JPH0146232B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is applicable to forming joints of metal containers, particularly side seams of can bodies of three-piece cans.
This invention relates to a wire electrode welding device for a metal container, which forms a side seam on the surface of which an oxide film of a predetermined thickness or more is not formed by exposing the moving metal container to a sprayed and retained inert gas atmosphere immediately after electric resistance welding. PRIOR TECHNOLOGY As a means of electrical resistance welding the joints of metal containers of this kind at high speed and continuously, the method is to pass an electrode wire between a pair of upper and lower electrode rollers, and high-temperature resistance heating is concentrated on the joint. It is well known that when the lap surface is melted, an oxidation reaction with the oxygen atmosphere surrounding the seam is inevitably excited, and an oxide film is formed on the seam surface that takes on a unique color depending on the thickness of the film. It is being This is caused by the interference of reflected light in the oxide film, and follows the general principle of light interference in thin films. Table 1 shows the thickness of the metal oxide film and its reflected light.

[Table] The oxidation of metals, which is a factor in the formation of film thickness, causes rust at room temperature, but the oxidation rate is not that great. However, at high temperatures of 550 degrees C or higher caused by resistance welding heat, the oxidation reaction occurs violently, causing the seams to deteriorate. naturally causes discoloration as shown in the table above. However, the discolored weld seam looks out of place with the other parts, which have the unique color and luster of the surface metal surface material, and this impairs the aesthetic appearance and weakens the consumer's desire to purchase, which is the biggest obstacle to its widespread use as a practical product. In addition, the thickness of the oxide film that forms on the seam surface exhibits the characteristic color shown in the table above, and the thicker it becomes, the more difficult it is for the transparent paint to coat the seam in the subsequent process. To make matters worse, during subsequent process operations (using flangiers, netscars, seamers, etc.), the oxide film often peels off along with the correction coating, exposing the bare metal, which only leads to elution of the bare metal and corrosion of the melt. However, it has been found that the oxide film looks bad and causes quality deterioration. Therefore, the biggest technical difficulty to be overcome for the widespread practical use of welded metal containers is how to reduce the thickness of the oxide film that is inevitably produced during welding, and how to maintain the unique color and luster of the surface metal material itself. It depends on whether the control is suppressed to the extent that it does not inhibit the process and also does not deteriorate the processing adhesion of the correction coating. Problems to be Solved by the Invention In view of the above-mentioned conventional drawbacks, the present invention seeks to provide a wire electrode welding device that is exposed to an inert gas atmosphere immediately after electrical resistance in order to suppress the oxide film formed on the joint surface to below a certain level. It is something. Means for Solving the Problems A first embodiment of the apparatus of the present invention applied to metal cans will be described with reference to FIGS. 1 to 3. The manufacturing apparatus A of the present invention includes an upper electrode roller 3 fixed between the bifurcated ends 1a and 1b of a drive roller shaft 2, which is rotatably supported through the bifurcated ends 1a and 1b of the lower end of the hanging bracket 1; A lower electrode roller 6 is rotatably attached to a fixed shaft 5 that is fixed through the bifurcated ends 4a and 4b at the end of the guide rod 4, which guides the can body β, which is held by wrapping the side seam α, and the upper and lower electrode rollers. 3,6
Upper and lower electrode wires W ₁ wrapped around the outer circumference,
Immediately after the side seam α passes the welding point P between W ₂ and over a predetermined section, inert gas blowing nozzles 7 and 8 are arranged facing each other in a vertical line with the feed line L of the side seam α sandwiched therebetween. It becomes. In the figure, 9 is a drive wheel that is fixed to the drive roller shaft 2 end and transmits torque by wrapping an endless chain or endless belt 10 around it, and 4c is a lower electrode wire W ₂
This is an ascending through groove. The upper and lower blow-off nozzle groups 7 and 8 have their starting bifurcated ends 11a and 11b straddled over one side of the upper electrode roller 3 and fixed to the front side of the lower part of the bifurcated ends 1a and 1b of the hanging bracket 1 with bolts 12 and 13. The lower surface of the upper gas distribution box 11, which is cantilevered over the entire length of a predetermined section at right angles and horizontally to the hanging bracket 1, and the T-shaped end 14 at the starting end.
straddle the fork ends 4a and 4b of the guide rod 4 and fix it with bolts 15 and 16 to complete the upper gas distribution box 1.
1 and the upper surface of the lower gas distribution box 14 cantilevered over the entire length of a predetermined section in parallel to the upper electrode wires W ₁ and W ₂ . Moreover, they are arranged opposite to each other in a staggered manner. In addition, the right-angled bent end of a supply pipe 17 that hangs vertically and communicates with the internal gas chamber 11c is connected to the upper part of the terminal surface of the upper gas distribution box 11 with a nut 18, and is connected to the terminal surface of the lower gas distribution box 14. A bent end of a supply pipe 19 extending along the lower side of the guide rod 4 and the lower gas distribution box 14 and communicating with the internal gas chamber 14c is connected to the lower part with a mounting nut 20. In the embodiment of the present invention, the upper and lower blowout nozzles 7,
The 8th group is a protruding type, but the upper and lower gas distribution boxes 11, 14
It is also possible to make the opposing surface side thicker directly or to attach a thick plate and pass the upper and lower blow-out nozzle hole groups therethrough. Function Since the present invention is constructed as described above, prior to welding work, an inert gas source (not shown) is supplied to the upper and lower gas distribution boxes 1 through intermediate supply pipes 17 and 19.
Inert gas is supplied into the gas chambers 11c and 14c of gas chambers 1 and 14. Upper and lower blow-off nozzles 7 and 8 groups or blow-off ports 37 and 3 are located on the outlet side of the metal container that moves at the same time as storage.
Inert gas is ejected from the 8th group toward the feed line L of the side seam α at a set pressure of 0.1 to 20 m ³ /hour to a predetermined section of the feed line L immediately after the welding point P between the upper and lower electrode wires W ₁ and W ₂ . is suspended and suspended to create a stable inert gas atmosphere. Under such environmental conditions, the can body β, which has been bent and held the side seam α wrapped, is wound around the guide rod 4 and rotated in the direction of the arrow at a speed of about 7 m/min or more, for example about 10 m/min.
When the wire is fed at a conveying speed of around m/min and passes between the upper and lower electrode rollers 3 and 6, the upper and lower electrode wires W ₁ and W ₂ become electrically connected through the side seam α, generating high-temperature resistance heat. Then, the lap surface is softened and pressure welded, but at this time, the starting end of the side seam α starts to penetrate into an inert gas atmosphere that cuts off contact with the outside air, and a predetermined section along the feed line L after passing between the upper and lower electrode rollers 3 and 6 is formed. , inert gas is sprayed onto the inner and outer surfaces of the side seam α from the upper and lower blowing nozzles 7 and 8, and the air is forced to rapidly cool down to a temperature that does not promote the formation of an oxide film while passing through an inert gas atmosphere. Send it to the paint film correction process. Effects Here, various experimental comparisons will be made between the case of the present invention in which lap seam welding is performed in an inert gas atmosphere and the case of a conventional example in which lap seam welding is performed in the atmosphere. (1) In the case of the present invention The present invention refers to reflow tinplate (plate thickness 0.23 mm,
Plating amount #25...Outer side FreeSn amount 2.12g/m ² ,
Alloy Sn content 0.60g/m ² ), chromium-treated steel plate (chromium oxide 15mg/m ² , metal chromium 100mg/m ² )
Seam welding was performed under the following welding conditions in a N2 gas stream using a black plate (from which the surface chromium layer of a chromium-treated steel plate has been peeled off), and then the appearance of the oxide film thickness of the welded area (reflected light),
Weldability, processing adhesion, and chemical resistance were measured. The measurement method was as follows. Oxide film thickness Using EXCA (X-ray photoelectron spectrometer), Ar
While etching the surface with gas, Sn, O,
The oxide film thickness is measured based on the Fe element concentration ratio. Appearance Visually observe the oxide film thickness. Adhesion Apply nylon powder as a paint to the welded area and bake at 300 to 320℃ for 15 to 20 seconds to a thickness of approx.
Form a coating film of 80 to 100μ and use it as a sample.
This coating film is forcibly peeled off from the board and the adhesion is visually observed to see if the oxide film has migrated to the coating side. Processing Adhesion Two types of paint are used: epoxy powder and epoxy urea solvent-based paint, and the epoxy powder forms a coating film with a thickness of about 40μ under the same method conditions as above. In addition, epoxy urea-based solvent-based paints are applied with a brush at 280°C.
Baked for 10 seconds to form a coating film with a thickness of approximately 13 to 15μ and use it as a sample. Each sample was bent into a U-shape and the micro-racks generated on the coating in the processed area were observed under a microscope to check the adhesion of the process. Chemical resistance A sample using the same method and conditions as above using epoxy powder as a paint was immersed in Glastar sol, which is the most corrosive type of aerosol product, and stored at 50°C for one month. Observe the bubbles generated at the bottom over time to check chemical resistance. However, the welding conditions are: Electrode: Cu wire wrap width: 0.4mm Welding speed: 35m/min Electrode pressure: 40Kg Primary side voltage: 200V (2) In the case of conventional example The conventional example is the same material and the same welding conditions as the present invention. However, seam welding was performed in the atmosphere without using N ₂ gas, and the oxide film thickness, appearance, adhesion, processing adhesion, and chemical resistance were measured under the same method conditions. The results are shown in Table 2.

[Table] In addition, ◎ is the best, ○ is good, × is poor, and xx is extremely poor, respectively.
As mentioned above, in seam welding in a _N2 gas stream, the oxide film is thin for all materials, and the appearance and
It is recognized that adhesion, processing adhesion, and chemical resistance are also excellent. Next, specific test examples will be given to confirm the effectiveness of the present invention. Test Example In the welding machine A of the present invention shown in FIGS. 1 to 3, a test on the effect of the amount of N ₂ gas on the welded seam of the can body was conducted under the following welding conditions. <Welding conditions 1> a Welding speed: 7 m/min b Plate material used: ET tinplate #25/25, 0.24 mm c Can body size: Diameter 74 mm, height 178 mm d Welding pressure: 52 Kg e Weld seam width: 0.35 mm 7 m/ In case of 0.13 seconds, pass through _N2 gas atmosphere for 0.13 seconds <Welding conditions 2> a Welding speed: 36 m/min b Plate material used: ET tin plate #50/25, 0.21 mm c Can body size: Diameter 65 mm, height 102 mm d Welding pressure: 40Kg e Welding seam width: 0.35mm At 36m/min, passing through _N2 gas atmosphere for 0.08 seconds <Welding conditions 3> b Plate material used, c Can body size, d Welding pressure, e Welding seam width Same condition as condition 2 a. Welding speed: 45 m/min At 45 m/min, pass through _N2 gas atmosphere for 0.08 seconds. However, quantitative measurement of oxide film thickness is performed using ESCA (X-ray photoelectron spectrometer). The measurement method is to use a CA wire (chromel alumel thermocouple) with resistance welded at the tip, and store the electromotive force (analog signal) in the memory of the waveform storage device, at a speed that matches the response speed of the pen recorder. The method is to output the stored signal to a recorder and read the electromotive force, and the measurement point is 0.5 from the rear end of the upper and lower gas distribution boxes 11 and 14.
The center of the side seam was ~1.0mm downstream. Results Table 3 shows the relationship data between the can body transport speed, _N2 gas spray amount, and side seam oxide film thickness for welding conditions 1 to 3, and the material areas divided by thick lines in the table based on Table 3. FIG. 4 is a graph showing the upper limit data value and lower limit data value for maintaining color against the N ₂ gas amount (vertical axis) and the can body conveyance speed (horizontal axis).
In FIG. 4, the two-dot chain line showing the relationship between the amount of N ₂ gas and the conveying speed of the can body shows the case of only one side of the inner surface or the outer cotton side of the can body, and the solid line shows the case of both the inner and outer sides. (The solid line shows operation at a transport speed of up to 60 m/min, but predictions were also made when the upper limit was set at 100 m/min.) The points plotted in Figure 4 were obtained as follows. Based on the experimental data shown in Table 3, the upper (or lower) gas amount is set between the maximum (or minimum) gas amount that gives the material background color and the gas amount that is one rank higher (or lower) than that. The following is an example of calculating the amount of gas that is assumed to be present. Calculated value In the case of the upper limit value at 45m/min (total of both the inside and outside) From Table 3 Maximum gas amount obtained for the material ground color = 4.8m ³ / hour Gas amount one rank higher than that = 7.2m ³ / Hour: Upper limit gas amount to be determined = 4.8 + 7.2/2 = 6.0m ³ /hour This 6.0m ³ /hour is plotted in Figure 4 as the upper limit gas amount. In this way, the lower limit for both the inner and outer surfaces of 45 m/min is 36
Upper and lower limits of m/min both inside and outside, 7m/min.
The upper and lower limits for both the inner and outer limits of the minute are determined and plotted. The upper and lower limits for one side of 45 m/min, 36 m/min, and 7 m/min were plotted as 1/2 of the upper and lower limits for both the inner and outer surfaces in each case.

【table】

[Table] According to the table, there is a correlation between the welding transport speed (7 m/min or more) and the amount of inert gas, and in order to maintain the ground color of the material, the minimum value is 0.05 m ³ /
hour to maximum limit 10m ³ o'clock inert gas amount is determined.
In the case of both the inner and outer surfaces, the lower limit and upper limit in the case of one side x 2 = 0.1 to 20 m ³ /hour. Here, to find the lower limit of 0.05 m ³ /hour, when the conveyance speed is 7 m/min, (minimum gas amount obtained for the material ground color 0.12 + gas amount one rank less than that 0.06)
÷2 = 0.09m ³ /hour, calculated from x 1/2 = 0.045 m ³ /hour, and the upper limit of 10m ³ /hour is 100m / hour.
The amount of gas in the case of 20 m ³ /hour x 1/2 = 10 was calculated. That is, it is known that in order to suppress the formation of a weld film of 400 Å or less on the side seam, it is extremely important to control the amount of inert gas according to the can body welding conveyance speed.

[Brief explanation of drawings]

1 is a schematic side view showing a first embodiment of the present invention, FIG. 2 is an enlarged partially cutaway sectional view taken from FIG. 1, and FIG. 3 is a plan view taken from FIG. The figure is a graph showing the correlation between the upper and lower limits of the _N2 gas amount and the can body welding conveyance speed to maintain the base color of the material even after side seam welding. A to C...Metal container manufacturing equipment, L...Feed line, α...Side seam, β...Can body,
3, 6... Upper and lower electrode rollers, 7, 8... Upper and lower blowing nozzles.

Claims (1)

[Scope of Claims] 1. Conveyance at a speed of 7 m/min or more between the upper and lower electrode rollers of the side seam via a pair of upper and lower electrode wires, while the thickness of the oxide film generated on the electric resistance welding surface can be suppressed to at least 400 Å or less. A plurality of inert gas blowing nozzle groups are installed to simultaneously blow out at a set pressure of 0.1 to 20 m ³ /hour in order to perform oxidation-free cooling to 550°C along the upper side of the feed line of the side seam over a predetermined section immediately after passing at a high speed. Wire electrode welding equipment for metal containers arranged downward. 2. The wire electrode welding device for a metal container according to claim 1, wherein the blowing nozzle group has a larger directivity with respect to the upper and lower electrode rollers as it approaches the starting end of the predetermined section. 3. The thickness of the oxide film generated on the electric resistance welding surface can be suppressed to at least 400 Å or less, and immediately after passing between the upper and lower electrode rollers of the side seam via a pair of upper and lower electrode wires at a conveyance speed of about 7 m/min or more. A plurality of inert gas blowing nozzle groups are arranged facing each other and eject all at once at a set pressure of 0.1 to 20 m ³ /hour in order to perform oxidation-free cooling up to 550 degrees Celsius above and below the feed line of the side seam over a predetermined section. Wire electrode welding equipment for metal containers. 4. The wire electrode welding device for a metal container according to claim 3, wherein the blowing nozzle group has a larger directivity with respect to the upper and lower electrode rollers as it approaches the starting end of the predetermined section. 5. The wire electrode welding device for a metal container according to claim 3, wherein the upper and lower blow-off nozzle groups are arranged opposite to each other in a staggered manner.