JP3694187B2

JP3694187B2 - Submerged arc welding method

Info

Publication number: JP3694187B2
Application number: JP08361399A
Authority: JP
Inventors: 伸一鈴木; 誠洋竹村; 薫長谷
Original assignee: JFE Steel Corp; Kobe Steel Ltd
Current assignee: JFE Steel Corp; Kobe Steel Ltd
Priority date: 1999-03-26
Filing date: 1999-03-26
Publication date: 2005-09-14
Anticipated expiration: 2019-03-26
Also published as: JP2000271786A

Description

【０００１】
【発明の属する技術分野】
この発明は、海岸地域等の塩水が関与した腐食環境に建設される橋梁や鉄塔などの溶接構造物の製造に用いられる潜弧溶接方法に関する。
【０００２】
【従来の技術】
橋梁などの鋼構造物は、その実用期間が数十年に及ぶため、何らかの防食処置を必要とする。防食手段のうち、塗装は非常に効果の高い方法であるが、大気暴露環境においては劣化が著しく、定期的な補修が必要とされるものの、近年における人件費の高騰や塗装工の減少などにより、その補修が困難になりつつある。また、溶接部で塗装欠陥を生じやすく、局部的な腐食量の増大がしばしば認められる。
【０００３】
このような問題を回避するため、橋梁などの鋼構造物に耐候性鋼の適用される例が増えている。しかし、建設省は耐候性鋼の使用に関し、国内各所での暴露腐食試験結果より、無塗装で使用する場合は飛来塩分量が０．０５ｍｄｄ以下の地域に限るという指針を提示し、従来、製造されてきたＪＩＳＳＭＡ４００／４９０／５７０等の耐候性鋼を、飛来塩分量が０．０５ｍｄｄ以上の地域における無塗装使用に十分な耐候性を有していないものとする判断を示した。
【０００４】
そこで、最近、海岸地域における耐候性を改善するため、従来のものより、Ｃｒ，Ｎｉなどの元素を多く添加した鋼材が開発されるようになり、それらに適した溶接材料についても要望されるようになった。耐候性鋼に用いられる潜弧溶接用溶接材料としてＪＩＳＺ３１８３に規定される溶着金属性能を有するものが広く使われているが、ＪＩＳＳＭＡ４００／４９０／５７０等の耐候性鋼用として開発されたものであり、海岸地域において高い耐候性を得ることは困難で、新たな溶接材料の開発が必要とされている。
【０００５】
【発明が解決しようとする課題】
本発明の目的は、０．０５ｍｄｄ以上１０ｍｄｄ未満の塩分が飛来する環境において高い耐候性と良好な溶接性を有する潜弧溶接方法を提供することにある。
【０００６】
【課題を解決するための手段】
本発明者らは、上記目的を達成すべく潜弧溶接用ワイヤおよびフラックスの成分組成について鋭意検討した。その結果、Ｍｏを適当な量のＮｉとともに複合添加した場合、耐候性が著しく改善されること、溶接材料のＮｉとＭｏの量と母材のＮｉとＭｏの量の比を規定することにより溶接部の選択腐食を防止することができること、溶接材料のＰの量と母材のＰの量の比を規定することにより、溶接金属の高温割れが生じにくくなることを見出した。
【０００７】
本発明はこれらの知見をもとになされたものである。
【０００８】
１．質量％でＣ：０．１５％以下、Ｓｉ：０．７％以下、Ｍｎ：０．１〜２．０％、Ｐ：０．０１〜０．１５％、Ｓ：０．０２％以下、Ｃｕ：０．１％未満、Ｎｉ：０．２〜４．０％、Ｃｒ：０．１％以下、Ｍｏ：０．１〜４．０％、Ａｌ：０．０１〜０．１０％を含有し、残部がＦｅおよび不可避的不純物からなる鋼板を、質量％で下記成分の耐食性に優れた潜弧溶接用ワイヤおよびフラックスを用いて溶接することを特徴とする潜弧溶接方法。
〔Ｃ〕＝〔Ｃ〕 _w ＋ａ＊〔Ｃ〕 _f ：０．００５〜０．１６％
〔Ｐ〕＝〔Ｐ〕 _w ＋ａ＊〔Ｐ〕 _f ：０．００２〜０．０５％
〔Ｎｉ〕＝〔Ｎｉ〕 _w ＋ａ＊〔Ｎｉ〕 _f ：０．２〜４．０％
〔Ｍｏ〕＝〔Ｍｏ〕 _w ＋ａ＊〔Ｍｏ〕 _f ：０．１〜４．０％
〔Ｃｒ〕＝〔Ｃｒ〕 _w ＋ａ＊〔Ｃｒ〕 _f ：≦０．１％
〔Ｎｉ〕＋３〔Ｍｏ〕≧１．２％
( 〔Ｎｉ〕＋３〔Ｍｏ〕 ) ／ ( 〔Ｎｉ〕 _p ＋３〔Ｍｏ〕 _p ) ≧１．０５
〔Ｐ〕／〔Ｐ〕 _p ≦０．９０
各記号は以下の内容を意味する。
〔Ｃ〕，〔Ｐ〕，〔Ｎｉ〕，〔Ｍｏ〕，〔Ｃｒ〕：溶接材料中の各成分を表す。
〔Ｃ〕 _w ，〔Ｐ〕 _w ，〔Ｎｉ〕 _w ，〔Ｍｏ〕 _w ，〔Ｃｒ〕 _w ：ワイヤ中の各成分を表す。
〔Ｃ〕 _f ，〔Ｐ〕 _f ，〔Ｎｉ〕 _f ，〔Ｍｏ〕 _f ，〔Ｃｒ〕 _f ：フラックス中の各成分を表す。
〔Ｐ〕 _p ，〔Ｎｉ〕 _p ，〔Ｍｏ〕 _p ：鋼板中の各成分を表す。
ａ：ワイヤ単位当たりの消費量（ｇ／ｍｉｎ）に対するフラックスの消費量（ｇ／ｍｉｎ）であって溶融型フラックスの場合は１．５０、ボンドフラックスの場合は１．００。
【００１６】
２．質量％で、Ｃ：０．１５％以下、Ｓｉ：０．７％以下、Ｍｎ：０．１〜２．０％、Ｐ：０．０１〜０．１５％、Ｓ：０．０２％以下、Ｃｕ：０．１％未満、Ｎｉ：０．２〜４．０％、Ｃｒ：０．１％以下、Ｍｏ：０．１〜４．０％、Ａｌ：０．０１〜０．１０％を含有し、Ｎｂ：０．００５〜０．１％、Ｖ：０．００５〜０．１％、及びＴｉ：０．００５〜０．１％のうち１種又は２種以上を含み、残部がＦｅおよび不可避的不純物からなる鋼板を潜弧溶接する際に用いることを特徴とする、１に記載の潜弧溶接方法。
【００１７】
【発明の実施の形態】
本発明で、成分組成を上記の範囲に限定した理由について説明する。
【００１８】
〔Ｃ〕：０．００５〜０．１６％
Ｃは所定の強度を確保するために添加する。０．００５％未満では溶接金属中のＣ量が低くなりすぎるため、耐高温割れ感受性が劣るとともに、溶接中のシールド効果が不足し、溶接金属中のＮ量が増大し、衝撃性能が低下する。一方、０．１６％を超えると溶接金属中のＣ量が多くなりすぎ、耐高温割れ感受性が低下するため、０．００５〜０．１６％含有する。
【００１９】
〔Ｐ〕：０．００２〜０．０５％
Ｐは溶接部の耐食性を向上させる効果があるので、添加する。０．００２％未満では溶接金属中のＰ量が不足し、耐候性が劣化し、製造コストの増加を招くため好ましくない。一方、０．０５％を超えると溶接金属中のＰ量が多くなりすぎ、耐高温割れ感受性が急激に低下するため、０．００２〜０．０５％とする。
【００２０】
〔Ｎｉ〕：０．２〜４．０％
ＮｉはＭｏとの共存により塩分の多い環境における耐食性を向上させる効果がある。０．２％未満では溶接金属中のＮｉ量が不足し、耐候性が劣化する。一方、４．０％を超えると溶接金属中のＮｉ量が多くなりすぎ、強度の増大により耐水素割れ感受性が低下し、経済性の点でも好ましくないため、０．２〜４．０％とする。
【００２１】
〔Ｍｏ〕：０．１〜４．０％
ＭｏはＮｉとの共存により塩分の多い環境における耐食性を向上させる効果がある。０．１％未満では溶接金属中のＭｏ量が不足し、耐候性が劣化する。一方、４．０％を超えると溶接金属中のＭｏ量が多くなりすぎ、強度の増大により耐水素割れ感受性が低下し、経済性の点でも好ましくないため、０．１〜４．０％とする。
【００２２】
〔Ｃｒ〕≦０．１％
本発明においてはＣｒは積極的に添加せず、不純物として扱い、その量を０．１％以下に規制する。Ｃｒは塩分の少ない環境においては鋼の耐食性を向上させるものとして、従来の耐候性鋼には添加されてきたが、本発明者らの検討によると、塩分の多い環境においては孔あき腐食を助長する作用があることが判明した。また、溶接性を劣化させるため、本発明では不純物として扱う。不純物として０．１％以下含まれる場合には本発明の効果を阻害しない。
【００２３】
〔Ｎｉ〕＋３〔Ｍｏ〕≧１．２％
本発明では耐食性を改善するために、ＮｉとＭｏの複合添加を行う。上記したように、その効果はＭを０．２％以上のＮｉとともに添加した場合に得られるが、〔Ｎｉ〕＋３〔Ｍｏ〕が１．２％未満では効果が十分でないため、〔Ｎｉ〕＋３〔Ｍｏ〕≧１．２％とする。
【００２４】
表１は潜弧溶接用ワイヤとフラックスの組合せにより、〔Ｎｉ〕＋３〔Ｍｏ〕の値を変化させた溶接材料の成分組成、およびその溶接部に図１に示す１サイクル２４時間の試験を２８サイクル、４週間実施した複合サイクル腐食試験の結果を示すもので、〔Ｎｉ〕＋３〔Ｍｏ〕≧１．２％の場合、良好な耐食性が認められる。
【００２５】
ＮｉとＭｏの複合添加による耐食性改善は、Ｍｏが錆の稠密性を高め、水分、塩分などの腐食因子を遮断し、ＮｉがそのＭｏによる錆の対クラック性を改善する相乗効果によるものと考えられるが詳細は必ずしも明らかではない。
【００２６】
(〔Ｎｉ〕＋３〔Ｍｏ〕)／(〔Ｎｉ〕_p＋３〔Ｍｏ〕_p)≧１．０５
母材のＮｉ，Ｍｏ量と溶接材料のＮｉ，Ｍｏ量の比、すなわち、(〔Ｎｉ〕＋３〔Ｍｏ〕)／(〔Ｎｉ〕_p＋３〔Ｍｏ〕_p)は溶接金属の選択腐食を防止するため１．０５以上とする。
【００２７】
表３に溶接材料と母材におけるＮｉおよびＭｏ量の比が溶接金属の選択腐食に及ぼす影響を示す。表３は表２のイに示す成分組成の鋼板を、成分組成を変えたワイヤとフラックスにより溶接し、継手部より図２に示す試験片を採取し、上述の複合サイクル腐食試験を行った結果を示すもので、(〔Ｎｉ〕＋３〔Ｍｏ〕)／(〔Ｎｉ〕_p＋３〔Ｍｏ〕_p)が１．０５以上の場合、選択腐食は認められない。
【００２８】
〔Ｐ〕／〔Ｐ〕_p≦０．９０
Ｐは溶接部の耐候性を向上させるため、添加する。〔Ｐ〕／〔Ｐ〕_pが０．９０を超えると溶接金属の耐高温割れ感受性が急激に低下するため、０．９０以下とする。表４は表２のロに示す組成の鋼板を、成分組成を変えたワイヤとフラックスにより溶接し、溶接金属の高温割れの有無を調査した結果を示すもので、〔Ｐ〕／〔Ｐ〕_pが０．９０を超えた場合、溶接金属に高温割れが認められる。図３に試験に用いた溶接条件、開先形状を示す。
【００２９】
尚、本発明では、上記以外の化学成分については特に限定せず、溶接金属の衝撃性能を確保するため、Ｔｉ，Ｂ等を添加することが可能である。また上述したＣ，Ｐ，Ｎｉ，Ｍｏ等の成分は、ワイヤおよびフラックスの両方もしくはいずれかより添加することができる。ワイヤはソリッドワイヤに限らず、成分が該当すればフラックス入りワイヤも用いることができ、フラックスは溶融タイプ、ボンドタイプおよびそれらの混合タイプのいずれを用いても良い。
【００３０】
【表１】

【００３１】
【表２】

【００３２】
【表３】

【００３３】
【表４】

【００３４】
【実施例】
表２に示す成分組成の鋼板を、表５および表６に示す各種のワイヤおよびフラックスを用いて溶接した。ワイヤおよびフラックスの組合せによる溶着金属の組成を表７に、鋼板との組合せによる〔Ｐ〕／〔Ｐ〕_pの値、(〔Ｎｉ〕＋３〔Ｍｏ〕)／(〔Ｎｉ〕_p＋３〔Ｍｏ〕_p)の値を表８に示す。得られた継手部より、図２に示す試験片を採取し、複合サイクル腐食試験を実施した。表８に試験結果として、溶接部の最大孔あき深さと溶接金属の選択腐食の有無を示す。尚、表８には図３に示すＶ溝型高温割れ試験の結果を併せて示した。
【００３５】
本発明の成分規定を満足する本発明例Ｎｏ．１〜９はいずれも最大孔あき深さ０．４ｍｍ以下と優れた耐食性で、溶接部の選択腐食も生じていない。また、溶接金属の高温割れも発生せず、良好な溶接性を示している。一方、比較例Ｎｏ．１４はワイヤとフラックスの組合せによる成分組成において、〔Ｎｉ〕が本発明より低く、比較例Ｎｏ．１８は〔Ｃｒ〕が本発明の範囲より高く、溶接部の最大孔あき深さが大きく、耐食性が十分でない。
【００３６】
比較例Ｎｏ．２０，２１，２２は(〔Ｎｉ〕＋３〔Ｍｏ〕)／(〔Ｎｉ〕_p＋３〔Ｍｏ〕_p)が本発明の範囲よりも低く、溶接部の選択腐食が生じている。比較例Ｎｏ．１３は〔Ｎｉ〕＋３〔Ｍｏ〕，(〔Ｎｉ〕＋３〔Ｍｏ〕)／(〔Ｎｉ〕_p＋３〔Ｍｏ〕_p)が本発明の範囲よりも低く、溶接部の最大孔あき深さが大きく、かつ、溶接部の選択腐食を生じている。
【００３７】
比較例Ｎｏ．１０，１６は〔Ｃ〕，〔Ｐ〕がそれぞれ本発明の範囲よりも高く、溶接金属の高温割れが生じている。比較例Ｎｏ．１２，１９は〔Ｐ〕／〔Ｐ〕_pが本発明範囲より高く、〔Ｎｉ〕＋３〔Ｍｏ〕，(〔Ｎｉ〕＋３〔Ｍｏ〕)／(〔Ｎｉ〕_p＋３〔Ｍｏ〕_p)が本発明範囲より低く、溶接金属の高温割れが生じるとともに、溶接部の選択腐食が生じている。
【００３８】
比較例Ｎｏ．１１は〔Ｐ〕／〔Ｐ〕_pが本発明の範囲より高く、かつ、〔Ｎｉ〕，(〔Ｎｉ〕＋３〔Ｍｏ〕)／(〔Ｎｉ〕_p＋３〔Ｍｏ〕_p)が本発明より低く、溶接金属に高温割れが生じるとともに溶接部の最大孔あき深さが大きく、かつ，溶接部の選択腐食が生じている。比較例Ｎｏ．１５は〔Ｃ〕，〔Ｍｏ〕，(〔Ｎｉ〕＋３〔Ｍｏ〕)／(〔Ｎｉ〕_p＋３〔Ｍｏ〕_p)が本発明の範囲より低く、同様な特性を示している。比較例Ｎｏ．１７は〔Ｎｉ〕，〔Ｍｏ〕がそれぞれ本発明の範囲よりも高く、強度が増大し、耐水素割れ感受性が低下し、低温割れが発生している。
【００３９】
【表５】

【００４０】
【表６】

【００４１】
【表７】

【００４２】
【表８】

【００４３】
【発明の効果】
以上説明したように、本発明の潜弧溶接方法は、良好な溶接性を有し、０．０５ｍｄｄ以上１０ｍｄｄ未満の塩分が飛来する環境においても溶接部の耐候性を十分に確保することが可能なため、海岸地域等の塩水が関与した腐食環境に建設される橋梁や鉄塔などの溶接構造物の製造に用いられ、無塗装でその溶接部に高い耐食性を与えることができる。
【図面の簡単な説明】
【図１】海岸地域をシミュレートした環境における耐食性を評価するための複合サイクル腐食試験条件を示す図
【図２】継手部の複合サイクル腐食試験片形状を示す図
【図３】Ｖ溝型高温割れ試験の溶接条件および開先形状を示す図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a submerged arc welding method used for manufacturing a welded structure such as a bridge or a steel tower constructed in a corrosive environment involving salt water such as a coastal area.
[0002]
[Prior art]
Steel structures such as bridges require some kind of anticorrosion treatment because their practical use spans several decades. Of the anti-corrosion measures, painting is a very effective method, but it has deteriorated significantly in the air exposure environment, and periodic repairs are required. The repair is becoming difficult. In addition, coating defects are likely to occur in the welded portion, and a local increase in the amount of corrosion is often observed.
[0003]
In order to avoid such a problem, an example in which weathering steel is applied to a steel structure such as a bridge is increasing. However, the Ministry of Construction, based on the results of exposure corrosion tests at various locations in Japan, has provided guidelines that the amount of incoming salt should be limited to 0.05 mdd or less when used without coating. It was judged that the weather-resistant steel such as JIS SMA 400/490/570, which had been used, did not have sufficient weather resistance for unpainted use in areas where the amount of incoming salt was 0.05 mdd or more.
[0004]
Therefore, recently, in order to improve the weather resistance in the coastal area, steel materials to which more elements such as Cr and Ni are added than conventional ones have been developed, and there is a demand for welding materials suitable for them. Became. As welding materials for submerged arc welding used in weathering steel, those with weld metal performance specified in JIS Z3183 are widely used, but those developed for weathering steel such as JIS SMA400 / 490/570 Therefore, it is difficult to obtain high weather resistance in the coastal area, and development of new welding materials is required.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a submerged arc welding method having high weather resistance and good weldability in an environment where a salt content of 0.05 mdd or more and less than 10 mdd is flying.
[0006]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present inventors diligently studied the component composition of the submerged arc welding wire and the flux. As a result, when Mo is added in combination with an appropriate amount of Ni, the weather resistance is remarkably improved, and the ratio of the amount of Ni and Mo in the welding material to the amount of Ni and Mo in the base material is specified for welding. It has been found that the selective corrosion of the part can be prevented, and that the ratio of the amount of P in the welding material and the amount of P in the base metal is regulated, so that hot cracking of the weld metal is less likely to occur.
[0007]
The present invention has been made based on these findings.
[0008]
1. By mass%: C: 0.15% or less, Si: 0.7% or less, Mn: 0.1 to 2.0%, P: 0.01 to 0.15%, S: 0.02% or less, Cu : Less than 0.1%, Ni: 0.2-4.0%, Cr: 0.1% or less, Mo: 0.1-4.0%, Al: 0.01-0.10% A submerged arc welding method characterized by welding a steel plate, the balance of which is Fe and inevitable impurities, using a submerged arc welding wire and flux having the following components in mass% and excellent in corrosion resistance.
[C] = [C] _w + a * [C] _f : 0.005 to 0.16%
[P] = [P] _w + a * [P] _f : 0.002 to 0.05%
[Ni] = [Ni] _w + a * [Ni] _f : 0.2 to 4.0%
[Mo] = [Mo] _w + a * [Mo] _f : 0.1 to 4.0%
[Cr] = [Cr] _w + a * [Cr] _f : ≦ 0.1%
[Ni] +3 [Mo] ≧ 1.2%
( [Ni] +3 [Mo] ) / ( [Ni] _p +3 [Mo] _p ) ≧ 1.05
[P] / [P] _p ≦ 0.90
Each symbol means the following contents.
[C], [P], [Ni], [Mo], [Cr]: each component in the welding material.
[C] _w , [P] _w , [Ni] _w , [Mo] _w , [Cr] _w : Represents each component in the wire.
[C] _f , [P] _f , [Ni] _f , [Mo] _f , [Cr] _f : Represents each component in the flux.
[P] _p , [Ni] _p , [Mo] _p : Represents each component in the steel sheet.
a: Flux consumption (g / min) relative to the consumption per wire unit (g / min), 1.50 in the case of a melt-type flux, and 1.00 in the case of a bond flux .
[0016]
2. By mass%, C: 0.15% or less, Si: 0.7% or less, Mn: 0.1~2.0%, P: 0.01~0.15%, S: 0.02% or less, Cu: Less than 0.1% , Ni: 0.2-4.0%, Cr: 0.1% or less, Mo: 0.1-4.0%, Al: 0.01-0.10% Nb: 0.005 to 0.1%, V: 0.005 to 0.1%, and Ti: 0.005 to 0.1%, or one or more of them, and the balance is Fe and 2. The submerged arc welding method according to 1, wherein the submerged arc welding method is used when submerged arc welding is performed on a steel plate made of inevitable impurities .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The reason why the component composition is limited to the above range in the present invention will be described.
[0018]
[C]: 0.005 to 0.16%
C is added to ensure a predetermined strength. If it is less than 0.005%, the amount of C in the weld metal becomes too low, so the resistance to hot cracking is inferior, the shielding effect during welding is insufficient, the amount of N in the weld metal increases, and impact performance decreases. . On the other hand, if it exceeds 0.16%, the amount of C in the weld metal is excessively increased and the resistance to hot cracking decreases, so 0.005 to 0.16% is contained.
[0019]
[P]: 0.002 to 0.05%
P is added because it has the effect of improving the corrosion resistance of the weld. If it is less than 0.002%, the amount of P in the weld metal is insufficient, the weather resistance is deteriorated, and the production cost is increased. On the other hand, if it exceeds 0.05%, the amount of P in the weld metal is excessively increased and the hot cracking resistance is drastically lowered.
[0020]
[Ni]: 0.2 to 4.0%
Ni has the effect of improving the corrosion resistance in a salty environment by coexistence with Mo. If it is less than 0.2%, the amount of Ni in the weld metal is insufficient, and the weather resistance deteriorates. On the other hand, if it exceeds 4.0%, the amount of Ni in the weld metal is excessively increased, and the resistance to hydrogen cracking is lowered due to the increase in strength, which is not preferable in terms of economy, so 0.2 to 4.0%. To do.
[0021]
[Mo]: 0.1-4.0%
Mo has the effect of improving corrosion resistance in a salty environment due to coexistence with Ni. If it is less than 0.1%, the amount of Mo in the weld metal is insufficient, and the weather resistance deteriorates. On the other hand, if it exceeds 4.0%, the amount of Mo in the weld metal is excessively increased, and the resistance to hydrogen cracking decreases due to the increase in strength, which is not preferable in terms of economy. To do.
[0022]
[Cr] ≦ 0.1%
In the present invention, Cr is not positively added, but is treated as an impurity, and its amount is restricted to 0.1% or less. Cr has been added to conventional weathering steels as a means to improve the corrosion resistance of steels in low salt environments, but according to the study by the present inventors, it promotes perforated corrosion in high salt environments. It was found that there is an action to do. Moreover, in order to degrade weldability, it treats as an impurity in this invention. When the content is 0.1% or less as an impurity, the effect of the present invention is not hindered.
[0023]
[Ni] +3 [Mo] ≧ 1.2%
In the present invention, in order to improve the corrosion resistance, Ni and Mo are added in combination. As described above, the effect is obtained when M is added together with Ni of 0.2% or more. However, if [Ni] +3 [Mo] is less than 1.2%, the effect is not sufficient, so [Ni] +3 [Mo] ≧ 1.2%.
[0024]
Table 1 shows the composition of the welding material in which the value of [Ni] +3 [Mo] was changed by the combination of the wire for arc welding and the flux, and the test for one cycle 24 hours shown in FIG. The results of a combined cycle corrosion test conducted for four weeks are shown. When [Ni] +3 [Mo] ≧ 1.2%, good corrosion resistance is recognized.
[0025]
Corrosion resistance improvement by combined addition of Ni and Mo is considered to be due to the synergistic effect that Mo increases the density of rust, blocks corrosion factors such as moisture and salt, and Ni improves the anti-cracking property of rust by Mo. Details are not always clear.
[0026]
([Ni] +3 [Mo]) / ([Ni] _p +3 [Mo] _p ) ≧ 1.05
The ratio of the amount of Ni and Mo in the base metal to the amount of Ni and Mo in the welding material, ie, ([Ni] +3 [Mo]) / ([Ni] _p +3 [Mo] _p ) prevents selective corrosion of the weld metal. Therefore, it is set to 1.05 or more.
[0027]
Table 3 shows the influence of the ratio of the amounts of Ni and Mo in the welding material and the base metal on the selective corrosion of the weld metal. Table 3 shows the results of performing the above-mentioned combined cycle corrosion test by welding a steel plate having the component composition shown in Table 2 to the steel plate with a wire and flux with different component compositions, collecting the test piece shown in FIG. When ([Ni] +3 [Mo]) / ([Ni] _p +3 [Mo] _p ) is 1.05 or more, selective corrosion is not recognized.
[0028]
[P] / [P] _p ≦ 0.90
P is added to improve the weather resistance of the weld. If [P] / [P] _p exceeds 0.90, the resistance to hot cracking of the weld metal is abruptly decreased. Table 4 shows the results of examining the presence or absence of hot cracking of the weld metal by welding the steel plate having the composition shown in Table 2 to the steel with different composition and wire and flux. [P] / [P] _p When the value exceeds 0.90, hot cracks are observed in the weld metal. FIG. 3 shows the welding conditions and groove shapes used in the test.
[0029]
In the present invention, chemical components other than those described above are not particularly limited, and Ti, B, and the like can be added to ensure the impact performance of the weld metal. Further, the above-described components such as C, P, Ni, and Mo can be added from either or both of the wire and the flux. The wire is not limited to a solid wire, and a flux-cored wire can be used as long as the component is applicable, and the flux may be any of a melting type, a bond type, and a mixed type thereof.
[0030]
[Table 1]

[0031]
[Table 2]

[0032]
[Table 3]

[0033]
[Table 4]

[0034]
【Example】
Steel plates having the composition shown in Table 2 were welded using various wires and fluxes shown in Tables 5 and 6. The composition of the weld metal by the combination of the wire and the flux is shown in Table 7. The value of [P] / [P] _p by the combination with the steel plate, ([Ni] +3 [Mo]) / ([Ni] _p + 3 [Mo]) The values of _p ) are shown in Table 8. A test piece shown in FIG. 2 was collected from the obtained joint, and a combined cycle corrosion test was performed. Table 8 shows the test results as to the maximum depth of the weld and the presence or absence of selective corrosion of the weld metal. Table 8 also shows the results of the V-groove hot cracking test shown in FIG.
[0035]
Invention Example No. 1 satisfying the component rules of the invention Nos. 1 to 9 are excellent corrosion resistances with a maximum perforation depth of 0.4 mm or less, and no selective corrosion of the welded portion occurs. Moreover, the hot crack of a weld metal does not generate | occur | produce and the favorable weldability is shown. On the other hand, Comparative Example No. No. 14 is a component composition by a combination of a wire and a flux, and [Ni] is lower than that of the present invention. No. 18 has [Cr] higher than the range of the present invention, the maximum drilling depth of the welded portion is large, and the corrosion resistance is not sufficient.
[0036]
Comparative Example No. 20, (21, 22) ((Ni) +3 [Mo]) / ([Ni] _p +3 [Mo] _p ) is lower than the range of the present invention, and selective corrosion of the weld occurs. Comparative Example No. 13 is [Ni] +3 [Mo], ([Ni] +3 [Mo]) / ([Ni] _p +3 [Mo] _p ) is lower than the range of the present invention, and the maximum hole depth of the welded portion is large. In addition, selective corrosion of the welded portion occurs.
[0037]
Comparative Example No. 10 and 16, [C] and [P] are higher than the range of the present invention, respectively, and hot cracking of the weld metal occurs. Comparative Example No. 12 and 19, [P] / [P] _p is higher than the range of the present invention, [Ni] +3 [Mo], ([Ni] +3 [Mo]) / ([Ni] _p + 3 [Mo] _p ) It is lower than the scope of the invention, and hot cracking of the weld metal occurs, and selective corrosion of the weld occurs.
[0038]
Comparative Example No. 11, [P] / [P] _p is higher than the range of the present invention, and [Ni], ([Ni] +3 [Mo]) / ([Ni] _p + 3 [Mo] _p ) is lower than the present invention. In addition, hot cracks occur in the weld metal, the maximum perforation depth of the weld is large, and selective corrosion of the weld occurs. Comparative Example No. No. 15 has [C], [Mo], ([Ni] +3 [Mo]) / ([Ni] _p +3 [Mo] _p ) lower than the range of the present invention, and shows similar characteristics. Comparative Example No. In No. 17, [Ni] and [Mo] are each higher than the range of the present invention, the strength increases, the hydrogen cracking susceptibility decreases, and low temperature cracking occurs.
[0039]
[Table 5]

[0040]
[Table 6]

[0041]
[Table 7]

[0042]
[Table 8]

[0043]
【The invention's effect】
As described above, the submerged arc welding method of the present invention has good weldability, and can sufficiently ensure the weather resistance of the welded part even in an environment where salt content of 0.05 mdd or more and less than 10 mdd is flying. Therefore, it is used for manufacturing a welded structure such as a bridge or a steel tower constructed in a corrosive environment involving salt water in a coastal area or the like, and can provide high corrosion resistance to the welded portion without painting.
[Brief description of the drawings]
[Fig. 1] Fig. 2 shows the combined cycle corrosion test conditions for evaluating corrosion resistance in a simulated coastal environment. [Fig. 2] Fig. 3 shows the shape of the combined cycle corrosion test piece at the joint. [Fig. Diagram showing welding conditions and groove shape in crack test

Claims

C: 0.15% or less, Si: 0.7% or less, Mn: 0.1-2.0%, P: 0.01-0.15%, S: 0.02% or less, Cu : Less than 0.1%, Ni: 0.2-4.0%, Cr: 0.1% or less, Mo: 0.1-4.0%, Al: 0.01-0.10% A submerged arc welding method characterized by welding a steel plate, the balance of which is Fe and inevitable impurities , using a submerged arc welding wire and flux having the following components in mass% and excellent in corrosion resistance .
[C] = [C] _w + a * [C] _f : 0.005 to 0.16%
[P] = [P] _w + a * [P] _f : 0.002 to 0.05%
[Ni] = [Ni] _w + a * [Ni] _f : 0.2 to 4.0%
[Mo] = [Mo] _w + a * [Mo] _f : 0.1 to 4.0%
[Cr] = [Cr] _w + a * [Cr] _f : ≦ 0.1%
[Ni] +3 [Mo] ≧ 1.2%
([Ni] +3 [Mo]) / ([Ni] _p +3 [Mo] _p ) ≧ 1.05
[P] / [P] _p ≦ 0.90
Each symbol means the following contents.
[C], [P], [Ni], [Mo], [Cr]: each component in the welding material.
[C] _w , [P] _w , [Ni] _w , [Mo] _w , [Cr] _w : represents each component in the wire.
[C] _f , [P] _f , [Ni] _f , [Mo] _f , [Cr] _f : Represents each component in the flux.
[P] _p , [Ni] _p , [Mo] _p : Represents each component in the steel sheet.
a: Flux consumption (g / min) relative to the consumption per wire unit (g / min) , 1.50 in the case of a melt-type flux, and 1.00 in the case of a bond flux .

In mass%, C: 0.15% or less, Si: 0.7% or less, Mn: 0.1 to 2.0%, P: 0.01 to 0.15%, S: 0.02% or less, Cu: Less than 0.1%, Ni: 0.2-4.0%, Cr: 0.1% or less, Mo: 0.1-4.0%, Al: 0.01-0.10% Nb: 0.005 to 0.1%, V: 0.005 to 0.1%, and Ti: 0.005 to 0.1%, or one or more of them, with the balance being Fe and The submerged arc welding method according to claim 1, wherein the submerged arc welding method is used when submerged arc welding is performed on a steel plate made of inevitable impurities.