重轨钢钢液与镁质耐火材料的润湿行为

采用座滴法研究了MgO、MgAl₂O₄和MgO-CaO三种镁质耐火材料与重轨钢钢液在1 550℃下的润湿行为,结合电子显微镜分析了润湿过程中钢液对不同耐火材料的渗透程度和不同耐火材料对钢液洁净度的影响。结果表明,1 550℃下,重轨钢与MgO、MgAl₂O₄和MgO-CaO耐火材料的起始接触角分别为116.8°、133.5°和147.1°,其平衡接触角分别为97.6°、91.0°和109.4°。MgAl₂O₄耐火材料会大量溶解于重轨钢钢液中,导致钢珠表面形成大量的MgAl₂O₄夹杂物,同时容易被钢液侵蚀渗透,平均渗透深度为163.4μm; MgO-CaO耐火材料与重轨钢钢液在界面处会生成致密Ca-Si-O反应层,阻碍了钢液向耐火材料的渗透,但反应物会进入钢液并弥散在其表层;MgO耐火材料与钢液的相互作用最小,最不易对钢液的洁净度产生影响,被钢液侵蚀的程度也较小。     

钢中稀土与耐火材料的作用和加稀土钢的水口结瘤

用金相、岩相、电子探针及X射线结构分析等手段分析了浸入含稀土钢液的各类耐火材料及现场取得的浇铸含稀土钢的堵塞水口。发现不同耐火材料反应不同:氧化硅与钢液中稀土反应,形成低熔点化合物或玻璃,不但不粘附钢中的稀土夹杂物,反而造成耐火材料本身的显著冲蚀;刚玉与钢中稀土反应,形成高熔点的铝酸稀土,固态的铝酸稀土对钢液中的夹杂物粘附力并不强;由硅铝质耐火材料制成的水口,与钢液中稀土反应形成的产物为由低熔点化合物或玻璃与高熔点化合物组成的粘滞性混合物,最易于粘附钢中的夹杂物。在水口处夹杂物聚集并烧结,进一步粘附更多的夹杂物,从而造成水口的堵塞。实验还发现,氧化镁耐火材料与钢中稀土反应较弱,比较稳定。     

钙处理低合金高强钢连铸过程中塞棒侵蚀机理及其改进

针对钙处理低合金高强钢浇铸过程中塞棒的异常侵蚀问题,通过对塞棒基质层和侵蚀层进行成分分析、物相分析以及元素分布观察,并进行热力学计算分析,探究了塞棒的侵蚀机理,并提出了相应的改进措施。结果表明,钢液中过量的钙与塞棒耐火材料中的Al_2O_3、SiO_2在塞棒界面反应生成CaO,进而与塞棒耐火材料中的Al_2O_3、SiO_2反应生成低熔点的硅酸盐、钙铝酸盐等化合物是造成塞棒侵蚀的原因之一。塞棒耐火材料中的C和SiO_2反应生成气态的SiO、CO,然后钢液中的钙元素与SiO,CO等气体反应生成的CaO,进而生成低熔点的硅酸盐、钙铝酸盐等化合物,也可以导致塞棒的侵蚀。在侵蚀层中存在低熔点的钙黄长石和镁黄长石类化合物也会导致塞棒的侵蚀。通过规范钙处理量、选用镁碳质棒头等措施,可以明显改善塞棒的异常侵蚀问题,中间包连浇炉数由4～8炉提高至10炉以上。     

不同碳含量的MgO-C耐火材料与超低碳钢液的相互作用

研究了3种C含量的(3%、5%、10%,质量分数)MgO-C耐火材料与超低碳钢的相互作用。利用ICPAES、氧氮分析仪、碳硫分析仪检测了与实验MgO-C耐火材料接触的钢液的成分,用XRD分析了耐火材料反应前后的物相变化,并利用SEM观察了耐火材料/钢界面。结果表明,随着镁碳耐火材料中C含量的增加,耐火材料/钢界面附近的渗透层厚度增加;反应后钢液中的C、N、Al含量以及Mg含量随着耐火材料中C含量的增加而增加,钢中O含量随之降低;反应前后的镁碳耐火材料都有镁铝尖晶石的存在,高C含量的耐火材料反应后镁铝尖晶石含量增加,因此低碳镁碳耐火材料更有利于超低碳钢的生产。     

CaO-Al2O3-SiO2系渣中Al2O3含量对铝镁质浇注料侵蚀的影响

摘要：钢中添加适量铝元素可以提高其韧性与耐腐蚀性,但在冶炼过程中会影响炉渣中Al2O3含量而改变其与现行铝镁质浇注料的界面反应,制约钢种冶炼及品质提升。因此,采用静态坩埚法开展铝镁质浇注料的抗CaO-Al2O3-SiO2渣蚀实验,并结合热力学模拟计算探究Al2O3含量（w(CaO)∶w(Al2O3),C/A）变化对耐火材料渣蚀的影响规律,得到以下结论：随着熔渣中Al2O3含量的增加,铝镁质浇注料与熔渣反应界面越易形成更厚的高熔点隔离层,将耐火材料组分向熔渣中的直接溶解转变为间接溶解,有利于提升铝镁质浇注料的抗侵蚀性;当渣中的Al2O3质量分数在32%左右时,熔渣的侵蚀性总体较弱,但当渣中的Al2O3质量分数不小于36%时,熔渣对铝镁质浇注料产生了严重的渗透性,也易造成材料变质剥落。这为面向含铝钢冶炼用耐火材料的优化设计提供参考。     

氧气顶吹转炉初期熔渣性能对镁白云石炉衬溶解速度的影响

镁白云石耐火材料在初期熔渣中的溶解速度,是以旋转试棒及其直径的减少进行测定的。碱度及液渣中的CaO和MgO的浓度差对溶解速度的影响是主要的。FeO和MnO的影响较小。粘度小,呈均一相的液渣对镁白云石的渗透快并加速耐火材料的溶解。但当反应界面有晶体析出,局部渣呈多相熔体,提高了界面的局部粘度从而减少渗透和缓溶解。当反应界面有固体保护膜形成,可以阻止渗透并极大地降低溶解速度。     

MgO与低密度钢液相互作用及其对夹杂物的影响

 为了研究高锰高铝低密度钢液与耐火材料间的相互作用规律,以Fe-20Mn-10Al-C(20%Mn、10%Al)低密度钢液与MgO耐火材料棒在1 600 ℃时界面反应为研究对象,分别反应30和60 min后对MgO耐火材料的微观结构以及钢中非金属夹杂物特征进行了观察。结果表明,反应后MgO耐火材料转变为3层结构,分别为致密的MgO·Al₂O₃尖晶石界面层,尖晶石颗粒、钙铝酸盐和MgO颗粒组成的过渡层以及MgO颗粒组成的原始层,且随着反应时间的增加,尖晶石界面层厚度增加;在高锰高铝低密度钢液与MgO耐火材料的相互作用下,钢中非金属夹杂物主要包括单一MgO·Al₂O₃夹杂、AlN夹杂、MgS夹杂和MgO·Al₂O₃-AlN、MgO·Al₂O₃-MgS等复合夹杂物。     

钢包内衬用耐火材料对钢中非金属夹杂物的影响

 炉外精炼是炼钢流程中控制钢中非金属夹杂物的重要转折点,作为整个精炼过程中与钢液实时接触的钢包内衬用耐火材料,因为高温物理化学反应易向钢中引入夹杂物,导致精炼效果达不到预期。通过对典型现役钢包内衬用耐火材料与不同脱氧钢之间的界面反应归纳发现,钢包内衬用耐火材料会对钢中夹杂物的形貌、成分和理化性能产生影响,既可向钢中引入夹杂物,也能够吸附去除夹杂物。提出未来钢包内衬用耐火材料应被赋予更多净化钢液等功能指标的发展方向。     

微孔MgO耐火材料对钢液洁净度的影响

摘要：通过浸泡实验研究了3种镁质（致密镁质、微孔MgO质、镁碳质）耐火材料与超低碳钢液(1560℃)的相互作用,考察了不同浸泡时间(0～35min)钢中O、N、C和Al、Si、Mn含量及钢中夹杂物的成分、数量、分布等特征的变化,并对耐火材料与钢的界面层进行了观测和分析。结果表明,随着浸泡时间的延长,3组钢中氧含量均先升高再降低,均对钢液有一定的污染,钢中夹杂物的数量增加,夹杂物种类由Al2O3-MnO夹杂逐渐转变为Al-Mg-Si-Mn-O复合夹杂。与致密镁质耐火材料相比,微孔MgO质和镁碳质耐火材料与钢的界面处分别能形成连续的镁铝尖晶石层和致密的MgO层,有助于降低耐火材料的侵蚀以及对钢液的污染。此外,与不含碳的镁质耐火材料相比,镁碳质耐火材料对钢液增碳严重。因此,微孔MgO质耐火材料不仅对钢液的二次污染小、不会向钢液增碳,而且还可以吸附钢中氧化铝夹杂,更有利于超低碳洁净钢的生产。     

微孔MgO耐火材料对钢液洁净度的影响

通过浸泡实验研究了3种镁质(致密镁质、微孔MgO质、镁碳质)耐火材料与超低碳钢液(1 560℃)的相互作用,考察了不同浸泡时间(0～35 min)钢中O、N、C和Al、Si、Mn含量及钢中夹杂物的成分、数量、分布等特征的变化,并对耐火材料与钢的界面层进行了观测和分析。结果表明,随着浸泡时间的延长,3组钢中氧含量均先升高再降低,均对钢液有一定的污染,钢中夹杂物的数量增加,夹杂物种类由Al_2O_3-MnO夹杂逐渐转变为Al-Mg-Si-Mn-O复合夹杂。与致密镁质耐火材料相比,微孔MgO质和镁碳质耐火材料与钢的界面处分别能形成连续的镁铝尖晶石层和致密的MgO层,有助于降低耐火材料的侵蚀以及对钢液的污染。此外,与不含碳的镁质耐火材料相比,镁碳质耐火材料对钢液增碳严重。因此,微孔MgO质耐火材料不仅对钢液的二次污染小、不会向钢液增碳,而且还可以吸附钢中氧化铝夹杂,更有利于超低碳洁净钢的生产。     

钢包工作衬用耐火材料的研究现状及最新进展

综述了近年来钢包工作衬用耐火材料的研究现状及最新进展, 尤其对传统钢包工作衬用耐火材料的应用背景及存在问题进行了分析和汇总.在此基础上, 进一步提出了适用于超低氧钢(或洁净钢)冶炼用耐火材料的研发方向, 即通过耐火原料组分选择和结构匹配设计, 实现对耐火材料性能的精确控制.新型钢包工作衬用耐火材料需兼顾优异热机械性能的同时, 还应具备钢水净化的功能.      

功能化新型耐火材料的设计、制备及应用

围绕两种新型耐火材料展开，即钢包精炼用高性能低碳镁碳耐火材料以及超低氧钢用耐火材料，初步实验表明，将大尺寸的碳硅化铝（Al₄SiC₄）引入到镁碳砖（MgO?C）中不仅可以提高其抗氧化能力，又能对含碳耐火材料氧化后的疏松结构进行修复，有望成为新一代钢包精炼用高性能低碳镁碳耐火材料；CaO?MgO?Al₂O₃（CMA）材料兼具优异的热机械和耐渣侵性能的同时，还可以在服役过程产生低熔点精炼渣相，具备净化钢水的潜力。可以预见，上述功能化新型耐火材料有望为高品质钢的进一步发展提供有力材料支撑。      

Interaction between molten steel and different kinds of MgO based tundish linings

Abstract

Interactions between the molten steel and the refractory linings are of fundamental importance for the steelmaking industry. During the casting process, the steel cleanliness can be made worse because of the reoxidation of the molten steel in contact with the atmosphere and/or other sources of oxygen (refractories, top slag, etc.). In the industrial trial periods, four tundish refractory linings (preformed boards, two kinds of gunning materials and dry vibrating material, all MgO based refractories) were used in order to evaluate the interactions between the refractories and the molten steel. Owing to the small dimension of the tundish (5 ton) used in the continuous casting at Villares Metals SA, after casting, the chilled steel was cut in order to show, in a single section, the stopper, submerged entry nozzle, MgO ramming and the working refractory lining. Cross-sections of samples from the steel/refractory interface were investigated by electron probe microanalysis (EPMA). Four major aspects were observed at the steel/refractory interface: steel infiltration into the tundish refractory lining, mainly in the gunning materials; a steel oxidised layer formed at the steel/refractory lining interface; formation of a spinel layer between steel and tundish working refractory lining; and many particles were found in the steel phase, near to the steel/refractory interface, being a potential source of non-metallic inclusions.     

Effect of Al2O3 content in CaO-Al2O3-SiO2 slag on corrosion resistance of alumina magnesia castable

The toughness and erosion resistance of steel can be improved by adding an appropriate amount of aluminum. However it will increase the content of Al2O3 in slag and react with the existing alumina magnesia castable, and affect smelting and quality of steel. Therefore, static crucible method was applied, corrosion experiments of the CaO-Al2O3-SiO2 slags on the alumina magnesia castable were carried out, and the influence of Al2O3 content (w(CaO)∶w(Al2O3), C/A ratio) on slag corrosion resistance was investigated by combining thermodynamic simulation. The following conclusions were obtained: with the increase of Al2O3 content in the slags, the thicker isolation layer with high melting point is easier to form at the reaction interface between alumina magnesia castable and the slags. The direct dissolution of the refractory components into the slags can be changed to indirect dissolution, which is conducive to improving the corrosion resistance of alumina magnesia castable. Nevertheless, when the content of Al2O3 in the slag is about 32 wt.%, the slag corrosion is generally weak, when the content of Al2O3 in the slag is more than 36 wt.%, the slag has serious permeability to the alumina magnesia castable, which is easy to cause the deterioration and spalling of the material. It provides guidance on the optimization and design of the refractories for Al containing steel smelting.     

A study on the mechanism of reaction between refractory materials and aluminium deoxidised molten steel

The conditions of formation of inclusions in steel during ladle refining in MgO-C lined ladles have been investigated in laboratory experiments at 1873 K in MgO-C crucibles with 50 g iron. From both the experimental results as well those of a thermodynamic study conducted in parallel, the following conclusions can be made about the reaction mechanism between the MgO-C refractory and aluminium deoxidised molten steel: At steelmaking temperature an internal oxidation-reduction occurs in the MgO-C refractory. The formation of a thin oxide layer at the interface is due to the reaction between magnesium vapour and aluminium dissolved into the molten steel and the CO(g) generated by the reaction between MgO and C in the crucible walls. The oxide inclusions formed in the steel have been shown mainly to consist of MgO, Al₂O₃ or mixture of them. Some of the finest inclusions are considered to be formed as secondary inclusions during cooling and solidification of the steel and they are connected only with the diffusion of magnesium from the crucible to the molten steel. The thermodynamic calculations indicate that during vacuum refining, as the pressure decreases, the chemical compatibility of carbon-bonded magnesia for ladle lining decreases.     

Transient flow and heat transfer in a steelmaking ladle during the holding period

Transient, turbulent flow and heat transfer in a ladle during the holding period are numerically investigated. The ladle refractories including the working lining, safety lining, insulation layer, and steel shell have been simultaneously taken into account. No assumptions are made for the heat transfer between the liquid steel and the inside ladle walls. Both the initial ladle heating and the heat loss from the slag surface are changed to examine their effect on thermal stratification in molten steel. A simplified model for the heat loss from the molten steel to the refractory is proposed. Correlations for the history of mean steel temperature, thermal stratification, and heat loss rate are obtained, which can be easily applied for industrial operations. Predictions are compared with experimental data in an industrial ladle and a pilot plant ladle, and those from previous studies.     

耐火材料对95Cr切割丝用钢中夹杂物的影响

 为了开发更优质的耐火材料以提高切割丝用钢的洁净度,试验采用MoSi₂炉研究了MgO、MgO-CaO两种耐火材料对95Cr切割丝用钢中夹杂物的影响。结果表明,MgO、MgO-CaO两种坩埚冶炼均能使钢成分控制在目标范围内,夹杂物成分落点控制在目标低熔点区内。但与MgO坩埚相比,MgO-CaO坩埚净化钢液的效果更好,主要表现为两个方面。一方面,钢中P、S、Al_s、T[O]含量均更低。特别是w([S])可降低至0.000 6%,w([Al]_s)降低到0.000 3%,w(T[O]) 降低到0.000 5%。另一方面,钢中夹杂物数量更少、尺寸更小、复合夹杂物中Al₂O₃的含量更低。具体表现为,经MgO-CaO坩埚冶炼后,钢中等效直径小于2 μm的夹杂物所占比例为91%,而经MgO坩埚冶炼的钢,此项值仅为78%;经MgO-CaO坩埚冶炼后,钢中复合夹杂物中w([Al₂O₃])几乎都低于10.0%。这主要是因为MgO-CaO耐火材料中的MgO、CaO均能脱磷,同时CaO还有间接脱硫、去除钢中Al₂O₃夹杂物的作用。