JPS63177988A - Production of laser welded can - Google Patents

Abstract

PURPOSE:To improve welding efficiency by coating a paint contg. fine metal grains near the weld zone of a can, then subjecting the metallic stock of the can to butt welding by a CO2 laser. CONSTITUTION:The paint is formed by filling fine granular metal powder of Al, Ni, etc., into an oily paint or resin such as polyester resin. The thin metallic stock is subjected to painting and baking with such paint to prepare a blank for the can. The ends of the blank are butted to each other after roll forming and are subjected to CO2 laser welding. Since the fine granular metal powder is incorporated into the coated film, the weld zone quickly attains the high temp. state of good laser absorption efficiency at the time of welding. The welding efficiency by the CO2 laser is thereby improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing cans made of thin metal plates such as cans for cans, exterior cans for dry cell batteries, parts for paint, etc.

[Conventional technology]

Conventionally, methods such as soldering, adhesive bonding, seam welding (lap welding), etc. have been used to manufacture can bodies by roll-forming thin metal plates and joining the ends. In these methods, since the plates are overlapped at the joint, holes are likely to occur at the seaming part, and in these methods, the metal plates are glued together under each other, so there are no holes in the joint of the can blank plates. It was necessary to have a large unpainted area called a margin, and the inner surface had to be repainted to prevent corrosion, and the surface had the disadvantage that the printing area was small.

For example, in the manufacture of welded cans by resistance welding, metal plates are stacked on top of each other and contact welded by heat welding, so the welded portions of can blank plates must be unpainted, and a minimum margin of 2# is required.

On the other hand, since the success of ruby laser oscillation in 1960, about 2000 types of lasers have now been developed and are being applied in a wide range of fields.

In the field of thermal processing such as welding and cutting, full-scale applications began with the development of continuous wave carbon dioxide lasers (CO2 lasers).

Currently, a CO□ laser with an output of 10 kW is commercially available2.
Products with an output of about 0kW are also possible, and thermal processing (
(welding, cutting, surface treatment, overlay, etc.). The features of laser welding are (1) Non-contact welding (2) The heating area is small and the welding speed is fast, so there is little heat effect on the welded area (3) It is possible to weld between dissimilar metals (4) High melting point materials It is possible to thermally process heat-resistant alloys, etc., but especially C
O2 laser ■Can achieve high output up to 2Qkw ■Can perform continuous oscillation and repeated pulse oscillation ■High laser conversion efficiency (approximately 20% or more) ■Low air propagation loss. ■
The accuracy requirements for optical elements are lenient ■As it is a gas laser, there is no destruction of the laser medium due to high output ■Most of the consumables are gas, so maintenance costs are lower than other lasers. You're right.

Welding metal cans using this CO2 laser has the following features compared to the conventional manufacturing method using resistance heating.

(a) Since butt welding is possible, there are no steps at the joint, and there is no problem in tightening the lid, which is excellent in terms of performance and appearance.

(b) The welded area is narrow, about 0.21M, so there is an advantage in appearance. As mentioned above, resistance welding requires a margin of about 2 m.

(C) Resistance welding requires an electrode bar to be installed inside the can, and there is a limit to the diameter that can be manufactured.
It is possible to manufacture small diameter cans such as dry battery outer cans and aerosol cans.

(d) Tin free steel other than tin
Welding of metals such as FS> and Aρ is also possible.

However, it is said that metals such as iron and iron have a reactivity rate of over 90% near the oscillation wavelength of a carbon dioxide laser, and if this continues, most of the laser output irradiated onto the material surface will be reflected by the surface and This means that less than 10% of the power is absorbed into the interior near the surface and becomes heat.

Therefore, it has been reported in patents and literature that the absorption rate of laser light can be increased by applying an appropriate coating to the metal surface (Japanese Patent Application Laid-Open No. 160-893-1989,
(JP-A-56-160.894, JP-A-60-18.291) These treatments have been studied for surface treatment and cutting (grooving) of metals.

There are no examples of studies on coating agents for welding.

[Problem that the invention attempts to solve]

The purpose of the present invention is to put into practical use the production of welded cans using a CO2 laser. Among the above characteristics, in order to take advantage of the appearance advantage of having a narrow welded area, it is necessary to use a can blank that is fully coated as it is extremely difficult to provide a narrow margin of approximately 0.2 mm. .

Therefore, in manufacturing cans by laser welding, there is a problem in that the metal plate must be heated and welded through the resin coating provided on the heated part (welded part). The above patent document describes surface treatment of metal by laser,
Certain types of coating agents are said to have the effect of increasing laser absorption when drilling holes, and examples include graphite-based coatings and coatings containing inorganic fillers. These materials are selected because they exhibit a high absorption rate for CO2 laser. However, the welding table has a power density of 10 W/in2, which is much higher than that of surface treatment.
, requires a power density of 6X 104 W/cri or more. This requires a high absorption of the laser energy by the metal plate and/or the coating. Judging from the infrared absorption pattern, the non-silica filler is not necessarily considered to be a good absorber for CO2 laser. This also means that the coating film containing metal powder that reflects most of the laser beam is
It was not thought that it would not exhibit good absorption for the 02 laser.

The present invention aims to solve the problem of what kind of coating film should provide good weldability.

[Means for solving problems]

As a result of detailed research on butt welding using a CO2 laser, the inventors of the present invention found that when using can blanks that are fully coated and welding by heating and melting the metal plate through the resin coating, the resin coating itself Even if it is not a good absorber for laser light, it will absorb even a small amount of laser light and generate heat.

Furthermore, even if the laser light absorption rate of the metal plate itself is low, if the metal plate is heated even slightly by the laser light that has passed through the coating film, the coating film will also be heated by that heat. In this way, the temperature of the coating film reaches an upper limit due to the effects of heat generation, heating, or both.

At this time, if the resin coating film is not easily thermally decomposed and absorbs less heat due to the decomposition reaction, the surface temperature will increase due to the effect of heat generation.

The laser light absorption rate of a metal plate increases as the temperature rises.

Therefore, the present invention was completed by discovering that if a resin coating film with high thermal decomposition resistance is used, the absorption of laser light into the metal plate can be increased as a result, and welding efficiency can be improved.

Although the resin itself does not necessarily have high thermal decomposition resistance, and despite the fact that the metal powder itself reflects most of the laser light, the present invention is able to improve the effectiveness of the metal powder in contrast to the resin normally used as paint for cans. This is based on the discovery that by incorporating fine powder, the heat decomposition resistance of the coating film can be improved and weldability can be improved.

The present invention can be made by welding metal materials! ! This is a laser-welded can manufacturing method characterized in that in an i-built structure, a paint containing fine metal powder is applied to at least the vicinity of the welding part, and the metal materials are butt-welded using a CO2 laser.

It is preferable that there is no part of the coating film that the fine metal powder cannot influence, and from this point of view, the particle size has a great influence on the effect. The average particle size is preferably 15 μm or less. Furthermore, if the metal powders are of the same type, the particle size is preferably smaller. The average particle size is determined by microscopic observation. Since most metal powders are scaly rather than spherical, in such cases the particle size is determined by the major axis of the metal scaly.

The amount of the filler is naturally related to the particle size, but if it is contained in the coating film in an amount of 5 (Vo 1%) or more based on the solid content of the resin, a sufficient effect can be obtained.

The more the amount is, the more effective it is, but if it is too much, the amount of resin as a vehicle for the paint is reduced, the adhesion strength is reduced, and the effect of reflection of the metal powder is also increased, so 40Vo1% or less is preferable.

Types of metal powder include A I, N i N S n
%7n, etc., and stainless steel powder etc. can also be used. It is not limited to one type of these, and two or more types may be mixed and added.

The resin used to fill this fine metal powder includes epoxy ester/amino resin, acrylic/amino resin, alkyd/amino resin, epoxy/yurya resin, oil-based paint, polyester, etc., which are conventionally used as paint for cans. good. The coating film itself containing these resins has low thermal decomposition resistance when irradiated with CO2 laser light, and thermogravimetric analysis (
Temperature (T2
O) is not very high. However, coating films made by uniformly containing fine metal powder in these resins have extremely high T2O. For example, T2O of epoxy ester/amino resin alone is 46
Although the temperature is 0°C, the T2O of the coating film containing He1 powder at 10Vo1% increases to 490°C. Of course, it is more preferable to incorporate fine metal powder into a resin obtained by mixing or copolymerizing the general-purpose resin with a resin such as a phenol resin, a fluorocarbon resin, or a polyimide, which itself has high heat decomposition resistance.

The coating film containing the fine metal powder may be provided only in the vicinity of the welded portion by printing or strip coating. It may also be used in an overlapping manner as an undercoat for printing on can blanks.

In laser welding, a can body blank is formed into a cylindrical shape using a roll form A-mer, the welded parts are butted together, and a laser beam with a small divergence angle emitted from an oscillating rod is focused on this part using a focusing optical system to form a microscopic beam with high energy density. Irradiates the workpiece as a spot, melts the irradiated area, and performs welding.

For this purpose, the C02 laser output must be 0.6 KW or more, and if it is less than this value, a uniform welding state cannot be achieved in the cross-sectional direction of the heated part.

Further, the laser beam diameter is in the range of 0.15 to 0.25 mm.If it is less than 0.15 mIII, it is difficult to match the can blanks accurately, and if it is more than 0.25 mm, the weld width becomes too wide. i8 contact speed is 10m/mi
n or more is required. If it is less than this value, not only can productivity will decrease, but when the laser output is sufficient,
The weld width becomes too wide. The matching accuracy of can blanks must be 0.05 m or less.

The output power and beam diameter are related to each other, and it is the power density (W
/~). To achieve a uniform welding condition in the cross-sectional direction of the weld, a power density of 1.6 x 104 W/ca! or more is required, which is much higher than the power density required for heat treatment etc. be.

Preferred metal materials for manufacturing can bodies by laser welding include steel plates with a thickness of 0.15 to 0.35, dimfried steel (TFS), tin-plated steel plates, ultra-thin Ni-plated steel plates,
Examples include 5n-Ni alloy plated steel sheets.

It is also possible to weld plates for cans with a thickness of 0.15 to 0.45 m.

Weldability is evaluated by visual observation and cross-sectional observation of the welded part using a microscope. The area of the part heated and melted by the laser was determined from the cross-sectional observation photograph (Fig. 1) with a microscope.
As a comparison standard, the case where only epoxy ester/amino paint was applied was set as 100, and the evaluation was made by multiplying this value by the area ratio.

[For production]

Since metal powder reflects most of the laser light, it is unlikely that its inclusion will increase the laser absorption rate of the coating film. However, when it is included as a filler in a paint, the heat resistance of the paint film is significantly improved. As mentioned above, the T2O of epoxy ester/amino resin for general-purpose color paint is 4.
Although the temperature is 60°C, the T2O of a coating film containing 1% A9 powder at 10Vo is 490°C.

When a coating film on a metal plate is irradiated with laser light, even if the absorption rate of the coating film itself or the metal plate itself is low, even a small amount is absorbed and heat is generated. When the temperature of both the coating film and the metal plate increases, the laser absorption rate increases significantly.

However, if the coating film thermally decomposes during this temperature raising process, it will endotherm and the temperature will drop, making the laser absorption effect less effective. When metal powder is included in the coating film, the thermal decomposition temperature rises, so the film quickly passes through the relatively low temperature rising region where laser absorption efficiency is poor, and quickly reaches high temperatures where laser absorption efficiency is good. This is thought to be for the purpose of This is especially important in welding where high power density is required.

[Execution VA] Table 1 shows coating components of Examples and Comparative Examples of the present invention. The right column shows the volume percentage of the metal powder filler added to the solid content of the paint. The paint is TFS (0.21m thick)
, Tinplate (0.2Lmm thickness), AN (0.23m
The coating was applied to one side of various metal plates (tn thickness) to a thickness of 10 μm, and baked under predetermined conditions.

This painted metal plate is cut into a specified size as a can blank, and after roll-forming so that the painted surface becomes the outer surface, the ends are butted together and a C is formed on the butted part.
Welding was performed by irradiating with O2 laser.

The welding conditions are (1) CO2 laser (wavelength: λ-10,6
um＞(2) Out crab 1 kw(3) L/ -+f-
Heam diameter: 0.20 order φ (4) Welding speed = 15m/
mtnThe power density under this condition is 3.2X106W/-
It is.

The welding condition was evaluated by visual observation and by measuring the area of the molten part in the cross section of the weld using a microscope.

As a comparative example, the area was set as 100 based on the area when only epoxy ester/amino paint was applied.

The results are shown in Table-2. When the paint according to the present invention was used, high heating efficiency and good welding conditions could be obtained.

Metal powder type 1, AI (a) Alpaste 0100M, manufactured by Toyo Aluminum, average particle size near μm (b) Toyo 7) AC-1003, manufactured by Li Minium, average particle size: 30 μIn2, Ni (a) Compensation metal foil powder Industrially manufactured, MP-287, average particle size: 5 μm (b) U
LVAC%l, N) IH-P4-03, average particle size:
0.03 μm3.8n Made by Compensation Metal Foil and Powder Industry, 5n-3, average particle size: 15μm4.2n
Manufactured by Fukuyama Metal Powder Industry, 1n-3, average particle size: 10μm
[Effect of the invention] By providing a coating film containing fine metal powder in the vicinity of the welding part of a can blank, it can be used as an undercoat of the coating film of the entire can or as a coating film only in the vicinity of the welding part, which has a metallic luster. Not only is it suitable as a coating with a strong hiding power, but also CO
It has become clear that the welding efficiency of J:2 laser can be kept extremely high. In other words, when using a CO2 laser with an output of 0.6 KW or more and a beam diameter of 0.15 to 0.25 mm, the welding speed is 10 m/m, which is required for can manufacturing.
It has become possible to obtain a necessary and sufficient cross-sectional area of the melt penetration, that is, the molten part, at the abutted part while satisfying the above requirements, and it has become possible to make it practical to manufacture welded cans using a CO2 laser. This invention is extremely useful in the can manufacturing industry, from the viewpoint of the aesthetic appearance of the can, the corrosion resistance, and the rationalization of can manufacturing by preventing through-holes in the seamed portion.

[Brief explanation of the drawing]

FIG. 1 shows an enlarged microscopic view of the cross-sectional shape of a butt-welded portion of a laser-welded can cut perpendicular to the weld line. Applicant's agent Hiromitsu Fujimoto [Figure 1] rIfr company shape ff4 inner side of S part

Claims (1)

[Claims] 1. In the production of cans by welding metal materials, a laser characterized in that a paint containing fine metal powder is applied to at least the vicinity of the welding part, and the metal materials are butt-welded using a CO_2 laser. Welded can manufacturing method. 2. The metal fine powder has an average particle size of 15 μm or less,
Filling 1: 5% by volume based on the resin solid content
The laser welded can manufacturing method according to claim 1, wherein the above is contained in the coating film. 3. The laser welding can manufacturing method according to claim 1 or 2, wherein the metal fine powder is one or more selected from the group consisting of Al, Ni, Sn, and Zn.