JP2004122263A

JP2004122263A - Coated cutting tool for highly precise work

Info

Publication number: JP2004122263A
Application number: JP2002287785A
Authority: JP
Inventors: Daisuke Murakami; 村上　大介; Hideki Moriguchi; 森口　秀樹
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 2002-09-30
Filing date: 2002-09-30
Publication date: 2004-04-22

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated cutting tool for the highly precise work providing a favorable working surface roughness and a shape precision and suppressing dispersion in the dimension caused by welding in a lathe turning of a highly precise component of generally a micro meter unit. <P>SOLUTION: This coated cutting tool for cutting the highly precise component is so formed that a cutting blade 5 is a sharp edge, the surface roughness of the cutting blade 5 is 0.4μm or less in a central line average roughness Ra, the thickness of a coating layer 2 of a cutting face is 0.5-2μm and the thickness of the coating layer 3 of a flank is 4-7μm. This constitution can prevent welding caused by abrasion of the cutting face, prevent welding between a base metal and a workpiece developed by the abrasion of the flank and highly precisely cut into a favorable finishing surface shining into a rainbow color. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、電子機器部品などのようにマイクロメーター単位の高い精度が要求される分野での利用に最適な高精度加工用被覆切削工具に関するものである。特に、切れ味に優れ、良好な加工面品位を得ることのできる高精度加工用被覆切削工具に関するものである。
【０００２】
【従来の技術】
一般にマイクロメートル単位の高い精度が要求される時計や、カメラ、電子機器部品の旋削加工では、寸法精度や加工面の表面粗さはもちろん、虹色に輝くような光沢のある加工面が要求される場合が多い。かかる高精度加工では、寸法精度と虹色に輝く良好な加工面が要求され、このためには切削工具の切れ味を向上させることと刃先への溶着を防止することが重要である。このような目的を達成するためには、公知技術であるＰＶＤ法によりＴｉＡｌＮやＴｉＣＮまたはＴｉＮで被覆された被覆切削工具が用いられる（例えば、特許文献１参照）。
【０００３】
しかし、一般的な被覆切削工具では４〜５μｍの厚みのコーティング層を被覆するために、切れ刃部にコーティング層厚み分の切れ刃の丸みが生じて切れ味が低下して、加工面の品位が低下する問題があった。このため、これら高精度加工用の被覆切削工具ではコーティング層をできるだけ薄くするなどの工夫がなされてきた（例えば、特許文献１および特許文献２参照）。
【０００４】
【特許文献１】
特開２００１−３４７４０３号公報（第２−３頁、図２）
【特許文献２】
特開２００１−２７７００４号公報（第２−３頁）
【０００５】
【発明が解決しようとする課題】
しかしながら、すくい面と逃げ面の両方のコーティング層を薄くすると、工具が摩耗したときに、母材の露出量が増加し、さらに露出した母材に溶着が発生して、加工面が白濁したり、寸法のバラツキが発生する問題があった。かかる問題を解決する手段として、特許文献２では、母材の刃先部分を研磨して面粗さを小さくし、その上に２μｍ以下の薄いコーティング層を配している。こうすることで安定して構成刃先を発生させて、刃先を構成刃先で保護することで寸法の安定を図っている。しかし、かかる発明は構成刃先を利用するために構成刃先脱落時に工具に小さな欠けを生じさせたり、コーティング層全体が薄いために摩耗して、逃げ面側の母材露出量が増加して、加工面が白濁するなどの問題があった。ここで加工面が白濁するとは、加工面がむしれて白くなることを意味する。
【０００６】
また、特許文献１では、すくい面の膜厚を０．５〜２μｍで、逃げ面の膜厚を１〜４μｍとする被覆切削工具が開示されている。この発明はコーティング層のチッピングによる寸法精度の低下を抑制することを目的としたものである。従って、コーティング層が摩耗して、逃げ面の母材露出量が増加してくると、加工面が白濁しやすくなる可能性がある。
【０００７】
【課題を解決するための手段】
発明者らは研究を重ねた結果、虹色に輝く良好な加工面を得るために逃げ面側の母材を露出させないことが重要であることを見出した。すなわち、超硬合金もしくはサーメットを母材としてコーティング層を被覆した高精度加工用被覆切削工具において、切れ刃がシャープエッジで、かつ、該切れ刃の表面粗さが中心線平均粗さＲａ：０．４μｍ以下で、すくい面のコーティング層の膜厚が０．５〜２μｍで、かつ、逃げ面のコーティング層の膜厚が４〜７μｍである高精度加工用被覆切削工具を提供するものである。
【０００８】
本発明においてシャープエッジとは、超硬合金やサーメットを構成する硬質粒子の脱落により生じたと推定される小さな凹凸がある部分を除き、すくい面と逃げ面を研削して得られたままの切れ刃のことである。そして被覆層は、複層でもよく母材から順に例えば、ＴｉＮ／ＴｉＡｌＮ、ＴｉＡｌＮ／ＣｒＮ、ＴｉＮ／ＴｉＡｌＮ／Ａｌ_２Ｏ_３、ＴｉＮ／ＴｉＳｉＮ／ＴｉＳｉＣＮ、ＴｉＮ／ＴｉＺｒＮ／ＺｒＮ、ＴｉＡｌＮ／ＶＮのような組み合わせも採用可能である。また、ＴｉＮとＴｉＡｌＮ膜の単層の厚さが２．５ｎｍで、これを交互に１２００層積層し全体の膜厚が３μｍとすることもできる。本発明において被覆層のさらに望ましい範囲は、すくい面のコーティング層の膜厚が０．５〜１μｍで、かつ、逃げ面のコーティング層の膜厚が４μｍを越えて５μｍ以下である。
【０００９】
前記超硬合金は、３〜１２質量％の結合材と残部が炭化タングステン及び不可避不純物からなり、ビッカース硬度が１４〜２２ＧＰａであり、かつ該炭化タングステンの平均粒径が０．３〜２μｍであることが好ましい。結合材の量が３質量％未満では、強度の高い超硬合金とならず、１２質量％を超えると硬度が不足する。また、平均粒径０．３〜２μｍの微粒な炭化タングステンを用いることで母材の表面粗さが小さくなり、安定して本発明の高精度加工用被覆切削工具を製作できる。
【００１０】
前記サーメットは、１０〜２０質量％の結合材と３〜６質量％の窒素を含むチタン系硬質粒子及び不可避不純物からなり、かつビッカース硬度が１４〜２２ＧＰａでかつ、該チタン系硬質粒子の平均粒径が０．３〜２μｍであるサーメットを母材とすることもできる。
【００１１】
超硬合金とサーメットにおいて、結合材としては通常ＣｏやＮｉが使われる。超硬合金においてはＣｏが、またサーメットにおいてはＣｏとＮｉが併用されることが多い。しかしながら、いずれの場合にもＣｏやＮｉは、単独でも使用できるし併用することも出来る。
【００１２】
本発明のコーティング層は、Ｔｉ、Ｚｒ、Ｃｒ、Ａｌ、Ｓｉから選ばれる１種以上の元素の炭化物、窒化物、硼化物、酸化物およびこれらの固溶体からなる群より選ばれた１種からなる化合物の１層以上で形成されることが好ましい。このようなコーティング層を具える本発明の高精度加工用被覆切削工具を用いると白濁のない、良好な加工面品位が得られ、被削材の寸法変化も小さくなることを確認した。
【００１３】
切削時、コーティング層厚み分の切れ刃の丸みが発生して切れ味が低下する。これを防止するために、すくい面のコーティング層を薄くすれば、逃げ面側は厚くても、逃げ面摩耗により刃先丸みが生じないことを見いだした。本発明は、かかる発見に基づいてなされたものである。図１は、本発明に係わる刃先交換チップを示し、（ａ）は、切れ刃５部分の拡大図である。即ち、図１（ａ）に示すごとく、少なくともすくい面のコーティング層２の厚みを一般的なＰＶＤ法で得られる被覆層の膜厚よりも薄くして、逃げ面のコーティング層３の厚みを厚くしたものである。こうすることで、摩耗しても良好な切れ味を維持し、かつ、逃げ面が摩耗したときの母材の露出量を小さくおさえることができる。従って、電子機器部品の加工で強く要求される良好な加工面品位を長く維持し、かつ溶着等による寸法変化をおさえることができる。
【００１４】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
（実施例１）
本発明の効果を実証するために、８種類の試料を作製した。試料に用いた母材は、炭化タングステンの平均粒径が約１μｍ程度、Ｃｏの含有量が１０質量％程度、ビッカース硬度１４ＧＰａ程度の超硬合金である。この母材を用いて、図２に示す形状の刃先交換チップを製作した。図２は、頂角５５°の菱形形状をなし、逃げ面側には７°の逃げ角が形成され、すくい面側には２０°のすくい角が形成された刃先交換チップである。また、高精度な加工を行うために、研磨された母材の刃先は切れ味の良いシャープエッジで、すくい面と逃げ面の面粗さは中心線平均粗さ０．４μｍ以下とした。
【００１５】
【表１】

【００１６】
【表２】

【００１７】
【表３】

【００１８】
前記の母材の上に公知のアークイオンプレーティング法により、ＴｉＡｌＮを表１に示すようにすくい面と逃げ面の膜厚が変化するように被覆した。なお、コーティング層の厚みはコーティングを施す時間を制御することで変化させた。また、すくい面と逃げ面の膜厚比は、すくい面側のコーティング層が厚くならないようコーティング時にすくい面の前方に障害物を設けたり、コーティング炉内にセットする刃先交換チップの向きを変化させることで制御した。
【００１９】
ここで、試料▲１▼〜▲４▼は、すくい面の膜厚が０．５〜２μｍの範囲にあり、かつ逃げ面の膜厚が４〜８μｍの範囲となる発明品であり、試料▲５▼〜▲８▼は、比較例である。次に前記形態の試料を一般的に用いられるホルダーに取り付けた切削工具として、切削加工実験を行った。実験は、直径１２ｍｍ、長さ１０ｍｍの丸材のＳＵＳ４３０Ｆからなる被削材を次の切削条件で、１０００ヶ加工して、加工面の品位と寸法のばらつきを調査した。切削条件は、一般的な高精度部品の旋削加工であって、切削速度５０ｍ／ｍｉｎ、切り込み量０．１ｍｍ、送り速度０．０５ｍ／ｒｅｖ．、不水溶性油剤を用いた湿式切削とした。
【００２０】
表２は、上記の切削試験において加工数量ごとに加工面品位を調べ、その変化を記載したものである。なお、加工面の品位は加工した被削材を目視により判定、特に良好な加工面を◎、良好な加工面を○、白濁した加工面を×とした。表２のように、本発明品である試料▲１▼〜▲４▼は長時間、良好な加工面が維持されている。さらに本発明品の中でもすくい面の膜厚を１μｍ以下、逃げ面の膜厚は４μｍを越えて５μｍ以下とした試料▲２▼、▲３▼は、特に１０００ヶ切削加工しても、まだ良好な加工面が得られている。
【００２１】
一方、逃げ面の膜厚が４μｍ未満と薄い試料▲５▼、▲７▼は、初期は面品位が良好であるが、逃げ面が摩耗して母材である超硬合金が露出してくると加工面が白濁してしまう。一方、膜厚が全体に厚い試料▲６▼では刃先にコーティング層の厚み分の切れ刃の丸みが発生するために、極初期より加工面が白濁してしまう。
【００２２】
一方、逃げ面の膜厚を８μｍと厚くした試料▲８▼は、逃げ面のコーティング層の膜厚が厚すぎるために途中で逃げ面の膜にチッピングが発生して、加工面の品位が悪化する結果となった。
【００２３】
さらに表３は寸法のバラツキを示すものである。寸法のバラツキはそれぞれ所定数加工したとき、直前１０ヶの被削材の外径を測定して、最大のものと最小のものの直径の差が５μｍ以下は◎、５μｍを超え２０μｍ未満は○、２０μｍ以上は×と表現した。表３のように発明品は寸法バラツキが小さく、特にすくい面のコーティング層の膜厚が１μｍ以下、逃げ面のコーティング層の膜厚を４〜５μｍとした試料▲２▼、▲３▼で非常に良好な結果となっている。
【００２４】
一方、比較例は、加工面品位と同様に母材の超硬合金の露出や、切れ刃の丸み、チッピングの影響で、初期に良好なものも加工数が増大すると、寸法ばらつきが増大する結果となっている。
【００２５】
また、図３は試料▲３▼、図４は試料▲６▼、図５は試料▲５▼の加工後の切れ刃の断面を模式的に示すものである。図４に示すように逃げ面とすくい面のコーティング層２、３の厚みの厚い試料▲６▼ではすくい面のコーティング層の厚み分の切れ刃の丸み７が生じて切れ味が低下している。また、図５に示すようにすくい面と逃げ面のコーティング層２、３の厚みを薄くした試料▲５▼では逃げ面のコーティング層３が摩耗して、母材が広い範囲で露出するために加工面が白濁してしまう。
【００２６】
しかし、本発明品である試料▲３▼では、図３に示すごとく、すくい面のコーティング層２の摩耗に起因する切れ刃の丸み７が小さく、かつ逃げ面のコーティング層３が厚い。従って、母材もほとんど露出せず、高い切れ味を保ちつつ、加工面の白濁も防止できた。
【００２７】
以上、本発明によれば、工具の切れ味を確保したまま、溶着を防ぎ、摩耗による母材の露出量を小さくできるので、良好な仕上げ面品位が長時間得られ、寸法のバラツキも小さくすることができた。
【００２８】
（実施例２）
超硬合金母材が切削性能に及ぼす影響を確認するために表４に示す超硬合金母材のすくい面に０．７μｍ、逃げ面に４．８μｍのＴｉＡｌＮを被覆した刃先交換チップを製作した。その他は実施例１と同じにした。次に前記形態の試料を一般的に用いられるホルダーに取り付けた切削工具として、切削加工実験を行った。
【００２９】
実験は、直径１２ｍｍ、長さ１０ｍｍの丸材のＳＵＳ４３０Ｆからなる被削材を次の切削条件で、１０００ヶ加工して、加工面の品位と寸法のばらつきを調査した。切削条件は、一般的な高精度部品の旋削加工を想定して、切削速度５０ｍ／ｍｉｍ、切り込み量０．１ｍｍ、送り速度０．０５ｍｍ／ｒｅｖ．、不水溶性油剤を用いた湿式切削とした。実験後、実施例１と同様の方法で被削材の寸法の変化量を測定した。
【００３０】
【表４】

【００３１】
表４に示すように、試料１ａ〜４ａでは寸法変化が１０μｍ以下と小さく、白濁のない美しい加工面が得られた。試料５ａ〜７ａのものは、前の例に比較すると被削材の寸法変化が大きく、また加工面品位が悪かった。表４の中の加工面品位の丸（○）や二重丸（◎）は、表２と同様の意味である。
【００３２】
（実施例３）
サーメット母材の切削性能に与える影響を確認するために表５に示すサーメット合金母材にすくい面に０．７μｍ、逃げ面に４．８μｍのＴｉＡｌＮを被覆し、硬質粒子としてＴｉＣＮを用いた刃先交換チップを作製した。その他は実施例１と同じにした。前記形態の試料を一般的に用いられるホルダーに取り付けた切削工具として、切削加工実験を行った。
【００３３】
切削試験は、直径１２ｍｍ、長さ１０ｍｍの丸材のＳＵＳ４３０Ｆからなる被削材を次の切削条件で、１０００ヶ加工して、加工面の品位と寸法のばらつきを調査した。切削条件は、一般的な高精度部品の旋削加工を想定して、切削速度５０ｍ／ｍｉｎ、切り込み量０．１ｍｍ、送り速度０．０５ｍｍ／ｒｅｖ．、不水溶性の油剤を用いる湿式切削とした。実験後、被削材の寸法の変化量を実施例１と同様に測定した。
【００３４】
【表５】

【００３５】
表５に示すように、超硬合金を母材とした場合と同様に、試料１ｂ、２ｂでは寸法変化が１０μｍ以下と小さく、加工面も白濁のない美しい加工面が得られた。これに対し試料３ｂと試料４ｂは、試料１ｂや試料２ｂに比較すると寸法変化が大きく、加工面品位が悪かった。
【００３６】
さらに言えば、被覆層としてＴｉＣＮ、ＴｉＮ、ＴｉＡｌＮ、ＴｉＳｉＮなどが適しており、さらにＡｌ_２Ｏ_３、ＴｉＳｉＣＮ、ＡｌＮ、Ｖｎ、ＣｒＮ、ＴｉＡｌＳｉＮ、ＴｉＺｒＮ、ＺｒＮなども使用できる。これらの化合物からなる単層であっても多層であっても効果は変わらないことを確認した。本実施の形態では外径の旋削加工にて、その効果を説明した。しかしながら、前挽き旋削加工だけではなく、図６に示すような内径旋削加工用工具や、図７に示すような後挽き施削用工具、または、溝入れ加工用工具、ねじ切り加工用工具などでも同様の効果が得られる。また本発明は、刃先交換工具や、一般の切削工具に使用できる。
【００３７】
更に、切削工具の形状としては、逃げ角が５°〜２０°程度のものが、切れ味と耐欠損性を両立する上で望ましい。すくい角については、一般的なステンレスや鋼の加工では５°〜３０°程度のすくい角をつけると切れ味が良く、本発明の効果を向上させることが可能である。しかし、例えば、真鍮や黄銅の加工においてすくい角は、むしろ０°の方が良い場合もある。
【００３８】
【発明の効果】
本発明の高精度加工用被覆切削工具は、特にマイクロメートル単位の高い精度が要求される時計やカメラ、電子機器部品の旋削加工に利用される。本発明の切削工具は、ステンレスなどの溶着しやすい被削材を、寸法ばらつきなく高精度かつ、白濁の無い虹色に輝く良好な仕上げ面で長時間加工することができる。
【図面の簡単な説明】
【図１】図１（ａ）は、本発明に係わる刃先交換チップの切れ刃の拡大断面図、図１（ｂ）は、刃先交換チップの側面図である。
【図２】実施例１で用いた刃先交換チップの外観図である。
【図３】実施例１の本発明に係わる試料▲３▼に記載された刃先交換チップであって、切削試験後の切れ刃の断面図である。
【図４】実施例１の比較例である試料▲６▼に記載された刃先交換チップであって、すくい面と逃げ面のコーティング層が厚いもので切削試験した後の切れ刃の断面図である。
【図５】実施例１の比較例である試料▲５▼に記載された刃先交換チップであって、すくい面と逃げ面のコーティング層が薄いもので切削試験した後の切れ刃の断面図である。
【図６】本発明の他の実施形態を示す高精度加工用被覆切削工具の外観図である。
【図７】本発明の他の実施形態を示す高精度加工用被覆切削工具の外観図である。
【符号の説明】
１　　刃先交換チップ
２　　すくい面のコーティング層
３　　逃げ面のコーティング層
４　　母材
５　　切れ刃
６　　逃げ面の摩耗部
７　　切れ刃の丸み[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated cutting tool for high-precision machining that is most suitable for use in a field requiring high precision on a micrometer scale, such as electronic device parts. In particular, the present invention relates to a coated cutting tool for high-precision machining, which is excellent in sharpness and can obtain good machining surface quality.
[0002]
[Prior art]
In general, turning of watches, cameras, and electronic equipment parts that require high precision in the order of micrometers requires not only dimensional accuracy and surface roughness of the machined surface, but also a shiny machined surface that shines in rainbow colors. In many cases. In such high-precision machining, dimensional accuracy and a good machining surface that shines in iridescence are required. For this purpose, it is important to improve the sharpness of the cutting tool and prevent welding to the cutting edge. In order to achieve such an object, a coated cutting tool coated with TiAlN, TiCN, or TiN by a well-known PVD method is used (for example, see Patent Document 1).
[0003]
However, with a general coated cutting tool, the coating layer having a thickness of 4 to 5 μm is coated, so that the cutting edge is rounded by the thickness of the coating layer at the cutting edge portion, and the cutting quality is reduced, and the quality of the machined surface is reduced. There was a problem of lowering. For this reason, in these coated cutting tools for high-precision processing, a device such as making the coating layer as thin as possible has been devised (for example, see Patent Documents 1 and 2).
[0004]
[Patent Document 1]
JP 2001-347403 A (page 2-3, FIG. 2)
[Patent Document 2]
JP 2001-277004 A (page 2-3)
[0005]
[Problems to be solved by the invention]
However, when both the rake face and the flank coating layer are thinned, the amount of exposure of the base material increases when the tool is worn, and further, the exposed base material is welded, and the processed surface becomes cloudy. In addition, there is a problem that dimensional variations occur. As means for solving such a problem, in Patent Document 2, a cutting edge portion of a base material is polished to reduce surface roughness, and a thin coating layer of 2 μm or less is provided thereon. By doing so, the component cutting edge is stably generated, and the dimension is stabilized by protecting the cutting edge with the component cutting edge. However, this invention uses a component cutting edge to cause a small chip in the tool when the component cutting edge falls off, or wears because the entire coating layer is thin, so that the base material exposed amount on the flank side increases, resulting in machining. There was a problem that the surface became cloudy. Here, that the processed surface becomes cloudy means that the processed surface is peeled and turned white.
[0006]
Patent Literature 1 discloses a coated cutting tool in which the rake face has a thickness of 0.5 to 2 μm and the flank has a thickness of 1 to 4 μm. An object of the present invention is to suppress a decrease in dimensional accuracy due to chipping of a coating layer. Therefore, when the coating layer is worn and the exposed amount of the base material on the flank increases, the processed surface may be easily clouded.
[0007]
[Means for Solving the Problems]
As a result of repeated studies, the inventors have found that it is important not to expose the base material on the flank side in order to obtain a good rainbow-colored processed surface. That is, in a coated cutting tool for high-precision machining in which a coating layer is coated using a cemented carbide or a cermet as a base material, the cutting edge is a sharp edge, and the surface roughness of the cutting edge is the center line average roughness Ra: 0. The present invention provides a coated cutting tool for high-precision machining in which the thickness of a rake face coating layer is 0.5 to 2 μm and the thickness of a flank coating layer is 4 to 7 μm. .
[0008]
In the present invention, a sharp edge is a cutting edge obtained by grinding a rake face and a flank, except for a portion having small irregularities presumed to be caused by falling off of hard particles constituting a cemented carbide or a cermet. That is. The coating layer may be a multi-layer, and may be, for example, TiN / TiAlN, TiAlN / CrN, TiN / TiAlN / Al ₂ O ₃ , TiN / TiSiN / TiSiCN, TiN / TiZrN / ZrN, TiAlN / VN in order from the base material. Combinations are also possible. In addition, the thickness of the single layer of the TiN and TiAlN films is 2.5 nm, and 1200 layers thereof are alternately laminated to make the entire film thickness 3 μm. In the present invention, a more desirable range of the coating layer is such that the thickness of the rake face coating layer is 0.5 to 1 μm and the thickness of the flank coating layer is more than 4 μm and 5 μm or less.
[0009]
The cemented carbide comprises 3 to 12% by mass of a binder and the balance of tungsten carbide and unavoidable impurities, has a Vickers hardness of 14 to 22 GPa, and has an average particle size of 0.3 to 2 μm. Is preferred. If the amount of the binder is less than 3% by mass, the cemented carbide will not be high in strength, and if it exceeds 12% by mass, the hardness will be insufficient. Further, by using fine tungsten carbide having an average particle diameter of 0.3 to 2 μm, the surface roughness of the base material is reduced, and the coated cutting tool for high-precision machining of the present invention can be stably manufactured.
[0010]
The cermet is composed of titanium-based hard particles containing 10 to 20% by mass of a binder and 3 to 6% by mass of nitrogen and unavoidable impurities, has a Vickers hardness of 14 to 22 GPa, and has an average particle size of the titanium-based hard particles. A cermet having a diameter of 0.3 to 2 μm may be used as a base material.
[0011]
In cemented carbide and cermet, Co or Ni is usually used as a binder. Co is often used in cemented carbide, and Co and Ni are often used together in cermets. However, in each case, Co and Ni can be used alone or in combination.
[0012]
The coating layer of the present invention is composed of one or more elements selected from the group consisting of carbides, nitrides, borides, oxides and solid solutions of one or more elements selected from Ti, Zr, Cr, Al, and Si. It is preferably formed of one or more layers of the compound. It was confirmed that the use of the coated cutting tool for high-precision machining of the present invention having such a coating layer provided a good machined surface quality without cloudiness and reduced the dimensional change of the work material.
[0013]
At the time of cutting, the cutting edge is rounded by the thickness of the coating layer, and the sharpness is reduced. To prevent this, it has been found that if the coating layer on the rake face is made thinner, the flank side is thicker but the flank wear does not cause roundness of the cutting edge. The present invention has been made based on such a finding. FIG. 1 shows a cutting edge replacement tip according to the present invention, and (a) is an enlarged view of a cutting edge 5 portion. That is, as shown in FIG. 1A, at least the thickness of the coating layer 2 on the rake face is made thinner than the thickness of the coating layer obtained by a general PVD method, and the thickness of the coating layer 3 on the flank is increased. It was done. By doing so, it is possible to maintain good sharpness even if worn, and to reduce the amount of exposure of the base material when the flank wears. Therefore, it is possible to maintain a good processed surface quality strongly required for processing of electronic device parts for a long time, and to suppress a dimensional change due to welding or the like.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
(Example 1)
In order to demonstrate the effect of the present invention, eight types of samples were prepared. The base metal used for the sample is a cemented carbide having an average particle size of tungsten carbide of about 1 μm, a Co content of about 10% by mass, and a Vickers hardness of about 14 GPa. Using this base material, a cutting edge replacement tip having the shape shown in FIG. 2 was manufactured. FIG. 2 shows a cutting edge replacement tip having a rhombic shape with a vertical angle of 55 °, a clearance angle of 7 ° formed on the flank side, and a rake angle of 20 ° formed on the rake surface side. In order to perform high-precision processing, the polished base material has sharp sharp edges, and the rake face and the flank have a center line average roughness of 0.4 μm or less.
[0015]
[Table 1]

[0016]
[Table 2]

[0017]
[Table 3]

[0018]
The base material was coated with TiAlN by a known arc ion plating method so that the film thickness of the rake face and the flank face changed as shown in Table 1. The thickness of the coating layer was changed by controlling the time for coating. In addition, the thickness ratio of the rake face and the flank is such that an obstacle is provided in front of the rake face at the time of coating so that the coating layer on the rake face does not become thicker, or the direction of the tip replacement tip set in the coating furnace is changed. Controlled by that.
[0019]
Here, Samples (1) to (4) are invention products in which the rake face film thickness is in the range of 0.5 to 2 μm and the flank face film thickness is in the range of 4 to 8 μm. 5) to 8) are comparative examples. Next, a cutting experiment was performed as a cutting tool in which the sample of the above embodiment was attached to a commonly used holder. In the experiment, a work material made of SUS430F, which is a round material having a diameter of 12 mm and a length of 10 mm, was machined 1000 times under the following cutting conditions, and the quality and dimensions of the machined surface were investigated. The cutting conditions are the turning of a general high-precision part. The cutting speed is 50 m / min, the depth of cut is 0.1 mm, and the feed speed is 0.05 m / rev. And wet cutting using a water-insoluble oil agent.
[0020]
Table 2 shows the change in the quality of the machined surface for each machining quantity in the above cutting test. The quality of the machined surface was determined by visually observing the machined work material. Particularly, ◎ indicates a good machined surface, 、 indicates a good machined surface, and x indicates a clouded machined surface. As shown in Table 2, the samples (1) to (4) of the present invention maintain a good processed surface for a long time. Further, among the products of the present invention, the samples (2) and (3) in which the rake face film thickness is 1 μm or less and the flank face film thickness is more than 4 μm and 5 μm or less are still good even after cutting 1000 pieces in particular. The machined surface is obtained.
[0021]
On the other hand, samples (5) and (7) having a thin flank of less than 4 μm have good surface quality at the beginning, but the flank wears and the cemented carbide as the base material is exposed. And the processed surface becomes cloudy. On the other hand, in the case of the sample (6) having a large film thickness, since the cutting edge is rounded at the cutting edge by the thickness of the coating layer, the processed surface becomes cloudy from the very beginning.
[0022]
On the other hand, in the sample (8) in which the thickness of the flank was increased to 8 μm, chipping occurred on the flank in the middle because the thickness of the coating layer on the flank was too large, and the quality of the processed surface deteriorated. Results.
[0023]
Table 3 shows the dimensional variation. When a predetermined number of workpieces were machined, the outer diameter of the last 10 workpieces was measured, and the difference in diameter between the largest and smallest workpieces was 5 μm or less. 20 μm or more was expressed as x. As shown in Table 3, the samples of the invention have small dimensional variations, and especially the samples (2) and (3) in which the thickness of the coating layer on the rake face is 1 μm or less and the thickness of the coating layer on the flank face is 4 to 5 μm. Good results.
[0024]
On the other hand, in the comparative example, as well as the quality of the machined surface, as a result of the exposure of the cemented carbide of the base material, the roundness of the cutting edge, and the effect of chipping, even if the number of machines that were initially good increased, the dimensional variation increased. It has become.
[0025]
FIG. 3 schematically shows the cross section of the cutting edge after processing the sample (3), FIG. 4 shows the sample (6), and FIG. 5 shows the sample (5). As shown in FIG. 4, in the case of the sample (6) in which the flank face and the rake

face coating layers

2 and 3 are thick, the cutting edge has a roundness 7 corresponding to the thickness of the rake face coating layer, and the sharpness is reduced. Further, as shown in FIG. 5, in the sample (5) in which the thicknesses of the rake face and the flank coating layers 2 and 3 were reduced, the flank coating layer 3 was worn and the base material was exposed in a wide range. The processed surface becomes cloudy.
[0026]
However, in the sample (3) of the present invention, as shown in FIG. 3, the roundness 7 of the cutting edge caused by the wear of the rake face coating layer 2 is small, and the flank face coating layer 3 is thick. Therefore, the base material was hardly exposed, the sharpness was maintained, and the turbidity of the processed surface was prevented.
[0027]
As described above, according to the present invention, welding can be prevented and the amount of exposure of the base material due to wear can be reduced while maintaining the sharpness of the tool, so that a good finished surface quality can be obtained for a long time and variation in dimensions can be reduced. Was completed.
[0028]
(Example 2)
In order to confirm the effect of the cemented carbide base material on the cutting performance, a cutting edge replacement tip was prepared in which the rake face of the cemented carbide base material shown in Table 4 was coated with 0.7 μm rake face and the flank face was coated with 4.8 μm TiAlN. . Others were the same as Example 1. Next, a cutting experiment was performed as a cutting tool in which the sample of the above embodiment was attached to a commonly used holder.
[0029]
In the experiment, a work material made of SUS430F, which is a round material having a diameter of 12 mm and a length of 10 mm, was machined 1000 times under the following cutting conditions, and the quality and dimensions of the machined surface were investigated. As for the cutting conditions, assuming the turning of a general high-precision part, the cutting speed is 50 m / mim, the depth of cut is 0.1 mm, and the feed speed is 0.05 mm / rev. And wet cutting using a water-insoluble oil agent. After the experiment, the amount of change in the dimensions of the work material was measured in the same manner as in Example 1.
[0030]
[Table 4]

[0031]
As shown in Table 4, in Samples 1a to 4a, the dimensional change was as small as 10 μm or less, and a beautiful processed surface without white turbidity was obtained. In the samples 5a to 7a, the dimensional change of the work material was large and the processed surface quality was poor as compared with the previous example. Circles (○) and double circles (◎) of the processed surface quality in Table 4 have the same meanings as in Table 2.
[0032]
(Example 3)
In order to confirm the effect of the cermet base material on the cutting performance, a cutting edge of a cermet alloy base material shown in Table 5 coated with 0.7 μm rake face and 4.8 μm flank flank face and using TiCN as hard particles was used. An exchange tip was prepared. Others were the same as Example 1. A cutting experiment was performed as a cutting tool in which the sample of the above-mentioned form was attached to a commonly used holder.
[0033]
In the cutting test, a work material made of SUS430F of a round material having a diameter of 12 mm and a length of 10 mm was machined under the following cutting conditions to 1000 pieces, and the quality and dimensions of the machined surface were examined. As for the cutting conditions, assuming the turning of a general high-precision part, the cutting speed is 50 m / min, the depth of cut is 0.1 mm, and the feed speed is 0.05 mm / rev. And wet cutting using a water-insoluble oil agent. After the experiment, the amount of change in the dimensions of the work material was measured in the same manner as in Example 1.
[0034]
[Table 5]

[0035]
As shown in Table 5, similarly to the case where the cemented carbide was used as the base material, the dimensional change was as small as 10 μm or less in Samples 1b and 2b, and a beautiful processed surface without white turbidity was obtained. On the other hand, the sample 3b and the sample 4b showed a large dimensional change as compared with the sample 1b and the sample 2b, and the quality of the processed surface was poor.
[0036]
Furthermore, TiCN, TiN, TiAlN, TiSiN and the like are suitable for the coating layer, and Al ₂ O ₃ , TiSiCN, AlN, Vn, CrN, TiAlSiN, TiZrN, ZrN and the like can also be used. It was confirmed that the effect was not changed whether the compound was a single layer or a multilayer. In the present embodiment, the effect has been described by turning the outer diameter. However, not only front turning, but also internal turning tools as shown in FIG. 6, rear turning tools as shown in FIG. 7, grooving tools, thread cutting tools, etc. Similar effects can be obtained. Further, the present invention can be used for a cutting edge replacement tool and a general cutting tool.
[0037]
Further, as the shape of the cutting tool, one having a clearance angle of about 5 ° to 20 ° is desirable in order to achieve both sharpness and chipping resistance. Regarding the rake angle, in general processing of stainless steel or steel, if a rake angle of about 5 ° to 30 ° is provided, sharpness is improved, and the effect of the present invention can be improved. However, for example, in machining brass or brass, the rake angle may be more preferably 0 °.
[0038]
【The invention's effect】
INDUSTRIAL APPLICABILITY The coated cutting tool for high-precision machining of the present invention is used for turning a watch, a camera, and an electronic device part that requires high precision, particularly in units of micrometers. ADVANTAGE OF THE INVENTION The cutting tool of this invention can machine a work material which is easy to weld, such as stainless steel, with high precision with no dimensional variation and a good rainbow-colored finish surface without cloudiness for a long time.
[Brief description of the drawings]
FIG. 1 (a) is an enlarged sectional view of a cutting edge of a blade tip replacement tip according to the present invention, and FIG. 1 (b) is a side view of the blade tip replacement tip.
FIG. 2 is an external view of a blade tip replacement tip used in Example 1.
FIG. 3 is a cross-sectional view of a cutting edge replacement tip described in a sample (3) according to the present invention of Example 1 and showing a cutting edge after a cutting test.
FIG. 4 is a cross-sectional view of a cutting edge after a cutting test with a cutting edge replacement tip described in a sample (6), which is a comparative example of Example 1, having a thick rake face and a flank coating layer. is there.
FIG. 5 is a cross-sectional view of the cutting edge after the cutting test, which is a cutting edge replacement tip described in a sample (5) which is a comparative example of Example 1 and has a thin rake face and a flank coating layer. is there.
FIG. 6 is an external view of a coated cutting tool for high-precision machining showing another embodiment of the present invention.
FIG. 7 is an external view of a coated cutting tool for high-precision machining showing another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF REFERENCE NUMERALS 1 Cutting edge exchange tip 2 Coating layer on rake face 3 Coating layer on flank 4 Base material 5 Cutting edge 6 Wear part on flank 7 Roundness of cutting edge

Claims

In a coated cutting tool for high-precision machining in which a coating layer is coated using a cemented carbide or a cermet as a base material, the cutting edge is a sharp edge, and the surface roughness of the cutting edge is a center line average roughness Ra: 0.4 μm Below,
A coated cutting tool for high-precision machining, characterized in that the rake face coating layer has a thickness of 0.5 to 2 μm and the flank coating layer has a thickness of 4 to 7 μm.

2. The high-precision processing according to claim 1, wherein the rake face coating layer has a thickness of 0.5 to 1 [mu] m, and the flank coating layer has a thickness of more than 4 [mu] m and 5 [mu] m or less. For coated cutting tools.

The cemented carbide comprises 3 to 12% by mass of a binder and the balance of tungsten carbide and unavoidable impurities, has a Vickers hardness of 14 to 22 GPa, and has an average particle size of 0.3 to 2 μm. The coated cutting tool for high-precision machining according to claim 1 or 2, wherein:

The cermet is composed of titanium-based hard particles containing 10 to 20% by mass of a binder and 3 to 6% by mass of nitrogen and unavoidable impurities, has a Vickers hardness of 14 to 22 GPa, and has an average particle size of the titanium-based hard particles. The coated cutting tool for high-precision machining according to claim 1, wherein the diameter is 0.3 to 2 μm.

The coating layer is formed of a compound selected from the group consisting of carbides, nitrides, borides, oxides, and solid solutions of at least one element selected from Ti, Zr, Cr, Al, and Si. The coated cutting tool for high-precision machining according to any one of claims 1 to 4, wherein the coated cutting tool is formed of one or more layers.

The coated cutting tool according to any one of claims 1 to 5, wherein the coating layer is any one of TiCN, TiN, TiAlN, and TiSiN.