Improvements relating to processes for the bonding of molten aluminium and aluminium alloys to cast iron and steel

摘要

In a method of bonding molten aluminium and aluminium alloys to cast iron and steel, the surface of the base metal is first mechanically cleaned, if necessary and coated with a flux, then immersed in a zinc bath at a temperature of 450 DEG -700 DEG C. for not less than one minute or more than sixty minutes and finally the aluminium or aluminium alloy is cast thereon at a temperature of 650 DEG -850 DEG C. Zinc chloride is a suitable flux but others may be used, for example 70 per cent. calcium chloride, 25 per cent. sodium chloride and 5 per cent. potassium chloride. In an example, grey cast iron was machined, treated with a saturated solution of zinc chloride containing 5 per cent. by volume of concentrated hydrochloric acid, dipped in a bath of electrolytic zinc for one minute at 660 DEG C. transferred to a mould and pure aluminium poured around it at 750 DEG C. In modifications the zinc bath was at 555 DEG C. or 520 DEG C. and the aluminium was poured at 760 DEG C. or 800 DEG C. respectively. In another modification the zinc bath was at 625 DEG C. and an aluminium alloy containing 13 per cent. zinc and 3 per cent. copper was cast at 780 DEG C. Alternatively the zinc bath treatment may be for three minutes at 580 DEG C. and an aluminium silicon alloy cast on at 700 DEG C. In another example cast p iron was de-greased, pickled in sulphuric acid inhibited with stannine for 30 seconds at 85 DEG C., washed, immersed for 15 minutes in equal parts of sodium nitrate and potassium nitrate at 400 DEG C. washed again, pickled in hydrofluoric acid for one minute, fluxed with zinc chloride and immersed in a zinc bath for six minutes at 670 DEG C. An aluminium silicon alloy was then cast on it at 620 DEG C.