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 ?
In addition to the varieties of classic electroslag remelting and, only electroslag feeding is used now in the industry for producing forging ingots.
Figure 4 compares the macrostructures of the ingots produced by electroslag remelting and ESR TC with a diameter of 500 mm, melted from the same electrodes in a single ESR furnace and at the same type of slag 1/3-1/3-1/3 and at the same power, generated in the slag pool.
In this article, special attention is given to investigating the possibilities of alloying titanium with oxygen directly from the gas phase during chamber electroslag remelting of titanium sponge with different initial oxygen content.
The amount of the weld the material should be minimum but sufficient for reliable joining of the elements of the consumable electrode taking into account the nature of the electroslag remelting process, and also the safety of the melting process.
Equipment for electroslag remelting of metals and alloys, Patent No.
Removal of hydrogen from steel during electroslag remelting, Dissertation, Donetsk, Moscow, 1985.
Investigations carried out at the Donetsk National Technical University yielded interesting data on the melting of titanium ingots by the method of electroslag remelting under fluxes of the [Ca.
1977) Investigation of heat exchange in electroslag remelting with various schemes.
1961) About alternative current rectification in electroslag remelting of consumable electrodes in water-cooled metal mould.
At the first stages, when electroslag remelting (ESR) was only began to be developed on the basis of the electroslag welding, and melting of ingots was realized using an electrode wire, the simple water-cooled vessels of a round section, as a rule, were used as moulds for the producing ingots [1].
Such technology can be developed on the basis of the special electrometallurgy processes, in particular chamber electroslag remelting (CESR).