JP2000233986A - Member for plating bath and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a durable member for a plating bath and the advantageous production method. SOLUTION: The substrate of this member for a plating bath is formed of a ceramic sintered or fused formed member free of through-pores, and a thermally sprayed film of an oxide ceramic is formed on the substrate surface. The member for the plating bath is produced by roughening the surface of the ceramic sintered or fused formed member and then plasma-spraying >=1 kind of oxide ceramic selected from Al2O3, TiO2, ZrO2, MgO, CaO, CeO2 and SiO2 on the surface of the substrate formed of the ceramic sintered or fused formed member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member for a plating bath and a method for producing the same, and in particular, to various members used in the fields of hot-dip galvanizing, hot-dip zinc-aluminum alloy plating, hot-dip aluminum plating, etc., such as rolls and bearings. It is a proposal for a member used in an environment that is in contact with hot-dip metal, such as a sleeve, a bush, and a metal fitting for adjusting a plating amount, and a surface treatment technology thereof. Further, the plating bath member according to the present invention is not limited to only the plating bath,
It is also useful as a member used in an environment that comes into contact with a molten metal such as a casting facility.

[0002]

2. Description of the Related Art Metal plating, particularly hot-dip galvanizing, hot-dip aluminum plating, hot-dip zinc-aluminum alloy plating, etc., provides excellent rust prevention and corrosion resistance.
It has been applied to members of automobiles, aircraft, vehicles, buildings, home appliances, and the like since ancient times, and is a useful surface treatment technology.

In general, hot-dip galvanized steel sheets are often manufactured by a continuous hot-dip galvanizing apparatus as shown in FIG. The hot dip galvanizing apparatus includes a sink roll 2 immersed in a plating bath 1, a support roll 3 disposed near the surface in the plating bath, and a steel plate 4 after plating.
In general, there are provided many so-called plating bath members such as a guide roll 5 for guiding the water or an injection nozzle 6 for blowing off excess zinc attached to the steel plate with nitrogen gas or water vapor.

As described above, the plating bath member is
It is immersed in a plating bath or installed in a place where molten zinc is easily scattered and adhered, and is used so as to come in contact with hot steel sheet to which molten zinc adheres. (1) Erosion by molten zinc occurs (2) It is hard to be worn even when it comes in contact with the passing material (steel plate), (3) It is easy to peel off the adhered molten zinc and maintenance is easy, and (4) The service life as a plating material is long and low. It is required to be cost-effective and (5) to withstand thermal shock when immersed in a high-temperature molten zinc bath.

In order to meet such demands, conventionally, a surface treatment film for a sink roll is taken as an example.
No. 108334, Japanese Unexamined Patent Publication No. 2-125833, etc., a coating of a Co-based self-fluxing alloy established by JIS H8303 (1976), (2) Japanese Patent Publication No. 3-54181 and Japanese Patent Publication No. 4-
As disclosed in No. 27290, etc., an oxide-based ceramic film composed of ZrO ₂ and Al ₂ O ₃ spray-coated, (3)
As disclosed in JP-A-4-13857 and JP-A-4-346640, non-oxide ceramics such as carbides, nitrides, and borides and a cermet spray coating made of Cr, Ni, Co and the like are used. Formed, (4) In addition, welded overlay of molten metal (JP-B-52-22934), W-sprayed (JP-A-53-128538), or Cr-sprayed (Japanese Unexamined Patent Publication No. 4-165058) and the like have been proposed.

[0006] The inventors of the present invention have conducted research and development of the same kind of technology as described above. That is,
(5) In a WC cermet proposed in Japanese Patent Application No. 63-49846 (Japanese Patent Application Laid-Open No. 1-257661), it contains 5-28% of Co,
The porosity of the film is 1.8% or less and the film thickness is 0.040 ~ 0.10mm
(6) A boride or a boride as proposed in Japanese Patent Application No. 63-192753 (JP-A-2-43352).
(7) Japanese Patent Application No. 1-54883 (Japanese Unexamined Patent Application Publication No.
No. 236266), using a material in which 5-40% of Ta and Nb are added to ZrB ₂ , TiB ₂ and various carbides, and using a low-pressure plasma spraying method, has a coating surface roughness Ra of 0.01 to 0.01.
5 μm, having a film with a porosity of 1.8% or less, (8)
On the cermet sprayed coating mainly composed of carbide, proposed in Japanese Utility Model Application No. 1-124010 (Japanese Utility Model Application No. 3-63565),
Film formed of Cr ₃ O ₃ by chemical densification method, (9) was proposed in Japanese Patent Application No. Hei 2-201187 (JP-A-4-88159), boride by boride handle some carbide thermally sprayed coating (10) Heat diffusion of Al or Al-Zn alloy to various carbides, borides or cermet sprayed coatings thereof proposed in Japanese Patent Application No. 3-31448 (Japanese Patent Application Laid-Open No. 4-254571). (11) Japanese Patent Application No. 3-31448 (JP-A-4-254571)
(1) Non-oxide ceramic sprayed coating made by diffusing and penetrating Al or Al-Zn; (12) Non-oxide ceramic proposed by Japanese Patent Application No. 3-222425 (Japanese Patent Application Laid-Open No. 4-358055) Thermal spray coating formed by using a thermal spray material obtained by adding Al or an Al-Zn alloy to a base ceramic powder or a powder obtained by mixing a metal with the ceramic powder;
No. 143 (JP-A-5-33113), a thermal spray material obtained by adding an Al-Fe alloy or an Al-Fe-Zn alloy to a non-oxide ceramic powder or a powder obtained by mixing a metal with the non-oxide ceramic powder. Sprayed film formed by using (14)
-266874 (JP-A-5-78801).
Various technologies and films have been proposed, such as a steel roll having an Al-Fe alloy layer having an Al content of 22% or more formed on the surface thereof.

[0007]

As can be seen from the above description, the research issues concerning the thermal spray coating formed on the conventional hot-dip galvanizing bath members are to select a hot-dip galvanizing coating material, to improve the adhesion of the coating, The main characteristics were improvements in the characteristics of the film itself, such as improvement in the denseness of the film and control of the surface roughness of the film, and each had an effect of improvement. However, with regard to hot-dip galvanized steel sheets, the demand for improving the operation rate of the plating plant and improving the quality of the hot-dip galvanized steel sheet has become extremely strong with the recent increase in demand. Fine dross component
(Zn-Fe, Zn-Fe-Al alloy) on the thermal spray coating surface,
As a result, it has become a situation that the adhered dross dislikes even the generation of a microscopic scratch on the steel sheet. Furthermore, in order to further reduce the production cost, a longer life of the sprayed coating has been strongly required.

Accordingly, the object of the present invention is not only to sufficiently satisfy the above-mentioned requirements as a member for a plating bath,
An object of the present invention is to propose a plating bath member having a longer life and an advantageous method for producing the same.

[0009]

The present invention has been developed based on the following concept. (1) As a base material to be sprayed, at least the surface portion thereof is a porous ceramic sintered molded member or a melt molded member without through-pores, and the surface of such a member to be a base material is used. Then, a thermal spray coating of an oxide ceramic was formed. By such a combination of the base material and the thermal spray coating, even if the hot-dip plating metal enters the pores of the thermal spray coating, the base material is not a steel material as in the related art, and the metal base reaction with the base material causes The phenomenon of melting and dross adhesion is eliminated.

(2) The ceramic sintered molded member or the ceramic melt molded member as the base material has a porosity of 5 to 2
In order to adjust the range to 0% and to eliminate through-holes in particular, as a basic component of ceramic molded parts, vitreous under high temperatures such as SiO ₂ , B ₂ O ₃ and P ₂ O ₅ A member containing an oxide powder composed of a component exhibiting a state is used. A member without such through pores, that is, a member consisting only of so-called closed pores, even if the molten metal comes into contact with the closed pores, is filled with gas in the pores, so that the molten metal (plated metal) (Molten metal)
There is no intrusion. In addition, since oxides generally have a small coefficient of thermal expansion, they are not damaged by thermal shock even when immersed in a high-temperature plating metal bath. Furthermore, since these members and the thermal spray coating are composed of oxide ceramics, their thermal expansion coefficients are close to each other, and the shear stress generated at the interface even when subjected to sudden temperature changes is small. Is completely eliminated. In the case of a roll, for example, in the case of a roll, a steel core material is provided at the center of the roll, and the ceramic tubular sintered or melt-formed member is fitted to the outside thereof by cold fitting or the like. Alternatively, it may be formed by casting.

(3) After forming the oxide ceramic sprayed coating on the surface of the base material, the pores of the sprayed coating are filled with a fine powder of oxide, boride or nitride or a solution (colloid) thereof. When the member is immersed in a plating bath, only the hot-dip metal penetrates into the film, and the dross component adheres. Can be prevented.

(4) In order to form a sprayed coating of homogeneous, that is, oxide ceramic on the surface of a porous oxide ceramic sintered or melt molded member having no through pores, the surface of the base material must be dried. It is important to have an appropriate surface roughness. Therefore, in the present invention, when using a coolant (water) when machining the molded member,
It is preferable to adopt a method of forming a thermal sprayed coating having good adhesion by heating to 100 ° C. or higher to remove water and then roughening the surface to a range of Ra 2 to 10 μm by blasting. Then, if necessary, the drying process may be performed after the blasting process. The surface of the molded member according to the present invention does not change.
It is no longer necessary to perform thermal spraying immediately after blasting as in the case of steel substrates.

The present invention completed under such an idea,
The plating bath member is characterized in that the substrate is formed of a porous oxide-based ceramic molded member having no through pores, and an oxide-based ceramic sprayed film is formed on the surface of the substrate.

In the above-mentioned plating bath member, the ceramic sintered or melt-molded member is made of at least SiO ₂ ,
Al ₂ O ₃ , Y containing at least one glass-forming oxide selected from B ₂ O ₃ and P ₂ O _5
It contains at least one oxide selected from the group consisting of ₂ O ₃ , Cr ₂ O ₃ , MgO, ZrO ₂ , TiO _2, etc., and has pores having a cross-sectional diameter of 1 to 100 μm. It is preferable that the pores are present as closed pores having an independent relationship within a range of 5 to 20% in terms of the sintered body porosity, and the oxide ceramic sprayed film is made of Al ₂ O ₃ , TiO ₂ , ZrO. ₂ , Mg
O, CaO, Y ₂ O ₃ , CeO ₂ and SiO _{2, made} of at least one oxide selected from the group consisting of oxides having a thickness of 50 to 800 μm.
Further, the oxide ceramic sprayed coating preferably has pores sealed with at least one fine powder selected from metal oxides, metal borides and metal nitrides. Is preferred.

Further, the present invention includes at least one glass-forming oxide selected from SiO ₂ , B ₂ O ₃ and P ₂ O ₅ , and also includes Al ₂ O ₃ , Y ₂ O ₃ , Cr ₂ O ₃ , MgO, Zr
Oxide ceramics without through pores by mixing and molding raw material powders containing at least one oxide selected from O ₂ , TiO _2, etc., and then firing or melting at a temperature of 1100 ° C or higher After forming a sintered molded member or a ceramic melt molded member, grinding the surface of these ceramic molded members, drying by heating to a temperature of 100 ° C. or more, then roughening the surface by blasting or grinding, After that, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , M
The present invention proposes a method for producing a plating bath member, which comprises plasma spraying at least one oxide ceramic selected from gO, CaO, CeO ₂ and SiO ₂ .

In the present invention, the thickness of the oxide ceramic is preferably 50 to 800 in the plasma spraying.
μm, it is preferable to adjust the surface of the obtained oxide ceramic sprayed coating to a roughness of Ra 2 to 10 μm, and the surface of the oxide ceramic sprayed coating and the pores in the coating. It is a preferable method to apply an aqueous solution or slurry of at least one selected from oxides, borides, and nitrides to the inside of the part and perform a sealing treatment.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted various experimental studies on the behavior of a sprayed coating formed on the surface of a sink roll immersed in a hot-dip metal bath and found the following facts. I do. (1) When the thermal spray coating is made of a metal or an alloy, its life is determined by the effect of a reaction product with the molten metal in addition to the metallurgical reaction between the coating and the hot-dip metal. For example, in the case of a self-fluxing alloy film formed as a film for a sink roll, although it reacts with a molten metal, its speed is slow, so that the required performance was initially exhibited. However, this film has a drawback that a reaction product (alloy) with the hot-dip plating metal damages the plated film.

(2) When the thermal spray coating is a carbide cermet coating, the cermet components such as Co, Cr and Ni-Cr react with the molten metal to cause dross adhesion. Also,
This type of thermal sprayed coating is hard and lacks ductility, and has a drawback that when it is immersed in molten metal from room temperature at once, it is locally peeled off by thermal shock. Furthermore, since a thin metal layer generally adheres to the surface of the used member together with dross, when this is dissolved and removed with an acid, the metal component in the film is selectively dissolved and the film itself is destroyed. is there.

(3) When the thermal spray coating is an oxide such as Al ₂ O ₃ or ZrO ₂ , it does not undergo metallurgical reaction with the molten metal, but the coating itself is porous (porosity: 5 to 15%). Molten metal easily penetrates inside, causing metallurgical reaction with base metal,
A phenomenon was observed in which the sprayed coating was destroyed from the bottom. Therefore, it is difficult to form a dense oxide-based thermal spray coating directly on the surface of a steel roll with the current technology, and it has not been put to practical use.

The problem with the prior art is that all research and development of conventional thermal spray coatings is based on the premise that a steel base material is used. However, even if such a film can be formed, the molten metal penetrates into the inside through the open pores of the film to erode the roll base material, so that it cannot be put to practical use. Turned out to be something.

Therefore, according to the present invention, the substrate (roll) is not made of steel, and at least the surface portion thereof is formed of an oxide-based ceramic sintered or melt-molded body to form a roll. It is proposed to directly spray-coat the surface with an oxide ceramic. In this way, even if the hot-dip plating metal enters the pores of the thermal spray coating, the base material is also made of ceramics and does not react, and the oxide ceramic coating remains healthy for a long period of time. State can be maintained. Further, since the oxide ceramic sprayed coating does not react with the dross component as well as the molten metal, the conventional problem caused by the dross does not occur. Further, it is not necessary to apply a cermet, undercoat or the like to coat the oxide base ceramic as a top coat on the surface of the steel substrate.

In the present invention, the roll
(At least the outer peripheral surface) is made of an oxide-based ceramic sintered or melt-molded body, and the following oxides are used from the viewpoint of eliminating open pores. That is, as essential components, SiO ₂ , B ₂ O ₃ and P ₂ O ₅
And at least one glass-forming oxide selected from the group consisting of Al ₂ O ₃ , Y ₂ O
_{3, Cr 2 O 3, MgO} , using a mixed powder of any one or more oxides selected from among such ZrO _2, TiO _2. Then, the mixed powder is formed into a predetermined shape (roll or the like), and the formed body is fired at a temperature of 1100 ° C. or higher to obtain a roll-shaped sintered compact. When the above-mentioned oxide formed body is fired or melted, any of the glass-forming components SiO ₂ , B ₂ O ₃ or P ₂ O ₅ becomes a glassy substance and becomes oxide particles. Fill the grain boundaries of
Improve the bonding force between particles. In addition, since the through-holes disappear in the molded article due to the presence of the glassy substance, the molten metal does not enter the inside of the base material, and the pores remaining in the molded article become independent.
All the pores are closed pores having a diameter of about 5 to 80 μm and are dispersed and scattered throughout, and the porosity is about 5 to 20%. For this reason, these substrates are ceramics,
Even if it receives a strong thermal shock, it does not break and has the mechanical strength necessary for a member for a hot-dip metal plating bath. Furthermore, since the material of the ceramic sprayed coating directly applied to the surface of the oxide ceramic sintered or melt-formed member is also the same oxide ceramic, the generation of shear stress due to the coefficient of thermal expansion is extremely small for both. Therefore, the risk of peeling due to thermal shock is extremely reduced.

Next, the manufacturing method of the present invention will be described. First, the above-mentioned ceramic sintered or melt-molded member as a base material is prepared, and the oxide ceramic is directly spray-coated on the surface of the oxide ceramic sintered or melt-molded member. In this thermal spraying, the following steps are employed. That is, at the time of thermal spraying of the oxide ceramic powder, the surface of the base material, which is the ceramic sintered or melt molded member, is smoothed by mechanical grinding, and then roughened by blasting using Al ₂ O ₃ particles. By carrying out, the surface roughness Ra: 2
Adjust to 10 μm. After that, the above-mentioned oxide ceramics by air plasma spraying method, 80 ~ directly on the substrate
Work to a thickness of 800 μm. However, since the base material is a porous oxide-based ceramic sintered or melt-molded member, if water or a water-soluble coolant is used when the surface is mechanically ground, these will remain in the pores of the base material. Therefore, it is preferable to remove water by heating to a temperature of about 100 ° C. or more prior to the blasting. Then, even after the blasting treatment, moisture may condense in the pores if placed in a highly humid environment. Therefore, it is desirable to dry the film at 100 ° C. or more as necessary.

If the oxide ceramic sintered or the surface roughening treatment of the melt-molded member becomes smoother than Ra: 2 μm, the adhesion of the thermal spray coating formed thereon becomes poor,
On the other hand, if the surface becomes rougher than Ra: 10 μm, “dent”
There is a disadvantage that irregularities or "undulations" are generated irregularly or large "dents" are locally generated.

The thermal sprayed coating of an oxide ceramic formed by the method described above generally has a thickness of 5 to 20 mm.
%, So that when immersed in a plating bath, the molten metal penetrates through the pores of the coating,
Since there is no reactive metal component, the sprayed coating can maintain a healthy state for a long period of time. Moreover,
The plating bath member according to the present invention, even if it is stored in the air for a long time, environmental components (for example, humidity,
It does not suffer from the corrosive action of acidic gases such as SO _{x and} NO _x ). However, moisture condenses on the surface of the oxide ceramic sprayed coating on the surface or the pores present in the sintered molded member, and when this is immersed in a high-temperature molten metal bath, it may become steam at once and destroy the coating. There is. In such a case, if the pores of the coating are filled with a sealant after the formation of the thermal spray coating, the above problem can be avoided. At the same time, even if these sealing agent components are immersed in the plating bath as they are, there is no operational problem.

The following method is suitable as a method for sealing such a thermal spray coating. (1) Apply an aqueous solution of chromic anhydride (CrO ₃ ), ammonium chromate (NH ₄ ) ₂ CrO ₄ , ammonium dichromate (NH ₄ ) ₂ Cr ₂ O _{7 to} the surface of the coating, and then 350 ° C. to 550 ° C. Heat and bake to ° C. Then, a method of repeating immersion in the above aqueous solution and heating and firing a plurality of times. (2) SiO ₂ , Al ₂ O ₃ , Cr ₂ O ₃ , MgO, Zr
Fine powder of O _2, Y ₂ O _3, oxides such as TiO ₂ or TiB _2,,
Fine powder of boride such as ZrB ₂ , HfB ₂ , VB ₂ , TaB ₂ , NbB ₂ , NiB ₂ , W ₂ B ₅ , CrB ₂ , or TiN, ZrN, VN, TaN, Al
A method of heating and firing using at least one of each of fine powders of nitrides such as N, BN, NbN, and Si ₃ N ₄ . (3) As a method other than the above, SiO ₂ , ZrO ₂ , TiO ₂ , Al
A method may be used in which a sol-gel sealant containing one or more oxides such as ₂ O ₃ and Y ₂ O ₃ is directly applied to a substrate and then dried.

[0027]

Example 1 In this example, Al ₂ O ₃ , MgO powder was heated and fired at a temperature of 1200 to 1250 ° C. to produce a substrate, and SiO ₂ , B ₂ O ₃ and P ₂ O _{5 were used.} 5 wt.
%, And the presence or absence of through-pores was compared with that of a sintered member without a vitreous forming material. The test sintering molded member is a flat plate having a width of 50 mm, a length of 50 mm and a thickness of 4 mm, and after standing horizontally, applies 5 cm ^{3 of a} blue ink liquid from the upper surface and appears on the rear surface. The presence or absence of blue spots was visually observed. As a result, Al with no glassy material added
_The 2O ₃ and MgO sintered plates penetrated the plate thickness within 1 hour after the blue ink solution was dropped, and blue color was observed on the back surface. However, in the sintered molded plate to which SiO ₂ , B ₂ O ₃ , and P ₂ O ₅ were added, no penetration of the blue ink liquid was observed even after 24 hours.

Embodiment 2 In this embodiment, a ceramic molded member having a diameter of 30 was used.
98 wt% SiO ₂ material with a length of 300 mm and 98.5 wt% ZrSiO ₂
The surface was finished to a roughness of 10 to 25 μm by machining using a round rod-shaped sintered specimen of the material. Then, Al ₂ O ₃ or 8 wt% Y ₂ O ₃ -92 wt% ZrO ₂ was applied to the surface thereof to a thickness of 300 μm by the atmospheric plasma spraying method. In addition, in the film formation process, water was used as a coolant during the surface grinding of the base material, so conditions for the presence or absence of preheating drying were added prior to the blasting treatment, and the adhesion of the sprayed coating, especially the application to the hot-dip galvanizing bath, was added. In consideration of this, the durability of the coating was investigated by repeating the operations of inserting into an electric furnace kept at 500 ° C. directly from normal temperature and taking out to room temperature. Table 1 shows the results. As is clear from these results, it has been found that the adhesion of the thermal spray coating by thermal shock is strongly affected by the preheating of the substrate. That is, the coolant at the time of mechanical grinding is introduced into the pores existing on the surface of the molded member.
When (water) remained, it was found that the film was peeled off due to vaporization and diffusion during the thermal shock test. Therefore, the substrate must be preheated to a temperature of at least 100 ° C, preferably at least 150 ° C.

[0029]

[Table 1]

Example 3 In this example, a SiO ₂ sintered substrate (diameter 15 mm, length 200 m) was used.
m) was preheated at 150 ° C. in the same manner as in Example 1 to obtain Al ₂
After blasting treatment with O _3, Al ₂ O ₃ by atmospheric plasma spraying _{method, Al 2 O 3 -15wt% TiO} 2, ZrSiO 2, 8 wt% Y 2 O 3 · Zr
The O _2, 10 wt% oxide ceramics such as CeO · ZrO ₂ 25
A film having a thickness of 0 μm was formed, immersed continuously in a 0.12 wt% Al-Zn bath (470 ° C.) for one week, pulled up, and the appearance thereof was observed. For comparison, a steel substrate (diameter 15
(mm, length: 200 mm) was sprayed under the same conditions with a 0.5 mm thick self-fluxing alloy or a 180 µm WC-12wt% Co coating. Table 2 shows the results. In the coatings of Comparative Examples (Nos. 6 and 7), an alloy product with molten zinc was formed on the surface, and zinc was firmly adhered to the coating. Erosion and WC-12wt% Co
(No. 7) Like the film, no erosion by zinc was observed, but the dross component was scattered along with the zinc thin film on the surface. In contrast, the film of the present invention (No. 1)
No. 5 to 5) did not show any adhesion of molten zinc at all, and showed a state before immersion, indicating that molten zinc exhibited almost complete durability.

[0031]

[Table 2]

Example 4 In this example, an SiO ₂ melt-molded member in a molten zinc bath of an actual machine: 8 wt.% On a roll (300 mm in diameter, 1900 mm in length)
A% Y ₂ O ₃ .ZrO ₂ film was applied to a thickness of 250 μm and used as a support roll (475 ° C., 0.11 wt% Al). as a result,
In the WC-12wt% Co thermal spray coating roll according to the prior art, dross components adhered to the surface, and as a result, adhesion of foreign matter as a quality defect was often observed on the surface of the plated steel sheet. No abnormalities were observed in the rolls formed with. In addition, WC-12wt% Co spraying roll removes zinc and dross components adhering to its surface with diluted hydrochloric acid.
(15wt% HCl) and phosphoric acid (30wt% H ₃ PO ₄ ).
Since the metal component (Co) in a healthy film also corrodes, there is a disadvantage that the film life is shortened even by these treatments. Since the coating of the present invention does not change at all even with these acids, the prospect of long-term use was obtained.

Example 5 In this example, the coating of the present invention used in Example 4 (8 wt.
% Y ₂ O ₃ .92 wt% ZrO ₂ ), and then sealed with a sealing agent as shown below. (1) After applying a concentrated aqueous solution of CrO ₃ (48 wt%),
(2) A mixture obtained by adding 5 wt% of NB fine powder to the CrO ₃ aqueous solution of (1) and calcining by the same operation as (1). (3) SiO ₂ · ZrO After applying the sol-gel containing ₂ as the main component,
These roles such that dried ° C. × 2 hours, water adsorption also be left in the room is not observed, also, 5 to 10 wt% HCl, the stable state even 20wt% H ₃ PO ₄ aqueous solution Indicated. Further, even when used as a support roll in a hot-dip zinc bath, a phenomenon that would cause a problem in the quality of the plated steel sheet did not occur, and the steel sheet could be used for a long time.

[0034]

As described above, according to the present invention, a sintered or melt-formed member of an oxide ceramic is used as a base material instead of a conventional steel base material. Is a glass forming component as a constituent of
By including any of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ to make the member without through pores, by directly applying a plasma spray coating of oxide ceramics on it, Both the base material and the thermal spray coating can be a member having excellent molten metal resistance that does not react with the molten metal. Further, members such as sink rolls and support rolls for a hot-dip galvanizing bath obtained by applying the method of the present invention do not react with hot-dip zinc and have excellent thermal shock resistance, so that the surface of the sprayed coating is A healthy state can be maintained for a long period of time, and the adhesion of dross components can be prevented. For this reason, the manufactured hot-dip galvanized steel sheet has high quality, and this state can be maintained for a long time, so that a high-quality galvanized steel sheet can be efficiently produced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a typical plating bath for continuously producing hot-dip galvanized steel sheets.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plating bath 2 Sink roll 3 Support roll 4 Plated steel plate 5 Guide roll 6 Injection nozzle

Claims (7)

[Claims] 1. A member for a plating bath, wherein the substrate is formed of a ceramic molded member, and a sprayed oxide ceramic film is formed on the surface of the substrate. 2. The ceramic molded member is at least one selected from SiO ₂ , B ₂ O ₃ and P ₂ O _5.
It includes seeds or more glass forming oxides as an essential component, Al ₂
A sintered or melt-formed member containing, as an additional component, at least one oxide selected from O ₃ , Y ₂ O ₃ , Cr ₂ O ₃ , MgO, ZrO ₂ , TiO _2, etc. Is 1 to 100
2. The member for a plating bath according to claim 1, wherein pores having a size of [mu] m are present as closed pores having an independent relationship within a range of 5 to 20% in porosity of the sintered body. 3. The sprayed oxide ceramic film,
Al ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, CaO, Y ₂ O ₃ , CeO ₂ and Si
O made from any one or more oxides selected from among _2, claim 1 or 2 plating bath member according thickness, characterized in that in the range of 50 to 800 [mu] m. 4. The sprayed oxide ceramic coating,
4. The plating bath member according to claim 1, wherein the pores are sealed with at least one kind of fine powder selected from metal oxides, metal borides and metal nitrides. 5. It contains at least one glass-forming oxide selected from among SiO ₂ , B ₂ O ₃ and P ₂ O ₅ ,
After mixing and molding a raw material powder containing at least one oxide selected from Al ₂ O ₃ , Y ₂ O ₃ , Cr ₂ O ₃ , MgO, ZrO ₂ , TiO _{2 and the} like, a temperature of 1100 ° C. or more By sintering or melting in, a ceramic sintered molded member or a ceramic melt molded member without through pores is formed, and the surface of these molded members is roughened. , Al ₂ O ₃ , TiO ₂ , ZrO ₂ ,
A method for manufacturing a member for a plating bath, comprising coating at least one oxide ceramic selected from MgO, CaO, CeO ₂ and SiO ₂ by plasma spraying. 6. The plasma spraying of the oxide-based ceramic is performed so that the film thickness is 50 to 800 μm, and the surface of the obtained oxide-based ceramic sprayed film is Ra
The roughness is adjusted to 2 to 10 µm.
Production method described in 1. 7. An oxide or boride or nitride aqueous solution or slurry of at least one selected from oxides, borides and nitrides is applied to the surface of the oxide ceramic sprayed coating and the pores in the coating and sealed. The method according to claim 5, wherein a hole treatment is performed.