Some Aspects in the Development of High Performance Refractories for Iron and Steel Making in China

In the past 25 years in China, to meet with the rapid increase in steel production accompanied by adoption of advanced metallurgical technologies, there has been fast development of China＇ s refractories industry in production capacity, in quality improvement and in development of new products. Sophisticated high performance refractory materials mainly based on our rich reserves of magncsite, bauxite and flake graphite have been developed, such as carbon-bonded products, high purity oxide products, bauxite-based low creep and high strength high alumina bricks and LC, ULC and ZC castables. They have been used in blast furnaces, BOFs, EAFs, secondary refining and continuous casting with considerable improvement in service pecformance.

Evolution of Phase Composition and Microstructure of Al_2O_3-Si-Al Composite at High Temperatures in Reducing Atmosphere

Al2 O3-Si-Al composite specimens with the size of 25 mm × 25 mm × 125 mm were prepared using fused alumina （as aggregates and fines）,ultra-fine α-Al2O3,Si and Al powders as starting materials,liquid phenol formaldehyde resin as the binder,pressing and heating at 800-1 500 ℃ for 3 h under carbon embedded condition.Evolution of phase composition and microstructure of Al2 O3-Si-Al composite during heating from 800 to 1 500 ℃ under carbon embedded condition were studied.The results show that：（1） Al4 C3,AlN and SiC are initially formed at 800-900 ℃ due to reactions of Al and Si with C or CO and N2 ; （2） at 1 000-1 300 ℃,the amounts of Al4C3,AlN and SiC increase with temperature rising and their crystals grow; （3） at 1 400-1 500 ℃,Al4 C3 and AlN disappear,and minor SiAlON crystals are observed; the nonoxide crystals develop well and they are interlaced in the corundum skeleton structure,which creates strengthening and toughening

Investigation on Synthesis of Sintered Mullite from Low-medium Grade Kyanite

Sintered mullite is prepared by kyanite powder with Al_2O_3 content of 45% and 50%(Yinshan, Nanyang City, China),and the industrial alumina is added to control the chemical composition. The different series of sintered mullite according to the Al_2O_3 content(45%-70%) are designed. The raw materials are mixed and compacted, and then sintered at different temperatures. Physical properties, phase composition, microstructure and refractoriness under load of the synthesized samples are characterized by physical property test, XRD, SEM and RUL test, in order to confirm the quality of sintering and the relationship between temperature and mullitization reaction. The results show that the sintered mullite from low-medium grade kyanite has well developed mullite crystals and a continuous staggered network structure is formed, which has a significant contribution to increasing the high temperature performance of mullite.

Properties and Microstructure Evolution of Al_2O_3-Si Material Fired in Different Atmospheres

A1203-Si composite specimens were prepared using fused corundum, ultra-fine α-A1203 and Si powder as starting materials and resin as binder. Effects of sintering atmospheres on properties, phase composition and microstructure of specimens after firing at 1 500 ℃ were investigated. The results show that： （ 1 ） after .firing in oxidizing or weak oxidizing atmosphere, there is some Si in the specimens and some glass phases containing mullite form on specimen surface, the density and strength at room temperature are relatively high, but hot modulus of rupture and thermal shock resistance are relatively poor; （2） after firing in, weak reducing or reducing atmosphere, Si reacts completely with CO or N2forming whisk-phere, Si reacts completely with CO or N2forming whisk-er-like SiC, granular Si2N20 or 0＇-SiAION, and the er-like SiC, granular Si2N20 or O＇-SiMON, and the thermo-mechanical properties of specimens are enhanced;（3） after firing in nitrogen atmosphere, Si reacts completely with N2, CO or G forming wbisker-like SiC and columnar β-SiA10N crystals, the hot modulus of rupture and thermal shock resistance of specimens are enhanced noticeably.

Rheological Behavior of Zero Cement Al_2O_3-MgO Castables

Al2O3 -MgO castables have been widely used for working linings of steel ladle due to their superior hot strength and corrosion resistance. In this- work, effects of＂ microsilica, ultrafine alumina and MgO fines additions on the rh, eological behavior of the castables were investi- gated by means of IBB rheometer V1. 0 to measure torque （shear stress） under varying shear rates. The re- sults show that rheological properties of castables at varying shear rates are significantly improved with increase of microsilica additions （from 1 mass% to 5 mass% ） and corresponding decrease in water addition; there is only little change in rheological behavior with variation of ultrafine alumina and MgO fines additions. Optimum ultrafine alumina and microsilica additions are recommended for castables with good rheological behavior.

The Future of the Refractory Industry,with a Chinese Perspective

Globalization is a reality resulting in many changes in the refractory industry. In this paper some of the threats and opportunities, which are influencing the future prosperity of the refractory industry on a worldwide basis, are being evoked. Some key technical and management issues are underlined, in terms of adjusting the productivity-quality-cost to the customers requirements ; producing unshapes versus shapes; innovations supported by research; international profile for the import-export game; training and education. Consequences for China, who does play a dominant role due to the size of its internal market （ customers demand） and the magnitude of its production capability （including raw materials availability）, are being drawn.

β-SiAlON含量对SiAlON结合刚玉材料性能的影响

以板状刚玉为骨料,以电熔白刚玉粉、Si粉、Al粉和α-Al_(2)O_(3)微粉为基质料,经1500℃保温3 h氮化烧成制备SiAlON结合刚玉材料,并通过调整Si粉和Al粉的加入量设计了β-SiAlON理论生成量(w)分别为10%、20%和30%的三种试样。采用XRD分析试样的物相组成,检测试样的致密度、强度、抗氧化性、抗热震性、抗渣侵蚀性和抗脱硫剂侵蚀性。结果表明:1)所制备的SiAlON结合刚玉材料由刚玉和β-SiAlON组成,其β-SiAlON含量与设计生成量基本吻合。2)随着β-SiAlON含量的增加,SiAlON结合刚玉材料的显气孔率逐渐减小,高温抗折强度、抗氧化性、抗热震性、抗渣侵蚀性和抗脱硫剂侵蚀性均明显提高。

Effect of Al_2O_3-SiC Composite Powder on Properties of Al_2O_3-SiC一C Bricks

Al2O3-SiC-C specimens were prepared using white fused corundum （3-1,≤1 and ≤0.044 mm）,Al2O3-SiC composite powders （d50 ≤ 5 μm）,α-Al2O3 micropowder （d50 =1.2 μm）,SiC powder （≤ 0.044 mm）,flake graphite （≤ 0.088 mm）,Si powder （d50 =42.8 μm） and B4C powder （d50 ≤10 μm） as main starting materials,and thermosetting phenolic resin as binder.4%,8%,12% and 16% （in mass,the same hereinafter） of Al2O3-SiC composite powders substituted the same quantity of α-Al2O3 micropowder ＋ SiC powder.Effects of composite powder additions on apparent porosity,bulk density,cold modulus of rupture,cold crushing strength,hot modulus of rupture （1 400 ℃）,thermal shock resistance （1 100 ℃,water quenching） and oxidation resistance （1 000 and 1 500 ℃） of Al2O3-SiC -C specimens after 180 ℃ curing,1 000 ℃ 3 h carbon-embedded firing and 1 500 ℃ 3 h carbon-embedded firing,respectively,were researched.The results indicate that：（1） with the increase of Al2O3-SiC composite powder,cold strengths of the cured specimens decline,those of the specimens fired at 1 000 ℃ change a little,and those of the specimens fired at 1 500 ℃ change a little except for an obvious improvement of cold crushing strength ; （2） with the increase of Al2O3-SiC composite powder,hot modulus of rupture at 1 400 ℃ decreases and thermal shock resistance enhances significantly; （3） when Al2O3-SiC composite powder addition is 4%,the oxidation resistance at 1 500 ℃ is the best,and the reason may be the composite powder is finer and more active,which is beneficial to form dense mullite protective layer to retard the O2 diffusion into the specimens.

Effect of Nano Calcium Carbonate on Properties of Corundum-spinel Castables

Using sintered corundum as aggregate, white fused corundum powder, fused spinel powder, ultra-fine a-A12 0 3, nano calcium carbonate and hydrated alumina as matrix, effects of nano calcium carbonate additions （0. 4%, O. 8%, 1.2%, 1.6% and 2. 0% in mass, the same hereinafter） on modulus of rupture, thermal shock resi.~tanee and slag resistance of corundum -spinel castables after treating at different temperatures were studied. The results show that nano calcium carbonate decomposes at high temperatures and in-situ forms ealci- ant aluminates, which can significantly increase the CMOR and HMOR of the castables after treating at 800 -1 400 ℃ ; adding nano calcium carbonate obviously improves the thermal shock resistance of the castables, and has little influence on the high basicity slag resist- ance, however, significantly decreases the corrosion and penetration resistance to low basicity slag.

Carbothermal Reduction Synthesis of Al_2O_3-SiC Powders from Coal Gangue

The Al2O3 -SiC composite powders were prepared in argon atmosphere rising coal gangue and carbonaceous materials （ carbon black, active carbon and antbravite） as starting materials by carbothermal reduction. Effects of excessive carbon addition, carbon types. temperature, soaking time. shaping pressure, types and amount of additives on phase composition and micro-structure of the Al2O3 - SiC composite powders were investigated. The re.suits indicate that： temperature, soaking time and chloride additi＇ve have significant influence on the synthesized Al2O3 -SiC composite powders. Based on the results, the optimized Al2O3 -SiC composite powders , Al2O3 58 mass% and SiC 42 mass%, with particle size d50 ≤5μm were prepared using coal gangue and carbon black as starting materials after 3 h firing at 1550 ℃. and proper additive addition could reduce the temperattlre by 50 ℃.