JP2004237333A

JP2004237333A - Solid wire for gas shielded arc welding, and welding method using the same

Info

Publication number: JP2004237333A
Application number: JP2003030232A
Authority: JP
Inventors: Kimihiro Tsuji; 公博辻; Isao Hatano; 勲波多野; Junya Ueda; 純也上田
Original assignee: Nippon Steel and Sumikin Welding Co Ltd
Current assignee: Nippon Steel Welding and Engineering Co Ltd
Priority date: 2003-02-07
Filing date: 2003-02-07
Publication date: 2004-08-26
Anticipated expiration: 2023-02-07
Also published as: JP3917084B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid wire for gas shielded arc welding which targets at 590 MPa class high tensile strength steel and provides the strength and toughness of weld metal even used for multi-layer build up welding under the welding procedure conditions of a quantity of weld heat input of 30 to 40 kJ/cm and an interpass temperature of 250 to 350°C, and to provide a welding method using the same. <P>SOLUTION: The solid wire for gas shielded arc welding comprises, by mass, 0.05 to 0.15% C, 0.7 to 1.1% Si, 2.0 to 2.6% Mn, 0.15 to 0.55% Mo, 0.15 to 0.30% Ti, 0.02 to 0.50% Ni, 0.005 to 0.012% B, ≤0.020% Al, 0.002 to 0.015% O, ≤0.010% N and 0.005 to 0.05% of one or more kinds of metals selected from V and Nb, and the balance Fe with inevitable impurities. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、主として５９０ＭＰａ級高張力鋼に使用する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係り、特に大入熱および高パス間温度の溶接施工条件で多層盛溶接を行っても、溶接金属の機械的性質に優れたガスシールドアーク溶接用ワイヤおよびその溶接方法に関する。
【０００２】
【従来の技術】
ガスシールドアーク溶接は、従来から高能率で母材への溶け込みが良好であり、また機械的性質に優れた溶接継手が得られることから、建築、鉄骨、橋梁等の大型構造物に広く使用されている。近年、更なる溶接効率の向上から、溶接入熱を大きくするとともに次の溶接パスまでの溶接部を過度に冷却することなく溶接を行う、いわゆる大入熱・高パス間温度での溶接施工方法が求められている。しかし、ＪＩＳＺ３３１２ＹＧＷ１１の溶接ワイヤでは溶接入熱量１５〜３０ｋＪ／ｃｍ、パス間温度最大２５０℃での溶接施工が一般的であり、前記大入熱・高パス間温度での溶接施工方法では溶接金属の強度が低下したり、靱性が劣化する。
【０００３】
大入熱・高パス間の溶接施工方法に対応するため、溶接入熱量４０ｋＪ／ｃｍ、パス間温度３５０℃の溶接施工条件下においても、例えば、特開平１０−２３０３８７号公報（特許文献１）、特開平１１−９０６７８号公報（特許文献２）および特開平１１−１０４８８６号公報（特許文献３）にあるように、ワイヤ中にＴｉ、Ｂを添加することにより４９０ＭＰａ級高張力鋼板に対し、良好な溶接金属の機械的性質が得られる大入熱、高パス間温度溶接用ワイヤおよび溶接方法が提案されている。しかしながら、上記の溶接用ワイヤおよび溶接方法は、いずれも４９０ＭＰａ級高張力鋼を対象としたものであり、近年の更なる大型化、高強度化に伴う、５９０ＭＰａ級高張力鋼を大入熱かつ高パス間温度の施工条件下で多層盛溶接を行った場合、所定の溶接金属の機械的性質が確保できないという問題がある。
【０００４】
【引用文献】
（１）特許文献１（特開平１０−２３０３８７号公報）
（２）特許文献２（特開平１１−９０６７８号公報）
（３）特許文献３（特開平１１−１０４８８６号公報）
（４）特許文献４（特開平１１−２３９８９２号公報）
（５）特許文献５（特開２００１−２８７０６８号公報）
（６）特許文献６（特開２００２−７９３９５号公報）
（７）特許文献７（特開２００２−１０３０８２号公報）
【０００５】
【発明が解決しようとする課題】
本発明は、溶接入熱量３０〜４０ｋＪ／ｃｍ、パス間温度２５０〜３５０℃の溶接施工条件で多層盛溶接する場合においても、溶接金属の強度および靱性が確保できる５９０ＭＰａ級高張力鋼を対象とした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を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明の要旨は、ガスシールドアーク溶接用ソリッドワイヤにおいて、質量％で、Ｃ：０．０５〜０．１５％、Ｓｉ：０．７〜１．１％、Ｍｎ：２．０〜２．６％、Ｍｏ：０．１５〜０．５５％、Ｔｉ：０．１５〜０．３０％、Ｎｉ：０．０２〜０．５０％、Ｂ：０．００５〜０．０１２％、Ａｌ：０．０２０％以下、Ｏ：０．００２〜０．０１５％、Ｎ：０．０１０％以下、さらにＶおよびＮｂの１種類以上を０．００５〜０．０５％含有し、残部がＦｅ及び不可避不純物からなり、かつ下記（１）式で示すＴｍｐが０．７〜１．２、（２）式で示すＫｅｊが０．２以上であることを特徴とする。
また、５９０Ｍｐａ級高張力鋼を溶接入熱量３０〜４０ｋＪ／ｃｍ、パス間温度２５０〜３５０℃の溶接施工条件で、前記ガスシールドアーク溶接用ワイヤを用いて多層溶接することを特徴とするガスシールドアーク溶接方法にある。

【０００７】
【発明の実態の形態】
従来、４９０ＭＰａ級高張力鋼板溶接用ガスシールドアーク溶接用ソリッドワイヤは、ＪＩＳＺ３３１２ＹＧＷ１８の規格化にともない、溶接入熱量４０ｋＪ／ｃｍ、パス間温度３５０℃の溶接が可能となったが、５９０ＭＰａ級高張力鋼は大入熱・高パス間温度での溶接施工が不可能であった。そこで、５９０ＭＰａ級高張力鋼に対し、溶接入熱量３０〜４０ｋＪ／ｃｍ、パス間温度２５０〜３５０℃で多層盛溶接する場合においても、５９０ＭＰａ以上の強度およびー５℃でのシャルピー吸収エネルギーが１００Ｊ以上を達成するためにはワイヤ成分について本質的な工夫が必要となる。
【０００８】
本発明者らは、上記従来の問題点を解決するため、５９０ＭＰａ級高張力鋼に対し、溶接効率の高い、溶接入熱量３０〜４０ｋＪ／ｃｍ、パス間温度２５０〜３５０℃の多層盛溶接においても優れた溶接金属性能が得られる溶接技術を探求した。一般に、溶接入熱量４０ｋＪ／ｃｍで溶接を行えば、溶着量の増加による溶接工数の低減が図れ、パス間温度３５０℃での溶接施工が可能となれば、次のパスまでの溶接待ち時間が低減し、溶接効率の向上に大きな効果がある。この点に着目し、溶接金属の強度、靭性等の機械的性質に優れた多層盛溶接用のガスシールドアーク溶接用ソリッドワイヤ成分および溶接施工方法について種々検討した。その結果、ワイヤの成分を適切にすることによって、５９０ＭＰａ級高張力鋼板を、溶接入熱量３０〜４０ｋＪ／ｃｍ、パス間温度２５０〜３５０℃の溶接施工が可能となるガスシールドアーク溶接用ソリッドワイヤおよびそれを用いた溶接方法を見出した。
【０００９】
以下に、本発明のガスシールドアーク溶接用ソリッドワイヤの成分組成を限定した理由について説明する。
Ｃは、溶接金属の引張強度を高める元素である。大入熱・高パス間温度での溶接施工において、溶接金属に必要な強度（５９０ＭＰａ以上）を得るためには、少なくとも０．０５質量％（以下、％という。）以上含有させる必要がある。しかし、０．１５％を超えると、靭性が低下し、溶接部に割れが発生する場合がある。したがって、Ｃ含有量は、０．０５〜０．１５％とする。
【００１０】
Ｓｉは、脱酸剤であり、酸素量を低下させ靱性向上に必要な元素である。特に、大入熱・高パス間温度での溶接施工においては、Ｓｉの消耗量が激しいため、含有量を高める必要がある。０．７％未満では、強度および靭性を低下させ、脱酸不足となりブローホールが発生する場合がある。しかし、１．１％を超えると靭性が低下する。したがって、Ｓｉ含有量は、０．７〜１．１％とする。
【００１１】
Ｍｎは、溶接金属の引張強度を高める元素であり、また、脱酸剤で靱性を高める元素である。大入熱・高パス間温度での溶接施工においては、溶接金属に必要な強度（５９０ＭＰａ以上）を得るため、また、脱酸剤としての消耗量が激しいため、含有量を高める必要がある。２．０％未満では焼き入れ性が低下し、靭性が低下するとともに、脱酸不足となりブローホールが発生する場合がある。しかし、２．６％を超えると溶接金属が硬化して靱性が低下する。したがって、Ｍｎ含有量は、２．０〜２．６％とする。
【００１２】
Ｍｏは、オーステナイトの粗大化を抑制し、オーステナイト粒径を微細化するとともに焼き入れ性が向上する元素であり、溶接金属の引張強度および靭性を高める。０．１５％未満では、結晶粒の粗大化により靭性が低下し、また、強度不足となる。しかし、０．５５％を超えると溶接金属が硬化して靱性が低下する。したがって、Ｍｏ含有量は、０．１５〜０．５５％とする。
Ｔｉ、は脱酸剤として作用するとともに、溶接金属中にＴｉ酸化物を生成し、これが、フェライト生成核となり、粒内に微細なフェライト組織であるアシュキュラーフェライト組織を形成して靱性を向上させる。０．１５％未満ではこの効果が得られない。また、０．３０％を超えると溶接金属は脆化して靱性が劣化する。したがって、Ｔｉ含有量は、０．１５〜０．３０％とする。
【００１３】
Ｎｉは、オーステナイトの安定化元素であり、溶接金属中のフェライトマトリックスの靭性を向上させる元素である。０．０２％未満では効果がなく、０．５０％を超えるとオーステナイト粒が粗大化し靱性が低下する。したがって、Ｎｉ含有量は、０．０２〜０．５０％とする。
Ｂは、オーステナイトから生成する粒界フェライトの発生を抑え、靱性を向上させる元素である。０．００５％未満では効果がなく、０．０１２％を超えると溶接金属に高温割れが発生し易くなる。したがって、Ｂ含有量は、０．００５〜０．０１２％とする。
【００１４】
Ａｌは、脱酸剤として溶鋼に添加する元素である。しかし、０．０２０％を超えると溶接金属の靱性が低下する。したがって、Ａｌ含有量は、０．０２０％以下とする。
Ｏは、アークを安定させるとともに溶滴の表面張力を低下させる元素でビード形状を良好する。０．００２％未満ではアークが不安定でビード形状も不良となる。０．０１５％を超えるとア−ク不安定を引き起こす。したがって、Ｏ含有量は、０．００２〜０．０１５％とする。
【００１５】
Ｎは、ＴｉおよびＢを窒化物として固定化し、微細粒フェライトの発生を低下させ、溶接金属の靭性を劣化させる元素であり、できるだけ低くすることが望ましい。したがって、Ｎ含有量は、０．０１０％以下とする。
ＶおよびＮｂは、大入熱・高パス間温度での溶接施工において、溶接金属に必要な強度（５９０ＭＰａ以上）を得るために必要な元素であり、また、微細な炭窒化物を形成し、溶接金属のオーステナイトから生成する粒界フェライトの発生を抑え、靱性を向上させる元素である。この効果を得るために、１種以上の合計で少なくとも０．００５％以上含有させる必要がある。しかし、１種以上の合計で０．０５％を超えると、脆化による靭性の低下や溶接部に高温割れが発生する場合がある。したがって、ＶおよびＮｂ含有量は、１種以上の合計で、０．００５〜０．０５％とする。
【００１６】
Ｔｍｐは、下記（１）式で得られる大入熱・高パス間温度での溶接施工で溶接金属に必要な強度（５９０ＭＰａ以上）を得るための強度確保の値である。種々の成分組成を有するワイヤを用いて、５９０ＭＰａ級高張力鋼を溶接入熱量４０ｋＪ／ｃｍ、パス間温度３５０℃の溶接で得られた溶接金属の引張試験を行い、ワイヤの成分元素と引張強さとの関係を調査した。その結果、図１に示すように、Ｔｍｐが０．７未満では強度が不足する。一方、１．２を超えると過剰な強度となり割れが発生する場合がある。したがって、Ｔｍｐは０．７〜１．２とする。
【００１７】
Ｋｅｊは、下記（２）式で得られる大入熱・高パス間温度での溶接施工で溶接金属が高靭性（−５℃でのシャルピー吸収エネルギー１００Ｊ以上）を得るための靭性確保の値である。種々の成分組成を有するワイヤを用いて、５９０ＭＰａ級高張力鋼を溶接入熱量４０ｋＪ／ｃｍ、パス間温度３５０℃の溶接で得られた溶接金属の衝撃試験を行い、ワイヤの成分元素とシャルピー吸収エネルギーとの関係を調査した。その結果、図２に示すように、Ｋｅｊが０．２未満では靭性が低下した。したがって、Ｋｅｊは０．２以上とする。

【００１８】
溶接入熱量は、大きくなれば１パス毎の溶着量が増加し、溶接工数の低減が図れ、溶接効率が向上する。しかし、４０ｋＪ／ｃｍを超える溶接入熱量で溶接を行えば、溶接金属の冷却速度が遅くなって、溶接金属の組織が粗大化し、強度および靭性が低下する。また、溶接金属部で融合不良、スラグ巻き込み、高温割れが発生し易くなる。一方、溶接入熱量が３０ｋＪ／ｃｍ未満であると、溶接能率の向上が得られず、また、溶接金属の強度が高くなり、低温割れ感受性も高くなる。したがって、溶接入熱量は３０〜４０ｋＪ／ｃｍとする。
【００１９】
パス間温度は、高くなれば次のパスまでの溶接待ち時間が低減し、溶接効率が向上する。しかし、３５０℃を超えるパス間温度で溶接を行えば、溶接金属の冷却速度が遅くなり、溶接金属の組織が粗大化し、強度および靭性が低下する。一方、パス間温度が２５０℃未満であると、溶接能率の向上が得られず、また、溶接金属の強度が高くなり、低温割れ感受性も高くなる。したがって、パス間温度は２５０〜３５０℃とする。
【００２０】
以下、実施例により本発明をさらに詳細に説明する。
【実施例】
（実施例１）
まず、表１に示す各種成分の１．４ｍｍ径の試作ワイヤを使用し、表２に示す成分の鋼板（鋼種：ＳＡ４４０、厚さ：４０ｍｍ）を、図３の開先形状（試験板幅：４００ｍｍ、溶接長：４００ｍｍ）にして、表３に示す溶接施工条件の条件Ｎｏ．１で多層盛溶接した。溶接金属の機械的性質は引張試験片（ＪＩＳＺ２２０１Ａ１号）およびシャルピー衝撃試験片（ＪＩＳＺ２２４２４号）を板表面から１０ｍｍを中心に採取して作成した。
なお、パス間温度を維持するために試験体下部から加熱しながら温度をコントロールして溶接した。引張強さは５９０ＭＰａ以上、シャルピー衝撃値は試験温度−５℃で５本の値の最低値で１００Ｊ以上を良好とした。それらの結果を表４にまとめて示す。
【００２１】
【表１】

【００２２】
【表２】

【００２３】
【表３】

【００２４】
【表４】

【００２５】
表４において、試験Ｎｏ．１〜９は本発明例、試験Ｎｏ．１０〜３１は比較例である。本発明例である試験Ｎｏ．１〜９のワイヤ記号Ａ１〜Ａ９はワイヤ化学成分、Ｔｍｐ、Ｋｅｊの値が適正であるので、溶接金属の強度および衝撃値が良好で、溶接欠陥がなく高能率に溶接でき極めて満足な結果であった。
比較例中試験Ｎｏ．１０は、ワイヤＡ１０のＣ値が低いので、引張強さが低くなった。試験Ｎｏ．１１は、ワイヤＡ１１のＣが高く、試験Ｎｏ．１５は、ワイヤＡ１５のＭｎが高く、試験Ｎｏ．１７は、ワイヤＡ１７のＭｏが高く、試験Ｎｏ．２４は、ワイヤＡ２４のＶ＋Ｎｂが高いので、いずれも強度が過剰となり衝撃値が低くなった。
【００２６】
試験Ｎｏ．１２は、ワイヤＡ１２のＳｉが低く、試験Ｎｏ．１４は、ワイヤＡ１４のＭｎが低く、試験Ｎｏ．１６は、ワイヤＡ１６のＭｏが低く、試験Ｎｏ．２３は、ワイヤＡ２３のＶ＋Ｎｂが低く、試験Ｎｏ．３０は、ワイヤＡ３０のＴｍｐおよびＫｅｊが低いので、いずれも引張強さ及び衝撃値が低くなった。試験Ｎｏ．１３は、ワイヤＡ１３のＳｉが高く、試験Ｎｏ．１８は、ワイヤＡ１８のＴｉが低く、試験Ｎｏ．１９は、ワイヤＡ１９のＴｉが高く、試験Ｎｏ．２０は、ワイヤＡ２０のＮｉが低く、試験Ｎｏ．２１は、ワイヤＡ２１のＮｉが高く、試験Ｎｏ．２２は、ワイヤＡ２２のＡｌが高く、試験Ｎｏ．２５は、ワイヤＡ２５のＢが低く、試験Ｎｏ．２９は、ワイヤＡ２９のＮが高いので、いずれも衝撃値が低くなった。試験Ｎｏ．２６は、ワイヤＡ２６のＢが高く、試験Ｎｏ．３１は、ワイヤＡ３１のＴｍｐが高いので、強度が過剰となるとともにクレータ部に高温割れが発生した。試験Ｎｏ．２７は、ワイヤＡ２７のＯが低く、試験Ｎｏ．２８はワイヤＡ２８のＯが高いので、ア−クが不安定になった。
【００２７】
（実施例２）
実施例１と同じ開先形状の鋼板にワイヤＡ５，Ａ６，Ａ７，Ａ９で、表３に示す溶接施工条件の条件２〜６で多層盛り溶接した。溶接金属の機械的性質の調査は実施例１と同様に実施した。その結果を表５に示す。表５中試験Ｎｏ．３２は、溶接施工条件Ｎｏ．２のパス間温度が低いので、次層までのパス間温度待ち時間が長く溶接能率が悪かった。試験Ｎｏ．３３は、溶接施工条件Ｎｏ．３のパス間温度が高いので、強度および靱性が低下した。試験Ｎｏ．３４は、溶接施工条件Ｎｏ．４の溶接入熱量が高いので、強度および靱性が低下した。さらに、１層目に高温割れが生じた。試験Ｎｏ．３５は、溶接施工条件Ｎｏ．５の溶接入熱量およびパス間温度が適正であるので、溶接金属の強度および衝撃値が良好で、溶接欠陥がなく高能率に溶接でき極めて満足な結果であった。試験Ｎｏ．３６は、溶接施工条件Ｎｏ．６の溶接入熱量が低いので、溶接時間が長くなり溶接能率が悪かった。
【００２８】
【表５】

【００２９】
【発明の効果】
以上詳述したように、本発明の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よれば、５９０ＭＰａ級高張力鋼を溶接入熱量３０〜４０ｋＪ／ｃｍ、パス間温度２５０〜３５０℃で多層盛溶接する場合においても、強度および靱性が優れた溶接金属が得られ、溶接作業効率の向上を図ることができる。
【図面の簡単な説明】
【図１】Ｔｍｐと引張強さの関係を示す図である。
【図２】Ｋｅｊとシャルピ−衝撃値の関係を示す図である。
【図３】本発明の実施例に用いた試験板の開先形状を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gas shielded arc welding solid wire mainly used for a 590 MPa class high-strength steel and a method for welding the same. Particularly, even when performing multi-pass welding under welding conditions of large heat input and high interpass temperature, welding is performed. The present invention relates to a gas shielded arc welding wire excellent in metal mechanical properties and a welding method thereof.
[0002]
[Prior art]
Gas shielded arc welding has been widely used for large structures such as buildings, steel frames, bridges, etc., because it has a high efficiency and good penetration into the base material, and also provides welded joints with excellent mechanical properties. ing. In recent years, from the further improvement of welding efficiency, the welding construction method that increases welding heat input and performs welding without excessive cooling of the welded part until the next welding pass, so-called large heat input and high interpass temperature Is required. However, in the welding wire of JIS Z3312 YGW11, welding heat input is generally 15 to 30 kJ / cm, and the maximum temperature between passes is 250 ° C. Welding is generally performed. Metal strength decreases and toughness deteriorates.
[0003]
In order to cope with the welding method between large heat input and high pass, even under welding conditions of a welding heat input of 40 kJ / cm and a pass-to-pass temperature of 350 ° C., for example, Japanese Patent Application Laid-Open No. 10-23087 (Patent Document 1) As disclosed in JP-A-11-90678 (Patent Document 2) and JP-A-11-104886 (Patent Document 3), by adding Ti and B to a wire, a 490 MPa class high-strength steel sheet can be obtained. A large heat input, high interpass temperature welding wire and a welding method that provide good weld metal mechanical properties have been proposed. However, the welding wire and the welding method described above are intended for 490 MPa class high-strength steels. When multi-pass welding is performed under a high pass temperature, there is a problem that mechanical properties of a predetermined weld metal cannot be secured.
[0004]
[References]
(1) Patent Document 1 (Japanese Patent Application Laid-Open No. H10-23087)
(2) Patent Document 2 (JP-A-11-90678)
(3) Patent Document 3 (JP-A-11-104886)
(4) Patent Document 4 (JP-A-11-239892)
(5) Patent Document 5 (JP-A-2001-287068)
(6) Patent Document 6 (JP-A-2002-79395)
(7) Patent Document 7 (Japanese Patent Application Laid-Open No. 2002-103082)
[0005]
[Problems to be solved by the invention]
The present invention is directed to a 590 MPa class high-strength steel capable of ensuring the strength and toughness of a weld metal even when performing multi-pass welding under welding conditions of a welding heat input of 30 to 40 kJ / cm and an interpass temperature of 250 to 350 ° C. It is an object to provide a solid wire for gas shielded arc welding and a welding method thereof.
[0006]
[Means for Solving the Problems]
The gist of the present invention is that in a solid wire for gas shielded arc welding, C: 0.05 to 0.15%, Si: 0.7 to 1.1%, and Mn: 2.0 to 2.6% by mass. %, Mo: 0.15 to 0.55%, Ti: 0.15 to 0.30%, Ni: 0.02 to 0.50%, B: 0.005 to 0.012%, Al: 0. 020% or less, O: 0.002 to 0.015%, N: 0.010% or less, further contains 0.005 to 0.05% of one or more of V and Nb, and the balance is Fe and unavoidable impurities. And Tmp represented by the following equation (1) is 0.7 to 1.2, and Kej represented by the following equation (2) is 0.2 or more.
Further, a gas shield characterized in that multi-layer welding of a 590 Mpa class high-tensile steel is performed using the gas shield arc welding wire under welding conditions of a heat input of 30 to 40 kJ / cm and an interpass temperature of 250 to 350 ° C. In the arc welding method.

[0007]
Embodiment of the present invention
Conventionally, a solid wire for gas shielded arc welding for welding a 490 MPa class high-tensile steel sheet has become capable of welding at a welding heat input of 40 kJ / cm and a pass-to-pass temperature of 350 ° C. with the standardization of JIS Z3312 YGW18. High strength steel could not be welded at high heat input and high interpass temperature. Therefore, even when multi-pass welding is performed on a 590 MPa class high-strength steel at a welding heat input of 30 to 40 kJ / cm and an interpass temperature of 250 to 350 ° C., the strength of 590 MPa or more and the Charpy absorbed energy at −5 ° C. In order to achieve 100 J or more, it is necessary to devise essential measures for the wire components.
[0008]
In order to solve the above-mentioned conventional problems, the present inventors have applied multi-pass welding to a 590 MPa class high tensile steel with a high welding efficiency, a heat input of 30 to 40 kJ / cm, and a temperature between passes of 250 to 350 ° C. Also sought welding technology that would provide excellent weld metal performance. Generally, if welding is performed at a welding heat input of 40 kJ / cm, welding man-hours can be reduced due to an increase in the amount of welding, and if welding at a temperature between passes of 350 ° C. becomes possible, the welding waiting time until the next pass will be shortened. This has a significant effect on reducing welding efficiency. Focusing on this point, various investigations were made on the solid wire components for gas shielded arc welding for multi-pass welding, which are excellent in mechanical properties such as the strength and toughness of the weld metal, and the welding method. As a result, a solid wire for gas shielded arc welding that enables a 590 MPa class high-tensile steel sheet to be welded at a welding heat input of 30 to 40 kJ / cm and a pass-to-pass temperature of 250 to 350 ° C. by appropriately setting the components of the wire. And a welding method using the same.
[0009]
Hereinafter, the reason for limiting the component composition of the solid wire for gas shielded arc welding of the present invention will be described.
C is an element that increases the tensile strength of the weld metal. In order to obtain the required strength (590 MPa or more) for the weld metal during welding at a large heat input and high inter-pass temperature, it is necessary to contain at least 0.05% by mass (hereinafter referred to as%) or more. However, if it exceeds 0.15%, the toughness is reduced, and cracks may occur in the weld. Therefore, the C content is set to 0.05 to 0.15%.
[0010]
Si is a deoxidizing agent, and is an element necessary for reducing the amount of oxygen and improving the toughness. In particular, in welding at a large heat input and a high inter-pass temperature, the amount of Si consumed is so great that it is necessary to increase the content. If it is less than 0.7%, the strength and toughness are reduced, and the deoxidation becomes insufficient, which may cause blowholes. However, if it exceeds 1.1%, the toughness decreases. Therefore, the Si content is set to 0.7 to 1.1%.
[0011]
Mn is an element that increases the tensile strength of the weld metal, and is an element that increases the toughness with a deoxidizing agent. In welding at a high heat input and a high inter-pass temperature, it is necessary to increase the content in order to obtain the strength (590 MPa or more) necessary for the weld metal and to consume a large amount of deoxidizing agent. If it is less than 2.0%, the hardenability will be reduced, the toughness will be reduced, and the deoxidation will be insufficient, which may cause blow holes. However, if it exceeds 2.6%, the weld metal is hardened and the toughness is reduced. Therefore, the Mn content is set to 2.0 to 2.6%.
[0012]
Mo is an element that suppresses austenite coarsening, refines austenite grain size, and improves hardenability, and increases the tensile strength and toughness of a weld metal. If it is less than 0.15%, toughness is reduced due to coarsening of crystal grains, and strength is insufficient. However, if it exceeds 0.55%, the weld metal is hardened and the toughness is reduced. Therefore, the Mo content is set to 0.15 to 0.55%.
Ti, while acting as a deoxidizing agent, generates Ti oxide in the weld metal, which becomes a ferrite generation nucleus and forms an ashular ferrite structure which is a fine ferrite structure in the grains to improve toughness. . If less than 0.15%, this effect cannot be obtained. On the other hand, if it exceeds 0.30%, the weld metal becomes brittle and the toughness is deteriorated. Therefore, the Ti content is set to 0.15 to 0.30%.
[0013]
Ni is an element for stabilizing austenite and is an element for improving the toughness of a ferrite matrix in a weld metal. If it is less than 0.02%, there is no effect, and if it exceeds 0.50%, austenite grains are coarsened and toughness is reduced. Therefore, the Ni content is set to 0.02 to 0.50%.
B is an element that suppresses generation of grain boundary ferrite generated from austenite and improves toughness. If it is less than 0.005%, there is no effect, and if it exceeds 0.012%, hot cracks are easily generated in the weld metal. Therefore, the B content is set to 0.005 to 0.012%.
[0014]
Al is an element added to molten steel as a deoxidizing agent. However, if it exceeds 0.020%, the toughness of the weld metal decreases. Therefore, the Al content is set to 0.020% or less.
O is an element that stabilizes the arc and lowers the surface tension of the droplet and improves the bead shape. If it is less than 0.002%, the arc becomes unstable and the bead shape becomes poor. If it exceeds 0.015%, arc instability is caused. Therefore, the O content is set to 0.002 to 0.015%.
[0015]
N is an element that fixes Ti and B as nitrides, reduces the generation of fine-grained ferrite, and degrades the toughness of the weld metal, and is desirably as low as possible. Therefore, the N content is set to 0.010% or less.
V and Nb are elements necessary for obtaining the strength (590 MPa or more) required for the weld metal during welding at high heat input and high interpass temperature, and form fine carbonitrides. It is an element that suppresses generation of grain boundary ferrite generated from austenite of weld metal and improves toughness. In order to obtain this effect, it is necessary to contain at least 0.005% or more in total of one or more kinds. However, if the total of one or more kinds exceeds 0.05%, the toughness may be reduced due to embrittlement and a hot crack may occur in the welded portion. Therefore, the V and Nb contents are set to 0.005 to 0.05% in total of one or more kinds.
[0016]
Tmp is a value for securing the strength required to obtain the strength (590 MPa or more) required for the weld metal in welding at a large heat input and a high interpass temperature obtained by the following equation (1). Using wires having various component compositions, a tensile test was performed on a weld metal obtained by welding a 590 MPa class high strength steel at a welding heat input of 40 kJ / cm and an interpass temperature of 350 ° C. We investigated the relationship with As a result, as shown in FIG. 1, if Tmp is less than 0.7, the strength is insufficient. On the other hand, if it exceeds 1.2, the strength becomes excessive and cracks may occur. Therefore, Tmp is set to 0.7 to 1.2.
[0017]
Kej is a value for securing toughness for a weld metal to obtain high toughness (Charpy absorbed energy at -5 ° C of 100 J or more) in welding at a large heat input and a high interpass temperature obtained by the following equation (2). is there. Using wires having various component compositions, an impact test was performed on a weld metal obtained by welding a 590 MPa class high-tensile steel at a welding heat input of 40 kJ / cm and a pass-to-pass temperature of 350 ° C. to determine the constituent elements of the wire and the Charpy absorption The relationship with energy was investigated. As a result, as shown in FIG. 2, when Kej was less than 0.2, toughness was reduced. Therefore, Kej is set to 0.2 or more.

[0018]
As the welding heat input increases, the amount of welding for each pass increases, thereby reducing welding man-hours and improving welding efficiency. However, if welding is performed with a welding heat input exceeding 40 kJ / cm, the cooling rate of the weld metal is reduced, the structure of the weld metal is coarsened, and the strength and toughness are reduced. In addition, poor fusion, entrapment of slag, and high-temperature cracking tend to occur in the weld metal. On the other hand, if the welding heat input is less than 30 kJ / cm, no improvement in welding efficiency can be obtained, the strength of the weld metal increases, and the susceptibility to low-temperature cracking increases. Therefore, the welding heat input is set to 30 to 40 kJ / cm.
[0019]
If the temperature between passes increases, the welding waiting time until the next pass decreases, and the welding efficiency improves. However, if welding is performed at an inter-pass temperature exceeding 350 ° C., the cooling rate of the weld metal becomes slow, the structure of the weld metal becomes coarse, and the strength and toughness decrease. On the other hand, if the temperature between passes is less than 250 ° C., improvement in welding efficiency cannot be obtained, and the strength of the weld metal increases, and the susceptibility to low-temperature cracking also increases. Therefore, the temperature between passes is set to 250 to 350 ° C.
[0020]
Hereinafter, the present invention will be described in more detail with reference to examples.
【Example】
(Example 1)
First, a steel plate (steel type: SA440, thickness: 40 mm) having the components shown in Table 2 was prepared using a prototype wire having a diameter of 1.4 mm of each component shown in Table 1 and the groove shape (test plate width: 400 mm, welding length: 400 mm). 1 was multi-layer welded. The mechanical properties of the weld metal were prepared by sampling a tensile test piece (JIS Z2201 A1) and a Charpy impact test piece (JIS Z22424) at a center of 10 mm from the plate surface.
In addition, in order to maintain the temperature between passes, welding was performed while controlling the temperature while heating from the lower part of the test piece. The tensile strength was 590 MPa or more, and the Charpy impact value was 100 J or more as the lowest value among the five values at the test temperature of -5 ° C. The results are summarized in Table 4.
[0021]
[Table 1]

[0022]
[Table 2]

[0023]
[Table 3]

[0024]
[Table 4]

[0025]
In Table 4, Test No. 1 to 9 are examples of the present invention, and test Nos. 10 to 31 are comparative examples. Test No. which is an example of the present invention. Since the wire symbols A1 to A9 of 1 to 9 have appropriate wire chemical components, Tmp, and Kej values, the strength and impact value of the weld metal are good, welding can be performed efficiently without welding defects, and extremely satisfactory results can be obtained. there were.
Test No. in the comparative example. In No. 10, since the C value of the wire A10 was low, the tensile strength was low. Test No. In Test No. 11, the C of the wire A11 was high and the test No. In Test No. 15, the Mn of the wire A15 was high, and In the test No. 17, the Mo of the wire A17 was high, and In No. 24, since V + Nb of the wire A24 was high, the strength was excessive and the impact value was low.
[0026]
Test No. In Test No. 12, the wire A12 had low Si, and Test No. In Test No. 14, the Mn of the wire A14 was low, In the test No. 16, the Mo of the wire A16 was low, and In Test No. 23, V + Nb of wire A23 was low, and In No. 30, since the Tmp and Kej of the wire A30 were low, the tensile strength and the impact value were all low. Test No. In Test No. 13, the wire A13 had high Si, In Test No. 18, the wire A18 had a low Ti, and In Test No. 19, the Ti of wire A19 was high, and In test No. 20, the Ni of wire A20 was low, and In Test No. 21, the Ni of the wire A21 was high, and In Test No. 22, the Al of the wire A22 was high, and In test No. 25, B of wire A25 was low, and In No. 29, since the N of the wire A29 was high, the impact value was low in each case. Test No. In test No. 26, B of wire A26 was high, and In No. 31, since the Tmp of the wire A31 was high, the strength became excessive and hot cracks occurred in the crater portion. Test No. In Test No. 27, the O of wire A27 was low, and In No. 28, since the O of the wire A28 was high, the arc became unstable.
[0027]
(Example 2)
Multi-layer welding was performed on steel plates having the same groove shape as in Example 1 using wires A5, A6, A7, and A9 under welding conditions 2 to 6 shown in Table 3. Investigation of the mechanical properties of the weld metal was performed in the same manner as in Example 1. Table 5 shows the results. In Table 5, Test No. 32 is a welding execution condition No. 32. Since the temperature between passes of No. 2 was low, the waiting time between passes to the next layer was long, and the welding efficiency was poor. Test No. No. 33 is the welding condition No. 33. As the inter-pass temperature of No. 3 was high, the strength and toughness decreased. Test No. No. 34 is a welding execution condition No. Since the welding heat input of No. 4 was high, the strength and toughness were reduced. Furthermore, hot cracking occurred in the first layer. Test No. No. 35 is the welding condition No. 35. Since the welding heat input and the pass-to-pass temperature of No. 5 were appropriate, the strength and impact value of the weld metal were good, and welding could be performed with high efficiency without welding defects, which was a very satisfactory result. Test No. No. 36 is a welding execution condition No. 6, the welding heat input was low, so that the welding time was long and the welding efficiency was poor.
[0028]
[Table 5]

[0029]
【The invention's effect】
As described in detail above, according to the solid wire for gas shielded arc welding of the present invention and the method for welding the same, multi-layer welding is performed on a 590 MPa class high-tensile steel at a welding heat input of 30 to 40 kJ / cm, an interpass temperature of 250 to 350 ° C. Even in the case of welding, a weld metal having excellent strength and toughness can be obtained, and the welding operation efficiency can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between Tmp and tensile strength.
FIG. 2 is a diagram showing a relationship between Kej and a Charpy impact value.
FIG. 3 is a view showing a groove shape of a test plate used in an example of the present invention.

Claims

In the solid wire for gas shielded arc welding, C: 0.05 to 0.15%, Si: 0.7 to 1.1%, Mn: 2.0 to 2.6%, Mo: 0. 15 to 0.55%, Ti: 0.15 to 0.30%, Ni: 0.02 to 0.50%, B: 0.005 to 0.012%, Al: 0.020% or less, O: 0.002 to 0.015%, N: 0.010% or less, further contains 0.005 to 0.05% of one or more of V and Nb, and the balance consists of Fe and unavoidable impurities. A solid wire for gas shielded arc welding, wherein Tmp represented by the formula (1) is 0.7 to 1.2, and Kej represented by the formula (2) is 0.2 or more.

A gas shielded arc welding method, comprising: performing multi-layer welding of a 590 MPa class high-tensile steel using the wire according to claim 1 under welding conditions of a heat input of 30 to 40 kJ / cm and an interpass temperature of 250 to 350 ° C. .