JPH04358055A - Powdery material for thermal-spraying excellent in molten metallic property and thermal-spraying film - Google Patents

Abstract

PURPOSE:To provide powdery material for thermal-spraying advantageously suitable for the formation of the thermal-spraying film excellent in durability to a molten metal like molten zinc, etc., and its thermal-spraying film. CONSTITUTION:To the powdery material for non-oxide based ceramic thermal- spraying or the powdery material for cermet thermal-spraying incorporating it as a main component and mixing the other metal, aluminum or zinc-aluminum alloy is added. In the thermal-spraying film formed by using the above-mentioned material for thermal-spraying adding the aluminum or zinc-aluminum alloy, for example, diffusion speed of zinc in the molten zinc is extremely reduced with the aluminum alloy on the film surface layer and service life in the molten zinc can be prolonged.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is applicable to the surface of hot-dip plating equipment and its parts, that is, bath members, which require durability against molten metal, such as molten zinc or molten zinc-aluminum, that is, molten metal resistance. The present invention relates to a powder material for thermal spraying that is advantageously suitable as a coating material, and to a thermal spray coating obtained by thermally spraying this material.

0002

[Prior Art] Hot-dip galvanized steel sheets, which are used as heat-resistant and corrosion-resistant steel sheets for automobiles, civil engineering and construction steel materials, and home appliances, are mostly coated with continuous hot-dip galvanized steel sheets as shown in Figure 1. Manufactured by plating process. This hot-dip galvanizing treatment equipment 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 plated steel sheet 4 that is guided after passing through these rolls. A guide roll 5, an injection nozzle 6 for blowing off excess zinc adhering to the steel plate with nitrogen gas, and the like are provided. The bath members are either immersed in the plating bath or installed in locations where molten zinc is likely to scatter and adhere, and are used in contact with hot steel plates to which molten zinc has adhered. ) corrosion by molten zinc is unlikely to occur; (2) threaded material (
(3) It is easy to remove adhering molten zinc and maintain and inspect; (4)
) It must have a long life as a roll and be low cost, and (5) it must have good resistance to thermal shock when immersed in a high-temperature molten zinc bath.

By the way, conventionally used plating bath rolls and bearing components such as bushes, bearings, collars, end balls, etc.
) C on the surface of JIS H8303 (1976)
Sprayed o-based self-fluxing alloy, (2) JP-A-61-1
ZrO2 and Al2O as disclosed in Japanese Patent No. 17260
A ceramic film formed by thermal spraying consisting of 3 (
3) As disclosed in Japanese Patent Publication No. 58-37386, hot corrosion resistant metals such as Ni and Si or oxides thereof are made to coexist with one or more of WC, Cr3C2, and TiC. 1-2.4 m
m-thick film formed mainly by thermal spraying,
and so on.

0004

[Problems to be Solved by the Invention] As can be seen from the above-mentioned examples, research issues regarding conventional thermal spray coatings for parts for hot-dip galvanizing baths include: ■ Selection of hot-dip zinc-resistant coating materials; ■ Coating adhesion. The improvement was mainly due to the properties of the film itself, such as (1) improving the density of the film, and (2) controlling the surface roughness of the film, each of which had an improvement effect. However, with the recent increase in demand for hot-dip galvanized steel sheets, there has been an extremely strong demand for improving the operating rate of galvanizing plants and improving the quality of galvanized steel sheets. development is desired. Therefore, the present invention aims to provide a powder material for thermal spraying which is advantageously suitable for forming a coating having excellent molten metal resistance by thermal spraying.

[0005]

[Means for Solving the Problems] As a result of various studies, the present inventors have found that the life of a thermally sprayed coating immersed in a hot-dip galvanizing bath depends on the diffusion rate of the molten zinc that diffuses into the coating. We have found that the addition of trace amounts of aluminum to molten zinc can significantly reduce the diffusion rate of zinc. Furthermore, when we investigated the surface of a sprayed coating immersed in a zinc bath containing aluminum, we found that aluminum in the bath was selectively adsorbed.
The content was several to several hundred times higher than that in the bath, and it was also confirmed that the aluminum alloy on the surface layer of the film significantly slowed down the diffusion rate of zinc into the film.

The present invention was made based on the above findings, and includes a thermal spraying material such as a non-oxide ceramic or a non-oxide cermet as a matrix.
The coating obtained by thermal spraying this material by containing aluminum or zinc-aluminum alloy is
The focus was on exhibiting excellent molten zinc resistance. That is, the present invention provides a molten metal resistant material characterized by adding and dispersing either aluminum or a zinc-aluminum alloy in a matrix composed of either non-oxide ceramics or similar cermets. An excellent thermal spray powder material and a thermal spray coating formed by thermal spraying this material.

[0007]

[Operation] The thermal spraying material of the present invention has a matrix of non-oxide ceramics or cermets mainly composed of non-oxide ceramics, and a predetermined amount of aluminum in the form of aluminum or zinc-aluminum alloy is added to this matrix. It is characterized by First, the reason why non-oxide ceramics or similar cermets are used as a matrix component in the thermal spraying material of the present invention is that oxide ceramics have poor "compatibility" with metals. In other words, oxide ceramics have little effect of aluminum addition, and metal thermal spray materials show the effect of aluminum addition, but when used as a thermal spray coating in molten zinc, aluminum elutes into the zinc bath. In addition to making it difficult to control the amount of aluminum in molten zinc, zinc-iron alloy (commonly known as dross) floating in the zinc bath adheres to the coating, which causes a reduction in the quality of the plated steel sheet.

[0008] As the non-oxide ceramics, C
r3C2, TiC, ZrC, WC, WTiC2
, B4C and carbides such as NbC or CrB
2. Borides such as TiB2 and ZrB2 are advantageously suitable, and as cermets thereof, the carbides and borides mentioned above include Co, Ni and Ni-Cr.

[0009] Furthermore, there are various methods for adding aluminum or a zinc-aluminum alloy to the above-mentioned non-oxide ceramics or cermets containing the same as a main component. That is, (1) Aluminum or zinc-aluminum alloy is precipitated on the powder surface by exposing non-oxide ceramic powder to high-temperature steam containing aluminum halide or a mixture of aluminum halide and zinc halide (CVD method). ). (2) Ceramic powder is mixed into a powder composed of aluminum powder or zinc-aluminum alloy powder, aluminum oxide, and a halogen compound, and after being maintained at a high temperature, it is cooled and the thermal spray powder is separated (pack cementation). law). (3) Aluminum or zinc-aluminum alloy is vaporized on the surface of the particles by vaporizing aluminum or zinc-aluminum alloy with an electron beam and exposing non-oxide ceramic powder to this environment (PVD).
law). (4) Add aluminum or zinc-aluminum alloy powder to non-oxide ceramic or cermet powder, add a polymer binder if necessary, and then stir to mechanically bond the two (mixing and stirring method) . (5) After the step (4) above, heat at high temperature and grind as necessary to adjust particle size suitable for thermal spraying (mixing heating method,
Mixed heating grinding method).

[0010] When a coating is formed on the surface of a steel component by thermal spraying using the thermal spray powder material prepared by the above method, the coating becomes a coating of non-oxide ceramics or non-oxide cermet containing aluminum. . When an aluminum-containing thermal spray coating is immersed in molten zinc, the aluminum in the top layer of the coating immediately reacts with the molten zinc.
Some of the aluminum diffuses into the zinc bath and is consumed, but most of the aluminum in the film alloys with the zinc that has entered and remains as is. The composition of this alloy is a zinc alloy with a very high aluminum content, so the operating temperature of the plating bath (
It can exist as a solid because it has a much higher melting point than 470°C to 480°C. Since the diffusion rate of zinc is extremely reduced in a film formed of this high aluminum zinc alloy, the service life in molten zinc is significantly extended.

The amount of aluminum or zinc-aluminum alloy added to the matrix is determined by the amount of Al added. That is, even in the case of an alloy, Al or its alloy is added so that the amount of aluminum added is 0.1 to 20 parts by weight per 100 parts by weight of the matrix. The effect becomes significant when the amount added is 1% or more, and the effect lasts up to 20 parts by weight per 100 parts by weight of the matrix. However, if the aluminum content is higher than this, the amount eluted into the zinc bath will increase, making it difficult to control the concentration of the zinc bath. Therefore, aluminum or its alloy is added within a range of 0.1 to 20 parts by weight based on 100 parts by weight of the matrix. In this way, the penetration rate of zinc can be suppressed even with a low aluminum content because aluminum exists only at the grain boundaries of the particles that make up the coating, and the non-oxide ceramic itself is also resistant. This is because the soft aluminum in the thermal spray material has a function of preventing the formation of through holes, which are a fatal defect in this type of coating, due to its excellent molten zinc properties.

[0012] In a thermal spray coating formed from a thermal spray material to which zinc-aluminum alloy has been added, the zinc-aluminum alloy is already present in the coating. Therefore, when this coating is immersed in a molten zinc bath, it exhibits the same effect as a coating containing only aluminum. However, the higher the aluminum content in the zinc-aluminum alloy, the better the corrosion resistance of molten zinc. When a film containing 10 parts by weight of -Co (12%) added to 100 parts by weight of cermet is immersed in a zinc bath containing 0.1% aluminum, the penetration rate of zinc is reduced by 20% compared to a film without alloy.
Can be suppressed back and forth.

According to the findings of the present inventors, even when a zinc-aluminum alloy is added, the aluminum content in the alloy is 0.1 to 100 parts by weight of non-oxide ceramic or non-oxide cermet. A sufficient effect can be achieved within the range of 20 parts by weight.

[0014] The purity of the added aluminum is J
There are no particular problems as long as the quality of the aluminum ingot is as specified in IS H2102 (1968), and the type and amount of impurities contained in non-oxide ceramics.
It can be used as long as it is contained in current commercially available products, for example, WC in the range of 3 to 8% free carbon and 0.1 to 5% of Fe, and these conditions meet the intended purpose of this invention. It does not affect the

On the other hand, the particle size of the powder material for thermal spraying of the present invention is
As with previous thermal spraying materials, those with a thickness of about 5 to 10 μm can be used, but those with a diameter of 5 to 40 μm are most suitable. Furthermore, the powder material for thermal spraying of the present invention can be used in all thermal spraying methods, including atmospheric plasma spraying, reduced pressure plasma spraying that can be performed in an environment substantially free of oxygen, various flame spraying that uses flammable gas as a heat source, and explosive spraying. Can be applied.

[0016]

【Example】

Example 1 Cermet and aluminum mixed and stirred at 680°C
Using the thermal spraying material obtained by heating for 2 hours at
The steel rod was immersed in a zinc bath maintained at 0°C for 10 days, then pulled out of the bath and observed for changes in appearance.The sprayed coating was then cut and an X-ray microanalyzer was used to examine the state of zinc penetration into the coating. Observed. In addition, as comparison materials, carbide cermet materials, self-fluxing alloys (JIS 8303
Using MSFCo1) and Al2O3 thermal spray materials, thermal spray coatings with a thickness of 100 μm were formed in the same manner, and the above tests were conducted. The test results are shown in Table 1 together with the component composition of each thermal spraying material.

[0017]

[Table 1]

[0018] The numbers in the column for thermal spray material composition in the same table are expressed in parts by weight, for example, No. 1 is WC: 94%
and Co: 3 for 100 parts by weight of 6% cermet
Thermal spraying materials having a composition in which aluminum is added in parts by weight are shown, and this also applies to the following tables.

As is clear from Table 1, the coatings (No. 6 to
10), although no damage was observed due to the erosion of molten zinc, the zinc that entered the film completely penetrated the film.
Its tip reached the surface of the base material. In addition, the self-fluxing alloy coating (No. 11) was locally eroded by molten zinc, exposing the base metal, and the reaction product of base metal components and zinc (Fe
-Zn alloy) grew, and zinc further adhered to this, giving it a lump-like appearance. Furthermore, Al2O3 film (No.1
In the case of 2), zinc penetrated through the pores of the film and the base metal was eroded, and local peeling of the Al2O3 film was observed. On the other hand, in all films formed using the thermal spray material according to the present invention, the penetration of zinc from the surface layer was 10%.
It was suppressed to about μm, and no abnormality was observed in appearance, maintaining a healthy state.

Example 2 Cermet powder having a composition of 88% WC and 12% Co was mixed with Al powder, Al2O3 powder and NH4Cl powder.
The difference in specific gravity between WC-Co (specific gravity approximately 14.5), Al, and Al2O3 is utilized from the mixture obtained by mixing well with a mixture of 1 and 2, then heating at 700°C for 2 hours in an argon gas atmosphere, and then cooling. The material for thermal spraying was separated. The surface of the WC-Co powder subjected to such treatment is diffused and coated with Al, and this powder is used to form SS41 round bars (diameter 1
2 x length 200 mm) was used as a base material to form a film with a thickness of 100 μm. After that, this test piece was heated to molten Zn-A.
The specimens were immersed in a l-alloy bath for 20 days and then pulled out to observe changes in the appearance of the thermally sprayed coatings.The coatings were also cut and the depth of diffusion of zinc into the coatings was observed using an X-ray microanalyzer. In addition, as a comparison material, untreated WC (8
8%)-Co (12%) powder, self-fluxing alloy (MFSCo
Similar tests were conducted on thermal spray coatings obtained using each of the thermal spray materials 1) and Al2O3. The test results are shown in Table 2.

[0021]

[Table 2]

As is clear from the table, self-fluxing alloy (No.
．． 10, 11) and the thermal spray coating formed using Al2O3 (No. 12), it was found that the coatings were severely destroyed by molten metal and had poor molten alloy resistance. In addition, the thermal spray coating formed using WC(88)-Co(12) powder had relatively good melting alloy resistance, but especially No. When the coating No. 9 was pulled out of the high-temperature molten alloy bath and cooled, local peeling occurred in the coating. On the other hand, the coating formed using the thermal spray material according to the present invention showed a sound condition even in any molten alloy, and the penetration of molten zinc was slight.

Example 3 ZrB2, Cr3C2 and Cr3C2 (75)
-Ni(20)-Cr(5) and 3 Al powders respectively
%, stirred thoroughly, and heated in an argon gas atmosphere at 700°C for 2 hours. Using this material as a thermal spraying material, a 100 μm thick coating was applied to the same steel rod as in Example 1 by plasma spraying. After forming, 480
It was immersed for 20 days in a molten zinc bath at . Afterwards, these steel bars were pulled out of the molten zinc bath and investigated for changes in the appearance of each coating and the state of zinc penetration into the cross section of the coating. As a result, all coatings maintained a healthy appearance and no zinc had penetrated into the interior of the coating. All of the penetrations remained at 5 μm or less, demonstrating excellent molten zinc resistance.

Example 4 The sink roll (
Material JIS G3445 (1983) STKM13A
), a film with a thickness of 150 μm was formed using the thermal spraying material according to the present invention by high-velocity gas flame spraying. Then, using the rolls on which these thermal spray coatings were formed, 4
Molten zinc maintained at 70-480°C (JIS H21
07 (1957), the plating equipment was operated and the plating equipment was 900mm wide and 0.22m thick.
m steel plates were continuously plated.

The thermal spray molten zinc material powder has the following composition and treatment. (1) 100 parts by weight of WC (88%) - Co (12%) cermet, 2 parts by weight of Al powder added, and heated at 700°C for 2 hours in an argon gas atmosphere (2) WTiC2 (80%) -Co (10%) cermet 3 parts by weight of Al powder attached to 000 parts by weight using a polymer binder (3) Cr3C2 ceramics 100 parts by weight to A
7. Add 2 parts by weight of l powder in an argon gas atmosphere.
Heated at 00℃ for 2 hours (4) 100 parts by weight of ZrB2 ceramics and 1 part by weight of Al powder attached using a polymer binder.

For comparison, the above materials (1) to (4) to which Al was not added were used, and 150
A similar treatment was also carried out using a roll on which a μm-thick thermal spray coating was formed.

[0027] After the above treatment was operated continuously for one week, the operation of pulling up the immersion roll and observing changes in the appearance of the film was repeated five times. The results are shown in Table 3.

[Table 3]

As is clear from the same table, the coatings of the comparative rolls (Nos. 5 to 8) showed no significant corrosion due to zinc, but they suffered from the heat generated when they were pulled up from hot molten zinc. Local peeling phenomenon was observed in the film due to impact and conversely thermal shock when immersed in the bath.In contrast, the film formed using the thermal spray material containing Al according to the present invention The film also withstands corrosion by zinc, and remains in good condition with almost no local peeling phenomenon.Al, which coexists with hard and brittle carbide and boride particles, gives the film toughness and resists thermal shock. It was confirmed that it exhibited excellent performance.

Example 5 In this example, zinc-aluminum alloy powders with different aluminum contents were added to non-oxide cermet.
After mechanically mixing well in an argon gas atmosphere at 50 to 300°C, excess zinc-aluminum alloy powder was removed using the difference in specific gravity. When these powders were analyzed, the aluminum content varied in the range of 3 to 20 wt%.

Using the thermal spray material thus produced,
SS41 round bar (diameter 1
A film with a thickness of 150 μm was formed on the 2×200 mm length. Thereafter, this test piece was placed in a zinc bath at 480°C (0
．． (containing 1 wt% aluminum) for 30 days, during which time the specimen was pulled out of the zinc bath every 12 hours and cooled to room temperature by blowing compressed air.
Thermal shock was applied by repeating the operation of immersing the specimen in the bath. In addition, as comparison materials, a thermal spray coating of a cermet material that does not contain zinc-aluminum alloy, and a self-fusing alloy coating (MSFCo) were used.
1) and an Al2O3 thermal spray coating were used. Table 4 shows the results.

The thermal sprayed coatings of Comparative Examples (Nos. 8 to 14) suffered local minute peeling or destruction due to thermal shock. In addition, in the self-fluxing alloy coating (No. 15), the coating is penetrated by zinc, and the base material component (Fe) is replaced by the bath component Z.
An alloy reaction was carried out with n, and a large amount of Fe-Zn alloy was deposited on the film. Most of the Al2O3 film was destroyed and fell off, and the base material was severely eroded by zinc. On the other hand, the films of the present invention all showed a healthy state,
Furthermore, even in cases where minute local peeling occurred, the number was less than 1 piece/cm2 per unit immersion area, and it was recognized that excellent molten zinc resistance was exhibited even under conditions where thermal shock was applied.

[0032]

[Table 4]

[0033]

Effects of the Invention As is clear from the above examples, the coating formed using the thermal spray powder material to which Al or Al-Zn alloy is added according to the present invention can be applied in molten zinc and molten zinc-aluminum alloy baths. It exhibits excellent molten metal resistance and thermal shock resistance, thus enabling long-term continuous operation of hot-dip coated steel sheets, and is expected to reduce equipment maintenance and inspection costs and production costs. In addition, the protective effect of the roll material of the thermal spray coating obtained with this thermal spraying material suppresses the elution of the base metal components into the molten metal and the resulting contamination, resulting in a stable composition of the molten metal components and high quality. It is possible to produce plated steel sheets in a stable state.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a hot-dip galvanizing bathtub and various rolls and members attached thereto.

[Explanation of symbols]

1 Molten zinc bath 2. Think roll 3 Support role 4 Steel plate for plating 5 Guide roll 6 Injection nozzle

Claims (5)

[Claims] 1. Thermal spraying with excellent molten metal resistance, characterized in that one of aluminum or zinc-aluminum alloy is added and dispersed in a matrix made of non-oxide ceramics or non-oxide cermets. powder material. 2. The powder material for thermal spraying according to claim 1, wherein the amount of aluminum or zinc-aluminum alloy added is such that the amount of aluminum is 0.1 to 20 parts by weight per 100 parts by weight of the matrix. [Claim 3] The non-oxide ceramics constituting the matrix include WC, Cr3C2, TiC, WTi.
Carbide consisting of any one or more selected from C2, B4C, NbC and ZrC, TiB2,
The thermal spray powder material according to claim 1 or 2, which is a boride consisting of one or more selected from CrB2 and ZrB2. 4. Non-oxide cermet contains one or two of Co, Ni and Cr for carbide or boride.
The powder material for thermal spraying according to claim 1, which is a mixture of at least one species. 5. A molten metal resistant material formed by thermally spraying the powder material for thermal spraying according to any one of claims 1 to 4 onto the surface of a base material used in contact with molten metal. Excellent thermal spray coating.