Multi-pass Rolling Process Research Articles

Microstructure Evolution in Nb-Ti Micro-Alloyed Steel during Hot Compression and Hot Rolling Simulation

Based on a improved mathematic model of predicting austenite grain size of hot rolled Nb-Ti micro-alloyed steel, a module for calculating microstructure evolution in the steel during hot-forming process was developed. To evaluate the recrystallization behavior according to the proposed model during plate multi-pass hot rolling, the multi-pass hot compression and its FE analysis in couple with the newly determined model were conducted. It indicated that the present models were capable of simulating the multi-pass hot compression and the actual multi-pass rolling process. After simulating an actual rolling process in factory by using the above models, evolution laws of microstructure were analyzed. Simulation results of microstructure had a good agreement with the measured ones.

極短パス間時間多パス圧延プロセスにおけるフェライト結晶粒微細化への内部組織変化の影響

The optimum conditions for manufacturing ultrafine-grained hot strips in super short interval multi-pass rolling (SSMR) process were discussed. As the first means of evaluation, the changes in austenite grain size and shape during multi-pass rolling were observed using experimental equipment. Deformed austenite grains could be observed with immediate quenching after each rolling pass. As the second means, a new numerical simulation method was used, which could predict the microstructure change of austenite, ferrite nucleation inside austenite grains, and ferrite grain growth. The effects of austenite grain size before finish rolling and also of temperature control between rolling passes on ferrite grain refinement were investigated. It was found that the temperature control between rolling passes is effective for grain refinement, whereas austenite grain refinement before finish rolling is not so effective. Therefore, deformation strain accumulation in austenite is important for ferrite grain refinement in SSMR process.

Thermal Mechanical Coupled 3D Finite Element Simulation of Large H-Beam in Hot Rolling Process

In order to research the forming process of H-beam, based on the large H-beam production line of HN600x200, the Standard and Explicit solver of ABAQUS are synthetically used to establish finite element model for rolling process and inter-pass thermolysis process. The reciprocation multi-pass rolling process simulation procedure based on the re-meshing technology is used to simulate the whole production process form blanks to finish products, and the continuity of data is ensured. Based on the simulation results, the deformation and rolling force of the roller as well as the metal flowing law and temperature field of workpiece are discussed emphatically. The results clearly show that the displacement of roller contains the elastic deformation and the deflection, and the counterforce of left adds to the counterforce of right is about equal to the resultant force. The simulation results are compared with the measuring results, which proves the correctness of simulation.

Rolling Force Research on Cogging Rolling of H-Beam

Due to the complexity of H-beam’s cross section, it is difficult to calculate the rolling force and force torque accurately using classic formulas conveniently when H-beams of new size are developed. This paper describes an investigation into the reversing process of H-beam using MARC software and compares the results with rolling data from the production line. A FEM model involving in three-dimensional, elastic-plastic and thermo-mechanical coupling has been established successfully to predict multi-pass rolling process. The analysis produces outputs such as deformation rules, rolling force and the web thickening. The influence of rolling reduction, the reduction rate between the web and flange are also discussed. The indications are that there is much difference between the measurement of rolling force and the rolling force calculated by using classic formulas. The reason is that real reduction during rolling process is much more than the scheduled one. A new revised method was suggested to calculate the rolling force. The simulation results show that this new method for calculating rolling force is feasible.

Grain Refinement Mechanisms of Plain C-Mn Steel by Super Short Interval Multi-Pass Rolling in Stable Austenite Region

One of noble grain refinement methods to attain ferrite grain size of around 1m in plain C-Mn steel has been so-called super short interval multi-pass rolling (SSMR) process, which is characterized by finish-rolling above Ae3, extreme short interpass time and then rapid cooling. The transformation mechanisms are demonstrated by the microstructural observation of an fcc Ni-Fe model alloy and C-Mn steels. In the Ni-Fe alloy hot-rolled by SSMR, equiaxed and cellar array of dislocation walls with low and high angle misorientations are observed in shear directions without recrystallization. The average spacing between the dislocation walls in the Ni-Fe alloy is in good agreement with the ferrite grain size of the C-Mn steel by SSMR process. On the other hand, in the C-Mn steel quenched to bypass ferrite transformation, the fine ferrite nuclei have been identified along intra-granular shear directions in the quenched martensite. It is concluded that the dislocation substructure in heavily deformed austenite by SSMR process have high potency as inherited ferrite nucleation

Simulation of deformation and temperature in multi-pass continuous rolling by three-dimensional FEM

This paper presents a new method for modeling a rod and wire continuous rolling process. Three-dimensional FE models of the whole rolling process are established by the proposed method that consists of a pushing technique of rigid body and a method of data transfer, and it is utilized to analyze the deformation and the temperature distribution of billet during the multi-pass rolling process. The pushing technique of rigid body is developed to keep the contact status between the deformable body and a rigid body and to push the deformable body forward during inter-pass time. The method of data mapping is adopted to transfer element field variations between meshes of different models by an interpolation function. The model was applied to simulate 18 stands rolling process of a 304 stainless steel and provides an insight into the process by studying the billet deformation and the temperature distribution. It shows fairly good agreement between the predictions and the measured values of temperature.

Super Short Interval Multi-pass Rolling Process for Ultrafine-grained Hot Strip

As a process to manufacture ultrafine-grained hot strip or plate of which ferrite grain size was about 1 μm, heavy reduction hot rolling at relatively low temperature, such as larger than 70% reduction per pass at lower than 700°C, had been presented. However, it is quite difficult to apply the process to commercial production because the rolling load is very large. A new process of multi-pass rolling at extremely short interval has been proposed and developed in order to manufacture ultrafine-grained hot strip at ordinary rolling load. Authors named it “Super Short interval Multi-pass Rolling (SSMR) process”. Ultrafine-grained hot strip of 1.2 mm thick was successfully manufactured in laboratory with the simple chemical composition of 0.15%C–0.74%Mn. Its grain size was 0.9 μm at 50 μm beneath the surface and 1.2 μm on the average over the thickness. The rolling load in SSMR was smaller than 30 kN/mm and it was relatively small owing to relatively small reduction, smaller than 50% per pass, and relatively high temperature, higher than 820°C. Consequentially it was confirmed that the rolling load in SSMR process could be reduced to half compared to the previously presented process of heavy reduction hot rolling at low temperature.

Modeling and Experimental Validation of Superconductor Tape Rolling

Efficient, defect-free manufacturing of high-temperature superconducting (HTS) wires and tapes is critical to a variety of defense and electrical power applications. To contribute to the improvement of these manufacturing operations, an analytical and experimental study of the early stages of the multipass rolling process for transforming HTS wires into tapes was conducted. The rolling process was simulated by a three-dimensional (3D) finite element model that uses the Drucker-Prager Cap plasticity model to represent the powder core and a Von-Mises plasticity model with isotropic hardening to represent the silver sheath. The predicted cross-sectional geometry of the tapes is compared with experiments. The results show that the tape cross-sectional geometry and powder core sizes can be predicted accurately. Further, alternate boundary conditions were found to have minimal effect on the predicted cross-sectional geometry for the range of reductions considered, even though the frictional shear stress distributions were significantly different.

Minimization of Energy in the Multipass Rolling Process

This research focuses on the optimization of the flat rolling process. In order to optimize the process effectively, the existing process model has been especially enhanced—in the neutral zone where the friction changes sign over a region rather than at a point. Pressure and frictional stress distributions as well as total load and torque are thereby estimated as functions of the various rolling parameters. Roll flattening has also been taken into account. The main problem of determining the optimum design parameters of multipass rolling has been considered. The problem has been formulated and solved as a constrained nonlinear programming problem by considering the radius of the rolls, the front and back tensions as design variables. Optimum number of passes have been found, so that the total energy consumed by the tandem mill is minimized. Constraints are placed on the induced stresses, the neutral angle, the angle of bite and the deflections of the rolls, for both cold and hot rolling processes.