Rolling Operation Research Articles

Effects of varying friction coefficient on rolling pressure distribution

Accurate characteristics of roll pressure distribution is essential in the estimation of the energy and power requirements for parts undergoing plastic deformation. The nature of the pressure distribution is very sensitive to the friction coefficient between the roller and the deformed part. The physics of the deformation process points to a variable friction coefficient, however, current research and practices result in the use of a constant friction coefficient. This work explored the development of a technique to determine a quantitative relationship between the variable friction coefficient and the process parameters. The pressure distribution was then developed within the contact region using the variable friction coefficient model. Results show that current approach used by industry (‘the rule of thumb’) overestimates the pressure distribution, compared to the current research, thus wasting power needed for the rolling operation by about 18%. Keywords: Rolling; varying friction coefficient; pressure distribution; power

Towards Energy Efficient Shape Rolling: Roll Pass Optimal Design and Case Studies

Shape rolling is widely employed in the production of long workpieces with appropriate cross-section profiles for other industrial applications. In the development of shape rolling systems, roll pass design (RPD) plays an essential role on the quality control of products, service life of rolls, productivity of rolling systems, as well as energy consumption of rolling operations. This study attempts to establish a generic strategy based on hybrid modeling and an improved genetic algorithm, to support the optimizations of RPD and shape rolling operations at a systematic perspective. Objectives include improving the quality and efficiency of RPD, reducing energy consumption of shape rolling, as well as releasing the demands on costly trails and expert knowledge in RPD. Hybrid modeling based on cross-disciplinary knowledge is developed to overcome the limitations of isolated single-disciplinary models. And conventional genetic algorithm is improved for the implementation of optimal design. Targeting to integrate empirical data and published reliable solutions into optimizations, a parameters estimation method is proposed to transfer the initially misaligned models into a uniform pattern. A tool based on the Matlab platform is developed to demonstrate the optimal design operations, with case studies involved to validate the proposed methodology.

Optimal design of side roller to minimize the roundness errors of lead wire sides

This study improved the roundness error of the side portion of a lead wire produced by rolling operations. In the conventional method, the side portion is cut after rolling. As an improvement, a side roller was designed for use after flat rolling to directly form the side portion of the lead wire to reduce the roundness error. A rolling analysis of lead wires was performed using LS-DYNA, which is a simulation program capable of analyzing the dynamic behavior of the material. Finite element modeling of the lead wire was carried out, and the change of the cross section was observed after the wire rolling process. The shape of the side roller was optimized to reduce the roundness error. The angle of the side roller, the installation position, and the shape radius were selected as the design variables. PIAnO (Process Integration, Automation, and Optimization), a commercial PIDO (Process Integration and Design Optimization) tool, was used for the optimum design of the side roller, and the results confirmed that the roundness error was reduced.

Hardness prediction of a cold rolled Nimonic 80A exhaust valve spindle

Purpose: of this paper is to predict the hardness of cold rolled exhausts valve spindle fabricated of Nimonic 80A via axisymmetric finite element analysis, compression testing, and hardness inspection. Design/methodology/approach: The stress-strain relationship of Nimonic 80A was obtained via compression testing with deformation ratios of 10%, 20%, and 30%. Hardness changes caused by the strain hardening effect were measured in cut specimens in both the axial and circumferential directions following compression testing. The effective strain at the measurement position was calculated via finite element analysis. The regression equation for hardness changes caused by work hardening was derived from analysed strain and inspected hardness. The cold-rolling deformation of an exhaust valve spindle was analysed using axisymmetric finite element analysis. Findings: The stress-strain relationship calculated from compression testing was well expressed using the Holloman equation and the strain-hardness relationship by strain hardening was successfully regressed using the shifted power law model for Nimonic 80A, Nickel-Chromium based super alloy. Research limitations/implications: This research focused hardness prediction of spindle after ring rolling operation for generating beneficial compressive surface residual stresses for enhancing fatigue life. Further research to quantify compressive residual stress after rolling shall be followed to increase fatigue life. Practical implications: The cold rolling process is a typical incremental forming method and should be analysed under three-dimensional conditions. However, it takes lots of time to solve incremental forming analysis. To predict hardness distribution after rolling in the manufacturing field, FE analysis was performed under two-dimensional axisymmetric conditions based on the assumption of no friction generated by the rolling tool. The deformed shapes and hardness distribution from the inspection quality standard and two-dimensional FE analysis showed very similar results. Simplified finite element analysis method for ring rolling process for local area could be very effective method in the industrial field. Originality/value: The stress-strain relationship and the hardness and strain relationship were derived by compression test and hardness measurement for compressed specimen for Nimonic 80A, Nickel-Chromium based super alloy. And simplified finite element analysis method was suggested to predict deformed shape and hardness distribution of locally cold rolled region and achieved similar result between FE analysis result and Quality standard. Suggested method would be very effective method to engine spindle manufacture to predict hardness of different size of product.

Performance investigation of magnetorheological finishing of rolls surface in cold rolling process

Cold rolling is one of the most vital manufacturing operation in the sheet metal industries. It produces controlled size and accurate thinner gauge components with a smooth surface. In cold rolling operation, the rolls are the most important component. If rolls surface gets finished at a greater level, a smooth surface on the final products can be achieved. This may improve functional performance for their practical use. To accomplish this requirement, the magnetorheological (MR) finishing process using rectangular-rotating tool core tip has been used to finish the external surface of the rolls. The process parameters such as roll workpiece rotation, tool feed, tool rotation, working gap and current intensity of the electromagnet and composition of MR polishing fluid are considered to investigate the performance of cold rolling rolls using the rectangular-rotating core tip-based MR finishing process. For effectively performing the MR finishing operation, the optimum process parameters are predicted by using the response surface methodology. These optimum parameters have been used to perform the MR finishing on the external surface of the industrial H13 die steel rolls as used in cold rolling process. The surface roughness gets reduced to 18 nm from the initial ground roughness value of 200 nm. After the MR finishing operation, the cold rolling rolls are tested its functional performance in the industry. The performance of the MR finished rolls surface is investigated as compared with the ground rolls surface. Experimentally and theoretically analyse the roll force, roll torque, and power consumption on use of before and after MR finished rolls surface in cold rolling operation. Almost all the performance parameters with MR finished rolls surface are found in favour of improvement in functional operation during its actual application in the cold rolling process.

Study of innovation technology possibilities of steel hot-rolled tempered strip production

Hot-rolled strip having normalized level of mechanical properties, produced with high accuracy as well as having decreased level of surface defects is considered often as an alternative to a cold-rolled product. An area of its utilization includes, in particular, production of automobile parts by cold stamping and blanking operations. Analysis of experience of mastering of hotrolled pickled strip technology instead of cold-rolled one as a marketable product revealed a series of problems related to provision of normalized level of surface roughness and obtained values of geometric parameters accuracy. Results of complex study represented, carried out by scientists of MGTU after G.I. Nosov together with PAO MMK within the period of mastering of new technology of hot-rolled pickled tempered strip production. Within the study a new technological flow-chart was elaborated for 3.1 mm thick steel hot-rolled pickled strip of steel 07ГБЮ production, excluding the stage of cold rolling. An operation of tempering was envisaged as a finished one, w enabled to increase resistance of hot-rolled pickled strip against cyclic loads. It was determined, that after tempering the coarseness uniformity increases along the whole surface and coil length of pickled strip. The carried out complex studies enabled to elaborate the technological effect, applied to hot-rolled products at the stage of finishing without cold rolling operation, that enables to have the level of properties in the hot-rolled pickled tempered strip, correspondent to existing world standards for such a product.

Application of the hole-drilling method for the evaluation of residual stresses near rounded ends

The experimental measurement of residual stresses by the hole-drilling method is a versatile technique due to its great simplicity. The technique consists of drilling on a material surface and measuring the relieved deformation on the surface by means of strain gauge rosettes. The most widespread method to obtain residual stresses from relieved deformation is the integral method and is found in the ASTM E837-13a standard. The procedure is standardised for very specific conditions, which are based on the application of the technique on a large flat-plate. To apply this technique to situations outside the standard scope, it is necessary to perform studies that validate its applicability. One of these situations is to evaluate the stresses introduced in hot- or cold-rolled profiles, where the residual stresses are concentrated on the rounded corners generated by rolling operations. In this study, a numerical simulation by finite elements has been carried out to obtain the relieved deformations for the case of drilling near rounded ends. The results show that the hole-drilling technique is applicable for the case of rounded ends; however, there is a significant deviation from the flat-plate condition which can be minimised by considering new matrices for the specific rounding radius and thickness of the analysed workpiece.

Design and analysis of a 2-DOF compliant gripper with constant-force flexure mechanism

This paper presents the design and testing of a novel flexure-based compliant parallel gripper with constant driving force. One uniqueness of the gripper lies in that it achieves two-degree-of-freedom (2-DOF) independent constant driving force in grasping and rolling operations. In each direction, the grasping and rolling operation is executed with the constant driving force. The parallel-kinematic flexure mechanism design enables nearly decoupled operations in 2-DOF manipulation. The constant driving force property enlarges the grasping range by reducing the required driving force. Analytical modeling of the gripper mechanism is carried out based on pseudo-rigid-body method, which is verified by conducting simulation study with nonlinear finite-element analysis (FEA). Parametric study is conducted to investigate the influence of each design variable on the gripper performance. To demonstrate the performance of the gripper, a prototype is fabricated by 3D printer. Experimental results reveal that the devised gripper owns a good constant driving force property during grasping.

The Study of Deformability of Heat-Resistant Alloy Named “Inconel Alloy 625” for Estimation of Plates Production Possibility at Wide-Strip Rolling “Mill 2300”

The hot deformation behavior of the Inconel alloy 625 was investigated through compression test within the temperature range of 850–1250 °C and the strain rate range of 0.1–30 s−1. Physically based mathematical model involving dynamic recovery and dynamic recrystallization processes has been proposed. Mathematical model allowed to calculate technological parameters of a rolling process of the “Inconel 625” at the hot rolling mill 2300. The pilot rolling operations showed that the possibility of the “Inconel 625” production exists. But it is necessary to provide the design changes of the cooling system of the work rolls. The article addressed the cracking behavior of nickel alloys in industries such as chemical process, nuclear generation, aircraft engine production.

Optimal sizing of energy storage considering the spatial‐temporal correlation of wind power forecast errors

Energy storage is considered as an effective approach to deal with the power deviation that caused by the stochastic wind power forecast error. Because of the spatial-temporal correlation of forecast errors for wind farms, which locate close to each other and integrate into the same regional power grid, energy storage could be deployed effectively and economically. Therefore, this study proposes an optimisation method to size the capacity of energy storage system (ESS) considering the spatial-temporal correlation of forecast errors for multiple nearby wind farms. The copula theory based correlation model of high-dimensional forecast errors is built to capture the spatial-temporal characteristics of forecast error. Then, according to multiple scenarios technique, an optimal ESS sizing model is established to minimise the investment and operation costs of the ESS. Meanwhile, an operation strategy considering the trend of prediction and correlation of errors is used to implement rolling operation strategy of ESS. The case studies demonstrate the effectiveness of the new method and illustrate the significant impact of the correlation of forecast error on the capacity of ESS.

Determination of system connections of hot rolled steel sheet manufacturing process

System analysis is used to state links between input and output parameters of any technical system taking into consideration flows of material, energy, and information. This approach makes it possible to find effective ways for improvement of technical system parameters. The paper presents results of system analysis application for multioperational technological process steel sheet of hot rolling. Structural scheme of metal sheet hot rolling process is presented based on principles of system analysis. Hot rolling technological operations such as workpiece heating, hot rolling, cooling, and coiling are presented as subsystems. Due to the obtained schemes metal sheet parameters are stated which have to be controlled during each technological operation of hot rolling technological process. The obtained results can be used as the basics for mathematical modeling of steel sheet hot rolling operation in order to get the final product with the required set of properties.

Modernization of No. 23 runway drives of 2800 HSM at sheet-rolling shop (LPZ-1) of JSC “Ural Steel”

Increasing of rolling and adjacent equipment operation reliability, decreasing of its emergency downtime, increasing of overall periods duration are actual tasks of personal of any sheet-rolling plant.Using data of the register of 2800 HSM of sheet-rolling shop (LPZ-1), JSC “Ural Steel”, the number and duration of downtimes of the mill No. 23 runway analyzed, caused by runway drive tooth coupling failure. The main reasons of tooth coupling failure determined. Modernization of No. 23 runway drives proposed, being its design modification by introducing of cardan shaft for rollers drives. This enabled for giving up the tooth coupling usage, pushing away the electric motors, that avoided water drops and vapor on them hitting, decrease unplanned equipment downtime. Certain parameters of drives determined and calculation of technical and economic indices before and after the runway drives modernization presented. The implementation of modernization actions resulted in a decrease of No. 23 runway repair and maintenance expenses, including the purchase and installation of the tooth coupling. The expenses for No. 23 runway drives modernization made1.7 mil Rubles and the payback period – 6 months.

Improvement in Operating Efficiency of Continuous Casting Machine Slab Rolls

Route maps for the production cycle of operation and repair of continuous casting machine slab rolls in the Azovstal’ and Il’ich Metallurgical Combines (Mariupol’) are presented. It is shown that the complete roll operating cycle in horizontal, curvilinear, and radial sections of the secondary cooling zone as their diameter changes as a result of wear, grinding, and surfacing, makes it possible to increase roll running time, to reduce purchasing expenditure, technical servicing, and restoration. It is established that an increase in secondary cooling zone roll life with diameter 380–270 mm with unchanged composition of the basic and surfacing metal is provided by surfacing technology with formation of a corrosion-resistant surface layer of individually deposited welds with a gap between adjacent welds.

Process-induced defects in an L-shape profile ring rolling process

The ring rolling is a process of gradually forming the cross section of the ring material according to the outer shape of the working roll. In this study, process-induced defects in L-shaped cross section ring rolling process have been analyzed. Major defects in the L-shaped ring rolling process include folding, unfilling and groove on the bottom surface of the material. In order to understand the formation mechanisms of process-induced defects, finite element analysis and physical modeling have been performed at various processing conditions. For the process analysis, the effects of process variables such as blank geometry, dimension and rotation speed of working roll, mandrel feed speed and working temperature on the generation of defects have been investigated. From the analysis results, methodologies to prevent process-induced defects are proposed and validated by shop-floor ring rolling operations.

Finite Element Based Analysis of Reinforcing Cords in Rolling Tires: Influence of Mechanical and Thermal Cord Properties on Tire Response

ABSTRACT Tires of passenger cars and other special tires are made of rubber compounds and reinforcing cords of different type to form a composite with distinct mechanical and thermal properties. One of the major load cases is the steady state rolling operation during the tire's service. In this contribution, attention is paid to the strain and force state as well as the temperature distribution in the carcass cord layer of a steady state rolling tire. A simple benchmark tire geometry is considered, which is made of one rubber compound, one carcass cord layer (textile), and two belt cord layers (steel). From the given geometry, two tire designs are derived by using two distinct types of reinforcing cords (polyester and rayon) for the carcass cord layer. Subsequently, the two tire designs are subjected to three load cases with different inner pressure, vertical force, and translational velocity. The strain and the force state as well as the temperature distribution in the cords are computed via a thermomechanically coupled finite element simulation approach for each tire design and load case. To realistically capture the thermomechanical behavior of the cords, a temperature- and deformation-dependent nonlinear elastic cord model is proposed. The cord model parameters can be directly derived from data of cord tensile tests at different temperatures. Finally, cord design parameters (minimum and maximum strains and forces in the cords, maximum strain and force range per cycle, and maximum cord temperature) are summarized and compared. Additionally, the global vertical stiffness and the rolling resistance for each tire design are addressed.

Mechanical Properties and Strain-Induced Martensite Transformation in Cold Rolling of 304L Stainless Steel Plate

In this work, cold rolling behavior of stainless steel 304L is investigated and the effects of different process parameters on the occurrence of strain-induced martensite and mechanical properties are studied. The rolling experiments are conducted under different rolling speeds and reductions in which a set of samples is deformed at room temperature and the other set is first cooled to the temperature of − 10 °C and then rolled. Afterward, the developed microstructures and mechanical properties of the rolled steel are evaluated employing different testing techniques. In order to justify the results, mathematical modeling of cold rolling operation is also performed using Abaqus/Explicit to estimate the distribution of equivalent plastic strain and temperature rise during rolling. The results show that strain-induced martensite may occur during cold rolling and it efficiently alters microstructure and mechanical performance of the rolled plate. The amount of reduction, initial temperature, rolling layout, and, to a lesser extent, rolling speed can affect the kinetics of martensite transformation as well as microstructure and mechanical properties of the rolled steel.

Features of roughness formation during production of the hot-rolled temper-rolled band

Active implementation of new technology processes is applied as one of way to increase the competitive ability of metal products. Today one of the modern trends is transfer of requirements of intermediate to final technological operations. The new production technology of a hot-rolled pickled temper-rolled band of a wide dimensional and branded range is developed by scientist of Nosov State Technical University jointly with specialists of PJSC Iron & Steel Works. Field of use this band is automobile wheel disk production at JSC AVTOVAZ. Researches on forming of band final properties showed a basic possibility of ensuring the rate band parameters at an exception of operation of cold rolling.

Effect of Post-Process Machining on Surface Properties of Additively Manufactured H13 Tool Steel

Abstract The tool steel AISI H13 is characterized by a high wear resistance and a good thermal shock resistance. H13 is mainly employed in applications such as tools for pressure die casting and forging. Processing of H13 by additive manufacturing techniques, such as selective laser melting (SLM), opens up new design possibilities with respect to e. g. internal cooling channels, in order to improve the tool performance during operation. However, due to high surface roughness and insufficient geometric accuracy imposed by SLM, additional cutting or forming processes are often required leading to an alteration of the surface and subsurface properties of the part. The presented work reveals the effect of SLM processing and subsequent face milling and/or deep rolling operations on the development of surface and subsurface properties and highlights adequate process windows.

Analysis of titanium nitrides precipitated during medium carbon steels solidification

For certain applications, coarse titanium nitride (TiN) precipitates can be deleterious for the final properties of the material. Hence, in order to better understand the mechanisms involved in the generation of these precipitates, a characterization of the particles observed in steels with different titanium and nitrogen content was carried out. Samples from liquid steel (tundish), continuous casting billets and final product were evaluated using an Automatic Particle Analyzer (APA) coupled to a Scanning Electron Microscope (SEM). The location, frequency, size distribution and composition of the different particles observed were assessed. While only few TiN precipitates were observed in liquid steel samples, the density of this type of particles significantly increased in the continuous casting billets samples. Particles ranging from 1 to 10μm were mainly found in the interdendritic zones of the as-cast structure. The density of TiN particles observed in these samples did not change after re-heating and rolling operations. A microsegregation model previously developed was adapted to predict TiN precipitation during solidification. A reasonable agreement was found between model results and measured data. Results of this analysis confirmed that the precipitated fraction of TiN increases as the product of steel Ti and N contents rises.

An innovative method for producing balls from scrap rail heads

The paper describes an innovative technological solution for producing balls from scrap rail heads. The proposed method consists in performing the following operations: the side pressing of a rail head to increase shape compactness, a process for forming a cylindrical rod by cross-wedge rolling (CWR), a CWR process for producing balls that have a diameter which is by 35% larger than that of the billet, quenching of the produced balls. Tools for the above manufacturing operations are designed, and numerical simulations are performed to verify whether the assumptions of the proposed technique are correct. A flat-wedge reversing mill is designed and constructed that enables performing the two abovementioned rolling operations without idle running, which makes the design innovative on a global scale. The implementation of the proposed method would enable producing balls for grinding media used in ball mills.