JP2004202598A

JP2004202598A - Throw away tip and method for manufacturing the same

Info

Publication number: JP2004202598A
Application number: JP2002372074A
Authority: JP
Inventors: Takashi Tokunaga; 隆司徳永
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2002-12-24
Filing date: 2002-12-24
Publication date: 2004-07-22
Anticipated expiration: 2022-12-24
Also published as: JP4035045B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a throw away tip made of cermet, which has fine hard phase structure, high cutting performance, and small dispersion of the cutting performance among the tips. <P>SOLUTION: The throw away tip is made of the cermet composed of 1-30mass% bonding phase having Co and/or Ni as main components, and 70-99mass% hard phase composed of compound metal carbonitride of Ti and one or more kinds of metals among 4a, 5a, and 6a group metals in the periodic table other than Ti, and has an almost flat plate shape. The average grain size of the hard phase is at most 1.5μm. The Weibull coefficient of the transverse rupture strength of the transverse rupture test pieces, which are taken so as to include the side surface of the tip from ten pieces of the throw away tips, is at least 5. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、高い切削性能を有するサーメット製スローアウェイチップに関し、特に、微細な組織を有するとともに特性のバラツキが少ないサーメット製スローアウェイチップとその製造方法に関するものである。
【０００２】
【従来の技術】
従来より、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の結合相からなるサーメットや、このようなサーメットの表面に、化学蒸着法や物理蒸着法を用いてＴｉＣ、ＴｉＮ、ＴｉＣＮ等の硬質被覆層を被覆したサーメット製スローアウェイチップが、鋼などの連続切削や断続切削などに用いられている（例えば、特許文献１、２）。
【０００３】
また、このようなサーメットにおいては、その硬度、強度を高めてスローアウェイチップの耐摩耗性および耐欠損性を向上させる目的で硬質相の粒径を制御することが行われており、例えば、特許文献３、４ではサーメット内部の平均粒径を２μｍ以下に制御することが記載されている。
【０００４】
【特許文献１】
特開平５−２２２５５１号公報
【特許文献２】
特開平４−２８９００３号公報
【特許文献３】
特開平５−１９２８０４号公報
【特許文献４】
特開平６−１７２２９号公報
【０００５】
【発明が解決しようとする課題】
しかしながら、特許文献３、４に見られるように、硬質相の粒径を微細に制御する上では、原料粉末の微細化が不可欠であるが、その場合、硬質相を形成する炭化物、窒化物、炭窒化物などの原料粉末が凝集したり、難焼結化に伴い焼成温度を高める必要があり、その結果、結合相の溶融や分解が促進されることによって結合相が偏析したり、焼結体表面や内部にボイドが生成される等、よって組織が不均質となり易く、チップ毎の機械的特性や切削性能に大きなばらつきが生じてしまうという問題があった。
【０００６】
このため、スローアウェイチップの使用に際して、定数交換を行うような場合には切削性能の低いチップに定数を合わせざるを得ず、高性能のチップが形成されても、その性能を発揮できず、工具費をも高める要因となっていた。
【０００７】
本発明は、このような課題を解決するためになされたものであり、その目的は、微細な硬質相組織を有し、高い切削性能を有するとともに、チップ間の特性バラツキを小さくしたスローアウェイチップとその製造方法を提供することにある。
【０００８】
【課題を解決するための手段】
本発明者は、上述のような観点から、微粒な硬質相からなる微粒サーメットの特性バラツキを抑制する方法について検討した結果、原料の性状、混合粉末の制御条件および焼成条件をコントロールすることによって、微粒サーメットの特性バラツキを抑制することができ、スローアウェイチップの切削性能の信頼性を高めることが可能となることを知見した。
【０００９】
すなわち、本発明のスローアウェイチップは、Ｃｏおよび／またはＮｉを主体とする結合相：１〜３０質量％と、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７０〜９９質量％からなるサーメットからなる略平板形状のスローアウェイチップであって、前記硬質相の平均粒径が１．５μｍ以下であるとともに、前記スローアウェイチップ１０個について、該チップの側面を含んで切り出された抗折試験片の抗折強度のワイブル係数が５以上であることを特徴とするものである。
【００１０】
また、前記サーメット中の硬質相の平均粒径を０．３〜１μｍとすること、前記サーメットの抗折強度測定の破面にて観察される破壊源となる結晶粒子の最大径が１０μｍ以下であることによってサーメットの抗折強度を高めることができ、スローアウェイチップの耐欠損性を向上することができる。
【００１１】
また、前記サーメットの表面には、（Ｔｉｘ，Ｍ１−ｘ）（ＣｙＮ１−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することによって、さらに耐摩耗性を向上することができる。
【００１２】
さらに、本発明のスローアウェイチップの製造方法は、平均粒径０．２〜０．９μｍ、酸素含有量１質量％以下のＴｉＣＮ粉末と、Ｔｉ以外の周期律表４ａ、５ａおよび６ａ族金属のうちの１種以上を含有する炭化物粉末、窒化物粉末、炭窒化物粉末の少なくとも１種とからなる硬質相形成成分７０〜９９質量％と、平均粒径０．０５〜１μｍのＣｏおよび／またはＮｉ粉末とからなる結合相形成成分１〜３０質量％とを秤量し、マイクロトラック法による粒度分布において粒径１μｍ以上の粉末の比率が１０質量％以下となるように粉砕、混合、分級した混合粉末を得、これをチップ形状に成形した後、室温から１１００〜１２５０℃の焼成温度Ａまで昇温し、該焼成温度Ａから１３００℃まで０．５〜３℃／ｍｉｎの昇温速度ａで昇温し、次に１３００℃から１４００〜１５００℃の焼成温度Ｂまで５〜１５℃／ｍｉｎの昇温速度ｂで昇温し、さらに、１５００〜１６００℃の焼成温度Ｃまで４〜１４℃／ｍｉｎの昇温速度ｂよりも遅い昇温速度ｃで昇温して保持した後、降温する条件で焼成することを特徴とする。
【００１３】
また、チップ表面に、（Ｔｉｘ，Ｍ１−ｘ）（ＣｙＮ１−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することもできる。
【００１４】
【発明の実施の形態】
以下に本発明のスローアウェイチップを製造する方法について説明する。
まず、ＴｉＣＮ粉末と、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、とりわけＷ、Ｍｏ、Ｔａ、Ｖ、ＺｒおよびＮｂのうちの１種以上を含有する炭化物粉末、窒化物粉末、炭窒化物粉末の少なくとも１種とからなる硬質相形成成分と、Ｃｏおよび／またはＮｉ粉末とからなる結合相形成成分とを所定の比率に秤量する。
【００１５】
ここで、前記硬質相形成成分は、いずれも平均粒径０．２〜０．９μｍ、特に０．５〜０．８μｍであることが必要である。これは、平均粒径が０．２μｍよりも小さいと、サーメット組織内に破壊源となりうる結合相の凝集部やこの結合相の凝集部が溶出してできるボイドが発生して抗折強度のバラツキが大きくなり、０．９μｍよりも大きいと、サーメットの抗折強度が全体的に低下してしまうためである。
【００１６】
また、前記結合相形成成分は、平均粒径が０．０５〜１μｍ、特に０．３〜０．６μｍであることが必要である。これは、平均粒径が０．０５μｍよりも小さいと、結合相が凝集しやすく破壊源の要因となる結合相の凝集部や凝集部中の金属が溶出したボイドが発生しやすく、１μｍよりも大きいと、結合相の分布が不均一となりやすくなるためである。
【００１７】
また、上記硬質相形成成分のうち、少なくともＴｉＣＮ粉末の酸素含有量を１質量％以下、特に０．０５〜０．８質量％に制御することが重要である。すなわち、かかるＴｉＣＮ粉末の酸素含有量が１質量％よりも多いと、焼結体中にボイドが発生したり結合相の凝集が生じて焼結体の抗折強度にバラツキが生じてチップの切削性能に大きなバラツキが発生するためである。
【００１８】
また、上記硬質相形成成分と結合相形成成分とは、硬質相形成成分７０〜９９質量％、特に８０〜９０質量％、結合相形成成分１〜３０質量％、特に１０〜２０質量％の割合で秤量混合する。
【００１９】
これは、硬質相形成成分量が上記範囲よりも少ないか、または結合相形成成分が上記範囲よりも多いと、硬質相の粒径が微粒なまま合金を緻密化することができなくなるためであり、硬質相形成成分量が上記範囲よりも多い、または結合相形成成分が上記範囲よりも少ないと、サーメットの硬度が低下してスローアウェイチップの耐摩耗性が低下するためである。
【００２０】
次に、上記粉末をアトライタミルにて混合、粉砕し、マイクロトラック法による粒度分布において混合粉末中に粒径１μｍ以上の粒子の比率が１０質量％以下の混合粉末を得る。本発明によれば、混合粉末中に含まれる粒径１μｍ以上の粒子の比率を１０質量％以下に制御することが重要であり、これによって、サーメット焼結体中に粗大粒子が存在することを防止できるとともに、粗大粒子生成に伴う焼結体表面の荒れや組織変動を抑制して均一な組織を有するサーメットを形成することができる。なお、この粒径１μｍ以上の粒子の比率が１０質量％以下とするには、粉砕処理を上記分布になった時点で終了するか、必要に応じ分級処理を行う。
【００２１】
そして、上記混合粉末をチップ形状に成形した後、
（ａ）室温から１１００〜１２５０℃の焼成温度Ａまで昇温し、
（ｂ）焼成温度Ａから１３００℃まで０．５〜３℃／ｍｉｎの昇温速度ａで昇温し、
（ｃ）１３００℃から１４００〜１５００℃の焼成温度Ｂまで５〜１５℃／ｍｉｎの昇温速度ｂで昇温し、
（ｄ）１５００〜１６００℃の焼成温度Ｃまで４〜１４℃／ｍｉｎで昇温速度ｂより遅い昇温速度ｃで昇温して保持し、
（ｅ）降温する条件で焼成する。
【００２２】
ここで、（ｂ）の昇温速度ａが０．５℃／ｍｉｎより遅いと硬質相が粒成長してしまう。また、昇温速度ａが３℃／ｍｉｎより速いと結合相形成成分が部分的に溶融して結合相の凝集部を生じる。
【００２３】
また、（ｃ）の昇温速度ｂが５℃／ｍｉｎより遅いと、焼結体全体が粒成長して硬質相の平均粒径を１．５μｍ以下に制御することができず耐欠損性が低下する。昇温速度ｂが１５℃／ｍｉｎより速いと焼結体の粒成長が不均質となり、局部的に結合相の凝集や異常粒成長によってチップのワイブル係数が５より小さくなる。また、焼成温度Ｂが１４００℃よりも低いと工程（ｂ）における予備焼結において液相を十分に出現させることができず、逆に焼成温度Ｂが１５００℃を超えると液相出現量が多すぎてサーメット基体の表面に多量のボイドが発生して、いずれもチップのワイブル係数が５より小さくなる。
【００２４】
また、（ｄ）の昇温速度ｃが４℃／ｍｉｎより遅いと基体表面において硬質相の平均粒径が１．５μｍ以上に粒成長して耐欠損性が低下し、逆に、昇温速度が１４℃／ｍｉｎより速いと焼結体組織が不均一となり耐摩耗性が低下する。さらにまた、焼成温度Ｃが１５００℃よりも低いと基体を十分に緻密化することができず、焼結体内部にボイド等が残存してチップのワイブル係数が５より小さくなる。逆に焼成温度Ｃが１６００℃を超えると焼結体が過焼結となって表面が荒れ、チップのワイブル係数が低下する。
【００２５】
なお、前記焼成条件で焼成する場合、ＣｏとＮｉとの固溶体を原料として使用すれば、一層焼結性が改善され、焼結体表面に発生するオープンポアや焼結不良の発生を抑制することができる。
【００２６】
そして、得られたサーメット基体に対して所望により研磨等の表面加工処理した後、化学的蒸着法または物理的蒸着法等のコーティング法を用いて硬質被覆層を単層または２層以上被覆することにより、本発明のサーメット製スローアウェイチップを作製することができる。また、コーティング法としては、硬質被覆層の粒径を微細化する点で、サーメット基体との反応性の低い物理的蒸着法を用いることが望ましい。
【００２７】
上記工程により作製された本発明のサーメットからなるスローアウェイチップは、ＣｏおよびＮｉからなる結合相にて、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結合してなるサーメットからなり、略平板のチップ形状のサーメット製スローアウェイチップであって、前記硬質相の平均粒径が１．５μｍ以下、特に０．３〜１μｍであるとともに、前記スローアウェイチップ１０個について、該チップから抗折試験片を切り出したときの抗折強度のワイブル係数が５以上、特に７以上、さらに１０以上であることを特徴とする特性バラツキの小さいものとなる。
【００２８】
なお、本発明におけるスローアウェイチップの抗折強度のワイブル係数とは、スローアウェイチップの側面（逃げ面）を含んで切り出された抗折試験片（試験片の形状はチップの大きさで取れる四角棒状形状、１０本以上）を試験片の形状以外はＪＩＳＲ１６０１に準じて測定し、ＪＩＳＲ１６２５に準じて算出されるワイブル係数のことを意味する。
【００２９】
なお、試験片の形状は、断面（縦、横）と抗折試験時のスパンが縦：横：スパン＝３：４：３０の関係になるように試験片を切り出し、側面（逃げ面）を引っ張り面（応力付加面と反対側）に配置して測定したものである。
【００３０】
なお、本発明における試験片の形状はスローアウェイチップから側面（逃げ面）を含んで切り出すことのできる最大の四角柱形状とし、縦:横：長さの比が３：４：１０となりように切り出したものとする。
【００３１】
また、本発明のサーメット製スローアウェイチップにおいては、チップの抗折強度測定後の破断面にて観察される異常粒やボイド等の破壊源となる結晶粒子の最大径が直径が１０μｍ以下、特に５μｍ以下、さらに３μｍ以下であることが望ましく、これによってサーメットの抗折強度を高めることができ、スローアウェイチップの耐欠損性を向上することができる結果、チップのワイブル係数を高くすることができて、チップの切削性能バラツキをより小さくすることができる。
【００３２】
また、本発明においては、前記サーメット基体の極表面に、結合相（Ｃｏ含有量＋Ｎｉ含有量）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く、これによって、前記硬質被覆層の前記サーメット基体との間に発生する剪断応力を緩和して両者間の密着性を著しく向上せしめることができることから、スローアウェイチップの耐欠損性を向上させることができる。
【００３３】
なお、本発明において、硬質被覆層の密着性を確保するとともに、熱伝導率が悪く、高温になりやすいＴｉ基サーメット基体の基体表面における熱伝導率を高め、かつ工具切刃における塑性変形を抑制する点で、前記結合相富化領域の厚みは０．０１〜５μｍ、さらに１〜３μｍ、さらに１〜２．５μｍであることが望ましい。
【００３４】
一方、本発明においては、焼結性および耐摩耗性、耐塑性変形性の点で、結合相の含有量が１〜３０質量％であることが重要である。すなわち、結合相の含有量が１質量％未満では所望の強度および耐摩耗性を得ることができず、逆に結合相の含有量が３０質量％を越えると急激に耐摩耗性が低下する。結合相の望ましい含有量は４〜２０質量％である。
【００３５】
さらに、本発明のスローアウェイチップをなすサーメットは、硬質相として、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、特にＷ、Ｚｒ、Ｖ、Ｔａ、Ｎｂ、Ｍｏの群から選ればれる少なくとも１種との複合金属炭窒化物からなり、特に、硬質相は、Ｔｉ（ＴｉＣＮ）からなる芯部と、Ｔｉと、Ｗ、Ｍｏ、ＴａおよびＮｂのうちの１種以上との複合化合物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。
【００３６】
また、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粒径ｒ₁が、サーメット基体内部におけるそれｒ₂よりも大きいことが望ましく、さらに、ｒ₁＝０．５〜２μｍ、ｒ₂＝０．２〜１μｍであることが望ましい。
【００３７】
さらには、本発明によれば、サーメット基体表面に、（Ｔｉｘ，Ｍ１−ｘ）（ＣｙＮ１−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Ｔｉ系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く、さらには、高硬度や高温安定性などの耐熱性の点で、（Ｔｉ，Ｍ１）Ｎ（ただし、Ｍ１はＡｌ、Ｓｉ、ＺｒおよびＣｒの群から選ばれる１種）、最適には（Ｔｉｘ，Ａｌ１−ｘ）Ｎからなる硬質被覆層を被覆することが望ましい。
【００３８】
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。
【００３９】
【実施例】
原料粉末として、表１に示す平均粒径（ｄ）、酸素含有量のＴｉＣＮ粉末と、いずれも０．５〜２μｍのＴｉＮ粉末、ＴａＣ粉末、ＮｂＣ粉末、ＷＣ粉末、ＺｒＣ粉末、ＶＣ粉末、および表１に示す平均粒径（ｄ）のＣｏとＮｉとの合金粉末（試料Ｎｏ．６と１６はＣｏ粉末とＮｉ粉末の単独粉末（平均粒径ｄはいずれも０．５μｍ））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し、粉砕時間を変えてマイクロトラック法による粒度分布において混合粉末中に粒径１μｍ以上の粉末の比率が表１となるまで粉砕して乾燥した。
【００４０】
次に、上記混合粉末を用いて、成形圧９８ＭＰａでプレス成形し、この成形体を表１の焼成条件で焼成してＣＮＭＧ１２０４０８形状のサーメットを１０個ずつ作製した（試料Ｎｏ．１〜１１）。
【００４１】
また、上記と同じ工程にて作製したサーメットそれぞれの表面に、アーク放電型イオンプレーティング法を用い、２．４μｍのＴｉＡｌＮの硬質被覆層を形成することにより表面にコーティングを施したサーメット製スローアウェイチップをそれぞれ１０個ずつ作製した（試料Ｎｏ．１２）。
【００４２】
得られたチップについて側面（逃げ面）を含む抗折試験片（すくい面幅０．７５ｍｍ×逃げ面幅１ｍｍ×逃げ面長さ１０ｍｍ）の形状を各２本ずつ（２本×チップ１０個＝２０本）を切り出し、それぞれ試験片の形状以外はＪＩＳＲ１６０１に準じてスパン７．５ｍｍで、逃げ面を引っ張り面として３点曲げ強度を測定するとともに、ＪＩＳＲ１６２５に準じてワイブル係数を算出した。また、抗折強度測定後の試験片の破断面についてＳＥＭ観察を行い、破壊源を特定するとともに破壊源となった結晶粒子の最大径を求めた。結果は表２に示した。
【００４３】
また、上記同様の条件で作製したスローアウェイチップ各１０個ずつについて、下記切削条件Ａにて切削評価を行った。
切削条件Ａ
被削材：Ｓ４５Ｃ
被削材：４本溝入り丸棒、
切削速度：１００ｍ／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、
評価項目：欠損するまでの総切削時間（平均値、バラツキ）
【００４４】
【表１】

【００４５】
【表２】

【００４６】
表１、２に示される結果から、本発明の範囲内である試料Ｎｏ．１〜１２では、いずれも優れた切削特性を示すとともに切削性能のバラツキが小さいものであった。これに対して、原料粉末の性状、混合工程の制御、焼成条件が本発明の工程から逸脱したチップの抗折強度のワイブル係数が５より小さい試料Ｎｏ．１３〜１９では、切削試験においてもチップ間で性能バラツキが大きいものであった。
【００４７】
【発明の効果】
以上詳述したように、本発明のスローアウェイチップは、原料の性状、混合粉末の制御条件および焼成条件などをコントロールし、硬質相を微粒子化するとともに、チップの抗折強度のばらつきを低減することによって、スローアウェイチップの切削性能の信頼性を高めることが可能となる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cermet indexable insert having high cutting performance, and more particularly, to a cermet indexable insert having a fine structure and little variation in characteristics, and a method of manufacturing the same.
[0002]
[Prior art]
Conventionally, a hard phase composed of a composite metal carbonitride of Ti and one or more of the metals in the Periodic Tables 4a, 5a and 6a other than Ti is replaced with a cermet composed of a Co and / or Ni binder phase, A cermet indexable insert in which the surface of such a cermet is coated with a hard coating layer of TiC, TiN, TiCN, or the like using a chemical vapor deposition method or a physical vapor deposition method is used for continuous cutting or interrupted cutting of steel or the like. (For example, Patent Documents 1 and 2).
[0003]
Further, in such a cermet, the hardness, the strength is increased, and the grain size of the hard phase is controlled for the purpose of improving the wear resistance and fracture resistance of the throw-away tip. Documents 3 and 4 describe that the average particle size inside the cermet is controlled to 2 μm or less.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 5-222551 [Patent Document 2]
JP-A-4-289003 [Patent Document 3]
JP-A-5-192804 [Patent Document 4]
JP-A-6-17229
[Problems to be solved by the invention]
However, as can be seen in Patent Documents 3 and 4, in order to finely control the particle size of the hard phase, it is indispensable to make the raw material powder finer. In that case, carbides, nitrides, Raw material powders such as carbonitrides agglomerate, and the firing temperature must be increased as sintering becomes difficult, and as a result, the melting and decomposition of the bonding phase is accelerated, so that the bonding phase segregates and sintering occurs. Therefore, there is a problem that the structure is likely to be non-uniform, for example, voids are generated on the body surface or inside, and that the mechanical characteristics and the cutting performance of each chip greatly vary.
[0006]
For this reason, when using constant inserts, constants must be adjusted to inserts with low cutting performance when constant exchange is performed, and even if a high-performance insert is formed, its performance cannot be exhibited. This was also a factor that increased tool costs.
[0007]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a throw-away insert having a fine hard phase structure, high cutting performance, and a small variation in characteristics between chips. And a method of manufacturing the same.
[0008]
[Means for Solving the Problems]
The present inventor has studied the method for suppressing the characteristic variation of the fine cermet composed of the fine hard phase from the above-described viewpoint, and by controlling the properties of the raw material, the control conditions and the firing conditions of the mixed powder, It has been found that variations in the characteristics of the fine cermet can be suppressed, and the reliability of the cutting performance of the indexable insert can be improved.
[0009]
That is, the throw-away tip of the present invention comprises a binder phase mainly composed of Co and / or Ni: 1 to 30% by mass, Ti, and one of metals of Group 4a, 5a and 6a other than Ti. A substantially plate-shaped throw-away chip made of a cermet comprising 70 to 99% by mass of a hard phase composed of a composite metal carbonitride as described above, wherein the hard phase has an average particle size of 1.5 μm or less, With respect to ten throw-away chips, the Weibull coefficient of the bending strength of the bending test piece cut out including the side surface of the chip is 5 or more.
[0010]
Further, the average particle diameter of the hard phase in the cermet is 0.3 to 1 μm, and the maximum diameter of the crystal grains serving as a fracture source observed on the fracture surface of the bending strength measurement of the cermet is 10 μm or less. With this, the bending strength of the cermet can be increased, and the fracture resistance of the throw-away tip can be improved.
[0011]
Further, on the surface of the cermet, (Tix, M1-x) (CyN1-y) (where M is at least one of metals of the periodic table 4a, 5a and 6a other than Ti, Al, Si, By coating the hard coating layer represented by 0.4 ≦ x ≦ 1, 0 ≦ y ≦ 1), the wear resistance can be further improved.
[0012]
Further, the method for producing a throw-away tip of the present invention comprises a TiCN powder having an average particle size of 0.2 to 0.9 μm and an oxygen content of 1% by mass or less, and a periodic table 4a, 5a and 6a group metal other than Ti. 70 to 99% by mass of a hard phase forming component composed of at least one of a carbide powder, a nitride powder, and a carbonitride powder containing at least one of the above, and Co and / or an average particle size of 0.05 to 1 μm. 1 to 30% by mass of a binder phase forming component composed of Ni powder and crushed, mixed, and classified so that the ratio of powder having a particle size of 1 μm or more is 10% by mass or less in a particle size distribution by a microtrack method. After the powder is obtained and formed into a chip shape, the temperature is raised from room temperature to a firing temperature A of 1100 to 1250 ° C, and from the firing temperature A to 1300 ° C at a heating rate a of 0.5 to 3 ° C / min. Heat up, The temperature is raised from 1300 ° C. to a firing temperature B of 1400 to 1500 ° C. at a heating rate b of 5 to 15 ° C./min, and further, a firing rate of 4 to 14 ° C./min to a firing temperature C of 1500 to 1600 ° C. It is characterized in that after the temperature is raised and held at a temperature raising rate c lower than b, the firing is carried out under the condition of lowering the temperature.
[0013]
Further, (Tix, M1-x) (CyN1-y) (where M is at least one of metals of the periodic table 4a, 5a and 6a other than Ti, Al, Si, 0.4 ≤ x ≤ 1, 0 ≤ y ≤ 1).
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method of manufacturing the indexable insert of the present invention will be described.
First, a carbide powder containing TiCN powder and one or more of metals of the periodic table 4a, 5a and 6a other than Ti, especially one or more of W, Mo, Ta, V, Zr and Nb, A hard phase-forming component composed of at least one of nitride powder and carbonitride powder and a binder phase-forming component composed of Co and / or Ni powder are weighed at a predetermined ratio.
[0015]
Here, all of the hard phase forming components need to have an average particle size of 0.2 to 0.9 μm, particularly 0.5 to 0.8 μm. When the average particle size is smaller than 0.2 μm, the aggregated portion of the binder phase which can be a fracture source in the cermet structure and the void formed by the elution of the aggregated portion of the binder phase are generated, and the bending strength varies. Is larger than 0.9 μm, so that the bending strength of the cermet is reduced as a whole.
[0016]
The binder phase forming component needs to have an average particle size of 0.05 to 1 μm, particularly 0.3 to 0.6 μm. This is because if the average particle size is smaller than 0.05 μm, the binder phase is likely to aggregate, and the aggregated portion of the binder phase, which is a cause of the destruction, and voids in which the metal in the aggregated portion is eluted are likely to be generated. This is because if it is large, the distribution of the binder phase tends to be uneven.
[0017]
Further, it is important to control at least the oxygen content of the TiCN powder to 1% by mass or less, particularly 0.05 to 0.8% by mass among the hard phase forming components. That is, if the oxygen content of the TiCN powder is more than 1% by mass, voids are generated in the sintered body or agglomeration of the binder phase is caused, and the bending strength of the sintered body is varied, thereby cutting the chip. This is because a large variation occurs in performance.
[0018]
In addition, the hard phase-forming component and the binder phase-forming component may have a ratio of 70 to 99% by mass, particularly 80 to 90% by mass, 1 to 30% by mass, particularly 10 to 20% by mass of the hard phase-forming component. Weigh and mix with.
[0019]
This is because if the amount of the hard phase forming component is less than the above range or the amount of the binder phase forming component is more than the above range, the alloy cannot be densified with the hard phase having a fine particle diameter. If the amount of the hard phase forming component is larger than the above range, or if the amount of the binder phase forming component is smaller than the above range, the hardness of the cermet is reduced and the wear resistance of the throw-away tip is reduced.
[0020]
Next, the powder is mixed and pulverized by an attritor mill to obtain a mixed powder in which the ratio of particles having a particle size of 1 μm or more in the mixed powder is 10% by mass or less in a particle size distribution by a microtrack method. According to the present invention, it is important to control the ratio of the particles having a particle diameter of 1 μm or more contained in the mixed powder to 10% by mass or less, whereby it is possible to confirm that coarse particles exist in the cermet sintered body. It is possible to form a cermet having a uniform structure by suppressing the roughness of the surface of the sintered body and the change in structure due to the generation of coarse particles. In order to make the ratio of the particles having a particle diameter of 1 μm or more to be 10% by mass or less, the pulverizing treatment is terminated when the above distribution is obtained, or a classification treatment is performed as necessary.
[0021]
And after shaping the mixed powder into a chip shape,
(A) The temperature is raised from room temperature to a firing temperature A of 1100 to 1250 ° C,
(B) The temperature is raised from the firing temperature A to 1300 ° C. at a temperature raising rate a of 0.5 to 3 ° C./min,
(C) The temperature is raised from 1300 ° C. to a firing temperature B of 1400 to 1500 ° C. at a temperature rising rate b of 5 to 15 ° C./min,
(D) heating to a firing temperature C of 1500 to 1600 ° C. at 4 to 14 ° C./min at a heating rate c lower than the heating rate b, and holding;
(E) Baking is performed under the condition of lowering the temperature.
[0022]
Here, if the temperature rise rate a in (b) is lower than 0.5 ° C./min, the hard phase will grow grains. On the other hand, if the heating rate a is higher than 3 ° C./min, the binder phase forming component is partially melted to form an aggregate of the binder phase.
[0023]
On the other hand, if the heating rate b in (c) is lower than 5 ° C./min, the entire sintered body grows and the average particle size of the hard phase cannot be controlled to 1.5 μm or less, and the fracture resistance becomes poor. descend. If the heating rate b is higher than 15 ° C./min, the grain growth of the sintered body becomes non-uniform, and the Weibull coefficient of the chip becomes smaller than 5 due to local aggregation and abnormal grain growth. On the other hand, if the firing temperature B is lower than 1400 ° C., the liquid phase cannot sufficiently appear in the preliminary sintering in the step (b). Conversely, if the firing temperature B exceeds 1500 ° C., the amount of liquid phase appearance becomes large. As a result, a large amount of voids are generated on the surface of the cermet substrate, and the Weibull coefficient of each chip becomes smaller than 5.
[0024]
On the other hand, if the heating rate c in (d) is lower than 4 ° C./min, the average grain size of the hard phase grows to 1.5 μm or more on the surface of the substrate, and the fracture resistance is reduced. If it is higher than 14 ° C./min, the structure of the sintered body becomes uneven and the wear resistance is reduced. Furthermore, if the firing temperature C is lower than 1500 ° C., the substrate cannot be sufficiently densified, voids and the like remain inside the sintered body, and the Weibull coefficient of the chip becomes smaller than 5. Conversely, if the firing temperature C exceeds 1600 ° C., the sintered body becomes over-sintered, the surface becomes rough, and the Weibull coefficient of the chip decreases.
[0025]
In the case of firing under the above firing conditions, if a solid solution of Co and Ni is used as a raw material, the sinterability is further improved, and the occurrence of open pores and sintering defects generated on the surface of the sintered body is suppressed. Can be.
[0026]
Then, after subjecting the obtained cermet substrate to a surface treatment such as polishing as required, a hard coating layer is coated with a single layer or two or more layers using a coating method such as a chemical vapor deposition method or a physical vapor deposition method. Thus, the cermet indexable insert of the present invention can be manufactured. Further, as the coating method, it is desirable to use a physical vapor deposition method having low reactivity with the cermet substrate from the viewpoint of reducing the particle size of the hard coating layer.
[0027]
The throw-away tip made of the cermet of the present invention produced by the above-described process is characterized in that, in a binder phase made of Co and Ni, Ti and one or more of the metals in the periodic table 4a, 5a and 6a other than Ti are used. A cermet indexable chip made of a cermet obtained by bonding a hard phase made of a composite metal carbonitride, wherein the hard phase has an average particle size of 1.5 μm or less, particularly 0.1 μm or less. 3 to 1 μm, and the Weibull coefficient of the bending strength when the bending test piece is cut out from the ten throw-away chips is 5 or more, particularly 7 or more, and further 10 or more. Characteristics variation is small.
[0028]
In addition, the Weibull coefficient of the bending strength of the throw-away tip in the present invention refers to a bending test piece cut out including the side surface (flank face) of the throw-away tip (the square of the shape of the test piece is determined by the size of the tip. A bar shape (10 or more) is measured according to JISR1601 except for the shape of the test piece, and means a Weibull coefficient calculated according to JISR1625.
[0029]
The shape of the test piece was cut out such that the cross section (vertical and horizontal) and the span in the bending test were in the relation of vertical: horizontal: span = 3: 4: 30, and the side surface (flank) was cut out. It was measured by arranging it on the tensile surface (the side opposite to the stress applying surface).
[0030]
In addition, the shape of the test piece in the present invention is the maximum rectangular prism shape that can be cut out from the throw-away tip including the side surface (flank surface), and the ratio of length: width: length is 3: 4: 10. It shall be cut out.
[0031]
Further, in the cermet indexable insert of the present invention, the maximum diameter of the crystal grains serving as a fracture source such as abnormal grains or voids observed in the fracture surface after the bending strength measurement of the tip is 10 μm or less, particularly The thickness is preferably 5 μm or less, more preferably 3 μm or less, whereby the bending strength of the cermet can be increased, and the fracture resistance of the throw-away tip can be improved. As a result, the Weibull coefficient of the tip can be increased. Thus, the variation in cutting performance of the insert can be further reduced.
[0032]
Further, in the present invention, it is desirable that a binder phase-enriched region in which the binder phase (Co content + Ni content) concentration gradually increases exists on the very surface of the cermet substrate. Since the shearing stress generated between the cermet substrate and the cermet substrate can be relieved and the adhesion between the two can be remarkably improved, the fracture resistance of the throw-away tip can be improved.
[0033]
In the present invention, the adhesion of the hard coating layer is ensured, the thermal conductivity is low, the thermal conductivity on the substrate surface of the Ti-based cermet substrate, which tends to be high in temperature, is increased, and the plastic deformation on the tool cutting edge is suppressed. In view of this, the thickness of the binder phase enriched region is preferably 0.01 to 5 μm, more preferably 1 to 3 μm, and further preferably 1 to 2.5 μm.
[0034]
On the other hand, in the present invention, it is important that the content of the binder phase is 1 to 30% by mass in terms of sinterability, wear resistance, and plastic deformation resistance. That is, if the content of the binder phase is less than 1% by mass, desired strength and wear resistance cannot be obtained, and if the content of the binder phase exceeds 30% by mass, the wear resistance rapidly decreases. A desirable content of the binder phase is 4 to 20% by mass.
[0035]
Further, the cermet constituting the throw-away tip of the present invention is characterized in that, as the hard phase, Ti and one or more metals of Group 4a, 5a and 6a other than Ti, especially W, Zr, V, Ta, Nb are used. , Mo, and at least one selected from the group consisting of composite metal carbonitrides. In particular, the hard phase comprises a core made of Ti (TiCN), Ti, and W, Mo, Ta and Nb. Having a double cored structure or a triple cored structure composed of at least one compound compound and a peripheral portion composed of a composite compound has a grain growth control effect, and the cermet substrate has a fine and uniform structure. In addition, it is desirable in that it has excellent wettability with the binder phase and contributes to increasing the strength of the cermet.
[0036]
Further, it is desirable that the average particle size r ₁ of the hard phase on the surface of the cermet substrate is larger than that r ₂ inside the cermet substrate in terms of adhesion to the hard coating layer, improvement in thermal conductivity, and suppression of plastic deformation. Further, it is desirable that r ₁ = 0.5 to ₂ μm and r ₂ = 0.2 to ₁ μm.
[0037]
Further, according to the present invention, (Tix, M1-x) (CyN1-y) (where M is a metal of the periodic table 4a, 5a and 6a other than Ti, Al, Si) And a hard coating layer (hereinafter abbreviated as Ti-based coating layer) represented by 0.4 ≦ x ≦ 1, 0 ≦ y ≦ 1), and the Ti-based coating layer may be a cermet. It is desirable to form it directly above the base material, and further, in terms of heat resistance such as high hardness and high-temperature stability, (Ti, M1) N (where M1 is selected from the group consisting of Al, Si, Zr and Cr). It is desirable to coat a hard coating layer composed of (Tix, Al1-x) N.
[0038]
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.
[0039]
【Example】
As the raw material powder, a TiCN powder having an average particle diameter (d) shown in Table 1 and an oxygen content, and a TiN powder, TaC powder, NbC powder, WC powder, ZrC powder, VC powder, Using an alloy powder of Co and Ni having an average particle diameter (d) shown in Table 1 (sample Nos. 6 and 16 were single powders of Co powder and Ni powder (the average particle diameter d was 0.5 μm)), These raw material powders are blended in the composition shown in Table 1, wet-mixed in a ball mill, and the ratio of powder having a particle diameter of 1 μm or more in the mixed powder in the particle size distribution by the microtrack method is changed as shown in Table 1 by changing the grinding time. And dried.
[0040]
Next, the mixed powder was press-molded at a molding pressure of 98 MPa, and the molded body was fired under the firing conditions shown in Table 1 to produce ten CNMG120408-shaped cermets (Sample Nos. 1 to 11).
[0041]
A cermet throwaway coated with a hard coating layer of 2.4 μm TiAlN on the surface of each cermet prepared in the same process as above using an arc discharge ion plating method. Ten chips were produced each (Sample No. 12).
[0042]
With respect to the obtained chip, the shape of the bending test piece (the rake face width 0.75 mm × the flank face width 1 mm × the flank face length 10 mm) including the side face (flank face) is set to two each (2 pieces × 10 chips = 20 pieces) were cut out, and the three-point bending strength was measured with a span of 7.5 mm according to JISR1601 and the flank as a tensile surface, and the Weibull coefficient was calculated according to JISR1625, except for the shape of the test piece. Further, SEM observation was performed on the fracture surface of the test piece after measuring the bending strength, the fracture source was specified, and the maximum diameter of the crystal particle which became the fracture source was obtained. The results are shown in Table 2.
[0043]
In addition, cutting evaluation was performed under the following cutting conditions A for each of ten indexable inserts manufactured under the same conditions as described above.
Cutting condition A
Work material: S45C
Work material: Round bar with 4 grooves,
Cutting speed: 100m / 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,
Evaluation item: Total cutting time until fracture (average value, variation)
[0044]
[Table 1]

[0045]
[Table 2]

[0046]
From the results shown in Tables 1 and 2, the sample No. which is within the scope of the present invention. In Nos. 1 to 12, all showed excellent cutting characteristics and small variations in cutting performance. On the other hand, the sample No. having the Weibull coefficient of the transverse rupture strength of the chip in which the properties of the raw material powder, the control of the mixing step, and the firing conditions deviated from the step of the present invention were smaller than 5. In Nos. 13 to 19, even in the cutting test, the performance variation between the chips was large.
[0047]
【The invention's effect】
As described in detail above, the throw-away chip of the present invention controls the properties of the raw materials, the control conditions of the mixed powder, the firing conditions, and the like, to reduce the hard phase into fine particles and to reduce the variation in the die strength of the chip. This makes it possible to enhance the reliability of the cutting performance of the indexable insert.

Claims

A binder phase mainly composed of Co and / or Ni: a composite metal carbonitride of 1 to 30% by mass, Ti, and one or more of metals of Group 4a, 5a and 6a other than Ti. A substantially plate-shaped throw-away chip made of a cermet comprising 70 to 99% by mass of a hard phase, wherein the average particle size of the hard phase is 1.5 μm or less, and 10 pieces of the throw-away chips are used. A throw-away tip, wherein the Weibull coefficient of the bending strength of the bending test piece cut out including the side surface is 5 or more.

2. The indexable tip according to claim 1, wherein the maximum diameter of the crystal grain serving as a fracture source observed at the fracture surface in the bending strength measurement of the cermet is 10 μm or less.

The indexable chip according to claim 1 or 2, wherein the average particle size of the hard phase in the cermet is 0.3 to 1 µm.

On the surface of the cermet, (Tix, M1-x) (CyN1-y) (where M is one or more of metals of the periodic table 4a, 5a and 6a other than Ti, Al and Si, 0.4 The indexable insert according to any one of claims 1 to 3, wherein the insert is coated with a hard coating layer represented by ≤ x ≤ 1, 0 ≤ y ≤ 1).

TiCN powder having an average particle size of 0.2 to 0.9 μm and an oxygen content of 1% by mass or less, and carbide powder and nitride containing one or more of metals of Group 4a, 5a and 6a other than Ti Powder and at least one of carbonitride powder, 70 to 99% by mass of a hard phase-forming component, and 1 to 30% by mass of a binding phase-forming component of Co and / or Ni powder having an average particle size of 0.05 to 1 μm. % And crushed and mixed so that the ratio of powder having a particle size of 1 μm or more is 10% by mass or less in a particle size distribution by a microtrack method. The temperature is raised to a firing temperature A of 1100 to 1250 ° C, the temperature is raised from the firing temperature A to 1300 ° C at a heating rate a of 0.5 to 3 ° C / min, and then the firing is performed from 1300 ° C to 1400 to 1500 ° C. 5 to temperature B The temperature was raised at a heating rate b of 15 ° C./min, and was further raised to a firing temperature C of 1500 to 1600 ° C. at a heating rate c lower than the heating rate b of 4 to 14 ° C./min. Thereafter, firing is performed under the condition of lowering the temperature.

On the chip surface, (Tix, M1-x) (CyN1-y) (where M is one or more of metals of the periodic table 4a, 5a and 6a other than Ti, Al, Si, 0.4 ≦ x 6. The method for producing a throw-away tip according to claim 5, wherein a hard coating layer represented by ≤1,0≤y≤1) is coated.