US2273834A - Powdered titanium metal - Google Patents

Description

Patented Feb. 24, 1942 POWDERED TITANIUM METAL George F. Comstock and Viatcheslav V. Efimofi, Niagara Falls, N. Y., assig'nors to The Titanium Alloy Manufacturing Company, New York, N. Y., a corporation of Maine No Drawing.

Application December 7, 1940,

Serial No. 369,128

Claims.

This invention relates to a new form of titanium metal and the method of producing the same. More particularly, it relates to a method of producing powdered titanium metal.

Metallic titanium is most conveniently produced by the well known method of reducing titanium tetrachloride with sodium in a closed vessel or bomb designed to resist considerable heat and pressure. The metal so produced is more or less completely fused, and when it is desired to use it in the form of powder, the fused lumps are found to be tough and very diflicult to crush. Most of the powdered metal heretofore available has been collected merely by screening the fines, without crushing, from the lumps of miscellaneous sizes that constitute the product of this method of manufacture. The difficulties encountered in crushing the coarser lumps of titanium, and the relatively small yield obtained from the fines, has caused workers in the art to seek for improved methods of obtaining powdered titanium metal. Although it has been suggested to prepare powdered titanium metal by reduction of titanium dioxide with calcium, the difficulty of the method and expense of the calcium metal used make it commercially undesirable. Furthermore, the particles formed by this method, and also the fine particles formed along with the fused lumps in reacting titanium tetrachloride with sodium, tend to become coated with a film of oxide, thus reducing the effectiveness of the titanium metal. The result is that this method employing calcium metal, as far as is llrnown, has been used only on a laboratory see. c.

Another method hitherto commercially in use for making powdered titanium metal has been by reduction of titanium dioxide with calcium hydride. The principal difiiculty with this method is that the product resulting therefrom tends to evolve gases under certain conditions, probably from occluded or combined hydrogen. This renders the product completely unuseable for some purposes.

It is therefore an object of this invention to prepare powdered titanium metal with a minimum content of titanium dioxide. It is another object to use sodium as the raw material for making powdered titanium metal instead of the more expensive calcium. to prepare powdered titanium metal free of 0ccluded gases including hydrogen. Other objects will appear hereinafter.

These objects are accomplished by reacting sodium with titanium tetrachloride in a closed It is a further object vessel in the presence of a small amount of a titanium compound containing oxygen or nitrogen, such as titanium dioxide or titanium cyanonitride, as an embrittling agent. The brittle metal thus formed is then easily crushed to the form of a powder.

The amount of titanium dioxide required is from about 2 to 10% of the sodium used, or preferably around 5.5%. The dioxide should be as pure as possible, and calcined-so as to be free from any trace of moisture. The brittle titanium metal produced by this process is not contaminated by the presence of more than 0.2 or 0.3% of any of the common impurities such as iron, silicon, carbon or aluminum.

An example of a reaction made in this way so as to produce brittle titanium metal that could be crushed readily to a powder is described herewith. Nine pounds of metallic sodium was placed in a suitable reaction vessel with 8 ounces of pure calcined titanium dioxide, and 4.5 liters of titanium tetrachloride was poured in just before closing the vessel. After heating the closed vessel ten minutes the outside temperature at the top reached 150 F. and the reaction occurred. Heating was continued 20 minutes longer, until the outside top temperature rose to 200 F. After cooling the vessel, the product of the reaction was removed and leached with water. The metal remaining undissolved was dried carefully and found to weigh 4 pounds 5 ounces, representing a recovery of titanium, from both dioxide and tetrachloride of 91%, assuming that the dioxide was completely reduced, or of 87.5% assuming that the dioxide was not reduced but merely dissolved as such in the metal formed from the tetrachloride. Probably the dioxide was only slightly reduced with the formation of sodium oxide, and was chiefly dissolved in the metal as titanium monoxide.

The titanium metal lumps produced by this reaction could be broken very easily with a hammer, and after crushing between rolls so as to pass through a mesh screen the powder was found to contain 94.72% titanium and 0.07% iron, with most of the balance being oxygen, probably in the form of titanium monoxide.

When titanium cyanonitride is used in this process, in place of titanium dioxide, for making brittle titanium metal, the product is contaminated to some extent by carbon and nitrogen, as well as oxide. though not appreciably by iron, silicon, or aluminum. The titanium cyanonitride used may be the product described in U. S. Patent No. 2,098,567, and contains generally about 80% titanium, 3%..carbon, 7% nitrogen and 5% oxygen. This material contains some free titanium, so that an improved recovery of powdered titanium metal is obtained.

, iron, 1% zirconium, and about 0.2% each of silicon, aluminum, vanadium and nickel. The closed vessel was heated 35 minutes to complete the reaction. After the vessel had cooled the product of the reaction was removed and leached with water. The metal recovered weighed 6 pounds 2 ounces after drying, and the particles were brittle. The material was crushed as .before. A sample prepared from the coarser lumps contained 0.84% nitrogen and 0.52% carbon, and the finer portions of the product were still less pure. Thus the improved yield through the use of titanium cyanonitride instead of titanium dioxide as the embrittling agent is obtained only at the expense of the purity of the product. If, however, a smaller improvement in yield is sufiicient, the addition of titanium cyanonitride may be decreased, with corresponding reduction in contamination by carbon, but without losing the embrittling eifect. For instance, with the use of only 1.5 pounds of titanium cyanonitride to 9 pounds of sodium, the titanium metal produced was sufliciently brittle to be readily crushed, and the yield was 5 pounds 5 ounces.

It will be observed that by following the present method, the powdered titanium metal is not formed directly. As the material comes from the closed reaction vessel or bomb it is in lump form. The lumps may be coated with an oxide film, but the particles formed by crushing these lumps are for the most part not coated with oxide, or at least are not coated to nearly the extent of the coating which would form on powdered metal at the high temperatures encountered in the closed reaction vessel. Thus the rather paradoxical result is secured that the addition of titanium dioxide results in either a lower oxide content of the product or renders the oxide present less harmful, because dissolved in the material and not present as a surface coating.

Obviously this invention is not limited to the use of the specific titanium compounds mentioned, but can also be practiced by using any oxide or nitride of titanium as the source of the embrittling agent. Oxides or nitrides of zirconium, vanadium, or other elements could also be used in addition to or in place of the corresponding titanium compounds, where small amounts of these metals are desired in the final product.

As many variations are possible within the scope of this invention, it is not intended to be limited except as defined by the appended claims.

We claim:

1. A method of preparing powdered titanium metal comprising heating titanium tetrachloride with sodium in a closed vessel in the presence of a minor quantity of a material taken from the class consisting of titanium dioxide, titanium nitride and titanium cyanonitride, and crushing the resulting product to the form of a powder.

2. A method of preparing powdered titanium metal comprising heating titanium tetrachloride with sodium in a closed vessel in the presence of a minor quantity of titanium dioxide, and crushing the resulting product to the form of a powder.

3. A method of preparing powdered titanium metal comprising heating titanium tetrachloride with sodium in a closed vessel in the presence of 2 to 10% of calcined titanium dioxide based on the weight of the sodium, and crushing the resulting product to the form of a powder.

4. A method of preparing powdered titanium metal comprising heating titanium tetrachloride with sodium in a closed vessel in the presence of a minor quantity of titanium cyanonitride, and crushing the resulting product to the form of a powder. 7

5. A method of preparing powdered titanium metal comprising heating titanium tetrachloride with sodium in a closed vessel in the presence