GB271798A - Improvements in or relating to the production of corrosionresistant articles - Google Patents

Abstract

271,798. Aluminum Co., of America, (Assignees of Dix, E. H.). Jan. 22, 1927, [Convention date]. Moulds.-Articles of aluminium base alloy are made corrosion-resistant by casting the base alloy on to facing plates of aluminium or corrosionresistant aluminium alloy and then applying pressure and heat to the casting. The well known base alloys containing, in addition to impurities such as iron, the following percentages of added metals may be used : -A copper 3 to 5, magnesium 0.5, manganese 0.6; B copper 4 to 5.5, manganese 0.6; C magnesium 0.7, silicon 0.9. One or two facing plates of electrolytically refined aluminium may be clamped to, or inserted in grooves to hold them against, the smooth inner face of an iron mould, which may be water-cooled to avoid fusion of the plates. Casting processes; castings.-The base alloy is preferably poured gently down an unlined face of the tilted mould. While still hot or after heating to a temperature well below the melting point of eutectics present, for instance 480 to 500‹ C. for alloy A, the compound ingot is rolled to complete the union and form a plate of the required thickness. The plate may then be cold rolled and given a suitable heat treatment, for instance 520‹ C. in fused sodium and potassium nitrate for 20 minutes followed by quenching in water and ageing at room temperature for alloy A. Alloy C is aged at 100‹ C. In casting ingots for drawing tubes, rods, wire &c. the facing metal may be in the form of a tube. If a hard surface is required alloys of aluminium with manganese or beryllium may be used for the facing metal.