Electric heating – Metal heating – Nonatmospheric environment at hot spot
Patent
1982-02-23
1984-06-12
Reynolds, Bruce A.
Electric heating
Metal heating
Nonatmospheric environment at hot spot
219 732, B23K 918, B23K 2500
Patent
active
044544065
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the art of welding and more particularly to a method for electroslag welding of light metals and alloys with a density less than that of the slag, to a welding flux based on alkali and alkali-earth metal halides and apparatus for accomplishing said method.
BACKGROUND ART
The invention may be employed in welding aluminium, magnesium, titanium, their alloys, and other light metals; it is particularly useful for welding aluminium busbars in the nonferrous metallurgy, chemical and electrical industries, and in other fields of engineering.
There is known a method for electroslag welding of metals (Elektroshlakovaja svarka, Ed. by B. E. Paton. Moscow-Kiev, "Mashgiz", 1959, pp. 90-149), which includes establishing a slag bath, fusing the electrode and the edges being weld-joined, and filling with molten metal the gap between the edges.
There is also known that in the course of electroslag welding of light metals and alloys with the use of prior art fluxes, the content of gases in the weld metal rises with the thickness of the workpieces being weld-joined.
For example, a flux has been proposed (USSR Inventor's Certificate No. 626,913, published Mar. 28, 1977), intended for electroslag welding of light metals and alloys and containing alkali and alkali-earth metal halides, the flux composition being as follows (in wt.%):
______________________________________ calcium fluoride 13-17
strontium fluoride 13-17
magnesium fluoride 10-14
lithium fluoride 16-20
potassium fluoride (concentrated
36-44
aqueous solution)
______________________________________
A weld produced with the use of the flux in the course of welding, without resorting to known techniques for reducing the gas content in the weld metal, is unsound, with an increased content of gases, which drastically impairs the mechanical properties of welded joints. Furthermore, the flux is highly hygroscopic (because its composition includes a concentrated aqueous solution of potassium fluoride), which in the course of electroslag welding may give rise to weld pool splash-outs upsetting the stability of the process.
The above-mentioned electroslag welding method contemplates the use of apparatus consisting of a bottom plate, moulding shoes, run-on plates, and a welding electrode.
The use of such methods, flux, and apparatus results in welds featuring an increased content of gas and calls for additional processing operations to upgrade the weld quality in welding critical structures.
A full degassing of the weld metal in the above method can be attained with inhibiting the weld metal crystallization process by performing an additional operation of a preliminary, accompanying, and subsequent heating of the weld metal, which is attainable only by the use of a complex additional equipment.
Moreover, the method calls for introduction in the course of welding into the weld metal of additional chemical elements which bind the gas-forming components into stable compounds and for an additional protection of the welding zone by inert gases.
The application of said method, flux, and apparatus with the additional processing steps greatly increases the labour consumption and the cost of the welding process.
There has also been proposed a method for vertical welding of aluminium (U.S. Pat. No. 3,585,343, published June 15, 1971), which includes (1) establishing a slag bath of the following composition; (2) formation of a slag bath (pool) (in wt. %):
______________________________________ potassium chloride 45
sodium chloride 27
sodium cryolite (3NaF.AlF.sub.3)
22
lithium chloride 6,
______________________________________
filling with metal the gap between the edges.
The above flux allows a stable electroslag welding process to be conducted, adequately deoxidizes an oxide film on the workpieces being weld-joined, but fails to ensure sound welds unless the above-mentioned weld metal degassing techniques are resorted to.
The method contemplates the use of an apparatus comprising a meta
REFERENCES:
patent: 2802762 (1957-08-01), Stetson
patent: 3529126 (1970-09-01), Reeh
patent: 3585343 (1971-06-01), Crichton
patent: 4207454 (1980-06-01), Safonnikov et al.
patent: 4376881 (1983-03-01), Safonnikov et al.
"The Technology of Electric Fusion Welding of Metals and Alloys", Paton, B. .
"Electroslag Welding", Edited by B. E. Paton, Moscow-Kiev, Mashgiz, 1959, pp. 90-149.
Antonov Anatoly V.
Safonnikov Anatoly N.
Institut Elektrosvarki Imeni E.O. Patona Akademii Nauk Ukrainsko
Reynolds Bruce A.
Sigda Catherine
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