JPS61144246A - Method and machine for continuous casting by belt type continuous casting machine - Google Patents

Abstract

PURPOSE:To improve the quality of a billet by providing electromagnetic induction coils to the position of short side walls and generating horizontal turbulent flow in a molten metal. CONSTITUTION:Metallic belts 1, 2 are rotated and moved respectively by means of plural pieces of guide rolls 3a, 3b, 3c and constitute a casting space together with the short side walls 4, 5. The electromagnetic induction coils 7 are disposed to the outside of the walls 4, 5 to generate the horizontal turbulent flow in the molten steel introduced through a pouring nozzle 6 into the casting space. The solidified shell is formed to the specified thickness in all parts and the front face of the solidified shell is subjected to a cleaning effect when the molten steel is stirred. The capturing of foam is therefore prohibited and the generation of pinholes and blowholes is drastically decreased. The growth of dendrite and the generation of segregation are decreased and the quality of the billet is improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a continuous casting method using a belt-type continuous casting machine and an apparatus used in the method, and relates to a continuous casting method for casting molten metal, especially molten steel, to a thickness of 50 mm or less. It belongs to the field of so-called 6-belt casters, which directly and continuously manufacture sheet bar-shaped thin slabs, and in particular cast slabs by applying electromagnetic induction to the molten steel pool and stirring the molten steel. This paper also proposes a technology to accelerate solidification speed and improve continuous efficiency.

(Prior art) There are various types of continuous casting machines, or "belt casters", that continuously manufacture W4 plates such as sheet bars directly from molten steel, and the one shown in Figure 1 is a representative one. This is an example of something like this. In other words, a metal belt supports a pair of opposing long side surfaces that move circularly via guide rolls while maintaining a gap (casting space) for holding casting materials such as molten steel or solidified shell over a predetermined distance. and a fixed short side wall for the short side surface which is located between the noble metal belts and in close contact near each side edge, thereby confining the casting space on four sides.

The above-mentioned belt caster injects molten steel into the casting space and pulls out the solidified slab from below, but since the back side of the above-mentioned metal belt is cooled by a running film of cooling water spouted from a cooling pad, Molten steel that comes into contact with the cooling belt immediately forms a solidified shell, which gradually grows and thickens to become a slab.

At this time, in the case of such a belt caster, there is a tendency that voids are likely to be formed between the generated solidified shell and the metal belt. As the thickness of the void increases, heat removal from the molten steel becomes worse and the formation of a solidified shell becomes slower. Therefore, it is necessary to suppress this void formation to a slight extent. In addition, in the case of cough heel casters, a gap is created during casting between the metal belt used to form the long side and the wall for the short side, and by inserting molten steel into this gap, the end of the slab is cast. It had the disadvantage that it could be stretched. In extreme overcast conditions, this part becomes a binding point and causes breakouts. In particular, compared to the copper molds etc. used in regular type continuous casting machines, there is a greater risk of molten steel being inserted into the gaps in belt-type continuous casting machines, and once molten steel is inserted, it may affect subsequent gaps above. There is a tendency to induce the following insertions, and measures to prevent this are particularly important.

Now, there are problems such as the formation of voids in contact with the solidified shell, which deteriorates quality, and the method of creating a horizontal flow of molten steel near the copper mold by electromagnetic stirring in normal continuous casting, which is not conventionally belt-type. For example, Special Publication No. 54-37086,
Special Publication No. 57-48305 or Japanese Patent Publication No. 54-651
No. 32, No. 55-64953, No. 56'-3453, No. 56-4356, No. 56-139262, No. 5
No. 6-139265, No. 57-188646, No. 58
-100954, 58-100955, 59-
No. 33061, No. 59-39454, No. 59-853
No. 53, etc., had overcome it. However, these prior technologies
All of these are applied to regular continuous casting molds, not so-called belt casters.

(Problem to be solved by the invention) Normally, in the case of a continuous casting mold, both the long side and the short side of the mold have a fixed structure, and are made small enough to prevent molten steel from being inserted. It is. However, since belt casters are a combination of a stationary short side wall and a moving metal belt on the long side, it is natural that the belt caster requires much more effort than a regular continuous casting mold. It becomes something big. Therefore, as mentioned above, a phenomenon peculiar to "belt casters" occurs in which molten steel enters the gap between the two and cast tension occurs at a part of the corner of the slab, and this must be overcome.

Further points to be solved by the present invention are to remove bubbles generated during solidification to eliminate bubble defects on or near the surface of the slab, to promote the floating of inclusions, and/or to prevent resin formation at the solid-liquid interface. By inhibiting the growth of crystals, it promotes the generation of equiaxed crystals and also reduces segregation and negative segregation within the slab.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention firstly transfers molten metal to a pair of circularly moving long side surfaces in which portions for receiving casting material are disposed opposite to each other. A belt-type continuous casting machine that injects slabs into the casting space created by the combination of a metal belt and a pair of fixed short walls that are in close contact between them, and draws slabs directly from below. A continuous casting method using a belt continuous casting machine, characterized in that during continuous casting, casting is performed in a state where a horizontal stirring flow is generated in the molten metal in the casting space by electromagnetic induction from the position of the short side wall. I would like to make a suggestion.

Second, a pair of long-side metal belts that move in a rotating manner and have portions that receive casting materials arranged opposite each other;
In a belt-type continuous casting machine in which a casting space is formed by combining these metal belts with mutually fixed short side walls, each of the short side walls is made of a non-magnetic material, and inside or outside of the short side walls there is a This paper proposes a belt-type continuous casting machine that is equipped with an electromagnetic induction coil that generates a horizontal stirring flow in molten steel.

By using the above method and a continuous casting machine, it is possible to obtain slabs of excellent quality with good slab shape, no occurrence of cast sagging, and less segregation, etc., as well as improve continuous casting efficiency. .

(Function) In the case of continuous casting using the belt caster according to the present invention, since the casting space is formed by the moving metal belt and the fixed short side wall, molten steel is likely to be inserted from the joint between the two. When molten steel enters the joint surface between the two, (1)
Problems occur such as the shape of the molten steel deteriorates and (2) when the amount of molten steel infiltrated is large, it becomes impossible to pull it out downward.

Therefore, the inventors of the present invention have studied various ways to keep the shape of the slab constant and prevent overcasting, and found that it is best to apply electromagnetic force from both short sides and rotate the molten steel in a constant direction within the mold. Experiments have shown that horizontal rotation perpendicular to the casting direction is particularly effective.

It has also been found that in order to effectively apply a magnetic field to molten steel, it is sufficient to use a nonmagnetic material such as austenitic stainless steel, high Mn nonmagnetic steel, or ceramics on the short sides.

Furthermore, by stirring the molten steel, the solidified shell that is being formed is formed with a constant thickness regardless of the location, so that the heat removal becomes constant. Moreover, as an additional effect, the solidification front receives the cleaning effect of electromagnetic stirring, which prevents the trapping of air bubbles and dramatically reduces the number of pinholes and blowholes on the surface layer of the cast slab, producing slabs with excellent internal quality. I also found that I could get it.

(Example) The first figure shows one of the preferred embodiments of the present invention, and shows a synchronous belt type continuous casting machine: a so-called belt caster, and particularly a squeezing type one. To explain its structure, while maintaining a gap to hold cast materials such as molten steel and solidified shell over a predetermined distance,
A plurality of guide rolls 3a, 3b, 3c, and 3a, respectively.
, 3b, 3c for supporting a pair of opposing long side surfaces, and a short side surface that is in close contact with each other near the side edges between the two metal belts. Fixed type short side walls 4 and 5 are used to confine the molding space on four sides to form a casting space. In particular, the short side wall 4°5
In order to obtain a thin plate with a thickness of 30 mm or less, considering the diameter of the injection nozzle 6 (approximately 100 mm + <), it is a substantially inverted triangular shape that is wide at the top and gradually tapers toward the bottom and has a constant width. Preferably, a structure using a non-magnetic material and having at least a refractory lining layer is suitable.

Electromagnetic induction coils 7 are disposed outside (or may be embedded inside) both short side walls 4 and 5 in order to generate a horizontal circulation flow for the molten steel introduced through the injection nozzle 6. Then, the molten steel in the casting space is stirred electromagnetically. As for the stirring method, any type that generates a horizontal stirring flow is fine;
A method using a moving magnetic field or a silent magnetic field monitoring method are used.

Next, a casting example will be described.

Heat 5 tons of molten steel (C10,04F%, 5t10
．． 2%.

Mn10.3%, Plo, 02%, S10.015
χ, ^110.04χ) was injected into a belt caster as shown in Figure 1, and the thickness was 30 mm, the width was 600 mm, and the length was about 1.
A 0m thin steel piece was cast.

At that time, austenitic stainless steel 5US304 was used for both short side walls. The electromagnetic force from this short side is 3
Hz, 800 A and 4 Hz, 650 A, and compared with cases where no electromagnetic stirring was performed. The application of electromagnetic force at this time was adjusted so that the maximum flow velocity was 200 mm below the meniscus. The molten steel flow was rotated horizontally perpendicular to the pouring direction.

Table 1 shows a comparison of slab properties with and without electromagnetic force. As a result, it was revealed that when electromagnetic force is used as in the present invention, slabs with stable quality can be obtained. ' It was found that the solidification rate constant k (mm/min!4), which is expressed by the relationship between the solidified shell thickness d and the solidification time t, was improved by about 10% by applying electromagnetic force, and the amount of casting could also be increased.

(Effects of the Invention) As described above, according to the present invention, molten steel does not leak from the joint surface between the metal belt and the short side wall, and the solidification rate can be quickly stopped to improve continuous casting efficiency. Furthermore, the occurrence of bubble defects, resinous crystal growth, and segregation caused by stirring work can be reduced, and thin slabs of good quality can be produced.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing a belt type continuous casting machine suitably used for carrying out the present invention. 1, 2... Metal belt 3... Guide roll 4.
5... Short side wall 6... Injection nozzle 7... Electromagnetic induction coil

Claims (1)

[Scope of Claims] 1. A pair of metal belts for circularly moving molten metal, the parts of which receive casting material being disposed opposite each other;
Continuous casting using a belt-type continuous casting machine that injects into the casting space created by the combination of a pair of fixed short side walls that are in close contact between them, and draws the slab directly from below. A continuous casting method using a belt continuous casting machine, characterized in that casting is performed in a state where a horizontal stirring flow is generated in the molten metal in the casting space by electromagnetic induction from the position of the short side wall. 2. Belt-type continuous casting in which a casting space is formed by combining a pair of rotatably moving long-side metal belts with opposing parts for receiving casting material and short-side walls that fix the metal belts to each other. The machine is characterized in that each of the short side walls is made of a non-magnetic material, and an electromagnetic induction coil that generates a horizontal stirring flow in the molten steel in the casting space is disposed inside or outside the short side walls. Belt type continuous casting machine.