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Macrosegregation In Ingot Cast Tool Steel
KTH, Tidigare Institutioner                               , Metallernas gjutning.
KTH, Tidigare Institutioner                               , Metallernas gjutning.
Scana Steel Björneborg AB.
KTH, Tidigare Institutioner                               , Metallernas gjutning.
2004 (Engelska)Rapport (Övrigt vetenskapligt)
Ort, förlag, år, upplaga, sidor
Stockholm: KTH , 2004. nr 09, s. 22
Nationell ämneskategori
Materialteknik
Identifikatorer
URN: urn:nbn:se:kth:diva-7084ISRN: KTH-MG-INR-04:09 SEOAI: oai:DiVA.org:kth-7084DiVA, id: diva2:11991
Anmärkning
QC 20101102Tillgänglig från: 2007-05-14 Skapad: 2007-05-14 Senast uppdaterad: 2010-12-20Bibliografiskt granskad
Ingår i avhandling
1. Slag inclusion formation during solidification of steel alloys and in cast iron
Öppna denna publikation i ny flik eller fönster >>Slag inclusion formation during solidification of steel alloys and in cast iron
2007 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2007. s. 21
Serie
ISSN KTH/MSE-07/10-SE+CER/AVH
Nyckelord
solidification, segregation, precipitation, inclusions, inoculation, EMPA
Nationell ämneskategori
Annan materialteknik
Identifikatorer
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
Handledare
Anmärkning
QC 20101102Tillgänglig från: 2007-05-14 Skapad: 2007-05-14 Senast uppdaterad: 2010-11-02Bibliografiskt granskad
2. On the analysis of cast structure and its changes during hot working of forging ingots
Öppna denna publikation i ny flik eller fönster >>On the analysis of cast structure and its changes during hot working of forging ingots
2009 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2009. s. 27
Serie
TRITA-MG, ISSN 1104-7127
Nationell ämneskategori
Materialteknik
Identifikatorer
urn:nbn:se:kth:diva-9774 (URN)
Disputation
2009-01-16, Sal F3, Lindstedtsvägen 26, KTH,, Stockholm, 13:00 (Engelska)
Opponent
Handledare
Anmärkning

QC 20100809

Tillgänglig från: 2008-12-15 Skapad: 2008-12-11 Senast uppdaterad: 2019-04-29Bibliografiskt granskad
3. Interaction between the alloying content, cast structure and forging process for large ingots
Öppna denna publikation i ny flik eller fönster >>Interaction between the alloying content, cast structure and forging process for large ingots
2005 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2005. s. 13
Serie
Trita-MG, ISSN 1104-7127 ; 2005:02
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:kth:diva-4072 (URN)
Presentation
2005-06-16, K014, Brinellvägen 23, Stockholm, 10:00
Handledare
Anmärkning
QC 20101220Tillgänglig från: 2006-08-15 Skapad: 2006-08-15 Senast uppdaterad: 2010-12-20Bibliografiskt granskad

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