METHOD FOR ADDING BORON TO METAL ALLOYS.

摘要

A method to grain refine and deoxidize a precious metal alloy or a master alloy includes the steps of (a) forming a precursor melt (10) consisting essentially of constituents of the precious metal alloy or master alloy and inevitable impurities; (b) dispersing (14) a compound selected from the group consisting of boron containing metal hydrides, boron containing metal fluorides and mixtures thereof throughout the precursor melt; and (c) solidifying (20) the boron containing precious melt alloy or master alloy. One suitable compound is solid sodium borohydride (sodium tetrahydroborate). To minimize evaporation of the boron on contact with the precursor alloy melt, the sodium 0 borohydride may be wrapped in a metal foil formed from constituents of the precious metal alloy or master alloy. The cast precious metal alloy or master alloy has been found to have a reduced number of hard spots and reduced silicon contamination when compared to conventional casting methods.