JPH0710437B2 - Matsushimu welding can barrel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a mash seam welded can barrel used for beer cans, carbonated beverage cans and the like.

(Prior Art) A welding can body used between beer cans and carbonated drinks is usually made by stacking opposing edges of metal blanks such as tin-plated steel plates, and electrical resistance mash seam welding at the stacked parts. (For example, by the method disclosed in Japanese Patent Publication No. 54-26213).

The thickness of the mash seam weld is usually about 1.1 to 1.8 times, preferably about 1.3 to 1.6 times the blank thickness, and the step with a relatively steep slope and irregular cross section is formed on the side of the weld. Parts occur. In order to prevent rusting and corrosion due to contents, this weld is usually repaired by applying paint, drying and forming a coating film. There is a problem that a thin portion is usually formed in the vicinity of the corner on the welding main surface side of the stepped portion, which makes it difficult to obtain a satisfactory repair effect.

(Problems to be Solved by the Invention) An object of the present invention is to provide a mash seam welded can body having an improved repairability by a paint.

(Means for Solving the Problems) In the mash seam welded can body of the present invention, at least one surface side of the welded portion, the stepped portion having the shelf portion substantially parallel to the main welding surface is repeated regularly in the welding direction. It is characterized in that an inclined step portion is formed between the shelf portion and the main welding surface and is connected to the main welding surface via the curved portion.

The shelves are preferably repeated in a wavy shape in plan view, and the total length of the boundary between the step portion on the welding seed surface side (hereinafter referred to as the upper step) and the shelves is It is preferable that the total length is about 20% or more.

(Operation) The applied coating easily accumulates near the boundary between each of the upper step portion and the lower step portion and the shelf portion substantially parallel to the main welding surface. An inclined step portion is formed between the shelf portion and the main welding surface so as to connect to the main welding surface via the curved portion. in this way,
Since the portion between the welding main surface and the step portion is the curved portion where the paint film is most likely to be thinnest during coating, the portion between the welding main surface and the step portion, that is, the curvature that is the corner on the welding main surface side of the step A relatively thick paint film is formed near the portion.

Further, the inclination of the stepped portion slows down the flow of the paint between the welding main surface and the shelf, and promotes the accumulation of the paint and the formation of a relatively thick paint film in the vicinity of the curved portion.

Therefore, the paint film in the vicinity of the curved portion and in the corner portion between the shelf portion and the lower step portion is prevented from being lost or extremely thinned, and the repairability by the paint is improved.

Further, since the step portions are repeatedly formed substantially regularly in the welding direction, and since large fluctuations of irregularities such as large protruding portions do not extend along the welding direction, the coating material can be applied in a stable state.

(Example) In FIGS. 1 and 2, 1 is a welding can barrel and 2 is a mash seam weld. The welded portion 2 includes an outer surface-side welded main surface 3 and an inner surface-side welded main surface 4 that substantially correspond to the outer surface and the inner surface of the overlapped portion, and the end surface (7 in FIG. The outer surface step portion 5 and the inner surface side step portion 6 are formed by the material in the vicinity (corresponding) extending outward in the circumferential direction.

Substantially flat shelves 8 and 9 extending substantially parallel to the main welding surface are formed on the step portions 5 and 6, respectively. Between the shelf 8 and the welding main surface 3, the welding main surface 3 and the curved portion 5a
A step portion 5a which is connected via 1 and which swells in a curved surface and is inclined is formed. Similarly, the shelf 9 and the welding main surface 4 are connected to each other via the welding main surface 4 and the curved portion 6a1.
A step portion 6a is formed which is gently curved and swells. As clearly shown in FIG. 1, the shelves 8 and 9 are repeatedly and regularly formed in the welding direction. Shelf 8,9
Is usually wavy corresponding to the waveform of the welding current,
That is, the vicinity of the portion corresponding to the peak value of the welding current is the peak portion, and the vicinity of the portion corresponding to the zero value of the welding current is the valley portion.

A boundary portion 10 between the upper step portion 5a, which is preferably a gently curved surface, and the shelf portion 8 which is a step portion 5 on the outer welding side main surface 3 side.
Extends linearly in the welding direction. Similarly, the boundary 11 between the upper step 6a of the inner surface side step 6 and the shelf 9 also extends linearly in the welding direction.

In the case of FIG. 1, the shelves 8 and 9 are formed over the entire length of the welded portion, but like the welded portion 12 shown in FIGS. 3 and 4, the shelving portion 18 is repeatedly formed on the step portion 15. It may be formed substantially regularly and intermittently. That is, the shelf portion is not formed in the portion 15b near the valley portion of the step portion 15 as clearly shown in FIG. Even in this case, the shelf 18
And the total length of the boundary portion 20 of the upper step portion 15a is about 20% or more, preferably about 50% or more of the total length of the welded portion,
Desirable for repair and improvement of paint.

For example, when the paint 13 is applied to the outer surface side of the welded portion 2, as shown in FIG. 2, the paint is applied on the vicinity of the boundary 10 between the shelf 8 and the upper step 5a, and on the shelf 8 and the lower step 5b. A portion of the coating material 13, that is, a relatively thick portion of the coating material, is likely to be formed on the vicinity of the boundary portion 14 between the welding main surface 3 and the welding main surface 3 via the welding main surface 3 and the curvature portion 5a1. Since the sloping step portion 5a is formed, it is possible to prevent the paint film in the vicinity of the curved portion 5a1 and in the corner portion between the shelf 8 and the lower end step portion 5b from being missing or becoming extremely thin. .

For that purpose, if the height h of the shelf 8 (9) from the can body body surface 1a on the lower step 5b side is H of the welding main surface 3,
It is preferably in the range of 0.2 to 0.8H, more preferably 0.4H to 0.6H. Also, the maximum circumferential width W of the shelf 8 (9) is
It is preferably 0.1 to 0.7 mm, more preferably 0.2 to 0.4 mm.

The welding can body having the mash seam welded portion as described above is manufactured, for example, as follows.

A tin cylinder steel plate, tin-free steel, ultra-thin nickel-plated steel plate, ultra-thin nickel-tin composite plated steel plate, etc. Mash seam welding is performed through the line electrodes 22 and 23 having the cross-sectional profile shown in FIG. Reference numerals 24 and 25 respectively denote an inner electrode roll and an outer electrode roll.

The line electrodes 22 and 23 are composed of a main portion 26 having a flat cross-section on the side facing the overlapping portion 21 and a side edge protruding portion 27.
27 is a sloped surface 27a connected to the main portion 26 via a curvature portion 28,
It has a protrusion surface 27b having a flat cross section and substantially parallel to the main portion 26. The side edge protrusions 27 of the inner line electrode 22 are located on the opposite side of the side edge protrusions 27 of the outer electrode 23 with respect to the overlapping portion 21 and pass through.

During welding, the can body preform 19 is placed on the electrode roll 2 with the end surface 7 of the overlapping portion 21 positioned on the main portion 26 near the inclined surface 27a or on the protruding surface 27a.
Ship between 4,25. End surface 7 by mash seam welding
The neighboring material extends outward in the circumferential direction as shown in FIG. 6, flows along the inclined surface 27a, and further flows along the protruding surface 27b as shown. Therefore, the welding can body 1 is formed with the welded portion 2 having the upper step portions 5a and 6a having a shape corresponding to the sloped surface 27a and the shelves 8 and 9 formed in contact with the protruding surface 27b.

When the welding current value is comparatively large and / or the welding pressure is comparatively high, the shelf portion like the welding portion 2 shown in FIG. 1 is used.
8,9 are formed along the entire length of the weld. When the welding current value is relatively small and / or the welding pressure is relatively low, the ledge 18 is likely to be intermittently formed along the weld, as in the weld 12 shown in FIG.

It should be noted that if a wire electrode having a cross-sectional profile of the above type is used, it is relatively electrically insulative like ordinary tin-free steel (the thickness of the chromium oxide layer is usually 10 to 25 mg / m ^{2 in} terms of metallic chromium). Even in the case of a surface-treated steel sheet having a high surface-treatment layer, it has practically satisfactory welding strength without removing the surface-treatment layer from the edge to be welded, and welding with substantially less splash etc. Parts can be formed. However, in this case, it is preferable to coat the wire electrode with a low-melting metal such as tin in order to prevent a pitting-like melt-damaged portion from being generated on the surface of the welded portion.

In the case of the special tein-free steel, which has a relatively low electrical insulation (contact resistance) of the surface treatment film, the wire electrode having the above-mentioned cross-section profile is left bare (that is, not covered with a low-melting metal such as tin). Even when used, a welded portion having a satisfactory weld strength can be formed without causing a pitting-like melt-dissipated portion, a splash, or the like.

As this type of special tein-free steel, the chrome oxide layer has a thickness of about ^{2 to} 8 mg / m ^{2 in} terms of metal chromium, or tein-free steel, or a large number of minute projections (for example, the diameter of the base portion on the metal chrome layer). Is 5 to 1000 nm and the density is 1
X 10 ¹¹ to 1 x 10 ¹⁴ pieces / m ² ) is formed, and the thickness of the chromium oxide layer is about 3 to 25 mg / m ^{2 in} terms of metallic chromium.

The present invention is not limited to the above embodiments,
For example, depending on the application of the can body, the welded body may have a stepped portion having a shelf formed only on the inner surface side or the outer surface side of the welded portion. When manufacturing a welding can body of this type, a normal linear electrode having a full width is brought into contact with the surface of the overlapping portion on the side of the step portion having no shelf portion.

(Specific example) Thein-free with a surface treatment layer consisting of a metal chromium layer with a thickness of 0.20 mm and a metal chromium content of 120 mg / m ² and a hydrated chromium oxide layer with a chromium oxide content of 18 mg / m ² (metal chromium conversion). From steel blank, without removing the surface treatment layer from the vicinity of the overlapping part, inner diameter 52 mm, overlapping part width 0.4 m
A can body preform having a height of m and a height of 136 mm was formed. The superposed portion of the can body preform was mash seam welded in a nitrogen gas atmosphere using the line electrodes 22 and 23 having a cross-sectional profile of the type shown in FIG.

The wire electrodes 23, 22 have a total width of 1.8 mm, and the protruding surface of the side edge protruding portion 27.
The height d of the 27b from the main portion 26 (Fig. 7) is 0.04 mm, the curvature radius γ of the inwardly sloped sloped surface 27a is 0.20 mm, the slope angle θ is 27 degrees, and the thickness is 6 g / m ² . It is made of tin-plated copper wire.

The can body preform 19 is fed between the electrode rolls so that the end surface 7 of the overlapping portion 21 is located on the inclined surface 27a,
As shown in Table 1, welding was performed at a welding speed of 55 m / min while changing the welding current and welding pressure to produce No. 2 to 5 welded can bodies. The can body of sample No. 1 has a bare wire electrode with a flat surface over the entire width, a thickness of 0.20 mm, and a tin plating amount of 2.
It was produced by welding in the same manner as above except that a tin-plated steel sheet of 8 g / m ² was used.

Epoxy phenol-based paint with a solid content of 20% by weight is applied to the inner surface of each welding can body by a spray method and dried (dry film thickness 15
μm), the product was canned, and the discolorability of the contents and the amount of iron elution were evaluated as shown in the notes of Table 1. First result
Show in vote.

Also, a metal micrograph of the inner surface of the welded part of the No. 5 can body (magnification 3
0) and a cross-sectional metallurgical micrograph (magnification: 120; corroded by a 5% picric acid alcohol solution) are shown in FIGS. 8 and 9, respectively. The inner surface metallographic micrograph (magnification 30) and cross-sectional metallographic micrograph (magnification 30) of the weld 32 of the No. 1 can body
120; corroded with 5% picric acid alcohol solution) are shown in FIGS. 10 and 11, respectively.

(Effect of the Invention) The mash seam welded can barrel of the present invention has an effect that the repairability of the welded portion by the paint is improved.

[Brief description of drawings]

FIG. 1 is a plan view of the vicinity of a welded portion of a welding can body which is a first embodiment of the present invention, FIG. 2 is a longitudinal sectional view taken along line II-II of FIG. 1, and FIG. A plan view of the vicinity of a welded portion of a welding can body which is a second embodiment, FIG. 4 is a vertical sectional view taken along line IV-IV of FIG. 3, and FIGS. 5 and 6 are welding can bodies of the present invention. FIG. 5 is a vertical cross-sectional view for explaining an essential part showing an example for manufacturing
FIG. 6 is a view just before welding is performed, FIG. 6 is a view showing a state immediately after the welding is finished, FIG. 7 is an enlarged longitudinal sectional view of an essential part of a wire electrode used in the example of FIG. 5, FIG. 8 and FIG. Is a surface metallurgical micrograph of a welded portion of a welding can body which is an embodiment of the present invention, FIG. 9 is a metallographic micrograph of a longitudinal section taken along line IX-IX in FIG. 8, and FIG. 10 is a comparative example. A surface metallographic photograph of the welded portion of the can body, and FIG. 11 is a metallographic photograph of a vertical section taken along the line XI-XI in FIG. 1 ... Welding can barrel, 2,12 ... Welded part, 3,4 ... Welding main surface,
5,6,15 ... Step, 5a, 6a ... Step, 5a1, 6a1 ... Curved section, 8,9,18 ... Shelf, 28 ... Curved section.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-56-113893 (JP, A) JP-A-56-33184 (JP, A) JP-A-57-7284 (JP, A) JP-A-59- 209490 (JP, A) Actually opened 61-14088 (JP, U)

Claims (1)

[Claims] 1. A stepped portion having a shelf portion substantially parallel to the main welding surface is formed on at least one surface side of the welded portion in a repeating manner in a substantially regular manner between the shelf portion and the main welding surface. A mash seam welded can body characterized in that an inclined step portion is formed which is connected to the main welding surface through a curved portion.