Effect of carbon recycle materials on properties of bench scale prebaked anodes for aluminum smelting

Bench scale aluminum smelting anodes were produced from aggregates having butts contents of 0 to 40 wt pct, from 100 pct mixer scrap or 100 pct green anode scrap, and from aggregates having used potlining contents of 0 to 25 pct to determine effects on important properties. Butts additions increased baked apparent density, decreased electrical resistivity, baking shrinkage, and thermal shock cracking resistance, and had little effect on excess carbon consumption. Use of 100 pct mixer scrap was equivalent to use of freshly blended coke and pitch. Use of 100 pct green anode scrap increased baked apparent density, decreased electrical resistivity, and may have reduced carbon consumption. Additions of used potlining increased carbon consumption, had little effect on electrical resistivity, and had a variable effect on thermal shock cracking resistance.     

Effect of anthracite properties and formulation on properties of bench scale cathode blocks for aluminum smelting

Bench scale cathode blocks for aluminum smelting having an aggregate of 70 pct anthracite calcined at 1135°C—30 pct ball milled graphite and a coal tar pitch binder were fabricated, baked at 1135°C, and tested for electrical resistivity and expansion during electrolysis in a test cell. Twelve anthracite samples, for which a number of chemical and physical properties were determined, were used in cathode fabrication so that relationships among anthracite properties and cathode properties could be determined. Cathode expansion during electrolysis increased with increasing sulfur content of the anthracite but appeared to decrease with increasing silicon content. Electrical resistivity decreased with an increase in the fraction of green anthracite exhibiting a conchoidal rather than laminar fracture. With the finer of two anthracite aggregate sizings used, both cathode expansion during electrolysis and electrical resistivity decreased sharply as binder content was increased from 16 to 22 pct. Baked apparent density also increased at the same time but was not,per se, a valid indicator of either electrical resistivity or expansion during electrolysis; cathodes produced using a coarser anthracite sizing, which resulted in higher baked apparent densities, had higher electrical resistivities and expansions during electrolysis. Electrical resistance of all cathodes increased during electrolysis in the test cell by an amount proportional to the amount of expansion.     

粘结剂含量对铝电解用炭间糊性能的影响

以电煅煤、沥青焦、熟碎为骨料,改质沥青和煤焦油为粘结剂制备铝电解用炭间糊,并研究粘结剂含量对炭间糊性能的影响。结果表明,随着粘结剂含量的增加,炭间糊的挥发分增加;灰分、膨胀/收缩率先减小后增大,而体积密度、电阻率和耐压强度则是先增大后减小。当粘结剂含量为17%时炭间糊的综合性能最佳。     

Effect of titanium additives on carbon anode reactivity

In order to ascertain the impact of titanium additives on carbon anode reactivity, different titanium content of carbon anodes were prepared with the single factor experimental method, and test its reactivity in CO₂ and air atmosphere respectively. The micro structure of carbon anodes and pitch cokes were tested by XRD. The pyrolysis process of pitch was tested with the TG-DTG method. The results show that the residual rate and chalking rate of carbon anode can also be significantly improved by increasing titanium content. Titanium additives can refine the crystallite size of carbon anode, promote the asphalt carbonization. The titanium additives can increase the apparent activation energy and pitch coke yield of the pyrolysis process, when the titanium content is 1.5%, E _a is 56.405 KJ/ mol, reaction order is 6.4, and the rate of pitch coke yield is 50.5%.     

莫来石/SiC复相材料的烧结工艺和成分优化

利用工业氧化铝和超细氧化硅合成莫来石，并结合SiC制备出了莫莱石／SiC复相材料。研究了烧结工艺及氧化铝和氧化硅的摩尔比对复相材料密度和强度的影响，并以材料的热震残余强度为指标、利用正交设计法研究了微量添加剂的影响效果。结果表明，复相材料的体积密度随烧结温度的升高和烧结时间的延均出现先升高后降低的规律，而开口气孔率的变化规律则相反；随结合相中Al2O3与SiO2的摩尔比的提高，复相材料的密度增加、气孔密度降低，而强度则先增后减，通过烧结工艺与结合相和添加剂成分的优化，材料密度最高可达2．5g/cm^2，抗折强度达34．5MPa，耐压强度可达90MPa，热震后的残余强度率为67．2％。     

尖晶石对刚玉-尖晶石浇注料性能的影响

以板状刚玉(6 mm～1 mm、1 mm～0.5 mm、0.5 mm～0mm)、烧结尖晶石颗粒(1mm～0.5 mm)为骨料,电熔尖晶石细粉(≤0.044 mm)、白刚玉细粉(≤0.044 mm)、α- Al2O3微粉(≤5μm,d50=2.01 μm)、纯铝酸钙水泥为基质,按骨料与基质的质量比为70∶30配料,以烧结...     

Thermal shock behavior of a three-dimensional SiC/SiC composite

Thermal shock behavior of a three-dimensional (3-D) SiC/SiC composite was studied using the water-quenched method. Thermal shock damage of the composite was assessed by scanning electron microscopy characterization and residual three-point-bending strength. In the thermal shock process, the composite displayed the same bending mechanical behaviors as those of the original composite and retained 80 pct of the original strength in the longitudinal direction after being quenched from 1200°C to 25°C in water for 100 cycles. However, the composite displayed anisotropy in resistance to thermal shock damage. The observed microdamage processes were as follows: (1) formation of micropores and long crack, (2) transfer and growth of pores, (3) saturation of the dimension and the density of pores, and (4) accelerated growth of the long crack along the longitudinal direction. The critical thermal shock number for the composite was about 50. When thermal shock was less than 50 cycles, the residual flexural strength of the composite decreased with thermal shock cycles increasing. When the number was greater than 50, the strength of the composite did not decrease further.     

石油焦煅烧程度对铝用炭阳极显微结构及电解消耗的影响

以不同煅烧程度石油焦为骨料,煤沥青为黏结剂制备铝用低煅焦炭阳极.通过激光共聚焦扫描显微镜和图像分析方法对炭阳极孔隙结构进行分析表征,并考察阳极反应性和电解消耗性能.在煅后焦微晶尺寸1.7~2.7 nm范围内降低石油焦煅烧程度,炭阳极小孔隙逐渐沿骨料-黏结剂界面演变为裂纹状大孔隙,炭阳极孔隙率、形状因子及连通率均先减小后增大,视孔隙比表面积呈减小趋势.煅后焦微晶尺寸降低至1.9 nm较为适宜,对应的炭阳极空气和CO₂反应质量损失率最少为9.6%和3.0%,每吨铝阳极碳耗为355.4 kg.低煅焦炭阳极过量消耗机制从以黏结剂选择性消耗转变为骨料与黏结剂共同消耗,使碳渣量减少.      

Effects of anthracite calcination and formulation variables on properties of bench scale aluminum smelting cell cathodes

Several anthracites were calcined at temperatures ranging from about 1100 to 2300°C and bench scale cathodes fabricated, baked, and tested for electrical resistivity and expansion during electrolysis. Cathode electrical resistivity did not decrease much with increasing anthracite calcination temperature to about 1800°C but decreased sharply thereafter. Cathode expansion during electrolysis was inversely proportional to anthracite calcination temperature to about 2000°C. Electrical resistivity generally decreased during test cell operation. A correlation between anthracite properties and cathode properties for anthracites calcined at 2100°C could not be made. With a commercial electrically calcined anthracite, the finer of two aggregate sizings resulted in cathodes with superior properties, and properties generally optimized at a binder level producing about a zero volume change during baking.     

Effects of anthracite calcination and formulation variables on properties of bench scale aluminum smelting cell cathodes

Several anthracites were calcined at temperatures ranging from about 1100 to 2300°C and bench scale cathodes fabricated, baked, and tested for electrical resistivity and expansion during electrolysis. Cathode electrical resistivity did not decrease much with increasing anthracite calcination temperature to about 1800°C but decreased sharply there-after. Cathode expansion during electrolysis was inversely proportional to anthracite calcination temperature to about 2000°C. Electrical resistivity generally decreased during test cell operation. A correlation between anthracite properties and cathode properties for anthracites calcined at 2100°C could not be made. With a commercial electrically calcined anthracite, the finer of two aggregate sizings resulted in cathodes with superior properties, and properties generally optimized at a binder level producing about a zero volume change during baking.     

干熄焦炉热震损毁机理分析

为了研究干熄焦炉的热震性及其对斜道区耐火材料的影响，开展了热震试验，并对干熄焦炉内换热情况进行了建模分析。结果表明，牛腿砖试样经历的热震温差越大，热震次数越多，其抗折强度损失率越大；干熄焦的工况变化会引起斜道出口风温波动，发生热震现象。对干熄焦炉进行三维建模，当从底部均匀进风时，干熄焦炉内部的流场呈现非均匀趋势，在靠近出口一侧循环气体风量较大、速度较快、温度较低，而远离出口一侧循环气体风量较小、速度较慢、温度较高，两侧最大温差为653 ℃。干熄焦炉内部温度不均匀分布加剧了热震现象。为提高干熄焦炉耐火材料尤其是牛腿砖的使用寿命，应稳定操作，减少工况波动，以减少干熄焦炉内热震现象。     

复合添加剂对氧化铝陶瓷烧结性和抗热震性的影响

研究了复合添加剂MnO2、MgO和Y2O3对Al2O3陶瓷烧结性和抗热震性的影响.试验结果表明:在复合添加剂中引入MgO和Y2O3大幅度提高了Al2O3陶瓷的致密度,促进了陶瓷的烧结,提高了材料的强度.Al2O3陶瓷的抗热震性能也得到提高,当MgO和Y2O3的含量为0.5%时,Al2O3陶瓷的临界热震温差在300℃左右,抗热震性能大大提高;继续增加MgO和Y2O3的含量,其抗热震性有所降低.添加复合添加剂的Al2O3陶瓷的抗热震性受到细晶强化和气孔的共同控制,对抗热震性提高的主要贡献为细晶强化,但气孔也会影响其抗热震性.     

改质沥青——煤焦油粘结剂添加B_4C对铝用炭间糊性能的影响

以改质沥青—煤焦油混合粘结剂为基体,添加B_4C制备改性粘结剂,并以电煅无烟煤、沥青焦、熟碎为骨料和改性粘结剂制备铝电解用炭间糊,研究B_4C添加量对制备炭间糊性能及微观结构的影响。结果表明,随着B_4C添加量的增加,制备炭间糊的灰分、电阻率、耐压强度、残炭率逐渐增大,挥发分、膨胀/收缩率、失重速率逐渐减小;B_4C在高温下与O_2、CO等小分子化合物发生化学反应,生成的氧化硼高温熔融,可以有效减缓粘结剂热解缩聚产生的体积变化和快速失重,并改善粘结焦的致密程度;当B_4C添加量为3%时,制备炭间糊具有较佳的综合性能。     

不同α-Al2O3和Cr2O3微粉对刚玉-尖晶石浇注料性能的影响

以板状刚玉、尖晶石、纯铝酸盐水泥、α-Al2O3、Cr2O3微粉等为原料,按骨料与基质之比为65：35进行配比,研究了不同类型的α-Al2O3、Cr2O3微粉对刚玉-尖晶石浇注料性能的影响。结果表明：分别以L1、G2形式引入α-Al2O3、Cr2O3微粉,试样的抗折强度、耐压强度、体积密度、热震性均最优,显气孔率最小。     

Fracture toughness and stress corrosion characteristics of a high strength maraging steel

The effect of heat treatment on the tensile, fracture toughness, and stress corrosion properties of a high strength maraging steel (nominal composition 16.3 Ni?12.87 Co?4.98 Mo?0.78 Ti) is described. A maximum ultimate tensile strength of 323 ksi, combined with a fracture toughnessK _Ic of 62 ksi \(\sqrt {in} \) , was achieved. This strength level appears to be the maximum which can be achieved in maraging type steels without decreasing the crack tolerance below that of currently used high strength low alloy steels. Reversion to austenite did not improve either the fracture toughness or stress corrosion resistance relative to completely martensitic microstructures with equivalent strength.     

RS-Si_3N_4/SiC复相耐火材料的组织与性能

利用三点弯曲试验 ,RXD,SEM等手段研究了原料组成对 RS-Si3N4 /Si C复相耐火材料的密度、抗折强度、抗热震能力以及相组成、显微组织和断口形貌的影响 .结果表明 ,当原料中硅质量分数为 2 5%时 ,Si3N4 /Si C复相耐火材料具有最高的抗折强度和抗热震稳定性 .论文中对此种材料的相结构、显微组织和断口形貌进行了分析     

改质沥青对电煅无烟煤和沥青焦浸润性的研究

以改质沥青为粘结剂、电煅无烟煤和沥青焦为骨料,研究骨料粒度、加热温度、保温时间及振动次数对改质沥青浸润性的影响,并对不同粒度分布的电煅无烟煤和沥青焦的比表面积进行测定。结果表明,随着骨料粒度的减小,骨料颗粒的比表面积逐渐增大;改质沥青对电煅无烟煤和沥青焦的浸润性均随骨料粒度的减小和振动次数的增加而大幅度降低,随加热温度和保温时间的增加而逐渐增大。通过适当调整骨料粒度分布、加热温度、保温时间、振动次数等工艺参数,能够改善改质沥青对电煅无烟煤和沥青焦的浸润效果。     

烧结温度对NiFe2O4/TiN复合陶瓷惰性阳极材料性能的影响

采用两步烧结法制备了掺杂质量分数为7%TiN的NiFe₂O₄/TiN复合陶瓷惰性阳极材料,重点研究了烧结温度对NiFe₂O₄/TiN复合陶瓷惰性阳极材料的微观结构及性能的影响.研究结果表明:随着烧结温度的升高,惰性阳极材料的晶粒间隙变小,气孔逐渐减少,晶粒间结合度提高,体积密度呈先升高后降低趋势,在1325℃时达到最大值5.20g/cm³,但材料内部存在微裂纹;烧结温度为1300℃时,材料表现出较好的综合性能,抗弯强度达到最大值66.77MPa,一次热震强度剩余率为95.54%,表现出良好的耐高温冰晶石熔盐腐蚀能力;烧结温度超过1300℃时,材料内部缺陷尺寸增加,电解质成分更容易渗入到阳极材料中,耐腐蚀性能下降.     

ZrO2加入量对刚玉-尖晶石浇注料性能的影响

以板状刚玉(6～3 mm、3～1 mm和≤1 mm)为骨料,以电熔尖晶石细粉(≤0.044 mm)、白刚玉细粉(≤0.088mm和≤0.044 mm)、α-Al2O3微粉(≤5μm,d50=2.01μm)为基质,以纯铝酸钙水泥为结合剂,按骨料与基质的质量比为70∶30配料,以ZrO2等量代替白刚玉细粉(≤0.044 mm)制备刚玉-尖晶石浇注料,并研究ZrO2质量分数分别为0、2％、4％、6％、8％时对刚玉-尖晶石浇注料性能的影响.结果表明:随着ZrO2引入量的增大,试样的体积密度和显气孔率均呈上升趋势,线变化率逐渐增大,强度降低,高温抗折强度呈降低趋势,抗热震性和抗渣侵蚀性逐渐增强.综合考虑,ZrO2的最佳引入量为4％～6％.     

添加氧化铈对反应烧结制备镁铝尖晶石材料性能的影响

为了进一步提高高品质钢冶炼用镁铝尖晶石耐火材料的关键性能,以电熔镁铝尖晶石、轻烧氧化镁和白刚玉为原料,镁铝溶胶为结合剂,氧化铈为添加剂,采用反应烧结工艺成功制备了镁铝尖晶石材料.系统研究了氧化铈添加量(质量分数,0、3％,6％、9％和12％)对合成镁铝尖晶石材料显气孔率、体积密度、线收缩率、体积收缩率、常温耐压强度和抗...