JP2020131293A - Cutting tool made of cubic crystal boron nitride-based sintered body - Google Patents
Cutting tool made of cubic crystal boron nitride-based sintered body Download PDFInfo
- Publication number
- JP2020131293A JP2020131293A JP2019023026A JP2019023026A JP2020131293A JP 2020131293 A JP2020131293 A JP 2020131293A JP 2019023026 A JP2019023026 A JP 2019023026A JP 2019023026 A JP2019023026 A JP 2019023026A JP 2020131293 A JP2020131293 A JP 2020131293A
- Authority
- JP
- Japan
- Prior art keywords
- cbn
- particles
- sintered body
- phase
- boron nitride
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Landscapes
- Cutting Tools, Boring Holders, And Turrets (AREA)
Abstract
Description
本発明は、立方晶窒化ほう素(以下、「cBN」で示す)基焼結体(以下、「cBN焼結体」で示す)からなるすぐれた耐チッピング性と耐クレータ摩耗性を兼ね備えたcBN焼結体製切削工具(以下、「cBN工具」で示す)に関する。 The present invention is a cBN composed of a cubic boron nitride (hereinafter referred to as "cBN") based sintered body (hereinafter referred to as "cBN sintered body"), which has excellent chipping resistance and crater wear resistance. The present invention relates to a sintered cutting tool (hereinafter referred to as “cBN tool”).
cBN焼結体は、ダイヤモンドに次ぐ高硬度、熱伝導性を有し、さらに、鉄系材料との親和性が低いという点から、鋼、鋳鉄等の鉄系被削材の切削加工用の工具として、従来から広く利用されている。
しかし、cBN焼結体からなるcBN工具に求められる性能は、被削材の種類、加工条件等に応じて異なるので、必要とされる性能に対応させるべく、従来からいくつかの提案がなされている。
The cBN sintered body has high hardness and thermal conductivity next to diamond, and has a low affinity for iron-based materials. Therefore, it is a tool for cutting iron-based work materials such as steel and cast iron. Has been widely used in the past.
However, the performance required for a cBN tool made of a cBN sintered body differs depending on the type of work material, processing conditions, etc., so some proposals have been made so far in order to meet the required performance. There is.
例えば、特許文献1には、焼入れ鋼やFCD鋳鉄、及びADI鋳鉄などの鉄系難削材切削加工用のcBN焼結体として、「体積%で、87%以上99%以下のcBN成分を有し、かつ熱伝導率が100W/m・K以上のcBN焼結体であり、cBN焼結体を構成しているcBN成分中のNに対するBのモル比が1.10以上1.17以下であり、さらに結合材成分として、Co化合物、Al化合物、W化合物及び酸素化合物から選択される少なくとも1種及び炭素とを含有するcBN焼結体の最表面が、4a,5a,6a族元素及びAlの中から選択される少なくとも1種以上の元素と、C,N,Oの中から選択される少なくとも1種以上の元素の化合物からなる0.5μm〜12μmの厚みを有する耐熱膜で被覆された高品位表面性状加工用cBN焼結体」が提案されている。 For example, Patent Document 1 states that a cBN sintered body for cutting iron-based difficult-to-cut materials such as hardened steel, FCD cast iron, and ADI cast iron has a cBN component of 87% or more and 99% or less in volume%. It is a cBN sintered body having a thermal conductivity of 100 W / m · K or more, and the molar ratio of B to N in the cBN component constituting the cBN sintered body is 1.10 or more and 1.17 or less. The outermost surface of the cBN sintered body containing at least one selected from Co compound, Al compound, W compound and oxygen compound and carbon as a binder component is a group 4a, 5a, 6a element and Al. It was coated with a heat-resistant film having a thickness of 0.5 μm to 12 μm composed of a compound of at least one element selected from among and at least one element selected from C, N, and O. A "cBN sintered body for high-quality surface texture processing" has been proposed.
また、特許文献2には、「体積%で、60%以上95%以下のcBN成分を有するcBN焼結体であって、該cBN焼結体の熱伝導率が70W/m・K以上であり、結合材成分として4a,5a,6a族元素の窒化物、炭化物、炭窒化物から選択される少なくとも1種と、前記結合材中の割合が重量%で20%以下のAl化合物を有し、前記cBN成分以外の成分においてCとNのモル数の和に対する4a,5a,6a族元素のモル数の和Mとの比が1.3以上1.6以下のcBN焼結体の最表面が、4a,5a,6a族元素、及びAlの中から選択される少なくとも1種以上の元素と、C,N,Oの中から選択される少なくとも1種以上の元素の化合物からなる0.5μm〜12μmの厚みを有する耐熱膜で被覆されている高品位表面性状加工用cBN焼結体」が提案されている。 Further, Patent Document 2 states that "a cBN sintered body having a cBN component of 60% or more and 95% or less in volume%, and the thermal conductivity of the cBN sintered body is 70 W / m · K or more. It has at least one selected from nitrides, carbides, and carbonitrides of group 4a, 5a, and 6a elements as a binder component, and an Al compound having a proportion in the binder of 20% or less in weight%. In the components other than the cBN component, the outermost surface of the cBN sintered body in which the ratio of the sum of the mole numbers of C and N to the sum of the mole numbers of the 4a, 5a, and 6a elements M is 1.3 or more and 1.6 or less is 0.5 μm to be composed of a compound of at least one element selected from 4, 5a, 6a elements and Al, and at least one element selected from C, N, O. A "cBN sintered body for high-quality surface texture processing" coated with a heat-resistant film having a thickness of 12 μm has been proposed.
また、特許文献3には、「cBNと結合材とを含む複合焼結体であって、前記cBNは、前記複合焼結体中に25体積%以上80体積%以下含まれ、前記結合材は、Ti系化合物群を含み、前記Ti系化合物群は、少なくともTiを含む化合物を1種以上含むものであって、かつ、少なくとも第1成分と第2成分とを含む2つ以上の成分により構成され、前記複合焼結体の少なくとも一断面における前記Ti系化合物群の粒度分布を、横軸を所定の粒径範囲で区分し、縦軸を前記各粒径範囲の粒子が占める割合とする粒度分布曲線で示す場合において、前記粒度分布曲線は、極大値を2つ以上有する形状を有し、その極大値のうち最大の極大値を示す場合の粒径をd1とし、2番目に大きい極大値を示す場合の粒径をd2とすると、前記第1成分は、平均粒径を前記d1とし、前記d1は、0.05μm以上0.15μm以下であり、前記第2成分は、平均粒径を前記d2とし、前記d2は、0.15μm以上0.5μm以下である複合焼結体」が提案されている。 Further, Patent Document 3 states that "a composite sintered body containing a cBN and a binder, the cBN is contained in the composite sintered body in an amount of 25% by volume or more and 80% by volume or less, and the binder is contained. , Ti-based compound group, and the Ti-based compound group contains at least one compound containing Ti, and is composed of two or more components including at least a first component and a second component. The particle size distribution of the Ti-based compound group in at least one cross section of the composite sintered body is divided into a predetermined particle size range on the horizontal axis and the vertical axis is the particle size occupied by the particles in each particle size range. When shown by the distribution curve, the particle size distribution curve has a shape having two or more maximum values, and the particle size when showing the maximum maximum value among the maximum values is d 1 , and the second largest maximum value is set. When the particle size showing the value is d 2 , the average particle size of the first component is d 1 , the d 1 is 0.05 μm or more and 0.15 μm or less, and the second component is A composite sintered body in which the average particle size is d 2 and the d 2 is 0.15 μm or more and 0.5 μm or less has been proposed.
そして、前記複合焼結体中において、結合材を構成する相対的に微粒の第1成分は、耐クレータ摩耗性と靭性を低下させるものの、耐衝撃チッピング性を向上すること、一方、結合材を構成する相対的に粗粒の第2成分は、耐衝撃チッピング性を低下させるものの、耐クレータ摩耗性および靭性を向上することから、結合材が前記第1成分と第2成分の組合せからなる複合焼結体は、耐衝撃チッピング性と耐クレータ摩耗性との両者が向上するとされている。 Then, in the composite sintered body, the first component of the relatively fine particles constituting the binder reduces the crater wear resistance and toughness, but improves the impact chipping resistance, while the binder is used. The second component of the relatively coarse grains that composes reduces the impact chipping resistance, but improves the crater wear resistance and toughness. Therefore, the binder is a composite composed of the combination of the first component and the second component. The sintered body is said to have improved both impact chipping resistance and crater wear resistance.
また、特許文献4には、「cBNと結合材とを含む複合焼結体であって、前記cBNは、前記複合焼結体中に25体積%以上80体積%以下含まれ、前記結合材は、Ti系化合物群を含み、前記Ti系化合物群は、少なくともTiを含む化合物を1種以上含むものであって、かつ粒径が0.1μm以下の粒子で構成される第1微粒成分を含み、また、前記第1微粒成分とともに第2微粒成分を含み、前記第2微粒成分は、粒径が0.1μmより大きく0.25μm以下の粒子で構成され、前記第1微粒成分および前記第2微粒成分は、これら両者を合わせて、前記複合焼結体の少なくとも一断面において、前記結合材が占める面積の90%以上を占める複合焼結体。」が提案されている。 Further, Patent Document 4 states that "a composite sintered body containing a cBN and a binder, the cBN is contained in the composite sintered body in an amount of 25% by volume or more and 80% by volume or less, and the binder is , Ti-based compound group, and the Ti-based compound group contains a first fine particle component composed of particles having a particle size of 0.1 μm or less and containing at least one compound containing Ti. Further, the second fine particle component is contained together with the first fine particle component, and the second fine particle component is composed of particles having a particle size larger than 0.1 μm and 0.25 μm or less, and the first fine particle component and the second fine particle component. As for the fine particle component, a composite sintered body that occupies 90% or more of the area occupied by the binder in at least one cross section of the composite sintered body is proposed. "
そして、粒径が0.1μm以下の前記第1微粒成分は、耐欠損性を向上させ、一方、粒径が0.1μmより大きく0.25μm以下の第2微粒成分は耐摩耗性を向上させることから、前記複合焼結体の耐欠損性と耐摩耗性が向上するとされている。 The first fine particle component having a particle size of 0.1 μm or less improves fracture resistance, while the second fine particle component having a particle size larger than 0.1 μm and 0.25 μm or less improves wear resistance. Therefore, it is said that the fracture resistance and abrasion resistance of the composite sintered body are improved.
前記特許文献1、2で提案されるcBN焼結体から作製されたcBN工具によれば、cBN焼結体の熱伝導性が高いことから、切削加工時に発生する高熱が、刃先から他の部位へ効率的に放熱され、切削中の刃先温度の上昇を抑制することができるため、耐クレータ摩耗性は向上するが、その反面、例えば、高硬度鋼(例えば、HRC58−62)の断続切削加工においては、チッピングを発生しやすく、これを原因として工具寿命が短命となるという問題があった。 According to the cBN tool produced from the cBN sintered body proposed in Patent Documents 1 and 2, since the cBN sintered body has high thermal conductivity, high heat generated during cutting is generated from the cutting edge to other parts. Since heat is efficiently dissipated to and the rise in cutting edge temperature during cutting can be suppressed, sinter wear resistance is improved, but on the other hand, intermittent cutting of high hardness steel (for example, HRC58-62) is performed. In the above, there is a problem that chipping is likely to occur and the tool life is shortened due to this.
また、前記特許文献3、4で提案される複合焼結体では、複合焼結体の結合相を構成する粒子の粒径を調整することで、耐衝撃チッピング性と耐クレータ摩耗性、あるいは、耐欠損性と耐摩耗性の両立を図っているが、この複合焼結体から作製した切削工具を、高硬度鋼の断続切削に供した場合、複合焼結体の結合相を構成する粒径の小さな粒子(特許文献3の第1成分、また、特許文献4の第1微粒成分)の存在が、複合焼結体の熱伝導性を低下させ、耐クレータ摩耗性を低下させるために、耐チッピング性と耐クレータ摩耗性の両立は未だ十分であるとはいえない。
そこで、高硬度鋼の断続切削加工に供した場合であっても、すぐれた耐クレータ摩耗性と耐チッピング性を発揮するcBN工具の開発が望まれている。
Further, in the composite sintered body proposed in Patent Documents 3 and 4, by adjusting the particle size of the particles constituting the bonded phase of the composite sintered body, impact chipping resistance and crater wear resistance, or crater wear resistance, or Although we are trying to achieve both fracture resistance and wear resistance, when a cutting tool made from this composite sintered body is used for intermittent cutting of high hardness steel, the particle size that constitutes the bonded phase of the composite sintered body The presence of small particles (the first component of Patent Document 3 and the first fine particle component of Patent Document 4) lowers the thermal conductivity of the composite sintered body and lowers the crater wear resistance. It cannot be said that both chipping resistance and crater wear resistance are sufficiently compatible.
Therefore, it is desired to develop a cBN tool that exhibits excellent crater wear resistance and chipping resistance even when it is subjected to intermittent cutting of high hardness steel.
本発明者等は、前記課題を解決するため、すぐれた耐クレータ摩耗性と耐チッピング性とを兼ね備えたcBN焼結体について鋭意研究を進めたところ、以下の知見を得た。 In order to solve the above problems, the present inventors have conducted intensive research on a cBN sintered body having excellent crater wear resistance and chipping resistance, and obtained the following findings.
cBN焼結体は、主として、硬質相成分であるcBN粒子と、結合相成分(例えば、TiN粒子、TiC粒子、TiCN粒子等のTi化合物粒子)からなるが、結合相粒子を微細化した場合には、結合相粒子間の界面が増加するため、前述のとおり、熱伝導性は低下し、耐クレータ摩耗性が低下することになり、一方、仮に、熱伝導性の低下を補い、耐クレータ摩耗性を高めるためにcBN含有量を増加させた場合には、前記特許文献1、2について述べたと同様に、耐チッピング性が低下する。 The cBN sintered body is mainly composed of cBN particles which are hard phase components and bonded phase components (for example, Ti compound particles such as TiN particles, TiC particles and TiCN particles), but when the bonded phase particles are miniaturized. As described above, since the interface between the bonded phase particles increases, the thermal conductivity decreases and the crater wear resistance decreases, while tentatively compensating for the decrease in thermal conductivity and crater wear resistance. When the cBN content is increased in order to enhance the properties, the chipping resistance is lowered as described in Patent Documents 1 and 2.
そこで、本発明者らは、cBN工具の耐クレータ摩耗性と耐チッピング性の両者を高めるためのcBN焼結体の結合相組織に着目して研究を進め、次のような知見を得た。
即ち、cBN焼結体の結合相を構成するTi化合物粒子の粒径を微細化した場合には、前述のとおり、耐チッピング性と耐クレータ摩耗性の両立を図ることは困難であるが、cBN焼結体の結合相組織として、結合相中にW成分とCo成分とFe成分が共存する熱伝導性にすぐれたW−Co−Fe相を形成し、さらに、このW−Co−Fe相が、Ti化合物粒子の界面に存在し、cBN粒子間を前記W−Co−Fe相を介して熱的に繋ぐ結合相組織を形成した場合には、cBN焼結体の熱伝導性の低下を抑制することができ、その結果、cBN工具の耐クレータ摩耗性が向上することを見出したのである。
Therefore, the present inventors have focused on the bonded phase structure of the cBN sintered body in order to improve both the crater wear resistance and the chipping resistance of the cBN tool, and obtained the following findings.
That is, when the particle size of the Ti compound particles constituting the bonded phase of the cBN sintered body is made finer, it is difficult to achieve both chipping resistance and crater abrasion resistance as described above, but cBN As the bonded phase structure of the sintered body, a W-Co-Fe phase having excellent thermal conductivity in which the W component, the Co component and the Fe component coexist in the bonded phase is formed, and further, this W-Co-Fe phase is formed. , When a bonded phase structure existing at the interface of the Ti compound particles and thermally connecting the cBN particles via the W—Co—Fe phase is formed, the decrease in thermal conductivity of the cBN sintered body is suppressed. As a result, it has been found that the sinter abrasion resistance of the cBN tool is improved.
つまり、本発明者らは、cBN焼結体において、微細なTi化合物粒子の界面に、W成分とCo成分とFe成分が共存するW−Co−Fe相が形成され、かつ、このW−Co−Fe相が、cBN粒子間の熱伝導路を形成するようにcBN粒子相互を熱的に繋ぐ結合相組織を形成した場合には、このcBN焼結体からなるcBN工具は、高熱発生を伴い、刃先に高負荷が作用する高硬度鋼の断続切削条件に供した場合でも、すぐれた耐チッピング性を発揮すると同時にすぐれた耐クレータ摩耗性をも兼ね備えるため、長期の使用にわたって、すぐれた切削性能を発揮し、また、工具の長寿命化が図られることを見出したのである。 That is, in the cBN sintered body, the present inventors have formed a W—Co—Fe phase in which the W component, the Co component and the Fe component coexist at the interface of the fine Ti compound particles, and the W—Co When the −Fe phase forms a bonded phase structure that thermally connects the cBN particles to each other so as to form a heat conduction path between the cBN particles, the cBN tool composed of this cBN sintered body is accompanied by high heat generation. Even when subjected to intermittent cutting conditions of high hardness steel where a high load acts on the cutting edge, it exhibits excellent chipping resistance and at the same time has excellent crater wear resistance, so it has excellent cutting performance over a long period of use. In addition, it was found that the life of the tool can be extended.
ここで、結合相を構成するTi化合物粒子の界面に、W成分とCo成分とFe成分が共存するW−Co−Fe相が存在し、かつ、このW−Co−Fe相がcBN粒子相互を熱的に繋ぐ熱伝導路の機能を備える結合相組織を有するcBN工具は、例えば、次のようにして作製することができる。 Here, at the interface of the Ti compound particles constituting the bonded phase, there is a W—Co—Fe phase in which the W component, the Co component, and the Fe component coexist, and the W—Co—Fe phase communicates with each other of the cBN particles. A cBN tool having a coupled phase structure having the function of a heat conduction path that is thermally connected can be manufactured, for example, as follows.
まず、Ti化合物からなる結合相形成用粉末を、粒径が30nm以上250nm以下になるように粉砕して微細化し、この微細粉砕粉に、ナノW粉末とナノCo粉末とナノFe粉末と、cBN焼結体の硬質成分であるcBN粒子粉末の混合粉末を投入したのち混合し、圧粉成形体を作製し、次いで、この圧粉成形体を超高圧焼結条件下で焼結することによって、Ti化合物粒子からなる結合相粒子の界面に、W−Co−Fe相が存在し、かつ、このW−Co−Fe相がcBN粒子相互を熱的に繋ぐ熱伝導路の作用を果たす結合相組織を有するcBN焼結体を作製することができる。
次いで、前記で作製したcBN焼結体を、WC基超硬合金製インサート本体のろう付け部(コーナー部)にろう付けし、必要に応じ、研磨加工、ホーニング加工等を施すことにより、少なくとも刃先が前記cBN焼結体で構成された所望のインサート形状をもったcBN工具を作製することができる。
First, a powder for forming a bonded phase made of a Ti compound is pulverized so that the particle size is 30 nm or more and 250 nm or less, and the finely pulverized powder contains nano W powder, nano Co powder, nano Fe powder, and cBN. A mixed powder of cBN particle powder, which is a hard component of the sintered body, is added and then mixed to prepare a powder compact, and then the powder compact is sintered under ultra-high pressure sintering conditions. Bonded phase composed of Ti compound particles A bonded phase structure in which a W-Co-Fe phase exists at the interface of the powder and the W-Co-Fe phase acts as a thermal conduction path that thermally connects the cBN particles to each other. A cBN sintered body having the above can be produced.
Next, the cBN sintered body produced above is brazed to the brazed portion (corner portion) of the WC-based cemented carbide insert body, and if necessary, polishing, honing, or the like is performed to at least the cutting edge. Can produce a cBN tool having a desired insert shape composed of the cBN sintered body.
そして、前記で作製したcBN工具は、所定の結合相組織を備えることから、高熱発生を伴い、刃先に高負荷が作用する高硬度鋼の断続切削条件等に供した場合、すぐれた耐チッピング性と耐クレータ摩耗性を兼ね備え、長期の使用にわたって、すぐれた切削性能を発揮し、工具の長寿命化が図られる。 Since the cBN tool produced above has a predetermined coupled phase structure, it has excellent chipping resistance when subjected to intermittent cutting conditions of high-hardness steel in which a high heat is generated and a high load acts on the cutting edge. It also has crater wear resistance, exhibits excellent cutting performance over a long period of use, and extends the life of the tool.
本発明は、上記知見に基づいてなされたものであって、
「(1)硬質相として立方晶窒化ほう素粒子を含有し、結合相としてTi化合物粒子を含有する立方晶窒化ほう素基焼結体によって少なくとも刃先が形成されている立方晶窒化ほう素基焼結体製切削工具において、
前記Ti化合物粒子の平均粒径は250nm以下であり、
前記Ti化合物粒子の界面には、W成分とCo成分とFe成分が共存するW−Co−Fe相が存在し、
前記W−Co−Fe相は、立方晶窒化ほう素粒子相互間を繋いで途切れることなく存在することで熱伝達路を構成していることを特徴とする立方晶窒化ほう素基焼結体製切削工具。
(2)前記立方晶窒化ほう素基焼結体の断面を走査型電子顕微鏡による元素マッピングで観察した場合、前記W−Co−Fe相が途切れずに、W−Co−Fe相を介して相互に繋がっている立方晶窒化ほう素粒子の個数は、観察視野に存在する立方晶窒化ほう素粒子の総個数の20%以上であることを特徴とする前記(1)に記載の立方晶窒化ほう素基焼結体製切削工具。
(3)前記W−Co−Fe相を構成するWとCoとFeが、前記立方晶窒化ほう素基焼結体に占める合計含有量は、2質量%以上10質量%以下であり、かつ、Feの含有量は0.03質量%以上1.0質量%以下であることを特徴とする前記(1)または(2)に記載の立方晶窒化ほう素基焼結体製切削工具。
(4)前記Ti化合物粒子は、TiN粒子、TiCN粒子およびTiC粒子の内から選ばれる何れか一種または二種以上であることを特徴とする前記(1)乃至(3)のいずれかに記載の立方晶窒化ほう素基焼結体製切削工具。」
を特徴とする。
The present invention has been made based on the above findings.
"(1) Cubic boron nitride base firing in which at least the cutting edge is formed by a cubic boron nitride base sintered body containing cubic boron nitride particles as a hard phase and Ti compound particles as a bonding phase. In the body cutting tool
The average particle size of the Ti compound particles is 250 nm or less.
At the interface of the Ti compound particles, there is a W—Co—Fe phase in which the W component, the Co component, and the Fe component coexist.
The W—Co—Fe phase is made of a cubic boron nitride-based sintered body, which is characterized in that a heat transfer path is formed by connecting cubic boron nitride particles to each other and existing without interruption. Cutting tools.
(2) When the cross section of the cubic boron nitride base sintered body is observed by element mapping with a scanning electron microscope, the W—Co—Fe phases are not interrupted and are mutually interposed via the W—Co—Fe phase. The number of cubic boron nitride particles connected to the above (1) is 20% or more of the total number of cubic boron nitride particles present in the observation field. Cutting tool made of base sintered body.
(3) The total content of W, Co, and Fe constituting the W—Co—Fe phase in the cubic boron nitride base sintered body is 2% by mass or more and 10% by mass or less, and The cutting tool made of a cubic boron nitride-based sintered body according to (1) or (2) above, wherein the Fe content is 0.03% by mass or more and 1.0% by mass or less.
(4) The above-mentioned (1) to (3), wherein the Ti compound particles are any one or more selected from TiN particles, TiCN particles and TiC particles. Cutting tool made of cubic boron nitride based sintered body. "
It is characterized by.
本発明のcBN工具は、cBN焼結体の結合相を構成するTi化合物粒子の界面に、W成分とCo成分とFe成分とが共存するW−Co−Fe相が存在し、このW−Co−Fe相がcBN粒子相互間を繋いで途切れることなく存在することで、cBN粒子間の熱伝導路の作用を果たす結合相組織を有することから、cBN含有量を増加させなくてもcBN焼結体の熱伝導性を向上させることができ、その結果、cBN含有量を増加させずにcBN工具の耐クレータ摩耗性を向上させることができる。 In the cBN tool of the present invention, a W-Co-Fe phase in which the W component, the Co component, and the Fe component coexist exists at the interface of the Ti compound particles constituting the bonded phase of the cBN sintered body, and this W-Co Since the −Fe phase has a bonded phase structure that acts as a heat conduction path between the cBN particles by connecting the cBN particles to each other and existing without interruption, cBN sintering is performed without increasing the cBN content. The thermal conductivity of the body can be improved, and as a result, the sinter abrasion resistance of the cBN tool can be improved without increasing the cBN content.
また、本発明のcBN工具は、cBN焼結体の結合相を構成するTi化合物粒子の界面に形成された前記W−Co−Fe相が、Ti化合物粒子の粒成長抑制作用を有し、結合相粒子の粗大化を抑制することから、cBN焼結体における結合相粒子の粒径を、例えば、平均粒径250nm以下に微細化することができ、これによって、cBN工具の耐チッピング性を向上させることができ、しかも、結合相粒子が微細であっても、前記W−Co−Fe相がcBN粒子間の熱伝導路を形成していることで、cBN焼結体の熱伝導性が低下することはなく、その結果、cBN工具の耐クレータ摩耗性を低下させることもない。
よって、本発明のcBN工具は、高熱発生を伴い、刃先に高負荷が作用する断続切削条件に供した場合でも、耐チッピング性、耐摩耗性ともにすぐれ、工具寿命の延命化が図られる。
Further, in the cBN tool of the present invention, the W—Co—Fe phase formed at the interface of the Ti compound particles constituting the bonded phase of the cBN sintered body has a grain growth suppressing effect of the Ti compound particles and is bonded. Since the coarsening of the phase particles is suppressed, the particle size of the bonded phase particles in the cBN sintered body can be reduced to, for example, an average particle size of 250 nm or less, thereby improving the chipping resistance of the cBN tool. Even if the bonded phase particles are fine, the W—Co—Fe phase forms a heat conduction path between the cBN particles, so that the heat conductivity of the cBN sintered body is lowered. As a result, the crater wear resistance of the cBN tool is not reduced.
Therefore, the cBN tool of the present invention is excellent in both chipping resistance and abrasion resistance, and the life of the tool can be extended even when it is subjected to intermittent cutting conditions in which high heat is generated and a high load acts on the cutting edge.
本発明のcBN工具について、以下に説明する。 The cBN tool of the present invention will be described below.
本発明のcBN工具の少なくとも刃先を構成するcBN焼結体は、硬質相成分としてcBN粒子を含有し、また、主たる結合相成分としてTiC粒子、TiN粒子あるいはTiCN粒子等のTi化合物粒子を含有する。
主たる結合相成分はTi化合物粒子であるが、これに加えて、製造工程で不可避的に混入する不純物成分、あるいは、焼結時の反応生成物であるAl2O3、AlN、TiAlN等のAl化合物等が結合相中に含有されることは許容される。
The cBN sintered body constituting at least the cutting edge of the cBN tool of the present invention contains cBN particles as a hard phase component, and also contains Ti compound particles such as TiC particles, TiN particles or TiCN particles as a main bonding phase component. ..
The main bonding phase component is Ti compound particles, but in addition to this, an impurity component that is inevitably mixed in during the manufacturing process, or Al such as Al 2 O 3 , AlN, and TiAlN, which are reaction products during sintering. It is permissible for compounds and the like to be contained in the binding phase.
cBN焼結体に占めるcBN粒子の含有割合:
本発明のcBN焼結体において、cBN焼結体に占めるcBN粒子の含有割合が40体積%未満となった場合には、cBN粒子同士が接触し結合相と十分に反応できない未焼結部分の形成は少なくなるが、その反面、cBN焼結体の硬さが低下し、工具としての寿命も低下してしまうため、cBN焼結体に占めるcBN粒子の含有割合は、40体積%以上とすることが好ましい。
一方、cBN粒子の含有割合が85体積%を超えるようになると、cBN粒子同士が直接接する部分が多くなることで高熱伝導性を有するものの、切削加工用工具として使用した場合に、焼結体中にクラックの起点となる空隙が生成しやすくなり、耐欠損性が低下するので、cBN焼結体に占めるcBN粒子の含有割合は、85体積%以下とすることが好ましい。
したがって、cBN粒子の含有割合は、40〜85体積%とすることが好ましく、より好ましくは、45〜80体積%である。
また、cBN粒子の含有割合を少なくして、しかも、cBN工具としての最高の特性を発揮するのに適したcBN粒子の含有割合は、好ましくは50〜75体積%、より好ましくは、60体積%以上70体積%以下の範囲である。
Content ratio of cBN particles in the cBN sintered body:
In the cBN sintered body of the present invention, when the content ratio of the cBN particles in the cBN sintered body is less than 40% by volume, the cBN particles come into contact with each other and cannot sufficiently react with the bonded phase. Although the formation is reduced, on the other hand, the hardness of the cBN sintered body is reduced and the life as a tool is also shortened. Therefore, the content ratio of cBN particles in the cBN sintered body is set to 40% by volume or more. Is preferable.
On the other hand, when the content ratio of the cBN particles exceeds 85% by volume, the cBN particles have a large number of parts in direct contact with each other and thus have high thermal conductivity, but when used as a cutting tool, they are contained in the sintered body. Since voids that are the starting points of cracks are likely to be generated and the fracture resistance is lowered, the content ratio of cBN particles in the cBN sintered body is preferably 85% by volume or less.
Therefore, the content ratio of the cBN particles is preferably 40 to 85% by volume, more preferably 45 to 80% by volume.
Further, the content ratio of cBN particles suitable for reducing the content ratio of cBN particles and exhibiting the best characteristics as a cBN tool is preferably 50 to 75% by volume, more preferably 60% by volume. The range is 70% by volume or less.
cBN粒子の含有割合の測定・算出:
cBN焼結体に占めるcBN粒子の含有割合は、cBN焼結体の断面をSEMによって観察して得た二次電子像内のcBN粒子に相当する部分を画像処理によって抜き出し、画像解析によってcBN粒子が占める面積を算出し、その値を画像総面積で除することでcBN粒子の面積比率を算出する。そして、この面積比率を体積%とみなすことで、cBN粒子の含有割合(体積%)を測定することができる。
また、本発明では、SEMで得られた倍率5、000の二次電子像の少なくとも3画像を処理し求めた値の平均値をcBN粒子の含有割合(体積%)としている。
なお、画像処理に用いる観察領域は、cBN粒子の平均粒径の5倍の長さの一辺をもつ正方形の領域とすることが望ましく、例えば、cBN粒子の平均粒径が3μmの場合、15μm×15μm程度、また、cBN粒子の平均粒径が6μmの場合、30μm×30μm程度の観察領域が望ましい。
Measurement / calculation of the content ratio of cBN particles:
Regarding the content ratio of cBN particles in the cBN sintered body, the portion corresponding to the cBN particles in the secondary electron image obtained by observing the cross section of the cBN sintered body by SEM is extracted by image processing, and the cBN particles are extracted by image analysis. The area ratio of the cBN particles is calculated by calculating the area occupied by the cBN particles and dividing the value by the total image area. Then, by regarding this area ratio as a volume%, the content ratio (volume%) of the cBN particles can be measured.
Further, in the present invention, the average value of the values obtained by processing at least three images of the secondary electron images having a magnification of 5,000 obtained by SEM is defined as the content ratio (volume%) of the cBN particles.
The observation region used for image processing is preferably a square region having one side having a length five times the average particle size of the cBN particles. For example, when the average particle size of the cBN particles is 3 μm, 15 μm × When the average particle size of the cBN particles is about 15 μm and the average particle size of the cBN particles is 6 μm, an observation region of about 30 μm × 30 μm is desirable.
cBN粒子の平均粒径:
本発明のcBN焼結体におけるcBN粒子の平均粒径は、特に限定するものではないが、0.2〜8μmの範囲とすることが好ましい。
これは次の理由による。
cBN焼結体を切削加工工具の刃先として使用する場合、平均粒径が0.2〜8μmのcBN粒子が焼結体内に分散することにより、工具使用中に工具表面のcBN粒子が脱落して生じる刃先の凹凸形状を起点とするチッピングの発生を抑制することができる。それに加え、工具使用中に刃先に加わる応力により生じるcBN粒子と結合相との界面から進展するクラック、あるいはcBN粒子を貫通して進展するクラックの伝播を、焼結体中に分散したcBN粒子により抑制することができる。そのため、このような切削加工工具は優れた耐欠損性を有する。
したがって、本発明のcBN焼結体におけるcBN粒子の平均粒径は、0.2〜8μmの範囲とすることが好ましく、より好ましい範囲は、0.5〜6μmである。
Average particle size of cBN particles:
The average particle size of the cBN particles in the cBN sintered body of the present invention is not particularly limited, but is preferably in the range of 0.2 to 8 μm.
This is due to the following reasons.
When the cBN sintered body is used as the cutting edge of a cutting tool, the cBN particles having an average particle size of 0.2 to 8 μm are dispersed in the sintered body, so that the cBN particles on the tool surface fall off during use of the tool. It is possible to suppress the occurrence of chipping starting from the uneven shape of the cutting edge that occurs. In addition, the propagation of cracks that grow from the interface between the cBN particles and the bonding phase caused by the stress applied to the cutting edge during tool use, or cracks that grow through the cBN particles, is caused by the cBN particles dispersed in the sintered body. It can be suppressed. Therefore, such a cutting tool has excellent fracture resistance.
Therefore, the average particle size of the cBN particles in the cBN sintered body of the present invention is preferably in the range of 0.2 to 8 μm, and more preferably in the range of 0.5 to 6 μm.
cBN粒子の平均粒径の測定・算出:
cBN粒子の平均粒径の測定・算出は、以下のようにして求めることができる。
cBN焼結体の断面の所定の領域(例えば、cBN粒子の平均粒径3μmの場合、15μm×15μm(cBN粒子の平均粒径の5倍角)の領域)をSEMで観察し二次電子像を得る。得られた画像を2値化処理してcBN粒子に相当する部分を画像処理にて抜き出し、画像解析により抜き出した各粒子に相当する部分の最大長を各粒子の直径として求める。この直径から、各粒子を球として各粒子の体積を計算する。求めた各粒子の体積を基に、粒子径の積算分布を求める。つまり、各粒子について、その体積とその粒子の直径以下の直径を有する粒子の体積の総和を積算値として求める。各粒子について、全粒子の体積の総和に対する各粒子の上記積算値との割合である体積百分率(%)を縦軸とし、横軸を各粒子の直径(μm)としてグラフを描画し、体積百分率が50%となる粒子の直径(メディアン径)の値を1画像におけるcBN粒子の平均粒径とする。そして、少なくとも3画像に対し上記の処理を行って求めた平均粒径の値の平均値を、cBN焼結体のcBN粒子の平均粒径(μm)とする。
Measurement / calculation of average particle size of cBN particles:
The measurement / calculation of the average particle size of the cBN particles can be obtained as follows.
A predetermined region of the cross section of the cBN sintered body (for example, in the case of an average particle size of cBN particles of 3 μm, a region of 15 μm × 15 μm (5 times the average particle size of the cBN particles)) is observed by SEM to obtain a secondary electron image. obtain. The obtained image is binarized and a portion corresponding to the cBN particles is extracted by image processing, and the maximum length of the portion corresponding to each particle extracted by image analysis is obtained as the diameter of each particle. From this diameter, the volume of each particle is calculated with each particle as a sphere. Based on the obtained volume of each particle, the integrated distribution of particle size is obtained. That is, for each particle, the sum of the volume and the volume of the particles having a diameter equal to or less than the diameter of the particles is obtained as an integrated value. For each particle, draw a graph with the volume percentage (%), which is the ratio of the total volume of all particles to the above integrated value, as the vertical axis and the diameter (μm) of each particle as the horizontal axis, and draw the volume percentage. The value of the particle diameter (median diameter) at which is 50% is taken as the average particle size of the cBN particles in one image. Then, the average value of the average particle size values obtained by performing the above processing on at least three images is defined as the average particle size (μm) of the cBN particles of the cBN sintered body.
結合相組織:
結合相としてTi化合物粒子を含有する本発明のcBN焼結体は、cBN焼結体の断面を、SEM−EDSにより元素分析すると、例えば、図1に示されるような元素マッピング図が得られる。
図1(a)〜(e)は、倍率50,000倍のSEM−EDSによって取得した本発明のcBN焼結体の断面についての元素マッピング図の一例を示すが、(a)はW、(b)はCo、(c)はFe、(d)はB、(e)はNについての元素マッピング図である。
Bonded phase structure:
In the cBN sintered body of the present invention containing Ti compound particles as a bonding phase, when the cross section of the cBN sintered body is elementally analyzed by SEM-EDS, for example, an element mapping diagram as shown in FIG. 1 can be obtained.
1 (a) to 1 (e) show an example of an element mapping diagram for a cross section of the cBN sintered body of the present invention acquired by SEM-EDS at a magnification of 50,000, while FIG. 1 (a) shows W, ( b) is an element mapping diagram for Co, (c) is Fe, (d) is B, and (e) is N.
図1(a)〜(e)に示されるような元素マッピング図を用い、B成分とN成分のマッピング図(図1(d)と(e)参照)を重ね合せることによって、図2(a)の模式図として示されるように、本発明のcBN焼結体におけるcBN粒子の組織状態を確認することができ、また、W成分とCo成分とFe成分のマッピング図(図1(a)と(b)と(c)参照)を重ね合せることによって、図2(b)の模式図として示されるように、本発明のcBN焼結体の結合相中のW−Co−Fe相の存在を確認することができる。 FIG. 2 (a) is obtained by superimposing the mapping diagrams of the B component and the N component (see FIGS. 1 (d) and 1 (e)) using the element mapping diagrams as shown in FIGS. 1 (a) to 1 (e). ) Can be confirmed as a schematic diagram of the cBN particles in the cBN sintered body of the present invention, and a mapping diagram of the W component, the Co component, and the Fe component (FIG. 1 (a)). By superimposing (b) and (c), the presence of the W—Co—Fe phase in the bonded phase of the cBN sintered body of the present invention can be determined as shown in the schematic diagram of FIG. 2 (b). You can check.
また、図2(a)と(b)に示される元素マッピング図をさらに重ね合せることによって、図3の模式図に示されるように、本発明のcBN焼結体の組織を確認することができる。
なお、前記の図2、図3は、結合相中のW−Co−Fe相の存在と、cBN焼結体の組織状態をわかりやすく理解するための模式図であって、図1の元素マッピング図とは直接には対応していないことに注意が必要である。
Further, by further superimposing the element mapping diagrams shown in FIGS. 2A and 2B, the structure of the cBN sintered body of the present invention can be confirmed as shown in the schematic diagram of FIG. ..
Note that FIGS. 2 and 3 are schematic views for easily understanding the existence of the W—Co—Fe phase in the bonded phase and the structural state of the cBN sintered body, and the element mapping of FIG. It should be noted that it does not correspond directly to the figure.
図2と図3から、本発明のcBN焼結体においては、は、W成分とCo成分とFe成分とが共存するW−Co−Fe相が、結合相を構成するTi化合物粒子の界面に、cBN粒子相互間を繋いで途切れなく存在しているが、前記W−Co−Fe相は、cBN粒子の周囲を覆う(取り囲む)ようには形成されていない(存在していない)ことが理解される。 From FIGS. 2 and 3, in the cBN sintered body of the present invention, the W—Co—Fe phase in which the W component, the Co component, and the Fe component coexist is at the interface of the Ti compound particles constituting the bonding phase. , CBN particles are connected to each other and exist without interruption, but it is understood that the W-Co-Fe phase is not formed (does not exist) so as to surround (surround) the cBN particles. Will be done.
そして、前記W−Co−Fe相は、Ti化合物粒子よりも熱伝導率が高く、cBN粒子相互間に途切れなく存在し、cBN粒子相互間を繋ぐ熱伝達路としての機能を備えるため、cBN焼結体の熱伝導性の向上が図られる。
さらに、前記W−Co−Fe相は、高温・高圧の焼結条件下での結合相粒子の粗大化を抑制することから、cBN焼結体の微細な結合相組織の維持に貢献する。
The W-Co-Fe phase has a higher thermal conductivity than the Ti compound particles, exists seamlessly between the cBN particles, and has a function as a heat transfer path connecting the cBN particles, so that the cBN firing is performed. The thermal conductivity of the body is improved.
Further, the W-Co-Fe phase suppresses coarsening of the bonded phase particles under high temperature and high pressure sintered conditions, and thus contributes to the maintenance of a fine bonded phase structure of the cBN sintered body.
cBN焼結体の熱伝導性を向上させるためには、cBN焼結体の断面をSEMで観察し、元素マッピングを求めた場合、W−Co−Fe相を介して相互に繋がっているcBN粒子の個数は、観察視野に存在するcBN粒子の総個数の20%以上、より好ましくは55%以上である。20%未満である場合には、cBN焼結体の熱伝導性の大きな向上効果を期待できない。 In order to improve the thermal conductivity of the cBN sintered body, when the cross section of the cBN sintered body is observed by SEM and the element mapping is obtained, the cBN particles connected to each other via the W—Co—Fe phase. The number of cBN particles is 20% or more, more preferably 55% or more of the total number of cBN particles present in the observation field. If it is less than 20%, the effect of greatly improving the thermal conductivity of the cBN sintered body cannot be expected.
また、cBN焼結体の断面について電子線マイクロアナライザー(以下、「EPMA」で表す)を用いた定性・定量分析を行い、定性分析で検出された元素についてZAF定量分析法によりWとCoとFeの含有量(質量%)を求めた場合、cBN焼結体全体におけるTi,Al,B,N,C,O,W,Co,Feの合計を100質量%としたときに占めるWとCoとFeの合計含有量は、2質量%以上10質量%以下であることが好ましく、さらに、Feの含有量は、0.03質量%以上1.0質量%以下であることが好ましい。
これは、WとCoとFeの合計含有量が2質量%未満であると、熱伝導性向上効果が得られず、一方、10質量%以上になると、W−Co−Fe相の粗大凝集粒が形成され、これがチッピングの発生起点となり、耐チッピング性が低下するという理由による。
特に、W−Co−Fe相におけるFeの含有量が0.03質量%以上で熱伝導性向上効果が大きくなるが、Feの含有量が1.0質量%を超えると粗大凝集粒の形成傾向が高まり、これがチッピングの発生起点となることから、W−Co−Fe相におけるFeの含有量は、0.03質量%以上1.0質量%とすることが好ましい。
In addition, the cross section of the cBN sintered body was subjected to qualitative and quantitative analysis using an electron probe microanalyzer (hereinafter referred to as "EPMA"), and the elements detected by the qualitative analysis were subjected to W, Co and Fe by the ZAF quantitative analysis method. When the content (% by mass) of is determined, W and Co occupying the total of Ti, Al, B, N, C, O, W, Co, and Fe in the entire cBN sintered body as 100% by mass. The total content of Fe is preferably 2% by mass or more and 10% by mass or less, and the Fe content is preferably 0.03% by mass or more and 1.0% by mass or less.
This is because if the total content of W, Co and Fe is less than 2% by mass, the effect of improving thermal conductivity cannot be obtained, while if it is 10% by mass or more, the coarse agglomerates of the W—Co—Fe phase Is formed, which is the starting point of chipping, and the chipping resistance is reduced.
In particular, when the Fe content in the W—Co—Fe phase is 0.03% by mass or more, the effect of improving thermal conductivity is large, but when the Fe content exceeds 1.0% by mass, the formation tendency of coarse agglomerates The content of Fe in the W—Co—Fe phase is preferably 0.03% by mass or more and 1.0% by mass, because this becomes the starting point of chipping.
Ti化合物粒子の平均粒径:
結合相を構成するTi化合物粒子の大きさは、cBN焼結体の強度、熱伝導性に影響を与え、平均粒径が250nmを超えると、熱伝導性が向上する反面、cBN焼結体の強度の低下を招き、また、cBN工具として使用した場合にチッピングを発生しやすくなることから、Ti化合物粒子の平均粒径は250nm以下であること、好ましくは、30nm以上200nm以下の範囲であることが望ましい。
なお、Ti化合物粒子の平均粒径が250nm以下、あるいは、30nm以上200nm以下の範囲に微細化され、Ti化合物粒子間の界面の長さが増加した場合であっても、本発明では、Ti化合物粒子の界面に熱伝達路としての機能を備えるW−Co−Fe相が存在するために、cBN焼結体の熱伝導性の低下は防止され、その結果、耐クレータ摩耗性の低下が防止される。
Average particle size of Ti compound particles:
The size of the Ti compound particles constituting the bonded phase affects the strength and thermal conductivity of the cBN sintered body, and when the average particle size exceeds 250 nm, the thermal conductivity is improved, but on the other hand, the cBN sintered body The average particle size of the Ti compound particles is 250 nm or less, preferably 30 nm or more and 200 nm or less, because it causes a decrease in strength and is likely to cause chipping when used as a cBN tool. Is desirable.
In the present invention, even when the average particle size of the Ti compound particles is refined to 250 nm or less, or 30 nm or more and 200 nm or less, and the length of the interface between the Ti compound particles is increased, the Ti compound is used. Since the W—Co—Fe phase having a function as a heat transfer path is present at the interface of the particles, the decrease in thermal conductivity of the cBN sintered body is prevented, and as a result, the decrease in crater wear resistance is prevented. To.
Ti化合物粒子の平均粒径の測定・算出は、例えば、以下のようにして求めることができる。
まず、cBN焼結体の断面の観察領域を、透過型電子顕微鏡(以下、「TEM」で表す)に付属する結晶方位解析装置を用いて観察する。より具体的に言えば、Ti化合物粒子を観察するために結晶粒径と同程度の厚さ以下に研磨された切片をTEMにセットし、200kVに加速された電子線を前記切片に照射することで、400nm×500nmの範囲で観察を行う。
前記の範囲で結晶方位のマップデータを得る解析方法は以下の通りである。
前記の切片に、0.5〜1.0度に傾けた電子線をPrecession照射しながら、電子線を任意のビーム径及び間隔でスキャンし、連続的に電子線回折パターンを取り込み、個々の測定点の結晶方位を解析する。なお、本測定に用いた回折パターンの取得条件は、カメラ長20cm、ビームサイズ2.2nmで、測定ステップは2.0nmである。
次に、得られた電子線回折パターンから個々の結晶粒を判別するための解析方法は、以下の通りである。
まず、測定点の隣接点同士の結晶方位が5度以上離れている場合に粒界とし、粒界以外の部分を結晶粒、つまりTi化合物粒子と定義した。
この画像を縦4枚×横4枚で連結させて縦1600nm×横2000nmの画像とし、cBN粒子の平均粒径を求めるための前述の手順と同様の手順でTi化合物粒子の平均粒径を求める。
このような測定・算出を複数(3箇所以上)の観察領域で実施し、その平均値を、Ti系化合物粒子の平均粒径(nm)とする。
The average particle size of the Ti compound particles can be measured and calculated as follows, for example.
First, the observation region of the cross section of the cBN sintered body is observed using a crystal orientation analyzer attached to a transmission electron microscope (hereinafter, referred to as “TEM”). More specifically, in order to observe Ti compound particles, a section polished to a thickness equal to or less than the crystal particle size is set in the TEM, and the section is irradiated with an electron beam accelerated to 200 kV. Then, the observation is performed in the range of 400 nm × 500 nm.
The analysis method for obtaining the map data of the crystal orientation in the above range is as follows.
While precession-irradiating the section with an electron beam tilted at 0.5 to 1.0 degrees, the electron beam is scanned at an arbitrary beam diameter and interval, and the electron diffraction pattern is continuously captured for individual measurement. Analyze the crystal orientation of the points. The conditions for acquiring the diffraction pattern used in this measurement are a camera length of 20 cm, a beam size of 2.2 nm, and a measurement step of 2.0 nm.
Next, the analysis method for discriminating individual crystal grains from the obtained electron diffraction pattern is as follows.
First, when the crystal orientations of the adjacent points of the measurement points are separated by 5 degrees or more, the grain boundary is defined, and the portion other than the grain boundary is defined as a crystal grain, that is, a Ti compound particle.
This image is connected by 4 vertical × 4 horizontal to obtain an image of 1600 nm in length × 2000 nm in width, and the average particle size of Ti compound particles is obtained by the same procedure as the above-mentioned procedure for obtaining the average particle size of cBN particles. ..
Such measurement / calculation is carried out in a plurality of observation regions (three or more locations), and the average value is defined as the average particle size (nm) of the Ti-based compound particles.
cBN焼結体の熱伝導率κ:
本発明のcBN焼結体は、結合相中に前記W−Co−Fe相が存在することによりすぐれた熱伝導性を有するが、具体的なcBN焼結体の熱伝導率κの測定法は、例えば以下のとおりである。
まず、cBN焼結体から測定試料を切り出し、切り出した測定試料の寸法を測定し、次いでアルキメデス法によって密度ρを測定する。
ついで、Xeフラッシュアナライザーを用いたレーザーフラッシュ法によって熱拡散率αと比熱容量CPを測定し、次の式を用いて熱伝導率κを算出する。
熱伝導率κ(W/m・k)
=熱拡散率α(mm2/sec)×密度ρ(g/cm3)×比熱容量CP(J/(K・g)
Thermal conductivity of cBN sintered body κ:
The cBN sintered body of the present invention has excellent thermal conductivity due to the presence of the W—Co—Fe phase in the bonded phase, but a specific method for measuring the thermal conductivity κ of the cBN sintered body is For example, it is as follows.
First, a measurement sample is cut out from the cBN sintered body, the dimensions of the cut out measurement sample are measured, and then the density ρ is measured by the Archimedes method.
Then, the thermal diffusivity α and the specific heat capacity CP are measured by the laser flash method using an Xe flash analyzer, and the thermal conductivity κ is calculated using the following formula.
Thermal conductivity κ (W / m · k)
= Thermal diffusivity α (mm 2 / sec) × Density ρ (g / cm 3 ) × Specific heat capacity CP (J / (K · g)
cBN焼結体の製造:
本発明のcBN焼結体は、好ましくは、0.2〜8μmの平均粒径のcBN粒子と、好ましくは、250nm以下の平均粒径のTi化合物粒子を、好ましくは、cBN粒子の体積割合が40〜85体積%(より好ましくは、60体積%以上70体積%以下)となるように配合した混合粉末を作製し、これを超高圧条件下で焼結することによって作製することができる。
まず、結合相を構成する原料粉末(TiN粉末、TiCN粉末、TiC粉末、TiAl3粉末、Al2O3粉末など)を準備する。これらの原料粉末を、例えば、超硬合金製容器内に超硬合金製ボールとアセトンと共に充填し、ボールミルにより粉砕及び混合を行う。
その後、cBN焼結体中でW−Co−Fe相を形成するナノW粉末(粒径:800nm以下)とナノCo粉末(粒径:30nm以下)とナノFe粉末(粒径:100nm以下)、さらに、cBN焼結体の硬質相となる平均粒径0.2〜8μmのcBN粒子を添加して、さらに、ボールミルによって混合し、混合粉末を得る。
次いで、この混合粉末を、例えば、5GPa以上の圧力、かつ、1200〜1600℃以上の温度の焼結条件で所定時間超高圧焼結することによって、結合相を構成するTi化合物粒子の粒子間界面に、W−Co−Fe相が存在する結合相組織が形成されたcBN焼結体を作製することができる。
Manufacture of cBN sintered body:
The cBN sintered body of the present invention preferably contains cBN particles having an average particle size of 0.2 to 8 μm, preferably Ti compound particles having an average particle size of 250 nm or less, and preferably has a volume ratio of cBN particles. It can be produced by producing a mixed powder blended so as to be 40 to 85% by volume (more preferably 60% by volume or more and 70% by volume or less) and sintering this under ultra-high pressure conditions.
First, raw material powders (TiN powder, TiCN powder, TiC powder, TiAl 3 powder, Al 2 O 3 powder, etc.) constituting the bonded phase are prepared. For example, these raw material powders are filled in a cemented carbide container together with cemented carbide balls and acetone, and pulverized and mixed by a ball mill.
Then, nano W powder (particle size: 800 nm or less), nano Co powder (particle size: 30 nm or less), and nano Fe powder (particle size: 100 nm or less) forming a W—Co—Fe phase in the cBN sintered body, Further, cBN particles having an average particle size of 0.2 to 8 μm, which is a hard phase of the cBN sintered body, are added and further mixed by a ball mill to obtain a mixed powder.
Next, the mixed powder is sintered at ultra-high pressure for a predetermined time under sintering conditions of, for example, a pressure of 5 GPa or higher and a temperature of 1200 to 1600 ° C. or higher, so that the interparticle interface of the Ti compound particles constituting the bonded phase In addition, a cBN sintered body having a bonded phase structure in which the W—Co—Fe phase is present can be produced.
図1は、前記工程で作製した本発明のcBN焼結体断面をSEM観察した際に得た元素マッピングの一例である。
また、cBN焼結体中のW−Co−Fe相の概略模式図を示す図2(b)、さらに、cBN焼結体組織の模式図を示す図3から、結合相を構成するTi化合物粒子の界面には、W−Co−Fe相がcBN粒子相互間を繋いで途切れることなく存在していることが観察される。
一方、W−Co−Fe相は、cBN粒子の周囲を覆う(取り囲む)ようには存在していない(形成されていない)ことは、後記する説明によって理解される。
FIG. 1 is an example of element mapping obtained by SEM observation of the cross section of the cBN sintered body of the present invention produced in the above step.
Further, from FIG. 2 (b) showing a schematic diagram of the W—Co—Fe phase in the cBN sintered body and FIG. 3 showing a schematic diagram of the cBN sintered body structure, the Ti compound particles constituting the bonded phase It is observed that the W—Co—Fe phase is present at the interface of the cBN particles without interruption by connecting the cBN particles to each other.
On the other hand, it is understood by the explanation described later that the W-Co-Fe phase does not exist (is not formed) so as to surround (surround) the cBN particles.
そして、前記で作製したcBN焼結体を、WC基超硬合金製インサート本体のろう付け部(コーナー部)にろう付けし、必要に応じ、研磨加工、ホーニング加工等を施すことにより、少なくとも刃先が前記cBN焼結体で構成された所望のインサート形状をもった耐欠損性、耐摩耗性にすぐれるcBN工具を作製することができる。 Then, the cBN sintered body produced above is brazed to the brazed portion (corner portion) of the WC-based cemented carbide insert body, and if necessary, polishing, honing, or the like is performed to at least the cutting edge. However, it is possible to manufacture a cBN tool having a desired insert shape composed of the cBN sintered body and having excellent fracture resistance and abrasion resistance.
以下に、本発明のcBN焼結体、cBN工具について、実施例に基づいて説明する。 Hereinafter, the cBN sintered body and the cBN tool of the present invention will be described based on examples.
まず、結合相を構成する原料粉末として、TiN粉末、TiCN粉末、TiC粉末を準備し、これらから選んだ原料粉末の一種を結合相形成用原料粉末とする。
次いで、上記で選択した結合相形成用原料粉末を、例えば、超硬合金製容器内に超硬合金製ボールとアセトンと共に充填し、ボールミルにより96時間〜120時間粉砕及び混合を行う。
次に、cBN粒子粉末とTi化合物粒子粉末の合量を100体積%としたときのcBN粒子粉末の含有割合が50〜75体積%の範囲内となるように平均粒径3μmのcBN粒子を配合し、さらにW−Co−Fe相となる平均粒径500nm〜900nmのナノW粉末と平均粒径20nm〜40nmのナノCo粉末と平均粒径60nm〜80nmのナノFe粉末を添加した後に、12時間〜24時間湿式混合し、乾燥した。
その後、油圧プレスにて成形圧1MPaで直径:50mm×厚さ:1.5mmの寸法にプレス成形して成形体を得た。
次いで、この成形体を、圧力:1Paの真空雰囲気中、1000〜1300℃の範囲内の所定温度に30〜60分間保持して熱処理し、次いで、通常の超高圧焼結装置に装入し、圧力:5GPa、温度:1400℃の条件で超高圧高温焼結することにより、本発明cBN焼結体1〜10を作製した。
First, TiN powder, TiCN powder, and TiC powder are prepared as raw material powders constituting the bonded phase, and one of the raw material powders selected from these is used as the raw material powder for forming the bonded phase.
Next, the raw material powder for forming the bonded phase selected above is filled in, for example, a cemented carbide container together with cemented carbide balls and acetone, and pulverized and mixed by a ball mill for 96 hours to 120 hours.
Next, cBN particles having an average particle size of 3 μm are blended so that the content ratio of the cBN particle powder is in the range of 50 to 75% by volume when the total amount of the cBN particle powder and the Ti compound particle powder is 100% by volume. Then, 12 hours after adding the nano W powder having an average particle size of 500 nm to 900 nm, the nano Co powder having an average particle size of 20 nm to 40 nm, and the nano Fe powder having an average particle size of 60 nm to 80 nm as the W—Co—Fe phase. Wet-mixed for ~ 24 hours and dried.
Then, a molded product was obtained by press molding with a hydraulic press at a molding pressure of 1 MPa to a size of diameter: 50 mm × thickness: 1.5 mm.
Next, the molded product was heat-treated by holding it at a predetermined temperature in the range of 1000 to 1300 ° C. for 30 to 60 minutes in a vacuum atmosphere at a pressure of 1 Pa, and then charged into a normal ultra-high pressure sintering apparatus. The cBN sintered bodies 1 to 10 of the present invention were produced by ultra-high pressure high-temperature sintering under the conditions of pressure: 5 GPa and temperature: 1400 ° C.
次に、前記で作製した本発明cBN焼結体1〜11の上下面をダイヤモンド砥石を用いて研磨し、ワイヤー放電加工装置にて分割し、さらに、Co:5質量%、TaC:5質量%、WC:残りの組成およびISO規格CNGA120408の形状をもったWC基超硬合金製インサート本体のろう付け部(コーナー部)に、質量%で、Cu:26%、Ti:5%、Ag:残りからなる組成を有するAg合金のろう材を用いてろう付けし、さらに上下面および外周研磨、ホーニング加工を施すことによりISO規格CNGA120408のインサート形状をもった表1に示す本発明cBN工具1〜12を作製した。 Next, the upper and lower surfaces of the cBN sintered bodies 1 to 11 of the present invention produced above are polished with a diamond grindstone, divided by a wire electric discharge machine, and further, Co: 5% by mass and TaC: 5% by mass. , WC: In the brazed part (corner part) of the WC-based cemented carbide insert body having the remaining composition and the shape of ISO standard CNGA120408, Cu: 26%, Ti: 5%, Ag: Remaining The cBN tools 1 to 12 of the present invention shown in Table 1 having an insert shape of ISO standard CNGA120408 by brazing using an Ag alloy brazing material having a composition consisting of the above, and further performing upper and lower surface and outer circumference polishing and honing processing. Was produced.
比較のため、実施例とほぼ同様の手法を用い、比較例cBN焼結体1〜7を作製した。
ただし、表2に示されるように、比較例cBN焼結体1〜6については、前記実施例の製造工程における「ナノW粉末とナノCo粉末とナノFe粉末を添加する」という条件を満足していない。
また、比較例7は、cBN焼結体のTi化合物粒子の平均粒径が、本発明で規定する条件を満たしていない。
ついで、実施例と同様の手法で、ISO規格CNGA120408のインサート形状をもった表2に示す比較例cBN工具1〜7を作製した。
For comparison, Comparative Examples cBN sintered bodies 1 to 7 were prepared using almost the same method as in Examples.
However, as shown in Table 2, Comparative Examples cBN sintered bodies 1 to 6 satisfy the condition of "adding nano W powder, nano Co powder, and nano Fe powder" in the manufacturing process of the above example. Not.
Further, in Comparative Example 7, the average particle size of the Ti compound particles of the cBN sintered body does not satisfy the conditions specified in the present invention.
Then, Comparative Examples cBN Tools 1 to 7 shown in Table 2 having an insert shape of ISO standard CNGA120408 were produced by the same method as in Examples.
上記で作製した本発明cBN焼結体1〜12および比較例cBN焼結体1〜7について、cBN粒子の含有割合(体積%)を測定・算出した。
cBN粒子の含有割合は、cBN焼結体の断面をSEM−EDSによって観察して得た元素マッピングのcBN粒子に相当する部分を画像処理によって抜き出し、画像解析によってcBN粒子が占める面積を算出し、その値を画像総面積で除することでcBN粒子の面積比率を算出し、そして、この面積比率を体積%とみなすことで、cBN粒子の含有割合(体積%)を測定・算出した。
また、この測定では、SEMで得られた倍率5,000の二次電子像の少なくとも3画像を処理し求めた値の平均値をcBN粒子の含有割合(体積%)とした。
なお、画像処理に用いた観察領域は、cBN粒子の平均粒径の5倍の長さの一辺をもつ正方形の領域(cBN粒子の平均粒径が3μmの場合、15μm×15μm程度の観察領域)とした。
表1、表2に、cBN粒子の含有割合(体積%)を示す。
The content ratio (volume%) of cBN particles was measured and calculated for the cBN sintered bodies 1 to 12 of the present invention and the cBN sintered bodies 1 to 7 of Comparative Examples produced above.
For the content ratio of cBN particles, the portion corresponding to the cBN particles of the element mapping obtained by observing the cross section of the cBN sintered body by SEM-EDS was extracted by image processing, and the area occupied by the cBN particles was calculated by image analysis. The area ratio of the cBN particles was calculated by dividing the value by the total area of the image, and the content ratio (volume%) of the cBN particles was measured and calculated by regarding this area ratio as the volume%.
Further, in this measurement, the average value of the values obtained by processing at least three images of the secondary electron images having a magnification of 5,000 obtained by SEM was defined as the content ratio (volume%) of the cBN particles.
The observation area used for image processing is a square area having one side having a length five times the average particle size of the cBN particles (when the average particle size of the cBN particles is 3 μm, an observation area of about 15 μm × 15 μm). And said.
Tables 1 and 2 show the content ratio (volume%) of the cBN particles.
また、上記で作製した本発明cBN焼結体1〜12および比較例cBN焼結体1〜7について、15μm×15μmの観察領域において、SEM−EDSの50,000倍によってW−Co−Fe相の存在の有無を確認した。
例えば、図2(b)の模式図に示されるように、本発明cBN焼結体の断面を、SEM(倍率:50,000倍)−EDSで観察して得た元素マッピングにより、Ti化合物粒子相互の界面にW−Co−Fe相が存在し、かつ、cBN粒子相互間を繋いで途切れることなく存在することを確認した。また、図2(b)からも明らかなように、cBN粒子の周囲は、W−Co−Fe相によって覆われて(取り囲まれて)いないことを確認した。
次いで、W−Co−Fe相を介して途切れることなく相互に繋がっているcBN粒子の個数をカウントし、該領域に存在するcBN粒子の全個数に占める割合を求めた。
また、cBN焼結体の断面を、EPMAを用いた定性・定量分析を行い、定性分析で検出された元素についてZAF定量分析法により、cBN焼結体全体に含有されるW,Co,Fe,B,NさらにTi,Al,C,O,の合計含有量を100質量%としたときに、前記W,Co,Fe,B,N,Ti,Al,C,Oの合計含有量に占めるWとCoとFeの合計含有量の割合(質量%)及びFeの含有量の割合(質量%)を測定した。
表1、表2に、W−Co−Fe相を介して繋がっているcBN粒子の個数割合(%)とWとCoとFeが占める合計含有量(質量%)及びFeの含有量(質量%)を示す。
Further, with respect to the cBN sintered bodies 1 to 12 of the present invention and the cBN sintered bodies 1 to 7 produced above, the W-Co-Fe phase was increased by 50,000 times that of SEM-EDS in an observation region of 15 μm × 15 μm. The existence of was confirmed.
For example, as shown in the schematic diagram of FIG. 2B, Ti compound particles are obtained by elemental mapping obtained by observing a cross section of the cBN sintered body of the present invention with SEM (magnification: 50,000 times) -EDS. It was confirmed that the W-Co-Fe phase was present at the mutual interface and that the cBN particles were connected to each other and existed without interruption. Further, as is clear from FIG. 2B, it was confirmed that the periphery of the cBN particles was not covered (surrounded) by the W—Co—Fe phase.
Next, the number of cBN particles connected to each other without interruption via the W—Co—Fe phase was counted, and the ratio of the cBN particles existing in the region to the total number was determined.
In addition, the cross section of the cBN sintered body is subjected to qualitative and quantitative analysis using EPMA, and the elements detected by the qualitative analysis are subjected to the ZAF quantitative analysis method, and W, Co, Fe, which are contained in the entire cBN sintered body. When the total content of B, N and Ti, Al, C, O is 100% by mass, W accounts for the total content of W, Co, Fe, B, N, Ti, Al, C, O. And the ratio of the total content of Co and Fe (mass%) and the ratio of the content of Fe (% by mass) were measured.
Tables 1 and 2 show the number ratio (%) of cBN particles connected via the W—Co—Fe phase, the total content (mass%) of W, Co, and Fe, and the content of Fe (mass%). ) Is shown.
W−Co−Fe相を介して繋がっているcBN粒子の個数割合の具体的な測定・算出方法は、以下のとおりである。
cBN焼結体の断面をSEM(倍率:50,000倍)−EDSでW、Co、Fe、B、Nの元素マッピングを行い、各マッピング像は対象元素が存在しない部分を黒、存在する部分を白とし、黒を0、白を255の256段調のモノクロ像にて取得し、各々のモノクロ像において元素が存在する位置が白となるように、画像解析ソフトImageJのThresholdツールのAuto機能を用いて閾値を決めて2値化処理を行うことで図1に示すような各元素の元素マッピング像を得る。
The specific measurement / calculation method of the number ratio of cBN particles connected via the W—Co—Fe phase is as follows.
Elemental mapping of W, Co, Fe, B, and N is performed on the cross section of the cBN sintered body with SEM (magnification: 50,000 times) -EDS, and each mapping image shows the part where the target element does not exist in black and the part where the target element exists. Is white, black is 0, and white is acquired as a 256-step monochrome image of 255, and the Auto function of the Threat tool of the image analysis software ImageJ is set so that the position where the element exists is white in each monochrome image. By determining the threshold value using the above and performing the binarization process, an element mapping image of each element as shown in FIG. 1 is obtained.
得られた像のBとNを重ね、重なった領域を抽出することでBとNの元素マッピング像(図2(a)の模式図参照)を得る。同様の手法で、WとCoとFeを重ね、重なった領域を抽出することでWとCoとFeの元素マッピング像(図2(b)の模式図参照)を得る。
前記BとNの元素マッピング像とWとCoとFeの元素マッピング像を重ね合わせることで、cBN粒子とW-Co−Fe相が一体化した像(図3の模式図参照)を得る。
By superimposing B and N of the obtained images and extracting the overlapping regions, an elemental mapping image of B and N (see the schematic diagram of FIG. 2A) is obtained. In the same manner, W, Co, and Fe are overlapped and the overlapping region is extracted to obtain an element mapping image of W, Co, and Fe (see the schematic diagram of FIG. 2B).
By superimposing the element mapping image of B and N and the element mapping image of W, Co and Fe, an image in which the cBN particles and the W—Co—Fe phase are integrated (see the schematic diagram of FIG. 3) is obtained.
次に、図3を1ピクセルが2nm角になるように画像編集ソフト(Adobe Photoshop)でサイズ変更する。サイズ変更した図3をグラフ作成ソフト(HULINKS IGOR PRO)で数値のマトリックスに変換する。このとき白い領域のピクセルは数値255、黒い領域のピクセルは数値0となる。得られたマトリックスにおいて、数値255であるピクセルの周りを囲む8つのピクセルのうち1つでも数値255である場合、それら数値255であるピクセルは連続している、つまり元素は連続的に存在していて繋がっていると定義する。言い換えると数値255であるピクセルと数値255であるピクセルの間に数値0であるピクセルが1つでも存在する場合、不連続となり繋がっていないことを意味する。 Next, the size of FIG. 3 is resized with image editing software (Adobe Photoshop) so that one pixel is 2 nm square. The resized FIG. 3 is converted into a numerical matrix using graph creation software (HULINKS IGOR PRO). At this time, the pixel in the white area has a numerical value of 255, and the pixel in the black area has a numerical value of 0. In the resulting matrix, if any one of the eight pixels surrounding the pixel with the number 255 is the number 255, then the pixel with the number 255 is contiguous, that is, the elements are continuously present. It is defined as being connected. In other words, if even one pixel having the numerical value 0 exists between the pixel having the numerical value 255 and the pixel having the numerical value 255, it means that they are discontinuous and not connected.
次にW−Co−Fe相を介して繋がっているcBN粒子を数値のマトリックスから求める方法は以下のようになる。
図4(a)において、図3と同様に1ピクセルが2nm角になるようにサイズ変更し、数値のマトリックスに変換する。ここで得られたマトリックスの数値255であるピクセルはcBN粒子とW−Co−Fe相の領域であり、この数値255であるピクセルのうちでcBN領域内から任意に1ピクセルを選ぶ。
図3で選んだピクセルと同じ位置の図4(a)のピクセルの数値を例えば255から160に変更する。つまり、図4(a)における任意の1つのcBN領域内の1つのピクセルの数値を255から160に変更する。この変更したピクセルを囲む8つのピクセルのうち数値が255であるピクセルを全て160に置き換える。ここで160に置き換えられた各ピクセルを囲む8つのピクセルのうち数値が255であるピクセルを全て160に置き換える作業を繰り返す。最終的に得られた0と160と255の数値のマトリックスを画像として出力する。画像として出力すると数値160は灰色となるため、得られる画像は図4(a)、(b)に示すように、白と黒と灰色の3色の画像となる。得られた画像において、灰色であるBN粒子はW-Co−Fe相を介して繋がっているcBN粒子であるとし、その個数をカウントし、cBN粒子の総個数から割合を算出する。cBN粒子の総個数は図2(a)を画像解析して求めることができる。
Next, the method of obtaining the cBN particles connected via the W—Co—Fe phase from the numerical matrix is as follows.
In FIG. 4A, the size is changed so that one pixel becomes a 2 nm square as in FIG. 3, and converted into a numerical matrix. The pixel having the numerical value 255 of the matrix obtained here is the region of the cBN particle and the W—Co—Fe phase, and one pixel is arbitrarily selected from the cBN region among the pixels having the numerical value 255.
The numerical value of the pixel of FIG. 4A at the same position as the pixel selected in FIG. 3 is changed from, for example, 255 to 160. That is, the numerical value of one pixel in any one cBN region in FIG. 4A is changed from 255 to 160. Of the eight pixels surrounding the modified pixel, all pixels with a numerical value of 255 are replaced with 160. Here, the work of replacing all the pixels having a numerical value of 255 out of the eight pixels surrounding each pixel replaced with 160 with 160 is repeated. The finally obtained matrix of numerical values of 0, 160, and 255 is output as an image. Since the numerical value 160 becomes gray when output as an image, the obtained image becomes an image of three colors of white, black, and gray as shown in FIGS. 4A and 4B. In the obtained image, it is assumed that the gray BN particles are cBN particles connected via the W-Co—Fe phase, the number of the cBN particles is counted, and the ratio is calculated from the total number of cBN particles. The total number of cBN particles can be obtained by image analysis of FIG. 2A.
例えば、W-Co−Fe相が途切れている場合、つまり数値が255であるピクセルと数値が255であるピクセルの間に1つ以上の数値が0であるピクセルが存在し不連続になっている場合、図4(b)で示すように繋がっていないcBN粒子(図4(b)の右上隅のcBN粒子)は灰色に変換されない。
つまり、図4(a)では、3個のcBN粒子のすべてがW−Co−Fe相を介して繋がっているとして扱い、一方、図4(b)によれば、3個のcBN粒子の内の2個はW−Co−Fe相を介して繋がっているが、残りの1個(図4(b)中右上隅のcBN粒子)はW−Co−Fe相を介して繋がってはいないとして扱った。
前記段落0051で行っている画像処理は、例えば、画像解析ソフトImageJのFlood Fill Toolを用いることで、任意の1つのcBN粒子に対してW-Co−Fe相を介して繋がっているcBN粒子を同様に判別することができる。
W−Co−Fe相によって繋がっているcBN粒子の個数割合(個数%)は倍率50,000倍で測定し、縦8μmx横12μmになるように画像を連結させて1視野としたのちに画像処理および画像解析を行い、少なくとも3視野の平均値とする。
表1、表2に、W−Co−Fe相によって繋がっているcBN粒子の個数割合(個数%)を示す。
For example, when the W-Co-Fe phase is interrupted, that is, between a pixel having a numerical value of 255 and a pixel having a numerical value of 255, one or more pixels having a numerical value of 0 exist and are discontinuous. In this case, the cBN particles that are not connected as shown in FIG. 4 (b) (cBN particles in the upper right corner of FIG. 4 (b)) are not converted to gray.
That is, in FIG. 4A, all three cBN particles are treated as being connected via the W—Co—Fe phase, while according to FIG. 4B, among the three cBN particles, The two particles are connected via the W-Co-Fe phase, but the remaining one (cBN particles in the upper right corner of FIG. 4B) is not connected via the W-Co-Fe phase. I handled it.
In the image processing performed in paragraph 0051, for example, by using the Flod Fill Tool of the image analysis software ImageJ, cBN particles connected to any one cBN particle via the W-Co-Fe phase can be obtained. It can be determined in the same way.
The number ratio (% number) of cBN particles connected by the W—Co—Fe phase was measured at a magnification of 50,000 times, and the images were connected so as to be 8 μm in length × 12 μm in width to form one field of view, and then image processing was performed. And image analysis is performed, and the average value of at least 3 fields of view is used.
Tables 1 and 2 show the number ratio (number%) of cBN particles connected by the W—Co—Fe phase.
Ti化合物粒子の平均粒径の測定・算出は、以下のようにして求めることができる。
まず、cBN焼結体の断面の観察領域を、TEMに付属する結晶方位解析装置を用いて観察する。より具体的に言えば、Ti化合物粒子を観察するために結晶粒径と同程度の厚さ以下に研磨された切片をTEMにセットし、200kVに加速された電子線を前記切片に照射することで、縦400nm×横500nmの範囲で観察を行う。
前記の範囲で結晶方位のマップデータを得る解析方法は以下の通りである。
前記の切片に、0.5〜1.0度に傾けた電子線をPrecession照射しながら、電子線を任意のビーム径及び間隔でスキャンし、連続的に電子線回折パターンを取り込み、個々の測定点の結晶方位を解析する。なお、本測定に用いた回折パターンの取得条件は、カメラ長20cm、ビームサイズ2.2nmで、測定ステップは2.0nmである。
次に、得られた電子線回折パターンから個々の結晶粒を判別するための解析方法は、以下の通りである。
まず、測定点の隣接点同士の結晶方位が5度以上離れている場合に粒界とし、粒界以外の部分を結晶粒、つまりTi化合物粒子と定義した。
この画像を縦4枚×横4枚で連結させて縦1600nmx横2000nmの画像とし、cBN粒子の平均粒径を求めるための前記手順と同様の手順でTi化合物粒子の平均粒径を求める。
このような測定・算出を複数の観察領域(3領域以上)で実施し、その平均値を、Ti系化合物粒子の平均粒径(nm)とする。
表1、表2に、その結果を示す。
The average particle size of the Ti compound particles can be measured and calculated as follows.
First, the observation region of the cross section of the cBN sintered body is observed using a crystal orientation analyzer attached to the TEM. More specifically, in order to observe Ti compound particles, a section polished to a thickness equal to or less than the crystal particle size is set in the TEM, and the section is irradiated with an electron beam accelerated to 200 kV. Then, the observation is performed in the range of 400 nm in length × 500 nm in width.
The analysis method for obtaining the map data of the crystal orientation in the above range is as follows.
While precession-irradiating the section with an electron beam tilted at 0.5 to 1.0 degrees, the electron beam is scanned at an arbitrary beam diameter and interval, and the electron diffraction pattern is continuously captured for individual measurement. Analyze the crystal orientation of the points. The conditions for acquiring the diffraction pattern used in this measurement are a camera length of 20 cm, a beam size of 2.2 nm, and a measurement step of 2.0 nm.
Next, the analysis method for discriminating individual crystal grains from the obtained electron diffraction pattern is as follows.
First, when the crystal orientations of the adjacent points of the measurement points are separated by 5 degrees or more, the grain boundary is defined, and the portion other than the grain boundary is defined as a crystal grain, that is, a Ti compound particle.
This image is connected by 4 vertical × 4 horizontal to obtain an image of 1600 nm in length × 2000 nm in width, and the average particle size of Ti compound particles is obtained by the same procedure as the above procedure for obtaining the average particle size of cBN particles.
Such measurement / calculation is carried out in a plurality of observation regions (3 regions or more), and the average value thereof is defined as the average particle size (nm) of the Ti-based compound particles.
The results are shown in Tables 1 and 2.
また、上記で作製した本発明cBN焼結体1〜12および比較例cBN焼結体1〜7について、以下の方法で、熱伝導率λ(W/m・K)を測定した。
cBN焼結体から測定試料を切り出し、切り出した測定試料の寸法を測定し、次いでアルキメデス法によって密度ρを測定する。
ついで、Xeフラッシュアナライザーを用いたレーザーフラッシュ法によって熱拡散率αと比熱容量CPを測定し、次の式を用いて熱伝導率κを算出する。
熱伝導率κ(W/m・K)
=熱拡散率α(mm2/sec)×密度ρ(g/cm3)×比熱容量CP(J/(K・g)
表1、表2に、測定値を示す。
Further, the thermal conductivity λ (W / m · K) of the cBN sintered bodies 1 to 12 of the present invention and the cBN sintered bodies 1 to 7 of Comparative Examples prepared above was measured by the following methods.
A measurement sample is cut out from the cBN sintered body, the dimensions of the cut out measurement sample are measured, and then the density ρ is measured by the Archimedes method.
Then, the thermal diffusivity α and the specific heat capacity CP are measured by the laser flash method using an Xe flash analyzer, and the thermal conductivity κ is calculated using the following formula.
Thermal conductivity κ (W / m · K)
= Thermal diffusivity α (mm 2 / sec) × Density ρ (g / cm 3 ) × Specific heat capacity CP (J / (K · g)
Tables 1 and 2 show the measured values.
また、本発明cBN焼結体1〜12および比較例cBN焼結体1〜7の断面研磨面について、荷重5kgでビッカース硬さ(HV)を測定し、10箇所の測定点における測定値を平均することによって、焼結体の硬さ(HV)を求めた。
表1、表2に、これらの値を示す。
Further, the Vickers hardness (HV) was measured with a load of 5 kg on the cross-sectional polished surfaces of the cBN sintered bodies 1 to 12 of the present invention and the cBN sintered bodies 1 to 7 of Comparative Examples, and the measured values at 10 measurement points were averaged. By doing so, the hardness (HV) of the sintered body was determined.
Tables 1 and 2 show these values.
ついで、前記本発明cBN工具1〜12および比較例cBN工具1〜7を、いずれも工具鋼製バイトの先端部に固定治具にてネジ止めした状態で、各工具について、以下に示す切削条件で乾式断続切削加工試験を実施し、切削工具としての耐チッピング性、耐クレータ摩耗性の良否を評価した。
《切削条件》
被削材:JIS・SCM420の(HRC58−62)の丸棒
(ただし、被削材の軸方向に等間隔で5本のスリットあり)
切削速度:150m/min、
送り:0.15mm/rev、
切込み:0.15mm、
の条件での、外周加工の乾式断続切削加工試験を行った。
上記の断続切削加工試験において、耐チッピング性の指標として、刃先チッピング発生までの衝撃回数を測定した。(衝撃回数が大であれば、耐チッピング性は優れると判定される。)
また、耐クレータ摩耗性の指標として、切削開始から150秒経過後のすくい面をレーザー顕微鏡で観察し、予め観察しておいた切削開始前のすくい面との比較からクレータ摩耗の最大深さを測定した。(最大深さが小さいほど、耐クレータ摩耗性は優れると判定される。)
表3、表4に、切削試験結果を示す。
Then, with the cBN tools 1 to 12 of the present invention and the comparative examples cBN tools 1 to 7 screwed to the tip of the tool steel tool with a fixing jig, the cutting conditions shown below are applied to each tool. A dry intermittent cutting test was conducted at the site, and the quality of chipping resistance and crater wear resistance as a cutting tool was evaluated.
《Cutting conditions》
Work material: JIS / SCM420 (HRC58-62) round bar (however, there are 5 slits at equal intervals in the axial direction of the work material)
Cutting speed: 150 m / min,
Feed: 0.15 mm / rev,
Notch: 0.15 mm,
A dry intermittent cutting test of outer circumference processing was performed under the conditions of.
In the above intermittent cutting test, the number of impacts until chipping of the cutting edge was measured as an index of chipping resistance. (If the number of impacts is large, it is judged that the chipping resistance is excellent.)
In addition, as an index of crater wear resistance, the rake surface 150 seconds after the start of cutting is observed with a laser microscope, and the maximum depth of crater wear is determined by comparing with the rake surface before the start of cutting that was observed in advance. It was measured. (The smaller the maximum depth, the better the crater wear resistance.)
Tables 3 and 4 show the cutting test results.
なお、クレータ摩耗良否判定の欄中の記号は、以下を意味する。
◎:耐クレータ摩耗性は優れる(クレータ摩耗の最大深さが20μm未満)
○:耐クレータ摩耗性は良い(クレータ摩耗の最大深さが20μm以上30μm未満)
△:耐クレータ摩耗性は劣る(クレータ摩耗の最大深さが30μm以上40μm未満)
×:耐クレータ摩耗性は非常に劣る(クレータ摩耗の最大深さが40μm以上)
The symbols in the crater wear quality determination column mean the following.
⊚: Excellent crater wear resistance (maximum crater wear depth is less than 20 μm)
◯: Good crater wear resistance (maximum crater wear depth is 20 μm or more and less than 30 μm)
Δ: Inferior crater wear resistance (maximum crater wear depth is 30 μm or more and less than 40 μm)
X: Crater wear resistance is very poor (maximum depth of crater wear is 40 μm or more)
表3、表4に示される結果によれば、本発明cBN工具1〜12は、結合相のTi化合物粒子が微粒であって、耐チッピング性にすぐれ、しかも、cBN粒子相互が熱伝導路の機能を備えるW−Co−Fe相を介して繋がっているためcBN焼結体は良熱伝導性を備えることから耐クレータ摩耗性にもすぐれる。
よって、高熱発生を伴い、刃先に高負荷が作用する切削条件下であっても、すぐれた耐チッピング性、耐クレータ摩耗性が長期の使用にわたって発揮される。
これに対して、比較例cBN工具1〜7は、結合相を構成するTi化合物粒子の平均粒径が本発明範囲外であるため、あるいは、W−Co−Fe相が形成されていない等のため、耐チッピング性、耐クレータ摩耗性に劣り、工具寿命が短命である。
なお、本発明cBN工具11は、W−Co−Fe相におけるFe含有量が本発明で規定する好ましい範囲を外れており、また、本発明cBN工具12は、W−Co−Fe相におけるW+Co+Feの合計含有量が本発明で規定する好ましい範囲を外れているため、本発明cBN工具1〜10に比べれば、刃先チッピング発生までの衝撃回数が少なく耐チッピング性の若干の低下がみられるものの、耐クレータ摩耗性には優れている。
ただし、本発明cBN工具11、12と比較例cBN工具1〜7と比べた場合には、耐チッピング性と耐クレータ摩耗性のいずれについても、本発明cBN工具11、12が優れていることは明らかである。
According to the results shown in Tables 3 and 4, in the cBN tools 1 to 12 of the present invention, the Ti compound particles in the bonding phase are fine particles and have excellent chipping resistance, and the cBN particles have mutual heat conduction paths. Since the cBN sintered body is connected via a functional W—Co—Fe phase, the cBN sintered body has good thermal conductivity and is excellent in crater wear resistance.
Therefore, excellent chipping resistance and crater wear resistance are exhibited over a long period of time even under cutting conditions in which high heat is generated and a high load acts on the cutting edge.
On the other hand, in Comparative Examples cBN Tools 1 to 7, the average particle size of the Ti compound particles constituting the bonded phase is outside the range of the present invention, or the W—Co—Fe phase is not formed. Therefore, it is inferior in chipping resistance and crater wear resistance, and has a short tool life.
In the cBN tool 11 of the present invention, the Fe content in the W—Co—Fe phase is out of the preferable range specified in the present invention, and in the cBN tool 12 of the present invention, W + Co + Fe in the W—Co—Fe phase. Since the total content is out of the preferable range specified in the present invention, the number of impacts until chipping of the cutting edge is smaller than that of the cBN tools 1 to 10 of the present invention, and the chipping resistance is slightly reduced. Excellent crater wear resistance.
However, when the cBN tools 11 and 12 of the present invention are compared with the cBN tools 1 to 7 of the comparative examples, the cBN tools 11 and 12 of the present invention are superior in terms of both chipping resistance and crater wear resistance. it is obvious.
本発明のcBN工具は、耐チッピング性、耐クレータ摩耗性にすぐれることから、切削工具の長寿命化が図られる。 Since the cBN tool of the present invention is excellent in chipping resistance and crater wear resistance, the life of the cutting tool can be extended.
Claims (4)
前記Ti化合物粒子の平均粒径は250nm以下であり、
前記Ti化合物粒子の界面には、W成分とCo成分とFe成分が共存するW−Co−Fe相が存在し、
前記W−Co−Fe相は、立方晶窒化ほう素粒子相互間を繋いで途切れることなく存在することで熱伝達路を構成していることを特徴とする立方晶窒化ほう素基焼結体製切削工具。 Cutting made of a cubic boron nitride-based sintered body in which at least the cutting edge is formed by a cubic boron nitride-based sintered body containing cubic boron nitride particles as a hard phase and Ti compound particles as a bonding phase. In the tool
The average particle size of the Ti compound particles is 250 nm or less.
At the interface of the Ti compound particles, there is a W—Co—Fe phase in which the W component, the Co component, and the Fe component coexist.
The W—Co—Fe phase is made of a cubic boron nitride-based sintered body, which is characterized in that a heat transfer path is formed by connecting cubic boron nitride particles to each other and existing without interruption. Cutting tools.
The cubic nitriding method according to any one of claims 1 to 3, wherein the Ti compound particles are any one or more selected from TiN particles, TiCN particles and TiC particles. Cutting tool made of base sintered body.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2019023026A JP2020131293A (en) | 2019-02-12 | 2019-02-12 | Cutting tool made of cubic crystal boron nitride-based sintered body |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2019023026A JP2020131293A (en) | 2019-02-12 | 2019-02-12 | Cutting tool made of cubic crystal boron nitride-based sintered body |
Publications (1)
Publication Number | Publication Date |
---|---|
JP2020131293A true JP2020131293A (en) | 2020-08-31 |
Family
ID=72261885
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP2019023026A Pending JP2020131293A (en) | 2019-02-12 | 2019-02-12 | Cutting tool made of cubic crystal boron nitride-based sintered body |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP2020131293A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN112935931A (en) * | 2021-03-01 | 2021-06-11 | 燕山大学 | Ultra-precision machining method for pure iron part and pure iron part |
-
2019
- 2019-02-12 JP JP2019023026A patent/JP2020131293A/en active Pending
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN112935931A (en) * | 2021-03-01 | 2021-06-11 | 燕山大学 | Ultra-precision machining method for pure iron part and pure iron part |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP6853951B2 (en) | cBN sintered body and cutting tool | |
US9120707B2 (en) | Cubic boron nitride sintered body and cubic boron nitride sintered body tool | |
JP6032409B2 (en) | Cutting tools and surface-coated cutting tools using a cubic boron nitride-based ultra-high pressure sintered body as a tool base | |
WO2013039093A1 (en) | Cutting tool made of cubic boron nitride-based sintered material | |
JP2013255986A (en) | Cutting tool of cubic crystal boron nitride based sintered material | |
WO2014208447A1 (en) | Cermet, and method for manufacturing same, as well as cutting tool | |
JP7185844B2 (en) | TiN-based sintered body and cutting tool made of TiN-based sintered body | |
JP7103565B1 (en) | Cemented carbide and cutting tools containing it as a base material | |
JP6198142B2 (en) | Cutting tool made of cubic boron nitride super high pressure sintered material | |
JP6968341B2 (en) | Cubic boron nitride-based sintered body with microstructural structure and cutting tools | |
JP7068657B2 (en) | Cutting tool made of cubic boron nitride base sintered body | |
JP2020131293A (en) | Cutting tool made of cubic crystal boron nitride-based sintered body | |
JP5804448B2 (en) | Cubic boron nitride based ultra-high pressure sintered body, cutting tool using this as a tool base, and surface-coated cutting tool | |
US11383305B2 (en) | cBN sintered compact and cutting tool | |
JP2018065228A (en) | Ticn-based cermet cutting tool | |
JP6819018B2 (en) | TiCN-based cermet cutting tool | |
WO2020179809A1 (en) | cBN SINTERED COMPACT AND CUTTING TOOL | |
JP7377463B2 (en) | cBN sintered body and cutting tools | |
JP6819017B2 (en) | TiCN-based cermet cutting tool | |
JP7161670B2 (en) | Cubic boron nitride-based sintered body and cutting tool | |
JP2022142894A (en) | cBN SINTERED COMPACT | |
JP6933017B2 (en) | Cubic boron nitride base sintered body and cutting tool | |
JP2022147104A (en) | cBN SINTERED BODY AND CUTTING TOOL INCLUDING THE SAME | |
JP2021155803A (en) | Wc-based hard metal cutting tool and surface-covered wc-based hard metal cutting tool having excellent in wear resistance and defect resistance | |
JP2024111448A (en) | Cubic boron nitride sintered body |