高炉炉缸凝铁层物相分析

在高炉炉缸破损调研的基础上对高炉炉缸耐火材料热面凝铁层进行取样,利用扫描电子显微镜、物相分析等分析手段揭示了凝铁层的物相组成,并运用Thermol-calc热力学计算软件结合TCFE8数据库对铁水中石墨碳的析出温度及析出相分数进行了计算,最后揭示了炉缸凝铁层物相的形成机理.结果表明,高炉炉缸凝铁层主要由Fe相和石墨碳相交替分布组成,铁水成分对石墨碳析出温度影响较大,石墨碳析出温度远高于铁水凝固温度,铁水中C、Si元素含量对石墨碳析出相分数影响较大,而石墨碳析出相可增大铁水黏度11.9%.凝铁层中石墨碳的析出主要是由于Fe-耐火材料界面温度低于石墨碳析出温度,使得铁水中C不断向耐火材料热面迁移,进而形成Fe-C交替的分层结构.     

石墨/Ni+Ti体系润湿性研究

陶瓷/金属润湿性研究对于陶瓷-金属连接以及金属陶瓷复合材料的制取有重要意义。采用座滴法研究了石墨/Ni+Ti体系的润湿性。测定了不同成分的焊料与石墨基体的接触角,并研究了界面结构和成分。1340℃时,在真空中石墨/Ni平衡接触角为78°,保温时间对接触角没有显著影响。添加剂Ti的质量分数达到40%后,能显著改善润湿性,在这种情况下,接触角随保温时间延长而减小。润湿界面存在明显的元素互扩散现象。     

沙钢3号高炉经济高效低钛护炉实践

针对沙钢3号高炉炉缸侧壁温度持续升高现象,提出了经济高效低钛护炉方案.经济高效低钛护炉,就是以析出石墨碳为核心,提高铁水[C]含量,降低铁水中碳不饱和度,改善炉缸活性,促进炉缸石墨碳析出.3号高炉低钛护炉期间,逐步减少钒钛矿使用量,铁水[Ti]降低至0.08％以下,炉缸侧壁炭砖温度基本处于400℃以下.同时,高炉日产量...     

Cu-Ti合金中Ti含量对C/C复合材料润湿性能的影响

利用超高温接触角测量仪、光学显微镜、扫描电镜、X射线衍射仪研究Ti含量对Cu-Ti合金与C/C复合材料润湿性的影响。结果表明,随Ti含量增加,Cu-Ti合金对C/C的接触角逐渐降低。当Ti的质量分数为4.8%时,接触角降低到90°以下,Cu-Ti合金与C/C复合材料部分润湿;当Ti的质量分数为8%时接触角降为0°,Cu-Ti合金与C/C复合材料完全润湿。润湿界面形貌与Ti含量相关,当Ti含量为8%时,界面出现宽大的层状剪切裂纹;当Ti含量为12%时,界面致密无裂纹,Cu-Ti合金能较好地渗入C/C复合材料中的孔隙;当Ti含量为16%时,界面出现数量较多的细小裂纹,Cu-Ti合金熔体中的钛元素向界面扩散形成富钛层,并与C/C复合材料中的碳元素反应生成厚度为3~5μm的连续TiC层,该TiC层可改善合金对C/C复合材料的润湿性能。     

高炉铁水中硫加速炉缸炭砖侵蚀机理及对策

为了延缓炉缸炭砖侵蚀，分析了炉缸铁水硫含量变化趋势，研究了硫元素加速炉缸炭砖侵蚀机理，提出了现代大型高炉脱硫技术措施。结果表明：高炉-铁水预处理联合脱硫、使用高比例球团是炉缸铁水硫含量升高的主要原因；炉缸炭砖与碳含量欠饱和的铁水接触是炭砖侵蚀的直接原因，硫含量升高使铁水表面张力下降、黏度下降，提高了界面反应速率，增大了铁水中碳的传质系数，加速了炭砖侵蚀。在低渣比条件下，控制炉渣碱度在1.12～1.18,MgO含量在9%～12%,Al₂O₃含量在13.5%～15.5%,并提高铁水中碳、硅、磷元素含量，降低锰、钛元素含量，采用控制炉渣成分和铁水成分的协同脱硫技术，是现代大型高炉脱硫的有效措施。     

焦炭床内铁水渗碳行为

摘要：高炉冶炼过程中铁水最终渗碳量接近饱和,相比而言,闪速炉中没有固体炉料的压迫作用,无法发生像高炉炉缸内死料柱根部与铁水之间的渗碳反应,最终渗碳量难以预料。为此,以电解铁和化学纯石墨为原料,利用管式电阻炉升温到1855K熔化铁块,以高纯Ar作为保护气体研究焦炭床内铁水渗碳行为,并对铁水渗碳行为进行数值模拟,为闪速炼铁工业化打下基础。实验结果表明,终铁C含量随焦炭粒度增大和渗碳床高度降低而减小,且铁水初始C含量对终铁C含量具有较大影响。对于不同条件下铁水渗碳反应中C元素的迁移规律,基于VB编程技术进行了数值模拟,模拟结果与高温实验结果较吻合,相对误差在3%以内。渗流速度控制因子始终控制在05左右,即铁水在焦炭床中的平均速度为初始滴落速度的一半左右。     

焦炭床内铁水渗碳行为

高炉冶炼过程中铁水最终渗碳量接近饱和,相比而言,闪速炉中没有固体炉料的压迫作用,无法发生像高炉炉缸内死料柱根部与铁水之间的渗碳反应,最终渗碳量难以预料。为此,以电解铁和化学纯石墨为原料,利用管式电阻炉升温到1 855K熔化铁块,以高纯Ar作为保护气体研究焦炭床内铁水渗碳行为,并对铁水渗碳行为进行数值模拟,为闪速炼铁工业化打下基础。实验结果表明,终铁C含量随焦炭粒度增大和渗碳床高度降低而减小,且铁水初始C含量对终铁C含量具有较大影响。对于不同条件下铁水渗碳反应中C元素的迁移规律,基于VB编程技术进行了数值模拟,模拟结果与高温实验结果较吻合,相对误差在3%以内。渗流速度控制因子始终控制在0.5左右,即铁水在焦炭床中的平均速度为初始滴落速度的一半左右。     

炼铁过程熔融渗碳行为研究

传统高炉冶炼过程中铁水最终含碳量是饱和的,而闪速炉中反应是在物料漂浮阶段发生,没有固态料柱的压迫作用,无法发生高炉炉缸内固体炉料与铁水的渗碳作用,最终铁水含碳量未知。为此对闪速炼铁炉中熔池底部渗碳反应进行了研究。首先,对铁碳相图进行了理论研究,基于此理论分析探讨了反应时间、焦炭粒径、焦炭床层高度及原料失重率等因素对铁水最终含碳量的影响。得出了最佳工艺条件为反应时间240 min、焦炭粒径5～8 mm、焦炭加入量70 g、原料失重率26%,在此最佳工艺条件下含碳量最大为4.73%。为了进一步探究渗碳过程中铁碳合金中元素的分布规律,对含碳量为4.73%的铁碳合金进行了SEM-EDS表征,结果显示条棒状石墨碳呈凝聚态不规则嵌布在铁碳合金中,在石墨碳边缘呈现两种不同衬度,分别为FeC相和Fe_3C相。     

炉缸炭砖侵蚀过程及基于AHP的界面反应调控

 为了延缓炉缸炭砖侵蚀,基于炉缸破损调查试样分析和试验结果,研究了炉缸炭砖侵蚀过程,提出了基于层次分析理论(analytic hierarchy process,AHP)的界面反应综合调控技术。结果表明,炭砖侵蚀经历3个过程:铁水润湿炭砖、铁水渗透炭砖和铁水溶解炭砖。非稳态下铁水对炭砖的润湿作用使界面迅速由气-固界面转变为液-固界面;铁水渗透在炭砖微晶结构的作用下呈现出树枝状特征,且渗透面积越大、渗透延展度越高,炭砖脆化现象就越明显;在铁水碳欠饱和度的作用下,脆化的炭砖易溶解进入铁水中,导致炭砖被侵蚀。基于AHP的界面反应综合调控技术可帮助高炉操作者明确调控方向和调控重点措施,应从铁水成分调控和炭砖性能调控的几个关键技术采取措施以延长炉缸寿命。     

高炉炉缸碳源渗碳性能及动力学

摘要：提高铁水碳饱和度,减弱侧壁炭砖侵蚀,实现炉缸长寿对高炉炼铁具有重要意义。利用静态法系统地研究了高炉系统中进入炉缸铁水的碳源的渗碳性能,并计算了表观反应速率常数K。研究结果表明,不同碳源的渗碳性能由强到弱为：NMA炭砖>碳棒>煤粉>焦炭>9RDN炭砖。碳源的渗碳性能随其石墨化程度的升高而降低。碳源中的灰分会极大影响其渗碳性能,但以团聚大颗粒形式存在的灰分并不能减弱其渗碳能力,同时Al2O3可明显降低碳源的渗碳速率。9RDN炭砖的渗碳性能低,预示着其可适应更加复杂的炉况条件。煤粉和焦炭渗碳性能偏差,煤粉以及炉料下行过程形成的焦粉进入炉缸会降低死料柱空隙度,造成炉缸不活跃,使得炉况波动频繁,并不利于死料柱渗碳和侧壁保护层的稳定。因此,要适当提升入炉焦炭粒度,增大风量,减弱未燃煤粉及焦粉对炉缸侧壁炭砖长寿的负面影响。     

Falling Angle of Fe-C-Based Alloy Droplet on Coke and Graphite

The hold-up of molten pig iron and slag melt in the coke packed bed of blast furnace (BF) causes a decrease of void between coke lumps and inhibits gas permeability. Smooth dripping of those liquids in the coke bed is desirable to keep the productivity of BF. Herein, the conditions for smooth flowing of molten iron on coke surface are calrified, and the falling angles of Fe-C and actual pig iron droplets on coke and graphite are measured at high temperature. It is found that Fe-C droplet easily slids down on coke because of small falling angle, and the falling angle of actual pig iron is even smaller, while those droplets adhere to a graphite substrate. The carbon in iron has only a small effect on the static contact angle with coke, but has a great influence on the falling angle. From the viewpoint of the roughness of coke surface, the variation of static contact angle and falling angle is discussed.     

Influence of melt carbon and sulfur on the wetting of solid graphite by Fe-C-S melts

The interfacial phenomena between carbonaceous materials such as graphite, coke, coal, and char and Fe-C-S melts are important due to the extensive use of these materials in iron processing furnaces. However, the understanding of the interfacial phenomena between these kinds of carbonaceous materials and molten iron alloys is far from complete. In this study, graphite was selected as the solid carbonaceous material because its atomic structure has been well established. The sessile drop method was adopted in this investigation to measure the contact angle between solid graphite and molten iron and to study the interfacial phenomena. The influence of carbon and sulfur content in Fe-C-S melts on the wettability of solid graphite has been investigated at 1600 °C. The melt carbon content was in the range of 0.13 to 2.24 wt pct, and the melt sulfur content was in the range of 0.05 to 0.37 wt pct. X-ray energy-dispersive spectrometer (EDS) analysis was conducted on an HITACHI S-4500 scanning electron microscope to detect composition distribution at the interfacial region. It was found that contact of solid graphite with Fe-C-S melts will result in a nonequilibrium reactive wetting. It involved carbon transfer from the solid to the liquid and iron transfer from the liquid to the solid. The Fe-C-S melts exhibited relatively poor wetting when the reactions were absent. The mass transfer between solid graphite and Fe-C-S melts was observed to strongly enhance the wetting phenomena. It is proposed that the decrease of system free energy corresponding to the mass transfer reactions strongly influences the formation of the interface region and results in the progressive spreading of the wetting line. The composition and thickness of the graphite/iron interfacial layer was dependent on the intensity of mass transfer across the interface. The resulting change in the interfacial energy γ _ls is a strong function of mass transfer, and it varies in accordance with time of contact. The influence of carbon content on the wetting phenomena could only be seen at in the initial stages, whereas the influence of sulfur on the wettability was found when the system approached equilibrium. Therefore, the interfacial tension in its equilibrium condition at the graphite/Fe-C-S melt interface was determined only by the extent of sulfur adsorption at this interface.     

Influence of ash on mass transfer and interfacial reaction between natural graphite and liquid iron

The interfacial reaction is a factor that plays an important role in governing the rate of many metallurgical processes. In the direct iron smelting process, interfacial reactions of carbonaceous materials, such as coals, with molten iron is one of the key factors that dictate the rate of carbon transfer from the carbonaceous materials into molten iron and establish a carbon concentrated melt to reduce iron oxide in the slag phase. In the current investigation, wetting of natural graphite, which contains 8.8 pct ash, by iron was studied in a horizontal tube furnace at 1600 °C using the sessile drop approach to establish a fundamental understanding of the influence of ash on interactions between graphite and iron. The mass-transfer phenomena between the solid substrate and the iron droplet were studied by withdrawing the assembly at different time intervals. After the wetting experiment, the contacting surface of the iron droplet was observed by a field emission scanning electron microscope (FESEM). The components of the interfacial layer formed during the experiment were examined by energy dispersive spectroscopy (EDS). The change in the carbon and sulfur contents of the droplet at different time intervals during the wetting experiment was analyzed by a LECO carbon and sulfur analyzer. It was found that the formation of an ash interfacial layer between the carbonaceous materials and the liquid iron has a strong influence on the mass transfer and interfacial reaction. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

含碳球团熔融渗碳机理

使用CaO-SiO_2-Al_2O_3合成渣与磁铁矿、石墨粉制备含碳球团,考察了球团中渣相成分、渣量以及碳含量对铁水渗碳量的影响,并探讨了含碳球团内铁的熔融渗碳行为和机理。结果表明,熔融渗碳分为熔融还原渗碳以及铁熔体聚合过程渗碳2个阶段,前一阶段熔渣中Fe2+含量与铁的渗碳量处于动态平衡过程,主要受熔渣化学成分的影响;后一阶段的渗碳过程决定铁的物理渗碳极限,主要与铁、碳颗粒的接触条件有关,且熔渣中Fe2+的还原极限与渣相碱度和SiO_2绝对含量有关,铁的熔融渗碳量(质量分数)可以达到4%左右,满足铁锍分离要求。     

Carburizing performance and kinetics of carbon sources in blast furnace hearth

It is of great significance to improve the carbon saturation of molten iron which weakens the erosion of sidewall carbon bricks, so as to realize the hearth longevity. Carburizing properties of various carbon sources in molten iron by static method was systematically investigated. The apparent reaction rate constant K of samples was calculated. The results show that the carburizing properties of different carbon sources from strong to weak are NMA carbon brick > carbon rod > pulverized coal > coke > 9RDN carbon brick. The carburizing performance of carbon sources decreases with the increase in its graphitization degree. Ash has a negative effect on the carburizing performance of carbon sources, but ash in the form of agglomerated large particles cannot weaken the carburizing performance of carbon sources. The Al2O3 phase can obviously degrade the carburizing performance of carbon sources. The 9RDN carbon bricks with low carburizing properties can be adapted to more complex furnace conditions. The carburizing properties of pulverized coal and coke are relatively weak. When the pulverized coal and coke powder formed in the tuyere raceway enter the hearth, the porosity of the deadman will be reduced, resulting in hearth inactivity and frequent fluctuation of furnace condition, and it is not conducive to the carburization of the deadman. Therefore, it is necessary to properly improve the coke particle size and increase the air volume for weakening the negative effects of unburned coal powder and coke powder on the longevity of the hearth sidewall carbon bricks.     

高炉焦炭在铁水中溶解行为研究现状及展望

在当前及未来大型高炉高冶炼强度的条件下,加快焦炭在铁水中的溶解速率、提高高炉炉缸铁水的碳饱和度是削弱碳不饱和铁水对炉缸炉衬侵蚀、保证炉缸正常工作及延长高炉寿命的重要措施,同时可以为下游的炼钢工序提供部分热量来源。首先对国内外焦炭在铁水中溶解的试验和模拟研究方法进行了概括,然后对焦炭自身结构性能、焦炭中矿物质、铁水的物理性质等影响焦炭溶解速率的因素进行了详细分析。结果表明,碳结构的有序度和铁水温度的升高有利于焦炭的溶解,而焦炭中矿物质及铁水中硫、磷等元素的存在会抑制铁水的进一步渗碳。研究结果为高炉操作者理解焦炭在铁水中的溶解行为提供借鉴,指导钢铁工业的节能减排。     

Analysis on the stamping coke dissolution of hot metal in the blast furnace hearth

By utilising the carburiser-cover methods, this article mainly focuses on the impacts of different carbon sources on hot metal carburising in the blast furnace hearth. The carburising rate, an indicator of the evaluation of coke including stamping coke and graphite, is compared at 1450–1550°C. Additionally, the apparent activation energy of carburisation of coke 1, coke 2 and graphite are 236.9, 178.8 and 46.0?kJ?mol^?1, respectively. The difference in activation energy for the three carbon sources in question is attributed to the mineral matters in coke, because it is capable of influencing the effective contact interface area between the liquid iron and carbon. As to the overall viscosity of the interface layer between the hot metal and carbon, it is mainly affected by the temperature and ash content and its composition. When the temperature increases from 1450 to 1550°C, the viscosity of the minerals on the interface layer will decrease correspondingly. The defined surface area of mineral reduces from 86.7 to 70.7% in coke 1 and from 82.5 to 69.3% in coke 2. Finally, to improve the carburising rate the basicity of the oxide contents in the coke should be increased by adding CaO or MgO.     

电场作用下熔铁与铝碳质水口耐材间的润湿和侵蚀行为

摘要：探究了外加电场作用下铁熔体与水口组成材料间的润湿和侵蚀行为。通过高温电润湿实验可知,在铁熔体和水口组成材料基板间施加电场,促进了铁熔滴与固体基板间的润湿,且在一定电场强度范围内,固 液相间的接触角随着电场强度的增加而减小,固 液相间的润湿性变好。对电润湿后两相界面的微观结构进行了分析,结果表明外加电场促进了铁熔体与水口组成材料间的原子迁移,显著改善固液两相界面间的传质、扩散和溶解等作用。电润湿反应过程中铝碳水口表面经脱碳后产生了孔隙,并且在外加电场作用下铁熔体易于向水口基板内部渗透,导致铁熔体对铝碳水口的侵蚀程度较高纯石墨和氧化铝基板更为严重。