ES346783A1 - Method for the formation of an alloy composed of metals reactive in their elemental form with a melting container - Google Patents

Abstract

In forming an alloy containing at least one metal component reactive in its elemental form with a melting container, the alloy itself being relatively unreactive with the container, a pre-alloyed material of the same constituents as the alloy to be obtained is first melted in the melting container and the component elemental metals of the alloy are thereafter incorporated in the molten material in such a manner as to substantially prevent direct contact between the component elemental metals and the container walls. As shown in Fig. 2a, blocks of mechanically mixed and compacted elemental Ti and Ni are placed on a Ti-Ni alloy starter plate in such manner that the elemental Ti and Ni do not touch the sides of a graphite crucible. The crucible is heated by induction heating in such manner that the Ti-Ni alloy first melts and the elemental Ti and Ni melt into the molten alloy. To prevent tilting of the stack of blocks during melting, the blocks may be guided through holes in their centres by a pre-alloyed rod that is fastened in a vertical position above the crucible. Alternatively, they can be centred and fed vertically through an alloy tube. To prevent excessive weight of the stack causing the blocks to contact the crucible bottom when the alloy is molten, the blocks can be released from above one or more at a time to allow the molten alloy to float the block(s). Instead of using blocks, a rod of partially sintered mixed Ti+ Ni can be fed downwardly into the molten Ti-Ni alloy. Figs. 2b and 2c (not shown) illustrate the feeding of Ti and Ni particles into a pool of molten Ti-Ni alloy in a graphite crucible. In the Fig. 2b arrangement, the particles are metered into the molten alloy and in the Fig. 2c arrangement the particles are within a Ni Sheet can which is lowered into the molten alloy. The Ti and Ni particles may be in the form of sponge and shot respectively and Co or Fe may be added. The graphite crucible may be dried before use. The induction melting may be in a chamber under a pressure of from a few microns to more than one atmosphere, e.g. under an Ar or He atmosphere. Alloys which may be produced by the method are:- (a) 55À1% Ni, remainder Ti and impurities, (b) 60% Ni, remainder Ti, (c) 54À59-55À40% Ni, 0À033-0À042C, remainder Ti and (d) the alloys TiCo, TiFe, TiNiICo1-x, TiNix Fe1-x and TiCox Fe1-x.