JPWO2005037731A1 - Hard material with high temperature resistance - Google Patents

Abstract

WC-based cemented carbide that does not have a binder phase has no structural defects such as pores or abnormal phases, provides a mirror surface with good surface accuracy, is excellent in high-temperature degradation resistance, Hardness and high strength, high Young's modulus, low thermal expansion coefficient, excellent corrosion resistance, especially high temperature hardness and strength, excellent machined surface accuracy and surface roughness, various optical The object is to provide characteristics suitable for a high-temperature precision molding die of the element. In a binderless cemented carbide composed of a solid solution double carbide phase of two or more metals of W, Ti and Ta, sintering is performed by using fine raw material powder having an average particle diameter of 1 μm or less. Even after densification, the fine crystal structure is maintained, and raw material powder of Si or SiC is added together with such particle size adjustment to form a solid solution double carbide phase with Si, or SiC is present as the third phase. It was.

Description

  The present invention relates to a hard material excellent in high temperature deterioration resistance suitable as a high-precision mold material for molding optical elements such as lenses and prisms.

  In recent years, when manufacturing optical elements such as optical pickup lenses used in CDs, DVDs, digital cameras, mobile phones, etc. and hard disk substrates for computers, glass, plastic, etc., high reliability at a low price As a method for obtaining the final product shape, press molding means in a high temperature that does not require complicated mechanical precision processing is employed.

  The mold material used in this high-temperature press molding is required to have excellent properties such as high-temperature deterioration resistance, mirror surface workability, high-temperature hardness, thermal conductivity, and low coefficient of thermal expansion. Hard materials such as cemented carbide and ceramics have been used as combined materials.

  For example, Patent Document 1 discloses that 3 to 10% by weight of cobalt is used as a cemented carbide for hot isostatic pressing suitable for an optical element molding die whose surface after processing forms a mirror surface having an Rmax of 0.05 μm or less. Including a WC-based cemented carbide is disclosed. 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 Cr, Mo and the like are further added.

  However, even if the cemented carbide binder phase is strengthened in this way, the binder phase itself is inferior in chemical stability as compared to the carbide phase. In this case, high-temperature deterioration due to nitriding or the like occurs in the binder phase, which causes the life of the mold to be shortened.

Therefore, if a cemented carbide consisting only of a carbide phase that does not contain a binder phase that causes high-temperature degradation, that is, a so-called binderless cemented carbide, is used as a material for precision molding, the improvement of the properties of these hard alloys can be expected. become. Such binderless cemented carbide itself is disclosed in Patent Documents 2 to 4.
Japanese Examined Patent Publication No. 62-51211 Japanese Patent Laid-Open No. 2-120244 Japanese Patent Laid-Open No. 10-7425 JP 2003-81649 A

  However, in order to use this binderless cemented carbide having no binder phase as a high-temperature mold material such as a high-precision mold material for optical element molding, higher strength, high temperature deterioration resistance, and high temperature hardness It is required to have excellent mirror surface workability, corrosion resistance, and the like.

  An object of the present invention is to provide a binderless WC-based cemented carbide that is free from systematic defects such as pores and abnormal phases, has a mirror surface with good surface accuracy, and has excellent resistance to high-temperature degradation. It is in.

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

  In addition, another object is to provide a binderless WC-based cemented carbide having hardness and strength at high temperatures, excellent machined surface accuracy and surface roughness, and properties suitable for high-temperature precision molding molds of various optical elements. Is in the provision of.

  Binderless cemented carbide comprising a WC phase and / or a solid solution double carbide phase of two or more metals of W, Ti, and Ta according to the present invention, and using a fine raw material powder having an average particle size of 1 μm or less , Which has been adjusted to maintain the fine grain state of the raw material powder and its fine crystal structure even after sintering densification, to a mold for high-temperature precision molding that maintains the fine crystal structure even after sintering densification Has suitable characteristics.

  In addition, when adjusting the particle size, Si or SiC may be added as a raw material powder to form a solid solution double carbide phase with Si, or SiC may be present as a third phase.

  In this cemented carbide, the WC phase is excellent in hardness, strength, surface roughness, etc., but by making the average particle diameter 1 μm or less, the structure becomes finer and the strength / hardness, mirror surface workability, etc. Can be improved.

  On the other hand, when the average particle diameter exceeds 1 μm, the strength and hardness decrease. Further, 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.

  The addition of Si facilitates the formation of a very stable glass phase containing Si when used at high temperatures, and the resistance to high temperature degradation is significantly improved. Further, the presence of the SiC phase makes it possible to suppress the grain growth of the solid solution double carbide phase composed of Ti or Ta and W or the WC phase and maintain the fine structure. If the addition amount is less than 0.1%, the effect is small, and if it exceeds 10%, the sinterability is remarkably deteriorated and material defects such as pores increase.

  When a part of Ti and Ta is replaced with one or more transition metals belonging to groups 4, 5, and 6 of the periodic table, grain growth is caused by solid solution or precipitation in the form of transition metals or carbides thereof. Is suppressed, hardness and strength are improved, and high temperature deterioration resistance is improved.

By substituting a part of C with N, the presence of a solid solution double carbonitride phase composed of Ti and / or Ta and W or Si ₃ N ₄ improves the high temperature deterioration resistance of the alloy. If the substitution amount of C by N exceeds 25% by weight, the sinterability is deteriorated and the strength and mirror finish of the alloy are remarkably deteriorated.

  In addition, although the sinterability is improved by the presence of Fe, Co, Ni, etc., it dissolves in a solid solution double carbide phase composed of Ti and / or Ta and W or WC phase, or segregates at grain boundaries. Thus, the content is preferably 1% by weight or less in order to have a significant adverse effect on mirror surface workability and high temperature resistance.

  In addition, unavoidable impurities cause abnormal grain growth and generation of abnormal phases, and have a significant adverse effect on strength, hardness, mirror surface workability, and the like.

  On the other hand, if pulsed current pressure sintering method is used, sintering densification can be done in a short time, so it is possible to suppress crystal grain growth itself and to reduce the occurrence of abnormal grain growth and abnormal phase. -Mirror finish processability is improved and productivity is improved.

  The hard material of the present invention has very few systematic defects such as pores and abnormal phases, provides a mirror surface with good surface accuracy, has excellent resistance to high-temperature deterioration, and has high hardness and high strength. In addition, the Young's modulus is large, the thermal expansion coefficient is small, the corrosion resistance is excellent, and the product life is longer than that of the conventional material.

  EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated based on an Example below.

  Table 1 shows the amount of C in the composition after sintering and HIP of the composition of the raw material powder according to the example of the present invention, and the WC average particle diameter together with the comparative example.

  As the raw material powders of the examples according to the present invention, those having an average particle diameter of 0.1 μm to 1 μm were used and adjusted so as to obtain a required composition as each raw material powder composition.

  The raw material powder is pulverized and mixed with a ball mill of methanol solvent, press-molded at 0.1 GPa, vacuum presintered at 500 ° C. to 750 ° C. and 1 to 5 H, and then at 1500 ° C. to 1800 ° C. and 0.5 to 2 H After vacuum sintering at 1500 ° C., HIP treatment was performed in an atmosphere of 1-2H and Ar at 1500 ° C. and finished to the final shape by grinding.

  The effect of WC average particle size and composition of the obtained hard material on mechanical properties such as hardness, bending strength and processed surface roughness, high temperature properties such as high temperature hardness and high temperature resistance, and corrosion resistance. investigated.

  Table 2 shows the results of investigating the structure observation, hardness, bending strength, high temperature deterioration resistance, that is, oxidation increase, of the hard material obtained from the raw material composition shown in Table 1 in comparison with the comparative example.

The hardness was measured by HRA (Rockwell A scale), 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 having a lapped surface was held in the atmosphere at 800 ° C. for 1 H, and the oxidation increase was calculated from the weight change before and after that. Moreover, although the WC average particle diameter was calculated | required from alloy structure observation, the alloy in which the WC phase was not recognized is shown by "-" in Table 1.

  According to the embodiment of the present invention, 1-4 are alloys in which the amount of Ti is changed by using a fine raw material powder and the WC or solid solution double carbide phase is refined by optimizing the sintering conditions. The hardness, bending strength, surface roughness and oxidation increase at ℃ are improved.

  Similarly in Example No. 5 to 9 are alloys in which a part of W is further substituted with transition metals Cr and V belonging to groups 4, 5 and 6 of the periodic table other than W. These metal carbides act as grain growth inhibitors. This shows that the WC average particle size is reduced, and the hardness (room temperature and 600 ° C.), bending strength, surface roughness, and oxidation increase are improved.

  In addition, Example No. Nos. 10 to 14 are alloys to which SiC (indicated by * indicates an example in which Si metal is used in combination). Although the bending strength is slightly reduced, the WC average particle diameter is reduced and the hardness ( Room temperature and 600 ° C.), surface roughness, and oxidation increase.

  Furthermore, Example No. 15 to 19 are alloys in which a part of WC is substituted with TiCN, and the increase in oxidation is particularly improved by the presence of carbonitrides and nitrides.

  Here, although the evaluation result about corrosion resistance is omitted, it was confirmed that all of the examples of the present invention have excellent corrosion resistance equivalent to or higher than that of the comparative material.

  The example which applied the hard material which concerns on this invention to the lens shaping | molding upper mold | type 21 and the lens shaping | molding lower mold | type 22 of the glass lens high temperature molding apparatus shown in FIG. 1 is shown.

  Glass lenses were press-molded with lens molding dies manufactured using the hard materials shown in Examples and Comparative Examples of the present invention shown in Table 1, and changes in the mold surface roughness were investigated.

  In the glass lens press molding test, spherical optical lens raw 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 molding mold, and the upper holder 11 and the lower side of the mold. It was fixed by the holder 12. After the gas in the apparatus is discharged from the oil diffusion pump 5 and the gas discharge pipe 4, nitrogen having an oxygen concentration of 50 ppm is introduced through the gas inflow pipe 3, and the heater 14 is used to form the body mold 13 using the temperature sensor 23. Was heated to 500 ° C. Further, the upper die 21 is held by the upper shaft pressurizing cylinder 1 through the upper shaft 7 and the lower die 22 is held by the shaft pressurizing cylinder 8 through the lower shaft 8 at a molding pressure of 2 Mpa for 3 minutes, and then cooled. An air purge was performed when the mold temperature reached 300 ° C. or lower.

Table 3 shows the results of measuring the change in mold surface roughness after 500 cycles, assuming this as one cycle. From the same table, Example No. It was confirmed that all of Nos. 1 to 19 have an excellent high temperature deterioration property because the change in surface roughness after the 500 cycle test is smaller than that of the comparative material.

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

  The amount of C in the compounding composition of the raw material powder used in Examples 106, 110, 114, and 118 in Table 1 and the WC average particle diameter are shown.

  As the raw material powders of these examples, those having an average particle diameter of 0.1 μm to 1 μm were used and adjusted so as to obtain a required composition as each raw material powder composition.

  The raw material powder was pulverized and mixed with a ball mill of a methanol solvent, and methanol was evaporated to obtain a granulated powder. The granulated powder was filled into a high-strength graphite sintering die (die and punch) and then sintered with a pulse current sintering apparatus. The sintering temperature was 1300 ° C. to 1900 ° C., the applied pressure was 10 to 80 MPa, the sintering was performed in vacuum, the temperature rising time was 5 to 30 minutes, and the holding time was 1 to 30 minutes. Finished to the final shape by grinding.

  The effect of WC average particle size and composition of the obtained hard material on mechanical properties such as hardness, bending strength and processed surface roughness, high temperature properties such as high temperature hardness and high temperature resistance, and corrosion resistance. investigated.

  No. in Table 2 106, 110, 114, and 118 show the results of investigating the structure observation, hardness, bending strength, high temperature deterioration resistance, that is, oxidation increase, of the obtained hard material.

  The hardness was 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 having a lapped surface was held in the atmosphere at 800 ° C. for 1 hour, and the increase in oxidation was calculated from the weight change before and after that. Moreover, although the WC average particle diameter was calculated | required from alloy structure observation, the alloy in which the WC phase was not recognized is shown by "-".

  From the same table, it is a hard material that has been sintered and densified using the pulse current sintering method, but the hardness, bending strength, surface roughness, and oxidation increase at room temperature and 600 ° C are improved compared to the comparative material. I understand.

  Here, although the evaluation result about corrosion resistance is abbreviate | omitted, it was confirmed that it has the outstanding corrosion resistance equivalent to or more than a comparative material.

  Since the hard material of the present invention has excellent wear resistance, heat resistance, mirror surface workability, corrosion resistance, etc., in addition to ultra-precision molding dies and peripheral devices, mechanical seal rings, shaft sleeve sliding bearings, etc. It can also be used as a component of heat-resistant sliding members, injection molding molds for metals, plastics, composites, etc., and vacuum chucks for electronic component manufacturing equipment.

It is sectional drawing which shows the optical glass lens element shaping | molding die to which the hard material based on this invention is applied, and its shaping | molding apparatus.

Explanation of symbols

1: Upper shaft pressurizing cylinder 2: Lens molding machine housing 3: Gas inflow pipe 4: Gas exhaust pipe 5: Oil diffusion pump 6: Lower shaft pressurizing cylinder 7: Upper shaft 8: Lower shaft 11: Mold upper holder 12 : Mold lower holder 13: Body mold 14: Heater 21: Lens molding upper mold 22: Lens molding lower mold 23: Temperature sensor

Claims (9)

It consists of a binderless cemented carbide consisting of a WC phase and / or a two-phase mixed structure with two or more metal carbides of W and Ti and / or Ta or a solid solution double carbide phase, and has an average particle size of 1 μm or less A hard material with excellent resistance to high-temperature deterioration that maintains the fine crystal structure of the raw material powder even after sintering and densification using fine raw material powder. The binderless cemented carbide comprises 37.5 to 93.5 wt% of W, 1 to 47 wt% in total of Ti and / or Ta, 6.18 to 14.2 wt% of C, Fe, The hard material excellent in high temperature deterioration resistance according to claim 1, wherein the total content of Co and Ni is 1% by weight or less, and the remainder is composed of inevitable impurities. The high temperature resistance deterioration according to claim 1 or 2, wherein a part of Ti and Ti and / or Ta is substituted by one or more transition metals belonging to groups 4, 5, and 6 of the periodic table. Hard material with excellent properties. The C content of 25 wt% or less is substituted with N, and a part of the carbide or solid solution double carbide forms a solid solution double carbonitride of WN or W. A hard material having excellent resistance to high temperature degradation as described in any one of the above. A WC phase and / or a mixed structure of a carbide phase of two or more metals of W and Ti and / or Ta and a carbide phase of Si or a binderless cemented carbide consisting only of these solid solution double carbide phases,
A hard material excellent in high-temperature deterioration resistance in which a fine crystal structure of a raw material powder is maintained even after sintering and densification using a fine raw material powder having an average particle diameter of 1 μm or less. In the binderless cemented carbide, W is 37.5 to 93.5% by weight, Ti and / or Ta is 1 to 47% by weight, Si is 0.1 to 10% by weight, and C is 6. The hard material excellent in high temperature deterioration resistance according to claim 5 having a composition comprising 18 to 16.1 wt%, Fe, Co and Ni in a total content of 1 wt% or less, and the remainder consisting of inevitable impurities. The high temperature deterioration resistance according to claim 5 or 6, wherein a part of Ti and Ti and / or Ta is substituted by one or more transition metals belonging to groups 4, 5, and 6 of the periodic table. Excellent hard material. 25% or less of the C content is replaced by N, WC carbide phase and part of solid solution double carbide form carbonitride, respectively, and part or all of SiC phase is Si ₃ N ₄ phase The hard material excellent in high temperature degradation resistance in any one of Claim 5 to 7. 9. High temperature degradation resistance according to any one of claims 1 to 8, which is formed by sintering densification by a pulsed current pressure sintering method or a pressure sintering method (hot press method) including a pulsed current pressure sintering method. Excellent hard material.

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