Provided is a steel sheet and a method for manufacturing same, the steel sheet, which is optimized a composition and microstructure, and which can be used for automobile parts and the like, having superb bendability, and superior balance of strength and ductility and of strength and hole expansion ratio.

Disclosed are an R-T-B-based permanent magnet material, a preparation method therefor and the use thereof. The R-T-B-based permanent magnet material comprises R, B, M, Fe, Co, X and inevitable impurities, wherein: (1) R is a rare earth element, and the R includes at least Nd and RH, M being one or more of Ti, Zr and Nb, and X including Cu, “Al and/or Ga”; and (2) in percentage by weight, R: 30.5-32.0 wt%, B: 0.95-0.99 wt%, M: 0.3-0.6 wt%, X: 0.8-1.8 wt%, and Cu: 0.35-0.50 wt%, and the balance is Fe, Co and inevitable impurities. According to the present invention, under the condition of 0.3-0.6 wt% of a high melting point metal, a permanent magnet material with an excellent magnet performance and a good squareness is obtained.

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 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 a hole expansion ratio and superior bending formability, and a method for manufacturing same.

Provided is a method of producing a target material with reduced particle generation during sputtering, which is a method of producing a sputtering target material whose material is an alloy M, including a sintering step of sintering a mixed powder obtained by mixing a first powder and a second powder. A material of the first powder is an alloy M1 in which the proportion of a B content is from 40 at. % to 60 at. %. A material of the second powder is an alloy M2 in which the proportion of a B content is from 20 at. % to 35 at. %. The proportion of a B content in the mixed powder is from 33 at. % to 50 at. %. A metallographic structure including a (CoFe).sub.2B phase and a (CoFe)B phase is formed in the sintering step. A boundary length per unit area Y (1/μm), which is obtained by measuring a boundary length between the (CoFe).sub.2B phase and the (CoFe)B phase using a scanning electron microscope, and a proportion X (at. %) of a B content of the alloy M satisfy the expression

Y<−0.0015×(X−42.5).sup.2+0.15.

Provided is a method of producing a target material with reduced particle generation during sputtering, which is a method of producing a sputtering target material whose material is an alloy M, including a sintering step of sintering a mixed powder obtained by mixing a first powder and a second powder. A material of the first powder is an alloy M1 in which the proportion of a B content is from 40 at. % to 60 at. %. A material of the second powder is an alloy M2 in which the proportion of a B content is from 20 at. % to 35 at. %. The proportion of a B content in the mixed powder is from 33 at. % to 50 at. %. A metallographic structure including a (CoFe).sub.2B phase and a (CoFe)B phase is formed in the sintering step. A boundary length per unit area Y (1/μm), which is obtained by measuring a boundary length between the (CoFe).sub.2B phase and the (CoFe)B phase using a scanning electron microscope, and a proportion X (at. %) of a B content of the alloy M satisfy the expression

Y<−0.0015×(X−42.5).sup.2+0.15.

This hot-rolled steel sheet has a predetermined chemical composition, in which a metallographic structure contains, by area %, more than 92.0% and 100.0% or less of martensite and tempered martensite in total, less than 3.0% of residual austenite, and less than 5.0% of ferrite, has a ratio S.sub.60/S.sub.7, which is a ratio of a density S.sub.60 of a length of a grain boundary having a crystal misorientation of 60° to a density S.sub.7 of a length of a grain boundary having a crystal misorientation of 7° about a <110> direction, of more than 0.34 and less than 0.60, has a standard deviation of a Mn concentration of 0.60 mass % or less, and has a tensile strength of 980 MPa or more.

This hot-rolled steel sheet has a predetermined chemical composition, in which a metallographic structure contains, by area %, more than 92.0% and 100.0% or less of martensite and tempered martensite in total, less than 3.0% of residual austenite, and less than 5.0% of ferrite, has a ratio S.sub.60/S.sub.7, which is a ratio of a density S.sub.60 of a length of a grain boundary having a crystal misorientation of 60° to a density S.sub.7 of a length of a grain boundary having a crystal misorientation of 7° about a <110> direction, of more than 0.34 and less than 0.60, has a standard deviation of a Mn concentration of 0.60 mass % or less, and has a tensile strength of 980 MPa or more.

A hot-stamping formed body has a predetermined chemical composition and includes microstructure which includes residual austenite of which an area ratio is in a range of 20% to 30%. Among grain boundaries of crystal grains of bainite and tempered martensite in the microstructure, a ratio of a length of a grain boundary having a rotation angle in a range of 55° to 75° to a total length of a grain boundary having a rotation angle in a range of 4° to 12°, a grain boundary having a rotation angle in a range of 49° to 54°, and a grain boundary having a rotation angle in a range of 55° to 75° to the <011> direction as a rotation axis is 30% or more.

A hot-stamping formed body has a predetermined chemical composition and includes microstructure which includes residual austenite of which an area ratio is in a range of 20% to 30%. Among grain boundaries of crystal grains of bainite and tempered martensite in the microstructure, a ratio of a length of a grain boundary having a rotation angle in a range of 55° to 75° to a total length of a grain boundary having a rotation angle in a range of 4° to 12°, a grain boundary having a rotation angle in a range of 49° to 54°, and a grain boundary having a rotation angle in a range of 55° to 75° to the <011> direction as a rotation axis is 30% or more.