DU Linxiu
,
ZHANG Zhongping
,
TIAN Yuwei
,
LIU Xianghua
,
WANG Guodong
钢铁研究学报(英文版)
gy Center, Benxi Steel Group, Benxi 117000, Liaoning, China)
Abstract： The fatigue properties of 400 MPa grade supersteel, plain low carbon steel SS400 and microalloyed steel Q340TM were investigated through tensilecompression fatigue experiment with R=-1. The results indicate that the fatigue limit of the 400 MPa supersteel is higher than that of SS400 steel and close to that of the 340TM steel. According to the analysis of fatigue fracture, the fatigue striations of supersteel SS400 is thinner than that of SS400 steel and 340TM steel, and grain refinement can increase the fatigue limit.
关键词:
supersteel;grain refinement;fatigue property
TANG Zhengyou
,
DING Hua
,
DU Linxiu
,
DING Hao
,
ZHANG Xin
钢铁研究学报(英文版)
In order to control retained austenite, the effect of hot deformation in the intercritical region on the microstructure of hotrolled transformationinduced plasticity (TRIP) steel was studied on a Gleeble 1500 hot simulator. Compressive strains varying in amounts from 0 to 60% were imposed in the intercritical region, and effects on the formation of polygonal ferrite, carbidefree bainite and retained austenite were determined. With increasing the hot deformation amount and the ferrite content and decreasing the carbidefree bainite content, the volume fraction of retained austenite decreases. Increased dislocation density, grain refinement of ferrite and carbon enrichment are the main factors which control retained austenite stability.
关键词:
TRIP steel;intercritical (α+γ) region;hot deformation;retained austenite
WANG Ning
,
LI Yi
,
DU Linxiu
,
WU Di
,
LIU Xianghua
钢铁研究学报(英文版)
The fatigue properties of the newly developed wheel steel used for commercial vehicles were studied using pushpull axial loading fatigue tests with stress ratio R=-1. Q235B steel, which is conventionally applied to commercial vehicle wheels, was also analyzed for comparison. Although the chemical composition and microstructure (ferrite and pearlite) of newly developed wheel steel were similar to those of Q235B, the 107 cycles fatigue limit of the new wheel steel was 260 MPa, which is 24% higher than that of Q235B (210 MPa). The improvement of the fatigue strength of the new wheel steel can be attributed to grain refinement. In order to investigate the effect of the decrease in thickness of the wheel steel on the fatigue property of the wheel, dynamic cornering fatigue tests were conducted on full scale wheels with the model of 825×225. The results indicated that the newly developed wheel steel had outstanding fatigue life even if the mass loss was 10% in comparison with Q235B.
关键词:
high strength wheel steel;fatigue strength;grain refinement;dynamic cornering
YAO Shengjie
,
DU Linxiu
,
LI Guanglong
,
JIAO Xing
,
WANG Guodong
钢铁研究学报(英文版)
Samples with ultrafine grained austenite were prepared by repetitive rapid heating and quenching for three times and were used to investigate the dynamic microstructural evolving behaviors at different temperatures. A simultaneous development of dynamic straininduced transformation (DSIT) and austenite grain growth was detected at the deformation temperatures above Ar3, while only DSIT happened as the deformation proceeded at lower temperatures close to and below Ar3. In addition, a reverse ferritetoaustenite transformation was also observed. Most of the straininduced ferrite nucleated on the boundaries of ultrafine prior austenite grains, especially at the corners and no evidence about intragranular nucleus was obviously obtained.
关键词:
ultrafine grained austenite
,
ferrite
,
dynamic straininduced transformation (DSIT)
,
grain growth
YAO Shengjie
,
DU Linxiu
,
LIU Xianghua
,
WANG Guodong
钢铁研究学报(英文版)
The austenite transformation characteristics for various warmrolled pearlite during rapid heating were investigated. The results indicate that the start temperature (Ts) is sensitive to the microstructural feature of pearlite, whereas the dislocation plays an important role in the transformation rate; at the same time, the uniformity of austenite grains is more or less affected by the amount of spheroidized pearlite. A critical effect on the state of austenite grain is created through the influence of initial microstructures on the start temperature of transformation.
关键词:
warm rolling;pearlite;dislocation;austenite;transformation
YI Hailong
,
DU Linxiu
,
WANG Guodong
,
LIU Xianghua
钢铁研究学报(英文版)
A hotrolled steel with high yield strength of 700 MPa, good elongation of about 20% and low ductilebrittle transition temperature (DBTT) lower than -70 ℃ has been developed in laboratory. The results show that adopting finishing rolling temperature of around 800 ℃ is rational, and coiling temperature is between 400 and 500 ℃. The strength of developed 700 MPa hotrolled high strength steel is derived from the cumulative contribution of fine grain size, dislocation hardening and precipitation hardening. The fine grain strengthening and precipitation hardening are the dominant factors responsible for such high strength, and good elongation and toughness are predominantly due to fine grain ferrite.
关键词:
high strength steel;precipitation hardening;ductilebrittle transition temperature;fine grain strengthening
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.
CAI Minghui
,
DING Hua
,
ZHANG Jiansu
,
LI Long
,
LI Xiaobin
,
DU Linxiu
钢铁研究学报(英文版)
Continuous cooling transformation behaviors of low carbon steels with two Si contents (050% and 135%) were investigated under undeformed and deformed conditions. Effects of Si contents, deformation, and cooling rates on γ transformation start temperature (Ar3), phase microstructures, and hardness were studied. The results show that, in the case of the deformation with the true strain of 04, the length of bainitic ferrite laths is significantly decreased in low Si steel, whereas, the M/A constituent becomes more uniform in high Si steel. An increase in cooling rates lowers the Ar3 greatly. The steel with higher level of Si exhibits higher Ar3, and higher hardness both under undeformed and deformed conditions compared with the steel with a lower Si content. Especially, the influence of Si on Ar3 is dependent on deformation. Such effects are more significant under the undeformed condition. The hardness of both steels increases with the increase of cooling rates, whereas, the deformation involved in both steels reduces the hardness.
关键词:
Si content;low carbon steel;cooling rate;transformation behavior;bainitic
