Pass Schedule Research Articles

FEM simulation on forming vacuum hexagon socket screws using tube workpiece

This study proposes a new forming design concept to produce vacuum hexagon socket screws using tube workpiece, and uses the finite element simulation software DEFORM-3D to simulate the multi-pass forming process of vacuum hexagon socket screws. The simulated material is SUS-304 stainless steel, and the frictional conditions are assumed to be constant shear friction, the die is assumed to be a rigid body. In the past, the traditional vacuum hexagon socket screw manufacturing process used a multi-pass process to manufacture a standard screw using a solid workpiece (wire rod), and then drilling an air channel in the core of the screw. This process not only wastes time, but also needs to increase the processing cost. In this study, the time and cost of drilling the air channel can be reduced by forming the vacuum hexagon socket head screw through the hollow tube. The finite element simulation results confirm that this design is a feasible method. The pass schedule can be reduced from 6 stages to 3 stages, the maximum effective stress decreased by 28.13%, and the total forming force decreased by 57.66%. The research results can be provided to relevant industry as the reference.

Numerical assessment of interstand tensions in continuous hot rolling processes of flat and long products

The paper deals with the calculation of interstand tensions in continuous rolling mills.In the rolling mill industry, continuous measurement and data collection of roll forces, roll torques, temperatures and roll velocities is possible. However, the important process parameter of interstand tensions is not directly measurable and no direct calculation of the interstand tensions is possible. The interstand tensions couple the effects of subsequent roll gaps and should therefore by known for a holistic recalculation of the process. It is straightforward to calculate the effects of the tensions on roll forces, torques and the stock velocity. The inverse problem of calculating the acting interstand tensions including their effects from the process parameters is of greater interest but also of a higher complexity, because the interactions between all the stands in the rolling mill must be regarded. The present paper aims at filling this research gap by presenting a mathematical model to solve the inverse problem by a linearization of the tensions influences in the rolling mill. The present model does not require measured roll forces or torques to find the interstand tensions, only the rotational velocities of the rolls and the rolling parameters (material, temperature, pass schedule or pass design) must be known. Tension-dependent spread is considered by an empirical sub-model. Results are shown for the tension distributions in strip and rod mills. The results indicate that the present friction conditions and the entry size of the rolled stock have a high impact on the tension distributions.

Coupling of an analytical rolling model and reinforcement learning to design pass schedules: towards properties controlled hot rolling

Rolling is a well-established forming process employed in many industrial sectors. Although highly optimized, process disruptions can still lead to undesired final mechanical properties. This paper demonstrates advances in pass schedule design based on reinforcement learning and analytical rolling models to guarantee sound product quality. Integrating an established physical strengthening model into an analytical rolling model allows tracking the microstructure evolution throughout the process, and furthermore the prediction of the yield strength and ultimate tensile strength of the rolled sheet. The trained reinforcement learning algorithm Deep Deterministic Policy Gradient (DDPG) automatically proposes pass schedules by drawing upon established scheduling rules combined with novel rule sets to maximize the final mechanical properties. The designed pass schedule is trialed using a laboratory rolling mill while the predicted properties are confirmed using micrographs and materials testing. Due to its fast calculation time, prospectively this technique can be extended to also account for significant process disruptions such as longer inter-pass times by adapting the pass schedule online to still reach the desired mechanical properties and avoid scrapping of the material.

Application of Variable Gauge Rolling Technology for Plate to Reduce the Head Impact

The Variable Gauge Rolling (VGR) technology is adopted for plate rolling. Two passes are treated as a group, with reducing the head reduction, increasing the tail reduction, to reduce the peak impact torque of the head, and give full play to the equipment capacity in the stable rolling stage to increase the pass reduction. The prediction models of plate width and length, rolling force and torque in VGR process are established. The using strategy of VGR are determined, and two methods for increasing reduction are put forward. The main body and head and tail sections of the rolled plate are calculated separated. The reduction corresponding to the target rolling torque is calculated by Newton iterative method, and pass schedule distribution of VGR process is shown. The VGR technology is applied for plate rolling process. The practical application shows that the influence of head impact in the plate rolling process can be reduced by using VGR. The torque amplification coefficient decreases linearly with the increase of gauge variation, and rolling passes number can be reduced through reasonable pass schedule distribution. The practical application shows that VGR can reduce the influence of head impact in the plate rolling process.

Multi-pass cold rolling and wire drawing process of gadolinium and its magnetocaloric effect

Owing to low ductility of magnetocaloric material (MCM)s, the plastic deformation process is quite challenging, and information available on the deformation process of MCMs is limited. In this study, the cold rolling and wire drawing processes of Gd wire including heat treatment were conducted. Uniaxial compression test of as-cast and heat treated Gd rod was conducted to evaluate the material property. The magnetocaloric effect (MCE) of drawn Gd wire was indirectly measured using a vibrating sample magnetometer (VSM). Pass schedule of cold rolling and wire drawing process for the Gd wire of Ø1.0 was designed. Finite element (FE) simulation of drawing process was conducted to investigate the drawing force for each drawing pass and strain distribution. Friction coefficient between the drawing die and Gd wire was evaluated via FE simulation and drawing experiments using a lubricant. Magnetic properties of the deformed and annealed Gd wire were evaluated and compared. The evaluated magnetic properties have shown that the presented process schedule is reasonable for manufacturing magnetocaloric wire without diminishing the magnetocaloric effect.

Optimization of roll calibrations for beam channel rolling. Part 2. Space of channel gauges

The optimization of roll pass design for rolling of channels based on the conception of two-stage optimization was realized. Roll pass design is independent functioning system and has two components of optimization: roll pass design scheme and pass schedule. Roll pass design will be considered truly optimal only if it has both an optimal scheme and an optimal pass schedule. During the first-stage optimization (search the optimal scheme of roll pass design), the most important moment is the formation of the “space of channel grooves” as the first space optimization. The above space consists of channel grooves of various types and shapes determined by known from the literature and practice roll pass designs. The “space of channel grooves” must be regularized with the use of the method of classification. As the main features of classification (groove space coordinates), the mostimp ortant geometric and technological features of the grooves were chosen: type of neck, type of actual flanges, type of false flanges, type of groove closure and quantity of rolls constituting the groove. Levels of variation for every criterion of classification have been identified and coded. Every admissible combination of variation levels specifies type and code of particular scheme of channel groove.Acknowledgements: The reported study was funded by RFBR, project number 20-38-90246.

Microstructures and Mechanical Properties of Cu–38 mass%Zn Alloy Fabricated by Different Rolling Pass Schedules

The heterogeneous-nano (HN) structure consisting of twin domains, shear bands, and lamellar grains developed by heavy cold rolling of FCC metals with low stacking fault energy is known to provide extremely high strength. In the present study, the effects of the rolling pass schedule on the development of HN structure and the mechanical properties in a Cu–38 mass%Zn alloy were investigated. Rolling was conducted on two different pass schedules; one was conventional unidirectional rolling (1-DR) up to 90% reduction in thickness, and the other was the two-directional rolling (2-DR), in which the specimen was unidirectionally rolled to 25% reduction, then rotated 90° around the rolling direction, and subsequently, unidirectionally rolled up to the total reduction of 90%. At a total reduction of 50%, the number of grains with deformation twins in the 2-DR specimen was higher than that in the 1-DR specimen. Further cold rolling up to 90% produced the HN structure in both specimens. The size of twin domains in the 2-DR specimen was finer and their volume fraction was larger than those in the 1-DR specimen. Also, the 2-DR specimen exhibited a better strength-elongation balance than the 1-DR specimen. It can be concluded that the finer size and larger volume fraction of the twin domains effectively improved the strength-elongation balance in the 2-DR specimen.

Successful Pass Schedule Design in Open-Die Forging Using Double Deep Q-Learning

In order to not only produce an open-die forged part with the desired final geometry but to also maintain economic production, precise process planning is necessary. However, due to the incremental forming of the billet, often with several hundred strokes, the process design is arbitrarily complicated and, even today, often only based on experience or simple mathematical models describing the geometry development. Hence, in this paper, fast process models were merged with a double deep Q-learning algorithm to enable a pass schedule design including multi-objective optimization. The presented implementation of a double deep Q-learning algorithm was successfully trained on an industrial-scale forging process and converged stably against high reward values. The generated pass schedules reliably produced the desired final ingot geometry, utilized the available press force well without exceeding plant limits, and, at the same time, minimized the number of passes. Finally, a forging experiment was performed at the institute of metal forming to validate the generated results. Overall, a proof of concept for the pass schedule design in open-die forging via double deep Q-learning was achieved which opens various starting points for future work.

Modeling and simulation of mass flow during hot rolling low carbon steel I-beam

Abstract Continuously cast near net shape blanks have been widely used in industry owing to the benefit of producing items close to final shape. However, for complicated shaped blanks, such as I and H beams, using near net shape blanks is not enough to prevent unwanted mass flow and deformation during hot rolling. The strength of the rolled material, pre-existing defects, and hot rolling parameters all have a major influence on the final shape of the rolled beam. In this study, the shaping of a low carbon steel during the breakdown mill hot rolling process was investigated using finite element analysis. The geometry of the as cast beam blank, mill roll profiles and hot rolling pass schedule were modeled identically to that used during the production hot rolling operation. The results showed that the I-beam has more deformation in the flange than in the web for breakdown mill rolling. A small depression or waviness was found to develop along the beam flange during the simulation. A parametric study of the effect of the roll gap on mass flow and beam blank surface depressions was performed. It was observed that for a larger roll gap, the surface depression increased in size. In contrast, the depression was found to decrease with a smaller rolling gap due to greater mass flow. These results agreed with the industrial produced I-beam. It was also predicted that the presence of a pre-existing surface defect on the beam blank flange has a significant influence on final size of the depression.

Optimization of Slab Edge in Roughing of Stainless Steel

To reach high demands of a stainless steel surface quality the location of a slab edge is optimized utilizing multiphysical finite element (FE) analysis. The slab edge forms in roughing process when the longitudinal edge of the stainless steel slab moves parallelly towards the center of a transfer strip surface due to several rough and edge rolling passes. Strip spreading and location of the slab edge are managed by edge rolling process which is accomplished concurrently with roughing. Deformation resistance has a significant role characterizing the strip spreading and material flow in the roll bite, thus experimental material compression testing was carried out and the results fitted to the Hensel-Spittel equation. Multiple edger roll profiles were designed, and the most feasible details of the roll profile were iteratively utilized for the new profiles. In this way the location of the slab edge was optimized closer to the edge of the transfer strip by developing a new edger roll profile and resetting edge rolling passes according to results of FE-simulations. To mimic an industrial-scale roughing process an automated pass schedule control was developed in the FE-model. Therefore, multipass simulations require only a pass schedule data to run simulation.

Microstructures and Mechanical Properties of Cu–38mass%Zn Alloy Fabricated by Different Rolling Pass Schedules

Microstructures and Mechanical Properties of Cu–38mass%Zn Alloy Fabricated by Different Rolling Pass Schedules

Enhanced Homogeneity of a Flat-rolled Wire in Twinning-induced Plasticity Steel Using the Pass Schedule Design

Enhanced Homogeneity of a Flat-rolled Wire in Twinning-induced Plasticity Steel Using the Pass Schedule Design

FEM Analysis and Experiment Validation on Multi-Pass Forging of Torx Round Flange Bolt

This study aims at exploring the multi-pass forging of Torx Round Flange Bolt (automotive fastener) to simulate each pass forging process using FEM simulation. The software is used to carry out the simulation analysis. Constant shear friction is always assumed at the interface between die and workpiece to explore the effective stress, the effective strain, the velocity filed, and the forging force for each pass. Through the pass schedule plan and design based on FEM analysis, the four-pass forging process is designed to form the Torx Round Flange Bolt compared the five-pass forging. It is noted that the total forging force is 1,204 kN, so the 200 tons machinery in the factory can be chosen to manufacture this automotive fastener. The die stress analysis for each pass has been explored to realize whether the dies are damaged or not. The forming feasibility of Torx Round Flange Bolt can be performed by FEM simulation. All dies designs and forming results can be proposed to the dies manufacture so as to perform the realistic experiments. Comparisons between FEM and experiment for final product dimensions can be carried out. The maximum dimension error is just around 3.32% to show a good agreement with the experiment. The research results can provide to the industries as the references of establishment of multi-pass forging technology.

Average austenite grain size evolution simulation during multi-pass shape metal hot rolling process

Constitutive equations describing the flow stress of Q235 steel undergoing hot plastic deformation have been developed by integrating the microstructure models and exponential flow stress models presented in literatures, in which the microstructure models parameters have been re-determined based on the related experiments carried out on cylindrical specimens of the Q235 steel. Therefore, the integrated constitutive equations are capable of calculating the evolution of austenite grain size and investigating the effects of average austenite grain size on the flow stress of Q235 steel during hot deformation. A three-dimensional thermo-mechanically coupled FEM simulation of an 11-pass H-shape metal roughing rolling process with the austenite grain size evolution taken into account have been carried out to verify the rationality of roll pass schedule. The accuracy of the integrated constitutive equations has been preliminary validated by the comparisons between measured and the calculated values of rolling force.

Prediction of Plate Crown during Aluminum Hot Flat Rolling by Finite Element Modeling

The roll deflection during hot rolling can result in uneven thickness distribution across the width of a plate (crown). A conventional rolling mill is equipped with bending systems that can control this convex shape of the plate. However, the determination of the proper bending load is very complicated as the plate crown is influenced by the rolling conditions. In this paper, a thermo-mechanical Finite Element Model on LS-DYNA™ software was utilized to predict crown evolution based on the rolling conditions in order to determine the setting values for achieving the target crown. The simulation results were compared and verified with actual industrial data for rolling force, plate temperature and plate crown. This approach is essential for pass schedule design and process parameter optimization in order to achieve the desired product quality.

Strain-Induced Ferrite Formation During Steckel Mill Simulations with Varying Roughing Pass Schedules

It has been previously demonstrated that austenite may undergo partial dynamic transformation (DT) during the plate rolling process. Austenite dynamically transforms into unstable ferrite during hot deformation even at very high temperatures. In this work, the plate rolling simulations, with emphasis on Steckel mill operations, through torsion testing under isothermal conditions were performed on an X70 steel. Four different roughing schedules were tested followed by five finishing passes with pass strains of 0.3 applied at 900 °C. The roughing schedules had zero, one, two and three roughing passes at a temperature of 1100 °C, strain of 0.4 and strain rate of 1 s−1. The stress–strain curves as well as the mean flow stress (MFS) behaviors indicated that both dynamic transformation (DT) and dynamic recrystallization (DRX) occurred during straining. The critical strains for the onset of DT and DRX were determined by means of the double differentiation method and the critical strain values decreased with the number of roughing and finishing strains from the first going to the last pass. It was observed that the volume fraction of the dynamically formed ferrite increased sharply during the finishing stage as the number of previous roughing passes increased, which can be attributed to higher strain accumulation. The results presented here indicate that improved models are needed to control the microstructure of the material during subsequent cooling.

Fabrication of 50.0 μm Ultra-Fine Pure Rhodium Wire, Using a Multi-Pass Wire Drawing Process, for Probe Card Pins.

Rhodium is a rare material that is widely used in electrical and electronic components due to its excellent mechanical and electrical properties. Ultra-fine rhodium wires in particular are widely used in electronic components. In this study, a multi-pass wire drawing process was designed to fabricate ultra-fine pure rhodium wire with a diameter of 50.0 µm from an initial diameter of 80.0 µm, which is used as probe card pins. An elastic–plastic finite element (FE) analysis was performed to validate the pass schedule that was designed for this study. A fine wire drawing experiment was also carried out to verify the effectiveness of the designed process. As a result, the ultra-fine rhodium wire was fabricated using the design process without wire breaks and the diameter of the final drawn wire was 47.80 µm.

Corrosion behaviour of cold‐rolled aluminium AA8015‐alloy in natural seawater at 0.18 μm surface roughness

AbstractAluminium is one of the most produced and used metals globally, second to ferrous metals. Its good corrosion resistance is one of the reasons for its heavy usage in typical applications, such as in marine applications. Electrochemical corrosion study of cold‐rolled aluminium AA8015‐alloy at 0.18 μm surface roughness in natural seawater was explored. The aluminium AA8015‐alloy utilized in this study was cold rolled in a reversible Achenbach cold rolling mill in four pass schedules to a thickness gauge of 1.2 mm. A surface roughness of 0.18 μm with three cold mounted samples was achieved on an automated grinding/polishing machine using 320 grit, 800 grit, and 1200 grit SiC paper. Electrochemical corrosion experiments were conducted on the samples in natural seawater using a computer‐controlled potentiostat in an open polarization cell set‐up at room temperature. The corrosion behaviour on surface morphologies of the samples was observed by high mega pixel camera and scanning electron microscope. Findings reveal asymmetric polarization curves for all the samples and energy dispersive X‐ray spectrometry elemental analysis shows the existence of insoluble substrate complexes formed on the surfaces. Consequently, the scanning electron microscope analysis confirms localised corrosion in the mode of pitting.

New approach for the optimization of pass-schedules in open-die forging

Open-die forging is an incremental forming process, which is mainly used for the production of large parts with high requirements regarding the mechanical properties and reliability of the forged parts. Finite element analysis (FEA) is able to simulate open die forging sequences. It is therefore very suitable to confirm, whether a selected schedule will be successful in terms of reaching the desired geometry and internal product quality. However, it is comparably slow and therefore not suitable for early process design, when out of an almost infinite number of potential sequences of strokes, an appropriate pass schedule needs to be designed. This is today usually achieved by pass schedule planning software, which takes into account volume constancy, empirical spread behavior and average temperature evolution. However, they do not account for product quality characteristics like microstructure and voids closure. In this paper recently developed fast models, which are able to calculate the temperature, equivalent strain and microstructure evolution along the core fibre of a forged workpiece are coupled with an optimization algorithm to allow automatic pass schedule layout and optimization. Different cost functions are evaluated regarding their impact on the resulting properties of the workpiece. The results indicate that for an overall optimization of open-die forging processes different phenomena and influencing parameters need to be considered, since all of these parameters have a significant influence on the resulting properties such as equivalent strain, temperature and grain size of the ingot.

Physical and numerical simulation of the multipass AHSS strip rolling, cooling and coiling

Abstract Evaluation of the effect of precipitation on mechanical properties of Advanced High Strength Steel strip was the objective of the project. Physical simulations of the multipass rolling were performed in plane strain compression. Different pass schedules were applied to investigate the influence of strain accumulation during the last two deformations on the subsequent microstructure and product properties. Various coiling temperatures were applied and an effect of precipitation in the coil was investigated. VirtRoll computer system, which is a digital twin of the full scale mill, was applied to reproduce investigated hot rolling routes.