WO2003101844A1

WO2003101844A1 - Surface-modified aluminum can and method for manufacture thereof

Info

Publication number: WO2003101844A1
Application number: PCT/JP2003/006616
Authority: WO
Inventors: Akira Shirakura; Teruyuki Yamasaki; Noriyasu Yoshimura
Original assignee: Kirin Brewery Company, Limited
Priority date: 2002-05-31
Filing date: 2003-05-27
Publication date: 2003-12-11
Also published as: AU2003235440A1; JP4429899B2; JPWO2003101844A1

Abstract

A surface-modified aluminum can, characterized in that it is a two piece aluminum can having a thickness of an aluminum material in its trunk portion of 65 to 200 μm, and almost the whole of the outer surface of the trunk portion is covered with a surface hardening layer containing 1 to 50 atom % of at least one element of nitrogen, carbon, oxygen, boron, hydrogen and phosphorus. The employment of the surface-modified aluminum can allows the reduction of the percentage of the formation of pin holes, which is a problem inherent in an aluminum can using a thin aluminum material, with little change of the present manufacturing equipment and no effect on the DI working in the manufacture thereof.

Description

Specification

TECHNICAL FIELD The present invention relates to a surface-modified aluminum can and a method for producing the same.

The present invention relates to a surface-treated aluminum can having excellent perforation resistance and a method for producing the same. Background art

There are the following two types of conventional technologies for improving the strength of the body of aluminum cans without increasing the thickness.

(1) Devising the shape of the can body: The can body is made to be a polyhedron in the vertical direction to increase the deformation resistance. In addition, we will improve the resistance to deformation by subjecting the body of the can to an uneven pattern (die cut, etc.), beading, and performing group processing on the circumference.

(2) Method of coating cans with dissimilar materials: Laminating plastic films on aluminum and processing them into cans (talc can technology). In addition, cover the can with a film (shrink label).

All of the above prior art techniques do not improve the strength of the can material itself, but the effect of improving the strength is secondary and minute. In particular, an increase in surface hardness, which is effective for improving puncture resistance (pinhole resistance), could not be expected.

On the other hand, it is possible to increase the rigidity and hardness of the can material itself by changing the composition of the aluminum alloy (such as increasing the amount of magnesium added). ) It could not be used as a can because of the difficulty in processing. Disclosure of the invention

Aluminum cans, especially aluminum cans for beverages, are being reduced in weight for cost reduction, and the thickness of the can body has been reduced to about 100 microns by DI processing. Drinks in aluminum cans During the process of consumption, the frequency of accidents that cause small holes called pinholes in the can body when contacting with objects having sharp protrusions is increasing. Since the formation of pinholes is a serious defect that causes loss of commercial value due to leakage of the contents, it is required to increase the strength of the can body and reduce the generation of holes.

The challenges for improving the strength of the can body are (1) keeping the wall thickness thin so as not to increase the material cost, (2) the processing cost being considerably lower than the material cost, ( 3) Use of aluminum material from the viewpoint of recycling system; and (4) Improvement of strength is linked to reduction of pinholes (improvement of piercing resistance).

In order to prevent the occurrence of pinholes, which is a problem inherent in aluminum cans made of thin aluminum materials, the present invention uses a hardened surface layer on almost the entire outer surface layer of the can body where pinholes are likely to occur. Another object of the present invention is to reduce the occurrence of pinholes by forming a hard coating on almost the entire outer surface of the can body.

Conventionally, as a method of hardening the surface of metal products, a thermal diffusion surface treatment method (a carburizing treatment to increase the amount of carbon in the surface layer by maintaining contact with hydrocarbons etc. at a high temperature of several hundred degrees Celsius or higher; Nitrogen ionization method), and ion nitriding method (a method of performing nitrogen discharge of a mixed gas of nitrogen and hydrogen under low pressure to nitrogenate the surface layer). These were intended to improve the wear resistance of metal parts and required several hours of treatment at high temperatures (hundreds of degrees) (the surface hardened layer was several ten microns or more).

On the other hand, recently, attempts have been made to attempt surface hardening by ion implantation technology (accelerating ions to form a solid solution in a metal at a reduced temperature and at a low temperature).

An object of the present invention is to apply these surface treatment techniques to the surface of a can body to economically increase the surface hardness at a low temperature and at a high speed to improve the perforation resistance. Here, when forming a hardened surface layer or a hard coating, the thickness of the hardened surface layer or the hard coating should be reduced in order to reduce the thickness of the can body to 65 to 2001. The problem is how much is formed.

Further, in the present invention, by forming the surface hardened layer as a so-called gradient composition layer, the object is to simultaneously improve the adhesion between the aluminum base material and the hardened surface layer and harden the outer surface of the can body. And

Another object of the present invention is to reduce the pinhole occurrence rate by forming a surface hardened layer in the manufacturing process of a two-piece aluminum can in order to increase the surface hardness of the body of the can after molding. It is an object to manufacture cans. At this time, it is important to form a hardened surface layer with little change to existing can manufacturing equipment and without affecting DI processing at all. The impact on can manufacturing equipment and DI processing can lead to enormous cost increases.

Here, an object of the present invention is to form a surface hardened layer by converting a raw material gas into plasma using normal pressure plasma or reduced pressure plasma.

An object of the present invention is to increase the surface hardness of the can body after forming the can in the manufacturing process of a two-piece aluminum can.

(Chemical vapor deposition) or PVD (physical vapor deposition) to produce aluminum cans with a reduced pinhole generation rate by forming a hard coating on the bottom of the bottomed can body. Make it an issue. As with the formation of the hardened surface layer, the task is to form the hardened surface layer with little change to the existing can manufacturing equipment and without affecting DI processing at all. In the surface-modified aluminum can of the present invention, the body of the two-piece aluminum can has an aluminum material thickness of 65 to 20 Oj ^ m, and almost the entire outer surface layer of the body is formed of nitrogen, carbon, oxygen, Surface hardened layer containing at least one of boron, hydrogen and phosphorus elements at 1 to 50 atom% It is characterized by that.

2. The surface-modified aluminum can according to claim 1, wherein the body of the two-piece aluminum can has an aluminum material thickness of 65 to 200 m, and a hard coating is formed on almost the entire outer surface of the body. Is preferred.

In the surface-modified aluminum can according to claim 1 or 2, it is preferable that the hardened surface layer or the hard coating is formed to have a thickness of 0.1 to 30 m.

4. The surface-modified aluminum can according to claim 1 or 3, wherein the surface hardened layer is inclined such that the element content ratio of the element according to claim 1 decreases from the outer surface of the body to the inside of the aluminum material. It is preferable to form the composition.

The method for producing a surface-modified aluminum can according to the present invention is a method for producing a two-piece aluminum can, comprising: forming a bottomed can body from an aluminum plate; washing the bottomed can body; While rotating around the center axis of the bottomed can body, the body portion of the body portion is made of a plasma gasified raw material gas containing at least one of each element of nitrogen, carbon, oxygen, boron, hydrogen or phosphorus. Almost the entire outer surface layer is formed as a surface hardened layer containing at least one of the above elements at 1 to 50 atom%.

The cleaning method according to claim 5, wherein after cleaning the bottomed can body, the bottomed can body is charged into a vacuum chamber, and substantially the entire outer surface layer of the body portion is reduced under reduced pressure with the plasma-converted raw material gas. It is preferable to form on the surface hardened layer.

The method for producing a surface-modified aluminum can according to the present invention is a method for producing a two-piece aluminum can, comprising: forming a bottomed can body from an aluminum plate; washing the bottomed can body; A hard coating is formed on almost the entire outer surface of the body of the bottomed can body by phase growth method) or PVD (physical vapor phase growth method). The aluminum can of the present invention has a surface hardened layer or a hard coating formed on almost the entire outer surface layer of the can body where pinholes are likely to occur. A certain pinhole generation rate could be reduced. Here, the present invention is to improve the piercing resistance by economically increasing the surface hardness at a low temperature and at a high speed. Here, by specifying the thickness of the surface hardened layer or hard coating, even if the thickness of the can body is as thin as 65 to 200 ^ m, the strength and adhesion can be ensured while maintaining the strength and adhesion. Meets economics. Further, in the present invention, by making the surface hardened layer a graded composition layer, the adhesion between the aluminum base material and the hardened surface layer and the hardening of the outer surface of the can body are simultaneously satisfied.

The aluminum surface-modified can of the present invention can improve the puncture resistance because the surface hardened layer or the hard coating is formed, but with this, the body part was thickened to obtain the predetermined puncture resistance. It is possible to reduce the thickness of the aluminum material as compared with the case where no hardened surface layer or hard coating is formed. By reducing the thickness of the aluminum material, an increase in cost for forming a hardened surface layer or a hard coating can be absorbed.

In addition, the production method of the present invention uses an ion implantation technique, a diffusion infiltration technique, a normal pressure plasma or a reduced pressure plasma technique, or a CVD or PVD technique to convert the surface-modified aluminum can into an existing can manufacturing equipment. The hardened surface layer was able to be formed with almost no change in DI and without affecting DI processing at all. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a conceptual diagram showing one embodiment of an apparatus for performing a surface treatment on a surface-modified aluminum can of the present invention.

FIG. 2 is a conceptual diagram showing another embodiment of an apparatus for performing a surface treatment on a surface-modified aluminum can of the present invention. FIG. 3 is a conceptual diagram showing a longitudinal section of a bottomed can body of a surface-modified aluminum can having a surface hardened layer formed thereon.

FIG. 4 is an enlarged view of a part AA ′ in FIG.

FIG. 5 is a conceptual diagram showing a vertical cross section of a bottomed can body of a surface-modified aluminum can having a hard coating formed thereon.

FIG. 6 is a graph showing a comparison of piercing strength between a surface-modified aluminum can and an untreated aluminum can when an aluminum nitride film is formed on the surface of the can body.

The meanings of the symbols are as follows. 1 is an atmospheric pressure plasma generating means, a plasma generating means, an ion accelerating means or a microwave generating means, 2 is a plasma discharge, 3 is a positive / negative voltage adjusting means, 4 is a can body with a bottom, 5 is a surface hardened layer or Hard coating, 6 is raw material source, 7 is raw material supply means, 8 is raw material supply pipe, 9 is plasma raw material gas supply means, 10 is high frequency power supply or microwave generator, 11 is plasma jet outlet, 12 Is a hard coating, and 13 is a hardened surface layer. BEST MODE FOR CARRYING OUT THE INVENTION

[Example]

(Aluminum can with surface hardened layer)

Hereinafter, the present invention will be described in detail, but the present invention is not construed as being limited to these descriptions.

In one embodiment of the surface-modified aluminum can of the present invention, the body of the two-piece aluminum can has an aluminum material thickness of 65 to 20 Om, and almost the entire outer surface layer of the body is formed of nitrogen or carbon. It is a surface hardened layer containing at least one of oxygen, boron, hydrogen, and phosphorus at 1 to 50 atom%.

Cans, especially beverage cans, can be broadly divided into aluminum cans and steel cans depending on the material. In the present invention, the reason why the can was limited to an aluminum can is that accidents caused by pinholes frequently occur in aluminum cans. Because it occurs. Since aluminum cans have lower perforation resistance than steel cans, improved strength is required.

The cans are roughly divided into two-piece cans and three-piece cans. A three-piece can is a three-piece can body consisting of a can body and a top and bottom lid. A two-piece can, on the other hand, is a can body consisting of a can body with a bottom and a lid with an opening, and is formed by a combination of extraction from a flat plate, deep drawing and ironing. It forms a bottomed can body. Generally, the body of a three-piece can is formed by bending a flat plate that is considerably thicker than the thickness of the body of a two-piece can into a cylindrical shape. Therefore, although there are aluminum three-piece cans, the perforation resistance is not required as much as two-piece cans due to the thick wall of the body. Accordingly, in the present invention, an attempt is made to improve the surface strength of the outer surface of the can body of a two-piece aluminum can, for which puncture resistance is strongly required.

The reason why the thickness of the aluminum material of the body is 65 to 200 m is that if the thickness is less than 65 m, the strength of the aluminum can itself becomes weak, so that a practical aluminum can cannot be manufactured. On the other hand, if it exceeds 200 m, the strength of the aluminum material itself of the can body is ensured, so that the pinhole problem is reduced without applying surface treatment. Thickness is closely related to capacity. For example, in the case of beverage cans, the thickness of the aluminum part of the body is 350 to 110 m for 350 m1 cans and 500 ml cans, and 120 to 150 m for 1 liter cans. 5 m, 1.5 liter cans to 140 to 180 m, 2 liter cans to 150 to 190 um, 3 liter cans to 160 to 200 m Is preferred. For other capacities, these thickness values can be extrapolated to the capacity of the container to obtain the capacities appropriately.

The thickness of the can body is usually in the range of 90 to 120 microns, and in order to improve the perforation resistance of the can, the surface hardness of the can body is more than twice the original hardness, preferably 4 times. The above is necessary. That is, the micro-Vickers hardness Hv30 to 60 (untreated) is preferably Hv60 to 120, It is desirable to set Hv 120 to 240.

Almost the entire outer surface layer of the torso is made of a hardened surface layer because pinholes are likely to occur in this area. The lid of a two-piece can usually has a pinhole accident because the thickness of the lid is larger than the thickness of the body, and magnesium is added to aluminum as a hardener. It is rare. On the other hand, the bottom of the can is concave toward the inner surface of the can to withstand pressure. Therefore, a pinhole accident is rarely caused at the bottom, because the possibility of a sharp end that causes pinholes is small. Furthermore, since external shocks cause pinholes, it is necessary to harden the outer surface of the can body, so almost the entire outer surface layer of the body is made into a hardened surface layer. .

Here, the surface hardened layer referred to in the present invention is classified into two, an ion implantation hardened layer and a diffusion hardened layer.

The ion-implanted hardened layer is formed by a plasma method. For example, ions generated by glow discharge are accelerated by an ion accelerator and solid-dissolved in a metal under vacuum and low temperature. For example, when nitrogen gas and hydrogen gas are introduced into the glow generated by the glow discharge, positive ions such as Ν +, Η Η + are generated. When these ions collide with the aluminum material on the outer surface of the can body, the surface of the aluminum material is subjected to ion nitriding (plasma nitriding), and aluminum nitride is formed on the outer surface layer of the can body. At this time, the surface is hardened even if all of the aluminum does not react with the aluminum nitride.In addition, when methane or propane is introduced into the glow as a carrier gas using hydrogen gas or argon gas, the surface of the aluminum material is plasma carburized. Carbonized, aluminum carbide is formed on the outer surface layer of the can body. This hardens the surface even if all of the aluminum does not react with the aluminum carbide. In addition to ion nitrogen and plasma carburization, oxygen, boron, hydrogen, or phosphorus can be implanted, and a plurality of these elements can be implanted. On the other hand, the diffusion hardened layer is formed by diffusion infiltration treatment. The diffusion and infiltration treatment is a treatment in which the object to be treated is brought into contact with a treatment agent containing the diffused element at a predetermined temperature or higher determined by the diffused element, and the treatment is carried out for a fixed time. Due to the concentration difference of the diffusion element, it diffuses from high concentration side to low concentration side. Diffusion Infiltration treatment includes carburizing treatment, nitriding treatment, carbonitriding (soft nitriding) treatment, oxidation treatment, oxynitridation treatment, oxycarbonitridation treatment, boration treatment, hydrogenation treatment or hydrogenation treatment, depending on the diffusion element. . By performing these diffusion treatments on the aluminum material on the outer surface of the can body, a diffusion hardened layer containing at least one of nitrogen, carbon, oxygen, boron, hydrogen, and phosphorus is contained. Is formed on the outer surface layer of the can body. In addition, they are roughly classified into solid method, liquid method and gas method according to the form of treatment agent. In the gas method, when this gas is introduced into the glow, the ionization and the ion acceleration are performed by the potential difference in the glow, which is the same as the above-described plasma method. According to the same principle as PVD, the surface hardened layer uses zirconium, titanium, etc. as a metal ion source and sets the can body to a negative voltage, thereby implanting metal ions into aluminum and dissolving predetermined ions into the aluminum alloy of the can body May be.

Further, in the present invention, it is preferable that the hardened surface layer is formed in a gradient composition in which the element content ratio of the above elements decreases from the outer surface of the body toward the inside of the aluminum material. The closer to the surface, the higher the hardness and the graded composition, the stronger the adhesion of the surface hardened layer and the less likely it is to peel off. The surface hardened layer tends to have a gradient composition due to the manufacturing principle based on ion implantation or diffusion infiltration.

In the present invention, since it is preferable to form the surface hardened layer at a low temperature and at a high speed, at least one of nitrogen, carbon, oxygen, boron, hydrogen or phosphorus is ion-implanted or diffused and permeated by a plasma method. Preferably. Such a surface hardened layer fills the aluminum crystal lattice defects in the surface layer or prevents the dislocation movement in the aluminum crystal grains in the surface layer from moving due to the presence of these elements. It is formed to increase the hardness by eliminating the slip deformability of the crystal. In order to further increase the hardness, it is effective to form aluminum nitride crystals, aluminum carbide crystals or aluminum oxide crystals with a predetermined thickness from aluminum crystals.

By the way, the aluminum plate used to form the bottom body of the aluminum can contains manganese element to prevent corrosion. A reaction between the manganese and each element of nitrogen, carbon, oxygen, boron, hydrogen, or phosphorus may be caused to form a compound such as manganese nitride or manganese carbide as a surface hardened layer.

If the surface hardened layer contains at least one of nitrogen, carbon, oxygen, boron, hydrogen or phosphorus in an amount of 1 to 50 atom%, the effect of the surface hardening is sufficient if it is less than 1 atom%. If it exceeds 50 atom%, the body becomes brittle.

For example, in the case of nitrogenation, the outermost surface layer must have a nitrogen atom content of 1% or more, preferably 5% or more.

The thickness of the surface hardened layer depends on the hardness, but is preferably in the range of 0.1 to 30 / m. Desirably, 4 to 10 / m is necessary to obtain a hardness improving effect. If it is less than 0.1 m, sufficient surface strength cannot be obtained, and if it exceeds 30 m, the can becomes brittle.

(Production method of aluminum can having surface hardened layer)

Next, in the method of manufacturing a two-piece aluminum can, a method of manufacturing a surface-modified aluminum can when forming a hardened surface layer will be described. First, a bottomed can body is formed from an aluminum plate and the bottomed can body is washed. When forming the bottomed can body, degreasing is performed because oil etc. adheres to the outer surface of the can. The washing step is, for example, washing with warm water (pre-process), washing with an inorganic acid-based detergent containing sulfuric acid and activator at 60 to 80 (washing), and again using sulfuric acid and an activator. Wash with acid-based detergent at 60-80 (approximately dry), and finally wash with tap water. Next, while rotating the bottomed can body about the central axis of the bottomed can body, a plasmatized raw material gas containing at least one of the elements nitrogen, carbon, oxygen, boron, hydrogen or phosphorus. Is brought into contact with almost the entire outer surface layer of the torso. The raw material gas may be introduced into the glow by the normal pressure plasma method, or the raw material gas may be turned into plasma and then sprayed. For example, as shown in Fig. 1, the can body is rotated around the cylinder axis, and plasma is generated by a high-frequency power source 10 and plasma generation means 1 provided in contact with the can body, and hydrogen-nitrogen-based gas is generated. Is turned into plasma. The can body 4 is converted to a negative voltage by the positive / negative voltage adjusting means 3 to generate a potential difference between the can body and the plasma generating means, and ionized N + and NH + are discharged to the can body by the sputtering effect. It is made to strike almost the entire outer surface. By this ion bombardment, nitrogen element is injected into the aluminum material in the body, and a hardened surface layer is formed. In order to adjust the charge of the ions, plasma may be applied with such an intensity that no glow discharge occurs. At this time, the implanted nitrogen is intended to prevent dislocation movement in the aluminum crystal grains. Alternatively, the aluminum surface is ion-nitrided, and aluminum nitride prevents dislocation movement in aluminum crystal grains. By this phenomenon, almost the entire outer surface layer of the trunk is hardened. The ion acceleration may be performed by an ion accelerator. After that, aluminum cans are manufactured through the can printing process, neck-in flange processing, and can inspection.

Further, as shown in FIG. 2, a plasma source gas supply unit integrating an atmospheric pressure plasma generation unit, a plasma generation unit, an ion acceleration unit or a microwave generation unit, and a source gas plasma generation unit having parallel plate electrodes. 9 is used to supply the source gas between the parallel plate electrodes to convert the source gas into plasma, and from the plasma project outlet 11 provided in the plasma source gas supply means 9 a bottomed can that rotates around the can cylinder axis The source gas which has been turned into plasma may be sprayed over the entire body of the body 4. In this case as well, a sputtering effect can be obtained due to the potential difference between the can body and the plasma source gas supply means 9. Through the above steps, a surface hardened layer 13 is formed on the outer surface of the can body 4 as shown in FIG. As shown in the partially enlarged view of FIG. 4, the surface hardened layer 13 has a diffusion element such as nitrogen diffused from the surface of the can body 4 toward the inside of the material. It is preferable that the surface of the can body 4 has the highest element concentration, and has a gradient composition such that the element concentration decreases toward the inside of the material.

The speed of forming the surface hardened layer varies depending on the degree of hardening and the thickness of the layer, but in order to form the layer economically, the film forming time should be 120 seconds or less, preferably 30 seconds or less. Is preferred.

After the washing process, the bottomed can body may be put into a vacuum chamber, and a hardened surface layer may be formed under reduced pressure on almost the entire outer surface layer of the body portion by using plasma of the raw material gas. By putting it in a vacuum chamber, it becomes a low-pressure plasma method, and it is possible to increase the deposition rate at low temperatures. (Aluminum can with hard coating)

As another form, the surface-modified aluminum can of the present invention has a body thickness of 65 to 20 O ^ m in the body of a two-piece aluminum can, and forms a hard coating on almost the entire outer surface of the body. You may. Here, a hard coating is formed on almost the entire outer surface of the torso. The characteristics of the can material, wall thickness, coating site, hardness, etc. are as described in the case of forming a hardened surface layer. The same applies as well. When a film is formed by plasma CVD, the raw material gas is turned into plasma, and titanium oxide, zirconia oxide, aluminum nitride, aluminum oxide, and the like are formed as a hard coating on the surface of the can body at a predetermined thickness. When forming a film by PVD, a hard film may be formed to a predetermined thickness on the surface of the can body by using zirconium, titanium, or the like as a metal ion source and setting the can body to a negative voltage. The thickness of the hard coating depends on the hardness, but is preferably formed to a thickness of 0.1 to 3 O / zm. Desirably, 1 to 5 m is necessary to obtain the effect of improving hardness. If less than 0.1 tm, sufficient surface strength cannot be obtained If it exceeds 30 / m, there is a risk of peeling.

(Method of manufacturing aluminum can having hard coating)

Next, in the method of manufacturing a two-piece aluminum can, a method of manufacturing a surface-modified aluminum can when forming a hard coating will be described. The cleaning step is the same as the above-described cleaning step. When a film is formed on the outer surface of the can body by plasma CVD after cleaning, for example, a metal alkoxide such as titanium tetra-iso-propoxide or zirconium tetra-t-butoxide may be used to form a metal chloride such as titanium chloride, zirconium chloride, or aluminum chloride. The raw material gas, which is a product, is turned into plasma, and a hard coating of titanium oxide, zirconium oxide, aluminum nitride, aluminum oxide, or the like is formed to a predetermined thickness on the surface of the can body. In order to adjust the charge of the ions, plasma may be applied at such an intensity that no glow discharge occurs. On the other hand, when the film is formed by PVD, a hard coating may be formed to a predetermined thickness on the surface of the can body by using zirconium, titanium, or the like as a metal ion source and setting the can body to a negative voltage. The film formation time required for forming the hard film varies depending on the film thickness and the like, but is preferably 120 seconds or less, and more preferably 30 seconds or less, in order to form the film economically. After that, aluminum cans are manufactured through the can printing process, neck-in-flange processing, and can inspection.

Through the above steps, a hard coating 12 is formed on the outer surface of the can body 4 as shown in FIG.

(Study on surface modification by aluminum nitride film formed by PVD film formation method)

As a hard coating, an aluminum nitride film was formed on the can body surface of the aluminum can by the PVD film forming method. The sputtering target was metal aluminum, and the film was formed in a nitrogen atmosphere. In Sample I, the thickness of the aluminum nitride film was 600 nm. The thickness of the aluminum film was set to 1300 nm. An uncoated aluminum can was used as a control.

The piercing strength was measured when a needle indenter with a sample indenter tip diameter of 2.25 mm (2.25 R) was pressed vertically into the can body surface. The evaluation was performed in comparison with the control. The measuring instrument used was an autograph (Ag-lOkND, manufactured by Shimadzu Corporation). Figure 6 shows the results.

In sample I, the improvement ratio of control was 144%, and in sample I, the improvement ratio of control was 149%. That is, the piercing strength was improved by 40 to 50% by forming the hard coating, which was effective in improving the perforation resistance (pinhole resistance).

According to the comparison between Samples I and II, the piercing strength did not depend on the film thickness. In the present invention, a high frequency power supply or a microwave power supply can be exemplified as an energy source for generating plasma.

In the present invention, the method of forming the hard coating directly on the aluminum material on the outer surface of the trunk portion has been described. However, in order to prevent peeling of the hard coating and the aluminum material, an adhesion layer is provided between them. Is also good.

After the formation of the surface hardened layer or the hard coating, a lubricating oil film may be formed for the purpose of imparting lubricity to the can surface.

As described above, the production method of the present invention forms a hardened surface layer or a hard coating after the cleaning step, so that the existing can production equipment is hardly changed and the surface treatment is performed without any influence on DI processing. A cured layer can be formed.

The present invention is not limited to the use of aluminum cans, but is particularly suitable for beverage cans.

Claims

The scope of the claims

The body thickness of the body of the 1.2-piece aluminum can is 65 to 200 m, and almost the entire outer surface layer of the body is made of nitrogen, carbon, oxygen, boron, hydrogen or phosphorus. A surface-modified aluminum can characterized in that it is a surface-hardened layer containing at least one of 1 to 50 atom%.

2. A surface-modified aluminum can having a body thickness of 65 to 200 m and a hard coating formed on almost the entire outer surface of the body of the two-piece aluminum can.

3. The surface-modified aluminum can according to claim 1, wherein the hardened surface layer or the hard coating is formed to have a thickness of 0.1 to 30 / m.

4. The surface hardened layer is formed in an inclined composition in which the element content ratio of the element according to claim 1 decreases from the outer surface of the body toward the inside of the aluminum material. Or the surface-modified aluminum can described in 3.

5.2 In the method for manufacturing a two-piece aluminum can, a bottomed can body is formed from an aluminum flat plate, and the bottomed can body is washed, and then the bottomed can body is rotated about a central axis of the bottomed can body. However, almost all of the outer surface layer of the body is made of a plasma-converted source gas containing at least one of the elements nitrogen, carbon, oxygen, boron, hydrogen, and phosphorus. A method for producing a surface-modified aluminum can, characterized by forming a surface-hardened layer containing 1 to 50 atom% of each type.

6. The bottomed can body according to claim 5, wherein the bottomed can body is washed. 6. The surface reforming method according to claim 5, wherein the surface reforming is performed by forming substantially the entire outer surface layer of the body under reduced pressure on the surface hardened layer using the raw material gas that has been turned into plasma. For manufacturing high quality aluminum cans.

7.2 In the method of manufacturing a two-piece aluminum can, a bottomed can body is formed from an aluminum flat plate, and the bottomed can body is cleaned and then subjected to plasma CVD (chemical vapor deposition) or PVD (physical vapor deposition). A method for producing a surface-modified aluminum can, characterized in that a hard coating is formed on almost the entire outer surface of the body of the bottomed can body by vapor phase growth.