Bar Rolling Process Research Articles

Analytical approximation and evaluation of roll separating force in bar rolling process

Analytical approximation and evaluation of roll separating force in bar rolling process

Numerical Simulation of Microstructure Evolution of Large GCr15 Bar during Multi-Pass Rough Rolling

Severe temperature gradients and inhomogeneous strain distribution exist in the large cross-section of GCr15 bearing steel during the hot bar rolling process, resulting in a complex microstructure evolution in the bar. To promote the performance of the bar, a thermal-mechanical coupled finite element (FE) model was developed to capture the variations in temperature and deformation strain. A subroutine, considering the dynamic recrystallization (DRX), meta-dynamic recrystallization (MDRX), static recrystallization (SRX), and grain growth (GG) of austenite grains of GCr15 steel, was developed and coupled to the FE model to predict the microstructure’s evolution during rough rolling. The simulation implies that the inner part of the bloom is deformed at high temperatures due to the heat generated by plastic deformation and slow heat conduction, while the surface temperature decreases along with the passes. The heavy reduction design with 11 passes was found to introduce higher strains at the center regions than those of the same rough rolling reduction divided into 13 passes. The higher strains at the center regions refined the grain size and promoted microstructure homogeneity. The observation of the microstructures after hot bar rolling confirmed the refinement of the heavy reduction design for rough rolling. Furthermore, the heavy rough rolling reduction was found to be beneficial for alleviating the macrosegregation of the casting bloom.

Literature review of the stress, strain and separating force evaluation during hot bar rolling of different types of steels

Designing new rolling mills, optimization of the number of passes and online control of dimensional accuracy are the processes in which the accurate prediction of roll separating force (RSF) for different types of material is necessary. The formula of RSF is mainly a function of flow stress of the material, strain, strain rate, mean effective pressure and area of contact which further depend on the complexity of deformation and complex diversified boundary conditions in velocity as well as friction. Researchers in the last decades have used finite element analysis (FEA), experimental methods, fluid-like consideration of the material and many more techniques to estimate these parameters for low carbon steel and alloy steel. Based on the reviewed literature, the available formulas are classified into two major categories i.e. (i) Analytical and Empirical solutions and (ii) Finite element-based solutions. The majority of the existing models in the literature rely on empirical adjustments of theories of flat rolling dating back to 1943, whereas FEA-based formulae are only applicable to a single circumstance. In conclusion, it is suggested that it is important to create a fully analytical and relatively simple formula that can more precisely predict the RSF for the bar rolling process.

Dual-Objective Mixed Integer Linear Program and Memetic Algorithm for an Industrial Group Scheduling Problem

Group scheduling problems have attracted much attention owing to their many practical applications. This work proposes a new bi-objective serial-batch group scheduling problem considering the constraints of sequence-dependent setup time, release time, and due time. It is originated from an important industrial process, i.e., wire rod and bar rolling process in steel production systems. Two objective functions, i.e., the number of late jobs and total setup time, are minimized. A mixed integer linear program is established to describe the problem. To obtain its Pareto solutions, we present a memetic algorithm that integrates a population-based nondominated sorting genetic algorithm II and two single-solution-based improvement methods, i.e., an insertion-based local search and an iterated greedy algorithm. The computational results on extensive industrial data with the scale of a one-week schedule show that the proposed algorithm has great performance in solving the concerned problem and outperforms its peers. Its high accuracy and efficiency imply its great potential to be applied to solve industrial-size group scheduling problems.

Prediction of Surface Wrinkle Defect of Welding Wire Steel ER70S-6 in Hot Bar Rolling Process Using Finite Element Method and Experiments

High quality products are demanded due to increasingly fierce market competition. In this paper, the generation of surface wrinkle defect of welding wire steel ER70S-6 was studied by the combination of the experimental method and finite element simulation. Firstly, a thermal compression test was conducted on the Gleeble-3500 thermosimulator under different strain rates and temperatures and a strain dependent Arrhenius-type constitutive function was employed to fit the flow stress–strain curves obtained from the experiments. Then, the elastoplastic constitutive relationship was implemented using radial return mapping algorithm by means of the user subroutine VUMAT of Abaqus/Explicit. A new instability criterion was proposed to predict the possibility of the surface wrinkle defect during the multipass hot bar rolling process. In order to verify the reliability of the finite element model of the six-pass continuous rolling process, the simulated results were compared with experimental data. Finally, the effects of groove width and groove radius on the billet were investigated by the orthogonal test method, and the friction coefficient and rolling temperature. The results show that the groove width and groove radius are key factors to suppress the surface wrinkle defect. Decreasing the groove width can be beneficial for improving the surface quality and reducing the fillet radius. The optimized combination of the rolling process parameters was further applied in an industrial test and the surface quality of the billet was greatly improved.

Decomposition Method for New Single-Machine Scheduling Problems From Steel Production Systems

Production scheduling is a crucial task in modern steel plants. The scheduling of a wire rod and bar rolling process is challenging in many steel plants, which has a direct impact on their production efficiency and profit. This article studies a new single-machine scheduling problem with sequence-dependent setup time, release time, and due time constraints originated from a wire rod and bar rolling process in steel plants. In this problem, jobs have been assigned to batches in advance. The objective is to schedule the batches and jobs on continuous time to minimize the number of late jobs. A mixed-integer program is created as a baseline model. A baseline method is used to solve this NP-hard problem by solving the baseline model. We further design a two-stage decomposition method after analyzing the characteristics of this problem. Both actual and simulated instances with varying sizes are solved by using the proposed methods. The results demonstrate that the baseline method can only solve some small-scale cases, while the decomposition method can solve all small-scale cases and some medium-scale cases. Finally, we reveal the impacts of different instances on the performance of the proposed decomposition method. Note to Practitioners —This article deals with a new single-machine scheduling problem arising from an industrial wire rod and bar rolling process. A baseline method is given to tackle this problem by solving an established mixed-integer program. Afterward, a two-stage decomposition method is proposed such that an industrial size problem can be solved. Computational results of both actual and simulated cases show that it is more efficient than the baseline method in solving the scheduling problem. It can get an optimal solution of the concerned problem with one-week-scale batches and jobs in short time, thereby proving the readiness to put it in industrial use.

Finite element–based inverse approach to estimate the friction coefficient in hot bar rolling process

This article proposes a finite element analysis–based inverse approach to estimate the friction coefficient in hot bar rolling. The focus is to minimize the difference between the spread of material measured from the pilot hot bar rolling test and that computed from finite element analysis. The recursive response surface method was used with a changed observation range to minimize the difference. The pilot hot bar rolling test was conducted at temperatures ranging from 850 °C to 1150 °C and reduction ratios from 20% to 40%. Finite-element simulation of the pilot hot bar rolling test was carried out. A fast running model that can rapidly determine the friction coefficient at the arbitrary reduction ratios and temperatures in the ranges mentioned above was also presented. The estimated friction coefficient was approximately 10%–17% higher than the friction coefficient typically used in hot strip rolling. The effect of temperature variation on the friction coefficient was greater at higher reduction ratios (30%–40%) than at a lower reduction ratio (20%).

Analysis of Al-Cu Bimetallic Bars Properties After Explosive Welding and Rolling in Modified Passes

Abstract The paper presents the results of the experimental tests of Al-Cu bimetallic bars rolling process in multi-radial modified passes. The bimetallic bars consist of aluminium core, grade 1050A and copper outer layer, grade M1E. The stocks were round bars with diameter 22 mm with a copper layer share of 15 and 30%. As a result of rolling in four passes, bars of a diameter of about 16.0 mm were obtained. A bimetallic stock was manufactured using an explosive welding method. The use of the designed arrangement of multi-radial modified stretching passes resulted in obtaining Al-Cu bimetallic bars with the required lateral dimensions, an uniform distribution of the cladding layer over the bar perimeter and high quality of shear strength between individual layers.

3D FEM modelling and experimental investigations of Al–Cu bimetallic bars rolling process in modified grooves

The paper presents the results of the numerical modelling and experimental tests of Al–Cu bimetallic bars groove rolling process. A bimetallic feedstock was manufactured using an explosive cladding method. The feedstocks were round bars with diameter of 22 mm and a cladding layer share of 15 and 30 %. As a result of rolling in 4 passes bars of a diameter of 16 mm were obtained. By applying the multi‐radial modified grooves to the rolling of Al–Cu bimetallic bars the stability of the rolling process was improved, whereby, finished bars with a uniform cladding layer distribution along the core and small diameter dimensional deviations were obtained. Forge2011®, a FEM‐relying software program, was employed for the theoretical examinations.

Analysis of the AZ31 magnesium alloy bars rolling process in modified stretching passes

Production of AZ31 magnesium alloy round bars can be realized in hot rolling process. Application of modified stretching passes to the rolling process will allow obtaining bars which will characterised by more homogeneous microstructure in the cross‐section of bars in comparison to bars rolled in classical passes. As a result of applying a new strain scheme created by using the modified stretching passes it was possible to obtain bars with mechanical properties similar to the bars obtained in the extrusion process.

Influence of Temperature Change on the Energy Parameters during Round Bars Rolling Process

The paper presents results of experimental studies on the effect of non-uniform temperature distribution over the metallic charge length on the energy parameters change during round bars rolling process. Experimental tests were conducted on the D370 Continuous Shape Mill in industrial works. From the tests carried out, it has been found that the main cause of occurrence of the non-uniform distribution of temperature over the charge length is the process of heating the metallic charge in the walking beam furnace. During rolling of bars from metallic charge with non-uniform temperature distribution over its length, changes in friction conditions in the zone of contact between the band and the rolls and in the plastic properties of steel being rolled occur. For decrease temperature during metallic charge rolling process about 100 °C (Fig. 2) in walking beam furnace, increase of rolling torque and total rolling power about 30% during rolling process metallic charge in first continuous shape mill stand was observed.

The Influence of the Interstand Tension of the Band on Roll Wear during the Continuous Groove-Rolling Process

Numerical modelling of the round bar rolling process, while considering the wear of passes depending on their shape, was carried out within the present work. The analysis of the rolling process was conducted thus analysing the influence of interstand tension on roll wear. For the theoretical study of the rolling process, Forge2011® was employed, which is finite element method-relying software that enables the thermo-mechanical simulation of rolling processes in a triaxial state of strain. The wear model implemented in Forge2011® permits no quantitative evaluation, but only a comparative analysis of the wear of rolls. In order to use the results of simulation employing the simplified Archard model for the quantitative evaluation of roll wear, it is necessary to define the factor of wear and the hardness of the tool as a function of temperature.

Investigation of the non-uniform temperature distribution on the metallic charge length during round bars rolling process

Investigation of the non-uniform temperature distribution on the metallic charge length during round bars rolling process

New Groove Design and Three-Dimensional Numerical Simulation of Ultra-Fine Grain of Bar Rolling

A new groove design method of uniform strong strain of bar rolling was proposed based on the principle of strong plastic deformation to manufacture ultra-fine grain(UFG), and flat-oval groove type with the characteristics of big crushed and multidirectional deformation was set up. The numerical analysis model of hot continuous bar rolling process was created using nonlinear finite element method. The study of the law of plastic strain distribution after each rolling pass of the caliber series indicated that the caliber can satisfy with the precise size and shape, and can also better introduce the plastic strain to the center of cross section and get uniform strong strain. The largest strain was more than 5.0 in the center of cross section, in which condition ultra-fine grain can be fabricated. Therefore, this study provides important theoretical basis for the ultra-fine grain of bar rolling development.

3D FEM Modelling and Experimental Verification of the Rolls Wear during the Bar Rolling Process

Numerical modelling of the round bar rolling process, while considering the wear of the passes depending on their shape, was carried out within the present work. For the theoretical study of the rolling process, the Forge2008® was employed, which is finite element method-relying software that enables the thermomechanical simulation of rolling processes in a triaxial strain state. The wear model implemented in the Forge2008® permits no quantitative evaluation, but only comparative analysis of the wear of rolls. In order to use the results of simulation employing the simplified Archard model for the quantitative evaluation of roll wear, it is necessary to define the wear factor and hardness of the tool as a function of temperature. The paper present a methodology for the determination of the quantitative wear of rolls based on the results of computer simulations performed using the Forge2008® software for a selected round pass during rolling of round bars.

Groove Design and Microstructure Research of Ultra-Fine Grain Bar Rolling

New flat-oval groove rolling process of multi-direction deformation is proposed to manufacture ultra-fine grain bar. Application of new groove series can introduce uniform large plastic strain into whole cross section of the material, and meanwhile satisfy the requirements of shape and size. Principle of grain refinement, based on experimental research of small specimen, is that grain refinement of ferrite is mainly dynamic recrystallization when low-carbon alloy steel is at low temperature deformation. Relationship of grain size and z-factor is also obtained through experimental research, as well as ultra-fine ferrite grain less than 1 micron. To predict strain, shape, dimensions and grain size of the material in rolling process, numerical simulation model of the warm groove bar rolling process is established via nonlinear finite element method, and distribution of grain size of the final section is obtained via finite element subroutine. The result indicates that ultra-fine grain bar rolling can accomplish at low temperature region.

Numerical Simulation and Analysis for Surface Defect Prediction in the Hot Bar Rolling Process

Establishment of numerical model for hot rolled bar and analysis the changes from the discrete points on surface during the hot bar rolling process (includes velocity, displacement, equivalent stress, equivalent strain). And the position of surface defects can be effectively predicted form this. Compared with the actual hot rolling bar production, numerical simulation was in good agreement with it. So that the numerical simulation analysis has practical significance for optimizing processing parameters and process design to ensure product quality.

Vibration Research of Gear Box in H5 Mill for Alloy Bar's Rolling Process

The abnormal vibration of H5 mill’s gear box has influenced the implementation of the energy-saving process in the alloy bar production line of special steel branch, Baosteel limited company. The reasons of the abnormal vibration have been determined by experiment and ANSYS finite element analysis, and corresponding measures have been provided. The rigidity of the gear box has improved by reinforcing ribs. By applying the reinforced gear box, the abnormal vibration has been effectively inhibited and the implementation of the energy-saving process has been guaranteed.

Finite Element Simulation of the Hot-Rolling Process of Titanium Alloy Bar

In order to overcome the drawbacks in the process of the titanium alloy, the authors propose to produce this kind of bar by Y-type rolling mill. The deforming process of titanium alloy has been simulated dynamically using MSC.Marc finite element software. The stress, strain, temperature and residual stress distributions of deformation area have been analyzed. The rolling force and torque have been obtained. The model could provide the foundation for further theoretical research and engineering application of titanium alloy bar rolling process.

Numerical Modelling of the Microstructure during Rolling of Flat Bars

This paper presents theoretical analysis of microstructure changes in the material during standard rolling and normalizing rolling of the 35x20 mm flat bars. The analysis was carried out by means of computer software Forge 2007® that is based on finite element method. Two cases of accelerated cooling during rolling process were considered. Numerical results of 35x20 mm flat bars rolling process allowed to determine the average recrystallized austenite diameter as well as basis energy and force parameters. Proposed modification of the 35x20 mm flat bar rolling technology with accelerated cooling results in the reduction of average austenite diameter, which could improve the strength of the final product.