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 （...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.展开更多
Three-wire submerged arc welding was utilized to weld a newly developed Zr-Ti microalloyed X120 linepipe with heat input of 21 kJ/cm. The microstructure in the heat-affected zone （HAZ）, predominantly consisted of ba...Three-wire submerged arc welding was utilized to weld a newly developed Zr-Ti microalloyed X120 linepipe with heat input of 21 kJ/cm. The microstructure in the heat-affected zone （HAZ）, predominantly consisted of bainite, was examined by means of optical and scanning electron microscope. The average Vickers hardness of grain coarsening heat-affected zone （GCHAZ） is about 290 HV0. 2. The lowest Vickers hardness in HAZ is about 265 HV0. 2. No obvious softening occurred in HAZ. The average impact toughness at -30 ℃ in HAZ was 186 -191 J. The tested results indicated that HAZ of newly developed Zr-Ti microalloyed X120 linepipe steel had high strength and excellent low temperature toughness which met the requirements of API 5L standard.展开更多
文摘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.
基金Acknowledgements The authors greatly acknowledge the support from National Natural Science Foundation of China （ under Grant No. 50734004） and Shanghai Baosteel Group Corporation.
文摘Three-wire submerged arc welding was utilized to weld a newly developed Zr-Ti microalloyed X120 linepipe with heat input of 21 kJ/cm. The microstructure in the heat-affected zone （HAZ）, predominantly consisted of bainite, was examined by means of optical and scanning electron microscope. The average Vickers hardness of grain coarsening heat-affected zone （GCHAZ） is about 290 HV0. 2. The lowest Vickers hardness in HAZ is about 265 HV0. 2. No obvious softening occurred in HAZ. The average impact toughness at -30 ℃ in HAZ was 186 -191 J. The tested results indicated that HAZ of newly developed Zr-Ti microalloyed X120 linepipe steel had high strength and excellent low temperature toughness which met the requirements of API 5L standard.
