US3387971A - Master alloy consisting essentially of molybdenum-vanadium-aluminum - Google Patents

Description

3,387,971 MASTER CONSESTENG ESSENTIALLY F lviilILi/BDENUM-VANAEiUM-ALUMHNUM John B. Vogt, Avon Lake, @hio, and Louis E. Matricardi,

Tonawanda, N.Y., assignors to Union (Iarnide Corporation, a corporation at New York No Drawing. Filed Feb. 21, 1966, Ser. No. 528,774

2 Claims. (Cl. 75-138) The present invention relates to master alloys for use in the making of titanium-base alloys. More particularly, the present invention relates to a master alloy of molybdenum, vanadium and aluminum for use in the manufacture of a titanium base alloy containing these elements.

At the present time, titanium base alloys containing aiurninum and substantially equal amounts of molybdenum and vanadium are rather Widely used in the aircraft industry for both structural and engine components. A particularly popular alloy has a composition of 8% Al, 1% Mo, 1% V, balance titanium.

In making this particular alloy the proportions of which are considered critical, and in making other titanium base alloys, the usual practice is to melt the molybdenum, vanadium and aluminum, in the form of a master alloy, with titanium.

in following this practice, it is of course important that the master alloy be fairly easily melted and have not too high a melting temperature so that it will easily and uniformly combine with the titanium base metal.

Also, the master alloy should be of high purity so that detrimental contaminants are not introduced into the base metal. As a matter of industrial utility, the cost of producing the master alloy should be as low as possible.

it is therefore an object of the present invention to provide a molybdenum, vanadium, aluminum master alloy for use in the manufacture of titanium-base alloys containing these elements, the master alloy being relatively low melting, of high purity, and relatively inexpensive to maize.

A master alloy in accordance with the present invention consists essentially of about to molybdenum, 20 to 2% vanadium, balance essentially aluminum.

This alloy has been found to have a combination of advnatages not found in previously known master alloys.

For example, molybdenum-vanadium alloys, having 1:1 Mo-V ratio, which contains more than about 50% Mo-l-V, have increasingly higher melting points, on the order of the melting point of titanium, which make uniform combination with the titanium base metal very difficult due to poor solution characteristics and often result in hard to detect Mo-V inclusions in the final alloy. For example, a Mo, 35% V, balance Al alloy has a melting point of :more than l750 C.

On the other hand, alloys of the present invention have melting points less than about 1400 C. which makes these alloys well suited to uniform solution with molten titanium.

Other 1:1 bio-V alloys containing less than NiO-l-V have generally satisfactory melting points, however, such alloys are not readily crushable due to their inherent malleability and cannot be routinely manufactured by the relatively inexpensive method of aluminothermic smelting but instead require multi-step processing.

The alloys of the present invention, however, can be readily made aluminotherrnically, i.e., by ignition of aluminum-containing mixture of molybdenum oxide and vanadium oxide whereby the oxides are reduced by the aluminum and the reduced metal combines with a predetermined excess of aluminium. Iviorcover, by virtue States Patent 0 3,387,971 Patented June 11, 1968 "ice of its method of manufacture, i.e., aluminothermic reduction, the alloy of the present invention has a very low impurity content for example the alloy is at least 99% M0+V+Al, with less than 0.5% in the aggregate of carbon, oxygen, hydrogen and nitrogen, which ensures the advantageous properties disclosed herein.

A further advantage of the present invention is that its low density about 3.8 to 4.2 permits convenient examination for impurities by X-ray fluoroscope whereas molybdenum-vanadium alloys with lesser amounts of aluminum cannot be effectively inspected by such techniques.

In the use of the present invention, the Mo+V+Al alloy obtained by aluminothermic reduction is suitably sized A inch and finer and is blended with titanium sponge, about /4 inch, and aluminum shot, about /8 inch and finer in suflicient amounts to provide a 1% Mo, 1% V, 8% Al alloy and compacted at room temperature and at pressures of about 40,000 psi. to a convenient generally cylindrical shape. Several of such compacts are then welded together to form a size convenient for use as an electrode and the thus formed electrode is electrically melted in a conventional manner to produce the desired alloy.

The following examples will further illustrate the present invention.

EYAMPLE I The charge materials shown in Table I were mixed together by coning in a mixing pan.

TABLE I Analyses, percent Mixture order Weight Molybdic Oxide (M003) 99. 5 Vanadium Oxide (V205) S9 Aluminum Shot. 178 Lime r 65 Fluorspar 10 After mixing the charge was placed in an electric furace comprising a magnesia-lined crucible equipped with two 3 inch diameter graphite electrodes. The furnace was operated at volts and the total power applied was about 50 kw.-hr., this being sutlicient on account of the cxoihermicity 01": the reaction.

The total furnace time was 12 minutes and when the reaction was complete, the resulting alloy product was tapped into an Alundum lined tapping pot.

The analysis of the product is shown in Table II.

EXAMPLE H An alloy of the present invention (approximately Mo, 25 V, balance Al) in the form of 48 inch lumps crushed to 1 /2 inches by D and then processed in a gymtory crusher to obtain a nominal A inch by D product.

The results are shown in Table III.

TABLE I 11 Screen Percent Percent Designation Opening cumulative Retained on in Inches O. 185 15. )3 20. 77 0.131 19. 41 40. 18 0. 093 14. 37 54. 55 0. 055 1b. 76 71. 31 0. 0328 10. 42 S1. 73 O. 0195 6. 8O 88. 53 0.0116 4. 14 92. 67 1O 0. 0082 2. 19 J4. 86

What is claimed is:

1. Master alloy for use in making titanium base alloys consisting essentially of about 20 to 25% molybdenum, about to vanadium, balance aluminum.

References Cited UNITED STATES PATENTS Towncr et a1. -438 Roberts et al. 75138 staggers et al 75-138 HYLAND BIZOT, Primary Examiner.

RICHARD O. DEAN, Assistant Examiner.

Claims (1)

1. MASTER ALLOY FOR USE IN MAKING TITANIUM BASE ALLOYS CONSISTING ESSENTIALLY OF ABOUT 20 TO 25% MOLYBDENUM, ABOUT 20 TO 25% VANADIUM, BALANCE ALUMINUM.