JP5837837B2 - High-hardness BN free cutting steel with a tool life of 300HV10 or higher - Google Patents
High-hardness BN free cutting steel with a tool life of 300HV10 or higher Download PDFInfo
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Description
本発明は、快削鋼に関するものであり、特に硬度が３００ＨＶ１０以上の高硬度なＢＮ系快削鋼を提供するものである。 The present invention relates to free-cutting steel, and in particular, provides high-hardness BN-based free-cutting steel having a hardness of 300 HV10 or higher.
快削鋼は、低融点金属や非金属介在物を鋼中に含有させることにより、被削性を向上させたもので、非金属介在物としてはＭｎ硫化物、Ｔｉ硫化物、Ｃａ酸化物及びＢＮ介在物を用いたもの、低融点金属としてはＰｂやＢｉを用いたものが種々開発されてきた。 Free-cutting steel has improved machinability by including low-melting point metals and non-metallic inclusions in the steel. Examples of non-metallic inclusions include Mn sulfide, Ti sulfide, Ca oxide, and Various materials using BN inclusions and materials using Pb or Bi have been developed as low melting point metals.
これらの快削鋼のうち、Ｐｂ快削鋼は安価で性能に優れるため広範囲に使用されてきたが、地球環境保全の観点からＰｂの適用が制限されるようになり、新たにＢＮ快削鋼への関心が高まっている。 Among these free-cutting steels, Pb free-cutting steel has been used extensively because it is inexpensive and has excellent performance. However, the application of Pb has been restricted from the viewpoint of global environmental protection, and BN free-cutting steel is newly added. Interest in is growing.
特許文献１は、広範囲の用途に対応可能な、被削性の優れた機械構造用鋼に関し、特定量のＢＮを鋼中に含有させることにより、ギヤ、シャフトなど種々の形状の部品加工に優れるものが記載されている。 Patent Document 1 relates to a steel for machine structure having excellent machinability that can be used for a wide range of applications, and is excellent in processing parts of various shapes such as gears and shafts by containing a specific amount of BN in the steel. Things are listed.
特許文献２は、ＢＮを鋼中に含有させた場合に生じる機械的性質や、熱間延性を低下させることなく被削性を向上させたＢＮ快削鋼に関し、エンジン部品や足回り部品などの自動車部品として好適なものが記載されている。 Patent Document 2 relates to mechanical properties generated when BN is contained in steel and BN free-cutting steel with improved machinability without reducing hot ductility, such as engine parts and undercarriage parts. Those suitable as automobile parts are described.
特許文献３は、調質処理を行うことなく切削加工などの仕上加工を施して製品とする非調質型の快削鋼に関し、優れた被削性を強度を低下させることなく得るため、ＢＮを特定量含有したＢＮ快削鋼が記載されている。 Patent Document 3 relates to a non-tempered free-cutting steel that is finished by performing a finishing process such as a cutting process without performing a tempering treatment, so that excellent machinability can be obtained without reducing the strength. BN free-cutting steel containing a specific amount of is described.
特許文献４は、歯車の切削等の機械加工後に実施される浸炭焼入れに代えて高周波焼入れによる表面硬化処理を可能とした快削鋼に関し、微細粒子となって材料組織中に均等に分散したＢＮの潤滑効果により被削性を高めたＢＮ快削鋼が記載されている。 Patent Document 4 relates to free-cutting steel that enables surface hardening treatment by induction hardening instead of carburizing and quenching performed after machining such as gear cutting, and BN dispersed in a material structure as fine particles. BN free-cutting steel with improved machinability due to the lubrication effect is described.
特許文献５は、圧延や鋳造により加工方向に展伸するＢＮと一定の角度の方向の疲労強度や耐衝撃特性を改善するため、硫化物（サルファイド）を微細に分散させ、硫化物を析出核とするＢＮの悪影響を軽減させることが記載されている。 Patent Document 5 discloses that sulfide (sulfide) is finely dispersed to improve the fatigue strength and impact resistance characteristics in the direction of a certain angle with BN that extends in the processing direction by rolling or casting, and the sulfide is precipitated as a nucleus. It is described that the adverse effect of BN is reduced.
特許文献６は、被削性に優れた機械構造用鋼に関し、Ｐｂを用いることなしに、従来のＰｂ複合添加快削鋼と同等以上の被削性を得るため、成分組成においてＡｌ、Ｂ、Ｎを複合添加し、金属組織をフェライトおよび黒鉛相とすることを特徴とするＢＮ快削鋼が記載されている。 Patent Document 6 relates to a machine structural steel excellent in machinability, and in order to obtain machinability equivalent to or higher than that of a conventional Pb composite-added free-cutting steel without using Pb, in the component composition, Al, B, A BN free-cutting steel characterized in that N is added in combination and the metal structure is made into a ferrite and graphite phase is described.
ところで、快削鋼の硬度が被削性に及ぼす影響については以下のことが知られている。１．非ＢＮ快削鋼で高硬度材の場合、切削温度の上昇が顕著となることから、工具側から被削材側への工具の成分組成の拡散が顕著となる結果、工具の拡散摩耗が顕著となり、工具寿命が大幅に短くなる。
２．一方、ＢＮ快削鋼で高硬度材の場合は、切削中にＡｌＮの皮膜が工具面上に生成し、この皮膜が前述の工具の拡散摩耗を抑制するため、工具寿命が飛躍的に向上する。
By the way, the following is known about the influence which the hardness of free-cutting steel has on machinability. 1. In the case of non-BN free-cutting steel and high-hardness material, the increase in cutting temperature becomes significant, and as a result, the diffusion of the component composition of the tool from the tool side to the work material side becomes significant, resulting in remarkable diffusion wear of the tool. Thus, the tool life is significantly shortened.
2. On the other hand, in the case of a BN free-cutting steel and a high-hardness material, an AlN coating is formed on the tool surface during cutting, and this coating suppresses the diffusion wear of the above-mentioned tool, so the tool life is dramatically improved. .
切削中のＡｌＮ皮膜生成は、温度が高い方が顕著に進行するところ、高硬度材ほど切削温度が高くなることから、被削材が高硬度になるほどＢＮ快削鋼の工具寿命は非ＢＮ快削鋼と比較して優れることが予測されるが、特許文献１〜６に記載のＢＮ快削鋼はＢＮが、微細なため、被削性向上に対する効果が充分とは言い難い。 The generation of the AlN film during cutting progresses remarkably at higher temperatures. The higher the hardness, the higher the cutting temperature. Therefore, the higher the hardness of the work material, the longer the tool life of the BN free-cutting steel. Although it is expected to be superior to cutting steel, it is difficult to say that the effect of improving machinability is sufficient because the BN free cutting steel described in Patent Documents 1 to 6 has fine BN.
特に硬度が３００ＨＶ１０（ＨＶ１０：試験荷重１０ｋｇｆのビッカース硬さ）を上回るような高硬度材の場合において、被削性のうち工具寿命が短くなる。 In particular, in the case of a high hardness material having a hardness exceeding 300HV10 (HV10 : Vickers hardness with a test load of 10 kgf), the tool life of the machinability is shortened.
そこで、本発明は、硬度が３００ＨＶ１０（ＨＶ１０：試験荷重１０ｋｇｆのビッカース硬さ）以上の高硬度材であって、切削性が良好で工具寿命に優れたＢＮ快削鋼を提供することを目的とする。 Accordingly, the object of the present invention is to provide a BN free-cutting steel having a hardness of 300 HV10 (HV10 : Vickers hardness with a test load of 10 kgf) or more, having good machinability and excellent tool life. To do.
本発明者等は、上記課題を解決するため、ＢＮ快削鋼のうち硬度が３００ＨＶ１０以上となる高硬度材について、ＡｌＮ皮膜生成条件の観点から鋭意研究を重ね、ＡｌＮ皮膜生成には、Ｂ、Ｎ、およびＡｌの含有量、およびこれら元素間の含有量のバランスが大きな影響を与えることを見出した。 In order to solve the above-mentioned problems, the inventors of the present invention have made extensive studies from the viewpoint of AlN film generation conditions for a high-hardness material having a hardness of 300 HV10 or more among BN free-cutting steels. It has been found that the contents of N and Al and the balance of the contents between these elements have a great influence.
本発明は得られた知見を基に更に検討を加えてなされたもので、すなわち、本発明は、
１）ｍａｓｓ％で、Ｃ：０．３０〜０．５０％、Ｓｉ：０．２５超え０．５０％未満、Ｍｎ：０．３０〜１．００％未満、Ｐ：０．０３０％以下（０％は含まず）、Ｓ：０．０１５超え０．２００％以下、Ａｌ：０．０１０〜０．０５０％、Ｂ：０．００５０〜０．０１００％、Ｎ：０．００７０〜０．０２００％を含有し、更に、Ｃｒ：０．０１〜１．５０％、Ｍｏ：０．０１〜０．５０％、Ｖ：０．１５０超え０．２５０％以下のうちから選んだ１種または２種以上、以下に示すＦ値が（１）式を満足し、残部Ｆｅ及び不可避的不純物であることを特徴とする工具寿命に優れた硬度が３００ＨＶ１０以上の高硬度ＢＮ系快削鋼。
Ｆ値＝（Ｂ＋Ｎ／１．７）×Ａｌ−（４００−ＨＶ１０）／１０６
５．０×１０−４＞Ｆ値＞１．５×１０−４ ・・・・・・・・・・・・ （１）
ここで、各合金元素は含有量（ｍａｓｓ％）、ＨＶ１０は、切削時点での被削材のビッカース硬度（荷重１０ｋｇｆ）を示す。
The present invention was made by further study based on the obtained knowledge, that is, the present invention is
1) Mass%, C: 0.30 to 0.50%, Si: more than 0.25 and less than 0.50%, Mn: 0.30 to less than 1.00%, P: 0.030% or less (0 %: S: 0.015 to 0.200% or less, Al: 0.010 to 0.050%, B: 0.0050 to 0.0100%, N: 0.0070 to 0.0200% In addition, Cr: 0.01 to 1.50%, Mo: 0.01 to 0.50%, V: 0.150 to 0.250% or less selected from one or more A high-hardness BN-based free-cutting steel having a tool life of 300 HV10 or more, wherein the F value shown below satisfies the formula (1), and the balance is Fe and inevitable impurities.
F value = (B + N / 1.7) × Al− (400−HV10) / 10 6
5.0 × 10 −4 > F value> 1.5 × 10 −4 (1)
Here, the content of each alloy element (mass%), HV10 indicates the Vickers hardness (load 10 kgf) of the work material at the time of cutting.
本発明によれば、工具寿命に優れた高硬度なＢＮ快削鋼が得られるので、切削時の能率が向上し、産業上きわめて有用である。 According to the present invention, since a hard BN free-cutting steel having an excellent tool life can be obtained, the efficiency at the time of cutting is improved, which is extremely useful industrially.
以下に成分組成の限定理由について説明する。説明において％はｍａｓｓ％とする。
Ｃ：０．３０〜０．５０％
Ｃは被削性に大きな影響を及ぼす元素である。その含有量が０．３０％未満では、被削性のうち切屑処理性が充分確保できない。一方、０．５０％を超えると工具寿命が低下する。従って、含有量は０．３０〜０．５０％にする。
The reason for limiting the component composition will be described below. In the explanation,% is mass%.
C: 0.30 to 0.50%
C is an element that greatly affects the machinability. If the content is less than 0.30%, it is not possible to ensure sufficient chip disposal among the machinability. On the other hand, if it exceeds 0.50%, the tool life is reduced. Accordingly, the content is made 0.30 to 0.50%.
Ｓｉ：０．２５超え０．５０％未満
Ｓｉは切屑処理性を向上させるのに有用な元素であり、その含有量が０．２５％以下では、充分な向上効果が得られない。一方、０．５０％以上であるとフェライトの硬化が顕著となり、被削性のうち工具寿命が低下してしまう。従って、含有量は０．２５超え０．５０％未満にする。
Si: More than 0.25 and less than 0.50% Si is an element useful for improving chip disposal, and if the content is 0.25% or less, a sufficient improvement effect cannot be obtained. On the other hand, if it is 0.50% or more, the hardening of the ferrite becomes remarkable, and the tool life is reduced in the machinability. Therefore, the content is more than 0.25 and less than 0.50%.
Ｍｎ：０．３０〜１．００％未満
Ｍｎは工具寿命の向上に有効なＭｎ硫化物を生成させるために必要な元素である。その含有量が０．３０％未満では、充分な量のＭｎ硫化物を生成することが出来ないため工具寿命の向上効果が認められない。一方、１．００％を超えると焼入性が向上し、硬度上昇が顕著となり、工具寿命が低下する。従って、含有量は０．３０〜１．００％未満にする。
Mn: Less than 0.30 to 1.00% Mn is an element necessary for generating Mn sulfide effective for improving the tool life. When the content is less than 0.30%, a sufficient amount of Mn sulfide cannot be generated, and thus the effect of improving the tool life is not recognized. On the other hand, if it exceeds 1.00%, the hardenability is improved, the hardness rises significantly, and the tool life is reduced. Therefore, the content is made 0.30 to less than 1.00%.
Ｐ：０．０３０％以下（０％は含まず）
Ｐは工具寿命を低下させるため少ない方が良く、含有量は０．０３０％以下（０％は含まず）、好ましくは０．０１５％以下（０％は含まず）とする。
P: 0.030% or less (excluding 0%)
P is preferable to be small in order to reduce the tool life, and the content is 0.030% or less (0% is not included), preferably 0.015% or less (0% is not included).
Ｓ：０．０１５超え０．２００％以下
Ｓは工具寿命の向上に有効なＭｎ硫化物を生成させるために必要な元素である。その含有量が０．０１５％以下では、充分な量のＭｎ硫化物を生成することが出来ないため工具寿命の向上効果が認められない。一方、０．２００％を超えると熱間延性が低下する。従って、含有量は０．０１５超え０．２００％以下にする。
S: 0.015 to 0.200% or less S is an element necessary for producing Mn sulfide effective for improving the tool life. When the content is 0.015% or less, a sufficient amount of Mn sulfide cannot be generated, and thus the effect of improving the tool life is not recognized. On the other hand, when it exceeds 0.200%, hot ductility will fall. Therefore, the content exceeds 0.015 and is 0.200% or less.
Ａｌ：０．０１０〜０．０５０％
Ａｌは脱酸に必要な元素で、また、ＢＮ快削鋼においては工具面上にＡｌＮ皮膜を生成させ、工具側から被削材側への拡散（摩耗）を抑制するために必要な元素である。０．０１０％未満ではその効果が得られないため、０．０１０％以上、好ましくは０．０２０％以上とする。一方、０．０５０％を超えるとその効果が飽和するとともに硬質のアルミナ系酸化物が増加し、工具寿命が低下することから、含有量は０．０１０〜０．０５０％とする。
Al: 0.010 to 0.050%
Al is an element necessary for deoxidation, and in BN free-cutting steel, it is an element necessary for generating an AlN film on the tool surface and suppressing diffusion (wear) from the tool side to the work material side. is there. If less than 0.010%, the effect cannot be obtained, so 0.010% or more, preferably 0.020% or more. On the other hand, if it exceeds 0.050%, the effect is saturated and hard alumina-based oxides are increased, and the tool life is reduced. Therefore, the content is made 0.010 to 0.050%.
Ｂ：０．００５０〜０．０１００％
Ｂは工具寿命の向上に有効なＢＮ介在物を生成させるために必要な元素であり、本発明の根幹に関わる重要な元素である。その含有量が０．００５０％未満では、充分な量のＢＮ介在物を生成することが出来ないため工具寿命の向上効果が認められない。一方、０．０１００％を超えると焼入性が向上し、硬度上昇が顕著となるため工具寿命が低下する。従って、含有量は０．００５０〜０．０１００％とする。
B: 0.0050 to 0.0100%
B is an element necessary for generating BN inclusions effective for improving the tool life, and is an important element related to the basis of the present invention. If the content is less than 0.0050%, a sufficient amount of BN inclusions cannot be generated, so that the effect of improving the tool life is not recognized. On the other hand, if it exceeds 0.0100%, the hardenability is improved and the hardness rises remarkably, so that the tool life is reduced. Therefore, the content is made 0.0050 to 0.0100%.
Ｎ：０．００７０〜０．０２００％
Ｎは工具寿命の向上に有効なＢＮ介在物を生成させるために必要な元素であり、本発明の根幹に関わる重要な元素である。その含有量が０．００７０％未満では、充分な量のＢＮ介在物を生成することが出来ないため工具寿命の向上効果が認められない。一方、０．０２００％を超えると熱間延性が低下する。従って、含有量は０．００７０〜０．０２００％とする。
N: 0.0070 to 0.0200%
N is an element necessary for generating BN inclusions effective for improving the tool life, and is an important element related to the basis of the present invention. If the content is less than 0.0070%, a sufficient amount of BN inclusions cannot be generated, so that the effect of improving the tool life is not recognized. On the other hand, when it exceeds 0.0200%, hot ductility will fall. Therefore, the content is made 0.0070 to 0.0200%.
Ｃｒ：０．０１〜１．５０％、Ｍｏ：０．０１〜０．５０％、Ｖ：０．１５０超え０．２５０％以下のうちから選んだ１種または２種以上
Ｃｒ、Ｍｏ、Ｖは、高硬度化するために必要な元素である。しかしながら、その添加量がＣｒ：０．０１％未満、Ｍｏ：０．０１％未満、Ｖ：０．１５０％以下では充分な効果が得られない。一方、Ｃｒ：１．５０％、Ｍｏ：０．５０％、Ｖ：０．２５０％を超えて含有しても高硬度化の効果が飽和し、また、経済的にも不利であるため、Ｃｒ：０．０１〜１．５０％、Ｍｏ：０．０１〜０．５０％、Ｖ：０．１５０超え０．２５０％以下とする。
Cr: 0.01 to 1.50%, Mo: 0.01 to 0.50%, V: 0.150 or more and 0.250% or less selected from Cr, Mo, V It is an element necessary for increasing the hardness. However, if the added amount is less than Cr: 0.01%, Mo: less than 0.01%, and V: 0.150% or less, sufficient effects cannot be obtained. On the other hand, even if the content exceeds Cr: 1.50%, Mo: 0.50%, V: 0.250%, the effect of increasing the hardness is saturated and also disadvantageous economically. : 0.01 to 1.50%, Mo: 0.01 to 0.50%, V: more than 0.150 and 0.250% or less.
本発明に係る快削鋼は以上の成分組成を有し、残部Ｆｅ及び不可避的不純物で、更にＢ、Ｎ、および、Ａｌ量および切削時点での被削材のビッカース硬度（荷重１０ｋｇｆ）からなるパラメータ：Ｆ値が特定範囲を満足することを特徴とする。 The free-cutting steel according to the present invention has the above component composition, and the balance is Fe and unavoidable impurities, and further includes B, N, and the amount of Al and the Vickers hardness of the work material at the time of cutting (load 10 kgf). Parameter: F value satisfies a specific range.
５．０×１０−４＞Ｆ値＞１．５×１０−４
但し、Ｆ値＝（Ｂ＋Ｎ／１．７）×Ａｌ−（４００−ＨＶ１０）／１０６で、各合金元素は含有量（ｍａｓｓ％）、ＨＶ１０は、切削時点での被削材のビッカース硬度（荷重１０ｋｇｆ）。
5.0 × 10 −4 > F value> 1.5 × 10 −4
However, F value = (B + N / 1.7) × Al− (400−HV10) / 10 6 , each alloy element is content (mass%), and HV10 is Vickers hardness of the work material at the time of cutting ( Load 10 kgf).
切削時点における被削材の硬度が上昇するにつれて、工具寿命は低下するようになるため、切削時点の硬度に応じた、最適なＢ、Ｎ、および、Ａｌ量が存在する。Ｆ値は切削時点での硬度が３００ＨＶ１０以上の場合において、Ｂ、Ｎ、および、Ａｌ量の必要量を表すパラメータで、Ｆ値が１．５×１０−４以下であると工具面上にＡｌＮ皮膜が充分に生成しないため、工具寿命の向上効果が認められない。 Since the tool life decreases as the hardness of the work material at the time of cutting increases, there are optimum B, N, and Al amounts according to the hardness at the time of cutting. AlN when F value hardness at the cutting point above 300HV10, B, N, and, a parameter representing the required amount of Al content, the F value is 1.5 × 10 -4 or less on the tool surface Since the film is not sufficiently formed, the effect of improving the tool life is not recognized.
一方、Ｆ値が５．０×１０−４以上になるとＡｌＮ皮膜が安定的に生成しないため、工具寿命の向上効果が認められない。そのため、Ｆ値は、１．５×１０−４超え、５．０×１０−４未満とする。なお、切削時点における被削材の硬度とは、切削開始直前の硬度を指す。 On the other hand, when the F value is 5.0 × 10 −4 or more, the AlN coating is not stably generated, and thus the effect of improving the tool life is not recognized. Therefore, the F value is more than 1.5 × 10 −4 and less than 5.0 × 10 −4 . The hardness of the work material at the time of cutting refers to the hardness immediately before the start of cutting.
本発明に係るＢＮ快削鋼は、常法に従い、所定の成分組成に溶製した溶鋼を、鋳造後、所望の形状に熱間圧延して製造する。その後、切削開始までに、ミクロ組織を調整するために焼入れ焼もどし等の熱処理、あるいは、再加熱後、熱間鍛造を実施して構わないが、ミクロ組織に黒鉛が存在しないようにする必要がある。その理由としては、黒鉛の生成核として、ＢＮが作用・消費されるため、ＡｌＮ皮膜の生成が阻害されること、同時に、３００ＨＶ１０以上の硬度が得られないこと、から黒鉛の生成は避けなければならない。 The BN free-cutting steel according to the present invention is manufactured by casting a molten steel melted in a predetermined component composition into a desired shape after casting according to a conventional method. Then, before the start of cutting, heat treatment such as quenching and tempering may be performed in order to adjust the microstructure, or hot forging may be performed after reheating, but it is necessary to prevent the presence of graphite in the microstructure. is there. The reason for this is that since BN acts and consumes as a graphite nucleus, the formation of an AlN film is inhibited, and at the same time, a hardness of 300 HV10 or higher cannot be obtained. Don't be.
以下に本発明を実施例を用いて更に詳細に説明する。 Hereinafter, the present invention will be described in more detail with reference to examples.
表１に示すＮｏ．１〜２６の化学成分組成に溶製した溶鋼を、鋳造断面４００×３００ｍｍ鋼塊に鋳造後、それぞれ直径２０ｍｍの棒鋼に熱間圧延した。Ｎｏ．１〜１１は本発明の範囲内の化学成分組成を有する鋼（以下、本発明鋼という）、Ｎｏ．１２〜２６は本発明の範囲外の化学成分組成を有する鋼（以下、比較鋼という）である。 No. shown in Table 1. Molten steel melted to a chemical composition of 1 to 26 was cast into a steel ingot having a cast cross section of 400 × 300 mm, and then hot-rolled to steel bars having a diameter of 20 mm. No. Nos. 1 to 11 are steels having chemical composition within the scope of the present invention (hereinafter referred to as the present invention steel), No. 1-11. 12 to 26 are steels having chemical composition compositions outside the scope of the present invention (hereinafter referred to as comparative steels).
得られた棒鋼に対して、切削試験、硬さ試験および熱間延性の評価試験を実施した。切削試験は、最初に外周を１ｍｍ切削して、表面のスケール、脱炭層を除去後、表２に示す条件で実施し、工具寿命、切屑処理性を評価した。硬度は、径断面中間部（軸中心〜外周部）の任意の位置でビッカース硬度を測定荷重１０Ｋｇｆにて４点求め、その平均値とした。熱間延性評価は、圧延棒鋼を３００ｍｍ長さに切断し、ショットブラストにて、表面のスケールを除去した後、目視で表面疵の総長さを測定した。 A cutting test, a hardness test, and a hot ductility evaluation test were performed on the obtained steel bar. In the cutting test, the outer periphery was first cut by 1 mm, and after removing the surface scale and the decarburized layer, the cutting test was carried out under the conditions shown in Table 2 to evaluate the tool life and chip disposal. As for the hardness, four points of Vickers hardness were obtained at an arbitrary position in the intermediate portion of the radial cross section (axial center to outer peripheral portion) with a measurement load of 10 kgf, and the average value was obtained. In the hot ductility evaluation, a rolled steel bar was cut to a length of 300 mm, the surface scale was removed by shot blasting, and then the total length of surface defects was measured visually.
表３にこれらの試験結果を示す。Ｎｏ．１〜１１の本発明例はいずれもＮｏ．１２〜２６の比較例に比較して、工具寿命と切屑処理性に優れる被削性を有していることが認められた。以下に各比較例について記述する。 Table 3 shows the results of these tests. No. Examples 1 to 11 of the present invention are all Nos. Compared to Comparative Examples 12 to 26, it was recognized that the material has machinability superior in tool life and chip disposal. Each comparative example is described below.
比較例Ｎｏ．１２は、Ｃ量が本発明の請求範囲の下限値以下のため、フェライト主体の組織となり、切屑が折れにくくなるため、切屑処理性が本発明例に比較して劣っている。 Comparative Example No. No. 12, because the amount of C is not more than the lower limit value of the claims of the present invention, it becomes a structure mainly composed of ferrite, and the chips are difficult to break, so the chip disposability is inferior to the examples of the present invention.
比較例Ｎｏ．１３は、Ｃ量が本発明の請求範囲の上限値以上のため、パーライト主体の組織となり、硬度上昇が顕著となるため、工具寿命が本発明例に比較して劣っている。 Comparative Example No. In No. 13, since the C amount is equal to or greater than the upper limit of the claims of the present invention, it becomes a pearlite-based structure, and the increase in hardness becomes remarkable, so the tool life is inferior to that of the present invention example.
比較例Ｎｏ．１４は、Ｓｉ量が本発明の請求範囲の下限値以下のため、フェライトの脆化が不充分となり、切屑が折れにくいため、切屑処理性が本発明例に比較して劣っている。 Comparative Example No. In No. 14, since the Si amount is less than the lower limit value of the claims of the present invention, the brittleness of the ferrite becomes insufficient and the chips are not easily broken, so the chip disposability is inferior to that of the present invention example.
比較例Ｎｏ．１５は、Ｓｉ量が本発明の請求範囲の上限値以上のため、フェライトの硬化が顕著となり、そのため、工具寿命が本発明例に比較して劣っている。 Comparative Example No. In No. 15, since the amount of Si is not less than the upper limit value of the claims of the present invention, the hardening of the ferrite becomes remarkable, so that the tool life is inferior to the examples of the present invention.
比較例Ｎｏ．１６は、Ｍｎ量が本発明の請求範囲の下限値以下のため、充分な量のＭｎ硫化物を生成することが出来ない。そのため、工具寿命が本発明例に比較して劣っている。 Comparative Example No. No. 16 cannot produce a sufficient amount of Mn sulfide because the amount of Mn is not more than the lower limit of the claims of the present invention. Therefore, the tool life is inferior compared with the example of the present invention.
比較例Ｎｏ．１７は、Ｍｎ量が本発明の請求範囲の上限値以上のため、焼入性が向上し、硬度上昇が顕著となる。そのため、工具寿命が本発明例に比較して劣っている。 Comparative Example No. In No. 17, since the amount of Mn is not less than the upper limit value of the claims of the present invention, the hardenability is improved and the increase in hardness becomes remarkable. Therefore, the tool life is inferior compared with the example of the present invention.
比較例Ｎｏ．１８は、Ｓ量が本発明の請求範囲の下限値以下のため、充分な量のＭｎ硫化物を生成することが出来ない。そのため、工具寿命が本発明例に比較して劣っている。 Comparative Example No. No. 18 cannot produce a sufficient amount of Mn sulfide because the amount of S is not more than the lower limit of the claims of the present invention. Therefore, the tool life is inferior compared with the example of the present invention.
比較例Ｎｏ．１９は、Ａｌ量が本発明の請求範囲の下限値以下のため、工具面上にＡｌＮ皮膜が充分に生成しないことにより、工具寿命が本発明例に比較して劣っている。 Comparative Example No. In No. 19, since the Al amount is not more than the lower limit value of the claims of the present invention, the AlN coating is not sufficiently formed on the tool surface, so that the tool life is inferior to that of the present invention example.
比較例Ｎｏ．２０は、Ａｌ量が本発明の請求範囲の上限値以上のため、硬質のアルミナ系酸化物が増加することにより、工具寿命が本発明例に比較して劣っている。 Comparative Example No. In No. 20, since the amount of Al is not less than the upper limit value of the claims of the present invention, the life of the tool is inferior to that of the present invention example due to an increase in the hard alumina-based oxide.
比較例Ｎｏ．２１は、Ｂ量が本発明の請求範囲の下限値以下のため、充分な量のＢＮ介在物が生成されないことにより、工具面上にＡｌＮ皮膜が充分に生成しないため、工具寿命が本発明例に比較して劣っている。 Comparative Example No. No. 21 is that the amount of B is less than the lower limit of the claims of the present invention, and since a sufficient amount of BN inclusions are not generated, an AlN film is not sufficiently formed on the tool surface. Inferior to
比較例Ｎｏ．２２は、Ｂ量が本発明の請求範囲の上限値以上のため、焼入性が向上し、硬度上昇が顕著となる。そのため、工具寿命が本発明例に比較して劣っている。 Comparative Example No. No. 22 has an amount of B equal to or greater than the upper limit of the claims of the present invention, so that the hardenability is improved and the increase in hardness becomes remarkable. Therefore, the tool life is inferior compared with the example of the present invention.
比較例Ｎｏ．２３は、Ｎ量が本発明の請求範囲の下限値以下のため、充分な量のＢＮ介在物が生成されないことにより、工具面上にＡｌＮ皮膜が充分に生成しないため、工具寿命が本発明例に比較して劣っている。 Comparative Example No. In No. 23, since the amount of N is less than the lower limit value of the claims of the present invention, a sufficient amount of BN inclusions are not generated, so that an AlN film is not sufficiently formed on the tool surface. Inferior to
比較例Ｎｏ．２４は、Ｎ量が本発明の請求範囲の上限値以上のため、熱間延性が低下し、そのため、圧延材の表面性状が本発明例に比較して劣っている。 Comparative Example No. In No. 24, since the N amount is not less than the upper limit value of the claims of the present invention, the hot ductility is lowered, and therefore the surface properties of the rolled material are inferior to those of the examples of the present invention.
比較例Ｎｏ．２５は、Ｆ値が本発明の請求範囲の下限値以下のため、工具面上にＡｌＮ皮膜が充分に生成しない。このため、工具寿命が本発明例に比較して劣っている。 Comparative Example No. In No. 25, the F value is not more than the lower limit value of the claims of the present invention, so that an AlN film is not sufficiently formed on the tool surface. For this reason, the tool life is inferior compared with the example of this invention.
比較例Ｎｏ．２６は、Ｆ値が本発明の請求範囲の上限値以上のため、ＡｌＮ皮膜が安定的に生成しない。このため、工具寿命が本発明例に比較して劣っている。 Comparative Example No. In No. 26, since the F value is not less than the upper limit value of the claims of the present invention, an AlN film is not stably formed. For this reason, the tool life is inferior compared with the example of this invention.
Claims (1)
Ｆ値＝（Ｂ＋Ｎ／１．７）×Ａｌ−（４００−ＨＶ１０）／１０６
５．０×１０−４＞Ｆ値＞１．５×１０−４ ・・・・・・・・・・・・ （１）
ここで、各合金元素は含有量（ｍａｓｓ％）、ＨＶ１０は、切削時点での被削材のビッカース硬度（荷重１０ｋｇｆ）を示す。 mass: C: 0.30 to 0.50%, Si: more than 0.25 and less than 0.50%, Mn: 0.30 to less than 1.00%, P: 0.030% or less (0% is Not including), S: more than 0.015 and not more than 0.200%, Al: 0.010-0.050%, B: 0.0050-0.0100%, N: 0.0070-0.0200% Furthermore, one or more selected from Cr: 0.01 to 1.50%, Mo: 0.01 to 0.50%, V: 0.150 to 0.250%, and below A high-hardness BN-based free-cutting steel having a tool life of 300 HV10 or more, wherein the F value shown in (1) satisfies the formula (1) and the balance is Fe and inevitable impurities.
F value = (B + N / 1.7) × Al− (400−HV10) / 10 6
5.0 × 10 −4 > F value> 1.5 × 10 −4 (1)
Here, the content of each alloy element (mass%), HV10 indicates the Vickers hardness (load 10 kgf) of the work material at the time of cutting.
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