JP2006193353A - Alumina sintered body, cutting insert, and cutting tool - Google Patents

Alumina sintered body, cutting insert, and cutting tool Download PDF

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JP2006193353A
JP2006193353A JP2005004833A JP2005004833A JP2006193353A JP 2006193353 A JP2006193353 A JP 2006193353A JP 2005004833 A JP2005004833 A JP 2005004833A JP 2005004833 A JP2005004833 A JP 2005004833A JP 2006193353 A JP2006193353 A JP 2006193353A
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sintered body
silicon carbide
alumina
alumina sintered
cutting
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Yuuki Hatano
祐規 波多野
Hiroko Nakayama
裕子 中山
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Niterra Co Ltd
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NGK Spark Plug Co Ltd
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<P>PROBLEM TO BE SOLVED: To provide an alumina sintered body containing silicon carbide and exhibiting excellent abrasion resistance while maintaining high heat resistance suitable for a high temperature structural material, to provide a cutting insert and a cutting tool using the alumina sintered body and exhibiting excellent chipping resistance and abrasion resistance at the time of high speed cutting work. <P>SOLUTION: This alumina sintered body comprises silicon carbide particles of 0.5-2 μm average particle diameter in an amount of 5-35 wt.% and the content of magnesium is ≤0.05 wt.% in terms of oxide. Preferably the average diameter of the alumina is 0.5-5 μm, the silicon carbide is substantially α-type silicon carbide and the ratio of whisker in the silicon carbide is ≤50%. Both the cutting insert and the cutting tool are obtained by using the alumina sintered body. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明はアルミナ焼結体、切削インサートおよび切削工具に関し、詳しくは、優れた耐熱性と耐摩耗性を持つアルミナ焼結体、並びにこれを利用した切削インサートおよび切削工具に関する。   The present invention relates to an alumina sintered body, a cutting insert, and a cutting tool, and more particularly, to an alumina sintered body having excellent heat resistance and wear resistance, and a cutting insert and a cutting tool using the same.

切削用工具は図2に例示する外径加工用ホルダーのように、ホルダーと呼ばれる支持体の先端に使い捨ての刃先である切削インサート(スローアウェイチップ、刃先交換チップなどを言う。)を取り付けた構造が多い。この切削インサートには被削材の種類、加工工程、切削速度などによって各種の材料が使用されている。例えば、超硬合金、サーメット、セラミック、CBN、さらにはこれらの表面に被膜を被覆した材料が用いられている。その中でも普通鋳鉄(FCと略称する)材の粗加工、特に高速加工には炭化珪素を複合化させたアルミナ焼結体は高硬度であると共に優れた耐熱性を有するため好適とされている。   The cutting tool has a structure in which a cutting insert which is a disposable blade tip (referred to as a throw-away tip, a blade tip replacement tip or the like) is attached to the tip of a support body called a holder, like the outer diameter processing holder illustrated in FIG. There are many. Various materials are used for the cutting insert depending on the type of work material, the machining process, the cutting speed, and the like. For example, cemented carbide, cermet, ceramic, CBN, and materials having a coating film on the surface thereof are used. Among them, an alumina sintered body combined with silicon carbide is suitable for rough machining of ordinary cast iron (abbreviated as FC), particularly high-speed machining, because it has high hardness and excellent heat resistance.

一般に、アルミナ焼結体は高硬度であると共に優れた化学的安定性、耐熱性を有するため、高温構造材料として知られている。特に炭化珪素を複合化させたアルミナ焼結体は靭性が高く、優れた高温構造材料とされている窒化珪素系セラミックと比較して鉄との親和性が低いため、鉄系材料の切削工具として優れた耐欠損性と耐摩耗性を示す。しかし、炭化珪素、特に炭化珪素ウィスカーをアルミナ中に分散させて焼結すると焼結体の緻密化が抑制されて難焼結性となる。このためホットプレスによる焼結を行わなければならず簡単な焼結法であるニアネットシェイプで製造することが困難であった。さらに、炭化珪素ウィスカーは非常に高価であり製造コストが高くなる問題があった。   In general, an alumina sintered body is known as a high-temperature structural material because it has high hardness and excellent chemical stability and heat resistance. In particular, alumina sintered bodies combined with silicon carbide have high toughness and low affinity with iron compared to silicon nitride ceramics, which are considered to be excellent high-temperature structural materials. Excellent fracture resistance and wear resistance. However, when silicon carbide, particularly silicon carbide whiskers are dispersed in alumina and sintered, densification of the sintered body is suppressed and the sintering becomes difficult. For this reason, sintering by hot pressing must be performed, and it has been difficult to manufacture with a near net shape which is a simple sintering method. Furthermore, silicon carbide whiskers are very expensive and have a problem of high manufacturing costs.

そのため特許文献1ではホットプレスによらなくとも、常圧焼結で緻密化が可能な2〜10重量%の粒状炭化珪素を複合化させることを提案している。特許文献2には5〜50容量%の粒状の炭化珪素に2〜30容量%のジルコニアを複合化させることが提案されている。ジルコニアの複合化により焼結性が改善され、炭化珪素の含有量が多くてもある程度まで緻密化可能となった。特許文献3には10〜25重量%の炭化珪素ウィスカーと2〜7.5重量%の窒化珪素、窒化アルミニウムを複合化させることが提案されている。窒化珪素、窒化アルミニウムの複合化により、焼結性が改善され常圧焼結による緻密化が可能となるとしている。また、特許文献4には粒状の炭化珪素とウィスカーを合計で5〜50重量%複合化したものに二硫化モリブデンを複合化させることが提案されている。二硫化モリブデンの複合化により焼結性が改善され、また低摩擦係数であるため摺動部材として使用すると耐摩耗性が改善されることが示されている。   Therefore, Patent Document 1 proposes to combine 2 to 10% by weight of granular silicon carbide that can be densified by atmospheric pressure sintering without using hot pressing. Patent Document 2 proposes that 2 to 30% by volume of zirconia is combined with 5 to 50% by volume of granular silicon carbide. The sinterability was improved by the compounding of zirconia, and it became possible to be densified to a certain extent even if the silicon carbide content was large. Patent Document 3 proposes to combine 10 to 25% by weight of silicon carbide whiskers with 2 to 7.5% by weight of silicon nitride and aluminum nitride. The compounding of silicon nitride and aluminum nitride improves the sinterability and enables densification by atmospheric pressure sintering. Further, Patent Document 4 proposes that molybdenum disulfide is compounded with a total of 5 to 50% by weight of granular silicon carbide and whiskers. It has been shown that by combining molybdenum disulfide, the sinterability is improved and the wear resistance is improved when used as a sliding member because of its low friction coefficient.

特許第2981689号公報Japanese Patent No. 2981689 特表平1−140901号公報Japanese National Publication No. 1-140901 特許第3554379号公報Japanese Patent No. 3554379 特許第2836866号公報Japanese Patent No. 2836866

上述のように、切削工具材料をはじめとする高温構造材料は、近年益々その要求性能が過酷化しているうえ、さらに高性能化、低コスト化も求められている。そして、これに応えるべくアルミナに炭化珪素を複合化させたセラミックをさらに改良した材料の実用化が検討されてきた。しかし、炭化珪素含有量が少ないと最近の過酷な使用条件下では性能が不十分という問題があった。炭化珪素含有量を増加するため焼結助剤としてジルコニアを用いると、1000℃を超える高温下では急激に強度が低下してしまう悪影響があり、1000℃以上の高温構造材料としては使用し難かった。窒化珪素や窒化アルミニウムを加える方法では、窒化珪素は鉄との親和性が高く、また窒化アルミニウムは低硬度であるため、耐摩耗性が低下してしまう問題があった。また、二硫化モリブデンの添加法も二硫化モリブデンの分解温度が低いためアルミナの粒成長が難しく、焼結体を完全に緻密化するのに工夫が必要である。その他にも低融点、低分解温度の成分を複合化し焼結性を改善させて緻密化を達成しようとするものが多数提案されているが、これらの材料を高温下で使用すると軟化や分解が生じやすくなり高温構造材料としては性能が不十分だった。   As described above, high-temperature structural materials such as cutting tool materials are increasingly demanding in recent years, and further, higher performance and lower cost are also required. In order to meet this demand, practical application of a material obtained by further improving a ceramic in which silicon carbide is combined with alumina has been studied. However, when the silicon carbide content is low, there is a problem that the performance is insufficient under recent severe use conditions. When zirconia is used as a sintering aid to increase the silicon carbide content, there is an adverse effect that the strength rapidly decreases at a high temperature exceeding 1000 ° C., and it is difficult to use as a high-temperature structural material at 1000 ° C. or higher. . In the method of adding silicon nitride or aluminum nitride, silicon nitride has a high affinity with iron, and aluminum nitride has a low hardness, so there is a problem that the wear resistance is lowered. Also, the addition method of molybdenum disulfide also makes it difficult to grow alumina grains because the decomposition temperature of molybdenum disulfide is low, and it is necessary to devise a method for completely densifying the sintered body. In addition, there have been many proposals to improve the sintering property by combining low melting point and low decomposition temperature components, but when these materials are used at high temperatures, softening and decomposition occur. It was likely to occur and the performance as a high-temperature structural material was insufficient.

本発明の目的はこうした観点から、高い耐熱性を維持したまま優れた耐摩耗性を発揮する高温構造材料に適した、炭化珪素を含有するアルミナ焼結体を提供することである。また、このアルミナ焼結体を用いて高速切削時に優れた耐欠損性、耐摩耗性を発揮する切削インサート、および切削工具を提供することである。   The objective of this invention is providing the alumina sintered compact containing a silicon carbide suitable for the high temperature structural material which exhibits the outstanding abrasion resistance, maintaining high heat resistance from such a viewpoint. Another object of the present invention is to provide a cutting insert and a cutting tool that exhibit excellent fracture resistance and wear resistance during high-speed cutting using the alumina sintered body.

本発明者らは上述の課題を解決するため以下の手段を見出した。
(1)平均粒径が0.5〜2μmの炭化珪素粒子を5〜35重量%含有し、マグネシウム含有量は酸化物換算で0.05重量%以下であるアルミナ焼結体である。
(2)炭化珪素粒子の含有率が10〜30重量%である(1)に記載のアルミナ焼結体である。
(3)アルミナの平均粒径が0.5〜5μmである(1)または(2)に記載のアルミナ焼結体である。
(4)炭化珪素が実質的にα型炭化珪素である(1)〜(3)のいずれかに記載のアルミナ焼結体である。
(5)炭化珪素中のウィスカーの比率が顕微鏡写真による面積比で50%以下である(1)〜(4)のいずれかに記載のアルミナ焼結体である。
(6)表面を硬質被膜で被覆した(1)〜(5)のいずれかに記載のアルミナ焼結体である。
(7)(1)〜(6)のいずれかに記載のアルミナ焼結体を用いた切削インサートである。
(8)ホルダーに(7)に記載の切削インサートを備えた切削工具である。
The present inventors have found the following means to solve the above-mentioned problems.
(1) An alumina sintered body containing 5 to 35% by weight of silicon carbide particles having an average particle size of 0.5 to 2 μm and a magnesium content of 0.05% by weight or less in terms of oxide.
(2) The alumina sintered body according to (1), wherein the content of silicon carbide particles is 10 to 30% by weight.
(3) The alumina sintered body according to (1) or (2), wherein the average particle diameter of alumina is 0.5 to 5 μm.
(4) The alumina sintered body according to any one of (1) to (3), wherein the silicon carbide is substantially α-type silicon carbide.
(5) The alumina sintered body according to any one of (1) to (4), wherein a ratio of whiskers in silicon carbide is 50% or less as an area ratio according to a micrograph.
(6) The alumina sintered body according to any one of (1) to (5), wherein the surface is coated with a hard coating.
(7) A cutting insert using the alumina sintered body according to any one of (1) to (6).
(8) A cutting tool provided with the cutting insert according to (7) in a holder.

本発明の焼結体はアルミナを主体とし、炭化珪素粒子を含むアルミナ焼結体である。炭化珪素は平均粒径が0.5〜2μm、好ましくは0.5〜1.5μmの粒子であり、焼結体に対し5〜35重量%、好ましくは10〜30重量%含んでいる。なお、炭化珪素ウィスカーも炭化珪素粒子とみなしている。炭化珪素含有量が10重量%未満、特に5重量%未満では、焼結時のアルミナの粒成長抑制効果が十分でないためアルミナ粒子が粗大化し焼結体の強度が低下する。炭化珪素含有量が30重量%、特に35重量%超えると、焼結性が低下し完全には緻密化できなくなり、やはり焼結体の強度が低下する。また、炭化珪素粒子の平均粒径が0.5μm未満であると、焼結時に炭化珪素粒子がアルミナ粒子内部に取り込まれてしまいアルミナの粒成長抑制効果が発揮できなくなり、アルミナ粒子が粗大化し焼結体の強度が低下する。5μmを超えると炭化珪素粒子自身が欠陥の原因となり、破壊の起点となって強度低下やチッピングを発生しやすい。   The sintered body of the present invention is an alumina sintered body mainly composed of alumina and containing silicon carbide particles. Silicon carbide is a particle having an average particle diameter of 0.5 to 2 μm, preferably 0.5 to 1.5 μm, and is contained in an amount of 5 to 35% by weight, preferably 10 to 30% by weight, based on the sintered body. Silicon carbide whiskers are also regarded as silicon carbide particles. If the silicon carbide content is less than 10% by weight, particularly less than 5% by weight, the effect of suppressing the grain growth of alumina during sintering is not sufficient, and the alumina particles become coarse and the strength of the sintered body decreases. When the silicon carbide content exceeds 30% by weight, particularly 35% by weight, the sinterability is lowered and cannot be completely densified, and the strength of the sintered body is lowered. Further, if the average particle size of the silicon carbide particles is less than 0.5 μm, the silicon carbide particles are taken into the alumina particles during sintering, and the effect of suppressing the grain growth of alumina cannot be exhibited, and the alumina particles are coarsened and sintered. The strength of the knot is reduced. If the thickness exceeds 5 μm, the silicon carbide particles themselves cause defects, and tend to cause strength reduction and chipping as a starting point of destruction.

本発明のアルミナ焼結体ではマグネシウムは少なくする必要がある。焼結体中のマグネシウムが酸化物、すなわちMgOとして換算したとき焼結体に対し0.05重量%以下、好ましくは0.03重量%以下となるようする。マグネシウム含有量が0.05重量%を超えるとアルミナや炭化珪素の粒界に低融点のマグネシウム化合物が形成され焼結体の高温強度が低下する。原料中の不純物や粉砕時の混入を抑制し、含有するマグネシウムを0.05重量%以下となるように制御することにより、焼結体は微細なアルミナ粒子中に炭化珪素粒子が均一に分散された組織となり緻密な焼結体となる。これにより耐熱性改善のための焼結性向上成分を多量に加えなくとも完全に緻密な焼結ができる。   Magnesium needs to be reduced in the alumina sintered body of the present invention. When magnesium in the sintered body is converted into an oxide, that is, MgO, it is 0.05% by weight or less, preferably 0.03% by weight or less based on the sintered body. When the magnesium content exceeds 0.05% by weight, a low melting point magnesium compound is formed at the grain boundaries of alumina and silicon carbide, and the high temperature strength of the sintered body is lowered. By controlling the impurities in the raw material and mixing at the time of pulverization and controlling the contained magnesium to be 0.05% by weight or less, silicon carbide particles are uniformly dispersed in fine alumina particles. It becomes a dense structure and becomes a dense sintered body. As a result, completely dense sintering can be performed without adding a large amount of a sinterability improving component for improving heat resistance.

本発明の好ましい態様は、アルミナの平均粒径が0.5〜5μm、好ましくは0.5〜2μmであるアルミナ焼結体である。アルミナの平均粒径が0.5μm未満ではクラックが直線的に成長し易く、炭化珪素の引き抜きが起こり易い。そのため、焼結体破壊時の破壊エネルギーが大きくできず破壊靱性が向上しない。またアルミナの平均粒径が大きすぎるとアルミナ粒子自身が破壊源となり強度が低下し、欠損やチッピングが発生しやすくなる。   A preferred embodiment of the present invention is an alumina sintered body having an average particle diameter of alumina of 0.5 to 5 μm, preferably 0.5 to 2 μm. If the average particle diameter of alumina is less than 0.5 μm, cracks are likely to grow linearly and silicon carbide is likely to be pulled out. Therefore, the fracture energy at the time of fracture of the sintered body cannot be increased and the fracture toughness is not improved. On the other hand, if the average particle diameter of alumina is too large, the alumina particles themselves become a source of destruction and the strength is reduced, and defects and chipping are likely to occur.

本発明の好ましい態様には、炭化珪素が実質的に多面体構造からなるα型炭化珪素である上記のアルミナ焼結体がある。α型炭化珪素はβ型炭化珪素に較べ耐熱性があり、α型炭化珪素を含む本発明のアルミナ焼結体を切削工具の刃先として使用した際に炭化珪素粒子の焼結体中からの脱落が生じ難く、刃先の強度を保持できる。   In a preferred embodiment of the present invention, there is the above-described alumina sintered body in which silicon carbide is α-type silicon carbide substantially having a polyhedral structure. α-type silicon carbide has higher heat resistance than β-type silicon carbide, and when the alumina sintered body of the present invention containing α-type silicon carbide is used as a cutting edge of a cutting tool, silicon carbide particles fall off from the sintered body. Is difficult to occur, and the strength of the blade edge can be maintained.

また、本発明のアルミナ焼結体は炭化珪素のうちウィスカーの比率が50%以下であることが好ましい。炭化珪素ウィスカーが存在すると、通常のα型炭化珪素に較べ焼結体は強靭となり耐欠損性が向上する。しかし、ウィスカーの比率が50%を超えると焼結性が低下し完全に緻密化することが困難になり、残留ポアが破壊源となって強度低下を招く。ウィスカーの比率は5〜40%、好ましくは10〜30%とすることが望ましい。なお、ウィスカーは高価であるので経済的側面からはあまり多いと好ましくない。炭化珪素中のウィスカーの比率は光学顕微鏡写真または電子顕微鏡写真による炭化珪素粒子全体に対するウィスカー炭化珪素粒子の面積比で算出する。図3には本発明のアルミナ焼結体の走査型電子顕微鏡(SEM)写真を、図4には光学顕微鏡写真を示す。光学顕微鏡写真の白く見える粒子が炭化珪素粒で、細長い粒子がウィスカーである。なお、電子顕微鏡写真の黒い線は混在するアルミナ粒子と炭化珪素粒子の輪郭であり、この写真では明確に区別することは困難であった。アルミナ粒子と炭化珪素粒子はこの写真では明確に区別することは困難であるが、SEMに取り付けたエネルギー分散X線分析(EDS)装置により面の元素分析を行うことで、アルミナ粒子と炭化珪素粒子を区別することができる。   The alumina sintered body of the present invention preferably has a whisker ratio of 50% or less in silicon carbide. When silicon carbide whiskers are present, the sintered body becomes tougher than normal α-type silicon carbide, and the fracture resistance is improved. However, if the whisker ratio exceeds 50%, the sinterability is lowered and it becomes difficult to achieve complete densification, and the residual pores become a fracture source, causing a reduction in strength. The whisker ratio is 5 to 40%, preferably 10 to 30%. In addition, since a whisker is expensive, it is unpreferable if there are too many from an economical side. The ratio of the whisker in silicon carbide is calculated by the area ratio of the whisker silicon carbide particles to the whole silicon carbide particles by an optical micrograph or an electron micrograph. FIG. 3 shows a scanning electron microscope (SEM) photograph of the alumina sintered body of the present invention, and FIG. 4 shows an optical microscope photograph. The particles that appear white in the photomicrograph are silicon carbide particles, and the elongated particles are whiskers. The black line in the electron micrograph is the outline of the mixed alumina particles and silicon carbide particles, and it was difficult to clearly distinguish them in this photo. Alumina particles and silicon carbide particles are difficult to distinguish clearly in this photograph, but by performing elemental analysis of the surface with an energy dispersive X-ray analysis (EDS) apparatus attached to the SEM, the alumina particles and silicon carbide particles Can be distinguished.

本発明の焼結体は上述の焼結体表面をセラミックスなどの硬質被膜で被覆してもよい。硬質被膜による被覆により高性能、長寿命の切削工具の刃先等として利用できる。硬質被膜としては、例えば窒化チタン、窒化ホウ素、炭化珪素、炭化ホウ素、炭化チタン、アルミナ、ダイアモンド、あるいはこれらの複合的な被膜が挙げられる。被覆法としてはCVD,PVD、スパッタリングおよび溶射などがあるが、CVD法やスパッタリング法が利用しやすい。   In the sintered body of the present invention, the surface of the above-mentioned sintered body may be coated with a hard film such as ceramics. It can be used as a cutting edge of a cutting tool with high performance and long life by coating with a hard coating. Examples of the hard coating include titanium nitride, boron nitride, silicon carbide, boron carbide, titanium carbide, alumina, diamond, or a composite coating thereof. Examples of the coating method include CVD, PVD, sputtering, and thermal spraying, but CVD and sputtering are easy to use.

上述した本発明のアルミナ焼結体は高温での硬度および耐摩耗性に優れた材料であり、高速切削用の切削工具の刃先として優れた性質を持っている。本発明のアルミナ焼結体を焼結前の成形時におよび焼結後の加工により切削インサートとしての所望の形状にすれば、本発明の切削インサートとなる。この切削インサートは耐熱性、耐摩耗性に優れた長寿命の切削用スローアウェイチップとして有用である。さらに、この切削インサートを切削工具用のホルダーに設置した本発明の切削工具は優れた切削工具として各種の切削加工、特に高速切削加工に好適に使用できる。   The above-described alumina sintered body of the present invention is a material excellent in hardness and wear resistance at high temperatures, and has excellent properties as a cutting edge of a cutting tool for high-speed cutting. If the alumina sintered body of the present invention is formed into a desired shape as a cutting insert during molding before sintering and by processing after sintering, the cutting insert of the present invention is obtained. This cutting insert is useful as a throw-away tip for long-life cutting having excellent heat resistance and wear resistance. Furthermore, the cutting tool of the present invention in which this cutting insert is installed in a holder for a cutting tool can be suitably used as an excellent cutting tool for various types of cutting, particularly high-speed cutting.

本発明のアルミナ焼結体の製造方法は、粒度を調節したアルミナ、炭化珪素等の原料粉末を、例えば窒素、アルゴン等の不活性ガス雰囲気下でホットプレス、常圧焼結、熱間静水圧加圧焼結等種々の焼結方法により焼結すればよい。製造コストが安価な常圧焼結を適用する場合には、通常の焼結同様、焼結助剤を添加し、必要に応じてバインダーを加えて、成形して焼結用成形体としておく。焼結助剤は好ましくは1000℃以上の融点、分解温度、またはアルミナとの共晶温度を有する酸化物を適宜選択する。さらに好ましくは希土類酸化物、例えばYb、Dyなどを、0.1〜2重量%の範囲で用いることができる。製造コストは高くなるがホットプレス焼結や熱間静水圧加圧焼結(HIPという)も適用することができる。この場合はバインダーや焼結助剤を不使用または低減できるので焼結体をより高性能化することができる。焼結温度、焼結時間、昇降温速度などは原料粉末、焼結助剤、焼結体性能等を考慮して適宜選択する。通常は最高温度1500〜1850℃で1〜10時間程度焼結すればよい。また、通常の焼結とHIPを組み合わせた二段階焼結する方法も効果的である。 The method for producing an alumina sintered body according to the present invention is a method in which raw material powders such as alumina and silicon carbide having a controlled particle size are hot-pressed, pressureless sintered, hot isostatic pressure in an inert gas atmosphere such as nitrogen and argon. What is necessary is just to sinter by various sintering methods, such as pressure sintering. In the case of applying atmospheric pressure sintering at a low manufacturing cost, a sintering aid is added and a binder is added as necessary to form a sintered compact as in the case of normal sintering. As the sintering aid, an oxide having a melting point of 1000 ° C. or higher, a decomposition temperature, or a eutectic temperature with alumina is appropriately selected. More preferably, rare earth oxides such as Yb 2 O 3 and Dy 2 O 3 can be used in the range of 0.1 to 2 % by weight. Although the manufacturing cost is increased, hot press sintering and hot isostatic pressing (referred to as HIP) can also be applied. In this case, since the binder and the sintering aid can be used or reduced, the sintered body can be improved in performance. The sintering temperature, the sintering time, the temperature raising / lowering speed, etc. are appropriately selected in consideration of the raw material powder, the sintering aid, the sintered body performance and the like. Usually, the sintering may be performed at a maximum temperature of 1500 to 1850 ° C. for about 1 to 10 hours. A two-step sintering method combining normal sintering and HIP is also effective.

本発明のアルミナ焼結体は炭化珪素の平均粒径と含有量を特定することで緻密で優れた耐摩耗性を有する焼結体としている。さらに、低融点の化合物を形成しないようマグネシウム含有量を特定して、高温下でも高強度の焼結体としている。例えばこのアルミナ焼結体を切削インサートとした切削工具や耐摩耗部材、摺動部材として使用した場合、材料の欠損やチッピングが発生することなく優れた耐摩耗性を発揮する。これらの工具や部材は長寿命で信頼性のある材料として非常に多くの用途に用いられる。   The alumina sintered body of the present invention is a dense sintered body having excellent wear resistance by specifying the average particle size and content of silicon carbide. Furthermore, the magnesium content is specified so as not to form a compound having a low melting point, and a high-strength sintered body is obtained even at a high temperature. For example, when this alumina sintered body is used as a cutting tool, wear-resistant member, or sliding member using a cutting insert, it exhibits excellent wear resistance without causing material loss or chipping. These tools and members are used for many purposes as long-lived and reliable materials.

本発明を実施するための最良の形態を実施例および比較例によって示す。   The best mode for carrying out the present invention will be described with reference to examples and comparative examples.

(1)インサートの作製
それぞれ表1に示すような平均粒径のアルミナ粉末に炭化珪素粉末または炭化珪素ウィスカー粉末を表1に示す割合で加え、さらに焼結助剤としてDy粉末を全体の1重量%加えた。この原料粉末をエタノールとともに混合用樹脂ポットに入れ、高純度アルミナボールを使用して混合し混合粉末を得た。この混合粉末を金型プレス成形し成形体を得た。この成形体を0.1MPaのアルゴンガス雰囲気中1600〜1800℃で1時間熱処理し、さらに100MPaのアルゴンガス雰囲気中1500℃で1時間HIP処理して焼結体を得た。この焼結体をISO規定SNGN120408の形状に加工し、切削インサートを作製した。作製した焼結体、切削インサートの性状、性能を表1に示した。
(1) Production of Inserts Silicon carbide powder or silicon carbide whisker powder is added to alumina powder having an average particle diameter as shown in Table 1 in the ratio shown in Table 1, and Dy 2 O 3 powder is further added as a sintering aid. Of 1% by weight. This raw material powder was put together with ethanol into a mixing resin pot and mixed using a high purity alumina ball to obtain a mixed powder. The mixed powder was press-molded to obtain a molded body. This compact was heat-treated at 1600-1800 ° C. for 1 hour in an argon gas atmosphere of 0.1 MPa, and further subjected to HIP treatment at 1500 ° C. for 1 hour in an argon gas atmosphere of 100 MPa to obtain a sintered body. This sintered body was processed into the shape of ISO regulation SNGN120408 to produce a cutting insert. Table 1 shows the properties and performance of the produced sintered body and cutting insert.

(2)焼結体の性状(机上性能と呼ぶ)
上記焼結体のマグネシウムの含有成分量は蛍光X線分析装置により測定し、MgO換算で表示した。焼結体中の粒子の平均粒径は走査型電子顕微鏡写真から算出した。炭化珪素中のウィスカーの量は上述の方法で比率を求め算出した。炭化珪素の結晶型は焼結しても変化しないので、α型、β型それぞれ特定された原料を購入して使用した。なお、ウィスカーはα型炭化珪素の一種である。焼結体のビッカース硬さはJIS R1610、破壊靭性はJIS R1607に示すIF法、高温曲げ強さはJIS R1604に示す3点曲げにより大気中1000℃で測定した。
(2) Properties of the sintered body (referred to as desk performance)
The content of magnesium in the sintered body was measured with a fluorescent X-ray analyzer and displayed in terms of MgO. The average particle size of the particles in the sintered body was calculated from a scanning electron micrograph. The amount of whiskers in silicon carbide was calculated by determining the ratio by the method described above. Since the crystal form of silicon carbide does not change even when sintered, raw materials specified for the α type and β type were purchased and used. Whisker is a kind of α-type silicon carbide. Vickers hardness of the sintered body was measured at 1000 ° C. in the atmosphere by JIS R1610, fracture toughness by IF method shown in JIS R1607, and high temperature bending strength by three-point bending shown in JIS R1604.

(3)切削インサートの切削性能の評価条件
切削インサート形状:SNGN120408 刃先処理:0.1mm×25°
被削材:普通鋳鉄(FC200),加工距離:8km
切削速度:500mm/min, 送り:f=0.4mm/rev
切り込み:d=0.5mm, 切削油:あり
(3) Evaluation condition of cutting performance of cutting insert Cutting insert shape: SNGN120408 Cutting edge treatment: 0.1 mm × 25 °
Work material: Normal cast iron (FC200), processing distance: 8km
Cutting speed: 500 mm / min, Feed: f = 0.4 mm / rev
Cutting depth: d = 0.5mm, Cutting oil: Available

Figure 2006193353
Figure 2006193353

注)1.第1列のNo1〜8は本発明の実施例、No9〜13は比較例を表す。
注)2.炭化珪素のpは非ウィスカー状の粉末、wはウィスカー状の粉末を表す。
注)3.切削性能の*は加工後僅かにチッピングありを、**はチッピングのため切削中止距離を示す。
注)4.No8はCVD法により膜厚2μmのアルミナ被膜を被覆したものを示す。組成、粒径、机上性能は被覆前の基材の値を示す。
Note) Nos. 1 to 8 in the first column represent examples of the present invention, and Nos. 9 to 13 represent comparative examples.
Note) 2. P of silicon carbide represents a non-whisker-like powder, and w represents a whisker-like powder.
Note) 3. The cutting performance * indicates slight chipping after processing, and ** indicates the cutting stop distance for chipping.
Note) 4. No8 shows what coated the alumina film with a film thickness of 2 micrometers by CVD method. The composition, particle size, and desktop performance indicate the values of the base material before coating.

表1に示す様に、本発明の実施例の焼結体は、ビッカース硬さは1900以上、破壊靭性値4.1以上、高温曲げ強さ750以上を示し、明らかに比較例の焼結体より優れている。また、この焼結体を用いた本発明の切削インサートは切削距離8kmにおいても刃先の欠損がなく、チッピングもほとんど起こらなかった。それに対して、比較例の切削インサートは欠損性、チッピングにより目標の切削距離8kmの半分も加工することができなかった。   As shown in Table 1, the sintered bodies of the examples of the present invention have a Vickers hardness of 1900 or more, a fracture toughness value of 4.1 or more, and a high temperature bending strength of 750 or more. Better. Further, the cutting insert of the present invention using this sintered body had no chipping at the cutting edge even at a cutting distance of 8 km, and almost no chipping occurred. On the other hand, the cutting insert of the comparative example could not process half of the target cutting distance of 8 km due to chipping and chipping.

本発明のアルミナ焼結体は各種の高温構造材料に使用でき、本発明の切削インサートおよびこれを備えた切削工具は耐摩耗性、耐欠損性に優れた長寿命のスローアウェイチップおよび切削工具として各種材料の加工に使用できる。   The alumina sintered body of the present invention can be used for various high-temperature structural materials, and the cutting insert of the present invention and the cutting tool equipped with the same are used as a long-life throw-away tip and cutting tool with excellent wear resistance and fracture resistance. Can be used for processing various materials.

図1は切削インサートの例である。FIG. 1 is an example of a cutting insert. 図2は外径加工用ホルダーにインサートを取り付けた切削工具の例である。FIG. 2 shows an example of a cutting tool in which an insert is attached to an outer diameter processing holder. 図3は本発明のアルミナ焼結体の電子顕微鏡写真(SEM)の例である。倍率は2,000倍である。FIG. 3 is an example of an electron micrograph (SEM) of the alumina sintered body of the present invention. The magnification is 2,000 times. 図4は本発明のアルミナ焼結体の光学顕微鏡写真の例である。倍率は600倍である。FIG. 4 is an example of an optical micrograph of the alumina sintered body of the present invention. The magnification is 600 times.

符号の説明Explanation of symbols

1:インサート 2:ホルダー 3:押さえ金 1: Insert 2: Holder 3: Presser foot

Claims (8)

平均粒径が0.5〜2μmの炭化珪素粒子を5〜35重量%含有し、マグネシウム含有量は酸化物換算で0.05重量%以下であるアルミナ焼結体。   An alumina sintered body containing 5 to 35% by weight of silicon carbide particles having an average particle size of 0.5 to 2 μm and a magnesium content of 0.05% by weight or less in terms of oxide. 炭化珪素粒子の含有率が10〜30重量%である請求項1に記載のアルミナ焼結体。   The alumina sintered body according to claim 1, wherein the content of silicon carbide particles is 10 to 30% by weight. アルミナの平均粒径が0.5〜5μmである請求項1または2に記載のアルミナ焼結体。   The alumina sintered body according to claim 1 or 2, wherein the average particle diameter of alumina is 0.5 to 5 µm. 炭化珪素が実質的にα型炭化珪素である請求項1〜3のいずれかに記載のアルミナ焼結体。   The alumina sintered body according to any one of claims 1 to 3, wherein the silicon carbide is substantially α-type silicon carbide. 炭化珪素中のウィスカーの比率が顕微鏡写真による面積比で50%以下である請求項1〜4のいずれかに記載のアルミナ焼結体。   The alumina sintered body according to any one of claims 1 to 4, wherein a ratio of whiskers in silicon carbide is 50% or less in terms of an area ratio according to a micrograph. 表面を硬質被膜で被覆した請求項1〜5のいずれかに記載のアルミナ焼結体。   The alumina sintered body according to any one of claims 1 to 5, wherein the surface is coated with a hard coating. 請求項1〜6のいずれかに記載のアルミナ焼結体を用いた切削インサート。   The cutting insert using the alumina sintered compact in any one of Claims 1-6. ホルダーに請求項7に記載の切削インサートを備えた切削工具。
The cutting tool provided with the cutting insert of Claim 7 in the holder.
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KR20110066939A (en) * 2008-09-17 2011-06-17 다이아몬드 이노베이션즈, 인크. Cubic boron nitride ceramic composites and methods of making thereof
JP2012502810A (en) * 2008-09-17 2012-02-02 ダイヤモンド イノベイションズ インコーポレーテッド Cubic boron nitride ceramic composite and method for producing the same
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