JPH08302479A - Functionally-gradient sn alloy-plated steel sheet for welded can excellent in weldability and film adhesion and its production - Google Patents

Abstract

PURPOSE: To produce a functionally-gradient Sn alloy-plated steel sheet for a welded can excellent in weldability and adhesion and to provide the method thereof. CONSTITUTION: An Sn alloy plating contg. 0.5-30% Ni or 1.0-30% Cu or 0.05-20% Fe and with the content of Ni, Cu or Fe continuously decreased from the surface layer toward a steel sheet is formed on the sheet at 500-2000mg/m<2> , and a chromate film is formed thereon at 1-40mg/m<2> , expressed in terms of Cr, to obtain a steel sheet for a welded can excellent in weldability and film adhesion. Otherwise, an Sn plating is formed as a lower layer, a Ni, Cu or Fe plating is formed as an upper layer, heat treatment is applied, and then a chromate film is formed as the outermost layer to produce a steel sheet for a welded can.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a functionally graded Sn-based alloy-plated steel sheet for welding cans having excellent weldability and film adhesion, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, the technology for producing welded cans by the wire seam resistance welding method has made rapid progress, and its practical application in the field of beverage cans has made rapid progress. The steel plate for a can used in this kind of welding can is formed by performing Fe-Ni alloy plating by electroplating, then Sn plating, and then molten tin, as disclosed in JP-A-60-208494. Method for producing a surface-treated steel sheet for can making which is excellent in seam weldability by subjecting to surface treatment and chromate treatment, or a method for producing a surface-treated steel sheet for seam welding can as disclosed in JP-A-60-13098. It is produced by. Certainly, the manufacturing method according to the present invention provides a surface-treated steel sheet for a welding can having weldability, corrosion resistance, and paint adhesion. Furthermore,
Using these surface-treated steel sheets for containers, paint baking is performed on the inner surface of the can to ensure corrosion resistance, and multicolor printing is performed on the outer surface of the can. After that, the cans are made by the wire seam welding method and put into practical use.

[0003]

In recent years, with the further advancement of can manufacturing technology and the cost reduction of cans, the aim is to greatly improve the productivity of the can manufacturing process, instead of painting and printing. , Materials in which an organic film is laminated on the inner surface and / or the outer surface of the can have come to be used. However, when the above-mentioned container surface-treated steel sheet is applied as a material for laminating the organic film on at least one of the inner surface and the outer surface of the can, poor film adhesion occurs near the welded portion.
This is because the above-mentioned surface-treated steel sheet for a container contains the metal Sn which is not alloyed in the plating layer, so that the plating layer melts in the vicinity of the weld where the temperature is raised to the Sn melting point or higher by the residual heat of welding. At this time, since the film on the plating layer is in a state of floating on the molten liquid metal Sn, the film adhesion is extremely low, and film peeling due to cooling air or film shrinkage due to internal stress of the film occurs. It becomes easy and poor film adhesion occurs.

[0004]

The present invention has been made to solve these problems, and the gist of the present invention is as follows: (1) On the surface of a steel sheet, the average content of Ni: 0.5-30
%, Cu: 1.0 to 30%, Fe: 0.05 to 20%, the balance being Sn and inevitable impurities, and one of Ni, Cu, and Fe. concentration decreased continuously toward the surface of the steel sheet from the plating layer surface has a Sn-based alloy plating layer of the plated amount ^{500~2000mg / m 2, 1~40mg / m} 2 still Cr terms of the plating layer surface A functionally graded Sn-based alloy-plated steel sheet for welding cans having excellent chromatability and excellent weldability and film adhesion.

(2) The surface of the steel sheet is plated with Sn, and the S
The surface of the n-plated layer is plated with one of Ni, Cu and Fe, and heat-treated to obtain an average content of Ni: 0.
5-30%, Cu: 1.0-30%, Fe: 0.05-
1% of 20%, the balance consisting of Sn and unavoidable impurities, and 1 of the above Ni, Cu, Fe
The concentration of the seeds decreased continuously from the surface of the plating layer to the surface of the steel sheet, and the plating amount of S was 500 to 2000 mg / m ² .
A functionally graded Sn for welding can excellent in weldability and film adhesion characterized by forming an n-based alloy plating layer and further applying a chromate film of 1 to 40 mg / m ^{2 in} terms of Cr on the surface of the plating layer. Provided is a functionally graded Sn-based alloy-plated steel sheet for a welding can and a method for manufacturing the same, which is solved by the method for producing a system-based alloy-plated steel sheet.

[0006]

The function of the present invention will be described in detail below.
In the present invention, the original plating plate is not particularly limited, and normally a steel plate used as a container material is used. There is no particular restriction on the manufacturing method, material, etc. of the original plating plate, and the original plate is manufactured through ordinary steps such as hot rolling, pickling, cold rolling, annealing and tempering.
Further, this plated original plate may be manufactured in a step of performing cold rolling, annealing and then re-cold rolling (that is, 2CR method) according to the required strength and plate thickness of the can. Next, the coating composition that exhibits good weldability and film adhesion will be described. As described above, the required film adhesion is to have sufficient adhesion strength even if the temperature is raised to the Sn melting point or higher by the residual heat of welding. For that purpose, a metal having a melting point higher than that of Sn must be plated. In addition, not only the adhesiveness, but also the characteristics that do not impair good weldability must be provided.

In order to solve this, Sn-based intermetallic compounds are generated by adding a trace amount of Ni, Cu, Fe into Sn, and the melting point of the plating layer is increased.
The system alloy plating layer does not melt, and it is possible to prevent the above-mentioned poor adhesion due to melting of the plating layer. Furthermore, N
Since the i, Cu, and Fe metals have good film adhesiveness, the film adhesiveness improves as the Ni, Cu, Fe content in the plating layer increases. However, when the Ni, Cu, and Fe contents increase, the characteristics of Sn plating having good weldability are lost, and the weldability deteriorates. That is, it is difficult for Sn-based alloy plating having a uniform composition distribution to sufficiently satisfy both properties of weldability and film adhesion.

As a result of various studies, the present inventors have found that
Sn-based alloy plating (hereinafter referred to as functionally graded Sn-based alloy plating) in which Ni, Cu, Fe plating is performed on the Sn-plated layer, and the Ni, Cu, Fe content decreases continuously from the surface layer to the steel plate by heat treatment. It has been found that good film adhesion can be ensured by applying (. That is, Ni, near the outermost surface where the film contacts,
It has been revealed that both the weldability and the film adhesiveness can be sufficiently satisfied by the functionally graded Sn-based alloy plating in which Cu and Fe are enriched and Sn is enriched in the vicinity of the steel sheet. The outermost layer is enriched with Ni, Cu, Fe, and therefore exhibits extremely excellent film adhesion. On the other hand, good weldability is exhibited in the Sn-rich portion in the vicinity of the steel sheet. The alloy-plated steel sheet can secure both film adhesion and weldability. Further, the Ni, Cu, Fe concentration distribution of the functionally graded Sn-based alloy plating layer is adjusted according to the desired film adhesion and weldability.

As described above, in order to exert the excellent function of the functionally graded Sn-based alloy plated steel sheet, the plating amount and the like are defined as follows. In order to prevent the film peeling due to the residual heat of welding, it is effective to add a small amount of Ni, Cu, Fe as described above. In order to exert the effect of improving the peeling of the film by adding a small amount of Ni, Cu, Fe, the average Ni content in the Sn-based alloy plating layer is 0.5% or more, and Cu
Average content of 1.0% or more, Fe average content of 0.05
% Or more is required. When the content of Ni, Cu, Fe is less than the predetermined content, the effect of increasing the melting point of the plating layer is not exhibited,
Film adhesion during welding is not ensured.

On the other hand, Ni, Cu, Fe in the Sn plating layer
As the content increases, the effect of improving the film adhesion increases, but the Ni content is 30%, the Cu content is 30%, and the F content is F.
If the e content exceeds 20%, the excellent weldability of the Sn metal is impaired, so the Ni content in the functionally graded Sn-based alloy plating layer is 30% or less, and the Cu content is 30. %, And the Fe content needs to be 20% or less. The weldability also depends on the Sn-based alloy plating amount. That is, the Sn-based alloy plating amount is 500 mg /
If it is less than m ² , practically sufficient weldability will not be exhibited, so the plating amount is required to be 500 mg / m ² or more per one surface. The weldability becomes better as the Sn-based alloy plating amount increases, but if the plating amount exceeds 2000 mg / m ² , the effect of improving the weldability is saturated, so that the Sn-based alloy plating amount is 2000 mg economically. / M ² or less is sufficient.

A method of performing functionally graded Sn-based alloy plating having the above-mentioned plating composition on a steel sheet is as follows.
Plating is performed, and then Ni, Cu, Fe plating is performed. By heat treatment of this Sn / Ni, Cu, Fe double-layer plated steel sheet, diffusion of Sn and Ni, Cu, Fe occurs, and an Sn-based alloy plated steel sheet having a gradient function can be manufactured. The method of applying Sn plating on the steel sheet is not particularly limited, but S is obtained by electroplating using a known Sn plating bath such as a phenolsulfonic acid bath or a sulfuric acid bath.
n plating can be obtained. Further, Sn plating may be performed by a vacuum vapor deposition method. N on Sn plating
Although the method of applying i, Cu, Fe plating is not particularly limited,
Ni, Cu, Fe plating on Sn plating can be obtained by electroplating using a known Ni, Cu, Fe plating bath such as a sulfuric acid bath. In addition, N is formed by the vacuum deposition method.
i, Cu, Fe plating may be performed. Industrially, the electroplating method is useful for both Sn plating and Ni, Cu, Fe plating.

Subsequently, heat treatment is carried out in order to diffuse Sn and Ni, Cu, Fe to produce a functionally graded Sn-based alloy plated steel sheet. The heat treatment method is not particularly limited, and for example, a heating method in an ordinary heating furnace, a heating method by electric heating, or a method of performing heat treatment by immersing in a heating liquid such as hot water, the functional gradient type S
An n-based alloy plated steel sheet can be manufactured. Furthermore, the concentration distribution of Ni, Cu, Fe of the functionally graded Sn-based alloy plated steel sheet can be controlled by the degree of this heat treatment. The higher the heating temperature and the longer the heating time, the more Ni and C
The u and Fe distributions tend to be uniform. Therefore, the required Ni, Cu, Fe concentration distribution can be obtained by controlling the heating temperature and the heating time. Further, by cooling with water or air immediately after the treatment, it becomes possible to more strictly control the Ni, Cu, Fe distribution of the functionally graded Sn-based alloy plated steel sheet.

Subsequently, a chromate film is applied to a steel sheet having a Sn-based alloy plating layer for the purpose of film adhesion and corrosion resistance (prevention of undercutting corrosion). The chromate film referred to here is a single film of hydrated chromium oxide, that is, the original chromate film,
The other one refers to two cases of a film consisting of a metallic chromium layer as the lower layer and a hydrated chromium oxide layer as the upper layer. The hydrated chromium oxide layer may contain sulfate ions, fluorine ions, etc., which are plating aids described later. The film adhesion and corrosion resistance are ensured by the strong chemical bond between the functional group of the hydrated chromium oxide and the functional group of the film to be laminated.

However, the hydrated chromium oxide film is electrically isolated.
Since it is an edge, it has a very high electrical resistance, and metallic chromium also has a melting point.
Both of them have high electrical resistance, which deteriorates weldability.
This is a negative factor. Therefore, a good film
Adhesion, corrosion resistance and practicality that does not deteriorate weldability
The amount of such a chromate coating is extremely important. In the present invention
The amount of chromate coating applied is equivalent to one side in terms of metallic chromium.
1 to 40 mg / m ² Is selected.

That is, the amount of chromate film adhered is 1 mg / m
^If it is less than ² , the effect of improving the film adhesion and preventing undercutting corrosion cannot be obtained, so 1 m
An adhesion amount of g / m ² or more is desirable. On the other hand, when the amount of the chromate coating adhered exceeds 40 mg / m ² , the contact resistance is remarkably increased, and scattering due to local heat generation is apt to occur and the weldability is deteriorated. Therefore, the amount of chromate film adhered is 40m
It is regulated to g / m ² or less.

The chromate treatment may be carried out by any method such as dipping treatment with an aqueous solution of various chromic acid sodium salts, potassium salts and ammonium salts, spraying treatment and electrolytic treatment, but cathodic electrolytic treatment is particularly excellent. In particular, SO ₄ ²⁻ ions, F ⁻
Cathodic electrolysis in an aqueous solution containing ions (including complex ions) or a mixture thereof is the most excellent.

[0017]

EXAMPLES Examples of Sn-Ni alloy plating according to the present invention will be described below. The results are shown in Tables 1, 2 and 3. By cold rolling or double rolling after annealing, the plating base plate adjusted to a predetermined plate thickness is electrolytically degreased in 5% caustic soda, washed with water and then electrolytically pickled in 10% sulfuric acid, and surface-treated after surface activation. It was First, (1)-
After performing Sn plating under the conditions shown in (A) and (B),
(2) -Ni, Cu, Fe under the conditions shown in (A) to (F)
Plating is performed, heat treatment is performed under the conditions shown in (3)-(A) to (C), and then a chromate film is formed in the treatment baths shown in (4)-(A) to (C). did.

(1) Sn Plating Conditions (A) Sulfuric Acid Bath Bath Composition Sn Ion 20 g / l, Sulfate Ion 15 g / l Plating Conditions 20-60 ° C., 5-30 A / dm ² (B) Phenolsulfonic Acid Bath Bath Composition Sn Ion 15 g / l, phenol sulfonate ion 15 g / l Plating condition 30-55 ° C., 5-40 A / dm ²

(2) Ni, Cu, Fe Plating Conditions Ni Plating Conditions (A) Sulfuric Acid Bath Bath Composition Ni Ion 15 g / l, Sulfate Ion 15 g / l, Boric Acid 20 g / l Plating Conditions 20-40 ° C., 5-15 A / Dm ² (B) Sulfuric acid-hydrochloric acid bath bath composition Ni ion 15 g / l, sulfate ion 15 g / l, chloride ion 10 g / l, boric acid 20 g / l Plating conditions 30-55 ° C., 5-40 A / dm ²

Cu plating condition (C) sulfuric acid bath bath composition Cu ion 20 g / l, sulfate ion 15 g / l plating condition 20 to 40 ° C., 5 to 15 A / dm ² (D) pyrophosphoric acid bath bath composition Cu ion 15 g / l , Pyrophosphate ion 30g / l Plating condition 30-55 ° C, 5-40A / dm ²

Fe Plating Conditions (E) Sulfuric Acid Bath Bath Composition Fe Ion 25 g / l, Sulfuric Acid Ion 15 g / l Plating Conditions 20-60 ° C., 5-10 A / dm ² (F) Pyrophosphate Bath Composition Fe Ion 20 g / l , Pyrophosphate ion 30 g / l Plating condition 30 to 65 ° C., 5 to 15 A / dm ²

(3) Heat Treatment Conditions (A) Heating Furnace Method The furnace is placed in a heating furnace having an atmosphere of 400 ° C. for 5 to 30 seconds, taken out, and immediately cooled with water. (B) Electric heating method The electric current is applied so that the alternating current is heated up to 220 ° C. in 4 to 15 seconds, and immediately after the electric current, water cooling is performed. (C) Immerse in warm water at 90 ° C. for 15 to 30 seconds.

(4) Chromate treatment conditions (A) Chromium oxide 100 g / l, sulfate ion 0.6 g / l Plating conditions 20-60 ° C., 5-80 A / dm ² (B) Sodium dichromate 15-45 g / l Plating conditions 30 to 50 ° C., 10 to 40 A / dm ² (C) Chromic acid 80 g / l, Sulfate ion 0.05 g / l, Sodium fluorosilicate 2.5 g / l, Ammonium fluoride 0.5 g / l Plating conditions 15-75 ° C, 10-85 A / dm ²

Regarding the above-mentioned treated materials, the following (A) to
It carried out about each item of (C), and evaluated the performance. (A) Seam weldability The test piece is assumed to be a coating baking condition at a high temperature and a short time.
Baking was performed under the condition that the temperature was raised to 0 ° C. in 23 seconds, and the seam weldability was evaluated under the following welding conditions. Lap fee 0.
5 mm, pressing force 45 kgf, welding wire speed 80
Welding is carried out by changing the current under the condition of m / min, and the width of the proper current range consisting of the minimum current value at which sufficient welding strength can be obtained and the maximum current value at which welding defects such as scattering start to stand out and welding defects Was evaluated comprehensively from the occurrence situation of.

(B) Film Adhesion Evaluation Test After laminating a PET (polyethylene terephthalate) film having a thickness of 15 μm on a test piece, a cross cut is inserted until the base metal is reached, and it is rapidly heated to 240 ° C.
An air gas of 5 kg / cm ² was vertically blown to the central portion of the cross cut to evaluate the peeling state of the film.

(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 PET (polyethylene terephthalate) film having a thickness of 15 μm was laminated on the surface corresponding to the inner surface of the can.
After that, insert a cross cut until reaching the base iron, 1.5
% Citric acid-1.5% sodium chloride mixed solution was immersed in a test solution at 55 [deg.] C. for 4 days under open air. After the test was completed, the scratch portion and the flat surface portion were rapidly peeled off with a tape, and the corrosion situation near the scratch portion, the pitting situation of the scratch portion and the film peeling situation of the flat surface portion were judged and comprehensively evaluated.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

As described above, Ni, Cu, Fe plating is performed on the Sn plating layer according to the present invention, and the Ni, Cu, Fe contents are continuously reduced from the surface layer toward the steel sheet by heat treatment. It is an extremely excellent Sn-based alloy-plated steel sheet for a welding can that can ensure both good film adhesion and weldability by applying Sn-based alloy plating to the steel sheet.

Claims (2)

[Claims] 1. The average content of Ni on the surface of a steel sheet is 0.5: 0.5.
-30%, Cu: 1.0-30%, Fe: 0.05-2
0% of 1%, the balance consisting of Sn and unavoidable impurities, and the concentration of 1 of Ni, Cu, Fe continuously decreased from the plating layer surface to the steel sheet surface, Sn with a plating amount of 500 to 2000 mg / m ²
It has a system alloy plating layer, and further Cr on the surface of the plating layer.
A functionally graded Sn-based alloy-plated steel sheet for welding cans having excellent weldability and film adhesion, which has a chromate film of 1 to 40 mg / m ^{2 in} terms of conversion. 2. A steel plate surface is Sn-plated, and the surface of the Sn-plated layer is plated with one of Ni, Cu, and Fe, and heat-treated to obtain an average content of Ni: 0.5 to 0.5.
30%, Cu: 1.0 to 30%, Fe: 0.05 to 20
%, The balance consists of Sn and unavoidable impurities, and the concentration of one of Ni, Cu, and Fe decreases continuously from the surface of the plating layer toward the surface of the steel sheet. An Sn-based alloy plating layer having an amount of 500 to 2000 mg / m ² is formed, and Cr is further formed on the plating layer surface.
A method for producing a functionally graded Sn-based alloy-plated steel sheet for a welding can having excellent weldability and film adhesion, which comprises applying a chromate film of 1 to 40 mg / m ^{2 in} terms of conversion.