JPH0451259B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a twin-belt continuous casting machine, and more particularly to an improvement in equipment for continuously casting thin slabs using an inclined twin-belt overflow trough. [Prior art and its problems] As shown in Fig. 6, conventionally, in this type of twin-belt continuous casting machine, molten steel 1 is injected into the meniscus portion 4 on the twin belt 3 through the overflow gutter 2. is proposed, and by such proposal,
This prevents the formation of slabs solidified in two stages as in the past, thereby preventing double skin, and also preventing the meniscus portion 4.
This prevents the molten steel 1 from entraining air and causing poor surface texture of the slab (Japanese Patent Laid-Open No. 58-218361). According to this proposal, the molten steel 1 is transferred to the meniscus portion 4.
When injecting the molten steel 1, it is explained that the surface condition of the molten steel 1 existing in the meniscus portion 4 (therefore, prevention of surface defects) should be taken into account. The factors are the depth h of the meniscus part 4 at the position where the molten steel 1 flows down, the head difference H, the width of the injection flow (meniscus part 4
The lower width of the molten steel 1 in FIG. 6 is defined as the length in the direction perpendicular to the plane of the paper in FIG. By the way, such a proposal does not disclose a means for controlling, in an actual machine, the various factors that influence the surface condition of the molten steel 1 in the meniscus portion 4. [Means for Solving the Problems] Therefore, the present inventor has decided to control the above-mentioned factors all at once in order to obtain a good surface condition of the molten steel 1 in the meniscus portion 4 in an actual twin-belt continuous casting machine. As a result of searching for a means to achieve this, it was possible to achieve the desired state simply by controlling the inclination angle of the twin belts, that is, the casting angle, and this is provided here as an invention. That is, a thin slab is continuously cast using a twin belt overflow gutter, and the upper belt of the twin belt is slightly shifted parallel to the lower belt in the casting direction to form a space at the end above the lower belt.
The above-mentioned overflow gutter is installed in the space, and the twin belt is tilted to configure the meniscus depth at the position where molten steel flows down from the overflow gutter to be 15 to 20 mm or more depending on the thickness of the slab. In a twin-belt continuous casting machine that allows the casting angle to be changed within a maximum range of 15°, the support part of the slab following the twin belt curves the pass line and horizontally casts it according to the change in the casting angle of the twin belt. To provide a twin belt type continuous casting machine characterized by having a device for conveying in the direction. [Example] Hereinafter, the structure of the present invention will be explained in detail with reference to an example shown in the accompanying drawings. Slab thickness of this example: 30 to 50
This equipment continuously casts thin slabs with a slab width of 450 to 2000 mm at a high speed (10 m/min). Hot water is supplied to caster 14 via 13. The tundish 13 is provided with an overflow gutter 2 and is set horizontally. The overflow gutter 2 has a flat lip. The caster 14 is composed of twin belts, and the upper belt 15 is parallel to the lower belt 16 and slightly shifted in the casting direction (to form a pool length L), and a space 17 is formed at the upper end of the upper belt 15. , the overflow gutter 2 is provided in the space 17.
The caster 14 is provided with dam blocks (not shown) on both sides of the upper and lower belts 15 and 16 in the width direction, and is mounted on the continuous casting machine frame 18 so as to be tiltable as a whole. Reference numeral 19 denotes a secondary cooling section composed of a roller apron, in which the slab is pulled out while being cooled with spray water, and solidification is completed up to the center of the slab before the pinch rolls 20. 21 indicates a torch cutter, and 22 indicates a piler. Here, in the caster 14, as shown in FIG. Set the hot water level position to S (constant)
According to the actual machine test of the continuous casting machine, as explained in the above proposal, the meniscus depth h should be increased to prevent internal defects and surface defects in the slab.
It turned out that it was necessary to secure at least 15 to 20 mm. Note that the injection flow and the pulley interval Z are constant. In order to increase the meniscus depth h, it is possible to plunge the molten steel deep into the space 17 of the overflow gutter 2 or increase the amount of molten steel, but by setting the pouring angle θ small, As shown in Table 1, the meniscus depth h can be increased. Table 1 shows the relationship between slab thickness and pouring angle θ.

【table】

[Function and effect of the invention]

Adjust the pouring angle within a maximum of 15° according to the thickness of the slab.
By making appropriate selections, we were able to minimize the negative impact on slab quality caused by the falling flow of hot water in the twin-belt overflow trough. For example, when pouring into a slab with a thickness of 50 mm and pouring into a meniscus depth of 20 mm and pouring into a 10 mm depth, the amount of wrinkles on the slab surface is reduced by 70%.
In addition, there was no more double skin. In addition, the amount of blowholes generated in internal quality is 1/
The number of impurities and inclusions was significantly reduced to 10 or less. On the other hand, it has also become possible to eliminate local dents on the surface caused by local solidification delay of the slab due to partial separation of the casting shell and twin belt. This is because the falling flow from the overflow gutter is injected into the deep part of the meniscus, so it can absorb the falling energy and does not dissolve the initial solidified shell that has started to grow on the lower belt surface. This is because the minute velocity of the downstream flow inside the caster was suppressed, allowing air bubbles and impurities to float to the meniscus surface. In particular, according to the present invention, even if the casting angle of the twin belt is changed, a smooth pass line corresponding to the casting angle can be obtained up to the part where the slab is conveyed in the horizontal direction following the twin belt. without compromising the quality of the product.

[Brief explanation of drawings]

Fig. 1 is an overall side view of an embodiment of the present invention, Fig. 2 is a detailed view of the main part of Fig. 1, Fig. 3 is a detailed view of another main part of Fig. 1, and Fig. 4 is a detailed view of the main part of Fig. 3. Diagram showing transition, 5th
The figure shows a more detailed view of the main part of FIG. 3, and FIG. 6 shows a side view of the conventional example. 2... Overflow gutter, 15... Upper belt, 16...
Lower belt, 17... Space, h... Meniscus depth, θ
...Cast angle.

Claims (1)

[Claims] 1 Thin slabs are continuously cast using a twin belt overflow gutter, and the upper belt of the twin belt is slightly shifted parallel to the lower belt in the casting direction, a space is formed at the end above the lower belt, and the space is The above-mentioned overflow gutter is temporarily installed in the slab, and the casting angle is formed by slanting the twin belt in order to configure the meniscus depth at the position where molten steel flows down from the overflow gutter to 15 to 20 mm or more depending on the thickness of the slab. In a twin-belt continuous casting machine that can change the casting angle within a maximum range of 15 degrees, the support part of the slab following the twin belt bends the pass line horizontally in response to changing the casting angle of the twin belt. A twin belt continuous casting machine characterized by having a conveying device.