GB796682A - Improvements in and relating to promoting the flow of molten metals on metal surfaces - Google Patents

Abstract

The flow of molten metal on a metal surface is promoted by first applying a finely-powdered metal to the surface. The molten metal is applied in an environment ensuring oxide- and nitride-free metal surfaces and should be capable of forming a bond both with the metal surface and with the metal powder. Specifically, the surface may be of Fe, steel, chrome-iron, Mo, Ni, Co, Cu, Ni-Fe, Ni-Fe-Co, Ni-Cu, Mo-Cu, Mo-Ni-Cu, W-Cu, and compacted and infiltrated alloys including Mo-Ni, W-Ag, W-Ni-Cu, Mo-Ag and Ni-Ag; the powder may be of Fe, Ni, Co, Mo, W, Cu, Cr, V, Mn, Cb, Ta, Ti and Zr; the molten metal may be Ag, Cu, Ag-Cu eutectic, Pb, Sn, Sn-Pb, Ni, Ni-Cu, Au, Co, Cd, Zn, Sb and Bi; and the environment may be hydrogen, forming gas, cracked ammonia or vacuum. The powder is preferably applied as a suspension in nitrocellulose thinned with 50 : 50 acetone/anyl acetate, and the following applications of the invention are disclosed:- (i) brazing, e.g. of tungsten carbide tool-tips to shanks, and metallized ceramic insulators to vacuum envelopes, (ii) the formation of a decorative finish on a metal surface by applying the powder in the form of a pattern and then flowing molten metal thereover, the spreading liquid remaining confined to the pattern, (iii) the closing of cavities in a metal component having an open porous structure, and (iv) the production of electrical contacts in which a highly-conducting strip of metal is superimposed on a support of different metal.