JPH0775745B2 - Welding can manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a welding can body.
To do .

2. Description of the Related Art In recent years, welded cans have been used as food cans or beverage cans. Tin-plated steel sheets (tinplate materials) and tin-free steel sheets are used as the material for this welding can. Of these, the tin-plated steel sheet that is conventionally used for solder cans is generally used. However, the tin plating amount was 2.8 g / m ² or more in order to maintain the so-called solderability as a solder can.
However, recently, the tin price tends to rise due to resource reasons, and particularly in the case of welding cans, the tin plating adhesion amount as much as that of solder cans is not required to secure weldability, so the tin plating amount is small. Researches using tin-plated steel sheets as a material for welding cans are being actively conducted.

[0002]

However, even in the case of a welded can, it is inevitable that the weldability and corrosion resistance will deteriorate as the tin plating amount is reduced. Even if it was reduced, it was said that the attached amount was about 1.8 g / m ² at the most. That is, in order to ensure weldability in tin-plated steel sheets, at least a certain amount of pure tin must be present. However, in the case of a can material, an alloy of tin and iron is used in the paint baking process performed before welding. As a result, the amount of tin-iron alloy layer increases and the amount of tin decreases. Since such a tin-iron alloy layer has a higher melting point than tin itself, it deteriorates the weldability. Therefore, when the amount of tin plating adhered is reduced to achieve thin plating, the tin-iron alloy layer does not correspond to the tin plating amount. The proportion of layers increases, and in the case of ultra-thin tin plating, the total amount of tin is alloyed, and the weldability is significantly deteriorated. Further, such thinning of tin impairs the adhesiveness of the coating film, and as a result, also adversely affects the corrosion resistance.

[0003]

In order to solve such conventional problems, the present inventors have made various studies on a coating structure of a welding can body having a tin plating layer and a manufacturing method thereof. As a result, selecting the adhesion structure of the tin layer consisting of unalloyed pure tin at the stage after the coating film forming step at the time of welding can manufacturing and before the pressure seam welding step, specifically, the above tin By discontinuously distributing the layers with respect to the steel plate surface, the weldability is not improved by the reduction of the tin plating amount, but rather improved, and further, by adopting a specific coating structure including the tin layer. It was found that excellent corrosion resistance can be obtained regardless of the reduction of the tin plating amount. The present invention has been made on the basis of such findings, and provides a method for manufacturing a welding can body which is excellent in corrosion resistance as well as excellent weldability even though it is ultrathin tin plating.

That is, according to the present invention, the amount of plating on the steel plate surface is 5
After tin plating of 60 mg / m ² or more, reflow treatment
The amount of residual free tin is 310 mg / m ²
Metal chrome and chrome with the above-mentioned adhesion amount of 2 to 20 mg / m ^2.
Consisting of 3 to 20 mg / m ² of deposited chromium oxide
Chrome / chromate coating, and then at least
Also for the surface of the surface-treated steel plate that should be the inner surface of the can body,
After forming a coating film on both sides of the
After the treatment, the discontinuous tin layer had a tin adhesion amount of 50 mg / m ²
Above, and distributed in the range of 10 to 60% of the steel plate surface
The coating film is heat-treated so as to be in a state, and then, after a molding process, the surface-treated steel sheet forming the body of the can is formed by superposing pressure seam welding on both side edges of the coated can material. Yes least Suzutetsu alloy layer on the steel sheet, a chrome-chromate coatings consisting of chromium oxide coating weight 3 to 20 mg / m ² tin layer and deposition amount 2 to 20 mg / m ² of metallic chromium and chromium terms in this order However, the tin layer of the portion excluding the welded portion has a tin adhesion amount of 50 mg / m ² or more and is 10
It is a manufacturing method of the welding can body characterized by manufacturing the welding can body distributed in the range of -60%.

[0005]

According to the present invention, the tin layer of the steel sheet after the coating film is formed, that is, 50 mg / m ² or more of tin which is not alloyed by the heat treatment during the coating film formation and is retained, and Welding is carried out in a state where the layers are distributed in the range of 10 to 60% in a discontinuous (island or mottled) form, rather than covering the entire surface of the steel plate. Extremely excellent weldability can be obtained while suppressing.

In the conventional plating technology, it is common knowledge that not only tin plating but also plating uniformity is maintained, and various studies have been conducted to ensure this uniformity. Also, when discussing the limit of thinning the tinplate material in the related art, only the problem is whether or not the uniformity of the plating film can be secured by the thinning. In contrast to such conventional technical common sense, the inventors of the present invention allow pure tin (free tin) of a predetermined amount or more to remain at a stage after welding after coating film formation and before welding, even if the adhesion amount of the tin plating amount itself is reduced. Moreover, by forming this tin in a discontinuous manner on the surface of the steel sheet at a predetermined distribution ratio, the weldability in the subsequent welding has a tin plate amount which is the same as that of the conventional tin deposit despite the reduction of the tin plating amount. We have found the fact that it is greatly improved even compared to wood. The following points can be considered as the reasons for such improvement in weldability.

That is, although one of the criteria for evaluating the weldability is the range of the welding effective current range (hereinafter referred to as ACR), the first reason is that the ACR can be widely set in the present invention. . When welding tin-plated steel sheets, a certain amount of welding current is required to ensure welding strength, but on the other hand, if the welding current becomes large, splashing will occur and the quality of the can body will be deteriorated. The above-mentioned ACR is the range of the welding current that does not occur and can be welded to a predetermined welding strength. In this respect, in the present invention, tin is discontinuously distributed in an island shape at a predetermined distribution ratio with respect to the surface of the steel sheet, so that it melts during welding to reduce the contact resistance, and welding is performed with a relatively large welding current equivalent to that of an ordinary tin plate. However, it is considered that the occurrence of splash is suppressed, and therefore the ACR can be satisfactorily ensured.

Secondly, the function of preventing the occurrence of cracks at the welded portion can be mentioned. Although the painted can material before welding is not painted on both side edge parts which are welded parts, in reality, it is inevitable that fume of the paint adheres. In a conventional coating can, a large amount of tin plating reduces the contact resistance between plates, so a large current is required to obtain a predetermined heat generation state and welding strength resulting from this. It is considered that a large current inevitably flows between the roller and the drum roller having a small diameter, and a crack is generated on the surface thereof. That is, such a large current causes a defect in the melting of the can material due to welding, which appears as cracks in the welded portion. In this regard, in the present invention, since the amount of tin deposition is reduced and distributed in an island shape, the contact resistance between the plates is slightly higher, and a current smaller than the tin plate is sufficient to obtain a predetermined welding heat generation. As a result, the occurrence of cracks on the weld surface can be properly suppressed.

In order to reduce the amount of tin plating deposited, in particular, in the case of the coating structure in which the tin layer is discontinuously distributed as in the present invention, it is possible to avoid that the tin layer alone is inferior in corrosion resistance to some extent when compared with the conventional tin-plated steel sheet. However, the inventors of the present invention have found that the problem of the corrosion resistance can be solved by forming a predetermined chromium / chromate film on the tin layer. Therefore, in the present invention, a surface-treated steel sheet on which a chromium / chromate coating composed of a predetermined range of metallic chromium and chromium oxide is formed on a tin layer is used as a material. In addition, according to the present invention, the tin layer is partially distributed, not on the entire surface of the steel sheet, and therefore, it is possible to obtain excellent characteristics of sulfastene resistance as compared with the conventional tinplate material.

The present invention will be described in detail below. The present invention is
Applying tin plating to the steel plate surface and subsequent reflow treatment
Forming a tin layer distributed in a discontinuous shape by, click on the upper layer thereof
Chromate / chromate coating is formed by romate treatment ,
Then, it is a method of manufacturing a welded can body by sequentially carrying out a coating film forming step involving heat treatment, a forming step and a pressure seam welding step.

As described above, according to the present invention, the tin layer is discontinuous with respect to the surface of the steel sheet under a specific condition after the coating film forming step involving the heat treatment during the production of the welding can and before the pressure seam welding step.
It is intended to ensure excellent weldability by keeping the state of continuous distribution . Such a tin layer discontinuously distributed on the surface of the steel sheet is derived from the coating structure of the surface-treated steel sheet as a raw material, and the tin-plated steel sheet as a raw material is distributed in a discontinuous manner on the steel sheet surface. It is necessary to have layers. This tin-plated steel sheet discontinuity (island
For the tin layer), select the reflow treatment conditions after tin plating.
Can be obtained by Specifically, if the immersion of the steel sheet in the usual flux solution is stopped and the tin is melted in a non-uniform state by reflow ,
A continuous tin layer is obtained.

Here, a part of the tin layer of the surface-treated steel sheet is alloyed by the heating of the steel sheet in the coating film forming step at the time of manufacturing a welding can. Needless to say, in the previous stage, that is, as a surface-treated steel sheet as a raw material, the tin content is different from that of the coating can material. Therefore , in the method for producing a welded can body of the present invention, tin plating is performed according to the target tin amount of the coating can material and the alloying amount of tin during coating.
However, this is to ensure the tin content of the surface-treated steel sheet.
Coating weight 560 mg / m ² or less with respect to the steel sheet surface for
Applying tin plating on top and removing residual solder after reflow treatment.
Reflow to ensure that the amount of tin release is more than 310 mg / m ^2.
-Process. Perform tin plating with the above plating amount
To ensure the amount of residual free tin above after reflow treatment
In addition, the amount of residual free tin can be secured.
And the tin content and surface of the discontinuous tin layer after heat treatment of the coating film.
The product ratio can be secured.

Further, in order to ensure the corrosion resistance of the welded can body as described above, surface-treated steel sheet as a material, will require an have a chrome chromate film on the upper layer of the tin plating, and therefore the tin Tin plated after reflow process after plating
Chromate treatment is applied to the steel plate
A coating film is formed . This chromium / chromate coating has a metallic chromium content of 2 to 20 mg /
m ² and chromium oxide are regulated within the range of 3 to ²⁰ mg / m ^{2 in} terms of chromium. This chromium / chromate coating is effective for corrosion resistance, but if the amount of adhesion is too large, the weldability deteriorates. Therefore, it is necessary to set the above upper limit. On the other hand, if it is less than the above lower limit, there arises a problem in corrosion resistance.

Next, in the coating film forming step, a coating film is formed on at least the steel plate surface to be the inner surface side of the can body portion. In this coating film forming step, heat treatment is performed to thermoset the coating film, but as described above, a part of tin in the surface-treated steel sheet is alloyed by this heat treatment, and as a result, the present invention is finished.
As a result, a discontinuous tin layer having a target tin content and a distribution state is formed. Specifically, the discontinuous tin layer after heat treatment has tin.
50 % / m ² or more and 10 to 60% of the steel plate surface
The coating film is heat-treated so that it is distributed in the range of.
The reason for limiting the amount of tin layer deposited and the distribution ratio will be described later.
I will describe. The coating film is not formed on both side edge portions of the steel plate to be welded portions.

The coating film formed in this manner protects the can material from the contents filled in the can when the can body is used as a food can or a beverage can, and the contents caused by the elution of the can material. In the present invention, which is intended to prevent discoloration and a decrease in flavor and to reduce the amount of tin plating adhered, it is preferable to consider the coating film components. As this coating material, a thermosetting epoxy phenolic resin coating material is suitable, and in particular, a phenol resin containing 65 wt% or more of a resole type phenol resin formed from bisphenol A and a number average molecular weight of 14
5 to 7,000 bisphenol A type epoxy resin
A preferable example is a thermosetting epoxyphenol resin-based coating material contained in a weight ratio of 0/50 to 5/95, and such a coating material is applied to form a resin coating film having a film thickness of 2 to 10 μm. Is preferred.

Next, the coated can material is cut into a can body blank size in the forming step, then rolled and the both side edge portions thereof are overlapped, and the portion is subjected to pressure seam welding by a welding machine to form a can body. Manufactured. Then, the can body as the final product is further subjected to covering correction of the exposed iron surface of the welded joint and the vicinity thereof, then flange processing is applied to the body end of the can, and the lid is tightened at one end of the can body. It can be obtained by applying correction coating to the inside of the can .

The thus produced can body has at least a tin-iron alloy layer, a tin layer and a chromium / chromate coating on the surface side corresponding to the inner surface of the can body from the lower side, and a coating film thereon. Is formed. FIG. 1 shows a coating structure in a non-welded portion of a can body manufactured by the method of the present invention. 1 is a base steel plate, 2 is a tin-iron alloy layer, 3 is a tin layer, 4 is a chromium / chromate coating. 5 is a coating film.

The tin layer 3 has a tin content of 50 mg / m ^2.
The above is required, and if it is less than this, sufficient weldability cannot be secured in the pressure seam welding described above. Further, the tin layer 3 needs to be distributed discontinuously on the surface of the steel sheet, but its distribution ratio, that is, the ratio of the area of the steel plate to the area is regulated to 10 to 60%. If the distribution ratio exceeds 60%, splash is likely to occur during welding, the weldability is deteriorated, and the tin content is inevitably increased, which is not preferable. On the other hand, if it is less than 10%, it is difficult to secure the above tin content, and therefore the lower limit is 10
%.

Further, a base layer can be provided on the surface of the base steel plate, whereby the corrosion resistance can be improved.
A layer containing nickel is particularly preferable as the underlayer in order to secure corrosion resistance. In this case, the amount of nickel is 5
The nickel-containing layer of up to 200 mg / m ² is a nickel plating layer provided on the surface of the base steel sheet, and nickel formed by annealing and diffusing the nickel plating to diffuse a part or all of the nickel plating into the base steel sheet. There is a containing layer, and a nickel-iron alloy plating layer provided on the surface of the base steel plate. Reference numeral 6 in FIG. 1 shows a nickel-containing layer formed in the steel sheet by diffusion treatment after nickel plating. The lower portion of the tin-iron alloy layer 2 is necessarily an alloy layer containing nickel.

[0020]

EXAMPLES Under the manufacturing conditions shown in Tables 1 and 2,
Welded can bodies were manufactured by the method of the present invention and the comparative method, and the weldability and corrosion resistance of the cans were investigated. The results are shown in Tables 3 and 4. In Comparative Example 9, Comparative Example 9 is a surface-treated steel sheet disclosed in Japanese Patent Laid-Open No. 59-100285, that is, after tin plating, the entire amount is alloyed, and then tin plating is performed to perform tin-iron plating. It is a comparative example in which a surface-treated steel sheet in which granular metal tin is electrodeposited on the alloy layer is used as a material. The test conditions for each characteristic test are as described in * 5 to * 8 as an annotation. Here, the coating materials (a) and (b) in Tables 1 and 2 have the following contents.

Paint (a) Resol type phenol resin 15 obtained by reacting mixed phenol of 75 parts of p-cresol and 25 parts of m-cresol with formaldehyde in the presence of an ammonia catalyst.
Parts and 85 parts of a bisphenol A type epoxy resin having a number average molecular weight of about 3000 are dissolved in a mixed solvent composed of an alcohol-based, ketone-based, ester-based or aromatic organic solvent to obtain a solid content of 30% and a viscosity (Fc ₄ #, 25 ℃)
Epoxy / phenolic resin-based paint for 40 seconds ・ Paint (b) Resol type phenolic resin 20 parts obtained by reacting bisphenol A with formaldehyde in the presence of an ammonia catalyst and 80 parts bisphenol A type epoxy resin having a number average molecular weight of 3410. Thermosetting epoxyphenolic paint with solid content 29% and viscosity (Fc ₄ #, 25 ° C) 40 seconds obtained by dissolving and in a mixed solvent

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

[Table 4]

* 1 The amount of unalloyed tin * 2 The area ratio of the tin layer to the steel sheet area * 3 The diameter of tin distributed in the form of islands * 4 The amount inside the parentheses * 5 Before painting and printing Each plating layer of the original plate is measured by the following method. (A) The amount of nickel was obtained by measuring the Ni-K count number with a fluorescent X-ray from a standard sample that had been quantified in advance by a chemical analysis method and creating a calibration curve. (B) The amount of total tin was measured by the fluorescent X-ray method, and the amount of residual free tin was measured by the electrolytic stripping method described in JIS G3303. (C) As for the amount of chromium, the total amount of chromium was measured by the fluorescent X-ray method, and further the amount of metallic chromium was measured by the constant current electrolysis method in a 0.1 M Na ₂ HPO ₄ solution. The difference was defined as the amount of chromium oxide.

* 6 The tin content and tin distribution state of the painted plate before welding are 0.5% for the original plate that has been baked for a predetermined period.
The following measurements were carried out after anodizing for 3 seconds in Na ₂ CO ₃ and cathodic treating for 60 seconds. (A) Residual free tin was measured by the electrolytic stripping method described in JIS G3303. (B) The distribution state of residual free tin and the diameter of tin were measured from a photograph taken by enlarging 1000 times with a scanning electron microscope.

* 7 For weldability, an electric resistance seam welder (500 Hz sine wave) was used and the plate thickness was 0.22 mm.
Of the overlapping part width 0.40mm, welding speed 5
The can is made at 6 m / min, and the effective range of the welding current, that is, the maximum welding current that does not generate 5 or more splashes of 1 mm or more in one can by naked eye judgment and the welding strength that does not tear off or break the weld The range of the minimum welding current to have was determined. Furthermore, the welded surface was observed with a stereoscopic microscope, and the maximum welding current at which cracks did not occur was determined and set as the welding suitability range. ⊚: The welding suitability range is extremely wide, and good welding can be stably obtained. ◯: It is a practically feasible range. Δ: Flap and cracks increase, and it is difficult to correct the welding surface with paint. X: There is no welding suitability range.

* 8 Corrosion resistance was evaluated by the following test method. (A) UFC property (corrosion under the coating film) A 20 mm cross cut is put on a coated plate, and it is overhanged with 5 mm Erichsen centering on the intersection, containing 0.071 mol of citric acid and 0.26 mol of salt, and pH = caustic soda. 3.
The solution adjusted to 0 was heated to 95 ° C. to bring the test piece into contact, and the peeled area of the coating film from the substrate after holding at 70 ° C. for 20 hours was measured. (B) FFC property (filamentous rust property) A 20 mm cross cut is put on a 70 mm square coated plate,
Overhang with Erichsen centering on the intersection, 1 in 3% saline
After soaking for a period of time, take it out, wipe off the adhering solution,
Subsequently, the filamentous rust property was measured after storage at 45 ° C x RH for 10 days. (C) Sulfastene property A coated plate is punched out on a 202 diameter lid, boiled trout is filled and tightened, retorted at 120 ° C for 90 minutes, then stored at 55 ° C for 1 month, and can be opened to generate sulfastene. The degree was evaluated. (D) Actual can test Filling an empty can with milk coffee, sealing it with a lid made of tin coating on the inner surface, retorting at 125 ° C for 30 minutes, and then at 37 ° C x 6
After storing for a month, after opening the can, the state of the inner surface of the can body is observed and judged, and the amount of iron eluted into the contents is measured and the flavor is judged. ◯: Good condition without the above △: Quality unstable although within practical range ×: Not practical

[0030]

EFFECTS OF THE INVENTION According to the present invention described above, a welding can having excellent weldability in can-making welding and excellent corrosion resistance while reducing the amount of tin plating deposited as compared with the conventional tin-plated steel sheet. It has an excellent effect that a body can be manufactured, and a welding can of excellent quality can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a coating structure of a welding can body manufactured by the method of the present invention.

Claims (2)

[Claims] 1. A plating amount of 560 mg / m ² or more on a steel plate surface
By applying the reflow treatment after the tin plating of
The residual free tin content is 310 mg / m ² or more
Form a distributed tin layer and then chromate over it
Depending on the treatment, the amount of adhered chromium and metallic chromium of ^{2 to} 20 mg / m ²
Chromium oxide with an adhesion amount of 3 to 20 mg / m ^{2 in} terms of ROM
Chrome / chromate coating consisting of
For the surface of the surface-treated steel plate that should be the inner surface of the can body at least
After forming a coating film on the part excluding the edge parts on both sides,
The discontinuous tin layer after heat treatment has a tin adhesion amount of 50 mg.
/ M ² or more and distributed in the range of 10 to 60% of the steel plate surface
The coating film is heat treated so as to be in a state of, then, after undergoing a forming step, by applying pressure seam welding to both side edge portions of the coated can material, a surface-treated steel sheet forming a can body portion is obtained. at least Suzutetsu alloy layer, a chrome-chromate coatings consisting of chromium oxide coating weight 3 to 20 mg / m ² tin layer and deposition amount 2 to 20 mg / m ² of metallic chromium and chromium terms in this order on a substrate steel sheet Manufacturing of a welding can body characterized in that the tin layer in the portion excluding the welded portion has a tin adhesion amount of 50 mg / m ² or more and is distributed in the range of 10 to 60% of the steel plate surface. Method. ^2. An amount of adhesion of 5 to 200 mg / m ^{2 on} a steel plate surface
The method for manufacturing a welded can body according to claim 1 , wherein tin plating is performed after forming a base layer containing nickel .