Cold Rolling Process Research Articles

STUDY OF THE ROLLING PROCESS WITH TECHNOLOGICAL LUBRICANT AT SINGLE-ZONE SLIPPING METAL IN THE ZONE OF DEFORMATION

One of the controversial provisions the rolling theory is the question of the possibility the stable process of cold rolling with lubrication at a complete lag of the strip’s metal in the deformation zone, i.e. in conditions of negative advancing.
 The equilibrium state in the zone of deformation with negative advance can be maintained due to the change in the thickness of the lubricating film. This is evidenced by experimental data from the study of the dependence of the advancing and the thickness of the lubricant layer on the grip angle during cold rolling with castor oil the copper samples in sizes 5x60 mm. Rolling was carried out on a duo 180 laboratory mill in steel rolls with a diameter of 190 mm. The rolling speed was 0.35 m/s.
 Then stress state modeling is used to theoretically substantiate the possibility of a stable process with single-zone sliding of metal in rolls during cold rolling with effective technological lubricants. According to Newton's law, the frictional forces acting in the zone of deformation depend on the sliding speed of the metal on the rolls and on the thickness of the lubricating film.
 Substituting the chooses model of specific friction forces into T. Karman's differential equation of equilibrium and solving it under known boundary conditions, expressions for the distribution of contact stresses were obtained.
 The results of calculations in the conditions of contact-hydrodynamic friction prove that the maximum of normal pressure shifts closer to the entrance to the deformation zone. In the case of rolling with a negative advancing, the longitudinal normal tensile stresses occur near the cross-section at the exit of the metal from the rolls. The average pressure in the deformation zone is always greater than the forced yield strength for the rolling strip.
 With an increase in the lag of the metal from the rolls at the exit from the zone of deformation, the average pressure decreases. Rolling with single-zone strip sliding is an energy-efficient process.

Interface evolution and strengthening of two-step roll bonded copper/aluminum clad composites

The laminated metal composite plate has drawn great focus in view of its advantages of high performance. In this study, a two-step roll bonded Cu/Al clad composites was developed. The micromorphology, components, mechanical properties, and interfacial bonding strength of the Cu/Al clad composites were characterized by scanning electron microscope (SEM), electron back scattered diffraction (EBSD), transmission electron microscope (TEM), energy dispersive spectrometer (EDS), and universal materials testing machine, respectively. The results indicate that the interfacial bonding strength firstly increases and then decreases with the increase of the intermetallic compounds (IMCs) thickness, which can reach to 90 MPa with the process of cold rolling 40% reduction → pre-heating at 400 °C for 20 min → hot rolling 60% reduction. Further, the growth of the interfacial IMCs of Cu9Al4, CuAl2 and CuAl is related to the pre-heating strategy and cold deformation. Thus, the kinetic equation is established. Moreover, the interfacial bonding mechanism is that the interfacial IMCs are fractured during the hot-rolling composite process and formed multiple ‘microscopic extrusion dies’ (MEDs) at the interface. Then, the fresh copper and aluminum are extruded from the MEDs (fractured IMCs) under the strong pressure by the hot rollers, and a solid welding interface between fresh copper and aluminum is achieved. Finally, the substrate metals and the intermetallic compound is formed into a serrated-like interface.

Roll gap prediction in acceleration and deceleration process of cold rolling based on a data-driven method

Roll gap prediction in acceleration and deceleration process of cold rolling based on a data-driven method

Online Prediction of Deformation Resistance for Strip Tandem Cold Rolling Based on Data-Driven

An online model is proposed for predicting deformation resistance in the strip tandem cold rolling by combining the back propagation neural network optimized by the mind evolutionary algorithm (MEA-BP) and the deformation resistance analytical model. The real-time collection of hot and cold rolling process data is achieved by constructing a “hot and cold rolling” cross-process data platform. Based on this, a dataset including historical production data of hot and cold rolling is established to train and test the model. The application result of the proposed model shows that the deformation resistance prediction error can be reduced from ±12% to ±5% compared with the traditional analytical model, which demonstrates the model established in this work can effectively improve the prediction accuracy of the deformation resistance in the strip tandem cold rolling.

Evaluation of Microstructure High Chrome Austenitic Stainless-Steel grade 253MA after Creep Test at Temperature of 700°C

High Chrome Austenitic Stainless-Steel grade 253 MA is a material that widely used for high temperature. This is due the fact this material has excellent mechanical properties and creep resistance. However, changes in microstructure can occur in long-term use, which will affect the creep resistance (shortened service life of the material). The microstructure of High Chrome Austenitic Stainless-Steel 253 MA creep test specimens was investigated. Creep testing at a temperature of 700 °C with a loading of 150 MPa was carried out. The cold rolling process with 53% reduction in thickness was applied followed by annealing at 900°C, 1000°C, and 1100°C for 3600s to obtain different grain size. Grain size after annealing and after creep test was measured to see the effect of annealing temperature on the grain size of tested steel and to see its effect on creep resistance based on the creep test conducted. Grain size and morphology of the phase after creep test were observed by scanning electron microscope and optical microscope

Texture evolution and twinnability prediction of the most compliant orientation in GH3536 superalloy during cold rolling

In this study, GH3536 superalloy was subjected to the cold rolling processing up to 60% of thickness reductions for meticulously investigating the evolutions of both microstructure and texture. Crucial findings of deformation microstructures such as the twinning of the grain with Copper orientation and the occurrence of shear bands in matrix were captured by electron backscatter diffraction (EBSD). Twin trace analysis (TTA) was concomitant with resolved shear stress (RSS) analysis for identifying active twin variants. Higher strength and lower ductility were developed with increasing reduction ratios, which was evaluated in mechanical properties tests implemented by using nonstandard miniaturized specimens. The RSS ratio analysis was carried out to predict the twinnability of the most compliant orientation and disclose the orientation dependence of deformation twinning. Experimental and calculated results proved the discovery of the deformation twinning in a Copper orientation.

Assessment of Deformation Flow in 1050 Aluminum Alloy by the Implementation of Constitutive Model Parameters

The behavior of technically pure aluminum was examined, and this investigation allowed the determination of the material constants by various models. The model parameters derived were subsequently used for the finite element simulations (FEM) of a cold rolling process. To determine the tuning parameters such as the strain-hardening coefficient K, strain-hardening exponent n, or elastic constant E, a tensile test was performed on the heat-treated sheet of 1050 Al alloy and the experimentally observed deformation behavior was compared to the simulated counterpart. The results of the FEM calculations reveal that the strain-hardening characteristics can be alternatively derived from the Brinell indentation. Additionally, the determined constitutive model parameters (E = 69.8 GPa, K = 144.6 MPa, and n = 0.3) were verified by simulating both the symmetric and asymmetric rolling processes. The distribution of the equivalent strain across the sheet thickness was computed by the FEM, and it was found that the modeled deformation profiles tend to reproduce the experimentally observed ones with high accuracy for different strain modes inasmuch as the mentioned rolling trials accommodate diverse amounts of shear and normal strain components.

The influence of microstructure and texture on the hardening by annealing effect in cold-rolled titanium

The purpose of this study was to compare the influence of microstructural and textural changes on the hardening by annealing effect in cold-rolled titanium. Ultrafine-grained (UFG) Ti Grade 2 was produced by multi-pass cold rolling (or warm rolling at 400 °C at the final stage) to different thickness reductions (90%, 95% and 97%) aimed at varying both the microstructural features of the material (dislocation density, grain size distribution and grain boundary characteristics) and its texture (the intensity and volume fraction of texture components). The hardening effect of UFG Ti Grade 2 sheets was obtained by a short-time annealing at 250 °C for 15 min. The highest strengthening, of about 4–5%, was observed for the UFG Ti Grade 2 sheet rolled to 90%; the strengthening gradually decreased for higher thickness reductions (down to ∼ 2% for 97%). The texture intensity and volume fractions of texture components for the annealed UFG Ti Grade 2 sheets were very close to their as-rolled counterparts, so this did not demonstrate any clear reason for the hardening effect. Instead, the dislocation substructure recovered during annealing at 250 °C, i.e. the dislocation density declined significantly, the remaining dislocations became rearranged, and it was easier to differentiate more nanosized subgrains of about 50–150 nm. The hardening by annealing effect was a result of the annihilation of mobile dislocations and the ordering of the dislocation substructure, mostly within coarse grains (>500 nm). The level of strengthening by low-temperature annealing was mainly affected by the fraction of coarse grains with a tangled-dislocation substructure in the as-rolled state, i.e. a higher fraction of coarse grains favored more pronounced strengthening. These observations seem to be very promising for optimizing the cold rolling process and short-time annealing of the UFG Ti Grade 2 sheets, which could be a simple and cost-effective way of enhancing their mechanical properties.

Multi-objective optimal edge-drop control in tandem cold rolling of silicon steel strip

In cold rolling of silicon steel strip, edge drop directly affects the side cutting and yield of silicon steel. To improve the edge drop of silicon steel in the cold rolling process, a multi-stand coordinated control strategy and model based on multi-objective optimization are proposed. The first step is to analyze the influence of each control stand work roll shifting (WRS) on edge drop through the finite element model (FEM), then determine the edge drop control effectiveness of each work roll shifting actuator. Meanwhile, a fitting model is proposed to solve the limitation caused by the discrete change of efficiency factors in solving the optimal adjustments of each WRS. On this basis, the target model for silicon steel edge drop control is formulated, and the optimal adjustment model of WRS of each stand is established. To realize the optimal coordinated control among the rolling mill stands, a multi-objective optimal model of edge drop control has been established by the overall modeling method. The improved penalty function algorithm is developed to calculate the optimal adjustment of WRS for each stand. The experiments and application show that the proposed multi-objective optimal control strategy and model can effectively improve the accuracy of edge drop control in silicon steel continuous cold rolling.

Formation of recrystallization texture and its effect on deep drawability for high-purified ferritic stainless steel by two step cold rolling

For working out the approach of acquiring low planar anisotropy while achieving high ridging resistance and r-value, during two step cold rolling processes with different total reductions the texture evolution and corresponding mechanism were investigated for ferritic stainless steel. During cold rolling, the crystallites having orientations near {111} 〈112〉 and Goss were induced by shear bands and with further deformation Goss orientation tended to rotate towards more stable {111} 〈112〉. During subsequent annealing, these crystallites induced the recrystallized nuclei and {111} 〈112〉 nuclei consumed preferentially the adjacent matrixes, generating the γ-fiber recrystallization texture having the main component of {111} 〈112〉. With increasing total cold rolling reduction, the γ-fiber recrystallization textures were gradually intensified and band-like grain colonies having approximate r-value and those having variant with ε23 of same sign became more obvious and their distribution more uneven, the average r-value and ridging resistance exhibited a monotonous upward and downward trend, respectively, and the planar anisotropy of r-value first deteriorated and then improved and reached lowest value at 90 %. Considering acceptable ridging resistance in practical application, the excellent deep drawability can be acquired at the total reduction of 90 %.

Inhibition Behavior of Edge Cracking in the AZ31B Magnesium Alloy Cold Rolling Process with Pulsed Electric Current

To solve the edge crack problem of AZ31B magnesium alloy cold rolling, a strong pulsed electric current was introduced to the cold rolling process. The influence of intensity, frequency, width of pulsed electric current and other parameters on edge cracking of AZ31B magnesium alloy plate cold rolling was analyzed based on the principle of a single variable. According to the experimental results, the assistance of pulsed electric current cut down edge cracking and the inhibition effect increased obviously with larger current parameters. When the parameters of pulsed electric current reached 4800 A, 500 Hz, 50 μs, zero edge cracking was achieved. Statistics of edge cracks, rolling load change, and microstructure analysis showed that the current thermal effect was not obvious and non-thermal effect played a more important role in the rolling process under pulse electric current. Edge cracks initiate at the shear bands. The addition of pulse current increases the number of shear bands and presents a blanket structure. Therefore, the amount of strain experienced by a single shear band decrease, which has a positive effect on inhibiting the formation of edge cracks. Furthermore, electroplastic rolling refines the grains and weakens the basal plane. As the current parameter increases, the hardness of the magnesium strip decreases and the yield and tensile strengths increase.

Rolling force prediction during FGC process of tandem cold rolling based on IQGA-WNN ensemble learning

Rolling force prediction during FGC process of tandem cold rolling based on IQGA-WNN ensemble learning

Microstructure and mechanical properties of multi-scale α-Fe reinforced Cu–Fe composite produced by vacuum suction casting

Cu–10Fe composites were produced by the vacuum suction casting and traditional vacuum mold casting, respectively. The evolution of microstructure and properties of the composites during cold rolling and aging processes was analyzed. Compared with the traditional mold-casted Cu–Fe composites, the suction-casted Cu–Fe composite had better mechanical properties, with microhardness, tensile strength and elongation of 146 HV, 526 MPa and 23.7%, respectively. The softening temperature of the suction-casted Cu–Fe composite was 520 °C, which was 220 °C higher than that of traditional mold-casted Cu–Fe composite. The good performance of the suction-casted Cu–Fe composite was mainly attributed to the refinement of the Cu matrix and the formation of the multi-scale α-Fe particles caused by the effect of solute trapping during vacuum suction casting. The yield strength of the composites was mainly attributed to the contribution of Orowan strengthening, refinement strengthening and dislocations strengthening, which count for 31.1%, 25.8% and 24.1%, respectively.

Comparative study on microstructure and texture evolution of low silicon non-oriented electrical steels along one-stage and two-stage cold rolling processes

Fe-0.9% Si-0.3% Al non-oriented electrical steels were fabricated by two-stage cold rolling process including hot rolling, first cold rolling, intermediate batch annealing, second cold rolling and final annealing, in which the first cold rolling reduction varied from 15% to 54%. One-stage cold rolling process with hot band normalization was also investigated for comparison. The findings revealed that, in two-stage cold rolling process, the final recrystallization texture and magnetic properties heavily relied on the rolling reduction schedule. As the first rolling reduction increased, the core loss increased and the magnetic induction decreased owing to the enhanced γ-fiber (〈111〉//ND) texture in the final annealed sheets. Relatively lower first cold rolling reduction (15%) was beneficial to generate coarse grains during intermediate annealing and led to large grains with weakened γ-fiber and enhanced Goss textures in final sheets. By contrast, relatively higher first cold rolling reduction (30% and 54%) caused small grains by promoting the occurrence of recrystallization during intermediate annealing and resulted in small grains with stronger γ-fiber texture after final annealing. The hot band normalization in one-stage cold rolling process could also effectively improve the grain size prior to cold rolling, though MnS precipitate and sharp γ-fiber recrystallization texture were promoted in the final sheets due to the high normalization temperature and much higher cold rolling reduction, respectively. Therefore, two-stage cold rolling process was propitious to reduce γ-fiber recrystallization texture and MnS precipitate compared with one-stage cold rolling process. The appropriate rolling reduction schedule (15%+75.6%) and suitable intermediate annealing process (750 °C for 1.5 h) were propitious to produce high-performance non-oriented silicon steel with lowest core loss and highest magnetic induction.

Вейвлет-преобразования в задачах контроля и диагностики автоколебаний стана холодной прокатки

Self-excited oscillations remain a frequent problem of cold rolling of thin strips. When self-oscillations occur, the amplitude increases by a jump of more than a hundred times, that is from 2–3 m/s2 to 200–250 m/s2. Oscillation frequencies (from 100 to 500 Hz, i.e. the number of loading cycles) can reach several thousands per a few seconds. Intense self-oscillations normally occur on thin strips with a thickness of less than 1 mm and high rolling speeds. The control of the occurrence of self-oscillations includes special systems, according to the level of vibrations or technological parameters, for example, by fluctuations in the tension of the strip. In control systems, classical methods include the decomposition of the controlled signal into a Fourier series. For stationary processes, Fourier series decomposition provides complete information about the signal structure and is sufficient to diagnose the technical condition of machines and mechanisms. As for a nonstationary non-harmonic signal, the information about the spectral composition of the diagnostic signal is insufficient, since it does not allow for determining the moment of occurrence of an undesirable process. In metallurgy and rolling production, processes are frequently not stationary. The cold rolling process is continuous, but discrete. It takes 5–6 minutes to roll one coil. The process of selfoscillation, even when using control systems, can last no more than 2–3 seconds. A high frequency of vibrations and a high level of stress can lead to the formation of cracks in the elements of the mill stands, for example, CVC plates. A signal conversion wavelet can become an alternative way of monitoring and diagnostics. If the FFT allows you to determine the presence of self-oscillations only in the developed state, the wavelet transform allows you to determine the origin of the selfoscillation process at low oscillation amplitudes. It also allows you to determine it in the absence of fluctuations by changing the signal of the technological parameters.

Modeling and numerical analysis of helical rolling process of small diameter bearing tubes

The three-dimensional finite element modeling of the process for obtaining of cold-deformed bearing pipes of small diameter is performed. The cold helical rolling process of a pipe workpiece (sleeve) on a mandrel in three rolls of a planetary mill is studied. As a result of the modeling, a stress-strain state of the workpiece is studied and factors that affect the microstructure and plasticity of the metal are considered. The energy parameters of the rolling are determined.

Numerical simulation of cold longitudinal asymmetric rolling process

The modeling of the asymmetric cold rolling process of steel strip is carried out using the Deform program. During the study, the diameter of the barrel of the upper work roll is varied from 570 to 600 mm, the diameter of the barrel of the lower work roll was left unchanged at 600 mm, and changes in the structural parameters of the deformation zone, as well as the required rolling torques and forces, are recorded. The results are obtained for the conditions of rolling strips made of low-carbon steels with a thickness of 2 mm or more, as well as 0.35...0.5 mm. It is found that the discrepancy in power between the drives of the upper and lower rolls during asymmetric rolling can reach 25 % of the power required to conduct the process on rolls with the same barrel diameter. It is also shown that the changing of the contact arc with the indicated changes in power and a decrease in the diameter of the working roll barrel from 600 to 570 mm ranges from 3 to 5 % of the length of the arc of contact in the absence of a difference in the diameters of the barrels of the rolls. Fluctuation in moments when taking into account the factor of asymmetric rolling reaches 20 % of the corresponding values typical for the technological process on rolls with the same barrel diameter. An increase in the asymmetry of the rolling process leads to a slope of the neutral section in the deformation zone with an increase in the proportion of the advance zone in the arc of contact of the upper work roll with a smaller diameter of the barrel and the strip. An assumption is made, which requires further research, about the possibility of creating only one advance section along the entire length of the interaction of the roll with a smaller diameter of the barrel and the strip. Such a structure of the contact zone is theoretically able to reduce the required power of the main drive.

Neural networks with dimensionality reduction for predicting temperature change due to plastic deformation in a cold rolling simulation

Abstract Cold rolling involves large deformation of the workpiece leading to temperature increase due to plastic deformation. This process is highly nonlinear and leads to large computation times to fully model the process. This paper describes the use of dimension-reduced neural networks (DR-NNs) for predicting temperature changes due to plastic deformation in a two-stage cold rolling process. The main objective of these models is to reduce computational demand, error, and uncertainty in predictions. Material properties, feed velocity, sheet dimensions, and friction models are introduced as inputs for the dimensionality reduction. Different linear and nonlinear dimensionality reduction methods reduce the input space to a smaller set of principal components. The principal components are fed as inputs to the neural networks for predicting the output temperature change. The DR-NNs are compared against a standalone neural network and show improvements in terms of lower computational time and prediction uncertainty.

Hot and cold rolling of a novel near-α titanium alloy: Mechanical properties and underlying deformation mechanism

In this work, mechanical properties, microstructure evolution mechanism, texture variation process and deformation mechanism of a near-α CT20 titanium alloy with different hot and cold rolling reductions are investigated and uncovered comprehensively. The tensile strength of the alloy gradually increases, and the ductility decreases as the rolling reduction grows along both rolling direction (RD) and transverse direction (TD) due to the increase in grain boundary and dislocation density, while the mechanical properties along RD are better than those along TD. The high strain carried in α phases reduces the proportion of high-angle grain boundaries and increases the content of low-angle grain boundaries, with growing dislocation density in α phase. During cold rolling process, basal <a> slip shifts {0001} pole toward ND, and prismatic <a> slip inclines {11 2‾0} pole and {10 1‾ 0} pole toward TD. The intragranular orientation is enhanced with increasing rolling reduction, and the texture intensity of α and β phase is weakened as rolling reduction gradually grows. It is also noteworthy that prismatic <a> slip dominates the slip mode along RD, while basal <a> slip and pyramidal slip are activated along TD during cold rolling. The work-hardening rates of cold-rolled alloys are higher than that of the hot-rolled alloy as a large number of dislocations and grain boundaries were introduced by severe plastic deformation. The different work-hardening rates and mechanical properties of the rolled alloy along RD and TD are verified to be associated with the preferred orientation of α phase and the slip distances of dislocation during deformation.

Effect of boron on the microstructure and mechanical properties of as-cast and annealed CrFeNi medium-entropy alloys

A Co-free Bx(CrFeNi)100-x (x = 0, 0.25, 0.5, 1.0, 1.5, 2.0, 3.0, 4.5, and 6 at%, denoted as Bx alloys hereafter) medium-entropy alloys (MEAs) system was designed to investigate the effect of boron (B) content on the microstructure and mechanical properties of as-cast and annealed CrFeNi MEA. The as-cast Bx(CrFeNi)100-x MEAs exhibited an FCC + Cr2B dual-phase structure and dendritic morphology, whose volume fraction gradually increased with an increase in B content. The addition of B element promoted the improvement of yield strength due to the synergistic effect of solution strengthening and precipitation strengthening, but caused an obvious reduction in elongation. Then B0 and B0.25 alloys experienced the subsequent cold rolling and recrystallization annealing process. Compared with B0 alloy, B0.25 alloy in all states exhibited a considerable improvement in yield strength but only a slight decline in elongation. Thereinto, B0.25 alloy annealed at 800 °C presented a favorable strength-plasticity configuration with a yield strength of 745 MPa and an elongation of 24.32%, which profited from the refinement strengthening caused by the inhibition of B element on recrystallization and the precipitation strengthening caused by the formation of BCC-structured precipitates and Cr2B borides. These findings provide a deep insight into the design and optimization of MEAs as structural applications.