JPS63154245A - Continuous casting method for cast strip - Google Patents

Abstract

PURPOSE:To prevent breakout and roughness or cracking of cast strip surface by coating the molten metal surface poured in a casting space by plate-like or granular-like heat-insulating material. CONSTITUTION:Preceding the supplying of molten steel from pouring nozzle 8, beforehand after setting the heat-insulating material 12 composing of refractory board by wire 11 near the meniscus, the molten steel is poured into the casting space through the pouring nozzle 8. As the heat-insulating material 12 is brought into contact with the molten steel near the meniscus, the surface is prevented from contacting with the air, to execute the heatinsulation of molten steel surface. In this way, the development of oxidizing molten surface is prevented and the continuous casting is smoothly executed.

Description

Detailed Description of the Invention (Industrial Application Field) This specification describes a method for directly and continuously casting molten metal, such as molten steel, into thin slabs with a thickness of 50 mm or less. Preventing face peeling will be described below.

(Prior Art) Japanese Unexamined Patent Publication No. 58-38642 discloses a belt-type continuous casting machine having a casting space surrounded by a side plate and a circulating body as a movable support, that is, a belt.

In this belt-type continuous casting machine, heat is removed from the surface of the molten steel in the casting space by cooling through the belt, which is cooled by a cooling pad installed on the back of the metal belt, and by heat radiation from the molten steel itself. It is easy to cause so-called hot water surface skinning, where the water solidifies. In particular, if the surface of the molten steel near the molten steel injection nozzle solidifies, the nozzle will become clogged. On the other hand, if the temperature of the molten steel in the mold decreases, it becomes impossible to pour the molten steel for a long time, and in particular, anchors are formed due to the skin on the molten metal surface, making it impossible to pull out the slab.

Therefore, it was proposed to use a coating agent that has a high rate of slag formation as described in JP-A No. 60-9559, but due to the high casting speed, etc., it was not possible to convert it into slag, resulting in scum and unmolten coating. Powder gets caught in the metal belt, causing frequent slag bites, uneven cooling of the slab in the mold and breakouts occurring from insufficiently cooled areas, and cracks on the surface of the slab and irregularities on the slab. be the cause of something that occurs.

The above-mentioned problems similarly occur in a continuous casting machine for thin slabs in which a casting space is formed by a pair of rolls and a pair of side plates.

(Problems to be Solved by the Invention) Therefore, it is an object of the present invention to propose a continuous casting method that avoids the formation of a skin on the molten metal surface within the casting space.

(Means for Solving the Problems) The present invention provides a continuous casting machine in which a casting space is constituted by a pair of movable supports disposed opposite to each other and a pair of side plates disposed at both side edges of the movable supports. In this continuous casting method of thin slabs, the surface of the molten metal injected into the casting space is covered with a heat insulating material in the form of a plate or agglomerates.

Note that a belt, roll, etc. are suitable as the movable support.

Now, the continuous casting method according to the present invention will be explained using a belt type continuous casting machine shown in FIG.

In the figure, 1.2 is an opposing roller that moves circularly via a plurality of guide rolls 3a, 3b, 3c, 4a, 4b, and 4c while maintaining a gap for holding the molten steel and solidified shell over a predetermined distance. For example, a metal belt arranged in such a manner as to be in close contact with the belts 1 and 2 near the side edges of the belts 1 and 2 constituting the long sides of the mold,
A casting space 7 is constituted by the side plates 5 and 6 which constitute the short sides of the mold. In particular, the diameter of the injection nozzle 8 of the side plate 5°6 is approximately 1
00 mm or more, and the thickness of the thin slab 9 to be manufactured is 50 m.
m or less, it has an approximately inverted triangular shape that is wide at the top and gradually tapers toward the bottom, and has a constant width at the bottom, and is provided with refractory lining layers 5a and 6a.

A cooling pad 1o having a plurality of water supply ports and drainage ports is disposed on the back surface of the belts 1 and 2.

The water supply ports are arranged in rows corresponding to the width direction of the belt, the drain ports are provided in the next row, and the rows of water supply ports and the rows of drain ports are provided alternately in the casting direction. By causing the cooling water flowing out from the water supply port to flow into the drain port, a water film is formed between the belt 1 or 2 and the cooling pad 1o, thereby cooling and supporting the belt.

When continuously casting thin slabs using the above-mentioned continuous casting machine, first, before supplying molten steel from the injection nozzle 8, as shown in FIG. After the heat insulating material 12 is inserted, molten steel is poured into the casting space 7 through the injection nozzle 8.

['rThe heating material 12 comes into contact with the molten steel near the meniscus and prevents its surface from coming into contact with the atmosphere, thereby insulating the surface of the molten steel.

Therefore, the occurrence of skinning on the molten metal surface is prevented, and smooth continuous casting can be performed.

As shown in FIG. 3, refractory granules 13 may be used as a heat insulating material placed near the meniscus, and the molten steel surface may be insulated by uniformly distributing the refractory granules 13 over the area.

Furthermore, this invention is not limited to belt type continuous casting, for example,
In the twin roll type continuous casting shown in the figure, the same application is possible to the molten steel in the casting space 15 surrounded by the pair of rolls 14a, 14b and the side plates 5, 6.

(Function) When 80 tons of molten steel is continuously cast in one heat using a belt-type continuous casting machine, the molten steel surface is coated as follows (1) to (3).
) method was used.

(11 Method of adding the coating agent described in JP-A-60-9559 mentioned above: 43 heat (conventional example) (2) Method of coating with a heat insulating material of refractory board mainly composed of alumina = 47 heat (Compatible example 1) (3) Method of covering foamed alumina granules with uniformly dispersed heat insulating material = 45 heat (Compatible example 2) For continuous casting applying the above (1) to (3), each (I) ) The amount of molten steel passing through until the surface skin forms, and (b) the amount of cast slabs in 1,000 pieces.
It is shown in Table 1.

Table 1 Note) *: From the same table with the conventional example as 1, it can be seen that there is a great effect when this invention is applied. The difference between Compatible Example 1.2 and the conventional example in the same table (a) is the difference in heat insulation effect, and the difference in (b) is thought to be due to unevenness occurring on the surface of the slab due to entrainment of coating material in the conventional example. .

Incidentally, since plate-like or lump-like heat insulating materials are hard to wear out, solidified iron gradually adheres to them, but the method for removing it is as follows. That is, in the case of a plate-shaped heat insulating material, the plate-shaped heat insulating material is pulled up and removed using a wire, and then a new plate-shaped heat insulating material is inserted.

In this case, it is convenient to use a plate-shaped heat insulating material with a two-part structure. In the case of bulk and granular thermal insulation material, the iron-adhered bulk and granular thermal insulation material is scooped up and removed with a ceramic or coated metal ladle, and then a new bulk and granular thermal insulation material is placed on the surface of the molten metal.

During the experiment, the plate-shaped and granular insulation material adheres to the molten metal or the shell, causing defects in the slab, and greatly contributes to preventing the surface of the molten metal from forming around the injection nozzle.

(Example) 1 heat 80 tons of melt 14 (C: 0.04-0.0
6 wtX.

Si: 0.05 wtX or less, Mn: 0
．． 30-1.00 wtX, P: 0.010-0
．． 030 wtX, S: 0.010-0.03
0 wtX and Al: 0.03-0.06 wt
X) was injected into the casting space of the belt-type continuous casting machine shown in Figure 1 at a temperature of 1550 to 1565°C, and a thickness of 30 m was obtained.
A slab with a width of 1,200 mm and a width of 1,200 mm was produced as follows.

That is, while coating the molten steel surface with a refractory boat containing alumina as the main component, continuous groove formation was performed with 47 heats, and while coating the molten steel surface with foamed alumina granules (particle size of 0.5 to Immφ or more). Continuous casting was performed for 45 heats. There was no breakout in either continuous casting, and the amount of maintenance of the obtained slab was 0.0.
It was 15%.

(Effects of the Invention) According to the present invention, breakouts and irregularities and cracks on the surface of the slab can be prevented, the yield can be improved, and multiple continuous casting can be performed, resulting in great effects.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a belt-type continuous casting machine suitable for carrying out the present invention, Figs. 2 and 3 are explanatory diagrams showing the coating of the molten steel surface with a heat insulating material, and Fig. 4 is a twin-roll continuous casting machine. FIG. 1.2...Belts 3a to 3c, 4a to 4c...Guide rolls 5.6.
... Side plate 7 ... Casting space 8 ... Injection nozzle 9 ... Thin slab 10 ... Cooling pad
11...Wire 12...Insulating material 13.
...Refractory granules 14a, 14b...Roll 1
5...Casting space Figure 1 Figure 2 B

Claims (1)

[Claims] 1. Thin slabs are continuously produced by a continuous casting machine in which a casting space is formed by a pair of movable supports disposed opposite to each other and a pair of side plates disposed on both side edges of the movable supports. A continuous casting method for thin slabs, characterized in that during casting, the surface of the molten metal injected into the casting space is covered with a plate-shaped or block-shaped heat insulating material.