Abstract: In a material for a ceramic ball according to an embodiment, a sphericity is 2% or less, and an arithmetic mean roughness Ra is 0.2 ?m or more and 2 ?m or less. In the material for the ceramic ball, a total height of profile Rt is preferably 4 ?m or more and 20 ?m or less. In the material for the ceramic ball, when a surface roughness Ra in a circumferential direction of a belt-like portion mark is defined as Ra1, and a surface roughness Ra of a circumference in a direction perpendicular to the belt-like portion mark is defined as Ra2, Ra1/Ra2 is preferably 0.2 or more and 2 or less.

Abstract: A ceramic ball material according to an embodiment includes a spherical portion; and a band-shaped portion formed over a circumference of a surface of the spherical portion. The ceramic ball material has a ratio R1/R2 of 0.3 or more and less than 1.0, where R1 denotes a surface roughness of an end portion of the band-shaped portion; and R2 denotes a surface roughness of a center portion of the band-shaped portion.

Abstract: A ceramic ball material according to an embodiment includes a spherical portion; and a band-shaped portion formed over a circumference of a surface of the spherical portion. In the ceramic ball material, the ceramic ball material has a ratio Rab/Rap of 0.70 or more and 1.03 or less, where Rab denotes an arithmetic average roughness on an outer peripheral surface of the band-shaped portion; and Rap denotes an arithmetic average roughness on an outer peripheral surface of the spherical portion.

Abstract: A friction stir welding tool member including: a shoulder portion; and a probe portion. A helical concavo-convex portion including a ridge and a valley is provided on a side peripheral surface of the probe portion. In a cross-section passing through a rotation axis of the probe portion, a differential rate of areas of valley parts adjacent along an axis parallel to the rotation axis out of the valley is within a range of 5% or more and 30% or less. A difference between pitches of ridge parts adjacent along the axis parallel to the rotation axis out of the ridge is preferably within a range of 0.01 mm or more and 0.2 mm or less. A difference between depths of valley parts adjacent along the axis parallel to the rotation axis out of the valley is preferably within a range of 0.01 mm or more and 0.1 mm or less.

Abstract: A ceramic ball material according to an embodiment including: a spherical portion; and a band-shaped portion formed in a band shape. When C denotes circularity of the band-shaped portion as observed from a height direction thereof, the circularity C is in a range of more than 0% and 2.5% or more.

Abstract: A ceramic ball material according to an embodiment including: a spherical portion; and a band-shaped portion formed over a circumference of a surface of the spherical portion. The ceramic ball material has a ratio Rtb/Rts of 1.0 or more, where Rtb denotes a maximum cross-sectional height of a roughness profile on an outer peripheral surface of the band-shaped portion; and Rts denotes a maximum cross-sectional height of roughness on an outer peripheral surface of the spherical portion.

Abstract: A rubber mold according to an embodiment is for CIP processing of a green compact with a plate shape. The rubber mold includes one or more approximately columnar hole sections are provided on at least one or more bottom surfaces. Further, when a diameter of an opening of the hole section is denoted by a and a maximum depth of the hole section is denoted by b, a/b<2.0 is satisfied.

Abstract: According to an embodiment, a silicon nitride sintered body includes silicon nitride crystal grains and a grain boundary phase. In a case where Raman spectroscopy of a 20 ?m×20 ?m region at any cross section of the silicon nitride sintered body is performed, seven or more peaks are detected within a range of not less than 400 cm?1 and not more than 1200 cm?1, and the most intense peak of the seven or more peaks is not in a range of not less than 515 cm?1 and not more than 525 cm?1. Favorably, at least three of the seven or more peaks exist within a range of not less than 530 cm?1 and not more than 830 cm?1. It is favorable for at least one of the seven or more peaks to be within a range of not less than 440 cm?1 and not more than 460 cm?1.

Abstract: A friction stir welding tool member according to the present embodiment has a shoulder portion and a probe portion concentrically projecting from an upper surface of the shoulder portion. The shoulder portion includes a curved surface processed portion that is curved to have a curved shape on an outer peripheral edge of the shoulder portion. A space occupancy occupied by the two-dimensional space in which neither the shoulder portion nor the probe portion exists is in a range of 30% to 70%, the space occupancy being determined based on a projection drawing of a side surface region surrounded from a tip of the probe portion to the curved surface processed portion of the shoulder portion.

Abstract: A ceramic ball material according to the present embodiment includes a spherical portion, and a band-shaped portion formed over a circumference of a surface of the spherical portion. The band-shaped portion has a width in a range of 0.5 mm or more and 4.0 mm or less, both shoulders of which are provided with an R section having a radius of curvature of 0.02 mm or more. Any one of aluminum oxide, silicon nitride, boron nitride, and zirconium oxide is used as the ceramic.

Abstract: A silicon nitride sintered body includes a silicon nitride crystal grains and grain boundary phases. Further, when D stands for width of the silicon nitride sintered body before being subjected to surface processing, relations between an average grain diameter dA and an average aspect ratio rA of the silicon nitride crystal grain in a first region from an outermost surface to a depth of 0 to 0.01D and an average grain diameter dB and an average aspect ratio rB of the silicon nitride crystal grain in a second region inside the first region satisfy the inequalities: 0.8? dA/dB? 1.2; and 0.8? rA/rB? 1.2.

Abstract: A silicon nitride sintered body includes at least one black portion with a major axis of 10 ?m or more in a field of view with a unit area of 5 mm×5 mm, when observing an arbitrary cross-section of the silicon nitride sintered body using a metallurgical microscope. A major axis of the black portion is Preferably 500 ?m or less. The number of the black portion within the field of view with a unit area of 5 mm×5 mm is preferably 2 or more and 10 or less. A segregation portion of Fe is preferably included in the black portion.

Abstract: The friction stir welding tool member according to the present invention is made of a ceramic member in which a shoulder portion and a probe portion are integrally formed, wherein a root portion of the probe portion and an end portion of the shoulder portion have a curved surface shape; and the friction stir welding tool member has a ratio (R1/D) of 0.02 or more and 0.20 or less when a curvature radius of the end portion of the shoulder portion is defined as R1 (mm) and an outer diameter of the shoulder portion is defined as D (mm). In addition, the ceramic member is preferably made of a silicon nitride sintered body having a Vickers hardness of 1400 HV1 or more. According to the above-described configuration, a friction stir welding tool member having excellent durability can be provided.

Abstract: The sliding member according to the embodiment includes a silicon nitride sintered body that includes silicon nitride crystal grains and a grain boundary phase, in which a percentage of a number of the silicon nitride crystal grains including dislocation defect portions inside the silicon nitride crystal grains among any 50 of the silicon nitride crystal grains having completely visible contours in a 50 ?m×50 ?m observation region of any cross section or surface of the silicon nitride sintered body is not less than 0% and not more than 10%. The percentage is more preferably not less than 0% and not more than 3%.

Abstract: The friction stir welding tool member according to the present invention is made of a silicon nitride sintered body, wherein the silicon nitride sintered body contains 15% by mass or less of additive components except silicon nitride in such a manner that the additive components include at least one element selected from lanthanoid elements and at least one element selected from Mg, Ti, Hf, and Mo. In addition, it is preferable that the additive components further include at least one element selected from Al, Si, and C. According to the above-described configuration, a friction stir welding tool member having an excellent durability can be provided.

Abstract: The present invention provides a silicon nitride sintered body including silicon nitride crystal grains and a grain boundary phase, wherein the silicon nitride crystal grains are covered with the grain boundary phase and width of the grain boundary phase is 0.2 nm or more. It is preferable that the width of the grain boundary phase is 0.2 nm to 5 nm. Additionally, it is preferable that the silicon nitride sintered body includes 15% by mass or less of the grain boundary phase. According to the above-described configuration, it is possible to provide a high-temperature-resistant silicon nitride sintered body in which degradation of the grain boundary phase under high temperature environment is suppressed. This silicon nitride sintered body is suitable for constituent material of a high-temperature-resistant member, use environment of which is 300° C. or higher.

Abstract: The present invention provides a welding tool member for friction stir welding comprising a silicon nitride sintered body, wherein the silicon nitride sintered body includes an additive component other than silicon nitride in a content of 15% by mass or less, and the additive component includes three or more elements selected from Y, Al, Mg, Si, Ti, Hf, Mo and C. It is preferable that the content of the additive component is 3% by mass or more and 12.5% by mass or less. It is also preferable that the additive component includes four or more elements selected from Y, Al, Mg, Si, Ti, Hf, Mo and C. Due to above structure, there can be provided a welding tool member for friction stir welding having a high durability.

Abstract: The friction stir welding tool member according to the present invention is made of a ceramic member in which a shoulder portion and a probe portion are integrally formed, wherein a root portion of the probe portion and an end portion of the shoulder portion have a curved surface shape; and the friction stir welding tool member has a ratio (R1/D) of 0.02 or more and 0.20 or less when a curvature radius of the end portion of the shoulder portion is defined as R1 (mm) and an outer diameter of the shoulder portion is defined as D (mm). In addition, the ceramic member is preferably made of a silicon nitride sintered body having a Vickers hardness of 1400 HV1 or more. According to the above-described configuration, a friction stir welding tool member having excellent durability can be provided.

Abstract: The friction stir welding tool member according to the present invention is made of a silicon nitride sintered body, wherein the silicon nitride sintered body contains 15% by mass or less of additive components except silicon nitride in such a manner that the additive components include at least one element selected from lanthanoid elements and at least one element selected from Mg, Ti, Hf, and Mo. In addition, it is preferable that the additive components further include at least one element selected from Al, Si, and C. According to the above-described configuration, a friction stir welding tool member having an excellent durability can be provided.

Abstract: The present invention provides a silicon nitride sintered body including silicon nitride crystal grains and a grain boundary phase, wherein the silicon nitride crystal grains are covered with the grain boundary phase and width of the grain boundary phase is 0.2 nm or more. It is preferable that the width of the grain boundary phase is 0.2 nm to 5 nm. Additionally, it is preferable that the silicon nitride sintered body includes 15% by mass or less of the grain boundary phase. According to the above-described configuration, it is possible to provide a high-temperature-resistant silicon nitride sintered body in which degradation of the grain boundary phase under high temperature environment is suppressed. This silicon nitride sintered body is suitable for constituent material of a high-temperature-resistant member, use environment of which is 300° C. or higher.