JP3762278B2 - Cemented carbide and method for producing the same - Google Patents
Cemented carbide and method for producing the same Download PDFInfo
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- JP3762278B2 JP3762278B2 JP2001298672A JP2001298672A JP3762278B2 JP 3762278 B2 JP3762278 B2 JP 3762278B2 JP 2001298672 A JP2001298672 A JP 2001298672A JP 2001298672 A JP2001298672 A JP 2001298672A JP 3762278 B2 JP3762278 B2 JP 3762278B2
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- cemented carbide
- iron
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- carbide
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Links
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- 239000011651 chromium Substances 0.000 claims description 80
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 67
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 52
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 41
- 229910052804 chromium Inorganic materials 0.000 claims description 41
- 229910052751 metal Inorganic materials 0.000 claims description 38
- 239000002184 metal Substances 0.000 claims description 38
- 238000010304 firing Methods 0.000 claims description 28
- 239000000843 powder Substances 0.000 claims description 27
- 239000010941 cobalt Substances 0.000 claims description 24
- 229910017052 cobalt Inorganic materials 0.000 claims description 24
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 24
- 229910052759 nickel Inorganic materials 0.000 claims description 22
- 238000000576 coating method Methods 0.000 claims description 19
- 239000011248 coating agent Substances 0.000 claims description 18
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 claims description 15
- 150000004767 nitrides Chemical class 0.000 claims description 14
- 230000000737 periodic effect Effects 0.000 claims description 12
- 239000002994 raw material Substances 0.000 claims description 11
- 150000002739 metals Chemical class 0.000 claims description 8
- 229910052799 carbon Inorganic materials 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 6
- 230000001590 oxidative effect Effects 0.000 claims description 6
- 238000010298 pulverizing process Methods 0.000 claims description 6
- 150000001247 metal acetylides Chemical class 0.000 claims description 5
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 3
- 229910010037 TiAlN Inorganic materials 0.000 claims description 3
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 239000000956 alloy Substances 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- 229910003460 diamond Inorganic materials 0.000 claims description 3
- 239000010432 diamond Substances 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 238000005520 cutting process Methods 0.000 description 29
- 239000000463 material Substances 0.000 description 20
- 239000012071 phase Substances 0.000 description 14
- 238000003466 welding Methods 0.000 description 10
- 238000000034 method Methods 0.000 description 9
- 239000002245 particle Substances 0.000 description 9
- 230000007423 decrease Effects 0.000 description 8
- 239000010408 film Substances 0.000 description 8
- 239000007791 liquid phase Substances 0.000 description 5
- 238000000465 moulding Methods 0.000 description 5
- 238000005245 sintering Methods 0.000 description 5
- 239000010935 stainless steel Substances 0.000 description 5
- 229910001220 stainless steel Inorganic materials 0.000 description 5
- 238000000151 deposition Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 239000011812 mixed powder Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 229910009043 WC-Co Inorganic materials 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- 239000003610 charcoal Substances 0.000 description 2
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000001694 spray drying Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000009694 cold isostatic pressing Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 239000002612 dispersion medium Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004993 emission spectroscopy Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 238000005469 granulation Methods 0.000 description 1
- 230000003179 granulation Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000004949 mass spectrometry Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 239000012808 vapor phase Substances 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
- C23C28/044—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material coatings specially adapted for cutting tools or wear applications
Description
【０００１】
【発明の属する技術分野】
本発明は超硬合金およびその製造方法に関し、特に炭素鋼、合金鋼、ステンレス鋼等の一般鋼の切削加工に適する切削工具や摺動部材、耐摩耗部材等に使用される高強度かつ高靭性な表面を有する超硬合金とその製造方法に関する。
【０００２】
【従来の技術】
金属の切削加工や摺動部材、耐摩耗部材等に広く用いられている超硬合金は、炭化タングステン（ＷＣ）を主体とする硬質相をコバルト（Ｃｏ）やニッケル（Ｎｉ）の結合相中で結合させたＷＣ−Ｃｏ（Ｎｉ）合金、もしくはこのＷＣ−Ｃｏ（Ｎｉ）合金に周期律表第４ａ、５ａ、６ａ族金属の炭化物、窒化物、炭窒化物の硬質相を分散せしめた系が知られている。これらの超硬合金は、特に、炭素鋼や合金鋼、ステンレス鋼等の一般鋼の切削工具として利用されている。
【０００３】
一般的に、かかる超硬合金を製造する方法としては、上記のような超硬合金を構成する原料粉末を粉砕して混合して成形した後、１３５０〜１６００℃で１〜３時間程度焼成する方法が知られている。
【０００４】
【発明が解決しようとする課題】
しかしながら、上記従来の超硬合金においては、これを切削工具等として用いた場合、超硬合金中に不純物として含まれる鉄（Ｆｅ）およびクロム（Ｃｒ）が切削加工中に高温となった被削材に多量に含まれる鉄（Ｆｅ）やクロム（Ｃｒ）と結合し、被削材が切削工具表面に溶着や凝着して切れ刃等の作用部が異常に摩耗したり、切削抵抗が増大して切削工具表面に損傷が発生しやすくなったり、溶着物や凝着物の凹凸によって被削物表面の仕上面粗さが劣化する等の問題があった。
【０００５】
なお、超硬合金中の鉄（Ｆｅ）とクロム（Ｃｒ）は、一次原料に不可避不純物として含有していたり、製造工程において混入したりするものであるが、工業上完全に取り除くことはできず、また、製造工程で混入する鉄（Ｆｅ）およびクロム（Ｃｒ）の含有量は工程の変更や、粉砕機等の表面状態に伴って変動するために制御できないものであった。
【０００６】
また、鉄（Ｆｅ）は炭素との親和性が高いために、超硬合金の表面における鉄（Ｆｅ）の含有量が多いと、ＣＶＤ法やＰＶＤ法等の気相合成法で硬質被膜をコーティングする場合には炭素と鉄（Ｆｅ）とが優先的に結合し、超硬合金と硬質被膜との界面にη相等の脆化相が生成しやすく、硬質被膜の密着強度が低下する結果、硬質被膜が剥離して破壊したり、これを切削工具や摺動部材として使用した場合には寿命が低下するという問題があった。
【０００７】
したがって、本発明は上記課題を解決するためになされたもので、その目的は、切削時や摺動時等の被削材との溶着や凝着を抑制でき、また、良好な硬質被膜を形成することも可能な超硬合金を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明者は、上記課題、特に超硬合金中の鉄（Ｆｅ）およびクロム（Ｃｒ）が被削材に与える影響を抑制できる構成について検討した結果、超硬合金中の鉄（Ｆｅ）およびクロム（Ｃｒ）の含有量を制御し、かつ超硬合金表面におけるコバルト（Ｃｏ）および／またはニッケル（Ｎｉ）に対する鉄（Ｆｅ）およびクロム（Ｃｒ）の含有比率を超硬合金内部よりも低減させることにより、被削材との溶着や凝着が抑制でき、硬質被膜を被着形成する際にも良好な硬質被膜を被着形成できる超硬合金が得られることを知見して本発明に至った。
【０００９】
すなわち、請求項１に係る超硬合金は、コバルト（Ｃｏ）および／またはニッケル（Ｎｉ）の結合金属を２〜２０重量％、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、窒化物および／または炭窒化物を０〜３０重量％含有するともに、鉄（Ｆｅ）を１０〜３００ｐｐｍ、クロム（Ｃｒ）を１００〜１０００ｐｐｍ含有し、残部が炭化タングステンと不可避不純物から成る超硬合金において、この超硬合金の表面近傍に、この超硬合金内部の前記結合金属の総含有量をｗ1in、この超硬合金内部の鉄（Ｆｅ）およびクロム（Ｃｒ）の総含有量をｗ2in、この超硬合金表面領域の前記結合金属の総含有量をｗ1suf、この超硬合金表面領域の鉄（Ｆｅ）およびクロム（Ｃｒ）の総含有量をｗ2sufとし、ｐin＝ｗ2in／ｗ1in、ｐsuf＝ｗ2suf／ｗ1sufとしたとき、ｐsuf＜ｐinの条件を満足する表面領域を有することを特徴とするものである。
【００１０】
上記超硬合金では、前記表面領域における前記ｐsufとｐinとの比（ｐsuf／ｐin）の最大値が０．５〜０．９５であることが望ましく、前記表面領域の厚みが１〜２０μｍであることが望ましい。
【００１１】
また、上記超硬合金では、超硬合金の表面に、周期律表第４ａ、５ａ、６ａ族金属の炭化物、窒化物、炭窒化物、ＴｉＡｌＮ、ＴｉＺｒＮ、ＴｉＣｒＮ、ＤＬＣ（ダイヤモンドライクカーボン）、ダイヤモンドおよびＡｌ2Ｏ3の群から選ばれる少なくとも１種からなる硬質被膜を少なくとも１層を総厚み１〜３０μｍで被着形成してなることが望ましい。
【００１２】
請求項５に係る超硬合金の製造方法は、炭化タングステン粉末と、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、窒化物および／または炭窒化物粉末と、コバルト（Ｃｏ）および／またはニッケル（Ｎｉ）粉末とからなる原料粉末を粉砕混合して成形した後、非酸化性雰囲気中の１３５０〜１６００℃の第１の焼成温度で０．３〜２時間保持し、この第１の焼成温度よりも２０〜２００℃低い第２の焼成温度に冷却し、続いて真空中の前記第２の焼成温度で１〜３時間保持することを特徴とするものである。
【００１３】
上記超硬合金の製造方法では、前記原料粉末を粉砕混合する際に用いる容器および粉砕部材の前記原料粉末と接触する部分が鉄（Ｆｅ）およびクロム（Ｃｒ）を含有しないことが望ましい。
【００１４】
【発明の実施の形態】
以下、本発明の実施の形態を詳細に説明する。
本発明の超硬合金は、炭化タングステン相と、コバルト（Ｃｏ）および／またはニッケル（Ｎｉ）の結合金属を２〜２０重量％、特に６〜１５重量％と、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、窒化物および／または炭窒化物からなる結晶相を０〜３０重量％、特に２〜２０重量％、さらに５〜１５重量％と、不可避不純物とからなるものである。
【００１５】
ここで、コバルト（Ｃｏ）およびニッケル（Ｎｉ）の結合金属の総含有量が２重量％より少ないと、焼結時に発生する液相量が不足して焼結不良となる結果、超硬合金の強度が低下し、逆に、結合金属の総含有量が３０重量％より多いと、超硬合金に占める結合金属相量が過剰となり、硬度が低下するとともに、切削加工として金属加工に使用した場合に大きく塑性変形する。
【００１６】
また、本発明によれば、超硬合金の硬度を向上させるとともに、鉄（Ｆｅ）、クロム（Ｃｒ）、コバルト（Ｃｏ）およびニッケル（Ｎｉ）の各金属濃度を所定の範囲内に制御する点で、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、窒化物および／または炭窒化物を３０重量％以下の割合で含有せしめることが望ましい。
【００１７】
本発明によれば、超硬合金中の鉄（Ｆｅ）の含有量が１０〜３００ｐｐｍ、クロム（Ｃｒ）の含有量が１００〜１０００ｐｐｍに制御され、かつ、超硬合金内部の結合金属の総含有量をｗ1in、超硬合金内部の鉄（Ｆｅ）およびクロム（Ｃｒ）の総含有量をｗ2in、超硬合金表面領域の結合金属の総含有量をｗ1suf、超硬合金表面領域の鉄（Ｆｅ）およびクロム（Ｃｒ）の総含有量をｗ2sufとし、ｐin＝ｗ2in／ｗ1in、ｐsuf＝ｗ2suf／ｗ1sufとしたとき、ｐsuf＜ｐinの条件を満足する表面領域を具備する。すなわち、超硬合金の表面における結合金属に対する鉄（Ｆｅ）およびクロム（Ｃｒ）の含有比率を超硬合金の内部のそれよりも小さくすることが大きな特徴である。これによって、被削材との溶着や凝着が抑制でき、硬質被膜を被着形成する際にも良好な硬質被膜を被着形成できる超硬合金が得られる。
【００１８】
ここで、超硬合金中の鉄（Ｆｅ）の含有量は、工業的に１０ｐｐｍより低くすることができず、また、超硬合金中の鉄（Ｆｅ）の含有量が３００ｐｐｍを越えると、被削材との溶着や凝着が顕著となり、切削性が低下する。一方、クロム（Ｃｒ）の含有量が１００ｐｐｍより低いと、炭化タングステン相の粒成長が顕著となり、超硬合金の強度と靭性が低下する。逆に、クロム（Ｃｒ）の含有量が１０００ｐｐｍを越えると、被削材との溶着や凝着が顕著となり、切削性が低下する。
【００１９】
なお、本発明において、超硬合金中の鉄（Ｆｅ）およびクロム（Ｃｒ）の含有量を測定するには、焼結後の超硬合金を超硬合金製乳鉢などを使って粉砕した粉末を公知の方法で溶解した溶液を作製し、ＩＣＰ発光分光分析法で測定する方法によって定量することができる。また、これら鉄（Ｆｅ）、クロム（Ｃｒ）、コバルト（Ｃｏ）およびニッケル（Ｎｉ）の表面と内部の局所的な含有量の比を測定するには、レーザーＩＣＰ質量分析法を用いることができる。さらに、本発明における超硬合金の内部とは、超硬合金の表面から１ｍｍ以上深い領域をいう。
【００２０】
また、表面領域におけるｐsufとｐinとの比（ｐsuf／ｐin）の最大値は、超硬合金表面の耐溶着性と耐凝着性を改善するために、０．５〜０．９５、特に０．６〜０．８であることが望ましい。
【００２１】
また、表面領域の厚みは、被削材等の溶着や凝着を抑制し、かつ表面領域の硬度を維持して、塑性変形を防止する点で、１〜２０μｍであることが望ましい。
【００２２】
なお、超硬合金中の炭化タングステン相は六方晶であって、その平均粒径が０．５〜３．０μｍであることが望ましい。ここで、本発明における炭化タングステン相等の結晶相の平均粒径とは、超硬合金断面のＳＥＭ写真からインターセプト法によって求められる値をいう。
【００２３】
また、本発明によれば、超硬合金の表面に、周期律表第４ａ、５ａ、６ａ族金属の炭化物、窒化物、炭窒化物、ＴｉＡｌＮ、ＴｉＺｒＮ、ＴｉＣｒＮ、ＤＬＣ（ダイヤモンドライクカーボン）、ダイヤモンドおよびＡｌ2Ｏ3の群から選ばれる少なくとも１種からなる硬質被膜を少なくとも１層を被着形成してなるものであってもよく、これによって、超硬合金表面の硬度および耐摩耗性を著しく向上させることができる。
【００２４】
さらに、本発明によれば、超硬合金の表面に硬質被膜を被着形成する際においても、超硬合金表面における鉄（Ｆｅ）やクロム（Ｃｒ）の含有比率が低いために、フェライトや炭化クロム等の生成による炭素の減少が起きないために、界面付近にコバルトの低級炭化物であるη相（Ｗ3Ｃｏ3Ｃ、Ｗ6Ｃｏ6Ｃなど）等の脆化層が生成することなく、良好な硬質被膜を形成することができる。
【００２５】
なお、硬質被膜の膜厚は、耐摩耗性と靭性をともに維持する点で総厚み１〜３０μｍであることが望ましく、また、硬質被膜は従来公知のＰＶＤ法やＣＶＤ法等の薄膜形成法によって被着形成される。
【００２６】
（製造方法）
次に、上述した超硬合金の製造方法を説明する。
まず、例えば鉄（Ｆｅ）およびクロム（Ｃｒ）の含有量がそれぞれ０．００５〜０．１重量％で平均粒径が０．５〜１０μｍの炭化タングステン粉末を７０〜９０重量％と、鉄（Ｆｅ）とクロム（Ｃｒ）の含有量がそれぞれ１５〜５００ｐｐｍで平均粒径が０．５〜１０μｍの周期律表第４ａ、５ａ、６ａ族金属の群から選ばれる炭化物、窒化物および／または炭窒化物粉末またはその固溶体粉末を０．１〜３０重量％と、鉄（Ｆｅ）の含有量が１〜１５ｐｐｍでクロム（Ｃｒ）の含有量が１〜２０ｐｐｍで平均粒径が０．５〜１０μｍのコバルト（Ｃｏ）および／またはニッケル（Ｎｉ）を５〜１５重量％と、さらには所望により金属タングステン（Ｗ）粉末あるいはカーボンブラック（Ｃ）とを秤量して混合する。
【００２７】
これらの混合粉末を鉄（Ｆｅ）およびクロム（Ｃｒ）を含まない材料、例えば純度９９．９％以上の超硬合金からなる内張りやメディアや攪拌アーム等を有する粉砕機内に投入し、アルコール、アセトン、炭化水素等の分散媒を加えて５〜３０時間湿式粉砕した後、噴霧乾燥等の公知の造粒方法によって所望の粒径に造粒する。ここで、粉砕時間が５時間より短いと原料粉末を十分に粉砕して混合することができず、所望の均一な表面領域を形成することができない。逆に、粉砕時間が３０時間より長いと粉砕機から炭化タングステン成分および他の不純物が多量に混入して混合粉末の組成ずれを引き起こす。
【００２８】
次に、得られた混合粉末を用いて、プレス成形、鋳込成形、押出成形、冷間静水圧プレス成形等の公知の成形方法によって所定形状に成形した後、２０Ｐａ以上の非酸化性雰囲気中、１〜２０℃／分で１３５０〜１６００℃の第１の焼成温度に昇温し、次いで第１の焼成温度で０．３〜２時間、特に０．５〜１時間保持する。なお、非酸化性雰囲気とは、特に、窒素ガス（Ｎ2）、ヘリウムガス（Ｈｅ）、アルゴンガス（Ａｒ）、キセノンガス（Ｘｅ）等の不活性ガスを封入またはフローさせる状態をいう。
【００２９】
かかる非酸化性雰囲気中、第１の焼成温度で短時間保持することによって、コバルト（Ｃｏ）および／またはニッケル（Ｎｉ）からなる結合金属の一部が金属液相となる。このとき、鉄（Ｆｅ）とクロム（Ｃｒ）は、コバルト（Ｃｏ）とニッケル（Ｎｉ）に伴って溶融して拡散する。
【００３０】
続いて上記第１の焼成温度から２０〜２００℃低い第２の焼成温度に、望ましくは、超硬合金中における各々の金属の分布状態を最適化するために降温速度５〜５０℃／時間で降温し、１０Ｐａより低い第２の焼成温度の真空中、特に１２００〜１３８０℃で１〜３時間保持し、表面からＣｏ（コバルト）および／またはニッケル（Ｎｉ）が選択的に真空雰囲気中に蒸発するとともに、内部に存在するＣｏ（コバルト）および／またはニッケル（Ｎｉ）が選択的に表面へと拡散する結果、焼結体中に所定の金属の濃度勾配をつけることができる。その後、室温まで冷却することにより本発明の超硬合金を作製することができる。
【００３１】
ここで、第１の焼成温度が１３５０℃より低いと、温度が低くて適量の液相を生成させることができず、焼結体を十分に緻密化させることができなくなり、逆に第１の焼成温度が１６００℃より高いと、焼結が過度に進行して炭化タングステン粒子等の硬質粒子が粒成長して靭性や強度が低下するとともに、金属液相中のコバルト（Ｃｏ）および／またはニッケル（Ｎｉ）が選択的に表面から多量に蒸発して表面における金属の濃度分布を所定の範囲とすることができず、かつ表面が脆化する。
【００３２】
また、第１の焼成温度での保持時間が０．１時間よりも短いと、適量の液相を生成させることができず、焼結体を十分に緻密化させることができず、逆に第１の焼成温度での保持時間が２時間よりも長いと、焼結が過剰に進んで靭性や強度が低下するとともに、鉄（Ｆｅ）とクロム（Ｃｒ）が所定量を超えて表面に析出したり、表面が脆化する。
【００３３】
さらに、第２の焼成温度と第１の焼成温度との差が２０℃よりも小さいと、コバルト（Ｃｏ）およびニッケル（Ｎｉ）と鉄（Ｆｅ）およびクロム（Ｃｒ）との移動速度（拡散速度）に差が生じないため、超硬合金中に所望の濃度分布をつけることができず、逆に第２の焼成温度と第１の焼成温度との差が２００℃よりも大きいと、各金属の拡散速度が全体的に低下して所定の金属濃度勾配をつけることができなくなる。
【００３４】
【実施例】
表１に示す量で鉄（Ｆｅ）およびクロム（Ｃｒ）を含有する平均粒径が９μｍの炭化タングステン（ＷＣ）粉末、金属コバルト（Ｃｏ）粉末および化合物粉末を表１に示す比率で秤量し、純度９９．９９％以上の超硬合金からなる内壁、メディア、および攪拌アームを有するアトライタミル内に導入し、これに２−プロパノールを添加して１８時間湿式粉砕し、スプレードライによって造粒した後、プレス成形によって切削工具形状（ＳＤＫ１２０３）に成形した。
【００３５】
次に、得られた成形体を真空焼結炉にセットし、１２℃／分の速度で昇温して表１に示す第１の焼成温度で所定時間保持し、続いて表１に示す降温速度で第２の焼成温度に降温した後、この第２の焼成温度で所定時間保持し、その後室温まで冷却した。なお、表中の真空雰囲気とは真空度８Ｐａ以下の状態に制御し、かつ表中の各種ガス（Ａｒ、Ｎ2、Ｈｅ）雰囲気とは２５Ｐａの状態に制御した。
【００３６】
得られた超硬合金に対して、超硬合金からなる乳鉢で粉砕し、この粉末を溶解した溶液に対してＩＣＰ発光分光分析を行ない、鉄（Ｆｅ）およびクロム（Ｃｒ）の含有量を測定した。また、超硬合金の表面と、１ｍｍ以上研削した面の鉄含有量をレーザーＩＣＰ−ＭＳで測定した。なお、レーザーＩＣＰ−ＭＳの測定面積は１０μｍφとした。
【００３７】
【表１】
そして、得られた超硬合金を用いて下記（テスト１）の条件によりステンレス鋼の切削を１５分間行ない、切削工具のフランク摩耗量および境界損傷量を測定した。なお、切削試験中にフランク摩耗量が０．２ｍｍあるいは境界損傷量が０．５ｍｍに達した場合にはその切削時間を測定した。さらに、切削試験後の工具の刃先を観察し、変形や損傷の有無を確認した。その結果を表２に示す。
【００３９】
テスト１
被削材 ：ステンレス鋼（ＳＵＳ３０４）
工具形状：ＳＤＫＮ１２０３ＡＵＴＮ
切削速度：２００ｍ／分
送り速度：０．２ｍｍ／刃
切り込み：２ｍｍ
その他 ：乾式切削
【００４０】
【表２】
表１、表２の結果より、原料中の鉄（Ｆｅ）の含有量が多い試料Ｎｏ．１および粉砕メディアおよび撹拌アームとしてステンレスを用いた試料Ｎｏ．２では、超硬合金全体中の鉄（Ｆｅ）の含有量が３００ｐｐｍを越えてしまい、切削加工中に硬質被膜が摩滅して超硬合金が露出した後に、急激に摩耗が進行して工具寿命に達してしまった。また、第１の焼成温度のみで保持する（一段焼成）パターンの焼成を行った試料Ｎｏ．３および第１の焼成温度と第２の焼成温度との差が２００℃を越える試料Ｎｏ．４では、いずれも表面におけるコバルト（Ｃｏ）および／またはニッケル（Ｎｉ）に対する鉄（Ｆｅ）およびクロム（Ｃｒ）の含有比率が同等以上となり、被削材の溶着や凝着が顕著で切削性能が低下した。さらに、第１の焼成温度での保持と第２の焼成温度での保持をともに真空中で行った試料Ｎｏ．５ではＰsuf／Ｐinがほぼ１．０となり、表面と内部における（鉄＋クロム）と（コバルト＋ニッケル）の存在比に差がない。つまり発明品に比べて表面における脆化相の生成量が多いため、硬質被膜の付着力が低下し、切削加工中に被膜の剥離が発生した。この結果、摩耗量は増大し、切削工具切れ刃に溶着物が多量に付着する結果となった。
【００４２】
これに対して、本発明に従う試料Ｎｏ．６〜１３では、いずれもフランク摩耗量０．２ｍｍ（加工時間／１５ｍｉｎ）以下の優れた耐摩耗性を有するものであった。
【００４３】
（実施例２）
また、試料Ｎｏ．２、１２、１３については、表面にＰＶＤ法により表３に示す材質と厚みの硬質被膜を成膜し、上記と同様の条件で切削試験を行った。
【００４４】
【表３】
表３から明らかなように、鉄の含有量が多い試料２を母材とした試料Ｎｏ．２−１では硬質被膜が剥離して被削物が工具表面に多量に溶着したのに対して、本発明に従う試料Ｎｏ．１２を母材にした試料１２−１、２、３、および試料Ｎｏ．１３を母材にした試料１３−１では硬質被膜が剥離することはなく、かつ被削材の溶着も少ないものであった。
【００４６】
本発明品については、旋盤で使用する旋削加工用工具、フライス盤やマシニングセンターで使用する正面フライス、エンドミル、ボールエンドミル、ドリル用の工具材種等、汎用的に使用することができる。
【００４７】
【発明の効果】
以上詳述したとおり、請求項１に係る超硬合金によれば、超硬合金中の鉄（Ｆｅ）およびクロム（Ｃｒ）の含有量を制御し、かつ超硬合金表面におけるコバルト（Ｃｏ）およびまたはニッケル（Ｎｉ）に対する鉄（Ｆｅ）およびクロム（Ｃｒ）の含有比率を超硬合金内部よりも低減させることにより、被削材との溶着や凝着が抑制でき、硬質被膜を被着形成する際にも良好な硬質被膜を被着形成できる超硬合金が得られる。
【００４８】
また、請求項５に係る超硬合金の製造方法によれば、炭化タングステン粉末と、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、窒化物および／または炭窒化物粉末と、コバルト（Ｃｏ）および／またはニッケル（Ｎｉ）粉末とからなる原料粉末を粉砕混合して成形した後、非酸化性雰囲気中、１３５０〜１６００℃の第１の焼成温度で０．３〜２時間保持し、続いて前記第１の焼成温度よりも２０〜２００℃低い第２の焼成温度に冷却し、この第２の焼成温度の真空中で１〜３時間保持することから、超硬合金中の鉄（Ｆｅ）およびクロム（Ｃｒ）の含有量を制御し、かつ超硬合金表面におけるコバルト（Ｃｏ）およびまたはニッケル（Ｎｉ）に対する鉄（Ｆｅ）およびクロム（Ｃｒ）の含有比率を、超硬合金内部よりも低減させた超硬合金となり、被削材との溶着や凝着が抑制でき、硬質被膜を被着形成する際にも良好な硬質被膜を被着形成できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cemented carbide and a method for producing the same, and in particular, high strength and high toughness used for cutting tools, sliding members, wear-resistant members and the like suitable for cutting of general steels such as carbon steel, alloy steel, and stainless steel. The present invention relates to a cemented carbide having a smooth surface and a method for producing the same.
[0002]
[Prior art]
Cemented carbides widely used in metal cutting, sliding members, wear-resistant members, etc., have a hard phase mainly composed of tungsten carbide (WC) in a bonded phase of cobalt (Co) or nickel (Ni). A bonded WC—Co (Ni) alloy, or a system in which a hard phase of 4a, 5a, 6a group metal carbide, nitride, carbonitride of the periodic table is dispersed in the WC—Co (Ni) alloy. Are known. These cemented carbides are particularly used as cutting tools for general steels such as carbon steel, alloy steel, and stainless steel.
[0003]
In general, as a method for producing such a cemented carbide, the raw material powder constituting the cemented carbide as described above is pulverized, mixed and molded, and then fired at 1350-1600 ° C. for about 1 to 3 hours. The method is known.
[0004]
[Problems to be solved by the invention]
However, in the above conventional cemented carbide, when this is used as a cutting tool, iron (Fe) and chromium (Cr) contained as impurities in the cemented carbide become a high temperature during cutting. Combined with iron (Fe) and chromium (Cr) contained in a large amount in the material, the work material is welded and adhered to the surface of the cutting tool, the working part such as the cutting edge is abnormally worn, and the cutting resistance increases. As a result, the surface of the cutting tool is likely to be damaged, and the roughness of the finished surface of the work surface is deteriorated due to the unevenness of the welded material or the adhered material.
[0005]
In addition, iron (Fe) and chromium (Cr) in cemented carbide are contained as inevitable impurities in the primary raw material or mixed in during the manufacturing process, but cannot be completely removed industrially. In addition, the contents of iron (Fe) and chromium (Cr) mixed in the manufacturing process cannot be controlled because they fluctuate in accordance with changes in the process or the surface condition of a pulverizer or the like.
[0006]
Also, since iron (Fe) has a high affinity with carbon, if the content of iron (Fe) on the surface of the cemented carbide is high, a hard film is coated by a vapor phase synthesis method such as CVD or PVD. In this case, carbon and iron (Fe) are preferentially bonded, and an embrittled phase such as η phase is likely to be generated at the interface between the cemented carbide and the hard coating, resulting in a decrease in the adhesion strength of the hard coating. When the coating peels and breaks, or when it is used as a cutting tool or a sliding member, there is a problem that the life is shortened.
[0007]
Therefore, the present invention has been made to solve the above problems, and its purpose is to suppress welding and adhesion to the work material during cutting or sliding, and to form a good hard film. An object of the present invention is to provide a cemented carbide that can be used.
[0008]
[Means for Solving the Problems]
As a result of studying the above-described problem, particularly the configuration that can suppress the influence of iron (Fe) and chromium (Cr) in the cemented carbide on the work material, the present inventors have found that iron (Fe) and chromium in the cemented carbide To control the content of (Cr) and reduce the content ratio of iron (Fe) and chromium (Cr) to cobalt (Co) and / or nickel (Ni) on the surface of the cemented carbide than in the cemented carbide. By this, it was found that a cemented carbide capable of suppressing welding and adhesion to the work material and capable of depositing a good hard film even when depositing a hard film was obtained, leading to the present invention. .
[0009]
That is, the cemented carbide according to claim 1 contains at least 2 to 20% by weight of a cobalt (Co) and / or nickel (Ni) bond metal, and is selected from the group of metals in groups 4a, 5a, and 6a of the periodic table. It contains 0 to 30% by weight of one type of carbide, nitride and / or carbonitride, 10 to 300 ppm of iron (Fe), 100 to 1000 ppm of chromium (Cr), the balance being tungsten carbide and inevitable impurities In the cemented carbide comprising, in the vicinity of the surface of the cemented carbide, the total content of the bonding metal in the cemented carbide is w 1in , the total amount of iron (Fe) and chromium (Cr) in the cemented carbide. The content is w 2in , the total content of the binding metal in the cemented carbide surface region is w 1suf , the total content of iron (Fe) and chromium (Cr) in the cemented carbide surface region is w 2suf , p in = w 2in w 1in, when the p suf = w 2suf / w 1suf , it is characterized in that it has a surface area that satisfies the conditions of the p suf <p in.
[0010]
In the cemented carbide, it is desirable maximum value of the ratio between the p suf and p in in the surface region (p suf / p in) is 0.5 to 0.95, the thickness of the surface region 1 It is desirable that it is ˜20 μm.
[0011]
In the above cemented carbide, the carbides, nitrides, carbonitrides, TiAlN, TiZrN, TiCrN, DLC (diamond-like carbon), diamond of the periodic table group 4a, 5a, 6a metal are provided on the surface of the cemented carbide. It is desirable that at least one hard film made of at least one selected from the group consisting of Al 2 O 3 is deposited and formed with a total thickness of 1 to 30 μm.
[0012]
A method for producing a cemented carbide according to claim 5 includes tungsten carbide powder, and at least one carbide, nitride and / or carbonitride powder selected from the group of metals in groups 4a, 5a and 6a of the periodic table. Then, after pulverizing and mixing the raw material powder composed of cobalt (Co) and / or nickel (Ni) powder, it is 0.3 to 2 hours at a first firing temperature of 1350 to 1600 ° C. in a non-oxidizing atmosphere. Holding and cooling to a second baking temperature 20 to 200 ° C. lower than the first baking temperature, and subsequently holding at the second baking temperature in vacuum for 1 to 3 hours. is there.
[0013]
In the above-mentioned cemented carbide manufacturing method, it is desirable that the container used when pulverizing and mixing the raw material powder and the portion of the pulverized member that contacts the raw material powder do not contain iron (Fe) and chromium (Cr).
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The cemented carbide of the present invention comprises a tungsten carbide phase and a cobalt (Co) and / or nickel (Ni) bond metal in an amount of 2 to 20% by weight, particularly 6 to 15% by weight, and periodic tables 4a and 5a. 0-30 wt%, especially 2-20 wt%, more preferably 5-15 wt% of the crystal phase comprising at least one carbide, nitride and / or carbonitride selected from the group 6a metal, unavoidable impurities It consists of
[0015]
Here, if the total content of the binding metal of cobalt (Co) and nickel (Ni) is less than 2% by weight, the amount of liquid phase generated during sintering becomes insufficient, resulting in poor sintering. When the strength decreases, conversely, if the total content of the bonding metal is more than 30% by weight, the amount of the bonding metal phase in the cemented carbide becomes excessive, the hardness decreases, and when used for metal processing as cutting Greatly plastically deforms.
[0016]
Further, according to the present invention, the hardness of the cemented carbide is improved, and each metal concentration of iron (Fe), chromium (Cr), cobalt (Co) and nickel (Ni) is controlled within a predetermined range. Therefore, it is desirable to contain at least one carbide, nitride and / or carbonitride selected from the group of metals in Groups 4a, 5a and 6a of the Periodic Table in a proportion of 30% by weight or less.
[0017]
According to the present invention, the content of iron (Fe) in the cemented carbide is controlled to 10 to 300 ppm, the content of chromium (Cr) is controlled to 100 to 1000 ppm, and the total content of bonded metals inside the cemented carbide is included. The amount of w 1in , the total content of iron (Fe) and chromium (Cr) in the cemented carbide is w 2in , the total content of bonded metal in the cemented carbide surface region is w 1suf , the iron in the cemented carbide surface region (Fe) and the total content of chromium (Cr) and w 2suf, p in = w 2in / w 1in, when the p suf = w 2suf / w 1suf , surface satisfies the conditions of the p suf <p in region It comprises. That is, it is a great feature that the content ratio of iron (Fe) and chromium (Cr) to the bonding metal on the surface of the cemented carbide is smaller than that in the cemented carbide. As a result, welding and adhesion to the work material can be suppressed, and a cemented carbide capable of depositing a good hard coating even when the hard coating is deposited is obtained.
[0018]
Here, the iron (Fe) content in the cemented carbide cannot be industrially made lower than 10 ppm, and if the iron (Fe) content in the cemented carbide exceeds 300 ppm, Welding and adhesion with the cutting material become prominent, and machinability deteriorates. On the other hand, when the content of chromium (Cr) is lower than 100 ppm, the grain growth of the tungsten carbide phase becomes remarkable, and the strength and toughness of the cemented carbide decreases. On the other hand, when the chromium (Cr) content exceeds 1000 ppm, welding and adhesion with the work material become remarkable, and machinability deteriorates.
[0019]
In the present invention, in order to measure the content of iron (Fe) and chromium (Cr) in the cemented carbide, a powder obtained by pulverizing the sintered cemented carbide using a cemented carbide mortar or the like is used. A solution dissolved by a known method can be prepared and quantified by a method of measuring by ICP emission spectrometry. Laser ICP mass spectrometry can be used to measure the ratio of the local content of the surface and the interior of iron (Fe), chromium (Cr), cobalt (Co) and nickel (Ni). . Furthermore, the inside of the cemented carbide in the present invention refers to a region deeper than 1 mm from the surface of the cemented carbide.
[0020]
The maximum value of the ratio of the p suf and p in the surface region (p suf / p in), in order to improve the adhesion resistance and adhesion resistance of the cemented carbide surface, from 0.5 to 0. 95, especially 0.6 to 0.8 is desirable.
[0021]
Further, the thickness of the surface region is desirably 1 to 20 μm from the viewpoint of preventing welding and adhesion of the work material and the like, and maintaining the hardness of the surface region to prevent plastic deformation.
[0022]
The tungsten carbide phase in the cemented carbide is a hexagonal crystal, and the average particle size is preferably 0.5 to 3.0 μm. Here, the average particle diameter of a crystal phase such as a tungsten carbide phase in the present invention refers to a value obtained by an intercept method from an SEM photograph of a cemented carbide cross section.
[0023]
In addition, according to the present invention, carbide, nitride, carbonitride, TiAlN, TiZrN, TiCrN, DLC (diamond-like carbon), diamond of the periodic table group 4a, 5a, 6a metal are provided on the surface of the cemented carbide. And at least one hard coating composed of at least one selected from the group consisting of Al 2 O 3 may be formed, thereby significantly increasing the hardness and wear resistance of the cemented carbide surface. Can be improved.
[0024]
Furthermore, according to the present invention, even when a hard coating is deposited on the surface of the cemented carbide, the content of iron (Fe) or chromium (Cr) on the cemented carbide surface is low, so Since there is no reduction in carbon due to the generation of chromium or the like, an embrittlement layer such as a η phase (W 3 Co 3 C, W 6 Co 6 C, etc.) which is a lower carbide of cobalt is not generated near the interface, A good hard film can be formed.
[0025]
The film thickness of the hard coating is preferably 1 to 30 μm in terms of maintaining both wear resistance and toughness, and the hard coating is formed by a conventionally known thin film forming method such as PVD or CVD. It is deposited.
[0026]
(Production method)
Next, the manufacturing method of the cemented carbide mentioned above is demonstrated.
First, for example, a tungsten carbide powder having a content of 0.005 to 0.1% by weight of iron (Fe) and chromium (Cr) and an average particle size of 0.5 to 10 μm is 70 to 90% by weight, Carbides, nitrides and / or charcoal selected from the group of Group 4a, 5a and 6a metals in the periodic table having an Fe) and chromium (Cr) content of 15 to 500 ppm and an average particle size of 0.5 to 10 μm, respectively. 0.1-30 wt% of nitride powder or solid solution powder thereof, iron (Fe) content of 1-15 ppm, chromium (Cr) content of 1-20 ppm and average particle size of 0.5-10 μm 5 to 15% by weight of cobalt (Co) and / or nickel (Ni) and, if desired, metallic tungsten (W) powder or carbon black (C) are weighed and mixed.
[0027]
These mixed powders are put into a material not containing iron (Fe) and chromium (Cr), for example, a pulverizer having a lining made of cemented carbide having a purity of 99.9% or more, a media, a stirring arm, etc., and alcohol, acetone Then, a dispersion medium such as hydrocarbon is added and wet pulverized for 5 to 30 hours, and then granulated to a desired particle size by a known granulation method such as spray drying. Here, if the pulverization time is shorter than 5 hours, the raw material powder cannot be sufficiently pulverized and mixed, and a desired uniform surface region cannot be formed. Conversely, if the pulverization time is longer than 30 hours, a large amount of tungsten carbide components and other impurities are mixed from the pulverizer, causing a composition shift of the mixed powder.
[0028]
Next, using the obtained mixed powder, after molding into a predetermined shape by a known molding method such as press molding, casting molding, extrusion molding, cold isostatic pressing, etc., in a non-oxidizing atmosphere of 20 Pa or more The temperature is raised to a first baking temperature of 1350 to 1600 ° C. at 1 to 20 ° C./min, and then held at the first baking temperature for 0.3 to 2 hours, particularly 0.5 to 1 hour. Note that the non-oxidizing atmosphere refers to a state in which an inert gas such as nitrogen gas (N 2 ), helium gas (He), argon gas (Ar), or xenon gas (Xe) is sealed or flowed.
[0029]
By holding in the non-oxidizing atmosphere for a short time at the first firing temperature, a part of the binding metal composed of cobalt (Co) and / or nickel (Ni) becomes a metal liquid phase. At this time, iron (Fe) and chromium (Cr) melt and diffuse along with cobalt (Co) and nickel (Ni).
[0030]
Subsequently, to a second firing temperature that is 20 to 200 ° C. lower than the first firing temperature, preferably at a temperature lowering rate of 5 to 50 ° C./hour in order to optimize the distribution state of each metal in the cemented carbide. The temperature is lowered and kept in a vacuum at a second firing temperature lower than 10 Pa, particularly at 1200 to 1380 ° C. for 1 to 3 hours, and Co (cobalt) and / or nickel (Ni) is selectively evaporated from the surface into the vacuum atmosphere. In addition, as a result of the selective diffusion of Co (cobalt) and / or nickel (Ni) to the surface, a predetermined metal concentration gradient can be provided in the sintered body. Thereafter, the cemented carbide of the present invention can be produced by cooling to room temperature.
[0031]
Here, if the first firing temperature is lower than 1350 ° C., the temperature is low and an appropriate amount of liquid phase cannot be generated, and the sintered body cannot be sufficiently densified. When the firing temperature is higher than 1600 ° C., the sintering proceeds excessively, hard particles such as tungsten carbide particles grow and the toughness and strength decrease, and cobalt (Co) and / or nickel in the metal liquid phase decreases. A large amount of (Ni) selectively evaporates from the surface, the metal concentration distribution on the surface cannot be kept within a predetermined range, and the surface becomes brittle.
[0032]
If the holding time at the first firing temperature is shorter than 0.1 hour, an appropriate amount of liquid phase cannot be generated, and the sintered body cannot be sufficiently densified. If the holding time at the firing temperature of 1 is longer than 2 hours, the sintering proceeds excessively and the toughness and strength decrease, and iron (Fe) and chromium (Cr) are deposited on the surface exceeding a predetermined amount. Or the surface becomes brittle.
[0033]
Furthermore, if the difference between the second firing temperature and the first firing temperature is less than 20 ° C., the moving speed (diffusion speed) of cobalt (Co) and nickel (Ni) and iron (Fe) and chromium (Cr) ), A desired concentration distribution cannot be obtained in the cemented carbide, and conversely, if the difference between the second firing temperature and the first firing temperature is greater than 200 ° C., each metal As a result, the diffusion rate of the metal decreases as a whole, and a predetermined metal concentration gradient cannot be established.
[0034]
【Example】
Tungsten carbide (WC) powder having an average particle size of 9 μm containing iron (Fe) and chromium (Cr) in the amounts shown in Table 1, metal cobalt (Co) powder, and compound powder are weighed at the ratio shown in Table 1, After being introduced into an attritor mill having an inner wall made of cemented carbide with a purity of 99.99% or more, media, and a stirring arm, 2-propanol was added thereto, and the mixture was wet pulverized for 18 hours, and granulated by spray drying. A cutting tool shape (SDK1203) was formed by press molding.
[0035]
Next, the obtained molded body was set in a vacuum sintering furnace, heated at a rate of 12 ° C./minute, held at a first firing temperature shown in Table 1 for a predetermined time, and subsequently cooled in temperature shown in Table 1. After the temperature was lowered to the second firing temperature at a rate, the second firing temperature was maintained for a predetermined time, and then cooled to room temperature. The vacuum atmosphere in the table was controlled to a vacuum degree of 8 Pa or less, and the various gas (Ar, N 2 , He) atmospheres in the table were controlled to 25 Pa.
[0036]
The obtained cemented carbide is pulverized in a mortar made of cemented carbide, and ICP emission spectroscopic analysis is performed on the solution in which this powder is dissolved, and the contents of iron (Fe) and chromium (Cr) are measured. did. Moreover, the iron content of the surface of the cemented carbide and the surface ground by 1 mm or more was measured by laser ICP-MS. The measurement area of the laser ICP-MS was 10 μmφ.
[0037]
[Table 1]
The obtained cemented carbide was used to cut stainless steel for 15 minutes under the following conditions (Test 1), and the flank wear amount and boundary damage amount of the cutting tool were measured. When the flank wear amount reached 0.2 mm or the boundary damage amount reached 0.5 mm during the cutting test, the cutting time was measured. Furthermore, the cutting edge of the tool after the cutting test was observed to confirm the presence or absence of deformation or damage. The results are shown in Table 2.
[0039]
Test 1
Work material: Stainless steel (SUS304)
Tool shape: SDKN1203AUTN
Cutting speed: 200 m / min Feeding speed: 0.2 mm / blade cutting: 2 mm
Other: Dry cutting [0040]
[Table 2]
From the results of Tables 1 and 2, Sample No. with a high content of iron (Fe) in the raw material was obtained. 1 and sample No. 1 using stainless steel as grinding media and stirring arm. In No. 2, the iron (Fe) content in the entire cemented carbide exceeds 300 ppm, and after the hard coating is worn and the cemented carbide is exposed during the cutting process, the wear progresses rapidly and the tool life is increased. I have reached. Sample No. 1 was fired with a pattern held only at the first firing temperature (single-stage firing). 3 and Sample No. 3 in which the difference between the first firing temperature and the second firing temperature exceeds 200 ° C. No. 4, the content ratio of iron (Fe) and chromium (Cr) to cobalt (Co) and / or nickel (Ni) on the surface is equal to or greater than that, the welding and adhesion of the work material are remarkable, and the cutting performance is remarkable. Declined. Furthermore, sample No. 1 in which holding at the first baking temperature and holding at the second baking temperature were both performed in a vacuum. 5, P suf / P in is approximately 1.0, and there is no difference in the abundance ratio of (iron + chromium) and (cobalt + nickel) on the surface and inside. That is, since the amount of embrittlement phase generated on the surface is larger than that of the inventive product, the adhesion of the hard coating is reduced, and the coating is peeled off during the cutting process. As a result, the amount of wear increased, resulting in a large amount of deposits adhering to the cutting tool cutting edge.
[0042]
On the other hand, sample no. Nos. 6 to 13 had excellent wear resistance with a flank wear amount of 0.2 mm (processing time / 15 min) or less.
[0043]
(Example 2)
Sample No. About 2, 12, and 13, the hard coating of the material and thickness shown in Table 3 was formed into the surface by PVD method, and the cutting test was done on the same conditions as the above.
[0044]
[Table 3]
As is apparent from Table 3, the sample No. 2 with the sample 2 having a large iron content as the base material was used. In Sample 2-1, the hard coating peeled off and a large amount of work was welded to the tool surface. Samples 12-1, 2, 3, and Sample No. In the sample 13-1 using 13 as a base material, the hard coating was not peeled off, and the welding of the work material was small.
[0046]
The product of the present invention can be used for general purposes such as a turning tool used in a lathe, a face mill used in a milling machine or a machining center, an end mill, a ball end mill, and a drill tool grade.
[0047]
【The invention's effect】
As described above in detail, according to the cemented carbide according to claim 1, the contents of iron (Fe) and chromium (Cr) in the cemented carbide are controlled, and cobalt (Co) on the cemented carbide surface and Alternatively, by reducing the content ratio of iron (Fe) and chromium (Cr) to nickel (Ni) as compared to the inside of the cemented carbide, welding and adhesion with the work material can be suppressed, and a hard coating is deposited. In particular, a cemented carbide capable of depositing a good hard coating is obtained.
[0048]
According to the method for producing a cemented carbide according to claim 5, at least one carbide, nitride and / or charcoal selected from the group consisting of tungsten carbide powder and Group 4a, 5a and 6a metals of the periodic table. After a raw material powder composed of a nitride powder and cobalt (Co) and / or nickel (Ni) powder is pulverized and mixed, it is molded at a first firing temperature of 1350 to 1600 ° C. in a non-oxidizing atmosphere. Hold for 3 to 2 hours, then cool to a second firing temperature 20 to 200 ° C. lower than the first firing temperature, and hold for 1 to 3 hours in a vacuum at this second firing temperature, The content ratio of iron (Fe) and chromium (Cr) to cobalt (Co) and / or nickel (Ni) on the surface of the cemented carbide is controlled and the content of iron (Fe) and chromium (Cr) in the cemented carbide is controlled. The super hard joint It becomes cemented carbide with reduced than the internal, can suppressed welding or adhesion of the work material, the hard film can be deposited forming a good hard coatings even when deposited form.
Claims (6)
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| JP2001298672A JP3762278B2 (en) | 2001-09-27 | 2001-09-27 | Cemented carbide and method for producing the same |
| US10/256,275 US6797369B2 (en) | 2001-09-26 | 2002-09-26 | Cemented carbide and cutting tool |
| DE10244955.4A DE10244955C5 (en) | 2001-09-26 | 2002-09-26 | Cemented carbide, use of a cemented carbide and method for making a cemented carbide |
| US10/916,671 US7018726B2 (en) | 2001-09-26 | 2004-08-12 | Cemented carbide and cutting tool |
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| JP2001298672A JP3762278B2 (en) | 2001-09-27 | 2001-09-27 | Cemented carbide and method for producing the same |
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| CN116940700A (en) * | 2021-03-25 | 2023-10-24 | 京瓷株式会社 | Cemented carbide and cutting tool |
| CN116103561A (en) * | 2023-01-17 | 2023-05-12 | 株洲硬质合金集团有限公司 | Preparation method of manganese steel-based steel bonded hard alloy |
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