JP7137119B2 - cBN sintered body and cutting tool - Google Patents
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Description
本発明は、靭性に優れた立方晶窒化ほう素(以下、「cBN」で示す)基超高圧焼結体(以下、「cBN焼結体」という)、および、これを工具基体とする切削工具(以下、「CBN工具」という)に関する。 The present invention provides a cubic boron nitride (hereinafter referred to as "cBN")-based ultrahigh-pressure sintered body (hereinafter referred to as "cBN sintered body") having excellent toughness, and a cutting tool using this as a tool base. (hereinafter referred to as "CBN tool").
従来から、cBN焼結体は、靭性に優れることが知られており、鋼、鋳鉄等の鉄系被削材の切削工具材料として広く用いられている。 Conventionally, cBN sintered bodies have been known to have excellent toughness, and are widely used as cutting tool materials for iron-based work materials such as steel and cast iron.
例えば、特許文献1には、硬質相としてのcBNを20~80体積%含有し、残部が、周期律表の4a、5a、6aの炭化物、窒化物、ほう化物等のセラミックス化合物を結合相としたcBN工具が記載されている。 For example, Patent Document 1 contains 20 to 80% by volume of cBN as a hard phase, and the balance is a ceramic compound such as carbides, nitrides, and borides of 4a, 5a, and 6a in the periodic table as a binder phase. A cBN tool is described.
また、例えば、特許文献2には、20体積%以上80体積%以下のcBN粒子と結合材とを有する複合焼結体であって、前記結合材は、周期律表第4a族元素、第5a族元素、第6a族元素の窒化物、炭化物、硼化物、酸化物、およびこれらの固溶体からなる群の中から選択された少なくとも一種と、Zr、Si、W、Co等の単体、化合物、および固溶体からなる群の中から選択された少なくとも1種と、Alの化合物とからなり、前記複合焼結体中にW及び/又はCoが含有される場合には、該W及び/又はCoの合計質量は2.0質量%未満であり、かつ前記Zr、Si等(以下、「X」とする。)のいずれか一以上を含有し、該Xはそれぞれ0.005質量%以上2.0質量%未満であり、かつX/(X+W+Co)が0.01以上1.0以下を満たし、かつAlの質量が2.0質量%以上20.0質量%以下であるcBN焼結体が記載されている。 Further, for example, Patent Document 2 discloses a composite sintered body having 20% by volume or more and 80% by volume or less of cBN particles and a binder, wherein the binder is an element of Group 4a of the periodic table, 5a At least one selected from the group consisting of group elements, nitrides, carbides, borides, oxides of group 6a elements, and solid solutions thereof, and elements such as Zr, Si, W, Co, compounds, and At least one selected from the group consisting of solid solutions and an Al compound, and when the composite sintered body contains W and/or Co, the total of W and/or Co The mass is less than 2.0% by mass and contains one or more of the above Zr, Si, etc. (hereinafter referred to as "X"), and each of the X is 0.005% by mass or more and 2.0% by mass %, X / (X + W + Co) satisfies 0.01 or more and 1.0 or less, and the Al mass is 2.0 mass% or more and 20.0 mass% or less. there is
さらに、例えば、特許文献3には、立方晶窒化硼素粒子と結合相とを含む焼結体を工具基体とする立方晶窒化硼素焼結体切削工具において、前記焼結体は、立方晶窒化硼素粒子を40容量%以上60容量%未満およびAlが下限値で2質量%、上限値でYをAl含有割合(質量%)、Xを立方晶窒化硼素粒子含有割合(容量%)としたとき、Y=-0.1X+10の関係を満足する範囲となるように含有し、前記結合相は、少なくともTi系化合物とAl2O3と不可避不純物を含有し、前記Al2O3のうち、直径10nm~100nmの微粒Al2O3が結合相中に分散、生成しており、前記結合相の断面1μm×1μmの領域において、前記微粒Al2O3が30個以上生成していることを特徴とする立方晶窒化硼素焼結体切削工具が記載されている。 Furthermore, for example, Patent Document 3 discloses a cubic boron nitride sintered cutting tool having a sintered body containing cubic boron nitride particles and a binder phase as a tool base, wherein the sintered body is cubic boron nitride When the particles are 40% by volume or more and less than 60% by volume and Al is 2% by mass at the lower limit, Y is the Al content ratio (% by mass) at the upper limit, and X is the cubic boron nitride particle content ratio (% by volume), Y = -0.1X + 10 The binding phase contains at least a Ti-based compound, Al 2 O 3 and inevitable impurities, and the Al 2 O 3 has a diameter of 10 nm Fine grains of Al 2 O 3 of up to 100 nm are dispersed and generated in the binder phase, and 30 or more of the fine grains of Al 2 O 3 are formed in a region of a cross section of 1 μm×1 μm of the binder phase. A cubic boron nitride sintered cutting tool is described.
特許文献1に記載されたcBN焼結体は、結合相としてセラミックス化合物を用いているため、Co等の金属を結合相として用いた場合に比べて、強度、耐熱性、耐摩耗性の向上が認められる。しかし、このcBN焼結体は、切れ刃に高負荷が作用する断続切削加工用切削工具として用いた場合には、靱性が十分であるとはいえないため、チッピング、欠損等の異常損傷を発生し、短期間で寿命に至るという問題があった。 Since the cBN sintered body described in Patent Document 1 uses a ceramic compound as the binder phase, it has improved strength, heat resistance, and wear resistance compared to the case where a metal such as Co is used as the binder phase. Is recognized. However, when this cBN sintered body is used as a cutting tool for interrupted cutting where a high load acts on the cutting edge, it cannot be said that it has sufficient toughness, so abnormal damage such as chipping and fracture occurs. However, there is a problem that the life span is reached in a short period of time.
特許文献2に記載されたcBN焼結体は、結合相の強度と靱性を高めるためにW及び/又はCo、Si又はZrを結合相中に所定量含有させているが、例えば、Wが焼結体中に占める割合が多いと焼結体の靱性が低下、Siが多いと結合材の拡散反応が過剰に抑制され、cBN粒子と結合材および結合材同士の結合力が低下し、焼結体の靱性が低下する問題があった。また、混合時の分散性が悪いと局所的に添加物の濃度が高い部分が生じ、cBN粒子と結合材との結合力の低下により焼結体の靱性が低下し、切削工具として使用した場合、破壊の起点となることによって耐欠損性が低下するという問題があった。 The cBN sintered body described in Patent Document 2 contains a predetermined amount of W and/or Co, Si or Zr in the binder phase in order to increase the strength and toughness of the binder phase. If the proportion of Si in the body is large, the toughness of the sintered body is lowered. There was a problem that the toughness of the body decreased. In addition, if the dispersibility at the time of mixing is poor, a portion with a high concentration of the additive locally occurs, and the toughness of the sintered body decreases due to the decrease in the bonding force between the cBN particles and the binder, and when used as a cutting tool. , there is a problem that the chipping resistance is lowered by becoming a starting point of fracture.
特許文献3に記載されたcBN焼結体は、平均粒径5~15nmの超微粒Al2O3を用いることで粒径100nm以下の微粒Al2O3の均一分散化をしているが、含有させるAl2O3が少ない場合、微粒なためクラックを偏向させる効果はあるが、Tiを主とするセラミックス結合相成分とAl2O3のビッカース硬さは同程度のため、クラックを誘導させる効果が低減し、cBN焼結体の破壊靭性が低下する虞があった。 The cBN sintered body described in Patent Document 3 uses ultrafine Al 2 O 3 with an average particle size of 5 to 15 nm to uniformly disperse fine Al 2 O 3 with a particle size of 100 nm or less. When the amount of Al 2 O 3 to be contained is small, it has the effect of deflecting cracks because of its fine grains, but since the Vickers hardness of the ceramic binder phase component mainly composed of Ti and Al 2 O 3 is about the same, it induces cracks. There was a possibility that the effect would be reduced and the fracture toughness of the cBN sintered body would be lowered.
本発明は、前記先行技術においてcBN焼結体が十分な靱性を確保できないという課題を解決するものであって、靱性の高いcBN焼結体およびこれを工具基体とするCBN工具を提供することを目的とする。 The present invention solves the problem that the cBN sintered body cannot ensure sufficient toughness in the prior art, and provides a cBN sintered body with high toughness and a CBN tool using this as a tool base. aim.
本発明者は、cBN焼結体及びこれを工具基体とするcBN工具について前記課題を解決すべく、cBN焼結体中のAl化合物粒子の分散と靱性の向上について鋭意検討を行った。その結果、微粒のイットリウム・アルミニウム・ガーネット(Y3Al5O12:YAG)をcBN焼結体中に1体積%以上20体積%以下含有し、かつ、結合相中に形成されるYAGの平均粒径を200nm以下とすることにより、cBN焼結体内で生じたクラックの進展がY3Al5O12粒子により迂回されること、すなわち、細かく迂回されることに加えて、結合相中でのクラックの細かな伝播の誘導を強くすることにより、靱性の高いcBN焼結体を得ることができること、また、このcBN焼結体を切削工具として使用すれば、刃先への負荷の大きい断続切削にあたって刃先が欠損しにくいという優れた切削性能を有することを知見した。 In order to solve the above-mentioned problems with respect to a cBN sintered body and a cBN tool using the same as a tool base, the present inventors have made earnest studies on dispersion of Al compound particles in the cBN sintered body and improvement of toughness. As a result, fine grains of yttrium aluminum garnet (Y 3 Al 5 O 12 : YAG) are contained in the cBN sintered body at 1% by volume or more and 20% by volume or less, and the average amount of YAG formed in the binder phase By setting the grain size to 200 nm or less, the progress of cracks generated in the cBN sintered body is detoured by the Y 3 Al 5 O 12 grains, that is, in addition to being detoured finely, It is possible to obtain a cBN sintered body with high toughness by strengthening the induction of fine crack propagation . It has been found that it has excellent cutting performance that the cutting edge is less likely to break on impact.
本発明は、前記知見に基づいてなされたものであって、
「(1)立方晶窒化硼素粒子と結合相とからなるcBN焼結体において、
前記結合相には、平均粒径が10nm以上200nm以下のY3Al5O12が、前記cBN焼結体に対する含有割合として1体積%以上20体積%以下となるように分散していることを特徴とするcBN焼結体。
(2)前記(1)に記載のcBN焼結体を工具基体とすることを特徴とする切削工具。」
である。
The present invention was made based on the above findings,
"(1) In a cBN sintered body consisting of cubic boron nitride particles and a binder phase,
In the binder phase, Y 3 Al 5 O 12 having an average particle size of 10 nm or more and 200 nm or less is dispersed so that the content ratio of the cBN sintered body is 1 volume % or more and 20 volume % or less. A cBN sintered body characterized by:
(2) A cutting tool comprising the cBN sintered body according to (1) above as a tool substrate. ”
is.
本発明は、焼結体の結合相中にY3Al5O12の微粒子を分散させるため、cBN焼結体中で生じたクラックの進展を細かく迂回させ、直線的な進展を抑えて靱性を高めるとともに、結合相の材料であるTiN、TiCに比してビッカース硬さが同程度のAl2O3ではなく、ビッカース硬さが低いY3Al5O12を使用することにより、焼結体中を進行するクラックの先端を硬さの低いY3Al5O12へ誘導させることにより、その進展をより細かく迂回させ、より一層のcBN焼結体の靱性の向上がなされるという優れた効果を奏することができる。 In the present invention, since the fine particles of Y 3 Al 5 O 12 are dispersed in the binding phase of the sintered body, the progress of cracks generated in the cBN sintered body is finely detoured, and the linear progress is suppressed to improve toughness. By using Y3Al5O12 , which has a lower Vickers hardness than Al2O3 , which has a similar Vickers hardness to TiN and TiC , which are the materials of the binder phase, the sintered body By guiding the tip of the crack that progresses inside to Y 3 Al 5 O 12 with low hardness, the progress of the crack is diverted more finely, and the toughness of the cBN sintered body is further improved. can be played.
以下、本発明を詳細に説明する。なお、本明細書において、数値範囲を「~」を用いて表現する場合、その範囲は上限および下限の数値を含むものである。 The present invention will be described in detail below. In this specification, when a numerical range is expressed using "-", the range includes upper and lower limits.
1.cBN焼結体中の結合相に分散させるY3Al5O12
(1)平均粒径
焼結体中に占めるY3Al5O12粒の平均粒径は、10nm以上200nm以下とする。Y3Al5O12の平均粒径が、200nmを超えると、結合相中のY3Al5O12粒子を起点とするクラックの発生や進展を生じやすくなるため、cBN焼結体の靱性が低下する。したがって、結合相中に存在するY3Al5O12の平均粒径の上限値は200nmとする。より好ましい上限値は100nmである。また、Y3Al5O12の粒径が10nm未満であればクラックの進展を細かく迂回させ、直線的な進展を抑えることが十分でないことから、Y3Al5O12の粒径の下限値は10nmとした。
1. Y3Al5O12 dispersed in the binder phase in cBN sintered bodies
(1) Average grain size The average grain size of the 12 Y 3 Al 5 O grains in the sintered body is set to 10 nm or more and 200 nm or less. When the average grain size of Y 3 Al 5 O 12 exceeds 200 nm, cracks originating from the Y 3 Al 5 O 12 grains in the binder phase are likely to occur and propagate, so the toughness of the cBN sintered body is reduced. descend. Therefore, the upper limit of the average grain size of Y 3 Al 5 O 12 present in the binder phase is 200 nm. A more preferable upper limit is 100 nm. In addition, if the grain size of Y 3 Al 5 O 12 is less than 10 nm, the progress of cracks is finely detoured, and it is not sufficient to suppress linear growth, so the lower limit of the grain size of Y 3 Al 5 O 12 was 10 nm.
(2)含有割合
焼結体の結合相中に占めるY3Al5O12粒の含有割合は、cBN焼結体に対する含有割合として1体積%(vol%)以上20体積%以下とする。その理由は、1体積%未満であるとクラックを細かく迂回させてその進展を抑制することが十分にできずcBN焼結体の靱性を向上させるには十分な量ではなく、一方、20体積%超えるとcBN焼結体中においてY3Al5O12粒同士が接する確率が高くなり、隣り合ったY3Al5O12粒が焼結時に粒成長し肥大なY3Al5O12粒となり、その肥大なY3Al5O12を起点としたクラックの発生が生じやすくなり、cBN焼結体の靱性が低下し、好ましくないからである。
(2) Content ratio The content ratio of 12 Y 3 Al 5 O grains in the binder phase of the sintered body is 1 volume % (vol %) or more and 20 volume % or less relative to the cBN sintered body . The reason for this is that if the amount is less than 1% by volume, the cracks cannot be finely detoured and their progress cannot be sufficiently suppressed, and the amount is not sufficient to improve the toughness of the cBN sintered body. If it exceeds, the probability that the Y 3 Al 5 O 12 grains will contact each other in the cBN sintered body increases, and the adjacent Y 3 Al 5 O 12 grains grow during sintering to become enlarged Y 3 Al 5 O 12 grains. , cracks tend to occur starting from the enlarged Y 3 Al 5 O 12 , and the toughness of the cBN sintered body decreases, which is not preferable.
2.Y3Al5O12の平均粒径と含有割合の測定方法
(1)Y3Al5O12の平均粒径
Y3Al5O12の存在は、X線回折(XRD:ターゲットCu)において、Y3Al5O12の回折ピークが現れることにより確認できる。
平均粒径は、cBN焼結体の断面組織をオージェ電子分光(Auger Electron Spectrography:以下、AESという)装置を用いて、Al元素、O元素およびY元素のマッピング像を得て、Al元素、O元素およびY元素が重なる部位を画像処理によって抜き出し、当該部位をY3Al5O12粒子と特定し、次いで、特定した各粒子に対して画像解析を行って平均粒径を求める。具体的には、結合相中のY3Al5O12粒子を明確に判断するため、AESを用いて得た同一視野におけるAl元素、O元素およびY元素の各マッピング像は、対象元素が存在しない部位を黒、存在する部位を白とし、黒を0、白を255の256階調のモノクロにて取得し、各々のモノクロ像において各元素が存在する位置が白色となるように2値化処理する。2値化処理し得られた同一視野内におけるAl元素、O元素およびY元素のマッピング像において、3元素が存在する、すなわち3元素の各マッピング像を比較しいずれも白色となる部位をY3Al5O12粒子と特定する。
なお、Y3Al5O12粒同士が接触していると考えられる部分を切り離すような処理、例えば、画像処理法の1つであるウォーターシェッドを用いて接触していると思われるY3Al5O12粒同士を分離する処理を、3元素の各マッピング像を比較しいずれも白色である部分を抜き出した後の像へ行ってもよい。
2値化処理後に得られた画像内のY3Al5O12粒にあたる部分(白の部分)を粒子解析し、求めた最大長を各粒子の直径とする。最大長を求める粒子解析としては、例えば、1つのY3Al5O12粒子に対してフェレ径を算出することより得られる2つの長さから大きい長さの値を最大長とし、その値を各粒子の直径とする。この直径を有する理想球体と仮定して計算より求めた体積を各粒子の体積として累積体積を求め、この累積体積を基に縦軸を体積百分率[%]、横軸を直径[μm]としてグラフを描画させ、体積百分率が50%のときの直径をY3Al5O12粒子の平均粒径とし、これを3観察領域に対して行い、その平均値をY3Al5O12の平均粒径[μm]とした。粒子解析を行う際には、あらかじめSEMにより分かっているスケールの値を用いて、1ピクセル当たりの長さ(μm)を設定しておく。画像処理に用いる観察領域としては、5.0μm×3.0μm程度の視野領域が望ましい。
2. Method for measuring the average particle size and content ratio of Y 3 Al 5 O 12 ( 1) Average particle size of Y 3 Al 5 O 12 It can be confirmed by the appearance of a diffraction peak of Y 3 Al 5 O 12 .
The average grain size is determined by obtaining a mapping image of Al element, O element and Y element using an Auger Electron Spectrography (AES) apparatus for the cross-sectional structure of the cBN sintered body. A portion where the element and the Y element overlap is extracted by image processing, and the portion is identified as a Y 3 Al 5 O 12 particle, and then image analysis is performed on each identified particle to obtain an average particle size. Specifically, in order to clearly determine the Y 3 Al 5 O 12 particles in the binder phase, each mapping image of the Al element, the O element, and the Y element in the same field of view obtained using AES shows that the target element is present. The non-absent part is black, the existing part is white, black is 0, white is 255, and 256 gradations are obtained in monochrome, and binarization is performed so that the position where each element is present in each monochrome image is white. process. In the mapping images of the Al element, the O element, and the Y element in the same field of view obtained by binarization, the three elements are present, that is, the portion where each mapping image of the three elements is compared and all are white is denoted by Y 3 They are identified as Al 5 O 12 particles.
In addition, the Y 3 Al 5 O 12 particles that are considered to be in contact with each other are separated by a process such as a water shed, which is one of the image processing methods. The process of separating the 5 O 12 grains may be performed on the image after comparing the mapping images of the three elements and extracting the white portion.
A portion (white portion) corresponding to 12 Y 3 Al 5 O grains in the image obtained after the binarization processing is subjected to particle analysis, and the obtained maximum length is taken as the diameter of each particle. As a particle analysis for determining the maximum length, for example, the value of the larger length from the two lengths obtained by calculating the Feret diameter for one Y 3 Al 5 O 12 particle is the maximum length, and that value is Let it be the diameter of each particle. Assuming an ideal sphere with this diameter, the volume obtained by calculation is the volume of each particle, and the cumulative volume is obtained. Based on this cumulative volume, the vertical axis is the volume percentage [%] and the horizontal axis is the diameter [μm]. is drawn, and the diameter when the volume percentage is 50 % is taken as the average particle size of the Y 3 Al 5 O 12 particles. The diameter [μm] was used. When performing particle analysis, the length (μm) per pixel is set using the scale value known in advance from the SEM. A viewing area of about 5.0 μm×3.0 μm is desirable as an observation area used for image processing.
(2)含有割合
含有割合は、AESを用いて、Al元素、O元素およびY元素のマッピング像を得て、Al元素、O元素およびY元素が重なる部位を画像処理によって抜き出し、当該部位をY3Al5O12粒子と特定し、画像解析によりY3Al5O12粒子が占める面積を算出して、Y3Al5O12粒子の面積割合を求める。これを少なくとも3画像に対して行い、算出した各Y3Al5O12粒子の面積割合の平均値をcBN焼結体に占めるY3Al5O12の含有割合として求める。画像処理に用いる観察領域として、5.0μm×3.0μm程度の視野領域が望ましい。
(2) Content ratio The content ratio is obtained by using AES to obtain a mapping image of the Al element, the O element, and the Y element, extracting the portion where the Al element, the O element, and the Y element overlap by image processing, and extracting the portion where the Y element overlaps. The 3 Al 5 O 12 particles are specified, and the area occupied by the Y 3 Al 5 O 12 particles is calculated by image analysis to determine the area ratio of the Y 3 Al 5 O 12 particles. This is performed for at least three images, and the average value of the calculated area ratio of each Y 3 Al 5 O 12 particle is obtained as the content ratio of Y 3 Al 5 O 12 in the cBN sintered body. A viewing area of about 5.0 μm×3.0 μm is desirable as an observation area used for image processing.
3.cBN焼結体中のcBN粒子の平均粒径と含有割合
本発明で用いるcBN粒子の平均粒径は、特に限定されるものではないが、0.2~8.0μmの範囲であることが好ましい。
これは、硬質なcBN粒子を焼結体内に含むことにより耐欠損性を高める効果に加えて、平均粒径が0.2~8.0μmのcBN粒子を焼結体内に分散させることにより、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欠損、チッピングを抑制するだけでなく、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粒子が割れて進展するクラックの伝播を抑制することにより、優れた耐欠損性を有することができるためである。
cBN焼結体に占めるcBN粒子の含有割合は、特に限定されるものではないが、40体積%未満では、焼結体中に硬質物質が少なく、工具として使用した場合に、耐欠損性が低下することがあり、一方、78体積%を超えると、焼結体中にクラックの起点となる空隙が生成し、耐欠損性が低下することがある。そのため、本発明が奏する効果をより一層発揮するためには、cBN焼結体に占めるcBN粒子の含有割合は、40~78体積%の範囲とすることが好ましい。
3. Average particle size and content ratio of cBN particles in cBN sintered body The average particle size of the cBN particles used in the present invention is not particularly limited, but is preferably in the range of 0.2 to 8.0 μm. .
In addition to the effect of increasing chipping resistance by including hard cBN particles in the sintered body, dispersing cBN particles with an average particle size of 0.2 to 8.0 μm in the sintered body In addition to suppressing fracture and chipping caused by the uneven shape of the cutting edge caused by cBN particles falling off the tool surface during use, the interface between the cBN particles and the binder phase caused by the stress applied to the cutting edge during use of the tool This is because excellent chipping resistance can be obtained by suppressing the propagation of cracks that propagate or cracks that propagate due to splitting of cBN grains.
The content of cBN particles in the cBN sintered body is not particularly limited, but if it is less than 40% by volume, there is little hard material in the sintered body, and when used as a tool, the fracture resistance is reduced. On the other hand, if it exceeds 78% by volume, voids that act as starting points for cracks may form in the sintered body, resulting in a decrease in chipping resistance. Therefore, in order to further exhibit the effects of the present invention, the content of cBN grains in the cBN sintered body is preferably in the range of 40 to 78% by volume.
cBN粒子の平均粒径と含有割合は、以下のとおりにして求めることができる。
cBN焼結体の断面組織をSEMにてcBN焼結体組織を観察し、二次電子像を得る。得られた画像内のcBN粒子の部分を画像処理にて抜き出し、画像解析より求めた各粒子の最大長を基に平均粒径を算出する。
画像内のcBN粒子の部分を画像処理にて抜き出すにあたり、cBN粒子と結合相とを明確に判断するため、画像は0を黒、255を白の256階調のモノクロで表示し、cBN粒子部分の画素値と結合相部分の画素値の比が2以上となる画素値の像を用いてcBN粒が黒となるように2値化処理を行う。
ここで、cBN粒子部分や結合相部分の画素値を求めるための領域として、0.5μm×0.5μm程度の領域内の平均値より求め、少なくとも同一画像内から異なる3個所より求めた平均の値を各々のコントラストとすることが望ましい。
なお、2値化処理後はcBN粒同士が接触していると考えられる部分を切り離すような処理、例えば、ウォーターシェッドを用いて接触していると思われるcBN粒同士を分離する。
2値化処理後に得られた画像内のcBN粒にあたる部分(黒の部分)を粒子解析し、求めた最大長を各粒子の直径とする。最大長を求める粒子解析としては、例えば、1つのcBN粒子に対してフェレ径を算出することより得られる2つの長さから大きい長さの値を最大長とし、その値を各粒子の直径とする。この直径を有する理想球体と仮定して計算より求めた体積を各粒子の体積として累積体積を求め、この累積体積を基に縦軸を体積百分率[%]、横軸を直径[μm]としてグラフを描画させ、体積百分率が50%のときの直径をcBN粒子の平均粒径とし、これを3観察領域に対して行い、その平均値をcBNの平均粒径[μm]とした。粒子解析を行う際には、あらかじめSEMにより分かっているスケールの値を用いて、1ピクセル当たりの長さ(μm)を設定しておく。画像処理に用いる観察領域として、cBN粒子の平均粒径が3μmの場合、15.0μm×15.0μm程度の視野領域が望ましい。
The average particle size and content of cBN particles can be determined as follows.
A cross-sectional structure of the cBN sintered body is observed with an SEM to obtain a secondary electron image. The portion of cBN grains in the obtained image is extracted by image processing, and the average grain size is calculated based on the maximum length of each grain determined by image analysis.
When extracting the cBN particle portion in the image by image processing, in order to clearly determine the cBN particle and the bonding phase, the image is displayed in 256-gradation monochrome, with 0 being black and 255 being white, and the cBN particle portion A binarization process is performed so that the cBN grain becomes black using the image of the pixel value in which the ratio of the pixel value of and the pixel value of the bonded phase portion is 2 or more.
Here, as a region for obtaining the pixel values of the cBN grain portion and the bonding phase portion, it is obtained from the average value in the region of about 0.5 μm × 0.5 μm, and at least the average value obtained from three different points in the same image. It is desirable to let the values be the respective contrasts.
After the binarization process, the cBN grains considered to be in contact with each other are separated by a process such as separating the portions where the cBN grains are considered to be in contact with each other, for example, using a water shed.
Part corresponding to cBN grains (black part) in the image obtained after the binarization process is subjected to particle analysis, and the obtained maximum length is taken as the diameter of each particle. As a particle analysis for determining the maximum length, for example, the value of the larger length from the two lengths obtained by calculating the Feret diameter for one cBN particle is the maximum length, and that value is the diameter of each particle. do. Assuming an ideal sphere with this diameter, the volume obtained by calculation is the volume of each particle, and the cumulative volume is obtained. Based on this cumulative volume, the vertical axis is the volume percentage [%] and the horizontal axis is the diameter [μm]. was drawn, and the diameter when the volume percentage was 50% was taken as the average particle size of the cBN particles. When performing particle analysis, the length (μm) per pixel is set using the scale value known in advance from the SEM. As an observation area used for image processing, a viewing area of about 15.0 μm×15.0 μm is desirable when the average particle size of cBN particles is 3 μm.
cBN焼結体に占めるcBN粒子の含有割合は、cBN焼結体の断面組織をSEMによって観察し、得られた二次電子像内のcBN粒子の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、1画像内のcBN粒子が占める割合を求め、少なくとも3画像を処理し求めた値の平均値をcBN粒子の含有割合として求める。画像内のcBN粒子の部分を抜き出す画像処理は、cBN粒の平均粒径の2値化処理後の像を得る手順と同様に行う。画像処理に用いる観察領域として、例えば、cBN粒子の平均粒径0.3μmの場合、5.0μm×3.0μm程度の視野領域が望ましい。 The content ratio of cBN particles in the cBN sintered body is obtained by observing the cross-sectional structure of the cBN sintered body by SEM, extracting the cBN particles in the obtained secondary electron image by image processing, and analyzing the cBN particles by image analysis. The area occupied by is calculated, the ratio occupied by cBN particles in one image is obtained, and the average value of the values obtained by processing at least three images is obtained as the content ratio of cBN particles. The image processing for extracting the cBN grain portion in the image is performed in the same manner as the procedure for obtaining the image after the binarization processing of the average grain size of the cBN grains. As an observation area used for image processing, for example, when the average particle size of cBN particles is 0.3 μm, a viewing area of about 5.0 μm×3.0 μm is desirable.
4.製造方法
本発明の製造方法の一例を以下に示す。
(1)結合相を構成する成分の原料粉末の準備
結合相を構成する原料粉末として、Y3Al5O12原料と結合相の主となる原料を用意する。Y3Al5O12原料として、平均粒径3~5μmのY3Al5O12粉末を用意する。Y3Al5O12粉末は、所望の粒径に粉砕したY3Al5O12原料粉とするため、例えば、超硬合金で内張りされた容器内に超硬合金製ボールとアセトンと共に充填し、蓋をした後にボールミルにより粉砕を行った後、遠心分離装置を用いて分級することにより、縦軸を体積百分率、横軸を粒子径とした場合のメディアン径D50を粉砕したY3Al5O12原料粉の平均粒径とし、その値が10~200nmのY3Al5O12原料粉を得る。また、結合相の主となる原料としては、従来から知られている結合相形成原料粉末(TiN粉末、TiC粉末、TiCN粉末、TiAl3粉末)を準備する。
4. Manufacturing Method An example of the manufacturing method of the present invention is shown below.
(1) Preparation of Raw Material Powders of Components Constituting Binder Phase As raw material powders constituting the binder phase, a Y 3 Al 5 O 12 raw material and a raw material for the main binder phase are prepared. Y 3 Al 5 O 12 powder having an average particle size of 3 to 5 μm is prepared as a Y 3 Al 5 O 12 raw material. The Y 3 Al 5 O 12 powder is pulverized to a desired particle size to obtain Y 3 Al 5 O 12 raw material powder. For example, a container lined with a cemented carbide is filled with cemented carbide balls and acetone. Y 3 Al 5 O pulverized with a median diameter D50 when the vertical axis is the volume percentage and the horizontal axis is the particle diameter by classifying using a centrifugal separator after pulverizing with a ball mill after closing the lid. Y 3 Al 5 O 12 raw material powder having an average particle diameter of 10 to 200 nm is obtained. As raw materials for the binder phase, conventionally known binder phase forming raw material powders (TiN powder, TiC powder, TiCN powder, and TiAl 3 powder) are prepared.
(2)粉砕・混合
これらの原料粉末を、例えば、超硬合金で内張りされた容器内に超硬合金製ボールとアセトンと共に充填し、蓋をした後にボールミルにより粉砕および混合を行う。
その後、硬質相として機能させる平均粒径0.2~8.0μmのcBN粉末を焼結後のcBN粒子の含有割合が所定の体積%となるように添加して、さらに、ボールミル混合を行う。
(2) Pulverization and Mixing These raw material powders are filled, for example, in a container lined with cemented carbide together with cemented carbide balls and acetone, and after the lid is closed, they are crushed and mixed with a ball mill.
After that, cBN powder having an average particle size of 0.2 to 8.0 μm, which functions as a hard phase, is added so that the content of cBN particles after sintering is a predetermined volume %, and ball mill mixing is performed.
(3)成形、焼結
得られた焼結体原料粉末を、所定圧力で成形して成形体を作製し、これを真空下、1000℃で仮焼結し、その後、超高圧焼結装置に装入して、例えば、圧力:5GPa、温度:1200~1600℃の範囲内の所定の温度で焼結することにより、本発明のcBN焼結体を作製する。
(3) Molding and sintering The obtained sintered raw material powder is molded at a predetermined pressure to produce a molded body, which is pre-sintered at 1000 ° C. under vacuum, and then placed in an ultra-high pressure sintering device. The cBN sintered body of the present invention is produced by charging and sintering at a predetermined temperature in the range of, for example, pressure: 5 GPa and temperature: 1200 to 1600°C.
5.CBN工具
このように作製した本発明の、靭性に優れたcBN焼結体を工具基体とするcBN基超高圧焼結体製切削工具は、例えば、高硬度鋼の断続切削加工においても、耐欠損性に優れ、長期の使用にわたって優れた耐摩耗性を発揮する。
5. CBN Tool The cBN-based ultra-high-pressure sintered cutting tool, which uses a cBN sintered body with excellent toughness as a tool base, according to the present invention manufactured in this way is resistant to chipping even in interrupted cutting of high-hardness steel, for example. Excellent wear resistance over long-term use.
以下、本発明の実施例について記載する。 Examples of the present invention are described below.
本実施形態のcBN焼結体の製造では、結合相を構成するための原料粉末として、Y3Al5O12粉末を準備し、Y3Al5O12の粒径制御のため、ボールミルにて粉砕の処理を施した後、遠心分離法を用いて分級することにより所望の粒径範囲のY3Al5O12原料粉を用意した。
すなわち、平均粒径3μmのY3Al5O12粉末を準備し、超硬合金で内張りされた容器内に超硬合金製ボールとアセトンと共に充填し、蓋をした後にボールミルを用いて粉砕を実施後、混合したスラリーを乾燥させた後、遠心分離装置を用いて分級することにより平均粒径が10~200nmのY3Al5O12原料粉を得ることができる。
上記のように事前に準備したY3Al5O12原料粉と、平均粒径が0.3μm~0.9μmのTiN粉末、TiC粉末、TiCN粉末、TiAl3粉末を用意し、これら原料粉末の中から選ばれたいくつかの結合相構成用原料粉末(各原料粉末の体積%を表1に示す)と、硬質相用原料としてのcBN粉末の合量を100体積%としたときの焼結後のcBN粒子の含有割合が40~78体積%となるように配合し、湿式混合し、乾燥した。
次いで、得られた焼結体原料粉末を、成形圧1MPaで直径:50mm×厚さ:1.5mmの寸法にプレス成形し、ついでこの成形体を、圧力:1Pa以下の真空雰囲気中、1000℃の範囲内の所定温度に保持して仮焼結し、その後、超高圧焼結装置に装入して、圧力:5GPa、温度:1400℃の温度で焼結することにより、表2に示す本発明のcBN焼結体1~15(本発明焼結体1~15という)を作製した。なお、成形体に施す熱処理は、湿式混合時の溶媒を除去することが主な目的である。
また、上記作製工程は、超高圧焼結までの工程において原料粉末の酸化を防止することが好ましく、具体的には非酸化性の保護雰囲気中での取り扱いを実施することが好ましい。
本発明焼結体1のXRD図を図2に示す。
In the production of the cBN sintered body of the present embodiment, a Y 3 Al 5 O 12 powder is prepared as a raw material powder for forming the binder phase, and a ball mill is used to control the particle size of the Y 3 Al 5 O 12 . After pulverization, a Y 3 Al 5 O 12 raw material powder having a desired particle size range was prepared by classifying using a centrifugal separation method.
That is, a Y 3 Al 5 O 12 powder having an average particle size of 3 μm was prepared, filled with cemented carbide balls and acetone in a container lined with cemented carbide, covered, and then pulverized using a ball mill. Thereafter, the mixed slurry is dried and then classified using a centrifugal separator to obtain Y 3 Al 5 O 12 raw material powder having an average particle size of 10 to 200 nm.
The Y 3 Al 5 O 12 raw material powder prepared in advance as described above, and TiN powder, TiC powder, TiCN powder, and TiAl 3 powder having an average particle size of 0.3 μm to 0.9 μm were prepared, and these raw material powders were prepared. Sintering when the total amount of some raw material powders for forming the binder phase selected from among (the volume % of each raw material powder is shown in Table 1) and the cBN powder as the raw material for the hard phase is 100% by volume It was blended so that the content of cBN particles afterward was 40 to 78% by volume, wet-mixed, and dried.
Next, the obtained sintered raw material powder was press-molded into a size of diameter: 50 mm x thickness: 1.5 mm at a molding pressure of 1 MPa, and then this compact was placed in a vacuum atmosphere with a pressure of 1 Pa or less at 1000 ° C. Preliminarily sintered at a predetermined temperature within the range of, then charged into an ultra-high pressure sintering device and sintered at a pressure of 5 GPa and a temperature of 1400 ° C. The book shown in Table 2 Inventive cBN sintered bodies 1 to 15 (referred to as inventive sintered bodies 1 to 15) were produced. The main purpose of the heat treatment applied to the compact is to remove the solvent during wet mixing.
In addition, it is preferable that the raw material powder is prevented from being oxidized in the manufacturing process up to ultra-high pressure sintering.
FIG. 2 shows an XRD diagram of the sintered body 1 of the present invention.
比較のため、本発明において規定する範囲外のY3Al5O12平均粒径、含有割合を検討すべく、Y3Al5O12を含まないおよび含む原料をボールミルを用いて粉砕し、遠心分離装置を用いて分級し、平均粒径0.3μm~0.9μmのTiN粉末、TiCN粉末、TiAl3粉末を用意し、これら原料粉末の中から選ばれたいくつかの結合相構成用原料粉末(各原料粉末の体積%を表3に示す)と、硬質相としてのcBN粉末との含量を100体積%としたときの焼結後のcBN粒子の含有割合が56~65体積%となるように配合し、湿式混合し、乾燥した。
その後、本発明焼結体1~15と同様な条件で成形体を作製し、熱処理し、この成形体を、本発明焼結体1~15と同様な条件で超高圧高温焼結することにより、表4に示す比較例のcBN焼結体(以下、比較例焼結体という)1~5を作製した。
For comparison, raw materials containing and not containing Y 3 Al 5 O 12 were pulverized using a ball mill and centrifuged to examine the average particle size and content of Y 3 Al 5 O 12 outside the range specified in the present invention. TiN powder, TiCN powder, and TiAl3 powder having an average particle size of 0.3 μm to 0.9 μm are classified by using a separation device, and several raw material powders for forming a binder phase are selected from these raw material powders. (Volume % of each raw material powder is shown in Table 3) and the content of cBN powder as a hard phase is 100% by volume. , wet mixed and dried.
After that, a molded body is produced under the same conditions as the sintered bodies 1 to 15 of the present invention, heat treated, and this molded body is sintered at ultrahigh pressure and high temperature under the same conditions as the sintered bodies 1 to 15 of the present invention. , Comparative example cBN sintered bodies (hereinafter referred to as comparative example sintered bodies) 1 to 5 shown in Table 4 were produced.
次に、上記で作製した本発明品1~15、比較品1~5を、ワイヤー放電加工機で所定寸法に切断し、Co:5質量%、TaC:5質量%、WC:残りの組成およびISO規格CNGA120408のインサート形状をもった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、Cu:26質量%、Ti:5質量%、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、上下面および外周研磨、ホーニング処理を施すことにより、ISO規格CNGA120408のインサート形状をもつ本発明のcBN基超高圧焼結体切削工具(本発明工具という)1~15、および、比較例のcBN基超高圧焼結体切削工具(比較例工具という)1~5を製造した。 Next, the products 1 to 15 of the present invention and the comparative products 1 to 5 prepared above were cut into predetermined dimensions with a wire electric discharge machine, and Co: 5% by mass, TaC: 5% by mass, WC: the remaining composition and An Ag alloy having a composition consisting of Cu: 26% by mass, Ti: 5% by mass, and Ag: the rest is added to the brazing portion (corner portion) of a WC-based cemented carbide insert body having an insert shape according to ISO standard CNGA120408. The cBN-based ultra-high pressure sintered body cutting tool of the present invention having an insert shape of ISO standard CNGA120408 (referred to as the tool of the present invention) 1 to 15, and comparative cBN-based ultrahigh-pressure sintered cutting tools (referred to as comparative example tools) 1 to 5 were produced.
次いで、本発明工具1~15と比較工具1~5に対して、以下の切削条件で切削加工を実施し、欠損に至るまでの工具寿命(回数)を測定した。
<切削条件>
被削材:浸炭焼き入れ鋼(JIS・SCM415、硬さ:HRC58~62)の長さ方向等間隔8本縦溝入り丸棒、
切削速度:200m/min、
切り込み:0.1mm、
送り:0.1mm/rev
の条件での、高硬度鋼の乾式切削加工試験を実施。
各工具の刃先がチッピングあるいは欠損に至るまでの断続回数を工具寿命とし、断続回数500回毎に刃先を観察し、刃先の欠損やチッピングの有無を確認した。
表5に、上記切削加工試験の結果を示す。
Next, the tools 1 to 15 of the present invention and the comparative tools 1 to 5 were subjected to cutting under the following cutting conditions, and the tool life (number of times) until breakage was measured.
<Cutting conditions>
Work material: Carburized and quenched steel (JIS/SCM415, hardness: HRC58-62) round bar with 8 equally spaced longitudinal grooves,
Cutting speed: 200m/min,
Notch: 0.1 mm,
Feed: 0.1mm/rev
Conducted a dry cutting test of high-hardness steel under the conditions of
The tool life was defined as the number of interruptions until the cutting edge of each tool chipped or fractured.
Table 5 shows the results of the cutting test.
表5に示される結果から、本発明工具は、比較例工具に比して、突発的な刃先の欠損、チッピングが発生することなく、工具寿命が延命化されており、靱性が向上したことが分かる。 From the results shown in Table 5, it was found that the tool of the present invention had a longer tool life and improved toughness without the occurrence of sudden breakage and chipping of the cutting edge as compared with the comparative example tool. I understand.
本発明の靱性に優れたcBN焼結体は、靱性が高くCBN工具の工具基体として用いると、欠損、破損を発生することなく長期の使用にわたって、優れた耐欠損性を発揮し、工具寿命の延命化が図られるものであることから、切削加工装置の高性能化、並びに切削加工の省力化および省エネ化、低コスト化に十分満足に対応できるものである。 The cBN sintered body having excellent toughness of the present invention has high toughness and when used as a tool substrate of a CBN tool, exhibits excellent chipping resistance over a long period of use without causing chipping or breakage, and extends the tool life. Since it is intended to extend the life, it can satisfactorily meet demands for higher performance of cutting equipment, labor saving and energy saving in cutting, and cost reduction.
Claims (2)
前記結合相には、平均粒径が10nm以上200nm以下のY3Al5O12が、前記cBN焼結体に対する含有割合として1体積%以上20体積%以下となるように分散していることを特徴とするcBN焼結体。 In a cBN sintered body consisting of cubic boron nitride particles and a binder phase ,
In the binder phase, Y 3 Al 5 O 12 having an average particle size of 10 nm or more and 200 nm or less is dispersed so that the content ratio of the cBN sintered body is 1 volume % or more and 20 volume % or less. A cBN sintered body characterized by:
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
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US20070134494A1 (en) | 2003-12-03 | 2007-06-14 | Dole Stephen L | Cubic boron nitride sintered body and method for making the same |
JP2015193072A (en) | 2014-03-28 | 2015-11-05 | 三菱マテリアル株式会社 | Cutting tool comprising sintered body of cubic boron nitride |
WO2017204152A1 (en) | 2016-05-23 | 2017-11-30 | 三菱マテリアル株式会社 | Cubic boron nitride sintered compact cutting tool |
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US20070134494A1 (en) | 2003-12-03 | 2007-06-14 | Dole Stephen L | Cubic boron nitride sintered body and method for making the same |
JP2015193072A (en) | 2014-03-28 | 2015-11-05 | 三菱マテリアル株式会社 | Cutting tool comprising sintered body of cubic boron nitride |
WO2017204152A1 (en) | 2016-05-23 | 2017-11-30 | 三菱マテリアル株式会社 | Cubic boron nitride sintered compact cutting tool |
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