US3736132A - Method for producing refractory metals - Google Patents

Abstract

A PROCESS FOR THE MANUFACTURE OF TITANIUM FROM TITANIUM TETRACHLORIDE BY REDUCTION WITH SODIUM, IN WHICH A PARTIALLY REDUCED MATERIAL PRINCIPALLY CORRESPONDING TO NA2TICL4 IS CONTINUOUSLY FORMED, IS IMPROVED BY CONTINUOUSLY MIXING THE PARTIALLY REDUCED MATERIAL WITH SODIUM AT A TEMPERATURE BELOW ABOUT 200*C. SO AS TO FORM AN INTERMEDIATE MATERIAL CORRESPONDING TO AT LEAST 15% BY WEIGHT NA3TICL4, COMPACTING THE INTERMEDIATE MATERIAL AT A TEMPERATURE OF LESS THAN 100*C. TO FORM A CONTINUOUS ROD OF THE COMPOSITE MATERIAL WITHOUT SUBSTANTIAL FURTHER REDUCTION OF THE TITANIUM CHLORIDE CONTENT THEREOF AND CONTINUOUSLY HEATING THE ROD FORMED AT TEMTERATURES ABOUT 800*C. TO COMPLETE REDUCTION OF TITANIUM CHLORIDE COMPONENT THEREOF, TO EFFECT SINTERING OF THE RESULTING TITANIUM METAL, AND TTO SIMULTANEOUSLY MELT THE SALT BY-PRODUCT AND THEREBY FACILITATE SEPARATION AND REMOVAL OF THE SALT FROM THE ROD-SHAPED, SINTERED TITANIUM METAL PRODUCT.

Description

May 29, 1973 H, H, MQRSE ET AL 3,736,132

METHOD FOR PRODUCING REFRACTORY METALS Filed Dec. 17, 1971 PLL-00615?? ET AL United States Patent O 3,736,132 METHOD FOR PRODUCING REFRACTORY METALS Harold H. Morse, Cincinnati, and Cecil L. Easterday, deceased, by Dorothy E. Easterday, representative, Washington Court House, and Layne S. Plock, Geneva, Ohio, and Fred K. Morgan, Cold Springs, Ky., assignors to United States Steel Corporation, Pittsburgh, Pa.

Filed Dec. 17, 1971, Ser. No. 209,094 lnt. Cl. BZZE 1/00; C22b 53/00, 61/02 U.S. Cl. 75-200 7 Claims ABSTRACT F THE DISCLOSURE A process for the manufacture of titanium from titanium tetrachloride by reduction with sodium, in which a partially reduced material principally corresponding to NazTiCl.L is continuously formed, is improved by continuously mixing the partially reduced material with sodium at a temperature below about 200 C. so as to form an intermediate material corresponding to at least 15% by weight Na3TiCl4, compacting the intermediate material at a temperature of less than 100 C. to form a continuous rod of the composite material without substantial further reduction of the titanium chloride content thereof and continuously heating the rod formed at temperatures above 800 C. to complete reduction of the titanium chloride component thereof, to effect sintering of the resulting titanium metal, and to simultaneously melt the salt by-product and thereby facilitate separation and removal of the salt from the rod-shaped, sintered titanium metal product.

BACKGROUND OF THE INVENTION Quin, U.S. Pat. 2,827,371, describes a process for manufacturing titanium by reacting titanium tetrachloride with metallic sodium at a temperature between about 200 C. and the melting point of sodium chloride in an agitated solid bed. There are numerous problems encountered with this process. The reduction of the titanium chloride with the sodium is a highly exothermic reaction and it is therefore necessary to rapidly remove the heat produced in order to maintain the desired temperature. In many instances, hot spots in the reaction mixture are formed resulting in fused non-crystalline particles of the metal in the final product. Additionally, since the reduction occurs rapidly, there is little opportunity for crystal growth. Finally. it is necessary to sinter the final product in order to handle the titanium in air.

An improved method of obtaining metallic titanium sponge and/or crystals is described in Schott et al., U.S. Pat. 2.950.963. The titanium chloride is continuously partially reduced with a controlled deficiency of sodium and thereafter, in a batch operation, is brought into contact with additional alkali metal, suicient for complete reduction, and the batch heated for completion of the reduction and formation of the metal. This process is a hatch process and is not adapted to the manufacture of titanium by a continuous process because the final reduction is so exothermic that the reaction mixture quickly loses processability. The mixture fuses and must thereafter be broken up to facilitate further handling.

Accordingly, it is a principal object of this invention to provide a method of manufacturing titanium continuously which eliminates the dificulties encountered in prior art methods, particularly the fusion of the reaction mixture. Other objects will become apparent to those skilled in the art from the following detailed description and drawing, in which the sole gure is a flow sheet of the process of the invention.

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SUMMARY OF THE INVENTION This invention relates to the manufacture of titanium or zirconium. More particularly, the invention relates to an improved process for continuously producing titanium or zirconium in which a partially reduced material corresponding to a metal tetrahalide-sodium mixture in which about 45% to 55% of the stoichiometric reduction of the metal tetrahalide to the metal has occurred is continuously mixed with an alkali metal at a temperature between 10D-200 C. to form an intermediate material corresponding to a metal tetrahalide-sodium mixture in which about 55% to 95% of the stoichiometric reduction to the metal has occurred, compacting the intermediate material at a temperature of less than C. to form a continuous rod of the composite material without substantial further reduction of the metal halide content thereof, and continuously heating the rod thus formed at a temperature above 800 C. to complete reduction of the metal halide, to effect sintering of the metal and to simultaneously melt the salt by-product and thereby facilitate separation and removal of the salt from the sintered rod. The process of this invention provides a' continuous process in which the reaction mixture has good processahility at all stages of the process and in which the intermediate material can be compacted into the continuous rod without particles sloughing off or the application of undue pressures or the use of temperatures which can cause alloying of the highly reactive metal to any of the process equipment.

The invention also provides a non-compacted, nonaking intermediate material which can be compacted and extruded into a unique self-supporting, continuous rod without using undue pressure and without the probability of sloughing off of particles from the reaction mass.

The unique self-supporting continuous rod, both sintered and non-sintered is another feature of this invention. The continuous rod provides a means of achieving a continuous reduction process and thereby convert the semicontinuous, semi-batch process of the prior art into a large scale, continuous commercial process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS While the invention is described with particular reference to the manufacture of titanium from titanium halide, those skilled in the art will recognize that the described process is similarly applicable to the production of zirconium by the controlled partial reduction of zirconium halide.

ln the first step of the preferred embodiment of the invention, a partially reduced material, a TiCl4-Na mixture in which about 45% to 55% of the stoichiometric reduction to the metal has occurred, is continuously mixed with sodium. The partially reduced material is obtained in any suitable manner and preferably as described in the first step of the aforementioned Schott et al patent.

In the Schott et al. procedure, titanium tetrachloride is reduced with an insuicient amount of sodium for stoichiometric reduction to the metal. Usually, hte sodium is employed at about 45% to 55%, preferably about 50%, of the theoretical amount required to completely convert the titanium tetrachloride to titanium. The average composition of the partially reduced material principally corresponds to NagTiCh, i.e., the composition, on the average, is equivalent to Na2TiCl4 (TiCl2:2NaCl). Such sodium titanium chloride complex, which can, of course, be admixed with varying proportions of unreacted TiCl4 and varying proportions of other partially reduced or totally reduced materials, will hereinafter be referred ot as the reducer product because the reaction is usually accomplished in a reactor commonly called the reducer,

The reducer product and sodium are mixed and partially reacted in an inert atsmosphere, such as argon, at a temperature between 100-200 C., preferably about 130-160 C., to insure that complete reduction of the titanium chloride content of the Na2TiCl4 to titanium does not occur. At temperatures below about 100 C., either no reduction occurs or the reduction is so slow as to be impractical. At temperatures above about 200 C., it is too dicult to practically control the degree of reaction.

The sodium employed in this step, hereinafter referred to as the mixing step, is employed in an amount sucient to complete stoichiometric reduction of the reducer product to titanium metal and preferably a slight excess over the stoichiometric amount. Thus, the amount of sodium employed is generally about 50% of the theoretical stoichiometric amount necessary to reduce the original amount of titanium tetrachloride to titanium and preferably, slightly in excess of 50%.

The mixing and further reducing is continued in the mixer until an intermediate product (mixer product) corresponding to a TiCl4-Na mixture in which about 55% to 95%, preferably about 75% of the stoichiometric reduction of the initial TiCl4 has occurred. At about 75% stoichiometric reduction, the reacted portion of the mass has u an average composition principally corresponding to NasTiCl., and is in the presence of the remaining sodium for complete reduction. As the composition of the mixer product approaches 100% Na3TiCl4, the material approaches its lightest color and becomes extremely fluffy, with a high angle of repose, and has the appearance and consistency of dirty wet snow. Additionally, as the concentration of the Na3TiCl4 complex approaches 100%, compaction, the next step in the preferred process, can be performed at low pressures and without particles of the mixer product sloughing off.

The reaction of the additional sodium over and above that required to form the Na3TiCl4 is very slow at the reaction remperature employed in the mixing step. As a result, complete reduction to the metal is avoided by cooling the mixer product to 100 C. or lower when the desired amount of complex has been formed without a significant amount of the complex being converted to titanium.

It is necessary to employ, as the mixer utilized herein, a. mixing device which does not put any appreciable force on the mix as would be done in a paddle or dough mixer because the partially reduced material would pack and eventually jam the apparatus. Thus, any of the known rotating tumbling type mixers can be employed. Mixers containing mixing blades or other mechanical parts which move relative to one another in which the reactants could be subjected to high unit pressures should be avoided.

While it is possible to form the mixer product in a single step with some metal halides, such a procedure is generally impractical. The two-step procedure of the present process allows the heat of reaction to be controlled and does not result in the existence of hot spots in the reaction mixture.

In the next step of the preferred embodiment of the invention, the mixer product, cooled to less than 100 C., is compacted into a continuous rod. Incremental charges of the granular intermediate material are continuously compacted into a die and each charge is compacted against and into engagement with a prior compacted charge to form the continuous bar or rod. The compacting is preferably accomplished under an inert atmosphere such as argon, and ambient temperature is generally ernployed. At this temperature, no substantial amount of further reduction of the titanium chloride content of the mixer product by the non-reacted sodium in the material occurs.

By regulating the degree of reaction in the mixer product to produce principally Na3TiCl4, the compacting can be accomplished without employing excessive pressure. lf

the average composition of the mixer product does not correspond to at least 15 weight percent Na3TiCl4, it is necessary to use pressure in excess of 4000 p.s.i. and even with such pressures, a substantial amount of the material will not compact into a continuous rod or will flake off the rod formed.

1f the temperature is not below 100 C., further reduction will occur resulting in the production of titanium in a highly reactive state while still in the compactor which may alloy with the steel of the apparatus. As a result of precisely regulating the temperature and composition of the mixer product, no more than about 4000 p.s.i., and preferably about 1000 to 3000 p.s.i. is needed to compact the granular mixer product into the continuous rod.

Any appropriate compacting device known in the art could be employed in this step such as, for example, the compacting devices described in }U.S. Pats. 2,651,952, 2,656,743 and 3,014,238.

The continuous rod thus produced is unique, and can only be produced when the foregoing procedures are employed. lt is self-supporting, and can be fed wherever desired for subsequent processing. It is relatively unreactive and stable under aimbient conditions.

The compacted rod or bar is thereafter heated to a temperature of at least about 800 C. and preferably about 900-1500 C. The heating accomplishes three things: the remaining titanium chloride is reduced to titanium metal; the metallic sponge formed is sintered; and simultaneously, the salt (NaCl) by-product is melted which facilitates separation and removal of the salt from the rod-shaped, sintered titanium metal product. Any temperature above the melting point of salt will serve to complete the reaction and provide some sintering of the bar. Since salt can be removed during the heating, it is desirable to ha-ve the temperature as high as is practical considering the equipment and materials of construction in order to remove the maximum amount of salt and to secure the densest sintering.

The heating step is preferably accomplished under an inert atmosphere such as argon and the rod is maintained at the sintering temperature for about 1-10 minutes or more, preferably about 3-5 minutes. When vacuum conditions are employed, the salt left in the titanium can be reduced to less than 0.1% and subsequent purification can, if desired, be omitted. However, due to the problems involved in a vacuum operation at these temperatures, it may be preferable to operate under an inert atmosphere, and at or slightly above atmospheric pressure and to remove the remaining salt by a further purification procedure. In general, at least and usually 85% of the total salt produced is separated during this step.

The sintered rod so produced is unique-it is very flexible when hot and, with proper guides, can be fed wherever desired for subsequent processing. The rodshaped, sintered titanium metal product generally contains at least about 50% titanium, usually at least 60% and the remainder is salt.

The titanium thus produced is sufficiently inert so that when cooled, it can easily be handled and does not react with air or water. Any salt remaining with the titanium can be further removed by any of the several continuous processes known to those skilled in the art such as leaching, drip melting, plasma arc melting, and the like.

As an example of the preferred process of this invention, the figure shows the sequence of steps of the process. Sodium via line l, at a rate of 1210 parts per hour, and titanium tetrachloride via line 2, at the rate of 5000 parts per hour, are continuously introduced into a stirred reducer 3 maintained under an argon blanket and controlled at a temperature of about -175 C. The resulting partially reduced material (reducer product), which is substantially all Na2TiCl4 is withdrawn via line 4 from the reducer at a rate of 6210 parts per hour and introduced into a mixer S. Additional sodium is introduced via line 6 into mixer 5 at a rate of 1210 parts per hour. The particular mixer employed is described in copending application Ser. No. 209,104, entitled Mixer For Preparing An Easily Compactable Material, filed of e-ven date herewith, which is hereby incorporated by reference.

The temperature within mixer S is controlled at about 150 C. at the reaction zone thereof and decreased to about 90 C. at the outlet. The mixer product is continuously withdrawn from the apparatus via line 7 at the rate of 7420 parts per hour. The mixer product thus formed contains about 92% Na3TiCl4 and about 8% free sodium. The mixer product is compacted at the rate of 7420 parts per hour at room temperature in compactor 8. The material enters a compacting section and is subjected to a pressure of 2000 p.s.i. by means of a hydraulically operated ram. Continuous self-supporting rods of the compacted mixer product are prepared by the interlocking action of pressing one compact against the preceding compact due to the irregular face of the piston head.

The resulting compacted rod is continuously withdrawn from compactor 8 via conduit 9 and introduced into a tube 10 heated to 1100 C. by an induction coil at the rate of 7420 parts per hour. Tube 10 can also be heated by resistance heat, or by a gas tired furnace, and the like. The rod is maintained in sintering tube 10 for about 3 minutes when operating at atmospheric pressure. The tube 10 has provision 11 for drainage of liquid salt and 5210 parts per hour of sodium chloride, i.e., about 85% of the salt produced per hour, is removed. The sintered rod is removed from the hot tube 10 via conduit 12 at a rate of 2210 parts per hour. The thus formed sintered titanium metal rod contains about 57% titanium and about 43% salt.

The rm, sintered titanium sponge is continuously fed vertically downward into a vertical tube furnace 13 and the lower end melted. The titanium metal, free from salt impurity, is thereafter recovered at 14.

An atmosphere of argon is employed throughout the preparation of the metal.

It will be recognized by those skilled in the art that various changes and modifications can be made in the process and products of this invention without departing from the spirit and the scope thereof. For example, any of the multivalent metal halides and reducing agents disclosed in the aforementioned Schott et al. patent can also be used in the process of this invention. The various ernbodiments of the invention herein disclosed were intended to further illustrate the invention but not to limit it. All temperatures have been stated in degrees centigrade and all parts and percentages by weight unless otherwise specied.

We claim:

1. In a process for the manufacture of titanium or zirconium from titanium tetrachloride or zirconium tetrahalide by reduction with an alkali metal reducing agent in which a partially reduced material corresponding to a mixture of the metal tetrahalide and alkali metal in which about 45%55% of the total stoichiometric reduction of the metal tetrahalide to the metal has occurred is continuously formed, the improvement which comprises:

(a) continuously mixing said partially reduced material with an alkali metal at a temperature between 100-200 C. with regulating the feed rate of the respective reactants such that an intermediate material corresponding to a mixture of the metal tetrahalide and alkali metal in which about 55%-95% of the total stoichiometric reduction of the metal tetrahalide to the metal has occurred is formed;

(b) compacting the intermediate material thus formed at a temperature below C. to form a eonunuous rod of the intermediate material without substantial further reduction of the metal halide content thereof; and

(c) continuously heating the rod at a temperature above 800 C. to complete reduction of the metal halide component thereof, to effect sintering of the resulting metal, and to simultaneously melt the salt by-product and thereby facilitate separation and removal of the salt from the rod-shaped, sintered metal product.

2. The process of claim 1 wherein the tetrahalide is tetrachloride and the alkali metal is sodium.

3. In a process for the manufacture of titanium from titanium tetrahalide by reduction with an alkali metal reducing agent in which a partially reduced material corresponding to a mixture of the metal tetrahalide and alkali metal in which about 45%-55% of the total stoichiometric reduction of the metal tetrahalide to the metal has occurred is continuously formed, the improvement which comprises:

(a) continuously mixing said partially reduced material with an alkali metal at a temperature between 100-200 C. while regulating the feed rate of the respective reactants such that an intermediate material corresponding to a mixture of the metal tetrahalide and alkali metal in which about 55%-95% of the total stoichiometric reduction of the metal tetrahalide to the metal has occurred is formed;

(b) compacting the intermediate material thus formed at a temperature below 100 C. to form a continuous rod of the intermediate material Without substantial further reduction of the metal halide content thereof; and

(c) continuously heating the rod at a temperature above 800 C. to complete reduction of the metal halide component thereof, to effect sintering of the resulting metal, and to simultaneously melt the salt by-product and thereby facilitate separation and removal of the salt from the rod-shaped, sintered metal product.

4. The process of claim 3 wherein the titanium tetrahalide is TiCl4 and the alkali metal is sodium.

5. The process of claim 4 wherein the temperature in step (a) is about -160 C.

6. The process of claim S wherein the feed rates of the respective reactants in step (a) are regulated such that an intermediate material is formed corresponding to a titanium tetrachloride-sodium mixture in which about 75% of the total stoichiometric reduction of the titanium tetrachloride to titanium metal has occurred and wherein the intermediate material is compacted in step (b) at a maximum pressure of 4000 p.s.i.

7. The process of claim 6 wherein the rod in step (c) is heated to about 900-1500 C.

References Cited UNITED STATES PATENTS 2,824,799 2/ 1958 Hansley et al. 75-223 2,880,084 3/1959 Schott et al. 75--84.5 2,950,963 8/ 1960 Schott et al. 75-84.5

CARL D. QUARFORTH, Primary Examiner B. HUNT, Assistant Examiner v.UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3 f 736 :132 Dated May 29 1973 g Harold H. Morse et al. lnyentods) a It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading'ztovthe printed specification, lines 7 and 8, "assignors to lUnited States Steel Corporation, Pittsburgh, Pa." should read -eassignors by direct and mesne assignments l/.Z interest toNational Distillers and Chemical Corporation, New YArk, N. YI.-', a corporation of Va., and l/Z interest to United Statesl Steel Corporation, Pittsburgh, Pa. a corporation of Del.

Signedand sealed this 27th day of August 1974.

(SEAL) Attest: MCCOY M. GIBSON, JR. C.MARSHALL DANN Attesting Officier` Commissioner of Patents FORM Po'wso (1o-G9) UscoMM-oc ooa1e'pe9 n UAS. GOVERNMENT PRINTING OFYICE I 0 366-33.

vUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,736,132 Dated May 29, 1973 i Harold H. Morse et al. Inventods) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as show-n below:

In the heading tothe printed specification, lines 7 and 8, "assignors to United States Steel Corporation, Pittsburgh, Pa." should read assignors by direct and mesne assignments l/Z interest toational Distillers and Chemical Corporation, New YArk, N.-

a corporation of Va., and l/Z interest to United States Steel Corporation, Pittsburgh, Pa. a corporation of Del.

Signedand sealedA this 27th day of August 1974.

(SEAL) Attest: y

MCCOY M. GIBSON, JR. omARsHALL DANN Attesting Officer Commissioner of Patents

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