JPS62288155A - Limy refractory composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a calcareous refractory composition used as a lining material for the inner surface of a container for molten steel such as a tundish.

Conventionally used as a lining material for molten steel containers such as tanditshu.
Fire-resistant compositions are used that contain maknesia as a main component and add fine silica powder, clay, etc. to provide adhesion and prevent slag penetration.

However, fine silica powder and clays are unstable in high temperature ranges, tend to become a pick-up source of Si, O, etc., and are undesirable because they reduce metallurgical effects such as improving the quality of steel cleaning.

Refractory compositions based on lime (Cab), which is effective in cleaning steel because it easily reacts with impurities in steel, are also used. However, when lime is mixed with water when lining the inner surface of a container with a refractory composition, it is digested during drying, significantly reducing the strength of the refractory composition applied as a lining (hereinafter referred to as a construction body). Therefore, when lining with a fireproof composition containing lime, water cannot be used and the work is extremely difficult.

Therefore, attempts have been made to use limestone and magnesia limestone, which contain a large amount of calcium rehydrate (CaCO3) that generates CaO through thermal decomposition and are not digested by water. However, limestone and magnesium limestone generate CaO when heated and also have the drawback of carbon dioxide gas. Therefore,
If these are used in large amounts, the strength of the refractory composition will decrease. Furthermore, the adhesion to the inner surface of the container is not sufficient.

In order to solve the above problems, limestone and magnesia limestone,
Basic refractories to which thickening agents such as silicates and/or phosphates and clays have been added have been proposed (Japanese Patent Publication No. 5
No. 8-34423, Special Publication No. 59-34674). Silicates and phosphates form high melting point bonds with CaO produced by heating limestone and magnesia, and suppress shrinkage of the refractory composition during heating. Furthermore, adhesion is improved by adding clays. However, silicates and phosphates act as pick-up sources for Si and P, and as mentioned above, clays act as pick-up sources for Si and O, so it is not enough to purify steel and improve steel quality. Undesirable and undesirable.

In view of the above problems, the inventor has conducted extensive research and found that
It was discovered that by adding oxalium, borax and sodium fluoride to limestone and magnesium, a refractory for lining that exhibits high strength when heated and does not have a negative effect on steel can be obtained, and the present invention was developed. completed.

That is, the present invention uses limestone and/or magnesium limestone 50 to 10
100 parts by weight of refractory aggregate consisting of 0 weight percent and the balance being Macnezia linker, 0.5 to 3 parts of oxalic acid, 0 borax.
．． The present invention relates to a calcareous refractory composition containing 5 to 5 parts by weight and 0.5 to 5 parts by weight of sodium fluoride.

In the present invention, limestone and/or magnesia limestone is used as the refractory aggregate. Further, if necessary, MacNesia linker may be used in combination with the rounding to improve the erosion resistance, with the upper limit being equal to the content of limestone and/or magnesia limestone.

When the content of limestone and/or magnesia limestone is 50 weight ≦ ungrooved, less C40'kk is generated during heating, and forsterite (425*
Oa ), spinel (MfA1204) and other high melting point compounds prevent contact between CaO and molten steel.
This is undesirable because metallurgical effects such as cleaning of molten steel deteriorate. The particle size of limestone, magnesium limestone, and Macnesia linker 0 is not particularly limited, and may be selected as appropriate. For example, regardless of the K of limestone, magnesia limestone, and Macnesia linker, if the K is about 3 to IM, the one about 1 to 0.151 m, and the one less than 0.15 cod 9 can be appropriately mixed and used. good.

In the present invention, by using silicic acid, sodium fluoride, and borax in combination, the steel can be treated without adversely affecting the steel.
Mainly in a wide temperature range from room temperature to about 1200℃,
The strength of the construction body can be increased.

Silicic acid is used when kneading each raw material of the fireproof composition with water.
It reacts with limestone and limestone or magnesium to form fine crystals of calcium oxalate, which is effective in imparting strength to construction bodies as a matrix filler in low temperature ranges. Furthermore, when calcium oxalate becomes red hot, it acts as a melting aid for sodium fluoride, and then decomposes into calcium carbonate and carbon monoxide, so it does not remain in the construction body and does not have any adverse effect on the steel. The blending amount of oxalic acid is preferably about 0.5 to 3 parts per 100 parts of the refractory aggregate. 0.
If the amount is less than 5 parts by weight, the above effects cannot be sufficiently exhibited, while if it exceeds 3 parts by weight, carbon dioxide gas is often generated due to reaction with aggregate when the raw materials are kneaded with water. Otherwise, the strength of the construction structure will decrease.

*'+8 ("2B4'7 ・10 H2') is 7
Melt at 5 °C to act as a binder, then 350-4
It dehydrates at about 00°C and solidifies as a white anhydride. This solidified material melts at 878° C. and becomes a glass-like transparent body, again acting as a binder. Additionally, the glassy transparency melts the metal oxide and thus promotes sintering of the matrix. Also, during steel receiving, it acts as a slag-forming agent and does not have any negative effects. The blending amount of borax is 100% of fireproof aggregate.
The amount is preferably about 0.5 to 5 parts by weight.

If it is less than 0.5mM, it has little effect as a binder;
On the other hand, if the amount exceeds 5 parts by weight, the action as a slag forming agent becomes stronger and the corrosion resistance of the construction object decreases.

Sodium fluoride has a melting point of 992°C, and at temperatures below the melting point, it acts as a sintering agent, and after melting, it acts as a binder. Also, during pig iron receiving, it acts as a slag agent like borax, so it is effective in cleaning steel. The blending amount of sodium fluoride is 0.5 to 5 parts by weight per 100 parts by weight of the refractory aggregate! It is preferable to set it to about the ffi section. If it is less than 0.5 parts by weight, it will not be effective as a binder, while if it exceeds 5 parts by weight, it will act strongly as a slag-forming agent, similar to borax, and the corrosion resistance of the construction object will decrease. Furthermore, water-soluble polymeric substances such as polyvinyl alcohol and polyethylene oxide may be added to the composition of the present invention to improve workability during construction.

The composition of the present invention is produced by mixing predetermined amounts of the above-mentioned various raw materials.

When lining the inner surface of a container for molten steel with the composition of the present invention, 1 liter of the composition of the present invention is added to 100 parts by weight of refractory aggregate.
Add 0 to 20 parts of water by weight, and if necessary, add the water-soluble polymeric substance mentioned above and knead well. Apply this kneaded material to the inner surface of the container by a normal method such as applying with a trowel. Bye.

Effects of the Invention The composition of the present invention has high strength in a wide temperature range from room temperature to about 1200°C, and also has excellent metallurgical effects such as cleaning steel and improving image quality.

Examples and comparative examples are given below to further clarify the present invention.

51! Examples 1 and 2 Oxalic acid, sodium fluoride, and borax were added and mixed to 100 parts of limestone in the proportions (parts by weight) shown in Table 1 to produce a composition of the present invention.

Water was added to the obtained composition of the present invention in the proportions (parts by weight) shown in Table 1 and kneaded to produce a lining material. The obtained lining material was subjected to a strength test.

The results are shown in Table 1.

Comparative Examples 1 to 3 Except for using only one or two of the essential components of the composition of the present invention, oxalic acid, sodium fluoride, and sand, fil! In the same manner as in Example 1.2, lining materials were produced using the blending ratios (parts by weight) shown in Table 1. The obtained lining material was subjected to the same strength test as in Example 1.2. The results are shown in Table 1.

*A 30X30X150sa* test piece was directly heated with the flame of a gas burner.

From Table 1, it can be seen that even if any one of oxalic acid, sodium fluoride, and borax is missing, the strength of the constructed body decreases. A composition of the present invention was produced at the blending ratio (overlapping portion) shown in Table 2, and then water was added thereto to produce a lining material. The obtained inner *b material was applied to the inner surface of the tundish to a thickness of 201 mm with a trowel.
Preheated drying was performed at 0°C for 2 hours. No cracks, peeling, etc. were observed.

This tanditshu was made of aluminum cored steel and the condition of the lining material was examined. The results are shown in Table 2.

As is clear from Table 2, the accumulation of oxides (non-metallic inclusions) is significantly reduced compared to the conventional product (magnesia-based lining material), and the amount of non-metallic inclusions per ml is significantly reduced. It was effective for removal and got 6 points.

(that's all)

Claims (1)

[Claims] 1 100 parts by weight of fireproof aggregate consisting of 50-100% by weight of limestone and/or magnesia limestone and the balance being magnesia clinker, 0.5-3 parts by weight of oxalic acid, 0.5-5 parts by weight of borax, and sodium fluoride. A calcareous refractory composition containing 0.5 to 5 parts by weight.