JP2820990B2 - Surface treated steel sheet excellent in weldability and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a surface-treated steel sheet and a method for producing the same, particularly excellent in rust prevention, direct paintability and weldability, and suitably used as a material for cans. It relates to the manufacturing method.

<Conventional technology> Art cans, beverage cans,
Tin cans, TFS (tin-free steel), thin Sn-plated steel sheets, and Ni-plated steel sheets are widely used as materials for cans such as food cans. In particular, TFS, thin Sn-plated steel sheet, and Ni-plated steel sheet are mainly used in beverage cans as a low-cost alternative to tinplate.

Thin Sn-plated steel sheets are coated with Sn plating as a base, and then Ni plating
-A Fe-Sn alloy layer is formed to improve corrosion resistance. Furthermore, in order to improve the weldability of this thin Sn-plated steel sheet, a minimum amount of a metal Sn layer required for welding is formed on the surface thereof.
However, metal Sn forms Sn oxide on its surface,
Paint adhesion is extremely poor. Therefore, in order to improve paint adhesion and improve corrosion resistance after coating, further chromate treatment is performed, and eventually, a structure composed of a number of plating layers is exhibited. Therefore, in a thin _Sn plated steel sheet,
It is necessary to control not only the cost of the plating metal material used for each plating to be applied, but also the coating weight.
There are many factors that cause cost increases.

The Ni-plated steel sheet, in order to improve the corrosion resistance, current, than the Ni that is followed by a high in the market was used in an amount of more than 0.5 g / m ² of the current coating weight can not be expected cost benefits .

In addition, TFS is generally poor in weldability because Cr ^OX having a high contact resistance exists thickly.

By the way, due to the sharp appreciation of the yen in recent years, low-priced imported cans and even low-priced imported cans have been rapidly available on the domestic market. So, to compete with this low-priced imported can,
The demand for lower cost can materials has been rapidly increasing.

As a low-cost material for cans, Japanese Patent Application Laid-Open No. Sho 59-145076 proposes a steel sheet for cans using a temper rolling oil having excellent rust prevention and direct coating properties. This steel sheet for cans is used as a component of temper rolling oil as FDA (Food and Drug Administrat).
(Ion), it can be used as a can material for food and drink.

However, when used as a welding can, a method of welding while removing the oxide film is used because the contact resistance of the iron oxide film on the surface is high. Among the cans for eating and drinking, they can be used as art cans, but when used as beverage cans into which liquid can enter, their corrosion resistance is insufficient and their use as steel plates for cans has been limited.

Therefore, the present inventors have examined Ni-plated steel sheets and Ni-plated diffusion-treated steel sheets as low-cost can materials.

By the way, in order to have sufficient performance as a material for welding cans for food cans and beverage cans, good rust resistance, corrosion resistance after painting, paint adhesion, and weldability are required.

In the case of low-cost Ni-plated steel sheets, it is necessary to satisfy the corrosion resistance by using as little as possible the amount of Ni, which continues to be high in the market. Especially, when plating equipment is installed on the continuous annealing line, the line speed of continuous annealing is usually as high as 400 mpm or more, so the number of plating tanks required is increased even with the same amount of plating. Considering the system, it is necessary to reduce the amount of Ni plating to about 1/5 to 1/10 that of conventional Ni-plated steel sheets.

Until now, as a thin Ni plated steel sheet, for example,
There are those described in JP-A-57-61829. However, thin Ni plating has many plating defects, for example, when pinholes exist, a battery is formed between electrochemically noble Ni and base Fe, so Fe elution preferentially occurs. Proceeds and pitting-like corrosion occurs. For this reason, in order to make the corrosion resistance of Ni plating sufficient, a method of increasing the amount of Ni plating or covering the pinholes by chromate treatment is adopted. Therefore, the thin Ni-plated steel sheet was insufficient as a material for cans.

In addition, Ni-plated diffusion treated steel sheet, after applying Ni plating,
By annealing and diffusing Ni, Ni and Fe are completely alloyed, and a Fe—Ni alloy layer excellent in corrosion resistance can be formed. Therefore, this Ni-plated diffusion treated steel sheet
Preferable anodic elution of Fe does not occur, and excellent corrosion resistance can be obtained. However, in order to obtain this Ni-plated diffusion-treated steel sheet at low cost, the amount of Ni plating also needs to be small. For this reason, the amount of Ni becomes uneven, and Ni in the Fe-Ni alloy layer formed by the subsequent annealing
The content is uneven. Therefore, in temporary storage,
Although Fe oxides are not easily formed, Fe oxides are formed during baking. Therefore, when trying to manufacture this Ni-plated diffusion-treated steel sheet at low cost, when the obtained steel sheet is used as a welding can, Fe oxides are generated at the time of paint baking, thereby deteriorating the weldability. This is because Fe oxide has a high contact resistance like the hydrated chromium oxide (Cr ^OX ) layer in TFS (for example, Asano et al .:
Metal Surface Technology (1982) 33 (10) 509-515). Therefore, the Ni-plated diffusion-treated steel sheet was also excellent in corrosion resistance but poor in weldability.

<Problems to be Solved by the Invention> Accordingly, an object of the present invention is to provide excellent corrosion resistance, corrosion resistance, direct paintability, corrosion resistance after painting, paint adhesion, weldability, and low cost. An object of the present invention is to provide a surface-treated steel sheet suitable as a material for welding cans such as cans and beverage cans, and a method for producing the same.

<Means for Solving the Problems> Hereinafter, the present invention will be described in detail.

The present inventors, black plate, Ni diffusion treatment steel sheet,
If TFS etc. uses the conoweld method of welding while shaving the passive film on the surface, welding is possible,
It has been found that Fe itself as a metal constituting the steel sheet does not have poor weldability, and that the Fe oxide formed on the surface over time or during baking of paint is a cause of poor weldability.

Then, first, it was found that the above-mentioned Ni diffusion plating was good as plating excellent in corrosion resistance and not forming Fe oxide.

Also, in order to reduce the cost, the amount of plating must be reduced in order to save the amount of plating metal used.
In particular, in order to finish the final product in the annealing line, not only to save the plating metal, but also to add plating equipment to the annealing line where the line speed is faster than normal plating, many plating tanks are required, Since capital investment increases, it is necessary to reduce the amount of plating. In the case of single-layer plating, if the plating amount is small, pinholes are present and the corrosion resistance cannot be satisfied. In addition, an iron oxide film is formed on the pinhole portion, and the weldability deteriorates. Therefore, annealing is performed after Ni plating to completely diffuse and infiltrate the Ni layer into the steel, so that the pinholes that exist immediately after Ni plating can also form a Fe--Ni alloy layer without pinholes due to the diffusion of Ni. it can. The formed Fe-Ni alloy layer itself is extremely excellent in corrosion resistance, but since the potential is closer to Fe than Ni, even if there are scratches reaching the base iron,
Excellent corrosion resistance because Fe is hardly eluted.

Immediately after finishing this Ni-plated diffusion treated steel sheet,
It is considered that there is no Fe oxide and the weldability is good. However, welding was difficult in practice, and was not suitable as a material for welding cans. Therefore, according to an experiment performed by the present inventors, it was possible to weld even a Ni-plated diffusion-treated steel sheet when paint baking was not performed, but it became difficult to perform welding when paint bake was performed. Therefore, it was considered that Fe oxide was formed at the time of baking, and that the weldability was reduced as described above.

Therefore, in order to prevent the formation of Fe oxide after baking, further plating may be considered, but it is not only impossible to manufacture at low cost, but also to perform different kinds of plating when the amount of plating is small. In this case, a battery is formed between the new plated metal and the Fe-Ni alloy, which causes a reduction in corrosion resistance. Therefore, the present inventors, Ni
It has been found that the formation of Fe oxide can be reduced by performing a wet skin pass using a rolling oil having excellent rust resistance on a steel sheet subjected to Ni diffusion treatment by annealing after plating.

In addition, the steel sheet for cans is always subjected to temper rolling after annealing, and it is common to apply a rust preventive oil after this temper rolling. However, when the rust-preventive oil was applied after temper rolling, sufficient weldability was not yet obtained. Therefore, the present inventors apply a large number of strains to the surface of the steel sheet during the temper rolling, and think that Fe oxides may be easily formed in the distorted portions, and performed a temper rolling by using a rolling oil excellent in rust prevention. When the coating was performed while coating, a surface-treated steel sheet having sufficient weldability even after baking was able to be obtained.

That is, the present invention has a Fe-Ni alloy layer having a weight ratio of Ni / (Fe + Ni) of 0.02 to 0.5 and a thickness of 10 to 5000 mm on the surface layer of the steel sheet, and drying the rust-preventive oil film on the Fe-Ni alloy layer. 1-100m by weight
An object of the present invention is to provide a surface-treated steel sheet formed of g / m ² and having excellent weldability.

The rust-preventive oil film is formed by adding (a) a petroleum wax and / or a synthetic wax and / or lanolin specified in FDA (Food and Drug Administration) paragraph No. 178-3910 to 10-60.
(B) 5 to 40% by weight of a fatty acid specified in FDA paragraph No. 178-3910; (c) 5 to 30% by weight of triethanolamine specified in FDA paragraph No. 178-3910; d) 10-40% by weight of mineral oil as defined in FDA paragraphs 178-3910, (e) polyethylene glycol monostearate as a nonionic activator and / or FDA paragraphs 178-3340.
It is preferably made of a rust preventive oil containing 1 to 20% by weight of a nonionic activator defined as 0.

As the method the present invention can be obtained suitably the surface treated steel sheet, plated with Ni of 0.02 to 0.5 g / m ² on the surface of the steel sheet, subsequently the Ni and continuous annealing in a reducing atmosphere into the base steel sheet in Ni / (Fe + Ni) on the surface layer of steel sheet by diffusion and infiltration
After forming a Fe-Ni alloy layer having a weight ratio of 0.02 to 0.5 and a thickness of 10 to 5000 mm, the steel sheet is subjected to temper rolling continuously using rust-preventive rolling oil, and the dry weight of the steel sheet surface is 1 to 100 mg. An object of the present invention is to provide a method for producing a surface-treated steel sheet having excellent weldability, characterized by forming a rust-preventive oil film of / m ² .

The weight ratio of Ni / (Fe + Ni) in the Fe-Ni alloy layer formed on the surface layer of the surface-treated steel sheet of the present invention is 0.02 to 0.5, preferably 0.05 to 0.20. Ni / (Fe + N) in Ni diffusion layer
If the weight ratio of i) is less than 0.02, the corrosion resistance of the Fe-Ni alloy layer itself becomes insufficient. The melting of the base steel sheet becomes remarkable.

The thickness of the Fe—Ni alloy layer is 10 to 5000 °, preferably 200 to 5000 °. If the thickness of the Fe-Ni alloy layer is less than 10 mm, the corrosion resistance becomes insufficient, and if it exceeds 5000 mm,
Usually, since an Fe—Ni alloy is hard and brittle, when a welded can is manufactured using the obtained steel sheet, many defects occur during forming such as flange processing of a can body, and the corrosion resistance is reduced.

The rust-preventive oil used for the rust-preventive oil film formed on the Fe-Ni alloy layer is not particularly limited as long as it is a rust-preventive oil that can be directly applied in a temper rolling step of a steel sheet and that can be directly applied.

In particular, as a rust preventive oil, (a) Petroleum wax and / or synthetic wax and / or lanolin specified in FDA (Food and Drug Administration) paragraph NO.
(B) 5 to 40% by weight of a fatty acid specified in FDA paragraph No. 178-3910; (c) 5 to 30% by weight of triethanolamine specified in FDA paragraph No. 178-3910; d) 10-40% by weight of mineral oil as defined in FDA paragraphs 178-3910, (e) polyethylene glycol monostearate as a nonionic activator and / or FDA paragraphs 178-3340.
When a composition oil obtained by dispersing and emulsifying 1 to 20% by weight of a nonionic activator specified in 0 in an aqueous solvent, specifically, a composition oil described in JP-A-59-145076, It is possible to obtain a surface-treated steel sheet which is very hygienic and suitable as a can for eating and drinking.

The rust oil film, the 1 to 100 mg / m ² by dry weight on top of the Fe-Ni alloy layer, is preferably 1~23mg / m ² Katachi設. If the rust-preventive oil film is formed in the range of 1 to 100 mg / m ² , it is possible to obtain a surface-treated steel sheet having excellent rust-preventive properties, weldability and direct paintability. When the composition is used as a rust-preventive oil to make a surface-treated steel sheet for food and drink cans, the upper limit of the coating amount is limited for food and drink cans, so the dry weight is 1 to 1. Preferably, it is in the range of 23 mg / m ² .

The present invention, as a preferred method of producing the surface-treated steel sheet having the above configuration, the surface of the steel sheet of 0.02 to 0.5 g / m ² Ni
After plating, the steel is continuously annealed in a reducing atmosphere to diffuse and infiltrate Ni into the base steel sheet, and Ni / (Fe
+ Ni) Fe-Ni with a weight ratio of 0.02 to 0.5 and a thickness of 10 to 5000 mm
After forming the alloy layer is subjected to temper rolling with a rust-preventive rolling oil continuous, and forming a rust-preventive oil film of 1 to 100 mg / m ² by dry weight to the steel plate surface, welding It is intended to provide a method for producing a surface-treated steel sheet having excellent heat resistance.

In this method, first, 0.02-
0.5 g / m ^2, preferably for the Ni plating 0.05 to 0.2 g / m ^2.
When Ni plating amount is less than 0.02 g / m ^2, the corrosion resistance is lowered,
If it exceeds 0.5, no further effect of improving corrosion resistance can be obtained, which is disadvantageous in cost.

Next, the steel sheet is continuously annealed in a reducing atmosphere, and Ni is diffused and penetrated into the base steel sheet to form an Fe-Ni alloy layer.

The reducing atmosphere used is not particularly limited, and examples thereof include a mixed atmosphere of N ₂ and H ₂ .

The continuous annealing is usually performed at 650 ° C. to 750 ° C. for 30 seconds to 10 minutes.

Thus, the above-mentioned Fe-
After forming the Ni alloy layer, a temper rolling treatment is continuously performed using the rust-preventive oil to form the rust-preventive oil film on the surface layer.

The temper rolling can be performed according to a conventional method, and is not particularly limited. For example, it may be performed under the condition of 1.5 to 2%.
By performing rolling using the rust-preventive oil in this temper rolling step, there is no need to degrease before can making, and there is no need to provide an oiling step, so that the surface treatment is not only economical but also excellent in weldability. Steel sheet can be obtained. Further, in order to carry out the present invention most effectively, it is preferable to provide a Ni plating facility before the continuous annealing line and provide a temper rolling facility on the exit side of the annealing line. By connecting the plating annealing temper rolling as one line and finishing the final product at once,
Significant cost reduction can be achieved by continuation. In addition, since each facility is connected, the steps of plating → annealing → temper rolling can be performed continuously without time delay, and the formation of Fe oxide can be prevented, improving the weldability. Is even larger.

<Examples> Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention.

(Examples 1 to 3 and Comparative Examples 1 to 8) In each example, a steel plate for plating (Al killed steel) having a thickness of 0.1 mm was used.
After cold rolling to 2 mm and electrolytic cleaning, Table 1
A sample of a surface-treated steel sheet was prepared according to the manufacturing process shown in FIG. The Ni plating bath and annealing conditions used are as follows.

Ni plating bath Composition: Nickel sulfate 250g / l Nickel chloride 45g / l Boric acid 30g / l Bath temperature 60 ° C Current density 5A / dm ² Annealing condition Atmosphere: NHX gas atmosphere (10% H ₂ + 90% N ₂ ) Annealing temperature: 700 ° C. The rust-proof rolling oil used had the following composition.

Ni plating amount of this sample, Ni / (Fe + Ni) in surface layer
The ratio, rust prevention, corrosion resistance, paint adhesion by T-peel test, and high-speed weldability were measured or evaluated according to the following methods. For comparison, tinplate (Comparative Example 6), TF
The same measurement and evaluation were performed for S (Comparative Example 7) and thin Sn-plated steel sheet (Comparative Example 8).

Ni plating amount Measured using fluorescent X-rays.

Ni / (Ni + Fe) ratio The GDS was used to determine the weight ratio in the search direction.

Rust prevention The sample was exposed using a dry / humidity cycle tester under conditions where a dry state at a temperature of 25 ° C and a relative temperature of 50% and a wet state at a temperature of 50 ° C and a relative humidity of 98% ° C were repeated every 30 minutes. The number of rusts generated on the sample surface was measured, and the rust prevention was evaluated according to the following criteria.

Corrosion resistance After coating the surface of the sample with an epoxyphenol-based paint to a thickness of 5 μm, 70 ml of 90 ° C. tomato juice was hot-packed using this. After the hot pack was aged at 55 ° C. for 10 days, it was taken out, the state of corrosion was observed, and the corrosion resistance was evaluated according to the following criteria.

High-speed weldability Using a copper wire having a wire diameter of about 1.5 mmφ as a welding electrode, two samples were overlapped under constant pressure, and electric resistance welding was performed at a welding speed of 50 m / min while moving the welding electrode. At this time, the weldability was evaluated from the appropriate range of the welding current and the pressing force determined based on the condition that the welded portion had sufficient strength and no splash was generated.

Paint Adhesion After applying an epoxyphenol-based paint to the surface of each of the two samples to a thickness of 5 μm, the painted surfaces are coated to a thickness of 40 μm.
A μm nylon 12 film was sandwiched by pressing to adhere to each other to prepare a tensile test piece. This test piece was subjected to a T-peel test using a tensile tester to measure the adhesive strength, which was used as an index of paint adhesion.

In the above results, the steel sheets obtained in Comparative Examples 1 to 3 are equivalent to or less than the present invention in terms of cost,
Both corrosion resistance and weldability are poor, and there is no practicality as a steel plate for welding cans. Although the steel sheets of Comparative Examples 4 and 5 are similar to the present invention, Comparative Example 4 does not use the rust-preventive rolling oil at the time of temper rolling, so that not only the rust-prevention property is slightly poor but also the weldability is poor. In Comparative Example 5, since the Ni / (Ni + Fe) ratio was as high as 0.8 on the steel sheet surface, paint adhesion and corrosion resistance were poor, and pitting-like corrosion occurred.

Examples 1 to 3 satisfy the present invention and have the rust prevention, corrosion resistance, paint adhesion and high-speed weldability required for a steel plate for a welding can, and are low in place of conventional tinplate and thin Sn-plated steel plates. It has been found that cost can materials can be provided.

<Effect of the Invention> The surface-treated steel sheet of the present invention is excellent in corrosion resistance, rust prevention, direct paintability, corrosion resistance after painting, paint adhesion and weldability, and can be manufactured at low cost. Therefore, the present invention greatly contributes to resource saving and energy saving,
The economic value is extremely high.

Further, the method of the present invention is suitable as a method for producing the above surface-treated steel sheet.

Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI C25D 5/48 C25D 5/48 (72) Inventor Fumio Kozuka 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Corporation Chiba Works (72) Invention Person Yuji Shimoyama 1 Kawasaki-cho, Chiba-shi, Chiba Pref. In the Chiba Works of Kawasaki Steel Corporation (72) Inventor Hideo Kugaminato 1 Kawasaki-cho, Chiba-shi, Chiba Pref. 62-33795 (JP, A) JP-A-60-114596 (JP, A) JP-A-59-145076 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B32B 15/08 C25D 5/26 B05D 7/14 C25D 5/48 C09D 5/00 B05D 3/10

Claims (4)

(57) [Claims] The weight ratio of Ni / (Fe + Ni) is 0.02 to the surface layer of a steel sheet.
A Fe-Ni alloy layer having a thickness of 10 to 5000
Excellent surface treated steel sheet rust oil film 1 to 100 mg / m ² formed comprising weldability by dry weight -Ni alloy layer. 2. The rust-preventive oil film comprises: (a) a petroleum wax and / or a synthetic wax and / or lanolin specified in FDA (abbreviation of Food and Drug Administration) paragraph No. 178-3910;
(B) 5 to 40% by weight of a fatty acid specified in FDA paragraph No. 178-3910; (c) 5 to 30% by weight of triethanolamine specified in FDA paragraph No. 178-3910; d) 10-40% by weight of mineral oil as defined in FDA paragraphs 178-3910, (e) polyethylene glycol monostearate as a nonionic activator and / or FDA paragraphs 178-3340.
2. The surface-treated steel sheet according to claim 1, comprising a rust preventive oil containing 1 to 20% by weight of a nonionic activator defined as 0. 3. A steel sheet surface is coated with a Ni plating of 0.02 to 0.5 g / m ² , and then continuously annealed in a reducing atmosphere to diffuse and infiltrate Ni into the base steel sheet, thereby forming Ni / (Fe + Ni) on the surface layer of the steel sheet. After forming a Fe-Ni alloy layer with a weight ratio of 0.02 to 0.5 and a thickness of 10 to 5000 Å, temper rolling is continuously performed using rust-preventive rolling oil, and a dry weight of 1 to 100 mg / and forming a rust-preventive oil film of m ^2, the production method of the excellent surface treatment steel sheet weldability. 4. The rust-preventive rolling oil used for the temper rolling includes: (a) a petroleum wax and / or a synthetic wax and / or lanolin specified in FDA (abbreviation of Food and Drug Administration), paragraph No. 178-3910. From 10 to 60
(B) 5 to 40% by weight of a fatty acid specified in FDA paragraph No. 178-3910; (c) 5 to 30% by weight of triethanolamine specified in FDA paragraph No. 178-3910; d) 10-40% by weight of mineral oil as defined in FDA paragraphs 178-3910, (e) polyethylene glycol monostearate as a nonionic activator and / or FDA paragraphs 178-3340.
The method for producing a surface-treated steel sheet according to claim 3, which is a rust-preventive oil containing 1 to 20% by weight of a nonionic activator defined as 0.