LAN Liangyun
,
QIU Chunlin
,
ZHAO Dewen
,
GAO Xiuhua
,
DU Linxiu
钢铁研究学报(英文版)
The recrystallization behavior of a low carbon high Nb microalloyed steel was investigated using Continuous and interrupted hot compression tests. The results showed that the onset of dynamic recrystallization (DRX) could be detected from inflection in the plot of the strain hardening rate θ against stress σ regardless of whether the stress peak appears or not. According to Zener-Hollomon parameter the activity energy of DRX (Qdef) was obtained, and a new modified expression calculating Qdef was proposed in consideration of the chemical composition of experimental steel. Applying the 2% offset method the static softening fraction was determined. The graphic representation of the softening fraction vs. interrupt time gave the information of the non-static recrystallization temperature (about 1000℃)and the relationship of precipitation-time-temperature. Static recrystallization kinetics follow Avrami’s law in high deformation temperature, and different values of the exponent n were given to illustrate the different effects of Nb element on static recrystallization at different deformation temperature.
关键词:
dynamic recrystallization;static recrystallization;high Nb microalloyed steel;activity energy.
Z.X. Wu and X.F. Sun ( Institute of Applied Mechanics
,
Southwest Jiaotong University
,
Chengdu 610031
,
China State Key Laboratory for Fatigue and Fracture of Materials
,
Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)
金属学报(英文版)
The behavior of part-through and through short cmcks in single edge blunt notched specimens of a medium carbon steel was investigated by a replication method. It is found that the fatigue failure of these notched specitnensis caused mainly by the growth of short surface cracks originating from the sudece of notch root. More than 70% of the fatigue lofe is spent in the regimes in which short surface cracks initiate and propagate as part-through cracks before joining up to form a single through-thickness cmck. The effect of original crack profile which is forsned through the coalescence of multiple part-through cracks is the main reason causing the "anomalous" propagation behavior of the through-thickness cruck in its early stage.
关键词:
medium carbon steel
,
null
,
null
,
null
,
null
DU Jiaju TONG Shihua Institute of Solid State Physics
,
Academia Sinica
,
Hefei
,
China [Originally published in ACTA METALL SIN(CHINESE EDN)25(3)1989 pp A226—A228
,
Associate Professor
,
Institute of Solid State Physics
,
Academia Sinica
,
Hefei
,
China
金属学报(英文版)
Optical microscope,SEM and IMMA investigation show that a strong interaction between hydrogen and calcium aluminate inclusions containing MgO may occur in medium carbon steels.This causes the hydrogen accumulating around the inclusions and reducing the ductility of the steel.
关键词:
hydrogen
,
null
,
null
B.Eghbali
,
A.Abdollah-zadeh
材料科学技术（英文）
Grain refinement is one of the effective methods to develop new generation low carbon microalloyed steels possessing excellent combination of mechanical properties. The microstructural evolution and ferrite grain refinement at the deformation temperature of 865℃, above Ar3, with different strain rates were investigated using single pass isothermal hot compression experiments for a low carbon Nb-Ti microalloyed steel. The physical processes that occurred during deformation were discussed by observing the optical microstructure and analyzing the true stress-true strain responses. At strain rates of 0.001 and 0.01 s-1, there is no evidence of work hardening behavior during hot deformation and strain-induced transformation (SIT) leads to dynamic flow softening in flow curves. Optical microscopy observation shows that ultrafine and equiaxed ferrite with grain sizes of 2μm can be obtained by applying deformation with strain rate of 0.1 s-1 due to SIT just after deformation. Furthermore, increasing the strain rate from 0.001 to 0.1 s-1 reduces both the grain size of the equiaxed ferrite and the amount of deformed ferrite.
关键词:
Low carbon microalloyed steel
,
null
,
null
,
null
NIE Yihong
,
HUI Weijun
,
FU Wantang
,
WENG Yuqing
钢铁研究学报(英文版)
The delayed fracture behavior of mediumcarbon high strength spring steel containing different amounts of boron (0000 5%, 0001 6%) was studied using sustained load delayed fracture test. The results show that delayed fracture resistance of boron containing steels is higher than that of conventional steel 60Si2MnA at the same strength level and it increases with the increase of boron content from 0000 5% to 0001 6%. The delayed fracture mode is mainly intergranular in the boron containing steels tempered at 350 ℃, which indicates that the addition of boron does not change the fracture character. However, the increase of boron content enlarges the size of the crack initiation area. Further study of phase analysis indicates that most boron is in solid solution, and only a very small quantity of boron is in the M3(C, B) phase.
关键词:
boron;delayed fracture resistance;mediumcarbon high strength spring steel
