JP2004218048A - Composite hard sintered compact and composite member and cutting tool using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite hard sintered compact possessing excellent chipping resistance and excellent abrasion resistance and to provide a cutting tool using the same. <P>SOLUTION: A composite hard sintered compact 11 is characterized in that the Young's modulus E of the whole sintered product 11 is at least 85% of the theoretical Young's modulus Et, wherein the sintered compact 11 is prepared by coating the circumference of a long core material 12 comprising a cemented carbide, which is prepared by binding tungsten carbide particles with a binding metal comprising cobalt and/or nickel, with a coating layer 13 comprising a cemented carbide or a binding metal different from the core material 12 in composition. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２２】
なお、式１のｆ_ＷＣ（炭化タングステン粒子の含有体積比率）は走査型電子顕微鏡写真から画像解析法により測定することができる。また、硬質結晶粒子として炭化タングステン粒子以外に、４ａ、５ａおよび６ａ族金属の他の炭化物であるいわゆるβ相が３０体積％以下、特に１０体積％以下の割合で少量存在する場合には、本発明においては計算の簡便のために炭化タングステン粒子とみなして計算する。
【００２３】
本発明によれば、複合硬質焼結体１１の構成を制御して組み合わせることにより、芯材１２と被覆層１３との間に圧縮残留応力を付与することができる結果、上記ヤング率の比（実測ヤング率Ｅ／理論ヤング率Ｅｔ）×１００（％）を８５％以上、特に９０％以上と高めることができ、これによって、複合硬質焼結体が剥離せず、かつ剛性が向上して、変形しにくい切削工具、特に耐欠損性、耐摩耗性、耐折損性および穴位置精度の高いドリルを作製できる。
【００２４】
すなわち、上記ヤング率の比（Ｅ／Ｅｔ）が８５％より低くなると切削工具の変形が顕在化して加工寸法精度が低下したり、ドリル加工等の穴あけ加工においては穴位置精度が低下する。
【００２５】
また、本発明によれば、芯材１２および被覆層１３の両方に結合金属が存在し、両者間で若干結合金属の移動が生じるために、芯材１２および被覆層１３間、または隣接する複合硬質焼結体１１，１１間で剥離が生じることなく良好な密着性を有するものである。
【００２６】
なお、芯材１２の熱膨張係数αｃと被覆層１３の熱膨張係数αｓの比（αｓ／αｃ）を１．１以上とするには、芯材１２と被覆層１３の炭化タングステン粒子の平均粒径、結合金属量（炭化タングステン粒子量）、および製造方法を後述する方法に制御することが必要である。
【００２７】
ここで、複合硬質焼結体１１を構成する芯材１２の直径ｄ_ｃの被覆層１３の厚さｄ_ｓに対する比率ｄ_ｃ／ｄ_ｓは用途によって異なるが、切削工具に使用する際には、５〜１００、好ましくは１０〜５０、より好ましくは２０〜３０であるのがよい。特に、芯材１２の直径は、その用途に応じて適宜設定されるが、切削工具に用いる場合には、５〜５０μｍ、特に１０〜３０μｍが適当である。
【００２８】
また、本発明によれば、複合硬質焼結体は、上記した複合硬質焼結体１１単体からなる構造のみならず、図２に示すように、（ａ）複合硬質焼結体１１を複数本集束した複合部材１５、（ｂ）複合硬質焼結体１１または集束された複合硬質焼結体を複数本配列してシート化した複合部材１５ａ、さらに、（ｃ）このシート化した複合部材１５ａを複数枚積層した複合部材１５ｂなどが挙げられる。複合部材１５ｂの場合、（ｄ）に示すように、上下のシートの向きを変えることも可能である。
【００２９】
（製法）
次に、本発明の複合硬質焼結体１１の製造方法について図３および図４の模式図を参照して説明する。
【００３０】
＜芯材用成形体の成形工程＞
まず、望ましくは平均粒径０．７μｍ以下の前記硬質粒子と、平均粒径が０．５〜３μｍの結合金属粉末とを混合し、必要に応じて、さらにこの混合物に焼結助剤成分粉末、有機バインダ、可塑剤、溶剤、分散剤、滑剤等を添加して混練した後、得られた混合物をプレス成形または鋳込み成形等の成形法により円柱形状に成形して芯材用成形体１２ａを作製する（図３（ａ）参照）。ここで、後述する共押出成形によって均質な複合成形体を得るためには、前記有機バインダの添加量を３０〜７０体積％、特に４０〜６０体積％とするのが望ましい。
【００３１】
有機バインダ、可塑剤としては、パラフィンワックス、ポリスチレン、ポリエチレン、エチレン‐エチルアクリレート、エチレン‐ビニルアセテート、ポリブチルメタクリレート、ポリエチレングリコール、ジブチルフタレート等を使用することができる。溶剤、分散剤および滑剤としてはポリエチレングリコール、ミネラルオイル、ブチルオリエート、ステアリン酸等を使用することができる。
【００３２】
＜被覆層用成形体の成形工程＞
また、被覆層１３を、芯材１２と同様の硬質焼結体によって形成する場合、平均粒径が０．１〜２μｍの炭化タングステン原料と、平均粒径が２μｍ以下の結合金属粉末とを混合して混合物を得、必要に応じて、さらにこの混合物に上記した焼結助剤成分粉末、有機バインダ、可塑剤、溶剤等を添加し、得られた混合物をプレス成形または鋳込み成形等の成形法により半割円筒形状に成形して２つの被覆層用成形体１３ａ，１３ａを作製する（図３（ｂ）参照）。
【００３３】
さらに、被覆層１３を金属によって形成する場合、平均粒径が１〜１０μｍの金属粉末をプレス成形または鋳込み成形等の成形法により半割円筒形状に成形して２つの被覆層用成形体１３ａ、１３ａを作製する。
【００３４】
その後、上記のようにして得られた芯材用成形体１２ａの外周面を被覆層用成形体１３ａ、１３ａによって覆うように配置して複合成形体１１ａを作製する（図３（ｃ）参照）。
【００３５】
（共押出成形工程）
ついで、図３（ｄ）に示すように、押出機１００を用いて、上記複合成形体１３ａを押出成形（芯材用成形体１２ａと被覆層用成形体１３ａ，１３ａを同時に押出す共押出成形）することによって、芯材用成形体１２ａの周囲に被覆層用成形体１３ａが被覆され、細い径に伸延された複合成形体１１ｂを作製する。このとき、複合成形体１１ｂの断面は、押出機１００の出口形状を変えることによって、円形の他、三角形、四角形、五角形、六角形、楕円形等の任意形状に成形することもできる。
【００３６】
なお、上記共押出成形において、複合成形体１１ａの最大径Ｄ１と共押出成形後の複合成形体１１ｂの最大径Ｄ２との比率Ｄ２／Ｄ１は、０．０２〜０．２が適当である。
【００３７】
（マルチフィラメント構造の作製）
また、本発明によれば、図３に示したような、複合硬質焼結体を束ねた複合部材、いわゆるマルチフィラメント構造を有する部材を形成する場合には、図４（ａ）に示すように、前述のようにして作製した複合成形体１１ｂを束ねて集束成形体１４を形成する。その場合、複合成形体１１ｂ間に上記バインダなどの接着材を介在させ、さらに、この集束成形体１４にＣＩＰなどによって圧力を印加するものであってもよいが、必要に応じ、集束成形体１４を押出成形して、集束成形体１４を細い径に伸延することもできる。この方法によれば、成形体中の複合硬質焼結体同士のより強固な密着性を得ることもできる。
【００３８】
さらには、複合成形体１１ｂまたは集束成形体１４を平面方向に複数本配列してシート化することも、またそのシートを積層することも可能である。シートを積層する場合、各複合成形体１１ｂの軸方向をシート間で任意の角度（例えば０°、４５°、９０°等）に変化させて積層することも可能である。その場合、図４（ｂ）に示すように、シート単体やシート積層体からなる複合成形体１４をロール圧延することもできる。
【００３９】
上記のようにして得られた複合硬質成形体は、さらに公知のラピッドプロトダイビング法等の成形方法によって任意の形状に成形することも可能である。また、上記したシートまたはこのシートを断面方向にスライスしたものを従来の超硬合金等の硬質焼結体の表面に貼り合わせ、または接合することも可能である。
【００４０】
（焼成工程）
ついで、上記各種の成形体を３００〜７００℃で１０〜２００時間昇温または保持して脱バインダ処理した後、真空中または不活性雰囲気中において、使用する材質に応じた所定温度および所定時間で焼成することにより、図１に示すようなシングルフィラメント構造の複合硬質焼結体１１または図２のマルチフィラメント構造の複合部材１５を作製することができる。
【００４１】
特に、芯材１２を周期律表第４ａ，５ａ，６ａ族金属の群から選ばれる少なくとも１種の炭化物、窒化物、炭窒化物からなる硬質結晶粒子と、鉄族金属からなる結合金属によって形成する場合には、Ａｒ、Ｎ_２または真空雰囲気中で１３００〜１６００℃で０．５〜２時間程度焼成することが望ましい。
【００４２】
また、芯材１２と被覆層１３とは、上記のように同時焼成されることから、芯材１２を形成する材料と被覆層１３を形成する材料の各最適焼成温度が１００℃以内に近似した材質からなることが望ましい。
【００４３】
本発明の複合硬質焼結体は、耐欠損性および耐摩耗性に優れているので、例えばドリル、フライス、エンドミル、ドリルビット等の切削工具等の材料として使用した場合であっても、充分な耐欠損性および耐摩耗性が得られる。
【００４４】
特に略円柱状で高い穴位置精度が要求されるプリント基板加工用または金属加工用ドリルの材料として好適である。この場合、ドリルは、図２（ａ）のように複合焼結体を集束させた円柱状の複合部材を用いて形成され、ドリルの長手方向と複合焼結体の長手方向とが平行になるようにして用いられる。これらの切削工具は、例えば上記した手順で円柱形状や直方体形状に成形された複合硬質焼結体を、公知の方法により切削加工して切削工具形状に成形することにより製造することができる。
【００４５】
【実施例】
実施例１〜４，比較例１
平均粒径が０．３〜０．５μｍの炭化タングステン、平均粒径１．５μｍの他金属炭化物、平均粒径が１．０〜２．０μｍのＣｏ粉末を用いて、表１に示す組成物からなる芯材および被覆層の組み合わせにおいて複合硬質焼結体を以下の手順で作製した。
【００４６】
まず、表１に示した調合組成において芯材用および被覆層用の原料粉末を秤量混合し、これに有機バインダ（セルロースおよびポリエチレングリコール）３０体積％と溶剤（ポリビニルアルコール）２０体積％の割合で添加して混合物を得た。この混合物を芯部材については直径が２０ｍｍの円柱形状に押出成形して図３（ａ）に示すような芯材用成形体１２ａを作製した。
【００４７】
ついで、被覆層用の混合物を半割円筒形状に押出成形して図３（ｂ）に示すような厚みが１ｍｍの被覆層用成形体１３ａを２つ作製した。得られた２つの被覆層用成形体１３ａ，１３ａを上記芯材用成形体１２ａの外周面を覆うように配置して、図３（ｃ）に示すような成形体１１ａを作製した。
【００４８】
ついで、この成形体１１ａを共押出成形して、図２（ｄ）に示すような伸延された直径が１ｍｍの複合成形体１１ｂを作製した。
【００４９】
さらに複合成形体１１ｂを３８０本集束して集束成形体を得、この集束成形体を図４（ａ）に示すように、上記した押出成形工程と同様にして再度共押出成形してマルチフィラメント構造の複合成形体１１ｃを得た。この際マルチフィラメント構造の複合成形体１１ｃ中の単一構造体セル径は約３０μｍであった。
【００５０】
ついで、この複合成形体１１ｃを３００〜７００℃まで７２時間で昇温させることによって脱バインダ処理を行った後、昇温速度２．５℃／分でさらに昇温し、真空中、１５００℃で２時間焼成し、さらに３℃／分で降温することにより、図２（ａ）に示すような形状で、長さ５５ｍｍ、直径５ｍｍの複合硬質焼結体１５を作製した。得られた焼結体を波長分散型Ｘ線マイクロアナリシス分析を行い、鉄族金属結合相（Ｃｏ）硬質相（ＷＣ、Ｂ１型固溶体相）の体積比率を算出した。ＥＰＭＡの条件は、加速電圧１５ｋＶ、プローブ電流３×１０^−７Ａ、スポットサイズ２μｍである。
【００５１】
得られた複合硬質焼結体１５をドリル形状に加工し、外径０．３ｍｍφのドリルを得た。
【００５２】
【表１】

【００５３】
比較例２
平均粒径１μｍのＷＣ粉末を９０質量％、平均粒径１．５μｍのＣｏ粉末を１０質量％の割合で秤量混合し、これに有機バインダ（パラフィンワックス）を１５体積％の割合で添加して、円柱形状に圧粉成形し、これを実施例１と同様の条件で焼成して硬質焼結体を得た。この硬質焼結体から実施例１と同様にしてドリルを得た。
【００５４】
実施例１〜４および比較例１，２で得たドリルについて、ひずみゲージ法にて実測ヤング率Ｅを測定し、また、このドリルの芯材および被覆層の結合金属の含有比率を走査型電子顕微鏡写真から画像解析法にて求め、理論ヤング率Ｅｔを算出し、その比率（Ｅ／Ｅｔ）を求めた。
【００５５】
また、実施例１〜４および比較例１，２で得た各ドリルを取り付けた穴あけ工具を用いて、下記条件にて、穴あけ加工試験を行った。
【００５６】
主軸回転数：１２ｋｒｐｍ
送り：２．０ｍ／ｍｉｎ．
基板：エポキシ系０．８ｍｍ厚みの３枚重ね
寿命評価：上記条件によりドリルが折れるまで加工できた穴数を測定した。
【００５７】
穴位置評価：上記条件により１５００穴を加工し、基板上面での穴位置に対する基板下面でのそれぞれ穴位置分布から平均ばらつき：Ｘ、標準偏差３σを算出することによって穴位置精度を求めた。なお、今回の試験では平均ばらつきＸが７０μｍ未満、標準偏差３σが６５未満を合格とした。また、穴開け終了後のドリルの刃先を顕微鏡で観察し、切刃の欠損の有無を調べた。結果を表２に示す。
【００５８】
【表２】

【００５９】
表２の結果から、複合硬質焼結体のヤング率比（Ｅ／Ｅｔ）が８５％以上の実施例１〜４については耐折損性およびチッピングに対して優れた性能を示すとともに高い穴位置精度を示した。これに対し複合硬質焼結体のヤング率比（Ｅ／Ｅｔ）が８５％より低い比較例１、および単一の材質からなり複合硬質焼結体のヤング率比（Ｅ／Ｅｔ）が８５％より低い比較例２には折損やチッピングが生じ、穴位置精度についても劣る結果であった。
【００６０】
【発明の効果】
以上詳述した通り、本発明によれば、芯材に結合金属量の少ない超硬合金、被覆層に結合金属量の多い超硬合金またはコバルトやニッケルの結合金属を組み合わせたり、または芯材に熱膨張の小さい超硬合金、被覆層に熱膨張の大きい超硬合金または結合金属を組み合わせる等、焼結における収縮過程および実使用環境における高温時に複合硬質焼結体中に残留応力が付与されて複合硬質焼結体のヤング率を高める組み合わせを選択することにより、複合硬質焼結体が剥離せず、かつ剛性が向上して、変形しにくい切削工具、特に耐欠損性、耐摩耗性、耐折損性および穴位置精度の高いドリルを作製できる。
【図面の簡単な説明】
【図１】本発明の複合硬質焼結体の一実施形態を示す斜視図である。
【図２】本発明の複合部材の一実施形態を示す斜視図である。
【図３】（ａ）〜（ｄ）は、本発明の複合硬質焼結体の製造方法を説明するための工程図である。
【図４】本発明の複合部材の製造方法を説明するための図である。
【符号の説明】
１１ 複合硬質焼結体（シングルフィラメント構造）
１２ 芯材
１３ 被覆層
１５ 複合部材（マルチフィラメント構造）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a composite hard sintered body in which a long core material is covered with a coating layer, a composite member having a structure in which a plurality of these are bundled, and a cutting tool using the same.
[0002]
[Prior art]
Conventionally, in order to improve the toughness together with the hardness and strength of the material, the outer peripheral surface of a long core material formed of a sintered body such as a metal oxide, carbide, nitride, carbonitride, etc. Studies have been made on a composite hard sintered body covered with a coating layer made of a sintered body, and proposed in Patent Documents 1 to 3, for example. It is described that the composite hard sintered bodies described in these documents can increase the fracture resistance of the structure and increase the toughness without lowering the hardness.
[0003]
Further, cemented carbide is commonly used as a cutting tool such as a drill. For example, as shown in Table 1 in Patent Document 4 below, by setting the content of a bonding metal in a cemented carbide to 5% by weight or less, Young is used. It is described that a drill made of a high-hardness cemented carbide can be manufactured.
[0004]
[Patent Document 1]
US Pat. No. 6,063,502 [Patent Document 2]
US Pat. No. 5,645,781 [Patent Document 3]
JP 2001-506930 A [Patent Document 4]
JP 10-138027 A
[Problems to be solved by the invention]
However, when the amount of the bonding metal is simply reduced as in Patent Literature 4, the toughness of the cemented carbide is reduced, so that the cemented carbide may be broken from the base of the drill depending on the processing conditions of the drill. On the other hand, when a conventional composite hard sintered body as described in Patent Documents 1 to 3 above is used as it is for a cutting tool such as a drill, peeling occurs between the core material and / or the coating layer, or rigidity is reduced. As a result, the hole position accuracy of the drill decreases, and the deformation of the drill and other cutting tools becomes apparent, and in any case, the cutting performance of the cutting tool, especially the drill and the end mill, etc., was not sufficiently satisfied. .
[0006]
Therefore, an object of the present invention is to increase the rigidity to such an extent that the entire composite member having a structure in which the long core material is coated with a coating layer and a plurality of the composite hard sintered bodies is not peeled off. To provide a composite hard sintered body having excellent fracture resistance, wear resistance, breakage resistance and high hole position accuracy, a composite member using the same, and a cutting tool such as a drill using the same. It is.
[0007]
[Means for Solving the Problems]
The present inventors have studied the configuration of the core material and the skin member of the composite hard sintered body with respect to the above-described problems, and as a result, have found that a cemented carbide having a small amount of binding metal in the core material and an ultra-hard alloy having a large amount of binding metal in the coating layer. Shrinkage process and actual use in sintering, such as combining hard metal or binding metal such as cobalt or nickel, or cemented carbide with low thermal expansion for core material and cemented carbide or bonding metal with high thermal expansion for coating layer By selecting a combination that increases the Young's modulus of the composite hard sintered body by applying residual stress to the composite hard sintered body at high temperatures in the environment, the composite hard sintered body does not peel off, and the rigidity is improved. It has been found that a cutting tool that is not easily deformed, in particular, a drill having high chipping resistance, wear resistance, breakage resistance and hole position accuracy can be manufactured.
[0008]
That is, in the composite hard sintered body of the present invention, the outer peripheral surface of a long core material made of a cemented carbide in which tungsten carbide particles are bonded with a bonding metal made of cobalt and / or nickel is defined as the core material. A composite hard sintered body coated with a coating layer made of a cemented carbide or a bonding metal having a different composition, wherein the Young's modulus E of the entire composite hard sintered body is 85% or more of the theoretical Young's modulus Et. It is characterized by being.
[0009]
Further, since the average particle size of the tungsten carbide particles in the cemented carbide as the core material is 0.7 μm or less, a cutting tool such as a drill having high wear resistance and breakage resistance can be obtained.
[0010]
Further, a cemented carbide having a binding metal amount of less than 10% by volume as the core material and a cemented carbide or a binding metal having a binding metal amount of 10% by volume or more as the coating layer, or When the ratio (αs / αc) of the thermal expansion coefficient αc at room temperature (25 ° C.) to the thermal expansion coefficient αs of the coating layer at room temperature (25 ° C.) is 1.1 or more, the entire composite hard sintered body is obtained. The Young's modulus E can be 85% or more of the theoretical Young's modulus Et.
[0011]
According to the present invention, the composite hard sintered body may be a single filament having a structure in which the outer periphery of one core material is covered with a coating layer, but a plurality of the single filaments are bundled. It may be a composite member having a multifilament structure.
[0012]
The single-filament structure made of the composite hard sintered body can improve the fracture resistance and wear resistance depending on the material selected for the core material / coating layer. In the structure, since the concentration gradient of the bonding metal is continuously generated between the adjacent sintered bodies in the entire circumferential direction, the distribution of the core material and the coating layer is averaged, and the local characteristic variation is equalized. As a result of stabilizing the properties as a whole, the fracture resistance is remarkably improved, and the wear resistance can be easily improved by controlling the amount of the bonding metal of the selected material and the particle size of the hard phase. For this reason, the multifilament structure is useful for a wide range of cutting tools such as milling, a drill, and an end mill.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a composite hard sintered body of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a composite hard sintered body 11 of the present embodiment. As shown in the figure, the composite hard sintered body 11 has a structure in which an outer peripheral surface of a long core material 12 is covered with a coating layer 13.
[0014]
The core 12 is made of a hard sintered body in which hard crystal particles are bonded with a bonding metal, and the coating layer 13 is made of a material different from the core 12.
[0015]
(Core material)
The cemented carbide forming the core material 12 is, specifically, formed by bonding tungsten carbide particles, which are hard crystal particles, with a bonding metal made of Co and / or Ni. In addition, at least one carbide, nitride, or carbonitride selected from the group of metals of Groups 4a, 5a, and 6a excluding tungsten carbide, specifically, TiC, TiCN, TiN, TaC, and NbC , ZrC, ZrN, VC, Cr ₂ C, and Mo ₂ C may be dispersed and contained.
[0016]
The hard crystal particles in the core material preferably have an average particle size of 0.7 μm or less, and more preferably 0.2 to 0.5 μm in terms of enhancing the fracture resistance, wear resistance, and breakage resistance of the drill, and In this hard sintered body, the core material has a bonding metal content of less than 10% by volume, particularly 6 to 8% by volume, and the coating layer 13 has a bonding metal content of 10% by volume or more, particularly 12 to 16% by volume. It is effective to increase the wear resistance and breakage resistance, increase the Young's modulus of the composite hard sintered body, improve the drill hole position accuracy, and increase the deformation resistance of the cutting tool as a whole. .
[0017]
(Coating layer material)
On the other hand, the coating layer 13 is made of a single bonding metal or a cemented carbide having a different composition from the core material 12.
[0018]
The hard crystal particles in the coating layer 13 vary depending on the performance expected of the composite sintered body 11, but, for example, have an average particle diameter of 0.1 to 10 μm, preferably at least 10 μm, in order to achieve optimal characteristics as a cutting tool. The thickness is preferably 1 to 3 μm.
[0019]
(Young's modulus)
According to the present invention, in order to increase the Young's modulus of the entire composite hard sintered body 11, a cemented carbide having a bonding metal amount of 10% by volume or less as the core material 12 and a bonding metal amount of 15 vol. Volume percent or more of a cemented carbide or a bonding metal, or a ratio (αs / αs / coefficient of thermal expansion coefficient αc of the core material 12 at room temperature (25 ° C.) to thermal expansion coefficient αs of the coating layer 13 at room temperature (25 ° C.) When αc) is 1.1 or more, a residual stress is generated between the core material 12 and the coating layer 13 and the Young's modulus E of the composite hard sintered body 11 can be increased.
[0020]
Here, the actually measured Young's modulus E of the composite hard sintered body 11 in the present invention can be obtained by the strain gauge method of JISZ2280, and the theoretical Young's modulus Et can be calculated by the following equation 1.
[0021]
(Equation 1)

[0022]
Note that f _WC (volume ratio of tungsten carbide particles) in Formula 1 can be measured from a scanning electron micrograph by an image analysis method. In addition, in addition to the tungsten carbide particles as hard crystal particles, when a so-called β phase, which is another carbide of metals of groups 4a, 5a and 6a, is present in a small amount of 30% by volume or less, particularly 10% by volume or less, In the present invention, the calculation is performed assuming tungsten carbide particles for simplicity of calculation.
[0023]
According to the present invention, by controlling and combining the configuration of the composite hard sintered body 11, a compressive residual stress can be applied between the core material 12 and the coating layer 13, and as a result, the Young's modulus ratio ( The measured Young's modulus E / theoretical Young's modulus Et) × 100 (%) can be increased to 85% or more, particularly 90% or more, whereby the composite hard sintered body does not peel off and the rigidity is improved. A cutting tool that is not easily deformed, in particular, a drill with high chipping resistance, wear resistance, breakage resistance and hole position accuracy can be manufactured.
[0024]
That is, when the Young's modulus ratio (E / Et) is lower than 85%, the deformation of the cutting tool becomes apparent and the processing dimensional accuracy is reduced, or the hole position accuracy is reduced in drilling such as drilling.
[0025]
Further, according to the present invention, since the bonding metal exists in both the core material 12 and the coating layer 13 and the movement of the bonding metal slightly occurs between the two, the bonding between the core material 12 and the coating layer 13 or the adjacent composite The hard sintered bodies 11, 11 have good adhesion without peeling.
[0026]
In order to make the ratio (αs / αc) of the thermal expansion coefficient αc of the core material 12 to the thermal expansion coefficient αs of the coating layer 13 equal to or more than 1.1, the average particle size of the tungsten carbide particles of the core material 12 and the coating layer 13 is required. It is necessary to control the diameter, the amount of binding metal (the amount of tungsten carbide particles), and the production method to the methods described below.
[0027]
Here, when it ratio d _{c /} d _s to the thickness d _s of the coating layer 13 having a diameter d _c of the core 12 of the composite hard sintered body 11 varies depending on the application, to be used for cutting tools, It is good to be 5-100, preferably 10-50, more preferably 20-30. In particular, the diameter of the core material 12 is appropriately set according to its use, but when used for a cutting tool, 5 to 50 μm, particularly 10 to 30 μm is appropriate.
[0028]
Further, according to the present invention, the composite hard sintered body has not only the structure consisting of the above-described composite hard sintered body 11 alone, but also a plurality of (a) composite hard sintered bodies 11 as shown in FIG. The bundled composite member 15, (b) a composite member 15a formed by arranging a plurality of composite rigid sintered bodies 11 or a bundle of composite rigid sintered bodies into a sheet, and (c) the composite member 15a formed into a sheet. The composite member 15b in which a plurality of sheets are laminated is exemplified. In the case of the composite member 15b, the directions of the upper and lower sheets can be changed as shown in FIG.
[0029]
(Production method)
Next, a method for manufacturing the composite hard sintered body 11 of the present invention will be described with reference to the schematic diagrams of FIGS.
[0030]
<Molding process of molded body for core material>
First, desirably, the hard particles having an average particle size of 0.7 μm or less and a binding metal powder having an average particle size of 0.5 to 3 μm are mixed, and if necessary, the mixture is further mixed with a sintering aid component powder. After adding and kneading an organic binder, a plasticizer, a solvent, a dispersant, a lubricant, and the like, the resulting mixture is molded into a cylindrical shape by a molding method such as press molding or cast molding to form a core material molded body 12a. It is manufactured (see FIG. 3A). Here, in order to obtain a homogeneous composite molded article by co-extrusion molding described below, the amount of the organic binder to be added is preferably 30 to 70% by volume, particularly preferably 40 to 60% by volume.
[0031]
As an organic binder and a plasticizer, paraffin wax, polystyrene, polyethylene, ethylene-ethyl acrylate, ethylene-vinyl acetate, polybutyl methacrylate, polyethylene glycol, dibutyl phthalate and the like can be used. As the solvent, dispersant and lubricant, polyethylene glycol, mineral oil, butyl oleate, stearic acid and the like can be used.
[0032]
<Molding step of molding for covering layer>
When the coating layer 13 is formed of the same hard sintered body as the core material 12, a tungsten carbide raw material having an average particle size of 0.1 to 2 μm and a bonding metal powder having an average particle size of 2 μm or less are mixed. To obtain a mixture, and if necessary, further add the above-mentioned sintering aid component powder, an organic binder, a plasticizer, a solvent, and the like to the mixture, and mold the resulting mixture into a molding method such as press molding or cast molding. To form two coating layer forming bodies 13a, 13a (see FIG. 3B).
[0033]
Further, when the coating layer 13 is formed of a metal, the metal powder having an average particle size of 1 to 10 μm is formed into a half-cylindrical shape by a molding method such as press molding or cast molding to form two coating layer moldings 13a, 13a is produced.
[0034]
Thereafter, the composite molded body 11a is manufactured by arranging the outer peripheral surface of the core molded body 12a obtained as described above so as to be covered with the coating layer molded bodies 13a, 13a (see FIG. 3C). .
[0035]
(Co-extrusion molding process)
Next, as shown in FIG. 3D, the composite molded body 13a is extrusion-molded using an extruder 100 (co-extrusion molding for simultaneously extruding the molded body for core material 12a and the molded bodies for coating layer 13a, 13a). ), The molding 13a for the covering layer is coated around the molding 12a for the core material, and the composite molding 11b elongated to a small diameter is produced. At this time, by changing the exit shape of the extruder 100, the cross section of the composite molded body 11b can be formed into an arbitrary shape such as a triangle, a quadrangle, a pentagon, a hexagon, and an ellipse in addition to a circle.
[0036]
In the coextrusion molding, the ratio D2 / D1 of the maximum diameter D1 of the composite molded body 11a to the maximum diameter D2 of the composite molded body 11b after the coextrusion molding is appropriately 0.02 to 0.2.
[0037]
(Preparation of multifilament structure)
According to the present invention, when forming a composite member obtained by bundling composite hard sintered bodies as shown in FIG. 3, that is, a member having a so-called multifilament structure, as shown in FIG. Then, the composite molded body 11b produced as described above is bundled to form the bundle molded body 14. In this case, the adhesive such as the binder may be interposed between the composite molded bodies 11b, and further, pressure may be applied to the bundle molded body 14 by CIP or the like. Can be extruded to extend the bundle formed body 14 to a small diameter. According to this method, stronger adhesion between the composite hard sintered bodies in the molded body can be obtained.
[0038]
Further, a plurality of composite molded bodies 11b or bundle molded bodies 14 may be arranged in a plane direction to form a sheet, or the sheets may be stacked. When laminating the sheets, it is also possible to change the axial direction of each composite molded body 11b between the sheets at an arbitrary angle (for example, 0 °, 45 °, 90 °, or the like). In this case, as shown in FIG. 4B, the composite molded body 14 composed of a sheet alone or a sheet laminate can be roll-rolled.
[0039]
The composite hard molded body obtained as described above can be further molded into an arbitrary shape by a molding method such as a known rapid proto diving method. Further, the above-described sheet or a sheet obtained by slicing the sheet in a cross-sectional direction can be bonded or joined to a surface of a conventional hard sintered body such as a cemented carbide.
[0040]
(Baking process)
Then, after the above various molded bodies are heated or held at 300 to 700 ° C. for 10 to 200 hours and subjected to binder removal treatment, in a vacuum or an inert atmosphere, at a predetermined temperature and a predetermined time according to the material to be used. By firing, a composite hard sintered body 11 having a single filament structure as shown in FIG. 1 or a composite member 15 having a multifilament structure as shown in FIG. 2 can be produced.
[0041]
In particular, the core material 12 is formed by at least one kind of hard crystal particles made of a carbide, nitride, or carbonitride selected from the group of metals of Groups 4a, 5a, and 6a of the periodic table, and a bonding metal made of an iron group metal. In this case, it is desirable to perform firing at 1300 to 1600 ° C. for about 0.5 to 2 hours in an atmosphere of Ar, N ₂ or a vacuum.
[0042]
Further, since the core material 12 and the coating layer 13 are co-fired as described above, the optimum firing temperatures of the material forming the core material 12 and the material forming the coating layer 13 approximated to within 100 ° C. Desirably, it is made of a material.
[0043]
Since the composite hard sintered body of the present invention is excellent in fracture resistance and wear resistance, even when used as a material for cutting tools such as drills, milling cutters, end mills, drill bits, etc. Breakage resistance and abrasion resistance are obtained.
[0044]
In particular, it is suitable as a drilling material for processing a printed circuit board or a metal for which a substantially cylindrical shape and high hole position accuracy are required. In this case, the drill is formed using a cylindrical composite member obtained by converging the composite sintered body as shown in FIG. 2A, and the longitudinal direction of the drill and the longitudinal direction of the composite sintered body are parallel. It is used as follows. These cutting tools can be manufactured, for example, by cutting a composite hard sintered body formed into a columnar shape or a rectangular parallelepiped shape by the above-described procedure and cutting it into a cutting tool shape by a known method.
[0045]
【Example】
Examples 1-4, Comparative Example 1
Composition shown in Table 1 using tungsten carbide having an average particle size of 0.3 to 0.5 μm, other metal carbides having an average particle size of 1.5 μm, and Co powder having an average particle size of 1.0 to 2.0 μm. A composite hard sintered body was produced by the following procedure using a combination of a core material and a coating layer composed of:
[0046]
First, the raw material powders for the core material and the coating layer in the composition shown in Table 1 were weighed and mixed, and 30% by volume of an organic binder (cellulose and polyethylene glycol) and 20% by volume of a solvent (polyvinyl alcohol) were added thereto. Add to obtain a mixture. The mixture was extruded into a cylindrical shape having a diameter of 20 mm for the core member to produce a core material molded body 12a as shown in FIG.
[0047]
Then, the mixture for the coating layer was extruded into a half-cylindrical shape to produce two coating layer forming bodies 13a having a thickness of 1 mm as shown in FIG. 3 (b). The obtained two molded body 13a for a coating layer were arranged so as to cover the outer peripheral surface of the molded body 12a for a core material, thereby producing a molded body 11a as shown in FIG. 3 (c).
[0048]
Then, the molded body 11a was co-extruded to produce an elongated composite molded body 11b having a diameter of 1 mm as shown in FIG. 2 (d).
[0049]
Further, 380 composite molded bodies 11b are bundled to obtain a bundle molded body, and as shown in FIG. 4A, the bundle molded body is co-extruded again in the same manner as the above-mentioned extrusion molding step to form a multifilament structure. Was obtained. At this time, the cell diameter of the single structure body in the composite molded body 11c having the multifilament structure was about 30 μm.
[0050]
Then, after performing a binder removal treatment by raising the temperature of the composite molded body 11c from 300 to 700 ° C. for 72 hours, the temperature is further increased at a rate of 2.5 ° C./min, and the temperature is increased in vacuum at 1500 ° C. By firing for 2 hours and further lowering the temperature at 3 ° C./minute, a composite hard sintered body 15 having a shape as shown in FIG. 2A and a length of 55 mm and a diameter of 5 mm was produced. The obtained sintered body was subjected to wavelength-dispersive X-ray microanalysis analysis to calculate the volume ratio of the iron group metal binding phase (Co) hard phase (WC, B1 type solid solution phase). The EPMA conditions are an acceleration voltage of 15 kV, a probe current of 3 × 10 ⁻⁷ A, and a spot size of 2 μm.
[0051]
The obtained composite hard sintered body 15 was processed into a drill shape to obtain a drill having an outer diameter of 0.3 mmφ.
[0052]
[Table 1]

[0053]
Comparative Example 2
90 mass% of WC powder having an average particle diameter of 1 μm and 10 mass% of Co powder having an average particle diameter of 1.5 μm are weighed and mixed, and an organic binder (paraffin wax) is added thereto at a ratio of 15 vol%. Then, the powder was compacted into a cylindrical shape and fired under the same conditions as in Example 1 to obtain a hard sintered body. A drill was obtained from this hard sintered body in the same manner as in Example 1.
[0054]
With respect to the drills obtained in Examples 1 to 4 and Comparative Examples 1 and 2, the actually measured Young's modulus E was measured by a strain gauge method. The theoretical Young's modulus Et was calculated from the micrograph by an image analysis method, and the ratio (E / Et) was calculated.
[0055]
Further, a drilling test was performed under the following conditions using the drilling tools to which the drills obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were attached.
[0056]
Spindle speed: 12krpm
Feed: 2.0 m / min.
Substrate: Three layers of epoxy-based 0.8 mm thick laminated life evaluation: The number of holes processed until the drill was broken under the above conditions was measured.
[0057]
Hole position evaluation: 1500 holes were machined under the above conditions, and the hole position accuracy was determined by calculating the average variation: X and the standard deviation 3σ from the hole position distribution on the substrate lower surface with respect to the hole position on the substrate upper surface. In this test, the average variation X was less than 70 μm and the standard deviation 3σ was less than 65, which was regarded as acceptable. After drilling, the tip of the drill was observed under a microscope to determine whether the cutting edge was defective. Table 2 shows the results.
[0058]
[Table 2]

[0059]
From the results in Table 2, it is found that Examples 1-4 having a Young's modulus ratio (E / Et) of the composite hard sintered body of 85% or more exhibit excellent breakage resistance and chipping performance and high hole position accuracy. showed that. On the other hand, in Comparative Example 1 where the Young's modulus ratio (E / Et) of the composite hard sintered body was lower than 85%, and the Young's modulus ratio (E / Et) of the single hard material was 85%. In Comparative Example 2 which was lower, breakage and chipping occurred, and the result was also inferior in hole position accuracy.
[0060]
【The invention's effect】
As described in detail above, according to the present invention, a cemented carbide having a small amount of a binding metal in a core material, a cemented carbide having a large amount of a binding metal in a coating layer or a binding metal of cobalt or nickel, or a core material Residual stress is applied to the composite hard sintered body during the shrinkage process in sintering and at high temperatures in the actual use environment, such as combining a hard metal with low thermal expansion, a hard metal with high thermal expansion or a bonding metal in the coating layer. By selecting a combination that enhances the Young's modulus of the composite hard sintered body, the composite hard sintered body does not peel off and the rigidity is improved, and the cutting tool is hard to deform, especially chipping resistance, wear resistance, A drill with high breakage and hole position accuracy can be manufactured.
[Brief description of the drawings]
FIG. 1 is a perspective view showing one embodiment of a composite hard sintered body of the present invention.
FIG. 2 is a perspective view showing an embodiment of the composite member of the present invention.
3 (a) to 3 (d) are process diagrams for explaining a method for producing a composite hard sintered body of the present invention.
FIG. 4 is a view for explaining a method of manufacturing a composite member according to the present invention.
[Explanation of symbols]
11 Composite sintered body (single filament structure)
12 core material 13 coating layer 15 composite member (multifilament structure)

Claims (6)

The outer peripheral surface of a long core material made of a cemented carbide in which tungsten carbide particles are bound with a binding metal made of cobalt and / or nickel is made of a cemented carbide or a binding metal having a composition different from that of the core material. A composite hard sintered body covered by a coating layer, wherein the composite hard sintered body has a Young's modulus E of 85% or more of a theoretical Young's modulus Et. . The composite hard sintered body according to claim 1, wherein the average particle size of the tungsten carbide particles in the cemented carbide as the core material is 0.7 µm or less. The cemented carbide having a bonding metal content of less than 10% by volume as the core material, and a cemented carbide or a bonding metal having a bonding metal content of 10% by volume or more as the coating layer. The described composite hard sintered body The ratio (αs / αc) of the thermal expansion coefficient αc of the core material at room temperature (25 ° C.) to the thermal expansion coefficient αs of the coating layer at room temperature (25 ° C.) is 1.1 or more. 4. The composite hard sintered body according to any one of 1 to 3. A composite member having a structure in which a plurality of the composite hard sintered bodies according to claim 1 are bundled. A cutting tool comprising the composite hard sintered body according to claim 1 or a composite member according to claim 5.

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