JP6198142B2 - Cutting tool made of cubic boron nitride super high pressure sintered material - Google Patents
Cutting tool made of cubic boron nitride super high pressure sintered material Download PDFInfo
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- JP6198142B2 JP6198142B2 JP2014063687A JP2014063687A JP6198142B2 JP 6198142 B2 JP6198142 B2 JP 6198142B2 JP 2014063687 A JP2014063687 A JP 2014063687A JP 2014063687 A JP2014063687 A JP 2014063687A JP 6198142 B2 JP6198142 B2 JP 6198142B2
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23B—TURNING; BORING
- B23B27/00—Tools for turning or boring machines; Tools of a similar kind in general; Accessories therefor
- B23B27/14—Cutting tools of which the bits or tips or cutting inserts are of special material
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/583—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on boron nitride
- C04B35/5831—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on boron nitride based on cubic boron nitrides or Wurtzitic boron nitrides, including crystal structure transformation of powder
Description
本発明は、耐欠損性にすぐれた立方晶窒化ホウ素（以下、ｃＢＮで示す）基超高圧焼結材料製切削工具（以下、ｃＢＮ工具という）に関する。 The present invention relates to a cutting tool (hereinafter referred to as a cBN tool) made of a cubic boron nitride (hereinafter referred to as cBN) -based ultrahigh pressure sintered material having excellent fracture resistance.
従来、鋼、鋳鉄等の鉄系被削材の切削加工には、被削材との親和性の低い工具材料としてｃＢＮ基超高圧焼結材料（以下、場合により、「ｃＢＮ焼結体」ともいう）を用いたｃＢＮ工具が知られている。
例えば、特許文献１に示すように、ｃＢＮ焼結材の結合相としてＡｌ２Ｏ３またはＡｌ２Ｏ３を主体とし炭化物、窒化物を含み、ｃＢＮ含有量を２０〜８０ｖｏｌ％の範囲にすることにより、熱衝撃特性を高めたｃＢＮ工具が知られている。
また、特許文献２に示すように、ｃＢＮ焼結体の結合相がＡｌ２Ｏ３とＴｉの炭窒化物を含み、ｃＢＮ含有量が３０〜７０ｖｏｌ％の範囲であり、ｃＢＮ粒子を結合相に用いる材質でコーティングし、圧力０．５ＧＰａ〜２ＧＰａで焼結することにより、緻密な組織とし靭性と強度の向上を図ったｃＢＮ工具が知られている。
さらに、特許文献３に示すように、ｃＢＮ焼結体の結合相が２次元的にみて連続で、結合相はＴｉの窒化物、炭化物、炭窒化物、ほう化物、Ａｌの窒化物、ほう化物、酸化物、Ｆｅ、Ｃｏ、Ｎｉの窒化物、炭化物、炭窒化物、ほう化物であり、ｃＢＮ含有量を４５〜７０ｖｏｌ％の範囲、ｃＢＮの平均粒径を２〜６μｍ、結合相厚みの平均値を１．５μｍ以下、標準偏差を０．９以下にすることで、結合相の平均厚みのばらつきを小さくし、これによって、欠陥となる部分を減らし、耐欠損性を改善したｃＢＮ工具が知られている
Conventionally, for cutting of iron-based work materials such as steel and cast iron, a cBN-based ultra-high pressure sintered material (hereinafter sometimes referred to as “cBN sintered body”) is used as a tool material having low affinity with the work material. CBN tools using the above are known.
For example, as shown in Patent Document 1, the binder phase of the cBN sintered material is mainly composed of Al 2 O 3 or Al 2 O 3 and contains carbide and nitride, and the cBN content is set in the range of 20 to 80 vol%. Thus, a cBN tool with improved thermal shock characteristics is known.
Moreover, as shown in Patent Document 2, the binder phase of the cBN sintered body contains Al 2 O 3 and Ti carbonitride, the cBN content is in the range of 30 to 70 vol%, and the cBN particles are used as the binder phase. There is known a cBN tool which is coated with a material to be used and sintered at a pressure of 0.5 GPa to 2 GPa to obtain a dense structure and to improve toughness and strength.
Furthermore, as shown in Patent Document 3, the binder phase of the cBN sintered body is continuous in two dimensions, and the binder phase is Ti nitride, carbide, carbonitride, boride, Al nitride, boride. Oxide, Fe, Co, Ni nitride, carbide, carbonitride, boride, cBN content in the range of 45-70 vol%, cBN average particle size of 2-6 μm, average of binder phase thickness By making the value 1.5 μm or less and the standard deviation 0.9 or less, the variation in the average thickness of the binder phase is reduced, thereby reducing the number of defective parts and improving the fracture resistance. Has been
特許文献１〜３に示されるように、ｃＢＮ工具の特性改善のために種々の提案がなされているが、刃先に高負荷が作用する条件で使用した場合には、工具寿命は比較的短いものであった。
例えば、特許文献１には、ｃＢＮ含有量が８０ｖｏｌ％まで可能とあるが、ｃＢＮ含有量が増加するとｃＢＮ粒子同士が接触する割合が高くなるが、ｃＢＮ粒子同士の接触部はｃＢＮ粒子を保持する効果を持つ結合相がないために刃先の強度が低下し、負荷の高い切削条件で使用した場合には、刃先が欠損しやすくなり、工具寿命が短命であるという問題があった。
また、特許文献２に記載されるｃＢＮ工具は、ｃＢＮ含有量が７０ｖｏｌ％を超えると、連続したネットワークを形成する結合相の緻密化が阻害され、緻密でかつ高硬度の焼結体を得ることができなくなり、しかも、焼結圧力が２．０ＧＰａを超えると焼結体のじん性および強度が低下傾向を示すようになるため、ｃＢＮ工具として使用した場合、寿命が短命であるという問題があった。
さらに、特許文献３には、結合相が２次元的に見て連続とあるが、ｃＢＮ含有量が増加するとｃＢＮ粒子が接触する割合が高くなり、ｃＢＮ粒子同士の接触部においては刃先の強度が低下し、刃先が欠損を発生し易くなるという引用文献１記載のｃＢＮ工具と同様な問題があった。
As shown in Patent Documents 1 to 3, various proposals have been made for improving the characteristics of cBN tools. However, when used under conditions where a high load acts on the cutting edge, the tool life is relatively short. Met.
For example, in Patent Document 1, the cBN content can be up to 80 vol%, but when the cBN content increases, the ratio of contact between the cBN particles increases, but the contact portion between the cBN particles holds the cBN particles. Since there is no effective binder phase, the strength of the cutting edge is reduced, and when used under high-load cutting conditions, the cutting edge tends to be broken, resulting in a short tool life.
Moreover, when the cBN tool described in Patent Document 2 has a cBN content exceeding 70 vol%, densification of the binder phase forming a continuous network is inhibited, and a dense and high hardness sintered body is obtained. In addition, when the sintering pressure exceeds 2.0 GPa, the toughness and strength of the sintered body tend to decrease, and when used as a cBN tool, there is a problem that the life is short. It was.
Furthermore, in Patent Document 3, the binder phase is continuous when viewed two-dimensionally. However, when the cBN content increases, the ratio of contact of cBN particles increases, and the strength of the cutting edge is increased at the contact portion between the cBN particles. There was a problem similar to that of the cBN tool described in the cited document 1 in that the cutting edge is liable to be lowered and the chip is likely to be damaged.
本発明者等は、上記課題を解決するため、ｃＢＮ工具のｃＢＮ焼結材構成成分であるｃＢＮ粒子に着目し、鋭意研究したところ、次のような知見を得た。 In order to solve the above-mentioned problems, the present inventors paid attention to cBN particles that are constituents of a cBN sintered material of a cBN tool, and conducted earnest research. As a result, the following knowledge was obtained.
従来のｃＢＮ工具の作製に際して、ｃＢＮ焼結体構成成分であるｃＢＮ粉末を、バインダー（結合相）形成成分であるＴｉＮ粉末、ＴｉＡｌ３粉末、Ａｌ２Ｏ３粉末等と混合し、これを超高圧高温条件下で焼結することによりｃＢＮ焼結材を作製し、これを超硬合金母材にろう付け接合し刃先を形成していた。特に、工具の耐クレータ摩耗性向上のために、化学蒸着等によるＡｌ２Ｏ３硬質膜の蒸着形成を行ったような場合には、蒸着時の高温にさらされることによる刃先の脱落が生じていた。 When producing a conventional cBN tool, cBN powder, which is a constituent component of a cBN sintered body, is mixed with TiN powder, TiAl 3 powder, Al 2 O 3 powder, etc., which are binder (binding phase) forming components, and this is mixed with ultra high pressure. A cBN sintered material was produced by sintering under high temperature conditions, and this was brazed to a cemented carbide base material to form a cutting edge. In particular, when an Al 2 O 3 hard film is formed by chemical vapor deposition or the like in order to improve the crater wear resistance of the tool, the cutting edge is dropped due to exposure to high temperatures during vapor deposition. It was.
そこで、本発明者らは、ｃＢＮ焼結体の作製に際し、ｃＢＮ焼結体の構成成分であるｃＢＮ粒子表面に、例えば、ＡＬＤ（Ａｔｏｍｉｃ Ｌａｙｅｒ Ｄｅｐｏｓｉｔｉｏｎ。真空チャンバ内の基材に、原料化合物の分子を一層ごと反応させ、Ａｒや窒素によるパージを繰り返し行うことで成膜する方法で、ＣＶＤ法の一種である。）法等により、微小膜厚のＡｌ２Ｏ３膜を予め形成しておき、この予めＡｌ２Ｏ３膜でコーティングされたｃＢＮ粒子とＡｌ２Ｏ３粉末を原料粉末として用いてｃＢＮ焼結体を作製したところ、ｃＢＮ粒子の表面はＡｌ２Ｏ３膜で予めコーティングされているため、このｃＢＮ焼結体のｃＢＮ含有割合を高めた場合であっても、ｃＢＮ粒子同士が接触する頻度が少なくなり、ｃＢＮ粒子が結合相により強固に保持されているため、高負荷が作用する切削条件で使用した場合であって、刃先の欠損発生が抑制されることを見出した。 Therefore, the present inventors, when producing the cBN sintered body, on the surface of the cBN particle, which is a constituent component of the cBN sintered body, for example, ALD (Atomic Layer Deposition). Is formed by repeatedly purging with Ar and nitrogen, and is a kind of CVD method.) A thin Al 2 O 3 film is formed in advance by the method or the like, were manufactured cBN sintered body of this advance the Al 2 O 3 film has been coated with cBN particles and Al 2 O 3 powder used as a raw material powder, the surface of the cBN particles are pre-coated with an Al 2 O 3 film Therefore, even when the cBN content ratio of the cBN sintered body is increased, the frequency of contact between the cBN particles decreases, and the cBN particles are stronger due to the binder phase. Because it is held in a high load even when used in cutting condition acting, we have found that defects occur in the cutting edge is suppressed.
さらに、本発明者らは、ｃＢＮ焼結体の原料粉末として、表面がＡｌ２Ｏ３膜でコーティングされた前記ｃＢＮ粒子を使用することに加え、所定の粒径分布となるように焼結体中の該ｃＢＮ粒子の粒径を定めることにより、ｃＢＮ粒子が結合相中により一層確実にかつ強固に保持されるようになるため、一段と耐欠損性が向上することを見出したのである。
つまり、ｃＢＮ焼結体の構成成分であるｃＢＮ粒子として、予め微小膜厚のＡｌ２Ｏ３膜をコーティングしたｃＢＮ粒子を用い、さらに、その粒径分布を所定のものに規定した場合には、ｃＢＮ粒子が結合相中に強固にかつ確実に保持されるため、高負荷が作用する切削加工に供した場合であっても、耐欠損性が改善されることを見出したのである。
Furthermore, the present inventors have used the cBN particles whose surfaces are coated with an Al 2 O 3 film as a raw material powder for the cBN sintered body, and in addition, the sintered body has a predetermined particle size distribution. It was found that by determining the particle size of the cBN particles therein, the cBN particles are more reliably and firmly held in the binder phase, so that the fracture resistance is further improved.
In other words, as cBN particles that are constituents of a cBN sintered body, cBN particles that have been coated with an Al 2 O 3 film having a very small film thickness are used, and the particle size distribution is defined as a predetermined one. It has been found that the cBN particles are firmly and securely held in the binder phase, so that the fracture resistance is improved even when the cBN particles are subjected to cutting with high loads.
本発明は、上記知見に基づいてなされたものであって、
「（１） 立方晶窒化ほう素基超高圧焼結材料製切削工具において、
立方晶窒化ほう素基超高圧焼結材料の構成成分は立方晶窒化ほう素が５０〜８５ｖｏｌ％、残りが酸化アルミニウムを主体とし、かつ、前記立方晶窒化ほう素基超高圧焼結材料の断面について測定した場合、立方晶窒化ほう素粒子の平均粒径より算出できる立方晶窒化ほう素粒子の平均面積の２．５倍より大きい面積を有する立方晶窒化ほう素粒子群が占める合計面積割合は、立方晶窒化ほう素粒子の総面積の０．１０より大きく０．３５以下であることを特徴とする立方晶窒化ほう素基超高圧焼結材料製切削工具。
（２） 立方晶窒化ほう素基超高圧焼結材料中の立方晶窒化ほう素粒子の含有割合は、７０〜８５体積％であることを特徴とする前記（１）に記載の立方晶窒化ほう素基超高圧焼結材料製切削工具。」
を特徴とするものである。
The present invention has been made based on the above findings,
“(1) In a cutting tool made of cubic boron nitride based ultra-high pressure sintered material,
The components of the cubic boron nitride-based ultrahigh-pressure sintered material are 50 to 85 vol% of cubic boron nitride, the remainder is mainly aluminum oxide, and the cross section of the cubic boron nitride-based ultrahigh-pressure sintered material When measuring about the total area ratio occupied by cubic boron nitride particles having an area larger than 2.5 times the average area of cubic boron nitride particles, which can be calculated from the average particle size of cubic boron nitride particles is A cubic boron nitride-based ultrahigh pressure sintered material cutting tool, wherein the total area of the cubic boron nitride particles is greater than 0.10 and less than or equal to 0.35.
(2) The cubic boron nitride described in (1) above, wherein the cubic boron nitride particle content in the cubic boron nitride-based ultrahigh pressure sintered material is 70 to 85% by volume. Cutting tool made of basic super high pressure sintered material. "
It is characterized by.
本発明について、以下に説明する。 The present invention will be described below.
本発明のｃＢＮ工具では、ｃＢＮ焼結材料で工具基体が構成されるが、該ｃＢＮ焼結材のｃＢＮ原料粉末としては、微小膜厚のＡｌ２Ｏ３膜を予めコーティングしたｃＢＮ粒子を使用する。
ｃＢＮ粒子表面への微小膜厚のＡｌ２Ｏ３膜のコーティングは、例えば、ＡＬＤ法により行うことができる。
ＡＬＤ法において、流動層炉内にｃＢＮ粒子を装入し、３５０℃程度に昇温し、Ａｌ（ＣＨ３）３ガス流入工程、Ａｒガスパージ工程、Ｈ２Ｏガス流入工程、Ａｒガスパージ工程を１サイクルとして、このサイクルを目標膜厚になるまで繰り返す（例えば、１時間かけて１０ｎｍのＡｌ２Ｏ３膜を成膜する）ことにより、ｃＢＮ粒子の平均粒径の１／２以下の平均被覆厚さのＡｌ２Ｏ３膜をｃＢＮ粒子表面に形成することができる。
ここで、Ａｌ２Ｏ３膜の平均被覆厚さがｃＢＮ粒子の平均粒径の１／２を超えるようになると、刃先エッジに存在するＡｌ２Ｏ３がｃＢＮ粒子より先に摩滅するためｃＢＮ粒子の脱落が顕著になり、刃先のシャープさを維持できなくなり、また、耐欠損性も低下することから、Ａｌ２Ｏ３膜の平均被覆厚さは、ｃＢＮ粒子の平均粒径の１／２以下とすることが望ましい。
ｃＢＮ粒子表面のＡｌ２Ｏ３膜の被覆の均一性については、ＳＥＭ（走査型電子顕微鏡）あるいはＴＥＭ（透過型電子顕微鏡）観察を行うことによって確認することができる。
In the cBN tool of the present invention, the tool base is composed of a cBN sintered material. As the cBN raw material powder of the cBN sintered material, cBN particles pre-coated with a very thin Al 2 O 3 film are used. .
The cBN particle surface can be coated with an Al 2 O 3 film having a small thickness by, for example, an ALD method.
In the ALD method, cBN particles are charged into a fluidized bed furnace, heated to about 350 ° C., and an Al (CH 3 ) 3 gas inflow process, an Ar gas purge process, an H 2 O gas inflow process, and an Ar gas purge process are performed as 1 As a cycle, this cycle is repeated until the target film thickness is reached (for example, a 10 nm Al 2 O 3 film is formed over 1 hour), whereby an average coating thickness of 1/2 or less of the average particle diameter of cBN particles The Al 2 O 3 film can be formed on the surface of the cBN particles.
Here, when the average coating thickness of the Al 2 O 3 film exceeds 1/2 of the average particle diameter of the cBN particles, the Al 2 O 3 present at the edge of the blade is worn away before the cBN particles, so that the cBN particles Dropout becomes noticeable, the sharpness of the cutting edge cannot be maintained, and the chipping resistance also decreases, so the average coating thickness of the Al 2 O 3 film is ½ or less of the average particle diameter of the cBN particles. Is desirable.
The uniformity of the coating of the Al 2 O 3 film on the surface of the cBN particles can be confirmed by performing SEM (scanning electron microscope) or TEM (transmission electron microscope) observation.
本発明のｃＢＮ工具は、ｃＢＮ粒子がＡｌ２Ｏ３膜でコーティングされているため、ｃＢＮ粒子同士の直接接触が低減され、ｃＢＮ焼結材中で確実・強固に保持されるようになるが、ｃＢＮ焼結体の断面を走査型電子顕微鏡（Ｓｃａｎｎｉｎｇ Ｅｌｅｃｔｒｏｎ Ｍｉｃｒｏｓｃｏｐｙ：ＳＥＭ）により観察し得られるＳＥＭ像を基に画像解析を行った場合、ｃＢＮ粒子同士が接触し、画像解析上では１つのｃＢＮ粒として処理するｃＢＮ粒の集合体をｃＢＮ粒子群とし、このｃＢＮ粒子群のうち、ｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群が占める合計面積割合が、ｃＢＮ粒子の総面積の０．３５より大きくなると、ｃＢＮ粒子同士が直接接触する割合が高くなり、結合相により十分に保持されていないｃＢＮ粒子が増加するため、高負荷切削加工においては、欠損を発生し易くなり、その結果、工具寿命も短命となる。
また、原料として用いるｃＢＮ粒子は単一の粒子の集まりではなく、ある粒度の分布を持ち、ｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子をあらかじめ０．１０以下含んでいる。
したがって、この発明では、ｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群が占める合計面積割合を、ｃＢＮ粒子の総面積の０．１０より大きく、０．３５以下と定めた。
In the cBN tool of the present invention, since the cBN particles are coated with an Al 2 O 3 film, direct contact between the cBN particles is reduced, and the cBN tool is surely and firmly held in the cBN sintered material. When image analysis is performed based on an SEM image obtained by observing a cross section of a cBN sintered body with a scanning electron microscope (SEM), the cBN particles are in contact with each other, and one cBN particle is included in the image analysis. An aggregate of cBN particles to be processed as a cBN particle group, and among the cBN particle group, a cBN particle group having an area larger than 2.5 times the average area of the cBN particle that can be calculated from the average particle diameter of the cBN particle occupies When the total area ratio is larger than 0.35 of the total area of the cBN particles, the ratio of the cBN particles directly contacting each other increases, Since cBN particles increases not fully retained by, in the high-load cutting, liable to generate defects, resulting, it is short-lived tool life.
The cBN particles used as a raw material are not a collection of single particles, but have a distribution of a certain particle size and have an area larger than 2.5 times the average area of cBN particles that can be calculated from the average particle size of cBN particles. Is included in advance by 0.10 or less.
Therefore, in this invention, the total area ratio occupied by the cBN particle group having an area larger than 2.5 times the average area of the cBN particles is set to be larger than 0.10 of the total area of the cBN particles and 0.35 or less. .
ここで、ｃＢＮ粒子の平均粒径は、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求め、それを各粒子の直径とし各粒子の体積を計算する。体積は、理想球と仮定して計算する。
ここで、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。
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、例えば画像処理操作の１つであるｗａｔｅｒｓｈｅｄ（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粒同士を分離しない。
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最大長とし、それを各粒子の直径として各粒子の体積を計算する。体積は理想球と仮定して計算する。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。また、粒子解析の際、ノイズを除去するため、直径０．０２μｍより小さい領域は粒子として計算しない。
体積の積算％と直径の分布曲線におけるメディアン径を１画像から求め、少なくとも３画像から求めた平均値をｃＢＮの平均粒径（μｍ）とした。画像処理に用いる観察領域としては、ｃＢＮ粒子の平均粒径３μｍの場合、１５μｍ×１５μｍ程度の視野領域が望ましい。
Here, the average particle size of the cBN particles can be determined as follows.
The cross-sectional structure of the cBN sintered body is observed with a SEM, and a secondary electron image is obtained. The portion of the cBN particles in the obtained image is extracted by image processing, the maximum length of each particle obtained by image analysis is obtained, and the volume of each particle is calculated using this as the diameter of each particle. The volume is calculated assuming an ideal sphere.
Here, in extracting the cBN particle portion in the image by image processing, in order to clearly determine the cBN particle and the binder phase, the image is displayed in monochrome of 256 gradations of 0, black, and 255, and white. A binarization process is performed so that the cBN grain becomes black using an image of a pixel value in which the ratio between the pixel value of the cBN particle part and the pixel value of the binder phase part is 2 or more.
As an area for obtaining the pixel values of the cBN particle part and the binder phase part, the average value obtained from an average value in an area of about 0.5 μm × 0.5 μm and at least three average values obtained from the same image, respectively. It is desirable to set the contrast.
It should be noted that after binarization processing, it seems that the cBN grains are in contact using a process that separates the parts that are considered to be in contact with each other, for example, watershed, which is one of image processing operations. Do not separate cBN grains.
Particle analysis of the portion corresponding to cBN grains (black part) in the image obtained after binarization processing is performed, and the volume of each particle is calculated using the obtained maximum length as the maximum length of each particle and using it as the diameter of each particle. To do. The volume is calculated assuming an ideal sphere. When performing particle analysis, a length (μm) per pixel is set using a scale value known in advance by SEM. Further, in the particle analysis, in order to remove noise, a region having a diameter smaller than 0.02 μm is not calculated as a particle.
The median diameter in the volume integration% and diameter distribution curve was obtained from one image, and the average value obtained from at least three images was defined as the average particle size (μm) of cBN. As an observation region used for image processing, a visual field region of about 15 μm × 15 μm is desirable when the average particle size of cBN particles is 3 μm.
また、ｃＢＮ粒子の面積と、ｃＢＮ粒子の総面積に対してｃＢＮ粒子群が占める合計面積の割合は、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。ここで、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。
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。
得られた画像内のｃＢＮ粒子の部分（黒の部分）の面積を画像処理より算出し、ｃＢＮ粒子の総面積とする。この際、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）を設定する。次に、画像解析を用いて画像内の各ｃＢＮ粒子の面積を求める。
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、粒子と認識した各領域面積を算出する。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、例えば画像処理操作の１つであるｗａｔｅｒｓｈｅｄ（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粒同士を分離しない。また、粒子解析の際、ノイズを除去するため、直径０．０２μｍより小さい領域は粒子として計算しない。
求めた各ｃＢＮ粒子の面積から、ｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群の面積の合計をｃＢＮ粒子の総面積で除した値が、ｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群が占める合計面積割合となる。
ここで、ｃＢＮ粒子の平均面積とは、ｃＢＮ平均粒径を基に求められる面積であり、面積は、理想円と仮定して計算する。
１画像よりｃＢＮ粒子の平均面積の２．５倍より大きい面積のｃＢＮ粒子群の合計面積を総ｃＢＮ粒の面積で除した値を求め、少なくとも３画像から求めた平均値を、ｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群が占める合計面積割合とした。画像処理に用いる観察領域として、ｃＢＮ粒子の平均粒径３μｍの場合、１５μｍ×１５μｍ程度の視野領域が望ましい。
Further, the area of the cBN particles and the ratio of the total area occupied by the cBN particle group to the total area of the cBN particles can be determined as follows.
The cross-sectional structure of the cBN sintered body is observed with a SEM, and a secondary electron image is obtained. Here, in order to clearly determine the cBN particle and the binder phase, the image is displayed in monochrome with 256 gradations of 0, black, and 255, and the ratio of the pixel value of the cBN particle portion to the pixel value of the binder phase portion. A binarization process is performed so that the cBN grains are black using an image having a pixel value of 2 or more.
As an area for obtaining the pixel values of the cBN particle part and the binder phase part, the average value obtained from an average value in an area of about 0.5 μm × 0.5 μm and at least three average values obtained from the same image, respectively. It is desirable to set the contrast.
The area of the cBN particle portion (black portion) in the obtained image is calculated by image processing, and is defined as the total area of the cBN particles. At this time, a length (μm) per pixel is set using a scale value known in advance by SEM. Next, the area of each cBN particle in the image is obtained using image analysis.
The part corresponding to the cBN grain (black part) in the image obtained after the binarization process is subjected to particle analysis, and the area of each region recognized as a particle is calculated. It should be noted that after binarization processing, it seems that the cBN grains are in contact using a process that separates the parts that are considered to be in contact with each other, for example, watershed, which is one of image processing operations. Do not separate cBN grains. Further, in the particle analysis, in order to remove noise, a region having a diameter smaller than 0.02 μm is not calculated as a particle.
A value obtained by dividing the total area of cBN particles having an area larger than 2.5 times the average area of cBN particles, which can be calculated from the average particle diameter of cBN particles, by the total area of cBN particles, from the obtained area of each cBN particle. Is the total area ratio occupied by the cBN particle group having an area larger than 2.5 times the average area of the cBN particles, which can be calculated from the average particle diameter of the cBN particles.
Here, the average area of the cBN particles is an area obtained based on the cBN average particle diameter, and the area is calculated assuming an ideal circle.
A value obtained by dividing the total area of the cBN particle group having an area larger than 2.5 times the average area of the cBN particles from one image by the area of the total cBN particles is obtained, and an average value obtained from at least three images is calculated as an average of the cBN particles. It was set as the total area ratio which the cBN particle group which has an area larger than 2.5 times the average area of the cBN particle which can be calculated from a particle size accounts. As an observation region used for image processing, when the average particle size of cBN particles is 3 μm, a visual field region of about 15 μm × 15 μm is desirable.
本発明では、ｃＢＮ粒子の表面をＡｌ２Ｏ３膜で被覆したｃＢＮ粒子とＡｌ２Ｏ３とＡｌを主な原料とし、通常の超高圧高温条件下で焼結することにより、ｃＢＮ焼結材を作製し、これを、超硬合金からなる母材にろう付け接合することにより、本発明ｃＢＮ工具を作製する。本発明ｃＢＮ工具に用いるｃＢＮ焼結体は、ｃＢＮ粒子の表面がＡｌ２Ｏ３によって覆われ、かつ、ｃＢＮ粒子群の合計面積割合を０．１より大きく０．３５以下としていることによって、ｃＢＮ焼結体中のｃＢＮ粒子の含有割合を高くしても、工具として使用した場合に、欠損を発生する恐れがない。ｃＢＮ焼結体に占めるｃＢＮ粒子の含有割合が５０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。一方、８５体積％を超えると、ｃＢＮ粒子はＡｌ２Ｏ３膜で被覆しているためｃＢＮ粒子同士の接触は低減するが、隣り合う被覆したＡｌ２Ｏ３膜同士では埋められないクラックの起点となる空隙が焼結体中に生成し、耐欠損性が低下する。本発明では、ｃＢＮ焼結体に占めるｃＢＮ粒子の含有割合を５０〜８５体積％とすることができ、好ましくは７０〜８５体積％である。
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た。画像処理に用いる観察領域として、ｃＢＮ粒子の平均粒径３μｍの場合、１５μｍ×１５μｍ程度の視野領域が望ましい。
また、一般に鋳鉄材料の切削においては、主としてＪＩＳ．Ｂ．０１７０の分類の識別記号Ｋの切削用超硬質工具材料が使用されるが、より高速度の加工という観点ではＡｌ２Ｏ３を主成分とするセラミックス工具が使用される。そのため、鋳鉄材料の切削に用いるｃＢＮ工具のｃＢＮ焼結体としては、ｃＢＮ以外の成分はＡｌ２Ｏ３を主体とすることが望ましい。
In the present invention, a cBN sintered material is obtained by sintering cBN particles whose surfaces are coated with an Al 2 O 3 film, Al 2 O 3 and Al as main raw materials and sintering them under normal ultrahigh pressure and high temperature conditions. Is manufactured, and this is brazed to a base material made of a cemented carbide to produce a cBN tool of the present invention. The cBN sintered body used in the cBN tool of the present invention has a cBN particle whose surface is covered with Al 2 O 3 and the total area ratio of the cBN particle group is set to be larger than 0.1 and 0.35 or less. Even if the content ratio of the cBN particles in the sintered body is increased, there is no risk of occurrence of defects when used as a tool. When the content ratio of the cBN particles in the cBN sintered body is less than 50% by volume, the sintered body has a small amount of hard material, and when used as a tool, the fracture resistance decreases. On the other hand, when it exceeds 85% by volume, but the contact of cBN particles with each other because cBN particles are coated with the Al 2 O 3 film is reduced, the unfilled a coated the Al 2 O 3 film between adjacent cracks origin Voids are formed in the sintered body, and the fracture resistance is reduced. In the present invention, the content ratio of the cBN particles in the cBN sintered body can be 50 to 85% by volume, and preferably 70 to 85% by volume.
The content ratio of cBN particles in the cBN sintered body is determined by observing the cross-sectional structure of the cBN sintered body by SEM, extracting the cBN particle portion in the obtained secondary electron image by image processing, and analyzing the cBN particles by image analysis. The area occupied by cBN particles was calculated, the ratio occupied by cBN particles in one image was determined, and the average value of values obtained by processing at least three images was defined as the content ratio of cBN particles. As an observation region used for image processing, when the average particle size of cBN particles is 3 μm, a visual field region of about 15 μm × 15 μm is desirable.
In general, in the cutting of cast iron materials, JIS. B. Although an ultra hard tool material for cutting having an identification symbol K of 0170 classification is used, a ceramic tool mainly composed of Al 2 O 3 is used from the viewpoint of higher speed machining. Therefore, as a cBN sintered body of a cBN tool used for cutting a cast iron material, it is desirable that components other than cBN are mainly Al 2 O 3 .
なお、本発明でいう「酸化アルミニウム（Ａｌ２Ｏ３）を主体」とするとは、Ａｌ２Ｏ３の他に、Ａｌ２Ｏ３の焼結助剤として公知である、Ｔｉ、Ｙ、Ｎｉ、Ｃｒ、Ｚｒの酸化物等の１種以上が、合計体積割合で、５ｖｏｌ％まで含有されることが許容されることを意味する。 In the present invention, “mainly composed of aluminum oxide (Al 2 O 3 )” is known as a sintering aid for Al 2 O 3 in addition to Al 2 O 3 , Ti, Y, Ni, It means that it is allowed to contain up to 5 vol% of one or more of Cr, Zr oxide and the like in a total volume ratio.
上記のとおり、本発明ｃＢＮ工具は、ｃＢＮ粒子の表面がＡｌ２Ｏ３膜で被覆されていること、また、ｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群の合計面積割合が０．１より大きく０．３５以下と少ないことから、鋼や鋳鉄の刃先に高負荷が作用する切削加工においても、すぐれた耐欠損性を発揮し、工具寿命の延命化を図ることができる。 As described above, the cBN tool of the present invention has a surface of cBN particles covered with an Al 2 O 3 film, and is larger than 2.5 times the average area of cBN particles that can be calculated from the average particle size of cBN particles. Since the total area ratio of the cBN particle group having an area is less than 0.35 and less than 0.35, it exhibits excellent fracture resistance even in a cutting process in which a high load acts on the cutting edge of steel or cast iron, The tool life can be extended.
以下に、本発明のｃＢＮ工具を実施例に基づいて説明する。 Below, the cBN tool of this invention is demonstrated based on an Example.
微小膜厚のＡｌ２Ｏ３膜でコーティングされたｃＢＮ粒子粉末の作製：
表１に示すメディアン径（Ｄ５０）を有するｃＢＮ粒子を基材とし、これに、ＡＬＤ（Ａｔｏｍｉｃ Ｌａｙｅｒ Ｄｅｐｏｓｉｔｉｏｎ）法により、ｃＢＮ粒子に表１に示される平均膜厚のＡｌ２Ｏ３膜を被覆する。より具体的にいえば、炉内に、表１に示すメディアン径（Ｄ５０）を有するｃＢＮ粒子を装入し、炉内を３５０℃に昇温し、成膜用ガスとして、Ａｌの先駆体であるＡｌ（ＣＨ３）３ガス、および、反応ガスとしてＨ２Ｏガスを用い、
（１）Ａｒ＋Ａｌ（ＣＨ３）３ガス流入工程、
（２）Ａｒガスパージ工程、
（３）Ａｒ＋Ｈ２Ｏガス流入工程、
（４）Ａｒガスパージ工程
前記（１）〜（４）を１サイクルとして、このサイクルを目標膜厚になるまで繰り返し行い、所定の膜厚のＡｌ２Ｏ３膜をｃＢＮ粒子表面に形成する。
なお、上記で得られた微小膜厚のＡｌ２Ｏ３膜でコーティングされたｃＢＮ粒子粉末について、ＳＥＭ（走査型電子顕微鏡）を用いて観察したところ、ｃＢＮ粒子表面に表１に示される平均膜厚のＡｌ２Ｏ３膜がコーティングされていることが確認された。
Preparation of cBN particle powder coated with a very thin Al 2 O 3 film:
A cBN particle having a median diameter (D50) shown in Table 1 is used as a base material, and this is coated with an Al 2 O 3 film having an average film thickness shown in Table 1 on the cBN particles by an ALD (Atomic Layer Deposition) method. . More specifically, cBN particles having a median diameter (D50) shown in Table 1 are charged into the furnace, the temperature inside the furnace is raised to 350 ° C., and a precursor of Al is used as a film forming gas. A certain Al (CH 3 ) 3 gas, and H 2 O gas as a reaction gas,
(1) Ar + Al (CH 3 ) 3 gas inflow process,
(2) Ar gas purge step,
(3) Ar + H 2 O gas inflow process,
(4) Ar gas purge step The above (1) to (4) are set as one cycle, this cycle is repeated until the target film thickness is reached, and an Al 2 O 3 film having a predetermined film thickness is formed on the surface of the cBN particles.
The cBN particle powder coated with the Al 2 O 3 film having a small film thickness obtained above was observed using an SEM (scanning electron microscope), and the average film shown in Table 1 on the surface of the cBN particle was observed. It was confirmed that a thick Al 2 O 3 film was coated.
上記で作製した微小膜厚のＡｌ２Ｏ３膜でコーティングされた所定のメディアン径を有するｃＢＮ粒子粉末と、０．３〜０．９μｍの範囲内の平均粒径を有するＡｌ２Ｏ３粉末、Ａｌ粉末を用意し、これら原料粉末を、表２に示される組成に配合し、湿式混合し、乾燥した後、油圧プレスにて成形圧１ＭＰａで直径：５０ｍｍ×厚さ：１．５ｍｍの寸法にプレス成形し、ついでこの成形体を、圧力：１Ｐａの真空雰囲気中、１０００〜１３００℃の範囲内の所定温度に３０〜６０分間保持して熱処理し、揮発成分および粉末表面への吸着成分を除去して切刃片用予備焼結体とし、この予備焼結体を、別途用意した、Ｃｏ：８質量％、ＷＣ：残りの組成、並びに直径：５０ｍｍ×厚さ：２ｍｍの寸法をもったＷＣ基超硬合金製支持片と重ね合わせた状態で、通常の超高圧焼結装置に装入し、通常の条件である圧力：５ＧＰａ、温度：１５００℃、保持時間：３０分間の条件で超高圧高温焼結し、ｃＢＮ焼結材を得る。ＸＲＤよりｃＢＮ焼結材中のｃＢＮ、Ａｌの窒化物とほう化物と酸化物を確認した。ｃＢＮ焼結材円板を、ワイヤー放電加工装置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、質量％で、Ｃｕ：２６％、Ｔｉ：５％、Ａｇ：残りからなる組成を有するＡｇ合金のろう材を用いてろう付けし、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表２に示す組成の本発明ｃＢＮ工具１〜１３を製造した。 A cBN particle powder having a predetermined median diameter coated with a micro-thickness Al 2 O 3 film prepared as described above, and an Al 2 O 3 powder having an average particle diameter in the range of 0.3 to 0.9 μm, Prepare Al powder, mix these raw material powders with the composition shown in Table 2, wet mix, dry, and then use a hydraulic press to form a pressure of 1 MPa, diameter: 50 mm x thickness: 1.5 mm Press molding, and then heat-treating this compact at a predetermined temperature within a range of 1000 to 1300 ° C. for 30 to 60 minutes in a vacuum atmosphere of 1 Pa to remove volatile components and components adsorbed on the powder surface. Thus, a pre-sintered body for a cutting edge piece was prepared, and this pre-sintered body was prepared separately. Co: 8% by mass, WC: remaining composition, and diameter: 50 mm × thickness: 2 mm WC Overlap with base cemented carbide support piece In this state, the sample was charged into a normal ultra-high pressure sintering apparatus and subjected to ultra-high pressure and high temperature sintering under normal conditions of pressure: 5 GPa, temperature: 1500 ° C., holding time: 30 minutes, and cBN sintered material Get. XBN confirmed cBN and Al nitrides, borides, and oxides in the cBN sintered material. cBN sintered material disc is cut to a predetermined size with a wire electric discharge machine, Co: 5 mass%, TaC: 5 mass%, WC: remaining composition and WC-base carbide with ISO CNCN120408 insert shape The brazing part (corner part) of the alloy insert body is brazed using a brazing material of an Ag alloy having a composition of Cu: 26%, Ti: 5%, and Ag: the rest, and the upper and lower surfaces. Further, the present invention cBN tools 1 to 13 having the composition shown in Table 2 having the insert shape of ISO standard CNGA120408 were manufactured by performing peripheral grinding and honing treatment.
比較のため、原料粉末として、微小膜厚のＡｌ２Ｏ３膜コーティングを行っていない表３に示す粒径分布を有するｃＢＮ粒子粉末、微小膜厚のＡｌ２Ｏ３膜でコーティングされた表３に示す粒径分布を有するｃＢＮ粒子粉末と、０．３〜０．９μｍの範囲内の平均粒径を有するＡｌ２Ｏ３粉末、Ａｌ粉末を用意し、これら原料粉末を表４に示される組成に配合し、上記本発明ｃＢＮ工具１〜１３と同様な方法で、ＩＳＯ規格ＣＮＧＡ１２０４０８のインサート形状をもつ表４に示す比較例ｃＢＮ工具１〜１３を製造した。 For comparison, the raw material powder, cBN particles having a particle size distribution shown in Table 3 is not performed an Al 2 O 3 film coating of fine thickness, Table 3 coated with the Al 2 O 3 film of fine thickness CBN particle powder having the particle size distribution shown in FIG. 1, Al 2 O 3 powder having an average particle size in the range of 0.3 to 0.9 μm, and Al powder are prepared. The comparative example cBN tools 1-13 shown in Table 4 having the insert shape of ISO standard CNGA120408 were produced in the same manner as the above-described cBN tools 1-13 of the present invention.
上記で作製した本発明ｃＢＮ工具１〜１３および比較例ｃＢＮ工具１〜１３について、ｃＢＮ粒子の平均粒径、ｃＢＮ粒子の平均面積・総面積、ｃＢＮ粒の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群の合計面積を測定し、これらの値から、（ｃＢＮ粒の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群の合計面積）／（ｃＢＮ粒子の総面積）の値を算出した。
即ち、ｃＢＮ粒子の平均粒径については、ｃＢＮ焼結体の断面組織を走査型電子顕微鏡（ＳＥＭ）にて観察して、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求め、それを各粒子の直径とし各粒子の体積を計算する。なお、体積は、理想球と仮定して計算する。
体積の積算％と直径の分布曲線におけるメディアン径を１画像から求め、少なくとも３画像から求めた平均値をｃＢＮの平均粒径（μｍ）とした。なお、画像処理に用いた観察領域は、１５μｍ×１５μｍである。
About this invention cBN tool 1-13 produced above and the comparative example cBN tool 1-13, the average particle diameter of cBN particle | grains which can be calculated from the average particle diameter of cBN particle | grains, the average area and total area of cBN particle | grains, and the average particle diameter of cBN particle | grains The total area of the cBN particle group having an area larger than 2.5 times the area was measured, and from these values, an area larger than 2.5 times the average area of the cBN particles calculated from the average particle diameter of the cBN grains was calculated. The total area of cBN particle group having) / (total area of cBN particles) was calculated.
That is, about the average particle diameter of cBN particle | grains, a cross-sectional structure | tissue of a cBN sintered compact is observed with a scanning electron microscope (SEM), and a secondary electron image is obtained. The portion of the cBN particles in the obtained image is extracted by image processing, the maximum length of each particle obtained by image analysis is obtained, and the volume of each particle is calculated using this as the diameter of each particle. The volume is calculated assuming an ideal sphere.
The median diameter in the volume integration% and diameter distribution curve was obtained from one image, and the average value obtained from at least three images was defined as the average particle size (μm) of cBN. The observation area used for image processing is 15 μm × 15 μm.
また、ｃＢＮ粒子の平均面積と、ｃＢＮ粒子の総面積に占めるｃＢＮ粒の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群が占める合計面積の割合は、以下のとおり求めた。
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。ここで、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。
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、各部において０．５μｍ×０．５μｍ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画素値とすることが望ましい。
得られた画像内のｃＢＮ粒子の部分（黒の部分）の面積を画像処理より算出し、ｃＢＮ粒子の総面積とする。この際、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）を設定する。次に、画像解析を用いて画像内の各ｃＢＮ粒子の面積を求める。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、粒子と認識した各領域面積を算出する。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、例えば画像処理操作の１つであるｗａｔｅｒｓｈｅｄ（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粒同士を分離しない。また、粒子解析の際、ノイズを除去するため、直径０．０２μｍより小さい領域は粒子として計算しない。
求めた各ｃＢＮ粒子の面積から、ｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子の面積の合計をｃＢＮ粒子の総面積で除した値がｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群が占める合計面積割合となる。
ここで、ｃＢＮ粒子の平均面積とは、ｃＢＮ平均粒径を基に求められる面積であり、面積は、理想円と仮定して計算する。
１画像より平均ｃＢＮ粒子面積の２．５倍より大きい面積のｃＢＮ粒、すなわちｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群の合計面積を総ｃＢＮ粒の面積で除した値を求め、少なくとも３画像から求めた平均値を、ｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群が占める合計面積割合とした。画像処理に用いた観察領域は、１５μｍ×１５μｍである。
表２、表４に、これらの値を示す。
The ratio of the total area occupied by the cBN particle group having an area larger than 2.5 times the average area of the cBN particles, which can be calculated from the average area of the cBN particles and the average particle diameter of the cBN particles in the total area of the cBN particles is It was determined as follows.
The cross-sectional structure of the cBN sintered body is observed with a SEM, and a secondary electron image is obtained. Here, in order to clearly determine the cBN particle and the binder phase, the image is displayed in monochrome with 256 gradations of 0, black, and 255, and the ratio of the pixel value of the cBN particle portion to the pixel value of the binder phase portion. A binarization process is performed so that the cBN grains are black using an image having a pixel value of 2 or more.
As an area for obtaining the pixel values of the cBN particle part and the binder phase part, the average value obtained from at least three different points in the same image is obtained from the average value in the 0.5 μm × 0.5 μm area in each part. Each pixel value is desirable.
The area of the cBN particle portion (black portion) in the obtained image is calculated by image processing, and is defined as the total area of the cBN particles. At this time, a length (μm) per pixel is set using a scale value known in advance by SEM. Next, the area of each cBN particle in the image is obtained using image analysis. The part corresponding to the cBN grain (black part) in the image obtained after the binarization process is subjected to particle analysis, and the area of each region recognized as a particle is calculated. It should be noted that after binarization processing, it seems that the cBN grains are in contact using a process that separates the parts that are considered to be in contact with each other, for example, watershed, which is one of image processing operations. Do not separate cBN grains. Further, in the particle analysis, in order to remove noise, a region having a diameter smaller than 0.02 μm is not calculated as a particle.
A value obtained by dividing the total area of cBN particles having an area larger than 2.5 times the average area of cBN particles, which can be calculated from the average particle diameter of cBN particles, by the total area of cBN particles, from the obtained area of each cBN particle. This is the total area ratio occupied by the cBN particle group having an area larger than 2.5 times the average area of the cBN particles that can be calculated from the average particle diameter of the cBN particles.
Here, the average area of the cBN particles is an area obtained based on the cBN average particle diameter, and the area is calculated assuming an ideal circle.
The total area of cBN particles having an area larger than 2.5 times the average cBN particle area from one image, that is, the cBN particle group having an area larger than 2.5 times the average area of cBN particles, which can be calculated from the average particle diameter of cBN particles. CBN particles having an area greater than 2.5 times the average area of cBN particles, which can be calculated from the average particle size of cBN particles by calculating the average value obtained from at least three images. The total area ratio occupied by. The observation area used for image processing is 15 μm × 15 μm.
Tables 2 and 4 show these values.
上記の本発明ｃＢＮ工具１〜１３および比較例ｃＢＮ工具１〜１３について、以下の切削条件Ａで切削加工試験を実施し、切削時間：１０分経過後のクレータ摩耗深さを測定するとともに、欠損の有無を観察した。
《切削条件Ａ》
被削材： ＦＣ２５の軸方向に２本の溝入りφ２００ｍｍ丸棒 、
切削速度： １５０ ｍ／ｍｉｎ、
送り： ０．６ ｍｍ／ｒｅｖ、
切込み： ２．０ ｍｍ、
の条件での、外周加工の乾式断続切削加工試験により断続回数２５００回後における刃先の欠損の有無を確認した。
なお、刃先の確認は、光学顕微鏡により行った。
切削加工試験の測定結果を表５に示した。
For the cBN tools 1 to 13 of the present invention and the comparative cBN tools 1 to 13 of the present invention, a cutting test was performed under the following cutting conditions A, and the crater wear depth after 10 minutes of cutting time was measured, and the chipping was lost. The presence or absence of was observed.
<Cutting condition A>
Work material: φ200mm round bar with two grooves in the axial direction of FC25,
Cutting speed: 150 m / min,
Feed: 0.6 mm / rev,
Cutting depth: 2.0 mm,
The presence or absence of chipping of the cutting edge after 2500 interrupts was confirmed by a dry interrupted cutting test of outer periphery processing under the above conditions.
The blade edge was confirmed with an optical microscope.
Table 5 shows the measurement results of the cutting test.
特に、表２、４、５、６に示される結果から、本発明ｃＢＮ工具１〜１３は、ｃＢＮ粒子の表面がＡｌ２Ｏ３膜によってコーティングされ、互いのｃＢＮ粒の接触を防ぐことにより、焼結体組織として画像解析から得られるｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群の合計面積割合が０．１より大きく０．３５以下と少ないことから、切れ刃に高負荷が作用する切削加工において、ｃＢＮ粒子が結合相により強固に保持されるため、すぐれた耐欠損性を発揮する。
これに対して、比較例ｃＢＮ工具１〜１３は、ｃＢＮ粒子表面にＡｌ２Ｏ３膜コーティングがないため、あるいは、ｃＢＮ粒子の平均粒径より算出できるｃＢＮ粒子の平均面積の２．５倍より大きい面積を有するｃＢＮ粒子群の合計面積割合が０．３５より大きいため耐欠損性に劣ることが明らかである。
In particular, from the results shown in Tables 2, 4, 5, and 6, the cBN tools 1 to 13 of the present invention are coated with an Al 2 O 3 film on the surface of the cBN particles to prevent contact between the cBN particles. The total area ratio of cBN particles having an area larger than 2.5 times the average area of cBN particles, which can be calculated from the average particle diameter of cBN particles obtained from image analysis as a sintered body structure, is larger than 0.1 and larger than 0.35. Since cBN particles are firmly held by the binder phase in the cutting process in which a high load acts on the cutting edge because of the small amount below, excellent fracture resistance is exhibited.
On the other hand, Comparative Examples cBN tools 1 to 13 have no Al 2 O 3 film coating on the surface of cBN particles, or 2.5 times the average area of cBN particles that can be calculated from the average particle size of cBN particles. Since the total area ratio of the cBN particle group having a large area is larger than 0.35, it is apparent that the chipping resistance is inferior.
上述のように、この発明のｃＢＮ工具は、耐欠損性にすぐれ、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。
As described above, the cBN tool of the present invention has excellent fracture resistance, and can sufficiently satisfy the high performance of the cutting device, the labor saving and energy saving of the cutting work, and the cost reduction.
Claims (2)
立方晶窒化ほう素基超高圧焼結材料の構成成分は立方晶窒化ほう素が５０〜８５ｖｏｌ％、残りが酸化アルミニウムを主体とし、かつ、前記立方晶窒化ほう素基超高圧焼結材料の断面について測定した場合、立方晶窒化ほう素粒子の平均粒径より算出できる立方晶窒化ほう素粒子の平均面積の２．５倍より大きい面積を有する立方晶窒化ほう素粒子群が占める合計面積割合は、立方晶窒化ほう素粒子の総面積の０．１０より大きく０．３５以下であることを特徴とする立方晶窒化ほう素基超高圧焼結材料製切削工具。 In the cutting tool made of cubic boron nitride based ultra high pressure sintered material,
The components of the cubic boron nitride-based ultrahigh-pressure sintered material are 50 to 85 vol% of cubic boron nitride, the remainder is mainly aluminum oxide, and the cross section of the cubic boron nitride-based ultrahigh-pressure sintered material When measuring about the total area ratio occupied by cubic boron nitride particles having an area larger than 2.5 times the average area of cubic boron nitride particles, which can be calculated from the average particle size of cubic boron nitride particles is A cubic boron nitride-based ultrahigh pressure sintered material cutting tool, wherein the total area of the cubic boron nitride particles is greater than 0.10 and less than or equal to 0.35.
2. The cubic boron nitride-based ultrahigh pressure according to claim 1, wherein a content ratio of cubic boron nitride particles in the cubic boron nitride-based ultrahigh pressure sintered material is 70 to 85% by volume. Cutting tool made of sintered material.
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| JP5574277B2 (en) * | 2010-10-29 | 2014-08-20 | 三菱マテリアル株式会社 | Cutting tool made of surface-coated cubic boron nitride-based ultra-high pressure sintered material with excellent peeling resistance |
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| EP3061738B1 (en) * | 2013-10-22 | 2018-09-26 | Tungaloy Corporation | Cubic boron nitride sintered body and coated cubic boron nitride sintered body |
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2014
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| CN104942555A (en) | 2015-09-30 |
| CN104942555B (en) | 2018-06-08 |
| JP2015182219A (en) | 2015-10-22 |
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