Shape Rolling Research Articles

Research on the behavior of transversal crack in slab V–H rolling process by FEM

Cracks appear on slab corner which is an important quality problem in some steel works. The closure and growth of transversal crack on slab corner during multi-pass vertical–horizontal (V–H) rolling was simulated with the explicit dynamic finite element method (FEM) and the updating geometric method. The influences of the friction coefficient, the crack size, the edger roll shape, and the fillet radius of grooved edger roll on the closure and growth of cracks were analyzed with the crack width and the contact pressure on crack surfaces. For vertical rolling, the contact pressure on crack surfaces when the grooved edger roll is used is larger than that when the flat edger roll is used. However, after horizontal rolling, the cracks open again when using the grooved edger roll, which may close well when using the flat edger roll. With increase of the fillet radii of the grooved edger roll, the contact pressure on crack surfaces increases during V 1 pass and decreases during V 2, V 3 pass. Reduction of the friction coefficient between the slab and the rolls is helpful for the crack closure for both the flat edger roll and the grooved edger roll during vertical rolling. The experiments were performed for the behavior of transversal crack on the pure lead slab corner, and the calculated results have the same tendency of the crack behavior as the experimental ones.

Mechanical and Microstructural Characterization of Al-6082 Ultrafine-Grained Alloys Processed by ECAP Combined with Traditional Forming Techniques

An Al-6082 alloy was subjected to equal channel angular pressing (ECAP) and subsequently to conventional forming methods such as shape rolling and rotary forging. The effect of different deformation techniques on the microstructure and the mechanical properties was studied. It was found that the shape rolling and rotary forging increased further the strength of ECAP-processed samples and induced a loss of ductility.

Influence of counterface topography on sliding friction and wear of some elastomers under dry sliding conditions

In this work, the friction and wear behaviour of acrylonitrile butadiene rubber (NBR), hydrogenated acrylonitrile butadiene rubber (HNBR), acrylate rubber (ACM), and fluoroelastomer (FKM) against steel surfaces under unidirectional dry sliding conditions have been studied. The influence of surface roughness of the steel counterface on friction and wear was studied using a block-on-ring test configuration. At low load, the friction coefficient decreased after a running-in period and the wear was insignificant, especially for the ACM and FKM. The running-in time in terms of achieving a stable dry friction for the different elastomers, from longest to shortest, is in the order HNBR, NBR, FKM, and ACM, with an exception in case of FKM sliding against a smooth steel counterface. At higher contact pressure, powdery worn particles on the ACM and a decrease in friction coefficient were observed, but for FKM and HNBR, worn particles with roll shapes were produced. The worn particles of FKM were significantly larger than those of the other tested materials, and a considerably higher wear in FKM was observed.

Prediction of Rolling Force during Temper Rolling

In temper rolling thickness reduction is small (0,5 – 2%) and the elastic deformation of the work roll should be taken into account. During finishing rolling, classical cold rolling theories fail to predict the roll flattening and thus the rolling force. Numerous different mathematical models have been developed for temper rolling process. However, often the non-circular theories are computationally expensive and the range of usability is questionable. In this study, elasto- plastic finite element analysis, laboratory rolling tests and inverse computing from skin pass mill process data has been carried out. The aim is to find the roll shape, contact length and the rolling force to create a simplified model for controlling of temper rolling. In addition, the ability of different skin pass rolling theories has been compared with measured process values.

Salt rollers: Structure and kinematics from analogue modelling

Salt rollers are low-amplitude deflections of the upper surface of a salt layer which occur below zones of normal faulting in the overlying sediments. They are widely recognised in association with tilted blocks or listric fault rollover systems. Laboratory experiments on brittle ductile models made of sand and silicone putty are used to study the modes of development, the external shape and the internal structures of these salt rollers. Firstly, flow and strain patterns within décollement zones are described. Finite strain combines layer-perpendicular shortening and layer-parallel shear. Additional flow cells within rollers perturb the laminar flow of the décollement, inducing a passive folding of planar markers. The same type of flow and strain patterns occur in all types of rollers, ranging from those occurring below tilted blocks to those associated with growth faults. Finally, an analysis of roller shapes through the measurement of aspect ratios and asymmetry ratios shows that the shapes of tilted blocks rollers and growth fault rollers—which differ at initiation tend to converge with increasing deformation.

Laying on of Hands

Laying on of Hands Steven Harvey (bio) A dark slick rising and falling in silky waves—that caught my eye. Some dusky residue of night. The sun had just risen above the Gulf, igniting the sky momentarily in pinks and reds and giving definition to the dunes and sea oats all about me while the house, the wooden walkway, even my arms turned golden in the glow. The water, which lay placid and still against the bowed horizon, culminated along the beach in a hush of long, perfect waves. I had been sitting in a beach chair strumming a ukulele when a black shape appeared—materialized, it seemed, in folds of blue—undulating with the water. I set my instrument down and stood to get a better look, shading my eyes. Suddenly a shape like a wind-lifted lapel emerged briefly out of the spray, and I knew that the darkness I saw could not be a shadow, but an object of some kind, though the movement seemed involuntary, more the rocking of the lovely and indifferent semitropical waters than a thing alive. In Moby Dick Herman Melville compares a morning like this one to the morning after the nuptial night when formality and romance have given way to the act of engendering. The air, he writes, is “pensive” and “transparently pure and soft, with a woman’s look” while “man-like” the sea heaves with “long, strong, lingering swells.” The gulls, he imagines, float like the winking and fluttering thoughts of the woman roused from sleep, so different from the dark and “murderous” underwater creatures slithering through the man’s mind, and the horizon trembles with passion, “the fond, throbbing trust, the loving alarms, with which the poor bride gave her bosom away.” I often think of Melville on sunlit mornings at the beach when the sea takes the sky, the combination of elements creating life and offering it as a gift to the planet. It is a lovely metaphor. But this gift, this offering to the dawn, I wondered, looking at the [End Page 114] black shape in the breakers. What have we here? Rarely is it delivered so literally. And a leviathan, to boot. I did not realize at first that the shape rolling in the water was a whale—a baby sperm whale to be exact—but I did walk down to the water’s edge and on closer look saw that it was a large sea creature. Most of the enormous body lay hidden under water that was slowly turning azure in the morning sun, but I saw the tail clearly—the black lapel—that roiled with the waters and, when a breaker tumbled in, rose out of the wave with a gush and slapped back at the sea. We had often seen dolphins play here—St. George Island is famous for them—so I thought it might be a dolphin though it looked far too large. Recently we had heard reports of sharks attacking children at the water’s edge so that thought glided ominously through my mind. I kept my distance. I’m pretty sure that I was the first on the scene since I had watched the shape emerge out of the night with no one else around. After a long look—in which the body rose and fell with the swelling of the waves—I went back to my ukulele and sat in the sand, wondering what is done when an enormous, dead sea creature washes up on the beach. But it was not dead. I walked back to the beach house. Louisa, whose family shared the St. George house with ours, was pouring coffee and blinking her eyes to wake up. Louisa is usually game for anything, even the sight of a whale at the crack of dawn, so soon she and I were headed down the beach, holding coffee mugs in front of us as we tried to negotiate the tricky sand, making our way to the spot where the whale had washed up. It still looked lifeless and out of place, like a sofa rolling on the waves, but two plucky volunteers who were in the water, their...

Calculation of thermal stress affecting strip flatness change during run-out table cooling in hot steel strip rolling

To fulfill further reducing production costs at the meantime enhancing product quality is always one of the objectives pursued by steel enterprises and researches. With increasing demand on higher quality of hot rolled strip shape, strip flatness change developed during cooling on the run-out table has received significant attention and should be considered in online strip shape control model. Non-uniformity of transverse temperature distribution in strip is the ultimate reason for the occurring of strip flatness defect after hot rolled flat strip is cooled to room temperature. Based on the large amount of thermal image field measurements on strip surface, transverse temperature distribution rules of strip were concluded. A FE model was established to analyze the thermal stresses developed during the cooling of hot rolled strip on the run-out table using finite element program ABAQUS. Analysis results demonstrate that temperature drop within strip edge region will make strip flatness develop to the trend of edge wave and are verified by the actual strip flatness observation on skin pass rolling line. This viewpoint agrees well with the actual production condition. One compensation control strategy, named slight center wave rolling, is proposed based on the FE analysis work. The main idea is that steel strip is rolled with slight center wave at the exit of the last stand of finishing mill to compensate the flatness change trend of edge wave during the cooling.

Managing Pile-Height through Image-Based Compensation in Digital Flexible Package Printing

Printing in flexible packaging is often done on very thin films whose thickness ranges from 12 micron to more than 100 microns. When the thickness of the printed ink layer approaches the thickness of the film, it often introduces severe roll distortion in normal roll-to-roll applications. This distortion is also observed in a less pronounced manner in applications that use stacking, such as labels and books. This distortion is conventionally managed by reducing the ink-pile height. In digital printing (inkjet and also in xerographic) the pile height problem limits the applicability of printing for flexible packaging applications.In this paper we describe an imaging based for managing pile height that normalizes the surface height across the substrate. The solution proposed here tries to intelligently balance the ink-layer discrepancies across the roll width using image-based compensation so that cylindrical shape of roll is maintained. This enables the film/substrate to advance at a uniform rate, and the differential rolling stress across the substrate cross section to approach the normal operational range. This innovation will enable digital printing to play a more significant role in roll-toroll based packaging applications such as flexible packaging.

A taper tension profile maker in a converting machine

Winding is an integral operation in almost every web handling process, and a center-wound roll is one of the suitable and general schemes in a winding system. However, improper internal stresses within a center-wound roll can cause damage such as buckling, spoking, cinching, etc. Wound roll quality and performance are known to be related to the distribution of in-roll stresses. It is therefore necessary to analyze the relationship between taper tension in the winding section and internal stress distribution within the center-wound roll to prevent winding failure. But it is hard to compensate for an undesirable winding roll shape such as starring, buckling, and telescoping. This is because the winding section is the final process in a roll to roll system and has no feedback control system to correct winding roll shape directly. A time varying tension profile and accurate control of it in a winding section is one way to shape the fail-safe in-roll stress distribution of a winding roll. In this study, a new taper tension profile making method is aimed for designing high quality wound rolls. A new method to determine the proper taper tension profile was designed by analyzing the winding mechanism which includes the stress model in center-wound rolls, nip induced tension model, relationship between taper tension profile and telescoping, relationship between taper tension type and internal stress distribution. An auto taper tension profile making method was proposed not only to optimize radial stress distribution but also to minimize lateral error (telescoping). Simulation results show that the proposed method is very useful for determining the desirable taper tension profile during the winding process and preventing defects of winding roll shape such as telescoping, starting, and dishing and so on.

A Study of Surface Deformation during Wire‐Rod Rolling of High Speed Steels using Experimental and Computational Techniques

The evolution of surface defects during shape rolling of high‐speed steel billets is studied using longitudinal surface defects prepared by machining and welding. The reduction of the defects during rolling in a production mill is compared to the total area reduction of the billets. Samples are collected after pass 4, 6, 8, 14, 19 and the final pass, 28, representing the finished 5.5mm wire. By inspecting the cross sections, the rotation of the billets from pass to pass is evaluated. Results from FE simulations on solid billets are compared to the experimental results. Generally, simulations predict less reduction than observed experimentally. In most cases cracks reduce most effectively followed by carbon steel welds and stainless steel welds.

Inhomogeneous deformation and residual stress in skin-pass axisymmetric drawing

Abstract Skin-pass drawing is usually conducted in the final stage of wire, rod or shaped-section drawing or shape rolling. It helps improve shape accuracy and reduce residual stress of the drawn or rolled workpieces. However, its characteristic low reduction induces large Δ-parameter, and causes significant inhomogeneous deformation in the workpiece. In this work, finite-element software DEFORM 2D was utilized to investigate the effect of Δ-parameter on inhomogeneous deformation and residual stress of mid-carbon steel through various combinations of area reduction and die semi-angle. The effect of the friction was also investigated. The results showed that the inhomogeneity factor of effective strain decreased with area reduction and increased with die semi-angle and friction. The level of inhomogeneous deformation could be reduced by drawing with small die semi-angle, and the influence of the friction was only substantial near the surface of the drawn workpiece. The axial and circumferential residual stresses would approach to compressive on the drawn surface in extreme light reductions.

Experimental investigation of helicoidal rolls in an advective flow over a hot horizontal surface

A digital tracer technique is applied to reconstruct the velocity fields in a convective flow developing in a rectangular cavity filled with a layer of fluid and having a bottom consisting of two heat exchangers kept at different temperatures. The upper boundary of the fluid is free. The structure of the secondary flows in the form of streamwise helicoidal rolls generated in the boundary layer over a hot plate is studied. It is shown that the centers of roll rotation coincide with temperature minima in the boundary layer, while the roll shape and dimensions vary with the distance from the temperature jump. With increase in the temperature difference the roll dimensions decrease but the velocity of their rotation increases.

타이타늄합금 형상 링 압연공정 연구

The profile ring rolling process of Ti-6Al-4V alloy was investigated by finite element(FE) simulation and experimental analysis. The process design of the profile ring rolling includes geometry design and optimization of process variables. The geometry design such as initial billet and blank sizes, and final rolled ring shape was carried out with the calculation method based on the uniform deformation concept between the wall thickness and ring height. FEM simulation was used to calculate the state variables such as strain, strain rate and temperature and to predict the formation of forming defects during ring rolling process. Finally, the mechanical properties of profiled Ti-6Al-4V alloy ring product were analyzed with the evolution of microstructures during the ring rolling process.

Ti-6Al-4V 합금의 대형 링 압연공정설계

The process design for large-scale ring rolling of Ti-6Al-4V alloy was performed by calculation method, processing map approach and FEM simulation. The ring rolling design includes geometry design and optimization of process variables. The calculation method was used to make geometry design such as initial billet and blank sizes, and final rolled ring shape. A commercial FEM code, SHAPE-RR was used to simulate the effect of process variables in ring rolling on the distribution of the internal state variables such as strain, strain rate and temperature. In order to predict the forming defects during ring rolling and the formation of over-heating above -transus temperature due to deformation heating, the process-map approach based on Ziegler`s instability criterion was used with FEM simulation. Finally, an optimum process design to obtain sound Ti-6Al-4V rings without forming defects was suggested through combined approach of Ziegler`s instability map and FEM simulation results.

The role of the tribofilm and roll-like debris in the wear of nanoscale nitride PVD coatings

Reciprocating (ball on flat) dry sliding wear tests of TiAlN/VN and CrN/NbN multilayer coatings were undertaken under ambient conditions with either an alumina or tungsten carbide counterface. Wear rates were found to be in the mild wear regime. Worn surfaces and wear debris were examined by using scanning electron microscopy (SEM) and Fourier transformed infrared (FTIR) microscopy. Surface smoothing by the wear process was associated with wear debris with a roll shape, which adhered to the worn surface. Analysis of wear debris suggests they are probably hydrated. The properties of the tribofilm and rolls are correlated with the friction.

Analysis of cold and hot plate rolling using dual stream functions

Three dimensional deformation of the plate rolling process is modeled using an upper bound method. A kinematically admissible velocity field including spread is derived by means of dual stream function (DSF). The rigid plastic boundary at the inlet zone is assumed as quadratic and spread function is also assumed in quadratic form. The upper bound equation was solved numerically and optimization is carried out via Matlab 6.0 optimization toolbox. The rolling force and shape changes in three principal directions are determined for different deformations, friction factors and temperatures. The experiments are carried out with AA5454-O aluminum alloy at different %deformations and temperatures to show the validity of the analysis. The results obtained from the analysis are compared with experimental results and a good agreement is found. The conducted theoretical and experimental analysis showed that it is possible to determine the required optimum rolling force and final shape by using the DSF. The results could well be an important feedback for metal flow and workpiece manipulation, and so can be used in metal rolling plants having or aiming automation in large scale continuous manufacturing routes.

Cyclic loading behavior of EBF links constructed of ASTM A992 steel

Cyclic loading tests were conducted to study the behavior of link beams in steel eccentrically braced frames. A total of thirty-seven link specimens were constructed from five different wide-flange sections, all of ASTM A992 steel, with link length varying from short shear yielding links to long flexure yielding links. The occurrence of web fracture in shear yielding link specimens led to further study on the cause of these fractures. Since the link web fracture appeared to be a phenomenon unique to modern rolled shapes, the potential role of material properties on these fractures is discussed. Based on the test data, a change in the flange slenderness limit is proposed. The link overstrength factor of 1.5, as assumed in the current U.S. code provisions, appears to be reasonable. The cyclic loading history used for testing was found to significantly affect link performance. Test observations also suggest new techniques for link stiffener design and detailing for link-to-column connections.

Roll Shape Setting Technology of Hot Galvanizing and Planishing Mill

A roll shape setting model was built for the hot galvanizing and planishing mill. The uniform transversal distributions of the front tension in the exit and the unit pressure were considered as the objective function. At the same time, the quality of the products, the stability of zinc layer, and the homogeneity of spangles were of considerable significance in the planishing process. The model was applied to the roll shape setting of the 1800 cold rolling 3# CGL hot galvanizing and planishing mill of Baosteel Co Ltd. After being planished, the flatness of a strip that was less than 6 I was more than 97%, and the flatness of others were less than 10 I; the pass percentage of the zinc layers reached 100%.

냉간 비조질강을 이용한 볼 스터드의 정형가공 공정연구

Micro-alloyed steel or heat-treatment-free used in clean technology have been replacing for conventional quenched-and-tempered structural steels since the micro-alloyed forging steel was developed in early 1970s in Germany for saving money of heat treatment, simplified process, short delivery and good productivity. In this paper, ball stud assembled in steering system for automobile was selected to compare conventional process making heat treatment with new process using high strength micro-alloyed steel without heat treatment. The conventional process for ball stud was composed of a total of 6 steps including upsetting, forward extrusion, machining, burnishing and tread rolling with heat treatment and shot blasting. As opposed to conventional process, newly proposed process for ball stud using the clean technology without heat treatment is simplified such as forward extrusion, heading, upsetting, forming having a flange shape and tread rolling. Also net shape forming process to achieve specified process not to include machined step fur manufacturing the ball stud was applied to newly simplified process since micro-alloyed steel is difficult to be formed.

Fault diagnosis of roll shape under the speed variation in hot rolling mill

The metal processing system usually consists of various components such like motors, work rolls, backup rolls, idle rolls, sensors, etc. Even a simple fault in a single component in the system may cause a serious damage on the final product. It is therefore necessary to diagnose the faults of the components to detect and prevent system failure. Especially, the defects in a work roll are critical to the quality of strip. It is especially difficult to detect faults of a roll by using the existing frequency analysis method if the speed of the roll is changing. In this study, a new diagnosis method for roll eccentricity under the roll speed changes was developed. The new method was induced from analyzing the rolling mechanism by using rolling force models, radius -speed relationship, and measured rolling force, etc. Simulation results by using the field data show that the proposed method is very useful.