Electric heating – Metal heating – Nonatmospheric environment at hot spot
Patent
1990-02-06
1991-12-03
Shaw, Clifford C.
Electric heating
Metal heating
Nonatmospheric environment at hot spot
219 732, B23K 918
Patent
active
050702254
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
1. Background of the Invention
The present invention relates to arc welding, and more specifically, to a method for overhead submerged arc welding and apparatus to implement the same.
2. Description of the Related Art
A large amount of work in producing welded structures is taken up by circumferential rotatable welds of hollow articles with limited access on the inside to the joints being welded. The latter include circumferential joints of closed vessels, reservoirs and housings, circumferential joints of pipelines, field welds and slots in the outer plating of ships' hulls; longitudinal welds of large-area articles which are quite difficult to manouver into a position convenient for welding. They also include joints of panels which are difficult to manipulate, and also joints of segments, three-dimensional and flat sections etc.
The method of overhead submerged arc welding is characterized by that the weldpool, as compared with downhand submerged arc welding, is sort of turned by 180.degree., the flux and the electrode being fed in the vertical upward direction. Incidentally, the electrode is fed through a compacted layer of flux.
That is why the method is called overhead welding.
It is also called the submerged arc welding, because the arc burns in the thick of metal.
Such kind of welding produces so-called overhead welds.
Overhead welds may be of different types, e.g. overhead root welds and overhead back-up welds. There may also be overhead single-pass welds and other types of overhead welds.
Overhead root welds are those which are the first to be run in welding a joint and located in the upper part of the joints being welded on the side opposite to that of the electrode feed. Subsequent welding, i.e. making subsequent welds, is performed by any method known in the art, the electrode being fed from the same direction as in making overhead root welds, e.g. internal root welds in circumferential rotatable joints of vessels, reservoirs, connections of ships' outer bottom plating and other articles.
Overhead root arc welding makes it essentially possible to omit circumferential rotatable welding inside vessels and welding in hardly accessible spaces in making rectilinear welds in structures with limited access on the side opposite to the ceiling.
Overhead back-up welds are those which are the first to be run in making a joint and located in the lower part of the sections being welded on the side closest to that of the electrode feed. Subsequent welding is performed by any method known in the art, with the electrode being fed from the side opposite to that compared with overhead root welding.
Root welds are practically used in welding overhead circumferential and longitudinal joints of articles with limited access on the inside, and backup welds are used in welding longitudinal joints of hardly manoeuverable articles, e.g. sheet structures made of segments and other articles.
Overhead single-pass welds are those used in making limited-width joints and located on the whole section being welded. Characteristically, subsequent welding of the joint on either side is not required.
Molding a ready-made weld presents many problems in making back-up and single pass welds.
In overhead welding, the molten flux and metal of the weldpool produced by burning of the arc as a result of melting of the welded metal, electrode material and welding flux are held from beneath by a crust of partially molten flux and by the action of molding devices. The latter may be of different shapes and sizes and made in the form, for instance, of plates, shoes and back-up plates and other structural elements.
The flux is pressed from beneath to the welding spot, the expended amount being constantly replenished in the welding process. To mold the upper portion of the weld, the flux may be fed both from the bottom through the gap between the edges of the article being welded and from the top, by any known method, with a loose layer of flux being formed in the process. Back-up plates or flux-holding arrangements may a
REFERENCES:
patent: 4153832 (1979-05-01), Iio
Galinich Vladimir I.
Kovalev Valentin D.
Paton Boris E.
Podgaetsky Vladimir V.
Privalov Nikolai T.
Institut Elekctrosvarki Imeni E. O. Patona Akademii Mauk Ukrains
Shaw Clifford C.
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