Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B33/00—Clay-wares
  • C04B33/32—Burning methods
  • C04B33/326—Burning methods under pressure
• • 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
  • B22F3/12—Both compacting and sintering
  • B22F3/1208—Containers or coating used therefor
  • B22F3/1258—Container manufacturing
  • B22F3/1283—Container formed as an undeformable model eliminated after consolidation
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B33/00—Clay-wares
  • C04B33/32—Burning methods
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
  • C04B35/583—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on boron nitride
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
  • C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
  • C04B35/593—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride obtained by pressure sintering

Definitions

• This invention relates to a method of producing a hot pressed component, the method being of the kind in which a pair of die parts are positioned within a die cavity with material to be hot pressed being received therebetween, and the die parts are used to transmit pressure to the material at an elevated temperature so as to hot press the material into the required hot pressed component.
• a method of the kind specified includes the step of forming at least one of the die parts by:
• the ratio of the density of said one die part, prior to hot pressing, to the density of said one die part, after hot pressing is substantially equal to the ratio of the density of the material to be hot pressed to the final density of the hot pressed component.
• the particle size of the boron nitride powder isnot less than 50 microns, and conveniently the particle size of the refractory powder is also not less than 50 microns.
• iso-propyl alcohol was mixed with 57 parts by weight of silicon carbide powder and 43 parts by weight of boron nitride powder to produce a slurry containing 64 percent by weight of solids.
• the silicon carbide powder used in producing the slurry was that sold by Carborundum Company Limited as type CG4k2 and had a particle size varying between 150 and 200 microns.
• the boron nitride powder used was that sold by New Metals and Chemicals Limited and had a particle size varying between 50 and 150 microns.
• the slurry was caused to flow into a mould, defining the shapeof a hot pressing die part, by using a vibrator and was then dried to produce av compressible powder compact of the shape of the required die part and of substantially uniform density.
• Tests were carried out on the compressibility of a number of powder compacts produced by the above method by applying a pressure of 1.5 tons/square inch to the compacts at temperatures varying between 25C and 1,720C.
• the ratio of the density of the compact prior to hot pressing to the density of the compact when pressed to full densification was 2.0;1, irrespective of the temperature of the pressing opera tion.
• Powder compacts produced according to the above method were therefore found to be particularly suitable for use as die parts in the hot pressing of ceramic materials, such as silicon nitride.
• a pair of die parts produced according to the above method were successfully employed to hot press compacted silicon nitride powder at a temperature of 1,700C and a pressure of 1.5 tons/square inch the resultant silicon nitride product being substantially of full theoretical density, that is 3.2 gm/c.c.
• the compacted silicon nitride powder was preferably arranged to have an initial density of 1.6 gm/c.c., which resulted in the ratio of the density of the compacted silicon nitride to the density of the hot pressed component being the same as the compression ratio of each of the compressible die parts.
• a suitable material in this respect was found to be alumina 'which, at the hot pressing temperature, produced at the surface of the silicon nitride a protective layer which was believed to be silicon aluminium oxynitride. After hot pressing the silicon aluminium oxynitride layer was either removed or more preferably was retained since it was found to improve the high temperature properties of the resultant hot pressed silicon nitride product.
• iso-propyl alcohol was mixed with 56 parts by weight of silicon carbide powder and 44 parts by weight of boron nitride powder to produce a slurry containing 72 percent by weight of solids.
• the silicon carbide had a particle size varying between 50 and 75 microns, whereas the particle size of the boron nitride powder varied between and 200 microns.
• a die part produced from this slurry was found to have a compression ratio of 2.0: 1 at an applied pressure of 1.5 tons/square inch, the compression ratio remaining constant as before between 25C and 1,720C. The die part behaved in the same way as the die parts produced according to the previous examples when used to hot press ceramic materials.
• a fourth example 54 parts by weight of magnesium oxide powder and 46 parts by weight of boron nitride powder were mixed with iso-propyl alcohol to produce a slurry containing 70 percent by weight of solids.
• the boron nitride powder was the same as that used in the previous example, whereas the magnesium oxide powder was that supplied by Thermal Syndicate Limited and had a particle size which varied between 75 and microns.
• a die part was produced from this slurry and the compression ratio of the die part was measured in the same way as in the previous examples.
• the compression ratio was found to be 2.011 over a wide range of temperatures so that again the die part was useful for hot pressing ceramic materials.
• hot pressing silicon nitride it was found that successful results were obtained without the presence of a protective material between the silicon nitride and the die parts at the hot pressing temperature.
• a slurry was formed by mixing isopropyl alcohol with 64 parts by weight of magnesium oxide powder and 36 parts by weight of boron nitride powder, both the powders being those used in the fourth example.
• the slurry so formed contained 72 percent by weight of solids and a die part produced from this slurry was found to have a compression ratio of 1.78:! at an applied pressure of 1.5 tons/square inch.
• a slurry containing 60 percent by weight of solids was produced by mixing 49 parts by weight of aluminium oxide powder and 51 parts by weight of boron nitride powder with iso-propyl alcohol.
• the boron nitride powder was that used in each of the third to fifth examples, whereas the aluminium oxide powder was supplied by Universal Abrasives Limited and had a particle size in the region of 230 microns.
• a die part produced from this slurry had a compression ratio of 2.011 at an applied pressure of 1.5 tons/square inch and was found to be suitable for the hot pressing of silicon nitride without the provision of an intervening protective layer.
• each of the die parts produced in the above examples was suitable for effecting only a single hot pressing operation since each die part was necessarily compressed and permanently deformed during hot pressing.
• the particle size of the boron nitride powder, and also of the refractory non-sinterable powder was not less than 50 microns.
• the upper limit on the particle sizes on these powders was determined by the surface imperfections which could be tolerated in the die parts produced therefrom.
• Suitable carrier media were those which were readily available as dry liquids, that is containing less than 0.05 percent water, and which evaportated on heating completely without decomposition and without leaving a carbonaceous residue.
• the carrier medium was, of course, also required to be inert to the boron nitride powder and to the particular refractory, non-sinterable powder employed with the boron nitride, as well as being able to produce a slurry of the required consistency for casting into the die parts.
• organic liquids having reasonably high boiling points, since this allowed more time for preparation and casting of the slurry before evaporation occurred.
• examples of other organic liquids which could have been employed as the carrier medium are acetone, ethyl alcohol and butyl alcohol.
• the particular refractory, non-sinterable powder employed in each of the above examples was chosen because its rheological properties were such as to enable a slurry to be produced which could be cast into the required die parts.
• the particle size of the refractory, nonsinterable powder was in each case arranged so as to be similar to the particle size of the boron nitride powder employed. It was, however, found to be necessary to determine empirically for each slurry the required liquid content and the relative proportions of the boron nitride powder and refractory non-sinterable powder in the slurry, the criterion in each case being that, after casting, the slurry would not undergo any substantial shrinkage when the carrier medium was removed.
• a method of producing a hot pressed component comprising the steps of:
• a method as claimed in claim 1 wherein the refractory, non-sinterable powder is silicon carbide, magnesium oxide, or aluminium oxide.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Dispersion Chemistry (AREA)
• Mechanical Engineering (AREA)
• Ceramic Products (AREA)
• Press-Shaping Or Shaping Using Conveyers (AREA)
• Powder Metallurgy (AREA)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

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Cited By (2)

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Citations (6)

• 1972
  • 1972-05-16 GB GB2281172A patent/GB1425166A/en not_active Expired
• 1973
  • 1973-05-04 US US00357278A patent/US3857157A/en not_active Expired - Lifetime
  • 1973-05-08 CA CA170,723A patent/CA1006341A/en not_active Expired
  • 1973-05-12 DE DE2324193A patent/DE2324193A1/de active Pending
  • 1973-05-14 IT IT49933/73A patent/IT988184B/it active
  • 1973-05-14 NL NL7306704A patent/NL7306704A/xx unknown
  • 1973-05-15 JP JP48054047A patent/JPS4941407A/ja active Pending
  • 1973-05-16 FR FR7317669A patent/FR2190765B1/fr not_active Expired
  • 1973-05-16 AT AT430273A patent/ATA430273A/de not_active Application Discontinuation
  • 1973-05-16 BE BE131172A patent/BE799603A/xx unknown

Patent Citations (6)

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