JPH0160339B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tundish in a continuous casting machine.

As is well known, in continuous casting, when the linear velocity of molten metal, such as molten steel, supplied from the tundish into the mold is high, the molten steel jet entrains mold powder and scum and causes them to penetrate deep into the mold. However, there was a problem in that the mold powder and scum did not float to the surface of the molten metal in the mold and remained as inclusions in the slab, resulting in a deterioration in the quality of the slab. Therefore, the present applicant has already proposed a method capable of solving the above-mentioned problems, and FIG. 1 shows what has already been proposed as a ternary for carrying out the method. That is, this tundish is composed of a first tundish 1 and a second tundish 2, the first tundish 1 is open to the atmosphere, and the second tundish 2 has a lid attached to its upper opening via a sealing material 3. The first and second tundishes 1 and 2 are connected to each other at their lower portions through a sliding nozzle 5 disposed between them. A vacuum pump 7 is connected to the lid 4 of the second tundish 2 through an exhaust pipe 6, and the vacuum pump 7 maintains a constant reduced pressure inside the second tundish 2. Further, an immersion nozzle 8 is connected to the bottom of the second tundish 2, and hot water is supplied to the mold 9 through the immersion nozzle 8. Therefore, according to the tundish shown in FIG. 1, molten steel 10 is supplied into the first tundish 1 from the ladle 11 through the long nozzle 13 while adjusting the flow rate by the sliding nozzle 12. The molten steel 10 inside the second tundish 2 is depressurized to below atmospheric pressure (for example, 0 to 0.5 atmospheres), so that the molten steel 10 flows through the sliding nozzle 5.
The molten steel 10 flows into the second tundish 2 while the flow rate is controlled by the tundish 2, and the molten steel 10 that has once flowed into the second tundish 2 flows down into the mold 9 via the immersion nozzle 8. In this case, since the internal pressure of the second tundish 2 is maintained below atmospheric pressure, the flow rate of the molten steel 10 flowing down from the second tundish 2 to the mold 9 is such that it flows directly into the mold from the tundish opened to the atmosphere. Therefore, there is less risk that the molten steel jet flow into the mold 9 will involve mold powder or scum, and deterioration in slab quality can be prevented.

However, in the case of a tundish as shown in FIG. 1 already proposed by the present applicant, the above-mentioned sliding nozzle 5 is used as a flow rate control mechanism for the molten steel 10 flowing from the first tundish 1 to the second tundish 2. Therefore, air enters into the molten steel 10 and the second tundish 2 from between the plates 5a forming the sliding nozzle 5 and between the plates 5a and the first tundish 1 and the second tundish 2, As a result, the molten steel 10 is oxidized, non-metallic inclusions increase, and the number of inclusions in the slab increases, leading to a risk of deterioration in quality. Furthermore, when air enters as described above, it becomes difficult to maintain a constant reduced pressure inside the second tundish 2, and as a result, the amount of hot water supplied from the second tundish 2 to the mold 9 fluctuates. The surface of the water is disturbed,
As a result, there were problems such as the mold powder 14 getting caught up in the solidified shell 15, resulting in deterioration of the surface quality of the slab.

Furthermore, in the tundish shown in FIG. 1, the first tundish 1 and the second tundish 2 are
Since two units are required, the overall refractory cost increases, and furthermore, since hot water is supplied to the mold 9 from the first tundish 1 to the second tundish 2, the temperature drop of the molten steel 10 during that time is large. As a result, the viscosity of the molten steel 10 increases, making it difficult to float and separate non-metallic inclusions.

This invention was made in view of the above circumstances,
When performing so-called reduced-pressure hot water supply to slow the linear velocity of molten metal relative to the mold, continuous casting is possible without air intake or associated pressure fluctuations in the reduced-pressure chamber, and without deteriorating slab quality. The purpose of this invention is to provide a tundish that can perform the following.

An embodiment of the present invention will be described below with reference to FIG. In FIG. 2, molten metal, for example, molten steel 10
The container 20 for accommodating the container has a structure in which a refractory material is lined on the inner surface of the iron shell, and the inside of the container 20 is divided into two accommodating portions 22a and 22 by a partition wall 21.
These accommodating parts 22a, 22
b is a through hole 23 formed in the lower part of the partition wall 21;
communicated by. That is, the through hole 23
is opened upward with respect to the housing portion 22a on the right side in FIG. 2, and the opening portion 23a is tapered so that the opening area becomes smaller at the bottom as shown in FIG. Opening 2
3a is provided with a valve member 24 made of refractory material whose tip end shape corresponds to the shape of the opening 23a, and is movable up and down, and by moving the valve member 24 up and down, The substantial opening area of the opening 23a is increased or decreased.

Of the two accommodating parts 22a and 22b, the second
The housing section on the right side in the figure (hereinafter referred to as the first housing section) 22a is open to the atmosphere, while the housing section on the left side in FIG. 2 (hereinafter referred to as the second housing section) 22b
is sealed by a lid 26 attached to the upper end via a sealing material 25. A vacuum pump 28 is connected to the lid 26 through an exhaust pipe 27, and an inert gas holder 31 such as Ar gas is connected to the lid 26 through an air supply pipe 29 and a control valve 30. , the vacuum pump 28
The gas inside the second housing section 22b, which is sealed by the lid body 26, is exhausted and the flow rate is adjusted by the control valve 30 from the inert gas holder 31. By supplying inert gas to the second housing part 2
The internal pressure of 2b is adjusted.

The second housing section 2 is sealed by the lid body 26.
An immersion nozzle 32 is connected to the bottom of 2b, and the tip of the immersion nozzle 32 is inserted into the mold 9.

Note that the same reference numerals in FIG. 2 as those in FIG. 1 indicate the same members as those shown in FIG. 1.

Next, a method of supplying hot water to the mold 9 using the tundish constructed as described above will be explained. First, the ladle 1 is placed in the first housing part 22a.
1, the molten steel 10 is supplied into the mold 9 through the long nozzle 13 through the through hole 23, the second storage part 22b, and the immersion nozzle 32 while controlling the flow rate with the sliding nozzle 12, and the level of the molten steel 10 is immersed. It should be higher than the tip of the nozzle 32. In this state, the vacuum pump 28 is started, and the control valve 30 is slightly opened to set the inside of the second housing part 22b to a reduced pressure state of a predetermined pressure. During this pressure reduction, the inside of the second housing part 22b is gradually filled with molten steel 10 according to the pressure to a height H, and casting (drawing) of the slab 5 is started accordingly. In this case, the molten steel 10 flowing from the first accommodating part 22a to the second accommodating part 22b
The flow rate is determined by adjusting the opening area of the opening 23a of the through hole 23 using the valve member 24. Note that when the opening 23a of the through hole 23 is open, the second housing part 22b is in communication with the atmosphere through the through hole 23 and the first housing part 22a, but the pressure loss in the through hole 23 is Therefore, the internal pressure of the second housing part 22b is maintained at a predetermined vacuum state without rising to atmospheric pressure, and the through hole 23 is completely submerged in the molten steel 10. Air does not enter into the second housing part 22b, and therefore the pressure inside the second housing part 22b does not fluctuate irregularly. Furthermore, when the height from the hot water level in the mold 9 to the hot water level in the second housing part 22b is H, the internal pressure P' of the second housing part 22b is atmospheric pressure.
Since the pressure is set to less than Pa, molten steel 10
flows into the mold 9 at a speed expressed by υ=√2('-+) (ρ: molten steel density, g: gravitational acceleration).Therefore, in the tundish with the above configuration, the tundish is of the conventional type open to the atmosphere. The flow rate of the molten steel 10 can be made slower than when the molten steel 10 is directly supplied to the mold. As is clear from the above equation, changing the internal pressure P' of the second housing section 22a changes the flow rate, that is, the flow rate of the molten steel 10.
This is done by adjusting the internal pressure P' of the second accommodating portion 22b by 0, thereby controlling the flow rate of the molten steel 10 into the mold 9. Alternatively, if P' is controlled constant, the passage between the through hole 23, the housing part 22b, and the immersion nozzle 32 becomes a so-called communication pipe, so the flow rate into the mold 9 and the control of the molten metal level are controlled by the valve. This is also possible by moving the mechanism 24 up and down.

Note that in the above embodiment, the through hole 23 that communicates the first accommodating part 22a and the second accommodating part 22b is opened upward at the bottom of the first accommodating part 22a. The valve member is not limited to the one shown in the above embodiment, but it is sufficient that the first accommodating part 22a and the second accommodating part 22b are communicated with each other at their bottom sides, and the valve member is not limited to that shown in the above embodiment. First, it is sufficient that the flow rate of the molten steel 10 can be controlled by increasing or decreasing the opening area of the through hole.

As is clear from the above description, according to the tundish of the present invention, the inside of the container is divided by the partition wall to form at least two storage parts, and these storage parts are formed in the through holes formed at the lower part of the partition wall. a valve member for communicating with the through hole and increasing or decreasing the opening area of the through hole; further, one of the housing portions has a sealed structure and the inside thereof is depressurized by suction, and Since the immersion nozzle is connected to the bottom of the sealed housing, even if the pressure inside the sealed housing is reduced, the through hole is completely submerged in the molten metal and is not exposed to the atmosphere. Since there are no communicating gaps, air will not inadvertently enter the molten metal flowing into the sealed housing or the sealed housing, thereby preventing oxidation of the molten metal and non-metallic inclusions. In addition, since the pressure inside the sealed housing part does not fluctuate unintentionally, the flow rate of the molten metal from the housing part can be appropriately controlled. It is possible to prevent disturbances in the level of the molten metal in the mold. Furthermore, since the tundish of the present invention has an integral structure, it is possible to reduce the overall refractory cost, and at the same time, it is possible to suppress the temperature drop of the molten metal housed inside, and as a result, the viscosity of the molten metal does not increase. Therefore, the floating and separation of non-metallic inclusions therein will not be hindered. Therefore, in general, according to the tundish of the present invention, it is possible to obtain a continuously cast slab of good quality with few inclusions and surface defects.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a tundish proposed by the applicant to carry out the hot water supply method already proposed, and FIG. 2 is a schematic cross-sectional view showing an embodiment of the present invention. 10... Molten steel, 20... Container, 21... Partition wall,
22a, 22b...Accommodating part, 23...Through hole, 2
4... Valve member, 26... Lid, 28... Vacuum pump, 30... Control valve, 32... Immersion nozzle.

Claims (1)

[Claims] 1. A container for storing molten metal, at least two accommodating portions defined within the container by partition walls, a through hole formed at the lower part of the partition wall to communicate these accommodating portions, and a valve member for increasing or decreasing the opening area of the through hole; a lid body for sealing any one of the housing parts;
a vacuum pump for reducing the pressure inside the container sealed by the lid; a control valve for controlling the flow rate of inert gas to be supplied into the container sealed by the lid; A tundish in a continuous casting machine consisting of an immersion nozzle connected to the bottom of a container sealed by a tundish.