Abstract: The ceramic insert made from a silicon nitride ceramic material and formed with a recess for fastening in the center of its rake face. The recess has a surface roughness Rmax not exceeding 4 .mu.m. The angle between a side face of the recess and a centerline perpendicular to the rake face of the insert is 50-70 degrees. The ratio of the diameter of the recess to the diameter of a circle inscribing the perimeter of the rake face is 30-85%. The recess has a flat or curved bottom. The connecting portion between the side face and the bottom of the recess forms a smoothly curved surface.

Abstract: A slide member has a sliding surface made of ceramic and a has surface roughness of not more than 1.0 .mu.m in center line average roughness Ra. The ceramics includes a silicon nitride sintered body which contains crystal grains having a linear density of at least 35 per 30 .mu.m in length with a boundary phase volume ratio of not more than 15 volume %, and which contains pores of not more than 20 .mu.m in maximum diameter in a content of not more than 3%. In a method of manufacturing the slide member, it is possible to ensure smoothness of the sliding surface by grinding the sliding surface and thereafter heating the ceramic in an either an inert gas or atmospheric air. A slide member that can be used under severe sliding conditions of high-speed sliding or the like and that has excellent wear resistance is obtained.

Abstract: A sintered silicon nitride-based body comprising 20% or less by weight of a grain boundary phase and the balance being a major phase of grains of silicon nitride and/or sialon, wherein the major phase contains a grain phase of a .beta.-Si.sub.3 N.sub.4 phase and/or a .beta.'-sialon phase, and a quantitative ratio of the grain phase of the .beta.-Si.sub.3 N.sub.4 phase and/or the .beta.'-sialon phase is in a range of 0.5 to 1.0 relative to the major phase; the grain boundary phase contains Re.sub.2 Si.sub.2 O.sub.7 (wherein Re represents a rare-earth element other than Er and Yb) as a first crystal component and at least one of ReSiNO.sub.2, Re.sub.3 Al.sub.5 O.sub.12, ReAlO.sub.3, and Si.sub.3 N.sub.4.Y.sub.2 O.sub.3 as a second crystal component; and a quantitative ratio of the first and second crystal components in the grain boundary phase to the grain phase of .beta.-Si.sub.3 N.sub.4 phase and/or the .beta.'-sialon phase ranges from 0.03 to 1.6.

Abstract: A composite bearing structure that has a high rotational accuracy and that can withstand high-speed rotation comprises first bearing means, second bearing means, third bearing means and fourth bearing means. The first bearing means supports a radial impact force which is applied to a rotator during rotation, and is formed by an inner ring (1) and an outer ring (2) consisting of silicon nitride ceramics sintered bodies. The second bearing means supports an axial load which is applied to the rotator while maintaining a prescribed clearance with the rotator, and is formed by a magnetic bearing body of two permanent magnets (12) and (13) which are thrust-directionally opposed to each other. The third bearing means maintains the radial rotational accuracy of the rotator, and is formed by a radial dynamic pressure producing groove (5) which is formed in a cylindrical surface of the inner ring (1).

Abstract: A sintered silicon nitride-based body comprising 20% or less by weight of a grain boundary phase and the balance being a major phase of grains of silicon nitride and/or sialon, wherein the major phase contains a grain phase of a .beta.-Si.sub.3 N.sub.4 phase and/or a .beta.'-sialon phase, and a quantitative ratio of the grain phase of the .beta.-Si.sub.3 N.sub.4 phase and/or the .beta.'-sialon phase is in a range of 0.5 to 1.0 relative to the major phase; the grain boundary phase contains Re.sub.2 Si.sub.2 O.sub.7 (wherein Re represents a rare-earth element other than Er and Yb) as a first crystal component and at least one of ReSiNO.sub.2, Re.sub.3 Al.sub.5 O.sub.12, ReAlO.sub.3, and Si.sub.3 N.sub.4.Y.sub.2 O.sub.3 as a second crystal component; and a quantitative ratio of the first and second crystal components in the grain boundary phase to the grain phase of .beta.-Si.sub.3 N.sub.4 phase and/or the .beta.'-sialon phase ranges from 0.03 to 1.6.

Abstract: A ceramic die for cutting and shaping lead frames, in which at least a working section thereof is made of a specific ceramic material having an iron and cobalt content of less than 100 ppm in total. The ceramic die can be formed in a complex shape with a high precision and has a prolonged lifetime because of its superior mechanical properties, such as high wear resistance and high strength, and less probability of adhesion of foreign matter such as solder or the lead frame material thereto. Even if the solder or lead frame material is adhered onto the die, the adhered matter can be removed through a simple procedure in a shortened time. The die is further improved by depositing a hard carbon film onto the surface of the working section.

Abstract: A slide member has a sliding surface made of ceramic and has a surface roughness of not more than 1.0 .mu.m in center line average roughness Ra. ceramic includes a silicon nitride sintered body, which contains crystal grains having a linear density of at least 35 per 30 .mu.m in length with a boundary phase volume ratio of not more than 15 volume %, and which contains pores of not more than 20 .mu.m in maximum diameter in a content of not more than 3%. In a method of manufacturing the slide member, it is possible to ensure smoothness of the sliding surface by grinding the sliding surface and thereafter heating the ceramic in either inert gas or an atmospheric air. A slide member that can be used under severe sliding conditions of high-speed sliding or the like and that has excellent wear resistance is obtained.

Abstract: A zirconia vane used in a rotary compressor, the zirconia vane being formed of a partially stabilized zirconia sintered body containing 92 through 98 molar percent of ZrO.sub.2 and being stabilized with Y.sub.2 O.sub.3, zirconia crystals constituting the zirconia sintered body having a mean grain diameter of 0.1 to 0.6 .mu.m and a maximum grain diameter of not greater than 2 .mu.m, the zirconia sintered body having a mean three-point flexural strength of not less than 120 kg/mm.sup.2 measured in conformity with JIS R1601, a surface of the zirconia sintered body in contact with a rotor of the rotary compressor having a first surface roughness in a direction of rotations of the rotor, specified by a ten-point mean roughness Rz, of not greater than 1 .mu.m and a second surface roughness in a direction perpendicular to the direction of rotation of the rotor, specified by the ten-point mean roughness Rz, of not greater than 0.6 .mu.m.

Abstract: A high-strength silicon nitride sintered body having a flexural strength of 100 kg/mm.sup.2 or higher and a process for producing the same are disclosed, the sintered body comprising not less than 90% by weight of a single crystalline phase of silicon aluminum oxynitride (Si.sub.6-z Al.sub.2 O.sub.z N.sub.8-z, wherein z is a number of from 0 to 4.2) having an average longer diameter of not more than 5 .mu.

Abstract: A composite bearing structure can withstand high speed rotation has first, second and third bearing components. The first bearing component supports a radial impact force applied to a rotator during rotation, and is made of an inner ring (1) and an outer ring (2) of silicon nitride ceramic sintered bodies. The second bearing component supports an axial load applied to the rotator while maintaining a required clearance between itself and the rotator and is made of two permanent magnets (12, 13) positioned thrustdirectionally opposite to each other. The third bearing component maintains a radial rotational accuracy of the rotator, and is made of a radial dynamic pressure producing groove (5) provided on a cylindrical surface of the inner ring (1).

Abstract: A high-strength silicon nitride sintered body having a flexural strength of 100 kg/mm.sup.2 or higher and a process for producing the same are disclosed, the sintered body comprising not less than 90% by weight of a single crystalline phase of silicon aluminum oxynitride (Si.sub.6-z Al.sub.2 O.sub.z N.sub.8-z, wherein z is a number of from 0 to 4.2) having an average longer diameter of not more than 5 .mu.

Abstract: There is provided a process for the production of a sintered article which comprises steps ofshaping a raw material powder comprising silicon nitride,thermally treating a shaped article in a non-oxidizing atmosphere at a temperature of 1300.degree. to 1650.degree. C. for at least 2 hours to form .beta.-silicon nitride of not less than 85% calculated from X-ray diffraction patterns and to increase a relative density of the article to not less than 80%, preferably to 80 to 85 %, andsintering the thermally treated article at a temperature of 1700.degree. to 2000.degree. C.

Abstract: The present invention relates to a method of hot rolling copper or copper alloys such as copper wires and coppr plates. The present invention has succeeded in remarkably prolonging useful life of the tools used for hot rolling, and improving the surface quality of the rolled products by replacing the conventional methods of hot rolling copper using tools made of cemented carbide, die steel, high-speed steel, etc. by a method using tolls made essentially of Si.sub.3 N.sub.4. Si.sub.3 N.sub.4 tools used in the present invention contain at least one kind of sintering aid selected from the group consisting of Al.sub.2 O.sub.3, AlN, MgO, Y.sub.2 O.sub.3 and ZrO.sub.2, have a sintering density of 90% or more, Rockwell hardness of 88 or more and an average particle diameter of 2.mu. or less, and contain .beta.-type Si.sub.3 N.sub.4 as a main ingredient.

Abstract: A novel method of hot rolling iron and iron alloy rods, using a hot rolling tool comprising .beta.-Si.sub.3 N.sub.4 and a sintering aid selected from the group consisting of Al.sub.2 O.sub.3, AlN, MgO, Y.sub.2 O.sub.3 and ZrO.sub.2, and having a sintered density of 90% or more, Rockwell hardness of 88 or more and a mean particle size of 2.mu. or less.

Abstract: A method for manufacturing a fiber reinforced silicon carbide or silicon nitride ceramic sintered body having silicon carbide or silicon nitride ceramic whiskers dispersed therein, which method involves mixing together silicon carbide or silicon nitride ceramic powder, whisker formation agents made up of at least one material selected from metal Si or an inorganic compound containing Si, an organic containing Si, amorphous silicon ceramic powder or a mixture of SiO.sub.2 and carbon, or Si, sintering additives, and a whisker accelerating amount of a whisker formation accelerator selected from Fe, Ni, Co, Cr, V, Ti, Ta, W or Mo; molding the mixture into a predetermined shape; heat treating the molded body at a temperature of 1300.degree. C. to 1750.degree. C. to produce silicon carbide or silicon nitride whiskers in the molded body and thereafter densifying and sintering the molded body at sintering temperatures in a non-oxidizing atmosphere.

Abstract: Less dispersion and more homogenized ceramics are produced by sintering ceramic materials, in particular, containing silicon nitride or silicon carbide as a predominant component with other assistants or additives, machining the surface of the resulting sintered compact and then subjecting the sintered compact to a heat treatment for homogenizing in a non-oxidizing atmosphere such as nitrogen or argon gas at a temperature of from the mass-transfer temperature at which the mass-transfer takes place in the interior of the ceramics to blunt the fine point of a crack to the sintering temperature of the ceramics.

Abstract: An electrically-conductive sintered compact of silicon nitride which is machinable by electrical discharge machining and a process to produce the same. TiN and/or TiC powder is added to a powder of silicon nitride in an amount 15-40% by volume to act as a conductivity-supplying agent while 0.01-3.0% by volume MgO and/or Al.sub.2 O.sub.3 powder is added as a sintering assistant. The mixed powders are then preformed in a desired shape and sintered in a nonoxidizing environment at 1,600.degree. C.-2,000.degree. C. to obtain a compact of silicon-nitride machinable by electrical discharge machining due to its electrical conductivity being at least 1 S.multidot.cm.sup.-1.

Abstract: A tool for warm and hot forgings is proposed which is made by bonding cemented carbide to steel by applying electron beams or laser to the joint. The cemented carbide includes a hard phase of tungsten carbide and a binder metal phase containing at least one of Ni, Co and Fe, and at least one of Cr, Mo and W, the latter forming a solid solution. A process for manufacturing such a tool is also proposed in which unfocussed high-energy beams are applied to each side of the joint and focussed beams are then applied to a point slightly away from the joint toward the cemented carbide.

Abstract: A process and an apparatus for manufacturing a fine powder of metals or ceramics are proposed in which a mixed gas of volatile metal compound and/or evaporated metal and a reaction gas is reacted in a discharged state while heating by laser beam.