JP3131000B2 - Surface treated steel sheet for welding cans - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel sheet for welding cans suitable for various foods, beverages and other filling and storage.

[0002]

2. Description of the Related Art As materials for containers used for foods, beverages, etc., there are generally tinplate and tin-free steel sheets.
In recent years, thin tin-plated steel sheets with a reduced amount of tin plating (some have Ni plating on the base to ensure weldability), nickel-plated steel sheets, etc. are also used for the purpose of reducing material costs. It is used. Simply, in terms of cost and various qualities, tin-free steel sheet is a very good material for cans, but there is a very big drawback that tin-free steel sheet cannot be welded.
Alternatively, the coating on the welded portion is ground to produce a can.
Therefore, improving the weldability of a tin-free steel sheet has a very great industrial significance.

[0003] Various attempts have been made to improve the weldability of a tin-free steel sheet.
No. 9386 provides a surface-treated steel sheet for welded cans that has improved the weldability while securing the excellent properties of a tin-free steel sheet.

The surface-treated steel sheet has a grain size of 0.2 to 20% so that the area percentage of tin grains occupies 5 to 20% on the surface of the steel sheet and the area percentage occupied by the exposed portion of the steel sheet becomes 95 to 80%.
2.0 μ tin particles are dispersed and adhered, and a 30 to 150 mg / m ² metal chromium layer is formed on the tin particles and the exposed portion of the steel sheet, and a chromium hydrated oxide layer of ^{2 to} 40 mg / m ² as chromium is formed thereon. It is characterized by being formed.

[0005] According to this surface-treated steel sheet, the contact resistance is reduced by the tin particles having an area percentage of 5 to 20% occupied by tin particles and having a particle diameter of 0.2 to 2.0 µ scattered and adhered to the surface of the steel sheet, thereby improving the weldability. Can be secured. In addition, the area percentage occupied by tin particles is 5 to 5.
20%, the area percentage occupied by the exposed portion of the steel plate is 95 to 80.
% Of a chromium metal layer of 30 to 150 mg / m ^{2 on} the base, and a chromium hydrated oxide layer of ^{2 to} 40 mg / m ² as chromium on the upper layer.
Metallic chromium layer of 150 mg / m ² , and metallic glazing appearance, excellent paintability, paint adhesion, paint equivalent to that of a tin-free steel sheet having a chromium hydrated oxide layer of ^{2 to} 40 mg / m ² as chromium formed thereon Corrosion resistance can be secured.

[0006]

However, a strict comparison between a weld can made of the above-mentioned tin-free steel sheet and a weld can made of the above-mentioned surface-treated steel sheet shows that the weld can made of the above-mentioned surface-treated steel sheet has a tin grain base. Under the influence, depending on the contents of the can, it was found that the inner surface corrosion resistance of the can was slightly inferior to that of the weld can made of the above-mentioned tin-free steel sheet.

That is, for the contents of most foods, beverages, paints, and other chemical products, the tin particles on the base are rather effective in improving the corrosion resistance, but for only a small portion of the contents, tin particles are not. It has been found to selectively corrode. Some consumers consider such slight deterioration of the corrosion resistance of the inner surface of the can as a problem, and a demand has arisen for a surface-treated steel sheet capable of securing the same inner corrosion resistance of the can as the weld can made of the above-mentioned tin-free steel sheet when the can is made by welding.

The present invention has been made in response to such a demand, and has the same corrosion resistance as that of a tin-free steel sheet on one side serving as an inner surface of a welding can, and has a tin-free steel sheet on the other side serving as an outer surface of the welding can. It is an object of the present invention to provide a surface-treated steel sheet for a welding can which has substantially the same characteristics and has the same weldability as the surface-treated steel sheet provided in JP-A-2-159386.

[0009]

The gist of the present invention is as follows.

[0010] 50-150mg on the steel plate surface inside the can
/ M ² metal chromium layer, ^{2 to 2} chromium on this layer
It has a chromium hydrated oxide layer of 0 mg / m ² , and is scatteredly adhered to the outer surface of the can at an area percentage of tin particles of 5 to 20% and an exposed area of the steel sheet at an area percentage of 95 to 80%. Tin particles having a particle size of 0.5 to 3.0 μm, a metal chromium layer of 50 to 150 mg / m ² on the exposed portion of the tin particles and the steel plate, and chromium hydrated oxidation of ^{2 to} 20 mg / m ² as chromium on this layer A surface treated steel sheet for a welding can, characterized by having a material layer.

For example, an area percentage of 10.99% occupied by tin particles having a particle size of 1.5 μm corresponds to a tin amount of 200 mg / m ² .

Hereinafter, the present invention will be described in detail.

According to the present invention, the coating composition on the steel sheet surface serving as the inner surface of the can is made of the same metal chromium layer and chromium hydrated oxide layer as the tin-free steel sheet, and the coating composition on the steel sheet surface serving as the outer surface of the can is provided. A coating composition comprising tin particles scattered and attached to the surface of the steel sheet, a metal chromium layer, and a chromium hydrated oxide layer; tin particles having a particle size of 0.5 to 3.0 μ; It is important that the area percentage occupied by tin particles scattered and attached to the surface is 5 to 20%.

According to Japanese Patent Application Laid-Open No. 2-159386, it is preferable to use 0.1.
It is stated that if the tin particles having a diameter of 2 to 2.0 μ are scattered and adhered to the steel sheet surface so that the area percentage of the tin particles is 5 to 20%, weldability can be imparted. Was scatteredly adhered, and when one side had the same film configuration as the taine-free steel sheet, sufficient weldability could not be secured. The present inventors have conducted intensive studies on this point, and as a result, first, the particle size of the tin particles was set to 0.5 μ or more, preferably 1.0 μ or more, and then the area percentage occupied by the tin particles was 5%. With the above, it has been found that good weldability can be ensured.

When tin particles are scattered on both surfaces, 0.2
When tin particles having a small particle size of about μ are 5% or more in terms of the area percentage occupied by the tin particles, the necessary minimum weldability can be provided. However, as in the present invention, tin particles are scattered and adhered to only one surface. If the particle size of tin particles and the area percentage occupied by tin particles are not in the above ranges, weldability cannot be ensured.

Next, the upper limit of the area percentage occupied by tin particles will be described. According to the results of investigations by the present inventors, when the area percentage occupied by tin particles exceeds 20%, the appearance becomes white. The appearance is different from that of the tin-free steel sheet. Therefore, it is necessary that the area percentage occupied by the tin particles is 20% or less.

Next, the upper limit of the tin particle size will be described.
When the area percentage occupied by tin grains is the same within the range of 5 to 20%, the larger the grain size of tin grains, the better the weldability.
If the particle size of the tin particles is large, the adhesion between the steel sheet base and the tin particles is deteriorated, and a surface-treated steel sheet having a uniform surface appearance and a good distribution of tin particles cannot be obtained. Therefore, the particle size of the tin particles is 3.0.
μ or less, preferably 2.0 μ or less.

Next, the reasons for limiting the amounts of metal chromium and chromium hydrated oxide will be described.

The amount of chromium metal is adjusted to 50 to 150 mg / m ^2.
The reason is that the lower limit is that the coating corrosion resistance cannot be ensured, and the upper limit is that the weldability deteriorates.

The amount of the chromium hydrated oxide is 2 to 20 m
The reason why the amount is limited to g / m ² is that the coating adhesion cannot be ensured below the lower limit, and the weldability cannot be ensured above the upper limit.

Hereinafter, a detailed description will be given based on embodiments.

[0022]

EXAMPLE A low-carbon cold-rolled steel sheet having a thickness of 0.23 mm, which had been cold-rolled, continuously annealed, and temper-rolled by an ordinary method, was subjected to ordinary degreasing (NaOH 50 g / l, 60 ° C., current density 10 A / dm). ² , 0.5 seconds of cathodic electrolysis), normal pickling (H ₂ SO ₄ 50 g / l, room temperature, current density 10 A /
dm ² for 0.5 seconds). Next, tin particles were precipitated on only one surface of the steel sheet under the following tin plating conditions, and then chromium plating was performed on both surfaces under the following chrome plating conditions. Table 1 shows the results of evaluating the following evaluation items for the obtained surface-treated steel sheet.

1. Tin plating conditions (1) Bath conditions Sn ^{2+ 2 to} 30 g / l Free acid concentration (converted to sulfuric acid) 10 to 30 g / l [Phenolsulfonic acid was used as the acid. Bath temperature 45 ° C. (2) Electrolysis conditions Current density 3 to 20 A / dm ² 2. 2. Chrome plating (1) Bath conditions CrO ₃ 100 g / l H ₂ SO ₄ 1.2 g / l Bath temperature 50 ° C. (2) Plating conditions Current density 50 A / dm ² Electric quantity 20-100 C / dm ² Evaluation items (1) Evaluation of color tone (L value) It was measured based on JISZ8701 using an automatic colorimeter (Suga Test Instruments Co., Ltd. AU-CH-1). The lighter the color, the larger the L value.

(2) Paint Corrosion Resistance An epoxy phenol paint (Kansai Paint Co., Ltd. SJ-6256) was applied to the test material and baked (coating amount 50 mg /
dm ² ), the coated film was cross-cut with a knife, immersed in 1.5% NaCl, 1.5% citric acid solution (40 ° C.) for 4 days, and then subjected to a tape peeling test of the cross-cut portion. Evaluation (5 (good) ← → 1 (poor)) (3) Tin removal corrosion resistance Epoxy phenol paint (Sakuramiya Chemical Co., Ltd. S)
K-2305) and baking (coating amount 50 mg / dm ² )
Then, it is processed into a can lid, immersed in a solution of 2.0% thiocyanic acid and 5.0% sulfuric acid for one week, and the corrosion state under the coating film is evaluated (5 (good) ← → 1 (bad)) ( 4) Contact resistance The test material was first heat-treated at 210 ° C for 30 minutes,
The sample was cut into 50 mm square, the two samples were overlapped with the tin-grained surface and the tin-grain-free surface, and sandwiched between electrodes having an electrode diameter of 4.5 mmφ. Then, a pressure of 70 kgf was applied between the electrodes to reduce the contact resistance. It was measured. (The current flowing between the electrodes is 1000m
A) Pass if 300 μΩ or less (good weldability) (5) Evaluation of tin plated particles The test material was examined with a scanning electron microscope at a magnification of 5000 to 1000
Observation was performed at 0 magnification to measure the typical size of tin particles.

(6) Area percentage occupied by tin particles (tin area percentage)

[0026]

[Table 1]

Examples 1 to 12 and Conventional Examples 1 to 2 in Table 1
From the comparison, 50-150 mg
/ M ² metal chromium layer, ^{2 to 2} chromium on this layer
It has a chromium hydrated oxide layer of 0 mg / m ² and is scatteredly adhered to the outer surface of the can at an area percentage of tin grains of 5 to 20% and an exposed area of the steel sheet at an area percentage of 95 to 80%. Tin particles having a particle size of 0.5 to 3.0 μm, a metal chromium layer of 50 to 150 mg / m ² on the exposed portion of the tin particles and the steel plate, and chromium hydrated oxidation of ^{2 to} 20 mg / m ² as chromium on this layer The surface-treated steel sheet with the material layer has exactly the same corrosion resistance as the tin-free steel sheet on the steel sheet surface serving as the inner surface of the can, and has the same appearance characteristics as the tin-free steel sheet on the steel sheet surface serving as the outer surface of the can. It is clear that weldability equivalent to that of a surface-treated steel sheet having tin particles dispersedly adhered to both surfaces can be ensured. Further, from Comparative Examples 1 to 7, those in which the area percentage occupied by tin particles were out of the lower limit and upper limit of the present invention (Comparative Examples 1 and 2), the chromium content of the metal chromium layer was lower limit of the present invention,
When the chromium content of the chromium hydrated oxide layer deviated from the lower limit and the upper limit of the present invention (Comparative Examples 5 and 6), the particle diameter of the tin particles was out of the upper limit (Comparative Examples 3 and 4). It is evident that the one out of the lower limit of the present invention (Comparative Example 7) lacks any of the coating corrosion resistance, appearance characteristics, and weldability.

[0028]

As described above, according to the surface-treated steel sheet for a welding can of the present invention, it is possible to make a welding can without grinding a welded portion, and at the time of making a can, the surface of the steel sheet to which tin particles are scattered and adhered. By setting the side as the outer surface of the can, it is possible to obtain a welded can having substantially the same properties as the outer surface of the can and the same corrosion resistance as the inner surface of the can.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-159386 (JP, A) JP-A-2-282498 (JP, A) JP-A-4-128386 (JP, A) JP-A-4-128386 247897 (JP, A) JP-A-62-124296 (JP, A) JP-A-60-67677 (JP, A) JP-A-56-44793 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) C25D 11/38

Claims (1)

(57) [Claims] 1. A steel plate, which is an inner surface of a can, has a surface of 50 to 150 m.
g / m ² metal chromium layer, on this layer 2 to 2 chromium
A chromium hydrated oxide layer of 20 mg / m ² , and the area percentage of tin grains occupying 5-20% of the area of tin particles on the outer surface of the steel sheet,
Tin particles having a particle diameter of 0.5 to 3.0 μ which are scattered and adhered at an area percentage of 95 to 80% occupied by the exposed portion of the steel sheet, a 50 to 150 mg / m ² metal chromium layer on the tin particles and the exposed steel plate,
A surface-treated steel sheet for a welding can, comprising a chromium hydrated oxide layer of ^{2 to} 20 mg / m ² as chromium on this layer.