JP3567222B2 - High corrosion-resistant austenitic stainless steel and welding materials with excellent bead width uniformity and back bead forming ability - Google Patents
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Description
【０００１】
【発明の属する技術分野】
【０００２】
本発明は、ビード幅の均一性と裏ビード形成能に優れた高耐食オーステナイト系ステンレス鋼とその溶接用材料に関し、より詳しくは、化学工業用装置あるいは核燃料再処理設備の配管等、高い耐食性が要求される部位に使用されるビード幅の均一性と裏ビード形成能に優れた高耐食オーステナイト系ステンレス鋼とその溶接材料に関する。
【従来の技術】
【０００３】
ＳＵＳ３０４、同３１０、同３１６に代表されるオーステナイト系ステンレス鋼は、その優れた耐食性から広範な用途に使用されている。使用される環境が、特に厳しい腐食環境の場合には、ＳＵＳ３０４Ｌのように炭素量を低くし、耐食性を高めたオーステナイト系ステンレス鋼が使用されている。
【０００４】
これらのステンレス鋼が、構造用あるいは配管用の母材材料として用いられる場合には、溶接によって施工されることが多い。溶接法としては、アーク溶接法が一般的であり、溶接される母材材料は勿論、溶接に際して用いられる溶接材料（ワイヤ）に対しては、当然のことながら良好な溶接性が要求される。
【０００５】
このため、オーステナイト系ステンレス鋼の溶接性の向上対策としては、従来から数多くの提案がなされている。
【０００６】
例えば、特開昭５９−１５３８７０号公報には、溶接熱影響部の割れ感受性を低減するために、Ｃｕの含有量を低く制限するとともに、Ｎｉバランスを所定の範囲内に規定したオーステナイト系ステンレス鋼が提案されている。また、特開昭６１−２８８０５３号公報には、薄鋼板のＴＩＧ溶接時に溶着金属のセンター落ちおよびアンダーカットの発生を防止することを目的として、ＭｎとＳｉ含有率の比Ｍｎ／Ｓｉを３以上としたオーステナイト系ステンレス鋼が提案されている。この他、特開昭６３−６０２６０号公報には、薄鋼板のＴＩＧ溶接時のアンダーカットの発生を抑制し、かつ高速溶接を可能にするために、Ｃｕを所定の範囲とし、ＳｉとＭｎとＳ含有率の関係を規定したオーステナイト系ステンレス鋼が開示されている。
【０００７】
一方、溶接材料としては、例えば、特開昭６２−１３４１９６号公報には、Ｃｒ、Ｍｏの含有量を高くし、かつＮｉバランスを規定することにより、オーステナイト鋼、特に１８Ｃｒ−１０Ｎｉ−２Ｓｉ−０．１Ｎのオーステナイト系ステンレス鋼に優れた継手強度および耐食性を有する溶接金属部を提供しうる溶接材料が提案されている。また、特開昭６０−１３０４９６号公報には、Ｍｏ、Ｖ、Ｔｉ等を添加することにより、溶接継手の高温強度を改善したオーステナイト系ステンレス鋼用の溶接材料が提案されている。さらに、特開昭６２−２４０１９３号公報には、ＳとＯ（酸素）量を所定の範囲内に規定することにより、裏ビード形成能の改善を図った溶接材料が提案されている。
【０００８】
しかし、これらの溶接性を改善したオーステナイト系ステンレス鋼および溶接材料も、化学工業装置あるいは核燃料再処理設備の配管等の母材材料および溶接材料として使用される場合には問題が多い。例えば、オーステナイト系ステンレス鋼が、化学工業装置、核燃料再処理設備等の配管として使用される場合、母材材料および溶接材料に対して、優れた耐食性を備えることに加えて、円周溶接性に優れていることが要求される。ここで、円周溶接性とは、溶接時の高温割れやアンダーカットなどの溶接欠陥が発生しないのは勿論であり、健全な溶接ビードが容易に得られるという溶接施工性をも意味する。具体的には、ビード幅の均一なビードが得られること、裏ビードが形成され易いことといった特性を備えたオーステナイト系ステンレス鋼および溶接材料が求められている。
【０００９】
この溶接施工性の改善策として、従来は、上記特開昭６２−２４０１９３号公報に見られるように、裏ビード形成能を有するＳの含有量を可及的に高くする対策が講じられていた。すなわち、表面活性元素であるＳの作用により、溶融池内に内向きの対流を発生させ、その熱輸送の効果により溶け込み深さを増大させ、これによって裏ビード形成能を向上させようとする考え方であった。この対策により、溶接施工性については、一応の成果を得ていた。
【００１０】
しかし、Ｓには裏ビード形成能を向上させる働きがある反面、溶接欠陥発生の原因となり得る溶接ビード幅の均一性を著しく劣化させるとともに、オーステナイト系ステンレス鋼およびその溶接金属の耐食性を低下させる弊害がある。そのため、化学工業用装置、核燃料再処理設備の配管等、高耐食性を要求される部位への適用には、ビード幅の均一性と裏ビード形成能および耐食性の面で満足できるものではなかった。
【００１１】
このように、溶接時のビード幅の均一性や裏ビード形成能に優れていることに加えて、耐食性にも優れるオーステナイト系ステンレス鋼および溶接材料は、未だ開発されていないのが実状である。
【発明が解決しようとする課題】
【００１２】
本発明の課題は、上記の実状に鑑みなされたもので、化学工業用装置、核燃料再処理設備の配管等、厳しい腐食環境での使用に耐える耐食性を備えるとともに、ビード幅の均一性と裏ビード形成能に優れたオーステナイト系ステンレス鋼と溶接材料を提供することにある。
【課題を解決するための手段】
【００１３】
本発明者らは、厳しい腐食環境における耐食性を備え、かつビード幅の均一性と裏ビード形成能に優れたオーステナイト系ステンレス鋼と溶接材料を開発することを目標に調査研究を行った結果、次の（ａ）〜（ｄ）の知見を得た。
【００１４】
（ａ）鋼中のＳには、裏ビード形成能を高める働きがある。その反面、耐食性および溶接ビード幅の均一性を悪くする作用がある。Ｓについては、裏ビード形成能を犠牲にしてでも、高耐食性と溶接ビード幅の均一性を確保できる条件を選ぶべきである。そのためには、Ｓ含有量を０．００５重量％（以下、化学成分の含有率の％表示は重量％を表す）とする必要がある。ただし、溶接材料については後述する本発明の成分範囲外のオーステナイト系ステンレス鋼を溶接対象とする場合においても優れたビード幅の均一性と裏ビード形成能を確保するためには、母材の希釈を考慮して０．００４％以下とする必要がある。
【００１５】
（ｂ）Ｓの低減によって低下する裏ビード形成能は、Ｓと同様に表面活性作用を有するＯ（酸素）の含有量を適正化することによって補うことができる。しかし、Ｏ（酸素）含有量が過剰になると、溶融池で生成するスラグ量が増加し、湯流れが悪くなるために、溶接ビード幅の均一性が低下する。スラグの生成量は、溶融池のＯ（酸素）含有量とＡｌ含有量の関係が、下記(1)式の条件を超えると顕著になる。
【００１６】
Ｏ＝０．０００１２／（％Ａｌ）2/3 ＋０．００５
ここで、元素記号は、各元素の含有率（重量％）を表す。
【００１７】
従って、Ｏ（酸素）含有率は下記(1)式を満足させる必要がある。
【００１８】
０．００２５≦（％Ｏ）≦０．０００１２／（％Ａｌ）2/3 ＋０．００５・・・(1) 式
ただし、溶接材料については、前述したＳの場合と同じ理由により、下記(2)式の条件を満足させる必要がある。
【００１９】
０．００３０≦（％Ｏ）≦０．０００１２／（％Ａｌ）2/3 ＋０．００５・・・(2) 式
なお、上記特開昭６２−２４０１９３号公報に開示される技術では、Ａｌとは無関係にＯ（酸素）量を単独に規定しているに過ぎず、両者を関連つけることの必要性については何らの記載もない。
【００２０】
（ｃ）Ａｌ含有率が０．０１０％以上の場合には、溶融池に溶解できるＯ（酸素）量が低くなり過ぎる傾向がある。従って、裏ビード形成能を確保するために、Ａｌ含有率は０．０１０％以下に制限する必要がある。ただし、溶接材料については、上記ＳおよびＯ（酸素）の場合と同様、母材との希釈を考慮すると、０．００８％以下に制限する必要がある。
【００２１】
（ｄ）Ｍｎはアーク電流の集中の度合いを増し、入熱を集中させるため、溶け込み深さを大きくし、裏ビード形成能を向上させる働きがある。この効果を得るには、０．０５〜４．０％のＭｎ含有率が必要である。ただし、溶接材料については、熱間圧延による線材加工時の加工性を確保するためには０．８〜５．０％のＭｎ含有率が必要である。
【００２２】
上記の知見に基づく本発明の要旨は、次の（１）及び（２）のビード幅の均一性と裏ビード形成能に優れた高耐食オーステナイト系ステンレス鋼、並びに、（３）及び（４）のビード幅の均一性と裏ビード形成能に優れた高耐食オーステナイト系ステンレス鋼用溶接材料にある。
【００２３】
（１）重量％で、Ｃ：０．０２５％以下、Ｓｉ：０．０５〜１．５％、Ｍｎ：０．０５〜４．０％、Ｃｒ：１５〜２７％、Ｎｉ：８〜２３％、Ａｌ：０．０１０％以下を含有し、残部Ｆｅおよび不可避不純物からなり、不純物中のＰ、Ｓがそれぞれ０．０４０％以下、０．００５％以下であり、さらに不純物中のＯ（酸素）が下式を満たすことを特徴とするビード幅の均一性と裏ビード形成能に優れた高耐食オーステナイト系ステンレス鋼。
０．００２５≦（％Ｏ）≦０．０００１２／（％Ａｌ）2/3 ＋０．００５
（２）重量％で、Ｃ：０．０２５％以下、Ｓｉ：０．０５〜１．５％、Ｍｎ：０．０５〜４．０％、Ｃｒ：１５〜２７％、Ｎｉ：８〜２３％、Ａｌ：０．０１０％以下、Ｍｏ：１．８〜３．２％を含有し、残部Ｆｅおよび不可避不純物からなり、不純物中のＰ、Ｓがそれぞれ０．０４０％以下、０．００５％以下であり、さらに不純物中のＯ（酸素）が下式を満たすことを特徴とするビード幅の均一性と裏ビード形成能に優れた高耐食オーステナイト系ステンレス鋼。
０．００２５≦（％Ｏ）≦０．０００１２／（％Ａｌ） 2/3 ＋＋０．００５
（３）重量％で、Ｃ：０．０２５％以下、Ｓｉ：０．０５〜１．５％、Ｍｎ：０．８〜５．０％、Ｃｒ：１７〜２９％、Ｎｉ：８〜２４％、Ａｌ：０．００８％以下を含有し、残部Ｆｅおよび不可避不純物からなり、不純物中のＰ、Ｓがそれぞれ０．０４０％以下、０．００４％以下であり、さらに不純物中のＯ（酸素）が下式を満たすことを特徴とするビード幅の均一性と裏ビード形成能に優れた高耐食オーステナイト系ステンレス鋼用溶接材料。
０．００３０≦（％Ｏ）≦０．０００１２／（％Ａｌ）2/3 ＋０．００５
（４）重量％で、Ｃ：０．０２５％以下、Ｓｉ：０．０５〜１．５％、Ｍｎ：０．８〜５．０％、Ｃｒ：１７〜２９％、Ｎｉ：８〜２４％、Ａｌ：０．００８％以下、Ｍｏ：１．８〜３．２％を含有し、残部Ｆｅおよび不可避不純物からなり、不純物中のＰ、Ｓがそれぞれ０．０４０％以下、０．００４％以下であり、さらに不純物中のＯ（酸素）が下式を満たすことを特徴とするビード幅の均一性と裏ビード形成能に優れた高耐食オーステナイト系ステンレス鋼用溶接材料。
０．００３０≦（％Ｏ）≦０．０００１２／（％Ａｌ） 2/3 ＋０．００５
なお、上記本発明のオーステナイト系ステンレス鋼および溶接材料は、Ｍｏを含有してもしなくてもよいが、Ｍｏを含有させる場合は１．８％以上含有させるのが好ましい。
【発明の実施の形態】
【００２４】
本発明のオーステナイト系ステンレス鋼（以下、母材という）および溶接材料の各化学成分の作用とその限定理由を以下に述べる。なお、以下において「％」は重量％を意味する。
【００２５】
Ｃ：０．０２５％以下Ｃは、オーステナイト形成元素としてオーステナイト相の安定化に寄与するとともに、固溶して強度の向上に寄与する。しかし、過剰に含有させるとＣｒ炭化物を生成し、耐食性の劣化を招く。この耐食性劣化の問題は、特に溶接熱影響部で顕著になる。このため、Ｃｒ炭化物を生成させないため、母材および溶接材料ともに、Ｃ含有量は０．０２５％以下とする。望ましい上限は０．０２３％であり、さらに望ましい上限は０．０２０％である。また、下限は特に設ける必要ないが、製造コストの上昇を抑制するためには０．００２％以上が望ましく、さらに０．００４％以上とするのがより望ましい。
【００２６】
Ｓｉ：０．０５〜１．５％Ｓｉは、溶製時に脱酸元素として添加される元素であり、耐酸化性を向上させる働きもある。これらの効果を得るためには、母材および溶接材料ともに、０．０５％以上のＳｉ含有量が必要である。一方、Ｓｉ含有量が１．５％を超えると溶接高温割れ感受性が増大する。
【００２７】
よって、母材および溶接材料ともに、Ｓｉ含有量は０．０５〜１．５％とした。望ましい範囲は０．０６〜１．２％、さらに望ましい範囲は０．０８〜１．０％である。
【００２８】
Ｍｎ：母材は０．０５〜４．０％、溶接材料は０．８〜５．０％Ｍｎは、溶製時に脱酸元素として添加され、この他、ステンレス鋼の熱間加工性の向上、オーステナイト相の安定化に寄与する。また、Ｍｎは溶接部でＳを固定して高温割れ感受性を低減させる。さらに、Ｍｎはアーク電流の集中の度合いを増し、入熱を集中させるため、溶け込み深さを大きくし、裏ビード形成能を向上させる。これらの効果を得るためには、母材については０．０５％以上、溶接材料については熱間圧延による線材加工時の加工性確保のためには０．８％以上のＭｎ含有量が必要である。一方、その含有量が母材については４．０％を超えると、また溶接材料については５．０％を超えると多量の介在物が生成し、溶接部の靱性が著しく劣化する。
【００２９】
よって、母材のＭｎ含有量は、０．０５〜４．０％とした。望ましい範囲は０．０８〜３．５％、さらに望ましい範囲０．１〜３．０％である。また、溶接材料のＭｎ含有量は、０．８〜５．０％とした。望ましい範囲は０．９〜４．８％、さらに望ましい範囲１．０〜４．５％である。
【００３０】
Ｃｒ：母材は１５〜２７％、溶接材料は１７〜２９％Ｃｒは、溶接部の耐酸化性、耐食性の確保に不可欠の元素である。このためには、母材では１５％以上、溶接継手部は凝固ままの組織で母材に比べて耐食性が劣るため、溶接材料では１７％以上のＣｒ含有量が必要である。一方、その含有量が母材では２７％を、溶接材料では２９％を超えるとＣｒ炭化物の粒界析出を招き、耐食性が劣化するのみならず、組織の安定性を劣化させる。よって、母材のＣｒ含有量は１５〜２７％、溶接材料のＣｒ含有量は１７〜２９％とした。
【００３１】
Ｎｉ：母材は８〜２３％、溶接材料は８〜２４％Ｎｉは、強力なオーステナイト生成元素であり、オーステナイト組織の安定化に必須の元素である。このためには、母材および溶接材料ともに８％以上のＮｉ含有量が必要である。一方、Ｎｉは極めて高価であり、その含有量が母材では２３％を、溶接材料では２４％を超えて含有させてもその効果が飽和し、大幅なコスト上昇を招く。よって、母材のＮｉ含有量は８〜２３％、溶接材料のＮｉ含有量は８〜２４％とした。
【００３２】
なお、上記のＣｒとＮｉは、本発明の母材および溶接材料の一般的な耐食性、耐孔食性、耐応力腐食割れ性、耐硝酸腐食性、溶接性、溶接施工性、加工性、機械的性質、組織安定性などの諸特性を左右する元素であり、上記の範囲内の含有率で適宜組み合わせることができる。例えば、上記諸特性のうち、特に、(a)耐硝酸腐食性を付与したい場合、(b)耐硝酸腐食性に加えて耐孔食性を向上させたい場合、(c)高濃度硝酸に対する耐食性を向上させたい場合には、ＣｒとＮｉと下記の範囲で組み合わせるのが好ましい。
【００３３】
(a)の場合：母材では、Ｃｒ：１７〜２１％、Ｎｉ：８〜１４％。好ましくはＣｒ：１７．２〜２０．８％、Ｎｉ：８．２〜１３．８％、さらに好ましくはＣｒ：１７．５〜２０．５％、Ｎｉ：８．５〜１４．５％。
【００３４】
溶接材料では、Ｃｒ：１８〜２５％、Ｎｉ：８〜１５％。好ましくはＣｒ：１８．２〜２４．８％、Ｎｉ：８．２〜１４．８％、さらに好ましくはＣｒ：１８．５〜２４．５％、Ｎｉ：８．５〜１４．５％。
【００３５】
(b)の場合：母材では、Ｃｒ：１５〜１９％、Ｎｉ：１１〜１６％。好ましくはＣｒ：１５．２〜１８．８％、Ｎｉ：１１．２〜１５．８％、さらに好ましくはＣｒ：１５．５〜１８．５％、Ｎｉ：１１．５〜１５．５％。に加え、後述のＭｏを含有させる。
【００３６】
溶接材料では、Ｃｒ：１７〜２１％、Ｎｉ：１０〜１５％。好ましくはＣｒ：１７．２〜２０．８％、Ｎｉ：１０．２〜１４．８％、さらに好ましくはＣｒ：１７．５〜２０．５％、Ｎｉ：９．５〜１４．５％。に加え、後述のＭｏを含有させる。
【００３７】
(c)の場合：母材では、Ｃｒ：２３〜２７％、Ｎｉ：１８〜２３％。好ましくはＣｒ：２３．２〜２６．８％、Ｎｉ：１８．２〜２２．８％、さらに好ましくはＣｒ：２３．５〜２６．５％、Ｎｉ：１８．５〜２２．５％。に加え、後述のＭｏを含有させる。
【００３８】
溶接材料では、Ｃｒ：２４〜２９％、Ｎｉ：１９〜２４％。好ましくはＣｒ：２４．２〜２８．８％、Ｎｉ：１９．２〜２３．８％、さらに好ましくはＣｒ：２４．５〜２８．５％、Ｎｉ：１９．５〜２３．５％。
【００３９】
Ｐ：０．０４０％以下Ｐは、不可避不純物であり、多量に存在すると溶接部の加熱脆化を招くため、母材および溶接材料ともに、その含有量は０．０４０％以下とする。
【００４０】
なお、Ｐは少なければ少ないほど好ましいが、極度の低Ｐ化には多大なコストの増加を伴う。このため、その下限は０．００１％程度、望ましくは０．００２％程度に留めるのが好ましい。また、望ましい上限は０．０３５％であり、さらに望ましい上限は０．０３０％である。
【００４１】
Ｓ：母材は０．００５％以下、溶接材料は０．００４％以下Ｓは、その含有率が本発明の母材および溶接材料を特徴付ける元素の一つである。Ｓは、上記Ｐと同様、不可避不純物であるが、前述したように、本発明の課題に対しては重要な影響を及ぼす元素である。すなわち、Ｓは溶融池の溶け込み深さを深くし、裏ビード形成能を向上させるのに有用な元素である。しかし、その含有量が母材では０．００５％を、溶接材料では０．００４％を超えると耐食性を劣化させるとともに、溶融池が変動し易くなるために、溶接ビード幅の均一性を劣化させる。このため、本発明においては、母材のＳ含有量は０．００５％以下、溶接材料のＳ含有量は０．００４％以下とした。
【００４２】
なお、Ｐと同様、Ｓは少なければ少ないほど好ましいが、極度の低Ｓ化には多大なコストの増加を伴う。このため、その下限は、母材および溶接材料ともに、０．０００３％程度、望ましくは０．０００５％程度に留めるのが好ましい。また、望ましい上限は、母材では０．００４５％、さらに望ましい上限は０．００４０％であり、溶接材料では０．００３５％、さらに望ましい上限は０．００３０％である。
【００４３】
Ａｌ：母材は０．０１０％以下、溶接材料は０．００８％以下Ａｌは強力な脱酸元素であり、溶製時に添加され、その一部は溶鋼中のＯ（酸素）と結合し、酸化物としてＯ（酸素）とともに系外に取り除かれる。鋼中に残ったＡｌは、溶接時に溶融池の中で、Ｏ（酸素）の溶解量とスラグ生成量に影響を及ぼす。Ａｌの含有量が母材では０．０１０％を、溶接材料では０．００８％を超えると、溶融池のＯ（酸素）が低くなりすぎ、かつスラグ生成量が多くなりすぎるので、溶け込み深さが浅くなり、十分な裏ビード形成能を確保できなのみならず、湯流れが悪くなるために溶接ビード幅の均一性が低下する。そのため、Ａｌの含有量は、母材では０．０１０％以下、溶接材料では０．００８％とした。
【００４４】
なお、上記Ｐ、Ｓと同様、Ａｌは少なければ少ないほど好ましいが、極度の低Ａｌ化には溶製時のコストの上昇を伴う。このため、母材および溶接材料ともに、その下限は０．０００５％程度、望ましくは０．００１％程度に留めるのが好ましい。また、望ましい上限は、母材では０．００９０％、さらに望ましくは０．００８０％であり、溶接材料では０．００７５％であり、さらに望ましくは０．００７０％である。
【００４５】
Ｏ（酸素）：母材の下限は０．００２５％、溶接材料の下限は０．００３０％以上、いずれも上限は［０．０００１２／（％Ａｌ）2/3 ＋０．００５］％Ｏ（酸素）は、Ｓと同様、その含有率が本発明の母材および溶接材料を特徴付ける元素である。Ｏ（酸素）は、溶製の段階から、溶鋼中に不可避的に存在する不純物元素であり、一般的には少なければ少ないほどよいとされる。しかし、本発明においては、必要な元素であり、溶融池の溶け込み深さを深くし、裏ビード形成能を向上させるのに必要不可欠である。この効果を得るためには、母材では０．００２５％以上、溶接材料では０．００３０％以上、のＯ（酸素）含有量が必要である。しかし、過剰に含有させると、溶鋼中に溶解できないＯ（酸素）がＡｌと結合し、スラグとなって溶湯池上に浮遊して湯流れを悪くし、溶接ビードの均一性を劣化させる。
【００４６】
このため、母材および溶接材料ともに、Ｏ（酸素）含有量の上限は、Ａｌ含有量との関係から、下記のように限定した。
Ｏ（％）≦０．０００１２／Ａｌ2/3 ＋０．００５
従って、母材のＯ（酸素）含有量は下記(1)式、溶接材料のＯ（酸素）含有量は下記(2) 式として、それぞれ、規定される。
０．００２５≦（％Ｏ）≦０．０００１２／（％Ａｌ）2/3 ＋０．００５・・・(1) 式
０．００３０≦（％Ｏ）≦０．０００１２／（％Ａｌ）2/3 ＋０．００５・・・(2) 式
図１は、後述の実施例結果を示し、本発明の母材を溶加材（溶接材料）を用いることなくＴＩＧなめ溶接接合した場合における母材のＯ（酸素）含有量とＡｌ含有量が裏ビード形成能およびビード幅の均一性に及ぼす影響を示す図である。この図から明かなように、上記(1)式を満たす場合に良好な裏ビード成形能と均一なビード幅が得られていることがわかる。
【００４７】
なお、Ｏ（酸素）含有量の望ましい下限は、母材では０．００２８％、さらに望ましくは０．００３０％であり、溶接材料では０．００３２％、さらに望ましくは０．００３５％である。
【００４８】
本発明の母材および溶接材料は、上記の成分の他に、強度および耐食性を向上させる目的でＭｏを含有させることができる。
【００４９】
Ｍｏ：１．８〜３．２％Ｍｏは、基地に固溶し、強度の向上に寄与するとともに、不働態皮膜の安定化を図り、耐食性、特に耐孔食性の向上に寄与する元素である。このため、強度および耐孔食性の向上を図りたい場合に添加含有させることができる。その効果は１．８％以上を含有させる場合に得られる。しかし、３．２％を超えて含有させると、σ相の析出を招き、衝撃性能、耐食性が劣化する。従って、含有させる場合のＭｏ含有量は１．８〜３．２％とする。望ましい範囲は１．９〜３．１％、さらに望ましい範囲は２．０〜３．０％である。
【００５０】
以上のべたように、本発明の母材および溶接材料は、炭素含有量の低いオーステナイト系ステンレス鋼において、Ａｌ、ＳおよびＯ（酸素）の含有量を特定の範囲に規定したことに特徴がある。
【００５１】
本発明の母材および溶接材料は、通常の工業的なステンレス鋼の製造方法によって製造することができる。精錬については、アーク式電気炉による溶解法、ＡＯＤ（アルゴン−酸素脱酸）法、ＶＯＤ（真空酸素脱炭）法などが適している。Ｓの低減（脱硫）については、脱炭の前工程で脱硫処理を行うのが効果的である。
【００５２】
また、ＡｌおよびＯ（酸素）含有量を本発明の範囲内に収めるためには、所定の化学組成に成分調整された溶鋼に対して真空処理を施し、これらの元素の成分調整精度を向上させる方法が有効である。成分調整された溶鋼は、連続鋳造法または造塊法によって、スラブ（ビッレト）またはインゴットに鋳造する。このスラブまたはインゴットから、例えば継目無鋼管を製造する場合には、ユジーンセジュルネ法に代表される熱間押出し製管法やマンネスマン穿孔圧延法に代表されるマンネスマン−プラグミル製管法、あるいはマンネスマン−マンドレルミル製管法によって製管することができる。その他、圧延することによって鋼板を製造することもでき、鍛造することによって鍛鋼部品とすることもできる。また、溶接材料については、熱間圧延によって線材とし、これをそのままあるいは冷間引き抜き加工した後、溶接材料（ワイヤ）とする。
【実施例】
【００５３】
《その１》表１および表２に示す化学組成を有する３５種類の鋼管を準備した。これらの鋼管は、いずれも溶製、熱間押出し製管、冷間引抜き加工の工程を経て外径２７．２ｍｍ、肉厚２．５ｍｍの鋼管に成形した。溶接は、鋼管の端面を機械加工により、Ｒｍａｘで１００μｍに仕上げ、ルート間隔０ｍｍのＩ開先で突き合わせて円周自動ＴＩＧ溶接機により、平均入熱量が約５ｋＪ／ｃｍになる条件で溶加材（溶接材料）を用いることなく、ＴＩＧなめ溶接して溶接継手を作製した。
【００５４】
【表１】
【表２】
母材鋼管の性能は、引張強さと耐食性を、以下に述べる方法によって調べた。
【００５７】
引張強さは、ＪＩＳ−Ｚ２２０１に規定の１２Ａ号試験片を採取し、常温で引張試験を行い、ＳＵＳ３０４ＬおよびＳＵＳ３１６Ｌの引張強さ基準値である５２０Ｎ／ｍｍ2 以上のものを良として判定した。
【００５８】
また、耐食性は、溶接継手を６５％硝酸溶液中に４８時間浸漬する操作を５回繰り返す沸騰浸漬試験を行って腐食速度を求め、腐食速度が０．３ｇ／ｍ2 ・ｈ以下となるか否かで良否判定した。
【００５９】
一方、継手の性能（引張強さと耐食性）とビード幅の均一性と裏ビード形成能は、以下に述べる方法によって評価した。
【００６０】
継手の引張強さは、継手部からＪＩＳ−Ｚ３１２１に規定の２号管状試験片を採取し、母材の場合と同様に、常温で引張試験を行い、ＳＵＳ３０４ＬおよびＳＵＳ３１６Ｌの引張強さ基準値である５２０Ｎ／ｍｍ2 以上のものを良として判定した。また、耐食性は、部継手部を、母材の場合と同様に、６５％硝酸溶液中に４８時間浸漬する操作を５回繰り返す沸騰浸漬試験を行って腐食速度を求め、腐食速度が０．３ｇ／ｍ2 ・ｈ以下となるか否かで良否判定した。
【００６１】
溶接ビードの均一性については、得られた溶接ビードの定常部のビード幅を円周方向に３ｍｍの等間隔で測定し、最大ビード幅と最小ビード幅の差（変動幅）を求め、その差が２ｍｍ以上となるか否かで良否判定を行った。また、裏ビード形成能については、管内面側を観察し、１００％裏ビードが形成されているか否かで良否判定を行った。
【００６２】
これらの試験結果を、表３に示した。また、溶接ビードの均一性と裏ビード形成能については、Ａｌ含有量とＯ（酸素）含有量との関係を図１に示した。
【００６３】
【表３】
表３および図１に示す結果から明らかなように、本発明鋼からなる鋼管（No.Ａ１〜Ａ２０）およびその溶接継手部（No. ＡＷ１〜ＡＷ２０）は、十分な引張強さを有し、かつ優れた耐食性を有している。また、溶接施工時には均一な幅の溶接ビードが得られ、溶接ビードの均一性と裏ビード形成能にも優れている。
【００６５】
これに対し、本発明の成分範囲を外れる鋼からなる鋼管（No. Ｂ１〜Ｂ１５）およびその溶接継手部（No. ＢＷ１〜ＢＷ１５）の引張強度については良好であるが、優れた耐食性とビード幅の均一性と裏ビード形成能のすべてに満足のゆくものは得られなかった。
【００６６】
すなわち、No. Ｂ１、Ｂ２、Ｂ６およびＢ１１の鋼管は、鋼中のＳ含有量がそれぞれ０．００６０％、０．００８２％、０．００５８％および０．００６５％といずれも過剰であるため、母材および溶接継手部（No. ＢＷ１、ＢＷ２、ＢＷ６およびＢＷ１１）とも腐食速度が０．３ｇ／ｍ2 ・ｈ以上で、耐食性が劣っている。また、最大ビード変動幅が２ｍｍ以上で、均一なビード幅の溶接ビードも得られなかった。
【００６７】
また、No. Ｂ３、Ｂ７、Ｂ８およびＢ１２の鋼管では、鋼中のＡｌ含有量が、それぞれ０．０１２％、０．０１２％、０．０１８％および０．０１６％といずれも過剰で、溶接時の溶鋼中に溶解できるＯ（酸素）量が少なくなるため、その溶接継手部（No. ＢＷ３、ＢＷ７、ＢＷ８およびＢＷ１２）には、裏ビードが形成されない部分が存在し、裏ビード形成能が劣っていた。また、これらのうち、No. ＢＷ１２の溶接継手部は、母材鋼管中のＯ（酸素）含有量が［０．０００１２／（％Ａｌ）2/3 ＋０．００５］を超えているため、ＡｌとＯ（酸素）が結合して溶融池上に多量のスラグが浮遊し、溶融池の湯流れが悪くなり、均一なビード幅の溶接ビードも得られなかった。
【００６８】
さらに、No. Ｂ４、Ｂ９、Ｂ１３およびＢ１４の鋼管では、上記No. Ｂ１２の鋼管と同様、母材鋼管中のＯ（酸素）含有量がいずれも［０．０００１２／（％Ａｌ）2/3 ＋０．００５］％を超えているため、ＡｌとＯ（酸素）が結合して溶融池上にスラグが浮遊し、溶融池が不安定となり、その溶接継手部（No. ＢＷ４、ＢＷ９、ＢＷ１３およびＢＷ１４）の最大ビード変動幅がいずれも２ｍｍ以上となっている。
【００６９】
また更に、No. Ｂ５、Ｂ１０およびＢ１５の鋼管では、鋼中のＯ（酸素）含有量がそれぞれ０．００１８％、０．００２０％および０．００１０％と少ないため、その溶接継手部（No. ＢＷ５、ＢＷ１０およびＢＷ１５）には、いずれも裏ビードが形成していない部分が存在し、裏ビード形成能に劣っていた。
【００７０】
《その２》表４および表５に示す化学組成を有する３５種類の溶接材料を準備した。これらの溶接材料は、いずれも溶製、熱間加工、線引加工の工程を経て外径０．８ｍｍの線材に成形した。溶接は、表６に示す化学組成を有する外径２７．２ｍｍ、肉厚２．５ｍｍの３種類の鋼管の管端部に図２に示す形状寸法の開先加工を施し、ルート間隔０ｍｍで突き合わせ、円周自動ＴＩＧ溶接機によって平均入熱量が約５ｋＪ／ｃｍになる条件でビードオン溶接して溶接継手を作製した。
【００７１】
なお、表６中のNo. Ｐ１の供試鋼管については表４中のNo. Ｃ１〜Ｃ７および表５中のNo. Ｄ１〜Ｄ５の溶接材料を、No. Ｐ２の供試鋼管については表４中のNo. Ｃ８〜Ｃ１３および表５中のNo. Ｄ６〜Ｄ１０の溶接材料を、No. Ｐ３の供試鋼管については表４中のNo. Ｃ１４〜Ｃ２０および表５中のNo. Ｄ１１〜Ｄ１５の溶接材料を、それぞれ用いた。
【００７２】
【表４】
【表５】
【表６】
得られた各継手部の継手性能とビード幅の均一性と裏ビード形成能を、上記実施例《その１》と同じ方法によって調べた。
【００７６】
すなわち、溶接ビードの均一性については、得られた溶接ビードの定常部のビード幅を円周方向に３ｍｍの等間隔で測定し、最大ビード幅と最小ビード幅の差（変動幅）を求め、その差が２ｍｍ以上となるか否かで良否判定を行った。また、裏ビード形成能については、管内面側を観察し、１００％裏ビードが形成されているか否かで良否判定を行った。
【００７７】
また、継手性能は、継手の引張強と耐食性について調べ、引張強さについては、継手部からＪＩＳ−Ｚ３１２１に規定の２号管状試験片を採取し、常温で引張試験を行って引張強さを求め、引張強さが５２０Ｎ／ｍｍ2 以上であるか否かで良否判定した。また、耐食性については、継手部を６５％硝酸溶液中に４８時間浸漬する操作を５回繰り返す沸騰浸漬試験を行って腐食速度を求め、腐食速度が０．３ｇ／ｍ2 ・ｈ以下となるか否かで良否判定した。
【００７８】
これらの試験結果を、表７に示した。なお、表７中、ＤＷ２、ＤＷ３、ＤＷ７〜ＤＷ９、ＤＷ１２およびＤＷ１３については、裏ビード形成能が不芳であったので、引張試験を省略した。
【００７９】
【表７】
表７に示す結果から明らかなように、本発明の溶接材料（No. Ｃ１〜Ｃ２０）を用いて溶接した鋼管（No. Ｐ１〜Ｐ３）の継手部（No. ＣＷ１〜ＣＷ２０）は、十分な引張強さを有しており、かつ優れた耐食性を有している。また、溶接施工時には均一な幅の溶接ビードが得られ、裏ビード形成能にも優れている。
【００８１】
これに対し、本発明の成分範囲を外れる溶接材料（No. Ｄ１〜Ｄ１５）を用いて溶接した比較例の鋼管の継手部（No. ＤＷ１〜ＤＷ１５）では、引張強度は良好であるが、優れた耐食性とビード幅の均一性と裏ビード形成能のすべてに満足のゆくものは得られなかった。
【００８２】
すなわち、No. ＤＷ１、ＤＷ２、ＤＷ６およびＤＷ１１の継手部は、用いた溶接材料（No. Ｄ１、Ｄ２、Ｄ６およびＤ１１）中のＳ含有量が、それぞれ０．００５０％、０．００７５％、０．００４５％および０．００６５％といずれも過剰であるため、母材、溶接継手部ともに腐食速度が０．３ｇ／ｍ2 ・ｈ以上で、耐食性が劣っている。また、最大ビード変動幅が２ｍｍ以上で、均一なビード幅の溶接ビードも得られなかった。
【００８３】
また、No. ＤＷ３、ＤＷ７、ＤＷ８およびＤＷ１２の継手部では、用いた溶接材料（No. Ｄ３、Ｄ７、Ｄ８およびＤ１２）中のＡｌ含有量が、それぞれ０．００９０％、０．０１２０％、０．００８５％および０．００９８％といずれも過剰で、溶接時の溶鋼中に溶解できるＯ（酸素）量が少なくなるため、裏ビードが形成されない部分が存在し、裏ビード形成能が劣っている。
【００８４】
さらに、No. ＤＷ５、ＤＷ１０、ＤＷ１４およびＤＷ１５の継手部では、用いた溶接材料（No. Ｄ５、Ｄ１０、Ｄ１４およびＤ１５）中のＯ（酸素）含有量が、いずれも［０．０００１２／（％Ａｌ）2/3 ＋０．００５］％を超えているため、ＡｌとＯ（酸素）が結合して溶融池上にスラグが浮遊し、溶融池が不安定となり、最大ビード変動幅が２ｍｍ以上となっている。
【００８５】
また更に、No. ＤＷ４、ＤＷ９およびＤＷ１３の継手部では、用いた溶接材料（No. Ｄ４、Ｄ９およびＤ１３）中のＯ（酸素）含有量が、それぞれ０．００２５％、０．００１０％および０．００２０％と少ないため、裏ビードが形成していない部分が存在し、裏ビード形成能が劣っている。
【発明の効果】
【００８６】
本発明鋼または溶接材料によれば、完全な裏ビードを有する均一なビード幅の優れた強度と耐食性を有する溶接継手が得られる。特に、本発明の溶接材料を用いる場合には、母材との希釈を考慮した成分組成としたので、被溶接材料である母材の成分組成、特にＡｌ、Ｏ（酸素）およびＳが本発明鋼の範囲内であるか否かに関係なく、完全な裏ビードを有する均一なビード幅の優れた強度と耐食性を有する溶接継手が得られる。
【図面の簡単な説明】
【００８７】
【図１】母材のＯ（酸素）含有量とＡｌ含有量が裏ビード形成能およびビード幅の均一性に及ぼす影響を示す図である。
【図２】実施例で用いた溶接開先の形状と寸法を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
[0002]
The present inventionBead width uniformity and back bead forming abilityHighly corrosion resistant austenitic stainless steel with excellent corrosion resistance and its welding materials, more specifically used for parts requiring high corrosion resistance, such as piping for chemical industry equipment or nuclear fuel reprocessing equipmentBead width uniformity and back bead forming abilityHighly corrosion resistant austenitic stainless steel with excellent weldability
[Prior art]
[0003]
Austenitic stainless steels represented by SUS304, 310, and 316 are used for a wide range of applications because of their excellent corrosion resistance. If the environment to be used is a particularly severe corrosive environment, an austenitic stainless steel having a low carbon content and improved corrosion resistance, such as SUS304L, is used.
[0004]
When these stainless steels are used as base materials for structures or pipes, they are often constructed by welding. As a welding method, an arc welding method is generally used, and naturally, good weldability is required for not only a base material to be welded but also a welding material (wire) used for welding.
[0005]
For this reason, many proposals have conventionally been made as measures for improving the weldability of austenitic stainless steel.
[0006]
For example, Japanese Unexamined Patent Publication (Kokai) No. 59-153870 discloses an austenitic stainless steel in which the Cu content is limited to a low value and the Ni balance is regulated within a predetermined range in order to reduce the cracking susceptibility of the heat affected zone. Has been proposed. Japanese Patent Application Laid-Open No. Sho 61-288053 discloses that the ratio Mn / Si of Mn / Si content is 3 or more for the purpose of preventing the center drop of weld metal and the occurrence of undercut during TIG welding of a thin steel sheet. Austenitic stainless steel has been proposed. In addition, Japanese Patent Application Laid-Open No. 63-60260 discloses that in order to suppress the occurrence of undercut during TIG welding of a thin steel sheet and to enable high-speed welding, Cu is set to a predetermined range, and Si and Mn are mixed. An austenitic stainless steel in which the relationship of the S content is specified is disclosed.
[0007]
On the other hand, as a welding material, for example, Japanese Unexamined Patent Publication (Kokai) No. 62-134196 discloses an austenitic steel, particularly 18Cr-10Ni-2Si-0, by increasing the contents of Cr and Mo and defining the Ni balance. There has been proposed a welding material capable of providing a weld metal portion having excellent joint strength and corrosion resistance to a 1N austenitic stainless steel. Japanese Patent Application Laid-Open No. Sho 60-130496 proposes a welding material for austenitic stainless steel in which the high-temperature strength of a welded joint is improved by adding Mo, V, Ti, and the like. Further, Japanese Unexamined Patent Publication (Kokai) No. 62-240193 proposes a welding material in which the amount of S and O (oxygen) is defined within a predetermined range to improve the back bead forming ability.
[0008]
However, these austenitic stainless steels and welding materials with improved weldability also have many problems when used as base materials and welding materials for piping of chemical industry equipment or nuclear fuel reprocessing equipment. For example, when austenitic stainless steel is used as piping for chemical industry equipment, nuclear fuel reprocessing equipment, etc., in addition to having excellent corrosion resistance to the base material and welding material, it is also necessary to improve circumferential weldability. It is required to be excellent. Here, the term “circumferential weldability” means not only that welding defects such as high-temperature cracking and undercutting do not occur during welding, but also welding workability that a sound weld bead can be easily obtained. Specifically, there is a demand for an austenitic stainless steel and a welding material having characteristics such that a bead having a uniform bead width is obtained and a back bead is easily formed.
[0009]
As a measure for improving the welding workability, conventionally, as seen in the above-mentioned Japanese Patent Application Laid-Open No. 62-240193, a measure for increasing the content of S having a back bead forming ability as much as possible has been taken. . In other words, by the action of S, which is a surface active element, an inward convection is generated in the molten pool, and the penetration depth is increased by the effect of heat transfer, thereby improving the back bead forming ability. there were. With this measure, the welding workability has been achieved to some extent.
[0010]
However, while S has the function of improving the ability to form a back bead, the uniformity of the weld bead width, which may cause welding defects, is significantly deteriorated, and the corrosion resistance of austenitic stainless steel and its weld metal is reduced. There is. Therefore, application to parts that require high corrosion resistance, such as chemical industry equipment and nuclear fuel reprocessing equipment piping,Bead width uniformity and back bead forming abilityAnd corrosion resistance were not satisfactory.
[0011]
As described above, austenitic stainless steels and welding materials that are excellent in corrosion resistance as well as in bead width uniformity and back bead forming ability during welding have not yet been developed.
[Problems to be solved by the invention]
[0012]
The object of the present invention has been made in view of the above-described circumstances, and has corrosion resistance enough to withstand use in a severe corrosive environment, such as a chemical industrial apparatus, piping of a nuclear fuel reprocessing facility, and the like.Bead width uniformity and back bead forming abilityIt is to provide an excellent austenitic stainless steel and a welding material.
[Means for Solving the Problems]
[0013]
The present inventors have provided corrosion resistance in a severe corrosive environment, andBead width uniformity and back bead forming abilityAs a result of conducting research with the aim of developing an excellent austenitic stainless steel and a welding material, the following findings (a) to (d) were obtained.
[0014]
(A) S in steel has a function of enhancing the ability to form a back bead. On the other hand, it has the effect of deteriorating the corrosion resistance and the uniformity of the weld bead width. Regarding S, conditions that can ensure high corrosion resistance and uniformity of the weld bead width should be selected even at the expense of the ability to form a back bead. For that purpose, the S content needs to be 0.005% by weight (hereinafter, the percentage of the content of the chemical component is represented by% by weight). However, the welding material is excellent even when austenitic stainless steel outside the component range of the present invention described below is to be welded.Bead width uniformity and back bead forming abilityIn order to ensure the above, it is necessary to set the content to 0.004% or less in consideration of the dilution of the base material.
[0015]
(B) The ability to form a back bead, which is reduced due to the reduction of S, can be compensated by optimizing the content of O (oxygen), which has a surface activity like S. But O(oxygen)If the content is excessive, the amount of slag generated in the molten pool increases, and the flow of the molten metal deteriorates, so that the uniformity of the weld bead width decreases. The amount of slag generated depends on the O(oxygen)The relationship between the content and the Al content is as follows:(1)It becomes remarkable when the condition of the expression is exceeded.
[0016]
O = 0.00012 / (% Al)2/3 +0.005
Here, the element symbols indicate the content (% by weight) of each element.
[0017]
Therefore, O(oxygen)The content is as follows(1)It is necessary to satisfy the formula.
[0018]
0.0025 ≦ (% O) ≦ 0.00012 / (% Al)2/3 +0.005 ・ ・ ・(1) formula
However, for the welding material, for the same reason as in the case of S described above,(2)It is necessary to satisfy the condition of the expression.
[0019]
0.0030 ≦ (% O) ≦ 0.00012 / (% Al)2/3 +0.005 ・ ・ ・(2) formula
In the technique disclosed in Japanese Patent Application Laid-Open No. 62-240193, O is independent of Al.(oxygen)It merely specifies the amount alone, and does not disclose any need to link the two.
[0020]
(C) When the Al content is 0.010% or more, O(oxygen)The amount tends to be too low. Therefore, it is necessary to limit the Al content to 0.010% or less in order to secure the back bead forming ability. However, for the welding material, the above S and O(oxygen)As in the case of the above, when the dilution with the base material is taken into consideration, the content must be limited to 0.008% or less.
[0021]
(D) Mn has the function of increasing the degree of concentration of the arc current and concentrating the heat input, thereby increasing the penetration depth and improving the back bead forming ability. To obtain this effect, a Mn content of 0.05 to 4.0% is required. However, as for the welding material, a Mn content of 0.8 to 5.0% is necessary in order to secure workability during wire processing by hot rolling.
[0022]
The gist of the present invention based on the above findings is as follows (1)as well as(2)Bead width uniformity and back bead forming abilityAustenitic stainless steel with excellent corrosion resistanceAnd high corrosion resistant austenitic stainless steel with excellent bead width uniformity and back bead forming ability of (3) and (4)In the welding material.
[0023]
(1) By weight%, C: 0.025% or less, Si: 0.05 to 1.5%, Mn: 0.05 to 4.0%, Cr: 15 to 27%, Ni: 8 to 23% , Al: 0.010% or less, the balance being Fe and unavoidable impurities, P and S in the impurities are 0.040% or less and 0.005% or less, respectively, and O (oxygen) in the impurities is further included. Satisfies the following equationBead width uniformity and back bead forming abilityExcellent corrosion resistant austenitic stainless steel.
0.0025 ≦ (% O) ≦ 0.00012 / (% Al)2/3 +0.005
(2)By weight%, C: 0.025% or less, Si: 0.05 to 1.5%, Mn: 0.05 to 4.0%, Cr: 15 to 27%, Ni: 8 to 23%, Al: 0.010% or less, Mo: 1.8 to 3.2%, the balance is composed of Fe and unavoidable impurities, and P and S in the impurities are 0.040% or less and 0.005% or less, respectively. Further, a high corrosion resistant austenitic stainless steel excellent in bead width uniformity and back bead forming ability, characterized in that O (oxygen) in impurities satisfies the following formula.
0.0025 ≦ (% O) ≦ 0.00012 / (% Al) 2/3 ++ 0.005
(3)By weight%, C: 0.025% or less, Si: 0.05 to 1.5%, Mn: 0.8 to 5.0%, Cr: 17 to 29%, Ni: 8 to 24%, Al: 0.008% or less, the balance being Fe and unavoidable impurities, P and S in the impurities are 0.040% or less and 0.004% or less, respectively, and O (oxygen) in the impurities is represented by the following formula. Characterized by satisfyingBead width uniformity and back bead forming abilityExcellent welding material for high corrosion resistant austenitic stainless steel.
0.0030 ≦ (% O) ≦ 0.00012 / (% Al)2/3 +0.005
(4) By weight%, C: 0.025% or less, Si: 0.05 to 1.5%, Mn: 0.8 to 5.0%, Cr: 17 to 29%, Ni: 8 to 24% , Al: 0.008% or less, Mo: 1.8 to 3.2%, the balance being Fe and unavoidable impurities, and P and S in the impurities are 0.040% or less and 0.004% or less, respectively. And a high corrosion resistant austenitic stainless steel welding material excellent in bead width uniformity and back bead forming ability, wherein O (oxygen) in impurities satisfies the following formula.
0.0030 ≦ (% O) ≦ 0.00012 / (% Al) 2/3 +0.005
In addition,The austenitic stainless steel and the welding material of the present invention may or may not contain Mo, but when Mo is contained, it is preferable to contain 1.8% or more.
BEST MODE FOR CARRYING OUT THE INVENTION
[0024]
The action of each chemical component of the austenitic stainless steel (hereinafter, referred to as base metal) and the welding material of the present invention and the reason for limiting the same will be described below. In the following, "%" means% by weight.
[0025]
C: 0.025% or less C contributes to the stabilization of the austenite phase as an austenite-forming element, and also to the solid solution to improve the strength. However, when it is contained excessively, Cr carbide is generated, which causes deterioration of corrosion resistance. This problem of corrosion resistance deterioration is particularly noticeable in the heat affected zone. For this reason, in order not to generate Cr carbide, the C content of both the base metal and the welding material is set to 0.025% or less. A desirable upper limit is 0.023%, and a more desirable upper limit is 0.020%. The lower limit is not particularly required, but is preferably 0.002% or more, and more preferably 0.004% or more, in order to suppress an increase in manufacturing cost.
[0026]
Si: 0.05 to 1.5% Si is an element added as a deoxidizing element at the time of melting, and also has a function of improving oxidation resistance. In order to obtain these effects, both the base metal and the welding material require a Si content of 0.05% or more. On the other hand, if the Si content exceeds 1.5%, the susceptibility to welding hot cracking increases.
[0027]
Therefore, the Si content is set to 0.05 to 1.5% for both the base material and the welding material. A desirable range is 0.06 to 1.2%, and a more desirable range is 0.08 to 1.0%.
[0028]
Mn: 0.05 to 4.0% for the base material and 0.8 to 5.0% for the welding material Mn is added as a deoxidizing element at the time of melting, and in addition, improves the hot workability of stainless steel. Contributes to stabilization of the austenite phase. In addition, Mn fixes S at the welded portion and reduces hot cracking susceptibility. Further, Mn increases the degree of concentration of arc current and concentrates heat input, so that the penetration depth is increased and the back bead forming ability is improved. In order to obtain these effects, a Mn content of 0.05% or more for the base material and 0.8% or more of the welding material is required for ensuring the workability of the wire rod by hot rolling. is there. On the other hand, if the content exceeds 4.0% for the base material and 5.0% for the welding material, a large amount of inclusions are generated, and the toughness of the welded portion is significantly deteriorated.
[0029]
Therefore, the Mn content of the base material is set to 0.05 to 4.0%. A desirable range is 0.08 to 3.5%, and a more desirable range is 0.1 to 3.0%. Further, the Mn content of the welding material was set to 0.8 to 5.0%. A desirable range is 0.9 to 4.8%, and a more desirable range is 1.0 to 4.5%.
[0030]
Cr: 15-27% of base material and 17-29% of welding material Cr is an element indispensable for securing the oxidation resistance and corrosion resistance of the welded portion. For this purpose, the base material has a Cr content of 15% or more, and the welded joint portion has a Cr content of 17% or more because the structure is as solidified and has lower corrosion resistance than the base material. On the other hand, if the content exceeds 27% in the base material and exceeds 29% in the welding material, it causes grain boundary precipitation of Cr carbide, which deteriorates not only corrosion resistance but also structure stability. Therefore, the Cr content of the base material was set to 15 to 27%, and the Cr content of the welding material was set to 17 to 29%.
[0031]
Ni: 8 to 23% of base material and 8 to 24% of welding material Ni is a strong austenite-forming element and is an essential element for stabilizing the austenite structure. For this purpose, both the base material and the welding material require a Ni content of 8% or more. On the other hand, Ni is extremely expensive. Even if the content of Ni is more than 23% in the base material and more than 24% in the welding material, the effect is saturated and a significant increase in cost is caused. Therefore, the Ni content of the base material was set to 8 to 23%, and the Ni content of the welding material was set to 8 to 24%.
[0032]
The above-mentioned Cr and Ni are used for the general corrosion resistance, pitting corrosion resistance, stress corrosion cracking resistance, nitric acid corrosion resistance, weldability, welding workability, workability, mechanical properties of the base material and welding material of the present invention. It is an element that affects various properties such as properties and tissue stability, and can be appropriately combined at a content within the above range. For example, among the above characteristics,(a)If you want to give nitric acid corrosion resistance,(b)To improve pitting corrosion resistance in addition to nitric acid corrosion resistance,(c)When it is desired to improve the corrosion resistance to high concentration nitric acid, it is preferable to combine Cr and Ni in the following range.
[0033]
(a)In the case of: In the base material, Cr: 17 to 21%, Ni: 8 to 14%. Preferably, Cr: 17.2 to 20.8%, Ni: 8.2 to 13.8%, more preferably Cr: 17.5 to 20.5%, Ni: 8.5 to 14.5%.
[0034]
In the welding material, Cr: 18 to 25%, Ni: 8 to 15%. Preferably, Cr: 18.2 to 24.8%, Ni: 8.2 to 14.8%, more preferably Cr: 18.5 to 24.5%, Ni: 8.5 to 14.5%.
[0035]
(b)In the case of: In the base material, Cr: 15 to 19%, Ni: 11 to 16%. Preferably, Cr: 15.2 to 18.8%, Ni: 11.2 to 15.8%, more preferably Cr: 15.5 to 18.5%, Ni: 11.5 to 15.5%. In addition, Mo described below is contained.
[0036]
In the welding material, Cr: 17 to 21%, Ni: 10 to 15%. Preferably, Cr: 17.2 to 20.8%, Ni: 10.2 to 14.8%, more preferably Cr: 17.5 to 20.5%, Ni: 9.5 to 14.5%. In addition, Mo described below is contained.
[0037]
(c)In the case of: In the base material, Cr: 23 to 27%, Ni: 18 to 23%. Preferably, Cr: 23.2 to 26.8%, Ni: 18.2 to 22.8%, more preferably Cr: 23.5 to 26.5%, Ni: 18.5 to 22.5%. In addition, Mo described below is contained.
[0038]
In the welding material, Cr: 24 to 29%, Ni: 19 to 24%. Preferably, Cr: 24.2 to 28.8%, Ni: 19.2 to 23.8%, more preferably Cr: 24.5 to 28.5%, Ni: 19.5 to 23.5%.
[0039]
P: 0.040% or less P is an unavoidable impurity, and if present in a large amount, heat embrittlement of the welded portion is caused. Therefore, the content of both the base metal and the welding material is set to 0.040% or less.
[0040]
It should be noted that the smaller the P, the better. However, the extremely low P involves a great increase in cost. Therefore, the lower limit is preferably set to about 0.001%, and more preferably to about 0.002%. A desirable upper limit is 0.035%, and a more desirable upper limit is 0.030%.
[0041]
S: 0.005% or less of base material and 0.004% or less of welding material S is one of the elements whose content rate characterizes the base material and welding material of the present invention. S is an unavoidable impurity like P as described above, but as described above, is an element that has an important effect on the object of the present invention. That is, S is an element useful for increasing the penetration depth of the molten pool and improving the back bead forming ability. However, if the content exceeds 0.005% in the base material and exceeds 0.004% in the welding material, the corrosion resistance is deteriorated, and the weld pool tends to fluctuate, thereby deteriorating the uniformity of the weld bead width. . For this reason, in the present invention, the S content of the base metal is set to 0.005% or less, and the S content of the welding material is set to 0.004% or less.
[0042]
Note that, like P, the smaller the S, the better. However, extremely low S involves a large increase in cost. For this reason, it is preferable that the lower limit is set to about 0.0003%, preferably about 0.0005% for both the base material and the welding material. Further, a desirable upper limit is 0.0045% for the base material, a more desirable upper limit is 0.0040%, and a more desirable upper limit is 0.0035% for the welding material, and a more desirable upper limit is 0.0030%.
[0043]
Al: 0.010% or less of base material, 0.008% or less of welding material Al is a strong deoxidizing element, and is added at the time of smelting, and a part of it is combined with O (oxygen) in molten steel, O as oxide(oxygen)Is removed out of the system. Al remaining in the steel becomes O in the molten pool during welding.(oxygen)Affects the amount of slag produced and the amount of slag produced. If the Al content exceeds 0.010% in the base material and exceeds 0.008% in the welding material, the O(oxygen)Is too low, and the amount of slag generated is too large, so that the penetration depth becomes shallow and not only the back bead forming ability cannot be secured sufficiently, but also the uniformity of the weld bead width due to poor molten metal flow. descend. Therefore, the content of Al is set to 0.010% or less for the base material and 0.008% for the welding material.
[0044]
Like P and S, the smaller the amount of Al, the better. However, extremely low Al involves an increase in the cost of melting. Therefore, the lower limit of both the base metal and the welding material is preferably set to about 0.0005%, and more preferably to about 0.001%. A desirable upper limit is 0.0090% for the base material, more preferably 0.0080%, and 0.0075% for the welding material, and more preferably 0.0070%.
[0045]
O (oxygen): The lower limit of the base material is 0.0025%, the lower limit of the welding material is 0.0030% or more, and the upper limit is [0.00012 / (% Al).2/3 +0.005]% O (oxygen), like S, is an element whose content characterizes the base material and the welding material of the present invention. O(oxygen)Is an impurity element inevitably present in molten steel from the stage of smelting, and it is generally said that the smaller the amount, the better. However, in the present invention, it is a necessary element and is indispensable for increasing the penetration depth of the molten pool and improving the back bead forming ability. In order to obtain this effect, O of 0.0025% or more in the base material and 0.0030% or more of the welding material is required.(oxygen)Content is required. However, if it is contained excessively, it cannot be dissolved in molten steel.(oxygen)Combines with Al and becomes a slag and floats on the molten metal pond to deteriorate the flow of the molten metal and deteriorate the uniformity of the weld bead.
[0046]
Therefore, both the base material and the welding material(oxygen)The upper limit of the content was limited as described below in relation to the Al content.
O (%) ≦ 0.00012 / Al2/3 +0.005
Therefore, the base material O(oxygen)The content is as follows(1)Formula, welding material O(oxygen)The content is as follows(2) formulaAs,Respectively,Stipulated.
0.0025 ≦ (% O) ≦ 0.00012 / (% Al)2/3 +0.005 ・ ・ ・(1) formula
0.0030 ≦ (% O) ≦ 0.00012 / (% Al)2/3 +0.005 ・ ・ ・(2) formula
FIG. 1 shows the results of examples described later, and shows that the base metal of the present invention was subjected to TIG tanning welding without using a filler material (welding material).(oxygen)It is a figure which shows the influence which content and Al content give to back bead formation ability and uniformity of bead width. As can be seen from this figure,(1)It can be seen that when the formula is satisfied, good back bead molding ability and uniform bead width are obtained.
[0047]
Note that O(oxygen)A desirable lower limit of the content is 0.0028%, more preferably 0.0030% for the base material, and 0.0032%, more preferably 0.0035% for the welding material.
[0048]
The base material and the welding material of the present invention can contain Mo for the purpose of improving strength and corrosion resistance in addition to the above-mentioned components.
[0049]
Mo: 1.8 to 3.2% Mo is an element that forms a solid solution in the matrix and contributes to the improvement of the strength, stabilizes the passive film, and contributes to the improvement of corrosion resistance, particularly pitting corrosion resistance. . Therefore, it can be added and contained when it is desired to improve the strength and the pitting resistance. The effect is obtained when the content is 1.8% or more. However, when the content exceeds 3.2%, precipitation of the σ phase is caused, and impact performance and corrosion resistance are deteriorated. Therefore, when Mo is contained, the Mo content is set to 1.8 to 3.2%. A desirable range is 1.9 to 3.1%, and a more desirable range is 2.0 to 3.0%.
[0050]
As described above, the base metal and the welding material of the present invention can be used for austenitic stainless steel having a low carbon content in Al, S and O.(oxygen)Is defined in a specific range.
[0051]
The base material and the welding material of the present invention can be manufactured by a general industrial stainless steel manufacturing method. For refining, a melting method using an electric arc furnace, an AOD (argon-oxygen deoxidation) method, a VOD (vacuum oxygen decarburization) method, and the like are suitable. Regarding the reduction of S (desulfurization), it is effective to perform a desulfurization treatment before the decarburization.
[0052]
Al and O(oxygen)In order to keep the content within the scope of the present invention, it is effective to apply a vacuum treatment to molten steel whose components have been adjusted to have a predetermined chemical composition to improve the accuracy of adjusting the components of these elements. The molten steel whose composition has been adjusted is cast into a slab (billet) or ingot by a continuous casting method or an ingot casting method. When producing a seamless steel pipe from this slab or ingot, for example, the Mannesmann-plug mill pipe method represented by the hot extrusion pipe method represented by the Eugene Sejournet method or the Mannesmann piercing and rolling method, or the Mannesmann method It can be manufactured by a mandrel mill manufacturing method. In addition, a steel plate can be manufactured by rolling, and a forged steel part can be formed by forging. The welding material is made into a wire by hot rolling, and is used as it is or after cold drawing, and then used as a welding material (wire).
【Example】
[0053]
<< Part 1 >> 35 types of steel pipes having the chemical compositions shown in Tables 1 and 2 were prepared. Each of these steel pipes was formed into a steel pipe having an outer diameter of 27.2 mm and a wall thickness of 2.5 mm through the steps of melting, hot extrusion, and cold drawing. For welding, the end face of the steel pipe is finished to 100 μm in Rmax by machining, butted at an I groove with a root interval of 0 mm, and is joined by a circumferential automatic TIG welding machine under the condition that the average heat input is about 5 kJ / cm. Without using (welding material), TIG tanning welding was performed to produce a welded joint.
[0054]
[Table 1]
[Table 2]
The performance of the base steel pipe was examined for tensile strength and corrosion resistance by the method described below.
[0057]
For the tensile strength, a No. 12A test piece specified in JIS-Z2201 was sampled, subjected to a tensile test at room temperature, and 520 N / mm, which is the standard value of the tensile strength of SUS304L and SUS316L.Two The above was judged as good.
[0058]
The corrosion resistance was determined by performing a boiling immersion test in which the operation of immersing the welded joint in a 65% nitric acid solution for 48 hours was repeated five times to determine the corrosion rate. The corrosion rate was 0.3 g / m3.Two -The pass / fail was determined based on whether or not h or less.
[0059]
On the other hand, the joint performance (tensile strength and corrosion resistance) andBead width uniformity and back bead forming abilityWas evaluated by the method described below.
[0060]
For the tensile strength of the joint, a No. 2 tubular test piece specified in JIS-Z3121 was sampled from the joint part, and a tensile test was performed at room temperature in the same manner as in the case of the base material, and the tensile strength standard value of SUS304L and SUS316L was used. Some 520 N / mmTwo The above was judged as good. In addition, the corrosion resistance was determined by performing a boiling immersion test in which the operation of immersing the joint part in a 65% nitric acid solution for 48 hours was repeated five times, as in the case of the base material, to determine the corrosion rate. / MTwo -The pass / fail was determined based on whether or not h or less.
[0061]
Regarding the uniformity of the weld bead, the bead width of the steady portion of the obtained weld bead was measured at equal intervals of 3 mm in the circumferential direction, and the difference (fluctuation width) between the maximum bead width and the minimum bead width was determined. Was determined based on whether or not is 2 mm or more. Regarding the back bead forming ability, the pass / fail judgment was made based on whether or not a 100% back bead was formed by observing the inner surface of the tube.
[0062]
Table 3 shows the test results. Further, regarding the uniformity of the weld bead and the ability to form the back bead, the Al content and O(oxygen)FIG. 1 shows the relationship with the content.
[0063]
[Table 3]
As is clear from the results shown in Table 3 and FIG. 1, the steel pipes (No. A1 to A20) made of the steel of the present invention and the welded joints thereof (No. AW1 to AW20) have a sufficient tensile strength. And it has excellent corrosion resistance. Further, a weld bead having a uniform width can be obtained during welding, and the uniformity of the weld bead and the ability to form a back bead are excellent.
[0065]
On the other hand, although the tensile strength of the steel pipe (No. B1 to B15) and the welded joint thereof (No. BW1 to BW15) made of steel out of the component range of the present invention is good, it has excellent corrosion resistance andBead width uniformity and back bead forming abilityofSatisfied with everythingNothing was obtained.
[0066]
That is, in the steel pipes of Nos. B1, B2, B6 and B11, the S content in steel is 0.0060%, 0.0082%, 0.0058% and 0.0065%, which are all excessive, Corrosion rate of 0.3 g / m for both base metal and welded joints (No. BW1, BW2, BW6 and BW11)Two -At h or more, the corrosion resistance is inferior. Further, the maximum bead fluctuation width was 2 mm or more, and a weld bead having a uniform bead width was not obtained.
[0067]
Further, in the steel pipes of Nos. B3, B7, B8 and B12, the Al content in the steel was 0.012%, 0.012%, 0.018% and 0.016%, respectively, all of which were excessive. O that can be dissolved in molten steel at the time(oxygen)Since the amount was small, the welded joints (No. BW3, BW7, BW8, and BW12) had portions where no back bead was formed, and the back bead forming ability was poor. Of these, the welded joint of No. BW12 has O(oxygen)The content is [0.00012 / (% Al)2/3 +0.005], so that Al and O(oxygen)And a large amount of slag floated on the molten pool, the molten metal flow in the molten pool deteriorated, and a weld bead with a uniform bead width could not be obtained.
[0068]
Further, in the steel pipes of Nos. B4, B9, B13 and B14, as in the steel pipes of No. B12, O(oxygen)All contents are [0.00012 / (% Al)2/3 +0.005]%, so that Al and O(oxygen)Are combined, the slag floats on the molten pool, the molten pool becomes unstable, and the maximum bead fluctuation width of the welded joints (Nos. BW4, BW9, BW13, and BW14) is 2 mm or more.
[0069]
Furthermore, in the steel pipes of Nos. B5, B10 and B15, O(oxygen)Since the content is as small as 0.0018%, 0.0020% and 0.0010%, respectively, there is a portion where no back bead is formed in any of the welded joints (No. BW5, BW10 and BW15). However, the back bead forming ability was inferior.
[0070]
<< Part 2 >> 35 kinds of welding materials having the chemical compositions shown in Tables 4 and 5 were prepared. Each of these welding materials was formed into a wire rod having an outer diameter of 0.8 mm through the steps of melting, hot working, and drawing. In welding, three types of steel pipes having an outer diameter of 27.2 mm and a wall thickness of 2.5 mm having the chemical composition shown in Table 6 were subjected to groove processing of the shape and dimensions shown in FIG. 2 at the root ends of 0 mm. A bead-on welding was carried out by a circumferential automatic TIG welding machine under the condition that the average heat input was about 5 kJ / cm to produce a welded joint.
[0071]
In addition, No. C1 to C7 in Table 4 and No. D1 to D5 in Table 5 were used for the test steel pipe of No. P1 in Table 6, and Table 4 was used for the test steel pipe of No. P2. No. C8 to C13 in Table 5 and No. D6 to D10 in Table 5 were used. For the test steel pipe of No. P3, No. C14 to C20 in Table 4 and No. D11 to D15 in Table 5 were used. Were used, respectively.
[0072]
[Table 4]
[Table 5]
[Table 6]
The joint performance of each joint obtainedBead width uniformity and back bead forming abilityWas examined by the same method as in Example << Part 1 >>.
[0076]
That is, regarding the uniformity of the weld bead, the bead width of the steady portion of the obtained weld bead was measured at equal intervals of 3 mm in the circumferential direction, and the difference (fluctuation width) between the maximum bead width and the minimum bead width was obtained. Pass / fail judgment was made based on whether the difference was 2 mm or more. Regarding the back bead forming ability, the pass / fail judgment was made based on whether or not a 100% back bead was formed by observing the inner surface of the tube.
[0077]
For the joint performance, the tensile strength and corrosion resistance of the joint were examined. Regarding the tensile strength, a No. 2 tubular test piece specified in JIS-Z3121 was sampled from the joint and subjected to a tensile test at room temperature to determine the tensile strength. Determined, tensile strength is 520N / mmTwo Pass / fail was determined based on whether or not the above was true. The corrosion rate was determined by performing a boiling immersion test in which the operation of immersing the joint portion in a 65% nitric acid solution for 48 hours was repeated five times to determine the corrosion rate. The corrosion rate was 0.3 g / m3.Two -The pass / fail was determined based on whether or not h or less.
[0078]
Table 7 shows the results of these tests. In Table 7, for DW2, DW3, DW7 to DW9, DW12 and DW13, the back bead forming ability was unsatisfactory, so the tensile test was omitted.
[0079]
[Table 7]
As is clear from the results shown in Table 7, the joint portions (No. CW1 to CW20) of the steel pipes (No. P1 to P3) welded using the welding materials (No. C1 to C20) of the present invention were sufficient. It has tensile strength and excellent corrosion resistance. In addition, a weld bead having a uniform width can be obtained during welding, and the back bead forming ability is excellent.
[0081]
On the other hand, in the joint part (No. DW1 to DW15) of the steel pipe of the comparative example which was welded using the welding material (No. D1 to D15) out of the component range of the present invention, the tensile strength was good but excellent. With corrosion resistanceBead width uniformity and back bead forming abilityofSatisfied with everythingNothing was obtained.
[0082]
That is, in the joints of Nos. DW1, DW2, DW6 and DW11, the S contents in the welding materials (Nos. D1, D2, D6 and D11) used were 0.0050%, 0.0075% and 0%, respectively. 0.0045% and 0.0065%, the corrosion rate of both the base metal and the welded joint was 0.3 g / mTwo -At h or more, the corrosion resistance is inferior. Further, the maximum bead fluctuation width was 2 mm or more, and a weld bead having a uniform bead width was not obtained.
[0083]
In the joints of Nos. DW3, DW7, DW8 and DW12, the Al contents in the used welding materials (Nos. D3, D7, D8 and D12) were 0.0090%, 0.0120% and 0%, respectively. 0.0085% and 0.0098%, both of which are excessive and can be dissolved in molten steel during welding(oxygen)Since the amount is small, there is a portion where no back bead is formed, and the back bead forming ability is inferior.
[0084]
Further, in the joints of Nos. DW5, DW10, DW14 and DW15, O in the welding materials (Nos. D5, D10, D14 and D15) used(oxygen)The content is [0.00012 / (% Al)2/3 +0.005]%, so that Al and O(oxygen)Are combined, slag floats on the molten pool, the molten pool becomes unstable, and the maximum bead fluctuation width is 2 mm or more.
[0085]
Furthermore, in the joints of Nos. DW4, DW9 and DW13, O in the welding materials (Nos. D4, D9 and D13) used(oxygen)Since the contents are as small as 0.0025%, 0.0010% and 0.0020%, respectively, there are portions where no back bead is formed, and the back bead forming ability is inferior.
【The invention's effect】
[0086]
According to the steel or welding material of the present invention, a welded joint having excellent strength and corrosion resistance with a uniform bead width having a complete back bead can be obtained. In particular, when the welding material of the present invention is used, the composition of the component is determined in consideration of the dilution with the base material.(oxygen)Irrespective of whether and S is within the range of the steel of the present invention, a welded joint having excellent strength and corrosion resistance with a uniform bead width having a complete back bead is obtained.
[Brief description of the drawings]
[0087]
FIG. 1 O of base material(oxygen)It is a figure which shows the influence which content and Al content give to back bead formation ability and uniformity of bead width.
FIG. 2 is a view showing the shape and dimensions of a welding groove used in an example.
Claims (4)
０．００２５≦（％Ｏ）≦０．０００１２／（％Ａｌ）2/3 ＋０．００５C: 0.025% or less, Si: 0.05 to 1.5%, Mn: 0.05 to 4.0%, Cr: 15 to 27%, Ni: 8 to 23%, Al: It contains 0.010% or less, the balance being Fe and unavoidable impurities, P and S in the impurities are 0.040% or less and 0.005% or less, respectively, and O (oxygen) in the impurities is expressed by the following formula. High corrosion resistant austenitic stainless steel with excellent bead width uniformity and back bead forming ability characterized by satisfying the following conditions.
0.0025 ≦ (% O) ≦ 0.00012 / (% Al) 2/3 +0.005
０．００２５≦（％Ｏ）≦０．０００１２／（％Ａｌ）2/3 ＋０．００５C: 0.025% or less, Si: 0.05 to 1.5%, Mn: 0.05 to 4.0%, Cr: 15 to 27%, Ni: 8 to 23%, Al: 0.010% or less, Mo: 1.8 to 3.2%, the balance is composed of Fe and unavoidable impurities, and P and S in the impurities are 0.040% or less and 0.005% or less, respectively. Further, a high corrosion resistant austenitic stainless steel excellent in bead width uniformity and back bead forming ability , characterized in that O (oxygen) in impurities satisfies the following formula.
0.0025 ≦ (% O) ≦ 0.00012 / (% Al) 2/3 +0.005
０．００３０≦（％Ｏ）≦０．０００１２／（％Ａｌ）2/3 ＋０．００５% By weight, C: 0.025% or less, Si: 0.05 to 1.5%, Mn: 0.8 to 5.0%, Cr: 17 to 29%, Ni: 8 to 24%, Al: 0.008% or less, the balance being Fe and unavoidable impurities, P and S in the impurities are 0.040% or less and 0.004% or less, respectively, and O (oxygen) in the impurities is represented by the following formula. A high corrosion resistant austenitic stainless steel welding material with excellent bead width uniformity and back bead forming ability characterized by satisfying the following conditions.
0.0030 ≦ (% O) ≦ 0.00012 / (% Al) 2/3 +0.005
０．００３０≦（％Ｏ）≦０．０００１２／（％Ａｌ）2/3 ＋０．００５% By weight, C: 0.025% or less, Si: 0.05 to 1.5%, Mn: 0.8 to 5.0%, Cr: 17 to 29%, Ni: 8 to 24%, Al: 0.008% or less, Mo: 1.8 to 3.2%, the balance consists of Fe and unavoidable impurities, and P and S in the impurities are 0.040% or less and 0.004% or less, respectively. Further, a welding material for a high corrosion-resistant austenitic stainless steel excellent in bead width uniformity and back bead forming ability , wherein O (oxygen) in impurities satisfies the following formula.
0.0030 ≦ (% O) ≦ 0.00012 / (% Al) 2/3 +0.005
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29073995A JP3567222B2 (en) | 1995-11-09 | 1995-11-09 | High corrosion-resistant austenitic stainless steel and welding materials with excellent bead width uniformity and back bead forming ability |
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| Application Number | Priority Date | Filing Date | Title |
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| JP29073995A JP3567222B2 (en) | 1995-11-09 | 1995-11-09 | High corrosion-resistant austenitic stainless steel and welding materials with excellent bead width uniformity and back bead forming ability |
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| Publication Number | Publication Date |
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| JP3567222B2 true JP3567222B2 (en) | 2004-09-22 |
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| KR101230137B1 (en) * | 2010-12-28 | 2013-02-05 | 주식회사 포스코 | method of welding austenitic stainless steel |
| JP5853281B2 (en) * | 2011-03-25 | 2016-02-09 | 日新製鋼株式会社 | Austenitic stainless steel sheet with excellent surface gloss |
| PL399967A1 (en) * | 2012-07-13 | 2014-01-20 | Instytut Wysokich Cisnien Polskiej Akademii Nauk | A method of producing high strength rods and rods of such steel from austenitic steel |
| JP6627373B2 (en) * | 2015-03-04 | 2020-01-08 | 日本製鉄株式会社 | Austenitic stainless steel |
| JP6519009B2 (en) * | 2015-04-08 | 2019-05-29 | 日本製鉄株式会社 | Austenitic stainless steel |
| JP7042057B2 (en) * | 2017-10-25 | 2022-03-25 | 日鉄ステンレス株式会社 | Stainless steel materials and welded structural members with excellent slag spot generation suppression ability and their manufacturing methods |
| CN116377321A (en) * | 2023-03-24 | 2023-07-04 | 鞍钢股份有限公司 | Ultra-pure urea-grade austenitic stainless steel plate without ferrite and preparation method thereof |
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