TAN Wen
,
LIU Zhenyu
,
WU Di
,
WANG Guodong
钢铁研究学报(英文版)
An artificial neural network (ANN) model for predicting transformed microstructure in conventional rolling process and thermomechanical controlled process (TMCP) is proposed. The model uses austenite grain size and retained strain, which can be calculated by using microstructure evolution models, together with a measured cooling rate and chemical compositions as inputs and the ferrite grain size and ferrite fraction as outputs. The predicted results show that the model can predict the transformed microstructure which is in good agreement with the measured one, and it is better than the empirical equations. Also, the effect of the alloying elements on transformed products has been analyzed by using the model. The tendency is the same as that in the reported articles. The model can be used further for the optimization of processing parameters, microstructure and properties in TMCP.
关键词:
artificial neural network;TMCP;microstructure;ferrite grain size
MA Liqiang
,
LIU Zhenyu
,
JIAO Sihai
,
YUAN Xiangqian
,
WU Di
钢铁研究学报(英文版)
Using a Gleeble 3800 thermomechanical simulator, the effect of niobium and titanium on the dynamic recrystallization (DRX) behavior of low carbon steels was investigated. Isothermal single compression tests were performed in the temperature range of 850 to 1 150 ℃ at constant strain rates of 01 to 5 s-1. The experimental results showed that the addition of niobium and titanium to the low carbon steels significantly increased both the peak stress and steady state stress. The activation energy of deformation Qd was larger than the activation energy associated with the steady state stress Qss. Furthermore, the difference between Qd and Qss became significant because of the addition of niobium and titanium. DRX is effectively retarded because of solute dragging and dynamic precipitate pinning of niobium and titanium, resulting in higher values of the peak strain and steady state strain. Finally, the influence of niobium and titanium on the DRX kinetics and steady state grain size was determined.
关键词:
peak strain;activation energy;dynamic recrystallization It is known that the experimental
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
ZHOU Xiaoguang
,
LIU Zhenyu
,
YUAN Xiangqian
,
WU Di
,
WANG Guodong
,
LIU Xianghua
钢铁研究学报(英文版)
Considering the effect of strain and chemical composition on precipitation behavior, new models for the start and end time of Nb(C,N) precipitation in austenite under the conditions of different temperatures and strains have been investigated for Nb microalloyed steel. The value of n in the precipitation kinetic equation has been determined by using the available experimental data in literature, which indicated that n is a constant and independent of temperature. The values of the start and end time of the predicted precipitation are compared with the experimental values. Calculated results are in good agreement with the experimental results. Also, the evolution of austenite grains before ferrite transformation is simulated by taking the effect of precipitation into consideration. The measured austenite grain size is in good agreement with predicted one prior to ferrite transformation.
关键词:
straininduced precipitation;start time;precipitation;static recrystallization;grain size
HOU Xiao-ying
,
XU Yun-bo
,
ZHAO Yan-feng
,
WU Di
钢铁研究学报(英文版)
The microstructure characteristics and mechanical properties of a low-silicon TRIP steel containing phosphorus and vanadium at different finish rolling temperatures were studied by laboratory hot rolling experiments. Different ratios of multiphase microstructure (ferrite, granular bainite and retained austenite) are obtained. With a decrease in finish rolling temperature, the volume fractions of ferrite and retained austenite increase. EBSD analysis reveals that most of the ferrite grains are fine, and decreasing of finish rolling temperature leads to an increase in low angle boundaries. Under the joint effects of fine grain strengthening, dislocation strengthening and precipitation strengthening, higher strength is obtained. When the finish rolling temperature is decreased to 800 ℃, the steel has excellent mechanical properties: Rp02=470 MPa; Rm=960 MPa; Rp02/Rm=049; A50=197%; n=025.
关键词:
hot rolling
,
low silicon
,
TRIP steel
,
phosphorus
,
vanadium
,
EBSD
,
precipitation
ZHU Lijuan
,
WU Di
,
ZHAO Xianming
钢铁研究学报(英文版)
Transformation behavior in low carbon SiMn TRIP steel was investigated by means of microstructural observation and computer modelling. A transformation model in which transformation is controlled by carbon diffusion was suggested, which well described the volume fractional change of ferrite, pearlite, and bainite during continuous cooling. The influence of Si content and austenite grain size was thoroughly investigated. The calculated results indicated that Si retards pearlite transformation, accelerates polygonal ferrite transformation, refines the austenite grain, and increases the ferrite transformation rate.
关键词:
TRIP steel;transformation;incubation time;ferrite;bainite;pearlite
LI Zhuang
,
WU Di
,
L Huisheng
钢铁研究学报(英文版)
The effect of thermomechanical processing (TMP) on the mechanical properties of hot rolled multiphase steel was investigated. TMP was conducted using a laboratory hot rolling mill, in which three different kinds of finish rolling deformation degrees and temperatures were applied. The results indicate that polygonal ferrite, granular bainite, and a considerable amount of stabilized retained austenite can be obtained by TMP. The stability of the retained austenite increases with decreasing finish rolling temperature and increasing finish rolling deformation degrees. Ultimate tensile strength (σb), total elongation (δ), and the product of ultimate tensile strength by total elongation (σb·δ) for 50% reduction at finish rolling temperature of 700 ℃ reach maximum values [791 MPa, 36% and 28 476 (MPa·%), respectively].
关键词:
hot rolled multiphase steel;finish rolling deformation degree;finish rolling temperature;retained austenite;mechanical property
ZHU Lijuan
,
WU Di
,
ZHAO Xianming
钢铁研究学报(英文版)
By means of hot compression single and double hit experiments, the kinetics of dynamic and static recrystallization in hotrolled SiMn TRIP steel was studied, and the emphasis was put on the influence of high silicon content. The results show that the calculated parameters are consistent with the experimental ones, and addition of silicon retards both dynamic and static recrystallization as well as increases the flow stress of austenite, and the nonrecrystallization zone can be enlarged by increasing the silicon contents.
关键词:
dynamic recrystallization;static recrystallization;mathematical model;TRIP steel;silicon
