JP2549035B2 - Fireproof powder for thermal spraying - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame-retardant powder for thermal spraying suitable for use as a furnace wall repair material for converters and other kilns.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 60-53273 discloses an M
Disclosed is a flame spray repair method for a kiln in which a powdery refractory raw material containing gO as a main component is sprayed together with a flux by a flame to form a sprayed layer on the furnace wall.

In Japanese Examined Patent Publication No. 63-53153, an aluminum compound and a magnesium compound are appropriately mixed and fired at 1000 to 1650 ° C., and thereafter, an average particle size is 30 to 1
A spinel thermal spray material pulverized to 00 μm is disclosed.

Japanese Patent Publication No. 61-10418 discloses a thermal spray material having a structure in which primary particles made of a refractory material having an average particle size of 10 μm or less are combined with an organic binder to form secondary particles having an average particle size of 30 to 500 μm. It is disclosed.

Further, in Japanese Patent Laid-Open No. 61-186258, a surface of a high melting point refractory material powder having a particle size adjusted to 200 to 10 μm is formed on a surface of an easily sinterable oxide having an average particle size of 10 to 0.1 μm. A flame spray refractory powder coated with a fine powder is disclosed.

Further, in Japanese Patent Laid-Open No. 61-118131, a powder of an inorganic composition is melted in a combustion region to form a molten particle,
A combustion furnace apparatus for particle production is shown which cools them rapidly in a cooling zone to prevent fusing and form independent spherical particles.

Conventionally, the refractory powder used as a furnace wall repair material for a kiln has alumina, chromium, magnesia, etc. as its main components to enhance the meltability and to improve workability and adhesiveness. It has been heat-treated and granulated to increase the specific surface area, add converter slag or iron powder, or coat the refractory material with a low-melting material.

[0008]

However, the conventional treatments such as granulation and coating on the surface of the refractory material have the drawback of increasing the manufacturing cost of the thermal spray material. Further, the addition of converter slag tends to cause phosphorus and sulfur contained in the slag to become inclusions in the molten steel and cause a significant adverse effect.

Therefore, an object of the present invention is to provide a refractory powder for thermal spraying which can be manufactured easily and inexpensively and which is excellent in corrosion resistance.

[0010]

SUMMARY OF THE INVENTION The present invention is a sintered magnesia clinker, electrofused magnesia clinker, sintered spinel, dolomite clinker, lime clinker, alumina, chromite, chamotte or a combination thereof 60 to 98 weight parts. % Of the refractory raw material is mixed with shale or pearlite in an amount of 1 to 40% by weight.

The particle size range of shale or pearlite is preferably 5
Adjust to 00-25 μm.

[0012]

In the present invention, one or a combination of sintered magnesia clinker, electrofused magnesia clinker, sintered spinel, dolomite clinker, lime clinker, alumina, chromite and chamotte is used as a refractory raw material, and shale is used. Alternatively, since pearlite is mixed, the peculiar thermal expansion curve of shale or pearlite described later synergistically acts on such a refractory material, and gives good results as a refractory powder for thermal spraying.

The present invention makes good use of the thermal characteristics of shale or pearlite, and improves the adhesion to furnace wall bricks and the densification of the molten layer. In a thermal spray material in which shale or pearlite is mixed with a refractory raw material, the shale or pearlite starts to expand abnormally due to the flame when passing through the flame, the specific surface area is expanded, and the meltability is high. As a result, it becomes possible to easily attach the refractory raw material to the furnace wall having a small specific surface area and a poor weldability. That is, instead of spraying a material having an increased specific surface area by a pretreatment such as granulation, the refractory raw material is welded to the molten surface of shale or pearlite spread over the entire surface due to abnormal expansion to improve adhesion. is there.

[0014]

EXAMPLE The present invention is a sintered magnesia clinker, a fused magnesia clinker, a sintered spinel as a refractory raw material,
Dolomite clinker, lime clinker, alumina,
A refractory powder for thermal spraying, characterized in that shale or pearlite is mixed using one kind of chromite and chamotte or a combination thereof.

Further, in the case of a converter slag or a thermal spray material to which other flux is added, phosphorus and sulfur contained in the additive material penetrate into the molten steel to cause a remarkable adverse effect. However, the refractory powder according to the present invention does not contain converter slag or flux, and since it is composed of a raw material containing very little phosphorus and sulfur, the inclusion of phosphorus and sulfur in molten steel does not affect it. It is a very preferable composition as a repairing material. The refractory raw material preferably has a particle size of 300 to 25 μm. The reason is that if it exceeds 300 μm, the particle surface tends to lack meltability, it becomes relatively difficult to form an adhesive property or a dense welding layer, and corrosion resistance deteriorates. On the other hand, if the particle size is less than 25 μm, clogging or scattering to the spray burner part becomes too vigorous, it becomes difficult to set appropriate spraying to the repaired part, it becomes difficult to form a weld layer, and fluidity deteriorates. Therefore, the ejection from the nozzle pulsates and the density of the thermal spraying material often becomes non-uniform in the thickness direction of the layer.

The amount of refractory material added is limited to 60 to 98% by weight. The reason is that when the refractory raw material is less than 60% by weight, the corrosion resistance is deteriorated and the desired service condition cannot be obtained. On the contrary, when it exceeds 98% by weight, the weldability and the adhesion to the furnace wall brick are increased. This is because it tends to result in loss of sex. It may contain impurities in an amount of 1% by weight or less.

As the refractory raw material, it is desirable to use one kind or a combination of two or more kinds according to changes in kiln furnace conditions and operating conditions.

Commercially available raw materials can be added as the refractory raw material.

The shale or pearlite added to the refractory raw material is a raw material having a relatively low melting point and has a composition as shown in Table 1, for example. This raw material plays a major role in forming a dense sprayed layer and high adhesion strength to the furnace wall refractory.
Both shale and pearlite cause abnormal expansion by rapid heating at 900 to 1200 ° C.

Pearlite is a kind of rock forming a volcano, belongs to acidic rocks containing a large amount of silicic acid (SiO ₂ ), and is a kind of glass naturally produced. Although its chemical composition varies depending on the place of origin, it is roughly a silicic acid content (SiO ₂ ) and an alumina content (Al
80% or more of the sum of ₂ O ₃ ) and alkali content (Na ₂ O, K
₂ O) to some extent, and always 2-5 crystallization water (H ₂ O).
%have.

[0021] The specific gravity is 2.3 to 2.5, and it always has a pearly luster, and is often slightly transparent and has a seemingly pale smoke crystal color or gray.

Further, a product obtained by crushing and expanding raw stones is called perlite, and is widely used for heat insulating materials and building materials.

The reason why the fired pearlite, that is, perlite, expands when heated rapidly is that the moisture and volatile components contained in the rough stone are heated to cause explosive escape, This is because glassy pumice with many vacuum-like bubbles is created inside.

A shale is a kind of sedimentary rock that is crushed by the action of wind, running water, and rainwater into fine clay particles and deposited on the ocean or lake bottom, and is distributed as a stratum. Many are brown to dark black.

The chemical composition differs depending on the place of origin, but in all cases, clay is vitrified by heating and contains the gas generated inside. It is said that the gas expands by acting on organic substances, sulfides and oxides in shale to generate carbon dioxide gas, anhydrous sulfuric acid gas and the like.

As described above, pearlite and shale are raw materials having a relatively low melting point, and at a temperature of 900 to 1200 ° C., a phenomenon of abnormal expansion accompanying the melting of the raw materials is observed.

The particle size of shale or pearlite is 300 to 25 μm
It is best to adjust to. When shale or pearlite with a particle size of more than 300 μm is added, the sprayed powder passes through the high-speed flame for an extremely short time, so it is difficult to melt instantly in the flame, and the adhesiveness decreases. The resulting adhesive layer may lack strength or corrosion resistance. On the other hand, if the particle size is less than 25 μm, good working conditions and formation of a weld layer tend to be difficult, as described in the refractory raw material.

As described above, shale or pearlite decomposes and melts at a relatively low temperature, and plays a role of significantly improving the adhesiveness of the thermal spray material.

The amount of shale or pearlite added is preferably 1 to 40% by weight from the viewpoint of adhesion and corrosion resistance. 1% by weight
If it is less than the above range, the adhesiveness and the corrosion resistance are deteriorated, and it tends to be difficult to form a good welding layer. On the other hand, if the amount of shale or pearlite added exceeds 40% by weight, the adhesiveness is good, but the adhesiveness and corrosion resistance are often inferior, and it becomes necessary to increase the amount of repair material, which causes Cause deterioration. Among these ranges, the optimum addition amount of shale or pearlite is most preferably 5 to 25% by weight from the viewpoint of adhesion and corrosion resistance.

Examples 1 to 8 and Comparative Examples 1 to 3 will be described to more specifically show the present invention. The raw material compositions and test results of Examples 1 to 8 and Comparative Examples 1 to 3 are as shown in Table 2.

In Table 2, "adhesiveness" is the ratio of the material that has not adhered to it, subtracted. And the adhesive is a measure of the shear force between the adhesive layer and the bricks _{(MgO-Cr 2 O 3)} . The term "corrosion resistance" refers to the erosion dimension of a welded layer that has been tested by a rotary erosion machine.

[0032]

[Example 1] The raw material consisted of sintered magnesia clinker, dolomite clinker, and pearlite, and the amount of sintered magnesia clinker added as a refractory raw material was 68% by weight, and that of dolomite clinker was 30% by weight. Pearlite is 2% by weight. These raw materials were mixed to obtain a thermal spray material. The thermal spray material was tested for adhesion, adhesion and corrosion resistance.

The adhesiveness of Example 1 was 75% by weight, the adhesiveness was 4.2 kgf / cm ² , and the erosion amount was 15 mm.

[0034]

Example 2 5% by weight of pearlite was added to 45% by weight of sintered magnesia clinker and 50% by weight of dolomite clinker as refractory raw materials, and they were mixed to obtain a thermal spray material. When the sprayed material was tested, the adhesion was 85% by weight, the adhesion was 6.8 kgf / cm ² , and the erosion amount was 1.
It was 2 mm.

[0035]

Example 3 To 80% by weight of alumina as a refractory raw material and 15% by weight of chamotte, 5% by weight of pearlite was added,
These were mixed to obtain a thermal spray material. The test result of the thermal spray material shows that the adhesiveness is 95% by weight and the adhesiveness is 10.2 kgf /
The erosion amount was 22 mm in cm ² .

[0036]

Example 4 25% by weight of pearlite was added to 75% by weight of sintered magnesia clinker as a refractory raw material, and they were mixed to obtain a thermal spray material. The test result shows that the adhesiveness is 97.
% By weight, the adhesion was 7.1 kgf / cm ² and the erosion amount was 18 mm.

[0037]

Example 5 40% by weight of shale was added to 60% by weight of sintered magnesia clinker as a refractory raw material, and they were mixed to obtain a thermal spray material. The test results of this thermal spray material are
Adhesiveness is 95% by weight and adhesiveness is 3.9 kgf / cm ²
The erosion amount was 20 mm.

[0038]

Example 6 5% by weight of shale was added to 55% by weight of sintered spinel as a refractory raw material and 40% by weight of electrofused magnesia clinker to obtain a thermal spray material. The test results of the thermal spray material showed that the adhesiveness was 80% by weight, the adhesiveness was 6.5 kgf / cm ² , and the erosion amount was 15 mm.

[0039]

Example 7 A thermal spray material was obtained by adding 10% by weight of pearlite to 60% by weight of refractory raw material and 30% by weight of sintered magnesia clinker. The test result of the thermal spray material shows that the adhesiveness is 75% by weight and the adhesiveness is 5.5 kgf /
cm ² , and the amount of erosion was 20 mm.

[0040]

Example 8 15% by weight of pearlite was added to 30% by weight of chromite and 55% by weight of lime clinker as refractory raw materials to obtain a thermal spray material. The test results of the thermal spray material showed that the adhesiveness was 80% by weight, the adhesiveness was 6.2 kgf / cm ² , and the erosion amount was 25 mm.

In the above-mentioned Examples 1 to 8, the adhesion, adhesiveness and erosion amount were all good results.

Next, Comparative Examples 1 to 3 which are outside the scope of the present invention will be described.

[0043]

Comparative Example 1 70% by weight of sintered magnesia clinker as a refractory raw material and 30% by weight of alumina particles were mixed to obtain a thermal spray material. No shale or pearlite was added. When a test was performed on such a thermal spray material, the test results showed that the adhesiveness was 38% by weight and the adhesiveness was 0.8 kg.
The erosion amount was 38 mm at f / cm ² . That is, the adhesiveness and adhesiveness were poor.

[0044]

Comparative Example 2 45% by weight of pearlite was added to 55% by weight of sintered magnesia clinker as a refractory raw material, and they were mixed to obtain a thermal spray material. According to the test results of this thermal spray material, the adhesiveness was 93% by weight, and high characteristics were obtained. However, the adhesiveness was 2.3 kgf / cm ² , and the erosion amount was 43 mm, and the adhesiveness and the erosion amount were significantly inferior to any of Examples 1 to 8 of the present invention. .

[0045]

[Comparative Example 3] 50% by weight of chamotte as a refractory raw material
50% by weight of shale was added to the above, and they were mixed to obtain a thermal spray material. The test results of this thermal spray material are shown in Comparative Example 2 above.
Similarly, the adhesiveness was excellent, but the adhesiveness and the corrosion resistance were inferior to the examples of the present invention. That is, Comparative Example 3
Adhesiveness is 95% by weight and adhesiveness is 1.8 kgf
/ Cm ² , the erosion amount was 68 mm.

[0046]

Example 9 10% by weight of pearlite was added to 75% by weight of sintered magnesia clinker as a refractory raw material and 15% by weight of dolomite clinker, and they were mixed to obtain a refractory powder for thermal spraying. The flame-retardant powder for thermal spraying was used as a repair material for the actual converter repair section, and was sprayed. When the service life was measured, it was found that the service life was about twice as high as that of the repaired portion of the conventional thermal spray material which was used for comparison.

Further, when the characteristics of the welded layer were investigated by spraying spraying the brick panel under the same conditions as when the converter was repaired, the sprayed material of the present invention showed better weldability than conventional sprayed materials. , Revealed that the physical properties are extremely excellent. That is, the weld layer of the present invention had an apparent porosity of 0.8 to 1.4, a water absorption rate of 0.2 to 0.4%, and an adhesion rate of 96%, whereas The sprayed body had an apparent porosity of 8 to 12%, a water absorption rate of 2 to 2.5%, and an adhesion rate of 93%.

[0048]

As is apparent from the above description, the present invention provides one or a combination of sintered magnesia clinker, electrofused magnesia clinker, sintered spinel, dolomite clinker, lime clinker alumina, chromite and chamotte. It is a refractory powder for thermal spraying characterized by mixing shale or pearlite in a predetermined ratio, so when used as a repair material for converters, etc., it has better adhesion, adhesion and erosion than conventional ones. It is remarkably superior in terms of quantity.

Further, according to the present invention, since commercially available general raw materials can be used, it is not necessary to carry out any pretreatment such as heat treatment or granulation treatment as in the conventional case, and a desired refractory powder can be produced at low cost. it can.

The formation of the sprayed layer was made possible only by mixing the existing raw material and the raw material having a relatively low melting point which is naturally produced.

Further, according to the present invention, it is possible to sufficiently use a raw material having a so-called unnecessary particle size, which cannot be used for a general standard refractory or an irregular refractory produced from a raw material manufacturer, as an appropriate material. In that respect, the manufacturing cost can be reduced.

[Table 1]

[Table 2]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Aoki 1st Nanto, Ogakie-cho, Kariya city, Aichi Toshiba Ceramics Co., Ltd. Kariya Plant (72) Inventor Yagi Juki, 1850 Minato, Wakayama, Wakayama Sumitomo Metal Industries, Ltd. Inside the Wakayama Works (72) Inventor Yoshikazu Kubo 1850 Minato, Wakayama, Wakayama Sumitomo Metal Industries, Ltd. Inside the Wakayama Works (72) Inventor Atsumori Mizuguchi 4-5-33 Kitahama, Chuo-ku, Osaka City, Osaka Sumitomo Metal Industries Within the corporation

Claims (1)

(57) [Claims] 1. One or a combination of sintered magnesia clinker, electrofused magnesia clinker, sintered spinel, dolomite clinker, lime clinker, alumina, chromite, chamotte and 60 to 98% by weight thereof.
A refractory powder for thermal spraying, characterized in that 1 to 40% by weight of shale or pearlite is mixed with the refractory raw material .