Abstract: The present invention provides an oxide dispersion strengthened alloy in which even with aluminum contained, the particle diameter and dispersion spacing of the oxide are decreased, and the strength at high temperature, the high temperature oxidation and the corrosion resistance can be improved. An oxide dispersion strengthened alloy being a nickel-base alloy containing aluminum, hafnium, and yttrium oxide, wherein a complex oxide of the yttrium oxide and hafnium oxide is dispersed in a matrix of the nickel-base alloy, with the aluminum contained.

Abstract: A method of manufacturing an oxide dispersion strengthened ferritic steel excellent in high-temperature creep strength having a coarse grain structure. The method comprises mixing alloy powders and an Y2O3 powder, subjecting the mixed powder to mechanical alloying treatment, solidifying the alloyed powder by hot extrusion, and subjecting the extruded solidified material to final heat treatment involving heating to and holding at a temperature of not less than the Ac3 transformation point and slow cooling at a rate of not more than a ferrite-forming critical rate which comprises, 0.05-0.25% C, 8.0-12.0% Cr, 0.1-4.0% W, 0.1-1.0% Ti, 0.1-0.5% Y2O3 by weight, with the balance being Fe. In this method, by using a TiO2 powder as a Ti component to be mixed at the mechanical alloying treatment or by adding a Fe2O3 powder, the bonding of Ti with C is suppressed, and the C concentration in the matrix does not decrease.

Abstract: An oxide dispersion strengthened martensitic steel excellent in high-temperature strength having residual ?-grains can be manufactured by a method comprising mixing either element powders or alloy powders and a Y2O3 powder; subjecting the resulting mixed powder to mechanical alloying treatment; solidifying the resulting alloyed powder by hot extrusion; and subjecting the resulting extruded solidified material to final heat treatment involving normalizing and tempering heat treatment to thereby manufacture an oxide dispersion strengthened martensitic steel in which Y2O3 particles are dispersed in the steel, wherein ?to ?transformation is not allowed to occur during the described hot extrusion and the proportion of residual ?-grains in which oxide particles are finely dispersed in high density is increased by controlling the mixture ratio of the powders for the mechanical alloying treatment.

Abstract: There is provided a method for producing oxide dispersion strengthened ferritic steel tube by fabricating a raw tube by mixed sintering of a metal powder and an oxide powder and producing a tube of the desired shape by repeating cold rolling and heat treatment for a total of three times or more. The method comprises performing each of the intermediate heat treatments during the cold rolling by a two-step heat treatment consisting of a first step heat treatment of 1100° C. or lower and a second step heat treatment of 1100 to 1250° C. and higher than the first step temperature, and performing the final heat treatment at 1100° C. or higher.

Abstract: In an oxide dispersion strengthened martensitic steel which comprises, by % by weight, 0.05 to 0.25% C, 8.0 to 12.0% Cr, 0.1 to 4.0% W, 0.1 to 1.0% Ti, 0.1 to 0.5% Y2O3 with the balance being Fe and unavoidable impurities and in which Y2O3 particles are dispersed in the steel, by adjusting the Ti content within the range of 0.1 to 1.0% so that an excess oxygen content Ex.O in steel satisfies [0.22×Ti (% by weight)<Ex.O (% by weight)<0.46×Ti (% by weight)], the oxide particles are finely dispersed and highly densified to thereby obtain an oxide dispersion strengthened martensitic steel excellent in high-temperature strength. It is also possible to reduce the amount of oxygen contamination in steel during the mechanical alloying of raw material powders to provide Ex.O within a predetermined range, by carrying out the mechanical alloying in an Ar atmosphere having a super purity of not less than 99.

Abstract: An oxide dispersion strengthened martensitic steel excellent in high-temperature strength having residual ?-grains can be manufactured by a method comprising mixing either element powders or alloy powders and a Y2O3 powder; subjecting the resulting mixed powder to mechanical alloying treatment; solidifying the resulting alloyed powder by hot extrusion; and subjecting the resulting extruded solidified material to final heat treatment involving normalizing and tempering heat treatment to thereby manufacture an oxide dispersion strengthened martensitic steel which comprises, as expressed by % by weight, 0.05 to 0.25% C, 8.0 to 12.0% Cr, 0.1 to 4.0% W, 0.1 to 1.0% Ti, 0.1 to 0.

Abstract: In an oxide dispersion strengthened martensitic steel which comprises, by % by weight, 0.05 to 0.25% C, 8.0 to 12.0% Cr, 0.1 to 4.0% W, 0.1 to 1.0% Ti, 0.1 to 0.5% Y2O3 with the balance being Fe and unavoidable impurities and in which Y2O3 particles are dispersed in the steel, by adjusting the Ti content within the range of 0.1 to 1.0% so that an excess oxygen content Ex.O in steel satisfies [0.22×Ti (% by weight)<Ex.O (% by weight)<0.46×Ti (% by weight)], the oxide particles are finely dispersed and highly densified to thereby obtain an oxide dispersion strengthened martensitic steel excellent in high-temperature strength. It is also possible to reduce the amount of oxygen contamination in steel during the mechanical alloying of raw material powders to provide Ex.O within a predetermined range, by carrying out the mechanical alloying in an Ar atmosphere having a super purity of not less than 99.

Abstract: A method of manufacturing an oxide dispersion strengthened ferritic steel excellent in high-temperature creep strength having a coarse grain structure is provided. This method comprises mixing either element powders or alloy powders and a Y2O3 powder, subjecting the mixed powder to mechanical alloying treatment, solidifying the resulting alloyed powder by hot extrusion, and subjecting the resulting extruded solidified material to final heat treatment involving heating to and holding at a temperature of not less than the AC3 transformation point and slow cooling at a rate of not more than a ferrite-forming critical rate to thereby manufacture an oxide dispersion strengthened ferritic steel which comprises, as expressed by % by weight, 0.05 to 0.25% C, 8.0 to 12.0% Cr, 0.1 to 4.0% W, 0.1 to 1.0% Ti, 0.1 to 0.5% Y2O3 with the balance being Fe and unavoidable impurities and in which Y2O3 particles are dispersed in the steel.

Abstract: There is provided a method for producing oxide dispersion strengthened ferritic steel tube by fabricating a raw tube by mixed sintering of a metal powder and an oxide powder and producing a tube of the desired shape by repeating cold rolling and heat treatment for a total of three times or more. The method comprises performing each of the intermediate heat treatments during the cold rolling by a two-step heat treatment consisting of a first step heat treatment of 1100° C. or lower and a second step heat treatment of 1100 to 1250° C. and higher than the first step temperature, and performing the final heat treatment at 1100° C. or higher.

Abstract: A method of producing an iron-based dispersion-strengthened alloy tube (2-1) by utilizing a rolling machine having grooved rolls (5, 5-1) and a mandrel (9)for forming the tube (2-1) from a raw rolling tube (2). In the method, a length of contact between a rolling surface (6, 6-1) of a caliber formed by the grooved rolls and an outer circumference of the rolling tube is set to be 0.9 times or more of a circumferential length of the rolling tube over the entire area of the rolling region. It is preferred that the method be performed by a Pilger type rolling machine.

Abstract: A high-Ni austenitic stainless steel having swelling resistance, high-temperature creep strength, and phase stability under irradiation. The irradiation resistance and high-temperature strength of the high-Ni austenitic stainless steel are enhanced when it is composed of the following percentages by weight: Si, not exceeding 0.5 wt. %; Mn, not exceeding 1.0 wt. %; Cr, 13-18 wt. %; Ni, 30-50 wt. %; Mo+W=2.0-6.0 wt. %; Nb+V=0.1-0.8 wt. % (Nb/(Nb+V) ?weight ratio!=0.20-0.85 ?weight ratio!; N, 0.01-0.2 wt. %; and the residual consisting of Fe and unavoidable impurities.