Papers by Keyword: Cold Rolling

Abstract: The method of determination of the force of counter flexure of the working rolls was designed, ensuring improvement of the degree of flatness of cold rolled strips with due regard to the influence of unevenness of distribution of inter-rolls linear load. On the basis of the analysis of numerical realization of this method an essential influence of the width of the rolled strips upon the optimal value of the force of counter flexure was found out. Also, it was suggested to approximate the connection between increments of the force of counter flexure with linear equations, the application of which is promote to improvement efficiency of systems of automatic adjustment of shape and profile at rolling of sheets. For the condition of 4-stand cold rolling mill the values of transmission coefficients depending on widths of rolled strips were determined.

Abstract: The paper presents the results of research of the structural blocking influence in Al-Mg sheet aluminum alloys on the change in mechanical properties and the stamp ability after cold working and annealing. The study was provided on sheet billets of AlMg1, AlMg5 and AlMg6 alloys containing respectively 1, 5 and 6 mass.% Mg. The initial thickness of the blanks is 2.5 mm. The blanks were cold rolled with a reduction rate of 30%. To eliminate the cold working hardening alloys were subjected to annealing at temperatures of 380 and 420°C for 1 hour. The charts of tensile strength, yield stress, and elongation change are plotted, depending on the state of the samples. Stamping was evaluated by the stamping ratio σ_0.2/σ_b. To analyze the alloys’ grain structure blocking, the change in the size of the coherent scattering areas was estimated on the basis of X-ray diffraction studies. It is established that annealing leads to a significant decrease in the tensile strength, yield stress and elongation growth of alloys AlMg1, AlMg5 and AlMg6 sheet samples in the annealing temperature interval 380...420 ̊С. Despite the high plasticity of the AlMg1 alloy, it has lower stamping characteristics than alloys with higher magnesium content (AlMg5 and AlMg6). The yield stress of alloys decreases with increasing of annealing temperature, which indicates an increase in their stamping ability after annealing. The change in the coherent scattering areas sizes in alloys depends on the magnesium content. With an increase in the magnesium content, the coherent scattering area size increase with the annealing temperature. For an AlMg1 alloy, annealing after cold rolling does not lead to a change in the coherent scattering area size.

Abstract: We have investigated the cold rolling mesostructure and recrystallization of BCC crystals {110} <110> Fe-3%Si using a method of orientation microscopy. The 40% deformation caused shear bands with habit plane at a slope of ~20 ... 28° to the direction of rolling to form a "fishbone"-type structure. The orientation of the crystal lattice in SBs was close to {100} <001>. It can be represented as a rotation around TD close to the crystallographic direction [001] at an angle of ~ ± 37°. Such disorientation corresponds to the special disorientation CSL Σ5 (36.87о, axis [001]) between SBs and the matrix. Primary recrystallization centers in previously deformed crystal {110} <110> are formed primarily in SBs. Their orientation appears to be close to the orientation {100} <001>. It has been shown that the usage of patterns of texture formation in the shear bands of original crystallites {110} <110> allows to obtain electrical steel with a cubic texture {100} <001>.

Abstract: The grain refinement is an effective approach to strengthen high-Mn TWIP/TRIP steels. The development of recrystallized microstructure with a grain size of about one micron increases the yield strength of high-Mn steels above 500 MPa. The fine grained microstructures can be easily developed by cold rolling followed by primary recrystallization. The recrystallized grain size can be expressed by a power law function of the strain hardening during the previous cold rolling with an exponent of -2. Taking the dislocation density as the main strengthener, the grain size is an inverse proportion to the dislocation density. Then, the number density of recrystallized grains can be expressed by a power law function of dislocation density evolved during cold rolling with an exponent of about 2.

Abstract: The work presents the results on the structure of CuNi2Si1 copper alloy. The alloy was treated in two variants: supersaturation - aging (variant I) and supersaturation - cold rolling - aging (Variant II).The structure of the CuNi2Si1 alloyed copper were analyzed by high resolution transmission electron microscopy (HRTEM). The TEM investigation showed in the Cu matrix after applying cold rolling after solution heat treatment, during aging at 600°C, causes the Ni₂Si phase occurrence immediately after the begin of aging. Cold rolling (50% reduction) of the CuNi2Si1 alloy after supersaturation changes the mechanism and kinetics of precipitation and provides possibilities for production of broader sets of functional properties.

Abstract: “Detachable iron particles” or iron fines due to abrasive interactions in the roll bite between the roll surface and the strip are one of the major cleanliness defects. They may induce surface defects in particular on galvanizing lines. Chrome plating of rolls is generally recognized to result in a better strip surface cleanliness. In the present paper, the reasons for the success of chrome plating in this respect are investigated. An end-of-life industrial roll has been ground by parts under several conditions (Ra = 0.4 μm, 1.0 μm, 1.6 μm ± 0.1 μm), then cut into pieces for observation as well as for manufacturing tribological test tools (Plane Strain Compression Test, PSCT). Some of these pieces have been chrome-plated, the others not for comparison. Careful examination of just ground and chrome-plated roll has revealed that ground surface bears a number of rather aggressive features. Chrome plating covers them with a gentler pattern, although preserving the roughness in terms of Ra to maintain sufficient friction for correct mill operation. PSCT confirms that there is less wear debris on the strip when using Cr-plated tools.

Abstract: Deformation characteristics of brass alloy are still under discussion, particularly concerning the critical level of when the change of deformation mechanism occurs. Previous research showed that the addition of Mn on brass alloys resulted in grain refinement and mechanical properties alteration. However, the effects of Mn on the deformation characteristic of brass alloys have not been investigated. In this research, Cu-Zn-xMn alloys were manufactured by gravity casting process using pure Cu and Zn ingots, as well as Mn chips as the feeding materials. Mn addition was varied to 1.26, 3.48, and 5.83wt.%. As-cast samples were homogenized at 800 °C for 2 h in a muffle furnace. The samples were then cold-rolled with the level of deformation of 20, 40, and 70 %. Samples characterization includes chemical composition analysis, microstructure observation, tensile and hardness testing. The results showed that addition of Mn for 5.83 wt.% and above created β’ phase, which is richer in Mn compare to that in the matrix. This phase segregated in the grain and along the grain boundary with irregular forms. Significant increase in hardness, yield and tensile strengths was observed with addition of Mn. The maximum elongation was achieved by addition of 3.48 wt.% Mn, while further addition tended to decrease it. At 20% deformation, slip dominated and its density reduced with addition of Mn. When the deformation level increased to 40%, twinning replaced slip as the predominant mechanism. Twinning density is slightly increase with the presence of Mn. Further deformation at 70% produced shear bands and flattened the β’ phase. Greater Mn content led to formation of more shear band.

Abstract: The microstructure and hardness changes of a non-equiatomic Al₅Cr₁₂Fe₃₅Mn₂₈Ni₂₀high-entropy-alloys (HEA) with cold rolling are presented here. Using a variety of characterization methods, it is shown that the alloy is single FCC phase structure which doesn't change with cold rolling up to90%CR. With increasing the cold rolling reduction ratio, the hardness increased and the dendritic structures are broken and refined.

Abstract: In this study, temperature distribution that occurred during cold and hot rolling of AA5454-O alloy has been investigated. Temperature variation taking place in the aluminium alloy that has undergone plastic deformation between the rollers during hot and cold rolling process is of major importance in terms of determining the positive and negative characteristics or features which such temperature variation adds to the formation of the internal structure of the material concerned. Temperature distribution has been measured by use of the installed laboratory equipment and respective data recorded has been presented in the form of graphic charts. Temperature distribution has varied depending on the application of hot or cold rolling process and it has been noted that variations in terms of temperature reduction took place depending on the number of roll passes. While average temperature variation has occurred as a 16°C increase in the case of cold rolling, it has been observed that such variation appeared as a 100°C decrease on the average in the case of hot rolling.

Abstract: AA1235 aluminum alloys were twin roll cast into a 7.0 mm-thick billet and further rolled into a plate with 70% reduction, followed by annealing at 500 C for 8 h. Abnormal grains were found to be formed on the plate bottom surface. SEM, EBSD, and micro X-ray diffraction were used to analyze the mechanism underlying the abnormal growth of these grains. Results showed that the {100} <001> texture was formed in the surrounding normal grains adjacent to the abnormal grain. The orientation angle between the abnormal grain and its adjacent normal grains was 45°. The {100} <001> texture formed during rolling and annealing accelerated abnormal grain growth. The partially dissolved Fe precipitates were heterogeneously distributed in the plate bottom heterogeneously, which also mainly explained abnormal grain growth.