US2785971A - Process for the manufacture of titanium metal - Google Patents

Description

PROCESS 'FOR THEMANUFACTURE 'oF TITANIUM METAL Jonas Kamlet, Easton, Conn., assignor'to National Distillers Products Corporation, New York, N. Y., a corporation of Virginia No Drawing. Application September 24, 1953, Serial No. 382,206

13 Claims. (CL 75---84) This invention relates to a process for the manufacture of titanium metal. More particularly, it relates to a process for the manufacture of titanium 'meta'l by the reaction of a readily preparable series of inorganic titanium compounds with metallic aluminum. It has for its purpose to provide arelativ'ely simpleprocess for the Patent 2,205,854 (1940); British Aluminum Co, British Patent 638,840 (1950); Bureau of Mines Information Circular 7381 (1946), and Report'of Investigations 4519 (1949); Worner, Metallurgia, June 1949, 69-76; Stark A-G, German Patent 812,117 (1951); Jordan, U. S Patent 2,647,826 (1953); Winter, U. S. latent 2,607,674 (1952) and 2,621,121 (1952). Other processes which have attracted attention involve the reactionof titanium tetrachloride with sodium metal or sodium amalgam (FIAT Final Report 798, Glasser et al., U. S. latent 2,618,549 (1952); Hampel et 211., U. S. Patent 2,6l8,5 50 (1952); Potvin and Farnham, Transactions ofthe Qanadian Institute of Mining and Metallurgy, XLIX, 516-524 (1946), the reaction of titanium dioxide with calcium metal or With calcium hydride (FIAT Final Report 798, Kroll, Zeitschr. Anorg. Chem. 234, 42-50 (1937); Ruif and Brintzinger, Zeitschr. Anorg. Chem. 129, 267-275 (1923); Dominion Magnesium Ltd., British Patent 675,933 (1952); the thermal disassociat-ion of titanium tetraiodide or tetrabromide (Fairweather, British Patent 675,571 (1952), FIAT Final Report 798) and the electrolysis of titanium compounds .in fused-salt baths under specified conditions (Cordner and Werner, Australian Journal of Applied Science 2, #3, 358-367 (1951); Proceedings of the Australian institute ofjMining and Metallurgy, N. S. 158-9, .pp, 65-104 (1950;);

Shawinigau Water and Power (30., British Patent678,807

Several attempts have been described in the .past to manufacture metallic titanium by the reaction of atitanium compound with metallic aluminum. Aluminum metal is low in cost, highly reactive at advanced temperature and avm'lable in huge quantities. It has, however, heretofore been impossible 'tomanufact'ure titanium Patented -Mar. =19, 1957 (1910); Weiss and vNaurharin, Zeit. Anorg. Chem. ;65, 248-278 (1910); Vlanchot and Richter, Annalen 357, 140-144 (1907), r g

Whenevenatitanium compound is reduced with metallic aluminum, an alloy of titanium and aluminum is obtained. The basis of this invention-is the discovery that certain alloys of titanium and aluminum lend themselves quite readily to selective reaction with chemical-reagents whereby apure metallic titanium'may be obtained, whereas other alloys oftitanium and aluminum are completely unsuitable for such selective reaction and can therefore not be used for the recovery of metallic titanium.

Binary alloys containing up to 37.28% of titanium consist of crystals of titanium aluminide (TiAla) dis persed in excess aluminum. The binary alloy containing 37.28% of titanium corresponds to TiAla injcomposition.

Selective leaching with dilute acid or dilute soda HSh'SOliltion permits the separation of TiAls crystals from excess aluminum, but no method has heretofore been described for the separation of titanium from the intermetallic compounds.

Binary alloys containing from 37.28% to 53% of titanium consist of crystals of titanium aluminide dispersed in excess titanium metal. No method has heretofore been described for the separation of titanium from such binary alloys containing 37.28% to 53%,of Ti.

However, binary alloys containing 53% to "of titanium comprise simple solutions'of the aluminum :in the titanium and do not form intermetallic compounds. (Gruhl, MetalL, March 1952, 134; Cueilleron and Pascaud, Comptes rendus, 233, 745-747 (1951'), -ibid;, 235,

122M221 1952 Such-binary-a'lloys devoid of i'ntermetallic compounds may be treated with an aqueous solution 'of a'member of the groupconsistiug of the hydroxides, carbonates, bicarbo'natesand aluminat'es of the alkali metals, preferably at advanced temperatures, whereby the aluminum is leached from the alloy and dissolved as alkali metal aluminate, and the titanium metal remains behind substantially unat'tacked, e. g

2A1+2Na0r1+2nzo 2NaAio2+3 i2 2A1+NaaAlOa+ 6HiO- 3NaAlO2-l-6Hz I have also found that such binary alloys devoid of intermetallic compounds, containing more than 53% of titanium, may betractionally distilled at advanced temperature, preferably under reduced pressures, for the separation of the aluminum and the recovery of a pure metallic titanium.

The basis of the present invention is the reaction ofan alkali metal fluotitanate With aluminum metal according to the equation:

3M2TiFs+4Al 2M3AlFs+2AlP3+3Ti Where M is an alkali metal (lithium, sodium and potassium). From theoretical considerations, 1.33 gram-atoms of aluminum is required .per gram-mole of alkali metal liuotitanate. However, the use of theoretical or stoichiometric quantities of reagents almost invariably results in anincomplete utilization of the alkali metal fiuotitanate and the formation of an aluminum-titanium alloy contaminated 'witha trivalent and bivalent titaniumcompound. I have found that it is desirable to use an excess of aluminum over that amount required by theoretical considerations, but that such excess of aluminum must be strictly limited in amount so that the excess aluminum forms with the titanium metal liberated a binary alloy containing not less t an 53% of titanium. This binary alloy c'an thenbc isolated from the reaction p rc iduc t and th' titanic titanium recover d therefrom by seminar s the arena-an f ith an alkaline solution.

. r hays reuse that iris, ble to use nan 38.5 grams to 78.5 "grams bf metallic alumina pelgrain 3 mole of alkali metal fluotitanate (i. e. per 207.9 grams of NaaTiFs, or per 175.8 grams of LizTiFe, or per 240.1 grams of KaTiFs). The use of such proportions of reagents results in a complete utilization of the alkali metal fluotitanates and yields binary alloys containing from 53% to-95% of titanium, devoid of intermetallic compounds and suitable for the recovery of metallic titanium. (The theoretical amount of aluminum required by the above equation is 36.0 grams per gram-mole of alkali metal fiuotitanate.)

The more aluminum that is used (within the limits above described), the more rapid and complete the formation of the binary alloy becomes. Similarly, the more aluminum that is used, the lower the melting point of the regulus becomes and the tendency of the binary alloy to coalesce into larger globules becomes more pronounced. Thus, the more aluminum that is used (within the described limits), the easier the recovery of the desired alloy end-product becomes. The less aluminum that is used, the higher the melting point of the binary alloy formed becomes and the alloy tends to form finer, more dispersed metallic particles within the reaction product upon cooling. The recovery of the alloy becomes more difficult and the period required for the reaction to come to completion becomes progressively greater. However, the less aluminum that is used (within the prescribed limits), the lower the reagent costs become and the more economically the process of the present invention can be operated.

As a practical balance, I therefore prefer to use a quantity of aluminum suflicient to yield an alloy containing 60% to 70% of titanium. This requires the use of 56.5 grams to 68.0 grams of aluminum per gram-mole of alkali metal fluotitanate. However, this is by no means a critical range, since (as above described), the aluminum used may vary within the limits of 38.5 grams to 78.5 grams per gram-mole of alkali metal fluotitanate.

The temperatures at which this reaction is effected may vary quite widely. It is desirable to have at least one of the reagents (i. e. the aluminum) in a molten state, and preferably both the aluminum and the alkali metal fluotitanates should be in a molten state. Thus, the lower limit of temperature for this reaction is set by the melting point of aluminum, i. e. 660 C. Both reagents are molten in the range of 900-1100 C. The upper limit of temperature for this reaction is set by the boiling point of aluminum (1800 C.) and the melting point of titanium (1850 C.), as well as the excessive tendency of the alkali metal fluotitanates to sublime at temperatures above 1500 C. Thus, the temperature range for this reaction may be given as 660 C. to 1850 C.

In practice, I have found it desirable to mix the reagents and to heat the mixture in a crucible or reaction vessel of suitable construction, with agitation. until the contents of the reaction vessel attain an internal temperature of 1300 C. to 1500 C. A practical consideration is always the attack of the reagents on the refractory lining of the reaction vessel. As a rule, the higher the terminal temperature of the reaction mixture can be brought, the greater is the tendency of the binary alloy formed to coalesce into large globules and the easier the separation of the alloy from the concomitant salts becomes. Magnesia-lined crucibles are as a rule suitable for the effecting of the reaction of this invention since they are not excessively attacked at the indicated reaction temperatures,

separated by screening, washing or any other convenient means. The salts obtained as a residue of this separa tion, comprising a mixture of alkali metal fluoaluminate and aluminum fluoride, may be utilized in any desired manner. In my co-pending applications Serial No.5. 389,503 and 485,325, I describe a process for the conversion of this by-product salt mixture to alkali metal fiuo titanate required as a raw material in the process of the present invention, aluminum oxide being recovered as a lay-product.

Although the alkali metal fiuotitanates are known to form crystalline hydrates at lower temperatures, they are, of course, employed as anhydrous salts at the temperature ranges involved in the process of this invention. Since the aluminum is always employed in the molten state, it need not be comminuted prior to addition to the reaction mixture, but may be added as bar or pig to the crucible.

The titanium-aluminum alloys obtained above may now be treated with aqueous alkali solutions, preferably at advanced temperatures, to leach out the aluminum (as soluble alkali metal aluminate), and leave behind a relatively pure titanium metal. It is usually desirable to grind or otherwise comminute the titanium-aluminum alloy prior to the alkaline leach in order to obtain a most complete separation.

The leaching agents are preferably aqueous solutions of alkali metal hydroxides. These may be used in any convenient concentrations, preferably at temperatures above room temperature for periods sufiicient to dissolve substantially all of the aluminum. Refiuxing with 2% to 20% NaOH solution, employing 3 moles of NaOH per mole of aluminum to be extracted, for 6 to 12 hours, usually sutfices for a complete separation of the aluminum from the titanium. Solutions of alkali metal aluminates, preferably such as have Mao/M203 ratios in excess of 1.5 (M being an alkali metal), may also be used as leaching agents. Solutions of alkali metal carbonates and bicarbonates are also suitable leaching agents but are less suitable than the hydroxides and aluminates since they require higher temperatures and are considerably slower and less effective.

The leachate from this treatment comprises a solution of alkali metal aluminate. This by-product solution may be carbonated (e. g. with a COz-containing gas) to recover aluminum hydroxide and an alkali metal carbonate solution. If the Mao/A1203 ratio in the solution is favorable (i. e. in excess of 1.6), the alkali metal aluminatc leachate may be used in the Bayer process to dissolve an additional quantity of alumina from bauxite or a related ore, prior to treatment for recovery of pure aluminum hydroxide. Thus, all of the aluminum used in the process of this invention may ultimately be recovered and reused, either as an alkali metal fluoaluminate, aluminum fluoride or aluminum hydroxide. In my co-pending applications Serial Nos. 389,503, and 485,325, I describe the conversion of these by-products to alkali metal fluotitanate and electrolyte grade alumina.

The residual titanium metal powder usually is coated with a thin film of oxide which can be removed by washing with a solution containing 10% H280; and 1% HP in Water. The residual titanium powder assays 98.0%-99.5% Ti and contains less than 0.3% oxygen as TiOz. It is interesting to note that the tendency of the titanium to oxidize or react with atmospheric components is a major problem in the Kroll process and requires working in an atmosphere of argon gas. In the process of this invention, the titanium is protected from oxidation by the presence of a stronger oxygen acceptorthe aluminum-and by the surrounding melt of fiuotitanate and fluoaluminate salts.

The end product titanium powder may be compressed, sintered, fused, arc melted, cold worked, heated in vacuo at advanced temperatures, induction melted or otherwise compacted and consolidated for further metallurgical treatment. If the titanium powder is to be stored. this should be done under an inert solvent to prevent surface oxidation, especially if the powder is in a very fine state of subdivision.

in. Obvious improvements will occur to any person skilled in the art. All proportions given are parts by weight.

Example A magnesia-lined mullite crucible is charged with a mixture of 207.9 grams of powdered sodium fluotitanate (1 mole) and 60.0 grams of aluminum chips. The crucible is placed in an electric furnace and is heated, with stirring, until the contents are molten. The fusion is continued until the temperature of the reaction mixture has reached 1400 C.l500 C. The contents of the crucible are maintained for several minutes at this temperature, and are then allowed to cool slowly to room temperature. The solidified melt is broken into lumps and is ground into a coarse powder, from which globules of the hard titanium-aluminum alloy can be removed by screening and washing in running water. There is thus recovered 65.2 grams of an alloy assaying 65% Ti and 35% Al. This is equivalent to an 88.5% titanium recovery.

The alloy thus obtained is ground to a powder of 200 mesh fineness. 60.0 grams of the powdered alloy (containing 21.0 grams of aluminum (0.777 mole)) is added to 933 cc. of 10% aqueous NaOI-I solution (2.33 moles), and the mixture is boiled under reflux for ten hours. During this refluxing, hydrogen gas is evolved and is conducted ofi. The insoluble residue of titanium powder is filtered ofi, washed free of alkali, then washed free of oxide with a 10% H2SO41% HF solution, then washed with water and stored under an inert solvent until required. The yield of titanium powder, assaying 99% Ti, is 34.5 grams, representing an 88.4% recovery of titanium metal from the alloy.

Having described my invention, what I claim and desire to protect by Letters Patent is:

l. A process for the manufacture of titanium metal which comprises the steps of: (a) reacting an alkali metal fluotitanate with aluminum metal in quantity sufficient to form a titanium-aluminum binary alloy containing from 53% to 95% of titanium, (b) separating the said binary alloy from the concomitant salts formed during said reaction, selectively leaching the aluminum from said binary alloys with an aqueous solution of a member of the group consisting of the hydroxides, carbonates, bicarbonates andfaluminates of the alkali metals, leaving a residue of titanium metal.

2. The process of claim lwherein an alkali metal fluotitanate is reacted with aluminum in the proportions of 38.5 grams to 78.5 grams of aluminum per gram-mole of alkali metal fluotitanate. a

3. The process of claim 1 wherein an alkali metal fiuotitanate is reacted with aluminum in the proportions of 56.5 grams to 68.0 grams of aluminum per gram-mole of alkali metal fiuotitanate.

4. The process of claim 1 wherein. an alkali metal fluotitanate is reacted with aluminum in quantity sufiicient to form a binary titanium-aluminum alloy which does not contain any intermetallic compounds.

5. The process of claim 1 wherein a binary alloy of titanium and aluminum containing more than 53% of titanium is treated with an aqueous solution of a member of the group consisting of the hydroxides, carbonates, bicarbonates and aluminates of the alkali metals, which selectively dissolves the aluminum from said alloy and leaves a residue of titanium metal.

6. The process of claim 1 wherein a binary alloy of titanium and aluminum containing more than 53% of titanium is treated with an aqueous solution of sodium hydroxide, which selectively dissolves the aluminum from said alloy and leaves a residue of titanium metal.

7. The process of claim 1 wherein a binary alloy of titanium and aluminum containing more than 53% of titanium is treated with an aqueous solution of a sodium aluminate which selectively dissolves the aluminum from said alloy, and-leaves a residue of titanium metal.

8. The process of claim 1 wherein the reaction of the alkali metal fluotitanate and the aluminum is effected within a temperature range of 660 C. to 1850 C.

9. The process of claim. 1 wherein the reaction mixture of alkali metal fluotitanate and aluminum are heated to a final reaction temperature within the range of 1300 C. to 1500 C.

10. The process of claim 1 wherein the titanium-aluminum alloy obtained is comminuted prior to the selective extraction of the aluminum by leaching with an alkaline solution.

11. The process of claim 1 employing sodium fluotitanate.

12. The process of claim 1 employing lithium fluotitanate.

13. The process of claim 1 employing potassium fluotitanate.

' Journal of Metals, June 1952, page 612. Published by the A. I. M. E., New York, New York.

Claims (1)

1. A PROCESS FOR THE MANUFACTURE OF TITANIUM METAL WHICH COMPRISES THE STEPS OF: (A) REACTING AN ALKALI METAL FLUOTITANATE WITH ALUMINUM METAL IN QUANTITY SUFFICIENT T FORM A TITANIUM-ALUMINUM BINARY ALLOY CONTAINING FROM 53% TO 95% OF TITANIUM, (B) SEPARATING THE SAID BINARY ALLOY FROM THE CONCOMITANT SALTS FORMED DURING SAID REACTION, (C) SELECTIVELY LEACHING THE ALUMINUM FROMS SAID BINARY ALLOYS WITH AN AQUEOUS SOLUTION OF A MEMBER OF THE GROUP CONSISTING OF THE HYDROXIDES, CARBONATES, BICARBONATES AND ALUMINATES OF THE ALKALI METALS, LEAVING A RESIDUE OF TITANIUM METAL.