A 980 MPa-grade ultra-low-carbon martensite and retained austenite ultra-high hole expansion steel and a manufacturing method therefor. The hole expansion steel comprises the following chemical components in percentage by weight: C 0.03%-0.06%, Si 0.8%-2.0%, Mn 1.0%-2.0%, P≤0.02%, S≤0.003%, Al 0.02%-0.08%, N≤0.004%, Mo 0.1%-0.5%, Ti 0.01%-0.05%, and O≤0.0030%. The high hole expansion steel of the present invention has the yield strength ≥800 MPa, the tensile strength ≥980 MPa, the elongation rate (horizontal A50≥10%), the cold bending property (d≤4a, 180°), and the hole expansion ratio ≥80%, and can be applied to a chassis part of a passenger vehicle such as a control arm, an auxiliary frame and other parts that require high-strength thinning.

A 980 MPa-grade ultra-low-carbon martensite and retained austenite ultra-high hole expansion steel and a manufacturing method therefor. The hole expansion steel comprises the following chemical components in percentage by weight: C 0.03%-0.06%, Si 0.8%-2.0%, Mn 1.0%-2.0%, P≤0.02%, S≤0.003%, Al 0.02%-0.08%, N≤0.004%, Mo 0.1%-0.5%, Ti 0.01%-0.05%, and O≤0.0030%. The high hole expansion steel of the present invention has the yield strength ≥800 MPa, the tensile strength ≥980 MPa, the elongation rate (horizontal A50≥10%), the cold bending property (d≤4a, 180°), and the hole expansion ratio ≥80%, and can be applied to a chassis part of a passenger vehicle such as a control arm, an auxiliary frame and other parts that require high-strength thinning.

A sintered R-T-B based magnet includes a main phase formed of an R.sub.2T.sub.14B compound and a grain boundary phase at grain boundaries of the main phase. The grain boundary phase contains an R-T-M compound (M is at least one selected from the group consisting of Ga, Cu, Zn, Al and Si) and an R-M compound. In any cross-section of the sintered R-T-B based magnet, a sum of an area ratio of the R-T-M compound and an area ratio of the R-M compound is not lower than 1.5% and not higher than 3.5%, the area ratio of the R-T-M compound is not lower than 0.4% and not higher than 2.5%, and the area ratio of the R-M compound is not lower than 0.4% and not higher than 2.5%.

A sintered R-T-B based magnet includes a main phase formed of an R.sub.2T.sub.14B compound and a grain boundary phase at grain boundaries of the main phase. The grain boundary phase contains an R-T-M compound (M is at least one selected from the group consisting of Ga, Cu, Zn, Al and Si) and an R-M compound. In any cross-section of the sintered R-T-B based magnet, a sum of an area ratio of the R-T-M compound and an area ratio of the R-M compound is not lower than 1.5% and not higher than 3.5%, the area ratio of the R-T-M compound is not lower than 0.4% and not higher than 2.5%, and the area ratio of the R-M compound is not lower than 0.4% and not higher than 2.5%.

The present invention discloses a high nitrogen steel with high strength, low yield ratio and high corrosion resistance for ocean engineering, comprising the following chemical components by weight percentage: C≤0.01%, Si≤0.1%, Cr 17%-19%, Mn 14%-16%, Mo 1%-1.5%, Ti≤0.05%, N 0.45%-0.6%, P≤0.01%, S≤0.01%, O≤0.02%, and the balance of iron. The present invention also discloses a preparation method as follows: (1) raw material weighing; (2) ingot preparation, remelting and smelting; (3) solution and forging treatments; and (4) hot rolling and post-rolling treatment. A product provided by the present invention has high tensile strength, low yield ratio and high corrosion resistance. At the same time, the present invention does not need pressurized equipment in the preparation process, therefore the preparation method is simple, the cost is low, and the present invention is suitable for industrial popularization in China.

The present invention discloses a high nitrogen steel with high strength, low yield ratio and high corrosion resistance for ocean engineering, comprising the following chemical components by weight percentage: C≤0.01%, Si≤0.1%, Cr 17%-19%, Mn 14%-16%, Mo 1%-1.5%, Ti≤0.05%, N 0.45%-0.6%, P≤0.01%, S≤0.01%, O≤0.02%, and the balance of iron. The present invention also discloses a preparation method as follows: (1) raw material weighing; (2) ingot preparation, remelting and smelting; (3) solution and forging treatments; and (4) hot rolling and post-rolling treatment. A product provided by the present invention has high tensile strength, low yield ratio and high corrosion resistance. At the same time, the present invention does not need pressurized equipment in the preparation process, therefore the preparation method is simple, the cost is low, and the present invention is suitable for industrial popularization in China.

Disclosed is provided a low yield ratio and superhigh-strength hot-rolled Q&P steel and a method for manufacturing the same, having the following chemical composition in weight percentage: C: 0.2-0.3%, Si: 1.0-2.0%, Mn: 1.5-2.5%, P: ≤0.015%, S: ≤0.005%, Al: 0.5-1.0%, N: ≤0.006%, Nb: 0.02-0.06%, Ti: ≤0.03%, O: ≤0.003%, and the balance being Fe and inevitable impurities. The manufacture method comprises a stepped cooling process to finally obtain the steel with a three-phase structure containing a certain volume fraction of proeutectoid ferrite; martensite; and residual austenite, and having an excellent comprehensive performance with a yield strength of ≥600 MPa, a tensile strength of ≥1300 MPa, a good elongation, and a low yield ratio. The obtained Q&P steel also shows an excellent match of high plasticity suitable for easy deformabilities and wear-resistances.

Disclosed is provided a low yield ratio and superhigh-strength hot-rolled Q&P steel and a method for manufacturing the same, having the following chemical composition in weight percentage: C: 0.2-0.3%, Si: 1.0-2.0%, Mn: 1.5-2.5%, P: ≤0.015%, S: ≤0.005%, Al: 0.5-1.0%, N: ≤0.006%, Nb: 0.02-0.06%, Ti: ≤0.03%, O: ≤0.003%, and the balance being Fe and inevitable impurities. The manufacture method comprises a stepped cooling process to finally obtain the steel with a three-phase structure containing a certain volume fraction of proeutectoid ferrite; martensite; and residual austenite, and having an excellent comprehensive performance with a yield strength of ≥600 MPa, a tensile strength of ≥1300 MPa, a good elongation, and a low yield ratio. The obtained Q&P steel also shows an excellent match of high plasticity suitable for easy deformabilities and wear-resistances.

The present invention provides a method for preparing ferrovanadium alloys based on aluminothermic self-propagating gradient reduction and slag washing refining. The method includes the steps of (1) performing aluminothermic self-propagating gradient reduction; (2) performing heat preserving and smelting to obtain an upper layer alumina-based slag and a lower layer alloy melt; (3) jetting refining slags into the lower layer alloy melt, and performing stirring and slag washing refining; and (4) cooling the refined high-temperature melt to room temperature, and removing an upper layer smelting slag to obtain the ferrovanadium alloys.

Provided is a dephosphorizing flux configured to adjust a phosphorous component contained in molten steel, the dephosphorizing flux includes a main material including BaCO.sub.3 and a supplementary material, wherein the supplementary material includes a first material containing either of NaHCO.sub.3 or Na.sub.2CO.sub.3 and a second material containing CaF.sub.2. Thus, in accordance with a dephosphorizing flux and a method for preparing the same of the present disclosure, the plugging of a lower blowing nozzle that blows a carrier gas during dephosphorization may be prevented while improving a dephosphorization ratio. In addition, since environment polluting substances are not used as in conventional arts, environment pollution risk may be reduced, and the cost burden due to the facility for pollution prevention and harmful substance management may be alleviated.