JPH0749141B2 - 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 a tundish having an induction heating device capable of improving the required quality level due to non-metallic inclusions in continuous casting of steel.

[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.

In molten steel at the final stage of casting in continuous casting, inclusion quality generally deteriorates due to the influence of ladle slag flowing into the tundish and SH reduction. In the case of groove-type induction heating, when the molten steel head in the tundish is lowered, a pinch effect occurs and the secondary current circuit is cut off, so that the molten metal cannot be heated.

Therefore, at the final stage of casting, where the quality of inclusions is the worst, the effect of improving the quality of inclusions by induction heating cannot be obtained.

As a conventional report of the induction heating method, there is a method in which both spaces are connected by a stepless hollow refractory which is in contact with the TD bottom surface, as in Japanese Patent Publication No. 63-39343. However, this method has a problem that the quality of the slab is deteriorated by pouring a molten metal having poor quality of inclusions into the mold at the end of casting.

[0008]

As an induction heating device in continuous casting, as shown in FIG. 4, a tundish is shielded by a shield block 1 and a hot water supply unit 2 for receiving molten steel from a ladle and 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 apparatus, 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 section to the hot water supply section.

When the pouring from the ladle is completed, the molten steel level in the tundish lowers and the pinch effect makes it impossible to supply induction power, resulting in a decrease in SH of molten steel.

Therefore, the molten steel at the final stage of casting becomes low SH, and the effect of floating inclusions due to induction stirring cannot be expected. Further, inclusion of slag in the tundish due to lowering of the molten steel head causes very poor inclusion quality. .

[0012]

The present invention is to solve the above-mentioned problems. FIG. 1 is a longitudinal sectional view of an essential part of the present invention, and FIG. 2 is a plan sectional view.

According to the present invention, the tundish is divided 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 by a shielding block 1, and a space vertically penetrating the shielding block. In an induction heating tundish in which an iron core wound with an induction heating coil is provided and two hot refractory 5 are connected to each other by a hollow refractory 5 embedded in a shielding block, the hot water receiving part is provided. 2 and hollow refractory 5
A hot water reservoir 6 having a height h, a width d, and a length l is provided between the bottom of the hot water receiving portion 7 and the bottom surface 8 of the hollow refractory material on the hot water receiving portion side.

The volume (h × l × d) of the molten metal pool can be changed according to the required quality level of inclusions in the molten metal.
When connecting the hot water receiving portion 2 and the hollow refractory 5 to each other, the reason for providing a hot water reservoir having a height h, a width d, and a length l between them is as follows.
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 heating becomes impossible due to the interruption of the secondary current passage in the hollow refractory due to the pinch effect, so that the residual molten steel and the molten steel surface slag cannot be heated. Superheat decreases and the effect of floating inclusions deteriorates.

In addition, the floating effect of inclusions due to induction stirring disappears, and further, as the molten steel head is lowered, a vortex flow is generated and the phenomenon of slag inclusion in the tundish occurs.

In the induction heating tundish of the present invention, the quality of inclusions is deteriorated by leaving the molten metal in which the level of inclusions is deteriorated, that is, the inclusions are concentrated in the pool 6 in the tundish. It is possible to prevent the molten metal from being poured into the mold and obtain a continuously cast slab with excellent inclusion quality.

The volume of the molten metal pool is changed in accordance with the required quality level of inclusions to prevent a decrease in molten metal yield due to excessive residual metal.

[0020]

According to the present invention, since the groove is provided on the front surface of the hot-water receiving portion side which is the inlet of the hollow refractory, there is also an effect of adhering and collecting inclusions due to the turbulent flow of the molten steel, thus reducing the volume of the hot water pool portion. It is possible to obtain a continuously cast slab having excellent inclusion quality while preventing deterioration of the molten metal yield due to excessive residual molten metal by changing according to the required level of inclusion quality.

That is, if the volume of the basin is increased, the amount of residual hot water in the tundish increases and the yield decreases. Therefore, when the required quality level differs depending on the steel grade, Accordingly, by changing the volume of the molten metal pool and performing the casting operation, it becomes possible to perform the operation at the optimum points of the both depending on the steel types.

[0022]

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.

Casting was carried out by using TDs having different volumes of the basin and changing the length 1 with the height h = 0.2 m and the width d = 1.0 m. The results of inclusions in the slab at the end of casting were evaluated by ultrasonic flaw detection results of steel bar products.

FIG. 3 shows the relationship between the volume of the pool and the ultrasonic flaw detection results of the product. It can be seen that the larger the volume of the basin, the better the inclusions in the product. Therefore, the volume of the basin is set in accordance with the required quality level under economically most advantageous conditions while taking into consideration the decrease in yield.

[0025]

According to the present invention, the volume of the basin can be optimally set according to the required quality level which differs depending on the steel type, so that there is an advantage that it can be operated as the most economical yield without lowering the quality level. Yes, it is extremely useful in industry.

[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 molten metal pool.

FIG. 4 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 supply room 4 Induction heating coil installation space 5 Hollow refractory 6 Hot water pool 7 Bottom of hot water receiving part 8 Bottom of hollow refractory on hot water receiving part side

 ─────────────────────────────────────────────────── ─── 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 are embedded in a shielding block so that they communicate with each other, a hot water pool having a height h, a width d, and a length 1 is provided between the hot water receiving portion and the hollow refractory material during the connection. An induction heating tundish that is installed at a position lower than the bottom of the hot water receiving part and the bottom of the hollow refractory on the side of the hot water receiving part so that the inclusions are trapped and the molten steel with the inclusions concentrated remains.