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  Production of titaniumUSPTO Application #: 20070181436Title: Production of titanium Abstract: A method of producing titanium semi-finished or ready-to-use products from titanium oxide powders and/or pellets is disclosed. The method produces products that are not affected adversely by levels of chlorine that have an impact on performance, particularly weldability, of products made by other methods. (end of abstract) Agent: Brinks Hofer Gilson & Lione - Chicago, IL, US Inventors: Kannapar Mukunthan, Ivan Ratchev, Andrew Arthur Shook USPTO Applicaton #: 20070181436 - Class: 205398000 (USPTO) Related Patent Categories: Electrolysis: Processes, Compositions Used Therein, And Methods Of Preparing The Compositions, Electrolytic Synthesis (process, Composition, And Method Of Preparing Composition), Utilizing Fused Bath, Single Metal Produced, Titanium, Zirconium, Or Hafnium (ti, Zr, Or Hf), Titanium The Patent Description & Claims data below is from USPTO Patent Application 20070181436. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application is a continuation-in-part of and claims priority to PCT application PCT/AU2005/000907 published in English on Jan. 5, 2006 as WO 2006/000025 and to Australian application no. 2004903532 filed Jun. 28, 2004, the entire contents of each are incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to the production of titanium metal and titanium metal alloys. The present invention relates particularly, although by no means exclusively, to a method of producing semi-finished or ready-to-use products, such as products in sheet, bar, tube and other forms, of titanium metal (which term includes titanium alloy) from titanium oxide powders and/or pellets. BACKGROUND OF THE INVENTION [0003] Currently, the Kroll and Hunter processes are the only commercial processes for producing titanium metal. These processes include chemical reduction of TiCl4 with molten magnesium or sodium metal in a sealed reactor that has been evacuated and back-filled with an inert gas. In one process route, after reduction has been completed the material in the hot reactor is vacuum distilled to vaporise magnesium and sodium metal and chlorides. The reactor is allowed to cool and the solid material, i.e. titanium sponge, is then recovered from the reactor. [0004] The titanium sponge may be processed by two process routes. One process route, a remelting route, includes melting the sponge in an inert atmosphere and forming ingots from the melt. Thereafter, the ingots are then converted into semi-finished or ready-to-use products, such as sheet, bar, tube and other forms, by hot working techniques such as forging, rolling and extrusion. [0005] The other process route, a direct compaction route, includes crushing the sponge into particulate form, typically powders, and directly compacting particles into semi-finished or ready-to-use products using standard powder metallurgy processing, such as roll compaction. [0006] One of the disadvantages of Kroll and Hunter products formed by the direct compaction route is poor weldability when welded using arc welding technology. The poor weldability has been attributed to high levels of chlorine, typically 1000-1500 ppm, in the products reacting with tungsten electrodes causing unstable arcs when arc welding the products. Poor weldability is not an issue with Kroll and Hunter products formed by the remelting route because the remelted products have substantially lower concentrations of chlorine. However, the remelting route is a more expensive processing route than the direct compaction route. [0007] During the 1950s and 1960s E I Du Pont Nemours & Company developed: (a) technology for producing titanium metal powders that were suitable for the direct compaction route by powder metallurgical processing to form titanium metal products in semi-finished or ready-to-use forms, such as sheet, bar, tube and other forms; and (b) titanium metal powder processing technology for producing these end products. [0008] The Du Pont technology is described in a number of US patents, including U.S. Pat. Nos. 2,984,6560, 3,072,347, 3,478,136, and 3,084,042. The Kroll process was the source technology for the titanium sponge used by Du Pont in the Du Pont technology. Du Pont found that it could produce a friable titanium metal sponge that, when ground in the presence of a salt, produced a high purity acicular powder. Du Pont also found that the powder was well suited to be compacted directly in the nip of a rolling mill to produce sheet. In addition, Du Pont found that the powder was well suited to be compacted into billets which could then be processed in an extruder to produce semi-finished or ready-to-use products, such as bar, tube and other shapes. [0009] However, Du Pont found that the Du Pont products had poor weldability. As is the case with conventionally produced directly compacted Kroll products, the poor weldability of the Du Pont products has been attributed to chlorine in the products. Du Pont has reported finding that the chlorine in the Kroll products volatilised rapidly during welding and caused a build-up of salts on tungsten welding electrodes that resulted in an unstable arc and consequently poor weldability. The chlorine was present in amounts greater than 50 ppm. Du Pont was not able to reduce the concentration of chlorine in the titanium metal or otherwise solve the poor weldability problem caused by the chlorine and consequently Du Pont did not commercialise the technology. [0010] The applicant has been carrying out extensive research into an electrochemical method for reducing metal oxides, such as titania. The electrochemical method of the applicant is described, by way of example, in International application PCT/AU03/00306 in the name of the applicant. The disclosure in the International application is incorporated herein by cross-reference. [0011] The electrochemical method of the applicant is an alternative technology to the Kroll and Hunter processes. The electrochemical method of the applicant, as described in the International application, is concerned with reducing a metal oxide in a solid state in an electrolytic cell of the type that includes an anode, a cathode, and a molten electrolyte that includes cations of a metal that is capable of chemically reducing the metal oxide. [0012] The International application focuses particularly on reducing titanium oxides, such as titania, to titanium metal. The electrochemical method of the applicant, as described in the International application, is characterised by a step of operating the cell at a potential that is above a potential at which cations of the metal that is capable of chemically reducing the metal oxide can deposit as the metal on the cathode, whereby the metal chemically reduces the metal oxide. [0013] The applicant has found surprisingly that, whilst the electrochemical method of the applicant produces titanium metal (which term includes titanium alloy) powders and/or pellets with high concentrations of chlorine, the chlorine does not have the same adverse impact on weldability of products made from the powders and/or pellets as is the case with chlorine in Kroll and Hunter products formed by the direct compaction route. [0014] Experimental work carried out by the applicant indicates that products made from titanium metal produced by the electrochemical method of the applicant that has comparable chlorine concentrations to that of Kroll and Hunter products formed by the direct compaction route, typically 1000-1500 ppm, has considerably better weldability than these Kroll products. [0015] The applicant believes that the forms of the chlorine in the Kroll and Hunter products formed by the direct compaction route (predominantly magnesium and sodium chlorides) and in the applicant's products (predominantly calcium chlorides) is a relevant factor in the comparatively minor impact of chlorine concentration on weldability of the applicant's products. Specifically, the chlorine in the Kroll and Hunter products formed by the direct compaction route appears to be in a more volatile form that readily reacts with tungsten welding electrodes and makes the arcs unstable. [0016] On the other hand, the chlorine in the applicant's products appears to be less volatile. This is a significant finding because it means that it may no longer be necessary to carry out extensive post-cell treatment of titanium metal powders and/or pellets made by the electrochemical method of the applicant to lower the chlorine concentration to levels, typically less than 50 ppm. These chlorine concentrations were thought to be necessary to achieve acceptable weldability of semi-finished or ready-to-use products made from titanium metal powders and/or pellets given the experience with Kroll and Hunter products made by the direct compaction route. Thus, in situations where weldability is important, the applicant's products may be a lower cost alternative to Kroll and Hunter products formed by the remelting processing route. SUMMARY OF THE INVENTION [0017] According to the present invention there is provided a method of producing titanium metal (which term includes titanium alloy) semi-finished or ready-to-use products from titanium oxide powders and/or pellets. DETAILED DESCRIPTION OF THE EMBODIMENTS [0018] The method according to the present invention includes the steps of: (a) electrochemically reducing titanium oxide powders and/or pellets in an electrolytic cell and producing titanium metal powders and/or pellets, which electrolytic cell includes an anode, a cathode, and a molten electrolyte that includes cations of a metal that is capable of chemically reducing titanium oxide and chloride anions; and (b) processing the titanium metal powders and/or pellets produced in step (a) and forming semi-finished or ready-to-use products having a concentration of chlorine of at least 100 ppm. [0019] The chlorine concentration of the semi-finished or ready-to-use products produced by step (b) may be at least 200 ppm, typically may be at least 500 ppm, and more typically may be at least 1000 ppm without affecting adversely the weldability of the products. Typically, the chlorine concentration of the semi-finished or ready-to-use products is less than 2000 ppm. [0020] Preferably, the titanium oxide powders and/or pellets have a size of 3.5 mm or less in a minor dimension of the powders and/or pellets. In a situation in which the powders and/or pellets are generally spherical, the "minor" dimension will be the diameter of the powders and/or pellets and the reference to "minor" dimension is not significant. However, in a situation in which the powders and/or pellets are formed into selected shapes, such as discs, and have different dimensions, the reference to "minor" dimension is significant. For example, in a situation in which the pellet is disc shaped with a cylindrical side wall and flat top and bottom walls and a diameter of 20 mm and a thickness of 2 mm, identifying the dimension to be measured as the minimum dimension is an important consideration. Continue reading... Full patent description for Production of titanium Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Production of titanium patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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