JPH08247136A - Roll for molten metal plating bath - Google Patents

Abstract

PURPOSE: To prevent generation of slippage and sink roll marks by making only an irregular rough surface serve as a roll outer periphery brought into contact with a steel strip, and specifying its roughness. CONSTITUTION: Only an irregular rough surface is made to serve as a roll outer periphery brought into contact with a steel strip, provided that its roughness exceeds Rmax 150μm and is less than Rmax 500μm. A covering layer of fluoride, carbide or oxide, or these cermet material. For forming roughness, any of cutting, rolling, electric discharge machining and grid blasting or combination of these can be applied. By employing only roughness higher than the size of foreign matter in a plating bath, no slippage occurs even at a steel strip driving speed of 100 m/min, so it is possible to attain a plated surface with no sink roll marks. It is also possible to restrain surface roughness from changing with formation of the covering layer, thus increasing the service life of the roll.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten metal bath dipping roll in a molten metal plating apparatus for steel strips, etc., especially a sink roll for reversing the traveling direction of a traveling strip when plating a steel strip in a molten metal bath. Regarding

[0002]

2. Description of the Related Art Conventionally, in hot-dip galvanizing, hot-dip aluminum coating, and hot-dip zinc-aluminum alloy plating bath equipment, the direction roll of a running strip in the bath is called a sink roll. The uniform rotation of the sink roll is required for uniform plating of the steel strip. In order to meet this demand, cross-groove-shaped grooves may be provided on the outer peripheral surface of the sink roll (Japanese Patent Laid-Open No. 64-64-
No. 79356), it is proposed to provide a large number of spiral grooves in the roll width direction (Japanese Patent Laid-Open No. 2-228458).

[0003]

However, in these rolls, the optimum conditions are not always grasped, and slip between the steel strip and the sink roll, or a roll groove pattern transfer called a sink roll mark to the plated steel strip is performed. Was occurring.

The above-mentioned prior art can be expected to have the effect of reducing the adhesion of foreign matter in the plating bath, which tends to adhere to the surface of the plated steel strip, by regularly forming grooves on the surface of the sink roll, but the roll groove and its We have not been able to solve the problems of slip phenomenon due to the adhesion of the alloy layer on the periphery and the generation of sink roll marks accompanying changes in plating bath conditions. The present invention solves the above-mentioned conventional problems, a hot-dip galvanizing bath, a hot-dip aluminum coating bath, hot-dip zinc-aluminum alloy plating bath, a roll for hot-dip metal plating bath in which no sink roll mark occurs on the steel strip plating surface It is intended to be provided.

[0005]

In order to achieve the above object, the inventors of the present invention have improved the running conditions of the steel strip, the operating conditions such as the tension of the steel strip, and the shape of the groove engraved on the outer peripheral surface of the sink roll. As a result of various studies to eliminate slips and sink roll marks, we found that the sink roll mark can be eliminated by eliminating the groove engraved on the outer peripheral surface of the sink roll, but the groove disappears from the outer peripheral surface of the roll. As a result, the inventors have found that there is a close relationship between the traveling speed of the steel strip and the surface roughness of the outer peripheral surface of the roll regarding the occurrence of slip, and have completed the present invention.

That is, according to the present invention made on the basis of the above findings, the outer peripheral surface of the roll contacting the steel strip is only an irregular rough surface, and the roughness is Rmax. Rmax. The gist is a plating bath roll characterized by having a thickness of less than 500 μm. Further, a roll for a plating bath having a coating layer of boride, carbide or oxide or a cermet material thereof on a part or the whole of the outer peripheral surface of the roll is also a subject of the present invention.

[0007]

The structure and operation of the present invention will be described. Cross-groove-like grooves on the outer peripheral surface of the above-mentioned sink roll (Japanese Patent Laid-Open No. 64-64-
No. 79356) or a large number of spiral grooves in the roll width direction (JP-A-2-228458), sink roll marks do not occur on the steel strip even if plating is performed.

However, the running speed of the steel strip is 40 m /
min. Slip occurs between the steel strip and the sink roll, and when the groove is carved, the traveling speed of the steel strip is 100 m / min. However, although no slip occurred, it was found that sink roll marks were generated on the plated surface depending on the steel strip tension and plating bath conditions.

Therefore, in the present invention, the surface roughness Rmax. The steel strip traveling speed is 100 m / mi by making only the rough surface larger than the size of the foreign matter in the plating bath.
n. However, it was confirmed that no slip occurred and a plated surface without sink roll marks could be obtained.

That is, in the roll for a molten metal plating bath of the present invention, the outer peripheral surface of the roll is only a rough surface without grooves,
The roughness is Rmax. Rmax. 5
It must be less than 00 μm. For rough surface formation,
Any of cutting, rolling, electric discharge, grid blasting, or a combination thereof can be applied.

When the sink roll comes into contact with the steel strip in the molten metal plating bath, the molten metal intervenes on the contact surface between the outer peripheral surface of the roll and the steel strip. Slip occurs depending on the tension condition. The grooves on the outer peripheral surface of the sink roll disclosed in JP-A-64-79356 and JP-A-2-228454 show a difference in the running speed of the steel strip that does not slip compared to the case where they are not carved. It is considered to act as a route for discharging the molten metal interposed between the sink roll and the strip. It is also conceivable that the groove causes a difference in surface pressure and a difference in bath component between the contact portion and the non-contact portion of the sink roll and the steel strip, and acts as a cause of the sink roll mark.

Therefore, in order to analyze the action of the groove on the outer peripheral surface of the sink roll, various reproduction experiments of slip and sink roll mark generation were conducted by changing the groove cross-sectional area and the ratio of the groove and the contact surface. As a result, the groove cross section contributes to slip,
It was found that by increasing the cross-sectional area, it acts as a route for discharging the intervening molten metal and an effect on slip is obtained. Further, it was found that the ratio of the groove to the contact surface contributes to the generation of the sink roll mark, and by setting the ratio to 1: 1 it acts as a surface pressure dispersion and a bath component difference dispersion, and an effect on the sink roll mark is obtained. did.

However, the object of the present invention is to eliminate slips and sync roll marks in the sync roll, and it is not necessary to solve only one of them. To seek both solutions, the relationship between the groove and the contact surface is
Paying attention to the relationship between peaks and valleys in the sectional curve in the limit, the maximum depth Rmax. Using the as an index, the outer peripheral surface of the sink roll in the hot dip galvanizing bath was roughened and the occurrence of slip and sink roll marks was observed.

Tables 1 (inventive examples) and 2 (comparative examples) show surface roughness Rmax. Shows the relationship between the slip during use of the roll and the occurrence of sink roll marks on the surface of the plated steel strip. In the example of the present invention, neither slip nor syncroll mark is generated, but in the comparative example, slip occurs when the surface roughness is small, and when the roughness is high, the pattern is transferred to a state similar to the syncroll mark. It was confirmed that As a result, Rmax. Rmax. Fifty
It was revealed that neither slip nor sink roll mark was generated in the sink roll whose surface roughness was adjusted in the range of less than 0 μm.

[0015]

[Table 1] * Remark: No occurrence △: May occur x: Always occur **: Grid blasting

[0016]

[Table 2] * Remarks: No occurrence △: May occur x: Always occurs ―: Slip occurs at steel strip speed of 100 m / min., Evaluation is not possible ***: EDM

[0017]

EXAMPLES The present invention will be specifically described with reference to Examples.
This does not limit the invention. Example 1 Molten zinc having a diameter of 650 mm and a roll body length of 1500 mm
Rmax. Is applied to the outer peripheral surface of the sink roll for the aluminum alloy plating bath. 196 μm (see FIG. 1) surface roughness adjusting rolling process was performed and used in a plating bath. As a result, a steel strip running speed of 100 m / min. It was possible to use it without the occurrence of slip or sync roll marks.

Example 2 A surface roughness adjusting process was performed on the roll outer peripheral surface of a sink roll for hot dip galvanizing bath having a diameter of 650 mm and a roll body length of 1500 mm, and a boride cermet of 60 μm was formed on the surface.
Thermal spraying was performed, and the final surface roughness was set to Rmax. As a result of using 174 μm (see FIG. 2) in the plating bath, conventional grooves were carved without the occurrence of slips or sink roll marks, and boride cermet was sprayed to 60 μm to obtain a final surface roughness of R.
max. Compared with the roll used as 50 μm (see FIG. 3), it was possible to extend the life of the conventional product to 20 days, which is three times more than 70 days.

[0019]

Since the present invention is configured as described above, it is possible to carry out a stable plating treatment of a quality which does not cause slips or sink roll marks, and further boride, carbide or oxide or By forming these cermet material coating layers, suppressing the change in surface roughness,
The effect that the roll life can be further extended is exhibited,
It has great industrial value and is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is an enlarged explanatory view schematically showing a three-dimensional surface roughness profile that is rolled on the outer peripheral surface of a sink roll for a molten metal plating bath of the present invention.

FIG. 2 is an enlarged explanatory view schematically showing a three-dimensional surface roughness profile obtained by cutting and thermal spraying on the roll outer peripheral surface of the sink roll for a molten metal plating bath of the present invention.

FIG. 3 is an enlarged explanatory view schematically showing a roll outer peripheral surface three-dimensional surface roughness profile of a conventional plating bath sink roll.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomio Kondo 4-53-3 Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd.

Claims (2)

[Claims] 1. A roll outer peripheral surface in contact with a steel strip is only an irregular rough surface, and its roughness is Rmax. 150μ
m, Rmax. A roll for a molten metal plating bath, which is less than 500 μm. 2. The roll for a molten metal plating bath according to claim 1, wherein a part or the whole outer peripheral surface of the roll is provided with a coating layer of boride, carbide or oxide or a cermet material thereof.