Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
  • C25C3/26—Electrolytic production, recovery or refining of metals by electrolysis of melts of titanium, zirconium, hafnium, tantalum or vanadium
  • C25C3/28—Electrolytic production, recovery or refining of metals by electrolysis of melts of titanium, zirconium, hafnium, tantalum or vanadium of titanium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
  • C22B1/24—Binding; Briquetting ; Granulating
  • C22B1/2406—Binding; Briquetting ; Granulating pelletizing
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B34/00—Obtaining refractory metals
  • C22B34/10—Obtaining titanium, zirconium or hafnium
  • C22B34/12—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08
  • C22B34/129—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 obtaining metallic titanium from titanium compounds by dissociation, e.g. thermic dissociation of titanium tetraiodide, or by electrolysis or with the use of an electric arc
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C5/00—Electrolytic production, recovery or refining of metal powders or porous metal masses
  • C25C5/04—Electrolytic production, recovery or refining of metal powders or porous metal masses from melts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

• 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.
• 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.
• 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.
• 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.
• the remelting route is a more expensive processing route than the direct compaction route.
• 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.
• 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.
• 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.
• the forms of the chlorine in the Kroll and Hunter products formed by the direct compaction route is a relevant factor in the comparatively minor impact of chlorine concentration on weldability of the applicant's products.
• 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.
• 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.
• titanium metal which term includes titanium alloy
• semi-finished or ready-to-use products from titanium oxide powders and/or pellets.
• 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.
• 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.
• the “minor” dimension will be the diameter of the powders and/or pellets and the reference to “minor” dimension is not significant.
• 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.
• the size of the titanium oxide powders and/or pellets is less than 2.5 mm. More preferably, the size of the powders and pellets is 1-2 mm.
• step (a) includes electrochemically reducing titanium oxide to titanium metal having a concentration of oxygen that is no more than 0.5% by weight. More preferably, the oxygen concentration is no more than 0.3% by weight. More preferably, the oxygen concentration is no more than 0.1% by weight.
• the electrolyte is a CaCl 2 -based electrolyte that includes CaO as one of the constituents.
• step (a) includes maintaining the cell potential above the decomposition potential for CaO.
• step (a) includes maintaining the cell potential below the decomposition potential for CaCl 2 .
• Step (a) may be carried out on a batch, continuous, or semi-continuous basis.
• step (a) may be carried out on a continuous or semi-continuous basis as described in International application PCT/AU03/001657 in the name of the applicant. The disclosure in the International application is incorporated herein by cross reference.
• step (b) includes processing the titanium metal powders and/or pellets produced in step (a) by quenching the titanium metal powders and/or pellets from an elevated temperature to a lower temperature at which there is a comparatively low rate of oxidation of titanium metal in air.
• the lower temperature is ambient temperature.
• step (b) may include the steps of roll compacting the titanium metal powders and/or pellets into strip, sintering the strip to increase the mechanical properties of the strip, ant cold rolling the sintered strip into sheet.
• step (b) may include processing the titanium metal powders and/or pellets produced in step (a) by powder metallurgically processing the titanium metal powders and/or pellets into semi-finished or ready-to-use products other than by roll compacting the powders and/or pellets.
• step (b) includes compacting the titanium metal powders and/or pellets to form semi-finished or ready-to-use products, such as products in sheet, bar, tube and other forms.
• the chlorine concentration of the semi-finished or ready-to-use products 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.
• the chlorine concentration of the semi-finished or ready-to-use products is less than 2000 ppm.
• the NTC samples were prepared by the following procedure.
• the titanium metal pellets produced in accordance with the method described in International application PCT/AU03/0030 were of the order of 15 mm.
• the pellets were washed to remove retained electrolyte and thereafter processed to remove carbides adhered to the surface of the pellets.
• the pellets were then crushed to a particle size of 1-1.5 mm and washed again to remove further retained electrolyte.
• the particles were then die compacted to a density of 80-85% and thereafter sintered to increase the density to 85-90%.
• the particles were then cold rolled to form fully dense strips, i.e. strips having a density of at least 98%, and cut into the strips of the above-mentioned size.
• the WM samples were formed by cutting small strips of the above-mentioned size from titanium strip having a chlorine concentration of less than 20 ppm produced from Kroll or Hunter products formed by the remelting route.
• the WK samples were made from commercially available Kroll or Hunter powders formed by the direct compaction route into fully dense strips by the same sequence of die compacting, sintering, and cold rolling steps described above in relation to the NTC samples and then cut into the strips of the above-mentioned size.
• An initial weld run was made on an austenitic stainless steel strip with approximately the same dimensions as the titanium metal strips to establish the welding parameters and shielding effectiveness.
• the titanium metal strips (Samples NTC (1) to NTC(3), WM(1), WM(2), and WK (1) to WK(4)) were then butt welded at a nominal current of 25 amps.
• the titanium metal strips were welded using standard practice for titanium in an inert gas enclosure using GTAW.
• the samples NTC(1) TO NTC(3) produced in accordance with the present invention were weldable with good arc stability and good weld bead appearance.
• samples WK(1) to WK(4) made from Kroll/Hunter powders and pellets having 1000-1500 ppm chlorine were easily identified by arc instability, unacceptable weld beads and severe electrode erosion.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Materials Engineering (AREA)
• Geology (AREA)
• Manufacturing & Machinery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Mechanical Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Geochemistry & Mineralogy (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Electrolytic Production Of Metals (AREA)
• Powder Metallurgy (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)

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• 2005
  • 2005-06-23 CA CA002572300A patent/CA2572300A1/fr not_active Abandoned
  • 2005-06-23 EP EP05752414A patent/EP1776491A4/fr not_active Withdrawn
  • 2005-06-23 WO PCT/AU2005/000907 patent/WO2006000025A1/fr not_active Ceased
  • 2005-06-23 BR BRPI0512782-3A patent/BRPI0512782A/pt not_active IP Right Cessation
  • 2005-06-23 AU AU2005256146A patent/AU2005256146B2/en not_active Ceased
  • 2005-06-23 RU RU2007103181/02A patent/RU2370575C2/ru not_active IP Right Cessation
  • 2005-06-23 CN CNA2005800253377A patent/CN101018894A/zh active Pending
  • 2005-06-23 JP JP2007518407A patent/JP2008504438A/ja active Pending
• 2006
  • 2006-12-27 US US11/616,419 patent/US20070181436A1/en not_active Abandoned
• 2007
  • 2007-01-02 ZA ZA200700107A patent/ZA200700107B/en unknown

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