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MODELING OF MICROSTRUCTURAL EVOLUTION IN MICROALLOYED STEEL DURING HOT FORGING PROCESS
J Wang,J Chen,Z Zhao,XY Ruan,
J.Wang
,J.Chen,Z.Zhao and X.Y.Ruan National Die & Mold CAD Engineering Research Center,Shanghai Jiaotong University,Shanghai,China

金属学报(英文版) , 2006,
Abstract: The microstructural evolution of microalloyed steel during hot forging process was investigated using physical simulation experiments. The dynamic recrystallized fraction was described by modifying Avrami's equation, the parameters of which were determined by single hit compression tests. Double hit compression tests were performed to model the equation describing the static recrystallized fraction, and the obtained predicted values were in good agreement with the measured values. Austenitic grain growth was modeled as: Dinc5 = D05 + 1.6 × 1032 t·exp () using isothermal tests. Furthermore, an equation describing the dynamic recrystallized grain size was given as Ddyn = 3771·Z-0.2. The models of microstructural evolution could be applied to the numerical simulation of hot forging.
THE MICROSTRUCTURAL BANDING IN THE CENTER OF HOT ROLLING STRIP
THE MICROSTRUCTURAL BANDING IN THE CENTER OF HOT ROLLLNG STRIP

CL Mo,YT Zhang,DZ Li,YY Li,
C.L.
,Mo,Y.,T.,Zhang,D.Z.,Li,Y.,Y.,Li

金属学报(英文版) , 2005,
Abstract: The microstructural banding in steels is often found in hot rolling strips, which plays a very important role in mechanical properties. Much work has been done to investigate how the microstructural banding is formed during hot rolling. In the present study, the microstructure of hot rolling strips was examined in term of optical microscopy and transmission electron microscopy. Electron probe microanalysis was also used to decide the distribution of microchemical bands, by this means, the phases in these strips were found to be ferrite and pearlite. The average distance between the carbon lamellas in pearlite is about 0. 06-0. 1μm. It is also shown that microstructural banding in hot rolled carbon steel was closely related to the segregation of manganese and silicon into those bands. Based on the transformation kinetic, the simulated results pointed out that the thermodynamic stability of austenite would increase with the increasing of Mn, which led to a decrease of ferrite growth rate. The effect of Mn on the decomposition of austenite is attnbuted to segregation of Mn atoms along the ferrite/austenite phase boundary which causes a strong solute drag effect. The addition of Mn to steel decreases the activity of austenite, thereby it is beneficial to the formation of non-equilibrium phase, such as degenerate pearlite.The formation of banded structure on the hot rolled process was discussed.
Modelling the microstructural evolution during hot rolling
Gómez,G.R.; Pérez,T.;
Latin American applied research , 2002,
Abstract: a metallurgical model that describes the microstructural evolution of c-mn steels in the hot strip mill, and that predicts the yield strength and the ultimate tensile strength based on the steel chemistry and the processing conditions is presented. the model comprises the microstructural evolution during hot deformation in the austenitic range (taking into account the effects recrystallization and grain growth), and the austenite decomposition during cooling (formation of ferrite, perlite and/or bainite). a comparison between calculated and measured yield strength and ultimate tensile strength values for several steels and processing conditions is also included.
Modelling the microstructural evolution during hot rolling
G.R. Gómez,T. Pérez
Latin American applied research , 2002,
Abstract: A metallurgical model that describes the microstructural evolution of C-Mn steels in the hot strip mill, and that predicts the yield strength and the ultimate tensile strength based on the steel chemistry and the processing conditions is presented. The model comprises the microstructural evolution during hot deformation in the austenitic range (taking into account the effects recrystallization and grain growth), and the austenite decomposition during cooling (formation of ferrite, perlite and/or bainite). A comparison between calculated and measured yield strength and ultimate tensile strength values for several steels and processing conditions is also included.
EXPERIMENTAL-NUMERICAL AND MICROSTRUCTURAL CONTROL OF HOT STRIP ROLLING
R Turk,M Knap,R Robic,
R. Turk
,M. Knap and R. Robic

金属学报(英文版) , 2000,
Abstract: On a local level, thermomechanical states during the passing of hot metallic material through the de- formation volume in a process of plane rolling with smooth rools were analysed by an experimental-nu- merical method. These states,which are markedly inhomogeneous in the length as well as in the height of the deformation zone,were taken as the basis for physical simulation of rolling the material at a certain lavel(i. e. stream line) of the deformation zone.Their influences on local yield stresses and on the development of the microstructure were checked.The efficiency of physical simulation of rolling with the Gleeble 1500 simulating equipment was examined.The states at which the transport of metallic material through the deformation zone between smooth rolls takes place were analysed by a visioplastic method,while physical simulation of rolling was made by thermomechanically controlled cylindrical compression tests.The tests were made with industrially manufactrued X5Grni8.9 austenitic stainless steel.
Modelling of Microstructural Evolution and Prediction of Mechanical Properties of Plain Carbon Strip Steel in Hot Rolling Process
Xiaochun SHA,Chunli MO,Dianzhong LI,Yiyi LI,
Xiaochun SHA
,Chunli MO,Dianzhong LI and Yiyi LI Institute of Metal Research,Chinese Academy of Sciences,Shenyang,China Shenyang Institute of Technology,Shenyang,China Anshan Iron and Steel Group Corporation,Anshan,China

材料科学技术学报 , 2004,
Abstract: Based on hot rolling production line of strip steel, the of-line in-house software, termed as ROLLAN (Rolling Analysis),is developed. The code is mainly used to predict the evolution of temperature, rolling force, fraction and grain size of recrystallization, fraction and grain size of phase transformation and final mechanical properties. Almost all the processing parameters affecting microstructure and mechanical properties in the schedule from reheating to the coiling process are considered in detail. Self-learning coefficient is adopted to adjust the deviation between predicted and measured temperatures, such as roughing exit temperature (RT2), finishing exit temperature (FT7) and coiling temperature (CT). Due to the application of low-speed-threading, increasing-speed-rolling and decreasing-speeddelivery process during finishing rolling and different cooling condition, after coiling the thermal-mechanical history of different position, along strip longitudinal direction is different resulting in inhomogeneous mechanical properties.So the segments are divided along longitudinal direction to identify the variation of microstructure and mechanical properties. An example of plain carbon strip steel Q235 with various thickness is used to compare the calculated mechanical properties with measured ones. For the specific grade of Q235, the maximum deviation of tensile strength is less than 10.3 MPa, the yield strength is less than 13.2 MPa, and elongation is less than 1.99%. Further work will focus on the on-line application and consider the effect of macrosegregation and sulfur content of cast slab.
Forging and Rolling of magnesium alloy AZ61  [PDF]
M. Greger,R. Kocich,L. ?í?ek
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: The paper summarises results of experiments aimed at development of structure of modified alloyAZ61 at hot deformation.Design/methodology/approach: Deformation behaviour of alloy was verified at the temperature of 420°C byrolling at 380°C by forging, respectively.Findings: Magnesium alloy AZ 61 have hexagonal structure and their forming is at room temperatures verydifficult, that’s why big plastic deformations are carried out in hot condition. After plastic deformations wasobtained that original grain size decreased 15 times.Research limitations/implications: This paper provide data about magnitude of deformation, strain rate andtemperature of forming at different techniques of plastic deformation. It was aimed to determine the conditionsfor non problem rolling and forging respectively.Practical implications: Initial structure was as cast and after heat treatment T4. Heat treatment appeared muchbetter for forming as well as forging than rolling because of state of stress.Originality/value: Role of βphase (Mg17Al12 ) in these alloys at plastic forming is very important, such thathow it was obtained, best final properties of AZ 61 alloy supports very fine particles, distributed into Mg matrix.Next a relevant information is that multi stage forming process is much better in comparison with a big singlereduction.
Two-dimensional Model of the Microstructural Evolution in Hot-strip Rolling Processes of C-Mn Steels by Computer Simulations
Zhenyu LIU Wei WANG Guodong WANG Qiang ZHANG Northeast University of Technology,Shenyang,ChinaDongqing MA Guoliang WU Jingshan LI Benxi Iron,Steel Company,Benxi,China,

材料科学技术学报 , 1993,
Abstract: In the present paper,the two-dimensional comprehensive model,which integrates the temperaturemodel developed by the authors using finite difference methods and microstructural evolutionmodel,has been developed.By using different microstructural evolution equations developed bySellars,Senuma et al.and Easka et al.,the comparison studies have been made,which present that(1) the calculated γ-grain sizes show good agreements with the measured;(2) these equationsshow consistencies at the end of finishing stands.
AN INVESTIGATION ON THE DEFORMATION AND CRACK FORMATION OF METALS IN CROSS FORGING AND CROSS ROLLING

CHANG TSO-MEI,LEE TSUN-JEH,

金属学报 , 1964,
Abstract: The key to successful cross rolling is to understand fully the distribution of deformation and the mechanism of crack formation at the centre of the rolled material as well as the optimum parameters for the technological process. With these points in mind, the authors carried out investigations by means of microscopic examinations and hardness tests on the distribution of deformation and the mechanism of crack formation at the centre of certain steel specimens at various temperatures, various rates of deformation, different ratios between the length of the plastic zone and the specimen diameters as well as at different lengths of material at both ends of the plastic zone.As the deformation of metals in cross rolling is in many ways similar to that in cross forging, the authors carried out experiments on the cross forging of aluminium and lead which had been marked with concentric circles at the ends in a 35-ton mechanical press at room temperatures, and then compared the results thus obtained with those in the cross rolling of carbon and alloy steels.The results of these experiments show that:(1) With only one strike of the press in cross forging, the deformation is greatest at the surface and diminishes towards the centre of the specimen. When reduction is small, only elastic deformation occurs at the centre.(2) With several strikes of the press on rotating specimens, the deformation at the surface and in the centre is greater than that in the intermediate zone. When reduction is very small, plastic deformation also does not penetrate into the centre.(3) Similar to cross forging, the deformation of metal in cross rolling is also greatest at the surface, less at the centre and least in the intermediate zone. This distribution of deformation remains practically unchanged in different metals and various rolling temperatures as well as under other testing conditions mentioned above. Under conditions of the present experiments, when reduction is small, the deformation at the centre may be only elastic. In this case, the distribution of deformation is similar to that with only one strike of the press in cross forging.In cross rolling, the greater the reduction, the higher the rolling temperature, the higher the rate of deformation, the greater the ratio between the length of the plastic zone and the specimen diameter, and the shorter the length of the material on either side of the plastic zone, the greater is the tendency for crack formation at the centre. Alloy steels seem less liable to crack formation than carbon steels.
Impact of Forging Conditions on Plasma Nitrided Hot-forging Dies and Punches  [cached]
Ravindra Kumar,Ram Prakash,J. Alphonsa,Jalaj Jain
Journal of Materials Science Research , 2012, DOI: 10.5539/jmsr.v1n4p11
Abstract: In this work an effort has been made to study the effect on the performance of the plasma nitrided AISI H13 hot-forging dies and punches in two different forging service conditions –namely, fully-automatic and semi-automatic processes. The plasma nitriding is performed to increase the surface properties like –wear resistance and surface hardness of these components. After plasma nitriding the surface hardness of these materials has increased typically from ~500 HV0.01 to ~1200 HV0.01. In the plasma nitriding process high-voltage electrical energy is used to form plasma through which nitrogen ions are accelerated to impinge on the workpiece. The ion bombardment heats the workpiece, cleans the surface, and provides active nitrogen to make iron-nitride compounds. The iron-nitride compounds then diffuse to the workspace to harden the surface. In these two service conditions the plasma nitrided hot-forging dies and punches have shown typically 2.5 to 4 times increment during the performance. It is observed that the increment in the performance of the dies and punches depends on the forging service conditions, i.e., temperature of the dies and punches, shot repetition time and effective cooling of dies and punches in service conditions. Four times increment in the performance of dies and punches is found in the semi-automatic process, whereas two and half times increment in performance of dies and punches is observed in the fully-automatic process.
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