WEI Min-xian
,
WANG Shu-qi
,
WANG Lan
,
CUI Xiang-hong
,
CHEN Kang-min
钢铁研究学报(英文版)
Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50-300 N at 400 ℃ by a pin-on-disc high-temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS); wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1120 ℃, then decreased at up to 1220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order: 700 ℃ (tempered sorbite), 200 ℃ (tempered martensite), 440 to 650 ℃ (tempered troostite). An appropriate combination of hardness, toughness, microstructural thermal stability was required for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1120 ℃, quenched in oil, then tempered at 440 to 650 ℃ for 2 h.
关键词:
cast hot-forging die steel
,
heat treatment process
,
high-temperature wear mechanism
,
wear behavior
,
microstructure
ZHAO Xin
,
YANG Xiao-ling
,
JING Tian-fu
钢铁研究学报(英文版)
In order to investigate the effect of initial microstructure on warm deformation behavior, some specimens of 45 steel were annealed and some quenched. Then the specimens were isothermally compressed on a Gleeble 3500 machine. The deformation temperature range was 550 to 700 ℃ and the strain rate range was 0.001 to 0.1 s-1. An optical microscope (OM) and a transmission electron microscope (TEM) were used to study the microstructures. The results show that the microstructure of annealed specimens is ferrite and pearlite and that of quenched specimens is martensite. The flow stress of quenched specimens is higher than that of annealed ones at 550 ℃ when strain rates are greater than 0.001 s-1. However, at 600 to 700 ℃ and strain rate of 0.001 s-1, the whole flow curves of quenched specimens are below that of annealed ones. Under the rest conditions, the flow stress of quenched specimens is higher at the beginning of compression and then the opposite is true after the strain is greater than a critical value. The microstructure examination proves that the tempering and dynamic recrystallization easily occur in the specimens with martensite during warm compression, which results in the above phenomena.
关键词:
warm deformation
,
flow stress
,
steel
,
microstructure
ZHENG Lei
,
YUAN Ze-xi
,
SONG Shen-hua
,
XI Tian-hui
,
WANG Qian
钢铁研究学报(英文版)
Austenite grain sizes in the heat affected zone (HAZ) of a high heat input welded Zr-Ti bearing microalloyed steel are measured under different welding conditions simulated by a Gleeble-1500 thermal-mechanical simulator. The austenite grain growth is divided into two regimes in terms of temperature. When the temperature is lower than 1250 ℃ where the pinning effect of precipitates is strong, the austenite grain size increases slowly with increasing peak temperature, but it increases drastically when the temperature is higher than 1250 ℃ where the pinning effect of precipitates is weak. Based on the experimental measurements, an analytical model for predicting the austenite grain size in the heat affected zone is derived. Model predictions indicate that the initial grain size has little effect on the final one, and the grain growth depends mainly on heat input and peak temperature as well as growth activation energy and exponent. With the use of the model, the width of coarse grained heat affected zone (CGHAZ) for a thick plate is predicted.
关键词:
welding
,
high heat input
,
microstructure
黄盛
,
宋志刚
,
郑文杰
,
尹建成
钢铁
研究了不同固溶处理温度对特超级双相不锈钢00Cr27Ni7Mo5N组织及力学性能的影响。采用光镜、扫描电镜、能谱仪、显微硬度、冲击和拉伸测试等手段研究σ相的析出规律及其对力学性能的影响。运用Thermo-Calc热力学软件计算00Cr27Ni7Mo5N相含量随温度的变化，并与测试结果进行对比分析。研究结果表明,当固溶温度在800～1050℃之间，00Cr27Ni7Mo5N有大量金属间化合物σ相析出，导致钢的强度和硬度增加，塑韧性显著下降。当固溶温度在1070～1200℃时，钢中σ相溶解，钢的塑韧性提高，硬度下降。1100℃固溶处理时，00Cr27Ni7Mo5N具有最佳的综合力学性能。
关键词:
特超级双相不锈钢
,
σ phase
,
microstructure
GAO Wen and LI ChunzhiInstitute of Aeronautical Materials
,
Beijing
,
Beijing Laboratory of Electron Microscopy
,
Chinese Academy of Sciences
,
Beijing
,
China Manuscript received 11 April
,
1994
金属学报(英文版)
The mierostructure of an AuNiFeCrlnZr alloy has been studied by means of TEM,CBED. SEM and EDS. The results show that the alloy contains Au-rich solid solution, Ni-rich solid solution, and η- and -ωphases. The η-phase containing 90at%Cr possesses an orlhorhombic .structure with a = 0.448nm. b = 1.40nm and c = 1.21nm, and space group of Pmm2 or Pmmm. The ω-phase is an fee structure with a = 0.682nin and space group of Fm3m. The ω-phase dispersed in the alloy matrix plays an important role in increasing strength and wear resistance of the alloy.
关键词:
Au-base alloy
,
null
,
null
,
null
C.H. Zhou
,
K. Yang and Y.X. Lu (Liaoning Key Lab for Hydrogen and Materich
,
Institute of Metal Research
,
The Chinese Academy of Sciences
,
Shenyan 110015
,
China)
金属学报(英文版)
In order to alleviate the severe interface reaction, which is likely to occur during the fabrication of continuous SiC fiber reinforced titanium matrix composite, hydrogen was temporarily introduced in the fabrication to lower the consolidation temperature of Ti/SiC composites in the present work. Effects of different fabrication conditions, with or without hydrogen, on the bonding state and the matrix microstructure were investigated. In-situ hydrogenation method was found to larpely improve the interface bonding of the composite, and full consolidation could be achieved at 750 or even 700° C more than 100°C lower than the normal fabrication temperature of Ti/SiC composite, which consequently reduced the interfacial reaction layer between Ti matrix and SiC fiber. Different hydrogenation condition led to different matrix microstructure. In order to avoid the embrittling effect of residual hydrogen on the composite,Ti/SiC composite needs to be held in vacuum at the fabrication temperature for longer time after consolidation.
关键词:
Ti/SiC composite
,
null
,
null
