A method of manufacturing a martensitic stainless steel sheet by allowing ingot steel to pass through two casting rolls rotating in opposing directions through a twin roll strip caster is provided. The method includes rolling a steel sheet cast between the casting rolls at a temperature of 1000 to 1200 C. and a draft percentage of 25 to 50% with a first roller, and rolling the steel sheet at a temperature of 800 to 1000 C. and a draft percentage of 5 to 15% with a second roller.

In a continuous casting device 100 for casting a stainless steel billet 3c, a long nozzle 2 extending into a tundish 101 is provided at a ladle 1. A molten stainless steel 3 is poured through the long nozzle 2 into the tundish 101, and a spout 2a of the long nozzle 2 is immersed into the poured molten stainless steel 3. During pouring, an argon gas 4a is supplied around the molten stainless steel 3 in the tundish 101. Further, continuous casting is performed, in which, while immersing the spout 2a of the long nozzle 2 into the molten stainless steel 3 in the tundish 101, the molten stainless steel 3 is poured from the ladle 1 into the tundish 101 and poured from the tundish 101 into a casting mold 105. During casting, a nitrogen gas 4b is supplied instead of the argon gas 4a around the molten stainless steel 3 inside the tundish 101.

A method for manufacturing a plate, a band, or a coil of hot-rolled steel is provided. The method includes providing an ingot or a slab of steel with a desired composition and a microstructure composed of austenite and 35 to 65% ferrite by volume and hot rolling the ingot or slab at a temperature between 1150 and 1280 C. to obtain a plate, a band or a coil. A method for manufacturing a hot-rolled bar or wire of steel, a steel profile and a forged steel piece are also provided.

The present invention provides an austenite-ferrite stainless steel. The steel composition contains in % by weight: 0.01%C0.10% 20.0%Cr24.0% 1.0%Ni3.0% 0.12%N0.20% 0.5%Mn2.0% 1.6%Cu3.0% 0.05%Mo1.0% W0.15% 0.05%Mo+W/21.0% 0.2%Si1.5% Al0.05% V0.5% Nb0.5% Ti0.5% B0.003% Co0.5% REM0.1% Ca0.03% Mg0.1% Se0.005% O0.01% S0.030% P0.040% the rest being iron and impurities resulting from the production and the microstructure being composed of austenite and 35 to 65% ferrite by volume, the composition furthermore obeying the following relations:
40IF65
with
IF=10% Cr+5.1% Mo+1.4% Mn+24.3% Si+35% Nb+71.5% Ti595.4% C245.1% N9.3% Ni3.3% Cu99.8
and
IRCGCU32.0
with
IRCGCU=% Cr+3.3% Mo+2% Cu+16% N+2.6% Ni0.7% Mn
and
0IU6.0
with
IU=3% Ni+% Cu+% Mn100% C25% N2(% Cr+% Si)6% Mo+45 as well as a method of manufacture of plates, bands, coils, bars, wires, profiles, forged pieces and molded pieces of this steel.

A process for producing clean steel products with low nitrogen content, below 35 ppm, in a steelmaking plant comprising a direct reduced iron (DRI) source, which may be a direct reduction plant or a DRI storage facility, an electric arc furnace (EAF), a vacuum degassing system (DS), and a continuous casting system (CC) is disclosed. The process comprises a first stage of melting and refining a metallic iron charge, a second stage of tapping molten steel from the electric arc furnace (EAF) into a ladle, a third stage of exposing molten steel to a pressure below the atmospheric pressure and a fourth stage of casting molten steel to clean steel products. Optionally, the molten steel tapped from the EAF is treated in a ladle furnace (LF) prior to being treated in the degassing system (DS). The metallic iron charge fed to the EAF comprises more than 70% by weight of DRI in the form of pellets or briquettes having a carbon content above 2.5 weight %. Preferably, the metallic iron charge is fed to the EAF at a temperature of 400 C. or higher. The low nitrogen level in the steel products made according to the Application is achieved by forming a first foamy slag in said first process stage and is maintained in a foamy state by controlling the feed of fluxes, oxygen, and carbonaceous materials to the EAF and by forming a second slag, after molten steel is tapped from the EAF, having a predetermined composition capable of continuing the desulfurization and providing a thermal and chemical insulation to prevent nitrogen pickup and promote nitrogen removal of molten steel. The process also comprises carrying out one or more of the following actions: (a) controlling the concentration of nitrogen and sulfur in the raw materials at each process stage, (b) promoting nitrogen removal from steel, (c) decreasing the time spent by the molten steel at each process stage and between each and subsequent process stages, and (d) preventing nitrogen pickup by the molten steel all along said process stages. Steel products made according to the Application comprise the following elements expressed in weight %: C0.05%, Si4.5%, Al2.0%; Mn2.0%; P0.20%; Ni0.200%, Cu0.200%; N0.0030%, Ni0.200%, S0.0035%.

A process for producing clean steel products with low nitrogen content, below 35 ppm, in a steelmaking plant comprising a direct reduced iron (DRI) source, which may be a direct reduction plant or a DRI storage facility, an electric arc furnace (EAF), a vacuum degassing system (DS), and a continuous casting system (CC) is disclosed. The process comprises a first stage of melting and refining a metallic iron charge, a second stage of tapping molten steel from the electric arc furnace (EAF) into a ladle, a third stage of exposing molten steel to a pressure below the atmospheric pressure and a fourth stage of casting molten steel to clean steel products. Optionally, the molten steel tapped from the EAF is treated in a ladle furnace (LF) prior to being treated in the degassing system (DS). The metallic iron charge fed to the EAF comprises more than 70% by weight of DRI in the form of pellets or briquettes having a carbon content above 2.5 weight %. Preferably, the metallic iron charge is fed to the EAF at a temperature of 400 C. or higher. The low nitrogen level in the steel products made according to the Application is achieved by forming a first foamy slag in said first process stage and is maintained in a foamy state by controlling the feed of fluxes, oxygen, and carbonaceous materials to the EAF and by forming a second slag, after molten steel is tapped from the EAF, having a predetermined composition capable of continuing the desulfurization and providing a thermal and chemical insulation to prevent nitrogen pickup and promote nitrogen removal of molten steel. The process also comprises carrying out one or more of the following actions: (a) controlling the concentration of nitrogen and sulfur in the raw materials at each process stage, (b) promoting nitrogen removal from steel, (c) decreasing the time spent by the molten steel at each process stage and between each and subsequent process stages, and (d) preventing nitrogen pickup by the molten steel all along said process stages. Steel products made according to the Application comprise the following elements expressed in weight %: C0.05%, Si4.5%, Al2.0%; Mn2.0%; P0.20%; Ni0.200%, Cu0.200%; N0.0030%, Ni0.200%, S0.0035%.

A casting-rolling integrated plant that is capable of producing, from a steel melt, in a cost-effective manner and with high productivity, a hot-rolled finished strip having a thickness of 0.6 mm, an excellent flatness, and an excellent profile by dividing the thickness reduction into at least three stages (roughing, intermediate and finishing train), measuring the actual profile after the roughing, intermediate and finishing train, and equipping the stands in the roughing, intermediate and finishing train with actuators for influencing the strip profile and/or the strip flatness.