JP4126451B2 - Cemented carbide - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は切削工具等に使用される超硬合金に関し、特に高硬度かつ高靭性で優れた耐酸化性を有し、炭素鋼、合金鋼などの鋼や鋳鉄のみならず、ステンレス鋼をはじめとする難削材の切削に適する超硬合金に関する。
【０００２】
【従来の技術】
従来より、超硬合金は、ＷＣ（炭化タングステン）を主体とする硬質相と、コバルト等の鉄族金属の結合相からなるＷＣ−Ｃｏ系合金、もしくはこれに周期律表第４ａ、５ａ、６ａ族金属の炭化物、窒化物、炭窒化物等のいわゆるＢ−１型固溶体相を分散せしめた系が知られており、金属の切削加工や耐摩耗材等に広く用いられ、中でも切削工具としては炭素鋼・合金鋼などの鋼や鋳鉄の切削に主に利用されているが、最近ではステンレス鋼等の難削材の切削も進められている。
【０００３】
また、例えば、特許第２９４３８９５号によれば、Ｚｒを主体とする硬質相とＴｉを主体とする硬質相を共存させることにより、合金の強度維持と硬度不足の解消を両立できることが記載されている。
【０００４】
【発明が解決しようとする課題】
しかしながら、上記従来の超硬合金では、特に高温強度が低下することにより、過酷な条件での切削中に切刃にチッピングが生じたり、変形したりする恐れがあり、強度のさらなる向上が要求されているのが現状である。
【０００５】
本発明は上記課題を解決するためになされたもので、その目的は、特に高温にて高い硬度と靭性を有し、切削時に切刃部が部分的に高温に曝されるような過酷な環境下においても高い耐欠損性と耐摩耗性をともに維持できる超硬合金を提供することにある。
【０００６】
【課題を解決するための手段】
本発明者は、上記課題に対し超硬合金母材の構成について検討した結果、ＺｒＣ（炭化ジルコニウム）を０．０５〜１．５重量％、ＮｂＣ（炭化ニオブ）を０〜３．５重量％、ＴｉＣ（炭化チタン）を１〜２．５重量％、ＴａＣ（炭化タンタル）を０〜１重量％、Ｃｏ（コバルト）を５〜１０重量％の比率で含有し、残部がＷＣ（炭化タングステン）および不可避不純物からなる超硬合金のＷＣ粒子とともに含有される固溶体相を、ＺｒＣ（炭化ジルコニウム）、ＮｂＣ（炭化ニオブ）、ＴｉＣ（炭化チタン）、ＴａＣ（炭化タンタル）およびＷＣ（炭化タングステン）の群から選ばれる少なくとも１種以上の金属元素の炭化物からなり、原子比で０．７≦Ｔｉ／（Ｔｉ＋Ｚｒ）≦０．９の第１固溶体相と、０．４≦Ｔｉ／（Ｔｉ＋Ｚｒ）≦０．６の第２固溶体相の２種とし、かつ前記第１固溶体相と前記結合材マトリックスとの間に前記第２固溶体相が介在するように隣接して共存することにより、超硬合金の特に高温における強度および靭性を高めることができ、切削時に切刃部が部分的に高温に曝されるような過酷な環境下においても高い耐欠損性と耐摩耗性をともに向上できることを知見した。
【０００７】
すなわち、本発明の超硬合金は、ＺｒＣ（炭化ジルコニウム）を０．０５〜１．５重量％、ＮｂＣ（炭化ニオブ）を０〜３．５重量％、ＴｉＣ（炭化チタン）を１〜２．５重量％、ＴａＣ（炭化タンタル）を０〜１重量％、Ｃｏ（コバルト）を５〜１０重量％の比率で含有し、残部がＷＣ（炭化タングステン）および不可避不純物からなり、Ｃｏ（コバルト）の結合材マトリックス中に、ＷＣ粒子と、ＺｒＣ（炭化ジルコニウム）、ＮｂＣ（炭化ニオブ）、ＴｉＣ（炭化チタン）、ＴａＣ（炭化タンタル）およびＷＣ（炭化タングステン）の群から選ばれる少なくとも１種以上の金属元素の炭化物からなる固溶体相を分散せしめてなる超硬合金において、前記固溶体相が原子比で０．７≦Ｔｉ／（Ｔｉ＋Ｚｒ）≦０．９の第１固溶体相と、０．４≦Ｔｉ／（Ｔｉ＋Ｚｒ）≦０．６の第２固溶体相の２種からなるとともに、前記第１固溶体と前記結合材マトリックスとの間に前記第２固溶体相が介在するように隣接して共存することを特徴とするものである。
【０００８】
ここで、前記固溶体相中に、原子比で０．２≦Ｎｂ／（Ｔｉ＋Ｎｂ＋Ｚｒ）≦０．７のＮｂを含有すること、前記超硬合金の耐酸化性が０．０１ｍｇ／ｍｍ2以下であることが望ましい。
【０００９】
また、前記第１固溶体相の平均粒径が０．５〜４μｍで、かつ前記第２固溶体相の平均粒径が５０〜１０００ｎｍであることが望ましい。
【００１０】
【発明の実施の形態】
本発明の超硬合金は、ＺｒＣ（炭化ジルコニウム）を０．０５〜１．５重量％、ＮｂＣ（炭化ニオブ）を０〜３．５重量％、ＴｉＣ（炭化チタン）を１〜２．５重量％、ＴａＣ（炭化タンタル）を０〜１重量％、Ｃｏ（コバルト）を５〜１０重量％の比率で含有し、残部がＷＣ（炭化タングステン）および不可避不純物からなり、Ｃｏ（コバルト）の結合材マトリックス中に、ＷＣ粒子と、ＺｒＣ（炭化ジルコニウム）、ＮｂＣ（炭化ニオブ）、ＴｉＣ（炭化チタン）、ＴａＣ（炭化タンタル）およびＷＣ（炭化タングステン）の群から選ばれる少なくとも１種以上の金属元素の炭化物からなる固溶体相を分散せしめてなるものである。
【００１１】
本発明によれば、その一例についての透過電子顕微鏡写真（ＴＥＭ像）である図１に示すように、前記固溶体相が原子比で０．７≦Ｔｉ／（Ｔｉ＋Ｚｒ）≦０．９の第１固溶体相Ｂ、Ｅと、０．４≦Ｔｉ／（Ｔｉ＋Ｚｒ）≦０．６の第２固溶体相Ｃの２種からなるとともに、前記第１固溶体Ｂと前記結合材マトリックスＤとの間に前記第２固溶体相Ｃが介在するように隣接して共存することが大きな特徴である。
【００１２】
これによって、超硬合金の高温強度を高めて過酷な条件の切削に対しても耐欠損性および耐摩耗性を向上させることができることから、炭素鋼・合金鋼などの鋼や鋳鉄のみならず、ステンレス鋼等難削材の切削等のように高温環境下で作動させるような場合においても優れた耐欠損性と耐摩耗性を有し、特に切削加工用の切削工具として最適な超硬合金が得られる。
【００１３】
すなわち、本発明によれば、Ｔｉの含有量が多い第１固溶体相Ｂと結合相Ｄとの間にＺｒの含有量の多い第２固溶体相Ｃが介在することにより、主体となる第１固溶体相Ｂが高温に晒されても変質しないように安定化を図りつつ、第１固溶体相Ｂと結合相との中間の熱膨張係数を有する第２固溶体相Ｄを間に介在させることにより、第１固溶体相Ｂと結合相Ｄとの結合力を高めて超硬合金の高温強度を高めることができる。
【００１４】
なお、第２固溶体相Ｃは第１固溶体相Ｂと結合相Ｄとの間すべてに存在してもよいが、本発明によれば必ずしもすべての数および長さ領域にわたって存在する必要はなく、例えば、図１に示すように第１固溶体相Ｂと結合相Ｄとの一部のみの数および長さ領域に存在しても十分に高温強度を高める働きをなす。
【００１５】
ここで、第１固溶体相において、Ｔｉ／（Ｔｉ＋Ｚｒ）が０．７より小さいと、焼結性が低下するために部分的に硬度が著しく低下して耐摩耗性および耐塑性変形性が低下する。逆に、０．９より大きいと、耐塑性変形性が低下し、特に高温域で連続的に使用すると母材の表面が変質してチッピングが発生しやすくなる。
【００１６】
また、第２固溶体相において、Ｔｉ／（Ｔｉ＋Ｚｒ）が０．４より小さいと、第１固溶体相と第２固溶体相との結合力が低下し、逆に、Ｔｉ／（Ｔｉ＋Ｚｒ）が０．６より大きいと、第２固溶体相と結合相との結合力が低下して、いずれの場合でも第１固溶体相と結合相との間の結合力を向上できず高温強度が低下して耐塑性変形性が低下し、特に高温域で連続的に使用すると切刃における塑性変形が生じやすく耐摩耗性の低下を招く。
【００１７】
なお、本発明における各相（ＷＣ粒子、固溶体相、結合相）中の金属元素の含有比率は、合金の任意位置における透過型電子顕微鏡写真（ＴＥＭ像）から、エネルギー分散型Ｘ線分光分析（ＥＤＳ）によって求めることができる。
【００１８】
さらに、本発明によれば、耐酸化性を高めて高温切削時に超硬合金が変質して塑性変形を生じることを防止できる点で、０．２≦Ｎｂ／（Ｔｉ＋Ｎｂ＋Ｚｒ）≦０．７、特に、第１固溶体相および第２固溶体相はともにＮｂの含有量が最も多く、かつ０．４≦Ｎｂ／（Ｔｉ＋Ｎｂ＋Ｚｒ）≦０．７を満足することが望ましい。
【００１９】
また、前記第２固溶体相の結合相の含有量は第１固溶体相と比べて多いことが望ましく、具体的な組成としては、第１固溶体相が２０原子％≦Ｔｉ≦６０原子％、１０原子％≦Ｎｂ≦６０原子％、５原子％≦Ｚｒ≦１０原子％、１０原子％≦Ｗ≦４０原子％、０原子％≦Ｃｏ≦１．５原子％からなり、前記第２固溶体相が１０原子％≦Ｔｉ≦２０原子％、４０原子％≦Ｎｂ≦６０原子％、１２原子％≦Ｚｒ≦４０原子％、０原子％≦Ｗ≦２０原子％、２原子％≦Ｃｏ≦５原子％であることが、切削工具としての耐欠損性、耐摩耗性、高温での耐塑性変形性を高める上で望ましい。
【００２０】
なお、第１固溶体相−第２固溶体相−結合相マトリックス間の結合力を高める上では、前記第１固溶体相の平均粒径が０．５〜４μｍであり、かつ第２固溶体相の平均粒径は５０〜１０００ｎｍが望ましく、特に３００〜７００ｎｍが望ましい。
【００２１】
また、本発明によれば、ＷＣ相と第１固溶体相との結合力を維持するという点で、前記ＷＣ粒子中に、０原子％≦Ｔｉ＜１原子％、０原子％≦Ｎｂ＜１０原子％、０原子％≦Ｚｒ＜１０原子％、０原子％≦Ｃｏ＜１０原子％の金属元素を含有することが望ましい。
【００２２】
さらに、結合相と第１固溶体相または第２固溶体相との結合力を維持するという点では、前記結合相マトリックスの組成としては、鉄族金属（Ｃｏ，Ｎｉ，Ｆｅ）中に、０原子％≦Ｔｉ＜１０原子％、０原子％≦Ｎｂ＜１０原子％、０原子％≦Ｚｒ＜１０原子％、０原子％≦Ｗ＜１０原子％の金属元素を含有することが望ましい。
【００２３】
そして、上記構成からなる本発明の超硬合金は、耐酸化性が０．０１ｍｇ／ｍｍ2以下の優れた特性を有するものであり、ステンレス等の難削材を切削する際などのように、高温域で安定に作動させて耐摩耗性および耐欠損性を維持することができる。
【００２４】
なお、本発明における耐酸化性とは、硬質被覆層を被着形成した超硬合金を大気中の８００℃×３０分の条件で保持する酸化試験を行った場合の試験前後における酸化増量割合を示す。
【００２５】
また、本発明によれば、上記超硬合金の表面に、周期律表第４ａ、５ａ、６ａ族金属またはＡｌの炭化物、窒化物、酸化物、炭窒化物、炭酸化物、窒酸化物、炭酸窒化物およびダイヤモンドの群から選ばれる少なくとも１種の単層または複数層からなる被覆層を形成することもできる。
【００２６】
さらにまた、超硬合金（母材）の具体的な組成は、ＺｒＣ（炭化ジルコニウム）を０．０５〜１．５重量％、ＮｂＣ（炭化ニオブ）を０〜３．５重量％、ＴｉＣ（炭化チタン）を１〜２．５重量％、ＴａＣ（炭化タンタル）を０〜１重量％、Ｃｏ（コバルト）を５〜１０重量％の比率で含有し、残部がＷＣ（炭化タングステン）および不可避不純物からなり、耐酸化性、耐摩耗性と耐塑性変形性および耐欠損性を両立するために、ＺｒＣ（炭化ジルコニウム）を０．０５〜１．５重量％、特に０．０５〜０．８重量％、さらに０．０５〜０．３重量％、ＮｂＣ（炭化ニオブ）を０．５〜３．５重量％、ＴｉＣ（炭化チタン）を１〜２．５重量％、ＴａＣ（炭化タンタル）を０〜１重量％、Ｃｏ（コバルト）を５〜１０重量％の比率で含有し、残部がＷＣ（炭化タングステン）および不可避不純物からなることが望ましい。
【００２７】
なお、上記成分のうち、コストの低減のためには高価なＴａＣの含有量を０．５重量％以下、特に０．１重量％以下、さらには実質的に含有させないことが望ましい。
【００２８】
さらにまた、上記組成範囲の中でも、耐摩耗性を重視して旋削用切削工具として用いる上では、ＴｉＣを１．５〜２．０重量％、ＮｂＣを２．０〜３．５重量％、ＺｒＣを０．０５〜０．３重量％、Ｃｏを５．０〜７．５重量％含有し、残部がＷＣからなることが望ましい。
【００２９】
（製造方法）
上述した超硬合金を製造するには、まず、例えば平均粒径０．５〜１０μｍの炭化タングステン粉末を８０〜９０重量％、平均粒径０．１〜２μｍのＺｒの炭化物、窒化物、炭窒化物粉末またはその固溶体粉末を総量で０．０５〜１．５重量％、平均粒径０．５〜５μｍのＮｂの炭化物、窒化物、炭窒化物粉末またはその固溶体粉末を総量で０〜１０重量％、平均粒径０．５〜５μｍの炭化チタン粉末を０．８〜２．５重量％、Ｔａの炭化物、窒化物、炭窒化物粉末またはその固溶体粉末を０〜１重量％、平均粒径０．５〜１０μｍのＣｏを５〜１５重量％の割合で混合する。
【００３０】
本発明によれば、上記原料中の炭化チタン粉末についてはＴｉxＣyとしたときｙ／ｘ＝０．６〜０．９となる比率に調製した粉末を用いることが重要であり、かかる炭素含有比率が低い原料を用いることによって異なる金属成分の配合比率からなる第１固溶体相および第２固溶体相の２種の固溶体相を隣接して析出せしめることができる。
【００３１】
さらに、本発明によれば、上記金属化合物粉末に加えて、炭素（Ｃ）粉末を０．０１〜０．１１重量％、特に０．０４〜０．１重量％の割合で混合することが重要であり、かかる炭素量の調整により各金属成分が各相中に最適な割合で固溶して最適な組成および組織からなる超硬合金を作製することができる。
【００３２】
次に、上記混合粉末を用いて、プレス成形、鋳込成形、押出成形、冷間静水圧プレス成形等の公知の成形方法によって所定形状に成形した後、０．１〜１５Ｐａの真空中、１０００℃以上における昇温速度を０．３〜４℃／分で昇温し、真空度１０-3〜０．０５Ｐａの真空中、１３５０〜１５００℃で０．２〜５時間、特に０．５〜２時間焼成した後、１２５０℃までの温度域を０．３〜２℃／分、特に０．５〜２℃／分で降温することによって超硬合金（母材）を作製することができる。
【００３３】
そして、所望により、上記超硬合金（母材）表面にＣＶＤ法やＰＶＤ法等の公知の薄膜形成法で硬質被覆層を０．１〜２０μｍ被着形成することも可能である。
【００３４】
なお、上述した本発明の超硬合金は、高硬度、高靭性、高強度の優れた機械的特性および高い耐酸化性を有することから、金型、耐摩耗部材、高温構造材料等に適応可能であり、中でも炭素鋼、合金鋼などの鋼や鋳鉄の加工用切削工具、さらにはステンレス鋼等の難削材加工用の切削工具として好適に使用可能である。
【００３５】
【実施例】
（実施例１）
平均粒径１．５μｍの炭化タングステン（ＷＣ）粉末、平均粒径１．２μｍの金属コバルト（Ｃｏ）粉末および平均粒径２．０μｍの表１に示す金属元素Ｍ化合物粉末および炭素粉末を表１に示す比率で添加、混合して、プレス成形で切削工具形状（ＣＮＭＧ１２０４０８）に成形した後、脱バインダ処理を施し、さらに、１０００℃以上を３℃／分の速度で昇温して、０．０１Ｐａの真空中、１４５０℃で１時間焼成した後、１２５０℃までを表１に示す降温速度で降温し、さらに１２５０℃以下を５℃／分で降温して超硬合金を作製した。
【００３６】
得られた超硬合金の表面にＣＶＤ法でＴｉＮを１μｍ、ＴｉＣＮを７μｍ、Ａｌ2Ｏ3を３μｍ、ＴｉＮを１μｍの順に硬質被覆層を成膜することによって超硬合金を作製した。
【００３７】
得られた超硬合金に対して、任意位置にて透過型電子顕微鏡（ＴＥＭ）観察を行い、また、透過型電子顕微鏡写真（ＴＥＭ像）の各相における金属元素の組成をエネルギー分散型Ｘ線分光分析（ＥＤＳ）によって測定した。なお、図１に表１の試料Ｎｏ．３についてのＴＥＭ像の一例を示すが、組成分析に関しては、Ａ〜Ｆの各相をそれぞれ任意の５点づつについて測定し、その平均値を算出した。結果は表２に示した。
【００３８】
また、８００℃の大気圧雰囲気で３０分間酸化処理し、酸化前後における重量増加量を測定して耐酸化性とした。結果は表１に示した。
【００３９】
【表１】
【表２】
さらに、表１の切削工具を用いて下記の条件で合金鋼の切削を２５分間行い、切削工具のフランク摩耗量および先端摩耗量を測定した。なお、切削試験中にフランク摩耗量あるいは先端摩耗量が０．２ｍｍに達した場合にはその切削時間を測定した。さらに、溝付き鋼材で断続試験を行い、欠損したときの衝撃回数を比較した。その結果を表３に示す。
【００４２】
（摩耗試験）
被削材 ：合金鋼（ＳＣＭ４３５）
工具形状：ＣＮＭＧ１２０４０８
切削速度：２５０ｍ／分
送り速度：０．３ｍｍ／ｒｅｖ
切り込み：２ｍｍ
その他 ：水溶性切削液使用
（断続試験）
被削材 ：合金鋼（ＳＣＭ４４０）
工具形状：ＣＮＭＧ１２０４０８
切削速度：２００ｍ／分
送り速度：０．４ｍｍ／ｒｅｖ
切り込み：１．５ｍｍ
その他 ：水溶性切削液使用
【００４３】
【表３】
表１および表３の結果より、炭化チタン（ＴｉxＣy）原料としてｙ／ｘ＝１．０の原料を用い、いずれも第１固溶体相（第１β相）中および／または第２固溶体相（第２β相）中のＴｉ／（Ｔｉ＋Ｚｒ）が所定の範囲より外れ、かつこれらが独立して存在した試料Ｎｏ．１、２では、高温強度が低くなり切削性能が低下した。
【００４５】
また、焼成温度から１２５０℃までの温度域における降温速度が２℃／分より速く、第１および第２固溶体相中のＴｉ／（Ｔｉ＋Ｚｒ）が所定の範囲より外れ、かつこれらが独立して存在した試料Ｎｏ．７でも、高温強度が低くなり切削性能が低下した。
【００４６】
これに対して、第１および／または第２固溶体相中のＴｉ／（Ｔｉ＋Ｚｒ）が所定の範囲からなり、かつこれらが隣接して存在する試料Ｎｏ．３〜６、８では、いずれも耐酸化性に優れるとともに、硬度、靭性とも高く、優れた切削性能を有するものであった。
【００４７】
【発明の効果】
以上詳述したとおり、本発明の超硬合金によれば、ＺｒＣ（炭化ジルコニウム）を０．０５〜１．５重量％、ＮｂＣ（炭化ニオブ）を０〜３．５重量％、ＴｉＣ（炭化チタン）を１〜２．５重量％、ＴａＣ（炭化タンタル）を０〜１重量％、Ｃｏ（コバルト）を５〜１０重量％の比率で含有し、残部がＷＣ（炭化タングステン）および不可避不純物からなる超硬合金のＷＣ粒子とともに含有される固溶体相を、ＺｒＣ（炭化ジルコニウム）、ＮｂＣ（炭化ニオブ）、ＴｉＣ（炭化チタン）、ＴａＣ（炭化タンタル）およびＷＣ（炭化タングステン）の群から選ばれる少なくとも１種以上の金属元素の炭化物からなり、原子比で０．７≦Ｔｉ／（Ｔｉ＋Ｚｒ）≦０．９の第１固溶体相と、０．４≦Ｔｉ／（Ｔｉ＋Ｚｒ）≦０．６の第２固溶体相の２種とし、かつ上記第１固溶体とＣｏ（コバルト）の結合材マトリックスとの間に上記第２固溶体相が介在するように隣接して共存することにより、超硬合金の特に高温における強度および靭性を高めることができ、切削時に切刃部が部分的に高温に曝されるような過酷な環境化においても高い耐欠損性と耐摩耗性をともに向上できる。
【図面の簡単な説明】
【図１】本発明の超硬合金の任意位置におけるＴＥＭ（透過型電子顕微鏡）像である。
【符号の簡単な説明】
Ａ：ＷＣ粒子、Ｂ：第１固溶体相、Ｃ：第２固溶体相、Ｄ：結合剤マトリックス、Ｅ：第１固溶体相、Ｆ：ＷＣ粒子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cemented carbide used for cutting tools and the like, and particularly has high hardness and high toughness and excellent oxidation resistance, including not only steel and cast iron such as carbon steel and alloy steel, but also stainless steel. The present invention relates to a cemented carbide suitable for cutting difficult-to-cut materials.
[0002]
[Prior art]
Conventionally, a cemented carbide is a WC-Co alloy composed of a hard phase mainly composed of WC (tungsten carbide) and a binding phase of an iron group metal such as cobalt, or periodic tables 4a, 5a, 6a. A system in which a so-called B-1 type solid solution phase such as a carbide, nitride, carbonitride, etc. of a group metal is dispersed is known, and is widely used for metal cutting and wear-resistant materials. Although it is mainly used for cutting steel and cast iron, such as steel and alloy steel, recently, cutting of difficult-to-cut materials such as stainless steel has also been promoted.
[0003]
Further, for example, according to Japanese Patent No. 2943895, it is described that the coexistence of the hard phase mainly composed of Zr and the hard phase mainly composed of Ti can achieve both maintenance of the strength of the alloy and elimination of insufficient hardness. .
[0004]
[Problems to be solved by the invention]
However, in the above conventional cemented carbides, especially the high temperature strength is lowered, there is a possibility that the cutting edge may be chipped or deformed during cutting under severe conditions, and further improvement in strength is required. This is the current situation.
[0005]
The present invention has been made to solve the above-mentioned problems, and its purpose is to have a high hardness and toughness especially at high temperatures, and a severe environment in which the cutting edge portion is partially exposed to high temperatures during cutting. An object of the present invention is to provide a cemented carbide capable of maintaining both high fracture resistance and wear resistance.
[0006]
[Means for Solving the Problems]
As a result of examining the structure of the cemented carbide base material with respect to the above problems, the present inventor has found that ZrC (zirconium carbide) is 0.05 to 1.5% by weight, and NbC (niobium carbide) is 0 to 3.5% by weight. TiC (titanium carbide) 1 to 2.5% by weight, TaC (tantalum carbide) 0 to 1% by weight, Co (cobalt) 5 to 10% by weight, the balance WC (tungsten carbide) And a solid solution phase contained together with WC particles of cemented carbide composed of inevitable impurities , ZrC (zirconium carbide), NbC (niobium carbide), TiC (titanium carbide), TaC (tantalum carbide) and WC (tungsten carbide) at least one consists of a carbide of the above metal element, 0.7 ≦ Ti / (Ti + Zr) ≦ 0.9 first solid solution phase in atomic ratio selected from, 0.4 ≦ Ti / (Ti + Zr) By making two kinds of the second solid solution phase of 0.6 and coexisting adjacent to each other so that the second solid solution phase is interposed between the first solid solution phase and the binder matrix, In particular, it has been found that the strength and toughness at high temperatures can be increased, and that both high fracture resistance and wear resistance can be improved even in harsh environments where the cutting edge is partially exposed to high temperatures during cutting.
[0007]
That is, the cemented carbide of the present invention has 0.05 to 1.5% by weight of ZrC (zirconium carbide), 0 to 3.5% by weight of NbC (niobium carbide), and 1 to 2% of TiC (titanium carbide). 5% by weight, 0 to 1% by weight of TaC (tantalum carbide) and 5 to 10% by weight of Co (cobalt), with the balance being WC (tungsten carbide) and inevitable impurities , In the binder matrix, at least one metal selected from the group consisting of WC particles, ZrC (zirconium carbide), NbC (niobium carbide), TiC (titanium carbide), TaC (tantalum carbide) and WC (tungsten carbide). in cemented carbide comprising dispersed carbide material or Ranaru solid solution phase of the elements, and 0.7 ≦ Ti / (Ti + Zr ) ≦ 0.9 first solid solution phase of the solid solution phase in an atomic ratio, 4 ≦ Ti / (Ti + Zr) ≦ 0.6, and the second solid solution phase is adjacent so that the second solid solution phase is interposed between the first solid solution and the binder matrix. It is characterized by coexistence.
[0008]
Here, the solid solution phase contains Nb of 0.2 ≦ Nb / (Ti + Nb + Zr) ≦ 0.7 in atomic ratio, and the oxidation resistance of the cemented carbide is 0.01 mg / mm 2 or less. It is desirable.
[0009]
In addition, it is desirable that the average particle diameter of the first solid solution phase is 0.5 to 4 μm and the average particle diameter of the second solid solution phase is 50 to 1000 nm.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The cemented carbide according to the present invention comprises 0.05 to 1.5% by weight of ZrC (zirconium carbide), 0 to 3.5% by weight of NbC (niobium carbide), and 1 to 2.5% by weight of TiC (titanium carbide). %, TaC (tantalum carbide) 0 to 1% by weight, Co (cobalt) 5 to 10% by weight, the balance being WC (tungsten carbide) and inevitable impurities, Co (cobalt) binder In the matrix, WC particles and at least one metal element selected from the group consisting of ZrC (zirconium carbide), NbC (niobium carbide), TiC (titanium carbide), TaC (tantalum carbide) and WC (tungsten carbide) . the carbides or Ranaru solid solution phase are those formed by dispersed.
[0011]
According to the present invention, as shown in FIG. 1 which is a transmission electron micrograph (TEM image) of one example, the solid solution phase is a first in which the atomic ratio is 0.7 ≦ Ti / (Ti + Zr) ≦ 0.9. The solid solution phases B and E, and the second solid solution phase C of 0.4 ≦ Ti / (Ti + Zr) ≦ 0.6, and the first between the first solid solution B and the binder matrix D It is a great feature that two solid solution phases C coexist so as to intervene.
[0012]
As a result, the high-temperature strength of the cemented carbide can be increased to improve the fracture resistance and wear resistance even for severe conditions of cutting, so not only steel and cast iron such as carbon steel and alloy steel, It has excellent fracture resistance and wear resistance even when it is operated in a high temperature environment such as cutting difficult-to-cut materials such as stainless steel. Especially, it is the best cemented carbide as a cutting tool for cutting. can get.
[0013]
That is, according to the present invention, the second solid solution phase C having a high content of Zr is interposed between the first solid solution phase B having a high content of Ti and the binder phase D. By interposing a second solid solution phase D having an intermediate coefficient of thermal expansion between the first solid solution phase B and the binder phase while stabilizing so that the phase B does not change even when exposed to high temperatures, The high-temperature strength of the cemented carbide can be increased by increasing the binding force between the single solid solution phase B and the binder phase D.
[0014]
The second solid solution phase C may be present between the first solid solution phase B and the binder phase D, but according to the present invention, the second solid solution phase C is not necessarily present over all the numbers and length regions. As shown in FIG. 1, even if the first solid solution phase B and the binder phase D are present only in a part of the number and length, they serve to sufficiently increase the high temperature strength.
[0015]
Here, in the first solid solution phase, when Ti / (Ti + Zr) is smaller than 0.7, the sinterability is lowered, so that the hardness is partially lowered and the wear resistance and plastic deformation resistance are lowered. . On the other hand, when it is larger than 0.9, the plastic deformation resistance is lowered, and particularly when used continuously in a high temperature range, the surface of the base material is altered and chipping is likely to occur.
[0016]
Further, in the second solid solution phase, when Ti / (Ti + Zr) is smaller than 0.4, the binding force between the first solid solution phase and the second solid solution phase is lowered, and conversely, Ti / (Ti + Zr) is 0.6. If it is larger, the bonding force between the second solid solution phase and the bonding phase is lowered, and in any case, the bonding force between the first solid solution phase and the bonding phase cannot be improved, and the high-temperature strength is lowered and the plastic deformation is reduced. In particular, when used continuously in a high temperature range, plastic deformation is likely to occur in the cutting edge, resulting in a decrease in wear resistance.
[0017]
In addition, the content ratio of the metal element in each phase (WC particle, solid solution phase, bonded phase) in the present invention is determined by energy dispersive X-ray spectroscopy (TEM image) from a transmission electron micrograph (TEM image) at an arbitrary position of the alloy. EDS).
[0018]
Furthermore, according to the present invention, 0.2 ≦ Nb / (Ti + Nb + Zr) ≦ 0.7, in particular, in that the oxidation resistance can be improved and the cemented carbide can be prevented from being deteriorated during high temperature cutting to cause plastic deformation. It is desirable that both the first solid solution phase and the second solid solution phase have the highest Nb content and satisfy 0.4 ≦ Nb / (Ti + Nb + Zr) ≦ 0.7.
[0019]
Further, the content of the binder phase of the second solid solution phase is preferably larger than that of the first solid solution phase. As a specific composition, the first solid solution phase is 20 atomic% ≦ Ti ≦ 60 atomic%, 10 atoms. % ≦ Nb ≦ 60 atomic%, 5 atomic% ≦ Zr ≦ 10 atomic%, 10 atomic% ≦ W ≦ 40 atomic%, 0 atomic% ≦ Co ≦ 1.5 atomic%, and the second solid solution phase is 10 atoms. % ≦ Ti ≦ 20 atomic%, 40 atomic% ≦ Nb ≦ 60 atomic%, 12 atomic% ≦ Zr ≦ 40 atomic%, 0 atomic% ≦ W ≦ 20 atomic%, 2 atomic% ≦ Co ≦ 5 atomic% However, it is desirable to improve the fracture resistance, wear resistance, and plastic deformation resistance at high temperatures as a cutting tool.
[0020]
In order to increase the bonding force between the first solid solution phase, the second solid solution phase, and the binder phase matrix, the average particle size of the first solid solution phase is 0.5 to 4 μm, and the average particle of the second solid solution phase The diameter is preferably 50 to 1000 nm, particularly preferably 300 to 700 nm.
[0021]
In addition, according to the present invention, 0 atomic% ≦ Ti <1 atomic%, 0 atomic% ≦ Nb <10 atoms in the WC particles in that the bonding force between the WC phase and the first solid solution phase is maintained. %, 0 atomic% ≦ Zr <10 atomic%, and 0 atomic% ≦ Co <10 atomic%.
[0022]
Furthermore, in terms of maintaining the binding force between the binder phase and the first solid solution phase or the second solid solution phase, the composition of the binder phase matrix is 0 atomic% in the iron group metal (Co, Ni, Fe). ≦ Ti <10 atomic%, 0 atomic% ≦ Nb <10 atomic%, 0 atomic% ≦ Zr <10 atomic%, 0 atomic% ≦ W <10 atomic% are desirably contained.
[0023]
And, the cemented carbide of the present invention having the above-mentioned configuration has excellent characteristics with an oxidation resistance of 0.01 mg / mm 2 or less, such as when cutting difficult-to-cut materials such as stainless steel, Abrasion resistance and fracture resistance can be maintained by operating stably in a high temperature range.
[0024]
The oxidation resistance in the present invention refers to the rate of increase in oxidation before and after the test in the case of performing an oxidation test in which the cemented carbide with the hard coating layer formed thereon is held at 800 ° C. for 30 minutes in the atmosphere. Show.
[0025]
Further, according to the present invention, a carbide, nitride, oxide, carbonitride, carbonate, nitride oxide, carbonic acid of Group 4a, 5a, 6a metal or Al of the periodic table is provided on the surface of the cemented carbide. It is also possible to form a coating layer comprising at least one single layer or a plurality of layers selected from the group consisting of nitride and diamond.
[0026]
Furthermore, the specific composition of the cemented carbide (base metal) is as follows: ZrC (zirconium carbide) 0.05 to 1.5 wt%, NbC (niobium carbide) 0 to 3.5 wt%, TiC (carbonized) 1 to 2.5 wt% of titanium), 0 to 1 wt% of TaC (tantalum carbide), and 5 to 10 wt% of Co (cobalt), with the balance from WC (tungsten carbide) and inevitable impurities becomes, oxidation resistance, in order to achieve both wear resistance and plastic deformation resistance and chipping resistance, ZrC (zirconium carbide) of 0.05 to 1.5 wt%, in particular 0.05 to 0.8 wt% Furthermore, 0.05 to 0.3 wt%, NbC (niobium carbide) 0.5 to 3.5 wt%, TiC (titanium carbide) 1 to 2.5 wt%, TaC (tantalum carbide) 0 to 1% by weight, containing Co (cobalt) in a ratio of 5 to 10% by weight, The balance is preferably made of WC (tungsten carbide) and inevitable impurities.
[0027]
Of the above components, in order to reduce costs, it is desirable that the content of expensive TaC is 0.5 wt% or less, particularly 0.1 wt% or less, and not substantially contained.
[0028]
Furthermore, among the above composition ranges, when using as a cutting tool for turning with an emphasis on wear resistance, TiC is 1.5 to 2.0% by weight, NbC is 2.0 to 3.5% by weight, ZrC. It is desirable to contain 0.05 to 0.3% by weight of Co, 5.0 to 7.5% by weight of Co, and the balance being WC.
[0029]
(Production method)
In order to manufacture the cemented carbide described above, first, for example, tungsten carbide powder having an average particle size of 0.5 to 10 μm is 80 to 90 wt%, Zr carbide, nitride and charcoal having an average particle size of 0.1 to 2 μm. Nb carbide, nitride, carbonitride powder or solid solution powder of Nb having a total amount of 0.05 to 1.5% by weight and an average particle size of 0.5 to 5 μm in a total amount of 0 to 10 0.8% to 2.5% by weight of titanium carbide powder having an average particle size of 0.5 to 5 μm, 0 to 1% by weight of Ta carbide, nitride, carbonitride powder or its solid solution powder, average particle the Co diameter 0.5~10μm mixed at a ratio of 5 to 15 wt%.
[0030]
According to the present invention, with respect to the titanium carbide powder in the raw material, it is important to use a powder prepared at a ratio of y / x = 0.6 to 0.9 when Ti x C y is used. By using a raw material with a low content ratio, the two solid solution phases of the first solid solution phase and the second solid solution phase having different blending ratios of metal components can be deposited adjacent to each other.
[0031]
Furthermore, according to the present invention, in addition to the metal compound powder, it is important to mix carbon (C) powder in a proportion of 0.01 to 0.11 wt%, particularly 0.04 to 0.1 wt%. Thus, by adjusting the carbon content, each metal component is dissolved in an optimum ratio in each phase, and a cemented carbide having an optimum composition and structure can be produced.
[0032]
Next, the mixture powder is molded into a predetermined shape by a known molding method such as press molding, cast molding, extrusion molding, cold isostatic pressing, and then in a vacuum of 0.1 to 15 Pa. The temperature rise rate is higher at 0.3 to 4 ° C./min at a temperature higher than or equal to 0 ° C., and in a vacuum of 10 −3 to 0.05 Pa at 1350 to 1500 ° C. for 0.2 to 5 hours, particularly 0.5 to After firing for 2 hours, a cemented carbide (base material) can be produced by lowering the temperature range up to 1250 ° C. at 0.3 to 2 ° C./min, particularly 0.5 to 2 ° C./min.
[0033]
If desired, a hard coating layer having a thickness of 0.1 to 20 μm can be formed on the surface of the cemented carbide (base material) by a known thin film forming method such as a CVD method or a PVD method.
[0034]
The above-mentioned cemented carbide of the present invention has high hardness, high toughness, excellent mechanical properties such as high strength and high oxidation resistance, so it can be applied to molds, wear-resistant members, high-temperature structural materials, etc. In particular, it can be suitably used as a cutting tool for machining steel and cast iron such as carbon steel and alloy steel, and a cutting tool for machining difficult-to-cut materials such as stainless steel.
[0035]
【Example】
(Example 1)
Table 1 shows tungsten carbide (WC) powder having an average particle diameter of 1.5 μm, metallic cobalt (Co) powder having an average particle diameter of 1.2 μm, metal element M compound powder and carbon powder shown in Table 1 having an average particle diameter of 2.0 μm. Are added and mixed at the ratio shown in FIG. 5 and formed into a cutting tool shape (CNMG120408) by press molding, then subjected to binder removal treatment, and further heated to 1000 ° C. or higher at a rate of 3 ° C./min. After firing at 1450 ° C. for 1 hour in a vacuum of 01 Pa, the temperature was lowered to 1250 ° C. at the rate of temperature reduction shown in Table 1, and the temperature was further lowered to 1250 ° C. or less at 5 ° C./min to prepare a cemented carbide.
[0036]
A cemented carbide was prepared by depositing a hard coating layer in the order of TiN 1 μm, TiCN 7 μm, Al 2 O 3 3 μm, TiN 1 μm on the surface of the obtained cemented carbide by CVD.
[0037]
The obtained cemented carbide is observed with a transmission electron microscope (TEM) at an arbitrary position, and the composition of the metal element in each phase of the transmission electron micrograph (TEM image) is expressed by an energy dispersive X-ray. Measured by spectroscopic analysis (EDS). In addition, in FIG. Although an example of the TEM image about 3 is shown, regarding the composition analysis, each phase of A to F was measured for each arbitrary 5 points, and the average value was calculated. The results are shown in Table 2.
[0038]
Moreover, it oxidized for 30 minutes in 800 degreeC atmospheric pressure atmosphere, the weight increase amount before and behind oxidation was measured, and it was set as oxidation resistance. The results are shown in Table 1.
[0039]
[Table 1]
[Table 2]
Further, the alloy steel was cut for 25 minutes under the following conditions using the cutting tool of Table 1, and the flank wear amount and the tip wear amount of the cutting tool were measured. When the flank wear amount or the tip wear amount reached 0.2 mm during the cutting test, the cutting time was measured. Furthermore, an intermittent test was conducted with a grooved steel material, and the number of impacts when chipped was compared. The results are shown in Table 3.
[0042]
(Abrasion test)
Work material: Alloy steel (SCM435)
Tool shape: CNMG120408
Cutting speed: 250 m / min Feeding speed: 0.3 mm / rev
Cutting depth: 2mm
Other: Use of water-soluble cutting fluid (intermittent test)
Work material: Alloy steel (SCM440)
Tool shape: CNMG120408
Cutting speed: 200 m / min Feed speed: 0.4 mm / rev
Cutting depth: 1.5mm
Other: Uses water-soluble cutting fluid [0043]
[Table 3]
From the results of Table 1 and Table 3, the raw material of y / x = 1.0 was used as the titanium carbide (Ti x C y ) raw material, both in the first solid solution phase (first β phase) and / or the second solid solution phase. Sample No. in which Ti / (Ti + Zr) in (second β phase) was out of the predetermined range and these were present independently. In 1 and 2, the high-temperature strength decreased and the cutting performance decreased.
[0045]
In addition, the temperature lowering rate in the temperature range from the firing temperature to 1250 ° C. is faster than 2 ° C./min, Ti / (Ti + Zr) in the first and second solid solution phases is out of the predetermined range, and these exist independently. Sample No. Even at 7, the high-temperature strength decreased and the cutting performance deteriorated.
[0046]
On the other hand, sample No. 1 in which Ti / (Ti + Zr) in the first and / or second solid solution phase is in a predetermined range and these are adjacent to each other. In 3-6 and 8, all were excellent in oxidation resistance, high in hardness and toughness, and had excellent cutting performance.
[0047]
【The invention's effect】
As described above in detail, according to the cemented carbide of the present invention, ZrC (zirconium carbide) is 0.05 to 1.5 wt%, NbC (niobium carbide) is 0 to 3.5 wt%, TiC (titanium carbide). ) 1 to 2.5% by weight, TaC (tantalum carbide) 0 to 1% by weight, Co (cobalt) 5 to 10% by weight, with the balance being WC (tungsten carbide) and inevitable impurities. The solid solution phase contained together with the WC particles of the cemented carbide is at least one selected from the group consisting of ZrC (zirconium carbide), NbC (niobium carbide), TiC (titanium carbide), TaC (tantalum carbide) and WC (tungsten carbide). consists carbide species or more metal elements, 0.7 ≦ Ti / in atomic ratio (Ti + Zr) a first solid solution phase of ≦ 0.9, 0.4 ≦ Ti / ( Ti + Zr) ≦ 0.6 second solid solution of By the two, and coexist adjacent to said second solid solution phase is interposed between the coupling member matrix of the first solid solution and Co (cobalt), the strength in particular at high temperature of the cemented carbide and Toughness can be increased, and both high fracture resistance and wear resistance can be improved even in harsh environments where the cutting edge is partially exposed to high temperatures during cutting.
[Brief description of the drawings]
FIG. 1 is a TEM (transmission electron microscope) image at an arbitrary position of a cemented carbide of the present invention.
[Brief description of symbols]
A: WC particles, B: first solid solution phase, C: second solid solution phase, D: binder matrix, E: first solid solution phase, F: WC particles
Claims (4)
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| JP2002081865A JP4126451B2 (en) | 2002-03-22 | 2002-03-22 | Cemented carbide |
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| JP2002081865A JP4126451B2 (en) | 2002-03-22 | 2002-03-22 | Cemented carbide |
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| JP4126451B2 true JP4126451B2 (en) | 2008-07-30 |
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| SE527679C2 (en) * | 2004-01-26 | 2006-05-09 | Sandvik Intellectual Property | Carbide body, especially spiral drill, and its use for rotary metalworking tools |
| CN111918978B (en) * | 2018-03-29 | 2022-11-25 | 京瓷株式会社 | Cemented carbide, coated cutting tool and cutting tool |
| CN112004954B (en) * | 2018-03-29 | 2022-06-28 | 京瓷株式会社 | Hard alloy, and coated cutting tool and cutting tool using the same |
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| JPS54115610A (en) * | 1978-02-28 | 1979-09-08 | Sumitomo Electric Ind Ltd | Mo-containing sintered hard alloy and manufacture thereof |
| JP2503770B2 (en) * | 1987-04-21 | 1996-06-05 | 三菱マテリアル株式会社 | Tungsten carbide based cemented carbide for cutting tools |
| JPH0696751B2 (en) * | 1990-04-06 | 1994-11-30 | 日立金属株式会社 | Cemented carbide |
| JP3850085B2 (en) * | 1996-12-11 | 2006-11-29 | 京セラ株式会社 | Coated cermet for cutting tools |
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