JPH01321047A - Short side plate in cast strip continuous casting machine - Google Patents

Abstract

PURPOSE:To prevent solidification of molten metal at refractory face, to increase continued length of casting and to enable stable casting by rising up refractory as almost triangular shape to casting space side in a short side plate and constituting mountain chain state projection part gradually reducing the height toward the cast strip drawing direction. CONSTITUTION:The side plate body 8 provides a frame part 9 at both edge parts and the projection part 10 is composed of the refractory supported with the frame part 9. The projection part 10 rises up as triangular shape in the horizontal cross sectional face and the height is formed to the mountain chain state gradually reducing toward the cast strip drawing direction. The frame part 9 is sufficiently cooled to the surface thereof with cooling water flowing in coolant passage 11 and there, molten steel is cooled to develop solidified shell. In casting space constituted with the short side plates, as the inclinations are mutually made reverse at center of the short sides and at the frame part, breakout caused by wedge effect developing with detachment of the solidified shell from the short side face or surface defect of the cast strip are prevented.

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) A continuous casting machine (which continuously manufactures thin slabs such as sheet bars directly from molten metal (explained below using the example of "molten steel"))
In other words, various types of belt casters have recently been proposed. Figure 2 shows 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 bells l-1 and 2 support a pair of long side surfaces that are arranged opposite to each other and move axially, and support a short side surface that is in close contact with each other near the side edges between the two metal belts. The upper and lower concave-shaped short side plates 4.5 are used to 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, which 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.

Here, to delay solidification on the short side, what about the short side plate? g
It is advantageous to form the inner surface in contact with Wf4 with a refractory material, and Japanese Patent Application Laid-Open No. 58-218360 discloses a method in which a metal plate is provided with a frame portion on the side edge in contact with a metal belt, and the refractory is supported by the frame portion. A short side plate provided therein is disclosed.

(Problem to be Solved by the Invention) Although it is preferable that there is no solidification of molten steel on the refractory surface at the center of the short side plate, it is difficult to completely prevent solidification of molten steel on the refractory surface. This is because when the temperature of the molten steel supplied into the casting space is low or when the flow rate of molten copper near the refractory surface is slow, a solidified shell develops on the refractory surface due to heat transfer from the molten steel to the refractory surface. Because it does. The solidified shell, which has become sufficiently thick, is captured by the shell generated on the frame of the short side plate or by the long side shell and pulled downward, but at this time, the shell generated on the refractory surface (the short shell formed on the frame) When the thickness (including the amount of side shells) grows thicker than the final thickness of the slab, it becomes dendritic. When the dendritic shell is low in strength, it is easily crushed, but when the strength is high, the metal belt on the long side is pushed outward, creating a gap between the belt and the short side plate, and molten steel enters this gap. This leads to the insertion of bullion. In any case, the short side plate is restrained and only the metal belt moves, resulting in a serious operational failure leading to breakout or belt breakage directly below the short side plate. Another problem is that when the generated shell moves down the short side surface, scratches occur on the short side, shortening the life of the short side.

On the other hand, Japanese Unexamined Patent Publication No. 58-218356 discloses an effective means for preventing solidification of refractories by burying a heating element in the refractories to actively heat the refractories. However, problems remain in that it is costly and may lead to disasters such as electric shock.

An object of the present invention is to propose a short side plate that can avoid solidification of molten steel on the refractory surface.

(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, which constitutes a casting space with a pair of short side side plates having a concave shape with an upper width and a lower width located at the top, a picture frame portion formed on both side edges in contact with the above-mentioned circulating body. and a refractory supported between the frame parts, the refractory forming a mountain-like protrusion that protrudes toward the casting space side in a substantially triangular shape and whose height gradually decreases in the slab drawing direction. This is the short side plate of a single slab continuous casting machine.

Further, in practice, it is advantageous that the portion of the short side plate facing the casting space excluding the refractory has a taper such that the casting space narrows in the direction of drawing the slab.

(Function) The short side plate according to the present invention has a casting space in which the wedge shape is easily crushed even if the shape of the solidified shell becomes a pattern by making the refractory protrude toward the molten steel, and the protruding part of the refractory The horizontal cross section of the solidified shell is made into a substantially triangular shape to avoid damage to the short side plate, which occurs frequently when the solidified shell is drawn downward, and the protrusion at the center of the protrusion (the apex angle of the substantially triangular shape in the horizontal cross section) prevents the flow of molten steel. When it hits a protrusion, it prevents the formation of a solidified shell at the center of the short side plate and prevents the formation of a wedge, thereby realizing stable continuous casting.

In addition, the surface of the short-side side plate excluding the refractory material is tapered so that the casting space narrows in the direction of slab withdrawal, which minimizes the gap between the solidified shell that has grown in the frame and the short-side side plate, allowing the molten steel to This is advantageous in preventing the occurrence of paris due to the intrusion of foreign substances.

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

In the figure, reference numeral 8 denotes a side plate main body having a frame portion 9 on both side edges, 10 a protrusion made of refractory material supported by the frame portion 9, and 11 a refrigerant passage through which cooling water and the like circulate.

The protrusion 10 has a raised triangular horizontal section, and
As shown in the AA and BB cross-sectional views, it is formed in the shape of a mountain range whose height gradually decreases in the slab drawing direction (downward). Therefore, the protruding portion 10 is given a positive taper of δI/21 in the slab drawing direction, as shown in the CC cross-sectional view.

On the other hand, the surface of the side plate main body 8 excluding the protrusion 10 that contacts the molten steel has a reverse taper of δ2/12 in the slab drawing direction corresponding to the amount of shrinkage on the long side of the solidified shell, as shown in the CC cross-sectional view. It is granted.

The surface of the frame portion 9 is sufficiently cooled by the cooling water flowing in the refrigerant passage 11 and maintained at high strength and high thermal conductivity, and the molten steel is cooled here to form a solidified shell. Here, in the casting space formed by the short side plates in Figure 1, the taper at the center of the short side and the frame part is reversed, so breakage due to the drafting effect caused by the separation of the solidified shell from the short side surface occurs. Outs or defects on the surface of the slab are eliminated.

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

Using the belt caster shown in FIG. 2 and the short side plate shown in FIG. 1, low carbon aluminum killed steel was cast into a slab having a thickness of 30+++ m and a width of 1200 mm at a casting speed of 12 m/min.

The protruding portions of the short side plates were made of fused siliceous bricks, and the dimensions in the cross-sectional view taken along line CC in FIG. 1 were as follows.

Record L = 65 cm 1 g = 100 cm δ + = 35 + nm δ2 = 12 Continuous casting for 1゛ heat (600 m) was carried out under reasonable conditions, and the operation was always stable and there was no breakage of the solidified shell. The surface quality of the slab was also good.

(Effects of the Invention) According to the present invention, it is possible to prevent solidification of molten metal on the refractory surface, thereby realizing an increase in continuous casting length and stable casting, and also achieving improvement in the surface properties of the obtained slab.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a short side plate according to the present invention, and FIG. 2 is an explanatory diagram of a belt caster. ■, 2...Metal belts 3a, 3b, 3c...Guide rolls 4.5...
Short side plate 6...Immersion nozzle 7a, 7b...
Cooling pad 8...Side plate body 9...Picture frame part
10... Protrusion 11... Refrigerant passage

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 side plate of a continuous thin slab casting machine that constitutes a casting space with a pair of short-side side plates that have a concave shape with an upper width and lower width, a frame portion formed on both side edges in contact with the above-mentioned circulating body, and this frame portion. A continuous thin cast slab is provided with a refractory supported between the casting spaces, and the refractory forms a mountain-like protrusion that protrudes toward the casting space in a substantially triangular shape and whose height gradually decreases in the direction of slab withdrawal. The short side plate of the casting machine. 2. The short side plate according to claim 1, wherein the portion of the short side plate on the surface facing the casting space excluding the refractory has a taper such that the casting space narrows in the slab drawing direction.