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Macrosegregation In Ingot Cast Tool Steel
KTH, Superseded Departments, Casting of Metals.
KTH, Superseded Departments, Casting of Metals.
Scana Steel Björneborg AB.
KTH, Superseded Departments, Casting of Metals.
2004 (English)Report (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH , 2004. no 09, 22 p.
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-7084ISRN: KTH-MG-INR-04:09 SEOAI: oai:DiVA.org:kth-7084DiVA: diva2:11991
Note
QC 20101102Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2010-12-20Bibliographically approved
In thesis
1. Slag inclusion formation during solidification of steel alloys and in cast iron
Open this publication in new window or tab >>Slag inclusion formation during solidification of steel alloys and in cast iron
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis explores the formation of segregation and inclusions during solidification of steel and cast iron. A better understanding of the formation mechanism should result in decreasing fraction of defects during solidification of ingot and strand material.

Density driven macrosegregation was studied both experimentally and theoretically to see the effect of channel segregation on the total segregation. Formation of these pencil-like segregations is due to natural convection in the solidifying metal caused by liquid enrichment of elements with lower density compared to the bulk. It is suggested to change the composition to compensate for this density difference.

Inclusion precipitation can be finite by limitations in segregation. Saturated liquid is found in the last solidified areas, often between dendrites. Here the enrichment of the liquid is possible due to microsegregation. Meanwhile crystals form and solidify the elements with low solubility in the solid is pushed out in the remaining liquid. Soon the liquid is saturated to the level where spontaneous formation of inclusions occurs. Microstructure studies by aid of SEM and micro-probe measurements are analysed to find at what point during solidification process the inclusions start to form. In steel making this formation has a detrimental effect on the mechanical properties in contrary to the production of nodular cast iron where the inclusions have a beneficial effect on the graphite formation.

Inoculation of cast iron aims at reaching higher number density of graphite nodules, nodule morphology modification and control of nodule distribution during solidification. Late precipitation of nucleation sites has shown to have a positive impact on preventing chill. To find the most potent inoculation agent different additives were tested. Special effort has been made to analyse the effect of oxides and sulphides as nucleation sites.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 21 p.
Series
ISSN KTH/MSE-07/10-SE+CER/AVH
Keyword
solidification, segregation, precipitation, inclusions, inoculation, EMPA
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-4371 (URN)978-91-7178-624-1 (ISBN)
Presentation
2007-05-11, Rum B1, MSE, KTH, Brinellvägen 23, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101102Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2010-11-02Bibliographically approved
2. On the analysis of cast structure and its changes during hot working of forging ingots
Open this publication in new window or tab >>On the analysis of cast structure and its changes during hot working of forging ingots
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Forging ingots are hot worked to consolidate structural imperfections and refine the microstructure. Possible imperfections are segregations, porosities, cracks, and inclusions. In this thesis, techniques and methods for the characterisation of behaviour and properties of ingots and forgings. The root causes for quality issues in open-die forgings are shown to be numerous. Ingot structure in cast tool steel was analyzed, and the main imperfections were centre macrosegregation, and mid radius A-segregations.For overheated steel forgings and low reductions after reheating, a high ultrasonic attenuation and low Charpy-V toughness was found. It could be related to the coarse grain structure found. Only a high forging reduction after reheating will break down the coarse structure. Shorter reheating times and lower forging temperatures gave higher toughness and lower ultrasonic attenuation. Some reduction in toughness was also found from the inclusion field from the bottom of the ingot. Accurate attenuation measurements require a lathe turned surface, complicating in-between-measurements in heat treatment sequences. But on carefully surface prepared forgings, attenuation measurement can be used to determine the success of grain refinement in the heat treatment. A new method for ultrasonic macrography of cast ingot samples is presented. In addition, a new method for hot compression testing of cylindrical metal samples is presented.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 27 p.
Series
Trita-MG. AVH, 2009:01Trita-MG, ISSN 1104-7127
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-9774 (URN)
Public defence
2009-01-16, Sal F3, Lindstedtsvägen 26, KTH,, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20100809Available from: 2008-12-15 Created: 2008-12-11 Last updated: 2010-12-20Bibliographically approved
3. Interaction between the alloying content, cast structure and forging process for large ingots
Open this publication in new window or tab >>Interaction between the alloying content, cast structure and forging process for large ingots
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 13 p.
Series
Trita-MG, ISSN 1104-7127 ; 2005:02
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-4072 (URN)
Presentation
2005-06-16, K014, Brinellvägen 23, Stockholm, 10:00
Supervisors
Note
QC 20101220Available from: 2006-08-15 Created: 2006-08-15 Last updated: 2010-12-20Bibliographically approved

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