JP6060604B2 - Submerged arc welding method - Google Patents

Submerged arc welding method Download PDF

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JP6060604B2
JP6060604B2 JP2012222935A JP2012222935A JP6060604B2 JP 6060604 B2 JP6060604 B2 JP 6060604B2 JP 2012222935 A JP2012222935 A JP 2012222935A JP 2012222935 A JP2012222935 A JP 2012222935A JP 6060604 B2 JP6060604 B2 JP 6060604B2
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篤史 石神
篤史 石神
早川 直哉
直哉 早川
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JFE Steel Corp
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本発明は、鋼板のサブマージアーク溶接方法に関するものである。   The present invention relates to a submerged arc welding method for steel plates.

鋼板を溶接する際に用いられるサブマージアーク溶接は、大電流を供給して溶込み深さおよびワイヤ溶着量を増加することができるので、高能率の溶接技術として広く普及している。特に厚鋼板のサブマージアーク溶接では、多電極を採用して、下面側と上面側をそれぞれ1パスで溶接(いわゆる両面一層盛り溶接)することも可能である。
鋼板の両面一層盛り溶接では、下面側の溶接金属と上面側の溶接金属が十分に重なり、未溶融部が生じないように、溶込み深さを確保する必要があるので、1000A以上の大電流を供給して溶接を行なうのが一般的である(たとえば特許文献1、2)。
Submerged arc welding used when welding steel sheets is widely used as a highly efficient welding technique because it can supply a large current to increase the penetration depth and the amount of wire welding. In particular, in the submerged arc welding of thick steel plates, it is possible to employ multiple electrodes and weld the lower surface side and the upper surface side in one pass each (so-called double-sided single layer welding).
In double-sided single-layer welding of steel sheets, it is necessary to secure a depth of penetration so that the weld metal on the lower surface side and the weld metal on the upper surface side are sufficiently overlapped, and no unmelted portion is formed. Is generally performed by welding (for example, Patent Documents 1 and 2).

また、アンダーカット等の表面欠陥を抑制するために、幅の広いビードを形成する必要があるので、電圧を増加する等の溶接条件の調整も行なわれている。
しかしながら電流や電圧を増加すると、溶接入熱の増大を招き、溶接熱影響部の靭性が劣化するという問題が生じる。このような問題に対して、溶接熱影響部の靭性を向上するために、鋼板の特性を改善する技術(たとえば特許文献3、4、5)、溶接施工にて細径ワイヤを使用する技術(たとえば特許文献6、7)、ビード形状を制御する技術(たとえば特許文献8、9)等が検討されている。
Further, since it is necessary to form a wide bead in order to suppress surface defects such as undercuts, adjustment of welding conditions such as increasing the voltage is also performed.
However, increasing the current or voltage causes an increase in welding heat input, resulting in a problem that the toughness of the weld heat affected zone deteriorates. In order to improve the toughness of the weld heat-affected zone with respect to such a problem, a technique for improving the characteristics of the steel sheet (for example, Patent Documents 3, 4, and 5), a technique for using a thin wire in welding construction ( For example, Patent Documents 6 and 7), techniques for controlling the bead shape (for example, Patent Documents 8 and 9), and the like have been studied.

ところが、これら特許文献3〜9に開示された技術は、溶接熱影響部の靭性を安定して高めることが困難である。つまり、下面側を溶接する際の溶接熱影響部(特に粗粒域)が、上面側の溶接によって再び加熱されるので、シャルピー衝撃試験で靭性を評価する場合に、溶接熱影響部の形状や溶接熱影響部とシャルピー衝撃試験片との位置関係によって、試験結果が大きく変動する。そのため、同じ溶接条件で鋼板の両面一層盛り溶接を行なっても、溶接施工後の材料試験において、靭性の評価にばらつきが生じる。   However, it is difficult for the techniques disclosed in Patent Documents 3 to 9 to stably increase the toughness of the weld heat affected zone. In other words, the weld heat affected zone (especially the coarse grain region) when welding the lower surface side is heated again by welding on the upper surface side. Therefore, when evaluating toughness in the Charpy impact test, The test results vary greatly depending on the positional relationship between the weld heat affected zone and the Charpy impact test piece. Therefore, even if double-sided single-layer welding of steel sheets is performed under the same welding conditions, the toughness evaluation varies in the material test after welding.

特開平11-138266号公報Japanese Patent Laid-Open No. 11-138266 特開平10-109171号公報Japanese Patent Laid-Open No. 10-109171 特開2002-146471号公報JP 2002-146471 A 特開2004-52104号公報JP 2004-52104 A 特開2009-91653号公報JP 2009-91653 A 特開2006-272377号公報JP 2006-272377 A 特開2009-241128号公報JP 2009-241128 特開2010-274275号公報JP 2010-274275 A 特開2010-274276号公報JP 2010-274276 A

本発明は、鋼板の突き合わせ溶接、特に厚鋼板の両面一層盛り溶接を行なうにあたって、高靭性の溶接熱影響部を安定して得ることができるサブマージアーク溶接方法を提供することを目的とする。   An object of the present invention is to provide a submerged arc welding method capable of stably obtaining a high toughness weld heat-affected zone when performing butt welding of steel plates, particularly double-sided single layer welding of thick steel plates.

発明者は、種々の溶接条件で鋼板のサブマージアーク溶接を行ない、溶接継手の溶接熱影響部の靭性を調査した。その結果、溶融した後に凝固して形成された溶接金属と未溶融の鋼板に形成された溶接熱影響部との境界線(以下、溶融境界線という)の形状を、下面側と上面側でそれぞれ適正に制御することによって、両面一層盛り溶接にて溶接熱影響部の優れた靭性を安定して得られることを見出した。   The inventor conducted submerged arc welding of the steel sheet under various welding conditions, and investigated the toughness of the weld heat affected zone of the welded joint. As a result, the shape of the boundary line (hereinafter referred to as the melting boundary line) between the weld metal formed by solidification after melting and the weld heat affected zone formed on the unmelted steel sheet is referred to as the lower surface side and the upper surface side, respectively. It has been found that by controlling properly, it is possible to stably obtain excellent toughness of the weld heat affected zone by double-sided single-layer welding.

とりわけ板厚が30mm以上の厚鋼板では、従来と同様に、ワイヤ径の大きいワイヤ(以下、太径ワイヤという)を用いて鋼板の両面を溶接すると、図2に示すように、下面側の溶融境界線4と鋼板1表面に垂直な線とのなす角θ2(°)、および上面側の溶融境界線5と鋼板1表面に垂直な線とのなす角θ1(°)が、いずれも小さくなる。つまり、下面側の溶融境界線4と上面側の溶融境界線5が、ともに鋼板1表面に対してほぼ垂直に形成されるので、溶接熱影響部の靭性を評価するためのシャルピー衝撃試験片の採取位置(すなわち試験片のノッチ位置)と溶融境界線の位置との配置を安定して制御することが極めて難しくなる。その結果、シャルピー衝撃試験で得られるデータのばらつきが大きくなることが分かった。   In particular, in the case of a thick steel plate having a thickness of 30 mm or more, when both surfaces of the steel plate are welded using a wire having a large wire diameter (hereinafter referred to as a thick wire) as in the conventional case, as shown in FIG. The angle θ2 (°) formed between the boundary line 4 and a line perpendicular to the surface of the steel sheet 1 and the angle θ1 (°) formed between the molten boundary line 5 on the upper surface side and a line perpendicular to the surface of the steel sheet 1 are both small. . That is, since the lower boundary side melting boundary line 4 and the upper boundary side melting boundary line 5 are both formed substantially perpendicular to the surface of the steel plate 1, the Charpy impact test piece for evaluating the toughness of the weld heat affected zone It becomes extremely difficult to stably control the arrangement of the sampling position (that is, the notch position of the test piece) and the position of the melting boundary line. As a result, it was found that the dispersion of data obtained by the Charpy impact test became large.

これに対して、ワイヤ径の小さいワイヤ(以下、細径ワイヤという)を用いると、溶融境界線を傾けることができる。たとえば、下面側の溶接にて細径ワイヤを使用すると、図1に示すように、下面側の溶融境界線4と鋼板1表面に垂直な線とのなす角θ2が大きくなる。したがって、試験片のノッチ位置が溶融境界線と交差するようなシャルピー衝撃試験片を容易に採取することが可能となり、シャルピー衝撃試験で得られるデータのばらつきを抑え、ひいては靭性の適正な評価が可能となる。   On the other hand, when a wire having a small wire diameter (hereinafter referred to as a thin wire) is used, the melting boundary line can be inclined. For example, when a thin wire is used for welding on the lower surface side, as shown in FIG. 1, the angle θ2 formed by the fusion boundary line 4 on the lower surface side and a line perpendicular to the surface of the steel sheet 1 increases. Therefore, it is possible to easily collect Charpy impact test specimens where the notch position of the test specimen intersects the melt boundary line, suppressing variations in data obtained by the Charpy impact test, and thus enabling proper evaluation of toughness. It becomes.

ただし細径ワイヤを使用すると、溶接金属の最深奥部、すなわち図1の下面側溶接金属2の先端部にスラグが溜まりやすくなるという問題がある。そこで、細径ワイヤを用いて溶接した後に、太径ワイヤを用いて溶接を行なうことによって、スラグを溶融させる。つまり、厚鋼板の両面一層盛り溶接にて、細径ワイヤによる溶接と太径ワイヤによる溶接とを組み合わせることによって、溶接熱影響部の靭性を安定して向上させ、欠陥発生を抑制させることが可能となる。   However, when a thin wire is used, there is a problem that slag tends to accumulate at the deepest part of the weld metal, that is, at the tip of the lower surface side weld metal 2 in FIG. Then, after welding using a thin wire, the slag is melted by welding using a large wire. In other words, it is possible to stably improve the toughness of the heat affected zone and suppress the occurrence of defects by combining the welding with a thin wire and the welding with a large wire in double-sided single layer welding of thick steel plates. It becomes.

本発明は、このような知見に基づいてなされたものである。
すなわち本発明は、板厚30mm以上の鋼板の突き合わせ溶接において、上面側から仮付け溶接を行なった後に、2個以上の電極を使用するサブマージアーク溶接にて、第1電極のワイヤ径を2.4〜3.2mmかつ溶接電流を1000A以上として下面側の溶接を行ない、さらに2個以上の電極を使用するサブマージアーク溶接にて、第1電極のワイヤ径を4.0〜6.4mmとして上面側の溶接を行ない、鋼板の下面側の溶接入熱と上面側の溶接入熱との全電極の合計入熱をQ(kJ/cm)とし、合計入熱Qが鋼板の板厚t(mm)に対して下記の(3)式を満足するサブマージアーク溶接方法である。
The present invention has been made based on such knowledge.
That is, according to the present invention, in butt welding of steel sheets having a thickness of 30 mm or more, after performing tack welding from the upper surface side, the wire diameter of the first electrode is set to 2.4 to 2 in submerged arc welding using two or more electrodes. Weld the bottom side with a welding current of 1000A or more at 3.2mm, and further weld the top side with a wire diameter of 4.0 to 6.4mm for the first electrode in submerged arc welding using two or more electrodes. Q (kJ / cm) is the total heat input of all electrodes of the welding heat input on the lower surface side and the welding heat input on the upper surface side of the steel plate, and the total heat input Q is the thickness t (mm) of the steel plate. This is a submerged arc welding method that satisfies the following formula (3) .

本発明のサブマージアーク溶接方法においては、鋼板の下面側の溶接を、第1電極の溶接電流I1(A)と第2電極の溶接電流I2(A)とが下記の(2)式を満足するように行なうことが好ましい。
1.37 Q≦1.3×t1.37 ・・・(3)
0.70≦I2/I1≦0.95 ・・・(2)
なお、ここでは、溶接する鋼板の両面のうち、仮付け溶接を行なう側の面を上面、その上面に対向する面を下面と記す。また、2個以上の電極を各々区別するために、溶接進行方向の先頭に配置される電極を第1電極とし、それ以降の電極を順に第2電極、第3電極等とする。
In submerged arc welding method of the present invention, the lower surface side of the welding of steel plates, the welding current I 2 (A) and the following equation (2) of the welding current I 1 (A) and the second electrode of the first electrode It is preferable to carry out so as to satisfy the above.
t 1.37 Q ≤ 1.3 x t 1.37 (3)
0.70 ≦ I 2 / I 1 ≦ 0.95 (2)
Here, of both surfaces of the steel plates to be welded, the surface on the side where tack welding is performed is referred to as the upper surface, and the surface facing the upper surface is referred to as the lower surface. In order to distinguish two or more electrodes from each other, an electrode arranged at the head in the welding progress direction is referred to as a first electrode, and the subsequent electrodes are sequentially referred to as a second electrode, a third electrode, and the like.

本発明によれば、サブマージアーク溶接によって厚鋼板の突き合わせ溶接を、両面一層盛り溶接で行なうにあたり、高靭性の溶接熱影響部を安定して得ることができるので、産業上格段の効果を奏する。   According to the present invention, when performing butt welding of thick steel plates by submerged arc welding by double-sided single-layer welding, it is possible to stably obtain a high toughness heat-affected zone.

本発明で形成される溶接継手の例を模式的に示す断面図である。It is sectional drawing which shows typically the example of the welded joint formed by this invention. 従来の突き合わせ溶接で形成される溶接継手の例を模式的に示す断面図である。It is sectional drawing which shows typically the example of the welded joint formed by the conventional butt welding. 鋼板の開先形状の例を模式的に示す断面図である。It is sectional drawing which shows the example of the groove shape of a steel plate typically. シャルピー衝撃試験片の採取位置を模式的に示す断面図である。It is sectional drawing which shows typically the collection position of a Charpy impact test piece.

本発明を適用して鋼板の突き合わせ溶接を行なう手順について、以下に説明する。
まず、図3に示すように、鋼板1の端部に開先を加工する。図1中のtは鋼板1の板厚(mm)、αとβは開先角度(°)、UとVは開先深さ(mm)である。
本発明は、板厚tが30mm以上の鋼板に適用するものとする。板厚が30mm未満の鋼板は、従来の溶接方法で形成された溶接熱影響部の靭性の評価に大きな問題はなかったので、上記したような本発明の効果は小さい。一方、板厚が45mmを超えると、両面一層盛り溶接が困難になることがある。したがって、鋼板の板厚tは30〜45mmの範囲内が好ましい。
A procedure for performing butt welding of steel plates by applying the present invention will be described below.
First, as shown in FIG. 3, a groove is processed at the end of the steel plate 1. In FIG. 1, t is the thickness (mm) of the steel plate 1, α and β are the groove angle (°), and U and V are the groove depth (mm).
The present invention is applied to a steel plate having a thickness t of 30 mm or more. Since the steel plate having a thickness of less than 30 mm has no significant problem in the evaluation of the toughness of the weld heat affected zone formed by the conventional welding method, the effect of the present invention as described above is small. On the other hand, if the plate thickness exceeds 45 mm, double-sided single layer welding may be difficult. Therefore, the thickness t of the steel plate is preferably in the range of 30 to 45 mm.

なお、開先角度α、β、および開先深さU、Vは、図1に示すように溶接金属が重なり合うように形成されるように設定すれば良く、数値は特に限定しない。
開先を加工して突き合わせた鋼板の片面側から、開先の仮付け溶接を行なう。以下では、仮付け溶接を行なう側の面を上面、その上面に対向する面を下面と記す。
次に、下面側のサブマージアーク溶接を1パスで行ない、図1に示すような下面側溶接金属2を形成する。図1中の4は、下面側の溶融境界線である。多層、多パス溶接では、能率低下の問題が生じる。
The groove angles α and β and the groove depths U and V may be set so that the weld metals are overlapped as shown in FIG. 1, and the numerical values are not particularly limited.
The groove is tack-welded from one side of the steel sheets which are processed and faced together. Hereinafter, the surface on the side where tack welding is performed is referred to as an upper surface, and the surface facing the upper surface is referred to as a lower surface.
Next, submerged arc welding on the lower surface side is performed in one pass to form the lower surface side weld metal 2 as shown in FIG. 1 in FIG. 1 is a melting boundary line on the lower surface side. Multi-layer, multi-pass welding has the problem of reduced efficiency.

下面側の溶接は、2個以上の電極を用いて行なう。電極が1個で溶接を行なうと、溶接速度の向上が期待できないからである。なお電極を過剰に増やすと、溶接装置の構成および溶接施工の操業管理が複雑になることから、電極は5個以下が好ましい。以下では、2個以上の電極を各々区別するために、溶接進行方向の先頭に配置される電極を第1電極とし、それ以降の電極を順に第2電極、第3電極等と記す。   Welding on the lower surface side is performed using two or more electrodes. This is because if one electrode is used for welding, an improvement in welding speed cannot be expected. In addition, since the structure of a welding apparatus and the operation management of welding construction will become complicated when an electrode is increased excessively, five or less electrodes are preferable. Hereinafter, in order to distinguish two or more electrodes from each other, the electrode arranged at the head in the welding progress direction is referred to as a first electrode, and the subsequent electrodes are sequentially referred to as a second electrode, a third electrode, and the like.

下面側の溶接では、第1電極にてワイヤ径2.4〜3.2mmの細径ワイヤを使用する。第1電極のワイヤ径が2.4mm未満では、ワイヤ送給速度が速くなりすぎて、大電流が適用できず、深い溶込みが得られない。一方、3.2mmを超えると、角θ2が大きくなるような下面側溶接金属2を形成できないので、靭性が劣化する。
第2電極以降のワイヤ径は、特に限定しない。ただし、ワイヤ径を3.2mm以上とすれば、安定して溶接を行なうことができるので好ましい。より好ましくは3.2〜4.8mmである。
In welding on the lower surface side, a thin wire having a wire diameter of 2.4 to 3.2 mm is used at the first electrode. If the wire diameter of the first electrode is less than 2.4 mm, the wire feeding speed becomes too fast, so that a large current cannot be applied and deep penetration cannot be obtained. On the other hand, if the thickness exceeds 3.2 mm, the lower surface side weld metal 2 that increases the angle θ2 cannot be formed, so that the toughness deteriorates.
The wire diameter after the second electrode is not particularly limited. However, a wire diameter of 3.2 mm or more is preferable because welding can be performed stably. More preferably, it is 3.2 to 4.8 mm.

また第1電極の溶接電流I1は、1000A以上とする。溶接電流I1が1000A未満では、十分な溶込み深さが得られず、図1に示すように溶接金属を重なり合わせることが困難になる。一方、1400Aを超えると、ワイヤ送給速度が速くなりすぎて、ワイヤの安定送給が困難になる。したがって、第1電極の溶接電流I1は1000〜1400Aの範囲内が好ましい。
第2電極以降の溶接電流は、特に限定しない。ただし第2電極の溶接電流をI2(A)として、I2/I1が(2)式を満足することが好ましい。I2/I1が0.70未満では、溶接が安定せず、その結果、ビード幅が不安定になり、下面側溶接金属2や溶融境界線4の形状を制御し難くなることがある。一方、0.95を超えると、余盛り高さが大きくなり、下面側溶接金属2や溶融境界線4の形状を制御し難くなることがある。
0.70≦I2/I1≦0.95 ・・・(2)
このようにして下面側の溶接を行なうことによって、角度θ2の大きい下面側溶接金属2を形成することができる。しかし細径ワイヤを使用することによって、下面側溶接金属2の最深奥部にスラグ巻き込みが発生することがある。
The welding current I 1 of the first electrode is 1000 A or more. When the welding current I 1 is less than 1000 A, a sufficient penetration depth cannot be obtained, and it becomes difficult to overlap the weld metals as shown in FIG. On the other hand, if it exceeds 1400A, the wire feeding speed becomes too fast, making it difficult to stably feed the wire. Thus, the welding current I 1 of the first electrode is preferably in the range of 1000~1400A.
The welding current after the second electrode is not particularly limited. However, it is preferable that the welding current of the second electrode is I 2 (A) and I 2 / I 1 satisfies the formula (2). If I 2 / I 1 is less than 0.70, welding is not stable, and as a result, the bead width becomes unstable, and the shape of the lower-surface side weld metal 2 and the molten boundary line 4 may be difficult to control. On the other hand, if it exceeds 0.95, the surplus height increases, and it may be difficult to control the shape of the lower surface side weld metal 2 and the molten boundary line 4.
0.70 ≦ I 2 / I 1 ≦ 0.95 (2)
By performing the lower surface side welding in this way, the lower surface side weld metal 2 having a large angle θ2 can be formed. However, by using a small-diameter wire, slag entrainment may occur at the deepest innermost portion of the lower surface side weld metal 2.

そこで、次に、太径ワイヤを用いて上面側のサブマージアーク溶接を行なうことによって、図1に示すように、下面側溶接金属2に重なり合わせて上面側溶接金属3を形成し、スラグを溶融し、溶接欠陥の抑制を図る。
上面側の溶接は、2個以上の電極を用いて行なう。電極が1個で溶接を行なうと、溶接速度の向上が期待できないからである。電極は5個以下が好ましいが、その理由は上記と同じである。
Therefore, by performing submerged arc welding on the upper surface side using a large-diameter wire, as shown in FIG. 1, the upper surface side weld metal 3 is formed so as to overlap the lower surface side weld metal 2, and the slag is melted. To suppress welding defects.
The upper surface side welding is performed using two or more electrodes. This is because if one electrode is used for welding, an improvement in welding speed cannot be expected. The number of electrodes is preferably 5 or less, for the same reason as described above.

上面側の溶接では、第1電極にてワイヤ径4.0〜6.4mmの太径ワイヤを使用する。第1電極のワイヤ径が4.0mm未満では、下面側溶接金属2内のスラグを溶融し難いばかりでなく、上面側溶接金属3の最深奥部にスラグが溜まる惧れがある。なおサブマージアーク溶接では、通常はワイヤ径は6.4mmまでである。
第2電極以降のワイヤ径は、特に限定しない。
In welding on the upper surface side, a thick wire having a wire diameter of 4.0 to 6.4 mm is used at the first electrode. If the wire diameter of the first electrode is less than 4.0 mm, not only is it difficult to melt the slag in the lower surface side weld metal 2, but there is a possibility that the slag may accumulate in the deepest part of the upper surface side weld metal 3. In submerged arc welding, the wire diameter is usually up to 6.4 mm.
The wire diameter after the second electrode is not particularly limited.

サブマージアーク溶接の溶接入熱は、下面側と上面側の全電極の合計入熱Q(kJ/cm)が、鋼板の板厚tに対して下記の(3)式を満足することが必要となる。Qが1.3×t1.37 kJ/cmを超えると、溶接入熱が大きすぎて溶接熱影響部の靭性が劣化することがある。一方、t1.37 kJ/cm未満では、十分な溶込み深さを確保し難くなる。そのため、下記の(3)式を満足させる
Q≦1.3×t1.37 ・・・(1)
1.37≦Q≦1.3×t1.37 ・・・(3)
以上に説明した通り、本発明によれば、溶接熱影響部の靭性を向上することができる。しかも、下面側溶接金属の溶融境界線を傾けることができるので、図4に示すように、シャルピー衝撃試験片を採取した場合に、試験片のノッチが下面側の溶融境界線と交差するようになる。また、下面側と上面側の溶融境界線の交点近傍では、上面側の溶融境界線も傾いているので、試験片のノッチと交差する。その結果、試験片の採取位置の変動や溶融境界線の形状の変化が靭性の評価に及ぼす影響を大幅に抑えることができ、安定した靭性が得られる。
Welding heat input submerged arc welding, the total heat input of all the electrodes of the lower surface and the upper surface side Q (kJ / cm) is required to satisfy the following formula (3) with respect to the thickness t of the steel sheet Become . When Q exceeds 1.3 × t 1.37 kJ / cm, the welding heat input is too large and the toughness of the weld heat affected zone may deteriorate. On the other hand, if it is less than t 1.37 kJ / cm, it is difficult to secure a sufficient penetration depth. Therefore, it makes satisfy the following equation (3).
Q ≦ 1.3 × t 1.37 (1)
t 1.37 ≦ Q ≦ 1.3 × t 1.37 (3)
As described above, according to the present invention, the toughness of the weld heat affected zone can be improved. Moreover, since the melting boundary line of the lower surface side weld metal can be tilted, as shown in FIG. 4, when a Charpy impact test piece is taken, the notch of the test piece intersects the lower surface side melting boundary line. Become. Further, in the vicinity of the intersection of the melting boundary line on the lower surface side and the upper surface side, the melting boundary line on the upper surface side is also inclined, so that it intersects with the notch of the test piece. As a result, it is possible to greatly suppress the influence of the change in the sampling position of the specimen and the change in the shape of the melt boundary line on the evaluation of toughness, and stable toughness can be obtained.

本発明で使用するワイヤについては、ソリッドワイヤ、コアードワイヤいずれも使用できる。   As the wire used in the present invention, either a solid wire or a cored wire can be used.

表1に示す成分を有する2種類の鋼板(板厚t:31.8mm,38.1mm)に、図3に示すような形状の開先を形成した後、下面側のサブマージアーク溶接(1パス)を行ない、次いで上面側のサブマージアーク溶接(1パス)を行なった。   After forming a groove having the shape shown in FIG. 3 on two types of steel plates (thickness t: 31.8 mm, 38.1 mm) having the components shown in Table 1, submerged arc welding (one pass) on the lower surface side is performed. Then, submerged arc welding (one pass) was performed on the upper surface side.

鋼板1の開先形状を表2に示す。表2中の下面の開先角度は図3に示す角β(°)、上面の開先角度は図3に示す角α(°)である。また、表2中の下面の開先深さは図3に示すV(mm)、上面の開先深さは図3に示すU(mm)である。   Table 2 shows the groove shape of the steel plate 1. In Table 2, the groove angle of the lower surface is an angle β (°) shown in FIG. 3, and the groove angle of the upper surface is an angle α (°) shown in FIG. In Table 2, the groove depth on the lower surface is V (mm) shown in FIG. 3, and the groove depth on the upper surface is U (mm) shown in FIG.

サブマージアーク溶接の条件を表3〜6に示す。表3、4に示すように、溶接記号9は上面溶接、下面溶接ともに3電極(1パス)、溶接記号10は上面溶接、下面溶接ともに5電極(1パス)で溶接を行ない、その他は全て4電極(1パス)で溶接を行なった。表5、6に示す電流は、いずれも第1電極を直流とし、第2電極以降を交流とした。表5、6中の極間距離は、鋼板1表面(下面または上面)におけるワイヤ先端の間隔(mm)である。母材−電極間距離は、鋼板1表面(下面または上面)とコンタクトチップ下面との間隔(mm)である。電極角度は、前進角(°)を正、後退角(°)を負として示す。ここで前進角は、ワイヤ先端がトーチよりも溶接進行方向の前方に位置するようにワイヤを傾斜させて、鋼板に垂直な線とワイヤとのなす角であり、後退角は、ワイヤ先端がトーチよりも溶接進行方向の後方に位置するようにワイヤを傾斜させて、鋼板に垂直な線とワイヤとのなす角である。   The conditions of submerged arc welding are shown in Tables 3-6. As shown in Tables 3 and 4, welding symbol 9 is welded with 3 electrodes (1 pass) for top surface welding and bottom surface welding, welding symbol 10 is welded with 5 electrodes (1 pass) for top surface welding and bottom surface welding, and all others Welding was performed with 4 electrodes (1 pass). In the currents shown in Tables 5 and 6, the first electrode was a direct current, and the second and subsequent electrodes were an alternating current. The distance between the electrodes in Tables 5 and 6 is the distance (mm) between the wire tips on the surface (lower surface or upper surface) of the steel plate 1. The distance between the base material and the electrode is the distance (mm) between the surface (lower surface or upper surface) of the steel plate 1 and the lower surface of the contact chip. The electrode angle is shown with the forward angle (°) as positive and the backward angle (°) as negative. Here, the advancing angle is an angle formed by a wire perpendicular to the steel sheet and the wire so that the wire tip is positioned in front of the welding direction with respect to the torch, and the receding angle is the wire tip. The angle between the wire and the wire perpendicular to the steel plate is such that the wire is inclined so as to be located behind the welding progress direction.

これらの各条件(溶接記号1〜18)で溶接を行なった後、作製した溶接継手の定常部にてビード幅を確認して、その最大値と最小値を測定し、その差を求めてビード幅の安定性を評価した。その結果を表7に示す。
さらにX線撮影によって、溶接金属のスラグ巻き込みの有無、溶込み不良の有無を調査した。その結果を表7に示す。
After welding under each of these conditions (welding symbols 1 to 18), the bead width is confirmed at the steady portion of the welded joint produced, the maximum value and the minimum value are measured, and the difference is obtained to obtain the bead. The stability of the width was evaluated. The results are shown in Table 7.
Furthermore, the presence or absence of slag inclusion of weld metal and the presence or absence of poor penetration were investigated by X-ray photography. The results are shown in Table 7.

また各条件の溶接によって、それぞれ5個ずつ溶接継手を作製し、図4に示す試験片採取位置6からシャルピー衝撃試験片および断面マクロ試験片を採取した。
シャルピー衝撃試験片は、JIS規格Z3111に規定する4号試験片として、各溶接継手から20個ずつ(すなわち各溶接記号ごとに100個ずつ)採取した。シャルピー衝撃試験片は、ノッチが板厚方向に平行となり、かつ溶融境界線の交点を含む面(鋼板1表面に平行な面)が試験片の板厚方向中央となるように採取した。そのノッチの位置は、ノッチ底における溶接金属と溶接熱影響部の比率が50%ずつとなる位置とした。
Further, five welded joints were prepared by welding under each condition, and Charpy impact test pieces and cross-sectional macro test pieces were collected from the test piece collection position 6 shown in FIG.
Charpy impact test pieces were collected from each welded joint as No. 4 test pieces as defined in JIS standard Z3111 (ie, 100 pieces for each weld symbol). The Charpy impact test piece was sampled so that the notch was parallel to the plate thickness direction and the plane including the intersection of the melting boundary lines (plane parallel to the surface of the steel plate 1) was the center of the test piece in the plate thickness direction. The position of the notch was a position where the ratio of the weld metal and the weld heat affected zone at the notch bottom was 50%.

シャルピー衝撃試験は、JIS規格Z2242に準拠(試験温度:−30℃)して行ない、吸収エネルギーV-30(J)を測定した。その結果を表7に示す。なお、表7中の吸収エネルギーV-30は、各溶接記号ごとに100回のシャルピー衝撃試験で得られた測定値のうち最も低い値を示す。
断面マクロ試験片は、各溶接継手から3個ずつ(すなわち各溶接記号ごとに15個ずつ)採取した。それぞれの断面マクロ試験片から余盛り高さ(mm)を測定した結果を表7に示す。なお、表7中の余盛り高さは、各溶接記号ごとに15個の試験片の測定値の平均値を示す。
The Charpy impact test was performed in accordance with JIS standard Z2242 (test temperature: −30 ° C.), and the absorbed energy V E -30 (J) was measured. The results are shown in Table 7. The absorbed energy V E -30 in Table 7 represents the lowest value among the measured values obtained by 100 Charpy impact tests for each welding symbol.
Three cross-section macro specimens were collected from each weld joint (ie, 15 for each weld symbol). Table 7 shows the result of measuring the extra height (mm) from each cross-section macro test piece. In addition, the surplus height in Table 7 shows the average value of the measured values of 15 test pieces for each welding symbol.

溶接記号1、2は参考例、溶接記号3〜10は発明例である。溶接記号1、2は、下面溶接の第1電極のワイヤ径を2.4〜3.2mmかつ第1電極の溶接電流を1000A以上とし、上面溶接の第1電極のワイヤ径を4.0〜6.4mmとする例であり、安定して優れた靭性が得られ、同時に良好な溶接部品質が得られた。溶接記号3〜6は、さらに、下面側と上面側の溶接入熱の合計が(3)式を満足するように設定した例であり、100J以上の極めて高い吸収エネルギーが得られた。また溶接記号7〜10は、さらに、下面側の溶接にて第1電極と第2電極の溶接電流が(2)式を満足するように設定した例であり、ビードの余盛り高さを3mm以下、ビード幅の最大値と最小値の差を3mm以下に抑えることができ、優れた形状のビードが得られた。
Welding symbols 1 and 2 are reference examples, and welding symbols 3 to 10 are invention examples. The welding symbols 1 and 2 are examples in which the wire diameter of the first electrode for bottom surface welding is 2.4 to 3.2 mm, the welding current for the first electrode is 1000 A or more, and the wire diameter of the first electrode for top surface welding is 4.0 to 6.4 mm. Therefore, stable and excellent toughness was obtained, and at the same time, good weld quality was obtained. The welding symbols 3 to 6 are examples in which the total welding heat input on the lower surface side and the upper surface side satisfies the formula (3) , and extremely high absorbed energy of 100 J or more was obtained. In addition, welding symbols 7 to 10 are examples in which the welding current of the first electrode and the second electrode is set so as to satisfy the expression (2) by welding on the lower surface side, and the extra height of the bead is 3 mm. Hereinafter, the difference between the maximum value and the minimum value of the bead width could be suppressed to 3 mm or less, and a bead having an excellent shape was obtained.

溶接記号11〜18は比較例である。溶接記号11、12は、下面溶接の第1電極のワイヤ径を2.4mm未満であるから、1000A以上の高い溶接電流を設定したため、安定した溶接ができず、ビード幅が安定しない。溶接記号13、14は、下面側の溶接にて第1電極のワイヤ径が3.2mmを超えるので、吸収エネルギーが小さかった。溶接記号15、16は、下面溶接の第1電極の溶接電流が1000A未満であるから、溶込み不良が発生した。溶接記号17、18は、上面溶接の第1電極のワイヤ径が4.0mm未満であり、スラグ巻き込みが発生した。   The welding symbols 11 to 18 are comparative examples. In welding symbols 11 and 12, since the wire diameter of the first electrode of the bottom surface welding is less than 2.4 mm, a high welding current of 1000 A or more is set, so that stable welding cannot be performed and the bead width is not stable. The welding symbols 13 and 14 had low absorbed energy because the wire diameter of the first electrode exceeded 3.2 mm in the lower surface side welding. In welding symbols 15 and 16, a penetration failure occurred because the welding current of the first electrode of the bottom surface welding was less than 1000 A. In welding symbols 17 and 18, the wire diameter of the first electrode of top surface welding was less than 4.0 mm, and slag entrainment occurred.

1 鋼板
2 下面側溶接金属
3 上面側溶接金属
4 下面側の溶融境界線
5 上面側の溶融境界線
6 試験片採取位置
DESCRIPTION OF SYMBOLS 1 Steel plate 2 Lower surface side weld metal 3 Upper surface side weld metal 4 Lower surface side melting boundary line 5 Upper surface side melting boundary line 6 Test piece sampling position

Claims (2)

板厚30mm以上の鋼板の突き合わせ溶接において、上面側から仮付け溶接を行なった後に、2個以上の電極を使用するサブマージアーク溶接にて、第1電極のワイヤ径を2.4〜3.2mmかつ溶接電流を1000A以上として下面側の溶接を行ない、さらに2個以上の電極を使用するサブマージアーク溶接にて、第1電極のワイヤ径を4.0〜6.4mmとして上面側の溶接を行ない、前記鋼板の下面側の溶接入熱と上面側の溶接入熱との全電極の合計入熱をQ(kJ/cm)とし、該合計入熱Qが前記鋼板の板厚t(mm)に対して下記の(3)式を満足することを特徴とするサブマージアーク溶接方法。
1.37 ≦Q≦1.3×t 1.37 ・・・(3)
In butt welding of steel plates with a thickness of 30 mm or more, after performing tack welding from the upper surface side, the wire diameter of the first electrode is 2.4 to 3.2 mm and the welding current is submerged arc welding using two or more electrodes. It performs welding of the lower surface side as above 1000A, still in submerged arc welding using two or more electrodes, the row stomach welding of the upper surface side of the wire diameter of the first electrode as 4.0~6.4Mm, the steel sheet Q (kJ / cm) is the total heat input of all electrodes of the welding heat input on the lower surface side and the welding heat input on the upper surface side, and the total heat input Q is as follows with respect to the plate thickness t (mm) of the steel sheet. A submerged arc welding method characterized by satisfying the expression (3) .
t 1.37 ≦ Q ≦ 1.3 × t 1.37 (3)
前記鋼板の下面側の溶接を、第1電極の溶接電流I1(A)と第2電極の溶接電流I2(A)とが下記の(2)式を満足するように行なうことを特徴とする請求項1に記載のサブマージアーク溶接方法。
0.70≦I2/I1≦0.95 ・・・(2)
The welding of the lower surface side of the steel sheet is performed so that the welding current I 1 (A) of the first electrode and the welding current I 2 (A) of the second electrode satisfy the following expression (2): The submerged arc welding method according to claim 1 .
0.70 ≦ I 2 / I 1 ≦ 0.95 (2)
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