JPH0343945B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for manufacturing a welded can body, and more specifically to a method for manufacturing a welded can body, and more specifically, a food can body produced by electric resistance pine seam welding, which improves the repairability and aesthetic appearance of the welded part. This invention relates to a method of manufacturing a welded can body used for carbonated beverage cans, etc.

(Prior art) Opposite edges of metal blanks are overlapped,
A method for manufacturing a welded can body by forming a molded can body having an overlapping part, and electrically resistance mating seam welding the overlapping part using a pair of opposing electrode rolls having flat electrode surfaces. Are known.

The thickness of the welded portion resulting from this pine seam welding is approximately 1.3 to 1.7 times the thickness of the normal plate, and a relatively steeply sloped step portion (see 22 in FIG. 2) is formed on the side of the welded portion. During welding, when the welding pressure is increased or the welding current is increased in order to increase the welding strength, irregularly shaped so-called protruding iron (second
(see Figure 23), or a splash (splash of molten iron,
(not shown) are likely to adhere to the surface.

Therefore, when repairing these parts by applying paint, drying, etc. to prevent corrosion of the inner welds and their vicinity due to the contents, missing or very thin parts of the paint film are likely to occur. , it is difficult to obtain a satisfactory repair effect.

When used in a bad corrosive environment on the outside, similar problems occur at the weld on the outside.

If the contents are dry products, oily liquids, or oily aerosols, problems of internal corrosion are unlikely to occur. However, even in this case, irregularly shaped protruding iron or splashes that occur on the outer surface near the welded portion impairs the appearance and tends to reduce the commercial value. Further, on the inner surface side, the welded portion near the opening is visible after the can is opened, and the same problem is likely to occur.

Furthermore, in the conventional welding method described above, when using a can body formed body made of a surface-treated steel plate having a surface treatment layer with relatively high electrical insulation, such as stain-free steel, from the edge to be welded. It has been practically impossible to manufacture a welded can body with satisfactory welding strength without removing the surface treatment layer.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for manufacturing a welded can body having a pine seam welded portion, with improved repairability on at least one of the inner and outer surfaces.

Another object of the present invention is to provide a method for manufacturing a welded can body having a pine seam welded portion with improved aesthetic appearance on at least one of the inner and outer surfaces.

Even if the can body formed body is made of a surface-treated steel sheet having a surface-treated layer with relatively high electrical insulation properties, such as stain-free steel, the present invention provides for Still another object of the present invention is to provide a method for manufacturing a welded can body having a pine seam weld, which has a practically satisfactory welding strength without removing a treated layer.

(Means for Solving the Problems) The present invention includes forming a molded can body having an overlapping portion by overlapping opposing edge portions of metal blanks, and forming a can body molded body having an overlapping portion, and A method for manufacturing a welded can body by electrical resistance pine seam welding using electrode rolls, the electrode surface of at least one of the electrode rolls having a main part with a flat cross section and a sloped surface connected to the main part. The can body is formed of side edge protrusions, and the can body is formed such that the end face of the end edge in the overlapping portion is located above the main portion near the sloped surface or above the sloped surface. feeding the material so that the material near the end surface flows outward in the circumferential direction along the slope surface during the welding,
It is characterized by pine seam welding.

(Function) During welding, the material near the end face of the overlapping part flows outward in the circumferential direction along the slope, so even if protruding iron or splash is generated, it will not be possible to remove the material from the cross section corresponding to the side edge protrusion. It collapses into shape and substantially disappears, forming, with the flowed material, a weld step of a slope defined by the sloped surface, with improved aesthetics and repairability.

Even if there is a surface treatment layer with relatively high electrical insulation properties in the overlapping part of the can body molded body, if side edge protrusions are formed on both electrode surfaces, the overlapping part will be crushed by pine seam welding. When this happens, the bare end surface of the edge protrudes and comes into contact with the sloped surface, and the portion of the edge that comes into contact with the side edge protrusion is particularly deformed, causing cracks in the surface treatment layer. Since current easily flows between the sloped surfaces of both electrode rolls, through the protruding end face and the above-mentioned crack, welding is performed relatively smoothly, and a pine seam welded part with a practically satisfactory welding strength is formed. be done.

(Example) In FIG. 1, 11 is a molded can body, and 12 is an overlapping portion. The can body molded body 11 (only the main parts are shown) is made of tin-plated steel plate, stain-free steel, ultra-thin nickel-plated steel plate, ultra-thin nickel-tin composite plated steel plate, ultra-thin tin-plated steel plate, black plate, etc. is formed by overlapping opposing edges 11a and 11b of a metal blank (not shown). 13 and 14 are an inner electrode roll and an outer electrode roll, respectively.

In FIG. 1, the electrode surface 13a of the inner electrode roll 13 consists of a main portion 17 having a short cylindrical shape with a flat cross section and a side edge protrusion 18. Side edge protrusion 18
, a sloped surface 18a connected to the main portion 17, preferably having a relatively gentle slope, and a short cylindrical protruding surface 1.
It is equipped with 8b. The electrode surface 14a of the outer electrode roll 14 is flat and has a uniform short cylindrical shape.
Note that the width of the electrode surfaces 13a and 14a is set to the width of the overlapping portion 12 to enable pine seam welding.
is set to be larger than the width of the

During welding, as shown in FIG _.
The can body formed body 11 is fed between the electrode rolls so that the can body body 11 is positioned above the portion 17a of the main portion 17 near the sloped surface 18a. Note that, as shown in FIG. 3, which will be described later, the material may be fed so that the end surface _11a1 is located above the sloped surface 18a.

As the pine seam welding progresses, the thickness of the area corresponding to the overlap 12 decreases, and the material in this area flows outward in the circumferential direction, or extrudes. Therefore, the material near the end surface 11a ₁ is the slope surface 1
8a, or further along the protruding surface 18b, in a circumferentially outward direction. At this time, even if protruding iron (see 23 in FIG. 2) or splash (not shown) is generated on the outside of the lower surface 20 of the end surface 11a ₁ of the upper edge portion 11b, they will not be removed from the side edge protrusion 18. is crushed into a cross-sectional shape corresponding to the shape, substantially disappears, and together with the fluidized material,
As shown in Fig. 2, the inner step part 2 has a relatively gentle slope and is easy to repair with paint, etc.
form.

On the other hand, since the electrode surface 14a of the outer electrode roll 14 is entirely cylindrical, on the outer surface side of the welded part 1 of the obtained welded can body 3, protruding iron 23 with an irregular and highly uneven shape and welded Depending on the conditions, a substantially drooping outer surface step portion 2 with a steep slope may be formed by a splash (not shown).
2 is generated.

If you want to obtain a stepped portion 2 on the outer surface of the welded portion 1 that is similar to the inner stepped portion 2 and preferably has a relatively gentle slope, as shown in FIGS. 3 and 4, an outer electrode roll is used. The side edge protrusion 18 may also be provided on the right side of the electrode surface 14a of 14.

Depending on the use of the welded can body, if it is desired to obtain a stepped portion with a relatively gentle slope only on the outer surface side of the welded part, the electrode surface 14a of the outer electrode roll 14 may be
It is only necessary to provide the side edge protrusion 18 only on this side.

The height h, width, etc. of the side edge protrusion 18 are determined so that the side edge protrusion 18 does not come into contact with the lower surface of the upper edge 11b or the upper surface of the lower edge 11a during welding. is desirable. This is because spark marks are generated on the lower or upper surface portions that come into contact, impairing corrosion resistance. For that, height h is 0.5 x g
(g is blank plate thickness) or less, preferably 0.35
It is desirable that it be less than xg. Alternatively, in order to crush the protruding iron and obtain the stepped portion 2 having a relatively gentle slope, the height h is preferably 0.1×g or more, more preferably 0.2×g or more.

The shape of the stepped portion 2 of the obtained welded portion is the sloped surface 1
8a and becomes equal to the latter shape, but the slope angle θ (Fig. 1) of the slope surface 18a is
Desirably, the temperature is about 5 to 70 degrees, more preferably about 10 to 40 degrees. If the angle is less than about 40 degrees, it is possible to prevent extremely thin areas of the repair coating from occurring. Furthermore, it is preferable that the sloped surface 18a and the main portion 17 are connected via a curvature portion _18a1 having a radius of curvature of 0.1 mm or more. This is to prevent the occurrence of extremely thin parts of the repair coating.

The sloped surface can have an appropriate cross-sectional shape, and may be a curved surface slightly concave inward, as shown by 18a in FIG. 5, for example. In this case, the slope angle θ is A straight line connecting the end 17b on the slope surface 18a side of 17 and the end 18b ₁ on the slope surface 18a side of the protrusion surface 18b of the side edge protrusion 18,
It is defined as the angle θ formed with the extension line of .

As shown in FIG. 1, when the slope surface 18 and the protruding surface 18b are connected via the curved portion _18a2 ,
The curvature portion 18a ₂ becomes a part of the slope surface 18a.

Further, there may be no protruding surface 18b and only the sloped surface 18a. However, in this case, in order to prevent the generation of irregularly shaped protruding iron, the material is
It is desirable to weld under conditions that do not flow outward beyond 8a.

The metal blank that forms the can body is made of relatively thick top surface layer (typically 10 mg/m of metal chromium equivalent), such as stain-free steel (electrolytic chromic acid treated steel sheet) or ultra-thin nickel-plated steel sheet. ² or more), even if the steel plate is made of a surface-treated steel plate on which an electrically insulating chromate layer (hydrated chromium oxide layer) is formed, the side edge projections 18 are not formed as shown in FIG. By using the inner electrode roll 13 and the outer electrode roll 14, the welded part has a practically satisfactory welding strength over the entire length without removing the surface treatment layer including the chromate layer at the edge to be welded. Welded can bodies can be manufactured.

In this case, welding may be performed in air, but it is preferable to perform welding in an inert gas atmosphere (nitrogen, argon, helium, carbon dioxide, etc.) to prevent blackening of the welded portion due to oxidation.

According to the experience of the present inventors, the above type of
When performing pine seam welding using a conventional electrode roll with a flat electrode surface on a can body molded body having an electrically insulating surface treatment layer in the overlapped portion, the can body formed body made of tinned steel sheets is The welding force is much higher than that in the case (per the same overlap width)
By adding , the surface treatment layer (chromate layer) is destroyed and the electrical resistance of the surface is reduced, making pine seam welding possible.

However, in this case, due to the high pressure,
During welding, both lengthwise ends of the overlapping part, especially the blank edge at the tail end, shift outward in the circumferential direction.
The weld width in this area may decrease, or in extreme cases, the weld may become a butt weld, reducing the weld strength in this area, making it impossible to obtain a satisfactory weld that can withstand flanging, neck-in processing, etc. do not have.

In the case of the present invention, a satisfactory weld can be obtained for the above-described type of can body molded body even if the welding pressure is low enough to prevent the above-mentioned displacement of the overlapped portion. The reason is assumed to be as follows.

As soon as a specific part in the length direction of the overlapping part comes into contact with the electrode surface, it is heated by electrical resistance and becomes softened (the softening start temperature of low carbon steel sheets is approximately 500 to 600°C), and the overlapping part is crushed. begins to be As a result, the bare end surfaces of both edges without the electrically insulating surface treatment layer protrude and come into contact with the sloped surfaces of the corresponding electrode rolls. Furthermore, during crushing, the amount of deformation of the portions of both end edges of the overlapping portion that are in contact with the side edge protrusions becomes particularly large, so that cracks occur in the surface treatment layer. Therefore, it becomes easier for current to flow between the two sloped surfaces, through the protruding end surface and the above-mentioned crack.
It is assumed that welding is performed relatively smoothly.

(Effects of the Invention) According to the method of the present invention, at least one of the inner and outer surfaces has a stepped portion with a relatively gentle slope, and most of irregularly shaped protruding iron or splashes are present in the vicinity of the step portion with a relatively gentle slope. It is possible to manufacture a welded can body having a pine seam welded part that is rarely seen and has improved repairability and appearance.

Furthermore, even if the molded can body is made of a metal blank having a surface treatment layer with relatively high electrical insulation, the side edge protrusions can be removed without removing the surface treatment layer near the overlapped portion. By using the inner and outer electrode rolls, it is possible to manufacture a welded can body that has improved repairability and appearance as described above, and has a pine seam welded part that has practically satisfactory welding strength over the entire length. play.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are explanatory longitudinal sectional views of main parts showing the state just before welding is performed and immediately after welding according to the first example of the method of the present invention, respectively;
3 and 4 are explanatory longitudinal sectional views of main parts showing the state just before welding is performed and immediately after welding according to the second example of the method of the present invention, and FIG. It is an explanatory drawing showing a main part profile of an example of an electrode roll used in the method of the invention. DESCRIPTION OF SYMBOLS 1... Welding part, 2... Step part, 3... Welded can body, 11... Can body molded body, 11a... Lower edge part, 11a ₁ ... End surface, 12... Overlapping part, 13
... (inner) electrode roll, 14 ... (outer) electrode roll, 17 ... main part, 18 ... side edge protrusion, 1
8a...Slope surface.

Claims (1)

[Claims] 1. Opposing edge parts of metal blanks are overlapped to form a can body molded body having an overlapping part, and the overlapping part is electrically resistance mat seam welded by a pair of opposing electrode rolls to form a welded can. In the method for manufacturing a fuselage, the electrode surface of at least one of the electrode rolls is composed of a main part having a flat cross section and a side edge protrusion having a sloped surface connected to the main part, and The can body formed body is fed so that the end surface of the edge portion is located above the main portion near the slope surface or above the slope surface, and the surface near the end surface during the welding is A method for manufacturing a welded can body, comprising performing pine seam welding so that the material flows circumferentially outward along the sloped surface.