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Hot crack formation during peritectic reaction in steels
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
2010 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 37, no 1, 63-72 p.Article in journal (Refereed) Published
Abstract [en]

Hot crack formation during solidification was investigated during the peritectic reaction in steels. A series of in situ solidification experiments was performed using a MTS tensile testing machine combined with a mirror furnace. Sample temperature and force change were measured during the solidification process. The force measurements showed a sudden drop during the solidification of samples, which occurred around the peritectic temperature of the alloy, were accompanied by cracks or refilled cracks in the microstructure. Furthermore, the peritectic reaction types were studied theoretically and experimentally to understand their effects on the force change during solidification. The theoretical analyses showed that the volume change due to the peritectic transformation is one of the reasons for crack formation. In addition, when the peritectic reaction occurs in a diffusionless (partition less) manner in an alloy with sufficiently high primary precipitation, crack formation is more probable.

Place, publisher, year, edition, pages
2010. Vol. 37, no 1, 63-72 p.
Keyword [en]
Hot crack, Peritectic reaction, Steel alloy
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-14201DOI: 10.1179/030192309X12506804200429ISI: 000273918200010Scopus ID: 2-s2.0-77949457560OAI: oai:DiVA.org:kth-14201DiVA: diva2:331747
Note
QC 20100726Available from: 2010-07-26 Created: 2010-07-26 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Volume Change Effects during Solidification of Alloys
Open this publication in new window or tab >>Volume Change Effects during Solidification of Alloys
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Volume change during solidification is an important concept in achieving of casting soundness. The solidification shrinkage can cause different defects in the ingot casting as well as the shape casting. The volume change due to phase transformation during solidification is the other concept which has to be studied. In addition, the solidification shrinkage can be affected by the volume change of liquid metals due to the structure change of liquid.

In this work, first, the solidification shrinkage was measured in copper-lead base alloys by a dilatometer which was developed to use for melting and solidification processes. The volume change was measured during primary solidification and monotectic reaction. The macrostructure evaluation of samples was used to explain the volume change results. A shrinkage model was used to explain the volume changes during solidification. In addition, the microsegregation of alloying elements was studied in the alloys.

 

In the second part, the solidification of brass alloys was investigated in different cooling rates. Microstructure evaluation showed that the peritectic transformation occurred as diffusionless (partitionless) as well as the diffusion-controlled transformation. In addition, the volume change was measured in the peritectic alloys. A theoretical analysis was developed to evaluate the volume change effect on the peritectic reaction.

 

Hot crack formation was investigated during the solidification of peritectic steels as a volume change concept during the transformation of ferrite to austenite. A series of in situ solidification experiments was performed using a MTS tensile testing machine combined with a mirror furnace to measure the sample temperature and the force change during solidification. It was observed that a rise in tensile force began with the start of solidification and suddenly dropped. The sudden drop of force, which occurred around the peritectic temperature of the alloy, was accompanied by a crack or a refilled crack in the microstructure. Furthermore, the peritectic reaction types were studied theoretically and experimentally to understand their effects on the force change during solidification. The analyses showed that the volume change due to the peritectic transformation is a reason for crack formation. In addition, when the peritectic reaction occurred as a diffusionless manner (partitionless), the crack formation is more probable.

 

In the last study, the effect of cooling rate and super heat temperature were studied on the precipitation of primary silicon in Al-Si hypereutectic alloys. The liquidus temperature was found to decrease with cooling rate. In addition, the fraction of primary silicon decreased with increasing the cooling rate and the super heat temperature. Furthermore, the morphology of the primary silicon changed as an effect of cooling rate and super heat temperature. It was concluded that the solidification characteristic and silicon morphology relate to the liquid structure.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2009. xii, 46 p.
Series
Trita-MG, ISSN 1104-7127 ; 2009:3
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-10527 (URN)978-91-7415-351-4 (ISBN)
Public defence
2009-06-12, F3, Lindstedtsvägen 26, KTH, 13:00 (English)
Opponent
Supervisors
Note
QC 20100726Available from: 2009-06-04 Created: 2009-05-25 Last updated: 2011-03-21Bibliographically approved

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