JPS6124258B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a welded metal can having an impulse-line welded seam on the side surface of the can body. In this specification, an impulse-line welded seam can refers to a can body in which the entire length of the metal can body side seam is simultaneously electrical resistance welded. Conventionally, a material metal plate (metal blank) was cut into a rectangular shape from a raw metal plate, the opposite sides of which were slightly overlapped, formed into a can body shape, and the overlapping portion of the formed body was electrically resistance welded. , can bodies having a welded seam on the side of the can body are known. These conventional methods of welding joints in can 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. Due to the high level of wear and tear, work must normally be stopped every few hours to replace the electrodes, leading to problems such as reduced productivity, lack of maintenance personnel, and unstable weld quality. There is. 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) Occurrence of go stone-like nuggets: This is a common phenomenon in rotating roller electrode welding, in which the structure of the material metal changes periodically along the length of the seam due to differences in thermal effects. This occurs because a portion heated to a high temperature and a portion heated to a low temperature occur periodically in each 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 is a phenomenon in which molten metal jumps 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 a protective coating, 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 tin plate (stainless steel plate) is used, so both can lead to corrosion of the contents. , leakage, decrease in vacuum level, etc. are likely to occur. (4) Formation of a black oxide film: The areas directly above and below the roller electrodes in the overlapped area and the surrounding areas become red hot, but the surrounding areas are exposed to the air, so an oxide film develops. To prevent this, special operations such as spraying with expensive inert gas are required. Since this oxide film is porous and cannot perform a corrosion protection function, it must be covered by applying a protective paint after welding. However, this oxide film is fragile and has poor adhesion to the base steel, so it is likely to peel off from the base steel together with the protective coating when the double seam portion is bent. Therefore, this type of can is not suitable for applications requiring corrosion resistance. Further, when the metal blank is tin plated (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 weld is also heated, tin reflow occurs in that area, increasing the amount of iron-tin alloy metal, which tends to cause corrosion and sulfide blackening. (5) Thermal distortion: The high-temperature area directly above, directly below, and in the vicinity of the roller electrode expands thermally and is welded as it is, 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. According to this proposal, at least one side of the metal blanks constituting the overlapping portion is embossed to provide a large number of small protrusions, and welding is first started by melting the tips of the small protrusions. . Therefore, this method has the disadvantage that splashes are likely to occur in the welded area. Furthermore, since the fixed electrode comes into direct contact with the overlapping part, the electrode becomes contaminated and
The electrodes are easily 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. Further, U.S. Patent No. 2,854,561 discloses a first electrode extending parallel to the inner surface of the overlapping portion of the can body-shaped molded body, and a first electrode that is in contact with the outer surface of the overlapping portion and is movable in a direction perpendicular to the overlapping portion. A method has been proposed in which each of the second thin plate-shaped electrodes is connected to a welding power source, and pressure is applied by a pressing body provided on the second plate-shaped electrode to simultaneously weld the entire overlapped portion. 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 multi-bead that is beautiful without the occurrence of black oxide film or thermal distortion, is sound and has excellent corrosion resistance without tearing, leakage, corrosion, etc. in the double seamed parts, etc. An object of the present invention is to provide a lap welded metal can having a welded part that can withstand processing and neck-in processing. Another object of the present invention is to provide a stack welded metal can made of tin plate, which has no exposed iron and a welded part with a narrow reflow width and excellent corrosion resistance. The above object of the present invention is to provide impulse-
In a metal can with a line-welded seam, the uniformity of the thickness in the longitudinal direction of the seam is determined by the ratio of the plate thickness tmax at the maximum thickness to the plate thickness tmin at the minimum thickness (tmax/ tmin), the uniformity is in the range of 1<tmax/tmin<1.05, and the amount of metal extension Mc in the can circumferential direction at the joint is equal to the metal blank plate thickness t.
This is achieved by the welded metal can of the present invention, which is characterized in that it satisfies the relationship Mc<1×t. In the above impulse-line welded metal can of the present invention, the plate thickness tmax of the maximum thickness portion of the joint on the side of the can body and the amount of extension of the metal in the height direction
Mh has the relationship tmax < 1.7 × t Mh < 0.5 × t with respect to the metal blank plate thickness t, and the maximum width W of the part affected by the welding heat is greater than 0.2 mm and less than 0.8 mm. Preferably, it is small. In the welded metal can of the present invention, the amount of metal extending in the circumferential direction of the can at the joint is defined as the end of the metal extending beyond the ends of the overlapping metal blanks at the joint. It refers to the length measured in the circumferential direction of the can (i.e., the direction perpendicular to the length direction of the seam), and in the present invention, it is considered to be based on the hot rolling that the seam undergoes when it is electrically welded with low resistance. This includes the length of both normal metal extrusion and splash caused by excessive heating at the nugget. FIG. 8 of the attached drawings is a schematic diagram of the joint portion for explaining the definition of the above-mentioned extension amount, and A of FIG.
B-1 in FIG. 8 shows the overlapping to form a seam before welding, B-1 in FIG. 8 shows the normal protrusion after welding, and B-2 in FIG. 8 shows the splash. In A of FIG. 8, E and E' indicate each end of the overlapping part 1a of the blank formed into the shape of a can body, and E and E' in B-1 and B-2 of FIG.
E' indicates each end after welding. In B-1 and B-2 of Fig. 8, the shaded parts are the extensions (protrusion and splash), and the amount of extension is the distance between the tips P, P' and the ends E, E'.
Represented by Mc. In FIG. 8 described above, the step at the overlapped end after welding is enlarged and schematically shown for convenience of explanation. This includes those welded by pressing until it is almost completely gone. As a result of research, the present inventors have found that the joints of metal cans welded using the rotating roller electrode method, which is the most commonly used conventional method, have a periodic change in plate thickness along the length due to the occurrence of nuggets. It has been found that this change in plate thickness is the main cause of various defects in welded metal cans produced by the roller electrode method.
In addition, in welded metal cans made using the parallel electrode method proposed in the past, the amount of metal extending in the circumferential direction of the can (including protrusion and splash) is large, and if this amount of extension exceeds a certain limit, the contents may It has also been found that this causes defects such as corrosion and elution of the extended metal or the occurrence of black sulfide, black spots, and rust. The present invention has been made based on these discoveries. The welded metal can of the present invention has the above-mentioned requirements for uniformity of joint plate thickness (tmax/tmin) and extension amount Mc. ―
It has the following advantages compared to wire welded cans. (1) The tmax/tmin requirements suppress the generation and development of oxide films on welds, improve adhesion and wettability with paint, provide excellent corrosion resistance to can contents, and prevent rust and sulfide blackening. Also, there is no occurrence of black spots, the storage stability of the contents is good, and no perforation occurs even after long-term storage. (2) Due to the requirements of Mc, it is easy to cover with correction paint, there is no corrosion or elution of the extended metal by the contents, there is no occurrence of black sulfide discoloration, sunspots, or rust, and the preservation of the contents is good. It is. Furthermore, in a preferred embodiment of the present invention, tmax
By making the value smaller than 1.7 times the blank plate thickness, it becomes easier to cover the seam with correction paint, and the amount of metal extension in the can height direction is reduced to 1/2 of the blank plate thickness. The smaller size prevents damage to the sealing rubber and thus provides a leak-free can. Furthermore, by reducing the width of the heat-affected zone to less than 0.8 mm, it suppresses the development of dendrite structures in the metal material, prevents damage caused by processes such as double seaming, and prevents the development of corrosion due to bubbles. can do. If the plate material is tin, tin reflow can be used to
It can suppress the occurrence and development of black oxidation, tin oxidation, and tin diffusion into the base iron, and prevent corrosion caused by the contents, and also prevent iron-tin, which causes sulfide blackening and corrosion. Increase in alloy layer can be suppressed. 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. The can of the present invention can be manufactured as follows. 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 method for manufacturing a can of 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 formed 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 molded can 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, 5b, a pair of wire electrodes 10a,
10b is fitted so as to be slidable and protrude. Each wire electrode 10a, 10b is provided on the right side in FIG. 2 and is supplied from a feed reel (29 in FIG. 5), 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.
is turned against the direction of travel of the can body and then passed through a guide hole 18 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 during welding and presses the overlapping portion. Similarly, the overlapping portion 1a needs to be pressed uniformly in the width direction as well. Therefore, it is necessary that the upper and lower line electrodes 10a and 10b are also parallel to each other in the width direction, that is, the interval 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 molded can body. In addition, the surface of the line electrode 10a in contact with the groove 5a and the overlapping portion 1a
It is preferable from the viewpoint of workability and wire electrode production that the surface 10c in contact with is parallel. Line electrode 10b
The same applies to 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 formed can 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 result in incomplete seaming and the risk of leakage of contents. . For this purpose, it is important that the entire overlapped portion 1a be located on the opposing surfaces 10c and 10d of the wire electrodes during welding. By doing so, the entire overlapped 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 surrounding areas. 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 well. The mandrel 2 is equipped with a paint supply pipe 11 and an air supply pipe 12 for supplying paint and air for spray protective painting of the inner surface of the welded part of the metal can body after welding. 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 right and left 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 formed can 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 formed can body 1. It rises when the molded can body is delivered. 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 (spring, (hydraulic, pneumatic, etc.) is provided. Further, a screw 8c is provided between the pressing body sliding portion 8b and the cam follower 8d, so that the height of the pressing body sliding portion 8b can be adjusted. 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 pressing of the overlapped portion immediately starts when the can body formed body 1 is positioned at the welding station 3 of the mandrel and comes to rest. 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 used to maintain a good temperature. 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 electrodes 4a and 4b via the transformer 22c. At the same time as the discharge ends, the thyristor 22e 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 is moved 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 molded can 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, very slight undulations may occur on the flat surface, but these undulations disappear after welding several times. Furthermore, as the number 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 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 the 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, and
When the output of circuit 24 is ON, the clutch engages,
The brakes are designed to work when turned off. 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 less than approximately 0.1 mm, it will be difficult to stack the cans uniformly along the length of the can body, and the overlapped portion will likely slip when pressed after stacking, 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 amount of current 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. In addition, in the welding station 3, the outer periphery of the formed can body 1 is pressed against the mandrel by a presser wink 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 about 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 at the overlapping part will be uneven, causing excessive current to flow locally, causing overheating, causing splashes, and forming a black oxide film. The stability of the weld is lost. 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 bond 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, if the time is longer than 80 msec, the heat will be transmitted to the vicinity of the overlapping part of the molded bodies, and the black oxidation in this part will become 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 longer the plate thickness and the 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, weld metal can body 1A along guide 30 extending from the tip of 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 non-porous, strong coating film 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, water-based 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. Although the spray coating method was described in the above embodiments, 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 double seaming, it is filled with carbonated drinks, non-carbonated drinks, fruit juice, fish and shellfish, other foods, and non-food items such as aerosols, and then sealed. The can manufacturing method of the present invention is not limited to the above-mentioned example. For example, as shown in FIG. It may be 5d.
Further, the opposing surfaces of the parallel electrodes may be simply flat surfaces. Alternatively, as shown in FIG. 7, two small protrusions 33 may be provided in the length direction on the opposing surfaces of the parallel electrodes, and a line electrode may be placed between them. In addition, the metal blank is formed into the shape of a can body by a so-called inverted type can making method, at welding station 3.
In this case, it may be performed using a presser wing. 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 clarified by way of 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 margin painted and printed. Made of 0.23mm thick stain-free steel (electrolytic chromic acid treated steel plate),
A blank of 234 mm x 85 mm was created. Next, the electrolytic chromic acid treated coating layer on both sides of the short edges of this blank having a width of about 1 mm was peeled off by ultrasonic waves to completely expose the iron surface. The blanks were formed into a cylindrical shape using a roll former so that the short side was oriented in the axial direction, and after being stacked and fixed at a welding station, a pressing force (35 kg/ mm ² ) and welded by applying current for 15 msec to obtain a welded can body (301 diameter, No. 5 can). The overlap width before welding was 0.3 mm, and the overlap width after welding was approximately 0.4 mm. The resulting welded can body was cut open, and the ratio of the maximum plate thickness (tmax) to the minimum plate thickness (tmin) of the welded part in one can was determined to examine the uniformity of the weld thickness. Furthermore, the amount of iron protruding in the circumferential direction of the welded part on the inner surface of the can was investigated and expressed as a multiple of the original plate thickness. Furthermore, the presence or absence of iron splatter in areas other than the welded areas was investigated. Furthermore, the welded area was filled with resin, the cross section perpendicular to the welding direction was polished, and the width of the heat-affected zone (a part that is structurally different from the base metal) was examined using 5% nital. FIG. 9 shows a micrograph of the cross section magnified 75 times. Furthermore, the amount of iron protruding from the welded end in the can height direction was measured and expressed as a multiple of the original plate thickness. Further, the maximum plate thickness of the welded portion was defined as the plate thickness of the welded portion, and this was expressed as a magnification of the original plate thickness. The samples for the above evaluation were 10 cans. Next, use a powder coating gun to apply epoxyphenol powder paint to the welded part of the outer surface of the can body so that the width is 7 mm and the dry coating thickness is 30 to 50 microns. Baked for 15 minutes in a hot air drying oven. This can body was flanged, and a lid made of stain-free steel whose inner surface was coated with epoxyphenol paint was double-sealed using a conventional method to prepare an empty can. When 300 ml of 2% ammonium thiocyanate aqueous solution is poured into this empty can and electrolysis is 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, the time required for a red reaction to appear on the inside of the can is The red color reaction value (seconds) was determined by measuring (10 samples). Furthermore, the above empty can was filled with boiled tuna, double-sealed with the same stain-free steel lid as above, sterilized by retort, stored at 50℃ for 6 months, and then opened. The state of corrosion and the occurrence of sunspots were examined (○...no sunspots, △...slightly present, ×...extremely present).
Furthermore, the number of perforated cans that occurred within six months was investigated (the number of samples in the above actual can test was 100 cans). Table 1 shows the results. No. 1 to No. 6 show that when welding is performed by applying pressure to the overlapping part with a parallel electrode via a wire electrode,
No.7 is No.8 when welding with a rotating roller electrode.
No. 9 is the result when welding was performed by applying pressure to the overlapping part with a rotating roller electrode via a wire electrode, and No. 9 is the result when only parallel electrodes were used. Experiments No. 1 to No. 6 are the can bodies of the present invention.
No. 7 to No. 9 are comparative examples. As is clear from the table, it can be seen that the can bodies of the present invention have excellent properties. Example 2 A welded can body (202 diameter,
200ml), the ratio of the maximum thickness (tmax) to the minimum thickness (tmin) of the weld, the amount of iron protruding in the circumferential direction of the weld, the presence or absence of splash, the width of the heat affected zone, and the weld edge. The amount of protrusion in the can height direction and the thickness of the welded part were investigated. Next, the inner welded part of the welded can body was coated with a polyester solvent slurry paint using an airless gun, and after baking for 4 minutes in a hot air drying oven at 180°C, the entire inner surface of the can body was coated with a polyester solvent slurry paint. It was spray painted using paint and an airless gun, and then baked. This can body is flanged, double-sealed with an aluminum easy-open lid coated with PVC paint on the inside, filled with colored carbonated beverages at 2°C, and the inside surface coated with epoxy phenol paint.
Furthermore, a lid made of stain-free steel coated with PVC paint was double-sealed, and the can was stored at 50℃ for 6 months.
The dissolved iron mg per 1000g (average value of 10 samples) and the discoloration of the contents were examined, and the flavor evaluation (10 panels, 5...excellent, 4...good, 3...fair, 2...Poor, 1...Poor). Furthermore, the number of perforated cans that occurred within 6 months was investigated. The results are shown in Table 2. No. 10 to No. 15 are welded by applying pressure to the overlapping parts with a parallel electrode via a wire electrode, No. 16 is welded with a rotating roller electrode, and No. 17 is a weld with a wire electrode. No. 18 shows the results when welding was performed by applying pressure to the overlapping portions using rotating roller electrodes, and when only parallel electrodes were used. Experiments No. 10 to No. 15 are can bodies of the present invention, and Experiments No. 16 to No. 18 are comparative examples. As is clear from the table, it can be seen that the can bodies of the present invention have excellent properties. Example 3 Epoxyphenol-based paint was applied to the inner surface of the can, and the seams of the can body were painted with a margin, and then baked, and the outer surface was also painted and printed with a margin of 0.23 mm, tin plating. 234mm from an electroplated tin plate with a thickness of 25ld/BB (tin layer thickness approx. 0.6μm)
A blank of ×85 mm was created. The blanks were formed into a cylindrical shape using a roll former with the short side oriented in the axial direction, and after being stacked and fixed at a welding station, a pressing force (30 kg/ mm ² ) and
Welding was carried out in the same manner as in Example 1 by applying current for 15 msec to obtain a welded can body (301 diameter, No. 5 can). The overlap width before welding was 0.3 mm and the overlap width after welding was approximately 0.4 mm. It was hot. From the obtained can body, the ratio of the maximum thickness (tmax) to the minimum thickness (tmin) of the welded part, the amount of iron protruding from the welded part in the can circumferential direction, the presence or absence of splash, the width of the heat affected zone, and the welded edge. The amount of protrusion in the can height direction, the plate thickness of the welded part, and the tin reflow width near the welded part were investigated (10 cans sampled). Next, the welded parts on the inner and outer surfaces of the welded can body were coated with a powder coating gun to a width of 7 mm and a dry coating thickness of 30 to 50 mm.
After applying epoxyphenol powder paint to a micron size, it was placed in a hot air drying oven at 180℃ for 15 minutes.
Bake for a minute. The above-mentioned can body was flanged and a tin lid whose inner surface was coated with epoxyphenol paint was double-sealed using a conventional method to prepare an empty can, and the red color reaction value was examined. Furthermore, the empty can was filled with boiled salmon, double-sealed with the same tin lid as above, sterilized in a retort, stored at 50℃ for 6 months, and then opened. The occurrence of black discoloration and the occurrence of rust were investigated (100 samples each).
can). Table 3 shows the results. No. 19 to No. 24 are welded by applying pressing force to the overlapping part with a parallel electrode via a wire electrode, and No. 25 is welding by applying a pressing force to the overlapping part with a parallel electrode via a wire electrode. When welding with pressure applied, and
No. 26 is the result when only parallel electrodes were used. Experiments No. 19 to No. 24 are can bodies of the present invention, and Experiments No. 25 to No. 26 are comparative examples. As is clear from the table, it can be seen that the can bodies of the present invention have excellent properties. Example 4 Welded a can body (202 diameter, 200ml) using an electroplated tin plate with a thickness of 0.17mm in the same manner as in Example 3.
After creating the weld, the ratio of the maximum thickness (tmax) to the minimum thickness (tmin) of the weld, the amount of iron protruding in the circumferential direction of the weld can, the presence or absence of splash, the width of the heat affected zone, and the weld edge of the can The amount of protrusion in the height direction, the thickness of the welded part, and the reflow width of tin near the welded part were investigated. Next, the can body was subjected to multi-beat processing, and then subjected to neck-in processing, and then the inner welded part of the can body was
After applying a polyester solvent slurry paint using an airless gun and baking it in a hot air drying oven at 180℃ for 4 minutes, the can body was flanged and an aluminum easy-open lid coated with a vinyl chloride resin paint was attached. Double-seal the can, fill it with orange juice at 90℃, double-seal the tin lid with an epoxy phenol paint applied to the inside, store it at 50℃ for 6 months, open the can, and remove the welds on the inside of the can. Corrosion state, iron elution amount, discoloration state of contents, flavor evaluation, and 6
The number of perforated cans that occurred within months was investigated. The results are shown in Table 4. No. 27 to No. 32 are welded by applying pressure to the overlapped part with a parallel electrode via a wire electrode, and No. 33 is a pressure applied to the overlap part by a rotating roller electrode via a wire electrode. No. 34 is the result when only parallel electrodes are used. Experiments No. 27 to No. 32 are can bodies of the present invention, and Experiments No. 33 to No. 34 are comparative examples. As is clear from the table, it can be seen that the can bodies of the present invention have excellent properties. Example 5 Plate thickness obtained by the same method as Example 1
After 0.17 mm stain-free steel cylindrical molded bodies (202 diameter, 200 ml) were stacked and fixed on a welding station, a pressing force (40 Kg/mm ² ) and welded by changing the welding voltage and applying current for 15 msec to create a welded can body. The amount of iron protruding from this welded can body in the can height direction at the inner welded end was investigated. Next, polyolefin solvent slurry paint was applied to the welded parts of the inner and outer surfaces of the welded can body using an airless gun to a width of 7 mm and a dry coating thickness of 30 to 50 microns, and then placed in a hot air drying oven at 170°C. Bake for 4 minutes. Further, a vinyl chloride resin paint was applied to the inner surface of the can body using an airless gun and baked. This can body is double-sealed with an aluminum easy-open lid coated with PVC paint on the inside, then filled with Coke at 2°C, base coated with phenol epoxy paint, and then coated with PVC paint. Double-seal the free steel lid and heat at 50℃ for 6 hours.
After storage for several months, the can was opened and the amount of iron eluted and flavor were examined. Table 5 shows the results. It can be seen that the can body of the present invention has excellent properties. Example 6 Plate thickness obtained by the same method as Example 3
Cylindrical molded body of 0.23mm tin plate (202 diameter, 200ml)
After overlapping and fixing them at a welding station, a pressing force (35 kg/mm ² ) was applied to the overlapping part of the molded bodies using a parallel electrode via a wire electrode, and welding was performed by changing the welding voltage and applying current for 15 msec. , a welded can body was created. The thickness of the welded portion was determined from this welded can body. Next, after correcting the welds on the inner and outer surfaces of the welded can body with polyester solvent slurry paint, an aluminum easy-open lid whose inner surface is coated with vinyl chloride resin paint is double-sealed using a conventional method, and the apple juice is Fill at 90℃, double seal with a tin lid coated with epoxyphenol paint on the inside, and heat to 50℃.
After being stored for 6 months, the can was opened and the welds inside the can were found to be corroded.
The amount of iron elution, flavor, and number of perforated cans were investigated. Table 6
The results are shown in It can be seen that the can body of the present invention has excellent properties.

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【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 shows a longitudinal cross-sectional view perpendicular to the axial direction of a parallel electrode according to one embodiment, and FIG. 7 shows a longitudinal cross-sectional view of a parallel electrode according to another embodiment. FIG. 8 is a schematic diagram for explaining the definition of the amount of protrusion of weld metal in the present invention. FIG. 9 is a micrograph showing a cross section of the joint of the welded metal can of the present invention, taken in a direction perpendicular to the joint. Main symbols in the drawings indicate the following parts of the device, respectively. 1...Molded object, 1a...Overlapping portion, 2...
Mandrel, 4a, 4b...Parallel electrode, 5a, 5
b...Guide recess, 6...Cooling hole, 10a, 10b
... wire electrode, 11 ... paint supply pipe, 12 ... air supply pipe.

Claims (1)

[Claims] 1. In a metal can having an impulse-line welded seam on the side of the can body, the uniformity of the thickness in the longitudinal direction of the seam is defined as the plate thickness at the maximum thickness ( The uniformity is in the range of 1<tmax/tmin<1.05 when expressed as the ratio (tmax/tmin) of the plate thickness (tmin) at the minimum part, and the can circumference at the joint part is A welded metal can characterized in that the amount of metal extension Mc in the direction satisfies the relationship Mc<1×t with respect to the metal blank plate thickness t. 2 Plate thickness tmax at the part where the thickness of the joint is maximum
The welded metal can according to claim 1, wherein tmax<1.7t with respect to the metal blank plate thickness t. 3. The welded metal can according to claim 1 or 2, wherein the maximum width W of the part of the joint affected by the heat of welding is 0.2 mm<W<0.8 mm. 4. The welded metal can according to any one of claims 1 to 3, wherein the amount of metal extension Mh in the height direction of the can satisfies the relationship Mh<0.5t with respect to the metal blank plate thickness t.