Electroslag Remelting


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Electroslag Remelting

 

an electrometallurgical process in which a metal in the form of a consumable electrode is re-melted in a bath of an electrically conducting synthetic slag by the action of heat released upon the passage of electric current through the slag. The method, which significantly increases the quality of the metals and alloys produced, was developed in the early 1950’s at the E. O. Paton Institute of Electric Welding of the Academy of Sciences of the Ukrainian SSR on the basis of the electroslag welding process (seeWELDING). The consumable electrode may be manufactured by casting, rolling, or forging metal produced in an open-hearth, arc, or vacuum induction furnace or oxygen converter.

Figure 1. Electroslag remelting: (a) with one consumable electrode, (b) with two consumable electrodes; (1) consumable electrode, (2) slag bath, (3) metal bath, (4) ingot

During electroslag remelting, the temperature of the slag, which consists of various components (CaF2, CaO, SiO2, Al2O3, and others), exceeds 2500°C. Drops of the molten electrode metal pass through the slag layer to form a layer of metal underneath; subsequent solidification of the molten metal in a water-cooled crystallizer produces an ingot (Figure 1). As melting progresses, the consumable electrode continues to be introduced into the slag layer to maintain the volume of crystallizing metal. The slag functions as a refining medium. Electroslag refining of a metal occurs in the film of molten metal on the melting tip of the electrode, in the drops of molten metal passing through the slag bath, and on the boundary surface of the slag and metal baths.

Selective refining is achieved by changing the composition of the slag and the temperature regime of the process. As a result of electroslag refining, the sulfur content in the metal can be lowered by a factor of 2–5, and the content of oxygen and nonmetallic inclusions can be lowered by a factor of 1.5–2.5. The ingot produced is characterized by a compact, ordered microstructure that is free of casting and shrinkage flaws. The chemical and structural homogeneity of the ingot ensures isotropy of the physical and mechanical properties of the metal in the cast and deformed states.

Electroslag remelting is used to produce ingots weighing from several tens of grams to 200 tons in virtually any required shape, as determined by the shape of the crystallizer. In addition to intermediate ingots (for rolling shaped sections, pipes and tubing, and sheets) and forging ingots (for conventional forging, extrusion, and sheet-metal forming and forging), the technique is also used to produce shaped castings (for crankshafts, fastening hardware, pressure vessels, and gear teeth). Electroslag remelting is used in ferrous metallurgy (for the production of ball-bearing, structural, stainless, and tool steels and heat-resistant alloys), nonferrous metallurgy (for the production of chromium bronze and nickel-copper alloys), and heavy machine building (for the production of heat-resistant, high-strength die and roller steels). The process has been patented and is used under Soviet licenses in many countries.

REFERENCES

Elektroshlakovyi pereplav. Moscow, 1963.
Latash, Iu. V., and B. I. Medovar. Elektroshlakovyi pereplav. Moscow, 1970.

B. I. MEDOVAR

References in periodicals archive ?
The chamber electroslag remelting methods, used for metallurgical processing, guarantees the supply of oxygen from the gas phase into titanium during remelting of the sponge.
Since the slag contains unavoidably the oxides of metals with variable valence of the type of iron, manganese, titanium, etc, the oxidation--reduction processes taking place in electroslag remelting (this must be taken into account) should be accompanied by deoxidation of the slag pool during melting.
The optimum process of secondary refining remelting (in the group of the processes VAR, PAR, EBR and ESR) for the nickel-based creep-resisting alloys of this composition is electroslag remelting ensuring gradual solidification of the relatively small volume of liquid metal which is constant in time.
In: Electroslag technologies, proceedings of the conference devoted to 30 years of electroslag remelting, Naukova Dumka, Kiev, 1988, 5-11.
It was shown in [19] that chamber electroslag remelting as the metallurgical process makes it possible, by additional alloying with an oxygen-containing master alloy, to introduce the required concentration of oxygen into titanium and ensure chemical homogeneity of the metal of the ingot.
The addition of metallic calcium is to the slags used in chamber electroslag remelting ensures refining of titanium to remove nitrogen and oxygen, by respectively 10-15 and 20-25%.
Electroslag remelting of metals and alloys under fluxes with active additions in furnaces of the chamber type, in: Proceedings of the 2005 International symposium on liquid metal processing and casting, Santa Fe, USA, 2005, 227-232.
1972) Specifics of structure and properties of electroslag remelting hollow ingots.
on Processes of Electroslag Remelting (Tokyo, Japan, 1973).
There are many schemes of electroslag remelting of non-compact materials.
1972) Electroslag remelting with ingot drawing from single- and multi-passage moulds.
2005) Electroslag remelting of metals and alloys using the fluxes containing active additives in furnaces of chamber type.