Calculation Model of Resistance to Hot Deformation in Consideration of Metallurgical Phenomena in Continuous Hot Deformation Processes

Industry hot deformation processes such as hot rolling are complex in nature. Setting up a rolling mill requires precise knowledge of the loads needed to shape the metal. This in turn, demands the ability to predict the strength of the material when deformed to a value of strain and strain rate at a given temperature. On and off-line models need, however, to be fed with constitutive equations relating the stresses required to deform a certain metal under the usual process variables. This paper shows how a set of stress-strain curves can be modeled so that both hardening and softening mechanisms commonly present during hot deformation are taken into account. The model predictions are compared to a set of literature data in order to be validated. Reasonable agreement between published results and predicted values were obtained indicating how efficiently the model can assess values of stresses under hot working conditions.

Download Full-text

Physical Simulation at Hot Deformation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.2591 ◽

2010 ◽

Vol 638-642 ◽

pp. 2591-2597

Author(s):

Rudolf Kawalla ◽

Wolfhart Müller ◽

Werner Jungnickel

Keyword(s):

Hot Deformation ◽

Physical Simulation ◽

Microstructure Development ◽

Property Development ◽

Processing Technologies ◽

Annealing Conditions ◽

Optimal Processing ◽

Steel Grades ◽

Deformation Processes ◽

Multi Phase

Today the numerical simulation of hot deformation processes is very advanced. But it requires mathematical models for metalphysical processes as for microstructure development, which take place during the deformation. Until now such models were developed for many steel grades and non-ferrous materials. For new steels as multi-phase steels laboratory investigations are required, in order to determine the optimal processing technologies of these materials. This applies also to the modelling. So far it is impossible, to calculate sole by mathematical solutions the manifold parameters of metalphysical processes and microstructure, for this reason laboratory trials and simulations are needed implicitly. Even for well known materials such procedures can be essential and useful. Using the multi-functional simulation system Gleeble HDS-V40 it is shown, which possibilities a physical simulation offers today. Starting with the annealing conditions, followed by microstructure development up to cooling, selected examples reflect the results of property development during hot deformation processes. The differences between conventional deformation after re-heating and deformation after direct-charging will be presented. The last-mentioned concept offers in its combination of near-netshape casting and direct charging special benefits, especially saving of energy.

Download Full-text

Mathematical Modeling of Flow Behaviour of API-X70 during Hot Torsion Testing

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.264-265.60 ◽

2011 ◽

Vol 264-265 ◽

pp. 60-65 ◽

Cited By ~ 2

Author(s):

Bahman Mirzakhani

Keyword(s):

Finite Element ◽

Hot Deformation ◽

Dynamic Recovery ◽

Strain Curve ◽

Flow Behaviour ◽

Element Analysis ◽

Deformation Processes ◽

Hot Torsion ◽

Semi Empirical

The flow behaviour of material is strongly influenced by the microstructure evolution during hot deformation processes. In this work, a comprehensive mathematical modelling of heat transfer and plastic deformation was carried out employing finite element analysis based on rigidviscoplastic formulation. Semi-empirical models of dynamic recovery and recrystallization were utilized to develop the microstructure dependent constitutive equations. They were then integrated into the finite element code to simulate stress-strain curve of API-X70 steel during hot deformation process. Hot torsion tests were carried out at various deformation conditions for characterization of microstructure equations and model validation. The good agreement between experimental data and simulation results were achieved. The model predicts work hardening, dynamic recovery and recrystallization simultaneously and it considers their effects on the flow stress of the material during hot deformation.

Download Full-text