JPH0428796B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a steel plate for cans suitable for use in food cans, miscellaneous cans, etc., and particularly to a steel plate for cans that has excellent paint adhesion to the outer surface of the can. <Prior art and its problems> Steel sheets for cans used for food cans, miscellaneous cans, etc.
In the past, tin-plated steel sheets, generally called tinplate, have been widely used, but since tin is an extremely expensive metal, thinning has been promoted to reduce costs. In recent years, in the joining method of can bodies,
In place of the conventional solder bonding method, electric resistance welding using copper wire electrodes has come to be widely used, and thinning of tin has progressed, and thin tin-plated steel sheets have been put into practical use. In addition to tin-plated steel sheets, there are chromium-type stain-free steel sheets for cans. This is a steel plate with an extremely thin chromate layer made of metallic chromium and hydrated chromium oxide.
Since chromium hydrated oxide is a high electrical resistance material, it is difficult to join the can body by electrical resistance welding, so a special adhesive is used to join the can body. Such steel sheets for cans are being made thinner in order to save resources and cost. When cans are manufactured using these thinned steel sheets, the inside and outside surfaces of the cans are coated to improve rust and corrosion resistance. In other words, the inner surface of the can is coated with a highly corrosion-resistant coating to prevent corrosion from liquid and other contents, and the outer surface of the can is coated with a beautiful coating to prevent rusting in the atmosphere and to attract consumers to purchase. Painted and printed. In recent years, in the field of cans, especially beverage cans, there has been intense competition among beverage manufacturers, and there are many competing materials such as paper, glass, and plastic, so all cans are painted and printed regardless of the type of steel plate. By the way, in canned food manufacturing as well, efforts have been made to increase production speed with the aim of increasing production efficiency.
Cans are made at a rate of 600 cans per minute and contents are filled at high speed, but at such high speeds, cans collide with each other on the production line, causing the paint film on the outside of the cans to peel off due to the impact. This may damage the commercial value of the can. Such peeling of exterior paint rarely occurs with stain-free steel, but it tends to occur with tin-plated steel sheets, and is a serious problem, especially for manufacturers who place importance on exterior coating. Until now, there has only been research on the adhesion of paint to tinplate using paint for the inside of cans, and little consideration has been given to the adhesion with paint for the outside of cans, especially the printing base paint commonly known as "white." do not have. Prior art related to improving paint adhesion of thin tin-plated steel plates include JP-A-53-23833 and JP-A-53-23833.
No. 26236, and JP-A-58-96891 discloses prior art related to improving paint adhesion of tinplate. JP-A No. 53-23833 discloses a steel sheet consisting of a layer mainly composed of iron and tin alloy and a layer of hydrated chromium oxide of 5 to 50 mg/ ^m2 .
A layer consisting mainly of tin alloy alone does not have sufficient corrosion resistance, and even if a chromium hydrated oxide layer is combined, a layer of chromium hydrated oxide alone cannot provide sufficient adhesion to the exterior paint, and the paint on the contents of the can cannot be coated properly. Post-corrosion resistance is also insufficient. JP-A No. 53-26236 discloses a steel sheet having a tinned layer of 0.05 to 0.60 g/m ² and a chromium hydrated oxide layer of 5 to 50 mg/m ² thereon. Since it is a layer consisting only of hydrated oxide, adhesion to the external paint is insufficient, and corrosion resistance is insufficient if only tin and chromium hydrated oxide are used. In JP-A No. 58-96891, 30 to 100 mg/ ^m2 of metallic chromium and 5 to 25
A method for precipitating chromium hydrated oxide of mg/m ² is disclosed, but the amount of metallic chromium is 30 to 100 mg/m ²
This makes welding and soldering difficult and limits the methods of joining the can body.In addition, when such a large amount of metallic chromium is present on the inside of the can, the hard metallic chromium causes scratches on the tinned layer. corrosion resistance becomes insufficient. Therefore, the present inventors focused on the fact that the characteristics required of steel sheets for cans differ between the outside surface and the inside surface of cans, and based on a thin tin-plated steel sheet, which has a proven track record of being used as a steel sheet for welded cans and has excellent economic efficiency. In addition, a surface structure suitable for the outer surface of the can,
As a result of intensive research into the surface structure and weldability suitable for the inside of a can, we have ensured excellent weldability, a surface structure with excellent paint adhesion on the outside of the can, and a surface structure with excellent corrosion resistance after painting on the inside of the can. We have discovered a new combination of these, leading to the present invention. In addition, prior art related to can steel sheets with different surface structures on the outside and inside of the can is disclosed in Japanese Patent Application Laid-open No. 57
No. 35693 discloses a steel plate with thicker tin plating on the inner surface of the can, thinner tin plating on the outer surface of the can, or no tin plating, and coated with metallic chromium and chromium hydrated oxide on both sides. However, the combination of tin plating, metallic chromium, and hydrated chromium oxide alone does not provide sufficient corrosion resistance. Also, as a similar prior art, JP-A-59-
No. 145794 has an Fe-Sn alloy layer on the outside of the can, and 0.1 to 12 g/ ^m2 of residual metal tin on the inside of the can.
A steel sheet is disclosed in which chromium hydrated oxide is present on the Fe-Sn alloy layer, and metallic chromium and chromium hydrated oxide are present on the metallic tin, but Fe
-Since it only contains Sn alloy and chromium hydrated oxide, the adhesion of the paint on the outside is insufficient, and the corrosion resistance on the inside of the can is also insufficient. <Object of the Invention> An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and to provide a steel plate for cans that is less expensive, has excellent corrosion resistance, and has excellent external paint adhesion. <Invention Structure> Such an object is achieved by the following present invention. That is, in the present invention, the surface of a steel plate having Fe-Ni-Sn alloy layers on both sides, which will become the outer surface of the can after can manufacturing, is coated with Sn such that the amount of metal Sn remaining after coating is printed is 0.05 g/m ² or less. having a plating layer and a chromate layer consisting of 10 to 30 mg/m ² of metallic chromium and 3 to 15 mg/m ² of chromium hydrated oxide in terms of chromium, the inner surface of the can after the steel plate is made; On the surface to be coated, the amount of metal Sn remaining after coating is 0.2 to 1.0 mg/ ^m2 .
An outer surface characterized by having a Sn plating layer and a chromate layer comprising 3 to 10 mg/m ² of metallic chromium and 3 to 15 mg/m ² of chromium hydrated oxide in terms of chromium. The present invention provides a steel sheet for cans that has excellent paint adhesion. Hereinafter, the steel plate for cans of the present invention having excellent adhesion to the external paint will be described in detail. FIG. 1 is an enlarged sectional view showing an example of the structure of a steel sheet for cans 1 according to the present invention. As shown in the figure, the steel plate 1 for cans of the present invention has one surface and the other surface, that is, a can outer surface side 2 that becomes the outside of the can when the steel plate 1 is used to make a can. Can inner side 3 which is the inside of the can
The composition of the formed layer (coating) is different between the two. That is, the can steel sheet 1 is basically composed of Fe-Ni-Sn alloy layers formed on both sides of a base steel sheet 4, and the can outer surface 2 is coated with residual metal after coating and printing performed during can manufacturing. It consists of a Sn plating layer 6 with an Sn content of 0.05 g/m ² or less, and on top of that, 10 to 30 mg/m ² of metallic chromium and 3 to 15 mg/m ² of chromium hydrate in terms of chromium. forming a chromate layer 7,
The amount of metal Sn remaining after coating printing is on the inner surface of the can 3.
A Sn plating layer 9 with a density of 0.2 to 1.0 g/m ² and a chromate layer on top of the Sn plating layer 9 consisting of 3 to 10 mg/m ² of metallic chromium and 3 to 15 mg/m ² of chromium hydrated oxide in terms of chromium. 10. Each layer constituting the can steel sheet 1 will be explained below. Fe-Ni-Sn alloy layers 5 and 8 on both sides of the steel plate
is dense, has excellent continuity, and exhibits excellent corrosion resistance. This Fe-Ni-Sn alloy layer 5, 8
For example, the following methods (a) to
Method (c) is possible. (a) Ni plating is performed on the base steel plate 4, and then Sn
Plating is performed, and Ni and Sn are diffused by heat treatment to form a Fe-Ni-Sn alloy layer. (b) Fe-Ni alloy plating is performed on the base steel plate 4,
Furthermore, Sn plating is performed, and Sn is diffused by heat treatment to form a Fe-Ni-Sn alloy layer. (c) After Ni plating is performed on the base steel plate 4 and Ni is diffused into the base steel plate 4 by heat treatment,
Sn plating is performed and Sn is diffused by heat treatment to form a Fe-Ni-Sn alloy layer. When the above methods (a) to (c) are carried out, Fe-Ni-Sn alloy layers 5 and 8 are formed, and at the same time the Fe-Ni-Sn alloy layers 5 and 8 are formed, and on top of these, there are also Fe-Ni-Sn alloy layers 5 and 8 that do not participate in alloy formation, that is, do not diffuse during heat treatment. Sn remains, Sn plating layers 6 and 9
becomes. In FIG. 1, the Sn plating layer 6 is drawn as a continuous and uniform layer, but in reality it is often discontinuously dispersed because it is a small amount. Sn plating in methods (a) to (c) above can be carried out according to the usual method, and the amount of Sn plating is selected appropriately for the inside and outside of the can, and the molten tin is treated under appropriate conditions. By performing (heat treatment), a desired amount of Fe-
Ni-Sn alloy layers 5, 8 and Sn plating layers 6, 9
can be formed. In general, tinplate manufacturing equipment is equipped with a heating device called a "reflow device" that melts the Sn after Sn plating, and it is convenient to perform the molten tin treatment (reflow treatment) using this device. Further, the molten tin treatment may be performed using any method such as current resistance heating, high frequency heating, external heating, etc. In the present invention, Fe-Ni-Sn alloy layers 5, 8
Although the amount of Sn deposited is not particularly limited, it is preferable that Sn
The amount is preferably 0.05 to 1.8 g/m ² . The reason is that if it is less than 0.05g/ ^m2 , the corrosion resistance will be insufficient.
This is because if it exceeds 1.8 g/m ² , the Fe-Sn-Ni alloy layer will be hard and will be prone to cracking during processing, which may even reduce its corrosion resistance. The amount of the Sn plating layer 6 on the outer surface 2 of the can should be such that the remaining amount of metallic tin is 0.05 g/m ² or less after the coating printing (baking coating) performed during can manufacturing. For this purpose, it is necessary to actually form the can outer surface 2 of the can steel sheet 1 of the present invention before coating printing.
The amount of Sn plating deposited (hereinafter referred to as the actual amount of Sn plating) is approximately 0.1 to 0.6 g/ ^m2 , and the baking conditions for coating printing (baking temperature, baking time, number of baking times, etc.)
should be selected appropriately. The reason why the amount of residual metallic tin after coating and printing on the outer side 2 of the can is set to 0.05 g/m ² or less is because metallic tin is soft and easily deformed by impact, so the amount of residual metallic tin is 0.05 g/m ² Exceeding this applies extra deformation stress to the paint film, making it easy for paint to peel off, and since the tin oxide on the metal tin surface is fragile, paint peels off due to destruction of the tin oxide due to impact, etc. This is because it becomes easier. The actual amount of Sn plating on the outer surface 2 of the can is 0.1 to 0.6.
The reason for setting it to g/m ² is as follows. actual
This is because if the amount of Sn plating is less than 0.1 g/m ² , the amount of Fe-Sn-Ni alloy formed in the heat treatment after Sn plating will be small and the corrosion resistance will be insufficient. There is no upper limit to the actual amount of Sn plating on the outer surface 2 of the can, but the actual amount of Sn plating on the outer surface 2 of the can is 0.6.
If it exceeds g/ ^m2 , the amount of metal tin remaining after coating printing will be reduced.
In order to reduce the amount to 0.05 g/m ² or less, a large amount of tin must be purchased as an alloy through molten tin treatment, which is technically difficult. On the other hand, the amount of Sn plating layer 9 on the inside surface 3 of the can should be such that the amount of metal tin remaining after coating and printing is 0.2 to 1.0 g/m ² .
It is sufficient to set the amount of Sn plating to about 0.8 to 2.0 g/m ² and appropriately select the baking conditions for coating printing. The amount of metal tin remaining after coating printing on the inner surface of the can 3.
The reason for limiting it to 0.2 to 1.0 g/m ² is as follows. The steel plate of the present invention is mainly welded and made using a seam welding machine such as a Soudronic welding machine, but since such seam welding is done after paint printing, generally the steel plate is made after paint printing. Metallic tin of 0.1 g/m ² or more per side is required on both sides of the steel plate. Therefore, in the steel plate of the present invention, since the amount of metallic tin remaining after coating printing on the outer surface 2 of the can is set to 0.05 g/m ² or less in order to improve the adhesion of the outer paint, it is considered that sufficient weldability cannot be obtained in the first place. . However, the inventors reconsidered the amount of metal tin required for welding and found that it was 0.1 g/metal tin per side.
It has been found that even when the steel plate does not contain ^{m2 or} more of metallic tin on both sides, the same effect, that is, sufficient weldability, can be obtained as long as the total amount of metallic tin inside and outside the can is 0.25 g/m2 or more. Therefore, in order to ensure sufficient weldability, the lower limit of the amount of metallic tin remaining after coating and printing on the inner surface 3 of the can was set to 0.2 g/m ² . Further, the greater the amount of metallic tin remaining after coating printing, the better the weldability will be, but if this amount exceeds 1.0 g/m ² , not only will the welding improvement effect become saturated, but it will also become uneconomical, which is not desirable. The actual amount of Sn plating on the inner surface of the can is 0.8 to 2.0.
The reason for setting g/ ^m2 is that the actual amount of Sn plating is
If it is ^less than 0.8g/m2, the amount of metal tin remaining after painting and printing should be
It becomes technically difficult to secure 0.2g/ ^m2 , and 2.0
This is because if the amount exceeds 1.0 g/m ² , a large amount of tin must be alloyed in a molten tin treatment in order to reduce the amount of residual metallic tin to 1.0 g/m ² or less, which is technically difficult. In the upper layer of the Sn plating layers 6 and 9 mentioned above,
Chromate layers 7 and 10 are formed of metallic chromium and chromium hydrated oxide, respectively. The metallic chromium in the chromate layers 7 and 10 is
It strengthens the bond with the Sn plating layers 6 and 9 and the upper coating film, and since the metal chromium itself is hard, it is resistant to impact.
It has the effect of curing the paint film. The amount of metallic chromium in the chromate layer 7 on the can outer surface side 2 is 10 to 30 mg/m ² , and the amount of chromate hydrated oxide is 3 to 15 mg/m ² in terms of chromium.
The amount of metallic chromium in the chromate layer 10 is 3 to 10
mg/m ² , the amount of chromium hydrated oxide is 3~3 in terms of chromium.
15mg/ ^m2 , chromate layer inside and outside the can 10
and No. 7 differ in the range of the amount of metallic chromium contained. The reason for limiting the amount of metallic chromium in the chromate layer 7 on the outer surface side ² of the can to 10 to 30 mg/m2 is that if it is less than 10 mg/ ^m2 , the effect of improving the adhesion of the external paint is insufficient, and the coating film is difficult to resist impact. This is because the anti-peeling effect is insufficient, and if it exceeds 30mg/ ^m2 , the effect of improving paint adhesion and preventing paint film peeling is sufficient, but
This is because metallic chromium, which is a high-melting point metal, impairs weldability and is therefore undesirable. The reason for limiting the amount of metallic chromium in the chromate layer 10 on the can inner side 3 to 3 to 10 mg/m2 is that if it is less ^than 3 mg/ ^m2 , the adhesion to the inner surface paint will be weak and the corrosion resistance of the paint will be insufficient. If it exceeds m ² , the paint adhesion is good, but the soft Sn plating layer 9 underneath is likely to be scratched due to the hard metal chromium, which deteriorates the corrosion resistance against the contents of the can after painting. The amount of chromium hydrated oxide in the chromate layers 7 and 10 on both the can outer surface 2 and the can inner surface 3 may be in the range of 3 to 15 mg/m ² in terms of chromium. Chromium hydrated oxide has the function of ensuring rust resistance and improving paintability until it is painted through sealing treatment, but since it is itself a high electrical resistance substance, the content is low. Too much content impedes weldability. Therefore, the amount of chromium hydrated oxide in chromate layers 7 and 10 is
The reason for limiting it to ~15mg/ ^m2 is that if the amount of chromium hydrated oxide in the chromate layer is less than 3mg/ ^m2 , rust resistance and
This is because paintability is also insufficient, and if it exceeds 15 mg/m ² , rust resistance and paintability are sufficient, but weldability deteriorates. As a method for forming such chromate layers 7 and 10, 20 ₄ ^2- , F ^- , In an aqueous solution containing one or more types of anions such as SiF ₆ ^2- , a steel plate is applied to the cathode by changing the amount of electricity so that the required amount of metallic chromium is obtained on the outer side 2 and the inner side 3 of the can. Just do electrolysis. When the amount of cathode electrolysis electricity is changed on the outer side 2 and the inner side 3 of the can, the amount of hydrated chromium oxide that precipitates at the same time as metallic chromium changes in the same way. The chromate layers 7, 10 are formed by processing such as
What is necessary is just to adjust the amount of chromium hydrated oxide in the above-mentioned limited range. In order to form the chromate layers 7 and 10 efficiently, activation treatment may be performed in an alkaline aqueous solution, for example, cathodic electrolysis treatment with a 10 g/aqueous sodium carbonate solution, before the chromate treatment. Preferred structural examples of the steel sheet for cans 1 of the present invention described above are summarized as shown in Table 1 below.

[Table] <Example> Examples of the steel plate for cans of the present invention will be specifically described below. (Manufacturing method 1) After electrolytically degreasing a tinplate plate after normal cold rolling, Ni plating is performed on both sides using bath A.
The steel plate was annealed in a so-called HN _x gas atmosphere of 10% H ₂ +90% N ₂ , and the entire amount of plated Ni was diffused to form an Fe-Ni alloy layer (Ni diffusion layer) on the surface of the steel sheet. This steel plate was subjected to skin pass rolling at a reduction rate of 1.5%, electrolytically degreased and pickled, then Sn plating was applied to both sides of the steel plate using B bath, followed by molten tin treatment, and 10 g/carbonate was applied to the steel plate. 1c/d in soda aqueous solution
After cathodic electrolytic treatment of ² m2, cathodic electrolytic treatment is performed using D bath so that the amount of metallic chromium on the outer surface of the steel plate and the inner surface of the can becomes the specified amount shown in Table 2 below, and then The steel plate was immersed in a 100 g/aqueous chromic acid solution to adjust the amount of hydrated chromium oxide to the predetermined amount shown in Table 2. (Manufacturing method 2) Fe-Ni is added to the steel plate by the same method as manufacturing method 1.
After forming the alloy layer, secondary cold rolling was performed at a reduction rate of 20%. After electrolytically degreasing and pickling this steel plate, C
Sn plating was applied to both sides of the steel plate using a bath, followed by molten tin treatment. After that, cathodic electrolytic treatment is performed using an E bath so that the amount of metallic chromium on the outer surface of the can and the inner surface of the can becomes the prescribed amount shown in Table 2 below, and then the steel sheet is placed in a 70 g/a chromic acid aqueous solution. The amount of chromium hydrated oxide was adjusted to the predetermined amount shown in Table 2 by immersion. (Manufacturing method 3) After electrolytically degreasing and pickling a tin plate plate that has been subjected to ordinary cold rolling, annealing, and temper rolling, Ni plating is performed on both sides using bath A, and then Ni plating is performed using bath B. Sn plating was then carried out, followed by hot tin treatment. After that, cathodic electrolysis treatment is performed using D bath so that the amount of metallic chromium on the outer surface of the can and the inner surface of the can becomes the prescribed amount shown in Table 2 below, and then the steel sheet is placed in a 100 g/a chromic acid aqueous solution. The amount of chromium hydrated oxide was adjusted to the predetermined amount shown in Table 2 by immersion. (Manufacturing method 4) After degreasing the original plate for tin plate after normal cold rolling,
Annealed in a so-called HN _x gas atmosphere of 10% H ₂ + 90% N ₂ . This steel plate was temper rolled at a reduction rate of 1.5%,
After electrolytic degreasing and pickling, both sides of the steel plate are coated using C bath.
Sn plating was performed, followed by hot tin treatment.
After that, using an E bath, cathode electrolysis treatment was performed so that the amount of metallic chromium on the outer surface of the can and the inner surface of the can became the specified amounts shown in Table 2 below, and the steel sheet was further treated with 70%
The amount of hydrated chromium oxide was adjusted to the predetermined amount shown in Table 2 by immersing it in a chromium pickling solution of 1.5 g/g/g. Bath A (Ni plating bath) Nickel sulfate 250g / Nickel chloride 45g / Boric acid 30g / Bath B (Sn plating bath) Stannous chloride 50g / Sodium fluoride 45g / Sodium hydrogen fluoride 13g / Sodium chloride 54g / Yellow blood Salt 0.8g / Brightener appropriate amount C bath (Sn plating bath) Stannous sulfate 55g / Phenolsulfonic acid (65%)
35g/brightener appropriate amount D bath (chromate bath) Chromic acid 17g/sulfuric acid 0.12g/E bath (chromate bath) chromic acid 15g/ _NH4F 1.5g/of the steel plate for cans obtained by the above manufacturing methods 1 to 3 Test pieces No. 1 to 8 (No. 1 to 4 are examples of the present invention, No. 5 to 8
Comparative Example) was examined for external paint adhesion, post-painting corrosion resistance, and weldability. The results are shown in Table 2 below. The above characteristics were evaluated by the following methods. Evaluation of external paint adhesion
After heat treatment for 10 minutes, a modified alkyd white coat 170 mg/dm ² and an alkyd amino external varnish 80 mg/dm ² were applied to the surface corresponding to the outer surface of the can, and a Mitsubishi Uni-Pencil was used to coat this coating. Perform a pencil hardness test to determine the peel strength of the paint film.
Evaluation was made based on the maximum pencil hardness without peeling of the coating film. Evaluation of corrosion resistance after painting After applying 60mg/ ^dm2 of epoxyphenol paint to the surface corresponding to the inner surface of the can of each test piece, and sealing the edges and unpainted surface of the test piece with tape, Half of the test piece was immersed in 55°C for 2 weeks, and blisters due to corrosion were observed.
It was evaluated as follows.

[Table] Evaluation of weldability Each test piece was given 210
After heat treatment for ℃ x 20 minutes, welding speed 40
m/min, welding force 40Kgf, overlap
Electric resistance seam welding was performed using a 0.4 mm copper wire as an electrode, and evaluation was made based on whether or not there was an appropriate welding current range that would provide sufficient welding strength and would not cause "splashing".

[Table] As is clear from the results in Table 2 below, the steel plates for cans of the present invention (test pieces No. 1 to 4) have superior weldability compared to the comparative examples (test pieces No. 5 to 8), and It can be seen that the paint adhesion on the outside of the can and the corrosion resistance after painting on the inside of the can are excellent.

[Table] Note: Underlined items indicate items outside the scope of the present invention.
<Effects of the Invention> As described above, according to the steel sheet for cans of the present invention which has excellent paint adhesion on the outside surface, cans with excellent paint adhesion on the outside surface of the can, corrosion resistance after painting on the inside surface of the can, and weldability can be obtained through can manufacturing. can be provided at low cost.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view showing an example of the structure of the steel plate for cans of the present invention. Explanation of symbols, 1... Steel plate for cans of the present invention, 2...
Can outer side, 3... Can inner side, 4... Base steel plate,
5, 8...Fe-Ni-Sn alloy layer, 6,9...Sn
Plating layer, 7, 10... chromate layer.

Claims (1)

[Scope of Claims] 1 A steel plate having Fe-Ni-Sn alloy layers on both sides has residual metal after paint printing on the surface that will become the outer surface of the can after can manufacturing.
A chromate layer consisting of a Sn plating layer with an Sn content of 0.05 g/m ² or less, and 10 to 30 mg/m ² of metallic chromium and 3 to 15 mg/m ² of chromium hydrated oxide in terms of chromium. The surface of the steel plate that will become the inner surface of the can after can manufacturing is coated with a layer such that the amount of metal Sn remaining after coating and printing is 0.2 to 1.0 g/ ^m2 .
An outer surface comprising a Sn plating layer and a chromate layer comprising 3 to 10 mg/m ² of metallic chromium and 3 to 15 mg/m ² of chromium hydrated oxide in terms of chromium. Steel plate for cans with excellent paint adhesion.