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 for manufacturing an austenitic stainless steel workpiece including the following successive steps: 1) providing a powder and sintering the powder to form a sintered alloy with an austenitic structure; the alloy having a nitrogen content greater than or equal to 0.1% by weight, 2) treating the sintered alloy to transform the austenitic structure into a ferritic structure or ferrite+austenite two-phase structure on a surface layer of the alloy, 3) treating the sintered alloy to transform the ferritic or ferrite+austenite two-phase structure obtained in step 2) into an austenitic structure and, after cooling, forming the workpiece which, on the layer subjected to the transformations in steps 2) and 3), has a density higher than that of the core of the workpiece. The present description also relates to the workpiece obtained by the method which has a very dense surface layer (99%).

A method for manufacturing FeNi ordered alloy having a L1.sub.0 type order structure is provided. After a nitrification process for nitriding a powder sample of a FeNi disordered alloy arranged in a tube furnace is performed using a NH.sub.3 gas, a de-nitrification process for removing a nitrogen from the FeNi disordered alloy which is processed by the nitrification process is performed using a H.sub.2 gas. Thus, the L1.sub.0 type FeNi ordered alloy with a regularity defined by S equal to or higher than 0.5 is obtained.

A method for manufacturing FeNi ordered alloy having a L1.sub.0 type order structure is provided. After a nitrification process for nitriding a powder sample of a FeNi disordered alloy arranged in a tube furnace is performed using a NH.sub.3 gas, a de-nitrification process for removing a nitrogen from the FeNi disordered alloy which is processed by the nitrification process is performed using a H.sub.2 gas. Thus, the L1.sub.0 type FeNi ordered alloy with a regularity defined by S equal to or higher than 0.5 is obtained.

The present invention provides a soft magnetic iron sheet exhibiting a high saturation magnetic flux density and a low iron loss as compared with an electromagnetic pure iron sheet, a method for producing the soft magnetic iron sheet, and, an iron core and a dynamo-electric machine, each using the soft magnetic iron sheet. The soft magnetic iron sheet according to the present invention includes: iron as a main component; and nitrogen, in which the soft magnetic iron sheet includes, along a thickness direction of the soft magnetic iron sheet: a high nitrogen concentration layer having a nitrogen concentration of 2 at. % to 11 at. %; a low nitrogen concentration layer having a nitrogen concentration of half or less of the nitrogen concentration of the high nitrogen concentration layer; and a nitrogen concentration transition layer connecting the nitrogen concentration of the high nitrogen concentration layer and the nitrogen concentration of the low nitrogen concentration layer, and wherein a surface layer region including at least both main surfaces of the soft magnetic iron sheet is the low nitrogen concentration layer.

The present invention provides a soft magnetic iron sheet exhibiting a high saturation magnetic flux density and a low iron loss as compared with an electromagnetic pure iron sheet, a method for producing the soft magnetic iron sheet, and, an iron core and a dynamo-electric machine, each using the soft magnetic iron sheet. The soft magnetic iron sheet according to the present invention includes: iron as a main component; and nitrogen, in which the soft magnetic iron sheet includes, along a thickness direction of the soft magnetic iron sheet: a high nitrogen concentration layer having a nitrogen concentration of 2 at. % to 11 at. %; a low nitrogen concentration layer having a nitrogen concentration of half or less of the nitrogen concentration of the high nitrogen concentration layer; and a nitrogen concentration transition layer connecting the nitrogen concentration of the high nitrogen concentration layer and the nitrogen concentration of the low nitrogen concentration layer, and wherein a surface layer region including at least both main surfaces of the soft magnetic iron sheet is the low nitrogen concentration layer.