ZHAO Jiarong YANG Jie Wuhan Iron and Steel University
,
Wuhan
,
China ZHAO Jiarong
,
associate professor
,
Faculty of Rolling
,
Wuhan Iron and Steel University
,
Wuhan 430081
,
China
金属学报(英文版)
Based on the analyses of hot-deformation mechanism of the steel,a new constitutive equation describing the flow stress of steels was derived.The flow stress data of steel 55SiMnVB have been determined at 900—1200℃,strain rates of 1—100s~(-1)and true-strain of 0.08—0.8.An available evaluated formula on the flows tress has been obtained by means of non-linear regression.It can express clearly the physical process of hot-deformation.
关键词:
flow stress
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null
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null
XU Yunbo
,
YU Yongmei
,
LIU Xianghua
,
WANG Guodong
钢铁研究学报(英文版)
The recrystallization kinetics and grain size models were developed for the CMn and niobiumcontaining steels to describe the metallurgical phenomenon such as softening, grain growth, and strain accumulation. Based on the recrystallization kinetics equations, the mean flow stress and the rolling load of each pass were predicted and the optimum rolling schedule was proposed for hot strip rolling. The austenite grain refinement is associated with the addition of niobium, the decrease of starting temperature of finish rolling, and the reduction of finished thickness. The mean flow stress curve with a continuous rising characteristic can be usually observed in the finish rolling of niobiumcontaining steel, which is formed as a result of the heavy incomplete softening and strain accumulation. The predicted rolling loads are in good agreement with the measured ones.
关键词:
hot strip rolling;recrystallization;mean flow stress;strain accumulation;grain size
DU Feng-shan
,
WANG Gui-guo
,
et al
钢铁研究学报(英文版)
To improve the accuracy and speed of finite element calculation, a new friction model is proposed with a layer of thin friction element being introduced between the roller and workpiece to consider the contact friction. This model is used in the three-dimensional elastic-plastic finite element model of strip rolling process. With the consideration of the geometry size and physical characteristics of intermediate medium between roller and workpiece, this stiffness of the friction element is corrected by two factors (the thickness of friction element and β factor). Without any assumption about the value and direction of friction force and neutral point position, the rolling processes is simulated using this model. The results obtained by this model have been compared with experimental results to verify the feasibility of the model. The model is of great important to the research of the friction model in the strip rolling process, and can be extended to all press-working process.
关键词:
contact friction;FEM;rolling;friction element
TIAN Yong
,
GUO Yanhui
,
WANG Zhaodong
,
WANG Guodong
钢铁研究学报(英文版)
The plane strain asymmetrical rolling was analyzed using slab method. The contact arc was replaced by parabola, and the constant surface friction status was adopted during the analysis. The deformation area was divided into three zones according to the direction of the friction. Then, the three zones were studied, respectively. A rolling force model and a rolling torque model were developed based on the analysis, and they were used to analyze the influence of asymmetrical rolling factors on deformation area and unit pressure if they had good precision which was determined by comparing the calculated results with the measured ones.
关键词:
asymmetrical rolling;slab method;asymmetrical factor;specific pressure distribution
He YANG
材料科学技术（英文）
Cold ring rolling is an advanced but complex metal forming process under coupled effects with multi-factors, such as geometry sizes of rolls and ring blank, material, forming process parameters and friction, etc. Among these factors, friction between rolls and ring blank plays an important role in keeping the stable forming of cold ring rolling. An analytical method was firstly presented for proximately determining the critical friction coefficient of stable forming and then a method was proposed to determine the critical friction coefficient by combining analytical method with numerical simulation. And the influence of friction coefficient on the quality of end-plane and side spread of ring, rolling force, rolling moment and metal flow characteristic in the cold ring rolling process have been explored using the three dimensional (3D) numerical simulation based on the elastic-plastic dynamic finite element method (FEM) under the ABAQUS software environment, and the results show that increasing the friction on the contact surfaces between rolls and ring blank is useful not only for improving the stability of cold ring rolling but also for improving the geometry and dimension precision of deformed ring.
关键词:
Cold ring rolling
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null
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null
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null
QI Xiang-dong
,
WANG Tao
,
XIAO Hong
钢铁研究学报(英文版)
Rolling schedule not only determines the rolling process to be going smoothly, but also affects the shape accuracy and structure properties of finished strip. In order to gain good strip crown and flatness, the calculation formulas of the most suitable rolling force and bending force are deduced. By taking relatively equal load of rolling power and good shape as objective functions, the optimization mathematical models of finish rolling schedule are established. By contrast, the rolling schedules after optimization can improve the rolling mill working status and ensure the strip crown and flatness to be good. At the same time, the setting value of bending force is improved and this leaves more space for on-line shape control.
关键词:
optimization
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rolling schedule
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rolling force
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bending force
,
shape
J.Z. Zhang
,
X.P. Zhang
金属学报(英文版)
The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow”. Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.
关键词:
tension
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null
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null
YU Hui
,
DU Feng-shan
,
XU Zhi-qiang
钢铁研究学报(英文版)
Roller pass is one of the key factors affecting the product quality in the retained mandrel rolling process. The metal flow condition of rolling deformation area was researched using the FEA (finite element analysis) software Marc. The influences of the pass bottom radius, the sidewall radius, the sidewall angle, the roller shoulder fillet radius, as well as the roller gap on the rolling process under the conditions of different friction were discussed. Based on these results, the changes of the workpiece exit width, the mandrel axial force, the rolling force, and the rolling torque associated with various parameters were determined, which would provide the basis for designing the pass and determining the rolling condition reasonably.
关键词:
finite element analysis
J.X. Li
,
X.H. Liu
,
G.D. Wang
金属学报(英文版)
Two kinds of cold rolling experiments, single cold rolling and double cold rolling, werecarried out on one titanium stabilized interstitial free (IF) steel that has been warmrolled at ferrite temperature. The main aim was to investigate the evolution of rollingand annealing textures from the well known behavior observed under single cold rollingcondition to the less understood double cold rolling by using orientation distributionfunction (ODF). In the twice cold rolled samples, the annealing texture comprises onlyfirst round of rolling. Accordingly both the once cold rolled sample and the twice coldrolled sample with heavy reduction in the first round of rolling have much complextexture components. They are related to the formation of initial {111} subgrain andthe priority growth of stable {111} nucleus.
关键词:
double rolling
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null
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null
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null
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null
DONG Yong-gang
钢铁研究学报(英文版)
In rail rolling by universal mill, a simplified 3-dimention theoretical model has been built firstly. The kinematically admissible velocity field of the web, head and base of rail have been determined respectively, moreover the corresponding strain rate field and the strength of shear strain rate have been also obtained. Then the plastic deformation power of corresponding deformation zone, the powers consumed on the velocity discontinuity surface and the powers generated for backward slip and forward slip have been proposed. According to the upper-bound method, the roll force of horizontal roll and two vertical rolls can be obtained. Moreover, The process of 18kg/m light rail and 60kg/m heavy rail universal rolling have been simulated by rigid-plastic FEM(finite element method) for verifying the theoretical model. And the universal rolling experiments of 18kg/m light rail has been accomplished in Yanshan University Rolling Laboratory. Compared the results of numerical simulation and the experimental data, the roll force from upper-bound method is somewhat greater than experimental data but in general do not exceed them by 20 percent. So, it is reliable and feasible to preset and optimize the parameter of rolling technology according to the upper-bound method.
关键词:
rail rolling;universal mill;upper-bound method;rigid-plastic FEM(finite element method);roll force;experiments
