JP2013104075A - Free-cutting stainless steel having diplophase inclusion - Google Patents

Free-cutting stainless steel having diplophase inclusion Download PDF

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JP2013104075A
JP2013104075A JP2011247402A JP2011247402A JP2013104075A JP 2013104075 A JP2013104075 A JP 2013104075A JP 2011247402 A JP2011247402 A JP 2011247402A JP 2011247402 A JP2011247402 A JP 2011247402A JP 2013104075 A JP2013104075 A JP 2013104075A
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JP6120303B2 (en
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Takashi Hosoda
孝 細田
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Sanyo Special Steel Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To propose free-cutting stainless steel, wherein non-Pb steel generates low environmental loads, that has machinability equivalent to or higher than that of Pb steel and sufficient corrosion resistance, and is not easily deformed or caused to fall by external force.SOLUTION: The free-cutting stainless steel includes, in mass%, 0.01-1.50% of C, 0.05-2.00% of Si, 0.001-0.050% of Al, and 0.002-0.040% of O, and further includes 10.00-20.00% of Cr, 0.05-3.00% of Mn, 0.05-1.00% of S, and 0.005-0.050% of N as basic constituents, with the balance comprising Fe and unavoidable impurities. The free-cutting stainless steel includes a sulfide, and when formula A is A=Mn/S, A≤3.0 is satisfied. Furthermore, when each concentration of Cr, Mn, and S in the sulfide is represented by [Cr], [Mn], and [S] and formula B is B=([Cr]-[Mn])/[S], B≥0.1 is satisfied. Also, diplophase inclusions are formed from these sulfides.

Description

本発明は、精密機器部品、産業用機械構造部品などの部材として使用できる、優れた耐食性および被削性を有する快削ステンレス鋼に関する。   The present invention relates to a free-cutting stainless steel having excellent corrosion resistance and machinability that can be used as a member such as precision equipment parts and industrial machine structural parts.

耐食性、耐久性および切削加工を必要とする機器などには、生産性向上のためにPb、S、Se、Teなどを含有した快削ステンレス鋼が使用されている。ところで、Pbは耐食性を殆んど低下させずに被削性を向上させる有用な元素である。その反面、環境保護に対する関心が地球規模で高まっている近年では、Pbは環境を害する元素であるとして、添加が敬遠される。一方、S、Se、Teは鋼中で非金属介在物を形成して被削性を向上させるが、その介在物は、マトリクスよりも腐食環境に弱いため、材料の耐食性を劣化させてしまう。また、軟質であるため、外力の影響を受けて変形や脱落を起こしやすく、材料の良好な表面性状を保つことが難しい。   Free cutting stainless steel containing Pb, S, Se, Te, or the like is used for improving productivity, for devices that require corrosion resistance, durability, and cutting. Pb is a useful element that improves machinability without substantially reducing the corrosion resistance. On the other hand, in recent years when interest in environmental protection is increasing on a global scale, addition of Pb is avoided because it is an element that harms the environment. On the other hand, S, Se, and Te improve the machinability by forming non-metallic inclusions in the steel, but the inclusions are weaker than the matrix in a corrosive environment, so that the corrosion resistance of the material is deteriorated. In addition, since it is soft, it is easily deformed or dropped due to the influence of external force, and it is difficult to maintain good surface properties of the material.

環境負荷を考慮して、非Pb鋼であると共に、硫化物系介在物組成を制御し、耐食性および被削性を改善した発明が提案されている(例えば、特許文献1参照。)。しかしながら、この発明は、材料の表面性状を保つための介在物形態の制御については言及していない。   In consideration of the environmental load, an invention has been proposed in which non-Pb steel is used, the composition of sulfide inclusions is controlled, and corrosion resistance and machinability are improved (for example, see Patent Document 1). However, this invention does not mention the control of the inclusion form for maintaining the surface properties of the material.

特許第3923184号公報Japanese Patent No. 3923184

精密機器の部品や、産業用機械の構造部品などの部材は、使用環境における十分な耐食性を有することが必須である。その上に、これらの部材は精密加工や量産加工に対応できる被削性も要求される。このような鉄鋼材料において、耐食性を損なうことなく被削性を向上させる元素としては、Pbが良く知られている。しかしながら、環境負荷への低減を考慮するとき、Pbの使用は避ける必要がある。さらに、上記の部品などの部材は、それぞれ搭載される機器に向けて綿密な設計がされることが多い。したがって、これらの部材では、それらの材料の表面状態の安定性も重要な要件である。   It is essential that members such as precision instrument parts and industrial machine structural parts have sufficient corrosion resistance in the usage environment. In addition, these members are also required to have machinability that can be used for precision machining and mass production. In such steel materials, Pb is well known as an element that improves machinability without impairing corrosion resistance. However, the use of Pb should be avoided when considering a reduction to environmental load. Furthermore, members such as the above-mentioned parts are often designed carefully for each device to be mounted. Therefore, in these members, the stability of the surface state of these materials is also an important requirement.

そこで、本発明が解決しようとする課題は、非Pbで環境負荷が小さく、かつ、十分な耐食性と被削性を有し、さらに外力などによる変形や脱落のしにくい材料である快削ステンレス鋼を提案することである。   Therefore, the problem to be solved by the present invention is a free-cutting stainless steel that is non-Pb, has a small environmental load, has sufficient corrosion resistance and machinability, and is not easily deformed or dropped by an external force. Is to propose.

上記の課題を解決するための本発明の手段は、環境負荷の低減のために、非Pb鋼であるが、Pb鋼並みあるいはそれ以上の被削性を有する鋼であることを特徴とする複相介在物を有する快削ステンレス鋼である。   The means of the present invention for solving the above-mentioned problems is a non-Pb steel for reducing the environmental load, but is a steel having machinability equivalent to or higher than that of Pb steel. Free-cutting stainless steel with phase inclusions.

すなわち、本発明の第1の手段は、質量%で、C:0.01〜1.50%、Si:0.05〜2.00%、Al:0.001〜0.050%、O:0.002〜0.040%を含有し、さらに、Cr:10.00〜20.00%、Mn:0.05〜3.00%、S:0.05〜1.00%、N:0.005〜0.050%の基本成分に加えて、さらに、Ni:0.01〜20.00、Mo:0.01〜3.00%、Cu:0.01〜2.00%のいずれか1種または2種以上を含有し、残部Feおよび不可避不純物からなる鋼である。そして、この鋼は硫化物を含有しており、この硫化物を含有する鋼は、式AをA=Mn/Sとするとき、A≦3.0を満足し、さらに硫化物中のCr、Mn、Sの濃度をそれぞれ[Cr]、[Mn]、[S]で表し、式BをB=([Cr]−[Mn])/[S]とするとき、B≧0.1を満足し、かつ、これらの硫化物から複相介在物を形成している、快削ステンレス鋼である。   That is, the first means of the present invention is mass%, C: 0.01 to 1.50%, Si: 0.05 to 2.00%, Al: 0.001 to 0.050%, O: 0.002 to 0.040%, Cr: 10.00 to 20.00%, Mn: 0.05 to 3.00%, S: 0.05 to 1.00%, N: 0 In addition to 0.005 to 0.050% of basic components, Ni: 0.01 to 20.00, Mo: 0.01 to 3.00%, Cu: 0.01 to 2.00% It is a steel that contains one or more types, and is composed of the balance Fe and inevitable impurities. And this steel contains sulfide, and steel containing this sulfide satisfies A ≦ 3.0 when formula A is A = Mn / S, and further Cr in sulfide, The concentrations of Mn and S are represented by [Cr], [Mn], and [S], respectively, and when formula B is B = ([Cr] − [Mn]) / [S], B ≧ 0.1 is satisfied. In addition, it is a free-cutting stainless steel that forms double-phase inclusions from these sulfides.

第2の手段は、第1の手段に記載した鋼の化学成分に、さらに、Se:0.20%以下、Te:0.30%以下、Bi:0.20%以下のいずれか1種または2種以上を含有する快削ステンレス鋼である。   The second means includes any one of Se: 0.20% or less, Te: 0.30% or less, Bi: 0.20% or less, in addition to the chemical components of the steel described in the first means. It is a free-cutting stainless steel containing two or more types.

第3の手段は、第1の手段または第2の手段に記載した鋼の化学成分に、さらに質量%で、Ti:0.001〜1.00%、Zr:0.001〜1.00%、V:0.001〜1.00%、W:0.001〜1.00%、Nb:0.001〜1.00%のいずれか1種または2種以上を含有する快削ステンレス鋼である。   The third means includes, in addition to the chemical components of the steel described in the first means or the second means, in mass%, Ti: 0.001 to 1.00%, Zr: 0.001 to 1.00%. V: 0.001 to 1.00%, W: 0.001 to 1.00%, Nb: 0.001 to 1.00% free cutting stainless steel containing one or more of them is there.

第4の手段は、第1の手段〜第3の手段のいずれかの一つの手段に記載した鋼の化学成分に、さらに質量%で、B:0.02%以下、Ca:0.05%以下、Mg:0.05%以下、REM:0.05%以下のいずれか1種または2種以上を含有する快削ステンレス鋼である。   According to a fourth means, the chemical composition of the steel described in any one of the first means to the third means is further added in terms of mass%, B: 0.02% or less, Ca: 0.05% Hereinafter, it is a free-cutting stainless steel containing one or more of Mg: 0.05% or less and REM: 0.05% or less.

上記の手段とすることで、本願のステンレス鋼は精密機器部品、産業用機械構造部品などの部材の用途に使用するとき、この材料は硫化物中に高Cr相と低Cr相が共存する複相硫化物となっており、高Cr相が硬質であるため、この材料は外力による変形や複相硫化物の脱落や無く、したがって材料を加工した際の表面性状が良好で安定しており、さらに高温湿潤化での錆の発生も無く、孔食電位も十分に高く、耐食性に優れ、かつ快削性の極めて優れた材料となっている。   By using the above means, when the stainless steel of the present application is used for parts such as precision equipment parts and industrial machine structural parts, this material is a compound in which high Cr phase and low Cr phase coexist in sulfide. Since this is a phase sulfide and the high Cr phase is hard, this material is free from deformation due to external forces or dropping off of the multiphase sulfide, and therefore the surface properties when processing the material are good and stable. Furthermore, there is no generation of rust due to high temperature wetting, the pitting corrosion potential is sufficiently high, the material has excellent corrosion resistance, and extremely excellent free-cutting properties.

上段は本発明例1および比較例1の組成をEPMA(電子プローブX線マイクロアナライザー)で確認した写真であり、下段はその中の高Cr相を示す倍率400倍の顕微鏡写真である。The upper part is a photograph in which the compositions of Invention Example 1 and Comparative Example 1 are confirmed by EPMA (Electron Probe X-ray Microanalyzer), and the lower part is a micrograph at a magnification of 400 times showing a high Cr phase therein. 横軸に式A=Mn/Sとし、縦軸に式B=[Cr]−[Mn])/[S]とし、本発明例の組成のおよび比較例の組成における耐食性の良し悪しおよび加工性である表面性状の良し悪しを示すグラフである。Formula A = Mn / S on the horizontal axis and formula B = [Cr]-[Mn]) / [S] on the vertical axis, and the corrosion resistance in the composition of the present invention and the composition of the comparative example and good workability It is a graph which shows the quality of the surface property which is.

本発明の合金のFe以外の各成分の含有量の限定理由並びに式Aの値および式Bの値の限定理由について、以下に説明する。なお、%は質量%である。   The reasons for limiting the content of each component other than Fe in the alloy of the present invention and the reasons for limiting the values of Formula A and Formula B will be described below. In addition,% is the mass%.

C:0.01〜1.50%
Cは、材料の強度に寄与する元素であり、そのためには0.01%以上必要である。しかし、Cが1.50%を超えると炭化物形成により耐食性を悪下し、さらに硬度上昇により被削性を悪化する。そこで、Cは0.01〜1.50%とする。
C: 0.01 to 1.50%
C is an element contributing to the strength of the material, and for that purpose, 0.01% or more is necessary. However, if C exceeds 1.50%, the corrosion resistance deteriorates due to carbide formation, and the machinability deteriorates due to the increase in hardness. Therefore, C is set to 0.01 to 1.50%.

Si:0.05〜2.00%
Siは、製鋼時の脱酸剤として有用な元素であり、また材料強度に企図する元素であり、そのためには、0.05%以上必要である。しかし、Siが2.00%を超えると硬度上昇により被削性を悪化する。そこで、Siは0.05〜2.00%とする。
Si: 0.05-2.00%
Si is an element useful as a deoxidizer during steelmaking, and is an element intended for material strength. For this purpose, 0.05% or more is necessary. However, if Si exceeds 2.00%, the machinability deteriorates due to an increase in hardness. Therefore, Si is set to 0.05 to 2.00%.

Al:0.001〜0.050%
Alは、製鋼時の強力な脱酸剤として有用な元素であり、そのためには0.001%以上が必要である。しかし、Alが0.050%を超えると、硬質な酸化物の形成により、加工性および被削性を悪化する。そこで、Alは0.001〜0.050%とする。
Al: 0.001 to 0.050%
Al is an element useful as a powerful deoxidizer during steelmaking, and for that purpose, 0.001% or more is necessary. However, if Al exceeds 0.050%, the workability and machinability deteriorate due to the formation of a hard oxide. Therefore, Al is made 0.001 to 0.050%.

O:0.002〜0.040%
Oは製鋼時に脱酸元素の過剰添加等の原因で過少になると、硫化物が熱間で延伸しやすくなり被削性改善に不適当な形状になる。また、多すぎると被削性改善効果が飽和し、酸化物量が増加し、靱性が低下する。従って、Oは0.002〜0.040%とする。
O: 0.002 to 0.040%
If O becomes too small due to excessive addition of a deoxidizing element during steelmaking, the sulfide tends to be stretched hot, resulting in an unsuitable shape for improving machinability. On the other hand, if the amount is too large, the machinability improving effect is saturated, the amount of oxide increases, and the toughness decreases. Therefore, O is 0.002 to 0.040%.

Cr:10.00〜20.00%
Crは、耐食性の向上に必須の元素であり、また、固溶強化元素として材料強度の向上に寄与する元素である。そのためには、Crは10.00%以上が必要である。しかし、Crが20.00%を超えると、材料の基地および硫化物が硬化することで材料の被削性が悪化する。そこで、Crは10.00〜20.00%とする。
Cr: 10.00-20.00%
Cr is an element essential for improving corrosion resistance, and is an element contributing to improvement of material strength as a solid solution strengthening element. For that purpose, Cr needs to be 10.00% or more. However, if Cr exceeds 20.00%, the machinability of the material deteriorates due to hardening of the base of the material and sulfide. Therefore, Cr is 10.00 to 20.00%.

Mn:0.05〜3.00%
Mnは、Sと結合して硫化物を形成して被削性を改善する元素であり、そのためには、Mnは0.05%以上が必要である。しかし、Mnが3.00%を超えて含有されると耐食性が悪化する。そこで、Mnは0.05〜3.00%とする。
Mn: 0.05 to 3.00%
Mn is an element that combines with S to form a sulfide to improve machinability, and for that purpose, Mn needs to be 0.05% or more. However, if Mn exceeds 3.00%, corrosion resistance deteriorates. Therefore, Mn is set to 0.05 to 3.00%.

S:0.05〜1.00%
Sは、Mnと結合して硫化物を形成して被削性を改善する元素であり、そのためには、Sは0.05%以上が必要である。しかし、Sが1.00%を超えて含有されると、被削性の改善効果は飽和し、さらに低融点の硫化物を生成して熱間加工性を悪化する。そこで、Sは0.05〜1.00%とする。
S: 0.05-1.00%
S is an element that combines with Mn to form a sulfide to improve the machinability, and for that purpose, S needs to be 0.05% or more. However, if S is contained in an amount exceeding 1.00%, the machinability improving effect is saturated, and a sulfide having a low melting point is generated to deteriorate the hot workability. Therefore, S is set to 0.05 to 1.00%.

N:0.005〜0.050%
Nは、耐食性の向上および強度の向上に役立つ元素である。しかし、Nが0.005%未満ではその効果が乏しくなる上、精錬が難しく、生産性が低下し製造コストの上昇を招く。一方、Nが0.050%を超えて含有されると鋼中に欠陥が形成され、熱間加工性が悪化する。そこで、Nは0.005〜0.050%とする。
N: 0.005 to 0.050%
N is an element useful for improving corrosion resistance and strength. However, if N is less than 0.005%, the effect becomes poor, and refining is difficult, resulting in a decrease in productivity and an increase in manufacturing cost. On the other hand, if N is contained in excess of 0.050%, defects are formed in the steel and hot workability is deteriorated. Therefore, N is set to 0.005 to 0.050%.

Ni:0.01〜20.00%
Niは、材料の延性および靱性に寄与する元素であり、また、非酸化性の酸に対する耐食性を向上させる元素である。そのためには、Niは0.01%が必要である。しかし、Niは20.00%を超えるとコスト高となる。そこでNiは0.01〜20.00%とする。
Ni: 0.01-20.00%
Ni is an element that contributes to the ductility and toughness of the material, and is an element that improves the corrosion resistance against non-oxidizing acids. For that purpose, Ni needs to be 0.01%. However, if Ni exceeds 20.00%, the cost becomes high. Therefore, Ni is set to 0.01 to 20.00%.

Mo:0.01〜3.00%
Moは、耐食性を向上させる元素であり、そのためには0.01%以上が必要である。しかし、Moは3.00%を超えるとコスト高となり、かつ脆化相の析出を促進する。そこでMoは0.01〜3.00%とする。
Mo: 0.01 to 3.00%
Mo is an element that improves the corrosion resistance, and for that purpose, 0.01% or more is necessary. However, if Mo exceeds 3.00%, the cost increases and the precipitation of the embrittled phase is promoted. Therefore, Mo is set to 0.01 to 3.00%.

Cu:0.01〜2.00%
Cuは、耐食性および冷間加工性の改善に役立つ元素であり、そのためには0.01%以上が必要である。しかし、Cuは2.00%を超えると熱間加工性を悪化する。そこで、Cuは0.01〜2.00%とする。
Cu: 0.01 to 2.00%
Cu is an element useful for improving corrosion resistance and cold workability, and for that purpose, 0.01% or more is necessary. However, when Cu exceeds 2.00%, the hot workability deteriorates. Therefore, Cu is made 0.01 to 2.00%.

Se:0.20%以下
Seは、被削性の改善効果を有する元素であるが、Seが0.20%を超えて含有されても、被削性の改善効果は飽和し、熱間加工性を悪化する。そこで、Seは0.20%以下とする。
Se: 0.20% or less Se is an element having an effect of improving machinability, but even if Se is contained in an amount exceeding 0.20%, the effect of improving machinability is saturated and hot working is performed. Worsens sex. Therefore, Se is set to 0.20% or less.

Te:0.30%以下
Teは、被削性の改善効果を有する元素であるが、Teが0.30%を超えて含有されても、被削性の改善効果は飽和し、熱間加工性を悪化する。そこで、Teは0.30%以下とする。
Te: 0.30% or less Te is an element having an effect of improving machinability, but even if Te is contained exceeding 0.30%, the effect of improving machinability is saturated and hot working is performed. Worsens sex. Therefore, Te is set to 0.30% or less.

Bi:0.20%以下
Biは、被削性の改善効果を有する元素であるが、BiはPbと同様に環境負荷を増大する元素であり、かつ、Biが0.20%を超えて含有されても、被削性の改善効果は飽和し、熱間加工性を悪化する。そこで、Biは0.20%以下とする。
Bi: 0.20% or less Bi is an element having an effect of improving machinability, but Bi is an element that increases the environmental load similarly to Pb, and Bi is contained in excess of 0.20%. However, the machinability improving effect is saturated and the hot workability is deteriorated. Therefore, Bi is set to 0.20% or less.

Ti:0.001〜1.00%
Tiは、C固定による耐食性の改善効果および熱間加工性の改善効果を有する元素で、そのためには0.001%以上が必要である。しかし、Tiは1.00%を超えて過剰に添加されると熱間加工性が悪化し、材料を脆化する。そこで、Tiは0.001〜1.00%とする。
Ti: 0.001 to 1.00%
Ti is an element having an effect of improving the corrosion resistance and the effect of improving the hot workability by C fixation, and for that purpose, 0.001% or more is necessary. However, when Ti is added excessively exceeding 1.00%, hot workability deteriorates and the material becomes brittle. Therefore, Ti is made 0.001 to 1.00%.

Zr:0.001〜1.00%
Zrは、C固定による耐食性の改善効果および熱間加工性の改善効果を有する元素で、そのためには0.001%以上が必要である。しかし、Zrは1.00%を超えて過剰に添加されると熱間加工性が悪化し、材料を脆化する。そこで、Zrは0.001〜1.00%とする。
Zr: 0.001 to 1.00%
Zr is an element having an effect of improving the corrosion resistance and the effect of improving the hot workability by C fixation, and 0.001% or more is necessary for that purpose. However, if Zr exceeds 1.00% and is added excessively, the hot workability deteriorates and the material becomes brittle. Therefore, Zr is set to 0.001 to 1.00%.

V:0.001〜1.00%
Vは、C固定による耐食性の改善効果および熱間加工性の改善効果を有する元素で、そのためには0.001%以上が必要である。しかし、Vは1.00%を超えて過剰に添加されると熱間加工性が悪化し、材料を脆化する。そこで、Vは0.001〜1.00%とする。
V: 0.001 to 1.00%
V is an element having an effect of improving the corrosion resistance by fixing C and an effect of improving the hot workability, and for that purpose, 0.001% or more is necessary. However, if V exceeds 1.00% and is added excessively, the hot workability deteriorates and the material becomes brittle. Therefore, V is set to 0.001 to 1.00%.

W:0.001〜1.00%
Wは、C固定による耐食性の改善効果および熱間加工性の改善効果を有する元素で、そのためには0.001%以上が必要である。しかし、Wは1.00%を超えて過剰に添加されると熱間加工性が悪化し、材料を脆化する。そこで、Wは0.001〜1.00%とする。
W: 0.001 to 1.00%
W is an element having an effect of improving corrosion resistance and an effect of improving hot workability by C fixation, and for that purpose, 0.001% or more is necessary. However, when W exceeds 1.00% and is added excessively, hot workability deteriorates and the material becomes brittle. Therefore, W is set to 0.001 to 1.00%.

Nb:0.001〜1.00%
Nbは、C固定による耐食性の改善効果および熱間加工性の改善効果を有する元素で、そのためには0.001%以上が必要である。しかし、Nbは1.00%を超えて過剰に添加されると熱間加工性が悪化し、材料を脆化する。そこで、Nbは0.001〜1.00%とする。
Nb: 0.001 to 1.00%
Nb is an element having an effect of improving corrosion resistance and an effect of improving hot workability by C fixation, and 0.001% or more is necessary for that purpose. However, if Nb exceeds 1.00% and is added excessively, the hot workability deteriorates and the material becomes brittle. Therefore, Nb is made 0.001 to 1.00%.

B:0.02%以下
Bは、熱間加工性の改善効果を有する元素であるが、Bが0.02%を超えて過剰に添加されると熱間加工性を悪化する。そこで、Bは0.02%以下とする。
B: 0.02% or less B is an element having an effect of improving hot workability, but when B is added in excess of 0.02%, hot workability is deteriorated. Therefore, B is set to 0.02% or less.

Ca:0.05%以下
Caは、熱間加工性の改善効果および脱酸効果を有する元素であるが、Caが0.05%を超えて過剰に添加されると熱間加工性を悪化する。そこで、Caは0.05%以下とする。
Ca: 0.05% or less Ca is an element having an effect of improving hot workability and a deoxidation effect, but when Ca is added in excess of 0.05%, hot workability is deteriorated. . Therefore, Ca is set to 0.05% or less.

Mg:0.05%以下
Mgは、熱間加工性の改善効果および脱酸効果を有する元素であるが、Mgが0.05%を超えて過剰に添加されると熱間加工性を悪化する。そこで、Mgは0.05%以下とする。
Mg: 0.05% or less Mg is an element having an effect of improving hot workability and deoxidation effect, but when Mg is added excessively exceeding 0.05%, hot workability is deteriorated. . Therefore, Mg is made 0.05% or less.

REM:0.05%以下
REMは、熱間加工性の改善効果および脱酸効果を有する元素であるが、REMが0.05%を超えて過剰に添加されると熱間加工性を悪化する。そこで、REMは0.05%以下とする。
REM: 0.05% or less REM is an element having an effect of improving hot workability and deoxidation effect, but when REM is added excessively exceeding 0.05%, hot workability is deteriorated. . Therefore, REM is set to 0.05% or less.

A=Mn/Sとするとき、A≦3.0
MnとSはステンレス鋼中に硫化物を形成し、その被削性を改善させる。しかし、硫化物中のMn濃度が高まると、硫化物中のCr濃度が低下し、それを含有するステンレス鋼の耐食性を悪化させる。この耐食性の悪化を回避するには、鋼中のMnとS濃度比を制限し、硫化物のMn濃度の上昇を抑制してCrリッチな組成にする必要がある。Aの値が3.0を超えると、耐食性が悪化する。そこで、A=Mn/Sとするとき、A≦3.0を満足するものとする。
When A = Mn / S, A ≦ 3.0
Mn and S form sulfides in stainless steel and improve their machinability. However, when the Mn concentration in the sulfide increases, the Cr concentration in the sulfide decreases, and the corrosion resistance of the stainless steel containing it decreases. In order to avoid this deterioration of the corrosion resistance, it is necessary to limit the Mn and S concentration ratio in the steel and suppress the increase in the Mn concentration of the sulfide to make the composition rich in Cr. When the value of A exceeds 3.0, the corrosion resistance deteriorates. Therefore, when A = Mn / S, A ≦ 3.0 is satisfied.

B=([Cr]−[Mn])/[S]とするとき、B≧0.1
精密機器の部品や、産業用機械の構造部品などの部材は、精密加工や量産加工に対応できる被削性が要求されると同時に、それぞれ搭載される機器に向けて綿密な設計がされることが多いため、材料の表面状態の安定性も重要な要件である。表面状態の安定性を確保するには、被削性を付与する硫化物が加工中に脱落することを防ぐ必要がある。このためには、硫化物自体の硬さを高め、外力による硫化物の変形や脱落を抑制することが有効である。発明者らは硫化物組成を制御することで、硫化物中に硬質な高Cr相を形成させ、硫化物の硬さを高める方策を見出した。鋼材内に存在する硫化物中のCr、Mn、Sの濃度をそれぞれ[Cr]、[Mn]、[S]とするとき、B=([Cr]−[Mn])/[S]で表される。ところで、このBの値が0.1を超えると、硫化物中に硬質な高Cr相を形成し、外力による硫化物の変形や脱落を抑制するが、Bの値が0.1を下回ると、硫化物中に高Cr相が形成されず、外力による硫化物の変形や脱落を抑制することができなくなる。そこで、B=([Cr]−[Mn])/[S]とするとき、B≧0.1とする。
When B = ([Cr] − [Mn]) / [S], B ≧ 0.1
Parts such as precision machine parts and industrial machine structural parts are required to have machinability that can be applied to precision machining and mass production, and at the same time, they must be carefully designed for each machine. Therefore, the stability of the surface state of the material is also an important requirement. In order to ensure the stability of the surface state, it is necessary to prevent the sulfide imparting machinability from falling off during processing. For this purpose, it is effective to increase the hardness of the sulfide itself and suppress the deformation and dropout of the sulfide due to external force. The inventors have found a measure to increase the hardness of the sulfide by controlling the sulfide composition to form a hard high Cr phase in the sulfide. When the concentrations of Cr, Mn, and S in the sulfide existing in the steel material are [Cr], [Mn], and [S], respectively, B = ([Cr] − [Mn]) / [S]. Is done. By the way, when the value of B exceeds 0.1, a hard high Cr phase is formed in the sulfide, and the deformation and falling off of the sulfide due to external force are suppressed, but when the value of B is less than 0.1, In addition, a high Cr phase is not formed in the sulfide, and it becomes impossible to suppress the deformation and dropping of the sulfide due to external force. Therefore, when B = ([Cr] − [Mn]) / [S], B ≧ 0.1.

上記したように、A=Mn/Sとするとき、A≦3.0とし、および、B=([Cr]−[Mn])/[S]とするとき、B≧0.1Cr、Mn、Sの組成、および式A=Mn/Sおよび被削性を改善する介在物である硫化物中の組成をCrリッチとして耐食性を良好とし、さらにBの範囲に制御し、硫化物中にCr濃度が質量%で40を超える高Cr相と、Cr濃度が質量%で40以下である低Cr相が共存する複相硫化物に形成し、特に硬質である高Cr相が外力による硫化物の変形や脱落を起こり難くし、かつ、加工性である材料の表面性状を良好に保つものとする。   As described above, when A = Mn / S, A ≦ 3.0, and when B = ([Cr] − [Mn]) / [S], B ≧ 0.1Cr, Mn, The composition of S and the formula A = Mn / S and the composition in the sulfide, which is an inclusion improving machinability, are Cr-rich so that the corrosion resistance is good, and further controlled to the range of B, the Cr concentration in the sulfide Is formed into a double-phase sulfide in which a high Cr phase exceeding 40% by mass and a low Cr phase having a Cr concentration of 40% or less coexist, and the hard high Cr phase is deformed by an external force. It is assumed that the surface property of the material that is easy to process and the workability is kept good.

次いで、本発明を実施するための形態について、表および図面を参照して以下に説明する。本発明の快削ステンレス鋼の表1にFe以外の成分を示す成分組成からなる溶鋼を100kgVIM(真空誘導溶解炉)で溶製し、これをインゴットに鋳造し、このインゴットからなる鋼材を径が25mmの棒鋼に鍛伸し、それぞれ鋼種に応じた熱処理をした。   Next, modes for carrying out the present invention will be described below with reference to tables and drawings. In Table 1 of the free-cutting stainless steel of the present invention, molten steel having a component composition showing components other than Fe is melted in a 100 kg VIM (vacuum induction melting furnace), cast into an ingot, and the steel material made of this ingot has a diameter of It was forged into a 25 mm steel bar and heat-treated according to the steel type.

上記の鋼種に応じた熱処理とは、表1の発明例のNo.1〜5、No.9、No.11、および、比較例のNo.1〜9のマルテンサイト系の鋼種では、被削性試験の各試験片の作製のために、870℃で焼鈍することであり、また、介在物観察、組成分析、耐食性評価、表面性状の安定性評価の各試料の作製のために、870℃で焼鈍し、950〜980℃で焼入れし、720〜800℃で焼戻することである。   The heat treatment according to the above steel types is the No. of the invention example in Table 1. 1-5, no. 9, no. 11 and Comparative Example No. In the martensitic steel types 1 to 9, annealing is performed at 870 ° C. in order to produce each test piece of the machinability test. In addition, inclusion observation, composition analysis, corrosion resistance evaluation, and surface property stability In order to produce each sample for property evaluation, annealing at 870 ° C., quenching at 950 to 980 ° C., and tempering at 720 to 800 ° C.

さらに熱処理とは、表1の発明例のNo.6〜8、No.10のフェライト系の鋼種では、各種試験や評価の各試料の作製のために、750〜850℃で焼鈍することである。   Further, heat treatment refers to No. of the invention example in Table 1. 6-8, no. In 10 ferritic steel types, annealing is performed at 750 to 850 ° C. in order to prepare samples for various tests and evaluations.

また、さらに熱処理とは、表1の発明例のNo.12〜15のオーステナイト系の鋼種では、各種試験や評価の各試料の作製のために、1000〜1150℃で固溶化処理することである。   Further, heat treatment refers to No. of the invention example in Table 1. In the case of 12-15 austenitic steel types, a solution treatment is performed at 1000 to 1150 ° C. in order to prepare samples for various tests and evaluations.

表1に示す硫化物中の組成は、エネルギー分散X線解析(EDXD)により各試料のL断面に観測された介在物を観察、分析して得た値である。   The composition in the sulfide shown in Table 1 is a value obtained by observing and analyzing inclusions observed in the L cross section of each sample by energy dispersive X-ray analysis (EDXD).

表1に示す発明例のNo.1〜15と比較例のNo.1〜9についてのそれぞれの被削性、耐食性および表面安定性の評価結果を下記の表2に示す。   No. of the invention example shown in Table 1. 1-15 and No. of the comparative example. Table 2 below shows the evaluation results of machinability, corrosion resistance, and surface stability for 1 to 9.

この表2における被削性評価は、表1の各発明例おとび比較例の組成及び硫化物を含有する鋼をそれぞれ上記した熱処理などにより作製した各試料を、ドリルにより深さ10mmに穿孔するに要する穿孔時間を測定し、その所要時間が、9.5秒以下のものを○、9.6秒以上10秒以下を△、10.1秒以上を×として評価した。   The machinability evaluation in Table 2 is performed by drilling each sample prepared by heat treatment as described above for each invention example and comparative example of Table 1 and steel containing sulfide to a depth of 10 mm using a drill. The time required for drilling was measured, and the time required was evaluated as ◯ for 9.5 seconds or less, Δ for 9.6 to 10 seconds, and x for 10.1 seconds or more.

表2における耐食性試験の評価は、同じく、表1の各発明例おとび比較例の組成および硫化物を含有する鋼をそれぞれ上記した熱処理などにより作製した各試料から、径φ12mmで長さ21mmの腐食試験用試料を作製し、この試料を用いて、以下の(1)高温湿潤試験、(2)孔食電位測定および(3)加工性である表面性状安定性評価の3種の腐食試験を実施した。なお、表2の比較例のNo.5は表1の比較例のNo.5に示すようにPbを意図的に含有する鉛含有鋼である。   Similarly, the evaluation of the corrosion resistance test in Table 2 is that each of the inventive examples in Table 1 and the composition of the comparative example and the steel containing sulfides were each prepared by heat treatment as described above, and each of the samples having a diameter of 12 mm and a length of 21 mm. A sample for corrosion test was prepared, and using this sample, the following three types of corrosion tests were conducted: (1) high temperature wetness test, (2) pitting potential measurement, and (3) surface property stability evaluation as workability. Carried out. In Table 2, the comparative example No. No. 5 of the comparative example of Table 1. 5 is a lead-containing steel intentionally containing Pb.

(1)高温湿潤試験は、湿度が90%の雰囲気下にて、20℃と50℃の間を20回繰り返して温度変化させて、試料の発銹状況を調査し、発銹なしのものを○、発銹ありのものを×として評価した。   (1) In the high temperature wet test, in a 90% humidity atmosphere, the temperature was repeatedly changed between 20 ° C and 50 ° C 20 times, and the state of the sample was examined to determine whether or not the sample was ignited. ○, those with spout were evaluated as x.

(2)孔食電位測定は、試験溶液には液温度が30℃、濃度が3.5%NaClの溶液を用い、電位掃引速度を20mV/minにして孔食電位を測定し、孔食電位が−0.050以上のものを○、−0.051以下から−0.100以上のものを△、−0.101以下のものを×として評価した。
この場合の穿孔試験条件は、ドリル材質がSKH51からなり、ドリル径が5mmを用い、切削油は使用せず、推力を414Nで、回転数を1190rpmとした。
(2) For pitting potential measurement, a solution having a liquid temperature of 30 ° C. and a concentration of 3.5% NaCl was used as a test solution, and the pitting potential was measured at a potential sweep rate of 20 mV / min. Of -0.050 or more was evaluated as O, -0.051 or less to -0.100 or more as Δ, and -0.101 or less as x.
The drilling test conditions in this case were such that the drill material was SKH51, the drill diameter was 5 mm, no cutting oil was used, the thrust was 414 N, and the rotation speed was 1190 rpm.

(3)加工性である表面性状の安定性評価は、EPMA(電子プローブX線マイクロアナライザー)を用いて行った。すると硫化物中に高Cr相すなわち図1の硫化物中の白色部および低Cr相すなわち図1の硫化物中の黒色部が存在することを確認した。そこで各試料から横方向の断面625mm2を被検面とした試料を作製して、被検面を98Nで圧下しながら♯150のペーパーで10分間の湿式研磨を実施した後、光学顕微鏡で400倍にて被検面を観察し、その100視野のうち介在物の脱落が確認された視野数をカウントして示した。この視野数が、30視野以下を○、31から50視野を△、51視野以上を×として評価した。 (3) Evaluation of the stability of the surface property, which is workability, was performed using EPMA (Electron Probe X-ray Microanalyzer). Then, it was confirmed that a high Cr phase, that is, a white portion in the sulfide of FIG. 1 and a low Cr phase, that is, a black portion in the sulfide of FIG. Accordingly, a sample having a cross section of 625 mm 2 in the lateral direction as a test surface was prepared from each sample, wet-polished with # 150 paper for 10 minutes while reducing the test surface with 98 N, and then subjected to 400 using an optical microscope. The surface to be examined was observed at a magnification of 2, and the number of fields in which inclusions were confirmed to drop out of 100 fields was counted and shown. The number of fields of view was evaluated as 0 for 30 fields or less, Δ for 31 to 50 fields, and x for 51 fields or more.

図2は、横軸に式A=Mn/Sの値をとり、縦軸に式B=([Cr]−[Mn])/[S]の値をとり、本発明の範囲を横軸の式Aの値の3以下および縦軸の式Bの値の0.1以上として、表2における発明例のNo.1〜15の鋼を白抜きの菱形で示し、さらに、表2における比較例のNo.1〜4およびNo.8〜9の鋼を黒の菱形で示して、加工性である表面性状の良し悪しの関係および耐食性の良し悪しの関係を示している。なお、比較例のNo.5〜7は、硫化物中の[Mn]、[Cr]および[S]の値は確認できなかった。   FIG. 2 shows the value of the formula A = Mn / S on the horizontal axis and the value of the formula B = ([Cr] − [Mn]) / [S] on the vertical axis. No. of the invention example in Table 2 as 3 or less of the value of Formula A and 0.1 or more of the value of Formula B on the vertical axis. Steels 1 to 15 are indicated by white diamonds, and No. 1-4 and No.1. Steels 8 to 9 are indicated by black rhombuses, which indicate the relationship between the surface properties as workability and the relationship between corrosion resistance. The comparative example No. For 5 to 7, the values of [Mn], [Cr] and [S] in the sulfide could not be confirmed.

Claims (8)

質量%で、C:0.01〜1.50%、Si:0.05〜2.00%、Al:0.001〜0.050%、O:0.002〜0.040%を含有し、さらに、Cr:10.00〜20.00%、Mn:0.05〜3.00%、S:0.05〜1.00%、N:0.005〜0.050%を基本成分として含有し、さらに、Ni:0.01〜20.00%、Mo:0.01〜3.00%、Cu:0.01〜2.00%のいずれか1種または2種以上を含有し、残部Feおよび不可避不純物からなる鋼であり、該鋼は硫化物を含有しており、この硫化物を含有する鋼は、式AをA=Mn/Sとするとき、A≦3.0を満足し、さらに硫化物中のCr、Mn、Sの濃度をそれぞれ[Cr]、[Mn]、[S]で表し、式BをB=([Cr]−[Mn])/[S]とするとき、B≧0.1を満足し、かつ、これらの硫化物から複相介在物を形成していることを特徴とする快削ステンレス鋼。   In mass%, C: 0.01 to 1.50%, Si: 0.05 to 2.00%, Al: 0.001 to 0.050%, O: 0.002 to 0.040% Further, Cr: 10.00 to 20.00%, Mn: 0.05 to 3.00%, S: 0.05 to 1.00%, N: 0.005 to 0.050% as basic components Further, Ni: 0.01 to 20.00%, Mo: 0.01 to 3.00%, Cu: 0.01 to 2.00% any one or two or more types, It is a steel composed of the remaining Fe and inevitable impurities, and the steel contains sulfide, and the steel containing this sulfide satisfies A ≦ 3.0 when formula A is A = Mn / S. Furthermore, the concentrations of Cr, Mn, and S in the sulfide are represented by [Cr], [Mn], and [S], respectively, and the formula B is expressed as B = ([Cr] − [Mn] ) / [S], a free-cutting stainless steel satisfying B ≧ 0.1 and forming a multiphase inclusion from these sulfides. 質量%で、C:0.01〜1.50%、Si:0.05〜2.00%、Al:0.001〜0.050%、O:0.002〜0.040%を含有し、さらに、Cr:10.00〜20.00%、Mn:0.05〜3.00%、S:0.05〜1.00%、N:0.005〜0.050%を基本成分として含有し、さらに、Ni:0.01〜20.00%、Mo:0.01〜3.00%、Cu:0.01〜2.00%のいずれか1種または2種以上を含有し、さらに、Se:0.20%以下、Te:0.30%以下、Bi:0.20%以下のいずれか1種または2種以上を含有し、残部Feおよび不可避不純物からなる鋼であり、該鋼は硫化物を含有しており、この硫化物を含有する鋼は、式AをA=Mn/Sとするとき、A≦3.0を満足し、さらに硫化物中のCr、Mn、Sの濃度をそれぞれ[Cr]、[Mn]、[S]で表し、式BをB=([Cr]−[Mn])/[S]とするとき、B≧0.1を満足し、かつ、これらの硫化物から複相介在物を形成していることを特徴とする快削ステンレス鋼。   In mass%, C: 0.01 to 1.50%, Si: 0.05 to 2.00%, Al: 0.001 to 0.050%, O: 0.002 to 0.040% Further, Cr: 10.00 to 20.00%, Mn: 0.05 to 3.00%, S: 0.05 to 1.00%, N: 0.005 to 0.050% as basic components Further, Ni: 0.01 to 20.00%, Mo: 0.01 to 3.00%, Cu: 0.01 to 2.00% any one or two or more types, Furthermore, Se: 0.20% or less, Te: 0.30% or less, Bi: 0.20% or less of any one or two or more types, the balance Fe and steel unavoidable impurities, The steel contains sulfide, and the steel containing sulfide satisfies A ≦ 3.0 when formula A is A = Mn / S, Further, when the concentrations of Cr, Mn, and S in the sulfide are represented by [Cr], [Mn], and [S], respectively, and formula B is B = ([Cr] − [Mn]) / [S], A free-cutting stainless steel satisfying B ≧ 0.1 and forming a multiphase inclusion from these sulfides. 質量%で、C:0.01〜1.50%、Si:0.05〜2.00%、Al:0.001〜0.050%、O:0.002〜0.040%を含有し、さらに、Cr:10.00〜20.00%、Mn:0.05〜3.00%、S:0.05〜1.00%、N:0.005〜0.050%を基本成分として含有し、さらに、Ni:0.01〜20.00%、Mo:0.01〜3.00%、Cu:0.01〜2.00%のいずれか1種または2種以上を含有し、さらに、Ti:0.001〜1.00%、Zr:0.001〜1.00%、V:0.001〜1.00%、W:0.001〜1.00%、Nb:0.001〜1.00%のいずれか1種または2種以上を含有し、残部Feおよび不可避不純物からなる鋼であり、該鋼は硫化物を含有しており、この硫化物を含有する鋼は、式AをA=Mn/Sとするとき、A≦3.0を満足し、さらに硫化物中のCr、Mn、Sの濃度をそれぞれ[Cr]、[Mn]、[S]で表し、式BをB=([Cr]−[Mn])/[S]とするとき、B≧0.1を満足し、かつ、これらの硫化物から複相介在物を形成していることを特徴とする快削ステンレス鋼。   In mass%, C: 0.01 to 1.50%, Si: 0.05 to 2.00%, Al: 0.001 to 0.050%, O: 0.002 to 0.040% Further, Cr: 10.00 to 20.00%, Mn: 0.05 to 3.00%, S: 0.05 to 1.00%, N: 0.005 to 0.050% as basic components Further, Ni: 0.01 to 20.00%, Mo: 0.01 to 3.00%, Cu: 0.01 to 2.00% any one or two or more types, Further, Ti: 0.001 to 1.00%, Zr: 0.001 to 1.00%, V: 0.001 to 1.00%, W: 0.001 to 1.00%, Nb: 0.00. 001 to 1.00% of any one or two or more types of steel, the balance being Fe and inevitable impurities, the steel containing sulfide. This sulfide-containing steel satisfies A ≦ 3.0 when the formula A is A = Mn / S, and the Cr, Mn, and S concentrations in the sulfide are [Cr], [Mn], [S], and when formula B is B = ([Cr]-[Mn]) / [S], B ≧ 0.1 is satisfied, and these sulfides are combined into a multiphase. Free-cutting stainless steel characterized by forming inclusions. 質量%で、C:0.01〜1.50%、Si:0.05〜2.00%、Al:0.001〜0.050%、O:0.002〜0.040%を含有し、さらに、Cr:10.00〜20.00%、Mn:0.05〜3.00%、S:0.05〜1.00%、N:0.005〜0.050%を基本成分として含有し、さらに、Ni:0.01〜20.00%、Mo:0.01〜3.00%、Cu:0.01〜2.00%のいずれか1種または2種以上を含有し、さらに、Se:0.20%以下、Te:0.30%以下、Bi:0.20%以下のいずれか1種または2種以上を含有し、さらに、Ti:0.001〜1.00%、Zr:0.001〜1.00%、V:0.001〜1.00%、W:0.001〜1.00%、Nb:0.001〜1.00%のいずれか1種または2種以上を含有し、残部Feおよび不可避不純物からなる鋼であり、該鋼は硫化物を含有しており、この硫化物を含有する鋼は、式AをA=Mn/Sとするとき、A≦3.0を満足し、さらに硫化物中のCr、Mn、Sの濃度をそれぞれ[Cr]、[Mn]、[S]で表し、式BをB=([Cr]−[Mn])/[S]とするとき、B≧0.1を満足し、かつ、これらの硫化物から複相介在物を形成していることを特徴とする快削ステンレス鋼。   In mass%, C: 0.01 to 1.50%, Si: 0.05 to 2.00%, Al: 0.001 to 0.050%, O: 0.002 to 0.040% Further, Cr: 10.00 to 20.00%, Mn: 0.05 to 3.00%, S: 0.05 to 1.00%, N: 0.005 to 0.050% as basic components Further, Ni: 0.01 to 20.00%, Mo: 0.01 to 3.00%, Cu: 0.01 to 2.00% any one or two or more types, Furthermore, it contains any one or more of Se: 0.20% or less, Te: 0.30% or less, Bi: 0.20% or less, and Ti: 0.001 to 1.00% , Zr: 0.001 to 1.00%, V: 0.001 to 1.00%, W: 0.001 to 1.00%, Nb: 0.001 to 1.0 It is a steel containing any one or more of 0%, the balance being Fe and inevitable impurities, the steel containing sulfide, and the steel containing this sulfide contains formula A as A = Mn / S, A ≦ 3.0 is satisfied, and the concentrations of Cr, Mn, and S in the sulfide are represented by [Cr], [Mn], and [S], respectively. Free cutting stainless steel characterized by satisfying B ≧ 0.1 and forming a multiphase inclusion from these sulfides when ([Cr] − [Mn]) / [S] steel. 質量%で、C:0.01〜1.50%、Si:0.05〜2.00%、Al:0.001〜0.050%、O:0.002〜0.040%を含有し、さらに、Cr:10.00〜20.00%、Mn:0.05〜3.00%、S:0.05〜1.00%、N:0.005〜0.050%を基本成分として含有し、さらに、Ni:0.01〜20.00%、Mo:0.01〜3.00%、Cu:0.01〜2.00%のいずれか1種または2種以上を含有し、さらに、B:0.02%以下、Ca:0.05%以下、Mg:0.05%以下、REM:0.05%以下のいずれか1種または2種以上を含有し、残部Feおよび不可避不純物からなる鋼であり、該鋼は硫化物を含有しており、この硫化物を含有する鋼は、式AをA=Mn/Sとするとき、A≦3.0を満足し、さらに硫化物中のCr、Mn、Sの濃度をそれぞれ[Cr]、[Mn]、[S]で表し、式BをB=([Cr]−[Mn])/[S]とするとき、B≧0.1を満足し、かつ、これらの硫化物から複相介在物を形成していることを特徴とする快削ステンレス鋼。   In mass%, C: 0.01 to 1.50%, Si: 0.05 to 2.00%, Al: 0.001 to 0.050%, O: 0.002 to 0.040% Further, Cr: 10.00 to 20.00%, Mn: 0.05 to 3.00%, S: 0.05 to 1.00%, N: 0.005 to 0.050% as basic components Further, Ni: 0.01 to 20.00%, Mo: 0.01 to 3.00%, Cu: 0.01 to 2.00% any one or two or more types, Furthermore, it contains any one or more of B: 0.02% or less, Ca: 0.05% or less, Mg: 0.05% or less, REM: 0.05% or less, the balance Fe and inevitable It is a steel made of impurities, and the steel contains sulfide, and the steel containing this sulfide has a formula A = Mn / S , A ≦ 3.0, and the concentrations of Cr, Mn, and S in the sulfide are represented by [Cr], [Mn], and [S], respectively, and the formula B is represented by B = ([Cr] − [Mn ] Free cutting stainless steel characterized by satisfying B ≧ 0.1 and forming a multiphase inclusion from these sulfides. 質量%で、C:0.01〜1.50%、Si:0.05〜2.00%、Al:0.001〜0.050%、O:0.002〜0.040%を含有し、さらに、Cr:10.00〜20.00%、Mn:0.05〜3.00%、S:0.05〜1.00%、N:0.005〜0.050%を基本成分として含有し、さらに、Ni:0.01〜20.00%、Mo:0.01〜3.00%、Cu:0.01〜2.00%のいずれか1種または2種以上を含有し、さらに、Se:0.20%以下、Te:0.30%以下、Bi:0.20%以下のいずれか1種または2種以上を含有し、さらに、B:0.02%以下、Ca:0.05%以下、Mg:0.05%以下、REM:0.05%以下のいずれか1種または2種以上を含有し、残部Feおよび不可避不純物からなる鋼であり、該鋼は硫化物を含有しており、この硫化物を含有する鋼は、式AをA=Mn/Sとするとき、A≦3.0を満足し、さらに硫化物中のCr、Mn、Sの濃度をそれぞれ[Cr]、[Mn]、[S]で表し、式BをB=([Cr]−[Mn])/[S]とするとき、B≧0.1を満足し、かつ、これらの硫化物から複相介在物を形成していることを特徴とする快削ステンレス鋼。   In mass%, C: 0.01 to 1.50%, Si: 0.05 to 2.00%, Al: 0.001 to 0.050%, O: 0.002 to 0.040% Further, Cr: 10.00 to 20.00%, Mn: 0.05 to 3.00%, S: 0.05 to 1.00%, N: 0.005 to 0.050% as basic components Further, Ni: 0.01 to 20.00%, Mo: 0.01 to 3.00%, Cu: 0.01 to 2.00% any one or two or more types, Furthermore, it contains any one or more of Se: 0.20% or less, Te: 0.30% or less, Bi: 0.20% or less, B: 0.02% or less, Ca: 0.05% or less, Mg: 0.05% or less, REM: 0.05% or less A steel composed of unavoidable impurities, the steel contains sulfide, and the steel containing sulfide satisfies A ≦ 3.0 when formula A is A = Mn / S, Further, when the concentrations of Cr, Mn, and S in the sulfide are represented by [Cr], [Mn], and [S], respectively, and formula B is B = ([Cr] − [Mn]) / [S], A free-cutting stainless steel satisfying B ≧ 0.1 and forming a multiphase inclusion from these sulfides. 質量%で、C:0.01〜1.50%、Si:0.05〜2.00%、Al:0.001〜0.050%、O:0.002〜0.040%を含有し、さらに、Cr:10.00〜20.00%、Mn:0.05〜3.00%、S:0.05〜1.00%、N:0.005〜0.050%を基本成分として含有し、さらに、Ni:0.01〜20.00%、Mo:0.01〜3.00%、Cu:0.01〜2.00%のいずれか1種または2種以上を含有し、さらに、Ti:0.001〜1.00%、Zr:0.001〜1.00%、V:0.001〜1.00%、W:0.001〜1.00%、Nb:0.001〜1.00%のいずれか1種または2種以上を含有し、さらに、B:0.02%以下、Ca:0.05%以下、Mg:0.05%以下、REM:0.05%以下のいずれか1種または2種以上を含有し、残部Feおよび不可避不純物からなる鋼であり、該鋼は硫化物を含有しており、この硫化物を含有する鋼は、式AをA=Mn/Sとするとき、A≦3.0を満足し、さらに硫化物中のCr、Mn、Sの濃度をそれぞれ[Cr]、[Mn]、[S]で表し、式BをB=([Cr]−[Mn])/[S]とするとき、B≧0.1を満足し、かつ、これらの硫化物から複相介在物を形成していることを特徴とする快削ステンレス鋼。   In mass%, C: 0.01 to 1.50%, Si: 0.05 to 2.00%, Al: 0.001 to 0.050%, O: 0.002 to 0.040% Further, Cr: 10.00 to 20.00%, Mn: 0.05 to 3.00%, S: 0.05 to 1.00%, N: 0.005 to 0.050% as basic components Further, Ni: 0.01 to 20.00%, Mo: 0.01 to 3.00%, Cu: 0.01 to 2.00% any one or two or more types, Further, Ti: 0.001 to 1.00%, Zr: 0.001 to 1.00%, V: 0.001 to 1.00%, W: 0.001 to 1.00%, Nb: 0.00. Any one or more of 001-1.00%, B: 0.02% or less, Ca: 0.05% or less, Mg: 0.05% or less Below, REM: 0.05% or less of any one or two or more types of steel, the balance being Fe and inevitable impurities, the steel contains sulfide, and contains this sulfide When the formula A is A = Mn / S, the steel satisfies A ≦ 3.0, and the concentrations of Cr, Mn, and S in the sulfide are [Cr], [Mn], and [S], respectively. When formula B is B = ([Cr] − [Mn]) / [S], B ≧ 0.1 is satisfied, and a multiphase inclusion is formed from these sulfides. Free-cutting stainless steel characterized by 質量%で、C:0.01〜1.50%、Si:0.05〜2.00%、Al:0.001〜0.050%、O:0.002〜0.040%を含有し、さらに、Cr:10.00〜20.00%、Mn:0.05〜3.00%、S:0.05〜1.00%、N:0.005〜0.050%を基本成分として含有し、さらに、Ni:0.01〜20.00%、Mo:0.01〜3.00%、Cu:0.01〜2.00%のいずれか1種または2種以上を含有し、さらに、さらに、Se:0.20%以下、Te:0.30%以下、Bi:0.20%以下のいずれか1種または2種以上を含有し、Ti:0.001〜1.00%、Zr:0.001〜1.00%、V:0.001〜1.00%、W:0.001〜1.00%、Nb:0.001〜1.00%のいずれか1種または2種以上を含有し、さらに、B:0.02%以下、Ca:0.05%以下、Mg:0.05%以下、REM:0.05%以下のいずれか1種または2種以上を含有し、残部Feおよび不可避不純物からなる鋼であり、該鋼は硫化物を含有しており、この硫化物を含有する鋼は、式AをA=Mn/Sとするとき、A≦3.0を満足し、さらに硫化物中のCr、Mn、Sの濃度をそれぞれ[Cr]、[Mn]、[S]で表し、式BをB=([Cr]−[Mn])/[S]とするとき、B≧0.1を満足し、かつ、これらの硫化物から複相介在物を形成していることを特徴とする快削ステンレス鋼。   In mass%, C: 0.01 to 1.50%, Si: 0.05 to 2.00%, Al: 0.001 to 0.050%, O: 0.002 to 0.040% Further, Cr: 10.00 to 20.00%, Mn: 0.05 to 3.00%, S: 0.05 to 1.00%, N: 0.005 to 0.050% as basic components Further, Ni: 0.01 to 20.00%, Mo: 0.01 to 3.00%, Cu: 0.01 to 2.00% any one or two or more types, Furthermore, it contains any one or more of Se: 0.20% or less, Te: 0.30% or less, Bi: 0.20% or less, Ti: 0.001 to 1.00% , Zr: 0.001 to 1.00%, V: 0.001 to 1.00%, W: 0.001 to 1.00%, Nb: 0.001 to 1.0 Any one of 0%, B: 0.02% or less, Ca: 0.05% or less, Mg: 0.05% or less, REM: 0.05% or less Or a steel containing the balance Fe and inevitable impurities, and the steel contains sulfide, and the steel containing sulfide has the formula A = Mn / S When A ≦ 3.0 is satisfied, the concentrations of Cr, Mn, and S in the sulfide are represented by [Cr], [Mn], and [S], respectively, and the formula B is represented by B = ([Cr] -Free cutting stainless steel characterized by satisfying B≥0.1 and forming a multiphase inclusion from these sulfides when [Mn] / [S].
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