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Wettability and Agglomeration Characteristics of Non-Metallic Inclusions
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. (Division of Processes)ORCID iD: 0000-0003-4107-8405
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, both the wettability and the agglomeration characteristics of non-metallic inclusions in liquid iron/steel were studied by using both experimental results and thermodynamic considerations. The mechanisms of the wettability of different types of inclusions were discussed. Also, the agglomeration behaviors of the inclusions were analyzed.

Firstly, the wettability of different types of inclusions (including Al2O3, MgO, Ti2O3, TiO2 and TiN) in contact with the liquid iron/steel was studied. For the TiNcase, there is no reaction formation at the interface between TiN and pureiron/steel. In the caseo f pure Fe, the oxygen increase is the main factor for a contact angle decrease. As for the steel case, a sharp decrease of the contact angle is due to the effects of both an increased oxygen content in the liquid steel and a formation of a Ti(N,C,O) phase at the interface. For the Al2O3 and MgO cases, the formation of a FeAl2O4 and a MgO-FeO reaction layer at the interface, respectively, lead to a contact angle decrease. In the case of the Ti2O3/pure Fe case, the reaction at the interface cannot be identified. For the Ti2O3/steel case, the formation of an Al2TiO5 reaction layer is the main reason for a steep decrease of the contact angle. In the TiO2 case, the melting region appears at the temperature below the melting point of pure iron. This is due to the strong formation of a solid solution TiOx-FeO. The main source of the oxygen for the solid solution formationis due to a TiO2 substrate decomposition and a low partial pressure of oxygen in the chamber.

Regarding to the non-metallic particle additions (TiO2 and TiN) into the molten steel, the steel composition should be controlled to have a small Al content (<0.005mass%) and a high Ti content (>0.035mass%), so as togeta high number of Ti-rich oxide inclusions with a small size. This conclusionis supported from the view point of the van der Waals force, liquid-capillary force and wettability.

Regarding the Ti/Al complex deoxidation in the melt, the “mainly occupied clustered inclusions” with spherical shape is due to a TiOx-FeO liquid inclusion precipitation after an addition of Ti as a pre-deoxidizer. The much lower cluster number in the Ti/Al case than that in the Al case is mainly due to a coagulation of single TiOx-FeO liquid inclusions. Also, the cluster formation in a complex Ti/Al deoxidation is started after an Al addition rather than after a Ti addition.

Regarding the Al2O3 cluster formation in deoxidation, the cavity bridge forceis larger than the van der Waals force. However, the difference between them is smaller than 7 times. In the reoxidation process, the influence of the cavity bridge force due to the wettability decreased, and became similar to that of the liquid-capillary force.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , x, 66 p.
Keyword [en]
wettability, non-metallic inclusion, agglomeration mechanism, attraction force, complex deoxidation, particle addition
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-183069ISBN: 978-91-7595-867-5OAI: oai:DiVA.org:kth-183069DiVA: diva2:907511
Public defence
2016-03-30, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160301

Available from: 2016-03-01 Created: 2016-02-26 Last updated: 2016-03-01Bibliographically approved
List of papers
1. Wettability of TiN by Liquid Iron and Steel
Open this publication in new window or tab >>Wettability of TiN by Liquid Iron and Steel
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2015 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 55, no 8, 1642-1651 p.Article in journal (Refereed) Published
Abstract [en]

The wettability of liquid iron and steel in contact with TiN substrates was studied. Initially, Spark Plasma Sintering (SPS) was used to prepare the samples using different operational conditions. It was found that a relative density of 96% and surface roughness values smaller than 250 nm could be obtained by using the following settings: a 1 873 K temperature, a 89.2 MPa pressure and a 5 min sintering time. Thereafter, the wettability of the liquid iron and steel in contact with the TiN substrates was measured based on video recordings, at the moment when the metals started to melt. The results show that the contact angle value for a TiN/pure Fe system (130 to 87.9 degrees for 900 s) is larger than the value for a TiN/steel system (110 to 50 degrees for 981 s). Therefore, it is concluded that TiN has good resistance to the corrosion of the liquid iron and steel. In the liquid iron case, its wetting behaviour occurs mainly due to the oxygen increase in liquid iron after a full melting. However, in the liquid steel case the contact angle decreases sharply due to both the effects of an oxygen increase in liquid steel and a precipitation of Ti(N,C,O) at the interface.

Keyword
contact angle, TiN, iron, steel, solubility
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-173453 (URN)10.2355/isijinternational.ISIJINT-2014-819 (DOI)000359891900013 ()2-s2.0-84941087853 (ScopusID)
Note

QC 20150918

Available from: 2015-09-18 Created: 2015-09-11 Last updated: 2016-03-01Bibliographically approved
2. Wettability of Al2O3, MgO and Ti2O3 by Liquid Iron and Steel
Open this publication in new window or tab >>Wettability of Al2O3, MgO and Ti2O3 by Liquid Iron and Steel
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2015 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 55, no 9, 1882-1890 p.Article in journal (Refereed) Published
Abstract [en]

The wetting behavior of liquid iron and steel on Al2O3, MgO and Ti2O3 substrates was measured by using the sessile drop method. Measurements were carried out using a controlled oxygen partial pressure and using an argon protected atmosphere. For the Al2O3 and MgO substrates, reaction layers in form of FeAl2O4 and MgO-FeO (solid solution) were formed. These layers slightly decreased the contact angle and surface tension values after a full melting. For a Ti2O3 substrate in contact with pure Fe, no-reaction could be observed at the interface. Furthermore, the contact angle and surface tension values were almost stable after a full melting. For a Ti2O3 substrate in contact with steel, the contact angle and surface tension values decreased steeply after a full melting, due to the formation Al2TiO5 reaction layer formation at the interface.

Keyword
contact angle, Al2O3, MgO, Ti2O3, reaction layer
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-175952 (URN)10.2355/isijinternational.ISIJINT-2014-820 (DOI)000362154800012 ()2-s2.0-84943192537 (ScopusID)
Note

QC 20151102

Available from: 2015-11-02 Created: 2015-10-26 Last updated: 2016-03-01Bibliographically approved
3. Effect of the Ti, Al Contents on the Inclusion Characteristics in Steels with TiO2 and TiN Particle Additions
Open this publication in new window or tab >>Effect of the Ti, Al Contents on the Inclusion Characteristics in Steels with TiO2 and TiN Particle Additions
2015 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86Article in journal (Refereed) Published
Abstract [en]

The effect of the Ti, Al contents on the metamorphic evolution of inclusions of Ti–Al complex oxides including TiN and MnS are investigated in common carbon steels with TiO2 and TiN particle additions. The study is carried out based on both SEM-EDS analyses and Thermo-Calc equilibrium calculations. Moreover, the particle size distributions are investigated by using the electrolytic extraction method. Based on the results of this study, the following is suggested: (i) the steel composition is controlled to contain small amount of the Al content (<0.005 mass%) and large amount of the Ti content (>0.035 mass%) in order to obtain a high number of fine particles containing a Ti-rich oxide phase when adding TiO2 and TiN particles; (ii) this consideration is reasonable from the view point of the agglomeration degree of different inclusion materials, which are estimated from the attractive force (van der Waals force and liquid-capillary force) and the contact angle.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2015
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-183067 (URN)10.1002/srin.201500267 (DOI)
Note

QC 20160301

Available from: 2016-02-26 Created: 2016-02-26 Last updated: 2016-03-01Bibliographically approved
4. Wetting Behaviorof Single Crystal TiO2by Liquid Iron
Open this publication in new window or tab >>Wetting Behaviorof Single Crystal TiO2by Liquid Iron
(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-183107 (URN)
Note

QS 2016

Available from: 2016-02-29 Created: 2016-02-29 Last updated: 2016-03-01Bibliographically approved
5. Evaluation of Agglomeration Mechanisms of Non-metallic Inclusions and Cluster Characteristics Produced by Ti/Al Complex Deoxidation in Fe-10 mass%Ni Alloy
Open this publication in new window or tab >>Evaluation of Agglomeration Mechanisms of Non-metallic Inclusions and Cluster Characteristics Produced by Ti/Al Complex Deoxidation in Fe-10 mass%Ni Alloy
(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-183109 (URN)
Note

QS 2016

Available from: 2016-02-29 Created: 2016-02-29 Last updated: 2016-03-01Bibliographically approved
6. Attraction Force Estimations of Al2O3Agglomerationsin the Melt
Open this publication in new window or tab >>Attraction Force Estimations of Al2O3Agglomerationsin the Melt
(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-183110 (URN)
Note

QS 2016

Available from: 2016-02-29 Created: 2016-02-29 Last updated: 2016-03-01Bibliographically approved

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Available from 2017-02-28 09:56

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