Ferritic stainless steel securing corrosion resistance while being excellent in ridging resistance able to be stably provided, that is, ferritic stainless steel with excellent ridging resistance having a composition comprising, by mass %, C: 0.001 to 0.01%, Si: 0.3% or less, Mn: 0.3% or less, P: 0.04% or less, S: 0.01% or less, Cr: 10 to 21%, Al: 0.01 to 0.2%, Ti: 0.015 to 0.3%, O: 0.0005 to 0.0050%, N: 0.001 to 0.02%, Ca: 0.0015% or less, and Mg: 0.0003% to 0.0030% and having a balance of Fe and impurities, in which steel, when defining complex inclusions including oxides and having a long axis of 1 μm or more as complex inclusions (A) and defining complex inclusions satisfying (Formula 1) to (Formula 3) in the complex inclusions (A) as complex inclusions (B), a number ratio of the number of complex inclusions (B) to the number of complex inclusions (A) satisfies (Formula 4), and among the complex inclusions (B), a number density of complex inclusions having a long axis of 2 μm or more and 15 μm or less is 2/mm.sup.2 or more and 20/mm.sup.2 or less:
Al.sub.2O.sub.3/MgO≤4  (Formula 1)
CaO≤20%  (Formula 2)
Al.sub.2O.sub.3+MgO≥75%  (Formula 3)
Number of complex inclusions (B)/Number of complex inclusions (A)≥0.70  (Formula 4) where, in (Formula 1) to (Formula 3), Al.sub.2O.sub.3, MgO, and CaO indicate the respective mass % in the oxides.

A value of a parameter Q represented by “Q=([Ti]/48+[V]/51+[Zr]/91+[Nb]/93)/([C]/12)” is not less than 0.9 nor more than 1.1, when contents of Ti, V, Zr, Nb, and C (mass %) are represented as [Ti], [V], [Zr], [Nb], and [C] respectively. A matrix of a metal structure is a ferrite phase, and the metal structure does not contain a non-recrystallized structure. An average grain size of ferrite grains constituting the ferrite phase is not less than 30 μm nor more than 200 μm. A precipitate containing at least one selected from the group consisting of Ti, V, Zr, and Nb exists with a density of 1 particle/μm.sup.3 or more in the ferrite grain. An average grain size of the precipitate is not less than 0.002 μm nor more than 0.2 μm.

A manufacture method of high-efficiency non-oriented silicon steel with excellent magnetic property includes the steps of smelting a chemical composition of non-oriented silicon steel, by weight percent, is: C≤0.0040%, Si:0.1˜0.8%, Al:0.002˜1.0%, Mn:0.10˜1.50%, P:≤0.2%, Sb:0.04˜0.08%, S≤0.0030%, N≤0.0020%, Ti≤0.0020%, and the rest is Fe and unavoidable inclusions. The molten steel is then cast into billets which are hot-rolled into a hot-rolled product. The heating temperature for the billet is 1100°˜1150° and the finish-rolling temperature is 860°˜920°. The hot-rolled product is then air cooled for a period of time within a range determined by air cooling time t: (2+30×Sb%)s≤t≤7 s. The hot-rolled product is reeled at a temperature ≥720° and cold-rolled to form cold-rolled plate with a target thickness at a reduction ratio of 70˜78% followed by heating up the cold-rolled plate to 800˜1000° at heating rate of ≥15°/s, and holding time of 10s˜25s.

The ferritic stainless steel sheet contains, in mass %, C: 0.020% or less, Si: 0.6% or less, Mn: 0.5% or less, P: 0.04% or less, S: 0.010% or less, Al: 0.015% or more and 0.20% or less, Cr: 17.0% or more and 24.0% or less, Ni: less than 0.6%, N: 0.020% or less, Ca: 0.0002% or more and 0.0020% or less, and O: 0.0050% or less and further contains one or two selected from Ti: 0.01% or more and 0.45% or less and Nb: 0.01% or more and 0.55% or less, with the balance being Fe and unavoidable impurities. The ferritic stainless steel sheet satisfies (Ti+Nb×48/93)/(C+N)≧8.0 (where Ti, Nb, C, and N represent the contents (% by mass) of these elements, respectively).

Disclosed are an oriented electrical steel sheet and a manufacturing method thereof. An exemplary embodiment of the present invention provides a method of manufacturing an oriented electrical steel sheet, including: providing a slab including Si at 1.0 to 4.0 wt %, C at 0.1 to 0.4 wt %, and the remaining portion including Fe and other inevitably incorporated impurities; reheating the slab; producing a hot rolled steel sheet by hot rolling the slab; performing annealing of the hot rolled steel sheet; cold rolling the annealed hot rolled steel sheet; decarburizing and annealing the cold rolled steel sheet; cold rolling the decarburized and annealed steel sheet; and final annealing the cold rolled steel sheet.

A non-oriented electrical steel sheet has a chemical composition having C: not more than 0.005 mass %, Si: 2-7 mass %, Mn: 0.033 mass %, Al: not more than 3 mass %, P: not more than 0.2 mass %, S: not more than 0.005 mass %, N: not more than 0.005 mass %, Se: 0.0001˜0.0005 mass %, As: 0.0005˜0.005 mass % and the remainder being Fe and inevitable impurities, and an iron loss W.sub.15/50 in excitation at 50 Hz and 1.5 T of not more than 3.5 W/kg and a ratio (x/t) of amount of shear drop x (mm) to thickness t (mm) in punching of steel sheet of not more than 0.15 and is excellent in the iron loss property before punching and less in the deterioration of the iron loss property by punching.

A non-oriented electrical steel sheet is obtained by subjecting a slab containing C: not more than 0.005 mass %, Si: 1.0-5.0 mass %, Mn: 0.04-3.0 mass %, sol. Al: not more than 0.005 mass %, P: 0.03-0.2 mass %, S: not more than 0.005 mass %, N: not more than 0.005 mass %, B: not more than 0.001 mass %, and Se: not more than 0.001 mass % and satisfying sol. Al+C+5B+5Se≦0.005 mass % to hot rolling, cold rolling and finish annealing. A sheet temperature at the outlet side of the rolling machine in at least one pass of the final cold rolling is set to a range of 100-300° C. to provide S/2M of not less than 1.0 and S/5C of not less than 1.0 when X-ray intensity ratios of {001}<250>, {111}<112> and {001}<100> in a central layer in a thickness direction are S, M and C, respectively.

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 method produces a high strength electrical steel sheet in which a cumulative rolling reduction ratio in rough rolling is 73.0% or more, in which in a hot band annealing step, an annealing condition is selected that satisfies an area ratio of recrystallized grains after hot band annealing of 100%, and a recrystallized grain size of 80 μm to 300 μm, under a condition where annealing temperature is 850° C. to 1000° C., and annealing duration is 10 seconds to 10 minutes, and in which in a final annealing step, an annealing condition is selected that satisfies an area ratio of recrystallized grains after the final annealing of 30% to 95%, and a length in the rolling direction of a connected non-recrystallized grain group of 2.5 mm or less, under a condition where annealing temperature is 670° C. to 800° C., and annealing duration is 2 seconds to 1 minute.

A steel sheet for electroplating includes, by mass %, C: 0.0005% to 0.0050%, Si: 0.20% to 1.0%, Mn: 0.40% to 2.5%, P: 0.05% or less, Ti: 0.010% to 0.050%, Nb: 0.010% to 0.040%, B: 0.0005% to 0.0030%, S: 0.02% or less, Al: 0.01% to 0.30%, N: 0.0010% to 0.01%, and the balance including Fe and impurities, in which when Si content is represented by [Si] and Mn content is represented by [Mn], “[Mn]+5[Si]” is 2.0 to 7.0, and the steel sheet has surface property in which an average of displacements of a measurement point obtained based on a moving average of continuous 31 points in total including 15 front points and 15 back points in a cross-sectional profile of a surface obtained by measuring the average of displacements in an evaluation length of 10 μm or more at an interval of 0.07 μm, is 0.005 μm to 0.10 μm.