JP2020011261A - Method and device for producing fine oxide-dispersed metal lump - Google Patents

Abstract

To provide a device and a method for producing a metal lump in which fine oxide based inclusions are largely dispersed so as to obtain sufficient HAZ toughness even upon high heat input welding.SOLUTION: A device for producing a fine oxide-dispersed metal lump comprises: a molten metal container 21 storing a molten metal 20; a refractory 22 in which at least a part is composed of a solid electrolyte 15; counter electrodes 17 in contact with the molten metal 20 stored in the molten metal container 21; and a direct current power source 9, in which a part of the refractory 22 is immersed into the molten metal 20, the refractory 22 is provided with a contact electrode 16, a positive electrode 18 of the direct current power source 9 is connected to the counter electrodes 17, and a negative electrode 19 is connected to the contact electrode 16, and a production method uses the device. When energization is performed using the direct current power source 9, oxygen is fed to the molten metal 20 via the solid electrolyte 15, and is reacted with a deoxidation material component in the molten metal, thus a metal lump in which fine oxide based inclusions are largely dispersed can be produced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus and a method for manufacturing a fine oxide-dispersed metal lump, which can produce a metal lump in which a large amount of fine oxide-based inclusions are dispersed in solidifying a molten metal to produce a metal lump. The present invention relates to a method for manufacturing a metal lump dispersed with a substance.

  Although the kind of the metal material to which the present invention is applied is not limited, a steel material will be described below as an example.

  In recent years, structures using steel materials, such as ships and buildings, have been increasing in size, and there is a strong demand for higher strength and thicker steel materials. Steel materials are generally joined by welding, but as the thickness of steel materials increases, it is required from the viewpoint of efficiency to perform large heat input welding for applying a large amount of heat to the steel materials. However, at the time of large heat input welding, the heat affected zone (hereinafter referred to as HAZ) is exposed to a high temperature close to the melting temperature of steel, and the cooling rate from the high temperature is reduced. The formation of a structure that reduces the toughness of a steel material such as a site and island martensite is promoted. Therefore, in the large heat input welded structure, there has been a problem that the toughness of the HAZ portion is reduced.

  With respect to a method of improving the toughness of the HAZ portion, a technique is widely known in which fine TiN is dispersed and precipitated and used as pinning particles to suppress austenite grain coarsening during welding. However, in large heat input welding in which the heat input exceeds 50 kJ / mm, the temperature of the HAZ reaches a high temperature, so that TiN in the steel material dissolves and disappears, and coarsening of austenite grains cannot be prevented. There's a problem.

  In order to solve such a problem of high heat input welding HAZ toughness, in recent years, oxide inclusions, which are hard to form a solid solution even at a high temperature, are dispersed in a large amount in a steel material at a molten steel stage, and are effectively utilized as pinning particles. Attention has been focused on such techniques, and techniques such as those disclosed in Patent Documents 1 and 2 have been proposed.

Patent Literature 1 relates to a base material and a steel material having excellent HAZ toughness and a method for producing the same. Specifically, of the total amount of Ti contained in the steel material, the amount of Ti contained in the steel material as a Ti-containing inclusion exceeding 2.0 μm is 0.010% or less, and as the Ti-containing inclusion exceeding 0.1 μm. is intended that a value obtained by subtracting from the total amount of Ti total Ti amount included in the steel material is the percentage of from 0.30 to 0.70 relative to the total Ti amount in the steel material, the amount of Si in the molten steel stage defines and Al ₂ O ₍₃₎ It is stated that it can be manufactured by casting after reducing the number of inclusions contained to 10 or less per 1 mm ² . Thereby, it is stated that the toughness of the base material and the HAZ can be more accurately improved.

Patent Document 2 relates to a high-strength steel sheet excellent in base metal toughness and HAZ toughness. Specifically, the point is that oxides having a maximum diameter of 0.2 to 2 μm or less are present in an amount of 200 / mm ² or more, a martensite structure is contained in an amount of 29% by volume or more, and the remainder is bainite. Thereby, a high-strength steel sheet excellent in base material toughness and HAZ toughness can be provided.

  BACKGROUND ART A solid electrolyte is known as a substance capable of moving ions (charged substance) by an externally applied electric field. Since it can move oxygen ions, it is also called an oxygen ion conductor. Stabilized zirconia has long been used as a solid electrolyte. When a voltage is applied to zirconia from the outside, oxygen ions move from the negative electrode side to the positive electrode side, so that an oxygen pump can be configured and used for atmosphere control and the like (for example, see Non-Patent Document 1). In Patent Document 3, the surface in contact with the molten metal is formed of an oxygen ion conductor, and a current is applied from the oxygen ion conductor side to the molten metal side by applying a voltage to form a deposit formed of a metal oxide. A method of preventing this is disclosed.

JP 2013-60631 A JP 2014-9387 A JP-A-2001-170761

“Utilization of Solid Electrolyte for Metallurgy” The Bulletin of the Japan Institute of Metals 10 (1971) No. 1 pp. 28-43

  Patent Literature 1 and Patent Literature 2 both mention improvement of HAZ toughness by dispersing a large number of oxide-based inclusions in a steel material as a method for coping with a decrease in HAZ toughness due to welding heat. However, these methods have a problem that oxide-based inclusions generated in steel cannot be sufficiently refined, and sufficient HAZ toughness cannot be obtained particularly when the heat input is large.

  The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to disperse a large amount of fine oxide-based inclusions such that sufficient HAZ toughness can be obtained even during large heat input welding. It is to provide a method of manufacturing a metal lump which has been made.

That is, the gist of the present invention is as follows.
(1) A molten metal container containing a molten metal, a refractory at least partially composed of a solid electrolyte, a counter electrode contacting the molten metal contained in the molten metal container, and a DC power supply A part of the refractory is immersed in the molten metal when the molten metal is accommodated in the molten metal, and a contact electrode is provided on a part of the refractory that does not come into contact with the molten metal; Is connected to the counter electrode, and the negative electrode of the DC power supply is connected to the contact electrode.
(2) The apparatus for producing a fine oxide-dispersed metal lump according to (1), wherein the refractory composed of the solid electrolyte is a refractory forming a stopper.
(3) Using the apparatus for producing a fine oxide-dispersed metal lump according to the above (1) or (2),
When the molten metal is accommodated in the molten metal container and energized by using the DC power supply, when the molten metal is poured into the mold from the molten metal container to produce a metal lump,
A method for producing a fine oxide-dispersed metal mass, characterized in that the average current density at the contact surface between the solid electrolyte and the molten metal is 0.05 to 1.5 A / cm ² .
(4) The method for producing a fine metal oxide-dispersed metal lump as described in (3) above, wherein oxide inclusions having a maximum diameter of 1 μm or less are present in the metal lump at 350 or more / mm ² or more.

  According to the present invention, a metal lump (a slab or a metal material) in which a large amount of fine oxide-based inclusions are dispersed can be produced.

It is the figure which showed typically the stopper of the bottom part of the tundish to which this invention was applied, and the longitudinal cross section of an injection port. It is the figure which showed typically the stopper of the bottom part of the tundish to which this invention was applied, and the longitudinal cross section of an injection port. It is a figure showing the situation of the experiment using the atmospheric melting furnace.

Regarding the pinning of the crystal grain growth by the dispersed particles in the steel, as a basic formula, the Zener formula shown in the following formula (a) and the modified Zener formula shown in the formula (b) are well known. The crystal grain size is formulated by the diameter of the dispersed particles and the volume ratio thereof.
D = (4/3) · (d / f) (a)
D = (8/3) · (d / f ^2/3 ) (b)
Here, D: crystal grain diameter, d: radius of dispersed particles, and f: volume ratio of dispersed particles. That is, in order to obtain a larger pinning effect using oxide-based inclusions, it is considered that the larger the volume ratio of the inclusions and the smaller the diameter of the oxide-based inclusions, the better.

  Conventionally, as a method of dispersing more fine oxide-based inclusions in steel, (1) oxide-containing inclusions are formed by adding a deoxidizer to molten steel containing a large amount of oxygen, and (2) deoxidation. A method is known in which a gas or solid oxygen source is added to molten steel containing a large amount of a chemical component to form oxide-based inclusions. However, these methods have failed to form a sufficiently fine oxide in a large amount as described above. The present inventors have formed a larger amount of oxide-based inclusions in molten steel than slabs manufactured by a general manufacturing method and thought that it is desirable that they be fine and large in amount, and realized that. We examined the method of squatting.

  As described above, by applying an electric field to the solid electrolyte (oxygen ion conductor) from the outside, oxygen ions can be moved. The surface in contact with the molten metal is composed of an oxygen ion conductor, and current is applied from the solid electrolyte (oxygen ion conductor) side to the molten metal side by applying a voltage to prevent the formation of deposits made of metal oxide. The way to do it was known. The present inventors, on the contrary, the surface in contact with the molten metal is composed of a solid electrolyte, the direction of the voltage is reversed, and if a current flows from the molten metal side to the solid electrolyte side, from the solid electrolyte to the molten metal Oxygen was supplied, and it was conceived that a large amount of fine oxide-based inclusions could be generated in the molten metal by the supplied oxygen. That is, (3) a method of adding oxygen from a solid electrolyte to molten steel containing a large amount of a deoxidizer component was conceived.

  In addition, as a process of adding oxygen or a deoxidizing agent to a molten metal by the above-mentioned methods (1) to (3), (A) a method of adding oxygen or a deoxidizer before a casting step (for example, a smelting step); It was considered that the degree of the effect of the two methods of adding at the stage should be comparatively evaluated.

  In order to confirm the most appropriate method for dispersing a large amount of fine oxides in molten steel among these combinations, the following experiment was performed.

  100 kg of molten steel was manufactured in each of the atmospheric melting furnace and the vacuum melting furnace, and adjusted to the component systems of component 1 and component 2 shown in Table 1. Regarding the component 1, free oxygen remains in the molten steel and is used in the method (1). The component 2 has been completely deoxidized by Al and used in the methods (2) and (3).

With respect to those produced from molten steel in an air melting furnace, the steps of forming oxide-based inclusions in the molten steel by the above-described methods (1) to (3) are performed in an air melting furnace, and immediately through a tundish. Molten steel was poured into a mold to produce a steel ingot. That is, the method (A) is used.
In the case of manufacturing molten steel in a vacuum melting furnace, the step of transferring the molten steel to a tundish and forming oxide-based inclusions in the molten steel by the above-described methods (1) to (3) is performed in a tundish. To produce a steel ingot. That is, the method (B) is used.

(A) and (B) In each case, a sample for observing inclusions having a size of 20 mm × 20 mm was cut out from the obtained steel ingot and observed by SEM to obtain an oxide system having a circle equivalent diameter of 0.05 to 1 μm and 1 μm or more. The number density (pieces / mm ² ) of inclusions was investigated.

A method of adding oxygen from a solid electrolyte to molten steel containing a large amount of a deoxidizer component by the method (3) will be described. As the solid electrolyte, 5 mol% CaO-stabilized ZrO ₂ was used.
When oxygen was added from the solid electrolyte in the air melting furnace by the method (A), the means shown in FIG. 3 was used. The rod-shaped oxygen supply body 13 formed of the solid electrolyte 15 is immersed in the molten metal 20 in the atmosphere melting furnace 12. The contact area between the oxygen supplier 13 and the molten metal 20 is 30 cm ² . The contact electrode 16 is provided on the outer periphery of the oxygen supply body 13 above the molten metal 20. A counter electrode 17 is provided in the atmospheric melting furnace 12. A DC power supply 9 was prepared, and the contact electrode 16 provided on the oxygen supply body 13 was on the negative electrode 19 side, and the counter electrode 17 provided on the atmospheric melting furnace 12 was on the positive electrode 18 side. In the atmosphere melting furnace 12, a current was passed at a current of 1 A to the component system (complete deoxidation) of the component 2 in Table 1 for 360 seconds, and then transferred from the atmosphere melting furnace 12 to the tundish 1.
When the oxygen content was added from the solid electrolyte in the tundish by the method (B), the means shown in FIG. 1 was used. An upper nozzle 6 and an immersion nozzle 7 are provided at the bottom of the tundish 1, and the flow rate of the molten metal is adjusted by the stopper 2. The stopper 2 is formed by a stopper core 3, a stopper head 4, and a stopper sleeve 5. Here, the stopper sleeve 5 is formed of the solid electrolyte 15. The contact area between the solid electrolyte 15 and the molten metal 20 is 30 cm ² . The contact electrode 16 is provided on the outer periphery of the stopper sleeve 5 above the molten metal 20. Since the immersion nozzle 7 was made of alumina graphite and had conductivity, the lead wire 8 was brought into contact with the outer periphery of the immersion nozzle 7, and the immersion nozzle 7 was used as the counter electrode 17. A DC power supply 9 was prepared, and the contact electrode 16 provided on the stopper sleeve 5 was used as a negative electrode, and the immersion nozzle 7 (counter electrode 17) was used as a positive electrode. In the process of transferring the molten metal 20 from a vacuum melting furnace (not shown) to the tundish 1 and flowing out the molten metal 20 from the tundish 1 via the immersion nozzle 7, the component system of the component 2 in Table 1 (complete deoxidation) ), A current of 1 A was applied for 360 seconds.

The method (1) (adding a deoxidizing agent to molten steel containing a large amount of oxygen) targets component 1 (non-deoxidized) in Table 1, and the method (A) uses the inside of the atmospheric melting furnace 12 and the method (B). In the method, the amount of Al shown in Table 2 was added to the molten metal in the tundish 1.
Regarding the method (2) (adding an oxygen source to molten steel containing a large amount of a deoxidizer component), in the method of (A), in the air melting furnace 12, in the method of (B), in the tundish 1, and in the molten metal. The total amount of gaseous oxygen shown in Table 2 was blown for 360 seconds as a mixed gas with argon.
Al addition amount, oxygen gas blowing amount, energization conditions, sol. Al and T.I. Table 2 also shows the concentration of O and the number of oxide-based inclusions.

  In the tundish to which oxygen was added by energization via the solid electrolyte (B3), the fine oxide-based inclusions were dispersed in the largest amount. The reason is not clear in detail, but can be guessed as follows. That is, in the case where the deoxidizing agent was added (A1) and (B1), the deoxidizing agent was melted in the steel and the oxide forming reaction proceeded rapidly, so that a coarse oxide was formed. Similarly, it is presumed that the oxide-added reaction (A2) and (B2) to which oxygen was added rapidly progressed around the oxygen gas bubbles to form a coarse oxide. Also, at the same energization, when the energization was carried out in a tundish (B3) than in the melting furnace (A3), a large amount of fine oxide-based inclusions was present. The molten steel is injected into the mold immediately after it is supplied and fine oxide-based inclusions are formed, so it takes a short time to solidify in the mold, and it is difficult for aggregates of the fine oxide-based inclusions to occur. Presumed.

  Further, oxide-based inclusions generated by addition of oxygen due to energization through the solid electrolyte are mainly smaller than 1 μm, and as shown in Table 2, fine inclusions without increasing the oxygen content of the entire molten steel greatly. Molten steel in which a large number of oxide-based inclusions are dispersed can be obtained.

  The results of this experiment show that the fine oxide-based inclusions were also energized in a tundish even in an experiment in which the deoxidizing agent was changed to the above-mentioned Al and various oxide combinations such as Zr and REM were used. The tendency to be present in the largest amount did not change.

  Here, in order to supply oxygen into molten steel using a solid electrolyte, oxygen gas in the atmosphere is taken into the solid electrolyte as oxygen ions, oxygen ions are transported in the solid electrolyte, and molten oxygen is introduced into the molten steel as molten oxygen. Need to release. That is, a part of the solid electrolyte is immersed in the molten steel, and the other part is in contact with the contact electrode connected to the conductor, and the contact electrode part is set in the atmosphere. Further, since oxygen is taken into the solid electrolyte at a three-phase interface between the solid electrolyte, the contact electrode, and the atmosphere, it is desirable that the contact area between the solid electrolyte and the contact electrode be large.

The present invention has been made based on the above findings. The apparatus for producing a fine metal oxide-dispersed metal lump according to the present invention includes a molten metal container 21 containing a molten metal 20, a refractory 22 at least partially composed of the solid electrolyte 15, and a refractory 22 contained in the molten metal container 21. The refractory 22 has a counter electrode 17 in contact with the molten metal 20 and a DC power supply 9, and a part of the refractory 22 is immersed in the molten metal 20 when the molten metal 20 is accommodated in the molten metal container 21. A contact electrode 16 is provided on a portion of the refractory 22 that does not contact the molten metal 20, a positive electrode 18 of the DC power supply 9 is connected to the counter electrode 17, and a negative electrode 19 of the DC power supply 9 is connected to the contact electrode 16. It is characterized by the following. As shown in FIGS. 1 and 2, the molten metal container 20 can be a tundish 1. The counter electrode 17 can be the immersion nozzle 7.
As the solid electrolyte, an oxide-based solid electrolyte can be used. Stabilized zirconia (ZrO ₂ ) is preferred. For example, CaO stabilized ZrO ₂ and Y ₂ O ₃ (yttria) stabilized ZrO ₂ can be used.

  It is preferable that the refractory 22 composed of the solid electrolyte is a refractory forming the stopper 2. In the example shown in FIGS. 1 and 2, the stopper sleeve 5 is formed of the solid electrolyte 15. In the solid electrolyte 15, the temperature from the part in contact with the molten metal 20 to the part in which the contact electrode 16 is provided should secure a temperature of 600 ° C. or more as a result of radiant heat and heat conduction from the molten metal 20. Can be.

  In the method for producing a fine metal oxide-dispersed metal lump using the apparatus for producing a fine metal oxide-dispersed metal lump of the present invention, the molten metal 20 is accommodated in a molten metal container 21 and energized using a DC power supply 9. Thereafter, the molten metal 20 is poured from the molten metal container 20 into a mold (not shown) to produce a metal lump. Since the positive electrode 18 of the DC power supply 9 is connected to the counter electrode 17 and the negative electrode 19 of the DC power supply 9 is connected to the contact electrode 16, when current is supplied using the DC power supply 9, the current flows from the positive electrode 18 to the counter electrode 17. Through the molten metal 20 in the molten metal container 21, flows from the contact portion of the refractory 22 with the molten metal, flows into the refractory 22, and contacts the DC electrode 9 via the contact electrode 16 that contacts the refractory. To the negative electrode 19. At this time, in the refractory 22 which is a solid electrolyte, oxygen is taken into the refractory 22 from the atmosphere at the portion of the contact electrode 16 and the portion of the refractory 22 coming into contact with the molten metal 20 from the portion of the contact electrode 16 in a direction opposite to the direction of the current. Oxygen ions move toward the molten metal to supply oxygen into the molten metal.

  In the method for dispersing fine oxide-based inclusions by energization according to the present invention, the positive electrode 18 of the DC power supply 9 is connected to the counter electrode 17 on the molten metal 20 side, and the negative electrode 19 is connected to the contact electrode 16 on the solid electrolyte 15 side. Is performed, oxygen can be supplied to the molten metal 20. However, in order to cause a certain number or more of fine oxide-based inclusions in the slab without spending excessive time and cost, the average current density must be reduced. It is desirable to control to an appropriate range. Here, the average current density is a current value per unit area obtained by dividing an amount of current by an area of a portion of the solid electrolyte immersed in molten steel.

If the average current density is less than 0.05 A / cm ² , a sufficient amount of oxygen cannot be efficiently supplied into the steel, and the amount of molten steel to be processed per hour must be reduced, and This causes undesirable aggregation of fine oxide-based inclusions. On the other hand, if the average current density exceeds 1.5 A / cm ² , the proportion of electrons that occupy the charge carrier in the solid electrolyte increases. Since electric conduction by electrons does not contribute to oxygen enrichment in steel, an excessive current causes an increase in manufacturing cost. From the above, it is desirable that the current density be 0.05 A / cm ² or more and 1.5 A / cm ² or less.

Inside the metal block produced by the production method of the dispersed metal mass of the fine oxide inclusions of the present invention, the following oxide inclusions maximum diameter 1μm is present 350 / mm ² or more. As a result of dispersing such a fine oxide, it is possible to obtain an effect that a metal structure manufactured using this metal lump has excellent HAZ toughness when large heat input welding is performed.

In the method for producing a metal lump according to the present invention, since the oxygen concentration in the molten steel irreversibly increases, coarse oxide-based inclusions such as Al ₂ O ₃ clusters are contained in the molten steel brought into the molten metal container. The effect of removing is not expected. Even if coarse oxide-based inclusions are contained, the effect of dispersing a large amount of fine oxide-based inclusions obtained by the present invention can be obtained without any problem, but clogging of the immersion nozzle, cracking during processing of metal lump And so on. Therefore, it is desirable to sufficiently reduce the oxygen concentration in the molten steel before pouring into the molten metal container.

  In order to obtain the effects of the present invention, it is necessary to immerse the solid electrolyte in molten steel and then to conduct electricity between the portion where the solid electrolyte contacts an atmosphere containing oxygen and the molten steel. As a method, for example, as in the apparatus shown in FIG. 1, the stopper sleeve 5 of the stopper 2 is a solid electrolyte 15, a contact electrode 16 is provided in a non-immersion part above the stopper sleeve 5, and the immersion nozzle 7 is a counter electrode 17. It is effective to apply a current through a contact portion between the solid electrolyte 15 and the molten metal 20. In the apparatus shown in FIG. 2, the stopper sleeve 5 is the same as the solid electrolyte 15 in FIG. On the other hand, in FIG. 2, a contact electrode 16 is provided on the inner periphery of the cylindrical stopper sleeve 5. A method is conceivable in which a ventilation portion is provided between the inner peripheral side of the stopper sleeve 5 and the outer periphery of the stopper core 3, and a contact electrode 16 made of metal mesh is provided on the inner periphery of the stopper sleeve 5. A ventilation pipe may be provided between the inner peripheral side of the stopper sleeve 5 and the outer peripheral side of the stopper core 3. With the device shown in FIG. 2, the distance between the contact portion of the solid electrolyte 15 with the molten metal 20 and the contact electrode 16 can be shortened, so that current can be supplied efficiently. In FIG. 2, an electrode 23 immersed in a molten metal 20 is used as the counter electrode 17.

  In the present invention, the method using a stopper type injection system is shown as a typical example.However, a method in which a solid electrolyte is immersed in molten steel, in which a stopper is used as an electrode for connecting a negative electrode of a DC power supply, In this case, the effect can be obtained irrespective of the position of the refractory using charged particles as the electrode, which connects the immersion nozzle to the positive electrode of the DC power supply with molten steel. In addition, the present invention can be applied not only to a tundish of a stopper type, but also to a tundish of a SN (sliding nozzle) type or a tundish of a type using both an SN and a stopper.

  The present invention was applied when continuously casting molten steel. The molten steel refined by the primary refining device is discharged to a ladle, then degassed by a vacuum refining device, the molten steel in the ladle is transferred to a tundish of a continuous casting device, and the tundish is poured into a continuous casting mold. And molten steel was continuously cast to form a slab. An opening for pouring is provided at the bottom of the tundish 1 (see FIG. 1), and the opening includes an upper nozzle 6 and a dipping nozzle 7. The stopper 2 is provided above the upper nozzle 6, and the opening area between the tip of the stopper (stopper head 4) and the opening of the upper nozzle 6 is adjusted, so that a mold (not shown) can be formed from the tundish 1. Adjust the injection speed into the

In the tundish 1 for continuously casting molten steel by the stopper type injection device as described above, as shown in FIG. 1, the stopper sleeve 5 of the body of the stopper _{2 is} made of ZrO ₂ (Stabilized with 5 mol% CaO). It consisted of a solid electrolyte 15). A contact electrode 16 was provided above the stopper sleeve 5 so as to surround the stopper sleeve 5. A DC power supply 9 was prepared, and the negative electrode 19 of the DC power supply 9 and the contact electrode 16 were connected by a lead wire 8. The immersion nozzle 7 was used as a counter electrode 17, and a lead wire 8 was connected between the positive electrode of the DC power supply 9 and the counter electrode 17. By setting as described above, the electric circuit was configured via the molten steel.

To the tundish 1, degassing treatment was previously performed in the vacuum refining facility as described above, and molten steel adjusted to the component a or b shown in Table 3 was injected. From the positive electrode 18 of the DC power supply 9 to the counter electrode 17 while controlling the surface of the molten steel in the tundish to be maintained above the lower limit position of the solid electrolyte 15 (stabilized ZrO ₂ ) of the stopper sleeve 5 and below the contact electrode 16. Then, a current flows through the molten metal 20 in the tundish 1 via the immersion nozzle 7, and a current flows through the solid electrolyte 15 at a contact portion between the molten metal 20 and the solid electrolyte 15. In the solid electrolyte 15, a current further flows to the contact electrode 16, and the current returns from the contact electrode 16 to the negative electrode 19 of the DC power supply 9 via the lead wire 8. In this manner, molten steel at 1550 ° C. was poured into a 200 mm × 200 mm rectangular mold while a direct current was flowing, and was continuously cast at a casting speed of 0.80 m / min. Oxygen is supplied from the atmosphere into the solid electrolyte 15 at the position of the contact electrode 16 in response to the DC current in the solid electrolyte 15, and oxygen ions move in a direction opposite to the current in the solid electrolyte 15, and Oxygen is supplied into the molten metal 20 from a contact portion with the molten metal 20. In the comparative example, the connection between the positive electrode 18 and the negative electrode 19 was reversed, and the current in the solid electrolyte 15 was reversed, and the comparative example and the comparative example in which no current was passed were also cast.

The measurement of the number of oxide-based inclusions in the slab manufactured by continuous casting was performed by cutting out a sample for observation having a size of 20 mm × 20 mm from the center of the thickness of the slab and performing SEM observation on the mirror-polished surface. . Oxide-based inclusions having a size of 0.05 to 1 μm were measured at a magnification of 10,000 to 50,000 times over an area of 10 mm ² , and the number of oxide-based inclusions having a size of 1 μm or more was measured at a magnification of 1,000 to 5,000 times. Each was observed over an area of 200 mm ² .

  Table 3 shows the chemical composition of the steel, Table 4 energizing conditions, and the dispersion state of the inclusions.

As can be seen from Table 4, in Examples 1 to 4 in which the contact electrode 16 side of the stopper 2 was connected to the negative electrode 19 and the immersion nozzle 7 (counter electrode 17) side was connected to the positive electrode 18 to flow a current, 0.05 to 1 μm. In each case, the fine oxide-based inclusions were present in excess of 350 / mm ² , and the average value of the number of oxide-based inclusions of 1 μm or more was not significantly different from the level at which no current was passed. .

On the other hand, in Comparative Example 5 in which the average current density was as low as 0.04 A / m ² even in the same direction of current application, the number of minute oxide-based inclusions of 0.05 to 1 μm did not reach 350 / mm ^2. And inferior to the examples of the present invention. Comparative Examples 6 to 8 in which the contact electrode 16 side of the stopper 2 was connected to the positive electrode 18 and the immersion nozzle 7 (counter electrode 17) side was connected to the negative electrode 19 to flow a current, and Comparative Example 9 in which no DC power supply was connected. In Nos. To 10, the number of fine oxide-based inclusions of 0.05 to ¹ μm was less than 50 / mm ² .

DESCRIPTION OF SYMBOLS 1 Tundish 2 Stopper 3 Stopper iron core 4 Stopper head 5 Stopper sleeve 6 Upper nozzle 7 Immersion nozzle 8 Lead wire 9 DC power supply 10 Tuyere brick 11 Metal mesh 12 Atmospheric melting furnace 13 Oxygen supplier 15 Solid electrolyte 16 Contact electrode 17 Counter electrode 18 Positive electrode 19 Negative electrode 20 Molten metal 21 Molten metal container 22 Refractory 23 Electrode rod

Claims (4)

  A molten metal container that contains the molten metal, a refractory at least partially composed of a solid electrolyte, a counter electrode that contacts the molten metal contained in the molten metal container, and a DC power supply; When the molten metal is contained in the molten metal, a part thereof is immersed in the molten metal, and a contact electrode is provided in a portion of the refractory that does not come into contact with the molten metal, and the positive electrode of the DC power supply is the counter electrode. An apparatus for producing a fine metal oxide-dispersed metal block, wherein the apparatus is connected to an electrode and a negative electrode of a DC power supply is connected to the contact electrode.   2. The apparatus according to claim 1, wherein the refractory composed of the solid electrolyte is a refractory forming a stopper. 3. Using the apparatus for producing a fine oxide-dispersed metal lump according to claim 1 or claim 2,
When the molten metal is accommodated in the molten metal container and energized by using the DC power supply, when the molten metal is poured into the mold from the molten metal container to produce a metal lump,
A method for producing a fine oxide-dispersed metal mass, characterized in that the average current density at the contact surface between the solid electrolyte and the molten metal is 0.05 to 1.5 A / cm ² . The method for producing a fine oxide-dispersed metal lump according to claim 3, wherein oxide inclusions having a maximum diameter of 1 µm or less exist in the metal lump at a rate of 350 / mm ² or more.

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