Effect of Slag on Titanium, Silicon, and Aluminum Contents in Superalloy During Electroslag Remelting
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TROSLAG remelting (ESR) is employed for producing high-quality alloys as for its exclusively outstanding advantages,[1,2] such as secondary refining, homogeneous composition, and the removal of non-metallic inclusions. It is a significant advantage that a good contact between metal and slag makes the steel chemically refined. However, the existence of the slag phase has the disadvantage for controlling the chemical composition of steel, especially for remelting alloys containing easily oxidative elements such as titanium, silicon, and aluminum. Reactions will happen between slag/metal interfaces so that the concentrations of the elements vary from the bottom to the top of the ingot. Therefore, it is essential to have a good understanding of the effect of slag on the titanium, silicon, and aluminum contents in electroslag ingot.
ZHOU-HUA JIANG, Professor, DONG HOU, YU-LONG CAO, and HAI-BO CAO, Ph.D. Candidates, and YAN-WU DONG and WEI GONG, Associate Professors, are with the School of Materials and Metallurgy, Northeastern University, Shenyang 110819, Liaoning, China. Contact e-mail: [email protected] Manuscript submitted May 6, 2015. Article published online February 1, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
Many measures[3–20] have been investigated for the improvement of macrosegregation of ESR ingot. As a mater of fact, the critical path to solve this problem is to choose appropriate slag, which has been studied by many investigators.[8–19] They found the loss of titanium caused by reacting with the alumina of the ESR slag could be avoided by adjusting the compositions of the ESR slag and the electrodes according to the slag-metal equilibria. Pateisky[18] investigated the relationship between titanium, aluminum, and silicon, and then the TiO2 content in slag was determined in order to make the titanium uniform from the top to bottom in ingot. Cheng[19] studied the change of aluminum and titanium in steel and obtained the appropriate slag for electroslag remelting of superalloy based on the experiments and thermodynamic equilibrium. Schwerdtfeger and Wei[20,21] investigated the kinetics mechanism of electroslag remelting stainless steel and pointed out that the activities of SiO2, Al2O3, and TiO2 in slag played an important role in controlling titanium content. To the best of the authors’ knowledge, investigation on the activities of Al2O3, SiO2, and TiO2 control and its effect on the aluminum, silicon, and titanium contents during ESR process have not been reported so far. The current work focuses on the titanium content control during ESR process and the effect of each component in slag on activities of Al2O3, SiO2, and TiO2. In addition, VOLUME 47B, APRIL 2016—1465
based on the ion and molecule coexistence theory of slag, the mechanism of CaO and MgO on activities of Al2O3, SiO2, and TiO2 is investigated. This study aims to provide appropriate slag which can be effectively applied to control titanium content during the ESR.
II.
The contents of titanium, silicon, and soluble aluminum in each metal s
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