JPS6025519B2 - Manufacturing method of stain-free steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the production of Tissot-free steel (hereinafter abbreviated as TFS-CT) having a chromium hydrated oxide layer on top of a chromium plating layer. It relates to methods of forming things.

TFS-C was developed as a countermeasure to the global tin resource lagoon.
T is recognized for its low cost and excellent performance as a material for cans, and in particular, 3-piece adhesive cans made of TFS-CT with can Tsukioka glued on and packed with carbonated drinks or beer are on the market. It is widely spread.

Recently, there has been a noticeable movement to use TSF adhesive cans for other contents, but it is difficult to obtain the required adhesive strength for contents that require high-temperature sterilization or high-temperature packaging. . The cross section of the adhesive part of the adhesive can has a structure as shown in FIG.

In the figure, 1 indicates TFS, 2 indicates coating, and 3 indicates adhesive. When a large stress is applied to the adhesive part of such a structure in the direction of peeling it off, breakage occurs at weak points within each layer and between each layer. It is not limited to failure within or between specific layers, but parts of the same strength will fail at the same time. Generally, a nylon strip is used as an adhesive, and failure caused by excessive peeling stress often results in cohesive failure within the nylon layer. However, there are cases in which peeling at the interface between the nylon and the paint film and peeling of the paint film from the material occur, and furthermore, there are cases in which all of these types of failure occur simultaneously. The period when a large force is applied to the adhesive part is during the vertical winding process of the top and bottom plates (lids) in the can making process and the packing process.

The vicinity of both ends of the bonded portion, which undergoes winding during the seaming process, undergoes bending. This process is harsh, and even in the case of soldered cans, a defect called "lap cracking" is likely to occur at this location, requiring careful soldering work. That is, the outside of the wrap is subjected to 1800 degree bending with a diameter equal to the thickness of the lid, and the inside of the wrap is subjected to 180 degree bending with a diameter equal to the thickness of the lid plus the thickness of the wrap itself. And the adhesive between the wraps, the coating layer, and the interlayers.
Not only a simple bending stress but also a shearing stress in the circumferential direction of the can, that is, in the width direction of the adhesive is applied. The reason why it is difficult to obtain sufficient adhesive strength in high-temperature sterilization and high-temperature packs, as mentioned above, is that compared to cases where the contents are carbonated drinks or beer,
This is due to the fact that a larger force is applied between the laps and the type of fracture changes.

In the case of carbonated beverage cans and beer cans, since they are internal pressure cans, thin plates are used as the material, whereas non-internal pressure cans have relatively thick plates.

When the board is thicker, the force applied between the wraps during winding is greater. Furthermore, due to the stress applied between the wraps, the layers within and between the layers of the wraps are subject to considerable damage even if complete delamination does not occur. The most troublesome damage to the performance of cans is damage to the paint film, and the phenomenon in which the adhesion between the paint film and metal becomes extremely low when water or non-aqueous solutions penetrate into the interface is a phenomenon that can cause damage to the paint film after this damage. Occurs submembrane (on the TFS surface). Particularly in high-temperature packs, stress and temperature are at their highest at the same time, which tends to reduce the adhesion between the paint film and TFS, which can lead to corrosion under the paint film or leaking cans. Similar defects can occur in high temperature sterilization, ie, post-pack retort processing, although the point at which stress and temperature peak is shifted. The present invention has been made with the object of solving such problems that occur when winding adhesive cans by using the properties of the can material, that is, TFS.

That is, the objective is to improve the adhesion between the paint film and TFS to prevent peeling of the paint film due to stress applied to the wrap, and the corrosion and leakage that accompanies this. Originally, TFS-CT
was developed on the premise of being painted, and was developed to exhibit its in-can performance through interaction with the paint film.
Adhesion to can paints is at an extremely high level compared to other can materials.

This is largely due to the structure of chromium hydrated oxide on the TFS-CT surface. The paint for cans is a type of paint, and when it is applied to the TFS-CT surface and baked, it is said that the paint film is bonded to the TFS-CT surface by hydrogen bonding. Therefore, the chromium hydrated oxide on the TFS-CT surface needs to be a hydrated and active film before painting. However, in general, in the production of food and beverage cans, after the outer surface of the material is coated with a primer called sizing, the inner surface is coated with gold, and then the outer surface is printed. Therefore, the inner surface of the can is dry fired after sizing and before painting. This bride is TFS-C
A reaction occurs to dehydrate and oxidize the coordinated water and adsorbed water in the hydrated oxide film on the T surface, causing a loss of bonds with the coating film when the coating film is cured. In order to suppress this deactivation due to air racing, the inventors considered changing the chromium hydrated oxide film from the conventional one. In the production of TFS-CT, we separated the chromic acid treatment, which mainly produces a chromium hydrated oxide film, from the chromium plating, and reduced the S04 concentration in the chromic acid treatment, in which only sulfuric acid was added to chromic acid. We have found that the method of control is effective. Furthermore, by surface analysis, it was found that there is a relationship between the SO4 concentration in this chromic acid-treated material and the SO4 concentration in the produced chromium hydrated oxide. S04 in the chromium hydrated oxide film has the effect of controlling the dehydration reaction during the air-baking process mentioned above and maintaining the activity after the air-baking process.

The results of the experiment to determine the effective S04-concentration range are in the second section.
As shown in the figure, the concentration of 2S04 in the chromic acid treatment Rakuchu, which mainly consists of an aqueous solution of C, is 0.01 evening/so 0.6 evening/that is, 0.01 for chromic acid.
It can be said that a range of 0.7% (weight %) is an appropriate range. In the experiment whose results are shown in Figure 2, steel sheets electrolytically plated with chromium under certain conditions were treated with chromic acid at various concentrations of S04, that is, 80% of the Cr03 aqueous solution was treated with chromic acid, and the amount of S04 added was varied. A TFS-CT sample treated with chromic acid was coated and bonded, and then the bond strength was measured using a tensile tester.

The chromium hydrated oxide was prepared to a thickness of 12 mm/mm, and after 5.5 coats of epoxy/phenol paint was applied, it was applied for 10 minutes at 210 oo. Using a nylon 12 strip with a width of 5 ribs and a thickness of 100 mm as an adhesive, two TFS specimens with a width of 5 ribs and a length of 10 mm were heated at 200° C. by pressing between 1 inkstone and sand. The thus obtained lap specimen was subjected to a peel test at a tensile speed of 20 yen/min.

Add 20% to 80q0 of 0.4% citric acid aqueous solution.
A test in which the material is immersed for a minute and then peeled off is called a secondary adhesive strength test, and is a test to determine the performance of adhesives in high-temperature packs and high-temperature sterilization cans.

On the other hand, the primary adhesive strength test is a test in which the sample is peeled off without being immersed in a citric acid aqueous solution, and the results of both tests are shown in FIG. The appropriate S04 range can be determined from the results shown in FIG. 2, but it has been found that surface stains occur when S04 is set to 0.7 mm/or more. In order to control the S04 concentration within the appropriate range obtained in this way, the plating grade and the chromic acid treated grade must be separated, and the plated steel plate (strip) must be separated from the chromic acid treated grade. It is necessary to take measures such as installing a drag-out tank and washing with water to prevent this from being brought in.

Next, the method of the present invention will be explained with reference to Examples.

Example 1DCRO. After degreasing and pickling the 17th side TFS original plate, C 3180, Sun 2S040.30NabujF6
5 evenings/70A/d with that liquid and 0. After the sand plating was kept in the plating solution for 1 second without applying electricity, it was placed in a bath different from the plating solution, that is, in a 380° C/aqueous solution with 0 and 0 sulfuric acid.
It was treated for 1 second at 8 A/d with three types of chemical bath components to which 2 and 1.0 t/d were added. This TFS is 1 in 20000
After baking for 0 minutes, apply epoxy phenol paint to 45~5
5m9/d was painted and baked at 20500 for 10 minutes.

After that, a nylon 12, 50 thick x 5 synthetic resin tape for adhesion was interposed between the two sheets of TFS after the paint was baked, and 19°C was applied at a pressure and temperature of 200 to 205°C at 3k9/cm.
Sand pressure bonded.

After that, cut out the adhesive part of the 5th side x 7th side and pull at 2
A T-peel test was conducted at 0 min. In addition, in order to check the secondary adhesive strength as well as the primary adhesive strength test, 80% citric acid 0.0.
A peel test was conducted by immersing the sample in a 6% aqueous solution for 20 minutes and keeping the peeled part wet with the aqueous solution during the tensile test.

The above results are shown in Table 1.

Example 2 After cold rolling to a side thickness of 0.23, degreasing was carried out on the Houzuki Yakinori line,
The original plate was milled (spotted oqo x 2 seconds) and temper rolled to 1% to Cr03180, H2040.30 Na2S.
iF65 evening/70A/d power 0. After sand and chromium plating, it was treated for 1 second at 8A'd with four types of chemicals: Cr03809, sulfuric acid, 0, 0.15, and 0.40.8.

Apply epoxyphenol paint to this TFS about 60 minutes.
I painted it with d〆 and applied it at 21000 for 10 minutes.

After that, a can body was manufactured using high-frequency heating using nylon 12 tape with a thickness of 50 mm as an adhesive, and the can end was attached.
5 qo of 0.5% citric acid solution was completely poured and the lid was immediately tightened. After cooling, the temperature was maintained at 40:00 for 10 days.
The number of leaking cans was investigated on day 0 and day 90. The results are shown in the table below.

The number of defective cans in the solid can pack No. 2 is shown.

All of the leakage areas are due to minute peeling between the adhesive TFS and the coating.

As described above, the present invention has shown excellent effects.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the state of adhesion, and FIG. 2 is an explanatory chart showing the relationship between adhesive strength and sulfuric acid concentration in a chromate (chromic acid) treated solution. 1... TFS, 2... Paint film, 3...
···glue. Figure 1 Figure 2

Claims (1)

[Claims] 1. In the production of a type of stain-free steel having a hydrated oxide layer on a metallic chromium layer, a chromium plating bath and a chromic acid treatment bath are separated, and the chromic acid treatment bath consists of chromic acid (CrO_3) and sulfuric acid. Consisting of only SO_4^-
＾-Concentration is 0.0 relative to chromic acid (CrO_3 equivalent)
1 to 0.7% (weight %).