JPH0749142B2 - Induction heating tundish - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to continuous casting in which continuous induction heating is performed by reducing the amount of molten steel remaining in the tundish in the continuous casting of steel and preventing the secondary current passage from being blocked by the pinch effect. The present invention relates to induction heating tundish.

[0002]

2. Description of the Related Art The degree of heating of a molten metal in a tundish for continuous casting (hereinafter referred to as SH) has a great influence on the quality of a slab and the stability of operation.

Therefore, it is desirable for the quality and operation to always control the SH within the target range, but in general, due to the effect of the heat dissipation of the molten metal in the atmosphere or to the refractory, especially in the early and final stages of casting Could not be compensated sufficiently.

Therefore, in recent years, attempts have been made to impart a heating function to a 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.

As a conventional report of an induction heating type tundish, as shown in Japanese Patent Publication No. 63-39343, a stepless hollow refractory contacting the bottom of the tundish is used to connect both spaces separated by the refractory. There are things.

In this method, there are problems that the molten metal and the slag remain on the side of the hot water receiving chamber at the end of casting, which makes it difficult to repair the tundish and reduces the yield of the molten metal.

In Japanese Patent Publication No. 63-39343, there is described a stepless opening which is in contact with the bottom of the hot water receiving chamber, but in this method, molten steel and slag are removed from the hot water receiving chamber after the casting is completed. There is a problem of remaining in the opening.

In Japanese Examined Patent Publication No. 2-37813, a shield block is formed between the hot water supply room and the hot water supply room in the tundish.
A tundish induction heating device in which two holes communicating with the hot water receiving chamber and the pouring chamber are provided in this shielding block, and a core having an induction heating coil is detachably communicated with the hole communicating vertically is described. ing.

In Japanese Examined Patent Publication No. 2-8821, a shield block is formed between the hot water supply room and the hot water supply room in the tundish, and the hot water supply room and the pouring room are connected to this shield block and the hot water is received. Although it is mentioned to drill two holes or grooves which are inclined to make the chamber higher, this method concerns the levitation separation of inclusions.

[0010]

As an induction heating device in continuous casting, as shown in FIG. 5, a tundish is shielded by a shield block 1 and a hot water supply portion 2 for receiving molten steel from a ladle and hot water for pouring molten steel into a mold. And a space 4 penetrating in the vertical direction in the shielding block.
A device is used in which an iron core 4-1 wound with an induction heating coil is passed through, and a hot water receiving part and a hot water supplying part are connected by a plurality of hollow refractories 5 embedded in a shielding block.

In casting using this induction heating device, generally, molten steel injected from a ladle is heated by a secondary current in the hollow refractory in the process of moving from the steel receiving part to the hot water supply part.

When the pouring from the ladle is completed, the molten steel in the tundish and the slag and heat insulating material on the surface of the molten steel descend as the casting continues, and at the end of casting, part of the molten steel and the slag / heat insulating materialヾ All remains in the tundish.

In particular, when the molten steel in contact with the slag is partially left in the tundish in order to reduce the inclusion defect in the cast slab, several tons to 10 tons of molten steel and slag remain.

At this time, when the steel receiving portion and the hollow refractory are in contact with each other without steps, the residual molten steel and the slag are solidified and clogged in the hollow refractory, which causes a serious problem during reuse.
The same applies to the case where the hot water supply portion and the hollow refractory material are in contact with each other without steps.

[0015]

The present invention is to solve the above problems. FIG. 1 is a longitudinal sectional view of an essential part of the present invention, and FIG. 2 is a plan sectional view. As shown in the figure, the tundish is divided by a shielding block 1 into a hot water receiving portion 2 for receiving molten steel from a ladle and a hot water supplying portion 3 for injecting molten steel into a mold, and a space 4 vertically penetrating the shielding block. Provided, through an iron core (not shown) wound with an induction heating coil,

In an induction heating tundish in which the hot water receiving portion and the hot water supplying portion are connected by two hollow refractory materials 5 buried in a shielding block, when the hot water receiving portion 2 and the hollow refractory material 5 are connected, a hollow refractory material is connected. The bottom surface 6 is made lower than the bottom surface 7 of the hot water receiving portion, and a groove 8 having a front depth h and a width d of the hollow refractory is formed by [1].
It is provided so as to communicate with the two refractory materials so as to satisfy the formula, and when the hot water supply portion 3 and the hollow refractory material 5 are connected,
In order to allow a part of the molten steel discharged from the hot water receiving portion 2 through the hollow refractory 5 and the slag to stay,

By making the bottom surface 9 of the hot water supply portion lower than the bottom surface of the hollow refractory material, it is possible to prevent molten steel and slag from remaining in the hot water reception portion and the hollow refractory material after the completion of casting. Groove 8
Cross-sectional area (h × d) ≧ cross-sectional area of hollow refractory ・ ・ ・
[1] However, h ≧ 50 mm and d ≧ 50 mm. Here, the cross-sectional area of the hollow refractory material means the cross-sectional area of the molten steel as a passage.

First, when connecting the hot water receiving part 2 and the hollow refractory 5 to each other, the hollow refractory bottom 6 is made lower than the hot water receiving part bottom 7 and the groove 8 is provided in the front part of the hollow refractory 5. This will be described below.

The superheat of the molten steel in the tundish after the completion of pouring the ladle generally decreases as the amount of residual molten steel decreases.

In addition, even if induction heating is attempted, since the height of the molten steel is low, the secondary current passage in the hollow refractory 5 is interrupted by the pinch effect, so that heating cannot be performed. The superheat of is reduced and the liquidity deteriorates. Therefore, in the present invention, the bottom surface of the hollow refractory material is made lower than the bottom surface of the hot water receiving portion.

A groove having a depth h and a width d from the bottom surface of the steel receiving part to the bottom surface of the hollow refractory is provided in the front part of the hollow refractory.
The cross-sectional area (h × d) of this groove is made equal to the cross-sectional area inside the hollow refractory.

The reason for this is that the two hollow refractories and the groove form a passage for a secondary current generated by induction heating to ensure high heating efficiency and reduce the amount of residual molten steel when the pinch effect occurs. This is because.

The depth h and width d of the groove are shown in FIG.
From the results of the experiment on the blockage of the hollow refractory inlet by the metal shown in (2), both h and d are set to 50 mm or more.

Next, in the present invention, when the hot water supply portion and the hollow refractory are connected, the bottom surface of the hot water supply portion is provided so that a part of the molten steel discharged from the hot water reception portion through the hollow refractory and the slag can be retained. Is set to be lower than the bottom surface of the hollow refractory to prevent molten steel and slag from remaining in the hot water receiving portion and the hollow refractory after the casting is completed.

[0025]

According to the present invention, the presence of the groove prevents the interruption of the secondary current due to the pinch effect during the induction heating until the end. In addition, the performance of discharging molten steel and slag to the hot water receiving part and the hot water supplying part in the hollow refractory is significantly improved, which enables smooth casting work.

[0026]

Example An Al-killed steel for a steel bar was cast by a 4-strand Bloom continuous casting machine. An induction heating device having a capacity of 1000 KW was installed on each of the 1st, 2nd strand side, 3rd and 4th strand side of the T type TD having a capacity of 35 tons.

The tundish of the present invention and the tundish of the conventional construction (a system in which there is no step between the bottom of the hot water supply chamber, the bottom of the hot water supply chamber and the bottom of the hollow refractory) are tundish cast by 5 charges each. The amount of molten metal remaining in the tank was measured by a load cell at the bottom of the tundish and compared.

The inner diameter of the hollow refractory material is 100 mm, and the groove sizes are d = 90 mm and h = 87 mm. The applied power is 250 kWhr for each heating device.

FIG. 4 shows a comparison of the molten steel residual hot water contents in the tundish when the tundish of the present invention is used and when the conventional tundish is used.

According to the present invention, it can be seen that the amount of remaining tundish hot water is greatly reduced from the conventional average of 2.6 tons to the average of 0.6 tons. Further, even when the molten steel amount was considerably reduced, the secondary current was not interrupted due to the pinch effect.

[0031]

According to the present invention, it is not necessary to remove the solidified metal in the tundish after casting and to frequently replace the hollow refractory, so that the effect of improving the productivity and reducing the cost of the refractory is extremely large.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing an induction heating tundish according to the present invention.

FIG. 2 is a plan sectional view of the tundish shown in FIG.

FIG. 3 is a diagram showing the relationship between the blockage of the metal at the inlet of the hollow refractory and the dimensions of the groove.

FIG. 4 is an explanatory diagram showing an effect of the present invention.

FIG. 5 is a perspective view showing a configuration of a conventional tundish.

[Explanation of symbols]

 1 Shielding block 2 Hot water receiving part 3 Hot water supplying part 4 Space 5 Hollow refractory 6 Bottom of hollow refractory 7 Hot water receiving part bottom 8 Groove 9 Hot water supplying part bottom

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor, Aoyanagi, 12 Nakamachi, Muroran-shi, Hokkaido Inside of Muroran Works, Nippon Steel Corporation (56)

Claims (1)

[Claims] 1. A shield block for the tundish,
It is divided into a hot water receiving part for receiving molten steel from a ladle and a hot water supplying part for injecting it into a mold, and a space passing vertically is provided in the shielding block, and an iron core wound with an induction heating coil is inserted through the hot water receiving part and the hot water supplying part. In a tundish in which two hollow refractory materials embedded in a shielding block are connected to each other, the bottom surface of the hollow refractory material is set lower than the bottom surface of the hot water receiving portion, and at the front of the hollow refractory material on the hot water receiving portion side, A groove having a depth h and a width d was provided so as to satisfy the following formula [1] and communicate with the two hollow refractories, and the bottom surface of the hot water supply portion was installed at a position lower than the bottom surface of the hollow refractories. An induction heating tundish characterized by the following. Cross-sectional area of groove ≧ cross-sectional area of hollow refractory ・ ・ ・ [1] where h ≧ 50 mm d ≧ 50 mm