JPH1160342A - Thermal spraying material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermal spraying material for use in a metal spraying method, low in the porosity of a thermally sprayed body, excellent in hot wear resistance and high in compressive strength and hot shearing adhesive strength. SOLUTION: The thermal spraying material consists of 75-95 wt.% refractory oxide powder and 5-25 wt.% easily oxidizable metal powder, preferably Si powder. As a part of the refractory oxide powder, 2-50 wt.% petalite is used and the balance is one kind or more selected from the group consisting of SiO2 , Al2 O3 , ZrO2 and MgO.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to joint breaks, cracks, brick peeling, and the like which occur during the use of kilns and furnaces for molten metal.
The present invention relates to a thermal spray material suitable as a repair material for wear and the like.

[0002]

2. Description of the Related Art For thermal spray repair, a plasma spraying method and a flame spraying method using a flame such as oxygen-propane are known. However, these thermal spraying methods have the disadvantage that the thermal spraying equipment is very large. In this regard, the thermal spraying method utilizing the heat of combustion of metal powders such as Al and Si mixed in the thermal spraying material (hereinafter referred to as a metal thermal spraying method) has a feature that the apparatus is simple and easy to handle.

As for the metal spraying method, for example,
No. 13308 discloses that particles of an exothermic oxidizing material 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 onto one surface to form a coherent refractory aggregate on the surface. And wherein the oxidizing material comprises silicon and aluminum, the aluminum being present in an amount of up to 12% by weight of the total mixture, the aluminum and silicon being present in a total amount not exceeding 20% by weight of the total mixture. A method for producing a refractory aggregate characterized by being present is disclosed.

Japanese Patent Publication No. Hei 5-21865 discloses that
Spraying a mixture of refractory granules and oxidizing granules on the surface, causing the oxidizing granules to undergo an exothermic reaction with oxygen and generating sufficient heat to soften or melt at least the surfaces of the refractory granules,
In the refractory molding method in which the refractory is formed on the surface, the average particle size of the particles sprayed as a mixture is 80% of the refractory particles and the average of the 20% particle size is 80% of the oxidizable particles. % And 20% larger than the average of the particle size,
The average of 80% and 20% particle size of the refractory granules is 2.5 m
m or less, the average of the 80% and 20% particle diameters of the oxidizable particles is 50 μm or less, and the particle size range distribution ratio of the refractory particles is 1.2 or more and 1.9 or less. There is disclosed a method for forming a refractory body, wherein the particle size range distribution ratio of the granular material is 1.4 or less. Here, it is described that the refractory particles are at least one of sillimanite, mullite, zircon, zirconium dioxide, aluminum oxide, and magnesium oxide. It is also described that the oxidizable particles are at least one of silicon, aluminum, magnesium, and zirconium.

Further, JP-A-3-60472 discloses a method in which a mixture of an oxidizing gas, a refractory and a fuel powder is projected onto a surface to burn the fuel so that the refractory powder is at least partially melted or softened. Generate enough heat to become
In a ceramic spraying process in which the adhered refractory mass is progressively attached to its surface, a fuel powder is applied to the entire mixture.
Weight percent or less, wherein the fuel powder contains at least two metals selected from aluminum, magnesium, chromium and zirconium, and at least a major portion of the refractory powder is composed of magnesia, alumina and chromic oxide. It consists of one or more kinds, and when present, the molar ratio of silica and calcium oxide present in the refractory powder is represented by the following formula:

## EQU1 ## A ceramic spraying method characterized by satisfying [SiO ₂ ]% ≦ 0.2 + [CaO]% is disclosed.

[0006] Japanese Patent Application Laid-Open No. 5-17237 discloses that
MgO, the Al ₂ O _3, ZrO ₂ used as the refractory oxide powder, Al-Si as a heat generating material, Al-Mg, Al-C
a, Mg-Ca, Ca-Si or other alloy powder alone or with the alloy powder of Si, Al, Mg, Zr, Ca, M
A thermal spray material using a metal powder such as n or Fe is disclosed.

As described above, in the thermal spraying material used in the conventional metal spraying method, SiO 2 is used as a refractory oxide powder.
_{2. A} material having a high melting point and a large coefficient of thermal expansion, such as Al ₂ O ₃ , MgO, sillimanite, mullite, and zircon, is used.

[0008]

However, when such a high melting point refractory oxide powder is used for a metal spraying method, a sufficient amount of heat is generated by a plasma spraying method or a flame spraying method such as oxygen-propane. Unlike the method, unmelted part occurs,
A sprayed body with a high porosity results. Therefore, wear resistance and compressive strength are low, resulting in poor durability. At the same time, the adhesion to the brick surface to be repaired is also poor, so that the problem of peeling is likely to occur.

Further, since the refractory powder conventionally used as a thermal spray material for a metal spraying method has a relatively large coefficient of thermal expansion, the thermal spray expands and contracts due to a temperature change in the furnace, and cracks occur. And peeling easily.

Accordingly, an object of the present invention is to provide a thermal spray material for use in a metal spraying method in which the porosity of a thermal spray body is low, the hot wear resistance is excellent, and the compressive strength and the hot shear adhesive strength are high. It is in.

[0011]

Means for Solving the Problems That is, the present invention relates to 75-
In a thermal spray material comprising 95% by weight of a refractory oxide powder and 5 to 25% by weight of an easily oxidizable metal powder, 2 to 50% by weight of petalite is used as a part of the refractory oxide powder, The remainder of the refractory oxide powder is SiO ₂ , Al ₂ O ₃ , Z
An object of the present invention is to provide a thermal spray material characterized in that it is at least one member selected from the group consisting of rO ₂ and MgO.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The thermal spraying material for use in the metal spraying method of the present invention has a basic composition of 75 to 95% by weight of refractory oxide powder and 5 to 25% by weight of easily oxidizable metal powder. Have

In the thermal spray material of the present invention, petalite is used as the refractory oxide powder to be blended.
The refractory oxide powder is used in an amount of 50% by weight, and one or more selected from the group consisting of SiO ₂ , ZrO ₂ and MgO is used in the remainder, and the refractory oxide powder is 75 to 95% by weight in total.
By using the composition, a good thermal spraying body free from cracks and peeling due to expansion and contraction of the obtained thermal spraying body can be constructed.

This is because petalite has a melting point of SiO ₂ (melting point: 1713 ° C.), Al ₂ O ₃ (melting point: 2054 ° C.), Zr
This is considered to be because it is relatively low at 1400 ° C. as compared with O ₂ (melting point: 2677 ° C.) and MgO (melting point: 2825 ° C.), and easily vitrifies. That is, refractory oxide powders such as SiO ₂ , Al ₂ O ₃ , ZrO ₂ , and MgO which cannot be sufficiently melted by the amount of heat derived from the easily oxidizable metal powder mixed with the thermal spray material used in the metal spraying method. By filling the gaps between the bodies with vitreous petalite, the porosity decreases and the body becomes denser. Therefore, wear resistance and compressive strength are improved, and durability is increased. Further, the vitrified petalite reacts with the furnace wall brick and further fills the gap between the furnace wall bricks, so that the adhesiveness is improved and the peeling resistance is improved.

[0015] Incidentally, petalite is known as a low thermal expansion material used for ceramics and the like, and the thermal shock resistance of a sprayed body is improved by using it as a refractory oxide powder. For this reason, cracking and peeling are suppressed even when the furnace temperature fluctuates.

Next, when the amount of petalite is set to 2 to 50% by weight, if the amount is less than 2% by weight, a sufficient amount of glass cannot be obtained due to a small amount of glass formed. Is unfavorable because it decreases.

As the easily oxidizable metal powder of the present invention, any known metal powder may be used, but Si is particularly preferably used. The amount of the easily oxidizable metal powder is in the range of 5 to 25% by weight. If the amount is less than 5% by weight, it is not preferable because a sufficient amount of heat cannot be provided to the thermal sprayed material, and if it exceeds 25% by weight, flashback is likely to occur during thermal spraying, which is not preferable.

[0018]

EXAMPLES The thermal spraying material of the present invention will be further described below with reference to examples. Examples In the mixing ratios shown in Table 1, various refractory oxide powders having a particle size of approximately 0.05 to 1 mm, a petalite having a particle size of 0.7 mm or less, and a particle size as an easily oxidizable metal powder. 0.2
The powder was dry-mixed with a metal Si powder having a diameter of less than 1 mm using a mixer to prepare a thermal spray material. SiO ₂ was heated to 600 ° C. -
A sprayed body was obtained by spraying on the surface of an Al ₂ O ₃ brick (thickness: 65 mm) and cooling. Note that SiO ₂ —Al ₂ O ₃
A sprayed body having a thickness of 60 mm was formed on the surface of the brick. Next, the obtained sprayed body was 40 mm × 40 mm × 40 mm.
mm, and the apparent porosity was measured based on JISR2205. Further, in order to measure the hot abrasion resistance, a sprayed body (114 mm × 114 m
m, thickness 60 mm), and after spraying the surface of the sprayed body to 1000 ° C. with an oxygen-propane burner, 3 kg of alumina particles having a particle size of 0.5 to 1.4 mm previously heated to 900 ° C.
And the wear volume at that time was measured. Table 1 also shows the obtained results.

[0019]

[Table 1]

From the results shown in Table 1, with respect to the apparent porosity, the decrease in the apparent porosity is not recognized when the amount of petalite is less than 2% by weight, but the apparent porosity sharply increases when the amount of petalite is 2% by weight or more. A decrease was observed, and it was confirmed that a dense thermal spray was obtained. Further, with respect to hot abrasion resistance, improvement in hot abrasion resistance, which is considered to be due to a decrease in apparent porosity when the amount of petalite was 2% by weight or more, was recognized. However, when the amount of petalite exceeded 50% by weight, the amount of glass was excessively increased, and the hot abrasion resistance was reduced.

Example 2 A sprayed material was prepared by mixing a petalite powder having a particle size of 0.7 mm or less and a metal Si powder with SiO ₂ powder having a particle size of approximately 0.05 to 1 mm at the mixing ratio shown in Table 2. This is 600
SiO ₂ -Al ₂ O ₃ brick (thickness: 65m) heated to ℃
m) was sprayed and cooled to obtain a sprayed body. The thickness of the SiO ₂ —Al ₂ O ₃ brick was 80 mm.
Was formed. Next, a test piece of 60 mm × 60 mm × 60 mm was cut out from the obtained thermal sprayed body, and the compression strength was measured by a pressure resistance tester based on JISR2206. In addition, the sprayed material having the above composition
A metal frame having an inner diameter of 68 mmφ, a thickness of 5 mm, and a height of 20 mm was placed on a SiO ₂ -Al ₂ O ₃ brick and a silica brick heated at a temperature of 0 ° C., and sprayed therein to obtain a sprayed body having a thickness of 20 mm. When the temperature of the sample heated by thermal spraying decreased to 600 ° C with a surface thermometer, a force was applied in parallel to the bonding surface, and the force with which the sprayed body was peeled together with the metal frame was measured. did. The measurement results are also shown in Table 2.

[0022]

[Table 2]

According to Table 2, both the compressive strength and the hot shear adhesive strength were improved by increasing the amount of petalite added. Further, regarding the hot shear adhesive strength, by adding petalite,
Significant improvement in adhesive strength was observed not only for silica brick but also for SiO ₂ —Al ₂ O ₃ brick.

Example 3 The sprayed material of the product 19 of the present invention and the comparative product 21 of Example 2
SiO ₂ —Al ₂ O ₃ brick (thickness: 65) heated to 00 ° C.
mm), and a sprayed body was obtained by cooling. The thickness of the SiO ₂ —Al ₂ O ₃ brick is 6
A 0 mm thermal spray was formed. Next, 40 mm × 40 mm × 80 m in length such that the center of the long side becomes the bonding surface.
m was cut out and subjected to a thermal shock test. The test conditions were as follows: after holding in an electric furnace heated to 1000 ° C. for 20 minutes,
A cycle of cooling in the air at 20 ° C. for 10 minutes was repeated to determine the number of thermal shocks until peeling from the joint surface, and the thermal shock resistance was determined. The results are also shown in Table 2. From the results in Table 2, it was confirmed that the addition of petalite, which is known as a low thermal expansion material, significantly improved the thermal shock resistance.

[0025]

As described above, by using petalite as the refractory oxide powder in the thermal spraying material used in the metal spraying method, a dense sprayed body having a low porosity was obtained. Further, since the porosity is low, the hot wear resistance is excellent, and the compressive strength and the hot shear adhesive strength are also high. Further, even if the porosity is low, petalite is a low-expansion material and therefore has good thermal shock resistance. From these facts, it can be expected that the life of the kiln and the molten metal furnace can be greatly extended by the thermal spray repair as compared with the related art.

Claims (2)

[Claims] 1. A thermal spray material comprising 75 to 95% by weight of a refractory oxide powder and 5 to 25% by weight of an easily oxidizable metal powder, wherein petalite is used as a part of the refractory oxide powder. To 50% by weight, and the remainder of the refractory oxide powder is S
A thermal spray material characterized in that it is at least one member selected from the group consisting of iO ₂ , Al ₂ O ₃ , ZrO ₂ and MgO. 2. The thermal spray material according to claim 1, wherein the easily oxidizable metal powder is Si.