JP2006176365A - Method of machining forming mold and forming mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of machining a forming mold by a single crystal diamond cutting tool by which a mirror finished surface is formed on a base mold composed essentially of tungsten while preventing wear of the tip of the diamond tool, the forming mold having the mirror finished surface and further the forming mold which has excellent mirror surface profile and shape precision and by which even an optical glass device having a non-spherical surface, a flyeye shape or groove shape is formed. <P>SOLUTION: In the method of machining the forming mold used for the manufacture of the glass optical device by hot forming using a glass mold method, the forming surface for the glass is formed by machining a base mold (2) composed essentially of tungsten by a vibration and cutting method such as an ellipse vibration cutting method and other vibration cutting method accompanying vibration in at least one direction using the single crystal diamond cutting tool as the cutting tool (1). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a processing method of a molding die used for hot forming a high-precision optical glass element by a glass molding method, and a molding die processed by the processing method.

As a member for hot forming an optical glass element by a glass mold method, for example, a cemented carbide containing no SiC or Co shown in Patent Document 1 has been known.
However, a cemented carbide containing no SiC or Co is highly reactive with glass at high temperatures when it is repeatedly hot-formed as a molding die. There was a problem of sticking.
Further, a cemented carbide containing no SiC or Co could not obtain a mirror surface by cutting. Furthermore, since the hardness is high, it has been very difficult to cut into a desired shape such as an aspherical surface, a fly-eye shape, or a groove shape.

  For this reason, in order to solve the former problem, the inventors of the present invention have proposed a base mold material mainly composed of tungsten as shown in Patent Document 2. Since a base mold containing tungsten as a main component has extremely low reactivity with glass even at high temperatures, glass as a molding material does not adhere even when repeated hot forming is performed. Furthermore, it satisfies the requirement that the grain growth required for the molding die does not occur on the surface of the molding die for hot forming glass.

  On the other hand, the latter problem can be solved by using single crystal diamond having the highest hardness and high contour accuracy as the tool.

  However, single crystal diamond is extremely reactive to tungsten. Therefore, when a base die mainly composed of tungsten is cut with a single crystal diamond binder, the tip of the single crystal diamond bid is severely worn and it is difficult to process the base die into a necessary and sufficient mirror surface. There was a problem.

JP 52-45613 A JP 2003-239034 A

For this reason, the present invention provides a machining method and a surface capable of preventing the tip of a diamond tool from being worn and forming a mirror surface on the die when a die made of tungsten as a main component is cut with a single crystal diamond bid. An object is to provide a molding die having a mirror surface.
It is another object of the present invention to provide a molding die excellent in specular properties and shape accuracy that can be molded even with an aspherical, fly-eye or groove-shaped optical glass element.

  The invention according to claim 1 is a processing method of a molding die used for manufacturing a glass optical element by hot molding by a glass molding method, and a base die mainly composed of tungsten is used as a tool. According to another aspect of the present invention, there is provided a molding die processing method in which a molding surface of the glass optical element is formed by an elliptical vibration cutting method using a crystal diamond binder or other vibration cutting methods involving vibration in at least one direction.

  The invention according to claim 2 is a molding die used for manufacturing a glass optical element by hot molding by a glass mold method, wherein the molding surface of the glass optical element is the molding according to claim 1. A molding die formed by a die processing method and made of a material mainly composed of tungsten.

  The invention according to claim 3 is a molding die used for manufacturing a glass optical element by hot molding by a glass mold method, wherein the molding surface of the glass optical element is a material mainly composed of tungsten. And a molding die having a maximum surface roughness of 50 nm or less.

The invention according to claim 4 is the molding die according to claim 3, wherein the molding surface of the glass optical element is 0.2 to 1.5% by mass of Ni and 0.1 to ₂ of Y ₂ O ₃ . It is made of a material containing 1% by mass and the balance being W.

Invention of claim 5, 0.1 in the molding die according to claim 3, the forming surface of the glass optical element, the Ni 0.2 to 1.5 mass%, the Y ₂ O ₃ It is made of a material containing 0.5 to 4% by mass of 1% by mass, at least one of Mo, Cr, Nb, and Re (hereinafter referred to as “M”) and the balance being W.

  The invention according to claim 6 is the molding die according to claim 4 or 5, wherein the molding surface of the glass optical element is made of a material further containing 0.05 to 0.5 mass% of VC.

  The invention according to claim 7 is the molding die according to any one of claims 4 to 6, wherein the molding surface of the glass optical element is further at least one of Co and Fe (hereinafter, “Co / Fe”)).

  According to the first aspect of the present invention, as a result of using an elliptical vibration cutting method or other vibration cutting method involving vibration in at least one direction, when a base die mainly composed of tungsten is processed with a diamond tool, Effects such as reduction of cutting heat, miniaturization of cutting, and reduction of cutting force can be brought about. For this reason, abrasion of the diamond tool tip caused by cutting heat can be prevented, and a molding die for producing an optical glass element having a desired mirror surface and shape accuracy can be obtained.

  According to the second aspect of the present invention, since the molding surface of the glass is mainly composed of tungsten, the constituent oxide of the glass as the molding material does not react with the molding die and adhere to it. . In addition, a high-precision optical glass element can be repeatedly formed by the synergistic effect of being formed by the molding die processing method according to claim 1 and not causing grain growth by tungsten.

  According to invention of Claim 3, since the maximum surface roughness of the molding surface of the glass is 50 nm or less, a highly accurate glass element can be shape | molded by the transcription | transfer of the mold precision. In addition, due to the synergistic effect that the grain growth does not occur due to the stability of the composition of the tungsten alloy and the maximum surface roughness is 50 nm or less, it is possible to repeatedly form an ultrahigh precision glass element.

According to the invention described in claim 4, since Ni is contained in an amount of 0.2 to 1.5% by mass, Y ₂ O ₃ is contained in an amount of 0.1 to 1% by mass, and the balance is W, glass forming is performed. The surface hardness and strength can be improved. For this reason, the molding die has a fine grain structure and durability, and the shape accuracy of the optical glass element to be molded can be maintained.

  According to the fifth aspect of the present invention, since M is contained in an amount of 0.5 to 4% by mass, the formed surface of the glass is affected by the action of the WM alloy phase that is solid-dissolved in W and has a hardness higher than W. Abrasion resistance can be improved. For this reason, the shape accuracy of the optical glass element molded by the molding die can be maintained.

According to the invention described in claim 6, since VC is contained in an amount of 0.05 to 0.5% by mass, when it coexists with Y ₂ O ₃ during sintering, an Ni phase or an alloy of Ni and Co / Fe (hereinafter referred to as “Ni”). , "Ni-Co / Fe".) It can be dissolved in the phase to suppress the growth coarsening of the W phase or WM alloy phase, and to suppress the maximum particle size of the W phase or WM alloy layer. . For this reason, the shape accuracy of the ultra-high precision optical glass element molded by the molding die can be maintained.

  According to the seventh aspect of the invention, since Co / Fe is contained in an amount of 0.01 to 0.5% by mass, Ni and an alloy are formed, and the strength of the boundary portion of the W phase or the WM alloy phase is increased. It contributes to improving the strength of the glass molding surface. For this reason, a molding die having a long service life can be provided.

  Next, an embodiment of a molding die according to the present invention will be described.

  In the molding die in the present embodiment, at least a surface on which a glass optical element that is a material to be molded is molded (hereinafter referred to as a “glass molding surface”) has the following first composition or second composition whose main component is tungsten. Since the base mold made of the sintered material is processed by an elliptical vibration cutting method described later or other vibration cutting method with vibration in at least one direction, it is made of a material having the first composition or the second composition.

1st composition and Ni: 0.2-1.5 mass%
· Y ₂ O _3: 0.1~1 wt%
-Further (a) and / or (b) as required
(A) VC: 0.05 to 0.5% by mass
(B) At least one of Co and Fe (hereinafter referred to as “Co / Fe”)
: 0.01 to 0.5% by mass
・ W: balance

Second composition: Furthermore, at least one of Mo, Cr, Nb and Re is 0.5 to 4% by mass.
The composition is the same as the first composition except for blending.

  The glass molding surface preferably has a maximum surface roughness of 50 nm or less. This is because if the maximum surface roughness is 50 nm or less, the transfer-molded glass element becomes an ultra-high precision glass element. In addition, the measuring method of the maximum surface roughness is based on JIS B0601: 601.

As described above, since the glass molding surface is made of a material mainly composed of tungsten, when hot molding is performed at a high temperature in the glass molding method, adhesion due to the reaction of the glass with the molding die hardly occurs. Rich in releasability.
Furthermore, since a mold mainly composed of tungsten has high high-temperature strength and hardness, there is no risk of breakage even if it is repeatedly molded. Further, since the tungsten does not grow, the mirror surface property and shape accuracy of the molding die are maintained. For this reason, the shape accuracy of the repeatedly molded glass element is maintained, and the service life of the molding die is long.

Furthermore, the W phase (in the case of the second composition, the WM phase) is sintered and bonded to each other, and has a high microstructure and thermal stability at the molding temperature of the glass lens, and a fine Ni phase or The Ni—Co / Fe phase and the Y ₂ O ₃ phase are distributed and distributed at the boundary of the W phase (in the case of the second composition, the WM phase). These alloy phases contribute to the bonding of the W phase (in the case of the second composition, the WM phase), whereby the strength of the base mold is improved.

Ni exists as a Ni phase or a Ni—Co / Fe phase dispersed and distributed in the boundary portion of the W phase or the WM alloy phase, and improves the strength.
As described above, Ni is 0.2 to 1.5% by mass because when Ni is less than 0.2% by mass, the sinterability and the distribution ratio of Ni phase or Ni—Co / Fe phase are When it becomes insufficient, the strength of the mold tends to decrease. Conversely, when Ni exceeds 1.5% by mass, not only the hardness of the base mold is lowered, but also the Ni phase or Ni—Co / Fe phase having a maximum particle size exceeding 5 μm is distributed, and glass molding is performed. This is because the surface becomes worn.

Y ₂ O ₃ suppresses the growth and coarsening of the W phase or WM alloy phase during sintering, and the maximum particle size thereof is 30 μm or less. This improves hardness and strength.
As described above, Y ₂ O _{3 is set} to 0.1 to 1% by mass when Y ₂ O ₃ is less than 0.1% by mass. This is because if it exceeds 50%, Y ₂ O _{3 at} the boundary between the W phase and the WM alloy phase is likely to condense, causing a decrease in strength.

Furthermore, in order to prevent the strength from significantly decreasing, the particle size of the Y ₂ O ₃ powder is adjusted so that the maximum particle size of the Y ₂ O ₃ phase dispersed at the boundary of the W phase or the WM alloy phase is 5 μm. It is preferable not to exceed.

Furthermore, in the case of the second composition, 0.5 to 4% by mass of M is mixed and dissolved in W, and the wear resistance of the base mold is caused by the action of the WM alloy phase having a hardness higher than W. To improve.
Here, the mixing ratio of M is set to 0.5 to 4% by mass when the above-described hardness improving action cannot be obtained when it is less than 0.5% by mass, and conversely when it exceeds 4% by mass. This is because M precipitates as a free M phase at the grain boundary of the WM alloy phase, causing a decrease in strength.

If necessary, VC is compounded by solid solution in the Ni phase or Ni—Co / Fe phase at the time of sintering, suppressing the growth coarsening of the W phase or WM alloy phase, and the largest grain of the W phase. This is because the diameter is 30 μm and the maximum particle size of the WM alloy layer is 15 μm or less.
As described above, the VC is set to 0.05 to 0.5% by mass because when the VC is less than 0.05% by mass, the above-described effect cannot be obtained sufficiently, and conversely, the content exceeds 0.5% by mass. In some cases, it is distributed and distributed at the boundary between the W phase and the WM alloy phase, causing a decrease in strength.

Co / Fe is blended as needed to form an alloy with Ni to form a Ni—Co / Fe phase, improving the strength of the boundary portion of the W phase or the WM alloy phase, and the material of the base mold This contributes to improving the strength of the steel.
As described above, Co / Fe is 0.01 to 0.5% by mass (when Co and Fe are blended), when Co / Fe is less than 0.01% by mass. This is because the above-mentioned effect cannot be obtained sufficiently, and conversely if it exceeds 0.5% by mass, the glass molding surface is worn.

  As described above, since the base mold mainly composed of tungsten is processed by the vibration cutting method described later to obtain a molding mold having a mirror surface, a highly accurate glass element can be repeatedly formed. In addition, since the molding die is made of a material containing tungsten as a main component and has a maximum surface roughness of 50 nm or less, it is possible to repeatedly mold an ultra-high precision glass element.

  Hereinafter, an embodiment of a processing method of a molding die using an elliptical vibration cutting method according to the present invention and other vibration cutting methods with vibration in at least one direction will be described.

[Oval vibration cutting method]
First, an embodiment of a molding die processing method using an elliptical vibration cutting method will be described with reference to FIGS. 1 and 2.
In the elliptical vibration cutting method, as shown in FIG. 1, the tool 1 is simply vibrated in the cutting direction (x direction) and the cutting direction (z direction), and these are combined to generate elliptical vibration generated in the xz plane. The above-described foundation mold 2 is cut.

Further, elliptical vibration cutting may be performed in the xyz space by applying a vibration in the y direction and generating a vibration having an arbitrary amplitude and phase difference in the x direction and the y direction, respectively.
Or, in the plane (referred to as the xa plane) passing through the axis (referred to as the a-axis) and the x-axis inclined by Θ to the y-axis arrow side (front side in FIG. 1) around the x-axis. Alternatively, inclined elliptical vibration may be performed. Thus, the tool 1 is caused to elliptically vibrate in the xz plane, the xa plane, and the xyz space, and a molding die having a mirror surface is machined by cutting the base die 2 described above.

  By applying this elliptical vibration cutting method to the above-described base mold mainly composed of tungsten with a single crystal diamond cutting tool, the contact time and the contact area of the single crystal diamond cutting tool with respect to the base mold are reduced. At the same time, the cutting depth is reduced and cutting resistance is reduced. As a result, wear of the diamond tool blade edge, brittle fracture of the die, plastic deformation and work alteration are prevented, and the tool 1 forms a molding die having desired mirror surface properties and shape accuracy as a molding die.

  As shown in FIG. 2, the tool 1 includes a blade 11 made of single crystal diamond at a tip portion thereof. As long as the opening angle of the single crystal diamond blade 11 is 5 ° or more, the transferability of the tool blade edge is dramatically improved in the elliptical vibration cutting method, so that the blade edge of an arbitrary shape is used according to the machining shape. It is done. If a tool with an opening angle of less than 5 ° is used, the width of the bottom surface of the main cutting edge will be approximately the same as the width of the upper part of the tool, and when there is a deviation between the vibration direction and the shape of the tool, Since the surface of the dies other than the rake face interferes with the base mold at the moment of rising in elliptical vibration, wear or wear is likely to occur.

  The tool 1 is brought into contact with the base mold 2 so that the rake angle is preferably -30 ° to 20 ° (including 0 °). When the rake angle is less than −30 °, the shear angle is minimized and the cutting resistance increases, so that the mirror surface properties and the shape accuracy are likely to deteriorate. In addition, when the rake angle exceeds 20 °, the strength of the tool edge decreases and chipping is likely to occur.

Further, the tool 1 is brought into contact with the base mold 2 so that the clearance angle is preferably 5.0 ° or more, and more preferably 14.0 ° to 16.0 °.
When the clearance angle is less than 5.0 °, the angle of entry of the tool edge into the base mold is likely to be larger than the clearance angle, and when the tool edge is cut into the base mold every vibration cycle, the clearance The surface comes into contact with the base mold, and the tool edge is likely to be worn and worn. If the cutting speed is slowed down to reduce the approach angle in order to prevent the tool edge from being worn and worn, the machining efficiency is lowered. For example, when performing elliptical vibration cutting with a 20 kHz perfect circle with a vibration amplitude of 6 μm _pp between the cutting direction and the cutting direction, if the cutting speed is 0.67 m / min or more, the tool blade tip entry angle is 5.0 °. That's it. This is much less efficient than ordinary grinding or diamond turning.

Furthermore, when the clearance angle is 14.0 ° or more, the upper limit of the cutting speed is increased to about 2 m / min, and the machining efficiency is high.
On the contrary, when the clearance angle exceeds 16.0 °, the strength of the tool edge is deteriorated and chipping is likely to occur.

  When cutting is performed with elliptical vibration in the xz plane, the cutting edge of the tool 1 moves along an elliptical trajectory with the x-axis and z-axis as the main axes, but cutting is performed with elliptical vibration in the xa plane. In this case, the cutting edge of the tool 1 moves along an arbitrary elliptical trajectory in a plane tilted by Θ about the xz plane about the x-axis toward the y-axis arrow side (front side in FIG. 1).

  When cutting in the xa plane, the vibration trajectory is inclined to the y-axis side, so that the vibration amplitude in the z-axis direction, that is, the cutting direction is reduced. , And the mirror surface property and the shape accuracy can be obtained from the cutting that elliptically vibrates in the xz plane.

  On the other hand, since the cutting edge of the tool 1 moves not only in the z-axis direction but also in the x-axis and y-axis directions that are parallel to the cutting direction, the cutting resistance is slightly reduced, but the effect of raising chips is small. Therefore, the cutting resistance with respect to the mold is increased. For this reason, the effect of suppressing the wear of the cutting edge of the tool 1 is also slightly reduced.

  Further, when elliptical vibration cutting is performed in the xy plane with an inclination angle Θ of 90 °, the cutting edge of the tool 1 is always in contact with the work material and wear of the cutting edge of the tool is increased, which is not desirable.

  Of the cutting direction (x direction) and its vertical direction (a direction), the amplitude in the vertical direction (a direction) contributes to specular properties and shape accuracy. The amplitude in the vertical direction (direction a) is preferably 0.1 μm to 20 μm, more preferably 0.1 μm to 10 μm. When the vibration amplitude is less than 0.1 μm, the tool edge easily rotates backward when the vibration amplitude fluctuates due to the influence of disturbance factors such as cutting resistance. When this reverse rotation of the tool edge occurs, the diamond is cleaved and large-scale chipping is likely to occur. In addition, when the thickness exceeds 20 μm, the vibration mark formed by the transfer of the motion trajectory becomes large, and it becomes difficult to obtain good specular properties and shape accuracy with a maximum roughness of 50 nm or less.

  On the other hand, the amplitude in the cutting direction is preferably 0.5 μm to 100 μm, more preferably 1 μm to 40 μm. If it is less than 0.5 μm, it is difficult to increase the vibration speed. Therefore, in order to perform good elliptical vibration cutting, the cutting speed has to be reduced, and the processing efficiency is significantly reduced. . Moreover, when it exceeds 100 micrometers, it is because the contact time with the base metal mold | die of a tool blade edge becomes long, and it becomes easy to generate | occur | produce the diffuse wear of a tool blade edge.

Furthermore, the cutting speed, which is the moving speed in the cutting direction (x direction), is preferably 30 mm / min to 5000 mm / min, and more preferably 50 mm / min to 2000 mm / min.
When the cutting speed is less than 30 mm / min, the progress of the processing is slow and the efficiency is poor. Further, the adverse effect of disturbance elements such as thermal deformation of the tool edge tends to appear remarkably in the mirror surface properties and the shape accuracy of the die mold working surface. On the other hand, if it exceeds 5000 mm / min, the above-mentioned tool blade tip entry angle tends to be large, and the vibration mark formed on the surface of the die mold becomes large, making it difficult to obtain good mirror surface properties and shape accuracy. It is.

  Furthermore, the speed ratio (vibration speed / cutting speed) is preferably 10.0 or more, and more preferably 25-100. When the speed ratio is less than 10.0, the cutting speed is faster than the vibration speed, so that the tool blade tip entry angle is likely to be large as described above, and the vibration mark formed on the base die machining surface is large. Good mirror surface and shape accuracy are difficult to obtain. In particular, when the speed ratio is 25 or more, the height of the vibration mark formed on the processed surface of the base mold is easily set to 50 nm or less, that is, the maximum surface roughness is easily set to 50 nm or less. On the other hand, if the speed ratio exceeds 100, the progress of the processing becomes slow, which is not desirable.

  Thus, after operating the tool 1 in the cutting direction and the cutting direction, the tool 1 is moved back in the direction opposite to the cutting direction and the cutting direction, whereby elliptical vibration is realized, whereby the base die 2 is cut. And the front-end | tip 11 of the tool 1 is cooled because cutting oil enters into the clearance gap formed by cutting. Thereby, abrasion of the front-end | tip of the diamond tool 1 is prevented.

By repeating such a cutting direction and a movement in the cutting direction and the opposite direction with a phase difference provided every cycle, the base mold 2 is cut to form a molding mold having a mirror surface.
The phase difference at this time is preferably 70 ° to 110 °. When the phase difference is less than 70 °, the above-mentioned tool entry angle tends to increase, and when the phase difference exceeds 110 °, the chip pulling time is shortened and the cutting resistance tends to increase. Further, it is not desirable because the phase difference is deviated from 90 ° and the vibration mark formed on the surface of the die mold is likely to be large, and it becomes difficult to obtain mirror surface properties and shape accuracy.

  The vibration frequency is preferably 18 KHz or higher. When the vibration frequency is less than 18 KHz, the vibration speed cannot be increased, so that the machining efficiency is deteriorated. In addition, the contact time between the tool and the mold increases, and tool wear tends to occur.

[Vibrating cutting method with vibration in at least one direction]
In the machining method of the molding die according to the present invention, even if the cutting method is other than the above-described elliptical vibration cutting method, the vibration accompanied by vibration in at least one direction in which cutting is performed while the tool edge is vibrated in an arbitrary direction in the xyz three-dimensional space. A cutting method is sufficient. Generally, the cutting direction vibration cutting that vibrates in the cutting direction, that is, the x-axis direction, the feed direction vibration cutting that vibrates in the feeding direction, that is, the y-axis direction, and the cutting direction vibration cutting that vibrates in the cutting direction, that is, the z-axis direction. There are three methods, and machining is performed by vibrating the tool 1 in an arbitrary linear direction using these vibration cutting methods.

  Of these, vibration cutting in the feed direction and the cutting direction tends to increase the surface roughness of the base mold processing surface, and tool wear and chipping are likely to occur, making it difficult to obtain desired mirror surface properties and shape accuracy as a molding die. Not desirable.

  On the other hand, in vibration cutting in the cutting direction, it is desirable that the vibration direction be inclined in the cutting direction (z-axis minus direction) by about 0.1 ° to 8 ° with respect to the x-axis. When the angle is less than 0.1 °, the tool tip easily contacts the base mold even at the moment when the cutting edge of the tool 1 is not cut. For example, when the cutting direction and the vibration direction completely coincide, Will be in contact. Next, when the vibration cutting is completed and the tool is moved in the direction opposite to the cutting direction, a shearing force acts on the cutting edge of the tool, and cleavage cleavage is likely to occur. Conversely, if it exceeds 8 °, it is not desirable because it is difficult to obtain mirror surface properties and shape accuracy due to vibration marks formed on the surface of the die mold.

As described above, the above-described cutting method is used to cut the above-described base mold material mainly composed of tungsten with a single crystal diamond binder, thereby obtaining a desired mirror surface and shape as a molding die for glass optical elements. Can be formed.
In particular, among the conditions in the above numerical range, the cutting speed and the speed ratio have a great influence on the mirror surface properties and the shape accuracy. For this reason, by satisfying these conditions, even a mold for molding an aspherical optical glass element that is thin and is difficult to form while maintaining shape accuracy can be easily processed.

  Thus, the mirror surface property and shape accuracy of the molding die are remarkably improved by the synergistic effect of cutting the base die having the sintered material of the first composition or the second composition by the above-described cutting method. It is possible to repeatedly form an ultra-high precision optical glass element.

  A base mold mainly composed of tungsten was obtained as follows.

As Ni source, Ni (NO ₃ ) ₂ 6H ₂ O powder having a purity of 99.6% is 0.5% by mass in terms of Ni, and Co source is cobalt nitrate hydrate powder having a purity of 99.6% in terms of Co. As a Fe source, 0.2 mass%, iron nitrate hydrate powder having a purity of 99.6% was blended in an amount of 0.1 mass% in terms of Fe to obtain a mixed raw material powder.

  The mixed raw material powder was completely dissolved in a solvent such as acetone or pure water, and then mixed with W powder having an average particle size of 2.5 μm to obtain a slurry.

  This slurry was kneaded with a mixer and then dried to obtain W powder whose surface was coated with the mixed raw material powder. Thereafter, the mixed raw material powder on the surface was thermally decomposed by heating at a temperature of 800 ° in a hydrogen atmosphere for 1 hour. Thus, a coated W powder whose surface was coated with Ni and Co / Fe was obtained.

In this coating W powder, 0.5% by mass of Y ₂ O ₃ having an average particle diameter of 1 μm and 0.2% by mass of VC powder having an average particle diameter of 1 μm are blended so that there is no particle diameter of 5 μm or more. did.

  Next, the mixture was wet-mixed under normal conditions, dried, and press-molded at a hydrostatic pressure of 150 MPa to obtain a green compact having a diameter of 50 mm and a height of 40 mm. This green compact was sintered as a preliminary sintering in a hydrogen atmosphere at a sintering temperature of 900 ° for 5 hours, and then as a main sintering in a hydrogen atmosphere at a sintering temperature of 1,470 ° for 2 hours. And a mold was obtained.

  This base mold was subjected to groove or plane cutting by hail processing under the following conditions, and the amount of tool wear, the surface state of the base mold processing surface and the surface roughness were examined. The tool used was a single crystal diamond having a circular cutting edge with a radius of 0.98 mm, an opening angle of 55 ° (however, a window angle of 90 °), a rake angle of 0 °, and a relief angle of 15 °. The incision was 5 μm, the feed in plane cutting was 10 μm, and the cutting oil was white kerosene.

[Example]
Examples 1-10 performed grooving by the above-mentioned elliptical vibration cutting method under the conditions shown in Table 1, and Examples 11-14 performed grooving by the above-described cutting direction vibration cutting under the conditions shown in Table 1. . In Examples 15 to 18, planar machining was performed by the elliptical vibration cutting method or the cutting direction vibration cutting method under the conditions shown in Table 1.
As vibration conditions, the inclination angle Θ in the elliptical vibration cutting method is 40 ° and the phase difference is 90 °, and in the cutting direction vibration cutting method, the vibration direction is in the range of 0.1 ° to 8 ° with respect to the x-axis. A vibration component in the cutting direction was applied so as to incline in the cutting direction (minus z-axis direction). The vibration frequency was 20 kHz for both the elliptical vibration cutting method and the cutting direction vibration cutting method.
The vertical direction in Table 1 means the vibration amplitude (μm) with respect to the a-axis direction in the elliptical vibration cutting method, and the vibration amplitude (μm) with respect to the cutting direction (z-axis minus direction) in the cutting direction vibration cutting method. ).

[Comparative example]
In Comparative Examples 1 to 5, normal grooving and plane machining without vibrations were performed on the tool edge under the conditions shown in Table 1.

The surfaces of Examples 1 to 18 and Comparative Examples 1 to 5 after processing were photographed with SEM photographs, the surface states were examined, and are shown in Table 2. In Table 2, ◎ indicates a state in which there is no remarkable defect due to brittle fracture or plastic deformation on the surface of the die mold, ○ indicates a state in which good shape accuracy and mirror surface properties are obtained although the above-mentioned defects are mixed slightly, X means a state where brittle fracture or plastic deformation is severe. The SEM photograph of Example 4 is shown in FIG. 3 and the SEM photograph of Comparative Example 2 is shown in FIG.
Furthermore, the average surface roughness Ra and the maximum surface roughness Ry on the cut surfaces of Examples 15 to 18 and Comparative Example 5 were measured according to JIS B0601: 01 and are shown in Table 2.
Furthermore, the abrasion amount (μm) of the diamond blade edge used as a tool in Examples 1 to 17 and Comparative Examples 1 to 3 was measured and shown in Table 2.

[Evaluation]
As can be seen from Table 2, in the grooving of Examples 1 to 14, the wear of the diamond blade edge is not observed, and it can be seen that the cut surface has a mirror surface from the evaluation by the SEM photograph. Further, in the planar processing of Examples 15 to 18, the wear amount of the diamond-blade cutting edge is as small as 0.2 μm or less, the average roughness of the machined surface is 9 nmRa or less, the maximum surface roughness is 60 nmRy or less, and unevenness is present. I understand that there are few. In particular, those obtained by elliptical vibration cutting have an average surface roughness of 7 nmRa or less and a maximum surface roughness of 50 nmRy or less, and it is understood from the evaluation by SEM photographs that they have very excellent mirror surface properties.

  On the other hand, in the grooving of Comparative Examples 1 to 4, it can be seen that the work material is pseudo-attached to the diamond cutting edge, and the cut surface has unevenness and peeling from the evaluation by the SEM photograph. In addition, in the flat processed surface of Example 5, the wear amount of the diamond blade edge is as large as 17 μm, the surface roughness of the processed surface is 29 nmRa, the maximum surface roughness is very rough as 192 nmRy, and a highly accurate glass element is obtained. It turns out that it is not suitable for shaping.

  In Example 19, the above-mentioned base mold was cut by the elliptical vibration method under the conditions shown in Table 3, a spherical lens mold was manufactured, and the specular properties and shape accuracy of the base mold processing surface were examined. As a result, the obtained processed surface had an average surface roughness of 7.9 nmRa and a maximum surface roughness of 45 nmRy. Further, the shape accuracy based on the PV value was 0.27 μm, and both had sufficiently good mirror surface properties and shape accuracy as an optical molding die.

It is a cross-sectional schematic diagram of the cutting method shown as one Embodiment of this invention. It is a whole explanatory view of the tool 1 in FIG. It is a SEM photograph of the base metal mold processing surface of Example 4 which performed groove processing by the elliptical vibration cutting method. It is a SEM photograph of the base metal mold processing surface of comparative example 2 which performed groove processing by normal cutting.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Tool 2 ... Base mold 11 ... Blade

Claims (7)

  A processing method of a molding die used for manufacturing a glass optical element by hot molding by a glass mold method, and a base die having tungsten as a main component is subjected to elliptical vibration cutting using a single crystal diamond binder as a tool. A molding die processing method, wherein the molding surface of the glass optical element is formed by a vibration cutting method involving vibration in at least one direction.   A molding die used for producing a glass optical element by hot molding by a glass mold method, wherein the molding surface of the glass optical element is formed by the molding die processing method according to claim 1, A molding die comprising a material mainly composed of tungsten.   A molding die used for manufacturing a glass optical element by hot molding by a glass mold method, wherein the molding surface of the glass optical element is made of a material mainly containing tungsten and has a maximum surface roughness. Is a molding die characterized by being 50 nm or less. The molding surface of the glass optical element is made of a material containing 0.2 to 1.5% by mass of Ni, 0.1 to 1% by mass of Y ₂ O ₃ , and the balance being W. The molding die according to claim 3. As for the molding surface of the glass optical element, Ni is 0.2 to 1.5% by mass, Y ₂ O ₃ is 0.1 to 1% by mass, and at least one of Mo, Cr, Nb, and Re is 0.5 to 0.5%. The molding die according to claim 3, wherein the molding die is made of a material containing 4% by mass and the balance being W.   6. The molding die according to claim 4, wherein the molding surface of the glass optical element is made of a material further containing 0.05 to 0.5 mass% of VC.   The molding surface of the glass optical element is made of a material further containing at least one of Co and Fe in an amount of 0.01 to 0.5% by mass. Mold as described in 1.