JPH11279740A - Powder mixture for repair of flame thermal spraying - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a crystallization rate under a wide thermal spraying condition and to obtain a dense thermal spray repaired layer by containing a specified value in each of SiO2 , Na2 O and the balance inevitable impurities. SOLUTION: The SiO as a main component of a mixture has a component roughly same as a fluorite brick used for a furnace inner face. A content of SiO2 is >=89 wt.% in term of a concentration as oxide. An impurity component of Al2 O3 , etc. is increased in the case that SiO2 content is less than this value, the crystallization rate of a repaired layer immediately after thermal spray is turned to <80%, thereby a crack is likely generated to a joining face between the repaired layer and furnace wall brick. In adding Na2 O and/or Li2 O in addition to SiO2 , crystallizing of the thermal spray repaired layer immediately after thermal spray is promoted, and a dense and strong repaired layer having a compression strength of 200 kgf/cm can be formed. A content of Na2 O is <2.0-4.0 wt.% in term of a concentration of a refractory, a content of Li2 O is >=0.2 wt.% and (Na2 O+Li2 O) is 0.2-4.0 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an inner wall of an industrial furnace,
More particularly, the present invention relates to a powder mixture for flame spray repair, which is a material for repairing an inner wall of a coke oven in a high heat state, in which a powdery refractory is melted by a flame and sprayed and repaired using an injection nozzle.

[0002]

2. Description of the Related Art The furnaces of industrial furnaces, especially coke ovens, blast furnaces, steelmaking furnaces and the like as steel facilities, are carbonized coal,
It is in a harsh environment where it is exposed to high temperatures of 1000 ° C or more in contact with molten materials such as hot metal, molten steel, and slag. In particular, during the operation of extruding coke from the coke oven carbonization chamber and the operations of pouring, storing, and discharging hot metal and molten steel in a steelmaking furnace, these inner walls encounter remarkable temperature fluctuations. Therefore, these inner walls are not only damaged by the infiltration of the melt, but also frequently damaged by thermal spalling, such as cracks and peeling. To deal with such various damage factors, it is necessary to select an appropriate material brick at the stage of design or furnace construction, and to improve its life, it is necessary to repair it halfway. .

For example, as a repair technique, there is a flame spraying repair method in which a repair material is hot-sprayed on a refractory damaged portion. This flame spraying repair method is mainly used for repairing refractory oxide powder or easily oxidizable powder having the same composition as the material of the furnace wall refractory to be repaired, mainly for the inner wall of the furnace at high temperature. This is a technique for 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 the combustible gas, and the easily oxidizable powder is heated and melted by its own combustion to become an oxide, and the refractory oxide powder is melted. A thermal spray repair layer can be formed with the body. In particular, coke ovens
Since the furnace temperature cannot be lowered except at the time of renovation and the furnace wall must be repaired in a high temperature state, such a flame spraying repair method is effective.

[0004] As a prior art relating to such a flame spraying repair method, there is, for example, a method disclosed in Japanese Patent Publication No. 2-45110. In this method, a powdery refractory oxide is mixed with a combustible substance and a combustible gas and supplied to a supporting gas containing oxygen, such as oxygen or air, and the refractory oxide is heated by the heat of the combustion flame. This is a dry method in which the material powder is melted and instantaneously blown to the damaged part of the inner wall of the furnace. In this method, the sprayed repair refractory is more durable than a repair refractory constructed based on a method in which water and a blasting material are mixed in advance and mudified material is sprayed from a tank, that is, a wet spray method. There is a characteristic that the sex is extremely high.

[0005] By the way, as a thermal spraying material used for such a flame spraying repair method, for example, Japanese Patent Publication No. Hei 3-9185, SiO ₂ : 93.9 to 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 propose a high-silica spray material consisting of ₂ O: 0.4-2.0 wt%. Generally, this type of material has a crystallization rate of 60% or more immediately after thermal spraying, but cracks are generated due to expansion when the amorphous (glassy) part (<40%) crystallizes. And a decrease in adhesive strength due to a difference in thermal expansion characteristics between the thermal spray repair layer and the coke oven wall brick. That is, the materials according to the above proposals have been developed to overcome the adverse effects caused by such a low crystallization rate.

However, the technique disclosed in Japanese Patent Publication No. Hei 3-9185 discloses that the thermal spraying conditions for forming a thermal spray repair layer having a crystallization ratio of a material of 60% or more, that is, the oxygen gas flow rate and the propane gas flow rate are extremely narrow. There was a problem that it was limited to the range. Further, under a spraying condition in which a sprayed repair layer having a crystallization rate of 60% or more can be obtained, it is difficult to obtain a dense sprayed repair layer, that is, a sprayed repair layer having a high compressive strength. There was a problem that the life of the layer was short. As described above, in the prior art, since the crystallization rate is low, the problem that cracks are easily generated in the repair layer and the adhesive strength to the substrate surface remains low, but at least to increase the crystallization rate Are severe, the compressive strength is not increased, the abrasion resistance is poor, and the life is short.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermal spray repair material which has a high crystallization rate immediately after thermal spraying and is effective for applying a dense thermal spray repair layer under a wide range of thermal spray conditions. It is in. Another object of the present invention is to provide a thermal spray repair material which is excellent in abrasion resistance and durability (life) by ensuring high compressive strength without cracking of the repair layer or reduction in adhesive strength to the repair surface. Is to provide.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies on the above-mentioned problems of the prior art and found that the crystallization ratio immediately after thermal spraying was 80% under a wide range of thermal spraying conditions.
As described above, a powdery mixture has been developed as a flame spray repair material effective for obtaining a spray repair layer having high compressive strength.

That is, the present invention basically relates to an oxide
Concentration is SiO_Two: 89wt% or more, Na _TwoO: 2.0-4.0wt
%, With the remainder being inevitable impurities for flame spraying repair
It is a powdery mixture.

A second aspect of the present invention has a concentration as an oxide of at least 89% by weight of SiO _{2 and} 0.2 to 4.0% by weight of Li ₂ O, with the balance being an inevitable impurity. It is a powdery mixture.

Further, a third aspect of the present invention is to provide an oxide
Concentration is SiO_Two: 89wt% or more, Li _TwoO: 0.2wt% or more,
And (Na_TwoO + Li_TwoO): More than 0.2 to 4.0 wt%, with the balance being
It is a powdery mixture for flame spray repair which is an inevitable impurity.
You.

In the present invention, a powdery mixture capable of forming a thermal spray repair having a crystallization ratio after flame spraying of 80% or more and a compressive strength of 200 kgf / cm ² or more is preferable. It becomes an aspect.

Here, the meaning of the concentration as an oxide means the amount of the remaining oxides, carbonates, metals, and other components excluding moisture contained in the material, assuming 100 as the oxide. (Wt%).

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention contains SiO ₂ as a main component. This SiO ₂ is almost the same component as the silica brick used on the inner surface of the furnace wall of a coke oven, etc., and when these inner wall surfaces are used as repair parts, the thermal expansion between the furnace wall brick and the sprayed repaired refractory layer It is an essential component to make the characteristics almost match. In the present invention, the content of SiO ₂ is set to 89 wt% or more in terms of an oxide concentration. 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 increases, and due to this effect the crystallization rate of the repair layer immediately after thermal spraying Is 80%
It is because it falls below. If the crystallization rate of the repaired layer immediately after thermal spraying becomes less than 80%, the joining of the repaired layer and the furnace wall brick is caused by the difference in thermal expansion when the sprayed repaired layer crystallizes 100%. Cracks are likely to occur on the surface, and the sprayed repair layer peels off. In the present invention, as a raw material of the SiO ₂ component, silica brick waste, silica stone, silica sand, or the like can be used.

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

The adhesive strength is a value obtained by comparing the values obtained by the method shown in FIG. 1 and obtained as follows. With a push rod (a refractory with a cross section of 20 x 200 mm square) pressed against the side of the silica brick, the repair material (about 500 g) is flame-sprayed below the push rod. Then, the pressing rod was pressurized from above, and the pressing force of the pressing rod when the sprayed repair layer was peeled off from the silica brick was measured by the following formula, and was defined as the adhesive strength.

(Equation 1)

The material according to the present invention is, in addition to SiO ₂ , Na ₂ O
And / or a predetermined amount of Li ₂ O is added. With such a component composition, crystallization of the thermal spray repair layer immediately after thermal spraying is promoted, and a dense and strong repair layer having a compressive strength of 200 kgf / cm ² or more can be formed. In this regard, when the compressive strength of the thermal spray repair layer is 200 kgf / cm ² or more, the abrasion resistance against coke extrusion in a coke oven becomes sufficient. The above-mentioned compressive strength is a value measured in accordance with the test method for compressive strength of refractory bricks specified in JIS R2206.
A sample was cut out from the sprayed repair layer having a thickness of at least mm and used for the test.

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

Next, Li ₂ O is converted into the concentration of refractory,
Add 0.2-4.0wt%. This Li ₂ O is usually the above Na ₂ O
A smaller amount has an effect of increasing the crystallization rate of the thermal spray repair layer. If the Li ₂ O content is 0.2 wt% or less, the compressive strength
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 the content exceeds 4.0 wt%, the crystallization ratio of the thermal spray repair layer does not reach 80%, so that the thermal spray repair layer tends to peel off. this
The preferred range of the content of Li ₂ O is 0.3 to 1.0 wt%.
Note that a raw material such as lithium carbonate can be used as the Li ₂ O source.

In the present invention, when both of the above Li ₂ O and Na ₂ O are contained, the same or more effects can be obtained. That is, (Li ₂ O + Na ₂ O) is in the range of more than 0.2 to 4.0 wt%. These total weight of less 0.2 wt%, the compressive strength is difficult to 200 kgf / cm ² or more spray repair layer Oru, whereas the crystallization rate of the repair layer immediately after thermal spraying exceeds 4 wt% 80% And there are problems such as peeling of the sprayed layer. Preferably, 0.3wt% ≦ (Li ₂ O + Na ₂ O) ≦ 2.5wt%
Range is good.

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. Particularly, Al ₂ O ₃ has a strong tendency to inhibit crystallization. , 1.0 wt% or less.

The particle size of the material according to the present invention is not particularly limited, but is preferably set to a particle size of 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 the material.

In a first embodiment of the present invention, SiO ₂ is used.
3.6% sodium carbonate in materials such as silica containing 93wt% or more
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 are adjusted to be in the range of wt%.

In a second embodiment of the present invention, SiO ₂ is used.
Lithium carbonate 0.5 ~
When added in the range of 9.9 wt%, converted to oxide concentration, SiO ₂ : 89 wt% or more, and Li ₂ O: 0.2 to 4.0 wt%
% Is adjusted to be in the range of%.

According to a third embodiment of the present invention, SiO ₂ is used.
3.6% sodium carbonate in materials such as silica containing 93wt% or more
wt% or more, and then adding lithium carbonate to give addition levels (sodium carbonate + lithium carbonate) is in the range of 3.6 to 9.9 wt%, and the concentration of the oxides, the SiO ₂ 89 wt% or more, and Li ₂ O: 0.2 wt% or more and (Na ₂ O + Li ₂ O): 2.1
Some of them are blended and adjusted so as to be in the range of super to 4.0 wt%.

In each of the above embodiments, the reason for using sodium carbonate as the Na ₂ O source and lithium carbonate as the Li ₂ O source is that sodium carbonate and lithium carbonate are easy to handle, and are easily melted during thermal spraying. This is because it easily reacts with SiO ₂ . It is preferable that these materials are uniformly mixed.

[0027]

The present invention will be described below in more detail with reference to examples. The materials (grain size -0.15 mm) of the chemical components shown in Table 1 (Example of the present invention) and Table 2 (Comparative Example) were sprayed at a gas flow rate (Nm ³ / h) of 50 kg / h shown in the same table. Thermal spraying was performed on the furnace wall (silica brick) of a coke oven with a furnace wall temperature of 750 ° C to form a thermal spray repair layer. The thickness of the thermal spray repair layer was about 25 mm. Sprayed 3
One minute later, the sprayed repair layer was collected, and the crystallization ratio was measured by compressive strength and X-ray diffraction. Ten minutes after the thermal spraying, the adhesive strength to the silica brick after the sprayed repair layer was maintained at 1200 ° C. and crystallized 100% was measured. The melting rates of the materials during thermal spraying are all 90% or more. The respective measurement results are shown in Tables 1 and 2.

As is apparent from the above measurement results, the oxide concentration is at least 89 wt% for SiO ₂ and 2.1 for Na ₂ O:
_{~ 4.0wt%, SiO 2: 89wt} % or more, and Li ₂ O 0.2~ 4.0
_{wt%, SiO 2 89: wt} % or more, and Li ₂ O: more than 0.2 wt% and _{(Na 2 O + Li 2 O} ): 2.1 For such material to the present invention in the range of ultra ～4.0Wt%,, after spraying After 3 minutes, the crystallization ratio was 80% or more, and the compressive strength was 200 kgf / cm ² or more. Further, these materials according to the present invention have a crystallization rate of 80% or more after 3 minutes of thermal spraying and a compressive strength of 200 kgf / cm ² or more when propane and oxygen utilities are in a range of ± 15% or more. It satisfies the characteristics required as a high-temperature furnace wall repair material for furnaces. Moreover, 1
The rate of decrease in the adhesive strength with the silica brick after the crystallization of 00% was 30% or less in all cases.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

As described above, according to the repair material of the present invention, the crystallization rate immediately after thermal spraying is high, and a dense thermal spray repair layer can be obtained. Therefore, when the crystallization rate of the thermal spray repair layer becomes 100% ( (Due to expansion), there is almost no difference in thermal expansion characteristics with the furnace wall brick, so that cracks and bond strength do not occur, and a sprayed repair layer with high compressive strength is obtained, so that end wear and durability ( Life). In addition, the material of the present invention can apply the above-mentioned thermal spray repair layer with a small amount of oxygen gas and propane gas.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method of measuring an adhesive strength.

Claims (4)

[Claims] 1. A powder mixture for repairing by flame spraying, wherein the concentration as an oxide is at least 89% by weight of SiO ₂ , more than 2.0 to 4.0% by weight of Na ₂ O, and the balance is inevitable impurities. 2. A powder mixture for repairing by flame spraying, wherein the concentration as an oxide is at least 89% by weight of SiO _{2 and} 0.2 to 4.0% by weight of Li ₂ O, with the balance being inevitable impurities. 3. The concentration as an oxide is as follows: SiO ₂ : 89 wt% or more, Li ₂ O: 0.2 wt% or more, and (Na ₂ O + Li ₂ O): more than 0.2 to 4.0 wt%, with the balance being inevitable Flame spray repair powder mixture as an impurity. 4. The powdery mixture for repairing flame spraying according to claim 1, wherein the crystallization ratio after flame spraying is 80% or more and the compressive strength is 200 kgf / cm ² or more.