JP3502332B2 - Molten metal plating bath member and manufacturing method thereof - Google Patents

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 during hot metal plating and a method for producing the same.

[0002]

2. Description of the Related Art In a hot-dip galvanized steel sheet manufacturing facility,
One of the major facilities that determines the quality of plated steel sheets is the hot dip metal plating bath. Various devices are immersed in the plating bath. As the equipment in the bath provided in such a dipping type hot metal plating apparatus for steel strip, there are various rolls for guiding and running the steel strip. For example,
As shown in a typical example of the molten metal plating apparatus in FIG. 1, inside the molten metal plating bath 1, in order from the entrance side of the steel strip 2,
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 device, and a wiping nozzle 8 is arranged on the plating bath 1.

These equipments require various performances. Above all, rolls such as sink rolls and support rolls which are in direct contact with the steel strip in the bath to control the transportation have various characteristics as follows. Required. That is, the secular change in dimensional accuracy is sufficiently small, especially the busbar straightness is excellent, it is not corroded by the molten metal because it comes into direct contact with the molten metal plating bath, that is, the roll surface is difficult to wet with the plating bath and the molten metal. Is less reactive,
Fe-Zn and Fe-Al-Zn formed in the plating bath
The intermetallic compound is fixed on the surface of the roll, and further difficult to grow, and the shape accuracy of the surface can be maintained.

This type of roll is coated on its peripheral surface with a Co-based alloy film, an oxide ceramics film, a carbide cermet film or the like by various construction methods including a thermal spraying method. The material of the coating layer is properly used according to the type of plated steel sheet and the quality requirement.

The film thickness of the roll is about 1 to 2 mm for the Co-based alloy film and 0.3 for the oxide ceramic film.
~ 0.8 mm and 0.0 with carbide cermet coating
Those having a diameter of about 4 to 0.2 mm are put to practical use.

For example, regarding a carbide cermet film,
Japanese Examined Patent Publication No. 58-7386 discloses forming a film having a thickness of 0.1 to 2.4 mm, which contains one or more kinds of WC, CrC and TiC and the balance is made of a hot corrosion resistant metal or its oxide. Rolls are disclosed. Regarding the carbide cermet thin film, Patent No. 1771297
Japanese Patent Laid-Open Publication No. WC-Co has porosity of 1.8% and thickness of 0.04.
Rolls with a sprayed coating of 0 to 0.10 mm have been proposed. Further, regarding oxide ceramics, in Japanese Patent No. 2955625, a carbide is added in an amount of 0.08 to 0.1.
It is disclosed that after coating with a thickness of 0 mm, oxide ceramics including SiO _{2 and the} like are 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, so-called alloying, and also suppress the adhesion and growth of the plating bath components. However, in some cases, the covering layer alone cannot provide a sufficient protective function.

That is, although all of these coatings have a suitable performance as a protective layer for a roll base material, the above-mentioned surface characteristics (1) to (4) required for this type of roll are still problems to be overcome. Is left. For example, the surface appearance of a plated steel sheet is becoming more and more demanding as a main quality factor, and therefore, the surface characteristics required for a roll base material that is in direct contact with the plated steel sheet, especially the above-mentioned characteristics, are required. The requirements are becoming more and more stringent.

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

That is, as described above, the film of the roll is generally thicker than 0.1 mm except for the single application of the carbide cermet, and it is difficult to maintain the fine shape of the roll surface. It was difficult to faithfully reproduce the fine grooves previously formed on the roll base material by coating the film.

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

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

[0013]

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

[0014]

The gist of the present invention developed to achieve the above object is as follows. A bath member used in molten metal plating on the surface of the substrate, a chromium oxide-impregnated layer formed on the surface layer portion and the SiO ₂ -Cr ₂ O ₃ -Al consisting ₂ O ₃ composite ceramic layer A member for a molten metal plating bath, which has a composite coating consisting of

In the present invention, SiO ₂ —Cr ₂ O ₃ —Al ₂ O
₃ composite ceramic _{layer, SiO 2: 60~ 70 mass%} , Cr
A composition of ₂ O ₃ : 20 to ₃₀ mass% and Al ₂ O ₃ : 1 to 10 mass% is preferable. 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 molten metal plating treatment is a roll, on the surface of the roll base material, a groove extending in the roll circumferential direction with a depth of 0.03 to 0.3 mm and a width of 0.05 mm or more is formed in the roll axial direction. It is preferable to use those provided with a pitch of 1.0 mm or more.

The present invention also relates to the production of a bath member used for hot metal plating treatment, in which the surface of the base material of the member is coated with Si.
A composite oxide composed of O ₂ —Cr ₂ O ₃ —Al ₂ O ₃ is coated, and then a layer of the composite ceramic is impregnated with a chromic acid-containing aqueous solution and then fired to form a chromium oxide-impregnated layer. A method for manufacturing a member for a molten metal plating bath, which is 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 _Two-Cr_TwoO_Three-A
l_TwoO_ThreePlasma oxide or gas combustion flame with complex oxide powder
Is preferably used for thermal spraying. In addition, in the method of the present invention
Then, on the surface of the base material, SiO_Two-Cr_TwoO_Three-Al_Two
O _ThreeA slurry containing, by coating, spraying or dipping
After applying, it is preferable to bake. Further invention
In the method, after forming microgrooves on the surface of the substrate,
Use fine powder with an average particle size of 15 μm or less in median size
Oxide whose surface roughness is less than 2.0 μm in terms of arithmetic average roughness
It is possible to use a coating that covers the surface of the base material.
preferable.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In a molten metal plating bath,
It is preferable that the steel strip and the member that controls the function of guiding and running the steel strip, for example, the surface of the roll, are basically in direct contact with each other with a molten bath component interposed therebetween. Therefore, in order to reduce the true contact area between the roll surface and the steel strip, it has been proposed to form various grooves on the roll surface, and some of them have been put into practical use. However, when the roll surface passes through the steel sheet, it comes into contact with the molten metal at a high relative velocity and melts early, causing a change in the shape of the microgrooves on the roll surface and increasing the contact area between the steel sheet and the roll. This is as described above.

Therefore, the inventors of the present invention maintain the roll surface shape by coating the surface of the roll base material on which the microgrooves are formed with a film having a thickness of several tens of μm and made of a stable material in the plating bath. In order to obtain this, on the premise that this coating is formed by thermal spraying, the denseness of the coating is assumed to be SiO ₂ , the abrasion resistance is to be shared by Cr ₂ O _3, and the heat resistance is to be shared by A 1 ₂ O _{3. The} focus was on the _2- Cr ₂ O ₃ -A1 ₂ O ₃ -based ceramic coating, and the composition of the coating was earnestly studied. That is, with SiO ₂ -A1 ₂ O ₃ as the basic composition, the mixing ratio and the amount of Cr ₂ O ₃ added thereto were set so that the reaction with the plating bath and the peeling resistance of the film against the heat history from room temperature to the bath temperature were observed. Determined based on gender. As a _{result, SiO 2: 60~80mass%, Cr} 2 O 3: 20
～30Mass% and _A1 2 _O 3: _1~10mass% is was found to be suitable composition.

Next, in a 55% Al-Zn alloy plating bath.
In order to investigate the melting loss resistance of the film of
Specimen coated test pieces used in plating bath
Dynamically mounted on the side end of a sink roll and rotated in a bath
An immersion test was carried out. The test results are shown in Table 1. Na
The test piece is a SU with a diameter of 30 mm and a length of 100 mm.
S316L material, film is A1_TwoO_Three, Cr_TwoO_ThreeOh
And A1_TwoO_Three-TiO_TwoEach ceramics, WC-1
2Co carbide cermet and SiO of the present invention _Two-Cr
_TwoO_Three-A1_TwoO_ThreeA member having a composite coating layer.

[0021]

[Table 1]

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

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

In this respect, 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 has practically sufficient adhesion to the base material and exhibits melt resistance to molten metal.

From the above experimental results, the surface of the roll base material
As a film to be formed, SiO_Two-Cr_TwoO_Three-A1_Two
O_ThreeConsisting of, especially SiO_Two: 60-80 mass%,
Cr _TwoO_Three: 20 to 30 mass% and A1_TwoO_Three: 1 to
A composite ceramic with a composition of 10 mass% is suitable.
It turned out that Because Al_TwoO_Three, SiO_TwoOh
And Cr_TwoO_ThreeThe coating composed of the three components of
Has a large contact angle, low wettability with the plating bath, and
Because it is made of oxide ceramics, it can be used as a steel base material for rolls.
This is because it is extremely rich in wear resistance as compared with the above.

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

By this treatment, the chromic acid applied to the surface of the above-mentioned coating is heated and calcined to deposit fine particles of chromium oxide in the pores and cracks.
As a result, the composite ceramic layer is further densified, and at the same time, the cross-sectional hardness of the coating is from Hv 400 to 500 to Hv 600.
It becomes as high as ~ 800, and exhibits excellent wear resistance, molten metal resistance, and intermetallic compound adhesion suppression properties.

The thickness of the composite coating layer is preferably 30 to 70 μm. That is, the composite coating layer is 30 to 7
When the thickness is 0 μm, for example, when the roll base material is austenitic stainless steel that is widely used, the influence of shear stress due to the difference in thermal expansion characteristics is reduced, and the peeling of the film is suppressed to a level where 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 original roll base material coated surface. Therefore, it is possible to sufficiently reproduce the groove shape function when minute grooves are formed on the roll base material.

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 linear grooves 10 having a width 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 axial direction. Because the average size of the intermetallic compound particles in the plating bath that causes harmful defects to the plated steel sheet product is 300 μm or more, it is necessary to regulate the groove shape to a depth that does not capture them. Is.

The above composite ceramic film is
A raw material powder of the ceramics is converted into a plasma flame or a gas combustion flame.
Spraying method using SiO or SiO_Two-Cr_TwoO_Three-A1
_TwoO _ThreeMethod of applying, spraying or dipping a slurry containing
Can be formed by firing after applying
It

The composite ceramic film is S
In order to reduce the surface roughness of the iO ₂ —Cr ₂ O ₃ —A1 ₂ O ₃ composite material when forming a film, the particle size is smaller than that of the powder used in a normal plasma sprayed coating, and in particular, the median diameter is 15 μm. The following is preferable. By thus adjusting the particle size and forming the film, the surface roughness of the obtained film can be made to be 2.0 μm or less in terms of the maximum average roughness.

[0032]

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

Then, using a plasma spraying apparatus, Si
_{O 2: 70mass%, Cr 2} O 3: 24mass% 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. After that, the process of impregnating the chromic acid aqueous solution prepared using chromic anhydride and then firing at 470 ° C. was repeated three times to seal the coating layer with Cr oxide. The arithmetic average roughness of the coating layer surface after this treatment was 1.5 μmRa or less.

The support roll for hot dip galvanizing bath thus obtained was immersed in a galvanizing bath for producing ordinary 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 given. In particular, the reduction in service life due to partial peeling of the coating was significantly improved.

Example 2 As the support roll for a plating bath shown in FIG. 1, first, a peripheral 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 at a pitch of 1 mm. A roll base material was prepared. Then, as a pretreatment prior to the coating of the film, a roughening treatment of the coated surface was performed. This roughening was made milder than that for a normal metal substrate. That is, white alumina artificial abrasive WA # 60 was used and the driving air pressure was 0.2 to 0.3.
MPa, blasting distance was 500 to 600 mm. The surface roughness of the roll base material at this time was 2 μm in terms of arithmetic average roughness (Ra).

Then, using a plasma spraying apparatus, Si
_{O 2: 70mass%, Cr 2} O 3: 24mass% 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. After that, the process of impregnating the chromic acid aqueous solution prepared using chromic anhydride and then firing at 470 ° C. was repeated three times to seal the coating layer with Cr oxide. The arithmetic average roughness of the coating layer surface after this treatment was 1.5 μmRa or less.

The thus obtained support roll for hot dip galvanizing bath was galvanized (55% Al-Z).
n) When immersed in a plating bath for steel sheet production and used,
The service life shown in Table 2 was obtained, and the effect of protecting the roll base material was recognized. In particular, the reduction in service life due to partial peeling of the film was remarkably improved.

[0038]

[Table 2]

Example 3 As the support roll for a 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 this roll base material was a ground surface of 1 μmRa without forming grooves. Then, as a pretreatment prior to the coating of the film, a roughening treatment of the coated surface was performed. This roughening was made milder than that for a normal metal substrate. That is, white alumina artificial grinding material W
A # 60 is used, the driving air pressure is 0.2 to 0.3 MPa,
The blasting distance was 500 to 600 mm. The surface roughness of the roll base material at this time is 2 in terms of arithmetic average roughness (Ra).
was μm.

Then, using a plasma spraying apparatus, Si
_{O 2: 70mass%, Cr 2} O 3: 24mass% 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. After that, the process of impregnating the chromic acid aqueous solution prepared using chromic anhydride and then firing at 470 ° C. was repeated three times to seal the coating layer with Cr oxide.

The support roll for hot dip galvanizing bath thus obtained was galvanized (55% Al-Z).
n) When immersed in a plating bath for steel sheet production and used,
The service life shown in Table 3 was obtained, and the effect of protecting the roll base material was recognized. In particular, the reduction in service life due to partial peeling of the film was remarkably improved.

[0042]

[Table 3]

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

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

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

[0046]

[Table 4]

The thus-produced snout member for a hot dip galvanizing bath was immersed in a galvalume-plated steel sheet producing bath for use. As a result, the service life shown in Table 3 was obtained, and the effect of protecting the snout base material was recognized. That is, the melting loss of the base material due to the plating bath can be reduced, and the reduction in service life can be remarkably improved.

[0048]

EFFECTS OF THE INVENTION According to the present invention, since the peripheral surface of the substrate is coated with a thin film excellent in durability, wear resistance, molten metal resistance, and intermetallic compound adhesion inhibiting property in the bath, peeling is caused. Difficult,
It is possible to provide plating equipment having a long service life. Further, when grooves are formed on the surface of the base material, there is also an advantage that the surface can be made ceramic without damaging the groove shape.

[Brief description of drawings]

FIG. 1 is a view showing various kinds of equipment used for hot metal plating treatment.

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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C23C 26/00 C23C 26/00 K 30/00 30/00 C (72) Inventor Kazumi Tani 2-Kamidai-shi, Nishinomiya-shi, Hyogo 3-5 (72) Inventor Kazuyuki Namerikawa 1-20-18 Kanda, Kurashiki City, Okayama Prefecture (72) Inventor Ikinori Miyajima 3-5-11 Higuredori, Chuo-ku, Kobe City, Hyogo Prefecture (56) -195178 (JP, A) JP-A-5-311369 (JP, A) JP-A-59-13073 (JP, A) Actual development 6-979741 (JP, U) (58) Fields investigated (Int.Cl) . ^7, DB name) C23C 2/00 - 2/40 C23C 4/10 C23C 4/18 C23C 26/00 C23C 30/00

Claims (5)

(57) [Claims] 1. A bath member used in molten metal plating on the surface of the _{substrate, Si O 2: 60 ~ 70mass} %, Cr 2 O
₃ : 20 to 30 mass % and Al ₂ O ₃ : 1 to 10 mass % composition
And _{SiO 2 -Cr 2 O 3 -Al 2} O 3 multi if ceramic layer having,
A member for a molten metal plating bath, which has a composite coating having a thickness of 30 to 70 μm, which is composed of a chromium oxide-impregnated layer formed on the surface layer portion. 2. The member used in the molten metal plating process according to claim 1, wherein the member is a roll, and the surface of the roll substrate has a groove extending in the circumferential direction of the roll with a depth of 0.03 to 0.3 mm and a width of 0.05 mm or more. the molten metal plating unit, characterized in that provided in the above pitch 1.0mm in the roll axial direction
Material . To 3. A base surface of bath member used in molten metal _{plating, Si O 2: 60 ~ 70mass} %, Cr 2 O 3: 20 ~ 30mass
% And Al ₂ O ₃ : SiO ₂ -C having a composition of 1 to 10 mass %
r ₂ O ₃ -Al ₂ O ₃ coated with the double engagement ceramics, then in a layer of the composite ceramics, chromium oxide impregnated layer is formed by firing after impregnated with a chromium-containing aqueous solution, the thickness 30 A method for producing a member for a molten metal plating bath, which is a composite coating having a thickness of 70 μm . 4. The composite ceramic according to claim 3, wherein the surface of the substrate is a composite ceramic.
When forming a mixed film, the average particle size is
A powder of SiO ₂ —Cr ₂ O ₃ —Al ₂ O ₃ composite oxide with a Dian diameter of 15 μm or less was sprayed using a plasma flame or a gas combustion flame, and the surface roughness was 2.0 μm or less in terms of arithmetic average roughness . Oxide
A method for producing a member for a molten metal plating bath, which comprises coating with a film . 5. The composite ceramic according to claim 3, wherein the surface of the substrate is a composite ceramic.
In forming the mixed film, SiO ₂ —Cr ₂ O ₃
A method for producing a member for a molten metal plating bath, which comprises applying a slurry containing Al ₂ O ₃ by coating, spraying or dipping, and then firing.