Haibo Cao

Effect of Slag on Titanium, Silicon, and Aluminum Contents in Superalloy During Electroslag Remelting

Many factors influence the chemical composition in electroslag remelting (ESR) steel, including atmosphere in crucible, melting rate, slag composition, deoxidation, and so on. Fluoride-based slag, which is exposed to liquid metal directly, influences the chemical composition of ESR ingots to a large extent. The present paper focuses on the effect of slag on the titanium, silicon, and aluminum contents in ingots based on the interaction of the slag and metal. In present work, superalloy of GH8825 and several slags containing different CaO contents have been employed for investigating the effect of slag on titanium, silicon, and aluminum contents in an electrical resistance furnace under argon atmosphere. Results indicate that the higher CaO content in slag has better capacity for avoiding loss of titanium caused by the reaction of titanium with silica in slag, especially in case of remelting superalloy with high titanium and low silicon content. The CaO has a great effect on the activities of TiO2, SiO2, and Al2O3. Thermodynamic analysis is applied to investigate the CaO behavior. Based on the ion and molecule coexistence theory of slag, activity model is established to calculate the activities of components containing titanium, silicon, and aluminum elements in a six-component slag consisting of CaO-CaF2-Al2O3-SiO2-TiO2-MgO. The components containing titanium, silicon, and aluminum in slag are mainly CaO·TiO2, 2CaO·SiO2, CaO·SiO2, CaO·Al2O3, and MgO·Al2O3. With the increase of CaO mass fraction in slag, the activity coefficient of SiO2 decreases significantly, whereas slightly change happens for Al2O3. As a result, the

Comprehensive Mathematical Model for Simulating Electroslag Remelting

\lg ({{\gamma_{{{\text{SiO}}_{2} }} } \mathord{\left/ {\vphantom {{\gamma_{{{\text{SiO}}_{2} }} } {\gamma_{{{\text{TiO}}_{2} }} }}} \right. \kern-0pt} {\gamma_{{{\text{TiO}}_{2} }} }})

Study of a Single-Power Two-Circuit ESR Process with Current-Carrying Mold: Mathematical Simulation of the Process and Experimental Verification

lg(γSiO2γTiO2) decreases with increasing CaO content, which is better for preventing loss of titanium caused by the reaction of titanium with silica in slag. The slag with high CaO and appropriate TiO2 content is suitable for electroslag remelting of GH8825.

A Novel Single Power Two Circuits Electroslag Remelting with Current Carrying Mould

Physical simulation of a single-power, two-circuit electroslag remelting (ESR) process with current conductive mold (ESR-STCCM) is carried out in this paper. Wood alloy and sodium chloride solution are used to study the current distribution ratio of passing electrode and conductive part of current carrying mold (conductor). A conventional ESR (CESR) process has been studied as a comparison. The total current of ESR-STCCM is larger than the CESR process, which indicates that the resistance in ESR-STCCM is smaller than in CESR. Results show that the ratio of Ielectrode/Iconductor changes with filling ratio, electrode immersion depth, and effective conductor height. Electrode immersion depth plays an important role on the current distribution ratio. Nevertheless, the effective conductor height has a little influence on the current distribution ratio. A larger filling ratio has an obvious effect on the current distribution ratio in ESR-STCCM. Current flowing through the electrode increases with the increasing of electrode immersion depth under a certain filling ratio. The physical model established can provide an important direction to real ESR-STCCM.

Thermodynamic design of electroslag remelting slag for high titanium and low aluminium stainless steel based on IMCT

Droplet formation and departure from an electrode tip affect the temperature distribution in liquid slag and a molten steel pool, as well as the removal of nonmetallic inclusions in the electroslag remelting process. In this article, magneto-hydrodynamics modules coupled with a volume of fluid (VOF) model (as described in VOF model theory) for tracking phase distribution have been employed to develop the electrode fusion model and to investigate formation and departure of a droplet from the electrode tip. Subsequently, the remelting rate and molten steel pool have been achieved based on the electrode fusion model. Results indicate that a droplet can increase the flow rate of liquid slag, especially the region of droplet fall through the slag pool; yet it has little impact on the flow distribution. Asymmetric flow can take place in a slag pool due to the action of the droplet. The depth of the molten steel pool increases in the presence of droplets, but the width of the mushy zone decreases. In addition, the shape of the electrode tip is not constant but changes with its fusion. The remelting rate is calculated instead of being imposed in this work. The development of the model supports further understanding of the process and the ability to set the appropriate operating parameters, especially for expensive and easy segregation materials.

Effect of Slag Composition on the Oxidation Kinetics of Alloying Elements during Electroslag Remelting of Stainless Steel: Part-2 Control of Titanium and Aluminum Content

A better understanding of droplet formation and dripping behavior would be useful in the efficient removal of impurity elements and nonmetallic inclusions from liquid metals. In the present work, we developed a transparent experimental apparatus to study the mechanisms of droplet formation and the effects of filling ratio on droplet behavior during the electroslag remelting (ESR) process. A high-speed camera was used to clearly observe, at small time scales, the droplet formation and dripping phenomenon at the slag/metal interface during a stable ESR process. The results illustrate that a two-stage process for droplet formation and dripping occurs during the ESR process and that the droplet diameter exhibits a parabolic distribution with increasing filling ratio because of the different shape and thermal state of the electrode tip. This work also confirms that a relatively large filling ratio reduces electricity consumption and improves ingot quality.