Ring Rolling Process Research Articles

Microstructure evolution and deformation behaviors of pulse electro-assisted deformation in M50 bearing steel

M50 bearing steel, as a typical high-carbon and high-alloy steel, exhibits low cold working capacity with high susceptibility to produce voids during the ring rolling process. In this paper, the deformation behavior and microstructure evolution during the pulse electro-assisted tensile of M50 bearing steel was studied. The results show that the maximum flow stress of the pulse electro-assisted deformation (PEAD) specimen decreases by 24.4% compared with that of the traditional deformation (TD) specimen. However, the section shrinkage rate of the PEAD specimen is increased by 32.2%, which is even higher than that of the hot deformation (HD) specimens. This indicates the positive role of pulse current on the increase of plasticity. Besides, a constitutive model of the PEAD process was established by fitting the experimental data. With the assistance of pulse current, the deformation resistance and work hardening are reduced, so the number of voids is significantly reduced due to the easier metal flow. Moreover, the energy barrier of recrystallized grain nucleation is decreased, while the nucleation rate is increased under pulse current. As a result, the occurrence of recrystallization leads to the reduction of average grain size from 4.51 μm to 1.62 μm. According to the high-resolution transmission electron microscopy (HRTEM) and electron backscatter diffraction (EBSD) characterizations, the dislocation density decreases by 24% under the applied current, which should be ascribed to the increase of atomic flux and lattice diffusion coefficient. This work provides a new idea for solving the plastic deformation problem of M50 bearing steel.

Extreme gradient boosting-inspired process optimization algorithm for manufacturing engineering applications

Design and process optimization are key aspects of manufacturing engineering. This contribution details a machine learning (ML) methodology capable of learning from simulation results, experimental data, or sensor signals, and able to predict and optimize specific user-defined process and design parameters. The prediction-optimization algorithm is based on an enhanced Extreme Gradient Boosting (XGB) algorithm, highly responsive and accurate even for large datasets and complex variable interactions. Once the XGB function is trained, the optimization is carried out by a metaheuristic search algorithm defined according to the Differential Evolution (DE) architecture, allowing for the definition of the combination of independent variables that grant the minimization, or maximization, of the user’s defined objective function. The prediction and optimization capabilities have been assessed by applying the XGB-DE algorithm to a previously published authors' dataset and experimental results relevant for the radial-axial ring rolling (RARR) process, showing a prediction accuracy and optimization capability equal to 2.33% and 27.4%, respectively, with respect to authors’ previous finite element and experimental results. The XGB-DE methodology showed a remarkable capability in catching the trend and global minimum of a multi-variable and complex objective function, such as the one involved in complex thermo-mechanical forming processes.

Optimization of Ti-6Al-4V ring rolling process by FE simulation using RSM

Ring rolling is a process to manufacture seamless rings. The process is characterised by high non-linearity, asymmetry, unsteady state and non-uniformities in plastic strain and temperature distribution in the ring cross-section. Inhomogeneities in distribution of plastic strain and temperature have significant effects on deformation behavior, microstructure and mechanical properties. Fishtail defect, one of the form defects, is also a major concern. In this study, a reliable coupled 3D thermo-mechanical finite element model of the ring rolling process was developed using dynamic explicit code in ABAQUS/Explicit environment. Nine simulations with different combinations of feed rate and rotational speed were ascertained using Central Composite Design (CCD). CCD model is an integral part of Response Surface Methodology (RSM). Strain and temperature heterogeneities and fishtail defect were predicted using the simulated models. Coefficient of Variation (CoV) was introduced as a heterogeneity index for strain and temperature analysis. The fishtail coefficient was used to quantify fishtail defect. ANOVA was carried to find out the significant factors and interactions affecting the ring rolling process. Feed rate was found to be the only significant factor in the range of parameters studied. Multi-response optimization was performed to find out the feed rate at which the process is most optimized with an aim to minimize both strain and temperature heterogeneity and fishtail defect. Feed rate of 1.61 mm/s was found to be the most optimized process parameter.

Multi-objective optimization of cavity design for GH4738 superalloy profile ring rolling process based on FEM and RSM

Multi-objective optimization of cavity design for GH4738 superalloy profile ring rolling process based on FEM and RSM

Numerical Simulation of Intelligent Fuzzy Closed-Loop Control Method for Radial–Axial Ring Rolling Process of Super-Large Rings

During the radial–axial ring rolling (RARR) process of super-large rings, abnormal deformation states such as instability and out of circularity often lead to rolling termination and quality fluctuation of ring products. In this work, an intelligent fuzzy closed-loop control method for RARR process of super-large rings is proposed, i.e., the ring’s offset adaptive fuzzy control (ROAFC) based on the regulation of the axial roll’s rotational speed and the ring’s circularity fuzzy control (RCFC) based on the regulation of the mandrel’s feed speed. In addition, a recursive average filtering algorithm is added to smooth the axial roll’s rotational speed and the mandrel’s feed speed according to the actual situation. Using the ABAQUS/Explicit software and its subroutine VUAMP, the intelligent fuzzy controller of the ring’s offset and circularity in the RARR process is designed, and the finite element (FE) model for RARR process of a Φ10 m super-large ring with an integrated intelligent fuzzy control algorithm is established. The variation laws of the ring’s offset and circularity error in the RARR process are studied with regard to different control methods such as conventional planning control (CPC), ROAFC, RCFC, and comprehensive control of ROAFC combined with RCFC (ROAFC + RCFC). The results obtained show that, compared with the CPC, the ring’s offset is reduced by 84.6% and the circularity error is decreased by 51.9% in the RARR process utilizing comprehensive control of ROAFC + RCFC. The research results provide methodological guidance for realizing the intelligent forming of super-large rings.

An innovative constraining ring rolling process for manufacturing conical rings with thin sterna and high ribs

Conical rings with thin sterna and high ribs (CRTSHR) are key bearing-load parts of aerospace equipment, which are required to be manufactured with high performance and efficiency. Traditional ring rolling is the most preferred method for manufacturing high-performance ring parts, but it can hardly achieve the forming of CRTSHR due to the extreme geometry of CRTSHR. To solve this difficulty, an innovative constraining ring rolling process (CRR) is proposed in this paper to manufacture CRTSHR. To evaluate the proposed CRR and reveal its deformation behaviors, a thermomechanical coupled FE model for CRR of CRTSHR is established. Then, the experiment for CRR of CRTSHR is performed on a modified ring rolling machine, which proves that CRR of CRTSHR is feasible and the established FE model is reliable. Based on the reliable FE model, the metal flow mode in deformed CRTSHR is analyzed, and the deformation characteristics such as the stress state, strain distribution and the evolution of power parameters in CRR of CRTSHR are revealed. Finally, the influences of key parameters such as the friction factor between ring and molds, the diameter of idle roll and the feed velocity of idle roll on CRR of CRTSHR are investigated by FE simulation.

Evaluation of the roll elastic deformation and thermal expansion effects on the dimensional precision of flat ring rolling products: A numerical investigation

Ring rolling is a near-net shape forming process that produces ring products with relatively good dimensional accuracy. Two main factors that lower the precision of the final products are the inability to determine the effects of elasticity and the thermal expansion of rolls during the process. This work focuses on the creation and evaluation of suitable finite element models of a ring rolling process based on available experimental data found in literature. Through these numerical models, the elastic and thermal deformations of the rolls were thoroughly studied and the deformation effect on the produced ring was predicted. A difference of a few millimeters was calculated on the outer and inner diameters of the ring as a result of the two effects, which is far greater than the annotation levels of these products. On the other hand, the effects of the tools’ elasticity and thermal expansion of the ring rolling loads were proven negligible. Based on our analysis it was made clear that slight deformation deviations (thermal and elastic deformations) from the targeted values may cause instabilities to the process if the rolls fail to compensate for these deformations. Material combinations seem to influence the process. Regarding final dimensional deviations it can be concluded that thermo-elastic tool deformations are considerable in case of high product precision requirements.

Multi-objective optimization of parametric design for profile ring rolling process based on residual stress control

Multi-objective optimization of parametric design for profile ring rolling process based on residual stress control

Research on dynamic measurement of hot ring rolling dimension based on machine vision

In the process of ring rolling, the rolling process parameters of the equipment have an important influence on the forming process and forming quality of the ring. The ring rolling process has the characteristics of non-linearity, easy interference, rapid growth and asymmetric shape. These factors have resulted in the inability to measure the dimensions of the ring directly. In this work, we established a vision measurement system, and performed a series of operations on the image, such as threshold segmentation, hot ring contour extraction, oxide scale filtering, inner and outer ring extraction, inner and outer ring sampling, data visualization, etc. Moreover, we measured the dynamic dimension characteristics of small and medium size hot ring in the rolling process. The circularity, dimensional difference, center swing and vibration characteristics of the ring in the rolling process are obtained through the algorithm design, which characterizing the size change of the hot ring. The study provides practical methods and theoretical guidance for the subsequent measurement of large-size rings and feedback control of the rolling ring.

On a plastic instability criterion for ultra-large radial-axial ring rolling process with four guide rolls

A dynamic mechanical model is proposed to describe the complexing actions of all the rolls on the ring during the ultra-large radial-axial ring rolling (RARR) process with four guide rolls. Based on the model, the calculation models for bending moment and normal stress at any section of the ring are deduced by force method. If the maximum section bending normal stress exceeds the yield stress of the ring materials, the ring will be distorted thus leading to the instability of the RARR process. According to this, a plastic instability criterion for the ultra-large RARR process with four guide rolls is developed, based on which a mathematical model to calculate the critical guide force for avoiding plastic instability of ring is obtained. The influence rule of the position of guide roll on the dangerous ring section of plastic instability is revealed, from which it is found the dangerous ring section mainly appears at the radial and axial deformation regions and the contact positions of the guide rolls and ring. The optimized layout of guide roll around the ring in favor of stability is determined to be about α1 = 61° and α2 = 119°. The plastic instability criterion is proven to be reliable from the aspects of the critical guide force, the section bending moment and normal stress and the dangerous ring section of plastic instability. Intelligent simulation case studies for the RARR process of ultra-large aluminum alloy ring indicate that the stable forming of the process can be effectively realized by regulating the guide force based on the plastic instability criterion. This work could provide a valuable guidance for the control of guide rolls and the optimization of the ultra-large RARR process with four guide rolls.

Prediction of work-rolls failure in hot ring rolling process

The work-rolls of the hot ring rolling process are subjected to various damages due to the contact with hot metal. Thermo-mechanical fatigue is one of these damages. In order to predict failure due to the thermo-mechanical stress in the work-rolls, the developed code in ABAQUS has been used. The comparison between three- and two-dimensional models and, also, thermal and thermo-mechanical response of work-rolls with variable boundary conditions has been investigated. The results have shown that by applying mechanical and thermal loads separately or simultaneously, the response of work-rolls is completely different. In the mandrel, the location of the maximum equivalent stress is on the surface, while the location of equivalent maximum stress is in the subsurface of the main-roll. By making use of cumulative damage rules and the stress life method, the thermo-mechanical fatigue life was estimated. The cumulated damage in the mandrel’s surface was higher than subsurface regions. In contrast to the mandrel, the cumulated damage in the main-roll’s subsurface was higher than surface regions. In hot ring rolling machines, these locations are prone to crack initiation as a result of the thermo-mechanical fatigue in the work-rolls.

Grain evolution during hot ring rolling of as-cast 42CrMo ring billets

Abstract During hot ring rolling and subsequent air-cooling processes, the as-cast metal alloy undergoes a complicated microstructural evolution. In this paper, the grain refinement of as-cast 42CrMo ring billet during hot ring rolling and air-cooling was conducted by FEM simulation and tests. Moreover, the grain refinement mechanism of as-cast 42CrMo was also studied by comparison of single-pass deformation and multi-pass deformation with short pass interval time, with the purpose of studying the influence of the deformation process on grain refinement supported by the results of FEM simulation. As a result, effective strain and average grain size of the ring show zonal distribution characteristics The effective strain on the inner and outer layers of the ring is large, contributing to fine and homogeneous grains. In contrast, the cumulated effective strain on the interlayer of the ring is small, resulting in inhomogeneous and mixed grains and large average grain size. Grain growth occurs during subsequent air-cooling. The microstructural distribution of the hot rolled ring was confirmed by a hot ring rolling test.

Machine Learning-Based Models for the Estimation of the Energy Consumption in Metal Forming Processes

This research provides an insight on the performances of machine learning (ML)-based algorithms for the estimation of the energy consumption in metal forming processes and is applied to the radial-axial ring rolling process. To define the mutual influence between ring geometry, process settings, and ring rolling mill geometries with the resulting energy consumption, measured in terms of the force integral over the processing time (FIOT), FEM simulations have been implemented in the commercial SW Simufact Forming 15. A total of 380 finite element simulations with rings ranging from 650 mm < DF < 2000 mm have been implemented and constitute the bulk of the training and validation datasets. Both finite element simulation settings (input), as well as the FI (output), have been utilized for the training of eight machine learning models, implemented with Python scripts. The results allow defining that the Gradient Boosting (GB) method is the most reliable for the FIOT prediction in forming processes, being its maximum and average errors equal to 9.03% and 3.18%, respectively. The trained ML models have been also applied to own and literature experimental cases, showing a maximum and average error equal to 8.00% and 5.70%, respectively, thus proving once again its reliability.

Investigation of cavity filling in profile ring rolling process for T-shape ring

In this paper, key parameters affecting the cavity filling in single and double T-shape profile rings are comprehensively investigated via numerical and experimental analysis. A three-dimensional finite element model was developed in Abaqus\Explicit to assess the influence of crucial ring rolling process parameters, including feed speed, main roll rotational velocity, the existence and the absence of axial rolls on the cavity filling of single and T-shape rings and the main roll torque. Besides, a ring rolling machine was built to conduct practical experiments and validate the numerical evaluation, while for the first time, the role of the axial roll and the main roll torque on the quality of the cavity filling is experimentally evaluated. Power requirements and the final ring profile geometry were obtained by the simulation method, and the results were confirmed by the experiments. The results showed that axial rollers significantly reduced the cavity filling rate, and in contrast, the effect of mandrel feed speed and the main roll rotational velocity was much lower. Also, the axial forces were considerably less than the radial forces. However, the rolling operation was done in both radial and axial directions. The existence of axial rolls had an intensive effect on the process’ required power, as a result the main roll torque increased more than three times in case of applying axial rolls, compared with not considering them. Severe effects of axial rollers on increasing force and decreasing cavity filling rate can be attributed to frictional forces between the ring and axial rolls, restricted ring motion, which has to be compensated by a higher torque of the main roll. When the axial rolls are used, the material flow in the ring’s height direction is restricted. Therefore, the material cannot move easily to form the profile. All experimental and simulation results, including mandrel force, cavity filling, and ring profile geometry, were in good agreement, and in all cases, the simulation error was less than 10%.

Multivariable regression and gradient boosting algorithms for energy prediction in the radial-axial ring rolling (rarr) process

Energy prediction and starvation have become an essential part of process planning for the XXI century manufacturing industry due to cost-saving policies and environmental regulations. To this aim, the research presented in this paper details how machine learning-based algorithms can be an effective way to predict and minimize the energy consumptions in the widely spread radial-axial ring rolling (RARR) process. To analyze this bulk metal forming process, 380 numerical simulations have been developed using the commercial SW Simufact Forming 15 and considering three largely utilized materials, the 42CrMo4 steel, the IN 718 superalloy, and the AA6082 aluminum alloy. To create the database for both multi-variable regression and machine learning models, ring outer diameters ranging from 650 mm to 2000 mm and various process conditions including different sets of tool speeds and initial temperatures have been considered. For the case of the multi-variable regression model, to account for all the cross-influences between all the parameters, a second-order function including 26 parameters has been developed, resulting in a reasonable average accuracy (94 %) but also in an impractical huge equation. On the other hand, the machine learning model based on the Gradient Boosting (GB) approach allows obtaining a similar accuracy (96 %) but its compact form allows a more practical utilization and its training can be expanded almost indefinitely, by adding more results from both numerical simulations and experiments. The proposed approach allows to quickly and precisely predict the energy consumption in the RARR process and can be extended to other manufacturing processes.

Limits to making L-shape ring profiles without ring growth

A novel ring rolling process is proposed to flexibly produce shaped rings without circumferential ring growth, potentially saving material and energy as well as reducing upstream and downstream processing requirements. In this paper, six circumferential constraint rolls are used constrain circumferential growth and enable L-shape profiles to be developed through axial material flow, via a compressive hoop stress. Process limits were studied in 22 experiments on lead rings and a set of axisymmetric thermally coupled simulations on a high value engineering material, Inconel 718. Profile depths of 75 % of the original wall thickness were achieved in a range of rings and operating conditions, and material savings of up to 60 % demonstrated over rectilinear rolling. There was no evidence of cracking or void formation, unlike processes where under-deformed regions are stretched circumferentially and are vulnerable to cracking. In several cases a non-circular ring shape developed, limiting the achievable profile depth especially for small wall thicknesses, large reductions in thickness per pass, or large profile heights. The constraint roll forces when this ‘collapse’ occurs was studied and an upper bound predicted by a plastic hinge model. The thermal simulations showed that in all except 4 cases reheats would be required to keep within safe temperature bounds, thus suggesting an optimum reduction in thickness per pass to avoid both excessive cooling and collapse.

Studying the residual stress homogenization and relief in aerospace rolling ring of GH4169 alloy using ageing treatment

In the manufacturing process of aerospace large ring parts, a large number of exterior materials are removed, which makes the ring parts become a thin-walled structure with low stiffness. In the actual production process of the aerospace industry, the processing deformation caused by a series of internal and external factors is ubiquitous. The studies show that the main factor causing the machining deformation is the initial residual stress (RS) inside the blank ring. The ring rolling process is accompanied by local severe plastic deformation, resulting in large and uneven RS. The homogenization and reduction of initial RS are of great significance to reduce the adverse effect of machining deformation. The research object in this study is a sizeable GH4169 alloy aerospace rolling ring. First, a long-term natural ageing treatment was designed for homogenizing residual stresses in sizeable GH4169 alloy ring. Second, a finite element model was established to simulate the rolling process and the thermal ageing process. The corresponding rolling and thermal ageing experiments were carried out to verify the simulation results. The purpose of this process is to explore and verify the effect of natural ageing and artificial ageing on homogenizing and reducing the RS in the rolling ring. The results show that the homogenization of RS distribution was enhanced significantly by natural ageing treatment, while the RS magnitudes descended by 15~35%. Combined with the subsequent thermal stress relief, the RS is significantly reduced or even eliminated. This study is of great significance to the homogenization and reduction of RS in large GH4169 alloy ring.

Establishment of Thermal Ductile Fracture Criterion for As‐Cast 42CrMo Steel and Its Application in Hot Ring Rolling Process

The casting‐rolling compound forming process of ring parts is an advanced plastic forming technology that has been developed due to the merits of high efficiency and energy and material saving. However, cracks often occur during the hot ring rolling process, especially at the edges of the ring parts, which severely affects the forming quality. To predict and try to avoid the occurrence of cracks in the casting‐rolling compound forming process of ring parts, the high‐temperature fracture behaviors of as‐cast 42CrMo steel were investigated by thermodynamic experiment method. The high‐temperature tensile tests were carried out using the Gleeble‐3500D thermomechanical simulator at various temperatures and strain rates. Stress‐strain curves and fracture morphology were examined, through which the sensitivity of stress to temperature and strain rate and the effect of dynamic recrystallization and cavity evolution on fracture were found. The law of critical fracture strains was analyzed, and the model of critical fracture strain as a function of temperature and strain rate was established. Based on Oyane criterion, the thermal ductile fracture criterion was established in conjunction with the model of critical fracture strain. By embedding this thermal damage model into the finite element (FE) model for hot ring rolling of an as‐cast 42CrMo ring, the damage prediction for this process was realized, and the thermal ductile fracture criterion was proved to be reliable. From the FE results for hot ring rolling, mechanism of damage and fracture in the hot ring rolling process was analyzed. The damage threshold Cf is small, and the damage ratio D is large at the top and bottom edges of the inner surface area of the ring, which have the greatest propensity to cracking in the course of hot ring rolling. This is of great significance in terms of improving the forming quality of ring parts in the casting‐rolling compound forming process.

Microstructural evolution and enhanced mechanical properties of Mg–Gd–Y–Zn–Zr alloy via centrifugal casting, ring-rolling and aging

A ring-shaped Mg–8.5Gd–4Y–1Zn–0.4Zr (wt%) alloy was manufactured via centrifugal casting and ring-rolling process. The effects of accumulative ring-rolling reduction amount on the microstructure, texture, and tensile properties of the alloy were investigated. The results indicate that the microstructure of centrifugal cast alloy consists of equiaxed grains and network-like eutectic structure present at grain boundaries. The ring-rolled alloy exhibits a characteristic bimodal microstructure composed of fine dynamic recrystallized (DRXed) grains with weak basal texture and coarse un-DRXed grains with strong basal texture, along with the presence of LPSO phase. With increasing amount of accumulative ring-rolling reduction, the coarse un-DRXed grains are refined via the formation of increasing amount of fine DRXed grains. Meanwhile, the dynamic precipitation of Mg 5 RE phase occurs, generating a dispersion strengthening effect. A superior combination of strength and ductility is achieved in the ring-rolled alloy after an accumulative rolling reduction of 80%. The tensile strength of this ring-rolled alloy after peak aging is further enhanced, reaching 511 MPa, while keeping a reasonable ductility. The salient strengthening mechanisms identified include the grain boundary strengthening of fine DRXed grains, dispersion strengthening of dynamic precipitated Mg 5 RE phase, short fiber strengthening of LPSO lamellae/rods, and precipitation strengthening of nano-sized prismatic β′ precipitates and basal γ′ precipitates.

A novel polygonal ring rolling method

Polygonal rings are widely applied to fabricate critical ring components, such as cabin of aerospace equipment and large nuts. The traditional ring rolling method is difficult to fabricate polygonal rings owing to their non-rotary geometry characteristics. This paper proposes a novel polygonal ring rolling method using a simple rotary plain ring as the ring workpiece. Firstly, the motivations and principles of polygonal ring rolling method are proposed. Then, four typical feeding tool paths are designed and the plastic deformation modes and geometry evolutions of polygonal ring under these four feeding tool paths are revealed. Meanwhile, four typical feeding tool paths are optimized based on the stability of the polygonal ring rolling process. Finally, the polygonal ring rolling experiments are carried out and it is demonstrated that the proposed polygonal ring rolling method is feasible.