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Modeling Phase Transformations and Volume Changes during Cooling of Case Hardening Steels
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (Mekanisk metallografi)
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Case hardening distortions are a major problem for gear manufacturers. The aim of the current work is to create a simulation model, able to predict how and when case hardening distortions arise. The results presented in this thesis form a basis for such a model.

Two case hardening steels, with base carbon contents of 0.20 and 0.21 % C were studied using dilatometer experiments. One of them was carburized to 0.36, 0.52 and 0.65 % C in order to investigate the influence of carbon content. Experiments were performed during both isothermal and continuous heating and cooling conditions. The results were used to evaluate phase transformations, heat expansion behaviors and phase transformation strains. The expansion behavior of the material was modeled as a function of temperature, carbon content and phase fractions. The phase transformations to martensite and bainite were modeled, using the Koistinen-Marburger equation and a transformation rate equation based on Austin-Rickett kinetics, respectively. Experiments were simulated using the COMSOL Multiphysics software, to verify the model with respect to martensite and bainite transformations, heat expansion behavior and phase transformation strains.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , x, 37 p.
Series
ISRN KTH/MSE--09/47--SE+MEK/AVH
Keyword [en]
Phase transformation, volume changes
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-11369ISBN: 978-91-7415-459-7 (print)OAI: oai:DiVA.org:kth-11369DiVA: diva2:274821
Presentation
2009-11-18, M312, Brinellvägen 68, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2009-11-05 Created: 2009-11-02 Last updated: 2010-11-02Bibliographically approved
List of papers
1. A Material Model for Simulating Volume Changes during Phase Transformations
Open this publication in new window or tab >>A Material Model for Simulating Volume Changes during Phase Transformations
2007 (English)In: Proceedings of the COMSOL Users Conference 2007 Grenoble, 2007, 648-653 p.Conference paper, Published paper (Refereed)
Abstract [en]

The present work describes the first steps in creating a robust material model able to predict volume changes due to thermal expansion and phase transformations. A dilatometer test is simulated starting from room temperature with an original microstructure constituting a mixture of ferrite and pearlite. During heating, the structure transforms to austenite, which upon quenching will transform into martensite. Both thermal expansion and phase transformations will give rise to volume changes which are modeled in the present work. After adjusting the model parameters to experimental data, a simulation of a dilatometer test is favorably compared to experimental data. The successful reproduction of volume changes allows accurate simulations of distortions during industrial heat treatments, which is the aim of the on-going research.

Keyword
Thermal expansion, volume changes, distortion, phase transformation, low carbon steel
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-25843 (URN)
Conference
European COMSOL Conference 2007, 23 - 24 October 2007 Grenoble, France
Note
QC 20101102Available from: 2010-11-02 Created: 2010-11-02 Last updated: 2010-11-02Bibliographically approved
2. Modeling Bainitic Transformation in a Case Hardening Steel
Open this publication in new window or tab >>Modeling Bainitic Transformation in a Case Hardening Steel
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The paper contains experimental and simulated results for the phase transformation of austenite to bainite during isothermal conditions. A case hardening steel is studied at four carbon contents, using a dilatometer. The bainite fraction is calculated by time integration of a time-independent transformation rate equation, derived from Austin-Rickett kinetics. Simulations in COMSOL Multiphysics produces bainite fractions correlating to experiments.

National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-25850 (URN)
Note
QC 20101102Available from: 2010-11-02 Created: 2010-11-02 Last updated: 2010-11-02Bibliographically approved
3. Modeling Volume Changes during Cooling of Case Hardening Steels
Open this publication in new window or tab >>Modeling Volume Changes during Cooling of Case Hardening Steels
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Results regarding martensitic and bainitic phase transformations, heat expansion behaviors and phase transformation strains during constant heating and cooling rates are presented. Equations describing heat expansion behavior, phase transformation strain and martensitic formation are evaluated as functions of carbon content. The equation for bainitic transformation described in Supplement 2 is used during constant cooling rates for two different case hardening steels. COMSOL Multiphysics is used to simulate experiments, producing good agreement between experimental and simulated dilatometer curves.

National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-25852 (URN)
Note
QC 20101102Available from: 2010-11-02 Created: 2010-11-02 Last updated: 2010-11-02Bibliographically approved

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CiteExportLink to record
Permanent link

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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
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  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
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