Kabushiki Kaisha Kobe Seiko Sho

Masato Moritoki

Takao Fujikawa

Junichi Miyanaga

Hiroshi Okada

Kazuo Kitagawa

Tsuneo Tatsuno

Katuhiko Honma

Toshiro Fukutsuka

Akira Asari

Shigeo Kofune

Takeshi Kanda

Takefumi Horiuchi

Yoshio Kawate

Hidehiro Tsuzuki

Shigeki Tojyo

Shiro Matsuura

Yohichi Inoue

Masayoshi Iwaskai

Tatsuo Uesaka

Norio Gennai

The specification describes a method for producing high density sintered silicon nitride (Si.sub.3 N.sub.4) having a relative density of at least 98%. In a first step, silicon nitride powder is compacted into a desired shape. It is then pre-sintered in a second step, generally, under normal pressure to obtain a presintered body having a relative density of at least 92%. In a third step, the presintered body is subjected to a hot isostatic pressing (HIP) in an inert gas atmosphere of 1500.degree.-2100.degree. C. and of nitrogen gas partial pressure of at least 500 atm. Since the presintering does not require any capsule, it is possible to produce high density sintered Si.sub.3 N.sub.4 of complex configurations. As a sintering aid, Y.sub.2 O.sub.3 --Al.sub.2 O.sub.3 --MgO system sintering aid is particularly effective. To improve the strength of sintered Si.sub.3 N.sub.4, it is effective to add a heat treatment step after the HIP and maintain the temperature of the sintered Si.sub.3 N.sub.4 above 500.degree. C. for a while. Between the second and third steps, the temperature of the presintered body is preferably maintained above 500.degree. C. These temperature controls are effective not only to improve the strength of sintered Si.sub.3 N.sub.4 but also to save the thermal energy and to shorten the production cycle.

Method for producing high density sintered silicon nitride(Si.sub.3 N.sub.4

The specification describes a method for producing high density sintered silicon nitride(Si.sub.3 N.sub.4) having a relative density of at least 98%. In a first step, silicon nitride powder is compacted into a desired shape. It is then presintered in a second step, generally, under normal pressure to obtain a presintered body having a relative density of at least 92%. In a third step, the presintered body is subjected to a hot isostatic pressing(HIP) in an inert gas atmosphere of 1500-2100.degree. C. and of nitrogen gas partial pressure of at least 500 atm. Since the presintering does not require any capsule, it is possible to produce high density sintered Si.sub.3 N.sub.4 of complex configurations. As a sintering aid, Y.sub.2 O.sub.3 -Al.sub.2 O.sub.3 -MgO system sintering aid is particularly effective. To improve the strength of sintered Si.sub.3 N.sub.4, it is effective to add a heat treatment step after the HIP and maintain the temperature of the sintered Si.sub.3 N.sub.4 above 500.degree. C. for a while. Between the second and third steps, the temperature of the presintered body is preferably maintained above 500.degree. C. These temperature controls are effective not only to improve the strength of sintered Si.sub.3 N.sub.4 but also to save the thermal energy and to shorten the production cycle.

Method for producing high density sintered silicon nitride (SI.sub.3 N.sub.

The specification describes a method for producing high density sintered silicon nitride(Si.sub.3 N.sub.4) having a relative density of at least 98%. In a first step, silicon nitride powder is compacted into a desired shape. It is then presintered in a second step, generally, under normal pressure to obtain a presintered body having a relative density of at least 92%. In a third step, the presintered body is subjected to a hot isostatic pressing(HIP) in an inert gas atmosphere of 1500-2100.degree. C. and of nitrogen gas partial pressure of at least 500 atm. Since the presintering does not require any capsule, it is possible to produce high density sintered Si.sub.3 N.sub.4 of complex configurations. As a sintering aid, Y.sub.2 O.sub.3 --Al.sub.2 O.sub.3 --MgO system sintering aid is particularly effective. To improve the strength of sintered Si.sub.3 N.sub.4, it is effective to add a heat treatment step after the HIP and maintain the temperature of the sintered Si.sub.3 N.sub.4, above 500.degree. C. for a while. Between the second and third steps, the temperature of the presintered body is preferably maintained above 500.degree. C. These temperature controls are effective not only to improve the strength of sintered Si.sub.3 N.sub.4 but also to save the thermal energy and to shorten the production cycle.

Method for producing high density sintered silicon nitride (Si.sub.3 N.sub.

Pressure crystallization equipment

A method of measuring the temperature in a high pressure furnace of a hot isostatic pressing apparatus, wherein a closed-end pipe having its inside communicated with the inside of the high pressure furnace and enabling a pressure medium to pass therethrough is disposed in the furnace, an incident top end of an optical fiber, a bundle of optical fibers or like other equivalent optical rod-like memeber is disposed to the open end of the closed-end pipe so as to be capable of receiving thermally radiated light from the inside of the closed-ended pipe and an exit rear end thereof is led out through a cover and to the outside of said high pressure vessel and a measuring system is connected to said exit rear end to detect heat radiation power from the top end of the closed-end pipe to thereby measure the temperature inside of the furnace.

Method and apparatus for measuring temperature in the high pressure

A heat insulator for a hot isostatic pressing apparatus including a plurality of non-perforated graphite sheets; a plurality of perforated graphite sheets, each one of the plurality of perforated graphite sheets being sandwiched between and making at least substantially planar contact with, but not being bonded to, adjoining ones of the plurality of non-perforated graphite sheets; and a gas having an extremely low thermal conductivity substantially confined in the perforations in the plurality of perforated graphite sheets.

Heat insulator for hot isostatic pressing apparatus

A hot isostatic pressing system including a hot isostatic pressing station having a high pressure container constituted by a vertical pressure-resistant cylinder closed at the top end thereof and a lower lid detachably fitted to the bottom of the pressure resistant cylinder and a treating chamber internally provided with a heater and enclosed by a heat insulating wall, and a mechanism for adjusting an atmospheric gas pressure and temperature of the pressing station into a condition suitable for the hot isostatic pressing of a work item accommodated in the treating chamber; a plurality of auxiliary stations each provided with an opening for receiving from beneath thereof the heat insulating wall of the treating chamber accommodating the internal heater and a work item, a support structure for supporting the heat insulating wall, and a mechanism for cooling the work item and internal heater in an inert gas atmosphere; a carriage for transferring the lower lid and work item or the lower lid, work item, heat insulating wall and internal heater between the hot isostatic pressing station and one of the auxiliary stations; and a lift mechanism for lifting up and down the lower lid and work item or the lower lid, work item, heat insulating wall and heater at the hot isostatic pressing station and each one of the auxiliary stations.

Method and apparatus for hot isostatic pressing

A method of producing compound-type superconducting wires which are dense and free of voids. The method comprises the step of holding a compound-type superconducting wire having voids in an atmosphere of sufficiently high temperature high pressure gas to collapse the voids and weld the collapsed areas, thereby forming a dense, void-free superconducting wire.

Method of producing compound-type superconducting wires

A heater for use in the HIP apparatus for treating a work item or work items in a high temperature and pressure gas atmosphere by isostatic application of pressure in a heated condition, the heater including at least one heater assembly unit including a meandering heating element arranged into a cylindrical grid-like form having axial slits open alternately at the upper and lower ends thereof; a plurality of radial projections of a predetermined width extending radially outward from the upper ends of the meandering heating element at a number of predetermined positions including terminal ends thereof; a number of mounted holes formed through the radial extensions of the heating element; a number of support columns fixedly erected respectively on retaining members and having a male screw portion at the upper ends thereof respectively protruded upwardly through the mounting holes in the radial extensions of the heating element; and a number of nuts respectively threaded and tightened on the protruded ends of the male screw portions of the support columns to thereby support in suspended state the heating element securely on the support columns, forming a cylindrical space therein.

Heater for hot isostatic pressing apparatus

A method of hot isostatic pressing in which a shaped work immersed in molten glass is subjected to a hot isostatic pressing treatment, the method basically including embedding a shaped item to be worked on in glass powder filled in a crucible; loading the crucible into a movable heating furnace having a heater and a heat insulating structure; charging the furnace into an atmospheric chamber; adjusting the atmosphere in the chamber into a predetermined condition and heating the crucible by the heater to soften and melt the glass in the crucible; transferring the furnace from the atmospheric chamber into a high pressure container while maintaining a high temperature in the furnace; admitting a pressing gas medium into the high pressure container while raising the temperature of the furnace to let the work in the crucible undergo a hot isostatic pressing treatment; and upon completion of the hot isostatic pressing treatment, taking out the furnace from the high pressure container with the work still in loaded state in the heating furnace. In an alternate embodiment of the invention, a plurality of heating furnaces are provided. and more than one atmospheric chamber for a single high pressure container to realize efficient HIP operation with a markedly shortened cycle time.

Method of hot isostatic pressing treatment

A heater which includes: at least two electrically conductive heating element units having generally a self-standing cylindrical shape and stacked one on another to define a series of at least two cylindrical heating zones, the heating element units each including of a grid-like structure alternately having a vertically disposed portion and a horizontally extending bridge portion; insulator blocks fitted on the ends of stacked upper and lower cylindrical heating element units which meet and which are made of a material having a sufficient electric resistance that will not conduct electric current at a maximum operating temperature of the heating element units; and an annular shaped connector conforming with the ends of the upper and lower heating element units which meet and which is interposed between the insulating blocks on the ends which meet to provide a mechanical connection between the stacked upper and lower heating element units.

A high density sintering method for powder molded products by applying preliminary sintering to powder molded products previously molded into a predetermined shape and then applying hot isostatic press process to the sintered products thereby producing high density sintered product which includes the steps of loading the powder molded products into a movable heating furnace equipped with at least one heating means and having a heat insulating structure, introducing the heating furnace into an atmosphere chamber, applying preliminary sintering to the powder molded products in the heating furnace by the heating means while conditioning the inside of the atmosphere chamber to a vacuum or predetermined gas atmosphere, subsequently removing the heating furnace while maintaining the inside thereof at a high temperature from the atmosphere chamber and directly introducing the furnace into a high pressure vessel, thereafter, applying the hot isostatic press process to the sintered products in the furnace while charging a gas as a pressure medium under pressure into the high pressure vessel and elevating the temperature in the heating furnace by the heating means, thereby producing high density sintered products, and then removing the heating furnace together with the high density sintered products loaded therein out of the high pressure vessel after completion of the hot isostatic press process.

High density sintering method for powder molded products

The specification describes a method for producing compound-type superconducting wire of excellent mechanical and electrical properties. A green compact is first formed with copper powder and one of two metals which form a superconducting compound through a reaction therebetween. The latter metal is in a very fine hydrogenated form. The green compact is then heated in vacuo so as to dehydrogenate the hydride of the latter metal and sinter the green compact into a sintered mass. Before or after drawing the sintered mass into a wire, it is composited with the other metal of the two metals, thereby forming a composite wire. It is then subjected to a further heat treatment to cause the reaction to occur between the two metals. To improve its properties, it may be held in a high temperature, high pressure gaseous atmosphere to cause plastic deformation to occur. Since the dehydrogenation and annealing are performed in a single step, the overall process has been simplified. Since the latter metal is dispersed uniformly in the form of highly pure and ultra-fine particles in the Cu-matrix of the sintered mass, it can be drawn very smoothly into a wire and the reaction between the two metals can occur easily. The two metals may for example be Nb and Sn or V and Ga.

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Miki, Japan

Masato Moritoki