JPS62192240A - Molten metal bubbling apparatus - Google Patents

Abstract

PURPOSE:To prevent clogging of a tundish nozzle by arranging a refractory made lance body having a gas injecting part at the end part and also executing bubbling as rotating the lance body to make a center of its axis. CONSTITUTION:The lance 7 is arranged at a cover 6 of the tundish 1 through a hole 8, and also the rotating device 11 of the lance 7 is set on a bracket 10 arranged at a side wall of the tundish 1. A gas passage 21 and a gas injecting part 22 are arranged in the inner part of the refractory made lance body 20 and its end respectively. Inert gas, such as Ar gas, etc., is supplied in the lance 7 while rotating the lance 7 by rotation of a motor 12 in the rotating device 11, to inject into the molten steel 2 from the gas injecting part 22. In this way, as fine bubbles are developed in wide area, nonmetallic inclusions in the molten steel 2 are effectively separated as floating up. Therefore, the clogging of the nozzle 5a-5d is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a molten metal bubbling device that performs bubbling by blowing gas into molten metal in a tundish.

[Conventional technology]

In continuous casting, the temperature of the molten steel in the tundish is
There is a problem in that nonmetallic inclusions such as 203 adhere around the tundish nozzle, causing nozzle clogging.

Therefore, conventional methods for preventing clogging of tundish nozzles include a method in which non-metallic inclusions such as An203 in the tundish are adsorbed to a filter and removed, and a method in which non-metallic inclusions are floated and separated by blowing gas from a casting stopper and an immersion nozzle. A method of floating and separating non-metallic inclusions by blowing gas/V from porous bricks laid in a tundish are known.

[Problem that the invention seeks to solve]

In the method of preventing tundish nozzle clogging using the filter described above, there is a limit to the adsorption of nonmetallic inclusions (including the case of melting and loss), and it is difficult to obtain a satisfactory effect, such as nonmetallic inclusions falling off due to the flow of molten steel. This is the actual situation.

In addition, in methods for preventing clogging of tundish nozzles, such as blowing gas from a casting stopper and immersion nozzle, and blowing gas from porous bricks laid in tundish, the gas blown into the molten metal can be increased from room temperature to several dozen at once. Since the gas is continuously blown into the molten metal at a temperature of 100 degrees, the blown gas undergoes rapid thermal expansion and bubbles coalesce, making it difficult to feed the molten metal into fine bubbles. It is not possible to sufficiently float and remove fine nonmetallic inclusions. In this case, it is conceivable to reduce the pore diameter of the porous material for gas injection, but the air permeability deteriorates and a satisfactory result cannot be obtained. Furthermore, since the gas is blown from a fixed position, the stirring ability is poor, and non-metallic inclusions floating in the molten steel cannot be effectively removed.

As described above, the conventional method for preventing tundish nozzle clogging cannot effectively prevent the phenomenon of tundish nozzle clogging within 1 m.

The present invention has been made based on the above circumstances, and its object is to effectively float and separate molten metal inclusions to stably prevent clogging of tundish nozzles. The purpose of the present invention is to provide a bubbling device.

[Failure to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a refractory lance body that has a gas discharge section made of porous refractory at its tip and a gas passage that supplies gas to the gas discharge section. The feature is that bubbling is performed by rotating around the shaft, and in order to prevent contamination of the molten metal and promote the flotation and separation of inclusions, the amount of inert gas blown is 0.25j2 / ton of retained molten metal. It is characterized in that it is used under bubbling conditions in the range of 20 to 150 ppm, and the rotational speed of the lance body is 20 to 150 ppm.

[Effect]

To efficiently miniaturize and diffuse bubbles in molten metal in a tundish.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

Reference numeral 1 in FIGS. 1 and 2 indicates a tundish, and this tundish 1 includes an introduction part 3 into which molten water is introduced from a ladle (not shown), and a molten g4 introduced into this introduction part 3.
The structure includes a storage section 4 for storing molten uA2, and tundish nozzles 5a to 5d for casting the molten uA2 stored in the storage section 4 into a mold (not shown).

A tundish lid 6 is provided on the top of the tundish 1, and the lid 6 is provided with an insertion hole 8 through which a lance 7 is inserted into the tundish 1.

A seal member 9 made of glass fiber or the like is provided around the insertion hole 8 of the lid 6.
Melt! ? This prevents the splash 42 from entering the insertion hole 8.

A bracket 10 is attached to the side wall of the tundish 1, and this bracket 10 is provided with a lance rotating device (rotating means) 11. That is, a drive motor 12 and an arm 13 are supported on the bracket 10,
The tip of the arm 13 is located above the insertion hole 8,
A rotary shaft 14 that supports the lance 7 is rotatably supported at this tip via a bearing 15. A driven sprocket 16 is fixed to this rotating shaft 14, and this driven sprocket 16 and the shaft 12a of the drive motor 12
An endless chain 18 is stretched between the drive sprocket 17 and the drive sprocket 17 fixed to the drive sprocket 17 . The lance 7 is rotated by the drive of the motor 12. In addition,
This lance rotation device 11 is designed to allow a desired rotation speed to be selected.

Further, an air pipe 19 is provided near the bearing 15, and the bearing 15 portion is cooled by air guided through this single air pipe.

Further, as shown in FIGS. 3 and 4, the lance 7
This has a structure in which a gas passage 21 and a gas discharge part 22 are provided inside a refractory lance main body 2o. As mentioned above, the lance main body 20 has fire resistance, is not easily eroded by the molten steel 2, does not cause deformation, is resistant to abrasion with the molten steel 2 due to high speed rotation, and is made of a material with high thermal conductivity. (Tatoeha A203-C-3i C series). The gas protrusion 22 has a cylindrical porous refractory embedded in the tip of the lance body 2o along its diameter, and both end surfaces 22a, 22a are exposed on the circumferential surface of the lance body 20. The gas passage 21 is provided along the central axis of the lance body 20, and its tip communicates with the gas protrusion 22, and its base end opens to the base end 20a of the lance body 20. Further, the rotary shaft 14 is screwed to the base end of the lance body 2o and connected to the gas passage 21, and gas is supplied to the gas passage 21 through a gas introduction passage 23 provided inside the rotary shaft 14. The gas is guided and further discharged into the molten steel 2 from the gas discharge section 22. In addition, 24 in FIG. 1 is a rotary join 1 to connect the gas supply pipe 26 from the gas supply device 25 to the gas introduction path 23 in the rotating shaft 14. Further, the pressure and flow rate of the gas discharged from the gas discharge section 22 can be controlled by a gas control device (not shown).

When an inert gas such as Ar gas is supplied into the lance 7 and the lance 7 is rotated, gas is discharged from the gas discharge part 22 into the molten steel 2 as the lance 7 rotates, and this discharge Bubbling is performed by gas.

According to the above configuration, not only the gas is blown from the lance 7 but also the lance 7 is rotated at the same time, so that the degree of ventilation can be controlled by adjusting the rotational speed of the lance 7. Moreover, since the bubbles of the gas discharged from the gas discharge part 22 float in a spiral pattern, not only do the bubbles not easily coalesce into large bubbles in the molten steel 2, but the bubbles float in a spiral pattern and the molten steel 2 becomes difficult to form.
diffuses widely and uniformly into li12. Therefore, fine bubbles can be generated over a wide range in molten tA2, and since the finer (smaller diameter) bubbles have a larger interface and better inclusion adsorption ability, non-metallic inclusions in molten t1g2 can be effectively removed. By floating and separating the particles, clogging of the tundish nozzles 5a to 5d can be stably prevented. As a result, casting can be performed stably.

In addition, since the lance body 20 is made of a highly thermally conductive refractory material, it has excellent thermal shock resistance, and the rapid thermal expansion of the inert gas is suppressed by allowing the gas to pass through the gas passage 21 formed in the lance body 20. This makes it possible to easily form fine bubbles.

As shown in FIG. 5, the lance 7 may be provided with a disc 31 to prevent splash from adhering to the insertion hole 8 of the tundish lid 9. As shown, a refractory sleeve 32 may be provided to prevent the slag that comes into contact with the lance 7 from becoming entangled.

Next, an experimental example will be explained.

FIG. 7 shows the results of checking the flow situation by adding 8ρ as a tracer in a 1/3 water model.

As shown in the figure, several flows are generated near the lance 7 due to bubbling. That is, interfacial flows A and B are generated at the molten steel interface, and this is considered to promote the reaction between the molten steel and the heat insulating material on the upper surface of the molten steel. In addition, a vortex E is generated, which causes the refractory to become entangled. These flows A, B and vortex E are factors that contaminate the molten steel. Further, upward flows C and D are generated around the lance 7, and these promote floating of inclusions. In order to optimize the Ar injection amount and the rotation speed of the lance 7, the fluidity of these A to E was evaluated, and at the same time, the amount of surface disturbance a, the bubble diameter b, and the bubble condition C were investigated.

First, FIG. 8 shows the relationship between the amount of Ar injection and the amount of surface disturbance a. As the amount of Ar injection increases, the surface disturbance Ia increases, but by rotating the lance 7, the increase in the surface disturbance amount a is suppressed.

Moreover, FIGS. 9(a) to 9(C) show the relationship between the rotational speed of the lance 7, the bubble diameter b, and the bubble condition C when the amount of Ar injection is changed. Although the bubble diameter increases as the amount of Ar blowing increases, by rotating the lance 7, the bubbles can be made finer and a spiral flow of the bubbles can be obtained. However, when the rotational speed of the lance 7 is about 20 rl) m or less, the bubbles flow in a straight line, and when the rotational speed of the lance 7 is about 15 rpm or more, a situation occurs in which the bubbles generated by the spiral flow coalesce. However, the bubble size increases. In addition, as the number of revolutions of the lance 7 increases and the amount of Ar injection increases, the interfacial flow A,
B and eddy current E increase, and it is necessary to suppress both the rotational speed of the lance 7 and the amount of Ar injection to a certain level due to the LIC.

FIG. 10 shows how the Affi 20 is applied to the tundish nozzles 5a to 5d by changing the Ar injection amount and the rotation speed of the lance 7.
: Shows the results from an actual machine that investigated the adhesion of +. Lance 7
When the rotation speed is Orpm and 20Orpm, the nozzle clogging tends to increase as the Ar injection amount increases, but when the rotation speed is 1100 rD, the Ar injection amount is 2.
In the range of ~5ff/min, nozzle clogging is improved compared to the conventional method without bubbling.

The amounts of Ar blown in the experimental examples shown in FIGS. 8 to 10 are values for 20 tons of molten rA.

Based on the above experimental results, the amount of inert gas blown into the retained molten metal 1
0.25 n/min or less per unit, lance rotation speed 2
It was confirmed that it is desirable to use bubbling conditions in the range of 0 to 150 rIllIl.

〔Effect of the invention〕

As explained above, according to the present invention, there is provided a refractory lance body, a gas discharge portion formed of a porous refractory at the distal end of the lance body, and a gas discharge portion formed in the lance body. and a rotating means for rotating the lance body around its axis, non-metallic inclusions can be effectively floated and separated to stabilize clogging of the tundish nozzle. It has excellent effects such as being able to prevent

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which Fig. 1 is a sectional view of the entire device, Fig. 2 is a plan view of the lance, Fig. 3 is a sectional view of the lance, and Fig. 4 is a side view of the tip of the lance. Figures 5 and 6 are perspective views showing other different embodiments of the lance, Figure 7 is a schematic diagram showing the flow situation in a 1/3 water model, and Figure 8 is an Ar blower model. Figures 9(a) to 9(c) are diagrams showing the relationship between lance rotation speed, bubble diameter, and bubble condition when the Ar injection rate is changed. , Figure 10 shows the flow of Ar into the tundish nozzle by changing the Ar injection dma and the lance rotation speed.
It is a figure which shows the result by the actual machine which investigated the adhesion state of j2203. DESCRIPTION OF SYMBOLS 11... Rotating means (lance rotating device), 20... Lance main body, 21... Gas passage, 22... Gas discharge part. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Whistle C, ffl Value 6M (One 7th ring)

Claims (2)

[Claims] (1) A lance body made of a refractory, a gas discharge part formed of a porous refractory at the tip of the lance body, and a gas passage formed in the lance body and supplying gas to the gas discharge part; A molten metal bubbling device comprising a rotating means for rotating the lance body around its axis. (2) The amount of inert gas blown is 0.00 per ton of retained molten metal.
25l/min or less, lance body rotation speed 20-150
The molten metal bubbling device according to claim 1, wherein the molten metal bubbling device is used under bubbling conditions in the rpm range.