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.906. 北京科技大学学报 第29卷 Effect of deformation on the temper process of lath martensite XU Shilong,LI Longfei),YANG Wangyue),SUN Zuqing) 1)State Key Laboratory for Advanced Metals and Materials.University of Science and Technology Beijing,Beijing 100083.China 2)Materials Science and Engineering School.University of Science and Technology Beijing.Beijing 100083.China ABSTRACI The microstructure evolution during multi pass warm deformation at 550C and subsequent an- nealing process of lath martensite was investigated and compared with that of SPD (severe plastic deformation) cold-rolled lath martensite during annealing at 550C.In comparison with tempered martensite at the same tem- perature,the effects of warm and cold deformation on ferrite grain size and cementite precipitation were dis- cussed.The results showed that both warm and cold deformation significantly promoted the precipitation of ce- mentite as well as recovery and recrystallization of ferrite.The grain size of recrystallized ferrite after warm de- formation was 0.5m,meanwhile rod-type cementite particles changed to spherical-type,the size of cementite grew along with the increase of deformation reduction.Then ferrite grains grew up to 1/m when subsequently annealed at 550C for 60min,and Ostwald ripening occurred during annealing process.In cold-rolled specimens which annealed at 550C for 30min,0.3-0.4m ferrite grains and dispersed cementite particles with the size below 150nm formed.The mean sizes of ferrite grains and cementite particles grew up to 1.9m and 160nm during subsequent annealing. KEY WORDS martensite:deformation:tempering treatment;ferrite;cementite (上接第883页) Temperature rising characteristic of chromite ore fines containing coal in a mi- crowave field CHEN Jin),LI Ning),WANG Shebin),YAN Hong).LIU Jinying?) 1)College of Materials Science and Engineering.Taiyuan University of Technology.Taiyuan 030024.China 2)No-12 Research Institute.China Electronics Technology Group Company,Beijing 100016.China ABSTRACI The microwave heating technique can avoid the non-homogeneous phenomenon of transferring heat and mass in pulverous ore materials by conventional heating.The temperature rising characteristic of chromite ore fines containing coal in a microwave field was experimentally investigated with a microwave metal- lurgy oven.The results showed that chromite ore fines containing coal had a better temperature-rising character- istic in the microwave field of 2.45GHz in frequency.Under the condition of the microwave power of 10k W and the ore fines'mass of lkg,chromite ore fines containing coal reached 1100C in7min with a temperature rising rate of 157.1C.min,whereas magnetite ore fines containing coal reached 1000C in 10min with a tempera ture-rising rate of only 100Cmin.Increasing the carbon-oxygen mole ratio can enhance the heating effect of chromite ore fines containing coal and reduce the effect of lime addition on the temperature rising rate. KEY WORDS chromite ore fines;magnetite ore fines;microwave heating;microwave field;temperature ris- ing characteristicEffect of deformation on the temper process of lath martensite XU Shilong 1）LI Longfei 1）Y A NG Wangyue 2）SUN Zuqing 1） 1） State Key Laboratory for Advanced Metals and MaterialsUniversity of Science and Technology BeijingBeijing100083China 2） Materials Science and Engineering SchoolUniversity of Science and Technology BeijingBeijing100083China ABSTRACT The microstructure evolution during mult-i pass warm deformation at 550℃ and subsequent annealing process of lath martensite was investigated and compared with that of SPD （severe plastic deformation） cold-rolled lath martensite during annealing at550℃．In comparison with tempered martensite at the same temperaturethe effects of warm and cold deformation on ferrite grain size and cementite precipitation were discussed．The results showed that both warm and cold deformation significantly promoted the precipitation of cementite as well as recovery and recrystallization of ferrite．The grain size of recrystallized ferrite after warm deformation was0∙5μmmeanwhile rod-type cementite particles changed to spherica-l typethe size of cementite grew along with the increase of deformation reduction．Then ferrite grains grew up to1μm when subsequently annealed at 550℃ for60minand Ostwald ripening occurred during annealing process．In cold-rolled specimens which annealed at 550℃ for30min0∙3—0∙4μm ferrite grains and dispersed cementite particles with the size below 150nm formed．The mean sizes of ferrite grains and cementite particles grew up to 1∙9μm and160nm during subsequent annealing． KEY WORDS martensite；deformation；tempering treatment；ferrite；cementite （上接第883页） Temperature-rising characteristic of chromite ore fines containing coal in a microwave field CHEN Jin 1）LI Ning 1）WA NG Shebin 1）Y A N Hong 1）LIU Jinying 2） 1） College of Materials Science and EngineeringTaiyuan University of TechnologyTaiyuan030024China 2） No．12Research InstituteChina Electronics Technology Group CompanyBeijing100016China ABSTRACT The microwave heating technique can avoid the non-homogeneous phenomenon of transferring heat and mass in pulverous ore materials by conventional heating．The temperature-rising characteristic of chromite ore fines containing coal in a microwave field was experimentally investigated with a microwave metallurgy oven．The results showed that chromite ore fines containing coal had a better temperature-rising characteristic in the microwave field of2∙45GHz in frequency．Under the condition of the microwave power of10kW and the ore fines’mass of1kgchromite ore fines containing coal reached1100℃ in7min with a temperature-rising rate of 157·1℃·min —1whereas magnetite ore fines containing coal reached1000℃ in10min with a temperature-rising rate of only100℃·min —1．Increasing the carbon-oxygen mole ratio can enhance the heating effect of chromite ore fines containing coal and reduce the effect of lime addition on the temperature-rising rate． KEY WORDS chromite ore fines；magnetite ore fines；microwave heating；microwave field；temperature-rising characteristic ·906· 北 京 科 技 大 学 学 报 第29卷