KR20120054600A - High velocity gas spraying apparatus and apparatus for producing molten metal-resistant member - Google Patents

Abstract

An object of the present invention is to provide a high-speed gas spraying apparatus capable of extending the life of the sprayed coating sprayed on the molten metal member. The high speed gas spray apparatus includes an injection nozzle for injecting combustion gas and a spray material supply unit for supplying sprayed particles into the combustion gas flowing inwardly of the injection nozzle. The said high-speed gas spraying apparatus is characterized in that the thermal spraying material supply part includes a thermal spraying material supply port formed in the inner surface of the jetting nozzle at a position within 30 mm from the end of the jetting nozzle.

Description

HIGH VELOCITY GAS SPRAYING APPARATUS AND APPARATUS FOR PRODUCING MOLTEN METAL-RESISTANT MEMBER}

The present invention relates to a high speed gas spraying device for spraying thermal spraying particles together with combustion gases.

One known method of forming a coating on the surface of a steel sheet will immerse the steel sheet in a bath containing molten metal such as zinc, aluminum or a zinc-aluminum alloy or the like. The conveyance roller which conveys a steel plate is provided in this cylinder, and there exists a possibility that this conveyance roller may penetrate and corrode with molten metal. One known countermeasure for preventing such penetration and corrosion is to coat the surface of the conveying roller with a protective film.

One known method of forming such a protective film is a high speed gas spraying method. Patent documents 1 and 2 disclose the thermal spraying method of thermally spraying the cement material of WC-Co type | system | group or WC-WB-Co type | system | group by the high speed gas spraying method. Patent document 3 discloses the method of performing pore sealing process to the sprayed layer formed by plasma-spraying ceramics, such as alumina.

JPS48-11237 A JP 2553937 B JPH10-306362 A

However, in the conventional thermal spraying method, when the service period of a conveyance roller becomes long, the protective film on the surface of a conveyance roller peels and wears out, and the conveyance roller must be replaced. Background Art [0002] In recent years, further longer life of conveying rollers is required in view of cost reduction, improvement in production efficiency, and the like. In addition, even when the conveying roller is used in an acidic corrosion environment, long life is required.

Accordingly, an object of the present invention is to provide a high speed gas spraying apparatus capable of extending the life of the thermal sprayed coating on the molten metal member.

The present inventors analyzed the conventional sprayed coating and analyzed the cause of the peeling and abrasion of the sprayed coating. 1 is a cross-sectional view schematically showing a cross section of a conventional thermal spray coating. The sprayed particles 1 sprayed from a spray gun (not shown) move in the air in a semi-molten state and melt-resistant metal member (in this case, a conveying roller for conveying a steel sheet in molten zinc). (Absent). The thermal spraying particle | grains 1 reach | attain high speed (about 600 m / s) and high temperature (about 1750 degreeC), when it collides with a conveyance roller. Therefore, the said particle | grains 1 spread out at the time of collision, and deform | transform into a flat shape. By spraying these flattened spray particles 1 sequentially, a sprayed coating is formed.

As shown in Fig. 1, a large number of pores 3 and through pores 4 are formed in a conventional thermal spray coating. When the conveying roller is immersed in molten zinc, the molten zinc penetrates into the thermal spray coating through the pores 3 and the through pores 4, causing corrosion.

As a result of analyzing the causes of the generation of these pores 3 and the through pores 4, it was found that the diameter of the sprayed particles greatly influences the formation of the pores 3 and the through pores 4. More specifically, when the thermal spray particles 1 collide with the solidified thermal spray particles 2 that have been thermally sprayed on the conveying roller and solidified thereon, the thermal spray particles 1 have a low temperature, so that the thermal spray particles do not spread out sufficiently. do. Therefore, the opposing faces of the solidified thermal spray particles 2 and the thermal spray particles 1 do not completely contact each other. As a result, a gap is generated and the pores 3 are formed. Moreover, the strain rate at the time of the collision of the thermal spraying particle 1 is very high. Therefore, while the thermal spray particles 1 are being deformed, there is no place for the air around them to escape. After deformation, this air is released to the outside through the gap between the spray particles 1. For this reason, the through passage connected from the pore 3 to the outside of the thermal spray layer is formed, and the through pore 4 is formed by this. According to the analysis by the present inventors, the area ratio of the pores existing in the thermal spray coating was about 1 to 3%. In addition, the oxide 5 of the molten particles 1 was formed around the solidified sprayed particles 2. This weakens the bonding force between the molten particles 1 and facilitates the formation of the through pores 4.

2 is an optical micrograph showing a state in which zinc intruded into the conventional thermal spray coating. As shown in the figure, when zinc enters the thermal spray coating, corrosion progresses, and the thermal spray coating peels off and wears off.

3A is a cross-sectional view illustrating a state in which conventional sprayed particles are laminated, and FIG. 3B is a cross-sectional view illustrating a state in which fine spray particles having a smaller diameter than the conventional sprayed particles are stacked. Assuming that the sprayed particles are complete spheres, the size of the gap formed between adjacent sprayed particles is proportional to the square of the particle diameter. Therefore, by reducing the diameter of the sprayed particles, the filling rate of the fine particles can be improved to form a dense sprayed coating which is hard to invade molten zinc.

In order to solve the above problems, the high-speed gas spraying apparatus according to the present invention, the injection nozzle for injecting combustion gas; And a thermal spray material supply unit supplying the thermal spray particles into the combustion gas flowing inwardly of the injection nozzle, wherein the thermal spray material supply unit is formed on the inner surface of the injection nozzle at a position within 30 mm from an end of the injection nozzle. Characterized in that it comprises a supply port.

According to the present invention, it is possible to provide a high speed gas spraying apparatus capable of producing a molten metal member having a dense thermal spray coating.

1 is a cross-sectional view schematically showing a cross section of a conventional thermal spray coating;
2 is an optical micrograph showing a state in which zinc has invaded the conventional thermal spray coating;
Figure 3a is a cross-sectional view showing a state in which the conventional sprayed particles are laminated;
3B is a cross-sectional view showing a state in which sprayed particles having a smaller particle diameter are laminated than conventional sprayed particles;
4 is a cross-sectional view of the high speed gas spraying device according to the first embodiment;
5 is a view showing a relationship between the particle diameter of the thermal sprayed particles and the porosity when the particle diameter is changed;
FIG. 6 is a view of a case in which the non-oxidizing gas of the second embodiment is exhaled; FIG.
7A shows a backscattered electron image of the thermal sprayed coating of the comparative example;
7B shows an EDS mapping image of the thermal sprayed coating of the comparative example;
8A is a view showing a reflected electron image of the thermal spray coating of Example 1;
8B is a view showing an EDS mapping image of the thermal spray coating of Example 1;
9A is a view showing a reflected electron image of the thermal spray coating of Example 2;
FIG. 9B is a plane showing an EDS mapping image of the thermal spray coating of Example 2; FIG.
FIG. 10 shows the blast abrasion test method of Example 3. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described, referring drawings. It is an object of the present invention to prevent corrosion caused by molten metal containing Zn and / or Al.

Therefore, the molten metal member manufactured by the high speed gas spraying apparatus of the present invention includes various members in contact with the molten metal. Examples of such a member include a conveyance roller which is disposed in a storage container in which molten metal for steel sheet plating is stored and conveys a steel sheet; A conveying roller which is disposed outside the storage container and conveys the steel sheet to which the molten metal is attached; A mold into which molten metal is injected; Ladles used for moulds; And a pump for feeding molten metal.

(First Embodiment)

4 is a cross-sectional view of the high speed gas spraying device. Moreover, X axis | shaft, Y axis | shaft, and Z axis | shaft are three different axes orthogonal to each other, and an X-axis direction is the spraying direction of a sprayed particle. In this embodiment, the molten metal for steel plate plating is arrange | positioned in the storage container which stored, and demonstrates it as an example the conveyance roller (solvent metal member) which conveys a steel plate.

The high speed gas spray device 300 includes a combustion chamber 101 and a spray nozzle 103 disposed in front of the injection direction of the combustion chamber 101. The combustion chamber 101 is formed in a tubular shape and extends in the injection direction. The rear end of the combustion chamber 101 is closed by a combustion chamber tail plug 105. The combustion chamber tail stopper 105 includes a fuel supply 106 and an oxygen gas supply 107. The fuel supply unit 106 communicates with the combustion chamber 101, and the fuel injected into the fuel supply unit 106 moves at high speed toward the combustion chamber 101. The oxygen gas supply unit 107 communicates with the combustion chamber 101, and oxygen in the oxygen gas supply unit 107 moves at high speed toward the combustion chamber 101. Kerosene may be used as the fuel injected into the fuel supply unit 106. The flow rate of kerosene is preferably 15.5 L / h to 26.5 L / h. The flow rate of oxygen is preferably 40 m 3 / h to 53 m 3 / h.

The Laval nozzle 102 is formed in the connection part between the combustion chamber 101 and the thermal spray nozzle 103. As shown in FIG. By controlling the temperature and pressure of the fluid supplied to the Laval nozzle 102, the velocity of the fluid can be increased to supersonic speed.

The thermal spray nozzle 103 is formed in the tubular shape with constant internal diameter dimension, and is extended in the thermal spraying direction. The length of the thermal spray nozzle 103 is preferably 10 to 20 cm. This thermal spray nozzle 103 adjusts the flow of the high speed combustion gas supplied from the combustion chamber 101, and improves the convergence of the flow. Therefore, if the length of the thermal spray nozzle 103 is below the said range, a flow adjustment effect and a convergence effect will become small. Moreover, when the said length exceeds the said range, the speed of combustion gas will fall. The injection port 103a is formed in the edge part of the thermal spray nozzle 103. As shown in FIG. The spraying material is injected from the injection port 103a together with the combustion gas.

The thermal spray material supply nozzle 104 is formed in the vicinity of the injection port 103a of the thermal spray nozzle 103. The thermal spray particle supply port 104a of the thermal spray material supply nozzle 104 is formed in the inner peripheral surface of the thermal spray nozzle 103. Moreover, it is preferable that the thermal spraying material supply opening 104a is formed on the said inner peripheral surface within 30 mm from the edge part of the thermal spraying material supply nozzle 104. Subsequently, since the thermal spray material supplied into the combustion gas flowing through the thermal spray material supply nozzle 104 hardly adheres on the inner circumferential surface of the thermal spray material supply nozzle 104, the occurrence of spitting can be suppressed. However, spitting is a phenomenon in which the sprayed material adhered on the inner peripheral surface of the thermal spraying material supply nozzle 104 is peeled off from the inner peripheral surface, and combustion gas is sprayed on the surface of the thermal spraying material (conveyance roller). The thermal spray material supply device (not shown) feeds the thermal spray material to the thermal spray material supply nozzle 104. As a conveying means, carrier gas, such as nitrogen gas, can be used. Thus, the thermal spray material flows into the combustion gas inside the thermal spray nozzle 103 together with the carrier gas.

5 is a graph showing the change in porosity when the particle diameter of the WC12Co sprayed particles is changed. In the conventional thermal spraying, the thermal spraying material whose particle diameter is about 40 micrometers is sprayed by the thickness of about 150 micrometers. However, the generation of pores in the proportion of about 3% is inevitable. When the particle | grain whose particle diameter was 40 micrometers was immersed in 10% dilute sulfuric acid at 40 degreeC, the sprayed specimen sprayed 150 micrometers thick, the diluted sulfuric acid penetrated into the thermal spray coating, and the thermal spray coating peeled from the base material within 5 days. Using the thermal spraying apparatus shown in FIG. 4, the test was carried out using the thermal spraying particles having various particle diameters. As a result of this test, it was found that the porosity was 0.15% in the 15 µm sprayed particles. Even after this test piece was immersed in 10% dilute sulfuric acid at 40 ° C for 20 days, dilute sulfuric acid did not penetrate into the sprayed coating. When the particle diameter of a thermal spraying material was 15 micrometers or less, it turned out that formation of a through pore can be prevented.

By using fine thermal spray particles having a particle diameter of 15 µm or less, a dense thermal spray coating without penetrating pores can be formed. This effectively suppresses intrusion of molten metal containing Zn and / or Al into the interior of the thermal spray coating, whereby corrosion of the conveying roller can be prevented. In addition, when Zn and / or Al or the like adhered to the surface of the conveying roller used in the molten metal is removed using an acidic solution, corrosion by this acidic solution can be prevented. However, the particle diameter of a thermal spraying material is an average particle diameter of a thermal spraying material, ie, the median diameter computed using the laser diffraction scattering measurement method.

Moreover, it is preferable to use the sprayed particle whose particle diameter is 1 micrometer or more. As a result, the thermal spray particles can be prevented from adhering to the region near the thermal spray particle supply port 104a of the thermal spray material supply nozzle 104. More specifically, when the diameter of the thermal sprayed particles is small, the kinetic energy of the particles when sprayed from the thermal sprayed particle supply port 104a becomes small, and the thermal sprayed particles may be deposited in a region near the thermal sprayed particle supply port 104a. There is. Therefore, deposition of the thermal spray particles can be effectively suppressed by setting the diameter of the thermal spray particles to 1 µm or more.

As the thermal spraying material, various materials can be used as a binder for bonding the thermal spraying particles. For example, Ni-based alloys, Ni-Cr-based alloys, Co-based alloys (for example, about 30 mass% Cr and 4-15 mass% W based on Co as a main component) Containing a stellite alloy.

In the conventional method, the pores of the thermal sprayed coating were sealed with a pore sealant to prevent corrosion caused by molten metal and acidic solutions containing Zn and / or Al penetrated through the through pores. However, when the steel sheet comes into contact with the conveying roller, surface wear and internal stress occur. Therefore, a crack arises in a pore sealant, and the effect of a pore sealing process falls by this, and the lifetime of a conveyance roller is shortened. The conveyance roller of this embodiment has almost no pore and a through pore. Therefore, a pore sealing process is not essential and the life of this conveyance roller can be made longer than the conventional conveyance roller which performed the pore sealing process. Moreover, a pore sealing process can also be given to the conveyance roller of this embodiment. In this case, the pore sealant can more effectively suppress corrosion due to penetration of the molten metal and the acidic solution.

(2nd Embodiment)

The tubular gas supply part 310 is provided in the high speed gas spraying apparatus 300 shown in FIG. As viewed from the X-axis direction, the tubular gas supply port 310a which is the gas outlet of the tubular gas supply part 310 surrounds the injection port 103a. Therefore, the tubular gas dome is formed by the gas injected from the tubular gas supply port 310a. The combustion gas injected from the injection nozzle 103 moves the inside of this gas dome in the X-axis direction. However, not only air but also non-oxidizing gases, such as nitrogen gas, argon gas, and helium gas, and combustible gases, such as propane gas or acetylene gas, can be used as said gas.

The surface of the thermal spray material supplied into the combustion gas from the thermal spray material supply nozzle 104 is oxidized by oxygen remaining in the combustion gas and oxygen in the air drawn around the combustion gas. As a result, the bonding force between the thermal sprayed particles in the thermal sprayed coating is lowered, thereby lowering the strength of the thermal sprayed coating. In particular, when the particle diameter of the thermal spraying material is small, the specific surface area thereof becomes large, and thus the influence of oxidation becomes large. In the case where a non-oxidizing gas is used as the gas, the non-oxidizing gas serves as a barrier to prevent oxygen from the atmosphere from being introduced into the combustion gas. In addition, since the non-oxidizing gas is introduced into the combustion gas, the partial pressure of oxygen in the combustion gas is reduced. Thereby, oxidation of the thermal spraying material in combustion gas can be suppressed. The shape of the tubular gas supply port 310a may be changed to another shape (eg, a rectangular shape) as long as it can surround the combustion gas injected from the thermal spray nozzle 103.

(Embodiment 3)

FIG. 6 is a schematic diagram showing a method of spraying on a roller serving as a spraying object (i.e., sprayed material) 204 using the high speed gas spraying device of FIG. The thermal spray material is heated and accelerated by being sprayed into the combustion gas 203 flowing at supersonic speed from the thermal spray material supply nozzle 104. The heated and accelerated thermal spray material is sprayed onto the thermal spraying object 204 to form a film to be used as the thermal spray coating 205. A gas dome formed from a tubular gas stream is supplied from the tubular gas supply port 310a to prevent oxidation of the thermal spray material. When a non-oxidizing gas is used as the gas flow injected from the tubular gas supply port 310a, the antioxidant effect can be improved. In addition, since the sprayed object 204 is rotated in the direction of the arrow, the sprayed coating is evacuated from the gas dome and exposed to the atmosphere. The temperature of the sprayed coating immediately after spraying is about 800 degreeC, and this temperature is higher than the range of 250 degreeC-350 degreeC which is the oxidation start temperature of a thermal spraying material. Therefore, the surface of the thermal sprayed coating immediately after thermal spraying is oxidized by exposure to the atmosphere, and the bonding force between the oxidized thermal sprayed coating and the new thermal sprayed coating formed thereon is lowered. In this embodiment, cooling gas is blown out from the cooling gas injection nozzle 206 to the surface of the thermal spray coating 205. Thereby, since the surface of the sprayed coating 205 immediately after spraying cools rapidly below oxidation start temperature, oxidation of the sprayed coating 205 can be prevented. When a non-oxidizing gas such as nitrogen gas, argon gas, helium gas or the like is used as the cooling gas, a larger effect can be obtained.

Hereinafter, an Example demonstrates this invention concretely.

[ Example  One]

The test conditions of Example 1 were as follows, and the method of 1st Embodiment was used. Mo, B, Co, and Cr were used as a thermal spraying material. The average particle diameter of the thermal sprayed particles was 3 µm. As the thermal spraying device, the high speed gas thermal spraying device of the first embodiment shown in FIG. 4 was used, and the thermal spraying thickness was 200 µm. As a test material for the conveyance roller, a round bar made of SUS410 was used. The diameter of this round rod was 30 mm and its length was 200 mm.

Test conditions of Comparative Example 1 are as follows. The average particle diameter of the thermal spray particles was 40 µm. A high speed gas spray gun (JP-5000, manufactured by TAFA) was used as the spray device. As a conveyance roller, the round rod similar to Example 1 was used. The average particle diameter of the thermal sprayed particles is a median diameter measured by laser diffraction scattering measurement.

After the round rods of these Example 1 and Comparative Example 1 were immersed in molten zinc for 10 days without using a pore sealing material, the cross section of the thermal sprayed coating on each round rod surface was analyzed from the EDS mapping image. FIG. 7A shows the reflected electron image of the cross section of the thermal spray coating of the comparative example, and FIG. 7B shows its EDS mapping image. FIG. 8A shows the reflected electron image of the cross section of the thermal spray coating of the above embodiment, and FIG. 8B shows its EDS mapping image. In addition, the test results are shown in Table 1. In Example 1, no penetration of zinc into the thermal sprayed coating was observed. However, in Comparative Example 1, zinc penetrated into the thermal sprayed coating and reached the base of the round rod. In Example 1, it was immersed in molten zinc for 10 more days, but no penetration of zinc into the sprayed coating was observed at all.

Warrior
Particle
diameter
Porosity
(%)
In molten zinc Immersion  Test result
(10 days later) Champion condition Kerosene
Supply flow rate
(ℓ / h) Oxygen
Supply flow rate
(ℓ / min ) 40 μm
Conventional method
2.6 Zinc penetrated and eroded throughout the cross section of the coating, and part of the zinc reached the substrate. The test could not continue.
26.4
829 3㎛
Invention
0 Corrosion due to the penetration of zinc in the cross-sectional direction of the coating was not observed. The sample was examined after 20 days and no corrosion was observed.
19.7
700

[ Example  2]

The test conditions of Example 2 were as follows, and the method of 2nd Embodiment was used. Mo, B, Co, and Cr were used as a thermal spraying material. The average particle diameter of the thermal sprayed particles was 3 µm. This invention was applied to the support roller which conveys a steel plate in the molten zinc for steel plate plating, and corrosion resistance was evaluated. The service period of the support roller was set to 30 days. As the thermal spraying device, the high speed gas thermal spraying device shown in FIG. 4 was used, and nitrogen gas was supplied as a non-oxidizing gas from the tubular gas supply unit. The spray thickness was 100 micrometers. The material of the conveyance roller was SUS410. The diameter of the support roller was 350 mm and its length was 2690 mm.

As a comparison, using a high-speed gas spray gun (JP-5000, manufactured by TAFA) as a spraying device, particles having a conventional average particle diameter of 40 µm were sprayed onto the ends of the rollers that do not contact the steel sheet. Pore sealing was performed for both cases.

In the comparison part using the conventional method, zinc penetrated the excess layer and the thermal spray coating which sealed the pore, and reached | attained the base material of a support roller, and the thermal spray coating peeled. In Example 2 of the present invention, penetration of Zn into the excess layer sealed with pores was observed, but no penetration of zinc into the thermal sprayed coating was observed. 9A shows the reflected electron image of the cross section of the thermal spray coating of Example 2, and FIG. 9B shows its EDS mapping image. In addition, the test results are shown in Table 2.

Warrior
Particle
diameter
Porosity
(%)
In molten zinc Immersion  Test result
(10 days later) Champion condition Kerosene
Supply flow rate
(ℓ / h) Oxygen
Supply flow rate
(ℓ / min ) 40 μm
Conventional method
2.7 Zinc penetrated and eroded throughout the cross section of the excess layer and the film with the pores sealed, and part of the zinc reached the substrate. The film was peeled off.
26.4
829 3㎛
Invention
0 Zn penetrated the excess layer sealed with pores, but no corrosion by zinc penetration was observed at the cross section of the film.
19.7
700

[ Example  3]

The tests shown in Table 3 were performed to confirm the effect of the non-oxidizing tubular gas dome and the flushing effect of the non-oxidizing gas on the surface of the sprayed coating immediately after the spraying. Mo, B, Co, and Cr were used as a thermal spraying material. The average particle diameter of the thermal sprayed particles was 3 µm. As the thermal spraying apparatus, the high speed gas thermal spraying apparatus of 1st Embodiment shown in FIG. 4 was used, and the thermal spraying thickness was 200 micrometers. As the test material, a flat plate having a width of 30 mm, a length of 50 mm, and a thickness of 5 mm made of SUS410 was used. The thermal spraying was performed under conditions of a feed flow rate of kerosene of 19.7 L / h and a flow rate of oxygen of 700 NL / min.

Condition 1: Non-oxidizing tubular gas dome was not used and no non-oxidizing gas was emitted (base)

Condition 2: A non-oxidizing tubular gas dome was used and no non-oxidizing gas was blown

Condition 3: A non-oxidizing tubular gas dome was used and exhaled non-oxidizing gas.

By using the non-oxidizing tubular gas dome, oxidation of the surface of the sprayed particles flowing in the combustion gas was suppressed, thereby improving the bonding force between the particles in the sprayed coating. Thus, the amount of blast wear decreased, while the thickness of the deposited film per one pass of the thermal spray was improved. Moreover, the same effect was acquired when non-oxidizing gas was sprayed on the sprayed coating immediately after spraying, and it cooled rapidly below the high temperature oxidation start temperature. Oblique blast abrasion test to evaluate the interparticle binding force was performed by the method shown in FIG.

Condition 1 Condition 2 Condition 3 Blast  Wear One 0.96 0.94 1 pass  The thickness of the deposited film One 1.15 1.21

Claims (4)

An injection nozzle for injecting combustion gas; And
A spray material supply unit for supplying the sprayed particles into the combustion gas flowing into the injection nozzle,
And the thermal spraying material supply unit includes a thermal spraying material supply port formed in the inner surface of the injection nozzle at a position within 30 mm from an end of the injection nozzle. The high-speed gas spraying apparatus according to claim 1, wherein a particle diameter of the thermal spray particles supplied from the thermal spray material supply unit is 15 mm or less. The tubular gas supply unit according to claim 1 or 2, wherein the gas is supplied in a tubular shape extending from the injection nozzle in the direction of injecting the combustion gas so that the combustion gas surrounds the gas in the tubular shape. Further comprising a high speed gas spray device. An apparatus for manufacturing a molten metal member in which a thermal spray coating covers a contact portion in contact with a molten metal containing Zn and / or Al,
An injection nozzle for injecting combustion gas toward the contact portion; And
A spray material supply unit for supplying the sprayed particles into the combustion gas flowing into the injection nozzle,
And the thermal spray material supply unit includes a thermal spray material supply port formed in the inner surface of the spray nozzle at a position within 30 mm from an end of the spray nozzle.

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