Experimental identification of flow properties of a S355 structural steel for hot deformation processes

The determinination of material properties is an essential step in the simulation of manufacturing processes. For hot deformation processes, consistently assessed Carreau fluid constitutive model derived in prior works by Schmicker et al. might be used, in which the flow stress is described as a function of the current temperature and the current strain rate. The following paper aims to extend the prior mentioned model by making a distinction, whether the material is being heated or cooled, enhancing the model capabilities to predict deformations within the cooling process. The experimental identifaction of the material parameters is demonstrated for a structural carbon steel with 0.54% carbon content. An approach to derive the flow properties during cooling from the same samples used at heating is presented, which massively reduces the experimental effort in future applications.

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In Situ Synchrotron Diffraction Studies on Hot Deformation of Austenite in a High Strength Quenched and Tempered Structural Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.922.126 ◽

2014 ◽

Vol 922 ◽

pp. 126-131 ◽

Cited By ~ 1

Author(s):

R.K. Dutta ◽

R.M. Huizenga ◽

M. Amirthalingam ◽

H. Gao ◽

A. King ◽

...

Keyword(s):

Structural Steel ◽

Elastic Constants ◽

Hot Deformation ◽

Retained Austenite ◽

Room Temperature ◽

Elevated Temperatures ◽

High Strength ◽

Lattice Parameters ◽

Temperature Load ◽

Diffraction Patterns

The effect of plastic deformation of austenite at elevated temperatures on the kinetics ofphase transformations during continuous cooling was studied in a high strength quenched and tem-pered structural steel S690QL1 (Fe-0.16C-0.2Si-0.87Mn-0.33Cr-0.21Mo (wt.%)) by means of in-situsynchrotron diffraction. The steel was heated to 900 C (above Ac3) in the austenite region and elon-gated by 6% followed by quenching to room temperature. Time-temperature-load resolved 2D syn-chrotron diffraction patterns were recorded and used to calculate the local d-spacings between latticeplanes. The plane specific diffraction elastic constants of austenite at 900 C in the steel were deter-mined from the local d-spacings. The effect of the deformation of austenite on the phase transforma-tion kinetics was studied. The evolution of lattice parameters and the phase fraction of the bcc phasesduring the quenching process were calculated.The calculated plane specific elastic constants of austenite at 900 C varied between 32 GPa to140 GPa for the different fhklg reflections of austenite. The deformation of austenite at 900 C re-sulted in the formation of a mixture of 38 % bainite, 59 % martensite and 3 % retained austenite afterquenching to room temperature. Without hot deformation, austenite transformed to 9 % bainite and88 % martensite with 3 % retained austenite. The presence of the bainitic and the martensitic phaseswas observed fromthe change in the slopes of the lattice parameters of the bcc phase during quenchingand confirmed by microscopy.

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Constitutive Modeling of Stress-Strain Curves of IF Austenite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.539-543.4202 ◽

2007 ◽

Vol 539-543 ◽

pp. 4202-4207

Author(s):

Roney Eduardo Lino ◽

Ronaldo Barbosa

Keyword(s):

Constitutive Modeling ◽

Hot Deformation ◽

Stress Strain ◽

A Value ◽

Strain And Strain Rate ◽

Precise Knowledge ◽

Model Predictions ◽

Deformation Processes ◽

Predicted Values ◽

Usual Process

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.

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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.

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