US20130205862A1

US20130205862A1 - Die for press working

Info

Publication number: US20130205862A1
Application number: US13/756,713
Authority: US
Inventors: Masakuni Takahashi; Satoru Higano; Takuya Kubo
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2012-02-09
Filing date: 2013-02-01
Publication date: 2013-08-15
Also published as: JP5787094B2; JP2013163187A; CN103639288A

Abstract

A die for press working includes a punch part and a die part. The outer peripheral surface and tip surface of the punch part and the inner peripheral surface of the die part are coated with carbon films having a surface roughness Ra of 0.05 μm or lower. An intra-punch refrigerant flow channel in the punch part allows a cooling medium to flow. An intra-die refrigerant flow channel in the die part allows the cooling medium to flow. The intra-punch refrigerant flow channel has a central flow channel portion where a tip on the central axis of the punch part is disposed at a tip of the punch part. Radial flow channel portions have base ends connected to the tip of the central flow channel portion, extending radially at mutually equiangular intervals. Outer peripheral flow channel portions have base ends connected to the tips of the radial flow channel portions.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of Japanese Patent Application No. 2012-026028, filed Feb. 9, 2012, which is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to a die for press working suitable for a die for dry press working for producing a can barrel made of an aluminum alloy.

BACKGROUND OF THE INVENTION

In the related art, since dies coated with carbon films, such as diamond films or DLC (diamond-like carbon) films have high-lubricity surfaces, attention is paid that the dies can perform dry press working, such as press forming that is made oilless or cleaning-less in working of metal. It is known that the carbon films have high slip characteristics between non-carbon solid soluble alloys due to termination of surfaces by hydrogen, and adhesion caused by the alloy to be worked can be suppressed.
These carbon films are produced mainly by performing seeding treatment on cemented carbide having tungsten carbide as a principal component, and directly vapor-depositing films of diamond or DLC by gas-phase synthesis of a CVD method (see JP-A-10-137861, JP-A-09-314253 and JP-A-11-277160). For example, JP-A-10-137861 suggests a drawing and ironing method for performing ironing after a metal blank is drawn. In this drawing and ironing method, a die in which the surface of a die base material that comes into contact with the metal blank is coated with a DLC film having the surface roughness Ra of 0.05 μm or lower is used as the die of an ironing pass of at least a final stage in the ironing.
The following problems are left unsolved in the above related art.
That is, in the techniques described in the above references, for an alloy is formed in a high working ratio, the temperature between a die and the alloy to be worked must be at the high temperature (locally, equal to or higher than 300° C.) In such a high-temperature state, even if the surface of the die is made smooth, the coefficient of dynamic friction of the carbon film becomes high, and the adhesion or deposition of the alloy to be worked cannot be avoided. Particularly, if the temperature becomes equal to or higher than 300° C., the carbon film on the die surface has problems in that hydrogen may be released, slip characteristics may degrade, and the above adhesion may likely occur. For this reason, generally, in order to avoid this phenomenon, cooling lubricant is interposed between the die and the alloy to be worked by emitting the cooling lubricant during molding. However, since a large amount of non-circulating cooling lubricant is required, there is a disadvantage in that the production costs may increase.
The invention has been made in view of the aforementioned problems, and an object of the invention is to provide a die for press working that suppresses adhesion without using a large amount of cooling lubricant and allows excellent forming working.

SUMMARY OF THE INVENTION

In order to solve the above problems, the invention has adopted the followings configurations. That is, a die for press working related to a first invention includes a punch part and a die part that perform forming process of a workpiece, the outer peripheral surface and tip surface of the punch part and the inner peripheral surface of the die part are coated with carbon films having the surface roughness Ra of 0.05 μm or lower, an intra-punch refrigerant flow channel that allows a cooling medium to flow therethrough is formed inside the punch part, and an intra-die refrigerant flow channel that allows the cooling medium to flow therethrough is formed inside the die part, the punch part is formed in a columnar shape, and the intra-punch refrigerant flow channel has a central flow channel portion where a tip formed on the central axis of the punch part is disposed at a tip portion of the punch part; a plurality of radial flow channel portions that have base ends connected to the tip of the central flow channel portion and are formed to extend radially at mutually equiangular intervals; and a plurality of outer peripheral flow channel portions that have base ends connected to the tips of the radial flow channel portions and are formed along the central axis in the vicinity of the outer peripheral surface of the punch part.
In this die for press working, the intra-punch refrigerant flow channel that allows the cooling medium to flow therethrough is formed inside the punch part, and the intra-die refrigerant flow channel that allows the cooling medium to flow therethrough is formed inside the die part. Thus, even when a large amount of cooling lubricant is not used, the punch part and the die part together with the carbon films on the surfaces thereof can be efficiently cooled from the insides thereof by the cooling medium that flows therethrough. Accordingly, the cooling medium that is made to flow through the intra-punch refrigerant flow channel and the intra-die refrigerant flow channel can be easily circulated, and has to be only prepared in an amount required for a circulation medium to actively cool the punch part and the die part. Additionally, an active cooling method can be used, and it is possible to always monitor the temperature of the circulating cooling medium, thereby performing temperature management during forming process more rigorously than in the related art. This makes it possible to eliminate unstable factors in terms of production caused by the thermal expansion/contraction of the die.
In addition, the reason why the surface roughness Ra of the carbon films are set to be 0.05 μm or lower is that, if Ra exceeds 0.05 μm, there is a concern that sufficient slip characteristics cannot be obtained during working, and the adhesion, deposition, or the like of the alloy to be worked may occur.
Additionally, in this die for press working, the intra-punch refrigerant flow channel has the central flow channel portion, the plurality of radial flow channel portions, and the plurality of outer peripheral flow channel portions. Thus, the cooling medium is first supplied to the center of the punch part by the central flow channel portion, then spreads radially and flows by the plurality of radial flow channel portions on the tip side, and further flows in the vicinity of the outer periphery by the plurality of outer peripheral flow channel portions, so that the carbon films on the tip surface and the outer peripheral surface can be efficiently cooled. Additionally, the punch part can be cooled symmetrically about the central axis, the uniformity of temperature at the outermost periphery of the same section can be obtained, occurrence of an uneven form of the die caused by thermal expansion/contraction can be suppressed, and an increase in resistance during working and the resulting adhesion or deposition of the alloy to be worked can be prevented.
A die for press working related to a second invention is the die for press working in the first invention in which the die part is formed in an annular shape, and the intra-die refrigerant flow channel is formed in an annular shape along the circumferential direction of the die part.
That is, in this die for press working, the die part is formed in an annular shape, and the intra-die refrigerant flow channel is formed in an annular shape along the circumferential direction of the die part. Thus, the carbon film formed on the inner peripheral surface of the die part can be efficiently cooled.
A die for press working related to a third invention is the die for press working in the first or second invention, further including a refrigerant supply source that supplies the cooling medium into the intra-punch refrigerant flow channel and the intra-die refrigerant flow channel. The refrigerant supply source causes the cooling medium to flow with turbulence where the Reynolds number is equal to or higher than 3000, while the cooling medium is traveling through the inside of the intra-punch refrigerant flow channel and the inside of the intra-die refrigerant flow channel flow.
That is, in this die for press working, the refrigerant supply source causes the cooling medium to flow with turbulence where the Reynolds number is equal to or higher than 3000, while the cooling medium is traveling through the inside of the intra-punch refrigerant flow channel and the inside of the intra-die refrigerant flow channel flow. Thus, temperature distribution is not easily made within the flow channels compared to a laminar flow, and uniform cooling is possible in the whole flow channels.
A die for press working related to a fourth invention is the die for press working in any of the first to third inventions, further including a refrigerant supply source that supplies the cooling medium into the intra-punch refrigerant flow channel and the intra-die refrigerant flow channel. The refrigerant supply source controls the temperature of the carbon films so as to be lower than 300° C. by controlling the flow of the cooling medium.
That is, in this die for press working, the refrigerant supply source controls the temperature of the carbon films so as to be lower than 300° C. by controlling the flow of the cooling medium, and as a result, hydrogen can be prevented from being released from the carbon films, and stable high slip characteristics can be maintained.
A die for press working related to a fifth invention is the die for press working in any of the first to fourth inventions in which the punch part includes a bottomed cylindrical outside substrate that has the carbon films formed on the outer peripheral surface and tip surface thereof and is formed from cemented carbide, and an inside substrate that is provided inside the outside substrate, has the intra-punch refrigerant flow channel formed therein, and is formed from copper or a copper alloy.
That is, in this die for press working, the inside substrate, which is provided inside the outside substrate, has the intra-punch refrigerant flow channel formed therein, and is formed from copper or a copper alloy, is included. Thus, the heat exchange with the cooling medium can be performed via the inside substrate of copper or a copper alloy with high thermal conductivity, and the outside substrate and the carbon film can be efficiently cooled.
A die for press working related to a sixth invention is the die for press working in any of the first to fifth inventions in which the workpiece is a aluminum alloy thin sheet, and the die for press working is a die for dry press working that performs drawing and ironing on the aluminum alloy thin sheet.
That is, this die for press working is made into a die for dry press working that performs DI (Drawing and Ironing) working on an aluminum alloy thin sheet. Thus, a can barrel made of an aluminum alloy with stable product quality can be produced at low costs and with a low environmental load.

ADVANTAGE OF THE INVENTION

According to the invention, the following effects are exhibited.
That is, according to the die for press working of the invention, the intra-punch refrigerant flow channel that allows the cooling medium to flow therethrough is formed inside the punch part, and the intra-die refrigerant flow channel that allows the cooling medium to flow therethrough is formed inside the die part. Thus, even if a large amount of cooling lubricant is not used, the punch part and the die part together with the carbon films on the surfaces thereof can be efficiently cooled from the insides thereof by the cooling medium that flows therethrough.
Accordingly, the die for press working of the invention can be applied to a die for dry press working in DI process or the like of aluminum can, product quality can be stabilized by suppressing adhesion, and resource-saving/energy-saving process can be realized at low costs without using a large amount of cooling lubricant.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein like designations denote like elements in the various views, and wherein:

FIG. 1 is a cross-sectional view showing a die during working in one embodiment of the die for press working related to the invention.

FIG. 2 is a cross-sectional view in a radial flow channel portion showing a punch part, in the present embodiment.

FIG. 3 is a cross-sectional view in an intra-die refrigerant flow channel showing an outside annular portion of a die part, in the present embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Best Mode for Carrying Out the Invention

Hereinafter, one embodiment of a die for press working related to the invention will be described referring to FIGS. 1 to 3. In addition, in respective drawings to be used for the following description, there are portions of which the scales are appropriately changed if needed in order to make respective parts have recognizable or easily recognized sizes.
As shown in FIGS. 1 to 3, a die 1 for press working of the present embodiment is a die for dry press working that performs DI working on an aluminum alloy thin sheet, using the aluminum alloy thin sheet as a workpiece W. The die has a punch part 2 and a die part 3 that perform forming process of the workpiece W. The outer peripheral surface and tip surface of the punch part 2 and the inner peripheral surface of the die part 3 are coated with carbon films 4 having the surface roughness Ra of 0.05 μm or lower.
Additionally, an intra-punch refrigerant flow channel 5 that allows a cooling medium L to flow therethrough is formed inside the punch part 2, and an intra-die refrigerant flow channel 6 that allows the cooling medium L to flow therethrough is formed inside the die part 3.
The punch part 2 is formed in a columnar shape, and the intra-punch refrigerant flow channel 5 has a central flow channel portion 5 a where a tip formed on the central axis of the punch part 2 is disposed at a tip portion of the punch part 2, a plurality of radial flow channel portions 5 b that have base ends connected to the tip of the central flow channel portion 5 a and are formed to extend radially at mutually equiangular intervals, and a plurality of outer peripheral flow channel portions 5 c that have base ends connected to the tips of the radial flow channel portions 5 b and are formed along the central axis in the vicinity of the outer peripheral surface of the punch part 2.
The punch part 2 is provided with a bottomed cylindrical outside substrate 7 that has the carbon films 4 formed on the outer peripheral surface and tip surface thereof and is formed from cemented carbide, and an inside substrate 8 that is provided inside the outside substrate 7, has the intra-punch refrigerant flow channel 5 formed therein, and is formed from copper or a copper alloy. That is, the carbon films 4 are formed on the outer peripheral surface and tip surface of the outside substrate 7 that are portions that directly abut against the workpiece W during DI working.
The die part 3 is formed in an annular shape, and the intra-die refrigerant flow channel 6 is formed in an annular shape along the circumferential direction of the die part 3.
The die part 3 is provided with an inside annular portion 9 that has the carbon films 4 formed on the inner peripheral surface thereof and is formed from cemented carbide, and an outside annular portion 10 that is provided at an outer periphery of the inside annular portion 9, has the intra-die refrigerant flow channel 6 formed therein, and is formed from iron-based materials, such as stainless steel (sus). That is, the carbon film 4 is formed on the inner peripheral surface of the inside annular portion 9 that is a portion that directly abuts against the workpiece W during DI working.
Additionally, the die 1 for press working is equipped with a refrigerant supply source 11 that supplies the cooling medium L into the intra-punch refrigerant flow channel 5 and the intra-die refrigerant flow channel 6.
The refrigerant supply source 11 has the function of controlling flow velocity so that the cooling medium L flowing through the inside of the intra-punch refrigerant flow channel 5 and the inside of the intra-die refrigerant flow channel 6 is made to flow in a turbulence of which the Reynolds number is equal to or higher than 3000. That is, the refrigerant supply source 11 forms a turbulence in which the flow velocity of the cooling medium L is set to 0.5 m/s or higher and the Reynolds-number is equal to or higher than 3000, in a case where the internal diameter of each refrigerant flow channel is set to, for example, 5 mm in diameter. In addition, as the cooling medium L of this example, cooling water of 30° C. is adopted.
Moreover, the refrigerant supply source 11 also has the function of making the cooling medium L circulate and flow to control the temperature of the carbon films 4 to be lower than 300° C. That is, the refrigerant supply source 11 has the temperature detection function of a temperature sensor or the like that measures the temperature of the cooling medium L that is being circulated, and has a control mechanism that always monitors the temperature of the cooling medium L to control the temperature or flow velocity of the cooling medium L so that the temperature in the carbon films 4 estimated from this temperature does not become equal to or higher than 300° C.
As the cemented carbide, for example, those using tungsten carbide (WC) as a chief material and containing less than 10% of CO or the like as a binder, or WC with no binder is adopted. These cemented carbides remove Co in the vicinity of surfaces, which reduce the attachment strength of the carbon films 4, by chemical treatment, and the carbon films 4 are formed thereon by gas-phase synthesis.
The carbon films 4 are DLC films or polycrystal diamond films, and the diamond films are adopted in the present embodiment. In a stage where these carbon films 4 are synthesized, undulations of an uppermost surface have Ra of about several micrometers. This is ground using pulsed laser light with a wavelength of 360 nm or less, and is made to have Ra≦0.05 μm. That is, the carbon films 4 are ground with laser light so that the surface roughness Ra thereof becomes 0.05 μm or lower.
In the die 1 for press working, as shown in FIG. 1, the punch part 2 is pushed into the die part 3 in a state where the punch part is inserted into the workpiece W formed into a cup, drawing and ironing of the workpiece W is performed in a plurality of steps to produce a can barrel. In this case, the cooling refrigerant L is supplied from the refrigerant supply source 11 to the respective refrigerant flow channels on the above conditions, and the carbon films 4 of the punch part 2 and the die part 3 are appropriately cooled.
As such, in the die 1 for press working of the present embodiment, the intra-punch refrigerant flow channel 5 that allows the cooling medium L to flow therethrough is formed inside the punch part 2, and the intra-die refrigerant flow channel 6 that allows the cooling medium L to flow therethrough is formed inside the die part 3. Thus, even if a large amount of cooling lubricant is not used, the punch part 2 and the die part 3 together with the carbon films 4 on the surfaces thereof can be efficiently cooled from the insides thereof by the cooling medium L that flows therethrough. That is, by water-cooling the inside of the die, the temperature rise of the carbon film 4 on the surface of the die generated during working can be prevented, and sliding characteristics on the workpiece W can be maintained.
The cooling medium L that is made to flow through the intra-punch refrigerant flow channel 5 and the intra-die refrigerant flow channel 6 can be easily circulated, and has only to be prepared by an amount required as a circulation medium for actively cooling the punch part 2 and the die part 3. Additionally, an active cooling method can be used, and it is possible to always monitor the temperature of the circulating cooling medium L, thereby performing temperature management during forming process more rigorously than in the related art. This makes it possible to eliminate unstable factors in terms of production caused by the thermal expansion/contraction of the die.
Additionally, since the intra-punch refrigerant flow channel 5 has the central flow channel portion 5 a, the plurality of radial flow channel portions 5 b, and the plurality of outer peripheral flow channel portions 5 c, the cooling medium L is first supplied to the center of the punch part 2 by the central flow channel portion 5 a, then spreads radially and flows by the plurality of radial flow channel portions 5 b on the tip side, and further flows in the vicinity of the outer periphery by the plurality of outer peripheral flow channel portions 5 c, so that the carbon films 4 on the tip surface and the outer peripheral surface can be efficiently cooled. Additionally, the punch part 2 can be cooled symmetrically about the central axis, the uniformity of temperature at the outermost periphery of the same section can be obtained, occurrence of an uneven form of the die caused by thermal expansion/contraction can be suppressed, and an increase in resistance during working and the resulting adhesion or deposition of the alloy to be worked can be prevented.
Since the die part 3 is formed in an annular shape, and the intra-die refrigerant flow channel 6 is formed in an annular shape along the circumferential direction of the die part 3, the carbon film 4 formed on the inner peripheral surface of the die part 3 can be efficiently cooled.
Additionally, since the refrigerant supply source 11 causes the cooling medium L to flow through the inside of the intra-punch refrigerant flow channel 5 and the inside of the intra-die refrigerant flow channel 6 flow with turbulence where the Reynolds number is equal to or higher than 3000, so the temperature distribution is not easily made within the flow channels compared to a laminar flow, and uniform cooling is possible in the whole flow channels.
Additionally, since the refrigerant supply source 11 controls the temperature of the carbon films 4 to be lower than 300° C. by controlling the flow of the cooling medium L, hydrogen can be prevented from being released from the carbon films 4, and stable high slip characteristics can be maintained.
Moreover, since the inside substrate 8, which is provided inside the outside substrate 7, has the intra-punch refrigerant flow channel 5 formed therein, and is formed from copper or a copper alloy, is included, heat exchange with the cooling medium L can be performed via the inside substrate 8 of copper or a copper alloy with high thermal conductivity, and the outside substrate 7 and the carbon film 4 can be efficiently cooled.
Accordingly, the die 1 for press working of the present embodiment is made into a die for dry press working that performs DI working on an aluminum alloy thin sheet, so that a can barrel made of an aluminum alloy with stable product quality can be produced at low costs.

EXAMPLE

Next, the evaluation results after DI working is performed using the die for press working of the above embodiment will be described.
As for the die for press working used, the outside substrate of the punch part and the inside annular portion of the die part that are portions that directly act during working were made of cemented carbide containing 6% of Co, and the carbon films of polycrystal diamond, which are formed by gas-phase synthesis, are coated thereon.
Additionally, the coated carbon films of polycrystal diamond were ground using pulsed laser light with a wavelength of 262 nm and 10 kHz, and were ground to Ra<0.03 μm.
In addition, the surface roughness (surface undulations) of the carbon films was measured using an optical microscope, an electron microscope, and a laser microscope. Additionally, the structure evaluation of the carbon films was measured using Raman spectroscopy.
Moreover, the diameter of the respective refrigerant flow channels was 3 mm, 25° C. water was used as the cooling medium, and ironing in which the working ratio of an aluminum alloy was 40% was performed while the flow medium was made to flow in a turbulence state where the cross-sectional average speed was 1 m/s. Additionally, even in a case where the cooling medium is not made to flow for comparison, ironing was similarly performed.
As a result, in a case where the cooling medium was not made to flow, the adhesion and deposition of the aluminum alloy were confirmed in continuation ironing. However, in a case where the cooling refrigerant was circulated to perform cooling of the die, the adhesion and the deposition were not able to be confirmed.
In addition, the technical scope of the invention is not limited to the above embodiment and example, and various changes can be made without departing from the spirit of the invention.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

1: DIE FOR PRESS WORKING
2: PUNCH PART
3: DIE PART
4: CARBON FILM
5: INTRA-PUNCH REFRIGERANT FLOW CHANNEL
5 a: CENTRAL FLOW CHANNEL PORTION
5 b: RADIAL FLOW CHANNEL PORTION
5 c: OUTER PERIPHERAL FLOW CHANNEL PORTION
6: INTRA-DIE REFRIGERANT FLOW CHANNEL
7: OUTSIDE SUBSTRATE
8: INSIDE SUBSTRATE
11: REFRIGERANT SUPPLY SOURCE
L: COOLING MEDIUM
W: WORKPIECE

Claims

1. A die for press working comprising:

a punch part;

a die part;

an intra-punch refrigerant flow channel provided inside the punch part; and

an intra-die refrigerant flow channel provided inside the die part, wherein

the punch part and the die part perform a forming process on a workpiece,

an outer peripheral surface and a tip surface of the punch part and an inner peripheral surface of the die part are coated with carbon films having a surface roughness Ra of 0.05 μm or lower,

the intra-punch refrigerant flow channel allows a cooling medium to flow therethrough,

the intra-die refrigerant flow channel allows the cooling medium to flow therethrough,

the punch part has a columnar shape, and

the intra-punch refrigerant flow channel includes:

a central flow channel portion where a tip formed on the central axis of the punch part is disposed at a tip portion of the punch part;

a plurality of radial flow channel portions that have base ends connected to the tip of the central flow channel portion, said radial flow channel portions extending radially at mutually equiangular intervals; and

a plurality of outer peripheral flow channel portions that have base ends connected to the tips of the radial flow channel portions and are provided along the central axis in a vicinity of the outer peripheral surface of the punch part.

2. The die for press working according to claim 1,

wherein the die part has an annular shape, and the intra-die refrigerant flow channel has an annular shape disposed along the circumferential direction of the die part.

3. The die for press working according to claim 1, further comprising:

a refrigerant supply source that supplies the cooling medium into the intra-punch refrigerant flow channel and the intra-die refrigerant flow channel,

wherein the refrigerant supply source causes the cooling medium to flow with turbulence where the Reynolds number of the flow is equal to or higher than 3000, the cooling medium traveling through the inside of the intra-punch refrigerant flow channel and the inside of the intra-die refrigerant flow channel.

4. The die for press working according to claim 1, further comprising:

wherein the refrigerant supply source controls the temperature of the carbon films to be lower than 300° by controlling a flow of the cooling medium.

5. The die for press working according to claim 1,

wherein the punch part includes:

a bottomed cylindrical outside substrate that has the carbon films provided on the outer peripheral surface and tip surface thereof and is made of cemented carbide, and

an inside substrate that is provided inside the outside substrate, has the intra-punch refrigerant flow channel formed therein, and is made of copper or a copper alloy.

6. The die for press working according to claim 1,

wherein the workpiece is an aluminum alloy thin sheet, and

wherein the die for press working is a die for dry press working that performs drawing and ironing on the aluminum alloy thin sheet

7. The die for press working according to claim 2, further comprising:

wherein the refrigerant supply source causes the cooling medium to flow with turbulence where the Reynolds number of the flow is equal to or higher than 3000, the cooling medium traveling through the inside of the intra-punch refrigerant flow channel and the inside of the intra-die refrigerant flow channel.

8. The die for press working according to claim 2, further comprising:

9. The die for press working according to claim 3, further comprising:

a refrigerant supply source that supplies the-cooling medium into the intra-punch refrigerant flow channel and the intra-die refrigerant flow channel,

10. The die for press working according to claim 2,

wherein the punch part includes:

11. The die for press working according to claim 3,

wherein the punch part includes:

12. The die for press working according to claim 4,

wherein the punch part includes:

13. The die for press working according to claim 2,

wherein the workpiece is an aluminum alloy thin sheet, and

wherein the die for press working is a die for dry press working that performs drawing and ironing on the aluminum alloy thin sheet.

14. The die for press working according to claim 3,

wherein the workpiece is an aluminum alloy thin sheet, and

15. The die for press working according to claim 4,

wherein the workpiece is an aluminum alloy thin sheet, and

16. The die for press working according to claim 5,

wherein the workpiece is an aluminum alloy thin sheet, and