JP3405669B2 - Nickel-plated steel sheet excellent in corrosion resistance and surface appearance and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-plated steel sheet excellent in corrosion resistance and surface appearance, which is suitable for electric and electronic parts such as a battery case in which an alkaline solution is sealed, stationery such as a binder and other materials, and a surface appearance thereof. Concerning the law.

[0002]

2. Description of the Related Art Nickel plating is widely used for electric and electronic parts such as a battery case in which an alkaline solution is sealed, and for stationery and other materials such as a binder. Since nickel plating has a high stress of the plated film and pits are easily generated, an organic additive-containing bath is usually used for the purpose of stress relaxation and pit suppression. Further, in the case of obtaining bright plating, an additive for refining plated crystals is also used in addition to these.

In the nickel plating obtained from the additive bath as described above, although the pits are reduced, the additive is incorporated as an impurity in the plating film, so that it is not always possible to obtain sufficient corrosion resistance. . For applications such as battery cases that undergo severe processing, steel plates with a nickel-nickel alloy part of the nickel-plated layer are often used to prevent the plating from peeling off during processing. However, when the above-mentioned impurities are contained in the plating layer during this thermal diffusion treatment, the plating layer becomes brittle and the corrosion resistance is significantly deteriorated. As described above, the organic additive that prevents the nickel plating pit does not necessarily contribute to the improvement of the corrosion resistance, and when suppressing the pit to improve the corrosion resistance, there is no other method than thickening the plating film. It was an economy.

On the other hand, for example, Japanese Unexamined Patent Publication No. 6-2104 discloses a method in which nickel or nickel-cobalt strike plating is applied to a nickel-plated base to obtain a dense nickel plating with few pits. . However, even with this method, the corrosion resistance is not sufficiently improved, and the number of pre-plating treatment steps is increased by one, which causes a problem in cost. In addition to the problem of corrosion resistance, the conventional nickel plating method also has an economical problem. That is, since nickel has a low reaction rate in its precipitation and dissolution, it has been difficult to efficiently produce nickel with a high current density. For example, in the case of standard nickel plating known as a watt bath, the maximum current density is at most about 10 A / dm ² because the plating surface is easily burnt.

In order to improve this, JP-A-63-186
In Japanese Patent No. 889, the plate passing speed is increased to make the relative speed very large, thereby enabling plating at a high current density of about 100 A / dm ² . However, if it is attempted to obtain a plating adhesion amount capable of ensuring sufficient corrosion resistance under such conditions, a large number of plating cells are required, resulting in enormous equipment cost. Moreover, although not mentioned in Japanese Patent Laid-Open No. 63-186889, in the conventional plating method using a soluble anode, at such a high current density, the dissolution of metallic nickel in the anode becomes a problem, resulting in a problem of dissolution efficiency. As the bath concentration fluctuated with the decrease, stable production was difficult.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a nickel-plated steel sheet which has few pits and which does not contain impurities in the plating layer and which is excellent in corrosion resistance, and an economical manufacturing method thereof.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention considered that the corrosion resistance cannot be satisfied with an organic addition system bath, and as a result of studying suppression of pits in a system without such an additive, the crystal orientation of nickel plating was found. The inventors have found that there is a close relationship between the existence of pits and pits, and pits can be suppressed by controlling the crystal orientation, leading to the present invention. That is, according to the first aspect of the present invention, a steel sheet is nickel-plated in which both the S content and the C content are 0.01% or less and the (220) plane crystal orientation index is 0.5 or more. It is a nickel-plated steel sheet with excellent corrosion resistance and surface appearance. A second aspect of the present invention is the nickel-plated steel sheet according to the first aspect of the present invention, wherein a part of the plated layer forms a nickel-iron alloy. The third, fourth and fifth aspects of the present invention are the first and second methods for producing a nickel-plated steel sheet according to the present invention.

However, here, the crystal orientation index is defined as follows. By X-ray diffraction (Cu, Kα), five representative faces of nickel crystal (111 face, 200 face, 220 face)
Surface, 311 surface, 222 surface), and is defined by the following formula. (I is the strength of each surface) (220) plane crystal orientation index = I (220) / 21 × 5 /
(I (220) / 21 + I (111) / 100 + I (2
00) / 42 + I (311) / 20 + I (222) /
7)

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION When observing the surface of nickel plating plated from a bath containing no organic additive such as a pit suppressor or a leveling agent by SEM, many crystal grains with a grain size of several μ or less are observed. On the other hand, no remarkable crystal grains can be observed on the plated surface from the organic addition bath. Since plating pits are considered to occur in the gaps between crystal grains, it is important to suppress grain growth and obtain a smooth surface. In addition, the plating layer of the organic addition bath contains impurities such as C and S due to the additive, and although the plating pits are reduced, the corrosion resistance is not good, so the suppression of the plating pits without additives is considered. did.

When observing the surface of the plated product under various conditions from various plating baths without organic additives, depending on the conditions, as with the plated surface from the organic additive bath, remarkable crystal grains were not observed. . As a result of investigating the relationship between the plating crystal orientation and the existence state of crystal grains on the surface by X-ray diffraction, it was found that the crystal grains tended to decrease as the number of (220) planes increased. When the (220) plane orientation index defined by the following formula is 0.5 or less, the whole surface is covered with crystal grains, but when it exceeds 0.5, there is a smooth plated surface without crystal grains. It was way.

FIG. 1 shows the (220) plane orientation index and SEM.
3 shows the relationship with the abundance ratio of a smooth surface having no crystal grains when observed in (1). FIG. 2 shows the relationship between the (220) plane orientation index and corrosion resistance (red rust occurrence rate after flat plate SST6Hr). (220) plane orientation index is 0.5
In the above, no red rust was generated at the time of SST6Hr, and the corrosion resistance was good. Even when plating is performed in a system without organic additives, C and S are detected due to measurement errors and inevitable mixing from raw materials, so the upper limit of C and S concentrations in the plating layer is 0.
It was set to 01%.

As described above, the (220) plane orientation index is set to 0.
By setting the ratio to 5 or more, it was found that the plating pits were reduced and a nickel-plated steel sheet with high corrosion resistance could be obtained without using an organic additive. As a side effect, (22
It was also found that the higher the (0) plane orientation index, the smoother the surface and the more beautiful the appearance is. In addition, (22
The crystal orientation index of the 0) plane was defined as follows. By X-ray diffraction (Cu, Kα), five typical faces of nickel crystal (111 face, 200 face, 220 face, 311 face, 22 face)
It is defined by the following formula based on the strength of the second surface). (I
Is the strength of each surface) (220) crystal orientation index = I (220) / 21 × 5 /
(I (220) / 21 + I (111) / 100 + I (2
00) / 42 + I (311) / 20 + I (222) /
7)

Even when a part of the plated layer is made into an iron-nickel alloy by heat treatment, excellent corrosion resistance can be obtained by using the above nickel plated material. Especially when compared to plating with organic additives, it exhibits excellent corrosion resistance. As a material used for DI processing such as a battery case, it is desirable to use a nickel-plated steel sheet whose corrosion resistance after processing is further improved by this heat treatment.

Next, a specific method for obtaining nickel plating having a (220) plane orientation index of 0.5 or more will be described. The steel material of the original plate is not particularly limited, and both annealed material and unannealed material can be used. No special treatment is required for the pre-plating treatment, and the usual degreasing / pickling treatment is performed. In addition, when plating the original plate after passing through the electric cleaning line, it is possible to omit the degreasing treatment.

The current density is important in the plating conditions, and as a result of studies by the present inventors, as the current density increases, (2
20) It was found that the plane orientation index also increased. However, simply increasing the current density does not provide the desired (220) plane orientation, and in some cases causes uneven plating, which makes practical production difficult. Further, the dissolution of metallic nickel on the anode side is also a problem. As the plating bath, a bath containing chlorine ions, which is generally known as a Watt bath, and an organic additive-free bath is required. It is known that chlorine ion lowers the resistance of the plating solution and also lowers the precipitation overvoltage of iron group ions such as nickel, and is essential for performing good plating with high current density according to the present invention.

Chlorine ion is preferably supplied by nickel chloride, and its concentration is 65 g as nickel chloride.
/ L or more is required. If less than this, desired (22
Not only the 0) plane orientation could not be obtained, but plating and burn were generated depending on the current density condition and the nickel dissolution efficiency at the anode was significantly reduced. FIG. 3 compares the effect of the current density on the plating deposition efficiency between the case of nickel chloride of 40 g / l and the case of the invention range of 70 g / l. In the case of nickel chloride of 40 g / l, the deposition efficiency decreased as the current density increased, and plating burn occurred at a current density of 50 A / dm ² or more. On the other hand, in the case of 70 g / l of nickel chloride, the deposition efficiency remained as high as 95% or more even if the current density was increased, and the plating appearance was also good.

Similar to FIG. 3, FIG. 4 shows the dissolution efficiency of metallic nickel on the anode side. Nickel chloride 4
In the case of 0 g / l, the dissolution efficiency decreased as the current density increased, but in the case of 70 g / l, a high value of 95% or more was maintained. The upper limit of the nickel chloride concentration is not particularly important, but the corrosiveness of the equipment increases as the concentration increases, so it is desirable to control it to about 100 g / l. In addition, even if the nickel chloride concentration increases more than this,
Since good plating with few pits can be obtained, there is no problem with corrosion resistance in unprocessed or light processing. On the other hand, since the plated layer is hard and the stress is large, the corrosion resistance during processing is deteriorated.
From the above viewpoints, the plating bath of the present invention needs to have a nickel chloride concentration of 65 g / l or more, and preferably 70 to 100 g / l, with no organic additive added.

Regarding the concentrations of components other than nickel chloride, the Watt bath of the conventional knowledge may be used, and more preferably nickel sulfate (300 to 400 g / l) and boric acid (40 to 60).
Concentrations in the range of g / l), pH (3.5-4.5) are used. A more preferred form of the nickel plating method of the present invention is to use pure nickel as the soluble anode. In general, nickel containing a slight amount of impurities such as S is often used to facilitate the dissolution of the anode nickel. In this case, the impurities (NiS in the case of nickel containing S) become sludge. It deteriorates the plating quality (such as scratches and stains). In the prior art, when pure nickel was used, it was difficult to dissolve at high current density, but according to the plating bath conditions of the present invention, since pure nickel anodes can be used, sludge generation is small and plating Quality is stable. In addition, no special equipment is required to remove sludge.

Further, the liquid flow velocity on the surface of the steel sheet during plating is also important, and at a flow velocity of less than 0.1 m / sec, it is impossible to achieve both a good appearance and a (220) plane orientation index of 0.5 or more. It was The upper limit of the flow velocity may be determined by the facility restrictions. It was found that when the flow velocity is 0.1 m / sec or more and the current density is 50 A / dm ² or more, the (220) plane orientation index of 0.5 or more can be secured. It was found that the upper limit of the current density depends on the flow velocity and is represented by the following formula. (Current density upper limit A / dm ² ) = 67 ×
(Flow rate m / sec) +73 At a current density exceeding this upper limit, a good appearance could not be obtained due to uneven plating.

When heat-treating the above-mentioned nickel-plated steel sheet, a continuous annealing furnace is used at a temperature of about 600 to 850 ° C. for 10 hours.
By performing a heat treatment for 120 seconds, a part of the plated layer is made into a nickel-iron alloy layer, and after the heat treatment, a part of the (220) -oriented nickel plated layer having good corrosion resistance is left. As a result, excellent corrosion resistance can be obtained both unprocessed and processed. In the heat treatment in the annealing box, the treatment time is long and the diffusion proceeds too much, so that good corrosion resistance cannot be obtained. Note that, economically, a method of nickel-plating an unannealed material and then heat-treating the steel sheet for both annealing and diffusion treatment is effective, and in this case, treatment at a recrystallization temperature of the steel sheet or higher is required. . After heat treatment, it is also possible to finish the surface appearance to bright or dull by temper rolling.

[0021]

EXAMPLES The present invention will be described in detail below with reference to examples. (Example 1) Nb-Ti-Sulc having a plate thickness of 0.25 mm
Steel was used as a base plate, and degreasing, pickling and plating were performed. The degreasing conditions were as follows: caustic soda 50 g / l, bath temperature 60 ° C., anode treatment (20 A / dm ² ) × 5 seconds and cathode treatment (20 A / dm ² ) × 5 seconds. The pickling conditions were 50 g / l of sulfuric acid and 10 seconds of immersion at room temperature. The following plating baths were used, and plating was performed using a vertical circulation cell. Nickel sulfate: 350 g / l Nickel chloride: 70 g / l Boric acid: 45 g / l pH: 4.2

In addition to this basic bath, a bath containing 1 g / l of saccharin was also used in the comparative example. Bath temperature is 60
C., a linear flow rate of 1 m / sec, and a pure nickel plate was used as the anode. The amount of nickel deposited was 27 g / m ² . The alloying treatment carried out in some cases was performed at 790 ° C. for 40 seconds in a non-oxidizing atmosphere. The corrosion-resistant flat plate was evaluated by the rate of occurrence of red rust after SST6Hr and described according to the following criteria. (◎; 0.
Less than 5%, ◯: 0.5% or more and less than 2%, Δ; 2% or more and 5
The processing corrosion resistance was evaluated by the red rust occurrence rate in SST6Hr after being processed into a battery case having a diameter of 30 mm and a height of 50 mm, and was described by the following criteria. (◎;
Less than 0.5%, ◯: 0.5% or more and less than 2%, Δ; 2% or more and less than 5%, ×; 5% or more)

In this example, as shown in Table 1, good corrosion resistance was obtained, and alloyed Nos. 5 to 8 were used.
The processing corrosion resistance was also very good. In the comparative example, 22
The 0-plane orientation index was out of the range of the present invention, and the corrosion resistance was poor. Further, in the comparative example with the organic additive and the alloying treatment (Nos. 15 and 16), the plating was embrittled by the alloying treatment, and the corrosion resistance was poor as compared with the inventive examples.

[0024]

[Table 1]

(Embodiment 2) After subjecting the same original plate as in Embodiment 1 to the same pretreatment, nickel plating was performed by changing the plating bath and the plating conditions. The plating baths used were the same basic bath as in Example 1, and the non-chlorinated baths and low-chlorinated baths shown below. (Non-chlorinated bath) Nickel sulfate; 350 g / l Boric acid; 45 g / l pH; 2.5 (Low chloride bath) Nickel sulfate; 350 g / l Nickel chloride; 40 g / l Boric acid; 45 g / l pH; 4.2 The plating flow rate was variously changed. The other conditions are the same as those in Example 1.

As shown in Table 2, in the example, there was a region where the 220 plane orientation index was 0.5 or more and the plating appearance was good, but in the comparative example, the orientation index and the plating appearance were not compatible. There wasn't. In Table 2, the plating appearance Δ or × indicates that plating burns have occurred (especially marked occurrence is indicated by ×) and has no commercial value as a plated steel sheet. For these (22
0) It was difficult to reliably calculate the plane orientation index.

[0027]

[Table 2]

[0028]

According to the present invention, excellent corrosion resistance can be obtained by specifying the crystal orientation of the plating and smoothing the surface to suppress the generation of pits regardless of the organic additive. Further, the manufacturing method for obtaining such excellent corrosion resistance plating is a simple method of regulating the flow velocity, the current density, and the nickel chloride concentration, and is a method that is excellent in productivity and cost effective.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the orientation index of the (220) plane and the smoothness of the surface.

FIG. 2 is a diagram showing the relationship between the orientation index of the (220) plane and corrosion resistance.

FIG. 3 is a diagram showing a relationship between current density and plating deposition efficiency.

FIG. 4 is a diagram showing a relationship between current density and anode nickel dissolution efficiency.

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-63-186889 (JP, A) JP-A61-270390 (JP, A) JP-A-50-109820 (JP, A) JP-A-6- 174053 (JP, A) JP-A-6-174051 (JP, A) JP-A-6-36702 (JP, A) JP-A-6-2104 (JP, A) JP-A-2-129395 (JP, A) JP-A-4-6298 (JP, A) JP-A-3-104855 (JP, A) JP-A-63-38595 (JP, A) JP-A-62-202093 (JP, A) JP-A-55-50483 (JP, A) JP-A-52-140433 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C25D 5/26 C25D 5/50

Claims (5)

(57) [Claims] 1. A steel plate is nickel-plated with an S content and a C content of 0.01% or less and a (220) plane crystal orientation index of 0.5 or more. Nickel-plated steel sheet with excellent corrosion resistance and surface appearance. However, here, the crystal orientation index was defined as follows. By X-ray diffraction (Cu, Kα), five typical faces of the nickel crystal (111 face, 200 face, 220 face,
It is defined by the following formula from the strengths of the 311th surface and the 222nd surface). (I is the strength of each surface) (220) plane crystal orientation index = I (220) / 21 × 5 /
(I (220) / 21 + I (111) / 100 + I (2
00) / 42 + I (311) / 20 + I (222) /
7) 2. The nickel-plated steel sheet according to claim 1, wherein a part of the plated layer forms a nickel-iron alloy. 3. A nickel plating solution containing 65 g / l or more of nickel chloride and containing no organic additive is used, and the plating solution flow rate on the surface of the steel sheet is 0.1 m / sec.
The method for producing a nickel-plated steel sheet according to claim 1, wherein the plating is performed at a current density of 50 A / dm ² or more. 4. The method for producing a nickel-plated steel sheet according to claim 3, wherein a soluble anode of pure nickel is used. 5. The method for producing a nickel-plated steel sheet according to claim 2, wherein the steel sheet plated under the conditions of claim 3 or 4 is heat-treated.