JP7415319B2 - Seamless can manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a seamless can body, and more specifically to a method for manufacturing a seamless can body using a coolant suitable for molding aluminum cans, for example.

Conventionally, press working has been used as a manufacturing method for producing industrial products in large quantities at low cost. Such press working is suitable for processing various workpiece materials, and examples of workpiece materials include metal materials such as steel, copper, and aluminum, as well as titanium and magnesium.

An example of the above-mentioned industrial product is, for example, can stock. For example, in a two-piece can body (so-called seamless can body) illustrated in Patent Document 1, the can body and the like are formed by drawing and ironing using the above-described press mold. A press mold for performing press processing for manufacturing a seamless can body includes a punch section and a die section, and a workpiece is press-formed with a proper clearance between the punch section and the die section.

In recent years, punch parts and die parts are placed under harsh environments during press processing, so carbon films such as diamond films and DLC (diamond-like carbon) films are applied to the processing surfaces of molds, as shown in Patent Documents 2 to 5, for example. It has been proposed to coat the mold with a membrane to improve the durability of the mold.

Patent No. 6012804 Japanese Patent Application Publication No. 10-137861 Japanese Patent Application Publication No. 11-277160 Japanese Patent Application Publication No. 2013-163187 International Publication WO2017/033791 Publication

As mentioned above, press molds are placed in harsh processing environments, and therefore, for example, the processing surfaces of die parts and the like are coated with various surface treatment films. As such a surface treatment film, it is desirable that the processed surface be coated with a carbon film such as a diamond film or a DLC film that has high slip properties and can suppress adhesion by the workpiece during pressing.

When press working is performed using a mold in which a diamond film or the like having high sliding properties as described above is formed on the work surface, there is also the advantage that so-called dry press work can be performed. Dry press processing is press processing performed in a dry environment without using a lubricant during press processing. Dry press processing has attracted attention because it can omit processes such as cleaning the lubricant after can manufacturing and treating waste water after cleaning, reducing costs and environmental impact.

However, in dry press processing, there have been some points that need to be improved. Points to be improved include, for example, points (a) to (c) below.
(a) During dry pressing, powder from the workpiece material (for example, aluminum powder) is generated and gets caught in the mold, potentially causing damage to the molded can body.
(b) During dry pressing, high temperatures (locally over 300°C) must be generated between the mold and the workpiece, so when performing severe processing (strong processing) such as ironing, for example. It has been difficult to increase the degree of processing (for example, the limit ironing rate).
(c) For the same reasons as (a) and (b) above, cans can be produced stably over a long period of time without problems such as adhesion or accumulation of workpiece materials on the mold or breakage of the can body. However, it has been difficult to improve the so-called molding stability.

On the other hand, conventionally, when manufacturing a seamless can body using an aluminum material, for example, it has been common to perform molding in a wet environment using a lubricant such as oil or a coolant. In this case, after the can manufacturing process, a cleaning process (washing process) is essential to degrease the lubricant etc. adhering to the can body using a detergent or chemical.
However, since this cleaning process requires a large amount of water, there is a need to review the process in these days when people are promoting the effective use of limited water resources.
Furthermore, since various chemical substances are contained in the wastewater discharged in the cleaning process, it has been pointed out that there is a need to reduce the labor and cost required for wastewater treatment.

The present inventors have repeatedly conducted intensive studies in view of the problems exemplified above. As a result, it has been found that when pressing is performed using a coolant under specific conditions, advantages over the dry pressing described above can be obtained.
In other words, when pressing is performed with a specific oil content in the coolant while using a mold with a diamond film or the like formed on the processing surface that has high sliding properties, severe processing such as ironing may be performed. Also, it was possible to obtain a degree of processing (e.g., limit ironing rate) equal to or higher than that of pressed products manufactured using conventional amounts of lubricant.
Furthermore, it has been discovered that the problems in the above-mentioned cleaning process and wastewater treatment process can also be solved, leading to the present invention.

In order to achieve the above object, a method for manufacturing a seamless can body according to an embodiment of the present invention includes: (1) using a molded member having a diamond film formed on the processed surface; The method is characterized in that it includes a step of press working a metal material on the processed surface of.
In the method for manufacturing a seamless can body of (1) above, (2) it is preferable that the oil content contained in the coolant is 4% by volume or less.
In the seamless can manufacturing method of (1) or (2) above, (3) it is preferable that the molded member includes at least a die portion.
Further, in the method for manufacturing a seamless can body according to any one of (1) to (3) above, (4) the pressing process includes ironing the metal material, and the ironing rate in the ironing process is 10%. It is preferable to form the can body by squeezing the metal material as described above.
Further, in the method for manufacturing a seamless can body according to any one of (1) to (4) above, (5) the surface roughness of the molded member used in the ironing process is Ra = 0.12 μm or less. It is preferable.
Furthermore, in the method for manufacturing a seamless can body according to any one of (1) to (4) above, (6) the surface roughness of the molded member used in the ironing process is Ra = 0.08 μm or less. It is even more preferable.

According to the method for manufacturing a seamless can body of the present invention, since it includes a step of press working such as ironing using a molded workpiece (for example, a punch part and a die part) on which a diamond film is formed on the work surface, the mold High processing durability can be achieved.
Since press processing such as ironing is performed with coolant intervening, the powder (metal powder) of the workpiece generated during ironing is washed away, and the metal powder is caught in the mold, resulting in the can being molded. It is possible to suppress damage to the appearance of the product.

(a) is a schematic diagram showing a press working step in the method for manufacturing a seamless can body of the present invention, and (b) is a schematic diagram in Example 1.

Hereinafter, the method for manufacturing a seamless can body of the present invention will be specifically described with reference to the drawings as appropriate. In addition, the following embodiment shows an example of this invention and explains the content, and does not limit this invention intentionally.

<Molded parts>
As shown in FIG. 1, in the seamless can manufacturing method of this embodiment, a metal material 10 is pressed on the processed surface of the formed member D using a formed member having a diamond film formed on the processed surface. including the step of

To explain this embodiment more specifically, as shown in FIGS. 1(a) and 1(b), there is a die part D in which a diamond film 20 is formed on the processed surface, and a surface treatment film 30 different from the diamond film. It includes a step of ironing the metal material 10 on the processing surfaces of the die section D and the punch section P using the ironing punch section P formed on the processing surface, with coolant C intervening.

Here, in this embodiment, as shown in FIG. 1, the present invention will be explained by taking ironing processing as an example among can manufacturing processing.
However, it goes without saying that the method for manufacturing a seamless can body of the present invention is not limited to ironing, but can also be applied to known can manufacturing processes such as drawing, doming, necking, trimming, etc. .
Further, the present invention can be appropriately applied to known metal press working other than can manufacturing, such as shearing work, bending work, etc.

In this embodiment, the molded member includes a die portion D and a punch portion P. However, the molded parts in the present invention are not limited to these, and may also include known molded parts used in metal press working, such as draw pads, blank punches, cutters, blank holders (wrinkle suppressors), plugs, etc. Applicable as appropriate.

In this embodiment, the diamond film 20 is formed on the processed surface of the die portion D, as shown in FIG. 1(b). However, the present invention is not limited to this form, and the diamond film 20 may be formed on the processed surfaces of both the die part D and the punch part P.
Further, a diamond film 20 may be formed on the processed surface of the punch portion P, and a surface treatment film 30 different from the diamond film may be formed on the processed surface of the die portion D.
That is, in the present embodiment, it is sufficient that the diamond film 20 is formed on the working surface of at least one of the male die and the female die in the die for press working.

In this embodiment, a known film forming method can be applied as a method for forming the diamond film 20 on the processed surface of the molded member. For example, in addition to CVD (Chemical Vapor Deposition) methods such as hot filament CVD, microwave plasma CVD, high frequency plasma CVD, and thermal plasma CVD, it is possible to apply a known PVD (Physical Vapor Deposition) method.

The thickness of the diamond film 20 is preferably 5 μm to 30 μm. If the thickness is less than 5 μm, the obtained diamond film is likely to crack and peel off, which is not preferable. On the other hand, if the thickness exceeds 30 μm, it is not preferable because the internal stress of the diamond film increases and it becomes easy to peel off.

In Raman spectroscopy, the diamond film has an intensity ratio I D _/ , where I _D is the intensity of the maximum peak existing at 1333 ± 10 cm ^-1 , and I _G is the intensity of the maximum peak existing at 1500 ± 100 cm ^-1 . It is preferred that the I _G is greater than 0.6, and particularly preferably less than 1.1. When the Raman intensity ratio I _D /I _G is less than 0.6, the content of graphite in the diamond film becomes high, and the performance inherent to diamond cannot be obtained. On the other hand, when the Raman intensity ratio I _D /I _G is 1.1 or more, impact resistance is poor, which is not preferable.

On the other hand, in the present embodiment, the surface treatment film 30 different from the diamond film, which may be formed on the processed surface of at least one of the male mold and the female mold during press working, is, for example, Examples include a carbon film such as a known diamond-like carbon (DLC) film, a TiC film, a TiCN film, and the like.

There are no particular restrictions on the method of forming these diamond-like carbon films; for example, a chemical vapor deposition (CVD) method that uses gas as a raw material and decomposes the gas in a chamber to form a film, or a method that uses solid carbon as a raw material. A known forming method such as a physical vapor deposition (PVD) method in which a film is formed by evaporating carbon can be applied. Furthermore, known film forming methods can be applied to TiC films, TiCN films, and the like.

As the thickness of the above-mentioned surface treatment film 30, a thickness within a reasonable range for a film formed based on the above-described known method can be applied. Specifically, the thickness of the surface treatment film 30 is preferably about 0.1 μm to 10 μm, for example.
In other words, the thickness of the surface treatment film 30 in this embodiment is set to be thinner than the thickness of the diamond film 20.

Note that in the above case, the hardness of the surface treatment film 30 is preferably lower than the hardness of the diamond film 20. For example, in this embodiment, the hardness of the diamond film 20 is preferably 10,000 to 12,000 in terms of Vickers hardness HV ₂₀ from the viewpoint of durability of the mold. On the other hand, the hardness of the surface treatment film 30 is preferably relatively low compared to the hardness of the diamond film 20, and is preferably 1000 to 8000 in Vickers hardness _HV30 , for example. This is due to the following reasons.

That is, because the diamond film 20 cannot be easily polished due to its nature, it is very difficult to adjust the dimensions, and it is difficult to control the dimensions between molds, resulting in an increase in costs.

In recent years, dimensional control within ±several μm is required even in the ironing process in can manufacturing. In such a situation, as shown in FIG. 1, a diamond film 20 is formed on the processing surface of one tool (for example, the die part) of the forming workpiece, and a diamond film 20 is formed on the processing surface of the other tool (for example, the punch part). By forming the surface treatment film 30 different from the above, there are the following advantages.
First, when controlling dimensions, since the surface treatment film 30 is thinner than the diamond film 20, the deviation from the target dimension is small, and even if it deviates from the target range, the surface treatment film 30 has a lower hardness. Polishing the treated film 30 has the advantage of facilitating dimensional adjustment.
Additionally, in the event that the male and female molds collide for some reason, the less hard mold absorbs the impact, which has the advantage of minimizing damage to the mold. .

In this embodiment, the surface roughness Ra (JIS B-0601-1994) of the diamond film 20 is preferably 0.12 μm or less from the viewpoint of imparting high sliding properties to the mold. Furthermore, when Ra is 0.08 μm or less, even in severe processing (strong processing) such as ironing, the appearance of the workpiece (for example, a can body) can be made into a mirror surface or a smooth surface close to a mirror surface. More preferred.
In this case, the friction coefficient μ between the diamond film 20 and the workpiece during press working is preferably lower than 0.1.

In this embodiment, the material of the molded member on which the diamond film 20 and the surface treatment film 30 are formed can be any known material used for molds.
For example, so-called cemented carbide obtained by sintering a mixture of tungsten carbide (WC) and a metal binder such as cobalt, metal carbides such as titanium carbide (TiC), and titanium compounds such as titanium carbonitride (TiCN). Examples include cermets obtained by sintering a mixture with a metal binder such as nickel or cobalt, or hard ceramics such as silicon carbide (SiC), silicon nitride (Si3N4), alumina (Al2O3), and zirconia (ZrO2). .

<Coolant>
Next, the coolant used in this embodiment will be explained.
The coolant used in this embodiment preferably contains oil in its components, but it may also be a coolant that does not contain oil. For example, water such as pure water may be used as the coolant. Good too.

In the coolant according to the present embodiment, the above-mentioned oil component includes an oil component contained in a general water-soluble metal working oil composition. This oil may be a natural oil or a synthetic oil.
Examples of natural oils include paraffinic, naphthenic, and aromatic mineral oils. Fatty acid glycerides can also be mentioned as natural oils.
Examples of synthetic oils include hydrocarbons such as polyolefins, esters such as fatty acid esters, ethers such as polyalkylene glycol, fluorine-containing oils such as perfluorocarbons, phosphorus-containing oils such as phosphoric acid esters, and silicate esters. Examples include silicon-containing systems.
The oils listed above may be used alone or in combination of two or more.

The above water-soluble metal working fluids include, for example, water-soluble metal working fluids of type A1 (emulsion type), type A2 (soluble type), and type A3 (solution type) specified in JIS K 2241. can be mentioned.
Although not specified in the JIS standards, there may also be mentioned water-soluble metal working fluids called synthetic types (metal working fluids that do not contain mineral oil but contain chemically synthesized oil).

In this embodiment, the concentration of the oil in the coolant is preferably 4.0% by volume or less. In this case, when using a coolant containing oil in this embodiment, first prepare a stock solution containing oil with a content of 4.0% by volume or more, store this until use, and then Alternatively, a coolant having an oil concentration of 4.0% by volume or less may be prepared by diluting this stock solution with a solvent such as water.
That is, the concentration of oil in the coolant only needs to be 4.0% by volume or less in the state of use.

In addition, components other than oil in the coolant include components included in general water-soluble metal processing fluid compositions, such as water, surfactants, rust inhibitors, extreme pressure additives, coupling agents, and non-ferrous metals. It may contain appropriate anticorrosive agents, preservatives, antifoaming agents, chelating agents, coloring agents, fragrances, and the like.

In this way, in the manufacturing method of this embodiment, even if the concentration of oil in the coolant is relatively low, it is possible to suppress molding defects during can manufacturing, and as a result, it is possible to improve molding stability. It is.

In addition, in this embodiment, as mentioned above, the oil content in the coolant is at a lower concentration than in the past, so in the oil cleaning process after can manufacturing, cleaning with chemicals or water that has a low environmental impact is possible. It becomes possible to reduce the burden on the environment. In addition, since wastewater treatment after washing has become easier, when wastewater is recycled and circulated, it becomes possible to improve the recycling rate, and it becomes possible to reduce costs and the burden on the environment.

<Metal material 10 (workpiece material)>
The metal material used as the workpiece in this embodiment is not particularly limited as long as it can be subjected to press working, and various known materials such as aluminum, copper, iron, steel, titanium, and not only pure metals but also alloys thereof can be used. Metal materials can be applied. Among these metal materials, aluminum alloy is particularly suitable for forming the can body.
There is no particular restriction on the thickness of the metal material 10 in this embodiment, and a normal thickness when manufacturing a can can be applied. For example, as an example of the thickness of the metal material 10 when can manufacturing is performed using an aluminum plate, the original plate thickness (thickness of the original plate) is 0.1 mm to 0.5 mm.

<Stringing rate>
The method for manufacturing a seamless can body of the present embodiment may include an ironing process in which the metal material is pressed to form a can body so that the ironing rate (plate thickness reduction rate) is 10% or more. preferable. In addition, the ironing process may be included multiple times, and the ironing rate may be changed each time. For example, the ironing rate in the initial ironing step may be 10% or more, and the ironing rate in the final ironing step may be 30% or more.
The ironing rate in this embodiment is expressed by the following formula, where the plate thickness before ironing is t ₀ and the plate thickness after processing (60 mm from the bottom of the can) is t ₁ .
Straining rate (%) = 100 x (t ₀ - t ₁ )/t ₀

In other words, according to the seamless can manufacturing method of the present embodiment, even in severe processing where the ironing rate is 30% or more, it is possible to suppress molding defects during can manufacturing, resulting in stable molding. It becomes possible to improve sexual performance.

As described above, according to this embodiment, the following effects can be achieved.
(A) Since press working such as ironing is performed with coolant interposed, it is possible to improve the limit ironing rate by improving the lubricity during ironing.

(B) Since press processing such as ironing is performed with coolant present, problems such as adhesion and accumulation of workpiece materials on the mold, variations in the wall thickness of the can body, and breakage of the can body can be avoided. This can improve molding stability.

(C) Press processing such as ironing is performed with coolant intervening using molded parts (e.g. punch and die parts) on which a diamond film is formed on the processing surface, resulting in high processing durability of the mold. can be realized, and by improving the lubricity during ironing, it is possible to improve the molding stability of the can.

(D) Since the oil content in the coolant used during press processing can be reduced compared to conventional methods, it is possible to use chemicals and water that have a low environmental impact in the oil cleaning process after can manufacturing, reducing the environmental impact. It becomes possible to reduce the
Furthermore, the amount of coolant used can be reduced, and the amount of waste liquid can also be reduced thereby, making it possible to reduce costs and the burden on the environment.
In addition, by reducing the amount of waste liquid, the factors in waste liquid treatment such as pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), and suspended solids (SS) can be improved. , n-hexane, fluorine, etc. can be reduced.

(E) In addition, since wastewater treatment after cleaning has become easier, it has become possible to improve the recycling rate when recycling wastewater and to reduce costs and the burden on the environment. Become.

Hereinafter, the content of the present invention will be explained in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

(Example 1)
A drawn and ironed can (DI can) having an internal volume of 350 mL was manufactured by the method shown below.
First, an aluminum alloy plate (JIS H 4000 3104 material, 0.28 mm) was prepared. Next, a predetermined amount of known cupping oil was applied to both surfaces of the aluminum alloy plate as cupping oil during drawing.

Next, the aluminum alloy plate was punched out into a disk shape with a diameter of 160 mm using a drawing machine, and immediately drawn into a cup body with a diameter of 90 mm.
The obtained cup body was transported to a body maker (can body making machine) and re-drawn to a shape with a diameter of 66 mm, and then, using coolant, it was shaped into a shape with a diameter of 66 mm and a height of 130 mm. I applied nishiki processing.

The ironing die used in this case had a diamond film formed on its surface with an average thickness of about 10 μm. The value of surface roughness Ra of the diamond film was set to Ra=0.08 μm. Further, the ironing punch used had a diamond-like carbon film formed on its surface with a thickness of 0.5 μm.

The ironing rate during ironing was as shown in Table 1. The coolant used during the ironing process contained synthetic ester as an oil component. The oil content in the coolant was as shown in Table 1. Known surfactants, rust inhibitors, extreme pressure additives, and preservatives were added to the coolant.

(Example 2)
A drawn ironing can (DI can) having an internal volume of 350 mL was produced in the same manner as in Example 1, except that the oil content in the coolant used during ironing was changed.

(Example 3)
A drawn and ironed can (DI can) having an internal volume of 350 mL was produced in the same manner as in Example 1 above, except that the ironing rate during the ironing process was changed.

(Example 4)
A drawn and ironed can (DI can) with an internal volume of 350 mL was produced in the same manner as in Example 1 above, except that the surface roughness Ra of the diamond film of the ironing die used for ironing was set to Ra = 0.12 μm. did.

(Comparative example 1)
A drawn ironing can (DI can) having an internal volume of 350 mL was produced in the same manner as in Example 1, except that the oil content in the coolant used during ironing was changed.

(Comparative example 2)
A drawn and ironed can (DI can) with an internal volume of 350 mL was produced in the same manner as in Example 1 above, except that dry press processing was performed without using a coolant during ironing.

(Comparative example 3)
A drawn and ironed can (DI can) having an internal volume of 350 mL was produced in the same manner as in Comparative Example 2 above, except that the ironing rate was changed.

(Comparative example 4)
A drawn and ironed can (DI can) with an internal volume of 350 mL was produced in the same manner as in Example 1 above, except that the surface roughness Ra of the diamond film of the ironing die used for ironing was set to Ra = 0.20 μm. did.

[evaluation]
The DI can obtained by the above method was evaluated by the following method. The results are shown in Table 1.

[Ironing workability]
Three items were visually observed: (i) presence or absence of breakage during ironing, (ii) bleed-through (black streaks) at the opening of the resulting DI can, and (iii) flaws on the outer surface of the can body. ◎ if there is no problem with any of the above four items and the can surface is mirror-like, ○ if there is no problem in any of the above and is excellent, △ if there is a problem with any of the above, but it can withstand practical use. Items that had problems and could not be put to practical use were marked as ×.

[Cleanability]
The obtained DI cans were spray-cleaned using a cleaning solution and washed with water, and the presence or absence of water repellency on the surface of the DI cans was visually observed and determined. In addition, when water splashing occurs, oil in the coolant remains on the surface of the DI can, which is said to affect subsequent processes. Therefore, those in which water splashing did not occur were evaluated as ○, and those in which water splashing occurred were evaluated as ×. Further, as the cleaning liquid, a sulfuric acid-based degreasing agent that is commonly used in the degreasing process of DI cans was used. Furthermore, the degreasing temperature was set at 50°C, which is lower than the conventional 70°C.

[Wastewater treatment properties]
The DI can was spray-cleaned using the above-mentioned cleaning solution and rinsed with water, and then the waste water was stored in a beaker, and the chemical oxygen demand (COD) was measured by a known method. If the COD was less than 200 ppm, it was judged as ○ (good wastewater treatment properties), and if it was 200 ppm or more, it was judged as × (poor wastewater treatment properties). The results are shown in Table 1.

It is clear that the method for manufacturing a seamless can body of the present invention has all of ironing workability, washability, and wastewater treatment properties.

INDUSTRIAL APPLICABILITY The present invention can be suitably used in the field of metal press working that is environmentally friendly while maintaining workability and molding stability.

D Die part P Punch part C Coolant 10 Metal material 20 Diamond film 30 Surface treatment film

Claims (8)

One of the die part or the punch part on which a diamond film with a thickness of 5 to 30 μm is formed on the processed surface, and the die part or the punch part on which a surface treatment film different from the diamond film and having a lower hardness than the diamond film is formed. A method for producing a seamless can body, comprising the step of press-working a metal material on the processed surface of the formed member in the presence of a coolant, using a formed member including the other punch portion. .
2. The method of manufacturing a seamless can body according to claim 1, wherein the surface treatment film is thinner than the diamond film.
The surface treatment film is a diamond-like carbon film,
The method for manufacturing a seamless can body according to claim 1 or 2 , wherein the surface treatment film has a thickness of 0.1 to 10 μm .
The method for manufacturing a seamless can body according to any one of claims 1 to 3, wherein the oil content contained in the coolant is 4% by volume or less.
The pressing process includes ironing the metal material,
The method for manufacturing a seamless can body according to any one of claims 1 to 4, wherein the can body is formed by squeezing the metal material so that the ironing rate in the ironing process is 30% or more.
The method for manufacturing a seamless can body according to claim 5, wherein the molded member used for the ironing process has a surface roughness of Ra=0.12 μm or less.
The method for manufacturing a seamless can body according to claim 5, wherein the molded member used for the ironing process has a surface roughness of Ra=0.08 μm or less.
The method further includes a wastewater treatment step of treating wastewater discharged in a cleaning step of washing the metal material after the press working step , and in the wastewater treatment step, the chemical oxygen demand (COD) of the wastewater is 200 ppm. The method for producing a seamless can body according to any one of claims 1 to 7, wherein