Analysis of rolling load generated by pair crossed rolling mill

Abstract

Although a pair crossed rolling mill has a very high control capability of strip crown, a frictional force always occurs in the strip width direction between the strip and the work rolls. An analysis of rolling load was carried out, considering the shear deformation of strip cross-section caused by the frictional force. From the examination of the calculated results for a large-scale mill for production, the following conclusions were obtained: (a) the cross angle hardly influences the rolling force and torque, (b) the thrust force on the roll induced by the frictional force decreases as a result of shear deformation, (c) the thrust factor, i.e. the thrust force divided by the rolling force, is little influenced by the strip deformation resistance and the friction coefficient between the work rolls and the strip during hot rolling, (d) the thrust force applied to the rolls during hot rolling is 3–6% of the rolling force for the cross angle of 1° and this is not an obstacle related to the design of rolling mills.     

Spherical Nanoparticle–Substrate Adhesion Interaction Simulations Utilizing Molecular Dynamics

From a molecular perspective, the fundamental rolling and sliding elasto-adhesion interactions between a spherical nano-particle and an elastic substrate is studied using a computational technique based on the Molecular Dynamics (MD) approach. Initially, the particle and the substrate were equilibrated individually at 300 K. The covalent bonds interactions between the atoms of the nanoparticle are modeled by constraining the atoms to stay together throughout the simulation. The temperature of the substrate atoms is regulated by periodically scaling to mimic the bulk substrate effect to minimize the effects of the finite substrate size. The intermolecular interaction between the particle and the substrate is defined by the Lennard–Jones (LJ) 12-6 potential. The total force–displacement curves of the 4.2 and 7.89 nm particles in the cases of particle being pushed normally towards the substrate and the particle pushed tangentially, while in adhesion with substrate, are obtained. The rolling resistance moment exhibited by the smaller nanoparticle (4.2 nm) is calculated from the force–displacement curve obtained from simulations and compared to the theoretical predictions based on a two-dimensional adhesion model. It is found that the moments as a function of the rotation angle are of the same order (3.64 nN nm). The rolling and sliding force–displacement profiles when the nanoparticle is subjected to tangential load are also presented.     

Working range of roll pass sequences in wire rod rolling with interstand tensions

Abstract

In the high speed rolling of wire rod in blocks, interstand tensions are utilised in order to keep the process stable. However, interstand tensions influence the rolling process, and especially the spread and forward slip, which are dependent of tensions between the stands. By the influence on spread, the tolerances of the rolled product depend on the tensions and usually the interstand tensions are kept as low as possible in order to obtain required tolerances. A narrow spread technology is used to utilise interstand tensions in order to increase the working range of a pass sequence and move the product range towards smaller sizes. By adapting a certain amount of interstand tensions, smaller sizes can be rolled by a given roll pass schedule. A practical problem in this method is the fixed gearings in the common blocks, which require a certain and given level of interstand tensions and corresponding reductions. In the latest generation of blocks, where the stands are arranged in units, two by two, with each unit driven by a dedicated electrical motor, it is possible to introduce 'inter unit' tensions, and by this method extend the working range of the pass sequence. A special computer program for analysis of interstand tensions has been developed by combining a program TENSION, developed at the Royal Institute of Technology in Stockholm, dealing with the basic principles of rolling with interstand tensions, with the recently published program WORKRAN, which analyses the working range of any roll pass sequence built up by common two-symmetrical grooves. From the analysis and experimental data it is shown that interstand tensions at the level of 10% of the yield stress of the material increase the working range in a six stand block by 2% and reduce the lower limit of the exit section area by about 15%. Higher tension levels have a larger effect both on the extension of the working range and on the reduction of the minimum exit area but it becomes more difficult to control the tolerances at higher tension levels. The influence of interstand tensions on the reduction and on the working range of the pass sequence is mainly obtained by the influence on the round passes, while the oval passes have a counteracting effect on the influence of interstand tensions.     

Effect of residual austenite on properties of tool steel following shortened treatments in lower bainitic phase

Abstract

Recent investigations show the possibility of shortened low-cost treatment of chromium alloyed tool steels in the lower bainitic state. But with these treatments just above the martensite start temperature remains still an amount of residual austenite. For better understanding of the reactions due to the transformation of austenite into lower bainite metallographic, studies completed by dilatometric tests have been carried out. Structural characteristics due to applied heat treatment processes are discussed and special changes of specific properties are discussed by example of the steel 100Cr6 (SAE 52100).     

Electric Metal Melting—a Review

This paper presents a detailed review of the present status of electric melting with particular reference to the needs of the cast metals sector. The survey covers the use of arc-furnaces; coreless induction furnaces; channel induction furnaces, and electric-resistance units. In the case of arc and induction furnaces, applications are shown to embrace the melting of iron and steel, while induction furnaces also find use in the production of castings in non-ferrous metals. Resistance-type units are now finding widespread adoption in the melting and holding of light alloys.     

Orientation of polyoxymethylene by plane strain compression and rolling with side constraints

Abstract

In this paper, the authors describe the application of the constrained rolling process to produce highly oriented polyacetal bars with enhanced mechanical properties. The focus is on two commercial grades of polyoxymethylene Delrin 100 and Tarnoform 300. Tarnoform, unlike Delrin, is a copolymer. The structure and properties of the samples rolled to different compression ratios are described.     

Transformation of austenite remaining after intercritical rolling to ferrite

Abstract

The impact of austenite deformation in the intercritical range on the rate of transformation in continuous cooling to ferrite, pearlite, bainite or martensite has been studied. The austenite associated with the rolled ferrite is much higher in carbon content, which does not influence the pearlite transformation but retards bainite and martensite. Furthermore, in comparison with rolling of stable austenite the increased strain hardening of the intercritically cooled austenite accelerates the formation of ferrite and pearlite (+ 10–30°C) and refines them but retards the bainite and martensite transformations (?20–40°C). At the intermediate cooling rate near 16 K s^?1, these several influences combined with near doubling of the ferrite production give rise to the suppression of bainite formation and to maximum increased delay of martensite start.     

Modelling flow stress behaviour of aluminium alloys during hot rolling

Abstract

A mathematical model is proposed to predict the flow stress behaviour of aluminium alloys under hot rolling conditions. To do so, a dislocation model for evaluating flow stress during deformation is coupled with a finite element analysis to access metal behaviour under non-isothermal and variable strain rate conditions. Then, with the aid of the proposed model, a hot strip rolling process was simulated. In order to verify modelling results, flow stress behaviour of an aluminium alloy is studied employing hot compression tests in various temperatures and strain rates and the model was examined on this material. Non-isothermal hot rolling experiments were carried out and good agreement was found between predictions and experiments.     

Three-dimensional thermomechanical coupled FEM analysis of static recrystallisation during two-pass tube tension reducing process

Abstract

In this paper, a thermal dynamic numerical method was carried out to model the austenite static recrystallisation behaviour of steel 33Mn2V used in new non-quenched/tempered oil well tubes at different deformation temperatures, strain rates, deformation amounts and initial microstructures. Based on the MARC/AutoForge software, a three-dimensional thermomechanical coupled elastoplastic finite element model (FEM) was applied to simulate static recrystallisation amount of the two-pass tube tension reducing process of steel 33Mn2V for oil well. The distribution law of static recrystallisation inside the workpiece is analysed. It is indicated that the simulation results are much reliable through comparison with experimental data.     

Hot working of Fe3Al based alloy

Abstract

For many years Fe₃Al based alloys have been of interest because of their excellent oxidation and sulphidation resistance. However, there are still some obstacles to industrial application of these materials, including the poor hot workability of Fe₃Al based alloys. Four types ofhot working (hotrolling, hotforging, hotpressing, and hotpressing plus hot forging) for the processing of Fe₃Al ingots have been studied in the present work, and the results indicate that a combination of hot pressing and hot forging might be an optimal method for breakdown of the Fe₃Al ingot.