JP3691289B2 - Composite mold - Google Patents

Description

に設定され、残部が金属である。これらセラミックス成分の粒度は、平均粒径がサブμｍの超微粒子組成から３０μｍ程度の範囲内で使用可能である。
【００２２】
本実施形態では、セラミックス粒子が焼結による緻密化の前段階として、あるいは緻密化と同時に急激に成長するような粒成長促進剤を原子に近い大きさで加え、その濃度を制御することによって粒子の成長とそれに伴う粒子再配列および金属濃度の勾配とを惹起させるものである。従って、初期状態のセラミックス粒子の大きさが小さいほど、粒成長促進剤の効果が大きくなって成長度合いも大きくなる一方、初期状態のセラミックス粒子の大きさが大きいほど、この成長度合いが小さくなる。
【００２３】
そこで、これらの成長に伴う高硬質層部の形成、金属が漸減する傾斜機能層の形成および金属量の増加する高強度かつ高靱性層の形成が効果的に行われる条件として、セラミックス成分の平均粒径が０．３μｍ〜３０μｍに設定される。平均粒径が０．３μｍ未満の粉末原料は、相当に高価であって実質的に使用することが困難である一方、３０μｍを超える粉末原料では、セラミックス粒子の成長が１０倍に満たないために特性の向上がさほど図られず、またコストも高くなってしまう。
【００２４】
複合材中の金属成分およびセラミックス成分は、使用条件等によって適宜選択されたり、それぞれの量が変更されたりする。例えば、非磁性化、ワークとの反応防止または反応抑制、耐熱性の向上、剛性および耐摩耗性の向上等を図る目的から、金属成分としてニッケルを主体にすることや、セラミックス成分の炭化チタン、窒化チタン、炭化クロムまたは炭化バナジウムの添加や除去が行われる。
【００２５】
セラミックス成分が９７ｗｔ％を超えると、金属成分の量が少なすぎて強度的に不十分となり、従来の材料と比べても、引っ張り強度に差異が見られない。しかも、鍛造金型１０の使用中にエッジ部にチッピング等が発生し易く、実用に供することが難しい。ここで、セラミックス成分が９７ｗｔ％であると金属成分が３ｗｔ％になるが、内部は７ｗｔ％以上の金属成分でかつ表面が０．３ｗｔ％〜１．５ｗｔ％の金属成分となり、高剛性を有し高強度および高靱性な鍛造金型１０を得ることができる。
【００２６】
セラミックス成分は、より好ましくは９５ｗｔ％とすればよく、その際、表面の金属成分は０．３ｗｔ％〜２ｗｔ％となる。このため、高剛性、高耐摩耗性および高耐熱性を有するとともに、内部の金属成分が１０ｗｔ％程度となって強度および靱性に優れ、現状の超硬材（現状材）を凌ぐ特性を有するものとなる。一方、セラミックス成分が７０ｗｔ％未満では、金属量が多くなって物性等が飽和してしまい、耐摩耗性、剛性および耐食性等が劣化してしまう。
【００２７】
従って、セラミックス成分が７０ｗｔ％〜９７ｗｔ％の範囲内であれば、表面の金属量が０．１ｗｔ％〜８ｗｔ％となり、しかも内部金属量が７ｗｔ％〜４０ｗｔ％程度となる。これにより、耐摩耗性、熱伝導度、強度、剛性および耐衝撃性等の殆どの値が現状材を大きく上回るという効果が得られる。
【００２８】
金属量が漸減あるいは漸増する傾斜部４２ａ、４２ｂ、５０ａおよび５０ｂの厚さは、数百μｍ以上、好ましくは０．３ｍｍ以上必要である。すなわち、熱の発生や応力の発生によって作用する熱応力や負荷応力を緩和するために、鍛造金型１０の設計上の要請があるからである。例えば、熱応力について説明すると、金属量と熱伝導、粒子の大きさと熱伝導はそれぞれ相関を有しており、発生する熱応力が熱伝達の勾配であることから、傾斜部４２ａ、４２ｂ、５０ａおよび５０ｂの厚さが変化すれば、発生する熱応力そのものも変化する。このため、厚さが数μｍ〜数十μｍでは、発生する熱応力や加工時に生ずる応力の緩和量が小さくなってしまい、耐久性の向上を図ることができない。また、セラミクッス部４０ａ、４０ｂ、４８ａおよび４８ｂの厚さは、０．３ｍｍ以上必要である。これは、セラミックス成分が仕上げ加工工程で除去されてしまい、その効力を喪失するとともに、コーティングの際に密着力が低下することを回避するためである。
【００２９】
鍛造金型１０を構成するダイリング２４、ノックアウトピン２８およびパンチ３６の表面硬度は、ＨＲＡ９０以上に設定される。表面硬度がＨＲＡ９０未満では、コーティングする際に前処理としてエッチング等を施す必要があり、効果が少なくなるとともに、表面への金属の露出割合が多くなり、コーティング層の密着力や強度に課題が生じる。しかも、ワークと鍛造金型１０との摩擦係数（μ）が高くなってしまい、発熱の増大や発生する応力や金型への負荷応力の増大を招いてしまい、凝着が惹起されるとともにワークの表面荒れの他、鍛造金型１０自体の摩耗が発生し易くなってしまう。従って、表面硬度をＨＲＡ９０以上、好ましくはＨＲＡ９１以上に設定すれば、得られる製品の面粗さや精度が有効に向上するとともに、鍛造金型１０の型寿命も向上するという効果がある。
【００３０】
粒成長促進剤は適宜選択されるものであり、例えば、ニッケルが用いられる場合、金属成分を１０ｗｔ％としかつセラミックス成分を単純な炭化タングステンのみとした場合であっても、金型表面硬度をＨＲＡ９３以上とすることができる。さらに、セラミックス成分の一部を炭化チタンや窒化チタン等と置換したり、粒成長促進剤をマンガン、クロム、チタンまたはアルミニウムに変えたりすることにより、表面硬度がＨＲＡ９６近くにもなる。
【００３１】
上記の表面硬度は、セラミックス等の硬質皮膜コーティングを施した値以上となり、表面金属量も殆どない状態にすることができる。その際、金型表面に硬質皮膜層、例えば、硬質セラミックスコーティングを施せば、従来の超硬材や複合材の金型に比べて表面の金属量が大きく減少しているため、前記硬質セラミックスコーティングの密着性を一挙に向上させることが可能になる。
【００３２】
金型表面に硬質セラミックスコーティングを施すことにより、被加工材との凝着性や被加工材と金型表面との摺動性が改善される。しかも、被加工材や工程に合わせて金型素材から変更する必要がなく、硬質皮膜材の変更で対応することができ、コストの削減が容易に可能になる。硬質皮膜材としては、ＤＬＣ膜（ダイヤモンドライクカーボン）、ダイヤモンド、ＴｉＮ、ＴｉＣ、ＴｉＣＮ、Ａｌ₂ Ｏ₃ またはＣｒ₃ Ｃ₂ 等が挙げられる。
【００３３】
硬質皮膜層の厚さは、３μｍ〜１５μｍの範囲内に設定される。厚さが３μｍ未満では、膜厚として充分ではなく、所望の効果が得られない。一方、厚さが１５μｍを超えると、ＣＶＤ、ＰＶＤ等により膜を形成した後に、その膜による残留応力が大きくなって該膜自体に亀裂が生じ、機能の低下が惹起されてしまう。従って、硬質皮膜層であるＴｉＮコーティング部４５ａ、４５ｂ、５２ａおよび５２ｂの厚さを、３μｍ〜１５μｍの範囲内、さらに好ましくは、５μｍ〜１０μｍの範囲内に設定すれば、不具合が生ずることがなく、また、金型の嵌め合い精度であるｈ５、Ｈ５、ｈ６およびＨ６等にも、通常の金型加工精度で充分に対応することができる。
【００３４】
通常、超硬材製金型に硬質皮膜コーティングを施す場合、この金型形状やキャビティ形状が複雑化すると、均質なコーティングが困難であり、１０μｍ程度の膜厚において数μｍの厚さの差が生じていた。このため、硬質皮膜コーティングとして充分な機能を有するために、この硬質皮膜コーティングの厚さが数十μｍ〜数百μｍの範囲内に設定されていた。
【００３５】
これに対して、本実施形態では、金型表面自体が既に略セラミックスの状態であるセラミックス部４０ａ、４０ｂ、４８ａおよび４８ｂを構成しており、セラミックスとしての機能は、このセラミックス部４０ａ、４０ｂ、４８ａおよび４８ｂが担っている。従って、ＴｉＮコーティング部４５ａ、４５ｂ、５２ａおよび５２ｂは、被加工材との反応性、凝着性および耐酸化性等の向上を図るだけでよく、その厚さが３μｍ〜１５μｍの範囲内で充分である。これにより、傾斜複合材の成分を被加工材に応じて種々用意する必要がなく、硬質皮膜層を変更するだけでよいため、経済的であるという効果が得られる。
【００３６】
また、本実施形態では、複合材の構成成分であるセラミックス成分が焼結工程で粒子成長し易いような添加剤を原子に近い大きさ、例えば、イオン溶液として含浸により供給している。このため、粒成長促進剤の濃度勾配を乾燥工程や、含浸の際の溶媒の蒸発速度条件や、浸積時間等の条件および焼結時の雰囲気管理や温度管理等によって調整している。これにより、ダイリング２４、ノックアウトピン２８およびパンチ３６の形状に沿って高硬質層であるセラミックス部４０ａ、４０ｂ、４８ａおよび４８ｂや、金属が漸増あるいは漸減する傾斜部４２ａ、４２ｂ、５０ａおよび５０ｂを形成することができる。従って、機能および性能が向上して耐久性に優れる鍛造金型１０を得ることが可能になる。しかも、金型表面に硬質皮膜層を施すことにより、被加工材に合わせた硬質皮膜層を最適な条件下で最適に施工することができる。
実施例１
実施例１では、平均粒径が２．２μｍの炭化タングステン（ＷＣ）粉末を８９ｗｔ％、平均粒径が２μｍの炭化ニオブ（ＮｂＣ）を２ｗｔ％、平均粒径が２．４μｍの炭化タンタル（ＴａＣ）を１ｗｔ％、平均粒径が０．８μｍの金属コバルト（Ｃｏ）を８ｗｔ％の組成で用意し、有機溶媒を媒液としてボールミルにより７２時間充分に混合した。これは、ＪＩＳ分類におけるＫ−１０乃至Ｖ−１０、２０の組成に相当するものである。
【００３７】
また、通常の超硬製金型組成材として、平均粒径が３μｍの炭化タングステンと平均粒径が０．８μｍの金属コバルトとを、それぞれ９５ｗｔ％〜７０ｗｔ％および５ｗｔ％〜３０ｗｔ％の範囲内で構成し、同様な混合条件によって充分に混合した。
【００３８】
上記混合後、含有する有機溶媒の液分が９％になるように調整し、成形用バインダの影響を回避するためにバインダレスで、金型内静水圧加圧成形法により１００ＭＰａの成形圧力にて焼結後の直径が１８ｍｍでかつ長さが１５０ｍｍになるように成形体を成形した。焼結後の片面取り代は、０．１ｍｍ〜０．２ｍｍに設定している。成形体は、窒素ガス中において５０Ｐａの成形圧力にてこの成形体に残存する有機溶媒を除去した後、９００℃で３０分間の仮焼成を行い、仮焼成体を得た。成形体含浸時の破壊を防ぐためである。
【００３９】
次いで、粒成長促進剤として取り扱い性、利便性および安全性等を考慮し、１０％濃度のＮｉ塩水溶液を用意し、これに仮焼成体を浸漬した後に１３０℃の排気型熱風乾燥で充分乾燥し、前記仮焼成体内におけるニッケル濃度の傾斜化を図った。そして、窒素ガス流通下で、５０Ｐａの加圧下に１４００℃で１．５時間保持し、焼結体を得た。なお、表面層の影響を除去するために、焼結体の表面層を片面０．１ｍｍ〜０．２ｍｍだけ除去し、試験材を得た。
【００４０】
一方、Ｎｉイオン濃度を変更させた溶液を仮焼成体に含浸させたものを用意し、これらを粉体中に埋設して水分の急激な蒸発による濃度差が生じないように調整し、同様に焼結および加工を施して試験材を得た。
【００４１】
そこで、得られた試験材の中、炭化ニオブおよび炭化タンタルを配したコバルトが８ｗｔ％の試験材の硬質層は、加工前では０．３ｍｍ〜０．４ｍｍ、加工後では０．２ｍｍ〜０．３ｍｍ程度となり、その表面硬度がＨＲＡ９３．４となった。この値は、硬質皮膜コーティングを施したものに近い値であり、そのまま金型素材として使用することが可能である。
【００４２】
図５は、試験材（焼結体）の表面から内部に向かって変化する硬度の値が示されている。これにより、硬度は、焼結体内部に向かって金属イオンが増加するのに伴って漸減し、この硬度の変化量はＨＲＡ６程度と非常に大きなものとなった。さらに、この硬度の減少から傾斜機能層の厚さが約８ｍｍであることが検出された。この試験材では、表面の金属量が面積率で３％程度であり、最初の組成状態から比べると１／７〜１／８に低減している。中央部の金属量は面積率で２６％にも及び、初期状態と比べて２倍以上となっていた。
【００４３】
次に、試験材の断面を顕微鏡や電子顕微鏡等により観察し、粒子の大きさ（μｍ）を測定したところ、図６および図７に示す結果が得られた。図６は、炭化ニオブ等を含有する試験材を示しており、その表面近くの粒子の大きさが４倍〜５倍程度に成長していた。一方、図７は、同一のコバルト量でセラミックス成分が炭化タングステンのみであるＷＣ−８Ｃｏの組成の試験材を示しており、その表面近くの粒子の大きさが３０μｍ〜４０μｍにも成長しており、粒子の大きさが１０倍〜１３倍程度となっていた。
【００４４】
図６および図７に示すように、粒子の大きさは金属量の増加と共に漸減し、中央部では殆ど粒成長しておらず、初期状態での粒度のままであった。なお、炭化ニオブや炭化タンタルを加えたものに比べて、単純組成のＷＣ−８Ｃｏの粒成長が著しいのは、これらの添加粉末が粒成長を抑制しているからである。
【００４５】
図８は、粒成長促進剤であるＮｉイオン濃度を１０％にし、複合材に含まれる金属コバルト量を変えて調整するとともに、Ｎｉイオンの含浸を行うもの（試験材）と含浸を行わないもの（現状材）とにおいて、抗折強度（ＧＰａ）を比較する実験を行った結果を示している。対象試料は炭化ニオブ等を含むものである。Ｎｉ含浸の試験材では、含浸後に粉体中に埋設してイオン濃度の移動を抑制し均質体組成を構成している。この試験材では、現状材に比べて抗折強度が有効に向上している。すなわち、通常、粒成長することにより強度の低下が惹起されるが、原子に近い大きさで粒成長剤を加えることにより、逆に強度の向上が図られたからである。
【００４６】
図９は、粒成長促進剤であるＮｉイオン濃度を変化させ、複合材組成をコバルトが８ｗｔ％と一定として試験材の硬度を測定した結果を示している。これにより、図８と同様に、Ｎｉイオン量の極大の存在が示唆されている。
【００４７】
図１０は、粒成長促進剤であるＮｉイオン濃度を１０％と一定にしたときの剛性の変化を示している。剛性を検出するために、実際上の縦弾性率を測定した。図１０に示すように、表面が粒成長することによって見かけ剛性である縦弾性率が増加するとともに、均質複合材においても剛性の変化が複合粒子の粒度と関係していることが分った。
【００４８】
図１１は、図９と相関するものであり、Ｎｉイオン濃度（％）と破壊靱性値（ＭＰａｍ^1/2 ）との関係を示している。現状材では、強度が上がるにつれて靱性が低下しており、試験材では特有の物性を示している。
【００４９】
図１２は、温度変化に対する硬度（ＨＲＡ）の変化を示している。図１２中、通常超硬材は市販のＶ−１０相当品であり、試験材の硬度がこの通常超硬材に比べてＨＲＡ１０以上の高い値となった。しかも、試験材では、高温に至ってもその硬度を高い値に維持することができ、高温環境下における有効利用が図られるという効果がある。温度による硬度の変化が小さいということは、その熱膨張が小さいということである。従って、硬質皮膜層の熱膨張が非常に小さくなり、母材との密着性が向上する。
【００５０】
図１３は、試験材と現状超硬材との圧縮応力を比較した結果を示している。なお、疲労特性を得られ易いように、ＷＣ−１５Ｃｏ組成が用いられた。これにより、現状超硬材を用いるものに比べ、試験材ではその圧縮応力が大きく向上し、実際上、３０％程度の向上が認められた。
【００５１】
図１４は、現状構成と試験材とについて、ＷＣ−Ｃｏ組成でコバルト量を変えてそれぞれの引っ張り強度（ＭＰａ）を測定した結果を示している。これにより、ニッケルを含浸していない（均質体）試験材では、その測定が難しく、測定値のばらつきが大きくなるとともにその脆さが目立った。その傾向は、金属Ｃｏ量が２０ｗｔ％を超えても同様であった。これに対して、ニッケル含浸した（傾斜組成）試験材では、コバルト量が５ｗｔ％までの測定値の差が大きかったものの、コバルト量がそれ以上ではばらつきも小さくなって、引っ張り強度自体も大きな値になった。引っ張り強度を比較したところ、現状構成に比べて均質材の試験材で２倍〜３倍の値が得られ、傾斜組成である試験材では、この均質材よりもさらに値が増加した。これは剛性の増加や表面硬質効果等によるものである。
【００５２】
従って、実施例１では、現状の超硬材やＳＫＤ材およびＳＫＨ材等に比べ、鍛造金型１０として具備すべきあらゆる特性について凌駕しており、これまでの鍛造金型に比べて耐用性や機能の点で著しい向上が図られるという効果が得られる。
実施例２
図１に示す鍛造金型１０を製作し、この鍛造金型１０の試験を行った。この鍛造金型１０を構成するダイリング２４、ノックアウトピン２８およびパンチ３６はＷＣ−Ｃｏ組成とし、コバルト量が１０ｗｔ％および１５ｗｔ％であるとともに、粒成長促進剤としてＮｉ塩水溶液を用い、基本的に実施例１と同様の製法で製造された。鍛造金型１０の精度および面粗さは、現状の金型と同様にした。嵌め合い交差はＨ６―ｈ６とした。硬質皮膜層の構成は、ＣＶＤにより１μｍ、３μｍ、８μｍ、１４μｍおよび２０μｍとし、ＴｉＮコーティング部４５ａ、４５ｂ、５２ａおよび５２ｂを形成した。
【００５３】
ダイリング２４、ノックアウトピン２８およびパンチ３６では、高硬質層部であるセラミックス部４０ａ、４０ｂ、４８ａおよび４８ｂの厚さがそれぞれ５ｍｍ、５ｍｍ、１ｍｍおよび１ｍｍとなり、それぞれの硬度はＷＣ−１０ＣｏでＨＲＡ９３．３、ＨＲＡ９３．４およびＨＲＡ９３．４となり、ＷＣ−１５ＣｏでＨＲＡ９３．２、ＨＲＡ９３．４およびＨＲＡ９３．４と略同一となった。その際、それぞれの表面露出金属量は略同一であった。
【００５４】
また、傾斜部４２ａ、４２ｂ、５０ａおよび５０ｂの厚さは、ＷＣ−１０Ｃｏでそれぞれ１４ｍｍ、１４ｍｍ、６ｍｍおよび６ｍｍとなり、ＷＣ−１５Ｃｏでそれぞれ１３ｍｍ、１３ｍｍ、６ｍｍおよび６ｍｍとなり、残部が高強度かつ高靱性層である金属部４４、４６ａおよび４６ｂとなった。
【００５５】
ダイリング２４は、図２に示すように、ドーナツ形状を有しており、この内周面側からセラミックス部４０ｂ、傾斜部４２ｂおよび金属部４４が設けられ、さらにその金属部４４の外側に傾斜部４２ａおよびセラミックス部４０ａが設けられている。このため、ダイリング２４は、全体として非常に強靱となり、有効な構成を有している。ノックアウトピン２８およびパンチ３６では、同心円上に金属部４６ａ、４６ｂ、傾斜部５０ａ、５０ｂおよびセラミックス部４８ａ、４８ｂが構成されており、それぞれノックアウトピン２８およびパンチ３６の形状に沿った構成になっている。
【００５６】
そこで、被加工材としてセラミックス分散型銅合金を用い、鍛造金型１０により後方押し出し加工を行った。この銅合金は、引っ張り強度が４５０ＭＰａで、縦弾性率が１２０ＭＰａで、破断伸びが２８％であった。この銅合金は、図１５に示すように円柱状の素材６０として用意され、この素材６０が鍛造金型１０により製品６２に鍛造加工された。加工前の素材６０の硬度は、ＨＲＢ６０〜７０であり、鍛造後の製品６２の硬度は、ＨＲＢ７８〜８４となった。
【００５７】
この場合、現状の金型による鍛造加工では、数百ショットで素材６０の銅合金がパンチ３６の先端をコーティングしたような状態でこのパンチ３６に凝着してしまい、通常、１００ショット毎に前記パンチ３６をクリーニングする必要があった。これは、ＳＫＤ材の場合に一層顕著となり、数十ショットで凝着が生じるとともに、ＳＫＤ材そのものの中にまで浸透してしまい、ヤスリ等による除去が不可能であった。
【００５８】
これに対して、実施例２では、パンチ３６に凝着が生じるまでのショット数が数千ショットとなり、凝着が数十分の一に低減された。しかも、硬質皮膜層を施したものでは、より顕著な向上が図られた。これは、パンチ３６の表面が略セラミックス組成となり、熱伝導率が大きく向上して鍛造加工により発生する熱が速やかに加工部から移動したことと、前記パンチ３６自体の熱膨張も現状組成の金型に比べて小さいこと等による効果である。
【００５９】
この凝着を放置しておくと、加工圧力が急激に上昇して製品精度が悪くなるとともに、製品に傷を発生させかつ鍛造金型１０にかじりが生じてしまい、この鍛造金型１０が破壊に至るおそれがある。このため、パンチ３６先端のクリーニングを、現状超硬型では１００ショット毎に行い、本発明の無垢構成の鍛造金型１０では３０００ショット毎に行った。
【００６０】
次いで、現状超硬型と本発明に係る鍛造金型１０とを用い、型寿命までの総ショット数を検出する実験を行った。その結果、現状超硬型のＷＣ−１５Ｃｏの型寿命が８７００ショットである一方、本発明の無垢構成では、ＷＣ−１０Ｃｏ−Ｎｉ含浸の型寿命が４５万ショット、ＷＣ−１５Ｃｏ−Ｎｉ含浸の型寿命が３８万ショットと大幅に伸び、約５０倍〜４０倍の型寿命の向上が図られた。さらに、硬質皮膜層を施したものでは、ＷＣ−１０Ｃｏ−Ｎｉ含浸の型寿命が、１μｍの厚さのもので４２万ショット、３μｍ品で５０万ショット、８μｍ品で６０万ショット、１４μｍ品で５２万ショットおよび２０μｍ品で４５万ショットとなり、ＷＣ−１５Ｃｏ−Ｎｉ含浸の型寿命が、１μｍ品で３３万ショット、３μｍ品で４５万ショット、８μｍ品で５４万ショット、１４μｍ品で４８万ショットおよび２０μｍ品で３０万ショットとなった。
【００６１】
これにより、鍛造金型１０では、型寿命が大幅に向上するとともに、製品精度を有効に維持することができるという効果が得られる。なお、硬質皮膜層を施したものでは、１μｍ品および２０μｍ品の結果がよいものでなかった。
【００６２】
【発明の効果】
本発明に係る複合材製金型では、金型内部から金型表面に向かうに従って複合材中の金属成分の割合が漸減するため、実際に加工を行う金型表面部分が高硬度でかつ耐摩耗性を有する一方、金型内部が高靱性かつ高強度を有するとともに、この間の組成や物性が緩やかに変化する。これにより、耐用性に優れ、かつ、製品精度の向上が図られる。しかも、硬質皮膜層の密着性が向上するとともに、この硬質皮膜層を有効に薄く構成することができる。
【図面の簡単な説明】
【図１】本発明の実施形態に係る複合材製金型の縦断面説明図である。
【図２】前記金型を構成するダイリングの横断面図である。
【図３】前記金型を構成するノックアウトピンの横断面図である。
【図４】前記金型を構成するパンチの横断面図である。
【図５】焼結体の内部硬度変化を示す説明図である。
【図６】焼結体の粒成長状態を示す説明図である。
【図７】焼結体の粒成長状態を示す説明図である。
【図８】コバルト量と抗折強度の関係を示す説明図である。
【図９】ニッケル含浸量と硬度の関係を示す説明図である。
【図１０】コバルト含有量と弾性率の関係を示す説明図である。
【図１１】ニッケル濃度と破壊靱性値の関係を示す説明図である。
【図１２】温度と硬度の関係を示す説明図である。
【図１３】サイクル数と圧縮応力の関係を示す説明図である。
【図１４】コバルト量と引っ張り強度の関係を示す説明図である。
【図１５】前記金型で成形される前の素材を示す説明図である。
【図１６】前記素材に鍛造加工を施した後の製品の縦断面説明図である。
【符号の説明】
１０…鍛造金型 １２…固定型
１４…可動型 ２４…ダイリング
２８…ノックアウトピン ３６…パンチ
４０ａ、４０ｂ、４８ａ、４８ｂ…セラミックス部
４２ａ、４２ｂ、５０ａ、５０ｂ…傾斜部
４４、４６ａ、４６ｂ…金属部
４５ａ、４５ｂ、５２ａ、５２ｂ…ＴｉＮコーティング部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composite mold made of a composite material including a ceramic component and a metal component.
[0002]
[Prior art]
In general, forging processing is widely adopted as a highly productive processing method because a semi-finished product shape that approximates the product shape can be obtained from the raw material in a short processing time, or a desired product shape can be obtained. It is used for processing various kinds of metal.
[0003]
In this type of forging process, the work (material) is placed in the mold and a large force is applied to form and process the work through the stress. Therefore, the mold itself is very large. Power is acting. Furthermore, since the machining speed is high and the impact load is large, the mold material is required to have high hardness, high strength, and high toughness so as to be excellent in wear resistance and not to cause work galling. In particular, recently, demands for lower cost and higher added value of forged products have increased, and there is a tendency to increase the stress acting on the mold, and there is a demand for a mold that is tougher and has higher wear resistance. .
[0004]
In hot and warm forging, in order to further improve the oxidation resistance and heat resistance, SKD materials and SKH materials are mainly used as general mold materials in this field. not being used. This is because when a super hard material is used, the mold material is easily damaged or cracked due to impact stress, and the required characteristics cannot be satisfied. On the other hand, when an SKD material, an SKH material, or the like is used, there is a problem that a large stress cannot be applied because the hardness decreases and the strength decreases greatly as the temperature increases.
[0005]
In cold forging, the material is cut, annealed, and lubricated in separate steps, and the impact is reduced by a knuckle mechanism or link mechanism to set the collision speed to about 50 mm / s to 400 mm / s. Molding and processing are performed. Many molds (punch and die) used in this field are made of a hard and high wear-resistant cemented carbide and are shrink-fitted with an SKD material, an SKH material or the like. This type of mold can withstand about several hundred thousand shots, and has a mold life of 10 times or more compared to several thousand shots to tens of thousands shots in the case of iron-based materials. However, if the process and equipment management are not strictly performed, defects such as mold cracking and extremely short life will occur. Accordingly, there is a need for a mold material that is tougher and has higher wear resistance.
[0006]
As an improvement in wear resistance, for example, a hard coating is applied, but PVD has pointed out a problem of adhesion to the substrate of the coating. In addition, although the seizure resistance and the wear resistance are improved by CVD, there is a problem that cracks and embrittlement occur on the treated surface and the strength is reduced by about 30%.
[0007]
[Problems to be solved by the invention]
As described above, the characteristics required for a forging die are impact resistance, wear resistance, high compressive strength, high tensile strength, high toughness, high rigidity, heat resistance, high thermal conductivity, low thermal expansion, and the like. . Improving these characteristics using a homogeneous composite or super hard material conflicts with each other, such as a technique for increasing or decreasing the amount of metal and a technique for reducing or coarsening the size of ceramic particles. The technique must be taken.
[0008]
For example, from the viewpoint of impact resistance, it is necessary to increase the amount of metal by coarsening ceramic particles, but this reduces heat resistance, rigidity, etc. in addition to wear resistance. At that time, if the amount of metal is reduced and the ceramic particles are atomized, the wear resistance, rigidity and heat resistance are improved, but the impact resistance is greatly impaired, and the mold may be easily broken. . Therefore, in reality, forging dies that satisfy these various characteristics are not put into practical use, and are only dealt with by measures such as reinforcement and measures by surface treatment.
[0009]
Further, as a factor for reducing the die life, it has been pointed out that the fatigue strength resulting from the adhesion and deposition of the work material to the die, the increase in forging pressure and the increase in the heat generation amount due thereto. For this reason, conventionally, the metal on the surface of the die made of cemented carbide is reduced by dry etching using plasma or the dry method of chemically removing it, and the exposure rate of the ceramic is increased to improve the adhesion of the film. . However, when processing with a net shave, the forging pressure exceeds 100 MPa, and there are problems in film strength, film thickness, and adhesion.
[0010]
Therefore, when the development of a mold in which the vicinity of the mold surface layer where the forging process is actually performed has high hardness and wear resistance and the inside of the mold has high strength was examined, Japanese Patent No. 2593354 by the present applicant. And the application of “a composite material having a gradient function including ceramic powder and a metal component” disclosed in JP-A-8-127807 and the like.
[0011]
That is, the present invention provides a composite mold made of a composite material that has a gradient function in which physical properties such as toughness and strength are improved as the surface goes to the inside with high hardness, and that can improve film adhesion and the like. With the goal.
[0012]
[Means for Solving the Problems]
The composite material mold according to the present invention contains at least one ceramic component selected from WC, TiC, TiN, Mo ₂ C, TaC, NbC, Cr ₃ C ₂ or VC, and a metal component. And the ratio of the ceramic component is set to 70 to 97 wt%. Further, the composite material includes a ceramic part having a metal component of 3 wt% or less, a metal part having a larger proportion of the metal component than the ceramic component, and as the metal part moves from the metal part toward the ceramic part. A slope portion where the ratio of the metal component gradually decreases, the thickness of the ceramic portion is set to 0.3 mm or more, and the thickness of the slope portion is set to 0.3 mm or more. The ceramic portion is covered with a hard coating layer.
[0013]
That is, in the mold, three layers of a layer in which the amount of metal gradually decreases from the inside toward the surface, a layer in which the metal is accumulated, and a layer in which the metal is greatly reduced to have a substantially ceramic composition are organically linked. . For this reason, the vicinity of the mold surface is a highly hard layer with reduced metal, an inclined layer in which the metal gradually decreases or gradually increases from the vicinity of the surface inward, and the interior has an increased amount of metal than in the initial state. It becomes a high strength and high toughness layer. Accordingly, the propagation of stress is gradually relaxed and resistance to a large stress increases. The strength is improved by 30% to 50%, and the toughness is improved by 200% to 300% or more.
[0014]
In addition, the amount of metal in the high-hardness layer (mold surface) can be reduced to 3 wt% or less, and the adhesion and the like during hard film coating can be improved. In addition, since the hard coating is provided on the highly hard layer, the thickness of the coating can be reduced, and the stress generated at the interface between the coating and the material can be effectively reduced. As a result, the mold life can be improved and the product accuracy can be reliably maintained.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a longitudinal cross-sectional explanatory view of a composite forging die 10 according to an embodiment of the present invention. The forging die 10 performs backward extrusion molding, and includes a fixed die 12 that constitutes a lower die and a movable die 14 that constitutes an upper die. The pressure ring 20 and the die 22 are clamped and supported via the member 18. A die ring 24 is fixed to the center of the die 22, and a product cavity 26 is formed in the die ring 24. A knockout pin 28 is slidably disposed in the cavity 26 through the pressure ring 20.
[0016]
The movable die 14 includes a punch attachment body 30, and a punch 36 is attached to the punch attachment body 30 via a punch guide 32 and a nut member 34. The die ring 24, the knockout pin 28, and the punch 36 are made of a composite material including a ceramic component and a metal component.
[0017]
As shown in FIG. 2, the die ring 24 is provided with ceramic-rich ceramic portions 40a and 40b on the outer peripheral surface and inner peripheral surface, which are surfaces, and inclined portions 42a and 42b on the inner side of the ceramic portions 40a and 40b. A metal-rich metal portion 44 is provided via the. In the inclined portions 42a and 42b, the ratio of the metal component gradually decreases from the metal portion 44 toward the outer surface and the inner surface, respectively. Hard coating layers, for example, TiN coating portions 45a and 45b are provided on the surfaces of the ceramic portions 40a and 40b.
[0018]
As shown in FIGS. 3 and 4, the knockout pin 28 and the punch 36 are provided with metal-rich metal portions 46 a and 46 b inside and ceramic-rich ceramic portions 48 a and 48 b on the surface. Between the metal parts 46a and 46b and the ceramic parts 48a and 48b, inclined parts 50a and 50b in which the ratio of the metal component gradually decreases from the inside toward the surface are provided. Hard coating layers, for example, TiN coating portions 52a and 52b are provided on the surfaces of the ceramic portions 48a and 48b.
[0019]
The metal component in the composite material is mainly composed of most metals except for aluminum (Al) and magnesium (Mg), which are low melting point metals, and practically group VIII elements iron (Fe) and nickel in the periodic table. (Ni) or cobalt (Co) is at least one selected from the group consisting of manganese (Mn), chromium (Cr), vanadium (V), molybdenum (Mo), etc. It is mixed for improvement.
[0020]
Ceramic components in the composite material include tungsten carbide (WC), titanium carbide (TiC), titanium nitride (TiN), dimolybdenum carbide (Mo ₂ C), tantalum carbide (TaC), niobium carbide (NbC), chromium carbide ( Cr ₃ C ₂ ) or vanadium carbide (VC) is mainly used.
[0021]
The amount of ceramics is

And the balance is metal. The particle size of these ceramic components can be used within the range of an ultrafine particle composition having an average particle size of sub-μm to about 30 μm.
[0022]
In the present embodiment, a grain growth accelerator is added in a size close to atoms so that the ceramic particles grow rapidly at the same time as densification by sintering or at the same time as densification, and the concentration is controlled by controlling the concentration of the particles. And the accompanying particle rearrangement and metal concentration gradient. Therefore, the smaller the size of the ceramic particles in the initial state, the greater the effect of the grain growth accelerator and the greater the degree of growth. On the other hand, the larger the size of the ceramic particles in the initial state, the smaller the degree of growth.
[0023]
Therefore, the average of the ceramic component is a condition under which the formation of the hard layer portion accompanying the growth, the formation of the functionally graded layer in which the metal gradually decreases, and the formation of the high strength and toughness layer in which the amount of metal increases is effectively performed. The particle size is set to 0.3 μm to 30 μm. Powder raw materials having an average particle size of less than 0.3 μm are considerably expensive and difficult to use substantially. On the other hand, powder raw materials having an average particle size of more than 30 μm are less than 10 times the growth of ceramic particles. The characteristics are not improved so much and the cost is increased.
[0024]
The metal component and the ceramic component in the composite material are appropriately selected depending on use conditions or the like, or the respective amounts are changed. For example, for the purpose of demagnetization, prevention or suppression of reaction with the workpiece, improvement of heat resistance, improvement of rigidity and wear resistance, etc., nickel as a metal component, titanium carbide as a ceramic component, Addition or removal of titanium nitride, chromium carbide or vanadium carbide is performed.
[0025]
When the ceramic component exceeds 97 wt%, the amount of the metal component is too small and the strength becomes insufficient, and no difference in tensile strength is observed even when compared with conventional materials. Moreover, chipping or the like is likely to occur at the edge portion during use of the forging die 10, and it is difficult to put it to practical use. Here, when the ceramic component is 97 wt%, the metal component is 3 wt%, but the inside is a metal component of 7 wt% or more and the surface is a metal component of 0.3 wt% to 1.5 wt%, and has high rigidity. In addition, a forging die 10 having high strength and high toughness can be obtained.
[0026]
The ceramic component is more preferably 95 wt%, and the metal component on the surface is 0.3 wt% to 2 wt%. For this reason, it has high rigidity, high wear resistance, and high heat resistance, has an internal metal component of about 10 wt%, has excellent strength and toughness, and has characteristics superior to the current cemented carbide (current material) It becomes. On the other hand, if the ceramic component is less than 70 wt%, the amount of metal increases and the physical properties and the like are saturated, and the wear resistance, rigidity, corrosion resistance, and the like deteriorate.
[0027]
Therefore, if the ceramic component is in the range of 70 wt% to 97 wt%, the amount of metal on the surface is 0.1 wt% to 8 wt%, and the amount of internal metal is about 7 wt% to 40 wt%. Thereby, the effect that most values, such as abrasion resistance, thermal conductivity, intensity | strength, rigidity, and impact resistance, greatly exceed the present material is acquired.
[0028]
The thickness of the inclined portions 42a, 42b, 50a and 50b where the amount of metal gradually decreases or gradually increases is several hundred μm or more, preferably 0.3 mm or more. That is, there is a demand in the design of the forging die 10 in order to relieve the thermal stress and load stress acting by the generation of heat and the generation of stress. For example, the thermal stress will be described. The amount of metal and heat conduction, the particle size and heat conduction have a correlation, and the generated thermal stress is a gradient of heat transfer. Therefore, the inclined portions 42a, 42b, and 50a. And if the thickness of 50b changes, the generated thermal stress itself also changes. For this reason, when the thickness is several μm to several tens of μm, the amount of thermal stress that is generated and the amount of relaxation of stress generated during processing become small, and durability cannot be improved. Moreover, the thickness of the ceramic portions 40a, 40b, 48a and 48b needs to be 0.3 mm or more. This is to prevent the ceramic component from being removed in the finishing process, losing its effectiveness, and reducing the adhesion during coating.
[0029]
The surface hardness of the die ring 24, the knockout pin 28 and the punch 36 constituting the forging die 10 is set to HRA90 or higher. If the surface hardness is less than HRA90, it is necessary to perform etching or the like as a pretreatment at the time of coating, and the effect is reduced, and the exposure ratio of the metal to the surface is increased, and there are problems in the adhesion and strength of the coating layer. . In addition, the coefficient of friction (μ) between the workpiece and the forging die 10 becomes high, which causes an increase in heat generation, an increase in generated stress, and an increase in load stress on the die, causing adhesion and causing the workpiece. In addition to the rough surface, the forging die 10 itself is easily worn. Therefore, if the surface hardness is set to HRA 90 or higher, preferably HRA 91 or higher, the surface roughness and accuracy of the obtained product are effectively improved, and the die life of the forging die 10 is improved.
[0030]
The grain growth promoter is appropriately selected. For example, when nickel is used, even if the metal component is 10 wt% and the ceramic component is only simple tungsten carbide, the mold surface hardness is HRA93. This can be done. Further, by replacing a part of the ceramic component with titanium carbide, titanium nitride or the like, or changing the grain growth accelerator to manganese, chromium, titanium or aluminum, the surface hardness becomes close to HRA96.
[0031]
Said surface hardness becomes more than the value which gave hard film coatings, such as ceramics, and it can be in the state which has almost no surface metal amount. At that time, if a hard coating layer, for example, a hard ceramic coating is applied to the mold surface, the amount of metal on the surface is greatly reduced as compared with conventional cemented carbide or composite molds. It becomes possible to improve the adhesiveness of all at once.
[0032]
By applying a hard ceramic coating to the mold surface, adhesion with the work material and slidability between the work material and the mold surface are improved. In addition, it is not necessary to change from the mold material in accordance with the work material and process, and it is possible to cope with the change of the hard coating material, and the cost can be easily reduced. Examples of the hard coating material include a DLC film (diamond-like carbon), diamond, TiN, TiC, TiCN, Al ₂ O _3, or Cr ₃ C ₂ .
[0033]
The thickness of the hard coating layer is set within a range of 3 μm to 15 μm. If the thickness is less than 3 μm, the film thickness is not sufficient, and a desired effect cannot be obtained. On the other hand, if the thickness exceeds 15 μm, after the film is formed by CVD, PVD or the like, the residual stress due to the film increases, the film itself cracks, and the function is lowered. Therefore, if the thickness of the TiN coating portions 45a, 45b, 52a and 52b, which are hard coating layers, is set within the range of 3 μm to 15 μm, more preferably within the range of 5 μm to 10 μm, no problems occur. Further, h5, H5, h6, H6, etc., which are the fitting accuracy of the mold, can be sufficiently handled with normal mold processing accuracy.
[0034]
Normally, when a hard film coating is applied to a cemented carbide mold, if the mold shape or cavity shape becomes complicated, uniform coating is difficult, and there is a difference of several μm in thickness of about 10 μm. It was happening. For this reason, in order to have a sufficient function as a hard film coating, the thickness of this hard film coating was set in the range of several tens to several hundreds of μm.
[0035]
On the other hand, in this embodiment, the mold surface itself already constitutes ceramic parts 40a, 40b, 48a and 48b in a substantially ceramic state, and the function as ceramics is the ceramic parts 40a, 40b, 48a and 48b are responsible. Accordingly, the TiN coating portions 45a, 45b, 52a and 52b need only improve the reactivity with the workpiece, adhesion, oxidation resistance, etc., and the thickness is sufficient within the range of 3 μm to 15 μm. It is. Thereby, it is not necessary to prepare various components of the gradient composite material according to the workpiece, and it is only necessary to change the hard coating layer, so that it is economical.
[0036]
In the present embodiment, an additive that allows the ceramic component, which is a constituent component of the composite material, to easily grow particles in the sintering process is supplied by impregnation as a size close to an atom, for example, as an ionic solution. For this reason, the concentration gradient of the grain growth accelerator is adjusted by the drying process, the evaporation rate condition of the solvent during the impregnation, the conditions such as the immersion time, the atmosphere management and the temperature management during the sintering, and the like. Thereby, the ceramic portions 40a, 40b, 48a and 48b which are high-hardness layers along the shapes of the die ring 24, the knockout pin 28 and the punch 36, and the inclined portions 42a, 42b, 50a and 50b where the metal gradually increases or decreases are provided. Can be formed. Therefore, it becomes possible to obtain the forging die 10 with improved function and performance and excellent durability. In addition, by applying a hard coating layer on the mold surface, the hard coating layer matched to the workpiece can be optimally applied under optimal conditions.
Example 1
In Example 1, 89 wt% of tungsten carbide (WC) powder having an average particle size of 2.2 μm, 2 wt% of niobium carbide (NbC) having an average particle size of 2 μm, and tantalum carbide (TaC) having an average particle size of 2.4 μm. 1 wt% and metallic cobalt (Co) having an average particle size of 0.8 μm were prepared in a composition of 8 wt%, and the mixture was sufficiently mixed for 72 hours by a ball mill using an organic solvent as a medium. This corresponds to the composition of K-10 to V-10, 20 in the JIS classification.
[0037]
In addition, as an ordinary carbide mold composition material, tungsten carbide having an average particle diameter of 3 μm and metallic cobalt having an average particle diameter of 0.8 μm are within a range of 95 wt% to 70 wt% and 5 wt% to 30 wt%, respectively. And mixed well under similar mixing conditions.
[0038]
After the above mixing, the organic solvent content is adjusted to 9%, and binder-less in order to avoid the influence of the molding binder, and the molding pressure is 100 MPa by the hydrostatic pressure molding method in the mold. The molded body was molded so that the diameter after sintering was 18 mm and the length was 150 mm. The single-side machining allowance after sintering is set to 0.1 mm to 0.2 mm. After removing the organic solvent remaining in the molded body at a molding pressure of 50 Pa in nitrogen gas, the molded body was calcined at 900 ° C. for 30 minutes to obtain a calcined body. This is to prevent breakage when the molded body is impregnated.
[0039]
Next, in consideration of handleability, convenience and safety as a grain growth accelerator, a 10% strength Ni salt aqueous solution is prepared, and after calcination is immersed in this, it is sufficiently dried by exhaust hot air drying at 130 ° C. And the inclination of the nickel concentration in the pre-fired body was attempted. And it hold | maintained under 1400 degreeC under 50 Pa pressurization under nitrogen gas distribution for 1.5 hours, and obtained the sintered compact. In addition, in order to remove the influence of the surface layer, the surface layer of the sintered body was removed by 0.1 mm to 0.2 mm on one side to obtain a test material.
[0040]
On the other hand, a solution in which the Ni ion concentration is changed is prepared by impregnating a pre-fired body, and these are embedded in the powder and adjusted so as not to cause a concentration difference due to rapid evaporation of moisture. Sintering and processing were performed to obtain test materials.
[0041]
Therefore, among the obtained test materials, the hard layer of the test material having 8 wt% cobalt with niobium carbide and tantalum carbide arranged is 0.3 mm to 0.4 mm before processing, and 0.2 mm to 0.00 mm after processing. The surface hardness was about 3 mm and HRA93.4. This value is close to that with a hard coating, and can be used as a mold material as it is.
[0042]
FIG. 5 shows hardness values that change from the surface to the inside of the test material (sintered body). As a result, the hardness gradually decreased as the metal ions increased toward the inside of the sintered body, and the amount of change in the hardness was as large as about HRA6. Furthermore, it was detected from this decrease in hardness that the thickness of the functionally graded layer was about 8 mm. In this test material, the amount of metal on the surface is about 3% in terms of area ratio, which is reduced to 1/7 to 1/8 as compared with the initial composition state. The amount of metal in the central part reached 26% in terms of area ratio, which was more than twice that in the initial state.
[0043]
Next, the cross section of the test material was observed with a microscope, an electron microscope, or the like, and the particle size (μm) was measured. The results shown in FIGS. 6 and 7 were obtained. FIG. 6 shows a test material containing niobium carbide and the like, and the size of the particles near the surface grew to about 4 to 5 times. On the other hand, FIG. 7 shows a test material having a composition of WC-8Co in which the ceramic component is only tungsten carbide with the same amount of cobalt, and the particle size near the surface has grown to 30 μm to 40 μm. The particle size was about 10 to 13 times.
[0044]
As shown in FIGS. 6 and 7, the size of the particles gradually decreased with the increase in the amount of metal, and almost no grain growth occurred in the central portion, and the grain size in the initial state was maintained. The reason why the grain growth of WC-8Co having a simple composition is remarkable as compared with those added with niobium carbide or tantalum carbide is that these additive powders suppress the grain growth.
[0045]
Fig. 8 shows the adjustment of Ni ion concentration, which is a grain growth accelerator, to 10%, changing the amount of metallic cobalt contained in the composite material, and impregnating Ni ions (test material) and not impregnating. (Current material) shows the results of an experiment comparing the bending strength (GPa). The target sample contains niobium carbide and the like. In the Ni-impregnated test material, it is embedded in the powder after impregnation to suppress the movement of the ion concentration to constitute a homogeneous composition. In this test material, the bending strength is effectively improved as compared with the current material. That is, the strength is usually lowered by the grain growth, but the strength is increased by adding the grain growth agent in a size close to that of the atom.
[0046]
FIG. 9 shows the results of measuring the hardness of the test material while changing the Ni ion concentration as the grain growth accelerator and keeping the composite composition constant at 8 wt% cobalt. This suggests the existence of a maximum Ni ion amount, as in FIG.
[0047]
FIG. 10 shows the change in rigidity when the Ni ion concentration as a grain growth accelerator is kept constant at 10%. In order to detect the stiffness, the actual longitudinal modulus was measured. As shown in FIG. 10, it has been found that the longitudinal elastic modulus, which is apparent rigidity, is increased by the grain growth of the surface, and that the change in rigidity is related to the particle size of the composite particles even in a homogeneous composite material.
[0048]
FIG. 11 correlates with FIG. 9 and shows the relationship between the Ni ion concentration (%) and the fracture toughness value (MPam ^1/2 ). In the current material, the toughness decreases as the strength increases, and the test material exhibits specific physical properties.
[0049]
FIG. 12 shows the change in hardness (HRA) with respect to temperature change. In FIG. 12, the normal cemented carbide is a commercially available V-10 equivalent, and the hardness of the test material is higher than HRA10 compared to the normal cemented carbide. In addition, the test material can maintain its hardness at a high value even when the temperature reaches high, and has an effect that it can be effectively used in a high temperature environment. A small change in hardness due to temperature means that its thermal expansion is small. Therefore, the thermal expansion of the hard coating layer becomes very small, and the adhesion with the base material is improved.
[0050]
FIG. 13 shows the result of comparison of the compressive stress between the test material and the current super hard material. Note that the WC-15Co composition was used so that fatigue characteristics could be easily obtained. As a result, the compressive stress was greatly improved in the test material as compared with that using the present super hard material, and an improvement of about 30% was recognized in practice.
[0051]
FIG. 14 shows the results of measuring the tensile strength (MPa) of the current configuration and the test material by changing the cobalt content with the WC-Co composition. As a result, in the test material not impregnated with nickel (homogeneous), the measurement was difficult, the variation of the measured value was increased, and the brittleness was conspicuous. The tendency was the same even when the amount of metallic Co exceeded 20 wt%. In contrast, in the nickel-impregnated (gradient composition) test material, the difference in the measured value up to 5 wt% of cobalt was large, but the variation was small when the cobalt amount was higher, and the tensile strength itself was also large. Became. When the tensile strength was compared, a value of 2 to 3 times was obtained with the test material of the homogeneous material as compared with the current configuration, and the value of the test material with the gradient composition was further increased than that of the homogeneous material. This is due to an increase in rigidity and a hard surface effect.
[0052]
Therefore, in Example 1, compared with the present superhard material, SKD material, SKH material, etc., it surpasses all the characteristics which should be provided as the forging die 10, and compared with the conventional forging die, durability and The effect that remarkable improvement is achieved in terms of function is obtained.
Example 2
A forging die 10 shown in FIG. 1 was manufactured, and the forging die 10 was tested. The die ring 24, the knockout pin 28 and the punch 36 constituting the forging die 10 have a WC-Co composition, the cobalt amounts are 10 wt% and 15 wt%, and a Ni salt aqueous solution is used as a grain growth accelerator. The same production method as in Example 1 was used. The precision and surface roughness of the forging die 10 were the same as those of the current die. The mating intersection was H6-h6. The composition of the hard coating layer was 1 μm, 3 μm, 8 μm, 14 μm and 20 μm by CVD, and TiN coating portions 45a, 45b, 52a and 52b were formed.
[0053]
In the die ring 24, the knockout pin 28, and the punch 36, the thicknesses of the ceramic portions 40a, 40b, 48a, and 48b, which are the high-hardness layer portions, are 5 mm, 5 mm, 1 mm, and 1 mm, respectively. .3, HRA93.4 and HRA93.4, and WC-15Co was substantially the same as HRA93.2, HRA93.4 and HRA93.4. At that time, the amount of each surface exposed metal was substantially the same.
[0054]
In addition, the thicknesses of the inclined portions 42a, 42b, 50a and 50b are 14 mm, 14 mm, 6 mm and 6 mm for WC-10Co, respectively, 13 mm, 13 mm, 6 mm and 6 mm for WC-15Co, respectively, and the remaining portions are high in strength and high. Metal parts 44, 46a and 46b which are tough layers were formed.
[0055]
As shown in FIG. 2, the die ring 24 has a donut shape, and is provided with a ceramic portion 40 b, an inclined portion 42 b and a metal portion 44 from the inner peripheral surface side, and further inclined to the outside of the metal portion 44. A portion 42a and a ceramic portion 40a are provided. For this reason, the die ring 24 is very tough as a whole and has an effective configuration. In the knockout pin 28 and the punch 36, metal portions 46a and 46b, inclined portions 50a and 50b, and ceramic portions 48a and 48b are formed on concentric circles, and are configured along the shapes of the knockout pin 28 and the punch 36, respectively. Yes.
[0056]
Therefore, a ceramic-dispersed copper alloy was used as a work material, and backward extrusion was performed using a forging die 10. This copper alloy had a tensile strength of 450 MPa, a longitudinal elastic modulus of 120 MPa, and an elongation at break of 28%. The copper alloy was prepared as a columnar material 60 as shown in FIG. 15, and the material 60 was forged into a product 62 by the forging die 10. The hardness of the raw material 60 before processing was HRB 60 to 70, and the hardness of the product 62 after forging was HRB 78 to 84.
[0057]
In this case, in the forging process using the current mold, the copper alloy of the material 60 adheres to the punch 36 in a state where the tip of the punch 36 is coated in several hundred shots. It was necessary to clean the punch 36. This was even more remarkable in the case of the SKD material. Adhesion occurred in several tens of shots and penetrated into the SKD material itself, so that removal with a file or the like was impossible.
[0058]
On the other hand, in Example 2, the number of shots until adhesion was generated on the punch 36 became several thousand shots, and the adhesion was reduced to several tenths. Moreover, in the case where the hard coating layer was applied, a more remarkable improvement was achieved. This is because the surface of the punch 36 has a substantially ceramic composition, the heat conductivity is greatly improved, and the heat generated by the forging process is quickly transferred from the processed part, and the thermal expansion of the punch 36 itself is also a gold of the current composition. This is the effect of being smaller than the mold.
[0059]
If this adhesion is left unattended, the processing pressure will rise rapidly, resulting in poor product accuracy, scratches on the product, and galling in the forging die 10, which will break the forging die 10. There is a risk of reaching. For this reason, the tip of the punch 36 was cleaned every 100 shots in the present cemented carbide die, and every 3000 shots in the forging die 10 of the solid configuration of the present invention.
[0060]
Next, an experiment was performed to detect the total number of shots up to the die life using the current cemented carbide die and the forging die 10 according to the present invention. As a result, while the mold life of the current cemented carbide WC-15Co is 8700 shots, in the solid configuration of the present invention, the mold life of WC-10Co-Ni impregnation is 450,000 shots, and the mold of WC-15Co-Ni impregnation is The service life was greatly increased to 380,000 shots, and the mold life was improved by about 50 to 40 times. Furthermore, with a hard coating layer, the mold life of WC-10Co-Ni impregnation is 420,000 shots with a thickness of 1 μm, 500,000 shots with a 3 μm product, 600,000 shots with an 8 μm product, and 14 μm products with a 14 μm product. With 520,000 shots and 20μm products, the WC-15Co-Ni impregnation mold life is 330,000 shots with 1μm products, 450,000 shots with 3μm products, 540,000 shots with 8μm products, and 480,000 shots with 14μm products And it became 300,000 shots with a 20 μm product.
[0061]
Thereby, in the forging die 10, the die life is greatly improved and the product accuracy can be effectively maintained. In addition, in what gave a hard film layer, the result of a 1 micrometer product and a 20 micrometer product was not good.
[0062]
【The invention's effect】
In the composite material mold according to the present invention, since the ratio of the metal component in the composite material gradually decreases from the inside of the mold toward the mold surface, the surface portion of the mold that is actually processed has high hardness and wear resistance. On the other hand, the inside of the mold has high toughness and high strength, and the composition and physical properties in the meantime change gradually. Thereby, it is excellent in durability and improvement in product accuracy is achieved. In addition, the adhesion of the hard coating layer is improved, and the hard coating layer can be effectively made thin.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view illustrating a composite material mold according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a die ring constituting the mold.
FIG. 3 is a cross-sectional view of a knockout pin constituting the mold.
FIG. 4 is a cross-sectional view of a punch constituting the mold.
FIG. 5 is an explanatory view showing a change in internal hardness of a sintered body.
FIG. 6 is an explanatory view showing a grain growth state of a sintered body.
FIG. 7 is an explanatory view showing a grain growth state of a sintered body.
FIG. 8 is an explanatory diagram showing the relationship between cobalt content and bending strength.
FIG. 9 is an explanatory diagram showing the relationship between nickel impregnation amount and hardness.
FIG. 10 is an explanatory diagram showing the relationship between cobalt content and elastic modulus.
FIG. 11 is an explanatory diagram showing the relationship between nickel concentration and fracture toughness value.
FIG. 12 is an explanatory diagram showing the relationship between temperature and hardness.
FIG. 13 is an explanatory diagram showing the relationship between the number of cycles and compressive stress.
FIG. 14 is an explanatory diagram showing the relationship between cobalt content and tensile strength.
FIG. 15 is an explanatory view showing a material before being molded by the mold.
FIG. 16 is a longitudinal cross-sectional explanatory view of a product after forging the material.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Forging die 12 ... Fixed die 14 ... Movable die 24 ... Die ring 28 ... Knockout pin 36 ... Punch 40a, 40b, 48a, 48b ... Ceramic part 42a, 42b, 50a, 50b ... Inclined part 44, 46a, 46b ... Metal parts 45a, 45b, 52a, 52b ... TiN coating part

Claims (5)

A composite material containing at least one ceramic component selected from WC, TiC, TiN, Mo ₂ C, TaC, NbC, Cr ₃ C ₂ or VC, and a metal component, A composite material mold in which the ratio is set to 70 to 97 wt%,
The composite material includes: a ceramic part in which the metal component is 3 wt% or less; a metal part in which the ratio of the metal component is larger than the ceramic component; And a slope portion where the ratio of
The ceramic part has a thickness of 0.3 mm or more, and the inclined part has a thickness of 0.3 mm or more,
And composite material mold the ceramic part, characterized that you have been coated with a hard coating layer. 2. The composite metal mold according to claim 1, wherein the hard coating layer contains TiN, TiC , diamond-like carbon, diamond, TICN, Cr ₃ C ₂ or Al ₂ O _3. Type.   3. The composite material mold according to claim 1, wherein the thickness of the hard coating layer is set in a range of 3 μm to 15 μm. The composite metal mold according to any one of claims 1 to 3 , wherein the metal component is at least one selected from Fe, Ni, and Co. Type. 5. The composite material mold according to claim 4 , wherein the metal component further contains Mn, Cr, V, or Mo.

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