JPH05177763A - Laminated steel plate for welded can - Google Patents

Abstract

PURPOSE:To obtain a material for a welded can enabling the high speed welding and bonding of a can body even when a resin film is not removed and excellent in corrosion resistance inclusive of a bonded part. CONSTITUTION:A strip like varnish avoiding part 1 is provided on the surface of a plated steel plate and a resin laminated strip 2 is provided to the surface of said steel plate in parallel to the varnish avoiding part 1. The varnish avoiding part 1 is composed of a tin plating layer (1.0-2.5g/m<2>) subjected to chromate treatment and the resin laminated strip 2 is formed by laminating a resin film on a plating layer composed of tin, nickel or chrominum through a chromate layer. Therefore, at the time of the production of a can, the adverse effect accompanid by the removal of the film of a welded part, that is, the detachment of the plating layer or the mixing with cut dust is prevented and the plating layer enables high speed welding and the plating layer is strongly bonded to the film or resin film through the chromate film to bring about high corrosion-resistant effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel plate for cans used for welding cans such as food cans. The present invention relates to a steel plate for a welding can, which is easy to seam weld.

[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 method has a limit in reducing the amount of tin, and in this respect as well, it is expected to be a material for a welding can that can be joined by plating layers of other metals.

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 countermeasures against environmental pollution due to painting are required, which is one of the tasks for streamlining 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-5
8-82717 discloses a method in which a polyester resin is used in two layers, the lower layer is laminated with an amorphous polyester having good adhesion to a metal plate, and the upper layer is laminated with a crystalline saturated polyester having good corrosion resistance and mechanical properties. ..

[0006]

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

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 existing 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 dust. Also, when plating is performed in consideration of high-speed welding, the weldability naturally deteriorates.

The present invention has been made in order to solve such a problem. It is not necessary to grind and remove the resin film at the time of welding during can-making, and the welded portion is repair-painted to ensure sufficient corrosion resistance. It is intended to provide a steel plate for cans.

[0009]

[Means for Solving the Problems] A means for achieving this object is a surface-treated steel sheet in which a resin laminate band and a varnish avoiding portion in consideration of welding are alternately provided, which are parallel to the running direction of the strip. A laminated steel sheet for a welding can, which has a strip-shaped varnish avoiding portion having a width of 5 mm or more and 20 mm or less at a predetermined interval, and is a resin laminate strip having the above-mentioned spacing width on at least one surface of the steel sheet, wherein the varnish avoiding portion and the resin laminate strip Are laminated steel plates for welded cans having the configurations (i) and (b) respectively, but regarding the resin layer, the plating layer and the chemical conversion coating, the following (1), (2), (3) or these It is more desirable that the above conditions are combined.

(B) The varnish avoidance part is 1.0 g / m ^{2 on the} steel plate surface.
A chemical conversion treatment film of metallic chromium and chromium oxide is provided on the tin plating layer of 2.5 g / m ² or less. The (ro) resin laminate band is provided with a tin, nickel, or chromium single-layer plating layer, a two-layer plating layer in which a tin plating layer is stacked on a nickel plating layer, or a tin-nickel alloy plating layer on the steel plate surface. It has a chemical conversion treatment film made of metallic chromium and chromium oxide on the plated layer, and has a resin layer of polyethylene terephthalate, polyethylene naphthalate or polypropylene laminated thereon.

(1) The thickness of the resin layer is 4 μm or more and 60 μm
Being below. (2) The adhesion amount of tin, nickel or chromium single layer plating layer is 0.4 g / m ² or more and 11.5 g / m ² or less and 30 mg / m ^{2 respectively.}
More than 1000 mg / m ² less than 30 mg / m ² more than 150 mg / m ²
Being below. (3) The amount of metallic chromium in the chemical conversion coating is 5 mg / m ² or more 50
Must be below mg / m ² .

[0012]

[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 portions 1 and the resin laminate strips 2 are provided alternately in parallel. 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,
By using the varnish avoidance portion as a welding allowance, it is not necessary to remove the resin film at the time of welding at the time of can making, even for a steel plate on which the resin 3 is laminated in advance.

The width of the varnish avoiding portion has an important meaning. The temperature of the weld exceeds 1000 ° C during welding, 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. 5mm to avoid the influence of heat during welding
The above-mentioned width of the varnish avoidance part is necessary. 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.

Further, the varnish avoidance portion is plated with a small amount of tin so that seam welding can be performed easily and surely. Since tin is a soft metal and has a low melting point, a large contact area with the electrode can be easily obtained. Therefore, the current required for welding flows uniformly at a relatively low voltage, and a reliable welded surface can be obtained continuously. In welding, when an excessive current locally flows, a phenomenon in which a part of metal is scattered (called splash) occurs, and the welded part is soiled or the part lacking current is insufficiently joined. This phenomenon becomes more remarkable as the welding speed increases. When tinned, the tin content is 1.0 g /
If it is m ² or more, it can withstand high speed welding.
An amount exceeding 2.5 g / m ² results in excess quality.

Since repair coating is applied to the varnish avoiding portion after welding, it is necessary to apply a chemical conversion treatment on the tin plating to enhance the paintability. Chromate treatment is recommended as the chemical conversion treatment, and it is desirable to form a film having an amount of metallic chromium of 5 mg / m ² or more. In this case, stronger adhesion can be obtained with the film. The effect does not change even if the amount of metallic chromium exceeds 50 mg / m ² .

The resin laminate strip, which occupies most of the area of the can material, must withstand processing and have sufficient corrosion resistance after can making. Therefore, it becomes a multi-layer of the metal plating layer and the resin layer. If only the resin layer is used, the ion permeability of the resin is limited, and even if it does not cause significant corrosion, a slight elution of iron may change the taste and aroma of the contents in the food can. The resin to be laminated is preferably a resin having a great effect as a barrier, that is, a resin such as polyethylene terephthalate, polyethylene naphthalate, polypropylene or the like. Among them, the biaxially stretched film is known to have high crystallinity and a large barrier effect. In order to further expect a sufficient barrier effect, the thickness of the resin layer is preferably 4 μm or more, but even if it exceeds 60 μm, the effect does not change so much. In the case of laminating a resin film, unlike the case of applying a paint, a single step is enough even if the thickness is several tens of μm.

As the lower plating layer, tin, nickel, chromium or the like is suitable for corrosion resistance and harmlessness in consideration of foods. In the case of tin and nickel, tin plating may be applied on the nickel plating layer, or an alloy plating layer of tin and nickel may be provided. For foods in which a subtle change in taste or aroma is a problem, the thicker these plating layers are, the more preferable they are. However, if they are too thick, the effect does not change and the cost increases. The preferred range is 0.4 g / m ² or more and 11.5 g / m ² or less for tin single-layer plating, 30 mg / m ² or more and 1000 mg / m ² or less for chromium single-layer plating, and chromium plating layer In this case, it is 30 mg / m ² or more and 150 mg / m ² or less. The tin-nickel multilayer plating or alloy plating, according to the case of a single layer, the adhesion amount of 0.4g / m ² ~11g / m ² is desirable.

Further, a chemical conversion treatment is performed on the plating layer in order to improve the adhesion with the resin layer. During can manufacturing, the can body is not only bent in a round shape, but also welded and subjected to a drawing process called neck-in after repair painting. That is, it is narrowed down from the body of the can to the neck. When subjected to such processing, the layer that does not adhere well is peeled off. In order to secure sufficient adhesion, chromate treatment is recommended as the chemical conversion treatment, as in the varnish avoidance portion, and it is desirable to form a film containing 5 mg / m ² or more of metallic chromium. The amount of metallic chromium is 50 mg
The effect does not change even if it exceeds / m ² . However, when the plating layer is chromium, the chemical conversion treatment does not necessarily have to be performed. The width of the resin laminate band is determined by the diameter of the can, and is about 161 mm for a 200 ml beverage can, for example.

The longitudinal direction of these strips is the running direction of the strip at the time of production in consideration of the production cost of the product. When the directions are different, the mechanism and operation for continuously forming the plating or resin layer becomes complicated and the manufacturing equipment becomes large, so that the manufacturing cost is inevitably increased.

Since the varnish avoiding portion is welded on the front and back sides, it is necessary 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 or a white layer, which is a treated surface according to demand.

[0021]

EXAMPLE A 0.20 mm-thick cold rolled steel sheet was cleaned by degreasing and pickling, plating was applied to the resin laminate band, and then tin was electrodeposited in a ferrostane bath on the varnish avoidance portion, and then reflowed. Chromate treatment was performed. While heating this treated steel plate to 200 ° C and pressing the resin film with a roll, make a varnish avoiding part in the range of 2.5 mm to 15 mm,
Laminated continuously. The characteristics of the laminated steel sheet for welding cans manufactured in this manner were examined.

In the characteristic investigation, tests were conducted on the weldability, resin film adhesion, and corrosion resistance required for materials for welding cans. The weldability was evaluated by welding a 200 ml can body using a pseudoronic type welder and at the maximum speed (the number of cans per minute) at which no splash occurred.

The resin film adhesion was evaluated on the basis of the percentage of the peeled area, targeting the resin laminate band, by cutting cross cuts on the film at 1 mm intervals, extruding 5 mm of Erichsen and forcibly peeling with an adhesive tape. The test results are summarized as ⊚ when there is no peeling, ◯ when the peeled area is 1 to 5%, Δ when the peeled area is 5 to 20%, and × when the peeled area is 20% or more.

Corrosion resistance is determined by applying a repair coating with an epoxy / phenolic can inner surface coating to the varnish avoiding portion welded after the can body is manufactured, and then corroding the resin laminated band together with 1.5% each of NaCl and citric acid. It was immersed in the liquid at 38 ° C. for 96 hours, and the amount of eluted iron (hereinafter referred to as iron elution value) was measured and evaluated. The characteristics were also investigated for comparative examples outside the scope of the present invention and for conventional examples having no varnish avoidance portion, and compared with the examples of the present invention.

In the conventional example, the resin film was scraped off at the time of welding to make a welding allowance, and after welding, this portion was subjected to repair painting as in the example to examine the corrosion resistance. Table 1 shows the detailed conditions of the test pieces used for the investigation and the test results.

[0026]

[Table 1]

In the Examples of Test Nos. 1 to 18, satisfactory results were obtained in all the tests. On the other hand, in the comparative example, the test No. 1 in which the tin plating amount in the varnish avoidance part is insufficient
9 and 20 are inferior in welding speed, Test No. 21 without chemical conversion treatment has poor film adhesion, and Test No. 22 without undercoating has slightly inferior film adhesion and corrosion resistance. .. Also, in Test No. 23, where the width of the varnish avoidance part is narrow, the resin film in the vicinity of the varnish avoidance part is burned due to the propagation heat during welding, and the adhesion is poor in this part, and as a result, the iron elution amount is slightly small. It was increasing.

In the conventional example, since no varnish avoiding portion is provided, most of the plating layer is scraped off during the grinding of the welding allowance regardless of the type of the base plating, and the repair coating is applied. Inferior corrosion resistance as well as welding speed.

[0029]

As described above, according to the present invention, the surface of the steel sheet is provided with the varnish avoiding portion and the resin laminate band, the former is tin-plated and the latter is corrosion-resistant metal-plated. A resin film with a large barrier effect is laminated. In addition, the plated surface is subjected to a chemical conversion treatment that provides sufficient adhesion with the coating film or resin film.
For this reason, stable welding can be performed at high speed during can manufacturing, and the repair coating film on this portion is sufficiently resistant to neck-in processing as well as the laminate film and adheres well. In addition, the synergistic effect of the plating layer and the resin film after the can is made to exert sufficient corrosion resistance that does not change the taste and aroma of the contents of the can.

By providing such an excellent can material, the effect of the present invention that enables the omission of painting and printing operations that require the processing of 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 (4)

[Claims] 1. A width of 5 parallel to the running direction of the strip.
mm to 20 mm in strip-shaped varnish avoiding portions at a predetermined interval, and at least one surface of the steel sheet has a resin laminate strip having the above-mentioned interval width, and the varnish avoiding portion and the resin laminate strip are each of the following (i) A laminated steel plate for a welding can, which is characterized in that (B) The varnish avoidance part is 1.0 g / m ² or more and 2.5 g /
It has a chemical conversion coating film of metallic chromium and chromium oxide on the tin plating layer of m ² or less. The (ro) resin laminate band is provided with a tin, nickel, or chromium single-layer plating layer, a two-layer plating layer in which a tin plating layer is stacked on a nickel plating layer, or a tin-nickel alloy plating layer on the steel plate surface. It has a chemical conversion treatment film made of metallic chromium and chromium oxide on the plated layer, and has a resin layer of polyethylene terephthalate, polyethylene naphthalate or polypropylene laminated thereon. 2. The laminated steel sheet for a welding can according to claim 1, wherein the resin layer has a thickness of 4 μm or more and 60 μm or less. 3. A single-layer plating layer of tin, nickel or chromium
Adhesion amount of 0.4g / m each²11.5g / m or more²Below 3
0 mg / m² 1000mg / m or more² Below, 30mg / m ² Above 15
0 mg / m² The following is for welding according to claim 1 or claim 2.
Laminated steel sheet. 4. The amount of metallic chromium in the chemical conversion coating is 5 mg / m ^2.
The laminated steel sheet for a welding can according to claim 1, claim 2 or claim 3, which has a content of 50 mg / m ² or less.