GB463434A - Improvements in or relating to the welding of magnesium and magnesium alloys - Google Patents

Abstract

In welding magnesium and magnesium alloys a flux is used consisting predominantly of one or more halides of the alkali and/or alkaline earth metals and also an acid, either as such as in the form of an acid salt, which acid, at the welding temperature, is less volatile than any halogen hydracid derived from the halides of the flux, the acid or acid salt being of such a nature that neither it nor any reaction product formed during the welding has any corrosive action if left in contact with the magnesium or magnesium alloy. The acids or acid salts are normally those having an acid radical which combines with magnesium to give insoluble or sparingly soluble salts. Examples of acids are boric acid, oxalic acid, and metaphosphoric acid, and acid salts which may be used include alkali metal or ammonium acid orthophosphates or acid pyrophosphates, e.g. monopotassium orthophosphate. Small quantities, e.g. from 0,2-1 per cent, of manganese dioxide may be added to the flux to facilitate the expulsion of the halogen hydracid. The flux may be applied in the form of an aqueous or alcoholic suspension. Particular fluxes described are: (a) 10 parts of lithium chloride, 5 parts of potassium fluoride, and 2 parts of metaphosphoric acid; (b) 12,5 parts of lithium bromide, 5 parts of potassium fluoride, and 2 parts of monopotassium phosphate; (c) 100 gms. of monosodium phosphate, 5-10 gms. of manganese dioxide, and 1000 gms. of a mixture of sodium chloride, potassium chloride, and lithium fluoride.