JPH01309768A - Method and apparatus for continuously casting molten steel under non-oxidization - Google Patents

Abstract

PURPOSE:To improve the yield and the quality of a continuously cast slab by continuously casting while exhausting invaded air into inner part, etc., in a refractory passage to outside. CONSTITUTION:In the continuous casting, a tundish nozzle 2, sliding nozzles 3-5 and submerged nozzle 7 are jointed from upper side to lower side in order, to form the refractory passage 14 for molten steel and the casting the executed through the passage 14. The air invaded in inner part or inner circumferential face of the refractory passage 14 or jointing part of each nozzles 2-5, 7 is exhausted to outside with a suction device 11 through space 10 and exhaust pipe 12. The continuous casting is executed during exhausting. Double packing is arranged at each between the nozzles to form the space and the inner part of the submerged nozzle is made porous. By this method, the yield and the quality of the continuously cast slab can be improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention reduces inclusions, blowholes, etc. in molten steel in the continuous casting process of steel, thereby obtaining clean continuously cast slabs with few inclusions. The present invention relates to a continuous casting method and an oxidation-free casting device that can prevent nozzle clogging.

<Conventional technology> What happens when casting slabs of steel by continuous casting? 8. When inclusions present in steel are captured in molten steel, they often cause flaws and defects in finished products, and various studies have been conducted to reduce the inclusions in molten steel. For example, there is a method for promoting the floating of nonmetallic inclusions by blowing inert gas bubbles or flux into molten steel in a ladle, and a method for promoting the floating of nonmetallic inclusions.
A method for filtering and separating non-metallic inclusions by adding a filter function to an immersion nozzle that injects molten steel into a mold from a T/D (hereinafter abbreviated as T/D); 2. A method for degassing inert gas in molten steel using a porous nozzle. (Refer to Japanese Unexamined Patent Publication No. 54-2936) has been proposed.

However, none of the above methods can prevent oxidation of molten steel due to air entering from the immersion nozzle or the joint between the immersion nozzle and the sliding nozzle (hereinafter referred to as S/N) due to cracks, etc. There was a problem in that metal inclusions caused defects and nozzle clogging.

Also, for air intrusion from the gap between the S/N and the S/N,
A device for sealing N (for example, JP-A-57-206566
However, even with such a seal, it was not possible to completely prevent air from entering through cracks in the immersion nozzle itself.

<Problems to be Solved by the Invention> In view of the above problems, the present invention provides a continuous casting method and an oxidation-free casting apparatus that can effectively prevent the formation of inclusions in the molten steel flow path between the T/D and the mold. It was created to provide the following.

<Means for Solving the Problems> The present invention provides (1) a method for continuous casting through a refractory passage for molten steel formed by connecting a tundish nozzle, a sliding nozzle, and an immersion nozzle of a continuous casting device from above to below; This is an oxidation-free continuous casting method in which continuous casting is performed while exhausting air that has entered the inside of the refractory passage or the inner peripheral surface or each nozzle joint to the outside. In a continuous casting device that is connected to a tundish nozzle and a sliding nozzle to form a refractory passage for molten steel, a double packing is provided between the tundish nozzle and the sliding nozzle, between each plate of the sliding nozzle, and between the sliding nozzle and the immersion nozzle. A space is formed by each nozzle, and the inside or inner peripheral surface thereof is porous over the entire length of the immersion nozzle, and the upper end of the porous portion is formed by the double packing, the sliding nozzle, and the immersion nozzle. This is an oxidation-free casting device in which exhaust pipes are connected to the above-mentioned spaces, and exhaust pipes are further connected to each of the above-mentioned spaces.

For Kusaku In the present invention, T/D nozzle, S/D nozzle.

By forcibly exhausting gas that has entered the inside or inner surface of the fire-resistant passage for molten steel connected to the immersion nozzle or the joints of each nozzle, contact between molten steel and air is prevented, and inclusions in molten steel are removed. can be reduced.

In addition, double backings are provided between the T/D nozzle and S/N nozzle, between each plate of the S/N nozzle, and between the S/N nozzle and the immersion nozzle, and each nozzle is surrounded by the double backing and each nozzle. By creating a space, evacuating this space, and making the inside or inner peripheral surface of the immersion nozzle porous and connecting this porous part to the front space, the porous part can be evacuated. nozzle,
It is possible to prevent the molten steel in the S/D nozzle and immersion nozzle portion from coming into contact with air.

<Example> FIG. 1 shows one embodiment of the present invention.

The refractory passage for molten steel from T/D 1 to mold 13 is as follows:
It is composed of a T/D nozzle 2, each S/D plate 3, 11° 5, and an immersion nozzle 7. When the molten steel 9 passes through this refractory passage 14, no matter how tightly the joint is sealed, gaps and cranks will occur due to the heat, creating negative pressure in the joint and allowing air to infiltrate. In order to prevent this, the joints of each component 1, 2, 3, 4°5. Air infiltration is prevented by exhausting at step 11. In addition, sealing properties are ensured for the gaskets between the 3.4 and 4.5 degrees of each S/N plate by pumping grease or the like.

The immersion nozzle 7 has a porous part 8, and an exhaust pipe may be directly connected to the porous part for exhaust, or as shown in FIG. It is also possible to connect the parts and exhaust them together. The porous portion may be provided on the entire inner surface of the immersion nozzle, or may be provided inside the immersion nozzle in a three-layer structure as shown in FIG. Further, in order to prevent air from entering the immersed part, the lower end of the porous part is preferably immersed in molten steel, preferably having the structure shown in the first article. Also,
The inside of the T/D nozzle 2 and the S/N plates 3, 4.5 may be made porous and suction may be applied in the same manner.

The device of the present invention also has the advantage that each nozzle can be easily attached and detached.

Using the apparatus shown in Fig. 1, Ti-containing low-order aluminum killed steel is produced from a ladle of 200 tons per heat.

Ti-less low-order aluminum killed steel, 5US304.
T/D of Ti-containing low-order ferritic stainless steel and silicon steel
1 each through 60tT/D at molten steel superheating degree of 20~40°C
Continuous casting with 0 heat was performed. The exhaust pressure of the pump is 100 in It g, and the slab size is width '1
200 mm, thickness: 220 mm.

The casting components are shown in Table 1.

Table 2 shows a comparison with the conventional method for uniformly passing 31F molten steel per one immersion 1rI nozzle.

Table 2 *l　The conventional method is S/N∆ "blown, no seal.

*2 Passing amount when the nozzle passing amount in the conventional method is set to 1.

Here, the amount of molten steel passing through the conventional method is set as 1, and the amount of the method of the present invention is shown.

In addition, the results of comparing the number of non-metallic inclusions in the cross section of the slab C and the number of balls in the slab C section for low-order aluminum kill 1' steel are shown in the third section.
Shown in the table.

Table 3 Table 4 shows the incidence of blistering defects that occur during annealing. Table 5 shows the amount of N pick-up between the T/D and the mold (= inside the mold (N) - inside the T/D [N]). The results were expressed as an index and the comparison results were shown.

Table 5 *1 Values when the conventional method is set as 1.

The difference between the true nature of the amount of passage shown in Table 2 and the conventional method is that by preventing air intrusion, for case ■, 872 oz +
rhot reduction, case ■ is M2O, reduction, case ■
is Crypt, Ait (: h I decreases, case ■ is 81
tOs.

TiN reduction, case■ Ha! This is due to the reduction of aO,,S+Ot.

The difference in cleanliness shown in Table 3 is due to the same effect as above for the number of nonmetallic inclusions, and for the number of blowholes, due to the reduction in nozzle clogging, the difference in T/D and S/N etc. This is because the Ar-air blowing view can be reduced to 1/6 of the conventional one.

The differences shown in Table 4 are due to a significant reduction in the number of blowholes and the number of intervening particles.

The differences shown in Table 5 are due to the prevention of air infiltration.

<Effects of the Invention> According to the present invention, air entering from the joints of each nozzle or the cracks of the submerged nozzle can be prevented. 8 It was possible to prevent contact with the steel flow and reduce the number of nonmetallic inclusions and blowholes in the slab. As a result, immersion nozzle clogging is significantly reduced.
The blistering defects that often occur during conventional annealing can be reduced, and this greatly contributes to improving the small size and quality of continuously cast slabs.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view illustrating the main parts of one embodiment of the non-oxidation casting apparatus according to the present invention. 1...Tandateshiyu (T/r)), 2...T/
l) Nozzle, 3... S/N upper plate, 4...
・S/N middle plate, 5... S/N lower plate, 6... Banoni tongue, 7...? Jz? rl
Nozzle, 8... Porous part, 9... Molten steel, 10
...Space 11...Suction device, 12...
・Exhaust pipe, 13...mold, 14...
Fireproof walkway. Patent applicant: Kawasaki Steel Corporation Figure 1

Claims (1)

[Claims] 1. A method of continuously casting molten steel through a refractory passage formed by connecting a tundish nozzle, a sliding nozzle, and an immersion nozzle of a continuous casting device from above to below,
A non-oxidation continuous casting method, characterized in that continuous casting is carried out while exhausting air that has entered the interior or inner circumferential surface of the refractory passageway or the nozzle joints to the outside. 2. In a continuous casting device in which a tundish nozzle, a sliding nozzle, and an immersion nozzle are connected from above to below to form a fire-resistant passage for molten steel, there are A double packing is provided between each nozzle, and a space is formed between the double packing and each nozzle, and the inside or inner peripheral surface of the submerged nozzle is made porous over the entire length, and the upper end of the porous part is made porous. . An oxidation-free casting apparatus, characterized in that an exhaust pipe is connected to the space formed by the double packing, the sliding nozzle, and the immersion nozzle, and further connected to each of the spaces.