JPH05320979A - Thin chromium plating steel sheet excellent in lubricity - Google Patents

Abstract

PURPOSE:To improve the lubricity of a thin chromium plating steel sheet and to improve the wear of a can manufacturing jig and the scratching resistance of the steel sheet itself by applying granular tin plating with specified plating weight to the surface of a steel and applying metallic chromium and chromium oxide with specified plating weight, respectively thereto. CONSTITUTION:At least one side of a steel is applied with the granular tin plating having 0.5 to 3.0mum grain size by 50 to 300mg/m<2> per one side, thereafter, its upper layer is electrically plated with 30 to 150mg/m<2> metallic chromium and 3 to 30mg/m<2> chromium oxide (expressed in terms of metal chromium). Thus, the thin chromium plating layer is provided with ruggedness to reduce the contact area with a can manufacturing jig and to improve the lubricity of the contact part. In the case the grain size or the amt. of the tin plating is less than the lower limit, the effect of improving its lubricity is small, and in the case the grain size is the upper limit or above, its adhesion with the steel sheet is inferior and its manufacturing is difficult as well as falling-off partially occurs even at the time of can manufacturing. In the case the plating weight of tin is the upper limit or above, the occupancy ratio of the plating reaches >=20%, and unfavorable influences are occurred on the plating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is to provide a thin chromium-plated steel sheet having excellent lubricity and excellent scratch resistance.
The steel sheet of the present invention includes various canning containers, 18 liter cans,
It can also be used as a material for containers such as aerosol cans.

[0002]

2. Description of the Related Art A thin chrome plated steel sheet (TFS Tinfuri Steel) is often used as a surface-treated steel sheet for containers. This thin chrome-plated steel sheet has excellent characteristics such as paint adhesion, paint corrosion resistance, adhesive properties, and its metallic appearance, and is a very excellent material for cans. However, since the surface layer is covered with the metal chrome layer or the chrome oxide layer, there are drawbacks such as the wear of the can making jig during the can making and the steel plate itself being easily flawed. Therefore, in order to improve the surface lubricity, the lubricating oil is applied thickly or sometimes coated to prevent abrasion and scratches. In addition, the can-making machine also takes measures such as making the jig that comes into contact with the steel plate with plastic.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to improve the lubricity of the thin chrome-plated steel sheet itself and to improve the scratch resistance of the thin chrome-plated steel sheet itself as well as the wear of the can making jig. is there. The development task is to improve the surface lubricity without impairing the excellent properties of a thin chrome-plated steel sheet as a can-making material.

[0004]

[Means for Solving the Problems] The thin chromium-plated steel plate wears the can making jig because when the thin chromium-plated steel plate comes into contact with the thin Cr-plated steel plate, the chromium plating layer peels off, and fine metallic chromium and chromium oxide are removed. It is considered that it acts as an abrasive. Therefore, as a method for improving such wear and scratches, a method of improving the surface lubricity of the thin chromium-plated steel sheet to suppress the peeling of the chromium plating layer, a method of reducing the polishing action of the peeling powder, and the like can be considered. .. The present invention proposes, as a method for improving the surface lubricity of a thin chromium-plated steel sheet, a method for reducing the contact area by giving unevenness to the thin chromium-plated layer and improving the lubricity of the contact portion. .. That is, a granular Sn plating having a diameter of 0.5 to 3.0 μ is arranged below the chromium plating layer, and the protruding Sn plating (metal Cr and Cr oxide layers also exist on the Sn plating. However, it was devised so that the steel plates could come into contact with each other or with a jig or the like in a can-making machine. Under the chrome plating,
By disposing the granular Sn plating, the surface becomes uneven as described above, the lubricity is improved by the convex portion (the granular Sn is protruding) Sn, and a part of the chromium plating layer peels off. Sn powder is also mixed in the metallic chromium and chromium oxide powders, the polishing action by these peeling powders is reduced, and the scratches during can making are greatly reduced.

The present invention will be described in more detail below.

Thin chrome-plated steel sheets (TFS, tin-free steel) are excellent in paint adhesion, paint corrosion resistance, and adhesion. Also, because of its unique metallic luster appearance, it is excellent in printing finish when it becomes a can, so various beverage containers,
Widely used as canned containers, 18-liter cans, and other various metal containers. One of the disadvantages of this TFS is that the metal chrome and chromium oxide on the surface layer are very hard during can making, so that the jig of the can making machine that comes into direct contact with this surface is worn or touched. A small amount of metallic chrome,
There is a drawback that chromium oxide is deposited and these fine powders act as an abrasive to cause wear of the jig. In addition, when the jig of the can making machine is worn out, there is a problem that the worn jig will scratch the TFS itself. Furthermore, TFS
In general, when a steel strip is electrochromed, the steel strip is sheared to form a cutting plate. If the wear of the cutting edge during the shearing is TFS, an electric tin plate (Sn plated steel plate) is used. )
There is a problem that it is big compared to etc.

[0007] In many cases of TFS, the occurrence of scratches at the time of can making is done after coating and printing, so that the can is made, so that the organic resin is coated on the chrome plating layer, and conventionally, it is not a big problem. (The lubricity is improved by the organic resin layer.) However, there is a particularly strong demand in the can manufacturing industry for the cost reduction of the can material in recent years, and in some cases (for example, oil and dried contents), TFS is used without coating without coating. Thus, TFS
In the case of using N.A. nakedly, jig wear and TFS flaws in a can making machine are major problems. The problem of cutting edge wear during TFS shearing has traditionally been a problem among TFS manufacturers.

It is well known that the problems relating to such wear can often be solved by improving surface lubrication, and a measure of applying lubricating oil is most commonly adopted. However, in the case of TFS as a material for containers, if lubricating oil or the like is applied to the surface, the lubricating oil or the like will not be contained in the contents unless the lubricating oil is removed by a degreasing process after can making and before filling the contents. It is difficult to apply due to problems such as being mixed in Therefore, the present inventors have found that the amount of oil used at present (in the case of TFS, DOS (diioctyl sebacate),
Oil and fat such as cottonseed oil is applied in an amount of about 3 to 10 mg / m ² . ), And without compromising the properties of the current thin chrome-plated steel sheet, such as the excellent paint adhesion and corrosion resistance after painting, which are extremely important as container materials.
A method for improving the surface lubricity of a thin chrome plated steel sheet was examined.

As a result of intensive studies, the present inventors have found that granular Sn plating having a particle size of 0.5 to 3.0 μ is 50 to 300 mg / g.
It was found that the above problem can be solved by providing m ² in the lower layer of chrome plating. That is, it was found that the protrusions of the granular Sn plating became contact points and significantly improved the surface lubricity of the thin chromium-plated steel sheet. In addition, since the Sn plating is granular, 300 mg / m ²
Even if plating is performed, the space factor of the steel sheet surface (covering area of granular Sn plating / total surface area of steel sheet × 100) is 20% or less, and is the same as normal TFS except for the portion coated with granular Sn plating. Since the steel plate surface is directly covered with metallic chromium or a chromium oxide layer, the characteristics such as paint adhesion, coating corrosion resistance, and appearance characteristics are all metallic chromium,
Since it is determined by the chromium oxide plating layer, the surface lubricity can be improved without impairing the other properties of the current thin chromium plating steel sheet, and as a result, wear of the can making machine jig at the time of can making, TFS I was able to greatly improve the scratchability of itself. The qualitative conjecture was mentioned above as the reason why the granular Sn plating contributes to the surface lubricity.
The change of the surface condition when the steel ball rubs the surface of the
The results of the n-plated thin chromium-plated steel sheet are shown in the scanning electron micrograph and the Sn distribution of the same portion in FIG. By providing the granular Sn plating under the chrome plating layer, the scratched portion due to the steel ball collapses the Sn protrusion,
n is uniformly attached to the surface of the steel sheet. Therefore, it can be inferred that the protrusions of the granular Sn largely contribute to the improvement of the surface lubricity.

Although it has been described above that the base granular Sn plating is effective for improving the surface lubricity of the thin chromium plated steel sheet, the limited scope of the present invention will be described below.

First, the granular S applied to the lower layer of thin chromium plating
The grain size of the n-plating is 0.5μ or more.
If it is less than 0.5 μ, the effect of improving the lubricity is small and the practicability cannot be ensured. Therefore, the protrusion is not sufficiently large and the protrusion is larger than the steel plate roughness (usually, _Ra is 0.15 to 0.40 μ). It is considered that the lubrication effect by Sn does not appear because the function as a part cannot be fully fulfilled. Also, 3.0μ
The reason for the following is that Sn grains exceeding this size have poor adhesion to the steel sheet, are difficult to manufacture, and some are also dropped during can manufacturing. Therefore, the particle size of the granular Sn is
It was set to 0.5 to 3.0 μ.

Next, the plating amount of granular Sn is 30 to 300.
The reason for limiting to mg / m ^2, in 30 mg / m ² or less,
This is because the effect of improving the lubricity was small and it was poor in practicality. The upper limit was set to 300 mg / m ² or less. When the upper limit is exceeded, the space factor on the surface of the Sn-plated steel sheet is 20%.
This is because the adverse effect of Sn plating appears.
That is, when the space factor of the Sn plating layer exceeds 20%,
This is because the excellent coating adhesion and coating corrosion resistance that TFS originally has are slightly deteriorated due to the influence of the Sn plating layer. or,
The tint also becomes whitish under the influence of Sn plating, and the difference from the current TFS appearance becomes large, which is also the reason why the Sn plating amount was set to 300 mg / m ² . Next, the amount of metal chromium plating and the reason for limiting the chromium oxide layer will be described. These are all limited to the amount of chromium metal plating in TFS which is currently most used and the amount of chromium oxide layer, but preferably the amount of metal chromium plating is 50 to 120 mg / m ² , and The amount of chromium is 10 to 20 mg / m ² . The lower limit of the amount of metallic chrome plating is the amount of metallic chrome necessary for ensuring the corrosion resistance after coating, and the upper limit is determined for the purpose of ensuring the corrosion resistance after coating after processing and the economic efficiency of productivity. If the amount of metallic chromium increases, cracks may occur in the chromium plating layer during processing, and the corrosion resistance after coating deteriorates. In addition, in order to deposit a large amount of metallic chromium by electroplating, a large amount of electricity is required, which reduces productivity. Therefore, it leads to an increase in manufacturing cost, which is not preferable. For this reason, the amount of metallic chromium is limited.

With respect to the amount of chromium oxide, the lower limit is the amount necessary to secure the adhesiveness of the paint, and the upper limit is determined from the appearance of the chromium oxide film due to coloring. When the chromium oxide layer becomes thick, it exhibits a unique interference color, and when it exceeds 30 mg / m ² , it becomes brown, which is not preferable as a can material.

As a method for producing TFS, first, a so-called two-step method of forming a metal chromium plating layer and then forming a chromium oxide layer, and a metal chromium plating layer and a chromium oxide layer are electrolyzed in one solution. There are two kinds of so-called one-step method of treating and precipitating at the same time.
There is no particular limitation on the manufacturing method of. In both the one-step method and the two-step method, the surface lubricity was improved by providing granular Sn plating on the chrome plating lower layer.

Next, the contents of the present invention will be specifically described with reference to Examples and Comparative Examples.

[0016]

[Examples] Cold rolling, continuous annealing, and conditioning were performed by ordinary methods using continuous plating equipment having degreasing, pickling, tin plating, and chromium plating treatment steps, and a water washing step between each step. A low-carbon cold-rolled steel sheet having a thickness of 0.23 mm, which was quality-rolled, was subjected to normal degreasing (cathodic electrolysis treatment of NaOH 50 g / l, 60 ° C., current density 10 A / dm ² for 0.5 seconds), and normal pickling ( H ₂ SO ₄ 50 g / l, room temperature, current density 10
Example 1 to 6 and Comparative Examples 1 to 7 shown in Table 1 after performing a cathodic electrolysis treatment for 0.5 seconds at A / dm ² ) and then performing tin plating and chromium plating under the following treatment conditions. The following test items were investigated, and the current TFS as a conventional material was evaluated. The results are summarized in Table 1.

1. Tin plating conditions (1) Bath conditions Sn ²⁺ 20 g / l Free acid concentration (sulfuric acid conversion) 30 g / l [phenol sulfonic acid was used as acid] Ethoxy α-naphthol 0.2 g / l Bath temperature 40 ° C. (2 ) Electrolysis conditions Current density 10 to 20 A / dm < ² > Energization amount Energized according to the Sn plating amount.

2. Chromium plating conditions (1) Bath conditions CrO ₃ 100 g / l H ₂ SO ₄ 1.2 g / l Bath temperature 50 ° C. (2) Electrolysis conditions Current density 50 A / dm ² Electricity Electricity was appropriately applied according to the chromium plating amount.

3. Evaluation (1) Paint Adhesion Epoxyphenol-based paint (Kansai Paint Co., Ltd. SJ-6256) was applied and baked on the test material (coating amount 50 mg /
dm ² ) and then 110 ° C. × 60 in 3.0% NaCl solution
After carrying out the retort treatment for a minute, flaws were put on the cross board with a knife and a tape peeling test was carried out. (10 (good) ← → 1 (bad)).

(2) Coating corrosion resistance Epoxyphenol-based paint (Kansai Paint Co., Ltd. SJ-6256) was applied to the test material by baking (coating amount 50 mg /
dm ² ) and then cross-cutting the coating with a knife,
Evaluation was performed by immersing in 1.5% NaCl, 1.5% citric acid solution (50 ° C.) for 4 days, and then performing a tape peeling test on the cross cut part. (5 (good) ← → 1 (bad)).

(3) Lubricity Haydon type friction measuring device (Heidon, Shinto Scientific Co., Ltd.)
-14) was used to measure the coefficient of friction. The steel balls used were chromium plated and had a diameter of 10 mm. The weight of the steel balls used was 100 g.

(4) Evaluation of tin-plated grains The test material was observed with a scanning electron microscope at a magnification of 5,000 to 10,
Observed at 000 times, the particle size of typical tin particles and the tin coverage were measured.

(5) Tin deposition amount It was measured by a fluorescent X-ray analysis method.

(6) Measurement of L value The L value was measured as an evaluation of the appearance color tone of TFS. The higher the L value, the more vivid the painting / printing finish is. On the other hand, it is not preferable that the difference from the appearance of the current TFS occurs. For the measurement of the L value, an automatic color difference meter (model AU-CH-1) manufactured by Tokyo Science Co., Ltd. was used.

[0025]

[Table 1]

From Table 1, it can be presumed that the chrome-plated layer without the granular Sn plating has a large coefficient of dynamic frictional resistance, and the jig of the can-making machine is greatly worn during the can-making process. On the other hand, an appropriate granular Sn is used as the base of the chrome plating layer.
The plated one has a reduced dynamic friction resistance. Further, the other properties of TFS are the same as those of the current TFS which is not subjected to the granular underlayer Sn plating, and it was confirmed that the coating corrosion resistance was improved. The reason why the coating corrosion resistance is improved when granular Sn plating is applied to the chrome plating base has not been fully analyzed, but it is thought that Sn exerts its anticorrosion function when the tip of corrosion encounters granular Sn. Be done.

Further, a suitable granular Sn plating is performed by using L of a steel plate.
It can be seen that the value is improved. It is said that the improvement of the L value is very important as a finished appearance after printing, and it is said that the higher the L value is, the more vivid the coating and the printing finish are. It should be added that the fact that the L value can be improved without impairing the metallic appearance of TFS is one of the merits of the underlying granular Sn plating.

[0028]

As described above, according to the method of the present invention, the original excellent properties of the tin-free steel plate are not impaired,
It is possible to improve the fact that the friction coefficient, which has been a drawback of the current TFS, is large, and it is effective for preventing jig wear during can manufacturing and rubbing flaws of TFS.

[Brief description of drawings]

1A and 1B are diagrams showing a result of observation of a metallographic structure surface state by a scanning electron microscope after a friction test of a granular Sn underlayer TFS and a Sn distribution state at the same place.

Claims (1)

[Claims] 1. A steel sheet having 0.5 to 3.
50μm to 300m per surface of 0μ diameter granular Sn plating
After applying g / m ² , metal chromium 3 is continuously formed on the upper layer.
0 to 150 mg / m ² , chromium oxide 3 to 30 mg / m ²
A thin chromium-plated steel sheet excellent in surface lubricity, which is obtained by electroplating (in terms of metal chromium amount).