JPH04346640A - Immersing member in hot-dip zinc bath or the like excellent in corrosion resistance and wear resistance - Google Patents

Abstract

PURPOSE:To obtain an immersing member in a hot-dip zinc bath or the like excellent in corrosion resistance and wear resistance such as sink rolls, support rolls, bearing parts and snouts used in an immersing state in a plating bath such as hot-dip zinc. CONSTITUTION:This is an immersing member in a hot-dip zinc bath or the like excellent in corrosion resistance and wear resistance and characterized in that the surface layer with 5 to 200mum thickness of the main body of an immersing member contains, by weight, 10 to 80% tungsten boride, 5 to 15% Co and the balance tungsten carbide with inevitable impurities.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention is a method for manufacturing sink rolls, support rolls, bearing parts, snouts, etc., which are used while immersed in a plating bath such as hot-dip zinc, with excellent corrosion and wear resistance. This relates to immersed members such as zinc baths.

0002

BACKGROUND OF THE INVENTION In recent production lines for automobile rust-proof steel sheets, strict requirements have been imposed on surface modification of rolls associated with molten zinc baths, which is carried out as a means of improving and stabilizing product quality.

0003

SUMMARY OF THE INVENTION It is an object of the present invention to provide a member immersed in a molten zinc bath or the like that has excellent corrosion resistance and wear resistance and can meet these demands.

0004

[Means for Solving the Problems] The above-mentioned problems of the present invention can be solved by providing a member immersed in a molten zinc bath or the like having excellent corrosion resistance and wear resistance as described below. (1) The surface layer of the immersion member body with a thickness of 5 to 200 μm is made of 10 to 80% by weight of tungsten boride, Co5 to
15%, and the remainder consists of tungsten carbide and unavoidable impurities, and has excellent corrosion resistance and wear resistance.

(2) In the above item 1, one or two molybdenum borides or titanium borides are further added.
A member immersed in a molten zinc bath or the like having excellent corrosion resistance and wear resistance, characterized by containing 0% or less. (3) A member immersed in a molten zinc bath or the like having excellent corrosion resistance and wear resistance, characterized in that it further contains 15% or less of one or both of molybdenum carbide or titanium carbide, as set forth in item 2 above.

(4) A member immersed in a molten zinc bath or the like having excellent corrosion resistance and abrasion resistance, characterized in that the above items 1 to 3 further contain 15% or less of metallic chromium. The present invention will be explained in detail below. As a member immersed in a molten zinc bath, etc., ceramic materials are said to be suitable from the viewpoint of corrosion resistance, since corrosion occurs due to zinc. However, it is difficult to weld 100% ceramic material to the surface of the immersion member in a thick manner without peeling.

[0007] The present inventors have created a cermet-based film such as WB, MoB, or WC on the surface of a member to a thickness of 200 μm using a vapor phase synthesis method or a thermal spraying method. -A method has been devised to significantly improve corrosion resistance against Al baths. That is, Co5-15%,
It has been confirmed that by dispersing the above ceramic in a matrix containing 15% or less of Cr, if necessary, the life in a zinc bath or the like can be significantly improved.

The reasons for limiting the range of constituent components of the surface layer of the immersion member of the present invention and examples of forming the surface layer of the immersion member by thermal spraying will be explained. In terms of corrosion resistance against molten zinc and aluminum, ceramics that do not react with Zn or Al include WB, MoB, TiB2, WC, MoC,
Borides and carbides such as TiC are selected as good materials. Note that it is desirable that the ceramic react with the Co phase to some extent during thermal spraying or sintering to form a diffusion bond. In this respect as well, since the carbides and the like dissolve in solid solution to some extent in the Co phase, ceramics are preferable in order to maintain the strength of the coating layer. Note that borides such as WB and MoB alone cannot be expected to have a large solid solution effect with the Co phase;
There is no reaction with molten zinc, and coexistence with carbides does not reduce the strength of the coating, and high corrosion resistance can be obtained in coatings up to a thickness of 200 μm or less. Therefore, these ceramics are used alone or in combination.

On the other hand, the properties of the coating are also affected by the thermal spraying method, and when the coating thickness is less than 200 μm, high-speed gas spraying produces a higher quality coating than the plasma spraying method, which is widely used for general ceramic spraying. I confirmed that I could get it. In particular, when MoB and TiB2 are included, a dense and highly hard coating can be obtained by the thermal spraying method. Therefore, W.B.
It has become possible to obtain dense and highly hard coatings by high-speed gas spraying using thermal spraying materials containing borides and carbides such as , MoB, and TiB2. The reason for this is thought to be as follows. In the case of high-velocity gas spraying, high-density WB
is sprayed onto the substrate through the center of the spray flame, but MoB, TiB2, Mo2 C, etc. have a low density and are easily blown away by the outer flame. Furthermore, MoB,T
iB2, Mo2C, etc. are relatively easily oxidized, and Mo
Produces O3, B2 O3, TiO2, CO gas, etc. Therefore, it is thought that this is because the outer flame part of high-speed gas spraying exhibits a deoxidizing and atmosphere adjustment effect.

Next, the reason for limiting the range of ingredients will be explained. Regarding the amount of Co, when it exceeds 15%, the bonding strength of the film increases and the adhesion becomes good, but the corrosion resistance against molten zinc deteriorates, so the upper limit was set at 15%. The lower limit of Co is selected from the viewpoint of film strength and adhesion, and since strength is insufficient if it is less than 5%, it is set to 5% or more.

[0011] Cr forms a solid solution in the Co base and has the effect of forming an oxide film in the molten metal bath, so it is added as necessary. However, if added in a large amount, the toughness of the matrix decreases, so the upper limit was set at 15%. The possible coating thickness depends on the thermal spray method. Generally speaking, as the thickness of the coating increases, residual stress increases and there is a tendency for peeling to occur more easily. When the film thickness is 200 μm or less, a good quality film can be obtained regardless of the thermal spraying method, but when it exceeds 200 μm, residual stress increases and peeling occurs easily in the heat check test, so the upper limit was set at 200 μm. In addition, from the viewpoint of coating strength and long life corrosion resistance, the lower limit of coating thickness is 5 μm.
It was set as m.

WB is a main component that imparts corrosion resistance to a molten metal bath, and since the effect of adding WB is small if it is less than 10%, it is added in an amount of 10% or more. Furthermore, when the WB is over 80%, it is difficult to obtain a dense film due to its oxidizing properties.
The porosity increases. Therefore, the appropriate amount of WB is 10 to 80%. The remainder is WC, but WC is Co or Co
- It is reactive with the Cr matrix and has the effect of increasing the density of the film and reducing the porosity.

As explained above, MoB and TiB2 have a shielding effect for the frame and, like WB, can complement the corrosion resistance of the molten metal bath, so they can be added in an amount of 10% or less. However, if a large amount is added, it becomes a low-density powder and it becomes difficult to obtain a good quality film due to oxidation, so the addition was limited to 10% or less. Mo2C, TiC
In addition to complementing the effect of WC, it also has a deoxidizing effect in the outer flame area during thermal spraying, and has a CO gas shielding effect. Therefore, some amount of these ceramics may be added if necessary. However, if it exceeds 15%, it becomes difficult to obtain a dense film, so the upper limit was set at 15%.

[0014]

[Example] Next, an example of the present invention will be described. Table 1
No. 1~No. 11 is an example of the present invention. No
．． 12~No. In comparison with Comparative Example No. 15, in the molten Zn corrosion test, the WB-based coating material of the present invention showed no Zn adhesion due to corrosion. In particular, in the Cr-added system, there is no Zn adhesion even after two weeks. However, in the comparative material, molten Zn adheres at an area ratio of 8 to 15%.

[0015]

[Table 1]

[0016]

[Effects of the Invention] As described above, the WB-based film of the present invention has
It is clear that this film exhibits superior molten Zn corrosion resistance compared to the comparative example of the WC-based film, and has great utility value in this type of application.

Claims (4)

[Claims] Claim 1: The surface layer of the immersion member body with a thickness of 5 to 200 μm is made of 10 to 80% by weight of tungsten boride, C.
A member immersed in a molten zinc bath or the like having excellent corrosion resistance and abrasion resistance, characterized in that it contains 5 to 15% of O and the remainder consists of tungsten carbide and unavoidable impurities. 2. In claim 1, further containing 10% of one or two of molybdenum boride or titanium boride.
A member immersed in a molten zinc bath or the like having excellent corrosion resistance and wear resistance, characterized by containing the following: 3. In claim 2, further containing 15% of one or both of molybdenum carbide or titanium carbide.
A member immersed in a molten zinc bath or the like having excellent corrosion resistance and wear resistance, characterized by containing the following: 4. A member immersed in a molten zinc bath or the like according to any one of claims 1 to 3, further containing 15% or less of metallic chromium, which has excellent corrosion resistance and wear resistance.