JP4531617B2

JP4531617B2 - Flux-cored wire for gas shielded arc welding

Info

Publication number: JP4531617B2
Application number: JP2005111293A
Authority: JP
Inventors: 政男鎌田; 力也高山; 康伸重森
Original assignee: 日鐵住金溶接工業株式会社
Priority date: 2005-04-07
Filing date: 2005-04-07
Publication date: 2010-08-25
Anticipated expiration: 2025-04-07
Also published as: JP2006289404A

Description

本発明は軟鋼および４９０Ｎ／ｍｍ²級高張力鋼などの溶接構造物を製造する際に使用するガスシールドアーク溶接用フラックス入りワイヤに係わるものであり、特に鋼板の片面突き合わせ継手溶接（以後、片面継手溶接という。）の初層パスで問題となる耐高温割れ性を向上させたガスシールドアーク溶接用フラックス入りワイヤ（以下、フラックス入りワイヤという。）に関する。 The present invention relates to a flux-cored wire for gas shielded arc welding used when manufacturing welded structures such as mild steel and 490 N / mm ² grade high-strength steel. This relates to a flux-cored wire for gas shield arc welding (hereinafter referred to as a flux-cored wire) that has improved hot cracking resistance, which is a problem in the first layer pass of joint welding.

造船での溶接には、ＴｉＯ₂系フラックス入りワイヤを使用して、鋼板の片面継手溶接を自動および半自動溶接で行っている。図１（ａ）に片面継手の開先形状、図１（ｂ）にその溶接状況例（下向姿勢の場合）を示す。鋼板１を開先角度θ、ルート間隔Ｇの開先形状にして突き合わせ、開先裏面にセラミックス裏当材２（以下、裏当材という。）を当てて、初層パスで裏ビード３を形成した後、順に積層して継手溶接金属４を形成する。 For welding in shipbuilding, TiO ₂ flux-cored wires are used, and single-sided joint welding of steel plates is performed automatically and semi-automatically. FIG. 1 (a) shows the groove shape of a single-sided joint, and FIG. 1 (b) shows an example of the welding situation (in the downward posture). The steel plate 1 is abutted with a groove shape having a groove angle θ and a route interval G, and a ceramic backing material 2 (hereinafter referred to as backing material) is applied to the back surface of the groove to form a back bead 3 by the first layer pass. After that, the joint weld metal 4 is formed by sequentially laminating.

溶接姿勢は、下向、立向など全姿勢で行われるが、特に下向姿勢の片面継手溶接における初層パスはその凝固形態からビード中央に高温割れが発生しやすいので、高温割れ防止の観点から溶接電流および溶接速度を抑え、また、鋼板１の開先角度θおよびルート間隔Ｇもあまり小さくしないで溶接されている。 Welding postures are performed in all orientations, such as downward and vertical, but the first layer pass in single-sided joint welding, especially in downward orientation, tends to cause hot cracking in the center of the bead due to its solidification form, so the viewpoint of preventing hot cracking Therefore, the welding current and the welding speed are suppressed, and the groove angle θ and the route interval G of the steel plate 1 are not reduced so much.

しかるに、最近、溶接能率を上げるために、溶接電流を高めて溶接速度を速くすること、あるいは開先角度θおよびルート間隔Ｇを小さくした狭い開先形状にして、溶接パス数を少なくして溶接した場合でも、高温割れが発生しにくいフラックス入りワイヤの開発要望が強い。 However, recently, in order to increase the welding efficiency, welding is performed by increasing the welding current to increase the welding speed, or by forming a narrow groove shape with a small groove angle θ and route interval G, thereby reducing the number of welding passes. Even in this case, there is a strong demand for the development of flux-cored wires that do not easily generate hot cracks.

これに対し、Ｐ、Ｓの低減以外にＳｎ、Ｂ、Ｂｉ、Ｐｂの含有量を規制することにより耐高温割れ性を改良したフラックス入りワイヤの提案がある（例えば、特許文献１、２参照）。 On the other hand, there is a proposal of a flux-cored wire that has improved hot cracking resistance by regulating the contents of Sn, B, Bi, and Pb in addition to reducing P and S (see, for example, Patent Documents 1 and 2). .

しかし、前記技術のようなフラックス入りワイヤの不純物低減だけでは現場的に安定した耐高温割れ性向上効果が得られない。特に半自動下向姿勢で、鋼板の開先角度３０〜４０°、ルート間隔３〜５ｍｍのような狭い開先形状にして、初層パスを溶接電流２３０〜２５０Ａ程度（ワイヤ径１．２ｍｍ）と高くすると、ビード中央に微小な高温割れが点々と発生する場合がある。これは狭い開先形状や高電流の溶接条件になるほど、半自動溶接特有のアーク状態や溶接速度の変動が裏ビード形成に敏感に影響することによる。特に裏ビードの形状が不均一になって開先内ビード表面に凹んだ部分ができると、その箇所に微小な高温割れの発生頻度が高くなる。従って、狭い開先形状で、かつ高電流の溶接条件でも安定した耐高温割れ性を得るためには、裏ビードを安定して形成できる溶接が可能なフラックス入りワイヤが必要となる。 However, only the reduction of impurities in the flux-cored wire as in the above-described technique does not provide an on-site stable hot crack resistance improvement effect. Especially in a semi-automatic downward posture, the groove angle of the steel sheet is 30-40 °, and the narrow groove shape is such that the route interval is 3-5 mm, and the initial layer path is about 230-250 A welding current (wire diameter 1.2 mm). If it is increased, minute hot cracks may occur in the center of the bead. This is because the narrower groove shape and the higher current welding conditions are more sensitive to the back bead formation due to variations in arc conditions and welding speed that are unique to semi-automatic welding. In particular, if the shape of the back bead is non-uniform and a recessed portion is formed on the surface of the bead in the groove, the frequency of occurrence of minute hot cracks increases at that location. Therefore, in order to obtain a stable hot crack resistance even under high current welding conditions with a narrow groove shape, a flux-cored wire capable of welding that can stably form a back bead is required.

また、フラックス入りワイヤが含有するＰ、Ｓを始めとし、凝固時に不純物として高温割れを発生しやすくするＳｎ、Ｂ、Ｂｉ、Ｐｂを規制することは初層パスの高温割れ防止のための必須要件であるが、全姿勢溶接用フラックス入りワイヤにおいて、Ｂｉ、ＰｂおよびＳはスラグ剥離性、Ｂは溶接金属の衝撃靱性に効果的に作用する成分であり、これら溶接性能の劣化に対しての回復手段についても十分に配慮する必要がある。 In addition, P, S contained in the flux-cored wire, and Sn, B, Bi, Pb, which make it easy to generate hot cracks as impurities during solidification, are essential requirements for preventing hot cracks in the first layer pass. However, in all-position welding flux-cored wires, Bi, Pb, and S are components that effectively act on the slag peelability, and B is a component that effectively acts on the impact toughness of the weld metal. Sufficient consideration should be given to the means.

なお、ＴｉＯ₂を低めにし、ＣａＯ、ＭｇＯを含有させて溶融スラグの塩基度を高め、酸素量低減による耐高温割れ性向上を図ったフラックス入りワイヤの提案もある（例えば、特許文献３参照）。しかし、上向や立向姿勢でメタル垂れが発生しやすく、全姿勢溶接用フラックス入りワイヤとしては、耐高温割れ性向上に偏らず、溶接条件範囲が広く良好な溶接作業性が得られることも必要である。 In addition, there is also a proposal of a flux-cored wire in which TiO ₂ is lowered, CaO and MgO are contained to increase the basicity of the molten slag, and the high temperature crack resistance is improved by reducing the amount of oxygen (see, for example, Patent Document 3). . However, metal dripping is likely to occur in an upward or vertical position, and as a flux-cored wire for welding in all positions, there is a tendency to improve the hot cracking resistance and a wide welding condition range and good welding workability can be obtained. is necessary.

特開２００２−１３７０９０号公報JP 2002-137090 A 特開２００３−３１１４７６号公報Japanese Patent Laid-Open No. 2003-311476 特開昭６２−１５１２９３号公報Japanese Patent Laid-Open No. 62-151293

本発明は、片面継手溶接の初層パスで問題となる耐高温割れ性の一段の向上とともに、スラグ剥離性や上向や立向姿勢での耐メタル垂れ性など溶接作業性および溶接金属の衝撃靱性が良好なガスシールド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とする。 The present invention further improves the hot cracking resistance, which is a problem in the first pass of single-sided joint welding, as well as welding workability such as slag peelability and resistance to metal sag in upward and vertical positions, and the impact of weld metal. An object of the present invention is to provide a flux-cored wire for gas shielded arc welding with good toughness.

本発明の要旨は、構成外皮内にフラックスを充填してなるガスシールドアーク溶接用フラックス入りワイヤにおいて、ワイヤ全質量に対する質量％で、
ＴｉＯ_２：５．１〜６．５％、
ＳｉＯ_２：０．３〜０．７％、
ＺｒＯ_２：０．１〜０．４％、
ＣａＯ：０．０１〜０．０４％、
Ｎａ_２ＯおよびＫ_２Ｏの合計：０．０５〜０．２０％、
Ｆ：０．０２〜０．１５％、
Ｃ：０．０６〜０．１２％、
Ｓｉ：０．３〜０．６％、
Ｍｎ：１．８〜２．４％
但し、Ｍｎ／Ｓｉ：３．６以上、
Ａｌ：０．１〜０．６％、
Ｍｇ：０．１〜０．４％、
但し、Ａｌ＋Ｍｇ：０．４〜０．８％を含有し、かつ、
Ｐ：０．０１５％以下、
Ｓ：０．０１０％以下、
Ｂ：０．００２％以下、
Ｂｉ：０．００２％
以下で、残部は鋼製外皮およびフラックスのＦｅおよび不可避的不純物からなることを特徴とするガスシールドアーク溶接用フラックス入りワイヤにある。
The gist of the present invention is, in a flux-cored wire for gas shield arc welding formed by filling a flux in the outer skin, in mass% with respect to the total mass of the wire,
TiO _2: 5.1~6.5%,
SiO _2: 0.3~0.7%,
ZrO ₂ : 0.1 to 0.4%,
CaO: 0.01 to 0.04%,
Total Na ₂ O and _{K 2} O: _0.05~0.20%,
F: 0.02 to 0.15%,
C: 0.06 to 0.12%,
Si: 0.3-0.6%
Mn: 1.8 to 2.4%
However, Mn / Si: 3.6 or more,
Al: 0.1 to 0.6%,
Mg: 0.1 to 0.4%
However, Al + Mg: 0.4 to 0.8%, and
P: 0.015% or less,
S: 0.010% or less,
B: 0.002% or less,
Bi: 0.002%
In the following, the balance is in the flux-cored wire for gas shielded arc welding, characterized in that it consists of a steel sheath and Fe of flux and unavoidable impurities.

本発明のガスシールドアーク溶接用フラックス入りワイヤによれば、狭い開先形状の片面継手溶接の初層パスを高電流の溶接条件で行った場合でも高温割れが発生しにくく、かつ、全姿勢溶接用ワイヤとして保有すべき各種溶接作業性および溶接金属の衝撃靱性が得られるので、溶接の高能率化および溶接部の品質向上が図れる。 According to the flux-cored wire for gas shielded arc welding of the present invention, even when the first layer pass of narrow groove-shaped single-sided joint welding is performed under high current welding conditions, high temperature cracking is unlikely to occur, and all-position welding is performed. Since various welding workability and impact toughness of weld metal to be possessed as a wire for welding are obtained, it is possible to improve the welding efficiency and improve the quality of the welded portion.

本発明者らは、種々フラックス入りワイヤを試作して、狭開先片面継手溶接における耐高温割れ性、全姿勢溶接における溶接作業性および溶接金属の衝撃靱性に及ぼす各種成分の影響について詳細に検討した。 The inventors made various types of flux-cored wires and examined in detail the effects of various components on hot crack resistance in narrow groove single-sided joint welding, welding workability in all-position welding, and impact toughness of weld metal did.

片面継手溶接における半自動溶接では、高電流の溶接条件になるとアーク状態も激しさを増し、溶接速度も必然的に速くなるので、良好な形状の裏ビードの形成が難しくなる。特に狭開先の初層パスでの溶接では、アーク点近傍における溶融スラグの追従性が悪く、溶融スラグがアーク点より先行しすぎたり、或いは後退しすぎると、溶接作業者は裏ビードを出すために最適な位置にアーク点を移そうとして瞬間的に溶接速度を変化させる。この時、アーク状態が不安定となり裏ビードの形状が乱れ、開先内のビードが長手方向に凹凸（起伏）が生じた形状となり、その凹み部に微小な高温割れが発生しやすくなる。 In semi-automatic welding in single-sided joint welding, the arc state increases in intensity and the welding speed inevitably increases under high current welding conditions, making it difficult to form a well-shaped back bead. Especially in welding in the first layer pass with a narrow gap, the followability of the molten slag in the vicinity of the arc point is poor, and if the molten slag is too far ahead of the arc point or retreats too much, the welding operator gives a back bead. Therefore, the welding speed is changed instantaneously in an attempt to move the arc point to the optimum position. At this time, the arc state becomes unstable, the shape of the back bead is disturbed, and the bead in the groove has a shape with irregularities (undulations) in the longitudinal direction, and minute hot cracks are likely to occur in the recess.

そこで、スラグ剤について検討した結果、狭開先片面継手溶接の初層パスで重要な溶融スラグの追従性が、特にＣａＯを微量含有させたスラグ系により改善できることを見出し、凹凸がなく均一な裏ビードを安定して形成できるようにした。 Therefore, as a result of studying the slag agent, it was found that the followability of molten slag, which is important in the first layer pass of narrow groove single-sided joint welding, can be improved by a slag system containing a trace amount of CaO in particular. A bead can be formed stably.

また、開先形状が狭くなると裏ビードが出にくく不均一になることに対しては、特にＣを高めにして、アーク吹きつけを強めにした方が鋼板のルート部の溶融が容易になり、安定した裏ビード形成に効果的である。 In addition, when the groove shape becomes narrower, the back bead is less likely to be uneven, and in particular, it is easier to melt the root part of the steel plate by increasing C and strengthening the arc spray, Effective for stable back bead formation.

フラックス入りワイヤが不可避的不純物として含有し耐高温割れ性を著しく損なうＰ、Ｓ、ＢｉおよびＢについては、鋼製外皮、原料フラックスの選択および成分設計により極力低減した。 About P, S, Bi, and B which a flux cored wire contains as an unavoidable impurity and remarkably impairs hot cracking resistance, it was reduced as much as possible by selecting a steel outer shell, a raw material flux, and a component design.

スラグ剥離性および溶接金属の衝撃靱性に対しては、スラグ剤、合金剤、脱酸剤およびアーク安定剤を種々組み合わせることによって良好な結果が得られるようにした。 For slag peelability and impact toughness of weld metal, good results were obtained by various combinations of slag agents, alloying agents, deoxidizers and arc stabilizers.

以下に、本発明のフラックス入りワイヤの成分限定理由を述べる。 The reasons for limiting the components of the flux-cored wire of the present invention will be described below.

ＴｉＯ₂：５．１〜６．５質量％（以下、％という。）
ルチール、チタンスラグなどを原料として、ＴｉＯ₂が５．１％未満では、溶融スラグの粘性が不足して上向や立向姿勢でメタル垂れが発生しやすく、ビード形状が凸状になるなど全姿勢溶接用ワイヤとしての溶接作業性が劣化する。また、スラグ生成量が不足して、立向下進溶接ではスラグ剥離性が劣化する。一方、ＴｉＯ₂が６．５％を超えるとスラグ生成量が多すぎて、狭開先片面継手溶接の初層パスでスラグ追従性が不安定になり、裏ビードに凹凸が生じ高温割れが発生しやすくなる。 TiO ₂ : 5.1-6.5% by mass (hereinafter referred to as “%”)
If TiO ₂ is less than 5.1% using rutile, titanium slag, etc. as a raw material, the viscosity of the molten slag is insufficient, and metal dripping is likely to occur in an upward or vertical position, and the bead shape becomes convex. Welding workability as a posture welding wire deteriorates. Moreover, the amount of slag generation is insufficient, and the slag peelability deteriorates in vertical downward welding. On the other hand, if TiO ₂ exceeds 6.5%, the amount of slag generated is too large, and the slag followability becomes unstable in the first layer pass of the narrow groove single-sided joint welding, resulting in unevenness on the back bead and high temperature cracking. It becomes easy to do.

ＳｉＯ₂：０．３〜０．７％
珪砂、ジルコンサンドなどを原料として、ＳｉＯ₂が０．３％未満では、スラグ被包状態が悪く各姿勢溶接ともスラグ剥離性、ビード形状、外観が不良となる。一方、ＳｉＯ₂が０．７％を超えると、溶融スラグの凝固が遅れて上向、立向姿勢溶接でメタル垂れが発生しやすくなる。溶接金属のＳｉ歩留まりが上がり衝撃靱性が劣化する。片面継手溶接の初層パスでは溶融スラグの追従性が不安定になり、裏ビードに凹凸が生じ高温割れが発生しやすくなる。 SiO ₂ : 0.3 to 0.7%
When silica ₂ or less is less than 0.3% using silica sand, zircon sand, or the like as a raw material, the slag encapsulation state is poor and slag peelability, bead shape, and appearance are poor in each position welding. On the other hand, if SiO ₂ exceeds 0.7%, solidification of the molten slag is delayed, and metal dripping is likely to occur during upward and vertical position welding. The Si yield of the weld metal increases and the impact toughness deteriorates. In the first layer pass of single-sided joint welding, the followability of the molten slag becomes unstable, and irregularities are formed on the back bead and high temperature cracking is likely to occur.

ＺｒＯ₂：０．１〜０．４％
ジルコンサンド、酸化ジルコンなどを原料として、ＺｒＯ₂が０．１％未満では、立向姿勢溶接の耐メタル垂れ性や水平すみ肉溶接のビード形状が劣化する。また、狭開先片面継手溶接の初層パスでは、溶融スラグが先行しやすくなり裏ビードが出にくく、高温割れも発生しやすくなる。一方、ＺｒＯ₂が０．４％を超えるとスラグ剥離性が劣化する。 ZrO ₂ : 0.1 to 0.4%
If ZrO ₂ is less than 0.1% using zircon sand, zircon oxide or the like as a raw material, the metal drooping resistance of vertical position welding and the bead shape of horizontal fillet welding deteriorate. Further, in the first layer pass of the narrow groove single-sided joint welding, the molten slag is likely to precede, the back bead is not easily generated, and hot cracking is likely to occur. On the other hand, when ZrO ₂ exceeds 0.4%, the slag removability deteriorates.

ＣａＯ：０．０１〜０．０４％
ＣａＯを含有する溶融原料、Ｃａ化合物などを原料として、ＣａＯを０．０１％以上含有させることにより、溶融スラグの流動性か調整され狭開先片面継手溶接の初層パスの溶融スラグ追従性を改善できる。また、スラグ剥離性の改善効果も認められる。一方、ＣａＯが０．０４％を超えると溶融スラグの流動性が過剰になり上向や立向姿勢溶接の溶接作業性が劣化する。狭開先片面継手溶接の初層パスでは溶融スラグの追従性が不安定になり、裏ビードの凹凸とともに高温割れが発生しやすくなる。 CaO: 0.01 to 0.04%
By using 0.01% or more of CaO as a raw material containing a CaO-containing molten raw material or Ca compound, the fluidity of the molten slag is adjusted, and the molten slag followability of the first layer pass of narrow groove single-sided joint welding Can improve. Moreover, the improvement effect of slag peelability is also recognized. On the other hand, if CaO exceeds 0.04%, the fluidity of the molten slag becomes excessive, and the welding workability of upward and vertical posture welding deteriorates. In the first layer pass of narrow groove single-sided joint welding, the followability of the molten slag becomes unstable, and hot cracks are likely to occur along with the irregularities of the back bead.

Ｎａ₂ＯおよびＫ₂Ｏの合計：０．０５〜０．２０％
チタン酸ソーダ、カリ長石などを原料として、Ｎａ₂ＯおよびＫ₂Ｏの合計で０．０５％未満では、アーク状態が不安定になるとともに、上向や立向姿勢溶接でメタルが垂れやすくビード形状が不良になる。また、狭開先片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビードの凹凸とともに高温われが発生しやすくなる。一方、Ｎａ₂ＯおよびＫ₂Ｏの合計が０．２０％を超えると、溶融スラグの流動性が過剰になり、上向および立向姿勢溶接でメタル垂れが発生しやすく、スラグ剥離性も劣化する。狭開先片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、高温割れが発生しやすく、スラグ剥離性も劣化する。 Total Na ₂ O and K ₂ O: 0.05~0.20%
If the total amount of Na ₂ O and K ₂ O is less than 0.05% using sodium titanate, potash feldspar, etc. as the raw material, the arc state becomes unstable and the bead is prone to droop during upward and vertical welding. The shape becomes defective. Further, in the first layer pass of the narrow groove single-sided joint welding, the followability of the molten slag is unstable, and high temperature cracks are likely to occur along with the irregularities of the back bead. On the other hand, if the total of Na ₂ O and K ₂ O exceeds 0.20%, the fluidity of the molten slag becomes excessive, metal dripping is likely to occur during upward and vertical welding, and the slag peelability is also degraded. To do. In the first pass of narrow groove single-sided joint welding, the followability of the molten slag is unstable, high temperature cracking is likely to occur, and the slag peelability is also deteriorated.

Ｆ：０．０２〜０．１５％
弗化ソーダや珪弗化カリなどの弗化物を原料として、Ｆが０．０２％未満では、アークの集中性が弱く、立向下進溶接でメタル垂れが発生しやすくなる。また、狭開先片面継手溶接の初層パスで裏ビードが出にくく、さらに溶融スラグの流動性が不足気味で、溶融スラグ追従性が不安定せず、裏ビードの凹凸とともに高温割れが発生しやすくなる。一方、Ｆが０．１５％を超えると、溶融スラグの流動性が過剰で、上向、立向姿勢溶接でメタル垂れが発生しやすくなり、水平すみ肉溶接ではビード形状が凸気味になる。また、狭開先片面継手溶接の初層パスでは、アークの吹きつけが強すぎ、溶融スラグの流動性も過剰になり、溶融スラグの追従性が不安定で、裏ビードの凹凸とともに高温割れが発生しやすくなる。 F: 0.02 to 0.15%
If fluoride such as sodium fluoride or potassium silicofluoride is used as a raw material and F is less than 0.02%, the arc concentration is weak and metal dripping is likely to occur during vertical downward welding. In addition, the back bead is hard to come out in the first layer pass of narrow groove single-sided joint welding, and the fluidity of the molten slag seems to be insufficient, the molten slag followability does not become unstable, and hot cracks occur along with the unevenness of the back bead. It becomes easy. On the other hand, if F exceeds 0.15%, the fluidity of the molten slag is excessive, metal sag is likely to occur during upward and vertical position welding, and the bead shape becomes uneven in horizontal fillet welding. Also, in the first layer pass of narrow groove single-sided joint welding, the arc blowing is too strong, the fluidity of the molten slag becomes excessive, the followability of the molten slag is unstable, and hot cracks occur along with the unevenness of the back bead. It tends to occur.

Ｃ：０．０６〜０．１２％
フラックスおよび外皮成分の合計で、Ｃが０．０６％未満では溶接金属の衝撃靱性が低下する。一方、Ｃが０．１２％を超えると強度が高くなりすぎて衝撃靱性が低下する。
なお、狭開先片面継手溶接の初層パスの裏ビードが出にくいので、鋼製外皮のＣを０．０３％以上にしてアーク状態を強めにすることが好ましい。しかし、鋼製外皮のＣが０．０８％を超えると、アーク状態が強くなりすぎて、溶融スラグの追従性が不安定になるので、裏ビードの凹凸とともに高温割れが発生しやすくなる。したがって、鋼製外皮のＣは、０．０３〜０．０８％であることが好ましい。 C: 0.06 to 0.12%
When C is less than 0.06% in total of the flux and the skin component, the impact toughness of the weld metal is lowered. On the other hand, if C exceeds 0.12%, the strength becomes too high and the impact toughness decreases.
In addition, since the back bead of the first layer pass of the narrow groove single-sided joint welding is difficult to occur, it is preferable to make the arc state stronger by making C of the steel outer shell 0.03% or more. However, if C of the steel outer shell exceeds 0.08%, the arc state becomes too strong and the followability of the molten slag becomes unstable, so that hot cracks are likely to occur along with the irregularities of the back bead. Therefore, C of the steel outer shell is preferably 0.03 to 0.08%.

Ｓｉ：０．３〜０．６％
Ｓｉは、溶接金属の強度および衝撃靱性を確保するために、フラックスおよび外皮成分の合計で０．３％以上含有させる。Ｓｉが０．３％未満では、強度および衝撃靱性が低下する。一方、Ｓｉが０．６％を超えた場合も衝撃靱性が低下する。 Si: 0.3-0.6%
In order to ensure the strength and impact toughness of the weld metal, Si is contained in a total of 0.3% or more of the flux and the skin component. If Si is less than 0.3%, strength and impact toughness are lowered. On the other hand, impact toughness also decreases when Si exceeds 0.6%.

Ｍｎ：１．８〜２．４％
Ｍｎは、溶接金属の強度、衝撃靱性の確保および脱酸反応で生成するＭｎ酸化物を溶融スラグ成分として利用するために、フラックスおよび外皮成分の合計で１．８〜２．４％含有させる。Ｍｎが１．８％未満では強度および衝撃靱性が低下する。一方、Ｍｎが２．４％を超えるとＭｎ酸化物の生成が多くなり、片面継手溶接でスラグ追従性が不安定になり、裏ビードの凹凸とともに高温割れが発生しやすくなる。 Mn: 1.8 to 2.4%
Mn is contained in a total amount of 1.8 to 2.4% of the flux and the skin component in order to ensure the strength of the weld metal, impact toughness, and to use the Mn oxide generated by the deoxidation reaction as a molten slag component. If Mn is less than 1.8%, strength and impact toughness are lowered. On the other hand, if Mn exceeds 2.4%, the production of Mn oxide increases, the slag followability becomes unstable by single-sided joint welding, and hot cracks are likely to occur along with the unevenness of the back bead.

溶接金属の衝撃靱性を確保するために、ＭｎとＳｉの比Ｍｎ／Ｓｉを３．６以上とする。Ｍｎ／Ｓｉが３．６未満では衝撃靱性が低下する。 In order to ensure the impact toughness of the weld metal, the ratio Mn / Si of Mn / Si is set to 3.6 or more. When Mn / Si is less than 3.6, impact toughness is lowered.

Ａｌ：０．１〜０．６％
Ａｌは、フラックスおよび外皮成分の合計で、０．１％以上含有させることによって溶接金属の酸素量の低下とともにＳｉ、Ｍｎの歩留まりを上げ、強度および衝撃靱性を向上させる。一方、Ａｌが０．６％を超えると強度が高くなりすぎて衝撃靱性が低下し、また、脱酸生成物であるＡｌ₂Ｏ₃が溶融スラグ中に過剰に増加するため、狭開先片面継手溶接では溶融スラグの追従性が安定せず、裏ビードの凹凸とともに高温割れが発生しやすくなる。 Al: 0.1 to 0.6%
By adding 0.1% or more of the total amount of flux and skin component, Al increases the yield of Si and Mn as the oxygen content of the weld metal decreases, and improves strength and impact toughness. On the other hand, if Al exceeds 0.6%, the strength becomes too high and impact toughness decreases, and Al ₂ O ₃ which is a deoxidation product excessively increases in the molten slag. In joint welding, the followability of the molten slag is not stable, and high temperature cracks are likely to occur along with the unevenness of the back bead.

Ｍｇ：０．１〜０．４％
Ｍｇは、０．１％以上含有させることによって、スラグ剥離性を良好にし、溶接属の酸素量が低下して衝撃靱性を向上させる。また、脱酸生成物であるＭｇＯは水平すみ肉ビード形状を良好にする。一方、Ｍｇが０．４％を超えると、脱酸生成物であるＭｇＯが溶融スラグ中に過剰に増加し、立向姿勢溶接でメタル垂れが発生しやすくなる。また、狭開先片面継手溶接の初層パスでは、溶融スラグの追従性が不安定になり、裏ビードの凹凸とともに高温割れが発生しやすくなる。 Mg: 0.1 to 0.4%
When Mg is contained in an amount of 0.1% or more, the slag peelability is improved, and the oxygen content of the welding genus is reduced to improve the impact toughness. Moreover, MgO which is a deoxidation product makes a horizontal fillet bead shape favorable. On the other hand, if Mg exceeds 0.4%, MgO, which is a deoxidation product, excessively increases in the molten slag, and metal dripping is likely to occur during vertical position welding. Further, in the first layer pass of the narrow groove single-sided joint welding, the followability of the molten slag becomes unstable, and high temperature cracks are likely to occur along with the unevenness of the back bead.

溶接金属の衝撃靱性を確保するために、ＡｌとＭｇの合計を０．４％以上にする。また、狭開先片面継手溶接の初層パスでは、溶融スラグの追従性が安定し、耐高温割れ性、裏ビード形状、スラグ剥離性とも良好になる。 In order to ensure the impact toughness of the weld metal, the total of Al and Mg is made 0.4% or more. Further, in the first layer pass of the narrow groove single-sided joint welding, the followability of the molten slag is stabilized, and the hot crack resistance, the back bead shape, and the slag peelability are improved.

ＡｌとＭｇの合計が０．４％未満であると、溶接金属の衝撃靱性が低下する。一方、ＡｌとＭｇの合計が０．９％を超えると上向や立向姿勢溶接でメタルが垂れやすくビード形状不良、また、スラグがビード表面に焼き付きスラグ剥離性が劣化する。 When the total of Al and Mg is less than 0.4%, the impact toughness of the weld metal is lowered. On the other hand, if the total of Al and Mg exceeds 0.9%, the metal is liable to sag during upward or vertical welding, and the slag is seized on the bead surface and the slag peelability is deteriorated.

Ｐ：０．０１０％以下、Ｓ：０．００５％以下
Ｐ、Ｓはフラックス原料および鋼製外皮から不可避的不純物として含有される成分であるが、鋼製外皮およびフラックス原料の選択により、Ｐを０．０１５％以下、Ｓを０．０１０％以下に制限することは、耐高温割れ性および衝撃靱性に極めて効果的である。 P: 0.010% or less, S: 0.005% or less P and S are components contained as inevitable impurities from the flux raw material and the steel outer shell, but depending on the choice of the steel outer shell and the flux raw material, P Limiting to 0.015% or less and S to 0.010% or less is extremely effective for hot crack resistance and impact toughness.

Ｂ：０．００２％以下、Ｂｉ：０．００２％以下
ＢおよびＢｉは、狭開先片面継手溶接の初層パスの高温割れを防止するために含有させるもので、フラックスおよび鋼製外皮成分中に含有される合計でＢ：０．００２％以下、Ｂｉ：０．００２％以下とする。 B: 0.002% or less, Bi: 0.002% or less B and Bi are included to prevent high temperature cracking in the first layer pass of narrow groove single-sided joint welding. The total content of B is 0.002% or less and Bi is 0.002% or less.

本発明のフラックス入りワイヤは、上記構成により狭開先片面継手溶接の初層パスの耐高温割れ性が向上し、スラグ剥離性や立向姿勢溶接での耐メタル垂れ性などの溶接作業性が良好で、溶接金属の衝撃靱性（ＪＩＳ規格：ＳＭ４９０Ｂ鋼やＮＫ規格ＫＤ３６鋼など、衝撃試験温度０℃で４７Ｊ以上）を十分に確保できる。 With the above configuration, the flux-cored wire of the present invention improves the hot cracking resistance of the first layer pass of narrow groove single-sided joint welding, and has improved welding workability such as slag peelability and metal dripping resistance in vertical position welding. It is good and can sufficiently ensure the impact toughness of weld metal (JIS standard: SM490B steel, NK standard KD36 steel, etc., impact test temperature 0 ° C., 47 J or more).

なお、溶接金属の衝撃靭性を確保するためにＮｉを含有させることは、反面、耐高温割れ性にマイナスの影響をおよぼすので、本発明のフラックス入りワイヤは実質的にＮｉを含有しない。 Incidentally, it is contained Ni in order to ensure impact toughness of the weld metal, the other hand, since exerts a negative impact on resistance to hot cracking, flux cored wire of the present invention have a substantially free of Ni.

また、Ａｌ₂Ｏ₃は立向上進溶接の高電流使用性を向上させるが、狭開先片面継手溶接の初層パスの高温割れ防止およびスラグ剥離性から０．５％以下に抑えることが好ましい。 In addition, Al ₂ O ₃ improves the high current usability of vertical improvement welding, but is preferably suppressed to 0.5% or less from the prevention of high-temperature cracking and slag peelability of the first layer pass of narrow groove single-sided joint welding. .

Ｆｅ₂Ｏ₃、ＦｅＯなどの酸化鉄は、水平すみ肉溶接におけるビード形状を良好にするが、上向や立向姿勢溶接の耐メタル垂れ性および狭開先片面継手溶接の初層パスの耐高温割れ性、さらに溶接金属の衝撃靱性を確保するために、０．５％以下に抑えることが好ましい。 Iron oxides such as Fe ₂ O ₃ and FeO improve the bead shape in horizontal fillet welding, but the metal sagging resistance of upward and vertical position welding and the resistance of the first layer pass of narrow groove single face joint welding. In order to ensure the high temperature cracking property and further the impact toughness of the weld metal, it is preferable to suppress it to 0.5% or less.

フラックス入りワイヤが含有する全水素量は、耐低温割れ性のためにワイヤ全質量に対する質量％で０．００４０％以下、窒素量は溶接金属の強度、衝撃靱性が劣化しないように０．００３５％以下にすることが好ましい。 The total amount of hydrogen contained in the flux-cored wire is 0.0040% or less in terms of mass% with respect to the total mass of the wire for low temperature crack resistance, and the amount of nitrogen is 0.0035% so that the strength and impact toughness of the weld metal are not deteriorated. The following is preferable.

本発明のフラックス入りワイヤはフラックス充填後の伸線加工性が良好な軟鋼または合金鋼の外皮内にフラックスを、ワイヤ全質量に対して１０〜２０％程度充填後、ダイス伸線やローラ圧延加工により所定のワイヤ径（１．０〜１．６ｍｍ）に縮径して製造されるものである。ワイヤの断面構造などは、特に限定するものではない。 The flux-cored wire of the present invention is filled with flux in the outer shell of mild steel or alloy steel with good wire drawing workability after flux filling, about 10 to 20% with respect to the total mass of the wire, followed by die drawing or roller rolling. Thus, the diameter is reduced to a predetermined wire diameter (1.0 to 1.6 mm). The cross-sectional structure of the wire is not particularly limited.

溶接用シールドガスはＣＯ₂ガスが一般的であるが、Ａｒ−ＣＯ₂などの混合ガスも使用できる。 The welding shield gas is generally CO ₂ gas, but a mixed gas such as Ar—CO ₂ can also be used.

以下に、実施例により本発明の効果をさらに詳細に示す。 Hereinafter, the effects of the present invention will be described in more detail by way of examples.

表１に示す成分の軟鋼パイプにフラックスを充填後、縮径して（外皮部の軟化および脱水素のための中間焼鈍を１回実施）、フラックス充填率１５％でワイヤ径１．２ｍｍのシームレスタイプのフラックス入りワイヤを試作した。表２および表３に試作したワイヤを示す。なお、ワイヤの全水素量は全ワイヤとも０．００２０％以下、全窒素量は０．００３０％以下であることを確認した。 After filling flux into a mild steel pipe having the components shown in Table 1, the diameter is reduced (intermediate annealing for softening and dehydrogenation of the outer skin is carried out once), and the wire diameter is 1.2% and the wire diameter is 1.2 mm. A type of flux-cored wire was prototyped. Tables 2 and 3 show the prototyped wires. It was confirmed that the total hydrogen content of the wires was 0.0020% or less for all wires and the total nitrogen content was 0.0030% or less.

まず、これら試作ワイヤを使用して、図１に示す形状の片面継手溶接試験体（鋼種：ＫＤ３６鋼、板厚ｔ：２０ｍｍ、幅４００ｍｍ、長さ５００ｍｍ、開先角度θ：３０°、ルート間隔Ｇ：５ｍｍ、裏面の拘束：３箇所）に、裏当て材（Ａｌ₂Ｏ₃−ＳｉＯ₂−ＭｇＯ系）を当てて、表３に示す溶接条件で、半自動下向姿勢で、初層パスの耐高温割れ性試験を行った。初層パスの高温割れの発生状況はＸ線透過試験により判定した First, using these prototype wires, a single-sided joint weld specimen having the shape shown in FIG. 1 (steel type: KD36 steel, sheet thickness t: 20 mm, width 400 mm, length 500 mm, groove angle θ: 30 °, route interval) G: 5 mm, back surface restraint: 3 places) with a backing material (Al ₂ O ₃ —SiO ₂ —MgO system) applied under the welding conditions shown in Table 3, semi-automatic downward posture, A hot crack resistance test was conducted. The occurrence of hot cracks in the first layer pass was determined by X-ray transmission test.

次に、初層パスでの高温割れの発生が認められなかった試験体について、表４に溶接条件により半自動下向溶接で順次積層した。このときの溶接作業性観察とともに、溶接後ＪＩＳＺ３１１１に規定されるＡ２号丸棒引張試験片およびシャルピー衝撃試験片を採取し、溶接金属の機械的性質を試験した。なお、引張強さは４９０Ｎ／ｍｍ²以上、衝撃試験は０℃におけるシャルピー吸収エネルギーが４７Ｊ以上を良好とした。 Next, the specimens in which the occurrence of hot cracking in the first layer pass was not observed were sequentially laminated in Table 4 by semiautomatic downward welding according to the welding conditions. Along with the observation of welding workability at this time, A2 round bar tensile test pieces and Charpy impact test pieces defined in JIS Z3111 were collected after welding, and the mechanical properties of the weld metal were tested. In addition, the tensile strength was 490 N / mm ² or more, and the impact test showed that Charpy absorbed energy at 0 ° C. was 47 J or more.

さらに、全姿勢溶接用ワイヤとしての半自動溶接作業性を、板厚１２ｍｍ、幅１５０ｍｍ、長さ４５０ｍｍのＳＭ４９０Ｂ鋼をＴ字型に仮組みし、上向および立向（上進、下進）姿勢溶接で、特に問題となる耐メタル垂れ性とスラグ剥離性を中心に評価した。これらの結果を表５にまとめて示した。 Furthermore, semiautomatic welding workability as a welding wire for all postures is made by temporarily assembling SM490B steel with a plate thickness of 12mm, width of 150mm, and length of 450mm into a T-shape, and upward and vertical (upward and downward) postures. Evaluation was made mainly on metal sag resistance and slag peelability, which are particularly problematic in welding. These results are summarized in Table 5.

表５中のワイヤ記号Ｗ１〜Ｗ８が本発明例、ワイヤ記号Ｗ９〜Ｗ３３は比較例である。 The wire symbols W1 to W8 in Table 5 are examples of the present invention, and the wire symbols W9 to W33 are comparative examples.

本発明例であるワイヤ記号Ｗ１〜Ｗ８は、フラックス入りワイヤの成分がいずれも適正であるので、鋼板の開先角度３０°、ルート間隙５ｍｍという狭開先にして、溶接電流２５０Ａ（溶接速度：約２０ｃｍ／ｍｉｎ）というきびしい溶接条件にも拘わらず、初層パスで問題となる高温割れの発生はなく、また、スラグ剥離性および溶接金属の強度および吸収エネルギーも十分に満足した。また、上向や立向姿勢溶接で問題となる耐メタル垂れ性およびスラグ剥離性などの溶接作業性についても良好で、きわめて満足な結果であった。 In the wire symbols W1 to W8 according to the present invention, since the components of the flux-cored wire are all appropriate, the welding current 250A (welding speed: Despite severe welding conditions of about 20 cm / min), there was no hot cracking that would be a problem in the first layer pass, and the slag peelability, weld metal strength and absorbed energy were sufficiently satisfied. In addition, the welding workability such as metal sag resistance and slag peelability, which are problems in upward and vertical position welding, was also satisfactory, and the results were extremely satisfactory.

比較例中、ワイヤ記号Ｗ９は、ＴｉＯ₂が多いので、片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生した。 In the comparative example, since the wire symbol W9 has a large amount of TiO ₂ , the followability of the molten slag was unstable in the first layer pass of single-sided joint welding, the back bead shape was uneven, and hot cracking occurred.

ワイヤ記号Ｗ１０は、ＴｉＯ₂が少ないので、上向および立向姿勢溶接でメタル垂れが発生してビード形状が不良で、立向下進溶接ではスラグ剥離性も不良であった。また、Ｓｉが多いので、吸収エネルギーが低下した。 Since the wire symbol W10 has a small amount of TiO ₂ , metal dripping occurred in upward and vertical position welding and the bead shape was poor, and slag peelability was also poor in vertical downward welding. Moreover, since there is much Si, absorbed energy fell.

ワイヤ記号Ｗ１１は、ＳｉＯ₂が多いので、上向および立向姿勢溶接でメタル垂れが発生してビード形状が不良で、また、片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生した。 Since the wire symbol W11 has a large amount of SiO ₂ , metal drooping occurs in upward and vertical position welding, and the bead shape is poor, and in the first layer pass of single-sided joint welding, the followability of molten slag is unstable. The back bead shape was uneven and hot cracking occurred.

ワイヤ記号Ｗ１２は、ＳｉＯ₂が少ないので、上向および立向姿勢溶接でメタル垂れが発生してビード形状およびスラグ剥離性が不良になった。また、片面継手溶接の初層パスでは、スラグ剥離性が不良となった。さらに、Ｃが少ないので、吸収エネルギーが低下した。 Since the wire symbol W12 has a small amount of SiO ₂ , metal dripping occurred in the upward and vertical welding, resulting in poor bead shape and slag peelability. Moreover, in the first layer pass of single-sided joint welding, the slag peelability was poor. Furthermore, since there is little C, absorbed energy fell.

ワイヤ記号Ｗ１３は、ＺｒＯ₂が多いので、各姿勢溶接でスラグ剥離性が不良であった。また、Ｍｎ／Ｓｉが小さいので吸収エネルギーが低下した。 Since the wire symbol W13 has a large amount of ZrO ₂ , the slag peelability was poor in each position welding. Moreover, since Mn / Si was small, the absorbed energy decreased.

ワイヤ記号Ｗ１４は、ＺｒＯ₂が少ないので、上向および立向姿勢溶接でメタル垂れが発生してビード形状が不良となった。また、片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生した。 Since the wire symbol W14 has a small amount of ZrO ₂ , metal dripping occurred in the upward and vertical posture welding, resulting in a poor bead shape. Also, in the first layer pass of single-sided joint welding, the followability of the molten slag was unstable, the back bead shape was uneven and hot cracking occurred.

ワイヤ記号Ｗ１５は、ＣａＯが多いので、片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生した。また、上向および立向姿勢溶接でメタル垂れが発生してビード形状が不良となった。 Since the wire symbol W15 has a lot of CaO, the followability of the molten slag is unstable in the first layer pass of single-sided joint welding, the back bead shape is uneven, and hot cracking occurs. In addition, metal drooping occurred during upward and vertical welding, resulting in poor bead shape.

ワイヤ記号Ｗ１６は、ＣａＯが少ないので、片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生した。また、各姿勢溶接でスラグ剥離性が不良であった。 In the wire symbol W16, since CaO is small, the followability of the molten slag is unstable in the first layer pass of single-sided joint welding, the back bead shape is uneven, and hot cracking occurs. Moreover, slag peelability was inferior in each posture welding.

ワイヤ記号Ｗ１７は、Ｎａ₂ＯとＫ₂Ｏの合計が多いので、上向および立向姿勢溶接でメタル垂れが発生し、スラグ剥離性も不良であった。また、片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生し、スラグ剥離性も不良であった。 In the wire symbol W17, since the total of Na ₂ O and K ₂ O was large, metal dripping occurred in the upward and vertical posture welding, and the slag peelability was also poor. Further, in the first layer pass of single-sided joint welding, the followability of the molten slag was unstable, the back bead shape was uneven, hot cracking occurred, and the slag peelability was poor.

ワイヤ記号Ｗ１８は、Ｎａ₂ＯとＫ₂Ｏの合計が少ないので、アーク状態が不安定で、片面継手溶接では高温割れが発生し、また、上向および立向姿勢溶接でメタル垂れが発生した。 As for the wire symbol W18, since the total of Na ₂ O and K ₂ O is small, the arc state is unstable, hot cracking occurs in single-sided joint welding, and metal dripping occurs in upward and vertical position welding. .

ワイヤ記号Ｗ１９は、Ｆが多いので、上向および立向姿勢溶接でメタル垂れが発生した。また、片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生した。なお、アーク状態は吹きつけが強すぎて、不安定であった。 Since there are many Fs in the wire symbol W19, metal dripping occurred in the upward and vertical posture welding. Also, in the first layer pass of single-sided joint welding, the followability of the molten slag was unstable, the back bead shape was uneven and hot cracking occurred. The arc state was unstable because the spray was too strong.

ワイヤ記号Ｗ２０は、Ｆが少ないので、立向下進溶接でメタル垂れが発生した。また、片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生した。 Since the wire symbol W20 has less F, metal dripping occurred during vertical downward welding. Also, in the first layer pass of single-sided joint welding, the followability of the molten slag was unstable, the back bead shape was uneven and hot cracking occurred.

ワイヤ記号Ｗ２１は、Ｃが多いので、引張強さが高くなり吸収エネルギーが低下した。また、ＡｌとＭｇの合計量が多いので、上向および立向姿勢溶接でメタル垂れが発生し、スラグ剥離性も劣化した。 Since the wire symbol W21 has a large amount of C, the tensile strength increased and the absorbed energy decreased. Further, since the total amount of Al and Mg was large, metal dripping occurred during upward and vertical posture welding, and the slag peelability deteriorated.

ワイヤ記号Ｗ２２は、Ｓｉが少ないので、引張強さおよび吸収エネルギーが低下した。 Since the wire symbol W22 has a small amount of Si, the tensile strength and the absorbed energy decreased.

ワイヤ記号Ｗ２３は、Ｍｎが多いので、Ｍｎ酸化物の生成量が多くなり片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生した。 Since the wire symbol W23 has a large amount of Mn, the amount of Mn oxide generated is large, and the followability of the molten slag is unstable in the first pass of single-sided joint welding, and the back bead shape is uneven and hot cracking occurs.

ワイヤ記号Ｗ２４は、Ｍｎが少ないので、吸収エネルギーが低下した。 Since the wire symbol W24 has a small amount of Mn, the absorbed energy decreased.

ワイヤ記号Ｗ２５は、Ａｌが多いので、片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生した。 Since the wire symbol W25 has a large amount of Al, the followability of the molten slag is unstable in the first layer pass of single-sided joint welding, the back bead shape is uneven, and high temperature cracking occurs.

ワイヤ記号Ｗ２６は、Ａｌが少ないので、吸収エネルギーが低下した。 Since the wire symbol W26 has a small amount of Al, the absorbed energy decreased.

ワイヤ記号Ｗ２７は、Ｍｇが多いので、上向および立向姿勢溶接でメタル垂れが発生した。また、片面継手溶接の初層パスでは溶融スラグの追従性が不安定で、裏ビード形状が不均一で高温割れが発生した。 Since the wire symbol W27 has a large amount of Mg, metal dripping occurred in the upward and vertical posture welding. Also, in the first layer pass of single-sided joint welding, the followability of the molten slag was unstable, the back bead shape was uneven and hot cracking occurred.

ワイヤ記号Ｗ２８は、Ｍｇが少ないので、吸収エネルギーが低下し、スラグ剥離性も不良であった。 Since the wire symbol W28 has a small amount of Mg, the absorbed energy was lowered and the slag peelability was also poor.

ワイヤ記号Ｗ２９は、ＡｌとＭｇの合計が少ないので、吸収エネルギーが低下した。 In the wire symbol W29, the total energy of Al and Mg is small, so the absorbed energy is reduced.

ワイヤ記号Ｗ３０はＰが多いので、ワイヤ記号Ｗ３１はＳが多いので、ワイヤ記号Ｗ３２はＢが多いので、また、ワイヤ記号Ｗ３３はＢｉが多いので、いずれも片面継手溶接の初層パスで高温割れが発生した。 Since the wire symbol W30 has a lot of P, the wire symbol W31 has a lot of S, the wire symbol W32 has a lot of B, and the wire symbol W33 has a lot of Bi, so both are hot cracks in the first layer pass of single-sided joint welding. There has occurred.

下向片面継手溶接の開先形状および溶接状況を説明するために示した模式図で、（ａ）は片面継手の開先形状、（ｂ）は溶接状況例を示す図である。It is the schematic shown in order to demonstrate the groove shape and welding condition of downward single-sided joint welding, (a) is a groove shape of a single-sided joint, (b) is a figure which shows the example of a welding condition.

Explanation of symbols

１鋼板
２裏当材
３裏ビード
４溶接金属 1 Steel plate 2 Backing material 3 Back bead 4 Weld metal

Claims

In the flux-cored wire for gas shielded arc welding formed by filling the steel outer shell with flux,
TiO _2: 5.1~6.5%,
SiO _2: 0.3~0.7%,
ZrO ₂ : 0.1 to 0.4%,
CaO: 0.01 to 0.04%,
Total Na ₂ O and _{K 2} O: _0.05~0.20%,
F: 0.02 to 0.15%,
C: 0.06 to 0.12%,
Si: 0.3-0.6%
Mn: 1.8 to 2.4%
However, Mn / Si: 3.6 or more,
Al: 0.1 to 0.6%,
Mg: 0.1 to 0.4%
However, Al + Mg: 0.4 to 0.8%, and
P: 0.015% or less,
S: 0.010% or less,
B: 0.002% or less,
Bi: 0.002% or less,
The balance consists of a steel outer sheath, flux Fe and unavoidable impurities, a flux-cored wire for gas shielded arc welding.