Roll Speed Ratio Research Articles

Effects of Process Parameters on Microstructure Evolution of Pure Aluminum Target under Clock 135° Collaborative Hot Rolling: A Simulation Study

Based on the results of current research and experiments, clock 135° hot rolling has been widely considered to be the preferred method in target rolling. However, it has been found that the process parameters are of vital importance during the rolling. Therefore, this work focuses mainly on the investigation of the effects of the roll speed ratio and offset distance on the microstructure evolution of a pure aluminum (Al) target under clock 135° collaborative hot rolling. Taking the ultra-thick pure Al metal circular billet as a research object, firstly, the evolutionary behavior of the effective strain (ES) and grain refinement for a rolled piece under the clock counterclockwise 135° synchronous and asynchronous (the speed ratios between rollers are set to be 1:1.05, 1:1.1, 1:1.2, respectively) rolling modes has been comparatively studied based on numerical simulation by DEFORM-3D software. It has been shown that a large ES value of 5.835 mm/mm is obtained in the lower surface layer by counterclockwise 135° asynchronous rolling with a roll–speed ratio of 1:1.2. Meanwhile, the average grain size below 80 µm accounts for ~61.8% of the total grains. These results demonstrate that the clock counterclockwise 135° asynchronous rolling method with a roll speed ratio of 1:1.2 should be an ideal strategy in obtaining finer grains. Unfortunately, nevertheless, the maximum degree of the bad plate shape is generated after forging by clock asynchronous rolling with a speed ratio of 1:1.2. As a consequence, clock counterclockwise 135° snake rolling with a 30 mm offset distance was proposed on the basis of a rolling speed ratio of 1:1.2, which perfectly corrected the warping plate shape caused by clock asynchronous rolling. What is more important, the minimum damage value of 1.60 was achieved accordingly. Meanwhile, the ES value increased in the core of the plate for the clock counterclockwise 135° snake rolling with all of the four offset distances compared to clock synchronous rolling. This study should be significantly conducive to guidance on setting process parameters in the industrial production of hot rolling metal or alloy targets.

Numerical Simulation and Experimental Verification of Hot Roll Bonding of 7000 Series Aluminum Alloy Laminated Materials

In the present study, the hot roll bonding process of 7000 series aluminum alloy laminated materials was numerically simulated and investigated using the finite element method, and the process parameters were experimentally verified by properties testing and microstructure analysis after hot roll bonding. In the roll bonding process of aluminum alloy laminated materials, the effects of the intermediate layer, pass reduction ratio, rolling speed and thickness ratio of component layers were studied. The results of finite element simulations showed that the addition of a 701 intermediate layer in the hot roll bonding process could effectively coordinate the deformation of the 705 layer and 706 layer and prevented the warping of the laminated material during hot rolling. It is recommended to use a multi-pass rolling process with small deformation and high speed, and the recommended rolling reduction ratio is 20%~30%, the hot rolling speed is 1.5~2.5 m/s and the thickness ratio of the 705 layer and 706 layer is about 1:5. Based on the above numerical results, five-layer and seven-layer 7000 series aluminum alloy laminated materials were prepared by the hot roll bonding process. The results showed that metallurgical bonding was realized between each component layer, and no delamination was observed from the tensile fracture between the interfaces of component layers. The tensile strength of the prepared laminated materials decreased with the increase in the thickness ratio of the 705 layer, and the bonding strengths of the laminated materials were in the range of 88–99 MPa. The experimental results verified the rationality of the process parameters recommended by the numerical simulations in terms of warping and delamination prevention.

Effect of Multi-Path Asynchronous Rolling Process on Microstructure and Mechanical Properties of ZK60 Magnesium Alloy.

At the initial rolling temperature of 400 °C, ZK60 magnesium alloy was hot rolled by three different rolling paths with different roll speed ratios (RSR) of 1:1.15, 1:1.2, and 1:1.5, respectively. The effects of different rolling processes on the microstructure and mechanical properties of the alloy were studied. The microstructure, plasticity, strength, hardness, and texture intensity of rolled samples were analyzed in this work. The results show that the microstructure uniformity of the alloy under multi-path asynchronous rolling (MAR) is significantly improved, which improves the mechanical properties of the material to a certain extent, and effectively weakens the texture intensity of the basal plane and reduces the anisotropy. The amount of randomly oriented grains of ZK60 magnesium alloy rolled by the C-1.5 (path C combined with the RSR of 1:1.5) process are significantly increased, which significantly weakens the basal texture and improves the ductility of the alloy, greatly enhancing the processing and formability of ZK60 magnesium alloy.

Friction-mediated tuning of shear deformation and microstructure in asymmetrically rolled Mg–1Gd alloy strips

Asymmetric rolling (ASR) is distinguished from conventional symmetric rolling (SR) process as the mismatched rolling speeds of two rolls introduce additional shear deformation to the rolled strips. Friction between the rolls and strip plays an important role in the formation of shear during ASR, which further impacts the microstructures of metallic strips. In this study, finite element (FE) simulations are used to probe the effects of friction in ASR of magnesium (Mg) alloy strips with varied roll speed ratios. The results on shear deformation distributions through the thickness of the strips reveal that the increase of friction coefficient or roll speed ratio induces greater shear deformation simultaneously. It is also found that the roll speed ratio can only promote the shear formation up to a threshold value which is dictated by the friction coefficient, further increasing the mismatch of the roll speeds provides negligible improvement on the plastic deformation of the strips. Experimentally, Mg–1Gd alloy strips are processed by SR and ASR, followed by electropulse treatment (EPT) to induce static recrystallization (SRX). The predictions of the numerical models are verified via EBSD and XRD observations on the grain refinement and texture weakening in Mg–1Gd alloy, which are the direct microstructure consequences of plastic deformations during rolling. At the roll speed ratio of 1.67, the alloy shows a weakened basal texture with an average grain size of 6.0[Formula: see text][Formula: see text]m after SRX. Further increasing the roll speed ratio to 5, however, does not enhance the grain refinement or texture weakening significantly.

Enhanced mechanical properties of AZ91 magnesium alloy by asynchronously large-strain high-efficiency rolling with bimodal grain structure

The study describes large strain high-speed asynchronous rolling process to process AZ91 magnesium alloy sheets with an overall thickness reduction of 84 % via two-pass rolling at 350 °C. Rolling speed ratios of 1.0, 1.1, 1.2, and 1.3 were used to obtain bimodal grain structure with different organizational states. Microstructural analysis unraveled that the formation of the bimodal structure was a consequence of combined effect of precipitation-strengthening and the Zener pinning effect. The R3 exhibiting an asynchronous ratio of 1.2 exhibited an optimized bimodal grain structure characterized by smaller recrystallized grains and a more homogeneous distribution. This phenomenon underscored the beneficial impact on enhancing strength and alleviating the anisotropic behavior.

Recrystallization and Anisotropy of AZ31 Magnesium Alloy by Asynchronous Rolling

In this study, the microstructure and mechanical properties of AZ31 magnesium alloy were investigated through asynchronous rolling. The results demonstrate that the rolled sample exhibits a refined grain structure with a significant presence of continuous dynamic recrystallization. Notably, as the roll speed ratio increases, the grain refinement becomes more apparent. For the sample with a roll speed ratio of 1.3, the tensile strength in the rolling direction (RD) reaches 273 MPa, while the elongation measures 20.2%. Similarly, in the transverse direction (TD), the tensile strength reaches 282 MPa, accompanied by an elongation of 18.9%. These values indicate a substantial improvement in elongation compared to conventional rolling processes. The enhanced elongation can be attributed to two primary factors. Firstly, recrystallization contributes to a grain refinement recrystallization ratio of 86%, promoting improved mechanical properties. Secondly, the recrystallized grains induce a favorable Schmidt factor, further supporting elongation. Overall, the findings of this research highlight the benefits of asynchronous rolling in refining the microstructure and enhancing the mechanical properties of AZ31 magnesium alloy.

Research on wheat flour‐making technology based on discrete elements

AbstractThe operating characteristics of a mill's rolling distance and roller speed during wheat‐milling were studied to provide a reference for optimizing the operating parameters of the mill. The high‐performance discrete element method software (EDEM) was used to establish a roller‐crushing system for wheat flour production. Numerical simulations of wheat flour production were performed using this system. It was found that increasing the roller distance of the flour mill machine could reduce the wear of the grinding rolls and the power of the grinding roll system, which reduced the crushing rate of wheat during the milling process. Increasing the grinding roll speed can reduce the wear of the grinding rolls but will increase the wheat‐crushing rate. At a constant fast roller speed, increasing the speed ratio increased the wheat‐crushing rate which reduced the power of the grinding roller system. During the grinding roll wear process, the obtuse and sharp angles gradually disappear. A comparison of the simulation and experimental results shows that the discrete element method can accurately predict the wear of the grinding roll.Practical ApplicationsThe milling machine is a key piece of equipment used for making wheat flour. The rolling distance, speed, and speed ratio of grinding rolls are important operating parameters during mill operation. Selecting specific parameters will directly affect the quality of wheat‐milling and the economic efficiency of the milling enterprise. This study adopted a discrete element method to study the effects of these parameters on wheat milling, providing a good reference for the technical personnel of milling enterprises.

Influence of Diameter Increase Speed on Diameter-Axial Rolling of Large 40Cr13 Stainless Steel Ring

Rolling speed ratios during the rolling process are critical to ring forming in this pepper. The selected roll feed mode is constant with the increasing speed of ring diameter during the main rolling stage. Based on Deform-3D finite element software, a large size ring with a diameter of φ1530 mm was taken as the research object. The numerical model of a large 40Cr13 stainless steel ring is established. The radial-axial rolling process of rings under different diameter increase speeds was simulated, and the changes in radial rolling force, temperature, and strain distribution of rings after rolling were analyzed under different diameter increase speeds. The results show that under the same conditions as other parameters, increasing the ring diameter increase speed has less effect on the temperature and equivalent standard deviation of variation inside the ring after rolling, but has more effect on the external surface, and both SDP and SDT decrease with the increase of ring diameter increase speed. The ring diameter increase speed on the maximum rolling force is more obvious, with the diameter increasing speed increasing. Using the rolling force, temperature standard deviation, and equivalent effect variation standard deviation as reference indexes, the diameter increase rate suitable for 40Cr13 rings is 6 mm/s.

Numerical Simulation and Deformation Behavior of a Ti/Steel Clad Plate during the Rolling Process

The deformation mechanism is complex in the hot rolling process of clad plates, and head bending is a common defect. In this paper, an analytical computational mechanical model of a metal plate was established by the classical elastic mechanics method, and the relationship between uneven thickness extension and warpage was obtained. The hot rolling bonding process of dissimilar bimetallic plates of Ti/Steel was investigated. On this basis, the mechanical origins of the plate bending defects and the influence of various factors on the evolution of the plate bending defects of the metal plates were revealed. The results indicated that the rolling forces increased with the increase in reduction ratio and thickness ratio. As the total reduction ratios of the clad plates increased, the reduction ratio of each layer increased. Furthermore, it was found that the thickness reduction ratios of steel were larger than those of Ti at a certain total reduction ratio, which could reach up to 59.6%. When the reduction ratios were 0.4 and 0.45, the bending degree increased with the thickness ratio of the upper and lower plates increasing gradually. The maximum warpage could reach 0.349 m. The clad plate shape was better when the roll speed ratio was 1.02 and the reduction rate was 0.4. The present numerical results provide a valuable insight into the deformation behaviors and mechanisms involved in the hot rolling of clad plates.

Mechanical properties, microstructure, and texture evolution of copper sheets subjected to differential speed rolling process

Copper sheets were subjected to differential speed rolling (DSR) at roll speed ratios (RSRs) from 1 to 3. The effects of the RSR on the yield strength, uniform strain, microstructure, and texture evolution in the copper sheets were investigated. The grain refinement and uniformity were obviously enhanced, the yield strength and uniform strains increased slightly, and the shear texture components were further widely distributed when the RSR was increased up to 2. At RSR = 3, the yield strength decreased, with a distinct increase in the uniform strains due to dynamic recovery and recrystallization as a result of the steep reduction in the geometrically necessary dislocation (GND) density and the grain orientation spread (GOS), thereby increasing the work hardening coefficient (n) and decreasing the work hardening rate (θ).

Finite element analysis of the springback behavior after V bending process of sheet materials obtained by Differential Speed Rolling (DSR) method

The Differential Speed Rolling (DSR) process is a severe plastic deformation method used in the production of microstructured materials with both high deformation and superior mechanical properties. This study has focused on determining the springback behavior and formability of the materials obtained by using the DSR method after the V bending process. Rolling processes were carried out at 4 different rolling speed ratios (1.0, 1.33, 1.66, and 2.0), 25% thickness reduction ratio, and 2 different rolling temperatures (room temperature and 580 °C). Then, the rolled sheet materials were bent using 3 different bending die angles (60°, 90°, 120°). As a result of this study, the greatest plastic deformation was reached at a speed ratio of 2.0 at 580 °C. Again, the lowest springback was obtained at 580 °C. As the die angle increased, the springback decreased. Springback has occurred in the bending process of all sheet materials obtained by rolling. In the bending process of the unrolled sheet material, both spring-forward and springback events were observed depending on the die angle.

Microstructure and mechanical properties of ultrafine grained 5052 Al alloy fabricated by multi-pass differential speed rolling

This study examined the microstructural evolution and mechanical properties of an ultrafine grained (UFG) Al alloy processed by multi-pass differential speed rolling (DSR). For DSR operations with a thickness reduction of 30% in each pass and a roll speed ratio of 1:4 for the lower and upper rolls, respectively, plastic strain was imparted to the samples that were rotated 180° along the longitudinal axis between the adjacent passes. As the number of operations increased, the deformed microstructure developed gradually from a band-like structure, which was observed after a single pass, to one consisting of nearly equiaxed ultrafine grains (≈0.7 μm) divided by high angle grain boundaries (GB) after four-pass DSR. A close microstructural observation using high resolution transmission electron microscopy showed that the GBs of the UFG Al sample were curved and wavy. Based on microstructural observations, the grain refinement mechanism occurring in the Al sample during multi-pass DSR was found to be governed by geometric dynamic recrystallization and continuous dynamic recrystallization. In addition, the deformation texture of the DSR-treated samples developed into the ideal shear texture consisting of a rotated Cube {001}<110> orientation and γ-fiber (<111>//ND) with increasing number of operations. The tensile test results showed that the strength of the deformed samples increased with decreasing grain size while its tensile ductility was sacrificed. Moreover, the contribution of the strengthening mechanisms, such as solid solution, precipitation, grain size and dislocation strengthening, were discussed.

Effect of roll speed ratio on the texture and microstructural evolution of an FCC high-entropy alloy during differential speed rolling

A very coarse-grained (335 μm) Fe 41 Mn 25 Ni 24 Co 8 Cr 2 high-entropy alloy with a single FCC phase was cold rolling to a 80% reduction in thickness using the differential speed rolling technique with various speed ratios (SRs) ranging between 1 and 4. As the SR was increased, the volume fraction of the region of high-density micro-shear bands increased to accommodate the higher shear strain. At SR = 4, the entire thickness of the sheet was covered with micro-shear bands, and ultrafine (sub)grains with a size of 1.4 μm were uniformly formed along the shear bands. A continuous dynamic recrystallization (CDRX) mechanism occurred during rolling, and a higher SR accelerated the CDRX process. During conventional rolling (at SR=1), a brass { 110 } 〈 112 〉 orientation texture with minor components of S { 123 } 〈 634 〉 and Cu { 112 } 〈 111 〉 orientations developed. At higher SRs, shear texture developed as the main type, while the development of rolling texture was suppressed. The microstructure at SR=4 obtained after annealing at 973 K showed a fully recrystallized microstructure composed of a five times smaller grain size (4 μm) with a higher intensity of γ fiber texture compared with that prepared by conventional rolling. The samples processed with high SRs exhibited better tensile properties compared with the conventionally rolled sample in terms of strength and ductility after annealing. The current results demonstrate that by using differential speed rolling with a high SR, one can achieve a significantly finer and more homogeneous microstructure, stronger shear texture, and superior tensile mechanical properties for an FCC high-entropy alloy compared to that obtained by conventional rolling. The strength of the as-rolled and annealed samples was quantitatively explained by considering the contribution of grain size and dislocation density to strengthening.

The central deformation calculation and analysis of the heavy steel plate for the gradient temperature rolling

The traditional symmetrical rolling process may result in the insufficient central deformation of the heavy steel plate. The gradient temperature rolling (GTR) based on the ultra-fast cooling was adopted in order to improve the central deformation and keep the deformation along the thickness to be well distributed. The temperature and strain field of the gradient temperature rolling were obtained by the thermo-mechanical coupling finite element method combined with different surface heat transfer coefficient, plate thickness, work roll diameters and so on. The calculated results showed that the deformation was more likely to penetrate into the core compared with uniform temperature rolling (UTR). The central equivalent strain with GTR was increased by 44.3% maximum compared with UTR in the same case. The deformation along the thickness was well distributed compared to the UTR. The central deformation gradually increases with the increase of reduction rate, surface heat transfer coefficient, work roll diameters and speed ratio, while the central deformation almost unchanged with linear velocity. Furthermore, industrial application showed the deformation can penetrate into the core compared with the UTR and it can help to eliminate the band structure. In this study, the influencing law of equivalent strain along the thickness with different parameters was summarized. The fitting model to calculate the central equivalent strain after GTR was established according to the numerical results. It can provide reliable theory and technology support for the setting of various parameters for GTR.

Study on minimum rollable thickness in asymmetrical rolling

A new model for the asymmetrical rolling is proposed to calculate the minimum rollable thickness simply and fast by the slab method. The calculation formulas of the rolling pressure, the rolling force, the critical roll speed ratio, and the critical front tension under different deformation zone configurations are proposed, and the deformation zone configuration-rolling parameter relationship diagram is given and analyzed. The results show that the minimum rollable thickness can be reached when the rolling parameters keep the deformation zone configuration as cross-shear zone + backward-slip zone (C + B) or all cross-shear zone (AC). The calculation formulas of the minimum rollable thickness and the required rolling parameters for different deformation zone configurations are proposed, respectively. The calculated value agrees well with the experimental result.

Influence of roll speed difference on microstructure, texture and mechanical properties of 7075 aluminum plates produced via combined continuous casting and rolling process

Abstract The influences of the dissimilarity in the roll speeds on the microstructure, texture and mechanical properties of 7075 aluminum plates produced via combined continuous casting and rolling (CCCR) process were investigated. Several experiments were conducted with three different upper/lower roll rotational speed ratios (ω/ω0, ω is the upper roll rotational speed and ω0 is the lower roll rotational speed), namely 1:1, 1:1.2 and 1:1.4. It was found that the greatest dissimilarity in the roll speed (ω/ω0=1:1.4) improved the yield strength and ultimate tensile strength of 7075 Al plate in the rolling direction by 41.5% and 21.9%, respectively. Moreover, at a roll speed ratio of ω/ω0=1:1.4, the average grain size was decreased by 36% whereas the mean hardness of the transverse cross-section of the finally rolled plate was increased by about 9.2%. Texture studies also revealed that the more the difference in the roll speeds was, the greater the isotropy and the hardness of the final product were. Nevertheless, conducting CCCR operation with different roll speeds resulted in about 6% reduction in the elongation of the deformed plate.

The steel plate curvature analytic modeling for the snake rolling with the same roll diameters

The snake rolling can keep the plate shape well, and the larger shear strain produced by the snake rolling is conducive to the deformation penetrating into the center of the heavy plate. So it provides a new method for producing the high-performance heavy steel plate. However, there is little research on the plate curvature modeling which is the key to achieve the snake rolling process. The deformation region was divided into four different zones at most which was depended on the positions of the two neutral points, and this number could be dropped to three or two in some other conditions. It was divided into three different cases according to the neutral point position: I, II, III and IV; I, II and IV; II and IV. The unit pressure and the accumulated shear strain deviation between the top and bottom portions of the plate with every case were established, and the plate curvature caused by shear strain was calculated on this basis. The plate curvature caused by the axial strain was also calculated according to the flow criterion. The approximations are corrected by a fitting coefficient E. The homogeneity coefficient E was introduced during the plate curvature modeling process to make the model more accurate. Then the total plate curvature model was established. The simulation of snake rolling process is carried out by using ANSYS LS-DYNA, and the plate curvature results are compared with the theoretical method. The results showed that the maximum and minimum relative error of the model was 11.61% and 0.28% compared to the simulation method, which can be applied for the online plate curvature control application with the effect of some self-learning methods. The plate curvature affecting law with the different process parameters (roll offset, roll speed ratio, rolling reduction, plate thickness and so on) was obtained in this paper. The research about the plate curvature modeling will provide important references for the heavy steel plate snake rolling production.

Study on asymmetrical cold rolling considered sticking friction

A new model considered the sticking friction for analyzing the asymmetrical cold rolling process is proposed by the slab method. This friction model is composed of the Coulomb friction model and yield shear stress. The analytical models of the rolling pressure are given respectively based on Coulomb friction model, constant friction model and Orowan friction model to compare the effects of different friction models on the friction stress and rolling pressure. The proposed model can avoid the problems of the friction stress exce eding the yield shear stress in Coulomb model and the friction factor m>1in the mixed friction model. The influences of the rolling parameters on the friction stress and the proportion of the sticking zone in the deformation zone are analyzed. The results show that the proportion of the sticking zone increases with the increases of the reduction rate, friction coefficient and roll radius, and decreases with the increases of the roll speed ratio and tensions. The calculated values by the proposed model agree well with the experimental results.

Mechanical properties and microstructure evolution of a CrCoNi medium entropy alloy subjected to asymmetric cryorolling and subsequent annealing

CrCoNi medium entropy alloy sheets were fabricated by asymmetric cryorolling (ACR) with rolling speed ratios of 1.2 (ACR1.2) and 1.6 (ACR1.6), followed by annealing at 873 K, 973 K, and 1073 K for 0.5 h. The mechanical properties were tested by a tensile test, and the microstructures were examined by transmission electron microscopy (TEM), scanning electron microscopy, and X-ray diffraction. Results show that the tensile strength of the ACR1.6-processed sheet reached 1340 MPa. This ternary alloy exhibits high strength and plasticity with a concomitant improvement in fracture toughness after annealing at 873 K, 973 K, and 1073 K. In addition, ACR1.6-processed sheets displayed better mechanical properties than ACR1.2-processed sheets. TEM results show that the grain refinement and the formation of a large fraction of deformation twins contributed to the enhanced mechanical properties of the CrCoNi medium entropy alloy.

Study on the relationship between asymmetrical rolling deformation zone configuration and rolling parameters

A new model for analyzing asymmetrical cold rolling process is proposed by the slab method, which solves the problem of insufficient applicability of existing models in the face of multiple asymmetric rolling conditions. In the new model, six configurations of the deformation zone are proposed as, forward-slip zone + cross-shear zone + backward-slip zone (F + C + B), cross-shear zone + backward-slip zone (C + B), all cross-shear zone (AC), forward-slip zone + cross-shear zone (F + C), all forward-slip zone (AF) and all backward-slip zone (AB). By analyzing the effects of rolling parameters such as reduction rate, roll speed ratio, tension and friction coefficient on the deformation zone configuration, the critical roll speed ratio and critical tension required for different deformation zone configurations are proposed. According to the variations of the critical roll speed ratio and critical tension with different rolling parameters, the deformation zone configuration - rolling parameters relationship diagram is obtained. Based on this diagram, the deformation zone configurations produced by different rolling parameter ranges can be determined, and the reasonable asymmetrical rolling technology can be selected for different production objectives. The proposed model can comprehensively and accurately calculate the rolling pressure, rolling force and torques under various rolling conditions, the calculated values agree well with the experimental results, the maximum error is 9.97%.