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.

A soft magnetic iron alloy plate having saturation magnetic flux density higher than that of an electromagnetic pure iron plate without an excessive increase in an iron loss, a method for manufacturing the soft magnetic iron alloy plate, and an iron core and a rotating electric machine using the soft magnetic iron alloy plate are provided. A soft magnetic iron alloy plate according to the present invention includes chemical composition containing 2 to 10 at. % of N, 0 to 30 at. % of Co, 0 to 1.2 at. % of V, and a remaining portion including Fe and impurities, and in a thickness direction of the soft magnetic iron alloy plate, an outer nitrogen concentration transition region where N concentration on a main surface is 1 to 4 at. % and N concentration increases toward the inner side from the main surface, a high nitrogen concentration region where maximum N concentration is higher than N concentration of the main surface and less than 11 at. %, and a variation range of N concentration is within 1 at. %, and an inner nitrogen concentration transition region where N concentration decreases toward the inner side from the high nitrogen concentration region and minimum N concentration is lower than N concentration in the high nitrogen concentration region and is 1 at. % or more.

A soft magnetic iron alloy plate having saturation magnetic flux density higher than that of an electromagnetic pure iron plate without an excessive increase in an iron loss, a method for manufacturing the soft magnetic iron alloy plate, and an iron core and a rotating electric machine using the soft magnetic iron alloy plate are provided. A soft magnetic iron alloy plate according to the present invention includes chemical composition containing 2 to 10 at. % of N, 0 to 30 at. % of Co, 0 to 1.2 at. % of V, and a remaining portion including Fe and impurities, and in a thickness direction of the soft magnetic iron alloy plate, an outer nitrogen concentration transition region where N concentration on a main surface is 1 to 4 at. % and N concentration increases toward the inner side from the main surface, a high nitrogen concentration region where maximum N concentration is higher than N concentration of the main surface and less than 11 at. %, and a variation range of N concentration is within 1 at. %, and an inner nitrogen concentration transition region where N concentration decreases toward the inner side from the high nitrogen concentration region and minimum N concentration is lower than N concentration in the high nitrogen concentration region and is 1 at. % or more.

A method of treating a steel including, in percentages by weight: 0.2% to 0.33% carbon, 4% to 8% cobalt, 7% to 11% nickel, 0.8% to 3% chromium, 0.5% to 2.5% molybdenum, 0.5% to 5.9% tungsten, 0.05% to 0.2% vanadium, and not more than 0.02% titanium, the balance being constituted by iron and inevitable impurities, the method including subjecting the steel to solutionizing heat treatment at a temperature from 950 C. to 1100 C.; then subjecting the steel to quenching treatment; then placing the steel in a cryogenic enclosure; cooling the inside of the cryogenic chamber in which the steel is present to a treatment temperature less than or equal to 73 C.; and subjecting the steel to cryogenic treatment while the treatment temperature is maintained inside the enclosure, the time duration between the end of the quenching treatment and the beginning of the cryogenic treatment being less than or equal to 4 hours.

A method of treating a steel including, in percentages by weight: 0.2% to 0.33% carbon, 4% to 8% cobalt, 7% to 11% nickel, 0.8% to 3% chromium, 0.5% to 2.5% molybdenum, 0.5% to 5.9% tungsten, 0.05% to 0.2% vanadium, and not more than 0.02% titanium, the balance being constituted by iron and inevitable impurities, the method including subjecting the steel to solutionizing heat treatment at a temperature from 950 C. to 1100 C.; then subjecting the steel to quenching treatment; then placing the steel in a cryogenic enclosure; cooling the inside of the cryogenic chamber in which the steel is present to a treatment temperature less than or equal to 73 C.; and subjecting the steel to cryogenic treatment while the treatment temperature is maintained inside the enclosure, the time duration between the end of the quenching treatment and the beginning of the cryogenic treatment being less than or equal to 4 hours.

A martensitic stainless steel containing, by mass %, C: 0.20% to 0.40%, N: 0.1% or less, Mo: 3% or less, and Cr: 12.0% to 16.0%, such that 0.3%C+N0.4% and a PI value (=Cr+3.3 Mo+16 N) is 18 or more, with the remainder being substantially Fe and unavoidable impurities is quenched from a temperature of 1,030 C. to 1,140 C. and subjected to a subzero treatment and tempering so as to obtain a prior austenite crystal grain size of a surface layer of 30 m to 100 m and a surface hardness of 58 HRc to 62 HRc.

A martensitic stainless steel containing, by mass %, C: 0.20% to 0.40%, N: 0.1% or less, Mo: 3% or less, and Cr: 12.0% to 16.0%, such that 0.3%C+N0.4% and a PI value (=Cr+3.3 Mo+16 N) is 18 or more, with the remainder being substantially Fe and unavoidable impurities is quenched from a temperature of 1,030 C. to 1,140 C. and subjected to a subzero treatment and tempering so as to obtain a prior austenite crystal grain size of a surface layer of 30 m to 100 m and a surface hardness of 58 HRc to 62 HRc.

A cryogenic chamber system can include a vacuum chamber operable at a vacuum pressure of 100 mTorr or less, and a cold head assembly including an expander for receiving and expanding cryogenic fluid for cooling a cold head interface. The cold head assembly can be positioned within the vacuum chamber. The cryogenic chamber system can further include a thermally conductive platform thermally coupled to the cold head interface within the vacuum chamber, wherein the thermally conductive platform has a working surface having a surface area that is at least 10 times larger than a surface area of the cold head interface. The working surface can be configured to reach a temperature from about 4 K to about 120 K at the vacuum pressure as a result of thermal coupling with the cold head interface.

A soft magnetic iron alloy sheet has a saturation magnetic flux density comparable to that of Permendur, with the same iron loss as electromagnetic pure iron, and a lower cost than Permendur. The soft magnetic iron alloy sheet includes, as a chemical composition, 30 at % or less of Co, 0.1 at % or more and 11 at % or less of N, and 1.2 at % or less of vanadium, with the remainder being Fe and impurities. In a thickness direction of the soft magnetic iron alloy sheet, a surface layer region has an average nitrogen concentration of 1 at % or more and 15 at % or less and an internal region has a lower average nitrogen concentration than the surface layer region. In the surface layer region, a thickness is 1% or more and 30% or less from both main surfaces of the sheet and iron-nitride martensite having a tetragonal structure is formed.

A manufacturing method of precision machine tool bearing with high precision stability includes the procedures: (1) microstructural stabilization of bearing body: by cold ring rolling, two liquid quenching, ultrasonic assisted multiple cryo-tempering treatment and stress ageing treatment, the bearing body with high microstructure stability can be obtained; (2) precision machining; (3) internal stress relaxation of bearing body: after precision machining, by executing magnetic treatment on the bearing body, bearing ring with high microstructure stability and low internal stresses can be obtained; and (4) bearing assembly: finally precision machine tool bearing with high precision stability can be obtained. Considering that the critical factors affecting the precision stability of bearing is the degree of microstructure stability and internal stresses, by improving the microstructure stability and reducing residual stress in multistage manufacture phase, precision stability of precision machine tool bearing should be promoted.