JPH05177764A - Laminated steel plate for welded can and production thereof - Google Patents

Abstract

PURPOSE:To obtain a precoated steel plate bonding a can body at the time of the production of a can by seam welding and adapted to a welded can. CONSTITUTION:A resin film is laminated on a plated steel plate but a varnish avoiding part 1 with a width of 5-20mm is provided between resin laminated strips 2. A plating layer is formed by tin plating or two-layered plating of nickel and tin and a chromate layer is provided on the plating layer. The center line average roughness Ra of the surface of the plating layer is set to 0.02-0.35mum. At the time of the lamination of a resin, heating exceeding 230 deg.C is avoided to set the elongation characteristics of a product to 18% or more. The varnish avoiding part 1 omits a process for removing a resin deteriorating quality at the time of welding and the width thereof exerts no adverse effect of heat at the time of welding on the resin. The plating layer imparts sufficient corrosion resistance to the entire surface of the plating layer and the surface roughness thereof imparts sufficient close adhesiveness to the resin layer. In addition, the product has satisfactory elongation characteristics and sufficiently withstands flange processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a can steel plate used for welding cans such as food cans. The present invention relates to a steel plate for a welding can, which has easy workability, sufficient retort resistance, and the like.

[0002]

2. Description of the Related Art Can manufacturing methods include a solder can manufacturing method, a DI (drawing and ironing) can manufacturing method, an adhesive can manufacturing method, and a welding can manufacturing method.
The welded can manufacturing method has advantages such as a simpler device than other can manufacturing methods, low equipment cost, easy and reliable work, and high strength of the welded portion that can withstand advanced processing. This is a can-making method that has rapidly spread.

Initially, tin-plated steel sheet was used as a material for cans, but in recent years, it has been used in combination with a coating material or other metal or in combination in order to reduce the amount of tin, which is a resource problem. Nickel or chromium is used as the other metal, and in addition to single layer plating of these, double layer plating with tin or alloy plating is used. However, the solder can manufacturing method has a limit in reducing the amount of tin, and in this respect as well, the growth of the welding can manufacturing method capable of joining even the plating layers of other metals is expected.

On the other hand, the development of the inner coating of the can, the protective coating of the outer surface, the printing, etc. has been remarkable, and the resin film has been widely used. However, when these are applied, the plated steel sheet is cut into a sheet having a predetermined size, and each of these is coated or printed. However, in order to secure a coating film thickness on the inner surface in particular, the coating is often repeated. For this reason, physical distribution costs are required and measures for environmental pollution due to painting are required, which has been one of the issues to be rationalized in the can manufacturing process.

To solve this problem, a can material manufacturer has proposed a method of laminating a resin on the entire surface of a plated steel sheet in advance. For example, JP-A-58-3
Japanese Patent No. 9447 discloses a method in which a tin-plated steel sheet is preheated to a temperature equal to or lower than the melting point of tin to temporarily bond a resin film, and further heated to a temperature equal to or higher than the melting point of tin (240 ° C to 400 ° C) for main bonding. There is.

[0006]

However, the laminated steel sheet thus produced is suitable for punching cans and DI cans that do not require welding, and has the following problems when used for welding cans. ..

In the welding can, as shown in FIG.
The sheet 11 is made by rolling the sheet 11 and slightly overlapping the edges 12 of the sheet 11 and joining the portions by wire seam welding. The wire seam welding is electric resistance welding using a copper wire as an electrode, and the portion to be welded is required to have conductivity. However, since the entire surface of the sheet cut out from the above laminated steel sheet to the size of the can body is covered with the resin film, the resin film at the edge portion 12 must be ground and removed. With this grinding, most of the surface treatment layer such as plating under the resin film is also scraped off. Although repair coating is applied to this portion after welding, a considerable decrease in corrosion resistance cannot be avoided. Another problem with grinding is that some of the grinding debris remains in the can as trash.
Further, when the plating that takes into consideration high-speed welding is scraped off, the weldability naturally deteriorates.

[0008] Another problem is that, during the main adhesion, the material is heated above the melting point of tin. This heating causes most of the tin to alloy with iron. The tin-iron alloy is hard and has a high melting point, and at the time of welding, it no longer has the effect of reducing the contact resistance of the welding surface and causing the welding current to flow evenly like tin. Further, a major problem is that the elongation of the material is lowered due to the above heating effect. A material with a large decrease in elongation will crack during flanging.

The present invention has been made in order to solve such a problem, and facilitates high-speed welding without needing to grind away the resin film at the time of welding, and has good workability such as neck-in processing and flange processing. And not only for processing,
An object of the present invention is to provide a laminated steel sheet for a welding can, which has a good resin film adhesion to a retort.

[0010]

[Means for Solving the Problems] Means for achieving this object are as follows.
And the method for producing this laminated steel sheet shown in I).

(I) having a plating layer that has been subjected to chemical conversion treatment
However, the center line average roughness Ra of the surface of these plating layers is 0.
Fewer plated steel sheets with a size of 02 μm or more and 0.35 μm or less
On at least one side, strip-shaped varnish avoidance part and resin laminated strip
Are alternately provided in parallel with the rolling direction of the steel plate,
The layer, the varnish avoidance part and the resin laminate band are respectively
(I), (ro), and (ha) with an elongation of 18% or more
Laminated steel sheet for welding cans, which has a plating layer or
Indicates that the chemical conversion coating has the following ranges (1), (2), and (3)
Is desirable. (Ii) Tin on a single-layer plating layer or after nickel plating
The two-layer plating layer (boiled) that is not coated with resin, and the width is 5 mm or more 20
The varnish avoidance part which is less than mm. () The main component of the resin is polyethylene terephthalate or
Resin laminating strip made of polyethylene naphthalate. (1) Adhesion amount of tin single layer plating layer is 0.9g / m²Above 2.
0 g / m²It is the following. (2) Adhesion amount of double-layer plating layer is nickel 15mg / m² that's all
100 mg / m² Below, tin 0.8g / m²2.0g /
m²It is the following. (3) Amount of metallic chromium in the chemical conversion coating on the plating layer
Is 5 mg / m² 50 mg / m or more ² Below, chromium oxide
5 mg / m in terms of chromium² 25 mg / m or more² It is the following.

(II) Surface center average roughness Ra is 0.40 μ
The amount of tin plating is 0.9g / m ² or more and 2.0g / m ² or less on the surface of a steel sheet of m or less, or the nickel plating is 15mg / m ² or more and 100mg / m ² or less on the surface of the steel sheet. After application, tin plating is applied in an amount of 0.8 g / m ² or more and 2.0 g / m ² or less to obtain a plating surface center average roughness of 0.02 μm or more and 0.35 or more.
It is a method for producing a laminated steel sheet for welding cans in which after adjusting the thickness to less than μm, chromate treatment is applied, and the resin film is continuously laminated on at least one side of the plated steel sheet in the running direction under the conditions listed in (i) below. Therefore, it is desirable that the resin film has the following range (4). (1) With the melting point of the resin film being T _m ° C, the plated steel sheet is held for 1 second or more and 60 seconds or less at a temperature T ₁ ° C shown in Formula ₁ and preheated, and then the resin film is laminated by roll pressure bonding, and then the number 2 The temperature T ₂ ° C shown in (1) is maintained for 1 second or more and 10 minutes or less to perform post-heating and then cooling. (Equation 1) 230 ≧ T ₁ ≧ T _m −20 (Equation 2) 230 ≧ T ₂ ≧ T _m −15 (4) The melting point of the resin film is 180 ° C. or higher and 240 ° C. or lower.

[0013]

[Function] Resin is not laminated on the varnish avoiding part,
A chemical conversion treatment is applied on the tin plating to improve the adhesion of the paint. FIG. 1 shows the surface of this laminated steel sheet. The strip-shaped varnish avoiding portion 1 and the resin laminate strip 2 are provided alternately in parallel with the rolling direction of the steel sheet. A cross section is shown in FIG. 3 is a resin film, 4 is a chemical conversion treatment layer, 5 is a plating layer, and 6 is a steel plate. The film of the varnish avoiding portion 1 is composed only of the chemical conversion treatment layer 4 and the plating layer 5, and is not covered with the resin 3. Therefore, even if the steel plate is preliminarily laminated with the resin 3 by using the varnish avoidance portion as a welding allowance,
There is no need to remove the resin film during welding during can manufacturing.

On the other hand, in the resin laminated band 2, the plating layer is subjected to a chemical conversion treatment as in the varnish avoiding portion 1, and the resin is laminated thereon. For this reason, it is not necessary to apply troublesome coating at the time of can making. The width of this resin laminate strip is determined by the diameter of the can and is, for example, about 161 mm for a 200 ml beverage can.

Since the varnish avoiding portion is welded on the front and back sides, it is required on both sides of the steel sheet, but the resin laminate band may be provided on at least one inner surface of the can. Of course, it may be provided on both sides, and in this case, the inner surface and the outer surface of the can are taken into consideration. For example, the surface corresponding to the inner surface may have the resin laminate band according to the present invention, and the surface corresponding to the outer surface may be a plated layer only, a white coat or a resin laminate layer, or the like, which is a treated surface according to demand.

As described above, since at least one surface is preliminarily laminated with resin, welding during can making, outer surface printing,
It must be one that will not be damaged or deteriorated even after undergoing processes such as processing, and that will maintain the corrosion resistance and the adhesion of the film even after filling the contents.

First, at the time of welding, the width of the varnish avoiding portion has an important meaning. The temperature of the weld exceeds 1000 ° C and the heat also propagates in the circumferential direction of the can. This effect should not degrade the properties of the resin layer. If the width of the varnish avoidance part is too narrow, the resin may melt or deteriorate. When the heat propagation region is examined, the welding speed, plate thickness, thermal conductivity, etc. are related, but the welding speed has a large effect. In order to avoid the influence of heat during welding, the width of the varnish avoidance part of 5 mm or more is required. On the other hand, the varnish avoidance part is repaired after welding. It is not necessary to have a width of the varnish avoiding portion exceeding 20 mm, and by setting the width to 20 mm or less, it is possible to avoid repair painting of an extra area after welding. It goes without saying that when the varnish avoiding portion is located at the edge of the steel sheet, the width of the above half is sufficient.

Next, there must be an adhesive force between the resin film and the plating layer to withstand neck-in processing and the like. In particular, the resin film tends to shrink when it is heated by the external printing, but at this time, if there is air or water trapped between the resin film and the plating layer, sufficient adhesion cannot be obtained. Here, if there is a portion where the adhesion is reduced, peeling occurs during neck-in processing or stretch flange processing. If the surface of the plating layer is uneven, the tip of the softened resin film does not enter the bottom of the recess during lamination, and air or moisture is likely to be entrapped.

The resin film itself should also avoid cracks or breaks during processing. Polyolefin resin and polyester resin are preferable, and especially polyethylene terephthalate and polyethylene naphthalate, which have corrosion resistance in addition to workability, are recommended. These biaxially stretched films are particularly excellent in barrier effect.

The center average roughness Ra of the plating layer surface is 0.3.
If it is 5 μm or less, the inclusion of air and moisture is small,
Sufficient adhesion is obtained. The smaller the central average roughness Ra, the less entrainment of air and moisture. But 0.0
On the plated surface of less than 2 μm, scratches are likely to occur during handling such as printing and printing.

In order to reduce the roughness of the plated surface, it is effective to reduce the roughness of the base steel sheet. In order to obtain a plated layer surface having a center average roughness Ra of 0.35 μm or less, a steel sheet having a surface center average roughness Ra of 0.40 μm or less may be used. After cleaning the surface of this steel sheet by degreasing, pickling, etc., at least one surface is plated with tin or nickel.

The purpose of plating is to impart a high degree of corrosion resistance. If the resin layer alone is used, the ion permeability of the resin is limited, and even if major corrosion does not occur, slight elution of iron causes , The taste and aroma of the contents of cans may change. Further, the presence of the plating layer maintains the anticorrosion effect even if a portion where the adhesiveness of the resin film is deteriorated by the retort treatment exposed to high temperature occurs.

In the case of a tin-plated single layer, if the amount of adhesion is 0.9 g / m ² or more, the resin film to be laminated or the varnish avoiding portion is combined with the coating film to prevent the change of taste and fragrance, as a matter of course. Retort resistance is also greatly improved. 2.0 g / m ²
If the amount of tin plating exceeds 1, the quality will be excessive. When nickel plating is performed, tin plating is further performed. This is to ensure the above-mentioned corrosion resistance and to obtain a varnish avoiding portion that facilitates high-speed welding.

Since tin is a soft metal and has a low melting point, a large contact area with the electrode can be easily obtained due to the softening of tin during seam welding. Therefore, the current required for welding flows uniformly at a relatively low voltage, and a reliable welded surface can be obtained. In seam welding, if an excessive current locally flows, a splash of a part of the metal is generated, which may stain the welded part or may result in insufficient joining of the insufficient current part. This phenomenon becomes more remarkable as the welding speed increases. When tin plating is applied on a thin nickel plating layer, the tin content is 1 g / m ²
The effect is recognized even below, and if it is 0.8 g / m ² or more, it can sufficiently withstand high-speed welding. If the amount exceeds 2.0 g / m ² , the quality becomes excessive, and if the amount is more than that, tin having a low melting point may be splashed and scattered.

Nickel, like tin, is a harmless metal and has excellent corrosion resistance. If a nickel layer is interposed between the tin layer and the steel sheet, the formation of tin-iron alloy is suppressed. For this reason,
When the plating layer is a two-layer plating of nickel and tin, by depositing nickel of 15 mg / m ² or more as the lower layer, it is possible to reduce the adhesion amount of the tin plating, and 0.8 g / m ²
If it is above, sufficient effects can be obtained in both corrosion resistance and weldability. Further, in the two-layer plating with tin, the nickel plating of the lower layer has an excessive quality when it is 100 mg / m ² or more.

Since all of these plating layers are satisfactory in corrosion resistance and weldability, they can be used both on the inner surface and the outer surface. That is, the plating layer may be tin-plated or nickel-tin double-layer plating on both surfaces, or either one surface may be tin-plated and the other surface may be nickel-tin-two-layer plating.
The reason why the chemical conversion treatment is performed after plating is to form a chromate film and thereby improve the adhesion between the plating layer and the resin film or coating film.

At the time of can making, the can body is not only bent in a round shape, but also subjected to repair coating after seam welding and then subjected to a drawing process called neck-in. That is, the upper part of the body of the can is narrowed down to form the neck portion. In addition, the opening is stretch flanged to attach the can lid. When subjected to such processing, a film or a coating film which is not well adhered is peeled off.

Resin film by chromate treatment film
The adhesion between the coating film and the coating layer increases. This treated film
Chromium hydroxide or oxide (hereinafter referred to as chromium oxide
And the metallic chrome, but the amount of metallic chrome is 5
mg / m² Chromium oxide is 5mg / m² The above film
When formed, stronger adhesion can be obtained. Metal chrome
50mg / m² More than, also chromium oxide
Is 25 mg / m² The effect on adhesion will be
I don't know. In addition, chromium oxide is 25 mg / m ² Beyond
If the thickness is too thick, the brown color will be strong
Yes.

After the chemical conversion treatment, a resin film having a predetermined width is continuously laminated, but it is preferable that the traveling direction of the steel sheet and the longitudinal direction of the strip are aligned with each other. If this direction is different, the laminating mechanism and operation become complicated, and the manufacturing equipment becomes large, so an increase in manufacturing cost cannot be avoided.

The laminating method includes an adhesive method using an adhesive and a roll pressure bonding method in which the adhesive is applied by heat and pressure without using an adhesive. In the adhesive method, it takes time to dry the adhesive solvent. Or, since the film may be deformed, the roll crimping method is practical. The most important thing to be aware of in laminating is not to raise the temperature of the steel sheet too much during handling.

In flanging, the material is required to have elongation. Flange cracking occurs when the elongation is insufficient.
In particular, in this manufacturing method, since the length of the resin laminate strip is parallel to the running direction of the steel sheet, that is, the rolling direction, the elongation in the width direction of the steel sheet is required. The elongation in the width direction of the steel sheet is more easily affected by temperature than the elongation in the longitudinal direction, and tends to deteriorate when heated at a temperature higher than the melting point of tin (about 232 ° C.). For the same reason, the preheating temperature of the plated steel sheet during lamination is also 23.
The temperature is 0 ° C or lower, and the post-heating temperature is also 230 ° C or lower.

In the thermocompression bonding method, if the preheating temperature is too low, a sufficient adhesive force cannot be obtained, but the lower limit depends on the melting point of the resin film to be laminated. The lower limit is higher for a resin film having a higher melting point. If the temperature is 20 ° C. lower than the melting point or more, stable adhesive force can be obtained. From this, the steel plate temperature is T ₁ ℃, the melting point of the resin film is T _m ℃,
The range shown in Formula 1 is appropriate. (Equation 1) 230 ≧ T ₁ ≧ T _m −20

When this temperature is maintained for a suitable time, water and the like on the surface of the plated steel sheet scatter, and the above-mentioned factors that impede the adhesion can be eliminated. A suitable time is 1 to 60 seconds. The preheated plated steel sheet and the resin film are overlapped with each other, and the rolls are pressure-bonded by passing between rolls whose rolling force is controlled.

Then, post-heating is performed to obtain a perfect adhesion. Post-heating does not require pressure, but it needs to be heated to a temperature very close to the melting point of the resin film or higher. Sufficient adhesion can be obtained by heating at a temperature of 15 ° C. lower than the melting point for at least 1 second, preferably 2 seconds or more. That is, the post-heating temperature is set to T ₂ ° C.
The range shown in is appropriate. (Equation 2) 230 ≧ T ₂ ≧ T _m −15 If the heating time is too long, the degree of progress of alloying of tin and iron cannot be ignored, leading to a decrease in weldability. Therefore, the heating time is 10 minutes or less. It is good to say

As described above, since the heating temperature is limited, the melting point of the resin film used is limited.
A resin film having a melting point of more than 250 ° C cannot be used, but a resin film having a melting point of 240 ° C or less is preferable.

A resin film having a too low melting point is not preferable depending on the purpose of use of the material for cans. Since the retort can is exposed to a high temperature (125 ° C.) (30 minutes), a resin film having a low melting point tends to be softened and insufficient in heat resistance, so that peeling tends to occur. For such applications, the melting point is 180
A resin film having a temperature of ℃ or higher is desirable. Although not limited, the thickness of the resin film is 4 μm to 60 μm.
The degree is appropriate.

[0037]

Example A cold rolled steel sheet having a thickness of 0.20 mm was cleaned by degreasing and pickling, then plated on both sides and chromated. However, when Sn plating was applied, chromate treatment was applied after reflow treatment. This treated steel sheet was preheated and continuously adhered while a biaxially stretched resin film was pressure-bonded with a roll, followed by heating and cooling through a cooling roll to obtain a laminated steel sheet. The properties of the obtained laminated steel sheet were examined.

In the characteristic investigation, tests were conducted on the weldability, the resin film adhesion, the retort resistance and the elongation property required for the material for welding cans. Further, in the manufacturing process, it was observed whether or not swelling occurred in the film immediately after cooling after post-heating, and the degree of entrainment of air and water was evaluated.

Ferrostan bath was used for tin plating, and Watt bath was used for nickel plating. The chemical conversion treatment was performed using a chromic anhydride bath containing sodium sulfate. Lamination is a resin film with a width of 161 mm, and a varnish avoiding part is provided within a width of 2 mm to 15 mm, and the steel plate is coated on one side with 4
I glued them together.

The test and its evaluation were carried out as follows. Weldability: 200 ml using a Sudronic type welder
The can body was welded and evaluated at the maximum speed at which no splash occurred.

Adhesion of resin film: Targeting a resin laminate band, cut a cross-cut into 2 mm intervals on the film,
After extruding 4 mm of Erichsen, it was forcibly peeled off with an adhesive tape and evaluated based on the percentage of the peeled area. The test results are summarized as ⊚ when there is no peeling, ◯ when the peeled area is 1 to 10%, Δ when the peeled area is 10 to 30%, and × when the peeled area is 30% or more.

Retort resistance: A cross-cut test piece was immersed in an aqueous solution containing 1.5% NaCl at 125 ° C.
After soaking for 0 minute, the adhesive tape was forcibly peeled off, and the state of peeling was evaluated. The evaluations are: ◎: No peeling, ◯: Slight peeling in the crosscut peripheral area, Δ: Significant peeling in the crosscut peripheral area, ×: Whole surface peeling.

Elongation characteristics: The elongation E _{1 in the} width direction of the steel sheet was measured, and the elongation deterioration degree (1-E ₁ / E ₁₀ ) was obtained by taking the ratio with the elongation E ₁₀ when no lamination was performed. If the degree of elongation deterioration is less than 10%, △: 10% or more and less than 30%
The case of 30% or more was evaluated as x. The characteristics were also investigated for comparative examples outside the scope of the present invention and for conventional examples having no conventional varnish avoidance portion, and compared with the examples of the present invention.

In the conventional example, the resin film was scraped off to form a welding allowance and welding was performed. Table 1 shows the detailed conditions of the test pieces used for the investigation and the test results.

[0045]

[Table 1]

In the Examples of Test Nos. 1 to 16, satisfactory results were obtained in all the tests. On the other hand, in Comparative Example, Test No. 17 in which the center average roughness Ra of the plated surface was large
In this case, the plating surface roughness Ra is greatly swollen, and the swollen portion also has poor retort resistance. Test No. 18 in which the melting point of the resin film is extremely low is also poor in retort resistance, and High test No. 19 is inferior in adhesion and retort resistance of the resin film. Test No. 20, whose preheating temperature and post-heating temperature were too high,
No. 21, the elongation property is insufficient. In No. 20, the post-heating temperature was too low and the film adhesion was also poor. or,
In Test No. 22 in which the width of the varnish avoiding part is narrower than 5 mm, a part of the edge of the film adjacent to the varnish avoiding part is burned by the heat during welding, and this part reduces the film adhesion and the retort resistance. Was there.

In the conventional example, since the varnish avoidance portions are not provided for both the test Nos. 23 and 24, most of the plating layer is scraped off during the grinding of the welding allowance, and the welding speed is inferior.

[0048]

As described above, according to the present invention, the surface of the steel sheet is provided with the varnish avoiding portion and the resin laminating strip having an appropriate width, and the tin plating is applied to the base of the varnish avoiding portion and the resin laminating strip. Has been applied. Therefore, in the varnish avoiding portion, stable welding can be performed at high speed during can making. Moreover, the tin-plated surface is smooth and is subjected to a chemical conversion treatment to enhance the adhesion to the coating film or the resin film. Therefore, when laminating the resin film, the amount of air and water involved is extremely small, highly stable adhesion is obtained, and the retort resistance is enhanced together with the selected resin film. In addition, since the elongation property is maintained in the manufacturing process by avoiding excessive heating, it is possible to sufficiently prevent defects during processing.

By providing such an excellent can material, the effect of the present invention, which enables the omission of painting and printing operations that must be performed for each sheet in the can manufacturing process, is great.

[Brief description of drawings]

FIG. 1 is a plan view of a laminated steel plate for a welding can of the present invention.

FIG. 2 is a sectional view of a laminated steel plate for a welding can of the present invention.

FIG. 3 is a diagram showing steps for explaining a welding can manufacturing method.

[Explanation of symbols]

 1 varnish avoidance part 2 resin laminate band 3 resin 4 chemical conversion treatment layer 5 plating layer 6 steel plate.

Claims (6)

[Claims] 1. A plating layer which has been subjected to chemical conversion treatment, and the center line average roughness Ra of the surface of these plating layers is 0.02 μm.
Strip-shaped varnish avoiding portions and resin laminate strips are alternately provided in parallel to the rolling direction of the steel sheet on at least one surface of the plated steel sheet having a thickness of m or more and 0.35 μm or less, and the plating layer, the varnish avoiding portion and the resin laminate are provided. A laminated steel sheet for a welding can, which has the following bands (i), (b) and (ha), respectively, and has an elongation of 18% or more. (Ii) Tin single-layer plating layer or double-layer plating layer in which tin is plated after nickel plating (b) Width 5 mm or more in the area where resin is not laminated 20
Varnish avoidance area of less than or equal to mm () is a resin laminate band whose main resin component is polyethylene terephthalate or polyethylene naphthalate. 2. The adhesion amount of the tin single-layer plating layer is 0.9 g / m ²
The laminated steel sheet for a welding can according to claim 1, which has a content of 2.0 g / m ² or less. 3. The adhesion amount of the two-layer plating layer is 15 mg of nickel.
/ m² 100 mg / m or more ² Below, tin 0.8g / m²that's all
2.0 g / m²The laminator for a welding can according to claim 1, wherein:
Steel plate. 4. The metal of the chemical conversion treatment film applied to the plating layer
Chromium amount is 5mg / m²50 mg / m or more² Below, Chrome Oki
Side is 5 mg / m in terms of chromium² 25 mg / m or more ² Below
A welding can la according to claim 1 or claim 2 or claim 3.
Minated steel sheet. 5. An amount of tin plating of 0.9 g / m ² or more on the surface of a steel sheet having a surface center average roughness Ra of 0.40 μm or less.2.
0 g / m ² or less, or nickel plating on the surface of the steel sheet 15 mg / m ² or more and 100 mg / m ² or less, and then tin plating 0.8 g / m ² or more 2.0 g / m ² Apply the following to make the plating surface center average roughness 0.02 μm or more and 0.35 μm
Chromate treatment is performed after adjusting the following, on which the resin film is continuously laminated on at least one surface of the plated steel sheet in the running direction under the conditions listed in (i) below. Production method. (1) With the melting point of the resin film being T _m ° C, the plated steel sheet is held for 1 second or more and 60 seconds or less at a temperature T ₁ ° C shown in Formula ₁ and preheated, and then the resin film is laminated by roll pressure bonding, and then the number 2 The temperature T ₂ ° C shown in (1) is maintained for 1 second or more and 10 minutes or less to perform post-heating and then cooling. (Equation 1) 230 ≧ T ₁ ≧ T _m −20 (Equation 2) 230 ≧ T ₂ ≧ T _m −15 6. The melting point of the resin film is 180 ° C. or higher 24
The method for producing a laminated steel sheet for a welding can according to claim 5, which is 0 ° C or lower.