Disclosed is a martensitic stainless steel material for a hydrogen gas environment, having a composition consisting of: 0.03 mass %?C?1.20 mass %, Si?1.00 mass %, Mn?1.50 mass %, P?0.060 mass %, S?0.250 mass %, Cu?0.50 mass %, 8.0 mass %?Cr?22.0 mass %, Ni?1.00 mass %, and N?0.40 mass %, and optionally at least one selected from the group consisting of: Mo?3.00 mass %, V?1.50 mass %, Nb?1.00 mass %, Pb?0.30 mass %, and B?0.0500 mass %, with the balance being Fe and inevitable impurities; having: a content of a precipitate of 1.50 mass % or more, a crystal grain size number of prior austenite grains of 2.0 or more, a metal structure including a martensite structure, a tensile strength of 1,800 MPa or less, and satisfying D.sub.H2(0.7)/D.sub.air?0.8.

Disclosed is a martensitic stainless steel material for a hydrogen gas environment, having a composition consisting of: 0.03 mass %?C?1.20 mass %, Si?1.00 mass %, Mn?1.50 mass %, P?0.060 mass %, S?0.250 mass %, Cu?0.50 mass %, 8.0 mass %?Cr?22.0 mass %, Ni?1.00 mass %, and N?0.40 mass %, and optionally at least one selected from the group consisting of: Mo?3.00 mass %, V?1.50 mass %, Nb?1.00 mass %, Pb?0.30 mass %, and B?0.0500 mass %, with the balance being Fe and inevitable impurities; having: a content of a precipitate of 1.50 mass % or more, a crystal grain size number of prior austenite grains of 2.0 or more, a metal structure including a martensite structure, a tensile strength of 1,800 MPa or less, and satisfying D.sub.H2(0.7)/D.sub.air?0.8.

The present invention discloses a steel for bolts, which comprises the following chemical elements in percentage by mass in addition to Fe and inevitable impurities: C: 0.37 to 0.45%; Si: 0.01 to 0.08%; Mn: 0.45 to 0.80%; Cr: 0.90 to 1.30%; Mo: 0.20 to 0.45%; Ni: 0.10 to 0.30%; V: 0.15 to 0.30%; and Al: 0.015 to 0.035%. The present invention further discloses a method for manufacturing the steel for bolts, which comprises the following steps: (1) smelting; (2) casting; (3) rough rolling; (4) high-speed wire rolling; (5) Stelmor controlled cooling; and (6) heat treatment, wherein the holding temperature of spheroidizing heat treatment is 760 to 790? C. and the holding time is 4 to 12 h, followed by a slow cooling process after the holding with a cooling speed of lower than 40? C./h. The drawing area reduction rate of a coil rod is controlled to 5 to 30%. The heating temperature of quenching and tempering heat treatment is 850 to 950? C. The tempering temperature is 500 to 600? C. The steel for bolts disclosed in the present invention has a uniform structure and performance, has low production costs, and has high strength and good delayed fracture resistance.

The present invention discloses a steel for bolts, which comprises the following chemical elements in percentage by mass in addition to Fe and inevitable impurities: C: 0.37 to 0.45%; Si: 0.01 to 0.08%; Mn: 0.45 to 0.80%; Cr: 0.90 to 1.30%; Mo: 0.20 to 0.45%; Ni: 0.10 to 0.30%; V: 0.15 to 0.30%; and Al: 0.015 to 0.035%. The present invention further discloses a method for manufacturing the steel for bolts, which comprises the following steps: (1) smelting; (2) casting; (3) rough rolling; (4) high-speed wire rolling; (5) Stelmor controlled cooling; and (6) heat treatment, wherein the holding temperature of spheroidizing heat treatment is 760 to 790? C. and the holding time is 4 to 12 h, followed by a slow cooling process after the holding with a cooling speed of lower than 40? C./h. The drawing area reduction rate of a coil rod is controlled to 5 to 30%. The heating temperature of quenching and tempering heat treatment is 850 to 950? C. The tempering temperature is 500 to 600? C. The steel for bolts disclosed in the present invention has a uniform structure and performance, has low production costs, and has high strength and good delayed fracture resistance.

Provided is a repair-welding material for die having a composition containing, by mass %: 0.18%C0.35%, 0.01%Si0.20%, 1.30%Mn1.90%, 0.50%Cr1.50%, 1.50%Mo2.50%, 0.30%V1.00%, N0.020%, and O0.0050%, with a balance being Fe and inevitable impurities.

A bearing part according the present invention includes, as the chemical composition, by mass %, C: 0.95% to 1.10%, Si: 0.10% to 0.70%, Mn: 0.20% to 1.20%, Cr: 0.90% to 1.60%, Al: 0.010% to 0.100%, N: 0.003% to 0.030%, P: 0.025% or less, S: 0.025% or less, O: 0.0010% or less, and optionally Mo: 0.25% or less, B: 0.0050% or less, Cu: 1.0% or less, Ni: 3.0% or less, and Ca: 0.0015% or less, and a remainder including Fe and impurities; metallographic structure includes a retained austenite, a spherical cementite and a martensite; an amount of the retained austenite is 15% to 25%, by volume %; an average grain size of prior-austenite is 8.0 m or less; and a number density of a void having a circle equivalent diameter of 0.02 m to 3.0 m is 2000 mm.sup.2 or less in the metallographic structure.

A bearing part according the present invention includes, as the chemical composition, by mass %, C: 0.95% to 1.10%, Si: 0.10% to 0.70%, Mn: 0.20% to 1.20%, Cr: 0.90% to 1.60%, Al: 0.010% to 0.100%, N: 0.003% to 0.030%, P: 0.025% or less, S: 0.025% or less, O: 0.0010% or less, and optionally Mo: 0.25% or less, B: 0.0050% or less, Cu: 1.0% or less, Ni: 3.0% or less, and Ca: 0.0015% or less, and a remainder including Fe and impurities; metallographic structure includes a retained austenite, a spherical cementite and a martensite; an amount of the retained austenite is 15% to 25%, by volume %; an average grain size of prior-austenite is 8.0 m or less; and a number density of a void having a circle equivalent diameter of 0.02 m to 3.0 m is 2000 mm.sup.2 or less in the metallographic structure.

To provide: an inorganic oxide powder which, when filled in a resin material, can simultaneously achieve a high dielectric constant and a low dielectric dissipation factor; a method for producing the same; and a resin composition comprising the inorganic oxide powder.

Provided is an inorganic oxide powder comprising a spherical titanium oxide powder having a rutile phase, wherein the ratio of the rutile phase in the inorganic oxide powder is 90 mass % or more. Further provided is a resin composition comprising the inorganic oxide powder and at least one resin selected from a thermoplastic resin and a thermosetting resin.

To provide: an inorganic oxide powder which, when filled in a resin material, can simultaneously achieve a high dielectric constant and a low dielectric dissipation factor; a method for producing the same; and a resin composition comprising the inorganic oxide powder.

Provided is an inorganic oxide powder comprising a spherical titanium oxide powder having a rutile phase, wherein the ratio of the rutile phase in the inorganic oxide powder is 90 mass % or more. Further provided is a resin composition comprising the inorganic oxide powder and at least one resin selected from a thermoplastic resin and a thermosetting resin.

According to an embodiment, a coil spring is formed of a wire which is helically wound, and includes an end turn portion and an effective portion, and a surface of the wire in the end turn portion includes an area which is softer than a surface of the wire in the effective portion.