JP3545193B2 - Solid wire for carbon dioxide shielded arc welding and welding method thereof - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、４９０Ｎ／ｍｍ２ 級高張力鋼に使用する炭酸ガス溶接用ソリッドワイヤに関し、詳しくは高入熱、高パス間温度条件で使用される溶接金属の高靱性、高ＣＯＤが得られる炭酸ガスシールドアーク溶接用ソリッドワイヤおよびその溶接方法に関するものである。
【０００２】
【従来の技術】
近年、建築鉄骨の溶接においてはガスシールドアーク溶接が適用され、高能率化が図られている。しかし、高能率化により使用される溶接条件はより高電流、高入熱、高パス間温度側に移行しつつあるのが現状である。このような高入熱・高パス間温度条件の溶接金属の問題点の１つとして、衝撃靱性の低下が挙げられる。しかしながら、要求される溶接金属の靱性特性は高度化する傾向にある。また、衝撃靱性に加えてＣＯＤ特性の要求が付与される趨勢にあり、優れた高靱性に加えて高ＣＯＤ特性にも優れた溶接金属が得られる溶接材料の要望が極めて強い。従来から靱性向上手段の一つとして、Ｔｉ−Ｂ系溶接材料の検討が行われ、いくつかの提案が成されている。
【０００３】
例えば特開昭５４−４０２５０号公報には、パラメータ（Ｐａ＝Ｔｉ×Ｂ×１０４ ）を１〜２５に限定した高能率ガスシールドアーク溶接用ワイヤの提案がある。この技術は主にＡｒ−ＣＯ２ 混合ガスシールド溶接を対象として、溶接入熱量が最大４０ｋＪ／ｃｍ程度における１ラン溶接での低温靱性向上を目的としたもので、本発明のように炭酸ガスシールドアーク溶接を対象としていない。
また、特開昭６３−１５７７９５号公報も６０キロ級鋼以上のＡｒ−ＣＯ２ 等の混合ガス溶接におけるＰＷＨＴ後の低温靱性改善を目的としており、Ｔｉ（０．０１〜０．１０％）−Ｂ（０．００１〜０．０１０％）系に最大６％までのＮｉを添加した構成により低温靱性を向上させる技術であるが、本発明の炭酸ガスシールド溶接においての高靱性、ＣＯＤ特性改善は望めない。
【０００４】
さらに、特開昭５５−１４９７９７号公報に開示の技術は靱性改善を目的としているが、高パス間温度条件は対象としていないので、本発明が対象とする溶接条件での靱性向上は期待できない。また、特公平４−２０７２０号公報で開示の技術は、炭酸ガスシールドアーク溶接の高入熱条件での靱性向上を目的としているが、高パス間温度条件やＣＯＤ特性については検討されていないため、本発明の効果は期待出来ない。
前述のように、溶接金属の高靱化手法としてＴｉ−Ｂ系溶接ワイヤが提案されているが、本発明の意図する、高入熱−高パス間温度条件ではこのような単なるＴｉ−Ｂ化だけでは、高靱化は計れても高ＣＯＤ特性をも同時に満足することは出来ない。
【０００５】
すなわち、建築鉄骨等の溶接の溶接姿勢は、下向（含む水平姿勢）から横向姿勢までの溶接姿勢が多く、溶接入熱においても、下向継手では高電流の４０ｋＪ／ｃｍを超える高入熱でかつ高パス間温度条件（３５０℃を超える：以下、高入熱条件という）が取られる。また横向継手溶接においては、溶接電流、パス間温度も比較的低く、入熱も１５〜２０ｋＪ／ｃｍの比較的低入熱溶接が行われている（以下、低入熱条件という）。従って、溶接部の冷却速度は適用溶接姿勢によって大きく異なっており、同一のワイヤで溶接した場合は得られる継手溶接金属の強度も溶接姿勢によって異なる。
【０００６】
表１は従来のワイヤにより、高入熱条件と低入熱条件による溶接金属の特性変化を調査した場合を示したものである。表１の結果から明らかなように、従来ワイヤでは、低入熱条件では強度も適当かつ高靱性が得られるが、高入熱条件では強度、靱性共に低下する。また、高入熱条件で適当な強度が得られるワイヤを使用すると、低入熱条件では強度過剰となる。また衝撃靱性も高入熱条件では低下する。
【０００７】
【表１】
【発明が解決しようとする課題】
本発明は、このような状況のもとで、４９０Ｎ／ｍｍ２ 級高張力鋼の炭酸ガスシールドアーク溶接の低入熱溶接条件から高入熱溶接条件までの広い条件域の溶接を行って、適度な溶接金属強度と靱性に優れ、かつ高ＣＯＤ値が得られる強度、靱性のバランスに優れた炭酸ガスシールドアーク溶接用ソリッドワイヤおよびその製造方法を提供することにある。
【０００９】
【課題を解決するための手段】
本発明は、表１に示した横向姿勢で標準的に使用される低入熱条件から下向姿勢での標準的な高入熱条件の広範囲な溶接条件の溶接において、適当な継手溶接金属強度および良好な衝撃靱性、高ＣＯＤ特性、さらには歪時効が少ない溶接金属のソリッドワイヤ成分として、Ｓｉ，Ｍｎ，Ｔｉ，Ｂ，Ａｌ，Ｚｒの添加量範囲を規制し、さらにＣ，Ｐ，Ｓ，Ｍｏ，ＮおよびＶ，Ｎｂの添加範囲を抑制し、高電流域でのアーク安定性を向上する目的でＯ量の下限値を規制した点に特徴がある。
【００１０】
その発明の要旨とするところは、（１）重量％で、Ｃ：≦０．０６％、Ｓｉ：０．６〜１．５％、Ｍｎ：１．７〜２．５％、Ｐ：≦０．０１５％、Ｓ：≦０．０１０％、Ｍｏ：≦０．１０％、Ｔｉ：０．２０〜０．４０％を含有し、Ａｌ：０．００５〜０．０５０％、Ｚｒ：０．００５〜０．０５０％の１種以上を合計で０．００５〜０．０５０％、Ｂ：０．００３０〜０．０１２％であり、さらにＶ：≦０．０５％および、Ｎｂ：≦０．０５％の１種以上合計で≦０．０５％に抑制し、Ｎ：≦０．００３０％、Ｏ：≧０．００６０％であることを特徴とする炭酸ガスシールドアーク溶接用ソリッドワイヤ。
（２）高張力鋼を溶接入熱１５〜４０ｋＪ／ｃｍ、パス間温度１００〜４５０℃の溶接条件により、前記（１）記載のソリッドワイヤを使用して溶接を行うことにより、安定かつ高靱性および高ＣＯＤ特性に優れた溶接金属が得られることを特徴とする炭酸ガスシールドアーク溶接方法にある。
【００１１】
【発明の実施の形態】
以下、本発明について詳細に説明する。
本発明者らはすでに、低入熱条件から高入熱条件の広範囲な溶接条件の溶接において、適当な継手溶接金属強度および良好な衝撃靱性、高ＣＯＤ特性さらには歪時効が少ない鋼ワイヤ成分として、（１）高入熱条件において問題となるＮの影響を軽減して良好な衝撃靱性が得られる基本成分系を提案している。すなわち、Ｔｉ，Ｂ，Ａｌ，Ｚｒ量範囲の限定とＮ量を規制した。（２）また、高入熱条件の衝撃靱性をより効果的に確保することを目的に、Ｃ，Ｓｉ，Ｍｎ，Ｍｏ等の各元素の添加範囲を制限し、（３）ＣＯＤ特性向上、歪時効の軽減を目的にＣおよびＮ量のさらなる制限とＰ，Ｓ添加量を規制した点に特徴があるワイヤを提供している。
【００１２】
しかし、さらに検討を重ねた結果、ワイヤ中のＶ，Ｎｂが高入熱条件の衝撃靱性低下および低入熱条件におけるＣＯＤ特性の低下とその安定性に悪影響があることを突き止めて、本発明を構成した。すなわち、既に提案した前述の構成に若干の変更を加えて、ＶおよびＮｂの添加量を各々０．０５％以下、かつ双方の合計で０．０５％以下に抑制するものである。この構成に至った理由は、各種鋼板において横向き姿勢でのＣＯＤ特性を検討したところ、ＣＯＤ特性と衝撃靱性にバラツキが大きい現象が認められた。その理由について検討した結果、溶接金属中に含有する微量のＶ，Ｎｂが原因せることが判った。このＶ，Ｎｂは高入熱条件における強度低下を抑えるためにワイヤに極微量添加したものと、さらに鋼板中に含有していたものが加わったものである。
【００１３】
高入熱溶接条件における最大の課題は、溶接金属靱性の低下であるが、この靱性確保にＴｉ−Ｂ系は有効な手段である。しかしＴｉ−Ｂ量の添加量適正化によって高靱性は達成できるが、靱性のバラツキを少なくして安定な靱性確保にはＮ量の増加による弊害を軽減するＡｌおよびＺｒの適正添加が有効である。一方、低入熱条件における課題は溶接金属強度の増加と継手ルート部近傍の硬さ増加と不均一によるＣＯＤ値の低下である。強度増加の抑制とルート部の硬さを改善するには、Ｃ，Ｍｏの添加量制限が有効であり、高いＣＯＤ値要求の場合には、更なるこれら元素の添加量制限が必要である。しかし、Ｃ，Ｍｏ等の添加量制限は、高入熱溶接条件での溶接金属強度確保が問題となる。
【００１４】
このように、低入熱条件と高入熱溶接条件では、相反する性能上の課題があり、どちらの条件と性能を重視するかによって好ましいワイヤ成分範囲が異なる。そこで、両条件における性能のバランスを考慮してさらに検討した結果、Ｖ，Ｎｂの添加量を調整することにより、性能バランスが向上することが判った。表２に示すワイヤ（ワイヤ径：１．４ｍｍ）のうちから、ワイヤ記号Ｅ１，Ｆ７，Ｆ１２，Ｆ１３，Ｆ１５，Ｆ１６の６種類を用いて、表３の低入熱条件と高入熱溶接条件により継手溶接金属試験を実施して、表４の結果を得た。なお、鋼板はＳＮ４９０Ｂの３５ｍｍｔを用い、開先形状は図２、試験片採取位置は図３に示すものとした。表４から明らかなように、低入熱条件では強度が高くなりすぎて靱性が低い傾向にあり、高入熱条件では強度が低く靱性が低下する傾向を示す。
【００１５】
【表２】
【表３】
【表４】
図１は表４の結果からワイヤ中のＶ＋Ｎｂ量と衝撃靱性の関係を示したものである。Ｖ＋Ｎｂ量の増加に伴い衝撃靱性は低下するが、特にＶ＋Ｎｂ量が０．０５％を超えると著しく低下し、この傾向は低入熱条件のルート部で顕著である。これは、ＶおよびＮｂは炭・窒化物を形成し易い元素であり、ルート部では母材のＣ量の希釈により溶接金属のＣ量が他の部位より多く、またルート部はガスシールドが不十分となる傾向から若干の大気中からの窒素混入が起こりやすいために、溶接部が硬化することによると考えられ、冷却速度が大きく、硬さが高い低入熱条件では特に影響が大きい。これはルート部の平均硬さの推移からも推定される。また、Ｍｏ量が０．１０％を超える、ワイヤ記号Ｆ７やＦ１２では、Ｖ＋Ｎｂ量が同じレベルと比較して靱性低下が大きい。このように両条件で強度、靱性のバランスが良好なワイヤ成分の条件としては、Ｍｏ≦０．１０％，Ｖ≦０．０５％，Ｎｂ≦０．０５％、かつＶ＋Ｎｂ≦０．０５％であることが判る。
【００１９】
以下に、その他元素の作用効果について簡単に述べる。
高入熱条件において、高衝撃靱性を得るためには、Ｔｉ，Ｂの範囲が重量であり、Ｔｉは０．２０〜０．４０％、Ｂは０．００３０〜０．０１２％の範囲が必要である。また、Ｎは高電流、高パス間溶接条件のもとでは、０．００１０〜０．００３０％程度の侵入が避けられず、０．００３０％を超えると衝撃靱性は急激に低下する。従って、ワイヤ中のＮの規制量として０．００３０％以下が必要である。また、Ｎが溶接金属として０．００３０％を僅かに超えるレベルであれば、適正なＡｌおよびＺｒの添加により衝撃靱性の低下が抑制できることが判った。Ａｌ，Ｚｒの適正添加量は各々０．００５０〜０．０５０％であり、合計でも０．００５０〜０．０５０％である。これを超える添加は、靱性が低下する。Ａｌ，Ｚｒの微量添加がＮによる衝撃靱性低下程度を軽減するのは、Ｎとの親和力の強いＡｌ，Ｚｒが窒化物としてＮの固溶を抑制する作用によるものと考えられる。
【００２０】
しかしながら、このようなＴｉ，Ｂ，Ｎ等を良好な成分範囲に調整しても、Ｓｉ，Ｍｎ量が適正でない場合には靱性が低値を示す。靱性向上に有効なＳｉ，Ｍｎ添加量について検討の結果、ワイヤＳｉ量と０．６％程度を境に衝撃靱性が急激に変化し、０．６％未満では低下する。これは、高入熱条件において、溶着金属中のＳｉ量低下により、酸素量が増加したためと考えられる。一方、ワイヤ中のＳｉ量が１．５％程度以上では、Ｓｉの過剰固溶により素地の硬化が著しく、衝撃靱性が急激に低下する。
【００２１】
Ｍｎの影響はＳｉとほぼ同様な理由により衝撃靱性に影響しており、その適正添加量は１．７〜２．５％の範囲である。高入熱条件におけるＣ，Ｍｏの衝撃靱性に与えるＣ，Ｍｏの影響を検討した結果、Ｃの添加は、高入熱条件における継手強度を高めるには極めて有効であるが、一方、０．０６％を超えて添加した場合に衝撃靱性への悪影響が大きいことが判った。また、Ｍｏの添加は、溶接金属の強度確保に有効であり、さらに高入熱条件における、積層による前パス溶接金属の軟化を抑制して、全体の衝撃靱性向上する効果があるが、この効果も０．１０％を超える添加はむしろ衝撃靱性を低下させることが判った。
【００２２】
また、溶接電流が高い条件（４５０Ａ程度）ではアークが不安定になる現象が観察された。そこで、このアーク不安定現象を高速度ビデオカメラ等により詳細に観察した結果、高電流化により溶融プールが加熱されて振動が激しくなり、この振動が溶滴のスムースな移行を阻害して、スパッタ発生量の増加や官能検査によるアーク不安定の原因になっていることが判明した。そこで、アーク不安定、スパッタ増加抑制について検討した結果、ワイヤ中に酸素を添加することに効果があり、その添加量は０．００６０％以上で顕著である知見を得た。そこで、酸素添加手段について、ワイヤ溶解時に固溶した場合および製造時に酸化物として添加の場合について検討したがいずれの手段でも、アーク安定化に寄与し、酸素の存在形態によらずアーク安定化効果が得られることを確認した。
【００２３】
このように、ＳｉおよびＭｎ範囲の特定、Ｃ，Ｍｏ上限に規制、酸素の添加の構成によって、より高電流条件において、アーク安定化して衝撃靱性が向上することが達成される。これまでは、溶着金属の性能を中心に検討したが、実際の構造物では厚板が使用され、その溶接継手の開先形状はＫ型、Ｘ型などが多く用いられ、溶接は鋼板の両側から行われる。この場合、最初の溶接側（ＢＰ側）を終了した後、最終溶接側（ＦＰ側）を行う前に、ルート面を適当な形状に加工する方法（裏はつり）が行われる。ルート部は開先幅が狭いため、母材を最も多く溶融する箇所であり、また、狭隘のために積層厚が厚く、積層による再加熱が受け難く、継手のなかで最も硬化しやすく、また硬さのバラツキの大きい場所である。特に、高入熱（高電流）溶接条件においてはこの傾向が大きい。
【００２４】
Ｃは継手ルート部の硬さを平均的に硬化し、また溶接パス毎の変化が大きいため、衝撃靱性がある程度高くてもＣＯＤ値を低下せしむる。また、低入熱条件のＢＰ側がＦＰ側に比べて衝撃靱性が低下する現象（歪時効）が認められた。そこで、ワイヤ成分元素中微量微添加で硬さ、衝撃靱性に影響があるＣ，Ｎについて詳細に検討した結果、Ｃ≦０．０６％、Ｎ≦０．００３０％に抑制することが、ＣＯＤ特性向上および歪時効軽減に有効であることを見出した。また、ＰおよびＳについては、各々の添加量の制限に加えて、合計で０．０１５％以下が有効であるとの結果を得た。
【００２５】
以下に本発明に係わる溶接ワイヤの各成分元素の添加理由および限定理由について詳述する。
Ｖ：≦０．０５％
Ｖは、炭、窒化物を形成し、溶接金属の強度向上に有効な元素である。特に溶接金属の強度低下が著しい本発明の対象とする高入熱かつパス間温度の高い高入熱条件においては、比較的微量添加で溶接金属の強度が確保できる効果がある。しかしながら反面、衝撃靱性の低下が著しい。また、低入熱条件においては、ＣＯＤ特性を著しく劣化させる。その悪影響は０．０５％を超える添加量で顕著となるため上限を０．０５％とした。
【００２６】
Ｎｂ：≦０．０５％
Ｎｂは、Ｖと同様に炭、窒化物を形成し、溶接金属の強度向上に有効な元素である。特に溶接金属の強度低下が著しい本発明の対象とする高入熱かつパス間温度の高い溶接条件においては、比較的微量添加で溶接金属の強度が確保できる効果がある。しかしながら反面、衝撃靱性の低下が著しい。また、低入熱条件においては、ＣＯＤ特性を著しく劣化させる。その悪影響は０．０５％を超える添加量で顕著となるため上限を０．０５％とした。
Ｖ＋Ｎｂ：≦０．０５％
低入熱条件でのＣＯＤ特性を確保するためには、Ｖ＋Ｎｂの合計量を０．０５％以下に抑制する必要がある。
【００２７】
Ｃ：≦０．０６％
Ｃは固溶強化により溶接金属強度の確保に必要な元素である反面、硬さの増加や歪み時効による靱性低下を起こし易いため、ワイヤとしてはこれを勘案して上限を制限している。高入熱・高パス間条件では、０．０６％を超える添加は強度を過剰にし、靱性の損なうために０．０６％以下に制限した。一方、横向き姿勢のルート部近傍は硬さの最も高い部位であり、この硬さの不均一にはＣ量の抑制が最も有効である。従って、横向き溶接金属のＣＯＤ値確保の観点からＣ量の上限値を０．０６％と定めた。
【００２８】
Ｓｉ：０．６〜１．５％
Ｓｉは主要脱酸剤であり、溶接金属の酸素量を低下させ靱性向上に必要な元素である。特に高溶接電流域ではＳｉの消耗が大きいため、通常より高めの添加を必要とする。Ｓｉの歩留率は、例えば表１の横向溶接の場合は６０〜７０％程度であるが、同表の下向溶接では５０％以下となる。溶接中のＳｉ量が低い場合には溶接金属酸素量が増加し、０．６％未満では脱酸不足となり急激に靱性が劣化する。一方、１．５％を超えると溶接金属素地が硬化して靱性への悪影響が顕著となる。
【００２９】
Ｍｎ：１．７〜２．５％
ＭｎはＳｉと共に主要脱酸剤であると共に、溶接金属の強度確保およびオーステナイトを安定化させて靱性向上を図る目的で添加する。Ｓｉと同様に高電流条件での酸化消耗を考慮した添加が必要で、Ｓｉ量との兼ね合いもあるが、１．７％未満では靱性が確保できず、２．５％を超える添加量では過強度と低靱性化の傾向が顕著となる。
【００３０】
Ｔｉ：０．２０〜０．４０％
Ｔｉは、溶接金属の組織を微細化して、靱性向上、ＣＯＤ値向上に是非とも必要な元素として添加する。靱性確保に必要な適正Ｔｉ量は、溶接金属の酸素レベルによって異り、通常の炭酸ガスシールドアーク溶接条件レベルでは０．１５〜０．２０％程度が適正であるが、本発明が対象とする入熱、電流条件域では、０．２０％以上が必要である。しかし０．４０％を超えた添加では過剰にＳｏｌ．Ｔｉが固溶して硬化が著しくなり、靱性、ＣＯＤ値を著しく低下させる。
【００３１】
Ｂ：０．００３０〜０．０１２％
ＢはＴｉとの共存により高靱性溶接金属を得る為に不可欠の元素である。従来技術として前述した、例えば特開昭５４−４０２５０号公報ではパラメータＰａ（Ｔｉ×Ｂ×１０４ ）として１〜２５を推奨している。しかし本発明が対象とする炭酸ガスシールド溶接の高入熱、高パス間温度使用条件下では、０．００３０％以上の添加が必須である。しかし０．０１２％超の添加では靱性向上効果より硬さ上昇による靱性低下の弊害に加えて、継手溶接金属のルート部の高温割れ性の危険が高くなるため、上限を０．０１２％とした。
【００３２】
Ｍｏ：≦０．１０％
Ｍｏは変態温度を低下して組織を微細化して靱性向上に有効で、特に高入熱、高パス間温度条件での靱性向上に有効に作用し、靱性向上によるＣＯＤ値向上に寄与する。しかし過剰の添加は強度増加による靱性への効果が小さくなるため有効な範囲として０．３０％以下程度まで許容されるが、横向き姿勢等の低入熱条件では、ルート近傍の溶接金属の硬化が著しく、特に高ＣＯＤ特性が要求される場合には０．０１％超程度の抑制が必要であるが、通常の要求特性の場合は≦０．１０％の規制で十分である。
【００３３】
Ｐ：≦０．０１５％
Ｐは靱性に有害な元素であり、出来るだけ低く制限するのが好ましい。高入熱溶接条件では、０．０２０％以下に制限することが好ましい。特に、ＣＯＤ値が要求される場合には、０．０１５％以下の制限が必要である。
Ｓ：≦０．０１０％
ＳはＰと同様、靱性確保に対しては、０．０１５％以下が好ましく、ＣＯＤ特性を確保するためには、０．０１０％以下の制限が必要となる。
Ｎ：≦０．００３０％
Ｔｉ−Ｂ系により溶接金属の衝撃靱性を向上させるには、Ｎ量の低下が条件となるが、その限界量は０．０５０％以下までは満足できるが、厚板継手（Ｋ製，Ｔ型，Ｘ型開先）のＢＰ側の歪み時効による靱性低下を考慮した場合には、Ｎ量は０．００３０％以下が重要である。
【００３４】
Ａｌ：０．００５〜０．０５０％，Ｚｒ：０．００５〜０．０５０％の１種以上を合計で０．００５〜０．０５０％
高電流・高入熱・高パス間温度条件のガスシールドアーク溶接においては、溶融プールが大きくなり、場合によっては十分なシールド性が得られず溶接金属に大気中の窒素が侵入する場合がある。シールド性が大きく損なわれ多量の窒素が侵入した場合にはピット等の気孔欠陥として検知でき、また気孔欠陥に至らずともある程度の侵入の場合もスパッタの増加やスラグ色調変化などの溶接現象変化によって知ることが可能である。しかし、０．００１０〜０．００２０％程度の微量の侵入の場合には溶接現象への影響は無く溶接金属を切取って分析するしか知ることが出来ない。しかも、このような０．００１０〜０．００２０％程度の極微量の窒素侵入によって溶接金属の衝撃靱性は著しく劣化する。このような微量の窒素侵入による靱性低下を抑制する目的でＡｌ，Ｚｒを添加する。この靱性低下について検討した結果、Ａｌ，Ｚｒの微量添加が有効であることを突き止めた。これはＡｌ，ＺｒがＮとの調和力が強く固溶Ｎを固定して歪み時効の影響を軽減するものと考えられる。その効果は、０．００５％以上の添加から表れるが、０．０５０％を超える添加は靱性をむしろ低下させる。
【００３５】
Ｏ：≧０．００６０％
本発明での酸素は他の元素と異なる目的および効果で添加する。高入熱・高パス間温度の溶接では溶融プールは大きくかつ高温になるため、炭酸ガスシールドアーク溶接での溶滴移行状態が通常の溶接に比べて劣化することが判明した。すなわち、溶滴は大粒化し、スパッタ発生量も増加し溶接作業性が劣化する。この作業性の向上について検討した結果、酸素が寄与することが判った。この酸素の作業性向上効果は０．００６０％程度以上の添加で顕著になる。酸素の形態には特に制限が無く、溶解時に添加した場合、ワイヤ表面に潤滑剤や油脂とし塗布した場合あるいは素地に粒界酸化層や表面酸化物として表面の化成処理によって付与しても良い。酸素量の上限についても特にないが、０．０５０％程度以下がワイヤ送給性や製造コストの点で推奨される。
【００３６】
【実施例】
（実施例１）
表２に示す化学成分の溶鋼を真空溶解し、鍛造・圧延・めっき・巻取りの各工程を経てワイヤ径１．４ｍｍの鋼ワイヤを製作した。このワイヤを用い、表５の溶接条件で溶着金属試験（試験鋼板：ＳＮ４９０Ｂ ２０ｍｍｔ、開先形状，試験片採取位置はＪＩＳ Ｚ３３１２に準拠）を行った。この試験板を引張試験、衝撃試験、溶接作業性の各種試験を実施して評価した結果を表６に示す。試験結果の評価は、引張強さ（ＴＳ）を４９０Ｎ／ｍｍ２ 以上を合格とし、衝撃吸収エネルギーは１００Ｊ以上を、溶接作業性はワイヤが円滑に送給されてアークが安定しているものを合格とした。また、硬さ評価はビッカース硬さ試験機で行い、溶接金属の板厚中央部の１０点（荷重１０ｋｇ）の平均値で示した。
【００３７】
【表５】
【表６】
ワイヤＦ１は、Ｃ、Ａｌ＋ＺｒおよびＮが本発明の上限を超えているため衝撃吸収エネルギーが低い。ワイヤＦ２は、Ｓｉが限定未満であり、強度、靱性ともに要求レベルに至らなく、またピット発生が認められた。ワイヤＦ３は、Ｍｎが限定未満であり、強度、靱性ともに要求レベルに至らない。ワイヤＦ４は、Ｓｉが上限を超えており靱性が低い。ワイヤＦ５は、Ｍｎが上限を超えており靱性が低い。ワイヤＦ６は、Ｓが上限を超えており靱性が低い。ワイヤＦ７およびワイ ヤＦ１２は、Ｍｏが規定上限を超えたため靱性が低い。ワイヤＦ８は、Ｔｉが規定未満のため強度、靱性共に低い。ワイヤＦ９は、Ｂが発明の範囲未満で強度、靱性が不足である。
【００４０】
ワイヤＦ１０は、Ｂが過剰で靱性が極めて悪化する。ワイヤＦ１１は、Ｏが規定未満で溶接作業性が劣化した。ワイヤＦ１３は、Ｖが規定値を超えており靱性が低い。ワイヤＦ１４は、Ｖ＋Ｎｂが規定値を超えており靱性が低下した。ワイヤＦ１５は、Ｎｂが規定値を超えており靱性が低い。ワイヤＦ１６は、Ｖ＋Ｎｂが大幅に規定値を超えており、強度も高く、靱性も著しく劣化した。
一方、本発明ワイヤＥ１〜Ｅ５は、いずれも強度、衝撃靱性、溶接作業性ともに良好な結果であった。
【００４１】
（実施例２）
表２の内からワイヤ記号Ｅ１を用いて、表７の溶接条件で溶着金属試験を行い、表８の結果を得た。なお、鋼板は実施例１と同じものを用い、開先形状および試験片採取位置はＪＩＳ Ｚ３３１２に準拠して行った。表８に示すように、本発明のワイヤによれば、入熱２０ｋＪ／ｃｍ程度の低入熱条件から入熱４０ｋＪ／ｃｍ−パス間４５０℃程度までの高入熱条件まで健全で、良好な強度、靱性、ＣＯＤが得られる溶接が可能である。
【００４２】
【表７】
【表８】
【発明の効果】
以上のように、本発明のワイヤにおいては、低入熱から高入熱・高パス間条件の炭酸ガスシールドアーク溶接において、良好な強度特性、衝撃靱性向上、ＣＯＤ特性向上および厚板における歪時効が少ない溶接金属が可能となる。
【図面の簡単な説明】
【図１】ワイヤのＶ＋Ｎｂ量と継手溶接金属の衝撃靱性との関係を示す図、
【図２】継手試験の開先形状を示す図（θ：３５°、ｔ＝３５ｍｍ、Ｇ＝５ｍｍ、Ｒｆ＝５ｍｍ）、
【図３】継手試験の試験片採取位置を示す図であり、
（ａ）は溶接後のビード断面図、（ｂ）は継手試験の試験片採取位置を示す図である。
【符号の説明】
１、２ 被溶接鋼板
３ 溶接金属
４ 衝撃試験片
５ 引張試験片[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is 490 N / mm2Solid wire for carbon dioxide welding used for high-grade high-strength steel, specifically, a solid wire for carbon dioxide shielded arc welding that provides high heat input, high toughness of the weld metal used under high interpass temperature conditions, and high COD. It relates to the welding method.
[0002]
[Prior art]
In recent years, gas shielded arc welding has been applied to welding of building steel frames, and high efficiency has been achieved. However, at present, the welding conditions used for higher efficiency are shifting to higher current, higher heat input, and higher interpass temperature. One of the problems with the weld metal under such high heat input and high inter-pass temperature conditions is a reduction in impact toughness. However, the required toughness properties of the weld metal tend to be higher. In addition, there is a tendency that demands for COD characteristics in addition to impact toughness are given, and there is an extremely strong demand for welding materials capable of obtaining a weld metal excellent in high COD characteristics in addition to excellent high toughness. Conventionally, Ti-B-based welding materials have been studied as one of toughness improving means, and some proposals have been made.
[0003]
For example, Japanese Patent Application Laid-Open No. 54-40250 discloses a parameter (Pa = Ti × B × 104) Is limited to 1 to 25, and there is a proposal for a wire for high efficiency gas shielded arc welding. This technology is mainly based on Ar-CO2The purpose of the present invention is to improve low-temperature toughness in one-run welding with a maximum heat input of about 40 kJ / cm for mixed gas shield welding, and is not intended for carbon dioxide gas shielded arc welding as in the present invention.
Also, Japanese Patent Application Laid-Open No. 63-157795 discloses that Ar-CO2To improve the low-temperature toughness after PWHT in mixed gas welding of Ti, etc., adding up to 6% Ni to Ti (0.01-0.10%)-B (0.001-0.010%) system Although this is a technique for improving low-temperature toughness by the above-described configuration, high toughness and COD characteristic improvement cannot be expected in the carbon dioxide gas shield welding of the present invention.
[0004]
Furthermore, although the technique disclosed in Japanese Patent Application Laid-Open No. 55-149797 aims to improve toughness, it does not target high pass temperature conditions, so that improvement in toughness under welding conditions targeted by the present invention cannot be expected. The technique disclosed in Japanese Patent Publication No. Hei 4-20720 aims at improving the toughness of carbon dioxide shielded arc welding under high heat input conditions, but has not studied high pass temperature conditions or COD characteristics. However, the effects of the present invention cannot be expected.
As described above, a Ti-B-based welding wire has been proposed as a technique for increasing the toughness of a weld metal. However, under the conditions of high heat input and high interpass temperature, which is intended by the present invention, such a simple Ti-B welding wire is used. By itself, high toughness cannot be achieved, but high COD characteristics cannot be satisfied at the same time.
[0005]
That is, the welding position of welding of building steel frames and the like has many welding positions from a downward (including a horizontal position) to a horizontal position. Even in the case of welding heat input, a high heat input exceeding 40 kJ / cm of a high current is obtained in a downward joint. And a high pass-to-pass temperature condition (exceeding 350 ° C .; hereinafter, referred to as a high heat input condition). Further, in the transverse joint welding, a relatively low heat input welding with a relatively low welding current and an inter-pass temperature and a heat input of 15 to 20 kJ / cm is performed (hereinafter referred to as a low heat input condition). Therefore, the cooling rate of the welded portion greatly differs depending on the applied welding position, and when welding is performed with the same wire, the strength of the joint weld metal obtained also differs depending on the welding position.
[0006]
Table 1 shows a case where a change in the properties of a weld metal under high heat input conditions and low heat input conditions was investigated using a conventional wire. As is evident from the results in Table 1, the conventional wire has appropriate strength and high toughness under low heat input conditions, but decreases in both strength and toughness under high heat input conditions. In addition, when a wire that provides appropriate strength under high heat input conditions is used, the strength becomes excessive under low heat input conditions. The impact toughness also decreases under high heat input conditions.
[0007]
[Table 1]
[Problems to be solved by the invention]
Under such circumstances, the present invention provides a 490 N / mm2Welding in a wide range of conditions from low heat input welding conditions to high heat input welding conditions for carbon dioxide shielded arc welding of high-grade high-tensile-strength steel, resulting in moderate weld metal strength, excellent toughness, and high COD value. An object of the present invention is to provide a solid wire for carbon dioxide shielded arc welding excellent in balance between strength and toughness and a method for producing the same.
[0009]
[Means for Solving the Problems]
The present invention can be applied to a wide range of welding conditions from low heat input conditions, which are typically used in the horizontal position shown in Table 1, to standard high heat input conditions, in the downward position, to obtain appropriate joint weld metal strength. In addition, the addition amount range of Si, Mn, Ti, B, Al, and Zr as a solid wire component of a weld metal having good impact toughness, high COD characteristics, and low strain aging is regulated, and C, P, S, It is characterized in that the lower limit of the amount of O is regulated for the purpose of suppressing the addition range of Mo, N and V, Nb and improving the arc stability in a high current region.
[0010]
The gist of the invention is as follows: (1) In% by weight, C: ≤ 0.06%, Si: 0.6 to 1.5%, Mn: 1.7 to 2.5%, P: ≤ 0 .015%, S: ≦ 0.010%,Mo: ≦ 0.10%, Ti: 0.20 to 0.40%, Al: 0.005 to 0.050%, and Zr: 0.005 to 0.050% in total of 0.005 to 0.050 %, B: 0.0030 to 0.012%, V: ≦ 0.05%, and Nb: ≦ 0.05%. 0.0030%,O: ≧ 0.0060%A solid wire for carbon dioxide shielded arc welding, characterized in that:
(2) Stable and high toughness by welding a high-tensile steel using the solid wire described in (1) above under welding conditions of welding heat input of 15 to 40 kJ / cm and interpass temperature of 100 to 450 ° C. And a carbon dioxide shielded arc welding method characterized in that a weld metal excellent in high COD characteristics is obtained.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The present inventors have already found that, in welding under a wide range of welding conditions from low heat input conditions to high heat input conditions, appropriate joint weld metal strength and good impact toughness, high COD characteristics, and furthermore, as a steel wire component with little strain aging. (1) proposes a basic component system capable of obtaining good impact toughness by reducing the influence of N, which is a problem under high heat input conditions. That is, the limitation of the Ti, B, Al, and Zr amount ranges and the N amount were regulated. (2) In order to more effectively secure the impact toughness under high heat input conditions, the addition range of each element such as C, Si, Mn, and Mo is limited, and (3) the COD characteristics are improved and the strain is reduced. A wire is provided which is characterized by further limiting the amounts of C and N and regulating the amounts of P and S added for the purpose of reducing aging.
[0012]
However, as a result of further study, the present inventors have found that V and Nb in the wire have a decrease in impact toughness under high heat input conditions and a decrease in COD characteristics under low heat input conditions and adversely affect the stability thereof. Configured. That is, by slightly modifying the previously proposed configuration, the addition amounts of V and Nb are each suppressed to 0.05% or less, and the total amount of both is reduced to 0.05% or less. The reason for this configuration was that, when the COD characteristics of various steel sheets in a horizontal posture were examined, a phenomenon was observed in which the COD characteristics and impact toughness had large variations. As a result of studying the reason, it was found that trace amounts of V and Nb contained in the weld metal caused the problem. These V and Nb include those added to the wire in an extremely small amount in order to suppress a decrease in strength under high heat input conditions, and those added to the steel sheet.
[0013]
The biggest problem under high heat input welding conditions is a decrease in weld metal toughness, but Ti-B is an effective means for securing this toughness. However, although high toughness can be achieved by optimizing the amount of Ti-B added, proper addition of Al and Zr, which reduces the harmful effects of an increased amount of N, is effective in reducing the variation in toughness and ensuring stable toughness. . On the other hand, problems under low heat input conditions are an increase in weld metal strength, an increase in hardness near the joint root, and a decrease in COD value due to unevenness. In order to suppress the increase in strength and improve the hardness of the root portion, it is effective to limit the amount of addition of C and Mo. When a high COD value is required, it is necessary to further limit the amount of addition of these elements. However, the limitation of the addition amount of C, Mo, and the like poses a problem in securing the strength of the weld metal under high heat input welding conditions.
[0014]
As described above, the low heat input condition and the high heat input welding condition have contradictory performance problems, and the preferable wire component range differs depending on which condition and the performance are emphasized. Therefore, as a result of further study in consideration of the balance of the performance under both conditions, it was found that the performance balance was improved by adjusting the addition amounts of V and Nb. Among the wires (wire diameter: 1.4 mm) shown in Table 2, wire symbols E1,F7, F12, F13,F15, F166Using the types, joint weld metal tests were performed under low heat input conditions and high heat input welding conditions in Table 3, and the results in Table 4 were obtained. The steel plate used was SN490B 35 mmt, the groove shape was as shown in FIG. 2, and the test piece sampling position was as shown in FIG. As is clear from Table 4, under low heat input conditions, the strength tends to be too high and toughness tends to be low, and under high heat input conditions, the strength tends to be low and the toughness tends to decrease.
[0015]
[Table 2]
[Table 3]
[Table 4]
FIG. 1 shows the relationship between the amount of V + Nb in the wire and the impact toughness from the results in Table 4. Impact toughness decreases with an increase in the amount of V + Nb, but particularly decreases when the amount of V + Nb exceeds 0.05%, and this tendency is remarkable in the root portion under low heat input conditions. This is because V and Nb are elements that easily form carbon and nitride, the C content of the weld metal is larger in the root part than in other parts due to the dilution of the C content of the base material, and the root part has no gas shield. Because of the tendency to become sufficient, slight nitrogen contamination from the atmosphere is likely to occur, which is considered to be due to the hardening of the welded part.ButThe effect is particularly great under low heat input conditions with large hardness. This is also estimated from the transition of the average hardness of the root portion. In addition, the Mo content exceeds 0.10%,Wire symbol F7 or F12In this case, the decrease in toughness is large as compared with the same level of V + Nb. As described above, the conditions of the wire component having a good balance of strength and toughness under both conditions are Mo ≦ 0.10%, V ≦ 0.05%, Nb ≦ 0.05%, and V + Nb ≦ 0.05%. It turns out that there is.
[0019]
The effects of other elements will be briefly described below.
In order to obtain high impact toughness under high heat input conditions, the range of Ti and B is weight, and the range of Ti is 0.20 to 0.40% and the range of B is 0.0030 to 0.012%. It is. Further, under the conditions of high current and high inter-pass welding, N cannot avoid intrusion of about 0.0010 to 0.0030%,0.0030%If it exceeds 2,000, the impact toughness rapidly decreases. Therefore, the regulated amount of N in the wire0.0030%You need: Also, N is a weld metal0.0030%It has been found that if the level is slightly higher than the above, a reduction in impact toughness can be suppressed by adding appropriate Al and Zr. The appropriate addition amounts of Al and Zr are 0.0050 to 0.050%, respectively, and the total is 0.0050 to 0.050%. Addition beyond this lowers the toughness. It is considered that the addition of a small amount of Al and Zr reduces the degree of impact toughness reduction due to N due to the action of Al and Zr, which have a strong affinity for N, as nitrides to suppress solid solution of N.
[0020]
However, even if such Ti, B, N, etc. are adjusted to a favorable component range, if the amounts of Si and Mn are not appropriate, the toughness shows a low value. As a result of examining the addition amounts of Si and Mn effective for improving the toughness, the impact toughness changes abruptly when the Si amount of the wire is about 0.6%, and decreases when it is less than 0.6%. This is considered to be because the amount of oxygen increased due to a decrease in the amount of Si in the deposited metal under high heat input conditions. On the other hand, when the amount of Si in the wire is about 1.5% or more, the base is hardened significantly due to the excessive solid solution of Si, and the impact toughness rapidly decreases.
[0021]
The effect of Mn affects the impact toughness for substantially the same reason as that of Si, and the appropriate addition amount is in the range of 1.7 to 2.5%. As a result of examining the effects of C and Mo on the impact toughness of C and Mo under high heat input conditions, the addition of C is extremely effective in increasing the joint strength under high heat input conditions.0.06%It has been found that when added in excess of, the adverse effect on impact toughness is large. Further, the addition of Mo is effective in securing the strength of the weld metal, and further has the effect of suppressing the softening of the pre-pass weld metal due to lamination under high heat input conditions and improving the overall impact toughness. Also0.10%It has been found that the addition of more than 10% rather reduces the impact toughness.
[0022]
Further, a phenomenon was observed in which the arc became unstable under the condition where the welding current was high (about 450 A). Therefore, as a result of observing the arc instability phenomenon in detail with a high-speed video camera, etc., the molten pool was heated by the increase in current and the vibration became violent, and this vibration hindered the smooth transfer of the droplet, It has been found that this is the cause of the increase in the generation amount and arc instability by sensory inspection. Then, as a result of studying arc instability and suppression of increase in spatter, it was effective to add oxygen to the wire, and it was found that the addition amount was remarkable at 0.0060% or more. Therefore, as to the oxygen adding means, we examined the case of solid solution at the time of wire melting and the case of adding as an oxide at the time of manufacturing.Either means contributes to arc stabilization, and the arc stabilizing effect regardless of the form of oxygen. Was obtained.
[0023]
As described above, by specifying the Si and Mn ranges, limiting the upper limits of C and Mo, and adding oxygen, it is possible to stabilize the arc and improve the impact toughness under higher current conditions. Until now, the performance of the welded metal has been mainly studied, but thick plates are used in actual structures, and the K-shaped and X-shaped grooves of the welded joint are often used, and welding is performed on both sides of the steel plate. Done from In this case, after finishing the first welding side (BP side) and before performing the final welding side (FP side), a method of processing the root surface into an appropriate shape (rear hanging) is performed. The root part is the place where the base material is melted most because the groove width is narrow, and the lamination thickness is thick due to the narrowness, it is hard to be reheated by lamination, and it is the hardest joint among the joints, This is a place where the hardness varies widely. This tendency is particularly large under high heat input (high current) welding conditions.
[0024]
C hardens the hardness of the joint root part on average, and has a large change in each welding pass. Therefore, even if the impact toughness is high to some extent, the COD value is lowered. In addition, a phenomenon (strain aging) in which the impact toughness is lower on the BP side under the low heat input condition than on the FP side was observed. Therefore, as a result of a detailed study of C and N, which have an effect on hardness and impact toughness when added in a trace amount in a wire element, it is found that the COD characteristic can be suppressed to C ≦ 0.06% and N ≦ 0.0030%. It has been found that it is effective in improving and reducing strain aging. Further, as for P and S, in addition to the restrictions on the respective addition amounts, a result was obtained in which a total of 0.015% or less was effective.
[0025]
Hereinafter, the reasons for addition and limitation of each component element of the welding wire according to the present invention will be described in detail.
V: ≦ 0.05%
V is an element that forms carbon and nitride and is effective for improving the strength of the weld metal. In particular, under the high heat input condition where the strength of the weld metal is remarkably reduced and the heat input between passes is high, there is an effect that the strength of the weld metal can be secured by adding a relatively small amount. However, on the other hand, the impact toughness significantly decreases. Further, under low heat input conditions, the COD characteristics are significantly deteriorated. Since the adverse effect becomes remarkable when the amount exceeds 0.05%, the upper limit is set to 0.05%.
[0026]
Nb: ≦ 0.05%
Nb is an element that forms carbon and nitride similarly to V and is effective for improving the strength of the weld metal. In particular, under the welding conditions in which the strength of the weld metal is remarkably reduced and the heat input and the inter-pass temperature are high, there is an effect that the strength of the weld metal can be secured by adding a relatively small amount. However, on the other hand, the impact toughness significantly decreases. Further, under low heat input conditions, the COD characteristics are significantly deteriorated. Since the adverse effect becomes remarkable when the amount exceeds 0.05%, the upper limit is set to 0.05%.
V + Nb: ≦ 0.05%
In order to ensure COD characteristics under low heat input conditions, it is necessary to suppress the total amount of V + Nb to 0.05% or less.
[0027]
C: ≦ 0.06%
C is an element necessary for securing the strength of the weld metal by solid solution strengthening, but on the other hand, the upper limit of the wire is limited in view of the fact that it tends to cause an increase in hardness and a decrease in toughness due to strain aging. Under high heat input and high interpass conditions,0.06%If the addition exceeds the above, the strength becomes excessive and the toughness is impaired.0.06%Limited to: On the other hand, the vicinity of the root portion in the lateral posture is the highest hardness portion, and the suppression of the C amount is most effective for uneven hardness. Therefore, the upper limit of the C content is set to 0.06% from the viewpoint of securing the COD value of the laterally-welded metal.
[0028]
Si: 0.6-1.5%
Si is a main deoxidizing agent and is an element necessary for reducing the oxygen content of the weld metal and improving the toughness. Particularly, in a high welding current region, Si is largely consumed, so that a higher addition than usual is required. The yield rate of Si is, for example, about 60 to 70% in the case of the horizontal welding in Table 1, but is 50% or less in the downward welding in the same table. When the amount of Si during welding is low, the amount of oxygen in the weld metal increases,0.6%If the amount is less than the above, deoxidation becomes insufficient, and the toughness rapidly deteriorates. on the other hand,1.5%If it exceeds, the weld metal base is hardened, and the adverse effect on toughness becomes significant.
[0029]
Mn: 1.7-2.5%
Mn is a main deoxidizing agent together with Si, and is added for the purpose of securing the strength of the weld metal and stabilizing austenite to improve toughness. Similar to Si, it is necessary to take into account oxidation consumption under high current conditions, and there is a trade-off with the amount of Si. However, if it is less than 1.7%, toughness cannot be secured, and if it exceeds 2.5%, excessive addition occurs. The tendency of strength and toughness becomes remarkable.
[0030]
Ti: 0.20 to 0.40%
Ti is added as a necessary element for refining the structure of the weld metal and improving the toughness and the COD value. The appropriate amount of Ti required for ensuring toughness depends on the oxygen level of the weld metal, and is appropriate in the ordinary carbon dioxide shielded arc welding condition at a level of about 0.15 to 0.20%. In a heat input and current condition region, 0.20% or more is required. However, if the addition exceeds 0.40%, the amount of Sol. Ti becomes a solid solution and hardening becomes remarkable, thereby significantly reducing toughness and COD value.
[0031]
B: 0.0030 to 0.012%
B is an indispensable element for obtaining a high toughness weld metal by coexistence with Ti. For example, in Japanese Patent Application Laid-Open No. 54-40250 described above as a conventional technique, a parameter Pa (Ti × B × 104) Are recommended as 1 to 25. However, under the conditions of high heat input and high interpass temperature of carbon dioxide shield welding targeted by the present invention, addition of 0.0030% or more is essential. However, if the addition exceeds 0.012%, the toughness is not improved and the toughness is reduced due to the increase in hardness, and the risk of hot cracking at the root of the joint weld metal is increased. Therefore, the upper limit is set to 0.012%. .
[0032]
Mo: ≦ 0.10%
Mo is effective for improving the toughness by lowering the transformation temperature and refining the structure, particularly effective for improving the toughness under high heat input and high interpass temperature conditions, and contributing to the improvement of the COD value by improving the toughness. However, excessive addition is allowed to be about 0.30% or less as an effective range because the effect on toughness due to the increase in strength is reduced. However, under low heat input conditions such as a lateral posture, the hardening of the weld metal near the root may occur. Significantly, particularly when high COD characteristics are required, suppression of more than about 0.01% is necessary, but in the case of normal required characteristics, a regulation of ≤0.10% is sufficient.
[0033]
P: ≦ 0.015%
P is an element harmful to toughness, and is preferably limited as low as possible. Under high heat input welding conditions, it is preferable to limit it to 0.020% or less. In particular, when a COD value is required, a limit of 0.015% or less is required.
S: ≦ 0.010%
S is, like P, preferably 0.015% or less for securing toughness, and a 0.010% or less limit is required to secure COD characteristics.
N: ≦ 0.0030%
In order to improve the impact toughness of the weld metal by using the Ti-B system, the condition is that the amount of N is reduced.Is 0. Although it is satisfactory up to 050% or less, considering the decrease in toughness due to strain aging on the BP side of thick plate joints (made of K, T type, X type groove), the N content is importantly 0.0030% or less. It is.
[0034]
Al: 0.005 to 0.050%, Zr: 0.005 to 0.050%, at least 0.005 to 0.050% in total
In gas shielded arc welding under high current, high heat input, and high interpass temperature conditions, the molten pool becomes large, and in some cases, sufficient shielding properties cannot be obtained and nitrogen in the atmosphere may enter the weld metal. . If the shielding performance is greatly impaired and a large amount of nitrogen has entered, it can be detected as a pore defect such as a pit. It is possible to know. However, in the case of a small amount of intrusion of about 0.0010 to 0.0020%, there is no influence on the welding phenomenon, and it can be known only by cutting and analyzing the weld metal. Moreover, the impact toughness of the weld metal is significantly degraded by such a very small amount of nitrogen infiltration of about 0.0010 to 0.0020%. Al and Zr are added for the purpose of suppressing a decrease in toughness due to such a small amount of nitrogen penetration. As a result of examining this reduction in toughness, it was found that the addition of trace amounts of Al and Zr was effective. This is presumably because Al and Zr have a strong harmony with N and fix solid solution N to reduce the influence of strain aging. The effect appears from the addition of 0.005% or more, but the addition exceeding 0.050% rather lowers the toughness.
[0035]
O: ≧ 0.0060%
In the present invention, oxygen is added for a purpose and effect different from other elements. In welding with high heat input and high interpass temperature, the molten pool became large and high temperature, and it was found that the droplet transfer state in carbon dioxide shielded arc welding deteriorated compared to normal welding. In other words, the droplets become large, the amount of spatter generated increases, and welding workability deteriorates. As a result of studying the improvement of the workability, it was found that oxygen contributed. The effect of improving the workability of oxygen becomes remarkable when added at about 0.0060% or more. The form of oxygen is not particularly limited, and may be added at the time of dissolution, when it is applied as a lubricant or oil or fat on the surface of the wire, or may be applied to the substrate as a grain boundary oxide layer or surface oxide by chemical conversion treatment of the surface. There is no particular upper limit for the amount of oxygen, but about 0.050% or less is recommended in terms of wire feedability and manufacturing cost.
[0036]
【Example】
(Example 1)
Molten steel having the chemical components shown in Table 2 was melted in vacuum, and a steel wire having a wire diameter of 1.4 mm was manufactured through the steps of forging, rolling, plating, and winding. Using this wire, the welding metal test (Test steel plate: SN490B 20mmt, The groove shape and the test piece sampling position conformed to JIS Z3312). Table 6 shows the results of the tensile strength test, the impact test, and various tests of the welding workability of the test plate, which were evaluated. The evaluation of the test results was conducted by setting the tensile strength (TS) to 490 N / mm.2The above was regarded as a pass, the impact absorption energy was 100 J or more, and the welding workability was determined as a pass when the wire was smoothly fed and the arc was stable. The hardness was evaluated using a Vickers hardness tester, and the average value at 10 points (load: 10 kg) at the center of the thickness of the weld metal was shown.
[0037]
[Table 5]
[Table 6]
Wire F1 is C, Al + Zr and NHowever, since the ratio exceeds the upper limit of the present invention, the impact absorption energy is low. In the wire F2, Si was less than the limit, the strength and toughness did not reach the required levels, and pit generation was observed. The wire F3 has Mn less than the limit, and the strength and toughness do not reach the required levels. In the wire F4, Si exceeds the upper limit and the toughness is low. The wire F5 has Mn exceeding the upper limit and has low toughness.Wire F6In S, the S exceeds the upper limit and the toughness is low.Wire F7 and Y Ya F12Has low toughness because Mo exceeds the specified upper limit.Wire F8Is low in both strength and toughness because Ti is less than the specified value.Wire F9Is insufficient in strength and toughness when B is less than the range of the invention.
[0040]
Wire F10In B, B is excessive and toughness extremely deteriorates.Wire F11In the case of O, the welding workability was deteriorated when O was less than the specified value.Wire F13In the case of V, V exceeds the specified value and toughness is low.Wire F14As for V, V + Nb exceeded the specified value and toughness was lowered.Wire F15Has a low toughness because Nb exceeds a specified value.Wire F16For V, V + Nb greatly exceeded the specified value, the strength was high, and the toughness was significantly deteriorated.
On the other hand, the wires E1 to E1 of the present invention.E5Showed good results in both strength, impact toughness and welding workability.
[0041]
(Example 2)
A weld metal test was performed under the welding conditions in Table 7 using the wire symbol E1 from Table 2, and the results in Table 8 were obtained. The same steel plate as in Example 1 was used.The groove shape and the test piece sampling position were determined according to JIS Z3312.As shown in Table 8, according to the wire of the present invention, a good and healthy heat input condition from a low heat input condition of about 20 kJ / cm to a high heat input condition of about 40 kJ / cm to 450 ° C. between passes. Welding that provides strength, toughness, and COD is possible.
[0042]
[Table 7]
[Table 8]
【The invention's effect】
As described above, in the wire of the present invention, the carbon dioxide gas under conditions of low heat input to high heat input and high inter-pass conditionsShield arcIn welding, a weld metal having good strength properties, improved impact toughness, improved COD properties, and less strain aging in thick plates can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between the amount of V + Nb in a wire and the impact toughness of a joint weld metal;
FIG. 2 is a view showing a groove shape in a joint test (θ: 35 °, t = 35 mm, G = 5 mm, Rf = 5 mm);
FIG. 3 Test of joint testPieceIt is a diagram showing a sampling position,
(A)weldingFIG. 4B is a cross-sectional view of a bead afterward, and FIG.
[Explanation of symbols]
1,2 steel plate to be welded
3 Weld metal
4 Impact test specimen
5 Tensile test specimen
Claims (2)
Ｃ：≦０．０６％、
Ｓｉ：０．６〜１．５％、
Ｍｎ：１．７〜２．５％、
Ｐ：≦０．０１５％、
Ｓ：≦０．０１０％、
Ｍｏ：≦０．１０％、
Ｔｉ：０．２０〜０．４０％を含有し、
Ａｌ：０．００５〜０．０５０％、
Ｚｒ：０．００５〜０．０５０％の１種以上を合計で０．００５〜０．０５０％、
Ｂ：０．００３０〜０．０１２％であり、さらに、
Ｖ：≦０．０５％および、
Ｎｂ：≦０．０５％の１種以上合計で≦０．０５％に抑制し、
Ｎ：≦０．００３０％、
Ｏ：≧０．００６０％、
であることを特徴とする炭酸ガスシールドアーク溶接用ソリッドワイヤ。In weight percent,
C: ≦ 0.06%,
Si: 0.6-1.5%,
Mn: 1.7-2.5%,
P: ≦ 0.015%,
S: ≦ 0.010%,
Mo: ≦ 0.10% ,
Ti: 0.20 to 0.40%,
Al: 0.005 to 0.050%,
Zr: 0.005 to 0.050% in total of one or more of 0.005 to 0.050%,
B: 0.0030 to 0.012%, and
V: ≦ 0.05% and
Nb: at least one kind of ≦ 0.05% is suppressed to ≦ 0.05% in total,
N: ≦ 0.0030%,
O: ≧ 0.0060% ,
A solid wire for carbon dioxide shielded arc welding, characterized in that:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP04350998A JP3545193B2 (en) | 1998-02-25 | 1998-02-25 | Solid wire for carbon dioxide shielded arc welding and welding method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP04350998A JP3545193B2 (en) | 1998-02-25 | 1998-02-25 | Solid wire for carbon dioxide shielded arc welding and welding method thereof |
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| Publication Number | Publication Date |
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| JPH11239892A JPH11239892A (en) | 1999-09-07 |
| JP3545193B2 true JP3545193B2 (en) | 2004-07-21 |
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| JP04350998A Expired - Lifetime JP3545193B2 (en) | 1998-02-25 | 1998-02-25 | Solid wire for carbon dioxide shielded arc welding and welding method thereof |
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| JP4614226B2 (en) * | 2005-04-07 | 2011-01-19 | 株式会社神戸製鋼所 | Solid wire for gas shielded arc welding |
| JP4625415B2 (en) * | 2006-03-20 | 2011-02-02 | 新日本製鐵株式会社 | Solid wire for gas shielded arc welding |
| JP6885219B2 (en) * | 2017-06-29 | 2021-06-09 | 日本製鉄株式会社 | Welding method of steel materials and manufacturing method of welded joints |
| JP7352253B2 (en) * | 2019-05-13 | 2023-09-28 | 国立大学法人大阪大学 | mechanical parts |
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Free format text: JAPANESE INTERMEDIATE CODE: R250 |
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| EXPY | Cancellation because of completion of term |