WO2008004656A1

WO2008004656A1 - Sintered hard material and mold comprising the same for molding high-precision optical element

Info

Publication number: WO2008004656A1
Application number: PCT/JP2007/063553
Authority: WO
Inventors: Hiroki Tanaka; Toru Okui; Shigeki Mori; Osamu Nakano; Kei Tokumoto
Original assignee: Nippon Tungsten Co., Ltd.
Priority date: 2006-07-07
Filing date: 2007-07-06
Publication date: 2008-01-10
Also published as: JP2008013418A; JP5134217B2; CN101460427A; CN101460427B

Abstract

A sintered hard material consisting mainly of a tungsten carbide phase. It is free from structural defects such as pores (voids) and abnormal phases, has a high hardness, high Young's modulus, and low coefficient of thermal expansion, and has excellent fracture toughness besides excellent processed-surface precision and surface roughness. (W,M1)2CX (0.8≤X<1.0) is crystallized as a second phase in a tungsten carbide phase, the WC phase being a first phase. Thus, the fracture toughness of the tungsten carbide phase is improved. The (W,M1)2CX (0.8≤X<1.0) is a solid solution of M1, which is one or more of the transition metal elements other than tungsten in Groups 4a, 5a, and 6a of the Periodic Table, in W2CX (0.8≤X<1.0)

Description

Specification

Sintered hard materials and molds for molding high-precision optical elements using the same

[0001] The present invention relates to a mold material for molding high-precision optical elements such as lenses, prisms, and gratings used in optical equipment, or a mold material for injection molding such as metals, plastics, and composite materials. It relates to a hard material.

Background art

[0002] Optical pickup lenses used in CDs, DVDs, digital cameras, mobile phones, etc. A method for obtaining the final product shape when manufacturing optical elements such as glass and plastic used for hard disk substrates of computers In order to achieve high reliability and low price, press molding at high temperatures that does not require complicated and precise mechanical processing has been adopted in recent years.

[0003] Mold materials used in this high-temperature press molding are required to have characteristics such as high-temperature hardness, high thermal conductivity, and low coefficient of thermal expansion in addition to excellent mirror surface processability. Sintered hard materials such as cemented carbide and ceramics are used as the materials.

[0004] For example, Patent Document 1 discloses cobalt as a cemented carbide for hot isostatic pressing suitable for an optical element molding die whose surface after processing forms a mirror surface with an Rmax of 0.05 μm or less. A base cemented carbide containing 3 to 10% by mass is disclosed.

[0005] However, as the accuracy of the optical lens increases, the surface of the molding part of the optical element molding die is also required to have a higher accuracy. It is indispensable that the surface of the lens molding part should have a mirror surface of Rmax 0.01 zm or less.

[0006] On the other hand, a WC-based cemented carbide containing 1% by mass or more of an iron group metal such as Fe, Co, and Ni as a binder phase has a large hardness difference between the WC phase and the iron group metal phase, so that a desired surface can be obtained by machining. Getting accuracy is difficult. Therefore, even in the past, a cemented carbide material consisting only of a carbide phase that does not include an iron group metal phase that has a large hardness difference from the carbide phase, that is, a so-called binderless cemented carbide material is used as a material for precision molds. 2 and 3 are disclosed.

[0007] In the sintered hard materials shown in Patent Documents 2 and 3, the processed post-processing is relatively easy. Force that can finish the surface of the molded part to a mirror surface with an Rmax of 0.01 μm or less As the second phase, there are comparatively more complex carbides that have a harder and more brittle NaCl-type crystal structure than the WC phase. Therefore, local processing performance differences such as sub-micron order or nano order are caused, which has been an obstacle to further pursuing higher precision of the surface of the molded part.

[0008] In addition, the second phase of the sintered hard material shown in Patent Documents 2 and 3 can have a non-stoichiometric composition, so that the amount of carbon in the material is controlled, so that iron group metals and W Of these composite carbides, the η phase (hereinafter referred to as anomalous phase) could be prevented relatively easily, so it was an indispensable phase.

[0009] On the other hand, in the sintered hard material shown in Patent Document 4, inevitable impurity components such as Fe, Co, and Ni that are constituent elements of the abnormal phase are suppressed to a very small amount of 0.02 to 0.10% by weight. As a result, it is considered that the crystallization of the abnormal phase can be prevented, so that it is no longer necessary to include the second phase in the material. In the sintered hard material shown in Patent Document 4, the ratio of WC to W C in tungsten carbide W C / (WC + W C) is set to 0 · 01 to 0

2 X 2 X 2 X

The hardness is improved by using the range of 15.

[0010] Certainly, according to the sintered hard material disclosed in Patent Document 4, the hardness is improved. However, the fracture toughness of the sintered hard material shown in Patent Document 4 is lower than that of the sintered hard material shown in Patent Documents 2 and 3. Therefore, it is considered that there is a higher possibility of chipping and chipping of the edge portion in machining and handling than the sintered hard material disclosed in Patent Documents 2 and 3.

[0011] The reason why the fracture toughness of the sintered hard material shown in Patent Document 4 is lower than that of the sintered hard material shown in Patent Documents 2 and 3 is that the iron group metal that is an impurity component is reduced. Conceivable. That is, the amount of iron group metal at the WCZWC interface, WC / WC interface or WC / WC interface of the sintered hard material shown in Patent Document 4 is shown in Patent Documents 2 and 3.

2 X 2 X 2 X

WC / WC interface, WC / W C interface or W C / W C interface of sintered hard materials

The amount of iron group metal on the 2 X 2 X 2 X plane is much less than or not present, so it is considered that the bond strength between these interfaces does not weaken.

Patent Document 1: Japanese Patent Publication No. 62-51211 Patent Document 2: JP-A-2-120244

Patent Document 3: Japanese Patent Laid-Open No. 10-7425

Patent Document 4: JP-A-9 25535

Disclosure of the invention

Problems to be solved by the invention

[0012] The problem to be solved in the present invention is high hardness in which a sintered hard material mainly composed of a tungsten carbide phase is free from structural defects such as pores (voids) and abnormal phases, and has a large Young's modulus. In addition to the characteristics such as excellent surface accuracy and surface roughness with a small coefficient of thermal expansion, it provides excellent fracture toughness.

Means for solving the problem

[0013] The sintered hard material of the present invention crystallizes (W, Ml) C (0.8 ≤ X <1.0) as the second phase in addition to the WC phase as the first phase in the tungsten carbide phase. Carbonized tandaste by letting out

2 X

This is intended to improve the fracture toughness of the N phase. Where (W, M1) C (0. 8 ≤ X <1. 0) is

2 X

WC (0, 8≤X <1.0) is fixed to transition metal elements other than W in Group 4a, 5a and 6a of the periodic table and Ml which is one or more of Fe, Co and Ni. It is melted.

2 X

[0014] In this sintered hard material, the WC phase is excellent in hardness, strength, machined surface roughness, etc. 1S When the average particle size is made 0.5 / im or less, the structure becomes finer. As a result, the hardness and mirror finish can be further improved. On the other hand, hardness and specular workability tend to decrease due to an increase in average particle diameter. In particular, when the average particle diameter exceeds 0.5 / im, the hardness and specular workability rapidly decrease. Therefore, in the present invention, the average particle size of the tungsten carbide phase is preferably 0.5 zm or less.

[0015] However, since fracture toughness generally tends to decrease as the structure becomes finer, there is a risk of cracking in processing and handling, especially when the average particle size is 1 μm or less. Get higher.

[0016] On the other hand, (W, Ml) C with X in the range of 0.8≤X <1.0 is similar to WC etc.

2 X

It retains a tetragonal crystal structure and therefore has a large plastic deformability compared to many other carbides that have a NaCl-type crystal structure. Therefore, this (W, Ml) C Fracture toughness can be improved by crystallizing it in ngsten. This (W, Ml) C grain

2 It is considered that the role of strengthening dispersion can also be achieved by dispersing the X element in the WC phase.

[0017] Regarding the crystallization amount of (W, M1) C, (W, M1) X-ray diffraction of (_ 1 _ 11) plane of C

2 X 2 X

Integral peak intensity of ί I ((W, Ml)) d Θ, and the integral of X-ray diffraction of (101) plane of WC

2

When the peak intensity is expressed as ί I (WC) d Θ, the ratio of these integrated peak intensities ί I ((W, Ml)

2

C) ά θ / ί I (WC) d Θ less than 0.5% (W, Ml) C phase is small and fracture toughness is improved.

X 2 X

Small contribution to good. On the other hand, if it exceeds 10.0%, the contribution to fracture toughness improvement is uncertain, but the sinterability decreases and a dense material cannot be obtained, and therefore it can be applied to the technical field of the present invention. Can not. From the above, the existence ratio of (W, Ml) C in the range of X in tungsten carbide where X is 0.8≤X <1.0 is

2 X

The range is from 0.5% to 10.0%.

[0018] Regarding the integrated peak intensity of X-ray diffraction, the main diffraction peak of WC is the force s that is the (101) plane and the (100) plane, of which the diffraction peak of the (100) plane of WC is (W , M1) C (1

2 X

Since the diffraction angle with the diffraction peak of the 10) plane is close and overlaps with each other, the diffraction peak of the (101) plane of WC was selected as the main diffraction peak of WC. In addition, the force (w, M 1) representing the (1-1 1) plane of the main diffraction peak as the C diffraction peak (w, M 1)

2 X

Ml) C (0, 8 ≤ X 1 0), for example, for W C, its main diffraction peak

2 X 5. 08 12

The (111) plane and (1-11-1) plane are the same {111} crystal system and are equivalent.

[0019] Furthermore, the diffraction peak of (W, Ml) C (0. 8 ≤ X <1. 0) described so far is fundamental.

2 X

In particular, the force S, which shows the diffraction peak of W C (0.8 ≤ X <1.0), is somewhat in the diffraction peak.

2 X

It has a width and is shifted slightly higher than the diffraction peak position of W C (0.8 ≤ X <1.0).

2 X

Have This is because the value of X has a non-stoichiometric value, and one or more transition metal elements other than W in groups 4a, 5a, and 6a of the periodic table are dissolved in the lattice. It is thought that However, the shift amount is very small, about 0.1 degree (2Θ / degree) or less.

[0020] In the sintered hard material of the present invention, the value of X in (W, M1) C (0.8 ≤ X <1.0) For (W, M1) C (1-11-1) plane and WC (101) plane X-ray diffraction integral

2

Strength ratio ((,)

In (W, Ml) C diffraction with a value of Χ = 0 · 84 as its intensity ratio increases

The 2 X peak is approached and the shift from the theoretical value of the diffraction peak is small. This is probably because (W, Ml) C exists stably at a value of X = 0.84.

2 X

As the amount decreases, X = 0.84 (W, Ml) because the amount of C phase increases.

2 X

Conceivable.

[0021] On the other hand, as shown in the sintered hard material of Patent Document 4, the range of X is 1.0≤X <2.0.

The existence of WC was confirmed in the high carbon region in the alloy carbon range where WC was originally crystallized.

2 X 2 X

Force S, and the range of X is 1.0≤X <2.0 W C is present in the sintered hard material.

2 X

However, its abundance is very small, so the effect of improving fracture toughness cannot be confirmed, and even if it can be confirmed, it is very small.

[0022] where W C (0.8 ≤ X <1.0), transition gold other than W in groups 4a, 5a, 6a of the periodic table

2 X

The genus is in solid solution, that is, the presence of Ml atom in (W, M1) C (0. 8≤X <1.0)

2 X

Affects the diffusion of each element and suppresses the coarsening of (W, Ml) C particles. W C

It is better to exist as (W, Ml) C than (W, Ml) C (0. 8≤X <1.

X 2 X 2 X

The 0) phase is thought to be more stable in tungsten carbide because of less lattice strain. Therefore, those who existed as (W, Ml) C rather than W C

2 X 2 X

However, the effect of improving fracture toughness is considered to be more stably exhibited, and the effect as dispersed particles as dispersion strengthening is also expected to be exhibited.

[0023] Further, the sintered hard material of the present invention has a WC phase as the first phase and a second phase (W, Ml) C (

2 X

As phases other than (0. 8 ≤ X <1.0), the phase of the M2 compound that is a transition metal element of Groups 4a, 5a, and 6a of the Periodic Table, that is, 1 of M2, carbides, nitrides, and carbonitrides. Species, two or more, or a composite carbide or composite carbonitride phase thereof may be included. This M2 compound phase has an effective force for suppressing grain growth in the WC phase. The integrated peak intensity of the maximum peak of X-ray diffraction in this M2 compound is expressed as ί Ι (compound 2) d Θ and When the integrated peak intensity of X-ray diffraction of the (101) plane of WC is expressed as ί I (WC) d Θ, the ratio of these integrated peak intensities ί I (compound of Μ2) d θ / ί I ( WC) d Θ exceeds 1.0%, The sinterability of the WC phase is reduced and a dense material cannot be obtained. Therefore, when the M2 compound phase is included, the integrated peak intensity ratio should be 1.0% or less.

[0024] Although the diffraction plane of the compound of M2 is not specified, this is because the M2 compound itself has various forms, and thus produces diffraction at various peak positions. Since the addition amount is extremely small, it is sufficient to compare each peak with the (101) plane, which is the maximum peak of WC.

[0025] In addition, some of the compounds of M2 are (W, M2) C (0. 8≤X <1.0) as W during sintering.

2 X 2

Solid solution in C (0. 8≤X <1. 0) and this dissolved M2 atom becomes W C (0. 8≤X <1. 0)

X 2 X

It is considered that the effect of suppressing phase grain growth is exhibited. W C as M2 atom (0. 8≤X

2 X

The amount of solid solution in the <1.0) phase has not been elucidated so far, but the number of M2 atoms in the sintered hard material and the number of Ml atoms are the W atoms in this sintered hard material. If the amount is less than 0.5%, the effect of adding it as a grain growth inhibitor is small.If it exceeds 5.0%, the remaining amount of M2 as a compound is too large. Getting worse.

[0026] On the other hand, the sinterability is improved by the presence of iron group metals such as Fe, Co, and Ni as impurity components, and the bonding strength at the interface between WC / WC, WC / W C or W C / W C is strong.

2 X 2 X 2 X

However, in the sintered hard material mainly composed of the tungsten carbide phase as in the present invention, the presence of these iron group metals causes crystallization of a composite carbide of W and iron group metals called phases. Mechanical strength deteriorates. However, if the content in the sintered hard material is extremely small, such as less than 0.05% by mass, the iron group metal and W can be easily controlled by controlling the carbon content in the material as shown in the following reference, for example. It can be considered that the composite carbide with the crystal structure can be crystallized as a hexagonal crystal structure such as the / c phase, which can prevent deterioration of mechanical properties. Therefore, the content of one or more of the impurity components Fe, Co, and Ni is preferably suppressed to less than 0.05% by mass.

[0027] (Reference) P. Schwarzkopf and R. Kieffer, CEMENTED CARBIDES,

The Macmillan Company, New York, U.S.A., p.p.74-101, (196 0).

The invention's effect [0028] According to the sintered hard material of the present invention, the surface accuracy is high hardness with very few structural defects such as pores (pores) and abnormal phases, large Young's modulus, and small thermal expansion coefficient. In addition to the characteristics that a good mirror surface can be obtained, excellent fracture toughness is obtained. Therefore, it is possible to perform machining similar to that of conventional materials and reduce the possibility of chipping and chipping in machining and handling, which can increase the service life. .

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described based on examples.

Example 1

[0030] As a raw material powder of the sintered hard material of the present invention, WC powder having an average particle size of 0.5 μm is used, and Cr C having an average particle size of 1.4 xm and VC of 1. And 1.1 μ

twenty three

m NbC was blended. The raw material powder blended with these materials is mixed with a carbide ball mill or resin ball mill in methanol solvent, pre-press molded with lOMPa, and then 1700 in a vacuum atmosphere. C ~ 2100 ° C, 0.5 ~ 2hours after hot press sintering (HP), Ar atmosphere at 1500 ° C:! ~ 2hour HIP treatment, grinding to final shape Finished. The (W, M1) C phase amount was adjusted by adjusting the carbon content in the material. sand

2 X

That is, it was adjusted by adding graphite carbon or tungsten powder. Then, the surface roughness (Rmax), fracture toughness value (K) after processing of the obtained sintered hard material,

C

(W, MI) c and wc integrated peak intensity ratio (

2 X n ((w, Ml) C) d 0 / J l (WC) d

2 X

Θ) was determined, and the results are shown in Table 1 (described as HP + HIP in the production column). Here, the sample numbers in Table 1 marked with * are examples of the present invention, and the others are comparative examples. Further, for the examples of the present invention, the relationship between the fracture toughness value (K) and the integrated peak intensity ratio.

C

Figure 1 shows the system.

[0031] The surface roughness (Rmax) was measured using a contact-type tally step manufactured by Taylor Hobson. Fracture toughness value (K) is measured with diamond by Vickers hardness tester.

C

An indenter was applied at a load of 30 kg for 5 seconds, and was calculated from the diagonal length and crack length of the resulting indentation using the following Evans equation. In addition, the average particle diameter of tungsten carbide was determined based on the observation of the fracture surface using a scanning electron microscope (SEM). It was confirmed that it was less than 5 / m. The amount of iron group impurities was determined by ICP emission analysis, and the total amount of Fe, Co, and Ni was confirmed to be less than 0.05% by mass. Furthermore, it was confirmed that the integrated peak intensity ratio 化合物 (compound of Μ2) d Θ / JI (WC) ά θ) of 化合物 2 and WC mentioned above was 1.0% or less.

[0032] (Κ φΖΗ &) = 0. 15k (cZa) — ^3/2 (Evans equation)

c

However, Ha: Pickers hardness, E: Young's modulus, a: Indentation radius, c: Crack radius, φ = 3, k = 3.

[0033] As shown in Table 1, the integrated peak intensity ratio of (W, Ml) C and WC (i I ((W, Ml) C)

2 X 2 X άθ / ί I (WC) d θ) deviates from the scope of the present invention 0.5% or less of the comparative examples, that is, sample Nos. 1, 2, 13, 25 and 26, fracture toughness values Is as low as 4.0 or less. On the other hand, for the examples in which the integrated peak intensity ratio is within the range of the present invention, the measurement value of the fracture toughness value is improved to about 4.0 or more, although there is some measurement error. In addition, regarding the surface roughness after processing, it is confirmed that all the examples of the present invention have Rmax of 7 nm or less. Sample No. 24 is a comparative example using WC powder with an average particle size of 1.0 / im as the raw material powder, and has the same composition and the product of (W, Ml) C and WC.

2 X minute peak intensity ratio (ί I ((W, M1) C Μθ / ί I (WC

Sample No. with the same 2 X) de)

Although the fracture toughness value is larger than 25, the surface roughness is deteriorated. This is because the average particle size of WC after sintering was 1.1 μm, which was larger than other samples.

[0034] Further, as shown in Fig. 1, the sintered hard material of the present invention has (W, Ml) C (0 8≤X <1. 0)

2 X

It is confirmed that the fracture toughness value (κ) increases as the value increases.

C

Example 2

An example in which the pulse current sintering (PCS) manufacturing method is applied to the present invention will be described. The results of this application example are also shown in Table 1 (described as PCS + HIP in the manufacturing method column).

[0036] In this example, only the sintering process and its conditions are different from the HP manufacturing method. That is, the raw material powder powder were mixed in a ball mill methanol solvent, temporarily pressed at LOMPa, pressed Caro in 20~40MPa in a vacuum ^{^{atmosphere, 1400 o C~1600 o C, lOmir}} ! After PCS sintering for ~ 60min, HIP treatment for l ~ 2hour at 1500 ° C in Ar atmosphere Finished to shape. Then, the processed hard surface roughness (Rmax), fracture toughness value (K), and (W, Ml) C and WC integrated peak intensity ratio (J "I ((W, M

C 2 X

1) c) d e / i (wc) d e) was obtained.

2 X

[0037] As shown in Table 1, (W, M1) C and WC

2 X integral peak intensity ratio (i I ((W, MI)

2 c X Μθ Ζ ί i (wc) d e) is within the scope of the present invention, it is confirmed that the fracture toughness value is 4.0 or more. Furthermore, with regard to the processed surface roughness, Rmax is 6nm or less, which is superior to the HP manufacturing method.

Example 3

[0038] An example in which the sintered hard material of the present invention is applied to a lens molding die of a glass lens high-temperature molding apparatus will be described.

[0039] A glass lens was press-molded with a lens-molding die manufactured using the sintered hard materials shown in the examples of the present invention and comparative examples shown in Table 1, and changes in the surface roughness of the glass lens were observed. investigated.

[0040] In the glass lens press molding test, spherical optical lens material glass is placed in the upper mold and lower mold cavities of the lens mold, and nitrogen with an oxygen concentration of 50 ppm is introduced through the gas inflow pipe. The body mold was heated to 500 ° C. Furthermore, after holding at a forming pressure of 2 MPa for 3 minutes, it was cooled to room temperature.

[0041] Table 2 shows the surface roughness of the obtained glass lens. From the table, the surface roughness of the glass lens molded using the example of the present invention is almost the same value as the surface roughness of the sintered hard material of the present invention shown in Table 1, respectively. It was confirmed that chipping is unlikely to occur during machining to molding dies and handling during lens molding.

[table 1]

However, those with * symbol in the sample No. are sintered hard materials within the scope of the present invention. 2]

However, a sample No. with a * symbol is a sintered hard material within the scope of the present invention. Industrial applicability

Since the sintered hard material of the present invention has excellent mirror surface workability, wear resistance, erosion wear resistance, etc., lenses, prisms, and gratings used in optical equipment are used. In addition to ultra-precise molding dies for molding high-precision optical elements such as rugs and their peripheral equipment, heat-resistant sliding members such as mechanical seal rings and shaft sleeve slide bearings, and injection molding of metal 'plastic' composites It can also be used as a component material for molds and vacuum chucks for electronic component manufacturing equipment.

Brief Description of Drawings

FIG. 1 shows the fracture toughness value (K) of the sintered hard material of the present invention.

Claims

The scope of the claims

[1] Tungsten carbide mainly containing WC and second phase (W, Ml) C (0. 8≤X <1.0)

2 X

Composed of phases

This (W, M1) C (0.8 ≤ X <1. 0) is a transition other than W in groups 4a, 5a and 6a of the periodic table.

2 X

W C (0.8 ≤ X <1. 0) is a solid solution of Ml, one or more of the transition metal elements.

2 X

And

Integrated peak intensity of X-ray diffraction of (1 1 1 1) plane of (W, M1) C (0 · 8≤Χ <1 · 0)

2 X

The integrated peak intensity of X-ray diffraction of i I ((W, Ml) C 01) plane

2 X Μ θ, WC (1 Π

When expressed as (WC) d Θ, these integrated peak intensity ratios J "I ((W, Ml) C) d Θ / J" I (

2 X

wc) d e force o. 5% ~: Sintered hard material in the range of ιο · 0%.

[2] The sintered hard material according to [1], wherein the tungsten carbide phase has an average particle size of 0.5 μm or less.

[3] As a phase other than WC and the second phase (W, Ml) C (0.8 ≤ X <1.0), Periodic Table 4a

2 X

Including a phase of one or more of M2 carbides, nitrides and carbonitrides which are transition metal elements of Group 5a and 6a, or a compound of M2 composed of a composite carbide or composite carbonitride thereof,

The integrated peak intensity of the maximum peak of X-ray diffraction of this M2 compound is expressed as ί I (M2 compound), and the integrated peak intensity of the X-ray diffraction of the (101) plane of wc is expressed as ί i (wc) d Θ. 3. The sintered hard material according to claim 1, wherein the integrated peak intensity ratio ί I (compound 2) d θ / ί I (WC) d Θ is 1.0% or less.

[4] The total number of atoms of Ml and Μ2 is in the range of 0.5% to 5.0% with respect to the number of W atoms in the sintered hard material,

The sintered hard material according to any one of claims 1 to 3, wherein the content of one or more of Fe, Co, and Ni is less than 0.05% by mass.

[5] A mold for molding high-precision optical elements such as lenses, prisms, and gratings used in optical equipment, which is formed of the sintered hard material according to any one of claims 1 to 4.