JPH02147151A - Short side plate in strip continuous casting machine - Google Patents

Abstract

PURPOSE:To increase continued length of life in continuous casting and to realize the stable casting by supporting refractory between both frame parts formed at both edge parts contacting with circulating body and constituting the refractory of assemble of a heat insulating refractory and a wear resistant refractory. CONSTITUTION:Molten metal is held with one pair of the facing arranged circulating bodies and one pair of short side plates positioned at both edge parts between of them to form strip continuous casting machine by constituting the casting space. In this short side plate, the refractory 10 is supported with both frame parts 9 formed at both end parts contacting with the circulating body. The refractory 10 is constituted with the assemble of the heat insulating refractory layer 10a and the wear resistant refractory layer 10b arranged on this.

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 3 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 belts 1.2 for supporting a pair of long side surfaces arranged opposite to each other for axial movement; The upper and lower sides are concave-shaped short side plates 4.5 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.

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 plate in which a refractory is supported by a frame part on a metal plate having a frame part.

In addition to supporting the refractories, providing 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. The melting loss on the surface is extremely large, making it disadvantageous for long-term casting.

(Problem B to be solved by the invention) It is advantageous for the refractory material in the center of the short side plate to have high heat insulation and thermal shock resistance, and specifically, it is made of fused silica and new materials such as silicon nitride, sialon or A mixture of these and boron nitride is suitable.

However, if the entire refractory is made of a new material, the molten metal will solidify on the surface of the short side plate due to the material's high heat conduction, increasing the drawing resistance of the slab, and if the strength of the solidified shell is low, the shell will 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 that the cost is high and there is a 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 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. The refractory is a combination of a heat-insulating refractory layer and a wear-resistant refractory layer provided on the heat-insulating refractory layer. Continuous casting of thin slabs in which an insulating refractory layer is further provided on the short side plate of the continuous thin slab casting machine and the wear-resistant refractory layer of the refractory, at least in the area from just below the meniscus to the end of drawing. This is the short side plate of the machine.

Here, the heat insulating refractory has a thermal conductivity of 0.002 Cal/
A material with a low thermal conductivity of cm・SpaC or less is recommended, such as MgO board, 5iOz board, fused silica brick, etc.

In addition to the above, asbestos cloth, glass fiber cloth, rock wool, etc. are suitable as the heat-insulating refractory provided on the wear-resistant refractory layer. The thickness is preferably 1 to 3 mm, because if the thickness is less than 1 mm, the heat insulating effect will be insufficient, while 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 since the Shore hardness of the slab immediately after casting is 10 or less, it is only necessary to have a Shore hardness of 10 or less. Preferably, a material having a Shore hardness of 15 or more at 1200°C, such as silicon nitride, sialon,
Alumina, mullite, and zirconium polide 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 caster is
The long side is cooled by the circulating body and the short side is cooled by the frame of the short side plate to form 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. Unable to move with the body, it remains in that position, and eventually the anchor shell 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, a two-layer refractory structure consisting of a heat-insulating refractory layer and a wear-resistant refractory layer provided on the heat-insulating refractory layer is used. This refractory is
The surface that comes into contact with the slab and molten steel has excellent wear resistance, corrosion resistance, and spalling resistance, and the back surface has high heat insulation properties, making it a high-strength refractory with low thermal conductivity overall. It becomes. Therefore, wear is suppressed in the part that comes into contact with the solidified shell, and furthermore, corrosion 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.

In addition, there is a short side plate provided with a heat insulating refractory layer (hereinafter referred to as the surface layer) on the wear-resistant refractory layer of the refractory at least in the area from just below the meniscus to the end of the narrowing, that is, on the surface in contact with molten steel. does not directly touch the wear-resistant refractory layer at least in the initial stage of casting, and can avoid solidification of molten steel on the refractory surface.

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 and the wear-resistant refractory layer is sufficiently heated. When the 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, reference numeral 8 indicates a side plate main body having frame portions 9 on both side edges, reference numeral 10 indicates a refractory supported by the frame portions 9, and reference numeral 11 indicates a refrigerant passage through which water or the like circulates. The refractory 10 is formed by combining a heat-insulating refractory layer 10a provided on the side plate main body 8 side and a wear-resistant refractory layer 10b provided on the heat-insulating refractory layer 10a.

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. . Furthermore, the surface of the two-layer refractory 10 held in the frame portion 9 is in contact with the molten steel;
Since the thermal conductivity is low, solidification of molten steel does not occur 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, the refractory 10 It is rarely scraped by the solidified shell.

The thickness of the wear-resistant refractory layer 10b is preferably 2 to 10 mm; that is, a thickness of less than 2 ffI11 is difficult to handle and may cause problems such as cracking when subjected to thermal shock; If this is exceeded, a shell will be formed on this surface due to heat absorption in the refractory layer in the early stage of casting, causing trouble in the early stages of casting.

Furthermore, FIG. 2 shows a short side plate according to the present invention in which a heat-insulating refractory layer 10c is provided on a wear-resistant refractory layer 10b. The figure shows an example in which a heat insulating refractory layer 10c on the surface is disposed in a region from just below the meniscus M to the narrowing end portion E.

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

The belt caster shown in Fig. 3 was used with the short side plate having the structure shown in Fig. 1, and low carbon aluminum killed steel was cast at a speed of 12 m/min.
It was cast into a slab with a thickness of 25 mm and a width of 1350 ma+. In addition, the frame part of the short side plate is made of Ag-containing Cu material, and the heat-insulating refractory layer (15 mm thick) is made of MgO board.
Furthermore, the wear-resistant refractory layer (5 mm thick) is made of Sialon-
BN (20%) material was used in each case. The characteristics of each refractory are shown in the table below.

For comparison, the single layer structure of Sialon-BN material and SiO
□Similar castings were also made using similar short side plates with a single layer of refractory 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 Sin and quality brick as the refractories of the short side plates, the amount of corrosion loss reached almost 100m in casting lengths of 300 m or more, leading to a breakout. When using 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, a refractory material with Sialon-BN material on the surface and MgO board on the front was used. When using the short side plate, stable casting was possible with almost no surface erosion.

In addition, asbestos cloth (2.0 Ita thickness) was further set on the surface of the refractory having the above structure as a heat insulating refractory layer according to Fig. 2, and low-order aluminum killed steel was cast at a casting speed of 10 m/min and a molten steel temperature in the mold of 1568 m/min. A slab with a thickness of 30 mm and a width of 1350 mm was cast at °C. For comparison, similar casting was also carried out using short side plates without asbestos cloth set.

As shown in FIG. 5, a thermocouple 12 was embedded at a position 1.5 mm below the surface of the wear-resistant refractory layer 10b, and the temperature at this position was measured. The measurement results are shown in FIG. In the figure, ■ indicates the case where asbestos is not set, and ■ indicates the case where asbestos cloth is set, and both eventually reach the same temperature about 14 seconds after the start of casting, but in ■, the temperature is the same after 9 seconds after the start of casting. Up to a certain degree, the insulation effect is large, so there is no solidification shell formation on the refractory surface.
On the other hand, in case ■, some solidification was observed within 5 seconds from the start of casting.

Although the above embodiment uses a twin-belt continuous casting machine,
In addition, it can be applied to any twin-roll ring type ring short-side side plate 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 the drawing]

Figures 1 and 2 are explanatory diagrams showing short side plates according to the present invention; Figure 3 is an explanatory diagram of a belt caster; Figure 4 is a graph showing the relationship between the total casting length and the amount of erosion of refractories; The figure is a side sectional view of the short side plate, and Figure 6 is a graph showing the temperature of the refractory during casting. 1.2...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... Refractories 10a, 10c... Insulating refractory layer 10b... Wear-resistant refractory layer 11... Refrigerant passage 12... Thermocouple patent applicant Kawasaki Steel Corporation Hitachi, Ltd. Applicant Kawasaki Reactor Stock % Formula % [2] Ki Δ (m) Figure 5 Figure 6 Figure 6 Between lft with main 1 start of 9 (SeC)

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 frame parts, and the refractory is a thin cast slab that is a combination of an insulating refractory layer and a wear-resistant refractory layer provided on the insulating refractory layer. Short side plate of continuous casting machine. 2. A pair of opposing circulating bodies that circulate while maintaining a gap to hold the molten metal over a certain distance, and a pair of overboards located on both side edges between the circulating bodies. In the short-side side plate of a continuous thin slab casting machine, which constitutes a casting space with the short-side side plate having a concave shape and a narrowed middle part, a picture frame part formed on both side edges in contact with the above-mentioned circulating body, and this picture frame part. The refractory includes an insulating refractory layer, an abrasion-resistant refractory layer provided on the insulating refractory layer, and at least from immediately below the meniscus on the abrasion-resistant refractory layer. A short side plate of a thin slab continuous casting machine that is combined with a heat insulating refractory layer provided in the area up to the end of squeezing.