JP2638718B2 - Roll for plating bath - 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 for guiding winding of a steel strip in a treatment tank filled with a plating solution, for example, a hot-dip bath. The present invention relates to an immersion roll (hereinafter simply referred to as a “sink roll”), and in particular to an improvement proposal for a surface structure of the sink roll, which includes non-ferrous metals such as hot-dip galvanizing, hot-dip aluminum coating, hot-dip zinc-aluminum alloy plating, and hot-tin plating. The present invention relates to a plating bath roll having no spiral grooves, which is applied to a hot-dip plating process for metals.

[0002]

2. Description of the Related Art As shown in FIG. 1, a sink roll used in a hot-dip galvanizing apparatus or a hot-dip aluminum plating apparatus has a plating solution (hereinafter simply referred to as a plating bath) stored in a processing tank. "). Since this sink roll is always immersed in a molten metal such as molten zinc, it is used under severe conditions, and is basically required to have the following functions. The roll surface is not easily eroded by molten metal. The surface is hardly worn even when it comes into contact with the passing steel strip, and the initial shape and accuracy can be maintained for a long time. Although it is a consumable, it has a long life and can reduce equipment costs.

In addition, since the sink roll is used for guiding the steel strip in the plating bath and for turning at the same time, the following performance is required. Foreign matter suspended in the plating bath ("dross", mainly particles of Fe-Zn alloy, or particles that are mechanically combined with the plating metal component. If adhered, it will cause a shape defect of the plating layer and cause a surface defect of the product). Generally, a spiral groove (groove) for discharging the dross is formed in the roll body of the sink roll, but the shape of this groove is transferred to a plated steel strip, so that the plating is not uniform, that is, And plating surface defects such as uneven color tone and uneven gloss (so-called “groove marks”) are unlikely to occur.

Conventional sink rolls that meet these requirements include: a. A roll provided with a coating layer having excellent resistance to molten metal erosion on the outer peripheral surface of the roll, b. There is one in which a groove shape formed on the outer peripheral surface of the roll is improved. As the former roll, a cobalt self-fluxing alloy as defined in JIS H8303-1989, spray-welded to the roll surface, as disclosed in JP-A-1-108334, in the self-fluxing alloy A coating layer formed by adding Mo, W for improving the molten zinc erosion resistance, as disclosed in JP-B-58-37386, such as WC or CrC, TiC and hot corrosion-resistant metal, etc. And a coating layer having a thickness of 0.1 to 2.4 mm.

[0005] As for the latter roll, a roll having a groove as shown in Figs. 2a and 2b is formed on the roll surface. These grooves are spiral grooves extending around the roll cylinder from one end to the other end, or spiral grooves extending toward the roll end in opposite directions to each other and distributed to the left and right at the center of the roll cylinder. In any case, the gap between the grooves is connected to the flat portion of the roll. Further, various proposals have been made for a method of engraving the spiral groove.
Japanese Patent Publication No. 356 proposes a hot-dip galvanizing sink roll having a cross-shaped groove having a pitch of 20 to 60 mm, a depth of 0.5 to 10 mm, a width of 5 to 10 mm, and an R of 3 to 10 mm on the outer peripheral surface of the roll. ing.

[0006]

Each of these prior arts could be expected to have a decent effect in stabilizing the roll surface shape for a long time and reducing dross that easily adheres to the surface of the steel strip. However, in recent galvanizing treatment of rust-proof steel sheets for automobiles and the like, higher quality is required, and sufficiently satisfactory results have not been obtained only by conventional improvement techniques. In other words, in addition to improving the mechanical properties of a plated steel sheet, in the field of performing a plating treatment as a base of coating as covered by the present invention, for example, the surface of the plated steel sheet, such as the color tone and luster of the plating, is also required. Although better quality is required, it is difficult to say that satisfactory results have been obtained to meet such requirements.

In view of such circumstances, the inventors proceeded with research to improve the quality of a plated steel strip.
In the case of the conventional roll which overcomes various problems before that by engraving a spiral groove on the roll cylinder of the sink roll as in the publication, this spiral groove is rather It is clarified that it is the main cause of uneven color tone or luster of plated steel strip. That is, as shown in FIGS. 2a and 2b, the sink roll used in the plating treatment of the steel strip is as follows.
Because it contacts the spiral groove for dross discharge and the flat part adjacent to it, there are differences in plating conditions, etc. in each area, which causes stripes called "groove marks" on the plated steel strip. This caused a pattern to cause plating appearance defects such as uneven color tone and uneven gloss on the plated surface. And it was also found that this groove mark is remarkably generated when the sink roll is new.

[0008] To prevent the generation of such groove marks, the following measures have been taken to prevent the tension of the steel strip, the threading speed,
How to adjust the temperature, bath composition, etc. of the steel strip, or
Although a method in which a pre-processed steel strip called a dummy steel strip was previously passed through for 8 to 24 hours to perform conditioning, and then a full-scale passing was attempted, the steel strip to be manufactured was used in the above method. The temperature and tension of the steel strip in the molten metal bath vary depending on the thickness and width of the bath, making it difficult to find stable conditions. In addition, the composition of the plating bath was incompatible with the adhesion of the plating layer on the surface of the steel strip, and it was extremely difficult to adjust the composition. On the other hand, in the method of performing the adjustment operation in which the dummy steel sheet is passed, the productivity is remarkably reduced, so that it is difficult to be effective.

As described above, in the conventional roll having a spiral groove, even if any operational improvement is made, the generation of the groove mark has not yet been completely prevented.

An object of the present invention is to mechanically examine the minute shape of the roll surface, to find a suitable condition under which a groove mark does not occur, and to maintain this preferable shape for a long period of time. Is to overcome.

[0011]

According to the study of the present inventors, in a sink roll as shown in FIGS. 2a and 2b, when a transport steel strip is wound in a plating bath, its winding angle is increased. It has been found that the smaller the groove is, the less the occurrence of groove marks due to the groove is, but it has been found that it is impossible to completely prevent such marks. Therefore, the present inventors have set the surface of the roll cylinder so that the steel strip can be wound around the roll cylinder of the sink roll through the bath component and guided without applying such a spiral groove. We came up with the idea of providing unevenness to the surface.

That is, the present invention relates to a roll for guiding the winding of a steel strip in a treatment tank filled with a plating solution, wherein the roll has a height difference within a range of 0.5 to 5 mm, A roll for a plating bath, characterized in that irregularities are provided such that the tips of the projections become flat.

In the present invention, the density of the projections is set to 10 to 10 cm / cm ² so that the above-mentioned plating bath roll (sink roll) can wind the steel strip through the bath components.
As fall within the 250 range, further the surface of the roll body, i.e. the uneven table surface, for example carbides, it is preferable to provide the oxide or boride or a coating layer made of these cermet.

[0014]

The sink roll used for guiding and running the steel strip in the molten metal plating bath should theoretically not have the spiral groove. However, in the hot-dip plating process, the generation and agglomeration of Zn-Fe alloy (dross) at the contact interface between the steel strip and the roll is inevitable. For this purpose, it is necessary to provide a path for automatically discharging the dross. By then, it was common to cut grooves of various sizes and shapes.

Here, the groove serves as a mechanism for moving and discharging dross existing between the steel strip and the roll drum to the end of the roll drum along the groove by rotation of the sink roll. Therefore, it is inevitably formed as a spiral groove shape (V, U, square, etc.). This groove (hereinafter, such a groove is referred to as a “helical groove”) is basically a single groove. For example, when the rotation axis of the roll is used as a reference, they do not communicate with each other and have a flat portion. Through a distant relationship. This means that when the roll is operated in the plating bath, the spiral groove has abundant plating bath components and makes fluid contact with the steel strip, whereas in the flat portion adjacent to the spiral groove, It means that the steel strip makes almost rigid contact with the roll surface, and here it is considered that there is a difference (effect difference) in the effects of plating bath components and plating conditions on both steel strip surfaces, resulting in so-called groove marks. .

Now, the inventors of the present invention have described the difference in the action between the spiral groove and the flat portion as the difference in the reaction time with the plating bath component, the difference in the plating bath component as viewed from the boundary layer theory, and the difference in the plating bath component. The difference in contact pressure with the pressure was discussed. And, assuming that the groove mark is generated by the microscopic plating reaction condition difference between the steel strip and the plating bath component as described above, the same function as the spiral groove without applying the spiral groove is applied. Various experiments and investigations have been made on means for setting the contact conditions so as to exhibit the same plating reaction at any contact surface of the roll drum on which the steel strip is wound.

As a result, it has been found that it is extremely effective to provide the surface of the roll cylinder of the sink roll with irregularities having regular or irregular shapes such as those shown in FIGS. The size and specific shape of such irregularities were variously changed, and the relationship with the groove marks was examined in more detail. It has been found that such a concept usually means that a plating bath component is essentially a molten metal and has a surface tension based on viscosity, so that there is also a suitable range for the height difference of unevenness. In addition, it has also been clarified that, when the projections among the projections and depressions have a certain size or more, a pattern corresponding to the groove mark is transferred to the plated steel strip.

In the present invention, as a method for imparting required irregularities to the roll cylinder, there are a cutting method, an electric discharge method, a laser beam processing method, a so-called blasting method in which shot or grit material is blown with high-pressure air,
Alternatively, a processing method in which a minute pin is bonded by embedding welding can be applied. The test rolls are made of two materials, SUS 304 stainless steel and 13Cr steel, with a diameter of 600mm and a surface length (roll body length) of 1500mm.
Applying the above-mentioned method to the surface (the entire surface of the roll cylinder) of the dimensions described above, irregularities of various sizes are formed in advance and immersed in a normal zinc plating bath to wind the steel strip. Guidance was conducted, and the occurrence of groove marks on the steel strip surface subjected to the plating treatment was observed.

Table 1 shows the relationship between the concave and convex shape of the roll cylinder, the engraving method, and the occurrence of groove marks on the surface of the plated steel strip. It is clear that the height difference between the irregularities is within the range of 0.5 mm or more and 5.0 mm or less, and that the shape of a truncated pyramid, a truncated quadrangular pyramid, a prism, or a cylinder does not generate a groove mark.

[0020]

[Table 1]

Table 2 shows the results of the density per unit area of the projections among the projections and depressions, and shows the relationship between the effect on the groove mark and the life that the shape can be maintained. is there. From the viewpoint of the function of the projections and the ability to maintain the projections, there is a suitable range for the number of projections per cm ² of the surface of the roll drum, and the engraving density of the projections per cm ²
It was found that no groove mark was generated when the number was 10 or more and 250 or less, and the maintenance ability, that is, the life was very good. It was also found that if the engraving density was too high, dross would accumulate in the gaps and fill the recesses.

[0022]

[Table 2]

It is preferable that the irregularities conforming to the present invention have locations as schematically shown in FIG. 4, for example. Because, by providing such irregularities, when the steel strip is wound around the roll drum, the plating bath is present in a uniform state between the steel strip and the irregularities of the roll drum. It is. Such a configuration can be said to be essentially different from a conventional roll as shown in FIG. 5 in which a simple spiral groove is provided in the roll cylinder. In the present invention, the tip of the convex portion among the irregularities on the surface of the roll body was flattened. This is because the contact surface pressure is reduced by increasing the contact area, and the roll life is improved.

As described above, according to the present invention, the roll body of the sink roll is provided with irregularities satisfying the above-mentioned conditions, so that the plating bath is provided between the steel strip and the roll without applying a spiral groove. The components can be retained abundantly, and the plating reaction conditions can be made almost equal at any part of the outer peripheral surface of the roll, and a uniform plating layer can be obtained on the surface of the steel strip, and as a result, there is no generation of groove marks. It can be.

Next, in the present invention, it is preferable to provide a coating layer of a carbide, an oxide, a boride or a cermet material thereof on the surface of the roll drum, particularly for the following reasons. The rolls in the bath of the continuous hot metal plating equipment are generally made of austenitic stainless steel or
Made of alloy steel such as 13Cr steel. However,
Molten metal such as zinc is active and has high reactivity with steel materials, so that various Fe alloys are formed on the surface of the roll. In particular, the sink roll in the hot-dip plating equipment reacts with the plating solution in the bath, and its surface is covered with the alloy layer in a short time. For this reason, it is extremely difficult to maintain the roll on which the fine irregularities are formed in the initial design state for a long period of time. Therefore, the inventors also investigated the shape change of the minute unevenness due to the erosion of the plating bath components,
As a result of the investigation, it was found that it is effective to coat the roll surface, that is, the roll body having irregularities, with carbide, oxide, boride or their cermet material over the entire surface.

Here, a roll made of the SUS 304 stainless steel base material and having the above-described irregularities engraved thereon, and a WC-Co cermet material spray-coated on the surface of the roll with a WC-Co cermet material of 40 μm or more and less than 100 μm. These rolls were manufactured, and these rolls were immersed in a hot-dip galvanizing bath at 480 ° C. to examine changes in surface shape. As a result, in the above roll, the uneven portion was melted and disappeared after 5 to 10 hours due to the erosion of molten zinc on the SUS 304 stainless steel base material, whereas the roll had the initial shape after 800 hours. Had been maintained. Therefore, in order to maintain the effect of unevenness over a long period of time,
It is effective to provide a coating layer such as a WC-Co cermet material.

As described above, according to the present invention, the roll body of the sink roll used in the hot-dip metal plating bath is provided with regular or irregular asperities, and a roll of ceramics or the like which is more excellent in hot-dip resistance is provided here. By providing the coating layer, the effect of the unevenness can be maintained for a long period of time. Regarding the thickness of the coating layer, various thicknesses can be selected as long as the requirements for the height difference of the irregularities defined in the present invention are satisfied.

In the above-mentioned case, the case where the surface of the roll cylinder is formed with irregularities and then the WC-Co cermet material is spray-coated is described. However, this processing procedure may be reversed depending on the surface coating material. Of course. For example, when providing a metal oxide coating layer such as chromium oxide on the uneven surface, first apply a thermal spray coating on the roll cylinder to the required thickness, and then irradiate a laser beam to apply a fine particle within the range not exceeding the sprayed film thickness. The projections may be engraved, and if the fine projections exceed the thickness of the sprayed film, it is necessary to provide a measure such as partial respraying to the groove.

Further, the shape of the convex portion in the present invention is not limited to only those described above, and as shown in FIG. 3, a polygonal truncated cone, a truncated cone, a cylinder,
It goes without saying that an elliptic cylinder or a spherical zone can be used.

[0030]

【Example】

Example 1 In order to provide irregularities to the roll drum of a hot-dip galvanizing roll (13Cr stainless steel) having a diameter of 700 mm and a roll drum length of 1800 mm, one side at the bottom is 2.2 mm and the height is 0.7 mm.
(See FIG. 3b) was formed by cutting to have a density of 20 pieces per 1 cm ² . And the WC with a further thickness of 0.08 to 0.09 mm on the surface of the roll body of this roll
A coating layer of -12% Co cermet material was applied by thermal spraying.

About the roll obtained in this way,
When it was actually used in a hot-dip galvanizing bath at a temperature of 480 ° C, no groove mark was observed immediately after operation, and bath components, bath temperature, and plating required for initial conditioning (adjustment of plating conditions) were not observed. No tension adjustment of the steel strip was required at all, and it was confirmed that a plated steel sheet with excellent surface quality was obtained from the beginning of the operation. Therefore,
According to this roll, it was possible to omit the step of passing a dummy steel strip, which was conventionally indispensable at the start of operation of the plating apparatus, for 8 to 24 hours. Conventionally, in order to reduce the occurrence of groove marks, it was necessary to lower the tension of the steel strip more than usual. (This causes a slip of the steel strip and causes surface defects such as scratches on the plated steel strip. In the roll according to the present invention, generation of surface defects and meandering of the steel strip hardly occurred even when the tension was increased. In addition, when the roll was lifted out of the bath at the time of replacing peripheral equipment such as a roll shaft, the shape of the unevenness of the roll body was hardly changed. The roll was subsequently reused, but no adjustment of the operating conditions with the dummy strip was necessary. The roll surface was gradually worn out, and the roll surface could be used for a total of 50 days before affecting the plating quality.

The product type in this embodiment is a plated steel sheet for an automobile exterior, which is required to have a beautiful plated surface and a deep drawability, and has been used when such a steel sheet is targeted. The operating life of a conventional roll (having a V-shaped spiral groove with a depth of 1.5 mm, a width of 6 mm, and a pitch of 25 mm) as shown in FIG. The roll according to the above was able to extend the life by about 3.5 times. In addition, productivity was significantly improved by simplification of the steps in the early stage of the plating operation. In this example, the spiral groove (depth
For a roll having only 1.5 mm, a width of 6 mm and a pitch of 25 mm (V-shape), a steel strip is formed by forming the roll body of this roll (a flat portion sandwiched between spiral grooves) with irregularities as specified in the present invention. Investigations were made on the occurrence of groove marks and the life of the roll when processed. As a result, according to such a roll, although the occurrence of groove marks due to the spiral groove could be extremely reduced as compared to a roll provided with only the spiral groove, by the time the occurrence of such marks was completely avoided. Did not reach. The operating life of the roll was about 30 to 50 days. FIG. 6 shows a cross section of a main part of the roll used at this time.

Example 2 A roll body of a sink roll for hot-dip galvanizing (SUS304 austenitic stainless steel) having a diameter of 800 mm and a roll body length of 1800 mm was placed in a circular shape having a diameter of 1.5 mm and a height of 4.2 mm.
(See FIG. 3h) by spot welding so as to have a density of 16 pieces per 1 cm ² to provide irregularities, and furthermore, a thickness of 0.08 to 0.09 on the surface of the roll body including the pins.
A coating layer of WC-12% Co cermet material having a thickness of mm was formed by thermal spraying, and its use in a hot-dip galvanizing bath at a temperature of 480 ° C was investigated. As a result, the same good results as in Example 1 could be obtained.

Example 3 A roll body of a hot-dip galvanizing sink roll (made of SUS304 austenitic stainless steel) having a diameter of 800 mm and a roll body length of 1500 mm was placed on a bottom surface of a regular triangle having a side length of 2.5 mm and a height of 0.5 mm. Triangular truncated pyramids (see Fig. 3a) are engraved by laser beam processing so as to have a density of 16 pieces per 1 cm ^2, and irregularities are given.
Was investigated for its use in hot-dip galvanizing baths. As a result, the quality of the plated steel strip is not inferior to the quality of the plated steel strip, though slightly inferior in the roll life as compared with the case where the ceramic coating layer is provided on the surface of the roll body, and the same good results as in Example 1 are obtained. Was completed.

Example 4 A roll drum of a hot-dip galvanizing sink roll (made of 13Cr stainless steel) having a diameter of 700 mm and a roll drum length of 1800 mm was divided into three regions consisting of A, B and C having the following constitution. Then, the usage of each area in a hot-dip galvanizing bath (temperature 480 ° C) was investigated. Area A: 0.3 mm deep, 1.5 mm wide, 3 mm gap between each other, forming a U-shaped spiral groove B area: 1.5 mm deep, 6 mm wide, V-shaped spiral groove with a 25 mm gap between each other And a frustum of square pyramid (see Fig. 3b) formed on the flat part connecting the grooves with 2.2 mm on a side, 0.7 mm in height, and a density of 20 per 1 cm ² . No groove is provided, and only the same quadrangular pyramid as that of the area B is formed, and a thickness of 0.08
A coating layer made of WC-12% Co cermet material of ~ 0.09mm is formed by thermal spraying. As a result, when the rolling of the steel strip is performed through the area A, the roll is rolled on the steel strip surface immediately after operation. The groove shape was transferred as a non-uniform pattern (groove mark), and it took about 20 hours for this to disappear. On the other hand, when the rolling guide of the steel strip was performed through the region B, the generation of the groove mark due to the transfer of the groove shape was extremely reduced as compared with the case where the rolling guide was performed through the region A. The mark was not completely prevented.
On the other hand, when the rolling of the steel strip was guided through the region C, no groove mark was observed even immediately after the operation, and the surface of the steel strip after the plating treatment was extremely good. . The service life (hour) of each area is C
It was confirmed that the life in the C region, which satisfies the requirements defined in the present invention, is extremely long, with 60 days in the region, 14 days in the A region, and 5 days in the B region.

[0036]

According to the present invention, it is possible to maintain the dross discharge function without providing a spiral groove in the roll cylinder, and to perform a stable plating process without the risk of uneven color tone and uneven gloss due to groove marks. It can be performed.
Further, according to the present invention, the process in the initial stage of the plating operation can be simplified, so that the productivity can be remarkably improved, and the roll body is coated with carbide, oxide or boride or a cermet material thereof. By providing the layer, the service life (life) of the roll can be further extended.

[Brief description of the drawings]

FIG. 1 is a schematic view of a continuous hot-dip metal plating treatment apparatus for a steel strip.

FIGS. 2a and 2b are schematic diagrams showing a form of a spiral groove provided in a roll drum of a sink roll.

FIGS. 3a to 3l are views showing the shape of the flat surface and the side surface of the convex portion of the unevenness provided on the roll drum of the sink roll.

FIG. 4 is a diagram showing a main part of a roll according to the present invention.

FIG. 5 is a diagram showing a main part of a conventional roll.

FIG. 6 is a diagram illustrating a main part of a roll as a comparative example in which both a spiral groove and irregularities are provided on a roll cylinder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sink roll 2 Support roll 3 Hot-dip metal plating bath 4 Wiping nozzle 5 Touch roll 6 Steel strip 7 Snout

Claims (2)

(57) [Claims] A roll having no spiral groove for discharging dross, which guides the winding of a steel strip in a treatment tank filled with a plating solution. Height difference is 0.5
A roll for a plating bath , wherein irregularities having a flatness of 10 to 250 per cm ² are provided within a range of 5 to 5 mm and the tip of a convex portion is flattened. 2. A roll part or the entire surface of the body surface, carbides, oxides or borides or claim 1 Symbol placement plating bath rolls comprises a coating layer of cermet material.