JP3718323B2

JP3718323B2 - Flux-cored wire for multi-electrode vertical electrogas arc welding for extra heavy steel

Info

Publication number: JP3718323B2
Application number: JP18462797A
Authority: JP
Inventors: 敦忠本江; 利宏三浦; 茂大北
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 1997-06-26
Filing date: 1997-06-26
Publication date: 2005-11-24
Anticipated expiration: 2017-06-26
Also published as: JPH1110391A

Description

【０００１】
【発明の属する技術分野】
本発明は多電極エレクトロガスアーク溶接用フラックス入りワイヤに係わり、さらに詳しくは、極厚鋼の多電極溶接において低温高靱性を溶接金属に付与できるとともに優れた溶接作業性が得られるフラックス入りワイヤに関するものである。
【０００２】
【従来の技術】
エレクトロガスアーク溶接は溶接能率が高いことから、軟鋼、５０キロＨＴ鋼、６０キロＨＴ鋼を用いる船舶、石油備蓄タンク等の製作に多用されており、特に最近、大型コンテナ船のシャーストレーキ部や、橋梁の橋桁部では板厚５０ｍｍ以上の厚板が使用されるようになったため、作業効率の点からエレクトロガスアーク溶接での施工が強く望まれている。
【０００３】
例えば特開平４−２７９２９５号公報に見られるように、溶接金属中の酸素量を低減し、低温靱性の向上を図る方法等が提案されているが、一般には特開平４−２７９２９５号公報のように、板厚が３５ｍｍ以上になるとＸ開先による多層盛り溶接法が用いられるが、その結果、再熱部の靱性の低下が発生し易くなる。また、施工も難しくなり、工程も増えるため、１パス溶接法が考えられるが、大入熱溶接となるため組織が肥大化し易く、また鋼板からの希釈や熱影響部も大きくなるため機械的性質が劣化しやすい。
【０００４】
そこで多電極化することにより、溶接速度を向上させ熱影響部を小さくし、溶接金属性能に影響を与える母材希釈及び組織の肥大化を抑えることができる。しかし既存の１電極用エレクトロガスアーク溶接用フラックス入りワイヤは多電極溶接用にスラグ成分及び合金成分が調整されていないため、スラグ跳ねの多発及び大入熱溶接での低温靱性の劣化が発生する。このことから多電極エレクトロガスアーク溶接用フラックス入りワイヤの開発が要望されている。
【０００５】
【発明が解決しようとする課題】
本発明は、かかる事情のもとで、板厚３５〜１００ｍｍの極厚大入熱溶接において、溶接金属の低温靱性を良好にし、かつ優れた溶接作業性が得られる多電極エレクトロガスアーク溶接用フラックス入りワイヤを提供することを目的にしたものである。
【０００６】
【課題を解決するための手段】
本発明者らは、前記課題を解決するために鋭意研究を重ねた結果、フラックス入りワイヤの化学成分及びフラックス充填率並びに溶接諸条件を規制することにより、優れた高い低温靱性が得られると同時に、良好な溶接作業性、特にスラグ跳ねを少なくできること究明し、ここに本発明を見出した。
【０００７】
すなわち、本発明は、板厚３５〜１００ｍｍの極厚鋼用多電極エレクトロガスアーク溶接フラックス入りワイヤであって、該ワイヤの組成がワイヤ全重量に対し、金属弗化物をＦ量換算で０．２０〜１．００％、金属弗化物を含むスラグ生成剤：１．０〜３．０％、Ｃ：０．０４〜０．１５％、Ｓｉ：０．１５〜０．８０％、Ｍｎ：０．８０〜２．５０％、Ａｌ：０．０５〜０．２５％、Ｍｇ：０．０５〜０．４０％、Ｎｉ：０．５０〜４．００％、Ｍｏ：０．０５〜０．５０％、Ｔｉ：０．０５〜０．４０％、Ｂ：０．００２０〜０．０１５０％を含有し、且つ下式▲１▼を満足するＦ量を含有することを特徴とする極厚鋼用多電極立向エレクトロガスアーク溶接フラックス入りワイヤを基本とし、鋼製外皮中にフラックスを充填してなるワイヤ径が２．０ｍｍφ以下で、充填するフラックスがワイヤ全重量に対し１５〜３５％であり、かつ鉄粉が１０〜３０％を含有し、溶接金属中の酸素量が１８０〜４００ｐｐｍとなる極厚鋼用多電極エレクトロガスアーク溶接フラックス入りワイヤである。なお、本発明は低温鋼以外にも一般の軟鋼・５０又は６０ＨＴ鋼板にも使用可能である。
１．０≧弗素換算量≧３Ａｌ＋０．０５・・・・・ ▲１▼
【０００８】
【発明の実施の形態】
板厚：３５〜１００ｍｍ
本発明は大入熱多電極溶接用に開発されているため、板厚が３５ｍｍ以下の小入熱溶接を行うと、溶接速度が１電極溶接時と比べて溶接速度が上昇することによって冷却速度も速くなるため、各合金成分の歩留りが上昇し、良好な機械性能が得られない。また既存の１電極用装置及びフラックス入りワイヤは３５ｍｍ程度までの１パス溶接用に設計され、すでに確立されている技術であるため、多電極溶接の際の板厚は３５ｍｍ以上とする。また現在用いられている鋼板は１００ｍｍ程度までが一般的であることから上限は１００ｍｍとする。
【０００９】
金属弗化物をＦ量換算で０．２０〜１．００％
金属弗化物はアークの安定を高めるとともに脱酸促進作用によって溶接金属中の酸素量を低減させ、低温靱性を向上させる作用がある。また、スラグ生成剤中のＦ量を規制することによってスラグ生成剤の粘性を調節でき、極厚鋼における多電極溶接時に問題となるスラグ跳ね及びスパッタの発生を防止できる。金属弗化物中のＦ量換算を０．２０〜１．００％としたのは、０．２０％未満ではスラグの良好な流動性の流動性が得られず、スラグ跳ね等の溶接作業性の劣化、及び脱酸促進作用の効果が得られず、溶接金属中の酸素量が上昇し、低温靱性の劣化が発生する。また１．００％を越えると粘性が低くなりすぎ、スラグが垂れやすくなり良好なビード形状が得られない。また、過剰な脱酸促進作用によって強度が上昇し、良好な低温靱性が得られない。
【００１０】
金属弗化物を含むスラグ生成剤：１．０〜３．０％
スラグ生成剤の量を１．０〜３．０％としたのは、１．０％未満ではスラグ生成量がビード表面を覆うには不十分で溶接金属が垂れやすくなり、健全な溶接金属が得られない。また３．０％以上では、スラグが過剰となってスラグ垂れ及びアークが不安定となり、健全な溶接作業性が得られない。
【００１１】
Ｃ：０．０４〜０．１５％
ＣはＣＯ生成反応による脱酸作用とともに、溶接金属の焼入れ性を高め、強さと硬さを増す作用が強く、ワイヤ中のＣが０．０４％未満ではそのような効果が得られず、０．１５％を超えると、溶接金属中のＣ量が増加してマルテンサイトが発生し易くなり、靱性が劣化する。またスパッタ量が多くなり、溶接作業性が劣化するので、Ｃの範囲は０．０４〜０．１５％とする。
【００１２】
Ｓｉ：０．１５〜０．８０％
Ｓｉは脱酸作用によって溶接金属中の酸素量を低減し、あるいは一部が溶接金属中に歩留って強度を高める作用がある。またアークを安定にし、ビード形状を良好にする作用もある。Ｓｉが０．１５％未満ではそのような効果が得られず、０．８０％を超えると溶接金属中の酸素量が低くなり過ぎ溶接金属が硬化するため靱性の低下が起こる。またスパッタが多発するためＳｉの範囲は０．１５〜０．８０％とする。
【００１３】
Ｍｎ：０．８０〜２．５％
ＭｎもＳｉと同様、脱酸及び合金作用があり、Ｍｎが０．８０％未満では脱酸効果が少なくなるばかりではなく、溶接金属の強度が得られなくなると共に靱性が劣化する。一方２．５％を超えると、強度が必要以上に高くなって靱性や耐割れ性が低下するので、Ｍｎの範囲は０．８〜２．５％とする。
ワイヤ中のＳｉ−Ｍｎ源としては、鋼製鞘中のＳｉ、Ｍｎ以外に、Ｆｅ−Ｓｉ、Ｆｅ−Ｍｎ、Ｆｅ−Ｓｉ−Ｍｎ等の合金あるいはＳｉＯ₂ 、ＭｎＯ、ＭｎＯ₂ 等の酸化物が含まれる。
【００１４】
Ａｌ：０．０５〜０．２５％
Ａｌは大入熱溶接時に微細な組織を形成するために必要な元素であり、その効果を得るためには少なくとも０．０５％は添加する必要がある。しかし、０．２５％以上添加するとＡｌ酸化物が急激に増大し、Ｔｉ酸化物と大型の複合酸化物を形成し、低温靱性が劣化するためＡｌの範囲は０．０５〜０．２５％とする。
【００１５】
Ｍｇ：０．０５〜０．４０％
強脱酸剤であるＭｇは０．０５％未満では脱酸効果を期待できなくなるが、０．４０％を超えると合金成分の過剰な歩留り、溶接金属中の酸素量が低くなり過ぎることによる過剰な焼入性となり、強度の上昇及び靱性低下を招く。またスパッタ量も多くなるので、Ｍｇの範囲は０．０５〜０．４０％とする。
【００１６】
Ｎｉ：０．５０〜４．０％
Ｎｉを添加するのは、大入熱溶接でも安定した溶接金属の靱性を得るためである。そのためには０．５％添加する必要があり、一方４．０％を超えると溶接金属の強度が高くなり過ぎ、また割れが発生するため、Ｎｉの範囲は０．５〜４．０％とする。
【００１７】
Ｍｏ：０．０５〜０．５０％
Ｍｏを添加するのは大入熱溶接時における溶接金属の強度を得ることと、溶接金属微細化による靱性改善のためである。そのためには少なくとも０．０５％添加する必要があり、一方０．５０％を超えると溶接金属の強度が高くなりすぎ、靱性が低下する。従ってＭｏの範囲は０．０５〜０．５０％とする。
【００１８】
Ｔｉ：０．０５〜０．４０％
Ｔｉの添加はアーク現象の改善と後述するＢとの相乗効果で溶接金属の靱性を向上させる効果がある。Ｔｉが０．０５％未満ではそのような効果が得られず、逆に０．４０％を超えると溶接金属が硬化して靱性が劣化するので、Ｔｉは０．０５〜０．４０％とする。
【００１９】
Ｂ：０．００２０〜０．０１５０％
Ｂは上述のＴｉとの相乗効果で溶接金属の初析フェライトの生成を抑制し、かつ組織を均一微細化して靱性向上に効果がある。Ｂが０．００２０％未満であると上記した効果が期待し得ず、０．０１５０％を超えると焼入れ効果の大きい元素であるＢが過剰となって溶接金属が硬化し、耐割れ性や靱性が低下する。従って、Ｂの範囲は０．００２０〜０．０１５０％とする。Ｂ源としてはＦｅ−Ｂの他、Ｂ₂ Ｏ₃ 等のＢ化合物を用いても良い。
【００２０】
１．０≧Ｆ量換算≧３Ａｌ＋０．０５
Ｆ量換算とＡｌの添加量を上式に規定したのは、Ａｌの効果は前記した通りであるが、溶接の際にスラグの流動性を劣化させ、スラグ跳ねが発生する。そこで、溶接作業性及びＦ量換算とＡｌの添加量を変化させ、溶接金属の低温靱性を調査した結果、図１に示す範囲において、スラグの流動性を劣化させることなく、溶接金属の低温靱性が得られることを見いだした。この範囲を上式とする。
【００２１】
ワイヤ径：≦２．０ｍｍφ
ワイヤ径は２．０ｍｍを超えると入熱の増大、溶着速度の低下が挙げられ、また既存送給装置の能力から２．０ｍｍ以下とした。
【００２２】
充填フラックス：１５〜３５％
充填フラックスは１５％未満であると、溶着量の低下、スパッタの増大を招く。また３５％を超えると生産性が低下するので、充填フラックスは１５〜３５％とする。
【００２３】
鉄粉：１０〜３０％
鉄粉は溶着速度を高め、施工能率を上げるために添加するが、１０％未満であると溶着速度が遅くなり、生成スラグ量が溶着金属に対して多すぎたりする。また３０％を超えると、生成スラグ量が不足したり、充填率の不安定や伸線性が困難になるので鉄粉の範囲は１０〜３０％とする。
【００２４】
溶接金属中の酸素量：１８０〜４００ｐｐｍ
極厚鋼による１パス多電極エレクトロガスアーク溶接のような大入熱溶接法は、合金成分を適量添加すると共に溶接金属中の酸素量の低減が良好な低温靱性を得るために必要である。本発明は良好な低温靱性が得られる１８０〜４００ｐｐｍになるよう金属弗化物、脱酸剤を規制しており、本発明範囲を下回ると酸素量上昇による溶接金属組織の粗大化、上回ると酸素量低減による引張強度の上昇による低温靱性の劣化が起こる。そこで、溶接金属中の酸素量は１８０〜４００ｐｐｍとする。
【００２５】
【実施例】
表１ないし表２の組成となるワイヤ１〜１１を作成した。鋼製外皮としてはＣ：０．０４％、Ｓｉ：０．０２％、Ｍｎ：０．３０％、Ｐ：０．０１％、Ｓ：０．００８％、Ａｌ：０．０２％なる成分を含む軟鋼を用い、表１ないし表２の脱酸剤・合金剤、スラグ生成剤、鉄粉を混合したフラックスを充填してワイヤ径１．６ｍｍφに仕上げた。
【００２６】
【表１】

【００２７】
【表２】

【００２８】
また表３の組成となる板厚５０、７０、９０ｍｍの鋼板を用い、溶接は以下に示す開先形状及び表４に示す溶接条件でそれぞれ１パスで仕上げた。各試験板の板厚中央より試験片を採取し、作業性、溶接金属の衝撃特性について調査した溶接金属試験結果を結果を表４に示す。衝撃特性は−４０℃におけるシャルピー吸収エネルギーが、４０Ｊ以上のものを合格とした。
【００２９】
〈開先条件〉

【００３０】
【表３】

【００３１】
【表４】

【００３２】
【表５】

【００３３】
【表６】

【００３４】
本発明のＮｏ．１〜５は各板厚とも良好な作業性と低温靱性が得られた。Ｎｏ．６はＣ量とＭｏ量が本発明範囲を超えたためスパッタが多発し、また靱性が劣化した。Ｎｏ．７はＳｉ量が本発明範囲を超えたため、スパッタが多発し、また溶接金属中の酸素量が本発明範囲を下回った結果、過剰な焼入性となり低靱性となった。
【００３５】
Ｎｏ．８は鉄粉と充填率が本発明範囲を下回った結果、板厚５０ｍｍの溶接でも溶着量の低下及び不安定なアーク状態となった。またＡｌ量が本発明範囲を下回ったため、脱酸力が低下した結果、溶接金属中の酸素量が本発明範囲を超えたため、靱性が劣化した。
【００３６】
Ｎｏ．９は本発明範囲のＦ量及び▲１▼式を満足していないため、スラグの流動性が劣化し、溶接中にスラグ跳ねが多発した。またＢ量が本発明範囲を超えたため、溶接後割れが発生し試験片を採取できなかった。
【００３７】
Ｎｏ．１０はＮｉ及びＴｉ量が本発明範囲を下回ったため、板厚７０、９０ｍｍで焼き入れ不足となり、組織が肥大化し低靱性となった。Ｎｏ．１１は本発明範囲の▲１▼式を満足していないため、板厚５０および７０ｍｍで溶接中にスラグ跳ねが多発した。
【００３８】
【発明の効果】
以上のように本発明のエレクトロガスアーク溶接用フラックス入りワイヤを用いることにより、板厚３５〜１００の鋼板を多電極で１パス溶接した際に良好な低温靱性及び作業性を得ることができる。
【図面の簡単な説明】
【図１】ＡｌとＦの適正範囲を示すグラフ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flux-cored wire for multi-electrode electrogas arc welding, and more particularly to a flux-cored wire that can impart low-temperature high toughness to weld metal in multi-electrode welding of extra-thick steel and can provide excellent welding workability. It is.
[0002]
[Prior art]
Since electrogas arc welding has high welding efficiency, it is frequently used for the production of ships using mild steel, 50 kg HT steel, 60 kg HT steel, oil storage tanks, etc. Since a thick plate having a thickness of 50 mm or more is used in the bridge girder portion of the bridge, construction by electrogas arc welding is strongly desired from the viewpoint of work efficiency.
[0003]
For example, as seen in Japanese Patent Laid-Open No. 4-279295, a method for reducing the amount of oxygen in the weld metal and improving the low temperature toughness has been proposed. In addition, when the plate thickness is 35 mm or more, the multi-layer welding method using the X groove is used, but as a result, the toughness of the reheated portion tends to decrease. In addition, since the construction becomes difficult and the number of processes increases, a one-pass welding method can be considered. However, since the heat input welding becomes large, the structure tends to enlarge, and the dilution from the steel plate and the heat-affected zone also increase, resulting in mechanical properties. Tends to deteriorate.
[0004]
Therefore, by increasing the number of electrodes, it is possible to improve the welding speed, reduce the heat-affected zone, and suppress the dilution of the base material and the enlargement of the structure that affect the weld metal performance. However, existing flux cored wires for electrogas arc welding for one electrode are not adjusted for slag components and alloy components for multi-electrode welding. Therefore, slag jumps frequently and low temperature toughness deteriorates in high heat input welding. For this reason, development of a flux-cored wire for multi-electrode electrogas arc welding is desired.
[0005]
[Problems to be solved by the invention]
Under such circumstances, the present invention provides a multi-electrode electrogas arc welding flux that improves the low temperature toughness of the weld metal and provides excellent welding workability in ultra-thick heat input welding with a plate thickness of 35 to 100 mm. The purpose is to provide a cored wire.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have been able to obtain excellent high low temperature toughness by regulating the chemical components and flux filling ratio of the core with flux and various welding conditions. The present inventors have found that good welding workability, in particular, slag splash can be reduced, and found the present invention here.
[0007]
That is, the present invention is a multi-electrode electrogas arc welding flux-cored wire for extra-thick steel with a plate thickness of 35 to 100 mm, and the composition of the wire is 0.20 in terms of F amount in terms of metal fluoride with respect to the total weight of the wire. -1.00%, slag generator containing metal fluoride: 1.0-3.0%, C: 0.04-0.15%, Si: 0.15-0.80%, Mn: 0.0. 80 to 2.50%, Al: 0.05 to 0.25%, Mg: 0.05 to 0.40%, Ni: 0.50 to 4.00%, Mo: 0.05 to 0.50% , Ti: 0.05-0.40%, B: 0.0020-0.0150%, and an F content satisfying the following formula (1): It is based on the electrode-facing electrogas arc welding flux-cored wire, and the steel sheath is filled with flux. An electrode having a wire diameter of 2.0 mmφ or less, a filling flux of 15 to 35% with respect to the total weight of the wire, an iron powder content of 10 to 30%, and an oxygen content in the weld metal of 180 to 400 ppm. This is a multi-electrode electrogas arc welding flux cored wire for thick steel. In addition, this invention can be used also for general mild steel and 50 or 60HT steel plate besides low temperature steel.
1.0 ≧ fluorine conversion amount ≧ 3Al + 0.05 (1)
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Plate thickness: 35-100mm
Since the present invention has been developed for large heat input multi-electrode welding, when small heat input welding with a plate thickness of 35 mm or less is performed, the welding speed increases compared to the one electrode welding, so that the cooling speed is increased. Therefore, the yield of each alloy component increases, and good mechanical performance cannot be obtained. In addition, since the existing one-electrode apparatus and flux-cored wire are designed for one-pass welding up to about 35 mm and are already established, the plate thickness for multi-electrode welding is set to 35 mm or more. Moreover, since the steel plate currently used is generally up to about 100 mm, the upper limit is set to 100 mm.
[0009]
0.20 to 1.00% of metal fluoride in terms of F
Metal fluoride has the effect of improving the low temperature toughness by increasing the stability of the arc and reducing the amount of oxygen in the weld metal by promoting deoxidation. Further, by regulating the amount of F in the slag generating agent, the viscosity of the slag generating agent can be adjusted, and the occurrence of slag jumping and spatter, which are problems during multi-electrode welding in extra heavy steel, can be prevented. The reason why the F amount conversion in the metal fluoride is 0.20 to 1.00% is that if it is less than 0.20%, good fluidity of slag cannot be obtained, and welding workability such as slag splashing is reduced. The effect of the deterioration and the deoxidation promoting action cannot be obtained, the amount of oxygen in the weld metal is increased, and the low temperature toughness is deteriorated. On the other hand, if it exceeds 1.00%, the viscosity becomes too low and the slag tends to sag and a good bead shape cannot be obtained. Further, the strength is increased by the excessive deoxidation promoting action, and good low temperature toughness cannot be obtained.
[0010]
Slag generator containing metal fluoride: 1.0-3.0%
The amount of the slag generating agent is set to 1.0 to 3.0%. If the amount of slag is less than 1.0%, the amount of slag generated is insufficient to cover the bead surface, and the weld metal tends to sag. I can't get it. If it is 3.0% or more, the slag becomes excessive, the slag sag and the arc become unstable, and a sound welding workability cannot be obtained.
[0011]
C: 0.04 to 0.15%
C has a strong effect of increasing the hardenability of the weld metal and increasing the strength and hardness in addition to the deoxidation action by the CO production reaction, and if C in the wire is less than 0.04%, such an effect cannot be obtained. If it exceeds 15%, the amount of C in the weld metal increases, martensite is easily generated, and the toughness deteriorates. Moreover, since the amount of spatter increases and the welding workability deteriorates, the range of C is set to 0.04 to 0.15%.
[0012]
Si: 0.15-0.80%
Si has the effect of reducing the amount of oxygen in the weld metal by deoxidation, or partially increasing the yield in the weld metal and increasing the strength. It also has the effect of stabilizing the arc and improving the bead shape. If Si is less than 0.15%, such an effect cannot be obtained. If it exceeds 0.80%, the amount of oxygen in the weld metal becomes too low and the weld metal is hardened, resulting in a decrease in toughness. Moreover, since sputtering occurs frequently, the Si range is set to 0.15 to 0.80%.
[0013]
Mn: 0.80 to 2.5%
Similar to Si, Mn also has deoxidation and alloying action. If Mn is less than 0.80%, not only the deoxidation effect is reduced, but also the strength of the weld metal cannot be obtained and the toughness deteriorates. On the other hand, if it exceeds 2.5%, the strength becomes higher than necessary and the toughness and crack resistance deteriorate, so the Mn range is set to 0.8 to 2.5%.
The Si-Mn source in the wire, Si in a steel sheath, other than Mn, Fe-Si, Fe- Mn, alloy or SiO _2, MnO, such as Fe-Si-Mn, oxides such MnO ₂ is included.
[0014]
Al: 0.05-0.25%
Al is an element necessary for forming a fine structure at the time of high heat input welding, and in order to obtain the effect, it is necessary to add at least 0.05%. However, when 0.25% or more is added, the Al oxide increases rapidly, forms a large composite oxide with Ti oxide, and the low temperature toughness deteriorates, so the Al range is 0.05 to 0.25%. To do.
[0015]
Mg: 0.05-0.40%
Mg, which is a strong deoxidizer, cannot be expected to have a deoxidation effect if it is less than 0.05%, but if it exceeds 0.40%, it is excessive due to excessive yield of alloy components and excessively low oxygen content in the weld metal. Hardenability leads to an increase in strength and a decrease in toughness. Further, since the amount of sputtering increases, the Mg range is set to 0.05 to 0.40%.
[0016]
Ni: 0.50 to 4.0%
Ni is added to obtain stable weld metal toughness even in high heat input welding. For that purpose, it is necessary to add 0.5%. On the other hand, if it exceeds 4.0%, the strength of the weld metal becomes too high and cracks occur, so the range of Ni is 0.5 to 4.0%. To do.
[0017]
Mo: 0.05 to 0.50%
The reason for adding Mo is to obtain the strength of the weld metal during high heat input welding and to improve the toughness by refining the weld metal. For that purpose, it is necessary to add at least 0.05%. On the other hand, if it exceeds 0.50%, the strength of the weld metal becomes too high and the toughness decreases. Therefore, the range of Mo is set to 0.05 to 0.50%.
[0018]
Ti: 0.05 to 0.40%
The addition of Ti has the effect of improving the toughness of the weld metal by the synergistic effect of improvement of the arc phenomenon and B described later. If Ti is less than 0.05%, such an effect cannot be obtained. Conversely, if it exceeds 0.40%, the weld metal is hardened and the toughness deteriorates, so Ti is 0.05 to 0.40%. .
[0019]
B: 0.0020 to 0.0150%
B has the effect of improving the toughness by suppressing the formation of pro-eutectoid ferrite of the weld metal due to a synergistic effect with Ti described above, and by making the structure uniform and fine. If B is less than 0.0020%, the above effects cannot be expected, and if it exceeds 0.0150%, B, which is an element having a large quenching effect, becomes excessive and the weld metal is hardened, resulting in crack resistance and toughness. Decreases. Therefore, the range of B is 0.0020 to 0.0150%. As the B source, in addition to Fe—B, B compounds such as B ₂ O ₃ may be used.
[0020]
1.0 ≧ F amount conversion ≧ 3Al + 0.05
The amount of F and the amount of addition of Al are defined in the above equation, while the effect of Al is as described above, but the fluidity of slag is deteriorated during welding, and slag splash occurs. Therefore, as a result of investigating the low temperature toughness of the weld metal by changing the welding workability, F amount conversion and Al addition amount, the low temperature toughness of the weld metal within the range shown in FIG. 1 without deteriorating the fluidity of the slag. I found out that This range is the above equation.
[0021]
Wire diameter: ≦ 2.0mmφ
When the wire diameter exceeds 2.0 mm, the heat input increases and the welding speed decreases, and it is set to 2.0 mm or less due to the ability of the existing feeding device.
[0022]
Filling flux: 15-35%
When the filling flux is less than 15%, the amount of welding decreases and the spatter increases. Moreover, since productivity will fall when it exceeds 35%, a filling flux shall be 15-35%.
[0023]
Iron powder: 10-30%
Iron powder is added to increase the welding speed and increase the work efficiency, but if it is less than 10%, the welding speed becomes slow, and the amount of generated slag is too much for the weld metal. If it exceeds 30%, the amount of generated slag becomes insufficient, the instability of the filling rate and the wire drawing become difficult, so the range of iron powder is 10-30%.
[0024]
Oxygen content in weld metal: 180-400 ppm
A high heat input welding method such as one-pass multi-electrode electrogas arc welding with extra-thick steel is necessary to obtain a low temperature toughness in which an appropriate amount of alloy components are added and the amount of oxygen in the weld metal is reduced. The present invention regulates the metal fluoride and the deoxidizer so that good low temperature toughness is obtained to 180 to 400 ppm, and if it is below the range of the present invention, the weld metal structure becomes coarse due to an increase in oxygen content, and if it exceeds, the oxygen content is Degradation of low temperature toughness due to increase in tensile strength due to reduction occurs. Therefore, the amount of oxygen in the weld metal is set to 180 to 400 ppm.
[0025]
【Example】
Wires 1 to 11 having the compositions shown in Tables 1 and 2 were prepared. The steel shell includes components of C: 0.04%, Si: 0.02%, Mn: 0.30%, P: 0.01%, S: 0.008%, Al: 0.02% Using mild steel, a flux mixed with the deoxidizer / alloy agent, slag generator, and iron powder shown in Tables 1 and 2 was filled to finish the wire diameter to 1.6 mmφ.
[0026]
[Table 1]

[0027]
[Table 2]

[0028]
In addition, steel plates having a thickness of 50, 70, and 90 mm having the compositions shown in Table 3 were used, and welding was finished in one pass each with the groove shape shown below and the welding conditions shown in Table 4. Table 4 shows the results of the weld metal test in which test pieces were collected from the center of the thickness of each test plate and investigated for workability and impact characteristics of the weld metal. As the impact characteristics, those having Charpy absorbed energy at −40 ° C. of 40 J or more were accepted.
[0029]
<Bevel condition>

[0030]
[Table 3]

[0031]
[Table 4]

[0032]
[Table 5]

[0033]
[Table 6]

[0034]
No. of the present invention. For Nos. 1 to 5, good workability and low temperature toughness were obtained for each plate thickness. No. In No. 6, since the amount of C and the amount of Mo exceeded the range of the present invention, spatter occurred frequently and the toughness deteriorated. No. In No. 7, since the amount of Si exceeded the range of the present invention, spatter occurred frequently, and the amount of oxygen in the weld metal fell below the range of the present invention, resulting in excessive hardenability and low toughness.
[0035]
No. As a result of the iron powder and the filling rate falling below the range of the present invention, the welding amount decreased and the arc became unstable even when welding with a plate thickness of 50 mm. Moreover, since the amount of Al was less than the range of the present invention, the deoxidizing power was reduced. As a result, the amount of oxygen in the weld metal exceeded the range of the present invention, so that the toughness was deteriorated.
[0036]
No. No. 9 did not satisfy the F amount and the formula (1) within the scope of the present invention, so the slag fluidity deteriorated and slag jumping occurred frequently during welding. Moreover, since the amount of B exceeded the range of the present invention, cracks occurred after welding, and the test piece could not be collected.
[0037]
No. In No. 10, the amount of Ni and Ti was below the range of the present invention, so that quenching was insufficient at a plate thickness of 70 and 90 mm, the structure was enlarged and low toughness was obtained. No. No. 11 did not satisfy the formula (1) within the scope of the present invention, so slag jumping occurred frequently during welding at plate thicknesses of 50 and 70 mm.
[0038]
【The invention's effect】
As described above, by using the flux cored wire for electrogas arc welding according to the present invention, good low temperature toughness and workability can be obtained when a steel plate having a thickness of 35 to 100 is welded by one pass with multiple electrodes.
[Brief description of the drawings]
FIG. 1 is a graph showing appropriate ranges of Al and F

Claims

In a flux-cored wire for a plate thickness of 35 to 100 mm and an extremely thick one-pass multi-electrode electrogas arc welding, the composition of the wire is based on the total weight of the wire,
0.20 to 1.00% of metal fluoride in terms of F amount,
Slag generator containing metal fluoride: 1.0-3.0%,
C: 0.04 to 0.15%,
Si: 0.15-0.80%,
Mn: 0.80 to 2.50%,
Al: 0.05 to 0.25%,
Mg: 0.05-0.40%,
Ni: 0.50 to 4.00%,
Mo: 0.05 to 0.50%,
Ti: 0.05 to 0.40%,
B: 0.0020 to 0.0150%
And a flux-cored wire for multi-electrode vertical electrogas arc welding for heavy-thick steel, characterized by containing an F amount satisfying the following formula (1).
1.0 ≧ F amount conversion ≧ 3Al + 0.05 (1)

The wire diameter formed by filling the steel outer shell with flux is 2.0 mmφ or less, the flux to be filled is 15 to 35% with respect to the total weight of the wire, and the iron powder contains 10 to 30%. The multi-electrode vertical electrogas arc welding flux-cored wire for extra heavy steel described.

The flux cored wire for multi-electrode vertical electrogas arc welding for extra-thick steel according to claim 1 or 2, wherein the amount of oxygen in the weld metal is 180 to 400 ppm.