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On deoxidation practice and grain size of austenitic manganese steel
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.ORCID iD: 0000-0002-3671-8087
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The exceptional wear resistance and work hardenability, place Hadfield steel as one of themost important materials for manufacturing cast components used in the mining, crashing,drilling, and excavation industries. In all metallic alloys used for component casting, themechanical properties are highly influenced by the microstructure of the material. Castcomponents with finer microstructural characteristics are known to present bettermechanical properties and reduced risk of defects when compared with components witha coarser microstructure. A reduced grain size in Hadfield steel can increase the strengthof the material up to 30% and reduce the risk of porosity formation during solidification.The practice of adding selected compounds or alloying elements in a metal melt to modifyand refine the microstructure is called inoculation. It is currently one of the trendingmethods utilized in light-metal alloys and cast-iron components production but has not,yet, gained adequate acceptance in the steel casting industry because researchers have notbeen able to find proper inoculants.The main objective of this work is to investigate the qualitative and quantitativecharacteristics of the by-products of deoxidation of Hadfield steel that remain in thematerial after solidification and their positive or negative effect on the coarseness of thefinal as-cast microstructure. This type of research can help to identify the type of particlesor alloying elements that are most effective for refining the microstructure of austeniticsteels and pave the way for developing new or improving conventional deoxidation andinoculation processes that will, in turn, result in the improvement of the properties of thecomponent.The precipitation of particles and the as-cast grain size are studied in aluminum andtitanium deoxidized Hadfield steel samples acquired under pilot scale experimentalconditions. In the first part of this work, the qualitative and quantitative characteristics ofparticles such as type, morphology, composition amount and size are identified. Thesequence of precipitation is established. A model for predicting particle size and growth isdeveloped. The experimental results are compared against thermodynamic equilibriumcalculations and the precipitation mechanisms for each type of particles are described. Inthe second part, the as-cast grain size of samples with varying deoxidation treatments ismeasured. Then, the grain-size is correlated with certain particle characteristic and theparticles are ranked according to their ability to refine the microstructure. The particledisregistry with austenite is calculated and compared to the experimentally acquiredranking.

Abstract [sv]

Hadfieldstålen exceptionella slitstyrkan och deformationshårdnande har gjort dessa till ettav de viktigaste materialen för tillverkning av gjutna komponenter som används inomgruv-, kross-, borr-och gruvindustrin. I alla metallegeringar som används för tillverkningav gjutna komponenter styrs de mekaniska egenskaperna av materialets mikrostruktur.Gjutna komponenter med fin mikrostruktur presentera bättre mekaniska egenskaper ochminskad risk för defekter jämfört med komponenter med grov mikrostruktur. En minskadkornstorlek i Hadfieldstål kan öka materialets hållfasthet upp till 30% och minska riskenför porositetsbildning vid stelning.Tillsatsning av spårämnen eller legeringselement i en metallsmälta för att modifiera ochförbättra mikrostrukturen kallas ympning. Denna metod används i lättmetaller och vidtillverkning av gjutjärnskomponenter, men har ännu inte fått acceptans i stålindustrineftersom forskningen inte har funnit effektiva kärnbildare att användas som ympmedel.Huvudsyftet med detta arbete är att undersöka kvalitativa och kvantitativa egenskaper hosde desoxideringsprodukter som skapas under tillverkningen av Hadfield stål och hur deunder och efter stelning påverkar mikrostrukturens grovlek. Arbetet syftar till att identifierapartikeltyper och legeringselement som är effektiva för att förfina den austenitiskamikrostrukturen och bana väg för utveckling nya och förbättra desoxiderings- ochympningsprocesser som i sin tur kommer att resultera i en förbättring av den gjutnakomponentens egenskaper.Partiklarnas utskiljning och materialet resulterande kornstorlek studerades i aluminiumochtitan-desoxidiserade Hadfieldstål, tillverkade i pilotskala. Den första delen av dettaarbete var att identifiera kvalitativa och kvantitativa egenskaper hosdesoxidationspartiklar, som typ, morfologi, sammansättning och storlek.Utskiljningssekvensen fastställdes. En modell för att förutsäga partikelstorlek och derastillväxt utvecklades. De experimentella resultaten jämfördes med termodynamiskajämviktberäkningar och utskiljningen för varje typ av partikel beskrevs. I den andra delenstuderades kornstorleken och hur denna varierade desoxideringsbehandlingen. Därefterkorrelerades kornstorleken med partikeltyp och dess karaktäristika och rangordnades efterderas förmåga att förfina mikrostrukturen. Partiklarnas kristallografiska missanpassningmot austenitens kristallstruktur beräknades och jämfördes med experimentellt fastställdarangordningen.

Place, publisher, year, edition, pages
Jönköping: Jönköping University, School of Engineering , 2017. , 47 p.
Series
JTH Dissertation Series, 29
Keyword [en]
Hadfield steel, deoxidation, grain size, inoculation, particles, carbides, oxides
Keyword [sv]
Hadfield stål, desoxidering, kornstorlek, ympning, partiklar, karbider, oxider
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:hj:diva-37788ISBN: 978-91-87289-30-9 (print)OAI: oai:DiVA.org:hj-37788DiVA: diva2:1153020
Presentation
2017-11-10, E1405 (Gjuterisalen), Gjuterigatan 5, Högskolesområdet, Hus E, 551 11, Jönköping, 09:32 (English)
Opponent
Supervisors
Projects
InDeGrainS I
Funder
Knowledge Foundation, 20130149
Available from: 2017-10-30 Created: 2017-10-27 Last updated: 2017-10-30Bibliographically approved
List of papers
1. Particles precipitation in Ti and Al deoxidized Hadfield steels
Open this publication in new window or tab >>Particles precipitation in Ti and Al deoxidized Hadfield steels
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2016 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, no 10, 1344-1355 p.Article in journal (Refereed) Published
Abstract [en]

The characteristics and precipitation mechanism of particles in titanium and aluminum treated Hadfield steel casted during pilot scale experiments have been studied. Light Optical Microscopy (LOM), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were utilized for the particle analysis and characterization. Additionally, thermodynamic equilibrium calculations were performed using Thermo-Calc software. Aluminum oxides, titanium carbon nitrides, titanium carbides and manganese sulfides were the main types of particles found. The order of precipitation during solidification and chemical composition range of each type of particle was determined. Aluminum Oxides were found to act as nucleation sites fortitanium carbon nitrides. Thermodynamic equilibrium calculation for particles characteristics were in good agreement with the experimental findings. Titanium carbides were found to form during initial stages of the Ferro-titanium additions dissolution.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keyword
Hadfield steel; particles; Titanium; Aluminum; Deoxidation
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-29401 (URN)10.1002/srin.201500400 (DOI)000387017200011 ()2-s2.0-84959496093 (Scopus ID)
Projects
InDeGrainS
Funder
Knowledge Foundation, 20130149
Available from: 2016-02-15 Created: 2016-02-15 Last updated: 2017-11-30Bibliographically approved
2. A particle population analysis in Ti- and Aldeoxidized Hadfield steels
Open this publication in new window or tab >>A particle population analysis in Ti- and Aldeoxidized Hadfield steels
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2017 (English)In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336Article in journal (Refereed) Accepted
Abstract [en]

A quantitative analysis of the amount, size and number of particles that precipitate in situ in titanium- and aluminium-treated Hadfield steel cast during pilot-scale experiments has been performed. SEM with EDS and automated particle analysis abilities was utilized for the analysis. Additionally, Thermo-Calc was used for thermodynamic calculations and Magma 5 for solidification and cooling simulations. Predicted particles sizes calculated with a model based on the Ostwald ripening mechanism were compared with the experimental data. The effect of solute availability, cooling rate and deoxidation practice on the particle population characteristics was determined. It was concluded that the amount, size and number of precipitating particles in Hadfield steel castings is possible to be controlled according to certain requirements by a careful selection of proper additives in proper amounts and also by the optimization of the casting process in aspects of deoxidation timing and control of the cooling rate of the castings.

Place, publisher, year, edition, pages
Taylor & Francis, 2017
Keyword
Hadfield steel, particles population, deoxidation, casting, titanium, aluminum, inclusion control, particle growth
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-37418 (URN)10.1080/13640461.2017.1379262 (DOI)
Available from: 2017-09-27 Created: 2017-09-27 Last updated: 2017-10-27
3. The Influence of Deoxidation Practice on the As-Cast Grain Size of Austenitic Manganese Steels
Open this publication in new window or tab >>The Influence of Deoxidation Practice on the As-Cast Grain Size of Austenitic Manganese Steels
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2017 (English)In: Metals, ISSN 2075-4701, Vol. 7, no 6, 186Article in journal (Refereed) Published
Abstract [en]

The effect of in-situ precipitating particles on the grain size of Al-Ti-treated and untreated Hadfield steel cast in a pilot scale environment was studied. Hadfield steel was melted in an induction furnace and cast in Y-Block samples. Light Optical Microscopy (LOM) and the intercept method were utilized for the grain size measurements. Additionally, Thermo-Calc Software TCFE7 Steels/Fe-alloys database version 7 was used for thermodynamic equilibrium calculations of the mole fraction of particles. The planar disregistry values between the austenite and the precipitating particles were calculated. It was observed that increasing oxide content in samples with low Ti(CN) content resulted in a finer microstructure, while increasing the Ti(CN) content under similar oxide content levels led to a coarser microstructure. The potency of each type of particle to nucleate austenitic grains was determined. Spinel (MnAl2O4, MgAl2O4) particles were characterized as the most potent, followed by olivine (Mn2SiO4), corundum (Al2O3, TiO2), and finally Ti(CN), the least potent particle.

Place, publisher, year, edition, pages
MDPI, 2017
Keyword
Hadfield steel, grain size, austenite, deoxidation, particles, aluminum, titanium, oxides, titanium nitrides
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-35598 (URN)10.3390/met7060186 (DOI)000404056600003 ()2-s2.0-85019680224 (Scopus ID)
Available from: 2017-05-24 Created: 2017-05-24 Last updated: 2017-10-27Bibliographically approved

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