Roll Profile Research Articles

Simulation of Thermomechanical Control Processing of Steels through the Use of Experimental Planning and FEM

The experimental planning method has been used for the examination of the combined effect of the temperature, strain, strain rate and time elapsed from the end of deformation to the start of quenching parameters of the Thermomechanical Control Processing on the structure and mechanical properties. Simulation of Thermomechanical Control Processing for the definite cross-section of profile by Finite Element Method on the base of the data obtained by the experimental planning method allowed to predict structure and mechanical properties and to develop computer modelling for the different cross-section of rolling profile.

Use prospect of the of athermic technologies of metal softening for rolling stock elements

Purpose. The purpose of work is the possibility estimation of аthermic technologies use of cold-deformed metal softening for elements of railway car body and wheel. Methodology. The material for research is the carbon steel of the wheel rim fragment containing 0.55%С, 0.74%Mn, 0.33%Si, and the steel 20. The wheel steel is studied after heat strengthening and cold work after operation. Steel 20 is studied after plastic cold work by rolling. Electric pulse treatment (ET) is carried out on the special equipment. As the property of metal strength the Vickers hardness number is used. The microstructure research is carried out using the light and electronic microscope. Findings. During operation of the rolling stock elements with different strength level origin of damages on metallic surfaces is caused by a simultaneous load action. Taking into account that forming of breakdown sites is largely determined by the state of metal volumes nearby the places of maximal active voltages, the technology development of defect accumulation slowdown or the level of active voltages development allow one to prolong the operating term of rolling stock elements. After electric pulse treatment of the wheel rim fragment the regular changes of metal internal structure corresponded to the hardness changes. The hardness of low carbon steel increases proportional to the increase of the level of cold work by rolling. Alternating bending of the cold-deformed flat is accompanied by strength decrease, which is caused by the metal substructure changes. Originality. The softening process of the cold-worked steel is accompanied by substructure changes, which to a greater extent correspond to the hardening development from the plastic cold-work: dispersion of the dislocation cellular structure, formation of the new sub boundaries and displacement of the formed sub boundaries. Practical value. Introduction of electric pulse treatment in the conditions of railway depots repair base allow one to attain the required level of softening of the cold-worked steel on the wheel thread of railway wheel without heating of metal. The given treatment reduces the metal hardness and prolongs the term of incisors use during the renovation of the rolling profile of the railway wheel

Size Effects in Winding Roll Formed Profiles: A Study of Carcass Production for Flexible Pipes in Offshore Industry

Carcass production of flexible offshore oil and gas pipes implies winding and interlocking of a roll formed stainless steel profile around a mandrel in a spiral shape. The location of the dividing point between the left and right half of the s-shaped profile in the finished carcass is very important as it directly influences carcass flexibility. The target location of the dividing point can be difficult to achieve since undesired degrees of freedom in the winding stage allows the profile to change geometry. The present work investigates this issue by performing production tests of a single carcass profile size on three mandrel sizes showing a size effect to be evident; smaller mandrel size increases a shift of the dividing point during initial mandrel contact in the winding stage. The cause is high strains in the open profile, which are minimized by the material moving closer to profile neutral plane. Other parameters such as profile entry angle on the mandrel and spiral pitch are likely to have significant importance. Proper dividing point position is shown to be obtainable by adjusting the profile in the roll forming stage. The profile rolling is successfully modeled by Finite Element Analysis (FEA), whereas a simplified FE-model of the subsequent winding operation shows that full interlock modeling is required for proper prediction of profile deformation.

AVALIAÇÃO NUMÉRICA DA DISTRIBUIÇÃO DE TEMPERATURA EM CILINDROS DE LAMINAÇÃO

In hot rolling processes occur changes in the profile of the rolling mill rolls (expansion and contraction) and constant wear due to mechanical stress and continuous thermal cycles of heating/cooling caused by contact rolled material- working roll and the cooling system by water jets in their surface, decreasing their lifetime. This paper presents a computational model to simulate the thermal performance of rolling mill rolls. The model was developed using the finite volume method for a transient two-dimensional system and allows calculating the temperature distribution of the rolling mill rolls under various conditions of service. Here it is investigated the influence of flow rate and temperature of the cooling water on the temperature distribution. The results show that the water temperature has greater influence than the water flow to control the surface temperature of the cylinders

Rolling of profiles with a rhombic cross section

Selection of the optimal blank in the rolling of profiles with a rhombic cross section may be based not only on the consumption of metal and the rolling force but also on the utilization of the material’s margin of plasticity and the profile’s margin of stability in rolling. Calculations of four groove configurations permit the identification of the rectangle-rhombus configuration as optimal. The performance of the product is more stable in that case.

Design of roll profile in shape rolling of an irregular angle bar by the modified butterfly method

The roll profile of an angle bar is generally designed by the butterfly method however, the design of the roll profile of an irregular angle bar requires a special rule to take a tapered leg or a protrusion on the leg into account. For this purpose, the butterfly method has been modified in this study to design the roll profile for an irregular angle bar by introducing the equivalent leg thickness. The thickness of the tapered leg or the leg with the protrusion is changed into the equivalent leg thickness to calculate the thickness and length of the leg for the next pass. Shape rolling processes for inverted and unequal angle bars are designed by the proposed method, and its effectiveness is verified by FE-simulation and experiments using plasticine. In addition, the design method is applied to the shape rolling of more complicated irregular angle bar, such as an automotive door hinge. The cross-sectional shapes at each pass are compared with those obtained from the experiment using steel. The results of FE-simulation and experiment show that the proposed design method effectively designs the roll profile for an irregular angle bar, leading to accurate shape and dimensions in the final product within the allowable tolerance of ± 0.4 mm in thickness and ± 1.5 mm in length. Therefore, the proposed design method can be widely used to design roll profiles for variously shaped angle bars in industrial fields.

유한요소해석과 반응표면법을 이용한 앵글바의 폭퍼짐 예측 및 공형설계에 관한 연구

In this paper, a method for prediction of spread is proposed to design proper roll profile taking into account spread in shape rolling of angle bar. The effect of the process variables on spread, such as draught ratio, bending angle and aspect ratio, is analyzed by FE-analysis and response surface method (RSM). Roll profiles for equal angle bar are designed with the spread predicted by the regression equation. Effectiveness of the designed roll profiles are verified by FE-analysis in which the flange length, strain distribution, mean strain and roll torque are compared with those by Geuze. Finally, the proposed method is applied to the design of roll profile for unequal angle bar. As a result, the final product can be obtained within the allowable tolerance of ±0.5 mm in length. Therefore, it is found that the prediction of spread can improve the efficiency of design roll profile in shape rolling of angle bar.

다단 압연기에서의 롤 변형 프로파일 예측 모델 - Part II : 젠지미어 압연기로의 적용

The work roll of a Sendzimir mill has a small diameter in comparison to its length, so it is easily deformed by the rolling pressure. It also has a complex back up roll system, so it is difficult to analyze the roll deformation. For this reason in Part I we have developed a model which predicts the radial displacement of the roll. In this paper, we apply the model to a Sendzimir mill and propose a new model for the prediction of the deformed roll profile in a Sendzimir mill. The prediction accuracy of the new model is demonstrated through comparison of the predictions from the FE model.

Displacement of Multiple, Coupled Timoshenko Beams in Discontinuous Nonlinear Elastic Contact, With Application to Rolling Mills

Introduced is an efficient numerical method to calculate the displacements of structures involving multiple, shear-deformable beams in lengthwise nonlinear elastic contact. Applicability of the method is general, and includes structures such as stacked beams, pipes, or machine components. A particularly relevant application, which is discussed and demonstrated in this paper, is the prediction of deflections and contact conditions between the rolls and strip in rolling mills used to process flat metals. The presented nonlinear displacement calculation method involves iteration using an efficient, simplified mixed finite element formulation. Nonlinearities in the general coupled beam problem can arise either from changing contact conditions between the lengthwise-coupled shear-deformable beams (opening/closing of gaps) or from nonlinear elastic coupling-stiffness between the beams. Unlike the conventional problem of end-connected beams resting on elastic foundations, this work presents an element stiffness matrix formulation and sample nonlinear solution techniques for the problem involving multiple beams that are mutually coupled along their lengths by intervening, nonlinear elastic foundations. Important practical examples of the method are given, based on production cold rolling mill data for type 301 stainless steel on a four-high mill. The examples demonstrate efficiency and value of the nonlinear coupled beam formulation in identifying appropriate machined roll profiles to produce desired strip flatness quality. The cold rolling applications presented are characterized by nonlinear Hertz foundations with stiffness-hardening, and by discontinuous contact conditions arising from nonuniform, machined roll diameter profiles. Solution efficiencies for the new formulation are compared using modified Newton–Raphson, average stiffness, and direct substitution techniques. While the average stiffness method is relatively slower, its characteristics may make it beneficial for transfer function development in flatness control systems. Application of the method to cold rolling mills illustrates the importance of including discontinuous contact nonlinearities, and enables reduced trial and error to determine suitable roll profiles. Presented is a new efficient variational formulation for computing displacements in structures involving multiple beams laterally coupled with nonlinear elastic foundations and changing contact conditions. Practical value of the method is demonstrated for identification of machined roll profiles in cold rolling mills in order to achieve desirable flatness of rolled products.

Built-up T-stub connections for moment resisting frames: Experimental and finite element investigation for prequalification

As a result of the SAC project, rolled T-stub connections have been demonstrated to be a viable alternative to welded connections for steel frames in seismic areas. One difficulty with these connections is that oftentimes the rolled profiles needed to fabricate the T-stub needed for deep beams are not immediately available to fabricators and so built-up sections are the only alternative. The goal of this investigation is to demonstrate through experimental and finite element studies that built-up T-stub connections can be successfully detailed for use in special and intermediate moment frames in seismic areas. The results of a series of component tests on built-up T-stubs, obtained by means of complete joint penetration welding (CJP) and fillet welding are presented and discussed, providing supporting evidence for the best fabrication choice. Component tests investigating hole fabrication practices are also presented, studying their effect on ductility under monotonic and cyclic loads. Furthermore, finite element models of thick flange T-stub connections is presented and finite element simulation results are compared to experimental results to demonstrate the applicability of built-up T-stub connections for use in special and intermediate moment frames. The finite element results show an acceptable agreement with the experimental results and describe the behavior. A partial yielding of the T-stub flange followed by bolt fracture is highlighted as a failure mode based on the finite element and the experimental results. It is anticipated that the data collected from a forthcoming series of full-scale tests will lead to the prequalification of this connection typology.

The Behavior of Surface Roughness in EHL Contacts Under Small Slide to Roll Ratios

The amplitude attenuation theory represents a possible way how to predict the tribological performance of a surface having general roughness. There are applications of this theory for pure rolling and rolling–sliding conditions having different governing parameters. Obviously, pure rolling case is much simpler and it was already experimentally verified. Conversely, rolling–sliding conditions represent much complex case and its solution is still under development. Nevertheless, a lot of machine components operate under the conditions where only small slide to roll ratios are present. This study was carried out to find the reasonable validity of the pure rolling model for the applications where small amount of sliding is present. The behavior of roughness was observed under conditions of small sliding speed using optical tribometer for film thickness mapping. The results were analyzed and compared with the predictions according the amplitude attenuation theory for both pure rolling and rolling–sliding cases. The influence of slide to roll ratio on roughness profile shape was studied and differences to the pure rolling profile were evaluated. It was concluded that the pure rolling model can be applied with reasonable precision within the range of slide to roll ratios from −0.15 to 0.1. The correlation coefficients are better than 0.85, the RMS value changes are less than 3 %, and bearing area curves are almost unaffected.

Use of a finite element method to calculate roll profiles for broad-strip mills

A model is proposed to calculate the polishing profiling of rolls in broad-strip mills using a finite element method, and it is applied to develop new roll profiles. The finite element method is used to determine the polishing profiling of a roll with a complex shape, which substantially decreases the nonuniformity of reduction and drawing over the strip width. This profiling can be executed on numerical control roll grinders.

Optimization of oval–round pass design using genetic algorithm

The primary purpose of this paper is to propose a computer aided optimal design system to support a generalized oval-round pass design, which is widely used as both intermediate and final passes in the process of rod rolling. This system, which is based on a hybrid model and the genetic algorithm, is developed to improve the efficiency, to reduce the manufacturing errors, as well as to extend the useful life of rolls through uniform wear design. Generalized parametric equations are established for geometrical modeling, graphic plotting of oval-round passes, as well as calculation of the cross section area, contact area and the lengths of contact arcs along the cross section of round groove in the MATLAB programming environment. Moreover, these equations can also realize the parametric transformation between roll profile and mathematical models for the oval-round pass design and optimization. The genetic algorithm is employed for the optimal design of oval-round passes in this paper. The objective functions are formulated for minimization of power consumption in the rolling process, variances between ideal dimensions and design dimensions, as well as variances between the lengths of contact arcs. To reduce the complexity and computational burden of the system, some reliable empirical formulas for the calculations of contact area and contact arc length are applied. Finally, the proposed approach is applied to an oval-round pass design. Through simulation and comparison of results against experimental data acquired from literature, it is found that this system is reliable, effective and easier to use.

Study on Hot Roll Profile in the Initial Stage of Twin-Roll Continuous Strip Casting

Using nonlinear finite element method, the changes of roll temperature and hot roll profile are studied in the initial casting stage, and the changing rule of hot roll profile is described in the initial casting stage which can be the evidence to decide the initial roll profile and casting process.

Legged vehicle control and vibration reduction

This paper presents a design method of controller reducing the vibration of the upper body of a legged vehicle during locomotion. To design locomotion pattern generator, instead of using non-linear dynamics models and solving complex equations, the control strategy is simply based on the use of piecewise linear oscillators and a few parameters that can be easily obtained and tuned. In this research framework, we present tuning algorithms of both the rolling profile and the feedback controllers gains such that the mechanical vibration in the legged vehicle during locomotion is attenuated. As a result, stable and smooth locomotion is obtained. The effectiveness of the proposed method is demonstrated by experimental results.

Development of practical shape models and control system for strips

High-quality-oriented in the steel market encourages more severe tolerances of strip crown and flatness. GSM (Global Shape Model) provides the superior setup calculation with learning calculation and dynamic control functions in order to achieve targets of both crown and flatness. Adopted Models are simplified but contrived enough to cope with physical phenomena such as roll stack deflection, longitudinal and lateral flow of rolled strip and inter-stand relaxation. Systematic structure of GSM enables itself to be applied to actual hot strip mills with related functions as like roll profile prediction. The results of the application of GSM to a Hot Strip Mill are also shown in this paper.

Tailored Profiles Made of Tailor Rolled Strips by Roll Forming – Part 2 of 2

AbstractThe main scope of the presented work is to demonstrate the potential of load optimized tubes with a varying thickness distribution in circumferential direction produced by roll forming. As initial material a so called Tailor Rolled Strip (TRS) sheet metal coil produced by Strip Profile Rolling (SPR) method was used instead of plain sheet. The TRS sheet metal is manufactured in a continuously working process by rolling one or more groves in transverse direction into the sheet metal coil. In this paper, the secondary forming of the TRS sheet metal to TRS tubes is investigated by means of FE‐simulations and roll forming experiments. To simulate the manufacturing process of the TRS tube by FEM, an integrated consideration of the process is necessary because of the large local strain hardening in the groves of the initial SPR sheet metal. In experimental roll forming operations welded tubes could be manufactured successfully. The geometrical and material properties of these tubes are analyzed. The reprocessing of TRS tubes by hydroforming is investigated by means of tube bursting tests. It has been found that an additional annealing process is necessary to achieve deformations in the grooved area during the hydroforming process.

Tailored Profiles Made of Tailor Rolled Strips by Roll Forming – Part 1 of 2

AbstractTo fully exploit the potential of sheet and profiles, various technologies to produce tailored blanks and profiles have been developed [1,2]. In earlier work [3] it has been shown that Strip Profile Rolling (SPR) can be used to produce metal strips with a predefined thickness distribution across the width of the strip. Building upon this knowledge, in two subsequent papers the extended goal of the project is presented. Therein is demonstrated that Strip Profile Rolling can be applied very effectively using a combination of roll forming (part 1) as well as further processing by roll forming (see part 2) to allow for the production of profiles with varying wall thickness in their cross section. To achieve the goal of part 1, a numerical model describing SPR was developed and used to study the influencing process parameters on spread and bulge formation. As a result of this parametric study, an optimized roll design and rolling sequence was developed to produce a demonstrator strip on a 12 stand roll forming mill manufactured by the company Dreistern [4]. Starting with a conventional strip out of DC01 steel (width 170 mm, thickness 2.5 mm), 29 rolling passes were necessary to achieve the desired geometry (width 186 mm, thickness 2.5 mm with a longitudinal groove being 64 mm wide where the thickness is reduced to 1.5 mm). In the second part of the process chain the coils produced by Strip Profile Rolling were successfully roll formed into a circular tube of 60 mm.

Design of shaped rolls for wide-strip hot-rolling mills

An algorithm has been developed for the 2000 and 2500 mills at the Magnitogorsk Metallurgical Combine to obtain hot-rolled strip with prescribed characteristics for their cross-sectional profile and flatness. Roll profiles with parameters conforming to existing specifications are obtained by successive execution of the algorithms. The algorithms’ use makes it possible to produce strip that is of high quality in terms of its geometry, regardless of the type of product or its dimensions.

Experimental study on the prohibition of edge cracking of high-silicon steel strips during cold rolling

Two sets of roll profiles were designed such that the roll surface outline is larger in the centre than at the end and vice versa (i.e. convex and concave roll profiles) to simulate positive bending and negative bending profiles in actual cold rolling. Pilot cold rolling tests were then performed to show how waviness of high-silicon steel (3.0 per cent Si) specimens occurs during cold rolling and leads to edge cracking. A finite-element analysis was carried out to examine stress distributions in the region of the specimen where edge cracking initiates during cold rolling. Results show that these specially designed roll profiles create waviness in the specimen, even though the ratio of width to thickness of the specimen used in this study is 10. (Generally, the width to thickness ratio of actual high-silicon steel strip is greater than several 100s.) It has been found that the convex roll profile, corresponding to positive bending in the actual cold rolling, generates waviness in the specimen centre and subsequently the edges of the specimen start fracturing locally due to tensile stress in the rolling direction produced by the waviness. Hence, the best way to avoid edge cracking in actual cold rolling mills is to suppress occurrence of waviness in the centre of the high-silicon steel strip by controlling the roll bending profile.