JP2004223666A

JP2004223666A - Cutting tool for rough machining

Info

Publication number: JP2004223666A
Application number: JP2003015987A
Authority: JP
Inventors: Takashi Tokunaga; 隆司徳永
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2003-01-24
Filing date: 2003-01-24
Publication date: 2004-08-12
Anticipated expiration: 2023-01-24
Also published as: JP4069749B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting tool for rough machining made of cermet exerting cutting performance equal to or more than that of cemented carbide in a rough machining region. <P>SOLUTION: This cermet made of TiCN group cermet made of a binding phase mainly made of Co and Ni and a hard phase made of carbon nitride of 4a, 5a and 6a group metal in a periodic table mainly made of Ni, containing Co and Ni of 15 to 22 mass% in total amount, containing Ti of 55 to 80 mass% in relation to total amount of 4a, 5a and 6a group metal in the periodic table, and having an average crystal particle size of 0.5 to 1μm of the hard phase of the center part of the cermet is used as the cutting tool for roughing. It is desirable that a binding phase enriched region where binding phase concentration is gradually increased exists at a thickness of 0.01 to 5μm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、ＴｉＣＮ基サーメットからなり、荒加工用として高い切削性能を有する切削工具に関する。
【０００２】
【従来の技術】
従来より、切削加工用のスローアウェイチップの素材として炭化タングステンからなる硬質相をＣｏの結合相で結合した超硬合金（例えば、特許文献１、２参照）や、Ｔｉと、Ｔｉ以外の周期律表４ａ、５ａおよび６ａ族金属のうちの１種以上との複合金属炭窒化物からなる硬質相を、Ｃｏおよび／またはＮｉの結合相にて結合したＴｉＣＮ基サーメット（例えば、特許文献３、４参照）が主として用いられている。ところで、現状では超硬合金は仕上げ加工から荒加工に至る幅広い加工領域で用いられているものの、ＴｉＣＮ基サーメットは高い耐摩耗性、鋼材との優れた耐反応性を生かして仕上げ加工領域で用いられているのが実状である。
【０００３】
【特許文献１】
特開平８−５７７０３号公報
【特許文献２】
特開２００１−３２９３３１号公報
【特許文献３】
特開２００１−２７７００８号公報
【特許文献４】
特開平９―２３９６０５号公報
【０００４】
【発明が解決しようとする課題】
ところが、近年、炭化タングステンの枯渇が危惧されており、ＴｉＣＮ基サーメットにて広範囲な加工可能領域、特に荒加工領域で高い切削性能を発揮するＴｉＣＮ基サーメットが切望されている。
【０００５】
しかしながら、特許文献３、４などの従来のＴｉＣＮ基サーメットを荒加工に用いると、仕上げ加工よりも切削工具に加わる衝撃が大きいために、この切削時の衝撃によって工具が早期に欠損しやすく、超硬合金の切削性能には及ばないという問題があった。
【０００６】
従って、本発明は、上記課題を解決するためになされたものであり、その目的は、荒加工領域で超硬合金と同等またはそれ以上の切削性能を発揮するＴｉＣＮ基サーメットからなる荒加工用切削工具を提供することにある。
【０００７】
【課題を解決するための手段】
本発明者は、上記荒加工用に適したサーメットの構成について検討した結果、Ｔｉおよび結合相の含有量、硬質相の粒径を最適化することにより、荒加工領域にて超硬合金と同等またはそれ以上の高い切削性能を発揮するサーメットが得られることを知見した。
【０００８】
即ち、本発明の荒加工用切削工具は、Ｃｏおよび／またはＮｉを主成分とする結合相と、Ｔｉを主とする周期律表４ａ、５ａおよび６ａ族金属の炭窒化物からなる硬質相とからなるＴｉＣＮ基サーメットからなり、前記ＣｏおよびＮｉを総量で１５〜２２質量％含有し、前記周期律表４ａ、５ａおよび６ａ族金属総量に対してＴｉを５５〜８０質量％含有し、且つサーメット中心部の前記硬質相の平均結晶粒径が０．５〜１μｍであることを特徴とする。
【０００９】
また、前記サーメットの極表面には、結合相濃度が次第に増加する結合相富化領域が存在することによって、荒加工領域にも耐えうる耐欠損性を有しかつ物理蒸着もしくは化学蒸着膜などを形成した場合においても工具本体との優れた密着性を維持することができる。この前記結合相富化領域は０．０１〜５μｍの厚みで存在することが望ましい。
【００１０】
また、前記サーメットの表面には、（Ｔｉ_ｘＭ_１−ｘ）（Ｃ_ｙＮ_１−ｙ）（ただし、ＭはＴｉ以外の周期律表４ａ、５ａおよび６ａ族金属、Ａｌ、Ｓｉのうちの１種以上、０．４≦ｘ≦１、０≦ｙ≦１）で表わされる硬質被覆層を被覆してなることによって、優れた耐磨耗性と耐欠損性を両立し発揮とすることができる。
【００１１】
【発明の実施の形態】
本発明の切削工具は、Ｃｏおよび／またはＮｉを主成分とする結合相と、Ｔｉを主とする周期律表４ａ、５ａおよび６ａ族金属の炭窒化物からなる硬質相とからなるＴｉＣＮ基サーメットからなるものであるが、本発明によれば、特に荒加工に適した工具に関わるものである。
【００１２】
ここで、本発明における荒加工領域とは、送り０．３０ｍｍ／ｒｅｖ（回転）以上、かつ、切込み２．０ｍｍ以上、切削速度２５０ｍ／ｍｉｎ以上で、湿式または乾式状態での加工、特に旋削加工を指す。
【００１３】
この荒加工用に適した工具とする上で、本発明によれば、前記ＣｏおよびＮｉを総量で１５〜２２質量％含有することが重要である。すなわち、結合相の含有量が１５質量％未満では所望の強度および耐衝撃性を得ることができず、逆に結合相の含有量が２２質量％を越えると急激に耐摩耗性が低下する結果、いずれの場合も荒加工用として用いると即時欠損および刃先の塑性変形性が悪く、摩滅してしまい優れた切削性能を得ることができない。ＣｏおよびＮｉは、特に１６〜２０質量％、さらには１７〜１９．５質量％の割合で含有されることが望ましい。
【００１４】
また、本発明によれば、サーメット中における前記周期律表４ａ、５ａおよび６ａ族金属総量に対してＴｉを５５〜８０質量％含有することが重要である。これは、前記Ｔｉ量が５５質量％より少ないと荒加工に必要な強度を確保することができず、逆に、８０質量％より多いと靭性が低下して、荒加工時の耐衝撃性が低下する。特に前記Ｔｉ量は６５〜７７質量％であることが望ましい。
【００１５】
このＴｉを含む周期律表４ａ、５ａおよび６ａ族金属は、硬質相として複合金属炭窒化物を形成しており、特に、硬質相は、ＴｉＣＮからなる芯部と、Ｔｉと、Ｔｉ以外の周期律表４ａ、５ａおよび６ａ族金属、特にＷ、Ｍｏ、ＴａおよびＮｂのうちの１種以上との複合炭化物、複合窒化物、複合炭窒化物の少なくとも１種からなる周辺部とから構成される２重有芯構造、または３重有芯構造をなしていることが、粒成長制御効果を有しサーメット基体が微細で均一な組織となるとともに、結合相との濡れ性に優れてサーメットの高強度化に寄与する点で望ましい。
【００１６】
さらに、本発明によれば、切削工具の中心部における前記硬質相の平均結晶粒径が０．５〜１μｍ、特に０．６〜０．９μｍ、さらに０．７〜０．９μｍであることが重要である。すなわち、この硬質相の平均結晶粒径が０．５μｍより小さいと硬質相の凝集が生じやすく不均一な組織となってサーメットの耐衝撃性や硬度が低下し、工具の耐欠損性および耐摩耗性が低下する。逆に、硬質相の平均結晶粒径が１μｍを超えるとサーメットの強度が低下してチップの耐欠損性が低下する。
【００１７】
また、本発明の切削工具においては、前記サーメットの極表面に結合相濃度が次第に増加する結合相富化領域が存在することが望ましい。このような結合相富化領域の存在によって、切削工具の切刃における熱伝導性を高めることができる結果、切刃の放熱性を増し荒加工時における過酷な切削条件での耐欠損性を高めることができる。また、これによって切刃が被削材における加工面の形状に対してわずかに変形して被削材の加工面の面粗度をなめらかにする効果も有する。前記結合相富化領域の厚みは、切削工具の中心部分の結合相量に対して、１．１倍以上の結合相量を有する領域として、最表面からの厚みが０．０１〜５μｍ、さらに１〜３μｍ、さらに１〜２．５μｍであることが前記熱伝導性を高めるとともに、工具切刃における過度な塑性変形を抑制するために望ましい。
【００１８】
また、後述する硬質被覆層との密着性、熱伝導率向上、塑性変形の抑制の点でサーメット基体の表面における硬質相の平均結晶粒径ｒ_１が、サーメット中心部における硬質相の平均結晶粒径ｒ_２よりも大きいことが望ましく、具体的にはｒ_１＝０．５〜２μｍであることが望ましい。
【００１９】
さらには、本発明によれば、サーメット基体表面に、（Ｔｉ_ｘＭ_１−ｘ）（Ｃ_ｙＮ_１−ｙ）（ただし、ＭはＴｉ以外の周期律表４ａ、５ａおよび６ａ族金属、Ａｌ、Ｓｉのうちの１種以上、０．４＜ｘ≦１、０≦ｙ≦１）で表わされる硬質被覆層（以下、Ｔｉ系被覆層と略す。）を被覆してもよく、かかる被覆層はサーメット母材の直上に形成することが望ましい。さらには、高硬度や高温安定性などの耐熱性の点で、Ｍは、Ａｌ、Ｓｉ、ＺｒおよびＣｒの群から選ばれる１種、最適にはＡｌであることが最も望ましい。
【００２０】
また、硬質被覆層としては、上記Ｔｉ系被覆層に加えて、例えば、ダイヤモンド、立方晶窒化硼素、アルミナ、Ｚｒ、Ｈｆ、Ｃｒ、Ｓｉの炭化物、窒化物、炭窒化物の１種以上からなる他の硬質被覆層を形成することもできる。
【００２１】
本発明のＴｉＣＮ基サーメットからなる切削工具を製造するには、まず原料粉末として、硬質相形成成分として、ＴｉＣＮ粉末と、周期律表４ａ、５ａおよび６ａ族金属の炭化物、窒化物、炭窒化物の群から選ばれる少なくとも１種の粉末を用いて、周期律表４ａ、５ａおよび６ａ族金属総量に対するＴｉ量が５５〜８０質量％、特に６５〜７７質量％となるように秤量する。また、硬質相形成成分全体における炭素（Ｃ）と窒素（Ｎ）とのＮ／（Ｃ＋Ｎ）の比率が０．４〜０．６となるように調合する。
【００２２】
また、このときに用いるＴｉＣＮ粉末の平均粒径が０．４〜１．０μｍの微細な粉末であることが必要である。この時のＴｉＣＮ粉末の平均粒径が１．０μｍよりも大きいと、サーメットにおける硬質相の前記平均結晶粒径を１μｍ以下にすることが困難となる。また、０．４μｍよりも小さいと、硬質相の前記平均結晶粒径を０．５μｍ以上とすることが困難となる。
【００２３】
また、周期律表４ａ、５ａおよび６ａ族金属の炭化物、窒化物、炭窒化物の群から選ばれる少なくとも１種の粉末の平均粒径は０．５〜２μｍが適当である。
【００２４】
また、結合相形成成分として、平均粒径が０．３〜４μｍのＮｉおよび／またはＣｏの粉末を１５〜２２質量％の割合で添加する。
【００２５】
そしてこれらの秤量された粉末をボールミルなどによって混合した後、プレス成形、押出成形、射出成形などの公知の成形手法によって所定の切削工具形状に成形した後、焼成する。
【００２６】
焼成にあたっては、有芯構造の硬質相を形成し、また硬質相の粒成長を抑制するために、真空度０．０１Ｔｏｒｒ以下で、室温から９５０℃付近までを１０〜１５℃／分で昇温し、その後、１３００℃付近までを１〜５℃／分で昇温し、さらに１５００℃〜１６００℃までを３℃〜１５℃／分で昇温し保持時間１時間以内で放冷で室温まで１０℃〜１５℃／分で冷却する条件で焼成することが望ましい。
【００２７】
また、サーメット表面に結合相富化領域を形成するためには、上記の焼成条件において、室温から１２５０℃〜１３５０℃までを窒素ガスを０．１〜０．３ｋＰａの窒素ガス中で処理し、１２５０℃〜１３５０℃から１５００〜１６００℃の昇温過程のみ真空０．０１Ｔｏｒｒ以下とし、１５００℃〜１６００℃で焼成した後、冷却過程において真空０．０１Ｔｏｒｒ以下として室温まで１０℃〜１５℃／分で冷却することが望ましい。
【００２８】
また、上記の方法によって作製されたＴｉＣＮ基サーメットを母材として、その表面に、化学気相成長法（ＣＶＤ法）や、スパッタリング法、イオンプレーティング法、蒸着法などの物理気相成長法（ＰＶＤ法）などによって前述したような被覆層を形成すればよい。
【００２９】
【実施例】
原料粉末として、表１に示す平均粒径のＴｉＣＮ粉末と、いずれも平均粒径が０．５〜２μｍのＴｉＮ粉末、ＴａＣ粉末、ＮｂＣ粉末、ＷＣ粉末、ＺｒＣ粉末、ＶＣ粉末、および平均粒径が２μｍのＣｏ粉末、Ｎｉ粉末またはＣｏとＮｉとの合金粉末を用い、これら原料粉末を表１に示される配合組成に配合し、ボールミルで湿式混合粉砕した。なお、上記平均粒径はマイクロトラック法で測定したものである。
【００３０】
次に、上記混合粉末を用いて、成形圧９８ＭＰａでチップ形状および抗折試験片形状にプレス成形し、それぞれの成形体を０．０１Ｔｏｒｒ以下の真空中で９５０℃まで１２℃／ｍｉｎで昇温し、９５０℃から１３００℃までを２℃／分で昇温し、表１の焼成温度まで５℃／分で昇温し、１時間保持した後、真空中で１２℃／分で室温まで降温して、ＣＮＭＧ１２０４０８形状のサーメットを作製した。なお、試料Ｎｏ．８、９については、昇温過程で１３００℃までは０．２ＫＰａの窒素中とする以外は、上記と同様にして焼成した。
【００３１】
作製したサーメットについて、ＪＩＳＲ１６０１に従い、３点曲げ強度を測定するとともに、ＪＩＳＲ１６０７に従い、靱性（ＩＦ法）の測定を行った。結果は表２に示した。
【００３２】
さらに得られたチップ中心部の断面を電子顕微鏡観察して７×７μｍの観察領域２箇所をインターセプト法で硬質相の結晶粒径を測定し、その平均結晶粒径を測定した。
【００３３】
さらに、チップの表面付近における結合相のＮｉとＣｏの濃度分布をＥＰＭＡ法で濃度変化を測定し、ＮｉとＣｏの濃度変化の合算でＮｉ＋Ｃｏの濃度変化を観察し、表面から、中心部分の濃度に対して１．１倍以上の濃度を有する領域までの厚みを３箇所測定しその平均を求めた。
【００３４】
また、得られたスローアウェイチップ各１０個ずつについて、下記荒切削条件Ａで切削を行い、欠損した時の送りを表１に示した。
切削条件
被削材：ＳＣＭ４３５
被削材：４本溝入り丸棒
切削速度：２５０ｍ／ｍｉｎ
送りおよび切削時間：０．１ｍｍ／ｒｅｖで１０秒間切削後、送りを０．０５ｍｍ／ｒｅｖずつ上げて各１０秒間ずつ切削（最大送り０．５ｍｍ／ｒｅｖまで）
切込み：２ｍｍ
【００３５】
【表１】

【００３６】
表１の結果から明らかなように、本発明の試料Ｎｏ．１〜３、５〜１１は、いずれも高い強度、硬度を有するとともに荒加工切削においても試料Ｎｏ．１６の超硬合金なみの優れた切削特性を示した。
【００３７】
これに対して、Ｎｉ＋Ｃｏ含有量が１５質量％より少ない試料Ｎｏ．１３では抗折強度が低く、荒加工条件では早期に欠損が発生してしまった。また、Ｎｉ＋Ｃｏ含有量が２２質量％を超える試料Ｎｏ．１５では，金属冨化層が厚くなり耐酸化性および耐塑性変形性が低下し、刃先が摩滅した。
【００３８】
さらに、周期律表４ａ、５ａおよび６ａ族金属総量に対してＴｉの含有量が５５質量％より少ない試料Ｎｏ．１２ではチップの刃先が早期に欠損が発生してしまい、周期律表４ａ、５ａおよび６ａ族金属総量に対してＴｉの含有量が８０質量％を超える試料Ｎｏ．１２では摩耗が進行して早期に切削不能となった。さらに、複合金属炭窒化物の平均粒径が１μｍを超える試料Ｎｏ．４、１４では、荒加工切削で早期に欠損が発生してしまった。
【００３９】
【発明の効果】
以上詳述したように、本発明の切削工具は、ＴｉＣＮ基サーメットでありながら、Ｔｉおよび結合相の含有量、硬質相の粒径を最適化することにより、荒加工領域において超硬合金と同等またはそれ以上の高い切削性能を発揮する工具を提供することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cutting tool made of a TiCN-based cermet and having high cutting performance for roughing.
[0002]
[Prior art]
Conventionally, as a material of a cutting away insert for cutting, a cemented carbide in which a hard phase made of tungsten carbide is bonded with a binder phase of Co (for example, see Patent Documents 1 and 2), Ti, and a periodic rule other than Ti Tables 4a, 5a, and TiCN-based cermets in which a hard phase composed of a composite metal carbonitride with one or more of the Group 6a metals is bonded by a Co and / or Ni binder phase (for example, Patent Documents 3 and 4) ) Are mainly used. By the way, at present, cemented carbide is used in a wide range of processing areas from finishing to roughing, but TiCN-based cermet is used in the finishing area by taking advantage of high wear resistance and excellent reaction resistance with steel materials. It is the fact that it is being done.
[0003]
[Patent Document 1]
JP-A-8-57703 [Patent Document 2]
JP 2001-329331 A [Patent Document 3]
JP 2001-277008 A [Patent Document 4]
Japanese Patent Application Laid-Open No. 9-239605
[Problems to be solved by the invention]
However, in recent years, depletion of tungsten carbide has been feared, and there is a strong demand for a TiCN-based cermet that exhibits high cutting performance in a wide range of workable regions, particularly in a rough machining region.
[0005]
However, when conventional TiCN-based cermets such as Patent Literatures 3 and 4 are used for rough machining, the impact applied to the cutting tool is greater than that of the finishing machining. There is a problem that it does not reach the cutting performance of hard alloy.
[0006]
Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a rough machining cutting comprising a TiCN-based cermet that exhibits a cutting performance equal to or higher than that of a cemented carbide in a rough machining region. To provide tools.
[0007]
[Means for Solving the Problems]
The present inventor has studied the configuration of the cermet suitable for the above-mentioned rough machining, and as a result, by optimizing the content of Ti and the binder phase and the grain size of the hard phase, the same as the cemented carbide in the rough machining region Or, it has been found that a cermet exhibiting a higher cutting performance can be obtained.
[0008]
That is, the cutting tool for rough machining of the present invention comprises a binder phase containing Co and / or Ni as a main component, and a hard phase composed of carbonitride of a Group 4a, 5a or 6a group metal mainly composed of Ti. And containing 15 to 22% by mass of Co and Ni in total, and 55 to 80% by mass of Ti with respect to the total amount of Group 4a, 5a and 6a metals, and cermet An average crystal grain size of the hard phase at the center is 0.5 to 1 μm.
[0009]
Further, on the very surface of the cermet, the presence of a binder phase-enriched region in which the binder phase concentration is gradually increased. Even when formed, excellent adhesion to the tool body can be maintained. It is desirable that the binder phase enriched region exists with a thickness of 0.01 to 5 μm.
[0010]
Further, the surface of the _{_{_{cermet, (Ti x M 1-x}}} ) (C y N 1-y) ( however, M is the Periodic Table 4a other than Ti, 5a and 6a metals, Al, of Si By coating at least one kind of hard coating layer represented by 0.4 ≦ x ≦ 1, 0 ≦ y ≦ 1), it is possible to exhibit excellent wear resistance and fracture resistance at the same time. it can.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The cutting tool according to the present invention provides a TiCN-based cermet comprising a binder phase containing Co and / or Ni as a main component and a hard phase composed of a carbonitride of a Group 4a, 5a, or 6a metal mainly containing Ti. According to the present invention, the present invention relates to a tool particularly suitable for rough machining.
[0012]
Here, the rough machining area in the present invention refers to machining in a wet or dry state, particularly turning, with a feed of 0.30 mm / rev (rotation) or more, a cut of 2.0 mm or more, and a cutting speed of 250 m / min or more. Point to.
[0013]
According to the present invention, it is important to contain Co and Ni in a total amount of 15 to 22% by mass in order to obtain a tool suitable for the rough machining. That is, when the content of the binder phase is less than 15% by mass, the desired strength and impact resistance cannot be obtained, and when the content of the binder phase exceeds 22% by mass, the wear resistance rapidly decreases. In any case, when used for roughing, immediate chipping and poor plastic deformation of the cutting edge are abraded, making it impossible to obtain excellent cutting performance. Co and Ni are desirably contained at a ratio of 16 to 20% by mass, more preferably 17 to 19.5% by mass.
[0014]
Further, according to the present invention, it is important to contain 55 to 80% by mass of Ti with respect to the total amount of the metals in the periodic table 4a, 5a and 6a in the cermet. If the Ti content is less than 55% by mass, the strength required for rough working cannot be secured. If the Ti amount is more than 80% by mass, the toughness is reduced, and the impact resistance during rough working is reduced. descend. In particular, the amount of Ti is desirably 65 to 77% by mass.
[0015]
The group 4a, 5a and 6a metals of the periodic table containing Ti form a composite metal carbonitride as a hard phase. In particular, the hard phase is composed of a core made of TiCN, Ti, and a period other than Ti. Consisting of at least one of a complex carbide, a complex nitride, and a complex carbonitride with at least one of Group 4a, 5a, and 6a metals, particularly W, Mo, Ta, and Nb. Having a double cored structure or a triple cored structure has a grain growth control effect, makes the cermet substrate a fine and uniform structure, and has excellent wettability with the binder phase and high cermet height. It is desirable in that it contributes to strengthening.
[0016]
Further, according to the present invention, the average crystal grain size of the hard phase at the center of the cutting tool is 0.5 to 1 μm, particularly 0.6 to 0.9 μm, and further preferably 0.7 to 0.9 μm. is important. That is, if the average crystal grain size of the hard phase is smaller than 0.5 μm, the hard phase is liable to agglomerate, resulting in a non-uniform structure, thereby reducing the impact resistance and hardness of the cermet, and the chip resistance and wear resistance of the tool. Is reduced. Conversely, when the average crystal grain size of the hard phase exceeds 1 μm, the strength of the cermet decreases, and the chip resistance of the chip decreases.
[0017]
Further, in the cutting tool of the present invention, it is desirable that a binder phase-enriched region in which the binder phase concentration gradually increases exists on the extremely surface of the cermet. Due to the presence of such a binder-phase-enriched region, the thermal conductivity of the cutting edge of the cutting tool can be increased, and as a result, the heat dissipation of the cutting edge is increased and the fracture resistance under severe cutting conditions during rough machining is increased. be able to. This also has the effect that the cutting edge is slightly deformed with respect to the shape of the machined surface of the work material to smooth the surface roughness of the machined surface of the work material. The thickness of the binder phase enriched region is a region having a binder phase amount of 1.1 times or more with respect to the binder phase amount of the central portion of the cutting tool, and the thickness from the outermost surface is 0.01 to 5 μm, The thickness is preferably 1 to 3 μm, more preferably 1 to 2.5 μm, in order to increase the thermal conductivity and to suppress excessive plastic deformation in the tool cutting edge.
[0018]
Further, the average crystal grain size r ₁ of the hard phase on the surface of the cermet substrate in terms of adhesion to the hard coating layer described later, improvement in thermal conductivity, and suppression of plastic deformation are determined by the average crystal grain size of the hard phase in the center of the cermet. It is desirable that the diameter be larger than the diameter r _{2, and} more specifically, it is desirable that r ₁ = 0.5 to ₂ μm.
[0019]
Furthermore, according to the present invention, the cermet substrate _{_{_{surface, (Ti x M 1-x}}} ) (C y N 1-y) ( however, M is the Periodic Table 4a other than Ti, 5a and 6a metals, Al , Si, a hard coating layer (hereinafter abbreviated as Ti-based coating layer) represented by 0.4 <x ≦ 1, 0 ≦ y ≦ 1). Is desirably formed immediately above the cermet base material. Further, in terms of heat resistance such as high hardness and high-temperature stability, M is most preferably selected from the group consisting of Al, Si, Zr and Cr, and most preferably Al.
[0020]
The hard coating layer is made of, for example, at least one of diamond, cubic boron nitride, alumina, Zr, Hf, Cr, and Si carbide, nitride, and carbonitride in addition to the Ti-based coating layer. Other hard coating layers can be formed.
[0021]
In order to manufacture a cutting tool made of the TiCN-based cermet of the present invention, first, TiCN powder as a raw material powder, a hard phase forming component, and carbides, nitrides, and carbonitrides of metals of Group 4a, 5a and 6a of the periodic table. Is weighed using at least one powder selected from the group consisting of the metals in the periodic table 4a, 5a and 6a so that the Ti content is 55 to 80% by mass, especially 65 to 77% by mass. Further, the mixture is prepared so that the ratio of N / (C + N) of carbon (C) and nitrogen (N) in the entire hard phase forming component is 0.4 to 0.6.
[0022]
Further, it is necessary that the TiCN powder used at this time is a fine powder having an average particle diameter of 0.4 to 1.0 μm. If the average particle size of the TiCN powder at this time is larger than 1.0 μm, it is difficult to reduce the average crystal particle size of the hard phase in the cermet to 1 μm or less. On the other hand, when it is smaller than 0.4 μm, it is difficult to make the average crystal grain size of the hard phase 0.5 μm or more.
[0023]
The average particle size of at least one powder selected from the group consisting of carbides, nitrides, and carbonitrides of metals belonging to groups 4a, 5a and 6a of the periodic table is suitably 0.5 to 2 μm.
[0024]
Further, as a bonding phase forming component, Ni and / or Co powder having an average particle diameter of 0.3 to 4 μm is added at a ratio of 15 to 22% by mass.
[0025]
These weighed powders are mixed by a ball mill or the like, formed into a predetermined cutting tool shape by a known molding technique such as press molding, extrusion molding, or injection molding, and then fired.
[0026]
In the firing, in order to form a hard phase having a cored structure and suppress grain growth of the hard phase, the temperature is raised from room temperature to around 950 ° C. at a rate of 10 to 15 ° C./min at a degree of vacuum of 0.01 Torr or less. Then, the temperature is raised to around 1300 ° C. at 1 to 5 ° C./min, and further from 1500 ° C. to 1600 ° C. at 3 ° C. to 15 ° C./min. It is desirable to perform firing under the condition of cooling at 10 ° C. to 15 ° C./min.
[0027]
Further, in order to form a binder phase-enriched region on the cermet surface, under the above-described firing conditions, nitrogen gas is treated from room temperature to 1250 ° C. to 1350 ° C. in 0.1 to 0.3 kPa nitrogen gas, Vacuum is set to 0.01 Torr or less only in the temperature raising process from 1250 ° C. to 1350 ° C. to 1500 to 1600 ° C. After firing at 1500 ° C. to 1600 ° C., the vacuum is reduced to 0.01 Torr or less to 10 ° C. to 15 ° C./min. It is desirable to cool with.
[0028]
Further, using a TiCN-based cermet produced by the above method as a base material, a physical vapor deposition method such as a chemical vapor deposition method (CVD method), a sputtering method, an ion plating method, or a vapor deposition method is applied to the surface thereof. The above-mentioned coating layer may be formed by a PVD method or the like.
[0029]
【Example】
As the raw material powder, a TiCN powder having an average particle diameter shown in Table 1, a TiN powder, a TaC powder, an NbC powder, a WC powder, a ZrC powder, a VC powder, and an average particle diameter each having an average particle diameter of 0.5 to 2 μm. Was used, Co powder, Ni powder or an alloy powder of Co and Ni was used, and these raw material powders were blended in the composition shown in Table 1 and wet-mixed and pulverized with a ball mill. The average particle size is measured by a microtrack method.
[0030]
Next, the mixed powder is press-molded into a chip shape and a bending test piece shape at a molding pressure of 98 MPa, and each molded body is heated to 950 ° C. at a rate of 12 ° C./min in a vacuum of 0.01 Torr or less. Then, the temperature was raised from 950 ° C. to 1300 ° C. at a rate of 2 ° C./min, raised to the firing temperature shown in Table 1 at a rate of 5 ° C./min, held for one hour, and then cooled to room temperature in a vacuum at a rate of 12 ° C./min. Thus, a cermet in the shape of CNMG120408 was produced. The sample No. Regarding 8 and 9, calcination was carried out in the same manner as above except that the temperature was raised up to 1300 ° C. in nitrogen of 0.2 KPa.
[0031]
The prepared cermet was measured for the three-point bending strength according to JISR1601, and the toughness (IF method) was measured according to JISR1607. The results are shown in Table 2.
[0032]
Further, the cross section of the central part of the obtained chip was observed with an electron microscope, and the crystal grain size of the hard phase was measured by an intercept method at two observation regions of 7 × 7 μm, and the average crystal grain size was measured.
[0033]
Further, the concentration distribution of Ni and Co in the binder phase near the surface of the chip was measured by EPMA method, and the change in the concentration of Ni + Co was observed by adding the changes in concentration of Ni and Co. The thickness was measured at three locations up to a region having a density 1.1 times or more of the thickness, and the average was obtained.
[0034]
In addition, cutting was performed under the following rough cutting conditions A for each of the obtained 10 insert away inserts, and the feed at the time of chipping is shown in Table 1.
Cutting conditions Work material: SCM435
Work material: Round bar with 4 grooves Cutting speed: 250 m / min
Feed and cutting time: After cutting at 0.1 mm / rev for 10 seconds, feed is increased by 0.05 mm / rev and cut for 10 seconds each (up to a maximum feed of 0.5 mm / rev)
Cut: 2mm
[0035]
[Table 1]

[0036]
As is clear from the results in Table 1, the sample No. of the present invention. Sample Nos. 1 to 3 and 5 to 11 all have high strength and hardness and are rough even in cutting. 16 showed excellent cutting characteristics comparable to cemented carbide.
[0037]
On the other hand, the sample No. in which the Ni + Co content was less than 15% by mass. In No. 13, the transverse rupture strength was low, and chipping occurred early under rough working conditions. In addition, Sample No. having a Ni + Co content exceeding 22% by mass. In No. 15, the metal-enriched layer became thick, the oxidation resistance and the plastic deformation resistance were reduced, and the cutting edge was worn.
[0038]
Further, in the sample No. 4 in which the content of Ti was less than 55% by mass with respect to the total amount of metals of the group 4a, 5a and 6a of the periodic table. In Sample No. 12, the cutting edge of the chip was early fractured, and the content of Ti in Sample No. 12 in which the content of Ti exceeded 80% by mass with respect to the total amount of metals in Groups 4a, 5a and 6a of the periodic table. In No. 12, abrasion progressed and cutting became impossible early. Further, in Sample No. 1 in which the average particle size of the composite metal carbonitride exceeded 1 μm. In Nos. 4 and 14, chipping occurred early in rough machining cutting.
[0039]
【The invention's effect】
As described above in detail, the cutting tool of the present invention is equivalent to a cemented carbide in a rough machining region by optimizing the content of Ti and a binder phase and the particle size of a hard phase, while being a TiCN-based cermet. Alternatively, it is possible to provide a tool exhibiting higher cutting performance.

Claims

A TiCN-based cermet composed of a binder phase containing Co and / or Ni as a main component and a hard phase composed of a carbonitride of a metal of Group 4a, 5a or 6a containing Ti as a main component; Is contained in a total amount of 15 to 22% by mass, Ti is contained in an amount of 55 to 80% by mass with respect to the total amount of the metals in the periodic table 4a, 5a and 6a, and the average crystal grain size of the hard phase in the center of the cermet is A cutting tool for rough machining, having a diameter of 0.5 to 1 μm.

The cutting tool for rough machining according to claim 1, wherein a binder phase-enriched region in which the binder phase concentration is gradually increased is present on the very surface of the cermet.

The cutting tool for rough machining according to claim 2, wherein the binder phase enriched region exists with a thickness of 0.01 to 5 µm.

On the surface of the _{_{_{cermet, (Ti x M 1-x}}} ) (C y N 1-y) ( however, M is the Periodic Table 4a other than Ti, 5a and 6a metals, Al, 1 or more of Si The cutting tool according to any one of claims 1 to 3, wherein the cutting tool is coated with a hard coating layer represented by the following formula: 0.4 ≤ x ≤ 1, 0 ≤ y ≤ 1).