Rolling Pass Research Articles

Investigation into the Rolling Process of 20CrNiMo/Incoloy 825 Composite Materials

This paper is focused on the rolling finite element simulation and experimental study of 20CrNiMo/Incoloy 825 composite materials. Firstly, single-pass rolling finite element simulations of the composite materials were conducted. The effects of rolling pass reduction and rolling speed on the warpage, interface strain difference, and stress of the 20CrNiMo/Incoloy 825 composite materials were evaluated, highlighting an ideal first-pass reduction of 30% and a rolling speed of 0.117 m/s. Based on these results, rolling finite element simulations under total reduction–pass conditions of 65%–3 passes, 75%–4 passes, and 85%–5 passes were conducted on 20CrNiMo/Incoloy 825 composite materials. The rolling process was found to be optimal for a total reduction of 85%–5 passes based on the ratio of the vertical compressive stress experienced by the Incoloy 825-side metal to the yield strength of Incoloy 825 at 1150 °C. Based on the results of single- and multi-pass finite element simulation experiments, microstructural observations and interface analyses were then conducted on the 20CrNiMo/Incoloy 825 composite materials after rolling. The bonding interface of the composite materials was found to be undulating, indicating good composite effects. In addition, Cr, Ni, and Fe at the interface of the composite materials exhibited a steep gradient of change, indicating trace element diffusion with a distance of 8.27 μm in the 20CrNiMo/Incoloy 825 composite materials. Finally, the interfacial bonding mechanism of the 20CrNiMo/Incoloy 825 composite materials was studied, and the results indicate that this mechanism is based on a combination of diffusion and recrystallization bonding mechanisms.

Influence of different rolling passes and deformation amounts on the microstructure evolution and strengthening mechanism of Cu-Ni-Si alloy

Under the condition of controlling the total rolling deformation to 80.0%, the effects of multi-pass rolling, the ratio of deformation between the first and second stages in two-stage rolling, and aging parameters on the microstructural evolution and property enhancement of Cu-Ni-Si alloy were investigated. The results showed that the second-stage rolling promotes the formation of high-density dislocations, significantly enhancing dislocation strengthening. Simultaneously, the high-density dislocations facilitate the precipitation of the second phase during aging, and concurrently improving the strength and electrical conductivity of the alloy. In the two-stage rolling and aging process, a ratio of first-stage to second-stage rolling deformation less than 1 yields superior comprehensive properties. Specifically, when the first-stage rolling deformation is 35.0% and the second-stage deformation is 68.8%, the alloy achieves an optimal electrical conductivity of 49.53% IACS, hardness of 272.9 HV0.1, tensile strength of 773.0 MPa, and yield strength of 723.3 MPa. This is because a rolling ratio less than 1 results in higher dislocation density; the δ-Ni2Si precipitates have a coherent relationship with the Cu matrix, the interparticle spacing of precipitates is smaller. The average grain size is refined from 1.29 μm to 1.08 μm, significantly enhancing grain boundary strengthening. Dislocation strengthening and second-phase strengthening are the primary strengthening mechanisms of the alloy, and the calculated alloy strength agrees well with the experimental values, with errors less than 3.4%. Additionally, the Avrami equation in phase transformation kinetics was utilized to study the variation law of the volume fraction of the δ-Ni2Si phase with aging time.

Gray relational analysis for parametric optimization of micro-EDM of thermo-mechanically processed AA7075 and AA7075/SiC/Gr composite

The AA7075 alloy and AA7075/SiC/Gr hybrid composite prepared by the stir-casting method have been further thermo-mechanically processed through unidirectional hot rolling and hot cross-rolling routes to eliminate casting defects like voids, blow holes etc. Three initial sample temperatures, that is, 350℃, 400℃, and 450℃, have been considered for the hot cross-rolling. The Al alloy and its hybrid composite prepared at different rolling temperatures are studied to investigate their micro-machining behavior through micro-electric discharge machining (µ-EDM). The micro-holes are made on the rolled samples along the rolling direction of the final rolling pass using a tool with twist drill bit geometry. Further, multi-objective optimization of the µ-EDM process parameters considering the response parameters viz. material removal rate (MRR) and tool wear rate (TWR) has been carried out using the gray relational analysis (GRA) technique. The µ-EDM parameters chosen to optimize in this study are voltage, pulse on time, and tool rotation. The obtained GRA results are further analyzed through normality and equal variance tests. The R-squared values of 95.02% and 95.53% for AA7075 alloy and hybrid composite, respectively, indicate that the data fit well with the statistical model. In material removal, the different electrical and thermal characteristics of the Al matrix and the reinforcements possibly generate sparks with a different characteristic that ultimately affects the MRR of the composite. Through scanning electron microscopy (SEM), the morphological study confirmed the presence of globules and voids on the machined surface. The formation of globules and voids is more significant in the AA7075 alloy than in the composite.

Controlling the tensile properties of a high-strength-ductility Ti2AlNb alloy by hot rolling

In this work, a high-strength-ductility Ti2AlNb alloy is fabricated by hot rolling the compact prepared by spark plasma sintering. The microstructure and tensile properties of the rolled sheets were controlled by changing the thickness reduction and rolling pass. Results show that rolling causes grain growth, larger thickness reduction results in pronounced grain coarseness. Rolling cannot cause recrystallization but reheating can. Higher thickness reduction results into higher recrystallization ratio, which decreases with increasing the reheating times. All sheets have tensile strengths higher than 980 MPa with elongation higher than 9%. The multiple rolling process causes the increase in ultimate tensile strength (UTS) and yield strength but decrease in elongation (EL). The maximum UTS of 1048.1 MPa is obtained after two rolling passes with 42% thickness reduction per pass. The maximum EL of 12.6% is obtained after reheating the single pass rolled sheet with 30% thickness reduction. All the sheets present ductile fracture mode.

Efficient formability in Radial-Shear Rolling of A2024 aluminum alloy with screw rollers

The Radial-Shear Rolling (RSR) process, commonly utilizing traditional conical rollers, encounters challenges in achieving optimal deformation in high-strength aluminum alloy A2024, vital for aerospace applications due to its exceptional strength-to-weight ratio. This study explores the potential of screw rollers to enhance RSR efficiency for A2024 aluminum, aiming to evaluate their impact on microstructure, mechanical properties, and key deformation parameters (force, temperature) compared to conical rollers. Employing a combined approach of finite element simulations and experiments with force analysis, the study assesses the effects of screw rollers in a two-pass RSR process. The findings reveal significant advantages with screw rollers, achieving a 15 % increase in equivalent strain compared to conical rollers, indicating enhanced material formability. Consistent temperature distribution across roller types ensures stable processing conditions. Screw rollers also demonstrate a 9 % reduction in force required during the second rolling pass, potentially reducing equipment load demands and enabling higher compression per pass for improved process efficiency. Additionally, a more uniform microhardness distribution suggests consistent mechanical properties with screw rollers compared to conical ones. These results highlight the potential of screw rollers to optimize RSR of A2024 aluminum, offering improved plastic deformation efficiency, temperature control, and potentially lower equipment loads. This advancement holds promise for a more efficient and cost-effective RSR process in producing high-quality A2024 aluminum components for aerospace and other demanding applications.

Simulations of Texture Evolution in the Near-Surface Region During Aluminum Rolling

Prediction of texture changes during cold rolling is important because they affect the recrystallization and anisotropy of an aluminum sheet during successive forming steps. During cold rolling of aluminum alloys, the through-thickness textural change in the subsurface layer depends heavily on the shear stresses exerted on the material. The intensity of this shear stress is determined by the value of and change in the coefficient of friction as the contact length between the rolls and metallic sheet changes. The quality of the texture prediction under constant and variable coefficients of friction are assessed for three established texture models: the grain interaction (GIA) model, the viscoplastic self-consistent (VPSC) approach, and the full-field crystal plasticity Düsseldorf Advanced Material Simulation Kit (DAMASK) code. The simulation results are compared with subsurface layer textures obtained from conducting experimental cold-rolling trials on an aluminum alloy, which are designed to maximize shear in a single rolling pass. The formulation of a variable coefficient of friction is crucial for ensuring both the reasonable prediction of rolling forces and changes in texture. GIA and DAMASK yield the best texture prediction results for a variable coefficient of friction model.

Characterization of microstructure, texture, grain structure, and thermal properties of Al/Ni/Al multilayered composites fabricated through cross-accumulative roll bonding

This research investigates microstructure, texture, and thermal properties of Al/Ni/Al composites fabricated by cross-accumulative roll bonding (CARB) process. According to the microstructural results, ultra-fine grain structure was observed in severely deformed layers. More grain refinement occurred when the content of Ni increased. In addition, shear texture components became stronger by increasing the CARB passes and Ni content even though the Copper-based texture components of {112}<111> existed in all deformed samples. Also, despite an improvement in thermal features of deformed aluminum and nickel layers versus temperature rise, the TD, and TC decreased as the number of passes increased. However, by increasing the rolling passes, the measured thermal capacity values modestly increased while the thermal expansion values first decreased and then increased. Regarding composites, all thermal features decreased with an increase in Ni volume fraction. Due to the restricting effect of harder reinforcement layers, the measured thermal expansion declined from 17.01 × 10−6 1/k in Al/0.2 Vf Ni to 15.4 × 10−6 1/k in Al/0.8 Vf Ni.

Research on the Flatness Control Performance and Parameter Influence Law of Four-High Skin Pass Rolling Mill

Research on the Flatness Control Performance and Parameter Influence Law of Four-High Skin Pass Rolling Mill

Microstructure Evolution and Strengthening Mechanism of Dual-Phase Mg-8.3Li-3.1Al-1.09Si Alloys during Warm Rolling.

In this study, the rolling process of the warm-rolled duplex-phase Mg-8.3Li-3.1Al-1.09Si alloy and the strengthening mechanism of as-rolled Mg-Li alloy were investigated. The highest ultimate tensile strength (UTS, 323.66 ± 19.89 MPa) could be obtained using a three-pass rolling process with a 30% thickness reduction for each pass at 553 K. The strength of the as-rolled LAS831 alloy is determined by a combination of second-phase strengthening, grain refinement strengthening, dislocation strengthening, and load-transfer reinforcement. Of these factors, dislocation strengthening, which is caused by strain hardening of the α-Mg phase, can produce a good strengthening effect but also cause a decrease in plasticity. The Mg2Si phase is broken up into particles or strips during the rolling process. After three passes, the AlLi particles were transformed into an AlLi phase, and the Mg2Si particles and nanosized AlLi particles strengthened the second phase to form a hard phase. The average size of the DRXed β-Li grains decreased with each successive rolling pass, and the average size of recrystallized grains in the three-pass-rolled LAS831 alloy became as low as 0.27 μm. The interface between the strip-like Mg2Si phase and the α-Mg phase is characterized by semicoherent bonding, which can promote the transfer of tensile and shear forces from the matrix to the strip-like Mg2Si phase, thereby improving the strength of the matrix and thus strengthening the LAS831 alloy.

Pulsed current-assisted twelve-roll precision rolling deformation of SUS304 ultra-thin strips with exceptional mechanical properties

Innovative pulsed current-assisted multi-pass rolling tests were conducted on a 12-roll mill during the rolling deformation processing of SUS304 ultra-thin strips. The results show that in the first rolling pass, the rolling reduction rate of a conventionally rolled sample (at room temperature) is 33.8%, which can be increased to 41.5% by pulsed current-assisted rolling, enabling the formation of an ultra-thin strip with a size of 67.3 μm in only one rolling pass. After three passes of pulsed current-assisted rolling, the thickness of the ultra-thin strip can be further reduced to 51.7 μm. To clearly compare the effects of a pulsed current on the microstructure and mechanical response of the ultra-thin strip, ultra-thin strips with nearly the same thickness reduction were analyzed. It was found that pulsed current can reduce the degree of work-hardening of the rolled samples by promoting dislocation detachment, reducing the density of stacking faults, inhibiting martensitic phase transformation, and shortening the total length of grain boundaries. As a result, the ductility of ultra-thin strips can be effectively restored to approximately 16.3% while maintaining a high tensile strength of 1118 MPa.Therefore, pulsed current-assisted rolling deformation shows great potential for the formation of ultra-thin strips with a combination of high strength and ductility.

Elasto-plastic simulation of hot shape rolling of steel by a meshless method

This paper describes the development of meshless simulation of thermomechanics of steel in a continuous hot rolling process using a novel meshless solution procedure. During the process, steel billets at high temperatures are transferred through multiple roll passes, each with a specific groove shape and roll gap. The major outcome of this simulation system is to design the rolling schedule and confirm whether the final shape is inside the acceptable range. For this purpose, a perpendicular 2D slice model approach is used to obtain fast and reasonably accurate simulation results. A return mapping algorithm solves the elasto-plastic material model with linear hardening to obtain displacements, strains and stresses. They are calculated by the local radial basis function collocation method (LRBFCM), which uses the local interpolation of the strong form of partial differential equations. The predefined slice positions are entered into the rolling system, and for each position, the slice contact line and amount of reduction are predicted and used as boundary conditions. Thermal and mechanical models are run sequentially, which is repeated until the final slice position reaches the exit from the last roll. The simulation system was validated with multiple rolling schedules provided by the industrial partner and was successfully used in the steel production plant afterwards. The meshless LRBFCM successfully solves a complex elasto-plastic large deformation problem of hot rolling for the first time.

Formation mechanism of surface gradient microstructure and mechanical properties evolution of Mg–Y-Nd-Gd-Zr alloy by ultrasonic rolling

The evolution mechanism of the microstructure and mechanical properties of a Mg–Y-Nd-Gd-Zr alloy subjected to different numbers of passes of the ultrasonic surface rolling process (USRP) was investigated. The results demonstrated an initial decrease followed by an increase in the surface roughness of the alloy. The optimal surface roughness was achieved after four passes, with a contour mean deviation of 0.06 μm and micro-roughness 10-point height of 0.55 μm. After the USRP, the alloy exhibited a composite gradient structure characterized by increased grain size and decreased dislocation, lamination, and twin densities. The depth of the gradient layer increased with each additional USRP pass, ranging from 650 μm (1 pass) to 910 μm (8 passes). Furthermore, the USRP treatment effectively enhanced the alloy strength; compared with the untreated samples; the yield strength increased by 34.2% in the gradient sample after one pass. No significant change was observed in the YS with an increasing number of rolling passes for Mg alloys, whereas both the tensile strength and elongation showed improvements. High-density twinning played a crucial role in enhancing the YS of the gradient samples without significant variation across different numbers of rolling passes, thus following a consistent pattern. The formation of more nanocrystals on the surface of Mg alloys after multiple rolling cycles is key to preventing premature fracture failure and improving the work-hardening rate.

Effect of rolling reduction on microstructure and tension-compression yield asymmetry of rolled AZ31 magnesium sheet

Magnesium (Mg) alloys have been receiving significant applications in automotive and aerospace industries owing to its high strength-to-weight ratios. Approximately 30 % (by weight) of material used in automobiles are in the form of sheet metal. Therefore, in the present work AZ31 magnesium (Mg) alloy was hot rolled with different reduction ratios to produce Mg sheet. The results revealed that employing a 40 % reduction per pass led to a remarkable 92 % reduction in thickness, outperforming the 82 % reduction achieved with a 20 % reduction per pass, along with fine grain of 8 μm. Investigation has been conducted on the relationship between grain size and its impact on the tension-compression yield asymmetry in Mg sheet. This investigation unveiled that the suppression of {101‾2} extension twinning mode of deformation due to the back stress imposed by the simultaneous action of grain boundaries and twin overlap, effectively minimizing the asymmetry from 2.11 (as received AZ31 alloy) to 1.13 (5th pass rolling sheet). The study extensively explored the underlying mechanisms governing the yield asymmetry behavior of AZ31 Mg sheets. These mechanisms included strain hardening tendencies, Schmid Factor, and KAM (Kernel Average Misorientation) assessment, all of which were interconnected with microstructural attributes.

Cold rolling pass design and process based on controlling the distribution of material strain energy density

To address the problem of excessive grain boundaries and difficulty in eliminating defects on the inner surface of a pipe under a cold rolling pass, a method to control the distribution of material strain energy density is proposed, and a reasonable reduction in wall thickness is designed. An analysis model for inner surface defects was established using the inner wall adhesion value as the main criterion to quantitatively analyze the degree of defects on the pipe's inner surface. A systematic analysis of the rolling process of three different pass-opening shapes revealed that the opening shape dramatically affects the deformation and flow of the metal. During the rolling process, because of the unreasonable distribution of metal deformation caused by the existing pass design, the pipe is prone to high or concentrated stress, resulting in a low adhesion value for the inner wall and a greater degree of defects on the inner surface. Therefore, we propose a new opening shape and reasonably allocate the wall thickness reduction of the pipe to obtain a new pass. Numerical simulation reveals that, after rolling with the new pass, the inner wall adhesion value becomes relatively high, and the mechanics parameters have also been improved. The experimental results show that, under the new pass design, grain boundaries on the inner surface of the pipe are reduced and the smoothness is significantly improved, proving the feasibility of a cold rolling pass design based on controlling the distribution of material strain energy density.

Paving Low-Temperature Asphalt on the B 169 Highway Near Heyda

Abstract Research into lowering the temperature during the production and installation of hot asphalt has been going on for a long time. In addition to developing appropriate recipes, it is important to gain experience, particularly in asphalt paving technology, since in addition to the behavior of the different asphalt mixtures during their compaction, external factors such as the location of the project and weather conditions also play an important role. The testing of the low-temperature asphalt on the federal highway B 169 was carried out successfully. Due to the high pre-compaction by the paver screed, the required compaction values were achieved on the binder course with 4 rolling passes and on the surface course with 3 rolling passes. The viscosity-changing additives and the selected rolling technology had a positive influence on the results. However, precise measurement results for compaction could not be achieved using the PQI probe.

Improvement of the Technology of Precision Forging of Connecting Rod-Type Forgings in a Multiple System, in the Aspect of the Possibilities of Process Robotization by Means of Numerical Modeling.

The study refers to the application of numerical modeling for the improvement of the currently realized precision forging technology performed on a hammer to produce connecting rod forgings in a triple system through the development of an additional rolling pass to be used before the roughing operation as well as preparation of the charge to be held by the robot's grippers in order to implement future process robotization. The studies included an analysis of the present forging technology together with the dimension-shape requirements for the forgings, which constituted the basis for the construction and development of a thermo-mechanical numerical model as well as the design of the tool construction with the consideration of the additional rolling pass with the use of the calculation package Forge 3.0 NxT. The following stage of research was the realization of multi-variant numerical simulations of the newly developed forging process with the consideration of robotization, as a result of which the following were obtained: proper filling of the tool impressions (including the roller's impression) by the deformed material, the temperature distributions for the forging and the tools as well as plastic deformations (considering the thermally activated phenomena), changes in the grain size as well as the forging force and energy courses. The obtained results were verified under industrial conditions and correlated with respect to the forgings obtained in the technology applied so far. The achieved results of technological tests confirmed that the changes introduced into the tool construction and the preform geometry reduced the diameter, and thus also the volume, of the charge as well as provided a possibility of implementing robotization and automatization of the forging process in the future. The obtained results showed that the introduction of an additional rolling blank resulted in a reduction in forging forces and energy by 30% while reducing the hammer blow by one. Attempts to implement robotization into the process were successful and did not adversely affect the geometry or quality of forgings, increasing production efficiency.

Effect of variable thickness cross rolling on microstructure gradient of 2205 duple stainless steel

Quantitative description of the complex relationship between rolling process and microstructure is crucial for improving the performance of 2205 duplex stainless steel products. In this work, four distinct rolling processes were used for three passes of hot rolling of 2205 duplex stainless steel. The study delved into the macroscopic morphology, microstructural gradients, and texture evolution of 2205 duplex stainless steel sheets in various rolling states. In addition, a data expansion method was used to expand the original experimental data, and the support vector machine model optimized by genetic algorithm was used to accurately describe the complex relationship between different rolling processes and microstructures. The results indicate that the proposed variable thickness cross-rolling method renders a more uniform microstructure in the rolled piece, with significantly refined grains and the formation of a distinct structural gradient. Among them, when using process 3 rolling, the grain size in the edge area of the plate after three passes of rolling is finer and the degree of recrystallization is higher, which is conducive to improving the problem of poor thermal plasticity at the edges and providing a basis for studying the suppression of edge crack damage in 2205 duplex stainless steel. In addition, the proposed machine learning model accurately predicted the grain size of plates in different rolling states, aligning closely with experimental findings.

Effects of Deformation Penetration and Recrystallization on the Internal Quality of Casting Ingot

To investigate the influence of rolling passes on the internal quality during high‐temperature reduction pretreatment (HTRP), three cast ingots with identical total reduction but varying numbers of rolling passes are prepared. The 3D distribution, size, and quantity of defects are analyzed using ultrasonic nondestructive microscopy. The effect of rolling passes on defect healing is studied, with macrostructure, microstructure, and grain size analysis aided by finite element software. In contrast to the three‐pass HTRP, the one‐pass HTRP demonstrates a diminishment of 7% in defect dimensions and a notable decline of 66% in the quantity of defects. The results reveal that increasing the number of rolling passes leads to a deterioration in internal quality of the slab. Reducing the number of rolling passes improves internal strain penetration, facilitates the recrystallization process, and enhances the microstructure uniformity, ultimately improving the internal quality.

Microstructure and mechanical properties of high-temperature free-oxygen rolled Cu/1060Al bimetallic composite materials

In this work, Cu/1060Al bimetallic composite materials manufactured by high-temperature free-oxygen rolling process are reported. The results show that with the increase of rolling passes, the microstructure of Cu and 1060Al gradually extends and elongates in the rolling direction, and the interface that has few compounds is dominated by mechanical bonding. It is worth noting that layered fracture occurs during the tensile process. After annealing, the interface changes from mechanical bonding to metallurgical bonding, and the layered fracture is alleviated under the traction of the interface layer. With the increase of annealing time and temperature, the thickness of the interface compounds gradually increase, and the interface compounds from the copper layer to the aluminum layer are Cu9Al4, CuAl and CuAl2, respectively. Annealing at 350 °C for 2 h exhibits the best comprehensive performance, a tensile strength of 138 MPa and an elongation of 64 %. Tensile behavior in the rolled state and annealed state has been discussed based on failure theory, and compound growth after annealing has been analyzed on account of the theories of dynamics and thermodynamics.

Rolling theory-guided prediction of hot-rolled plate width based on parameter transfer strategy

Machine learning performs well in many problems. However, the tendency to generate predictions that violate theoretical knowledge makes it difficult to apply to practical processing. To resolve this situation, this paper combines domain knowledge with a data-driven model, proposes a theory-guided machine learning framework based on a parameter transfer strategy, and applies it to the width prediction of plates after multiple passes of hot rolling. The framework applies a swarm optimization algorithm to the original theoretical model and generates numerous highly-physical consistent samples. The established deep neural network (DNN) model is trained with simulated data, and the parameters are fine-tuned using a parameter transfer strategy combined with actual data to ensure excellent adaptation to the actual environment based on adequate learning of theoretical knowledge. In tests, the proposed model had the best overall prediction performance in this paper. Meanwhile, the developed model is consistent with the existing perception of rolling theory. This allows for the quick and reliable application of machine learning models in production.