JPH04224060A - Induction heating tundish for continuous casting - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention is applicable to the steel manufacturing industry.
This invention relates to an induction heating tundish for continuous casting to obtain high-cleanliness steel. [0002] The degree of heating of molten steel (hereinafter referred to as SH) in a tundish for continuous casting has a great influence on the quality of slabs and the stability of operation. [0003] Therefore, it is desirable for quality and operation to always control SH within a certain target range, but in general, due to the influence of heat dissipation of molten steel into the atmosphere or to refractories, it is generally It was not possible to sufficiently compensate for the decrease in SH. [0004] Therefore, in recent years, attempts have been made to provide a heating function to the continuous casting tundish to prevent a decrease in SH at the initial and final stages of casting. Specifically, induction heating and plasma heating are often used. [0005] As an example of a conventional induction heating method reported, as in Japanese Patent Publication No. 63-39343, there is a system in which two spaces partitioned by a refractory are connected by a stepless hollow refractory in contact with the bottom of a TD. Although this method can be expected to have an effect of flotation and separation of inclusions in molten steel due to thermal convection, it is becoming insufficient to obtain the high cleanliness that has been particularly required in recent years. [0007] Furthermore, it is said that the opening is seamless with the bottom of the receiving side compartment to prevent the remaining metal from remaining on the receiving side. is likely to remain. [0008] Japanese Patent Application Laid-Open No. 61-38752 reports that two holes or grooves are formed that communicate with the hot water receiving chamber and the pouring chamber and are inclined so that the hot water receiving chamber side is higher. By directing the communication hole downward from the receiving chamber to the pouring chamber, the purpose is to suppress heat convection on the pouring chamber side and eliminate inclusions, but in actual casting, the pouring chamber Since the flow of molten steel directly above the nozzle increases, the possibility of entrainment of inclusions is thought to increase. [0010] In order to obtain highly clean molten steel, it is desirable to actively collect inclusions within the tundish. The present invention improves the effect of collecting inclusions in the tundish and prevents the inclusions from deteriorating the heating function of induction heating. (1) Prevent blockage of hollow refractories. (2) Obtain molten metal with a high level of cleanliness that cannot be expected with conventional induction heating methods. The purpose is to [Means for Solving the Problems] The present invention is an induction heating tundish for continuous casting in which an induction heating means is provided to the tundish used in continuous casting of steel, and the gist thereof is as follows. (1) The tundish is divided by a weir into a receiving chamber for receiving molten steel and a pouring chamber for injecting it into the mold, and the iron core and primary coil are placed in the space that vertically penetrates the weir. In a tundish that performs induction heating of molten metal by forming a closed circuit with a molten steel passage communicating between a partitioned molten metal receiving chamber and a molten pouring chamber, the molten steel passage is formed by a hollow refractory having a convex step. An induction heating tundish for continuous casting featuring: (2) The shape of the convex step is determined by the following formula, with height h, width d, and the cross-sectional height of the hollow refractory being H: 0.1≦h/H≦0.5.・(1)
0.1≦d/h≦1.0 (2) Induction heating tundish for continuous casting. (3) The tundish is separated by a weir between the receiving chamber for receiving molten steel and the pouring chamber for injecting it into the mold, and the iron core and primary coil are placed in the space that vertically passes through the weir. In a tundish that performs induction heating of molten metal by forming a closed circuit with a molten steel passage communicating between a partitioned molten metal receiving chamber and a molten pouring chamber, the molten steel passage is formed with a hollow refractory having a concave step. A featured induction heating tundish for continuous casting. (4) The shape of the concave step is determined by the following formula, where the height h, the width d, and the cross-sectional height of the hollow refractory are H, 0.2≦h/H≦1.0... (4)
0.2≦d/h≦1.0 (5) Induction heating tundish for continuous casting. It is in. FIG. 1 is a sectional view showing an embodiment of the first invention of the present invention, FIG. 2 is a plan view, FIG. 1 is a sectional view taken along the line AA in FIG. 2, and FIG. 3 is a sectional view taken along the line BB in FIG. A cross-sectional view is shown, and Figure 4 is similar to Figure 1.
FIG. In the figure, 1 is a tundish weir;
It is provided between the hot water receiving chamber 2 and the hot water supply chamber 3. 4 is a molten steel passage, which is provided in the weir 1 to communicate the hot water receiving chamber 2 and the hot water supply chamber 3, and is for guiding the molten steel supplied to the hot water receiving chamber 2 from a ladle or the like (not shown) to the hot water supply chamber 3. be. Normally, a pair of left and right molten steel passages 4 are provided below the weir 1. 5 is an electromagnetic induction heating device, which is composed of an iron core and a primary coil. [0020] The illustrated example shows the installed state in a T-shaped tundish, but since there are hot water supply chambers on both sides of one hot water receiving chamber, the electromagnetic induction heating device 5 is installed in the hot water receiving chamber 2 and the hot water supply chamber 3. They are respectively provided in the weirs 1 provided in between. In this case, by installing the iron core and the primary coil in the center of the weir 1 and installing the molten steel passage 4 around the outer periphery, an electrically closed circuit (secondary circuit) using the molten steel as a conductor can be established. The electromagnetic induction heating device 5 can heat the molten steel with Joule heat using the molten steel in the molten steel passage 4 as the main heat source. 6 indicates a nozzle for flowing into the mold. In the first aspect of the present invention, a convex step 7 is provided in the molten steel passage 4 described above, and in the illustrated example, there are three convex steps 7 in the length direction of the molten steel passage 4. 7‥‥7
An example is shown below. This convex step 7 provides turbulence to the molten steel passing through the molten steel passage 4. The installation requirements, that is, the shape of the convex step 7 are as shown in the following equation, where H is the height h, the width d, and the cross-sectional height of the molten steel passage. 0.1≦h/H≦0.5 (1) 0.
1≦d/h≦1.0...(2) 002
4) The first installation location of the convex step 7 is the bottom surface of the part where the molten steel passage 4 and the molten metal receiving chamber 2 side are in contact, and the installation period l is according to the following formula. l≧h...(3)
Next, the second aspect of the present invention will be explained. 5 is a plan view showing an example of the embodiment, FIG. 6 is a sectional view taken along line CC in FIG. 5, FIG. 7 is a sectional view taken along line DD in FIG. It is. The basic configuration of the tundish and the function of electromagnetic induction heating are the same as those of the first invention, so the explanation will be omitted. A second aspect of the present invention is that a concave step 8 is provided in the molten steel passageway 4 provided within the weir 1. Figure 5~
In the example shown in FIG. 8, three concave steps 8 are provided in the length direction of the molten steel passage 4. This concave step 8 provides turbulence to the molten steel passing through the molten steel passageway 4. Its installation requirements, i.e.
The shape of the concave step 8 is expressed by the following equation, where h is the height, d is the width, and H is the cross-sectional height of the molten steel passage 4. 0.2≦h/H≦1.0 (4) 0.
2≦d/h≦1.0...(5) 002
8] The concave step 8 is first installed on the bottom surface of the part where the molten steel passage 4 and the molten metal receiving chamber 2 are in contact, and the installation period l follows the following formula. l≧2h...(6)
[Operation] When the molten metal enters the molten steel passage 4 from the molten metal receiving chamber 2 side, it collides with a convex or concave step, resulting in a turbulent flow state. As a result, non-metallic inclusions collide with the step and adhere and accumulate. With this mechanism, non-metallic inclusions in the molten steel are captured in the weir-like step portion, and as a result, the non-metallic inclusions are prevented from adhering and depositing on the inner wall of the molten steel passage 4, and the molten steel passage 4 is prevented from being blocked. Ru. Furthermore, the cleanliness of the molten steel on the outlet side of the molten steel passage is improved. The nonmetallic inclusion collection efficiency η of the convex step 7 depends on the height h, width d, installation period l, and installation position of the convex step. The relationship between the height h, the height H of the molten steel passage, and the collection efficiency η is shown in FIG. A peak with the best collection efficiency exists in the range of 0.1≦h/H≦0.5. FIG. 1 shows the relationship between the width d, height h, and collection efficiency η.
0. A peak with the best collection efficiency exists in the range of 0.1≦d/h≦1.0. FIG. 11 shows the relationship between the installation period l, the height h, and the collection efficiency η. The collection efficiency η decreases when l<h, and remains stable at a high level when l≧h. FIG. 12 shows the relationship between the installation position and the collection efficiency η. From the part where the molten steel passage 4 and the molten steel receiving chamber 2 meet, the molten steel receiving chamber 2
The collection efficiency η decreases as it moves away from the side. Although the collection efficiency η is constant inside the molten steel passage, considering the work efficiency of replacing and repairing the weir-like refractories, the molten steel passage 4
It is most rational to install it at the part where the hot water receiving chamber 2 and the hot water receiving chamber 2 are in contact with each other. The nonmetallic inclusion collection efficiency η of the concave step 8 depends on the height h, width d, installation period l, and installation position of the concave step. The relationship between the height h, the height H of the molten steel passage 4, and the collection efficiency η is shown in FIG. 0.2 ≦h/H≦1.0
The peak of the best collection efficiency exists in the range of . FIG. 1 shows the relationship between the width d, height h, and collection efficiency η.
4. A peak with the best collection efficiency exists in the range of 0.2≦d/h≦1.0. FIG. 15 shows the relationship between the installation period l, the height h, and the collection efficiency η. The collection efficiency η decreases when l<2h, and remains stable at a high level when l≧2h. Figure 1 shows the relationship between installation position and collection efficiency η.
6. The collection efficiency η decreases as the distance from the contact portion between the molten steel passageway 4 and the molten metal receiving chamber 2 toward the molten steel receiving chamber side increases. Although the collection efficiency η is constant inside the molten steel passage, considering the work efficiency of replacing and repairing the concave refractory, the molten steel passage 4
It is most rational to install it at the part where the hot water receiving chamber 2 and the hot water receiving chamber 2 are in contact with each other. [Example] When casting Al-killed steel for bar steel using a 4-strand bloom continuous caster, induction heating with a capacity of 1000 KW was applied to each of the 1st, 2nd, 3rd and 4th strand sides of a T-type TD with a capacity of 35 tons. The equipment was installed. Casting was carried out by setting the molten steel passages provided with convex steps on the strands 1 and 2, and the conventional molten steel passages on the strands 3 and 4. [0041] The inner diameter of the molten steel passage is 100 mm. The shape of the convex step was height h = 40 mm, width d = 20 mm, and it was installed on the entrance and exit sides of the molten steel passage (installation period 1400 m).
m). The applied power was 250 KWh to each heating device. The 3rd and 4th strand sides, which had the conventional molten steel passage, were blocked in 120 minutes, making it impossible to continue casting, but the 1st and 2nd strand sides, which had the molten steel passage with the convex step of the present invention, were blocked in 120 minutes, making it impossible to continue casting. The side could be cast even after 600 minutes had elapsed, and the anti-occlusion effect was observed. [0043] Also, the total oxygen content of the product, the ultrasonic flaw detection defect rate,
Both the 1st and 2nd strand sides, which were made into molten steel passages according to the present invention, were judged to have good inclusions by the ASTM method, and the molten metal cleaning effect was recognized. [0044] Regarding the concave step, the height h = 80 m.
Casting was performed using the same type of steel with m and width d = 50 mm, but almost the same effect as in the case of a convex step was obtained. As described above, according to the present invention, the collection and separation of inclusions is actively promoted in the molten steel passage of a tundish equipped with a tundish induction heating device, and the cleaning effect of molten steel is improved. can be obtained. Furthermore, since the molten steel passageway can be prevented from being blocked by inclusions, stable operations can be performed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a tundish of the present invention, and is a sectional view taken along line AA in FIG.

FIG. 2 is a plan view showing an example of the tundish of the present invention.

FIG. 3 is a sectional view taken along line BB in FIG. 2;

FIG. 4 is an enlarged sectional view of the main part of FIG. 1;

FIG. 5 is a plan view showing another example of the tundish of the present invention.

6 is a sectional view taken along line CC in FIG. 5. FIG.

7 is a sectional view taken along line DD in FIG. 5. FIG.

FIG. 8 is an enlarged sectional view of the main part of FIG. 6;

FIG. 9 is a chart showing the relationship between the shape of a convex step or a concave step and inclusion collection efficiency in the present invention.

FIG. 10 is a chart showing the relationship between the shape of a convex step or a concave step and inclusion collection efficiency in the present invention.

FIG. 11 is a chart showing the relationship between the shape of a convex step or a concave step and inclusion collection efficiency in the present invention.

FIG. 12 is a chart showing the relationship between the shape of a convex step or a concave step and inclusion collection efficiency in the present invention.

FIG. 13 is a chart showing the relationship between the shape of a convex step or a concave step and inclusion collection efficiency in the present invention.

FIG. 14 is a chart showing the relationship between the shape of a convex step or a concave step and inclusion collection efficiency in the present invention.

FIG. 15 is a chart showing the relationship between the shape of a convex step or a concave step and inclusion collection efficiency in the present invention.

FIG. 16 is a chart showing the relationship between the shape of a convex step or a concave step and inclusion collection efficiency in the present invention.

[Explanation of symbols]

1 Weir 2　Hot water room 3　Hot water supply room 4 Molten steel passage 5　Electromagnetic induction heating device 6 Nozzle 7 Convex step 8 Concave step

Claims (4)

[Claims] [Claim 1] A tundish is divided by a weir into a receiving chamber for receiving molten steel and a pouring chamber for injecting it into a mold, and an iron core and a primary coil are disposed in a space that vertically passes through the weir, and is partitioned by the weir. In a tundish that performs induction heating of molten steel by forming a closed circuit with a molten steel passage communicating between a molten metal receiving chamber and a molten pouring chamber, the molten steel passage is formed by a hollow refractory having a convex step. Induction heating tundish for continuous casting. Claim 2: The shape of the convex step has a height h, a width d,
0.1≦h/H≦0.5 (1) 0.1≦h/H≦0.5 determined by the following formula, where H is the cross-sectional height of the hollow refractory.
1≦d/h≦1.0 (2) Claim 1
The induction heating tundish for continuous casting described above. [Claim 3] The tundish is divided by a weir into a receiving chamber for receiving molten steel and a pouring chamber for injecting the molten steel into the mold, and the iron core and primary coil are disposed in a space that vertically passes through the weir, and is partitioned by the weir. In a tundish for induction heating of molten steel by forming a closed circuit with a molten steel passage communicating between a molten steel receiving chamber and a molten pouring chamber, the molten steel passage is formed by a hollow refractory having a concave step. Induction heating tundish for continuous casting. 4. The shape of the concave step has a height h, a width d,
0.2≦h/H≦1.0 (4) 0.2≦h/H≦1.0 determined by the following formula, where H is the cross-sectional height of the hollow refractory.
2≦d/h≦1.0 (5) Claim 3
The induction heating tundish for continuous casting described above.