JP2015045080A - Binderless superfine particle hard alloy and tool using the same - Google Patents
Binderless superfine particle hard alloy and tool using the same Download PDFInfo
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本発明は、特に非球面ガラスレンズ成形用金型などで優れた鏡面性を得易く、また、高硬度を要求される耐摩耗工具などで長寿命の、バインダーレス超微粒超硬合金に関する。 The present invention relates to a binderless ultrafine cemented carbide which is easy to obtain excellent specularity particularly in an aspherical glass lens molding die and has a long life with a wear-resistant tool or the like which requires high hardness.
耐摩耗工具のうち、高鏡面性または高硬度が要求される用途では、結合相を含まないか極少量含む、WC基超硬合金が用いられている。 Among wear-resistant tools, WC-based cemented carbides that do not contain a binder phase or contain a very small amount are used in applications that require high specularity or high hardness.
耐摩耗工具用超硬合金のうち、非球面ガラスレンズの成形で用いられる金型では、600℃〜1000℃の高温下でガラスレンズ素球をプレスして成形するため、金型には、耐酸化性、高硬度、高鏡面性が必要となっている。特に高鏡面性は、表面粗さを数nmRaとする必要がある。 Among the cemented carbides for wear-resistant tools, a mold used for molding an aspheric glass lens is formed by pressing a glass lens element ball at a high temperature of 600 ° C to 1000 ° C. High chemical properties, high hardness, and high specularity are required. Particularly for high specularity, the surface roughness needs to be several nmRa.
これを満たすには、結合相を含まないか、極少量とする。主に用いられているのは特許文献1に見られるWC相とTiC−WC固溶体複炭化物相の2相から成る超硬合金である。ただし、TiC−WC固溶体複炭化物相は被研削性がWC相と比べると高硬度でやや脆性があるため、加工し難い場合がある。 In order to satisfy this, the binder phase is not included or is made extremely small. Mainly used is a cemented carbide composed of two phases of WC phase and TiC-WC solid solution double carbide phase found in Patent Document 1. However, the TiC-WC solid solution double carbide phase has a high hardness and is slightly brittle compared to the WC phase, so that it may be difficult to process.
そこで、TiC−WC固溶体複炭化物相を用いない超硬合金が望まれ、特許文献2に見られる粒度0.3μm以下のWCとNiを主成分とするWC基超微粒超硬合金が提供された。 Accordingly, a cemented carbide that does not use a TiC-WC solid solution double carbide phase is desired, and a WC-based ultrafine cemented carbide comprising WC and Ni having a particle size of 0.3 μm or less as found in Patent Document 2 as main components is provided. .
このWC基超微粒超硬合金は、それまでのWC基超微粒超硬合金よりも作りやすく、かつ高鏡面性が得られるため、広く市場に受け入れられた。ところが、従来のWCとTiC−WC固溶体複炭化物相を用いた超硬合金と比べると、熱膨張係数が大きく異なる。ガラスレンズ成形用金型はnmレベルの寸法を制御するため、WC基超微粒超硬合金に変更する場合は、金型設計をやりなおす必要があるが、これは好まれていない。WC基超微粒超硬合金には、このような欠点があった。 This WC-based ultrafine cemented carbide is widely accepted in the market because it is easier to make than WC-based ultrafine cemented carbide and has high specularity. However, the coefficient of thermal expansion is greatly different from that of cemented carbide using conventional WC and TiC-WC solid solution double carbide phases. In order to control the size of the glass lens molding die on the nm level, when changing to a WC-based ultrafine cemented carbide, it is necessary to redesign the die, but this is not preferred. The WC base ultrafine cemented carbide has such drawbacks.
0.3μm以下のWCとNiを主成分とするWC基超微粒超硬合金には、VCとCr3C2が添加されているが、これは焼結時におけるWCの粒成長をV、Crで抑制する目的がある。 VC and Cr 3 C 2 are added to a WC-based ultrafine cemented carbide mainly composed of WC and Ni of 0.3 μm or less. This is because the grain growth of WC during sintering is caused by V, Cr. There is a purpose to suppress.
しかし、VC、Cr3C2の添加量がNiに対して多すぎると、V、Crを含む第3相の晶出寸法が大となって、破壊の起源になりやすくなり合金の破壊強度が劣化するなどの問題を生じるので上限がある。 However, if the amount of VC and Cr 3 C 2 added is too large relative to Ni, the crystallization size of the third phase containing V and Cr becomes large, which tends to cause fracture, and the fracture strength of the alloy is increased. There is an upper limit because it causes problems such as deterioration.
以上の理由で、本発明でもVについては、特許文献2と同じくV添加量は、Niに対して30mass%以上100mass%以下とした。30mass%より少ないと粒成長抑制効果が得られず、高強度の合金を作れなくなる。100mass%より多くなるとVC相を晶出しすぎて寸法が大となり、高強度の合金を作れなくなる。 For the reasons described above, in the present invention, V is added in an amount of 30 mass% or more and 100 mass% or less with respect to Ni as in Patent Document 2. If the amount is less than 30 mass%, the effect of suppressing grain growth cannot be obtained, and a high-strength alloy cannot be produced. If it exceeds 100 mass%, the VC phase will be crystallized too much, resulting in a large size, making it impossible to produce a high-strength alloy.
また、特許文献2ではCrの添加量をNiに対して11mass%以上300mass%以下と制限している。11mass%より少ないと粒成長抑制効果が得られなくなる。300mass%より多く添加すると、Cr3C2相の晶出を招き、このCr3C2相は巨大な炭化物を形成するので合金強度を低下させる。なお、Crの添加は通常、Cr3C2で添加されるので以下同様のこととして記載する。 Moreover, in patent document 2, the addition amount of Cr is restrict | limited to 11 mass% or more and 300 mass% or less with respect to Ni. If it is less than 11 mass%, the effect of suppressing grain growth cannot be obtained. When more is added than 300Mass%, leading to crystallization of Cr 3 C 2 phase The Cr 3 C 2 phase decreases the alloy strength because it forms a huge carbide. The addition of Cr is usually described as it follows the same because they are added by Cr 3 C 2.
しかし、Cr3C2の熱膨張係数がWCより大きいことに着目すると、Cr3C2を多量に添加することができれば、WC基超微粒超硬合金の熱膨張係数をWC相とTiC−WC固溶体複炭化物相から成る超硬合金のそれに近づけることが可能と思われる。 However, paying attention to the fact that the thermal expansion coefficient of Cr 3 C 2 is larger than WC, if a large amount of Cr 3 C 2 can be added, the thermal expansion coefficient of the WC-based ultrafine cemented carbide will be expressed as WC phase and TiC-WC. It seems possible to approximate that of cemented carbide consisting of solid solution double carbide phase.
そこで、本発明者らはCr3C2を多量に添加してもCr3C2相の晶出をしない方法について研究した。まず、図1はCr3C2−Ni系の状態図である(非特許文献1)。ここで、τ相はCr3C2相であり、θ相はCr7C3相である。 Therefore, the present inventors have studied a method in which the Cr 3 C 2 phase does not crystallize even when a large amount of Cr 3 C 2 is added. First, FIG. 1 is a Cr 3 C 2 —Ni phase diagram (Non-patent Document 1). Here, the τ phase is a Cr 3 C 2 phase, and the θ phase is a Cr 7 C 3 phase.
図1より、Cr3C2添加量を多くしても、L相(液相)しかない領域であれば、Cr3C2相を生じない可能性がある。例えばNiを20mol%まですなわちCr3C2を80mol%としても、1600℃程度の温度であれば、Cr3C2相を生じないことが分かる。すなわち、図1のL相の高温側であれば、Cr3C2相を生じない広い組成域があると推定される。これが第1の知見である。 From FIG. 1, even if the Cr 3 C 2 addition amount is increased, there is a possibility that the Cr 3 C 2 phase is not generated in the region having only the L phase (liquid phase). For example, it can be seen that even when Ni is up to 20 mol%, that is, Cr 3 C 2 is 80 mol%, a Cr 3 C 2 phase is not generated at a temperature of about 1600 ° C. That is, if the high-temperature side of the L-phase in Figure 1, it is estimated that there is a wide composition range which does not cause Cr 3 C 2 phase. This is the first finding.
次に、本発明者らは主成分をWC、Niとし、Cr3C2を種々の量添加した試料を作り、1600℃での相域をX線回折および組織観察により調べ図2を得た。この領域ではM3C2相すなわちCr3C2相を生じず、そして、M2C相を生じる領域のあることが注目される。なお、Mは、この場合W,Cr,Niである。さらに、Ni相のない領域もあることが分かった。 Next, the present inventors made samples with WC and Ni as main components and added various amounts of Cr 3 C 2 , and examined the phase region at 1600 ° C. by X-ray diffraction and structural observation to obtain FIG. . It is noted that in this region there is a region that does not produce M 3 C 2 phase, ie Cr 3 C 2 phase, and produces M 2 C phase. In this case, M is W, Cr, or Ni. Furthermore, it was found that there is a region where there is no Ni phase.
ここで、Vを添加しその量をNiに対して30mass%以上100mass%以下としても、M2C相を生じる場合は、VはM2Cに含まれ、この場合のMは、W、Cr、Niに加えてVであった。すなわち、VC添加でも図2とほぼ同じ状態図となることを確かめた。 Here, even if V is added and the amount thereof is 30 mass% or more and 100 mass% or less with respect to Ni, when M 2 C phase is generated, V is included in M 2 C. In this case, M is W, Cr V in addition to Ni. In other words, it was confirmed that even when VC was added, the phase diagram was almost the same as in FIG.
なお、M2C相を生じないWC−Ni領域はVC添加の場合、WC―VC−Ni三相となる(但し、V添加量が100mass%以下では日立製作所製走査型電子顕微鏡(以下SEMと記載する)S4800で2万倍程度ではVC相は確認できず、5万倍ぐらいから僅かに確認可能となったことから、VC相はかなり微細である)。 Incidentally, WC-Ni region that does not cause a M 2 C phase in the case of VC added, the WC-VC-Ni Three-phase (where the V added pressure amount is less 100 mass% Hitachi Scanning Electron Microscope (hereinafter SEM The VC phase cannot be confirmed at about 20,000 times in S4800, and can be confirmed slightly from about 50,000 times, so the VC phase is quite fine).
図3は、図2に中に示した試料No.1、試料No.6および試料No.10のX線回折結果である。試料No.6に認められるピークは非特許文献2によれば、W2C相であるが、この相をSEM付属のEDXで元素分析した結果、W、Cr、V、Niが認められたため、M2Cと表現することとする。よって、試料No.6はM2C相を生じていることが明瞭である。Ni相については、添加量が少ないためX線回折ではピークがほとんどない。 3 shows the sample No. shown in FIG. 1, sample no. 6 and sample no. 10 is an X-ray diffraction result of 10; Sample No. According peak observed in 6 Non-Patent Document 2, although a W 2 C phase, because this phase the result of the elemental analysis in the EDX of SEM accessories, W, Cr, V, Ni was observed, M 2 C It will be expressed as Therefore, sample no. It is clear that 6 produced M 2 C phase. As for the Ni phase, since there is little addition amount, there is almost no peak in X-ray diffraction.
そこで図3のNo.1、No.6およびNo.10の3種の試料についてSEM観察を行い、図4を得た。ここでこの写真の視野は6.4×4.8μmである。試料No.6の灰色の部分はWC相であり、黒色の部分はM2C相である。試料No.1および試料No.10には黒色相は見られないが、代わりに、試料No.6では見られない白色相を生じている。なお、WC相が各粒子ごとに濃淡が多少異なるのは、試料表面におけるWC相の結晶面と結晶方向が各粒子ごとに異なるために食刻程度および二次電子強度が各粒子ごとに異なるためである。 Therefore, No. 3 in FIG. 1, no. 6 and no. SEM observation was performed on three types of 10 samples, and FIG. 4 was obtained. Here, the field of view of this photograph is 6.4 × 4.8 μm. Sample No. The gray portion of 6 is the WC phase, and the black portion is the M 2 C phase. Sample No. 1 and sample no. No black phase is seen in sample 10, but instead of sample no. The white phase which is not seen in 6 is produced. Note that the WC phase has a slightly different density for each particle because the crystal plane and crystal direction of the WC phase on the sample surface are different for each particle, so that the degree of etching and the secondary electron intensity are different for each particle. It is.
白色相について、SEM付属のEDXで定性分析した結果、図5が得られ、Ni相であることが確認された。本来Ni相は、WC相より平均原子番号が小さいので、SEM像では、WC相より暗いコントラストを示すはずであるが、この場合、WC相が食刻された結果Ni相が凸になり、そのエッジ効果により白くなりかつ微細であるためNi相全体が図4の倍率では白くなっている。 As a result of qualitative analysis of the white phase using EDX attached to the SEM, FIG. 5 was obtained, and it was confirmed that the white phase was the Ni phase. Originally, the Ni phase has a smaller average atomic number than the WC phase, so the SEM image should show a darker contrast than the WC phase. In this case, the Ni phase becomes convex as a result of the etching of the WC phase. The entire Ni phase is white at the magnification shown in FIG. 4 because it is white and fine due to the edge effect.
なお、図3のX線回折図では、試料No.1とNo.10のいずれでもNi相のピークが認められないが、これは合金Ni量が微少すなわちNi相が微量であることなどに因ると見做せた。 In the X-ray diffraction diagram of FIG. 1 and No. No peak of Ni phase was observed in any of the samples No. 10, but this could be attributed to the fact that the amount of alloy Ni was very small, that is, the Ni phase was very small.
以上により、試料No.6にはNi相のないことが分かった。なお、No.1および10については、X線回折ではM2C相のピークを生じないが、図4のSEM像では若干の黒点として認められ、M2C相が極く僅か存在することが分かる。 As described above, the sample No. 6 was found to have no Ni phase. In addition, No. For 1 and 10, no peak of the M 2 C phase is generated by X-ray diffraction, but it is recognized as some black spots in the SEM image of FIG. 4, and it can be seen that there are very few M 2 C phases.
以上により、1600℃で焼結する場合、Cr3C2を多量添加しても、Cr3C2相を生じず、さらに、Ni相のない合金を作製できることが分かった。後述するが、Cr3C2相を生じないこと、およびM2C相はCr添加量がNiに対して1250mass%以下では比較的微細であるため、これらは破壊の起源にならないことにより、高強度である。これらは第2、第3の知見である。 From the above, it was found that when sintering at 1600 ° C., even if a large amount of Cr 3 C 2 is added, a Cr 3 C 2 phase is not generated, and an alloy without a Ni phase can be produced. By will be described later, since it does not cause Cr 3 C 2 phase, and M 2 C phase is relatively fine in the following 1250Mass% relative Cr added pressure amount Ni, these are not the origin of fracture, High strength. These are the second and third findings.
何故、M2C相を生じるかは、関連状態図が見当たらないため、よく分かっていないが、WCの存在および炭素量が関係していると考えている。Ni相のない合金が得られるのは、M2C相にNiが固溶するためと思われる。 The reason why the M 2 C phase occurs is not well understood because no related phase diagram is found, but it is thought that the presence of WC and the carbon content are related. The reason why an alloy having no Ni phase is obtained is that Ni is dissolved in the M 2 C phase.
ここで、特許文献2で示されるNiの粉砕特性の悪さも、粗いNi粒子またはNi相は焼結中にM2C相に固溶して消失するため、それほど影響しない。従って、Niを強粉砕して用いなくてもよい。これは第4の知見である。 Here, the bad grinding characteristics of Ni shown in Patent Document 2 are not so much affected because coarse Ni particles or Ni phase dissolves in M 2 C phase and disappears during sintering. Therefore, Ni may not be used after being strongly pulverized. This is the fourth finding.
次に、M2C相にNiが固溶した合金組織を詳しく調べた結果、WC粒度が、そうでない合金と比べて小さくなっていることが分かった。平均粒度(BET値より換算)が150nmのWC原料粉末を用いて、1600℃の高温焼結をしても、Fullmanの平均粒度測定方法で、WC粒度が120nm以上270nm以下の合金を作ることが出来た。 Next, as a result of examining the alloy structure in which Ni was dissolved in the M 2 C phase in detail, it was found that the WC grain size was smaller than that of the other alloy. Even if high temperature sintering at 1600 ° C. is performed using WC raw material powder having an average particle size (converted from the BET value) of 150 nm, an alloy having a WC particle size of 120 nm or more and 270 nm or less can be produced by the Fullman average particle size measurement method. done.
これは、(1)WC粒子のオストワルド機構による粒成長(すなわちWC小粒子のNi液相中への溶解→Ni液相中のW、C溶質原子のWC大粒子へ向かっての拡散→W、C溶質原子のWC大粒子上への析出)が、NiがM2C相中に固溶してNi液相が消失するため、起こらなくなるため、ならびに(2)WCも一部がM2C相に固溶し、その分、WC粒子が縮小するため、と思われた。これは第5の知見である。 This is because (1) grain growth by the Ostwald mechanism of WC particles (that is, dissolution of WC small particles into the Ni liquid phase → W in Ni liquid phase, diffusion of C solute atoms toward WC large particles → W, The precipitation of C solute atoms on the WC large particles) does not occur because Ni dissolves in the M 2 C phase and the Ni liquid phase disappears, and (2) WC is partially M 2 C. It seemed that the WC particles were reduced by the amount due to solid solution in the phase. This is the fifth finding.
以上のようにして、炭化タングステン(WC)を主成分とする0.12mass%Ni以上0.3mass%Ni以下の超硬合金において、V添加量を、Niに対して30mass%以上100mass%以下、Cr添加量を、Niに対して300mass%を超え1250mass%以下とすることにより、W、V、Cr、Niを含むM2C相を合金組織中に分散させ、SEM S4800で2万倍までに拡大観察した6.4×4.8μmの視野の写真において、添加したV、Cr、Niの炭化物相または金属相の寸法が10nm以上のものは存在せず、したがってV、Cr、Niは全てM2C相中に存在する、WC−M2C相のバインダーレス超微粒超硬合金の開発に成功した。ここで10nm以上としたのは、これより小さな粒子はこの装置のこの倍率の写真では分解能より小さく、認めることができないためである。 As described above, in the cemented carbide of tungsten carbide (WC) as the main component and 0.12 mass% Ni or more and 0.3 mass% Ni or less, the V addition amount is 30 mass% or more and 100 mass% or less with respect to Ni, the amount of Cr added, by less 1250mass exceed 300mass%% with respect to Ni, W, V, Cr, a M 2 C phase containing Ni is dispersed in the alloy structure, 20,000-fold with S EM S4800 In the photograph of the field of view of 6.4 × 4.8 μm that has been magnified up to , there is no added V, Cr, Ni carbide phase or metal phase with a dimension of 10 nm or more. We succeeded in developing a WC-M 2 C phase binderless ultrafine cemented carbide, all in the M 2 C phase. The reason why the particle size is 10 nm or more is that particles smaller than this are smaller than the resolution in the photograph of this magnification of this apparatus and cannot be recognized.
Ni量を0.12mass%以上0.3mass%以下としたのは、0.12mass%より少ないと焼結性が悪くなりすぎて工業的に生産し難かったためである。また0.3mass%より多いと組織中にNi相を生じて鏡面性およびまたは強度低下を生じるためである。 The reason why the amount of Ni is set to 0.12 mass% or more and 0.3 mass% or less is that when the amount is less than 0.12 mass%, the sinterability becomes too bad to be industrially produced. Further, if it is more than 0.3 mass%, a Ni phase is generated in the tissue, resulting in a decrease in specularity and / or strength.
前述したが、V添加量を、Niに対して30mass%以上100mass%以下としたのは、30mass%未満では粒成長抑制が不十分となって粒成長を生じ強度低下するためである。また100mass%より多くなるとVを主体とした相の晶出量及び寸法が大となりすぎて強度低下するためである。 As described above, the reason why the V addition amount is set to 30 mass% or more and 100 mass% or less with respect to Ni is that if it is less than 30 mass%, grain growth suppression is insufficient and grain growth occurs, resulting in a decrease in strength. Further, if it exceeds 100 mass%, the crystallization amount and dimensions of the phase mainly composed of V become too large and the strength is lowered.
さらに、Cr添加量をNiに対して300mass%を超え1250mass%以下としたのは、300mass%以下ではM2C相が少なくなりすぎてNi相を消滅させられないことおよびまたは熱膨張係数を大きく出来ないためである。また1250mass%より多く添加すると、M2Cの寸法が大となり過ぎて、合金が低強度・低高度となり鏡面性も低下するためである。 Furthermore, the Cr addition amount is more than 300 mass% and less than 1250 mass% with respect to Ni because the M 2 C phase becomes too small at 300 mass% or less and the Ni phase cannot be eliminated and / or the thermal expansion coefficient is increased. This is because it cannot be done. Also, if more is added than 1250Mass%, the dimensions of the M 2 C is too large, and the because the alloy also decreases specularity becomes low strength and low altitude.
最後に、NiをSEM S4800で2万倍までに拡大観察した6.4×4.8μmの視野の写真において、添加したV、Cr、Niの炭化物相または金属相の寸法が10nm以上のものが全てM2C相中に存在するように出来ることから、Niを一部または全てCoに置き換えた、WC−M2C相のバインダーレス超微粒超硬合金も同様の特性が得られると考え、NiをCoに置き換えた試料を作成した結果、やや粒度は大となったが同様の結果が得られた。 Finally, in the photograph of the field of view of 6.4 × 4.8 μm where Ni was observed up to 20,000 times with SEM S4800 , the added V, Cr, Ni carbide phase or metal phase had a dimension of 10 nm or more. considered since all possible to present in the M 2 C phase, all or part of Ni is replaced with Co, binderless ultra fine cemented carbide same properties of WC-M 2 C phase is obtained, As a result of preparing a sample in which Ni was replaced with Co, the particle size was slightly larger, but the same result was obtained.
粒度がNiの場合よりやや大となったのは、Coの場合の方がNiより液相出現温度が70℃程度低いことによると考えられた(非特許文献3)。なお、この場合のM2CのMは通常W、Cr、V、Niであるが、このNiの一部およびまたは全てがCoとなる。 The reason why the particle size was slightly larger than in the case of Ni was thought to be due to the liquid phase appearance temperature being about 70 ° C. lower than that of Ni (Non-patent Document 3). In this case, M in M 2 C is usually W, Cr, V, or Ni, but a part or all of Ni is Co.
以上の様にして得られたWC−M2C相のバインダーレス超微粒超硬合金の熱膨張係数は4.8MK−1以上5.1MK−1以下の範囲となり、WCとTiC−WC固溶体複炭化物相の超硬合金とほぼ同じ熱膨張係数とすることに成功したばかりでなく、より微粒で作ることが出来るため鏡面性の改良も達成した。さらに、高硬度であり耐摩耗性が改善され、かつCrが多いことから耐酸化性の改善も出来た。この詳細は表1に示しており、後記する。 The thermal expansion coefficient of the WC-M 2 C phase binderless ultrafine cemented carbide obtained as described above is in the range of 4.8 MK −1 to 5.1 MK −1 , and WC and TiC-WC solid solution composite Not only has it succeeded in making the thermal expansion coefficient almost the same as that of the carbide phase cemented carbide, but also improved the specularity because it can be made with finer particles. Furthermore, it has high hardness, improved wear resistance, and has a large amount of Cr, so that the oxidation resistance can be improved. The details are shown in Table 1 and will be described later.
WC−M2C超微粒超硬合金は、熱膨張係数を4.8MK−1 から5.1MK−1まで変化することが出来、既存のWCとTiC−WC固溶体複炭化物相で設計されたレンズ成形用金型を設計変更することなく代替できる。さらに、従来の合金より鏡面性、耐酸化性に優れ、従来にない高い精度の非球面ガラスレンズ成形が出来る。さらに、NiがM2C相に固溶していてNi相として存在しないため、高硬度でありながら高強度で、高硬度を要求される耐摩耗工具(流体噴霧用ノズル、超高圧発生用容器、金型、パンチ)で長寿命化を達成できる。 WC-M 2 C ultrafine cemented carbide can change the coefficient of thermal expansion from 4.8 MK −1 to 5.1 MK −1 and is a lens designed with existing WC and TiC-WC solid solution double carbide phase The mold can be replaced without changing the design. Furthermore, it is superior in specularity and oxidation resistance than conventional alloys, and can form aspherical glass lenses with high accuracy that has never been achieved. Furthermore, since Ni is dissolved in the M 2 C phase and does not exist as the Ni phase, the wear resistant tool (fluid spray nozzle, container for generating ultrahigh pressure is required to have high strength but high strength while having high hardness. , Molds, punches) can achieve longer life.
初めに、平均粒度(BET値より換算)が150nmのWC原料粉末を用い、配合組成をWC−0.15mass%VC−0.75mass%Cr3C2−0.2mass%Niとし、ボールミルによる湿式強粉砕を、粉砕メディアの超硬ボールと粉末の比率を5対1として、72hr行った。湿式粉砕後、乾燥し、冷間成形して、真空焼結を1600℃で1hr行い、1500℃、150MPa、1hrのAr雰囲気のHIP処理をして合金とした。 First, a WC raw material powder having an average particle size (converted from the BET value) of 150 nm is used, and the blending composition is WC-0.15 mass% VC-0.75 mass% Cr 3 C 2 -0.2 mass% Ni, and wet by a ball mill. The strong pulverization was performed for 72 hours with the ratio of the cemented carbide balls and the powder of the pulverization medium being 5: 1. After wet pulverization, drying and cold forming were performed, vacuum sintering was performed at 1600 ° C. for 1 hr, and HIP treatment was performed at 1500 ° C., 150 MPa, 1 hr in an Ar atmosphere to obtain an alloy.
こうして得られた合金は、日立製作所製走査型電子顕微鏡S4800で2万倍までに拡大観察した6.4×4.8μmの視野の写真によるとWC−M2C合金であった。これは表1と表2の発明合金試料No.3である。 The alloy thus obtained was a WC-M 2 C alloy according to a 6.4 × 4.8 μm field-of-view photograph that was magnified up to 20,000 times with a scanning electron microscope S4800 manufactured by Hitachi, Ltd. This corresponds to the invention alloy samples No. 1 in Tables 1 and 2. 3.
表1は、実施例1(試料No.3)と同様にして作成した発明合金(試料No.4〜No.8、試料No.13〜No.15)と比較合金(試料No.1〜No.2、試料No.9〜No.12)について、硬さ、抗折力、粒度、熱膨張係数、鏡面性、耐酸化性を調べた結果である。試料の原料配合組成は表2に示した。表1と表2の試料No.1〜9は、V添加があるために組成が僅かに変化するが、図2のNo.1〜9とほぼ対応するとしてよい。 Table 1 shows invention alloys (sample No. 4 to No. 8, sample No. 13 to No. 15) and comparative alloys (sample No. 1 to No. 1) prepared in the same manner as Example 1 (sample No. 3). .2, Sample Nos. 9 to 12) are the results of examining hardness, bending strength, particle size, thermal expansion coefficient, specularity, and oxidation resistance. The raw material composition of the sample is shown in Table 2. Sample No. in Table 1 and Table 2 Nos. 1 to 9 change slightly because of the addition of V. It may correspond approximately to 1-9.
発明合金No.3からNo.8を選択することにより、熱膨張係数を4.8MK−1から5.1MK−1まで変化させることができた。すなわち、従来のWCとTiC−WC固溶体複炭化物相の超硬合金である比較合金試料No.11、No.12の、熱膨張係数と一致できた。 Invention alloy no. 3 to No. By selecting 8, the thermal expansion coefficient could be changed from 4.8 MK −1 to 5.1 MK −1 . That is, comparative alloy sample No. 1 which is a cemented carbide of conventional WC and TiC-WC solid solution double carbide phase. 11, no. The thermal expansion coefficient of 12 could be matched.
比較合金試料No.2、No.9は、Ni相がまだ少ないため、微粒合金となっていて硬さが2500HV296N、2550HV296Nと高いが、鏡面性は0.84nmRa、0.60nmRaと低かった。これは僅かではあるが、Ni相があるためである。 Comparative alloy sample No. 2, no. No. 9 was a fine alloy because the Ni phase was still small, and its hardness was as high as 2500 HV296N and 2550HV296N, but the specularity was as low as 0.84 nmRa and 0.60 nmRa. This is because there is a Ni phase.
これに対して、発明合金は、日立製作所製走査型電子顕微鏡S4800で2万倍までに拡大観察した6.4×4.8μmの視野の写真によるとWC−M2C合金で、NiまたはCo相がないため、硬さが2600HV296N以上であった。それでいて、WC粒度が120nm〜270nmと非常に微細であった。このため、鏡面仕上げ後の表面粗さが0.44nmRa以下と非常に小さくなっていた。 On the other hand, the invention alloy is a WC-M 2 C alloy according to a 6.4 × 4.8 μm field of view observed with a scanning electron microscope S4800 manufactured by Hitachi, Ltd., up to 20,000 times, and is Ni or Co. because there is no phase, hardness was Tsu der more 2600HV296N. Nevertheless, the WC particle size was as very fine as 120 nm to 270 nm. For this reason, the surface roughness after mirror finishing was as very small as 0.44 nmRa or less.
また、破壊の起源が小さくなり、抗折力が2100MPa以上と優れていた。硬さが2600HV296N以上で抗折力が2100MPa以上となるのは発明合金だけである。 In addition, the origin of the destruction decreases, transverse rupture strength was superior to or greater than 2100MPa. Only the invention alloy has a hardness of 2600HV296N or more and a bending strength of 2100 MPa or more.
さらに、大気中800℃で30min加熱しても、酸化増量が150g/cm2以下と従来合金より耐酸化性が優れるが、これは従来合金よりCr3C2の添加量が多いためである。 Furthermore, even when heated in the atmosphere at 800 ° C. for 30 min, the oxidation increase is 150 g / cm 2 or less, which is superior to the conventional alloy in oxidation resistance, because this is because the amount of Cr 3 C 2 added is larger than that in the conventional alloy.
表3は、発明合金No.3の原料WC粉末の平均粒度(BET値換算値)を変化させ、その他は同様にして作成した合金のFullmanの式による平均粒度を測定した結果であるが、原料WC粉末の平均粒度の影響は少ないことが分かる。 Table 3 shows invention alloy Nos. The average particle size (BET value conversion value) of the raw material WC powder No. 3 was changed, and the others were the results of measuring the average particle size according to the Fullman formula of the alloy prepared in the same manner. I understand that there are few.
これは、粉末混合用ボールの硬質WC粉衝撃粉砕に対する軟質Ni粉の緩衝効果が、Ni粉量が少量であることにより、極めて小さいために、WC粉が粉砕平衡に達することにより、混合粉の平均粒度は、原料WC粉平均粒度によらずほぼ同じとなったためと考えている。 This is because the buffering effect of the soft Ni powder against the hard WC powder impact pulverization of the powder mixing ball is extremely small due to the small amount of Ni powder, so that when the WC powder reaches the pulverization equilibrium, It is considered that the average particle size is almost the same regardless of the raw material WC powder average particle size.
発明合金試料No.7は、比較合金試料No.11で設計されたレンズ成形用金型を設計変更することなく代替し、表面粗さを1/10まで小さくすることに成功し、より高精度のレンズ成形を可能とした。耐酸化性も優れることから、高温で使用されても、比較合金試料No.11と比べて約1.5倍の長寿命を達成した。 Invention Alloy Sample No. 7 is a comparative alloy sample No. The lens molding die designed in No. 11 was replaced without changing the design, and the surface roughness was successfully reduced to 1/10, enabling more accurate lens molding. Since the oxidation resistance is also excellent, the comparative alloy sample No. Compared to 11, a long life of about 1.5 times was achieved.
発明合金試料No.4は、高硬度を要求される耐摩耗工具(流体噴霧用ノズル、超高圧発生用容器、金型、パンチ)で高性能を示した。すなわち、比較合金試料No.1と比べて、流体噴霧用ノズルで1.5倍以上、超高圧発生用容器で2倍以上、金型で3倍以上、パンチで1.5倍以上の長寿命化を達成した。 Invention Alloy Sample No. No. 4 shows high performance with a wear-resistant tool (nozzle for fluid spraying, ultra-high pressure generating container, mold, punch) that requires high hardness. That is, comparative alloy sample No. Compared to 1, it has achieved a lifespan of 1.5 times or more with a fluid spray nozzle, 2 times or more with an ultra-high pressure generating container, 3 times or more with a mold, and 1.5 times or more with a punch.
レンズ成形用金型に応用することで、従来より表面粗さが小さく、かつ長寿命のレンズを容易に成形できるようになり、各種のカメラの映像が向上する。さらに、耐摩耗工具(流体噴霧用ノズル、超高圧発生用容器、金型、パンチ)に応用することで、それらに係るコストが大幅に削減される。 By applying it to a lens molding die, it becomes possible to easily mold a lens having a smaller surface roughness and a longer life than before, and the images of various cameras are improved. Furthermore, by applying to wear-resistant tools (fluid spray nozzles, ultra-high pressure generating containers, dies, punches), the costs associated with them are greatly reduced.
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