JP6093063B1 - High-strength stainless steel material excellent in workability and its manufacturing method - Google Patents
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- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 99
- 239000010935 stainless steel Substances 0.000 title claims abstract description 99
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- 238000004519 manufacturing process Methods 0.000 title claims description 16
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 44
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 43
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- 239000002184 metal Substances 0.000 claims abstract description 28
- 239000000203 mixture Substances 0.000 claims abstract description 18
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 18
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 12
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 11
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 8
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 23
- 229910052799 carbon Inorganic materials 0.000 claims description 10
- 229910052717 sulfur Inorganic materials 0.000 claims description 7
- 229910052742 iron Inorganic materials 0.000 claims 2
- 229910052759 nickel Inorganic materials 0.000 abstract description 10
- 230000007423 decrease Effects 0.000 abstract description 5
- 229910000831 Steel Inorganic materials 0.000 description 39
- 239000010959 steel Substances 0.000 description 39
- 238000005452 bending Methods 0.000 description 31
- 229910001566 austenite Inorganic materials 0.000 description 28
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- 150000001247 metal acetylides Chemical class 0.000 description 6
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- 229910052802 copper Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
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- 229910003470 tongbaite Inorganic materials 0.000 description 2
- -1 Mo: 1.0% or less Substances 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
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Abstract
【課題】フェライト相とマルテンサイト相の２相組織を有するステンレス鋼材について、強度の低下を抑制すると共に加工性を改善し、さらにコストを抑えた高強度ステンレス鋼材を提供する。【解決手段】本発明は、質量％で、Ｃ：０．０３〜０．１５％、Ｓｉ：０．１〜２．０％、Ｍｎ：０．１〜４．０％、Ｐ：０．０４％以下、Ｓ：０．０３％以下、Ｎｉ：０．０１〜４．０％、Ｃｒ：１０〜２０％、Ｎ：０．１２％以下、Ｂ：０．００３〜０．０１％を含有し、Ｔｉ：０．０５〜０．２％、Ａｌ：０．０５〜０．２％、Ｖ：０．０５〜０．２％を少なくとも一種以上含有する、残部がＦｅおよび不可避的不純物からなる組成を有するステンレス鋼材であって、フェライト相とマルテンサイト相の２相の金属組織を有し、（１）式により計算されるγｍａｘ（％）が５０以上８５以下を満足する、加工性に優れる高強度ステンレス鋼材である。【選択図】図１A stainless steel material having a two-phase structure of a ferrite phase and a martensite phase is provided which provides a high-strength stainless steel material that suppresses a decrease in strength, improves workability, and further reduces costs. In the present invention, the mass ratio is C: 0.03-0.15%, Si: 0.1-2.0%, Mn: 0.1-4.0%, P: 0.04. %: S: 0.03% or less, Ni: 0.01-4.0%, Cr: 10-20%, N: 0.12% or less, B: 0.003-0.01% , Ti: 0.05 to 0.2%, Al: 0.05 to 0.2%, V: 0.05 to 0.2%, at least one composition, the balance being Fe and inevitable impurities Is a stainless steel material having a two-phase metal structure of a ferrite phase and a martensite phase, and satisfying γmax (%) calculated by the formula (1) of 50 or more and 85 or less. It is a strength stainless steel material. [Selection] Figure 1
Description
本発明は、フェライト相及びマルテンサイト相の２相の金属組織を有する、加工性に優れた高強度ステンレス鋼材とその製造方法に関するものである。 The present invention relates to a high-strength stainless steel material excellent in workability having a two-phase metal structure of a ferrite phase and a martensite phase, and a method for producing the same.
従来、高強度ステンレス鋼材として、フェライト及びマルテンサイトの複相組織からなる金属組織を形成することで加工性を向上させたステンレス鋼材が商用化されている。この種のステンレス鋼材は、フェライト及びマルテンサイトの複相組織となるような熱処理を経ることによって製造される。このステンレス鋼材は、硬質なマルテンサイト相によって高強度化が図られると共に、軟質なフェライト相を存在させることで良好な加工性を有する。このような金属組織の複相化により、ステンレス鋼材の加工性を改良することが可能であるものの、更に加工性を向上させるには限界がある。 Conventionally, as a high-strength stainless steel material, a stainless steel material having improved workability by forming a metal structure composed of a multiphase structure of ferrite and martensite has been commercialized. This type of stainless steel material is manufactured through a heat treatment that results in a multiphase structure of ferrite and martensite. This stainless steel material is improved in strength by a hard martensite phase and has good workability by the presence of a soft ferrite phase. Although it is possible to improve the workability of the stainless steel material by making such a metal structure into a multiphase, there is a limit to further improve the workability.
そこで、曲げ加工などに適した加工性を得るため、延性に優れ、かつ強度−延性バランスに優れた高強度ステンレス鋼板が提案されている。例えば、特許文献１には、ステンレス鋼板を二相域の温度で加熱した後、５℃／ｓ以上の冷却温度で冷却する第一の熱処理工程、圧下率３０％以上の冷間圧延を行う冷延工程、４００℃以上Ａｃ１変態点未満の温度で加熱する第１の熱処理工程、を順次施す高強度ステンレス鋼板の製造方法が開示されている。当該ステンレス鋼板は、曲げ加工が施される用途に好適であると記載されている。 Therefore, in order to obtain workability suitable for bending, etc., a high-strength stainless steel plate having excellent ductility and excellent strength-ductility balance has been proposed. For example, Patent Document 1 discloses a first heat treatment step in which a stainless steel plate is heated at a temperature in a two-phase region and then cooled at a cooling temperature of 5 ° C./s or more, and cold rolling in which cold rolling at a reduction rate of 30% or more is performed. A method for producing a high-strength stainless steel sheet is disclosed in which a rolling step and a first heat treatment step of heating at a temperature of 400 ° C. or higher and lower than an A c1 transformation point are sequentially performed. The stainless steel sheet is described as being suitable for applications where bending is performed.
特許文献２には、複相組織を有するステンレス鋼板の表層部を脱炭させる手法が提案されている。脱炭により、ステンレス鋼板の表層部において軟質なフェライト相を多く形成させて、表層部における延性を改善し、曲げ加工性を向上させたステンレス鋼板が開示されている。 Patent Document 2 proposes a method of decarburizing a surface layer portion of a stainless steel plate having a multiphase structure. A stainless steel plate is disclosed in which a large amount of a soft ferrite phase is formed in the surface layer portion of the stainless steel plate by decarburization, thereby improving the ductility in the surface layer portion and improving the bending workability.
特許文献３には、複相組織を有するステンレス鋼板に時効熱処理を加えることで、マルテンサイトとフェライトの強度差を小さくする方法が提案されている。この手法により、ステンレス鋼材を加工する際の応力を分散でき、延性を向上させたステンレス鋼板が開示されている。 Patent Document 3 proposes a method of reducing the strength difference between martensite and ferrite by applying an aging heat treatment to a stainless steel plate having a multiphase structure. This technique discloses a stainless steel plate that can disperse stress when processing a stainless steel material and has improved ductility.
しかしながら、耐食性に優れるステンレス鋼材の適用分野が拡大するにつれて、ステンレス鋼材の加工性に対する要求が高くなっている。例えば、複相組織を有するステンレス鋼材の金属組織におけるマルテンサイト相の比率を低下させることにより、加工性を向上させる方法が考えられる。しかし、この方法では、鋼材全体の強度が低下するおそれがある。 However, as the application field of stainless steel materials having excellent corrosion resistance expands, the demand for the workability of stainless steel materials has increased. For example, a method of improving workability by reducing the ratio of the martensite phase in the metal structure of a stainless steel material having a multiphase structure can be considered. However, with this method, the strength of the entire steel material may be reduced.
特許文献１の上記の方法は、複相組織を有するスレンレス鋼を得た後、特定の条件で冷却、冷間圧延および熱処理を施すことにより、強度と延性のバランスを確保している。複相化処理のほかに特別な処理を必要とし、コストや手間を要する。 The method described in Patent Document 1 secures a balance between strength and ductility by obtaining a stainless steel having a multiphase structure and then performing cooling, cold rolling and heat treatment under specific conditions. In addition to the multi-phase treatment, special treatment is required, which requires cost and labor.
特許文献２の上記の方法は、脱炭するために１１００〜１２００℃の高温加熱処理を必要とする。さらに、軟質なフェライト相が形成される比率によっては、鋼材全体の強度が低下するおそれがある。また、特許文献３の上記の方法は、複相化処理を施した後、時効熱処理を必要とする。 The above-described method of Patent Document 2 requires high-temperature heat treatment at 1100 to 1200 ° C. for decarburization. Furthermore, depending on the ratio of forming a soft ferrite phase, the strength of the entire steel material may be reduced. In addition, the above-described method of Patent Document 3 requires an aging heat treatment after performing a multiphase treatment.
また、化学成分の見直しにより、フェライト相とオーステナイト相の複相ステンレス鋼材とする方法も考えられる。この手法の場合、強度および加工性の両方を満足させるため、Ｎｉのような高価な元素の添加が必要であり、コスト的に見合わない可能性がある。 In addition, a method of making a dual phase stainless steel material of a ferrite phase and an austenite phase by reviewing chemical components is also conceivable. In the case of this method, in order to satisfy both strength and workability, it is necessary to add an expensive element such as Ni, which may not meet the cost.
本発明は、上記の事情に鑑みてなされたものであり、フェライト相とマルテンサイト相の２相組織を有するステンレス鋼材について、強度の低下を抑制すると共に加工性を改善し、さらにコストを抑えた高強度ステンレス鋼材を提案することを目的とする。 The present invention has been made in view of the above circumstances, and for a stainless steel material having a two-phase structure of a ferrite phase and a martensite phase, while suppressing a decrease in strength and improving workability, further reducing costs. The purpose is to propose a high-strength stainless steel material.
本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、高温域で析出するオーステナイト相の析出形態に着目した。当該オーステナイト相は、通常、フェライト粒界に優先的に析出する傾向がある。このオーステナイト相をフェライト粒内で分散析出させることにより、組織の異方性が改善され、加工性が向上することを見出した。また、このようなステンレス鋼材を得る上で、Ａｌ、Ｔｉ、Ｖの少なくとも一種とＢを複合添加することが効果的であることを見出した。具体的には、本発明は、以下のようなものを提供する。 As a result of intensive studies to achieve the above object, the present inventors have focused on the precipitation form of the austenite phase that precipitates in a high temperature range. The austenite phase usually tends to precipitate preferentially at ferrite grain boundaries. It has been found that by dispersing and precipitating this austenite phase in ferrite grains, the anisotropy of the structure is improved and the workability is improved. Moreover, when obtaining such a stainless steel material, it discovered that it was effective to add at least 1 type of Al, Ti, V, and B in combination. Specifically, the present invention provides the following.
本発明に係る実施形態は、質量％で、Ｃ：０．０３〜０．１５％、Ｓｉ：０．１〜２．０％、Ｍｎ：０．１〜４．０％、Ｐ：０．０４％以下、Ｓ：０．０３％以下、Ｎｉ：０．０１〜４．０％、Ｃｒ：１０〜２０％、Ｎ：０．１２％以下、Ｂ：０．００３〜０．０１％を含有し、Ｔｉ：０．０５〜０．２％、Ａｌ：０．０５〜０．２％、Ｖ：０．０５〜０．２％を少なくとも一種以上含有する、残部がＦｅおよび不可避的不純物からなる組成を有するステンレス鋼材であって、フェライト相とマルテンサイト相の２相の金属組織を有し、下記（１）式により計算されるγｍａｘ（％）が５０以上８５以下を満足する、加工性に優れる高強度ステンレス鋼材である。
γｍａｘ（％）＝４２０×〔Ｃ〕−１１．５×〔Ｓｉ〕＋７×〔Ｍｎ〕＋２３×〔Ｎｉ〕−１１．５×〔Ｃｒ〕−１２×〔Ｍｏ〕＋９×〔Ｃｕ〕−４９×〔Ｔｉ〕−５２×〔Ａｌ〕＋４７０×〔Ｎ〕＋１８９・・・（１）
（ここで〔 〕は、元素の質量％を示す）
The embodiment according to the present invention is mass%, C: 0.03 to 0.15%, Si: 0.1 to 2.0%, Mn: 0.1 to 4.0%, P: 0.04. %: S: 0.03% or less, Ni: 0.01-4.0%, Cr: 10-20%, N: 0.12% or less, B: 0.003-0.01% , Ti: 0.05 to 0.2%, Al: 0.05 to 0.2%, V: 0.05 to 0.2%, at least one composition, the balance being Fe and inevitable impurities Is a stainless steel material having a two-phase metal structure of a ferrite phase and a martensite phase, and satisfying γmax (%) calculated by the following formula (1) of 50 or more and 85 or less, and excellent in workability. High strength stainless steel.
γmax (%) = 420 × [C] −11.5 × [Si] + 7 × [Mn] + 23 × [Ni] −11.5 × [Cr] −12 × [Mo] + 9 × [Cu] −49 × [Ti] −52 × [Al] + 470 × [N] +189 (1)
(Where [] indicates the mass% of the element)
本発明に係る実施形態は、質量％で、Ｃ：０．０３〜０．１５％、Ｓｉ：０．１〜２．０％、Ｍｎ：０．１〜４．０％、Ｐ：０．０４％以下、Ｓ：０．０３％以下、Ｎｉ：０．０１〜４．０％、Ｃｒ：１０〜２０％、Ｎ：０．１２％以下、Ｂ：０．００３〜０．０１％を含有し、Ｔｉ：０．０５〜０．２％、Ａｌ：０．０５〜０．２％、Ｖ：０．０５〜０．２％を少なくとも一種以上含有する、残部がＦｅおよび不可避的不純物からなる組成を有し、下記（１）式により計算されるγｍａｘ（％）が５０以上８５以下を満足するステンレス鋼片に、フェライト相とマルテンサイト相の２相組織とするための複相化処理を施す工程を備える、加工性に優れる高強度ステンレス鋼材の製造方法である。
γｍａｘ（％）＝４２０×〔Ｃ〕−１１．５×〔Ｓｉ〕＋７×〔Ｍｎ〕＋２３×〔Ｎｉ〕−１１．５×〔Ｃｒ〕−１２×〔Ｍｏ〕＋９×〔Ｃｕ〕−４９×〔Ｔｉ〕−５２×〔Ａｌ〕＋４７０×〔Ｎ〕＋１８９・・・（１）
（ここで〔 〕は、元素の質量％を示す）
The embodiment according to the present invention is mass%, C: 0.03 to 0.15%, Si: 0.1 to 2.0%, Mn: 0.1 to 4.0%, P: 0.04. %: S: 0.03% or less, Ni: 0.01-4.0%, Cr: 10-20%, N: 0.12% or less, B: 0.003-0.01% , Ti: 0.05 to 0.2%, Al: 0.05 to 0.2%, V: 0.05 to 0.2%, at least one composition, the balance being Fe and inevitable impurities A stainless steel piece having a γmax (%) calculated by the following formula (1) satisfying 50 or more and 85 or less is subjected to a multiphase treatment for forming a two-phase structure of a ferrite phase and a martensite phase. A method for producing a high-strength stainless steel material having a process and excellent workability.
γmax (%) = 420 × [C] −11.5 × [Si] + 7 × [Mn] + 23 × [Ni] −11.5 × [Cr] −12 × [Mo] + 9 × [Cu] −49 × [Ti] −52 × [Al] + 470 × [N] +189 (1)
(Where [] indicates the mass% of the element)
本発明に係る実施形態のステンレス鋼材は、上記の組成において、さらに、質量％で、Ｍｏ：１．０％以下、Ｃｕ：３．０％以下、または、Ｎｂ：１．０％以下を含有することが好ましい。 The stainless steel material of the embodiment according to the present invention further contains, in the above composition, Mo: 1.0% or less, Cu: 3.0% or less, or Nb: 1.0% or less in the above composition. It is preferable.
本発明により、機械的強度の低下を抑制すると共に、加工性を改善した高強度ステンレス鋼材を提供できる。とくに、曲げ加工性に優れるとともに、曲げ加工における異方性の少ない高強度ステンレス鋼材が得られる。そのため、曲げ方向によらず、曲げ加工を施すことができるから、複雑な形状の製品であっても成形可能な素材を提供できる。また、複相処理した後に特別な処理を必要としないので、コストを抑えて製造できる。 According to the present invention, it is possible to provide a high-strength stainless steel material that suppresses a decrease in mechanical strength and has improved workability. In particular, a high-strength stainless steel material having excellent bending workability and little anisotropy in bending work can be obtained. Therefore, since the bending process can be performed regardless of the bending direction, it is possible to provide a material that can be molded even if the product has a complicated shape. In addition, since no special treatment is required after the multiphase treatment, it can be produced at a reduced cost.
以下に本発明に関する実施形態について説明する。この説明は、本発明の範囲を限定するものではない。 Embodiments relating to the present invention will be described below. This description is not intended to limit the scope of the invention.
本実施形態の高強度ステンレス鋼材（以下、単に「ステンレス鋼材」または「鋼材」ということもある。）について説明する。 The high-strength stainless steel material of the present embodiment (hereinafter sometimes simply referred to as “stainless steel material” or “steel material”) will be described.
（ステンレス鋼材）
本実施形態の高強度ステンレス鋼材は、質量％で、Ｃ：０．０３〜０．１５％、Ｓｉ：０．１〜２．０％、Ｍｎ：０．１〜４．０％、Ｐ：０．０４％以下、Ｓ：０．０３％以下、Ｎｉ：０．０１〜４．０％、Ｃｒ：１０〜２０％、Ｍｏ：１．０％以下、Ｎ：０．１２％以下、Ｂ：０．００３〜０．０１％を含有し、Ｔｉ：０．０５〜０．２％、Ａｌ：０．０５〜０．２％、Ｖ：０．０５〜０．２％を少なくとも一種以上含有する、残部がＦｅおよび不可避的不純物からなる組成を有するステンレス鋼材であって、フェライト相とマルテンサイト相の２相の金属組織を有し、下記（１）式により計算されるγｍａｘ（％）が５０以上８５以下を満足する高強度ステンレス鋼材である。
γｍａｘ（％）＝４２０×〔Ｃ〕−１１．５×〔Ｓｉ〕＋７×〔Ｍｎ〕＋２３×〔Ｎｉ〕−１１．５×〔Ｃｒ〕−１２×〔Ｍｏ〕＋９×〔Ｃｕ〕−４９×〔Ｔｉ〕−５２×〔Ａｌ〕＋４７０×〔Ｎ〕＋１８９・・・（１）
（ここで〔 〕は、元素の質量％を示す）
(Stainless steel)
The high-strength stainless steel material of the present embodiment is mass%, C: 0.03 to 0.15%, Si: 0.1 to 2.0%, Mn: 0.1 to 4.0%, P: 0 0.04% or less, S: 0.03% or less, Ni: 0.01 to 4.0%, Cr: 10 to 20%, Mo: 1.0% or less, N: 0.12% or less, B: 0 0.003 to 0.01%, Ti: 0.05 to 0.2%, Al: 0.05 to 0.2%, and V: 0.05 to 0.2%, The balance is a stainless steel material having a composition composed of Fe and inevitable impurities, and has a two-phase metal structure of a ferrite phase and a martensite phase, and γmax (%) calculated by the following formula (1) is 50 or more. It is a high-strength stainless steel material that satisfies 85 or less.
γmax (%) = 420 × [C] −11.5 × [Si] + 7 × [Mn] + 23 × [Ni] −11.5 × [Cr] −12 × [Mo] + 9 × [Cu] −49 × [Ti] −52 × [Al] + 470 × [N] +189 (1)
(Where [] indicates the mass% of the element)
以下、本実施形態の高強度ステンレス鋼材における組成の限定理由について説明する。 Hereinafter, the reasons for limiting the composition of the high-strength stainless steel material of the present embodiment will be described.
Ｃｒ：１０．０〜２０．０質量％
Ｃｒは、ステンレス鋼としての耐食性および強度を確保するために含有される元素である。Ｃｒ含有量が低すぎると、酸化皮膜の形成が困難になり、優れた耐食性が得られなくなる。この観点からＣｒ含有量は１０．０質量％以上が好ましい。一方、Ｃｒの含有量が高すぎると、マルテンサイト相を生成させて高強度を得るために、ＮｉやＭｎなどのオーステナイト生成元素が多量に必要となると共にステンレス鋼材の靭性も低くなってしまう。そのため、Ｃｒ含有量は２０．０質量％以下が好ましい。
Cr: 10.0-20.0 mass%
Cr is an element contained in order to ensure corrosion resistance and strength as stainless steel. If the Cr content is too low, it becomes difficult to form an oxide film, and excellent corrosion resistance cannot be obtained. From this viewpoint, the Cr content is preferably 10.0% by mass or more. On the other hand, if the content of Cr is too high, a large amount of austenite-generating elements such as Ni and Mn are required to generate a martensite phase and obtain high strength, and the toughness of the stainless steel material also decreases. Therefore, the Cr content is preferably 20.0% by mass or less.
Ｃ：０．０３質量％〜０．１５質量％
Ｃは、強力なオーステナイト生成元素であるため、金属組織中のマルテンサイト相の割合を増加させる。また、Ｃは、固溶強化効果を発揮するため、マルテンサイト相およびフェライト相の両相の強度を高めるのに有効である。このような観点から、Ｃの含有量は、０．０１質量％以上であると好ましい。一方、本実施形態のステンレス鋼材の耐食性を十分に高める観点から、Ｃの含有量は、０．１５質量％以下が好ましい。本実施形態のステンレス鋼材の製造方法において、鋼片に熱処理を施す際、加熱によりクロム炭化物が固溶する。Ｃの含有量が０．１５質量％を超えると、複相化の熱処理をした後の冷却時に、クロム炭化物がフェライトまたはオーステナイト相の粒界に再析出しやすくなる。その結果、当該粒界近傍にＣｒ欠乏層が生じ、耐食性が低下するため、０．１５質量％以下とした。
C: 0.03 mass% to 0.15 mass%
Since C is a strong austenite-forming element, it increases the proportion of the martensite phase in the metal structure. Further, C exhibits a solid solution strengthening effect, and is effective in increasing the strength of both the martensite phase and the ferrite phase. From such a viewpoint, the C content is preferably 0.01% by mass or more. On the other hand, from the viewpoint of sufficiently increasing the corrosion resistance of the stainless steel material of the present embodiment, the C content is preferably 0.15% by mass or less. In the manufacturing method of the stainless steel material of this embodiment, when heat-treating a steel piece, chromium carbide is dissolved by heating. When the C content exceeds 0.15% by mass, chromium carbide tends to be re-precipitated at the grain boundaries of the ferrite or austenite phase during cooling after the heat treatment for forming a multiphase. As a result, a Cr-deficient layer was generated in the vicinity of the grain boundary, and the corrosion resistance was lowered.
Ｓｉ：０．１質量％〜２．０質量％
Ｓｉは、脱酸目的で添加される成分である。また、Ｓｉは、マルテンサイト相を硬くすると共に、オーステナイト相にも固溶してこれを硬化する。さらに、時効硬化の際には、歪時効により時効硬化能を促進する。これらの効果を有効に発揮する観点から、Ｓｉの含有量は０．１質量％以上であると好ましい。一方、過多に添加されると、ステンレス鋼材の加工性を低下させて高温割れを招く恐れがあり、マルテンサイト相が過多に形成されるため、Ｓｉの含有量は、２．０質量％以下が好ましい。
Si: 0.1% by mass to 2.0% by mass
Si is a component added for the purpose of deoxidation. Si hardens the martensite phase and also dissolves in the austenite phase to harden it. Furthermore, in the case of age hardening, the age hardening ability is promoted by strain aging. From the viewpoint of effectively exhibiting these effects, the Si content is preferably 0.1% by mass or more. On the other hand, if added excessively, the workability of the stainless steel material may be reduced and hot cracking may occur, and the martensite phase is excessively formed. Therefore, the Si content is 2.0% by mass or less. preferable.
Ｍｎ：０．１質量％〜４．０質量％、Ｎｉ：０．０１質量％〜４．０質量％
本実施形態のステンレス鋼材は、Ｍｎを０．１質量％〜４．０質量％、Ｎｉを０．０１質量％〜４．０質量％含有する。Ｍｎ、Ｎｉは、オーステナイト生成元素として機能するものである。これらの元素を含有することにより、本実施形態のステンレス鋼材は、高温でフェライト相とオーステナイト相との２相からなる金属組織を有することが可能となる。また、Ｍｎ、Ｎｉの含有割合が増加するほど、冷却後にマルテンサイト相が増加するため、鋼材の強度が高くなる。これらの効果を有効に確保するため、Ｍｎの含有量は、０．１質量％以上が好ましく、Ｎｉの含有量は、０．０１質量％以上が好ましい。また、ＭｎとＮｉの割合は、ＣｒおよびＣの含有量に応じて一定量であることが好ましい。一方、金属組織中のマルテンサイト相が多くなりすぎると、強度は十分得られるものの延性が低下する。この延性低下の観点から、Ｍｎ、Ｎｉは、それぞれ４．０質量％以下が好ましく、Ｍｎの含有量は、２．０質量％以下がより好ましい。
Mn: 0.1% by mass to 4.0% by mass, Ni: 0.01% by mass to 4.0% by mass
The stainless steel material of the present embodiment contains 0.1% by mass to 4.0% by mass of Mn and 0.01% by mass to 4.0% by mass of Ni. Mn and Ni function as austenite generating elements. By containing these elements, the stainless steel material of this embodiment can have a metal structure composed of two phases of a ferrite phase and an austenite phase at a high temperature. Moreover, since the martensite phase increases after cooling as the content ratio of Mn and Ni increases, the strength of the steel material increases. In order to effectively secure these effects, the Mn content is preferably 0.1% by mass or more, and the Ni content is preferably 0.01% by mass or more. Moreover, it is preferable that the ratio of Mn and Ni is a fixed quantity according to content of Cr and C. On the other hand, when the martensite phase in the metal structure is excessive, the ductility is lowered although sufficient strength is obtained. From the viewpoint of reducing ductility, Mn and Ni are each preferably 4.0% by mass or less, and the Mn content is more preferably 2.0% by mass or less.
Ｍｏ：１．０質量％以下
本実施形態のステンレス鋼材はＭｏを１．０質量％以下含有しても良い。Ｍｏは、ステンレス鋼材のステンレス鋼の耐食性を高めるのに有効である。この効果を発揮する観点から、０．０質量％を超えて含有しても良い。一方、Ｍｏはフェライト生成元素であるため、金属組織でマルテンサイト相の割合を減らし、強度が低下するため１．０質量％以下とする。
Mo: 1.0 mass% or less The stainless steel material of this embodiment may contain 1.0 mass% or less of Mo. Mo is effective for enhancing the corrosion resistance of stainless steel. From the viewpoint of exhibiting this effect, it may be contained in excess of 0.0 mass%. On the other hand, since Mo is a ferrite-forming element, the ratio of the martensite phase is reduced in the metal structure, and the strength is lowered.
Ｐ：０．０４質量％以下、Ｓ：０．０３質量％以下
Ｐ、Ｓは、鋼材の脆性を防止する観点から少ないほどよく、Ｐの含有量は、０．０４質量％以下が望ましく、Ｓの含有量は、０．０３質量％以下が望ましい。
P: 0.04 mass% or less, S: 0.03 mass% or less P and S are preferably as small as possible from the viewpoint of preventing brittleness of the steel material, and the P content is preferably 0.04 mass% or less. The content of is desirably 0.03% by mass or less.
Ｎ：０．１２質量％以下
Ｎは、強力なオーステナイト生成元素であるため、金属組織においてマルテンサイト相の割合を増加させる。また、固溶強化効果を発揮するため、マルテンサイト相の強度を高めるのに有効である。一方、多量に添加すると、鋼材表面の欠陥を増加させる要因となる。そのため、Ｎの含有量を０．１２質量％以下とした。
N: 0.12% by mass or less Since N is a strong austenite-forming element, it increases the ratio of the martensite phase in the metal structure. Moreover, since it exhibits a solid solution strengthening effect, it is effective in increasing the strength of the martensite phase. On the other hand, when added in a large amount, it becomes a factor of increasing defects on the surface of the steel material. Therefore, the content of N is set to 0.12% by mass or less.
Ｂ：０．００３〜０．０１質量％
Ｂは、結晶粒界の安定度を高め、オーステナイト相が粒界に析出するのを抑え、粒内にオーステナイト相を析出させ微細分散する効果があるため、０．００３質量％以上含有する。しかし、０．０１質量％を超えると、溶接高温割れを起こす。そのため、Ｂの含有量を０．０１質量％以下とした。
B: 0.003 to 0.01% by mass
B is contained in an amount of 0.003% by mass or more because it increases the stability of the crystal grain boundaries, suppresses the precipitation of the austenite phase at the grain boundaries, and precipitates and finely disperses the austenite phase in the grains. However, if it exceeds 0.01 mass%, welding hot cracking occurs. Therefore, the content of B is set to 0.01% by mass or less.
Ｔｉ：０．０５〜０．２質量％、Ａｌ：０．０５〜０．２％、Ｖ：０．０５〜０．２％
Ｔｉ、ＡｌまたはＶの少なくとも１種以上は、良好な加工性を確保する観点で添加される元素である。Ａｌは、Ｎを固定する作用があり、また、Ｔｉ、Ｖは、ＮおよびＣを固定する作用があり、ステンレス鋼材の高純度化に寄与する。さらに、これらの元素は、フェライト相とオーステナイト相の２相が存在する温度域を狭める効果を有するので、冷却時オーステナイト相の成長を抑制し、オーステナイト相の微細分散に寄与する。そのため、各元素の含有量は、０．０５質量％以上が好ましい。一方、０．２％を超えて添加されると、加工性の低下に繋がる。そのため、各元素の含有量を０．０５〜０．２質量％とした。
Ti: 0.05-0.2% by mass, Al: 0.05-0.2%, V: 0.05-0.2%
At least one of Ti, Al, and V is an element added from the viewpoint of ensuring good workability. Al has an action of fixing N, and Ti and V have an action of fixing N and C, contributing to high purity of the stainless steel material. Furthermore, these elements have the effect of narrowing the temperature range in which the two phases of the ferrite phase and the austenite phase exist, so that the growth of the austenite phase during cooling is suppressed and contributes to fine dispersion of the austenite phase. Therefore, the content of each element is preferably 0.05% by mass or more. On the other hand, when added over 0.2%, it leads to the fall of workability. Therefore, the content of each element is set to 0.05 to 0.2% by mass.
Ｃｕ：３．０質量％以下
Ｃｕは、オーステナイト生成元素として機能し、高温でフェライト相とオーステナイト相との２相からなる金属組織の形成に寄与する。また、金属組織でマルテンサイト相を増加させるので、含有しても良い。一方、３．０質量％を超えると、耐食性および加工性低下の要因となるため、Ｃｕの含有量は、３．０質量％以下が好ましい。
Cu: 3.0% by mass or less Cu functions as an austenite-generating element and contributes to the formation of a metal structure composed of two phases of a ferrite phase and an austenite phase at a high temperature. Moreover, since the martensite phase is increased in the metal structure, it may be contained. On the other hand, if it exceeds 3.0% by mass, it causes a decrease in corrosion resistance and workability, so the Cu content is preferably 3.0% by mass or less.
Ｎｂ：１．０質量％以下
Ｎｂは、ＣおよびＮを固定し、耐食性を向上させる作用を有するから、含有しても良い。一方、１．０質量％を超えると、加工性や靭性を低下させるため、Ｎｂの含有量は、１．０質量％以下が好ましい。
Nb: 1.0% by mass or less Nb may be contained because it has an action of fixing C and N and improving corrosion resistance. On the other hand, if it exceeds 1.0% by mass, the workability and toughness are lowered, so the content of Nb is preferably 1.0% by mass or less.
本実施形態のステンレス鋼材は、フェライト相とマルテンサイト相との２相からなる金属組織を有する。この鋼材は、軟質なフェライト相に起因して良好な加工性を有する一方で、硬質なマルテンサイト相に起因して高い強度も有する。このような金属組織は、後述する複相化熱処理により得られる。 The stainless steel material of this embodiment has a metal structure composed of two phases of a ferrite phase and a martensite phase. This steel has good workability due to the soft ferrite phase, but also has high strength due to the hard martensite phase. Such a metal structure is obtained by a multiphase heat treatment described later.
γｍａｘ（％）：５０〜８５
上記（１）式で表されるγｍａｘ（％）は、１１００℃程度に加熱保持した場合に生成するオーステナイト相の割合を表す指標である。（１）式の〔 〕は、元素記号で示された各元素の含有量である質量％を示す。γｍａｘが１００以上の場合はオーステナイト単相とみなすことができ、γｍａｘが０以下の場合はフェライト単相とみなすことができる。γｍａｘが０〜１００の範囲では、常温下のステンレス鋼材は、フェライト相とマルテンサイト相との２相からなる組織を有するとみなせる。本実施形態のステンレス鋼材は、高い強度および良好な加工性を得るために、γｍａｘが５０〜８５であることが好ましい。γｍａｘが５０未満では、十分な強度を有するステンレス鋼材が得られない。その一方で、γｍａｘが８５を超えると、金属組織におけるマルテンサイト相の割合が増えすぎて加工性が損なわれるので、好ましくない。
γmax (%): 50 to 85
Γmax (%) represented by the above formula (1) is an index that represents the ratio of the austenite phase that is generated when heated to about 1100 ° C. In the formula (1), [] indicates mass%, which is the content of each element indicated by the element symbol. When γmax is 100 or more, it can be regarded as an austenite single phase, and when γmax is 0 or less, it can be regarded as a ferrite single phase. When γmax is in the range of 0 to 100, the stainless steel material at room temperature can be regarded as having a structure composed of two phases of a ferrite phase and a martensite phase. The stainless steel material of this embodiment preferably has a γmax of 50 to 85 in order to obtain high strength and good workability. If γmax is less than 50, a stainless steel material having sufficient strength cannot be obtained. On the other hand, if γmax exceeds 85, the ratio of the martensite phase in the metal structure is excessively increased, and the workability is impaired.
本実施形態のステンレス鋼材は、２３０ＨＶ以上の硬さを有することが好ましい。このような高い硬さを有するステンレス鋼材は、高い機械的強度を有するから、高強度を必要とする用途に適している。 The stainless steel material of this embodiment preferably has a hardness of 230 HV or higher. A stainless steel material having such a high hardness has a high mechanical strength and is therefore suitable for applications that require high strength.
本実施形態のステンレス鋼材は、従来の鋼材に比べて加工性に優れている。加工性を改善する観点から、ＢとＴｉ、Ａｌ、Ｖの少なくとも一種を複合添加している。ＢとＴｉ、Ａｌ、Ｖの少なくとも一種を複合添加することにより、高温時に、オーステナイト相や炭化物を微細分散することができ、加工性が改善される。 The stainless steel material of this embodiment is excellent in workability compared with the conventional steel material. From the viewpoint of improving workability, B and at least one of Ti, Al, and V are added in combination. By compositely adding B and at least one of Ti, Al, and V, the austenite phase and carbide can be finely dispersed at high temperatures, and workability is improved.
本実施形態のステンレス鋼材は、板状のステンレス鋼板であってもよい。このステンレス鋼板はプレス成型加工や打抜加工等により、各種部品の形状に成形したものであってもよい。 The stainless steel material of the present embodiment may be a plate-shaped stainless steel plate. This stainless steel plate may be formed into various parts by press molding or punching.
以上、説明した本実施形態の高強度ステンレス鋼材は、フェライト相とマルテンサイト相の２相を有するため、高強度であり、しかも優れた加工性を示す。この加工性は、ＢとＴｉ、Ａｌ、Ｖの少なくとも一種以上を複合添加することで得られる。 As described above, since the high-strength stainless steel material of the present embodiment described above has two phases of a ferrite phase and a martensite phase, it has high strength and excellent workability. This workability can be obtained by composite addition of B and at least one of Ti, Al, and V.
そのメカニズムは、次のように推測している。従来の鋼材は、スラブ鋳造する際、フェライト相の粒界にはオーステナイト相やＴｉ等の炭化物が優先的に析出していた。本実施形態のステンレス鋼材は、ＢとＴｉ、Ａｌ、Ｖの少なくとも一種の元素を複合添加したものである。Ｂは、Ｃ、Ｎ、Ｓ等に比べて優先的にフェライト粒界に偏析する。このようなＢ粒界偏析は、粒界を安定化させるので、第２相の粒界析出を抑制する作用があると考えられる。そのため、第２相であるオーステナイト相は、フェライト粒界への析出が抑制され、フェライト粒内での生成が促進される。そして、炭化物を形成するＴｉ、ＡｌまたはＶを添加すると、これらの炭化物についてもフェライト粒内での生成が促進される。このように、Ｂと、Ｔｉ、Ａｌ、Ｖの少なくとも一種以上を複合添加することにより、スラブ鋳造する際、オーステナイト相やＴｉ等の炭化物は、フェライト粒界での析出が抑制されて、フェライト粒内で析出させることが可能となる。 The mechanism is presumed as follows. In conventional steel materials, when slab casting is performed, carbides such as austenite phase and Ti are preferentially precipitated at the grain boundaries of the ferrite phase. The stainless steel material of this embodiment is a composite addition of B and at least one element of Ti, Al, and V. B preferentially segregates at the ferrite grain boundaries as compared with C, N, S and the like. Such B grain boundary segregation stabilizes the grain boundary, and is therefore considered to have the effect of suppressing the grain boundary precipitation of the second phase. For this reason, the austenite phase as the second phase is prevented from being precipitated at the ferrite grain boundaries, and the generation within the ferrite grains is promoted. When Ti, Al, or V forming carbides is added, the formation of these carbides in the ferrite grains is also promoted. Thus, when slab casting is performed by adding at least one or more of B and Ti, Al, and V, the austenite phase and carbides such as Ti are suppressed from precipitation at the ferrite grain boundaries, and the ferrite grains It becomes possible to deposit in the inside.
鋳造時の冷却により、フェライト粒内のオーステナイト相は、マルテンサイト相に変化する。そして、熱延抽出前に加熱されると、その高温域では、フェライト粒内に析出していたマルテンサイト相や炭化物を核として、オーステナイト相が生成されるため、微細に分散したオーステナイト相が形成される。その後、微細分散した上記のオーステナイト相が冷却されてマルテンサイト相に変態し、微細分散したマルテンサイト相を有する金属組織が得られる。それとともに、フェライト相も分散されることとなり、金属組織の異方性が改善されると推察される。その結果、従来の異方性組織に起因して加工困難であった成形方法による加工が可能となった。また、０．２％耐力、引張強さ、伸び等の機械的特性についても、異方性の少ない素材を得ることができた。 Due to cooling during casting, the austenite phase in the ferrite grains changes to a martensite phase. And when heated before hot rolling extraction, in the high temperature range, the austenite phase is generated with the martensite phase and carbides precipitated in the ferrite grains as the core, so a finely dispersed austenite phase is formed. Is done. Thereafter, the finely dispersed austenite phase is cooled and transformed into a martensite phase, and a metal structure having a finely dispersed martensite phase is obtained. At the same time, the ferrite phase is also dispersed, and it is assumed that the anisotropy of the metal structure is improved. As a result, it became possible to perform processing by a molding method that was difficult to process due to the conventional anisotropic structure. In addition, a material with little anisotropy could be obtained with respect to mechanical properties such as 0.2% proof stress, tensile strength, and elongation.
（製造方法）
次に、本実施形態のステンレス鋼材の製造方法について説明する。本実施形態の製造方法は、ステンレス鋼材に、フェライト相とマルテンサイト相の２相組織を形成するための複相化処理を施す工程を備えている。必要成分として質量％で、Ｃ：０．０３〜０．１５％、Ｓｉ：０．１〜２．０％、Ｍｎ：０．１〜４．０％、Ｐ：０．０４％以下、Ｓ：０．０３％以下、Ｎｉ：０．０１〜４．０％、Ｃｒ：１０〜２０％、Ｍｏ：１．０％以下、Ｎ：０．１２％以下、Ｂ：０．００３〜０．０１％を含有し、Ｔｉ：０．０５〜０．２％、Ａｌ：０．０５〜０．２％、Ｖ：０．０５〜０．２％を少なくとも一種以上含有する、残部がＦｅおよび不可避的不純物からなる組成を有し、上記（１）式により計算されるγｍａｘが５０以上８５以下を満足するステンレス鋼片に対して、フェライト相とマルテンサイト相の２相組織とするための複相化処理を施すことにより、高強度であって、加工性に優れるステンレス鋼材を製造できる。
(Production method)
Next, the manufacturing method of the stainless steel material of this embodiment is demonstrated. The manufacturing method of the present embodiment includes a step of subjecting a stainless steel material to a multiphase treatment for forming a two-phase structure of a ferrite phase and a martensite phase. As necessary components in mass%, C: 0.03 to 0.15%, Si: 0.1 to 2.0%, Mn: 0.1 to 4.0%, P: 0.04% or less, S: 0.03% or less, Ni: 0.01 to 4.0%, Cr: 10 to 20%, Mo: 1.0% or less, N: 0.12% or less, B: 0.003 to 0.01% Ti: 0.05 to 0.2%, Al: 0.05 to 0.2%, V: 0.05 to 0.2%, and the balance is Fe and inevitable impurities For a stainless steel piece having a composition consisting of: γmax calculated by the above formula (1) satisfying 50 or more and 85 or less and having a two-phase structure of a ferrite phase and a martensite phase By applying this, a stainless steel material having high strength and excellent workability can be produced.
複相化処理を施す工程に用いられるステンレス鋼片は、上記特定の組成を有し、上記（１）式で表されるγｍａｘが５０〜８５であるステンレス鋼であれば、特に限定されない。所定の板厚を有するステンレス鋼であればよく、冷延板であっても熱延板であってもよく、出発素材の製造方法は、特に限定されない。例えば、連続鋳造して得られたスラブを１２００℃で加熱し、抽出する。その後、圧延率８０％の熱間圧延を行い、焼鈍と酸洗を施し、規定の厚さまで冷間圧延を行うことで得られたものでも良い。また、本実施形態の製造方法は、複相化処理を施す工程の後に、冷間加工工程を行わない場合もある。そのため、複相化処理工程の前に冷間加工を施すことが好ましい。なお、本明細書では、複相化処理工程後のステンレス鋼材と区別するために、複相化処理が施されるステンレス鋼材を、上記のように「ステンレス鋼片」と表記している。 The stainless steel piece used in the step of performing the multiphase treatment is not particularly limited as long as it has the above specific composition and γmax represented by the above formula (1) is 50 to 85. It may be stainless steel having a predetermined thickness, and it may be a cold-rolled plate or a hot-rolled plate, and the manufacturing method of the starting material is not particularly limited. For example, a slab obtained by continuous casting is heated at 1200 ° C. and extracted. Thereafter, it may be obtained by performing hot rolling at a rolling rate of 80%, annealing and pickling, and cold rolling to a specified thickness. Moreover, the manufacturing method of this embodiment may not perform a cold working process after the process of performing a multiphase process. Therefore, it is preferable to perform cold working before the multiphase process. In addition, in this specification, in order to distinguish from the stainless steel material after a multiphase process, the stainless steel material in which a multiphase process is performed is described as "stainless steel piece" as mentioned above.
また、上記ステンレス鋼片は、さらに質量％で、Ｍｏ：０．１％以下、Ｃｕ：３．０質量％以下、または、Ｎｂ：１．０質量％以下を含有してもよい。また、これらの元素の含有量は、上記（１）式のγｍａｘの範囲を満たすように選択するとよい。 Further, the stainless steel piece may further contain, by mass%, Mo: 0.1% or less, Cu: 3.0% by mass or less, or Nb: 1.0% by mass or less. Further, the content of these elements is preferably selected so as to satisfy the range of γmax in the above formula (1).
上記のステンレス鋼片は、本実施形態のステンレス鋼材として用いても良く、さらに必要に応じて、形状矯正を目的としたレベラー通板または酸洗等の公知の処理を施した後、本実施形態のステンレス鋼材として用いてもよい。 The above stainless steel piece may be used as the stainless steel material of the present embodiment, and further, if necessary, after performing a known treatment such as leveler threading or pickling for the purpose of shape correction, the present embodiment. You may use as a stainless steel material.
次に、複相化処理を施す工程において、上記のステンレス鋼片に複相化処理を施して、後の冷却によりマルテンサイト相に変態するオーステナイト相とフェライト相の２相の金属組織を生じさせる。複相化処理の条件（温度、時間）は、オーステナイト相とフェライト相の２相の金属組織を生じさせる条件であれば、特に限定されず、各元素の組成比に応じて変更することができる。例えば８００〜１２００℃の温度、１〜１０分間の均熱時間で、ステンレス鋼片に複相化処理を施してもよい。 Next, in the step of performing the multi-phase treatment, the above-mentioned stainless steel piece is subjected to the multi-phase treatment, and a two-phase metal structure of an austenite phase and a ferrite phase that are transformed into a martensite phase by subsequent cooling is generated. . The conditions (temperature, time) for the multi-phase treatment are not particularly limited as long as the two-phase metal structure of the austenite phase and the ferrite phase is generated, and can be changed according to the composition ratio of each element. . For example, the stainless steel piece may be subjected to a dual phase treatment at a temperature of 800 to 1200 ° C. and a soaking time of 1 to 10 minutes.
本実施形態の高強度ステンレス鋼材の製造方法は、上述の組成を有するステンレス鋼片に複相化処理を施すことにより、フェライト相とマルテンサイト相の２相からなる金属組織を形成できるため、高強度であって、かつ優れた加工性を有する高強度ステンレス鋼材が得られる。上記のステンレス鋼片に対して、高温域に加熱した後、冷却する複相化処理を施すことにより、高温時にオーステナイト相がフェライト粒内に微細分散されたオーステナイト相がマルテンサイト相に変態することで、微細分散されたマルテンサイト相を持った金属組織を得ることができる。そのため、金属組織の異方性が改善されると考えられる。その結果、方向に関係なく加工が可能になり、加工性が向上したと推察される。また、機械的特性（０．２％耐力、引張強さ、伸び）についても異方性が抑えられたものと推察される。 Since the manufacturing method of the high-strength stainless steel material of this embodiment can form the metal structure which consists of two phases of a ferrite phase and a martensite phase by performing the multiphase process to the stainless steel piece which has the above-mentioned composition, A high-strength stainless steel material having high strength and excellent workability can be obtained. The above austenite phase in which the austenite phase is finely dispersed in ferrite grains at a high temperature is transformed into a martensite phase by applying a dual phase treatment that is heated to a high temperature range and then cooled to the above stainless steel piece. Thus, a metal structure having a finely dispersed martensite phase can be obtained. Therefore, it is considered that the anisotropy of the metal structure is improved. As a result, processing is possible regardless of the direction, and it is presumed that workability is improved. Further, it is presumed that the anisotropy was also suppressed for the mechanical properties (0.2% proof stress, tensile strength, elongation).
以下、実施例によって本発明を更に詳細に説明するが、本発明は、これらの実施例に限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
（実施例１）
＜ステンレス鋼板の作製＞
表１に示す組成を有する鋼を３０ｋｇ真空溶解炉で溶製してインゴットを鋳造した。得られたインゴットをスラブに分塊し、そのスラブを１２００℃に３時間で加熱した後、抽出し、仕上げ温度を９２０℃で熱間圧延を施して、板厚約４．５ｍｍの熱延鋼板を得た。次いで、熱延鋼板に対して、８００℃で６時間の均熱処理を施した後、炉冷した。次いで、焼鈍処理を施し、さらに酸洗後、冷間圧延を施して、１．８ｍｍの第一の冷延板を得た。得られた第一に対して、７７０℃で１分間の焼鈍処理を施し、酸洗後、冷間圧延を施して、板厚が約１．０ｍｍの第２の冷延板を得た。
Example 1
<Production of stainless steel plate>
Steel having the composition shown in Table 1 was melted in a 30 kg vacuum melting furnace to cast an ingot. The obtained ingot is divided into slabs, the slabs are heated to 1200 ° C for 3 hours, extracted, hot-rolled at a finishing temperature of 920 ° C, and a hot-rolled steel sheet having a thickness of about 4.5 mm. Got. Next, the hot-rolled steel sheet was subjected to a soaking treatment at 800 ° C. for 6 hours and then cooled in a furnace. Next, annealing was performed, and after pickling, cold rolling was performed to obtain a 1.8 mm first cold-rolled sheet. The first obtained was annealed at 770 ° C. for 1 minute, pickled, and then cold-rolled to obtain a second cold-rolled sheet having a thickness of about 1.0 mm.
次に、第２の冷延板に、１０００℃で１分間の均熱条件で、複相化処理を施して、試験用のステンレス鋼板を得た。 Next, the second cold-rolled sheet was subjected to a dual phase treatment under a soaking condition at 1000 ° C. for 1 minute to obtain a test stainless steel sheet.
＜曲げ試験＞
得られた各鋼板を用いて、曲げ試験をＪＩＳ Ｚ ２２４８に準拠して行った。鋼板を幅３０ｍｍ（圧延方向）×長さ（６０ｍｍ板幅方向）の矩形に切削加工して試験片を作製した。先端部が０．２ｍｍＲ、９０°のＶブロック型治具の先端部に上記の試験片を押し付けて、９０°に曲げることにより、曲げ試験を行った。この曲げ試験は、曲げ稜線が圧延方向と平行になるようにして行った。曲げ試験後の鋼材表面を拡大鏡（倍率２０倍）で観察し、クラックの発生の有無を確認した。
<Bending test>
A bending test was performed according to JIS Z 2248 using each of the obtained steel plates. A steel sheet was cut into a rectangle of 30 mm width (rolling direction) × length (60 mm plate width direction) to prepare a test piece. The above test piece was pressed against the tip of a V block type jig having a tip of 0.2 mmR and 90 °, and bent to 90 ° to perform a bending test. This bending test was performed such that the bending ridge line was parallel to the rolling direction. The surface of the steel material after the bending test was observed with a magnifying glass (magnification 20 times) to confirm the presence or absence of cracks.
＜硬さ試験＞
得られた各鋼板を用いて、ＪＩＳ Ｚ−２２４０に準拠して、試験荷重３０ｋｇでビッカース硬さ（ＨＶ）を測定した。
<Hardness test>
Using each steel plate obtained, Vickers hardness (HV) was measured at a test load of 30 kg in accordance with JIS Z-2240.
表１に示すように、鋼材Ｎｏ．１〜Ｎｏ．４は、本発明の組成範囲及びγｍａｘ範囲に含まれる鋼材である。鋼材Ｎｏ．５〜Ｎｏ．９は、Ｔｉ、Ａｌ、Ｖの少なくとも１種以上、Ｂのいずれかが添加されていない鋼材である。また、鋼材Ｎｏ．１０は、γｍａｘが本発明の範囲外の鋼材である。 As shown in Table 1, the steel material No. 1-No. 4 is a steel material included in the composition range and γmax range of the present invention. Steel No. 5-No. 9 is a steel material to which at least one of Ti, Al, and V and any of B are not added. Steel No. 10 is a steel material having a γmax outside the range of the present invention.
図１に、曲げ試験後の鋼材の外観写真を示す。図１の（Ａ）が本発明例の鋼材Ｎｏ．１の外観であり、図１の（Ｂ）が比較例の鋼材Ｎｏ．５の外観である。本発明例の鋼材Ｎｏ．１ではクラックが確認されなかった。それに対し、比較例の鋼材Ｎｏ．５ではクラックが確認された。表１に、各鋼材について曲げ試験による結果を示す。クラックの発生が確認されたものを「×」、クラックの発生が確認されなかったものを「○」と評価した。 In FIG. 1, the external appearance photograph of the steel material after a bending test is shown. (A) of FIG. 1 (B) in FIG. 5 is the external appearance. Steel material No. of the present invention example. In 1, no crack was confirmed. On the other hand, the steel material No. of the comparative example. In 5, a crack was confirmed. Table 1 shows the results of the bending test for each steel material. The case where the occurrence of a crack was confirmed was evaluated as “×”, and the case where the occurrence of a crack was not confirmed was evaluated as “◯”.
表１に示すように、本発明の組成範囲及びγｍａｘ範囲に含まれる鋼材Ｎｏ．１〜鋼材Ｎｏ．４は、曲げ試験後のクラック発生がなく、良好な曲げ性（曲げ加工性）を示した。さらに、硬さの点でも２３０ＨＶ以上の高硬度を示した。それに対し、本発明の組成範囲外である比較例の鋼材Ｎｏ．５〜鋼材Ｎｏ．９は、２３０ＨＶ以上の硬さを示している。しかし、曲げ試験によりクラックが発生しており、曲げ加工性が低い。比較例の鋼材Ｎｏ．１０は、γｍａｘが５０未満の範囲にあり、硬さが低い。この結果によると、ステンレス鋼材において、Ｔｉ、Ａｌ、Ｖの少なくとも１種以上とＢが複合添加された組成とするとともに、γｍａｘを５０〜８０％とすることにより、良好な加工性と高硬度（高強度）を両立して備えたステンレス鋼材が得られることが明らかとなった。 As shown in Table 1, the steel materials No. included in the composition range and γmax range of the present invention. 1 to steel No. 1 No. 4 did not generate cracks after the bending test and showed good bendability (bending workability). Furthermore, also in terms of hardness, it showed a high hardness of 230 HV or higher. On the other hand, steel No. of the comparative example which is outside the composition range of the present invention. 5 Steel No. 9 shows a hardness of 230 HV or higher. However, cracks are generated by the bending test, and the bending workability is low. Steel No. of Comparative Example No. 10 has a γmax in the range of less than 50 and low hardness. According to this result, in the stainless steel material, at least one kind of Ti, Al, V and B are combined and B is added, and by making γmax 50 to 80%, good workability and high hardness ( It has been clarified that a stainless steel material having both high strength) can be obtained.
上記の曲げ試験は、曲げ稜線が圧延方向と平行になるようにして行った。図２に圧延された板材３を曲げるときの２種類の形態を示す。圧延された鋼板は、結晶粒が圧延方向に伸びた組織を有していることから、圧延方向と平行する方向１（本明細書では「Ｌ方向」という。）を曲げ稜線となるように曲げる形態（図２（Ａ））は、圧延方向と直交する方向２（本明細書では「Ｔ方向」という。）を曲げ稜線となるように曲げる形態（図２（Ｂ））と比べて、曲げ性に劣ると考えられる。上記の曲げ試験によると、本発明例は、図２（Ａ）の方向で曲げたときに良好な曲げ性を示した。このような試験片は、図２（Ｂ）の方向においても曲げ性に優れることが予測されることから、本発明例は、どの方向でも良好な曲げ性を有する点で曲げ加工性における異方性の少ない素材であることを確認できた。他方、比較例は、図２（Ａ）の曲げ方向ではクラックが発生し、曲げ性が不適であった。 The bending test was performed such that the bending ridge line was parallel to the rolling direction. FIG. 2 shows two types of forms when the rolled plate 3 is bent. Since the rolled steel sheet has a structure in which crystal grains extend in the rolling direction, the direction 1 parallel to the rolling direction (referred to as “L direction” in this specification) is bent so as to be a bending ridgeline. The form (FIG. 2 (A)) is bent as compared with the form (FIG. 2 (B)) in which the direction 2 (referred to as “T direction” in this specification) orthogonal to the rolling direction is bent to form a bending ridgeline. It is considered to be inferior. According to the above bending test, the inventive example showed good bendability when bent in the direction of FIG. Since such a test piece is expected to be excellent in bendability in the direction of FIG. 2B, the present invention example is anisotropic in bending workability in that it has good bendability in any direction. It was confirmed that the material was less prone. On the other hand, in the comparative example, cracks occurred in the bending direction of FIG.
（実施例２）
表２に示す組成を有する鋼を用いた。本発明例の鋼材Ｎｏ．１１は、ＡｌとＢを複合添加した例であり、比較例の鋼材Ｎｏ．１２は、Ａｌの単独添加の例である。両者の鋼材におけるγｍａｘが同程度となるようにＮｉ含有量を調整した。鋳造後のスラブ加熱温度として、実施例１と同様の手順で、複相化処理が施されたステンレス鋼板を得た。加熱時間は、３時間である。（ａ）鋳造後のインゴット（ａｓ ｃａｓｔ材）、（ｂ）加熱後の抽出スラブ（熱延前抽出材）、（ｃ）複相化処理が施された鋼板（複相化処理材）、のそれぞれからサンプルを採取した。
(Example 2)
Steel having the composition shown in Table 2 was used. Steel material No. of the present invention example. 11 is an example in which Al and B are added in combination. 12 is an example of adding Al alone. The Ni content was adjusted so that the γmax in both steel materials would be comparable. As a slab heating temperature after casting, a stainless steel plate subjected to duplexing treatment was obtained in the same procedure as in Example 1. The heating time is 3 hours. (A) Ingot after casting (as cast material), (b) Extracted slab after heating (extracted material before hot rolling), (c) Steel plate subjected to duplexing treatment (multiphased treated material) Samples were taken from each.
＜引張試験＞
得られたステンレス鋼板を用いて、ＪＩＳ１３号Ｂ引張試験片を採取した。引張り試験片は、圧延方向（Ｌ方向）を引張方向とするとき、圧延方向と直交する方向（Ｔ方向）を引張方向とするときの２種類の試験片を用意した。ＪＩＳ Ｚ ２２４１に準拠して、引張り試験を実施し、Ｌ方向およびＴ方向における、０．２％耐力（Ｎ／ｍｍ２）、引張強さ（Ｎ／ｍｍ２）、伸び（％）を求めた。また、実施例１と同様の硬さ試験により、ビッカース硬さ（ＨＶ）を求めた。得られた結果を表３に示す。異方性に関しては、Ｔ方向の数値とＬ方向の数値との比（Ｔ／Ｌ）により示す。
<Tensile test>
A JIS No. 13 B tensile test piece was collected using the obtained stainless steel plate. As the tensile test piece, two types of test pieces were prepared when the rolling direction (L direction) was the tensile direction and the direction perpendicular to the rolling direction (T direction) was the tensile direction. In accordance with JIS Z 2241, a tensile test was performed, and 0.2% proof stress (N / mm 2 ), tensile strength (N / mm 2 ), and elongation (%) in the L direction and the T direction were obtained. . Moreover, the Vickers hardness (HV) was calculated | required by the hardness test similar to Example 1. FIG. The obtained results are shown in Table 3. The anisotropy is indicated by the ratio (T / L) between the numerical value in the T direction and the numerical value in the L direction.
表３に示すように、本発明例は、比較例に比べて、引張強さおよび硬さがほぼ同じであり、高い強度を維持している。さらに、０．２％耐力、引張強さ、伸びといった機械的特性について、Ｔ方向とＬ方向との数値比をみると、本発明例は、１．０に近い範囲にあり、圧延方向による異方性が抑制されていた。それに対し、比較例は、Ｔ方向とＬ方向との数値比が１．０より離れて範囲にあり、機械的性質における異方性が大きいことが分かる。 As shown in Table 3, the examples of the present invention have substantially the same tensile strength and hardness as compared with the comparative examples, and maintain high strength. Further, regarding the mechanical characteristics such as 0.2% proof stress, tensile strength, and elongation, the numerical value ratio between the T direction and the L direction shows that the example of the present invention is in a range close to 1.0 and varies depending on the rolling direction. The directionality was suppressed. On the other hand, in the comparative example, the numerical ratio between the T direction and the L direction is in a range away from 1.0, indicating that the anisotropy in mechanical properties is large.
＜金属組織の観察＞
サンプルの表面をフッ酸と硝酸の混合液でエッチングして、金属顕微鏡で組織を観察した。観察した写真を図３に示す。
<Observation of metal structure>
The surface of the sample was etched with a mixed solution of hydrofluoric acid and nitric acid, and the structure was observed with a metal microscope. The observed photograph is shown in FIG.
本発明例の鋼材Ｎｏ．１１は、ＡｌとＢを複合添加した例であり、比較例の鋼材Ｎｏ．１２は、Ａｌの単独添加の例である。両者の鋼材におけるγｍａｘが同程度となるようにＮｉ含有量を調整した。図３において、白色部分がフェライト相を示し、黒色部分がマルテンサイト相を示す。ａｓ ｃａｓｔ材の段階で、本発明例は、比較例と比べて、フェライト粒内にマルテンサイト相や炭化物が析出した組織を形成していた。さらに、その後の所定の加熱が施された熱延前抽出材と複相化処理材は、ａｓ ｃａｓｔ材における上記の析出組織に影響され、マルテンサイト相が微細分散された組織を呈していた。この結果からＡｌとＢとの複合添加により微細分散したマルテンサイト相と微細なフェライト相からなる２相組織が得られることを確認できた。このような微細組織が形成されることで、高強度を維持したまま、加工性における異方性が改善されたと考えられる。 Steel material No. of the present invention example. 11 is an example in which Al and B are added in combination. 12 is an example of adding Al alone. The Ni content was adjusted so that the γmax in both steel materials would be comparable. In FIG. 3, a white part shows a ferrite phase and a black part shows a martensite phase. At the stage of the as cast material, the inventive example formed a structure in which the martensite phase and carbides were precipitated in the ferrite grains, as compared with the comparative example. Furthermore, the pre-hot-rolling extraction material and the multiphase-treated material subjected to subsequent predetermined heating were affected by the above-described precipitation structure in the as cast material, and exhibited a structure in which the martensite phase was finely dispersed. From this result, it was confirmed that a two-phase structure composed of a finely dispersed martensite phase and a fine ferrite phase was obtained by the combined addition of Al and B. By forming such a fine structure, it is considered that anisotropy in workability was improved while maintaining high strength.
本発明によれば、高い強度を維持したまま、加工性を改善でき、さらにコストを抑えた高強度ステンレス鋼を提供することができる。 According to the present invention, it is possible to provide high-strength stainless steel that can improve workability while maintaining high strength and further reduce costs.
１ Ｌ方向
２ Ｔ方向
３ 板材
1 L direction 2 T direction 3 Plate material
Claims (6)
フェライト相とマルテンサイト相の２相の金属組織を有し、下記（１）式により計算されるγｍａｘ（％）が５０以上８５以下を満足する、加工性に優れる高強度ステンレス鋼材。
γｍａｘ（％）＝４２０×〔Ｃ〕−１１．５×〔Ｓｉ〕＋７×〔Ｍｎ〕＋２３×〔Ｎｉ〕−１１．５×〔Ｃｒ〕−１２×〔Ｍｏ〕＋９×〔Ｃｕ〕−４９×〔Ｔｉ〕−５２×〔Ａｌ〕＋４７０×〔Ｎ〕＋１８９・・・（１）
（ここで〔 〕は、元素の質量％を示す） In mass%, C: 0.03-0.15%, Si: 0.1-2.0%, Mn: 0.1-4.0%, P: 0.04% or less, S: 0.03 %: Ni: 0.01-4.0%, Cr: 10-20%, N: 0.12% or less, B: 0.003-0.01 %, Al : 0.05-0.2 % the has free and the balance being a stainless steel having a composition consisting of Fe and unavoidable impurities,
A high-strength stainless steel material having excellent workability, having a two-phase metal structure of a ferrite phase and a martensite phase, and satisfying γmax (%) calculated by the following formula (1) of 50 to 85.
γmax (%) = 420 × [C] −11.5 × [Si] + 7 × [Mn] + 23 × [Ni] −11.5 × [Cr] −12 × [Mo] + 9 × [Cu] −49 × [Ti] −52 × [Al] + 470 × [N] +189 (1)
(Where [] indicates the mass% of the element)
γｍａｘ（％）＝４２０×〔Ｃ〕−１１．５×〔Ｓｉ〕＋７×〔Ｍｎ〕＋２３×〔Ｎｉ〕−１１．５×〔Ｃｒ〕−１２×〔Ｍｏ〕＋９×〔Ｃｕ〕−４９×〔Ｔｉ〕−５２×〔Ａｌ〕＋４７０×〔Ｎ〕＋１８９・・・（１）
（ここで〔 〕は、元素の質量％を示す） In mass%, C: 0.03-0.15%, Si: 0.1-2.0%, Mn: 0.1-4.0%, P: 0.04% or less, S: 0.03 %: Ni: 0.01-4.0%, Cr: 10-20%, N: 0.12% or less, B: 0.003-0.01 %, Al : 0.05-0.2 % the has free and the balance has a composition consisting of Fe and unavoidable impurities, to a stainless steel piece γmax which is calculated by the following equation (1) (%) satisfies more than 50 85 or less, the ferrite phase and martensite phase A method for producing a high-strength stainless steel material excellent in workability, comprising a step of performing a multi-phase treatment for obtaining a two-phase structure.
γmax (%) = 420 × [C] −11.5 × [Si] + 7 × [Mn] + 23 × [Ni] −11.5 × [Cr] −12 × [Mo] + 9 × [Cu] −49 × [Ti] −52 × [Al] + 470 × [N] +189 (1)
(Where [] indicates the mass% of the element)
Furthermore, the mass which is excellent in workability of Claim 4 or 5 which contains at least 1 sort (s) of Mo : 1.0% or less , Cu: 3.0% or less, and Nb: 1.0% or less by mass%. A manufacturing method of high strength stainless steel.
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| JP6806116B2 (en) * | 2018-08-24 | 2021-01-06 | 日立金属株式会社 | Foil for negative electrode current collector of secondary battery |
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