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Effect of the Ti, Al Contents on the Inclusion Characteristics in Steels with TiO2 and TiN Particle Additions
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. (Metallurgy)ORCID iD: 0000-0003-4107-8405
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0003-0533-6729
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
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. Vol. 86
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-183067DOI: 10.1002/srin.201500267OAI: oai:DiVA.org:kth-183067DiVA: diva2:907164
Note

QC 20160301

Available from: 2016-02-26 Created: 2016-02-26 Last updated: 2016-03-01Bibliographically approved
In thesis
1. Wettability and Agglomeration Characteristics of Non-Metallic Inclusions
Open this publication in new window or tab >>Wettability and Agglomeration Characteristics of Non-Metallic Inclusions
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
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:nbn:se:kth:diva-183069 (URN)978-91-7595-867-5 (ISBN)
Public defence
2016-03-30, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)
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Supervisors
Note

QC 20160301

Available from: 2016-03-01 Created: 2016-02-26 Last updated: 2016-03-01Bibliographically approved

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