炉外精炼用耐火材料提高寿命的途径及其发展动向

结合VOD与RH介绍了造成炉外精炼蚀损严重部位的原因。从MgO-Cr2O3、MgO-CaO、MgO-C、MgO-CaO-C、MgO-MgO·Al2O3等耐火材料性能及在精炼中的作用介绍了如何选择耐火材质;从接触角、熔渣粘度、形成高熔点化合物、气孔微细化以及炉渣成分控制、双饱和与精炼温度等方面介绍了提高炉外精炼用耐火材料寿命的途径。最后结合镁铬、镁钙、MgO-C、镁钙碳与无铬耐火材料介绍了炉外精炼用耐火材料的发展动向,并对MgAlON结合镁质耐火材料在炉外精炼中的研究与应用进行了评估与预期。     

不同碱度的脱硫渣对RH用镁铬砖的侵蚀

随着RH精炼技术的发展,在真空槽内顶加脱硫剂脱硫的RH真空脱硫技术已成为RH多功能化的一个重要方面。目前,RH真空脱硫技术常采用CaO-CaF2渣系,但该渣系对RH真空槽和插入管耐火材料的侵蚀较大,严重制约了该技术的推广应用。近年来,冶金工作者在开发低氟或无氟RH脱硫用预熔精炼渣脱硫方面取得了较大进步,获得了较好的工业应用效果,但采用该渣系仍对RH下部真空槽和插入管内部耐火材料造成一定程度的侵蚀,而其侵蚀机理目前尚不十分明确。因此,对RH用精炼脱硫渣对RH用镁铬砖的侵蚀行为进行研究具有重要的意义。本试验采用旋转圆柱体…     

钢液对连铸用含碳耐火材料的侵蚀作用研究

采用中频炉的实验室模拟试验(试验条件:钢液温度1600℃,浸入时间30min,气氛分别为空气和真空)和通过对用后耐火材料的显微结构分析,研究了钢液对3种连铸用含碳耐火材料(Al2O3-C、MgO-C和ZrO2-C)的侵蚀作用。结果表明,脱碳层的形成及钢液中夹杂物与脱碳层中耐火氧化物的反应是材料蚀损的主要原因。因此,在含碳耐火材料接触钢液的表面形成致密耐火层,能有效抑制钢液对连铸用含碳耐火材料的侵蚀。     

水煤浆气化炉耐火材料的损毁原因及改进

分析了水煤浆气化炉用耐火材料的损毁原因,认为熔渣侵蚀、剥落和机械磨损是导致炉衬耐火材料损毁的主要因素,其中以剥落为主;引起剥落的原因是多方面的,包括熔渣渗透引起的结构应力、温度变化引起的热应力、体积膨胀引起的机械应力及组分价态变化引起的体积效应等。以减少熔渣渗透为目的,通过添加适合金属外加剂,研制的新产品具有更高的体积密度和更小的气孔直径,预计可提高炉衬使用寿命10%以上。     

烧结点火炉炉衬耐火材料损毁原因分析

对某大型烧结厂点火炉的大修情况进行了跟踪和破损调查,并取样分析,探讨了炉衬损毁原因。得出结论:烧结混合物在高温下与点火炉炉衬接触,粘附到点火炉炉墙上,形成挂渣;渣通过耐火炉衬上的孔隙、裂缝进入其内部,其主要成分氧化铁逐渐扩散,与耐火材料发生反应,使其变质、侵蚀直至开裂、脱落。     

RH/DH炉用优质MgO-Cr_2O_3砖与无铬砖

据Veitsch－Rades报道，MgO－Cr2O3砖是RH／DH真空脱气炉用主要炉衬材料，包括直接结合砖，MgO－Cr2O3共合成熟料砖，熔粒再结合砖等。RH炉衬砖蚀损的主要原因有：①高温下富硅渣或含铅酸盐渣向砖内气孔的渗入；②渗人物与砖中方镁石及硅酸盐相反应生成三元低熔点硅酸盐相；③渗人带由于高温侵蚀造成的连续蚀损；④由于剥落造成的非连续性蚀损。针对这些因素，开发出了致密、透气性低、强度高、结构塑性好的新一代镁铬砖，其主要物理性能为体积密度3．379·cm－‘，气孔率13．5％，常温耐压强度85MPa，高温抗折强度llMPa。使用寿命…     

VHD精炼炉炉盖整体预制块的研制与应用

东北特殊钢集团抚钢股份有限公司第二炼钢厂VHD精炼炉的主要工艺参数见表1。VHD精炼炉的炉盖采用磷酸结合不烧高铝电炉顶砖砌筑,寿命一直较低(平均寿命不足80次),且波动大。研究发现,影响VHD精炼炉炉盖耐火材料使用寿命的主要因素为:1)熔渣侵蚀造成的结构剥落;2)VHD精炼炉为间歇操作,急冷急热频繁,导致耐火材料产生严重的热剥落;3)由于吹氩搅拌,钢水频繁喷溅到炉盖上,对耐火材料造成磨损。由于炉盖寿命低,炉盖更换频繁,不但严重影响了VHD炉的正常生产,而且剥落的耐火材料增加了钢中的非金属夹杂物。为此,有必要研制出一种适合VHD精…     

协同处置城市生活垃圾对水泥窑用耐火材料的侵蚀

为了合理选配水泥窑协同处置垃圾生产线用耐火材料,采用静态坩埚法并借助SEM研究了焚烧城市生活垃圾对水泥窑用耐碱砖、抗剥落高铝砖的侵蚀。结果表明:焚烧城市生活垃圾对水泥窑用耐火材料的侵蚀机制主要为渣渗透和渣侵蚀,焚烧垃圾时产生的含碱、硫、氯等的高温气体和耐火材料发生发应,生成了低熔点的硫酸盐、氯盐以及复合盐,使耐火材料产生反应变质,而反应变质层结构疏松,在热应力的作用下易造成剥落。因此,协同处置垃圾的水泥窑用耐火材料的选配应考虑到材料的抗侵蚀性和抗剥落性等因素,建议分解炉选用抗剥落高铝砖和抗结皮Si C浇注料,而预热器选用高强耐碱砖和高强耐碱浇注料。     

优质镁钙砖在AOD精炼炉上的应用

目前 ,AOD炉用耐火材料大体分为镁铬砖、镁白云石砖(镁钙砖 )及白云石砖 3种。欧洲的AOD炉衬普遍采用煅烧白云石砖 ,日本的AOD炉大多数仍采用MgO -Cr2 O3 砖 ,也有的采用综合砌筑 :风眼区 10层以下使用MgO -Cr2 O3 砖 ,前墙、炉底及其他部位使用MgO -CaO砖。太钢 18tAOD炉建成初期 ,炉衬全部使用镁铬砖。随着镁钙质材料的开发 ,在风眼区以外的部位逐步推广使用镁钙砖 ,风眼区一直使用电熔半再结合镁铬砖。这样的材料选择和综合砌筑方法一直延续到2 0 0 0年。随着AOD的扩容改造和单渣法精炼工艺的推行 ,MgO -Cr2 O3 砖区的侵蚀…     

德士古水煤浆气化炉耐火衬里介绍

简要介绍了耐火材料被熔渣侵蚀的机理，给出了水煤浆气化炉耐火衬里的性能指标及炉衬结构。     

Refractories for RH Degassers and Ways of Improving Their Lining Life

This paper attempts to clarify the systematic works of the refractories for the RH degassers and the ways of improving their lining life.It includes: (1) types of RH degassers; (2) the operating conditions of refining and the severely damaged areas in RH degassers; (3) the reasons why side wall and bottom of lower vessel, throat and snorkels become the severe wear areas are analyzed, such as erosion and abrasion caused by the high circulation rate of treated molten steel, thermal and structural spalling by ...     

Designing environment-friendly chromium-free Spinel-Periclase-Zirconia refractories for Ruhrstahl Heraeus degasser

Ruhrstahl Heraeus (RH) degassers are globally used to manufacture vacuum-treated steel for automotive and railroad applications. The state-of-the-art environment-friendly chromium-free alternatives for direct-bonded magnesia-chrome refractories used in RH degassers are expensive, and the scientific literature lacks direct correlation between materials chemistry, processing, and functional properties. We have designed a novel spinel-periclase-15 wt% ZrO₂ composition containing 14 wt% in situ spinel which exhibited 7.2 MPa hot modulus of rupture (1500℃), exceeding all reported Cr-free refractories for RH degasser applications. Investigation with scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) attributed this improvement to a reduction in interparticle Ca and Si content which forms low-melting phases, as supported by FactSage thermodynamic simulations. The spinel-periclase composition SP exhibited superior thermal shock resistance because thermal shock-induced cracks were stopped by fracture porosity around MgO particles, formed due to thermal expansion mismatch. SEM-EDS analysis of the SP composition corroded by RH slag at 1650°C revealed that Fe is the most corrosive element followed by Ca and Si. Contradicting the consensus, it was observed that corrosion resistance of fused MgO was better than that of ZrO₂. The cubic ZrO₂ phase reduced FeO_x penetration locally by incorporating CaO from the RH slag into a solid solution and forming a CaZrO₃ phase creating a “slag barrier”. Lastly, pore size was found to greatly exacerbate slag penetration following the Washburn percolation model.     

Experimental Investigation of Air Relative Humidity (RH) Cycling Tests on MEA/Cell Aging in PEMFC Part I: Study of High RH Cycling Test With air RH at 62%/100%

The effect of high air relative humidity (RH) cycling (RH_C 62%/100%) on the degradation mechanisms of a single (5 × 5 cm²) proton exchange membrane fuel cells was investigated. The cell performance was compared to a cell operated at constant humidification (RH_C = 62%). Runs were conducted over approximately 1,500 h at 0.3 A cm^–2. The overall loss in cell performance for the high RH cycling test was 12 μV h^–1 whereas it was at 3 μV h^–1 under constant humidification. Impedance spectroscopy reveals that the ohmic and charge transfer resistances were little modified in both runs. H₂ crossover measurement indicated that both high RH cycling and constant RH test did not promote serious effect on gas permeability. The electroactive surface loss for anode and cathode during high air RH cycling was more significant than at constant RH operation. The water uptake determined by ¹H nuclear magnetic resonance within the membrane electrode assembly (MEA) after high RH cycling was reduced by 12% in comparison with a fresh MEA. Transmission electron microscopy showed bubbles and pinholes formation in the membrane, catalyst particles agglomeration (also observed by X‐ray diffraction), catalyst particles migration in the membrane and thickness reduction of the catalytic layers. Scanning electron microscopy was conducted to observe the changes in morphology of gas diffusion layers after the runs.     

RH插入管的技术改进

介绍了RH插入管的使用条件、损毁机理,并从浇注料、镁烙砖、金属壳体等几方面入手,对现用插入管进行了技术改进。改造后的产品在大钢二炼钢RH炉上使用,最高寿命达到了108次,基本上满足了生产需要。     

Development and Application of Chrome-free Refractory Materials for RH Degasser

The research progress and industrial application of chrome-free refractories for RH degasser were introduced in the paper.It is proved that unburned magnesia-spinel refractories used for RH throat and snorkel in Baosteel have longer service life compared with traditional direct bonded fused magnesia-chrome materials.The new developed chrome-free unburned magnesia-spinel composite can fully meet the present demand for RH operation and can be applied extensively for RH processing.At present,instead of chrome-containing materials,chrome-free refractories have been applied widely for RH in Baosteel.Super low carbon MgO-C material with high mechanical properties at mild and high temperatures can be an alternative chrome-free material for RH.     

单元机组再热汽温控制系统

介绍单元发电机组锅炉的特点及再热蒸汽温度常规控制方案,并结合实际工程给出了超临界大型火电机组通常采用的摆动燃烧器控制再热汽温的系统设计方案及控制策略。     

Corrosion Resistance Mechanism of Magnesia Zirconia Brick to RH Furnace Slag

Magnesia zirconia brick containing 11 wt% zirconia was prepared with magnesia and monoclinic zirconia as starting materials in order to replace the chrome-containing materials for RH furnace.The corrosion resistance of magnesia zirconia brick and fused rebonded magnesia chrome brick (short for magnesia chrome brick) to high and low basicity slag of RH furnace was comparatively researched by rotary slag method and their slag resistance mechanisms were analyzed.The results show that:(1) because the reaction l...     

Limonene transport and mechanical properties of EVOH and nylon 6,6 films as influenced by RH

The transport properties of d‐limonene through ethylene vinyl alcohol copolymers (EVOH) and nylon 6,6 films as functions of relative humidity (RH) and temperature were studied. Permeation properties of these polymers were strongly influenced by temperature and RH. Compared to the EVOH films, the nylon 6,6 film had much greater limonene permeability. Mechanical property studies indicated that both the tensile modulus and yield strength of the EVOH films decreased with an increase in RH. The polymer changed from being stiff and brittle at low RH to being soft and ductile at high RH. In addition, ethylene content and orientation were found to affect the transport and mechanical properties of limonene through EVOH polymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1949–1957, 2001     

Development and Application of High-Performance Magnesia-Chrome Bricks for RH Degasser

The paper analyses the wear mechanism of magnesiachrome bricks for snorkel of RH degasser.High-performance magnesia-chrome bricks with good resistance to molten slag and infiltration resistance have been manufactured by means of reasonable fabricating technology.The application results of the developed magnesia-chrome bricks at 300t RH degasser of Baosteel indicate that the lining life has been increased up to 150 heats.     

不同弓形浸渍管RH钢液流动行为的物理模拟

为提高真空循环脱气(RH)真空精炼的效率,设计了3种新型弓形浸渍管RH真空室,并建立了物理模型。通过水模拟实验研究了浸渍管形状、提升气体流量、浸渍管浸入钢液深度对弓形浸渍管RH和传统圆形浸渍管RH钢液循环流动的影响。结果表明,在实验气体流量范围内,3个弓形浸渍管RH比传统圆形浸渍管RH的循环流量增加了45%~218%,均混时间减少了15%以上。圆形浸渍管RH达最大吹气流量时,3种弓形浸渍管RH的循环流量仍线性增加。新型弓形浸渍管RH的最大提升气体流量可在传统圆形浸渍管RH提升气体流量(60?130 m3/h)的基础上提高48%以上,方便短时间、高强度真空精炼操作。3种新型弓形浸渍管RH的循环流量随提升气体流量增加而线性增大,随浸渍管浸入钢液深度增加而增大,均混时间随提升气体流量和浸入深度增加而减小。现场应用时,弓形浸渍管其中2个面积较小的浸渍管浸入深度须大于545 mm,面积最大的浸入深度须大于818 mm,3个弓形浸渍管RH的最大提升气体流量需控制在约173 m3/h。在现场现行的提升气体流量范围(60~130 Nm3/h)内,1#, 2#和3#弓形浸渍管RH的循环流量较传统圆形浸渍管RH分别约增加100%, 42%和112%,均混时间分别缩短30%, 15%和34%以上。在实验提升气体流量范围内,非对称弓形浸渍管RH的循环流量最大,均混时间最少。