JPH06306560A - Sliding bearing for rolls in continuous molten metal plating bath - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the crack resistance of ceramic bearings. [Structure] (1) A roll in a continuous molten metal plating bath, characterized in that block-shaped ceramics having a curved inner surface that slides on a shaft are partially arranged only in a direction in which a bearing receives a load. Plain bearings. (2) A slide bearing characterized in that the above-mentioned ceramic has a structure in which only a portion where the ceramic is arranged is inserted and held in a metal bearing base which is hollowed out. (3) A slide bearing characterized in that, in a semi-cylindrical or partially cylindrical bearing, the bearing is divided in the circumferential direction and only the divided portion in the bearing receiving direction is made of ceramic and the other portion is made of metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding bearing for rolls in a bath of continuous molten metal plating.

[0002]

2. Description of the Related Art In general, an apparatus for continuously hot-dip plating a metal such as zinc or aluminum on a steel plate is shown in FIG.
It consists of a sink roll 4 for dipping the steel plate 1 in the molten metal 2 in the plating bath to change the direction to get out of the metal bath, and a support roll 3 for stabilizing the passing position of the steel plate and leveling the plating adhesion thickness. . Reference numeral 5 is a sink roll bearing.

FIG. 10 is a front view showing the structure of the sink roll 4 of the molten metal plating apparatus of FIG. 9, and the sink roll 4 is installed on the bearing 5 of the sink roll provided on the hanger 6. 4-a is a roll portion of the sink roll, and 4-b is a shaft portion of the sink roll.

The material of the bearing 5 of the sink roll is generally stainless steel, and the shape thereof is a cylinder similar to a general slide bearing as shown in 5-1 of FIG. 6, or the roll is always lifted upward by a steel plate when the roll is rotating. As shown in FIG.
It is used with the half-cylinder installed on the upper part like No. 5-2. 7 is a wedge.

In the bearing, the synergic action of erosion by molten metal and mechanical slippage causes the wear of the upper portion, which is subjected to a substantial load, to be extremely fast. Therefore, the roll is usually lifted from the metal bath in a short cycle of about two weeks to replace the bearing. This is a major problem because it leads to a decrease in productivity and an increase in maintenance costs, and also causes a deterioration in the surface quality of plated products due to the occurrence of rotational vibration due to bearing wear.

[0006]

As a countermeasure against this, the use of ceramics in bearings has been earnestly studied, and dramatic improvements in performance have been achieved in terms of wear resistance, and the life is semipermanent only from the viewpoint of wear. It has been improved to such a situation. However, this sink roll inevitably involves lifting and re-immersing work of a set of rolls due to factors other than bearings, for example, roll replacement due to wear of the roll body.
When the bearing is used as it is, the ceramics cracks due to thermal stress by repeating roll withdrawal and re-immersion once or twice, so the life is not extended so much even though the wear is minute. , There was a problem.

The mechanism of thermal stress cracking is shown in FIG. 8 (a).
Description will be made based on (c). The hanger 6 that normally supports the roll is also made of stainless steel, and the coefficient of thermal expansion is approximately α = 11 to 18 × 10 ⁻⁶ / ° C., which is larger than that of ordinary steel. On the other hand, a high-strength material such as silicon nitride or sialon is usually used as the bearing ceramic material, but the thermal expansion coefficient of this type of ceramic is very small at about α = 3 × 10 ⁻⁶ / ° C. Therefore, when the bearing 5-2 set outside the molten metal bath in the same figure (a) is soaked in the bath as shown in the same figure (b), the expansion allowance of the hanger 6 is much larger, so a large gap a is opened. It becomes a state. In the process of pulling up the roll and allowing it to cool in the same figure (c), the molten metal inserted in the gap does not completely escape, and most of it remains solidified as shown in (b). An extremely large bending stress acts on the ceramic bearing 5-2 to cause cracking.

[0008] As a countermeasure against that, the actual exploitation Sho 63-73349
There is a method of interposing a heat-resistant cushioning material sheet made of alumina fiber or the like between the hanger and the ceramic bearing disclosed in, but this is due to the inserted metal during the first dipping → lifting (cooling). The sheet is crushed and has an effect of relieving thermal stress to some extent, but after the second and subsequent times, the sheet has reached the compression plastic limit, and the effect cannot be expected. As another method, the idea of interposing a corrosion-resistant / heat-resistant ring having a coefficient of thermal expansion larger than that of stainless steel, which cancels the generation of gaps in the bath and makes it zero, is possible. There is no such material.

Another measure is to divide ceramics into smaller outer diameters and lengths to minimize the degree of insertion of molten metal, and to reduce bending stress by making ceramics compact. . As this method, there is an example disclosed in Japanese Utility Model Publication No. 57-125768. In this method, the cemented carbide plate is installed by opening downward in a V shape, but since the shape of the Cemented carbide plate is a straight line in the V shape, the lubricating effect by the molten metal, that is, the so-called Low friction rotation cannot be expected due to the action equivalent to the fluid lubrication effect that accompanies the formation of a wedge-type oil film in oil lubrication. Further, since the shaft rotates in contact with the V-shaped bearing so as to bite like a wedge, the friction is further increased. Since it is difficult to rotate the sink roll from the outside of the bath, the non-drive system that rotates by the contact friction torque between the body and the steel plate in the roll body is generally used.However, if the friction of the bearing is large, the steel plate and the roll will slip. May cause scratches on the steel plate or cause vibrations on the rolls, causing chatter marks. Therefore, stable low friction of the bearing and smooth rotation are important functions, and from this viewpoint, stable operation cannot be expected with the shaped bearing.

As another example, there is a bearing disclosed in Japanese Patent Laid-Open No. 1-316443 in which a block-shaped ceramic having a smooth sliding portion with a shaft is embedded in a metal bearing base at several places. Similar to the bearing, a good fluid lubrication effect cannot be expected, and there is a problem in that only the metal bearing portion between the ceramics is rapidly worn and a step is formed with the ceramic portion, so that vibration occurs early. Japanese Patent Laid-Open No. 3-177552 discloses a similar method. However, since this method uses the ceramic block completely protruding from the intermediate metal portion from the beginning, the fluid lubrication effect cannot be expected at all, and the ceramic It is hard to say that this structure has a complicated fixing method and a large number of component parts, and is highly durable.

[0011]

The present invention is proposed for the purpose of solving the problems of the prior art as described above, and the gist thereof is as follows.

(1) A roll in a continuous molten metal plating bath, characterized in that block-shaped ceramics having a curved inner surface that slides with respect to the shaft are partially arranged only in the direction in which the bearing is loaded. Is a plain bearing for use.

(2) The continuous structure according to the above item (1), wherein the ceramic is structured such that only a portion where the ceramic is arranged is inserted and held in a metal bearing base which is hollowed out. A sliding bearing for rolls in a molten metal plating bath.

(3) In a semi-cylindrical or partially cylindrical bearing, the bearing is divided in the circumferential direction, and only the divided portion in the bearing receiving direction is made of ceramics and the other portion is made of metal. , A sliding bearing for rolls in a continuous molten metal plating bath.

(4) In the bearings according to the above (1) to (3), the size of the inner circumferential side of the ceramic portion on which the mating shaft slides is defined by the size in the circumferential direction of rotation of the shaft and the center of rotation of the ceramic portion. A sliding bearing for a roll in a continuous molten metal plating bath, characterized in that an angle formed by two straight lines connecting both ends of the inner surface in the circumferential direction is set to 20 ° to 90 °.

(5) The continuous molten metal plating bath according to the bearing described in the above items (1) to (4), characterized in that the ceramic portion is divided in the axial direction, the circumferential direction, or the axial direction and the circumferential direction. It is a plain bearing for medium rolls.

[0017]

The block-shaped ceramics having an inner surface that comes into contact with and slides on the roll shaft and a curved surface having a diameter slightly larger than the outer diameter of the shaft are arranged such that the center of the block-shaped ceramics is substantially aligned with the load center. Since ceramics have extremely high wear resistance, the metal part other than the relevant part will not come into strong contact with the metal part and wear will not proceed because the metal part other than the relevant part will have a minimum circumferential length. No vibration occurs due to the stepped wear of.
Further, by making the ceramic compact, the degree of insertion of molten metal due to the difference in thermal expansion coefficient from the hanger can be reduced, and the distance between the fulcrum points of bending can be reduced even with respect to the bending action of the metal that is slightly inserted and solidified. , And when the direction of the force that gives the bending is made into ceramics with the conventional shape, that is, when the tunnel shape is compressed from all directions as shown in FIG. 8, the stress generated is the same even if the same force acts. It is advantageous because it becomes smaller. Based on the above principle, bending stress is greatly reduced and cracking becomes difficult.

The ceramic block is mounted by inserting it into a ceramic mounting hole formed on a hanger or a dedicated metal bearing base, or by dividing it into a semi-cylindrical or partially cylindrical bearing in the circumferential direction, and only the necessary portion is ceramics. , The other part is made of metal and arched so that the whole part is self-supporting. The ceramic block is fixed in the axial direction by attaching a stop plate to the hanger or by making the ceramic insertion hole of the metal bearing base into a frame shape to restrain the movement in all directions. It goes without saying that the metal bearing base can be easily fixed to the hanger by welding or a wedge. Therefore, it has a simple structure and is easy to maintain and durable. Also, the inner surface of the ceramic is made into a circle with a diameter slightly larger than the outer diameter of the shaft, and it is installed in the direction of the resultant force of the steel plate at the top and bottom of the bearing where the surface pressure is highest. And stable rotation can be realized.

Furthermore, the above ceramic parts may be divided in the axial direction or the circumferential direction, or in the axial direction and the circumferential direction in advance, and the divided surfaces may be closely adhered to each other to be used in a combined state. Even in this case, the movement within the ceramic portion is restrained by the ceramics, so that there is no problem in practical use. On the other hand, the ceramic is made more compact, which is a perfect countermeasure against thermal stress cracking.

Due to the above-mentioned actions, the ceramic bearing, which has excellent wear resistance but is prone to cracking and thus could not have a long service life, can be made extremely hard to crack and have a long service life while maintaining a good low friction state. It was Needless to say, the bearing of the present invention can be applied to a bearing for a support roll.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 Using a ceramic material as sialon, three-point bending strength of 95
using a material _{^{kgf / mm 2, K IC =}} 8MN / m -3/2, metal bearing base 1 to the hanger 6 shown in FIG. 1 (a)
1 and the ceramic block 10 was provided as a structure, and the dimensions were θ = 90 °, inner diameter 160 mm, outer diameter 190 mm, and length 200 mm. The mating shaft has a diameter of 150 mm, and the length of the part that makes contact with and slides on the bearing is 180 m.
m and slightly shorter than the bearing length. The metal bearing base was made of SUS316 and fixed to the hanger by spot welding to prevent misalignment. The material of the hanger is also SUS316
It is an equivalent product. In order to prevent the ceramic itself from coming off in the axial direction, the stopper plate 8 shown in FIG. The material of the stop plate was also SUS316.

This bearing was applied to a sink roll bearing of a hot dip galvanizing line, and an actual operation test was conducted 8 times at a steel plate speed of 150 mpm. As a result, there was no occurrence of vibration, and the sliding state was maintained in a good state, and there was no problem of cracking. Examining the circumferential length of the trace of sliding contact with the ceramic shaft after use, there is some variation depending on the operating conditions at that time, but the value measured as an angle is approximately θ = 15 ° to 75 °. It was found to be in the range of °. Therefore, this angle may be set to a size with a margin, but if it is set too large, the effect of preventing thermal stress cracking decreases, so in reality, depending on the situation of the line in the range of θ = 20 ° to 90 °. It may be selected appropriately. In order to determine the strength of the bearing of θ = 90 ° subjected to the above-mentioned actual machine test against thermal stress cracking, a short-time heat cycle test in which dipping → withdrawing → cooling → dipping was repeated and the situation was traced. Cracks occurred in the ceramic after a total of 13 uses. Since the number of days used per operation in actual operation is about 2 weeks, it was confirmed by this test that the product has a sufficient life equivalent to a little over half a year in total.

As a modification of this structure, FIG. 2 (a) and FIG.
By adopting the method in which the metal bearing bases 13 and 14 are hollowed out like a frame and the ceramic block 12 is inserted as shown in FIG. 8B, the ceramic block moves in the radial direction of the bearing by the bearing base and the hanger and in the axial direction by the bearing. Since it is fixed by the base, it is convenient because it does not require a stop plate.

Further, 12-1, 12-2, 1 of FIG.
Needless to say, if the ceramic portion is divided in advance in the axial direction, the circumferential direction or the axial direction and the circumferential direction as shown in 2-3 to make it more compact, it will be sufficient for thermal stress cracking.

Assuming that the hanger is newly manufactured, as shown in FIG.
The ceramic block 15 of the bearing and the metal bearing base 16 of the bearing are attached to the hanger 6 as shown in FIG.
It is needless to say that the same effect can be obtained by adopting the structure in which is provided or the ceramic block 15 of the bearing is provided.

Example 2 A ceramic material was used as a sialon equivalent to that of Example 1,
The bearing was a self-supporting arch type structure as shown in FIG. The angle θ of the ceramic block 10 was 60 °. Other inner diameters, outer diameters, lengths of the bearings, and materials of the metal bearing base 17 and the hanger 6 are the same as those in the first embodiment. The fixation of the ceramic block in the axial direction was also the same as in Example 1.
In addition, a double wedge 7 made of SUS316 was driven in and fixed to prevent the bearing from rotating in the circumferential direction. This bearing was used in the actual operation of the hot dip galvanizing line, but no particular abnormality was observed after 11 times of use (immersion / lifting).

As a modification of this structure, FIG. 3 (d) and FIG.
Even if the method such as (e) in which the ceramic blocks 10, 15 of the bearing and the metal bearing bases 17, 18 of the bearing are provided on the hanger 6 is adopted, the same effect can be obtained.

Example 3 Next, the results of applying the bearing of the present invention to the support roll 3 will be shown.

A sialon equivalent to that of Example 1 was used as the ceramic material, and the bearing having the structure shown in FIG. 4 was used. The metal bearing base 14 was hollowed out in a frame shape to insert and fix the ceramic block 12. The dimensions of the ceramic block are θ = 60 °, inner diameter 105mm, outer diameter 135m
m and length 200 mm. The opposite shaft has a diameter of 100m.
m, and the length of the portion that comes into contact with and slides on the bearing was 180 mm. The material of the metal bearing base is SUS316, the double wedge 7 is driven in, and the support roll hanger 20 is used.
Fixed to. The material of the hanger is equivalent to SUS316. The material of the support roll shaft retainer 19 is SU
S316 was used, in which stellite was welded to the shaft contact sliding portion by overlay welding. As a result of applying this bearing to a support roll bearing of a hot dip galvanizing line, it was confirmed that there was no problem at all by conducting an actual operation test eight times. Since the bearing of the support roll has a smaller size and a smaller thermal stress than the sink roll bearing, it is needless to say that it is safe against cracking and can surely be expected to have a long life longer than that of the sink roll bearing.

As a modification of this structure, the same effect can be obtained by adopting a method in which the ceramic block 15 of the bearing is provided on the support roll hanger 20 as shown in FIG.

[0032]

By adopting the bearing of the present invention, it is possible to greatly improve the crack resistance of a ceramic bearing which has been cracked in the past and had a life of about twice that of a stainless steel bearing. It is possible to extend the life by more than 13 times, and extend the life significantly by more than 6 months in the replacement cycle.

As a result, productivity can be improved and maintenance costs can be significantly reduced, and the surface quality of the steel sheet can be maintained at a high level and stable.

[Brief description of drawings]

FIG. 1A is a side view showing a bearing structure of the present invention. FIG. 1B is a sectional view of FIG. 1A viewed from the front.

FIG. 2A and FIG. 2B are perspective views showing another embodiment of the present invention.

3 (a) and 3 (b) are side views showing the structure of another embodiment of the present invention. (C) is a side view which shows another Example of this invention. (D) And (e) is a side view which shows the structure of the bearing which is a modification of FIG.3 (c), respectively.

FIG. 4 is a side view showing a structure when the present invention is applied to a support roll.

FIG. 5 is a side view showing a modification of the support roll.

FIG. 6 and

FIG. 7 is a side view showing the relationship between the conventional bearing shape and the roll shaft.

8 (a) to 8 (c) are views for explaining the mechanism of thermal stress cracking that occurs when a conventional bearing shape is made into ceramics.

FIG. 9 is a schematic side view illustrating the configuration of a molten metal plating apparatus.

FIG. 10 is a front view showing the structure of a sink roll.

[Explanation of symbols]

1 steel plate 2 molten metal 3 support roll 4 sink roll 4-a roll part of sink roll 4-b shaft part of sink roll 5 bearing of sink roll 5-1 〃 5-2 〃 6 hanger 7 wedge 8 stop plate 9 fixing bolt 10 Ceramics Block 11 Metal Bearing Base 12 Ceramics Block 12-1 Ceramics Block Divided Axial 12-2 Ceramics Block Divided Circumferentially 12-3 Ceramics Block Divided Axial and Circumferential 13 Metal Bearing Base 14 〃 15 Ceramic block 16 Bearing metal bearing base 17 〃 18 〃 19 Support roll shaft holder 20 Support roll hanger clearance Clearance of molten metal

Claims (5)

[Claims] 1. A roll in a continuous molten metal plating bath, characterized in that block-shaped ceramics having a curved inner surface that slides on a shaft are partially arranged only in a direction in which a bearing receives a load. Plain bearing. 2. The continuous hot-dip metal plating according to claim 1, wherein the ceramics has a structure in which only a portion where the ceramics are arranged is inserted into and retained in a metal bearing base which is hollowed out. Sliding bearing for rolls in the bath. 3. A continuous melting characterized in that in a semi-cylindrical or partially cylindrical bearing, the bearing is divided in the circumferential direction and only the divided portion in the bearing receiving direction is made of ceramics and the other portion is made of metal. Sliding bearing for rolls in metal plating bath. 4. The bearing according to any one of claims 1 to 3, wherein the size in the circumferential direction of rotation of the inner surface of the ceramic portion that slides on the mating shaft is the rotational center of the shaft and the inner surface of the ceramic portion. A sliding bearing for a roll in a continuous molten metal plating bath, wherein the angle formed by two straight lines connecting both ends in the circumferential direction is set to 20 ° to 90 °. 5. The continuous molten metal plating bath roll according to claim 1, wherein the ceramic portion is divided into an axial direction, a circumferential direction, or an axial direction and a circumferential direction. Plain bearings.