JP2005219072A - Continuous casting method for molten metal and continuous casting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous casting method and a continuous casting apparatus, wherein metallic components can be uniformly distributed in a continuously-cast slab and a high yield of metallic compounds is secured. <P>SOLUTION: In the continuous casting method for supplying the molten metal to a casting mold through a tundish, metal vapors and/or metal particles forming metallic compounds are supplied into the molten metal through an immersion lance dipped into the tundish or the immersion lance dipped into the casting mold, together with a mixed gas comprising one or more gases selected from among oxygen gas, hydrogen gas, nitrogen gas, carbon dioxide, hydrocarbon gas, and sulfur dioxide gas, and an inert gas. Instead of the metal vapors and/or the metal particles, a wire or a rod containing metallic elements to form the metallic compounds is inserted into a hole of the immersion lance. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a continuous casting method and a continuous casting apparatus capable of adding a compound of a metal element into molten metal at a high yield in the course of continuous casting of molten metal and uniformly dispersing it in a slab.

  In recent years, in order to improve the mechanical properties of metal products, metal crystal grains and precipitates have been refined. In order to refine crystal grains and precipitates, it is effective to crystallize or precipitate a minute compound, but the compounds effective to refine crystal grains and precipitates vary depending on the type of metal. In order to crystallize a desired metal compound by adding a metal element to a molten metal, it is necessary to control a solute component in the metal, resulting in an increase in cost and time in a refining process. In order to reduce these loads, a metal element compound may be added to the molten metal in advance.

  Addition of metal element compound to molten metal can be done by adding a bulk or powdery metal element compound to the molten metal surface, or by using an inert gas or molten metal flow into the molten metal. The method to do is adopted. However, when the melting point or boiling point of the metal element compound added to the molten metal is lower than the temperature of the molten metal, the metal element compound melts or decomposes and vaporizes in the vicinity of the molten metal surface. Therefore, it is difficult to control the amount of addition to the molten metal, and the addition yield is also reduced, making it difficult to add uniformly.

  In addition, since the volume expansion when the metal element is vaporized is large, when the metal element is vaporized in the vicinity of the molten metal surface, the molten metal is severely scattered and it is difficult to ensure operational safety. Further, when the melting point of the compound of the additive metal element is low, it is difficult to add a predetermined amount by softening or melting by the radiant heat of the molten metal before the addition. When a compound of a metal element having a density lower than that of the molten metal is added, the added metal compound is unevenly distributed only in the surface layer portion of the molten metal and does not penetrate into the inside of the molten metal. In the case of adding a metal element compound having a high density, it is difficult to uniformly mix the entire molten metal only by settling into the molten metal from the addition position.

  When the melting point or boiling point of the metal element compound added to the molten metal is higher than the temperature of the molten metal, the metal element compound is melted or vaporized before addition to the molten metal as described above. There is no problem and the solid state is maintained when added to the molten metal. However, when the particle size of the metal element compound is reduced, the particles aggregate and become difficult to finely disperse in the molten metal. As described above, there are many difficulties in adding a compound of a metal element into a molten metal, and in addition, in order to manufacture a compound of a metal element to be added into a molten metal in advance, a production facility for that is required. Incurs tremendous costs.

  Patent Document 1 discloses a method in which bismuth is added to a molten steel stream that is moving out of the ladle and moving to the molten steel bath surface in the tundish. However, bismuth has a low boiling point and reacts explosively when it comes into contact with the molten steel stream, so that it becomes a vapor and scatters in the atmosphere. Not evenly distributed within.

  Patent Document 2 discloses a method in which lead, bismuth, lead / bismuth-containing material is added to a molten steel in a ladle by injection using a lance, and gas is jetted from a porous plug at the bottom of the ladle and stirred. ing. Even in the method disclosed in this document, when lead and bismuth having a low melting point or boiling point are added, an explosive reaction occurs when these metals come into contact with the molten steel, and the addition of the metal into the molten steel is uneven. And the yield is low, and the metal is not uniformly dispersed in the continuous cast slab. Moreover, it is difficult to arbitrarily adjust the reaction products of lead and bismuth added to the molten steel.

  Non-Patent Document 1 describes a method of adding magnesium by blowing magnesium vapor into the hot metal using argon gas as a carrier gas to desulfurize the hot metal. Since magnesium vapor is added by immersing a lance in a magnesium melting furnace or ladle, the bubbles of argon gas containing magnesium vapor blown into the hot metal are large, and the magnesium will rise before this bubble rises to the molten metal surface. The reaction between hot metal and hot metal is not completed. Therefore, not only the addition yield is low and the concentration distribution after the addition becomes non-uniform, but also unreacted magnesium is diffused into the atmosphere and emits smoke, which causes environmental problems. Furthermore, it is difficult to specify a product resulting from the reaction between added magnesium and hot metal.

JP 2001-1116 (Claims and paragraph [0013])

JP-A-9-13119 (Claims and paragraphs [0004] and [0005]) Japanese Patent Application No. 2003-41399 (Claims and paragraphs [0012] to [0015]) Japanese Patent Application No. 2003-408822 (Claims and paragraphs [0012] to [0015]) G.A.Iron and R.I.Guthrie; Ironmaking Steelmaking, 1981, No. 3, p114-121, "Kinetic aspects of magnesium desulphurization of blast furnace iron"

The present invention has been made in view of the above problems, and the problem is that when a compound of a metal element is added to a molten metal, a high addition yield of the metal compound is ensured and the continuous cast slab is formed. It is an object of the present invention to provide a continuous casting method and a continuous casting apparatus that can be uniformly dispersed in a metal.

  In order to solve the above-described problems, the present inventor has studied a method and an apparatus for uniformly adding a compound of a metal element into a molten metal with a high yield in consideration of the above-described conventional problems. Alternatively, a lance is immersed in the molten metal in the mold, and from the lance hole, together with a mixed gas containing at least one of oxygen gas, hydrogen gas, nitrogen gas, carbon dioxide gas, hydrocarbon gas and sulfurous acid gas and an inert gas It has been found that the problem can be solved by supplying metal vapor or particles constituting a metal compound added to the molten metal, or a wire or rod containing the added metal.

  The present invention has been completed on the basis of the above knowledge, and the gist thereof is the continuous casting method for molten metal shown in the following (1) to (3) and the continuous casting apparatus for molten metal shown in (4). It is in.

  (1) A continuous casting method in which a molten metal is supplied to a mold through a tundish, and is melted through an immersion lance immersed in the molten metal in the tundish or an immersion lance immersed in the molten metal in the mold. The metal vapor and / or metal particles constituting the metal compound added to the metal contain one or more selected from oxygen gas, hydrogen gas, nitrogen gas, carbon dioxide gas, hydrocarbon gas and sulfurous acid gas and inert gas A continuous casting method of molten metal supplied into the molten metal together with a mixed gas.

  (2) A continuous casting method in which a molten metal is supplied to a mold through a tundish, and is melted through an immersion lance immersed in the molten metal in the tundish or an immersion lance immersed in the molten metal in the mold. One or more selected from oxygen gas, hydrogen gas, nitrogen gas, carbon dioxide gas, hydrocarbon gas, and sulfurous acid gas and an inert gas, or a wire or rod containing a metal element constituting a metal compound added to metal A continuous casting method of molten metal supplied into the molten metal together with a mixed gas containing

  (3) The molten metal is molten steel, and the metal constituting the metal compound added to the molten metal contains one or more selected from magnesium, bismuth, calcium, tellurium, lead, manganese, ytterbium and thallium. The molten metal continuous casting method according to (1) or (2), wherein the molten metal is a metal.

  (4) a tundish, an immersion nozzle provided at the lower part of the tundish for supplying molten metal in the tundish to the mold, a mold located below the tundish, and a molten metal in the tundish with a wire or An immersion lance for supplying a rod or an immersion lance for supplying a wire or a rod to molten metal in the mold; and a wire or rod supply device for supplying the wire or rod into a hole of the immersion lance A continuous casting apparatus for molten metal.

In the present invention, the “metal constituting the metal compound added to the molten metal” means a metal element constituting a metal oxide or a metal nitride added to the molten metal. For example, the metal oxide is MgO. In this case, Mg is used, and when the metal nitride is Ca ₃ N ₂ , Ca is used.

  “Metal vapor and / or metal particles” means metal vapor and / or metal particles present as liquid or solid particles due to insufficient evaporation, or metal particles formed by condensation of metal vapor. . “Metal” includes pure metal and metal alloys.

  Further, “inert gas” means an element belonging to Group 18 of the periodic table, for example, a gas such as argon, helium, neon, or a mixed gas thereof.

According to the molten metal continuous casting method of the present invention, a compound of a metal element can be added to molten metal at a high yield, and can be uniformly dispersed in a continuous cast slab. Moreover, the continuous casting apparatus of this invention is a suitable apparatus for adding the compound of the said metal element to molten metal.

  As described above, the present invention provides a metal vapor or metal particles constituting a metal compound to be added to the molten metal through the immersion lance immersed in the molten metal in the tundish or the immersion lance immersed in the molten metal in the mold. Or a continuous casting method and a continuous casting apparatus for molten metal in which a wire or rod containing a metal element constituting the metal compound is supplied into the molten metal together with a mixed gas of a reactive gas and an inert gas. is there.

  In the patent document 3 and patent document 4, the present inventor previously generated a vapor of a metal element to be added to the molten metal, and this vapor together with an inert gas in the molten metal in the tundish or in the continuous casting mold. A method of adding to was proposed. By this method, it has become possible to add the metal element uniformly to the molten metal with good yield. In the proposed method, the metal vapor is generated in the molten metal in both cases where the metal vapor is generated by the metal vapor generator and supplied into the molten metal, and the wire or rod is supplied into the molten metal. At the time of entry, the metal is a metal vapor or metal fine particles. Therefore, this method has a particle size of several tens of angstroms to several thousand angstroms when particles such as metal vapor penetrate into the molten metal, compared with the case where a bulk metal element is added as in the prior art. Thus, it is greatly different from the conventional method in that a metal element having a fine particle size can be added.

  The present inventor conducted further research based on these results, and replaced the inert gas used when adding the above metal vapor into the molten metal with a gas having the reactivity and the inert gas. By using a mixed gas, it has been found that fine particles of a compound of a metal and a gas having a particle size approximately the same as that of metal vapor can be generated, and that the fine particles can be added to the molten metal. The present invention has been completed.

  When a metal oxide is formed as a metal compound and added to the molten metal, oxygen gas or carbon dioxide gas may be used. When a hydride is formed, hydrogen or hydrocarbon may be used. Moreover, hydrocarbons may be used when forming carbides, and sulfurous acid gas may be used when forming sulfides. Furthermore, even if it is a compound of the same kind, when adjusting the form, what is necessary is just to control the composition etc. of said reactive gas.

  When gas is blown into the molten metal, even if the inner diameter of the nozzle hole of the blowing nozzle is reduced, if the nozzle gets wet with the molten metal, the diameter of the bubbles blown from the nozzle is larger than determined by the inner diameter of the nozzle. Become. In addition, when argon gas is blown into a high-temperature molten metal, bubbles expand rapidly due to rapid expansion, and bubbles containing unreacted metal vapor rise to the molten metal surface, resulting in a decrease in the addition yield. In addition, this metal vapor is diffused into the atmosphere, which deteriorates the working environment. In order to improve such a situation, it is necessary to reduce the diameter of the bubbles and promote the reaction between the molten metal and the metal vapor.

  In order to reduce the diameter of an inert gas bubble such as argon gas blown into the molten metal, the flow rate of the molten metal passing in front of the gas blowing nozzle is increased, and the bubble exiting the nozzle is broken by the molten metal flow. Good. For example, when trying to obtain bubbles having a diameter of 1 mm or less in the molten steel, it has been found that the flow rate of the molten steel in front of the nozzle should be about 1 m / s or more.

  In addition, when a compound of a metal element, such as an oxide, nitride, or sulfide, is added to the molten metal, if the density of these compounds is smaller than the density of the molten metal, the compound is deposited on the surface of the molten metal. Because of levitation, these compounds cannot remain in the continuous cast slab. Therefore, in order to keep these vapors and compounds in the continuous casting slab, it is effective to rupture the bubbles sufficiently deeply from the bath surface in the continuous casting mold or tundish, or by the flow of molten metal. It is necessary to blow metal vapor or metal compound particles from a position where it can be used.

  In order to confirm the effects of the continuous casting method and continuous casting apparatus of the present invention, the following continuous casting test was performed and the results were evaluated.

(Example 1)
〔Test conditions〕
Molten metal: low carbon steel (component composition is mass%, C: 0.04%, Ti: 0.12%, N: 0.004%)
Molten metal amount: Continuous casting at 4 tons / minute Addition metal: Magnesium, bismuth, calcium Addition form: metal vapor and / or metal particles Addition amount: 50 g of each additive metal per ton of molten steel
Addition position: In tundish Carrier gas: Mixed gas of oxygen (0.5 NL / min) and argon gas (20 L / min) Figure 1 shows mixing of metal vapor and / or metal particles generated by a metal vapor generator It is a figure which shows the method of continuously casting, supplying in molten steel through the lance immersed in the molten steel in a tundish with gas.

  The molten steel 1 supplied to the tundish 2 from the ladle 3 is subjected to level control of the molten metal surface in the tundish, injected into the continuous casting mold 8 through the immersion nozzle 6, and further drawn out below the mold to be solidified shell. 7 is formed into a slab. At this time, fine particles of the additive metal compound are supplied from the metal vapor supply device 40 and blown into the molten steel 1 through the immersion lance 4 immersed in the molten steel 1 in the tundish.

  The metal compound supply device 40 controls the temperature of the steam generating device 41, the burner 44 for heating the metal steam generating device, the temperature measuring device (thermocouple) 46, and the temperature measurement result by the temperature measuring device. It consists of a temperature control device 45, a mixed gas supply pipe 42 and a metal compound blowing pipe 43. The metal vapor and / or metal particles generated in the metal vapor generator 41 react with the mixed gas 54 supplied from the mixed gas supply pipe 42 to form a metal compound, and the mixed gas is used as a carrier gas to form a metal compound. It was supplied to the immersion lance 4 through the blowing pipe 43 and was blown into the molten steel 1.

  On the other hand, as a comparative example in Example 1, an attempt was made to add pre-manufactured fine powders of magnesium, bismuth and calcium oxide (average particle size: 0.05 mm) to the molten steel. In addition, when adding fine powder, instead of the metal compound supply device, a powder supply device is attached, the fine powder is charged into a container of the powder supply device, and the fine powder in the container is purged with an inert argon gas. An attempt was made to supply the carrier gas to a lance immersed in molten steel and add it to the molten steel.

  However, in the comparative example, the metal oxide fine powder charged in the container aggregates to form coarse particles, so that the fine powder is not uniformly added into the molten steel, but also the inert gas and the metal compound blowing pipe Couldn't even send to.

  Table 1 shows the addition yield of the metal element in the metal oxide obtained in the continuous casting test for the inventive example and the comparative example, and the concentration variation of the metal element in the metal oxide in the continuous cast slab.

  Here, the concentration variation index of the metal element in the metal oxide in the continuous cast slab was obtained by collecting 10 samples for analysis at intervals of 1 m from the center of the slab width, and the metal element concentration (mass%) at each position. ) And the average concentration (mass%) of these samples were divided by the average concentration to determine the relative variation (%), and the maximum value was displayed. Also, the yield of addition of metal elements in the metal oxide was determined by calculating the total mass of the metal elements in the slab based on the average concentration of the metal elements in the metal oxide measured with the continuous cast slab. The percentage was expressed by dividing by the total mass of metal elements in the metal oxide.

From the results in the table, it can be seen that in the examples of the present invention, the yield of addition of the metal element in the metal oxide is high, and the metal oxide is uniformly dispersed in the slab.
(Example 2)
〔Test conditions〕
Molten metal: low carbon steel (component composition is mass%, C: 0.04%, Ti: 0.12%, N: 0.004%)
Molten metal amount: Continuous casting at 4 tons / min. Added metal: magnesium, bismuth, calcium.
Addition amount: 50g of each added metal per ton of molten steel
Addition position: in tundish Mixed gas: mixed gas of oxygen (0.5 NL / min) and argon gas (20 L / min) It is a figure which shows the method of carrying out continuous casting.

  The molten steel 1 supplied to the tundish 2 from the ladle 3 is poured into the continuous casting mold 8 through the immersion nozzle 6 and further formed as a slab by forming a solidified shell 7 while being drawn downward. The metal constituting the metal oxide to be added is supplied into the molten steel 1 in the tundish 2 by the metal wire 50.

  An immersion lance 4 is immersed in the molten steel 1 in the tundish 2, and one end of the immersion lance 4 is connected to a metal wire feeder 5. The metal wire feeder 5 is loaded with a wire reel 51, and the metal wire 50 is inserted into the immersion lance at a speed controlled by the wire feeding roll 52. The rotation speed of the wire feeding roll is controlled by a signal from the wire feeding speed control device 53. A mixed gas 54 is introduced into the metal wire feeder and is supplied into the immersion lance together with the metal wire 50. The pressure in the metal wire feeder is measured by a pressure gauge 55, and the flow rate of the mixed gas 54 is controlled by a flow rate adjustment valve 56.

  In Example 2, the comparison test performed in Example 1 was used as a comparative example, and the results were compared. In the comparative example, as described above, the metal oxide fine powder could not even be sent to the metal compound blowing pipe.

  Table 2 shows the addition yield of the metal element in the metal oxide obtained in the continuous casting test for the inventive example and the comparative example, and the concentration variation of the metal element in the metal oxide in the continuous cast slab.

  In the same table, the concentration variation index and the addition yield of the metal element in the metal oxide were determined by the same method as in Example 1. From the results in the table, it can be seen that in the example of the present invention, the addition yield of the metal element is high, and the metal oxide is uniformly dispersed in the slab.

(Example 3)
〔Test conditions〕
Molten metal: Medium carbon steel (component composition is mass%, C: 0.10%, Mn: 1.0%)
Molten metal amount: Continuous casting at 4 tons / minute Addition metal: Magnesium, calcium Addition form: Metal wire (both wire diameters are 2mmφ)
Addition amount: 50g of each added metal per ton of molten steel
Addition position: in the continuous casting mold Mixed gas: mixed gas of nitrogen (0.5 NL / min) and argon gas (10 NL / min) It is a figure which shows the method of carrying out continuous casting.

  The immersion lance 4 was immersed in the molten steel 1 in the continuous casting mold 8, and one end of the immersion lance 4 was connected to the metal wire feeder 5. In the same manner as described in Example 2, the metal wire was fed into the molten steel 1 in the continuous casting mold through the immersion lance.

  As a comparative example in Example 3, fine powder of magnesium and calcium nitride (average particle diameter: 0.05 mm) prepared in advance was charged into a container, and the inert gas argon gas was used as carrier gas for the fine powder in the container. It tried to supply to the lance immersed in molten steel and to add in molten steel.

  However, even in this comparative example, since the metal nitride fine powder charged in the container aggregated to form coarse particles, not only the fine powder was uniformly added into the molten steel, but also in the immersion lance together with the inert gas. Even sending to was impossible.

  Table 3 shows the addition yield of the metal element in the metal nitride obtained in the continuous casting test and the concentration variation of the metal element in the continuous cast slab.

  From the results shown in the table, it can be seen that in the example of the present invention, the addition yield of the metal element is high, and the metal nitride is uniformly distributed in the slab.

  According to the molten metal continuous casting method of the present invention, a compound of a metal element can be added to molten metal at a high yield, and can be uniformly dispersed in a continuous cast slab. Moreover, the continuous casting apparatus of this invention is a suitable apparatus for adding the compound of the said metal element to molten metal.

  Therefore, the continuous casting method and continuous casting apparatus of the present invention can contribute widely to homogenization of the slab quality and, consequently, improvement of the quality of the metal processed product.

It is a figure which shows the method of continuously casting, supplying the metal vapor | steam generated with the metal vapor generator with the mixed gas through the immersion lance to the molten steel in a tundish. It is a figure which shows the method of performing continuous casting, supplying a metal wire with the mixed gas to the molten metal in a tundish through an immersion lance. It is a figure which shows the method of performing continuous casting, supplying a metal wire with the mixed gas to the molten metal in a casting_mold | die through an immersion lance.

Explanation of symbols

1: Molten steel 2: Tundish 3: Ladle 4: Dipping lance 40: Metal compound supply device 41: Metal vapor generator 42: Mixed gas supply pipe 43: Metal compound blowing pipe 44: Burner 45: Temperature control device 46: Temperature Measuring device 5: Metal wire feeder 50: Metal wire 51: Wire reel 52: Wire feeding roll 53: Wire feeding speed control device 54: Mixed gas 55: Pressure gauge 56: Flow control valve 6: Immersion nozzle 7: Solidified shell 8 : Continuous casting mold

Claims (5)

  A method of continuous casting in which molten metal is supplied to a mold through a tundish, and is added to the molten metal through an immersion lance immersed in the molten metal in the tundish or an immersion lance immersed in the molten metal in the mold. Together with a mixed gas containing at least one selected from oxygen gas, hydrogen gas, nitrogen gas, carbon dioxide gas, hydrocarbon gas and sulfurous acid gas and an inert gas. A molten metal continuous casting method, wherein the molten metal is supplied into the molten metal.   A method of continuous casting in which molten metal is supplied to a mold through a tundish, and is added to the molten metal through an immersion lance immersed in the molten metal in the tundish or an immersion lance immersed in the molten metal in the mold. A wire or rod containing a metal element constituting a metal compound to be mixed, containing one or more selected from oxygen gas, hydrogen gas, nitrogen gas, carbon dioxide gas, hydrocarbon gas and sulfurous acid gas and an inert gas A continuous casting method for molten metal, characterized in that the molten metal is supplied into the molten metal together with a gas.   The molten metal is molten steel, and the metal constituting the metal compound added to the molten metal is a metal containing one or more selected from magnesium, bismuth, calcium, tellurium, lead, manganese, ytterbium and thallium. The method for continuously casting a molten metal according to claim 1 or 2, wherein:   A tundish, a dipping lance for supplying a wire or rod to the molten metal in the tundish, a wire or rod supply device for supplying the wire or rod into the hole of the dipping lance, and a lower part of the tundish An apparatus for continuously casting molten metal, comprising: an immersion nozzle provided for supplying molten metal in the tundish to the mold; and a mold located below the tundish. A tundish, an immersion nozzle provided at the lower part of the tundish for supplying molten metal in the tundish to the mold, a mold located below the tundish, and for supplying a wire or a rod to the molten metal in the mold And a wire or rod supply device for supplying the wire or rod into the hole of the immersion lance.

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