Rolling Pass Research Articles

Grain Size Evolution during Multipass Hot‐Rolling of C‐Mn Steels: Comparison of Phase Field and Extended JMAK Modeling

The design of multipass hot‐rolling schedules is of great importance to steel industry and an effort is made to predict the microstructure evolution. In the present study, a multi‐phase field model is employed for the simulation of the grain size evolution due to static recrystallization and grain growth during multipass hot‐rolling of C‐Mn steels. A variable stored energy per rolling pass, a temperature dependent interface mobility, and nucleation site density are considered. The model is compared with an extended JMAK model and validated with experimental data obtained from two hot‐rolling schedules. The results indicate that both models describe the experimental data well, however the phase field model avoids certain discontinuities between static recrystallization and grain growth. A statistical analysis is conducted to investigate the effect of the microstructure domain size on the phase field results and grain size distributions. The effect of key process parameters on the kinetics of static recrystallization and grain growth are determined by the temporal evolution of equivalent circular grain diameter distributions. Both approaches have the potential to be used for the computational design of multipass hot‐rolling processes in steels.

Reliability Evaluation and Robust Design of a Sensor in an Entire Roller-Embedded Shapemeter.

The intermittence of the shape detection signal associated with an entire roller-embedded shapemeter roll, used in a seven-pass cold reversible rolling process, is considered. A transient interference at the sensor top surface and the distance between the sensor top surface and the roll outer surface are developed, and a sensor reliability evaluation model is derived. The reliability of the sensor is evaluated via the random perturbation method, and the reliability sensitivity of design variables is proposed. The analysis reveals that the reliability is smallest in the third rolling pass. Of the design variables considered, the initial interference exhibits the largest reliability sensitivity and has the greatest influence on the sensor reliability. A reliability robust design model of the initial interference is therefore developed. A new shapemeter roll is fabricated and tested in a 1050 reversible cold rolling mill. The test results are consistent with the theoretical results, thereby validating the proposed model. The selection of an appropriate initial interference provides an important means of overcoming the adverse effects associated with the thermal deformation of sensor contact surfaces.

Formation mechanism and prediction of plane shape in angular rolling of aluminum alloy thick plate

A finite element model (FEM) was developed to study the plane shape of an aluminum alloy thick plate after angular rolling. Results show that the plane shape is a parallelogram after the first pass of angular rolling. When the angular rolling process is completed after a second pass, the plane shape becomes symmetric about the center lines in both length and width directions. The width increases more at the edge that enters the deformation zone earlier. Next, a mathematical model to predict plane shape after angular rolling was proposed based on a sectional calculation method. By simulating the longitudinal rolling process, spreads from different plate widths were obtained and used in the mathematical model. By comparing these results with results from the FEM, the accuracy of the mathematical model was verified. Because of its short calculation time, the mathematical model can be used in practice during the production process.

THE CONCEPT OF OPTIMAL BAR ROLL DESIGN. REPORT 2. CALIBERS SPACE

Based on the system approach and on the experience accumulated at theoretical data, design and industrial development of bar rolling, the Chair “Metal Forming” of Ural Federal University develops the universal “Concept of optimum calibration”. The general ideology of roll pass design optimization is stated in article “The concept of optimal bar roll pass design. Report 1. Basic statements”. In the article “The concept of optimal bar roll pass design. Report 2. Calibers space” the structure, appointment and maintenance of the information block reflecting so-called “calibers space” are considered. According to the general concept of optimization, the following task that needs to be solved is the problem of creation of information block so-called “space of schemes of roll pass design” which will be used further as the first space of optimization. The concept “space of schemes of roll pass design of a bar-rolling mill” is considered as the space containing all possible virtual schemes of rolling of a concrete profile on the concrete rolling mill. For formation of the space of schemes of rail calibrations it is necessary to generate separate virtual schemes and to consistently fill this space with them. Thus, the space of calibrations schemes is formed of separate unique calibrations schemes. For formation of this space from separate calibers, it is offered to use the specialized algorithms which are “generators of schemes of roll pass design”. As an example, the structure of the generator prepared for creation of such space for rolling of railway rails is considered. It is revealed that all known rail calibrations can be presented in the form of essentially the same block structure which is used as the central element of the schemes generator of rail calibrations. Usage of described and similar generators in relation to rolling process of a concrete profile on the concrete rolling mill allows obtaining spaces of acceptable schemes of calibrations. Such spaces are necessary for the subsequent optimizing procedures for search of the best calibration scheme from all possible calibrations. The considered approach for creation of calibrations schemes space can be used during creation of computer-aided engineering systems and optimization of calibrations of rolling rolls.

Calculation method of spatial configuration of tube billet in roll forming process of a high strength steel drive shaft tube

The accurate calculation of the spatial configuration of the tube billet in roll forming process is the theoretical premise of roll pass design. But the currently existing shape function method for calculating the spatial configuration cannot describe the springback of the tube billet after bending deformation, so it cannot be applied to the accurate calculation of the spatial configuration of high strength steel with large springback. For this reason, this paper derived the formulas for calculating the bending moment of springback, proposed a trajectory function G(X) to describe the deformation path of the points on the neutral layer of the tube billet in forming direction, and finally established a new method which is called trajectory function for calculating spatial configuration of high strength steel. To verify the accuracy of the trajectory function method, the ∅120 × 5-mm-high strength steel shaft tube roll forming process was taken as an example in this paper; the spatial configurations in five stages of the breakdown stage were obtained by experimental method, the trajectory function method, and the shape function method respectively. The calculated results of the trajectory function method were compared with those of the shape function method and the experimental method. The comparison shows that the results of the trajectory function method are closer to the experimental ones, and its overall accuracy is higher than that of the shape function method.

Microstructure and Anisotropy of Plastic Properties of Thermomechanically-Processed HSLA-Type Steel Plates

The paper presents the investigation results of the impact of shear bands on microstructure, mechanical properties, and anisotropy of plastic properties of HSLA (high-strength, low-alloy) type steel plates, produced in the process of thermomechanical rolling. A lack of conditions ensuring the complete static recrystallization between successive roll passes leads to localization of plastic deformation and formation of shear bands in dynamically-recrystallized austenite enriched with carbon and other interstitial elements, which transform into carbide segregation bands during tempering. These bands are the cause of low impact resistance of rolled plates, especially in the transverse direction, and the high degree of anisotropy of plastic properties in the plates.

STATISTICAL ANALYSIS AND CALCULATION OF METAL FORMING DURING ROLLING OF H-BEAM PROFILES ON THE UNIVERSAL RAIL-BEAM MILL

The most economical way of producing steel H-beam profiles of wide assortment is the rolling on modern universal rail-beam mills equipped with continuous and reversible groups of stands with fourroll universal beam calibers. They are effectively used in the foreign metallurgy for the production of rails and beams. In Russia, the first two such mills are constructed and are currently being developed at the EVRAZ ZSMK (Novokuznetsk) and in the Chelyabinsk metallurgical plant. The proposed new method of calculating the roll pass design for universal rail-beam mills is based on the results of the statistical generalization of existing technological rolling modes of H-beam profiles on the universal beam, rail-beam and section mills equipped with universal stands, as well as on authors’mathematical model of metal forming by rolling in universal calibers based on variational principle of minimum total power. At the analysis and generalization of existing technological rolling modes of H-beam profiles a statistical sample was formed that includes the main characteristic parameters of calibration: number (N) and H-beam profile type, the number of passes (n), average reduction ratio in each pass (λi ), the total (common) reduction ratio (λΣ ) for “n” passes and distribution reductions ratio at the passes. The total volume of the sample amounted to 472 points, received at 55 rolls calibrations. Generated sample was investigated using correlation and regression analysis. As a result, regression dependences were obtained for calculation of basic characteristic parameters of calibration. With the application of the developed method roll pass design have been calculated for the finishing rail tandem of universal rail-beam mill for rolling 35B2H-beam. Characteristic features of the obtained mode are almost the same reduction ratio of the neck λш and flanges λф during rolling in every universal caliber and the difference of values λш and λф in passes are 0.4 – 2.4 %, i.e. uniform deformation of the metal is achieved along the profile elements, which contributes to a high quality H-beam.

Rockfill dam compaction quality evaluation based on cloud-fuzzy model

The quality of compaction is key to the safety of dam construction and operation. However, because of incomplete information about the construction process and the unknown relationship between compaction quality and the factors that influence it, traditional evaluation methods such as neural networks and multivariate linear regression models fail to take uncertainty fully into account. This paper proposes a cloud-fuzzy method for assessing compaction quality by considering randomness, fuzziness, and incomplete information. The compaction parameters and material source parameters are the key parameters in the assessment of compaction quality. A five-layer neural-network model of compaction quality assessment is established that considers compacted dry density and its classification membership and probability as the criteria, and the rolling speed, rolling passes, and compacted layer thickness as alternatives. Because of uncertainties in the criteria and alternatives, the cloud-fuzzy method, in which a fuzzy neural network is extended with a cloud model to handle uncertain and fuzzy problems more effectively, is introduced to determine the compaction quality. A case study is presented to evaluate the compaction quality of a hydropower project in China. The results indicate that the cloud-fuzzy model is feasible in relation to precision and makes up for the sole focus on precision by traditional methods. The proposed method provides a triple index for understanding compaction quality, which facilitates assessment of the compaction quality of an entire dam surface.

Study on hot rolling process of the D51 large-diameter threaded bars

The objective of this study is to design a hot rolling process for manufacturing large-diameter threaded bars. Threaded bars in which longitudinal ribs are eliminated and transverse ribs play a role as a screw thread can be used as rebars. To design the hot rolling process for the D51 threaded bar, the mean reduction and rolling pass numbers were determined. Calibers (box, oval and round caliber) were designed using the bar rolling theory. Six cases of the peanut caliber were designed by changing the main design parameters, namely caliber width (W) and center groove (R1), to analyze the shape of the threaded bar with respect to the shape of the peanut caliber. Furthermore, the rolling pass schedule including the average effective roll diameter (AERD) and rolling velocity was set. FE-simulation and artificial neural network (ANN) techniques were used to derive a combination of design parameter for the peanut caliber and rolling process of the D51 threaded bar. The rolling experiment was conducted using peanut caliber and rolling process derived by FE-simulation and ANN technique. After measuring cross-sectional area of the core part and transverse rib, the unfilled rate (U.R) of the core and transverse rib were compared and analyzed. The height of the transverse rib and cross-sectional area of the D51 threaded bar formed by rolling experiment was satisfied with the allowance tolerance of ±4 %. These results verified the reliability of the hot rolling process of the D51 threaded bar.

Microstructural and mechanical responses to various rolling speeds determined in multi-pass break-down rolling of AZ31B alloy

Different rolling operations of as-cast AZ31B alloy were performed under different rolling speed (18 ∼ 72 m min−1) and rolling pass conditions at 400 °C. Microstructural studies, tensile testing and formability evaluation relevant to each rolling operation were investigated. For 1-pass rolling, coarse average grain size (CAGS) region gradually approached the center layer as the rolling speed increased. Moreover, twins, shear bands and coarse-grain structures were the dominant components in the microstructure of plates rolled at 18, 48 and 72 m min−1, respectively, indicating the severe deformation inhomogeneity under the high reduction per pass condition. For 2-pass rolling and 4-pass rolling, dynamic recrystallization was observed to be well and CAGS region has substantially disappeared, indicating the significant improvement in deformation uniformity and further the grain homogenization under the conditions. Microstructure uniformity degree of 2-pass rolled plates did not vary much as the rolling speed varied. On this basis, shear band distribution dominated the deformation behavior during the uniaxial tension of the 2-pass rolled plates. However, microstructure uniformity accompanied by twin distribution played a leading role in stretching the 4-pass rolled plates.

Evolution of microstructure, texture and mechanical properties of ZK60 magnesium alloy in a single rolling pass

The evolution of microstructure and texture in a single rolling pass was investigated at rolling temperature of 250 ℃. Based on the analysis of microstructure evolution, thickness reduction of 31% was identified as a critical deformation strain for the occurrence of continuous dynamic recrystallization (CDRX) in this work. CDRX strikingly refined the grain size and improved the microstructure homogeneity. The results based on intragranular misorientation axis analysis showed that the activation of abundant stochastic stored dislocations with a broad range of orientations developed in CDRX was the main reason of the transformation from <10−10>//RD texture to randomized texture along <10−10>-<11−20> arc in inverse pole figure. Microhardness distribution was mainly influenced by the fraction of deformed grains. Grain refinement increased yield stress and uniform elongation, while weaker texture only increased uniform elongation.

Design of Experiment as a powerful tool when applying Finite Element Method: a case study on prediction of hot rolling process parameters

The ultimate goal in hot roll pass design is to manufacture a rolled product with the required dimensional accuracy, defect free surface, and mechanical properties. The proper selection of process parameters is crucial to meet increasing requirements for desired quality and geometrical properties of rolled products. Due to the complex behavior of the metal flow at high temperatures and the severe plastic deformations in shape rolling, most efforts that have been made so far only rely upon the practical experience gained by operators. The large number of variables involved and the difficulty in investigating the process characteristics, make the use of finite element (FE) tools an effective and attractive opportunity towards a thorough understanding of the rolling process. In this work, Design of Experiment (DOE) is proposed as a powerful and viable method for the prediction of rolling process parameters while reducing the computational effort. Nonlinear 3D FE models of the hot rolling process are developed for a large set of complex cross-section shapes and validated against experimental evidences provided by real plant products at each stage of the deformation sequence. Based on the accuracy of the validated FE models, DOE is applied to investigate the flat rolling process under a series of many parameters and scenarios. Effects of main roll forming variables are analyzed on material flow behavior and geometrical features of a rolled product. The selected DOE factors are the workpiece temperature, diameter size, diameter reduction (draught), and rolls angular velocity. The selected DOE responses are workpiece spread, effective stresses, contact stresses, and rolls reaction loads. Eventually, the application of Pareto optimality (a Multi-Criteria Decision Making method) allows to detect an optimal combination of design factors which respect desired target requirements for the responses.

Design of Online Spheroidization Process for 1.0C-1.5Cr Bearing Steel and Microstructure Analysis

Using thermo-mechanical control process, the online spheroidization annealing process of 1.0C-1.5Cr bearing steel was designed. Apart from intercritical online spheroidization (IS), a novel subcritical online spheroidization (SS) process was proposed, which is characterized by water-cooling to around 773 K (500 °C) after the final rolling pass, and then directly reheating to 973 K (700 °C) for isothermal holding. Compared with the results from the traditional offline spheroidization (TS) process, the size of spheroidized carbides is similar in both the TS and IS processes, whereas it is much smaller in the SS process. After spheroidization annealing, microstructure evolution during austenitization and quenching treatment was examined. It is shown that the refining of spheroidized carbides accelerates the dissolution of carbides during the austenitizing process, and decreases the size of undissolved carbides. In addition, the SS process can obtain finer prior austenite grain after quenching, which contributes to the enhancement of final hardness.

Effect of rolling passes on thermal parameters and microstructure evolution via ring-rolling process of GH4738 superalloy

As a key part of the aeroengine, the importance of seamless ring is self-evident. Obviously, the uniformity of thermal parameters and microstructure evolution of seamless ring has an extremely significant effect on its mechanical properties and service life. In this paper, a 3D FEM model was developed to analyze the influence of different rolling passes on thermal parameters and microstructure evolution via ring-rolling process of GH4738 superalloy. Meanwhile, two groups of experiment were designed: single-pass rolling with large deformation and multi-pass rolling with small deformation in each pass. Through comprehensive analysis of the results, conclusions can be summarized as follows. (1) The temperature distribution is more uniform under the condition of multi-pass rolling with small deformation in each pass. (2) The effective strain distribution is more non-uniform under the condition of single-pass rolling with large deformation. (3) Single-pass rolling with large deformation leads to smaller grains, while multi-pass rolling with small deformation leads to more homogeneous microstructure and less mixed crystal phenomenon. (4) We can, through distributing the deformation of each rolling pass reasonably, improve the thermal parameters and microstructure distribution.

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

Improving single pass reduction during cold rolling by controlling initial texture of AZ31 magnesium alloy sheet

Abstract The AZ31 magnesium alloy sheets obtained by multi-pass hot rolling were applied to cold rolling and the maximum single pass cold rolling reduction prior to failure of AZ31 magnesium alloy was enhanced to 41%. Larger single pass rolling reduction led to weaker texture during the multi-pass hot rolling procedure. The sheet obtained showed weak basal texture, while the value was only 1/3–1/2 that of general as-rolled AZ31 Mg alloy sheets. It was beneficial for the enhancement of further cold rolling formability despite of the coarser grain size. The deformation mechanism for the formation of texture in AZ31 magnesium alloy sheet was also analyzed in detail.

Effects of Rolling Passes on the Transport Properties of 37-Filamentary AgAu-Sheathed Bi-2223 Tapes

Thirty-seven-filamentary AgAu-sheathed Bi-2223 tapes were fabricated by a powder-in-tube (PIT) process. And, the round wires (ϕ 1.86 mm) were rolled to 0.35-mm tapes with 12, 7, 5, and 4 rolling passes through flat rolling, respectively. The influences of different rolling passes on the core density, deformation, and transport properties of Bi-2223/AgAu tapes were systematically investigated. It was noticed that after rolling, the Vickers microhardness of the superconducting core and deform homogeneity along both the horizontal and vertical directions on the cross section of seven-pass rolled tape were better than those on the tapes with other passes, which proved the larger core density and uniform deformation with the seven-pass rolling process. Meanwhile for the wires with 12 and 7 passes, the AgAu/superconducting core interfaces were much flatter. With the rolling passes decreasing from 12 to 4, the critical current density (Jc) first increased and then decreased. Due to the better homogeneity and flatter interfaces, Jc reached the maximum value of 17.3 kA/cm2 on the seven-pass sample. Meanwhile, the enhancement of current capacities in magnetic field applied parallel to the Bi-2223/AgAu tape surface could also be recognized as the evidence of improving intergrain connections due to the higher density in seven-pass rolled tapes.

Enhanced reactivity of Ni-Al reactive material formed by cold spraying combined with cold-pack rolling

Near-fully-dense (porosity<1%) Ni-Al reactive bulk materials were obtained by cold spraying and large deformation without crack was successfully achieved by the subsequent gradual cold-pack rolling, and the largest total thickness reduction could reach 95%. The influences of cold-pack rolling on the reactivity of the cold-sprayed Ni-Al reactive materials were investigated. The material reactivity was addressed through the solid-state reaction threshold temperature in thermal explosion mode conducted by differential scanning calorimetry and combustion wave velocity in self-propagating mode measured by a high-speed camera. For the cold-sprayed materials with rolling treatment, the onset of solid diffusion reaction shifted to a lower temperature range by 30–40 °C in the DSC experiment. An obvious increase in the combustion reaction reactivity of the cold-sprayed samples after treatment with cold-pack rolling was demonstrated. The combustion wave velocities for the materials with fifteen gradual rolling passes could reach 130–140 mm/s. The combustion reaction velocity showed a linear dependence on the statistic results of contact area per unit volume (Sv) between Ni and Al reactants and an expression was proposed, giving an activation energy of 129 kJ/mol.

Influence of Accumulative Roll Bonding on the Texture and Tensile Properties of an AZ31 Magnesium Alloy Sheets.

Deformation behaviour of rolled AZ31 sheets that were subjected to the accumulative roll bonding was investigated. Substantially refined microstructure of samples was achieved after the first and second pass through the rolling mill. Sheets texture was investigated using an X-ray diffractometer. Samples for tensile tests were cut either parallel or perpendicular to the rolling direction. Tensile tests were performed at temperatures ranging from room temperature up to 300 °C. Tensile plastic anisotropy, different from the anisotropy observed in AZ31 sheets by other authors, was observed. This anisotropy decreases with an increasing number of rolling passes and increasing deformation temperature. Grain refinement and texture are the crucial factors influencing the deformation behaviour.

The effect of thermomechanical processing on second phase particle redistribution in U-10 wt%Mo

The multi-pass hot-rolling process of an annealed uranium–10 wt% molybdenum (U10Mo) coupon was studied by plane-strain compression finite element modeling. As-cast U10Mo typically contains second phase particles such as uranium carbides (UC) and silicides along the grain boundaries. The volume fraction of UC is typically large, while the other phases can be redissolved in the matrix by certain heat treatments. The UC particle distribution is important due to its influence on the recrystallization processes (particle stimulated nucleation) that occur during annealing between rolling passes. Unfavorable particle distribution and fracture after rolling can affect the grain size and also influence the fuel performance in the reactor. A statistical method, i.e., the two-point correlation function (2PCF), was used to analyze the carbide particle distribution after each rolling reduction. The hot rolling simulation results show that the alignment of UC particles along grain boundaries will rotate during rolling until it is parallel to the rolling direction, to form stringer-like distributions which are typically observed in rolled products that contain inclusions. 2PCF analysis shows that the interparticle spacing shrinks along the normal direction (ND) and increases along the rolling direction (RD). The simulated particle distribution is very similar to that measured experimentally for similar rolling reductions. The magnitudes of major peaks of 2PCF along the ND decrease after large reduction. The locations of major peaks indicate the inter-stringer distances. Many more small peaks appear for the 2PCF along the RD, and this is related to the neighboring particles within stringers, which are along the RD.