The present invention aims at providing an iron-nitrogen-based soft magnetic steel sheet having a saturation magnetic flux density higher than that of pure iron, a method for manufacturing the soft magnetic steel sheet, and a core and a dynamo-electric machine in which the soft magnetic steel sheet is used. The soft magnetic steel sheet according to the present invention includes C, N, and the balance of Fe and inevitable impurities and is comprised of an α phase, an α′ phase, an α″ phase, and a γ phase. The α phase serves as a main phase, a volume ratio of the α″ phase is 10% or more, and a volume ratio of the γ phase is 5% or less. The core according to the present invention includes a laminated body of the soft magnetic steel sheets.

Disclosed is a highly anticorrosive martensitic stainless steel having uniformly distributed fine chromium carbide so as to have improved corrosion resistance and being applicable as tableware with suitable hardness when strengthened by heat treatment, and a manufacturing metho therefor.

The highly anticorrosive martensitic stainless steel according to an embodiment of the present disclosure includes, in percent by weight (wt%), 0.14 to 0.21% of C, 0.05 to 0.11% of N, 0.1 to 0.6% of Si, 0.4 to 1.2% of Mn, 14.0 to 17.0% of Cr, 0.2 to 0.32% of C+N, and the balance of Fe and inevitable impurities, has a PREN value, represented by Formula (1), of 16 or more, and has a precipitation temperature of chromium carbide of 950° C. or lower.

Disclosed is a highly anticorrosive martensitic stainless steel having uniformly distributed fine chromium carbide so as to have improved corrosion resistance and being applicable as tableware with suitable hardness when strengthened by heat treatment, and a manufacturing metho therefor.

The highly anticorrosive martensitic stainless steel according to an embodiment of the present disclosure includes, in percent by weight (wt%), 0.14 to 0.21% of C, 0.05 to 0.11% of N, 0.1 to 0.6% of Si, 0.4 to 1.2% of Mn, 14.0 to 17.0% of Cr, 0.2 to 0.32% of C+N, and the balance of Fe and inevitable impurities, has a PREN value, represented by Formula (1), of 16 or more, and has a precipitation temperature of chromium carbide of 950° C. or lower.

An object of the present invention is to provide a low thermal expansion cast steel having sufficient strength even at a high temperature and a low coefficient of thermal expansion. The low thermal expansion cast steel of the present invention is obtained by suitably heat treating a cast steel comprising, by mass %, C: 0 to 0.10%, Si: 0 to 1.00%, Mn: 0 to 1.00%, Co: 13.00 to 17.50%, Ni satisfying −3.5×% Ni+118%≤Co−3.5×% Ni+121 (% Ni and %≤Co respectively represent the contents of Ni and Co (mass %)), and a balance of Fe and unavoidable impurities so that the 0.2% proof stress in a tensile test at 400° C. becomes 100 MPa or more, the average coefficient of thermal expansion at 25 to 350° C. becomes 6.0 ppm/° C. or less, and the Curie temperature becomes 350° C. or more.

A low thermal expansion cast steel having a sufficient strength even at a high temperature and having a low coefficient of thermal expansion, that is, a low thermal expansion cast steel comprising, by mass %, C: 0 to 0.100%, Si: 0 to 1.00%, Mn: 0 to 1.00%, Co: 8.0 to 13.0%, and Ni satisfying −2.5×% Ni+85.5≤% Co≤−2.5×% Ni+90.5 (% Ni and % Co respectively being contents of Ni and Co (mass %)) and having a balance of Fe and unavoidable impurities and having, upon being subjected to suitable heat treatment, a 0.2% proof stress of a tensile test at 300° C. of 125 MPa or more, having an average coefficient of thermal expansion at 25 to 300° C. of 4.0 ppm/° C. or less, and having a Curie temperature of 250° C. or more.

A low thermal expansion cast steel having a sufficient strength even at a high temperature and having a low coefficient of thermal expansion, that is, a low thermal expansion cast steel comprising, by mass %, C: 0 to 0.100%, Si: 0 to 1.00%, Mn: 0 to 1.00%, Co: 8.0 to 13.0%, and Ni satisfying −2.5×% Ni+85.5≤% Co≤−2.5×% Ni+90.5 (% Ni and % Co respectively being contents of Ni and Co (mass %)) and having a balance of Fe and unavoidable impurities and having, upon being subjected to suitable heat treatment, a 0.2% proof stress of a tensile test at 300° C. of 125 MPa or more, having an average coefficient of thermal expansion at 25 to 300° C. of 4.0 ppm/° C. or less, and having a Curie temperature of 250° C. or more.

A method of processing ultra high hardness steel is provided to increase its usefulness in armor applications. The method involves slowly cooling the ultra high hardness steel to a cryogenic temperature, slowly returning the steel to an ambient temperature, slowly heating the steel, and again slowly returning it to an ambient temperature.

A method of processing ultra high hardness steel is provided to increase its usefulness in armor applications. The method involves slowly cooling the ultra high hardness steel to a cryogenic temperature, slowly returning the steel to an ambient temperature, slowly heating the steel, and again slowly returning it to an ambient temperature.

Methods of selectively cooling and quenching surface regions of high-strength transformation induced plasticity (TRIP) steel are provided. The method may comprise selectively cooling at least one region of an exposed surface of a hot-formed press-hardened component comprising a high-strength steel. Prior to selective cooling, the component has a microstructure comprising≧about 5% by volume retained austenite in a matrix of martensite. The selective cooling is conducted at a temperature of≦about −40° C. and forms at least one quenched region comprising≦about 2% by volume austenite. The TRIP steel may be zinc-coated and having a surface coating comprising zinc and substantially free of liquid metal embrittlement (LME). Zinc-coated hot-formed press-hardened components, including automotive components, formed from such methods are also provided.

Methods of selectively cooling and quenching surface regions of high-strength transformation induced plasticity (TRIP) steel are provided. The method may comprise selectively cooling at least one region of an exposed surface of a hot-formed press-hardened component comprising a high-strength steel. Prior to selective cooling, the component has a microstructure comprising≧about 5% by volume retained austenite in a matrix of martensite. The selective cooling is conducted at a temperature of≦about −40° C. and forms at least one quenched region comprising≦about 2% by volume austenite. The TRIP steel may be zinc-coated and having a surface coating comprising zinc and substantially free of liquid metal embrittlement (LME). Zinc-coated hot-formed press-hardened components, including automotive components, formed from such methods are also provided.