Symmetric rolling(SR)and asymmetric rolling(ASR)processes were carried out on 6 mm thick AZ31 magnesium alloy sheets that were produced by twin roll casting(TRC)technique.Before rolling processes,sheets were heat trea...Symmetric rolling(SR)and asymmetric rolling(ASR)processes were carried out on 6 mm thick AZ31 magnesium alloy sheets that were produced by twin roll casting(TRC)technique.Before rolling processes,sheets were heat treated in order to obtain a homogenized microstructure.In this study,for the ASR process the rolling speed ratio between upper roller and lower was selected as 1.25.Both SR and ASR processes were utilized with 40%reduction per passes using 2 pass schedule for a total reduction ratio of 0.67.Symmetric and asymmetric rolled sheets were characterized using optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)techniques.Texture measurements were performed by using X-ray diffraction(XRD)technique and mechanical properties were investigated by tensile tests and also hardness measurements.展开更多
AA1060 aluminum foil was rolled from 4 mm to 20 μm by asymmetric rolling without intermediate annealing. The microstructures and textures were investigated. The original coarse grains with an average grain size of 60...AA1060 aluminum foil was rolled from 4 mm to 20 μm by asymmetric rolling without intermediate annealing. The microstructures and textures were investigated. The original coarse grains with an average grain size of 60 μm were refined to fine equiaxed grains with an average grain size of about 500 nm with mainly large grain boundaries. During the rolling, the intensities of copper texture C-{112}<111> and brass texture B-{011}<211> gradually increased, and most crystallites aggregated along the β and τ orientation lines. The orientation intensity reached the maximum value 26 when the foil was rolled to 500 μm, but significantly decreased to 16 when the thickness became 20 μm, and the texture mainly consisted of a rotation cubic texture RC-{100}<011>. With the combined forces including drawing, compressing and shearing, severe plastic deformation was obtained during the asymmetric rolling, promoting dynamic recrystallization at room temperature. Because of a combined force in the deformation zone and shear force along the normal direction, dynamic recrystallization occurs during the asymmetric rolling; therefore, the average grain size is significantly refined. The texture intensity of ultrathin strip first increases, i.e., work hardening, and then decreases mainly because of dynamic recrystallization.展开更多
A rigid-plastic finite element method(FEM) simulation model for a multi-wedge cross wedge rolling(MCWR) was developed to analyze an asymmetric stepped shaft. To evaluate the MCWR process and better understand its defo...A rigid-plastic finite element method(FEM) simulation model for a multi-wedge cross wedge rolling(MCWR) was developed to analyze an asymmetric stepped shaft. To evaluate the MCWR process and better understand its deformation characteristics, the material flowing mechanisms, temperature distributions, strain and rolling force were analyzed. The correctness of the finite element simulation is experimentally verified. Numerical simulations and experiments led to the following conclusions: when α=36° and β=7.5°, the quality of the work piece can be significantly improved. Finally, the development of the asymmetric stepped shaft is applied to industrial production.展开更多
Asymmetric rolling(ASR), as one of severe plastic deformation(SPD) methods, was widely used to make ultra-fined materials with enhanced performance. Internal marks were used to show the shear deformation during asymme...Asymmetric rolling(ASR), as one of severe plastic deformation(SPD) methods, was widely used to make ultra-fined materials with enhanced performance. Internal marks were used to show the shear deformation during asymmetric rolling with pure aluminium as a model material. Effects of reduction ratio and mismatch ratio on the shear deformation were studied. With the observed shear deformation results, equivalent strain was calculated. For lager shear deformation, rolling equipment was modified to increase friction between specimen and the rollers. Consequently, extremely fine grains with size of 500 nm are obtained in pure aluminium. With improved asymmetric rolling, the ability of grain refinement of ASR is greatly improved.展开更多
In ferritic stainless steels, a significant non-uniform recrystallization orientation and a substantial texture gradient usually occur, which can degrade the ridging resistance of the final sheets. To improve the homo...In ferritic stainless steels, a significant non-uniform recrystallization orientation and a substantial texture gradient usually occur, which can degrade the ridging resistance of the final sheets. To improve the homogeneity of the recrystallization orientation and reduce the texture gradient in ultra-purified 17%Cr ferritic stainless steel, in this work, we performed conventional and asymmetric rolling processes and conducted macro and micro-texture analyses to investigate texture evolution under different cold-rolling conditions. In the conventional rolling specimens, we observed that the deformation was not uniform in the thickness direction, whereas there was homogeneous shear deformation in the asymmetric rolling specimens as well as the formation of uniform recrystallized grains and random orientation grains in the final annealing sheets. As such, the ridging resistance of the final sheets was significantly improved by employing the asymmetric rolling process. This result indicates with certainty that the texture gradient and orientation inhomogeneity can be attributed to non-uniform deformation, whereas the uniform orientation gradient in the thickness direction is explained by the increased number of shear bands obtained in the asymmetric rolling process.展开更多
Copper sheet with grain size of 30-60μm was processed by plastic deformation of asymmetrical accumulative rolling-bonding(AARB)with the strain of 3.2.The effects of annealing temperature and time on microstructural e...Copper sheet with grain size of 30-60μm was processed by plastic deformation of asymmetrical accumulative rolling-bonding(AARB)with the strain of 3.2.The effects of annealing temperature and time on microstructural evolution were studied by means of electron backscattered diffraction(EBSD).EBSD grain mapping,recrystallization pole figure and grain boundary misorientation angle distribution graph were constructed,and the characteristics were assessed by microstructure,grain size,grain boundary misorientation and texture.The results show that ultra fine grains(UFG)are obtained after annealing at 250℃ for 30?40 min.When the annealing is controlled at 250℃for 40 min,the recrystallization is finished,a large number of small grains appear and most grain boundaries consist of low-angle boundaries.The character of texture is rolling texture after the recrystallization treatment,but the strength of the texture is faint.While second recrystallization happens,{110}<1ī2>+{112}<11ī> texture component disappears and turns into{122}<212>cube twin texture component.展开更多
For refining grain and obtaining excellent properties, the experiments of asymmetric and symmetric monotonic hot rolling were carried out to investigate the role of shear strain on the microstructures and mechanical p...For refining grain and obtaining excellent properties, the experiments of asymmetric and symmetric monotonic hot rolling were carried out to investigate the role of shear strain on the microstructures and mechanical properties of V-microalloyed steel. The study demonstrates that the gradient ferrite distribution and dispersive pearlite through the sheet thickness are observed in asymmetric rolled specimen, and the homogeneous microstructure with ferrite and large pearlite is found in symmetric rolled specimen. The average grain size in asymmetric rolled specimen is smaller than the one in symmetric rolled specimen. The styles of precipitate morphology in asymmetric rolled specimen are random precipitate and obvious interphase precipitate, while the ones in symmetric rolled specimen are random precipitate and unobvious interphase precipitate. The additional shear strain results in the microstructure difference between asymmetric rolled specimen and symmetric rolled specimen. The impact energy of asymmetric rolled specimen, 58 J, is more than the one of symmetric rolled specimen, 48 J. Both deflection-energy curve and fracture morphology show that the fracture style of asymmetric rolled specimen is ductile, and the ones of symmetric rolled specimen are brittle and ductile.展开更多
The mechanical and microstructural properties as well as crystallographic textures of asymmetrically rolled low carbon steel were studied.The modelling of plastic deformation was carried out in two scales:in the macro...The mechanical and microstructural properties as well as crystallographic textures of asymmetrically rolled low carbon steel were studied.The modelling of plastic deformation was carried out in two scales:in the macro-scale,using the finite elements method,and in the crystallographic scale,using the polycrystalline deformation model.The internal stress distribution in the rolling gap was calculated using the finite elements method and these stresses were then applied to the polycrystalline elasto-plastic deformation model.Selected mechanical properties,namely residual stress distribution,deformation work,applied force and torques,and bend amplitude,were calculated.The diffraction measurements,X-ray and electron backscatter diffraction,enabled the examination of texture heterogeneity and selected microstructure characteristics.The predicted textures agree well with those determined experimentally.The plastic anisotropy of cold rolled ferritic steel samples,connected with texture,was expressed by Lankford coefficient.展开更多
To analyze and solve the problem of single-side long edge of hot rolled strip in certain domestic factory, the asymmetrical deformation of rolls and strip in asymmetrical stiffness mill stand based on slit beam model,...To analyze and solve the problem of single-side long edge of hot rolled strip in certain domestic factory, the asymmetrical deformation of rolls and strip in asymmetrical stiffness mill stand based on slit beam model, the strip profile and rolling force distribution at the exit of asymmetric stiffness stand mill were calculated using influence function method. Considering the character of in-site equipment and technology, a scheme of adjusting load distribution in finishing mill was made and the experiment was applied. Comparison of strip profile between new load distribution and the old one shows that the method can solve single-side long edge problem well.展开更多
The analysis of bending in finishing rolling was performed. An asymmetrical rolling force model was established, and the upper and lower neutral points were determined. Thc bending which resulted from the asymmetrical...The analysis of bending in finishing rolling was performed. An asymmetrical rolling force model was established, and the upper and lower neutral points were determined. Thc bending which resulted from the asymmetrical rolling force at the roll gap was studied and related flexibility equations were proposed according to elastic mechanics. Moreover, material mechanics was used to analyze the effects of temperature difference and self-weight on the bending out of the roll gap, and the flexibility equations were constructed. The main factors on bending were summed up, and the bending rule in the rolling could be obtained. In addition practical calculation was made with the production data of ribbon steel from Laiwu Iron & Steel Group Co. Ltd.展开更多
The texture evolution and lattice rotation in Al alloy 6111 with an initial {001} <110> component during symmetrical and asymmetrical rolling were investigated by means of orientation distribution function(ODF)....The texture evolution and lattice rotation in Al alloy 6111 with an initial {001} <110> component during symmetrical and asymmetrical rolling were investigated by means of orientation distribution function(ODF). The results show that the as-rolled initial {001}<110 > entation evolves into not only the copper orientation but also all the other orientations along the β fiber, including the brass orientation, by lattice rotation around special directions. Compared with the symmetrical rolling, the {001}<110 > component in the surface layer on the slower roller side evolves more quickly into the orientations along the β fiber during asymmetrical rolling, while that in the surface layer on the faster roller side evolves more slowly.展开更多
Since the research of flare slamming prediction is seldom when parametric rolling happens, we present an efficient approximation method for flare slamming analysis of large container ships in parametric rolling condit...Since the research of flare slamming prediction is seldom when parametric rolling happens, we present an efficient approximation method for flare slamming analysis of large container ships in parametric rolling conditions. We adopt a 6-DOF weakly nonlinear time domain model to predict the ship motions of parametric rolling conditions. Unlike previous flare slamming analysis, our proposed method takes roll motion into account to calculate the impact angle and relative vertical velocity between ship sections on the bow flare and wave surface. We use the Wagner model to analyze the slamming impact forces and the slamming occurrence probability. Through numerical simulations, we investigate the maximum flare slamming pressures of a container ship for different speeds and wave conditions. To further clarify the mechanism of flare slamming phenomena in parametric rolling conditions, we also conduct real-time simulations to determine the relationship between slamming pressure and 3-DOF motions, namely roll, pitch, and heave.展开更多
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 divide...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 influ- ence 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.展开更多
It is a complicated problem for cold-rolled strip to improve asymmetric strip shape in strip production. A roll system and strip coupled model of six-high cold rolling mill was established with finite element method t...It is a complicated problem for cold-rolled strip to improve asymmetric strip shape in strip production. A roll system and strip coupled model of six-high cold rolling mill was established with finite element method to estimate the effect of intermediate roll shifting, tilting, symmetric and asymmetric bending technologies on strip profile. To reduce asymmetric defects of strip shape as much as possible, some control strategies were proposed, including tilting and asymmetric bending of intermediate roll and work roll. The combinations of these three control strategies can effectively eliminate asymmetric strip shape defects. Finally, the closed-loop control model of asymmetric flat- ness at the last stand was given, and the flatness control system with the function of asymmetric strip shape control was also designed for cold tandem mill.展开更多
文摘Symmetric rolling(SR)and asymmetric rolling(ASR)processes were carried out on 6 mm thick AZ31 magnesium alloy sheets that were produced by twin roll casting(TRC)technique.Before rolling processes,sheets were heat treated in order to obtain a homogenized microstructure.In this study,for the ASR process the rolling speed ratio between upper roller and lower was selected as 1.25.Both SR and ASR processes were utilized with 40%reduction per passes using 2 pass schedule for a total reduction ratio of 0.67.Symmetric and asymmetric rolled sheets were characterized using optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)techniques.Texture measurements were performed by using X-ray diffraction(XRD)technique and mechanical properties were investigated by tensile tests and also hardness measurements.
基金Projects(51374069,U1460107) supported by the National Natural Science Foundation of China
文摘AA1060 aluminum foil was rolled from 4 mm to 20 μm by asymmetric rolling without intermediate annealing. The microstructures and textures were investigated. The original coarse grains with an average grain size of 60 μm were refined to fine equiaxed grains with an average grain size of about 500 nm with mainly large grain boundaries. During the rolling, the intensities of copper texture C-{112}<111> and brass texture B-{011}<211> gradually increased, and most crystallites aggregated along the β and τ orientation lines. The orientation intensity reached the maximum value 26 when the foil was rolled to 500 μm, but significantly decreased to 16 when the thickness became 20 μm, and the texture mainly consisted of a rotation cubic texture RC-{100}<011>. With the combined forces including drawing, compressing and shearing, severe plastic deformation was obtained during the asymmetric rolling, promoting dynamic recrystallization at room temperature. Because of a combined force in the deformation zone and shear force along the normal direction, dynamic recrystallization occurs during the asymmetric rolling; therefore, the average grain size is significantly refined. The texture intensity of ultrathin strip first increases, i.e., work hardening, and then decreases mainly because of dynamic recrystallization.
基金Projects(51375042,51505026)supported by the National Natural Science Foundation of ChinaProject(201312G02)supported by Yangfan Innovative&Entepreneurial Research Team,ChinaProject(2015M580977)supported by China Postdoctoral Science Foundation
文摘A rigid-plastic finite element method(FEM) simulation model for a multi-wedge cross wedge rolling(MCWR) was developed to analyze an asymmetric stepped shaft. To evaluate the MCWR process and better understand its deformation characteristics, the material flowing mechanisms, temperature distributions, strain and rolling force were analyzed. The correctness of the finite element simulation is experimentally verified. Numerical simulations and experiments led to the following conclusions: when α=36° and β=7.5°, the quality of the work piece can be significantly improved. Finally, the development of the asymmetric stepped shaft is applied to industrial production.
基金Project(5067062) supported by the National Natural Science Foundation of ChinaProject(NCET-04-0386) supported by New Century Scholarship of the Ministry of Education of China
文摘Asymmetric rolling(ASR), as one of severe plastic deformation(SPD) methods, was widely used to make ultra-fined materials with enhanced performance. Internal marks were used to show the shear deformation during asymmetric rolling with pure aluminium as a model material. Effects of reduction ratio and mismatch ratio on the shear deformation were studied. With the observed shear deformation results, equivalent strain was calculated. For lager shear deformation, rolling equipment was modified to increase friction between specimen and the rollers. Consequently, extremely fine grains with size of 500 nm are obtained in pure aluminium. With improved asymmetric rolling, the ability of grain refinement of ASR is greatly improved.
基金financially supported by the National Key R&D Program of China (2016YFB0300200)National Natural Science Foundation of China (Nos. U1660114 and 51174026)
文摘In ferritic stainless steels, a significant non-uniform recrystallization orientation and a substantial texture gradient usually occur, which can degrade the ridging resistance of the final sheets. To improve the homogeneity of the recrystallization orientation and reduce the texture gradient in ultra-purified 17%Cr ferritic stainless steel, in this work, we performed conventional and asymmetric rolling processes and conducted macro and micro-texture analyses to investigate texture evolution under different cold-rolling conditions. In the conventional rolling specimens, we observed that the deformation was not uniform in the thickness direction, whereas there was homogeneous shear deformation in the asymmetric rolling specimens as well as the formation of uniform recrystallized grains and random orientation grains in the final annealing sheets. As such, the ridging resistance of the final sheets was significantly improved by employing the asymmetric rolling process. This result indicates with certainty that the texture gradient and orientation inhomogeneity can be attributed to non-uniform deformation, whereas the uniform orientation gradient in the thickness direction is explained by the increased number of shear bands obtained in the asymmetric rolling process.
基金Projects(50804018,50564005)supported by the National Natural Science Foundation of ChinaProject(2003E0003Z)supported by the Key Science Foundation of Yunnan Province,China+1 种基金Project(08Y0055)supported by Scientific Research Fund of Yunnan Provincial Education Department,ChinaProject(2008-055)supported by Talents Cultivation Foundation of Kunming University of Science and Technology,China
文摘Copper sheet with grain size of 30-60μm was processed by plastic deformation of asymmetrical accumulative rolling-bonding(AARB)with the strain of 3.2.The effects of annealing temperature and time on microstructural evolution were studied by means of electron backscattered diffraction(EBSD).EBSD grain mapping,recrystallization pole figure and grain boundary misorientation angle distribution graph were constructed,and the characteristics were assessed by microstructure,grain size,grain boundary misorientation and texture.The results show that ultra fine grains(UFG)are obtained after annealing at 250℃ for 30?40 min.When the annealing is controlled at 250℃for 40 min,the recrystallization is finished,a large number of small grains appear and most grain boundaries consist of low-angle boundaries.The character of texture is rolling texture after the recrystallization treatment,but the strength of the texture is faint.While second recrystallization happens,{110}<1ī2>+{112}<11ī> texture component disappears and turns into{122}<212>cube twin texture component.
基金Funded by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China during the“12th Five-Year Plan”(No.2011BAE25B03)the National Natural Science Foundation of China(No.51274063)the National High Technology Research and Development Program of China(No.2015AA03A501)
文摘For refining grain and obtaining excellent properties, the experiments of asymmetric and symmetric monotonic hot rolling were carried out to investigate the role of shear strain on the microstructures and mechanical properties of V-microalloyed steel. The study demonstrates that the gradient ferrite distribution and dispersive pearlite through the sheet thickness are observed in asymmetric rolled specimen, and the homogeneous microstructure with ferrite and large pearlite is found in symmetric rolled specimen. The average grain size in asymmetric rolled specimen is smaller than the one in symmetric rolled specimen. The styles of precipitate morphology in asymmetric rolled specimen are random precipitate and obvious interphase precipitate, while the ones in symmetric rolled specimen are random precipitate and unobvious interphase precipitate. The additional shear strain results in the microstructure difference between asymmetric rolled specimen and symmetric rolled specimen. The impact energy of asymmetric rolled specimen, 58 J, is more than the one of symmetric rolled specimen, 48 J. Both deflection-energy curve and fracture morphology show that the fracture style of asymmetric rolled specimen is ductile, and the ones of symmetric rolled specimen are brittle and ductile.
基金Projects(DEC-2011/01/B/ST8/07394,DEC-2011/01/D/ST8/07399)supported by the Polish National Centre for Science(NCN)The support of the Polish Ministry of Science and Higher Education and of the French ANR 05-BLAN-0383 project
文摘The mechanical and microstructural properties as well as crystallographic textures of asymmetrically rolled low carbon steel were studied.The modelling of plastic deformation was carried out in two scales:in the macro-scale,using the finite elements method,and in the crystallographic scale,using the polycrystalline deformation model.The internal stress distribution in the rolling gap was calculated using the finite elements method and these stresses were then applied to the polycrystalline elasto-plastic deformation model.Selected mechanical properties,namely residual stress distribution,deformation work,applied force and torques,and bend amplitude,were calculated.The diffraction measurements,X-ray and electron backscatter diffraction,enabled the examination of texture heterogeneity and selected microstructure characteristics.The predicted textures agree well with those determined experimentally.The plastic anisotropy of cold rolled ferritic steel samples,connected with texture,was expressed by Lankford coefficient.
文摘To analyze and solve the problem of single-side long edge of hot rolled strip in certain domestic factory, the asymmetrical deformation of rolls and strip in asymmetrical stiffness mill stand based on slit beam model, the strip profile and rolling force distribution at the exit of asymmetric stiffness stand mill were calculated using influence function method. Considering the character of in-site equipment and technology, a scheme of adjusting load distribution in finishing mill was made and the experiment was applied. Comparison of strip profile between new load distribution and the old one shows that the method can solve single-side long edge problem well.
文摘The analysis of bending in finishing rolling was performed. An asymmetrical rolling force model was established, and the upper and lower neutral points were determined. Thc bending which resulted from the asymmetrical rolling force at the roll gap was studied and related flexibility equations were proposed according to elastic mechanics. Moreover, material mechanics was used to analyze the effects of temperature difference and self-weight on the bending out of the roll gap, and the flexibility equations were constructed. The main factors on bending were summed up, and the bending rule in the rolling could be obtained. In addition practical calculation was made with the production data of ribbon steel from Laiwu Iron & Steel Group Co. Ltd.
基金Project(0208) supported by the Science and Technology Research of Ministry of Education of China
文摘The texture evolution and lattice rotation in Al alloy 6111 with an initial {001} <110> component during symmetrical and asymmetrical rolling were investigated by means of orientation distribution function(ODF). The results show that the as-rolled initial {001}<110 > entation evolves into not only the copper orientation but also all the other orientations along the β fiber, including the brass orientation, by lattice rotation around special directions. Compared with the symmetrical rolling, the {001}<110 > component in the surface layer on the slower roller side evolves more quickly into the orientations along the β fiber during asymmetrical rolling, while that in the surface layer on the faster roller side evolves more slowly.
基金supported by the ChinaMinistry of Education Key Research Project "KSHIP-II Project"(Knowledge-based Ship Design Hyper-Integrated Platform)No.GKZY010004the National Key Basic Research Program of China No.2014CB046804
文摘Since the research of flare slamming prediction is seldom when parametric rolling happens, we present an efficient approximation method for flare slamming analysis of large container ships in parametric rolling conditions. We adopt a 6-DOF weakly nonlinear time domain model to predict the ship motions of parametric rolling conditions. Unlike previous flare slamming analysis, our proposed method takes roll motion into account to calculate the impact angle and relative vertical velocity between ship sections on the bow flare and wave surface. We use the Wagner model to analyze the slamming impact forces and the slamming occurrence probability. Through numerical simulations, we investigate the maximum flare slamming pressures of a container ship for different speeds and wave conditions. To further clarify the mechanism of flare slamming phenomena in parametric rolling conditions, we also conduct real-time simulations to determine the relationship between slamming pressure and 3-DOF motions, namely roll, pitch, and heave.
基金Item Sponsored by National Natural Science Foundation of China (50104006)National Key Technology Research and Development Program of China(2006BAE03A08)
文摘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 influ- ence 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.
基金Item Sponsored by National High Technology Research and Development Programof China(2009AA04Z163)
文摘It is a complicated problem for cold-rolled strip to improve asymmetric strip shape in strip production. A roll system and strip coupled model of six-high cold rolling mill was established with finite element method to estimate the effect of intermediate roll shifting, tilting, symmetric and asymmetric bending technologies on strip profile. To reduce asymmetric defects of strip shape as much as possible, some control strategies were proposed, including tilting and asymmetric bending of intermediate roll and work roll. The combinations of these three control strategies can effectively eliminate asymmetric strip shape defects. Finally, the closed-loop control model of asymmetric flat- ness at the last stand was given, and the flatness control system with the function of asymmetric strip shape control was also designed for cold tandem mill.