ELECTROPLATING CONDUCTOR ROLL

Abstract

The purpose of the present invention is to provide an electroplating conductor roll with excellent high temperature abrasion resistance and corrosion resistance and excellent high temperature hardness. In an electroplating conductor roll, a composite carbide cermet-based thermally sprayed coating, which includes a composite carbide of WC and Cr.sub.3C.sub.2, and a ternary intermetallic compound binder metal of Cr, Ni and W, is formed on the surface of a metal roll. When the thermally sprayed coating is 100 mass %, the content of the composite carbide is 55-93 mass % and the content of the ternary intermetallic compound is 7-45 mass %. When the composite carbide is 100 mass %, the content of WC is 64-85 mass % and the content of Cr.sub.3C.sub.2 is 15-36 mass %.

Claims

1. A conductor roll for electroplating, comprising a composite carbide cermet-based thermally-sprayed coating formed on a surface of a metal roll, the composite carbide cermet-based thermally-sprayed coating including a composite carbide comprising WC and Cr.sub.3C.sub.2, and a ternary intermetallic compound comprising Cr, Ni, and W as a binder metal.

2. The conductor roll for electroplating according to claim 1, wherein, when the thermally-sprayed coating is 100 mass %, the composite carbide is contained in an amount of 55 to 93 mass %, and the ternary intermetallic compound is contained in an amount of 7 to 45 mass %.

3. The conductor roll for electroplating according to claim 1, wherein, when the composite carbide is 100 mass %, the WC is contained in an amount of 64 to 85 mass %, and the Cr.sub.3C.sub.2 is contained in an amount of 15 to 36 mass %.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0017] FIG. 1 is a schematic view of a vertical continuous electroplating cell.

[0018] FIG. 2 is a front partial cross-sectional view of a conductor roll.

DESCRIPTION OF EMBODIMENTS

[0019] FIG. 1 is a schematic view of a vertical continuous electroplating cell to which a conductor roll according to an embodiment of the present invention is applied. With reference to the drawing, plating tanks 11 are disposed in a multistage manner, and a plating solution M is stored in each of the plating tanks 11. It is noted that only one of the plating tanks 11 is illustrated in FIG. 1 for simplification of the drawing. The plating solution M may include any known plating solution such as a galvanizing solution and a tinning solution. A sink roll 12 is disposed to the plating tank 11. The conveyance direction of a metal strip S is changed from downward to upward by this sink roll 12. Also, a pair of electrode plates 13 is disposed upstream and downstream from the sink roll 12 in such a manner that a metal strip S is positioned between the pair of electrode plates 13.

[0020] A conductor roll 14 is disposed between the neighboring plating tanks 11. The conveyance direction of the metal strip S is changed from upward to downward by the conductor roll 14. Here, since the plating solution M adheres to the metal strip S exiting from the plating tank 11, the plating solution M adheres onto the roll surface of the conductor roll 14 when the metal strip S reaches the conductor roll 14.

[0021] A roll polisher 15 is disposed below each of the conductor rolls 14. The roll polisher 15 is driven between a contact position at which the roll polisher 15 is brought into contact with the conductor roll 14 and a spaced position at which the roll polisher 15 is spaced apart from the conductor roll 14. The movement of the roll polisher 15 to the contact position enables the roll polisher 15 to remove the plating solution M adhering to the conductor roll 14. At this time, the conductor roll 14 is subjected to sliding wear by coming in contact with the roll polisher 15. On the other hand, when the roll polisher 15 is in the spaced position, the conductor roll 14 is exposed to the corrosion environment due to the adhering plating solution M.

[0022] A positive electrode of an unillustrated DC power source is connected to the electrode plate 13, and a negative electrode thereof is connected to the conductor roll 14. These are applied with voltages to energize between the electrode plate 13 and the strip S. Thus, while the strip S passes through the plating tank 11, its surface can be continuously subjected to a plating treatment. However, the invention according to the present application can also be applied to a horizontal continuous electroplating cell in which the conductor roll 14 is constantly immersed in the plating solution M.

[0023] FIG. 2 is a front partial cross-sectional view of a conductor roll. A thermally-sprayed coating 12b is formed on the surface of a roll body 12a of the conductor roll 12. The thermally-sprayed coating 12b is constituted by a composite carbide cermet-based thermally-sprayed coating which includes a composite carbide containing WC and Cr.sub.3C.sub.2 and a ternary intermetallic compound containing Cr, Ni, and W.

[0024] The present inventor can form a thermally-sprayed coating with excellent denseness, high temperature wear resistance, and corrosion resistance to the plating solution M, by thermally spraying the ternary intermetallic compound containing Cr, Ni, and W together with the above-described composite carbide as described above.

[0025] Here, when the total amount of the thermally-sprayed coating 12b is assumed to be 100 mass %, the content of the composite carbide is preferably 55 to 93 mass %, and more preferably 82 to 90 mass %. The content of the ternary intermetallic compound is preferably 7 to 45 mass %, and more preferably 10 to 18 mass %.

[0026] When the content of the composite carbide is less than 55 mass % (that is, when the content of the ternary intermetallic compound exceeds 45 mass %), the contents of WC and/or Cr.sub.2C.sub.3 contained in the thermally-sprayed coating 12b become short. Accordingly, there is a risk that the high temperature wear resistance of the thermally-sprayed coating 12b may become insufficient.

[0027] When the content of the composite carbide exceeds 93 mass % (that is, when the content of the ternary intermetallic compound becomes less than 7 mass %), there is a risk that the denseness of the thermally-sprayed coating may decrease resulting in insufficient high temperature hardness. At the same time, corrosion resistance, particularly acid resistance, decreases. Here, when the denseness of the thermally-sprayed coating decreases, there are formed through pores which penetrate the thermally-sprayed coating in a coating thickness direction. The plating solution M entering from this through pores reaches the interface between the thermally-sprayed coating and the substrate. Accordingly, the thermally-sprayed coating becomes likely to be peeled from the substrate.

[0028] Also, when the total of the composite carbide is 100 mass %, the content of WC is preferably 64 to 85 mass %, and more preferably 75 to 82 mass %. When the total of the composite carbide is 100 mass %, the content of Cr.sub.2C.sub.3 is preferably 15 to 36 mass %, and more preferably 18 to 25 mass %. When the content of WC becomes less than 64 mass % (the content of Cr.sub.2C.sub.3 exceeds 36 mass %), the absolute amount of WC becomes short. Accordingly, there is a risk that the high temperature wear resistance of the thermally-sprayed coating 12b may become insufficient. When the content of WC exceeds 85 mass % (the content of Cr.sub.2C.sub.3 becomes less than 15 mass %, the absolute amount of Cr.sub.2C.sub.3 becomes short. Accordingly, there is a risk that the thermally-sprayed coating 12b may corrode in the plating solution M (particularly in an acidic plating solution).

[0029] Here, a thermal spraying material can be obtained as a spherical secondary particle by, for example, stirring and mixing in pure water a primary particle of the ternary intermetallic compound including Cr, Ni, and W and a primary particle of the composite carbide including WC and Cr.sub.3C.sub.2 to prepare a slurry, and granulating and sintering this slurry by a spray dryer method.

[0030] The ternary intermetallic compound may be a first ternary intermetallic compound having an atomic ratio of Cr:Ni:W=1.14:0.71:0.14, a second ternary intermetallic compound having an atomic ratio of Cr:Ni:W=2.5:9:1, or a third ternary intermetallic compound having an atomic ratio of Cr:Ni:W=4:15:1. Also, the ternary intermetallic compound may be a mixed ternary intermetallic compound including a mixture of these first, second, and third ternary intermetallic compounds.

[0031] The average particle size of the first particles of the ternary intermetallic compound and the composite carbide is preferably 1 to 15 m. The average particle size of the second particles of the ternary intermetallic compound and the composite carbide is preferably 15 to 55 m. Here, the average particle size refers to a median diameter calculated by a laser diffraction scattering measurement method.

[0032] The thermally-sprayed coating 12b is formed by spraying the above-described thermal spraying material onto the roll body 12a by a high velocity frame spraying method (HVOF). Thermal spraying by a high velocity frame spraying method enables the thermal spraying material to have a particle velocity of 500 m/min or more and a particle temperature of 1400 C. or higher. This allows the formation of a denser coating. In brief, since the thermal spraying material sprayed at high velocity is largely deformed to a flat shape when colliding with the roll body 12a, the dense thermally-sprayed coating 12b can be formed. Thus, there can be formed the thermally-sprayed coating 12b in which the composite carbide is dispersed in the binder metal including the ternary intermetallic compound.

[0033] In the present embodiment, Cr in a state of the chemically stable ternary intermetallic compound is sprayed onto the roll body 12a. Accordingly, oxide particles (fumes) including a Cr oxide as a main component are unlikely to be generated in the thermal spraying process. Thus, problems caused by the deposition of a Cr oxide inside and on the thermally-sprayed coating can be solved. That is, the reduction in hardness of the thermally-sprayed coating, the falling-off due to wear, the permeation of corrosive substances, and the like can be suppressed.

[0034] Hereinafter, the present invention will be more specifically described by illustrating examples.

First Example

[0035] In the first example, high temperature wear resistance, denseness, high temperature hardness, and corrosiveness were evaluated while changing the ratio between the composite carbide and the ternary intermetallic compound. The corrosiveness was evaluated on the basis of both acid resistance and alkali resistance. The ratio between WC and Cr.sub.3C.sub.2 constituting the composite carbide was defined to be WC:Cr.sub.3C.sub.2=75:25 in terms of mass %. As the ternary intermetallic compound, a mixed ternary intermetallic compound including a mixture of the first, second, and third ternary intermetallic compounds was used.

[0036] (High Temperature Wear Resistance Test)

[0037] As a tester, a friction and wear tester manufactured by Shinko Engineering Co., Ltd. was used. Three pins including SKD11 (5 mm in diameter15 mm) as a material were pressed against a thermally-sprayed surface of a thermally-sprayed test piece with a load of 10 kg. With these pins, the test piece was subjected to sliding wear under a temperature atmosphere of 400 C. for 6 hours in an identical circular orbit. Thereafter, a cross-sectional profile image was captured at 8 locations to calculate a wear loss.

[0038] The wear loss was defined to be a volume wear loss obtained by multiplying a wear cross-sectional area by a wear track circumference. The volume wear loss of less than 3 mm.sup.3 was evaluated as very good indicating extremely favorable high temperature wear resistance. The volume wear loss of 3 mm.sup.3 or more and 6 mm.sup.3 or less was evaluated as good indicating mostly favorable high temperature wear resistance. The volume wear loss of more than 6 mm.sup.3 was evaluated as poor indicating unfavorable high temperature wear resistance.

[0039] (Denseness)

[0040] A thermally-sprayed coating formed on a test piece was cut, and the cross section was polished. Thereafter, the structure of the thermally-sprayed coating was observed at X400 magnification through a metallurgical microscope to check the presence or absence of pores. When pores were not clearly observed, it was evaluated as very good indicating extremely favorable denseness. When pores were slightly observed, it was evaluated as good indicating mostly favorable denseness. When pores were largely observed, it was evaluated as poor indicating unfavorable denseness.

[0041] (High Temperature Hardness)

[0042] As a tester, a high temperature micro hardness tester QM manufactured by Nikon Corporation was used. A diamond indenter was pressed against a test piece including a thermally-sprayed coating under a temperature atmosphere of 400 C. with a load of 300 g to measure Vickers hardness. The Vickers hardness of more than 900 HV was evaluated as very good indicating extremely favorable high temperature hardness. The Vickers hardness of 700 HV or more and 900 HV or less was evaluated as good indicating mostly favorable high temperature hardness. The Vickers hardness of less than 700 HV was evaluated as poor indicating unfavorable high temperature hardness.

[0043] (Acid Resistance)

[0044] A test piece including a thermally-sprayed coating was immersed in an aqueous solution of 5 vol % sulfuric acid (H.sub.2SO.sub.4)-0.5 vol % nitric acid (HNO.sub.3) for 300 hours. Thereafter, acid resistance was evaluated on the basis of the damage of the thermally-sprayed coating and the elution of metal ions to the acid aqueous solution. The temperature of the aqueous solution of sulfuric acid (H.sub.2SO.sub.4) and nitric acid (HNO.sub.3) was set to 40 C. under air bubbling. The elution of metal ions was judged on the basis of the change in color of the solution and the ion concentration.

[0045] When the damage (cracking, peeling) of the thermally-sprayed coating was identified, it was evaluated as very poor indicating extremely unfavorable acid resistance. When there was no damage of the thermally-sprayed coating and the change in color of metal ions in the solution was identified, it was evaluated as poor indicating unfavorable acid resistance. When there were no damage of the thermally-sprayed coating and no change in color of the solution, but the ion concentration detected by an ICP emission spectrochemical analysis was 5 ppm or more, it was evaluated as good indicating favorable acid resistance. When there was no damage of the thermally-sprayed coating and the ion concentration detected by an ICP emission spectrochemical analysis was not 5 ppm or more, it was evaluated as very good indicating extremely favorable acid resistance.

[0046] (Alkali Resistance)

[0047] A test piece including a thermally-sprayed coating was immersed in a 10 mass % aqueous solution of sodium hydroxide (NaOH) for 300 hours. Thereafter, alkali resistance was evaluated on the basis of the damage of the thermally-sprayed coating and the elution of metal ions to the aqueous solution of sodium hydroxide (NaOH). The temperature of the aqueous solution of sodium hydroxide (NaOH) was set to 40 C.

[0048] The elution of metal ions was judged on the basis of the generation state of deposits. When the damage (cracking, peeling) of the thermally-sprayed coating was identified, it was evaluated as very poor indicating extremely unfavorable alkali resistance. When there was no damage of the thermally-sprayed coating and deposits were identified in the solution, it was evaluated as poor indicating unfavorable acid resistance. When there were no damage of the thermally-sprayed coating and no identified deposits, but the ion concentration detected by an ICP emission spectrochemical analysis was 5 ppm or more, it was evaluated as good indicating favorable alkali resistance. When there was no damage of the thermally-sprayed coating and the ion concentration detected by an ICP emission spectrochemical analysis was not 5 ppm or more, it was evaluated as very good indicating extremely favorable alkali resistance. Table 1 is a table summarizing the test results for high temperature wear resistance, denseness, high temperature hardness, and corrosion resistance.

TABLE-US-00001 TABLE 1 TERNARY HIGH INTER- TEMPERATURE HIGH COMPOSITE METALLIC WEAR TEMPERATURE ACID ALKALI CARBIDE COMPOUND RESISTANCE DENSENESS HARDNESS RESISTANCE RESISTANCE EXAMPLE 1 51 MASS % 49 MASS % poor very good very good very good very good EXAMPLE 2 55 MASS % 45 MASS % good very good very good very good very good EXAMPLE 3 62 MASS % 38 MASS % good very good very good very good very good EXAMPLE 4 78 MASS % 22 MASS % good very good very good very good very good EXAMPLE 5 82 MASS % 18 MASS % very good very good very good very good very good EXAMPLE 6 90 MASS % 10 MASS % very good very good very good very good very good EXAMPLE 7 93 MASS % 7 MASS % very good good good good good EXAMPLE 8 96 MASS % 4 MASS % very good poor poor very poor poor

[0049] In Example 1, the content of the composite carbide was less than 55 mass %. Therefore, the high temperature wear resistance was evaluated as poor. In Examples 2 to 4, the content of the composite carbide was not less than 55 mass % and less than 82 mass %. Therefore, the high temperature wear resistance was evaluated as good. In Examples 5 to 8, the content of the composite carbide was 82 mass % or more. Therefore, the high temperature wear resistance was evaluated as very good. In Examples 1 to 6, the ternary intermetallic compound was contained in an amount of 10 mass % or more. Therefore, the denseness, high temperature hardness, acid resistance, and alkali resistance were evaluated as very good. On the other hand, in Examples 7 and 8, the content of the ternary intermetallic compound was less than 10 mass %. Therefore, the evaluations for denseness, high temperature hardness, acid resistance, and alkali resistance were lowered. In particular, the evaluation for acid resistance was drastically lowered.

Second Example

[0050] In the second example, high temperature wear resistance and corrosiveness were evaluated while changing the ratio between WC and Cr.sub.3C.sub.2 contained in the composite carbide. The corrosiveness was evaluated on the basis of both acid resistance and alkali resistance. As the ternary intermetallic compound, the first ternary intermetallic compound was used. The ratio between the composite carbide and the ternary intermetallic compound was the same as Example 5. The test methods were the same as those in the first example. Table 2 is a table summarizing the test results.

TABLE-US-00002 TABLE 2 HIGH TEMPERATURE ACID ALKALI WC Cr.sub.3C.sub.2 WEAR RESISTANCE RESISTANCE RESISTANCE EXAMPLE 9 61 MASS % 39 MASS % poor very good very good EXAMPLE 10 64 MASS % 36 MASS % good very good very good EXAMPLE 11 70 MASS % 30 MASS % good very good very good EXAMPLE 12 75 MASS % 25 MASS % very good very good very good EXAMPLE 13 80 MASS % 20 MASS % very good very good very good EXAMPLE 14 82 MASS % 18 MASS % very good very good very good EXAMPLE 15 85 MASS % 15 MASS % very good good very good EXAMPLE 16 90 MASS % 10 MASS % very good poor very good

[0051] In Example 9, the content of WC was less than 64 mass %. Therefore, the high temperature wear resistance was evaluated as poor. In Examples 10 and 11, the content of WC was not less than 64 mass % and less than 75 mass %. Therefore, the high temperature wear resistance was evaluated as good. In Examples 12 to 16, the content of WC was 75 mass % or more. Therefore, the high temperature wear resistance was evaluated as very good. In Examples 9 to 14, Cr.sub.3C.sub.2 was contained in an amount of more than 15 mass %. Therefore, the acid resistance and alkali resistance were both evaluated as very good. In Examples 15 and 16, decreasing the content of Cr.sub.3C.sub.2 to 15 mass % lowered the evaluation for acid resistance to good, and decreasing to 10 mass % lowered the evaluation for acid resistance to poor. However, the evaluation for alkali resistance remained very good. It is considered that the alkali resistance was not lowered because the ternary intermetallic compound was contained in the thermally-sprayed coating.

Comparative Example

[0052] Comparative Examples 1 to 4 illustrated in Table 3 were evaluated for high temperature wear resistance, denseness, high temperature hardness, acid resistance, and alkali resistance. The evaluation methods were the same as those in the first example and the second example.

TABLE-US-00003 TABLE 3 HIGH TEMPERATURE HIGH ACID ALKALI COMPOSITE BINDER WEAR TEMPERATURE RESIS- RESIS- CARBIDE METAL RESISTANCE DENSENESS HARDNESS TANCE TANCE REMARKS COMPARATIVE WC + Cr.sub.3C.sub.2 Cr poor poor poor poor poor WC: EXAMPLE 1 (82 MASS %) (18 MASS %) Cr.sub.3C.sub.2 = 4:1 COMPARATIVE WC + Cr.sub.3C.sub.2 CrCo ALLOY poor poor poor poor poor WC: EXAMPLE 2 (82 MASS %) (18 MASS %) Cr.sub.3C.sub.2 = 4:1 COMPARATIVE WC + Cr.sub.3C.sub.2 CrNi ALLOY poor poor poor poor poor WC: EXAMPLE 3 (82 MASS %) (18 MASS %) Cr.sub.3C.sub.2 = 4:1 COMPARATIVE WC + Cr.sub.3C.sub.2 Ni poor poor poor very poor good WC: EXAMPLE 4 (93 MASS %) (7 MASS %) Cr.sub.3C.sub.2 = 73:20
For Comparative Examples 1 to 3, acid resistance and alkali resistance were evaluated as poor. It is considered that this is because a Cr oxide was generated in a thermal spraying heat source at high temperature. Also, for Comparative Example 4, acid resistance was evaluated as very poor, and alkali resistance was evaluated as good. It is considered that the inclusion of Ni in Comparative Example 4 inhibited corrosion under an alkali corrosive environment, but caused corrosion in the acid solution of sulfuric acid and nitric acid. For Comparative Examples 1 to 4, high temperature wear resistance, denseness, and high temperature hardness were evaluated as poor. It is considered that this is because a Cr oxide was generated in a thermal spraying heat source at high temperature.

REFERENCE SIGNS LIST

[0053] 11 plating tank [0054] 12 sink roll [0055] 13 electrode plate [0056] 14 conductor roll [0057] 15 roll polisher