2质量分数为10%~12%,MgO质量分数为5%~8%。并使用该渣系进行齿轮钢（8620H）工业试验,铸坯中全氧质量分数由0.001 5%降至0.001 0%,且铸坯中显微夹杂物尺寸也明显降低,由2.1降至1.5μm,每10kg铸坯中大型夹杂物质量分数由31.9下降到26.4mg,试验效果良好。     

高碱度精炼渣对GCr15轴承钢洁净度的影响

 利用实验室渣-钢平衡试验研究了高碱度精炼渣对GCr15轴承钢中[w(T[O])]和夹杂物的影响。结合试验结果和热力学分析,探讨了钢中[w(T[O])、]夹杂物尺寸分布和粒径大小的变化规律,以及氧化物夹杂的转变过程。研究结果表明,碱度为6时,精炼渣(59.4%CaO-24.8%Al2O3-9.8%SiO2-6%MgO)可将钢中[w(T[O])]控制在0.000 6%以内,氧化物夹杂平均尺寸最小为2.26 μm。随着钢中[w([Ca])]和[w([Mg])]的增加,钢中氧化物夹杂转变过程为Al2O3→MgO·Al2O3→MgO→CaO-Al2O3-MgO复合夹杂物(核心为MgO,外围包裹着CaO-Al2O3)。渣-钢反应前期钢中以MgO·Al2O3为主,后期以MgO和CaO-Al2O3-MgO复合夹杂物为主。氧化物夹杂转变的试验结果与热力学分析结果相一致,大多数氧化物夹杂尺寸小于5 μm。     

SWRH82B硬线钢CaO- Al2O3- SiO2系夹杂物塑性化控制的生产实践

为了研究SWRH82B硬线钢通过控制精炼渣的组成实现夹杂物塑性化的可行性,通过对炼钢过程中各工序的精炼渣和钢液进行取样,并对精炼渣成分、钢液总氧含量以及夹杂物的形貌、尺寸、成分等进行检测分析。结果表明,采用无铝化脱氧,并将精炼渣的碱度控制在0.8~1.2,Al2O3质量分数控制在10%以下时,能使CaO- Al2O3- SiO2系夹杂物成为塑性夹杂物;钢水经过RH真空精炼后夹杂物尺寸变大,并且夹杂物的Al2O3质量分数降低,SiO2质量分数升高,通过相关检测分析了造成此现象的原因,并提出了改进措施。     

钢包初始状态对帘线钢夹杂物的影响

运用Aspex Explorer扫描电镜对比了3种不同初始状态钢包冶炼条件下的帘线钢盘条中夹杂物成分、变形性能以及数量密度等,指出不同初始状态的钢包对帘线钢精炼渣成分和成品[Al]含量的影响。结果表明,同等条件下,分别使用冶炼过Si、Al-Si以及Al脱氧钢的钢包冶炼帘线钢时,精炼渣碱度、渣中Al_2O_3含量和成品[Al]含量均呈上升趋势,对应精炼渣碱度分别为0.95、1.1、1.4,渣中Al_2O_3质量分数分别为7.0%、11.0%、15.0%,成品[Al]的质量分数分别为7×10~(-6)、13×10~(-6)、16×10~(-6)。采用冶炼过Al、Al-Si脱氧钢的钢包冶炼的帘线钢盘条夹杂物数量密度分别为0.96、1.20个/mm~2,夹杂物中Al_2O_3平均质量分数分别为25.9%、31.8%,夹杂物塑性差,轧制后长宽比平均值分别为5.6、5.1。采用冶炼过Si脱氧钢的钢包冶炼的帘线钢盘条中夹杂物数量密度为0.79个/mm~2,夹杂物中Al_2O_3平均质量分数为15.0%,为塑性夹杂物,轧制后长宽比均值为11.3。实验证明,冶炼帘线钢不宜使用初态为Al脱氧或者Al-Si脱氧的钢包。     

Inclusion Variations of Hot Working Die Steel H13 in Refining Process

 Inclusion variations of die steel H13, including changes of species, morphologies, compositions, amounts and sizes, in the production of EAF→LF→VD→ingot casting→electro-slag refining (ESR) procedure, were investigated by systematic sampling, and analyzed with scanning electron microscope (SEM), energy dispersive spectrum (EDS), and metallographic microscope. The variation mechanism was studied by comprehensive analysis of total oxygen, nitrogen, and acid soluble aluminum as well as chemical test of refining slag. Based on the investigations, technical measures for cleanness improvement were discussed. The results show that oxide inclusions in H13 steel change from irregular Al2O3→near globular CaO-MgO-Al2O3 and CaO-Al2O3-SiO2 complex inclusions→finer CaO-Al2O3-SiO2 inclusions with higher CaO content→CaO-Al2O3-SiO2 inclusions with higher Al2O3 content and irregular MgO-Al2O3 inclusions→fine irregular MgO-Al2O3-CaS inclusions in various steps of the production; the variations are related with changes of acid soluble aluminum content, reactions between slag and steel, re-oxidation of liquid steel during casting, and refining of ESR. It is also found that Al2O3 inclusions are modified by refining slag in LF and VD refining; and ESR plays a good role in inclusion removal, especially in controlling the large linear VC-CrC-MoC inclusions distributed in grain boundaries. It is suggested that casting protection should be improved, and the basicity of refining slag and acid soluble aluminum content in steel should be raised.     

LF处理过程中钢水增铝问题的研究

硅镇静钢及少量铝脱氧的钢在LF处理过程中会发生钢水中铝含量增加以及夹杂物组成改变的现象.通过理论计算和工业生产实践研究了不同的渣系、钢水成分、处理时间等对LF精炼过程增铝的影响,不同精炼渣系下钢中夹杂的组成,结果表明采用CaO-SiO2渣系LF处理过程几乎不发生增铝现象,而采用CaO-Al2O3渣系随着处理时间的延长以及钢种成分的区别,钢中铝有不同程度的增加,生产实践结果与理论计算趋势基本一致.采用CaO-Al2O3渣系精炼与CaO-SiO2渣系相比,钢中Al2O3夹杂数增加4倍,氧化物复合夹杂中w(Al2O3)提高113%,w(CaO)提高24.5%.在帘线钢72A以及HRB400、SS400钢的生产实践中加以应用,使得LF处理后72A的w(Al)小于0.000 5%,HRB400、SS400的小于0.003%,避免了有害夹杂物的形成,消除了在小方坯连铸过程中的水口堵塞现象.     

Inclusion evolution in 50CrVA spring steel by optimization of refining slag

In order to control the CaO-Al2O3 -SiO 2 -MgO system inclusions in 50CrVA spring steel in a lower melting temperature region, high temperature equilibrium experiments between steel and slag were performed in the laboratory, under the conditions of the initial slag basicity within 3-7 and the con-tent of Al2O3 between 18-35 mass%, to investigate the formation and evolution of this type of in-clusion.The results indicate that the total oxygen content in the steel decreases with the increase of slag basicity and the decrease of Al2O3 content in slags, and CaO-Al2O3 -SiO 2 -MgO inclusions tend to deviate from the low melting point region with the increase of Al2O3 content in slags.The most fa-vorable composition for the refining slag is composed of 51-56 mass% CaO, 9-13 mass% SiO2 , 20-25 mass% Al2O3 and 6 mass% MgO.In this case, the inclusions in 50CrVA spring steel are mostly in the low melting point regions, in which their plasticities are expected to improve during steel roll-ing.The MgO-based inclusions were observed in the steel matrix and the formation mechanism was theoretically and schematically revealed.It is also found that adding around 11 mass% of MgO into the refining slags is beneficial to reducing the refractory corrosion.Further work should be carried out focusing on the evolution rates of MgO-based inclusions.     

304不锈钢不同精炼渣碱度下夹杂物的演变

 为了提高304不锈钢的产品质量,结合生产实际,利用热力学计算和扫描电镜能谱分析方法, 研究了硅脱氧条件下,LF精炼渣碱度对304不锈钢在LF精炼、连铸过程夹杂物变化规律的影响。试验结果表明,随着冶炼过程进行,全氧质量分数和夹杂物数量依次减小。304不锈钢采用1.75高碱度炉渣,可以得到较低的全氧质量分数和夹杂物数量,但是夹杂物中Al2O3质量分数高,夹杂物熔点高。采用1.53低碱度炉渣,钢液中全氧质量分数较采用高碱度炉渣高,但是夹杂物中CaO、Al2O3质量分数相对较低,SiO2和MnO质量分数较高,夹杂物熔点低。针对304不锈钢产品可以采用不同的生产工艺路线来满足产品的不同需求。     

Thermodynamic Modeling of Deoxidation Products and Inclusion Chemistry in Mn/Si Killed Tire-Cord Steel

The present work deals with thermodynamic modeling of oxide systems, in the context of slags and inclusions in steelmaking. The work has emphasis on oxides encountered during the production of tire – cord steel. Control of inclusion chemistry and variation in eutectic temperature and eutectic composition of MnO-Al2O3-SiO2 slag system have been studied, using Thermo-CalcR software. Relatively low liquidus temperatures are obtained for ratio of MnO / SiO2 = 0.5 - 1.5 and Al2O3 content from 10 - 20 mass%. It has been observed that the addition of Alumina leads to further increase in the liquidus temperature. The stability of inclusions is analyzed in terms of free energy values of related slag systems; and an appropriate minimum of Gibbs free energy value of slag phase observed at around 50 ppm of Oxygen. The observations could not be verified using thermodynamic experiments, but have been compared with findings in the open literature.     

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1500℃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%。