JP2001064758A - Bearing for continuous hot dip metallic plating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a covalent bond ceramic member capable of obtaining a stable low friction coefficient while the wear resistance of a shaft sleeve and a bearing bush composing the sliding part of a bearing is made high, having good solid lubricity so as to be capable of securing a low friction coefficient even in the case the sliding face is contacted in a plating bath and capable of production at a low cost by atmospheric sintering. SOLUTION: The properties of boride-contg. ceramics using a carbon substance as a sintering assistant are utilized for a bearing used in a hot dip plating bath. For obtaining wettability and required strength as those of a bearing structural material, a high hardness ceramic composed of a sintered body contg. 80 to 98% TiB2, and the balance carbon sintering assistant such as SiC, B4C, C powder or the like is desirably used, and more desirably, the content of TiB2 is controlled to <=95%, and its bending strength is controlled to >=500 Mpa. In this case, atmospheric sintering is made possible even without depending on high pressure sintering using a hot press, so that the remarkable suppression of the production cost compared to the conventional one is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing for a continuous hot-dip metal plating apparatus, and more particularly to a bearing for a sink roll or a support roll provided in a continuous hot-dip metal plating apparatus to improve the function of a bearing sliding portion. The present invention relates to a bearing for a continuous hot-dip metal plating apparatus capable of improving the quality of a steel sheet and extending the life of a shaft by making the steel plate have a longer life.

[0002]

2. Description of the Related Art In general, components used in a hot-dip bath such as a sink roll and a support roll in a continuous hot-dip metal plating apparatus are melted and damaged by a hot-dip plating bath. In particular, parts having sliding parts, such as the roll bearings, have large wear and abrasion and are severely melted because the sliding parts are in a hot-dip plating bath under solid-liquid two-phase mixed lubrication. If the sliding part is melted, vibration and entrapment of sludge etc. into the sliding part will increase, and the friction coefficient will also fluctuate, causing the quality of the plated plate to deteriorate due to uneven wear and shortening the shaft life. Become.

[0003] This fact is that even stainless steel, which is generally regarded as corrosion-resistant steel, is easily melted and damaged by a hot-dip plating bath. When they are lubricated and slid in a hot-dip plating bath in a solid-liquid two-phase mixed state, both sliding surfaces scratch each other and cracks occur due to local high pressure and the like caused by dross entrainment. This makes it very difficult to solve the above problem.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 7-42562, when a carbide or oxide ceramic having good wettability is used simply for the purpose of lowering the friction coefficient of the ceramic, the use of the ceramic for a long time is not possible. As a result, the erosion progressed and the life as a bearing was insufficient.

[0005] To solve the above-mentioned problems, some of the conventional methods have been proposed. One of the methods is to combine a sialon with a carbon fiber reinforced graphite structure as disclosed in Japanese Patent Application Laid-Open No. Hei 3-177552. Then, there is a method of stabilizing the coefficient of friction and improving the wear resistance.

In addition, as disclosed in Japanese Patent Application Laid-Open No. 7-138721, one of a shaft sleeve and a bearing bush is made of a ceramic sintered body selected from carbide, nitride and oxide, and the other is used. Is composed of a sintered body composed of a metal and a boride, as a specific example, a mixed sintered body composed of molybdenum boride and nickel. Because of the configuration combining a sintered body made of boride with a metal having excellent properties and lubricating properties, smooth rotation of the roll and extension of the life of the bearing seemed to be somewhat improved.

[0007] Also, the Journal of the Ceramic Societ
y of Japan, 105 [2] (1997), pp. 136-140, in "TiB ₂ / SiAlON Friction and wear properties of the composite ceramic in the galvanizing bath" and JP-A 8-48985 discloses the axial sleeve and the bearing one of Bush by mixing high strength sialon good wettability titanium boride as sintering aids sintered composite ceramic (TiB ₂ /
SiAlON), and the other is made of Sialon.
It is disclosed that wear properties are obtained.

[0008] In addition to the above, one of the materials generally used as a material for a sink roll and a support roll bearing for a hot-dip plating bath has heretofore been one in which one of a shaft sleeve and a bearing bush is made of ceramic, ceramic sprayed, cermet sprayed. The other has been used in a combination of stainless steel, graphite-based ceramics, and ceramic spraying.

[0009]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open
As described in JP-177552, when a combination of sialon and a carbon fiber reinforced graphite structure is used, the carbon fiber reinforced graphite structure side wears out after a long use, and the vibration of the steel sheet and the sliding surface Because of the occurrence of sludge entrainment, no significant improvement was achieved.

Further, as described in JP-A-7-138721, one of the sintered bodies is formed of a ceramic sintered body selected from carbide, nitride and oxide, and the other is formed of a boride with a metal. In the case of comprising, a mixed sintered body of nickel, which is originally a metal having high corrosion resistance, and molybdenum boride, which is a boride, is systematically a cermet in a metal bond. In particular, a zinc plating bath) has a large melting loss, and therefore, the corrosion resistance is significantly reduced, so that the improvement of the service life is still insufficient.

[0011] Also, in the literature "Ti in a galvanizing bath"
B ₂ / SiAlON Friction and wear properties of the composite ceramic "and mixed sintered body of one of good wettability titanium boride and high strength sialon as described in JP-A-8-48985 discloses (TiB ₂ / SiAlON ), And the other is made up of Sialon,
Disadvantages include low strength, low solid lubricity, and high manufacturing costs. More specifically, TiB ₂ / SiAlON, which is considered to be the most effective among the above-mentioned prior arts, is sialon 2
It is as low as one-third to one-third, and the required low friction coefficient (0.
When the TiB ₂ content is 80% or more, the bending strength is lower than the required minimum strength of 400 MPa, which will be described later, and the coefficient of friction in the atmosphere is as high as when sliding between sialons. That is, since the solid lubricating property is extremely low, even if it is in a plating bath, if the sliding surface comes into contact, it will be severely worn. Also, since TiB ₂ / SiAlON cannot be sintered under normal pressure, hot pressing Therefore, the material is not optimal as a material of a sink roll for a hot-dip plating bath, a shaft sleeve of a support roll, and a bearing bush.

As described above, a number of combinations of optimal and rational materials have been sought for roll bearings for plating equipment to date, but the fundamental solution, that is, the height of the sliding portion (shaft sleeve, bearing bush) has been increased. Stability of strength, long-term erosion resistance, wear resistance, and low coefficient of friction have not been simultaneously obtained. Further, as described above, since the coefficient of friction varies greatly, there is no example in which a wear-resistant, high-hardness ceramic is simultaneously used for the sliding portion, and one of them is actually sacrificed.

It is an object of the present invention to provide a solid material having high strength and high wear resistance, a stable low coefficient of friction, and a low coefficient of friction even when the sliding surface comes into contact in a plating bath. It is an object of the present invention to provide a bearing for a continuous hot-dip metal plating apparatus which has a lubricating property so that a long service life and an improved quality of a plated plate can be attained, and a low-cost production by normal pressure sintering is possible.

[0014]

(1) In order to achieve the above object, the present invention relates to a bearing for a continuous hot-dip metal plating apparatus having a roll for continuously hot-dip coating a steel strip surface. At least one of the shaft sleeve and the bearing bush forming the roll bearing is a boride-containing ceramic containing boride as a main component and a carbon-based material as a sintering aid.

As described above, by using a covalently-bonded ceramic in which a carbon-based material is used as a sintering aid for the boride-containing ceramic, the ceramic has a low friction coefficient and the required strength as a bearing in a molten metal plating bath, and A bearing having good solid lubricity, high corrosion resistance and high wear resistance can be obtained so that a low friction coefficient can be ensured even when the sliding surfaces come into contact with the plating bath. Also, low-cost production by normal pressure sintering becomes possible.

(2) To achieve the above object,
The present invention is directed to a bearing for a continuous hot-dip metal plating apparatus having a roll and continuously hot-dip coating the surface of a steel strip, wherein one material of a shaft sleeve and a bearing bush constituting a bearing of the roll is formed of boride. It is assumed that a boride-containing ceramic containing a carbon-based material as a main component as a sintering aid is used, and the other material is a nitride ceramic.

Thus, in addition to the operation described in the above (1), a preferred form is obtained especially when the bearing requires strength.

(3) In the above (1) or (2),
Preferably, borides contained in the boride-containing ceramic is TiB _2, the content of 80% to 98
%.

[0019] Thereby, the wettability and strength required especially as a bearing structural member can be obtained at the same time.

(4) In order to achieve the above object,
The present invention provides a bearing for a continuous hot-dip metal plating apparatus having a roll and continuously hot-dip coating the surface of a steel strip, wherein a material of a shaft sleeve constituting a bearing of the roll is sialon, and a material of a bearing bush is It is assumed that the ceramic is a TiB ₂ -containing ceramic containing a carbon-based material as a sintering aid.

Accordingly, in addition to the effects described in the above (1) and (2), the material of the shaft sleeve which particularly requires strength is made of a high-strength sialon, resulting in a structurally favorable form.

(5) In any one of the above (1) or (2) or (4), preferably, the carbon-based material as the sintering aid is a combination of SiC, B ₄ C and C. And

Thus, the effects described in the above (1), (2) and (4) can be obtained.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a continuous hot-dip metal plating apparatus using the bearing of the present invention.

In FIG. 1, a sink roll 5 is immersed in a hot-dip plating bath 1 filled in a plating bath 2 and a sink roll shaft 5a is rotatably supported by a bearing 6 of the present invention. The steel plate strip 3 sent from the snout 4 is supported and turned upward. Then, the steel sheet strip 3 going upward is sandwiched between two support rolls 7 and sent out from the hot-dip plating bath 1. The support roll shaft 7a is a bearing 8 of the present invention.
It is rotatably supported by.

In such an operation configuration, a load is applied to the sink roll shaft 5a upward and the two support roll shafts 7a are separated from each other. Therefore, as shown in FIGS. 2 and 3, the bearings 6 and 8 have a cylindrical shaft sleeve 12 (the pressing ring 1 at the distal end) fitted to the roll shaft 11.
3 and a welding stopper 14) and a semi-cylindrical bearing bush 15 to be fitted into the support 6 (or 8).

The present invention relates to a boride-containing ceramic (carbon-based material and boride-based material) in which a carbon-based material is used as a sintering aid in a bearing having the above-described structure based on the knowledge obtained from the results of a friction test and a bending strength test described later. And covalently bonded ceramics).

The reason is that covalent ceramics mainly composed of borides originally have a stronger high-temperature bond than other metal-binding materials and ionic-bonding materials, and have been immersed in a zinc or aluminum bath. In particular, it has excellent erosion resistance despite its good wettability, and has the effects of abrasion resistance, low friction and dross resistance by satisfying the fluid lubrication conditions described below. Includes base materials as sintering aids, while having low friction coefficient, has higher strength required for bearings, and ensures low friction coefficient even when sliding surfaces come into contact in plating bath This is because a material having good solid lubricity and high corrosion resistance and abrasion resistance can be obtained.

Specifically, the above boride-containing ceramics have a TiB ₂ content of 80% or more and 98% or less from the viewpoint of wettability as a bearing structural material and required strength, and the remainder is made of SiC and B _4.
It is desirable to use a high-hardness ceramic made of a sintered body with a carbon-based sintering aid such as C or C powder, and more preferably T
iB ₂ content of 95% or less and bending strength of 500 Mp
a or more. Also, in this case, sintering at normal pressure is possible without using high-pressure sintering using an expensive hot press, so that the production cost can be significantly suppressed as compared with the conventional case.

With the above configuration, the boride-containing ceramic of the present invention has a hardness of Hv200.
When it is 0 to 3000, the wetting angle becomes 60 ° or less, and the hot-dip plating is always adhered in the plating bath. Since the shear resistance value of the molten metal attached to the surface layer of the sliding surface is increased, the pressure of the molten metal drawn in by the viscosity is increased, and a stable liquid film is formed in the gap between the bearing bush 15 and the shaft sleeve 12 to smoothly Lubrication, that is, good fluid lubrication conditions can be obtained.

Since the ceramics of the present invention contain a carbon component, sufficient solid lubrication can be obtained between the sliding surfaces, so that even if the sliding surfaces come into contact with each other in the plating bath, the lubricating property is secured. As a result, stable sliding becomes possible.

A description will now be given of a friction test and a bending strength test in a plating bath which have led to the finding of the present invention.

First, FIG. 4 is a view schematically showing a test apparatus performed in a plating bath in order to verify the friction coefficient between the shaft sleeve 12 and the bearing bush 15. In FIG. 4, a disk-shaped rotating side test piece 21 (φ60
The fixed side test piece 22 (10 mm × 10 mm) having a substantially cubic shape that looks like the bearing bush 15
mm × 10 mm) under pressure, and immersed in two types of plating baths, a zinc plating bath at 470 ° C. and an Al plating bath at 700 ° C. under the test conditions of a surface pressure of 2 MPa and a sliding speed of 40 m / min.

Then, TiB ₂ -containing ceramics were used for both test pieces. Regarding the formation and sintering, first, a mixture of SiC, B ₄ C, and C powder as a carbon-based sintering aid was added to Ti.
A mixture of B ₂ powders with different contents of TiB ₂ was prepared, acetone was added to each, mixed by a ball mill, and dried to obtain a molding powder. The powder was placed in a mold and pressed, and the resulting pressed body was sintered (2100 ° C. × 1 h) in a vacuum atmosphere to form a covalently-bonded ceramic, which was then processed to a predetermined size. Regarding the friction coefficient to be verified,
Calculated from the rotation torque measured from 1.

FIG. 5 is a graph showing the relationship between the content of TiB ₂ in the test piece and the coefficient of friction based on the measurement results of the above test. In this graph, a bar indicated by hatching 1 is a case of a 470 ° C. zinc plating bath, and a bar indicated by hatching 2 is a measured display of a 700 ° C. Al plating bath. The length of the bar display at each measurement point indicates the variation in the friction coefficient as a result of repeated measurement and calculation.

As can be seen from this graph, when the TiB ₂ content exceeds 80% in both plating baths, the coefficient of friction and the variation thereof are significantly reduced. Although not specifically shown in the graph, it has been found that substantially the same results can be obtained when a nitride (SiAlON) mainly composed of Si ₃ N ₄ is used for the rotating test piece 21.

FIG. 6 is a graph showing the relationship between the TiB ₂ content and the bending strength of the TiB ₂ -containing ceramic test piece, and the test method was performed in accordance with JISTP four-point bending. In this graph, although the value is somewhat lower than that of Sialon shown as a reference, the minimum bending strength of a normal bearing is required at any TiB ₂ content as long as it is 98% or less. It can be seen that 400 Mpa or more is secured and if it is 95% or less, 500 Mpa or more, which is a desirable value for the bending strength of the bearing, is secured. That is, in consideration of the verification in FIG. 5 described above, even if the TiB ₂ content is set to 80% or more to reduce the friction coefficient and its variation, the TiB ₂
If the content is 98% or less, there is no problem in strength.

As a comparative example, reference was made to the literature “Friction of TiB ₂ / SiAlON composite ceramics in galvanizing bath”.
The relationship between the flexural strength for TiB ₂ content in the case of wear characteristics "and TiB ₂ / sialon composite ceramics shown in JP-A-8-48985 discloses shown in FIG.
As can be seen from FIG. 7, when the TiB ₂ content reaches 80%, the strength of the TiB ₂ / SiAlON composite ceramics falls below the required minimum strength of 400 Mpa.

From the above, in the present invention, the content is set to 80% in order to obtain a low and low variation friction coefficient.
It has been found that even in the case described above, the strength problem which has been a conventional problem can be sufficiently solved.

As a combination of the bearing bush 15 and the shaft sleeve 12, only one side may be made of boride-containing ceramics, both may be made of boride-containing ceramics, and the other may be made of nitride mainly composed of Si ₃ N _4. Preferably, wear resistance and low friction are obtained. Among them, it is desirable to use sialon for the bearing that requires particularly high strength.

Further, since the shaft sleeve 12 is required to have higher strength than the bearing bush 15 because of the structural weight and the direct receiving of the weight of the rolls 5 and 7 and the locking load of the steel strip 3, the shaft sleeve 12 is required to have higher strength. It is most desirable that the twelfth material be a high-strength sialon.

The hardness of the TiB ₂ -containing ceramic member according to the present invention is from Hv2000 to Hv3000,
The hardness of silicon nitride ceramics is Hv1400 to Hv
1800, and from this combination, fluid lubrication conditions desirable as a measure against sludge and dross in the plating bath can be obtained.

In the above description, the boride is TiB ₂
Although the present invention has been described with reference to only the above, the present invention has almost the same effect by applying MoB ₂ or the like containing a carbon-based sintering aid.

In the above description, the sintering aid carbon-based material to be mixed with the boride-containing ceramic is preferably SiC,
Although only B ₄ C and C powders are specified, the present invention is not limited to this, and the same effect can be obtained by combining other materials containing carbon as a main component to form a sintering aid. Is possible.

Hereinafter, two practical examples of the present invention will be described to verify the effects of the present invention.

[0047]

[Example 1] First, 85% TiB ₂ , SiC
A shaft sleeve 12 and a bearing bush 15 as shown in FIGS. 2 and 3 are obtained by kneading, granulating, molding, and sintering the TiB ₂ -containing ceramics at a ratio of 10%, B ₄ C 2%, and carbon (C) 3%. (However, the outer diameter of the shaft sleeve 12 side is 80 mm, the inner diameter is 60 mm,
The width is set to 60 mm) and set on the roll shaft 11 of the actual support roll that receives a relatively light load.
It was actually operated in a hot dip galvanizing bath at 70 ° C.

As a result, it was found that the friction coefficient was much lower than that of the conventional structure, and that the fluctuation was small. Also, almost no wear was observed after two months of use.

[Embodiment 2] Next, the results when applied to a sink roll bearing will be described.

In the case of a sink roll, since a high load is applied, the material of the shaft sleeve 12 is made of sialon having high strength, and the material of the bearing bush 15 is made of TiB ₂ as in the first embodiment.
2 and 3 as ceramics containing 85% (however, the outer diameter of the shaft sleeve 12 side is 165 m)
m, the inner diameter was 120 mm, and the width was 150 mm) and set on the roll shaft 11 of the sink roll. In addition, load 1500k in hot-dip galvanizing bath at 470 ° C
g, the actual operation was performed under the conditions of a shaft rotation speed of 100 rpm.

FIG. 8 is a graph showing a change in the total wear amount with respect to the number of continuous use days based on the result of the actual operation, and is also shown together with reference data in the case of other conventionally used material combinations.

As is apparent from this graph, the total wear of the present embodiment is smaller than that of the conventional configuration in which both are made of stainless steel (SUS) or a combination of sialon and graphite ceramics. Of 10
It was possible to greatly reduce it to about one-half, and it was possible to use it for more than two months, and the vibration was greatly reduced, and very good results were obtained.

[0053]

The bearing used in the hot-dip plating bath of the present invention has high wear resistance by using high strength and high hardness ceramics for both the shaft sleeve and the bearing bush constituting the sliding portion. It has a stable low coefficient of friction and has good solid lubricity to ensure a low coefficient of friction even when the sliding surface comes into contact in the plating bath.As a result, long-term continuous operation of sink rolls and support rolls is possible. It is possible to further improve the quality of the plated plate. It also enables low-cost production by normal pressure sintering.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a continuous hot-dip metal plating apparatus using a bearing of the present invention.

FIG. 2 is a diagram showing a configuration of a shaft sleeve.

FIG. 3 is a diagram showing a configuration of a bearing bush.

FIG. 4 is a schematic diagram of a wear test in a plating bath.

FIG. 5 is a graph showing a relationship between a TiB ₂ content and a friction coefficient.

FIG. 6 is a graph showing a relationship between TiB ₂ content and bending strength.

FIG. 7 is a graph showing the relationship between TiB ₂ content and bending strength in the case of Sialon / TiB ₂ composite ceramics.

FIG. 8 is a graph showing the results of an actual operation test in Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot-dip plating bath 2 Plating bath 3 Steel plate strip 4 Snout 5 Sink roll 5a Sink roll shaft 6 Sink roll bearing 7 Support roll 7a Support roll shaft 8 Support roll bearing 11 Roll shaft 12 Ceramics sleeve 13 Press ring 14 Weld stopper 15 Ceramic bush 21 Rotating side test piece 22 Fixed side test piece

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Junji Sakai 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Akira Tsukiki 1-1-1 Kimitsu, Kimitsu City, Chiba Prefecture F Term in Kimitsu Works of Nippon Steel Corporation (Reference) 4G001 BA22 BA23 BA44 BA60 BB22 BB23 BB44 BB60 BC73 BD12 BD14 4K027 AA02 AA22 AB42 AD17

Claims (5)

[Claims] 1. A bearing for a continuous hot-dip metal plating apparatus having a roll and continuously performing hot-dip coating on a steel strip surface, wherein at least one of a material of a shaft sleeve and a bearing bush constituting a bearing of the roll is provided. A bearing for a continuous hot-dip metal plating apparatus, comprising a boride-containing ceramic containing boride as a main component and a carbon-based material as a sintering aid. 2. A bearing for a continuous hot-dip metal plating apparatus having a roll and continuously hot-dip coating the surface of a steel strip, wherein one of a shaft sleeve and a bearing bush constituting a bearing of the roll is made of boride. 1. A bearing for a continuous hot-dip metal plating apparatus, comprising: a boride-containing ceramic containing carbon as a main component and a sintering aid as a main component, and a nitride ceramic as the other material. 3. The bearing for a continuous hot-dip metal plating apparatus according to claim 1, wherein the boride contained in the boride-containing ceramic is T
an iB _2, continuous molten metal plating apparatus bearing, characterized in that its content is 80% to 98%. 4. A bearing for a continuous hot-dip metal plating apparatus having a roll and continuously hot-dip coating the surface of a steel strip, wherein a material of a shaft sleeve constituting a bearing of the roll is sialon, and a material of a bearing bush. Characterized by being a TiB ₂ -containing ceramic containing a carbon-based material as a sintering aid. 5. The bearing for a continuous hot-dip metal plating apparatus according to claim 1, wherein the carbon-based material as the sintering aid is SiC, B ₄ C, C
A bearing for a continuous hot-dip metal plating apparatus, which is a combination of the following.