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Open access

S. Sawicki and H. Dyja

Theoretical and Experimental Analysis of the Bimetallic Ribbed Bars Steel - Steel Resistant to Corrosion Rolling Process

The paper presents results of theoretical and experimental studies on the process of rolling bimetallic ribbed bars in the finishing pass. The work has determined the effect of the shape of oval preformed strip with a variable clad layer share on the distribution of clad layer thickness in bimetallic ribbed bars rolled in the finishing pass. The theoretical and experimental studies were carried out with the aim of determining the clad layer thickness that will ensure the appropriate corrosion resistance of finished product. A software application, Forge2007®, was used for numerical modeling.

Open access

K. Sobczak, H. Dyja and A. Kawałek

Abstract

The article discusses the influence of rolling in the newly designed slitting-bending grooves on closing internal material discontinuities in continuous ingots. The defects located in the axial area of a strand, i.e. axial porosity and contraction cavity, were analysed. Numerical and experimental studies of the rolling process of flat bars for feedstock with marked materials discontinuities simulating actual defects occurring in an ingot were conducted. For comparison purposes, rolling of feedstock with discontinuities in traditional grooves was conducted. The numerical simulations were carried out using the Forge 2008¯software programme. The experimental studies were conducted in a D150 laboratory rolling mill. In the research, the S355J2G3 structural steel and lead were used. Distributions of temperature, intensity of deformation and stress in a cross-section of strands after rolling were analysed. Changes in the surface areas of the discontinuities in feedstock after rolling in shape and traditional grooves were examined.

It was concluded that introduction of grooves with complex shapes may contribute to the improvement of internal quality of finished products. The complex shape of the tools has allowed for an almost 100% closure of the discontinuities located in the central part of a strand, already at the initial stages of the process, unlike in case of the traditional production method, where the discontinuities were transferred even until the final product. Applying the newly designed slitting-bending grooves enables utilisation of a smaller number of edge grooves at the initial stage of the rolling process, where reopening of freshly welded defects might occur.

Open access

K. Laber, H. Dyja and M. Kwapisz

Numerical Modelling of the Cooling Ability of Device for the Plain Round Bars Accelerated Cooling Process

The paper presents numerical modelling results of the band accelerated cooling during rolling process. For the numerical modelling the Forge3® and the SortRoll computer programs were used, which based on finite element method.

Research were carried out for one of the bar rolling mill technological conditions. The studies were carried out for 30mm-diameter plain round bars. Constructional steel S355J2G3 (according to DIN St 52-3) was used for the research.

The paper purpose was determination of the cooling ability of device for accelerated cooling process to checking possibility of the using this device in the rolling line, during normalizing rolling process. Investigation results elaborated in the paper made the basis for determination of the heat convection coefficients between cooled band and water for different pressure and water flow.

Open access

A. Stefanik, H. Dyja and S. Mróz

Determination of the Critical Value of Normalized Cocroft - Latham Criterion During Multi Slight Rolling Based on Tensile Test

The Multi Slit Rolling technology is generally employed during ribbed wired rods rolling process. This technology enabled of the making two, three, four rods simultaneously from a single strip (a continuous casting or billet) during hot rolling process. To analysis of the slitting process during MSR the normalized Cockroft - Latham criterion was used. Limit values of the normalized Cocroft - Latham criterion for different values of temperature and strain rates may be determined by using the comparative method for the uniaxial tensile test of notched specimens. In multi slitting rolling process determination of the critical values is difficult, and could be made by using the inverse method. In this paper comparison of the critical values of the normalized Cockroft - Latham criterion estimated in tensile test and during multi slitting rolling process were presented. A relationship enabled determination of the critical value of the normalized Cockroft - Latham criterion during multi slit rolling process based on tensile test was appointed.

Open access

M. Kwapisz, M. Knapiński, H. Dyja and K. Laber

Analysis of the Effect of the Tool Shape on the Stress and Strain Distribution in the Alternate Extrusion and Multiaxial Compression Process

The paper present the results of numerical simulations of the alternate indirect extrusion and multiaxial compression process, performed using commercial software designed for the thermomechanical analysis of plastic working processes, Forge 2009. The novel method of alternate indirect extrusion and multiaxial compression, proposed by the authors, is characterized by the occurrence of strain states in the material being plastically worked, which are similar to those occurring in the equal channel angular pressing and cyclic extrusion compression processes.

It can be found from preliminary studies carried out that the two alternate operations, i.e. extrusion and multiaxial compression, result in a strain accumulation and the formation of a strain state particularly favourable to grain refinement.

As shown by preliminary numerical studies performed by the authors, a zone of large plastic strains forms at the lateral side of the stamping during extrusion of material, which gradually fades along the stamping axis direction. After the multiaxial compression operation, when the material has been brought again to its original shape, the large strains zone moves and then settles in the form of a torus under the stamp. The subsequent extrusion process results in the formation of a new large strains zone being located at the lateral stamping side, and, at the same time, the displacement of the previously deformed material towards its axis. Repeating the above operations many times should bring about large magnitudes of homogeneous deformation within the entire volume of the material examined. The main problem during carrying out practical tests will be to determine the optimal shapes of dies and stamps, which would assure the intended strain state to be obtained in the material, and would also prevent the buckling and overlaps of the material during multiaxial compression.

The distribution of stresses and strains occurring during the compression tests and their correlation with the MaxStrain tests were analyzed within the work. The performed numerical simulations will enable the determination of the proper parameters of the compression test on the Gleeble simulator in order to obtain the strain accumulation which will allow a considerable refinement of the structure.

Open access

M. Kwapisz, M. Knapiński, H. Dyja and A. Kawałek

Abstract

The paper present the results of numerical simulations of the alternate indirect extrusion and multiaxial compression process, performed using commercial software designed for the thermomechanical analysis of plastic working processes, Forge 2009. The novel method of alternate indirect extrusion and multiaxial compression, proposed by the authors, is characterized by the occurrence of strain states in the material being plastically worked, which are similar to those occurring in the equal channel angular pressing and cyclic extrusion compression processes.

It can be found from preliminary studies carried out that the two alternate operations, i.e. extrusion and multiaxial compression, result in a strain accumulation and the formation of a strain state particularly favourable to grain refinement.

As shown by preliminary numerical studies performed by the authors, a zone of large plastic strains forms at the lateral side of the stamping during extrusion of material, which gradually fades along the stamping axis direction. After the multiaxial compression operation, when the material has been brought again to its original shape, the large strains zone moves and then settles in the form of a torus under the stamp. The subsequent extrusion process results in the formation of a new large strains zone being located at the lateral stamping side, and, at the same time, the displacement of the previously deformed material towards its axis. Repeating the above operations many times should bring about large magnitudes of homogeneous deformation within the entire volume of the material examined. The main problem during carrying out practical tests will be to determine the optimal shapes of dies and stamps, which would assure the intended strain state to be obtained in the material, and would also prevent the buckling and overlaps of the material during multiaxial compression.

Open access

P. Szota, S. Mróz, A. Stefanik and H. Dyja

Numerical Modelling of the Working Rolls Wear During Rods 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 oval pass during rolling of round bars.

Open access

J. Wypart, D. Rydz, G. Stradomski and H. Dyja

Abstract

This work presents the effect of plastic deformation and heat treatment on the properties of joint area of AL99,8 + M1E bimetallic plate. The joining zones were analyzed after rolling in three variants: directly after joining, after joining and annealing at 300°C, and after joining and annealing at 400°C.

Open access

A. Kawałek, H. Dyja, M. Knapinski, G. Banaszek and M. Kwapisz

Abstract

In order to enhance the quality of plates, various solutions are being implemented, including normalizing rolling, the process of rolling followed by accelerated cooling, as well as new roll gap control systems. The hydraulic positioning of rolls and the working roll bending system can be mentioned here. The implementation of those systems results in increased loads of the rolling stands and working tools, that is the rolls. Another solution aimed at enhancing the cross-sectional and longitudinal shape of rolled plate is the introduction of asymmetric rolling, which consists in the intentional change of the stress and strain state in the roll gap. Asymmetric rolling systems have been successfully implemented in strip cold rolling mills, as well as in sheet hot rolling mills.

The paper present results of studies on the effect of roll rotational speed asymmetry and other rolling process parameters on the change in the shape of rolled strip and the change of rolls separating force for the conditions of normalizing rolling of plates in the finishing stand. The variable process parameters were: the roll rotational speed asymmetry factor, av; the strip shape factor, h0/D; and the relative rolling reduction, ε. Working rolls of the diameter equal to 1000 mm and a constant lower working roll rotational speed of n = 50 rpm were assumed for the tests. The asymmetric rolling process was run by varying the rotational speed of the upper roll, which was lower than that of the lower roll. The range of variation of the roll rotational speed factor, av =vd/vg, was 1.01÷1.15. A strip shape factor of h0/D = 0.05÷0.014 was assumed. The range of rolling reductions applied was ε = 0.08÷0.50. The material used for tests was steel of the S355J2G3 grade. For the simulation of the three-dimensional plastic flow of metal in the roll gap during the asymmetric hot rolling of plates, the mathematical model of the FORGE 2008 ® program was used.

For the mathematical description of the effect of rolling parameters on the strip curvature and rolls separating force the special multivariable polynomial interpolation was used. This method of tensor interpolation in Borland Builder programming environment was implemented.

On the basis of the carried out analysis can be state, that by using the appropriate relative rolling reduction and working roll peripheral speed asymmetry factor for a given feedstock thickness (strip shape ratio) it is possible to completely eliminate the unfavorable phenomenon of strip bending on exit from the roll gap, or to obtain the permissible strip curvature which does not obstructs the free feed of the strip to the next pass or transferring the plate to the accelerated plate cooling stations. Additionally by introducing the asymmetric plate rolling process through differentiating working roll peripheral speeds, depending on the asymmetry factor used, the magnitude of the total roll separating force can be reduced and, at the same time, a smaller elastic deflection of rolling stand elements can be achieved. As a result smaller elastic deflection of the working rolls, smaller dimensional deviations across its width and length finished plate can be obtained.

Open access

H. Dyja, M. Knapiński, M. Kwapisz and J. Snopek

Physical Simulation of Controlled Rolling and Accelerated Cooling for Ultrafine-Grained Steel Plates

The work shows the possibilities of obtaining ultrafine-grained ferrite-pearlite and ferrite-bainite structures in the process of controlled rolling of sheet metal using immediate accelerated cooling after the final pass. Low-carbon steel without micro-alloy additives was analyzed. The analysis was conducted using the Gleeble 3800 device with Hydrawedge II MCU module which enabled a multiple cycle of fast compression of the material. During the test, 10×15×20 mm rectangular parallelepiped specimens were deformed in flat anvils gaining the flat state of deformation in the zone of compression. Then the influence of the used scheme of deformation, cooling rate, time of break between the last deformation and the beginning of the accelerated cooling was analyzed as well as the temperature at the end of accelerated cooling of the structure and the mechanical properties of the final item.