JPH0438503B2 - - Google Patents

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 circulation bodies in a continuous thin slab casting machine that directly produces thin slabs from molten metal. (Prior Art) Recently, various types of continuous casting machines (i.e., belt casters) have been used to continuously produce thin slabs such as sheet bars directly from molten metal (the following will be explained using the example of "molten steel"). something is proposed. Figure 3 shows a typical example. The illustrated synchronous belt caster is of a narrowing type, and has a plurality of guide rolls 3a each, while maintaining a distance for holding casting material such as molten steel or solidified shell over a predetermined distance. , 3b, 3c, the metal belts 1 and 2 support a pair of long side surfaces arranged opposite each other, and are in close contact near the side edges of each metal belt. A casting space is formed by confining the four sides of the short side plates 4 and 5 in the shape of a concave upper and lower side for supporting the short sides. When molten steel is supplied into the casting space from the immersion nozzle 6, the molten steel that comes into contact with the metal belts 1 and 2 cooled by the cooling pads 7a and 7b 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. The metal plate with the
A short side plate is disclosed in which a refractory is supported by a frame portion. In addition to supporting the refractory, the provision of the frame part is useful for
It is effective in promoting solidification in the corners of the casting space and preventing molten steel from penetrating between the short side plate and the metal belt, but it is disadvantageous for long-term casting because the refractory surface is extremely susceptible to erosion. It is. (Problem to be Solved by the Invention) It is advantageous that the refractory material in the center of the short side plate has high heat insulation properties and high thermal shock resistance. A mixture of boron nitride and boron nitride is suitable. However, when the entire refractory is made of a new material, the molten metal solidifies on the surface of the short side plate due to the high heat conductivity of the material, increasing the drawing resistance of the slab, and when the strength of the solidified shell is low, the shell It is difficult to apply because it has the disadvantages of rupture and eventual breakout, deformation of the frame holding the refractory due to its large coefficient of linear expansion, and high cost. Furthermore, when using a fused silica brick with low thermal conductivity as a refractory, the edges of the slab begin to solidify at the frame that holds the refractory, but the solidified layer also forms on the refractory surface. This solidified layer develops and easily scrapes off the refractory, eventually damaging the refractory, so it cannot withstand long casting. Note that solidification of molten steel on the refractory surface is unavoidable at the start of casting. That is, the temperature of the refractory at the start of casting is low and the molten steel once solidifies, which not only makes the initial casting operation unstable, but also significantly impairs the quality of the slab surface, which poses a particular problem. On the other hand, Japanese Patent Application Laid-Open No. 58-218356 discloses an effective means for preventing solidification on the surface of the refractory, which involves burying a heating element within the refractory and actively heating the refractory. Problems remain in terms of high costs and the risk of causing disasters such as electric shock. An object of the present invention is to propose a short side plate that can avoid wear of the refractory and 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 a mutual interaction between the circulating bodies. On the short side of the thin slab continuous casting machine, the casting space is constituted by a pair of short side side plates located on both side edges of the space, the short side plates having a concave shape with an upper width and lower width narrowed in the middle part. It has a frame part formed on both side edges that are in contact with the frame part, and a refractory supported between the frame parts, and the refractory has a heat-insulating refractory layer and a wear-resistant refractory layer provided on the heat-insulating refractory layer. This is a short side plate of a continuous thin slab casting machine, in which a heat-insulating refractory layer is further provided on the wear-resistant refractory layer at least in the area from just below the meniscus to the end of drawing. Here, the thermal conductivity of the insulating refractory is 0.002cal/
Materials with low thermal conductivity of cm・s・℃ or less are recommended.
For example, MgO board, SiO ₂ board, fused silica brick, etc. are suitable. In addition to the above-mentioned MgO board, SiO ₂ board, and fused silica brick, suitable materials for the heat-insulating refractory provided on the wear-resistant refractory layer include asbelt cloth, glass fiber cloth, and rock wool. The thickness is preferably 1 to 3 mm, because if it is less than 1 mm, the heat insulating effect will be insufficient, and if it exceeds 3 mm, the amount of slag will increase when melted. In addition, wear-resistant refractories have high corrosion resistance, spalling resistance, and mechanical strength, and the shore hardness of cast slabs immediately after casting is 10 or less, so it is preferable that the shore hardness is 10 or less. teeth
Materials having a shore hardness of 15 or more at 1200° C., such as silicon nitride, sialon, alumina, mullite, and zirconium boride alone, or a composite material of at least one of these and boron nitride, are advantageously suitable. (Function) The molten metal supplied to the casting space of the continuous thin slab casting machine is cooled on the long side by the circulating body and on the short side by the frame of the short side plate, thereby producing a solidified shell. Conventionally, when the solidified shell on the short side grows, it extends from the frame to the insulating refractory, and the solidified shell grows into a hollow shape with the same shape as the short side plate, so the solidified shell acts as an anchor and circulates. It remains in that position without being able to move along with the resistance, and eventually the shell that acts as an anchor grows to the bottom of the mold, leading to a breakout. Furthermore, when anchoring occurs, a solidification-delayed area is generated on the surface of the slab, causing surface cracks. Therefore, it is extremely effective to minimize the solidification on the short sides and prevent the formation of anchors in order to achieve stable operation. In the short-side side plate according to the present invention, first, a refractory that is a combination of a heat-insulating refractory layer and a wear-resistant refractory layer provided on the heat-insulating refractory layer is used. This refractory has excellent wear resistance, corrosion resistance, and spalling resistance on the surface that comes into contact with slabs and molten steel, and has high heat insulation properties on the back surface, resulting in low thermal conductivity overall. It is a high-strength refractory material. Therefore, wear is suppressed in the part that comes into contact with the solidification shell, furthermore, melting damage is prevented in the part that comes in contact with the molten steel, and solidification of the molten steel in this part is prevented to avoid the occurrence of anchors and achieve stable operation. Furthermore, in this invention, in order to deal with the situation at the initial stage of casting, at least an area on the wear-resistant refractory layer of the refractory from just below the meniscus to the end of the drawing,
That is, a heat insulating refractory layer (hereinafter referred to as surface layer) is provided on the surface that comes into contact with molten steel. This surface layer allows
At least in the initial stage of casting, the molten steel does not come into direct contact with the wear-resistant refractory layer, and solidification of the molten steel on the refractory surface can be avoided. That is, the surface layer that the molten steel comes into contact with has poor corrosion resistance but has a small heat capacity, so the molten steel does not solidify on this surface. In addition, as casting progresses, the surface layer is gradually eroded away, but at the same time, the wear-resistant refractory layer under the surface layer is sufficiently heated by heat transfer with the molten steel, so the entire surface layer is eroded away, making it resistant to corrosion. When the wear-resistant refractory layer and molten steel come into direct contact, the molten steel does not solidify on the wear-resistant refractory layer. (Example) FIG. 1 shows a short side plate according to the present invention. In the figure, 8 is a side plate main body having frame parts 9 on both side edges, 10 is a refractory supported by the frame parts 9, and 11
is a refrigerant passage through which water, etc. circulates. Refractory 10
A heat-resistant refractory layer 10a provided on the side plate main body 8 side and a refractory layer 1 provided on the heat-insulating refractory layer 10a.
0b and a heat-insulating refractory layer 10c provided on the wear-resistant refractory layer 10b. The surface of the frame portion 9 is sufficiently cooled by the cooling water flowing in the refrigerant passage 11, and is always given the necessary properties, namely high strength and high thermal conductivity, where the molten steel is cooled and a solidified shell is generated. . Further, the surface of the three-layer refractory 10 held in the frame portion 9 is in contact with molten steel, but since the surface layer of the refractory 10 has low thermal conductivity, the molten steel does not solidify in the refractory 10. The solidified shell generated in the frame portion 9 grows and partially extends to the surface of the refractory 10, but since the wear-resistant refractory layer 10b is formed on the surface layer of the refractory 10, this wear-resistant The refractory layer 10b is rarely scraped by the solidified shell. The thickness of the wear-resistant refractory layer 10b is 2 to 10 mm.
In other words, if it is less than 2 mm, it will be difficult to handle and cause problems such as cracking when subjected to thermal shock, and if it exceeds 10 mm, the shell will be damaged due to heat absorption in the refractory layer during the early casting stage. is generated, causing initial casting trouble. Note that it is important that the heat-insulating refractory layer 10c provided on the wear-resistant refractory layer 10b be provided in the area from just below the meniscus M to the narrowing end portion E, as shown in FIG. Next, 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. 1, low carbon aluminum killed steel was cast into a slab with a thickness of 25 mm and a width of 1350 mm at a casting speed of 12 m/min. In addition, the frame of the short side plate is made of Ag-containing Cu.
MgO is used for the heat insulating refractory layer 10a (15 mm thick).
The board is also coated with a wear-resistant refractory layer 10b (5mm thick)
Sialon-BN (20%) material was used for the material, and asbestos cloth was used for the heat insulating refractory layer 10c (2.0% thickness). The characteristics of each refractory are shown in the table below.

[Table] For comparison, similar castings were carried out using similar short side plates with refractories having a single layer structure of Sialon-BN material and a single layer structure of SiO ₂ material. The results of each casting are shown in Fig. 4 in terms of the relationship between the total casting length and the amount of erosion. When using _SiO2 brick as the refractory material for the short side plates, the amount of corrosion loss is 1 mm in castings with a casting length of 300 m or more.
reached close and led to a breakout. Furthermore, when the entire refractory was made of Sialon-BN material, the pull-out force of the slab increased from the early stage of casting, and breakout occurred at a casting length of 6 m. On the other hand, when the short side plate according to the present invention was used, stable casting was possible with almost no surface erosion. Although the above embodiment uses a twin-belt continuous casting machine, it can be applied to any other type such as a twin-roll type, as long as the short side plates are made of refractory material. (Effects of the Invention) According to the present invention, it is possible to suppress wear of the refractory and prevent solidification of molten metal on the surface of the refractory, thereby realizing an increase in continuous casting length and stable casting.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing short side plates according to the present invention, and FIG. 3 is an explanatory diagram of a belt caster.
FIG. 4 is a graph showing the relationship between the total casting length and the amount of erosion of the refractory. 1, 2...metal belt, 3a, 3b, 3c...
Guide roll, 4, 5... short side plate, 6... immersion nozzle, 7a, 7b... cooling pad, 8... side plate main body, 9... frame portion, 10... refractory, 10a,
10c...Insulating refractory layer, 10b...Abrasion-resistant refractory layer, 11...Refrigerant passage.

Claims (1)

[Scope of 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 positions on both side edges between the circulating bodies. Formed on both side edges in contact with the above-mentioned circulating body in the short side side plate of a thin slab continuous casting machine, which constitutes a casting space with a pair of short side side plates with a concave shape with an upper width and lower width narrowed at the middle part. The refractory includes a heat-insulating refractory layer, a wear-resistant refractory layer provided on the heat-insulating refractory layer, and a refractory supported between the frame parts. A short side plate of a continuous thin slab casting machine that is combined with an insulating refractory layer provided on the material layer at least in an area corresponding to the area from just below the meniscus to the end of drawing.