JPH0446077A - Fireproof heat insulating material and fireproof heat insulating structure - Google Patents

Abstract

PURPOSE:To improve fire resistance, heat insulating property and mechanical strength by arranging porous members made of a fireproof oxide having a prescribed m.p. and a prescribed void volume in a honeycomb shape and pouring castable refractories. CONSTITUTION:Porous members made of a fireproof oxide having 69-95% void volume and >=2,000 deg.C m.p. are arranged in a honeycomb shape in two or more layers and castable refractories are poured to form a fireproof heat insulating material. This material is applied to a permanent layer in the form of blocks to obtain a fireproof heat insulating structure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a fire-resistant heat-insulating material and a fire-resistant heat-insulating structure capable of imparting heat-insulating ability to the permanent layer of the refractory lining of various industrial kilns and at the same time increasing structural strength. Regarding.

Conventional technology In general, the lining refractories of various industrial kilns at temperatures of 1200°C or higher are
It is made up of a fireproof layer and a permanent layer. Conventionally, fire-resistant insulating bricks among fire-resistant heat-insulating materials have been used as the permanent layer to prevent energy loss due to heat radiation from the kiln.

In recent years, the use of monolithic refractories as fireproof materials has expanded, and various heat-insulating castables have been developed as shown in Table 1.

These fireproof and heat-insulating materials have numerous natural or artificial pores inside and have low thermal conductivity, but also have low bulk specific gravity and low compressive strength.

For this reason, these fireproof and insulating materials should be lined with sufficient consideration to avoid excessive unbalanced loads, such as by avoiding areas where special loads are applied, or by adding cushioning material against the thermal expansion of the furnace material. Construction is being adopted.

In addition, since most fireproof and heat insulating materials use porous aggregates, except for a few, they have a low melting point, and their normal use temperature is typically 1400°C or lower.

On the other hand, in recent industrial furnaces, particularly in the refractory linings used in steel processes, progress has been made in improving the refractories, which have significantly improved corrosion resistance and greatly contributed to extending the life of the furnace. for example,
Al t○3-3iC-C bricks in a pig iron mixer, MgO-C bricks in a converter, or AI in a ladle.
Examples include the use of Os M g〇-C type bricks for the wings.

However, these bricks all have high thermal conductivity, and the heat dissipation from the furnace body is greater than that of conventionally used refractories, which poses some operational problems.

When such a refractory lining is used as a self-refractory heat insulating material in the current furnace lining structure, it is impossible to ensure a sufficiently satisfactory heat insulating property.

In other words, the reheating shrinkage rate is a property value that determines the usage conditions of fireproof and insulating materials. You need something with a durability higher than 7 degrees, that is, something with good fire resistance.

For this reason, a method of increasing the thickness of the wear layer may be considered, but this would reduce the volume of the furnace and increase heat storage loss, and is not a drastic countermeasure.

In particular, if the permanent layer is mainly used for insulation, it not only lacks structural stability, but also has poor fire resistance as a safety lining when problems such as steel leakage occur. Thus, there is a need for a fireproof and insulating material that has these properties.

In addition, the low thermal conductivity materials that are commonly used as heat insulating materials are wool-like inorganic fiber aggregates that are highly flexible or shrinkable under pressure. When used, heat shrinkage and deterioration result in powdering due to vitrification and crystallization, making it unusable from the standpoint of volumetric stability.

As a countermeasure to this problem, fire-resistant flexible and pressure-resistant materials that exhibit flexibility after drying are produced by adding inorganic and/or organic fibers, synthetic resin emulsions, and/or rubber latex as resin components to fire-resistant raw materials at a predetermined ratio. A composite fire-resistant heat insulating material (Japanese Patent Publication No. 59-48779) consisting of a compressible fire-resistant flexible board and an inorganic fiber aggregate has also been proposed.

However, although the composite fire-resistant heat insulating material disclosed in Japanese Patent Publication No. 59-48779 has heat insulation properties in the thickness direction, it is highly flexible, so heat is generated in three axial directions during intense thermal cycles. In response to stress, it tends to become structurally unbalanced,
cannot be applied.

Problems to be Solved by the Invention When reinforcing the permanent layer of a tundish or a ladle for molten steel, which were studied by the present inventors, the following problems arise with conventional methods.

(1) If the iron shell of the conventional structure is lined with a thick wall, the furnace volume will become smaller and the heat storage loss will increase, making it easier for metal attachment to occur and increasing energy consumption for preheating.

(2) Low thermal conductivity (λ = 0.2kcal/m-hr
- Member 'c) has low compressive strength and cannot sufficiently support the weight of the lining brick. In addition, the conventional members mentioned above are
The serviceable temperature is low, and the lining structure tends to become unstable in terms of reheating shrinkage rate.

(3) Conventional composite fireproof insulation materials (for example, JP-A-56-1
60383) has thermal insulation properties in the thickness direction, but because it is highly flexible, it tends to cause structural imbalance in response to the thermal stress that occurs under severe thermal cycles. Not applicable.

(4) Insulated castables are difficult to raise in temperature due to the heat insulating ability of the refractory aggregates they are mixed with, and drying is insufficient, and there is a risk of steam explosion after receiving the steel, making them unreliable in terms of safety.

The purpose of this invention is to use a highly refractory material, a porous ultra-low thermal conductivity material, and a monolithic refractory material as a permanent fire-insulating material for a tundish or a ladle in the industrial kiln, particularly in a steel kiln. The object of the present invention is to provide a heat insulating material and a heat insulating structure that have low thermal conductivity, high fire resistance, and low heat capacity as a whole by combining these materials to form a honeycomb-shaped structural member.

Means for Solving the Problems The present inventors have developed a fireproof and insulating material for industrial kilns, particularly for continuous casting tundishes or molten steel ladles, which require particularly high insulation promotion in the current steel process. Various studies have been carried out.

As a result, we developed a fire-resistant heat insulating material in which ceramic foam, which has lower thermal conductivity and superior fire resistance than conventional ones, is cast in a fire-resistant castable, and has already been granted a patent No. 8 (Patent Application No. 2-43361).
are doing.

As a result of further research, it was discovered that low thermal conductivity and fire resistance can be further improved by laminating two or more layers of ceramic foam in a honeycomb shape with different positions.

That is, a diesel engine exhaust filter called ceramic foam (AlI3-90%, Zros
1O%, bulk specific gravity o, go, porosity 90%, compressive strength approximately 80kg/c+n''), we combined this ceramic foam with fireproof castable to produce a board-shaped fireproof insulation material as shown in Figure 1. .

The production of fireproof insulation material is made of ceramic foam with a thickness of 30 mm.
mn+, processed into a disc shape with a diameter of 60 mm and a height of 65 mm.
In a quadrilateral wooden frame with each piece measuring 450 mm, a plurality of disk-shaped ceramic foams (1) were installed in a honeycomb shape at equal intervals, and high alumina castables (2) of A I 10 s 75% were placed. was poured and hardened. Furthermore, by shifting the position of the cast ceramic form (1),
A plurality of ceramic foams (3) of the same shape as the previous three ceramic foams (1) were installed at equal intervals in a honeycomb shape, and high alumina castable (4) was poured again to form a 60m thick ceramic foam.
It was made into a board shape of m.

The ceramic foam used was previously coated with a water-impermeable membrane.

After curing, drying, and heat-treating this, the four boards mentioned above were combined into one
As a set, it was processed into a disc shape with a diameter of 700 mm, assembled, and lined in a ladle with a capacity of 2.5 L (7. The temperature of the upper and lower surfaces was measured. Also, for comparison, it was made using only the front and high alumina castables. The results were as follows: (1) Compared to a board made only of high alumina castables manufactured under the same conditions, the insulation and pressure resistance were dramatically improved.

(2) The heat insulation effect is proportional to the area ratio of the ceramic foams within the board, and is further improved by stacking the ceramic foams so that they are staggered in the thickness direction.

With this in mind, he completed this invention.

That is, in this invention, porous R members made of a refractory oxide with a porosity of 65 to 95% and a melting point of 2000° C. or higher are arranged in a honeycomb shape to form two or more intersecting layers, This is a fireproof insulation material made by casting with fireproof castable.

In addition, a porous member made of a refractory oxide with a porosity of 65 to 95% and a melting point of 2,000°C or higher is arranged in a honeycomb shape to form two or more intersecting layers, and then cast with a refractory caster. This is a fire-resistant and insulating structure made of a permanent layer of molded fire-resistant insulating material.

Function The reason why ceramic foam is used in this invention is that, as already mentioned, ceramic foam has a high porosity, so its apparent thermal conductivity is extremely low.
al/m ・hr ・t: Approximately. Moreover, the fire resistance of the material depends on the oxide composition of the raw material slurry, and can be adjusted freely by firing). Further, the composition of the oxide powder can be arbitrarily adjusted as long as it is 10 μm or less, and any fire resistance can be imparted as a so-called permanent layer. The thermal conductivity of ceramic foam is O,01kcal
/m -hr -'C or less, the porosity should be 65 to 9.
5% is necessary and desirable (2 or 85±5%).If the porosity is less than 65%, the heat insulation properties will be poor due to the heat transfer effect of the base material oxide, and if it exceeds 95%, the pressure resistance strength of the ceramic foam will deteriorate. becomes extremely low, making it unusable.

The size of the ceramic form is 30[[lInφ~3
00 mm (preferably 50 to 100 mmφ.3
If it is less than 0 mm≠, the work during board molding becomes complicated. 3
If it exceeds 00 [QIIlφ, damage may occur due to uneven loads from other lining materials after lining construction, which is not preferable.

In addition, the thickness of the ceramic foam is 10 tnm or more,
A range of 100+nm or less is suitable for ensuring the strength of a single unit.

The thickness of the insulation board to be manufactured is 20mm or more, 2001
Desirably 11m or less. If the thickness of the insulation board is less than 20 mm, the absolute thickness of the lining is small, and it is likely to break due to unbalanced structural loads. If it exceeds 200 mm 2 , it exceeds the thickness of a normal permanent layer, and there is no point in using the fireproof heat insulating material of the present invention.

Furthermore, the ceramic foam used is one whose surface is coated with an organic, water-impermeable film that is stable at room temperature before construction. Specifically, a method of applying and drying synthetic resin such as acrylic resin, phenol resin, or furan resin, or a method of wrapping a soft polyurethane sheet or tape can be applied, but the thickness of the coating must be 2 mm or less. . If the thickness of the coating exceeds 2 mm, the lining becomes a back air passage, and the insulation effect is significantly impaired.

On the other hand, as the monolithic refractory material forming the honeycomb-shaped heat insulating board, high alumina or high magnesia castable having a refractory rating of 34 or higher is used depending on the lining refractory material. The method for constructing monolithic refractories is to fill a predetermined shape frame using a casting vibration molding method or a method that can be filled with a trowel, depending on the composition, moisture content, and flow state of the monolithic refractory determined by the particle size.

Honeycomb-shaped insulation boards are manufactured by placing ceramic foam in a honeycomb shape in a mold, pouring in a monolithic refractory, and repeating this process. It is also effective to solidify the monolithic refractory into a predetermined shape, then insert the ceramic foam into the refractory and flatten the surface. After these steps, full-scale curing and drying or heat treatment are performed to create a honeycomb-shaped insulation board that integrates ceramic foam and monolithic refractories.

The area ratio of the ceramic foam to the plane of the honeycomb-shaped insulation board is adjusted to be 40 to 90%.

If the area ratio of the ceramic foams to the plane of the honeycomb-shaped insulation board is less than 40%, the desired insulation properties cannot be obtained, and if it exceeds 90%, the spacing between adjacent ceramic foams is small. The strength of the board tends to decrease locally.

The ceramic foam is arranged in two or more layers in the longitudinal direction of the honeycomb-shaped heat insulating board. By arranging the ceramic foams between the upper and lower layers so that they are discontinuous with respect to the direction of heat flow, the heat insulation can be improved in proportion to the area ratio. Therefore, the number of arrays is large (; and
That is, the more times the ceramic foam is laminated, the better the heat insulation properties will be, but when considering the workability of manufacturing the honeycomb-shaped heat insulation board, two or three layers is appropriate. Moreover, the arrangement interval of the ceramic foams is suitably 5 to 20 mm. If the spacing between the ceramic foams is less than 5 mm, the monolithic refractory filling between the ceramic foams is thin and has low strength.

The fireproof heat insulating material of the present invention is made by casting two or more layers of ceramic foam with high fire resistance and low thermal conductivity using monolithic refractories. It is reinforced by a shaped refractory, and inherits the high fire resistance and low thermal conductivity that are the advantages of ceramic foam, resulting in a fire-resistant and heat-insulating material with excellent fire resistance and heat insulation properties.

In addition, the fire-resistant heat-insulating structure for an industrial kiln in which the fire-resistant heat-insulating material of the present invention is used as a permanent layer and a fire-resistant material is lined thereon uses a fire-resistant heat-insulating material with excellent fire resistance and heat insulation properties as the permanent layer. Therefore, compared to using conventional insulating bricks or insulating castables, higher insulation efficiency can be achieved with a relatively thin layer.

Examples Example 1 A plurality of alumina ceramic foams (1) with a diameter of 80 mmφ and three different thicknesses were placed in a metal frame measuring 500 mm long, 500 mm wide, and 100 mm thick at an interval of 15 mm.
Set 1 to 3 layers each in the lamination pattern shown in Fig. 2 (a) to (d) with a thickness of ~20 mm, and pour high alumina castable (2) containing A, L, and 0.70%, and perform construction L.
After solidification, three types of honeycomb-shaped insulation boards with a thickness of 90 mm were manufactured. After curing, it was dried at 100°C, and the outside of the metal frame was further heat-treated at 800°C.

For comparison, a high alumina castable board was manufactured using the same procedure as above, except that the ceramic foam was not set.

The four types of boards produced were lined with a permanent layer at the bottom of a ladle with a capacity of 10 tons, and a thermocouple was inserted into the bottom of each board to receive molten steel at 1650°C and measure the temperature. The amount of heat dissipated was calculated for each time.

The wear layer of the upper ladle is Mg080% MgO.
- It was lined with 〇 series unfired bricks and received after preheating the inside of the pot to 1100°C. The results are shown in FIG. 3 as comparative values (indices) where the amount of heat dissipated in the area lined with conventionally used heat-insulating castable with a fire resistance of 34 is set as 100.

As shown in FIG. 3, the heat insulating effect of the honeycomb-shaped heat insulating board using the ceramic foam of the present invention is remarkable, and the heat insulating effect is greatly improved by laminating the ceramic foam.

Example 2 Ceramic foam was set on the side wall of a tundish for continuous casting with a capacity of 60 tons in the arrangement and lamination pattern shown in FIG. 1, and a honeycomb-shaped heat insulating board produced by the same method as in Example 1 was lined as a permanent layer.

The honeycomb insulation board has a diameter of 500mm and a thickness of 60m.
m, diameter 50+nm, thickness 30mm A l +0a
-Z r O1 ceramic foam (porosity 88~
92%) was used.

The poured castable is A1.0.70% high alumina castable with a diameter of 1.2 mm and a length of 25+n.
Added 2.5% of 5IJS304 fibers, and the area ratio of ceramic foam in the plane is 80%.
It has a two-layer structure.

The permanent layer of the honeycomb-shaped insulation board is laid with bricks using mortar according to the conventional procedure, and then A l t03
The interior was lined with 70% refractory bricks, dried, preheated (ambient temperature 1100°C), and put into operation, and the temperature of the side wall iron skin during operation was measured.

The comparison data was taken for the conventionally constructed furnace (permanent layer, chamotte brick), with a newly completely repaired furnace body. Ta.

Table 2 also shows data measured at the 5th charge during continuous casting (continuous casting index 7 to 8) as operating conditions.

As shown in Table 2 in the margin below, the dandy tsushu lined with a honeycomb-shaped insulation board as a permanent layer according to the present invention has a lower amount of heat dissipated from the surface of the iron skin than the conventional tundish tsushu with chamotte brick as a permanent layer. Therefore, the variation in molten steel temperature during the casting time of each charge is greatly reduced, and the effect of maintaining the molten steel temperature is obvious.

For this reason, the drawing speed in the continuous casting machine was kept almost constant, and stable operation could be achieved.

Effects of the Invention As described above, the fireproof heat insulating material of the present invention has higher fire resistance and heat insulation properties, as well as greater mechanical strength, than conventional fireproof heat insulating materials. In addition, the fireproof insulation structure in which the fireproof insulation material of the present invention is used as a permanent layer is suitable as a fireproof insulation layer in an industrial kiln, particularly a tundish of a steel furnace or a ladle for molten steel, and has a heat retention effect on the molten steel held. It is clear that this will improve. This also reduces thermal spalling in the lining wear layer, making it possible to extend the life of the lining, and the overall economic effect is extremely large.

[Brief explanation of the drawing]

Figure 1 is a schematic explanatory diagram of the prototype honeycomb block;
) is a plan view, (b) is a cross-sectional view taken along line A-A' in figure (a), (c) is a cross-sectional view taken along line B-B' in figure (a), and Figure 2 is a ceramic foam in Example 1. (a) is a plan view, (b) is a cross-sectional view along A-A' of (a) when two layers of ceramic foam are laminated, and (
C) The figure is a cross-sectional view taken along line A-A' in figure (a) when three layers of ceramic foam are laminated, and figure (d) is a cross-sectional view when three layers of ceramic foam are laminated.
Figure 3 shows the amount of heat dissipated in a ladle lined with heat-insulating castable as a comparative example of Example 1.
It is a graph showing a comparison of the amount of heat dissipated when the honeycomb-shaped heat insulating board of the present invention is lined with 0. ■, 3 Ceramic foam, 2.4 High alumina castable, Applicant: Sumitomo Metal Industries, Ltd.

Claims (1)

[Scope of Claims] 1. A porous member made of a refractory oxide with a porosity of 65 to 95% and a melting point of 2000°C or higher arranged in a honeycomb shape to form two or more intersecting layers. , a fireproof insulation material made by casting with fireproof castable. 2 A porous member made of a refractory oxide with a porosity of 65 to 95% and a melting point of 2,000°C or higher is arranged in a honeycomb shape to form two or more intersecting layers, and then cast with a refractory castable. A fire-resistant insulation structure made of a permanent layer of fire-resistant insulation material.