JPS6191393A - Surface treated steel sheet for can having superior corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain a surface treated steel sheet for a can having superior corrosion resistance by forming an alloy layer consisting of Ni and Fe in a specified ratio on the surfaces of a steel sheet with a specified thickness and by laminating an Ni-Sn alloy layer, an Sn layer and a chromate layer on the Ni-Fe alloy layer successively. CONSTITUTION:The alloy layer consisting of Fe and Ni in 0.02-0.90 weight ratio of Ni/(Fe+Ni) is formed on the surfaces of the steel sheet with 10-5,000Angstrom thickness per one side. The alloy layer consisting of Ni and Sn in about 0.50-0.95 weight ratio of Ni/(Ni+Sn) is formed on the Ni-Fe alloy layer by about 20-1,500mg/m<2>, an Sn layer is formed on the Ni-Sn alloy layer by about 50-1,000mg/m<2>, and a chromate film is formed on the Sn layer by <=about 30mg/m<2> to obtain the surface treated steel sheet for the can having superior corrosion resistance. Iron is not leached from the steel sheet even when pinholes are made in the resulting surface layer or the layer is scratched.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an alloy layer consisting of kF@ and Ni on the surface of a steel sheet, an alloy layer consisting of nickel and Sn, a Sn layer,
The present invention relates to a surface-treated steel sheet for cans, particularly food cans and beverage cans, which has excellent corrosion resistance and is made of 81 successive 11J layers.・ ・(Prior art and problems) ゛ - Sn-plated steel sheets, commonly referred to as tinplate, have been widely used as materials for food cans. The joining method for this can body is as follows:
- In the past, solder was used for joining, but due to the toxicity of PB contained in solder and solder, pure Sn solder has come to be used in recent years. However, since pure Sn solder has poor wettability during bonding, there are technical problems with soldering and bonding, and there is also the problem of increased manufacturing costs due to the use of more expensive pure Sn solder. -', In order to eliminate the above-mentioned drawbacks of tin cans, a method has recently been developed in which can bodies are joined by electric resistance welding instead of solder joining. , it has become popular, and for that purpose, a material for cans suitable for electric resistance welding is needed.
・, □, Conventional tin plate is plated with a thick layer of Sn, has sufficient gold m8n necessary for weldability, and has excellent welding performance.

-11, Food 1i in recent years! ＝For example, the entry of low-priced competing materials such as polyethylene, aluminum, aluminum, ÷ram, glass, and paper. Thickly plated tin cans, such as ``Tin cans,'' are expensive to manufacture, so they are forced into a difficult competitive position, even though they have characteristics that are immediately superior to corrosion resistance and weldability.

In order to reduce the cost, it is possible to reduce the amount of expensive Sn to make tinplate with a thinner coating, but the corrosion resistance deteriorates significantly and it cannot be put to practical use.

In addition to the tinplate mentioned above, chromium-type tin-free steel (hereinafter TF
S), which has been subjected to electrolytic chromate treatment 1
It is an inexpensive material with metal chromium and a chromium water-retention oxide layer formed on the surface, but the thick chromium water-retention oxide layer on the surface is a high electrical resistance material, resulting in poor weldability and lack of strength in the welded part. Although it is economically efficient, it is not suitable as a material for welded cans.

Can materials suitable for electric resistance welding must have excellent weldability and corrosion resistance. To explain this requirement specifically, it is necessary to have sufficient welding strength during welding, and to have an appropriate welding current range that does not cause welding defects such as so-called "spatter" in the welded part. It must have sufficient corrosion resistance against the contents. Also, most welded cans are used after being painted. Therefore, it is important to effectively utilize the corrosion resistance of the paint film, and excellent paint adhesion is required.

(Object of the Invention) An object of the present invention is to eliminate the above-mentioned conventional drawbacks of materials for welded cans, and to immediately provide a material for food cans that satisfies the above-mentioned requirements that the material for welded cans should have.

That is, 1 the present invention has a thickness of 10 to 10 mm per side on the steel plate surface.
5000 people, weight ratio of Ni/Fe+Ni is 0.02~
It is characterized by having an alloy layer consisting of 0.90 Fe and Xi, having an alloy layer consisting of old and Sn on top of that, having a Sn layer on top of that, and further having a chromate coating layer on top of that. The present invention provides a surface-treated steel sheet for cans with excellent corrosion resistance.

The present invention will be explained in more detail below.

Although Sn is an expensive metal, it is necessary to obtain weldability, especially high-speed weldability of 30 m/min or more, which is most often used in commercial production.

That is, since Sn is a soft metal with a low melting point, it easily melts and spreads during welding, forming a strong joint.

Sn is 50 mg/m'' or more, preferably rooms/m
The inventors of the present invention have already found that good high-speed weldability can be obtained if the temperature is higher than '. However, since Sn is an expensive metal, it is not preferable to increase the amount of Sns too much because it will be disadvantageous in terms of cost.

Sn itself is a metal with good corrosion resistance, but if you try to use it only in the Sn plating layer, it will require a Sn plating thickness equal to or greater than that of conventional tinplates, which is impractical.Regular tinplates require reflow treatment after Sn plating. Sn
The layer is melted to form an alloy layer of FeSn2 to improve corrosion resistance. Since the FeSn2 alloy layer is a relatively coarse alloy layer consisting of columnar crystals, its effect is insufficient unless the amount is increased, making it unsuitable for use as an inexpensive material.

The present inventors have already found that by using Ni-5n alloy plating, excellent corrosion resistance can be obtained with a small amount.

The present inventors disclosed a Sn/Ni-9n alloy double-layer plated steel sheet using old-Sn alloy plating in Japanese Patent Application No. 59-001094 ``Surface treated steel sheet for seam welded cans with excellent high-speed weldability and corrosion resistance''. However, the present inventors subsequently discovered that Ni
A more detailed study of the -9n alloy layer revealed that the old -Sn alloy plating layer and the upper Sn plating layer undergo alloying at room temperature over time after plating, and reach an equilibrium state within 7 to 10 days. I understand. That is, old-Sn
Alloy plating is NiSn, former 3Sna, Ni3S
n2 structure or a mixture of these structures, it was found that when alloyed with the upper Sn plating layer, an alloy with a composition approximately equal to the atomic ratio Ni:Sn=l:3 was found. Ta.

It is known that this phenomenon similarly occurs in Sn/NiZ layer plating. That is, in 1979, Tra
nsactions of the Ir+gtitu
te of ) Ietal Finishing Vol.
57 P, J, ni d! and the paper Barrier Layers Again by C. A. Mackal.
According to st Diffusion J, the Xi plating layer and the Sn plating layer form an alloy of prior Sr+3 at temperatures below 100°C.

Therefore, Xl-Sn alloy plating 1. Alternatively, when Sn plating is performed on the upper layer of the old plating, the alloying progresses during storage after plating, resulting in an alloy layer having an atomic ratio of approximately 5n71:3. It was found that this alloy layer was dense and had excellent corrosion resistance.

The present inventors further investigated alloying at a temperature higher than room temperature, that is, alloying when heat treated. As a result, the alloy becomes an alloy mainly composed of &Ni3Sn4, and the higher the temperature, the higher the temperature. It was found that alloying occurs between Fe(Xi)-5n2-type alloy and ferrous iron. Ta. All of these alloy layers are dense and have excellent corrosion resistance, and their performance is almost the same as that of an alloy formed at room temperature.

Although these alloy layers exhibit excellent stability in small amounts, they promote Fe elution 5 when the base iron is exposed. Sunashōchi, Ko 1
These alloys have a lower potential than the FeSn2 alloy normally used in tinplate, and have a large potential difference with the less base Fs, which promotes the dissolution of Fe. Therefore, if the base metal is exposed through a pinhole or is scratched, there is a risk that the dissolution of Fe will proceed rapidly and result in a can with holes. have newly discovered that the dissolution of Fe can be suppressed by providing an alloy layer consisting of Fe and Xi exhibiting an intermediate potential between the above-mentioned alloy layer and the base iron, and the present invention has been achieved.・ ・ As a prior art, JP-A-57-23091 ``R Welded Can Container - Method for Manufacturing Plate and Ri'', JP-A 57-87, 1
98:r High Corrosion Resistance Surface Treated Steel Sheet”, JP-A-58-737
92 ``Method for manufacturing steel plates for cylindrical shafts'', these are all made of Ni grade 7 and 1
．． It is a two-layer plated steel sheet with C5n plating, and it is written that the two-layer plating reduces pinholes and that the alloy of Ni and Sn that is formed during heat treatment has good corrosion resistance. Fe from diamond
No consideration was given to elution.

Also, JP-A-5J-1, Q? ! 14. r High corrosion resistance ma,
``Surface Treatment for Finishing Can Making - Spring''... JP-A-5. ．． 8-
According to the disclosure in 20.7388 “Surface treated steel sheet for puttu finish can making”, Ni or Xl-Sn
It is a metal plated with Sn plating on gold, and according to the examples, it is usually made with a thickness as thick as tin plate, but 1.
When using a thin basis weight, there is no 9-point equation, and no consideration is given to Fe elution from pinholes or scratches, etc.

In contrast, the steel sheet 1 of the present invention is characterized by suppressing Fe elution from pinholes or scratches as much as possible.
An alloy layer consisting of li, an alloy layer consisting of Qi and Sn, and an alloy layer consisting of S
Consisting of a 3-layer structure with n layers, it is even more! This steel plate for cans is provided with a mate layer and has excellent chamfer resistance, and is completely different from the above-mentioned invention in terms of product structure and technical concept. '-Now, in the present invention, the purpose of providing an alloy layer consisting of Is and Ni on the surface of the steel sheet is to suppress the elution of Fe from holes, holes, scratches, etc. The thickness of the alloy layer consisting of Fe and Ni is lO~5.0
00 people, preferably 10.9 to 3000 people. Fe
- Thickness of the former Gorei layer 2. The reason for limiting the number of people to 10 to 5,000 is that Fe1llff1. below 10λ. The effect of suppressing is insufficient, and if it is 590, Q^ or more, 2,000 F.
e The effect of suppressing elution is sufficient, but 1. This is because the alloy layer becomes hard and brittle, making it easier to crack and causing Fe to be leached from the cracks.What is the alloy composition of Fe and Ni in weight ratio? Ni/ (,Fs+N1)−〒(!
, 02 to 0.90 is preferable; if this Ti ratio is not set at 0.02, the effect of alloying due to oxidation disappears and 7tFa4
The effect of suppressing the output becomes insufficient, and 0. ,(,!1
This is because if 0 is reduced, (b) the potential of the alloy approaches noble Xi, and the effect of suppressing the elution of base Fe is lost.
, 1゛,゛,..., I As a method for forming a φ alloy layer made of Fv-Nj,
Industrially, any of the following methods may be used:
゛, i□・ (a) A method in which the surface of the II plate is plated with Ni, and then heat treated in a non-degrading atmosphere to completely diffuse the Ni plating into the steel.

(a method in which Fe-Ni alloy plating is applied to the surface of bBl plate and then heat-treated in a non-oxidizing atmosphere to diffuse part or all of the Fe-Ni alloy plating into the steel.

(c) A method of applying Fe-Ni alloy plating to the surface of a steel plate.

These methods may be used alone or in combination of two or more, and alloy layers made of Fe and Xi having various compositions in the depth direction can be formed by these methods.

In the present invention, an alloy layer made of N1 and Sn and having excellent corrosion resistance is provided on the Fe--Ni alloy layer.

The preferred range of the amount of the alloy layer consisting of N1 and Sn is 20~
1500 mg/rn', and a more preferable range is 20 to 400 mg/m'', especially for welded cans.Xl-
If the amount of Sn alloy is less than 20ss/lo', (c) the effect of improving corrosion resistance is insufficient;
If it exceeds I', (d) the effect of improving corrosion resistance will be saturated and it will become uneconomical. The composition ratio of old and Sn is not particularly limited, but preferably! ia) Ratio Sn/(N
i+5n)=0.5ONO,95. If this t ratio is less than 0.50, (e) the alloy layer becomes hard and tends to crack during processing, and if it exceeds 0.95 (f)
This is because the amount of Sn increases and becomes uneconomical.

As a method for forming an alloy layer consisting of Xi and Sn, any of the following methods may be used industrially.

(a) A method in which an alloy layer consisting of Ni and Sn and a Sn layer are simultaneously formed by applying Sn plating after performing lli or Ni-Sn alloy plating, and aging at room temperature without particular heating.

(b) A method in which after Ni or Xl-Sn alloy plating is performed, Sn plating is further applied, and heat treatment is performed for a short time at a temperature below the melting point of Sn to simultaneously form an alloy layer consisting of N1 and Sn and a Sn layer.

In the present invention, an sJI layer is provided on the Xl-Sn alloy layer.

The purpose of the Sn layer is weldability, and it is sufficient if it is 50+g/m' or more, preferably 100mg/m' or more.If the Sn layer is less than 50mg/m', (g) sufficient weldability cannot be obtained. be.

When used after painting, Sn is removed by baking treatment after painting.
Since alloying occurs, 5nI is taken into consideration for this alloying.
Just decide k, BBchi, 50ax/ln' after painting
As mentioned above, 5all should be determined so that the metal S+ layer is preferably Looms/rn' or more.* There is no particular upper limit for sni, but in order to use an inexpensive material.

It is preferable to keep it to 1000 layers g/rn' or less.

Although the steel plate of the present invention is intended as an inexpensive material for welded cans,
It may be used as a highly corrosion-resistant tinplate by increasing the amount of Sn to the same thickness as conventional tinplate.

In the present invention, chromated MFJ is provided on SnN for the purpose of improving paint adhesion and post-painting corrosion resistance.

The chromate coating may be composed only of chromium water-conserving oxide, or may be composed of metallic chromium and chromium water-conserving oxide.

Because chromate coating is a high electrical resistance material.

When used as a welded can, it is desirable to keep the RQ amount of chromate at 305 g/rn' or less in order to achieve good weldability.

<Example> Next, the present invention will be described in detail with reference to Examples and Comparative Examples.
I will do it.

(Example 1) After electrolytically degreasing a cold rolled steel sheet, Xi plating or Fe plating was applied.
- Old alloy plating, followed by 10% - +90% N
Heat treatment was performed in the gas atmosphere of No. 2 to form an alloy layer consisting of Fa and Ni. After a further 1% skin pass, electrolytic degreasing and pickling were performed.

Old plating or Xi'-Sn alloy plating was performed, followed by Si plating, and further chromate treatment, followed by aging at room temperature for 10 days.

(Example 2) After electrolytically degreasing and pickling a tin plate, Fe-X1
□-Gold plating followed by Ili
Or perform Xl-Sn alloy □ gold plating, and then perform Sn plating.
・I also performed chromate treatment.

Thereafter, the mixture was allowed to stand at room temperature for 10 days.

(Comparison @l) After electrolytically degreasing and pickling the tin plate, N1 or Xl-
Sn alloy plating is performed, followed by Sn plating,
Furthermore, chromate treatment was performed. Thereafter, the mixture was allowed to stand at room temperature for 10 days.

(Comparative Example 2)

The original tin plate was electrolytically degreased, pickled, Sn-plated, and further chromate-treated.

The composition of each plating bath used in Examples and Comparative Examples is as follows.・ (Ni plating bath) NiSO4e6H20' 250g/1Ni
C-cross 2 and 61420 45g/1) 13
BO330g1 sentence ((Fe-Xi gold alloy plating bath) F@CJLz ・41420 20-230g/IL
, old CJL2・61420 30-300g/
! L83 BO325g/Ni-3n alloy □ plating bath) Old CIL2 life 61420 250g/4So C
1z ・2) 120 50x/1
'N)In"HF2"
Door 08 I, see << Sn plating bath) Sn Cn2・2H2060x/R aHF2 ・Na F Na 0 sentence 50g 1 sentence'N
a2Cr20y *2 H2O: 30 gel or □ 'CrO315g/fL' H2O-0.12g/Appearance The performance of the steel plate treated as above was evaluated by the following method. .

(1) Weldability - The above steel plate was heated to 210'°C to simulate the baking process after painting.
After heat treatment for 20 minutes, seam welding was performed at a welding speed of □40cm, contact pressure of 40kxf, and OI (-cheap 0.4mm) without causing any "splashing". ) enough
The welding type - flow range (
The appropriate welding current range) was determined and evaluated as follows.

Table 1 (2) Corrosion resistance after painting The above steel plate was coated with epoxy phenol paint at 50cm2/df.
fI' I! After baking at 210°C for XIO minutes twice, use a sharp knife to make a cross cut that reaches the base metal.1.
55 in a mixed solution of 5% NaCJL and 1.5% citric acid.
After immersion at ℃ for 96 hours, the corrosion status was evaluated by the width of the coating peeled off from the cross-cut portion by tape peeling and the amount of Fs eluted from the cross-cut portion.

゛ Table 2 shows various performances of the above steel sheets)
As is clear from the above, the steel plate of the present invention has excellent weldability,
It can be seen that it has better corrosion resistance after painting than the comparative example.

<Effects of the invention> In the present invention, a special F@-Ni alloy layer,
Form Ni-Sn alloy layer, SnP+ and chromate layer, especially the thickness of Fe-X1 alloy layer is 10 to 5000,
By setting the t ratio of Ni/(former ◆F@) to 0.02 to 0.30, there is no elution of F@ even when pinholes, scratches, etc. occur in the surface treatment layer, that is, corrosion resistance. A surface-treated steel sheet for cans with excellent properties can be obtained.

Claims (1)

[Claims] Ni/Ni/
Fe and Ni with a Fe+Ni weight ratio of 0.02 to 0.30
A can with excellent corrosion resistance, characterized in that it has an alloy layer consisting of Ni and Sn, an Sn layer thereon, and a chromate coating layer thereon. Surface treated steel plate for use.