Refining agent and refining method

Abstract

A refining agent contains Al, MgO, and CaO as main components, and uses dolomite as a MgO source and CaO source. When the refining agent is supplied into molten iron, it produces Mg vapor due to a reaction in the molten iron, and causes a refining reaction by the Mg vapor.

1 . A refining agent containing Al, MgO, and CaO as main components, and including a material as a MgO source and CaO source, in which MgO and CaO are close to or in contact with each other in a minute state, the refining agent being arranged to produce Mg vapor due to a reaction in molten iron, when the refining agent is supplied into the molten iron.  
   
   
       2 . A refining agent according to  claim 1 , which performs desulfurization and/or deoxidation of the molten iron.  
   
   
       3 . A refining agent according to  claim 1 , which contains MgO, CaO, and Al summing to 75 mass % or more.  
   
   
       4 . A refining agent containing Al, MgO, and CaO as main components, and including dolomite as a MgO source and CaO source, the refining agent being arranged to produce Mg vapor due to a reaction in molten iron, when the refining agent is supplied into the molten iron.  
   
   
       5 . A refining agent according to  claim 4 , which performs desulfurization and/or deoxidation of the molten iron.  
   
   
       6 . A refining agent according to  claim 4 , which is in a state prepared by mixing or crushing and mixing a raw material including dolomite and an Al source containing 25 mass % or more metal Al, or a raw material including at least one of another MgO source and another CaO source in addition to them, to obtain mixture powder with an average particle size of 1 mm or less, or in a state prepared by changing the mixture powder into a pelletized or lumped form with a size of 3 mm to 40 mm.  
   
   
       7 . A refining agent according to  claim 6 , wherein the raw material in a pelletized or lumped form includes a forming binder mixed therein.  
   
   
       8 . A refining agent according to  claim 7 , wherein the binder has a viscosity of 2 to 10 poise at 60° C.  
   
   
       9 . A refining agent according to  claim 4 , wherein Al/MgO is 0.05 or more in mass ratio, and CaO/MgO is in a range of 0.5 to 10.0 in mass ratio.  
   
   
       10 . A refining agent according to  claim 9 , wherein Al/MgO is 0.2 or more in mass ratio.  
   
   
       11 . A refining agent according to  claim 9 , wherein CaO/MgO is more than 1.5 and up to 10.0 in mass ratio.  
   
   
       12 . A refining agent according to  claim 9 , wherein CaO/MgO falls in a dolomite composition range.  
   
   
       13 . A refining agent according to  claim 9 , wherein the MgO source and CaO source are formed of dolomite and another MgO source or CaO source for compensating for part of CaO and MgO, which exceeds dolomite composition, so as to obtain a predetermined CaO/MgO.  
   
   
       14 . A refining agent according to  claim 4 , which contains MgO, CaO, and Al summing to 75 mass % or more.  
   
   
       15 . A refining agent containing Al, MgO, and CaO as main components, and including dolomite as a MgO source and CaO source, wherein Al/MgO is 0.05 or more in mass ratio, and CaO/MgO is in a range of 0.5 to 10.0 in mass ratio.  
   
   
       16 . A refining agent according to  claim 15 , wherein Al/MgO is 0.2 or more in mass ratio.  
   
   
       17 . A refining agent according to  claim 15 , wherein CaO/MgO is more than 1.5 and up to 10.0 in mass ratio.  
   
   
       18 . A refining agent according to  claim 15 , wherein CaO/MgO falls in a dolomite composition range.  
   
   
       19 . A refining agent according to  claim 15 , wherein the MgO source and CaO source are formed of dolomite and another MgO source or CaO source for compensating for part of CaO and MgO, which exceeds dolomite composition, so as to obtain a predetermined CaO/MgO.  
   
   
       20 . A refining agent according to  claim 15 , which contains MgO, CaO, and Al summing to 75 mass % or more.  
   
   
       21 . A refining agent containing Al, C, MgO, and CaO as main components, and arranged to produce Mg vapor due to a reaction in molten iron, when the refining agent is supplied into the molten iron.  
   
   
       22 . A refining agent according to  claim 21 , which includes a material as a MgO source and CaO source, in which MgO and CaO are close to or in contact with each other in a minute state.  
   
   
       23 . A refining agent according to  claim 22 , which includes dolomite as the MgO source and CaO source.  
   
   
       24 . A refining agent according to  claim 21 , which performs desulfurization and/or deoxidation of the molten iron.  
   
   
       25 . A refining agent according to  claim 21 , which is in a state prepared by mixing or crushing and mixing a raw material including dolomite, an Al source containing 25 mass % or more metal Al, and carbon powder, or a raw material including at least one of another MgO source and another CaO source in addition to them, to obtain mixture powder with an average particle size of 1 mm or less, or in a state prepared by changing the mixture powder into a pelletized or lumped form with a size of 3 mm to 40 mm.  
   
   
       26 . A refining agent according to  claim 25 , wherein the raw material in a pelletized or lumped form includes a forming binder mixed therein.  
   
   
       27 . A refining agent according to  claim 26 , wherein the binder has a viscosity of 2 to 10 poise at 60° C.  
   
   
       28 . A refining agent according to  claim 21 , wherein Al/MgO is 0.05 or more in mass ratio, C/MgO is 0.1 or more in mass ratio, and CaO/MgO is in a range of 0.5 to 10.0 in mass ratio.  
   
   
       29 . A refining agent according to  claim 28 , wherein Al/MgO is 0.2 or more in mass ratio.  
   
   
       30 . A refining agent according to  claim 28 , wherein CaO/MgO is more than 1.5 and up to 10.0 in mass ratio.  
   
   
       31 . A refining agent according to  claim 21 , which contains MgO, CaO, Al, and C summing to 75 mass % or more.  
   
   
       32 . A refining agent containing Al, C, MgO, and CaO as main components, wherein Al/MgO is 0.05 or more in mass ratio, C/MgO is 0.1 or more in mass ratio, and CaO/MgO is in a range of 0.5 to 10.0 in mass ratio.  
   
   
       33 . A refining agent according to  claim 32 , wherein Al/MgO is 0.2 or more in mass ratio.  
   
   
       34 . A refining agent according to  claim 32 , wherein CaO/MgO is more than 1.5 and up to 10.0 in mass ratio.  
   
   
       35 . A refining agent according to  claim 32 , which contains MgO, CaO, Al, and C summing to 75 mass % or more.  
   
   
       36 . A refining method of performing desulfurization treatment of molten pig iron by adding a refining agent to the molten pig iron held in a container, the refining agent containing Al, MgO, and CaO as main components, and including a material as a MgO source and CaO source, in which MgO and CaO are close to or in contact with each other in a minute state.  
   
   
       37 . A refining method of performing desulfurization treatment of molten pig iron by adding a refining agent to the molten pig iron held in a container, the refining agent containing Al, MgO, and CaO as main components, and including dolomite as a MgO source and CaO source.  
   
   
       38 . A refining method according to  claim 37 , which performs the desulfurization treatment while stirring the molten pig iron in the container by a mechanically stirring method.  
   
   
       39 . A refining method according to  claim 38 , which performs a treatment of creating a new surface on desulfurization slag obtained by performing the desulfurization treatment with stirring by the mechanically stirring method, and uses the desulfurization slag thus treated to perform desulfurization treatment of molten pig iron.  
   
   
       40 . A refining method according to  claim 37 , which adds the refining agent to the molten pig iron in the container by injection.  
   
   
       41 . A refining method according to  claim 37 , which adds the refining agent to the molten pig iron in the container by a putting-in or putting-on method.  
   
   
       42 . A refining method according to  claim 37 , which adds the refining agent to the molten pig iron in the container, in a form prepared by mixing raw materials of the refining agent in advance.  
   
   
       43 . A refining method according to  claim 42 , which adds the refining agent to the molten pig iron in the container at one time or dividedly at several times.  
   
   
       44 . A refining method according to  claim 37 , which adds the refining agent to the molten pig iron in the container, in a form prepared by not mixing raw materials of the refining agent in advance.  
   
   
       45 . A refining method according to  claim 44 , which adds the raw materials to the molten pig iron in the container at the same position or at different positions.  
   
   
       46 . A refining method according to  claim 44 , which adds the raw materials to the molten pig iron in the container at the same time or at different times.  
   
   
       47 . A refining method according to  claim 44 , which adds the raw materials to the molten pig iron in the container at one time or dividedly at several times.  
   
   
       48 . A refining method according to  claim 37 , wherein the molten pig iron in the container is set to have a temperature of 1,200° C. or more.  
   
   
       49 . A refining method according to  claim 48 , wherein the molten pig iron in the container is set to have a temperature of 1,300° C. or more.  
   
   
       50 . A refining method of refining molten pig iron by performing a series of treatment, which is formed of desulfurization treatment and at least one of desiliconization treatment and dephosphorization treatment, on molten pig iron after tapping from blast furnace and before decarburization in converter, wherein the desulfurization treatment is performed by adding a refining agent to the molten pig iron held in a container, the refining agent containing Al, MgO, and CaO as main components, and including dolomite as a MgO source and CaO source.  
   
   
       51 . A refining method according to  claim 50 , wherein silicon concentration in molten pig iron is 0.2 mass % or less before the dephosphorization treatment, phosphorus concentration in molten pig iron is 0.03 mass % or less after the dephosphorization treatment, and sulfur concentration is 0.005 mass % or less after the desulfurization treatment.  
   
   
       52 . A refining method according to  claim 50 , which performs at least one of the desiliconization treatment and dephosphorization treatment before the desulfurization treatment.  
   
   
       53 . A refining method according to  claim 52 , which performs a treatment immediately before the desulfurization treatment, such that molten pig iron temperature becomes 1,300° C. or more before the desulfurization treatment.  
   
   
       54 . A refining method according to  claim 53 , which performs a treatment immediately before the desulfurization treatment, such that molten pig iron temperature becomes 1,350% or more before the desulfurization treatment.  
   
   
       55 . A refining method of refining molten pig iron by performing a series of treatment, which is formed of desulfurization treatment and at least one of desiliconization treatment and dephosphorization treatment, on molten pig iron after tapping from blast furnace and before decarburization in converter, wherein the desulfurization treatment is performed by adding a refining agent to the molten pig iron held in a container, the refining agent containing Al, MgO, and CaO as main components, and including dolomite as a MgO source and CaO source, and wherein a total consumption of fluorite in the series of treatment is set to be 0.1 kg or less per ton of molten pig iron.  
   
   
       56 . A refining method according to  claim 55 , wherein the refining agent contains substantially no fluorine.  
   
   
       57 . A refining method according to  claim 55 , wherein fluorine concentration is 0.2 mass % or less in slag generated in each treatment of the series of treatment.  
   
   
       58 . A refining method according to  claim 55 , wherein fluorine concentration is 0.2 mass % or less in slag in tapping from blast furnace.  
   
   
       59 . A refining method of performing at least one of desulfurization treatment, deoxidation treatment, and inclusion control of molten steel by adding a refining agent to the molten steel, the refining agent containing Al, MgO, and CaO as main components, and including dolomite as a MgO source and CaO source.  
   
   
       60 . A refining method according to  claim 59 , which adds the refining agent to one of molten steel in a melting furnace, molten steel pouring flow from a melting furnace, molten steel in a ladle, molten steel in a vessel incidental to a ladle, and molten steel in a tundish for continuous casting.  
   
   
       61 . A refining method according to  claim 60 , wherein the melting furnace is a converter for treating molten pig iron, or an electric furnace for melting a cold iron source.  
   
   
       62 . A refining method according to  claim 60 , wherein the vessel incidental to a ladle is a vacuum vessel of an RH vacuum degassing apparatus.  
   
   
       63 . A refining method according to  claim 59 , which uses the refining agent to perform a treatment of causing inclusions in the molten steel to contain MgO.  
   
   
       64 . A refining method according to  claim 63 , wherein the treatment is performed to control alumina inclusions to a spinel composition in all or in part in the molten steel, which contains 0.01 mass % or more solute Al and 30 ppm or less solute oxygen after deoxidation.  
   
   
       65 . A refining method according to  claim 63 , wherein the treatment is performed to increase MgO concentration in inclusions, formed mainly of silicate, in all or in part in the molten steel, which contains less than 0.01 mass % solute Al and 30 ppm or less solute oxygen after deoxidation.  
   
   
       66 . A refining method of performing making high clean molten steel by adding a refining agent to molten steel deoxidated by a predetermined element, the refining agent containing Al, MgO, and CaO as main components, and including dolomite as a MgO source and CaO source.  
   
   
       67 . A refining method of performing desulfurization treatment of molten pig iron by adding a refining agent to the molten pig iron held in a container, the refining agent containing Al, C, MgO, and CaO as main components.  
   
   
       68 . A refining method of refining molten pig iron by performing a series of treatment, which is formed of desulfurization treatment and at least one of desiliconization treatment and dephosphorization treatment, on molten pig iron after tapping blast furnace and before decarburization in converter, wherein the desulfurization treatment is performed by adding a refining agent to the molten pig iron held in a container, the refining agent containing Al, C, MgO, and CaO as main components.  
   
   
       69 . A refining method of refining molten pig iron by performing a series of treatment, which is formed of desulfurization treatment and at least one of desiliconization treatment and dephosphorization treatment, on molten pig iron after tapping from blast furnace and before decarburization in converter, wherein the desulfurization treatment is performed by adding a refining agent to the molten pig iron held in a container, the refining agent containing Al, C, MgO, and CaO as main components, and wherein a total consumption of fluorite in the series of treatment is set to be 0.1 kg or less per ton of molten pig iron.  
   
   
       70 . A refining method of performing at least one of desulfurization treatment, deoxidation treatment, and inclusion control of molten steel by adding a refining agent to the molten steel, the refining agent containing Al, C, MgO, and CaO as main components.  
   
   
       71 . A refining method of performing making high clean molten steel by adding a refining agent to molten steel deoxidated by a predetermined element, the refining agent containing Al, C, MgO, and CaO as main components.  
   
   
       72 . A desulfurization slag recycling method of performing desulfurization treatment of molten pig iron by adding a refining agent to the molten pig iron, and then recycling desulfurization slag thus generated as a raw material to be sintered for a blast furnace, the refining agent containing Al, MgO, and CaO as main components, and including dolomite as a MgO source and CaO source.