JPH0332622B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a current-carrying roll alloy for electroplating that has excellent wear resistance and corrosion resistance. [Prior Art] Current-carrying rolls used for electroplating such as continuous electrogalvanizing have corrosion resistance to plating solutions (for example, pH 1 to 2), which are strong acid solutions, and the ability to operate continuously in plating solutions. It must have friction resistance that can withstand friction with the running plated steel plate (threading material). As shown in FIG. 5, the current-carrying roll basically consists of a sleeve 10 that forms the roll body, and roll ends 2 that are power supply members that are fitted and fixed to both ends of the sleeve 10.
0, and the threading material contacts the circumferential surface of the sleeve 10. Hitherto, the sleeve (body) component material has been commonly used, such as "Hyteroy C", which is a Ni-Cr-Mo based nickel-based alloy, or SUS316, which is an austenitic stainless steel. [Problems to be solved by the invention] Although the energized roll made of the above-mentioned "Hyteroy C" as a sleeve material has excellent corrosion resistance, it has low hardness.
Hs: Low at around 25 to 30, causing problems in wear resistance. In particular, threading materials with high surface hardness (hardness Hs: approx. 25 to 35) such as high-strength steel plates are used at high speeds (for example, 150
Under plating conditions in which the sleeve travels at speeds of up to 180 m/min), flaws are likely to form on the sleeve surface, especially on the part where the edges of the threaded material come into contact. In addition, an energized roll whose sleeve material is made of austenitic stainless steel such as SUS316 has insufficient wear resistance and corrosion resistance, and is subject to flaws due to wear and surface roughness due to corrosion. For this reason, conventional current-carrying rolls have a short service life and require re-polishing of the sleeve surface within a very short period of time (approximately 10 to 30 days). Therefore, the energizing roll must be replaced frequently, and its maintenance requires a large amount of cost. The present invention provides a current-carrying roll alloy having improved wear resistance and corrosion 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 contains: Cr: 40 to 55%, Mo: 2 to 10%, C: 0.1% or less, Si: 1% or less, Mn: 1% or less, Fe: 10% or less, N: 0.2% or less, and Nb: 0.5 to 2%,
Ta: Contains one or two selected from 0.5 to 3% of two elements, and the total amount of Nb and Ta satisfies the following formula: 0.5Nb [%] + 0.3 Ta [%] ≦ 1 [%] However, the remainder consists essentially of Ni, and if desired, 1% of Ti: 0.1-1%, Al: 0.1-1%.
It has a composition in which a portion of Ni is replaced with one or two types of elements. The alloy for current-carrying rolls of the present invention has a 50Cr-50Ni alloy as its basic component, which maintains high wear resistance due to its thermal age hardening properties, and has a high degree of corrosion resistance when energized in a strongly acidic corrosive environment by adding an appropriate amount of Mo. Addition of elements such as Nb and Ta ensures good weldability for overlay welding to ensure resistance and repair surface damage caused by arc spots etc. during actual use of current-carrying rolls. At the same time, it is possible to prevent deterioration of corrosion resistance due to welding and maintain a healthy surface condition over a long period of time. The reasons for limiting the components of the current-carrying roll alloy of the present invention are as follows. Cr: 40-55% Cr is γ in the as-cast structure of the alloy of the present invention.
-The α-Cr phase precipitates in the Ni matrix, and when aging heat treatment is applied, the α-Cr phase further precipitates in the matrix and hardens the alloy. In Figure 1,
The relationship between the Cr content and the hardness (Hs) of the alloy after aging heat treatment (700°C to 50 hours) is shown. As shown in the figure, if the Cr content is less than 40%, the age hardenability is low, so the Cr content is set to 40% or more. Hardening ability increases as the amount of Cr increases, but when it exceeds 55%,
The upper limit is set at 55% since the alloy becomes significantly brittle. Mo: 2 to 10% Mo has a remarkable effect on improving the corrosion resistance of 50Cr-50Ni-based thermally aged alloys. Figure 2 shows 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 a 50Cr-50Ni alloy. The vertical axis of the figure is the boiling 5% sulfuric acid corrosion test (immersion time:
It represents the corrosion rate (g/m ² h) in 24 hours). As shown in the figure, it can be seen that corrosion resistance is significantly improved by adding 2% or more of Mo. In 50Cr-50Ni alloys, when thermal aging treatment is applied, Cr precipitates and becomes active, so Cr
However, by adding Mo, the unstable passive film is stabilized and the original high corrosion resistance of this alloy is maintained. It is considered that This effect of Mo addition increases as the amount added increases, but when added in a large amount, (Mo _x Ni _y ) Cr ₂
The upper limit is set at 10% because the alloy becomes extremely brittle with the formation of intermetallic compounds such as. C: 0.1% or less Since C is an element harmful to corrosion resistance, it is desirable to have a small amount. In particular, in the alloy of the present invention, C
When the amount exceeds 0.1%, additive elements such as Nb tend to precipitate as carbides, reducing the effectiveness of these additive elements and reducing the ductility of the alloy. Therefore, the amount of C should be 0.1% or less. Si: 1% or less Si 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. Therefore, the upper limit is set at 1%. Mn: 1% or less Mn is also effective as a deoxidizing agent like Si, but
Therefore, the amount added need not exceed 1%. In addition, addition of more than 1% causes the formation of nonmetallic inclusions such as MnS and a decrease in ductility due to this.
The upper limit is 1%. Fe: 10% or less Fe is not a necessary element for the alloy of the present invention, but its presence in an amount up to 10% is allowed. It is economically advantageous to allow a relatively large amount of Fe to be mixed. However, if the amount of mixture becomes too large,
Corrosion resistance deteriorates, and Fe-
Material deterioration due to the precipitation of Cr compounds, the so-called σ phase, cannot be avoided, but such problems will not occur if the amount is 10% or less. N: 0.2% or less If the amount of N exceeds 0.2%, 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%. N is an unavoidable impurity that is introduced from the atmosphere during the alloy melting process, especially due to the N absorption effect of Cr. However, by adopting a reduced pressure melting process such as vacuum melting,
The amount of contamination can be significantly reduced. Furthermore, even in the atmospheric dissolution process, the content can be suppressed to about 0.1 to 0.15% by controlling the operating conditions. Ni: balance Ni is a basic component of the alloy of the present invention together with Cr.
Ni forms a dense passive film on the alloy surface, suppressing the rate of corrosion and dissolution in plating liquids, which are strongly acidic corrosive liquids, and also compensates for the brittle nature of Cr, giving it good ductility. Nb: 0.5-2% Nb combines with C and N dissolved in the alloy matrix, and by fixing these, increases the ductility of the alloy. In particular, the effect of improving ductility by fixing N is large. This ductility improvement effect makes it easier to release thermal stress during welding (such as overlay welding to repair surface damage caused by arc spots on the roll body), and prevents cracks from occurring due to thermal stress in the weld and its vicinity. It becomes possible to prevent suppression. In addition, stabilizing solid solution C by combining with Nb not only contributes to improving corrosion resistance, but also prevents hot cracking during welding, and furthermore suppresses deterioration in corrosion resistance of the weld heat affected zone. The prevention effect makes it possible to guarantee high corrosion resistance after welding. These effects are ensured by adding 0.5% or more of Nb, and are enhanced as the amount added increases, but 2
%, the effect is almost saturated and excessive nitrides are produced, resulting in deterioration of ductility. Therefore, 0.5~
2%. Ta: 0.5-3% Ta is an element that has the same effects as Nb, improving ductility and ensuring good weldability by fixing C and N, and preventing a decrease in corrosion resistance of the weld heat affected zone. It is added for such purposes. To obtain this effect, it is necessary to add at least 0.5%, and the effect increases as the amount added increases. However, it is not necessary to add more than 3%, and since adding more than that will cause deterioration in ductility etc. due to the formation of nitrides, the upper limit is set at 3%. The above-mentioned Nb and Ta may be added singly, or both elements may be added in combination. When adding both in combination, the total amount [0.5Nb (%)
+0.3Ta (%)] is specified as 1 (%) because if it exceeds it, the ductility will decrease and the effect of preventing cracking during welding cannot be ensured. In addition to the above-mentioned elements, the alloy of the present invention may optionally contain one or both of Ti and Al. Ti: 0.1-1% Ti is a strong deoxidizing element and has the effect of reducing the amount of oxygen mixed in during alloy melting and improving the ductility of the alloy. Its ductility improvement effect facilitates the release of thermal stress during welding and increases resistance to cracking caused by welding. The amount of addition necessary 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%. Al: 0.1-1% Al is added for the same purpose as Ti, and its strong deoxidizing effect reduces the oxygen content of the alloy, increases the ductility of the alloy, and, like Ti, helps prevent cracking during welding. Effective. For this purpose, it is necessary to add at least 0.1%, but if excessively added, intermetallic compounds such as Ni ₃ Al will be generated, which will actually impair ductility, etc., so the upper limit is set at 1%. . Figure 3 shows the relationship between aging temperature and hardness after aging of the alloy of the present invention (however, aging time: 50Hr), and Figure 4 shows the relationship between aging time and hardness after aging of the alloy of the present invention (however, aging time: 50Hr). Temperature: 700℃). The composition of the joint sample material is Cr: 46.0%, Mo: 2.7%, C: 0.02
%, Si: 0.3%, Mn: 0.01%, Fe: 0.3%, N:
0.11%, remainder: Ni. As shown in the figure, an excellent thermal aging effect is achieved by aging treatment at an aging temperature of about 650 to 800℃ and an aging time of about 30Hr or more, and is especially best when the aging temperature is around 700℃ and the aging time is about 50Hr or more. It can be seen that the following results can be obtained. 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; Since the problem is related to the outer surface of
For example, by using carbon steel or the like, a sleeve 10 having a double structure of a surface layer 11 and an inner layer 12 as shown in FIG. 5 can be obtained. To give an example of the manufacturing process of a sleeve having a two-layer structure, 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 subjected to primary rough machining. Afterwards, heat aging treatment is performed and secondary machining is performed. This is shrink-fitted into a hollow cylindrical body as the inner layer part 12 made of a different kind of material prepared separately, and the appropriate part of the joint is welded W1.
By doing so, a sleeve 10 having a two-layer structure is obtained.
Roll ends 2 are attached to the openings at both ends of the sleeve 10.
By shrink-fitting 0 and 20 and welding W2 at appropriate locations at the joint, the desired current-carrying roll is completed. In addition, during actual use, the energized roll often suffers damage from arc spots on its body surface (approximately 1 inch in diameter).
Since flaws of about 3 mm or band-like flaws extending in the circumferential direction occur, weld overlay is applied in an appropriate manner to repair the surface. When performing overlay welding repair on the body surface of an energized roll to which the alloy of the present invention is applied, if the repair area is extremely small, such as a dot-shaped flaw, the overlay material should not be applied to the body base material ( It is acceptable to use a material different from the alloy of the present invention (e.g., Hastelloy C alloy), but if the surface damage is over a relatively wide area, such as a band-like flaw, the corrosion and wear resistance of the welded repair part may be lower than the roll. Since this has a substantial effect on the service life, it is better to carry out weld overlay repair using the same metal as the overlay material (the same alloy as the body base material made of the alloy of the present invention).In the overlay weld repair,
It is possible to achieve sound weld repair without cracking or deterioration of the corrosion resistance of the weld heat affected zone. [Example] Corrosion tests, abrasion tests, weldability tests, and weld heat-affected zone corrosion tests were conducted on heat-aged materials (700°C to 50Hr) of each test metal having the chemical composition shown in Table 1. The results shown in the right column of the table were obtained. In the table, trial numbers (No.) 1 to 13 are invention examples, and No. 101 to 113.
is a comparative example. Among the comparative examples, No. 101 is a material equivalent to "Hastelloy C", No. 102 is a material equivalent to SUS316 stainless steel (both are made of rolled plate material),
Nos. 103 to 113 have a similar composition to the alloy of the present invention, but either lack one of the elements or the content (underlined in the table) deviates from the specifications of the present invention. This is an example. [] Corrosion test Simulates the actual usage conditions of energized rolls,
As shown in Figure 6, strongly acidic corrosive liquid a [23
g/H ₂ SO ₄ , liquid temperature 55°C), test piece T1
[Test area: 1 cm ² ] is used as a cathode, and a pulse current of 1 A is applied between it and the anode Pt as shown in the figure, and the corrosion loss of the test piece is measured after 24 hours.
The reason why we decided to conduct the corrosion test by applying a pulsed current is that by applying a pulsed current, we can simulate the actual usage condition of the energized roll (the circumferential surface of the roll is held at the zenith of the circumferential surface as the roll rotates). This is because test results with a good correlation with corrosion on coated steel plates (where contact and separation are repeated continuously) can be obtained. [] Wear test As shown in Figure 7, rotating wheel b [SGP100A
(carbon steel), rotation speed 40 RPM] as the mating material,
Test piece T2 [15 x 20 x 10, mm] was pressed against this with a load of 2 kg, and the contact area was filled with plating liquid C [23 g/H ₂ SO ₄ , 150 g/ZnSO ₄ 7H ₂ O,
100g/NaSO ₄ ] to create a moist environment, and after 7 days (168Hr) have passed, the amount of wear (mg) of the test piece is measured. [] Weldability test As shown in Figure 8, a test specimen T3 with a recess d [diameter d: 10 mm, center depth h: 6 mm] formed on the surface was welded using the TIG welding method ( However, due to the current: 130A, voltage: 15V, and no preheating of the base metal, the build-up layer e of "Hastelloy C" alloy
(same figure), the surface of the build-up layer e is smoothed by machining (same figure), and after surface polishing, a color check is performed to evaluate the repair weldability of the roll surface based on the presence or absence of cracks. do.
In the table, "〇" in the "Weldability" column indicates good weldability (no cracks), and "×" indicates poor weldability (with cracks).
represents. [] Corrosion test after welding Instead of "Hastelloy C" alloy as overlay material,
A build-up layer was formed under the same conditions as the weldability test in [] above, except that an alloy with the same composition as the test piece (base metal) was used, and it was subjected to the same corrosion test as in [] above. and weld heat affected zone (HAZ)
The corrosion weight loss was determined. As shown in Table 1, the alloy of the present invention has a higher resistance to contact with plating solution than conventional materials such as "Hastelloy C" (No. 101) and SUS316 material (No. 102). It has extremely low wear and excellent corrosion and wear resistance. Regarding corrosion resistance, the alloy of the present invention has
Much superior to the conventional material SUS316 material (No. 102),
It can be seen that it has corrosion resistance similar to that of "Hastelloy C." It also has good weldability,
It is possible to perform welding for corrosion repair without cracking, and there is almost no deterioration in the corrosion resistance of the weld heat affected zone (HAZ), ensuring virtually the same corrosion resistance as the base metal. . On the other hand, Comparative Examples Nos. 103 to 113 have compositions similar to the alloys of the present invention, but because they lack one of the elements or have an excess or deficiency in the content, they have poor corrosion resistance or wear resistance. , or there is a problem with weldability. For example, No. 103 which does not contain Mo, No. 104 which contains excess C, and No. 104 which contains excess Fe.
107, No. 108 with insufficient Mo content has poor corrosion resistance, No. 105 with insufficient Cr content has low hardness and poor wear resistance, and No. 104 with excess C has an upper limit for Cr content. No. 106 that exceeds Mo, and No. 106 that contains excess Mo.
No. 109 and No. 110, in which the total amount of Nb and Ta is excessive, have poor weldability. Furthermore, Nos. 111 to 113 have excellent wear resistance, weldability, etc., and corrosion resistance is also superior to No. 101.
-103, but the invention examples (No.1-103) have poor corrosion resistance in the heat-affected zone due to welding.
13).

〔Effect of the invention〕

The alloy of the present invention has excellent corrosion resistance and wear resistance against strongly acidic corrosive liquids, and its corrosion resistance is not impaired even during welding. There is little corrosion and wear during plating operations, and there are only minor scratches and abrasions during the surface polishing process using a grindstone to remove the plating metal that adheres to the body surface, so it can last for a long time. Maintains smooth and beautiful surface texture. Therefore, the frequency of roll replacement is reduced, the cost of repolishing the rolls is reduced, stable continuous plating operations can be maintained, and the quality of the plated products is stabilized and improved. It will be done.

[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, Figures 3 and 4 are graphs showing the relationship between aging treatment conditions and hardness after aging, and Figure 5 is a portion showing an example of an energized roll. Cross-sectional front view, Figure 6 is a diagram explaining the corrosion test procedure, Figure 7 is a diagram explaining the wear test procedure, and Figure 8 is a diagram explaining the procedure for the wear test.
Figures 1 and 2 are explanatory diagrams of weldability test procedures. 10: roll body (sleeve), 20: roll end.

Claims (1)

[Claims] 1 Cr: 40-55%, Mo: 2-10%, C: 0.1% or less, Si: 1% or less, Mn: 1% or less, Fe: 10% or less, N: 0.2% or less , and Nb: 0.5-2%,
Ta: Contains one or two selected from 0.5 to 3% of two elements, and the total amount of Nb and Ta satisfies the following formula: 0.5Nb [%] + 0.3 Ta [%] ≦ 1 [%] The balance is essentially Ni, which is a current-carrying roll alloy for electroplating that has excellent wear and corrosion resistance. 2 Cr: 40~55%, Mo: 2~10%, C: 0.1% or less, Si: 1% or less, Mn: 1% or less, Fe: 10% or less, N: 0.2% or less, and Nb: 0.5~ 2%,
Contains one or two selected from two elements of Ta: 0.5 to 3%, one or two selected from two elements of Ti: 0.1 to 1%, Al: 0.1 to 1%, and Nb
The total amount of Ta and Ta satisfies the following formula: 0.5Nb [%] + 0.3 Ta [%] ≦ 1 [%], and the remainder is essentially Ni, which is used for electroplating with excellent wear and corrosion resistance. Current-carrying roll alloy.