JP3271236B2 - Tin-plated steel sheet excellent in tin peel resistance and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tin-plated steel sheet for welding cans suitable for filling and storing various foods and beverages, and a method for producing the same.

[0002]

2. Description of the Related Art In the field of beverage cans and food cans, welded cans occupy a large proportion, and it can be said that reducing material costs is an important industrial issue. Tin cans, LTS (thin tinplate), TFS (tin-free steel), and the like are common as can materials used in the field of beverage cans and food cans, and recently, many of these are used after being coated with an organic coating. Has become. When considered as a base steel sheet with organic coating,
TFS has the advantages of being inexpensive and having excellent paint and film adhesion, but has the disadvantage of being poor in weldability. On the other hand, tinplate and LTS are excellent in weldability, but inferior to TFS in terms of cost and adhesion of paint and film.

Conventionally, various attempts have been made to compensate for such disadvantages. One of them is a steel sheet in which a tin layer is non-uniformly (partially) present on a steel sheet surface, and this tin-plated steel sheet is known as a steel sheet excellent in both paint and film adhesion and weldability. Japanese Patent Application Laid-Open No. 57-23091 and Japanese Patent Application Laid-Open No.
Japanese Patent Application Laid-Open No. 2005022 discloses that a steel sheet in which tin is dispersed in an island shape by performing reflow after tin plating is used as a base steel sheet of an organic coating, and the material cost can be reduced by reducing the amount of tin plating. This is a practical technique in that the paint adhesion can be improved while ensuring weldability.

On the other hand, JP-A-2-298277, JP-A-2-310378 and JP-B-6-33506 disclose a method for producing a granular tin-plated steel sheet in which tin is scattered in a granular manner on a steel sheet surface without going through a reflow process. Is disclosed. This granular tin-plated steel sheet is excellent in color tone (white), corrosion resistance, weldability, etc., and has higher paint adhesion and film adhesion than tin-plated steel sheet in which tin is dispersed in an island shape through the above-mentioned reflow process. Can be said to be an epoch-making material as a material for welding cans, because it is extremely excellent, and can be manufactured at low cost because the required amount of tin is small and a reflow process is not required.

[0005]

However, the above-mentioned granular tin-plated steel sheet has a serious problem that tin particles on the surface of the steel sheet are easily peeled off, and the peeled tin adheres to the roll in the can making process and the quality is deteriorated after the can is made. This problem prevents widespread use in the market as a material for cans. To cope with such a problem, Japanese Patent Publication No. 8-996 discloses a method of tin-plating using a ferrostan bath containing a small amount of ethoxynaphtholsulfonic acid (ENSA) to flatten the shape of granular tin and to prevent tin peeling. It has been proposed that the shape of granular tin changes greatly in response to subtle changes in the ENSA concentration in the bath. Have difficulty. For this reason, a sufficient effect of improving tin peeling resistance cannot be expected.

Accordingly, an object of the present invention is to provide a tin-plated steel sheet produced by partially depositing tin on a steel sheet surface by tin plating to improve paint adhesion, film adhesion, corrosion resistance, weldability, and the like. An object of the present invention is to provide a tin-plated steel sheet which is not only excellent but also has excellent tin peeling resistance and a method for producing the same.

[0007]

A material having the highest quality as a material for welding cans can be expected if the disadvantages can be compensated for while maintaining the advantages of the granular tin-plated steel sheet as described above. The present inventor has repeatedly studied the form of partial tin plating formed on the steel sheet surface under such intention, and as a result, while appropriately leaving the exposed part of the ground iron on the steel sheet surface,
By adopting a plating film structure in which plate-shaped tin lumps of a specific form are interspersed, peeling of tin is less likely to occur compared to conventional granular tin plating, and paint adhesion, film adhesion, corrosion resistance, weldability, etc. It has been found that excellent characteristics can be obtained also in terms of. The present invention has been made based on such knowledge, and the characteristic configuration thereof is as follows.

(1) A tin-plated steel sheet manufactured by partially depositing tin on a steel sheet surface by tin plating, wherein at least one side of the steel sheet has a plate-like shape formed by tin plating. Tin lumps are dispersed and scattered, the total tin plating amount is 100 to 1500 mg / m ² ,
% Of the plate-shaped tin mass has an average height H from the steel plate surface of the tin mass.
And the diameter D of the circle when the area of the tin mass base is converted to a circle
Characterized by satisfying H / D ≦ 0.3, and the area ratio of the exposed portion of the ground iron not covered by the plate-shaped tin lump is 30% or more, characterized by excellent tin peeling resistance. Plated steel sheet. (2) In the tin-plated steel sheet according to (1) above, a metal having a chromium deposition amount of 5 to 50 mg / m ² covering both the plate-shaped tin lump and the exposed part of the ground iron on the steel plate surface where the plate-shaped tin lump exists. Chromium layer and the amount of metal chromium equivalent of the upper layer is 5 to 30 mg
/ M ² hydrated chromium oxide layer, characterized by having excellent tin peeling resistance.

(3) In a tin plating bath for obtaining the tin-plated steel sheet of (1), divalent tin ions are contained in an amount of 15 to 60 g /
l, phenolsulfonic acid in an amount of 5 to 40 g /
(1) A tin plating bath containing 0.5 to 30 g / l of polyethylene glycol having a molecular weight of 1,000 to 70,000 as an additive. (4) In the method for producing a tin-plated steel sheet according to the above (1), after the surface of the steel sheet is degreased and pickled, 15 to 6 divalent tin ions are added.
0 g / l, phenolsulfonic acid is 5 to 40 in terms of sulfuric acid.
a tin plating bath containing 0.5 to 30 g / l of a polyethylene glycol having a molecular weight of 1,000 to 70,000 as an additive at a current density of 1 ASD to 30 ASD. For producing tin-plated steel sheets with excellent resistance.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention and the reasons for limitation will be described below. The tin-plated steel sheet of the present invention is a tin-plated steel sheet manufactured by partially depositing tin on a steel sheet surface by tin plating similarly to a conventional granular tin-plated steel sheet. Such a partially tinned steel sheet has a much better paint than a tinned steel sheet manufactured by dispersing tin in a discontinuous or island shape by a reflow process after applying tin plating on the entire surface of the steel sheet. Shows adhesion and film adhesion.

As described above, the reason that the granular tin plating is easily separated from the steel sheet surface largely depends on the shape of the deposited tin. That is, when a physical action such as friction with a roll is applied to the surface of the plated steel sheet, granular tin having a small contact area with the steel sheet and a large height in a direction perpendicular to the steel sheet surface is likely to peel. On the other hand, the adhesion of a granular tin-plated steel plate to a film or paint of a steel plate for a welding can, which is chromium-plated, is more severe when the surface is more uneven and the exposed area of the ground iron is larger (that is, the exposed area of the ground iron). The larger the area of the chromium-plated portion on the portion, the greater the area), which is the reason why the granular tin-plated steel sheet has excellent film adhesion and paint adhesion.

Considering these facts, the surface of the steel sheet
By forming tin plating in such a form that tin ingots with a large contact area with the steel sheet and a low average height are scattered at an appropriate ratio, tin-peeling resistance can be maintained while maintaining the advantages of conventional granular tin-plated steel sheets. Can be improved. The present invention is based on such a premise that tin-plated tin-like lump is dispersed and scattered on at least one side of the steel plate, and the area ratio is 7%.
For a plate-shaped tin lump of 0% or more, the relationship between the average height H of the tin lump from the steel plate surface and the diameter D of the circle when the area of the tin lump base is converted into a circle is H / D ≦ 0. 3 are satisfied, the total tin plating amount is 100 to 1500 mg / m ² , and the area ratio of the exposed part of the ground iron that is not covered with the plate-shaped tin lump is 30% or more. .

FIGS. 1 and 2 schematically show the form of a plate-like tin mass formed on a steel sheet surface in the tin-plated steel sheet of the present invention, and the conventional granular tin-plated steel sheet as described above. In contrast, the present invention has a form in which granular tin is dispersed and scattered on the surface of a steel sheet, whereas the present invention has a form in which plate-shaped tin lumps are dispersed and scattered. Regarding the existence form of the plate-shaped tin lump, the relationship between the average height H of the tin lump from the steel plate surface and the diameter D of the circle when the area of the tin lump base is converted into a circle is H / D ≦ 0. 70% in terms of area ratio with respect to the steel plate surface
If not present, the tin block has poor peeling resistance. FIG. 3 shows the average height H / diameter D of the plate-shaped tin lump having an area ratio of 70% or more.
And the tin peeling resistance (the method of measuring the amount of tin peeling is the same as that described in Examples described later).
At 0.3, the tin peeling resistance is poor. In addition,
The average height of the tin mass can be calculated, for example, by performing a cross-sectional microscopy with an SEM to obtain an SEM image of about 10,000 times and processing the image.

If the area ratio of the portion where the plate-shaped tin lump does not exist on the steel plate surface, that is, the exposed portion of the base iron is less than 30%,
Excellent paint adhesion and film adhesion specific to this type of partially tinned steel sheet cannot be obtained. Total tin plating amount is 100 ~
It is 1500 mg / m ² . 100mg total tin plating
/ M ² , sufficient weldability cannot be obtained.
Even if it exceeds 0 mg / m ² , the effect of improving the weldability corresponding to the amount of tin cannot be obtained, so that the economic efficiency is rather deteriorated.

Usually, on the surface of the steel sheet on which the above-mentioned plate-like tin mass is formed, a coating comprising a chromium metal layer and a hydrated chromium oxide layer thereover is formed. The chromium coating weight of the metal chromium layer is 5 to 50 mg / m ^2, the adhesion amount of metal chromium conversion hydrated chromium oxide layer is set to 5 to 30 mg / m ^2. If the amount of chromium adhered to the metal chromium layer is less than 5 mg / m ² , sufficient paint adhesion and film adhesion cannot be obtained, while 50 m / m ²
If it exceeds g / m ² , the weldability will deteriorate. On the other hand, if the chromium oxide hydrated layer has an adhesion amount of less than 5 mg / m ^{2 in} terms of metal chromium, sufficient paint adhesion and film adhesion cannot be obtained,
On the other hand, if it exceeds 30 mg / m ² , the weldability will deteriorate.

Next, a preferred configuration example of a tin plating bath and a production method for obtaining the tin plated steel sheet of the present invention will be described. The tin plating bath for obtaining the tin-plated steel sheet of the present invention has a divalent tin ion of 15 to 60 g / l, a phenolsulfonic acid of 5 to 40 g / l in terms of sulfuric acid, and a molecular weight (number average molecular weight) as an additive. It is preferable to use a tin plating bath containing 0.5 to 30 g / l of polyethylene glycol of 1000 to 70000. If the concentration of divalent tin ions in the tin plating bath is less than 15 g / l, the electrolysis efficiency is remarkably inferior (electrolysis efficiency becomes 50% or less), and the tin plating partially deposits on the steel sheet surface. And it is difficult to secure the area ratio of the exposed part of the base iron specified by the present invention. On the other hand, when the concentration of divalent tin ions exceeds 60 g / l, the generation of sludge becomes remarkable, which is not preferable.

On the other hand, if the concentration of phenolsulfonic acid in the tin plating bath is less than 5 g / l in terms of sulfuric acid, the tin which has been electrodeposited becomes dendrite, so that a tin lump having the form specified by the present invention cannot be obtained. Tin peel resistance is inferior. On the other hand, the concentration of phenolsulfonic acid is 40 g /
If it exceeds 1, the amount of iron eluted from the steel sheet increases, and the plating bath deteriorates significantly. A major feature of the present invention is that polyethylene glycol is added to a tin plating bath, whereby the form of a tin lump defined by the present invention can be stably obtained. When the concentration of the polyethylene glycol in the tin plating bath is less than 0.5 g / l, the effect of adding the polyethylene glycol cannot be sufficiently obtained, and the form of the tin lump defined by the present invention cannot be stably obtained. On the other hand, even if polyethylene glycol is added in an amount exceeding 30 g / l, an effect commensurate with the added amount cannot be obtained, resulting in a loss of economy.

Further, polyethylene glycol having a molecular weight (number average molecular weight) of 1,000 to 70,000 is used. If the molecular weight of the polyethylene glycol is less than 1,000, the tin deposited on the steel sheet surface tends to be granular, and the form of the tin lump defined by the present invention cannot be stably obtained. On the other hand, when the molecular weight of polyethylene glycol exceeds 70,000, the area ratio of the exposed part of the base iron decreases, and the area ratio of the exposed part of the base iron defined by the present invention cannot be secured. The tin-plated steel sheet of the present invention is obtained by degreasing and pickling a base steel sheet (usually a cold-rolled steel sheet), and then applying 1 ASD to
It is manufactured by performing electrotin plating at a current density of 30 ASD. If the current density in the tin plating is less than 1 ASD, the plating time required to obtain a desired amount of tin plating becomes long, and the productivity is poor. On the other hand, when the current density is 30 AS
When D exceeds, the electrodeposited tin becomes dendritic,
The quality such as tin peeling resistance is inferior. Also, it tends to be difficult to secure the area ratio of the exposed part of the base steel.

[0019]

EXAMPLE A low-carbon cold-rolled steel sheet having a thickness of 0.22 mm, which has been cold-rolled, continuously annealed and temper-rolled by a conventional method, is degreased and pickled under normal conditions, and then the steel sheet is subjected to a cathode in a phenolsulfonic acid bath. Was applied to obtain a tin-plated steel sheet. This tin-plated steel sheet is subjected to chromium plating to form a metallic chromium layer having a metallic chromium adhesion amount of 15 mg / m ² and an upper metal chromium equivalent adhesion amount of 10 mg / m ^2.
A steel sheet having a hydrated chromium oxide layer of mg / m ² was produced. The form and coverage of tin plating of each of these steel sheets were measured, and the weldability (contact resistance), tin peel resistance, paint and film adhesion, and corrosion resistance were evaluated.

The area ratio of the tin lump plated on the steel sheet surface and the tin lump shape were measured as follows. That is, taking a photograph of each test steel sheet by SEM (× 1000)
Was performed, and the tin mass portion of the SEM image was transferred to a transparent sheet with a pen. The area of each tin mass was measured by pasting this on a piece of grid paper and counting 1 mm square with a colony counter, and for each tin mass, the diameter D of the circle when the area of the base was converted to a circle was calculated. did. Next, the test steel sheet is embedded in a resin, and the section height is determined by performing a cross-sectional microscopic examination with an SEM to obtain an average height H of the tin lump. Was calculated, and the area ratio of this to the steel sheet surface was calculated. Further, the tin coverage was determined from the total area of the tin mass. The tin plating conditions, the chromium plating conditions, and the evaluation methods for each characteristic are shown below.

(1) Tin plating (a) Plating bath conditions Divalent tin ion concentration: 10 to 60 g / l Phenolsulfonic acid concentration: 15 to 40 g / l (converted to sulfuric acid) Polyethylene glycol concentration: 0.3 to 30 g / l (Number average molecular weight: 1000 to 70000) (b) Electrolysis conditions (cathode electrolysis treatment conditions) Current density: 1 to 45 A / dm ² Electrolysis time: 0.01 to 9 seconds (2) Chromium plating (a) Plating bath conditions Oxidation Chromium concentration: 15 g / l Sulfuric acid concentration: 0.2 g / l Bath temperature: 45 ° C. (b) Electrolysis conditions Current density: 40 A / dm ² Electrolysis time: 0.2 seconds

(3) Evaluation of each characteristic (a) Weldability (contact resistance) After subjecting the test material to a heat treatment at 210 ° C for 30 minutes,
The sample was cut into a square of 50 mm, and two of the samples were overlapped and sandwiched between electrodes having an electrode diameter of 4.5 mm.
Pressure was applied at 0 kgf, and a current of 1 A was passed between the electrodes to measure the contact resistance. Based on the measured contact resistance value, the weldability is evaluated as follows. 30 μΩ or less: Passed 30 μΩ or more: Failed

(B) Tin Peeling Resistance After the test material was stuck to the bottom of the box with a bottom of 130 mm × 180 mm, alumina balls of 10 mmφ were placed in the box.
g, 1 reciprocation / 1 in the longitudinal direction of the box with a swing width of 600 mm
Shaking for 100 seconds at a speed of seconds. The amount of tin peeled off from the test material due to friction with the alumina ball was determined from the difference between the tin amounts measured by the fluorescent X-ray method before and after the test. Based on the measured tin peeling amount, the tin peeling resistance is evaluated as follows. 0.03 g / m ² or less: pass 0.03 g / m ^{2 or} more: reject

(C) Film adhesion (laminated plate deep drawing test) After laminating a polyethylene terephthalate film on a test material, punching into 58 mmφ, deep drawing with a 30 mmφ die, the critical deep drawing height at which the film does not peel off I asked. Based on the critical deep drawing height, the film adhesion is evaluated as follows. 18mm or more: pass Less than 18mm: reject

(D) Paint adhesion (T-peel test) After coating and baking an epoxyphenol-based paint on the test material,
The test piece was sheared into a 5 mm x 100 mm test piece. Two of these test pieces were stacked, and a 5 mm × 50 mm nylon film was sandwiched between the test pieces and heated and melt-pressed. Next, the T-shaped test piece was made by opening at 90 ° with the part without the film facing outward. The end of the open portion of the test piece was grasped, and the tensile strength when the test piece was peeled was measured. Based on the tensile strength, paint adhesion is evaluated as follows. 4.0 kg / 5 mm or more: pass 4.0 kg / 5 mm or less: reject

(E) Corrosion resistance test (FFC test) 50 m of epoxy phenolic paint was applied to the front surface of the test material.
g / m ² (baking conditions: 210 ° C x 1)
0 minutes → 190 ° C × 10 minutes), and after the same paint is applied and baked on the back side (baking conditions: 190 ° C × 10 minutes), a cross-cut is made on the coating film on the front side with a sharp cutter,
Then, a test piece subjected to an Erichsen 5 mm overhang process was used. The test piece was sprayed with salt water for 1 hour, then the salt water was wiped off with a filter paper, left in an atmosphere of a relative humidity of 85% and a temperature of 45 ° C. for 10 days, and the degree of rusting of the cut edge portion and the processed portion was visually observed. The following was evaluated. ：: No rusting or growth from end face and cut portion ×: Yarn rust growing from end face and cut portion

Table 1 shows the conditions of tin plating and the film composition of each test example.
To Table 4 and the results of the performance evaluation are shown in Tables 5 to 8. According to this, all of the present invention examples are weldability, paint adhesion,
It can be seen that the film adhesion, corrosion resistance, and tin peeling resistance are all excellent. On the other hand, in Comparative Example 1, since the concentration of divalent tin ions in the plating bath was too low, the form in which tin plating was partially deposited on the steel sheet surface was not obtained.
As a flat tin layer, the area ratio of the exposed part of the base iron is also 0%. For this reason, corrosion resistance, paint adhesion, and film adhesion are inferior. In Comparative Example 2, the tin lump (H /
This is a comparative example in which the abundance ratio of tin lump satisfying D ≦ 0.3 is too small, and the tin peeling resistance is inferior. In Comparative Example 3, the tin plating had a dendrite shape because the current density at the time of manufacture was too high, and thus the tin peeling resistance was poor.
Comparative Example 4 is inferior in weldability and corrosion resistance because the amount of tin plating is too small.

In Comparative Example 5, the current density at the time of production was too high, and the area ratio of the exposed part of the base iron was too low, so that the paint adhesion, film adhesion, and corrosion resistance were poor. Further, since tin becomes dendritic, tin peeling resistance is poor. Comparative Example 6 was obtained by adding ENSA to a tin plating bath and performing flat tin plating, and thus the paint adhesion and the film adhesion were inferior. Comparative Example 7 is inferior in paint adhesion, film adhesion, and corrosion resistance because the amount of chromium adhered to the metal chromium layer is too small. In Comparative Example 8, the adhesion of the hydrated chromium oxide layer was too small, so that the paint adhesion and the film adhesion were inferior. In Comparative Example 9, since the amount of polyethylene glycol added to the tin plating bath was too small, the area ratio of the exposed part of the base iron was low, and thus the paint adhesion and the film adhesion were poor, and the corrosion resistance was also poor.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

[Table 6]

[0035]

[Table 7]

[0036]

[Table 8]

[0037]

As described above, the tin-plated steel sheet of the present invention not only has excellent paint adhesion, film adhesion, corrosion resistance, weldability, etc., but also has excellent tin peeling resistance, and is suitable for welding cans. Is extremely useful as a material for Further, according to the manufacturing method of the present invention, such a tin-plated steel sheet can be stably manufactured at low cost and efficiently.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a form of a plate-shaped tin lump formed on a steel sheet surface of the present invention.

FIG. 2 is a cross-sectional view schematically showing a form of a plate-shaped tin lump formed on a steel sheet surface according to the present invention.

FIG. 3 shows an average height H of a plate-shaped tin lump having an area ratio of 70% or more in a tin-plated steel sheet in which plate-shaped tin lump is scattered on a steel plate surface.
/ Graph showing the relationship between diameter D and tin peel resistance

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Ichiro Iwai 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) References JP-A-5-320979 (JP, A) JP-A-7 JP-A-243093 (JP, A) JP-A-62-124296 (JP, A) JP-A-8-156184 (JP, A) JP-A-8-158068 (JP, A) JP-A-8-158092 (JP, A) JP-A-8-269770 (JP, A) JP-A-8-176882 (JP, A) JP-A-3-36288 (JP, A) JP-A-2-298277 (JP, A) JP-A-2- 310378 (JP, A) JP-A-2-282498 (JP, A) JP-A-4-247897 (JP, A) JP-A-10-121287 (JP, A) Patent 3252725 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) C25D 3/30 C23C 28/00 C25D 5/26

Claims (4)

(57) [Claims] 1. A tin-plated steel sheet produced by partially depositing tin on a steel sheet surface by tin plating, wherein at least one side of the steel sheet has a plate-like tin formed by tin plating. Lumps are dispersed and scattered, and the total tin plating amount is 1
00 to 1500 mg / m ² , 70% in area ratio conversion
In the above plate-shaped tin lump, the relationship between the average height H of the tin lump from the steel plate surface and the diameter D of the circle when the area of the tin lump base is converted into a circle is H / D ≦ 0.3. A tin-plated steel sheet having excellent tin-peeling resistance, characterized in that the area ratio of the exposed portion of the base iron which is not covered by the plate-shaped tin lump is 30% or more. 2. The chromium adhesion amount covering both the plate-shaped tin lump and the exposed part of the base iron on the steel sheet surface where the plate-shaped tin lump is present is 5 to 5.
And 0 mg / m ² of metallic chromium layer,耐錫peeling of claim 1 in which the deposition amount of chromium metal in terms of the upper layer is characterized by having a chromium hydrate oxide layer of 5 to 30 mg / m ² Tin-plated steel sheet with excellent properties. 3. A tin plating bath for obtaining the tin-plated steel sheet according to claim 1, wherein 15 to 60 g of divalent tin ions are added.
/ L, phenolsulfonic acid is 5 to 40 g /
(1) A tin plating bath containing 0.5 to 30 g / l of polyethylene glycol having a molecular weight of 1,000 to 70,000 as an additive. 4. The method for producing a tin-plated steel sheet according to claim 1, wherein after the surface of the steel sheet is degreased and pickled, 15 to 60 g / l of divalent tin ions and 5 to 40 g of phenolsulfonic acid in terms of sulfuric acid. / L, molecular weight of 100 as an additive
0.5 to 3 of polyethylene glycol of 0 to 70000
In a tin plating bath containing 0 g / l, 1 ASD to 30
A method for producing a tin-plated steel sheet having excellent tin-peeling resistance, wherein electro-tin plating is performed at a current density of ASD.