JP2000087206A - Vessel for molten metal and its surface treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treatment coating film excellent in property of absorbing or diffusing a gas generated from a molten metal and to provide a surface structure of a vessel contributing also toward upgrading a product casting. SOLUTION: A thermally sprayed dense metallic coating film is formed on the surface side of a substrate by thermally spraying a heat resistant alloy comprising a combination of two or more selected from Ni, Co, Cr, Al, Y and Ta and a thermally sprayed porous ceramic coating film is formed as a top coat on the surface side by thermally spraying a powdery ZrO2 mixture prepd. by adding 1-5 wt.% pure ZrO2 without contg. a stabilizing component and/or 2-20 wt.% unstabilized ZrO2 contg. <5 wt.% stabilizing component to stabilized or partially stabilized ZrO2 contg. 6-30 wt.% stabilizing component as a main component to obtain the objective vessel for a molten metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a container for molten metal, such as a steel or copper mold, and a method for treating the surface of the molten metal. In particular, a mold used for casting cast iron or molten metal of cast steel (iron, molten steel) is preferred. And a surface treatment method for the inner wall surface of the container.

[0002] The technology of the present invention is not limited to molds, but also includes various kinds of vessels as ancillary equipment for steelmaking furnaces such as a lance pipe for steelmaking in contact with molten steel, a tundish for continuous casting, a ladle, and ancillary equipment for nonferrous metal refining. Further, the present invention can be applied as a surface treatment technique for a container base material in a field requiring a heat shielding film and a heat insulating film in a boiler, a gas turbine, a heating furnace, and the like.

[0003]

2. Description of the Related Art Hereinafter, an example in which the technique of the present invention is applied to an inner wall surface of a mold used for producing a steel casting by a centrifugal casting method will be described. Conventionally, centrifugal casting molds used for the production of cast iron and cast steel products are heat-resistant cast steel (JIS G5122
SCH-1 to 3 and SCH 11 to 15), and a portion in contact with the molten metal (iron) is coated with diatomaceous earth. In addition, a technique for forming a ceramic film with a heat-resistant metal instead of applying diatomaceous earth has been proposed in Japanese Patent Application Laid-Open Nos. 55-156463 and 62-13236. Others
The inventors of the present invention also disclosed in JP-A-62-243615 and JP-A-1-210152, a heat-resistant alloy obtained by spraying a heat-resistant alloy or a heat-resistant alloy and an oxide-based ceramic film on a substrate surface of a mold. A technique for forming a thermal spray coating was proposed.

[0004]

By the way, the inner surface of the mold for centrifugal casting, especially the inner wall surface of the mold that comes into contact with the molten metal,
It receives a large heat load due to the centrifugal force generated during casting. Therefore, the inner wall surface of the mold used in such an application is severely deteriorated due to thermal fatigue, and is severely damaged due to crack generation and local crystal particle falling off due to crack growth. As a result, there is a problem that the function as a mold is reduced and the life is significantly shortened.

[0005] Further, in a method in which a thermal spray coating is not applied,
In each casting, it is necessary to apply diatomaceous earth powder to the inner wall surface of the mold. However, this operation requires a lot of manpower, and also requires time for drying the applied diatomaceous earth, and also has a problem that it is not preferable in the working environment.

On the other hand, the method of forming a thermal spray coating in place of diatomaceous earth has certainly obtained certain effects such as an improvement in productivity and a reduction in the thermal fatigue rate of the mold body. However, there is a problem that fine bubbles (ie, cavities) are generated due to a gas generated when the molten metal is solidified, thereby causing deterioration in quality.

Therefore, a main object of the present invention is to propose a surface treatment technique which contributes to the improvement of the life of a container such as a mold. Another object of the present invention is to propose a surface treatment film having excellent absorption and emission characteristics of gas generated from a molten metal, and to propose a surface structure of a container which also contributes to improvement in quality of a product casting. Still another object of the present invention is to propose a method for surface treatment of a container for molten metal such as a mold.

[0008]

As a result of intensive studies on the above-mentioned problems surrounding the mold in order to realize the above-mentioned object, the generation of gas which causes a porosity, in particular, indicates that the mold is filled with molten metal. When exposed to a high temperature environment, the oxide ceramic spray coating formed on the inner wall surface of this mold undergoes a sintering reaction and densifies, and the porosity maintained during spraying before use gradually decreases, resulting in gas They found that this was caused by the obstruction of distribution and the inability to emit. That is, the conventional ZrO ₂ sprayed coating formed on the inner wall of the mold cannot maintain the initial porosity for a long period of time, and loses the escape of the gas component released from the molten metal, thereby resulting in the casting. It has been found that bubbles (cavities) are generated. In addition, it has been found that there is a problem that a sprayed coating having no escape for gas components is often destroyed by gas pressure.

Therefore, in the present invention, as a means for overcoming the above-mentioned problems of the prior art, basically,
On the surface of the substrate in contact with the molten metal of the container, as an undercoat, 2 selected from Ni, Co, Cr, Al, Y and Ta
A stabilized / partially stabilized ZrO having a dense metal sprayed coating obtained by spraying a heat-resistant alloy according to a combination of more than one kind, and having a stabilizing component amount of 6 to 30 wt% as a top coat thereon. ₂ as a main component, and 1-5 wt% of pure ZrO ₂ containing no stabilizing component and / or an amount of stabilizing component of 5%.
Suggest molten metal container characterized by having a porous ceramic thermal sprayed coating obtained by unstabilized ZrO ₂ is less than wt% by spraying the mixed ZrO ₂ powder obtained by adding 2 to 20 wt%.

Further, according to the present invention, the lower layer of the base material side mainly comprises Ni, Co, Cr,
Consisting of a dense metal sprayed layer obtained by spraying a heat-resistant alloy according to a combination of two or more selected from Al, Y and Ta, the upper layer on the surface side is mainly used, and the amount of the stabilizing component is 6 to 30% by weight of stabilized / partially stabilized ZrO ₂ as a main component, and 1-5% by weight of pure ZrO ₂ containing no stabilizing component and / or unstabilized with less than 5% by weight of stabilizing component a porous ceramic thermal sprayed layer obtained by spraying a mixed ZrO ₂ formed by the ZrO ₂ was added 2 to 20 wt%, and, above thermal sprayed layer is much content of more heat resistant alloy closer to the substrate side,
On the other hand, a molten metal container characterized in that it is a single-layer sprayed coating having a concentration gradient in which the ZrO ₂ content is higher as it is closer to the surface side can also be an effective means for solving the problem.

In the present invention, the undercoated dense metal sprayed coating has a thickness of 50 to 500 μm and a porosity of 5% by weight or less, and the top coated porous ceramic sprayed coating has a thickness of 200 to 1000 μm. With porosity of 5 to 25 wt%
It is preferable that

[0012] The container of the present invention described above, first, Ni, Co, Cr, Al, Y, Ta on the substrate surface in contact with the molten metal of this container
A heat-resistant alloy powder according to a combination of two or more selected from the above is sprayed to form a dense metal sprayed coating, and then a stable component having a stabilizing component amount of 6 to 30 wt% is formed on the coating. to the reduction and partially stabilized ZrO ₂ as a main component, 1-5 wt% of pure ZrO ₂ containing no stabilizing ingredients and / or amount of the stabilizing component is 2 to the unstabilized ZrO ₂ is less than 5 wt% 20wt
% ZrO ₂ powder can be obtained by spraying the mixed ZrO ₂ powder to form a sprayed porous ceramic film having a porosity of 5 to 25%.

Further, according to the present invention, first, a heat-resistant material for a combination of two or more kinds selected from Ni, Co, Cr, Al, Y, and Ta is provided on the surface of the substrate in contact with the molten metal of the container. The alloy powder is sprayed, and then, stabilized and partially stabilized ZrO ₂ having a stabilizing component amount of 6 to 30 wt% as a main component, ₁ to 5 wt% of pure ZrO ₂ containing no stabilizing component and 2-20% by weight of unstabilized ZrO ₂ having an amount of stabilizing component of less than 5% by weight
Thermal spraying of the mixed ZrO ₂ powder that is added, at this time, a gradient in which the content of the heat resistant alloy is increased closer to the base material side and the ZrO ₂ content is increased closer to the surface side By spraying the sprayed material according to the formulation, the surface of the base material side is formed as a sprayed layer rich in dense metal and the surface side is formed as a sprayed coating having a concentration gradient in which the porous ceramic is a sprayed layer rich in porous ceramics. It can be obtained by employing a processing method.

In a preferred embodiment of the present invention, after forming the thermal spray coating, prior to use in an actual machine, a process of repeatedly raising and lowering the temperature in a temperature range of 1050 ° C. to 1100 ° C. is performed in an electric furnace. by pure ZrO ₂ containing no stabilizing components in the thermal spray coating, the content destruction of less than 1-5 wt% of the unstabilized ZrO ₂ in stabilizing component, by pre promote shedding, baked in use It is effective to perform a treatment to prevent the thermal spray coating from being densified due to the binding reaction.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, when a molten metal container according to the present invention is applied to a centrifugal casting mold, a spray material sprayed on an inner wall surface of the mold in contact with molten iron, and this material is sprayed. The operation mechanism of the composite sprayed coating formed by the above will be described.

(1) Thermal Spraying Material The thermal spraying material used in the present invention includes Ni, Co, Cr, Al,
A heat resistant alloy powder according to a combination of two or more selected from Y and Ta, and a mixed ZrO ₂ ceramic powder of pure ZrO ₂ , unstabilized ZrO ₂ and stabilized / partially stabilized ZrO ₂ are used. The former is mainly used for the undercoat, and the latter is used for the top coat. a. Thermal spray material for undercoat The chemical composition of the above-mentioned heat-resistant alloy thermal spray alloy for undercoat is as shown in Table 1, and all of them are Cr ₂ O ₃ , which has excellent heat resistance and high temperature oxidation resistance under high temperature environment. An alloy such as Al ₂ O ₃ that forms an oxide film.

[0017]

[Table 1]

B. Thermal Sprayed Material for Top Coat Table 2 shows examples of the above-mentioned mixed ZrO ₂ thermal sprayed material for the top coat. This exemplary mixed ZrO ₂ sprayed material contains Y ₂
A crystal stabilizing component such as O ₃ , CaO, CeO ₂ or MgO,
Includes stabilization and partially stabilized ZrO ₂ containing 6～30Wt%, and, if this relative stabilization, partially stabilized ZrO _2, further addition of pure ZrO ₂ containing no stabilizing components 1-5 wt%, and And / or a ZrO ₂ ceramic to which ₂ to 20 wt% of unstabilized ZrO ₂ having a stabilizing component content of less than 5 wt% is added.

In such a mixed ZrO ₂ spray material, the amount of pure ZrO ₂ added to the stabilized / partially stabilized ZrO ₂ is 1 to 5 wt%.
The reason is that if the content is less than 1 wt%, the porosity required as a top coat cannot be obtained, while the addition amount is 5 wt%.
Conversely, the porosity becomes so large that the steel may enter the pores, and the mechanical strength of the coating decreases.

In the case of unstabilized ZrO ₂ in which the content of the stabilizing component is less than 5% by weight, it is necessary to add it in the range of 2 to 20% by weight. The porosity of the thermal sprayed coating decreases, while the addition of 20 wt% or more conversely increases the porosity too much and lowers the mechanical properties of the coating.

When adding both pure ZrO ₂ and unstabilized ZrO ₂ , the range of the added amount of pure ZrO ₂ has priority (1 to 5 wt.
%), And the remainder may be the latter content of unstabilized ZrO ₂ . That is, in a top coat in which both coexist, the maximum content of both is 20 wt%, and the rest obtained by subtracting the pure ZrO ₂ content from this amount is unstabilized ZrO ₂ .

It is preferable that the mixed ZrO ₂ -based thermal spraying material for a top coat has a particle diameter in a range of 3 to 80 μm. The reason is that it is difficult to continuously supply the powder having a particle size smaller than 3 μm to the thermal spraying apparatus. On the other hand, a powder having a particle size of more than 80 μm is not preferable because it does not completely melt in the thermal spraying heat source, so that the mutual bonding force of the particles constituting the coating decreases.

[0023]

[Table 2]

(2) Formation of Thermal Sprayed Coating a. Formation of Undercoat by Dense Metal Sprayed Coating Ni, Co, Cr, Ni, Co, Cr, Al, Y
And an alloy powder composed of two or more kinds selected from Ta and an undercoat is applied (coated) to a thickness of 50 to 500 μm. In general, an undercoat applied to the inner wall surface of a mold needs to have excellent adhesiveness with a base material and also have excellent adhesiveness with a top coat. In addition, the top coat applied to the mold is required to form a porous thermal spray coating through which high-temperature gas and air from the outside easily enter to improve heat insulation. It is necessary to form a film that exhibits sufficient resistance to the oxidizing action caused by the film.

For these reasons, the undercoat is required to be as dense as possible, and in the present invention, a sprayed coating having a porosity in the range of 0.5 to 5% by weight. The reason is that a coating having a porosity of 0.5 wt% or less is difficult to form by the thermal spraying method. On the other hand, when the undercoat sprayed coating has a porosity of more than 5 wt%, it can prevent oxidation of the substrate. It is not possible. In this sense, in the present invention, in addition to controlling the spraying conditions (heat source, atmosphere, flying speed of the sprayed particles, etc.), the sprayed material powder (particle size of the alloy powder is controlled. For example, 5 to 80 μm,
Preferably, particles having a particle diameter of 10 to 50 μm are used. If the particle size is less than 5 μm, the supply of powder to the spray gun is poor.
If it is more than μm, the particle bonding strength is weak and a dense alloy sprayed coating having the above porosity cannot be obtained.

B. Formation of Top Coat from Sprayed Porous Ceramic Coating The top coat formed on the undercoat is well resistant to high-temperature molten metal such as molten iron, and the heat from the molten iron is under It is necessary to have a coating that does not spread over the coat and the substrate. For this reason, it is important that the top coat is excellent in heat resistance, has low thermal conductivity, and is porous so as to make use of the air heat insulation by the space. In order to respond to such a request, the present invention
As a material that satisfies the above conditions regarding heat resistance and thermal conductivity, we focused on ZrO ₂ -based thermal spray material. Moreover, this material is excellent in air heat insulation utilizing a space.

It should be noted that being excellent in the above-mentioned heat insulation means that a sufficient air layer can be formed in the pores of the film. For example, in a continuous casting mold for steel, since a gas component is contained in the molten steel to be cast, even if the gas is released along with solidification of the molten steel, the ceramic sprayed coating as the top coat is porous. If so, the released gas can be sufficiently absorbed. However, if
If there are few pores in the thermal spray coating to absorb the release gas and if the gas release path is not formed, the air heat insulation property will decrease and the gas will lose a refuge at the same time, forming pinholes in castings, forming Will be dropped.

In this regard, as in the prior art, the top coat sprayed coating is made of ZrO ₂ containing 6 to 30% by weight of a stabilizing component.
If the coating was formed only with the thermal spray material, even if the porosity of the coating in the initial stage of use was sufficient for releasing gas components, a sintering reaction occurred during use and the porosity decreased, Outgassing performance will gradually decrease.

Therefore, in the present invention, a thermal spray coating made of the following thermal spray material is formed as the dense ceramic thermal spray coating as the top coat. That is, stabilized / partially stabilized zirconia (ZrO) containing 6 to 30 wt% of a stabilizing component such as CgO, MgO, Y ₂ O ₃ or CeO ₂ as a main component.
₂ ) Using powder, pure ZrO ₂ containing no stabilizing component and / or unstabilized Zr containing less than 5 wt% of stabilizing component
A top coat was formed by plasma spraying a mixed ZrO ₂ spray material mixed with O ₂ . In general
ZrO ₂ spray material is plasma sprayed, and ZrO ₂ is heated by heating in contact with the plasma heat source, while the temperature drops by cooling due to the adhesion to the undercoat surface. Even after this, a temperature change occurs in which the temperature rises due to contact with the molten iron and the temperature falls due to cooling of the mold. Moreover, this temperature change passes through 1050 ° C. to 1100 ° C. where a change in crystal form occurs. In such a case, ZrO ₂ undergoes a phase transition from a monoclinic type to a tetragonal type in this temperature range, and vice versa. The change of these crystal types is 4 at the same time.
Since the volume change reaches ~ 7vol.%, Not only the ZrO ₂ particles themselves are destroyed, but they also fall off as fine powder, and the traces become pores, which lower the porosity due to the sintering reaction of the film. Will be complemented.

The stabilized and partially stabilized Zr containing 6 to 30% by weight of a stabilizing component which is a main component of the thermal spraying material for the top coat.
O ₂ is heated - when subjected to heat cycle of cooling has a property of generating a crack. However, the cracks are extremely fine, and these fine cracks are convenient for absorbing thermal stress generated during heating and cooling. Therefore, they are useful as a thermal spray material having both heat resistance and heat insulating properties. However, the cracks are so fine that when used in a high temperature environment, for example, in contact with molten steel, the cracks are joined by the sintering reaction, resulting in a decrease in porosity. Therefore, it is not sufficient to spray-coat only such stabilized and partially stabilized ZrO ₂ powder.

[0031] Therefore, as the thermal spraying material for the topcoat of the present invention, does not contain a stabilizing component pure ZrO ₂ powder or total amount of the components is used as a mixture of unstabilized ZrO ₂ powder of less than 5 wt% It was to be. These pure ZrO ₂ and unstabilized
ZrO ₂ , especially in the former case, has a large volume change rate accompanying the change in crystal form, and in the latter case, it is smaller than pure ZrO ₂ , but it contains stabilized or partially stabilized ZrO ₂ containing at least 6 wt% of stabilizing components. Compared to ₂ , it is much larger, and when subjected to a heat cycle of heating-cooling, a clear crack is generated in the coating. When this is repeated for a long period of time, the powder eventually falls off as a powder, and this portion becomes a pore, so that the gas component can be easily distributed. In other words, the thermal spray coating formed using such a ZrO ₂ mixed powder always generates new open pores with the passage of time, so that a constant porosity can be maintained for a long period of time.

As described above, the top coat can always maintain a substantially uniform porosity from the time of thermal spray deposition to the end of its life due to its use in an actual machine by such an operation mechanism. As described above, the porosity of the top coat is preferably in the range of 5 to 25% by weight, and if the porosity is less than 5% by weight, the flow of gas components becomes insufficient, and the thermal shock resistance of the film itself decreases. When the porosity is 25 wt% or more, although the gas components are excellent in flow, the mechanical strength of the coating decreases, so that even a slight vibration or impact may cause cracks or local peeling. This is not preferable because it increases the number of operations.

The thickness of the top coat is 100 to
When the range of 1000 μm is good and the thickness is thinner than 100 μm, the heat insulating effect is poor. On the other hand, when the thickness is 1000 μm or more, the mechanical strength of the film is unfavorably reduced. Preferably 200-500
μm is recommended.

The above-described example relates to the case where the thermal spray coating has a two-layer structure of a dense metal thermal spray coating (layer) as an undercoat and a porous ceramic (ZrO ₂ ) thermal spray coating (layer) as a top coat. It is description of. In addition to the example of such a two-layer structure, the present invention sprays a thermal spraying material in which two kinds of powders are mixed in a gradient, so that there is no boundary between an undercoat and a topcoat, that is, a single layer having a so-called concentration gradient. It can also be a thermal spray coating.

That is, in a typical embodiment of the present invention, the thermal spray coating has a two-layer structure of an undercoat and a top coat. The higher the content of the heat-resistant alloy component,
As the content of the ZrO ₂ component increases as the film surface side, is to that the proportion of spray material components inclined to varying thermal sprayed layer. Therefore, in this case, the outermost layer of the top coat is in a state where the thermal sprayed layer composed of only the mixed ZrO ₂ powder is formed.

[0036]

Example 1 In this example, after forming an undercoat and a top coat by a plasma spraying method, heating and cooling were repeated in an electric furnace, and the surface and cross section of the top coat were examined by an optical microscope and an image analyzer. The change of porosity was investigated by using. (1) Test Film Formation of Undercoat The alloy A shown in Table 1 was applied to a SUS 304 steel substrate (50 mm × 50 mm × 8 mm +) to a thickness of 300 μm by a plasma spraying method. Formation of Top Coat The following materials were formed to a thickness of 300 μm by plasma spraying. the a.8wt% Y ₂ O ₃ -92wt% of partially stabilized ZrO ₂ particles, 1 wt
%, 3 wt%, 5 wt% to which ZrO ₂ is added. b. 12 wt% CeO ₂ -88 wt% partially stabilized ZrO ₂ powder with pure ZrO ₂ powder added at a ratio of 3 wt%. _{c.8wt% Y 2 O 3 -5wt%} CaO-87wt% stabilized ZrO ₂ powder in pure
ZrO ₂ powder added at a ratio of 3% d. 8 wt% Y ₂ O ₃ -92 wt% ₂ wt% Y ₂ O ₃ is added to the partially stabilized ZrO ₂ powder
The -98Wt% unstabilized ZrO ₂ powder which was added at a physician proportion of 15 wt%. e. 8 wt% Y ₂ O ₃ -92 wt% partially stabilized ZrO ₂ powder and 1 wt% of pure ZrO ₂ powder and 12 wt% of 5% CeO ₂ -95 wt% unstabilized ZrO ₂ powder added. As a comparative example, f. Pure ZrO ₂ (containing no stabilizing component) g. 8 wt% Y ₂ O ₃ -92 wt% partially stabilized ZrO ₂ powder h. 8 wt% Y ₂ O ₃ -8 wt% CeO ₂ -84 wt Topcoats such as% stabilized ZrO ₂ powder were also investigated simultaneously. Heating Conditions The operation of heating at 1100 ° C. × 1 h in an electric furnace, cooling to 1000 ° C. in the furnace, and then raising the temperature to 1100 ° C. again was repeated 15 times.

Experimental results Table 2 shows the experimental results. As is clear from the results shown in this table, No. 8 of the comparative example is pure ZrO ₂ containing no stabilizing component, so that the sprayed coating is excessively porous, and the adhesion to the undercoat is weak. And it was in a situation where it easily peeled off when a mechanical shock was applied. For this reason, a part of the thermal spray coating was peeled off in one heating and cooling process. Also, 8YZ,
(No.9) In the example using only stabilized and partial ZrO ₂ like 8Y8CeZ (No.10), the sprayed coating has a moderate porosity (8-18%)
However, a sintering reaction was caused by heating, and the porosity gradually decreased. On the other hand, as in the thermal spray coatings (Nos. 1 to 7) conforming to the present invention, stabilized and partially stabilized Zr
In addition to O _2, in the example containing pure ZrO ₂ and unstabilized ZrO ₂ is pure ZrO ₂
Also, the presence of unstabilized ZrO ₂ maintained the porosity immediately after thermal spraying for a long time even after heating, indicating that an appropriate porosity could be secured over a long period of time.

Example 2 In this example, a sprayed coating conforming to the present invention and a sprayed coating of a comparative example were formed on the inner wall surface of a centrifugal casting mold made of cast iron.
Repeat the actual work each time, the soundness of the thermal spray coating,
The quality of castings was investigated. (1) Outline of the tested mold The tested mold is as shown in FIG. Among the reference numerals shown, the casting mold 1 includes a casting flask 2, a front lid 3, and a rear lid 4. An injection box 6 for injecting molten iron 5 is provided in a central opening of the front lid 3. I have. And the casting flask 2
Is in contact with a roller 7, the casting flask 2 is rotated by the driving force of the roller 7, and the molten metal is thereby pushed against the inner wall 8 of the mold to form a hollow casting. The mold used in this example is a heat-resistant steel cast steel product-JIS
G5122 (1980) It was formed using SCH12 and had an inner diameter of 300 mm and a length of 600 mm, and the following film was formed on the inner surface in contact with the molten iron. (2) Test Coating After undercoat spraying the C alloy shown in Table 1 to a thickness of 200 μm, the following top coat was applied to a thickness of 300 μm. a. Blend of pure ZrO ₂ powder at a ratio of 3 wt% to 8 wt% Y ₂ O ₃ -92 wt% partially stabilized ZrO ₂ powder. b. 2 wt% Y ₂ O ₃ -98 wt% unstabilized ZrO ₂ powder 3 wt%
Added. c. pure ZrO ₂ 1 wt% to supra and 4wt% Y ₂ O ₃ -96wt% unstabilized Zr
O ₂ powder 10 wt% and those added. For comparison, 8 wt% Y ₂ O ₃ -92 wt% partially stabilized ZrO ₂
A 300-μm-thick top coat formed from a thermal spray coating of powder only was used. The diatomaceous earth application method was also tested for reference.

(3) Investigation Items and Results The operation of pouring cast iron (equivalent to JIS G5501) into a container at a temperature of 1380 ° C. to 1420 ° C. to produce a product was continuously repeated 100 times.
Changes in the porosity of each sprayed coating, changes in the appearance of the coating,
The defect rate of the cast product, the soundness of the container body, etc. were investigated.
Table 3 shows the results. As is clear from the results shown in this table, in the 8YZ coating (No. 4) of the comparative example, although there was no particular abnormality in the sprayed coating itself, the porosity of the sprayed coating increased with the number of uses. As a result, the gas component release performance deteriorated, the air bubbles of the product increased, and the defective rate tended to increase. On the other hand, the thermal sprayed coatings (Nos. 1, 2, and 3) conforming to the present invention have a sound coating, do not decrease the porosity for a long time, and have a lower defect rate than the comparative example. Was. The application of diatomaceous earth (No. 5) of the comparative example required repeated application and the occurrence of thermal fatigue cracks in the container body was confirmed, and the coating method was the lowest in performance.

[0040]

[Table 3]

Example 3 In this example, after forming an undercoat to a thickness of 80 μm, a mixture of the undercoat alloy and the topcoat material of the present invention was used as the topcoat to be applied thereon, An experiment was conducted under the same conditions as in Example 2 using a single-phase sprayed coating having a concentration gradient such that the ZrO ₂ powder of the present invention increased on the surface side. (1) Test Coating After applying a heat-resistant alloy as an undercoat and the B and D alloys shown in Table 1 to the inner surface of the molten metal vessel, respectively, to a thickness of 80 μm, a mixed material as shown below was formed thereon to a thickness of 300 μm. The outermost layer having a thickness of 50 μm was a layer without any undercoat alloy. a. (B alloy _{80wt% / 8YZ · 3ZrO 2,} 20wt%) 100 μm (B alloy _{50wt% / 8YZ · 3ZrO 2,} 50wt%) 100 μm (B alloy _{30wt% / 8YZ · 3ZrO 2,} 70wt%) 100 μm _{(8YZ · 3ZrO 2, 100 wt} %) 50 μm b. (D alloy _{80wt% / 8YZ · 3ZrO 2,} 20wt%) 100 μm (D alloy _{50wt% / 8YZ · 3ZrO 2,} 50wt%) 100 μm (D alloy 30wt _{% / 8YZ · 3ZrO 2, 70wt} %) 100 μm (8YZ · 3ZrO 2, 100 wt%) 50 μm c. (B alloy _{80wt% / 8YZ · 3ZrO 2 +} 2YZ, 20wt%) 100 μ
m (B alloy 50wt% / 8YZ / 3ZrO ₂ + 2YZ, 50wt%) 100 μm (B alloy 30wt% / 8YZ / 3ZrO ₂ + 2YZ, 70wt%) 100 μm (8YZ / 3ZrO ₂ + 2YZ, 100wt%) 50 μm

Even when the molten iron of 100 charges is treated using the sprayed coating having the concentration gradient as described above, the sprayed coating maintains a healthy state and the defect rate is as low as that of the second embodiment. The value was shown.

Example 4 In this example, after forming a top coat using various ZrO ₂ having different contents of stabilizing components, a thermal shock test was performed to investigate durability under a high temperature environment. (1) Specimen coating Undercoat formation A alloy shown in Table 1 was SUS 30
4 300 μm thick steel base material (50mm × 100mm × 8mm +). Formation of Top Coat The following materials were formed to a thickness of 300 μm by plasma spraying. _{a.1wt% Y 2 O 3 -99wt%} ZrO 2 b.5wt% Y 2 O 3 -95wt% ZrO 2 c.1wt% Y 2 O 3 -2wt% CeO 2 -97wt% ZrO 2 d.6wt% Y 2 O ₃ -94 wt% ZrO ₂ e.10 wt% Y ₂ O ₃ -90 wt% ZrO ₂ f.12 wt% CeO ₂ -88 wt% ZrO ₂ g.24 wt% MgO -76 wt% ZrO ₂ h.28 wt% CaO -72 wt% ZrO using the characteristics of the ₂ unstabilized ZrO ₂ powder (stabilized component amount 1-5 wt%), which total amount of the components is used by mixing the 6～5Wt% of partially stabilized ZrO ₂ powder. (2) Thermal shock test conditions The test film was heated in an electric furnace at 1070 ° C x 0.5h, and then air-cooled to 600
The operation of cooling to ° C. was performed as one cycle, and 20 cycles were performed.

(3) Experimental Results The experimental results are summarized in Table 4. As is clear from these results, the sprayed coating of stabilized / partially stabilized ZrO ₂ in which the content of the stabilizing components Y ₂ O ₃ , CeO ₂ , MgO, CaO, etc. is 6 wt% to 28 wt% is increased. -High thermal shock resistance due to a change in crystal form accompanied by a heat cycle of cooling and a small volume change due to the change. Regarding this point, as described in Example 1, the coating sprayed with only the stabilized and partially stabilized ZrO ₂ has a porosity of the coating that gradually decreases due to the progress of the sintering reaction by heating, and As a coating of a container for molten metal as described above, there arises an inconvenience that the emission of gas components is hindered. That is, it was found that such a thermal spray coating was weak to thermal shock and could not be put to practical use.

[0045]

[Table 4]

[0046]

As described above, the molten metal container according to the present invention can be used for a long time in a high-temperature environment even if the pure metal contained in the thermal spray coating formed on the surface of the substrate is used.
Due to the presence of ZrO ₂ or unstabilized ZrO ₂ , the appropriate porosity is always maintained without the densification phenomenon due to the sintering reaction, and the diffusion of various gas components released from the molten steel is promoted. Therefore, it is possible to suppress the occurrence of the defective rate of the casting product due to the gas component. In addition, since the heat resistance function is comparable to that of the conventional film, it greatly contributes to improving the productivity of high quality products and reducing the production cost.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a casting mold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Casting frame 3 Front lid 4 Rear lid 5 Molten iron 6 Injection box 7 Roller 8 Mold inner wall

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C23C 4/12 C23C 4/12 4/18 4/18 28/00 28/00 B // B22D 11/10 310 B22D 11 / 10 310J F term (reference) 4E004 AB04 QA01 QB01 RA01 4K031 AA04 AA08 AB03 AB05 AB08 AB09 CB21 CB22 CB26 CB27 CB31 CB32 CB37 CB42 EA07 FA01 FA02 4K044 AA02 AA06 AB10 BA02 BA11 BA11 BB03 BB03 BB03

Claims (9)

[Claims] 1. A heat-resistant alloy according to a combination of two or more selected from Ni, Co, Cr, Al, Y and Ta as an undercoat on a surface of a substrate in contact with a molten metal of a container. Metal sprayed coating obtained by the above, the amount of stabilizing component is 6-30 as a top coat on it
wt.% of stabilized / partially stabilized ZrO ₂ as a main component, and 1-5 wt% of pure ZrO ₂ containing no stabilizing component and / or
Or an unstabilized ZrO ₂ in which the amount of the stabilizing component is less than 5 wt%
A molten metal container having a porous ceramic sprayed coating obtained by spraying a mixed ZrO2 powder obtained by adding ₂ to 20% by weight of ZrO2. 2. The undercoated dense metal sprayed coating has a thickness of 50 to 500 μm and a porosity of 5 wt% or less, and the top coated porous ceramic sprayed coating has a thickness of 200 to 10 μm.
2. The spray metal container according to claim 1, wherein the porosity is 5 to 25 wt% at 00 [mu] m. 3. A lower surface layer of the substrate, which is in contact with the molten metal of the container, mainly covers a combination of two or more selected from Ni, Co, Cr, Al, Y and Ta. It consists of a dense metal sprayed layer obtained by spraying a heat-resistant alloy. The upper layer on the surface side is mainly used, and the amount of the stabilizing component is 6 to 30 wt%.
The main component is stabilized / partially stabilized ZrO ₂
1-5 wt% of pure ZrO ₂ containing no stabilizing ingredients and / or amount of the stabilizing component is an unstabilized ZrO ₂ is less than 5 wt% 2
A porous ceramic sprayed layer obtained by spraying a mixed ZrO ₂ containing 〜20 wt%, and each of the above sprayed layers has a higher content of the heat-resistant alloy as it is closer to the base material side and is closer to one surface side A molten metal container characterized by being a single-layer sprayed coating having a concentration gradient with a higher ZrO ₂ content. 4. The porosity of the dense metal sprayed layer located on the base material side is 5% or less, and the porosity of the porous ceramic sprayed coating located on the surface side is 5 to 25% by weight. The container for molten metal as described in the above. 5. A heat-resistant alloy powder according to a combination of two or more selected from Ni, Co, Cr, Al, Y, and Ta is sprayed on a surface of a substrate in contact with a molten metal of a container. A dense metal spray coating is formed, and then a stabilized / partially stabilized ZrO ₂ having a stabilizing component amount of 6 to 30 wt% is formed on the coating, and a pure metal containing no stabilizing component is formed. ZrO ₂ to 1
By spraying a mixed ZrO ₂ powder obtained by adding ₂ to 20 wt% of unstabilized ZrO ₂ having 5 wt% and / or a stabilizing component amount of less than 5 wt%, a porous material having a porosity of 5 to 25% is obtained. A surface treatment method for a molten metal container, comprising forming a ceramic sprayed coating. 6. The undercoated dense metal sprayed coating has a thickness of 50 to 500 μm and a porosity of 5 wt% or less, and the top coated porous ceramic sprayed coating has a thickness of 200 to 10 μm.
The surface treatment method according to claim 1, wherein the porosity is 5 to 25 wt% at 00 µm. 7. A heat-resistant alloy powder according to a combination of two or more selected from Ni, Co, Cr, Al, Y, and Ta is first sprayed onto a surface of a substrate in contact with a molten metal of a container. Then, stabilized and partially stabilized ZrO ₂ having a stabilizing component amount of 6 to 30 wt% as a main component, and pure ZrO ₂ containing no stabilizing component in an amount of ₁ to 5 wt% and / or stabilizing. Thermal spraying of a mixed ZrO ₂ powder obtained by adding ₂ to 20 wt% of unstabilized ZrO ₂ having a component amount of less than 5 wt%, wherein the closer to the base material side, the higher the content of the heat-resistant alloy By spraying the sprayed material according to the gradient blending so that the ZrO ₂ content increases as it gets closer to the surface side, the base material side becomes a sprayed layer rich in dense metal and the surface side becomes porous ceramic A molten metal volume characterized by a thermal spray coating having a concentration gradient that makes the thermal spray layer rich. Surface treatment method. 8. The portion of the dense metal sprayed layer has a porosity of 5%, and the portion of the porous ceramic sprayed layer has a porosity of 5 to 5.
The surface treatment method according to claim 7, wherein the content is 25 wt%. 9. After spraying the mixed ZrO ₂ powder, the temperature is 1050 ° C. to 11 ° C.
The surface treatment method according to claim 5, wherein the temperature increase and the temperature decrease are repeated at least once in a temperature range of 00 ° C. 9.