JPS626756B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductor roll used for electroplating.

A conductor roll is installed in an electric plating line to contact the material to be plated and keep the potential of the material at zero. Conventionally, the roll surface is made of a metal with good conductivity, and during the line operation Part or all of the roll surface is immersed in plating liquid.

Next, a conductor roll for an electroplating line for plating steel strip with tin will be explained as an example.

Conventionally, conductor rolls for electroplating have been used by plating the roll base with chromium and polishing the roll surface to a roughness of about Ra 2.5 to 3.5 μm. However, the surface of the roll is corroded by the highly corrosive halogen plating liquid in the plater section of the electroplating line, and the surface is abraded by contact with the steel strip surface. As shown in the figure, the roughness gradually decreases. If the roll surface becomes corroded and its roughness deteriorates, it becomes easier for tin to be deposited on the roll surface or for foreign matter to adhere to it.
As shown in FIG. 2, more and more dens occur.

Next, the mechanism of the occurrence of DENT will be explained. Taking a commonly used conductor roll plated with chromium as an example, the chrome plating layer of the roll is eroded by the plating solution and becomes thinner due to contact with the steel strip after a while after the start of use. As shown in FIG. 3, fine cracks or pinholes 5 are formed in the chrome plating layer 3, which is a good conductor, on the outer periphery of the roll base 1, and the plating liquid penetrates into these parts 5, and the tin 7 is transferred to the roll base 1, which has a zero potential. Electrodeposited tin 7 gradually grows in the cracks or pinholes 5, and eventually rises on the surface of the chrome plating layer 3 and becomes visually visible, forming protrusions called dents 9.

As shown in Fig. 2, these dents 9 occur frequently as the roll usage time progresses, causing surface flaws in the tin plating and worsening the product yield, so the lifespan of the chrome plating conductor roll is approximately 3 The disadvantage is that it is only ~4 weeks old.

An object of the present invention is to provide a conductor roll that solves the drawback that the life span of the conductor roll is short, and by providing a conductor roll according to the claims of the present invention. , the object of the present invention can be achieved.

Next, the present invention will be explained in detail.

The present inventors believed that the following two points should be kept in mind in order to reduce the dents that occur on the conductor roll in the plater section of the electro-tinning line.

(a) The roll surface is configured so that it is difficult for tin to be electrodeposited, and even if tin is electrodeposited, the electrodeposited tin is easily peeled off.

(b) Reduce the active area or current-carrying area of the roll surface.

In other words, when looking at the roll surface locally, the electrically active surface, which is the part where the metal is exposed on the roll surface, is not in constant contact with the material to be plated, and the contact only occurs once the roll rotates. It is only for a short period of time, and even though it may seem like they are in contact, they may not be in electrical contact, so tin is likely to be electrodeposited on this part. Therefore, as this active area becomes larger, the probability that Dents will occur there increases. However, from a macroscopic point of view, a certain amount of conductive area is necessary for the function of the conductor roll. Therefore, it is desirable to have a shape in which a large number of small current-carrying portions are uniformly distributed on the roll surface. On the other hand, the rotation of the roll is
Since it is 200R.PM, it will apparently contact the steel strip to be plated approximately 5 million times or more in 20 days, so sufficient durability is required to maintain the correct roll surface condition.

In order to achieve the above requirements, the present inventors thought that the following conductor roll could be used. That is, after forming fine irregularities on the outer periphery of the roll base, which is the source of the shape and strength of the conductor roll, finer irregularities are added to the roll base coated with a wear-resistant coating made of a good conductor. A conductor layer is formed, and then the surface of the poor conductor layer is polished to expose the top surface of the convex portion of the good conductor, and the bad conductor layer is left in the concave portion of the good conductor. Conductor roll.

The roll base may be the roll base itself made of a good conductor.

In this conductor roll, the poor conductor surface covering almost the entire surface of the completed roll satisfies the requirements of item (a) above and resists wear, and the top surface of the convex portion of the good conductor becomes an effective active surface. The present invention has been completed because it satisfies the requirements in item (b) and constitutes an effective conductor roll.

The invention will be explained with reference to the drawings.

FIG. 4 is an enlarged sectional view of a portion where the steel strip 11 and the conductor roll of the present invention are in contact.
After forming fine irregularities on the outer circumference of the roll base 1, which is the source of the shape and strength of the conductor roll,
It is covered with a good conductor 13 to form a roll base. After rough polishing is applied to the surface of the roll base to form fine irregularities with a roughness of about Ra0.1 to 7 μm, a defective conductor layer 15 is formed on the entire coarsely polished surface. Next, the surface of the bad conductor layer 15 is polished so that the top surface 17 of the convex portion of the good conductor 13 is exposed. At this time, the defective conductor layer 15 remains in the recessed portion of the good conductor 13. Therefore, the steel strip 11 is supported by the polished surface of the defective conductor layer 15 and the top surface 17 of the convex portion.

The surface of the conductive layer 15 with poor abrasion resistance on the roll surface prevents tin from being electrodeposited, and even if tin is electrodeposited, the electrodeposited tin is easily peeled off. Since the releasability of tin in this part is better than that of the adjacent electrically active convex tip surface 17, the tin electrodeposited on this surface 17 can be easily peeled off before it grows and becomes a DENT. Resulting in. Furthermore, as is clear from the processing procedure described above, the active surface 17 has a large number of narrow surfaces 17 scattered on the roll surface on average and has a small area, so that the electrodeposited tin does not grow into dents. The narrow active surface 17 is in contact with the steel strip 11 and conducts electricity, so it should be worn away, but the poor conductor layer 15 surrounding the surface 17 is in contact with the steel strip 11 and the poor conductor layer 15 The abrasion resistance of protects the active surface 17 from abrasion. In addition, since the large number of active narrow surfaces 17 are uniformly scattered over the entire surface of the roll, the arc spots that conventionally occur locally while the steel strip 11 passes through the plating tank are reduced, and the roll Electrolytic corrosion on the surface can also be reduced.

Next, examples of the present invention will be shown.

Example: Approximately 35% WC, which has excellent wear resistance and corrosion resistance, is applied to the surface of the roll base, which is the source of the conductor roll.
An alloy consisting of about 40% Ni, 11% Cr, and the balance Fe is melted and coated to a thickness of about 1 mm, and the roll surface is roughly polished to a roughness of Ra 2.5 to 3.5 μm.
Added fine irregularities. Covering the entire uneven surface with a thin electrically conductive layer and subsequent processing are as follows:
We used the following two methods.

A roll: The roughly polished alloy coating on the roll surface is heated to form an oxide film with a thickness of several μm to several tens of μm on the entire surface, and then this is polished to coat the surface with fine metal with a diameter of 2 to 3 μm or less. The roll was made with many exposed surfaces.

B roll: Ceramics whose main component is chromium oxide is thinly coated in a molten state on the roughly polished alloy coating on the roll surface, and then the coated surface is polished, so that many fine metal surfaces of the alloy are formed on the polished surface. Dotted with exposed rolls.

When the above A and B rolls were attached to a halogen electric tinning line and put into practical use, the A and B rolls were replaced every 3 to 4 weeks as described above, whereas the conventional chrome plating rolls had to be replaced every 3 to 4 weeks. It is still in a fully usable condition even after more than two months have passed since it was first used.

For both A and B rolls, the part of the surface that is not electrically active is metal oxide (alloy oxide for A roll, ceramic for B roll), so it is in a state close to metallic bond with the base alloy. It is thought that they are strongly connected. Therefore, although these oxides are very thin, with a thickness of 1 μm or less and a thickness of several μm, it can be estimated that they can sufficiently withstand vibrations during roll operation and external forces caused by contact with the steel strip.

Although oxides of metals, including ceramics, are themselves poor conductors, it is thought that some of them are not completely oxidized and are close to remaining metals, so from a macroscopic perspective, If you look at it, it cannot be said that it is a completely bad conductor. However, the activity is lower than that of pure metal, and it has been experimentally confirmed that electrodeposited tin has good removability.

As described above, when the conductor roll for electroplating of the present invention is used in a tin plating line, it not only has a long life, but also has fewer dents and arc spots on the plating surface, improving product quality, and making it easier to replace the conductor roll. The line stop is also reduced, making it extremely effective for tin plating lines. The roll of the present invention is not limited to use in tin plating lines, but can also be applied to conductor rolls for other metal plating lines.

[Brief explanation of the drawing]

Figure 1 shows the Ra of the surface of a conventional conductor roll.
A diagram showing the relationship between changes in roughness and the date and time after the start of use of the roll. Figure 2 is a diagram showing the relationship between the number of dens occurrences of a conventional conductor roll and the date and time after the start of use of the roll. FIG. 4 is an explanatory view of the relationship between corrosion of the chrome plated roll and dents, and FIG. 4 is an enlarged sectional view of the portion where the conductor roll of the present invention is in contact with the steel strip. 1... Roll base, 3... Chrome plating layer, 5
... Cracks or pinholes, 7... Electroplated tin, 9...
... Denz, 11... Steel strip, 13... Good conductor, 1
5...Poor conductor layer, 17...Active surface at the top surface of the convex portion.

Claims (1)

[Claims] 1. A conductor roll for electroplating, comprising:
After providing fine irregularities on the surface of the roll base made of a good conductor, a thin bad conductor layer is further formed on the entire surface, and then the surface of the bad conductor layer is polished to improve the quality of the good conductor. 1. A conductor roll for electroplating, characterized in that the top surface of the convex portion is exposed, and a poor conductive layer remains in the concave portion of the good conductor. 2. The roll according to claim 1, wherein the roll base is a roll base having fine irregularities formed on the surface of the roll base and then further coated with a wear-resistant coating made of a good conductor. roll. 3. The roll according to claim 1, wherein the roll material is the roll material of the roll base itself made of a good electrical conductor. 4. In the roll according to claim 1 or 2, the good electrical conductor of the roll base comprises about 35% WC, about 40% Ni, about 11% Cr, which is thermally sprayed on the roll base surface. A roll characterized by being made of an alloy with the remainder being Fe. 5. In the roll according to any one of claims 1 to 4, the fine irregularities imparted to the good conductor have Ra0.1 to
A roll characterized by a roughness of 7 μm. 6. In the roll according to any one of claims 1, 2, and 4, the thin defective conductor formed on the entire uneven surface is thermally sprayed on the surface of the roll base. An oxide film is formed on the surface of the alloy when the alloy is heated. 7. In the roll according to any one of claims 1 to 3, the thin defective conductor formed over the entire uneven surface is formed by melting ceramics whose main component is chromium oxide. . A roll characterized in that the uneven surface of the roll is thinly coated.