JP2023181228A - Powder for thermal spraying - Google Patents

Abstract

To provide a powder for thermal spraying that exhibits excellent reactivity during thermal spraying and also excels in the adhesive strength of the thermal-sprayed body.SOLUTION: Disclosed is a powder for thermal spraying which is prepared by blending oxygen with a blend containing particles of raw silica stone or particles of raw silica sand and metal particles and used in a thermal spraying method where the blend is melted by an exothermic oxidation reaction of the metal particles and sprayed onto an application object, wherein the powder for thermal spraying contains 70-92 mass% of the particles of raw silica stone or the particles of raw silica sand and 8-22 mass% of the metal particles, the metal particles contain 90 mass% or over of Si metal, and the particles of raw silica stone or the particles of raw silica sand are composed of a mineral containing 90 mass% or over of silica and 0.40-5.00 mass% of potassium.SELECTED DRAWING: Figure 1

Description

The present invention relates to powder for thermal spray materials.

Kilns such as coke ovens are made of refractory materials such as silica bricks. The walls of a kiln may crack due to temperature changes during operation, or may be worn or damaged by friction or external force when objects to be heated are taken in and out of the kiln.

When repairing a kiln, a thermal spraying method is used, as shown in Patent Document 1 below. In this method, a mixture of refractory fine particles, metal particles, and a crystallization accelerator is sprayed together with oxygen onto a hot object to be repaired, and the mixture is melted and welded to the object by an oxidative exothermic reaction of the metal particles. .

Patent No. 4493404

In Patent Document 1, the refractory particles are unfired silica stone or silica sand, the metal particles are metal silicon, and the crystallization promoter contains one or more of sodium salt, potassium salt, and lithium salt. ing.

The present inventor verified that the reactivity of the thermal spray material powder and the adhesion strength of the thermal spray body were not sufficient in the thermal spray material powder to which potassium salt or sodium salt was added. Further, during thermal spraying, there was a large loss of thermal spray material powder (hereinafter referred to as rebound loss) due to the sprayed powder being repelled from the sprayed location.

SUMMARY OF THE INVENTION An object of the present invention is to provide a powder for a thermal spray material that is excellent in reactivity when thermally sprayed and in adhesive strength of the thermal spray body.

A thermal spraying material used in a thermal spraying method in which a mixture containing raw silica stone particles or raw silica sand particles and metal particles is mixed with oxygen, the mixture is melted by an exothermic reaction of oxidation of the metal particles, and the mixture is sprayed onto a workpiece. The powder for thermal spraying material contains 70 to 92% by mass of raw silica stone particles or raw silica sand particles and 8 to 22 mass% of metal particles, and the raw silica stone particles or raw silica sand particles contain The above-mentioned problems are solved by a powder for thermal spraying material, which is a mineral containing 90% by mass or more of silica and 0.40 to 5.00% by mass of potassium.

For thermal spray materials that contain silica as a main constituent, particles of raw silica sand or grains of raw silica stone derived from minerals containing potassium as an impurity, and metal particles, without artificially adding potassium. The present invention was achieved based on the discovery that the powder for thermal spraying material has excellent reactivity and adhesive strength of the formed thermal sprayed body.

According to the above powder for thermal spray materials, a test piece was prepared under the following conditions, and the coefficient of linear thermal expansion of the test piece was determined by the following method, and fell within the range of -0.300% to +0.300%. A sprayed body can be obtained. The test piece was made into a rectangular block with a length of 40 mm, a width of 160 mm, and a thickness of 40 mm by supplying oxygen to powder for thermal spraying material and thermal spraying in an environment of 400°C. After the test piece was prepared by thermal spraying, it was left at 400°C for 6 hours without cooling, and then the temperature was raised from 400°C to 1200°C at a rate of 4°C/min, and maintained at 1200°C for 24 hours. Then, it is cooled at a rate of 1°C/min until it reaches 400°C, and the coefficient of linear thermal expansion during that time is measured based on the method of JIS R 2207-1.

According to the above powder for thermal spraying material, it is possible to obtain a thermal sprayed body having a shear adhesive strength of 1.8 to 3.0 MPa when a test piece is prepared under the following conditions and the shear adhesive strength of the test piece is determined by the following method. can. A block-shaped silica brick is placed in an electric furnace, heated to 600°C, and a thermal spraying powder is sprayed onto a rectangular area of 50 mm in length and 65 mm in width set on the silica brick to a thickness of 20 mm. forming a sprayed body, maintaining the sprayed body at 600°C for 3 hours without cooling to obtain a test piece, raising the temperature of the test piece from 600°C to 1200°C at a rate of 3°C/min, One cycle consisted of maintaining the temperature at 1200°C for 24 hours, then gradually cooling it at a rate of 1°C/min to 600°C, and maintaining it at 600°C for 3 hours.The heating cycle was repeated 5 times in total, and the test piece was heated. Without cooling, in an environment of 600°C, the position of the test piece was fixed, and a push rod was applied from the side of the 2 cm thick thermal sprayed body at a loading rate of 68 N/sec, so that the adhesive surface of the thermal sprayed body was moved in the lateral direction. A load is applied in the direction of displacement, and the load (N) when the sprayed body breaks is measured, and the shear adhesive strength (MPa) is determined.

According to the present invention, it is possible to provide a powder for a thermal spray material that is excellent in reactivity when thermally sprayed and in adhesive strength of the thermal spray body.

A test piece prepared by thermal spraying the thermal spray material powder according to Example 1, a test piece 3 obtained by firing the test piece prepared by thermal spraying the thermal spray material powder according to Example 1 at a predetermined temperature cycle, and a silica brick. It is a graph summarizing the relationship between temperature change and linear thermal expansion coefficient for each of cut out test piece 1 and test piece 2. A test piece prepared by spraying the thermal spray material powder according to Example 1 and a test piece prepared by thermal spraying the thermal spray material powder according to Comparative Example 1 were measured after changing the temperature in a predetermined temperature cycle. It is a graph showing the shear adhesive strength (MPa).

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated. The embodiments shown below are only limited embodiments of the powder for thermal spray material of the present invention, and the technical scope of the present invention is not limited to the embodiments shown below.

[First embodiment]
The raw material powder for thermal spray material of this embodiment is obtained by mixing a mixture containing raw silica stone particles or raw silica sand particles and metal particles with oxygen, and melting the mixture by an oxidation exothermic reaction of the metal particles. A thermal spraying material powder used in a thermal spraying method for spraying onto a construction target, the thermal spraying material powder containing 70 to 92% by mass of raw silica stone particles or raw silica sand particles and 8 to 22% by mass of metal particles, The metal particles contain 90% by mass or more of metal Si, and the raw silica stone particles or raw silica sand particles contain 90% by mass or more of silica and 0.40 to 5.00% by mass of potassium. It is a mineral that In addition, the above-mentioned potassium content is the content obtained by converting the potassium content contained in the particles of raw silica stone or particles of raw silica sand into the content of potassium atoms. The upper limit of the potassium content is more preferably 2.00% by mass or less.

For example, when potassium is contained as K ₂ O, it is preferable to use raw silica stone particles or raw silica sand particles containing 0.48 to 6.03% by mass of K ₂ O. The upper limit of the content of K ₂ O is preferably 2.41% by mass or less.

In the above raw material powder for thermal spraying material, potassium is contained as an impurity in the particles of silica stone or particles of silica sand, and is not added in the form of potassium salt. In addition, in the raw material powder for thermal spray materials, calcium salts and sodium salts are not added.

The thermal spray material powder contains particles of raw silica stone or particles of raw silica sand. Particles of raw silica stone or particles of raw silica sand can be obtained, for example, by crushing raw silica stone produced as a mineral, or raw silica sand produced in a small particle size state such as river sand can be used as is. Alternatively, raw silica sand produced in a small particle size state such as river sand may be crushed and used. The crushed raw silica stone, raw silica sand, or crushed raw silica sand may be classified by sieving.

As the raw silica stone particles or the raw silica sand particles, a mineral containing 90% by mass or more of silica and 0.40 to 5.00% by mass of potassium is used. When referring to minerals, it includes crushed produced minerals, that is, produced silica stone or silica sand. The content of the above-mentioned silica is more preferably 92% by mass or more. The upper limit of the silica content is more preferably 97% by mass or less.

The particles of raw silica stone or the particles of raw silica sand refer to particles of unfired silica stone or particles of unfired silica stone. The main crystalline phase of raw silica stone particles or raw silica sand particles is quartz. For example, it is preferable that 90% by mass or more of the silica contained in the particles of raw silica stone or the particles of raw silica sand be quartz, and more preferably 95% by mass or more be quartz. The upper limit in this case is 100% by mass or less.

The detailed mechanism is unknown, but by including raw silica stone particles or raw silica sand particles, which are mainly composed of silica containing a predetermined amount of potassium as an impurity in minerals, together with metal particles, thermal spraying The reactivity of the material powder, the build-up performance, the porosity of the sprayed material, and the adhesive strength of the sprayed material are improved, and the rebound loss of the sprayed material is reduced.

In known powders for thermal spray materials, sodium salts, potassium salts, or lithium salts are sometimes intentionally added to powders for thermal spray materials as components that promote crystallization rather than as mineral impurities. Although the detailed mechanism is unknown, when sodium salts, potassium salts, or lithium salts are included in thermal spray powders rather than as mineral impurities, the physical properties such as the reactivity and adhesive strength of thermal spray powders are affected. Significantly decreased. Therefore, it is preferable not to include a component that promotes crystallization, and even if it is included, it is preferably at most 0.2% by mass.

The particles of raw silica stone or the particles of raw silica sand contain calcium-based impurities such as CaO, iron-based impurities such as Fe ₂ O ₃ , sodium-based impurities such as Na ₂ O, or magnesium-based impurities such as MgO. It is preferable to use less. For example, a material having a calcium content of 0.50% by mass or less when converted to a Ca atom content can be suitably used. Moreover, those having an iron content of 0.50% by mass or less when converted to the content of Fe atoms can be suitably used. Moreover, those having a sodium content of 0.50% by mass or less when converted to the content of Na atoms can be suitably used. Moreover, those having a magnesium content of 0.20% by mass or less when converted to the content of Mg atoms can be suitably used. The lower limit of these impurities is such that the content of each of them in terms of atoms is 0% by mass or more.

For example, when the calcium-based impurity is CaO, it is preferable to use one with a CaO content of 0.70% by mass or less. For example, when the sodium-based impurity is Na ₂ O, it is preferable to use one with a Na ₂ O content of 0.67% by mass or less. For example, when the iron-based impurity is Fe ₂ O ₃ , it is preferable to use one containing 0.71% by mass or less of Fe ₂ O ₃ . The lower limit values of these impurities are all 0% by mass or more.

The particles of raw silica stone or the particles of raw silica sand preferably contain an aluminum-based compound such as Al ₂ O ₃ , and the aluminum content when converted to the content of Al atoms is 0.90 to 7. The content is preferably 0.00% by mass or 0.90 to 1.80% by mass.

When the aluminum-based compound is Al ₂ O ₃ , it is preferable to use one having an Al ₂ O ₃ content of 1.70 to 3.40% by mass.

The metal particles preferably contain metal Si as a main component. In this case, the main component means that metal Si contained in the metal particles is 90% by mass or more. The upper limit of the metal Si contained in the metal particles is 100% by mass or less, excluding inevitable impurities.

The thermal spray material powder may contain particles containing magnesium such as spinel and MgO. Preferably, magnesium is included as a magnesium oxide such as spinel or MgO. By including particles containing magnesium, it is possible to further improve the adhesive strength of the thermal spray material. The content of particles containing magnesium is preferably such that the content in terms of magnesium atoms is 0 to 10% by mass, more preferably 0 to 5% by mass, and 1 to 3% by mass. %.

The particle size of raw silica stone particles or raw silica sand particles can be, for example, 50 to 3500 μm or 50 to 2000 μm. The particle size of the metal particles used may be, for example, 0.1 to 100 μm. The particle size range of the metal particles may be, for example, 0.1 to 75 μm. As described above, when particles containing magnesium are blended into the thermal spray material powder, the particle size range of the particles can be, for example, 50 to 3500 μm or 50 to 2000 μm. Note that the particle size in this specification is based on classification using a sieve.

The proportion of raw silica stone particles or raw silica sand particles contained in the powder for thermal spraying material is 70 to 92% by mass. The proportion of raw silica stone particles or raw silica sand particles contained in the powder for thermal spraying material may be 73 to 90% by mass, or 75 to 85% by mass.

The proportion of metal particles contained in the powder for thermal spraying material is 8 to 22% by mass. The proportion of metal particles contained in the powder for thermal spraying material is more preferably 14 to 20% by mass.

The above powder for thermal spraying is produced by pumping the powder for thermal spraying using compressed oxygen, mixing the oxygen and the powder for thermal spraying, and then using furnace heat to combine the powder with metal particles contained in the powder for thermal spraying. The spray can be sprayed onto the workpiece using a known thermal spraying machine that oxidizes with oxygen. The object to be applied is not particularly limited, and examples thereof include structures such as the wall, bottom, and ceiling of a kiln such as a coke oven.

According to the above-mentioned powder for thermal spray material, it is possible to obtain a thermal spray body having the following characteristics, for example. For example, it is possible to obtain a thermal sprayed body with build-up properties of 480 to 550 cc determined by the method described below. Further, for example, a dense thermal sprayed body having a porosity of 13% or less as determined by the method described later can be obtained. The lower limit of the porosity is not particularly limited, but is, for example, 7% by mass or more. Further, for example, it is possible to obtain a thermal sprayed body in which the change in porosity due to firing determined by the method described later is 0.1 to 2.0%. Furthermore, it is possible to obtain a thermal sprayed body having a high shear adhesive strength of 1.8 MPa or more, or 2.2 MPa or more, determined by the method described below, for example. The upper limit of the shear adhesive strength is not particularly limited, but is, for example, 3.0 MPa or less, or 2.6 MPa or less. Further, for example, the shear adhesive strength can be obtained both when measured after one predetermined temperature cycle and when measured after five predetermined temperature cycles. Further, for example, it is possible to obtain a thermal sprayed body having a rebound loss of 55% or less as determined by the method described later. The lower limit value of rebound loss is not particularly limited, but is, for example, 45% or more.

According to the above-mentioned powder for thermal spraying material, it is possible to obtain a thermal sprayed body whose coefficient of linear thermal expansion, determined by the method described later, falls within the range of -0.300 to +0.300.

When converting the amount of a compound containing aluminum, calcium, magnesium, iron, sodium, or potassium into the amount of each atom, the following numerical values are used as the atomic weight. Aluminum is 27, calcium is 40, magnesium is 25, iron is 56, sodium is 23, potassium is 39, and oxygen is 16. For other atomic weights, use the atomic weight values listed in the Atomic Weight Table (2021) published by the Chemical Society of Japan's Atomic Weight Expert Committee (2021), rounded to the first decimal place.

When converting the amount (B) of a compound containing aluminum, calcium, magnesium, iron, sodium, or potassium into the amount (A) of each atom, the calculation is performed as follows. The value of A is the value obtained by rounding off the value to the third decimal place.
A=B×(C/D)
However, A is the amount (mass%) (converted value) of each atom,
B is the amount (% by mass) of a compound containing aluminum, calcium, magnesium, iron, sodium, or potassium;
C is a value obtained by multiplying the atomic weight of aluminum, calcium, magnesium, iron, sodium, or potassium by the number of aluminum, calcium, magnesium, iron, sodium, or potassium shown in the composition formula,
D is the formula weight of the compound containing aluminum, calcium, magnesium, iron, sodium, or potassium.

Examples of thermal spraying material powders are listed below. The examples listed below are only limited examples of powders for thermal spray materials, and the technical scope of the present invention is not limited to the illustrated examples.

[Example 1]
Particles of raw silica sand having the chemical composition listed in Table 2 and the mineral composition listed in Table 3, produced by crushing raw silica sand 1 derived from natural minerals and then sieving. , and metal particles having a Si content of 100% by mass excluding unavoidable impurities were mixed in the proportions shown in Table 1 to obtain a thermal spray material powder according to Example 1. The particle size range of the raw silica sand 1 is 75 μm or more and less than 850 μm. The particle size range of the metal particles is 0.5 μm or more and 50 μm or less. Note that blank cells in Table 1 indicate that the blending amount or content is zero. The same applies to other tables.

[Example 2]
The raw silica sand 1 used in Example 1 has the chemical composition listed in Table 2 and the mineral composition listed in Table 3, and the raw silica sand 4 derived from natural minerals is crushed, and then, A thermal spray material powder according to Example 2 was produced in the same manner as in Example 1, except that the powder was changed to one produced by sieving. The particle size range of the raw silica sand 4 is 106 μm or more and less than 850 μm.

[Example 3]
The raw silica sand 1 used in Example 1 has the chemical composition listed in Table 2 and the mineral composition listed in Table 3, and the raw silica sand 2 derived from natural minerals is crushed, and then, A thermal spray material powder according to Example 3 was produced in the same manner as in Example 1, except that the powder was changed to one produced by sieving. The particle size range of the raw silica sand 2 is 75 μm or more and less than 850 μm.

[Example 4]
Except that the raw silica sand 1 used in Example 1 was changed to raw silica sand 3, which has the chemical composition listed in Table 2 and the mineral composition listed in Table 3, and is derived from natural minerals. In the same manner as in Example 1, a thermal spray material powder according to Example 4 was produced. The particle size range of the raw silica sand 3 is 106 μm or more and less than 850 μm.

[Example 5]
In the same manner as in Example 1, except that the amount of raw silica sand 1 used in Example 1 was changed to 78% by mass, and 5% by mass of spinel with a particle size range of 150 to 1700 μm was blended as magnesium particles, A powder for thermal spraying material was produced. Table 4 shows the chemical composition of the spinel used.

[Comparative example 1]
Comparison was carried out in the same manner as in Example 1, except that the raw silica sand 1 used in Example 1 was changed to silica brick waste having the chemical composition and mineral composition listed in Table 3. A thermal spray material powder according to Example 1 was produced. The silica brick waste is obtained by crushing silica bricks used in coke ovens, and the particle size range is 150 μm or more and less than 850 μm.

[Comparative example 2]
Except that the raw silica sand 1 used in Example 1 was changed to raw silica sand 5, which has the chemical composition listed in Table 2 and the mineral composition listed in Table 3, and is derived from natural minerals. In the same manner as in Example 1, a thermal spray material powder according to Comparative Example 2 was produced. The particle size range of the raw silica sand 5 is 150 μm or more and less than 1700 μm.

[Comparative example 3]
Except that the raw silica sand 1 used in Example 1 was changed to raw silica sand 6, which has the chemical composition listed in Table 2 and the mineral composition listed in Table 3, and is derived from natural minerals. In the same manner as in Example 1, a thermal spray material powder according to Comparative Example 3 was produced. The particle size range of the raw silica sand 6 is 150 μm or more and less than 1700 μm.

[Comparative example 4]
A thermal spraying material powder according to Comparative Example 4 was produced in the same manner as Comparative Example 2 except that K ₂ CO ₃ corresponding to 1% by mass of the total mass of the thermal spraying material powder of Comparative Example 2 was further blended.

[Comparative example 5]
A thermal spray material powder according to Comparative Example 5 was produced in the same manner as Comparative Example 2, except that CaCO ₃ corresponding to 1% by mass of the total mass of the thermal spray material powder of Comparative Example 2 was further blended.

[Comparative example 6]
A thermal spray material powder according to Comparative Example 6 was produced in the same manner as Comparative Example 2, except that Na ₂ CO ₃ corresponding to 1% by mass of the total mass of the thermal spray material powder of Comparative Example 2 was further blended.

[Chemical composition and mineral composition of raw materials]
The chemical composition of each raw silica sand or silica brick waste listed in Table 2 and the chemical composition of spinel shown in Table 4 were measured by fluorescent X-ray analysis in accordance with JIS R2216. Rigaku's ZSX primusII was used for measurement. The mineral composition of each raw silica sand or silica brick waste listed in Table 3 was determined by measuring the diffraction intensity by X-ray diffraction in accordance with JIS K0131. The numerical values in Table 3 indicate the abundance ratio (mass %) of each crystal phase. Moreover, the crystallinity degree described in Table 3 was calculated as follows.
Crystallinity = Area of X-ray diffraction intensity originating from crystals ÷ (Area of diffraction intensity originating from crystals + Area of diffraction intensity originating from amorphous) x 100-100

[Evaluation of physical properties of sprayed material]
Next, thermal spraying was carried out under the following conditions using the raw material powders for thermal spray materials of each of the above-mentioned Examples and Comparative Examples, and the physical properties of the formed thermal spray bodies were evaluated.

In preparation for thermal spraying, refractory bricks were arranged in two layers, one above the other, in a burner furnace, and heated until the temperature inside the burner furnace reached 600°C and the surface temperature of the refractory bricks reached 500°C. Thereafter, using a known thermal spraying machine, the thermal spray material powder of each of the above examples or comparative examples was sprayed together with compressed oxygen from the tip of a lance onto the joint portion of the heated refractory bricks. The conditions for thermal spraying are as follows. The flow rate of oxygen discharged by the thermal spraying machine was 28 Nm ³ /hour, and the discharge amount of powder for thermal spray material was 80 kg/hour. The length of the lance of the thermal spraying machine is 2 m, and the length of the hose that supplies the raw material powder for thermal spraying to the lance is 10 m. The metal particles contained in the thermal spray material powder discharged from the tip of the lance react with the supplied oxygen and are oxidized by the furnace heat. After blowing off 2.0 kg of thermal spray material powder, the refractory brick to which the thermal spray material was attached was taken out of the furnace and allowed to cool naturally, and the physical properties of the thermal spray material were evaluated.

The physical properties evaluated were rebound loss, porosity, porosity after firing, and build-up properties of the sprayed body. Additionally, during the thermal spraying process, the reactivity of the thermal spray powder was evaluated. The evaluation method for each physical property is as follows. Furthermore, the chemical composition of each formed sprayed body was determined by fluorescent X-ray analysis in accordance with the above JIS R2216. The results are shown in Table 6. In addition, the thermal spray material powders according to Comparative Examples 4 to 6 had poor reactivity, and no thermal spray bodies for measurement could be obtained.

[Reactivity]
When performing thermal spraying, the spraying lance is moved to change the location where the thermal spraying material is sprayed. If the quality of the thermal spray powder is poor, the reaction (reaction light) may not follow the movement of the nozzle when the lance is moved. If the reaction does not follow the movement of the nozzle, unreacted thermal spray material powder will be sprayed onto the workpiece, and no thermal spray body will be formed. In addition, the reaction caused by the oxidation reaction of the metal particles causes a change in brightness and darkness as if it were pulsating. If the reaction changes in a pulsating manner, the degree of melting of the thermal spray material powder becomes uneven. This phenomenon depends on whether or not the thermal spray material powder is susceptible to oxidation reactions due to heat and supplied oxygen. In this specification, the ease of reaction is referred to as reactivity. In order to evaluate the reactivity, spraying material was sprayed from the lance of the sprayer onto the refractory bricks installed in the burner furnace, and the pulsation of the reaction was checked to see if the reaction properly followed the movement of the nozzle. It was visually confirmed whether or not this occurred. Evaluation is performed in four stages: double circle, circle, triangle, and cross, and the higher the level, the better the reactivity.

[Rebound loss]
The proportion of the sprayed material that was lost without adhering to the refractory bricks, that is, the rebound loss (%) was determined using the following formula.
R=100-(A÷B×100)
However, R is the rebound loss (%), A is the mass (g) of the spray material attached to the refractory, and B is the total amount (g) of the spray material powder sprayed onto the refractory. ). Specifically, B is 2000g. A was determined by subtracting the mass (g) of the refractory brick before spraying the thermal spraying material from the mass (g) of the refractory brick after spraying the thermal spraying material.

[Porosity, bulk specific gravity]
From each of the refractory bricks to which the thermal sprayed material was attached, only the thermal sprayed material was cut out using a diamond cutter. Cut out two test pieces the size of half a standard brick from the cut out thermal sprayed body. The wet test piece was placed in a dryer set at 110°C and dried for 24 hours. The dried test piece was left to stand until it reached room temperature, and the porosity and bulk specific gravity were determined according to the method of JISR2205. The mass meter used was one capable of measuring to the nearest 0.1 g.

[Porosity after firing]
The two test pieces whose porosity was measured by the above method are fired in an electric furnace at 1200° C. for 24 hours. Regarding the test piece after firing, the porosity after firing was determined by the same method as above based on JISR2205.

[Change in porosity]
The difference in porosity obtained by subtracting the porosity value before firing from the porosity value after firing determined above is defined as the change in porosity (%).

[Build-up properties]
The build-up property (cc) was determined by the following formula from the bulk specific gravity determined in accordance with JISR2205 and the mass (A) (g) of the sprayed material adhered to the firebrick described above.
V=A÷C
However, V is the build-up property (cc) when 2 kg of thermal spray material is sprayed, A is the mass (g) of the thermal spray material attached to the refractory brick, and C is the bulk specific gravity determined by the above method. It is. In other words, build-up property is the volume of the thermal sprayed material attached to the object to be applied.

[Shear adhesive strength]
Next, we will discuss the thermal sprayed bodies formed by thermal spraying the thermal spray material powders according to each of the above examples and the thermal spray bodies formed by thermal spraying the thermal spray material powders according to each of the above comparative examples by the following method. , the shear adhesive strength was determined.

A block-shaped silica brick is placed in an electric furnace and heated to 600°C. 500 g of powder for thermal spraying material is thermally sprayed onto one piece of the silica brick. The thermal spraying conditions are the same as described above. During thermal spraying, the area other than the area to be sprayed with the thermal spraying material is masked using a heat-resistant formwork, and the thermal spraying powder is sprayed onto a rectangular area measuring 50 mm in length and 65 mm in width. A sprayed body having a thickness of 20 mm is formed in the area by thermal spraying. The silica brick immediately after spraying with the sprayed material attached is maintained at 600°C for 3 hours without cooling. The silica brick to which this thermal sprayed material is attached is used as a test piece. This temperature-controlled test piece is heated to 1200°C at a rate of 3°C/min and maintained at 1200°C for 24 hours. Thereafter, it was slowly cooled down to 600°C at a rate of 1°C/min and maintained at 600°C for 3 hours. In an environment of 600℃, the position of the silica brick to which the sprayed material was attached was fixed, and a push rod was applied from the side of the sprayed material with a thickness of 2 cm to apply a load in a direction that caused the adhesion surface of the sprayed material to shift laterally. The load (N) at which the sprayed body broke was measured. Based on the load, the shear adhesive strength (MPa) was determined by the following formula. The loading speed by the push rod is 68 N/sec. As mentioned above, the adhesion area of the thermal spray body is a value obtained by converting 50 mm x 65 mm into square meters.
Shear adhesive strength (MPa) = Load at break (N) ÷ Adhesive area of thermal sprayed body (m ² ) × 10 ^-6

Table 1 shows the rebound loss, porosity, porosity after firing, build-up properties, shear adhesive strength, and reactivity of the thermal spray material powder evaluated for each powder for thermal spray material in each example and each comparative example. Shown below. In Table 1, the locations where the shear adhesive strength is described as 2.46 or more indicate that the shear adhesive strength was recorded at 2.46 MPa or more, which is the detection limit of the measuring device.

As is clear from the description in Table 1, the thermal spray bodies formed using the thermal spray material powders of Examples 1 to 5 are comparable to the thermal spray bodies formed using the thermal spray material powders of Comparative Examples 1 to 6. It can be seen that the performance is superior in reactivity, build-up properties, porosity, porosity after firing, change in porosity due to heating, shear adhesive strength, and rebound loss.

The thermal spraying material powders of Examples 1 to 5 are excellent in reactivity, thermal spraying workability, and the like.

Since the thermal spray material powders of Examples 1 to 5 have excellent reactivity, a situation in which unreacted thermal spray material powders are sprayed onto the workpiece is unlikely to occur. According to the thermal spray material powders of Examples 1 to 5, dense thermal spray bodies with low porosity can be obtained. There is a correlation between low porosity and the strength of the sprayed material. In addition, thermal sprayed bodies with low porosity are less susceptible to changes over time such as carburization. In the thermal spray bodies formed with the thermal spray material powders of Examples 1 to 5, changes in porosity after firing are suppressed to a low level. It can be seen that changes in porosity due to thermal changes due to operation are suppressed to a low level. According to the thermal spray material powders of Examples 1 to 5, thermal spray bodies having high adhesive strength can be obtained. When stress is applied to the thermal sprayed body during operation, the thermal sprayed body is unlikely to easily peel off.

[Coefficient of linear thermal expansion]
Next, a test piece consisting of a thermal spray body of a predetermined size obtained by thermal spraying the powder for thermal spray material of Example 1 and a test piece 1 of a predetermined size cut from a silica brick after being used as a furnace wall of a coke oven were prepared. A test piece 2 of a predetermined size cut out from a silica brick after being used as the oven wall of a coke oven other than the coke oven, and a test piece made with the thermal spray material powder according to Example 1 above. Regarding test piece 3 fired at a predetermined temperature cycle, the coefficient of linear thermal expansion was determined based on the method of JIS R 2207-1, with the following changes in the test method.

For each test piece of Example 1, each thermal spray material powder according to Example 1 and Example 6 was sprayed onto the mold under the same conditions as above except that the temperature in the burner furnace was changed. A thermally sprayed body with predetermined dimensions was formed, and the thermally sprayed body was removed from the mold. The thermal spraying conditions were the same as those for the thermal spraying described above, except that the temperature inside the burner furnace was 400°C.

Test piece 1 was produced by cutting a test piece of a predetermined size into a predetermined dimension from a silica brick used as a wall of a coke oven. Test piece 2 was produced by cutting into a predetermined size a silica brick that had been used as the oven wall of a coke oven other than the coke oven.

Test piece 3 was prepared by thermally spraying the powder for thermal spray material according to Example 1, maintained at 400°C for 6 hours without cooling, and then heated from 400°C to 1200°C at a rate of 4°C/min. The temperature was raised to 1200°C, maintained at 1200°C for 24 hours, and cooled at a rate of 1°C/min until it reached 400°C.

The size of each of the above test pieces was a rectangular block with a length of 40 mm, a width of 160 mm, and a thickness of 40 mm.

For the test pieces according to Example 1 and test piece 3, instead of firing from room temperature, each test piece was heated in a furnace at 400°C for 6 hours while maintaining the hot state immediately after thermal spraying or the hot state after firing. The sample was left standing and heated under the following heating conditions, and the coefficient of linear thermal expansion was determined from the value measured with a displacement detector. The displacement detector was of a visible light projection type (camera: CV-035C manufactured by Keyence Corporation, image sensor: CV-5000 manufactured by Keyence Corporation). Test pieces 1 and 2 cut out from silica bricks were similarly left standing in a 400°C furnace for 6 hours, heated under the following heating conditions, and their linear thermal expansion coefficients were determined.

The heating conditions are as follows. Each test piece that had been maintained at 400°C for 6 hours was heated to 1200°C at a rate of 4°C/min and maintained at 1200°C for 24 hours. Thereafter, the temperature inside the furnace was lowered to 400°C at a rate of 1°C/min. The coefficient of linear thermal expansion is measured at intervals of once every 30 seconds.

FIG. 1 shows a graph summarizing the relationship between temperature change and linear thermal expansion coefficient for each test piece. As is clear from FIG. 1, a test piece made of the thermal spray raw material powder according to Example 1 and a test piece prepared by thermal spraying the thermal spray material powder according to Example 1 were fired at a predetermined temperature cycle. For piece 3, the linear thermal expansion coefficient falls within the range of -0.300 to +0.300 when the temperature is varied in the range of 400°C to 1200°C. This change in the coefficient of linear thermal expansion approximates the change in the coefficient of linear thermal expansion of test piece 1 cut from a used silica brick, and the change in the coefficient of linear thermal expansion of test piece 2 cut from another used silica brick. Approximate change. On the other hand, the thermal spray body made of the raw material powder for thermal spraying of Comparative Example 1 significantly deviated from the linear thermal expansion range of Test Piece 1. The test piece made of the raw material powder for thermal spraying of Example 1 and the test piece 3 prepared by thermally spraying the powder for thermal spraying material of Example 1 and calcined at a predetermined temperature cycle were tested in a coke oven. Its linear thermal expansion coefficient is similar to that of silica brick, which is often used as a constituent material. For this reason, the thermal sprayed body is less likely to peel off or be damaged due to the difference in expansion coefficient due to heating or cooling between the silica brick and the thermal sprayed body.

[Adhesive strength after temperature change]
Next, the thermal sprayed body formed by thermal spraying the thermal spray material powder according to Example 1 and the thermal sprayed body formed by thermal spraying the thermal spray material powder according to Comparative Example 1 were heated and cooled in a predetermined temperature cycle. The shear adhesive strength was determined when the process was repeated. The temperature cycle was to heat from 600°C to 1200°C at a rate of 3°C/min and maintain at 1200°C for 24 hours, then decrease to 600°C at a rate of 1°C/min and maintain at 600°C for 3 hours. do. This is regarded as one cycle, and a total of five cycles of temperature change are performed. The method for preparing the test piece and the method for measuring shear adhesive strength are the same as described above. In addition, after the thermal spraying of the powder for thermal spraying material according to Example 1, Example 6, and Comparative Example 1, the silica brick immediately after thermal spraying was maintained at 600°C for 3 hours, and the above-mentioned method was applied without cooling. The temperature was changed using a temperature cycle. For each test piece after changing the temperature in the above temperature cycle, the load at which the sprayed body broke was measured in an environment of 600° C. without cooling, by the same method as above. The shear adhesive strength (MPa) was determined based on the load.

Figure 2 shows the shear adhesive strength of the sprayed bodies after one cycle and the sheared adhesive strength of the sprayed bodies after five cycles for the sprayed bodies formed using the thermal sprayed powders according to Example 1 and Comparative Example 1. shows. As shown in FIG. 2, the thermal sprayed body obtained by thermal spraying the raw material powder for thermal sprayed bodies according to Example 1 recorded a shear adhesive strength of 2.46 MPa or more, which is the detection limit of the device. The pressure above is 2.46MPa.

As shown in FIG. 2, in the thermal spray body made of the thermal spray material powder according to Example 1, in both measurements after one heating cycle and after five heating cycles, The shear adhesive strength exceeded the detection limit of 2.46 MPa. On the other hand, in the thermal spray body made of the powder for thermal spray material according to Comparative Example 1, the shear adhesive strength (0.31 MPa) after passing through the heating cycle 5 times is the shear adhesive strength after passing through the heating cycle once. (0.81 MPa), it was significantly lower. From these results, it can be seen that the thermal spray material powder of Example 1 can provide a thermal sprayed body whose adhesive strength does not decrease even under repeated thermal fluctuations.

Claims (4)

A thermal spraying material used in a thermal spraying method in which a mixture containing raw silica stone particles or raw silica sand particles and metal particles is mixed with oxygen, the mixture is melted by an exothermic reaction of oxidation of the metal particles, and the mixture is sprayed onto a workpiece. It is a powder for
The powder for thermal spraying material contains 70 to 92% by mass of raw silica stone particles or raw silica sand particles and 8 to 22% by mass of metal particles,
The metal particles contain 90% by mass or more of metal Si,
The particles of raw silica stone or the particles of raw silica sand are minerals containing 90% by mass or more of silica and 0.40 to 5.00% by mass of potassium, which is a powder for a thermal spray material. Powder for thermal spraying material is
The content of the component that promotes crystallization is 0 to 0.2% by mass,
The thermal spray material powder according to claim 1, wherein the component is a sodium salt, potassium salt, or lithium salt. For the thermal spray material powder, a test piece is prepared under the following conditions, and the linear thermal expansion coefficient of the test piece determined by the following method forms a thermal spray body that falls within the range of -0.300 to +0.300%. The powder for thermal spray material according to claim 1 or 2, which is:
The test piece was made into a rectangular block with a length of 40 mm, a width of 160 mm, and a thickness of 40 mm by supplying oxygen to thermal spray material powder and thermal spraying in an environment of 400 ° C.
The coefficient of linear thermal expansion was determined by preparing the test piece by thermal spraying, leaving it at 400°C for 6 hours without cooling, and then increasing the temperature from 400°C to 1200°C at a rate of 4°C/min. ℃ for 24 hours, cooled at a rate of 1° C./min until it reaches 400° C., and the coefficient of linear thermal expansion during that time is measured based on the method of JIS R 2207-1. A claim that the powder for thermal spraying material forms a thermal sprayed body having a shear adhesive strength of 1.8 to 3.0 MPa, which is obtained by preparing a test piece under the following conditions and determining the shear adhesive strength of the test piece using the following method. Powder for thermal spray material according to any one of 1 to 3:
A block-shaped silica brick is placed in an electric furnace and heated to 600°C, and thermal spraying powder is sprayed onto a rectangular area of 50 mm in length and 65 mm in width set on the silica brick to form a 20 mm thick thermal sprayed body. was formed, and the sprayed body was maintained at 600°C for 3 hours without cooling to form a test piece,
The test piece was heated from 600°C to 1200°C at a rate of 3°C/min, maintained at 1200°C for 24 hours, and then slowly cooled to 600°C at a rate of 1°C/min. The heating cycle was repeated a total of 5 times, with the process of maintaining the temperature as one cycle, and the position of the test piece was fixed in an environment of 600°C without cooling the test piece, and the side of the thermal sprayed body with a thickness of 2 cm was Apply a push rod from the opposite direction at a loading rate of 68 N/sec to apply a load in a direction that shifts the adhesion surface of the sprayed body in the lateral direction, measure the load (N) when the sprayed body breaks, and measure the shear adhesive strength. Find (MPa).