Classifications

• • 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
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
  • B22F3/225—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
• • 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
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
• • 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
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/001—Starting from powder comprising reducible metal compounds
• • 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
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F3/1017—Multiple heating or additional steps
  • B22F3/1021—Removal of binder or filler
  • B22F3/1025—Removal of binder or filler not by heating only
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B19/00—Indicating the time by visual means
  • G04B19/06—Dials
  • G04B19/12—Selection of materials for dials or graduations markings
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B37/00—Cases
  • G04B37/22—Materials or processes of manufacturing pocket watch or wrist watch cases
• • 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 invention relates to a method for manufacturing a titanium part by powder technologies and in particular such a method for manufacturing titanium parts by sintering titanium hydride powder (TiH2), parts whose porosity is lower. at around 2%.
• TiH2 titanium hydride powder
• the invention also relates to a decorative article produced by such a method.
• the process of the invention is more particularly suited to the manufacture of semi-finished titanium products which are intended to produce decorative articles such as watch cases, bracelet links, watch dials or the like, which once polished have an intense shiny surface.
• the TiH2 powder is firstly mixed with a binder formed from a mixture of polymer, plasticizer and wax.
• the mixture thus obtained is then injected into a mold to obtain a part having the desired shape.
• the shaped part is then, firstly, freed of its binder by air heating and, secondly, it is introduced into an oven containing an atmosphere of argon, nitrogen or the vacuum in which it is gradually heated to about 1,100 ° C for sintering.
• micropores appear on the surface of the parts after they have been polished, these micropores producing scattering of the incident light which thus prevents perfect specular reflection of the light reaching the part. This then results in an unattractive matte or milky surface.
• polishing of titanium parts obtained by this process therefore does not make it possible to obtain sufficiently smooth and shiny surfaces allowing their use as decorative parts, so that these parts are limited to technical uses in which the aesthetic appearance does not has no importance.
• the main object of the invention is therefore to remedy the drawbacks of the above-mentioned prior art by providing a method of manufacturing by sintering a titanium part which has a very low porosity and which, once polished, has an aesthetic appearance. fulfilling the requirements required for the production of decorative pieces.
• the invention relates to a decorative article made of titanium sintered from a powder of titanium hydride and having a polished surface obtained by the process described above.
• Such an article thus has, after polishing, a more intense gloss than the sintered and polished titanium parts obtained according to the methods of the prior art and is particularly well suited to the production of decorative articles such as watch cases, links bracelets or the like.
• Titanium hydride powder (TiH2), having a high degree of purity (99.5%) and an average particle size of the order of a few microns, typically 10 microns, is mixed, in a conventional manner, with a binder temporary in the form of granules until a homogeneous mixture is obtained.
• the binder is formed from a thermal polymer or copolymer but can also be formed from wax.
• This mixing is carried out at a temperature between 120 ° and 180 ° C depending on the nature of the binder used.
• the temperature of the mixture is of the order of 170 ° C.
• the binder contained in the shaped part is removed. Disposal is done in accordance with the nature of the binder. Often this removal of the binder is carried out thermally. To do this, the shaped part is then introduced into an oven in which it is gradually brought to a temperature between 200 ° and 300 ° C. During this heating, the binder is gradually removed by evaporation and, in order not to deteriorate the shape of the part, this heating takes place in a time between 6 and 9 hours and preferably in 8 hours. It is also important that the removal of the binder is complete to avoid any pollution of the part by the carbon and / or oxygen of the binder, which can lead to a deterioration of the mechanical properties and the corrosion resistance of the part to to manufacture.
• the removal of the binder is carried out under vacuum or in a hydrogen atmosphere in order, on the one hand, to avoid any oxidation of the binder during its removal, and on the other hand, to increase the speed of the process of removing the binder from the part without deteriorating the shape of the part.
• the binder is a thermal polymer
• the latter can also be eliminated chemically, by decomposition using an appropriate acid vapor.
• the atmosphere of the furnace is replaced by a hydrogen atmosphere (if the removal of the binder has not already been carried out in a hydrogen atmosphere) and, preferably, this hydrogen atmosphere is produced in the form of a flow circulating continuously in the furnace.
• the temperature of the part is gradually increased until the desired sintering temperature is reached.
• the sintering temperature is between 1,000 and 1,400 ° C and preferably substantially equal to 1,200 ° C to avoid getting too close to a temperature where the part would begin to deform.
• This heating lasts approximately 5 to 7 hours.
• the titanium hydride gradually releases its hydrogen.
• the heating is not too rapid so as not to cause a rapid release of the hydrogen which could cause the formation of pores within the room and thereby alter the gloss of the surface once polished.
• the heating rate is between 150 ° C and 250 ° C per hour.
• the process according to the invention advantageously eliminates the risk of reaction of titanium with compounds other than hydrogen which could affect the purity of the part obtained.
• the atmosphere of the furnace that is to say the hydrogen
• a non-reactive atmosphere such as argon, or helium or vacuum. Argon will be preferred.
• the replacement of hydrogen by the non-reactive atmosphere is done while maintaining the part at its sintering temperature.
• the duration of this stage is between 5 and 80 minutes and is preferably approximately 20 minutes.
• the part is then cooled to ambient temperature in said non-reactive atmosphere at a cooling rate of the order of 300 ° C per hour. During this cooling, the part slowly releases the rest of its hydrogen which is eliminated gradually.
• the sintered titanium part obtained by the process which has just been described has a remarkably low porosity, less than 2%.
• this piece can be subjected to a specular polishing of its surface in order to obtain a decorative article such as a watch case, a bracelet link, a dial or the like, having a surface of a polish and a intense shine.
• a binder formed from a copolymer comprising 32% by volume of polyethylene oxide (246 g) and 4% by volume of polypropylene (26 g) is prepared in a container. This binder is heated to a temperature of about 170 ° C to obtain a homogeneous mass. 64% by volume of TiH2 (1920 g) having a degree are then added in addition. 99.5% purity which is mixed with the binder until a homogeneous paste is obtained.
• the cooled mixture is then granulated.
• the granules obtained are then introduced into an injection press and injected into a mold, for example having the shape of a watch case, at a temperature of approximately 140 ° C.
• the shaped part is then introduced into an oven in which a vacuum of about 10 ⁇ 2 millibar is created.
• the part is then brought to a temperature of approximately 300 ° C. by linear heating in 8 hours.
• the part is then sintered.
• the vacuum of the oven is replaced by a hydrogen atmosphere in the form of a flow having a flow rate of 150 ml / min and the part is brought from 300 ° C to 1,200 ° C linearly in 4 hours.
• the hydrogen atmosphere is replaced by an argon atmosphere in the form of a flow having a flow rate of 150 ml / min, and the temperature of 1200 is maintained. ° C for about 20 minutes.
• the part is then cooled linearly under the same argon atmosphere to room temperature.
• the cooling rate is 300 ° C per hour and a sintered titanium part is obtained, the porosity of which is 1.5%.
• the sintered element is finally subjected to electropolishing to obtain a watch case having an intense shiny appearance.
• polyacetal is used as binder and the latter is removed by decomposition in a vapor of nitric acid at 120 ° C.
• the result obtained with this variant is identical to that obtained with the previous example.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Powder Metallurgy (AREA)
• Adornments (AREA)

Applications Claiming Priority (5)

Publications (2)

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ID=25689892

Family Applications (1)

Country Status (6)

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Citations (3)

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• 1994
  • 1994-07-14 JP JP18412794A patent/JP3443175B2/ja not_active Expired - Fee Related
  • 1994-07-19 DE DE69429308T patent/DE69429308T2/de not_active Expired - Fee Related
  • 1994-07-19 EP EP94111197A patent/EP0635325B1/de not_active Expired - Lifetime
  • 1994-07-22 US US08/277,306 patent/US5441695A/en not_active Expired - Lifetime
  • 1994-07-22 CN CN94109194A patent/CN1074959C/zh not_active Expired - Fee Related
• 1998
  • 1998-12-17 HK HK98113864A patent/HK1012600A1/xx not_active IP Right Cessation

Patent Citations (3)

Non-Patent Citations (3)

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