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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

A. Stefanik, A. Morel, S. Mróz and P. Szota

Abstract

Technology of round bars rolling on a three-high skew rolling mills allows rolling of standard materials such as steel and aluminum, as well as new materials, especially hard deformable materials. The paper presents the results of theoretical and experimental rolling process of aluminum bars with a diameter of 20 mm. As the stock round bars with a diameter of 25 mm made of aluminum grade 1050A and aluminum alloy grade 2017A were used. The rolling process of aluminum bars has been carried out in a single pass. The numerical analysis was carried out by using computer program Forge2011®. On the basis of theoretical research it has been determined the state of deformation, stress and temperature distribution during rolling of aluminum bars. In addition, the results of theoretical research allowed to determine the schema of the metal plastic flow in the roll gap. Verification of the theoretical research was carried out during the rolling of aluminum bars on the RSP 40/14 laboratory three-high skew rolling mill. From the finished bars were taken the samples to set the shape and compared with the results of theoretical research. Finished aluminum round bars were characterized by low ovality and good surface quality.

Open access

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

Currently magnesium alloy bars are manufactured mainly in the extrusion process. This method has some drawbacks, which include: low process capacity, considerable energy demand, small length of finished products. Therefore it is purposeful to develop efficient methods for manufacturing of Mg alloy products in the form of bars, such methods include groove rolling and three-high skew rolling processes. Modified stretching passes provide change in material plastic flow, which contributes to the occurrence of the better distribution of stress and strain state than in the case of rolling in classical stretching passes. One of the modern method of Mg alloy bars production is rolling in a three-high skew rolling mill, which allows to set in a single pass a larger deformation compared to the rolling in the stretching passes.

The paper presents the results of experimental studies of the AZ31 round bars production in the modified stretching passes and in the three-high skew rolling mill. The study of microstructural changes, hardness and the static tensile tests were made for as-cast and ready-rolled bars in both analyzed technologies.

Open access

S. Mróz, P. Szota, A. Stefanik, S. Wąsek and G. Stradomski

Abstract

The paper presents the results of the experimental tests of Al-Cu bimetallic bars rolling process in multi-radial modified passes. The bimetallic bars consist of aluminium core, grade 1050A and copper outer layer, grade M1E. The stocks were round bars with diameter 22 mm with a copper layer share of 15 and 30%. As a result of rolling in four passes, bars of a diameter of about 16.0 mm were obtained. A bimetallic stock was manufactured using an explosive welding method. The use of the designed arrangement of multi-radial modified stretching passes resulted in obtaining Al-Cu bimetallic bars with the required lateral dimensions, an uniform distribution of the cladding layer over the bar perimeter and high quality of shear strength between individual layers.

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

A. Wierzba, S. Mróz, P. Szota, A. Stefanik and R. Mola

The paper presents the results of the experimental study of the three-layer Al-Mg-Al sheets rolling process by the ARB method. The tests carried out were limited to single-pass symmetric and asymmetric rolling processes. An Al-Mg-Al package with an initial thickness of 4 mm (1-2-1 mm) was subjected to the process of rolling with a relative reduction of 50%. To activate the shear band in the strip being deformed, an asymmetry factor of av=2 was applied. From the test results, an increase in the tensile strength of the multi-layer Al-Mg-Al sheets obtained from the asymmetric process was observed. Microhardness tests did not show any significant differences in aluminium layer between respective layers of sheets obtained from the symmetric and the asymmetric process. By contrast, for the magnesium layer, an increase in microhardness from 72 HV to 79 HV could be observed for the asymmetric rolling. The analysis of the produced Al-Mg-Al sheets shows that the good bond between individual layers and grain refinement in the magnesium layer contributed to the obtaining of higher mechanical properties in the multi-layer sheets produced in the asymmetric process compared to the sheets obtained from the symmetric process.

Open access

P. Szota, D. Strycharska, S. Mróz and A. Stefanik

Abstract

An analysis of the roll wear in the multi-strand rolling of reinforced concrete ribbed bars has been made in the study. In the technology under consideration, the longitudinal partition of the band takes place in special slitting passes, while the separation of individual strands – in idle separating rollers. During rolling, the slitting passes undergo fast wear compared to the remaining passes of the rolling line. The paper reports the results of theoretical and experimental examinations, on the basis of which the wear of the slitting passes in the 16 mm-diameter ribbed bar three-strand rolling process has been determined. The theoretical examination was done using the Forge2011® software program, while experimental tests were carried out in a D350 medium-size continuous rolling mill. Based on the analysis of the investigation results, the wear coefficient was established for the slitting passes, which allowed the determination of their quantitative wear.

Open access

S. Mróz, P. Szota, T. Bajor and A. Stefanik

Abstract

The paper has presented the results of theoretical studies and experimental tests of the plastic deformation of Mg/Al bimetallic specimens. Theoretical studies were carried out using the Forge2011® computer program. Physical modeling, on the other hand, was performed using the Gleeble3800 simulator. Bimetallic bars of an outer diameter of 22.5 mm and a cladding layer thickness of 1.7 mm were obtained by the explosive welding method. Samples for formability tests, characterized by a diameter-to-length ratio of 1, were taken from the bars. The theoretical studies and experimental tests were carried out for the temperature range from 300 to 400°C and for different strain rates. Based on the obtained investigation results it has been found that the main parameters influencing the formability of Mg/Al bimetallic bars are strain rate than the process temperature.