JP7441416B2 - WC-based cemented carbide and WC-based cemented carbide cutting tools - Google Patents
WC-based cemented carbide and WC-based cemented carbide cutting tools Download PDFInfo
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Description
本発明は、優れた耐摩耗性、耐塑性変形性を有し、さらに、耐欠損性、耐チッピング性にも優れたＷＣ基超硬合金、および、該超硬合金を工具基体として用いたＷＣ基超硬合金切削工具に関するものである。 The present invention provides a WC-based cemented carbide having excellent wear resistance and plastic deformation resistance, as well as excellent chipping resistance and chipping resistance, and a WC-based cemented carbide using the cemented carbide as a tool base. This invention relates to a base cemented carbide cutting tool.
従来、炭化タングステン（ＷＣ）を主成分とする硬質相と結合相とを有する超硬合金が切削工具の工具基体として用いられている。そして、この工具基体には、強度、靭性、硬さ、耐塑性変形性、耐摩耗性などの特性に加え、優れた耐欠損性や耐チッピング性を有することが求められており、耐欠損性や耐チッピング性が不足する場合には、Ｃｏ量の増加や、あるいは、ＷＣの粗粒化により、耐摩耗性や耐塑性変形性による効果を一部抑制することにより、耐欠損性および耐チッピング性の向上を図っている。 Conventionally, a cemented carbide having a hard phase mainly composed of tungsten carbide (WC) and a binder phase has been used as a tool base of a cutting tool. In addition to properties such as strength, toughness, hardness, plastic deformation resistance, and wear resistance, this tool base is required to have excellent fracture resistance and chipping resistance. If chipping resistance or chipping resistance is insufficient, increase the amount of Co or coarsen the grains of WC to partially suppress the effects of wear resistance and plastic deformation resistance. We are trying to improve sexual performance.
例えば、特許文献１では、ＷＣ基超硬合金において、焼結後、冷却速度１００℃／分以上にて超急冷することにより、硬質相の接触率を低減させて、靭性の向上を図り、工具基体として、耐欠損性や耐チッピング性を高めることが提案されている。
また、特許文献２では、ＷＣ基超硬合金において、１３５０℃以上、１４５０℃以下にて高温真空焼結を行い、Ａｒ雰囲気下にてシンターＨＩＰ処理を行った後、１０℃／ｍｉｎ以上、１５℃／ｍｉｎ以下の冷却速度にて冷却を行うことにより、ＷＣの平均粒径を０．８μｍ以下、結合相における平均粒径を２００μｍ以下とし、粒界部分における不純物や粒成長抑制成分の含有量を均一化することにより、靭性の向上を図り、耐欠損性を高めることが提案されている。
For example, in Patent Document 1, in a WC-based cemented carbide, after sintering, ultra-rapid cooling is performed at a cooling rate of 100°C/min or more to reduce the contact ratio of the hard phase and improve the toughness of the tool. It has been proposed that the substrate be improved in fracture resistance and chipping resistance.
Furthermore, in Patent Document 2, WC-based cemented carbide is subjected to high-temperature vacuum sintering at 1350°C or higher and 1450°C or lower, and then subjected to sinter HIP treatment in an Ar atmosphere, followed by 10°C/min or higher and 15°C. By cooling at a cooling rate of ℃/min or less, the average grain size of WC is 0.8 μm or less, the average grain size of the binder phase is 200 μm or less, and the content of impurities and grain growth inhibiting components at grain boundaries is reduced. It has been proposed to improve toughness and fracture resistance by making the steel uniform.
前記特許文献１に記載された超硬合金は、硬質相の接触率を低減させ、靭性を向上させて耐欠損性の向上を図るものであるが、他方、硬質相の接触率が低減することにより、切削工具の工具基体に用いた場合、耐塑性変形性が低下するという課題を有している。
また、前記特許文献２に記載された超硬合金は、粒界部における不純物や粒成長抑制成分の含有量の均一化、および、結合相粒界の健全化を図り、耐摩耗性と耐欠損性の両立を図るというものであるが、不純物や粒成長抑制成分の絶対量は変化するものではないため、その効果は、限定的であり、また、結合相の粒径はＷＣの粒径よりも大きく、結合相粒界の占める体積率は、ＷＣ／ＷＣ粒界やＷＣ／結合相粒界の占める体積率よりも極めて小さいことから、その効果は、同様に限定的であるため、かかる超硬合金を切削工具の工具基体として、例えば、鋼の高能率転削加工に用いた場合には、刃先の塑性変形に伴う偏摩耗や熱亀裂の発生、進展によるチッピングにより工具寿命に達してしまうという課題を有していた。
The cemented carbide described in Patent Document 1 aims to improve fracture resistance by reducing the contact ratio of the hard phase and improving toughness, but on the other hand, the contact ratio of the hard phase is reduced. Therefore, when used in a tool base of a cutting tool, there is a problem that the plastic deformation resistance decreases.
In addition, the cemented carbide described in Patent Document 2 is designed to have a uniform content of impurities and grain growth inhibiting components in the grain boundaries, and to make the binder phase grain boundaries healthy, thereby improving wear resistance and chipping resistance. However, the effect is limited because the absolute amount of impurities and grain growth inhibiting components does not change, and the particle size of the binder phase is smaller than the particle size of WC. is also large, and the volume fraction occupied by binder phase grain boundaries is extremely smaller than the volume fraction occupied by WC/WC grain boundaries and WC/bond phase grain boundaries, so the effect is similarly limited. When a hard alloy is used as a tool base for a cutting tool, for example for high-efficiency turning of steel, the tool life will be reached due to uneven wear due to plastic deformation of the cutting edge and chipping due to the occurrence and propagation of thermal cracks. There was a problem with this.
そこで、本発明は、超硬合金が優れた耐塑性変形性および耐摩耗性を有するとともに、耐熱亀裂性および耐チッピング性を合わせ持ち、切削工具の工具基体として用いた場合、特に、鋼の高能率転削加工において、長期の使用にわたり、優れた切削性能を発揮する超硬合金、および、該超硬合金を工具基体として用いた切削工具を提供することを目的とする。 Therefore, the present invention provides that cemented carbide has excellent plastic deformation resistance and wear resistance, as well as heat cracking resistance and chipping resistance, and that when used as a tool base of a cutting tool, it can be used as a tool base of a cutting tool. The object of the present invention is to provide a cemented carbide that exhibits excellent cutting performance over a long period of use in efficient milling, and a cutting tool using the cemented carbide as a tool base.
本発明者らは、超硬合金に優れた耐塑性変形性と、耐摩耗性、耐熱亀裂性、および耐チッピング性とを付与するために鋭意検討を重ねたところ、２つのＷＣ結晶粒間に存在する結晶粒界上の原子において、その位置の多くが両側の結晶粒の格子点に一致し、両結晶粒に共有された粒界、すなわち、ＷＣの対応粒界において、結晶配列の乱れが一般粒界（ランダム粒界）に比較して少なく、原子の結合が強固なΣ２対応粒界の、全ＷＣ／ＷＣ粒界における比率（以下、「Σ２対応粒界比率」ともいう。）を高めることにより、優れた耐塑性変形性、耐摩耗性、耐熱亀裂性、および、耐チッピング性を合わせ持ち、特に、用途に応じて優れた特性、すなわち、例えば、鋼の高能率転削加工に用いた場合において、耐摩耗性や耐塑性変形性を損なうことなく、耐熱亀裂特性および耐チッピング性を発揮することを知見した。 The present inventors have conducted intensive studies to impart excellent plastic deformation resistance, abrasion resistance, thermal cracking resistance, and chipping resistance to cemented carbide, and found that between two WC crystal grains, Many of the positions of the atoms on the grain boundaries that exist coincide with the lattice points of the crystal grains on both sides, and the disorder of crystal alignment occurs at the grain boundary shared by both grains, that is, the corresponding grain boundary of WC. Increase the ratio of Σ2-compatible grain boundaries, which are fewer in number than general grain boundaries (random grain boundaries) and have strong atomic bonds, in all WC/WC grain boundaries (hereinafter also referred to as "Σ2-compatible grain boundary ratio") As a result, it has excellent plastic deformation resistance, wear resistance, thermal cracking resistance, and chipping resistance, and has particularly excellent properties depending on the application. The inventors have discovered that, in cases where the material is exposed to heat, it exhibits heat cracking resistance and chipping resistance without impairing wear resistance or plastic deformation resistance.
本発明はかかる知見に基づいてなされたものであって、以下のとおりのものである。
すなわち、
「（１）ＷＣ基超硬合金において、
Ｃｏ、Ｎｉの少なくとも１種を１０．０質量％以上、１５．０質量％未満、
ＴｉＣ、ＴａＣ、ＮｂＣ、ＺｒＣ、ＨｆＣ、および、ＶＣのうちから選ばれる少なくとも１種以上を合計にて、０．５質量％以上、１２．０質量％未満、
さらに、Ｃｒ３Ｃ２を０．０質量％以上、０．８質量％未満にて含有し、
残部は、ＷＣおよび不可避的不純物とからなり、
ＷＣの平均粒径は、０．２μｍ以上、４．０μｍ以下であり、
ＷＣのΣ２対応粒界の、全ＷＣ／ＷＣ粒界に占める存在比率（Σ２対応粒界比率）が１５％以上であることを特徴とするＷＣ基超硬合金。
（２） 前記超硬合金において、前記Σ２対応粒界の、全ＷＣ／ＷＣ粒界に占める存在比率が２５％以上であることを特徴とする（１）に記載の超硬合金。
（３） （１）または（２）に記載されたＷＣ基超硬合金を基体とするＷＣ基超硬合金製切削工具。
（４） 前記（３）に記載されたＷＣ基超硬合金製工具の少なくとも切れ刃には、硬質被覆層が形成されている表面被覆ＷＣ基超硬合金製切削工具。」である。
The present invention was made based on this knowledge, and is as follows.
That is,
(1) In WC-based cemented carbide,
At least one of Co and Ni is 10.0% by mass or more and less than 15.0% by mass,
The total content of at least one selected from TiC, TaC, NbC, ZrC, HfC, and VC is 0.5% by mass or more and less than 12.0% by mass,
Furthermore, it contains Cr 3 C 2 at 0.0% by mass or more and less than 0.8% by mass,
The remainder consists of WC and unavoidable impurities,
The average particle size of WC is 0.2 μm or more and 4.0 μm or less,
A WC-based cemented carbide characterized in that the abundance ratio of WC Σ2-compatible grain boundaries to the total WC/WC grain boundaries (Σ2-compatible grain boundary ratio) is 15% or more.
(2) The cemented carbide according to (1), wherein the ratio of the Σ2 corresponding grain boundaries to all WC/WC grain boundaries is 25% or more.
(3) A cutting tool made of a WC-based cemented carbide having the WC-based cemented carbide described in (1) or (2) as a base.
(4) A surface-coated WC-based cemented carbide cutting tool, wherein a hard coating layer is formed on at least the cutting edge of the WC-based cemented carbide tool described in (3) above. ”.
本発明に係る超硬合金は、ＷＣ結晶粒同士の結合の強いΣ２対応粒界の比率を高めることにより、切削中に結合相がＷＣ／ＷＣ界面へ浸入することを防ぎ、ＷＣの高熱伝導性を維持でき、刃先温度の上昇を抑制できるため、耐摩耗性や耐塑性変形性を損なうことなく、耐熱亀裂性を高めることができ、熱亀裂の進展によるチッピングの発生を防ぐことができる。 The cemented carbide according to the present invention prevents the binder phase from penetrating into the WC/WC interface during cutting by increasing the ratio of Σ2-compatible grain boundaries with strong bonds between WC grains, and improves the high thermal conductivity of WC. can be maintained and the rise in cutting edge temperature can be suppressed, so heat cracking resistance can be increased without impairing wear resistance or plastic deformation resistance, and chipping due to the propagation of thermal cracks can be prevented.
以下、本発明の超硬合金および切削工具について、より詳細に説明する。 Hereinafter, the cemented carbide and cutting tool of the present invention will be explained in more detail.
１．超硬合金
Ｃｏ、Ｎｉ：
Ｃｏ、Ｎｉは、ＷＣ基超硬合金の主たる結合相形成成分として含有させるが、ＣｏとＮｉの含有量の少なくとも１種以上（すなわち、Ｃｏ、Ｎｉのいずれか一つであってもよいし、ＣｏとＮｉを組み合わせてもよい）の合計が超硬合金全体の１０．０質量％未満では、鋼の高能率転削加工に用いた場合において、耐チッピング性や耐欠損性が十分でなく、一方、その含有量の合計が１５．０質量％以上では、耐塑性変形性および耐摩耗性が不十分となる。
したがって、ＣｏとＮｉの含有量の少なくとも１種以上の合計は、１０．０質量％以上、１５．０質量％未満とした。
結合相中には、硬質相の成分であるＷやＣ、その他の不可避不純物が含まれていてもよい。また、結合相には、Ｃｒ、Ｔｉ、Ｔａ、Ｎｂ、Ｚｒ、ＨｆおよびＶの少なくとも１種を含んでいてもよいが、これらの元素は、結合相中に存在するときは、結合相中に固溶した状態であると推定される。
なお、Ｃｏ、Ｎｉの少なくとも１種以上の合計の質量％は、超硬合金の任意の表面または断面を鏡面加工し、その加工面を蛍光Ｘ線回折測定することにより求められる。
1. Cemented carbide Co, Ni:
Co and Ni are contained as the main binder phase forming components of the WC-based cemented carbide, but at least one of Co and Ni (that is, either one of Co or Ni may be included, If the total amount of (Co and Ni may be combined) is less than 10.0% by mass of the entire cemented carbide, the chipping resistance and fracture resistance will be insufficient when used for high-efficiency turning of steel. On the other hand, if the total content is 15.0% by mass or more, the plastic deformation resistance and wear resistance will be insufficient.
Therefore, the total content of at least one of Co and Ni was set to be 10.0% by mass or more and less than 15.0% by mass.
The binder phase may contain W and C, which are components of the hard phase, and other unavoidable impurities. Further, the binder phase may contain at least one of Cr, Ti, Ta, Nb, Zr, Hf, and V, but when these elements are present in the binder phase, It is presumed to be in a solid solution state.
The total mass % of at least one of Co and Ni can be determined by mirror-finishing any surface or cross section of the cemented carbide and measuring the processed surface by fluorescent X-ray diffraction.
ＴｉＣ、ＴａＣ、ＮｂＣ、ＺｒＣ、ＨｆＣ、ＶＣ：
本発明のＷＣ基超硬合金において、ＴｉＣ、ＴａＣ、ＮｂＣ、ＺｒＣ、ＨｆＣ及びＶＣは、γ相を形成する炭化物であり、鋼の高能率転削加工に用いた場合において、少なくとも炭化物換算にて１種以上の合計にて０．５質量％未満では、耐クレーター摩耗性が不十分となり、他方、１２．０質量％以上では、耐摩耗性が不十分となり、また、凝集体が生じやすく、欠損発生の起点となるため、耐クレーター摩耗性と耐摩耗性の両特性が発揮可能な、０．５質量％以上、１２．０質量％未満の範囲とすることが好ましい。
なお、ＴｉＣ、ＴａＣ、ＮｂＣ、ＺｒＣ、ＨｆＣ、ＶＣの含有量は、ＷＣ基超硬合金において、ＥＰＭＡにて測定された、Ｔｉ量、Ｔａ量、Ｎｂ量、Ｚｒ量、Ｈｆ量およびＶ量をいずれも炭化物換算した数値である。
TiC, TaC, NbC, ZrC, HfC, VC:
In the WC-based cemented carbide of the present invention, TiC, TaC, NbC, ZrC, HfC, and VC are carbides that form a γ phase, and when used for high-efficiency rolling of steel, at least in terms of carbides. If the total amount of one or more types is less than 0.5% by mass, the crater wear resistance will be insufficient, while if it is 12.0% by mass or more, the wear resistance will be insufficient, and aggregates are likely to occur. Since it becomes a starting point for the occurrence of defects, it is preferable that the content be in the range of 0.5% by mass or more and less than 12.0% by mass, which can exhibit both properties of crater wear resistance and wear resistance.
The contents of TiC, TaC, NbC, ZrC, HfC, and VC are based on the Ti amount, Ta amount, Nb amount, Zr amount, Hf amount, and V amount measured by EPMA in the WC-based cemented carbide. All values are calculated in terms of carbide.
Ｃｒ３Ｃ２：
Ｃｒ３Ｃ２は、結合相を形成するＣｏ中にＣｒとして固溶し、固溶強化することにより、ＷＣ基超硬合金の強度を高めるものであるが、添加量が増加するとＣｒとＷとの複合炭化物を析出し、靭性が低下し、また、欠損発生の起点となるため、鋼の高能率転削加工に用いた場合においては、炭化物換算にて０．８質量％未満とすることが好ましい。
すなわち、Ｃｒの含有割合は、Ｃｒ３Ｃ２として０．０質量％以上、０．８質量％未満とする。
Cr3C2 :
Cr 3 C 2 increases the strength of WC-based cemented carbide by forming a solid solution as Cr in Co forming the binder phase and solid solution strengthening, but as the amount added increases, Cr and W When used for high-efficiency turning of steel, the content should be less than 0.8% by mass in terms of carbide because it precipitates composite carbides, reduces toughness, and becomes a starting point for chipping. preferable.
That is, the content of Cr is 0.0% by mass or more and less than 0.8% by mass as Cr 3 C 2 .
ＷＣ：
ＷＣは、ＷＣ基超硬合金の主たる硬質相形成成分として含有される。硬質相には、製造過程で不可避的に混入する不可避不純物が含まれていてもよい。
（１）平均粒径：
ＷＣの平均粒径は、０．２μｍ未満では、切削加工中に硬質相同士のすべりが生じやすく耐塑性変形性が十分ではなくなり、一方、平均粒径が４．０μｍを超えると、十分な耐摩耗性が得られなくなるため、０．２μｍ以上、４．０μｍ以下の範囲より選択するのが好ましい。
ＷＣの平均粒径は、超硬合金の任意の表面または断面を鏡面加工し、その加工面を後方散乱電子回折（ＥＢＳＤ）で観察し、画像解析によって、少なくとも４０００個の各硬質相の面積を求め、その面積に等しい円の直径を算出して平均したものである。
なお、鏡面加工には、例えば、集束イオンビーム装置（ＦＩＢ装置）、クロスセクションポリッシャー装置（ＣＰ装置）等を用いる。
W.C.:
WC is contained as a main hard phase forming component of the WC-based cemented carbide. The hard phase may contain unavoidable impurities that are inevitably mixed in during the manufacturing process.
(1) Average particle size:
If the average grain size of WC is less than 0.2 μm, slippage between the hard phases tends to occur during cutting, resulting in insufficient plastic deformation resistance.On the other hand, if the average grain size exceeds 4.0 μm, sufficient resistance to plastic deformation is not achieved. Since abrasion resistance cannot be obtained, it is preferable to select from a range of 0.2 μm or more and 4.0 μm or less.
The average grain size of WC can be determined by mirror-finishing any surface or cross section of cemented carbide, observing the machined surface using backscattered electron diffraction (EBSD), and calculating the area of at least 4000 hard phases by image analysis. The diameter of a circle equal to that area is calculated and averaged.
Note that, for example, a focused ion beam device (FIB device), a cross-section polisher device (CP device), etc. are used for mirror finishing.
（２）Σ２対応粒界比率：
本発明者らは、超硬合金に優れた耐塑性変形性および耐摩耗性、耐熱亀裂性、耐チッピング性を付与するために鋭意検討を重ねたところ、２つのＷＣ結晶粒間に存在する結晶粒界上の原子において、その位置の多くが両側の結晶粒の格子点に一致し、両結晶粒に共有された粒界、すなわち、ＷＣの対応粒界において、結晶配列の乱れが一般粒界（ランダム粒界）に比較して最も少なく、原子の結合が強固なΣ２対応粒界長の、全ＷＣ／ＷＣ粒界長における比率、
すなわち、Σ２対応粒界比率を高めることにより、用途に応じ優れた耐塑性変形性、耐摩耗性、耐熱亀裂性および耐チッピング性を有することを知見した。
Σ２対応粒界比率は、１５％未満では、Ｃｏ相の侵入しづらいＷＣ／ＷＣ粒界の割合が不十分となり、耐熱亀裂性を満足しないため、１５％以上と規定した。さらには、２５％以上であることが好ましい。
Σ２対応粒界比率の測定は、例えば、ＳＥＭ－ＥＢＳＤ法を用いて測定することができる。すなわち、ＳＥＭにて、１視野２４μｍ×７２μｍの視野にてピクセルサイズを０．１μｍ×０．１μｍとし、かつＷＣ数が４０００個以上となるように複数視野観察し、ＥＢＳＤにて解析される、隣り合うＷＣが［１０－１０］方向を軸として９０°回転した方位関係を持つ粒界をΣ２対応粒界と定義し、全ＷＣ／ＷＣ粒界長に占めるΣ２対応粒界長の比率を算出することにより求めることができる。
ただし、Ｂｒａｎｄｏｎの条件式より、Σ２対応粒界は、前記９０°の方位関係から両方向に１０．６°以内の角度の範囲を含むものと定義されるので、隣り合うＷＣが［１０－１０］方向を軸として７９．４°以上、１００．６°以下の方位関係をもつものをΣ２対応粒界と定義した。
(2) Σ2 corresponding grain boundary ratio:
The inventors of the present invention conducted intensive studies to impart excellent plastic deformation resistance, wear resistance, thermal cracking resistance, and chipping resistance to cemented carbide, and found that the crystals present between two WC crystal grains Many of the positions of atoms on the grain boundary coincide with the lattice points of the crystal grains on both sides, and at the grain boundary shared by both grains, that is, the corresponding grain boundary of WC, the disorder of the crystal orientation is the general grain boundary. The ratio of the Σ2 corresponding grain boundary length, which is the smallest compared to (random grain boundaries) and has strong atomic bonds, to the total WC/WC grain boundary length,
That is, it has been found that by increasing the ratio of grain boundaries corresponding to Σ2, excellent plastic deformation resistance, wear resistance, heat cracking resistance, and chipping resistance can be obtained depending on the application.
The Σ2 corresponding grain boundary ratio was specified to be 15% or more because if it is less than 15%, the ratio of WC/WC grain boundaries where it is difficult for the Co phase to penetrate will be insufficient and the thermal cracking resistance will not be satisfied. Furthermore, it is preferably 25% or more.
The Σ2-compatible grain boundary ratio can be measured using, for example, the SEM-EBSD method. That is, multiple fields of view are observed using SEM with a pixel size of 0.1 μm x 0.1 μm in a field of view of 24 μm x 72 μm, and the number of WC is 4000 or more, and analyzed using EBSD. A grain boundary with an orientation relationship in which adjacent WCs are rotated by 90° around the [10-10] direction is defined as a Σ2-compatible grain boundary, and the ratio of the Σ2-compatible grain boundary length to the total WC/WC grain boundary length is calculated. It can be found by
However, according to Brandon's conditional expression, the Σ2 corresponding grain boundary is defined as including the range of angles within 10.6° in both directions from the 90° orientation relationship, so the adjacent WC is [10-10] Those having an orientation relationship of 79.4° or more and 100.6° or less with the direction as an axis were defined as Σ2-compatible grain boundaries.
不可避不純物：
前記のように、硬質相、結合相には製造過程で不可避的に混入する不純物を含んでいてもよく、その量は超硬合金全体に対して０．３質量％以下が好ましい。
Unavoidable impurities:
As described above, the hard phase and the binder phase may contain impurities that are inevitably mixed in during the manufacturing process, and the amount thereof is preferably 0.3% by mass or less based on the entire cemented carbide.
２．切削工具：
本発明の切削工具は、本発明の超硬合金に硬質皮膜を形成したものである。硬質皮膜の種類、成膜法は、それぞれ、当業者に既によく知られている膜種、成膜手法を採用すればよく、特に、制限するものではない。あえて例示をするならば、物理蒸着法（ＰＶＤ法）または化学蒸着法（ＣＶＤ法）により、Ｔｉ、Ａｌ、Ｃｒ、ＢおよびＺｒからなる群から選ばれた少なくとも一種の元素と、Ｃ、ＮおよびＯからなる群から選ばれた少なくとも一種の元素とを必須とする単層又は多層の硬質皮膜が有用である。具体的には、例えば、ＴｉＣ、ＣｒＣ、ＳｉＣ、ＶＣ、ＺｒＣ、ＴｉＮ、ＡｌＮ、ＣｒＮ、ＶＮ、ＺｒＮ、Ｔｉ（ＣＮ）、（ＴｉＳｉ）Ｎ、（ＴｉＢ）Ｎ、（ＴｉＺｒ）Ｎ、ＴｉＡｌ（ＣＮ）、ＴｉＣｒ（ＣＮ）、ＴｉＺｒ（ＣＮ）、Ｔｉ（ＣＮＯ）、ＴｉＡｌ（ＣＮＯ）、Ｔｉ（ＣＯ）、（ＴｉＣｒ）Ｎ、（ＴｉＡｌＣｒ）Ｎ、（ＡｌＣｒ）Ｎ、Ａｌ２Ｏ３およびＴｉＢ２等の単層または多層の皮膜が挙げることができ、硬質皮膜の膜厚は、例えば１．０～１５．０μｍである。
2. Cutting tools:
The cutting tool of the present invention is one in which a hard coating is formed on the cemented carbide of the present invention. The type and film forming method of the hard film are not particularly limited, and may be those that are already well known to those skilled in the art. To give an example, at least one element selected from the group consisting of Ti, Al, Cr, B, and Zr and C, N, and A single-layer or multi-layer hard coating containing at least one element selected from the group consisting of O is useful. Specifically, for example, TiC, CrC, SiC, VC, ZrC, TiN, AlN, CrN, VN, ZrN, Ti(CN), (TiSi)N, (TiB)N, (TiZr)N, TiAl(CN ), TiCr(CN), TiZr(CN), Ti(CNO), TiAl(CNO), Ti(CO), (TiCr)N, (TiAlCr)N, ( AlCr )N, Al2O3 and TiB2 , etc. For example, the hard coating may have a thickness of 1.0 to 15.0 μm.
３．製造方法：
本発明の超硬合金は、例えば、以下のようにして作製することができる。
まず、ＷＣ粉末、Ｃｏ、Ｎｉ粉末の少なくとも１種以上、ＴｉＣ粉末、ＴａＣ粉末、ＮｂＣ粉末、ＺｒＣ粉末、ＨｆＣ粉末、ＶＣ粉末のうちの１種以上、および、必要により、Ｃｒ３Ｃ２粉末を加えた原料粉末を、本発明の超硬合金にて規定する組成となるように配合し混合する。
特にＷＣ粉末は、他の原料粉末との混合前にプレス成形－熱処理－解砕処理を複数回実施し、ＷＣ粉末におけるΣ２対応粒界比率を高めた上で、他の原料粉末と混合する。
前処理されたＷＣ粉末と、他の原料粉末との混合には、例えば、超音波ホモジナイザー、サイクロンミキサーなどのメディアレス混合を用いることにより、大きな破砕力を加えることなく配合・混合するため、炭化時および前処理時に形成されたＷＣのΣ２対応粒界の消失を回避することができる。
次いで、前記混合粉末を成形して圧粉成形体を作製し、前記圧粉成形体の焼結工程においては、固相焼結が進むとその後の液晶焼結時にΣ２対応粒界が形成されにくくなるため、固相焼結が進む温度領域（１０００℃～１３５０℃）では昇温速度を５０℃／分以上に早め、固相焼結を抑制した上で、１３５０℃～１４５０℃にて、真空雰囲気下、１０～８０分の時間にて本焼結を行うことにより、微粒ＷＣに形成されるΣ２対応粒界が溶解・再析出により消失することを回避し、Σ２対応粒界比率が１５％以上、さらには、２５％以上に維持されたＷＣ焼結体を得ることができる。
3. Production method:
The cemented carbide of the present invention can be produced, for example, as follows.
First, at least one of WC powder, Co, and Ni powder, one or more of TiC powder, TaC powder, NbC powder, ZrC powder, HfC powder, and VC powder, and if necessary, Cr 3 C 2 powder. The added raw material powders are blended and mixed so as to have the composition specified for the cemented carbide of the present invention.
In particular, WC powder is subjected to press molding, heat treatment, and crushing several times before being mixed with other raw material powders to increase the ratio of Σ2-compatible grain boundaries in the WC powder, and then mixed with other raw material powders.
For mixing the pretreated WC powder and other raw material powders, for example, media-less mixing such as an ultrasonic homogenizer or cyclone mixer is used to blend and mix without applying a large crushing force, thereby preventing carbonization. It is possible to avoid the disappearance of the Σ2-compatible grain boundaries of the WC formed during the time and pre-treatment.
Next, the mixed powder is molded to produce a powder compact, and in the sintering process of the powder compact, as solid-phase sintering progresses, Σ2-compatible grain boundaries are difficult to form during subsequent liquid crystal sintering. Therefore, in the temperature range where solid-phase sintering progresses (1000°C to 1350°C), the temperature increase rate is increased to 50°C/min or more to suppress solid-state sintering, and at 1350°C to 1450°C, vacuum By performing main sintering in an atmosphere for 10 to 80 minutes, the Σ2 compatible grain boundaries formed in fine WC are prevented from disappearing due to dissolution and re-precipitation, and the Σ2 compatible grain boundaries ratio is 15%. Furthermore, it is possible to obtain a WC sintered body in which the WC concentration is maintained at 25% or more.
本発明の超硬合金および該超硬合金を工具基体として用いた切削工具について、以下、実施例により具体的に説明する。 EXAMPLES The cemented carbide of the present invention and the cutting tool using the cemented carbide as a tool base will be specifically described below with reference to Examples.
（ａ）原料粉末
まず、焼結用の原料粉末として、体積基準の平均粒径（ｄ５０）が０．５μｍ以上、４．０μｍ以下のＷＣ粉末、および、平均粒径（ｄ５０）が、いずれも、１．０μｍ以上、４．０μｍ以下の範囲内のＣｏ粉末、Ｎｉ粉末、Ｃｒ３Ｃ２粉末、ＴｉＣ粉末、ＴａＣ粉末、ＮｂＣ粉末、ＺｒＣ粉末、ＨｆＣ粉末、ＶＣ粉末を用意した。
特に、ＷＣ粉末については、表１に示すとおり、他粉末との混合前の事前の準備工程として、下記手順により、前記素原料ＷＣ粉末について、プレス成形－熱処理－解砕処理を複数回実施すことにより、結晶性に優れ、Σ２対応粒界比率を高めたＷＣ原料粉末を得て、これを原料として用いた。
以下、具体的に示すと以下のとおり。
１）前記素原料ＷＣ粉末を粒径１ｍｍ以上、３ｍｍ以下の球状にプレス成形し、１３００以上、１４００℃以下、アルゴン雰囲気１０Ｐａ以上、１００Ｐａ以下にて３０分間以上、９０分間以内の熱処理を施す。
２）前記熱処理により得られた粉末を乳鉢にて３分以上、１０分以下の解砕処理を施す。
３）１）と２）の工程を２回以上、１０回以下にて繰り返すことにより、Σ２対応粒界比率を高めたＷＣ粉末を得た。
すなわち、まず、１）工程では、別々の個体であったＷＣ粒子同士をプレス成形により接触させた状態にて熱処理を行うことにより、ＷＣ粒子同士を接合させ、その界面に対応粒界およびランダム粒界を形成させる。次いで、２）工程では、解砕処理により、粒界強度の低いランダム粒界やΣ値の高い粒界が優先して破壊され、粒界強度の高いΣ２対応粒界が残存する。そして、３）工程として、１）工程と２）工程とを繰り返すことにより、Σ２対応粒界比率の高いＷＣ粉末を作製することができた。
(a) Raw material powder First, as raw material powder for sintering, WC powder with a volume-based average particle size (d50) of 0.5 μm or more and 4.0 μm or less, and a WC powder with an average particle size (d50) of , Co powder, Ni powder, Cr 3 C 2 powder, TiC powder, TaC powder, NbC powder, ZrC powder, HfC powder, and VC powder within the range of 1.0 μm or more and 4.0 μm or less were prepared.
In particular, for the WC powder, as shown in Table 1, as a preliminary preparation step before mixing with other powders, the raw material WC powder is subjected to press molding, heat treatment, and crushing processes multiple times according to the following procedure. As a result, a WC raw material powder with excellent crystallinity and an increased ratio of grain boundaries corresponding to Σ2 was obtained, and this was used as a raw material.
The specific details are as follows.
1) The raw material WC powder is press-molded into a spherical shape with a particle size of 1 mm or more and 3 mm or less, and heat-treated at 1300° C. or more and 1400° C. or less and an argon atmosphere of 10 Pa or more and 100 Pa or less for 30 minutes or more and 90 minutes or less.
2) The powder obtained by the heat treatment is crushed in a mortar for at least 3 minutes and at most 10 minutes.
3) By repeating the steps 1) and 2) at least 2 times and at most 10 times, a WC powder with an increased ratio of grain boundaries corresponding to Σ2 was obtained.
That is, first, in step 1), WC particles, which were separate individuals, are brought into contact with each other by press molding, and heat treatment is performed to bond the WC particles together, and the corresponding grain boundaries and random grains are formed at the interface. form a world. Next, in step 2), random grain boundaries with low grain boundary strength and grain boundaries with high Σ values are preferentially destroyed by crushing treatment, and grain boundaries corresponding to Σ2 with high grain boundary strength remain. Then, as step 3), by repeating step 1) and step 2), it was possible to produce a WC powder with a high ratio of grain boundaries corresponding to Σ2.
（ｂ）混合工程（メディアレス混合工程）
次に、（ａ）にて、Σ２対応粒界比率を高めたＷＣ原料粉末と、事前に準備した、前記平均粒径（ｄ５０）が、いずれも、１．０μｍ以上、４．０μｍ以下の範囲内のＣｏ粉末、Ｎｉ粉末、Ｃｒ３Ｃ２粉末、ＴａＣ粉末、ＮｂＣ粉末、ＴｉＣ粉末、ＺｒＣ粉末、ＨｆＣ粉末、ＶＣ粉末とを、表２に示す配合組成となるように配合して焼結用粉末とし、特に、ＷＣ粉末について炭化時に形成されたΣ２対応粒界が破壊されるのを防ぐために、メディアレスのアトライター混合により、回転数５０ｒｐｍ、８時間湿式混合し、乾燥後、１００ＭＰａの圧力でプレス成形し、圧粉成形体を作製した。
(b) Mixing process (media-less mixing process)
Next, in (a), the WC raw material powder with a high Σ2 corresponding grain boundary ratio and the average particle size (d50) prepared in advance are both in the range of 1.0 μm or more and 4.0 μm or less. Co powder, Ni powder, Cr 3 C 2 powder, TaC powder, NbC powder, TiC powder, ZrC powder, HfC powder, and VC powder were mixed to have the composition shown in Table 2 and used for sintering. In particular, in order to prevent destruction of the Σ2-compatible grain boundaries formed during carbonization for WC powder, wet mixing was performed at a rotation speed of 50 rpm for 8 hours using a media-less attritor mixing, and after drying, a pressure of 100 MPa was applied. Press molding was performed to produce a powder compact.
（ｃ）焼結工程
昇温工程；
次いで、固相焼結となる１０００℃から焼結温度である１３５０℃までの昇温工程においては、昇温速度を５０℃／分以上に早めることにより、固相焼結を抑制した。
すなわち、液相温度領域における昇温後の液相焼結時には、また、新たなΣ２対応粒界が形成されるものの、液相が出現する前の温度域においては、ＷＣ同士が固相拡散により結合しネッキングが強固に形成されると本来液相焼結時に形成されるΣ２対応粒界が減少してしまうことから、固相拡散が進む１０００～１３５０℃の温度域において、昇温速度を速めたものである。
焼結工程；
次いで、焼結工程では、１３５０℃以上への昇温後、１３５０℃～１４５０℃にて１０～８０分、真空０．１Ｐａ以下とすることにより、微粒ＷＣに形成されるΣ２対応粒界の溶解、再析出による消失を防ぎ、ＷＣ基超硬合金焼結体を得た。
(c) Sintering process temperature raising process;
Next, in the temperature raising step from 1000° C., which is solid phase sintering, to 1350° C., which is the sintering temperature, solid phase sintering was suppressed by increasing the temperature raising rate to 50° C./min or more.
In other words, during liquid phase sintering after temperature rise in the liquidus temperature region, new Σ2-compatible grain boundaries are formed, but in the temperature region before the appearance of the liquid phase, WCs are separated by solid phase diffusion. If the bonding and necking are strongly formed, the Σ2 compatible grain boundaries that are originally formed during liquid phase sintering will decrease, so the temperature increase rate should be increased in the temperature range of 1000 to 1350 °C where solid phase diffusion occurs. It is something that
Sintering process;
Next, in the sintering process, after raising the temperature to 1350°C or higher, the temperature is 10 to 80 minutes at 1350°C to 1450°C and the vacuum is 0.1 Pa or less, thereby melting the Σ2 corresponding grain boundaries formed in the fine grain WC. , a WC-based cemented carbide sintered body was obtained by preventing disappearance due to redeposition.
次に、ＷＣ基超硬合金焼結体を機械加工、研削加工し、ＩＳＯ・ＳＥＥＮ１２０３ＡＦＳＮの形状に整え、表４に示す超硬合金基体１～１０（以下、本発明工具基体１～１０という）を作製した。 Next, the WC-based cemented carbide sintered body was machined and ground to the shape of ISO/SEEN1203AFSN, and cemented carbide bases 1 to 10 shown in Table 4 (hereinafter referred to as tool bases 1 to 10 of the present invention) were prepared. was created.
比較のために、比較例の超硬合金基体１～７（以下、比較例工具基体１～７という)を作製した。
その製造工程は、本発明工具基体１～１０の製造条件を外れた、表３に示す昇温速度、および、液相焼結条件にて、焼結工程を行い、ＷＣ基超硬合金焼結体を得た後、前記ＷＣ基超硬合金焼結体を機械加工、研削加工し、ＩＳＯ・ＳＥＥＮ１２０３ＡＦＳＮの形状に整えることにより、表５に示す比較例工具基体１～７として作製した。
For comparison, comparative examples of cemented carbide substrates 1 to 7 (hereinafter referred to as comparative example tool substrates 1 to 7) were produced.
In the manufacturing process, a sintering process is performed under the temperature increase rate and liquid phase sintering conditions shown in Table 3, which are different from the manufacturing conditions of the tool bases 1 to 10 of the present invention, and the WC-based cemented carbide sintering process is performed. After obtaining the body, the WC-based cemented carbide sintered body was machined and ground to prepare it into the shape of ISO SEEN 1203 AFSN, thereby producing Comparative Example Tool Bases 1 to 7 shown in Table 5.
本発明工具基体１～１０および比較例工具基体１～７の超硬合金の断面について、電子線マイクロアナライザ（ＥＰＭＡ）により、その成分であるＣｒ、Ｔｉ、Ｔａ、Ｎｂ、Ｚｒ、Ｈｆ、Ｖの各元素につき、その含有量を１０点測定し、その平均値を各成分の含有量とした。
なお、ここで、Ｃｒ、Ｔｉ、Ｔａ、Ｎｂ、Ｚｒ、Ｈｆ、Ｖは、それぞれの炭化物に換算して含有量を算出した。表４、表５に、それぞれの平均含有量を示す。
The cross sections of the cemented carbide of the present invention tool bases 1 to 10 and the comparative example tool bases 1 to 7 were analyzed using an electron beam microanalyzer (EPMA) to determine the components of Cr, Ti, Ta, Nb, Zr, Hf, and V. The content of each element was measured at 10 points, and the average value was taken as the content of each component.
Note that the contents of Cr, Ti, Ta, Nb, Zr, Hf, and V were calculated in terms of their respective carbides. Tables 4 and 5 show the respective average contents.
前記本発明工具基体１～１０および比較例工具基体１～７の表面に、表６に示す平均層厚の硬質被覆層をＣＶＤ法で被覆形成し、本発明表面被覆ＷＣ基超硬合金製切削工具（以下、本発明被覆工具という）１～１０、比較例表面被覆ＷＣ基超硬合金製切削工具（以下、比較例被覆工具という）１～７を作製した。 A hard coating layer having an average layer thickness shown in Table 6 was formed on the surfaces of the present invention tool bases 1 to 10 and comparative example tool bases 1 to 7 by CVD method, and the present invention surface-coated WC-based cemented carbide cutting material was Tools (hereinafter referred to as coated tools of the present invention) 1 to 10 and comparative example surface-coated WC-based cemented carbide cutting tools 1 to 7 (hereinafter referred to as comparative coated tools) were prepared.
切削条件：
乾式高速正面フライス加工、センターカット切削加工
被削材：ＳＣＭ４４０ 幅１００ｍｍ、長さ４００ｍｍのブロック材
カッタ径：１２５ｍｍ
回転速度：９６８ｍｉｎ－１
切削速度：３８０ｍ／ｍｉｎ
切り込み：１．０ｍｍ
送り：０．４ｍｍ／ｒｅｖ
切削時間：５分
Cutting conditions:
Dry high speed face milling, center cut cutting Workpiece material: SCM440 Block material with width 100mm and length 400mm Cutter diameter: 125mm
Rotation speed: 968min -1
Cutting speed: 380m/min
Cut: 1.0mm
Feed: 0.4mm/rev
Cutting time: 5 minutes
上記乾式高速正面フライス加工後の、切れ刃の逃げ面塑性変形量を測定するとともに、切れ刃の損耗状態を観察した。本切削試験では、切れ刃の逃げ面塑性変形量として次のものを採用した。すなわち、切削前の変形していない切れ刃稜線を基準とし、切削によって切れ刃稜線が押し込まれて変形した量を切れ刃の逃げ面塑性変形量として、切削時間終了後に測定した。具体的には、工具の主切れ刃側逃げ面について、切れ刃から十分離れた位置で主切れ刃側逃げ面とすくい面が交差する稜線上に線分を引き、同線分を切れ刃部方向に延伸し、延伸した線分と切れ刃部稜線間の距離（延伸した線分の垂直方向）が最も離れている部分を測定し、これを切れ刃の逃げ面塑性変形量として求めた（図２を参照）。
表７に、その結果を示す。
After the above-mentioned dry high-speed face milling, the amount of plastic deformation of the flank face of the cutting edge was measured, and the state of wear of the cutting edge was observed. In this cutting test, the following was adopted as the amount of plastic deformation on the flank face of the cutting edge. That is, using the undeformed cutting edge ridgeline before cutting as a reference, the amount by which the cutting edge ridgeline was pushed in and deformed by cutting was defined as the amount of plastic deformation of the flank face of the cutting edge, and was measured after the cutting time had ended. Specifically, for the flank face on the main cutting edge side of the tool, draw a line segment on the ridge line where the flank face on the main cutting edge side intersects with the rake face at a position sufficiently far from the cutting edge, and draw the line segment on the ridgeline where the flank face on the main cutting edge side intersects with the rake face, and draw the same line segment on the cutting edge side. The distance between the stretched line segment and the cutting edge ridgeline (perpendicular to the stretched line segment) was measured at the farthest point, and this was determined as the amount of plastic deformation on the flank surface of the cutting edge ( (see Figure 2).
Table 7 shows the results.
表７に示される試験結果によれば、本発明被覆工具は、熱亀裂によるチッピングを発生することなく、優れた耐塑性変形性を発揮した。これに対して、比較例被覆工具は、所定の切削時間において、工具が熱亀裂によるチッピングにより寿命を迎えた。
本発明被覆工具においては、全ＷＣ／ＷＣ粒界長に対して、粒界強度の高いΣ２対応粒界長の占める比率が１５％以上、より好ましくは、２５％以上であることにより、ＷＣ／ＷＣ粒界にＣｏ相が侵入しづらく、熱伝導率の低減が抑制されたため熱亀裂の発生および進展が抑制されたため、耐塑性変形性を損なうことなく高い耐熱亀裂性を発揮することができる。
According to the test results shown in Table 7, the coated tool of the present invention exhibited excellent plastic deformation resistance without causing chipping due to thermal cracking. On the other hand, the comparative coated tool reached the end of its life due to chipping due to thermal cracking within a predetermined cutting time.
In the coated tool of the present invention, the ratio of the Σ2 corresponding grain boundary length with high grain boundary strength to the total WC/WC grain boundary length is 15% or more, more preferably 25% or more, so that the WC/WC Since it is difficult for the Co phase to invade the WC grain boundaries and the reduction in thermal conductivity is suppressed, the occurrence and propagation of thermal cracks are suppressed, so high thermal crack resistance can be exhibited without impairing plastic deformation resistance.
以上のとおり、本発明の超硬合金および切削工具は、鋼の高能率転削加工に用いた場合、熱亀裂の進展によるチッピングを回避し、耐塑性変形性を損なうことなく耐熱亀裂性および耐チッピング性を向上させることができるため、長期の使用にわたって優れた切削性能を発揮し、工具の長寿命化が図られる。 As described above, when the cemented carbide and cutting tool of the present invention are used for high-efficiency turning of steel, chipping due to the propagation of thermal cracks can be avoided, and the cemented carbide and cutting tool of the present invention can improve heat cracking resistance and resistance without impairing plastic deformation resistance. Since chipping properties can be improved, excellent cutting performance can be achieved over long periods of use, resulting in a longer tool life.
Claims (4)
Ｃｏ、Ｎｉの少なくとも１種を１０．０質量％以上、１５．０質量％未満、
ＴｉＣ、ＴａＣ、ＮｂＣ、ＺｒＣ、ＨｆＣ、および、ＶＣのうちから選ばれる少なくとも１種以上を合計にて、０．５質量％以上、１２．０質量％未満、
さらに、Ｃｒ３Ｃ２を０．０質量％以上、０．８質量％未満にて含有し、
残部は、ＷＣおよび不可避的不純物とからなり、
ＷＣの平均粒径は、０．２μｍ以上、４．０μｍ以下であり、
ＷＣのΣ２対応粒界の、全ＷＣ／ＷＣ粒界に占める存在比率（Σ２対応粒界比率）が１５％以上である、
ことを特徴とするＷＣ基超硬合金。 In WC-based cemented carbide,
At least one of Co and Ni is 10.0% by mass or more and less than 15.0% by mass,
The total content of at least one selected from TiC, TaC, NbC, ZrC, HfC, and VC is 0.5% by mass or more and less than 12.0% by mass,
Furthermore, it contains Cr 3 C 2 at 0.0% by mass or more and less than 0.8% by mass,
The remainder consists of WC and unavoidable impurities,
The average particle size of WC is 0.2 μm or more and 4.0 μm or less,
The abundance ratio of the WC Σ2-compatible grain boundaries to the total WC/WC grain boundaries (Σ2-compatible grain boundary ratio) is 15% or more,
A WC-based cemented carbide characterized by the following.
The surface-coated WC-based cemented carbide cutting tool according to claim 3, wherein a hard coating layer is formed on at least the cutting edge of the WC-based cemented carbide tool.
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| JP2006320964A (en) | 2005-05-17 | 2006-11-30 | Hitachi Tool Engineering Ltd | Coated cemented carbide broach |
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