Evolution Mechanism of Oxide Inclusions in Titanium-Stabilized AISI 443 Stainless Steel
- PDF / 4,849,980 Bytes
- 13 Pages / 593.972 x 792 pts Page_size
- 78 Downloads / 220 Views
Evolution Mechanism of Oxide Inclusions in Titanium-Stabilized AISI 443 Stainless Steel JINGYU LI, GUOGUANG CHENG, QIANG RUAN, JIXIANG PAN, and XINGRUN CHEN The evolution mechanism of oxide inclusions in Ti-bearing AISI 443 stainless steel was investigated by industrial experiment and thermodynamic calculation. The chemical compositions of steel and the characteristics of inclusions in steel were analyzed. After the addition of Al, the main type of inclusions in molten steel was irregular MgOÆAl2O3 spinel. The MgOÆAl2O3 inclusions were modified to be spherical CaO-Al2O3-MgO inclusions after calcium treatment. Thermodynamic calculation results indicated that several ppm Ca could significantly expand the liquid oxide phase field and decrease the stability of spinel. After titanium addition, two types of inclusions were formed: spherical Al2O3-TiOx inclusions and complex CaO-TiOx-Al2O3-MgO inclusions. The compositions of steel after Ti addition were mostly located in Al2O3-TiOx stability phase field. Based on the characteristics of inclusions in steel and thermodynamic calculation, inclusions consisting of liquid and CaTiO3 were formed in molten steel with more than 10 ppm Ca during the Ti addition process. The evolution mechanism of oxide inclusions was discussed with the consideration of the initial calcium content before Ti addition. https://doi.org/10.1007/s11663-018-1331-7 The Minerals, Metals & Materials Society and ASM International 2018
I.
INTRODUCTION
TITANIUM has been widely used as an alloy element in stainless steel to suppress chromium carbide precipitation at grain boundary through the formation of more stable titanium carbide, which substantially improves the resistance to intergranular corrosion.[1,2] In addition, the heterogeneous nucleation of delta ferrite on the TiN formed during primary solidification of stainless steel promotes the generation of the equiaxed fine-grained structure.[3] However, the presence of oxide inclusions generally causes serious clogging of submerged entry nozzle (SEN) and surface defects of steel products.[4–7] Thence, it is crucial to predict and control the formation of oxide inclusions in Ti-bearing stainless steel during steelmaking process. Aluminum is a common final deoxidizer for its high oxygen affinity, which is usually added before the Ti alloy addition to reduce the formation of Ti-containing inclusions and improve Ti yield.[8,9] However, alumina JINGYU LI and GUOGUANG CHENG are with the State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China. QIANG RUAN, JIXIANG PAN, and XINGRUN CHEN are with the Hongxing Iron & Steel Jiuquan Iron and Steel Co., Ltd., Jiayuguan 735100, Gansu, China. Contact e-mail: [email protected] Manuscript submitted January 20, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS B
and spinel (MgOÆAl2O3) inclusions formed after the Al addition generally lead to the clogging of SEN.[10–12] Many researchers have found that calcium treatment was an effective countermeasure to modify
Data Loading...
