JPH02255253A - Short wall side plate for cast strip continuous casting machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a short side plate that forms a casting space together with a pair of circulating bodies in a continuous thin slab casting machine that directly produces thin slabs from molten metal. .

(Prior Art) Various types of continuous casting machines have recently been proposed for directly producing thin slabs such as sheet bars from molten metal (explained below using the example of "molten steel"). . For example, belt casters, block casters, twin roll casters, etc. are shown in FIG. 3 as a typical example.

The illustrated synchronous belt caster is of the narrowing type and is cast through a plurality of guide rolls 3a, 3b, 3c, respectively, while maintaining a gap for holding the cast material such as molten steel or solidified shell over a predetermined distance. metal belts 1.2 for supporting a pair of long side surfaces arranged opposite to each other for axial movement; The concave short side plates 4.5 on the upper and lower sides confine the casting space on four sides.

When molten steel is supplied into the casting space from the immersion nozzle 6, the metal belt 1 is cooled by the cooling pads 7a and 7b.
The molten steel that has come into contact with 2 is drawn downward while forming a solidified shell.

In order to delay solidification on the short sides, it is advantageous to form the inner surfaces of the short side plates in contact with the molten steel with a refractory material. This disclosure discloses a short-side side plate in which a refractory is supported by a frame part on a metal plate (cooled copper plate) having a frame part.

In addition to supporting the refractory, the provision of the frame is effective in promoting solidification in the corners of the casting space and preventing molten steel from entering between the short side plate and the metal belt.

(Problems to be Solved by the Invention) By the way, the formation rate of the solidified shell (short side shell) in the water-cooled picture frame, that is, the heat absorption rate in the picture frame, and the formation of the solidified shell (long side shell) in the metal belt. If the balance with the speed, that is, the heat absorption rate in the metal belt, is out of balance, and the growth of the long side shell is larger than the growth of the short side shell, casting can proceed because the long side shell pulls the short side shell together. . However, if the growth of the short-side shell is larger than that of the long-side shell, the sliding resistance between the short-side shell and the short-side side plate is large, so rupture occurs at the joint between the long-side shell and the short-side shell. The short side shell remains on the wall surface of the short side plate and continues to grow, and as this growth occurs, the fracture surface of the short side shell also moves toward the center of the long side of the mold, and finally breakout occurs. Even if breakout does not occur, surface defects such as double skin or surface cracks occur on the long side surface of the obtained slab.

Therefore, an object of the present invention is to propose a short side plate that can advantageously solve the problem caused by the difference in production speed between the short side shell and the long side shell.

(Means for Solving the Problems) The present invention provides a pair of circulating bodies disposed opposite each other that circulate while maintaining a gap for holding molten metal over a certain distance, and both side edges between the circulating bodies. In the short side plate of a continuous thin cast slab casting machine, the short side plate of the thin slab continuous casting machine constitutes a casting space, and the short side side plate is formed by a pair of upper wide and lower concave shapes located in the upper part and narrowed in the middle part. It is characterized by comprising a picture frame formed on the frame and a refractory supported between the picture frame parts, the picture frame being formed of a cooling metal plate from the upper end to the middle point and the rest made of refractory. This is the short side plate of a continuous thin slab casting machine.

In addition, in practice, it is advantageous to fix a thin metal plate to the surface of the frame made of refractory material that comes into contact with the circulating body.

(Function) The short side plate according to the present invention narrows down the frame portion in contact with a circulating body such as a metal belt, and consists of a cooling metal plate from its upper end to an intermediate point, that is, a cooling metal plate is used near the meniscus where molten steel begins to solidify. Since the part in contact with the remaining solidified shell is made of refractory material, the heat absorption rate in the picture frame can be reduced from top to bottom. Therefore, the growth of the short side shell is suppressed, and the growth of the long side shell is shortened. It becomes larger compared to the growth of the side shell.

(Example) FIG. 1 shows a short side plate according to the present invention.

In the figure, reference numeral 8 denotes a molten steel holding part which is approximately triangular in shape and has arcuate sides on both sides, and is composed of a frame part 9 provided on both side edges of the molten steel holding part 8 and a refractory 10 supported by the frame part 9. Further, 11 is a solidified piece holding part extending from the lower end of the molten steel holding part 8 with the same width;
12 is a refrigerant passage through which water and the like circulate.

The frame portion 9 is composed of a cooling metal plate 9A from the upper end of the molten steel holding portion 8 to an intermediate position of the narrowing portion, and the rest is made of a refractory 9B. In the illustrated example, the refractory 9B is integrated with the refractory 10. It will be set up. Note that the refractory 9B and the refractory 10 do not need to be provided integrally, and may be divided in the width direction or the casting direction and combined.

In addition, the range in which the refractory material 9B is provided in the frame portion 9 must be such that the solidified surface of the slab is reheated by the heat of the internal molten steel, and the length in the casting direction varies depending on the casting speed, but It is preferable to set the length to be such that the time required for the solidified shell (or circulating body) to pass through the portion is at least 0.2 seconds (general reheating time for sheet bar-like steel plates).

Here, the cooling metal plate 98 and the solidified piece holding part 11 are made of copper plates, etc., and the refractories 9B and 10 are made of MgO boards, etc.
Sialon, silicon nitride, zirconia, or composite materials with excellent corrosion resistance and hot abrasion resistance are each advantageously suitable.

The short side plate shown in FIG. 2 is an example in which a wear-resistant thin metal plate 13 is fixed to the surface of the refractory 9B of the frame portion 9 that comes into contact with the circulating body, which is advantageous for avoiding damage to the refractory 9B. be. Note that it is preferable that the thin metal plate be made of a metal that is softer than the material of the long side belt. Furthermore, in this example, it is important to suppress the formation of short side shells by making the thickness Tl+ of the thin metal plate 13 smaller than the width TA of the cooling metal plate 9A.
It is preferable that

Next, the growth of the solidified shell when using the short side plate described above will be described in comparison with the conventional short side plate.

FIG. 4 shows the growth of a solidified shell on the short side plate with the frame portion formed of a cooled metal plate.The short side shell 14 grows from the frame portion 9 of the cooled metal plate to the refractory 10, causing the so-called gill stretching phenomenon. It can be seen that this occurs.

This is difficult to avoid as long as heat transfer from the frame portion 9 to the refractory 10 exists. That is, as shown in the figure, when the solidified shell is drawn in A-B-C-D-+E, at a certain point, here, point E, the short side shells 14 that have grown from both sides come into contact and join together (this is This is called the anchor phenomenon, and the combined shell is hereinafter referred to as the anchor shell).

The thickness of the anchor shell 15 depends on the heat absorption rate at the frame portion, and becomes thicker as the short side shell grows larger. If the growth of the long side shell 16 at this time is small and the thickness is thin, it will be impossible to pull out the part of the anchor shell 15 on the refractory by the long side shell 16 synchronizing with the circulating body, A break 17 occurs on the side shell 16 side. Then, due to the breakage of the long side shell, the short side shell remaining on the short side plate surface grows further, and the fracture surface becomes the long side (circulating body).
It progresses to the center and leads to a breakout.

On the other hand, the growth of the solidified shell on the short side plate according to the present invention is as shown in FIG.
Although it is similar to the case shown in the figure, since the frame portion 9 provided after the 0 point is made of refractory material, the growth of the short side shell 14 after the 0 point is significantly suppressed. The shorter side shells 14 do not grow and join together. Moreover, even if an anchor shell is formed by combining, the anchor shell can be crushed and retracted by the long side shells because the thickness is extremely thin compared to the long side shells.

Furthermore, continuous casting using short side plates according to the present invention will be specifically explained.

Using the belt caster shown in Fig. 3 with the short side plate having the structure shown in Fig. 2, low carbon aluminum killed fi (50t) was cast at a casting speed of 5.10m/min to a thickness of 30mm and a width of 1000mm.
Casting was carried out 60 times to obtain a slab with a length of 300 m.

In addition, the frame part of the short side plate is composed of a cooled metal plate (99.9% Cu material) and a refractory material (MgO board), and the refractory material in the frame part and the refractory material between the frame parts are integrally formed. A thin metal plate (brass type) was fixed to the side of the refractory. Note that the width TA shown in the figure was 10 mm, the width TB was 1 to 11 mm, and the length was 50 mm.

The number of surface cracks per meter of length of the slab obtained by continuous casting under the above conditions was investigated over the entire length. The results are shown as average values in Table 1 along with the incidence of breakout.

For comparison, a similar evaluation was performed on a short side plate in which the entire frame portion was made of a cooling metal plate.

As is clear from the table, when the short side plate according to the present invention was used, the incidence of breakouts was reduced, and the surface cracking of the resulting product was also reduced. Note that this surface cracking was at a level that would not become a defect after the next step of hot rolling.

(Effects of the Invention) According to the present invention, it is possible to suppress the growth of so-called anchor shells in the solidification shell growth process, and to reduce the occurrence of breakouts and surface defects, thereby increasing the continuous casting length and achieving stable casting. It can be achieved.

[Brief explanation of drawings]

Figure 1 (a) to (d) and Figure 2 (a), (b)
is an explanatory view showing a short side plate according to the present invention, Fig. 3 is an explanatory view of a belt caster, and Figs. 4(a), (b) and 5(a), (b) are solidified shells on the short side plate. FIG. 1.2...Metal belts 3a, 3b, 3c"・Guide roll 4.5...Short side plate 6...Immersion nozzle 7a, 7b...Cooling pad 8... Molten steel holding part 9...・Picture frame
9A... Cooling metal plate 9B... Refractory
10... Refractory 11... Solidified piece holding part 1
2... Refrigerant passage 13... Metal thin plate 14.
...Short side shell 15...Anchor shell 16...
・Long side shell 17...Breakage (a) Fig. 1 Machiboshisho (b) Base 1μ Eibori Fig. 2 Ca) Fig. 4 (b) (a) Fig. 3 Fig. 5 (b) ( a)

Claims (1)

[Claims] 1. A pair of circulating bodies arranged opposite each other, which circulate while maintaining a gap for holding molten metal over a certain distance, and located on both side edges between the circulating bodies. In the short side plate of a thin slab continuous casting machine, which constitutes a casting space with a short side plate formed by a pair of upper and lower concave shapes narrowed at the middle part, a picture frame is formed on both side edges in contact with the above-mentioned circulating body. and a refractory supported between the picture frame parts, the picture frame part being made of a cooling metal plate from the upper end to the middle point, and the rest made of the refractory. The short side plate of the machine. 2. The short side plate according to claim 1, wherein a thin metal plate is fixed to the surface of the frame made of refractory material that comes into contact with the circulating body.