JP3470588B2 - Powder mixture for flame spray repair - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an inner wall of an industrial furnace,
In particular, the present invention relates to a powder mixture for flame spray repair, which is a material for repairing the high-heated inner wall of a coke oven, in which a powder refractory is melted by a flame and spray spray repair is performed using an injection nozzle.

[0002]

2. Description of the Related Art Industrial furnaces, particularly coke ovens as steel equipment, blast furnaces, steelmaking furnaces, and other furnace construction structures are equipped with carbonized coal,
It is in a harsh environment where it is exposed to a high temperature of 1000 ° C or more when it comes into contact with molten materials such as hot metal, molten steel and slag. In particular, when the coke is pushed out of the carbonization chamber of the coke oven, or when hot metal or molten steel is poured, stored, or discharged in the steelmaking furnace, these inner walls are exposed to remarkable temperature fluctuations. Therefore, these inner walls are not only infiltrated and melted by the melt, but also frequently damaged by thermal spalling such as cracks and peeling. In order to deal with such various damage factors, it is necessary to select a brick made of an appropriate material at the stage of design or furnace construction, and it is also necessary to repair it on the way to improve its life. .

For example, as a repairing technique, there is a flame spray repairing method in which a repairing material is hot sprayed onto a damaged portion of a refractory. This flame spray repair method is mainly used for repairing the refractory oxide powder or the oxidizable powder for repair, which has the same composition as the material of the furnace wall refractory to be repaired, mainly for the high temperature furnace inner wall surface. It is a technique of hot spraying a flame spray repair material composed of a mixture of the two. According to this method, the refractory oxide powder is melted by the heat of combustion of combustible gas, and the easily oxidizable powder is exothermicly melted by its own combustion to become an oxide, and the refractory oxide powder is A thermal spray repair layer can be formed with the body. In particular, the coke oven
The flame spray repair method is effective because the furnace temperature cannot be lowered except during repair and repair of the furnace wall under high heat conditions is essential.

As a conventional technique relating to such a flame spray repair method, for example, there is a method disclosed in Japanese Patent Publication No. 2-45110. This method mixes a powdery refractory oxide with a combustible substance and a combustible gas and supplies it to a combustion-supporting gas containing oxygen such as oxygen or air, and the heat of the combustion flame causes its refractory oxidation. This is a dry method in which the material powder is melted and instantly sprayed on the damaged part of the inner wall of the furnace. In this method, the sprayed repaired refractory is more durable than the repaired refractory constructed by the wet spraying method, which is a method in which water and a spraying material are mixed in advance and the sludge is sprayed from the tank. There is a feature that the sex is extremely high.

By the way, as a thermal spray material used in such a flame spray repair method, for example, in Japanese Patent Publication No. 3-9185, SiO ₂ : 93.9-99.6 wt% or more, Al ₂ O ₃ : 1.5 wt% or less, CaO : 2.0 wt% or less, Fe ₂ O ₃ : 1.0 wt% or less, Na
We have proposed a high-silica thermal spray material consisting of ₂ O: 0.4 to 2.0 wt%. Generally, this type of material has a crystallization rate of 60% or more immediately after thermal spraying, but cracks due to expansion when the amorphous (glassy) part (<40%) is crystallized A decrease in adhesive strength is observed due to the difference in thermal expansion characteristics between the thermal sprayed repair layer and the coke oven wall brick. That is, the material according to the above proposal was developed in order to overcome the adverse effects caused by such a low crystallization rate.

However, the technique disclosed in Japanese Examined Patent Publication No. 3-9185 has a very narrow spraying condition for forming a sprayed repair layer having a crystallization rate of 60% or more, that is, an oxygen gas flow rate and a propane gas flow rate are extremely narrow. There was a problem that it was limited to the range. Furthermore, under the thermal spraying conditions where a thermal spray repair layer with a crystallization rate of 60% or more is obtained, it is difficult to obtain a dense thermal spray repair layer, that is, a thermal spray repair layer with high compressive strength, which results in poor wear resistance and thermal spray repair. There is a problem that the life of the layer is short. As described above, in the conventional technology, since the crystallization rate is low, the problem that cracks are likely to occur in the repair layer and the adhesive strength to the substrate surface is low remains, but at least to increase the crystallization rate. There was a problem that the conditions were severe, the compressive strength did not increase, the abrasion resistance was poor, and the life was short.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a thermal spray repair material which has a high crystallization rate immediately after thermal spraying under a wide range of thermal spraying conditions and is effective for constructing a dense thermal spray repair layer. It is in. Further, another object of the present invention is to provide a thermal spray repair material having excellent wear resistance and durability (lifetime) through ensuring high compressive strength without cracks in the repair layer or reduction in adhesive strength to the repair surface. To provide.

[0008]

Means for Solving the Problems The inventors of the present invention have diligently studied the above-mentioned problems of the prior art, and as a result, have found that the crystallization rate immediately after thermal spraying is 80% under a wide range of thermal spraying conditions.
We have developed a powder mixture as a flame spray repair material that is effective for obtaining a spray repair layer having the above-mentioned high compressive strength.

That is, according to the present invention, the concentration as an oxide is SiO ₂ : 89 wt% or more, Na ₂ O: more than 2.0 to 4.0 wt%, the balance being unavoidable impurities , and crystallization immediately after thermal spraying.
Rate is 80% or more, compressive strength is 200kgf / cm ² or more, repair layer is 10
Adhesive strength with 30% or less decrease in strength when crystallized 0%
It is a powder mixture for flame spraying repair that indicates the degree .

[0010]

Further, according to the present invention, the concentration as an oxide is SiO ₂ : 89 wt% or more, Li ₂ O: 0.2 wt% or more, and (N
a ₂ O + Li ₂ O): more than 0.2 to 4.0 wt%, the balance consisting of unavoidable impurities , and the crystallization rate after flame spraying is 80% or more,
Compressive strength is over 200kgf / cm ² , repair layer is 100% crystallized
A powder mixture for flame spraying repair, which exhibits an adhesive strength with a strength reduction rate of 30% or less .

[0012]

Here, the meaning of the concentration as an oxide means the amount when the water content contained in the material is removed and the remaining components such as oxides, carbonates and metals are converted into oxides and taken as 100. (Wt%).

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention contains SiO ₂ as a main component. This SiO ₂ has almost the same composition as silica bricks used on the inner surface of furnace walls such as coke ovens.When these inner wall surfaces are used as repair sites, the thermal expansion of the furnace wall bricks and the thermal spray repair refractory layer It is an essential component for making the characteristics almost the same. In the present invention, the content of SiO ₂ is 89 wt% or more in terms of the concentration as an oxide. The reason for this limitation is that if the amount of SiO ₂ is less than 89 wt%, the amount of impurity components such as Al ₂ O ₃ and FeO, which are inevitably mixed in, increases, and this effect causes the crystallization rate of the repair layer immediately after thermal spraying. Is 80%
This is because it falls below. If the crystallization rate of the repair layer immediately after thermal spraying is less than 80%, the thermal expansion difference between the repair layer and the furnace wall brick when the thermal spray repair layer is 100% crystallized causes the joining of the two. The surface is easily cracked and the thermal spray repair layer is peeled off. In the present invention, silica raw material such as silica brick, silica stone, and silica sand can be used as the raw material of the SiO ₂ component.

Here, the crystallization rate means the sum of the weight percentages (wt%) of cristobalite, tridymite and quartz when the sprayed repair layer is quantitatively analyzed by X-ray diffraction. According to the inventors' research, when the crystallization rate of the repair layer immediately after thermal spraying is 80%, the adhesive strength is reduced by about 30% when the crystallization rate is 100% after that. It has been confirmed that if the decrease in the adhesive strength is 30% or less, the damage to the furnace wall due to the peeling of the sprayed layer is not so remarkable. That is, in the present invention, the reason why the crystallization rate after thermal spraying is 80% or more is based on this point.

The adhesive strength is a comparison made using the numerical values obtained by the method shown in FIG. 1, and was obtained as follows. With a push rod (20 × 200 mm square refractory section) pressed against the side of the silica brick, a repair material (about 500 g) is flame sprayed below the push rod. Then, the push rod was pressed from above, and the pressing force of the push rod when the sprayed repair layer was peeled off from the silica brick was measured by the following formula to obtain the adhesive strength.

[Equation 1]

The material according to the present invention includes Na ₂ O as well as SiO _2.
Alternatively, a predetermined amount of Li ₂ O is added together with this Na ₂ O. With such a component composition, crystallization of the thermal spray repair layer immediately after thermal spraying is promoted, and the adhesive strength after crystallization is improved .
It is possible to form a dense and strong repair layer having a reduction rate of 30% or less and a compressive strength of 200 kgf / cm ² or more. Especially ,
When the compressive strength of the thermal spray repair layer is 200 kgf / cm ² or more, the abrasion resistance against coke extrusion in the coke oven becomes sufficient. The above-mentioned compressive strength is a value measured according to the test method for the compressive strength of refractory bricks specified in JIS R2206. Here, the thermal spray repair material is sprayed on the surface of silica brick with a thickness of 80 mm or more. A sample was cut out from the repair layer and used for the test.

The content of Na ₂ O as an additive component is in the range of more than 2.0 to 4.0 wt% in terms of the refractory concentration. The reason is that if Na ₂ O is 2 wt% or less, it is difficult to obtain a thermal spray repair layer having a compressive strength of 200 kgf / cm ² or more, and the problem of abrasion resistance remains. On the other hand, if this Na ₂ O is contained in excess of 4 wt%,
Since the crystallization rate of the repair layer immediately after thermal spraying does not reach 80%, peeling of the thermal spray repair layer is likely to occur. It is preferable
The content of Na ₂ O is 2.1 to 3.0 wt%. Further, as the Na ₂ O source, sodium silicate, sodium carbonate and the like are preferable, but other raw materials can also be used.

Next, Li ₂ O is converted into a refractory concentration,
Add 0.2 to 4.0wt%. This Li ₂ O is usually Na ₂ O described above.
A smaller amount is effective in increasing the crystallization rate of the sprayed repair layer. When the content of Li ₂ O is 0.2 wt% or less, the compressive strength is
It is difficult to obtain a thermal spray repair layer of 200 kgf / cm ² or more,
Insufficient wear resistance. On the other hand, if this amount exceeds 4.0 wt%, the crystallization rate of the thermal spray repair layer does not reach 80%, so that the thermal spray repair layer is liable to peel off. this
The preferable range of the Li ₂ O content is 0.3 to 1.0 wt%.
A raw material such as lithium carbonate can be used as the Li ₂ O source.

[0020] The onset Ming, those containing both Li ₂ O and Na ₂ O
May be In this case, (Li ₂ O + Na ₂ O) exceeds 0.2 ~
The range is 4.0 wt%. These total weight of less 0.2 wt%, it is difficult to compressive strength Ru obtain a 200 kgf / cm ² or more spraying repair layer, whereas, the crystallization rate of the repair layer immediately after thermal spraying exceeds 4 wt% 80 %, And the adhesive strength is insufficient.
There is a problem such as peeling of the sprayed layer. Preferably 0.3 wt
The range of% ≦ (Li ₂ O + Na ₂ O) ≦ 2.5 wt% is preferable.

In the present invention, components other than SiO ₂ , Na ₂ O and Li ₂ O are unavoidable impurities. As these components, oxides such as Al ₂ O ₃ , CaO, Fe ₂ O ₃ , TiO ₂ , and K ₂ O can be considered, but especially Al ₂ O ₃ has a strong tendency to inhibit crystallization. , 1.0 wt% or less is desirable.

The particle size of the material according to the present invention is not particularly limited, but it is preferable that the particle size is 0.15 mm or less. This is because if the material particle size is coarse, a large amount of fuel gas and oxygen are required to melt this material.

In a first embodiment of the present invention, SiO ₂ is
Sodium carbonate is added to materials such as silica stone containing 93 wt% or more 3.6%
When added in the range of ~ 6.8 wt%, in terms of concentration as an oxide, SiO _2: 89 wt% or more, and Na ₂ O: 2.1~ 4.0
Some have been compounded and adjusted so as to be in the range of wt%.

[0024]

In a second embodiment of the present invention, SiO ₂ is
Sodium carbonate is added to materials such as silica stone containing 93 wt% or more 3.6%
Lithium carbonate is added so that the addition rate of (sodium carbonate + lithium carbonate) is in the range of 3.6 to 9.9 wt% and the concentration as an oxide is SiO ₂ of 89 wt% or more and Li ₂ O: 0.2 wt% or more , and (Na ₂ O + Li ₂ O): 2.
Some of them have been compounded and adjusted so as to be in the range of more than 1 to 4.0 wt%.

In each of the above-described embodiments, the reason why sodium carbonate is used as the Na ₂ O source and lithium carbonate is used as the Li ₂ O source is that sodium carbonate and lithium carbonate are easy to handle, and they are easily melted during thermal spraying. This is because it easily reacts with SiO ₂ . In addition, it is preferable to uniformly mix these raw materials.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples. Table 1 (Example of the present invention), Table 2 (Comparative example), the chemical composition of the material (particle size -0.15mm), sprayed amount 50kg / h at the gas flow rate (Nm ³ / h) shown in the table, It was sprayed on the furnace wall (silica brick) of a coke oven with a furnace wall temperature of 750 ° C to form a sprayed repair layer. The thickness of this thermal spray repair layer was about 25 mm. Sprayed 3
After a minute, the sprayed repair layer was recovered and the crystallization rate was measured by compressive strength and X-ray diffraction. Ten minutes after the thermal spraying, the adhesive strength with the silica brick after the thermal spray repair layer was kept at 1200 ° C. for 100% crystallization was measured. The melting rates of the materials during thermal spraying are all 90% or more. The respective measurement results are also shown in Tables 1 and 2.

As is clear from the above measurement results, oxides
As the concentration of SiO₂: 89wt% or more and Na₂O: 2.1
~ 4.0wt%, SiO₂: 89 wt% or more,Li₂O: 0.2 wt% or less
Up,OrOne (Na₂O + Li₂O): over 2.1 to 4.0 wt%
In the case of a material according to the present invention, after 3 minutes have elapsed after thermal spraying
The crystallization rate of each is 80% or moreAs, Compression strength
Degree is 200kgf / cm²The above is shown. Further, according to the present invention
These materials are utilities for propane and oxygen
Is ± 15% or more, the crystallization rate after 3 minutes of thermal spraying is
Over 80%Moreover,Compressive strength is 200kgf / cm²Is over,
The characteristics required for high temperature furnace wall repair material of coke oven
Meet Moreover, 100% crystallized silica brick
The rate of decrease in the adhesive strength of each was less than 30%.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

As described above, according to the repair material of the present invention, since the crystallization rate immediately after thermal spraying is high and a dense thermal spray repair layer can be obtained, when the thermal spray repair layer has a crystallization rate of 100% ( Since there is almost no difference in thermal expansion characteristics between the furnace wall brick (when expanded), cracks and adhesive strength do not occur, and a thermal spray repair layer with high compressive strength can be obtained, resulting in edge wear resistance and durability ( Excellent life). Moreover, the material of the present invention can be applied to the above-mentioned thermal spray repair layer with a small amount of oxygen gas or propane gas.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method for measuring adhesive strength.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-190155 (JP, A) JP-A-59-156967 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 4/10 F27D 1/16

Claims (2)

(57) [Claims] 1. The oxide concentration is SiO ₂ : 89 wt% or more, Na ₂ O: more than 2.0 to 4.0 wt%, the balance is unavoidable impurities , and the crystallization rate immediately after thermal spraying is 80% or more. , Compression strength
When the repair layer is 100% crystallized when the degree is 200 kgf / cm ² or more
A powder mixture for flame spray repair, which exhibits an adhesive strength with a strength reduction rate of 30% or less . 2. The concentration as an oxide is SiO ₂ : 89 wt% or more, Li ₂ O: 0.2 wt% or more, and (Na ₂ O + Li ₂ O): 0.2.
Ultra-4.0 wt%, the balance consists of unavoidable impurities ,
Crystallization rate after flame spraying is 80% or more, compressive strength is 200kgf / c
Reduction rate of strength when the repair layer is 100% crystallized for m ² or more
A powder mixture for repairing flame spraying, which has an adhesive strength of 30% or less .