JPH0631468B2 - Surface-treated steel plate for DI can - Google Patents

Description

TECHNICAL FIELD The present invention relates to a surface-treated steel sheet for DI cans having excellent corrosion resistance against carbonated beverages.

(Prior Art) A tin can made from tinplate is widely used as a container for carbonated drinks. The DI can is manufactured by drawing a tin plate and then performing an ironing process for reducing the can side wall thickness and increasing the can height. The side wall thickness of the ironed DI can is around 100 μm, which is one of the typical can thicknesses.
Since it is as thin as / 2 to 1/3, if there is a defect in the inner coating film, and if the content is a carbonated beverage having a strong corrosive property, it is very likely to be a perforated can. Therefore, tinplate D
In the case of the I can, the inner coating film is currently coated twice, so that there are almost no coating film defects. However, it is a fact that there is a strong demand for the development of a surface-treated steel sheet in which it is not economical to make the coating film thick in this way and in which perforation is unlikely to occur. As a method for improving the corrosion resistance in carbonated drinks, Japanese Patent Publication No. 42-26388 and Japanese Patent Laid-Open No. 3074/1975.
No. 9 publication is proposed. JP-B-42-26388 discloses that the corrosion resistance is improved by adding 0.02 to 0.10% of S to steel.
No. 9 discloses a method of applying a sulfur-containing substance before annealing and forming a sulfur-containing layer on the steel surface by annealing to improve the corrosion resistance in carbonated beverages. In any case, although the corrosion resistance is improved, when S is added to the steel, there are many problems that surface flaws caused by sulfide-based inclusions occur, and the yield of the product is deteriorated. At times, the method of forming the sulfur-containing layer has a problem that rust is likely to occur in the steps after annealing and before tin plating, and the adhesion of tin plating is poor. And such a problem makes implementation of these techniques difficult.

(Problems to be Solved by the Invention) When making a DI can economical by reducing the coating film thickness, it is indispensable to improve the puncture resistance of tinplate, and it is an object of the present invention. By the way.

(Means for Solving the Problems) In both JP-B-42-26388 and JP-A-50-30749, S improves the corrosion resistance of steel in carbonated beverages. However, as described above, they have the above problems and are not put to practical use. The present invention has led to the intended invention as a result of research from various aspects from the viewpoint of improving corrosion resistance by S without causing any adverse effects by S. The gist of the present invention is to arrange the eutectoid plating layer of Fe and S in the lower layer of tin plating. With such a structure, it is caused by S,
Problems such as sulfide-based inclusions, generation of rust, and decrease in adhesion between the tin plating layer and the base are solved all at once, and a surface-treated steel sheet for DI can having excellent corrosion resistance can be obtained. The contents and reasons for limitation will be described below.

In the production of the steel sheet of the present invention, the eutectoid of Fe and S can be electrodeposited immediately before tin plating, and the present invention prefers that, in which case S is electrodeposited. Since the time from the completion of the plating to the plating of tin on the upper layer is extremely short, the method is disclosed in JP-A-50-30749.
As described above, there is no problem of rusting due to S before tin plating. Needless to say, there is no increase in sulfide inclusions. Moreover, S electrodeposited on the steel surface is
Since it is in the eutectoid state with Fe, which is a metal element, and the ratio to Fe is small, the adhesion to the tin plating layer that is subsequently carried out is also very good. Here, Fe was selected as an element to be co-deposited with S from the viewpoint of corrosion resistance. S is
Although it can be co-deposited with Ni and other metals, Fe is more excellent in corrosion resistance in carbonated drinks. For the above reason, the composite plating layer of Fe and S is arranged as a base for tin plating. Next, the reason for limiting the numerical values will be described. When C is increased, it becomes hard and flange cracks are likely to occur, so 0.13% was made the upper limit. In addition, 0.001% was set as the lower limit from the economical point of view. Mn, like C, hardens the steel and makes it difficult to process, so 0.5% is the upper limit,
The lower limit is 0 to prevent ear cracking during hot rolling with S.
05% A is added for deoxidation, but if its amount increases, it causes surface scratches and is not economical, so 0.12% was made the upper limit. The lower limit was set based on the fact that a minimum of 0.01% is required for deoxidation. Also Fe
The composite plating amount of S and S is determined based on the amount of S contained in the composite plating film. That is, when the Fe plating amount is 30 mg / m ² or less, even if the S / Fe ratio is 0.2, which is the maximum, the effect of improving corrosion resistance is poor, so the lower limit was made 30 mg / m ² . Moreover, the upper limit of the Fe plating amount is set to 3,
The reason why 000 mg / m ² is used is from the economical point of view. Regarding the S / Fe ratio, the lower limit is determined from the point of effect. On the other hand, if the S / Fe ratio exceeds 0.2, there is a risk of rust after the ironing process, so 0.2 is set as the upper limit. did. Incidentally, the composite plating layer of Fe and S can fulfill the purpose of the present invention only by being present on the inner surface side of the can, and is not necessary on the outer surface side of the can. Even if the Fe-S composite plating layer is electrodeposited on the outer surface side, it does not impair the object of the present invention. Regarding the tin plating amount, the lower limit of the surface which is the outer surface side of the can is determined from the viewpoint of the ironing property. If it is 1.0 g / m ² or less, scratches will occur during the ironing process. Further, the lower limit of the amount of tin plating on the inner surface side was set to 0.1 g / m ² from the viewpoint of corrosion resistance. In addition, the upper limit on the inner surface side and the outer surface side of the can was both 11.2 g / m ² from the viewpoint of economy.

(Examples) Examples will be described below.

C: 0.035%, Mn: 0.28%, S: 0.02%, A: 0.058
%, The balance of Fe and the unavoidable impurities were pickled, cold-rolled, continuously annealed, and temper-rolled to obtain a plated original plate.

Fe-S composite plating and tin plating have the following bath composition:
It was performed under plating conditions.

Fe-S composite plating bath _{composition: FeSO 4 · 7H 2 O 300g} / (NH 4) 2 SO 4 100g / Na 2 S 2 O 3 · 5H 2 O 1~10g / current density: 20 to 50 A / dm ² Bath temperature : 50 ° C. tin plating bath composition (ferrostane bath) phenol sulfonic acid 50-80 g / SnSO ₄ 50-100 g / ENSA (additive) 5-10 g / current density: 5-10 A / dm ² bath temperature: 40-50 ° C. When performing plating in the plating bath and plating conditions, Fe
S / Fe ratio -S composite plating layer _{is, Na 2 S 2 O 3 ·} 5H 2 O added amount and the was adjusted by the current density, Fe-S composite plating amount, tin plating amount is adjusted by the quantity of electricity did.

The iron elution test and the pitting corrosion test were performed on the tin plate having the Fe-S composite plating layer as the lower layer and the tin plate having only the tin plating layer, which were prepared by the above method. Each test method is as follows, and the test results are shown in Table 1.

(1) Iron elution test After making each of the above tin plates into a DI can having a diameter of 53 mm, the inside of the can was coated with a phenol-based epoxy paint at about 50 mg / dm ^{2 by} spraying and baking, and a cola drink was packed. ℃
It was evaluated after 6 months.

(2) Pitting corrosion test The above-mentioned various tinplates are unpainted DI after DI processing. The can wall of the can was cut out, a plastic film having a pinhole with a diameter of about 0.2 mm was coated on the inner surface of the can, a corrosion test was performed through the pinhole, and the corrosion depth was evaluated. Regarding the test conditions, the content was a cola drink, and the time-dependent condition until evaluation was 37 ° C. for 2 weeks.

(Effect of the Invention) The steel sheet of the present invention having a Fe-S composite plating layer as a lower layer of the tin plating layer is suitable for the production of DI cans excellent in pitting corrosion in carbonated drinks and in elution of iron. is there.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaichi Kondo 1 775, Sachimachi, Shimomatsu-shi, Yamaguchi Prefecture (56) References JP-A-57-177991 (JP, A) JP-A-1-111853 (JP, A) JP-A-2-47048 (JP, A) JP-A-56-25991 (JP, A)

Claims (1)

[Claims] 1. C: 0.001-0.13%, Mn: 0.05-0.5%, A
: 0.01 to 0.12%, with the balance being iron and unavoidable impurities, and a Fe steel plate with a Fe content of 3 in the lower layer of the can inner surface of the steel sheet for cans.
0 to 3,000 mg / m ² , S content of 0.005 in S / Fe weight ratio
~ 0.2 Fe-S composite plating layer, the upper layer and
0.1 to 11.2 g / m ² , 1.0 respectively on the outer surface of the can
A surface-treated steel sheet for DI cans having an Sn layer of up to 11.2 g / m ² .