JP3298492B2 - Roll bearing for molten metal plating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll bearing used in a plating bath for continuous molten metal plating in which a steel sheet is immersed in a molten metal such as zinc or aluminum for plating.

[0002]

2. Description of the Related Art The structure of a continuous hot-dip metal plating apparatus is shown in FIG. The apparatus guides a steel sheet 1 heated and annealed in a heating furnace (not shown) to a molten metal tank 2,
, And pulled up via the sink roll 4 and the support roll 5 to continuously obtain a metal-plated steel plate 6. FIG. 2 shows the structure of the sink roll 4. The rotation side member 10 of the sink roll bearing 7 is a roll shaft or a cylindrical sleeve fitted to the roll shaft. The fixed-side member 11 has a flat or half-cylindrical cylindrical shape, and is made of a steel retainer.
Held by 12. Half-side cylindrical fixed side member 11
3 shows an example of the structure. FIG. 4 shows a structural example of the support roll bearing 8. The rotation side member 10 is a roll shaft or a cylindrical sleeve fitted to the roll shaft. The fixed-side member 11 has a half-cylindrical shape, and is held by a steel retainer 12. The sink roll 4 rotates using the movement of the steel plate 1 as power. The rotation of the support roll 5 may be driven by the movement of the steel plate 1 or by a dedicated motor.

[0003] The rotating member 10 of the above-described bath roll bearing.
And the fixed side member 11, stainless steel, high chrome steel,
Materials having excellent corrosion resistance to molten metal, such as stellite and cemented carbide, are used for the slip portion. Since the fixed-side member comes into sliding contact with the rotating-side member at a local portion, the amount of wear is greater than that of the rotating-side member. If the abrasion progresses and backlash occurs between the fixed-side member and the rotating-side member, the roll vibrates and the plating characteristics of the steel sheet are significantly impaired. For this reason, 10-20
In daily operation, even if the bearing members reach the end of their service life and the rolls are normal, production must be stopped and the entire part immersed in the hot-dip metal plating bath must be replaced, resulting in extremely low operational losses. large.

[0004] Stainless steel, high chromium steel, stellite,
It is difficult to eliminate corrosion caused by a molten metal even with a metal having relatively excellent corrosion resistance, such as a cemented carbide, and corrosion wear occurs in parallel with mechanical wear, thereby increasing the wear amount. That is, when corrosion proceeds to some extent, corrosion pits are formed on the sliding surface, which increases friction and accelerates wear. Therefore, the roll bearing in the molten metal plating bath is required to have high corrosion resistance and low wear. That is, it is important to select a material having excellent corrosion resistance for the fixed-side member and the rotating-side member, and to combine a material having a low friction coefficient.

In order to extend the life of a roll bearing used in a molten metal plating bath, Japanese Utility Model Application Laid-Open No. 55-142571 discloses a cemented carbide having a composition of WC 50 wt% or TiC 50 wt% or more. Japanese Patent Laying-Open No. 1-316443 proposes a roll for hot-dip metal plating having a shaft and a bearing, in which a ceramic sintered body is mounted on a metal bearing shell surface. Japanese Patent Application Laid-Open No. 5-44002 proposes a roll bearing in which the fixed-side member is ceramic and the rotating-side member is cermet. I have. Japanese Patent Application Laid-Open No. H5-222499 proposes a roll bearing in which one of a fixed-side member and a rotating-side member is a sintered ceramic body and the other is a combination of a solid lubricating material.As ceramics, alumina, zirconia, silicon carbide, Examples include hard ceramics such as silicon nitride and sialon, and ceramics containing graphite, boron nitride, molybdenum disulfide, and tungsten sulfide as solid lubricating materials. Hard foreign matter floats in the plating bath. When this enters between the fixed-side member and the rotating-side member and damages the slip surface, friction increases and there is a phenomenon that wear increases. For this reason, graphite and boron nitride are excellent lubricating materials, but because of their low hardness and strength, they are cut by such foreign matter and low wear cannot be achieved.

Academic Journal of the Ceramic Society of Japan, vol.10
5, No2 (1997), p136-140, use TiB ₂ -SiA
The friction coefficient was measured in a zinc bath using lON as the material and the rotating-side member as SiAlON, and it was found that the friction coefficient decreased as the amount of TiB ₂ increased, reaching an extremely low value of about 0.1 at 80 wt%. . But on the other hand, this TiB ₂ -SiAlON
In that, increasing the composition of TiB ₂ decreases the strength of the material,
It is pointed out that when the content exceeds 60% by weight, the hardness also decreases.

As described above, if any one of the hard ceramic sintered bodies having good corrosion resistance in the molten metal is applied to the fixed side member of the sliding bearing of the roll used in the molten metal plating bath, Is kept smooth, wear of both the solid side member and the rotating side member is reduced, and the life of the bearing can be extended.

[0008]

As shown in FIGS. 3 and 4, when a hard ceramic sintered body is applied to the fixed side member 11 of the sliding bearing, the ceramic sintered body is fixed by a steel retainer 12. Generally, the side member 11 is supported. In this case, the molten metal enters the gap between the fixed member 11 and the retainer 12. The intruded molten metal comes into contact with the retainer 12 and gradually generates an intermetallic compound of Fe-Al or Fe-Al-Zn, and pushes up the fixed-side member 11 from the back surface, causing the ceramic sintered body to break. This phenomenon determines the life of the roll bearing.

The present invention has been made in view of the above circumstances, and does not generate an intermetallic compound on the back surface, relieves the stress applied to the fixed member, has no fear of breakage, and is hard to be worn. It is an object of the present invention to provide a roll bearing for hot-dip metal plating capable of extending the life of a bearing and performing uncorrected long-term operation of continuous hot-dip metal plating.

[0010]

That is, the present invention provides: (1) A roll bearing used in a hot-dip metal plating bath, comprising: a stationary member provided with a hard ceramic sintered body; And a steel retainer supported through a boron nitride coating layer.

(2) In a roll bearing used in a hot-dip metal plating bath, a fixed-side member provided with a hard ceramic sintered body, and a WC supporting the sintered body from the back through a boron nitride coating layer A roll bearing for hot-dip metal plating, comprising: -Co sprayed steel retainers.

(3) The hard ceramic sintered body is TiB ₂ ,
_{ZrB 2, AlN, Si 3 N} 4, TiN, ZrN, B 4 C, SiC,
_{TiC, Al 2 O 3, Si0} 2, ZrO 2, AlON, SiAlON, TiCN
90wt% of one or more ceramics selected from the group
The roll bearing for molten metal plating according to (1) or (2), which includes the above.

(4) The roll bearing for hot-dip metal plating according to (1) or (2), wherein the boron nitride coating layer is composed of a ceramic containing 50 wt% or more of BN.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. First, the hard ceramic sintered body on the fixing member side is required not to react with a molten metal such as Zn or Al at a plating bath temperature.
For example, SiO ₂ must be used below 740 ° C. in a plating bath containing Al. This means that above 740 ° C,
This is because SiO ₂ is reduced by Al to produce Al ₂ O ₃ and form dross. Hardness is Vickers hardness 1000
kg / mm ² or more is desirably. If the weight is less than 1000 kg / mm ² , when the dross floating in the plating bath is caught in the bearing sliding contact portion, the fixed side member is damaged and the sliding friction increases. For this purpose, the ratio of the theoretical density of the material (ratio to the theoretical density) is preferably higher,
It is desirable to make it 90% or more. Materials satisfying such conditions include TiB ₂ , ZrB ₂ , AlN, Si ₃ N ₄ , TiN
_{, ZrN, B 4 C, SiC} , TiC, Al 2 O 3, SiO 2, Zr0
₂ , AlON, SiAlON, and TiCN. One or more ceramics selected from these are desirably contained in an amount of 90 wt% or more. Here, AlON, SiAlON, and TiCN each mean a general term for solid solutions, AlON is a solid solution of Al, O, and N, SiAlON is a solid solution of Si, Al, O, and N, and TiCN is Ti and C.
And a solid solution of N 2. From among the ceramic groups, for _{example, TiB2-TiC, TiB 2 -TiN} , TiB 2 -B 4 C, Al
_{N-ZrO 2, AlN-Al} 2 O 3, SiC-Al 2 O 3, Al2O 3 -ZrO2
, Etc. can be applied. 3Al ₂ O ₃・ 2SiO
_2. A composite oxide such as ZrO ₂ · SiO ₂ may be formed.
If it is less than 10 wt%, a material not included in the ceramic group may be added to the included material. Such _{materials, CaO, MgO, Cr 2 O} 3, TiO 2, Y oxides such ₂ O _3, CrB, borides such as CrB _2, carbides such as Cr ₃ C _2, nitride such as Cr ₂ N And metals such as Mo, W, and Co. _{Further, Al 2 O 3 · TiO 2} , Al 2 O 3 · 2TiO 2, MgO
A composite oxide such as Al ₂ O ₃ , MgO and Cr ₂ O ₃ may be formed.

Various stainless steels, heat-resistant steels, and heat-resistant cast steels can be used as the material of the steel retainer. For example, SUS3
16L. These materials have stable mechanical properties and do not cause severe damage, and have high reliability. However, they react with a plating bath such as Zn or Al and are worn from the surface. It also generates dross and causes product defects. Therefore, the reaction is suppressed by performing overlay welding of stellite, thermal spraying of a Co-based self-fluxing alloy, thermal spraying of WC-Co, and the like. For example, a thermal spray coating layer having a porosity of 1.8% or less made of a WC-Co cermet material containing Co5 to 28% by weight disclosed in Japanese Patent Publication No. 2-55502 can be used. However, although such measures are effective in improving the durability, they are not perfect. Co contained in the coating layer elutes into the plating bath. Therefore, the molten metal comes into contact with the main body material through pores generated by the elution of Co. As a result, formation of intermetallic compounds such as Fe-Al and Fe-Al-Zn cannot be avoided. The generation of such an intermetallic compound occurs on the back surface of the hard ceramic sintered body, causing damage to the ceramic sintered body.

The present inventors have found that the formation of an intermetallic compound on the back surface can be prevented by disposing a boron nitride coating layer between the back surface of the hard ceramic sintered body and the support surface of the steel retainer, and completed the present invention. I came to. Here, the boron nitride coating layer is coated with a BN-containing slurry and dried,
It means a layer in which volatile components are removed during the heating process up to the use temperature. The BN contained in the layer is desirably 50% by weight or more. When the layer contains 50 wt% or more of BN, the molten metal such as Zn or Al does not wet the layer and is prevented from entering the layer,
No intermetallic compounds are formed on the steel retainer support surface. If it is less than 50 wt%, this effect will be insufficient. Other than BN, there is no particular limitation as long as it is less than 50 wt%, but Li ₂ O,
Na ₂ O, K ₂ O, MgO, CaO, SiO ₂ , Al ₂ O ₃ , ZrO
_It may contain an oxide such as ₂ and C ₂ . Li ₂ O, Na ₂ O,
Aqueous solution of K ₂ O, MgO, CaO, etc., water glass, SiO ₂ forming binder such as ethyl silicate, boehmite sol, etc.
The coating liquid can be formed by dispersing BN such as an Al ₂ O ₃ generating binder, a C 2 generating binder such as a furan resin and a phenol resin. The liquid may be aqueous or non-aqueous.

The boron nitride coating layer is preferably applied to the steel retainer to form a film in close contact with the retainer. It is even better if the steel retainer is sprayed with WC-Co and applied on top. The sprayed metal may enter the gap between the hard ceramic sintered body and the boron nitride coating applied to the retainer, and may come into contact with the substrate through cracks that may occur in the boron nitride coating. Then, it is more preferable to apply also on the side of the hard ceramic sintered body. This is perfect. Since the boron nitride coating layer is soft and easily deformed, it is deformed according to the strain of the hard ceramic sintered body, thereby preventing generation of excessive stress. For this reason, applying the boron nitride coating layer also has the advantage of preventing the hard ceramic sintered body from being damaged.

The thickness of the boron nitride coating layer is preferably 0.1 to 3 mm. If it is less than 0.1 mm, it is not preferable because it is easily damaged by scratching. If it exceeds 3 mm, the distance between the fixed side member and the retainer is too large, and the backlash of the fixed side member is caused, which is not preferable.

[0019]

FIG. 5 shows an embodiment of a sink roll bearing. After forming a 0.5 mm thick boron nitride layer on both sides of the entire contact surface between the fixed side member 11 made of a hard ceramic sintered body and the steel retainer 12, it is assembled to a thickness of 1 m.
m 3 of boron nitride layer 13 was formed.

That is, the sectional dimensions of FIG. 5 are approximately 140 mm × 260 mm.
A steel retainer 12 having a length of 180 mm was made of SUS316L, and the entire surface was sprayed with WC-12 wt% Co at a thickness of 0.1 mm. On the other hand, the semicircular fixed side member 11 (inner diameter 140 mm,
Outer diameter 200mm, length 140mm) 80wt% TiB2, 20wt% B4C,
It was made of a material having a theoretical density ratio of 100%.

A water-based coating agent is separately applied to both the contact surface of the steel retainer 12 and the fixed side member 11, and the coating and drying are repeated to obtain 58wt% BN, 19wt% Li ₂ O, 23wt% SiO ₂
Was formed. The coating layers were assembled as shown in FIG. 5 while pressing each other. Thus, a boron nitride coating layer 13 having a thickness of about 1 mm was completed.

This slide bearing was applied to a sink roll bearing of a continuous galvanizing apparatus. The working side member is SU
A stellite alloy was overlaid on S316L to a thickness of 3 mm. The bearing has been used without damage for a total of 200 days. The maximum wear of the fixed side member was 0.4 mm.

(Embodiment 2) FIG. 6 shows an embodiment of a bearing of a support roll. After forming a boron nitride layer having a thickness of 0.5 mm on both sides of the entire contact surface between the stationary member 11 made of a hard ceramic sintered body and the steel retainer 12, a boron nitride layer 13 having a thickness of 1 mm was formed.

That is, the outer diameter is 170 mm and the innermost diameter is 120 m in FIG.
A steel retainer 12 having a length of 120 mm and a length of 120 mm was made of SUS316L, and the entire surface was sprayed with WC-12 wt% Co at a thickness of 0.1 mm. On the other hand, a semicircular fixed side member 11 (inner diameter 120 mm,
An outer diameter of 148 mm and a length of 80 mm) were made of 80 wt% TiB2, 20 wt% TiC, and a material having a theoretical density ratio of 100%.

A water-based coating agent is separately applied to both the contact surface of the steel retainer 12 and the fixed side member 11, and the coating and drying are repeated, and the coating of boron nitride having a composition of 80 wt% BN and 20 wt% SiO ₂ is applied. A layer was formed. The coating layers were assembled as shown in FIG. 5 while pressing each other. Thus, a boron nitride coating layer 13 having a thickness of about 1 mm was completed.

This slide bearing was applied to a bearing of a support roll of a continuous galvanizing apparatus. For the working side members, stellite alloy was build-up welded to SUS316L to a thickness of 3 mm. This bearing could be used for a total of 200 days without stopping rotation. The maximum wear force of the fixed side member was 0.8 mm.

(Comparative Example 1) An embodiment of a support roll bearing. The outer diameter 170mm, innermost diameter 120mm, length 12 in Fig. 4
A 0 mm steel retainer 12 was made of SUS316L, and the entire surface was sprayed with WC-12wt% Co with a thickness of 0.1mm. On the other hand, FIG.
The fixed semi-circular member 11 (inner diameter 120 mm, outer diameter 148 mm, length 80 mm) shown in Fig. 8 is made of 80 wt% TiB2, 20 wt% TiC,
It was made of a material having a theoretical density ratio of 100%.

This sliding bearing was applied to a bearing of a support roll of a continuous galvanizing apparatus. For the working side members, stellite alloy was build-up welded to SUS316L to a thickness of 3 mm. When this bearing was used, it could be used without stopping rotation for a total of 12 days, but then became unable to rotate. Inspection revealed that the fixed-side member 11 was broken at the center in the length direction. The cause of the fracture was found to be that the intermetallic compound generated on the back surface locally pushed up the fixed-side member.
In addition, no abrasion of the fixed side member was observed.

[0029]

As described above, according to the present invention, by disposing the boron nitride coating layer on the back surface of the stationary member made of the hard ceramic sintered body, no intermetallic compound is generated on the back surface. Since the stress applied to the fixed side member is reduced and there is no danger of breakage, the characteristics of the hard ceramic sintered body that is difficult to wear are exhibited, so the life of the bearing is extended, and long-term continuous repair of continuous molten metal plating is possible. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a continuous molten metal plating apparatus.

FIG. 2 is a diagram showing a structure of a sink roll.

FIG. 3 is a diagram showing a structural example of a sink roll bearing.

FIG. 4 is a diagram showing a structural example of a support roll bearing.

FIG. 5 is a view showing a structural example of a sink roll bearing according to one embodiment of the present invention.

FIG. 6 is a diagram showing a structural example of a support roll bearing according to one embodiment of the present invention.

[Explanation of symbols]

1 ... steel plate 2 ... molten metal tank 3 ... molten metal 4 ... sink roll 5 ... support roll 6 ... Metal plated steel plate, 7 ... Sink roll bearing, 8 ... Support roll bearing, 10 ... Rotating member, 11 .... .Fixed side member, 12 ...... retainer, 13 ... boron nitride layer.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-138721 (JP, A) JP-A-7-18395 (JP, A) JP-A-4-124254 (JP, A) 69155 (JP, U) Real opening 63-73349 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 2/00 F16C 13/02

Claims (4)

(57) [Claims] 1. A roll bearing used in a hot-dip metal plating bath, comprising: a fixed-side member provided with a hard ceramic sintered body; and a steel member supporting the sintered body from a back surface through a boron nitride coating layer. A roll bearing for molten metal plating comprising a retainer and a retainer. 2. A roll bearing for use in a hot-dip metal plating bath, comprising: a fixed member provided with a hard ceramic sintered body; and a WC-type supporting the sintered body from a back surface through a boron nitride coating layer. A roll bearing for hot-dip metal plating, comprising: a Co-sprayed steel retainer. 3. The hard ceramic sintered body is made of TiB ₂ or ZrB.
_{2, AlN, Si 3 N 4} , TiN, ZrN, B 4 C, SiC, TiC
_{, Al 2 O 3, Si0 2} , ZrO 2, AlON, SiAlON, for molten metal plating according to claim 1 or 2, characterized in that it comprises one or more ceramics selected from the group consisting of TiCN least 90 wt% Roll bearing. 4. The roll bearing for hot-dip metal plating according to claim 1, wherein the boron nitride coating layer is formed of a ceramic containing 50 wt% or more of BN.