EP0325242A2 - Method for refining molten steel in a vacuum - Google Patents
Method for refining molten steel in a vacuum Download PDFInfo
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- EP0325242A2 EP0325242A2 EP89100866A EP89100866A EP0325242A2 EP 0325242 A2 EP0325242 A2 EP 0325242A2 EP 89100866 A EP89100866 A EP 89100866A EP 89100866 A EP89100866 A EP 89100866A EP 0325242 A2 EP0325242 A2 EP 0325242A2
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- molten steel
- gas
- ladle
- vacuum vessel
- gases containing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
Definitions
- the present invention relates to a method for refining molten steel in a vacuum, and more particularly to a method for degassing molten steel.
- a large amount of gas components is contained in molten steel produced in a steel-making furnace such as converter and the like which smelts and refines steel.
- various vacuum processing methods wherein molten steel is degassed in a vacuum.
- RH vacuum degassing method molten steel is degassed in such a manner as described below.
- a ladle is filled up with molten steel to be processed.
- Two immersion nozzles arranged at the lower portion of a vacuum vessel are immersed in the molten steel from the upper side of the ladle.
- Inert gas is blown from the middle of one immersion nozzle to have the molten steel in the ladle circulated through the immersion nozzles inside the vacuum vessel. In this way, the molten steel is degassed in the vacuum vessel.
- Requirements for components of steel for a special use are more severe than those of molten steel processed with RH vacuum degassing method. Therefore, it is necessary to use other methods so as to process molten steel for a special use.
- a total amount of oxygen in the molten steel needs to be decreased.
- the total amount of oxygen in the molten steel can barely be decreased to approximately 10 ppm by use of RH vacuum degassing method. Therefore, the RH vacuum degassing method cannot be applied to steel which requires a total amount of oxygen of less than 10 ppm.
- the present invention provides a method for refining molten steel in a vacuum comprising: an immersion process, wherein two immersion nozzles arranged at the lower portion of a vacuum vessel are immersed in molten steel in a ladle, said two immersion nozzles are a rising tube and a sinking tube; a first degassing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated, having said molten steel circulated between said ladle and said vacuum vessel being kept evacuated by injecting gases containing at least an inert gas from the middle of said rising tube; and blowing in said molten steel gases containing at least gas soluble in said molten steel.
- a further method comprising: an immersion process, wherein two immersion nozzles are immersed in molten steel in a ladle, said immersion nozzles are a rising tube and a sinking tube; a dissolving process, wherein gases are dissolved in said molten steel by blowing in said molten steel gases containing at least gas soluble in said molten steel from a gas blow-in opening arranged in said ladle; a first degassing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated, having said molten steel circulated between said ladle and said vacuum vessel by injecting gases containing at least an inert gas from the middle of said rising tube in said molten steel, and blowing gases containing at least gas soluble in said molten steel from a gas blow-in opening arranged in said ladle; and a second degassing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated, stopping a gas blowing-in from said gas blow-
- a method for refining molten steel in a vacuum of the present invention comprises an immersion process, wherein immersion nozzles are immersed in molten steel, a dissolving process, wherein gases are dissolved in said molten steel, a first degassing process and a second degassing process.
- Two immersion nozzles arranged at the lower portion of vacuum vessel 4 are immersed in molten steel in a ladle.
- One of the two immersion nozzles is rising tube 5 and the other sinking tube 6.
- Fig. 1 is a sectional view schematically showing a dissolving process, wherein gases are dissolved in molten steel, according to the present invention.
- Molten steel 2 inside ladle 1 is pressurized by its static pressure. Gases containing at least gas soluble in molten steel are blown in molten steel 2 through gas blow-in opening 3 arranged at the bottom of ladle 1. It is, of course, possible to blow a mixed gas consisting of gas soluble in said molten steel and an inert gas in said molten steel. Molten steel 2 is bubbled by said mixed gas. Together with bubbling of said molten steel, a large amount of gas soluble in said molten steel dissolves in said molten steel.
- Gases can be simultaneously blown in said molten steel through gas blow-in opening 7 arranged in rising tube 5 of vacuum vessel 4.
- the amount of gases dissolved in said molten steel is expected to be quickly increased.
- a part of inclusions in molten steel 2 is trapped by bubbled gas and rises to the surface of said molten steel.
- a pressure to said molten steel is decreased.
- the gases having been dissolved in said molten steel convert to fine bubbles. Fine inclusions in said molten steel are trapped by produced gas bubbles and rise to the surface of said molten steel.
- Hydrogen gas, nitrogen gas and hydrocarbon gas as gases soluble in the molten steel are used out of a mixed gas blown in the molten steel.
- Ar gas and He gas are used as an inert gas. Only gases soluble in the molten steel can be used instead of the mixed gas.
- gases were blown in the molten steel from gas blow-in opening 3 arranged at the bottom of ladle 1, but ways of a gas blow-in are not limited to this. Gases can be blown in the lower portion of the molten steel in ladle 1.
- Gas blow-in opening 3, however, is desired to be arranged in the bottom wall of ladle 1 just under rising tube.
- a large amount of gas can be blown in the molten steel with the use of an immersion lance before an immersion nozzle is immersed in the molten steel.
- Said immersion lance is immersed from the surface of the molten steel into the molten steel.
- Fig. 2 is a sectional view schemtically showing a first degassing process of the present invention.
- Vacuum vessel 4 is kept evacuated.
- An inert gas is injected from gas blow-in opening 7 arranged in the middle of rising tube 5.
- molten steel is made to circulate between ladle 1 and vacuum vessel 4.
- Gases including at least gas soluble in the molten steel are blown in molten steel 2 from gas blow-in opening 3 of ladle 1.
- Molten steel 2 is bubbled by the gases blown in. Together with bubbling, the gas soluble in the molten steel dissolves in the molten steel.
- the molten steel is degassed. With the rise of the molten steel toward the surface of the molten steel in vacuum vessel 4, the gas dissolved in the molten steel converts to bubbles. The gas components having been dissolved in the molten steel in the dissolving process and having not appeared near the surface of the molten steel also appear in the form of bubbles. Fine inclusions contained in the molten steel are trapped by the produced gas bubbles and rise to the surface of the molten steel in vacuum vessel 4. A part of the inclusions contained in molten steel 2 are trapped by bubbled inert gas and rises to the surface of the molten steel in vacuum vessel 4.
- An inert gas was used in this Preferred Embodiment as gas which was injected from the gas blow-in opening arranged in the middle of rising tube 5.
- the gases to be used are not limited to the inert gas.
- a mixed gas of an inert gas and gas soluble in the molten steel can be used. In case the mixed gas is used severely, fine inclusions are expected to be removed because the gas is dissolved in the molten steel and fine gas bubbles are produced under decreased pressure.
- Ar gas and He gas can be used as an inert gas.
- the gas blown in molten steel 2 from gas blow-in opening 2 of ladle 1 can be either a mixed gas consisting of gas soluble in the molten steel and an inert gas or only gas soluble in the molten steel.
- Fig. 3 is a sectional view schematically showing a second degassing process of the present invention.
- Vacuum vessel 4 is kept evacuated.
- An inert gas is injected in vacuum vessel 4 from gas blow-in opening 7 arranged in the middle of rising tube 5 tomake molten steel circulate between ladle 1 and vacuum vessel 4.
- Gas blow-in from gas blow-in opening 3 of ladle 1 is stopped. Since the atmospheric pressure in vacuum vessel 4 is decreased to 2 to 3 Torr, the molten steel is degassed. Gas components, which have been dissolved in the molten steel in the first degassing process and have not been able to be removed, are removed. In this Preferred Embodiment, an inert gas was used.
- the gases to be used are not confined to the inert gas.
- a permissible concentration of final gas components soluble in molten steel is high, a mixed gas of an inert gas and gas soluble in molten steel can be used.
- the amount of N in the molten steel increases, but the molten steel is easily processed. Therefore, selection of the methods as mentioned above varies dependent on speicies of steel to be used and equipment which is owened.
- a mixed gas consisting of 40% Ar gas and 60% H2 gas was blown in said molten steel from gas blow-in opening 7 of rising tube 5 and from gas blow-in opening 3 of ladle 1 respectively at a rate of 180 Nm3/hr and at a rate of 60 Nm3/hr.
- gas blowing-in from gas blow-in opening 3 of ladle 1 was stopped and, at the same time, 100% Ar gas was blown in the molten steel from gas blow-in opening 7 of rising tube 5 at a rate of 180 Nm3/hr for 15 minutes.
- a change of a total amount of oxygen in the molten steel relative to a processing time is indicated in Fig. 4.
- the total amount of oxygen in the molten steel decreased to 5 ppm in processing of the molten steel for 35 minutes.
- the amount of hydrogen in the molten steel after having been processed could be decreased to 2 ppm or less.
- molten steel 250 tons of molten steel were processed with the use of the method (c). Firstly, a top-blow lance was immersed in the molten steel in a ladle and N2 gas was blown in the molten steel at a rate of 180 Nm3/hr for 30 minutes. Subsequently, immersion nozzles were immersed in the molten steel. Vacuum vessel 4 was kept evacuated, and a mixed gas consisting of 60% Ar gas and 40% N2 was blown through gas blow-in opening 7 of rising tube 5 and through gas blow-in opening 3 of ladle 1 respectively at 120 Nm3/hr and at 60 Nm3/hr for 35 minutes. The total amount of oxygen in the molten steel was decreased to approximately 5 ppm by 35 minutes processing of the molten steel. The amount of nitrogen in the molten steel after having been processed was decreased to approximately 90 ppm.
- molten steel 250 tons of molten steel were processed by use of the method (e). Firstly, a top-blow lance was immersed in the molten steel in a ladle and N2 was blown in the molten steel at 180 Nm3/hr for 30 minutes. Subsequently, immersion nozzles were immersed in the molten steel. Vacuum vessel 4 was kept evacuated and Ar gas was blown through gas blow-in opening 7 of rising tube 5 at 120 Nm3/hr for 35 minutes. The total amount of oxygen in the molten steel was decreased to approximately 6 ppm by 35 minutes processing of the molten steel. The amount of nitrogen in the molten steel after having been processed was decreased to approximately 35 ppm.
- molten steel 250 tons of molten steel were processed by use of the method (b).
- a mixed gas consisting of 20% Ar gas and 80% N2 gas was blown in the molten steel through gas blow-in opening 7 of rising tube 5 and N2 gas through gas blow-in opening 3 of ladle 1 respectively at 120 Nm3/hr and at 60 Nm3/hr.
- blowing-in of N2 gas through gas blow-in opening 3 of ladle 1 was stopped, and, at the same time, 100% Ar gas blown in the molten steel through gas blow-in opening 7 of rising tube 5 at 120 Nm3/hr for 15 minutes.
- the total amount of oxygen in the molten steel was decreased to approximately 6 ppm by 35 minutes processing of the molten steel.
- the amount of nitrogen in the molten steel was decreased to approximately 40 ppm.
- molten steel 250 tons of molten steel was processed by use of the method (a). Firstly, a top-blow lance was immersed in the molten steel in a ladle, and N2 gas was blown in the molten steel at 180 Nm3/hr for half an hour. Then, immersion nozzles were immersed in the molten steel. Vacuum vessel 4 was kept evacuated. For the first 20 minutes, a mixed gas consisting of 20% Ar gas and 80% N2 gas was blown in vacuum vessel 4 through gas blow-in opening 7 of rising tube 5 and N2 gas through gas blow-in opening 3 of ladle 1 respectively at 120 Nm3/hr and at 60 Nm3/hr.
- a mixed gas consisting of 20% Ar gas and 80% N2 gas was blown in vacuum vessel 4 through gas blow-in opening 7 of rising tube 5 and N2 gas through gas blow-in opening 3 of ladle 1 respectively at 120 Nm3/hr and at 60 Nm3/hr.
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Abstract
Description
- The present invention relates to a method for refining molten steel in a vacuum, and more particularly to a method for degassing molten steel.
- A large amount of gas components is contained in molten steel produced in a steel-making furnace such as converter and the like which smelts and refines steel. To remove the gas components, there are carried out various vacuum processing methods wherein molten steel is degassed in a vacuum. Out of those methods, for example, RH vacuum degassing method is known. In this RH vacuum degassing method, molten steel is degassed in such a manner as described below. A ladle is filled up with molten steel to be processed. Two immersion nozzles arranged at the lower portion of a vacuum vessel are immersed in the molten steel from the upper side of the ladle. Inert gas is blown from the middle of one immersion nozzle to have the molten steel in the ladle circulated through the immersion nozzles inside the vacuum vessel. In this way, the molten steel is degassed in the vacuum vessel.
- Requirements for components of steel for a special use, however, are more severe than those of molten steel processed with RH vacuum degassing method. Therefore, it is necessary to use other methods so as to process molten steel for a special use. To remove alumina inclusions in molten steel, for example, a total amount of oxygen in the molten steel needs to be decreased. The total amount of oxygen in the molten steel can barely be decreased to approximately 10 ppm by use of RH vacuum degassing method. Therefore, the RH vacuum degassing method cannot be applied to steel which requires a total amount of oxygen of less than 10 ppm.
- It is an object of the present invention to provide a method for refining molten steel in a vacuum which effectively removes inclusions in molten steel. To accomplish said object, the present invention provides a method for refining molten steel in a vacuum comprising: an immersion process, wherein two immersion nozzles arranged at the lower portion of a vacuum vessel are immersed in molten steel in a ladle, said two immersion nozzles are a rising tube and a sinking tube; a first degassing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated, having said molten steel circulated between said ladle and said vacuum vessel being kept evacuated by injecting gases containing at least an inert gas from the middle of said rising tube; and blowing in said molten steel gases containing at least gas soluble in said molten steel.
- A further method comprising: an immersion process, wherein two immersion nozzles are immersed in molten steel in a ladle, said immersion nozzles are a rising tube and a sinking tube; a dissolving process, wherein gases are dissolved in said molten steel by blowing in said molten steel gases containing at least gas soluble in said molten steel from a gas blow-in opening arranged in said ladle; a first degassing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated, having said molten steel circulated between said ladle and said vacuum vessel by injecting gases containing at least an inert gas from the middle of said rising tube in said molten steel, and blowing gases containing at least gas soluble in said molten steel from a gas blow-in opening arranged in said ladle; and a second degassing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated, stopping a gas blowing-in from said gas blow-in opening arranged in said ladle and having said molten steel circulated between said ladle and said vacuum vessel being kept evacuated by injecting gases containing at least an inert gas from the middle of said rising tube in said molten steel.
- The above objects and other objects and advantages of the present invention will become apparent from the detailed description to follow, taken in connection with the appended drawings.
- Fig. 1 is a sectional view schematically showing a dissolving process, wherein gases are dissolved in molten steel, according to the present invention;
- Fig. 2 is a sectional view schematically showing a first degassing process of the present invention;
- Fig. 3 is a sectional view schematically showing a second degassing process of the present invention; and
- Fig. 4 is a graphical representation indicating the relation between a processing time in a vacuum refining and a total amount of oxygen in molten steel in Example-1 of the present invention.
- A method for refining molten steel in a vacuum of the present invention comprises an immersion process, wherein immersion nozzles are immersed in molten steel, a dissolving process, wherein gases are dissolved in said molten steel, a first degassing process and a second degassing process.
- Two immersion nozzles arranged at the lower portion of
vacuum vessel 4 are immersed in molten steel in a ladle. One of the two immersion nozzles is risingtube 5 and the other sinking tube 6. - Fig. 1 is a sectional view schematically showing a dissolving process, wherein gases are dissolved in molten steel, according to the present invention.
Molten steel 2 insideladle 1 is pressurized by its static pressure. Gases containing at least gas soluble in molten steel are blown inmolten steel 2 through gas blow-in opening 3 arranged at the bottom ofladle 1. It is, of course, possible to blow a mixed gas consisting of gas soluble in said molten steel and an inert gas in said molten steel.Molten steel 2 is bubbled by said mixed gas. Together with bubbling of said molten steel, a large amount of gas soluble in said molten steel dissolves in said molten steel. Gases can be simultaneously blown in said molten steel through gas blow-in opening 7 arranged in risingtube 5 ofvacuum vessel 4. The amount of gases dissolved in said molten steel is expected to be quickly increased. A part of inclusions inmolten steel 2 is trapped by bubbled gas and rises to the surface of said molten steel. When said molten steel rises to the surface of said molten steel, a pressure to said molten steel is decreased. As a result, the gases having been dissolved in said molten steel convert to fine bubbles. Fine inclusions in said molten steel are trapped by produced gas bubbles and rise to the surface of said molten steel. - Hydrogen gas, nitrogen gas and hydrocarbon gas as gases soluble in the molten steel are used out of a mixed gas blown in the molten steel. Ar gas and He gas are used as an inert gas. Only gases soluble in the molten steel can be used instead of the mixed gas. In this preferred Embodiment, gases were blown in the molten steel from gas blow-in opening 3 arranged at the bottom of
ladle 1, but ways of a gas blow-in are not limited to this. Gases can be blown in the lower portion of the molten steel inladle 1. Gas blow-in opening 3, however, is desired to be arranged in the bottom wall ofladle 1 just under rising tube. In this process, a large amount of gas can be blown in the molten steel with the use of an immersion lance before an immersion nozzle is immersed in the molten steel. Said immersion lance is immersed from the surface of the molten steel into the molten steel. - Fig. 2 is a sectional view schemtically showing a first degassing process of the present invention.
Vacuum vessel 4 is kept evacuated. An inert gas is injected from gas blow-in opening 7 arranged in the middle of risingtube 5. Thereby, molten steel is made to circulate betweenladle 1 andvacuum vessel 4. Gases including at least gas soluble in the molten steel are blown inmolten steel 2 from gas blow-in opening 3 ofladle 1.Molten steel 2 is bubbled by the gases blown in. Together with bubbling, the gas soluble in the molten steel dissolves in the molten steel. On the other hand, since a pressure of the atmosphere inside the vacuum vessel is reduced to 2 to 3 Torr, the molten steel is degassed. With the rise of the molten steel toward the surface of the molten steel invacuum vessel 4, the gas dissolved in the molten steel converts to bubbles. The gas components having been dissolved in the molten steel in the dissolving process and having not appeared near the surface of the molten steel also appear in the form of bubbles. Fine inclusions contained in the molten steel are trapped by the produced gas bubbles and rise to the surface of the molten steel invacuum vessel 4. A part of the inclusions contained inmolten steel 2 are trapped by bubbled inert gas and rises to the surface of the molten steel invacuum vessel 4. - An inert gas was used in this Preferred Embodiment as gas which was injected from the gas blow-in opening arranged in the middle of rising
tube 5. The gases to be used, however, are not limited to the inert gas. A mixed gas of an inert gas and gas soluble in the molten steel can be used. In case the mixed gas is used, fine inclusions are expected to be removed because the gas is dissolved in the molten steel and fine gas bubbles are produced under decreased pressure. Ar gas and He gas can be used as an inert gas. As in case of gas blow-in in the dissolving process, the gas blown inmolten steel 2 from gas blow-inopening 2 ofladle 1 can be either a mixed gas consisting of gas soluble in the molten steel and an inert gas or only gas soluble in the molten steel. - Out of mixed gases blown in the molten steel, hydrogen gas, nitrogen gas and hydrocarbon gas are used as the gas soluble in the molten steel. Ar gas and He gas are used as an inert gas. In this Preferred Embodiment, the gas was blown in the molten steel from gas blow-in
opening 3 arranged at the bottom ofladle 1, but ways of gas blow-in are not confined to this example. It is sufficient to blow the gas in the lower portion of the molten steel inladle 1. It, however, is desirable to arrange gas blow-inopening 3 in the bottom wall ofladle 1 just under risingtube 5. - Fig. 3 is a sectional view schematically showing a second degassing process of the present invention.
Vacuum vessel 4 is kept evacuated. An inert gas is injected invacuum vessel 4 from gas blow-in opening 7 arranged in the middle of risingtube 5 tomake molten steel circulate betweenladle 1 andvacuum vessel 4. Gas blow-in from gas blow-inopening 3 ofladle 1 is stopped. Since the atmospheric pressure invacuum vessel 4 is decreased to 2 to 3 Torr, the molten steel is degassed. Gas components, which have been dissolved in the molten steel in the first degassing process and have not been able to be removed, are removed. In this Preferred Embodiment, an inert gas was used. However, dependent on the permissible range of the gas soluble in molten steel, the gases to be used are not confined to the inert gas. In case a permissible concentration of final gas components soluble in molten steel is high, a mixed gas of an inert gas and gas soluble in molten steel can be used. - The method for refining molten steel in a vacuum
- (a) comprising an immersion process, wherein immersion nozzles are immersed in molten steel, a dissolving process, wherein gases are dissolved in said molten steel, a first degassing process and a second degassing process were described above, but the method of the present invention is not limited to said processes. Methods as mentioned below can be used.
- (b) A method comprising an immersion process, wherein immersion nozzles are immersed in molten steel, a first degassing process and a second degassing process.
- (c) A method comprising an immersion process, wherein immersion nozzles are immersed in molten steel, a dissolving process, wherein gases are dissolved in molten steel and a first degassing process.
- (d) A method comprising an immersion process, wherein immersion nozzles are immersed in molten steel and a first degassing process.
- (e) A method comprising an immersion process, wherein immersion nozzles are immersed in molten steel, a dissolving process, wherein gases are dissolved in molten steel and a second degassing process.
- Differences in effects of the methods of from (a) to (e) during the use of N₂ gas as gas soluble in molten steel will be described. When molten steel is processed by use of the mehtod (a), a total amount of oxygen in the molten steel is decreased to the lowest level among the total amounts of oxygen decreased by use of the methods of from (a) to (e). The amount of N in the molten steel becomes low when the second degassing process is carried out longer by use of the method (e). The methods (b) and (d) which do not comprise the dissoloving process are useful because of a simplicity of the processes. The methods (b) and (d), however, are somewhat inferior to the methods (a), (c) and (e), which comprise the dissolving process, in the effects of removing oxygen in the molten steel. In the method (d), the amount of N in the molten steel increases, but the molten steel is easily processed. Therefore, selection of the methods as mentioned above varies dependent on speicies of steel to be used and equipment which is owened.
- 250 tons of molten steel were processed with the use of the method (b). For first 20 minutes, a mixed gas consisting of 40% Ar gas and 60% H₂ gas was blown in said molten steel from gas blow-in opening 7 of rising
tube 5 and from gas blow-inopening 3 ofladle 1 respectively at a rate of 180 Nm³/hr and at a rate of 60 Nm³/hr. Thereafter, gas blowing-in from gas blow-inopening 3 ofladle 1 was stopped and, at the same time, 100% Ar gas was blown in the molten steel from gas blow-in opening 7 of risingtube 5 at a rate of 180 Nm³/hr for 15 minutes. A change of a total amount of oxygen in the molten steel relative to a processing time is indicated in Fig. 4. The total amount of oxygen in the molten steel decreased to 5 ppm in processing of the molten steel for 35 minutes. The amount of hydrogen in the molten steel after having been processed could be decreased to 2 ppm or less. - 250 tons of molten steel were processed with the use of the method (c). Firstly, a top-blow lance was immersed in the molten steel in a ladle and N₂ gas was blown in the molten steel at a rate of 180 Nm³/hr for 30 minutes. Subsequently, immersion nozzles were immersed in the molten steel.
Vacuum vessel 4 was kept evacuated, and a mixed gas consisting of 60% Ar gas and 40% N₂ was blown through gas blow-in opening 7 of risingtube 5 and through gas blow-inopening 3 ofladle 1 respectively at 120 Nm³/hr and at 60 Nm³/hr for 35 minutes. The total amount of oxygen in the molten steel was decreased to approximately 5 ppm by 35 minutes processing of the molten steel. The amount of nitrogen in the molten steel after having been processed was decreased to approximately 90 ppm. - 250 tons of molten steel were processed by use of the method (d). A mixed gas consisting of 40% Ar gas and 60% H₂ gas was blown in the molten steel through gas blow-in opening 7 of rising
tube 5 and through gas blow-inopening 3 ofladle 1 respectively at 120 Nm³/hr and at 60 Nm³/hr for 35 minutes. The total amount of oxygen in the molten steel was decreased to approximately 8 ppm by 35 minutes processing of the molten steel. The amount of nitrogen in the molten steel after having been processed was decreased to approximately 80 ppm. - 250 tons of molten steel were processed by use of the method (e). Firstly, a top-blow lance was immersed in the molten steel in a ladle and N₂ was blown in the molten steel at 180 Nm³/hr for 30 minutes. Subsequently, immersion nozzles were immersed in the molten steel.
Vacuum vessel 4 was kept evacuated and Ar gas was blown through gas blow-in opening 7 of risingtube 5 at 120 Nm³/hr for 35 minutes. The total amount of oxygen in the molten steel was decreased to approximately 6 ppm by 35 minutes processing of the molten steel. The amount of nitrogen in the molten steel after having been processed was decreased to approximately 35 ppm. - 250 tons of molten steel were processed by use of the method (b). For the first 20 minutes, a mixed gas consisting of 20% Ar gas and 80% N₂ gas was blown in the molten steel through gas blow-in opening 7 of rising
tube 5 and N₂ gas through gas blow-inopening 3 ofladle 1 respectively at 120 Nm³/hr and at 60 Nm³/hr. Then, blowing-in of N₂ gas through gas blow-inopening 3 ofladle 1 was stopped, and, at the same time, 100% Ar gas blown in the molten steel through gas blow-in opening 7 of risingtube 5 at 120 Nm³/hr for 15 minutes. The total amount of oxygen in the molten steel was decreased to approximately 6 ppm by 35 minutes processing of the molten steel. The amount of nitrogen in the molten steel was decreased to approximately 40 ppm. - 250 tons of molten steel was processed by use of the method (a). Firstly, a top-blow lance was immersed in the molten steel in a ladle, and N₂ gas was blown in the molten steel at 180 Nm³/hr for half an hour. Then, immersion nozzles were immersed in the molten steel.
Vacuum vessel 4 was kept evacuated. For the first 20 minutes, a mixed gas consisting of 20% Ar gas and 80% N₂ gas was blown invacuum vessel 4 through gas blow-in opening 7 of risingtube 5 and N₂ gas through gas blow-inopening 3 ofladle 1 respectively at 120 Nm³/hr and at 60 Nm³/hr. Thereafter, blowing-in of N₂ gas through gas blow-in opening ofladel 1 was stopped, and at the same time, 100% Ar gas was blown through gas blow-in opening 7 of risingtube 5 at 120 Nm³/hr for 15 minutes. The total amount ofoxygen in the molten steel was decreased to approximately 4 ppm by 35 minutes processing of the molten steel. The amount of nitrogen was decreased to approximately 50 ppm. - 250 tons of molten steel were processed by use of a prior art RH vacuum degassing method. Two immersion nozzles were immersed in the molten steel in
ladle 1. The two immersion nozzles were risingtube 5 and sinking tube 6.Vacuum vessel 4 was kept evacuated. Ar gas was blown in saidvacuum vessel 4 from gas blow-in opening 7 arranged in the middle of risingtube 5 at a rate of 180 Nm³/hr. An amount of the molten steel circulating invacuum vessel 4 was 100 tons/min. The molten steel was processed for 35 minutes. A change of a total amount of oxygen in the molten steel relative to a processing time is indicated in Fig.4. The total amount of oxygen in the molten steel decreased to approximately 10 ppm in processing of the molten steel for 35 minutes.
Claims (22)
an immersion process, wherein two immersion nozzles arranged at the lower portion of a vacuum vessel (4) are immersed in molten steel (2) in a ladle(1), said two immersion nozzles are a rising tube(5) and a sinking tube (6);
characterized by a first degassing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated, having said molten steel circulated between said ladle and said vacuum vessel by injecting gases containing at least an inert gas from the middle of said rising tube and blowing in said molten steel gases containing at least gas soluble in said molten steel.
an immersion process, wherein two immersion nozzles arranged at the lower portion of a vacuum vessel (4) are immersed in molten steel (2) in a ladle(1), said two immersion nozzles are a rising tube(5) and a sinking tube (6);
characterized by a dissolving process, wherein gases are dissolved in said molten steel by blowing in said molten steel gases containing at least gas soluble in said molten steel from a gas blow-in opening (3) arranged in said ladle; and
a first degassing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated, having said molten steel circulated between said ladle and said vacuum vessel by injecting gases containing at least an inert gas from the middle of said rising tube in said molten steel and blowing gases containing at least gas soluble in said molten steel from a gas blow-in opening arranged in said ladle.
an immersion process, wherein two immersion nozzles arranged at the lower portion of a vacuum vessel (4) are immersed in molten steel in a ladle (1), said two immersion nozzles are a rising tube(5) and a sinking tube (6);
characterized by a dissolving process, wherein gases are dissolved in said molten steel by blowing in said molten steel gases containing at least gas soluble in said molten steel from a gas blow-in opening (3) arranged in said ladle;
a first degassing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated; having said molten steel circulated between said ladle and said vacuum vessel by injecting gases containing at least an inert gas from the middle of said rising tube in said molten steel and blowing gases containing at least gas soluble in said molten steel from a gas blow-in opening arranged in said ladle; and
a second degasing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated, stopping a gas blowing-in from said gas blow-in opening arranged in said ladle and having said molten steel circulated between said ladle and said vacuum vessel by injecting gases containing at least an inert gas from the middle of said rising tube in said molten steel.
an immersion process, wherein two immersion nozzles arranged at the lower portion of a vacuum vessel (4) are immersed in molten steel (2) in a ladle (1), said two immersion nozzles are a rising tube (5) and a sinking tube (6);
characterized by a dissolving process, wherein gases are dissolved in said molten steel by blowing in said molten steel gases containing at least gas soluble in said molten steel from a gas blow-in opening (3) arranged in said ladle; and
a second degassing process, wherein said molten steel is degassed by keeping said vacuum vessel evacuated, stopping a gas blowing-in from said gas blow-in opening arranged in said ladle and having said molten steel circulated between said ladle and said vacuum vessel by injecting gases containing at least an inert gas from the middle of said rising tube in said molten steel.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP9675/88 | 1988-01-21 | ||
JP63009675A JPH01188619A (en) | 1988-01-21 | 1988-01-21 | Method for rh vacuum degasification |
JP1031105A JPH02211974A (en) | 1988-01-21 | 1989-02-13 | Method for purifying molten metal by reduction of pressure |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0325242A2 true EP0325242A2 (en) | 1989-07-26 |
EP0325242A3 EP0325242A3 (en) | 1990-02-14 |
Family
ID=39689269
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP89100866A Withdrawn EP0325242A3 (en) | 1988-01-21 | 1989-01-19 | Method for refining molten steel in a vacuum |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0325242A3 (en) |
JP (2) | JPH01188619A (en) |
KR (1) | KR930005067B1 (en) |
AU (1) | AU601893B2 (en) |
BR (1) | BR8900249A (en) |
CA (1) | CA1338397C (en) |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0461415A1 (en) * | 1990-05-17 | 1991-12-18 | Kawasaki Steel Corporation | Method of producing ultra-low-carbon steel |
US5077255A (en) * | 1986-09-09 | 1991-12-31 | Exxon Chemical Patents Inc. | New supported polymerization catalyst |
WO2000034533A2 (en) * | 1998-12-04 | 2000-06-15 | Vai Technometal Gmbh | Method for removing nitrogen from steel melts |
FR2809745A1 (en) * | 2000-06-05 | 2001-12-07 | Sanyo Special Steel Co Ltd | High cleanness steel production includes adding a deoxidizing agent to a ladle before pouring steel melt into the ladle or adding deoxidizing agent to the melt during pouring of the melt into the ladle |
GB2406580A (en) * | 2000-06-05 | 2005-04-06 | Sanyo Special Steel Co Ltd | High-cleanliness steel and processes for producing the same |
GB2410503A (en) * | 2000-06-05 | 2005-08-03 | Sanyo Special Steel Co Ltd | High-cleanliness steel and process for producing the same |
EP1568790A1 (en) * | 2004-02-24 | 2005-08-31 | Paul Wurth S.A. | Apparatus for the treatment of liquid metal in a ladle |
CN109922905A (en) * | 2016-11-09 | 2019-06-21 | 株式会社Posco | Casting Equipment and the casting method for using the Casting Equipment |
CN113957203A (en) * | 2021-12-21 | 2022-01-21 | 太原科技大学 | Multifunctional non-centrosymmetric vacuum refining equipment |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102296159B (en) * | 2010-06-25 | 2013-05-01 | 鞍钢股份有限公司 | Handling method for blockage of insertion tube |
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GB954214A (en) * | 1959-08-14 | 1964-04-02 | Heraeus Gmbh W C | Improvements in or relating to the vacuum degassing of metals |
DE1222090B (en) * | 1960-09-09 | 1966-08-04 | Heraeus Gmbh W C | Process for degassing molten steel |
US3320053A (en) * | 1964-09-25 | 1967-05-16 | Bethlehem Steel Corp | Method of injecting gases into steel melts |
JPS57194206A (en) * | 1981-05-26 | 1982-11-29 | Kawasaki Steel Corp | Production of molten extra low carbon steel |
JPS57200514A (en) * | 1981-06-03 | 1982-12-08 | Nippon Kokan Kk <Nkk> | Method for degassing molten steel |
JPS5837112A (en) * | 1981-08-29 | 1983-03-04 | Kawasaki Steel Corp | Vacuum refining method of molten steel |
JPS60184619A (en) * | 1984-02-29 | 1985-09-20 | Sumitomo Metal Ind Ltd | Production of low-nitrogen steel |
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BR8803185A (en) * | 1987-06-29 | 1989-01-24 | Kawasaki Steel Co | PROCESS AND APPLIANCE FOR DEGASIFICATION OF METAL IN MELTING |
AU605949B2 (en) * | 1987-12-25 | 1991-01-24 | Nkk Corporation | Method for cleaning molten metal and apparatus therefor |
-
1988
- 1988-01-21 JP JP63009675A patent/JPH01188619A/en active Pending
-
1989
- 1989-01-13 AU AU28482/89A patent/AU601893B2/en not_active Ceased
- 1989-01-19 EP EP89100866A patent/EP0325242A3/en not_active Withdrawn
- 1989-01-19 BR BR898900249A patent/BR8900249A/en not_active IP Right Cessation
- 1989-01-20 KR KR1019890000602A patent/KR930005067B1/en active IP Right Grant
- 1989-01-20 CA CA000588802A patent/CA1338397C/en not_active Expired - Fee Related
- 1989-02-13 JP JP1031105A patent/JPH02211974A/en active Pending
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DE1222090B (en) * | 1960-09-09 | 1966-08-04 | Heraeus Gmbh W C | Process for degassing molten steel |
US3320053A (en) * | 1964-09-25 | 1967-05-16 | Bethlehem Steel Corp | Method of injecting gases into steel melts |
JPS57194206A (en) * | 1981-05-26 | 1982-11-29 | Kawasaki Steel Corp | Production of molten extra low carbon steel |
JPS57200514A (en) * | 1981-06-03 | 1982-12-08 | Nippon Kokan Kk <Nkk> | Method for degassing molten steel |
JPS5837112A (en) * | 1981-08-29 | 1983-03-04 | Kawasaki Steel Corp | Vacuum refining method of molten steel |
JPS60184619A (en) * | 1984-02-29 | 1985-09-20 | Sumitomo Metal Ind Ltd | Production of low-nitrogen steel |
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PATENT ABSTRACTS OF JAPAN, vol. 10, no.31 (C-327)[2088], 6th February 1986; & JP-A-60 184 619 (SUMITOMO KINZOKU KOGYO K.K.) 20-09-1985 * |
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Cited By (23)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5077255A (en) * | 1986-09-09 | 1991-12-31 | Exxon Chemical Patents Inc. | New supported polymerization catalyst |
US5183867A (en) * | 1986-09-09 | 1993-02-02 | Exxon Chemical Patents Inc. | Polymerization process using a new supported polymerization catalyst |
EP0461415A1 (en) * | 1990-05-17 | 1991-12-18 | Kawasaki Steel Corporation | Method of producing ultra-low-carbon steel |
WO2000034533A2 (en) * | 1998-12-04 | 2000-06-15 | Vai Technometal Gmbh | Method for removing nitrogen from steel melts |
WO2000034533A3 (en) * | 1998-12-04 | 2002-10-03 | Vai Technometal Gmbh | Method for removing nitrogen from steel melts |
WO2001094648A3 (en) * | 2000-06-05 | 2002-08-08 | Sanyo Special Steel Co Ltd | High-cleanliness steel and process for producing the same |
GB2410503A (en) * | 2000-06-05 | 2005-08-03 | Sanyo Special Steel Co Ltd | High-cleanliness steel and process for producing the same |
FR2812662A1 (en) * | 2000-06-05 | 2002-02-08 | Sanyo Special Steel Co Ltd | HIGH-CLEAN STEEL AND PROCESS FOR PRODUCING THE SAME |
FR2812663A1 (en) * | 2000-06-05 | 2002-02-08 | Sanyo Special Steel Co Ltd | HIGH-CLEAN STEEL AND PROCESS FOR PRODUCING THE SAME |
FR2812660A1 (en) * | 2000-06-05 | 2002-02-08 | Sanyo Special Steel Co Ltd | HIGH-CLEAN STEEL AND PROCESS FOR PRODUCING THE SAME |
WO2001094648A2 (en) * | 2000-06-05 | 2001-12-13 | Sanyo Special Steel Co., Ltd. | High-cleanliness steel and process for producing the same |
FR2809745A1 (en) * | 2000-06-05 | 2001-12-07 | Sanyo Special Steel Co Ltd | High cleanness steel production includes adding a deoxidizing agent to a ladle before pouring steel melt into the ladle or adding deoxidizing agent to the melt during pouring of the melt into the ladle |
GB2381537A (en) * | 2000-06-05 | 2003-05-07 | Sanyo Special Steel Co Ltd | High-cleanliness steel and process for producing the same |
GB2406580A (en) * | 2000-06-05 | 2005-04-06 | Sanyo Special Steel Co Ltd | High-cleanliness steel and processes for producing the same |
FR2812661A1 (en) * | 2000-06-05 | 2002-02-08 | Sanyo Special Steel Co Ltd | HIGH-CLEAN STEEL AND PROCESS FOR PRODUCING THE SAME |
US7396378B2 (en) | 2000-06-05 | 2008-07-08 | Sanyo Special Steel Co., Ltd. | Process for producing a high cleanliness steel |
GB2381537B (en) * | 2000-06-05 | 2005-09-14 | Sanyo Special Steel Co Ltd | High-cleanliness steel and process for producing the same |
GB2410503B (en) * | 2000-06-05 | 2005-09-07 | Sanyo Special Steel Co Ltd | High-cleanliness steel and process for producing the same |
GB2406580B (en) * | 2000-06-05 | 2005-09-07 | Sanyo Special Steel Co Ltd | High-cleanliness steel and process for producing the same |
WO2005080612A1 (en) * | 2004-02-24 | 2005-09-01 | Sms Mevac Gmbh | Device for treating liquid metal in a ladle |
EP1568790A1 (en) * | 2004-02-24 | 2005-08-31 | Paul Wurth S.A. | Apparatus for the treatment of liquid metal in a ladle |
CN109922905A (en) * | 2016-11-09 | 2019-06-21 | 株式会社Posco | Casting Equipment and the casting method for using the Casting Equipment |
CN113957203A (en) * | 2021-12-21 | 2022-01-21 | 太原科技大学 | Multifunctional non-centrosymmetric vacuum refining equipment |
Also Published As
Publication number | Publication date |
---|---|
EP0325242A3 (en) | 1990-02-14 |
KR930005067B1 (en) | 1993-06-15 |
JPH02211974A (en) | 1990-08-23 |
AU601893B2 (en) | 1990-09-20 |
JPH01188619A (en) | 1989-07-27 |
CA1338397C (en) | 1996-06-18 |
BR8900249A (en) | 1989-09-19 |
AU2848289A (en) | 1989-08-10 |
KR890012009A (en) | 1989-08-23 |
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