JPS5848510B2 - Hot repair material for fireproof structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot repair material for refractory constructions, and more particularly to a flame spray hot repair material for refractory linings of mixed pig iron cars.

Normally, the inner lining of a pig iron mixer car is lined with an Al203-SiO2-based refractory, but in recent years, as the desulfurization operation rate inside the pig iron mixer car has increased, erosion of the slag line has become significant, and the life of the lining has continued to decrease. following.

The repair of locally eroded parts of the inner lining of mixed pig iron cars has conventionally been carried out by the following method.

(a) Filling caster pulls (0) Replacing bricks (/→ Spraying water brick refractory powder) Of these, (b) and (x) are used inside the furnace of the pig iron mixer (hereinafter referred to as inside the furnace). Abbreviate.

) must be cooled down to around room temperature before a worker can enter the furnace and perform the repair, which requires a considerable amount of time, including the time for cooling and re-heating.

On the other hand, the spraying repair (c) can be done hot, so there is no problem in terms of time.

However, since this method involves spraying refractory powder containing an appropriate binder together with water onto the damaged area, the sprayed repair layer becomes quite porous and exhibits significantly less corrosion resistance (poorer corrosion resistance) than burnt refractory. Therefore, repair work must be carried out frequently.

Furthermore, conventional Al203SiO2 based spray repair materials cannot be said to be excellent in terms of thermal shock resistance, and phenomena such as cracking and falling off are often observed.

The purpose of the present invention is to improve the shortcomings of the conventional technology regarding repair materials for the refractory interior lining of mixed pig iron cars, and to create a repair layer that can be repaired without cooling the furnace interior and is extremely dense and has excellent corrosion resistance and thermal shock resistance. It is an object of the present invention to provide a hot repair material for a refractory lining of a pig iron car interior that can be formed in a short time.

This object of the invention is achieved by the invention as summarized below.

The gist of the present invention is to combine 20 to 70% of a mixture of one or more natural or synthetic oxide raw material powders such as chamotte, mullite, alumina, and zircon with silicon carbide or silicon nitride. or both powders 1
Refractory raw material consisting of 0 to 50φ and coke powder 20
~40φ, and is a hot repair material for a refractory construction, characterized in that the oxide-based raw material is semi-molten by burning the coke powder in an oxygen stream. .

The hot repair material of the present invention is extremely dense and has excellent corrosion resistance and thermal shock resistance when sprayed onto red-hot refractory walls. Forms the spiritual layer.

On the other hand, as already mentioned, the repair layer made of M203SiO wet spray repair material, which has been conventionally used for repairing mixed pig iron car interior refractories, has problems in terms of corrosion resistance and thermal shock resistance. .

In addition, in recent years, as a spray repair method for converters, a mixture of magnesia-based material powder and coke powder is sprayed together with oxygen onto red-hot refractory walls, and the coke burns to turn the magnesia raw material into a semi-molten state, thereby destroying the strong repair layer. Since the method has been put into practical use, the present inventors took a hint from this and first added coke powder to the conventional Al203S102 based spray repair material and sprayed it together with oxygen onto the red-hot refractory wall to form a semi-molten repair layer. A test was conducted in the form of

In this case, although the corrosion resistance was improved, the thermal shock resistance was significantly lowered and the purpose of the repair layer could not be achieved.

The present inventors further improved this and succeeded in developing the hot repair material of the present invention.

The hot repair material of the present invention forms a dense repair layer by ejecting a powder mixture from the center of concentrically arranged nozzles and jetting oxygen from the outer periphery to a locally damaged area in a red-hot state. do.

In this case, the coke powder mixed in the raw material is ignited by the heat of the red-hot wall, becoming a high-temperature flame that melts the oxide raw material, and some oxygen oxidizes the surface of silicon carbide or silicon nitride, solidifying it. Forms connective tissue.

In particular, when silicon nitride is added to a mixture containing an Al203-based material, the strength increases significantly.

Although the mechanism of action is still not clear, a portion of silicon nitride reacts with Al203-based materials in the raw material, resulting in S r
It is thought that it forms a solid solution (Sialon) of 3N4A1203 system, and a part of it forms silicon oxynitride bonds (Si20N2), which strongly binds the raw materials of each structure.

The mixing ratio of raw materials for the hot repair material of the present invention varies depending on the repair location, that is, the purpose.In the slag line and hot water contact areas, where there is severe erosion, a mixture containing a large amount of alumina, silicon carbide, etc. is used, and in the furnace belly and ceiling areas, a mixture containing SiO2 is used. Use raw materials in large quantities.

In this hot repair material, the blending ratio of oxide-based refractory raw material powder such as stone, chamotte, mullite, alumina, and zircon is 2
It is 0-70%.

If the blending ratio of oxide-based raw materials is less than 20%, there will be a lack of molten metal involved in bonding between particles, and the resulting sprayed repair layer will not have sufficient strength. Abrasion loss due to flow increases.

Also, if the number is more than 70φ, sufficient thermal shock resistance cannot be achieved.
It also has strong corrosion resistance that cannot be changed.

Next, the total amount of silicon carbide and silicon nitride is 10 to 5
It is assumed to be 0φ.

If this amount is less than 10 tfb, sufficient thermal shock resistance will not be obtained, and the rate of erosion will also increase, resulting in no effect of addition.

If the amount is more than 50, the mixing ratio of oxides involved in particle bonding will be too small to provide sufficient strength.

Further, the blending ratio of coke powder is 20 to 40%.

In fact, f is determined by the composition and blending ratio of the oxide-based raw materials, but in any case, if it is less than 20%, it will not be possible to obtain a high enough temperature to bring the refractory raw materials into a semi-molten state.
If the amount is more than that of rice cake, unburned carbon will remain in the sprayed repair layer, which will cause a decrease in strength.

In addition, the amount of oxygen required for complete combustion of coke is calculated and supplied, and the oxygen necessary to oxidize the surface of silicon carbide and/or silicon nitride is obtained from the air used as a carrier gas for blowing out the raw material. The amount supplied is sufficient.

The particle size of the raw material powder is 0. 90 particles less than 1 mm
It is desirable that it is φ or more.

If the particle size is too large, particle size segregation will occur during transportation, and problems will arise in the melting state of the particles during blowing, making it impossible to form a good sprayed layer.

Examples of the hot repair material of the present invention will be described below in comparison with a conventional method.

Alumina, mullite, clay, silicon carbide, silicon nitride,
Fine powders such as carbon were mixed at the compounding ratio shown in Table 1, and samples I61 and 42.3 were heated at 1300 f. using a conventional wet blower method and with an oxygen jet, respectively.
'CIζ was sprayed onto the heated refractory wall surface.

The obtained sprayed repair layer was sampled and various property tests were conducted.

The results are shown in Table 1.

Thermal shock resistance was determined by rapidly inserting a test piece cut into 30 x 30 x 100 (mm) into a furnace previously maintained at 1,400°C, heating it for 15 minutes, then taking it out of the furnace and cooling it in the air, and observing its appearance.

In addition, the corrosion resistance test was conducted by adding 10% CaO to blast furnace slag and melting it at 1500°C in a graphite crucible.
A test piece cut into φ×70 mm was heated at 30 O r. p
．． m. Determine the amount of decrease in diameter after rotating the sample for 1 hour.
It is expressed as a relative ratio when i61 is set as 100.

As is clear from Table 1, samples 2 and 3 according to the present invention were found to be significantly denser than sample I61 prepared by the conventional method, and were also superior in corrosion resistance and thermal shock resistance.

Although the effects of the present invention have been described individually, they can be summarized as follows.

(a) Since the repair material according to the present invention can be repaired hot and in a short time, the furnace can be operated with high efficiency.

In other words, the hot repair material of the present invention does not require furnace cooling, drying of the sprayed layer, or heating, and the spraying speed is 4 per minute.
60-120 compared to conventional spraying method at high speed of 00-1000 kg.
It can be completed in a fraction of the time compared to kg.

Due to the effects of the carbides and nitrides it contains, it is possible to form a very dense repair layer with excellent corrosion resistance and thermal shock resistance.

Therefore, the life of the lining can be extended and the number of repairs can be reduced.

The hot repair material of the present invention can be used not only for the inside of a mixed pig iron car, but also for repairing blast furnace shafts, bottoms, blast furnace gutter slagging, hot metal ladle, etc.

It is also clear that if the content of silicon carbide and silicon nitride in the material is reduced, it can be used for general refractory structures that require hot repair, such as the repair of steelmaking ladles, RH lower tanks, continuous casting tundishes, etc. It is.

Claims (1)

[Claims] 1. Chamotte, mullite, alumina by weight,
A refractory raw material consisting of 20 to 70 parts of a mixture of one or more types of natural or synthetic oxide raw material powder such as zircon, and 10 to 50 parts of powder of silicon carbide or silicon nitride, or both; coke powder of 20 to 40 φ, and the oxide-based raw material is semi-molten by burning the coke powder in an oxygen stream with a trowel. Interval repair material.