JPH1192989A - Surface treated steel sheet excellent in seam weldability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treated steel sheet excellent in seam weldability, capable of stably producing a welded can in a state of being nongrind, good in the color tone of the steel sheet and furthermore combining corrosion resistance. SOLUTION: In a surface treated steel sheet in which both sides of a steel sheet base are successively applied with a tinning layer, a metallic chromium layer and a chromium hydrated oxide layer, the coating weight of the tinning layer is regulated to 0.3 to 3.0<2> g/m per side of the steel sheet, furthermore, the existing form of tin is regulated to the one of being granularly scattered onto the surface of the steel sheet, also, the average particle diameter of the tin grains is regulated to 0.1 to 5 μm, its area ratio occupied in the steel sheet is regulated to 10 to 70%, the coating weight of the metallic chromium is regulated to 110 to 300 mg/m<2> per side of the steel sheet, and the coating weight of the chromium hydrated oxide layer is regulated to the range of 3 to 30 mg/m<2> per smde of the steel sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel plate used for containers such as 18-liter cans and pail cans, and more particularly to a steel plate used for welding cans for joining can bodies by electric resistance seam welding. The present invention relates to a surface-treated steel sheet having excellent seam weldability that can produce cans without maintaining high productivity.

[0002]

2. Description of the Related Art Thin chromium-plated steel sheets (so-called tin-free steel) are widely used for manufacturing 18-liter cans and pail cans, and are generally formed into can bodies by electric resistance seam welding. However, since this thin chromium-plated steel sheet has a hydrated oxide layer of chromium, which is a high electrical resistance substance, on its surface, it is difficult to weld the joint of the can body by electrical resistance seam welding as it is, It is common practice to grind the welded portion in advance to remove most of the chromium plating layer. However, at the time of grinding, the grinding powder containing metallic chromium is scattered around, which is not environmentally preferable, and it is difficult to completely remove the grinding powder by suction. Therefore, the grinding powder containing chromium remains in the manufactured can. There is also the problem of doing it. Furthermore, in grinding, in order to perform welding stably, the welded part is often grounded more than necessary, so there is a part where the chromium plating is cut off around the welded part and the ground iron is exposed,
There is also a problem that the part is corroded or rust is generated, and in order to solve these problems, direct welding of a thin chromium-plated steel sheet without grinding has been attempted.

As means for improving the weldability of such a thin chromium-plated steel sheet and enabling welding without grinding, Japanese Patent Application Laid-Open No. 61-213398 discloses a coating amount of a thin chromium-plated steel sheet, particularly chromium hydration. Although a steel sheet with a reduced amount of material has been disclosed, such means cannot stably perform welding, and depending on the type of welding machine, the weldability may be insufficient, and in practice, it is sufficiently satisfactory. Not something. Japanese Patent Publication No. Sho 63-26200 discloses a steel sheet in which the form of metallic chromium on the surface of a thin chromium-plated steel sheet is formed into fine projections or grains to reduce the contact resistance of a welded portion and improve weldability. Although the weldability is considerably improved depending on the form of the chromium metal, the color tone of the steel sheet becomes dark due to the presence of projections and grains, and fingerprints are easily formed, so that it is hardly accepted by can users. As a method for improving the weldability of thin chromium-plated steel sheets,
JP-A-35718 discloses a steel sheet in which metal tin is interposed between chromium metal and chromium oxide. This steel sheet has the advantage that good weldability can be obtained because metal tin quickly melts at the time of welding and wets the joint surface and can stabilize the contact resistance to a low value, but tin plating is performed on the entire steel sheet Therefore, the cost becomes high, and tin color of the steel plate becomes white, which is not preferred by can users.

As a means for solving the above problem, Japanese Patent Publication No. 6-9
Japanese Patent No. 6790 discloses a steel sheet in which metal tin is previously dispersed and plated in a granular form, and a thin chromium-plated steel sheet is further formed on the steel sheet. 20 mg / m ²
As described above, the weldability is not sufficient because it is as small as 200 mg / m ² or less. Similarly, Japanese Patent Publication No. 16397/1990 discloses a steel sheet in which metal tin is dispersed and thin chromium plating is performed thereon. This steel sheet has also been improved to such an extent that the color tone becomes slightly whitish. Since the amount of chromium is as small as 7 mg / m ² or more and 100 mg / m ² or less, corrosion resistance is not sufficient.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned various problems relating to the conventional surface-treated steel sheet, and to stably produce a welding can in a non-grinding state. It is an object of the present invention to provide a surface-treated steel sheet having a good color tone and also having excellent corrosion resistance and excellent seam weldability.

[0006]

In order to solve the above-mentioned problems, the present inventors have determined the amount of tin per unit area present on a steel sheet, its form (shape and size), the area coverage of the steel sheet, the amount of chromium plating, It was found that the amount of the hydrated oxides and the like had a complex effect, and the systematic elucidation resulted in the completion of the present invention. Accordingly, the present invention provides a surface-treated steel sheet having a tin-plated layer, a metal chromium layer and a hydrated oxide layer of chromium on both sides of a steel sheet base in order, and the basis weight of the tin-plated layer is 0.3 g / m3 per one side of the steel sheet. ² or more and 3.0 g / m ² or less, and the existence form of tin shall be scattered in the form of particles on the surface of the steel sheet substrate,
And the average particle diameter of the tin particles is 0.1 μm or more and 5 μm or more.
m, the area ratio of the steel sheet surface to 10% or more,
70% or less, the basis weight of the metal chromium layer is 110 mg / m ² or more and 300 mg / m ² or less per one side of the steel sheet, and the hydrated oxide layer of chromium is 3 mg / m ² or more and 30 mg per one side of the steel sheet. / M ² or less.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a tin plating layer is interposed between a steel sheet base and a chromium metal layer, and the tin plating layer is melted during welding to improve weldability. At this time, the weight of tin plating is set to 0.3 g / m ² or more and 3.0 g / m ² or less per one side of the steel sheet. The basis weight is 0.3 g / m ²
If it is less than 3, melting and spreading due to melting at the time of welding are not sufficient and weldability is insufficient, while the basis weight is 3.0 g / m.
^If it exceeds ² , the weldability is sufficient, but the cost for tin plating rises, which is not only uneconomical, but also the color of the product becomes whitish and unacceptable to the user of the can. In addition, a more preferable range is 0.35 g.
/ M ² or more and 1.5 g / m ² or less.

In the present invention, it is assumed that the tin plating layer is scattered in the form of particles on the steel sheet substrate. Thereby, it is possible to reduce the tin for reducing the contact resistance by allowing metal tin to be present in the direction perpendicular to the steel sheet surface. At that time, the diameter of the tin particles, the average particle size is 0.1μm or more,
The thickness is set to 5 μm or less. If the average particle size of the metal tin-plated particles is less than 0.1 μm, the melt spread during welding is insufficient and the weldability is insufficient, and if the average particle size exceeds 5 μm, the weldability is sufficient. Not only is the amount of plating too large, costly and uneconomical,
It is not preferable because the color tone becomes whitish and cannot be accepted by can users. More preferred average particle size is 0.5 μm
It is 3 μm or less.

[0009] The area ratio of the above-mentioned tin particles to the surface of the base steel sheet is 10% or more and 70% or less. If the area ratio is less than 10%, the melting and spreading of the tin during welding is insufficient and the weldability is insufficient, and the area ratio is 7%.
If it exceeds 0%, the weldability is sufficient, but the color tone becomes whitish and it becomes unacceptable to the user of the can. It is more preferable that the area ratio is 25% or more because the melting and spreading is sufficiently wide, and it is more preferable that the area ratio be 50% or less from the viewpoint of color tone.

[0010] A metal chromium plating is applied on the metal tin granular plating layer satisfying the above conditions and on the steel substrate on which no metal tin is deposited to impart corrosion resistance to the steel sheet. The basis weight of metallic chromium is 110 mg / m ² or more and 300 mg / m ² or less per one side of the steel sheet. If the plating amount of metallic chromium is less than 110 mg / m ² , the corrosion resistance is insufficient, and if it exceeds 300 mg / m ² , the corrosion resistance is not only saturated and uneconomical, but also requires a long time for plating, thereby increasing productivity. Is undesirably inhibited.

The chromium hydrated oxide is applied on the chromium metal layer in a range of 3 mg / m ² or more and 30 mg / m ² or less per one side of the steel sheet. The hydrated oxide of chromium not only improves the corrosion resistance by coating the steel sheet, but also has the function of improving the paintability. If the amount is less than 3 mg / m ² , not only the corrosion resistance is insufficient, but also the paintability is insufficient. It is not preferable because it lowers. On the other hand, when the amount of hydrated oxide of chromium exceeds 30 mg / m ² , corrosion resistance and weldability are sufficient, but the amount of hydrated oxide of chromium is a high electric resistance material, which is not preferable because it deteriorates weldability. The preferred range of the hydrated oxide amount of chromium is 5 mg / m ² or more and 25 mg / m ² or less.

The surface-treated steel sheet according to the present invention can be manufactured by the following method. First, a predetermined metal tin plating is applied to a steel plate substrate.When performing electroplating using a known sulfuric acid bath composed of tin sulfate and sulfuric acid, the acid concentration, tin ion concentration, current density, plating time, temperature, and flow rate are determined. By appropriately controlling, tin particles can be scattered at a predetermined particle size and area ratio on the steel sheet surface. At this time, hydroquinone, phenolsulfonic acid, or the like, which is an antioxidant for tin ions, may be appropriately added. The same plating can be obtained even if the plating conditions are appropriately adjusted by using a chloride bath mainly composed of tin chloride.

[0013] The metallic chromium and chromium hydrated oxide layer are formed on the steel sheet which has been subjected to the granular tin plating as described above. The means may be a conventional method of manufacturing a thin chromium-plated steel sheet, and is not particularly limited. For example, the metallic chromium and the hydrated oxide of chromium may be produced in the same plating bath, or they may be produced in different baths. Usually, metal chromium and a hydrated oxide of chromium can be formed and deposited on metal tin by electroplating using a plating solution containing chromic anhydride, sulfuric acid, and / or fluoride. At that time, the amount of deposited chromium metal and chromium hydrated oxide can be kept within the above-mentioned predetermined range by adjusting the amount of input electricity.

[0014]

The present invention will be specifically described below with reference to examples. The plating solution and the plating conditions were changed in the range shown in Table 1 to apply tin plating to the steel sheet for cans, and then the conditions were changed in the range shown in Table 2 to plate metal chromium. Generated and precipitated to obtain a product. The characteristic values of each plating layer of the obtained surface-treated steel sheet were as shown in Table 5 according to the change in the above-mentioned processing conditions.

[0015]

[Table 1]

[0016]

[Table 2]

These steel sheets were subjected to a welding test and a corrosion resistance test as steel sheets for cans. The test conditions are as shown in Tables 3 and 4, and the test results are as shown in Table 5. The appropriate welding current range serving as an evaluation criterion for the weldability is defined as the lower limit current value required for the mechanical strength of the welded portion to exceed the base metal strength and the welded portion when the welding conditions shown in Table 3 above are used. It is the difference from the upper limit current value that generates dust,
It is evaluated that the larger the difference, the better the weldability. As shown in Table 5, the steel sheet satisfying the conditions for metal tin plating, chromium plating, and chromium hydrate oxide according to the present invention had good weldability and excellent corrosion resistance. Further, the color tone was visually inspected separately, and the color tone was sufficiently satisfactory as a can.

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

According to the surface-treated steel sheet of the present invention, the properties of the tin-plated layer and the amounts of the chromium-plated layer and the chromium hydrated oxide layer existing on the steel sheet substrate are suitably determined. Although the surface steel sheet has good corrosion resistance, it has good weldability, and can can be stably formed.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroki Nakamaru 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Corporation (72) Inventor Hisao Yasunaga 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki (72) Inventor Katsuhito Kawamura 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Kawasaki Steel Corporation Chiba Works

Claims (1)

[Claims] 1. A surface-treated steel sheet having a tin-plated layer, a metal chromium layer and a hydrated oxide layer of chromium on both sides of a steel sheet substrate in sequence, wherein the tin-plated layer has a basis weight of 0.3 g per one side of the steel sheet.
/ M ² or more and 3.0 g / m ² or less, tin is scattered in the form of particles on the surface of the steel sheet substrate, and the average particle diameter of the tin particles is 0.1 μm or more and 5 μm or less. The occupied area ratio is 10% or more and 70% or less. The metal chromium layer has a basis weight of 110 m per one side of the steel plate.
g / m ² or more and 300 mg / m ² or less, and the hydrated oxide layer of chromium is 3
A surface-treated steel sheet having excellent seam weldability, which is in the range of not less than mg / m ^{2 and not} more than 30 mg / m ² .