One aspect of the present invention is to provide a superior steel plate and a method for manufacturing same, the steel plate, as an ultra-thick steel plate, having high strength as well as superb imact toughness low-temperature, and excellent resistance to formation of cracks.

A stainless steel seamless pipe having high strength and excellent corrosion resistance. The stainless steel seamless pipe has a specified composition in which C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfy a predetermined formula, a microstructure containing at least 25% martensitic phase, at most 65% ferrite phase, and at most 40% retained austenite phase by volume, and a yield strength of 758 MPa or more.

A stainless steel seamless pipe having high strength and excellent corrosion resistance. The stainless steel seamless pipe has a specified composition in which C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfy a predetermined formula, a microstructure containing at least 25% martensitic phase, at most 65% ferrite phase, and at most 40% retained austenite phase by volume, and a yield strength of 758 MPa or more.

A preparation method of glassless grain-oriented silicon steel includes the following operations. During a decarburization annealing, a thickness of an oxide film on a surface of strip is 1.5-2.5 μm; an atomic weight ratio of Si element and Fe element in the oxide film satisfies: Si/(Si+Fe)≥0.76; during a high-temperature annealing, a cooling stage includes sequentially: cooling with an inner cover when a temperature drops from 1200° C. to 500° C.; wherein a protective gas is a mixed gas containing nitrogen and hydrogen, and a volume percentage of the hydrogen in the mixed gas is >3%; cooling with the inner cover when the temperature drops from 500° C. to 200° C.; wherein the protective gas is nitrogen; and cooling in air by removing the inner cover when the temperature is <200° C.

A preparation method of glassless grain-oriented silicon steel includes the following operations. During a decarburization annealing, a thickness of an oxide film on a surface of strip is 1.5-2.5 μm; an atomic weight ratio of Si element and Fe element in the oxide film satisfies: Si/(Si+Fe)≥0.76; during a high-temperature annealing, a cooling stage includes sequentially: cooling with an inner cover when a temperature drops from 1200° C. to 500° C.; wherein a protective gas is a mixed gas containing nitrogen and hydrogen, and a volume percentage of the hydrogen in the mixed gas is >3%; cooling with the inner cover when the temperature drops from 500° C. to 200° C.; wherein the protective gas is nitrogen; and cooling in air by removing the inner cover when the temperature is <200° C.

Provided is an ultra-high-strength reinforcing bar and a method for manufacturing the same are disclosed. In an exemplary embodiment, the ultra-high-strength reinforcing bar includes an amount of 0.10 to 0.45 wt % carbon (C), an amount of 0.5 to 1.0 wt % silicon (Si), an amount of 0.40 to 1.80 wt % manganese (Mn), an amount of 0.10 to 1.0 wt % chromium (Cr), an amount greater than 0 and less than or equal to 0.2 wt % vanadium (V), an amount greater than 0 and less than or equal to 0.4 wt % copper (Cu), an amount greater than 0 and less than or equal to 0.5 wt % molybdenum (Mo), an amount of 0.015 to 0.070 wt % aluminum (Al), an amount greater than 0 and less than or equal to 0.25 wt % nickel (Ni), an amount greater than 0 and less than or equal to 0.1 wt % tin (Sn), an amount greater than 0 and less than or equal to 0.05 wt % phosphorus (P), an amount greater than 0 and less than or equal to 0.03 wt % sulfur (S), an amount of 0.005 to 0.02 wt % nitrogen (N), and the remainder being iron (Fe) and other inevitable impurities.

Provided is an ultra-high-strength reinforcing bar and a method for manufacturing the same are disclosed. In an exemplary embodiment, the ultra-high-strength reinforcing bar includes an amount of 0.10 to 0.45 wt % carbon (C), an amount of 0.5 to 1.0 wt % silicon (Si), an amount of 0.40 to 1.80 wt % manganese (Mn), an amount of 0.10 to 1.0 wt % chromium (Cr), an amount greater than 0 and less than or equal to 0.2 wt % vanadium (V), an amount greater than 0 and less than or equal to 0.4 wt % copper (Cu), an amount greater than 0 and less than or equal to 0.5 wt % molybdenum (Mo), an amount of 0.015 to 0.070 wt % aluminum (Al), an amount greater than 0 and less than or equal to 0.25 wt % nickel (Ni), an amount greater than 0 and less than or equal to 0.1 wt % tin (Sn), an amount greater than 0 and less than or equal to 0.05 wt % phosphorus (P), an amount greater than 0 and less than or equal to 0.03 wt % sulfur (S), an amount of 0.005 to 0.02 wt % nitrogen (N), and the remainder being iron (Fe) and other inevitable impurities.

A method for the heat treatment of a part made of maraging steel, which part is obtained by selective laser melting, it comprises the steps of: heating the said part made of maraging steel from ambient temperature T0 to a maximum temperature Tmax of between 600° C. and 640° C., maintaining the said maximum temperature Tmax for a duration of between 5 hours and 7 hours, and rapidly cooling the said part.

A method for the heat treatment of a part made of maraging steel, which part is obtained by selective laser melting, it comprises the steps of: heating the said part made of maraging steel from ambient temperature T0 to a maximum temperature Tmax of between 600° C. and 640° C., maintaining the said maximum temperature Tmax for a duration of between 5 hours and 7 hours, and rapidly cooling the said part.

A martensitic stainless steel sheet has a composition containing, (mass %), from 0.10 to 0.15% of C, from 0.05 to 0.80% of Si, from 0.05 to 2.00% of Mn, 0.040% or less of P, 0.003% or less of S, from 0.05 to 0.50% of Ni, from 11.0 to 15.0% of Cr, from 0.02 to 0.50% of Cu, from 0.005 to 0.06% of N, from 0.001 to 0.20% of Al, from 0 to 1.00% of Mo, from 0 to 0.50% of V, from 0 to 0.01% of B, balance Fe and unavoidable impurities. An M value=420C−11.5Si+7Mn+23Ni−11.5Cr−12Mo−10V+9Cu−52Al+470N+189 is 100 or more. A carbonitride number density having a circle equivalent diameter of 1.0 μm or more is 15.0 or less per 0.01 mm.sup.2. 0.2% yield strength is 1,100 N/mm.sup.2 or more.