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 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%).

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.

In a base sheet for a grain-oriented electrical steel sheet of the present invention, an amount of surface oxygen x per one surface of the base sheet and a value y of a peak (ΔR/R.sub.0 @1250 cm.sup.−1) of SiO.sub.2 on the surface of the base sheet obtained by infrared reflection spectroscopy satisfy y≥1500x.sup.2.5 and y≥0.24. A method of manufacturing the base sheet for a grain-oriented electrical steel sheet of the present invention includes: adjusting the amount of surface oxygen per one surface of a final-annealed grain-oriented silicon steel sheet to more than 0.01 g/m.sup.2 and 0.05 g/m.sup.2 or less, or more than 0.05 g/m.sup.2 and 0.10 g/m.sup.2 or less; and performing thermal oxidation annealing in an atmosphere in which an oxidation potential represented by a ratio P.sub.H2O/P.sub.H2 of water vapor pressure to hydrogen pressure is 0.0081 or less in a case where the amount of surface oxygen is more than 0.01 g/m.sup.2 and 0.05 g/m.sup.2 or less, or in an atmosphere in which the oxidation potential is 0.005 or less in a case where the amount of surface oxygen is more than 0.05 g/m.sup.2 and 0.10 g/m.sup.2 or less, at a soaking temperature of 1000° C. or lower to form an externally oxidized layer on a surface of the grain-oriented silicon steel sheet.

A method for refining magnetic domains of a grain-oriented electrical steel sheet according to an exemplary embodiment of the present invention includes: a step of preparing a grain-oriented electrical steel sheet; and a step of forming a groove by irradiating a quasi-continuous laser beam of which a duty is from 98.0 to 99.9% on a surface of the grain-oriented electrical steel sheet.

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 (100) of a FeNi disordered alloy arranged in a tube furnace (10) 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 (100) of a FeNi disordered alloy arranged in a tube furnace (10) 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.

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.