JPS6040519B2 - Manufacturing method of stain-free steel plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing a tin-free steel sheet for retort treatment, which has excellent adhesion between a metal chromium coating and a chromium hydrated oxide coating, and excellent adhesion between a chromium hydrated oxide coating and a paint. It is related to.

The two-component method of the prior art deposits the metallic chromium and the hydrated chromium oxide film separately, so it has the advantage that the amount of each deposited can be easily controlled.

In particular, when a chromic acid solution is used for electrolytic chromic acid treatment (for example, see Samurai Publication No. 47-35172),
Since the amount of chromium hydrated oxide deposited increases in proportion to the amount of electrolyzed electricity, strict control is possible. However, in the two-component system, the liquid compositions of both baths are different, so if a steel plate after chromium plating is directly transferred to electrolytic chromic acid treatment, co-refraction occurs in the chromium hydrated oxide produced during chromium plating. The adhesion aid anions remain in the coating of the final product or adhere to the steel surface. The smearing solution is brought into the electrolytic chromic acid treatment bath, causing inconveniences such as fluctuations in the amount of chromium hydrated oxide film deposited and re-precipitation of the partially deposited auxiliary anions. . Therefore, it is necessary to thoroughly wash with water after chromium plating and before electrolytic chromic acid treatment to prevent this. However, if only water washing after chrome plating is performed, the chromium hydrated oxidation produced during chromium plating will It is difficult to remove chromium plating aid anions from the product. In particular, in chromium plating using sulfuric acid or its compounds as an aid, sulfuric acid wires are deposited in the final chromium hydrated oxide even if electrolytic chromic acid treatment is performed using a chromic acid solution. This causes problems in adhesion with the paint film. As a result of repeated research to determine the shortcomings of tin-free steel manufactured by the two-component method as described above, the present inventors have discovered that chrome plating can be improved by performing reverse electrolysis in the solution after chromium plating. The amount of chromium hydrated oxide and auxiliary anions therein can be reduced during electrolytic chromic acid treatment. The present invention was developed based on the finding that applying the above is extremely effective in improving retort processing resistance.

By performing reverse electrolysis in the solution after chromium plating, the hydrated chromium oxide is eluted and the metal chromium is partially melted, thereby smoothing out the irregularities on the surface of the metal chromium deposited during plating.

At this time, a secondary cathode coating and a different anodic coating are formed simultaneously or after completion. It was confirmed that there was little co-refraction of the plating agent in this coating, and it was confirmed that the retort treatment resistance was significantly improved by electrolytic chromic acid treatment using a chromium aqueous solution through a washing tank. Ta. The present invention applies 20 to 200 9 on one side to a cold rolled steel plate.
This invention relates to a tin-free steel plate plated with metallic chromium and having a chromium hydrated oxide coating of 5 to 50% on one side on the surface of the metallic chromium layer, and is usually used after being painted.

That is, one side of the steel plate is coated with organic paint and baked, and the other side receives the hollow mound. Next, the opposite side is painted and baked in the same manner. After this, both sides are pasted together with an organic adhesive and bonded to form a can body.In order to obtain a tin-free steel sheet with excellent adhesive properties and retort treatment resistance after filling the contents, sulfuric acid or After chromium plating with a general-purpose solution that uses an auxiliary agent containing anions such as compounds, reverse electrolysis is performed in the same solution with an electricity amount of 0.1 to 15 coulombs/d〆, and then transferred to a chromic acid aqueous solution via a water washing tank. A feature of the method for manufacturing tin-free steel sheets for retort treatment of the present invention is to perform electrolytic chromic acid treatment. If the metal chromium layer has a density of less than 20%, there will be many microcracks and pinholes, resulting in poor corrosion resistance.
Since corrosion resistance cannot be expected to improve significantly even when the thickness is higher than M', ordinary chromium-plated steel sheets have a metallic chromium layer of 20 to 200%. On the other hand, if the hydrated chromium oxide film is less than 5x9/〆, the desired paint adhesion cannot be expected;
Moreover, if it is more than 50 o', the appearance will be poor and it is not practical.

In addition, if the amount of electricity in reverse electrolysis is 0.1 coulomb/d or less, the dissolution of the hydrated chromium oxide film and the metal chromium will be insufficient, and the effect will decrease. If the temperature exceeds d, the amount of metal chromium eluted is too large to be practical. The present invention will be explained in more detail. As a manufacturing method for tin-free steel sheets, there is also a one-component method in which metallic chromium and chromium hydrated oxide are simultaneously precipitated using electrolytic chromium oxide containing low concentration chromic acid as the main component. This invention relates to a method for producing tin-free steel sheets that have excellent retort treatment resistance due to the nature of the two-component chromium hydrated oxide coating. As a subsidiary, chromium plating solutions cannot precipitate metallic chromium using only chromic acid as the base agent, and chromium plating solutions cannot deposit metallic chromium using only chromic acid as the base agent. The addition of agent anions, alone or in combination, is essential.

These break the all bonds of all compounds in which hydroxyl groups and water are bound or adsorbed to low-valent chromium ions generated by intermediate reduction of hexavalent chromium ions during chromium plating.
Penetrates the coating and dissolves it. The coating is then renewed by dissolution and is always kept thin. In addition, the auxiliary anion that has entered the coating coordinates with low-valent chromium and replaces hydroxyl groups and water, promoting the reduction-precipitation reaction of metallic chromium.
Therefore, the presence of auxiliary anions is essential for chromium plating, and therefore, a large amount of the above-mentioned anions are eutectoid in the chromium hydrated oxide film formed during chromium plating. This remains even after manufacturing a tin-free steel sheet after electrolytic chromic acid treatment through a water washing tank. As described above, a large amount of the anion used as a chromium plating aid is co-resolved in the chromium hydrated oxide film, and this has a large effect on paint adhesion.

In other words, the above-mentioned anions exist as substitutes for the hydroxyl groups and bonded water necessary to form hydrogen bonds with the paint, and cause the problem of poor adhesion to the paint due to the lack of bonding hands required for paint adhesion. There is a direction. In addition, these anions remain in the hydrated chromium oxide after the paint is baked, and because of their solubility, they are undesirable because they elute in the retort filled with the contents or even after a period of time, deteriorating the retort resistance. . Therefore, it is essential to reduce the amount of anions remaining even after the decomposed chromic acid treatment.

For this reason, it is conceivable to reduce the content of the auxiliary anion used during chromium plating, but this is not practical because the metal chromium precipitation efficiency is low and the appearance may be poor. Additionally, rinsing with hot water or the like after chromium plating has been considered, but even this is not sufficient as a method for removing anions from the chromium hydrated oxide film.
Furthermore, although rinsing with hot water is performed after the electrolytic chromic acid treatment, this is still not sufficient. In contrast, the reverse electrolysis method of the present invention significantly reduces the amount of auxiliary anions that co-refract during chromium plating that remain after electrolytic chromic acid treatment, which was difficult to achieve with any conventional method. Therefore, retort processing resistance is significantly improved.
Tin-free steel plate obtained by the method of the present invention (Example 1
~3) and steel plates obtained by conventional methods (Comparative Examples 1 to 3)
), a T-beer peel test, a plating surface analysis, and an electron microscope observation of the surface condition were performed. These will be explained in detail below. [Example 1] A cold-rolled steel plate with a thickness of 0.22 was soaked in a 5% homezason solution.
After performing electrolytic degreasing for 10 seconds at a current density of 0qC and 1matsu'd, it was washed with water, immersed in 10% sulfuric acid at room temperature for 5 seconds, washed with water, and then subjected to the main treatment under the following conditions.

Chrome plating bath composition
Bath temperature: 550C Electrolysis conditions: 50A'd x 1. The sand was subjected to reverse electrolytic treatment in the chromium plating solution under the following conditions.

Reverse furnace starvation condition: 2 A/d x 0.2 sand After this, the sample was washed with water and immediately subjected to electrolytic chromic acid treatment under the following conditions.

Composition C 3 100 ta'so, high temperature 45℃ heating condition 10A/d x 1. After this electrolytic chromic acid treatment of Tochijiku,
It was immediately washed with water, further washed with hot water, and then dried to obtain a tin-free steel plate.

[Comparative Example 1] After applying chromium plating in the same manner as in Example 1, immersing the groove in the same solution for 5 seconds without performing reverse electrolysis, washing with water, and then performing the same treatment as in Example 1. A tin-free steel plate was obtained.

[Example 2] A tin-free steel plate was obtained by performing the same treatment as in Example 1 except for the electrolytic chromic acid treatment described below.

Electrolytic chromic acid treatment common silk formation C's 380 evening/Ku Toka BF
40.09 ta'〆bath temperature 45℃ electrolysis conditions 1 ship'
d〆×1. Late sand [Comparative Example 2] After applying chromium plating in the same manner as in Example 1, it was immersed in the same solution for 5 seconds without reverse electrolysis, then washed with water, and then immediately treated in the same manner as in Example 2. Electrolytic chromic acid treatment was performed, and a similar post-treatment was performed to obtain a tin-free steel sheet.

[Example 3] After performing the same pretreatment as in Example 1, chrome plating was performed under the following conditions.

Chromium plating bath composition: C 3250/so-10 ratio S041/so-10 day b2SiF810/ku bath 55 qo Electrolytic conditions: 6 M/d xl. After the top was chromium plated as described above, reverse electrolysis was performed in the same solution under the following conditions.

Reverse electrolysis conditions: 5A/d〆×0.1 seconds After this, it was washed with water and immediately subjected to electrolytic chromic acid treatment under the following conditions.

Electrolytic chromic acid treatment bath composition: C380/So1Na2SiF60.19
2/Bath temperature 45q0 Electrolysis conditions IQA'd × 1. The sand was then subjected to the same post-treatment as in Example 1 to obtain a tin-free steel plate.

[Comparative Example 3] After applying chromium plating using the same machine as in Example 1, immersing it in the same solution for 2 seconds without performing reverse electrolysis, washing with water, and then immediately applying electrolytic chromic acid in the same manner as in Example 3. After treatment, a similar post-treatment was carried out to obtain a Tinfree grade plate.

[Peel strength test]

Tin-free steel plates produced by the method of the present invention (Examples 1 to 3) and conventional steel plates (Comparative Examples 1 to 3) were treated as described below to prepare test pieces for peel tests.

'1' Test piece creation method: Coat one side of each tin-free steel plate with a coating film amount of 50±5 on each side.
After applying sizing coating at m9'd and dulling at 190 qo for 10 minutes, the same amount of gold coating was applied to the remaining opposite side and dulling was carried out at 210 oo for 10 minutes.

After this, apply a nylon adhesive synthetic resin tape (100mm thick) between the sizing painted surface and the gold painted surface.
y, width 5 sails) was narrowed and hot pressed to 190qo.
A plurality of test pieces were prepared by adhering the test pieces to each other by applying sand-gluing in step 3 using a lk9/ground. '21 Test method [11'] The test piece obtained as described above "immediately after adhesion" was subjected to a T-peel test using an Instron tensile tester at a constant tensile speed of 20 mjn/mjn. Peel strength was measured.

Furthermore, using another test piece, we added a sugar-acid solution containing 15 tb of tate and adjusted to pH 3.3 with citric acid for 7 hours at 70°C.
The peel strength after soaking for one day was measured under the same conditions as above.

All tests were conducted using five test pieces of each test piece.

The test results are shown in Table 1 below, and the results are expressed as average values.
Furthermore, the test results of Example 1 and Comparative Example are representatively shown in FIG. In the same figure, the maximum value is A, the minimum value is C,
The range is indicated by "1" and the average value is indicated by "B". Rigidity Test Results As is clear from Table 1 showing the results of the peel strength test and the drawings, in the case of the steel plates prepared by the conventional method in Comparative Examples 1 to 3,
The peel strength immediately after adhesion is low, and the peel strength after aging of bran acid immersion bridge is also significantly deteriorated to less than half of that.

However, in the method of the present invention, the peel strength immediately after post-adhesion is also improved compared to the conventional method, and the drop in peel strength after immersion in a bran acid solution is reduced.

That is, the adhesive obtained by the method of the present invention has a high peel strength immediately after adhesion, and also has significantly improved retort treatment resistance and aging deterioration resistance. Table I T-beer peel strength [Treatment surface analysis] Samples prepared by the method of the present invention (hereinafter referred to as the sample of the present invention) were subjected to reverse electrolysis in the same solution after chromium plating as described in Example 1, and immediately washed with water and dried. Regarding the sample by the secondary method (hereinafter referred to as the secondary method sample), which was chromium plated and immersed in the same solution for 5 seconds as described in Comparative Example 1, and immediately washed and dried, the following was performed. Various analyzes were conducted.

○} Amount of metallic chromium The amount of deposited metallic chromium was measured using the electrolytic stripping method for each of the above-mentioned five samples according to the present invention and the conventional method. The results (average values) were as follows.

From the results, it was confirmed that in the method of the present invention, some metal chromium was eluted due to the reverse electrolysis performed in the method of the present invention.

[21 Metal chromium electron micrograph The photograph in Figure 2 is a scanning electron microscope photograph of the above-mentioned inventive sample, and the photograph in Figure 3 is a scanning electron microscope photograph of the above-mentioned conventional method sample. This is a microscopic photograph.

From the photograph in Figure 3, it can be seen that the surface of the metal chromium plated using the conventional method has dendrite precipitation due to the poor uniform electrodeposition characteristic of chromium plating, making the surface uneven. . On the other hand, in the photograph shown in FIG. 2 of the sample subjected to reverse electrolysis according to the method of the present invention, no dendrites are observed as in the conventional method sample shown in FIG. This is thought to be due to reverse electrolysis, which caused the melting current to concentrate on the convex portions of the surface, which selectively melted and smoothed the surface. This is thought to work advantageously to reduce the exposure of metallic chromium in the chromium hydrated oxide film after electrolytic chromic acid treatment, and also to reduce the disturbance of the chromium hydrated oxide film structure and to increase the densification of the film. This seems to be useful and contributes to improving retort processing resistance.
'3} Amount of chromium hydrated oxide The amount of adhered chromium hydrated oxide was measured using the crab light X-ray method (X-ray 40 kv 60 mA monitor 60 seconds) for each of the above-mentioned inventive and conventional samples. The values) were as follows.

Sample of the present invention 1.5 days/day Sample of conventional method 3.4 days/time From these results, it was confirmed that in the process of the present invention, a portion of chromium hydrated oxide was eluted due to reverse electrolysis. '4' Amount of S in hydrated chromium oxide The amount of S in hydrated chromium oxide was determined using the crab light X-ray method (X-ray 40 kv 60 mA, monitor 60 seconds) for each of the above-mentioned invention and conventional method samples. It was measured.

The results are shown below as average values. Inventive sample Not detected Conventional method sample 350 counts From this result, the conventional method sample that does not undergo reverse electrolysis as in the present invention contains a large amount of S, and sulfate groups coexist in the chromium hydrated oxide. However, in the sample of the present invention, it was below the detection limit of the crab light It turned out to be very effective to do so.

As is clear from the above explanation, the tin-free steel sheet subjected to reverse electrolysis by the method of the present invention has good adhesion and is suitable for manufacturing can bodies such as coffee cans and food cans for retort processing. It is the material. Note that the paint on the front and back surfaces of the tin-free steel sheet according to the method of the present invention is not limited to the paint called sizing or gold, but may be any paint made with an organic solvent, and the adhesive is not limited to only nylon-based paints. .

[Brief explanation of the drawing]

Figure 1 is a graph showing the T-beer peel strength test results for samples obtained in Example 1 of the method of the present invention and Comparative Example 1 of the conventional method, and Figures 2 and 3 are electron micrographs of the surface structure of the metal. and 1 of the sample subjected to reverse electrolysis by the method of the present invention and the sample not subjected to reverse electrolysis by the conventional method, respectively.
This is a 10,000x electron micrograph. Explanation of symbols, A...Maximum value, 8...Average value, C...
・Skill value. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A stain-free steel plate having a metallic chromium coating on a steel plate and a coating mainly composed of chromium hydrated oxide formed over the metal chromium coating using an electrolytic chromic acid treatment bath separated by a chromium plating bath and a water washing bath. In manufacturing, after applying chromium plating to a steel plate in a chrome plating bath, reverse electrolysis is performed in the chromium plating bath to remove metallic chromium and a part of the chromium hydrated oxide film formed during chromium plating. In addition, the chromium plating aid anion eutectoided in the chromium hydrated oxide film is eluted, and then thoroughly washed with water in a water washing bath.
A method for producing a stain-free steel sheet, which further comprises performing electrolytic chromic acid treatment in a chromic acid treatment bath.