A method is for manufacturing a core plate having an annular core back and teeth extending from the core back toward the center. The core plate is obtained by performing a punching step, a winding step, a straining step and an annealing step. At the straining step, compressive strain is applied to the core back or the band-shaped core back that is to be the core back after winding. At the annealing step, the core back or the band-shaped core back is annealed to be recrystallized after the applying of strain.

A steel sheet is provided, having a tensile strength of 590 MPa or more, a particular composition and a steel structure that contains, in terms of area fraction, particular amounts of ferrite and martensite, in which the ferrite average crystal grain size is 20 m or less, the martensite average size is 15 m or less, the ratio of the average crystal grain size of the ferrite to the average size of the martensite (ferrite average crystal grain size/martensite average size) is 0.5 to 10.0, the ratio of the hardness of the martensite to the hardness of the ferrite (martensite hardness/ferrite hardness) is 1.0 or more and 5.0 or less, and, in the texture of the ferrite, the inverse intensity ratio of -fiber to the -fiber is 0.8 or more and 7.0 or less.

After an first heat treatment step, an ambient temperature of a stack is held so that the stack is kept in a temperature range that allows the stack to be crystallized by heating the end of the stack to a second temperature range in the second heat treatment step; and a following expression (1) is satisfied, where Q1 represents an amount of heat required to heat the stack to the first temperature range in the first heat treatment step, Q2 represents an amount of heat that is applied to the stack when heating the end of the stack to the second temperature range in the second heat treatment step, Q3 represents an amount of heat that is released during crystallization of the stack, and Q4 represents an amount of heat required to heat the entire stack to the crystallization start temperature

Q1+Q2+Q3Q4(1).

There is provided a method for manufacturing a soft magnetic member where a coating formed of an -Fe.sub.2O.sub.3 single phase having a high electrical resistivity is formed on a soft magnetic alloy substrate. A soft magnetic alloy substrate is heated in an atmosphere containing water vapor and inert gas to form a coating on the soft magnetic alloy substrate. The atmosphere has an oxygen partial pressure in a range of 0 to 1.5 kPa. A soft magnetic member including the soft magnetic alloy substrate and the coating formed on its surface can be obtained.

A continuous annealing method for low coercive force cold-rolled electromagnetic pure iron plate and strip. Control parameters of each stages in a continuous annealing process are as follows: 750-850 C. at a heating stage; 750-850 C. at a soaking stage, the soaking time is 100-150 s; an outlet temperature of 575-675 C. at a slow-cooling stage, the cooling speed in slow-cooling stage is 2.5-10 C./s; an outlet temperature of 380-420 C. at a fast-cooling stage, the cooling speed of the fast-cooling stage is 15-25 C./s; and 270-310 C. at an overaging stage. The annealing medium is a non-oxidizing atmosphere composed of H.sub.2 and N.sub.2. After annealing, the cold-rolled electromagnetic pure iron plate and strip is leveled and pressed such that the leveling elongation rate of the plate and strip is controlled within the range of 0.20.1%. The process of the continuous annealing method is simple, and the produced cold-rolled electromagnetic pure iron plate and strip can achieve an overall performance of low coercive force and good formability without further magnetic annealing.

A NdFeB magnet containing cerium and a manufacturing method thereof are provided. The manufacturing method includes steps of: refining a part of raw materials pure iron, ferro-boron, and rare earth fluoride in a crucible, adding a rest of the raw materials into the crucible and refining, casting a refined solution to a surface of a water-cooled rotation roller through a tundish and forming alloy flakes, processing the alloy flakes containing at least two different compositions with hydrogen decrepitation, milling powders, magnetic field pressing, vacuum presintering, machining and sintering, and obtaining the NdFeB magnet containing cerium. The NdFeB magnet containing cerium has a density of 7.5-7.7 g/cm.sup.3 and an average particle size of 3-7 m; comprises a main phase and a grain boundary phase distributed around the main phase. A composite phase containing Tb is provided between the main phase and the grain boundary phase.

The present disclosure relates to an iron (Fe)-based amorphous soft magnetic alloy and a method for manufacturing the soft magnetic alloy. According to the present disclosure, there is provided an Fe-based soft magnetic alloy including C and S meeting 1a+b6, wherein a is an atomic % content of C and b is an atomic % content of S, B meeting 4.5x13.0, wherein x is an atomic % content of B, Cu meeting 0.2y1.5, wherein y is an atomic % content of Cu, Al meeting 0.5z2, wherein z is an atomic % content of Al, and a remaining atomic % content of Fe and other inevitable impurities, wherein the Fe-based soft magnetic alloy includes a micro-structure, and wherein the micro-structure includes a crystalline phase with a mean crystalline grain size ranging from 15 nm to 50 nm in an amorphous base.

A method of manufacturing a grain oriented electrical steel sheet includes subjecting a steel slab to a rolling process including cold rolling to obtain a steel sheet with a final sheet thickness, the steel slab containing by mass % C: 0.01% to 0.20%, Si: 2.0% to 5.0%, Mn: 0.03% to 0.20%, sol. Al: 0.010% to 0.05%, N: 0.0010% to 0.020%, at least one element selected from S and Se in a total of 0.005% to 0.040%, and the balance including Fe and incidental impurities; forming, by a chemical process, a linear groove extending in a direction forming an angle of 45 or less with a direction orthogonal to a rolling direction of the steel sheet; subjecting the steel sheet to decarburization annealing; applying an annealing separator thereon mainly composed of MgO; and subjecting the steel sheet to final annealing to manufacture a grain oriented electrical steel sheet.

A manufacturing method for a motor core includes a preparing step, a coating step, a stacking step, and a forming step. In the preparing step, the silicon steel sheets are cleaned and dried. In the coating step, an electrically insulating colloid is coated between each pair of adjacent silicon steel sheets. In the stacking step, the silicon steel sheets on which the electrically insulating colloid is applied are stacked on each other to form a layered structure. In the forming step, the stacked silicon steel sheets are subjected to a colloid curing process so that the electrically insulating colloid forms a thermosetting plastic. This reduces the chance of forming eddy currents, reducing the eddy current loss of the motor core during operation.

An embodiment of the present invention provides a non-oriented electrical steel sheet, including Si at 2.0 to 4.0 wt %, Al at 1.5 wt % or less (excluding 0 wt %), Mn at 1.5 wt % or less (excluding 0 wt %), Cr at 0.01 to 0.5 wt %, V at 0.0080 to 0.015 wt %, C at 0.015 wt % or less (excluding 0 wt %), N at 0.015 wt % or less (excluding 0 wt %), and the remainder including Fe and other impurities unavoidably added thereto.

0.004([C]+[N])0.022 [Equation 1]

(In Equation 1, [C] and [N] represent a content (wt %) of C and N, respectively.)