Ultra-thin Strip Research Articles

An experimental and numerical investigation on micro rolling for ultra-thin strip

The demand for miniaturized parts and miniaturized semi-finished products is increasing nowadays, because microforming processes can improve production rate and minimize material waste due to less forming passes. However, traditional macro metal forming processes and modelling cannot be simply scaled down to produce miniaturized micro parts. In this study, a 2-Hi micro rolling mill has been successfully built. Experimental and numerical investigations on the micro rolling process for ultra-thin SUS 304 stainless steel strip have been conducted. The experimental results show that the micro rolling deformation of ultra-thin strip is influenced by size effect which results from the specimen size difference and this size effect is embodied in the flow stress and the friction coefficient. Analytical and finite element (FE) models in describing size effect related phenomena, such as flow stress, friction, rolling force and deformation behaviour, are proposed. The material surface constraint and the material deformation mode are critical in determination of material flow stress curve. The analysis of surface roughness evolution with rolling conditions has also been performed. The identified analysis on deformation mechanics provides a basis for further exploration of the material behaviour in plastic deformation of micro scale and the development of micro scale products via micro rolling.

Research on the Minimum Rolled Thickness of Strip Steel in Cold Tandem Rolling

In consideration of the zone between rolls and deformed area where friction at roll-sheet interface is lower than predetermined value of Coulomb friction in rolling process of ultrathin strip steel, fully integrated with equipment and process features of cold tandem mills, after a large number of field experiments and theoretical studies, on the basis of the improvement of ultrathin strip steel rolling force model, with the allowable rolling pressure and production efficiency as constraint condition, a new calculated theory about the minimum rolled thickness was put forward. What’s more, the theory will be used in the productive practice of 1220 five-rack cold tandem mills of China. The technique has the value to be further popularized.

Texture Evolution of Commercially Pure Copper during Ultra-Thin Strip Rolling

Experimental investigation on rolling texture evolution in commercially pure copper thinned from 5.8mm to 20μm by symmetrical rolling and asymmetrical rolling without annealing were carried out via orientation distribution functions and orientation line analysis. The results show that the rolling texture for the sample with initial rotate cube texture {100}<011>mainly consist of C and B, most crystallites aggregate along the α and β orientations lines. The texture density growth rate increased significantly in rolling process. That may relate to size effect of ultra-thin strip. The rate of dislocation reduction was more than dislocation multiplication due to disappear at grain size, when the thickness of ultra-thin strip decreased to an extremely value.

An innovative development of a four-high foil rolling mill

During foil or ultrathin strip rolling, elastic deflection variation of the work rolls at the contact surface with the strip causes non-uniform thickness distribution of the product in the width direction, which possibly causes a central wrinkling or an edge fracture on the product. This study developed a four-high prototype rolling mill, comprising two work rolls fabricated from an ultrastrength alloy. This prototype rolling mill was composed of a housing frame set, a roll set, a roll gap adjusting mechanism, and a power transmission system. The finite element analysis was used for determining the frame dimensions and work roll diameters. Several experimental rolling passes of stainless steel strips were conducted using this self-developed prototype rolling mill to achieve a 0.05-mm-thick foil product.

Study on Surface Roughness Transformation during Metal Rolling

Increasing the demand for cold rolled ultra thin strip as feedstock for miniaturized products has encouraged researchers to investigate the ways to increase the quality of such products, especially those related to strip surface roughness. Surface is known as quality factor in most of manufacturing processes. In this paper, the effect of the rolling parameters on the surface roughness transformation during metal rolling has been studied. The experimental results demonstrate that the surface roughness transformation during the metal rolling is highly affected by the designation of the processing parameters such as finishing temperature, reduction, rolling passes and lubrication. The results have been discussed to verify the validity of the new findings.

Modelling of Strip Shape and Profile during Cold Rolling of Ultra Thin Strip

In this paper, finite element models of the strip shape during cold rolling of ultra thin strip in both symmetrical and asymmetrical rolling cases have been successfully developed, and the strip shape such as the thickness distribution along the strip width has been obtained. The strip shape and edge drop are discussed under both symmetrical and asymmetrical rolling conditions. Simulation results show that the asymmetrical rolling can reduce strip edge drop dramatically. The work roll edge curve also affects strip shape significantly. The developed finite element model has been verified with the experimental values.

Study on Surface Roughness Transformation during Metal Rolling

Increasing the demand for cold rolled ultra thin strip as feedstock for miniaturized products has encouraged researchers to investigate the ways to increase the quality of such products, especially those related to strip surface roughness. Surface is known as quality factor in most of manufacturing processes. In this paper, the effect of the rolling parameters on the surface roughness transformation during metal rolling has been studied. The experimental results demonstrate that the surface roughness transformation during metal rolling is highly affected by the designation of the processing parameters such as finishing temperature, reduction, rolling passes and lubrication. The results have been discussed to verify the validity of the new findings.

Analysis of cold rolling of ultra thin strip

In this paper, the cold rolling experiments of ultra thin steel strip were carried out on an experimental rolling mill. The cold rolling of ultra thin strip with roll edge kiss was analysed theoretically, and the rolling force, intermediate force between the work roll and backup roll, the roll edge kiss force, the strip shape after rolling are obtained for this special rolling, and they are compared for various reduction and friction coefficients. Simulation results show that the reduction has a significant influence on the shape of rolled strip, and the calculated rolling forces and strip profile are consistent with the measured values. The effect of friction in the roll bite on cold rolling of ultra thin strip with roll edge kiss is also discussed. Surface characteristic was measured and it is shown that the steel surface roughness value reduces with an increase of reduction.

VAI pickling for ultra thin hot strip in ACB

In 2000, ACB decided to double the capacity of the thin slab caster and of the hot strip mill with a view to substitute ultra thin hot strip for conventional cold strip on the market. To cope with the extra tonnage, a new pickling line had to be installed. The main features of the new pickling lines that makes it possible to process thin gauges at reduced total costs, are presented.

Mathematical Modeling of Draft Schedule for In-line Rolling of Ultra Thin Strip in the Combined Single-belt Casting/Hot Rolling Process

The single-belt process is a new route to produce steel strips, in which the single-belt caster is directly connected with hot mills. This process should be able to roll strip with thickness 1 mm or below. In hot rolling of the ultra thin strip there are many limitations which are represented by the finishing rolling temperature of the strip, the oxidation of the strip, the overheat of the roll and the maximum rolling speed. In the present paper the possibility of hot rolling ultra thin strip in the single-belt process was investigated. On the basis of mechanical/thermal/metallurgical behavior of the strip a mathematical model of draft schedule was proposed. In terms of different criteria the draft schedule was optimized. The results show that austenitic hot rolling of ultra thin strip in the single-belt process can be carried out like the conventional hot rolling for low carbon steels. With consideration of roll life the maximal roll surface temperature has a large influence on the establishment of the draft schedule for hot rolling of ultra thin strips.

Numerical analysis of a new Eulerian–Lagrangian finite element method applied to steady‐state hot rolling processes

AbstractA finite element code for steady‐state hot rolling processes of rigid–visco‐plastic materials under plane–strain conditions was developed in a mixed Eulerian–Lagrangian framework. This special set up allows for a direct calculation of the local deformations occurring at the free surfaces outside the contact region between the strip and the work roll. It further simplifies the implementation of displacement boundary conditions, such as the impenetrability condition. When applied to different practical hot rolling situations, ranging from thick slab to ultra‐thin strip rolling, the velocity–displacement based model (briefly denoted as vu‐model) in this mixed Eulerian–Lagrangian reference system proves to be a robust and efficient method.The vu‐model is validated against a solely velocity‐based model (vv‐model) and against elementary methods based on the Kármán–Siebel and Orowan differential equations. The latter methods, when calibrated, are known to be in line with experimental results for homogeneous deformation cases. For a massive deformation it is further validated against the commercial finite‐element software package Abaqus/Explicit. It is shown that the results obtained with the vu‐model are in excellent agreement with the predictions of the vv‐model and that the vu‐model is even more robust than its vv‐counterpart. Throughout the study we assumed a rigid cylindrical work roll; only for the homogeneous test case, we also investigated the effect of an elastically deformable work roll within the frame of the Jortner Green's function method.The new modelling approach combines the advantages of conventional Eulerian and Lagrangian modelling concepts and can be extended to three dimensions in a straightforward manner. Copyright © 2004 John Wiley & Sons, Ltd.

Process Control System of Ultra Thin Strip Production line at Tangshan Iron and Steel Group Co. in China

Commissioning for a UTSP plant has been started for commercial production at Tangshan Iron & Steel Company Ltd in China. The plant was constructed by an international consortium from Japan, Italy and the USA, and production of hot coils has been begun in only 25 months. The annual production capacity for the first stage is 1.5 million tons and strip thickness ranges from 0.8 to 4.0 mm. The plant is featured by a high-performance PLC system and advanced process control technologies, with which semi-endless rolling operation was introduced for the first time in China. This paper describes these features and functions in detail.

The status of twin-roll casting technology. Comparison with conventional technology

The first industrial twin roll caster for carbon steel strips is under construction on the Nucor site at Crawfordsville. This installation based on the CASTRIP technology developed by BHP and IHI is expected to produce 500 000 tons per year of hot rolled strip with a thickness below 2 mm. In this paper the characteristics of the CASTRIP technology are presented, with reference to the economical aspects and further details on the main breakthroughs that had to be accomplished to improve the efficiency. The twin roll caster technology offers many advantages in terms of production costs, environment and production flexibility over more conventional production routes for carbon strips with a thickness below 2 mm. It is expected that the implementation of the new technology will foster the user demand for ultra thin gauge hot rolled strips.

Advanced measuring techniques for the production of ultra-thin hot strip

When producing ultra-thin hot strip, the yield and economy depend on achieving narrow geometrical and material properties fulfilling the increased customers demand. In production, the correct measurement of the strip properties is necessary. This paper gives advanced measuring and control techniques for the parameters concerning thickness profile, flatness profile, coil face profile, temperature profile, surface finish profile of ultra-thin hot rolled strip.

Technologies of the highest speed rolling in the world at a cold tandem mill

The increase of rolling speed is an eternal dream, especially for the production of ultra-thin gauge strip, such as tin mill black plate. Kawasaki Steel Corp. recently achieved the highest rolling speed in the world, 2,800 m/min, at No. 2 TCM in Chiba Works. The technologies consist in the development of :—a new direct rolling oil with special additives,—an advanced work roll coolant system,—a new Ti-enhanced work roll with high wear- resistance,—a new roller bearing system for high-speed back up rolls.

Innovation in hot rolling equipment for modern high performance mills

The severe requirements of tight tolerances for ultra-thin hot rolled strips need innovative equipment to be installed on the hot strip mill, as well as powerful and effective actuators for profile and flatness control. Danieli United has developed a new concept of rolling stand : the f2 CR™ stand that permits to cross and shift the rolls in dynamic conditions while rolling.

Endless rolling technology for No. 3 hot strip mill at Chiba Works of Kawasaki Steel

Fully continuous finishing rolling, so-called “endless hot strip rolling”, has started in operation for the first time in the world. This unique technology realizes finishing rolling under an uninterrupted tension between rolling stands. As a result, product quality, productivity, and stability of rolling were improved. In addition, ultra-thin strip, like 1.0 mm thickness, has been produced without trouble.

Microchannel Plate Pore Size Limited Imaging with Ultra-Thin Wedge and Strip Anodes

We describe a detector employing a curved channel microchannel plate (MCP) in front of an optimised, thin substrate wedge and strip anode (WSA) imaging readout. We obtain a position resolution better than 20?m FWHM allowing the images of individual MCP pores to be distinguished. The collimation provided by a single pore is used to probe the fundamental limitations in resolution of the WSA. Finally, having experimentally verified the limitations imposed by electronic and partition noise, we describe a detector which will produce 20?m FWHM resolution over a 50mm diameter imaging area.