JP2008179886A - Ferritic stainless steel sheet having excellent corrosion resistance in dissimilar weld with austenitic stainless steel, and method for producing the same - Google Patents

Ferritic stainless steel sheet having excellent corrosion resistance in dissimilar weld with austenitic stainless steel, and method for producing the same Download PDF

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JP2008179886A
JP2008179886A JP2007332400A JP2007332400A JP2008179886A JP 2008179886 A JP2008179886 A JP 2008179886A JP 2007332400 A JP2007332400 A JP 2007332400A JP 2007332400 A JP2007332400 A JP 2007332400A JP 2008179886 A JP2008179886 A JP 2008179886A
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stainless steel
corrosion resistance
ferritic stainless
austenitic stainless
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JP5205952B2 (en
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Shuji Okada
修二 岡田
Kazuhide Ishii
和秀 石井
Tomohiro Ishii
知洋 石井
Yoshimasa Funakawa
義正 船川
Takumi Ugi
工 宇城
Hiroshi Yano
浩史 矢埜
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JFE Steel Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a ferritic stainless steel sheet in which sufficient corrosion resistance can be secured even regarding dissimilar welds with an austenitic stainless steel (e.g., SUS304). <P>SOLUTION: The ferritic stainless steel sheet has a composition comprising, by mass, ≤0.030% C, ≤0.030% N, ≤0.050% (C+N), ≤0.50% Si, ≤0.50% Mn, ≤0.10% Al, 20.5 to 22.5% Cr, 0.30 to 1.00% Cu, ≤1.50% Ni, 0.20 to 0.70% Nb, ≤0.040% P and ≤0.010% S, and in which these components satisfy the relations in inequality; (Cr+1.5Si+0.5Nb)≤23.0 and inequality; (Ni+30C+0.5Mn+0.5Cu+30N)≥0.90, and the balance Fe with inevitable impurities. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、耐食性、中でもオーステナイト系ステンレス鋼(例えば、SUS304)との異材溶接部の耐食性に優れたフェライト系ステンレス鋼板およびその製造方法に関するものである。   The present invention relates to a ferritic stainless steel sheet excellent in corrosion resistance, particularly corrosion resistance of a welded portion of a dissimilar material with austenitic stainless steel (for example, SUS304), and a method for producing the same.

一般に広く使用されているステンレス鋼の代表例としては、鉄に約18%のCrと約8%のNiを含有させたオーステナイト系ステンレス鋼SUS304が知られている。
一方、フェライト系ステンレス鋼の代表は、鉄に約17%のCrを含有させたSUS430であるが、耐食性はSUS304よりも劣る。
As a typical example of stainless steel generally used widely, austenitic stainless steel SUS304 in which about 18% Cr and about 8% Ni are contained in iron is known.
On the other hand, a representative ferritic stainless steel is SUS430 in which about 17% Cr is contained in iron, but the corrosion resistance is inferior to that of SUS304.

近年、精錬技術の進歩によって、工業的に低炭素化することが容易となり、耐食性に優れた、SUS430LX、SUS430JIL、SUS436Lなどのフェライト系ステンレス鋼が開発され、自動車部品や厨房機器などに広く使用されている。
ステンレス鋼を用いて部品や製品を組み立てる場合、接合方法としては溶接を用いることが多い。広く用いられる溶接方法として、ティグ溶接、ミグ溶接およびマグ溶接などのアーク溶接がある。
In recent years, the advancement of refining technology has made it easy to industrially reduce carbon, and ferritic stainless steels such as SUS430LX, SUS430JIL, and SUS436L that have excellent corrosion resistance have been developed and are widely used in automobile parts and kitchen equipment. ing.
When assembling parts and products using stainless steel, welding is often used as a joining method. Widely used welding methods include arc welding such as TIG welding, MIG welding, and MAG welding.

ステンレス鋼は、溶接の際、Cr炭化物の析出によりクロム欠乏層が形成(鋭敏化)され、溶接部の耐食性が劣化することがある。フェライト系ステンレス鋼は、低炭素化で耐食性を確保しているので、オーステナイト系ステンレス鋼よりも溶接部の耐食性の劣化が生じ易い。   When stainless steel is welded, a chromium-deficient layer is formed (sensitized) due to the precipitation of Cr carbide, which may deteriorate the corrosion resistance of the weld. Since ferritic stainless steel has low carbon and secures corrosion resistance, the corrosion resistance of welds is more likely to deteriorate than austenitic stainless steel.

溶接ワイヤを用いる溶接に際し、オーステナイト系ステンレス鋼SUS304では、308系のワイヤ(D308、D308L、Y308、Y308L等)を用いて、また低炭素のフェライト系ステンレス鋼では、309L系(D309L、Y309L等)、316L系(D316L、Y316L等)および347L系(D347L、Y347L等)などの低炭素のワイヤを用いて、溶接部の耐食性を確保することが多い。   When welding with a welding wire, use a 308 series wire (D308, D308L, Y308, Y308L, etc.) for austenitic stainless steel SUS304, and a 309L series (D309L, Y309L, etc.) for low-carbon ferritic stainless steel. Often, low-carbon wires such as 316L (D316L, Y316L, etc.) and 347L (D347L, Y347L, etc.) are used to ensure the corrosion resistance of welds.

フェライト系ステンレス鋼においては、鋼成分により耐食性を改善する技術として、例えば特許文献1では、Tiの添加量を制限し、かつTiとAlを複合添加し、さらに適正量のMoとCuを添加することにより、溶接部の耐食性を向上させる技術を提案している。
特開平10−81940号公報
In ferritic stainless steel, as a technique for improving the corrosion resistance by using steel components, for example, in Patent Document 1, the addition amount of Ti is limited, Ti and Al are added in combination, and appropriate amounts of Mo and Cu are added. Therefore, a technique for improving the corrosion resistance of the welded portion is proposed.
JP-A-10-81940

近年、世界的な規模での消費拡大により、工業原料の需給がひっ迫している。オーステナイト系ステンレス鋼の主要成分の一つであるNiもその一つであり、価格が急激に上昇しているため、SUS304の価格も上昇している。この点、フェライト系ステンレス鋼は、Niを含有しないか、または含有してもその量はSUS304よりも少ないため、価格がSUS304に比較して安定している。このため、SUS304を使用する多くのメーカーが、フェライト系ステンレス鋼への変更の検討を始めている。   In recent years, the supply and demand of industrial raw materials has become tight due to the expansion of consumption on a global scale. Ni, which is one of the main components of austenitic stainless steel, is one of them, and the price of SUS304 is also rising because the price is rising rapidly. In this respect, ferritic stainless steel does not contain Ni, or even if it is contained, the amount thereof is less than that of SUS304, so the price is more stable than SUS304. For this reason, many manufacturers using SUS304 have begun to consider changing to ferritic stainless steel.

また、ステンレス鋼を用いる部品や製品は、幾つかのステンレス鋼板を接合して製造されることが多い。この際、全ての素材をSUS304からフェライト系ステンレス鋼に変更することは必ずしも経済的ではないので、部分的にフェライト系ステンレス鋼に切り替えることもあり得る。この場合、SUS304とフェライト系ステンレス鋼を接合、溶接する可能性が生じる。   Moreover, parts and products using stainless steel are often manufactured by joining several stainless steel plates. At this time, it is not always economical to change all materials from SUS304 to ferritic stainless steel, so it may be partially switched to ferritic stainless steel. In this case, there is a possibility of joining and welding SUS304 and ferritic stainless steel.

SUS304が含有する炭素量は、JIS G 4304で0.08mass%以下、一般に流通している製品で0.06mass%程度である。一方、低炭素のフェライト系ステンレス鋼が含有するC量は、JIS G 4304のSUS430LXで0.03mass%以下、SUS430JILやSUS436Lで0.025mass%以下である。
SUS304とフェライト系ステンレス鋼を溶接すると、フェライト系ステンレス鋼側の熱影響部あるいは溶接金属中の炭素量がフェライト系ステンレス鋼の値よりも高くなり、耐食性が母材よりも低下してしまう場合がある。
The amount of carbon contained in SUS304 is 0.08 mass% or less in JIS G 4304 and about 0.06 mass% in products that are generally distributed. On the other hand, the amount of C contained in the low carbon ferritic stainless steel is 0.03 mass% or less for SUS430LX of JIS G 4304 and 0.025 mass% or less for SUS430JIL or SUS436L.
When SUS304 and ferritic stainless steel are welded, the amount of carbon in the heat-affected zone on the ferritic stainless steel side or in the weld metal is higher than that of ferritic stainless steel, and the corrosion resistance may be lower than that of the base metal. is there.

前述した特許文献1の技術は、同一のフェライト系ステンレス鋼同士の溶接部について耐食性を確保する技術であることから、SUS304等との異材溶接部の耐食性は確保できないものと推定される。また、特許文献1の技術は、Niと同様に価格の上昇が著しい高価なMoを含有させる必要があるため、SUS304よりもコストが高くなる。さらに、特許文献1の技術は、Tiを含有するため、熱延板の靭性が低い。フェライト系ステンレス鋼の熱延板は、冷間圧延の前に連続焼鈍・酸洗ラインで焼鈍と酸洗を行う必要があるが、熱延板の靭性が低いと連続焼鈍・酸洗ラインに通板ができない場合がある。   Since the technique of Patent Document 1 described above is a technique for ensuring corrosion resistance for welds between the same ferritic stainless steels, it is presumed that the corrosion resistance of dissimilar welds with SUS304 or the like cannot be ensured. Moreover, since the technique of patent document 1 needs to contain the expensive Mo which raises a price remarkably similarly to Ni, cost becomes higher than SUS304. Furthermore, since the technique of patent document 1 contains Ti, the toughness of a hot-rolled sheet is low. Ferritic stainless steel hot-rolled sheets must be annealed and pickled in a continuous annealing and pickling line before cold rolling, but if the hot rolled sheet has low toughness, it passes through the continuous annealing and pickling line. The board may not be able to be made.

本発明は、上記の現状に鑑み開発されたもので、オーステナイト系ステンレス鋼(例えばSUS304)との異材溶接部についても十分な耐食性を確保できるフェライト系ステンレス鋼板を、かかる鋼板を安価かつ高効率で生産することができる製造方法と共に提案することを目的とする。   The present invention has been developed in view of the above-described situation, and a ferritic stainless steel sheet that can ensure sufficient corrosion resistance even for a dissimilar welded part with austenitic stainless steel (for example, SUS304) is obtained at low cost and high efficiency. The aim is to propose a manufacturing method that can be produced.

さて、発明者らは、上記の課題を達成するために、オーステナイト系ステンレス鋼として代表的なSUS304とフェライト系ステンレス鋼との異材溶接部の耐食性に及ぼす、フェライト系ステンレス鋼の化学成分の影響について、製造性も考慮しながら綿密な調査、検討を行った。
その結果、以下に述べる知見を得た。
(1) 母材部および溶接部の耐食性は、Crを20.5mass%以上にすると向上する。一方、Crが22.5mass%を超えると、溶接金属のフェライト分率を高めて、溶接金属の耐食性を劣化させるので、Crは22.5mass%以下に限定する必要がある。
(2) 溶接部の耐食性は、適量のNbを添加することにより向上する。
(3) 溶接金属の耐食性は、フェライト形成元素であるCrやSi,Nb量を制限することにより向上する。
(4) 溶接金属の耐食性は、オーステナイト形成元素であるNiやC,Mn,Cu,Nの添加量を増加することにより向上する。
(5) 溶接部の耐食性は、適量のNbと共にVを添加することにより、さらに向上する。
なお、溶接部とは、溶接金属および溶接熱影響部を含んだ部分の総称である。
本発明は、上記の知見に基づき、さらに検討を重ねた末に、完成されたものである。
Now, in order to achieve the above-mentioned problems, the inventors have studied the influence of the chemical composition of ferritic stainless steel on the corrosion resistance of dissimilar welds of SUS304 and ferritic stainless steel, which are typical austenitic stainless steel. A thorough investigation and examination was conducted while considering manufacturability.
As a result, the following knowledge was obtained.
(1) The corrosion resistance of the base metal part and the welded part is improved when Cr is 20.5 mass% or more. On the other hand, if Cr exceeds 22.5 mass%, the ferrite fraction of the weld metal is increased and the corrosion resistance of the weld metal is deteriorated, so Cr needs to be limited to 22.5 mass% or less.
(2) The corrosion resistance of the weld is improved by adding an appropriate amount of Nb.
(3) The corrosion resistance of weld metal is improved by limiting the amount of Cr, Si, and Nb that are ferrite forming elements.
(4) The corrosion resistance of the weld metal is improved by increasing the amount of Ni, C, Mn, Cu, and N, which are austenite forming elements.
(5) The corrosion resistance of the weld is further improved by adding V together with an appropriate amount of Nb.
In addition, a weld part is a general term for the part containing a weld metal and a weld heat affected zone.
The present invention has been completed after further studies based on the above findings.

すなわち、本発明の要旨構成は次のとおりである。
1.質量%で、
C:0.030%以下、 N:0.030%以下、 (C+N):0.050%以下、
Si:0.50%以下、 Mn:0.50%以下、 Al:0.10%以下、
Cr:20.5〜22.5%、 Cu:0.30〜1.00%、 Ni:1.50%以下、
Nb:0.20〜0.70%、 P:0.040%以下およびS:0.010%以下
を含有し、かつこれらの成分が、次式(1),(2)
(Cr+1.5Si+0.5Nb)≦23.0 ・・・ (1)
(Ni+30C+0.5Mn+0.5Cu+30N)≧0.90 ・・・ (2)
の関係を満足し、残部はFeおよび不可避的不純物からなることを特徴とする、オーステナイト系ステンレス鋼との異材溶接部の耐食性に優れたフェライト系ステンレス鋼板。
That is, the gist configuration of the present invention is as follows.
1. % By mass
C: 0.030% or less, N: 0.030% or less, (C + N): 0.050% or less,
Si: 0.50% or less, Mn: 0.50% or less, Al: 0.10% or less,
Cr: 20.5-22.5%, Cu: 0.30-1.00%, Ni: 1.50% or less,
Nb: 0.20 to 0.70%, P: 0.040% or less and S: 0.010% or less, and these components are represented by the following formulas (1) and (2)
(Cr + 1.5Si + 0.5Nb) ≦ 23.0 (1)
(Ni + 30C + 0.5Mn + 0.5Cu + 30N) ≧ 0.90 (2)
A ferritic stainless steel sheet excellent in the corrosion resistance of dissimilar welds with austenitic stainless steel, wherein the balance consists of Fe and inevitable impurities.

2.前記鋼板が、質量%で、さらに、
V:1.00%以下
を含有することを特徴とする、前記1に記載のオーステナイト系ステンレス鋼との異材溶接部の耐食性に優れたフェライト系ステンレス鋼板。
2. The steel sheet is in mass%, and
V: A ferritic stainless steel plate excellent in corrosion resistance of a dissimilar material welded portion to the austenitic stainless steel according to 1, characterized by containing 1.00% or less.

3.質量%で、
C:0.030%以下、 N:0.030%以下、 (C+N):0.050%以下、
Si:0.50%以下、 Mn:0.50%以下、 Al:0.10%以下、
Cr:20.5〜22.5%、 Cu:0.30〜1.00%、 Ni:1.50%以下、
Nb:0.20〜0.70%、 P:0.040%以下およびS:0.010%以下
を含有し、かつこれらの成分が、次式(1),(2)
(Cr+1.5Si+0.5Nb)≦23.0 ・・・ (1)
(Ni+30C+0.5Mn+0.5Cu+30N)≧0.90 ・・・ (2)
の関係を満足し、残部はFeおよび不可避的不純物の組成になるステンレス鋼素材を、熱間圧延したのち、連続焼鈍により800〜1100℃の温度で熱延板焼鈍を施し、ついで酸洗後、冷間圧延、仕上げ焼鈍、冷却および酸洗の工程を経て、冷延焼鈍板とすることを特徴とする、オーステナイト系ステンレス鋼との異材溶接部の耐食性に優れたフェライト系ステンレス鋼板の製造方法。
3. % By mass
C: 0.030% or less, N: 0.030% or less, (C + N): 0.050% or less,
Si: 0.50% or less, Mn: 0.50% or less, Al: 0.10% or less,
Cr: 20.5-22.5%, Cu: 0.30-1.00%, Ni: 1.50% or less,
Nb: 0.20 to 0.70%, P: 0.040% or less and S: 0.010% or less, and these components are represented by the following formulas (1) and (2)
(Cr + 1.5Si + 0.5Nb) ≦ 23.0 (1)
(Ni + 30C + 0.5Mn + 0.5Cu + 30N) ≧ 0.90 (2)
The stainless steel material with the balance of Fe and unavoidable impurities is hot-rolled, the hot-rolled sheet is annealed at a temperature of 800 to 1100 ° C by continuous annealing, and then pickling, A method for producing a ferritic stainless steel sheet having excellent corrosion resistance in a welded portion of a dissimilar material with austenitic stainless steel, characterized by being subjected to cold rolling, finish annealing, cooling, and pickling to form a cold rolled annealed sheet.

4.前記ステンレス鋼素材が、質量%で、さらに、
V:1.00%以下
を含有することを特徴とする、前記3に記載のオーステナイト系ステンレス鋼との異材溶接部の耐食性に優れたフェライト系ステンレス鋼板の製造方法。
4). The stainless steel material is in mass%,
V: The manufacturing method of the ferritic stainless steel plate excellent in the corrosion resistance of the dissimilar material weld part with the austenitic stainless steel of 3 characterized by containing 1.00% or less.

本発明のフェライト系ステンレス鋼は、オーステナイト系ステンレス鋼との異材溶接部についても耐食性を向上させたので、オーステナイト系ステンレス鋼を用いる部品や製品において、部分的に安価なフェライト系ステンレス鋼に切り替えて、オーステナイト系ステンレス鋼とフェライト系ステンレス鋼の異材溶接部が生じたとしても、異材溶接部の耐食性の劣化を抑制することができ、産業上格段の効果がある。   The ferritic stainless steel of the present invention has improved corrosion resistance even for dissimilar welds with austenitic stainless steel, so in parts and products that use austenitic stainless steel, switch to a partially inexpensive ferritic stainless steel. Even if dissimilar welds of austenitic stainless steel and ferritic stainless steel occur, deterioration of the corrosion resistance of the dissimilar welds can be suppressed, and there is a remarkable industrial effect.

以下、本発明を具体的に説明する。
まず、本発明において鋼の化学成分を上記の範囲に限定した理由について説明する。なお、成分に関する「%」表示は特に断らない限り質量%を意味するものとする。
C:0.030%以下、N:0.030%以下、(C+N):0.050%以下
CとNは、Crと結合してCrの炭化物や窒化物を形成し易い。溶接時、熱影響部にCrの炭化物や窒化物が析出してCr欠乏層が形成されると粒界腐食の原因となるので、CやNは低い程望ましい。そこで、本発明では、Cを0.030%以下、Nを0.030%以下、また両者の合計(C+N)を0.050%以下に限定した。好ましくはC:0.015%以下、N:0.015%以下、(C+N):0.030%以下である。
The present invention will be specifically described below.
First, the reason why the chemical composition of steel is limited to the above range in the present invention will be described. Unless otherwise specified, “%” in relation to ingredients means mass%.
C: 0.030% or less, N: 0.030% or less, (C + N): 0.050% or less C and N are liable to form Cr carbide and nitride by combining with Cr. During welding, if Cr carbide or nitride precipitates in the heat-affected zone to form a Cr-deficient layer, it causes intergranular corrosion, so C and N are preferably as low as possible. Therefore, in the present invention, C is limited to 0.030% or less, N is limited to 0.030% or less, and the total of both (C + N) is limited to 0.050% or less. Preferably, C is 0.015% or less, N is 0.015% or less, and (C + N) is 0.030% or less.

Si:0.50%以下
Siは、溶接部の耐食性を高めるのに有効な元素であり、通常はその含有量に比例して効果を発揮する。しかしながら、一方でSiは、熱延板の靭性を低下させるので、本発明では、Siを0.50%以下に限定した。好ましくは0.10%以下である。
Si: 0.50% or less
Si is an element effective for enhancing the corrosion resistance of the welded portion, and usually exhibits an effect in proportion to its content. However, on the other hand, Si reduces the toughness of the hot-rolled sheet, so in the present invention, Si is limited to 0.50% or less. Preferably it is 0.10% or less.

Mn:0.50%以下
Mnは、鋼中に存在するSと結合して、可溶性硫化物であるMnSを形成し、耐食性を低下させる。そこで、本発明では、Mnを0.50%以下に限定した。好ましくは0.30%以下である。
Mn: 0.50% or less
Mn combines with S present in steel to form MnS, which is a soluble sulfide, and lowers the corrosion resistance. Therefore, in the present invention, Mn is limited to 0.50% or less. Preferably it is 0.30% or less.

Al:0.10%以下
Alは、脱酸剤として有用な元素である。しかしなから、過剰な添加は、Al系の非金属介在物の増加により表面疵の発生を招くと共に、加工性も低下させる。このため、本発明では、Alは0.10%以下で含有させるものとした。
Al: 0.10% or less
Al is an element useful as a deoxidizer. However, excessive addition leads to generation of surface flaws due to an increase in Al-based non-metallic inclusions and lowers workability. Therefore, in the present invention, Al is contained at 0.10% or less.

Cr:20.5〜22.5%
Crは、本発明において、最も重要な元素の一つである。Crは、耐食性を向上させる元素であり、フェライト系ステンレス鋼では不可欠の元素である。SUS304相当の耐食性を得るためには、20.5%以上のCrを含有させる必要があるが、22.5%を超えて含有させると、溶接金属のフェライト分率を高めて、溶接金属の耐食性を劣化させる。このため、Crは20.5〜22.5%の範囲に限定した。
Cr: 20.5-22.5%
Cr is one of the most important elements in the present invention. Cr is an element that improves corrosion resistance, and is an indispensable element in ferritic stainless steel. In order to obtain corrosion resistance equivalent to SUS304, it is necessary to contain 20.5% or more of Cr. However, if it exceeds 22.5%, the ferrite fraction of the weld metal is increased and the corrosion resistance of the weld metal is deteriorated. For this reason, Cr was limited to the range of 20.5 to 22.5%.

Cu:0.30〜1.00%
Cuは、本発明において、重要な元素の一つである。Cuは、オーステナイト系ステンレス鋼との溶接部の耐食性を向上させる元素であり、そのためには0.30%以上の含有が必要である。一方、Cu量が1.00%を超えると熱間加工性が劣化する。よって、本発明では、Cuは0.30〜1.00%の範囲に限定した。好ましくは0.40〜0.70%の範囲である。
Cu: 0.30 to 1.00%
Cu is one of the important elements in the present invention. Cu is an element that improves the corrosion resistance of the welded portion with the austenitic stainless steel, and for that purpose, it must contain 0.30% or more. On the other hand, when the amount of Cu exceeds 1.00%, hot workability deteriorates. Therefore, in this invention, Cu was limited to 0.30 to 1.00% of range. Preferably it is 0.40 to 0.70% of range.

Ni:1.5%以下
Niは、オーステナイト系ステンレス鋼との溶接部の耐食性を向上させる効果がある。また、Cu添加による熱間加工性の低下を防ぐ効果もある。しかしながら、Niは高価な元素であるため、1.5%以下で含有させるものとした。好ましくは、1.0%以下である。
Ni: 1.5% or less
Ni has an effect of improving the corrosion resistance of the welded portion with the austenitic stainless steel. In addition, there is an effect of preventing a decrease in hot workability due to the addition of Cu. However, since Ni is an expensive element, it should be contained at 1.5% or less. Preferably, it is 1.0% or less.

Nb:0.20〜0.70%
Nbは、本発明において、最も重要な元素の一つである。Nbは、Crよりも優先的に炭窒化物を形成する。従って、オーステナイト系ステンレス鋼との異材溶接時、溶接熱影響部および溶接金属においてCr炭窒化物が析出するのを防いで粒界腐食を抑制する。さらに、最も耐食性が問題となる溶接金属においては、オーステナイト(冷却後はマルテンサイトに変態)の形成を促進し、CとNをオーステナイト(冷却後はマルテンサイト)中に固溶させて粒界腐食を抑制する、という効果がある。この効果は、Nb量が0.20%以上で顕著となるが、0.70%を超えると逆にオーステナイトの形成を抑制し、耐食性を低下させる。よって、本発明では、Nbは0.20〜0.70%の範囲に限定した。好ましくは0.30〜0.50%の範囲である。
なお、Nbと同様に、CとNを固定する元素であるTiは、オーステナイト(冷却後はマルテンサイト)形成を促進する効果が小さいので、本発明では、Tiは0.01%以下に抑制することが望ましい。
Nb: 0.20 to 0.70%
Nb is one of the most important elements in the present invention. Nb forms carbonitride preferentially over Cr. Therefore, at the time of dissimilar material welding with austenitic stainless steel, Cr carbonitride is prevented from precipitating in the weld heat affected zone and the weld metal, thereby suppressing intergranular corrosion. Furthermore, in weld metals where corrosion resistance is most problematic, the formation of austenite (transformed into martensite after cooling) is promoted, and C and N are dissolved in austenite (martensite after cooling) to cause intergranular corrosion. There is an effect of suppressing. This effect becomes significant when the Nb content is 0.20% or more, but when it exceeds 0.70%, the formation of austenite is suppressed and the corrosion resistance is lowered. Therefore, in this invention, Nb was limited to 0.20 to 0.70% of range. Preferably it is 0.30 to 0.50% of range.
Like Nb, Ti, which is an element that fixes C and N, has a small effect of promoting the formation of austenite (martensite after cooling). Therefore, in the present invention, Ti is suppressed to 0.01% or less. desirable.

P:0.040%以下
Pは、熱間加工性と耐食性に有害な元素である。特に0.040%を超えるとこの弊害が顕著になる。このため、Pは0.040%以下に限定した。
P: 0.040% or less P is an element harmful to hot workability and corrosion resistance. Especially when it exceeds 0.040%, this harmful effect becomes remarkable. For this reason, P was limited to 0.040% or less.

S:0.010%以下
Sは、熱間加工性と耐食性に有害な元素であり、含有量が0.010%を超えるとこの弊害が顕著になる。このため、Sは0.010%以下に限定した。好ましくは0.005%以下である。
S: 0.010% or less S is an element harmful to hot workability and corrosion resistance. When the content exceeds 0.010%, this adverse effect becomes remarkable. For this reason, S was limited to 0.010% or less. Preferably it is 0.005% or less.

以上、基本成分および抑制成分の組成範囲について説明したが、本発明では各成分が上記の組成範囲を単に満足しているだけでは不十分で、次式(1)および(2)の関係も併せて満足する必要がある。
(Cr+1.5Si+0.5Nb)≦23.0 ・・・ (1)
(Ni+30C+0.5Mn+0.5Cu+30N)≧0.90 ・・・ (2)
上掲式(1),(2)は、溶接金属において、オーステナイト(冷却後はマルテンサイト)形成を促進させるために必要な条件である。すなわち、フェライト形成元素であるCrやSi,Nbについては上掲式(1)に示す関係を満足するように上限を規制し、一方オーステナイト形成元素であるNiやC,Mn,Cu,Nについては上揚式(2)に示す関係を満足するように下限を規制する。
かくして、上掲式(1)、(2)の関係を満足させることにより、溶接金属において、オーステナイト(冷却後マルテンサイト)の形成が促進され、CとNがオーステナイト(冷却後マルテンサイト)に固溶するので、Cr炭窒化物の析出が抑制され、効果的に粒界腐食を防止できるようになる。
The composition range of the basic component and the suppression component has been described above.In the present invention, it is not sufficient that each component simply satisfies the above composition range, and the relationship of the following formulas (1) and (2) is also included. Need to be satisfied.
(Cr + 1.5Si + 0.5Nb) ≦ 23.0 (1)
(Ni + 30C + 0.5Mn + 0.5Cu + 30N) ≧ 0.90 (2)
The above formulas (1) and (2) are conditions necessary for promoting the formation of austenite (martensite after cooling) in the weld metal. In other words, the upper limit of ferrite forming elements Cr, Si, Nb is regulated so as to satisfy the relationship shown in the above formula (1), while the austenite forming elements Ni, C, Mn, Cu, N are controlled. The lower limit is regulated so as to satisfy the relationship shown in the lifting type (2).
Thus, by satisfying the relationship of the above formulas (1) and (2), formation of austenite (martensite after cooling) is promoted in the weld metal, and C and N are fixed to austenite (martensite after cooling). Since it dissolves, precipitation of Cr carbonitride is suppressed, and it becomes possible to effectively prevent intergranular corrosion.

また、本発明では、上記した基本成分の他、以下に述べる成分を必要に応じて適宜含有させることができる。
V:1.00%以下
Vは、Nbと同様に炭窒化物を形成し、CとNを固定する元素であるが、Nbと比べてその効果は小さい。しかしながら、Vは、表面性状を劣化させるおそれがなく、また、1.00%以下の範囲であれば機械的性質への影響も小さいので、本発明では、1.00%以下の範囲で含有できるものとした。
In the present invention, in addition to the basic components described above, the components described below can be appropriately contained as necessary.
V: 1.00% or less V is an element that forms a carbonitride like Nb and fixes C and N, but its effect is smaller than that of Nb. However, V has no risk of deteriorating the surface properties, and if it is in the range of 1.00% or less, the effect on the mechanical properties is small. Therefore, in the present invention, V can be contained in the range of 1.00% or less.

上記した成分以外の残部は、Feおよび不可避的不純物である。不可避的不純物としてはMgやCaが挙げられるが、それぞれMg:0.0020%以下、Ca:0.0020%以下で許容できる。   The balance other than the above components is Fe and inevitable impurities. Inevitable impurities include Mg and Ca, but Mg: 0.0020% or less and Ca: 0.0020% or less are acceptable.

次に、本発明の好適製造方法について説明する。
本発明の製造方法としては、好ましくは連続鋳造により鋼素材(スラブ)とし、1100〜1250℃に加熱後、熱間圧延したのちコイルに巻取り、ついで連続焼鈍・酸洗ラインで 800〜1100℃の温度で焼鈍したのち、酸洗し、次に冷間圧延を施して冷延板としたのち、連続焼鈍・酸洗ラインで冷延板の焼鈍と酸洗を行う方法が推奨される。
詳細には次のとおりである。
Next, the preferred manufacturing method of the present invention will be described.
The production method of the present invention is preferably a steel material (slab) by continuous casting, heated to 1100 to 1250 ° C, hot rolled, wound into a coil, and then continuously annealed and pickled at 800 to 1100 ° C. It is recommended that the steel sheet be pickled, then cold-rolled to form a cold-rolled sheet, and then annealed and pickled in a continuous annealing / pickling line.
Details are as follows.

まず、転炉、電気炉等と、強撹拌・真空酸素脱炭処理(VOD)法またはアルゴン酸素脱炭処理(AOD)法等による2次精錬で、上記の化学成分範囲に調整した溶鋼を溶製する。ついで、上記溶鋼から、連続鋳造法または造塊−分塊法によりスラブを製造する。なお、鋳造方法としては、生産性および品質の面から連続鋳造法を使用することが好ましい。得られたスラブは、必要に応じて1100〜1250℃に再加熱後、板厚:2.0〜6.0mmになるように熱間圧延し、800〜1100℃の温度で連続焼鈍を施したのち、酸洗する。この際、焼鈍温度が800℃未満では、圧延による歪が残留して硬くなるため表面疵が発生し易く、一方1100℃を超えると粗粒化して靭性が低下するので、熱延板の連続焼鈍温度は800〜1100℃の範囲に限定した。   First, molten steel adjusted to the above chemical composition range is melted by secondary refining using a converter, electric furnace, etc. and strong stirring, vacuum oxygen decarburization (VOD) method or argon oxygen decarburization (AOD) method. To make. Next, a slab is produced from the molten steel by a continuous casting method or an ingot-bundling method. As a casting method, it is preferable to use a continuous casting method from the viewpoint of productivity and quality. The obtained slab was re-heated to 1100-1250 ° C as necessary, hot-rolled to a thickness of 2.0-6.0mm, subjected to continuous annealing at a temperature of 800-1100 ° C, and then acidified. Wash. At this time, if the annealing temperature is less than 800 ° C, distortion due to rolling remains and hardens, and surface flaws are likely to occur.On the other hand, if it exceeds 1100 ° C, it becomes coarse and deteriorates toughness. The temperature was limited to the range of 800-1100 ° C.

酸洗された熱延板は、常法に従い、冷間圧延、仕上げ焼鈍、冷却および酸洗の各工程を順次経て、板厚:0.03〜5.0mmの冷延焼鈍板とする。
冷間圧延時における圧下率は、靭性や加工性などの機械的性質を確保するためには25%以上とすることが好ましい。より好ましくは50%以上である。また、冷間圧延は1回または中間焼鈍を含む2回以上の冷間圧延としてもよい。なお、冷間圧延、仕上げ焼鈍、酸洗の工程は繰り返し行ってもよい。また、必要に応じて、光輝焼鈍ラインで光輝焼鈍を行ってもよい。
The pickled hot-rolled sheet is made into a cold-rolled annealed sheet having a thickness of 0.03 to 5.0 mm through successive steps of cold rolling, finish annealing, cooling and pickling according to a conventional method.
The rolling reduction during cold rolling is preferably 25% or more in order to ensure mechanical properties such as toughness and workability. More preferably, it is 50% or more. Further, the cold rolling may be performed once or twice or more cold rolling including intermediate annealing. In addition, you may repeat the process of cold rolling, finish annealing, and pickling. Moreover, you may perform bright annealing with a bright annealing line as needed.

以下、実施例に基づいて、本発明をさらに詳しく説明する。
表1に示す成分組成になる鋼(No.1〜12と24〜26が発明例、No.13〜19が比較例、No.20〜23が従来例)を、小型真空溶解炉で溶製し、30kgの鋼塊とした。これらの鋼塊を、1100〜1250℃に加熱後、仕上げ温度:750〜950℃、巻取り温度:400〜850℃の条件で熱間圧延を施して4.0mm厚の熱延板とした。これらの熱延板に対して、連続焼鈍により800〜1100℃の熱延板焼鈍を施したのち、酸洗してから、冷間圧延により板厚:1.5mmの冷延板とした。ついで、アルゴン雰囲気中にて880〜1100℃で仕上げ焼鈍を施したのち、冷却し、酸洗を行った。
Hereinafter, the present invention will be described in more detail based on examples.
Steels with the composition shown in Table 1 (No. 1-12 and 24-26 are invention examples, No. 13-19 are comparative examples, and No. 20-23 are conventional examples) are melted in a small vacuum melting furnace. And a 30 kg steel ingot. These steel ingots were heated to 1100-1250 ° C. and then hot-rolled under conditions of finishing temperature: 750-950 ° C. and winding temperature: 400-850 ° C. to obtain 4.0 mm thick hot rolled sheets. These hot-rolled sheets were subjected to hot-rolled sheet annealing at 800 to 1100 ° C. by continuous annealing, pickled, and then cold-rolled to obtain cold-rolled sheets having a thickness of 1.5 mm. Subsequently, finish annealing was performed at 880 to 1100 ° C. in an argon atmosphere, followed by cooling and pickling.

かくして得られた各冷延焼鈍板から、試験片を採取し、#600番の研磨紙で鋼板表面を研磨して酸化膜およびテンパーカラーを除去した。ついで、ティグ溶接により、板厚:1.5mmのSUS304との突合せの溶接継手を作製した。この際、裏ビードが1.5〜3mmになるように、溶接電流を制御した。
溶接条件は以下の通りである。
・溶接電圧:10V
・溶按電流:150〜190A
・溶接速度:600mm/min
・電極:1.6mmタングステン電極
・シールドガス:Ar 20L/min
・溶接ワイヤ:なし、Y309L
A test piece was collected from each cold-rolled annealed plate thus obtained, and the surface of the steel plate was polished with # 600 polishing paper to remove the oxide film and the temper color. Next, a butt welded joint with SUS304 having a thickness of 1.5 mm was produced by TIG welding. At this time, the welding current was controlled so that the back bead was 1.5 to 3 mm.
The welding conditions are as follows.
・ Welding voltage: 10V
-Hot metal current: 150-190A
・ Welding speed: 600mm / min
・ Electrode: 1.6mm tungsten electrode ・ Shielding gas: Ar 20L / min
・ Welding wire: None, Y309L

溶接ビードを中心にして、60mmw×80mmlの試験片を採取し、#600番の研磨紙で研磨して溶接によるテンパーカラーを除去した。
ついで、得られた試験片の、SUS304との異材溶接継手の耐食性を調査するため、複合サイクル腐食試験を行った。
複合サイクル腐食試験の条件は以下のとおりである。
・1サイクル:塩水噴霧(35℃,5%NaCl,2hr)

乾燥(60℃,4hr)

湿潤(50℃,2hr)
・試験サイクル数:30サイクル
A test piece of 60 mmw × 80 mml was collected around the weld bead and polished with # 600 abrasive paper to remove the temper collar by welding.
Subsequently, in order to investigate the corrosion resistance of the dissimilar material welded joint with SUS304 of the obtained test piece, a combined cycle corrosion test was conducted.
The conditions of the combined cycle corrosion test are as follows.
-1 cycle: salt spray (35 ° C, 5% NaCl, 2 hr)

Dry (60 ℃, 4hr)

Wet (50 ℃, 2hr)
・ Number of test cycles: 30 cycles

複合サイクル腐食試験を行った試験片に対し、溶接部および母材部の発錆状況を、以下の基準で評価した。
A:発錆なし
B:赤錆面積10%未満
C:赤錆面積10%以上、30%未満
D:赤錆面積30%以上、70%未満
E:赤錆面積70%以上
得られた耐食性を表2に示す。
The test piece subjected to the combined cycle corrosion test was evaluated for the rusting state of the welded part and the base metal part according to the following criteria.
A: No rusting B: Red rust area less than 10% C: Red rust area less than 10%, less than 30% D: Red rust area less than 30%, less than 70% E: Corrosion resistance obtained is more than 70% red rust area is shown in Table 2 .

Figure 2008179886
Figure 2008179886

Figure 2008179886
Figure 2008179886

表2に示したとおり、発明例はいずれも、優れた溶接部の耐食性を有していた。これに対し、本発明の範囲を外れる比較例および従来例はいずれも、耐食性が劣っていた。   As shown in Table 2, all of the inventive examples had excellent corrosion resistance of welds. On the other hand, both the comparative example and the conventional example that are out of the scope of the present invention were inferior in corrosion resistance.

Claims (4)

質量%で、
C:0.030%以下、 N:0.030%以下、 (C+N):0.050%以下、
Si:0.50%以下、 Mn:0.50%以下、 Al:0.10%以下、
Cr:20.5〜22.5%、 Cu:0.30〜1.00%、 Ni:1.50%以下、
Nb:0.20〜0.70%、 P:0.040%以下およびS:0.010%以下
を含有し、かつこれらの成分が、次式(1),(2)
(Cr+1.5Si+0.5Nb)≦23.0 ・・・ (1)
(Ni+30C+0.5Mn+0.5Cu+30N)≧0.90 ・・・ (2)
の関係を満足し、残部はFeおよび不可避的不純物からなることを特徴とする、オーステナイト系ステンレス鋼との異材溶接部の耐食性に優れたフェライト系ステンレス鋼板。
% By mass
C: 0.030% or less, N: 0.030% or less, (C + N): 0.050% or less,
Si: 0.50% or less, Mn: 0.50% or less, Al: 0.10% or less,
Cr: 20.5-22.5%, Cu: 0.30-1.00%, Ni: 1.50% or less,
Nb: 0.20 to 0.70%, P: 0.040% or less and S: 0.010% or less, and these components are represented by the following formulas (1) and (2)
(Cr + 1.5Si + 0.5Nb) ≦ 23.0 (1)
(Ni + 30C + 0.5Mn + 0.5Cu + 30N) ≧ 0.90 (2)
A ferritic stainless steel sheet excellent in the corrosion resistance of dissimilar welds with austenitic stainless steel, wherein the balance consists of Fe and inevitable impurities.
前記鋼板が、質量%で、さらに、
V:1.00%以下
を含有することを特徴とする、請求項1に記載のオーステナイト系ステンレス鋼との異材溶接部の耐食性に優れたフェライト系ステンレス鋼板。
The steel sheet is in mass%, and
V: A ferritic stainless steel sheet excellent in corrosion resistance of a dissimilar material weld with the austenitic stainless steel according to claim 1, containing 1.00% or less.
質量%で、
C:0.030%以下、 N:0.030%以下、 (C+N):0.050%以下、
Si:0.50%以下、 Mn:0.50%以下、 Al:0.10%以下、
Cr:20.5〜22.5%、 Cu:0.30〜1.00%、 Ni:1.50%以下、
Nb:0.20〜0.70%、 P:0.040%以下およびS:0.010%以下
を含有し、かつこれらの成分が、次式(1),(2)
(Cr+1.5Si+0.5Nb)≦23.0 ・・・ (1)
(Ni+30C+0.5Mn+0.5Cu+30N)≧0.90 ・・・ (2)
の関係を満足し、残部はFeおよび不可避的不純物の組成になるステンレス鋼素材を、熱間圧延したのち、連続焼鈍により800〜1100℃の温度で熱延板焼鈍を施し、ついで酸洗後、冷間圧延、仕上げ焼鈍、冷却および酸洗の工程を経て、冷延焼鈍板とすることを特徴とする、オーステナイト系ステンレス鋼との異材溶接部の耐食性に優れたフェライト系ステンレス鋼板の製造方法。
% By mass
C: 0.030% or less, N: 0.030% or less, (C + N): 0.050% or less,
Si: 0.50% or less, Mn: 0.50% or less, Al: 0.10% or less,
Cr: 20.5-22.5%, Cu: 0.30-1.00%, Ni: 1.50% or less,
Nb: 0.20 to 0.70%, P: 0.040% or less and S: 0.010% or less, and these components are represented by the following formulas (1) and (2)
(Cr + 1.5Si + 0.5Nb) ≦ 23.0 (1)
(Ni + 30C + 0.5Mn + 0.5Cu + 30N) ≧ 0.90 (2)
The stainless steel material with the balance of Fe and unavoidable impurities is hot-rolled, the hot-rolled sheet is annealed at a temperature of 800 to 1100 ° C by continuous annealing, and then pickling, A method for producing a ferritic stainless steel sheet having excellent corrosion resistance in a welded portion of a dissimilar material with austenitic stainless steel, characterized by being subjected to cold rolling, finish annealing, cooling, and pickling to form a cold rolled annealed sheet.
前記ステンレス鋼素材が、質量%で、さらに、
V:1.00%以下
を含有することを特徴とする、請求項3に記載のオーステナイト系ステンレス鋼との異材溶接部の耐食性に優れたフェライト系ステンレス鋼板の製造方法。
The stainless steel material is in mass%,
V: 1.00% or less, The manufacturing method of the ferritic stainless steel plate excellent in the corrosion resistance of the dissimilar-material weld part with the austenitic stainless steel of Claim 3 characterized by the above-mentioned.
JP2007332400A 2006-12-26 2007-12-25 Ferritic stainless steel sheet with excellent corrosion resistance of dissimilar welds with austenitic stainless steel and method for producing the same Active JP5205952B2 (en)

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JPH0565600A (en) * 1991-09-05 1993-03-19 Kawasaki Steel Corp Ferritic stainless steel for porcelain enameling and pretreatment to porcelain enameling
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JP2010100909A (en) * 2008-10-24 2010-05-06 Jfe Steel Corp High corrosion-resistant ferritic stainless steel sheet having excellent joint strength, for resistance spot welding
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