Provided is a method for manufacturing a high-strength galvanized steel sheet. Heating in a first half of oxidizing treatment is performed at a temperature of 400° C. to 750° C. in an atmosphere having a particular O.sub.2 concentration and a particular H.sub.2O concentration, and heating in a second half of the oxidizing treatment is performed at a temperature of 600° C. to 850° C. in an atmosphere having a particular O.sub.2 concentration and a particular H.sub.2O concentration. Subsequently, heating in a heating zone for reduction annealing is performed to a temperature of 650° C. to 900° C. at a particular heating rate in an atmosphere having a particular H.sub.2 concentration and a particular H.sub.2O concentration with the balance being N.sub.2 and inevitable impurities, and soaking in a soaking zone for the reduction annealing is performed in an atmosphere having a particular H.sub.2 concentration and a particular H.sub.2O concentration with the balance being N.sub.2 and inevitable impurities.

Provided is a method for manufacturing a high-strength galvanized steel sheet. Heating in a first half of oxidizing treatment is performed at a temperature of 400° C. to 750° C. in an atmosphere having a particular O.sub.2 concentration and a particular H.sub.2O concentration, and heating in a second half of the oxidizing treatment is performed at a temperature of 600° C. to 850° C. in an atmosphere having a particular O.sub.2 concentration and a particular H.sub.2O concentration. Subsequently, heating in a heating zone for reduction annealing is performed to a temperature of 650° C. to 900° C. at a particular heating rate in an atmosphere having a particular H.sub.2 concentration and a particular H.sub.2O concentration with the balance being N.sub.2 and inevitable impurities, and soaking in a soaking zone for the reduction annealing is performed in an atmosphere having a particular H.sub.2 concentration and a particular H.sub.2O concentration with the balance being N.sub.2 and inevitable impurities.

Provided is an R—Fe—B-based sintered magnet which has a composition comprising R (wherein R represents at least one element selected from rare earth elements, and essentially contains Nd), B, M (wherein M represents at least one element selected from Si, Al, Mn, Ni, Co, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb and Bi), X (wherein X represents at least one element selected from Ti, Zr, Hf, Nb, V and Ta) and C, with a remainder comprising Fe, O and unavoidable impurities, and has a main phase comprising R.sub.2Fe.sub.14B and a grain boundary phase comprising an R—C phase having a higher R concentration and a higher C concentration than those in the main phase, the R—Fe—B-based sintered magnet being characterized in that the area ratio of the R—C phase in a cross section of the magnet is more than 0% and 0.5% or less.

Provided is an R—Fe—B-based sintered magnet which has a composition comprising R (wherein R represents at least one element selected from rare earth elements, and essentially contains Nd), B, M (wherein M represents at least one element selected from Si, Al, Mn, Ni, Co, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb and Bi), X (wherein X represents at least one element selected from Ti, Zr, Hf, Nb, V and Ta) and C, with a remainder comprising Fe, O and unavoidable impurities, and has a main phase comprising R.sub.2Fe.sub.14B and a grain boundary phase comprising an R—C phase having a higher R concentration and a higher C concentration than those in the main phase, the R—Fe—B-based sintered magnet being characterized in that the area ratio of the R—C phase in a cross section of the magnet is more than 0% and 0.5% or less.

The present invention is a stator core having a plurality of laminated electrical steel sheets, in which, among a plurality of teeth (121a to 121p) of the stator core, a width of teeth along a direction in which magnetic characteristics are excellent may be narrower than a width of teeth along a direction in which the magnetic characteristics are poor.

The present invention is a stator core having a plurality of laminated electrical steel sheets, in which, among a plurality of teeth (121a to 121p) of the stator core, a width of teeth along a direction in which magnetic characteristics are excellent may be narrower than a width of teeth along a direction in which the magnetic characteristics are poor.

A normalizing heat-treated steel sheet having good low-temperature impact toughness and a method for manufacturing the same is provided. The normalizing heat treated steel sheet of the present invention contains, by weight %, C: 0.04 to 0.1%, Si: 0.05 to 0.5%, Mn: 1.0 to 2.0%, Sol. Al: 0.015 to 0.04%, Nb: 0.003 to 0.03%, Ti: 0.005 to 0.02%, Cu: 0.35% or less, Ni: 0.05 to 0.8%, N: 0.002 to 0.008%, P: 0.01% or less (excluding 0%), S: 0.003% or less, and a balance of Fe and unavoidable impurities and has a steel microstructure composed of 70 to 90 area % of polygonal ferrite having a grain size of 20 μm or less, and 10 to 30 area % of spheroidized pearlite.

A normalizing heat-treated steel sheet having good low-temperature impact toughness and a method for manufacturing the same is provided. The normalizing heat treated steel sheet of the present invention contains, by weight %, C: 0.04 to 0.1%, Si: 0.05 to 0.5%, Mn: 1.0 to 2.0%, Sol. Al: 0.015 to 0.04%, Nb: 0.003 to 0.03%, Ti: 0.005 to 0.02%, Cu: 0.35% or less, Ni: 0.05 to 0.8%, N: 0.002 to 0.008%, P: 0.01% or less (excluding 0%), S: 0.003% or less, and a balance of Fe and unavoidable impurities and has a steel microstructure composed of 70 to 90 area % of polygonal ferrite having a grain size of 20 μm or less, and 10 to 30 area % of spheroidized pearlite.

A cold-rolled and heat-treated steel sheet having a microstructure consisting of, in surface fraction: between 10% and 30% of retained austenite, the retained austenite being present as films having an aspect ratio of at least 3 and as Martensite Austenite islands, less than 8% of the Martensite Austenite islands having a size above 0.5 μm, at most 1% of fresh martensite, at most 50% of tempered martensite, and recovered martensite containing precipitates of at least one element chosen among niobium, titanium and vanadium. A method for manufacturing the cold-rolled and heat-treated steel sheet is also described.

A cold-rolled and heat-treated steel sheet having a microstructure consisting of, in surface fraction: between 10% and 30% of retained austenite, the retained austenite being present as films having an aspect ratio of at least 3 and as Martensite Austenite islands, less than 8% of the Martensite Austenite islands having a size above 0.5 μm, at most 1% of fresh martensite, at most 50% of tempered martensite, and recovered martensite containing precipitates of at least one element chosen among niobium, titanium and vanadium. A method for manufacturing the cold-rolled and heat-treated steel sheet is also described.