JP4339449B2

JP4339449B2 - Carbide material for hob

Info

Publication number: JP4339449B2
Application number: JP19047399A
Authority: JP
Inventors: 功櫻木; 將隆米倉; 楠彦阪上; 信一河野; 勉山本
Original assignee: Dijet Industrial Co Ltd
Current assignee: Dijet Industrial Co Ltd
Priority date: 1999-07-05
Filing date: 1999-07-05
Publication date: 2009-10-07
Anticipated expiration: 2019-07-05
Also published as: JP2001020029A

Description

【０００１】
【発明の属する技術分野】
この発明は、歯車を加工するのに使用するホブを製造するのに用いるホブ用材料に係り、特に、耐チッピング性や耐熱亀裂性に優れ、安定した高速切削が行えるホブ用超硬材料に関するものである。
【０００２】
【従来の技術】
従来、歯車を加工するのにホブが最も多く使用されており、このホブを構成する材料としては、一般に高速度鋼が主流で用いられていた。
【０００３】
しかし、このような高速度鋼を用いたホブにより歯車を加工する場合、冷却用の切削オイル等を供給して切削させる湿式切削が行われており、発煙や切削オイルの飛散等によって工場環境が悪くなるという問題があり、またその切削速度が遅くて生産能率が低く、さらに溶着等によって、十分な歯切精度が得られにくいという問題があった。
【０００４】
このため、従来においても、ホブを構成する材料に超硬合金を用いた超硬ホブについて開発が行われていた。
【０００５】
ここで、超硬合金を用いた超硬ホブの場合、高速での切削が可能になって生産能率が向上すると共に、乾式での切削が行えて、工場環境等が悪化するのを抑制することができ、また歯切精度も高くなって仕上げ加工等の後加工が容易になり、さらに高硬度材料で構成された歯車の加工も行えるという利点もあった。
【０００６】
しかし、ホブにおいては切削機構が複雑なため、上記のような超硬ホブを用いて歯車加工を行った場合、この超硬ホブの切れ刃にチッピングや熱亀裂が発生しやすく、長期にわたって安定した歯車加工が行えないという問題があった。
【０００７】
このため、従来においては、超硬ホブにおける刃先形状やホブ形状を改善したり、ホブ盤を改善して、チッピングや熱亀裂の発生を防止することが検討されているが、十分な効果が得られていないのが現状である。
【０００８】
さらに、このような超硬ホブを大気中に放置した場合に、超硬ホブが次第に腐蝕されて劣化し、またこの超硬ホブを再研削した場合にも、超硬ホブが研削液によっては劣化し、その工具寿命が短くなるという問題もあった。
【０００９】
【発明が解決しようとする課題】
この発明は、超硬合金を用いた超硬ホブにおける上記のような問題を解決することを課題とするものであり、歯車を加工する時に超硬ホブにおける切れ刃にチッピングや熱亀裂が発生するのを抑制し、また超硬ホブが大気中において酸化されて劣化したり、再研削時における研削液によっては劣化するのを抑制し、長期にわたって安定した歯車加工が行える超硬ホブが得られるようにすることを課題とするものである。
【００１０】
【課題を解決するための手段】
この発明においては、上記のような課題を解決するため、ＷＣ−βｔ−Ｃｏ系の超硬合金からなるホブ用超硬材料において、上記の超硬合金中に結合相を構成するＣｏが８〜１３重量％の範囲で含有されると共に、上記のβｔ相を構成する成分中、ＷＣを除いた他の成分が超硬合金中に１６〜２８重量％の範囲で含有され、このＷＣを除いた他の成分中にＴｉＣが３５〜６０重量％の範囲で含有され、この超硬合金における飽和磁化％が７８〜８７％、抗磁力が１８０〜２８０Ｏｅの範囲になるようにしたのである。
【００１１】
ここで、この発明におけるホブ用超硬材料において、超硬合金中に結合相を構成するＣｏが８〜１３重量％の範囲で含有されるようにした理由は、Ｃｏの量が上記の範囲よりも少なくなると、超硬ホブにおける切れ刃の耐欠損性が低下して、初期にチッピングが生じやすくなる一方、Ｃｏの量が上記の範囲よりも多くなると、得られる超硬合金の硬さが低下して、超硬ホブにおける切れ刃の耐摩耗性が低下し、長期にわたって歯切精度を維持できない。また、切削速度を３００ｍ／ｍｉｎ以上にして歯車加工を行う場合には、切屑と超硬合金との親和性が増大して、溶着による欠損が生じやすくなると共に塑性変形しやすくなる。
【００１２】
また、この発明における上記のβｔ相は、一般に知られているようにＷＣ−ＴｉＣ−ＴａＣ（ＮｂＣ）の固溶体相を意味し、Ｂ１型構造の相であり、Ｔｉ，Ｔａ等の窒化物が固溶されていてもよい。
【００１３】
そして、この発明におけるホブ用超硬材料において、上記のβｔ相を構成する成分中、ＷＣを除いた他の成分が超硬合金中に１６〜２８重量％の範囲で含有されると共に、このＷＣを除いた他の成分中にＴｉＣが３５〜６０重量％の範囲で含有されるようにした理由は、ＷＣを除いた他の成分の量及びＷＣを除いた他の成分中におけるＴｉＣの量が上記の範囲よりも少なくなると、超硬合金中におけるβｔ相の量が少なくなり、超硬合金における耐溶着性が低下して、超硬ホブに切屑の溶着による欠損が生じやすくなるためであり、特に、超硬ホブにおいてはすくい面を再研削しながら使用するため、、すくい面にコーティング膜を設けないことが多く、このため、このような切屑の溶着による欠損が生じやすくなる。一方、ＷＣを除いた他の成分の量及びＷＣを除いた他の成分中におけるＴｉＣの量が上記の範囲よりも多くなると、超硬合金の靱性が低下し、超硬ホブの刃先に初期欠損が生じやすくなるためである。
【００１４】
また、この発明におけるホブ用超硬材料において、上記の超硬合金における飽和磁化％が７８〜８７％の範囲になるようにした理由は、飽和磁化％が上記の範囲よりも低くなると、Ｗ₃Ｃｏ₃Ｃ₃からなる脆いη相が超硬合金の組織中に現れ、超硬ホブの刃先に初期欠損が生じやすくなる一方、飽和磁化％が上記の範囲よりも高くなると、Ｃｏ結合相の固溶強化が不十分で、超硬ホブの切れ刃に欠損や熱亀裂が発生しやすくなると共に、疲労によるチッピングも生じやすくなるためである。なお、上記の飽和磁化％は、超硬合金の飽和磁化値をＭ₀、Ｃｏの飽和磁化値をＭ₁、超硬合金中におけるＣｏの量をａ（ｗｔ％）とした場合、下記の式によって求められる。
【００１５】
飽和磁化（％）＝［Ｍ₀／（Ｍ₁・ａ／１００）］×１００
【００１６】
また、この発明におけるホブ用超硬材料において、超硬合金における抗磁力が１８０〜２８０Ｏｅの範囲になるようにした理由は、抗磁力が上記の範囲より低くなると、超硬合金中に３μｍ以上の粗い粒子のＷＣ相が比較的多く存在する組織になり、超硬ホブの切れ刃に欠損や熱亀裂が発生しやすくなるためであり、特に、超硬ホブにおいては切れ刃にホーニングをしない場合が多いため、超硬合金中におけるＷＣ相の粒子を細粒にして刃立ち性を向上させ、加工する歯車の歯形精度を向上させる必要がある。一方、超硬合金における抗磁力が２８０Ｏｅを越える場合には、超硬合金中におけるＷＣ相の粒子が細かくなり過ぎると共に、特に超硬合金中におけるＣｏの量が８〜１０重量％と少ない場合には、超硬ホブの切れ刃に疲労によるチッピングが生じやすくなる。
【００１７】
特に、この発明におけるホブ用超硬材料のように、超硬合金における飽和磁化％を７８〜８７％の範囲にすると共に、超硬合金における抗磁力を１８０〜２８０Ｏｅの範囲にすると、これらの重畳作用によって、超硬ホブの切れ刃に欠損や熱亀裂が発生するのを抑制する効果が著しく向上する。
【００１８】
そして、上記のような特性を有するホブ用超硬材料を用いて超硬ホブを作製した場合、歯車を加工する時に超硬ホブの切れ刃にチッピングや熱亀裂が発生するのが十分に抑制されると共に、この超硬ホブが大気中において腐蝕されて劣化したり、再研削時における研削液によっては劣化するのが抑制され、長期にわたって安定した歯車加工が行えるようになる。
【００１９】
また、この発明の請求項２に示すように、超硬合金に対してＣｒが０．２〜１．０重量％の範囲になるようにして、Ｃｒを結合相を構成するＣｏ中に固溶させると、超硬合金の耐酸化性及び耐腐蝕性が向上し、超硬ホブが大気中において腐蝕されて劣化したり、研削液によっては劣化したりするのがより一層抑制されて、工具寿命が低下するのが軽減されると共に、疲労によるチッピングの発生も抑制されるようになる。ここで、結合相を構成するＣｏ中にＣｒを固溶させるにあたっては、他の原料粉末と一緒にＣｒ粉或いはＣｒ₃Ｃ₂粉を添加させて焼結させるようにする。
【００２０】
【実施例】
以下、この発明の条件を満たす実施例のホブ用超硬材料と、この発明の条件を満たしていない比較例のホブ用超硬材料とを比較し、この発明の条件を満たす実施例のホブ用超硬材料が優れている点を明らかにする。なお、この発明におけるホブ用超硬材料は下記の実施例に示したものに限定されず、その要旨を変更しない範囲において適宜変更して実施できるものである。
【００２１】
（実施例１〜１２及び比較例１〜１２）
実施例１〜１２及び比較例１〜１２においては、ホブ用超硬材料の原料粉末として、ＷＣ粉、（Ｗ，Ｔｉ）Ｃ粉、ＴａＣ粉、（Ｔａ，Ｎｂ）Ｃ粉、ＴｉＮ粉、ＴａＮ粉、Ｃｒ粉、Ｃｏ粉、Ｗ粉を用い、これら原料粉末を所定の割合で混合させて所定の形状に成形し、その後、真空又は不活性ガスの雰囲気下において、１４００℃で６０分間焼結させて、ＷＣ，ＴｉＣ，ＴａＣ等の合金組成が下記の表１に示す重量比率になった実施例１〜１２及び比較例１〜１２の各ホブ用超硬材料を得た。
【００２２】
そして、上記の各ホブ用超硬材料について、それぞれ飽和磁化％（Ｍｓ％）及び抗磁力（Ｈｃ）を求め、その結果を下記の表１に合わせて示した。
【００２３】
【表１】

【００２４】
次に、上記の実施例１〜１２及び比較例１〜１２の各ホブ用超硬材料の切削性能等を評価するため、各ホブ用超硬材料を用いてＪＩＳ３６−１に相当する各バイトを作製した。
【００２５】
そして、ＣＮＣ装置（ＦＡＮＵＣ・ＳＹＳＴＥＭ６Ｍ）付きの横型マシニングセンタ（日立精工社製：ＭＡＣＣＭＡＴＩＣ−５０ＨＬ）を改造し、主軸のヘッドに舞いツールホルダを両持ちで支えるようにオーバーアームを設け、この舞いツールホルダに上記のように製造した初期における各バイトをそれぞれ舞いツールの径が８０ｍｍになるように取り付けて、耐初期欠損性試験と耐熱亀裂性試験と疲労による欠損性試験とを行い、これらの結果を下記の表２に示した。
【００２６】
ここで、耐初期欠損性試験においては、被削材に鍛造したＳＮＣＭ４２０（ＨＢ１５５）を用い、送り０．３８ｍｍ／ｒｅｖ、切り込み０．７５ｍｍの条件で乾式のアップカット切削を行うようにし、切削速度を２５０ｍ／ｍｉｎから徐々に速め、各バイトに初期欠損が発生しなくなる切削速度（ｍ／ｍｉｎ）を測定し、その結果を表２に示した。なお、この切削速度が遅いほど初期欠損が発生しやすくなるため、この切削速度が遅いほど耐初期欠損性に優れているといえる。
【００２７】
また、耐熱亀裂性試験においては、被削材に鍛造したＳＮＣＭ４２０（ＨＢ１５５）を用い、送り０．３８ｍｍ／ｒｅｖ、切り込み０．７５ｍｍ、切削速度４００ｍ／ｍｉｎの条件で乾式のアップカット切削を行い、熱亀裂が発生し始める切削長（ｍ）を測定し、その結果を表２に示した。ここで、比較例１，７のものにおいては、切削速度が４００ｍ／ｍｉｎと上記の初期欠損が生じる切削速度より遅いため、直ぐに欠損が生じたため、熱亀裂が発生し始める切削長を測定することができなかった。
【００２８】
また、疲労による欠損性試験においては、被削材に鍛造したＳＮＣＭ４２０（ＨＢ１５５）を用い、送り０．９ｍｍ／ｒｅｖ、切り込み１．１２５ｍｍ、切削速度４５０ｍ／ｍｉｎの条件で乾式のアップカット切削を行い、欠損が発生し始める切削長（ｍ）を測定し、その結果を表２に示した。
【００２９】
また、実施例７，８，１０及び比較例２，５，８，９の各ホブ用超硬材料を用いて作製したバイトについては、上記のバイトを１５週間放置させた後において、上記の疲労による欠損性試験を行って欠損が発生し始める切削長（ｍ）を測定し、作製した初期における各バイトにおいて測定された上記の切削長（ｍ）に対する比率を求め、これを経年劣化による工具寿命の低下率（％）として下記の表２に示した。
【００３０】
次に、上記の実施例１，２，４，６，８，１０〜１２及び比較例１〜５，７，９，１０の各ホブ用超硬材料を使用して、モジュール：１．２５、外径：３２ｍｍ、歯数：１２、条数：１になったソリッドホブを作製し、これらのソリッドホブにおける切れ刃のすくい面以外の部分に（Ｔｉ，Ａｌ）Ｎコーティングを施した。
【００３１】
そして、上記の各ソリッドホブを使用し、被削材ＳＭｎ４３５（ＨＲｃ５４）に対して、それぞれ送り１．５ｍｍ／ｒｅｖ、切り込み０．２５ｍｍ、切削速度８０ｍ／ｍｉｎの条件で乾式のコンベンショナル切削を行い、モジュール：１．２５、圧力角：２０°、歯数：８、ねじれ角：１５°、歯幅：２８ｍｍになる歯車の仕上げホブ切り加工を行い、４０個の歯車の加工を行った後において、各ソリッドホブホブの切れ刃に生じた最大チッピング量（ｍｍ）を求め、その結果を表２に示した。
【００３２】
【表２】

【００３３】
この結果から明らかなように、この発明の条件を満たす実施例１〜１２のホブ用超硬材料を用いたものは、この発明の条件を満たさない比較例１〜１２のホブ用超硬材料を用いたものに比べて、切削速度を遅くした場合や長く切削を行った場合における切れ刃の欠損が抑制されると共に熱亀裂の発生が抑制され、さらに長い間使用せずに放置した場合における工具の劣化も少なくなっていた。
【００３４】
ここで、超硬合金中において、ＷＣ除いたβｔ成分の割合が２２ｗｔ％になった実施例２の材料と、１５ｗｔ％になった比較例３の材料と、３１ｗｔ％になった比較例４の材料とを用いて作製した各バイトを使用し、上記の耐初期欠損性試験において初期欠損が発生する領域と、耐熱亀裂性試験において熱亀裂が発生する領域とを、切削速度と切削長との関係で求め、その結果を図１に示した。
【００３５】
この結果、ＷＣ除いたβｔ成分の割合が２２ｗｔ％になった実施例２の材料で作製したバイトにおいては、ＷＣ除いたβｔ成分の割合が１６〜２８ｗｔ％の範囲外になった比較例３の材料や比較例４の材料で作製した各バイトに比べて、初期欠損や熱亀裂が発生しない安全領域が著しく拡大した。
【００３６】
また、超硬合金の抗磁力が２４５Ｏｅ，飽和磁化％（Ｍｓ）が８２．３％になった実施例２の材料と、抗磁力が２２０Ｏｅ，飽和磁化％（Ｍｓ）が９４．２％になった比較例５の材料と、抗磁力が１７０Ｏｅ，飽和磁化％（Ｍｓ）が８４．８％になった比較例９の材料とを用いて作製した各バイトを使用し、上記の耐初期欠損性試験において初期欠損が発生する領域と、耐熱亀裂性試験において熱亀裂が発生する領域とを、切削速度と切削長との関係で求め、その結果を図２に示した。
【００３７】
この結果、抗磁力が２４５Ｏｅ，飽和磁化％（Ｍｓ）が８２．３％になった実施例２の材料で作製したバイトにおいては、飽和磁化％（Ｍｓ）が８７％よりも大きい９４．２％になった比較例５の材料や、抗磁力が２００Ｏｅよりも低い１７０Ｏｅになった比較例４の材料で作製した各バイトに比べて、初期欠損や熱亀裂が発生しない安全領域が著しく拡大した。
【００３８】
また、飽和磁化％（Ｍｓ）が８２．３％になった実施例２の材料と、飽和磁化％（Ｍｓ）が８０．５％になった実施例６の材料と、飽和磁化％（Ｍｓ）が９４．２％になった比較例５の材料とを用いて作製した各バイトを使用し、上記の疲労による欠損性試験において欠損が発生し始める切削長を図３に示した。
【００３９】
この結果、飽和磁化％（Ｍｓ）が８０．５％になった実施例６の材料や、飽和磁化％（Ｍｓ）が８２．３％になった実施例２の材料で作製した各バイトにおいては、飽和磁化％（Ｍｓ）が８７％よりも大きい９４．２％になった比較例５の材料で作製したバイトに比べて、欠損が発生し始める切削長が著しく長くなっており、疲労による欠損が発生しにくくなっていた。
【００４０】
また、Ｃｏ中にＣｒを固溶させていない実施例８の材料と、Ｃｏ中にＣｒを固溶させた実施例１０の材料と、実施例８の材料と合金組成は同じであるが、飽和磁化％（Ｍｓ）が９５％と高く、抗磁力が１６０Ｏｅと低くなった比較例８の材料とを用いて作製した各バイトにおいて、バイトを作製した初期と、１５週間放置させた後とにおいて、それぞれ上記の疲労による欠損性試験において欠損が発生し始める切削長を測定して図４に示した。
【００４１】
この結果、飽和磁化％（Ｍｓ）が９５％と高く、かつ抗磁力が１６０Ｏｅと低くなった比較例８の材料で作製したバイトは、実施例８の材料や実施例１０の材料で作製した各バイトに比べて、欠損が発生し始める切削長が著しく短くなっており、疲労による欠損が発生しやすくなっており、また１５週間放置させた後においては、欠損が発生し始める切削長がバイトを作製した初期に比べて大きく低下しており、放置による劣化も大きくなっていた。
【００４２】
また、Ｃｏ中にＣｒを固溶させていない実施例８の材料で作製したバイトと、Ｃｏ中にＣｒを固溶させた実施例１０の材料で作製したバイトとを比較すると、Ｃｏ中にＣｒを固溶させた実施例１０の材料で作製したバイトの方が、Ｃｏ中にＣｒを固溶させていない実施例８の材料で作製したバイトに比べて、欠損が発生し始める切削長が長くなって、疲労による欠損が発生しにくくなっており、特に、Ｃｏ中にＣｒを固溶させた実施例１０の材料で作製したバイトにおいては、１５週間放置させた後においても、欠損が発生し始める切削長の変化が非常に少なくなっており、放置によって劣化するのが十分に抑制されるようになった。
【００４３】
【発明の効果】
以上詳述したように、この発明におけるホブ用超硬材料においては、ＷＣ−βｔ−Ｃｏ系の超硬合金中に、結合相を構成するＣｏが８〜１３重量％の範囲で含有されると共に、βｔ相を構成する成分中、ＷＣを除いた他の成分が超硬合金中に１６〜２８重量％の範囲で含有され、このＷＣを除いた他の成分中にＴｉＣが３５〜６０重量％の範囲で含有され、この超硬合金における飽和磁化％が７８〜８７％、抗磁力が１８０〜２８０Ｏｅの範囲になるようにしたため、このホブ用超硬材料を用いて超硬ホブを作製した場合、歯車を加工する時に超硬ホブの切れ刃にチッピングや熱亀裂が発生するのが十分に防止されると共に、この超硬ホブが大気中において酸化されて劣化したり、再研削時における研削液によっては劣化するのも抑制され、長期にわたって安定した歯車加工が行えるようになった。
【図面の簡単な説明】
【図１】実施例２の材料と、比較例３の材料と、比較例４の材料で作製した各バイトを用いて、欠損領域に及ぼすβｔ相形成成分量の影響を示した図である。
【図２】実施例２の材料と、比較例５の材料と、比較例９の材料で作製した各バイトを用いて、耐欠損性及び耐熱亀裂性に及ぼすＭｓ％値と抗磁力値の影響を示した図である。
【図３】実施例２の材料と、実施例６の材料と、比較例５の材料で作製した各バイトを用いて、耐疲労チッピング性に及ぼすＭｓ％値の影響を示した図である。
【図４】実施例８の材料と、実施例１０の材料と、比較例８の材料で作製した各バイトを用いて、耐疲労チッピング性に対するＣｒ添加の有無と比較材料との差を示した図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hob material used for manufacturing a hob used for processing gears, and particularly to a cemented carbide material for hob which has excellent chipping resistance and heat crack resistance and can perform stable high-speed cutting. It is.
[0002]
[Prior art]
Conventionally, a hob has been most frequently used to process gears, and high-speed steel has generally been used as a mainstream as a material constituting the hob.
[0003]
However, when gears are machined with a hob using such high-speed steel, wet cutting is performed by supplying cutting oil for cooling or the like, and the factory environment is affected by fuming or scattering of cutting oil. There is a problem that the cutting speed is slow, the production efficiency is low, and there is a problem that it is difficult to obtain sufficient gear cutting accuracy by welding or the like.
[0004]
For this reason, conventionally, a carbide hob using a cemented carbide as a material constituting the hob has been developed.
[0005]
Here, in the case of a cemented carbide hob using a cemented carbide, it is possible to cut at a high speed to improve the production efficiency, and to perform dry cutting to suppress deterioration of the factory environment and the like. In addition, the gear cutting accuracy is increased, post-processing such as finishing is facilitated, and gears made of a high-hardness material can also be processed.
[0006]
However, the hob has a complicated cutting mechanism, so when gear processing is performed using the above-mentioned carbide hob, chipping and thermal cracking are likely to occur on the cutting edge of this carbide hob, and it is stable over a long period of time. There was a problem that gear processing could not be performed.
[0007]
For this reason, in the past, it has been studied to improve the cutting edge shape and hob shape of the carbide hob or to improve the hobbing machine to prevent the occurrence of chipping and thermal cracking, but sufficient effects are obtained. The current situation is not.
[0008]
Furthermore, when such a carbide hob is left in the atmosphere, the carbide hob is gradually corroded and deteriorated, and when this carbide hob is reground, the carbide hob is deteriorated depending on the grinding fluid. However, there is also a problem that the tool life is shortened.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems in a cemented carbide hob using a cemented carbide alloy, and chipping and thermal cracks occur in the cutting edge of the cemented carbide hob when a gear is processed. It is possible to obtain a carbide hob capable of stable gear machining over a long period of time, suppressing deterioration of the carbide hob due to oxidation in the atmosphere and deterioration due to grinding fluid during regrinding. It is a problem to make.
[0010]
[Means for Solving the Problems]
In the present invention, in order to solve the above-described problems, in the cemented carbide material for hobs made of a WC-βt-Co based cemented carbide, the Co constituting the binder phase in the cemented carbide is 8 to It is contained in the range of 13% by weight, and in the components constituting the βt phase, other components excluding WC are contained in the cemented carbide in the range of 16 to 28% by weight, and this WC is excluded. The other components contain TiC in the range of 35 to 60% by weight so that the saturated magnetization% in this cemented carbide is in the range of 78 to 87% and the coercive force is in the range of 180 to 280 Oe.
[0011]
Here, in the cemented carbide material for hobs in the present invention, the reason why Co in the cemented carbide is contained in the range of 8 to 13% by weight is that the amount of Co is more than the above range. If the amount is too small, the chipping resistance of the cutting edge in the cemented carbide hob is reduced, and chipping is likely to occur in the initial stage. On the other hand, if the amount of Co is larger than the above range, the hardness of the resulting cemented carbide decreases. Thus, the wear resistance of the cutting edge in the carbide hob is lowered, and the gear cutting accuracy cannot be maintained for a long time. Further, when gear processing is performed at a cutting speed of 300 m / min or more, the affinity between the chips and the cemented carbide increases, and defects due to welding are likely to occur and plastic deformation is likely to occur.
[0012]
In addition, the βt phase in the present invention means a solid solution phase of WC—TiC—TaC (NbC) as is generally known, and is a phase of B1 type structure, and nitrides such as Ti and Ta are solid. It may be dissolved.
[0013]
And in the cemented carbide material for hobbs in this invention, in the component which comprises said (beta) t phase, other components except WC are contained in the cemented carbide alloy in the range of 16 to 28 weight%, and this WC The reason why TiC is contained in the range of 35 to 60% by weight in the other components excluding WC is that the amount of the other components excluding WC and the amount of TiC in the other components excluding WC If the amount is less than the above range, the amount of βt phase in the cemented carbide decreases, the welding resistance in the cemented carbide decreases, and chipping due to chip welding is likely to occur in the cemented carbide hob. In particular, in the carbide hob, since the rake face is used while being reground, a coating film is often not provided on the rake face, and therefore, defects due to such chip welding are likely to occur. On the other hand, if the amount of other components excluding WC and the amount of TiC in the other components excluding WC are larger than the above range, the toughness of the cemented carbide decreases, and the chipping of the cemented carbide hob is initially damaged. This is because it tends to occur.
[0014]
Moreover, in the cemented carbide material for hobs in this invention, the reason why the saturation magnetization% in the cemented carbide alloy is in the range of 78 to 87% is that when the saturation magnetization% is lower than the above range, W ₃ A brittle η phase composed of Co ₃ C ₃ appears in the structure of the cemented carbide, and initial defects are likely to occur in the cutting edge of the cemented carbide hob. On the other hand, if the saturation magnetization% is higher than the above range, the solid state of the Co bonded phase is increased. This is because the melt strengthening is insufficient, and the cutting edge of the carbide hob is likely to be damaged or cracked, and chipping due to fatigue is likely to occur. The saturation magnetization% is given by the following formula when the saturation magnetization value of the cemented carbide is M ₀ , the saturation magnetization value of Co is M ₁ , and the amount of Co in the cemented carbide is a (wt%). Sought by.
[0015]
Saturation magnetization (%) = [M ₀ / (M ₁ · a / 100)] × 100
[0016]
Moreover, in the cemented carbide material for hobs in this invention, the reason why the coercive force in the cemented carbide is in the range of 180 to 280 Oe is that when the coercive force is lower than the above range, 3 μm or more is contained in the cemented carbide. This is because the WC phase of coarse particles is present in a relatively large amount, and the cutting edge of the carbide hob is liable to be damaged or thermally cracked. In particular, in the case of a carbide hob, the cutting edge may not be honed. Therefore, it is necessary to improve the sharpness of the WC phase particles in the cemented carbide to improve the sharpness and to improve the tooth profile accuracy of the gear to be processed. On the other hand, when the coercive force in the cemented carbide exceeds 280 Oe, the particles of the WC phase in the cemented carbide become too fine, and particularly when the amount of Co in the cemented carbide is as small as 8 to 10% by weight. Is likely to cause chipping due to fatigue on the cutting edge of the carbide hob.
[0017]
In particular, when the saturation magnetization% in the cemented carbide is in the range of 78 to 87% and the coercive force in the cemented carbide is in the range of 180 to 280 Oe, as in the cemented carbide material for hobbs of the present invention, these superpositions. By the action, the effect of suppressing the occurrence of defects and thermal cracks in the cutting edge of the carbide hob is remarkably improved.
[0018]
And when a cemented carbide hob is made using a cemented carbide material for hob having the above characteristics, chipping and thermal cracks are sufficiently suppressed from occurring at the cutting edge of the cemented carbide hob when machining the gear. At the same time, the carbide hob is corroded and deteriorated in the atmosphere, and is prevented from being deteriorated depending on the grinding fluid at the time of regrinding, so that stable gear machining can be performed over a long period of time.
[0019]
Further, as shown in claim 2 of the present invention, Cr is dissolved in Co constituting the binder phase so that Cr is in the range of 0.2 to 1.0% by weight with respect to the cemented carbide. As a result, the oxidation resistance and corrosion resistance of the cemented carbide are improved, and the carbide hob is further corroded and deteriorated in the atmosphere, and depending on the grinding fluid, the tool life is further suppressed. Is reduced, and the occurrence of chipping due to fatigue is also suppressed. Here, in dissolving Cr in Co constituting the binder phase, Cr powder or Cr ₃ C ₂ powder is added together with other raw material powders and sintered.
[0020]
【Example】
In the following, the cemented carbide material for hobs according to the example satisfying the conditions of the present invention is compared with the cemented carbide material for hobbs according to the comparative example that does not satisfy the conditions of the present invention. Clarify the advantages of super hard materials. In addition, the cemented carbide material for hobs in this invention is not limited to what was shown to the following Example, It can implement by changing suitably in the range which does not change the summary.
[0021]
(Examples 1-12 and Comparative Examples 1-12)
In Examples 1-12 and Comparative Examples 1-12, WC powder, (W, Ti) C powder, TaC powder, (Ta, Nb) C powder, TiN powder, TaN are used as the raw material powder for the superhard material for hobbing. Using powder, Cr powder, Co powder and W powder, these raw material powders are mixed at a predetermined ratio and formed into a predetermined shape, and then sintered at 1400 ° C. for 60 minutes in a vacuum or inert gas atmosphere. Thus, cemented carbide materials for hobbs of Examples 1 to 12 and Comparative Examples 1 to 12 having alloy compositions such as WC, TiC, TaC, etc. having the weight ratios shown in Table 1 below were obtained.
[0022]
Then, saturation magnetization% (Ms%) and coercive force (Hc) were determined for each of the above-mentioned superhard materials for hobbs, and the results are shown in Table 1 below.
[0023]
[Table 1]

[0024]
Next, in order to evaluate the cutting performance and the like of the cemented carbide materials for hobbs in Examples 1 to 12 and Comparative Examples 1 to 12, the respective cutting tools corresponding to JIS36-1 were used using the cemented carbide materials for the hobbs. Produced.
[0025]
Then, a horizontal machining center (manufactured by Hitachi Seiko Co., Ltd .: MACCMATIC-50HL) with a CNC device (FANUC · SYSTEM 6M) was remodeled, and an overarm was provided to support the tool holder with both ends on the spindle head. Each initial tool manufactured as described above is mounted on the holder so that the diameter of the tool is 80 mm, and an initial fracture resistance test, a thermal crack resistance test, and a fatigue fracture test are performed. Is shown in Table 2 below.
[0026]
Here, in the initial fracture resistance test, SNCM420 (HB155) forged on the work material was used, dry upcut cutting was performed under conditions of a feed of 0.38 mm / rev and a cutting depth of 0.75 mm, and the cutting speed was Was gradually increased from 250 m / min, and the cutting speed (m / min) at which no initial chipping occurred in each cutting tool was measured. The results are shown in Table 2. In addition, since it becomes easy to generate an initial defect, so that this cutting speed is slow, it can be said that it is excellent in the initial defect resistance, so that this cutting speed is slow.
[0027]
In the heat crack resistance test, SNCM420 (HB155) forged on the work material was used, dry upcut cutting was performed under the conditions of feed 0.38 mm / rev, cutting 0.75 mm, cutting speed 400 m / min, The cutting length (m) at which thermal cracks started to occur was measured, and the results are shown in Table 2. Here, in the comparative examples 1 and 7, the cutting speed is 400 m / min, which is slower than the cutting speed at which the above-mentioned initial defect occurs, and therefore the defect is generated immediately, so the cutting length at which thermal cracks start to occur is measured. I could not.
[0028]
In the fracture test due to fatigue, SNCM420 (HB155) forged on the work material was used, and dry upcut cutting was performed under the conditions of feed 0.9 mm / rev, cutting 1.125 mm, cutting speed 450 m / min. The cutting length (m) at which defects started to occur was measured, and the results are shown in Table 2.
[0029]
In addition, for the tools manufactured using the carbide materials for hobbs of Examples 7, 8, and 10 and Comparative Examples 2, 5, 8, and 9, the fatigue was measured after the tool was left for 15 weeks. Measure the cutting length (m) at which chipping begins to occur by performing the fracturing test with, and determine the ratio to the above cutting length (m) measured at each initial bite that was produced. This is the tool life due to deterioration over time. The reduction rate (%) is shown in Table 2 below.
[0030]
Next, using the superhard materials for hobbs of Examples 1, 2, 4, 6, 8, 10 to 12 and Comparative Examples 1 to 5, 7, 9, and 10, the module: 1.25, Solid hobs having an outer diameter of 32 mm, the number of teeth of 12, and the number of strips of 1 were produced, and (Ti, Al) N coating was applied to portions other than the rake face of the cutting edge in these solid hobs.
[0031]
Then, using each of the above solid hobbs, dry conventional cutting is performed on the work material SMn435 (HRc54) under the conditions of a feed of 1.5 mm / rev, a cut of 0.25 mm, and a cutting speed of 80 m / min. : 1.25, pressure angle: 20 °, number of teeth: 8, helix angle: 15 °, tooth width: 28 mm Finish hobbing of gear and after 40 gears were processed, The maximum chipping amount (mm) generated on the cutting edge of the solid hob hob was determined, and the result is shown in Table 2.
[0032]
[Table 2]

[0033]
As is apparent from the results, the carbide materials for hobbs of Examples 1 to 12 satisfying the conditions of the present invention are the carbide materials for hobbs of Comparative Examples 1 to 12 that do not satisfy the conditions of the present invention. Compared to the tool used, the cutting edge is reduced when cutting speed is slow or when cutting for a long time and the generation of thermal cracks is suppressed, and the tool is left unused for a long time. The deterioration of was also reduced.
[0034]
Here, in the cemented carbide, the material of Example 2 in which the proportion of the βt component excluding WC became 22 wt%, the material of Comparative Example 3 that became 15 wt%, and the material of Comparative Example 4 that became 31 wt%. Using each tool manufactured using a material, the region where the initial defect occurs in the initial fracture resistance test and the region where the thermal crack occurs in the thermal crack resistance test The relationship was found and the result is shown in FIG.
[0035]
As a result, in the bite manufactured with the material of Example 2 in which the ratio of the βt component excluding WC was 22 wt%, the ratio of the βt component excluding WC was outside the range of 16 to 28 wt%. Compared to each bit made of the material and the material of Comparative Example 4, the safety region where no initial defects or thermal cracks occurred was significantly expanded.
[0036]
Also, the material of Example 2 in which the coercive force of the cemented carbide is 245 Oe and the saturation magnetization% (Ms) is 82.3%, and the coercive force is 220 Oe and the saturation magnetization% (Ms) is 94.2%. In addition, the above-mentioned initial fracture resistance was obtained using each tool manufactured using the material of Comparative Example 5 and the material of Comparative Example 9 in which the coercive force was 170 Oe and the saturation magnetization% (Ms) was 84.8%. The region where initial defects occur in the test and the region where thermal cracks occur in the thermal crack resistance test were determined from the relationship between the cutting speed and the cutting length, and the results are shown in FIG.
[0037]
As a result, in the tool manufactured from the material of Example 2 in which the coercive force is 245 Oe and the saturation magnetization% (Ms) is 82.3%, the saturation magnetization% (Ms) is 94.2%, which is larger than 87%. Compared to each of the tools manufactured with the material of Comparative Example 5 and the material of Comparative Example 4 with a coercive force of 170 Oe, which is lower than 200 Oe, the safety region in which initial defects and thermal cracks are not significantly increased.
[0038]
Further, the material of Example 2 in which the saturation magnetization% (Ms) is 82.3%, the material of Example 6 in which the saturation magnetization% (Ms) is 80.5%, and the saturation magnetization% (Ms). FIG. 3 shows the cutting length at which defects start to occur in the above-mentioned fatigue defect test using each bite manufactured using the material of Comparative Example 5 with 94.2%.
[0039]
As a result, in each tool manufactured using the material of Example 6 in which the saturation magnetization% (Ms) is 80.5% and the material of Example 2 in which the saturation magnetization% (Ms) is 82.3%. Compared to the bit made of the material of Comparative Example 5 in which the saturation magnetization% (Ms) is 94.2% which is larger than 87%, the cutting length at which the defect starts to occur is significantly longer, and the defect due to fatigue. It was hard to occur.
[0040]
Further, the material of Example 8 in which Cr is not dissolved in Co, the material of Example 10 in which Cr is dissolved in Co, and the material of Example 8 are the same in alloy composition but saturated. In each tool manufactured using the material of Comparative Example 8 in which the magnetization% (Ms) is as high as 95% and the coercive force is as low as 160 Oe, in the initial stage of manufacturing the tool and after leaving it for 15 weeks, Each of the cutting lengths at which defects began to occur in the above-described fatigue defect test was measured and shown in FIG.
[0041]
As a result, the bite made of the material of Comparative Example 8 having a high saturation magnetization% (Ms) as high as 95% and a coercive force as low as 160 Oe was produced using the material of Example 8 or the material of Example 10. Compared to the cutting tool, the cutting length at which defects start to occur is significantly shorter, and defects due to fatigue are more likely to occur. After leaving for 15 weeks, the cutting length at which defects start to occur Compared to the initial production, it was greatly reduced, and deterioration due to neglect was also large.
[0042]
Further, when comparing the bite made of the material of Example 8 in which Cr is not dissolved in Co with the bite made of the material of Example 10 in which Cr is solid-solved in Co, Cr Compared with the bite made of the material of Example 8 in which Cr is not solid-dissolved in Co, the cutting length produced with the material of Example 10 in which no. Thus, defects due to fatigue are less likely to occur. In particular, in the bite made of the material of Example 10 in which Cr was dissolved in Co, defects were generated even after being left for 15 weeks. The change in the cutting length to be started has become very small, and the deterioration due to neglect has been sufficiently suppressed.
[0043]
【The invention's effect】
As described above in detail, in the cemented carbide material for hobs according to the present invention, the WC-βt-Co-based cemented carbide contains Co in the range of 8 to 13 wt% in the binder phase. In addition, in the components constituting the βt phase, other components excluding WC are contained in the cemented carbide in the range of 16 to 28% by weight, and in the other components excluding this WC, TiC is 35 to 60% by weight. When the cemented carbide hob is made using this cemented carbide material for the hob, the saturated magnetization% in this cemented carbide is set to be 78 to 87% and the coercive force is in the range of 180 to 280 Oe. , Chipping and thermal cracks are sufficiently prevented from occurring on the cutting edge of the carbide hob when machining gears, and this carbide hob is oxidized and deteriorated in the atmosphere, and the grinding fluid during re-grinding Depending on the type of It became possible to perform stable gear machining over the period.
[Brief description of the drawings]
FIG. 1 is a graph showing the effect of the amount of βt phase forming component on a defect region using each tool manufactured with the material of Example 2, the material of Comparative Example 3, and the material of Comparative Example 4.
FIG. 2 shows the effect of Ms% value and coercive force value on fracture resistance and thermal crack resistance using each of the tools manufactured from the material of Example 2, the material of Comparative Example 5, and the material of Comparative Example 9. FIG.
FIG. 3 is a diagram showing the influence of Ms% value on fatigue chipping resistance using each of the cutting tools manufactured from the material of Example 2, the material of Example 6, and the material of Comparative Example 5.
FIG. 4 shows the difference between the presence or absence of Cr addition and the comparative material with respect to fatigue chipping resistance using each of the tools manufactured with the material of Example 8, the material of Example 10, and the material of Comparative Example 8. FIG.

Claims

In a cemented carbide material for a hob made of a WC-βt-Co based cemented carbide, Co constituting the binder phase is contained in the cemented carbide in the range of 8 to 13 wt%, and the βt phase Among the components constituting WC, other components excluding WC are contained in the cemented carbide in the range of 16 to 28% by weight, and TiC in the other components excluding WC is in the range of 35 to 60% by weight. A cemented carbide material for a hob which is contained and has a saturation magnetization% of 78 to 87% and a coercive force of 180 to 280 Oe in the cemented carbide.

The cemented carbide material for a hob according to claim 1, wherein Cr is in a range of 0.2 to 1.0 wt% with respect to the cemented carbide, and Cr is included in Co constituting the binder phase. A cemented carbide material for hobs, characterized by being dissolved.