JP2002004016A - Member for hot-dip metal bath and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member for hot-dip metal bath in which a coating film is thin and which has excellent durability, wear resistance, resistance to the hot-dip metal and restrait of sticking an intermetallic compound in the bath, and its production method. SOLUTION: In the apparatus for using the hot-dip metal coating treatment, a composite coated layer applying a sealing treatment with Cr oxide on a composite ceramics composed of SiO2-Cr2O3-Al2O3, is formed on the surrounding surface of this base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various equipment members used in a bath in a hot-dip metal plating process and a method for producing the same.

[0002]

2. Description of the Related Art In a hot-dip metal-plated steel sheet manufacturing facility,
One of the major facilities that determine the quality of plated steel sheets is a hot-dip metal plating bath. Various devices are immersed in the plating bath. The in-bath equipment provided in such a steel strip immersion type hot-dip metal plating apparatus includes various rolls for guiding and running the steel strip. For example,
As shown in FIG. 1, a typical example of the hot-dip metal plating apparatus is as follows.
A sink roll 3, a support roll 4, and a stabilizer roll 5 are arranged, and a touch roll 6 is arranged above the plating bath 1. In addition, there is a snout 7 as an in-bath apparatus, and a wiping nozzle 8 is arranged on the plating bath 1.

[0003] These equipments need various performances. Among them, rolls such as sink rolls and support rolls that directly contact the steel strip in the bath and convey them have the following various characteristics. Required. That is, the secular change of the dimensional accuracy is sufficiently small, in particular, the straightness of the bus is excellent, and it is not eroded by the molten metal because of direct contact with the molten metal plating bath. Has low reactivity,
Fe-Zn or Fe-Al-Zn generated in plating bath
The intermetallic compound is hardly fixed to the roll surface and hardly grows, and the shape accuracy of the surface can be maintained.

A roll of this kind is coated on its peripheral surface with a Co-based alloy film, an oxide ceramic film, a carbide cermet film or the like by various methods such as a thermal spraying method. The material of the coating layer is properly used depending on the type of the plated steel sheet and the quality requirement.

The film thickness of the roll is about 1 to 2 mm for a Co-based alloy film and 0.3 mm for an oxide ceramic film.
About 0.8 mm and 0.0% for carbide cermet film
Those having a size of about 4 to 0.2 mm are practically used.

For example, regarding a carbide cermet film,
Japanese Patent Publication No. 58-7386 discloses a coating having a thickness of 0.1 to 2.4 mm, comprising one or more of WC, CrC and TiC, and the balance consisting of a hot corrosion resistant metal or an oxide thereof. Rolls are disclosed. In addition, a carbide cermet thin film is disclosed in Japanese Patent No. 1771297.
In the publication, WC-Co has a porosity of 1.8% and a thickness of 0.04
Rolls with a thermal spray coating of 0 to 0.10 mm have been proposed. Further, with respect to oxide ceramics, Japanese Patent No. 2955625 discloses that carbide is contained in an amount of 0.08 to 0.1.
It is disclosed that after coating with a thickness of 0 mm, an oxide ceramic containing SiO ₂ or the like is coated with a thickness of 0.25 to 0.30 mm.

[0007] These roll coating layers basically protect the roll base material by reducing the reaction with the plating bath components on the roll surface, that is, so-called alloying, and also suppress the adhesion and growth of the plating bath components. However, in some cases, the protective layer alone cannot provide a sufficient protective function.

[0008] That is, all of these films have a suitable performance as a protective layer of a roll base material, but the above-mentioned surface characteristics required for this kind of roll must be overcome. Is leaving. For example, the appearance of the surface of a plated steel sheet as a major quality factor is becoming increasingly more demanding, so that the surface properties required for the roll base material that is in direct contact with the plated steel sheet inevitably, especially for the above-mentioned properties The requirements are becoming more and more strict.

In order to reduce the substantial contact area between the roll surface and the plated steel sheet, it has been proposed to form minute grooves on the roll surface, and its effect has been recognized. When a film is formed on the surface, there is a problem that the groove shape accuracy is reduced.

That is, as described above, the coating of the roll generally has a thickness exceeding 0.1 mm except for the application of the carbide cermet alone, and it is difficult to maintain the fine shape of the roll surface, Due to the coating of the film, it was difficult to faithfully reproduce the fine grooves previously provided on the roll substrate.

A film thinner than 0.1 mm can be formed by aqueous electroplating, chemical plating or vapor phase growth. It is extremely difficult to apply the above method by industrial means.

In addition, WC-12Co carbide cermet is partly put to practical use as a thin film that does not impair the shape of the fine grooves on the surface of the roll base material. However, this technology does not
Even if there is no problem with a zinc plating bath having a concentration of, for example, less than 3%, for a 55% Al-Zn alloy plating bath or the like, the metal or double carbide component in the WC-12Co component reacts with Al in the bath. As a result, an alloy layer may be formed on the roll surface, so that the applicable range has been limited.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and is a thin film having durability, abrasion resistance, resistance to molten metal and metal in a bath. It is an object of the present invention to propose a member for a hot-dip metal plating bath having a film having an excellent intermetallic compound adhesion suppressing property and an advantageous production method thereof.

[0014]

The gist of the present invention developed to realize the above object is as follows. A bath member used for a hot-dip metal plating treatment, wherein a composite ceramic layer composed of SiO ₂ —Cr ₂ O ₃ —Al ₂ O ₃ and a chromium oxide impregnated layer formed on a surface portion thereof are formed on the surface of the base material A member for a hot-dip metal plating bath, comprising a composite film comprising:

In the present invention, SiO ₂ —Cr ₂ O ₃ —
The Al ₂ O ₃ composite ceramics layer is SiO ₂ : 60 to 8
_{0mass%, Cr 2 O 3:} 20~30mass% and Al ₂
O ₃ : It is preferable that the composition becomes 1 to 10 mass%. In the present invention, the thickness of the composite coating is preferably 30 to 70 μm. In the present invention, the member used for the hot-dip metal plating treatment is a roll, and the surface of the roll base material has a depth of 0.03 to 0.3 mm and a width of 0.05 mm.
As described above, it is preferable to use grooves provided with a groove extending in the roll circumferential direction at a pitch of 1.0 mm or more in the roll axis direction.

The present invention also relates to a method for manufacturing a bath member used for hot-dip metal plating, wherein the surface of the base material of the member is coated with Si.
A chromium oxide impregnated layer is formed by coating a composite ceramic made of O ₂ —Cr ₂ O ₃ —Al ₂ O ₃ , then impregnating the composite ceramic layer with a chromic acid-containing aqueous solution and then firing. A method for producing a member for a hot-dip metal plating bath characterized by the above is proposed.

In the method of the present invention, the composite on the surface of the substrate
In forming the coating layer, SiO 2 ₂−Cr₂O₃-A
l₂O₃Combined oxide powder with plasma flame or gas combustion flame
It is preferable to carry out thermal spraying using. In addition, the method of the present invention
Then, on the surface of the substrate, SiO₂−Cr₂O₃-Al₂
O ₃By applying, spraying or dipping the slurry containing
After application, it is preferable to bake. Further, the present invention
In the method, after forming a fine groove on the surface of the substrate,
Use fine powder with an average particle diameter of 15 μm or less in median diameter
The oxide having an arithmetic average roughness of 2.0 μm or less
What coated the surface of the substrate with a film
preferable.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a hot-dip metal plating bath,
It is preferable that the steel strip and a member having a function of guiding and running the steel strip, for example, the surface of the roll, are in contact with each other through a molten bath component without being in direct contact with the steel strip. For this reason, it has been proposed to form various grooves on the roll surface in order to reduce the true contact area between the roll surface and the steel strip, and some of them have been put to practical use. However, as the roll surface passes through the steel plate, it contacts the molten metal at a high relative speed and is quickly melted down, causing micro-grooves on the roll surface to change shape and increasing the contact area between the steel plate and the roll. Is as described above.

Then, the present inventors coated the surface of the roll substrate on which the microgrooves were formed with a film having a thickness of several tens of μm made of a stable material in a plating bath, so that the roll surface shape was maintained. In order to obtain this film, on the premise that this film is formed by thermal spraying, SiO ₂ is used for the denseness of the film, Cr ₂ O ₃ is used for the abrasion resistance, and Al ₂ O ₃ is used for the heat resistance. We focused our attention on _2- Cr ₂ O ₃ -A1 ₂ O ₃ -based ceramic coatings and studied the composition of the components. That is, based on the basic composition of SiO ₂ -A 1 ₂ O ₃ , the mixing ratio and the amount of Cr ₂ O ₃ added thereto are determined by the reactivity with the plating bath and the peeling resistance of the coating against the heat history from room temperature to the bath temperature. Determined based on gender. As a _{result, SiO 2: 60~80mass%, Cr} 2 O 3: 20
It has been found that Ａ30 mass% and A ₁₂ O ₃ : 1 to 10 mass% are suitable compositions.

Next, in a 55% Al—Zn alloy plating bath,
In order to investigate the erosion resistance of the coating of
Specimen with a kind of film is used in a plating bath
Dynamic attached to the side edge of the sink roll and rotated in the bath
An immersion test was performed. Table 1 shows the test results. What
In addition, the test piece is SU of diameter 30mm and length 100mm.
S316L material, the film is A1₂O₃, Cr₂O₃You
And A1₂O₃-TiO₂Ceramics, WC-1
2Co carbide cermet and SiO of the present invention ₂−Cr
₂O₃-A1₂O₃It is a member having a composite coating layer.

[0021]

[Table 1]

As shown in Table 1, A1 ₂ O ₃ , Cr ₂ O
_In each of the ceramics No. ₃ and A1 ₂ O ₃ —TiO ₂ , peeling of the film occurred partially, and at the peeled portion, steel as a roll base material was eroded by a plating bath component to form an alloy layer. . The remaining portion of the film did not corrode, and no alloying with the components of the plating bath was observed. Although these ceramics basically have low reactivity with bath components, as a result of thermal stress generated due to the difference in thermal expansion characteristics from the roll base due to the coating thickness, partial roll base It is considered that the peeling of the film could not be suppressed.

Further, in the WC-12Co carbide cermet, formation of a thin alloy layer which was considered to be a reaction with bath components was observed on the entire surface of the coating. That is, although there is no film peeling,
It can be seen that alloying occurs depending on the bath components.

In this regard, the SiO ₂ —Cr _{2 according} to the present invention
O ₃ -A1 ₂ O ₃ composite ceramic coating member is not part peeling of the film, the tendency of alloying with only bath metal components deposited on the surface was observed. It was found that the thin film exhibited sufficient adhesion to a substrate for practical use, and also exhibited erosion resistance to molten metal.

From the above experimental results, the surface of the roll substrate
As the film to be formed, SiO₂−Cr₂O₃-A1₂
O₃Consisting especially of SiO₂: 60-80 mass%,
Cr ₂O₃: 20-30 mass% and A1₂O₃: 1
A composite ceramic with a composition of 10 mass% is suitable.
Turned out to be. Because Al₂O₃, SiO₂You
And Cr₂O₃The film composed of the three components
Large contact angle, low wettability with plating bath,
Because it is made of oxide ceramics,
This is because they have extremely high abrasion resistance.

Furthermore, it is important that at least the surface of the composite ceramic layer is subjected to a sealing treatment with chromium oxide to form a composite coating layer. Because
Such a sealing treatment is carried out by a method as disclosed in JP-A-63-126682 or the like, wherein chromium is added to the fine pores and cracks of the composite ceramic layer formed on the surface of the substrate or to the surface thereof. An acid solution or a soluble chromium compound solution, for example, chromic anhydride, ammonium dichromate, chromium sulfate, chromium chloride, chromium nitrate, chromium acetate, magnesium chromate, sodium chromate, etc. are applied and impregnated, and then these are oxidized. Heating to a temperature capable of forming chromium fine particles, for example, 300 to 450 ° C. (these operations are usually repeated about 2 to 15 times) to generate fine chromium oxide particles and fine pores in the composite ceramics layer. This is a process in which fine chromium oxide is generated in cracks and filled and filled in fine pores and cracks.

By this treatment, the chromic acid applied to the surface of the film is heated and fired to precipitate and fill chromium oxide fine particles in pores and cracks.
As a result, the composite ceramic layer is further densified, and at the same time, the coating cross-sectional hardness is from Hv 400 to 500 to Hv 600.
To 800, exhibiting properties such as excellent wear resistance, molten metal resistance, and intermetallic compound adhesion inhibitory property.

The thickness of the composite coating layer is preferably 30 to 70 μm. That is, the composite coating layer is made to have a thickness of 30 to 7
When the thickness is 0 μm, for example, when the roll substrate is a frequently used austenitic stainless steel, the influence of the shear stress due to the difference in thermal expansion characteristics is reduced, and the peeling of the film is suppressed to a level at which there is no practical problem. can do. In addition, it is possible to reduce the internal residual stress peculiar to the film which is the particle laminated structure, and the composite coating layer having a thickness in this range changes the shape accuracy of the initial roll substrate coating surface. Therefore, when a fine groove is formed on the roll base material, the groove shape function can be sufficiently reproduced.

When forming the fine grooves, as shown in FIG. 2, a depth of 0.03 to 0.3 m is formed on the surface of the roll base material.
It is advantageous to provide the grooves 10 with m and a width of 0.05 mm or more and extending in the roll circumferential direction at a pitch P of 1.0 mm or more in the roll axis direction. Because, in view of the fact that the average size of the intermetallic compound particles in the plating bath is 300 μm or more, which causes harmful defects to the plated steel sheet product, it is necessary to regulate the groove shape to a depth that does not catch them. It is.

The composite ceramic film described above is
The raw material powder of the ceramic is converted into a plasma flame or gas combustion flame.
Thermal spraying using SiO or SiO₂−Cr₂O₃-A1
₂O ₃For applying, spraying or dipping a slurry containing
After baking, it can be formed by firing.
You.

The coating of the composite ceramic is made of S
In order to reduce the surface roughness of the iO ₂ —Cr ₂ O ₃ —A1 ₂ O ₃ composite material at the time of film formation, the particle size is smaller than that of the powder used for ordinary plasma spray coating, and especially the median diameter is 15 μm. It is preferable to set the following. By forming a film by adjusting the particle size in this way, the surface roughness of the obtained film can be made 2.0 μm or less in terms of the most average roughness.

[0032]

EXAMPLE 1 As a support roll in a plating bath shown in FIG. 1, a circumferential groove having a diameter of 225 mm and an axial length of the roll surface of 1600 mm and a depth of 0.08 mm and a width of 0.05 mm was formed on the surface at a pitch of 1 mm. A formed roll substrate was prepared. And, as a pretreatment performed prior to or simultaneously with the formation of the film,
A roughening treatment was performed on the coated surface. This roughening was lighter than that for a normal metal substrate. That is, a white alumina artificial abrasive WA # 60 was used, the driving air pressure was 0.2 to 0.3 MPa, and the blast distance was 500 to 600.
mm. At this time, the surface roughness of the roll base material was 2 μm in terms of arithmetic average roughness (Ra).

Next, using a plasma spraying apparatus,
O ₂ : 70 mass%, Cr ₂ O ₃ : 24 mass% and A1
_A powder material having a composition of ₂ O ₃ : 6 mass% was coated on the surface of the roll base material to a thickness of 0.05 to 0.06 mm. Thereafter, the process of impregnating with a chromic acid aqueous solution prepared using chromic anhydride and firing at 470 ° C. was repeated three times, and the coating layer was sealed with Cr oxide. The arithmetic average roughness of the surface of the coating layer after this treatment was 1.5 μmRa or less.

The support roll for a hot-dip galvanizing bath thus obtained was immersed in a plating bath for producing a normal galvanized steel sheet and put into service. The service life shown in Table 2 was obtained, and the protective effect of the roll base material was recognized. Was done. In particular, the reduction in service life due to partial peeling of the coating was significantly improved.

Example 2 As a support roll for a plating bath shown in FIG. 1, a circumferential groove having a diameter of 225 mm and an axial length of the roll surface of 1600 mm and a depth of 0.08 mm and a width of 0.05 mm was formed on the surface at a pitch of 1 mm. A roll substrate was prepared. Then, a roughening treatment of the coated surface was performed as a pretreatment prior to coating of the coating. This roughening was lighter than that for a normal metal substrate. That is, using a white alumina artificial abrasive WA # 60, the driving air pressure was 0.2 to 0.3.
MPa and blast distance were performed at 500 to 600 mm. At this time, the surface roughness of the roll base material was 2 μm in terms of arithmetic average roughness (Ra).

Next, using a plasma spraying apparatus,
O ₂ : 70 mass%, Cr ₂ O ₃ : 24 mass% and A1
_A powder material having a composition of ₂ O ₃ : 6 mass% was coated on the surface of the roll base material to a thickness of 0.05 to 0.06 mm. Thereafter, the process of impregnating with a chromic acid aqueous solution prepared using chromic anhydride and firing at 470 ° C. was repeated three times, and the coating layer was sealed with Cr oxide. The arithmetic average roughness of the surface of the coating layer after this treatment was 1.5 μmRa or less.

The support roll for hot-dip galvanizing bath thus obtained was plated with galvalume (55% Al-Z).
n) When immersed in a plating bath for steel sheet production and put into service,
The service life shown in Table 2 was obtained, and the protective effect of the roll base material was recognized. In particular, a reduction in service life due to partial peeling of the coating was significantly improved.

[0038]

[Table 2]

Example 3 As the support roll for the plating bath shown in FIG. 1, first, a roll base material having a diameter of 225 mm and an axial length of the roll surface of 1600 mm was prepared. The surface of the roll base material was ground at 1 μm Ra without forming a groove. Then, a roughening treatment of the coated surface was performed as a pretreatment prior to coating of the coating. This roughening was lighter than that for a normal metal substrate. That is, white alumina artificial abrasive W
Using A # 60, the driving air pressure is 0.2 to 0.3 MPa,
The blast distance was set at 500 to 600 mm. At this time, the surface roughness of the roll substrate was 2 in arithmetic average roughness (Ra).
μm.

Next, using a plasma spraying apparatus,
O ₂ : 70 mass%, Cr ₂ O ₃ : 24 mass% and A1
_A powder material having a composition of ₂ O ₃ : 6 mass% was coated on the surface of the roll base material to a thickness of 0.05 to 0.06 mm. Thereafter, the process of impregnating with a chromic acid aqueous solution prepared using chromic anhydride and firing at 470 ° C. was repeated three times, and the coating layer was sealed with Cr oxide.

The support roll for the hot dip galvanizing bath thus obtained was coated with galvalume plating (55% Al-Z).
n) When immersed in a plating bath for steel sheet production and put into service,
The service life shown in Table 3 was obtained, and the protective effect of the roll base material was recognized. In particular, a reduction in service life due to partial peeling of the coating was significantly improved.

[0042]

[Table 3]

Example 4 As the plating bath snout 7 shown in FIG.
20 mm, surface length 1600 mm and depth 400 mm
A substrate made of US316L steel was prepared. Then, a roughening treatment of the coated surface was performed as a pretreatment prior to coating of the coating. This roughening was lighter than that for a normal metal substrate. That is, white alumina artificial abrasive WA
Using # 60, the driving air pressure was 0.4 to 0.5 MPa, and the blast distance was 350 to 400 mm. The surface roughness of the roll substrate at this time was 2 μm in arithmetic average roughness (Ra).
m.

Next, using a plasma spraying device,
O ₂ : 70 mass%, Cr ₂ O ₃ : 24 mass% and A1
_A powder material having a composition of ₂ O ₃ : 6 mass% was coated on the surface of the snout substrate to a thickness of 0.05 to 0.06 mm.
Thereafter, the process of impregnating with a chromic acid aqueous solution prepared using chromic anhydride and firing at 470 ° C. was repeated three times, and the coating layer was sealed with Cr oxide.

The thus obtained snout for hot dip galvanizing bath was immersed in a plating bath for producing a galvalume-plated (55% Al-Zn) steel sheet and put into service. As a result, the service life shown in Table 4 was obtained. A protective effect was observed. In particular, a reduction in service life due to partial peeling of the coating was significantly improved.

[0046]

[Table 4]

The snout member for a hot dip galvanizing bath manufactured in this manner was immersed in a bath for manufacturing a galvalume-plated steel sheet and used. As a result, the service life shown in Table 3 was obtained, and the effect of protecting the snout substrate was recognized. That is, the erosion of the base material due to the plating bath was reduced, and the reduction in service life was remarkably improved.

[0048]

According to the present invention, since the peripheral surface of the substrate is covered with a thin film having excellent durability, abrasion resistance, resistance to molten metal, and inhibiting adhesion of intermetallic compounds in a bath, the peeling is performed. Difficult
A plating device having a long service life can be provided. Further, when grooves are formed on the surface of the base material, there is also an advantage that the surface can be made ceramics without impairing the groove shape.

[Brief description of the drawings]

FIG. 1 is a diagram showing various devices used for a hot-dip metal plating process.

FIG. 2 is a diagram showing micro grooves formed on a roll base material.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 26/00 C23C 26/00 K 30/00 30/00 C (72) Inventor Eiji Kobayashi Kurashiki, Okayama Prefecture 1664-10 Sakazu (72) Inventor Kazumi Tani 2-3-5, Kamidai-shi, Nishinomiya City, Hyogo Prefecture (72) Inventor Kazuyuki Namerikawa 1-20-18 Kanda, Kurashiki-shi, Okayama Prefecture (72) Inventor Ikiyoshi Miyajima Hyogo Prefecture 3-5-11 Nippori-dori, Kobe-shi

Claims (8)

[Claims] 1. A bath member used in a hot-dip metal plating treatment, wherein a surface of a base material of the bath member is SiO ₂ —Cr ₂ O ₃ —A
molten metal plating baths member characterized by having a composite coating consisting of a chromium oxide-impregnated layer l ₂ O ₃ made of a composite ceramic layer is formed on the surface portion. 2. The method according to claim 1, wherein SiO ₂ —Cr ₂ O is used.
_{The 3-} Al ₂ O ₃ composite ceramic layer is made of SiO ₂ : 60
８０80 mass%, Cr ₂ O ₃ : 20-30 mass% and A
1 ₂ O ₃ : A member for a hot-dip metal plating bath having a composition of from 1 to 10 mass%. 3. A member for a hot-dip metal plating bath according to claim 1, wherein the thickness of the composite coating is 30 to 70 μm. 4. The member according to claim 1, 2 or 3, wherein the member used for the hot-dip metal plating treatment is a roll, and the surface of the roll substrate has a depth of 0.03 to 0.3 mm and a width of 0.05 mm or more. Wherein the grooves extending in the roll circumferential direction are provided at a pitch of 1.0 mm or more in the roll axis direction. 5. A composite ceramic made of SiO ₂ —Cr ₂ O ₃ —Al ₂ O ₃ is coated on the surface of a base material of a bath member used for a hot-dip metal plating treatment, and then a chromium-containing material is contained in the composite ceramics layer. A method for producing a member for a molten metal plating bath, comprising forming a chromium oxide impregnated layer by impregnating with an aqueous solution and then firing. 6. The method according to claim 5, wherein the surface of the substrate is made of Si.
O₂−Cr₂O₃-Al ₂O₃Remove the composite oxide powder
It is characterized by spraying using zuma flame or gas combustion flame
For producing a hot-dip metal plating bath member. 7. The method according to claim 5, wherein the surface of the substrate is made of Si.
O₂−Cr₂O₃-Al ₂O₃Slurry containing
After applying by cloth, spraying or dipping, bake
A method for producing a hot-dip metal plating bath member. 8. After forming microgrooves on the surface of the base material, using a fine powder having an average particle diameter of 15 μm or less in median diameter, forming an oxide film having an arithmetic average roughness of 2.0 μm or less in surface roughness. A method for producing a member for a hot-dip metal plating bath, comprising coating the surface of a substrate.