JP7268327B2 - ironing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a machining jig having a carbon film formed on the machining surface and a machining method using the jig.

A carbon film containing a diamond component, which is a carbon crystal, is known to have remarkably high hardness and excellent wear resistance. For this reason, by forming a carbon film on the surfaces of cutting tools such as cutting tools, end mills, and files, plastic working dies such as punches and dies, valve lifters, and sliding members such as bearings, workability and mechanical life are improved. Raising it has been done in the past.

The above carbon films include diamond films containing a large amount of diamond components and DLC films (diamond-like carbon films) containing a large amount of graphite components. Various studies have been conducted on the properties of

For example, in Patent Document 1, the intensity of the maximum peak present at 1333±10 cm ⁻¹ in Raman spectroscopic analysis, which is composed of diamond and amorphous carbon, has a surface roughness Rmax of 2 μm or less, and is measured as I _D , 1500±100 cm ⁻¹ , the intensity ratio I _G /I _D is 0.2 to 20 (I _D /I _G =0.05 to 5), where I _G is the intensity of the maximum peak. Metal working jigs have been proposed in which a carbon film is formed on a sliding surface with a metal to be processed. Specifically, this jig for metal working is a die or punch used for drawing, or a drawing die used for wire drawing.
Further, Patent Document 2 discloses a diamond coating for cutting tools formed on a base material, the coating being formed of a plurality of coating layers, and an intensity ratio (I _D /I _G Alternatively, it has been proposed to control the mechanical properties of the coating layer by (I _G /I _D ).

The peak in the region around 1333 cm ⁻¹ in the above Raman spectroscopic analysis is derived from the diamond component, and the peak in the region around 1500 cm ⁻¹ is derived from the graphite component. Therefore, the larger the intensity ratio (I _D /I _G ), the more the diamond component and the less the graphite component, indicating that the carbon film is a highly pure diamond, that is, has a high hardness.

In the above Patent Documents 1 and 2, the reason why the intensity ratio (I _G /I _D or I _D /I _G ) in Raman spectroscopic analysis is set within a certain range is that both improve wear resistance and This is for prolonging the life.

By the way, plastic working of metals is usually performed by press working, and representative techniques include drawing and ironing. For example, metal cans such as aluminum cans are manufactured by punching a flat metal plate into a disc shape of a predetermined size, drawing the can, forming a drawn can with a low height, and then ironing the can. It is manufactured through a molding process that uses a metal can base having a thin wall and a high height.

In the press working as described above, particularly in the drawing, the molding may be performed without lubrication by forming a carbon film on the die. For example, Patent Document 3 discloses a mold that can draw aluminum without using a lubricant. It is disclosed to provide

However, the ironing process is a severe forming process in which the jig to be used slides greatly against the workpiece. , As the ironing process (thinning) progresses, a large surface pressure is applied. For this reason, if the conventionally known carbon film as described above is provided, there is a problem that the forming limit is low and it cannot withstand ironing with a large ironing rate. For example, in ironing with an ironing ratio of 40% or more, the sliding resistance between the jig and the workpiece increases, and the thinning causes tensile stress exceeding the allowable stress to be applied to the workpiece, resulting in defective molding. occur.
The ironing rate is the plate thickness reduction rate, and is expressed by the following formula when the plate thickness before ironing is t ₀ and the plate thickness after processing is t ₁ . The pressure is high and the molding is severe.
Squeezing rate (%) = 100 × (t ₀ - t ₁ ) / t ₀

By the way, in Patent Document 4, in Raman spectroscopic measurement, an ironing die having a carbon film having an intensity ratio (I _D /I _G ) of 1.0 or more, particularly 1.2 or more is formed on the working surface. proposed by the applicant. This ironing die has a carbon film with high diamond purity formed on the processing surface, and has excellent ironing workability. It is possible to obtain a smooth molded product with a mirror surface or a level close to a mirror surface without causing defects.

However, although the carbon film as described above certainly exhibits excellent workability even when processed under severe conditions, further improvement is required in terms of its low impact resistance. That is, a jig for machining is formed from a rigid base material such as a so-called cemented carbide. A film is formed by vapor deposition or the like on the surface that comes into contact with an object), and when machining is performed using such a jig, film peeling occurs in a small number of processing cycles. Moreover, such film peeling poses a problem not only in dry processes, but also in processing in a liquid environment (processing in wet processes using a lubricant).

JP-A-5-169162 JP-A-6-297207 JP-A-8-90092 WO2017/033791

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ironing method using a ironing die having a carbon film having excellent impact resistance on the working surface.

According to the present invention, in the ironing method for ironing using a ironing die in which a carbon film is formed on the processing surface of a rigid base material,
The carbon film formed on the processed surface has the following formula:
_ID / _IG
During the ceremony,
I _D is the maximum peak intensity at 1333 ± 10 cm ^-1 in the Raman spectroscopic spectrum of the carbon film surface,
_IG is the maximum peak intensity at 1500 ± 100 cm ^-1 in the Raman spectroscopic spectrum of the carbon film surface,
Shows a Raman spectroscopy spectrum in which the intensity ratio represented by is more than 0.6 and 0.9 or less ,
There is provided an ironing method characterized in that the ironing is performed in a liquid environment .

In the ironing die used in the present invention,
(1) The surface of the carbon film is a smooth surface with an arithmetic mean roughness Ra of 0.08 μm or less ,
is preferred.

The carbon film provided on the working surface of the ironing die used in the present invention has an intensity ratio _ID / _IG in the range of more than 0.6 and 0.9 or less in Raman spectroscopic measurement. It has important characteristics for That is, in the conventional known technique, the greater the strength ratio I _D /I _G of the carbon film (the higher the diamond purity), the more excellent workability is exhibited. Then, in order to increase the impact resistance, it was found that, on the contrary, it is advantageous to decrease the strength ratio I _D /I _G and lower the diamond purity. For example, as shown in the examples described later, when a cemented carbide ball (sphere) having a diameter of 1/2 inch is repeatedly struck against the carbon film surface with a load of 200 N (400 shots/min) , film peeling was observed between _{100,000 and 200,000 shots in the case where the intensity ratio I D /I G exceeded 1.1 .} When the value is less than 0 (for example, 0.9), film peeling is not observed even when the number of shots exceeds 400,000.
Thus, according to the present invention, by providing a carbon film with a small strength ratio I _D /I _G , impact resistance can be enhanced and peeling of the carbon film can be effectively prevented.

As described above, in the ironing die used in the present invention, the carbon film formed on the surface thereof has excellent impact resistance, and even when machining is repeated many times, the film does not peel off and is stable. However, in order to maximize the excellent impact resistance of the carbon film of such ironing dies , machining should be performed in a liquid environment. .
That is, the carbon film provided on the working surface of the ironing die used in the present invention has a small strength ratio I _D /I _G and a low diamond purity, so a lubricant such as a dry process is used. If severe processing is performed without using the material, the formed surface of the resulting workpiece tends to be rough or poorly formed. However, when the ironing die described above is applied to processing in a liquid environment, that is, processing in a wet process using coolant, it is possible to obtain a molding surface with high smoothness.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side cross-sectional view showing a main part of a ironing die used in the present invention; Figure showing an example of Raman spectroscopy spectrum of the carbon film surface The figure which shows an example of the press molding process using ironing. 1 is a schematic partial side view of an annular ironing die to which the present invention is applied; FIG. FIG. 2 is a schematic side cross-sectional view of a testing machine for measuring the impact resistance of a carbon film formed on the machining surface of a machining jig;

The jig for machining of the present invention is used for machining hard materials such as various metals and alloys, for example, for severe machining such as drawing, ironing, drawing-ironing, and cutting. It has a rigid substrate 1 and a carbon film 3 provided on the surface of the rigid substrate 1, as shown in the schematic diagram of FIG.

The rigid base material 1 is made of a material having rigidity to withstand severe machining and heat resistance to withstand high-temperature heating during film formation of the carbon film 3 . Examples of materials having such rigidity and heat resistance include so-called cemented carbide obtained by sintering a mixture of tungsten carbide (WC) and a metal binder such as cobalt, and metals such as titanium carbide (TiC). Cermet obtained by sintering a mixture of a titanium compound such as carbide or titanium carbonitride (TiCN) and a metal binder such as nickel or cobalt, or silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), alumina ( Typical examples are hard ceramics such as Al ₂ O ₃ ) and zirconia (ZrO ₂ ).

The carbon film 3 has the following formula (1):
_ID / _IG (1)
During the ceremony,
I _D is the maximum peak intensity at 1333 ± 10 cm ^-1 in the Raman spectroscopic spectrum of the surface of the carbon film 3,
_IG is the maximum peak intensity at 1500±100 cm ⁻¹ in the Raman spectroscopic spectrum of the surface of the carbon film 3;
is in the range of more than 0.6, preferably 1.1 or less, more preferably less than 1.0, still more preferably 0.9 or less.

Referring to FIG. 2 showing the Raman spectroscopy spectrum of the carbon film formed in the experimental example described later, the maximum peak intensity I _D at 1333±10 ^cm is derived from the diamond component in the film and is 1500 The maximum peak intensity I _G at ±100 cm ⁻¹ originates from the graphite component in the film. Therefore, the smaller the peak intensity ratio, the higher the content of graphite, and the larger the peak intensity ratio, the closer the film is to diamond crystals. For example, a carbon film having an intensity ratio of 0.6 or less is called a diamond-like carbon (DLC film) rather than a diamond film. As can be understood from this, the carbon film 3 in the present invention is characterized by containing a graphite component so as to satisfy the above intensity ratio. Unlike conventional carbon films, which are required to contain diamond crystals.

In the present invention, the carbon film 3 satisfies the strength ratio as described above and contains a large amount of graphite component, so that the grain size of the diamond is small and the area of the crystal interface is large, thereby exhibiting excellent impact resistance. be. For example, even when the number of shots exceeds 400,000 in an impact resistance test, film peeling is effectively suppressed, and severe machining can be repeatedly performed. That is, the carbon film 3 containing a large amount of graphite component has a high conformability to the underlying rigid base material 1, and as a result, exhibits high impact resistance, and is considered to effectively prevent film peeling.

In the present invention, the carbon film 3 preferably has a surface roughness Ra (JIS B-0601-1994) of 0.12 μm or less, particularly 0.08 μm or less. That is, since the carbon film 3 contains diamond crystals with high hardness, its surface tends to be rough. For this reason, it is preferable to provide a smooth surface with the above-described roughness by subjecting the film to polishing treatment after film formation. In particular, when ironing is performed using a jig having such a carbon film 3, a large surface pressure is applied between the jig and the workpiece during machining, so that the slipperiness with the workpiece during ironing is reduced. It is preferable that the surface roughness of the carbon film 3 is set within the range described above in order to increase the surface roughness of the workpiece and make the surface of the work piece a smooth surface close to a mirror surface.

In the present invention, the carbon film 3 described above is formed on the surface of the rigid substrate 1 by a known method such as hot filament CVD, plasma CVD, such as microwave plasma CVD, high frequency plasma CVD, and thermal plasma CVD. Then, it is produced by surface polishing.

In the film formation, a gas obtained by diluting a hydrocarbon gas such as methane, ethane, propane, or acetylene to about 1% with hydrogen gas is generally used as a raw material gas. A small amount of gas such as oxygen, carbon monoxide, carbon dioxide, etc. may be optionally mixed for rate adjustment.
Using the raw material gas, the rigid base material 1 is heated to a high temperature of 700 to 1000° C., plasma is generated by microwaves, high frequencies, or the like, and the raw material gas is decomposed in the plasma to generate active species, The deposition is performed by growing diamond crystals on a rigid substrate 1 . During such film formation, the hydrogen atoms dissociated in the plasma selectively etch the graphite and amorphous carbon generated on the rigid substrate 1, thereby increasing the diamond component and increasing the peak intensity of the Raman spectroscopic spectrum of the film. The ratio can be within the range previously described.

However, since graphite and amorphous carbon are etched on the surface of the carbon film formed as described above, diamond crystals are likely to grow, and the surface roughness Ra becomes a rough surface larger than the range described above. put away. For this reason, in the present invention, the film formation conditions are controlled, for example, the film formation time is shortened, the formation of diamond crystals is suppressed, and the polishing process is performed to achieve the peak of the Raman spectroscopic spectrum described above. A carbon film 3 having both the strength ratio and the surface roughness Ra within the ranges described above can be formed on the rigid substrate 1 .

Incidentally, the surface polishing of the carbon film 3 formed by vapor deposition can be performed by a method known per se. For example, a mechanical polishing method in which diamond abrasive grains (grindstone) are used to perform co-shaving processing of the carbon film, or a polishing method utilizing a chemical action may be used. A polishing method combining these mechanical and chemical methods may be used. By these polishing methods, the surface roughness Ra of the film can be adjusted within the range described above.

In the present invention, the above-described machining jig provided with the carbon film 3 is suitably used as cutting tools such as cutting tools, end mills, and files, and plastic working dies such as punches and dies. As a die for ironing, it is suitable for ironing, which is a severe machining, and furthermore, it is applied to wet machining using coolant, in order to maximize the excellent impact resistance of the carbon film 3. optimal.

FIG. 3 shows a manufacturing process of a metal can by press working using the jig for machining according to the present invention as a die for ironing.

In FIG. 3, a blank plate (for example, an aluminum plate) 11 to be used for forming a metal can is first punched to obtain a disk 13 for the metal can (see FIG. 3(a)). ).
In such a punching process, a punch 15 having an outer diameter corresponding to the diameter of the disk 13 and a die 17 holding the blank 11 and having an opening corresponding to the diameter of the disk 13 are used. That is, by punching out the raw plate 11 held on the die 17 with the punch 15, the disk 13 of a predetermined size is obtained.
Note that the base plate 11 may be punched into other shapes (for example, a rectangular shape) depending on the shape of the molded product manufactured by such a manufacturing process.

The disk 13 obtained as described above is subjected to a drawing process to obtain a low-height drawn can (cylindrical body with a bottom) 19 (see FIG. 3(b)).
In such a drawing process, the disk 13 punched out is held on the die 21, and the periphery of this disk 13 is held by a jig 23 for suppressing wrinkles. An opening is formed in the die 21 , and the drawing can 19 is obtained by pressing the disk 13 into the opening of the die 21 using a drawing punch 25 .
In addition, a radius (curvature) is formed at the corner of the upper end of the opening of the die 21 (on the side where the disk 13 is held), so that the opening of the die 21 can be quickly opened without the disk 13 breaking. The outer diameter of the punch 25 is set to be smaller than the diameter of the opening of the die 21 by approximately the thickness of the disc 13 . That is, thinning is hardly performed in this drawing process. The drawing process may be performed multiple times depending on the shape of the molded product.

Next, the drawn can 19 obtained above is ironed to form a metal can base (drawn and ironed can) 27 having a high height and a thin wall (see FIG. 3(c). ).
In this ironing, a punch 29 for ironing is inserted into the interior of the drawing can 19 obtained by the above-described drawing, and the outer surface of the cylindrical body 19 is pressed against the inner surface of the annular ironing die 31. By lowering the punch 29, the side wall of the cylindrical body 19 is thinned by the die 31. As shown in FIG. As a result, the metal can base 27 is thinned and the height is increased according to the degree of thinning.

As can be seen from FIG. 3, in the series of steps of punching, drawing and ironing, the punching does not require slidability, but as the drawing progresses to the ironing, the die used and the workpiece become more difficult. Requires slidability between workpieces. Ironing, in particular, requires the most slidability because surface pressure exceeding the yield stress of the workpiece is applied.

In the present invention, as the ring-shaped ironing die 31, a jig for mechanical effect having the carbon film 3 described above is used.

That is, referring to FIG. 4 showing a partial side surface of the die 31 together with FIG. It has an inclined surface 33 located on the upstream side in the machining direction of 19, an inclined surface 35 located on the downstream side in the machining direction, and a flat surface 37 therebetween for contacting the workpiece 19. The region serves as a processed surface 41, and the above-described carbon film 3 is formed on the entire surface including these surfaces 33, 35, and 37. As shown in FIG.

By the way, in the ironing die 31 shown in FIG. 3, the carbon film 3 should be formed at least on the above-described working surface 41 (that is, the surface to which surface pressure is applied during ironing), but it is preferable. It is preferable that both ends of the carbon film 3 are located away from the processing surface 41 in order to more reliably prevent film peeling during severe ironing. The membrane 3 is usually formed on the entire surface of the rigid substrate 1 (except for the top surface in FIG. 3).
Although not shown in the figure, it is preferable that a cooling pipe or the like is passed through the interior of the rigid base material 1 so as to suppress the temperature rise of the processing surface 41 during the ironing process. .

Furthermore, in the example of FIG. 3, one ring-shaped ironing die 31 is arranged. is also possible. In this case, the gap D of the die 31 arranged on the downstream side in the processing direction becomes smaller, and as a result, the thickness is gradually reduced.

In the present invention, the ironing process using the ironing die 31 having the carbon film 3 described above is most preferably a so-called wet process performed in a liquid environment. That is, the carbon film 3 described above has excellent impact resistance, but has a low content of diamond crystals, resulting in low hardness and poor lubricity. Therefore, when applied to so-called non-lubricated dry machining, the critical ironing rate becomes small, and when the ironing rate is increased, surface roughness and the like are likely to occur, and molding defects may occur in some cases. However, in wet machining in which ironing is performed in a liquid environment, the liquid intervenes between the machining surface 41 (carbon film 3) of the die 31 and the molding surface of the workpiece 19, so that the limit ironing rate is increased and a high It is possible to perform ironing at a certain ironing rate, and the advantages of the present invention, such as excellent impact resistance and ability to perform repeated processing without film peeling, can be maximized.

In such wet ironing, the liquid used is called coolant, and water, mineral oil and oils (such as rapeseed oil) are added as base oils and various additives are added to dissolve or disperse in water. However, a particularly oil-free coolant, such as pure water, can be used to enhance the lubricity between the working surface 41 of the die 31 and the forming surface of the workpiece 19 as well as the cooling effect. Therefore, it is preferably used. The use of such a coolant can increase the critical ironing rate. For example, for ironing an aluminum plate, the limit ironing rate can be increased to 40% or more .

Further, in the present invention, ironing using the ironing die 31 having the carbon film 3 described above can be applied to various metals or alloy materials. For example, aluminum, copper, iron, or alloys containing these metals, tin-plated steel sheets such as tinplate, surface-treated steel sheets such as aluminum sheets subjected to chemical conversion treatment, pre-coated metal sheets having an organic coating on at least one surface, etc. Also, severe ironing with a high ironing rate can be repeatedly performed.
In particular, wet ironing using a tubular ironing die 31 can be suitably used for ironing when manufacturing a metal can substrate in the process shown in FIG. It is most preferably applied to the manufacture of cans.

The invention is illustrated by the following experimental examples.
In the following experimental examples, the measurement of surface roughness, the calculation of peak intensity in Raman spectroscopy, and the impact resistance test were carried out by the following methods.

Surface roughness:
Using a surface roughness meter (Surfcom 2000SD3) manufactured by Tokyo Seimitsu Co., Ltd., the arithmetic mean roughness Ra was measured according to JIS-B-0601.

Peak intensity in Raman spectrum:
A Raman spectroscopic spectrum was measured using a Raman spectrometer (DXR Raman Microscope) manufactured by Thermo Fisher Scientific Co., Ltd. FIG. 2 shows an example of the Raman spectrum at that time. It can be seen that a sharp peak I _D near 1333 cm ^-1 and a gentle peak I _G near 1500 cm ^-1 are detected. The curve of the obtained Raman spectroscopic spectrum was approximated by a second-order polynomial, and using this as a baseline, the Raman spectroscopic spectrum was corrected to obtain the highest peak intensity among peaks existing in an arbitrary section.

impact resistance test;
It was carried out using the testing machine shown in FIG.
That is, a sample plate having a carbon film on the surface of a rigid substrate is held by a spring and a load is applied, a hard ball made of cemented carbide is attached to the tip of an indenter attached to a rotating plate, and the indenter is rotated by rotating the rotating plate. A hard ball was hit repeatedly by sliding the plate, and the number of shots until film peeling occurred was measured, and the impact resistance was evaluated based on the number of shots.
Hard ball: Cemented carbide with a diameter of 1/2 inch Load: 200 N (Hertz contact stress 5 GPa)
Sliding speed: 400 shots/min
Evaluation criteria are as follows.
◎: 400,000 or more shots until film peeling ○: 200,000 or more, less than 400,000 shots until film peeling △: 100,000 or more, less than 200,000 shots until film peeling × : The number of shots until film peeling is less than 100,000

<Experimental example 1>
A carbon film exhibiting the Raman spectroscopy spectrum of the _ID / _IG intensity ratio shown in Table 1 was formed on a cemented carbide substrate and subjected to an impact resistance test to evaluate the impact resistance (film peeling). The results are shown in Table 1.

<Experimental example 2>
Using a die on the surface of which a carbon film exhibiting the Raman spectroscopic spectrum of the _ID / _IG intensity ratio shown in Table 2 was used, an aluminum plate was ironed and formed. The surface of the carbon film was polished so that the arithmetic mean roughness Ra was 0.12 μm.
In addition, the aluminum plate is punched by rolling A3104 material to a plate thickness of 0.29 mm, moving a punch with an outer diameter of Φ 66 mm at a speed of 200 spm, and first drawing is performed to form a cylindrical body (cup) of Φ 66 mm. Then, the outer surface of the cup was degreased and subjected to an ironing molding test.
The molding test was performed at the ironing rate shown in Table 2, and the ironing was performed by wet molding using water as a lubricant or dry molding without using a lubricant.
Table 2 shows the results of whether or not molding was possible in each ironing process.

Experiment No. above. The surface carbon film (I _D /I _G =0.9) of the ironing die used in 2-2 was further polished to have an arithmetic average roughness Ra of 0.10 μm, 0.08 μm and 0.05 μm. . Using this ironing die, ironing was performed at an ironing rate of 50% using water as a lubricant, and the surface of the compact was observed. When the arithmetic average roughness Ra was 0.12 μm and 0.10 μm, some scratches were observed on the surface, but when the arithmetic average roughness Ra was 0.08 μm and 0.05 μm, no scratches were observed and the surface was a mirror surface. was gotten. When the arithmetic mean roughness Ra was 0.14 μm and 0.20 μm larger than 0.12 μm, molding was not possible.

1: Rigid base material 3: Carbon film 19: Workpiece (cylinder)
31: Ironing die 41: Machining surface

Claims (2)

In the ironing method for ironing using a ironing die in which a carbon film is formed on the processing surface of a rigid base material,
The carbon film formed on the processed surface has the following formula:
_ID / _IG
During the ceremony,
I _D is the maximum peak intensity at 1333 ± 10 cm ^-1 in the Raman spectroscopic spectrum of the carbon film surface,
_IG is the maximum peak intensity at 1500 ± 100 cm ^-1 in the Raman spectroscopic spectrum of the carbon film surface,
Shows a Raman spectroscopy spectrum in which the intensity ratio represented by is more than 0.6 and 0.9 or less ,
A method of ironing, wherein the ironing is performed in a liquid environment . The ironing method according to claim 1, wherein the surface of the carbon film is a smooth surface having an arithmetic mean roughness Ra of 0.08 µm or less .

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