JP2016169421A - Austenitic stainless steel excellent in stress corrosion cracking resistance - Google Patents
Austenitic stainless steel excellent in stress corrosion cracking resistance Download PDFInfo
- Publication number
- JP2016169421A JP2016169421A JP2015050441A JP2015050441A JP2016169421A JP 2016169421 A JP2016169421 A JP 2016169421A JP 2015050441 A JP2015050441 A JP 2015050441A JP 2015050441 A JP2015050441 A JP 2015050441A JP 2016169421 A JP2016169421 A JP 2016169421A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- stress corrosion
- mass
- corrosion cracking
- stainless steel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Abstract
Description
本発明は、加工性、耐食性及び耐応力腐食割れ性に優れた低Ｎｉ高Ｍｎ型のオーステナイト系ステンレス鋼に関する。 The present invention relates to a low Ni high Mn type austenitic stainless steel excellent in workability, corrosion resistance and stress corrosion cracking resistance.
ＳＵＳ３０４を代表とするオーステナイト系ステンレス鋼は、加工性や耐食性に優れるため、様々な用途で幅広く利用されているが、Ｎｉを多く含むため高価であるのに加え、応力腐食割れがしばしば問題となっていた。
このため、従来より、安価で耐応力腐食割れ性に優れた高マンガン型のオーステナイト系ステンレス鋼について数々の提案がなされている。
例えば、下記の特許文献１には、上記の応力腐食割れ対策として、１．０〜３．５質量％のＣｕと複合添加された２．０〜４．０質量％のＳｉに加え、１６．０〜１８．０質量％のＣｒが添加され、ＳＵＳ４３０よりも良好な機械的性質を備えた耐応力腐食割れ性に優れた低Ｎｉオーステナイト系ステンレス鋼材が開示されている。
また、下記の特許文献２には、Ｎｉを０．０１〜１．０質量％に節減し、Ｃｒを１４〜２５質量％含む耐応力腐食割れ性に優れた高マンガン型のステンレス鋼が開示されている。
さらに、下記の特許文献３ではＣ＋Ｎ：０．１５〜０．３質量％、Ｃｕ:０．８〜４質量％、Ｍｎ:０．５〜２．５質量％、Ｃｒ:１６超〜２５質量％を含んだ良好な加工性、耐時期割れ性、耐食性及び耐応力腐食割れ性を兼ね備えたＮｉ節減型オーステナイト系ステンレス鋼が開示されている。
Austenitic stainless steel represented by SUS304 is widely used in various applications because of its excellent workability and corrosion resistance. However, it is expensive because it contains a large amount of Ni, and stress corrosion cracking is often a problem. It was.
For this reason, many proposals have been made on high manganese type austenitic stainless steels which are inexpensive and have excellent stress corrosion cracking resistance.
For example, in the following Patent Document 1, as a countermeasure against the above-described stress corrosion cracking, in addition to 2.0 to 4.0% by mass of Si added in combination with 1.0 to 3.5% by mass of Cu, 16. A low Ni austenitic stainless steel material excellent in stress corrosion cracking resistance having 0 to 18.0% by mass of Cr and having better mechanical properties than SUS430 is disclosed.
Patent Document 2 listed below discloses a high manganese type stainless steel that has excellent stress corrosion cracking resistance and contains 14 to 25% by mass of Cr with Ni reduced to 0.01 to 1.0% by mass. ing.
Furthermore, in the following Patent Document 3, C + N: 0.15 to 0.3 mass%, Cu: 0.8 to 4 mass%, Mn: 0.5 to 2.5 mass%, Cr: more than 16 to 25 mass% Ni-saving austenitic stainless steels having good workability, time cracking resistance, corrosion resistance, and stress corrosion cracking resistance, including steel are disclosed.
上述のように、Ｎｉを節減したオーステナイト系ステンレス鋼に関しては、Ｎｉの代替元素となるＭｎ、Ｃｕ、Ｎなどのオーステナイト相安定化元素の配合割合を調節した数々の技術が開示されているが、加工性及び耐食性と耐応力腐食割れ性とを高いレベルで両立できた例はほとんどなく、耐応力腐食割れ性向上のためにオーステナイト系ステンレス鋼の特徴である優れた加工性や耐食性の何れかが犠牲になっているのが実情である。 As described above, regarding austenitic stainless steel with reduced Ni, a number of techniques are disclosed in which the blending ratio of austenite phase stabilizing elements such as Mn, Cu, and N, which are substitute elements for Ni, is adjusted. There are very few examples where workability, corrosion resistance, and stress corrosion cracking resistance can be achieved at a high level. The reality is that you are sacrificed.
それゆえに、本発明の主たる課題は、経済的に鋼を生産するため、Ｎｉを極めて低い含有割合に抑制できるにも係わらず、フェライト系ステンレスであるＳＵＳ４３０にも匹敵するような機械的性質や加工性を有すると共に、ＳＵＳ３０４よりも優れた耐応力腐食割れ性を有するオーステナイト系ステンレス鋼を提供することである。 Therefore, the main problem of the present invention is to produce steel economically, and although it is possible to suppress Ni to a very low content ratio, mechanical properties and processing comparable to SUS430, which is a ferritic stainless steel. And austenitic stainless steel having stress corrosion cracking resistance superior to that of SUS304.
発明者らは、前記課題を解決するため、Ｃｒを１６質量％以上含む省Ｎｉ型のオーステナイト系ステンレス鋼について、様々な環境下で各合金元素が鋼の耐応力腐食割れ性に及ぼす影響を丹念に調査した結果、オーステナイト相を安定させる元素であるＮｉとＣｕの影響が他の元素と比べ著しく大きく、その含有量をＮｉ％＋Ｃｕ％≦４．７に制限することにより、耐応力腐食割れ性がＳＵＳ３０４より優れたものになることを見出し、以下に示す発明を完成するに至った。
すなわち、本発明は、
（ａ）質量％で、Ｃ：０．０６〜０．１０％、Ｓｉ：１．０％以下、Ｍｎ：９．０〜１０．５％、Ｐ：０．０５０％以下、Ｓ：０．０１０％以下、Ｎｉ：２．０〜３．０％、Ｃｒ：１６．０超〜１８．０％、Ｍｏ：０．２０％以下、Ｃｕ：０．５〜１．５％、Ｎ：０．１４〜０．２０％を含有し、残部がＦｅおよび不可避不純物からなり、
（ｂ）下記（１）式を満たすと共に、
Ｎｉ％+２Ｃｕ％≦４．７ …（１）
（ｃ）下記（２）式で定義されるＭｄ30（Ｍｎ）が−３５以下である、
Ｍｄ30（Ｍｎ）＝５５１−４６２([Ｃ％]＋[Ｎ％])−９．２[Ｓｉ％]−１９．１[Ｍｎ％]−１３．７[Ｃｒ％]−２９([Ｎｉ％]＋[Ｃｕ％])−１８．５[Ｍｏ％] …（２）
（ｄ）ことを特徴とする耐応力腐食割れ性に優れたオーステナイト系ステンレス鋼、である。
ここで、本明細書全般において「Ｎｉ％」や「Ｃｕ％」のように「元素記号＋％」で表したものは「鋼中における当該元素記号で表される元素の成分組成（配合割合）を質量％で表したもの」を意味する。
In order to solve the above-mentioned problems, the inventors have carefully considered the influence of each alloying element on the stress corrosion cracking resistance of steel in various environments for Ni-saving austenitic stainless steel containing 16 mass% or more of Cr. As a result, the influence of Ni and Cu, which are elements that stabilize the austenite phase, is remarkably larger than other elements, and the content is limited to Ni% + Cu% ≦ 4.7. Was found to be superior to SUS304, and the present invention shown below was completed.
That is, the present invention
(A) By mass%, C: 0.06 to 0.10%, Si: 1.0% or less, Mn: 9.0 to 10.5%, P: 0.050% or less, S: 0.010 %: Ni: 2.0 to 3.0%, Cr: more than 16.0 to 18.0%, Mo: 0.20% or less, Cu: 0.5 to 1.5%, N: 0.14 Containing ~ 0.20%, the balance consisting of Fe and inevitable impurities,
(B) While satisfying the following formula (1),
Ni% + 2Cu% ≦ 4.7 (1)
(C) Md 30 (Mn) defined by the following formula (2) is −35 or less,
Md 30 (Mn) = 551-462 ([C%] + [N%]) − 9.2 [Si%] − 19.1 [Mn%] − 13.7 [Cr%] − 29 ([Ni% ] + [Cu%]-18.5 [Mo%] (2)
(D) an austenitic stainless steel excellent in stress corrosion cracking resistance, characterized in that
Here, what is represented by “element symbol +%” such as “Ni%” and “Cu%” throughout this specification is “component composition (mixing ratio) of the element represented by the element symbol in steel” Is expressed in mass%.
この発明では、高価なＮｉの成分組成を２．０〜３．０質量％の範囲内に抑えているので、オーステナイト系ステンレス鋼を経済的に製造することができる。
また、Ｃｒを１６．０超〜１８．０質量％含有するので、汎用的な耐食性を維持できるのに加え、ＮｉとＣｕの成分組成に関し、Ｎｉ％＋２Ｃｕ％を４．７以下に制限しているので、耐応力腐食割れ性をＳＵＳ３０４より優れたものにすることができる。
さらに、鋼の伸びと云った加工性を示す指標や機械的性質等との間に相関があるＭｄ30（Ｍｎ）値を−３５以下にしているので、得られる鋼はＳＵＳ４３０に匹敵する加工性並びに機械的性質を有するものとなる。
In this invention, since the expensive Ni component composition is suppressed within the range of 2.0 to 3.0 mass%, austenitic stainless steel can be produced economically.
Moreover, since Cr is contained more than 16.0 to 18.0% by mass, in addition to maintaining general-purpose corrosion resistance, Ni% + 2Cu% is limited to 4.7 or less with respect to the component composition of Ni and Cu. Therefore, the stress corrosion cracking resistance can be made superior to SUS304.
Furthermore, since the Md 30 (Mn) value correlated with an index indicating the workability such as elongation of steel and mechanical properties is set to −35 or less, the obtained steel has workability comparable to SUS430. In addition, it has mechanical properties.
本発明によれば、経済的に鋼を生産するため、Ｎｉを３質量％以下といった極めて低い含有割合に抑制できるにも係わらず、フェライト系ステンレスであるＳＵＳ４３０にも匹敵する機械的性質や加工性を有すると共に、ＳＵＳ３０４よりも優れた耐応力腐食割れ性を有するオーステナイト系ステンレス鋼を提供することができる。 According to the present invention, in order to economically produce steel, the mechanical properties and workability comparable to SUS430, which is a ferritic stainless steel, although Ni can be suppressed to an extremely low content ratio of 3% by mass or less. An austenitic stainless steel having stress corrosion cracking resistance superior to that of SUS304 can be provided.
まず始めに、本発明に係る「耐応力腐食割れ性に優れたオーステナイト系ステンレス鋼」(以下、単に「鋼」とも称する。)を構成する各成分の限定理由について説明する。 First, the reasons for limitation of each component constituting the “austenitic stainless steel excellent in stress corrosion cracking resistance” (hereinafter also simply referred to as “steel”) according to the present invention will be described.
１）０．０６≦Ｃ≦０．１０質量％
Ｃ（炭素）は、耐応力腐食割れ性に対して悪影響を及ぼす元素であるが、０．１０質量％以下ならば他元素と比べてその影響は無視できるほど小さい。また、このＣは、オーステナイト形成元素であり、オーステナイト組織の安定化に寄与するため、必須のものであるが、過剰に添加すると、固溶強化により鋼の硬度が増して冷間加工性を低下させる。このため、Ｃの含有率（成分組成）を０．０６〜０．１０質量％の範囲とした。
1) 0.06 ≦ C ≦ 0.10 mass%
C (carbon) is an element that adversely affects the stress corrosion cracking resistance, but if it is 0.10% by mass or less, the influence is negligible compared to other elements. This C is an austenite forming element and is essential because it contributes to the stabilization of the austenite structure. However, when added in excess, the hardness of the steel increases due to solid solution strengthening and decreases the cold workability. Let For this reason, the content rate (component composition) of C was made into the range of 0.06-0.10 mass%.
２）Ｓｉ≦１．０質量％
Ｓｉ（ケイ素）は、一般に耐応力腐食割れ性の向上に有効な元素とされているが、高Ｍｎ型オーステナイト系ステンレス鋼の耐応力腐食割れ性には大きな影響を及ぼさない。また、製鋼時において脱酸剤としての効果を奏する元素であるが、鋼の軟質性(加工性)を維持するためには、その含有率がある程度低い方が好ましい。このため上記のように１．０質量％以下（より好ましくは０．６質量％以下）に制限した。
2) Si ≦ 1.0 mass%
Si (silicon) is generally regarded as an element effective for improving the stress corrosion cracking resistance, but does not greatly affect the stress corrosion cracking resistance of the high Mn type austenitic stainless steel. Further, it is an element that exerts an effect as a deoxidizer during steelmaking. However, in order to maintain the softness (workability) of the steel, it is preferable that its content is low to some extent. For this reason, it limited to 1.0 mass% or less (more preferably 0.6 mass% or less) as mentioned above.
３）９．０≦Ｍｎ≦１０．５質量％
Ｍｎ（マンガン）は、耐応力腐食割れ性に悪影響を与えるが、その効果は５質量％ほどで飽和し、それ以上含有させても悪影響を及ぼさなくなる。また、このＭｎは、オーステナイト形成元素であると共に、Ｎの固溶量を高めるため、鋼の軟質化には好ましい元素である。しかしながら、このＭｎの含有量が高すぎると製造性や鋼の耐食性を低下させる恐れがある。このため、Ｍｎの含有率を９．０〜１０．５質量％の範囲とした。
3) 9.0 ≦ Mn ≦ 10.5% by mass
Mn (manganese) adversely affects the stress corrosion cracking resistance, but the effect is saturated at about 5% by mass, and even if it is contained more than it does not have an adverse effect. Further, Mn is an austenite forming element and is a preferable element for softening steel because it increases the solid solution amount of N. However, if the Mn content is too high, the productivity and the corrosion resistance of the steel may be reduced. For this reason, the content rate of Mn was made into the range of 9.0-10.5 mass%.
４）Ｐ≦０．０５０質量％
Ｐ（リン）は、耐応力腐食割れ性には悪影響を与える元素であるが、０．０５０質量％以下ならば、他元素と比べてその影響は無視できるほど小さい。また、このＰは、鋼の耐食性および熱間加工性を劣化させる元素であることから、その上限を０．０５０質量％とした。
4) P ≦ 0.050 mass%
P (phosphorus) is an element that adversely affects the stress corrosion cracking resistance, but if it is 0.050 mass% or less, the influence is negligible compared to other elements. Moreover, since this P is an element which degrades the corrosion resistance and hot workability of steel, the upper limit was made 0.050 mass%.
５）Ｓ≦０．０１０質量％
Ｓ（硫黄）は、耐応力腐食割れ性に影響を及ぼさない。しかしながら、このＳは、介在物を増加させると共に、鋼の耐発銹性を低下させる要因となる元素である。また、Ｓの含有率の増加と共に鋼の熱間加工性および耐食性を低下させることから、このＳの含有率を０．０１０質量％以下に制限した。
5) S ≦ 0.010 mass%
S (sulfur) does not affect the stress corrosion cracking resistance. However, this S is an element that increases inclusions and decreases the resistance to galling of steel. Moreover, since the hot workability and corrosion resistance of steel were reduced with the increase in the S content, the S content was limited to 0.010 mass% or less.
６）２．０≦Ｎｉ≦３．０質量％
Ｎｉ（ニッケル）は、オーステナイト組織の安定化や良好な熱間加工性、冷間加工性および耐食性等に寄与する元素であるが，高Ｍｎ型のオーステナイト系ステンレス鋼においては、耐応力腐食性に対して非常に大きな悪影響を及ぼす元素である。したがって、オーステナイト組織の安定化や良好な加工性、耐食性を得るために、Ｎｉの含有率を２．０〜３．０質量％の範囲とする一方で、耐応力腐食割れ性に関しては、上記（１）式、すなわち、Ｎｉ％＋２Ｃｕ％≦４．７で規制することとした。
6) 2.0 ≦ Ni ≦ 3.0 mass%
Ni (nickel) is an element that contributes to stabilization of the austenite structure and good hot workability, cold workability, corrosion resistance, etc., but in high Mn type austenitic stainless steels, it has high stress corrosion resistance. On the other hand, it is an element that has a very large adverse effect. Therefore, in order to stabilize the austenite structure and to obtain good workability and corrosion resistance, the Ni content is in the range of 2.0 to 3.0% by mass. It was decided to regulate by 1) Formula, ie, Ni% + 2Cu% ≦ 4.7.
７)１６．０＜Ｃｒ≦１８．０質量％
Ｃｒ(クロム)は、鋼の耐食性を高めるのにもっとも有効な元素のひとつであり、十分な耐食性を得るためには１６．０質量％超のＣｒ含有量が必要である。しかし、鋼にクロムが多量に含有されると、凝固時および高温域において、多くのδフェライトが生成され、鋼の硬さが増加してオーステナイト単相を維持できなくなる。よって、Ｃｒ含有率の上限を１８．０質量％とした。
7) 16.0 <Cr ≦ 18.0% by mass
Cr (chromium) is one of the most effective elements for enhancing the corrosion resistance of steel, and in order to obtain sufficient corrosion resistance, a Cr content exceeding 16.0 mass% is required. However, if the steel contains a large amount of chromium, a large amount of δ ferrite is generated at the time of solidification and in a high temperature range, the hardness of the steel increases, and the austenite single phase cannot be maintained. Therefore, the upper limit of the Cr content is set to 18.0% by mass.
８）Ｍｏ≦０．２０質量％
Ｍｏ（モリブデン）は、鋼の耐食性を向上させることができる元素であるが、Ｍｏの含有によって凝固時および高温域において、多くのδフェライトが生成され、鋼の熱間加工性を低下させる虞がある。したがって、鋼の熱間加工性の低下を抑えつつ鋼の耐食性を向上させることができるようにするため、Ｍｏ含有量の上限を０．２０質量％とした。
8) Mo ≦ 0.20 mass%
Mo (molybdenum) is an element that can improve the corrosion resistance of steel, but the inclusion of Mo may generate a lot of δ ferrite at the time of solidification and in a high temperature range, which may reduce the hot workability of the steel. is there. Therefore, the upper limit of the Mo content is set to 0.20 mass% so that the corrosion resistance of the steel can be improved while suppressing the decrease in hot workability of the steel.
９）０．５≦Ｃｕ≦１．５％
Ｃｕ（銅）は、Ｎｉと同様、鋼の軟質化および耐食性の向上に寄与する元素であるが、高Ｍｎ型のオーステナイト系ステンレス鋼においては、耐応力腐食性に非常に大きな悪影響を及ぼす元素である。したがって、鋼の軟質化および耐食性の向上のために、Ｃｕの含有率を０．５〜１．５質量％の範囲とした。一方、耐応力腐食割れ性に関しては、上記（１）式、すなわち、Ｎｉ％＋２Ｃｕ％≦４．７で規制することとした。
9) 0.5 ≦ Cu ≦ 1.5%
Like Ni, Cu (copper) is an element that contributes to softening of steel and improvement of corrosion resistance. However, in high Mn type austenitic stainless steel, it is an element that has a very large adverse effect on stress corrosion resistance. is there. Therefore, in order to soften the steel and improve the corrosion resistance, the Cu content is set in the range of 0.5 to 1.5 mass%. On the other hand, the stress corrosion cracking resistance is regulated by the above formula (1), that is, Ni% + 2Cu% ≦ 4.7.
１０）０．１４≦Ｎ≦０．２０質量％
Ｎ（窒素）は、Ｃと同様にオーステナイト形成元素であり、オーステナイト組織の安定化に寄与すると共に、耐食性に対しても有効に作用する。しかしながら、炭素と同様に固溶強化能が大きいことから、鋼に多量に含まれると固溶強化により鋼の硬さが増す。このため、Ｎの含有率を０．１４〜０．２０質量％の範囲とした。
10) 0.14 ≦ N ≦ 0.20 mass%
N (nitrogen) is an austenite-forming element like C and contributes to the stabilization of the austenite structure and also effectively acts on corrosion resistance. However, since the solid solution strengthening ability is large like carbon, the hardness of the steel increases due to the solid solution strengthening when contained in a large amount in the steel. For this reason, the content rate of N was made into the range of 0.14-0.20 mass%.
１１）Ｍｄ30（Ｍｎ）≦−３５
Ｍｄ30（Ｍｎ）値は、オーステナイト系ステンレス鋼を加工した際に生じる加工誘起マルテンサイト(α’)変態のし易さを表す指標で、上記（２）式、すなわち、
Ｍｄ30（Ｍｎ）＝５５１−４６２（[Ｃ％]＋[Ｎ％]）−９．２[Ｓｉ％]−１９．１[Ｍｎ％]−１３．７[Ｃｒ％]−２９（[Ｎｉ％]＋[Ｃｕ％]）−１８．５[Ｍｏ％] に従って求められる。
この値が大きいほど、加工誘起マルテンサイト(α’)変態が生じ易い。つまり、Ｍｄ30（Ｍｎ）値が大きいと、圧延時に多量の加工誘起マルテンサイト(α’)相が生じ、調質圧延板の加工性が低下すると共に、圧延後のコイル形態における時期割れ懸念が高まるため、Ｍｄ30（Ｍｎ）≦−３５とした。
11) Md 30 (Mn) ≦ −35
The Md 30 (Mn) value is an index that represents the ease of processing-induced martensite (α ′ ) transformation that occurs when austenitic stainless steel is processed.
Md 30 (Mn) = 551-462 ([C%] + [N%]) − 9.2 [Si%] − 19.1 [Mn%] − 13.7 [Cr%] − 29 ([Ni% ] + [Cu%])-18.5 [Mo%].
The larger this value, the easier the processing-induced martensite (α ′ ) transformation occurs. In other words, if the Md 30 (Mn) value is large, a large amount of work-induced martensite (α ′ ) phase is generated during rolling, the workability of the temper rolled sheet is lowered, and there is a concern about time cracking in the coil form after rolling. Therefore, Md 30 (Mn) ≦ −35.
以上のような各元素で構成された本発明に係る鋼は、一般的なステンレス鋼製造工程により製造される。すなわち、溶解、鋳造、熱間圧延および冷間圧延を経た後、溶体化熱処理が行われる。そして、各種素材として要求される特性を得るため、冷間加工(調質圧延)が施され、所望の硬さに調質される。 The steel according to the present invention composed of the elements as described above is manufactured by a general stainless steel manufacturing process. That is, solution heat treatment is performed after melting, casting, hot rolling and cold rolling. And in order to acquire the characteristic requested | required as various raw materials, cold processing (temper rolling) is given and it refines to desired hardness.
以下に、本発明に係る実施例として、鋼試料の製造方法、試験の方法および結果について説明する。なお、本発明は当該実施例に限定されるものではない。 Below, the manufacturing method of a steel sample, the method of a test, and a result are demonstrated as an Example based on this invention. In addition, this invention is not limited to the said Example.
１）鋼試料の作製
下表１に示す化学組成を有するステンレス鋼を溶製し、熱間圧延にて板厚３．０ｍｍの熱延板を作製した。続いて、この熱延板を板厚１．０ｍｍまで冷間圧延し、２分間１１００℃で仕上焼鈍した後、硝弗酸に浸漬してスケールを除去して、本発明鋼及び比較鋼である冷延焼鈍酸洗板を得た。そして、得られた本発明鋼及び比較鋼を下記の特性評価試験に供した。
1) Preparation of steel sample Stainless steel having the chemical composition shown in Table 1 below was melted, and a hot rolled sheet having a thickness of 3.0 mm was manufactured by hot rolling. Subsequently, this hot-rolled sheet is cold-rolled to a thickness of 1.0 mm, subjected to finish annealing at 1100 ° C. for 2 minutes, and then dipped in nitric hydrofluoric acid to remove the scale. A cold-rolled annealed pickled plate was obtained. The obtained inventive steel and comparative steel were subjected to the following characteristic evaluation test.
２）試験の方法とその結果
（１）応力腐食割れ試験１
前述の工程で作製した発明鋼及び比較鋼となる冷延焼鈍酸洗板の中心部より厚さ１．０ｍｍ，幅１５ｍｍ，長さ７５ｍｍの試験片を採取し、ＪＩＳ Ｇ ０５７６に準拠してＵベンド試験片を作製した。
続いて、このＵベンド試験片の頂点部分に５μｌ×６滴の試験溶液を滴下し、恒温・恒湿槽の中に入れ、温度４０℃，相対湿度３０％の条件で４週間保持した。なお、試験溶液として、人工海水（八洲薬品(株)製の金属腐食試験用アクアマリン）を用いた。
そして、上記の保持の後、走査型電子顕微鏡を用いて割れの有無を観察した。得られた結果を表２に示す。なお、表２では、上記の観察の結果、割れが発生していたものは×印で、又、割れが生じなかったものは○印で表示している。
2) Test method and results (1) Stress corrosion cracking test 1
A test piece having a thickness of 1.0 mm, a width of 15 mm, and a length of 75 mm was taken from the center of the cold rolled annealed pickling plate to be the inventive steel and comparative steel produced in the above-described process, and U in accordance with JIS G 0576. A bend test piece was prepared.
Subsequently, 5 μl × 6 drops of the test solution was dropped onto the apex portion of the U-bend test piece, placed in a constant temperature / humidity bath, and maintained for 4 weeks under conditions of a temperature of 40 ° C. and a relative humidity of 30%. In addition, artificial seawater (Aquamarine for metal corrosion test manufactured by Yashima Pharmaceutical Co., Ltd.) was used as a test solution.
And after said holding | maintenance, the presence or absence of the crack was observed using the scanning electron microscope. The obtained results are shown in Table 2. In Table 2, as a result of the above observation, cracks are indicated by “x” marks, and those without cracks are indicated by “◯” marks.
（２）応力腐食割れ試験２
ＪＩＳ Ｇ ０５７６の（Ａ）法ｂに準拠して、沸騰４２％塩化マグネシウム溶液中に、上記「（１）応力腐食割れ試験１」と同じ方法で採取したＵベンド試験片を２４時間浸漬させて、耐応力腐食割れ性の評価を実施した。得られた結果を表２に示す。なお、表２では、上記の浸漬の結果、２４時間以内に割れが発生したものは×印で、又、割れが生じなかったものは○印で表示している。
(2) Stress corrosion cracking test 2
In accordance with JIS G 0576 (A) method b, a U-bend specimen taken in the same manner as in “(1) Stress corrosion cracking test 1” was immersed in a boiling 42% magnesium chloride solution for 24 hours. The stress corrosion cracking resistance was evaluated. The obtained results are shown in Table 2. In Table 2, the case where cracks occurred within 24 hours as a result of the above immersion is indicated by x, and the case where no cracks occurred is indicated by ○.
（３）ビッカース硬さ
前述の工程で作製した発明鋼及び比較鋼となる冷延焼鈍酸洗板から、厚さ１．０×３０×３０ｍｍのＪＩＳ１３Ｂ号試験片を切り出し、ＪＩＳ Ｚ ２２４４に準拠してビッカース硬さ試験を行い、硬さを評価した。得られた結果を表２に示す。
(3) Vickers hardness From the cold-rolled annealed pickled steel plate, which is the inventive steel and comparative steel produced in the above-mentioned steps, a 1.0 × 30 × 30 mm thick JIS13B test piece was cut out and conformed to JIS Z 2244 The Vickers hardness test was conducted to evaluate the hardness. The obtained results are shown in Table 2.
上記の２種類の応力腐食割れ試験は、応力腐食割れ試験１が、孔食を起点として割れに至るケースについて検証する試験であり、応力腐食割れ試験２は、極めて過酷な腐食環境であることから、孔食等を経由せず、試験片表面の変形部分から直接割れが発生するケースについて検証する試験と考えられている。
表２から明らかなように、本発明鋼は応力腐食割れ試験２のような厳しい高温・高濃度の塩化物溶液中においても割れが全く発生しておらず、極めて優れた耐応力腐食割れ性を有することが分かる。
これに対し、比較鋼の鋼Ｎｏ．３では、各成分が本発明成分の範囲内であるが、Ｎｉ＋２Ｃｕ≦４．７を満たさないため、応力腐食割れ試験１及び２の全ての条件で応力腐食割れが発生している。また、比較鋼の鋼Ｎｏ．４のようにＣやＭｎの含有量が小さくても同様の結果である。比較鋼の鋼Ｎｏ．５は、Ｃｕ含有量が高く、耐応力腐食割れ性に劣っている。そして、比較鋼の鋼Ｎｏ．６（ＳＵＳ３０４）は、Ｎｉ含有量が高く、応力腐食割れ試験１では割れが生じなかったが、より過酷な腐食条件の応力腐食割れ試験２では割れが生じた。
The above two types of stress corrosion cracking tests are tests in which the stress corrosion cracking test 1 verifies the case where cracks start from pitting corrosion, and the stress corrosion cracking test 2 is an extremely severe corrosion environment. It is considered to be a test for verifying a case where cracks are generated directly from the deformed portion of the surface of the test piece without passing through pitting corrosion.
As is apparent from Table 2, the steel of the present invention has no cracks even in a severe high temperature / high concentration chloride solution as in the stress corrosion cracking test 2, and exhibits excellent stress corrosion cracking resistance. It turns out that it has.
On the other hand, the steel No. of the comparative steel. In No. 3, each component is within the range of the component of the present invention, but Ni + 2Cu ≦ 4.7 is not satisfied. Therefore, stress corrosion cracking occurs in all the conditions of the stress corrosion cracking tests 1 and 2. Moreover, the steel No. of the comparative steel. Even if the content of C or Mn is small as in 4, the same result is obtained. Steel No. for comparison steel No. 5 has a high Cu content and is inferior in stress corrosion cracking resistance. And steel No. of comparative steel. No. 6 (SUS304) had a high Ni content, and no cracking occurred in the stress corrosion cracking test 1, but cracking occurred in the stress corrosion cracking test 2 under more severe corrosion conditions.
なお、機械的性質に関し、本発明鋼の硬さは、ＳＵＳ３０４に相当する鋼Ｎｏ．６と比べて大き過ぎることはなく、他の比較鋼とも同等である。 Regarding the mechanical properties, the hardness of the steel of the present invention is steel No. corresponding to SUS304. It is not too large compared to 6, and is equivalent to other comparative steels.
以上より、本実施例のオーステナイト系ステンレス鋼(本発明鋼)によれば、経済的に鋼を生産するため、Ｎｉを３質量％以下といった極めて低い含有割合に抑制できるにも係わらず、上述のようにＭｄ30Ｍｎ値を−３５以下に設定しているため、フェライト系ステンレスであるＳＵＳ４３０にも匹敵する機械的性質や加工性を有すると共に、上記の試験結果が示すように、ＳＵＳ３０４よりも優れた耐応力腐食割れ性を有するオーステナイト系ステンレス鋼を提供することができる。 From the above, according to the austenitic stainless steel of the present example (present invention steel), in order to economically produce steel, the above-described Ni content can be suppressed to a very low content of 3% by mass or less, but the above-mentioned Thus, since the Md 30 Mn value is set to −35 or less, it has mechanical properties and workability comparable to SUS430, which is a ferritic stainless steel, and is superior to SUS304 as the above test results show. An austenitic stainless steel having high stress corrosion cracking resistance can be provided.
Claims (1)
下記（１）式を満たすと共に、
下記（２）式で定義されるＭｄ30（Ｍｎ）が−３５以下である、ことを特徴とする耐応力腐食割れ性に優れたオーステナイト系ステンレス鋼。
Ｎｉ％+２Ｃｕ％≦４．７ …（１）
Ｍｄ30（Ｍｎ）＝５５１−４６２（[Ｃ％]＋[Ｎ％]）−９．２[Ｓｉ％]−１９．１[Ｍｎ％]−１３．７[Ｃｒ％]−２９（[Ｎｉ％]＋[Ｃｕ％]）−１８．５[Ｍｏ％] …（２）
In mass%, C: 0.06 to 0.10%, Si: 1.0% or less, Mn: 9.0 to 10.5%, P: 0.050% or less, S: 0.010% or less, Ni: 2.0-3.0%, Cr: more than 16.0-18.0%, Mo: 0.20% or less, Cu: 0.5-1.5%, N: 0.14-0. Containing 20%, the balance consisting of Fe and inevitable impurities,
While satisfying the following formula (1),
An austenitic stainless steel excellent in stress corrosion cracking resistance, characterized in that Md 30 (Mn) defined by the following formula (2) is −35 or less.
Ni% + 2Cu% ≦ 4.7 (1)
Md 30 (Mn) = 551-462 ([C%] + [N%]) − 9.2 [Si%] − 19.1 [Mn%] − 13.7 [Cr%] − 29 ([Ni% ] + [Cu%])-18.5 [Mo%] (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015050441A JP2016169421A (en) | 2015-03-13 | 2015-03-13 | Austenitic stainless steel excellent in stress corrosion cracking resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015050441A JP2016169421A (en) | 2015-03-13 | 2015-03-13 | Austenitic stainless steel excellent in stress corrosion cracking resistance |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2016169421A true JP2016169421A (en) | 2016-09-23 |
Family
ID=56983190
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2015050441A Pending JP2016169421A (en) | 2015-03-13 | 2015-03-13 | Austenitic stainless steel excellent in stress corrosion cracking resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2016169421A (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53106620A (en) * | 1977-03-02 | 1978-09-16 | Nippon Yakin Kogyo Co Ltd | Austenite stainless steel for cold forming |
| US4502886A (en) * | 1983-01-06 | 1985-03-05 | Armco Inc. | Austenitic stainless steel and drill collar |
| JP2000034546A (en) * | 1998-07-02 | 2000-02-02 | Ugine Sa | Austenitic stainless steel reduced in nickel content and excellent in corrosion resistance |
| JP2014019925A (en) * | 2012-07-20 | 2014-02-03 | Nippon Metal Ind Co Ltd | Ni SAVING TYPE AUSTENITIC STAINLESS STEEL |
| JP2014185367A (en) * | 2013-03-22 | 2014-10-02 | Nippon Steel & Sumikin Stainless Steel Corp | Stainless steel wire excellent in twisting processability and manufacturing method therefor, and stainless steel wire and manufacturing method therefor |
-
2015
- 2015-03-13 JP JP2015050441A patent/JP2016169421A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53106620A (en) * | 1977-03-02 | 1978-09-16 | Nippon Yakin Kogyo Co Ltd | Austenite stainless steel for cold forming |
| US4502886A (en) * | 1983-01-06 | 1985-03-05 | Armco Inc. | Austenitic stainless steel and drill collar |
| JP2000034546A (en) * | 1998-07-02 | 2000-02-02 | Ugine Sa | Austenitic stainless steel reduced in nickel content and excellent in corrosion resistance |
| JP2014019925A (en) * | 2012-07-20 | 2014-02-03 | Nippon Metal Ind Co Ltd | Ni SAVING TYPE AUSTENITIC STAINLESS STEEL |
| JP2014185367A (en) * | 2013-03-22 | 2014-10-02 | Nippon Steel & Sumikin Stainless Steel Corp | Stainless steel wire excellent in twisting processability and manufacturing method therefor, and stainless steel wire and manufacturing method therefor |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP6302722B2 (en) | High-strength duplex stainless steel wire excellent in spring fatigue characteristics, its manufacturing method, and high-strength duplex stainless steel wire excellent in spring fatigue characteristics | |
| JP5156293B2 (en) | Ferritic / austenitic stainless steel with excellent corrosion resistance and workability and manufacturing method thereof | |
| JP7252761B2 (en) | Precipitation hardening steel and its manufacture | |
| JP5726537B2 (en) | Duplex stainless steel with excellent toughness | |
| JP2010031313A (en) | Corrosion resistant austenitic stainless steel | |
| JP4190993B2 (en) | Ferritic stainless steel sheet with improved crevice corrosion resistance | |
| CN104726789A (en) | Low-nickel containing stainless steels | |
| CN108220813B (en) | Super-grade duplex stainless steel and alloy component optimization design method thereof | |
| JP2008038191A (en) | Austenitic stainless steel and its production method | |
| JP4645307B2 (en) | Wear-resistant steel with excellent low-temperature toughness and method for producing the same | |
| JP4207137B2 (en) | High hardness and high corrosion resistance stainless steel | |
| JP2018178144A (en) | Precipitation-hardened stainless steel having excellent hot workability | |
| JP5100144B2 (en) | Steel plate for spring, spring material using the same, and manufacturing method thereof | |
| JP6722286B2 (en) | Lean duplex stainless steel with improved corrosion resistance and workability and method for producing the same | |
| JP6583885B2 (en) | High hardness stainless steel with excellent corrosion resistance and manufacturability | |
| JP4841308B2 (en) | High-strength nonmagnetic stainless steel sheet and method for producing the same | |
| JP2022181634A (en) | Austenitic stainless steel and method for producing the same, and processed product | |
| JP2016169421A (en) | Austenitic stainless steel excellent in stress corrosion cracking resistance | |
| JP4757561B2 (en) | High manganese stainless steel with excellent stress corrosion cracking resistance | |
| JP4331731B2 (en) | Austenitic stainless steel and springs made of that steel | |
| JP2022064692A (en) | Austenitic stainless steel and method for producing austenitic stainless steel | |
| JP4823534B2 (en) | Low Ni austenitic stainless steel with excellent stress corrosion cracking resistance | |
| JP2004143576A (en) | Low nickel austenitic stainless steel | |
| JP7462439B2 (en) | Austenitic stainless steel and calculation method for upper limit of N | |
| JP5528459B2 (en) | Ni-saving stainless steel with excellent corrosion resistance |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20170714 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20180412 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20180424 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20180614 |
|
| A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20180731 |