US2800404A

US2800404A - Method of producing titanium alloys in powder form

Info

Publication number: US2800404A
Application number: US528536A
Authority: US
Inventors: Douglas W Rostron; Harold A Timm
Original assignee: Dominion Magnesium Ltd
Current assignee: Dominion Magnesium Ltd
Priority date: 1955-08-15
Filing date: 1955-08-15
Publication date: 1957-07-23
Anticipated expiration: 1974-07-23

Description

United States Patent METHOD OF PRODUCING TITANIUM ALLOYS IN POWDER FORM Douglas W. Rostron, Haley, Ontario, and Harold A. Timm, Westrneath, Ontario, Canada, assignors to Dominion Magnesium Limited, Toronto, Ontario, Canada No Drawing. Application August 15, 1955, Serial No. 528,536

9 Claims. (Cl. 75-.5)

This invention relates to the production of high purity titanium alloys in powder form directly from the oxide of titanium.

The present invention provides a direct method for the simultaneous reduction of titanium oxide and the alloying of the metal so formed with another metal or metals, which latter may itself also be reduced from its oxide or chloride during the operation. Without attaining the melting point of the desired alloy and with at least one of the meals remaining in the solid state the metals alloy by diffusion with one another and are recovered in the form of powder. These prealloyed powders can be melted much more readily and cast into homogeneous products than can mechanical mixtures of the individual metals which constitute the alloy powder. By this direct reduction and alloying method alloy powders containing titanium and one or more other metals are produced with greater ease and economy than by melting and alloying the individual metals.

In accordance with the invention an oxide of titanium is mixed with at least one other metal or an oxide or chloride thereof, a reducing agent and a chloride of the reducing agents. The mixture is heated at a temperature below the fusion point of the alloy to be formed but above the melting point of the reducing agent, in an inert atmosphere to reduce the titanium oxide and the oxide or chloride of the metal to be alloyed, if such is used rather than the metal per se, and cause the metals to diffuse one within the other to form an alloy of such metals within the reaction mass.

In proceeding from titanium dioxide the method requires reduction in two stages. In the first stage magnesium in the form of minus 4 mesh particles is the reducing agent which is used in an amount at least equal to 100 of the theoretical required to reduce the titanium oxide and alloying addition to at least 90% metal. Magnesium chloride in an amount of at least 40% by weight of the titanium dioxide plus oxides of alloying elements present is added to the mixture as a fiux. This reaction is highly exothermic and the flux insures control of the reaction rate and peak temperatures during the reaction. This prevents formation of insoluble impurities such as titanates. The reaction mass is cooled, broken up and leached with dilute hydrochloric acid to remove magnesium oxide, magnesium chloride and many unreacted magnesium.

This primary reaction product is mixed with alloying additions, minus 4 mesh calcium particles in an amount at least 100% in excess of the stoichiometric requirement and calcium chloride as a flux in an amount of 10 to 150% by weight of the titanium oxide plus oxides of alloying elements added. The product is then leached as in the first stage to free the alloy powder from the reac tion by-products.

In each stage the reaction mixture is placed in a closed reaction vessel, which is evacuated and filled with an inert atmosphere of argon or the like and such atmosphere is maintained throughout the heating operation. In the first stage the mixture is heated at not less than 1000 C. to reduce the titanium oxide and alloying additions to at least metal. In the second stage the mixture is heated to at least 1000 C. for a period of at least three hours after the reaction has been initiated to insure complete reduction and alloying.

It is essential that the reaction products formed, during the reacting operation, be readily removable from the mass by leaching in order that the alloy be recovered in the desired powder form. This is insured by use of the oxides and chlorides as stated and more fully described hereafter and no undesirable elements are introduced. When the reducing and alloying reactions are complete the mass is cooled. The dispersal of the soluble reaction products, including any unoxidized reducing agent and flux, within the mass leaves the cooled reaction product readily broken up for leaching. Dilute hydrochloric acid is used as the solvent.

Aluminum and tin stabilize titanium in the alpha phase. Iron, manganese, chromium, molybdenum and vanadium stabilize titanium in the beta phase.

Whether the alloying addition is made as elemental metal, oxide or chloride, will depend on such factors as purity available, particle size and stability. Where metals are available in high purity powder form such as aluminum, iron and tin, they may be added as such. Adding alloying additions in the form of solid chlorides is preferred, since they introduce no oxygen and facilitate leaching. Where chloride additions are used, they may be substituted for at least part of the flux addition. When the alloying addition is not readily available in high purity metal powder form, or as a stable chloride, an oxide is used. The form of the alloying element selected must be free of impurity elements other than oxygen, hydrogen and chlorine, so as to minimize any impurity contamination of the final alloy from this source. Elements such as oxygen, hydrogen and chlorine can be tolerated, as they are converted to a form during reaction that is readily separated from the alloy powder in subsequent processing.

Alloying additions are preferably introduced in the second reduction stage although when a high percentage of elements like vanadium and chromium are added as oxides that are difficult to reduce, it is best to make at least part of the addition in the primary stage to insure complete reduction and a pure alloy powder. Alloying in the second stage reduces the tendency to form titanates because of lower reaction temperatures and where compounds are used the heat generated by the reduction serves as a booster to effect complete reduction.

This method of direct reduction and alloying makes it possible to produce alloys, having adequate physical and mechanical properties using alloying additions which contain proportions of oxygen and like impurities which cannot be tolerated in the usual melting and alloying methods.

Because of the diffusion of the alloying metal into the titanium, during the direct reduction and alloying, the addition metal is more uniformly dispersed than when the metals are alloyed during melting by the usual methods.

The diffusion of the alloying metal takes place while the titanium is in the solid phase. When the reaction mass is leached the alloy remains in its finely divided form which is directly available for use by powder metallurgy methods.

The following specific examples illustrate the method:

1. Alloying chromium with titanium.--A titanium oxide product containing 93% titanium metal was mixed with 0.7 to 9.5% of its weight of chromic oxide, minus 4 mesh calcium particles to in excess of the stoichiometric requirement and 10 to 150% by weight of the titanium oxide product plus chromic oxide of calcium chloride. The reactor containing this mixture was heated Ultimate tensile-" ..p. s. i.-- 137,000

0.2% proof stress p. s. i. 126,200 Elongation percent 23.5 Reduction in area do 57 2. Alloying manganese with titanium.A titanium X- ide product containing 93% titanium metal was mixed with 1.0 to 21.4% of its weight of manganese chloride, minus 4 mesh calcium particles 100 to 150% in excess of the stoichiometric requirements and to 150% by weight of the titanium oxide product plus managanesc chloride of calcium chloride flux. The charge was heated in a reduction vessel as described in Example 1 and the product leached in the same manner.

Aluminum may be incorporated in this alloy by adding aluminum powder to the initial charge in any desired amount. The preferred proportions are 0.9 to 7.5% by weight of the titanium oxide product.

3. Alloying aluminum and vanadium with titanium.- A titanium oxide product containing 93% titanium metal was mixed with 0.9 to 10% of its weight of vanadium pentoxide together with calcium reducing agent and calcium chloride flux as in the previous examples. The reaction vessel was heated at 1125 C. and the heating continued until the reduction and alloying were complete. The reaction mass was then cooled and leached as in the previous examples.

Aluminum may be incorporated in this alloy by adding aluminum powder to the initial charge in any desired amount.

4. Alloying tin with titanium.A titanium oxide prod uct containing 93% titanium metal was mixed with 0.9 to 3.75% of its weight of tin powder together with calcium reducing agent and calcium chloride flux as in the preceding examples. The reaction vessel was heated at 1000 C. until the reaction was complete. The cooled product was then leached with dilute hydrochloric acid to free the alloy powder.

Aluminum may be incorporated in this alloy by adding aluminum powder to the initial charge.

5. Alloying chromium with titanium.-A titanium oxide product containing 63% titanium metal was mixed with 0.4 to 6.1% of its Weight of chromic oxide, minus 4 mesh magnesium particles in an amount 25% in excess of the theoretical and magnesium chloride in amount equal to 50% by weigh of the titanium oxide product plus chromic oxide. The charged reaction vessel was heated at 1000 C. for four hours to complete the reaction. The cooled reaction product was leached with dilute hydro chloric acid to free the alloy powder. This primary prodnot is used in the second stage reaction as described in the previous examples.

Alloys produced by the method described have physical and mechanical properties superior to those of the same alloys produced by known methods.

This application is a continuation-in-part of application S. N. 439,874 filed June 28, 1954, now abandoned.

What is claimed is:

1. A method of producing titanium alloys which comprises forming a mixture of titanium oxide containing not less than 90% metal, a'n alloying addition being at least one of a group consisting of a titanium phase stabi'lizing metal, its chloride and its oxide, minus 4 mesh calcium particles in an amount 100% in excess of the stoichiometric requirement and calcium chloride 10 to 150% by weight of the titanium oxide plus oxide of alloying addition, heating the mixture in an inert atmosphere at a temperature not substantially less than 1000 C. to effect reduction and alloying of the metals, leaching the reaction mass with dilute hydrochloric acid and separating the titanium alloy powder.

2. A method of producing titanium alloys which comprises forming a mixture of titanium oxide containing not less than titanium metal, 0.7 to 9.5% of its weight of chromic oxide, minus 4 mesh calcium particles at least by weight in excess of the stoichiometric and calcium chloride 10 to by weight of the titanium oxide plus chromic oxide, heating the mixture in an atmosphere at a temperature not substantially less than 1000 C. to eflect reduction of the oxides and alloying of the metals, leaching the reaction mass with dilute hydrochloric acid and separating the alloy powder.

3. The method defined in claim 2 wherein 0.7 to 4.2% by weight of the titanium oxide of molybdic oxide is incorporated in the charge. I

4. A method of producing titanium alloys which comprises forming a mixture of titanium oxide containing not less than 90% titanium metal, 1.0 to 21.4% of its weight of manganese chloride, minus 4 mesh calcium particles at least 100% by weight in excess of the stoichiometric and calcium chloride 10 to 150% by weight of the titanium oxide plus manganese chloride, heating the mixture in an inert atmosphere at a temperature not substantially less than 1000 C. to eifect reduction of the titanium oxide and the manganese chloride and alloying of the metals, leaching the reaction mass with dilute hydrochloric acid and separating the alloy powder.

5. A method of producing titanium alloys which comprises forming a mixture of titanium oxide containing not less than 90% titanium metal, 0.9 to 3.75% of its weight of tin in finely divided forrn, minus 4 mesh calcium particles at least 100% by weight in excess of the stoichiometric and calcium chloride 10 to 150% by weight of the titanium oxide, heating the mixture in an inert atmosphere at a temperature not substantially less than 1000 C. to efiectreduction of the titanium oxide and diffusion of the tin in the titanium, leaching the reaction mass with dilute hydrochloric acid and separating the alloy powder.

6. A method of producing titanium alloys which comprises forming a mixture of titanium oxide containing not less than 90% titanium metal, 0.9 to 7.5% of its weight of aluminum in finely divided form, minus 4 mesh calcium particles at least 100% by weight in excess of the stoichiometric and calcium chloride 10 to 150% by weight of 'the titanium oxide, heating the mixture in an inert atmosphere at a temperature not substantially less than 1000' C. to effect reduction of the titanium oxide and diffusion of the aluminum in the titanium, leaching the reaction 'mass with dilute hydrochloric acid and separating the alloy powder.

7. A method of producing titanium alloys which com prises forming a mixture of titanium oxide containing not less than 90% titanium metal, 0.9 to 10% of its weight of vanadium pentoxide, minus 4 mesh calcium particles at least 100% by weight in excess of the stoichiometric and calcium chloride 10 to 150% by weight of the titanium oxide plus vanadium oxide, heating the mix ture in an inert atmosphere at a temperature not substantially less than 1000 C. to effect reduction of the titanium oxide and vanadium oxide and alloying of the metals, leaching the reaction mass with dilute hydrochloric acid and separating the alloy powder.

8. A method of producing titanium alloys which comprises forming a mixture of titanium oxide with one of a group of alloying metals consisting of aluminum, tin, iron, manganese, chromium, molybdenum and vanadium, its oxideand chloride, minus 4 mesh particles of magnesium in an amount at least 100% of the theoretical requirement and with magnesium chloridelin an amount at least 40% by weight of the titanium oxide plus oxide of the alloying metal, heating the mixture in an inert atmosphere at 1000" C. to efiect partial reduction of the metals to form an alloy powder containing not more than 10% of combined oxygen, cooling the reaction product crushing, leaching it with dilute hydrochloric acid to dissolve unreacted magnesium, magnesium oxide and magnesium chloride, separating the alloy powder from the solution and drying it,

9. The method defined in claim 8 wherein the alloy powder is mixed with minus 4 mesh calcium particles and with calcium chloride as a flux, heating the mixture in a reaction zone filled with inert gas, continuing the heating at a temperature of at least 1000' C. until the titanium I oxide and alloying addition have been reduced to metal and alloyed, cooling, crushing and leaching the reaction mass in. dilute hydrochloric acid to dissolve unreacted calcium, calcium oxide and calcium chloride, separating the alloy powder from the solution and drying it.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Titanium, Report of Symposium on Titanium. Sponsored by the Oflice of Naval Research, December 16, 1948. Pages 20 and 21.

Claims

1. A METHOD OF PRODUCING TITANIUM ALLOYS WHICH COMPRISES FORMING A MIXTURE OF TITANIUM OXIDE CONTAINING NOT LESS THAN 90% METAL, AN ALLOYING ADDITION BEING AT LEAST ONE OF A GROUP CONSISTING OF A TITANIUM PHASE STABILIZING METAL, ITS CHLORIDE AND ITS OXIDE, MINUS 4 MESH CALCIUM PARTICLES IN AN AMOUNT 100% IN EXCESS OF THE STOICHIOMETRIC REQUIREMENT AND CALCIUM CHLORIDE 10 TO 150% BY WEIGHT OF THE TITANIUM OXIDE PLUS OXIDE OF ALLOYING ADDITION, HEATING THE MIXTURE IN AN INERT ATMOSPHERE AT A TEMPERATURE NOT SUBSTANTIALLY LESS THAN 1000*C. TO EFFECT REDUCTION AND ALLOYING OF THE METALS, LEACHING THE REACTION MASS WITH DILUTE HYDROCHLORIC ACID AND SEPARATING THE TITANIUM ALLOY POWDER.