Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Modeling the Effect of Solute Drag on Recovery and Recrystallization during Hot Deformation of Nb Microalloyed Steels
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2010 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 2, 239-247 p.Article in journal (Refereed) Published
Abstract [en]

The effect of solute drag on recovery and recrystallization during hot deformation of Nb microalloyed steels has been modeled using a newly developed microstructure model. The model is based on dislocation theory and the calculated dislocation density determines the driving force for recrystallization. Subgrains act as nuclei for recrystallization and have to reach a critical size and configuration in order for recrystallization to start. In the model, the solute drag effect of Nb in solution is described. Nb retards both dislocation and grain boundary movement giving retardation in both recovery and recrystallization. Calculations were compared to experimental results from axisymmetric compression tests combined with stress relaxation. In order to model the effect of solute drag, the experiments were carried out at temperatures where precipitation of Nb(C, N) should not occur. The calculated flow stresses for the compression tests show good fit with experimental data. Also, the calculated results of the relaxation tests show good agreement with experimental data.

Place, publisher, year, edition, pages
2010. Vol. 50, no 2, 239-247 p.
Keyword [en]
modeling, flow stress, recrystallization, recovery, solute drag, Nb microalloyed steel, DEFORMED AUSTENITE, PRECIPITATION, EVOLUTION
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-13992DOI: 10.2355/isijinternational.50.239ISI: 000275434300009OAI: oai:DiVA.org:kth-13992DiVA: diva2:328873
Note
QC 20100706Available from: 2010-07-06 Created: 2010-07-06 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Modeling the Microstructural Evolution during Hot Deformation of Microalloyed Steels
Open this publication in new window or tab >>Modeling the Microstructural Evolution during Hot Deformation of Microalloyed Steels
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

 

This thesis contains the development of a physically-based model describing the microstructural evolution during hot deformation of microalloyed steels. The work is mainly focused on the recrystallization kinetics. During hot rolling, the repeated deformation and recrystallization provides progressively refined recrystallized grains. Also, recrystallization enables the material to be deformed more easily and knowledge of the recrystallization kinetics is important in order to predict the required roll forces. Hot strip rolling is generally conducted in a reversing roughing mill followed by a continuous finishing mill. During rolling in the roughing mill the temperature is high and complete recrystallization should occur between passes. In the finishing mill the temperature is lower which means slower recrystallization kinetics and partial or no recrystallization often occurs. If microalloying elements such as Nb, Ti or V are present, the recrystallization can be further retarded by either solute drag or particle pinning. When recrystallization is completely retarded and strain is accumulated between passes, the austenite grains will be severely deformed, i.e. pancaking occurs. Pancaking of the grains provides larger amount of nucleation sites for ferrite grains upon transformation and hence a finer ferrite grain size is achieved.

In this work a physically-based model has been used to describe the microstructural evolution of austenite. The model is built-up by several sub-models describing dislocation density evolution, recrystallization, grain growth and precipitation. It is based on dislocation density theory where the generated dislocations during deformation provide the driving force for recrystallization. In the model, subgrains act as nuclei for recrystallization and the condition for recrystallization to start is that the subgrains reach a critical size and configuration. The retarding effect due to elements in solution and as precipitated particles is accounted for in the model.

To verify and validate the model axisymmetric compression tests combined with relaxation were modeled and the results were compared with experimental data. The precipitation sub-model was verified by the use of literature data. In addition, rolling in the hot strip mill was modeled using process data from the hot strip mill at SSAB Strip Products Division. The materials investigated were plain C-Mn steels and Nb microalloyed steels. The results from the model show good agreement with measured data.

 

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. x, 47 p.
Keyword
modeling, austenite, microalloyed steels, hot deformation, microstructure evolution, static recrystallization, dynamic recrystallization, metadynamic recrystallization<
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-10390 (URN)978-91-7415-267-8 (ISBN)
Public defence
2009-04-20, B3, KTH, Brinellvägen 23, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20100706Available from: 2009-05-08 Created: 2009-05-08 Last updated: 2010-07-21Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Bäcke, Linda
By organisation
Materials Science and Engineering
In the same journal
ISIJ International
Materials Engineering

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 97 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf