Effect of SiO2 on the Crystallization Behaviors and In-Mold Performance of CaF2-CaO-Al2O3 Slags for Drawing-Ingot-Type Electroslag Remelting

Abstract

The crystallization characteristics of CaF 2 -CaO-Al 2 O 3 slags with varying amounts of SiO 2 were experimentally studied. The effects of slag crystallization behaviors on the horizontal heat transfer and lubrication performance in drawing-ingot-type electroslag remelting (ESR) were also evaluated in terms of as-cast ingots surface quality and drawing-ingot operation. The results show that increasing SiO 2 addition from 0 to 6.8 mass pct strongly suppresses the crystallization of ESR type CaF 2 -CaO-Al 2 O 3 slags. The crystallization temperature of the studied slags decreases with the increase in SiO 2 addition. The liquidus temperatures of the slags also show a decreasing trend with increasing SiO 2 content. In CaF 2 -CaO-Al 2 O 3 -(SiO 2 ) slags, faceted 11CaOAE7Al 2 O 3 AECaF 2 crystals precipitate first during continuous cooling of the slag melts, followed by the formation of CaF 2 at lower temperatures. 11CaOAE7Al 2 O 3 AECaF 2 was confirmed to be the dominant crystalline phase in the studied slags. CaF 2 -CaO-Al 2 O 3 slags with a small amount of SiO 2 addition are favorable for providing sound lubrication and horizontal heat transfer in mold for drawing-ingot-type ESR, which consequently bring the improvement in the surface quality of ESR ingot and drawing-ingot operating practice as demonstrated by plant trials.

Development of Low-fluoride Slag for Electroslag Remelting: Role of Li₂O on the Crystallization and Evaporation of the Slag

“…The inappropriate horizontal heat transfer through slag film and/or poor lubrication performance of slag generally results in unreliable operating practice and surface defects on as-cast ESR ingot. 9,10) Therefore, in-depth knowledge on the melting and crystallization of low-fluoride ESR slag is necessary for the development of applicable low-fluoride slag.…”

Behavior of Alloying Elements during Drawing-Ingot-Type Electroslag Remelting of Stainless Steel Containing Titanium

“…As the Drawing-Ingot-Type ESR needs the slag having the excellent high temperature plasticity, more than 4% silica needs to be added into molten slag. 3 , which makes the active alloying element control difficultly. Therefore, it is important to have a good understanding of titanium and aluminum control during Drawing-Ingot-Type ESR with stainless steel under different remelting process, slag and metal electrode composition.…”

Review on Modeling and Simulation of Electroslag Remelting

“…Furthermore, the aforementioned oxides can change physical as well as physicochemical properties of the slag such as viscosity, density, etc . For instance, a lubricative skin layer forms on the surface of a short collar (moveable) mold by addition of SiO 2 to the slag, that is, in favor of producing ingots with superior surface quality . The physicochemical properties are dependent on both temperature and composition of the slag.…”

“…[19] For instance, a lubricative skin layer forms on the surface of a short collar (moveable) mold by addition of SiO 2 to the slag, that is, in favor of producing ingots with superior surface quality. [25] The physicochemical properties are dependent on both temperature and composition of the slag. Due to the difficulty of measurements at elevated temperature, a large uncertainty of the properties exists.…”