JPS6150075B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method and apparatus for manufacturing a welded metal can body, and more particularly to a method and apparatus for manufacturing a welded metal can body, and more specifically, a method and apparatus for manufacturing a welded metal can body, and more specifically, a method and apparatus for producing a welded metal can body that is beautiful and has excellent corrosion resistance by simultaneously electrical resistance welding the entire overlapped portion of can body shaped bodies through a wire electrode. The present invention relates to a manufacturing method and apparatus suitable for high-speed continuous production of welded metal can bodies. Conventional methods for manufacturing welded metal can bodies by welding overlapping portions of can body-shaped molded bodies are broadly classified into rotating roller electrode methods and parallel electrode methods. The rotating roller electrode method is described in U.S. Patent Specification No.
There is a method, such as that described in No. 3761671, in which fixed rotating roller electrodes are brought into direct contact with both sides of the overlapping part and seam welded under pressure. Since the welding process is intense, it is usually necessary to stop work every few hours and replace the electrodes, which causes problems such as reduced productivity, lack of maintenance personnel, and unstable weld quality. . As a means to solve this problem, a linear electrode that runs in synchronization with the workpiece is inserted between the rotating roller electrode and the overlapping part as described in U.S. Patent No. 2,838,651, and the seam is welded under pressure. A welding method has been proposed. In this case, the rotating roller electrode has a long lifespan, but the linear electrode is exposed to the air at the red-hot part of the welding area and is difficult to cool sufficiently, so it usually has a long lifespan due to contamination and wear. There is a problem in that only one round can be used, and therefore a linear electrode corresponding to the length of the welded can body is required. Furthermore, the following common drawbacks are generally recognized in the welded parts of metal can bodies welded by the above-mentioned rotating roller electrode method. (1) Generation of nuggets in the shape of a gossamer: This is a common phenomenon in seam welding, and occurs because high temperature areas and low temperature areas occur twice per cycle of the power supply. If you try to completely weld the middle between the nuggets, the temperature at the nuggets will become unnecessarily high, which will cause a thick oxide film to develop and cause corrosion or leakage when the can is filled with contents. easy. (2) Occurrence of splash: This refers to the phenomenon in which molten metal splashes out from the gap between the overlapping parts due to an excessive temperature rise in the nugget part and sticks to the periphery of the overlapping part. Splash that occurs on the inner surface of the can is Since it cannot be completely covered with paint, it is likely to cause corrosion, pitting, and deterioration of flavor due to metal leaching into the contents. (3) Metal protrusion: There are small triangular protrusions that protrude from the welded part of the can end in the height direction of the can, and protrusions that protrude in the circumferential direction of the can. This seems to be due to the fact that seam welding corresponds to a type of hot rolling. The former tends to damage the sealing rubber when double-sealing the can lid, thereby impairing its sealing ability, while the latter exposes the iron when tinplate is used, which can lead to corrosion, leakage, and vacuum of the contents. It is easy to cause a decrease in the degree of deterioration. (4) Generation of black oxide film: directly above the roller electrodes at the overlapping part,
The area immediately below and the surrounding area becomes red hot, but since the surrounding area is exposed to the air, an oxide film develops. To prevent this, special operations such as spraying with expensive inert gas are required. Because this oxide film is porous, it cannot perform the anticorrosion function, so it must be covered with a protective paint after welding. However, this oxide film is fragile and has poor adhesion to the base steel.
When the double seam part is bent, it is likely to peel off from the base metal along with the protective coating. Therefore, this type of can is not suitable for applications requiring corrosion resistance. Furthermore, if the metal blank is tinplate (tin-plated steel plate), as a black oxide film develops, tin oxidizes and diffuses into the base iron, resulting in iron exposure. Exposed iron may accelerate corrosion by the contents and may lead to leakage. Furthermore, since the vicinity of the welded part is also heated, tin reflow occurs in that part, increasing the iron-tin alloy layer and easily causing corrosion and sulfide blackening. (5) Thermal distortion: The high-temperature parts directly above, below, and in the vicinity of the roller electrode expand thermally and are welded as they are, so thermal distortion remains in the area near the welded part of the can after welding is completed. This spoils the appearance of the product. On the other hand, as a method for manufacturing a metal can body using parallel electrodes, U.S. Pat. , 1st
A method has been proposed in which an overlapping portion is inserted between a second electrode fixed to the upper end of a pressing body parallel to and facing the electrode, and resistance welding is performed under pressure. Then, as described in column 6, line 62 to column 7, line 13 and Figures 19 to 21 of the specification, at least one side of the metal blanks constituting the overlapping part is embossed to form a large number of A small protrusion is provided, and welding is started by first melting the tip of the small protrusion. Therefore, this method has the disadvantage that splashes are likely to occur in the welded area.
Furthermore, since the fixed electrodes come into direct contact with the overlapped parts, the electrodes are easily contaminated and worn out, and in the case of high-speed continuous can manufacturing, the electrodes often need to be replaced, which is a fatal defect from a productivity standpoint. have Further, in U.S. Patent No. 2,854,561, there is a first
and a second thin plate-like electrode that is in contact with the outer surface of the overlapping part and movable in a direction perpendicular to the overlapping part are connected to a welding power source, and the second thin plate-like electrode that is provided on the second plate-like electrode is A method has been proposed in which the entire overlapping portion is simultaneously welded by applying pressure using a pressing member. Although this method has the advantage of not requiring frequent exchange of electrodes, it has the following problems. Because the electrode is not forcedly cooled, the large current during welding causes the electrode to reach a high temperature, which tends to cause thermal distortion due to oxidation and thermal expansion of the welded part and the surface of the electrode.In particular, the second thin plate-shaped electrode is susceptible to thermal distortion. Therefore, it is difficult to apply uniform pressure to the overlapped portion, and splashes due to local melting are likely to occur. Furthermore, in the case of high-speed continuous production, the second plate-shaped electrode must be made longer in the lateral direction, which increases the size of the equipment. The present invention aims to solve the problems of the prior art as described above. In other words, the object of the present invention is to create a beautiful product without nuggets, splashes, protruding metal, black oxide film, or thermal distortion, and a sound product with no tearing, leakage, corrosion, etc. in double-seamed parts, etc. An object of the present invention is to provide a method and apparatus for manufacturing a lap welded metal can body that has a welded portion that is excellent in corrosion resistance and can withstand multi-bead processing and neck-in processing. Another object of the present invention is to provide a method and apparatus for manufacturing a lap welded metal can body made of tin plate, which has no exposed iron and a welded part with a narrow reflow width and excellent corrosion resistance. Still another object of the present invention is to provide a method and apparatus for manufacturing a lap resistance welded can body suitable for high-speed continuous can manufacturing with high productivity without interruption of work due to replacement of fixed electrodes. Another object of the present invention is to provide a method and apparatus for manufacturing a stacked resistance welded can body with a long wire electrode life. According to the present invention, in a method for manufacturing a welded metal can body by resistance welding the overlapping portions of the side edges of a molded body formed from a metal blank into a can body shape, a pair of metal can bodies cooled by a refrigerant are used. The molded body is placed so that the entire overlapped portion is located between the parallel surfaces of a pair of wire electrodes that are placed on the opposing surfaces of opposing parallel electrodes and whose opposing surfaces are parallel to each other. In the step of inserting, at least one of the parallel electrodes is moved so that the opposing surfaces approach each other to simultaneously press the entire overlapped portion, and then the parallel electrode is energized for a certain period of time to weld the overlapped portion. a step of moving at least one of the parallel electrodes to release the pressure, and then feeding the weld metal can body from between the wire electrodes; and a step of welding the wire electrodes after each weld at least once. There is provided a method for manufacturing a welded metal can body, comprising the step of moving the welded metal can body parallel to the direction of the overlapping portion. Further, according to the present invention, there is provided an apparatus for manufacturing a welded metal can body by resistance welding the overlapping portions of the side edges of a molded body formed from a metal blank into the shape of a can body, the above apparatus comprising parallel electrodes and A welding electrode made of a wire electrode is provided, the parallel electrode extends in the axial direction of the molded body, and is made of a pair of opposing parallel electrodes connected to a welding power source, and has a cooling hole therein through which a cooling medium flows. The first parallel electrode is fixed to the peripheral edge of the mandrel that supports the molded body, and the second parallel electrode is a pressing member that can move back and forth in a direction perpendicular to the central axis of the mandrel. The wire electrode is fixed to the tip of the body, and the wire electrode consists of a pair of wire electrodes slidably placed on the opposing surfaces of the parallel electrodes, and the opposing surfaces are mutually disposed. There is provided an apparatus for manufacturing a welded metal can body, which is equipped with welding electrodes that are parallel to each other, and the width of the opposing surfaces of the wire electrodes is larger than the width of the overlapping portion. The present invention will be explained in detail below. There are no particular restrictions on the type of metal blank used in the present invention, and aluminum plates, etc., can also be used, but among them, tinplate, which is commonly used as material for metal cans, stain-free steel, thin nickel-plated steel sheets, and phosphate-treated steel sheets. A coated or uncoated low carbon steel plate having a thickness of about 0.14 to 0.35 mm, such as a blackboard or a coated plate thereof, is preferably used. In the case of blanks with an electrically insulating film formed on their surfaces, such as stain-free steel, phosphate-treated steel plates, and painted plates, in order to obtain a good weld, at least both sides of the overlapping part of the blank should be Therefore, it is preferable to remove these films in advance using a suitable means such as a cutting tool, a milling cutter, a grinder, etc., or by applying ultrasonic waves to expose the iron surface. A metal blank cut to predetermined dimensions is formed into a cylindrical, square, or other can body shape, usually a cylindrical shape, and then the overlapped portions of the sides are resistance welded to form the can body. Welding in a broad sense includes fusion welding and forge welding, but
In the case of fusion welding, the welded part is once melted and then rapidly cooled, so it is easy to contain air bubbles, which can cause leakage of the contents of the can, and a fragile dendrite structure develops, which can cause breakage during the double seaming process. easy. Therefore, the welding in the present invention is preferably forge welding, that is, solid phase welding. The resistance welding method of the present invention is a method in which a pair of parallel electrodes presses and energizes the overlapped parts of the can body molded weights via a wire electrode, without using rotating roller electrodes, and welds all the overlapped parts at the same time. It is. The present invention will be described below with reference to the drawings. FIG. 1 is a schematic partially cutaway front view of a welded metal can body manufacturing apparatus showing an embodiment of the present invention, and FIG.
3 and 4 are partially enlarged sectional views of the vicinity of the overlapped portion in FIG. 1, respectively, immediately before pressing the overlapped portion. and the state after welding is completed. The can body molded body 1, which has been rolled by a can body forming machine (not shown), is fed by a feed pawl 16 from the right side in FIG. wing 9
is tightly attached to the mandrel. A pair of upper and lower parallel electrodes 4a and 4b are arranged in the welding station 3 in parallel to the axial direction of the mandrel 2. It is preferable that the parallel electrodes 4a, 4b have a length equal to or slightly longer than the entire length of the can body molded body 1. If it is too short, no current will flow to the lengthwise ends of the overlapping part, resulting in an unwelded part. If it is too long, an excessive current will flow to the ends due to the current wraparound phenomenon, resulting in a splash. This is because it is easy to cause Therefore, the can body molded body has upper and lower parallel electrodes 4a, 4
It is necessary to stand still directly above or below b. The opposing surfaces of the upper parallel electrode 4a and the lower parallel electrode 4b are parallel to each other. Grooves 5a and 5b, which are guide recesses, are formed on the opposing surfaces of the mandrel 2.
They are perforated parallel to each other in the axial direction, and have a U-shaped cross section. A cooling hole 6 penetrates inside the parallel electrode as close as possible to the guide grooves 5a and 5b, and cold water or cooling brine (for example, at -30°C) circulates inside the hole to cool the parallel electrode and the wire electrode. By cooling, the wire electrodes 10a, 10b are prevented from increasing in temperature during welding. If necessary, the cooling effect of the wire electrodes can be further improved by blowing cooling air from the outside. Further, the upper and lower parallel electrodes are connected to a welding power source (22 in FIG. 5) via conductive plates 7 provided in contact with each other above and below. The upper parallel electrode 4a is buried under the mandrel 2, and the lower parallel electrode 4b is fixed to the upper end of the pressing body 8. Preferably, the parallel electrodes are made of copper or a copper alloy. In the grooves 5a and 5b, a pair of wire electrodes 10a,
10b is fitted so as to be slidable and protrude. Each wire electrode 10a, 10b is supplied from a feed reel (29 in FIG. 5) provided on the right side of FIG. 2, and as the number of welding increases, the grooves 5a, 5b
The wire travels in one direction inside and is wound up by a take-up reel (28 in FIG. 5). Upper line electrode 10a
is the idler 14 attached to the tip of the mandrel.
After being turned in the direction opposite to the traveling direction of the can body, it is passed through a guide hole 13 passing through the mandrel and wound up. At least the opposing surfaces 10c and 10d of the line electrodes 10a and 10b are connected to the mandrel 2.
It is important that the plane be parallel to the axis of the plane. The overlapped portion 1a of the can body molded body 1 is directly pressed and energized by contacting the wire electrode, but if the pressing force is uneven, especially in the length direction, the overlapped portion 1a Contact surface 1 between blank edges in 1a
The electrical resistance at point (b) becomes non-uniform in the longitudinal direction of the overlapping length, and there is a risk that an excessive current will flow through the portion of low electrical resistance, causing local melting and splash. By the way, the inner surface of the can body molded body 1 is
It is in close contact with the mandrel 2 except for the vicinity of the overlapped portion, and therefore the overlapped portion 1a is also basically parallel to the axial direction of the mandrel 2. Therefore, the surfaces 10c and 10d of the wire electrodes that come into contact with the overlapping portion must be parallel to the axis of the mandrel 2 at least during welding. Therefore, the pressing body 9 also moves relative to the central axis of the mandrel 2 and presses the surfaces 10c and 10 of the wire electrodes.
d must be configured so that it is parallel to the axis of the mandrel 2 and presses the overlapping portion during welding. Similarly, the overlapping portion 1a needs to be pressed uniformly in the width direction as well. Therefore, the upper and lower line electrodes 10
It is necessary that a and 10b are also parallel to the width direction, that is, the distance between them is substantially constant.
Within the range that satisfies this condition, the opposing surfaces 10c and 10d of the wire electrodes may be flat or may be curved surfaces corresponding to the shape of the can body molded body. Further, it is preferable from the viewpoint of workability and wire electrode manufacturing that the surface of the wire electrode 10a in contact with the groove 5a and the surface 10c in contact with the overlapping portion 1a are parallel. The same applies to the line electrode 10b. Such a wire electrode can be easily produced by light flat rolling of a round wire. Furthermore, it is desirable that the entire overlapped portion be sufficiently matted by welding so that the thickness of the entire overlapped portion is substantially equal to the thickness of the other portions of the can body molded body. This is because if only a part of the width of the overlapped part is welded and the widthwise end of the overlapped part remains unwelded, it is difficult to completely protect this part with paint. This is because it is easily corroded by objects, etc., and in the case of double seams, only the overlapping joints are thick, creating a step, which may lead to incomplete seaming and leakage of contents. . For this purpose, it is important that the entire overlapping portion 1a be located on the opposing surfaces 10c and 10d of the wire electrodes during welding. By doing so, the entire overlapping portion can be sufficiently mashed as shown in FIG. 4. Furthermore, during welding, most of the overlapping part and its vicinity are in contact with the wire electrodes 10a, 10b cooled by the refrigerant, and are not exposed to the atmosphere, which means that the energization time described below is extremely short. Together,
This enables oxidation-free welding of overlap joints and their vicinity. The wire electrodes 10a, 10b are made of copper or a copper alloy, and preferably have a hardness (Witzkers hardness) of about 70 to 180. If it is lower than about 70, the part that contacts the overlapping part will be easily deformed locally due to the pressing force during welding, so it will be necessary to increase the amount of movement of the wire electrode. This is because if there are slight undulations on the parallel surfaces of the wire electrodes, it is difficult to apply a uniform pressing force because the parts do not fit together well. The mandrel 2 is equipped with a paint supply pipe 11 and an air supply pipe 12 for supplying paint and air for spraying and protective coating the inner surface of the welded portion of the metal can body after welding is completed. Further, since the mandrel 2 is cantilevered, a mandrel support 15 is provided at the upper part of the mandrel 2 in the gap between the left and right presser wings 9 to prevent it from bending upward when pressed by the pressing body 8. The mandrel support 15 is normally located above the mandrel 2 and the can body molded body 1, but when the pressing body 8 comes into contact with the overlapped portion 1a, it descends and supports the mandrel 2 through the can body molded body 1. The molded can body rises when it is fed out. FIG. 5 is a schematic diagram showing the welded metal can body manufacturing system of the present invention. The pressing body 8 is reciprocated up and down by a drive mechanism 18 driven by a motor. Drive mechanism 18
Although a cam mechanism, a crank mechanism, a cylinder mechanism, etc. are employed as the mechanism, a cam mechanism is illustrated in FIG. As is clear from FIG. 4, the position of the upper surface 10d of the lower wire electrode at the top dead center of the pressing body 8 is
It is located at a location lower than the lower surface 10c of the upper line electrode by the thickness of the metal blank. On the other hand, as is clear from FIG. 3, the position of the upper surface 10d of the lower line electrode at the initial stage of pressing is lower than the lower surface 10c of the upper line electrode by twice the thickness of the metal blank. Therefore, at the initial stage of pressing, the metal of the overlapped portion 1a is at a low temperature and thus has a large deformation resistance, and this combined with the fact that impact force is likely to be applied to the wire electrode. When an impact force is applied, a wire electrode made of copper or a copper alloy may be significantly deformed or, in extreme cases, may break. In order to prevent these accidents and to easily ensure the set pressing time, a buffer mechanism 20 ( (by spring, hydraulic pressure, pneumatic pressure, etc.)
will be provided. Further, a screw 8c is provided between the pressing body sliding portion 8b and the cam follower 8d,
The height of the pressing body sliding portion 8b is configured to be adjustable. This height adjustment makes it possible to adjust the pressing force and pressing time within a certain range. The cam mechanism 18 and the feed pawl 16 are synchronized so that when the can body molded body 1 is positioned at the welding station 3 of the mandrel and comes to rest, pressing of the overlapping portion immediately begins. It is desirable that the current be applied after a predetermined pressing force is reached. This is because if the current is applied when the pressing force is insufficient, the pressure on the overlapped portions will become uneven, leading to local overheating, which may cause splash. Therefore, a proximity switch 21 that is turned ON when the pressing body 8 rises to a position where a predetermined pressing force is applied is provided adjacent to the pressing body sliding portion 8b. , 4b are energized. There are no particular restrictions on the type of welding power supply circuit 22, but the energization time is approximately
If the time is longer than 20 msec, a commercial frequency power supply with a timer is preferably used. If the time is shorter than about 40 msec, a known electromagnetic energy storage type or electrostatic energy storage type power source is suitably used. FIG. 5 schematically shows an electrostatic storage type power source. When the proximity switch 21 is turned on, the thyristor 22a is triggered, thereby discharging the capacitor 22b and energizing the lower parallel electrode 4b via the transformer 22c. Thyristor 22e at the same time as the discharge ends.
is triggered, and the capacitor 22b is charged by the DC power supply 22d. The cam mechanism 18 is synchronized so that the lower parallel electrode 4b immediately starts descending after the energization (discharge) is finished and the welding is completed. It is not preferable to release the pressure while the current is being applied because sparks are generated and there is a risk of burnout of the welded portion. In synchronization with the above-mentioned lowering, the presser wing 9 is released, the feed pawl 16 slides on the feed pawl guide 17, and the welded can body formed body moves from the right side to the left side in Fig. 2. 1 from the welding station 3, ie between the wire electrodes. Subsequently, the next can body molded body 1 is fed into the welding station 3 and welded in the same manner as described above. As mentioned above, wire electrodes are usually manufactured by lightly flat rolling a round wire. At this time, slight undulations may occur on the flat surface, but these undulations disappear after several weldings. Furthermore, as the number of times of welding increases, the wire electrode adapts to the shape of the overlapping part, and an appropriate pressing force is applied to the entire area of the overlapping part. Under normal conditions, the wire electrodes 10a and 10b are welded repeatedly on the same part until the number of welds reaches several tens and the deformation of the wire electrode becomes large and it becomes difficult to obtain a uniform pressing force. Can be used for During this time, almost no oxidation of the wire electrode occurs. Therefore, the wire electrode may be moved in the same direction by the length of the can body every time several tens of cans are welded, or it may be moved little by little in the same direction every time one or several cans are welded. . After use, wire electrodes can be repaired and reused, or if they cannot be repaired, they can be melted and recycled into wire electrodes. In order to achieve the purpose of high-speed continuous can manufacturing, it is preferable that the wire electrodes be moved between the time when the pressing force by the pressing body 8 is released and the next pressing starts again. This embodiment will be explained with reference to FIG. Proximity switch 21 is turned on due to the rise of pressing body 8
A signal is input to the preset counter 23 each time. When the preset counter 23 receives a signal with a preset count value, it outputs an ON signal only until the next signal is input, and then turns ON again.
It is configured to start counting from. The output of the preset counter 23 mentioned above is sent to the AND circuit 2.
Enter 4. On the other hand, a proximity switch 25 is provided adjacent to a rotating plate 19 fixed to the rotating shaft of the cam mechanism 18. The rotary plate 19 is mainly made of a non-magnetic material, and is opposed to the proximity switch 25 so that the proximity switch 25 is turned ON only for a set time t during the period when the pressing body 8 is not pressing the overlapping portion. A magnetic body 19a is arranged on the surface. The set time t is the time required for the line electrode to move, and is determined from the set length of the line electrode's movement each time and the circumferential speed of the pinch roll 26, which is a drive device for the line electrode. The output of the proximity switch 25 is input to an AND circuit 24. The output of the AND circuit 24 is connected to a clutch/brake circuit 27 that constitutes the drive mechanism of the pinch roll 26.
When the output of the AND circuit 24 is ON, the clutch is engaged, and when it is OFF, the brake is engaged. Therefore, the pinch roll 26 rotates only for a set time t to feed the wire electrode in the direction of the take-up reel 28. Since the take-up reel 28 is driven by a torque motor, it takes up the wire electrode only while the pinch roll 26 is rotating. Next, the welding conditions will be explained when the substrate is a metal blank of 0.14 to 0.35 mm thick, which is a low carbon steel plate. The width of the overlapping portion 1a is preferably about 0.1 to 1.0 mm. As the plate thickness increases, this width increases within the above range. If the width is smaller than approximately 0.1 mm, it will be difficult to overlap the can uniformly along the length of the can body, and the overlapped portion will easily slip when pressed after overlapping, and the welding strength will also decrease. be. On the other hand, it is unnecessary for the width to be larger than about 1.0 mm from the viewpoint of welding strength, and on the contrary, the required current amount and pressing force increase, resulting in the disadvantage of making the equipment too large. From the overlapping width and the diameter of the mandrel at the welding station 3, the dimension of the metal blank in the direction perpendicular to the direction of movement of the mandrel is determined. Further, in the welding station 3, the outer periphery of the can body formed body 1 is pressed against the mandrel by a presser wing 9, which is provided on the outside of the mandrel and whose inner surface shape corresponds to the outer diameter of the mandrel. A portion 1a is formed. Pressure to press the overlapping part during welding (value obtained by dividing the pressing load by the pressing body 8 by the total area of the overlapping part)
is approximately 15 to 60 Kg/mm ² , preferably 25 to 45 Kg/mm ² . If the pressure is less than 15Kg/ ^mm2 ,
The contact resistance between the steels in the overlapping area becomes uneven, causing excessive current to flow locally, causing overheating, causing splashes, and forming a black oxide film, resulting in a loss of stability in the weld. . Furthermore, since sufficient mashing is not performed, the edges of the blank remain as they are even after welding, resulting in a step in the welded area. On the other hand, if the pressure is higher than 60 Kg/mm ² , the wire electrode will be severely deformed (indented) and the amount of movement must be increased. It is desirable that the current application time be approximately 3 to 80 msec, more preferably 5 to 30 msec. 3
If it is shorter than msec, a large welding current is required to obtain sufficient welding strength, and in this case, a large current is supplied in an extremely short period of time, so only the steel interface is locally melted. This is because splashes are likely to occur. On the other hand, when the time is longer than 80 msec, the heat is transmitted to the vicinity of the overlapped part of the molded bodies, and black oxidation in this part becomes significant. Heat also escapes to the wire electrodes, resulting in lower current efficiency and severe damage to the wire electrodes. The optimum energization time is determined by the plate thickness, width of the overlapped portion, pressing force, power supply voltage, waveform, etc. The larger the board thickness and overlap width, the longer the energization time needs to be. If it is necessary to cover the inner surface of the welded part with a protective coating, the welded metal can body 1A is attached along a guide 30 extending from the tip of the mandrel 2.
is sent to the left and, if necessary, is reheated to approximately 50 to 300°C by a preheating device 31 (such as a high-frequency heating coil or burner) to improve wetting of the paint, and then the paint is supplied. Pipe 11 and air supply pipe 12
The protective paint is sprayed onto the inner surface of the weld from a protective paint spray nozzle 32 (e.g., airless gas, in which case the air controls the spray pattern) provided at the tip of the weld. Next, the protective coating is melted or thermally hardened using a drying oven, burner, high frequency heating, etc., to form a strong, non-porous coating on the inner surface of the welded part and its periphery. Protective coatings include polyester, modified polyolefin, epoxy, acrylic, polyvinyl chloride, polyamide, vinyl acetate, polyvinyl acetal, polyether, polycarbonate, epoxy ester, phenol, amino, alkyd,
Powder coatings, dispersion-type coatings, hydrogen- or solvent-based slurry coatings, solution-type coatings, etc. obtained from one or more of polyurethane resins and silicone resins are used as appropriate depending on the purpose. In the above embodiments, a spray coating method has been described, but roll coating or other coating methods may also be used. The welded metal can body manufactured as described above is
After the bottom lid is usually secured by a double seaming method, carbonated drinks, non-carbonated drinks, fruit juice, fish and shellfish, other foods, non-food items such as aerosols, etc. are filled, and the bottom lid is sealed. In the overlap resistance welded can body manufactured by the method and apparatus of the present invention, most of the overlap part and its vicinity are not exposed to the atmosphere during welding, and the electrodes are sufficiently cooled by the refrigerant. Because of this, there is no need to install a special inert gas blowing device.
Beautiful welds with no black oxide film can be obtained. Therefore, the adhesion of the protective paint to the welded portion is excellent, and there is no fear that the protective paint will peel off during multi-bead processing, neck-in processing, and double seaming processing, and that part will be eroded. Also, when tinplate is used as a metal blank, a tin layer remains in the welded area, and almost no iron is exposed. Furthermore, since there is little alloying of tin around the weld, the corrosion resistance of the weld and its vicinity is excellent. In addition, since the entire overlapping part is welded simultaneously using a parallel electrode and a wire electrode without using a roller electrode, no gossel-like nuggets are generated, the surface of the welded part is flat and beautiful, and there is no thermal distortion. There are none. In addition, since there is almost no splash or protrusion of metal in the circumferential direction, the corrosion resistance after the protective coating is evaluated based on the amount of iron eluted, black sulfide, perforation, flavor of the contents, changes in can internal pressure, etc. ) is also excellent. Furthermore, by setting the pressing force during welding to an appropriate value and sufficiently mashing the weld, the thickness of the weld can be reduced to near the blank thickness, and the front and rear ends of the weld can be made of metal. Since protrusions do not occur due to protrusion, there is no risk of uneven welding during double seaming, resulting in incomplete seaming or damage to the sealing rubber, resulting in leakage of contents or changes in internal pressure. There is no possibility that this will occur. Furthermore, since the parallel electrodes do not come into direct contact with the welding area, they can be used semi-permanently and there is almost no need to replace them. In addition, the part of the wire electrode that comes into contact with the overlapping part, where the temperature rises the most during welding, is isolated from the atmosphere and is sufficiently cooled by the cooling fluid that circulates through the nearby cooling hole, so oxidation is prevented. This does not occur, and deformation is unlikely to occur. Therefore, not only when the blank is made of stain-free steel, but even when the blank is made of tinplate, welding can be performed several dozen times on the same part, as shown in the example below, which is unprecedented in the prior art. It has excellent effects. Furthermore, since the welding time is extremely short, high-speed can manufacturing of several hundred cans per minute can be easily achieved. The configuration of the present invention is not limited to the embodiments described above. For example, as shown in FIG. It may be hot. Further, the opposing surfaces of the parallel electrodes may be simply flat surfaces. Further, as shown in FIG. 7, two small protrusions 33 are provided in the length direction on the opposing surfaces of the parallel electrodes,
A wire electrode may be placed between them. Further, the metal blank may be formed into the shape of a can body by a so-called inverted type can manufacturing method using a presser wing at the welding station 3. Further, the upper parallel electrode may be on the top of the mandrel or other peripheral portions. The effects of the present invention will be further clarified by Examples below. Example 1 The seam part of the can body was painted with epoxyphenol paint on the surface that was to become the inner surface of the can (leaving an unpainted area), and then baked, and the surface that was to be the outer surface was also painted and printed with a thickness of margin. Made of 0.17mm stain-free steel (electrolytic chromic acid treated steel plate),
A blank of 165.7 mm x 101.3 mm was created. The electrolytic chromium-treated coating layer on both sides of the short edges of this blank, approximately 1 mm wide, was peeled off by ultrasonic application to completely expose the iron surface. Next, this blank is formed into a cylindrical shape using a roll former with the short side oriented in the axial direction, and this formed body is fed onto the mandrel of the welding station so that the overlapping part is located in the center of the wire electrode. Then, the overlapping width was set to 0.3 mm and fixed. Next, pressure was applied to the overlapping portion of the molded bodies with a parallel electrode via a wire electrode (welding pressure, that is, a pressing force of 45 kg/mm ² ), and then current was applied for 15 milliseconds to perform welding. Next, the surface temperature of the welded parts on the inner and outer surfaces of the can body was increased by high-frequency induction heating.
Preheated to 200℃, width 7mm, dry coating thickness.
After spray painting polyester slurry paint with an airless gun to a thickness of 30 to 50 microns, baking it in a hot air drying oven at 190℃ for 4 minutes, spray painting PVC paint on the entire inner surface of the can body with an airless gun. I did the baking. This can body is flanged, double-sealed with an aluminum easy-open lid whose inner surface is coated with PVC paint, filled with cola at 2°C, the inner surface is base coated with epoxy phenol paint, and the inner surface is coated with PVC paint. The container was double-sealed with a paint-coated stain-free steel lid and stored at 50°C for 6 months. The length of both the upper and lower parallel electrodes is 102 mm, and the grooves 5a and 5b provided in the parallel electrodes have a rectangular cross section.
It was 0.6 mm deep and 2.0 mm wide. Wire electrode is 1.4mm in diameter
Annealed copper wire (JIS 3102, electrical conductivity 100.0 or higher) was lightly rolled to a thickness of 1 mm, a flat part width of 1 mm, and a maximum width of 1.6 mm. The hardness after rolling is
Hv=95. In addition, the mechanism that applies pressure to the overlapped portion is implemented by a cam to avoid applying impact to the overlapped portion as much as possible. The power source was an electrostatic storage type (capacitor capacity 80,000 μF), which was charged to 380 volts and discharged by instantaneously passing current through the welding part via a welding transformer. The parallel electrodes were cooled with brine at -30°C, and cans were manufactured continuously at a welding speed of 450 cans/min. Note that the wire electrode was moved intermittently, and was moved by 3 mm for each welding. The overlapping width after welding was 0.4 mm. The surface of the welded part of the obtained can body had a metallic luster, was flat and beautiful, and there was no thermal distortion or formation of protrusions or splashes at the front and rear ends of the welded part. In addition, the thickness of the weld is determined by the cross-sectional micrograph perpendicular to the weld line in Figure 8 (magnification
135, etching solution 5% Pickleral, the welded area is near the tip of the arrow), the thickness is almost the same as that of the blank, and the structure is free of pores, indicating that forge welding, or solid-to-solid bonding, has been performed. This indicates that the A tensile test was conducted with the welded part perpendicular to the tensile direction, but fracture occurred at a location other than the welded part. Furthermore, the amount of iron protruding from the side seam of the can body and the presence or absence of splash were examined (the number of samples was 10 cans). Note that since the amount of protrusion varies along the weld line, the maximum value is shown in Table 1. The amount of protrusion was determined by microscopic observation of a cross section perpendicular to the weld line. Furthermore, after storage at 50°C for 6 months, the cans were opened and the corrosion state of the welded parts on the inside of the cans was examined (100 samples). Furthermore, iron elution amount (iron elution amount mg per 1000 g of content: number of samples
average value of 10 cans), and flavor (number of panels 10)
Person, 5...excellent, 4...good, 3...average, 2...
…Poor, 1…Poor) was investigated. Furthermore, the number of leaked cans and perforated cans that occurred within six months was investigated (100 cans each). The results are shown in Table 1. As a comparative example, Table 1 also shows the results of a method in which welding was performed by applying pressure to the overlapped portions only through parallel electrodes with flat opposing surfaces. In the case of the method of the comparative example, since continuous can manufacturing was not possible, can manufacturing was performed while replacing the parallel electrodes. Experiment No. 1 is an example of the present invention, and Experiment No. 2
is a comparative example. As is clear from the table, it can be seen that the method of the present invention has excellent properties.

[Table] Example 2 The seam part of the can body was painted with epoxy phenol paint on the surface that was to become the inner surface of the can with a margin, and then baked, and the surface that was to be the outer surface was also painted with a margin and printed to a thickness of 0.23 mm. , 234mm from an electroplated tin plate with a tin plating amount of 251b/B・B (tin layer thickness approximately 0.6μm)
A blank of ×85 mm was created. Next, this blank was formed into a cylindrical shape using a roll former, and by the same means as in Example 1, a pressing force (35 kg/mm ² ) of 15
Welding was performed continuously at a speed of 450 cans/min by applying current for msec. The power source was an electrostatic storage type (capacitor capacity: 80,000 μF), which was charged to 350 volts and discharged by instantaneously passing current through the welding area through the welding transformer. Next, the surface temperature of the welded parts on the inner and outer surfaces of the can body was raised to 190℃ using high-frequency induction heating.
Preheat to 6 mm in width and dry coating thickness of 40 to 60 mm.
Spray epoxy phenol powder paint with a powder coating gun so that it is 180 microns.
It was baked for 4 minutes in a hot air drying oven at . This can body is flanged, a tin lid with an epoxyphenol paint applied to the inside is double-sealed, the tuna boiled in water is filled, the same tin lid as above is double-sealed, and the retort is placed. It was sterilized and stored at 50°C for 6 months. The apparatus and other conditions used in the experiment were the same as in Example 1. From the obtained can body, the amount of iron protruding from the side seam and the presence or absence of splash, the amount of iron protruding from the welded edge in the can height direction, and the reflow width of tin near the weld were investigated (the number of samples was (10 cans each). Furthermore, when 300 ml of 2% ammonium thiocyanate aqueous solution was injected into a welded empty can and electrolysis was carried out at a voltage of 2 volts between the electrodes using the can as an anode and a carbon rod with a diameter of 6 mm as a cathode, it took until a red reaction appeared on the inner surface of the can. The time was measured and the red color reaction value (seconds) was determined (10 cans of samples). Furthermore, after storing at 50℃ for 6 months, the can was opened and the condition of black spots on the inner surface of the can was examined (〇...no black spots, ×
...Very likely). In addition, we investigated sulfide blackening, leakage status (indicated by change in can internal pressure in mmHg), and the number of perforations that occurred within 6 months (100 samples each).
can). The results are shown in Table 2. As a comparative example, an overlapping part was supplied between two fixed roll electrodes, one of which can be driven to rotate, through a wire electrode, pressure was applied, and an alternating current was passed through the overlapping part. I talked about how to weld. The inner and outer welded parts of the can body prepared in the comparative example were corrected using the same paint and method as described above. Experiment No. 3 is an example of the present invention; Experiment No. 4
is a comparative example. As is clear from the table, the method of the present invention has excellent properties.

[Table] Example 3 A can body (202 diameter, 200ml) was welded using the same method as in Example 2, using the same tin plate with a thickness of 0.23 mm.
was produced continuously at a rate of 450 cans/min. The welding conditions were a pressing force of 35 Kg/mm ² , a current application time of 15 msec, and an overlap width of 0.3 mm, and the wire electrode was moved by about 100 mm every 20 cans. Note that the power supply capacity and voltage were the same as in Example 1. Next, the welded parts on the inner and outer surfaces of the can body are preheated to a surface temperature of 200℃ using high-frequency induction heating, and epoxyphenol slurry paint is applied so that the width is 7 mm and the dry coating thickness is 40 to 60 microns. After the roll is painted,
It was baked for 4 minutes in a hot air drying oven at 180°C. Next, this can body was flanged, an aluminum easy-open lid whose inner surface was coated with PVC paint was double-sealed, Apple Youth was filled at 90°C, and the inner surface was coated with epoxy phenol paint. The tin lid was double-sealed and stored at 50°C for 6 months. The equipment and conditions used in the experiment were the same as in Example 2. From the obtained can body, we investigated the amount of protrusion of the side seam, the presence or absence of splash, the amount of protrusion of the welded edge in the can height direction, and the reflow width of tin near the welded part (the number of samples was 10 for each). can). Furthermore, after storage at 50°C for 6 months, the cans were opened and the corrosion state of the welded parts inside the cans, the amount of iron leached, the flavor, the changes in the internal pressure of the cans, and the number of perforations that had occurred within 6 months were investigated. 100 cans). The results are shown in Table 3. Note that the comparative example was conducted using the same method and conditions as the comparative example described in Example 2. Experiment No. 5 is an example of the present invention, and Experiment No. 6
is a comparative example. As is clear from the table, the method of the present invention has excellent properties.

[Table] Example 4 Using a tin plate with a thickness of 0.23 mm, a welded can body (301 diameter, 5
Cans) were produced continuously at a rate of 450 cans/min, filled with salmon water boiled in the same manner, and stored at 50°C for 6 months. The resulting can body was examined for red color reaction at the welded portion of the inner surface of the can body. Furthermore, after storage at 50°C for 6 months, the can was opened and the occurrence of black sulfide on the inside of the can was examined. In addition,
As a comparative example, welded parts were cooled with water at 25°C and cases where no cooling was performed. Regarding the comparative example, the other conditions were the same as described above. The results are shown in Table 4. Experiments No. 7 and No. 8 are examples of the present invention, and Experiment No. 9 is a comparative example. As is clear from the table, the method of the present invention has excellent properties.

[Table] Example 5 Using an electroplated tin plate with a thickness of 0.23 mm, a blank (234 mm x 85
mm), formed into a cylindrical shape, overlapped and fixed at a welding station, and then applied pressure to the overlapped part of the molded bodies with a parallel electrode via a wire electrode (welding pressure 40Kg/mm ² ), Welding was performed continuously using the welding time (current application time) and voltage shown in Table 5 to obtain a welded can body (30.1 diameter, No. 5 can). The power source is Example 2
The same one was used. Note that the wire electrode was moved 2 mm for each welding. Next, the welded parts on the inner and outer surfaces of the can body were corrected by the same method as in Example 1, the can body was flanged, and a tin lid whose inner surface was coated with epoxy phenol paint was double-sealed. Then, fill with boiled tuna, double-seal the same tin lid as above, perform retort sterilization, and heat to 50℃.
It was stored for 6 months. The apparatus and other conditions used in the experiment were the same as in Example 1. The condition of the inner welded part, presence or absence of splash, and red color reaction were examined from the resulting can bodies (10 cans each). Furthermore, after storing at 50°C for 6 months, the cans were opened and the corrosion state of the welded parts on the inner surface of the can and the occurrence of black sulfide discoloration were examined (100 samples each). The results are shown in Table 5. As is clear from the table, the method of the present invention has excellent properties.

[Table] Example 6 Using an electroplated tin plate with a thickness of 0.23 mm, a blank (165.7 mm x
101.3mm), formed into a cylindrical shape, overlapped and fixed at a welding station, and then applied pressure to the overlapping part of the molded bodies with a parallel electrode via a wire electrode (welding pressure 35Kg/mm ² ) , welding pressure shown in Table 6,
The welding can body (202
diameter, 200 ml). The same power source as in Example 1 was used. The apparatus and other conditions used in the experiment were the same as in Example 1. The obtained can bodies were examined for the amount of iron protruding from the side joints, the presence or absence of splash, the thickness of the welded parts, and the welding condition (10 samples each). Table 6 shows the results.
Shown below. As is clear from the table, the method of the present invention has excellent properties.

[Table] Example 7 Blackboard with a board thickness of 0.23 mm and the amount of tin plating on the board thickness 0.23 mm
From 251b/BB electroplated tin plate, 165.7mm×
A large number of 101.3 mm blanks were cut and can bodies were produced using the method of the present invention in Example 3. However, the wire electrode was not moved for each welding, but welding was performed repeatedly at the same position, and the feasibility of welding each time and the deformation of the wire electrode (expressed in thickness) were examined. The results are shown in Table 7. As is clear from Table 7, no welding defects due to wire electrode damage, oxidation, etc. occurred even after 40 weldings on either blackboard or tinplate. In other words, in the case of a blackboard, the welded part remains flat and beautiful even after 40 welding cycles, and has a metallic luster, while in the case of tinplate, although the luster characteristic of reflow tinplate disappears, it remains white.
There was no formation of a black oxide film. The thickness of the wire electrode decreased slightly as the number of welding increases, and in the case of tin, some tin adhesion was observed, but no adverse effect on welding strength was observed.

【table】 [Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view of a device that is an embodiment of the present invention, Fig. 2 is a longitudinal sectional view taken along line 2-2 in Fig. 1, and Fig. 3 is a superimposition of Fig. 1. FIG. 4 is an enlarged sectional view immediately before welding near the overlapping portion of FIG. 1, FIG. 5 is a schematic diagram of a system for carrying out the present invention, and FIG.
FIG. 6 is a longitudinal cross-sectional view perpendicular to the axial direction of a parallel electrode according to one embodiment, FIG. 7 is a vertical cross-sectional view of a parallel electrode according to another embodiment, and FIG. 8 is a longitudinal cross-sectional view of a parallel electrode according to the present invention. A microscopic photograph of the vicinity is shown. DESCRIPTION OF SYMBOLS 1... Molded object, 1a... Overlapping part, 2... Mandrel, 4a, 4b... Parallel electrode, 5a, 5b
...Guiding recess, 6...Cooling hole, 8...Press body, 1
0a, 10b... wire electrode, 11... paint supply pipe,
12...Air supply pipe.

Claims (1)

[Scope of Claims] 1. In a method for manufacturing a welded metal can body by resistance welding overlapping portions of side edges of a molded body formed from a metal blank into a can body shape, a pair of metal can bodies cooled by a refrigerant are provided. The molded body is arranged so that the entire overlapped portion is located between the parallel surfaces of a pair of wire electrodes, the opposing surfaces of which are parallel to each other. The step of inserting at least one of the parallel electrodes so that the opposing surfaces approach each other simultaneously presses the entire overlapped portion, and then energizes the parallel electrode for a certain period of time to weld the overlapped portion. moving at least one of the parallel electrodes,
After the pressure is released, the weld metal can body is sent out from between the wire electrodes, and the wire electrode is moved parallel to the direction of the welded overlapping portion after each welding is completed at least once. A method for manufacturing a welded metal can body, comprising: 2. The method for manufacturing a welded metal can body according to claim 1, wherein the base of the metal blank is a low carbon steel plate. 3. The method of manufacturing a welded metal can body according to claim 1, wherein the metal blank has a thickness of about 0.14 to 0.35 mm. 4. The method for manufacturing a welded metal can body according to claim 1, wherein the width of the overlapping portion is about 0.1 to 1.0 mm. 5 The pressure to press the overlapping part is approximately 15-60Kg/mm ²
A method for manufacturing a welded metal can body according to claim 1. 6. The method for manufacturing a welded metal can body according to claim 1, wherein the energization time is about 3 to 80 msec. 7. The method for manufacturing a welded metal can body according to claim 1, wherein cooling gas is blown onto the wire electrodes in the overlapped portion. 8. In an apparatus for manufacturing a welded metal can body by resistance welding the overlapping parts of the side edges of a molded body formed from a metal blank into the shape of a can body, the above-mentioned apparatus is a welding type consisting of parallel electrodes and wire electrodes. comprising a pair of parallel electrodes extending in the axial direction of the molded body and connected to a welding power source, each of which has a cooling hole through which a cooling medium flows, and The first parallel electrode is fixed to the peripheral edge of the mandrel that supports the molded body, and the second parallel electrode is fixed to the tip of the pressing body that can move back and forth in a direction perpendicular to the central axis of the mandrel. The line electrodes are comprised of a pair of linear electrodes slidably placed on opposing surfaces of the parallel electrodes, the opposing surfaces being parallel to each other and An apparatus for manufacturing a welded metal can body equipped with a welding electrode, wherein the width of the corresponding surface of the electrode is larger than the width of the overlapping portion. 9. The welded metal can body manufacturing apparatus according to claim 8, wherein the opposing surfaces of the parallel electrodes are provided with guide recesses whose vertical cross-sectional shape perpendicular to the axis is U-shaped. 10. The welded metal can body manufacturing apparatus according to claim 8, wherein the opposing surfaces of the parallel electrodes are provided with guide recesses whose vertical cross-sectional shape perpendicular to the axis is L-shaped. 11. The welded metal can body manufacturing apparatus according to claim 8, wherein the surface of the wire electrode in contact with the parallel electrode and the surface in contact with the overlapping portion are parallel. 12 The hardness (Witzkaas) of the wire electrode is approximately 70~
180. The welded metal can body manufacturing apparatus according to claim 8, wherein the welded metal can body is 180. 13. The welded metal can body manufacturing apparatus according to claim 8, wherein the mandrel is provided with a coating protection paint supply pipe and an air supply pipe for coating and protecting the inner surface of the welded part of the welded metal can body.