JP6048429B2 - Cobalt-nickel alloy material and article coated therewith - Google Patents

Description

  The present invention relates to a cobalt-nickel alloy material having a unique laminated structure that is not only excellent in heat resistance, corrosion resistance, and wear resistance, but also markedly improved in elongation, and an article coated with the cobalt-nickel alloy material.

  As a coating material for a steel continuous casting mold in recent years, it is well known to coat a cobalt-nickel alloy. In order to prevent corrosion wear at the part, a cobalt alloy containing 10 to 30 wt% of nickel is coated. That is, it is better that the amount of nickel is smaller for improving the wear resistance at the lower part of the mold, and it is better that the amount of nickel is better for improving the corrosion resistance at the lower part, and 16 to 30 wt% is appropriate. It is said. However, the elongation of the cobalt-nickel alloy is relatively inferior to that of pure nickel, particularly when the nickel content is 10 wt% or less, and when the casting speed is high, the heat at the top of the mold is high. There are problems such as cracking. To avoid the problem, keep the cobalt-nickel alloy coating on the lower half of the mold, and cover the upper half with the raw material or with a nickel film with good elongation. Yes.

  Patent Document 2 describes a proposal for improving the elongation and tensile strength of a film by co-depositing carbon in a cobalt-nickel alloy. The proposed method was traced to confirm whether carbon co-deposition was possible due to the presence of carbon powder and butynediol. However, the carbon powder should not completely dissolve in the form of ions in the plating solution, and simply contains carbon powder as a solid. The resulting coarse cobalt-nickel dispersion plating. In addition, when butynediol, which is well-known as the second type brightener for bright nickel plating disclosed in Patent Document 2, is added, even if gloss and flatness can be imparted to the cobalt-nickel alloy film, elongation or tension is achieved. Instead of improving the strength, it becomes a brittle film and cannot achieve its purpose at all.

  In Patent Document 3, a multilayer structure thin film in which a plurality of alloy thin film layers having a composition different from the composition of adjacent thin film layers are stacked by switching the current density of the plating current at a constant cycle using the same plating bath and a method for manufacturing the same Is a technology that improves the magnetic characteristics of a magnetic head by forming a multilayer structure thin film with a total film thickness of less than 3 μm by laminating a plurality of lamination units of sub-micron order. Yes, it has nothing to do with improvement in heat resistance, corrosion resistance, wear resistance and elongation.

  On the other hand, the characteristics required as a coating material for a continuous casting mold of steel cannot be grouped according to the steel type and casting conditions to be cast. In other words, heat resistance and wear resistance are required characteristics that are common to all molds, but in addition, the characteristics of the coating on the inner wall of the casting mold are slightly different for each continuous casting machine. In the case of molds, corrosion wear resistance at the lower part of the mold inner wall is strongly sought even at the expense of wear resistance to some extent, and in the case of another mold, the upper part of the mold inner wall where the heat temperature is high is higher than the wear resistance. Elongation of the film is the top priority for preventing cracks.

  The content disclosed in the patent document suggests that there is a limit to the improvement of wear resistance, corrosion resistance imparting, and elongation only with a cobalt-nickel alloy. That is, a high cobalt alloy is good for imparting wear resistance, and a high nickel alloy is good for imparting corrosion resistance and preventing heat cracks.

  However, in the case of a continuous casting copper mold coated with a cobalt-nickel alloy, it is almost impossible to satisfy all of the characteristics required by the alloy film alone. For this reason, nickel is coated on the entire inner wall surface of the mold, and then a cobalt-nickel alloy is locally coated on the lower half of the mold. In addition to these forms, or in addition to these forms, the actual condition is to use a cobalt alloy in which the alloy ratio of nickel is increased at the expense of wear resistance in order to improve the lower corrosion resistance.

  An example of creating a multilayer film of different metals, cobalt and platinum is found in Non-Patent Document 1, but it is laminated at the nano level using two baths and two power sources, and the purpose of the implementation method is fundamentally different. . Non-Patent Document 2 discloses the fabrication of a nano-level multilayer film using two types of plating solutions and the fabrication of a nano-level multilayer film using a single liquid. This was achieved because the electrode potentials of copper and nickel were extremely different. Cobalt and nickel were co-deposited at any electrode potential close, and the nickel deposition concentration (content) was intentional. This is fundamentally different from that of the present invention in which the layer structure is changed.

JP 2000-263190 A Japanese Patent No. 3506993 JP-A-6-196324

Technical magazine "Surface technology" vol.53, No12, 2002, 852-859, Automation of Co / Pd nano multilayer film fabrication by electrodeposition method Technical Journal "Surface Technology" vol.62, No12, 2011, 681-685, Wear Resistance of Cu / Ni Nano-Order Multilayer Plating Films Prepared by One-Part Method and Two-Part Method

  The present invention has been made in view of the problems of conventional cobalt-nickel alloy materials, and has been developed by using a cobalt-nickel alloy material that has significantly enhanced all of wear resistance, corrosion resistance, high tensile strength, and high elongation. It is intended to be obtained by plating.

The invention according to claim 1, unavoidable impurities, cobalt of cobalt and nickel - a nickel alloy, the two layers were repeatedly stacked alternately in the vertical direction structure of small layer with large layer of the nickel ratio a nickel alloy material - Yes, and cobalt, wherein the difference between the nickel ratio of the layer higher and lower layer of the nickel ratio is 1 to 20 wt%.
A second aspect of the present invention is the cobalt-nickel alloy material according to the first aspect, wherein the alloy having a laminated structure is manufactured by an electroplating method using the same plating solution. .
The invention according to claim 3, cobalt according to claim 1 or 2 - the nickel alloy material, the thickness of the small layer with large layer of nickel ratio, respectively a 1 to 500 [mu] m, each layer thickness ratio 1 1 to 1:10.
The invention of claim 4 is an article coated with the cobalt-nickel alloy material according to any one of claims 1 to 3 .

Cobalt present invention - nickel alloy material, have a two layers repeatedly stacked alternately in the vertical direction structure of small layer with large layer of nickel ratio, the nickel ratio of the layer higher and lower layer of the nickel ratio Since the difference is set to 1 to 20 wt%, there is an effect that a strong cobalt color property and a strong nickel color property appear at the same time , and the elongation, tensile strength, hardness, and corrosion resistance compared to an alloy manufactured by a normal method. Thus, it is possible to arbitrarily improve the characteristics, and it is possible to improve some characteristics without changing other physical properties.
The invention according to claim 2 can produce a material in which layers having various nickel alloy ratios are laminated by electroplating using only one kind of liquid. Specifically, it can be manufactured by using both current density strength and air blowing amount strength or both at intervals of 1 minute or more.
The invention according to claim 3, the thickness of the layer higher small layer of the nickel ratio, by which the respectively 1μm or more, a strong characteristic of cobalt color, appear clearly has a strong characteristic nickel color, yet each By combining these characteristics, the elongation, tensile strength, wear resistance, and corrosion resistance are improved unexpectedly.
That is, the cobalt-nickel alloy material of the present invention has an elongation, tensile strength, resistance to resistance even when the nickel ratio measured by the average value is the same as that of a normal cobalt-nickel alloy having no laminated structure. There is an effect that wear resistance and corrosion resistance are unexpectedly improved (see FIGS. 6 to 9).

It is a photograph which shows the cross-sectional microstructure of the cobalt-nickel alloy plating of this invention manufactured by the current density strength method. It is a photograph which shows the cross-sectional microstructure of the cobalt-nickel alloy plating produced by the electroplating method currently generally implemented. It is a photograph which shows the cross-sectional microstructure of the cobalt-nickel alloy plating of this invention manufactured by the air stirring strength method. It is a photograph which shows the cross-sectional microstructure of the cobalt-nickel alloy plating of this invention manufactured by the air stirring strength method. It is a photograph which shows the cross-sectional microstructure of the cobalt-nickel alloy plating of this invention manufactured by the air stirring strength method. It is the figure which showed the elongation at break of the cobalt-nickel alloy of this invention at room temperature compared with the conventional nickel-cobalt alloy. It is the figure which showed the abrasion resistance by the Taber method of the cobalt-nickel alloy of this invention compared with the conventional nickel-cobalt alloy. It is the figure which showed the corrosion rate by the typical mineral acid of the cobalt-nickel alloy of this invention compared with the conventional nickel-cobalt alloy. The figure which shows the result of having investigated the elongation of the cobalt-nickel alloy manufactured by the usual electroplating method and the cobalt-nickel alloy of this invention to 700 degreeC on the assumption that it applies to the surface coating of the copper material of a steel continuous casting mold. is there.

  In order to solve the problems of the present invention, as described in the above-mentioned patent document, it is a fact that cannot be simply achieved by reviewing the liquid composition of a cobalt-nickel alloy or using a new additive alone. The characteristics are fixed by the alloy ratio of the alloy. Therefore, the present inventors changed the way of thinking to construct elements of electroplating methods other than the composition of the liquid, for example, rectifiers (equipment that converts alternating current into direct current) essential for electroplating and liquid mixing. The experiment was repeated focusing on the convection method.

  In the experiment, electrolysis with a DC power source that simply rectified AC, pulsed electrolysis where the DC is intermittently turned on and off, and an alloy film is created using the presence or absence of energization time as a parameter, no energization time as a variation of pulse electrolysis, The alloy film is formed by electrolysis with different current values, and by periodically repeating the polarity of the cathode and anode and periodically changing the energization time of each cathode and anode (referred to as PR electrolysis). Created and investigated wear resistance, corrosion resistance, tensile strength, elongation, etc. As a result, in pulse electrolysis that electrolyzes DC current with time, the layer structure is clear and unique for the cobalt-nickel alloy film for the first time by setting the current strength time to 1 minute or more. It was found that can be expressed. The liquid composition of the cobalt-nickel alloy bath at this time is shown in Table 1. Cobalt ions and nickel ions, temperature, current density, and the amount of air blown into the plating solution were appropriately selected from the ranges shown in Table 1.

For example, FIG. 1 uses the current density strength method, and the composition of the liquid is 0.45 mol / L metal cobalt ion and 0.90 mol / L metal nickel ion, the temperature is 50 ° C., and the air stirring amount is 0.2 m ³ / m ^2. This is a cross-sectional microstructure in the case where pulsed electrolysis is repeated for 1 minute at a current density of 2 A / dm ² and 1 minute at 4 A / dm ² to cover a total thickness of 1 mm. The alloy has a structure in which the high current density layers of the alloy have a thickness of about 2 μm and the low current density layers have a thickness of about 1 μm alternately stacked.

On the other hand, as a constant current density method, FIG. 2 shows a cross-sectional microstructure of an alloy electrolyzed continuously to a thickness of 1 mm with the current density fixed at 3 A / dm ² using the same bath. In this case, there is no laminated structure only with a resinous structure.

Table 2 shows a comparison of the nickel content of cobalt-nickel alloys produced by applying current strength and cobalt-nickel alloys produced by electrolysis at a constant current density as a result of line analysis by EPMA from the cross section. Shown in The thickness of each layer can be achieved by arbitrarily changing the high current density application time and the low current density application time within a range of 1 minute or more. In addition, it has been clarified that the difference between the high current density and the low current density cannot produce a significant difference in the nickel content between the layers unless the difference is at least 2 A / dm ² or more. There is also a limit in strength, and there is a problem of damaging the appearance, and the high current density side cannot be made high without darkness. As a result, there is a limit in the difference in nickel content between the layers.

  FIG. 1 is a cross-sectional microstructure of a cobalt-nickel alloy having a laminated structure manufactured by the current density strength method shown in Table 2. The nickel content of the high current density layer and the low current density layer is changed by the current density difference. The layer thicknesses of the high current density layer and the low current density layer are changed depending on the energization time difference. FIG. 2 shows a cross-sectional microstructure of a cobalt-nickel alloy produced by the constant current density method.

Next, instead of changing the current density, the present inventors examined a method of causing a difference in the nickel alloy ratio by the strength of the air flow during air agitation, and the composition of the liquid was used in an experiment of the current density strength. Cobalt-nickel with the same composition as the one, with a temperature of 50 ° C., current density of 3 A / dm ² , and air flow rate of 0.1 m ³ / m ² and 0.4 m ³ / m ² , with the same target of 1 mm thickness An alloy was created. The time setting when the air flow rate was 0.1 m ³ / m ² and 0.4 m ³ / m ² was set to 3 minutes. The results are shown in Table 3, and it was discovered that the difference in the nickel content between the layers can be made much larger when the air flow rate is higher than the current density.

  It is also possible to arbitrarily change the thickness of each layer by arbitrarily setting the time of air flow for each individual, and physical properties such as film hardness, corrosion resistance, tensile strength, and elongation can be selected according to the application purpose. It is possible to change. Furthermore, if the current density strength and air flow rate strength are combined, it is possible to increase the difference in nickel content of each layer to be laminated.

3 to 5 show cross-sectional microstructures of cobalt-nickel alloys prepared by changing the air flow rate at a bath temperature of 50 ° C. and a current density of 3 A / dm ² and changing the air flow time. However, a preferable range of each air ventilation time is preferably set in a range of 1 to 40 minutes. The set time of strong air / weak air was strong 5 minutes / weak 3 minutes in FIG. 3, strong 5 minutes / weak 30 minutes in FIG. 4, and strong 30 minutes / weak 30 minutes in FIG. 3 to 5, it is apparent that the layer thickness ratio of each layer having a different nickel content can be arbitrarily set within a range of 1: 1 to 1:10.

FIG. 6 shows the results of measuring the elongation at N = 3 by preparing three types of 95 wt% nickel-cobalt alloy, laminated cobalt-15 wt% nickel alloy, and ordinary cobalt-16 wt% nickel alloy. Although the nickel content in the case of a multilayered cobalt-nickel alloy is shown as an average value of the entire layer, even if the nickel alloy ratio is about the same, an alloy having an elongation of 3 times or more can be obtained. Incidentally, each of the tensile breaking strength, respectively nickel -5Wt% cobalt alloy, 57.2Kg / mm ^2, in the case of the conventional cobalt -16Wt% nickel alloy, but was 59.3Kg / mm ^2, the laminated structure In the case of the cobalt-15 wt% nickel alloy, it is a strong alloy of 69.8 kg / mm ² .

  In the cobalt-nickel alloy, it is well understood that the wear resistance is improved when the cobalt content is increased. However, as shown in FIG. 7, a multilayered cobalt-nickel alloy is compared with a normal cobalt-nickel alloy. It shows a unique property that wear resistance is slightly improved. In this way, the reason why the elongation, tensile strength, and even the wear amount tend to be improved in the cobalt-nickel alloy is as follows. Are adjacent to each other and are laminated repeatedly based on this, so that the strong characteristics of cobalt color, the strong characteristics of nickel color in other cases, and the combination of these characteristics, it is unexpected It is thought that the effect of is demonstrated. In addition, the abrasion test of FIG. 7 is the result evaluated by the Taber ablation tester.

  For corrosion resistance, under the conditions shown in Table 3 for the solution and conditions, a test piece for evaluation of a multilayered cobalt-nickel alloy was prepared, and a corrosion test was performed on each 1M solution of hydrochloric acid, sulfuric acid, and hydrofluoric acid. As shown in FIG. 8, there is a difference in corrosion resistance even when the nickel content is almost the same.

When the alloy is applied to a steel continuous casting mold, there is a case where a cobalt-nickel alloy film exhibits strong heat cracks in the upper half of the mold inner wall by a continuous casting machine or a steel type to be cast. This is largely related to the elongation characteristics of the coating itself, and may not be able to cope with ordinary cobalt-nickel alloys. Fixing the liquid composition and temperature conditions to solve this problem, giving the current and air blowing amount, and setting each time appropriately maintains the wear resistance as seen in Fig. 9. However, it exhibited elongation at high temperatures, which is not possible with normal electroplating, and it was possible to reliably prevent heat cracking.
Note that the cobalt-nickel alloy material of the present invention can be manufactured only in an alloy film or in a state where it is coated on a specific substrate.

  Some examples of the present invention are listed in Table 4 below. In the example of Table 4, the Ni content of the low concentration layer is set to be less than 12 wt%, and the Ni content of the high concentration layer is set to be more than 13 wt%. According to Table 4, by providing a difference of 4 to 20 wt% in the Ni content of the low-concentration layer and the high-concentration layer, the physical properties of the Co—Ni alloy as compared with the comparative example having the same average Ni content It can be seen that is greatly improved. In particular, the improvement in elongation becomes even more remarkable in Examples 3 to 5 in which the difference in Ni content between the low concentration layer and the high concentration layer is 10 to 20 wt%.

  It goes without saying that the present invention is not limited to those described in the following examples, and that changes and modifications can be made as appropriate without departing from the technical scope of the present invention.

  The cobalt-nickel alloy material of the present invention can be used by coating the surface of a copper alloy material that becomes the base of a continuous casting mold for steel, or it can be produced only from the alloy because of its unique heat resistance, wear resistance, and corrosion resistance. It can also be used as an alternative to nickel electroforming as a forming mold material. Further, the present invention can be applied to a protective film such as a separator for a SOFC type fuel cell having a high combustion temperature of fuel and imparting corrosion resistance to a copper foil for a negative electrode current collector of a lithium battery.

Claims (4)

Cobalt inevitable impurities, cobalt and nickel - a nickel alloy, have a two layers repeatedly stacked alternately in the vertical direction structure of small layer with large layer of nickel ratio, small nickel ratio A cobalt-nickel alloy material characterized in that the difference in nickel ratio between the layer and the large layer is 1 to 20 wt% . 2. The cobalt-nickel alloy material according to claim 1, wherein an alloy having a laminated structure is produced by an electroplating method using the same plating solution. 3. The thickness of the small layer with large layer of nickel ratio, respectively a 1 to 500 [mu] m, each layer thickness ratio 1: according to claim 1 or 2, characterized in that from 1 range 1:10 Cobalt-nickel alloy material. An article coated with the cobalt-nickel alloy material according to any one of claims 1 to 3 .