JPH0160540B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a welded can body having a metal oxide film layer formed on the surface of the welded seam of the can body. Conventionally, soldered cans, adhesive cans, etc. have been used for food cans, beverage cans, etc., but in recent years, welded cans have also come to be used. Such welded cans are generally made by painting and printing the can material, which is made of thin metal sheets, except for the joints to be welded, and then cutting and forming can body blanks, and then welding the surfaces of the joints at the edges of the blanks as necessary. After removing inhibiting components, the blanks are formed into a cylindrical shape, the ends of the blanks are overlapped, and the overlapping parts are polymerized and welded under high temperature and pressurized conditions using an electric resistance welder to create a can body.Then, the inner and outer surfaces are welded as necessary. It is obtained by applying a corrective coating to the seam and then sealing the lid to the end of the can body.
During electric resistance welding, the can body joint of the welded can obtained by this method is heated to a high temperature of around 1000°C and pressurized to several tens of kilograms, so the can material at the joint has a large overlap. As it is crushed and spread thin, its surface is oxidized by oxygen in the air, and a brown or black metal oxide film with a thickness of usually 1000 Å or more is formed on the joint surface. Such an oxide film generally has poor adhesion to the metal base of the can, and poor workability with respect to bending, stretching, etc., and is likely to peel off from the interface of the metal base during can manufacturing processes, such as franging, netting, seaming, etc. Even if the seam is coated and corrected, it will fall off along with the correction coating, exposing the base material. After the oxide film is peeled off, the surface of the metal base is completely different from the original can material surface and the surface structure of the joint before the oxide film is peeled off. When filling a can with contents, corrosion of exposed metal parts, perforation, or metal elution into the contents may occur.
There is a problem with the quality of the can. Therefore, as a conventional method to solve such problems, during welding, the area around the welded area is kept in an inert gas atmosphere to block oxygen, and the area is cooled to prevent the formation of an oxide film so that the welded area is visible. A method has been adopted to maintain the condition close to that of the upper metal base. However, in order to suppress the formation of an oxide film using such a method, a large amount of low-temperature inert gas is required, and special equipment is also required to maintain a complete inert gas atmosphere without oxygen around the welding area. It is. Moreover,
Even if the formation of an oxide film is suppressed, the surface structure of the welded joint of the obtained welded can body is susceptible to deformation due to high temperature and pressure during welding, and peeling of the surface protective film due to contact with electrode members. The structure is different from that of the can material surface, and the protective effect of the metal base is reduced. For example, when a tin-plated steel plate is used as a metal material, the surface is tin-plated to protect the metal base, but during welding, a considerable amount of the tin-plated layer may scatter due to high temperature pressurization. It adheres to the welding electrode member, is exposed from the surface of the metal base, and is partially alloyed, resulting in a significant loss of the protective effect of the tinned layer compared to the original can material surface. In addition, even with stain-free steel for cans that has a chromium/chromate layer on its surface, it is common practice to remove the surface chromium/chromate layer from the edges to be welded before use in order to improve weldability. The welded seam surface that has been subjected to such removal treatment has a significantly reduced protective effect compared to the original tain-free steel surface because the chromium/chromate layer has been removed, and the surface chromium・Even if the chromate layer is used without removing it, due to the high temperature and pressure conditions during welding,
The chromium/chromate layer on the surface is expanded, and the structure of the protective layer on the surface changes, losing its initial protective effect. Furthermore, due to the high temperature and pressure conditions during welding of black plates or nickel-plated steel plates, the protective layers such as the surface oil coating layer or the nickel plating layer may be removed or stretched and thinned, resulting in unstable conditions. It becomes a surface structure. Even if the formation of an oxide film is prevented at the welded seam of the welded can body, the structure of the protective layer on the surface has a lower protective effect than before welding and becomes unstable, making it difficult to correct the coating with paint or resin film. becomes essential. Even if this paint or resin film is used to correct the coating, if the inner and outer surface correction paint or resin film that covers the joint is a thin film, or if the correction effect is low due to poor curing of the paint, corrosion, perforation, or damage to the contents may occur. Metal elution occurred, which caused a practical problem. The object of the present invention is to solve the above-mentioned problems of the welded joints of welded cans obtained by the prior art,
It is an object of the present invention to provide a welded can body with excellent can quality such as corrosion resistance and content resistance. In a welded can body obtained by polymerizing and welding both edges of a metal material with iron as a metal base, the welded joint surface contains mainly iron oxide with an oxygen atomic concentration ratio of 0.5 or more to iron. Film thickness 300~900
They discovered that by forming a metal oxide film layer of 100 Å, it was possible to obtain a welded can body that solved the above-mentioned problems of the prior art.Furthermore, they developed a tin-plated steel plate with a tin coating on one side of 14 g/ ^m2 or less as a metal material. The tin component is relative to the total amount of iron component and tin component in the metallized film used.
It was discovered that when the content is in the range of 10 to 50%, a welded can body with improved quality such as corrosion resistance of the surface of the weld joint and suitability for contents resistance was obtained, and the present invention was completed. In the welded can body of the present invention, the metal oxide film layer formed on the surface of the weld seam during welding has an oxygen atomic concentration ratio of 0.5 to iron.
Mainly composed of iron oxide with a film thickness of 300 to 900 Å
However, such a film layer can be forcibly removed from the weld joint surface to expose the underlying metal surface, or by using a large amount of inert gas to suppress the formation of an oxide film. Compared to the surface of the welded seam obtained using the above method, it is more stable in terms of corrosion resistance against the outside air and various contents filled in the welded can body. Furthermore, as a metal material, the amount of tin plating on one side is 14g/
Using a tin-plated steel plate with a size of ^less than m
When the content is in the range of 50%, the iron-tin alloy layer interposed between the metal oxide film and the iron substrate improves the adhesion of the metal oxide film, improving corrosion resistance and content resistance. Next, the present invention will be explained in more detail as follows. First, the metal materials used for the welded can body of the present invention include known can materials that have been conventionally applied to solder cans, adhesive cans, and welded cans, such as tin-plated steel sheets, stain-free steel, black plates, and nickel-plated cans. Steel plates, galvanized steel plates, aluminized steel plates, etc. can be used, but the amount of tin plating on one side should be 14 g / m ² or less, preferably the amount of tin plating
Suitable are tin-plated steel plates of 0.05 to 8.4 g/m ² , stain-free steel, black plates, and nickel-plated steel plates with a nickel plating thickness of preferably 0.05 to 0.5 μm. Among these, tinned steel plate,
Nickel-plated steel sheets and the like usually have a chromate layer on top of the plating layer, but in the present invention, they can be used as they are without any particular problem. The method for manufacturing welded cans using such can stock is as follows:
Conventionally, a can body blank is coated with paint or printing except for the edge to be welded, and if necessary, welding inhibiting components on the surface of the edge of the blank can be removed by means such as polishing or cutting. There is a known method of manufacturing a can body by overlapping the ends of the blanks and welding the blanks under pressure using an electric resistance welding machine. As a method and apparatus for preventing the formation of an oxide film, Japanese Patent Publication No. 38-15843, Japanese Patent Application Laid-open No. 84141-1987,
As disclosed in JP-A-55-156681, JP-A-55-103284, etc., a method is known in which oxidation is prevented by creating an inert gas atmosphere at the welding location and the process immediately after it. In the welded can body of the present invention, it is necessary to form an oxide film with a thickness of 300 to 900 Å on the surface of the weld seam.The method for forming such a film is to utilize the above-mentioned known method, and to The process immediately after that is made into an atmosphere mainly composed of inert gas, and the amount of inert gas is adjusted to reduce the amount of oxygen (or amount of air) in the atmosphere.
A method of maintaining the temperature at a level at which an oxide film layer having the thickness range described above is formed, or a temperature condition in which the temperature of the weld seam immediately after welding is suppressed using cooling gas, etc., so that the oxidation reaction does not proceed unnecessarily. Although there are methods of controlling the amount of inert gas, a method of controlling the amount of inert gas is preferable. In such a method, if the amount of inert gas is too small, or if the weld seam is not sufficiently cooled, the oxidation reaction will proceed too much and the metal oxide film layer will become too thick. On the other hand, if the amount of inert gas is too large or the cooling effect is too strong, the oxidation reaction will not proceed by the specified amount and the oxide film layer will become too thin. It is necessary to appropriately control the amount of inert gas used, the temperature and amount of cooling gas used, depending on the type of can stock, the can manufacturing speed, etc. It is preferable to use a device that maintains the atmospheric conditions under appropriate conditions, such as a gas injection device, a gas atmosphere maintenance chamber, etc. The oxide film layer on the joint surface of the welded can body of the present invention thus obtained is mainly composed of iron oxide, and the concentration of oxygen atoms relative to iron gradually decreases as it goes deeper from the outermost surface. It is preferable that the thickness of the metal oxide layer before the atomic concentration ratio reaches 0.5 is in the range of 300 to 900 Å, and the thickness including the layer where the atomic concentration ratio of oxygen to iron is 0.5 or less is in the range of 300 to 900 Å. The iron oxide film layer has low corrosion resistance and tends to reduce the protective effect of the metal substrate, so it is not preferable. Furthermore, even if the oxygen atomic concentration ratio to iron is 0.5 or more, if the film is thicker than 900 Å, it will crack or peel off during can manufacturing, which poses a practical problem. It does not crack or peel during processing and has good adhesion. Furthermore, if such an oxide film layer is thinner than 300 Å, it will not be possible to uniformly cover the underlying metal substrate, resulting in a surface structure where the substrate is locally exposed, but if the oxide film layer is thinner than 300 Å, preferably 400 Å or more, If the film is thick enough, the surface of the weld seam can be uniformly coated, and together with the stability of the oxide film, it has the effect of protecting the unstable metal base of the weld seam from outside air and contents. In addition, other metal components in such a metal oxide film layer include tin components in the form of tin oxides in the case of tin-plated steel sheets, and chromium oxides in the case of tin-free steel materials. In the case of nickel-plated steel sheets in which chromium components are present in the form of chromium hydrated oxide, etc., nickel oxide coexists. In particular, when tin-plated steel sheets are used, an iron-tin alloy layer is formed under the metal oxide film.
In addition, the tin component that coexists in the metal oxide film tends to increase as it goes deeper from the surface, so when a suitable amount of tin component coexists, the metal composition of the metal oxide film layer and the underlying iron-tin alloy layer becomes closer. This tends to improve the adhesion between both layers. In this case, when the metal oxide film coexists with the tin component in an atomic concentration ratio of 10 to 50% of the total of the iron component and the tin component, it has good adhesion, workability, corrosion resistance, and suitability for content resistance. It will be of excellent quality. In order to form such an oxide film, it is necessary to use a tinplate material with a relatively low amount of tin plating, specifically, a tin plate with a tin plating amount of 14 g/m ² or less on one side, preferably 0.05 to 8.4 g/m ² . It is desirable to use wood. In addition, when using stain-free steel, the chromium/chromate treatment layer on the surface of the edge is usually removed before welding, so the metal oxide film layer on the surface of the weld seam is mainly iron oxide, and some , chromium oxide, chromium hydrated oxide, etc. coexist. Unlike the lower layer of tinplate materials, the lower layer of the film does not have a tin component, so the adhesion tends to decrease somewhat. However, by setting the metal oxide film thickness to 300 to 900 Å, more preferably 300 to 700 Å, excellent adhesion, workability, corrosion resistance, etc. can be obtained. Further, even in black plates and nickel-plated steel plates, the corrosion resistance of the weld joint surface can be improved as long as the oxide film conditions of the present invention are met. The welded can body of the present invention thus obtained is
300, which usually has a light yellow to brown color on the weld seam surface.
It has a metal oxide film layer of ~900 Å, and the film layer itself is stable against various contents and has the effect of protecting the metal base, so it may remain as it is depending on the storage environment of the can or the contents filled. However, in order to improve can quality and suitability for contents resistance, a correction coating or resin film can be provided on the surface of the weld seam to correct the coating. Such coating correction paints include paints conventionally known as paints for the inside or outside of cans, such as epoxy resin paints, phenolic resin paints,
Solvent-based paints using aminoplast paints, vinyl resin paints, polyester resin paints, acrylic resin paints, polyamide resin paints, etc. alone or in combination;
It can be used in any desired paint form, such as a water-based paint, an organosol-based paint, a plastisol-based paint, or a powder paint. In addition, as for the painting method, the type of paint,
Depending on the form of the paint, an appropriate method can be selected from known coating methods such as spray coating, roller coating, and powder coating. In addition, resin films include polyester resin,
Polyamide resins, vinyl resins, acrylic resins, epoxy resins, aminoplast resins, and other known resins are used alone or in combination to form a single layer or multilayer resin film, and a known method is used, for example, in the
It can be attached by a method such as that disclosed in Japanese Patent No. 43350. Such a correction coating has a thickness of 10 to 90μ, preferably 20 to 60μ.
is suitable. The welded joint surface provided with the metal oxide film of the structure of the present invention is more stable against various contents than the joint surface of a conventional welded can body, which uses a large amount of inert gas to suppress the formation of the metal oxide film. In addition to being excellent in adhesion to correction paint, the can body of the present invention coated with correction paint has better corrosion resistance and content resistance than conventional correction welded can bodies. Become something. The can body obtained by the present invention has excellent corrosion resistance and content resistance against various contents, and can be used for food cans, beverage cans,
Particularly preferred for use in aerosol cans. The present invention will be explained below with reference to test examples. The oxide film thickness and component composition in this test example were determined using an Auger electron spectrometer (Auger electron spectrometer).
spectroscopy). Test example 1 A tinplate material (#50/#50 tinplate) with a plate thickness of 0.23mm and a tin plating amount of 5.6gr/ ^m2 on both the inner and outer surfaces (#50/#50 tinplate) was coated with epoxy/phenol based on the inner surface, excluding the edge joint. After forming a cured coating film of paint with a thickness of 4.0 μm and carrying out the desired printing on the outer surface side except for the edge seam, cut and mold the coated steel plate to the size of a can body blank for a 250 g welded can. The blanks are formed into a cylindrical shape, the edges are overlapped with a lap width of 0.5 mm, and a known welding machine is used to perform pressure seam welding between rotating roll electrodes via a copper electrode wire at a can manufacturing speed of 200 cans per minute. Welding was performed in air to produce a can body (can body number 1) having a black oxide film on the surface of the welded seam on the inner surface of the can. In addition, when manufacturing the welded can body with can body number 1, we use a special device that maintains an inert gas atmosphere at the welding point where the electrode roll is located and immediately after it, and uses a large amount of inert gas to prevent air from entering the can inner surface. Welding was carried out in a manner that prevented oxidation of the side seam surface to obtain a can body (can body number 4) in which the welded seam surface on the inner side of the can had an appearance substantially similar to that of the metal base. Next, in manufacturing a welded can body with can body number 4, the amount of inert gas used was adjusted and welding was performed in an atmosphere with air mixed in and oxygen concentration changed, and the appearance of the joint on the inner side of the can took on a brown to light brown color. Welded can bodies (can bodies numbers 2 and 3) were obtained. The thickness of the oxide film and the atomic concentration of the tin component in the oxide film at the weld seam on the inner surface of the can bodies of the obtained welded can bodies Nos. 1 to 4 were measured, and the workability, adhesion, and indoor The corrosion resistance of the seam surface was evaluated when stored in . Table 1 shows the results.
summarized in. From this result, the seam surface of can body No. 1, which has an oxide film of 1200 Å, developed microcracks due to deformation of the lid seaming process conditions, and when a peel test was performed on the cracked area using adhesive tape, the black oxide film peeled off. The metal base was exposed and the adhesion and workability were poor. Furthermore, the seam surface of can body No. 4 manufactured using a large amount of inert gas exhibited a silvery white color similar to that of the metal base, and there was no particular change due to deformation during the seaming process. However, after being stored indoors for about 3 months, red rust developed on the surface of the joint, and the corrosion resistance was poor. On the other hand, can bodies Nos. 2 and 3, which correspond to Examples of the present invention, had excellent adhesive workability, did not develop red rust even after being stored indoors for about 3 months, and had good corrosion resistance. . Test Example 2 Using the same tin material as Test Example-1, Test Example-
In the same method as in 1, the amount of oxygen (air) in the inert gas atmosphere around the weld seam on the outside of the can body was adjusted, and three types of welded can bodies (can bodies) with different oxide film thicknesses on the outside of the can body were adjusted. Nos. 5, 6 and 7) were obtained. Using the obtained can body, the physical properties of the oxide film were evaluated in the same manner as in Test Example 1. As shown in Table 1, can body number 6, which corresponds to the example of the present invention, had good oxide film physical properties. had. Test example 3 Tinplate material (#25/#25 tinplate) with a plate thickness of 0.23mm and a tin plating amount of 2.8gr/ ^m2 on both the inner and outer sides.
A welded can body (can body number 8) with a welded seam surface oxide film thickness of 460 Å on the inner surface of the can was manufactured in the same manner as in Test Example 1 (can body numbers 2 and 3) except that
I got it. Table 1 shows the evaluation results of the oxide film on the surface of the seam of the can body. From this result, it is clear that the can body joint surface of can body number 8, which corresponds to the example of the present invention, has good physical properties. Test Example 4 A cured coating of epoxy/phenol paint with a thickness of 4.3 μm was formed on the inner surface of a 0.23 mm thick stain-free steel plate, excluding the edge seam, and the edge seam was formed on the outer surface. After cutting and forming the coated steel plate, which has been printed except for the parts, into the size of a can body blank for a 250g welded can, the chromium/chromate layer on the edge surfaces of the inner and outer surfaces of the blank is removed,
A can body blank with easily welded edges was created. Next, we conducted two types of welded can bodies with different oxide film thicknesses by changing the inert gas atmosphere conditions on the welded seam surface on the outer side of the can, except for using this can body blank. (can body numbers 9 and 10) were obtained. The physical properties of the oxide film on the surface of the welded seam on the outer side of the can body of the obtained can body were evaluated. The results are shown in Table-1.
As is clear from this result, the oxide film thickness is 250Å.
Can body number 9 rusted during storage as an empty can, but
Can body No. 10, which corresponds to the example of the present invention, showed no rust and had good workability and adhesion. Test Example 5 The procedure was the same as in Test Example 2 except that a black plate with a thickness of 0.23 mm was used as the can material, and the amount of air mixed in the inert gas atmosphere around the weld seam on the outside of the can was changed to change the thickness of the oxide film on the outside of the can. Two types of welded can bodies with different sizes (can body numbers 11 and 12) were obtained. Table 1 shows the physical properties of the oxide film on the can body obtained.
From this result, in can body number 11 with an oxide film thickness of less than 300 Å, red rust occurred on the seam surface during storage of the empty can, and the corrosion resistance was poor. In contrast, can body No. 12, which corresponds to an example of the present invention, was in good condition with no corrosion. Test Example 6 A tin plate (#50/#25 tin plate) with a thickness of 0.24 mm and a tin coating of 5.6 g/m ² on the inner surface and 2.8 g/m ² on the outer surface was used, and an edge joint was formed on the inner surface. Peeking epoxy
A urea-based paint was applied to form a cured film with a film thickness of 7.6μ, and the blank was cut and molded to the size of a 420gr aerosol can body blank.The blank was then welded under the same welding conditions and inert gas as in Test Example-1. Using this method, three types of welded can bodies (can body numbers 13, 14, and 15) with different oxide film thicknesses on the inner side seam surface were obtained.
As is clear from the physical properties of the oxide film shown in Table 1, can body No. 14, which corresponds to the example of the present invention, has good physical properties. Test Example 7 The same procedure as Test Example 2 was used except that a nickel-plated steel plate with a thickness of 0.23 mm and a nickel plating layer of 0.8 g/m ² was applied on the inner and outer sides was used. Three types of welded can bodies (can body numbers 16, 17, and 18) with different metal oxide film thicknesses were obtained. Table-1
As is clear from the results shown in Figure 1, can body No. 17, which corresponds to the example of the present invention, had better adhesion, workability, and corrosion resistance than can bodies No. 16 and 18. Test Example 8 After producing welded can bodies with can body numbers 1, 2, 3, 4, and 8 in Test Example-1 and Test Example-3, epoxy/phenol-based paint was subsequently applied to the weld joint surface of the inner surface of the can body. An inner surface correction coating with a width of 8 mm and a film thickness of 10 to 40 μm was applied. Next, an aluminum lid with a coating made of vinyl chloride resin organosol paint on the inner surface of the lid was attached to one end of the inner surface correction can body.
Can body number 1, 2, 3, 3, installed by heavy tightening.
Can numbers 1 and 8 are can bodies corresponding to numbers 4 and 8, respectively.
Can bodies of 2, 3, 4, 5, and 6 were obtained. Milk coffee is poured into the resulting can, and the inner surface of the lid is sealed with a tin lid coated with epoxy/phenol paint. After being double-sealed, it is heated to room temperature. It was stored for 6 months. Thereafter, the can was opened and the contents and the welded seam of the can body were evaluated. The results are shown in Table-2.
The results show that the cans corresponding to the examples of the present invention (cans No. 2, 3, 4, and 6) were in good condition with no abnormalities, but the cans with a thick oxide film of 900 Å or more (can No. 1)
The can body with an oxide film of less than 300 Å and a thin correction coating (can body number 5) showed corrosion in the seamed part of the side seam, and the amount of iron leached from the contents was 0.5 ppm, which was more defective than the can body of the present invention. It was hot. Test Example 9 In Test Example 6, after welded can bodies with can body numbers 13, 14, and 15 were manufactured, epoxy/urea paint was applied to the welded joint surface of the inner surface of the can body with a coating width of 8.
An inner surface correction can body was obtained which was coated with a relatively thin film of inner surface correction coating in mm. Also, the amount of tin plating on the inner side is 11.2g/ ^m2 ,
Epoxy on the inner side of the tin plate with a weight of 8.4g/ ^m2 on the outer side.
The canopy and ground cover were made using painted boards coated with urea paint to form a cured film with a film thickness of 7.6μ.
A 420gr aerosol can body (can body numbers 7, 8, and 9) as shown in Table 2 was manufactured by attaching the inner surface corrected can body to both ends by double seaming. Water-based starch was sealed in the can using a mounting cap, and the can was stored at 45°C for 3 months to evaluate the quality of the can. As can be seen from Table 2, can number 7 has a thin oxide film when the inner surface correction paint is thin, and can number 9 has a thick inner surface correction paint and a significantly thick oxide film. Corrosion was observed in the side seam seaming area. On the other hand, in can body number 8, which corresponds to an example of the present invention, no corrosion was observed, and the oxide film with an appropriate thickness had a protective effect.

【table】

【table】

【table】

【table】

Claims (1)

[Scope of Claims] 1. In a welded can body obtained by welding both edges of a metal base made of iron, a film mainly composed of iron oxide with an oxygen atomic concentration ratio to iron of 0.5 or more on the surface of the weld joint. A welded can body characterized by forming a metal oxide film layer with a thickness of 300 to 900 Å. 2. A patent claim characterized in that the metal substrate is made of any one of stain-free steel, black plate, and nickel-plated steel plate from which the chromium/chromate treatment layer on the edge surface that will become the welding seam has been removed. A welded can body according to scope 1. 3. In a welded can body obtained by welding both edges of a metal base of a tin-plated steel plate with a tin plating amount of 14 g/m ² or less on one side, iron oxide with an oxygen atomic concentration ratio of 0.5 or more to iron is applied to the surface of the weld joint. A welded can body characterized by forming a metal oxide film layer having a thickness of 300 to 900 Å and containing a tin component in the range of 10 to 50% based on the total amount of iron and tin components.