JPS62259679A - Production of can body - Google Patents

Abstract

PURPOSE:To improve the weld quality of the can body by forming a side edge projecting part having a flat main part and the vertical side to the main part on wire electrodes of a welding machine and positioning an edge part of the can body in the neighborhood of the projecting part side to perform the mash- seam welding. CONSTITUTION:The inside and outside wire electrodes 15 and 16 are provided to a mash-seam welding machine and the side edge projecting part 18 having the flat main part 17 and the vertical side 18a is formed to the wire electrode surface in contact with a lap part 12 of a can body perform 11. When the can body edge part 12 is set in the neighborhood of the projecting part side 18a and the resistance welding is performed, the edge part side 18a and the projecting surface 18b control and prevent an irregular protrusion and splash of material. Accordingly, a flat difference part in level is formed to a weld zone and an eliminating stage of a surface treated layer of the edge part 12 is omitted and the weld quality can be improved.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention involves electric resistance mash seam welding of the overlapped portions of can body noriforms with wire electrodes facing each other on both sides.
This invention relates to a method for manufacturing can bodies used for food cans, carbonated beverage cans, etc.

(Prior art) Opposing edge parts of metal blanks such as tin-plated steel plates are overlapped using so-called Sudroninok welding of the type recently disclosed in Japanese Patent Publication No. 54-26213,
A method has been put into practical use in which a can body is manufactured by forming a can body silica foam having an overlapping part, and connecting the overlapping part with wire electrodes with flat surfaces on both sides, and welding the overlapping part with electrical resistance manotsuyu seam. There is.

In the case of this conventional mash seam welding method, the material near the end face of the edge portion freely protrudes in the circumferential direction in response to the waveform of the welding current, and a stepped portion with noticeable irregularities is likely to be formed in the welding direction. When the welding pressure is increased or the welding current is increased in an attempt to increase the welding strength, splash (molten iron droplets) tends to adhere to the vicinity of the stepped portion.

These noticeable irregularities and splashes on the step part can cause problems such as when the welded part is repaired with paint, etc., the paint film tends to be very thin or missing, making it difficult to obtain a satisfactory repair effect. arise.

In addition, in the conventional welding method described above, a surface-treated steel sheet having a surface-treated layer with relatively high electrical insulation, such as tin-free steel or ultra-thin nickel-plated steel sheet, is welded. It has been practically impossible to manufacture a can body with satisfactory weld strength by pine seam welding without removing the .

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for manufacturing a can body having a matte seam welded portion, which has improved repairability with paint or the like.

Even if the can body glyform is made of a surface-treated steel plate having a surface-treated layer with relatively high electrical insulation, such as tin-free steel, the present invention provides surface treatment from the edge to be welded. It is an object of the present invention to provide a method for manufacturing a can body having a mash seam welded portion having a practically satisfactory welding strength without removing any layers.

(Means for Solving the Problems) The present invention involves overlapping opposing edge parts of metal blanks to form a can body siliform having an overlapping part, and forming the overlapping part with wire electrodes on both sides thereof. A method of manufacturing a can body by welding electrically resistive seams to the wire electrodes, wherein the opposing surfaces of the wire electrode include a main portion with a flat cross section and a side surface substantially perpendicular to the main portion. A side edge protrusion is connected to the main part through the overlapping part, and the end surface of the edge part in the overlapping part is located on the main part near the side surface or is in contact with the side surface. Alternatively, the can body preform is fed in while slightly riding on the protrusion, so that the material near the end surface flows outward in the circumferential direction in close contact with the side surface during the welding, It is characterized by Manosh seam welding.

(Function) During mash seam welding, the material near the end face of the overlapping part flows outward in the circumferential direction closely to the side surface of the side edge protrusion, so the part corresponding to the conventional protruding iron or splash is It is crushed into a cross-sectional shape corresponding to the protrusion. Therefore, the stepped portion of the welded portion is defined by the side line protrusion, and is flat with no unevenness in the welding direction, and splash is also eliminated, improving repairability.

Even if there is a surface treatment layer with relatively high electrical insulation properties on the edge to be welded, the material near the end face of the ridge of the matshu seam welding will protrude, resulting in a surface that is almost perpendicular to the main part of the side edge protrusion. The amount of deformation of the material that is in close contact with the side surface and flows outward in the circumferential direction over the side surface onto the side edge protrusion is particularly large, and a large rack is generated in the surface treatment layer. Current can easily flow through the crack.

Therefore, even if the welding pressure is not particularly increased, welding can be performed relatively smoothly, and a pine seam welded portion having a practically satisfactory welding strength can be obtained.

(Example) In FIG. 1, 11 is a can body cylinder, and 12 is an overlapping portion. The can body preform 11 (only the main parts are shown) is made of tin-plated steel sheet, tin-free steel, ultra-thin nickel-plated steel sheet, ultra-thin nickel-tin composite plated steel sheet,
Ultra-thin tin-plated steel plate.

It is formed by overlapping opposing edges 11a and llb of a metal blank (not shown) such as a black plate. 13 and 14 are an inner electrode roll and an outer electrode roll, respectively; 15 and 1
6 are an inner line electrode and an outer line electrode, respectively. The inner wire electrode 15 and the outer wire electrode 16 are usually made of one continuous copper wire, and first serve as the inner wire electrode (or outer wire electrode) to weld the can body preform, and then become the outer wire electrode. (or the inner wire electrode) to weld the subsequent can body silicon ohm. As shown in the figure, the upper surface 15a of the inner line electrode 15 normally becomes the upper surface 16a of the outer line electrode 16. It is also possible to reverse the line electrode midway and use the same surface as the inner side for the outer line electrode.

Upper surface 15a1 of inner line electrode 15, that is, overlapping portion 12
The side facing the side is composed of a main portion 17 having a flat cross section and a side edge protrusion 18 extending along the side edge in the longitudinal direction.
The side edge protrusion 18 has a side surface 18a substantially perpendicular to the main portion 17;
The protruding surface 18b has a short cylindrical shape. The side surface 18a is preferably connected to the main portion 17 and the protruding surface 18b via a curved portion.

Similarly, the lower surface 16b of the outer line electrode 16 also consists of a main part 17 with a flat cross section and a side edge protrusion 18. It is formed to be located on the opposite side of the side edge protrusion 18. Therefore, side edge protrusions 18 are also formed on the lower surface 15b of the inner line electrode 15 and the upper surface 16a of the outer line electrode 16.

Therefore, the inner electrode roll 13 and the outer electrode roll 14
Grooves 13a and 14 for inserting the respective wire electrodes.
Recesses 9 and 20 corresponding to the side edge protrusions 18 are formed in the bottom surface of a, respectively, so that the main parts 17 of the inner wire electrode 15 and the outer wire electrode 16 are parallel to each other in cross section during welding. It has become.

In order to enable mash seam welding, the side surface 18 of each side edge protrusion of the inner wire electrode 15 and the outer wire electrode 16 is
Is the circumferential interval between a equal to the width of the overlapping portion 12?
It is set to be slightly larger than that. During welding of the loose mat seam, the protruding surface 18b comes into contact with the edge portions 11a and llb near the overlapped portion 12, causing a gap and a binting-like appearance near the welded portion 1 (see Fig. 2). Since there is no melted part of the side surface 18b,
The height is (thickness of overlapped part 12 - thickness of welded part 1) x
It is defined as slightly smaller than Richi. In addition to the short cylindrical shape, the shape of the protruding surface 18a is determined as appropriate within a range that satisfactorily performs mash seam welding.

The wire electrode having the above cross-sectional profile has a group with a cross-sectional shape corresponding to the side edge protrusion 18 provided upstream of the inner electrode roll 13 (or outer electrode roll 14) of the welding device. It can be formed by rolling a circle≠wire using rolling rolls. Alternatively, it can also be formed by passing a round steel wire through a die having a hole having the above-mentioned cross-sectional shape and die-molding it.

During welding, the lower edge portion 11 of the overlapped portion 12
The end surface 11a1 of a and the end surface 11b1 of the upper edge portion are,
Touching the corresponding side surface 18a or protruding surface 18b
The can body preform 11 is fed between the electrode rolls so that it slightly rests on top of the main part 17 or, as shown in FIG. 1, is located on the main part 17 near the side surface 18a.

As the manschume welding progresses, the thickness of the portion corresponding to the overlapped portion 12 decreases, and the material in this portion flows outward in the circumferential direction. Therefore, the material near the end surfaces 11a1 and 11b1 is in close contact with the side surface 18a, and normally the protruding surface 18b
A little will flow to the top. At this time, irregularly shaped so-called protruding iron and streak lashes with noticeable unevenness are regulated by the side surface 18a and the protruding surface 18b in the vicinity and disappear visually, and as shown in FIG. 2, the weld part IK welding A welded can body 3 in which a step portion 2 that is flat in the direction is formed is manufactured.

The metal blank that forms the can body preform is made of tin-free steel (electrolytic chromic acid treated steel sheet) or ultra-thin nickel-plated steel sheet, which has a relatively thick surface (usually 10 m9/m or more in metal chromium equivalent) and is electrically insulating. Even if the metal plate is made of a metal plate on which a chromate layer (hydrochromic oxide layer) is formed, as shown in Fig. By using inner and outer wire electrodes with
A can body having a welded portion with a practically satisfactory welding strength can be manufactured.

However, in this case, it is desirable to use a copper wire coated with tin or a tin alloy (for example, tin-zinc alloy, tin-lead alloy, etc.) (coating thickness is usually 05 to 10 g/m2) as the wire electrode. When bare copper wire is used for can body preforms made of the above-mentioned metal blanks from which the surface treatment layer has been removed, pitting and localized welding may occur. This is because it tends to occur on the surface of parts.

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

According to the findings of the present inventor, a so-called Sudroninok welding machine can be used to weld a can body preform having a relatively electrically insulating surface treatment layer in the overlapping portion of the above type using a conventional wire electrode with a flat surface. When welding a thick seam,
By applying a much higher welding force (per width of the overlapping part) than in the case of can bodies made of tin-plated steel sheets, the surface treatment layer (chromate layer) is destroyed and the electrical resistance of the surface is reduced. It has been found that, because of this, it is possible to perform Muncie seam welding.

However, in this case, due to the high pressure, both ends of the overlapping part, especially near the tail end, shift outward in the circumferential direction during welding, causing the weld width in this part to decrease, or in extreme cases. This results in a butt-like weld, and the weld strength of this part decreases, making it impossible to obtain a satisfactory weld that can withstand 7-run processing, neck-in processing, etc.

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 portion in the length direction of the overlapping part comes into contact with the wire electrode, it is heated by electrical resistance and becomes softened (the softening starting temperature of low carbon steel sheets is about 500 to 600°C), and the overlapping part is crushed. start. As a result, the bare material near the end surfaces of both edges, which have no electrically insulating surface treatment layer, protrudes.
It is in close contact with the side surface 18a of the corresponding line electrode. Also, the protruding surface 1
The material that rides on 8b undergoes large deformation, and the surface treatment layer thereon is destroyed. Therefore, it is presumed that the current from the wire electrode easily flows through the vicinity of the protruding end faces of both end edges, and the manosh seam welding progresses relatively smoothly.

(Effects of the Invention) According to the present invention, it is possible to manufacture a can body having a mash seam welded portion with improved repairability using paint or the like.

Furthermore, according to the present invention, even if the can body preform is made of a surface-treated steel plate having a surface-treated layer with relatively high electrical insulation, such as tin-free steel,
The present invention has the effect that a can body having a mash seam weld having a practically satisfactory welding strength can be manufactured without removing the surface treatment layer from the edge to be welded.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory longitudinal cross-sectional views of essential parts showing examples of the state immediately before and immediately after Manosh seam welding is performed by the method of the present invention, respectively. DESCRIPTION OF SYMBOLS 1... Welding part, 3... Can body, 11... Can body preform, 11 a, l l b --- Edge part,
1la1,11. b. ... End face, 12 ... Overlapping portion, 15 ... Inner line electrode, 16... Outer line electrode, 17... Main part, 13.
... Lateral protrusion, 18a... Side surface. Agent Patent Attorney Yue Zhou Fuji Department Figure 1 Figure 2

Claims (1)

[Claims] (1) Opposing edge parts of metal blanks are overlapped to form a can body preform having an overlapping part, and the overlapping part is made into electrical resistance mash seam by bringing wire electrodes into contact with both sides of the overlapping part. In a method of manufacturing a can body by welding,
The opposing surface of the wire electrode includes a main portion having a flat cross section;
It consists of a side edge protrusion that connects to the main part through a side surface that is substantially perpendicular to the main part, and the end surface of the edge part in the overlapping part is located on the main part near the side surface. Alternatively, the can body preform may be fed in such a state that it is in contact with the side surface or slightly rests on the protrusion, so that during the above welding, the material near the end surface is in close contact with the side surface and outward in the circumferential direction. A method for manufacturing a can body, characterized by performing mash seam welding so that the weld flows in one direction.