JPS5974294A - Manufacture of surface treated steel sheet for welded can - Google Patents

Abstract

PURPOSE:To obtain a surface treated steel sheet for a welded can with superior rust resistance, weldability and adhesive strength to a paint film by plating the surfaces of a steel sheet with an Ni-Fe alloy and by forming Cr films. CONSTITUTION:The surfaces of a cold rolled steel sheet are plated with an Ni- Fe alloy having a composition making the weight ratio of Ni/(Ni+Fe) 0.60-0.95, and a thickness of 0.01-0.2mum. The steel sheet is then treated in an aqueous soln. contg. sexivalent Cr ion to form metallic Cr-base films by 3-30mg/m<2>. Chromate films contg. Cr oxide hydrate as the principal component may be further formed in an aqueous soln. contg. sexivalent Cr ion about 5-15mg/m<2> when expressed in terms of Cr. The desired steel sheet is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a treated steel sheet for welded cans that has excellent rust resistance, weldability, paint film adhesion, and the like.

Traditionally, tin plates used to manufacture food and beverage cans were soldered.However, the harmful lead contained in solder can leak into the contents of the can, leading to food sanitation issues. For this reason, in recent years, soldering around the can body has gradually ceased, and instead, seam welding (with a SuPronik welding machine) has become popular. The overlapping part of is 0.3
Since the width is 0.4 M, the quality of mating is greatly influenced by the surface treatment method of the steel plate. Commercially available tinplates with lower tin adhesion properties tend to have better weldability, and as the price of tin has skyrocketed, consumers of can materials are looking for lighter weight tints, as well as lower tints that can replace these tinplates. There is a demand for new materials at low prices. In response to these demands, Ni-plated steel sheets, thin S
Trial production or practical use of surface-treated steel sheets in which chromium plating or a thick chromate film is formed on the Y+ plating layer is underway.

Although these new materials have excellent rust resistance and paintability, they have problems as described in F. Since Ni-plated steel sheets have a large potential difference between Ni and Fe, if minute scratches are made in the plating layer during handling, the Fe will rapidly corrode and oxidize in the scratched area, causing holes to form in the scratched area. There is. For this purpose, painting,
Great care must be taken when handling canning and canning products.

Welded cans are usually painted on both the inside and outside, but when filling a Ni-plated can with minute scratches on the coating, hydrogen gas is generated in a short period of time, causing the can to expand. Become.

Steel plates coated with chromium or a thick chromate coating on a thin Sn plating layer have poor weldability, and dust (spatter) or non-welded areas may occur, and the optimum welding current cannot be controlled properly. be. On the other hand, if the amount of chromium plating or chromate film is reduced in order to improve weldability with this steel sheet, the rust resistance will deteriorate and rust may occur before painting and can manufacturing are carried out at the 1M can manufacturer. .

The present inventors have discovered that even if minute defects occur on the plated or painted surface, the paintability and rust resistance will not be affected.
As a result of intensive research into materials for hot melt cans with excellent weldability, we have developed a method in which Ni-Fe alloy plating is applied to the surface of the steel plate, and a thin metal chromium plating is applied on top of that, and a method for water conservation is achieved by chromate treatment on the chromium plating layer. It was discovered that a method of forming a chromate film mainly composed of chromium oxide is effective, leading to the present invention.

That is, the first Ni-Fe alloy plating layer can make the potential difference with the base metal iron extremely smaller than the potential difference between Ni and Fe, and can suppress corrosion based on local batteries in plating defects. . The second layer of chromium plating is used to repair defects in the Ni-Fe alloy plating as a sealing treatment for the Ni-Fe alloy plating, and this treatment significantly improves rust resistance and corrosion resistance. Furthermore, by forming a chromate film mainly composed of water-retaining chromium oxide on the surface through chromate treatment, it has excellent paint film adhesion, paint film adhesion after retort treatment, corrosion resistance under the paint film, rust resistance, and weldability. We can provide surface-treated steel sheets.

The steel plate used in producing the welded can material by the method of the present invention may be either an ingot material or a continuous cast material.

The original plate is a boar plate that is cold rolled to 0.15 to 0.35 RII by a normal method, annealed, and then temper rolled. To make it clear, the original plate was subjected to the usual de-leasing and pickling process, and Ni/(1
A Ni-Fe alloy having a metal composition of 'Ji + Fe) = 0.60 to 0.95 (weight ratio) was used. Ni-Fe alloy plating can be carried out using commonly used sulfate baths, chloride baths, sulfamate baths, birophosphate baths, etc.
-Fe alloy plating has rust resistance, corrosion resistance, paintability, lδ1
The purpose is to improve workability, and the plating composition is changed to N.
i/(Ni + Fe) ==0.60 to 0.95, and the plating thickness was 0.01 to 0.2μ.

The plating composition is Ni/(Ni +Fe) = 0.60-
The reason for specifying 0.95 is as follows.

(1) Ni-Fe alloy steel, pure nickel was coupled with pure iron in 30% saline solution, and after being left for 4 hours, the iron ions eluted from a certain area were measured. Figure 1 shows the results of measuring the iron ions eluted from a certain area. Compared to when pure iron is coupled, N:/
(Nt + Fe) = Ni-Fe of 0.95 or less
In the case of a couple of alloy steel and pure iron, the elution of Chichi ions is extremely reduced.

(2) After the cold rolled steel sheets were conventionally degreased and pickled, Ni--Fe alloy plating was applied by varying the P'e ion concentration and current density of the sulfamate Ni--Fe alloy plating bath. The plating thickness at this time was all 0.2μ. Figure 2 shows the results of a rust resistance test using these Ni-Fe alloy coated steel sheets with different plating compositions.
When Ni + Fe) = 0.5 or less, the rust resistance deteriorates rapidly.

For reasons (1) and 12) above, the father of alloy assembly is Ni.
/(Ni + Fe) = 0.60 to 0.95. That is, if Ni/(Nt + Fe) is less than 0.6, it is advantageous against electrochemical corrosion at plating defects, but rust resistance deteriorates. Also, Ni/(Ni +
Although it is advantageous for rust resistance to make Fe) larger than 0.95.

- The phase difference with the base iron is too large, corrosion is accelerated in the plating defects, and the elution of iron ions increases rapidly.

Next, the plating thickness was set to 0. The reason why it is limited to O1 to 0.2μ is as follows. If the plating thickness is less than 0.01 μm, the coating on the surface of the steel plate is incomplete, and the dust, rust resistance, and corrosion resistance after painting deteriorate rapidly, and the rust resistance and corrosion resistance after painting are no different from those of the original plate. Furthermore, if the thickness is greater than 0.2, the rust resistance will improve, but the workability will deteriorate. Therefore, in this application, the plating thickness is limited to a range of o, oi to 0.2μ.

Q, which is coated with Ni'-Fe alloy to a thickness of 0.01 to 0.2μ, has several times the rust resistance compared to easily plated steel sheets with the same plating thickness, but Compared to #25 tin, which is conventionally used for food cans, it has insufficient rust resistance.

For this purpose, rust resistance, corrosion resistance? For further strengthening, metal chromium plating of Q3~30~/A is applied in an aqueous solution containing hexavalent chromium. Chrome plating after Ni-Fe plating can be done in a normal chromium plating bath. The plating conditions are not particularly limited, but in order not to impair the weldability of the resulting product, the amount of metallic chromium must be must be less than 30~/i.

In addition, for rust resistance and corrosion resistance, the amount of metallic chromium is 3 towns/
It is necessary to have more than

Furthermore, the amount of chromate coating applied in the method of the present invention is extremely important in terms of weldability. The most excellent effect can be obtained when the amount of chromate film is in the range of 5 to ts*p/m in terms of Or. That is, when it is less than 5~/rn', the rust resistance is insufficient and the effect of improving coating performance cannot be obtained, but when it exceeds 15~/rn', the above effect is good, but when welding K' This causes splintering and makes repair painting of the m-joint part difficult...not only does the welding strength decrease, but it also tends to cause welding defects.

The present invention will be specifically explained below with reference to examples.

[Example, comparative example]

After subjecting a cold-rolled steel sheet to regular degreasing and pickling treatment, - alloy composition within the above conditions? Plating was performed with various changes. The alloy composition is Ni/(Ni + Fe) = 0.5~
At 0.95, the plating thickness is 0.01~0.2μ
The amount of air per stroke was changed so that it was within the range of . For metal chromium plating after alloy plating, chromium density is 2 to 5 under the following conditions.
It was done by changing the air condition so that it became 0/d.

1. On some of the samples, a chromate film of 5 to 15 cm/i in terms of chromium was applied using the chromate bath described below.

(A) Ni -Fe * Poor plating conditions (1) Plating bath composition 77mm 4fR Nitsuke k (Ni”> 50-150
9/e Iron-41 sulfate (FeSO4・7H20) 15
~100 li/e Boric acid 30
g/e saccharin soda 0.69/g lauryl sulfate sorta'' 75 V'e sulfamino acid 5-30 g/e12) pH 1,
5-4.0. +3) Temperature 25-80'0'4
) heart ftff, "lPf degree 0.5~30Vdm2.15
) Plating thickness 0.01 to 0.2 μ (B) Plating bath with chromium anhydride (1) Plating bath composition Chromium anhydride
0.8 ri/e Sodium silicofluoride 1
．． 0!7/g12) Temperature 45゛C1+3)'it Flow density 50 A7/d+1 (C) Chromate treatment bath 11) Plating bath composition Chromic anhydride, og7I3 sodium dichromate 209/β (2)@degree 50℃ , +31 current density 5A/d [Reference Example 1] After performing conventional degreasing and pickling treatment on a cold rolled steel sheet, 0.2μ Ni plating was applied in a Watt bath, and then hexavalent resin ion was applied. Cathode treatment is carried out in an aqueous solution containing chromate film, which is IO in terms of ROM! [Reference Example 2] After degreasing and pickling a cold-rolled steel sheet in the usual manner, it was soaked in a halodane bath.
．． Tin plating was applied to a thickness of 20 .mu.m, followed by further treatment in an aqueous solution containing hexavalent chromium ions, and a chromate film was deposited in terms of chromium equivalent QIO.about./I.

(Reference Example 3) After degreasing and pickling a cold-rolled steel plate in a conventional manner, tin plating with a thickness of 0.4μ (#25 tin plate) was applied in a halogen bath,
Cathode treatment was carried out in an aqueous solution containing 61iIIIi chromium ions, and a chromate film was deposited at Q8wy/i in terms of chromium.

A test piece from the product obtained as described above? The bamboo was cut out and its characteristics investigated using the method described below. The results are shown in Table 1.

(1) Rust resistance evaluation method Place a specimen in the test tank of a dry-wet cycle device, 50C19
8% (relative humidity), 30 minutes at 25°C, 160% (4 (1
One test was conducted for a certain period of time by repeating dry and wet conditions for 30 minutes, and the degree of rust generation was evaluated. Evaluation is JI
Compliant with “S-Z-2912r Rust Incidence nil Elimination”, ◎
The test was performed in five stages: (no S), ○, Δ, ×, and XX (all over the surface).

(2) Evaluation method for melting and darkening Welding tests were conducted using a 164.7 x 110mm test piece under the following conditions. .4~0.5 Jls welding tool? 7T
, 1000 to 5000A (4 (evaluation of requirements is J-Te Natsuko in the 4 flow range where uniform nadette formation and sufficient welding times can be obtained.

130A or more Δ 90~125A × 85A or less Note that the strength of the m weld is the V
Make the shape of the cut with a person (t), hold the triangular part with pliers and pull it towards the other end... perform an in-test to determine the required strength so that the welded part does not break in the middle.

13) Performance evaluation after painting epoxy pheno-υ system coating 4”) coating edge is 45±5q
/ dm" and was baked and dried for 210'0110 minutes, and the following tests were conducted.

(3-1) Secondary adhesion test of paint film After immersion in an aqueous solution containing 1.5% citric acid for 96 hours, 100 Ipan eyes were peeled off and the number of peeled pieces was removed using tape. It was evaluated as follows.

Q No peeling -) 1 to 3 pieces Δ 4 to 1 ( ) pieces X 11 to 30 pieces The condition was evaluated as follows.

○ Good Slightly inferior × Significantly inferior According to the present invention, rust resistance and performance after painting are superior to #25 tin plate (064μ thick Sn plating, reference example 3), and the appropriate welding current is #25. It is as good as #9, but the minimum weldable current is 6 at a lower current value than #25.
．． It is possible to have a concubine, and the economic benefits are great. Comparing the μ flow side of the present invention with the comparative examples and reference examples, it is clear that the products of the present invention are significantly (excellent) in rust resistance, weldability, secondary adhesion after painting, and corrosion resistance.

In this way, Ni −Fe @gold plating is changed to Ni/(N
i + Fe) weight ratio - 0.60 to 0.95, thickness 0
．． 01~l), applied to 20μ, and then applied to 3~30t
ny/rrt chrome plating, or
By adding a chromate film of 5~15~/Tj to this with 1 ton of thread, the rust resistance, meltability, and paintability were all improved! #We can provide welding materials.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between Ni/(Ni + Fe) weight ratio and Fe elution amount, and Figure 2 is a graph showing the relationship between Ni/(Ni + Fe) weight ratio and Fe elution amount.
It is a graph showing the relationship between weight ratio and rust resistance. Applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] (1) Ni/(Ni+Fe)= on the surface of the cold rolled steel plate
Ni with a metal composition of 0.60 to 0.95 (weight ratio)
-Fe alloy plating is applied to a thickness of 0.01 to 0.2μ,
3 to 30 in an aqueous solution containing hexavalent chromium ions! /m
1. A method for manufacturing a surface-treated steel sheet for welded cans, which comprises forming a film mainly composed of metallic chromium. 12) Ni/(Ni+Fe) = on the surface of the cold rolled steel plate
Ni with a metal composition of 0.60 to 0.95 (weight ratio)
- Fe alloy plating is applied to a thickness of o, o i ~ 0.2μ, and a thickness of 3~3 um is applied in a high water solution containing hexavalent chromium ions.
A film mainly composed of metallic chromium of 5 to 15 p/m" is formed on the cedar, and is further heated in an aqueous solution containing hexavalent chromium ions.
A method for manufacturing a surface-treated steel sheet for welded cans, which comprises forming a chromate film mainly composed of hydrated chromium oxide of d (chromium equivalent).