JPS63195237A - Electrically conducting roll alloy for electroplating - Google Patents

Abstract

PURPOSE:To improve hardness and electro- and mechanical-corrosive wear resistance, by specifying the composition of 50Cr-50Ni alloy. CONSTITUTION:This alloy has a composition consisting of 40-55% Cr, 2-10% Mo, <=2% V, <=1% Si, <=1% Mn, <=10% Fe, <=0.1% C, <=0.2% N, and the balance Ni or a composition further containing, if necessary, one or more kinds among 0.5-2% Nb, 0.5-3% Ta, 0.1-1% Ti, and 0.1-1% Al, besides the above, and having the balance Ni. In the above composition, Mo is added by >=2% as it produces remarkable effects on the improvement in the corrosion resistance of a 50Cr-50Ni heat-ageing alloy, but the alloy is embrittled when its content exceeds 10%. Though V shows an intercrystalline shrinkage crack-preventing effect, embrittlement occurs when its content exceeds 2%. Fe is economically advantageous when mixed into the alloy, but it causes material deterioration when its content exceeds 10%. When Si content exceeds 1%, ductility after heat ageing and weldability are remarkably reduced. When Mn exceeds 1%, ductility is deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current-carrying roll alloy for electroplating that has excellent corrosion and wear resistance.

[Conventional technology]

The energized roll used for electroplating such as continuous electrogalvanization has a roll body (sleeve) as shown in Figure 5.
) At both ends of (10), roll ends (
20, 20) is fitted into the structure.

The steel plate to be plated is in contact with the surface of the roll body (10),
It is held between backup rolls and runs through the plating solution.

The body (10) of the current-carrying roll is subject to corrosion by a plating solution, which is a strongly acidic corrosive liquid, under current-carrying conditions.

The corrosion is not simple corrosion, but is galvanic corrosion that has a correlation with the amount of current applied, and as the amount of current applied increases, the amount of corrosion increases. Further, the roll body (10) is subjected to mechanical wear due to friction with the steel plate to be plated which contacts the surface thereof and passes through the plating solution. The body of the current-carrying roll develops roughness (irregularities and scratches) on its surface due to corrosive wear caused by the combination of current-carrying corrosion and mechanical wear. Corrosive wear on the surface of the roll body tends to occur particularly in areas where the current density is high and where the roll body contacts the edge of the plated steel sheet, and where the contact surface pressure caused by the backup roll is highest.

When roughness occurs on the body surface of the current-carrying roll due to corrosive wear, the flaws are transferred to the plating surface of the steel plate to be plated, causing deterioration in plating quality.

Therefore, the roll body must be resistant to galvanic corrosion and mechanical abrasion, and must be resistant to corrosive wear. Conventionally, austenitic stainless steel has been used as the material for the body. Some SO331
6 and Ni-Cr-M.

“Hastelloy C” is a Ni-based alloy, [Hastelloy C
-276J etc. have been used.

[Problem that the invention seeks to solve]

Recently, electroplating conditions have been changed from the conventional 10 to 15 KA to 4 KA due to demands for improved plating quality and productivity.
High current of 0~50KA, and plating solution with pH 1~
2 and a strongly acidic material are used, and the threading speed is 100 m.
There is a tendency for speeds to increase from around 150 to 200 m/min.

In response to these harsher plating conditions, energized rolls whose roll body is made of 5US316 austenitic stainless steel lack galvanic corrosion resistance in plating solutions, and their surface height is as low as Hs22, resulting in mechanical wear. It also has insufficient resistance to On the other hand, a current-carrying roll with a roll body made of Hastelloy C or Hastelloy C-276J has excellent current corrosion resistance against low pH plating solutions, and its surface height is also Hs25. ~28
Although the wear resistance is relatively high, it can sufficiently cope with recent high-speed transformation conditions, especially when it comes into contact with hard plated steel plates such as high-tensile strength plates (Hs: 25 to 35). I have a sexual problem.

For this reason, with conventional energized rolls, the surface of the body becomes rough due to corrosive wear in a short period of time, and the surface of the body must be re-polished frequently (for example, every 1 to 2 weeks).
It is necessary to spend a great deal of labor and cost on replacing the rolls and re-polishing them.

The present invention provides a current-carrying roll alloy having improved corrosion and wear resistance in order to solve the above-mentioned problems.

[Means and effects for solving the problems] The current-carrying roll alloy for electroplating of the present invention is made of 50Cr-5ON i
By focusing on the heat-age hardening properties of the alloy, and by devising its composition, it has a high hardness of Hs40 or higher, greatly increasing resistance to mechanical wear, and a high degree of galvanic corrosion comparable to conventional "Hastelloy" materials. It also has resistance.

The current-carrying roll alloy of the present invention has the following properties: Cr: 40-55%, Mo: 2-10%, v: 2% or less, Fe: 10% or less, Si: 1% or less, Mn: 1% or less, N1.2%. Hereinafter, C: 0.1% or less, the remainder substantially consists of Ni, and if desired, a part of Ni may be 0.5 to 2%.
% Nb, o, 5-3% Ta.

0, 1-1% (7) Ti% and 0.1-1% 0) Al
It has a chemical composition substituted with one or more elements selected from the following.

The current-carrying roll alloy of the present invention has a high hardness of Hs40 or higher due to its thermal age hardening properties, and exhibits resistance to mechanical wear that greatly exceeds that of conventional "Hastelloy" alloys. Also, its galvanic corrosion resistance is comparable to that of "Hastelloy" alloys. By combining this mechanical wear resistance and galvanic corrosion resistance, it has highly stable corrosion and wear resistance under the plating conditions of strong acidity with a pH of approximately 1, high current flow, and high speed plate passing. show.

The reasons for limiting the components of the current-carrying roll alloy of the present invention are as follows.

Cr: 40-55% Cr is precipitated as an α-Cr phase in the T-Ni matrix in the as-cast structure of the alloy of the present invention, and when aging heat treatment is applied, the α-Cr phase further forms the matrix. hardens the alloy. Figure 1 shows the Cr content and the hardness (Hs) of the alloy after aging heat treatment (700°C x 50 hours).
shows the relationship between As shown in the figure, if the Cr content is less than 40%, the age hardening ability is insufficient, so the Cr content is set to 40% or more.

Hardenability increases as the amount of Cr increases, but if it exceeds 55%, the alloy becomes significantly brittle, so the upper limit is set at 55%.

Mo: 2 to 10% Mo is extremely effective in improving the corrosion resistance of 50Cr-5ON i-based thermally aged alloys. In Figure 2, 50Cr -5ON
The relationship between the amount of Mo added and the corrosion resistance after thermal aging treatment (700°C x 50 hours) when Mo is added to an i-based alloy is shown. The vertical axis of the figure is the boiling 5% sulfuric acid corrosion test (soaking time: 24Hr).
) represents the corrosion rate (g/rd h). As shown in the figure, it can be seen that the corrosion resistance is significantly improved by adding 2% or more of Mo. However, if added in a large amount, intermetallic compounds such as Mo and Ni will form and the alloy will become extremely brittle, so the upper limit is set at 10%.

v: 2% or less The alloy of the present invention has a slow cooling rate after solidification in the casting process (
(approximately 0°C/min or less), Cr-N forms as a secondary precipitated phase from the α-Cr sum precipitated along macro grain boundaries.
An α-type solid solution of i-Moa element system or Cr-Ni-Mo-Nb quaternary system is likely to be formed, and this α-type solid solution has a Hv of about 6
00, which is extremely hard and brittle, and where the cooling rate is slow and the macrocrystalline grains are coarsened, intergranular cracks occur due to tensile stress generated on the outer surface during the casting solidification process or during subsequent heavy mechanical cutting.

(2) has the effect of suppressing the formation of the above α-type solid solution. That is, the addition of {circle around (2)} causes a phenomenon of refinement of the α-Cr phase, and this phenomenon prevents the α-Cr phase, which tends to precipitate along grain boundaries, from joining together. As a result, the formation of the α-type solid solution that is secondarily generated from the α-Cr phase is suppressed. The effect of preventing grain boundary cracking by suppressing the precipitation of this α-type solid solution can be obtained by adding a small amount of (2). The effect increases as the amount added increases, but the effect is approximately saturated when added at 2%. Furthermore, if added in excess of this amount, precipitation of carbides such as VC and resulting embrittlement will occur, so 2%
should be the upper limit. Preferably 0.4-0.7%
It is.

Fe: 10% or less Although Fe is not a necessary element for the alloy of the present invention,
Mixing up to % is allowed. It is economically advantageous to allow a relatively large amount of Fe to be mixed. However, if the mixed amount is too large, the corrosion resistance will deteriorate and the σ phase (Fe-Cr) will precipitate during thermal aging treatment, causing material deterioration, so the upper limit is set at 10%.

Si: 1% or less St is effective as a deoxidizing agent, and an amount of up to 1% is sufficient for this purpose. Moreover, if it exceeds 1%, the ductility and weldability after thermal aging will be significantly reduced.

Mn: 1% or less Mn is also effective as a deoxidizing agent like St, but the amount added for this purpose does not need to exceed 1%. Further, addition of more than 1% causes the formation of non-metallic inclusions such as MnS and the resulting decrease in ductility.

In the alloy of the present invention, if desired, a part of Ni may be Nb, Ta
% Al s Ti is substituted with one or more elements selected from Ti.

Nb: 0.5-2% Nb increases the ductility of the alloy by bonding with C, N, etc. and fixing these elements.

The presence of N has a large effect on ductility, so fixing N as Nb has a large effect on improving the ductility of heat-aged materials.
In addition, Nb combines with C present in the grain boundaries and stabilizes it, thereby exhibiting the effect of preventing hot cracking during welding and suppressing deterioration of corrosion resistance of the weld heat affected zone.

These effects are ensured by adding Nb in an amount of 0.5% or more, but the effects become substantially saturated when the amount exceeds 2%. In addition, excessive nitrides are formed and ductility deteriorates. Therefore, it is set at 0.5 to 2%.

Ta: 0.5-3% Ta has the same effect as Nb, and improves the ductility and weldability of the alloy by fixing C, N, etc. To obtain this effect, an addition of at least 0.5% is required. However, there is no need to add more than 3%;
Further, if more than this amount is added, ductility is impaired due to the formation of nitrides, so the upper limit is set at 3%.

Ti: 0.1-1% Ti is a strong deoxidizing element, and its deoxidizing action has the effect of improving the ductility of the alloy. The amount added for this purpose is 0.1% or more. However, if added in excess, ductility deteriorates due to the formation of nitrides and carbides, so the upper limit is set at 1%.

A/: 0.1 to 1% A/ is a strong deoxidizing element like Ti, and has the effect of improving the ductility of the alloy. For this purpose, a small amount (also 0.
1% addition is required, but if added in excess, Ni3
Since intermetallic compounds such as Affi are generated, which actually impairs ductility, etc., the upper limit is set at 1%.

C: 0.1% or less Since C is an element harmful to corrosion resistance, it is desirable that the content be small. In particular, in the alloy of the present invention, if the C content exceeds 0.1%, additive elements such as (1) and Nb tend to precipitate as carbides, reducing the effectiveness of these additive elements and reducing the alloy's performance. Ductility decreases. Therefore, Ci is 0.1
% or less.

N: 0.2% or less N is an unavoidable impurity that is mixed in during the alloy melting process due to the phenomenon of Cr absorbing N in the atmosphere. The amount of N mixed is 0.
If it exceeds 2%, a lamellar structure will appear significantly and the ductility and weldability of the alloy will deteriorate, so the upper limit is set at 0.2%.

Ni: remainder Ni, together with Cr, is a basic component of the alloy of the present invention.

Ni forms a dense passive film on the alloy surface and suppresses the rate of corrosion and dissolution in a plating solution, which is a strongly acidic etchant.

It also compensates for the brittle nature of Cr and imparts good ductility.

Figure 3 shows the relationship between the aging temperature and the hardness after aging of the alloy of the present invention (
Figure 4 shows the relationship between aging time and hardness after aging of the alloy of the present invention (however, aging temperature near 0).
0°C). The composition of the sample material is Cr:45
．． 4%, Mo: 2.7%, ■20.6%, Si: 0.3
%, Mn: 0.01%, Fe: 0.3%, C: 0.01
%, N: 0.11%, remainder: Ni. As shown, aging temperature: about 650-800℃, aging time: about 30H
An excellent thermal aging effect is achieved by aging treatment at a temperature of r or more, especially when the aging temperature is around 700℃ and the aging time is about 50H.
It can be seen that the best results are obtained for r or more.

When manufacturing the body (sleeve) of a current-carrying roll using the alloy of the present invention, the entire wall thickness may be made of the alloy of the present invention, but the wear resistance of the roll body and resistance to galvanic corrosion against plating solutions Since the problem is related to the outer surface of the roll body, the alloy of the present invention is applied only to the surface layer, and another suitable inexpensive material such as carbon steel is used for the inner layer, as shown in FIG. 5. The surface layer (11) and the inner layer (
The sleeve (10) may have a two-layer structure with the sleeve (12).

To give an example of the manufacturing process of an energized roll having a sleeve having a two-layer structure as the roll body, first, a hollow cylindrical body that will become the surface layer (11) of the sleeve is centrifugally cast using the alloy of the present invention, and the hollow cylindrical body is After primary rough machining is performed on the cylindrical body, thermal aging treatment is performed, and further secondary machining is performed. A sleeve (10) having a two-layer structure is obtained by shrink-fitting this to an inner layer member (12) which is a hollow cylindrical body made of a different material that has been separately 41 (1H).

The sleeve (10) has roll ends (2
0) By shrink-fitting (20) and reinforcing the strength of the body end by bolting (30) or welding, the desired current-carrying roll is completed.

〔Example〕

A galvanic corrosion test, a mechanical abrasion test, and a solidification cracking test were conducted on the thermally aged materials (700° C. x 50 hours) of each test specimen having the chemical composition shown in Table 1, and the results shown in the right column of the table were obtained.

In the table, incense (numbers) 1 to 12 are invention examples, and numbers 101 to 11
1 is a comparative example. Among the comparative examples, 101 is a material equivalent to "Hastelloy C", I'lh 102 is a material equivalent to 5US316 stainless steel (both are made of rolled plate material),
Further, llh 103 to 111 are examples in which the content of one of the elements (underlined in the table) deviates from the specifications of the present invention, although the alloys have a similar composition to the alloy of the present invention.

CI) Current-carrying corrosion test The actual operating conditions of the current-carrying roll were simulated, and the test piece [tested area: 1cal] was used as the cathode, and the anode (Pt) and During this period, a pulse current of IA is applied, and the corrosion weight loss of the test piece is measured after 24 hours.

[■] Wear test rotating wheel (SGP 100A (carbon steel), rotation speed 40
PPM) as the mating material, and a test piece (15x20x1
0, mm) with a load of 2 kg, and a plating solution (23 g/NHZSO4, 150 g/
4ZnSOn' 7Hz0,100g/1NazSOn
) to create a moist environment for 7 days (168Hr)
Measure the amount of wear (■) on the test piece after the test piece has passed.

(1) Solidification cracking test The surface of the test metal plate is preheated to 150 to 200°C, and the surface is remelted by generating arc discharge with a TXG welder. At this time, the arc current is at a voltage of 15
Control to ~17V/current 130-140A. After remelting for 10 seconds, the surface is covered with asbestos or the like and slowly cooled. After cooling, the surface is polished and the processed surface is inspected for cracks using a color check. This test evaluates castability, and in the table, "○" in the "Castability" column indicates no cracks, and "x" indicates cracks.

As shown in Table 1, the alloy of the present invention is different from the conventional material "
Hastelloy Cl (N[Llol), 5US316
The amount of mechanical wear under conditions of contact with the plating solution is significantly lower than that of the material (m102). In terms of corrosion resistance, it can be seen that the alloy of the present invention greatly exceeds the conventional material 5US316 [102] and has galvanic corrosion resistance comparable to [Hastelloy CJ (11h101)].

On the other hand, Comparative Examples m 103 to 111 have a composition similar to that of the alloy of the present invention, but because they lack one of the elements or have an excess or deficiency in the content, they have poor galvanic corrosion resistance or wear resistance. or there are problems with castability. For example, the steel 103 with insufficient Cr content has low hardness and poor wear resistance. The neck 104 containing excessive Cr has good galvanic corrosion resistance and wear resistance, but cracks occur during casting due to insufficient ductility. llh 105, which does not contain Mo, has no problems in wear resistance or castability, but has extremely poor galvanic corrosion resistance. On the other hand, if Mo is included excessively, the alloy becomes brittle, and solidification cracking cannot be avoided, as shown in Figure 106. ! 1h107 is F
This is an example containing an excessive amount of e, and although the wear resistance is good, the ductility is poor, and solidification cracking occurs. Also,
The amount of galvanic corrosion is also on the rise.

Although the neck 108 containing an excessive amount of C has good wear resistance, it suffers from significant galvanic corrosion and also suffers from solidification cracking due to lack of ductility. In addition, when Nb is included excessively (
It109), when Ta is contained excessively (caiio), and when V is contained excessively (ltllll), there is no problem in galvanic corrosion or wear resistance, but the occurrence of solidification cracking due to lack of ductility cannot be avoided.

〔Effect of the invention〕
Do.

The alloy of the present invention has excellent resistance to galvanic corrosion and abrasion against strongly acidic corrosive liquids. Therefore, a galvanized roll made of the alloy of the present invention as a material for the roll body is resistant to corrosion and abrasion during continuous electroplating operations. Furthermore, the occurrence of scratches and abrasion during the surface polishing process using a grindstone to remove plated metal adhering to the body surface is slight, and the surface maintains a smooth and beautiful surface quality for a long period of time. Therefore,
The frequency of roll replacement is reduced, the cost of re-polishing the rolls is reduced, stable continuous plating operations can be maintained, and the quality of plated products is stabilized and improved.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between Cr content and hardness, Figure 2 is a graph showing the relationship between Mo content and corrosion rate, Figure 3 is a graph showing the relationship between Mo content and corrosion rate,
FIG. 4 is a graph showing the relationship between aging treatment conditions and hardness after aging, and FIG. 5 is a partially sectional front view showing an example of an energized roll.

Claims (2)

[Claims] (1) Cr: 40-55%, Mo: 2-10%, V: 2
% or less, Si: 1% or less, Mn: 1% or less, Fe: 10
% or less, C: 0.1% or less, N: 0.2% or less, and the balance is substantially Ni. A current-carrying roll alloy for electroplating with excellent corrosion and wear resistance. (2) Cr: 40-55%, Mo: 2-10%, V: 2
% or less, Si: 1% or less, Mn: 1% or less, Fe: 10
% or less, C: 0.1% or less, N: 0.2% or less, and Nb: 0.5-2%, Ta: 0.5-3%, Ti: 0.
1% to 1%, Al: 0.1% to 1%, one or more kinds selected from Al: 0.1 to 1%, and the remainder substantially Ni, and has excellent corrosion and wear resistance.