JP2002180287A - CONDUCTOR ROLL FOR Cr-PLATING LINE AND ITS PRODUCTION METHOD - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductor roll which has excellent durability to a pitting corrosion by reverse-electrolytic treatment in a band steel Cr plating line and to a wear by high speed band steel carrying, and which can be inexpensively supplied and repaired. SOLUTION: By an inexpensive constitution of only forming the surface of the barrel part of the roll with a fusion coating of an Ni-Cr based alloy having a high Cr concentration of 25 to 45 mass% in a thickness of 500 to 2,000 μm, the above durability is secured, and further, the roll can repeatedly be used by inexpensive repair of only repolishing the coated layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention
The present invention relates to a conductor roll for supplying an electrolytic current to a steel strip in a plating line for plating, and to provide a technique for extending the life of the conductor roll.

[0002]

2. Description of the Related Art In the past, Sn-plated steel sheets (commonly known as tinplate) were mainly used as materials for cans and oil cans.
In recent years, inexpensive ultra-thin Cr-plated steel sheets (commonly known as tin-free steel = TFS) with excellent coating adhesion have become mainstream.

The Cr plating line that produces TFS includes:
Since the Cr plating is a plating with poor so-called “sticking around”, the concentration of current near the widthwise edge (edge) of the steel strip causes excessive deposition where the plating thickness becomes locally large. It is difficult to remove it mechanically because it is hard because of the deposits, and it is a method of removing the excess deposits by "reverse electrolytic treatment" with the anode polarity opposite to the cathode electrolytic treatment for plating. There is a unique situation that the plating surface is being processed. Thus, the anode electrolysis current for the reverse electrolysis treatment, and thus the anode supply current from the roll surface, also concentrates near the steel strip edge, and violently erodes the roll surface near this edge. Further, since the conveying speed of the steel strip in the line reaches a high speed exceeding 300 mpm (20 km / h), the roll is easily worn, and the wear near the steel strip edge where hard Cr is excessively deposited is particularly severe. For this reason,
The conductor roll of the Cr plating line is required to have particularly excellent corrosion resistance for power supply at the above-mentioned anode polarity and abrasion resistance for wear due to the high-speed steel strip conveyance. The corrosion resistance and the abrasion resistance are also important from the viewpoint of reducing bath contamination which increases the load of plating bath management.

[0004] Based on the above requirements, the corrosion resistance taking into account the anode polarity power supply should be first considered as the conductor roll of the Cr plating line, and a high corrosion resistance grade having excellent passivation characteristics so as to be able to respond as inexpensively as possible. Rolls made of austenitic stainless steel or rolls made of carbon steel roll base metal with industrial Cr plating have been used. However, in addition to the problem that the stainless steel roll has insufficient abrasion resistance, pitting occurs and Cr is concentrated and deposited in small projections on the activated pitting portion during plating. In addition, the life of the Cr-plated roll is controlled by the peeling of the plating caused by the network-like latent cracks specific to Cr-plating, and the abrasion resistance of the rolled steel strip is prominent. There was a problem that could not be solved, and improvement was desired. By the way, the repair after the conventional roll reaches the end of its service life is to completely eliminate the corrosion holes of the stainless steel roll or to flatten the base material surface of the Cr plating roll including the roughened plating peeling part. However, deep grinding and polishing are required, and expensive restoration with frequent replacement of essential parts of the base material has been required. Ni-Cr based self-fluxing alloy spraying was considered as a roll coating instead of Cr plating. However, as a result of a preliminary test using a currently used spraying material (JISH 8303, Cr concentration ≤ 20 mass%), a small amount of wear resistance was found. It was determined that only improvement could be expected.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is capable of meeting a high level of corrosion resistance required for a Cr plating line and having excellent wear resistance. An object of the present invention is to provide a conductor roll that can be supplied to and repaired.

[0006]

The conductor roll for a Cr plating line according to the present invention, which is a means for solving the above-mentioned problems, comprises a plating line for continuously performing Cr plating on a steel strip. A roll that performs cathode polarity power supply for electrodeposition and anode polarity power supply for reverse electrolytic treatment for refining the plating surface. Average Cr concentration is 25 ~ 45mass%
And a Ni-Cr-based alloy coating layer having a thickness of 500 to 2000 [mu] m is formed. In addition, the said limitation regarding the Cr concentration of a coating layer shall be regarding the Cr concentration of a coating material or a coating layer calculated | required by the analytical test method of JISH 8665-6.

In the above-mentioned roll of the present invention, in order to ensure the corrosion resistance associated with the above-mentioned anode polarity power supply, the roll has a high passivation property, which is a measure against anodic corrosion, so that the roll has a high passivation property. As the material of the working surface, that is, the outer peripheral surface of the body portion, is made of a Ni--Cr base alloy having a high Cr concentration, which is unprecedented for a conductor roll. The occurrence of projection Cr deposition is significantly reduced, and at the same time, due to the improved wear resistance, the skin roughness depth at the portion where the steel strip edge hits is also significantly reduced. For example, the roll used for 4 months has been reduced to at most about 300 μm. It can be restored to a reusable state just by cutting it. Moreover, since the above material specifications are realized by the technique of coating, the roll of the present invention can be supplied at low cost. Furthermore, by forming the above-mentioned coating in a form fused to the base material surface, there is no latent crack such as Cr plating, and the coating is integrated with the base material with a bonding force higher than that of Cr plating. Even if a coating with a thickness of 500 to 2000 μm is subjected to multiple re-polishing, the coating will not be damaged or peeled off. It has become possible. That is, the above problems have been solved by the above-described various improvements.

[0008]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, the Ni-Cr based alloy coating layer formed on the body of the roll has a Cr concentration of 25 mass%.
This is because the pitting corrosion resistance when the anode polarity power supply is performed in a Cr plating bath under the conditions corresponding to the specification of the reverse electrolysis treatment is highly stabilized before 25 mass%, and is improved. The pitting corrosion resistance increases with an increase in the Cr concentration, but the toughness of the coating decreases on the contrary. At a concentration exceeding 45 mass%, the coating layer breaks due to rolling contact with the steel strip under the high-speed steel strip transfer. There is a risk of loss. About 25-45ma
ss% is a preferable range of the Cr concentration. The thickness of the alloy coating layer is set to 500 μm or more from the viewpoint of cost performance and 2000 μm or less from the viewpoint of coating toughness, since the number of times of repolishing increases as the thickness increases.

As described above, the roll of the present invention has excellent abrasion resistance due to the high Cr alloy coating. In order to further improve the wear resistance in response to the trend toward higher speeds, WC, Cr ₃ C ₂ , TiC, Ti
Hard cermet hard ceramic was consolidated with Co or Ni, such as B _2, measures introduced into Ni-Cr based alloy coating is effective. However, the introduction of the above cermets in large quantities can lead to a decrease in toughness, so 50mass% (about 20vol%)
It is desirable to keep the following introduction.

Next, a method for producing the roll of the present invention will be described. The coating of the roll of the present invention obtained by fusing the Ni-Cr-based alloy is formed by spraying a mixed powder of a coating material having the above-described Cr concentration to form a sprayed layer, and then subjecting the sprayed layer to a re-melting process. Can be formed.

As a coating material, a Cr concentration of 10 to 20 mass
% Of self-fluxing alloy powder and Ni-
A mixed powder obtained by mixing a powder of a Cr-based alloy so as to obtain a desired Cr concentration is preferable. This is because a self-fluxing alloy having self-solubility is suitable for forming a fusion film, and a self-fluxing alloy having a high Cr concentration and a Cr concentration of 10 to 20% by mass is suitable for the present invention. This is because it is positive for orientation and easy to obtain. The Cr concentration is 30-50 mass
% Ni-Cr based alloy powder. 25-of the present invention
The Ni-Cr based alloy coating layer having a 45 mass% Cr concentration can be obtained by spraying a mixed powder obtained by mixing the above two kinds of powders at a mass ratio of 1: 9 to 3: 7. In addition, when it is desired to introduce a hard cermet into the coating, a hard cermet powder according to the amount to be introduced may be blended in the mixed powder.

[0012] Ni-C in the method of manufacturing the roll of the present invention
The method for forming the r-based alloy coating is not limited to the above-described spraying-remelting method. For example, the molten metal of the Ni-Cr-based alloy having a desired composition is directly applied to the outer peripheral surface of the body of the roll. Alternatively, the embodiment may be performed by directly casting and fusion-bonding.

(Example) <Roll base material> Material: S35C, body size: 610 mm diameter x 1220 mm length <Coating specification> (A) Ni-Cr based self-fluxing alloy powder having a Cr concentration of 15 mass% (JISH8303 / SFNi4 equivalent product) and a Ni—Cr-based alloy powder having a Cr concentration of 40 mass% were mixed at a mass ratio of 10:90 by thermal spraying and subjected to remelting treatment to form an average Cr concentration of 37.5 mass. % And N of 1500μm thickness
i-Cr based alloy coating. (B) A Ni-Cr-based self-fluxing alloy powder having a Cr concentration of 15 mass% (same as above), a Ni-Cr-based alloy powder having a Cr concentration of 40 mass%, and a WC-12 mass% Co hard cermet powder
The average Cr concentration of the metal phase formed by spraying the sprayed material mixed at a mass ratio of 0:70:54 and performing re-melting treatment is 32.5%.
WC cermet 35 mass% Ni-Cr base alloy coating with mass% and thickness 700 μm. <Evaluation method> Conductor roll coated with (A) above
(A) and the conductor roll (B) coated with (B),
The steel plate was produced by incorporating it into a Cr plating line (Surgent bath, 0.2-0.4mm thick strip steel, strip transfer speed 350mpm), and the wear of the rolls was investigated. <Results> ··· Situation after 4 months Roll (A): No coating peeling. Uneven wear was observed at the portion where the steel strip edge hit. The roll was restored to a reusable state by resharpening with a 250 μm shaving allowance. Roll (B): Uneven wear was not large at the portion where the steel strip edge hit, but slight surface roughness was observed over the entire surface. This roll could be repaired by regrind with a scraping allowance of 80 μm.

The above result that the roll of the present invention could be used only by shallow re-polishing that did not reach the base material surface even after 4 months of use was compared with the conventional stainless steel roll (SUS316) or Cr plating. Compared to the fact that the roll (plating thickness 100 µm) was used for about two months and the stainless steel roll itself or the steel roll base material required deep grinding and polishing due to the progress of pitting and plating peeling. The advantage of the roll of the present invention is clear.

[0015]

As described above, the conductor roll of the present invention has an unusually high N concentration on the outer peripheral surface of the roll body.
The inexpensive structure with only the fusion coating of the i-Cr base alloy achieves high corrosion resistance to the anode polarity power supply unique to the Cr plating line and high abrasion resistance to high-speed steel strip conveyance, and extends the service life until repair. It is more than twice as large as conventional stainless steel conductor rolls or Cr-plated conductor rolls. Moreover, since the coating is formed to a thickness suitable for repeated re-grinding and repairing, the coating layer can be formed without care of the roll base material surface each time, that is, while the roll base material can be used for several times longer than before. It enabled inexpensive repair of only re-grinding with only a small shaving allowance, resulting in a large reduction in roll costs.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 4/18 C23C 4/18 (72) Inventor Takashi Kogin 2-17 Tonomachi, Kawasaki-ku, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture No. 8 Daiichi High Frequency Industry Co., Ltd. Engineering Department (72) Inventor Satoru Midorikawa 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Chiba Works of Kawasaki Steel Corporation (72) Inventor Kei Yuki Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture No. 1 Kawasaki Steel Corporation Chiba Works (72) Inventor Yasufumi Yasufumi No. 1 Kawasakicho, Chuo-ku, Chiba-shi, Chiba Prefecture Kawasaki Steel Corporation Chiba Works F-term (reference) 4K024 AA02 AB01 BA03 CB10 4K031 AA02 AB02 AB08 CB10 CB13 CB22 CB30 FA02

Claims (3)

[Claims] In a plating line for continuously performing Cr plating on a steel strip, a reverse electrolytic treatment for removing excess deposits is performed on the steel strip in addition to a cathode polarity power supply for depositing Cr on the steel strip. For supplying polarity to the anode for welding, the average Cr of the metal phase fused to the surface of the base material on the body of the roll.
Ni-Cr with a concentration of 25-45 mass% and a thickness of 500-2000 μm
A conductor roll for a Cr plating line, wherein a base alloy coating layer is formed. 2. The method according to claim 1, wherein the hard cermet is blended in the Ni—Cr based alloy coating layer at a concentration of 50 mass% or less.
r Conductor roll for plating line. 3. The roll body has a Cr concentration of 10 to 20 mass%.
Ni-Cr based self-fluxing alloy powder and Cr concentration of 30-50 mass
% Of a Ni-Cr-based alloy powder is sprayed to form a sprayed layer, and the sprayed layer is subjected to remelting treatment to form a coating layer fused to the surface of the base material. C
Manufacturing method of conductor roll for r plating line.