JPH11106953A - Steel sheet for welded can excellent in weldability, corrosion resistance and film adhesion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel sheet for a welded can particularly excellent in seam weldability, corrosion resistance and film-adhesion as can making stock. SOLUTION: (1) On at least one surface of a steel sheet, an Fe-Ni alloy plating layer contg. 5 to 45% Ni is formed by 10 to 300 mg/m<2> by an Ni content, and, on its surface, a hydrated chromium oxide layer of 2 to 15 mg/m<2> by the amt. expressed in terms of metal Cr is formed. (2) On at least one surface of a steel sheet, an Fe-Ni alloy plating layer contg. 5 to 45% Ni is formed by 10 to 300 mg/m<2> by an Ni content, and, on its surface, a chromate coating layer composed of metal Cr of 2 to 20 mg/m<2> and hydrated chromium oxide of 2 to 15 mg/m<2> by the amt. expressed in terms of metal Cr is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel material for a can, which is excellent in seam weldability, corrosion resistance, and film adhesion, as a material for can production.

[0002]

2. Description of the Related Art The wire seam resistance welding method developed by Sudronic (Switzerland) has rapidly progressed as a joining technique for welding can bodies, and cans joined by this welding method are widely used in the field of beverage cans. Has been put to practical use. The wire seam resistance welding method is to overlap the welded portion by 0.5 to 0.6 mm, sandwich the copper wire between two circular electrodes wound with a constant pressure, and apply an alternating current to about 1 mm. This is a welding method in which a steel plate-steel plate interface that is in contact with the heat generated by electric resistance between the plates is melted or semi-molten, and the can body is joined. One of the features of this welding method is that by adjusting the waveform and frequency of the alternating current to be applied and the pressure between the electrodes, a 600-80
High-speed welding at 0 cans / minute can be performed stably. In addition, in this welding method, the lower the electrical contact resistance value of the surface of the steel plate to be welded, the more uniform the current distribution between the electrodes and the more uniform the welding can be performed. It is said to be excellent.

[0003] In recent years, in the beverage container market, the economical and quality competition of welding cans with materials such as aluminum cans, PET bottles and bottles has intensified. More economical materials have been required. As a result, as a steel plate for cans used in this type of welding can, a # 25 tin having an Sn plating amount of about 2.8 g / m ² was used.
As disclosed in JP-A-59-74294,
Steel plates using Ni instead of expensive Sn have been developed.

[0004] In the can making process, conventionally, about 1 m
Coating and print baking of the four sided plates were performed for each sheet.However, instead of coil coating technology to paint the coil product as it is, or printing on the outer surface of the can, a pre-printed film was laminated on the coil. A technology for laminating a clear film instead of painting on the inner surface of a can has been developed, and the painting and printing processes have been greatly shortened and the efficiency has been improved.

[0005]

On the other hand, in terms of quality, higher quality and weldability than before have been required. In particular, in a welded can with a laminated film, the welding spatter generated during welding (a spark of spark generated during welding, mainly iron) may damage the laminated film and induce iron elution into the contents. It has been pointed out that welding spatter may remain in the film and lead to the elution of iron into the contents.
Japanese Patent Application Laid-Open No. 74293/1984 and Japanese Patent Application Laid-Open No. 59-74294 have not yet sufficiently solved the problem.

[0006]

Means for Solving the Problems The present inventors have intensively studied the cause of the occurrence of welding spatter recognized in the above prior art, and as a result, welding spatter is caused by the difference in melting point between the plating layer and the ground iron. Found to happen. That is, S
In the case where a metal having a lower melting point than the base iron, such as n, covers the steel sheet surface, the Sn plating layer is molten at a temperature much lower than the temperature at which the base iron is melted and joined. In the case where a metal having a higher melting point than the ground iron, such as Ni, covers the steel sheet surface,
At the temperature at which the Ni plating layer melts and joins, it has been found that since the base iron has already melted, welding spatter mainly containing iron has been generated.

On the basis of the above findings, the inventors of the present invention applied Ni to the surface layer of Fe and Ni having a melting point difference, not as a Ni plating layer, but as an Fe—Ni alloy plating. By reducing the Ni content in the alloy layer to a certain ratio or less, the generation of welding spatter generated due to the difference in melting point between Ni and iron is microscopically dispersed, so that the generation of spatter during welding can be suppressed. It was discovered.

That is, the present invention relates to the following: (1) Ni is coated on at least one surface of a steel
% Of the Fe-Ni alloy plating layer in the amount of Ni is 10 to 3%.
00 mg / m ² , and the surface thereof has a metal Cr equivalent of 2 mg.
A welded steel sheet excellent in weldability, corrosion resistance, and film adhesion, wherein a hydrated Cr oxide layer of 15 mg / m ² is formed. (2) Ni is coated on at least one surface of the steel sheet by 5-45.
% Of the Fe-Ni alloy plating layer in the amount of Ni is 10 to 3%.
00 mg / m ² and ² to 20 mg / m 2
^A steel plate for a welded can excellent in weldability, corrosion resistance and film adhesion, characterized by forming a chromate coating layer comprising 2-15 mg / m ² of metal Cr and 2-15 mg / m ² of hydrated Cr oxide in terms of metal Cr; It is intended to provide.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A steel plate for a welding can having excellent weldability, corrosion resistance, paint and film adhesion, which are the effects of the present invention, will be described in detail below. In the present invention, the plating base sheet is not particularly limited, and a steel sheet usually used as a container material is used. The production method and material of the original plating sheet are not particularly limited, and the production is performed through the steps of normal rolling of a slab, hot rolling, pickling, cold rolling, annealing, pressure control, and the like. When plating the plating base plate, usually, degreasing and pickling are performed as a pretreatment in order to clean the surface of the plating base plate, but these methods are not particularly limited. For example, in a 10% sodium hydroxide solution, After degreasing, pickling may be performed in a 5% sulfuric acid solution.

[0010] Following degreasing and pickling, Fe-Ni alloy plating is performed. The method of applying the Fe-Ni alloy plating is not particularly limited, but in order to industrially and economically obtain a Fe-Ni alloy plating layer in which Ni is uniformly dispersed on the surface, it is necessary to use a known plating bath. Electrically Fe-Ni
Alloy plating may be performed. In the present invention, Fe-N
In view of the essence of the present invention, the Ni content in the i-alloy plating layer is restricted to 45% or less by weight. This is because, as described above, when the Ni content exceeds 45%, ground iron and N
This is because the occurrence of welding spatter due to the melting point difference between i becomes apparent. On the other hand, Ni in the Fe—Ni alloy plating layer
As the content is lower, the generation of welding spatter is suppressed,
If the Ni content is less than 5%, not only the excellent corrosion resistance of the Ni metal is impaired, but also the forgeability of the Ni is not sufficiently exhibited, the bonding at the interface is weakened, and the bonding strength is reduced. Therefore, weldability deteriorates. Therefore, Fe-
The Ni content in the Ni alloy plating layer needs to be 5 to 45%.

Further, the amount of Ni plating in the Fe—Ni alloy plating layer is also restricted to 10 to 300 mg / m ² . This is because if the amount of Ni plating is less than 10 mg / m ² ,
Not only does the excellent corrosion resistance of the metal deteriorate,
The forging property of i is not sufficiently exhibited, and the bonding property at the interface is weakened and the bonding strength is reduced, so that the weldability is deteriorated. Therefore, the Ni content in the Fe—Ni alloy plating layer needs to be 10 mg / m ² or more. On the other hand, Fe-Ni
As the amount of Ni plating in the alloy plating layer increases, the corrosion resistance and weldability also improve, but the amount of Ni plating is 300 mg / m.
^If it exceeds ² , these improvement effects will be saturated and economically disadvantageous. Therefore, the amount of Ni plating in the Fe—Ni alloy plating layer is also restricted to 10 to 300 mg / m ² .

After the Ni plating is applied to the steel sheet, a chromate treatment is subsequently performed. The purpose of the chromate treatment is to ensure excellent film adhesion and corrosion resistance, and excellent film adhesion and corrosion resistance are achieved by using a hydrated chromium oxide contained in the chromate film and a chemical compound in which the functional groups of the film are strong. Secured by performing a join. However, the hydrated Cr oxide in the chromate film is an electrical insulator and has a very high electric resistance, which is a negative factor that degrades the weldability. It is very important to have an appropriate amount of the chromate film deposited so as not to deteriorate the properties. Therefore, the amount of chromate film adhered was 2 in metal chromium equivalent per side.
１５15 mg / m ² is selected.

That is, the adhesion amount of the hydrated Cr oxide is 2 mg / m 2
^If it is less than ² , a sufficient effect for improving the film adhesion and corrosion resistance cannot be obtained, so that an adhesion amount of ² mg / m ² or more is desirable. On the other hand, the adhesion amount of hydrated Cr oxide was 15 mg /
If it exceeds m ² , the contact resistance increases remarkably, and scattering due to local heat is likely to occur, resulting in deterioration of weldability. Therefore, the amount of chromate film adhered is restricted to 15 mg / m ² or less.

Further, better film adhesion and corrosion resistance
The lower layer is metallic Cr and the upper layer is hydrated for the purpose of exhibiting
A chromate coating made of Cr oxide is provided. Especially,
Excellent film adhesion and corrosion resistance are due to the water
A feature that strengthens the bond between the oxidized Cr and the Fe-Ni alloy.
Depends greatly on the corrosion resistance and high corrosion resistance of metallic Cr
I have. Such excellent properties of metallic Cr are
2mg / m^TwoDemonstrated from the above. With metal Cr
As the amount of coating increases, the film adhesion and corrosion resistance improve.
But the amount of metallic Cr is 20 mg / m^TwoExceeds
It is similar to the fact that a large amount of Ni
Due to the reason, Cr, which is much higher melting point metal
Means that the adhesion of metallic Cr is 20
mg / m ^TwoIt is regulated as follows.

The chromate treatment may be carried out by any method such as immersion treatment with aqueous solutions of various sodium, potassium and ammonium salts of chromic acid, spray treatment, and electrolytic treatment. I have.
Particularly, it is considered that the cathodic electrolysis in an aqueous solution in which chromic acid is added with a sulfate ion, a fluoride ion (including a complex ion) or a mixture thereof as a plating aid is industrially most excellent.

[0016]

EXAMPLES Examples and comparative examples of the present invention are described below, and the results are shown in Table 1. After cold rolling, the annealed and pressure-adjusted plating base plate was subjected to Ni ion: 5-45 g / l, Fe
Ion: 30 g / l, sulfate ion: 15 g / l, chloride ion: 10 g / l, boric acid: 20 g / l
Immerse in a plating bath at 50 ° C., 0.05 to 40 A / dm
Apply Fe-Ni alloy plating by electrolysis in ² ,
Subsequently, this steel sheet was subjected to chromium oxide: 20 to 150 g /
1, sulfate ion: 30 to 0.2 to 2.2 g / l
The sample was immersed in a plating bath at 50 ° C. and electrolyzed at 5 to 45 A / dm ² to perform a chromate treatment to prepare a sample.

Regarding the above-mentioned treatment materials, the following (A) to (A)
Performance evaluation was performed for each item of (C). (A) Seam weldability 15 um thick PET pre-printed on the outer surface of the can of the test piece
A (polyethylene terephthalate) -based film was laminated, a PET-based film having a thickness of 20 μm was laminated on the inner surface side of the can, and seam weldability was evaluated under the following welding conditions. Welding is performed under the conditions of a lap margin of 0.5 mm, a welding pressure of 45 kgf, and a welding wire speed of 80 m / min. The welding is carried out while changing the current. Comprehensively judged from the width of the appropriate current range consisting of the maximum current value that starts to stand out, and evaluated in four stages (◎: very wide, ○: wide enough to have no practical problem, Δ: slightly narrow, ×: narrow) did.

(B) Film adhesion evaluation test A 25 μm thick PET (polyethylene terephthalate) -based film was laminated on a test piece, and then a can lid (En) was prepared.
d) After the processing, the peeling state of the film at the processed part such as the counter sink was evaluated in four stages (◎: no peeling at all, ○: extremely slight peeling of practically no problem, Δ: slight peeling, × : Mostly peeled).

(C) UCC (Undercutting Corrosion) Evaluation Test In order to evaluate the corrosion resistance of the surface of the test piece corresponding to the inner surface of the can,
A 20 μm thick PET (polyethylene terephthalate) film was laminated on the surface corresponding to the inner surface of the can.
After that, make a cross cut until the steel reaches
The sample was immersed in a test solution composed of a mixture of 1.5% citric acid and 1.5% sodium chloride at 55 ° C. for 4 days while being open to the atmosphere. After the test is completed, the scratch part and the flat part are immediately peeled off with a tape, and the corrosion state near the scratch part, the pitting state of the scratch part, and the film peeling state of the flat part are evaluated in four stages. Not possible, ：: Slight peeling to the extent that there is no practical problem, but no corrosion was observed, Δ: Slight peeling and slight corrosion were observed, ×: Extensive peeling and severe corrosion observed ) And comprehensively evaluated.

[0020]

[Table 1]

[0021]

As shown in Table 1, it has been found that the steel sheet for a welding can produced according to the present invention has excellent weldability, corrosion resistance and film adhesion.

Claims (2)

[Claims] 1. An Fe—Ni alloy plating layer containing 5 to 45% of Ni is formed on at least one surface of a steel sheet in an amount of 10 to 300 mg / m ^{2 in} terms of Ni, and the surface thereof is formed in an amount of 2 to 300 mg / m ² in terms of metallic Cr. A steel sheet for a welding can excellent in weldability, corrosion resistance, and film adhesion, wherein a hydrated Cr oxide layer of 15 mg / m ² is formed. 2. An Fe—Ni alloy plating layer containing 5 to 45% of Ni is formed on at least one surface of a steel sheet at a Ni content of 10 to 300 mg / m ² , and 2 to 20 mg / m ² is formed on the surface.
mg / m ² of metal Cr and ² to 15 mg in terms of metal Cr
/ M ^2, a steel sheet for welded cans having excellent weldability, corrosion resistance, and film adhesion, characterized by forming a chromate coating layer composed of hydrated Cr oxide.