Cold Rolling Passes Research Articles

Cold rolling pass design and process based on controlling the distribution of material strain energy density

To address the problem of excessive grain boundaries and difficulty in eliminating defects on the inner surface of a pipe under a cold rolling pass, a method to control the distribution of material strain energy density is proposed, and a reasonable reduction in wall thickness is designed. An analysis model for inner surface defects was established using the inner wall adhesion value as the main criterion to quantitatively analyze the degree of defects on the pipe's inner surface. A systematic analysis of the rolling process of three different pass-opening shapes revealed that the opening shape dramatically affects the deformation and flow of the metal. During the rolling process, because of the unreasonable distribution of metal deformation caused by the existing pass design, the pipe is prone to high or concentrated stress, resulting in a low adhesion value for the inner wall and a greater degree of defects on the inner surface. Therefore, we propose a new opening shape and reasonably allocate the wall thickness reduction of the pipe to obtain a new pass. Numerical simulation reveals that, after rolling with the new pass, the inner wall adhesion value becomes relatively high, and the mechanics parameters have also been improved. The experimental results show that, under the new pass design, grain boundaries on the inner surface of the pipe are reduced and the smoothness is significantly improved, proving the feasibility of a cold rolling pass design based on controlling the distribution of material strain energy density.

Comprehensive study on the through-process Goss texture evolution in Fe-3.78 wt.%Si grain oriented electrical steel

Cold rolled grain oriented steel is used in transformer cores due to its superior magnetic properties. Large Goss oriented grains develop after the final secondary recrystallization provide low hysteresis loss. The present study represents the development of Goss orientation after each processing stage of Fe-3.78 wt% Si steel with the help of electron backscatter diffraction and x-ray diffraction techniques. The Goss oriented grains developed during hot rolling and hot band annealing did not remain stable in cold rolling. On the other hand, shear bands developed inside {111}<112> component of γ-fiber texture during cold rolling. Partial recrystallization of the cold rolled sheet revealed that Goss oriented grains started evolving inside the shear bands of {111}<112> oriented grains. Intermediate annealing between cold rolling passes was found to be not essential to achieve Goss orientation in primary recrystallization. The optimum primary recrystallization temperature was in between 923 and 948 K where a significant amount of Goss oriented grains were present. Further, secondary recrystallization was attempted at different temperatures between 1173 and 1473 K. Grain boundary curvature of Goss oriented grains and all other grains after both primary and secondary recrystallization was studied. Despite the percentage of convex boundaries surrounding Goss oriented grains was found slightly higher than that around other grains, it was insufficient to cause abnormal grain growth.

Influence of cold rolling process on the Lankford coefficient, drawability and texture of AISI 430 ferritic stainless steel

The following paper addresses the large demand for further comprehension of the ferritic AISI 430 steels owing to deep drawing processes and accompanying forming technologies, such as rolling. Their good corrosion resistance and relative low cost, make them reasonably well competitors in a great deal of applications. There has been thus evaluated in a pilot mill the influence of three different cold rolling passes with 76% thickness reduction to the drawability and mechanical properties of stainless steel plates. Erichsen, Nakazima and tensile tests were complemented with ODF, pole figure, SEM-FEG observations. It was believed that changes on the cold rolling passes, which alters the anisotropy of materials, would favorably influence deep drawing applications. Experiments revealed, however, that changes defining the deep drawing parameters from 15, 20 and 24 passes, were not statistically significant after rolling. Notwithstanding, texture gradients are reported.

Research on New Technology of Metal Powder-Plate Composite Rolling

The metal powder-plate composite rolling, which combines the Monel 400 metal powder and 45# steel plate, is a novel method to prepare composite strips. By using a new high-rigidity two-high metallurgical powder 350mm test mill designed and developed independently, the composite sheet is achieved by the process of “cold rolling+sintering+hot rolling”. Then the cross-section of the rolled composite sheet is analyzed. The results show that 0.9mm Monel 400 powder and 4.3mm 45# steel plate can be successfully rolled into a 4.4mm composite sheet after 4 passes of cold rolling, sintering at 1200°C and hot rolling at 900°C with furnace cooling. The detection analysis shows that transition layer of the composite sheet has obvious element diffusion without interface. The bonding surface has changed from physical bonding to metallurgical bonding, and the combination is excellent.

Microstructure and properties of Cu-10 wt%Fe alloy produced by double melt mixed casting and multi-stage thermomechanical treatment

A Cu-10 wt%Fe alloy with high strength and high conductivity was prepared by double melt mixed casting and multi-stage thermomechanical treatment. The microstructure, mechanical property and electrical property evolutions and the strengthening mechanism during the preparation of the alloys were studied. The results showed that there were spherical Fe phase and dendritic Fe phase in the as-cast alloy. After cold rolling, the dendritic Fe phase was elongated along the rolling direction to form fibrous Fe phase, and the spherical Fe phase was flattened along the normal direction of sheet to form ellipsoidal particles after three passes of cold rolling. During aging, a large number of Fe phase particles with a diameter of 20–150 nm precipitated in the alloy. The tensile strength, yield strength and electrical conductivity of the alloys were 608 MPa, 583 MPa and 58% IACS, respectively. The main strengthening mechanism of the alloys was sub-structure strengthening calculated by strengthening model.

Microstructural evolution of twin-roll-cast Al–Mn alloy during cold rolling and subsequent annealing: Effect of number of cold-rolling passes

Variations in the shape and microstructure of a 3003 Al alloy strip fabricated by twin-roll casting during cold rolling and subsequent annealing are investigated as a function of the number of cold-rolling passes under the same total rolling reduction. With an increase in the number of cold-rolling passes, the length and width of the cold-rolled sheet increases and decreases, respectively, owing to a reduction in the ratio of the deformation zone length to the mean deformation-zone thickness. A homogenized twin-roll-cast strip has much coarser grains and more particles in the surface region than in the center region. The shape, amount, and distribution of the particles remain unchanged after cold rolling and subsequent annealing, and they are independent of the number of cold-rolling passes. However, as the number of cold-rolling passes increases, the amount of plastic deformation accumulated in the surface region of the cold-rolled sheet increases. As a result, the size of recrystallized grains in the surface region of the subsequently annealed sheet gradually decreases with increasing number of cold-rolling passes owing to the enhanced recrystallization behavior. Therefore, the grain size difference between the surface region and the center region of the annealed sheet reduces significantly, and the homogeneity of the microstructure in the thickness direction of the sheet improves with an increase in the number of cold-rolling passes.

The shock-induced chemical reaction behaviour of Al/Ni composites by cold rolling and powder compaction

Al/Ni composites are typical structural energetic materials, which have dual functions of structural and energetic characteristics. In order to investigate the influence of manufacturing methods on shock-induced chemical reaction (SICR) behaviour of Al/Ni composites, Al/Ni multi-layered composites with 3–5 cold-rolling passes and Al/Ni powder composites were obtained. Microstructural observation using scanning electron microscopy (SEM) and two-step impact initiation experiments were performed on the four Al/Ni composites. Furthermore, mesoscale simulations, through importing SEM images into the finite element analysis to reflect the real microstructures of the composites, were performed to analyse the particle deformation and temperature rise under shock compression conditions. The experimental results showed the distinct differences on the SICR characteristics among the four Al/Ni composites (i.e. by 3, 4 and 5 cold-rolling passes and powder compaction). The manufacturing methods provided the control of the particle sizes, particle distribution and the content of the interfacial intermetallics at scale of different microstructures, which ultimately affected the temperature distribution, as well as the contact between Al and Ni in Al/Ni composites under shock loading. As a result, the Al/Ni powder composites showed the highest energy release capacity among the four composites, while the energy release capability of Al/Ni multi-layered composites decreased with the growth of rolling passes.

Effect of cold rolling and ball milling on first hydrogenation of Ti0.5Zr0.5 (Mn1-xFex) Cr1, x = 0, 0.2, 0.4

The first hydrogenation of Ti0.5Zr0.5 (Mn1-xFex) Cr1, x = 0, 0.2, 0.4 alloys in their as-cast and heat-treated states at room temperature are reported. For alloys with x = 0.2 and x = 0.4, heat treatment had for effect of changing the rate-limiting steps of the first hydrogenation in comparison with the as-cast alloys. Effect of air exposition was investigated. We found that, after a 10 days exposure to the air, the alloys could not absorb hydrogen. However, they quickly absorb hydrogen after mechanical deformation such as ball milling for a short time or one passes of cold rolling. Ball milling produced fast kinetics but with a loss of capacity while cold rolling gave faster kinetics than the as-cast state and with minimal loss of capacity. Therefore, cold rolling is considered to be the best way to regenerate the air exposed alloys.

Effect of the Number of Cold Rolling Passes on the Formation of {110}&lt;001&gt; Goss-Oriented Grains in Fe-3.2 wt% Si Electrical Steel

Effect of the Number of Cold Rolling Passes on the Formation of {110}&lt;001&gt; Goss-Oriented Grains in Fe-3.2 wt% Si Electrical Steel

Residual-stress evolution of cold-rolled DC04 steel sheets for different initial stress states

Cold-rolling processes are commonly used in industrial production. Rolling-induced residual stresses influence the behavior of the material significantly. Thus, the prediction of this state is of high importance. In this study, the influence of the initial residual-stress state on the final state after cold rolling is investigated by means of finite-element analysis simulations and X-ray diffraction. It is shown that the initial residual-stress state of DC04 is eliminated after two cold-rolling passes even for comparably low plastic strains.

The Influence of Strain Path on Rare Earth Recrystallization Textures in a Magnesium-Zinc-Rare Earth Alloy

In this study, the effect of strain path on texture evolution during cold rolled and annealing of hot rolled Mg-Zn-Rare-Earth (RE) alloy (ZEK100) sheet has been investigated. Strain path during cold rolling has been varied by changing rolling direction with respect to the original hot rolling (HR) direction of the sheet. Cold rolling either parallel or perpendicular to the HR direction leads to spread and split of basal poles in the transverse direction (TD) during annealing, characteristic of Mg-Zn-RE alloys. However, when the sheet is continuously rotated between cold rolling passes, this texture spread is not produced. It is demonstrated that a change in dislocation activity, as predicted by crystal plasticity modeling, cannot explain the unusual textures developed in Mg-Zn-RE alloys. Instead, the role of strain path in determining shear band evolution is considered to be critical. When shear bands are suppressed by continuously rotating the specimen, the distinct Zn-RE texture is not produced. Furthermore, it is demonstrated the dominance of the TD spread grains emerges gradually during recrystallization, leading to the final observed texture.

Temperature behavior of exothermic reaction of Al/Ni multilayer powder materials based on cold-rolling and pulverizing method

In this paper, the characteristics of self-propagating exothermic reactions of an Al/Ni multilayer powder materials fabricated by a cold-rolling and powdering procedure are reported as initial findings of the first trial on a heat source for various applications with the energy-saving feature. Experimental results showed that, following the reaction of the developed Al/Ni multilayer powder materials in air atmosphere, the maximum temperature increased from approximately 1450 °C to over 1768 °C with increasing number of passes from 20 to 40 in cold-rolling. Furthermore, observations by scanning electron microscopy and crystallographic identification by X-ray diffraction measurements showed that the multilayer structure of powdered Al/Ni after 40 passes of cold-rolling was deformed, became thinner with below sub-micrometer thickness, and almost completely reacted to NiAl intermetallic compounds. It is possible that optimizing cold-rolling conditions enables us to control exothermic heat, which will be useful for heat sources.

Processing of MgH2 by extensive cold rolling under protective atmosphere

Cold rolling can significantly increase hydrogen storage properties of Mg and its alloys. Therefore in this paper, two important cold rolling processing parameters were investigated: the amount of passes and the roll rotation frequency, which directly influence particle and crystallite sizes and thus the interfaces for hydrogenation/dehydrogenation. Extensive cold rolling was conducted with MgH2 powder as starting material under an argon atmosphere to avoid contamination. The results indicate that the cold rolled MgH2 was free from oxides even after 50 cold rolling passes. Additionally, considerable improvements in the hydrogen storage properties were achieved with higher amounts of cold rolling passes. A similar effect could also be found for higher roll rotating frequency. This beneficial outcome originated from three important aspects: the decrease of the crystallite size reaching 88% reduction after 50 passes and 82% after 35 passes with rotating frequency of 50 rpm, the refinement of particle size, and a change in the morphology of the initial MgH2 powder from granules to flakes, and ultimately to small particles.

The Evolution of the Surface Morphologies and Microstructures of an Unleveled Hot-Rolled Steel Strip During Cold Rolling After Hydrogen Reduction

The removal of oxide scale from a hot-rolled strip surface can completely eliminate environmental pollution if performed by hydrogen-reduction descaling instead of traditional pickling descaling. However, a large number of cracks appear on the surface of a leveled hot-rolled steel strip after hydrogen reduction. This effect is likely to impede the application of reduction descaling to cold-rolled products. Nevertheless, there are almost no cracks on the surface of an unleveled hot-rolled steel strip if the hot-rolled steel strip is not subjected to repeated bending by the leveler machine. The surface quality of a reduced steel strip will be better than that of a pickled steel strip. To investigate the evolution of the surface morphologies, microstructures, and properties of an unleveled strip steel during cold rolling, unleveled strip steel samples were rolled using a four-high mill after hydrogen reduction and after pickling. The surface morphologies and cross-sectional microstructures of the samples were observed by SEM, and the surface-roughness values were measured using a TR200 profilometer before and after cold-rolling deformation. The evolution of the surface morphologies and cross-sectional microstructures of the sample after cold rolling were analyzed. The results show that the oxide scale formed on the surface turns into a metallic iron layer, and a decarburization layer appears between the metallic iron layer and the steel matrix after hydrogen reduction. Few cracks, besides pores, and bubbles, appeared on the surface of the sample after hydrogen reduction. The pores and bubbles were roll-flattened after five passes of cold rolling. The work hardening degree and mechanical properties of the reduced sample are similar to those of the pickled sample after cold rolling. Compared with the rolled sample after pickling, the surface qualities of the reduced samples are better than those of the pickled samples and better than those of the reduced samples that were subjected to leveling prior to reduction.

Effect of heat treatment in an ultra-high magnetic field on the formation of structure and texture in Fe-Si alloys

The structure and texture have been studied in Fe-Si alloys subjected to cold rolling and annealings in ultra-high dc magnetic fields (to 20 T) at temperatures both higher and lower than the Curie point. It has been shown that the prerecrystallization annealing between the cold-rolling passes in strong magnetic fields leads to the retardation of the recovery processes and to an increase in the amount of structure components in the samples with the easy axis oriented along the field direction. Upon the subsequent primary recrystallization in the samples subjected to magnetic treatment, an increase is observed in the intensity of the {hkl}〈001〉 texture component and a decrease in the {111}〈uvw〉 component, as well as a slight increase in the average size of grains with increasing applied magnetic field.

The evolution of surface morphologies and microstructures during cold rolling after hydrogen reduction

The removal of oxide scale on a cold-rolled strip surface can completely eliminate environmental pollution by hydrogen reduction descaling instead of the traditional pickling descaling. However, the cold-rolled strip surface morphologies after hydrogen reduction are different from those that result from pickling. To investigate the effects of cold rolling on the surface morphologies, microstructures and properties of cold-rolled strip steel, a cold rolling experiment was performed using a 4-high mill after hydrogen reduction and after pickling. The surface morphologies and cross-section microstructures of the samples were observed by SEM, and the surface roughnesses were measured by a TR200 profilometer before and after cold rolling deformation. The evolution of the surface morphologies and cross-section microstructures of the samples after cold rolling were analyzed. The results show that the oxide scale formed on the surface turns into a metallic iron layer, and a large number of micro cracks, pores and bubbles appear on the surface of the sample after hydrogen reduction. The pores, bubbles and some smaller cracks were roll-flattened, and the larger cracks were turned into micro-traces remaining on the sample surface after five passes of cold rolling. Compared with the rolled sample after pickling, more micro-traces remained on the surface of the rolled sample after hydrogen reduction. The surface roughnesses of the reduced samples are slightly greater than that of the pickled samples. A metallic iron layer and a decarburization layer appear on the sample surface after hydrogen reduction. After the fifth pass, both layers became thinner, and the metallic iron layer is characterized by non-uniform thickness and discontinuity. The work hardening degree and mechanical properties of the reduced sample are similar to that of the pickled sample after cold rolling.

Strain heterogeneities in the rolling direction of steel sheets submitted to the skin pass: A finite element analysis

Hot rolled, annealed or galvanized low carbon steel sheets display yield points in tensile testing. These are associated with deformation heterogeneities along the test specimen, known as Lüders bands, which cause an unacceptable surface appearance in steel sheet formed products. This problem is usually eliminated through a light cold rolling pass (“skin-pass”) in the material as a last step in its industrial manufacturing, imposing a reduction of thickness of about 1–2.0% on the sheet. Existing experimental results for these strain heterogeneities along the rolling direction are analyzed, as well as corresponding finite element analyses. The constitutive behavior of the material is described by a curve displaying an initial stress peak followed by the work hardening of the material. The FEAs led to distributions and shapes of Lüders bands in the sheets similar to the experimental ones. The bands nucleate intermitently and propagate from the surface of the sheets, at the initial contact region between the material and the rolls. For low and high friction between the material and the roll and for low sheet thickness reductions (0.5% and 1.0%), a limited influence of the roll diameter on the Lüders bands distribution was found. For sheet thickness reductions of 2.0% and higher, high friction between the roll and the material and large roll diameters, the distribution of LBs in the sheets was different from that obtained for small roll diameters and low friction between the rolls and the material. Increasing thickness reductions in the skin-pass led to changes in the Lüders bands distribution, involving an increasing homogeneity in the deformation. It is suggested that the critical thickness reduction in the skin-pass is associated to a minimum volume fraction of material deformed above a certain strain level.

Influence of Heat Treatment on Rolling and Final Properties of Welded Steels 1.4404 and 1.4571

This study investigates the influence of heat treatment on the properties of welded steels 1.4404 and 1.4571 of high thickness concerning the forming properties by rolling and the final properties. The weld seam is a region in the work piece where the material can have a higher resistance to deformation. The strength of the weld seam is often higher than in the parent metal. Therefore a suitable pre-heat treatment (1050°C for 30 min) was applied to the weld seam and heat affected zone within the cold rolling process to achieve a more homogeneous distribution of strength and ductility over the entire work piece. A second heat treatment (1050°C for 60 min) after the rolling was done to obtain the solution annealed structure of the steels. To compare the effect of the heat treatments and of the deformation during rolling (work hardening) tensile tests were performed after each process step. Here both materials behave slightly differently. Metallographic investigations show how the microstructure is influenced and give a clear picture of the fracture occurring. Force – time behaviour during rolling was monitored and provides information about the improvements by the preliminary heat treatment. Cold rolling of welded plates is characterized by a force peak just when the weld seam is within the gap of the rolls. The application of heat treatment has been found to lower that force peak and ensures less distortion in shape during the cold rolling passes.

600 MPa GRADE REBAR WITH HIGH DUCTILITY DEVELOPED BASED ON THEORY OF YIELDPLATEAU

Development of high strength and high ductility rebar with obvious yield plateau is a tendency for anti-seismic requirement in building steels.In this work,the basic relationship between ferrite grain size and mechanical property,especially the elongation of yield plateau,was investigated by the combination of cold-rolling and heat treatment.After several passes of cold rolling followed by recrystallization annealing for 5~300 min at 600 ℃,ferrite with grain size between 5.2~40.4 μm was obtained in plain steel plates with a carbon content of 0.1%(mass fraction).Mechanical properties were studied by tensile test.With the decrease of ferrite grain size,not only the strength but also the elongation of yield plateau increases.Base on the scanning electron microscopy observation,the deformation becomes more homogeneous with the decrease of grain size,resulting in a higher elongation of yield plateau.A quantitative relationship between grain size da and the elongation of yield plateau dLwas derived from the combination of Hollomon and Hall-Petch equations.The application range of dα-dLequation was also determined,which is well consistent with the experimental results.The narrow-slit spraying equipment was used to treat the HRB400 rebar,and refined ferrite and a considerable non-equilibrium pearlite were obtained due to high cooling rate in treatment.A novel rebar with yield strength of 600 MPa grade was manufactured successfully in commerce,which also verified the above theoretical analysis.

On the Influence of Cold Rolling Parameters for 14CrW-ODS Ferritic Steel Claddings

Oxide dispersion strengthened (ODS) steels, produced by powder metallurgy, are considered as promising material for high burn up cladding tubes for future Sodium Cooled Fast reactors. They present superior radiation resistance compared with austenitic steels and high creep strength due to reinforcement by the homogeneous dispersion of hard nano-sized particles. While the manufacturing route of 9Cr-based martensitic ODS steels are relatively well mastered thanks to the alpha  gamma phase transformation, the cold processing of ferritic ODS steels is more complicated because the material recovery after amounts of cumulative plastic strain is quite difficult. The aim of this study is to investigate several possible cold rolling routes for a Fe-14Cr-1W-0,3Ti-0,3Y2O3 ODS ferritic grade comparing the effects of annealing temperature on cold-workability, microstructure evolution and mechanical properties. A three-roll type HPTR rolling mill was used to manufacture ODS steel claddings. Cold rolling passes and intermediate annealing were repeated until reaching the final geometry: 10.73mm external diameter and 500µm thick. Depending of the cold rolling routes, different annealing temperatures of 1150°C, 1200°C and 1250°C were applied on the mother tube. Each pass was conducted using cross-section reduction ratio varying from at least 15% up to 25%. In each case, intermediate annealing at 1200°C for 1 hour were applied between one or several passes. The optical and SEM observations, hardness measurements, tensile tests were conducted to characterize the manufactured cladding tubes. The highest annealing temperature used on the mother tube enhances the recovery which leads to the lowest hardness level. The intermediate heat treatments applied in the course of the cold processing induces relatively low decrease of hardness. Microstructure characterization of hot extruded mother tubes shows highly anisotropic structures with equiaxed grains in the transverse direction but with significant elongation in the longitudinal direction. The elongated grain structure produced during hot extrusion is retained during cold rolling processes. Tensile tests are carried out on both longitudinal and circumferential directions by mean of respectively tile and ring tensile specimens for temperatures between 20°C and 700°C. The lowest is the annealing temperature applied on the mother tube the highest is the ultimate strength and the lowest is the uniform elongation. For the lowest annealing temperature, the UTS values measured at room temperature are ~1500MPa and ~1300MPa in the longitudinal direction and the circumferential direction, respectively. UTS values around 1000MPa in the both directions are found in case of lower annealing temperature showing a less pronounced anisotropy. For each test temperature, the uniform elongation values are relatively low compared to values obtained by other authors on 12%Cr-ODS ferritic steels. The lowest values of elongation are measured around 400°C.