JP2006000868A - Solid wire for gas shielded arc welding for primary build-up welding - Google Patents

Solid wire for gas shielded arc welding for primary build-up welding Download PDF

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JP2006000868A
JP2006000868A JP2004176771A JP2004176771A JP2006000868A JP 2006000868 A JP2006000868 A JP 2006000868A JP 2004176771 A JP2004176771 A JP 2004176771A JP 2004176771 A JP2004176771 A JP 2004176771A JP 2006000868 A JP2006000868 A JP 2006000868A
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welding
weld metal
toughness
wire
arc welding
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JP4469226B2 (en
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Toshinaga Hasegawa
俊永 長谷川
Shigeru Okita
茂 大北
Shigeo Oyama
繁男 大山
Ryuichi Motomatsu
隆一 元松
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Nippon Steel Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid wire for gas shielded arc welding for primary build-up welding capable of suppressing embrittlement of an upper layer part of a primary build-up weld metal and improving toughness when performing the secondary build-up welding from the top of the primary build-up weld metal by submerged arc welding or the like with the welding heat input being ≥4.5 kJ/mm. <P>SOLUTION: The solid wire contains, by mass, 0.01-0.2% C, 0.2-1% Si, 0.5-2.5% Mn, 0.002-0.1% Al, 0.01-0.3% Ti, 0.001-0.015% B, and 0.001-0.01% N, while P, S and O are limited to be ≤ 0.02%, 0.01% and 0.01%, respectively, the carbon equivalent (Ceq.) satisfies 0.3-0.5%, and one or two or more kinds of 0-0.2% Mo, 0-0.1% W, 0-0.01% Nb, 0-0.05% V, and 0-0.05% Ta are contained, with the balance inevitable impurities and Fe. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、引張強度が400〜570MPa級の厚鋼板において、Ar+CO2溶接あるいはCO2溶接等のガスシールドアーク溶接を下盛した後に、該ガスシールドアーク溶接部の上からサブマージアーク溶接等により溶接入熱が4.5kJ/mm以上の溶接を上盛して溶接ビードを形成する場合に、下盛ガスシールドアーク溶接金属、特に、上盛溶接による熱影響を受ける下盛ガスシールドアーク溶接金属において高い靱性を有することができる下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤに関する。 In the present invention, in a thick steel plate having a tensile strength of 400 to 570 MPa, after gas shield arc welding such as Ar + CO 2 welding or CO 2 welding is overlaid, welding is performed from above the gas shield arc welded portion by submerged arc welding or the like. When welding welds with a heat input of 4.5 kJ / mm or more are formed to form a weld bead, in the lower gas shielded arc weld metal, particularly the lower gas shielded arc weld metal that is affected by the heat of the upper weld. The present invention relates to a solid wire for gas shield arc welding for underlay welding that can have high toughness.

フラックスを使用しないガスシールドアーク溶接において使用されるソリッドワイヤは被覆アーク溶接棒等に比べて、含まれる水素量が少ない。このため、このソリッドワイヤは、耐低温割れ性に優れる、スラグの生成が少ないためスラグ剥離作業が不要または能率的である、等の利点があり様々な用途に使用されている。   Solid wire used in gas shielded arc welding without using flux contains less hydrogen than a coated arc welding rod or the like. For this reason, this solid wire has advantages such as excellent low-temperature cracking resistance and less slag generation, so that the slag peeling operation is unnecessary or efficient, and is used in various applications.

最近、高層建築物の箱形4面ボックス柱に溶接熱影響部(HAZ)の靱性に優れた高機能鋼が多く使用されるようになり、これに伴って溶接金属にも鋼材と同等の高靱性が要求されるようになってきている。4面ボックス柱の製造は、各面を構成するスキンプレート同士の4辺の角部分を溶接して中空の柱とすることにより行われる。また、溶接施工効率を高めるために、スキンプレート同士の角継手には1パス2電極サブマージアーク溶接(以下、SAWとが称する場合ある。)が用いられ、また、スキンプレートとダイヤフラムとの溶接にはエレクトロスラグ溶接(以下、ESWとが称する場合ある。)が用いられる場合が多い。   Recently, high-performance steels with excellent weld heat affected zone (HAZ) toughness have been used for box-shaped 4-sided box columns in high-rise buildings. Toughness has been required. The manufacture of a four-sided box column is performed by welding the corners of the four sides of the skin plates constituting each surface to form a hollow column. In order to increase the welding efficiency, 1-pass 2-electrode submerged arc welding (hereinafter sometimes referred to as SAW) is used for the corner joint between the skin plates, and for welding the skin plate and the diaphragm. In many cases, electroslag welding (hereinafter sometimes referred to as ESW) is used.

但し、スキンプレートの板厚が60mm程度を超えるような場合には、1パスSAWでの角継手溶接は困難となり、多層盛りSAW溶接や多層盛りガスシールドアーク溶接(Ar+CO2溶接、CO2溶接)が利用される。この場合、多層盛りSAWではガスシールドアーク溶接に比べてパス数が少ないため、溶接効率に優れるものの、溶接欠陥の回避や靱性確保が困難である点が課題であり、一方、多層盛りガスシールドアーク溶接では溶接部の品質に優れるものの、溶接能率の悪さが課題であった。 However, when the thickness of the skin plate exceeds about 60 mm, corner joint welding with one pass SAW becomes difficult, and multi-layer SAW welding or multi-layer gas shielding arc welding (Ar + CO 2 welding, CO 2 welding). Is used. In this case, multi-pass prime SAW has a smaller number of passes than gas shielded arc welding, so that although welding efficiency is excellent, it is difficult to avoid welding defects and to secure toughness. In welding, although the quality of the welded portion is excellent, poor welding efficiency has been a problem.

そこで、最近、初層から一定厚さ範囲までは溶接部の品質に優れるガスシールドアーク溶接で下盛り溶接し、後半は能率のよい中〜大入熱SAWで1〜数パスの上盛り溶接で行う方法が検討されている。   Therefore, recently, from the first layer to a certain thickness range, welded by gas shielded arc welding, which has excellent weld quality, and in the second half, by efficient, medium to large heat input SAW, one to several passes. The way to do it is being considered.

しかし、上記下盛り溶接と上盛り溶接の組み合わせ溶接を行う場合には、下盛り溶接ビードの上層部がSAWによる上盛り溶接時の入熱による熱影響を受け、特にSAWの入熱が高い場合には通常のガスシールドアーク溶接用ワイヤを用いる限り溶接金属が熱影響により脆化するという新たな課題が生じるようになった。したがって、ガスシールドアーク溶接単独で多層盛り溶接する際に用いられるソリッドワイヤではなく、上記のような組み合わせ溶接における下盛り溶接として使用され、その際に下盛り溶接金属の熱影響部の脆化を抑制し靭性を改善させるソリッドワイヤの開発が望まれている。   However, when combined welding of the above-described overlay welding and overlay welding is performed, the upper layer portion of the lower welding bead is affected by heat input during the overlay welding by SAW, and particularly when the heat input of SAW is high. However, as long as ordinary gas shielded arc welding wires are used, a new problem has arisen in that the weld metal becomes brittle due to thermal effects. Therefore, it is used not as a solid wire used for multi-pass welding with gas shield arc welding alone, but as a bottom welding in the above combination welding, and at that time, the heat affected zone of the bottom welding metal is embrittled. Development of a solid wire that suppresses and improves toughness is desired.

従来のガスシールドアーク溶接用ソリッドワイヤとして、特許文献1では銅ワイヤの含有水素量を低減による耐割れ性向上、特許文献2では銅メッキなしワイヤの適用による耐スパッタ性向上等があり、いずれも溶接作業性の改善に重点を置いたソリッドワイヤであり、上記新たな技術的課題を解決することはできない。また、高入熱・多パス条件でのガスシールドアーク溶接における溶接金属の靱性向上を目的として提案されたワイヤとして、特許文献3では溶接金属中での被脱酸元素の炭素当量への寄与の観点からその成分組成を最適化したガスシールドアーク溶接用ソリッドワイヤが開示されている。   As a conventional solid wire for gas shielded arc welding, Patent Document 1 has improved crack resistance by reducing the amount of hydrogen contained in a copper wire, and Patent Document 2 has improved spatter resistance by application of a wire without copper plating. It is a solid wire with an emphasis on improving welding workability and cannot solve the above new technical problems. In addition, as a wire proposed for the purpose of improving the toughness of weld metal in gas shielded arc welding under high heat input and multi-pass conditions, Patent Document 3 describes the contribution of deoxidized elements in the weld metal to the carbon equivalent. A solid wire for gas shielded arc welding whose component composition is optimized from the viewpoint is disclosed.

しかし、特許文献3で前提とするガスシールドアーク多層盛り溶接におけるパス間の入熱量差は、上記下盛り溶接と上盛り溶接の組み合わせ溶接における両者溶接間の入熱量差に比べて小さい。そのため、特許文献3で提案されるワイヤを上記下盛り溶接と上盛り溶接の組み合わせ溶接における下盛り溶接(ガスシールドアーク溶接)で使用する場合にその溶接金属の熱影響部の脆化を抑制し靱性を充分に改善することは困難である。   However, the difference in heat input between passes in gas shielded arc multi-layer welding assumed in Patent Document 3 is smaller than the difference in heat input between the two welds in combined welding of the above-described overlay welding and overlay welding. Therefore, when the wire proposed in Patent Document 3 is used for underlay welding (gas shield arc welding) in the combination welding of the above-described underlay welding and overfill welding, it suppresses embrittlement of the heat affected zone of the weld metal. It is difficult to sufficiently improve toughness.

また、ボックス柱角継手溶接方法に関して、ガスシールドアーク溶接を用いて角部の極一部をシーリング溶接した後、2電極サブマージ溶接を行う、異なる溶接方法の組み合わせ溶接方法が、特許文献4などに開示されている。しかし、上記組み合わせ溶接方法におけるシーリング溶接は、サブマージ溶接では溶け込み不良となりやすいボックス柱の角部分をガスシールドアーク溶接を用いて1パス溶接するものであり、シーリング溶接により角部分に形成された溶接金属は、1パスのサブマージアーク溶接時に再溶解されるため溶接金属の熱影響部の問題は生じない。   Moreover, regarding the box column corner joint welding method, a combination welding method of different welding methods in which two-electrode submerged welding is performed after sealing a pole part of a corner portion using gas shield arc welding is disclosed in Patent Document 4 and the like. It is disclosed. However, the sealing welding in the above-mentioned combination welding method is a method in which a corner portion of a box column, which is likely to be poorly welded by submerged welding, is welded by one pass using gas shield arc welding. Is remelted at the time of 1-pass submerged arc welding, so the problem of the heat affected zone of the weld metal does not occur.

つまり、上述した下盛り溶接と上盛り溶接の組み合わせ溶接では、4面ボックス柱の角継手溶接時の溶接効率を向上することを課題するため、下盛り溶接では溶接金属部の品質向上のために必要な溶接金属部をガスシールドアーク溶接により多層盛り溶接することが前提となる。このため、下盛り溶接後に引き続き行われる上盛りSAW溶接時にも、下盛り溶接金属上層部の一部は再溶解されるものの、その大部分は固相のままで残存し、この固相残存部の一部が下盛り溶接時の入熱による熱影響部となり、脆化および靭性低下が生じるという、新たな課題が生じるのである。この点で、特許文献4で開示される溶接方法では、このような技術的課題は生じず、また、特許文献4にはこの課題およびこれを解決するためのワイヤの成分組成についての開示は一切されていない。   In other words, in the combination welding of the above-described overlay welding and overlay welding, the problem is to improve the welding efficiency at the time of corner joint welding of a four-sided box column. It is assumed that necessary weld metal parts are multilayered by gas shielded arc welding. For this reason, even during the overlay SAW welding that is performed after the overlay welding, a part of the overlay weld metal upper layer portion is remelted, but most of it remains in the solid phase. Part of this becomes a heat-affected zone due to heat input during underlay welding, resulting in a new problem that embrittlement and toughness decrease occur. In this regard, the welding method disclosed in Patent Document 4 does not cause such a technical problem, and Patent Document 4 discloses nothing about this problem and the composition of the wire for solving the problem. It has not been.

建築用4面ボックス柱の製造時などに適用することを目的とする、上記ガスシールドアーク溶接による下盛り溶接と、中・大入熱サブマージアーク溶接による上盛り溶接の組み合わせ溶接では、溶接効率の向上とともに、建築用高HAZ靱性鋼に対応して、下盛り溶接金属の靭性は、0℃での2mmVノッチシャルピー衝撃試験における吸収エネルギーで70J以上を安定して確保できることが要求されている。   Combined welding of the above-mentioned overlay welding by gas shielded arc welding and overlay welding by medium / large heat input submerged arc welding, which is intended to be applied when manufacturing 4-sided box columns for buildings, etc. Along with the improvement, corresponding to high HAZ toughness steel for construction, it is required that the toughness of the underlay weld metal can stably secure 70 J or more in the absorbed energy in the 2 mmV notch Charpy impact test at 0 ° C.

しかしながら、上述の通り、従来のガスシールドアーク溶接用ソリッドワイヤでは、このような組み合わせ溶接方法に適用した場合に上記溶接金属靭性を充分に満足することは困難であった。   However, as described above, in the conventional solid wire for gas shielded arc welding, it has been difficult to sufficiently satisfy the weld metal toughness when applied to such a combination welding method.

特開平10−263876号公報Japanese Patent Laid-Open No. 10-263876 特開平11−342494号公報JP-A-11-342494 特開2003−136281号公報JP 2003-136281 A 特開10−314946号公報JP 10-314946 A

本発明は、上述した従来技術の現状を鑑みて、引張強度が400〜570MPa級の厚鋼板を用いてAr+CO2溶接あるいはCO2溶接等のガスシールドアーク溶接による下盛り溶接した後に、該下盛り溶接金属の上から溶接入熱が4.5kJ/mm以上のサブマージアーク溶接等により上盛り溶接する際に、前記下盛り溶接金属、特に前記上盛り溶接により熱影響を受けやすい下盛り溶接金属の上層部分の脆化を抑制し、靱性を向上できる下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤを提供することを目的とする。 In view of the current state of the prior art described above, the present invention uses a thick steel plate having a tensile strength of 400 to 570 MPa class to perform overlay welding by gas shield arc welding such as Ar + CO 2 welding or CO 2 welding. When overlay welding is performed from above the weld metal by submerged arc welding with a welding heat input of 4.5 kJ / mm or more, the lower weld metal, particularly the lower weld metal that is easily affected by the overlay welding. An object of the present invention is to provide a solid wire for gas shield arc welding for underlay welding that can suppress embrittlement of the upper layer portion and improve toughness.

本発明は、上記課題を解決するものであり、その発明の要旨とするところは下記の通りである。   The present invention solves the above-mentioned problems, and the gist of the invention is as follows.

(1)質量%で、
C :0.01〜0.2%、
Si:0.2〜1%、
Mn:0.5〜2.5%、
Al:0.002〜0.1%、
Ti:0.01〜0.3%、
B:0.001〜0.015%、
N:0.001〜0.01%
を含有し、
P:0.02%以下、
S:0.01%以下、
O:0.01%以下
に制限し、かつ下記(1)式で示される炭素当量(Ceq.)が0.3〜0.5%を満足し、
さらに、
Mo:0〜0.2%、
W:0〜0.1%、
Nb:0〜0.01%、
V:0〜0.05%、
Ta:0〜0.05%
の1種または2種以上を含有し、かつ下記(2)式で示されるNb当量(Nbeq.)が0.01%以下であり、残部が不可避不純物およびFeからなることを特徴とする下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤ。
Ceq.=C%+Mn%/6+Si%/24+Ni%/40+Cr%/5
・ ・ ・(1)
Nbeq.=Nb%+V%/5+Mo%/20+W%/10+Ta%/5
・ ・ ・(2)
(1) In mass%,
C: 0.01-0.2%
Si: 0.2-1%,
Mn: 0.5 to 2.5%
Al: 0.002 to 0.1%,
Ti: 0.01 to 0.3%,
B: 0.001 to 0.015%,
N: 0.001 to 0.01%
Containing
P: 0.02% or less,
S: 0.01% or less,
O: It is limited to 0.01% or less, and the carbon equivalent (Ceq.) Represented by the following formula (1) satisfies 0.3 to 0.5%,
further,
Mo: 0 to 0.2%,
W: 0 to 0.1%
Nb: 0 to 0.01%,
V: 0 to 0.05%,
Ta: 0 to 0.05%
1 or 2 or more, the Nb equivalent (Nbeq.) Represented by the following formula (2) is 0.01% or less, and the balance consists of inevitable impurities and Fe Solid wire for gas shielded arc welding for welding.
Ceq. = C% + Mn% / 6 + Si% / 24 + Ni% / 40 + Cr% / 5
(1)
Nbeq. = Nb% + V% / 5 + Mo% / 20 + W% / 10 + Ta% / 5
(2)

(2)質量%で、さらに、
Ni:0.01〜6%、
Cu:0.01〜1.5%、
Cr:0.01〜1.5%
の1種または2種以上を含有することを特徴とする前記(1)に記載の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤ。
(2) In mass%,
Ni: 0.01-6%,
Cu: 0.01 to 1.5%,
Cr: 0.01 to 1.5%
A solid wire for gas shielded arc welding for underlay welding as described in (1) above, comprising one or more of the above.

(3)質量%で、さらに、
Ca:0.0002〜0.01%、
Mg:0.0002〜0.01%、
REM:0.0002〜0.01%
の1種または2種以上を含有することを特徴とする前記(1)または(2)に記載の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤ。
(3) In mass%,
Ca: 0.0002 to 0.01%,
Mg: 0.0002 to 0.01%,
REM: 0.0002 to 0.01%
The solid wire for underlay welding gas shielded arc welding according to (1) or (2) above, comprising one or more of the above.

(4)多層盛ガスシールドアーク溶接において最大入熱量が最小入熱量の1.5倍以上である入熱条件で用いることを特徴とする前記(1)〜(3)のいずれかに記載の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤ。   (4) Under multi-layered gas shielded arc welding, the maximum heat input is 1.5 times or more the minimum heat input, and the heat input is used under any one of the above (1) to (3) Solid wire for gas shielded arc welding for prime welding.

本発明によれば、引張強度が400〜570MPa級の厚鋼板を用いてAr+CO2溶接あるいはCO2溶接等のガスシールドアーク溶接による下盛り溶接した後に、該下盛り溶接金属の上から溶接入熱が4.5kJ/mm以上のサブマージアーク溶接等により上盛り溶接する際に、前記下盛り溶接金属、特に前記上盛り溶接により熱影響を受けやすい下盛り溶接金属の上層部分の脆化を抑制し、靱性を向上できる下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤを提供することが可能となる。 According to the present invention, weld welding heat input from above the overlay weld metal after performing weld welding by gas shield arc welding such as Ar + CO 2 welding or CO 2 welding using a thick steel plate having a tensile strength of 400 to 570 MPa. Suppresses embrittlement of the lower weld metal, especially the upper weld metal that is susceptible to heat by the upper weld when the upper weld is performed by submerged arc welding of 4.5 kJ / mm or more. It becomes possible to provide a solid wire for gas shielded arc welding for underlay welding that can improve toughness.

その結果、高層建築物の建造時などで、特に板厚が60mm程度を超えるような厚手スキンプレートを用いてその角部分を溶接し中空の4面ボックス柱を製造する際の角継手溶接において、本発明ワイヤを適用した上記下盛りおよび上盛りの組み合わせ溶接により、溶接欠陥がなく靱性に優れた溶接部を確保しつつ、溶接効率を向上させることが可能となる。   As a result, at the time of construction of a high-rise building, etc., especially in corner joint welding when manufacturing a hollow four-sided box column by welding its corner part using a thick skin plate with a plate thickness exceeding about 60 mm, The combined welding of the above-described underlay and overlay to which the wire of the present invention is applied makes it possible to improve the welding efficiency while ensuring a welded portion having no welding defects and excellent toughness.

以下に、本発明を詳細に説明する。   The present invention is described in detail below.

本発明は、単独の多層盛り溶接方法に用いられる従来のガスシールドアーク溶接用ソリッドワイヤに比べると、その用途である溶接方法および溶接条件の前提および技術思想が以下の点で基本的に異なるものである。   The present invention is fundamentally different from the conventional solid wire for gas shielded arc welding used in a single multi-layer welding method in the following points in terms of the welding method and welding conditions used in the application, and the technical idea. It is.

つまり、本発明の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤは、下盛り溶接として、ガスシールドアーク溶接による多層盛り溶接(以下、単に「下盛り溶接」ということもある。)を行った後、引き続き、上盛り溶接として、ガスシールドアーク溶接に比べて大入熱量のサブマージアーク溶接(以下、単に「上盛り溶接」ということもある。)を行う、入熱量差の大きい下盛り溶接と上盛り溶接との組み合わせ溶接方法における下盛り溶接に適用することを前提とする。   That is, the solid wire for gas shield arc welding for underlay welding according to the present invention is subjected to multi-layer prime welding (hereinafter sometimes simply referred to as “underlay welding”) by gas shield arc welding as underlay welding. Then, as the overlay welding, submerged arc welding (hereinafter sometimes simply referred to as “superimposition welding”) with a larger heat input than gas shielded arc welding is performed. It is assumed that this is applied to underlay welding in a combination welding method with fill welding.

一方、従来のガスシールドアーク溶接用ソリッドワイヤは、単独のガスシールドアーク溶接による多層盛り溶接方法に用いられることを前提とする。   On the other hand, it is assumed that the conventional solid wire for gas shielded arc welding is used for a multi-layer welding method by independent gas shielded arc welding.

従来のガスシールドアーク溶接用ソリッドワイヤの成分設計においても、多層盛溶接を想定し、各溶接パス間の入熱量や、後続パス溶接による先行パス溶接金属の熱影響部における組織変化に起因する靭性などの機械的特性の影響を考慮することが行なわれている。しかし、単独のガスシールドアーク溶接による多層盛り溶接方法では、最初から最後まで各溶接パスの入熱は一定範囲内で行なわれるため、各パス間の入熱量差は、本発明が前提とする、例えば、入熱量比が1.5以上になるような、下盛り溶接と上盛り溶接の組み合わせ溶接方法に比べて非常に小さい。このため、本発明が前提とする、下盛り溶接と上盛り溶接の組み合わせ溶接方法において、下盛り溶接用ワイヤとして、従来のガスシールドアーク溶接用ソリッドワイヤを用いる場合には、下盛り溶接により形成された溶接金属(以下、単に「下盛り溶接金属」ということもある。)が上盛り溶接により熱影響を受け、その熱影響部の靱性が劣化する、という、新たな問題が生じることがわかった。   In the conventional component design of solid wire for gas shielded arc welding, assuming multi-layer welding, the toughness caused by the heat input between each welding pass and the structure change in the heat-affected zone of the preceding pass weld metal by the subsequent pass welding Considering the influence of mechanical properties such as However, in the multi-layer welding method by independent gas shielded arc welding, the heat input of each welding pass is performed within a certain range from the beginning to the end, so the difference in heat input between each pass is premised on the present invention, For example, it is very small as compared with a combination welding method of bottom welding and top welding in which the heat input ratio is 1.5 or more. For this reason, in the combined welding method of the bottom welding and the top welding, which is a premise of the present invention, when a conventional solid wire for gas shielded arc welding is used as the bottom welding wire, it is formed by bottom welding. It has been found that a new problem arises that the welded metal (hereinafter sometimes simply referred to as “underlay weld metal”) is affected by heat from the top weld and the toughness of the heat affected zone deteriorates. It was.

本発明者らは上記下盛り溶接と上盛り溶接の組み合わせ溶接方法における下盛り溶接金属熱影響部の靱性劣化の原因を調査した。その結果、以下に説明するように、ガスシールドアーク溶接で形成された下盛り溶接金属は、引き続き行なわれる大入熱サブマージアーク溶接により加熱され、その熱影響において粗大な粒界フェライトが生成するために溶接金属組織の有効結晶粒径が粗大化し、また、溶接金属の熱影響部において析出元素が炭窒化物として析出し、過度な析出強化または粗大析出物の形成による脆化が生じ、これらを原因として溶接金属の靭性が大きく劣化することを見いだした。   The present inventors investigated the cause of toughness deterioration in the heat-affected zone of the lower weld metal in the combination welding method of the lower weld and the upper weld. As a result, as described below, the underlay weld metal formed by gas shielded arc welding is heated by the subsequent high heat input submerged arc welding, and coarse grain boundary ferrite is generated due to the thermal effect. In addition, the effective crystal grain size of the weld metal structure becomes coarse, and the precipitated elements precipitate as carbonitrides in the heat-affected zone of the weld metal, resulting in excessive precipitation strengthening or embrittlement due to the formation of coarse precipitates. It was found that the toughness of the weld metal deteriorates significantly as a cause.

図1は本発明が前提とする入熱量差の大きい下盛り溶接(ガスシールドアーク溶接)と上盛り溶接(サブマージアーク溶接)との組み合わせ溶接方法における溶接金属およびその熱影響部を説明するための模式図を示す。   FIG. 1 is a view for explaining a weld metal and its heat-affected zone in a combined welding method of overlay welding (gas shield arc welding) and overlay welding (submerged arc welding) with a large difference in heat input, which is a prerequisite of the present invention. A schematic diagram is shown.

図1に模式的に示すように、下盛り溶接(ガスシールドアーク溶接)によって形成された下盛り溶接金属であるガスシールドアーク溶接金属2は、引き続き行なわれる上盛り溶接(サブマージアーク溶接)の入熱によりその上層領域が熱影響を受けるが、その熱影響程度は、上盛り溶接(サブマージアーク溶接)位置(上盛りSAW溶接金属1)からの伝熱距離に依存し再加熱温度に応じて異なる。上盛り溶接位置から近く、再加熱温度がAC3変態点以上となる熱影響部3では、下盛り溶接(ガスシールドアーク溶接)で形成された初期の溶接金属組織は消失し、相変態により結晶粒が粗大な組織が形成され靱性が劣化されやすい。   As schematically shown in FIG. 1, the gas shielded arc welding metal 2, which is a bottom welding metal formed by bottom welding (gas shielded arc welding), is used for subsequent overlay welding (submerged arc welding). Although the upper layer region is affected by heat due to heat, the degree of the heat effect depends on the heat transfer distance from the position of superposition welding (submerged arc welding) (superposition SAW weld metal 1) and varies depending on the reheating temperature. . In the heat-affected zone 3 where the reheating temperature is close to the AC3 transformation point and close to the overlay welding position, the initial weld metal structure formed by the overlay welding (gas shield arc welding) disappears, and crystal grains are formed by the phase transformation. However, a coarse structure is formed and toughness is easily deteriorated.

また、上盛り溶接位置から比較的離れた、再加熱温度がAC3変態点未満となる熱影響部4、特にAC1変態点未満〜500℃程度に再加熱された領域では、下盛り溶接(ガスシールドアーク溶接)溶接金属中にワイヤから供給された析出強化元素の析出が促進され、過度に強度が高まると脆化し靱性劣化が顕著となる場合がある。   Further, in the heat affected zone 4 where the reheating temperature is less than the AC3 transformation point, which is relatively far from the upper welding position, particularly in the region reheated to less than the AC1 transformation point to about 500 ° C., the lower welding (gas shield) Arc welding) Precipitation of the precipitation strengthening element supplied from the wire into the weld metal is promoted, and if the strength is excessively increased, the weld metal may become brittle and the deterioration of toughness may become remarkable.

さらに、下盛り溶接(ガスシールドアーク溶接)金属が特に焼き入れ性が高い成分組成の場合には、再加熱温度が二相域(AC1〜AC3変態点)となると、逆変態オーステナイト中にCが濃化した後、冷却時に靱性に悪影響を及ぼす硬質相である島状マルテンサイト(M*)が形成されやすくなる。また、再加熱温度がAC3変態点以上となると、溶接金属組織がラス間に粗大な島状マルテンサイトが形成されやすい上部ベイナイトになりやすく、何れの場合も下盛り溶接金属の熱影響部の靱性が損なわれやすい。 Furthermore, when the weld metal (gas shield arc welding) has a particularly high hardenability component composition, when the reheating temperature becomes a two-phase region (AC1 to AC3 transformation point), C is present in the reverse transformed austenite. After concentration, island martensite (M * ), which is a hard phase that adversely affects toughness during cooling, is likely to be formed. In addition, when the reheating temperature is equal to or higher than the AC3 transformation point, the weld metal structure tends to be upper bainite where coarse island martensite is easily formed between the laths, and in any case, the toughness of the heat affected zone of the lower weld metal Is easily damaged.

本発明は、これらの知見を基に、上記下盛り溶接と上盛り溶接の組み合わせ溶接方法における下盛り溶接金属熱影響部の靭性劣化を抑制するための具体的手段について詳細に調査・研究した。   Based on these findings, the present invention investigated and studied in detail the specific means for suppressing the toughness deterioration of the lower weld metal heat-affected zone in the above-described combination welding method of upper weld and upper weld.

その結果、下盛り溶接として使用するガスシールドアーク溶接用ソリッドワイヤの成分組成として、
(1)下盛り溶接金属の熱影響部において、Tiを適正量含有させることにより、オーステナイト粒径の微細化が促進されること、
(2)下盛り溶接金属の熱影響部において、Tiと同時にBも適正量含有させることにより、フェライト変態核が増加し、かつ粒界の焼入性が高まり旧オーステナイト粒界に生じる粗大な粒界フェライトの生成も抑制されること、
(3)下盛り溶接金属の熱影響部における上記(2)のTiおよびBの効果を十分に発現させるためには、ワイヤの合金組成を炭素当量(Ceq.)で適正量以上とし溶接金属の焼入れ性を高める必要があり、一方、下盛り溶接金属の熱影響部以外の過剰炭素当量による靭性劣化を防止するために炭素当量の上限を規制する必要があること、
(4)下盛り溶接金属の熱影響部において、Nbなどの析出強化元素の含有量を制限することにより、析出物の生成に起因した脆化を抑制できること、を新たに知見した。
本発明は、以上の知見および技術思想をもとになされたものであり、下盛り溶接(ガスシールドアーク溶接による多層盛り溶接)後に、上盛り溶接(大入熱量のサブマージアーク溶接)を行う溶接方法における下盛り溶接に用いられ、特に下盛り溶接金属の熱影響部の靭性に優れた下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤである。
As a result, as a component composition of the solid wire for gas shielded arc welding used as underlay welding,
(1) In the heat-affected zone of the underlay weld metal, by containing an appropriate amount of Ti, refinement of the austenite grain size is promoted,
(2) In the heat-affected zone of the underlay weld metal, the inclusion of an appropriate amount of B together with Ti increases the number of ferrite transformation nuclei and increases the hardenability of the grain boundaries, resulting in coarse grains generated in the prior austenite grain boundaries. The generation of field ferrite is also suppressed,
(3) In order to fully develop the effects of Ti and B of (2) above in the heat affected zone of the underlay weld metal, the alloy composition of the wire is set to an appropriate amount or more in terms of carbon equivalent (Ceq.). It is necessary to increase the hardenability, while on the other hand, it is necessary to regulate the upper limit of the carbon equivalent to prevent toughness deterioration due to excess carbon equivalent other than the heat affected zone of the underlay weld metal,
(4) It has been newly found out that embrittlement due to the formation of precipitates can be suppressed by limiting the content of precipitation strengthening elements such as Nb in the heat affected zone of the underlay weld metal.
The present invention has been made on the basis of the above knowledge and technical idea, and performs welding by overlay welding (submerged arc welding with a large heat input) after overlay welding (multilayer welding by gas shielded arc welding). This is a solid wire for gas shielded arc welding for underlay welding, which is used for underlay welding in the method, and is particularly excellent in the toughness of the heat affected zone of the underlay weld metal.

以下に本発明の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤの成分組成とその限定理由を説明する。
なお、以下に示される「%」は特に説明がない限りは、「質量%」を意味するものとする。
The component composition of the solid wire for gas shield arc welding for underlay welding according to the present invention and the reason for limitation will be described below.
“%” Shown below means “% by mass” unless otherwise specified.

先ず、本発明の目的を達成する上で特に必要とされる下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤの基本成分について説明する。   First, basic components of a solid wire for gas shielded arc welding for underlay welding that are particularly necessary for achieving the object of the present invention will be described.

Cは、溶接金属の強度を確保する上で必須な成分であり、強度向上効果を十分に得るためにワイヤの含有量として0.01%以上必要である。ただし、ワイヤの含有量が0.2%を超えると、溶接金属の硬さが過大となり、また、上盛り溶接による熱影響部において靱性に悪影響を及ぼす島状マルテンサイトの生成量も多くなり、その結果、下盛り溶接金属全体の靭性が低下し、かつ、上盛り溶接に起因する下盛り溶接金属の熱影響部の靭性劣化も著しくなるため好ましくない。これらの理由から、本発明のワイヤ中のC含有量を0.01〜0.2%とした。   C is an essential component for ensuring the strength of the weld metal, and is required to be 0.01% or more as the wire content in order to obtain a sufficient strength improvement effect. However, if the wire content exceeds 0.2%, the hardness of the weld metal becomes excessive, and the amount of island martensite that adversely affects toughness in the heat affected zone due to overlay welding also increases, As a result, the toughness of the entire lower weld metal is lowered, and the toughness deterioration of the heat affected zone of the lower weld metal resulting from the upper weld becomes significant. For these reasons, the C content in the wire of the present invention is set to 0.01 to 0.2%.

Siは、溶接金属中で脱酸剤として作用するとともに、溶接時のスパッタ低減に効果があるため、ワイヤ中に0.2%以上含有させる必要がある。一方、Siを1%超含有すると下盛り溶接金属全体および上盛り溶接に起因する下盛り溶接金属の熱影響部の硬さを過度に高め、また、島状マルテンサイト組織の割合を増加させる結果、靭性が顕著に劣化するため好ましくない。これらの理由から、本発明のワイヤ中のSi含有量を0.2〜1%に限定した。   Since Si acts as a deoxidizer in the weld metal and is effective in reducing spatter during welding, it is necessary to contain 0.2% or more in the wire. On the other hand, if the Si content exceeds 1%, the hardness of the heat affected zone of the underlay weld metal as a whole and the overfill weld metal is excessively increased, and the proportion of the island martensite structure is increased. This is not preferable because the toughness deteriorates significantly. For these reasons, the Si content in the wire of the present invention is limited to 0.2 to 1%.

Mnは、溶接金属中でSiと同じく脱酸剤としての働きを有し、また、溶接金属組織を微細化する作用を有し、溶接金属の強度・靭性向上に効果がある元素であるため、本発明においては、ワイヤ中に0.5%以上含有させる。しかし、Mnを2.5%超含有させると、溶接金属の焼入性が過大となって硬さを過度に高めて靭性を劣化させるため、本発明においてはワイヤ中のMnの上限を2.5%とする。   Since Mn has a function as a deoxidizer in the weld metal as well as Si, and has an effect of refining the weld metal structure, it is an element effective in improving the strength and toughness of the weld metal. In the present invention, 0.5% or more is contained in the wire. However, if Mn exceeds 2.5%, the hardenability of the weld metal becomes excessive and the hardness is excessively increased and the toughness is deteriorated. Therefore, in the present invention, the upper limit of Mn in the wire is 2. 5%.

Alは、溶接金属中でSiと同じく脱酸元素として働き、溶接金属中の酸素量制御に有効であり、脱酸に有効に寄与するためには溶接ワイヤ中のAl含有量の下限を0.002%とする必要がある。一方、溶接金属中にAlが過剰に含有されると、溶接金属組織中のアシキュラーフェライトの生成が抑制され、溶接金属全体の組織が粗大化される結果、下盛り溶接金属全体および上盛り溶接に起因する下盛り溶接金属の熱影響部の靭性が劣化するため好ましくない。これらの問題が生じさせない溶接ワイヤ中のAl含有量の上限は、0.1%であるため、本発明においては溶接ワイヤ中のAl含有量の上限を0.1%とした。   Al acts as a deoxidizing element in the weld metal like Si, and is effective in controlling the amount of oxygen in the weld metal. In order to contribute effectively to deoxidation, the lower limit of the Al content in the welding wire is set to 0. It needs to be 002%. On the other hand, if Al is excessively contained in the weld metal, the formation of acicular ferrite in the weld metal structure is suppressed, and the overall structure of the weld metal is coarsened. This is not preferable because the toughness of the heat-affected zone of the underlay weld metal resulting from the above deteriorates. Since the upper limit of the Al content in the welding wire that does not cause these problems is 0.1%, in the present invention, the upper limit of the Al content in the welding wire is set to 0.1%.

Tiは、溶接金属において酸化物を形成し、アシキュラーフェライトの生成核として溶接金属の組織微細化に寄与する。また、下盛り溶接金属の上盛り溶接による熱影響を受ける領域においても、再加熱オーステナイト粒径の微細化を促進させ、熱影響部の組織微細化に寄与するため、本発明の下盛り溶接用ワイヤにおいて最も重要な元素の一つである。上記効果を十分に発揮させ下盛り溶接金属、特にその熱影響部の靭性を向上させるためには、溶接ワイヤ中にTiを0.01%以上含有させる必要がある。一方、溶接ワイヤ中のTi含有量が0.3%を超えると、溶接金属中に脆性破壊の起点となるような粗大な酸化物や窒化物を形成して逆に溶接金属の靭性を劣化させるため、本発明においては、溶接ワイヤ中のTi含有量の上限を0.3%とした。   Ti forms an oxide in the weld metal and contributes to the refinement of the structure of the weld metal as a nucleus for the formation of acicular ferrite. In addition, in the area affected by the heat of the overlay welding metal overlay welding, it promotes the refinement of the reheated austenite grain size and contributes to the refinement of the structure of the heat affected zone. One of the most important elements in wire. In order to sufficiently exhibit the above effects and improve the toughness of the underlay weld metal, particularly its heat-affected zone, it is necessary to contain 0.01% or more of Ti in the welding wire. On the other hand, when the Ti content in the welding wire exceeds 0.3%, a coarse oxide or nitride that becomes a starting point of brittle fracture is formed in the weld metal, which adversely deteriorates the toughness of the weld metal. Therefore, in the present invention, the upper limit of the Ti content in the welding wire is set to 0.3%.

Bは、溶接金属中に適正量存在すると、固溶Bの効果により、溶接金属の焼入性を高め、粗大な粒界フェライトを抑制し、靭性向上に顕著な効果を発揮する。また、BはTiと共存することで溶接金属組織中のアシキュラーフェライト生成による溶接金属組織の微細化にも寄与し、特にBによる焼入性向上による変態組織の微細化促進作用により、上盛り溶接に起因する下盛り溶接金属の熱影響部の靭性を向上に顕著な効果がある。本発明では、これらの効果を十分発揮させ、下盛り溶接金属および上盛り溶接に起因する下盛り溶接金属の熱影響部の靭性を向上させるために、溶接ワイヤ中のB含有量の下限を0.001%とした。一方、溶接ワイヤ中のB含有量が0.015%超となると、溶接金属中のB量が過剰となり、焼入性が過大となって、溶接金属組織が粗大な上部ベイナイト組織になりやすいため、溶接金属の靱性確保上、好ましくない。そこで、本発明においては、溶接ワイヤのB含有量の上限を0.015%とした。   When an appropriate amount of B is present in the weld metal, the effect of the solid solution B enhances the hardenability of the weld metal, suppresses coarse grain boundary ferrite, and exhibits a remarkable effect in improving toughness. B also contributes to the refinement of the weld metal structure due to the formation of acicular ferrite in the weld metal structure by coexisting with Ti. There is a remarkable effect in improving the toughness of the heat-affected zone of the underlay weld metal caused by welding. In the present invention, in order to sufficiently exhibit these effects and improve the toughness of the heat-affected zone of the lower weld metal and the lower weld metal resulting from the upper weld, the lower limit of the B content in the welding wire is set to 0. 0.001%. On the other hand, if the B content in the welding wire exceeds 0.015%, the B content in the weld metal becomes excessive, the hardenability becomes excessive, and the weld metal structure tends to become a coarse upper bainite structure. It is not preferable for ensuring the toughness of the weld metal. Therefore, in the present invention, the upper limit of the B content of the welding wire is set to 0.015%.

Nは、溶接金属中でTiと結合しTiNを形成し、特に上盛り溶接に起因する下盛り溶接金属の熱影響部において、特にオーステナイト変態点以上に再加熱される領域のオーステナイト粒径を微細化させる作用があり、この効果を十分に得るためにNが含有量の下限を0.001%とした。   N combines with Ti in the weld metal to form TiN, especially in the heat-affected zone of the lower weld metal resulting from the upper weld, especially in the region that is reheated above the austenite transformation point. In order to obtain this effect sufficiently, the lower limit of the N content is set to 0.001%.

しかし、Nを溶接金属中に過剰に含有させると、Bと結びついてBNを形成し、上記Bの有効性が失われ、溶接金属組織の粗大化を招く結果となるため好ましくない。ワイヤ中のN含有量が0.01%を超えるとこれらの悪影響が顕在化し、また、溶接金属中で固溶状態のN量が増加しフェライトマトリックスの靭性を劣化させる悪影響も生じる。さらに、ワイヤ中のN含有量の過度な増加は溶接欠陥を増加させる原因ともなる。したがって、これらの問題を防止するために、本発明では、溶接ワイヤ中のN含有量の上限を0.01%とした。   However, if N is excessively contained in the weld metal, it is combined with B to form BN, and the effectiveness of B is lost, resulting in a coarse weld metal structure. When the N content in the wire exceeds 0.01%, these adverse effects become obvious, and the adverse effect of increasing the solid solution N content in the weld metal and degrading the toughness of the ferrite matrix also occurs. Furthermore, an excessive increase in the N content in the wire also causes an increase in weld defects. Therefore, in order to prevent these problems, the upper limit of the N content in the welding wire is set to 0.01% in the present invention.

本発明の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤにおいて、本発明の目的を達成する上で、以上の積極的に添加すべき元素とともに、以下の不可避的成分の含有量を制限する必要がある。   In the solid wire for gas shielded arc welding for underlay welding of the present invention, in order to achieve the object of the present invention, it is necessary to limit the contents of the following inevitable components together with the elements to be positively added. is there.

P、Sは本発明において不可避的不純物元素であり、溶接金属の靭性劣化を抑制するためにワイヤ中のPおよびSの含有量は少ないほど好ましい。本発明では、下盛り溶接金属の上盛り溶接による熱影響を受けた領域(熱影響部)、および、受けない領域ともに溶接金属の靭性劣化が許容できるワイヤ中の含有量として、P含有量の上限は0.02%、S含有量の上限は0.01%と定める。   P and S are unavoidable impurity elements in the present invention, and it is preferable that the P and S contents in the wire are as small as possible in order to suppress toughness deterioration of the weld metal. In the present invention, as the content in the wire in which the toughness deterioration of the weld metal can be allowed in both the region (heat-affected zone) affected by the overlay welding of the overlay welding metal and the region not subjected to the welding, The upper limit is 0.02%, and the upper limit of S content is 0.01%.

Oは、本発明溶接ワイヤにおいて不可避的不純物元素であり、多量に存在すると、溶接ワイヤの製造性を阻害する。また、溶接金属のO含有量を過剰に増加させて、溶接金属の延性、靱性を劣化させるため、好ましくない。
本発明においては、溶接ワイヤの製造性、溶接金属の材質劣化を生じない範囲として、ワイヤ中のO含有量の上限を0.01%とする。
O is an unavoidable impurity element in the welding wire of the present invention, and when present in a large amount, obstructs the productivity of the welding wire. Further, it is not preferable because the O content of the weld metal is excessively increased to deteriorate the ductility and toughness of the weld metal.
In the present invention, the upper limit of the O content in the wire is set to 0.01% as a range in which the manufacturability of the welding wire and the quality of the weld metal are not deteriorated.

本発明の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤにおいて、本発明の目的を達成する上で、以上の基本成分の規定とともに、ワイヤの成分組成を下記(1)で定義されるCeq.により規定する必要がある。   In the solid wire for gas shielded arc welding for underlay welding according to the present invention, in order to achieve the object of the present invention, the composition of the wire is defined by the Ceq. It is necessary to stipulate.

下記(1)で定義されるCeq.が0.3%未満であると、下盛り溶接(ガスシールドアーク溶接)金属の熱影響部において焼入性不足のために、上述したTi、Bの組織微細化効果が十分発揮されず、靭性を害する粗大な粒状フェライトの生成が抑制できず、靭性が顕著に劣化する。   Ceq. Defined in (1) below. If it is less than 0.3%, the effect of refining the structure of Ti and B described above is not sufficiently exhibited due to insufficient hardenability in the heat affected zone of underlay welding (gas shield arc welding) metal, and toughness The formation of coarse granular ferrite that damages the steel cannot be suppressed, and the toughness is significantly deteriorated.

一方、Ceq.が0.5%超になると、下盛り溶接(ガスシールドアーク溶接)金属の硬さが過剰となって脆化し靭性が劣化する恐れが生じる。さらには、上盛り溶接に起因する下盛り溶接金属の熱影響部において靭性に悪影響及ぼす硬質の島状マルテンサイト(Cが濃化した高炭素のマルテンサイトあるいは該マルテンサイトと残留オーステナイトとの混合組織)が生成する可能性が高くなる。これらの結果、下盛り溶接金属全体および下盛り溶接金属の熱影響部の何れも靭性を低下させることとなり好ましくない。
これらの理由から、本発明のワイヤ成分組成を下記(1)Ceq.が0.3〜0.5%になるように規定した。
Ceq.=C%+Mn%/6+Si%/24+Ni%/40+Cr%/5
・ ・ ・(1)
On the other hand, Ceq. If it exceeds 0.5%, the hardness of the overlay welding (gas shield arc welding) metal becomes excessive, which may cause embrittlement and deterioration of toughness. Further, hard island martensite (mixed structure of high carbon martensite enriched with C or martensite and residual austenite, which adversely affects toughness in the heat-affected zone of the lower weld metal resulting from the overlay welding ) Is likely to be generated. As a result, the entire underlay weld metal and the heat affected zone of the underlay weld metal both reduce toughness, which is not preferable.
For these reasons, the wire component composition of the present invention is changed to the following (1) Ceq. Was defined to be 0.3 to 0.5%.
Ceq. = C% + Mn% / 6 + Si% / 24 + Ni% / 40 + Cr% / 5
(1)

以上の基本成分、不可避的成分、および、Ceqの規定により、本発明の目的を達成することはできるが、本発明の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤにおいて、目的とする特性を害さない範囲で、以下の目的からさらに以下の成分元素を適量添加することができる。   Although the object of the present invention can be achieved by the above-mentioned basic components, unavoidable components, and Ceq, the target characteristics of the solid wire for gas shield arc welding for underlay welding according to the present invention are impaired. In the absence, an appropriate amount of the following component elements can be added for the following purposes.

Mo、W、Nb、V、Taは析出強化元素であり、溶接金属の強度向上の目的で、Mo、W、Nb、V、Taの1種または2種以上を以下の含有量、および、下記(2)式で定義されるNb当量(Nbeq.)の範囲で含有させることができる。   Mo, W, Nb, V, and Ta are precipitation strengthening elements. For the purpose of improving the strength of the weld metal, one or more of Mo, W, Nb, V, and Ta contain the following contents, and (2) Nb equivalent (Nbeq.) Defined by the formula can be contained.

MoはCrと同様、焼入性を高める作用を有する元素であり、溶接金属組織中のベイナイトあるいはアシキュラーフェライトを微細化し、靱性を向上させるために有効な元素である。この効果を発揮させるためには、Moの含有量を0.01%以上とすることが好ましい。   Mo, like Cr, is an element having an effect of improving hardenability, and is an effective element for improving the toughness by refining bainite or acicular ferrite in the weld metal structure. In order to exert this effect, the Mo content is preferably 0.01% or more.

しかし、Moは下盛り溶接金属の熱影響部において析出物を形成し、析出脆化により、靭性の劣化を招く可能性があるため、Moを含有させる場合には、その含有量の上限を0.2%に限定する必要がある。   However, since Mo forms precipitates in the heat-affected zone of the underlay weld metal and may cause toughness deterioration due to precipitation embrittlement, when Mo is contained, the upper limit of the content is 0. Must be limited to 2%.

WもMoと同様の作用を有する元素であり、Moと同様な効果を発揮させるためには、Wの含有量を0.001%以上とすることが好ましい。
また、Moと同様に析出に起因した脆化を避けるため、Wを含有させる場合には、その溶接ワイヤ中の含有量の上限を0.1%に限定する必要がある。
W is an element having the same action as Mo, and in order to exert the same effect as Mo, the W content is preferably 0.001% or more.
Moreover, in order to avoid the embrittlement resulting from precipitation similarly to Mo, when making W contain, it is necessary to limit the upper limit of content in the welding wire to 0.1%.

Nbは、微量で焼入性を高め、析出強化により溶接金属の強度を高めるためには有効な元素であり、この効果を発揮させるためには、Nbの含有量を0.001%以上とすることが好ましい。   Nb is an effective element for improving the hardenability in a small amount and increasing the strength of the weld metal by precipitation strengthening. In order to exert this effect, the Nb content is set to 0.001% or more. It is preferable.

しかし、Moと同様、析出脆化を顕著に生じる元素であるため、本発明においては、Nbを含有させる場合には、上盛り溶接による下盛り溶接金属の熱影響部の脆化を抑制すためにワイヤ中のNb含有量の上限を0.01%とする。   However, like Mo, it is an element that significantly causes precipitation embrittlement. Therefore, in the present invention, when Nb is contained, in order to suppress the embrittlement of the heat affected zone of the lower weld metal by the upper weld, The upper limit of the Nb content in the wire is 0.01%.

VもNbと同様の析出強化元素であり、溶接金属の強度向上の目的で含有させる場合、その効果を発揮するために0.001%以上含有させることが好ましい。しかし、本発明のワイヤへの多量の含有は好ましくなく、Vを含有させる場合には、上盛り溶接による下盛り溶接金属の熱影響部の脆化を抑制すためにワイヤ中のV含有量の上限を0.05%とする。   V is also a precipitation strengthening element similar to Nb, and when contained for the purpose of improving the strength of the weld metal, it is preferably contained in an amount of 0.001% or more in order to exert its effect. However, it is not preferable to contain a large amount in the wire of the present invention. When V is contained, in order to suppress embrittlement of the heat-affected zone of the lower weld metal by overlay welding, the V content in the wire The upper limit is 0.05%.

TaもNbと同様の作用を有する元素であり、溶接金属の強度向上の目的で含有させる場合、その効果を発揮するために0.001%以上含有させることが好ましい。しかし、本発明のワイヤへの多量の含有は同様に好ましくなく、Vを含有させる場合には、上盛り溶接による下盛り溶接金属の熱影響部の脆化を抑制すためにワイヤ中のTa含有量の上限を0.05%とする。   Ta is an element having the same action as Nb. When Ta is contained for the purpose of improving the strength of the weld metal, 0.001% or more is preferably contained in order to exert the effect. However, the inclusion of a large amount in the wire of the present invention is also not preferable, and when V is contained, the content of Ta in the wire is suppressed in order to suppress the embrittlement of the heat affected zone of the lower weld metal due to the upper weld. The upper limit of the amount is 0.05%.

以上のMo、W、Nb、V、Taの析出強化元素の1種または2種以上を添加する場合には、析出脆化を抑制するために上記含有量の規定とともに、下記(2)式で定義されるNb当量(Nbeq.)の範囲を満足させる必要がある。   In the case where one or more of the precipitation strengthening elements of Mo, W, Nb, V, and Ta are added, in order to suppress precipitation embrittlement, the following content (2) It is necessary to satisfy the defined range of Nb equivalent (Nbeq.).

下記(2)式で定義されるNbeq.が0.01%超になると、ワイヤ中のMo、W、Nb、V、Taの含有量が各々上記本発明の好ましい範囲内であっても、ガスシールドアーク溶接金属で形成される上盛り溶接金属の熱影響部の靭性を著しく低下させる可能性が高い。このため、本発明では、Mo、W、Nb、V、Taの析出強化元素の1種または2種以上を添加する場合には、下記(2)式で定義されるNb当量(Nbeq.)を0.01%以下に限定する。
Nbeq.=Nb%+V%/5+Mo%/20+W%/10+Ta%/5
・ ・ ・(2)
Nbeq. Defined by the following formula (2). When the content exceeds 0.01%, even if the contents of Mo, W, Nb, V, and Ta in the wire are each within the preferred range of the present invention, the overlay welding formed of the gas shielded arc weld metal There is a high possibility of significantly reducing the toughness of the heat-affected zone of the metal. For this reason, in this invention, when adding 1 type, or 2 or more types of the precipitation strengthening element of Mo, W, Nb, V, and Ta, Nb equivalent (Nbeq.) Defined by the following (2) Formula is added. It is limited to 0.01% or less.
Nbeq. = Nb% + V% / 5 + Mo% / 20 + W% / 10 + Ta% / 5
(2)

以上が、本発明の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤにおける基本構成要件とその限定理由である。   The above is the basic configuration requirements and the reasons for limitation in the solid wire for gas shield arc welding for underlay welding according to the present invention.

また、上記構成要件に加えて、本発明の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤでは、溶接金属の材質、特に強度の調整を目的として、本発明の目的とする特性を阻害しない範囲で、さらに、以下に説明するNi、Cu、Cr、の1種または2種以上を含有させることができる。   Further, in addition to the above-described structural requirements, the gas shield arc welding solid wire for underlay welding according to the present invention is within a range that does not impair the intended characteristics of the present invention for the purpose of adjusting the material of the weld metal, particularly strength. Furthermore, one or more of Ni, Cu, and Cr described below can be contained.

Niは、溶接金属中に一定以上含有させると、固溶靱化効果によって靱性を高め、かつ焼入性向上、固溶強化によって同時に強度も高めることが可能な非常に有用な元素である。溶接金属において、このNiの効果を明確に発揮するためには、溶接ワイヤ中のNi含有量は0.01%以上とするのが好ましい。一方、溶接ワイヤ中のNi含有量が6%超になると溶接金属の降伏応力の低下が著しく、必要な強度の確保が困難になるため、溶接ワイヤ中のNi含有量の上限は6%とするのが好ましい。   Ni is a very useful element that, when contained in a weld metal at a certain level or more, can increase toughness by a solid solution toughening effect, and at the same time increase strength by improving hardenability and solid solution strengthening. In the weld metal, in order to clearly demonstrate the effect of Ni, the Ni content in the welding wire is preferably 0.01% or more. On the other hand, when the Ni content in the welding wire exceeds 6%, the yield stress of the weld metal is remarkably reduced, and it becomes difficult to ensure the necessary strength. Therefore, the upper limit of the Ni content in the welding wire is 6%. Is preferred.

Cuは溶接ワイヤがめっきされて使用される場合には不可避的にワイヤ及び溶接金属に含有される。Cuは強度向上には有効な元素であり、効果を発揮させるためには0.01%以上含有させるのが好ましい。ただし、過剰に含有されると、溶接金属の靭性の劣化や耐高温割れ性の劣化を招く。ワイヤ表面に施されるめっきとして含有される場合、あるいは強度向上のために意図的に含有する場合とも、溶接金属の靭性の劣化や耐高温割れ性の劣化を生じない上限として、本発明においては、ワイヤのCu含有量の上限は1.5%とするのが好ましい。   Cu is inevitably contained in the wire and the weld metal when the welding wire is plated and used. Cu is an element effective for improving the strength, and in order to exert the effect, it is preferable to contain 0.01% or more. However, when it contains excessively, deterioration of the toughness and hot cracking resistance of a weld metal will be caused. In the present invention, as an upper limit that does not cause deterioration of the toughness and hot cracking resistance of the weld metal, even if it is contained as a plating applied to the surface of the wire or intentionally contained for strength improvement The upper limit of the Cu content of the wire is preferably 1.5%.

Crは、焼入性を高めて溶接金属組織のベイナイトあるいはアシキュラーフェライトの微細化を通して靱性向上に有効な元素であり、かつ、固溶強化、析出強化により強度向上にも有効な元素である。この効果を得るためには、溶接ワイヤ中に0.01%以上含有するのが好ましい。しかしながら、過剰に含有されると溶接金属を過剰に硬化させ、溶接金属の靭性を著しく劣化させるので、本発明ではその含有量の上限を1.5%とするのが好ましい。   Cr is an element effective for improving toughness by improving hardenability and making bainite or acicular ferrite fine in the weld metal structure, and is also effective for improving strength by solid solution strengthening and precipitation strengthening. In order to acquire this effect, it is preferable to contain 0.01% or more in a welding wire. However, if contained excessively, the weld metal is excessively cured and the toughness of the weld metal is remarkably deteriorated. Therefore, in the present invention, the upper limit of the content is preferably 1.5%.

また、上記構成要件に加えて、本発明においては、さらに溶接金属の延性、靭性を改善する必要がある場合には、必要に応じてさらに、Ca、Mg、REMの1種または2種以上を以下の含有量の範囲で含有させることができる。   Further, in addition to the above-described constituent requirements, in the present invention, when it is necessary to further improve the ductility and toughness of the weld metal, one or more of Ca, Mg, and REM are further added as necessary. It can contain in the range of the following content.

Ca、Mg、REMはいずれも溶接金属中で硫化物の構造を変化させ、また硫化物、酸化物のサイズを微細化して延性及び靭性向上に有効である。その効果を発揮するための下限の含有量は、Ca、Mg、REMのいずれも0.0002%とするのが好ましい。一方、Ca、Mg、REMを過剰に含有すると、硫化物や酸化物の粗大化を生じ、延性、靭性の劣化を招くため、また、溶接ビード形状の劣化、溶接性の劣化の可能性も生じるため、これらの含有量の上限をいずれも0.01%とするのが好ましい。   Ca, Mg, and REM are all effective in improving ductility and toughness by changing the structure of the sulfide in the weld metal and reducing the size of the sulfide and oxide. The lower limit content for exhibiting the effect is preferably 0.0002% for all of Ca, Mg, and REM. On the other hand, when Ca, Mg, and REM are contained excessively, sulfides and oxides are coarsened, resulting in deterioration of ductility and toughness. Also, there is a possibility of deterioration of weld bead shape and weldability. Therefore, it is preferable that the upper limit of these contents is 0.01%.

上述したように、本発明の下盛り溶接用ガスシールドアーク用溶接ワイヤは、下盛り溶接として、ガスシールドアーク溶接による多層盛り溶接(下盛り溶接)を行った後、引き続き、その上から上盛り溶接として、ガスシールドアーク溶接に比べて大入熱量のサブマージアーク溶接(上盛り溶接)を行う、入熱量差の大きい下盛り溶接と上盛り溶接との組み合わせ溶接方法において、その下盛り溶接に適用することを前提とし、下盛り溶接で形成された溶接金属の特に熱影響部の靭性を向上するものである。   As described above, the welding wire for gas shield arc for underlay welding according to the present invention is subjected to multi-layer build-up welding (bottom build-up welding) by gas shield arc welding as bottom build-up welding, and then continues to build up from above. As welding, submerged arc welding (superimposing welding) with a larger heat input than gas shielded arc welding is applied, and it is applied to the overlay welding in a combination welding method of overlay welding and overlay welding with a large heat input difference. This is intended to improve the toughness of the heat-affected zone of weld metal formed by underlay welding.

本発明は、上記入熱量差の大きい下盛り溶接と上盛り溶接との組み合わせ溶接方法において、特にサブマージアーク溶接等による上盛り溶接時の入熱が、ガスシールドアーク溶接の下盛り溶接時の入熱(通常、5kJ/mm程度以下の小〜中入熱)の1.5倍以上の場合に本発明の上記効果が顕著になる。   The present invention relates to a combination welding method of overlay welding and overlay welding with a large difference in heat input, and the heat input during overlay welding, particularly by submerged arc welding, The effect of the present invention becomes remarkable when the heat is 1.5 times or more of heat (usually small to medium heat input of about 5 kJ / mm or less).

つまり、下盛り溶接と上盛り溶接との入熱の比が1.5倍未満である場合は、本発明の上記効果は得られるものの、上盛り溶接による下盛り溶接金属の熱影響部の靭性など機械的特性の劣化は少なくなるため、本発明の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤの有利な効果がえられ難くなる。   That is, when the ratio of heat input between the overlay welding and the overlay welding is less than 1.5 times, the above effect of the present invention can be obtained, but the toughness of the heat affected zone of the overlay welding metal by the overlay welding. Therefore, the advantageous effects of the solid wire for gas shield arc welding for underlay welding according to the present invention are hardly obtained.

なお、下盛り溶接として適用されるガスシールドアーク溶接は、特に限定させるものではなく、例えば、MIG溶接、MAG溶接、CO2溶接等が適用できる。   In addition, the gas shield arc welding applied as underlay welding is not specifically limited, For example, MIG welding, MAG welding, CO2 welding, etc. are applicable.

なお、本発明における下盛り溶接は、通常のガスシールドアーク溶接による多層盛り溶接の溶接条件を前提とする。したがって、単独のガスシールドアーク溶接による多層盛り溶接において、例えば、各溶接パス間の入熱量差を意図に大きくする、あるいは、各溶接パス間の入熱量差が大きくばらつくような、特殊な溶接条件での多層盛り溶接において、最大入熱が最小入熱の1.5倍以上となる溶接条件で単独の多層盛り溶接を行なう場合にも、当然に本発明の上記効果を発揮することができる。このような場合は、上述の下盛り溶接と上盛り溶接とを区別する必要はない。   The underlay welding in the present invention is premised on the welding conditions of multi-layer prime welding by normal gas shield arc welding. Therefore, in multi-layer welding by single gas shielded arc welding, for example, special welding conditions that intentionally increase the difference in heat input between each welding pass or greatly vary the heat input difference between each welding pass. In the multi-layer prime welding, the above effect of the present invention can naturally be exhibited even when the single multi-layer prime welding is performed under welding conditions in which the maximum heat input is 1.5 times or more the minimum heat input. In such a case, it is not necessary to distinguish between the above-described bottom welding and top welding.

本発明の効果を実施例によりさらに詳細に説明する。   The effects of the present invention will be described in more detail with reference to examples.

種々の化学組成のガスシールドアーク溶接用ソリッドワイヤを用いて図2に示すような継手を作製し、2mmVノッチシャルピー衝撃試験により溶接金属の靱性を評価した。   A joint as shown in FIG. 2 was prepared using solid wires for gas shielded arc welding having various chemical compositions, and the toughness of the weld metal was evaluated by a 2 mm V notch Charpy impact test.

鋼板5は板厚100mmの引張強度490MPa級鋼を用い、開先角度20°のレ形開先の角溶接継手とし、表2の化学組成を有する直径1.4mmのソリッドワイヤを用いた炭酸ガスシールドアーク溶接(CO2溶接)により15パスの下盛り溶接8を行った後、2電極サブマージアーク溶接により上盛り溶接9を行った。その溶接条件を表1に示す。   The steel plate 5 is made of a 490 MPa class steel having a tensile strength of 100 mm, a square welded joint with a groove angle of 20 °, and carbon dioxide gas using a solid wire having a chemical composition shown in Table 2 and a diameter of 1.4 mm. After performing 15-pass overlay welding 8 by shielded arc welding (CO2 welding), overlay welding 9 was performed by 2-electrode submerged arc welding. The welding conditions are shown in Table 1.

Figure 2006000868
Figure 2006000868

サブマージアーク溶接の溶接材料は日鉄住金溶接工業製のワイヤ:Y−DLとフラックス:NSH60を用いた。下盛り溶接8は裏当て6隅部のシーリング溶接7を除いて入熱を36〜40kJ/cmとし、上盛り溶接9の入熱は133〜230kJ/cmとした。従って、サブマージアーク溶接による上盛り溶接9の入熱はCO2溶接による下盛り溶接8の3.3〜6.4倍となっており、上盛り溶接9の入熱は下盛り溶接8のガスシールドアーク溶接の入熱範囲を大きく超えている。   As the welding material for submerged arc welding, wire: Y-DL and flux: NSH60 manufactured by Nippon Steel & Sumikin Welding Industry were used. The bottom welding 8 had a heat input of 36 to 40 kJ / cm except for the sealing weld 7 at the six corners of the backing, and the heat input of the top welding 9 was 133 to 230 kJ / cm. Therefore, the heat input of the upper welding 9 by submerged arc welding is 3.3 to 6.4 times that of the lower welding 8 by CO 2 welding, and the heat input of the upper welding 9 is the gas shield of the lower welding 8. The heat input range of arc welding is greatly exceeded.

表2に、ガスシールドアーク溶接用ソリッドワイヤの化学組成と、該ワイヤを用いて作製した継手の2mmVノッチシャルピー衝撃試験結果を示す。   Table 2 shows the chemical composition of the solid wire for gas shielded arc welding and the 2 mm V notch Charpy impact test result of the joint produced using the wire.

Figure 2006000868
Figure 2006000868

2mmVノッチシャルピー衝撃試験片は図2に示す2カ所から採取し、−20℃で3本試験を行い、吸収エネルギーの平均値で靱性を評価した。すなわち、位置B11は、ガスシールドアーク溶接の溶接金属自体の靱性を評価するためのもので、下盛り溶接のほぼ中心の鋼板断面からノッチを入れた。一方、位置A10は、上盛り溶接による熱影響部の靱性を評価するためのもので、下盛り溶接と上盛り溶接との境界が試験片表面となる位置から試験片を採取し、ノッチは鋼板表面側から下盛り溶接に向かって破壊が進行する方向に入れた。   2 mm V notch Charpy impact test specimens were collected from two places shown in FIG. 2, three tests were performed at −20 ° C., and the toughness was evaluated by the average value of absorbed energy. That is, the position B11 is for evaluating the toughness of the weld metal itself of gas shielded arc welding, and a notch is made from the steel plate cross-section at the center of the underlay welding. On the other hand, the position A10 is for evaluating the toughness of the heat-affected zone due to the overlay welding. The specimen is taken from the position where the boundary between the overlay welding and the overlay welding becomes the specimen surface, and the notch is a steel plate. It was put in the direction in which the fracture progressed from the surface side toward the bottom welding.

本発明のガスシールドアーク溶接ワイヤを用いて作製した本発明の要件を満足している継手A1〜A10の場合は、ガスシールドアーク溶接金属自体の靱性(位置B)が、−20℃の吸収エネルギーで全て130J以上の高い値を有しているのに加えて、該下盛り溶接よりも大きな入熱で溶接された上盛り溶接により熱影響を受けた位置Aの吸収エネルギーもほぼ110J以上を有しており、下盛り溶接の溶接金属は、位置によらず非常に良好な靱性を有していることが明らかである。   In the case of the joints A1 to A10 that satisfy the requirements of the present invention manufactured using the gas shielded arc welding wire of the present invention, the toughness (position B) of the gas shielded arc welding metal itself is -20 ° C absorbed energy. In addition to having a high value of 130 J or more, the absorbed energy at the position A that is thermally affected by the overlay welding that is welded with a larger heat input than the overlay welding is approximately 110 J or more. It is clear that the weld metal of the overlay welding has very good toughness regardless of the position.

一方、継手B1〜B12は、下盛り溶接に供した溶接ワイヤの組成が本発明を満足していないため、下盛り溶接の溶接金属の靱性が本発明に比べて劣っている例である。   On the other hand, joints B1 to B12 are examples in which the toughness of the weld metal of the bottom welding is inferior to that of the present invention because the composition of the welding wire subjected to the bottom welding does not satisfy the present invention.

すなわち、継手B1は、溶接ワイヤ中のTi含有量が過小であるため、上盛り溶接の熱影響を受ける位置Aで下盛り溶接金属の組織が粗大となり、靱性が大きく劣っている。   That is, in the joint B1, since the Ti content in the welding wire is too small, the structure of the lower weld metal becomes coarse at the position A that is affected by the heat of the upper weld, and the toughness is greatly inferior.

継手B2は、溶接ワイヤ中にBが意図的には含有されていないため、Bによる組織微細化効果が上盛り溶接の熱影響を受ける位置Aで機能せず、粗大組織が残存するため、該位置の溶接金属靱性が本発明に比べて大きく劣っている。   Since the joint B2 does not intentionally contain B in the welding wire, the microstructure refining effect by B does not function at the position A that is affected by the heat of the overlay welding, and a coarse structure remains. The weld metal toughness at the position is greatly inferior to the present invention.

継手B3は、溶接ワイヤ中にTiが含有されておらず、またB含有量が過小であるため、上盛り溶接による熱影響を受けた領域の組織が粗大となり、位置Aの靱性劣化が大きい。   In the joint B3, since the welding wire does not contain Ti and the B content is excessively small, the structure of the region affected by the heat of the overlay welding becomes coarse, and the toughness deterioration at the position A is large.

継手B4は、溶接ワイヤ中にTi、Bは含有されているものの、両元素の含有量が過小であるため、上盛り溶接による熱影響を宇糧領域の組織微細化効果を十分発揮し得ず、従って、位置Aの靱性の劣化が著しく、好ましくない。   In joint B4, although Ti and B are contained in the welding wire, the contents of both elements are too small. Therefore, the deterioration of the toughness at the position A is remarkably undesirable.

継手B5は、溶接ワイヤ組成の炭素当量(Ceq.)が過小なため、下盛り溶接中、上盛り溶接による熱影響を受けた溶接金属とを問わず、再加熱を受けた領域の組織が粗大となるため、位置A、位置Bとも溶接金属の靱性が大きく劣っている。   In the joint B5, since the carbon equivalent (Ceq.) Of the welding wire composition is too small, the structure of the reheated region is coarse regardless of the weld metal affected by the overlay welding during the overlay welding. Therefore, the toughness of the weld metal is greatly inferior at both position A and position B.

継手B6は、逆に溶接ワイヤ組成の炭素当量(Ceq.)が過大であるため、溶接金属の硬さが過大となって、下盛り溶接の溶接金属靱性が劣る。   On the other hand, since the carbon equivalent (Ceq.) Of the welding wire composition is excessive in the joint B6, the hardness of the weld metal is excessive and the weld metal toughness of the overlay welding is inferior.

継手B7は、溶接ワイヤ組成のNb当量(Nbeq.)が過大なため、特に上盛り溶接による熱影響を受けた位置Aで析出脆化が生じるため、該位置の靱性劣化が大きい。   In the joint B7, since the Nb equivalent (Nbeq.) Of the welding wire composition is excessive, precipitation embrittlement occurs particularly at the position A that is affected by heat due to the overlay welding, so that the toughness deterioration at the position is large.

継手B8は、溶接ワイヤ中のC含有量が過大であるため、溶接金属の硬さが過大となり、また、靱性に悪影響を及ぼす島状マルテンサイトの量も多くなるため、下盛り溶接の溶接金属位置によらず、靱性が著しく劣化している。   In the joint B8, since the C content in the welding wire is excessive, the hardness of the weld metal is excessive, and the amount of island martensite that adversely affects toughness is also increased. Regardless of location, toughness is significantly degraded.

継手B9は、溶接ワイヤ中のMn含有量が過大であり、溶接金属の焼入性が過大となって硬さを過度に高めるため、下盛り溶接の溶接金属位置によらず、靱性が著しく劣化している。   In the joint B9, the Mn content in the welding wire is excessive, the hardenability of the weld metal is excessively increased, and the hardness is excessively increased. Therefore, the toughness is remarkably deteriorated regardless of the position of the weld metal in the overlay welding. is doing.

継手B10は、Tiが溶接ワイヤ中のTi含有量が過大なため、溶接金属中に粗大な酸化物、窒化物を形成して、位置A、位置Bとも溶接金属の靱性が大きく劣っている。   In the joint B10, since Ti has an excessive Ti content in the welding wire, coarse oxides and nitrides are formed in the weld metal, and the toughness of the weld metal is greatly inferior at both positions A and B.

継手B11は、溶接ワイヤ中のB含有量が過大であり、そのため、溶接金属中のB含有量も過大となり、下盛り溶接中、上盛り溶接による熱影響を受けた溶接金属とを問わず、強度の過大な組織を形成して靭性が劣化している。   In the joint B11, the B content in the welding wire is excessive, and therefore the B content in the weld metal also becomes excessive, regardless of the weld metal affected by the heat of the overlay welding during the overlay welding, An excessively strong structure is formed and the toughness is deteriorated.

継手B12は、溶接ワイヤ中のN含有量が過大であるため、Bによる組織微細化効果が阻害され、位置A、位置Bとも溶接金属の靱性が大きく劣っているが、特に再加熱を受ける位置Aの靭性劣化が著しい。   In the joint B12, since the N content in the welding wire is excessive, the effect of refining the structure due to B is hindered, and the toughness of the weld metal is greatly inferior at both positions A and B. The toughness degradation of A is remarkable.

以上の実施例からも、本発明によれば、大入熱のサブマージアーク溶接等の上盛り溶接による熱影響を受けても溶接金属の靱性が劣化せず、溶接金属全体の靱性が良好となる、下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤを提供できることが明白である。   Also from the above examples, according to the present invention, the toughness of the weld metal does not deteriorate and the toughness of the entire weld metal is improved even if it is affected by the heat build-up welding such as submerged arc welding with large heat input. It is clear that a solid wire for gas shielded arc welding for underlay welding can be provided.

サブマージアーク溶接の上盛り溶接とこれによるガスシールドアーク溶接による下盛り溶接の熱影響部との関係を示す模式図である。It is a schematic diagram which shows the relationship between the top welding of submerged arc welding, and the heat affected zone of the bottom welding by gas shield arc welding by this. ガスシールドアーク溶接による下盛り溶接とサブマージアーク溶接による上盛り溶接とによる溶接継手の開先形状、溶接の積層状態、及び下盛り溶接金属の靱性を評価するための2mmVノッチシャルピー衝撃試験片の採取位置、方向、ノッチ位置を模式的に示す継手断面図である。Sampling of 2mm V-notch Charpy impact specimens to evaluate weld joint shape, weld stacking, and weld metal toughness by underlay welding by gas shielded arc welding and overlay welding by submerged arc welding It is a joint sectional view showing typically a position, a direction, and a notch position.

符号の説明Explanation of symbols

1:サブマージアーク溶接(SAW)により形成された上盛り溶接金属
2:ガスシールドアークにより形成された下盛り溶接金属
3:AC3変態点以上に再加熱された下盛り溶接金属の熱影響部
4:AC3変態点未満に再加熱された下盛り溶接金属の熱影響部
5:鋼板
6:裏当
7:シーリング溶接
8:上盛り溶接の積層状態
9:下盛り溶接の積層状態
10:シャルピー試験片の位置、ノッチ方向(位置A)
11:シャルピー試験片の位置、ノッチ方向(位置B)
1: overlay weld metal formed by submerged arc welding (SAW) 2: overlay weld metal formed by gas shield arc 3: heat affected zone of overlay weld metal reheated to AC3 transformation point or higher: Heat-affected zone of under-welded metal reheated below AC3 transformation point 5: Steel plate 6: Back 7: Sealing weld 8: Overlay welding lamination state 9: Overlay welding lamination state 10: Charpy test piece Position, notch direction (position A)
11: Position of Charpy specimen, notch direction (position B)

Claims (4)

質量%で、
C :0.01〜0.2%、
Si:0.2〜1%、
Mn:0.5〜2.5%、
Al:0.002〜0.1%、
Ti:0.01〜0.3%、
B:0.001〜0.015%、
N:0.001〜0.01%
を含有し、
P:0.02%以下、
S:0.01%以下、
O:0.01%以下
に制限し、かつ下記(1)式で示される炭素当量(Ceq.)が0.3〜0.5%を満足し、
さらに、
Mo:0〜0.2%、
W:0〜0.1%、
Nb:0〜0.01%、
V:0〜0.05%、
Ta:0〜0.05%
の1種または2種以上を含有し、かつ下記(2)式で示されるNb当量(Nbeq.)が0.01%以下であり、残部が不可避不純物およびFeからなることを特徴とする下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤ。
Ceq.=C%+Mn%/6+Si%/24+Ni%/40+Cr%/5
・ ・ ・(1)
Nbeq.=Nb%+V%/5+Mo%/20+W%/10+Ta%/5
・ ・ ・(2)
% By mass
C: 0.01-0.2%
Si: 0.2-1%,
Mn: 0.5 to 2.5%
Al: 0.002 to 0.1%,
Ti: 0.01 to 0.3%,
B: 0.001 to 0.015%,
N: 0.001 to 0.01%
Containing
P: 0.02% or less,
S: 0.01% or less,
O: It is limited to 0.01% or less, and the carbon equivalent (Ceq.) Represented by the following formula (1) satisfies 0.3 to 0.5%,
further,
Mo: 0 to 0.2%,
W: 0 to 0.1%
Nb: 0 to 0.01%,
V: 0 to 0.05%,
Ta: 0 to 0.05%
1 or 2 or more, the Nb equivalent (Nbeq.) Represented by the following formula (2) is 0.01% or less, and the balance consists of inevitable impurities and Fe Solid wire for gas shielded arc welding for welding.
Ceq. = C% + Mn% / 6 + Si% / 24 + Ni% / 40 + Cr% / 5
(1)
Nbeq. = Nb% + V% / 5 + Mo% / 20 + W% / 10 + Ta% / 5
(2)
質量%で、さらに、
Ni:0.01〜6%、
Cu:0.01〜1.5%、
Cr:0.01〜1.5%
の1種または2種以上を含有することを特徴とする請求項1に記載の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤ。
In mass%,
Ni: 0.01-6%,
Cu: 0.01 to 1.5%,
Cr: 0.01 to 1.5%
The solid wire for gas shield arc welding for underlay welding according to claim 1, comprising one or more of the following.
質量%で、さらに、
Ca:0.0002〜0.01%、
Mg:0.0002〜0.01%、
REM:0.0002〜0.01%
の1種または2種以上を含有することを特徴とする請求項1または2に記載の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤ。
In mass%,
Ca: 0.0002 to 0.01%,
Mg: 0.0002 to 0.01%,
REM: 0.0002 to 0.01%
The solid wire for gas shielded arc welding for underlay welding according to claim 1 or 2, characterized by containing one or more of the following.
多層盛ガスシールドアーク溶接において最大入熱量が最小入熱量の1.5倍以上である入熱条件で用いることを特徴とする請求項1〜3のいずれかに記載の下盛り溶接用ガスシールドアーク溶接用ソリッドワイヤ。 The gas shield arc for underlay welding according to any one of claims 1 to 3, wherein the maximum heat input is 1.5 times or more of the minimum heat input in multi-layer prime gas shield arc welding. Solid wire for welding.
JP2004176771A 2004-06-15 2004-06-15 Solid wire for gas shielded arc welding for underlay welding. Expired - Fee Related JP4469226B2 (en)

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JP2007253163A (en) * 2006-03-20 2007-10-04 Nippon Steel Corp Solid wire for gas shielded arc welding
CN100462185C (en) * 2006-12-05 2009-02-18 金秋生 Welding wire for gas shielded arc welding for high-tensile structural steel
KR101568517B1 (en) * 2013-12-24 2015-11-11 주식회사 포스코 Solid wire for gas-metal arc welding
JP2016124025A (en) * 2015-01-08 2016-07-11 日鐵住金溶接工業株式会社 Gas shield arc welding solid wire
CN105848820A (en) * 2013-12-24 2016-08-10 Posco公司 Ultrahigh-strength gas metal arc welded joint having excellent impact toughness, and solid wire for producing same
JP2019005770A (en) * 2017-06-21 2019-01-17 新日鐵住金株式会社 Method for manufacturing joint by multilayer welding
CN110682028A (en) * 2019-10-15 2020-01-14 南京钢铁股份有限公司 Submerged arc welding wire for refractory steel with yield strength of 420MPa
JPWO2020090939A1 (en) * 2018-10-31 2021-09-30 旭化成建材株式会社 Welding method of square steel pipe and square steel pipe

Cited By (13)

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JP2007253163A (en) * 2006-03-20 2007-10-04 Nippon Steel Corp 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
CN100462185C (en) * 2006-12-05 2009-02-18 金秋生 Welding wire for gas shielded arc welding for high-tensile structural steel
JP2017508876A (en) * 2013-12-24 2017-03-30 ポスコPosco Ultra-high strength gas metal arc welded joint with excellent impact toughness, and solid wire for manufacturing the same
CN105848820A (en) * 2013-12-24 2016-08-10 Posco公司 Ultrahigh-strength gas metal arc welded joint having excellent impact toughness, and solid wire for producing same
KR101568517B1 (en) * 2013-12-24 2015-11-11 주식회사 포스코 Solid wire for gas-metal arc welding
JP2018047507A (en) * 2013-12-24 2018-03-29 ポスコPosco Solid wire for producing ultra-high strength gas-metal arc welded joint having excellent impact toughness
US10266929B2 (en) 2013-12-24 2019-04-23 Posco Ultrahigh-strength gas metal arc welded joint having excellent impact toughness, and solid wire for producing same
JP2016124025A (en) * 2015-01-08 2016-07-11 日鐵住金溶接工業株式会社 Gas shield arc welding solid wire
JP2019005770A (en) * 2017-06-21 2019-01-17 新日鐵住金株式会社 Method for manufacturing joint by multilayer welding
JPWO2020090939A1 (en) * 2018-10-31 2021-09-30 旭化成建材株式会社 Welding method of square steel pipe and square steel pipe
JP7252249B2 (en) 2018-10-31 2023-04-04 旭化成建材株式会社 Square steel pipe and welding method for square steel pipe
CN110682028A (en) * 2019-10-15 2020-01-14 南京钢铁股份有限公司 Submerged arc welding wire for refractory steel with yield strength of 420MPa

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