Abstract: Provided is an alloy steel manufacturing method, the method including: preparing a manganese-containing first molten ferroalloy; preparing a chromium-containing second molten alloy; preparing molten steel; mixing the first molten ferroalloy and the second molten ferroalloy to manufacture third molten ferroalloy; and mix pouring the third molten ferroalloy and the molten steel to manufacture an alloy steel, wherein the phosphorous concentration in the molten steel may efficiently be controlled by reducing the converter end point temperature of the molten steel to improve a phosphorous control capacity during converter refining.

Abstract: Provided is a method for producing alloy steel, the method comprising producing first alloy steel in a temperature holding furnace; maintaining the first alloy steel at a temperature of no lower than a melting point in the temperature holding furnace; and producing second alloy steel having an alloy content lower than the alloy content in the first alloy steel by melt mixing of the first alloy steel and molten steel. In the producing of the alloy steel, melting and storing of the ferroalloy are continuously performed, and thus, the temperature drop of the ferroalloy may be suppressed or prevented.

Abstract: Provided is a dephosphorizing flux configured to adjust a phosphorous component contained in molten steel, the dephosphorizing flux includes a main material including BaCO3 and a supplementary material, wherein the supplementary material includes a first material containing either of NaHCO3 or Na2CO3 and a second material containing CaF2. 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.

Abstract: Provided is an alloy steel manufacturing method, the method including: preparing a manganese-containing first molten ferroalloy; preparing a chromium-containing second molten alloy; preparing molten steel; mixing the first molten ferroalloy and the second molten ferroalloy to manufacture third molten ferroalloy; and mix pouring the third molten ferroalloy and the molten steel to manufacture an alloy steel, wherein the phosphorous concentration in the molten steel may efficiently be controlled by reducing the converter end point temperature of the molten steel to improve a phosphorous control capacity during converter refining.

Abstract: 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.

Abstract: 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.

Abstract: Provided is a dephosphorizing flux configured to adjust a phosphorous component contained in molten steel, the dephosphorizing flux includes a main material including BaCO3 and a supplementary material, wherein the supplementary material includes a first material containing either of NaHCO3 or Na2CO3 and a second material containing CaF2. 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.

Abstract: Provided is a method for producing alloy steel, the method comprising producing first alloy steel in a temperature holding furnace; maintaining the first alloy steel at a temperature of no lower than a melting point in the temperature holding furnace; and producing second alloy steel having an alloy content lower than the alloy content in the first alloy steel by melt mixing of the first alloy steel and molten steel. In the producing of the alloy steel, melting and storing of the ferroalloy are continuously performed, and thus, the temperature drop of the ferroalloy may be suppressed or prevented.

Abstract: An impeller for stirring a melt pool includes: an impeller body extending in the length direction; a blowing nozzle which is provided in such a way as to pass through one part at the bottom end of the impeller body; and a blade provided on the upper part of the impeller body. As a result, when the impeller is used, a stirring flow produced due to the blade and a stirring flow due to substances blown into the melt-pool via the blowing nozzle correspond to each other, and the two flows are combined such that the overall stirring force is improved. Consequently, it is possible to improve the efficiency of stirring by the impeller as compared with hitherto, and, as a result, refining efficiency in the refining step is improved as the rate of reaction between the melt-pool and additives is increased.

Abstract: A manganese-containing molten steel production method comprises: a preparation step in which a molten ferroalloy or a molten non-ferrous metal is prepared by carrying out denitrification or nitrogen-absorption prevention during a procedure of retaining the molten ferroalloy or molten non-ferrous metal, in order to prevent later processing or additional denitrification due to nitrogen absorption; a maintaining step in which the molten ferroalloy or molten non-ferrous metal is maintained at a temperature at or above the melting point thereof; and a united pouring step in which the molten ferroalloy or molten non-ferrous metal is subjected to united pouring together with pre-prepared molten steel. In the present invention, while the maintaining step is being carried out, so too is a nitrogen-absorption prevention or denitrification step in which the molten ferroalloy or molten non-ferrous metal is subjected to nitrogen-absorption prevention or denitrification.

Abstract: An impellor for stirring a melt pool includes: an impellor body extending in the length direction; a blowing nozzle which is provided in such a way as to pass through one part at the bottom end of the impellor body; and a blade provided on the upper part of the impellor body. As a result, when the impellor is used, a stirring flow produced due to the blade and a stirring flow due to substances blown into the melt-pool via the blowing nozzle correspond to each other, and the two flows are combined such that the overall stirring force is improved. Consequently, it is possible to improve the efficiency of stirring by the impeller as compared with hitherto, and, as a result, refining efficiency in the refining step is improved as the rate of reaction between the melt-pool and additives is increased.