JPH07166398A - Production of steel sheet for welded can excellent in high speed seam weldability, corrosion resistance and coating adhesion - Google Patents

Abstract

PURPOSE:To produce a material for a welded can excellent in high speed seam weldability, corrosion resistance and coating adhesion. CONSTITUTION:(1) The surface of a steel sheet is applied with Sn plating, which is thereafter subjected to tin melting treatment, and successively, Sn is partially peeled by anode treatment to form Sn plating with 0.02 to 1.8mum thickness in which an Sn-Fe alloy layer is exposed by 20 to 80% area ratio, and on the surface, a chromate film is moreover formed by 1 to 50mg/m<2> expressed in terms of Cr. (2) On the surface of a steel sheet, an Fe-Ni alloy plating layer contg. 20 to 70% Ni is made present by 10 to 1000mg/m<2> coating weight. After the application of Sn plating, it is subjected to tin melting treatment, and successively, Sn is partially peeled by anode treatment to form Sn plating with 0.02 to 1.8mum thickness in which an Sn-Fe Ni alloy layer is exposed by 20 to 80% area ratio, and on the surface, a chromate film is formed by 1 to 50mg/m<2> expressed in terms of Cr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a steel plate for a welding can having an Sn plating layer which is excellent in high-speed seam weldability, corrosion resistance and paint adhesion.

[0002]

2. Description of the Related Art In recent years, a can-making technique using the wire seamless resistance welding method has been rapidly developed, and its practical application has been rapidly made in the field of beverage cans. The material for the welding can is Japanese Patent Publication Sho 6
As disclosed in Japanese Patent Publication No. 2-14240, “a first layer of a Fe—Ni alloy and a second layer of a Fe—Sn—Ni alloy produced by Sn-plating and molten tin treatment on the surface of a steel sheet, and a metal. Surface-treated steel sheet for electric resistance welding comprising a third layer consisting of chromium and hydrated chromium oxide "and Japanese Patent Publication No. 62-54.
No. 399, "A metal Sn layer having a large number of protrusions is formed on the surface of a steel plate or the surface on which a passivation layer is formed, and metal chromium and hydrated chromium oxide are formed thereon. Many types of surface-treated steel sheets have been developed, such as "Chromate-coated surface-treated steel sheet for seam welding cans". These steel sheets are based on the Sn that has been used for a long time.
Compared to plated steel sheets (for example, # 25 tinplate) and Cr plated steel sheets (TFS), their weldability, corrosion resistance, and paint adhesion are improved, and they are widely used.

However, in recent years, due to the progress of the can manufacturing technology and the demand for the cost reduction of the can manufacturing, the thickness of the can manufacturing steel sheet has been reduced from the current 0.20 to 0.24 mm to an ultra thin thickness of 0.20 mm or less. Also, baking after painting is 200-210 ° C x 10
The process is shifting to harsh high-temperature short-time coating baking in which the temperature is raised from min to a high temperature above the melting point of Sn (232 ° C.) in several tens of seconds and the paint is baked during that time. In addition, the wire speed of the welding machine has been increased from the conventional 40-
There is also a plan to double from 60 m / min to 70-100 m / min. In this way, as can manufacturing technologies such as thinning of can manufacturing steel sheets, baking at high temperature for a short time, and high-speed seam welding have become more advanced, many types of conventionally used and developed can manufacturing steel plates have been applied. In this case, deterioration of the weldability due to thinning can be avoided by controlling the Sn plating amount on the inner and outer surfaces of the can, but the surface layer of the Sn plating layer in the high temperature short time coating baking step in which the baking temperature exceeds the melting point of Sn. There is a problem in that the coating surface of the metal Sn melts and expands, and the coating performance, particularly the coating adhesion, deteriorates significantly. That is, unless this problem is solved, a can-made steel sheet having excellent properties cannot be supplied.

[0004]

SUMMARY OF THE INVENTION The present invention addresses such problems and has a sufficiently wide proper welding range even after high-temperature short-time baking and high-speed seam welding, and has good paint adhesion and after coating. For the purpose of providing a steel plate for a welding can that exhibits excellent corrosion resistance, the present inventors have examined the surface coating structure of the steel plate for a can, and as a result, sufficient welding strength can be obtained without occurrence of spatter during high-speed welding. In order to secure a wide appropriate welding range, it is necessary to reduce the contact resistance of the welder's polar wheel / steel plate interface and steel plate / steel plate interface as much as possible. For that purpose, Free-Sn (non-alloyed metal after paint baking) is required. Although increasing the amount of Sn) is most effective, on the contrary, there is a problem that Free-Sn is melted during baking at high temperature for a short time and the coating performance (coating adhesion, corrosion resistance after coating) is deteriorated. Further, in order to make these performances compatible with each other, Sn plating is performed, then tin treatment is performed, and then S treatment is performed by anodic treatment.
It is necessary to peel off a part of the n-plated layer to expose the Sn-Fe alloy layer or the Sn-Fe-Ni alloy layer of the underlayer alloy layer, and to apply a chromate film on the exposed layer, which is the object of the present invention. It was found that

[0005]

The present invention has been constructed on the basis of such findings, and its gist is to provide a steel sheet directly or with an Fe--Ni alloy plating layer containing Ni of 20 to 70%. After applying 1000 mg / m ^{2 of} Sn plating layer, a part of the metallic Sn plating layer is peeled off by molten tin treatment and anode treatment, and the area ratio of Sn to F is 20 to 80%.
A plating layer having an exposed surface of the e alloy layer or the Sn-Fe-Ni alloy layer and a metal Sn surface having a thickness of 0.02 to 1.8 [mu] m is formed, and chromate of 1 to 50 mg / m < ² > in terms of Cr is formed thereon. This is a method for producing a steel plate for welded cans that has a coated high-speed seam weldability, corrosion resistance, and coating adhesion.

The present invention will be described in detail below.
There is no particular limitation on the material of the plate for can-making plating used in the present invention, the plate thickness and further the manufacturing conditions, and hot rolling, pickling, cold rolling, annealing, temper rolling from the usual billet manufacturing process. It is manufactured through processes such as (including re-cold rolling). The thus-produced steel sheet is directly or after being coated with a Fe-Ni alloy plating layer containing 20 to 70% of Ni, and then Sn plating. The Sn plating layer is provided in order to provide various properties required for a can-making steel sheet such as corrosion resistance and weldability. In particular, the Sn plating layer reduces the contact resistance at the electrode / steel plate interface and the steel plate / steel plate interface during seam welding as much as possible to prevent localized heat generation during that time, and the scattering that occurs due to the increase in contact resistance during high-speed welding. To prevent the occurrence of
In addition, it is an effective plating layer that secures a wide appropriate welding range while preventing a decrease in welding strength.

The amount of adhesion is not particularly limited.
No, the plating method is also sulfuric acid bath, ferrostan
Various plating such as bath, methanesulfonic acid bath, alkaline bath
A bath is used and is not particularly limited. Under Sn plating
The Fe-Ni alloy plating layer of the formation ensures corrosion resistance after painting
Fe-Ni alloy plating method, heat treatment after Ni plating
Ni diffusion treatment method and Fe-Ni alloy plating diffusion treatment
Fe-Ni alloy plating
When the Ni content in the steel is less than 20%, remarkable corrosion resistance can be obtained.
Absent. On the contrary, excessive Ni content exceeding 70%
In terms of the rate, Sn-Fe-Ni was used in the high temperature short time baking process.
As alloying progresses rapidly and the amount of soft metal Sn decreases,
The contact cannot be secured. Therefore, the Fe-Ni alloy mesh
While ensuring the Ni content in the ki to 20-70%,
The weight per unit area of the alloy layer is 10 to 1000 mg / m² Limited to
Need to That is, the Fe-Ni alloy plating amount of 10
mg / m² The above is an increase in the weight per unit area and improved corrosion resistance after painting.
Yes, but 1000 mg / m ² Excessive weight
Then, the effect of improving the corrosion resistance reaches the saturation range, causing film peeling.
Corrosion resistance becomes unstable.

For the above reasons, the steel sheet plated within the range specified by the present invention is subjected to molten tin treatment and anode treatment. The molten tin treatment is to protect the base metal with a pinhole-free coated surface and to improve corrosion resistance while the tin-plated steel sheet is molten tin by an electric heating method or a furnace heating method. The anode treatment is performed by immersing a tin-plated tin-plated steel sheet in an acidic aqueous solution such as a sulfuric acid solution or a tin sulfate solution while passing an anode current to partially remove a part of the metal Sn-plated layer by electrolytic stripping to remove a part of tin. Sn-Fe alloy layer or Sn-Fe that detinizes and strongly adheres the top chromate film
-This is a treatment method for exposing the Ni alloy layer. The exposed surface of the Sn-Fe alloy layer or the Sn-Fe-Ni alloy layer strongly adheres the chromate film to improve paint adhesion, but if the exposed area ratio is less than 20%, good paint adhesion cannot be obtained. Further, if it exceeds 80%, there is a problem that the Sn area ratio is relatively decreased and the weldability is impaired.

Further, regarding the thickness of the soft metal Sn surface which remains on the surface and is exposed without being peeled off by the anode treatment,
It is necessary to limit the thickness to 0.02 to 1.8 μm. Metal Sn
Is a polar wheel during seam welding / steel plate and superposed steel plate /
The contact area of the steel plate is easily deformed into a spread shape by the welding pressure, the contact area is expanded and local concentration of the welding current is reduced, and mutual fusion is achieved to prevent the occurrence of scattering and to form a solid weld area. Form. Such an effect has a thickness of 0.02-1.
Although a metal Sn surface of 8 μm can be obtained, a thin metal Sn plating layer of less than 0.02 μm has a small spread area of metal Sn and is insufficient, and when it exceeds 1.8 μm, it reaches a saturation region.

The plated steel sheet having such a coating layer is
Chromate treatment is applied to improve paint adhesion and corrosion resistance after painting for a long time. Chromate coating has a great effect on performance improvement, especially when it is used by coating.
Weldability deteriorates. The chromate film referred to here is a single film of hydrated chromium oxide, that is, the original chromate film and the other is a two-layered film consisting of a metallic chromium layer as the lower layer and a hydrated chromium oxide layer as the upper layer. Pointing to. Since the hydrated chromium oxide coating is an electrical insulator, it has a very high electrical resistance, and metallic chromium also has a high melting point and a high electrical resistance, so that both have a problem of deteriorating the weldability.

Therefore, it is very important to have a good coating performance and an appropriate amount of the chromate film deposited so as not to deteriorate the weldability for practical use. In the present invention, the amount of the chromate film deposited per metal chromium is 1 to 1 It is applied in the range of 50 mg / m ² . That is, the amount of chromate coating adhered is 1 mg / m
^If it is less than ² , the effect of improving paint adhesion and corrosion resistance after coating such as undercutting corrosion cannot be obtained, so an amount of adhesion of 1 mg / m ² or more is desirable. On the other hand, when the adhesion amount exceeds 50 mg / m ² , the contact resistance is remarkably increased, and scattering due to local heat generation is apt to occur to deteriorate the weldability. Therefore, the amount of chromate film deposited is 50 mg.
/ 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, calcium salts and ammonium salts, spraying treatment or electrolytic treatment, but cathodic electrolytic treatment is particularly excellent. In particular, the cathodic electrolysis treatment is most excellent in an aqueous solution obtained by adding SO ₄ ^2- ions, F ⁻ ions (including complex ions) or a mixture thereof to chromic acid. The concentration of chromic acid is not particularly limited, but a range of 20 to 200 g / l is sufficient.

The amount of anion added is 1/30 of Cr ⁶⁺
The best chromate film is obtained at 0 to 1/25, preferably 1/200 to 1/50. The amount of anion is Cr ⁶⁺
If it is 1/300 or less, a high-quality chromate film which is homogeneous and uniform and which greatly affects the coating performance cannot be obtained. Also, 1 /
When it is 25 or more, the amount of anions taken in the formed chromate film is large, and the coating performance, especially the secondary adhesion of the coating is deteriorated. The added anion is added to the chromic acid bath in the form of a compound such as sulfuric acid, chromium sulfate, ammonium fluoride or sodium fluoride.

The bath temperature is not particularly limited, but is 30
The range of 70 ° C is an appropriate temperature range from the viewpoint of workability. A cathode electrolysis current density of 5 to 100 A / dm ² is sufficient. The treatment time is 1 to 50 mg, which is the amount of chromium adhesion shown above in any combination of the treatment conditions.
Set to fall within the range of / m ² . Although the ratio of the metal chromium layer to the hydrated chromium oxide layer in the two-layer chromate coating is not particularly restricted within the above-mentioned range of the adhered amount, it is 0.
The range of 6≤hydrated chromium oxide / chromium metal≤3 is desirable. That is, when the amount of hydrated chromium oxide is smaller than that of metallic chromium, the uniform coating property of the hydrated chromium oxide layer on the metallic chromium layer is inferior, so that the coating adhesion tends to deteriorate. On the other hand, when the hydrated chromium oxide layer is more than the metallic chromium layer,
The anions and Cr ⁶⁺ ions contained in the hydrated chromium oxide layer increase, and when exposed to a high temperature environment after coating, these ions elute, causing minute swelling under the coating film, so-called blister rusting. It is not preferable because it becomes easy. Therefore, it is preferable to set the composition ratio of hydrated chromium oxide and metallic chromium in the range of 0.6 to 3 as described above.

[0015]

EXAMPLES Examples of the present invention will be described below, and the results are shown in Tables 1 and 2. 2 after cold rolling or annealing
5% of original plating plate adjusted to the specified thickness by rolling
After electrolytic degreasing in caustic soda, washing with water, electrolytic pickling with 10% sulfuric acid, surface activation and surface treatment. First, if necessary, an Fe-Ni alloy layer was formed on the surface under the conditions shown in (1), then Sn plating was performed under the conditions shown in (2), and molten tin treatment was performed by electric heating. Subsequently, an anode treatment was performed under the condition (3), and a chromate film was formed in the treatment bath (4) to prepare a sample.

[0016]

[Table 1]

[0017]

[Table 2]

[0018] (1) Fe-Ni plating condition Fe-Ni alloy plating Plating bath composition _{NiSO 4 · 6H 2 O 75g /} l NiCl 2 · 6H 2 O 140g / l FeSO 4 · 7H 2 O 110g / l H 3 BO 3 30g / l Plating bath temperature 50 ℃

Heat treatment after Ni plating Plating bath composition NiSO ₄ .6H ₂ O 75 g / l NiCl ₂ .6H ₂ O 140 g / l H ₃ BO ₃ 30 g / l Plating bath temperature 50 ° C. Heat treatment condition 500 ° C., 20 sec

Heat treatment after Fe-Ni plating Same as the composition of plating bath Plating bath temperature 50 ° C. Heat treatment condition 600 ° C., 20 sec

(2) Sn plating conditions Plating bath composition SnSO ₄ 10 g / l H ₂ SO ₄ 60 g / l Plating bath temperature 60 ° C. Current density 5-20 A / dm ² (electrolysis time is adjusted according to the Sn plating amount)

(3) Anode treatment conditions Treatment bath composition SnSO ₄ 20 g / l H ₂ SO ₄ 60 g / l Treatment temperature 40 ° C. Current density 5-20 A / dm ² (electrolysis time is adjusted according to Sn plating amount)

(4) Chromate treatment conditions (A) CrO ₃ 100 g / l SO ₄ ^2- 0.6 g / l (B) Na ₂ Cr ₂ O ₇ 24 g / l pH 4.5 (C) CrO ₃ 80 g / l ^{_{SO 4 2- 0.05g / l Na 2}} SiF 6 2.5g / l NH 4 F 0.5g / l

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) Paint adhesion The surface of the test piece, which corresponds to the inner surface of the can, is coated with epoxyphenol.
55 mg / dm of paint ² Apply and then correspond to the outer surface of the can
40 mg / dm of clear lacquer on the surface² Apply, 29
It was dried and cured under baking conditions up to 0 ° C. for 15 seconds. pull
Then, put scratches on each surface at 1 mm intervals, totaling 1
Produce 00 grids and quickly peel off the tape.
The peeling condition was observed and the paint adhesion was evaluated.

(C) Corrosion resistance after coating In order to evaluate the corrosion resistance after coating of the surface of the test piece corresponding to the inner surface of the can, the surface corresponding to the inner surface of the can was coated with a can epoxy resin (phenol rich) coating at 50 mg / dm / side.
^Two coatings were applied and baking was performed under the condition that the temperature was raised to 310 ° C. in 18 seconds. After that, scratches were placed so as to reach the iron surface of the coated plate, and the coated plate was immersed in a test solution, which was a 1.5% citric acid-1.5% sodium chloride mixed solution, at 55 ° C. for 4 days under open air. After the test, quickly remove the scratch and flat parts with tape to determine the corrosion condition under the coating near the scratch, the pitting condition of the scratch and the peeling of the coating on the flat part to determine the corrosion resistance after painting. Evaluated comprehensively.

[0027]

As described above, Sn plating according to the present invention is performed, and then tin treatment is performed, and then a part of the Sn plating layer is peeled off by anodic treatment to remove the Sn-Fe alloy layer or Sn of the base alloy layer. By exposing the -Fe-Ni alloy layer and forming a chromate film on it, it is possible to obtain a steel plate for a welding can excellent in high-speed seam weldability, corrosion resistance, and paint adhesion. is there.

Claims (2)

[Claims] 1. An exposed surface of a Sn—Fe alloy layer having an area ratio of 20 to 80% by exfoliating a part of the metal Sn plating layer by applying a tin tin treatment and an anode treatment after applying a Sn plating layer to a steel sheet. High-speed seam weldability and corrosion resistance characterized by forming a plating layer having a metal Sn surface with a thickness of 0.02 to 1.8 μm and applying a chromate coating of 1 to 50 mg / m ^{2 in} terms of Cr on it And a method for manufacturing steel plates for welding cans with excellent paint adhesion. 2. A steel sheet containing 20 to 70% Ni and Fe.
After applying a Ni alloy plating layer of 10 to 1000 mg / m ² and an Sn plating layer on it, a part of the metal Sn plating layer is peeled off by a molten tin treatment and an anode treatment, and the area ratio is 2
0-80% Sn-Fe-Ni alloy layer exposed surface and thickness 0.
High-speed seam weldability, corrosion resistance and coating adhesion, characterized by forming a plating layer having a metal Sn surface of 02 to 1.8 μm and applying a chromate film of 1 to 50 mg / m ^{2 in} terms of Cr on it Excellent manufacturing method of steel plate for welding can.