JPS60110881A - Manufacture of multiple-layer plated steel sheet for welded can - Google Patents

Abstract

PURPOSE:To provide corrosion resistance, rust resistance and coatability to a cold rolled steel sheet by plating the steel sheet with an Ni-Fe alloy having a specified composition to a specified thickness, further plating it with Sn to a specified thickness, and forming a Cr-base film of a specified thickness in an aqueous soln. contg. sexivalent Cr. CONSTITUTION:A degreased and pickled cold rolled steel sheet is plated with an Ni-Fe alloy having a composition satisfying an equation Ni/(Ni+Fe)=0.6- 0.95 to 0.01-0.2mum thickness, and it is further plated with Sn to 0.05-1g/m<2> thickness. A metallic Cr-base film of 3-30mg/m<2> thickness is then formed in an aqueous soln. contg. sexivalent Cr. It is preferable that a chromate film contg. chromium oxide hydrate as the base by 5-15mg/m<2> (expressed in terms of Cr) is further formed in an aqueous soln. contg. sexivalent Cr.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface-treated steel sheet that has excellent rust resistance, corrosion resistance, and paintability, and is mainly used as food cans handled by seam welding.

Conventionally, the handling bodies of plastics used to manufacture food and beverage cans have been soldered. However, harmful lead contained in the solder may be leached into the contents of the can, posing a food hygiene problem. For this reason, in recent years, handling cylinders using H1 has gradually ceased to be used, and instead, handling cylinders using seam welding (Sudronik welding machine) are now used. In the sudronic welding method, since the joint portion of the can body has a width of 0.3 to 0.4 ytrmO, the quality of the joint is greatly influenced by the surface treatment of the steel plate. Commercially available tinplates tend to have better weldability as the tin content is %'ft'l'l;
sr# for use in cans due to the lack of water.A new low-priced material 09 that can be used as a substitute for thinly coated furiki or as an alternative to this.
There are two demands. In response to these demands, trial production or practical use of surface-treated steel sheets in which Ni-plated lead sheets and thin Sn plating are coated with chrome plating or a thick chromate film is underway.

Although these new materials have excellent rust resistance and paintability, they have the following problems. Ni-plated steel plate is made of Ni and F.
Because the potential difference between e is large, if minute scratches are made on the plating layer during handling, the iron will be rapidly corroded and oxidized at the scratched area, and a hole may be formed in that area. For this reason, extreme care must be taken in handling during painting, can manufacturing, and can manufacturing processes. Welded cans are usually painted on both the inside and outside, but when Ni-plated cans with fine coatings are filled with contents, hydrogen gas is generated in a short period of time, and the cans expand. Steel plates with chromium or thick chromate coatings on 8N plating have poor bath weldability, dust (spatter) or non-welded areas may occur, and the drawback is that it is difficult to control the optimum welding current. On the other hand, if the amount of chromium plating or chromate film is reduced in order to improve the weldability of this steel sheet, the rust resistance will deteriorate, and rust may occur before painting and can manufacturing are performed at the can manufacturer.

The present inventors have demonstrated that even when minute defects occur on the plating surface or coating surface, paintability and rust resistance are maintained without impairing corrosion resistance or rust resistance.
As a result of intensive research on materials for welded cans with excellent weldability, we discovered a method in which Ni-Fe alloy plating is applied to the surface of a steel plate, a thin βn plating is applied as an upper layer, and then a thin metallic chromium plating is applied on the Sn plating, and Furthermore, we have arrived at a method in which a chromate film mainly composed of hydrated chromium oxide is formed on the surface layer by chromate treatment, and a method in which a similar treatment is performed after ladle treatment is performed before metal chromium plating in the above painting method.

In other words, the first Ni-Fe alloy plating layer can have a potential difference between it and the iron base material that is extremely smaller than the potential difference between Ni and li'e, and the potential difference between the Ni and Fe alloy plating layer can be made extremely smaller than the potential difference between Ni and li'e. <114 meals can be suppressed. The second layer of Sn plating has a sacrificial anticorrosion effect on the underlying iron and Ni-Fe alloy layers, and can significantly improve corrosion resistance.
By having a plating layer, weldability can also be significantly improved.

The third layer of metal chromium plating is used as a sealing treatment for the underlying Ni-Fe alloy plating and Sn plating to repair defects in the plating in the lower layer, and this treatment significantly improves rust and corrosion resistance. do. Furthermore, by forming a chromate film mainly composed of hydrated chromium oxide through chromate treatment on the WJ3 layer, we have improved the paint film adhesion and the paint film adhesion after retort treatment. A surface-treated copper plate with excellent corrosion, rust resistance, and weldability can be provided.

The present invention will be explained in more detail below.

The copper plate used in producing the material for welded cans according to the method of the present invention may be either an ingot material or a continuous casting material.It is cold rolled to 0.15 to 35 mm by the usual method and then annealed to a circular shape. A rolled copper plate is used as the base plate.For plating, the base plate is subjected to normal degreasing and pickling, and Ni/(N
Ni-Fe alloy plating having a metal composition of i+Fe)=0.60-0.95 is performed.

Ni-Fe alloy plating is performed using the commonly used sulfate bath,
Chloride baths, sulfamino acid salt baths, birophosphate baths, etc. can be used. The Ni-Fe alloy plating in the present invention is intended to improve rust resistance, corrosion resistance, paintability, weldability, and workability, and the plating composition is Ni / (Ni + F
e) = 0.60 to 0.95, plating thickness is 0. (11
It is preferable to set it to ~ci, 2oμ. i'Ji plating composition
/(Ni+Fe)-0,600,95 Immediately 1
1 mountain is in season” is the curve of S.

(1) Ni-1'e alloy copper, pure nickel, coupled with pure iron in 3% saline solution, left for 4 hours, -5J,!
From the area (the result of measuring the iron ions released is the first
De 4). +1, which combines pure nickel and pure iron. '
1 [Compared to the above, in the case of a couple of Ni-1・゛e Daikinmettsugi&ii4 with Ni-1・(Ni+Fe)=0.95 or less and pure iron, the elution of iron ions is as small as < M::l:.

(2) Cold 4! After removing the wound 1 & 1, after pickling, sulfamine M'=, - of N1-F'e alloy plating bath 1I
The IC ion ratio and concentration were varied, and Ni-Fe alloy plating with different alloy compositions was applied. The plating thickness at this time was 02μ in all cases. These Ni-
Fig. 2 shows the results of a rust resistance test using an Fe alloy plated copper plate. 'Ni/(Ni+Fe)=
When it is smaller than 0.6, rust resistance deteriorates rapidly.

Due to the above-mentioned <1), (210 reasons, the alloy composition Ni/
(Ni+Fe) = 0.60-0.95. That is, if Ni/(Ni+F'e) is less than 0.6, it is advantageous against recreational chemical corrosion at plating defects, but rust resistance deteriorates. On the other hand, Ni / (Ni+li
``c) If the amount is more than -0.95, it is advantageous for rust resistance, but the potential difference with the underlying iron becomes large, and when immersed in the electrolyte, corrosion at plating defects is accelerated. Elution of iron ions increases rapidly.

Plating of Ni-Fe alloy plating; 9 0.01~0.
The reason for limiting it to 2μ is as follows. Plating thickness is 0
．． If it is less than 0.01 μm, the coating on the surface of the steel plate is incomplete;
Rust resistance and corrosion resistance after painting deteriorate rapidly, and the rust resistance after painting remains the same as the original plate's rust resistance and corrosion resistance after painting. Furthermore, if the plating thickness is greater than 0.2μ, the rust resistance will improve, but the workability will deteriorate. For this reason, the plating thickness of the Ni-Fe alloy plating was set to 0.01 to 0.2 μm.

If Ni-Fe alloy plating is applied only to a thickness of 0.01 to 0.2μ, the 111IJεri performance is several times higher than that of a tin-plated steel sheet with the same plating thickness, but in terms of weldability, the tin-plated steel sheet has Are better. Therefore, in the present invention, in order to improve weldability, Sn plating of 0.05 to 1.0.9/m is applied to the Ni-I2e alloy plating. The reason why the Sn plating on the i-F'e alloy plating is limited to 0. (15 ~ hog/g) is as follows.
51 / less than rtr2 (in other words, the purpose of this application is to improve weldability and 5nc7), to i-1i”
Part 1 ((corrosion resistance 1'
This is probably because the improvement effect of 13 was almost no longer visible.

On the other hand, the Sn evaluation contribution is more than 1゜oII/go (
However, its effectiveness is saturated and it is disadvantageous in terms of economic value.

Ni-1" (J Satoyama treats the Sn plating on the secondary alloy plating in a hot pot for the following reasons. By treating the Sn plating layer with a hot pot, a smooth surface is formed. At the same time as forming a tin layer, a part of it forms a dense alloy layer with the underlying Ni-h'e base metal, which further improves the 1luJ and the corrosion resistance after painting. is remarkable.

A coating mainly composed of metallic chromium (simply referred to as metallic chromium plating) is applied on this Sn plating in an aqueous solution containing hexavalent chromium.
As a sealing treatment for plating, defects in the lower layer plating are repaired, and this treatment significantly improves rust resistance and corrosion resistance. The amount of metal chromium plating is 3 ~ chromium conversion > it
'r Orajj/m' 0) The most excellent effect can be obtained. In addition, when this metal chromium plating layer becomes the outermost surface, it is important in terms of weldability and paint film adhesion, but even in this case, the effect is only J >).In other words, the amount of 3 mg/
If it is less than m'', the rust resistance will be insufficient and the effect of improving the coating film adhesion performance will not be obtained.

Moreover, if it exceeds 30 mg/m2, the A'+J effect is good, but 1' chipping occurs during welding, and the bath welding temperature is 7'.
Not only does it make repair painting difficult, but the welding strength decreases, making welding defects more likely to occur.

In the present invention, the formation of a chromate film by the chromate treatment performed on the metal chromium plating in a water bath containing hexavalent chromium is essential in terms of weldability and coating adhesion. The amount of chromate film is 5 to 15 in terms of C and r conversion Rt.
The best effect can be achieved within a range of 77 m2.
. S/, C, chromate film land is 5m! //? I
+, "Miru 1111 has insufficient rust resistance, and the effect of improving coating film density; i?i ('; Ig fiPt7.) is also poor.
I can't do it. Also 15m9/m″4′ Koeroto,″ljI
The effect is good, but the filter produces "dust" during welding, and (
This not only makes it difficult to repair the sleeves of the joints, but also reduces the welding strength, making welding defects more likely.

Hereinafter, the surface treatment for welded cans of the present invention <Via & will be specifically explained with reference to Examples and Comparative Examples.

As the original plate, a rolled steel plate of the same lot with a thickness of 0.22π and 0.0) was used. The cold-rolled steel sheets were subjected to the usual degreasing and rinsing treatment J1 (!), and then Ni--Fe alloy plating was performed while changing the alloy composition within the range of the following conditions.

After Ni-Fc alloy plating, Sn plating was performed. After Sn plating, molten pot treatment was performed by heating in a hot pot depending on the town. S
After plating or hot pot treatment 1i1i, chromium plating was performed, and some were subsequently subjected to chromate treatment.

(A) Ni-Fe plating conditions Plating bath composition Boric acid 30 11/lj Satucalin sodium 0.6 g, /i Sodium milaurylate 75rn, y/11 Sulfamine enemy 5~
30 jj/11 pH 1.5-4.0, bath temperature 25-60
CFLn Confidentiality 0.5-30A/rln", a/y)
! 7+-0,01-0,2tt (B) Tin plating condition Plating bath composition Stannous chloride 6011/11 Acidic sodium fluoride 20 &71 Sodium fluoride 50 9/11 Sodium chloride 60 g/l Additive (thiosulfuric acid) Soda) Bath temperature 60℃, current density HsA/dm".

Plating amount 0.05-1.0 jj 77+L' (Q Metal chromium plating conditions - Plating bath composition Chromic anhydride 150 g/l Sulfuric acid 0.8 FI/1 1.1 Sodium fluoride 1., o9/1 1 'i'i?+71 45°0, current density 50A/
drn'(1)) Riυmate treatment conditions〆r[Ai Naruhisa jU-hydrochromic acid 301/l Shinchromium C1 female sodium 20 1//1i? '2i
! :11. 50 "C, T", flowing 3 5 A/
dm' [Reference example 1] Cold rolled j: j7! After the roots are subjected to the usual degreasing and pickling treatment,
() in a Watts bath, with 2μ N1 plating, then 3
01/l 71J Sodium chromate A chromate film was deposited overnight (I m!1/(chromium equivalent amount→).

[Reference Example 2] A cold-rolled 41ti sheet was subjected to normal degreasing and pickling treatment, then tin-plated at 1.111/m'' in a halogen bath, and then chromated in a 301/l sodium dichromate solution. A film of 8 m#/m' (chromium equivalent amount) was deposited.

[Reference Example 3] The same process as in Reference Example 2 was carried out except that the tin plating was 2.8#/m''.

Test pieces were cut from the multilayer plated steel machine obtained in the above Examples, Comparative Examples and Reference [Kawa], and various tests as described below were conducted. The results are shown in Table 1.

(1) Resistance test: Place the specimen in the test chamber of the dry/wet cycling device, = 50℃,
Humidity condition of 98% relative humidity for 30 minutes, 25℃, relative humidity 6
A test was conducted for a certain period of time by repeating dry and wet conditions for 30 minutes, and the degree of rust formation was evaluated. Rating is J
Based on the ISZ2912r Rust Incidence Measurement Method, the test was conducted in five stages: ◎ Rust/Good, O5Δ, X, and XX (full surface rust).

(2) Weldability test 1 (using a 54.7 x 110 mm test piece, using a fully automatic welding machine manufactured by Sudronik), the overlap was 0.4~
The welding was carried out under the following conditions: 0.5 Yen and a welding current of 1000 to 5000 A. Weldability was evaluated in the normal flow range where uniform nugget formation and sufficient welding strength were obtained. The minimum current value that can be connected to the bath is such that it does not generate dust.
jL value. The smaller this value is, the more economical it is.

○...More than 1508 △...100-150A 1) Do a vine test by pulling the triangular part toward the other end Qμ with pliers. The required strength is that MI5 does not turn off during the course of the test.

C31, performance measurement with paint I/Evo V diphenol paint coating amount is 45 ± 5 mf
The following tests were carried out by applying the coating to a coating of J/tn, baking it at 210°C for 10 minutes, and drying it for 10 minutes.

(3-i) Secondary adhesion test of paint film After immersion in an aqueous solution containing 1.5% NaC6, 1.5% citric acid for 96 hours, 100 base marks were scored and the number of peeled pieces was determined by tape. The following evaluation was performed.

◎・-・No peeling O... 1 to 3 Hard △... 4 to 10 pieces After soaking in the solution described in (3-1) for 96 hours, the corrosion state of scratches was evaluated.

○...Good △...Slightly inferior ×...Significantly inferior As is clear from Table 1 showing the above test results, the steel plate obtained by the method of the present invention is superior to the comparative examples and reference examples. It can be seen that the rust resistance, weldability, and performance after painting are superior to those of conventional products.

[Brief explanation of drawings]

Figure 1 shows the Ni/(Ni+Fe)M amount ratio and Fe.
A graph showing the relationship with elution amount, Figure 2 shows Ni/(Ni+
F'e) It is a graph showing the i2J relationship between the i amount ratio and rust resistance. Particularly, f(, Participant: Kawasaki Steel Co., Ltd. Patent attorney Nozomi Watanabe Fe)! t amount upper h

Claims (4)

[Claims] (1) Ni/(Ni+Fe) on degreased and pickled cold rolled steel sheet
= Ni-1i'e with a metal composition of 0.60 to 0.95
Alloy plating is applied to a thickness of 0.01-0.2 μ, followed by tin plating of 0.05-1.011/m2, and further 3-30 ml of an aqueous solution containing hexavalent Chrono.
1. A method for manufacturing a multilayer plated steel sheet for welded cans, characterized by forming a film mainly composed of chromium metal. (2) Ni/(Nj+Fe
)-0.60~0.95 Ni-Fe alloy plating is applied to a thickness of 0.01~0.2μ, and then
．． 05~1.01//nt2 tin plating and further 3430 mJ in an aqueous solution containing hexavalent chlorine.
5 to 15 m in a filtrate solution containing hexavalent chromium.
A method for manufacturing a multilayer plated steel sheet for welded cans, characterized by forming a chromate film mainly composed of aqueous chromium oxide of l/m' (chromium equivalent). (3) Ni/(Ni+Fe) on degreased and pickled cold-rolled steel sheet
) = Ni-Fe with a metal composition of 0.60 to 0.95
Alloy plating is applied to a thickness of 0.01-0.2μ, then 0.05-1. It is characterized by carrying out tin plating of 3 to 30 ml//m", followed by hot pot treatment, and further forming a film mainly composed of metallic chromium of 3 to 30 ml//m" in an aqueous solution containing hexavalent chromium. A method for producing multilayer plated steel sheets for welded cans. (4) N i/(N i+
Ni- with a metal composition of l'e ) = 0.60 to 0.95
Fe alloy plating is applied to a thickness of 0.01 to 0.2 μ, followed by tin plating to a thickness of 0.05 to 1.017 m, followed by hot pot treatment, and further in an aqueous solution containing hexavalent chromium. Forms a film mainly composed of metallic chromium of 3 to 30 ml/m, and further forms a chromate film mainly composed of hydrated chromium oxide of 5 to 15 ml/m" (chromium equivalent) in an aqueous solution containing hexavalent chromium. A method for producing a multilayer plated steel sheet for welded cans, which comprises forming a film.