JPH06199576A - Thermal spraying material - Google Patents

Abstract

PURPOSE:To improve the strength and adhesiveness of a thermally sprayed body as well as to retain flowability and to enable thermal spraying without pulsation by incorporating a prescribed percentage each of metallic Si powder and flake graphite powder, fine hydrophobic silica powder or hydroxyapatite powder. CONSTITUTION:This thermal spraying material consists of 20-40wt.% metallic Si, 0.01-3wt.% fluidization accelerator and the balance fired refractory powder. The fluidization accelerator is selected among flake graphite powder, fine hydrophobic silica powder, hydroxyapatite powder and boron nitride powder. The metallic silicon contains 5-10% powder having <=10mum particle diameter and 15-30% powder having 10-250mum particle diameter. The refractory powder contains <=10% fine powder having <=10mum particle diameter. This thermal spraying material is fed into a flow of gaseous oxygen in a hot state and the refractory powder is melted by the heat of combustion of the metallic silicon to repair the wall of a furnace made of silica brick.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal spray material (thermal spray repair material) used for thermal spray repair of furnace walls using silica bricks such as coke ovens. The present invention relates to a thermal spray material which is sprayed to melt the refractory powder by the combustion heat of metallic silicon.

[0002]

2. Description of the Related Art In a furnace such as a heating furnace, a soaking furnace, a coke oven, or a molten metal container such as a tundish or a ladle, an amorphous fire resistance is used during use. Local damage to the lining and brick walls can occur.

In recent years, as a method for repairing such local damage, a thermal spray repair method has been used in which refractory powder is melted by a high-temperature flame and is injected into the damaged part. Since this thermal spray repair method can perform hot repair, there is little deterioration of the base metal refractory (such as refractory bricks), the repair part is dense and has high strength, and adhesion to the base metal refractory Is also good.

As a thermal spray material used in such a thermal spray repair method, there is, for example, the thermal spray material disclosed in Japanese Patent Laid-Open No. 56-54276. This thermal spray material is a material obtained by mixing 100 parts by weight of refractory fine powder, 10 to 60 parts by weight of carbonaceous solid fuel, and 1 to 50 parts by weight of slag powder,
It is a type of material that is injected into an oxygen stream and sprayed by the combustion flame of carbonaceous solid fuel.

However, in this thermal spray material, since the slag powder is a low-melting substance, the adhesion rate is high, but when the thermal spraying temperature rises, the slag foams and the porosity of the thermal spray layer increases and the strength of the thermal spray layer increases. There is a problem in that

Further, Japanese Patent Application Laid-Open No. 49-46364 discloses a method of spraying with a combustion flame of at least one solid particle of metal or metalloid having an average particle diameter of 50 μm or less.

However, in this method, when a thermal spray material containing 10 μm or less of metallic silicon of 10 μm or more is jetted into an oxygen stream and ignited, it explosively burns and a backfire is likely to occur. However, there is a problem that it poses a danger to workers.

Further, the particle size range is 10 μm to 75 μm.
In the case of a thermal spray material containing 20% by weight or more of metallic silicon having an average particle size of 50 μm or less, the fluidity of the metallic silicon powder is poor, so the fluidity of the thermal spray material (powder) is deteriorated and pulsation occurs. There is a problem that it is easy. When pulsation occurs in the supply of the thermal spray material, the thermal spray flame becomes unstable, and the flame becomes extremely small or large, which is not only dangerous for the operator, but also the physical properties of the thermal spray layer are non-uniform. However, there is a problem that it is not preferable.

Further, in Japanese Patent Laid-Open No. 4-13308,
Particles of an exothermic oxidative material (metal silicon, metallic aluminum) having an average particle diameter of 50 μm or less are mixed with particles of a non-combustible refractory material, and the mixture is burned while being sprayed on one surface to be intimately fire-resistant on the surface. A method of forming aggregates is disclosed. As in this method, when metal silicon or metal aluminum is used, the amount of heat generated increases as the amount of metal aluminum added increases, and the strength of the sprayed structure increases and the adhesiveness improves, but flashback occurs. There is a problem that it tends to occur.

When the amount of metallic aluminum added is small and the total amount of metallic powder is 20% by weight or less, the calorific value is small. Therefore, a low melting point substance should be added to the refractory powder.
Unless the particle size composition is such that the refractory fine powder having a particle size of 10 μm or less is 10% by weight or more, the adhesion rate decreases. However, there is a problem that as the proportion of fine powder of 10 μm or less in the refractory powder increases, the amount of dust generated increases and the working environment deteriorates.

Further, unless the siliceous refractory powder subjected to the same firing treatment as in the case of making silica bricks is used, the crystal dislocation (573) occurs when the unmelted material remains.
(.Degree. C.), the change in the line becomes large, and the peeling of the spray-coated article increases, which is not preferable.

The present invention solves the above-mentioned problems. Even if the amount of metal silicon added is increased, the fluidity does not decrease, quantitative supply is possible, and the strength of the sprayed product is high. An object of the present invention is to provide a thermal spray material that is large and has excellent adhesiveness, and is particularly suitable for repairing a furnace wall using silica brick in a coke oven carbonization chamber or the like.

[0013]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors conducted various experimental studies and obtained the following findings.

That is, in the case of repairing a furnace wall made of silica stone brick such as a coke oven carbonization chamber, the thermal expansion coefficient of the sprayed work body having a composition close to that of silica stone brick is similar to that of silica stone brick, and Peeling due to change is less, which is preferable.

Further, although the heat-melted spalling product which is completely melted is inferior in heat resistance, the heat-resistant spalling property can be improved by using a heat-sprayed work product containing unmelted refractory particles.

As the unmelted refractory particles, the refractory particles fired so as to have the same mineral composition as the silica brick have a smaller change in line between heat due to repeated thermal changes, Peeling wear is low.

Further, in order to make the sprayed work body to have a composition equivalent to that of silica brick with a spraying material of the type that is sprayed by the combustion flame of solid fuel, it is preferable to use metallic silicon for solid fuel to produce silica by combustion. Therefore, it is advantageous.

Further, the metallic silicon powder has poor fluidity as a powder, and if added in a large amount, the fluidity of the powder of the thermal spray material is lowered and it becomes difficult to quantitatively supply the thermal spray material. Of powdery graphite powder, hydrophobic silica fine powder, hydroxyapatite powder, boron nitride powder, etc. by adding powders (fluid accelerators) that improve powder fluidity, and containing a large amount of metallic silicon powder It is possible to improve the fluidity of.

The inventors of the present invention, based on such knowledge,
Furthermore, experiments and studies were conducted to complete the present invention.

That is, the thermal spray material of the present invention is a thermal spray material which is hot-fed into an oxygen stream to melt the refractory powder by the combustion heat of the metallic silicon.
40% by weight (however, particles with a particle size of 10 μm or less 5-10% by weight, particles with a particle size 10-250 μm 15-30% by weight)
And at least one kind selected from the group consisting of phosphorous graphite powder, hydrophobic silica fine powder, hydroxyapatite powder, and boron nitride powder, and 0.01 to 3.0% by weight, and the balance is a baking treatment. Refractory powder (however,
The proportion of fine powder having a particle size of 10 μm or less is 10% by weight or less of the refractory powder).

In the thermal spray material of the present invention, the particle size is 10 μm.
Metallic silicon of m or less contributes to ignitability and sustainability of flame, and it is necessary to use 5% by weight or more, but if 10% by weight or more is used, flashback or explosive combustion will occur, which is a safety problem. There is a point. Therefore, the amount of metallic silicon having a particle size of 10 μm or less is preferably in the range of 5 to 10% by weight.

Further, in order to obtain a sprayed product having high strength and excellent heat resistance spall resistance, it is necessary to form a completely melted sprayed product into a composite containing unmelted refractory particles. . Therefore, the amount of metallic silicon added is 20% by weight.
As described above, it is preferable to increase the amount of heat generation to obtain a spray-coated construction body in which the refractory particles are firmly welded.

However, if the addition amount of metallic silicon exceeds 40% by weight, the unmelted particles of the refractory material become too small,
The heat-resistant spalling property decreases.

Therefore, the addition amount of metallic silicon is 20
It is preferably in the range of ˜40% by weight.

Further, the metal silicon powder has extremely poor fluidity as a powder, and when the metal silicon is used in an amount of 20% by weight or more, the fluidity becomes poor and pulsation easily occurs in the supply amount of the thermal spraying material, so that a fixed amount is obtained. Since it may not be possible to supply the powder in an appropriate amount, at least one selected from the group consisting of phosphorous graphite powder, hydrophobic silica fine powder, hydroxyapatite powder, and boron nitride powder is used as a flow promoter. 01 to 3.0 wt% (when used alone, specifically, 0.5 wt% or more of phosphorous graphite powder, 0.01 wt% or more of hydrophobic silica fine powder, 0.1 wt% or more of hydroxyapatite powder, It is necessary to add boron nitride powder 0.1% by weight or more). In addition, it is not preferable to add 3% by weight or more of these flow accelerators, because the influence of the flow accelerator remaining in the sprayed construction body increases. However, there is no problem even if it is added more than that for applications where there is no influence of residual.

Further, in the thermal spray material of the present invention, it is preferable to use heat-treated refractory powder as the refractory powder. This is to prevent the occurrence of cracks due to expansion due to crystal dislocation when the temperature is raised.

[0027]

EXAMPLES Hereinafter, examples of the present invention will be shown together with comparative examples, and the features thereof will be described in more detail.

Compositions of metallic silicon, calcined silica stone powder, silica stone powder (for preparation of samples of comparative examples) phosphorous graphite powder, hydroxyapatite powder, hydrophobic silica fine powder and boron nitride powder are shown in Table 1. To prepare the thermal spray materials of Examples 1 to 4 and Comparative Examples 1 to 3, and
It is sprayed on the furnace wall using silica stone brick of the coke oven, and the presence or absence of pulsation of the supply amount at the time of spraying is checked, and the physical properties (porosity, bending strength, compressive strength) of the sprayed product and 600 ° C
The adhesive strength to the wall surface was measured when it was sprayed onto the wall surface. The results are shown in Table 1.

[0029]

[Table 1]

As shown in Table 1, in the case of the thermal spray material of Comparative Example 1 in which the flow accelerator was not added, the pulsation of the supply amount was observed during the thermal spraying, and the thermal spraying state was unstable. As a result, the spray-coated article using the spray material of Comparative Example 1 has low strength and high porosity. Moreover, the adhesive strength when sprayed on the wall surface at 600 ° C. is low, and the sprayed layer is easily peeled off.

Further, in Comparative Examples 2 and 3, since the amount of metallic silicon used was small, the strength was low and the porosity was high. Further, as in Comparative Example 1, the adhesive strength when sprayed on the wall surface at 600 ° C. is low, and the sprayed layer is easily peeled off.

On the other hand, the thermal spray materials of Examples 1 to 4 were
In order to improve the fluidity of the powder, since a flow promoter such as phosphorous graphite powder, hydroxyapatite powder, hydrophobic silica fine powder, boron nitride powder, etc. is used, 26% by weight of metallic silicon is blended. Nevertheless, no pulsation was observed during spraying.

Further, in the thermal spraying materials of Examples 1 to 4, there is no pulsation of the supply amount at the time of thermal spraying, and the thermal spraying agent is quantitatively supplied,
Since the thermal spraying state is stable, the physical properties (porosity, bending strength, compressive strength) and the adhesive strength to the wall surface of the thermal sprayed product are superior to those of Comparative Examples 1 to 3.

The thermal spray material of the present invention is not limited to the above-mentioned examples, and is related to the content of metal silicon, the particle size distribution thereof, the combination and ratio of addition of the flow promoter, the composition of the refractory powder, and the like. Various modifications and applications can be added within the scope of the present invention.

[0035]

As described above, the thermal spray material of the present invention is 20 to 40% by weight of metallic silicon (5 to 10% by weight of particles having a particle size of 10 μm or less, 1 to 10 to 250 μm in particle size).
5 to 30% by weight), and at least one kind selected from the group consisting of phosphorous graphite powder, hydrophobic silica fine powder, hydroxyapatite powder and boron nitride powder, 0.01 to 3.0.
In addition to containing 10% by weight, the balance is a fire-resistant powder that has been subjected to a firing treatment (however, the proportion of fine powder having a particle size of 10 μm or less is 10% by weight or less of the refractory powder), so that the fluidity is improved. It can be held to enable pulsation-free supply (spraying), and also improve the strength and adhesiveness of the sprayed construction.

Note that some coke ovens in steelworks have undergone a considerable number of years after construction, and the furnace walls of the carbonization chamber using silica bricks require repair. However, when the silica brick is cooled, it cannot be cooled because it is cracked due to heat change and the damage becomes large. Therefore, for the repair, a thermal spray repair method that allows hot working is advantageous.

The thermal spray material of the present invention has such an application (repair of a furnace wall using silica brick in a coke oven carbonization chamber).
It is suitable as a thermal spraying material to be used for, and by using the thermal spraying material of the present invention, it becomes possible to extend the life of the construction body.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Yoshimura Inventor, Hideo Yoshimura 2 1576, East Offshore, Nakahiro, Ako City, Hyogo Prefecture Kawasaki Furnace Co., Ltd.

Claims (1)

[Claims] 1. A thermal spray material which is hot-fed into an oxygen stream to melt the refractory powder by the combustion heat of metallic silicon, wherein the metallic silicon is 20-40% by weight (provided that the particle size is 10 μm or less, 5-10). % By weight, particles having a particle diameter of 10 to 250 μm, 15 to 30% by weight), and at least one selected from the group consisting of phosphorous graphite powder, hydrophobic silica fine powder, hydroxyapatite powder, and boron nitride powder 0.01 to
A fire-resistant powder containing 3.0% by weight and the rest being calcined (provided that the particle size is 10 μm).
(The proportion of fine powder of m or less is 10% by weight or less of the refractory powder)
A thermal spray material characterized in that