JPH0223497B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a cast refractory for molten metal having excellent drying properties. Construction methods for monolithic refractories include (A) pouring (a vibrator may be used to improve fluid filling properties), (B) vibration molding (C) spraying (D) ramming (E) troweling, etc. There are several construction methods, but pour-in construction is often used from the viewpoint of labor-saving, working environment, and stability of the constructed structure.In the steel industry, pour-in construction is also used for ladle, tundish, blast furnace gutter, etc. It is being said. The refractories used in this construction are required not only to have various properties as refractories, but also to have fluidity due to the construction method and drying characteristics due to the large amount of added moisture. Recently, many refractories of this type have added refractory ultrafine powder and deflocculant to improve fluidity and compactness. However, on the other hand, as the tissue becomes denser, drying becomes increasingly difficult. Rapid drying causes defects such as internal cracks and explosions. These defects can be prevented by drying at a low temperature for a long time in the initial stage of drying, but the drying time must be kept as short as possible from the viewpoint of furnace operation rate, energy conservation, etc. [Prior art] As a solution to this problem, for example, as seen in JP-A No. 53-66917, metal aluminum is added and hydrogen gas generated by the hydration reaction described below is used to infuse the structure of refractories. A method was proposed to forcefully create ventilation holes to accelerate drying. Al＋3H ₂ O→Al(OH) ₃ +3/2H ₂ ↑ However, in this case, hydrogen gas pushes and spreads the refractory structure, which tends to cause internal defects, and when it is too much, the construction body swells and the structure becomes porous. is remarkable. Furthermore, due to the generation of hydrogen gas, there is a risk of ignition and explosion, so careful attention must be paid to exhaust gas. [Structure and operation of the invention] Due to the nature of this exhaust system, construction may not be possible in some cases. The present invention solves the above-mentioned conventional drawbacks, and the present invention solves the above-mentioned conventional drawbacks.
0.01 for organic fibers that melt or decompose below 180℃
This is a cast refractory for molten metal characterized by the addition of ~1wt%. In the present invention, ultrafine powder with a particle size of 5 μm or less in the refractory aggregate imparts fluidity to the refractory material and densification after construction. The organic fiber melts or decomposes at temperatures below 180°C and is immediately dissolved by dry heating, forming continuous vents in the refractory fabric that serve as a path for moisture evaporation. The formation of the ventilation holes in this case is because the organic fibers have previously occupied the portion corresponding to the ventilation holes, so there is no problem of expanding the refractory structure as in the case of adding metal aluminum. The organic fiber used in the present invention is selected from vinylon, nylon, polyester, polyethylene, polypropylene, etc. These organic fibers have different melting points and decomposition points depending on the degree of polymerization, etc., but the organic fibers used in the present invention are particularly limited to those that melt or decompose at 180° C. or lower. Table 1 shows the relationship between temperature and water vapor pressure, and according to it,
The vapor pressure increases significantly from around 200℃. For this reason,
No increase in vapor pressure that could cause cracks or explosions180
Use organic fibers that melt at temperatures below °C to form vents.

[Table] In addition, in cases where the strength of the refractory after construction is particularly weak, or where defects are likely to occur in the fiber assembly even at low steam pressure, organic fibers that melt at a temperature of 100°C or less may be added until steam is generated. is preferable because it has a large effect. Next, some experimental examples that led to the present invention will be shown. In this experimental example, organic fibers or aluminum powder were added to a poured refractory based on the following formulation, and the test pieces obtained were tested to see if they would explode.

[Table] These are 80×80 with 5.5wt% moisture added outside.
A sample was obtained by pouring into a mold of 1 mm in diameter by applying vibration at 4G for 2 minutes, and then curing for 24 hours. (Experiment conditions) Pattern: Placed in an electric furnace at 200°C, held for 1 hour, then immediately placed in an electric furnace at each test temperature, and held for 1 hour. Pattern: Immediately placed in an electric furnace at each test temperature after curing, held for 1 hour. Table 2 shows the results of explosion tests conducted on organic fibers with different melting temperatures, metal aluminum powder, or additive-free fibers. The organic fibers in this case were vinylon fibers with a diameter of 5 to 15 μm and a length of 3 mm, to which 0.1 wt% was added. However, 360℃
The one is rayon, a regenerated cellulose fiber that decomposes at that temperature. On the other hand, metal aluminum
0.1wt% of 200mesh or less was added.

〔Example〕

Next, as an example according to the present invention, different refractory aggregates and the like were poured into a molten metal container to a thickness of 130 mm, and then heated and dried with a gas burner to 1000° C. for 24 hours. The results are shown in Table 3. The additive vinylon fiber has a length of 3mm, a diameter of 4 to 6μ, and a melting temperature of A; 80℃.
B: 140°C C: 230°C.

〔Effect of the invention〕

As described above, since the present invention does not add metallic aluminum, there is no danger of ignition or explosion due to the generation of hydrogen gas, and the physical properties such as fluidity and strength as a pourable refractory are not impaired.
Can improve dryness. This makes it possible to shorten the drying time without causing drying defects, leading to energy savings.Also, since this construction has no drying defects and has excellent structural strength, the lifespan of refractories is extended and the amount used is reduced. This will be reduced.

[Brief explanation of drawings]

FIG. 1 shows an experiment on changes in fluidity due to fiber addition, and FIG. 2 shows a flow cone used in this experiment.

Claims (1)

[Claims] 1. With respect to 100 wt% of the total amount of the refractory aggregate containing 2 to 25 wt% of ultrafine powder with a particle size of 5 μ or less and the binder,
A cast refractory for molten metal characterized by adding 0.01 to 1 wt% of organic fibers selected from vinylon, nylon, polyester, polyethylene, polypropylene, etc. that melt or decompose at 180°C or lower. 2. The refractory according to claim 1, wherein the organic fibers have a diameter of 1 to 100 μm and a length of 1 to 15 mm.