The present invention is to provide a steel having high strength properties and also having superior elongation, and a manufacturing method therefor.

This hot-rolled steel sheet has a predetermined chemical composition, a microstructure includes 80% or more of tempered martensite by a volume percentage and a remainder consisting of one or more of ferrite, pearlite, bainite, fresh martensite, and residual austenite, the tempered martensite includes 5×10.sup.9 pieces/mm.sup.3 or more of precipitates containing Ti and having an equivalent circle diameter of 5 nm or less per unit volume, in a surface layer region that is a range from a surface to a 1/10 position of a sheet thickness, a sum of an average pole density of a crystal orientation group consisting of {211}<111> to {111}<112> and a pole density in a crystal orientation of {110}<001> is 6.0 or less, and a tensile strength is 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 10% or more and less than 20%, Among grain boundaries of crystal grains of bainite and tempered martensite 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 the 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 5% or more and less than 10%. 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. The tensile strength of the hot-stamping formed body is 1500 MPa or more.

A method of production non grain-oriented Fe—Si steel sheet is provided. The method includes the steps of melting a steel composition that contains in weight percentage: C≤0.006, 2.0≤Si≤5.0, 0.1≤Al≤3.0, 0.1≤Mn≤3.0, N≤0.006, 0.04≤Sn≤0.2, S≤0.005, P≤0.2, Ti≤0.01, the balance being Fe and other inevitable impurities, casting said melt into a slab, reheating said slab, hot rolling said slab, coiling said hot rolled steel, optionally annealing the hot rolled steel, cold rolling, annealing and cooling the cold rolled steel down to room temperature.

A method of production non grain-oriented Fe—Si steel sheet is provided. The method includes the steps of melting a steel composition that contains in weight percentage: C≤0.006, 2.0≤Si≤5.0, 0.1≤Al≤3.0, 0.1≤Mn≤3.0, N≤0.006, 0.04≤Sn≤0.2, S≤0.005, P≤0.2, Ti≤0.01, the balance being Fe and other inevitable impurities, casting said melt into a slab, reheating said slab, hot rolling said slab, coiling said hot rolled steel, optionally annealing the hot rolled steel, cold rolling, annealing and cooling the cold rolled steel down to room temperature.

The present invention relates to high-strength medium manganese steel for warm stamping, which contains 3-10 wt % of manganese (Mn), 0.05-0.3 wt % of carbon (C), and 0.1-1.0 wt % of silicon (Si) as components thereof, with the balance being iron (Fe) and unavoidably contained impurities. The present invention performs heat treatment at the low austenitizing temperature of medium manganese steel, and thus has the effect of reducing the high thermal energy consumption of the prior art hot stamping process. Furthermore, the present invention does not require an additional temperature process, and can obtain high strength by only slow cooling such as air cooling outside a mold without performing cooling at high rate inside the mold, and thus has the effects of simplifying a process and improving manufacturing efficiency.

The present invention relates to high-strength medium manganese steel for warm stamping, which contains 3-10 wt % of manganese (Mn), 0.05-0.3 wt % of carbon (C), and 0.1-1.0 wt % of silicon (Si) as components thereof, with the balance being iron (Fe) and unavoidably contained impurities. The present invention performs heat treatment at the low austenitizing temperature of medium manganese steel, and thus has the effect of reducing the high thermal energy consumption of the prior art hot stamping process. Furthermore, the present invention does not require an additional temperature process, and can obtain high strength by only slow cooling such as air cooling outside a mold without performing cooling at high rate inside the mold, and thus has the effects of simplifying a process and improving manufacturing efficiency.

The present disclosure relates generally to a method for improving the performance of sintered NdFeB magnet. A method of preparing a sintered NdFeB magnet therefore comprises the steps of: a) preparing alloy flakes from a raw material of the NdFeB magnet by a strip casting process; and b) preparing a coarse alloy powder from the alloy flakes by a hydrogen decrepitation process, the hydrogen decrepitation process including treatment of the alloy flakes under a hydrogen pressure of 0.10 MPa to 0.25 MPa for a duration of 1 to 3.5 hours, then degassing the hydrogen at a predetermined temperature between 300° C. to 400° C. for a duration time of 0.5 to 5 hours, and then mixing the resulting coarse alloy powder with a lubricant.

A neodymium-iron-boron permanent magnet material, a preparation method, and an application. The neodymium permanent magnet material includes R, Al, Cu, and Co; R comprises RL and RH; RL comprises one or many light rare earth elements among Nd, La, Ce, Pr, Pm, Sm, and Eu; RH comprises one or many heavy rare earth elements among Tb, Gd, Dy, Ho, Er, Tm, Yb, Lu, and Sc; the neodymium-iron-boron permanent magnet material satisfies the following relations: (1) B/R: 0.033-0.037; (2) AI/RH: 0.12-2.7. The neodymium-iron-boron permanent magnet material has uniquely advantageous magnetic and mechanical properties, with Br≥13.12 kGs, Hcj≥17.83 kOe, and bending strength≥409 MPa.