JP6814655B2 - Ferritic free-cutting stainless steel wire - Google Patents
Ferritic free-cutting stainless steel wire Download PDFInfo
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- JP6814655B2 JP6814655B2 JP2017027702A JP2017027702A JP6814655B2 JP 6814655 B2 JP6814655 B2 JP 6814655B2 JP 2017027702 A JP2017027702 A JP 2017027702A JP 2017027702 A JP2017027702 A JP 2017027702A JP 6814655 B2 JP6814655 B2 JP 6814655B2
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- 238000005520 cutting process Methods 0.000 title claims description 48
- 229910001220 stainless steel Inorganic materials 0.000 title claims description 15
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 46
- 239000000203 mixture Substances 0.000 claims description 15
- 238000005096 rolling process Methods 0.000 claims description 13
- 229910000859 α-Fe Inorganic materials 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 7
- 229910052748 manganese Inorganic materials 0.000 claims description 6
- 229910052804 chromium Inorganic materials 0.000 claims description 5
- 239000012535 impurity Substances 0.000 claims description 4
- 230000000694 effects Effects 0.000 description 23
- 229910000831 Steel Inorganic materials 0.000 description 15
- 239000010959 steel Substances 0.000 description 15
- 239000000463 material Substances 0.000 description 13
- 241000282341 Mustela putorius furo Species 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 8
- 229910052761 rare earth metal Inorganic materials 0.000 description 8
- 230000003746 surface roughness Effects 0.000 description 8
- 238000012360 testing method Methods 0.000 description 7
- 238000000137 annealing Methods 0.000 description 6
- 238000011156 evaluation Methods 0.000 description 5
- 229910052745 lead Inorganic materials 0.000 description 5
- 229920006395 saturated elastomer Polymers 0.000 description 5
- 238000005491 wire drawing Methods 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 238000005098 hot rolling Methods 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 230000006866 deterioration Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- 238000009628 steelmaking Methods 0.000 description 3
- 230000002411 adverse Effects 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 150000003568 thioethers Chemical class 0.000 description 2
- 229910000915 Free machining steel Inorganic materials 0.000 description 1
- 229910052765 Lutetium Inorganic materials 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000010730 cutting oil Substances 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 238000001192 hot extrusion Methods 0.000 description 1
- 238000003703 image analysis method Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052747 lanthanoid Inorganic materials 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000002480 mineral oil Substances 0.000 description 1
- 235000010446 mineral oil Nutrition 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 125000000101 thioether group Chemical group 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Description
本発明は、フェライト系快削ステンレス線材に関する。 The present invention relates to a ferrite-based free-cutting stainless steel wire rod.
ＯＡ機器、電子機器等の鋼部品のうち、切削で製造される部品には、切削時の切屑処理性に加え、切削加工面に高い寸法精度、および良好な表面性状が求められる。これらの要求に応える鋼素材として、Ｓを０．１５％以上添加したＳＵＳ４３０Ｆ、または切削性を更に向上させるためＰｂ、Ｓｅ、Ｔｅを単独もしくは複合添加したフェライト系快削ステンレス鋼がある（特許文献１）。 Among steel parts such as OA equipment and electronic equipment, parts manufactured by cutting are required to have high dimensional accuracy and good surface texture on the machined surface in addition to chip controllability at the time of cutting. As steel materials that meet these demands, there are SUS430F to which 0.15% or more of S is added, or ferritic free-cutting stainless steel to which Pb, Se, and Te are added alone or in combination to further improve machinability (Patent Documents). 1).
一方、Ｐｂ添加廃止の市場要求に対して、ＢｉまたはＳｎ添加、ならびにＣｕを主体とする第２相を分散させたフェライト系快削ステンレス鋼が提案されている（特許文献２、３、４）。 On the other hand, in response to the market demand for abolishing the addition of Pb, ferritic free-cutting stainless steel in which Bi or Sn is added and the second phase mainly composed of Cu is dispersed has been proposed (Patent Documents 2, 3, and 4). ..
しかしながら、特許文献１〜４の発明では、熱間加工性などの製造性、および切削後の表面性状において満足なものが得られていない。具体的には、上記部品は、切削速度≧２０ｍ／ｍｉｎ、切込み≧０．０５ｍｍ、送り≧０．００５ｍｍ／ｒｅｖ、の工業的な切削条件において、表面粗さＲａ≦０．５μｍの精度と優れた耐工具摩耗性が要求されるが、その際の表面性状については、特許文献１〜４のいずれにおいても開示されていない。 However, the inventions of Patent Documents 1 to 4 are not satisfactory in terms of manufacturability such as hot workability and surface texture after cutting. Specifically, the above-mentioned parts have excellent surface roughness Ra ≦ 0.5 μm accuracy under industrial cutting conditions of cutting speed ≧ 20 m / min, depth of cut ≧ 0.05 mm, and feed ≧ 0.005 mm / rev. Although tool wear resistance is required, the surface texture at that time is not disclosed in any of Patent Documents 1 to 4.
本発明の目的は、上記課題を解決し、熱間加工性が良好で、かつ通常の精密部品の切削加工条件下において、表面粗さ（Ｒａ）：０．５μｍ以下の優れた表面精度を得ることが可能な、Ｐｂ、およびＳｅを含まないフェライト系快削ステンレス線材を提供することにある。 An object of the present invention is to solve the above problems and obtain excellent surface accuracy of surface roughness (Ra): 0.5 μm or less under normal hot workability and cutting conditions of ordinary precision parts. It is an object of the present invention to provide a ferritic free-cutting stainless steel wire rod containing no Pb and Se.
本発明者らは、上記課題を解決するために種々検討した結果、Ｐｂ、およびＳｅを含まないＳ含有フェライト系ステンレス快削鋼において、微量のＴｅを含有させることで硫化物の形態を制御し、優れた表面精度を確保できることを知見した。詳細な知見は以下の（ａ）〜（ｄ）の通りである。 As a result of various studies to solve the above problems, the present inventors controlled the morphology of sulfides by containing a trace amount of Te in the S-containing ferritic stainless free-cutting steel containing no Pb and Se. It was found that excellent surface accuracy can be ensured. Detailed findings are as follows (a) to (d).
（ａ）表面粗さを改善するためには、切削中に工具の刃先に形成される構成刃先を小さくすることが有効である。これは、構成刃先が発生すると、切削の際、工具の切刃の輪郭と異なった凹凸が生じるためである。本発明では、線材中の硫化物のアスペクト比を小さくすることで構成刃先の形成を抑制する。 (A) In order to improve the surface roughness, it is effective to reduce the built-up edge formed on the edge of the tool during cutting. This is because when the built-up edge is generated, unevenness different from the contour of the cutting edge of the tool is generated during cutting. In the present invention, the formation of the built-up edge is suppressed by reducing the aspect ratio of the sulfide in the wire rod.
（ｂ）Ｔｅを含有させると、その硫化物の周囲に低融点のＭｎのＴｅ化合物（ＭｎＴｅ）が形成され、その潤滑作用によって熱間圧延後の加工（例えば、温間伸線加工や冷間伸線加工など）においても展伸しにくくなる。このため、硫化物のアスペクト比が小さくなる。しかし、ＭｎＴｅは熱間延性を低下させるので、部品の加工性が確保できなくなる。 (B) When Te is contained, a low melting point Mn Te compound (MnTe) is formed around the sulfide, and due to its lubricating action, processing after hot rolling (for example, warm wire drawing or cold) It becomes difficult to stretch even in wire drawing (such as wire drawing). Therefore, the aspect ratio of the sulfide becomes small. However, since MnTe lowers the hot ductility, the workability of the parts cannot be ensured.
（ｃ）一方で、ＭｎＴｅが形成しない程度の微量のＴｅを含有させても、そのＴｅが硫化物中に固溶することで、硫化物の変形抵抗が高まり、その結果、アスペクト比が小さくなる。 (C) On the other hand, even if a small amount of Te is contained so that MnTe is not formed, the Te is dissolved in the sulfide, so that the deformation resistance of the sulfide is increased, and as a result, the aspect ratio is reduced. ..
（ｄ）線材中のＭｎ、Ｃｒの含有量を調整することで、線材中に形成する硫化物中のＭｎ、Ｃｒの組成比も変化し、変形抵抗の向上に寄与する。 (D) By adjusting the contents of Mn and Cr in the wire, the composition ratio of Mn and Cr in the sulfide formed in the wire also changes, which contributes to the improvement of deformation resistance.
本発明は、上記知見に基づいてなされたものであり、その要旨とするところは以下の通りである。 The present invention has been made based on the above findings, and the gist thereof is as follows.
（１）質量％で、
Ｃ：０．００５〜０．０５０％、
Ｓｉ：０．１０〜１．０％、
Ｍｎ：０．１０〜０．５０％、
Ｐ：０．００５〜０．０５％、
Ｓ：０．２５〜０．６０％、
Ｃｒ：１０．５〜１９．５％、
Ｔｅ：０．００２〜０．０２４％、
Ａｌ：０．００１〜０．０１０％、
Ｎ：０．００５〜０．０５０％、
Ｏ：０．００１〜０．０２０％、
Ｃａ：０〜０．０１０％、
Ｂ：０〜０．０２％、
Ｎｉ：０〜３．０％、
Ｍｏ：０〜３．０％、
Ｎｂ：０〜１．００％、
Ｔｉ：０〜１．００％、
Ｖ：０〜０．５０％、
Ｔａ：０〜０．５％、
Ｗ：０〜０．５％、
Ｃｏ：０〜１．００％、
Ｚｒ：０〜０．０２０％、
Ｃｕ：０〜３．０％、
Ｓｎ：０〜０．５％、
Ｍｇ：０〜０．０５０％、
ＲＥＭ：０〜０．２００％、
残部がＦｅおよび不可避的不純物からなり、
Ｔｅ／Ｓが０．０４０以下である、フェライト系快削ステンレス線材。
(1) By mass%
C: 0.005 to 0.050%,
Si: 0.10 to 1.0%,
Mn: 0.10 to 0.50%,
P: 0.005-0.05%,
S: 0.25 to 0.60%,
Cr: 10.5 to 19.5%,
Te: 0.002-0.024%,
Al: 0.001 to 0.010%,
N: 0.005 to 0.050%,
O: 0.001 to 0.020%,
Ca: 0-0.010%,
B: 0-0.02%,
Ni: 0-3.0%,
Mo: 0-3.0%,
Nb: 0-1.00%,
Ti: 0-1.00%,
V: 0 to 0.50%,
Ta: 0-0.5%,
W: 0-0.5%,
Co: 0-1.00%,
Zr: 0-0.020%,
Cu: 0-3.0%,
Sn: 0-0.5%,
Mg: 0 to 0.050%,
REM: 0-0.200%,
The rest consists of Fe and unavoidable impurities,
A ferrite-based free-cutting stainless steel wire with a Te / S of 0.040 or less.
（２）前記化学組成を有する、フェライト系快削ステンレス線材であって、
硫化物中のＭｎとＣｒの組成比であるＭｎ／Ｃｒが０．１〜０．５、硫化物の外接する圧延方向に平行な径と圧延方向に垂直な径との比をアスペクト比とするとき、硫化物のアスペクト比が８．０以下である、（１）に記載のフェライト系快削ステンレス線材。
(2) A ferrite-based free-cutting stainless steel wire having the above chemical composition.
The aspect ratio is the ratio of Mn / Cr, which is the composition ratio of Mn and Cr in the sulfide, to 0.1 to 0.5, and the diameter parallel to the rolling direction in which the sulfide is inscribed and the diameter perpendicular to the rolling direction. The ferrite-based free-cutting stainless steel wire according to (1), wherein the aspect ratio of the sulfide is 8.0 or less.
（３）質量％で、さらに、
Ｃａ：０．０００５〜０．０１０％、
Ｂ：０．０００１〜０．０２％、
Ｎｉ：０．１〜３．０％、
Ｍｏ：０．１〜３．０％、
Ｎｂ：０．０５〜１．００％、
Ｔｉ：０．０５〜１．００％、
Ｖ：０．０５〜０．５０％、
Ｔａ：０．１〜０．５％、
Ｗ：０．１〜０．５％、
Ｃｏ：０．０５〜１．００％、
Ｚｒ：０．００１〜０．０２０％、
Ｃｕ：０．１〜３．０％、
Ｓｎ：０．０３〜０．５％、
Ｍｇ：０．０００５〜０．０５０％、
ＲＥＭ：０．０００５〜０．２００％、
から選択される１種以上を含有する、（１）または（２）に記載のフェライト系快削ステンレス線材。
(3) By mass%,
Ca: 0.0005 to 0.010%,
B: 0.0001 to 0.02%,
Ni: 0.1 to 3.0%,
Mo: 0.1 to 3.0%,
Nb: 0.05 to 1.00%,
Ti: 0.05 to 1.00%,
V: 0.05 to 0.50%,
Ta: 0.1-0.5%,
W: 0.1 to 0.5%,
Co: 0.05 to 1.00%,
Zr: 0.001 to 0.020%,
Cu: 0.1 to 3.0%,
Sn: 0.03 to 0.5%,
Mg: 0.0005 to 0.050%,
REM: 0.0005 to 0.200%,
The ferrite-based free-cutting stainless steel wire according to (1) or (2), which contains one or more selected from.
本発明では、環境に悪影響を与えるＰｂ、およびＳｅを含有することなく、熱間加工性が良好で、かつ通常の精密部品の切削加工条件において、切削加工後の部品に、表面粗さ（Ｒａ）：０．５μｍ以下の優れた表面精度を有する、フェライト系快削ステンレス線材を得ることができる。 In the present invention, the surface roughness (Ra) of the part after cutting is obtained under the cutting conditions of a normal precision part, which has good hot workability without containing Pb and Se, which adversely affect the environment. ): A ferritic free-cutting stainless steel wire having an excellent surface accuracy of 0.5 μm or less can be obtained.
以下に、本発明の各要件について説明する。 Each requirement of the present invention will be described below.
１．化学組成
各元素の限定理由は下記の通りである。なお、以下の説明において化学組成についての「％」は「質量％」を意味する。
1. 1. Chemical composition The reasons for limiting each element are as follows. In the following description, "%" for the chemical composition means "mass%".
Ｃ：０．００５〜０．０５０％
Ｃは、炭化物を生成し、強度を得るために必要である。このため、Ｃ含有量は、０．００５％以上とし、Ｃ含有量は、０．０１０％以上であるのが好ましい。一方、過剰な炭化物は、切削加工時に構成刃先の生成を促進して切削面精度を劣化させるため、Ｃ含有量は、０．０５０％以下とし、Ｃ含有量は０．０３０％以下であるのが好ましい。
C: 0.005 to 0.050%
C is required to produce carbides and gain strength. Therefore, the C content is preferably 0.005% or more, and the C content is preferably 0.010% or more. On the other hand, the excess carbide promotes the formation of landmarks during cutting and deteriorates the cutting surface accuracy. Therefore, the C content is 0.050% or less and the C content is 0.030% or less. Is preferable.
Ｓｉ：０．１０〜１．０％
Ｓｉは、脱酸のために使用される。このため、Ｓｉ含有量は０．１０％以上とし、Ｓｉ含有量は、０．３０％以上であるのが好ましい。一方で、１．０％超含有させると、棒線熱間圧延時のスケール生成を抑制し、熱間圧延疵の生成を助長する。そのため、Ｓｉ含有量は、１．０％以下とする。
Si: 0.10 to 1.0%
Si is used for deoxidation. Therefore, the Si content is preferably 0.10% or more, and the Si content is preferably 0.30% or more. On the other hand, when the content exceeds 1.0%, scale formation during hot rolling of rods is suppressed, and formation of hot rolling flaws is promoted. Therefore, the Si content is set to 1.0% or less.
Ｍｎ：０．１０〜０．５０％
Ｍｎは、Ｃｒと共に硫化物を生成し、被削性、特に切削面精度を向上させる元素である。このため、Ｍｎ含有量は、０．１０％以上とする。一方、Ｍｎ含有量が０．５０％を超えると、硫化物におけるＭｎ／Ｃｒが高くなり、硫化物が展伸してアスペクト比が大きくなる。そのため、Ｍｎ含有量は、０．５０％以下とし、Ｍｎ含有量は、０．４０％以下であるのが好ましい。
Mn: 0.10 to 0.50%
Mn is an element that produces sulfide together with Cr and improves machinability, especially cutting surface accuracy. Therefore, the Mn content is set to 0.10% or more. On the other hand, when the Mn content exceeds 0.50%, Mn / Cr in the sulfide becomes high, the sulfide spreads, and the aspect ratio becomes large. Therefore, the Mn content is preferably 0.50% or less, and the Mn content is preferably 0.40% or less.
Ｐ：０．００５〜０．０５％
Ｐは、粒界偏析して切削加工時の材料延性を低下させて、表面精度を向上させる。このため、Ｐ含有量は、０．００５％以上とし、Ｐ含有量は、０．０１％以上であるのが好ましい。しかしながら、０．０５％を超えて含有させると、その効果は飽和するばかりか、製造性が著しく劣化する。そのため、Ｐ含有量は、０．０５％以下とする。
P: 0.005-0.05%
P causes grain boundary segregation to reduce material ductility during cutting and improve surface accuracy. Therefore, the P content is preferably 0.005% or more, and the P content is preferably 0.01% or more. However, if it is contained in excess of 0.05%, not only the effect is saturated, but also the manufacturability is significantly deteriorated. Therefore, the P content is set to 0.05% or less.
Ｓ：０．２５〜０．６０％
Ｓは、硫化物を形成し、硫化物には切削加工時に応力が集中する。そして、切りくず生成時におけるせん断変形域で硫化物を起点にき裂が発生し、構成刃先の成長が抑制される。このため、線材の切削面精度が向上する。この効果を得るために、Ｓ含有量は、０．２５％以上とし、Ｓ含有量は、０．２８％以上であるのが好ましい。一方で、０．６０％を超えて含有させると、熱間加工性が著しく劣化する。そのため、Ｓ含有量は、０．６０％以下とし、Ｓ含有量は、０．５５％以下であるのが好ましい。
S: 0.25 to 0.60%
S forms sulfide, and stress is concentrated on the sulfide during cutting. Then, cracks are generated starting from sulfide in the shear deformation region at the time of chip formation, and the growth of the built edge is suppressed. Therefore, the accuracy of the cutting surface of the wire rod is improved. In order to obtain this effect, the S content is preferably 0.25% or more, and the S content is preferably 0.28% or more. On the other hand, if it is contained in excess of 0.60%, the hot workability is significantly deteriorated. Therefore, the S content is preferably 0.60% or less, and the S content is preferably 0.55% or less.
Ｃｒ：１０．５〜１９．５％
Ｃｒは、Ｍｎと共に硫化物を形成し、特に硫化物中のＭｎとＣｒの組成比（Ｍｎ／Ｃｒ）を適正化することで、硫化物のアスペクト比を小さくすることができる。アスペクト比を小さくし、切削面精度を向上させるためには、Ｃｒ含有量は、１０．５％以上とし、Ｃｒ含有量は、１５．０％以上であるのが好ましく、１６．０％以上であるのがより好ましい。しかしながら、多量に含有させると、硫化物中のＭｎ／Ｃｒが小さくなりすぎて、却って硫化物が展伸しやすくなり、アスペクト比が大きくなる。そのため、Ｃｒ含有量は１９．５％以下とし、Ｃｒ含有量は１８．５％以下であるのが好ましい。
Cr: 10.5 to 19.5%
Cr forms a sulfide together with Mn, and the aspect ratio of the sulfide can be reduced by optimizing the composition ratio (Mn / Cr) of Mn and Cr in the sulfide. In order to reduce the aspect ratio and improve the cutting surface accuracy, the Cr content is preferably 10.5% or more, and the Cr content is preferably 15.0% or more, preferably 16.0% or more. It is more preferable to have it. However, if it is contained in a large amount, Mn / Cr in the sulfide becomes too small, the sulfide tends to spread, and the aspect ratio becomes large. Therefore, the Cr content is preferably 19.5% or less, and the Cr content is preferably 18.5% or less.
Ｔｅ：０．００２〜０．０２４％
Ｔｅは、本発明において被削性、特に切削面精度を向上させるために重要な元素である。Ｔｅは、硫化物中への固溶により変形を抑制して、アスペクト比を小さくする。その結果、構成刃先の成長を抑制し、切削面精度を向上させる。このため、Ｔｅ含有量は、０．００２％以上とし、Ｔｅ含有量は、０．００３％以上であるのが好ましい。一方で、Ｔｅを、０．０２４％を超えて含有させると、その効果は飽和するばかりか、硫化物周囲のＭｎＴｅの形成により、却って製造性が著しく劣化する。そのため、Ｔｅ含有量は０．０２４％以下とし、Ｔｅ含有量は、０．０１５％以下であるのが好ましく、０．０１０％以下であるのがより好ましい。
Te: 0.002-0.024%
Te is an important element in the present invention for improving machinability, particularly cutting surface accuracy. Te suppresses deformation by solid solution in sulfide and reduces the aspect ratio. As a result, the growth of the built-up edge is suppressed and the cutting surface accuracy is improved. Therefore, the Te content is preferably 0.002% or more, and the Te content is preferably 0.003% or more. On the other hand, when Te is contained in an amount of more than 0.024%, not only the effect is saturated, but also the manufacturability is significantly deteriorated due to the formation of MnTe around the sulfide. Therefore, the Te content is preferably 0.024% or less, and the Te content is preferably 0.015% or less, more preferably 0.010% or less.
Ａｌ：０．００１〜０．０１０％
Ａｌは、脱酸元素として使用する。そのため、Ａｌ含有量は、０．００１％以上とする。一方で、０．０１０％を超えて含有させると、硬質なＡｌ系の酸化物を形成し、被削性を劣化させ、工具寿命を低下させる。そのため、Ａｌ含有量は、０．０１０％以下とし、Ａｌ含有量は、０．００８％以下であるのが好ましい。
Al: 0.001 to 0.010%
Al is used as a deoxidizing element. Therefore, the Al content is set to 0.001% or more. On the other hand, if it is contained in excess of 0.010%, a hard Al-based oxide is formed, the machinability is deteriorated, and the tool life is shortened. Therefore, the Al content is preferably 0.010% or less, and the Al content is preferably 0.008% or less.
Ｎ：０．００５〜０．０５０％
Ｎは、マトリックスのフェライト強度を高める。このため、Ｎ含有量は、０．００５％以上とし、Ｎ含有量は、０．００８％以上であるのが好ましい。しかし、Ｎ含有量を、０．０５０％を超えて含有させると、過度の強度上昇により工具寿命を劣化させる。そのため、Ｎ含有量は、０．０５０％以下とし、Ｎ含有量は０．０３０％以下であるのが好ましい。
N: 0.005 to 0.050%
N increases the ferrite strength of the matrix. Therefore, the N content is preferably 0.005% or more, and the N content is preferably 0.008% or more. However, if the N content exceeds 0.050%, the tool life is deteriorated due to an excessive increase in strength. Therefore, the N content is preferably 0.050% or less, and the N content is preferably 0.030% or less.
さらに本発明は、以下に記載する選択元素を含有させてもよい。 Furthermore, the present invention may contain the selective elements described below.
Ｏ：０．００１〜０．０２０％
Ｏは、凝固時の脱酸生成物を粗大化させることで被削性を向上させる。このため、Ｏ含有量は０．００１％以上とし、Ｏ含有量は、０．００３％以上であるのが好ましく、０．００５％以上であるのがより好ましい。しかし、０．０２０％を超えて含有させると、硬質な介在物が増加し、被削性を劣化させる。そのため、Ｏ含有量は、０．０２０％以下とする。
O: 0.001 to 0.020%
O improves machinability by coarsening the deoxidizing product during solidification. Therefore, the O content is preferably 0.001% or more, and the O content is preferably 0.003% or more, more preferably 0.005% or more. However, if it is contained in excess of 0.020%, hard inclusions increase and the machinability deteriorates. Therefore, the O content is set to 0.020% or less.
Ｃａ：０〜０．０１０％
Ｃａは、酸化物系介在物を軟質化し、被削性を向上させ、工具寿命を改善する効果があるため、含有させてもよい。しかしながら、０．０１０％を超えて含有させると、効果が飽和し、熱間加工性が低下する。このため、Ｃａ含有量は、０．０１０％以下とし、Ｃａ含有量は、０．００８％以下であるのが好ましい。一方、上記効果を得るためには、Ｃａ含有量は、０．０００５％以上であるのが好ましく、０．００１０％以上がより好ましい。またＣａ含有量が、０．００３％以上であるのが最も好ましい。
Ca: 0 to 0.010%
Ca may be contained because it has the effect of softening oxide-based inclusions, improving machinability, and improving tool life. However, if it is contained in excess of 0.010%, the effect is saturated and the hot workability is lowered. Therefore, the Ca content is preferably 0.010% or less, and the Ca content is preferably 0.008% or less. On the other hand, in order to obtain the above effect, the Ca content is preferably 0.0005% or more, more preferably 0.0010% or more. The Ca content is most preferably 0.003% or more.
Ｂ：０〜０．０２％
Ｂは、熱間加工性を改善するために使用する元素であり、安定した効果を得るために、含有させてもよい。しかしながら、過剰に含有させると、Ｂの化合物が析出し、熱間加工性を劣化させるので、Ｂ含有量は０．０２％以下とし、Ｂ含有量は、０．０１５％以下であるのが好ましい。一方で、上記効果を得るためには、Ｂ含有量は０．０００１％以上であるのが好ましく、Ｂ含有量は０．０００２％以上であるのがより好ましい。
B: 0-0.02%
B is an element used to improve hot workability, and may be contained in order to obtain a stable effect. However, if it is excessively contained, the compound of B is precipitated and the hot workability is deteriorated. Therefore, the B content is preferably 0.02% or less, and the B content is preferably 0.015% or less. .. On the other hand, in order to obtain the above effect, the B content is preferably 0.0001% or more, and the B content is more preferably 0.0002% or more.
Ｎｉ：０〜３．０％
Ｎｉは、固溶強化により材料の硬さを高めて構成刃先の生成を防止し、切削加工時の表面精度を向上させるため、含有させてもよい。しかしながら、３．０％を超えて含有させてもその効果は飽和し、また、線材が過度に硬質化して、工具寿命劣化を引き起こす。そのため、Ｎｉ含有量は、３．０％以下とし、Ｎｉ含有量は、１．５％以下であるのが好ましい。一方で、上記効果を得るためには、Ｎｉ含有量は、０．１％以上であるのが好ましく、Ｎｉ含有量は、０．１５％以上であるのがより好ましい。
Ni: 0-3.0%
Ni may be contained in order to increase the hardness of the material by strengthening the solid solution, prevent the formation of built-up cutting edges, and improve the surface accuracy during cutting. However, even if the content exceeds 3.0%, the effect is saturated, and the wire rod becomes excessively hard, causing deterioration of the tool life. Therefore, the Ni content is preferably 3.0% or less, and the Ni content is preferably 1.5% or less. On the other hand, in order to obtain the above effect, the Ni content is preferably 0.1% or more, and the Ni content is more preferably 0.15% or more.
Ｍｏ：０〜３．０％
Ｍｏは、耐食性を向上させる元素であり、含有させてもよい。しかしながら、Ｍｏを多量に含有させると、靭性を低下させる。このため、Ｍｏ含有量は、３．０％以下とし、Ｍｏ含有量は２．０％以下であるのが好ましい。一方で、上記効果を得るためには、Ｍｏ含有量は０．１％以上であるのが好ましい。
Mo: 0-3.0%
Mo is an element that improves corrosion resistance and may be contained. However, when a large amount of Mo is contained, the toughness is lowered. Therefore, the Mo content is preferably 3.0% or less, and the Mo content is preferably 2.0% or less. On the other hand, in order to obtain the above effect, the Mo content is preferably 0.1% or more.
Ｎｂ：０〜１．００％
Ｔｉ：０〜１．００％
Ｖ：０〜０．５０％
Ｔａ：０〜０．５％
Ｗ：０〜０．５％
Ｎｂ、Ｔｉ、Ｖ、Ｔａ、Ｗは炭窒化物を形成し、耐食性を改善する効果があるため、含有させてもよい。しかしながら、多量の含有は、被削性が劣化することから、Ｎｂ含有量は、１．００％以下とし、Ｔｉ含有量は、１．００％以下とする。また、Ｖ含有量は、０．５０％以下とし、Ｔａ含有量は、０．５％以下とし、Ｗ含有量は、０．５％以下とする。一方で、上記効果を得るためには、Ｎｂ含有量は、０．０５％以上であるのが好ましく、Ｔｉ含有量は、０．０５％以上であるのが好ましく、Ｖ含有量は、０．０５％以上であるのが好ましい。また、Ｔａ含有量は、０．１％以上であるのが好ましく、Ｗ含有量は、０．１％以上であるのが好ましい。
Nb: 0 to 1.00%
Ti: 0-1.00%
V: 0 to 0.50%
Ta: 0-0.5%
W: 0-0.5%
Nb, Ti, V, Ta, and W may be contained because they have the effect of forming a carbonitride and improving the corrosion resistance. However, since the machinability deteriorates when a large amount is contained, the Nb content is set to 1.00% or less, and the Ti content is set to 1.00% or less. The V content is 0.50% or less, the Ta content is 0.5% or less, and the W content is 0.5% or less. On the other hand, in order to obtain the above effect, the Nb content is preferably 0.05% or more, the Ti content is preferably 0.05% or more, and the V content is 0. It is preferably 05% or more. The Ta content is preferably 0.1% or more, and the W content is preferably 0.1% or more.
Ｃｏ：０〜１．００％
Ｃｏは、マトリックスの靭性を高めるため、含有させてもよい。しかしながら、過剰に含有させると、マルテンサイト組織が析出し、被削性を劣化させるため、Ｃｏ含有量は１．００％以下とし、Ｃｏ含有量は、０．６０％以下であるのが好ましい。一方で、上記効果を得るためには、Ｃｏ含有量は、０．０５％以上であるのが好ましい。
Co: 0-1.00%
Co may be contained in order to increase the toughness of the matrix. However, if it is excessively contained, the martensite structure is precipitated and the machinability is deteriorated. Therefore, the Co content is preferably 1.00% or less, and the Co content is preferably 0.60% or less. On the other hand, in order to obtain the above effect, the Co content is preferably 0.05% or more.
Ｚｒ：０〜０．０２０％
Ｚｒは、強度を向上させる効果があるので、含有させてもよい。しかしながら、多量の含有は靭性を低下させるため、Ｚｒ含有量は、０．０２０％以下とする。一方で、強度効果を十分に得るためには、Ｚｒ含有量は、０．００１％以上であるのが好ましい。
Zr: 0-0.020%
Since Zr has the effect of improving the strength, it may be contained. However, since a large amount of the content lowers the toughness, the Zr content is set to 0.020% or less. On the other hand, in order to obtain a sufficient strength effect, the Zr content is preferably 0.001% or more.
Ｃｕ：０〜３．０％
Ｃｕは、固溶強化により材料の硬さを高めて構成刃先の生成を防止し、切削加工時の表面精度を向上させるため、含有させてもよい。しかしながら、３．０％を超えて含有させても、その効果は飽和し、鋳片割れが発生するなど、製造性が劣化するため、Ｃｕ含有量は、３．０％以下とする。一方で、上記効果を得るためには、Ｃｕ含有量は、０．１％以上であるのが好ましい。
Cu: 0-3.0%
Cu may be contained in order to increase the hardness of the material by strengthening the solid solution, prevent the formation of built-up cutting edges, and improve the surface accuracy during cutting. However, even if the content exceeds 3.0%, the effect is saturated and the manufacturability deteriorates such as slab cracking, so the Cu content is set to 3.0% or less. On the other hand, in order to obtain the above effect, the Cu content is preferably 0.1% or more.
Ｓｎ：０〜０．５％
Ｓｎは、耐食性を劣化させる硫化物と共存させることで、耐食性劣化を抑制するため、含有させてもよい。しかしながら、０．５％を超えて含有させると、製造性を劣化させるため、Ｓｎ含有量は０．５％以下とし、Ｓｎ含有量は０．３％以下であるのが好ましい。一方で、上記効果を得るためには、Ｓｎ含有量は、０．０３％以上であるのが好ましく、Ｓｎ含有量は、０．０５％以上であるのが好ましい。
Sn: 0-0.5%
Sn may be contained in order to suppress deterioration of corrosion resistance by coexisting with sulfide that deteriorates corrosion resistance. However, if it is contained in excess of 0.5%, the manufacturability is deteriorated. Therefore, the Sn content is preferably 0.5% or less, and the Sn content is preferably 0.3% or less. On the other hand, in order to obtain the above effect, the Sn content is preferably 0.03% or more, and the Sn content is preferably 0.05% or more.
Ｍｇ：０〜０．０５０％
Ｍｇは、熱間加工性を向上させるため、含有させてもよい。しかしながら、０．０５０％を超えて含有させると、却って熱間加工性を劣化させるため、Ｍｇ含有量は、０．０５０％以下とする。一方で、上記効果を得るためには、Ｍｇ含有量は、０．０００５％以上であるのが好ましい。
Mg: 0 to 0.050%
Mg may be contained in order to improve hot workability. However, if the content exceeds 0.050%, the hot workability is deteriorated, so the Mg content is set to 0.050% or less. On the other hand, in order to obtain the above effect, the Mg content is preferably 0.0005% or more.
ＲＥＭ：０〜０．２００％
ＲＥＭは、熱間加工性の劣化を防止するのに有効な元素であり、含有させてもよい。しかしながら、０．２００％を超えて含有させると却って熱間加工性を劣化させるため、ＲＥＭ含有量は、０．２００％以下とする。一方で、上記効果を得るためには、ＲＥＭ含有量は、０．０００５％以上であるのが好ましい。
REM: 0 to 0.200%
REM is an element effective in preventing deterioration of hot workability and may be contained. However, if the content exceeds 0.200%, the hot workability is deteriorated, so the REM content is set to 0.200% or less. On the other hand, in order to obtain the above effect, the REM content is preferably 0.0005% or more.
ＲＥＭ（希土類元素）は、一般的な定義に従い、スカンジウム （Ｓｃ）、イットリウム （Ｙ）の２元素と、ランタン（Ｌａ）からルテチウム（Ｌｕ） までの１５元素（ランタノイド）の総称を指す。単独で含有させてもよいし、混合物であってもよい。 REM (rare earth element) is a general term for two elements, scandium (Sc) and yttrium (Y), and 15 elements (lanthanoids) from lanthanum (La) to lutetium (Lu), according to the general definition. It may be contained alone or as a mixture.
本発明の線材は、上記した元素以外は、Ｆｅおよび不可避的不純物から成る。但し、本発明の効果を損なわない範囲で、上記以外の元素を含有させても良い。また、ＰｂとＳｅは不可避的に混入する場合もあるが、Ｐｂは０．０３％未満、Ｓｅは０．０２％未満に制御する必要がある。 The wire rod of the present invention is composed of Fe and unavoidable impurities other than the above-mentioned elements. However, elements other than the above may be contained as long as the effects of the present invention are not impaired. Further, Pb and Se may be unavoidably mixed, but it is necessary to control Pb to less than 0.03% and Se to less than 0.02%.
不可避的不純物とは、鋼材を工業的に製造する際に、原料としての鉱石、スクラップ、または製造環境などから混入されるものであって、本発明の鋼材に悪影響を与えない範囲で許容されるものを意味する。 The unavoidable impurities are those that are mixed in from ore, scrap, or the manufacturing environment as a raw material when the steel material is industrially manufactured, and are allowed as long as they do not adversely affect the steel material of the present invention. Means things.
２．Ｔｅ／Ｓ
後述する硫化物中のＭｎ／Ｃｒが０．１〜０．５の範囲にある時、さらに、鋼材のＴｅ／Ｓが小さい場合に、製造性（熱間加工性）を維持しつつ、硫化物を効果的に球状化し、アスペクト比を８．０以下に小さくすることができる。このような効果を得るために、ＴｅおよびＳの組成比である、Ｔｅ／Ｓは０．０４０以下とする。Ｔｅ／Ｓは０．０４０未満であるのが好ましく、０．０３０以下であるのがより好ましい。
2. 2. Te / S
When Mn / Cr in the sulfide, which will be described later, is in the range of 0.1 to 0.5, and when the Te / S of the steel material is small, the sulfide while maintaining manufacturability (hot workability). Can be effectively spheroidized and the aspect ratio can be reduced to 8.0 or less. In order to obtain such an effect, Te / S, which is a composition ratio of Te and S, is set to 0.040 or less. The Te / S is preferably less than 0.040, more preferably 0.030 or less.
３．硫化物中のＭｎ／Ｃｒ
Ｓ含有のフェライト系快削ステンレス線材は、一般に、鋳造から最終圧延までの総減面率が９５％以上となるため、ＭｎＳ系硫化物は、線材長手方向に展伸する。展伸したＭｎＳ系硫化物は、切削加工した際の、表面精度低下の原因となる。そのため本発明では、硫化物にＣｒを固溶させて、硫化物中のＭｎ／Ｃｒを０．５以下にすることで、圧延中の硫化物変形を抑制し、アスペクト比を小さく維持する。また硫化物中のＭｎ／Ｃｒは０．４以下であるのが好ましい。一方、過剰な固溶は、却って変形能を大きくするので、硫化物中のＭｎ／Ｃｒは０．１以上とし、０．２以上であるのが好ましい。
3. 3. Mn / Cr in sulfide
Since the S-containing ferritic free-cutting stainless steel wire generally has a total surface reduction rate of 95% or more from casting to final rolling, MnS-based sulfide is stretched in the longitudinal direction of the wire. The expanded MnS-based sulfide causes a decrease in surface accuracy during cutting. Therefore, in the present invention, Cr is dissolved in the sulfide to reduce Mn / Cr in the sulfide to 0.5 or less, thereby suppressing the deformation of the sulfide during rolling and keeping the aspect ratio small. Further, Mn / Cr in the sulfide is preferably 0.4 or less. On the other hand, excessive solid solution increases the deformability, so the Mn / Cr in the sulfide is preferably 0.1 or more, preferably 0.2 or more.
４．硫化物のアスペクト比
Ｓ含有のフェライト系快削ステンレス線材は、ＭｎＳ系硫化物は線材長手方向に展伸するため、アスペクト比も通常の鋼板と比較し、大きくなる。しかしながら、硫化物のアスペクト比の値が大きくなりすぎると、切削加工した際の表面精度の低下原因となる。このため、硫化物のアスペクト比を、８．０以下とする。また、加工粗さを安定して低減するため、アスペクト比は５．０以下とすることが好ましい。尚、ここで、アスペクト比とは、硫化物に外接する圧延方向に平行な径、つまり水平フェレ径と、圧延方向に垂直な径、つまり垂直フェレ径との比であり、硫化物の水平フェレ径/垂直フェレ径で表される。
4. Aspect ratio of sulfide In the ferritic free-cutting stainless steel wire containing S, MnS-based sulfide extends in the longitudinal direction of the wire, so the aspect ratio is also larger than that of a normal steel sheet. However, if the aspect ratio value of the sulfide becomes too large, it causes a decrease in surface accuracy during cutting. Therefore, the aspect ratio of the sulfide is set to 8.0 or less. Further, in order to stably reduce the processing roughness, the aspect ratio is preferably 5.0 or less. Here, the aspect ratio is the ratio of the diameter parallel to the rolling direction circumscribing the sulfide, that is, the horizontal ferret diameter, to the diameter perpendicular to the rolling direction, that is, the vertical ferret diameter, and the horizontal ferret of the sulfide. It is represented by the diameter / vertical ferret diameter.
５．製造条件
本発明の線材の製造工程については、例えば（１）製鋼⇒（２）熱延⇒（３）線材への加工（伸線、切削等）⇒（４）焼鈍の工程よりなる。必要に応じて、製鋼工程後に熱間鍛造を施しても良い。製鋼においては、本発明の必須元素、および/または選択元素を含む鋼を、溶製・精錬し、溶製した溶鋼は、連続鋳造で鋳片とする。その後、鋳片は、熱間圧延される。この際の好ましい条件は、９００℃以上の仕上げ圧延温度で、熱間圧延を施すことである。続いて、伸線、切削が行われる。この際の好ましい条件は室温から１００℃程度である。最後に、焼鈍工程が行われる。
5. Manufacturing conditions The manufacturing process of the wire rod of the present invention includes, for example, (1) steelmaking ⇒ (2) hot spreading ⇒ (3) processing into the wire rod (wire drawing, cutting, etc.) ⇒ (4) annealing. If necessary, hot forging may be performed after the steelmaking process. In steelmaking, steel containing the essential elements and / or selective elements of the present invention is melted and refined, and the molten steel melted is made into slabs by continuous casting. The slab is then hot rolled. A preferable condition at this time is to perform hot rolling at a finish rolling temperature of 900 ° C. or higher. Subsequently, wire drawing and cutting are performed. The preferable conditions at this time are about room temperature to about 100 ° C. Finally, an annealing step is performed.
線材圧延後の焼鈍条件は、特に規定するものではないが、１４０Ｈｖ以上の硬さを得るために、６５０〜８５０℃以下にするのが望ましい。また、焼鈍時間についても十分確保する必要があるが、３００分を超えると１４０Ｈｖ以上が得られなくなる。組織の均質化の点からも、焼鈍時間を２〜３００分とすることが望ましい。さらに好ましくは、５〜１２０分である。 The annealing conditions after rolling the wire are not particularly specified, but it is desirable that the annealing conditions be 650 to 850 ° C. or lower in order to obtain a hardness of 140 Hv or more. Further, it is necessary to secure a sufficient annealing time, but if it exceeds 300 minutes, 140 Hv or more cannot be obtained. From the viewpoint of microstructure homogenization, it is desirable that the annealing time is 2 to 300 minutes. More preferably, it is 5 to 120 minutes.
なお、線材とは棒状に圧延した鋼で、断面が円、楕円、正方形、長方形、六角形等であり、コイル状に巻かれた鋼材を指す。 The wire rod is a steel material rolled into a rod shape, has a cross section of a circle, an ellipse, a square, a rectangle, a hexagon, or the like, and refers to a steel material wound in a coil shape.
表１及び表２に実施例の鋼の化学組成を示す。 Tables 1 and 2 show the chemical composition of the steels of the examples.
これらの化学組成の鋼は、１５０ｋｇの真空溶解炉にて溶解し、直径２００ｍｍの鋳片に鋳造し、その後、１２００℃加熱で、直径７０ｍｍに鍛造した。続いて、直径６６ｍｍにピーリング後、棒鋼圧延に相当する熱間押出しにより直径１８ｍｍに加工し、７８０℃で1時間焼鈍した。最後に直径１５ｍｍの線材に機械加工で仕上げ、評価用素材とし各評価試験を実施した。 Steels having these chemical compositions were melted in a vacuum melting furnace of 150 kg, cast into slabs having a diameter of 200 mm, and then forged to a diameter of 70 mm by heating at 1200 ° C. Subsequently, after peeling to a diameter of 66 mm, it was processed to a diameter of 18 mm by hot extrusion corresponding to rolling steel bars, and annealed at 780 ° C. for 1 hour. Finally, a wire rod having a diameter of 15 mm was finished by machining and used as an evaluation material, and each evaluation test was carried out.
前記線材を、その中心線を含む長手方向の断面上を観察するように樹脂に埋め込み、鏡面研磨を行って、硫化物の組成を走査型電子顕微鏡（ＳＥＭ）付属のＥＤＳ分析装置により分析し、硫化物中のＭｎ／Ｃｒを算出した。 The wire rod is embedded in a resin so as to be observed on a cross section in the longitudinal direction including the center line thereof, mirror-polished, and the composition of sulfide is analyzed by an EDS analyzer attached to a scanning electron microscope (SEM). Mn / Cr in the sulfide was calculated.
硫化物のアスペクト比は、ＳＥＭ−ＥＤＳに供したのと同じ試料を使用し、光学顕微鏡観察により、１００倍の倍率で１０視野撮影し、全硫化物に外接する圧延方向に平行な径(水平フェレ径)と、圧延方向に垂直な径(垂直フェレ径)とを画像解析法により測定した。各硫化物の水平フェレ径/垂直フェレ径をアスペクト比として算出し、全硫化物のアスペクト比の平均値を当該試料のアスペクト比とした。 For the aspect ratio of the sulfide, the same sample used for SEM-EDS was used, and 10 fields were photographed at a magnification of 100 times by observing with an optical microscope, and the diameter (horizontal) parallel to the rolling direction inscribed with the total sulfide. The diameter of the ferret and the diameter perpendicular to the rolling direction (vertical ferret diameter) were measured by an image analysis method. The horizontal ferret diameter / vertical ferret diameter of each sulfide was calculated as the aspect ratio, and the average value of the aspect ratios of all sulfides was taken as the aspect ratio of the sample.
製造性、すなわち熱間延性は、高温引張試験により評価した。具体的には、上記直径７０ｍｍの鍛造材の中心と、表面との中間部より丸棒長手方向に直径１０ｍｍの熱間延性評価試験片を採取し、試験温度１０００℃、歪み速度０．００１／ｓの条件で引張破断した後の絞り値で評価した。この際の試験片形状はＪＩＳ Ｚ ２２４１に記載の２号試験片に準拠し、φ１０ｍｍ×１００ｍｍの試験片とした。熱間延性の評価は、通電により試験片を加熱し、所定の温度で引張り破断が可能な評価装置であるＤｙｍａｎｉｃ ｓｙｓｔｍ社製のグリーブル試験機を用いる。 Manufacturability, that is, hot ductility, was evaluated by a high temperature tensile test. Specifically, a hot ductility evaluation test piece having a diameter of 10 mm in the longitudinal direction of the round bar was collected from the intermediate portion between the center of the forged material having a diameter of 70 mm and the surface, and the test temperature was 1000 ° C. and the strain rate was 0.001 /. It was evaluated by the drawing value after tensile fracture under the condition of s. The shape of the test piece at this time conformed to the No. 2 test piece described in JIS Z 2241, and was a test piece having a diameter of 10 mm × 100 mm. For the evaluation of hot ductility, a greeable tester manufactured by Dynamic systm, which is an evaluation device capable of tensile breaking at a predetermined temperature by heating the test piece by energization, is used.
ビッカース硬さは素材の横断面に鏡面研磨を行ったものについて、表層１ｍｍ部をマイクロビッカース（荷重１ｋｇｆ）により測定した。本発明鋼の硬さは１４０Ｈｖ以上であった。 The Vickers hardness was measured by micro-Vickers (load 1 kgf) on a 1 mm surface layer of a material whose cross section was mirror-polished. The hardness of the steel of the present invention was 140 Hv or more.
線材の外周切削後の表面粗さは、切削表面の中心線平均粗さ（Ｒａ）で評価した。
切削は旋削加工であり、材質が超硬Ｐ種、刃先Ｒが０．４ｍｍの工具を用い、切削速度５０ｍ／ｍｉｎ、送り量０．０２ｍｍ／ｒｅｖ、切込み０．１ｍｍ、切削油（鉱物油）塗布の条件下で行った。
The surface roughness after cutting the outer circumference of the wire rod was evaluated by the center line average roughness (Ra) of the cut surface.
Cutting is turning, using a tool with a carbide P type material and a cutting edge R of 0.4 mm, cutting speed 50 m / min, feed amount 0.02 mm / rev, depth of cut 0.1 mm, cutting oil (mineral oil) It was carried out under the conditions of application.
表面粗さＲａは、１５分旋削加工後の試料で測定した。測定には接触式の粗さ測定機を用い、基準長さ２．５ｍｍで、各５点ずつ測定して、その平均値を測定値とした。
本発明では表面粗さＲａが０．５μｍ以下の場合に良好と判断した。
The surface roughness Ra was measured on the sample after the 15-minute turning process. A contact-type roughness measuring machine was used for the measurement, the reference length was 2.5 mm, 5 points were measured at each point, and the average value was used as the measured value.
In the present invention, it was judged to be good when the surface roughness Ra was 0.5 μm or less.
また工具寿命は逃げ面の平均摩耗量が０．２ｍｍに達するまでの時間で評価し、１５分の加工で０．２ｍｍ未満であれば寿命達成とした。製造性の指標である熱間延性（１０００℃での絞り値）は、７０％以上で良好とした。 The tool life was evaluated by the time required for the average wear amount of the flank to reach 0.2 mm, and if it was less than 0.2 mm in 15 minutes of machining, the life was achieved. The hot ductility (throttle value at 1000 ° C.), which is an index of manufacturability, was considered to be good at 70% or more.
結果を表３にまとめて示す。 The results are summarized in Table 3.
発明例のＮｏ．１からＮｏ．４９は、成分及び硫化物の組成も規定の範囲を満たしており良好な表面粗さ、工具寿命、熱間加工性の全てにおいて所望の特性が得られている。一方で比較鋼のＮｏ．５０からＮｏ．７８は規定範囲を満たしておらず、いずれかの特性を満足していないことがわかる。 No. of the invention example. 1 to No. No. 49 also satisfies the specified range in composition of components and sulfide, and desired properties are obtained in all of good surface roughness, tool life, and hot workability. On the other hand, No. of comparative steel. From 50 to No. It can be seen that 78 does not satisfy the specified range and does not satisfy any of the characteristics.
実施例から明らかなように、本発明により、Ｐｂ等の毒性の高い重金属を含有させることなく、熱間加工性、切削加工後の表面精度、さらには工具寿命に優れた安価なフェライト系快削ステンレス鋼棒線を製造することができる。
As is clear from the examples, according to the present invention, inexpensive ferrite-based free-cutting excellent in hot workability, surface accuracy after cutting, and tool life without containing highly toxic heavy metals such as Pb. Stainless steel rods can be manufactured.
Claims (2)
Ｃ：０．００５〜０．０５０％、
Ｓｉ：０．１０〜１．０％、
Ｍｎ：０．１０〜０．５０％、
Ｐ：０．００５〜０．０５％、
Ｓ：０．２５〜０．６０％、
Ｃｒ：１０．５〜１９．５％、
Ｔｅ：０．００２〜０．０２４％、
Ａｌ：０．００１〜０．０１０％、
Ｎ：０．００５〜０．０５０％、
Ｏ：０．００１〜０．０２０％、
Ｃａ：０〜０．０１０％、
Ｂ：０〜０．０２％、
Ｎｉ：０〜３．０％、
Ｍｏ：０〜３．０％、
Ｎｂ：０〜１．００％、
Ｔｉ：０〜１．００％、
Ｖ：０〜０．５０％、
Ｔａ：０〜０．５％、
Ｗ：０〜０．５％、
Ｃｏ：０〜１．００％、
Ｚｒ：０〜０．０２０％、
Ｃｕ：０〜３．０％、
Ｓｎ：０〜０．５％、
Ｍｇ：０〜０．０５０％、
ＲＥＭ：０〜０．２００％、
残部がＦｅおよび不可避的不純物からなり、
Ｔｅ含有量とＳ含有量との比である、Ｔｅ／Ｓが０．０４０以下であり、
硫化物中のＭｎとＣｒとの組成比である、Ｍｎ／Ｃｒが０．１〜０．５であり、
硫化物の外接する圧延方向に平行な径と圧延方向に垂直な径との比をアスペクト比とするとき、硫化物のアスペクト比が８．０以下である、フェライト系快削ステンレス線材。 The chemical composition is mass%,
C: 0.005 to 0.050%,
Si: 0.10 to 1.0%,
Mn: 0.10 to 0.50%,
P: 0.005-0.05%,
S: 0.25 to 0.60%,
Cr: 10.5 to 19.5%,
Te: 0.002-0.024%,
Al: 0.001 to 0.010%,
N: 0.005 to 0.050%,
O: 0.001 to 0.020%,
Ca: 0-0.010%,
B: 0-0.02%,
Ni: 0-3.0%,
Mo: 0-3.0%,
Nb: 0-1.00%,
Ti: 0-1.00%,
V: 0 to 0.50%,
Ta: 0-0.5%,
W: 0-0.5%,
Co: 0-1.00%,
Zr: 0-0.020%,
Cu: 0-3.0%,
Sn: 0-0.5%,
Mg: 0 to 0.050%,
REM: 0-0.200%,
The rest consists of Fe and unavoidable impurities,
Which is the ratio of the Te content and the S content, Te / S is Ri der than 0.040,
Mn / Cr, which is the composition ratio of Mn and Cr in the sulfide, is 0.1 to 0.5.
A ferritic free-cutting stainless steel wire having an aspect ratio of sulfide of 8.0 or less, where the ratio of the diameter parallel to the rolling direction and the diameter perpendicular to the rolling direction is the aspect ratio .
Ｃａ：０．０００５〜０．０１０％、
Ｂ：０．０００１〜０．０２％、
Ｎｉ：０．１〜３．０％、
Ｍｏ：０．１〜３．０％、
Ｎｂ：０．０５〜１．００％、
Ｔｉ：０．０５〜１．００％、
Ｖ：０．０５〜０．５０％、
Ｔａ：０．１〜０．５％、
Ｗ：０．１〜０．５％、
Ｃｏ：０．０５〜１．００％、
Ｚｒ：０．００１〜０．０２０％、
Ｃｕ：０．１〜３．０％、
Ｓｎ：０．０３〜０．５％、
Ｍｇ：０．０００５〜０．０５０％、および
ＲＥＭ：０．０００５〜０．２００％、
から選択される１種以上を含有する、請求項１に記載のフェライト系快削ステンレス線材。 When the chemical composition is mass% ,
Ca: 0.0005 to 0.010%,
B: 0.0001 to 0.02%,
Ni: 0.1 to 3.0%,
Mo: 0.1 to 3.0%,
Nb: 0.05 to 1.00%,
Ti: 0.05 to 1.00%,
V: 0.05 to 0.50%,
Ta: 0.1-0.5%,
W: 0.1 to 0.5%,
Co: 0.05 to 1.00%,
Zr: 0.001 to 0.020%,
Cu: 0.1 to 3.0%,
Sn: 0.03 to 0.5%,
Mg: 0.0005 to 0.050%, and REM: 0.0005 to 0.200%,
The ferrite-based free-cutting stainless steel wire rod according to claim 1, which contains one or more selected from the above.
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