Provided is a steel sheet and a method for manufacturing same, the steel sheet, which can be used for automobile parts and the like, having superb bendability, and excellent balance of strength and ductility and of strength and hole expansion ratio. The steel sheet includes: by wt %, C: 0.25 to 0.75%, Si: 4.0% or less, Mn: 0.9 to 5.0%, Al: 5.0% or less, P: 0.15% or less, S: 0.03% or less, N: 0.03% or less, a balance of Fe, and unavoidable impurities; and as microstructures, ferrite which is a soft structure, and tempered martensite, bainite, and retained austenite which are hard structures.

Provided is a steel sheet and a method for manufacturing same, the steel sheet which can be used for automobile parts and the like, having excellent bending workability, and excellent balance of strength and ductility and of strength and hole expansibility.

Provided is a steel sheet which can be used for automobile parts and the like, and relates to a steel sheet having a superior balance of strength and ductility and strength and hole expansion ratio and superior bending formability, and a method for manufacturing same.

Provided is a steel sheet having properties particularly suitable as a material of automotive external panels because bake hardenability and room-temperature aging resistance are excellent, and a method of manufacturing the steel sheet.

Free-cutting steel includes a specific composition, with an A value defined by a following formula (1) satisfying 4.0 or more and 20.0 or less, and remainder having Fe and an unavoidable impurity; and texture with 1000 or more sulfide particles with an equivalent circle diameter of less than 1 μm per mm.sup.2, 500 or more sulfide particles with an equivalent circle diameter of 1 μm or more and 5 μm or less per mm.sup.2, and 1000 or more Pb particles with an equivalent circle diameter of 1 μm or less per mm.sup.2, wherein

A value=(Mn+5Cr)/S   (1)

here, symbols of elements in the formula indicate contents (% by mass) of the elements.

Provided herein is a high-strength seamless steel pipe, and a method for manufacturing same. A high-strength seamless steel pipe of the present invention has a steel microstructure with a prior austenite grain size of 11.0 or more in terms of a grain size number in compliance with ASTM E112, and has a yield strength of 862 MPa or more and 965 MPa or less.

Provided is a hot rolled steel sheet having a predetermined chemical composition and a microstructure comprising, by area ratio, pearlite: 90 to 100% and pro-eutectoid ferrite: 0 to 10%, wherein the pearlite has an average lamellar spacing of 0.08 to 0.30 μm, and the percentage of cementite in the pearlite having a major axis length of more than 0.3 μm and an aspect ratio of less than 3.0 is less than 15%.

A soft magnetic alloy powder includes soft magnetic alloy particles having an amorphous phase. Each of the soft magnetic alloy particles has chemical composition represented by Fe.sub.aSi.sub.bB.sub.cC.sub.dP.sub.eCu.sub.fSn.sub.gM1.sub.hM2.sub.i, where M1 is one or more elements of Co and Ni, M2 is one or more elements of Ti, Zr, Hf, Nb, Ta, Mo, W, Cr, Al, Mn, Ag, V, Zn, As, Sb, Bi, Y, and a rare earth element, and 79≤a+h+i≤86, 0≤b≤5, 7.2≤c≤12.2, 0.1≤d≤3, 7.3≤c+d≤13.2, 0.5≤e≤10, 0.4≤f≤2, 0.3≤g≤6, 0≤h≤30, 0≤i≤5, and a+b+c+d+e+f+g+h+i=100 (parts by mol) are satisfied.

A steel sheet has a predetermined chemical composition containing, in mass %, C: more than 0.18% and less than 0.30%, Mn: more than 2.50% and 4.00% or less, and other elements. The steel micro-structure at a position at a depth of ¼ of the sheet thickness from the surface in an L cross section of the steel sheet is, in area %, tempered martensite: 25 to 90%, ferrite: 5% or less, retained austenite: 10 to 50%, and bainite: 5% or less. At a position at a depth of ¼ of the sheet thickness from the surface of the L cross section, the proportion of a total area of retained austenite grains having an area of 1 μm.sup.2 or more and having a grain shape circularity of 0.1 or more is less than 50% with respect to the entire area of retained austenite. The steel sheet satisfies the formula C.sub.Mnγ/C.sub.Mnα≥1.2.

A method for producing an austempered steel is provided. The method includes subjecting a steel alloy having a silicon content of 1.5 to 4.4 weight percent and a carbon content of 0.3 to 0.8 weight percent to continuous cooling followed by annealing. The cooling rate is initially sufficiently fast to prevent predominant formation of proeutectoid ferrite or pearlite, while subsequently at intermediate temperatures, the cooling rate is sufficiently slow to allow a transformation of the austenite to mainly ausferrite during cooling. The annealing is able to complete the transformation of carbon enriched austenite to ausferrite and to temper any martensite previously formed. The method results in the cost-efficient production of one or more continuously cooled and annealed austempered steel components or semi-finished products having mainly an ausferritic microstructure.