JP2016211022A - Nitrided powder high speed tool steel excellent in hardness, toughness and wear resistance - Google Patents
Nitrided powder high speed tool steel excellent in hardness, toughness and wear resistance Download PDFInfo
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本発明は、切削工具や金型等の素材として用いられる高速度工具鋼に関し、特に粉末冶金法によって製造して得られる粉末高速度工具鋼に関する。 The present invention relates to a high-speed tool steel used as a material for a cutting tool, a die, or the like, and more particularly to a powder high-speed tool steel obtained by powder metallurgy.
近年の被加工材の高硬度化や加工速度の増加により、素形材や金型の加工に用いられる切削工具の使用環境は一層過酷なものとなっている。そのため、それらの工具に使用される高速度工具鋼には、それらの環境に耐え得るため、より高い特性が要求されている。この要求に応えるべく、これまでに様々な技術が開発されてきた。 Due to the recent increase in hardness of workpieces and the increase in machining speed, the use environment of cutting tools used for machining of molds and dies has become more severe. For this reason, high-speed tool steel used for these tools is required to have higher characteristics in order to withstand those environments. Various technologies have been developed to meet this demand.
その一例として、窒化粉末高速度工具鋼がある。この窒化粉末高速度工具鋼は、溶解法によって製造した高速度工具鋼に比べて、成分偏析を低減し、炭窒化物を分散析出させることで、硬さ、耐摩耗性および靭性を向上させている。この窒化粉末高速度工具鋼に関して、従来技術として、例えば、特許文献１、特許文献２が提案されている。 One example is nitride powder high speed tool steel. Compared with high-speed tool steel manufactured by the melting method, this nitrided powder high-speed tool steel reduces component segregation and disperses and precipitates carbonitride to improve hardness, wear resistance and toughness. Yes. For example, Patent Document 1 and Patent Document 2 have been proposed as conventional techniques for the nitride powder high-speed tool steel.
特許文献１は、耐凝着摩耗性に優れた高硬度・高耐摩耗性の粉末ハイスである。しかし、このものは（Ｗ＋２Ｍｏ）量が多く、合金元素量が過剰である。そのため粗大炭化物を形成し、靱性が損なわれる場合があり、一層の靱性の向上が要望される。 Patent Document 1 is a high hardness and high wear resistance powder HSS excellent in adhesion wear resistance. However, this has a large amount of (W + 2Mo) and an excessive amount of alloying elements. For this reason, coarse carbides are formed and the toughness may be impaired, and further toughness improvement is desired.
特許文献２は、耐食性、耐焼付き性に優れた高硬度、高靱性を有する、粉末から成形の窒化粉末高速度鋼で、析出する窒化物がバナジウム系窒化物からなり、その窒化物の平均粒径が１μｍ以下で、鋼材の断面積中に占める面積率が５％以上で、硬さが６５ＨＲＣ以上の窒化粉末高速度鋼である。含有のＮはＶと結合してＭＣ型炭窒化物を形成するが、Ｖ量が低いので、十分な炭窒化物量が得られずに、硬さや耐摩耗性が不足する場合があり、より一層の硬さや耐摩耗性の向上が要望されている。 Patent Document 2 is a nitrided powder high-speed steel formed from powder that has high hardness and high toughness with excellent corrosion resistance and seizure resistance, and the deposited nitride is composed of vanadium nitride, and the average grain of the nitride A nitride powder high speed steel having a diameter of 1 μm or less, an area ratio of 5% or more in the cross-sectional area of the steel material, and a hardness of 65 HRC or more. The contained N combines with V to form MC type carbonitride, but since the amount of V is low, a sufficient amount of carbonitride may not be obtained, and the hardness and wear resistance may be insufficient. There is a demand for improved hardness and wear resistance.
この発明は、高速度工具鋼として、種々の環境に耐え得るより高い特性が要望されるなかで、これまでに提案された窒化粉末高速度工具鋼よりもさらに高いレベルの硬さ、耐摩耗性および靭性を兼ね備えた窒化粉末高速度工具鋼を提供することである。 This invention is a high-speed tool steel, and higher properties that can withstand various environments are required. Even higher than the previously proposed nitrided powder high-speed tool steel, the present invention has a higher level of hardness and wear resistance. And to provide a nitrided powder high-speed tool steel having both toughness.
発明者は鋭意開発を進めた結果、請求項に示す合金成分と限定式とすることで、硬さ、耐摩耗性および靭性が従来に比して一層に優れている高速度工具鋼が得られることを見出し、本願の発明に係る手段を得た。 As a result of diligent development, the inventor can obtain a high-speed tool steel that is further superior in hardness, wear resistance, and toughness as compared with the prior art by using the alloy components and limiting formulas shown in the claims. As a result, the means according to the present invention was obtained.
上記の課題を解決するための本発明の手段について以下に説明する。先ず、第１の手段では、質量％で、Ｃ：０．７０〜１．５％、Ｓｉ：２．０％以下、Ｍｎ：１．０％以下、Ｃｒ：３．０〜７．０％、Ｍｏ：５．０〜８．０％、Ｗ：５．０〜８．０％、Ｖ：６．０〜９．０％、Ｃｏ：５．０〜１５％、Ｎ：０．５０〜２．５％からなり、残部がＦｅおよび不可避的不純物であり、ΔＣ：−１．０〜２．０を満足することを特徴とする硬度、靭性および耐摩耗性に優れた窒化粉末高速度工具鋼である。
ただし、ＭｏおよびＷは上記の範囲内で（２Ｍｏ＋Ｗ）：１６〜２３％であり、さらにΔＣ＝Ｃ＊−Ｃｅｑであり、Ｃ＊＝Ｃ＋（６×Ｎ）／７・・・（１）、Ｃｅｑ＝０．０６×％Ｃｒ＋０．０６３×％Ｍｏ＋０．０３３×％Ｗ＋０．２×％Ｖ＋０．１×％Ｎｂ・・・（２）である。
The means of the present invention for solving the above problems will be described below. First, in the first means, by mass%, C: 0.70 to 1.5%, Si: 2.0% or less, Mn: 1.0% or less, Cr: 3.0 to 7.0%, Mo: 5.0-8.0%, W: 5.0-8.0%, V: 6.0-9.0%, Co: 5.0-15%, N: 0.50-2. A nitride powder high-speed tool steel excellent in hardness, toughness and wear resistance, characterized by comprising 5%, the balance being Fe and inevitable impurities, and satisfying ΔC: -1.0 to 2.0 is there.
However, Mo and W are within the above range (2Mo + W): 16 to 23%, and further ΔC = C * −Ceq, C * = C + (6 × N) / 7 (1), Ceq = 0.06 ×% Cr + 0.063 ×% Mo + 0.033 ×% W + 0.2 ×% V + 0.1 ×% Nb (2)
第２の手段では、質量％で、Ｃ：０．７０〜１．５％、Ｓｉ：２．０％以下、Ｍｎ：１．０％以下、Ｃｒ：３．０〜７．０％、Ｍｏ：５．０〜８．０％、Ｗ：５．０〜８．０％、Ｖ：６．０〜９．０％、Ｃｏ：５．０〜１５％、Ｎ：０．５０〜２．５％、Ｎｂ：０．５０％以下からなり、残部がＦｅおよび不可避的不純物であり、ΔＣ：−１．０〜２．０を満足することを特徴とする硬度、靭性および耐摩耗性に優れた窒化粉末高速度工具鋼である。
ただし、ＭｏおよびＷは上記の範囲内で（２Ｍｏ＋Ｗ）：１６〜２３％であり、さらにΔＣ＝Ｃ＊−Ｃｅｑであり、Ｃ＊＝Ｃ＋（６×Ｎ）／７・・・（１）、Ｃｅｑ＝０．０６×％Ｃｒ＋０．０６３×％Ｍｏ＋０．０３３×％Ｗ＋０．２×％Ｖ＋０．１×％Ｎｂ・・・（２）である。
In the second means, by mass%, C: 0.70 to 1.5%, Si: 2.0% or less, Mn: 1.0% or less, Cr: 3.0 to 7.0%, Mo: 5.0 to 8.0%, W: 5.0 to 8.0%, V: 6.0 to 9.0%, Co: 5.0 to 15%, N: 0.50 to 2.5% Nb: 0.50% or less, the balance being Fe and inevitable impurities, and satisfying ΔC: -1.0 to 2.0, nitriding excellent in hardness, toughness and wear resistance Powdered high speed tool steel.
However, Mo and W are within the above range (2Mo + W): 16 to 23%, and further ΔC = C * −Ceq, C * = C + (6 × N) / 7 (1), Ceq = 0.06 ×% Cr + 0.063 ×% Mo + 0.033 ×% W + 0.2 ×% V + 0.1 ×% Nb (2)
第３の手段では、 第１および第２の手段の高硬度、高靭性、窒化粉末高速度工具鋼は、マトリクス中に分散する炭窒化物の平均粒径が２．５μｍ以下で、かつ炭窒化物の分布密度が１×１０4／ｍｍ2以上であることを特徴とする硬度、靭性および耐摩耗性に優れた窒化粉末高速度工具鋼である。 In the third means, the high hardness, high toughness, nitrided powder high speed tool steel of the first and second means has an average particle size of carbonitride dispersed in the matrix of 2.5 μm or less and carbonitrided. A nitride powder high-speed tool steel excellent in hardness, toughness, and wear resistance, characterized in that the distribution density of the object is 1 × 10 4 / mm 2 or more.
本願の第１の手段に係る発明は、上記の手段の鋼の化学成分と、パラメータを有するので、焼入焼戻し効果を有し、硬さが６８ＨＲＣ以上を有する高硬度であって、衝撃値が１５Ｊ／ｃｍ2以上の高靱性を有する粉末高速度工具鋼であり、第２の手段に係る発明は上記の手段の鋼の化学成分に加えてＮｂを０．５０％以下で有するので、微細な炭窒化物を生成して析出硬化による強度向上の効果を有し、硬さが６８ＨＲＣ以上を有する高硬度であって、衝撃値が１５Ｊ／ｃｍ2以上の高靱性を有する粉末高速度工具鋼であり、第３の手段に係る発明は、平均粒径が２．５μｍ以下である炭窒化物の分布密度が１×１０4以上であるので、耐摩耗性の向上効果を有し、硬さが６８ＨＲＣ以上を有する高硬度であって、衝撃値が１５Ｊ／ｃｍ2以上の高靱性を有する粉末高速度工具鋼である。 Since the invention according to the first means of the present application has the chemical components and parameters of the steel of the above means, it has a quenching and tempering effect, has a high hardness of 68 HRC or more, and has an impact value of It is a powder high-speed tool steel having a high toughness of 15 J / cm 2 or more, and the invention according to the second means has Nb of 0.50% or less in addition to the chemical components of the steel of the above means. It is a high-powder high-speed tool steel that produces carbonitride and has the effect of improving strength by precipitation hardening, has a hardness of 68 HRC or higher, and has a high toughness with an impact value of 15 J / cm 2 or higher. In the invention according to the third means, the distribution density of the carbonitride having an average particle diameter of 2.5 μm or less is 1 × 10 4 or more, so that it has an effect of improving the wear resistance and has a hardness of a high hardness having more than 68HRC, the impact value is 15 J / cm 2 or more A powder high speed tool steel with the toughness.
先ず、上記の課題を解決するための手段の粉末高速度工具鋼における化学成分およびパラメータにおける限定理由について、以下に説明する。なお、各化学成分における％は質量％を示す。 First, the reasons for limiting chemical components and parameters in powder high-speed tool steel as means for solving the above-described problems will be described below. In addition,% in each chemical component shows the mass%.
Ｃ：０．７０〜１．５％
Ｃは、高速工具鋼として十分な焼入性や焼入焼戻し硬さを確保し、炭化物を形成させることで耐摩耗性や高温強度を得るために必要な元素である。Ｃが０．７０％より少ないと、十分な硬さ、高温強度、耐摩耗性が得られない。一方、Ｃが１．５％より多すぎると、炭化物の偏析を助長し、靭性を低下させる。そこで、Ｃは０．７０〜１．５％、望ましくは０．８０〜１．３０％とする。
C: 0.70 to 1.5%
C is an element necessary for securing sufficient hardenability and quenching and tempering hardness as high-speed tool steel and for obtaining wear resistance and high-temperature strength by forming carbides. When C is less than 0.70%, sufficient hardness, high temperature strength and wear resistance cannot be obtained. On the other hand, when C is more than 1.5%, segregation of carbides is promoted and toughness is reduced. Therefore, C is 0.70 to 1.5%, preferably 0.80 to 1.30%.
Ｓｉ：２．０％以下
Ｓｉは、焼入性および硬さ向上に寄与する元素である。しかし、Ｓｉが２．０％より多すぎると靭性を低下させる。そこで、Ｓｉは２．０％以下とする。
Si: 2.0% or less Si is an element that contributes to improving hardenability and hardness. However, if Si is more than 2.0%, the toughness is lowered. Therefore, Si is set to 2.0% or less.
Ｍｎ：１．０％以下
Ｍｎは、脱酸剤、焼入性向上に寄与する元素である。しかし、Ｍｎが１．０％より多すぎると、マトリックスを脆化させ、靭性および熱間加工性を低下させる。そこで、Ｍｎは１．０％以下とする。
Mn: 1.0% or less Mn is an element that contributes to a deoxidizer and improved hardenability. However, if Mn is more than 1.0%, the matrix becomes brittle and toughness and hot workability are lowered. Therefore, Mn is 1.0% or less.
Ｃｒ：３．０〜７．０％
Ｃｒは、焼入性を改善する元素である。しかし、Ｃｒが３．０％未満では焼入性の改善は不十分である。一方、Ｃｒが７．０％より多すぎると、Ｃｒ系炭化物の凝集、粗大化を助長し、靭性、高温強度、軟化抵抗性を低下させる。そこで、Ｃｒは３．０〜７．０％、望ましくは３．５〜５．５％とする。
Cr: 3.0-7.0%
Cr is an element that improves hardenability. However, when Cr is less than 3.0%, the improvement of hardenability is insufficient. On the other hand, if the Cr content is more than 7.0%, the aggregation and coarsening of Cr-based carbides are promoted, and the toughness, high-temperature strength, and softening resistance are lowered. Therefore, Cr is 3.0 to 7.0%, preferably 3.5 to 5.5%.
Ｍｏ：５．０〜８．０％かつＷ：５．０〜８．０％の範囲内で、（２Ｍｏ＋Ｗ）：１６〜２３％
ＭｏとＷは、焼入性や焼戻し時の二次硬化、耐摩耗性、高温強度、軟化抵抗性に寄与する元素である。また、ＭｏとＷは、焼入時に未固溶となったこれら元素の微細な炭化物が結晶粒の粗大化を抑制する。しかし、ＭｏとＷはそれぞれ５．０％より少ないと上記の効果が得られない。一方、ＭｏとＷがそれぞれ８．０％より多すぎると、Ｍｏ系やＷ系の炭化物の凝集・粗大化を助長し、靭性を低下させ、またコスト高になる。特に、Ｗは、Ｍｏと同等の効果を得るには、２倍の量の添加が必要となり、過剰添加はコストがかかる。そこで、Ｍｏは５．０〜８．０％かつＷは５．０〜８．０％の範囲内で、（２Ｍｏ＋Ｗ）は１６〜２３％、望ましくは１７〜２１％とする。
Within the range of Mo: 5.0 to 8.0% and W: 5.0 to 8.0%, (2Mo + W): 16 to 23%
Mo and W are elements that contribute to hardenability, secondary hardening during tempering, wear resistance, high-temperature strength, and softening resistance. In addition, in Mo and W, fine carbides of these elements that have become insoluble during quenching suppress the coarsening of crystal grains. However, if Mo and W are less than 5.0%, the above effect cannot be obtained. On the other hand, if Mo and W are each more than 8.0%, the agglomeration and coarsening of the Mo-based and W-based carbides are promoted, the toughness is reduced, and the cost is increased. In particular, to obtain the same effect as Mo, W needs to be added twice as much, and excessive addition is costly. Therefore, Mo is in the range of 5.0 to 8.0% and W is in the range of 5.0 to 8.0%, and (2Mo + W) is 16 to 23%, preferably 17 to 21%.
Ｖ：６．０〜９．０％
Ｖは、焼戻時に微細で硬質なＭＣ型炭窒化物を析出し、高温強度や耐摩耗性に寄与する。また、焼入時には未固溶となった微細な炭窒化物が結晶粒の粗大化を抑制し、靭性の低下を抑制する。しかし、Ｖは６．０％より少ないと効果がこれらの効果は得られない。しかし、Ｖが９．０％より多すぎると、Ｖ系炭化物の凝集・粗大化を助長し、靭性を低下させ、またコストがかかる。そこで、Ｖは６．０〜９．０％、望ましくは６．０〜８．０％とする。
V: 6.0-9.0%
V precipitates fine and hard MC-type carbonitrides during tempering, and contributes to high-temperature strength and wear resistance. Moreover, the fine carbonitride which became insoluble at the time of hardening suppresses the coarsening of a crystal grain, and suppresses the fall of toughness. However, if V is less than 6.0%, these effects cannot be obtained. However, when V is more than 9.0%, it promotes aggregation and coarsening of V-based carbides, lowers toughness, and increases costs. Therefore, V is set to 6.0 to 9.0%, preferably 6.0 to 8.0%.
Ｃｏ：５．０〜１５％
Ｃｏは、焼入時のマトリックスへの炭化物固溶量を増加させ、焼入焼戻硬さの向上に寄与する。しかし、Ｃｏが５．０％より少ないと、上記の効果が得られない。一方、Ｃｏが多すぎると、靭性を低下させるとともに、コスト上昇の原因となる。そこで、Ｃｏは５．０〜１５％、望ましくは７．０〜１３．０％とする。
Co: 5.0-15%
Co increases the amount of carbide solid solution in the matrix at the time of quenching, and contributes to the improvement of quenching and tempering hardness. However, if Co is less than 5.0%, the above effect cannot be obtained. On the other hand, when there is too much Co, toughness is reduced and cost is increased. Therefore, Co is set to 5.0 to 15%, preferably 7.0 to 13.0%.
Ｎ：０．５０〜２．５％
Ｎは、主にＶと結合しＭＣ型炭窒化物を形成し、硬度・耐摩耗性に寄与する。これらのＭＣ型炭窒化物は、焼入時に結晶粒粗大化を抑制し、靭性を改善する。また、耐摩耗性や耐焼付き性も改善する。Ｎが０．５０％より少ないと、上記の効果が得られない。一方、Ｎが２．５％より多すぎると、ＭＣ型の窒化物および炭窒化物の凝集・粗大化を助長し、靭性を低下させる。そこで、Ｎは０．５０〜２．５％とする。
N: 0.50 to 2.5%
N mainly combines with V to form MC-type carbonitrides, and contributes to hardness and wear resistance. These MC type carbonitrides suppress grain coarsening during quenching and improve toughness. In addition, wear resistance and seizure resistance are improved. When N is less than 0.50%, the above effect cannot be obtained. On the other hand, when N is more than 2.5%, the aggregation and coarsening of MC type nitrides and carbonitrides are promoted, and the toughness is lowered. Therefore, N is set to 0.50 to 2.5%.
Ｎｂ：０．５０％以下
Ｎｂは、炭窒化物を形成して硬さや耐摩耗性を付与する元素である。しかし、Ｎｂが０．５０％より多すぎると炭窒化物の偏析を助長して靱性を低下させる。そこで、Ｎｂは０．５０％以下、望ましくは０．０５〜０．５０％とする。
Nb: 0.50% or less Nb is an element that forms carbonitride to impart hardness and wear resistance. However, when Nb is more than 0.50%, segregation of carbonitrides is promoted and toughness is reduced. Therefore, Nb is 0.50% or less, preferably 0.05 to 0.50%.
ΔＣ＝（Ｃ＊−Ｃｅｑ）：−１．０〜２．０
ΔＣが、−１．０未満であると、６８ＨＲＣ以上の高い硬度が得られにくくなるばかりでなく、炭窒化物が凝集および粗大化し、１５Ｊ／ｃｍ2以上の高い靱性が得られない。一方、ΔＣが２．０を超えるとＣやＮの偏析や炭化物の偏析を助長し、靭性を低下させる。そこで、ΔＣは−１．０〜２．０、望ましくは０．１０〜１．０とする。
ここで、Ｃ＊およびＣｅｑは、以下の式（１）および式（２）を示し、Ｃは質量％を示し、％元素は各合金元素の質量％を示す。
Ｃ＊＝Ｃ＋（６×Ｎ）／７・・・（１）
Ｃｅｑ＝０．０６×％Ｃｒ＋０．０６３×％Ｍｏ＋０．０３３×％Ｗ＋０．２×％Ｖ＋０．１×％Ｎｂ・・・（２）
なお、式（１）のＮは、Ｃと類似した性質を有し、鋼中で窒化物を形成し、硬さや耐摩耗性に寄与する。それぞれの添加量に対する寄与の大きさを、Ｃ量について統一した指標である。
式（２）のＣｅｑは、主に添加した各合金元素が全て炭化物となる場合に必要なＣ量の目安として用いられているＣ当量である。
以上より、ΔＣは、鋼中のＣ量およびＮ量並びに各合金元素量との関係から、焼入焼戻硬さ、靱性および耐摩耗性に影響する固溶Ｃ量に関して考慮した値である。本発明のΔＣに従った合金元素のバランスによって、高い硬度、靱性および耐摩耗性が得られる。
ΔC = (C * −Ceq): −1.0 to 2.0
When ΔC is less than −1.0, not only high hardness of 68 HRC or higher is hardly obtained, but carbonitride is aggregated and coarsened, and high toughness of 15 J / cm 2 or higher cannot be obtained. On the other hand, if ΔC exceeds 2.0, segregation of C and N and segregation of carbides are promoted and toughness is reduced. Therefore, ΔC is set to −1.0 to 2.0, preferably 0.10 to 1.0.
Here, C * and Ceq represent the following formula (1) and formula (2), C represents mass%, and% element represents mass% of each alloy element.
C * = C + (6 × N) / 7 (1)
Ceq = 0.06 ×% Cr + 0.063 ×% Mo + 0.033 ×% W + 0.2 ×% V + 0.1 ×% Nb (2)
Note that N in the formula (1) has properties similar to C and forms a nitride in the steel, contributing to hardness and wear resistance. The magnitude of contribution to each added amount is a unified index for the C amount.
Ceq in the formula (2) is a C equivalent that is used as a measure of the amount of C necessary when all the alloy elements added are all carbides.
From the above, ΔC is a value that takes into account the amount of solute C that affects the quenching and tempering hardness, toughness, and wear resistance from the relationship between the amount of C and N in steel and the amount of each alloy element. A high hardness, toughness and wear resistance are obtained by the balance of the alloying elements according to ΔC of the present invention.
窒化粉末高速度工具鋼のマトリクス中に分散する炭窒化物：平均粒径が２．５μｍ以下
窒化粉末高速度工具鋼のマトリクス中に分散する炭窒化物は、平均粒径が２．５μｍより粗大化すると、該鋼の靱性を低下させる。そこで、窒化粉末高速度工具鋼のマトリクス中に分散する炭窒化物の平均粒径は２．５μｍ以下とする。
Carbonitride dispersed in matrix of nitrided powder high speed tool steel: average particle size 2.5 μm or less Carbonitride dispersed in matrix of nitrided powder high speed tool steel is coarser than 2.5 μm in average particle size When it becomes, the toughness of the steel is lowered. Therefore, the average particle size of the carbonitride dispersed in the matrix of the nitride powder high-speed tool steel is 2.5 μm or less.
窒化粉末高速度工具鋼中の炭窒化物の分布密度：１×１０4／ｍｍ2以上
窒化粉末高速度工具鋼中の炭窒化物の分布密度は、１×１０4／ｍｍ2を下回ると、すなわち炭窒化物の凝集粗大化によって分布密度が低下すると、該鋼の耐摩耗性を低下させる。そこで、窒化粉末高速度工具鋼中の炭窒化物の分布密度は、１×１０4／ｍｍ2以上とする。なお、この場合の炭窒化物は平均粒径が２．５μｍ以下である。
Distribution density of carbonitride in nitrided powder high speed tool steel: 1 × 10 4 / mm 2 or more When distribution density of carbonitride in nitrided powder high speed tool steel is less than 1 × 10 4 / mm 2 , That is, when the distribution density decreases due to the coarsening of carbonitrides, the wear resistance of the steel decreases. Therefore, the distribution density of carbonitride in the nitride powder high-speed tool steel is set to 1 × 10 4 / mm 2 or more. In this case, the carbonitride has an average particle size of 2.5 μm or less.
次いで、本発明の実施の形態について、表を参照しながら以下に順次記載する。 Next, embodiments of the present invention will be sequentially described below with reference to the table.
先ず、表１に示される成分組成並びにＦｅおよび不可避不純物を有する各溶鋼をガスアトマイズして、各記号の発明鋼と比較鋼の粉末からなる高速度工具鋼を得た。これらの粉末からなる高速度工具鋼を８００〜９００℃の窒素雰囲気中に加熱保持して窒化処理を行い、窒化物を有する粉末である窒化粉末高速度工具鋼とした。これらの発明鋼および比較鋼の窒化粉末高速度工具鋼をＨＩＰ（熱間静水圧加圧法）処理して径１５０ｍｍの成形体とし、さらにこの成形体を径４０ｍｍに鍛伸し、１１８０〜１２２０℃に加熱して油冷して焼入れを行った後、５００〜６００℃に加熱して空冷する焼戻しを２回以上行って、焼入焼戻し試料を作製した。 First, each molten steel having the component composition shown in Table 1 and Fe and unavoidable impurities was gas atomized to obtain a high-speed tool steel composed of powders of the invention steel of each symbol and a comparative steel. The high-speed tool steel made of these powders was heated and held in a nitrogen atmosphere at 800 to 900 ° C. and subjected to nitriding treatment to obtain a nitrided powder high-speed tool steel which is a powder having nitride. These invention steel and comparative steel nitride powder high-speed tool steel are processed by HIP (hot isostatic pressing) to form a molded body having a diameter of 150 mm, and this molded body is forged to a diameter of 40 mm, and 1180-1220 ° C. And then quenching by oil cooling, followed by tempering by heating to 500 to 600 ° C. and air cooling twice or more to prepare a quenched and tempered sample.
上記で作成した焼入焼戻し試料を用いて、靱性および耐摩耗性（比摩耗量）並びにマトリックス中に分散する炭窒化物の平均粒径とその分布密度を評価した。 Using the quenched and tempered samples prepared above, the toughness and wear resistance (specific wear amount), the average particle size of carbonitride dispersed in the matrix, and the distribution density thereof were evaluated.
靱性の評価は、シャルピー衝撃試験機により評価を実施した。用いた試験片は上記の鍛伸材の中心部の圧延方向から採取して、上記のように加熱して油冷して焼入れし、さらに加熱して空冷する焼戻しを２回以上行う焼入焼戻しを行って試料とした後、１０ＲＣノッチのシャルピー試験片に加工し、焼入焼戻し硬さが６８ＨＲＣ以上の硬さにおいて、衝撃値が２０Ｊ／ｃｍ2以上であれば評価は◎とし、１５Ｊ／ｃｍ2以上で２０Ｊ／ｃｍ2未満であれば評価は○とし、それよりも低ければ×として評価して表２に示した。 The toughness was evaluated using a Charpy impact tester. The test piece used was sampled from the rolling direction of the center of the forged material, and was quenched and tempered by heating and oil cooling as described above, followed by tempering that was further heated and air-cooled twice or more. After being processed into a sample, it was processed into a 10 RC notch Charpy test piece, and when the quenching and tempering hardness was 68 HRC or more and the impact value was 20 J / cm 2 or more, the evaluation was ◎, and 15 J / cm If it is 2 or more and less than 20 J / cm 2 , the evaluation is ○, and if it is lower than that, it is evaluated as × and shown in Table 2.
耐摩耗性の評価は、大越式摩耗試験により評価を実施した。上記の焼入焼戻しを行った試料から、縦７ｍｍ、横２５ｍｍ、長さ５０ｍｍの大きさの試験片を作成した。この試験片を用いて大越式摩耗試験により比摩耗量を測定した。試験条件は、回転輪のＳＣＭ４２０、摩耗速度を２．０ｍ／ｓｅｃ、摩耗距離を４００ｍｍおよび最終荷重を６１．８Ｎとして試験片の比摩耗量を測定した。硬さ６８ＨＲＣにおいて、比摩耗量が２．０×１０-8以上であれば評価は◎とし、１．５×１０-8以上で２．０×１０-8未満であれば評価は○とし、それよりも低ければ×として評価して表２に示した。 The wear resistance was evaluated by the Ogoshi type wear test. A test piece having a length of 7 mm, a width of 25 mm, and a length of 50 mm was prepared from the sample subjected to the above quenching and tempering. Using this test piece, the specific wear amount was measured by an Ogoshi type wear test. The test conditions were SCM420 of a rotating wheel, the wear rate was 2.0 m / sec, the wear distance was 400 mm, and the final load was 61.8 N, and the specific wear amount of the test piece was measured. In hardness 68HRC, if the specific wear amount is 2.0 × 10 −8 or more, the evaluation is ◎, and if it is 1.5 × 10 −8 or more and less than 2.0 × 10 −8 , the evaluation is ○. If it is lower than that, it was evaluated as x and shown in Table 2.
上記の焼入焼戻し試料のマトリックス中に分散する炭窒化物の平均粒径とその分布密度は、ＳＥＭ（走査型電子顕微鏡）像を用いた画像解析により評価を実施した。上記の焼入焼戻し試料の中央部から２０ｍｍ幅、２０ｍｍ長さの大きさの試験片を作成して観察に用いた。炭窒化物の平均粒径が２．０μｍ以下であれば◎とし、２．０μｍを超え２．５μｍ以下であれば○とし、２．５μｍを超える場合は×として評価した。分布密度が１．５×１０4個／ｍｍ2以上であれば◎とし、１．０×１０4個／ｍｍ2以上で１．５×１０4個／ｍｍ2未満であれば○とし、１．０×4個／ｍｍ2未満であれば×として評価した。 The average particle diameter and distribution density of the carbonitride dispersed in the matrix of the above quenching and tempering sample were evaluated by image analysis using an SEM (scanning electron microscope) image. A test piece having a width of 20 mm and a length of 20 mm was prepared from the center of the quenched and tempered sample and used for observation. When the average particle size of the carbonitride was 2.0 μm or less, it was evaluated as “◎”, when it exceeded 2.0 μm and 2.5 μm or less, it was evaluated as “◯”, and when it exceeded 2.5 μm, it was evaluated as “x”. When the distribution density is 1.5 × 10 4 pieces / mm 2 or more, ◎, and when the distribution density is 1.0 × 10 4 pieces / mm 2 or more and less than 1.5 × 10 4 pieces / mm 2 , ◯ is given. If it was less than 0.0 × 4 pieces / mm 2 , it was evaluated as x.
Claims (3)
ただし、ＭｏおよびＷは上記の範囲内で（２Ｍｏ＋Ｗ）：１６〜２３％であり、さらにΔＣ＝Ｃ＊−Ｃｅｑであり、Ｃ＊＝Ｃ＋（６×Ｎ）／７・・・（１）、Ｃｅｑ＝０．０６×％Ｃｒ＋０．０６３×％Ｍｏ＋０．０３３×％Ｗ＋０．２×％Ｖ＋０．１×％Ｎｂ・・・（２）である。 In mass%, C: 0.70 to 1.5%, Si: 2.0% or less, Mn: 1.0% or less, Cr: 3.0 to 7.0%, Mo: 5.0 to 8. 0%, W: 5.0 to 8.0%, V: 6.0 to 9.0%, Co: 5.0 to 15%, N: 0.50 to 2.5%, the balance being Fe And nitride powder high-speed tool steel excellent in hardness, toughness and wear resistance, characterized in that it is an inevitable impurity and satisfies ΔC: −1.0 to 2.0.
However, Mo and W are within the above range (2Mo + W): 16 to 23%, and further ΔC = C * −Ceq, C * = C + (6 × N) / 7 (1), Ceq = 0.06 ×% Cr + 0.063 ×% Mo + 0.033 ×% W + 0.2 ×% V + 0.1 ×% Nb (2)
ただし、ＭｏおよびＷは上記の範囲内で（２Ｍｏ＋Ｗ）：１６〜２３％であり、さらにΔＣ＝Ｃ＊−Ｃｅｑであり、Ｃ＊＝Ｃ＋（６×Ｎ）／７・・・（１）、Ｃｅｑ＝０．０６×％Ｃｒ＋０．０６３×％Ｍｏ＋０．０３３×％Ｗ＋０．２×％Ｖ＋０．１×％Ｎｂ・・・（２）である。 In mass%, C: 0.70 to 1.5%, Si: 2.0% or less, Mn: 1.0% or less, Cr: 3.0 to 7.0%, Mo: 5.0 to 8. 0%, W: 5.0-8.0%, V: 6.0-9.0%, Co: 5.0-15%, N: 0.50-2.5%, Nb: 0.50 % Nitride powder high-speed tool steel excellent in hardness, toughness and wear resistance, characterized in that the balance is Fe and unavoidable impurities and ΔC: −1.0 to 2.0.
However, Mo and W are within the above range (2Mo + W): 16 to 23%, and further ΔC = C * −Ceq, C * = C + (6 × N) / 7 (1), Ceq = 0.06 ×% Cr + 0.063 ×% Mo + 0.033 ×% W + 0.2 ×% V + 0.1 ×% Nb (2)
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