VII 
Process Modeling  Numerical 





No 
Name 
Description 
Client / Employer 
54 
Measurement of flow stress with torsion test 
Flow stress of Steel DIN 19Mn6 was measured at 850?C, 900?C, 950?C and 1000?C, strain of 0.05 to 0.75, and strain rate of 0.05 to 5/s. Measured data was used to formulate a mathematical model for the flow stress, considering the temperature rise during the torsion test predicted by FEM simulation. 
DFG 
55 
FEM simulation of the steel torsion test to determine the temperature profile during the test 
FEM simulation of the torsion test was used to measure the flow stress. This is to study the actual temperature profile in every stage of the torsion test. Due to the heat generation, the actual temperature is higher than the initial temperature. This may cause the difference of the temperature pattern between the torsion sample and the sample for the hot rolling and, thus cause the error of the FEM simulation of the rolling process. In prior FEM modeling this negative factor was removed. 
DFG 
56 
Measurement of Emodulus 
The EModulus for steel was heavily temperaturedependent, so the EModulus for steel 19Mn6 used for the FEM investigation for the angle steel rolling was measured at various temperatures, from 200?C to 1200?C. A formula modeled with the measured data in the temperature range 850?C to 1000?C was used for the FEM calculation for the angle steel rolling. 
DFG 
57 
FEM Modeling for the hot flat rolling with thermomechanical model 
This wass a presimulation for the angle steel simulation. Due to the high technical challenge of the thermomechanical modeling of the angle steel rolling, a hot rolling model for the flat rolling was established at first. Rolling parameters for the FEM model corresponded to the hot flat rolling tests. Calculated data were compared with the testing results, so the model was verified and improved. 
DFG 
58 
FEM Analysis for the 6 passes of angle steel rolling with thermomechanical model 
The input file consisted of the data for mesh generation, material data and boundary conditions, rolling parameters, parameters relating to the output (outfile, post file and restart file), special control parameters for FEM calculations (such as convergence errors for temperature and stress or displacement, time step for each increment), etc. The rolls and stock were taken into account separately as rigid and elasticplastic. At first, the initial cross section of a groove was estimated. The inputs were the flow stress formula, temperature dependences of Emodulus, specific heat, thermal conductivity, coefficient of thermal expansion and mass density, etc. The directly calculated outputs were rolling force, rolling torque, elastic and plastic strain, elastic and plastic strain rate, plastic work, shape of deformation zone, stress and temperature distribution, as well as the stock geometry during and after rolling. The definitions for partial upsetting, partial spread and partial elongation were provided as input into the MARC main program through a user subroutine, so those forming technical parameters were also calculated. Both integrated and local metal flow, as well as the force and power, showed an excellent agreement of the measured and calculated results. 
DFG 
59 
FEM modeling for hot rolling of the Hbeam with thermomechanical model 
Hbeam rolling, starting with the cast profile, was analyzed for the example of rolling of IPE140. The pass sequence consisted of three universal and two edging passes in a continuous mill. The rolling processes of three universal passes in a continuous mill were simulated. Rolling parameters for the simulation corresponded to those of a practical rolling test: initial temperature was 1000 ? 1015?C, and rolling speed was 4 ? 6 m/s, etc. The model was improved by comparison of the measured and predicted parameters. 
DFG 
60 
FEM modeling for the castrolling with liquid core 
A study of the castrolling process of a thin slab with a liquid core. At first, the cooling process of the crosssection from liquid state of 1394?C to a state with a thickness of solid shell of 10mm, 15mm, 20mm, 25mm, respectively, was studied by means of twodimensional finite element simulation in which the liquidsolid interface was determined. Then the threedimensional simulation of workpieces with corresponding thicknesses of the solid shell was carried out, in which the workpieces were simplified to hollow bodies. Meshing of the cross section with each wall thickness was optimized. A comparison of the analytical results with those of experiments described in the literature followed for each calculation. 
DFG 
61 
Establishment of a simplified FEM model that takes only 5% of computing times 
After studies of the relative movement of the stock and the rolls, a special upsetting model for shape rolling simulation was developed through a functional combination of the slab method and the FEM, with direct modeling of the speed and the deformation pattern in the length direction. The simulation of an angle rolling pass was performed in only 5% of computing time of the regular model, with sufficient accuracy. (Due to the great interest in this simplified model from industry, German colleagues spent another year to further study it, after the initial development). The study was financed by DFG. There was a great potential for this simplified model to be integrated into a roll pass design program or a Level 2 model, to describe the microstructure parameters over the stock cross section. 
DFG 
62 
FEM analysis for RDOV and OVRD passes for force, temperature, grain size and recrystallization, etc. 
Data for the simulation was provided from Morgan?s lab mill data. A microstructure model was developed and provided to the FEM. The percentage of completion of the recrystallization and recrystallized grain size, etc. were predicted and graphically plotted, besides regular parameters such as force and temperature. 
Morgan 