JP2004083968A - Tungsten based sintered alloy die suitably used for hot press molding for high precision optical glass lens - Google Patents
Tungsten based sintered alloy die suitably used for hot press molding for high precision optical glass lens Download PDFInfo
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- 239000005304 optical glass Substances 0.000 title claims abstract description 17
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 12
- 239000000956 alloy Substances 0.000 title claims abstract description 12
- 229910052721 tungsten Inorganic materials 0.000 title claims abstract description 8
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 title claims abstract description 7
- 239000010937 tungsten Substances 0.000 title claims abstract description 7
- 238000000465 moulding Methods 0.000 title abstract description 16
- 239000013078 crystal Substances 0.000 claims abstract description 24
- 239000010419 fine particle Substances 0.000 claims abstract description 13
- 229910000990 Ni alloy Inorganic materials 0.000 claims abstract description 10
- 239000000203 mixture Substances 0.000 claims abstract description 9
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 4
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 claims abstract 4
- 239000000463 material Substances 0.000 claims description 7
- 239000011159 matrix material Substances 0.000 abstract 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 21
- 229910001080 W alloy Inorganic materials 0.000 description 20
- 239000000843 powder Substances 0.000 description 20
- 239000011521 glass Substances 0.000 description 14
- 230000007797 corrosion Effects 0.000 description 9
- 238000005260 corrosion Methods 0.000 description 9
- 238000002844 melting Methods 0.000 description 9
- 230000008018 melting Effects 0.000 description 9
- 239000002245 particle Substances 0.000 description 8
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000005245 sintering Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 239000005383 fluoride glass Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 5
- 230000003287 optical effect Effects 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 3
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 3
- XATZQMXOIQGKKV-UHFFFAOYSA-N nickel;hydrochloride Chemical compound Cl.[Ni] XATZQMXOIQGKKV-UHFFFAOYSA-N 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 230000008520 organization Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 230000003746 surface roughness Effects 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910016569 AlF 3 Inorganic materials 0.000 description 1
- 229910052582 BN Inorganic materials 0.000 description 1
- 229910016036 BaF 2 Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000001513 hot isostatic pressing Methods 0.000 description 1
- 230000002706 hydrostatic effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- DWAHIRJDCNGEDV-UHFFFAOYSA-N nickel(2+);dinitrate;hydrate Chemical compound O.[Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O DWAHIRJDCNGEDV-UHFFFAOYSA-N 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 239000005368 silicate glass Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- Powder Metallurgy (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
この発明は、例えば各種の電子・電気機器や光学装置などに装着されている光機能装置の部品である高精度光学ガラスレンズを熱間プレス成形するのに適したタングステン基焼結合金金型（以下、Ｗ合金金型という）に関するものである。
【０００２】
【従来の技術】
従来、一般に光学ガラスレンズの熱間プレス成形に用いられている金型には、
（ａ）耐ガラス腐食性
（ｂ）熱伝導性（放熱性）
（ｃ）低熱膨張係数
などの特性が要求されることから、各種のステンレス鋼や耐熱鋼、さらにＣｏ基合金やＮｉ基合金などで形成された金型（以下、これらを総称して耐熱合金金型という）が用いられている。
また、近年、光学ガラスレンズの熱間プレス成形用金型として、一段とすぐれた熱伝導性を有し、かつ熱膨張係数のきわめて小さい炭化タングステン基超硬合金金型（以下、超硬合金金型という）が注目されている（例えば特許文献１参照）。
【０００３】
【特許文献１】
特公昭６２−５１２１１号公報
【０００４】
【発明が解決しようとする課題】
一方、近年の各種の電子・電気機器や光学装置の高性能化および小型化はめざましく、これに伴い、これらの光機能装置に用いられている光学ガラスレンズも小寸化および極薄肉化、さらに高精度化の傾向にあり、これに対応して前記光学ガラスレンズの熱間プレス成形温度は高温化し、広く実用に供されている弗化ガラス製のもので、その成形温度は約６００℃から９００℃にも達しようとしている。
しかし、上記の従来耐熱合金金型は、
（ａ）融点：１４５０〜１５５０℃、
（ｂ）熱伝導率：２０〜３３Ｗ／ｍ・Ｋ、
（ｃ）熱膨張係数：１１〜１４×１０−６／Ｋ、
を有するものであるために、一段と高い熱伝導率および低い熱膨張係数が要求される、小寸化および極薄肉化、さらに高精度化した高精度光学ガラスレンズの熱間プレス成形には十分満足に対応できず、きわめて短い使用寿命しか示さないものである。
また、上記の従来超硬合金金型は、これを構成する超硬合金の主成分である炭化タングステン（以下、ＷＣで示す）が、
（ａ）融点：約３０００℃、
（ｂ）熱伝導率：約４５Ｗ／ｍ・Ｋ、
（ｃ）熱膨張係数：約４．４×１０−６／Ｋ、
を有し、これらの高融点、高熱伝導率、および低熱膨張係数は小寸化および極薄肉化、さらに高精度化した高精度光学ガラスレンズの熱間プレス成形には適した特性である。しかし、金型を構成する超硬合金は、その組織が全体に占める割合で、９０〜９７質量％の前記ＷＣ相（硬質相）と残りのＣｏ相（結合相）からなり、炭化物である前記ＷＣ相と酸化物を主体とする高温加熱ガラスとはきわめて反応性の高いものであり、特に弗化ガラスなどの高融点ガラスに対しては一段と高い親和性を示すものであるために、これが原因で金型キャビティの粗面化が促進されるようになることから、金型のキャビティ表面に、ダイヤモンド状炭素膜や炭窒化チタン膜、さらに窒化ボロン膜などの離型膜を０．５〜６μｍの膜厚で形成して実用に供しており、したがって、前記超硬合金金型の使用寿命は前記離型膜の摩耗によって決まることになり、この結果比較的短時間で使用寿命に至るのが現状である。
【０００５】
【課題を解決するための手段】
そこで、本発明者らは、上述のような観点から、上記の従来超硬合金金型のもつ高融点、高熱伝導率、および低熱膨張係数に匹敵する高融点、高熱伝導率、および低熱膨張係数を有し、さらにすぐれた耐ガラス腐食性も具備し、高精度光学ガラスレンズの熱間プレス成形に適した金型を開発すべく、研究を行った結果、
金型を、質量％（以下、％は質量％を示す）で、
Ｎｉ：０．１〜１％、
Ｙ２Ｏ３：０．２〜１．５％、
を含有し、残りがＷと不可避不純物からなる組成、
並びに素地を構成するＷ結晶細粒の粒界にそってＹ２Ｏ３微粒が分散分布し、かつＮｉ成分は、遊離Ｎｉとして存在せず、前記Ｗ結晶細粒の粒界に沿って形成されたＷ−Ｎｉ合金薄層として存在する組織を有するタングステン基焼結合金（以下、Ｗ合金という）で構成すると、このＷ合金は、
（ａ）融点：１８００〜２０００℃、
（ｂ）熱伝導率：９０〜１５０Ｗ／ｍ・Ｋ、
（ｃ）熱膨張係数：４．５〜５．５×１０−６／Ｋ、
を有し、これらの特性は高融点、高熱伝導率、および低熱膨張係数を有する従来超硬合金金型のもつ特性に匹敵するものであり、さらに上記の組織、すなわちＷ結晶細粒とＹ２Ｏ３微粒、さらにＷ−Ｎｉ合金薄層は高温加熱ガラスに対する反応性の著しく低いものであることから、前記従来超硬合金金型では不可欠であったキャビティ表面への離型膜の形成を必要としない、すぐれた耐ガラス腐食性を発揮し、この結果のＷ合金で構成された金型は、弗化ガラスや、さらに約１４００℃の成形温度を必要とする石英ガラスなどの高温プレス成形条件下での高精度光学ガラスレンズの熱間プレス成形にすぐれた性能を長期に亘って発揮するようになる、という研究結果を得たのである。
【０００６】
この発明は、上記の研究結果に基づいてなされたものであって、
Ｎｉ：０．１〜１％、
Ｙ２Ｏ３：０．２〜１．５％、
を含有し、残りがＷと不可避不純物からなる組成、
並びに素地を構成するＷ結晶細粒の粒界にそってＹ２Ｏ３微粒が分散分布し、かつＮｉ成分は、遊離Ｎｉとして存在せず、前記Ｗ結晶細粒の粒界に沿って形成されたＷ−Ｎｉ合金薄層として存在する組織を有するＷ合金で構成してなる、高精度光学ガラスレンズの熱間プレス成形に用いるのに適した金型に特徴を有するものである。
【０００７】
つぎに、この発明のＷ合金金型を構成するＷ合金の組成を上記の通りに限定した理由を説明する。
（ａ）Ｎｉ
Ｎｉ成分には、焼結前はＷ粉末の表面を被覆する状態で存在し、焼結時にはＷ粉末と拡散反応してＷ−Ｎｉ合金薄層を形成すると共に、Ｗ結晶細粒相互間の焼結性を著しく向上させ、Ｗ合金の強度向上に寄与する作用があり、また前記Ｗ−Ｎｉ合金薄層は前記Ｗ結晶細粒のもつすぐれた耐ガラス腐食性と同等のすぐれた耐ガラス腐食性を有するものであるから、従来超硬合金金型に施されるキャビティ表面への離型膜の形成を必要としないで金型として実用に供することを可能とするものであるが、その含有量が０．１％未満では焼結性が不十分で所望の強度確保することができず、一方その含有量が１％を越えるとＷ結晶細粒の粒界に遊離Ｎｉが存在するようになり、この遊離Ｎｉは高温加熱ガラスによって侵食され、キャビティ表面の荒れが著しく促進されるようになるなることから、その含有量を０．１〜１％と定めた。
【０００８】
（ｂ）Ｙ２Ｏ３
Ｙ２Ｏ３成分は、Ｗ結晶細粒の粒界に微粒の状態で分散分布して、焼結時のＷ結晶細粒の粒成長を抑制し、もって強度向上に寄与するほか、自身の分散強化による強度向上にも寄与する作用があるが、その含有量が０．２％未満では前記作用に所望の向上効果が得られず、一方その含有量が１．５％を越えるとＹ２Ｏ３微粒がＷ結晶細粒の粒界に凝集するようになり、この結果強度が急激に低下するようになることから、その含有量を０．２〜１．５％と定めた。
【０００９】
なお、この発明のＷ合金金型を構成するＷ合金の組織において、Ｗ結晶細粒の粒界に沿って存在するＷ−Ｎｉ合金薄層は、
（ａ）例えば９９％以上の純度をもった硝酸ニッケル粉末や塩酸ニッケル粉末、、あるいは硫酸ニッケル粉末などの所定量を、アセトンや純水などの溶媒中に完全に溶解した状態で、例えば０．５〜３μｍの平均粒径をもったＷ粉末に配合して、スラリーとし、これを混合機で混練、乾燥させて、所定量の硝酸ニッケル、塩酸ニッケル、あるいは硫酸ニッケルなどで表面が被覆された被覆Ｗ粉末とし、
（ｂ）ついで、上記の被覆Ｗ粉末を、例えば水素雰囲気中、温度：８００℃に１時間保持の加熱処理を施して、表面の硝酸ニッケル、塩酸ニッケル、あるいは硫酸ニッケルなどを熱分解することにより、表面がＮｉで被覆されたＮｉ被覆Ｗ粉末を形成し、
（ｃ）この結果得られたＮｉ被覆Ｗ粉末を原料粉末として用いることにより形成されるものである。
【００１０】
【発明の実施の態様】
つぎに、この発明のＷ合金金型を実施例により具体的に説明する。
（ａ）まず、純度：９９．６％の硝酸ニッケル水和物｛分子式：Ｎｉ（ＮＯ３）２・６Ｈ２Ｏ｝粉末の所定量をアセトン中に溶解し、２．５μｍの平均粒径をもったＷ粉末に配合して、スラリーとし、これを混合機で混練、乾燥させて、所定量の硝酸ニッケルで表面が被覆された被覆Ｗ粉末とし、
（ｂ）ついで、上記の被覆Ｗ粉末を、例えば水素雰囲気中、温度：８００℃に１時間保持の加熱処理を施して、表面の硝酸ニッケルを熱分解することにより、表面がＮｉで被覆されたＮｉ被覆Ｗ粉末を形成し、
（ｃ）これに０．６μｍの平均粒径をもったＹ２Ｏ３粉末の所定量を配合し、アセトン溶媒を用いてボールミル中にて４８時間湿式混合し、乾燥した後、これをゴム鋳型に充填し、１５０ＭＰａの静水圧にてプレス成形して、直径：５０ｍｍ×高さ：４０ｍｍの寸法をもった成形体を形成し、この成形体に、水素雰囲気中、９００℃に５時間保持の条件での予備焼結、および水素雰囲気中、１４５０℃に１時間保持の条件での本焼結、さらに温度：１３００℃、圧力：１００ＭＰａの条件での熱間静水圧プレス処理を施して、直径：４０ｍｍ×長さ：３２ｍｍの寸法、およびそれぞれ表１に示される組成をもった金型素材とし、これら金型素材のそれぞれ２個を１対の上下型とし、このうちの下型の上面に直径：３８ｍｍ×中心部深さ：５ｍｍの曲面キャビティを形成し、一方上型の下面は平面のままとし、これら両上下型のキャビティ面をＲｍａｘ：０．０５μｍ以下の面粗度に研磨することにより本発明Ｗ合金金型１〜９、およびＮｉおよびＹ２Ｏ３含有量がこの発明の範囲から外れた比較Ｗ合金金型１〜４をそれぞれを製造した。
なお、この結果得られた本発明Ｗ合金金型１〜４および比較Ｗ合金金型１〜４の組織を、光学顕微鏡（４００倍）を用いて観察したところ、本発明Ｗ合金金型１〜９は、いずれも２〜１０μｍの範囲内の所定の平均粒径を有するＷ結晶細粒を主体とし、前記Ｗ結晶細粒の粒界に沿って０．２〜１μｍの範囲内の所定の平均粒径を有するＹ２Ｏ３微粒が分散分布し、かつ前記Ｗ結晶細粒の粒界に沿ってＷ−Ｎｉ合金薄層が存在し、遊離Ｎｉの存在しない組織を示した。一方比較Ｗ合金金型１〜４では、Ｗ結晶細粒の粒径が相対的に大きいものや、Ｙ２Ｏ３微粒が凝集したもの、さらにＷ結晶細粒の粒界に遊離Ｎｉ相が存在した組織が見られた。
【００１１】
また、比較の目的で、原料粉末として、平均粒径：１．５μｍのＷＣ粉末と同４μｍのＣｏ粉末を、ＷＣ：９５％、Ｃｏ：５％の割合に配合したものを用いる以外は、上記の本発明Ｗ合金金型１〜９および比較Ｗ合金金型１〜４の製造条件と同じ条件で超硬合金金型素材を製造し、これのキャビティ表面に、通常の化学蒸着装置にて、
反応ガス組成−ＴｉＣｌ４：４．２％、Ｎ２：２０％、ＣＨ４：４％、Ｈ２：残り、
反応雰囲気温度：１０２０℃、
反応雰囲気圧力：７ＭＰａ、
の条件で離型膜として平均層厚：２０μｍの炭窒化チタン（ＴｉＣＮ）膜を形成することにより従来超硬合金金型を製造した。
【００１２】
つぎに、これらの各種の金型について、ガラスレンズ素材であるコブとして、容量％で、ＢａＦ２：４１％、Ａｌ（ＰＯ３）３：１４％、ＳｒＦ２：１２％、ＡｌＦ３：１０％、Ｂａ２Ｐ２Ｏ７：８％、を含有し、残りがＡｌ２Ｏ３、からなる組成をもった弗化ガラスを用い、前記ゴブの１個当たりの容量：０．２ｃｍ３、前記ゴブの加熱温度：９００℃、プレス成形圧力：１０ＭＰａ、プレス成形速度：６個／分の条件で光学ガラスレンズのプレス成形を行ない、キャビティ面の面粗度がＲｍａｘ：０．０６μｍに達するまでのレンズ成形個数を測定した。この測定結果を同じく表１に示した。また、表１には金型強度を評価する目的で、金型から切り出した試験片を用いて測定した圧壊強度を示した。
【００１３】
【表１】
【発明の効果】
表１に示される結果から、本発明Ｗ合金金型１〜９は、いずれもこれを構成するＷ合金の主体が耐ガラス腐食性にすぐれ、かつ高融点、高熱伝導性（高放熱性）、および低熱膨張係数を有するＷ結晶細粒からなり、かつ前記Ｗ結晶細粒の粒界に存在するＷ−Ｎｉ合金薄層も前記Ｗ結晶細粒と同等のすぐれた特性を有し、遊離Ｎｉが存在しない組織をもつことから、キャビティ面の高温加熱弗化ガラスゴブによる腐食進行が著しく抑制され、良好なキャビティ面を長期に亘って保持し、さらにＹ２Ｏ３微粒による粒成長抑制効果および分散強化によって従来超硬合金金型と同等の高強度を有するのに対して、比較Ｗ合金金型１〜４に見られるように、ＮｉおよびＹ２Ｏ３成分の含有量がこの発明の範囲から外れると、キャビティ面の高温加熱弗化ガラスゴブによる腐食進行が著しく促進されたり、強度が低下したりすることが明かである。また、従来超硬合金金型では、キャビティ表面の離型膜の摩耗によって使用寿命となることから、比較的短い使用寿命しか示めさないことが明白である。
上述のように、この発明のＷ基焼結合金製金型は、例えば比較的腐食性の弱い珪酸ガラスや硼化ガラスなどを用いた光学ガラスレンズの熱間プレス成形は勿論のこと、特に腐食性の強い弗化ガラスなどの高温加熱プレス成形においてもすぐれた耐腐食性を示し、かつ高強度を具備するものであるから、光学ガラスレンズの小寸化および極薄肉化、さらに高精度化に十分満足に対応できるものである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tungsten-based sintered alloy mold suitable for hot press forming a high-precision optical glass lens, which is a component of an optical function device mounted on various electronic / electric devices and optical devices, for example. Hereinafter, referred to as a W alloy mold).
[0002]
[Prior art]
Conventionally, molds generally used for hot press molding of optical glass lenses include:
(A) Glass corrosion resistance (b) Thermal conductivity (heat dissipation)
(C) Since characteristics such as a low coefficient of thermal expansion are required, molds made of various stainless steels and heat-resistant steels, as well as Co-based alloys and Ni-based alloys (hereinafter collectively referred to as heat-resistant alloy molds) Type).
In recent years, as a mold for hot press molding of an optical glass lens, a tungsten carbide-based cemented carbide mold (hereinafter referred to as a cemented carbide mold) having an even higher thermal conductivity and an extremely small coefficient of thermal expansion. (Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Publication No. 62-51211
[Problems to be solved by the invention]
On the other hand, the performance and miniaturization of various electronic / electrical devices and optical devices in recent years have been remarkable, and accordingly, the optical glass lenses used in these optical functional devices have also been reduced in size and ultrathin. In response to this trend, the optical glass lens has been hot-pressed at a high temperature, and is made of fluoride glass widely used in practice. It is about to reach 900 ° C.
However, the above-mentioned conventional heat-resistant alloy mold,
(A) melting point: 1450-1550 ° C.
(B) Thermal conductivity: 20 to 33 W / m · K,
(C) Coefficient of thermal expansion: 11 to 14 × 10 −6 / K,
Satisfactory for hot press forming of high-precision optical glass lenses that require higher thermal conductivity and lower thermal expansion coefficient because of their small size, ultra-thin wall thickness, and high precision. However, it does not correspond to the above, and shows only a very short service life.
Further, in the above-mentioned conventional cemented carbide mold, tungsten carbide (hereinafter, referred to as WC) which is a main component of the cemented carbide constituting the mold,
(A) melting point: about 3000 ° C.
(B) Thermal conductivity: about 45 W / m · K,
(C) Coefficient of thermal expansion: about 4.4 × 10 −6 / K,
These high melting point, high thermal conductivity, and low coefficient of thermal expansion are characteristics suitable for hot press molding of a high-precision optical glass lens having a small size, an extremely thin wall, and a high precision. However, the cemented carbide constituting the mold is composed of 90 to 97% by mass of the WC phase (hard phase) and the remaining Co phase (bonding phase) in a proportion of the entire structure, and is a carbide. This is because the WC phase and the high-temperature heated glass mainly composed of an oxide are extremely reactive, and particularly exhibit a higher affinity for a high melting point glass such as a fluoride glass. In such a case, a mold release film such as a diamond-like carbon film, a titanium carbonitride film, and a boron nitride film is formed on the surface of the mold cavity in a thickness of 0.5 to 6 μm. The service life of the cemented carbide mold is determined by the wear of the release film. As a result, the service life of the mold in a relatively short time is required. It is the current situation.
[0005]
[Means for Solving the Problems]
Therefore, from the above viewpoints, the present inventors have a high melting point, a high thermal conductivity, and a low thermal expansion coefficient comparable to the high melting point, high thermal conductivity, and low thermal expansion coefficient of the conventional cemented carbide mold described above. As a result of conducting research to develop a mold suitable for hot press molding of high precision optical glass lens with excellent glass corrosion resistance,
The mold is expressed in mass% (hereinafter,% indicates mass%)
Ni: 0.1-1%,
Y 2 O 3: 0.2~1.5%,
A composition comprising, with the balance being W and unavoidable impurities,
In addition, Y 2 O 3 fine particles are dispersed and distributed along the grain boundaries of the W crystal fine grains constituting the base material, and the Ni component does not exist as free Ni but is formed along the grain boundaries of the W crystal fine grains. When formed of a tungsten-based sintered alloy having a structure existing as a thin W-Ni alloy layer (hereinafter, referred to as a W alloy),
(A) melting point: 1800-2000 ° C.
(B) Thermal conductivity: 90 to 150 W / m · K,
(C) Thermal expansion coefficient: 4.5 to 5.5 × 10 −6 / K,
These properties are comparable to those of a conventional cemented carbide mold having a high melting point, a high thermal conductivity, and a low coefficient of thermal expansion. Further, the above-mentioned structure, that is, W crystal fine grains and Y 2 Since the O 3 fine particles and the W-Ni alloy thin layer have extremely low reactivity to high-temperature heated glass, it is necessary to form a release film on the cavity surface, which is indispensable in the conventional cemented carbide die. It exhibits excellent glass corrosion resistance, and the resulting mold made of W alloy is suitable for high-temperature press molding conditions such as fluoride glass and quartz glass requiring a molding temperature of about 1400 ° C. The research results show that the high-precision optical glass lens below will exhibit excellent performance for hot press molding over a long period of time.
[0006]
The present invention has been made based on the above research results,
Ni: 0.1-1%,
Y 2 O 3: 0.2~1.5%,
A composition comprising, with the balance being W and unavoidable impurities,
In addition, Y 2 O 3 fine particles are dispersed and distributed along the grain boundaries of the W crystal fine grains constituting the base material, and the Ni component does not exist as free Ni but is formed along the grain boundaries of the W crystal fine grains. And a mold suitable for use in hot press forming of a high-precision optical glass lens made of a W alloy having a structure existing as a W-Ni alloy thin layer.
[0007]
Next, the reason why the composition of the W alloy constituting the W alloy mold of the present invention is limited as described above will be described.
(A) Ni
Prior to sintering, the Ni component exists in a state of covering the surface of the W powder, and during sintering, it undergoes a diffusion reaction with the W powder to form a W-Ni alloy thin layer, and the sintering between the W crystal fine grains. It has the effect of significantly improving the bondability and contributing to the improvement in the strength of the W alloy, and the W-Ni alloy thin layer has excellent glass corrosion resistance equivalent to the excellent glass corrosion resistance of the W crystal fine grains. It does not require the formation of a release film on the surface of a cavity conventionally applied to a cemented carbide mold, so that it can be put to practical use as a mold. If the content is less than 0.1%, the sinterability is insufficient and the desired strength cannot be ensured. On the other hand, if the content exceeds 1%, free Ni is present at the grain boundaries of W crystal fine grains. This free Ni is eroded by the high-temperature heated glass and roughens the cavity surface. Since is made to be significantly accelerated, it determined the content of 0.1 to 1%.
[0008]
(B) Y 2 O 3
The Y 2 O 3 component is dispersed and distributed in the form of fine particles at the grain boundaries of the W crystal fine grains, thereby suppressing the grain growth of the W crystal fine grains during sintering, thereby contributing to the improvement of the strength and the dispersion of the Y grains. There is an effect that also contributes to the strength improvement by strengthening, but if the content is less than 0.2%, the desired effect of improving the effect cannot be obtained, while if the content exceeds 1.5%, Y 2 O Since the three fine particles aggregate at the grain boundaries of the W crystal fine particles, and as a result, the strength rapidly decreases, the content is determined to be 0.2 to 1.5%.
[0009]
In the structure of the W alloy constituting the W alloy mold according to the present invention, the W-Ni alloy thin layer existing along the grain boundaries of the W crystal fine grains includes:
(A) A predetermined amount of, for example, nickel nitrate powder, nickel hydrochloride powder, or nickel sulfate powder having a purity of 99% or more is completely dissolved in a solvent such as acetone or pure water. It was mixed with a W powder having an average particle size of 5 to 3 μm to form a slurry, which was kneaded and dried with a mixer, and the surface was coated with a predetermined amount of nickel nitrate, nickel hydrochloride, nickel sulfate or the like. As coated W powder,
(B) Then, the above-mentioned coated W powder is subjected to a heat treatment at, for example, a temperature of 800 ° C. for 1 hour in a hydrogen atmosphere to thermally decompose nickel nitrate, nickel hydrochloride, nickel sulfate or the like on the surface. Forming a Ni-coated W powder whose surface is coated with Ni,
(C) It is formed by using the Ni-coated W powder obtained as a result as a raw material powder.
[0010]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Next, the W alloy mold of the present invention will be specifically described with reference to examples.
(A) First, a predetermined amount of nickel nitrate hydrate having a purity of 99.6% {molecular formula: Ni (NO 3 ) 2 .6H 2 O} powder was dissolved in acetone, and the average particle size of 2.5 μm was determined. Blended with the W powder, a slurry, kneaded with a mixer, and dried to obtain a coated W powder whose surface is coated with a predetermined amount of nickel nitrate,
(B) Then, the coated W powder was subjected to a heat treatment at, for example, a temperature of 800 ° C. for 1 hour in a hydrogen atmosphere to thermally decompose nickel nitrate on the surface, whereby the surface was coated with Ni. Forming a Ni-coated W powder,
(C) A predetermined amount of Y 2 O 3 powder having an average particle size of 0.6 μm was mixed with the mixture, wet-mixed for 48 hours in a ball mill using an acetone solvent, dried, and then mixed with a rubber mold. And press-molded under a hydrostatic pressure of 150 MPa to form a molded body having a size of diameter: 50 mm × height: 40 mm. The molded body is maintained at 900 ° C. for 5 hours in a hydrogen atmosphere. Pre-sintering under the conditions, main sintering at 1450 ° C. for 1 hour in a hydrogen atmosphere, and hot isostatic pressing at a temperature of 1300 ° C. and a pressure of 100 MPa to obtain a diameter : Mold materials having dimensions of 40 mm x length: 32 mm and each having the composition shown in Table 1, and two of each of these mold materials were formed as a pair of upper and lower dies. Diameter: 38mm x center depth: 5m While the lower surfaces of the upper and lower dies remain flat, and the cavity surfaces of the upper and lower dies are polished to a surface roughness of Rmax: 0.05 μm or less, whereby the W alloy dies 1 to 9 of the present invention are formed. , And comparative W alloy molds 1 to 4 having Ni and Y 2 O 3 contents out of the range of the present invention, respectively.
The structures of the resulting W alloy molds 1 to 4 of the present invention and the comparative W alloy molds 1 to 4 were observed using an optical microscope (400 times). 9 is mainly composed of a W crystal fine grain having a predetermined average particle size in the range of 2 to 10 μm, and a predetermined average of 0.2 to 1 μm along the grain boundary of the W crystal fine grain. and Y 2 O 3 fine dispersion distribution having a particle size, and the W W-Ni alloy thin layer is present along the crystal granules of the grain boundary, indicating a non-existent organization of free Ni. On the other hand, in the comparative W alloy dies 1 to 4, the W crystal fine grains have a relatively large particle size, the Y 2 O 3 fine grains are agglomerated, and a free Ni phase is present at the grain boundaries of the W crystal fine grains. Organization was seen.
[0011]
For the purpose of comparison, the above-mentioned raw material powder was used except that WC powder having an average particle size of 1.5 μm and Co powder having the same size of 4 μm were blended at a ratio of 95% WC and 5% Co. Of the present invention W alloy molds 1 to 9 and comparative W alloy molds 1 to 4 were manufactured under the same conditions as those of the cemented carbide mold material.
The reaction gas composition -TiCl 4: 4.2%, N 2 : 20%, CH 4: 4%, H 2: remainder,
Reaction atmosphere temperature: 1020 ° C,
Reaction atmosphere pressure: 7 MPa,
A conventional cemented carbide mold was manufactured by forming a titanium carbonitride (TiCN) film having an average layer thickness of 20 μm as a release film under the conditions described above.
[0012]
Next, regarding these various molds, as a bump as a glass lens material, BaF 2 : 41%, Al (PO 3 ) 3 : 14%, SrF 2 : 12%, and AlF 3 : 10% by volume%. , Ba 2 P 2 O 7 : 8%, the balance being Al 2 O 3 , using a fluoride glass having a composition of: the capacity per one gob: 0.2 cm 3 , the gob Heating temperature: 900 ° C., press molding pressure: 10 MPa, press molding speed: 6 lenses / minute, press molding of optical glass lens, lens until surface roughness of cavity surface reaches Rmax: 0.06 μm The number of moldings was measured. The measurement results are also shown in Table 1. In addition, Table 1 shows the crushing strength measured using a test piece cut from the mold for the purpose of evaluating the mold strength.
[0013]
[Table 1]
【The invention's effect】
From the results shown in Table 1, in the W alloy dies 1 to 9 of the present invention, the main component of the W alloy constituting each was excellent in glass corrosion resistance, and had a high melting point, high thermal conductivity (high heat dissipation), And a W-Ni alloy thin layer composed of W crystal fine particles having a low coefficient of thermal expansion and present at the grain boundaries of the W crystal fine particles also has excellent characteristics equivalent to that of the W crystal fine particles. Since it has a non-existent structure, the progress of corrosion of the cavity surface due to the high-temperature heated fluorinated glass gob is remarkably suppressed, the good cavity surface is maintained for a long time, and the effect of suppressing the grain growth and enhancing the dispersion by the fine Y 2 O 3 particles. Have the same high strength as conventional cemented carbide dies, but the contents of Ni and Y 2 O 3 components are out of the scope of the present invention as seen in Comparative W alloy dies 1-4. And the high temperature Or corrosion proceeds due to fluoride glass gob is accelerated considerably, the strength is apparent be lowered. In addition, in the conventional cemented carbide mold, since the service life is extended due to the wear of the release film on the cavity surface, it is obvious that the service life is relatively short.
As described above, the W-based sintered alloy mold of the present invention can be used not only for hot press molding of an optical glass lens using, for example, silicate glass or boride glass having relatively low corrosiveness, but also for corroding. Because of its excellent corrosion resistance and high strength even in high-temperature heat press molding of highly fluorinated glass, etc., it is possible to reduce the size, ultrathinness, and precision of optical glass lenses. It can be satisfied enough.
Claims (1)
酸化イットリウム：０．２〜１．５質量％、
を含有し、残りがＷと不可避不純物からなる組成、
並びに素地を構成するＷ結晶細粒の粒界にそって酸化イットリウム微粒が分散分布し、かつＮｉ成分は、遊離Ｎｉとして存在せず、前記Ｗ結晶細粒の粒界に沿って形成されたＷ−Ｎｉ合金薄層として存在する組織を有するタングステン基焼結合金で構成したことを特徴とする高精度光学ガラスレンズの熱間プレス成形に用いるのに適したタングステン基焼結合金金型。Ni: 0.1 to 1% by mass,
Yttrium oxide: 0.2-1.5% by mass,
A composition comprising, with the balance being W and unavoidable impurities,
Yttrium oxide fine particles are dispersed and distributed along the grain boundaries of the W crystal fine grains constituting the base material, and the Ni component does not exist as free Ni, and W is formed along the grain boundaries of the W crystal fine grains. -A tungsten-based sintered alloy mold suitable for use in hot press forming of a high-precision optical glass lens, comprising a tungsten-based sintered alloy having a structure existing as a Ni alloy thin layer.
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| JP2002244551A JP4189723B2 (en) | 2002-08-26 | 2002-08-26 | Tungsten-based sintered alloy mold suitable for hot press molding of high-precision optical glass lens |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005085486A1 (en) * | 2004-03-05 | 2005-09-15 | Mitsubishi Materials C.M.I. Corporation | Tungsten based sintered material having high strength and high hardness and mold for hot press molding of optical glass lens |
| JP2006176365A (en) * | 2004-12-22 | 2006-07-06 | Mitsubishi Material Cmi Kk | Method of machining forming mold and forming mold |
| DE102010022888A1 (en) * | 2010-06-07 | 2011-12-08 | Kennametal Inc. | Alloy for a penetrator and method of making a penetrator of such an alloy |
| WO2016061721A1 (en) * | 2014-10-20 | 2016-04-28 | 中南大学 | Method for preparing rare-earth oxide dispersion strengthened fine-grained tungsten material |
-
2002
- 2002-08-26 JP JP2002244551A patent/JP4189723B2/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005085486A1 (en) * | 2004-03-05 | 2005-09-15 | Mitsubishi Materials C.M.I. Corporation | Tungsten based sintered material having high strength and high hardness and mold for hot press molding of optical glass lens |
| US7615094B2 (en) | 2004-03-05 | 2009-11-10 | Mitsubishi Materials C.M.I. Corporation | Tungsten-based sintered material having high strength and high hardness, and hot press mold used for optical glass lenses |
| JP2006176365A (en) * | 2004-12-22 | 2006-07-06 | Mitsubishi Material Cmi Kk | Method of machining forming mold and forming mold |
| DE102010022888A1 (en) * | 2010-06-07 | 2011-12-08 | Kennametal Inc. | Alloy for a penetrator and method of making a penetrator of such an alloy |
| DE102010022888B4 (en) * | 2010-06-07 | 2012-05-03 | Kennametal Inc. | Alloy for a penetrator and method of making a penetrator of such an alloy |
| WO2016061721A1 (en) * | 2014-10-20 | 2016-04-28 | 中南大学 | Method for preparing rare-earth oxide dispersion strengthened fine-grained tungsten material |
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