WO2005037731A1

WO2005037731A1 - Hard material excelling in resistance to high-temperature deterioration

Info

Publication number: WO2005037731A1
Application number: PCT/JP2004/015736
Authority: WO
Inventors: Kenji Nakahara; Hiroki Tanaka; Shuichi Imasato; Shigeya Sakaguchi; Yasuo Uchiyama
Original assignee: Nippon Tungsten Co., Ltd.
Priority date: 2003-10-22
Filing date: 2004-10-22
Publication date: 2005-04-28
Also published as: JPWO2005037731A1

Abstract

It is intended to impart to a WC base cemented carbide without any binding phase such characteristics that the cemented carbide has none of structural defects such as pore and abnormal phase; a specular surface of high surface precision can be obtained; the cemented carbide excels in the resistance to high-temperature deterioration and has high hardness and high strength; the Young’s modulus thereof is high while the thermal expansion coefficient is low; the cemented carbide excels in corrosion resistance; and the cemented carbide exhibits especially high-temperature hardness and strength and further excellent worked surface precision and surface roughness so that it is suitable for use as a material of high-temperature precision forming mold for various optical devices. There is provided a binder-less cemented carbide comprising a WC phase and/or a solid solution composite carbide phase of at least two metals selected from among W, Ti and Ta, wherein a microcrystalline structure is maintained even after sintering compaction by the use of raw material powder of microparticles with an average particle diameter of 1 μm or less and wherein either is a with-Si solid solution composite carbide phase formed or SiC is caused to be present as a third phase by effecting not only such particle size regulation but also addition of Si or SiC to the raw material powder.

Description

Specification

Hard material with excellent resistance to high temperature deterioration

Technical field

The present invention relates to a hard material having excellent resistance to high-temperature deterioration suitable as a high-precision mold material for molding an optical element such as a lens and a prism.

Background art

[0002] In recent years, optical pickup lenses used in CDs, DVDs, digital cameras, mobile phones, and the like! Low-priced optical elements such as glass and plastic used for substrates for computer hard disk substrates As a method of obtaining a highly reliable final product shape under high temperature, press forming means at high temperatures that does not require complicated mechanical precision processing is adopted.

[0003] The mold material used in the high-temperature press molding is required to have not only high-temperature degradation resistance but also excellent properties such as mirror workability, high-temperature hardness, thermal conductivity, and low coefficient of thermal expansion. Hard materials such as cemented carbides and ceramics have been used as materials to meet those requirements.

[0004] For example, Patent Document 1 discloses that cobalt is used as a cemented carbide for hot isostatic pressing suitable for an optical element molding die having a mirror surface with a Rmax of 0.05 μm or less after processing. — A WC-based cemented carbide containing 10% by weight is disclosed. Further, in order to improve the corrosion resistance and high-temperature deterioration resistance of the cemented carbide, the binder phase is changed from Co to Ni, and further, Cr, Mo, or the like is added.

[0005] Even when the binder phase of the cemented carbide is strengthened as described above, the binder phase itself is inferior to the carbide phase in ridge-like stability, and during the high-temperature forming operation, Corrosion and oxidation due to the working atmosphere, as well as high-temperature degradation due to nitridation, etc., occur from the binder phase, which shortens the life of the mold!

[0006] Therefore, if a cemented carbide that does not contain a binder phase that causes high-temperature deterioration is used, or a cemented carbide that is only a carbide phase, that is, a binderless cemented carbide is used as a material for precision molding, these hard alloys can be used. The characteristics can be expected to be improved. Such binderless cemented carbide itself Are disclosed in Patent Documents 2-4.

Patent Document 1: Japanese Patent Publication No. 62-51211

Patent Document 2: JP-A-2-120244

Patent Document 3: JP-A-10-7425

Patent document 4: JP-A-2003-81649

Disclosure of the invention

Problems to be solved by the invention

In order to use a binderless cemented carbide having no binder phase as a high-temperature molding material such as a high-precision molding material for optical element molding, it is necessary to provide higher strength and high-temperature deterioration resistance.

It is required that Sarako be excellent in high-temperature hardness, mirror workability, corrosion resistance and the like.

[0008] An object of the present invention is to provide a Noinderless WC-based cemented carbide that has a mirror surface with high surface accuracy and is free from structural defects such as pores and abnormal phases, and has excellent resistance to high-temperature deterioration. It is to do.

Another object is to provide a binderless WC-based cemented carbide having high hardness, high strength, a large Young's modulus, a small coefficient of thermal expansion, and excellent corrosion resistance.

[0010] Further, another object is to provide a binderless WC-based material having hardness and strength at high temperatures, excellent machined surface accuracy and surface roughness, and characteristics suitable for high-temperature precision molding of various optical elements. In providing cemented carbide.

Means for solving the problem

[0011] A binderless cemented carbide comprising a WC phase and a solid solution double carbide phase of two or more metals of Z or W, Ti and Ta according to the present invention, wherein the average particle diameter is 1 μm or less. Fine grained raw material powder is used, after sintering and densification, the particle size of the raw material powder is adjusted to maintain the fine grain state and its fine crystal structure. It has properties suitable for high-temperature precision molding molds with a maintained texture.

[0012] In the particle size adjustment, it is assumed that S is added as raw material powder to form a solid solution complex carbide phase with Si, or that SiC is present as a third phase. You can also.

[0013] In this cemented carbide, the WC phase is excellent in hardness, strength, machined surface roughness, etc. By reducing the average particle size to 1 μm or less, the structure becomes finer, and it becomes possible to improve the strength, hardness and mirror workability.

[0014] On the other hand, if the average particle size exceeds 1 µm, the strength and hardness decrease. In addition, the SiC phase formed by adding Si exhibits excellent properties such as hardness and resistance to high-temperature deterioration, but when the average particle diameter exceeds 1 μm, the strength is significantly reduced.

[0015] The addition of Si promotes the formation of a very stable glass phase containing Si when used at a high temperature, and significantly improves the resistance to high temperature deterioration. In addition, the existence of the SiC phase suppresses the grain growth of a solid solution double carbide phase such as Ti or Ta and W, or a WC phase, thereby maintaining a fine structure. If the addition amount is less than 0.1%, the effect is small. If it exceeds 10%, sinterability is remarkably deteriorated, and material defects such as pores increase.

[0016] When a part of Ti and Ta is substituted with one or more transition metals belonging to Groups 4, 5, and 6 of the periodic table, solid solution or precipitation occurs in the form of those transition metals or carbides thereof. Thereby, grain growth is suppressed, hardness and strength are improved, and resistance to high temperature deterioration is improved.

[0017] By substituting a part of C with N, the presence of a solid solution double carbonitride phase composed of Ti and Z or Ta and W or SiN improves the high-temperature resistance of the alloy.

3 4

However, if the substitution amount of C to N exceeds 25% by weight, the sinterability deteriorates and the strength-mirror workability of the alloy deteriorates remarkably.

[0018] Although sinterability is improved by the presence of Fe, Co, Ni, etc., it may form a solid solution double carbide phase such as Ti and Z or Ta and W, or form a solid solution with the WC phase. However, the content is preferably set to 1% by weight or less, since the crystal grain boundaries are unfavorably affected and the mirror workability and the high temperature deterioration resistance are significantly adversely affected.

[0019] In addition, unavoidable impurities cause abnormal grain growth and generation of an abnormal phase, and have a remarkable adverse effect on strength, hardness, mirror surface properties, and the like. Therefore, the content is preferably 1% by weight or less.

[0020] On the other hand, if pulse current pressure sintering or the like is used, sinter densification can be performed in a short time, crystal grain growth itself can be suppressed, and abnormal grain growth and occurrence of an abnormal phase can be reduced. Hardness · Strength · Mirror workability is improved, and productivity is also improved.

The invention's effect The hard material of the present invention has a surface with very few systematic defects such as pores and abnormal phases, a highly accurate mirror surface, excellent resistance to high temperature deterioration, and high hardness. 。High strength, high Young's modulus, low thermal expansion coefficient, excellent corrosion resistance, and longer product life than conventional materials.

BEST MODE FOR CARRYING OUT THE INVENTION

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

Example 1

[0023] Table 1 shows the C content in the composition of the raw material powder according to the examples of the present invention after sintering and the WC average particle size together with comparative examples.

[0024] As the raw material powder of the examples according to the present invention, those having an average particle diameter of 0.1 m to 1 µm were used, and the respective raw material powder compositions were adjusted to obtain required compositions.

[0025] The raw material powder was pulverized and mixed with a ball mill of a methanol solvent, and press-molded with O.lGPa.

Vacuum pre-sintering at 00 ° C-750 ° C 'l- 5H, then at 1500 ° C-1800 ° C, 0.5-2

After vacuum sintering with H, HIP treatment was performed at 1,200 ° C in an atmosphere of 1 to 2 H for Ar, and finished to the final shape by grinding.

[0026] The average WC particle size and composition of the obtained hard material is hardness. * Mechanical properties such as bending strength and machined surface roughness, and high temperature properties such as high temperature hardness and high temperature degradation resistance, and corrosion resistance. The effects were investigated.

[0027] The results of the microstructure observation, hardness, bending strength, and high temperature deterioration resistance of the hard material obtained from the raw material composition shown in Table 1, that is, the results of investigations on the increase in the amount of silicon oxide, were compared with those of the comparative example. See Figure 2.

[0028] The hardness was measured by HRA (Rockwell Kale), and the bending strength was measured by a three-point bending test method using a 5 x 8 x 25 mm test piece. For high temperature degradation resistance, a 5 x 8 x 10 mm test piece with its surface wrapped was kept in air at 800 ° C for 1H, and the weight increase before and after that was calculated from the weight change. In addition, the WC average particle diameter is the force determined from the alloy structure observation force. Alloys for which no WC phase was observed are indicated by “1” in Table 1! /.

[table 1] Raw material powder composition (% by weight)

Alloy C content

No. WC average particle size

WC TiC TiCN TaC C Cr3C2 SiC Si3N4 (% by weight)

(m)

1 98 1 1 6.3 1.0

2 90 8 2 7.2 0.9

3 72 26 2 9.7 0.9

4 53 45 2 12.4

5 89.6 8 2 0.2 0.2 7.2 0 7

6 88 8 2 1 1 7.4 0.5

7 81.6 16 2 0.2 0.2 8.3 0.6

8 71.6 26 2 0.2 0.2 9.7 0.8

9 43 45 2 5 5 13.2 ―

10 89.5 8 2 0.2 0.2 0.1 7.3 0.5

11 87.7 8 2 1 1 0.3 * 7.5 0.4 Actual

Alm 12 81.3 16 2 0.2 0.2 0.3 * 8.4 0.4 Example 13 70.6 26 2 0.2 0.2 1 * 9.9 0.5

14 38 45 2 5 5 5 * 14.5

15 87.6 8 2 2 0.2 0.2 7.4 1 0

16 76 16 2 2 1 1 2 9.1 0.8

17 77 16 4 2 0.2 0.2 0.3 0.3 8.6 1.0

18 68.6 26 2 2 0.2 0.2 1 9.8 0.8

19 35 45 2 2 5 5 5 1 14.4 ―

106 88 8 2 1 1 7.4 0.4

110 89.5 8 2 0.2 0.2 0.1 7.3 0.4

114 38 45 2 5 5 5 * 14.5 ―

118 68.6 26 2 2 0.2 0.2 1 9.8 0.7

1 96 2 2 6.4 2.0

2 90 8 2 7.2 2.5 Ratio

Comparison 3 82 16 2 8.3 2.3 Material 4 72 26 2 9.6 3.2

5 53 45 2 12.2 ―

*) (S + Si) amount

[Table 2]

Hardness (HRA) Flexural strength Surface roughness Ra Oxidation increase

No.

Main / dish 600 ° C (GPa) (nm) (g / m ² )

1 96.5 89.5 1.0 1.9 299

2 96.3 89.1 1.4 1.8 256

3 96.1 89 1.3 1.6 245

4 94.9 88.8 1.1 2.5 222

5 96.6 89.5 1.8 1.5 232

6 96.9 89.3 2.2 1.5 219

7 96.4 89 1.9 1.3 226

8 96.2 88.8 1.4 1.2 230

9 96.2 88.7 1.2 2.2 198

10 97 89.5 1.9 1.2 175

11 97.2 89.8 1.5 1.0 155

Real

Allocation 12 96.8 89.4 1.2 1.1 143 Examples

13 96.6 89.3 1.1 1.0 121

14 96.4 89.1 1.1 1.9 119

15 95.8 88.7 1.7 1.5 82

16 96 88.8 1.4 1.7 145

17 95.5 88.4 1.2 1.4 122

18 95.9 88.5 1.1 1.5 119

19 95.2 88.4 1.0 2.0 108

106 97 89.2 2.3 1,3 201

110 97 89.4 2.0 1.0 162

114 96,6 89.1 1.1 1.0 112

118 96.2 88.5 1.3 1.4 110

1 94.1 87 0.7 2.8 345

2 93.5 86.8 0.8 2.6 299

Ratio

Comparison 3 93.2 86.6 0.7 2.6 302

4 92.5 86.2 0.6 2.7 285

5 92.2 86 0.6 3.5 270

[0029] In No. 1-4 according to an example of the present invention, Ti content was changed by using a fine raw material powder and optimizing sintering conditions in an alloy in which WC or a solid solution complex carbide phase was refined. Although it is an alloy, its hardness, bending strength, surface roughness, and oxidation increase at room temperature and 600 ° C are improved over the comparative material.

[0030] Similarly, in Example Nos. 5 to 9, a part of W belongs to Groups 4, 5, and 6 of the periodic table other than W. The transition metal is an alloy that is substituted with Cr and V. These metal carbides act as grain growth inhibitors, reducing the average WC particle size, further increasing the hardness (room temperature and 600 ° C) and the transverse rupture strength. It is apparent that the surface roughness and the amount of acid addition have been improved.

[0031] Further, Example No. 14-14 is an alloy further added with SiC (the one marked with * is an example in which Si metal is used in combination.) The average particle size has been reduced and the hardness (room temperature and 600 ° C), surface roughness and oxidation weight gain have been improved.

Further, Example Nos. 15-19 are alloys in which a part of WC was replaced with TiCN, and the presence of carbonitrides and nitrides particularly improved the amount of oxidation.

Here, the force omitting the evaluation results for the corrosion resistance It was confirmed that all of the examples of the present invention had excellent corrosion resistance equal to or higher than that of the comparative material.

Example 2

An example in which the hard material according to the present invention is applied to the upper lens forming die 21 and the lower lens forming die 22 of the glass lens high-temperature forming apparatus shown in FIG.

[0035] Glass lenses were press-molded using lens-forming dies manufactured using the hard materials shown in the examples of the present invention shown in Table 1 and the comparative examples, and changes in the mold surface roughness were investigated.

[0036] In the glass lens press molding test, the spherical optical lens raw material glass placed in the lens molding machine housing 2 is placed in the cavities of the upper mold 21 and the lower mold 22 of the press mold, and the upper holder of the mold is placed. 11 and the lower holder 12 fixed. After the gas inside the device is discharged from the oil diffusion pump 5 and the gas discharge pipe 4, nitrogen with an oxygen concentration of 50 ppm is introduced through the gas inflow pipe 3, and the heater 14 Mold 13 was heated to 500 ° C. Further, the upper mold 21 is held by the upper shaft pressing cylinder 1 via the upper shaft 7 and the lower mold 22 is held by the shaft pressing cylinder 8 via the lower shaft 8 at a molding pressure of 2 MPa for 3 minutes, and then cooled. When the mold temperature became 300 ° C. or lower, the atmosphere was purged.

With this as one cycle, Table 3 shows the results of measuring the change in mold surface roughness after 500 cycles. From the table, it was confirmed that each of Examples No. 1 to 19 of the present invention had excellent high-temperature deterioration properties in which the change in surface roughness after the 500 cycle test was smaller than that of the comparative material.

[Table 3] Surface roughness Ra (nm)

No.

Before molding test After molding test

1 1.9 27.8

2 1.8 25.1

3 1.6 24.7

4 2.5 30.1

5 1.5 25.5

6 1.5 25.1

7 1.3 21.6

8 1.2 22.2

9 2.2 27.7

10 1.2 23.9 Actual 11 1.0 16.5 Application 12 1.1 17.3 Example 13 1.0 15.2

14 1.9 19.8

15 1.5 8.9

16 1.7 8.5

17 1.4 8.1

18 1.5 8.4

19 2.0 11.1

106 1.3 25

110 1.0 22.5

114 1.0 19.2

118 1.4 8.2

1 2.8 35.2 ratio 2 2.6 33.2 comparison 3 2.6 30.8 Wood 4 2.7 31.5

5 3.5 40.8 Example 3

This example shows an example of a hard material sintered and densified by using a pulse electric current sintering method.

[0039] The amount of C in the composition of the raw material powder used in Examples 106, 110, 114, and 118 of Table 1, and

Shows the WC average particle size.

[0040] As the raw material powders in these examples, those having an average particle diameter of 0.1 µm to 1 µm were used, and the respective raw material powder compositions were adjusted to obtain required compositions.

The raw material powder was pulverized and mixed in a ball mill of a methanol solvent, and methanol was evaporated to obtain a granulated powder. The granulated powder was filled in a high-strength graphite die (die and punch) and then sintered by a pulse current sintering apparatus. Sintering temperature is 1300 ° C-1900

. C, sintering in vacuum at a pressure of 10-80MPa, heating time was 5-30 minutes, and holding time was 1-130 minutes. Finished to the final shape by grinding.

[0042] The average WC particle size and composition of the obtained hard material are hardness * Mechanical properties such as bending strength and machined surface roughness, high temperature properties such as high temperature hardness and high temperature deterioration resistance, and corrosion resistance The effects were investigated.

Nos. 106, 110, 114, and 118 in Table 2 show the results of microstructure observation, hardness, bending strength, and resistance to high-temperature deterioration of the obtained hard material, that is, the results of investigations on the increase in oxidation.

Note that the hardness was measured by HRA, and the bending strength was measured by a three-point bending test method using a 5 × 8 × 25 mm test piece. For high-temperature deterioration resistance, a 5 × 8 × 10 mm test piece whose surface was wrapped was held at 800 ° C. in the air for 1 hour, and the weight change before and after the test was also calculated as an increase in iridescence. The average WC particle size is indicated by “1” for alloys in which no WC phase is observed, as determined by the force of observation of the alloy structure.

[0045] From the table, the hard material sintered and densified using the pulsed electric current sintering method is harder than the comparative material at room temperature and 600 ° C. It can be seen that both have been improved.

Here, it was confirmed that the material had excellent corrosion resistance equal to or higher than that of the force comparison material omitting the evaluation result on the corrosion resistance.

Industrial applicability

[0047] The hard material of the present invention also has excellent wear resistance, heat resistance, mirror workability, corrosion resistance, and the like. Since it is equipped, in addition to ultra-precision molding dies and peripheral equipment, heat-sliding moving members such as mechanical seal rings, shaft sleeve slide bearings, and injection molding molds such as metal * plastic 'composite materials, It can also be applied as a constituent material of a vacuum chuck for an electronic component manufacturing apparatus. Brief Description of Drawings

FIG. 1 is a cross-sectional view showing a mold for molding an optical glass lens element to which a hard material according to the present invention is applied, and a molding apparatus therefor.

Explanation of symbols

[0049] 1: Upper shaft pressurizing cylinder

2: Lens molding machine housing

3: Gas inflow pipe

4: Gas exhaust piping

5: Oil diffusion pump

6: Lower shaft pressure cylinder

7: Upper shaft

8: Lower shaft

11: Mold upper holder

12: MONOREDO lower HONOREDA

13: Body mold

14: heater

21: Upper lens mold 22: Lower lens mold 23: Temperature sensor

Claims

The scope of the claims

[1] It is made of a binderless cemented carbide that only has a two-phase mixed structure or a solid solution double carbide phase with WC phase and Z or carbides of two or more metals of W and Ti and Z or Ta, and has an average particle size of : A hard material with excellent high-temperature deterioration resistance in which the fine crystal structure of the raw material powder is maintained even after sintering and densification using fine raw material powder of m or less.

[2] Binderless cemented carbide power W is 37.5-93.5% by weight, Ti and Z or Ta are 1-47% by weight in total, C is 6.18-14.2% by weight, and Fe and Co are 2. The hard material having excellent resistance to high-temperature deterioration according to claim 1, wherein the total amount of Ni is 1% by weight or less, and the balance has a composition of unavoidable impurities.

[3] The method according to claim 1 or claim 2, wherein Ti and part of Ti and Z or Ta are replaced by one or more transition metals belonging to Groups 4, 5, and 6 of the periodic table. Hard material with excellent resistance to high temperature deterioration.

[4] The claim according to claim 1, wherein 25% by weight or less of the C content is replaced with N, and a part of the carbide or solid solution complex carbide forms WN or W solid solution complex carbonitride. Item 4. A hard material having excellent resistance to high temperature deterioration according to any one of Items 3.

[5] Binderless cemented carbide force in which only the mixed structure of the carbide phase of the WC phase and Z or the carbide phase of two or more metals of W and Ti and Z or Ta and the carbide phase of Si or the solid solution double carbide phase thereof Become

A hard material that uses fine raw material powder with an average particle diameter of 1 μm or less and maintains the fine crystal structure of the raw material powder even after sintering and densification, and has excellent resistance to high-temperature deterioration.

[6] Binderless cemented carbide power W is 37.5—93.5% by weight, Ti and Z or Ta are 1-147% by weight in total, Si is 0.1—10% by weight, and C is 6.18— 16. 1% by weight, Fe and Co

The hard material having excellent resistance to high-temperature deterioration according to claim 5, wherein the total content of Ni is 1% by weight or less, and the remainder has a composition having an unavoidable impurity power.

[7] The anti-resistance according to claim 5 or 6, wherein Ti and part of Ti and Z or Ta are replaced by one or more transition metals belonging to groups 4, 5, and 6 of the periodic table. A hard material with excellent high-temperature deterioration.

[8] Not more than 25% of the C content is replaced by N, and WC carbide phase and solid solution complex Some of the carbides form carbonitrides, and some or all of the SiC phase is the SiN phase.

8. The hard material according to claim 5, wherein the hard material is excellent in high-temperature deterioration resistance.

9. High-temperature deterioration resistance according to any one of claims 1 to 8, wherein the compact is formed by sintering and densification by a pressure sintering method (a hot press method) including a pulse current pressure sintering method or a pulse current pressure sintering method. Hard material with excellent properties.