A method for treating molten metals (4) and/or slags in metallurgical baths comprises the introduction of a process gas into a melt bath. The process gas is accelerated to supersonic speed and is introduced below the melt bath surface (5) by means of at least one supersonic nozzle (6) with supersonic speed into the liquid phase of the molten metal (4) and/or into the slag and/or into the region of a phase boundary between molten metal and slag. The disclosure further relates to a metallurgical plant for treating molten metals.

Disclosed is a slag discharging method in a process of producing ultra-low phosphorus steel, which relates to the technical field of iron and steel smelting, and in which molten steel is mixed with lime first to produce basic slag; then converting is performed with oxygen to increase the oxidizability of the basic slag; and a carbon-containing reducing agent is finally added, so that in the process that the carbon is oxidized to release a large amount of carbon monoxide gas, phosphates are captured, and the basic slag is rapidly foamed and overflows from the opening of the steel ladle, so that conditions are no longer available for rephosphorization. The slag discharging method is simple and convenient to operate, does not have high requirements on the equipment, has relatively good dephosphorization effect, and can be used to prepare an ultra-low phosphorus steel containing less than 0.003% phosphorus. Also disclosed is a method for producing ultra-low phosphorus steel, which comprises the above-described slag discharging method in a process of producing ultra-low phosphorus steel, and refining and ingotting after slag discharge. The production method has good dephosphorization effect, has a low production cost, and can high-efficiently produce an ultra-low phosphorus steel containing less than 0.003% phosphorus.

Disclosed is a slag discharging method in a process of producing ultra-low phosphorus steel, which relates to the technical field of iron and steel smelting, and in which molten steel is mixed with lime first to produce basic slag; then converting is performed with oxygen to increase the oxidizability of the basic slag; and a carbon-containing reducing agent is finally added, so that in the process that the carbon is oxidized to release a large amount of carbon monoxide gas, phosphates are captured, and the basic slag is rapidly foamed and overflows from the opening of the steel ladle, so that conditions are no longer available for rephosphorization. The slag discharging method is simple and convenient to operate, does not have high requirements on the equipment, has relatively good dephosphorization effect, and can be used to prepare an ultra-low phosphorus steel containing less than 0.003% phosphorus. Also disclosed is a method for producing ultra-low phosphorus steel, which comprises the above-described slag discharging method in a process of producing ultra-low phosphorus steel, and refining and ingotting after slag discharge. The production method has good dephosphorization effect, has a low production cost, and can high-efficiently produce an ultra-low phosphorus steel containing less than 0.003% phosphorus.

When performing dephosphorization treatment of hot metal by adding a refining agent as a lime source and an oxygen source (dephosphorizing agent(s) and a gaseous oxygen source into the hot metal accommodated in a hot metal holding container, the refining agent used is a refining agent having an Ig-loss value of from 4.0% by mass to 35.0% by mass and including 60% by mass or more of quicklime.

Provided is a method for producing steel including: preparing a first molten steel and a manganese-containing melt; supplying a nitrogen gas into a storage to blow nitrogen into the melt received in the storage and thereby adjusting a nitrogen content (wt %) in the melt to a required nitrogen content (wt %); and mixing the melt and the first molten steel to produce a second molten steel containing manganese and nitrogen. Since nitrogen is not blown while melting large amounts of solid materials, the oxidation of manganese due to a high temperature may be minimized or prevented. In addition, a large amount of solid material is not added, and a small amount of manganese-containing nonferrous metal or a FeMn ferroalloy is added, if necessary, into a produced melt in a molten state, and thus, a problem of temperature drop due to the input of the solid material may be minimized or prevented.

Provided is a method for producing steel including: preparing a first molten steel and a manganese-containing melt; supplying a nitrogen gas into a storage to blow nitrogen into the melt received in the storage and thereby adjusting a nitrogen content (wt %) in the melt to a required nitrogen content (wt %); and mixing the melt and the first molten steel to produce a second molten steel containing manganese and nitrogen. Since nitrogen is not blown while melting large amounts of solid materials, the oxidation of manganese due to a high temperature may be minimized or prevented. In addition, a large amount of solid material is not added, and a small amount of manganese-containing nonferrous metal or a FeMn ferroalloy is added, if necessary, into a produced melt in a molten state, and thus, a problem of temperature drop due to the input of the solid material may be minimized or prevented.

Ti, N, Al, Mg, and Ca concentrations are controlled in order to prevent aggregation of TiN inclusions. Furthermore, not only is a FeCrNi alloy having superior surface property provided, but also a method is proposed in which the FeCrNi alloy is produced at low cost using commonly used equipment. The FeCrNi alloy includes C0.05%, Si: 0.1 to 0.8%, Mn: 0.2 to 0.8%, P0.03%, S0.001%, Ni:16 to 35%, Cr: 18 to 25%, Al: 0.2 to 0.4%, Ti: 0.25 to 0.4%, N0.016%, Mg: 0.0015 to 0.008%, Ca0.005%, O: 0.0002 to 0.005%, freely selected Mo: 0.5 to 2.5% in mass % and Fe and inevitable impurities as the remainder, wherein Ti and N satisfy % N% Ti0.0045 and the number of TiN inclusions not smaller than 5 m is 20 to 200 pieces/cm.sup.2 at a freely selected cross section.

When storing a molten ferroalloy or molten nonferrous metal, the molten ferroalloy or molten nonferrous metal is denitrified or prevented from absorbing nitrogen, and thus post processing such as a denitrification process may not be performed. For this, there is provided a method of producing molten manganese-containing steel, the method including: preparing a molten ferroalloy or a molten nonferrous metal; maintaining the molten ferroalloy or the molten nonferrous metal at a temperature equal to or higher than a melting point thereof; and pouring the molten ferroalloy or the molten nonferrous metal into prepared molten steel, wherein in the maintaining of the molten ferroalloy or the molten nonferrous metal, the molten ferroalloy or the molten nonferrous metal is subjected to a nitrogen-absorption prevention process or a denitrification process.

When storing a molten ferroalloy or molten nonferrous metal, the molten ferroalloy or molten nonferrous metal is denitrified or prevented from absorbing nitrogen, and thus post processing such as a denitrification process may not be performed. For this, there is provided a method of producing molten manganese-containing steel, the method including: preparing a molten ferroalloy or a molten nonferrous metal; maintaining the molten ferroalloy or the molten nonferrous metal at a temperature equal to or higher than a melting point thereof; and pouring the molten ferroalloy or the molten nonferrous metal into prepared molten steel, wherein in the maintaining of the molten ferroalloy or the molten nonferrous metal, the molten ferroalloy or the molten nonferrous metal is subjected to a nitrogen-absorption prevention process or a denitrification process.

A clean and rapid smelting method in an electric arc furnace with full scrap steel, is suitable for smelting process of 30-300 t electric arc furnace with full scrap steel. In the smelting process of the electric arc furnace with full scrap steel, different kinds of mediums are injected by an injection lance which is installed inside refractory material of sidewall at the bottom of the electric arc furnace in different stages of smelting. Carburization is utilized in molten pool to accelerate melting down and improve carbon content of the molten pool at the stage of recarburizing and fluxing. A reaction in the molten pool is intensified at the stage of high efficiency dephosphorization and deep denitrogenation, to enhance efficient dephosphorization and deep denitrification of the reaction in the molten pool, thereby accelerating the smelting speed of the electric arc furnace with full scrap steel, improving effect of dephosphorization and denitrification.