Sintered alloys and dies

Abstract

A sintered alloy characterized in that it forms a solid solution phase consisting of at least one metal element selected from the group consisting of Ti, Ta, Nb, and V, and at least one of C and N, and that it contains 38 to 95 volume % of said compound phase, which is composed of 80 volume % or more of a compound phase having a NaCl type structure and a Cr3C2 phase.

Description

[Technical field]

[0001] The present invention relates to a sintered alloy and a mold made of the sintered alloy. [Background technology]

[0002] Materials used for dies for molding various optical lenses include SUS420J2, ultrafine grain cemented carbide, and binderless cemented carbide. However, when high geometric precision is required, such as for dies for aspheric lenses, binderless cemented carbide, which has a small thermal expansion coefficient, is used.

[0003] On the other hand, a variety of materials are being used as lens materials, and lens materials with larger thermal expansion coefficients than conventional materials are being used. In addition, mold materials with large thermal expansion coefficients may be used when molding objects that are difficult to mold using the thermal expansion coefficients of conventional mold materials.

[0004] Japanese Patent No. 2574426 (Patent Document 1) discloses an optical element molding die used for press molding of glass optical elements, in which at least the portion of the die that comes into contact with glass has a composition of (a) 65.7 to 92.9 wt % tungsten, 24.0 to 0.8 wt % titanium, 10.3 to 6.3 wt % carbon, and the remainder unavoidable impurities, and (b) a two-phase mixed structure in which a first phase is a tungsten carbide phase and a second phase is a solid solution double carbide phase of titanium and tungsten in a NaCl-type crystal.

[0005] Patent No. 6049978 (Patent Document 2) describes a steel sheet containing 20 mass% or more and 40 mass% or less of NbC, 0.3 mass% or more and 10 mass% or less of Ni, unavoidable impurities, and the balance being Cr3C2. r3 The present invention discloses a sintered alloy for molding dies with a large thermal expansion coefficient, which has a C2-NbC-Ni composition and is advantageous for molding glass materials with a large thermal expansion coefficient. This sintered alloy for molding dies with a large thermal expansion coefficient not only enables molding of materials with a large thermal expansion coefficient, but also enables molding of materials with shapes that are difficult to mold with conventional materials.

[0006] In Japanese Patent No. 7351582 (Patent Document 3), the oxidation resistance of the sintered alloy for molding dies having a large thermal expansion coefficient is improved, thereby extending the life of the dies and improving the quality of the molded products. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 2574426 [Patent Document 2] Patent No. 6049978 [Patent Document 3] Patent No. 7351582 Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, with the diversification of products to be molded, molding materials with various thermal expansion coefficients have been proposed, and opportunities to mold unusual shapes that have not been seen before are increasing. In order to meet these applications, it is necessary to provide molding dies with appropriate thermal expansion coefficients. [Means for solving the problem]

[0009] The present invention relates to a lens molding die material that can obtain any required thermal expansion coefficient and can also be imparted with properties such as specularity, thermal conductivity, strength, and oxidation resistance as required.

[0010] That is, the present inventors have found that a sintered alloy that forms a solid solution phase containing at least one metal element selected from Ti, Ta, Nb, and V, and at least one of C and N, and that contains 80 volume % or more of a compound phase having a NaCl type structure (hereinafter also referred to as an "MC phase"), a Cr3C2 phase, and a WC phase, has a thermal expansion coefficient of 10.3 MK -1 The thermal expansion coefficient of the WC phase is about 4.2 to 5.0 MK -1 This is about the same as the thermal expansion coefficient of conventional binderless cemented carbide, which is 4 to 5 MK. -1Therefore, the thermal expansion coefficient of the materials in Patent Documents 2 and 3 is 9MK -1 The inventors have discovered that the above-mentioned polyimide is suitable as a molding die material that can be given properties such as specularity, thermal conductivity, strength, and oxidation resistance as required, and that the above-mentioned polyimide is suitable as a molding die material, thereby arriving at the present invention.

[0011] That is, the sintered alloy according to the first embodiment of the present invention forms a solid solution phase consisting of at least one metal element selected from Ti, Ta, Nb, and V, and at least one of C and N, and is composed of a compound phase having an NaCl type structure and a Cr3C2 phase, with 80 volume % or more of the solid solution phase being composed of the NaCl type structure and the Cr3C2 phase, The composition is characterized in that the compound phase is contained in an amount of 38 to 95% by volume.

[0012] The sintered alloy according to the second embodiment of the present invention forms a solid solution phase consisting of at least one metal element selected from the group consisting of Ti, Ta, Nb, and V, at least one of W and Mo, and at least one of C and N, and is composed of a compound phase having an NaCl type structure and a Cr3C2 phase, with 80 volume % or more of the compound phase being composed of the NaCl type structure and the Cr3C2 phase, The compound phase is contained in an amount of 38 to 95% by volume, The compound phase is characterized in that at least one of W and Mo is dissolved in the compound phase at 0.1 to 45 atomic % based on the total amount of metal elements in the compound phase.

[0013] The sintered alloy according to the third embodiment of the present invention forms a solid solution phase consisting of at least one metal element selected from the group consisting of Ti, Ta, Nb, and V, and at least one of C and N, and is composed of a compound phase having a NaCl type structure of 80 volume % or more, a binder phase consisting of at least one of Ni, Co, and Fe, and a Cr3C2 phase; The composition is characterized in that the compound phase is contained in an amount of 38 to 95% by volume, and the binder phase is contained in an amount of 8.2% by volume or less.

[0014] The sintered alloy according to the fourth embodiment of the present invention forms a solid solution phase consisting of at least one metal element selected from Ti, Ta, Nb, and V, at least one of W and Mo, and at least one of C and N, and is composed of a compound phase having a NaCl type structure of 80 volume % or more, a binder phase consisting of at least one of Ni, Co, and Fe, and a Cr3C2 phase; The compound phase is contained in an amount of 38 to 95% by volume, and the binder phase is contained in an amount of 8.2% by volume or less, The compound phase is characterized in that at least one of W and Mo is dissolved in the compound phase at 0.1 to 45 atomic % based on the total amount of metal elements in the compound phase.

[0015] The sintered alloy according to the fifth embodiment of the present invention forms a solid solution phase consisting of at least one metal element selected from Ti, Ta, Nb, and V, and at least one of C and N, and is composed of a compound phase having a NaCl type structure of 80 volume % or more, a binder phase consisting of at least one of Ni, Co, and Fe, and a WC phase; The composition is characterized in that the compound phase is contained in an amount of 8 to 95% by volume, and the binder phase is contained in an amount of 2.0% by volume or less.

[0016] The sintered alloy according to the sixth embodiment of the present invention forms a solid solution phase consisting of at least one metal element selected from the group consisting of Ti, Ta, Nb, and V, at least one of W and Mo, and at least one of C and N, and is composed of a compound phase having a NaCl type structure of 80 volume % or more, a binder phase consisting of at least one of Ni, Co, and Fe, and a WC phase; The compound phase is contained in an amount of 8 to 95% by volume, and the binder phase is contained in an amount of 2.0% by volume or less, The compound phase is characterized in that at least one of W and Mo is dissolved in the compound phase at 0.1 to 45 atomic % based on the total amount of metal elements in the compound phase.

[0017] The sintered alloy according to the seventh embodiment of the present invention comprises a WC phase and a Cr3C2 phase, The material is characterized in that the Cr3C2 phase is contained in an amount of 10 to 90% by volume.

[0018] The sintered alloy according to the eighth embodiment of the present invention comprises a WC phase, a binder phase comprising at least one of Ni, Co, and Fe, and a Cr3C2 phase; The composition is characterized in that the Cr3C2 phase is contained in an amount of 10 to 90% by volume, and the binder phase is contained in an amount of 2.0% by volume or less.

[0019] The sintered alloy according to the ninth embodiment of the present invention is characterized in that it forms a solid solution phase consisting of at least one metal element selected from the group consisting of Ti, Ta, Nb, and V, and at least one of C and N, and that 80% or more by volume of the solid solution phase consists of a compound phase having a NaCl type structure, a WC phase, and a Cr3C2 phase.

[0020] The sintered alloy according to the tenth embodiment of the present invention forms a solid solution phase consisting of at least one metal element selected from the group consisting of Ti, Ta, Nb, and V, at least one of W and Mo, and at least one of C and N, and is composed of a compound phase having a NaCl type structure, a WC phase, and a Cr3C2 phase, with 80 volume % or more of the compound phase being composed of the NaCl type structure, The compound phase is characterized in that at least one of W and Mo is dissolved in the compound phase at 0.1 to 45 atomic % based on the total amount of metal elements in the compound phase.

[0021] The sintered alloy according to the eleventh embodiment of the present invention forms a solid solution phase consisting of at least one metal element selected from Ti, Ta, Nb, and V, and at least one of C and N, and is composed of a compound phase having a NaCl type structure of 80 volume % or more, a binder phase consisting of at least one of Ni, Co, and Fe, a WC phase, and a Cr3C2 phase; The binder phase is contained in an amount of 2.0% by volume or less.

[0022] The sintered alloy according to the twelfth embodiment of the present invention forms a solid solution phase consisting of at least one metal element selected from Ti, Ta, Nb, and V, at least one of W and Mo, and at least one of C and N, and is composed of a compound phase having a NaCl type structure of 80 volume % or more, a binder phase consisting of at least one of Ni, Co, and Fe, a WC phase, and a Cr3C2 phase; The binder phase contains 2.0% by volume or less, The compound phase is characterized in that at least one of W and Mo is dissolved in the compound phase at 0.1 to 45 atomic % based on the total amount of metal elements in the compound phase.

[0023] In the ninth to twelfth embodiments, the compound phase is preferably contained in an amount of 10 to 90% by volume.

[0024] In the ninth to twelfth embodiments, the volume ratio of the content of the Cr3C2 phase to the content of the WC phase is preferably 0.125-8.

[0025] The grain size of the WC phase is preferably 0.1 to 2.5 μm.

[0026] In the first to twelfth embodiments, the material is preferably sintered by hot pressing.

[0027] A mold according to one embodiment of the present invention is characterized in that it is made of the above-mentioned sintered alloy. Effect of the Invention

[0028] According to the present invention, a lens molding die material can be obtained that can obtain any desired thermal expansion coefficient and can also be imparted with properties such as specularity, thermal conductivity, strength, and oxidation resistance as required. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] [1] First embodiment The sintered alloy according to the first embodiment of the present invention is characterized in that it forms a solid solution phase consisting of at least one metal element selected from the group consisting of Ti, Ta, Nb, and V, and at least one of C and N, and is composed of a compound phase (hereinafter also referred to as "MC phase") having an NaCl type structure and a Cr3C2 phase, with the MC phase being 38 to 95 volume %.

[0030] The MC phase is a carbide, carbonitride, nitride, or solid solution thereof (including a single compound) of at least one metal element selected from Ti, Ta, Nb, and V, and has a NaCl type structure. By containing an MC phase containing at least one of Ti, Ta, Nb, and V and having a NaCl type structure, the oxidation resistance of the sintered alloy is improved. In particular, by containing Ti in the MC phase, particularly excellent oxidation resistance can be obtained. The MC phase may be a solid solution phase containing Ti in addition to Ta, Nb, or V. In that case, the content of Ti is preferably 10 to 90 mol%, more preferably 40 to 80 mol%, based on the amount of metal elements contained in the MC phase. The MC phase is preferably a carbide or carbonitride. Among Ti, Ta, Nb, and V, Ti carbide has high hardness, so when the MC phase contains a large amount of Ti, the material has excellent wear resistance, but it also tends to be hard and brittle, so it may be difficult to obtain a mirror finish. In such a case, it is better to add Ti in a small amount. The inclusion of V improves the adhesion resistance of the die. The MC phase may be a solid solution phase containing V in addition to at least one of the metal elements Ti, Ta, and Nb. If it is desired to prevent the Ti, Ta, Nb, and V components from being mixed into the processed material, the amount of the element can be reduced. The MC phase may further contain oxygen and boron, and may further contain Zr, Hf, and Cr.

[0031] The sintered alloy (MC-Cr3C2 alloy) according to the first embodiment has a thermal expansion coefficient of 7 to 9 MK -1 By setting the MC phase content at 38-95 volume %, it is possible to obtain a sintered alloy with a 7-9MK phase. -1 When the MC phase content is more than 95% by volume, the grain growth of the MC phase structure is likely to occur, making it difficult to obtain a mirror finish in the sintered alloy. When the MC phase content is less than 38% by volume, the 9MK -1 It is difficult to obtain a thermal expansion coefficient smaller than about 40 to 90% by volume of the MC phase, and more preferably 45 to 85% by volume of the MC phase.

[0032] The MC phase may have at least one of W and Mo dissolved in it at 0.1 to 45 atomic % relative to the total amount of metal elements in the MC phase. WC and Mo2C have a hexagonal crystal structure when used alone, but when dissolved in the MC phase, the grain growth of the MC phase can be suppressed while maintaining the NaCl-type crystal structure, and the oxidation resistance can be further improved. In this case, the rigidity, hardness, thermal expansion coefficient, etc. of the alloy can be changed by changing the content of W or Mo, so that a composition that allows the alloy to obtain desired characteristics depending on the application can be selected, and the ease of mirror finishing and wear resistance can be adjusted by changing the hardness of the alloy. A small amount of W or Mo may be dissolved in it within the range of 0.1 to 43 atomic % so as to improve the oxidation resistance while maintaining the NaCl-type crystal structure. In order to obtain appropriate rigidity, hardness, and thermal expansion coefficient, it is more preferable that at least one of W and Mo is dissolved in it at 5 to 43 atomic %, and even more preferable that it is dissolved in it at 10 to 40 atomic % relative to the total amount of metal elements in the MC phase.

[0033] Here, the MC phase has a NaCl type crystal structure means that 80% or more by volume of the MC phase has a NaCl type crystal structure. In other words, in addition to the NaCl type crystal structure, the MC phase may contain a small amount of crystals, oxides, borides, etc. having a hexagonal structure, and when the MC phase contains multiple metal elements, it may contain an MC phase having a core-rim structure in addition to a solid solution having a NaCl type crystal structure. The MC phase may also be composed of multiple types of phases with different compositions.

[0034] Cr3C2 phase is 10.3 MK -1 Since it has a high thermal expansion coefficient and a hardness close to 1300 HV, the inclusion of the Cr3C2 phase increases the thermal expansion coefficient of the sintered alloy, making it easier to achieve a mirror finish and improving the mirror finish. In addition, the sintered alloy contains the Cr3C2 phase and does not contain any hard phases other than the MC phase with a NaCl structure that has excellent oxidation resistance, resulting in a synergistic effect that allows the excellent mirror finish to be maintained for a long period of time.

[0035] Cr 23When a phase consisting of chromium compounds other than Cr3C2, such as the C6 phase or Cr7C3 phase, is formed, the thermal expansion coefficient decreases in proportion to the content. In addition, it is more brittle than the Cr3C2 phase, so it is prone to problems as a tool. 23 Small amounts of chromium compounds other than Cr3C2, such as C6 and Cr7C3, may be contained, and here, the term "Cr3C2 phase" means that 80 volume % or more of the chromium compounds are the Cr3C2 phase.

[0036] The atomic ratio of the amount of light elements such as C and N contained in the MC phase to the amount of metal elements contained in the MC phase is preferably 0.8 or more. If the atomic ratio of the amount of light elements is smaller than 0.8, the sintered alloy is not sufficiently densified, and if the ratio is even smaller, compound phases other than the MC phase of the Cr3C2 phase and NaCl type structure are likely to occur, making it impossible to obtain high oxidation resistance. The atomic ratio of metal elements to light elements is calculated by subtracting the amount of carbon in the Cr3C2 phase calculated from the amount of carbon in the Cr3C2 raw material powder used and the addition ratio from the amount of alloy carbon in the sintered body, and calculating the atomic ratio from the remaining components, or by directly analyzing the MC phase with EDS. The atomic ratio of the amount of light elements such as C and N contained in the MC phase to the amount of metal elements contained in the MC phase is preferably 1.0 or less. If the atomic ratio of the amount of light elements is larger than that, free carbon is likely to be generated in the alloy.

[0037] The grain size of the MC phase is preferably 0.1 to 6 μm. The grain size of the MC phase is the diameter of a circle having the same area as the cross-sectional area of ​​the MC phase in any cross section of the sintered alloy. In order to make the grain size of the MC phase less than 0.1 μm, it is necessary to make the raw material powder fine, which leads to an increase in cost and also deteriorates the moldability of the powder. When the grain size of the MC phase is larger than 6 μm, the specularity decreases, and problems may occur when used in a mold. The grain size of the MC phase can be determined by photographing the cross section of the sintered alloy with a scanning electron microscope (SEM) and using image analysis software from the obtained SEM photograph. The grain size of the MC phase is more preferably 0.5 to 3 μm.

[0038] The grain size of the Cr3C2 phase is preferably 9 μm or less. If the grain size of the Cr3C2 phase exceeds 9 μm, the mirror finish may be deteriorated. The grain size of the Cr3C2 phase can be determined in the same manner as the grain size of the MC phase. The grain size of the Cr3C2 phase is more preferably 0.5 to 7 μm.

[0039] The sintered alloy according to the first embodiment of the present invention may further contain a metal phase consisting of at least one of Ni, Co, and Fe. By containing the metal phase, it is possible to obtain the desired thermal expansion coefficient and toughness. The content of the metal phase is preferably 8.2% by volume or less. By containing Ni as the metal phase, it is possible to improve the sinterability and toughness. Co and Fe increase the strength of the sintered alloy at room temperature and high temperatures. In addition, Fe is relatively inexpensive. The content of each element can be selected to obtain the required characteristics depending on the use of the tool. If the content of the metal phase exceeds 8.2% by volume, the surface roughness Ra after finishing becomes rough, and the tool deformation resistance during use at high temperatures decreases. The content of the metal phase is more preferably 8% by volume or less.

[0040] [2] Second embodiment The sintered alloy according to the second embodiment of the present invention is characterized in that it forms a solid solution phase consisting of at least one metal element selected from the group consisting of Ti, Ta, Nb, and V, and at least one of C and N, and is composed of a compound phase (hereinafter also referred to as "MC phase") having an NaCl type structure of 80 volume % or more, a binder phase consisting of at least one of Ni, Co, and Fe, and a WC phase, containing 8 to 95 volume % of the MC phase and 2.0 volume % or less of the binder phase.

[0041] The sintered alloy (MC-WC alloy) according to the second embodiment has a thermal expansion coefficient of 5 to 7 MK -1 It is easy to obtain a sintered alloy of this order. The MC phase may be the same as in the first embodiment. If the MC phase is less than 8% by volume, the required thermal expansion coefficient is not obtained, and the oxidation resistance is also reduced. If the MC phase is more than 95% by volume, the structure is prone to grain growth, making it difficult to obtain a mirror finish, and the strength is also reduced. The content of the MC phase is preferably 10 to 92% by volume, and more preferably 12 to 90% by volume.

[0042] The sintered alloy according to the second embodiment contains 2.0% by volume or less of a metal phase consisting of at least one of Ni, Co, and Fe, so that the sinterability is improved and the sintering temperature can be lowered. In addition, since a small amount of metal component is present between each particle, the growth due to the coalescence of particles can be suppressed, so that a fine grain structure is easily obtained and the specularity and strength are improved. Furthermore, the desired toughness can be obtained, and defects due to chipping during use of the tool are unlikely to occur. In addition, as in the first embodiment, the content of each element can be selected to obtain the characteristics required depending on the use of the tool. If the content of the metal phase exceeds 2.0% by volume, the tool deformation resistance during use at high temperatures decreases. The content of the metal phase is preferably 1.5% by volume or less, more preferably 1% by volume or less.

[0043] The grain size of the WC phase is preferably 0.1 to 2.5 μm. The grain size of the WC phase can be determined in the same manner as the grain size of the MC phase. By adjusting the WC grain size to the range of 0.1 to 2.5 μm, an MC-WC alloy having a fine grain structure can be obtained, and therefore high mirror finish can be obtained. On the other hand, since the WC phase is included, the oxidation resistance is somewhat inferior to that of the first embodiment. The grain size of the WC phase is more preferably 0.11 to 2.0 μm, more preferably 0.12 to 1.5 μm, even more preferably 0.13 to 1.0 μm, and particularly preferably 0.14 to 0.7 μm.

[0044] In the MC phase of the sintered alloy according to the second embodiment, as in the first embodiment, at least one of W and Mo may be dissolved in an amount of 0.1 to 45 atomic % based on the total amount of metal elements in the MC phase. A small amount of W or Mo, about 0.1 to 43 atomic %, may be dissolved in the MC phase in order to improve oxidation resistance while maintaining a NaCl type crystal structure. In order to obtain appropriate rigidity, hardness and thermal expansion coefficient, at least one of W and Mo may be dissolved in an amount of 5 to 43 atomic %, more preferably 10 to 40 atomic %, based on the total amount of metal elements in the MC phase. As light elements, oxygen and boron may be included. As metal elements, Zr, Hf and Cr may be included.

[0045] [3] Third embodiment The sintered alloy according to the third embodiment of the present invention is characterized in that it is composed of a WC phase and a Cr3C2 phase, and contains 10 to 90 volume % of the Cr3C2 phase.

[0046] The sintered alloy (Cr3C2-WC alloy) according to the third embodiment can obtain a wide range of thermal expansion coefficients by changing the ratio of each phase. By setting the content of the Cr3C2 phase at 10 to 90 volume %, the thermal expansion coefficient can be increased to 5 to 9MK. -1 It has a wide range of thermal expansion coefficients. It also tends to have a high thermal conductivity compared to other alloys with similar thermal expansion coefficients. The Cr3C2 phase may be the same as in the first embodiment. When the content of the Cr3C2 phase exceeds 90 volume %, the grains of the Cr3C2 phase tend to grow, making it difficult to obtain a mirror finish. When the content of the Cr3C2 phase is less than 10 volume %, the oxidation resistance tends to be poor. The content of the Cr3C2 phase is preferably 15 to 85 volume %, more preferably 20 to 80 volume %. When the WC phase ratio is high, the oxidation resistance is somewhat poor, but the toughness and strength are excellent.

[0047] The grain size of the alloy structure can be easily adjusted by the mixed grinding conditions and the selection of the raw material of the WC phase, and for example, an ultrafine grain alloy can be obtained, so that a Cr3C2-WC alloy with good mirror finish can be easily obtained. The grain size of the WC phase may be the same as that of the second embodiment. As a result, a fine grain Cr3C2-WC alloy can be obtained, so that a high mirror finish can be obtained.

[0048] In the sintered alloy according to the third embodiment, when the sinterability of the alloy is insufficient, the sintered alloy may contain 2.0% by volume or less of a metal phase consisting of at least one of Ni, Co, and Fe. This makes it possible to obtain the desired toughness, and defects due to chipping during use of the tool are unlikely to occur. In addition, since the sinterability is also improved, the sintering temperature can be lowered, and since grain growth is also suppressed, the specularity and strength also tend to be improved. As in the first embodiment, the content of each element can be selected to obtain the characteristics required depending on the use of the tool. If the content of the metal phase exceeds 2.0% by volume, the tool deformation resistance during use at high temperatures decreases. The content of the metal phase is preferably 1.5% by volume or less, more preferably 1% by volume or less.

[0049] [4] Fourth embodiment The sintered alloy according to the fourth embodiment of the present invention is characterized in that it forms a solid solution phase consisting of at least one metal element selected from the group consisting of Ti, Ta, Nb, and V, and at least one of C and N, and that 80% or more by volume of the solid solution phase is composed of a compound phase having a NaCl type structure (hereinafter also referred to as the "MC phase"), a WC phase, and a Cr3C2 phase.

[0050] In the MC-Cr3C2 alloy and MC-WC alloy of the present invention, 7MK -1 When trying to obtain an intermediate thermal expansion coefficient of about 100%, it is possible to increase the ratio of the MC phase, but the increase in the ratio of the MC phase tends to cause coarsening of the MC phase, which tends to cause problems such as a decrease in specularity and strength. For this reason, by making an MC-Cr3C2-WC alloy in which the three phases of the MC phase, Cr3C2 phase, and WC phase coexist, it is possible to prevent the structure from coarsening. The MC phase, Cr3C2 phase, and WC phase may be the same as those in the first to third embodiments.

[0051] The sintered alloy (MC-Cr3C2-WC alloy) according to the fourth embodiment preferably contains 10 to 90% by volume of the MC phase. If the MC phase is less than 10% by volume, the oxidation resistance decreases. If the MC phase is more than 90% by volume, the structure is prone to grain growth, making it difficult to obtain a mirror finish and reducing strength. The content of the MC phase is preferably 20 to 90% by volume, and more preferably 40 to 85% by volume. If the WC phase ratio is increased, the oxidation resistance tends to decrease, but it is easy to obtain a small thermal expansion coefficient, a large thermal conductivity, and high toughness. If the MC phase ratio is increased, the oxidation resistance is increased and it is easy to obtain a medium thermal expansion coefficient, improving sinterability.

[0052] The volume ratio of the Cr3C2 phase content to the WC phase content is preferably 0.125 to 8. If the volume ratio of the Cr3C2 phase content to the WC phase content is less than 0.125, the oxidation resistance tends to be low, and if it exceeds 8, the specularity tends to be low. The volume ratio of the Cr3C2 phase content to the WC phase content is preferably 0.15 to 6.6, and more preferably 0.2 to 5.

[0053] Increasing the Cr3C2 phase ratio improves oxidation resistance and makes it easier to obtain a large thermal expansion coefficient. When the MC phase amount is 10 volume percent, and the volume ratio of the Cr3C2 phase to the WC phase is 0.125 to 8, the MK -1 When the MC phase content is 90 volume %, the thermal expansion coefficient is 6.5 to 7.5 MK. -1 A thermal expansion coefficient of about

[0054] The sintered alloy according to the fourth embodiment can obtain the required thermal expansion coefficient and required characteristics by changing the ratios as necessary. Note that the thermal expansion coefficient of the Cr3C2-WC alloy is 7MK. -1 However, when oxidation resistance is particularly important, it is better to choose the MC-Cr3C2-WC alloy, and when high thermal conductivity is desired, it is better to choose the Cr3C2-WC alloy.

[0055] The sintered alloy according to the fourth embodiment may contain 2.0 vol% or less of a metal phase consisting of at least one of Ni, Co and Fe when alloy strength is required or when the sinterability of the alloy is insufficient. If the content is more than 2.0 vol%, the wear resistance may be poor. The content of the metal phase is preferably 1.5 vol% or less, more preferably 1 vol% or less.

[0056] In the MC phase of the sintered alloy according to the fourth embodiment, as in the first embodiment, at least one of W and Mo may be dissolved in an amount of 0.1 to 45 atomic % based on the total amount of metal elements in the MC phase. A small amount of W or Mo, about 0.1 to 43 atomic %, may be dissolved in the MC phase to improve oxidation resistance while maintaining a NaCl type crystal structure. In order to obtain appropriate rigidity, hardness and thermal expansion coefficient, at least one of W and Mo is more preferably dissolved in an amount of 5 to 43 atomic %, and even more preferably dissolved in an amount of 10 to 40 atomic %, based on the total amount of metal elements in the MC phase.

[0057] A lens molding die using the sintered alloy of the present invention may be coated with a hard film such as DLC, or a metal film such as platinum. Not only the lens molding die, but also members and tools using the sintered alloy of the present invention may be coated with various coatings in order to maximize the features of the present invention.

[0058] [5] Manufacturing method of sintered alloy The sintered alloy of the present invention can be obtained by normal sintering, hot press sintering, etc. That is, a predetermined amount of powder is weighed, wet mixed, crushed, dried, and then pressure molded in a die to obtain a powder compact. This powder compact may be cut or ground to obtain a required shape, or the powder compact may be pre-sintered and then machined to obtain a desired shape. Also, the powder may be filled into a mold of a predetermined shape and hot press sintered to obtain a desired shape. In the case of normal sintering, this powder compact is sintered in a vacuum or in an inert gas atmosphere such as nitrogen or argon at a sintering temperature of 1300 to 1540°C.

[0059] After sintering, HIP treatment may be further performed. This can reduce pores that occur during sintering. The temperature of the HIP treatment can be set appropriately depending on the composition of the sintered alloy, but it may be a temperature below the sintering temperature. If the temperature is higher than the sintering temperature, Cr carbide and other particles will grow into grains, causing a decrease in strength. The grain size of the structure can also be adjusted by HIP treatment.

[0060] Regardless of the amount of metallic phase, either normal sintering or hot press sintering may be used. When hot press sintering is used, the sintering temperature can be lowered to make it easier to obtain a fine grain structure. When the amount of metallic phase is small and it is difficult to obtain a dense alloy by normal sintering, sintering by hot press may be used. In this case, the content of metallic phase is preferably 0 to 2.0% by volume, and more preferably 0 to 1% by volume. By hot press sintering a sintered alloy that does not contain metallic phase or contains a small amount of metallic phase, it becomes a dense alloy and the mirror surface can be further improved, so that a sintered alloy suitable for a mold can be obtained.

[0061] The hot press is not particularly limited as long as it is capable of forming a sintered alloy in general, but the sintering conditions are preferably in a vacuum or in an inert gas atmosphere such as nitrogen or argon, at a pressure of 20 to 100 MPa, and at a sintering temperature of 1200 to 1500° C. Also, an apparatus other than the hot press, such as an electric current sintering apparatus, may be used.

[0062] [6] Molds and other uses The sintered alloy of the present invention can be suitably used as a material for dies, particularly dies for molding lenses, and in order to mold parts without problems, it is necessary to select a sintered alloy having a thermal expansion coefficient of 5 to 9 MK taking into consideration the thermal expansion coefficient of the lens material and the shape of the molded parts. -1 It is possible to select a die material having an optimal thermal expansion coefficient within a certain range. In addition, the present invention is not limited to this, and can be suitably used in cases where a die for molding a part requires a thermal expansion coefficient larger than that of a normal cemented carbide or a binderless cemented carbide and excellent oxidation resistance, and can be suitably used for members, tools, etc. that require a high thermal expansion coefficient, high wear resistance, and excellent oxidation resistance. EXAMPLES

[0063] The present invention will be described in more detail with reference to the inventive products, but the present invention is not limited thereto.

[0064] Example 1 The raw material powders include Cr3C2 (2.4μm), Ni (2.3μm), Co (1.4μm), Fe (2.9μm), TaC (1.6μm), NbC (1.6μm), TiC (1.6μm), Ti(C 0.5 ,N 0.5 )(2.1μm), TaN(2.0μm), Nb(C 0.7 N 0.3 The solid solution powders used were carbide (2.5 μm), WC (0.8 μm), Mo2C (3.1 μm), and various solid solution powders shown in Table 1. The solid solution powders were prepared by wet mixing carbides, nitrides, and carbonitrides to obtain the compositions shown in Table 1, subjecting the resulting powders to a solid solution treatment in a high-temperature furnace, and then pulverizing and sieving the powders to obtain raw powders (1.3 to 3.1 μm).

[0065] [Table 1]

[0066] For samples containing a small amount of metallic phase components, powders pre-ground by wet grinding metallic powders and other powders were used, while for samples containing 4% or more by volume of metallic phase components, they were used as is without pre-grinding. Depending on the sample, C powder was added to reduce oxides contained in the powder and adjust the amount of carbon.

[0067] Sintering was performed by normal sintering or hot press sintering under an inert gas atmosphere of nitrogen or argon, and the obtained sintered body was subjected to HIP treatment to produce sintered alloys of invention products 1 to 20 and comparison products 1 to 5. In normal sintering, the sintering temperature was 1400°C to 1540°C, the pressure was 40 kPa to 90 kPa, and the sintering atmosphere was N2 or Ar. In hot press sintering (invention products 6, 7, 8, 11, 12, 15, 17, 19, and 20), the sintering temperature was 1200°C to 1650°C, and the sintering atmosphere was Ar. For the sintered alloys of invention products 1 to 20 and comparison products 1 to 5 that contain an MC phase, the compound ratio constituting the MC phase was obtained. The obtained results are shown in Table 2. The compound ratio constituting the MC phase shown in Table 2 was calculated by converting it to each compound, taking into account the compound ratio at the time of blending and the carbon amount and nitrogen amount of the sintered alloy.

[0068] [Table 2]

[0069] The obtained samples were examined for transverse strength, hardness, thermal expansion coefficient, high-temperature oxidation resistance, thermal conductivity, and surface roughness by the following methods. The results are shown in Table 3 together with the overall evaluation.

[0070] (transverse rupture strength) The flexural strength (MPa) of the sintered alloys of the invention products 1 to 20 and the comparison products 1 to 5 was determined by flexural strength measurement (three-point bending test) according to the method of JIS B4104.

[0071] (Rockwell hardness HRA) The Vickers hardness (HRA) of the sintered alloys of the invention products 1 to 20 and the comparison products 1 to 5 was measured by the Rockwell A hardness testing method for CIS027B sintered alloy.

[0072] (Thermal expansion coefficient RT-700℃) The sintered alloys of the invention products 1 to 20 and the comparison products 1 to 5 were heated from room temperature to 700°C using a vertical thermal expansion meter, and the thermal expansion coefficients RT-700°C (MK -1 ) measurements were carried out.

[0073] (Oxidation resistance 700℃) The sintered alloys of the invention products 1 to 20 and the comparison products 1 to 5 were heated in air at 700°C for 30 minutes, and the oxidation weight gain (oxidation weight per unit area) (g / m 2 ) was sought.

[0074] (Thermal Conductivity) The thermal conductivity of the sintered alloys of the invention products 1 to 20 and the comparison products 1 to 5 was determined by a laser flash method thermal constant measuring device.

[0075] (surface roughness after finishing Ra) The sintered alloys of the invention products 1 to 20 and the comparison products 1 to 5 were mirror-finished using diamond slurry, and the surface roughness Ra (nm) was measured.

[0076] (evaluation) Molds were made using the sintered alloys of invention products 1-20 and comparison products 1-5, glass lenses were repeatedly molded, and the molds were evaluated based on the number of times they were used and the specularity of the molded surface after repeated use. If they could be used a predetermined number of times or more and still maintained good specularity, they were marked with an ⊚, if they could be used a predetermined number of times or more, they were marked with an ◯, if they could be used up to the predetermined number of times, they were marked with a △, and if they could not be used up to the predetermined number of times, they were marked with an ×.

[0077] [Table 3]

[0078] As can be seen from Table 3, inventions 1 to 20 have a range of 4.9 to 9.2 MK -1In addition to having various required thermal expansion coefficients in the range, they were excellent in necessary properties such as specularity, thermal conductivity, strength, and oxidation resistance. That is, the MC-Cr3C2 alloy has excellent oxidation resistance, the MC-WC alloy has excellent strength and specularity, and the Cr3C2-WC alloy has excellent specularity and high thermal conductivity, and it was found that the MC-Cr3C2-WC alloy can suppress the grain growth of the phase, thereby improving specularity and strength. In addition, in order to improve oxidation resistance, Mo and / or W may be dissolved in a solid solution of 0.1 to 45 atomic % relative to the total amount of metal elements in the MC phase. The thermal expansion coefficient of the MC phase can be changed by changing the amount of W.

[0079] In the case of Comparative Example 1, the MC-Cr3C2 alloy contained a large amount of MC phase at 97 volume percent, which caused the MC phase to grow into grains, resulting in poor surface roughness in particular. In the case of Comparative Example 2, the MC-WC alloy contained a small amount of MC phase at 3.0 volume percent, resulting in a thermal expansion coefficient of 4.7 MK -1 The thermal expansion coefficient was low, and the required thermal expansion coefficient was not obtained, and the oxidation resistance was also poor. Comparative sample 3 contained only the MC phase, so the MC phase grains grew, resulting in poor surface roughness. Comparative sample 4 had a high Cr3C2 phase content of 96 volume percent in the Cr3C2-WC alloy, resulting in a thermal expansion coefficient of 10.1 MK -1 The required thermal expansion coefficient was not obtained, and the Cr3C2 phase grew into grains, resulting in poor surface roughness. Comparative sample 5 had poor oxidation resistance because the Cr3C2 phase content in the Cr3C2-WC alloy was only 5.7 volume %.

Claims

1. A solid solution phase is formed consisting of at least one metallic element from Ti, Ta, Nb, and V, and at least one element from C and N, and a compound phase having an NaCl-type structure in which 80% or more by volume is present, and Cr 3 C 2 It consists of, A sintered alloy characterized by containing 38 to 95 volume percent of the aforementioned compound phase.

2. A solid solution phase is formed consisting of at least one metallic element from Ti, Ta, Nb, and V, at least one element from W and Mo, and at least one element from C and N, and a compound phase having an NaCl-type structure comprising 80% or more by volume, and Cr 3 C 2 It consists of, The compound phase contains 38 to 95% by volume, A sintered alloy characterized in that the compound phase contains a solid solution of at least one of W and Mo in an amount of 0.1 to 45 atomic percent relative to the total amount of metal elements in the compound phase.

3. A solid solution phase is formed consisting of at least one metallic element from Ti, Ta, Nb, and V, and at least one element from C and N, and a compound phase having an NaCl-type structure in 80% by volume or more, and a bonded phase consisting of at least one element from Ni, Co, and Fe, and Cr 3 C 2 It consists of, A sintered alloy characterized by containing 38 to 95 volume percent of the compound phase and 8.2 volume percent or less of the binder phase.

4. A compound phase having an NaCl-type structure, comprising a solid solution phase consisting of at least one metallic element from Ti, Ta, Nb, and V, at least one element from W and Mo, and at least one element from C and N, with 80% or more by volume being a compound phase; a bonded phase consisting of at least one element from Ni, Co, and Fe; and Cr 3 C 2 It consists of, The compound phase is contained in 38 to 95% by volume, and the binding phase is contained in 8.2% by volume or less. A sintered alloy characterized in that the compound phase contains a solid solution of at least one of W and Mo in an amount of 0.1 to 45 atomic percent relative to the total amount of metal elements in the compound phase.

5. It consists of a compound phase having an NaCl-type structure, comprising a solid solution phase consisting of at least one metallic element from Ti, Ta, Nb, and V, and at least one element from C and N, with at least 80% by volume being a bonded phase consisting of at least one element from Ni, Co, and Fe, and a WC phase. A sintered alloy characterized by containing 8 to 95 volume percent of the compound phase and 2.0 volume percent or less of the binder phase.

6. It consists of a compound phase having an NaCl-type structure, comprising a solid solution phase consisting of at least one metallic element from Ti, Ta, Nb, and V, at least one element from W and Mo, and at least one element from C and N, with at least 80% by volume being a compound phase; a bonded phase consisting of at least one element from Ni, Co, and Fe; and a WC phase. The compound phase is contained in 8 to 95% by volume, and the binding phase is contained in 2.0% by volume or less. A sintered alloy characterized in that the compound phase contains a solid solution of at least one of W and Mo in an amount of 0.1 to 45 atomic percent relative to the total amount of metal elements in the compound phase.

7. WC phase and Cr 3 C 2 phase, and The aforementioned Cr 3 C 2 A sintered alloy characterized by containing 10 to 90 volume percent of a phase.

8. A WC phase, a bonded phase consisting of at least one of Ni, Co, and Fe, and Cr 3 C 2 It consists of, The aforementioned Cr 3 C 2 A sintered alloy characterized by containing 10 to 90 volume percent of a phase and 2.0 volume percent or less of the binder phase.

9. A solid solution phase is formed consisting of at least one metallic element from Ti, Ta, Nb, and V, and at least one element from C and N, and a compound phase having an NaCl-type structure in 80% by volume or more, and a WC phase, Cr 3 C 2 A sintered alloy characterized by being composed of a phase.

10. A solid solution phase is formed consisting of at least one metallic element from Ti, Ta, Nb, and V, at least one element from W and Mo, and at least one element from C and N, and a compound phase having an NaCl-type structure in which 80% or more by volume is present, and a WC phase, Cr 3 C 2 It consists of, A sintered alloy characterized in that the compound phase contains a solid solution of at least one of W and Mo in an amount of 0.1 to 45 atomic percent relative to the total amount of metal elements in the compound phase.

11. A solid solution phase is formed consisting of at least one metallic element from Ti, Ta, Nb, and V, and at least one element from C and N, and a compound phase having an NaCl-type structure in 80% by volume or more; a bonded phase consisting of at least one element from Ni, Co, and Fe; a WC phase; and Cr 3 C 2 It consists of, A sintered alloy characterized by containing 2.0 volume percent or less of the aforementioned binder phase.

12. A solid solution phase is formed by at least one metallic element from Ti, Ta, Nb, and V, at least one element from W and Mo, and at least one element from C and N, and a compound phase having an NaCl-type structure in 80% by volume or more; a bonded phase consisting of at least one element from Ni, Co, and Fe; a WC phase; and Cr 3 C 2 It consists of, The aforementioned binding phase is contained in 2.0% by volume or less. A sintered alloy characterized in that the compound phase contains a solid solution of at least one of W and Mo in an amount of 0.1 to 45 atomic percent relative to the total amount of metal elements in the compound phase.

13. The sintered alloy according to any one of 9 to 12, characterized in that it contains 10 to 90 volume percent of the compound phase.

14. The Cr content relative to the WC phase 3 C 2 A sintered alloy according to any one of 9 to 12, characterized in that the volume ratio of the phase content is 0.125 to 8.

15. The sintered alloy according to any one of 7 to 12, characterized in that the particle size of the WC phase is 0.1 to 2.5 μm.

16. A sintered alloy according to any one of claims 1 to 12, characterized by being sintered by hot pressing.

17. A mold made of a sintered alloy according to any one of claims 1 to 12.