JP4998353B2 - Manufacturing method of welded steel pipe - Google Patents

Manufacturing method of welded steel pipe Download PDF

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JP4998353B2
JP4998353B2 JP2008091908A JP2008091908A JP4998353B2 JP 4998353 B2 JP4998353 B2 JP 4998353B2 JP 2008091908 A JP2008091908 A JP 2008091908A JP 2008091908 A JP2008091908 A JP 2008091908A JP 4998353 B2 JP4998353 B2 JP 4998353B2
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welding
surface side
steel pipe
welded steel
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JP2009241128A (en
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直哉 早川
篤史 石神
健次 大井
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JFE Steel Corp
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Description

本発明は、シームの外面側と内面側をサブマージアーク溶接にてそれぞれ1層ずつ溶接する溶接鋼管の製造方法に関するものであり、特に大径の溶接鋼管の製造方法に関するものである。   The present invention relates to a method for manufacturing a welded steel pipe in which one outer layer side and an inner surface side of a seam are welded one by one by submerged arc welding, and particularly to a method for manufacturing a large-diameter welded steel pipe.

大径の溶接鋼管(たとえばUOE鋼管,スパイラル鋼管等)の継ぎ目(いわゆるシーム)を溶接する際には、サブマージアーク溶接が採用される。その溶接には、溶接施工の効率向上の観点から、2電極以上を備えた溶接機が使用され、シームの内面側を1パスで溶接しかつ外面側を1パスで溶接する技術(いわゆる両面1層盛り溶接)が広く採用されている。  When welding a seam (so-called seam) of a large-diameter welded steel pipe (for example, UOE steel pipe, spiral steel pipe, etc.), submerged arc welding is employed. For the welding, a welding machine having two or more electrodes is used from the viewpoint of improving the efficiency of welding work, and a technique of welding the inner surface side of the seam in one pass and welding the outer surface side in one pass (so-called double-sided 1 Laminate welding) is widely adopted.

両面1層盛り溶接では、内面側の溶接金属と外面側の溶接金属が十分な溶込み深さを確保し、両側の溶接金属が互いに重なるように施工する必要がある。そのために溶接入熱を増大しなければならないので、溶接熱影響部(いわゆるHAZ)の靭性が劣化するという問題がある。特に、内面側のHAZと外面側のHAZが重なり合う部位の靭性が著しく劣化する。   In double-sided one-layer welding, it is necessary to ensure that the weld metal on the inner surface side and the weld metal on the outer surface side have a sufficient penetration depth so that the weld metals on both sides overlap each other. Therefore, since the welding heat input must be increased, there is a problem that the toughness of the weld heat affected zone (so-called HAZ) deteriorates. In particular, the toughness of the portion where the HAZ on the inner surface side and the HAZ on the outer surface side overlap significantly deteriorates.

そこで溶接鋼管の両面1層盛り溶接では、シームのHAZの靭性を高める技術が種々検討されている。たとえば特許文献1では、溶接鋼管の素材となる鋼板の成分と圧延条件を規定している。この技術では、鋼板を管状に成形する加工条件やシームを接合する溶接条件等に応じて、HAZの靭性が変動するのは避けられない。
特許文献2には、1パスあたりの溶接入熱を規定して、内面側と外面側にそれぞれ複数パスを施工する技術が開示されている。この技術では、パス回数が増加するばかりでなく、1層目を施工した後、2層目を施工する前にスラグを剥離しなければならないので、両面1層盛り溶接に比べて溶接鋼管の生産性が低下する。
特開平8-35011号公報 特開平6-328255号公報
Therefore, various techniques for increasing the toughness of the HAZ of the seam have been studied in double-sided one-layer welding of a welded steel pipe. For example, in patent document 1, the component and rolling conditions of the steel plate used as the raw material of a welded steel pipe are prescribed | regulated. In this technique, it is inevitable that the toughness of the HAZ varies depending on the processing conditions for forming the steel sheet into a tubular shape, the welding conditions for joining the seams, and the like.
Patent Document 2 discloses a technique for defining welding heat input per pass and constructing a plurality of passes on the inner surface side and the outer surface side, respectively. This technique not only increases the number of passes, but also requires the slag to be peeled off after the first layer is constructed and before the second layer is constructed. Sex is reduced.
JP-A-8-35011 JP-A-6-328255

本発明は、溶接鋼管のシームをサブマージアーク溶接で接合するにあたって、両面1層盛り溶接を行ない、靭性に優れたHAZを有する溶接鋼管を製造する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 method of manufacturing a welded steel pipe having HAZ excellent in toughness by performing double-sided one-layer welding when joining seams of a welded steel pipe by submerged arc welding.

溶接熱影響部(すなわちHAZ)の靭性を向上させ、特に内面側のHAZと外面側のHAZが重なり合う部位の靭性を確保するためには、溶接入熱の低減が有効であることは従来から知られており、シームの開先断面積を小さくすることによって、溶接入熱を低減する等の技術が検討されている。しかし、溶接入熱を低減すると、内面側の溶接金属と外面側の溶接金属が十分に接合せず、シームの強度低下を引き起こす。   It has been known from the past that reducing the heat input of welding is effective in improving the toughness of the weld heat affected zone (ie, HAZ), and in particular to ensure the toughness of the area where the HAZ on the inner surface side and the HAZ on the outer surface side overlap. Therefore, a technique for reducing welding heat input by reducing the groove cross-sectional area of the seam has been studied. However, when the welding heat input is reduced, the weld metal on the inner surface side and the weld metal on the outer surface side are not sufficiently joined, causing a decrease in the strength of the seam.

そこで発明者らは、内面側の溶接入熱HIIN(J/cm)と外面側の溶接入熱HIOUT(J/cm)の影響を個別に調査した。その結果、内面側の溶接入熱HIINを所定の範囲内に低減すれば、内面側と外面側の溶接入熱の合計(=HIIN+HIOUT)が増加しても、内面側のHAZと外面側のHAZが重なり合う部位の靭性を向上できることが判明した。ただし両面1層盛り溶接では、内面側を1パスで溶接した後、外面側を1パスで溶接するので、内面側の溶接入熱HIINを低減して内面側のHAZの結晶粒を微細化するにも関わらず、外面側の溶接入熱HIOUTを著しく増大すると、内面側のHAZが加熱されてその結晶粒が粗大化して、HAZの靭性が劣化する。そこで、内面側の溶接入熱HIINと外面側の溶接入熱HIOUTの比(=HIOUT/HIIN)を規定する。 Therefore, the inventors individually investigated the influence of the welding heat input HI IN (J / cm) on the inner surface side and the welding heat input HI OUT (J / cm) on the outer surface side. As a result, if the welding heat input HI IN on the inner surface side is reduced within a predetermined range, even if the sum of the welding heat inputs on the inner surface side and the outer surface side (= HI IN + HI OUT ) increases, It has been found that the toughness of the portion where the outer surface side HAZ overlaps can be improved. However, in the double-sided single layer up welding, after welding the inner surface side in one pass, so welding the outer side in one pass, fine crystal grains of the HAZ inner surface to reduce the welding heat input HI IN the inner surface Nevertheless, if the welding heat input HI OUT on the outer surface side is significantly increased, the HAZ on the inner surface side is heated and its crystal grains become coarse, and the toughness of the HAZ deteriorates. Therefore, the ratio (= HI OUT / HI IN ) between the welding heat input HI IN on the inner surface side and the welding heat input HI OUT on the outer surface side is defined.

次に発明者らは、このように溶接入熱を制御するための溶接の施工条件を検討した。その結果、サブマージアーク溶接で広く使用されている直径4.0mmの溶接用ワイヤでは、溶接入熱の制御が難しいことが判明した。つまり、3電極以上を備えた溶接機を使用して、その少なくとも2電極に直径3.2mm以下の溶接用ワイヤを供給すれば、上記した条件を満足するように溶接入熱を制御することが可能である。ただし細径の溶接用ワイヤを使用すると、溶融メタルの幅も狭くなり、余盛り高さ不良やスラグ巻き込み等の溶接欠陥が発生し易くなる。   Next, inventors examined the welding construction conditions for controlling welding heat input in this way. As a result, it was found that it is difficult to control the welding heat input with a welding wire having a diameter of 4.0 mm widely used in submerged arc welding. In other words, if a welding machine with three or more electrodes is used and a welding wire with a diameter of 3.2 mm or less is supplied to at least two electrodes, the welding heat input can be controlled so as to satisfy the above conditions. It is. However, if a small-diameter welding wire is used, the width of the molten metal is narrowed, and a welding defect such as a defective height of the surplus or entrainment of slag is likely to occur.

そこで、全電極に交流電流を供給し、かつ互いに隣り合う電極の位相差を規定する。あるいは溶接機の進行方向の先頭に位置する第1電極に直流電流を供給するとともに、その他の第2電極以降に交流電流を供給し、第2電極以降の互いに隣り合う電極の位相差を規定する。さらに、溶接鋼管の表面と溶接機のコンタクトチップとの距離を規定する。
このようにして溶接欠陥を防止し、かつ十分な溶込みを得ることができ、かつ靭性に優れたHAZを有する溶接鋼管を製造できる。
Therefore, an alternating current is supplied to all the electrodes, and the phase difference between the adjacent electrodes is defined. Or while supplying a direct current to the 1st electrode located in the head of the advancing direction of a welding machine, an alternating current is supplied to the other 2nd electrode and the following, and the phase difference of the mutually adjacent electrodes after the 2nd electrode is specified. . Furthermore, the distance between the surface of the welded steel pipe and the contact tip of the welder is defined.
In this manner, a welded steel pipe having a HAZ that can prevent welding defects and can obtain sufficient penetration and is excellent in toughness can be manufactured.

本発明は、これらの知見に基づいてなされたものである。
すなわち本発明は、溶接鋼管のシームの外面側と内面側をサブマージアーク溶接にてそれぞれ1層ずつ溶接する溶接鋼管の製造方法において、内面側の溶接における溶接入熱HIIN(J/cm)と外面側の溶接における溶接入熱HIOUT(J/cm)の比が下記の(1)式を満足し、かつHIIN(J/cm)と溶接鋼管の厚みt(mm)が下記の(2)式を満足する溶接鋼管の製造方法である。
The present invention has been made based on these findings.
That is, the present invention relates to a method for manufacturing a welded steel pipe in which the outer surface side and the inner surface side of the seam of the welded steel pipe are welded one layer at a time by submerged arc welding, and the welding heat input HI IN (J / cm) in welding on the inner surface side The ratio of welding heat input HI OUT (J / cm) in the outer surface side welding satisfies the following formula (1), and HI IN (J / cm) and the thickness t (mm) of the welded steel pipe are the following (2 This is a method for manufacturing a welded steel pipe that satisfies the formula (1).

1.1≦HIOUT/HIIN≦1.5 ・・・(1)
HIIN≦231×t1.56 ・・・(2)
HIIN:内面側の溶接における溶接入熱(J/cm)
HIOUT:外面側の溶接における溶接入熱(J/cm)
t:溶接鋼管の厚み(mm)
本発明の溶接鋼管の製造方法においては、シームの外面側の溶接と内面側の溶接を行なうにあたって3電極以上の溶接機を用い、溶接機の進行方向の先頭に位置する第1電極に直径3.2mm以下の溶接用ワイヤを供給するとともに、その他の第2電極以降の少なくとも1個の電極に直径3.2mm以下の溶接用ワイヤを供給し、溶接鋼管の表面と溶接機のコンタクトチップ先端との距離をいずれも30mm以上とし、溶接機の全電極に交流電流を供給し、互いに隣り合う電極に供給される交流電流の位相差を90〜120°の範囲内とすることが好ましい。
1.1 ≦ HI OUT / HI IN ≦ 1.5 (1)
HI IN ≦ 231 × t 1.56 (2)
HI IN : Weld heat input (J / cm) in inner side welding
HI OUT : Weld heat input (J / cm) for welding on the outer surface side
t: thickness of welded steel pipe (mm)
In the method for manufacturing a welded steel pipe according to the present invention, a welder having three or more electrodes is used to weld the outer surface side and the inner surface side of the seam, and the diameter of the first electrode located at the head in the traveling direction of the welder is 3.2. A welding wire with a diameter of 3.2 mm or less is supplied to at least one other electrode after the second electrode, and the distance between the surface of the welded steel pipe and the tip of the contact tip of the welding machine Is 30 mm or more, AC current is preferably supplied to all electrodes of the welding machine, and the phase difference between AC currents supplied to adjacent electrodes is preferably in the range of 90 to 120 °.

あるいは、シームの外面側の溶接と内面側の溶接を行なうにあたって3電極以上の溶接機を用い、溶接機の進行方向の先頭に位置する第1電極に直径3.2mm以下の溶接用ワイヤを供給するとともに、その他の第2電極以降の少なくとも1個の電極に直径3.2mm以下の溶接用ワイヤを供給し、溶接鋼管の表面と溶接機のコンタクトチップ先端との距離をいずれも30mm以上とし、溶接機の第1電極に直流電流を供給するとともに、その他の第2電極以降に交流電流を供給し、第2電極以降の互いに隣り合う電極に供給される交流電流の位相差を90〜120°の範囲内とすることが好ましい。   Alternatively, when welding the outer surface side and the inner surface side of the seam, a welding machine having three or more electrodes is used, and a welding wire having a diameter of 3.2 mm or less is supplied to the first electrode located at the head in the traveling direction of the welding machine. In addition, a welding wire with a diameter of 3.2 mm or less is supplied to at least one electrode after the second electrode, and the distance between the surface of the welded steel pipe and the tip of the contact tip of the welder is 30 mm or more. A direct current is supplied to the first electrode of the first electrode, an alternating current is supplied to the second and subsequent electrodes, and the phase difference of the alternating current supplied to the adjacent electrodes after the second electrode is in the range of 90 to 120 °. It is preferable to be inside.

本発明によれば、溶接鋼管のシームをサブマージアーク溶接で接合するにあたって、両面1層盛り溶接を行ない、靭性に優れたHAZを有する溶接鋼管を製造できる。   ADVANTAGE OF THE INVENTION According to this invention, when joining the seam of a welded steel pipe by submerged arc welding, a double-sided one-layer welding is performed, and the welded steel pipe which has HAZ excellent in toughness can be manufactured.

本発明では、溶接鋼管のシームをサブマージアーク溶接で接合するにあたって、両面1層盛り溶接を行なう。
すなわち本発明では、まずシームの内面側を1パスで溶接する。
その際、内面側の溶接における溶接入熱HIIN(J/cm)は、溶接鋼管の厚みt(mm)に対して下記の(2)式を満足する必要がある。HIINが(2)式を満足すれば、HIINに起因する溶接熱影響部(すなわちHAZ)のオーステナイト粒径が平均80μm以下となるので、優れた靭性を有するHAZを得ることができる。HIINが(2)式の範囲を外れると、HAZのオーステナイト粒が粗大化するので、HAZの靭性が劣化する。
In this invention, when joining the seam of a welded steel pipe by submerged arc welding, double-sided one-layer welding is performed.
That is, in the present invention, first, the inner surface side of the seam is welded in one pass.
At that time, the welding heat input HI IN (J / cm) in the inner surface side welding needs to satisfy the following expression (2) with respect to the thickness t (mm) of the welded steel pipe. If HI IN satisfies the formula (2), the austenite grain size of the weld heat-affected zone (ie, HAZ) due to HI IN becomes 80 μm or less on average, so that HAZ having excellent toughness can be obtained. If HI IN is out of the range of the formula (2), the HAZ austenite grains become coarse, and the toughness of the HAZ deteriorates.

HIIN≦231×t1.56 ・・・(2)
HIIN:内面側の溶接における溶接入熱(J/cm)
t:溶接鋼管の厚み(mm)
次いで外面側を1パスで溶接する。
その際、内面側の溶接における溶接入熱HIIN(J/cm)と外面側の溶接における溶接入熱HIOUT(J/cm)の比が下記の(1)式を満足する必要がある。HIOUT/HIINが1.1未満では、溶込みを十分に確保できないので、内面側の溶接金属と外面側の溶接金属が十分に接合せず、シームの強度低下を引き起こす。一方、1.5を超えると、内面側のHAZと外面側のHAZが重なり合う部位の靭性が劣化する。
HI IN ≦ 231 × t 1.56 (2)
HI IN : Weld heat input (J / cm) in inner side welding
t: thickness of welded steel pipe (mm)
Next, the outer surface side is welded in one pass.
At that time, it is necessary the ratio of heat input HI IN in the welding of the inner surface side (J / cm) Welding in welding the outer surface side and the heat input HI OUT (J / cm) satisfies the following equation (1). If HI OUT / HI IN is less than 1.1, sufficient penetration cannot be secured, so that the weld metal on the inner surface side and the weld metal on the outer surface side are not sufficiently joined, and the strength of the seam is reduced. On the other hand, if it exceeds 1.5, the toughness of the portion where the HAZ on the inner surface side and the HAZ on the outer surface side overlap is deteriorated.

1.1≦HIOUT/HIIN≦1.5 ・・・(1)
HIIN:内面側の溶接における溶接入熱(J/cm)
HIOUT:外面側の溶接における溶接入熱(J/cm)
以上に説明した通り、本発明では、まずシームの内面側を1パスで溶接する。その際、内面側の溶接入熱HIINを(2)式の範囲内に低減することによって、HAZの結晶粒を微細化する。次に、外面側を1パスで溶接する。その際、外面側の溶接入熱HIOUTは、内面側の溶接金属と外面側の溶接金属を十分に接合するために、HIINより大きくする。ただし、HIINとHIOUTの比を(1)式の範囲内に規定することによって、HAZの結晶粒の粗大化を防止する。
1.1 ≦ HI OUT / HI IN ≦ 1.5 (1)
HI IN : Weld heat input (J / cm) in inner side welding
HI OUT : Weld heat input (J / cm) for welding on the outer surface side
As described above, in the present invention, first, the inner surface side of the seam is welded in one pass. At that time, the HAZ crystal grains are refined by reducing the welding heat input HI IN on the inner surface within the range of the formula (2). Next, the outer surface side is welded in one pass. At this time, the welding heat input HI OUT on the outer surface side is set larger than HI IN in order to sufficiently join the welding metal on the inner surface side and the welding metal on the outer surface side. However, the coarsening of the HAZ crystal grains is prevented by defining the ratio of HI IN and HI OUT within the range of the equation (1).

このような溶接入熱の制御を可能にするサブマージアーク溶接について、図1を参照して以下に説明する。
図1は、溶接鋼管と電極の配置の例を模式的に示す断面図である。図1中の矢印Aは溶接機の進行方向を示す。本発明は3電極以上を備えた溶接機を使用するが、ここでは3電極の溶接機を使用する例について説明する。なお溶接機の本体は図示を省略し、コンタクトチップと溶接用ワイヤを図示する。
Submerged arc welding that enables such control of welding heat input will be described below with reference to FIG.
FIG. 1 is a cross-sectional view schematically showing an example of the arrangement of welded steel pipes and electrodes. An arrow A in FIG. 1 indicates the traveling direction of the welder. The present invention uses a welding machine having three or more electrodes. Here, an example in which a three-electrode welding machine is used will be described. The main body of the welder is not shown, and the contact tip and the welding wire are shown.

コンタクトチップと溶接用ワイヤとで構成される電極は溶接機の進行方向に沿って1列に配置される。ここでは、進行方向の先頭に位置する電極を第1電極とし、それ以降を順に第2電極,第3電極とする。
第1電極のコンタクトチップ2aには直径3.2mm以下の溶接用ワイヤを供給する。第1電極は溶込みの深さに多大な影響を及ぼすので、細径(すなわち直径3.2mm以下)の溶接用ワイヤ3を使用してアーク圧力を高めることによって、十分な深さの溶込みを確保する。また、溶接鋼管1の表面とコンタトクチップ2aの先端との距離Lは30mm以上とする。距離Lを30mm以上とすることによって、溶接用ワイヤ3の抵抗発熱を利用した高溶着速度を得ることができる。
The electrodes composed of the contact tips and the welding wires are arranged in a line along the traveling direction of the welding machine. Here, the electrode located at the head in the traveling direction is the first electrode, and the subsequent electrodes are the second electrode and the third electrode in order.
A welding wire having a diameter of 3.2 mm or less is supplied to the contact tip 2a of the first electrode. Since the first electrode has a great influence on the depth of penetration, a sufficient depth of penetration can be achieved by increasing the arc pressure using a welding wire 3 having a small diameter (ie, a diameter of 3.2 mm or less). Secure. The distance L between the surface of the welded steel pipe 1 and the tip of the contact tip 2a is 30 mm or more. By setting the distance L to 30 mm or more, it is possible to obtain a high welding speed using resistance heating of the welding wire 3.

さらに、第2電極以降(図1の例では第2電極,第3電極)のうちの少なくとも1個の電極に直径3.2mm以下の溶接用ワイヤを供給する。これも第1電極と同様に、アーク圧力を高めて、十分な深さの溶込みを確保するため、および高溶接速度を得るためである。その電極についても、溶接鋼管の表面とコンタトクチップの先端との距離Lは30mm以上とする。   Further, a welding wire having a diameter of 3.2 mm or less is supplied to at least one of the second and subsequent electrodes (second electrode and third electrode in the example of FIG. 1). This is because, like the first electrode, the arc pressure is increased to ensure a sufficient depth of penetration and to obtain a high welding speed. Also for the electrode, the distance L between the surface of the welded steel pipe and the tip of the contact tip is 30 mm or more.

第2電極以降の細径の溶接用ワイヤの適用電極は特に限定せず、溶接鋼管の寸法や溶接機の仕様等に応じて適宜選択する。
このようにして細径(すなわち直径3.2mm以下)の溶接用ワイヤを使用すると、アーク圧力が高まり、シームの表面に凹凸が発生し易い。そこで、溶接機に交流電流を供給し、互いに隣り合う電極に供給する交流電流の位相差を90〜120°の範囲内とすることが好ましい。交流電流は、溶接機の全電極に供給する、あるいは第2電極以降に供給することが好ましい。
The applicable electrode of the small-diameter welding wire after the second electrode is not particularly limited and is appropriately selected according to the dimensions of the welded steel pipe, the specifications of the welding machine, and the like.
When a welding wire having a small diameter (that is, a diameter of 3.2 mm or less) is used in this way, the arc pressure increases and irregularities are likely to occur on the surface of the seam. Therefore, it is preferable that an alternating current is supplied to the welding machine and the phase difference between the alternating currents supplied to the electrodes adjacent to each other is within a range of 90 to 120 °. The alternating current is preferably supplied to all the electrodes of the welding machine, or supplied after the second electrode.

全電極に交流電流を供給する場合は、全ての電極(図1の例では第1電極〜第3電極)の位相差を90〜120°の範囲内とする。
第2電極以降に交流電流を供給する場合は、第2電極以降の電極(図1の例では第2電極,第3電極)の位相差を90〜120°の範囲内とする。第1電極には直流電流を供給する。第1電極は溶込みの深さに多大な影響を及ぼすので、直流電流を供給して溶込みを容易に調整できるようにするためである。
When supplying an alternating current to all the electrodes, the phase difference of all the electrodes (the first electrode to the third electrode in the example of FIG. 1) is set within a range of 90 to 120 °.
When an alternating current is supplied to the second and subsequent electrodes, the phase difference between the second and subsequent electrodes (second electrode and third electrode in the example of FIG. 1) is set within a range of 90 to 120 °. A direct current is supplied to the first electrode. This is because the first electrode has a great influence on the depth of penetration, so that a direct current can be supplied to easily adjust the penetration.

互いに隣り合う電極に供給する交流電流の位相差を90〜120°の範囲内とすることによって、細径の溶接用ワイヤを使用しても、美麗なシームを得ることが可能となる。
なお本発明を適用する溶接鋼管の素材となる鋼板の成分は特に限定しない。ただし質量%で、C:0.02〜0.08%,Si:0.02〜0.35%,Mn:1.10〜2.00%,P:0.010%以下,S:0.005%以下,Cu:0.3%以下,Ni:0.35%以下,Cr:0.3%以下,Mo:0.5%以下,Nb:0.05%以下,V:0.05%以下,Al:0.03%以下,Ti:0.02以下%,B:0.0010%以下,N:0.010%以下,Ca:0.0025%以下を含有し、残部がFeおよび不可避的不純物からなる鋼板を用いて溶接鋼管を製造する際に適用することが好ましい。
By setting the phase difference of the alternating current supplied to the electrodes adjacent to each other within the range of 90 to 120 °, it is possible to obtain a beautiful seam even when a small-diameter welding wire is used.
In addition, the component of the steel plate used as the raw material of the welded steel pipe to which this invention is applied is not specifically limited. However, in mass%, C: 0.02 to 0.08%, Si: 0.02 to 0.35%, Mn: 1.10 to 2.00%, P: 0.010% or less, S: 0.005% or less, Cu: 0.3% or less, Ni: 0.35% or less, Cr: 0.3% or less, Mo: 0.5% or less, Nb: 0.05% or less, V: 0.05% or less, Al: 0.03% or less, Ti: 0.02% or less, B: 0.0010% or less, N: 0.010% or less, Ca: It is preferably applied when producing a welded steel pipe using a steel plate containing 0.0025% or less and the balance being Fe and inevitable impurities.

表1に示す成分の鋼素材を圧延して板厚38mm,33mm,27mm,25mmの鋼板を製造した。これらの鋼板を表2,3に示す条件で溶接した。その後、溶接部からシャルピー試験片を採取してシャルピー試験を行ない、−30℃における吸収エネルギー(J)を測定した。なおボンド部のシャルピー試験片は、図2(a)に示すように、溶接ビード止端部より2mm下の位置がシャルピー試験片の表面と一致するように採取し、ノッチ位置は50%が溶接金属,50%が熱影響部となるようにした。ルート部のシャルピー試験片は、図2(b)に示すように、内面溶接金属と外面溶接金属が会合する位置がシャルピー試験片の中央と一致するように採取し、ノッチ位置は50%が溶接金属,50%が熱影響部となるようにした。シャルピー試験は、それぞれ3回ずつ行ない、各測定値とその平均値を示す。   The steel materials having the components shown in Table 1 were rolled to produce steel sheets with thicknesses of 38 mm, 33 mm, 27 mm, and 25 mm. These steel plates were welded under the conditions shown in Tables 2 and 3. Thereafter, a Charpy test piece was collected from the welded portion and subjected to a Charpy test, and the absorbed energy (J) at −30 ° C. was measured. As shown in Fig. 2 (a), the Charpy test piece at the bond part was taken so that the position 2mm below the weld bead toe coincides with the surface of the Charpy test piece, and the notch position was 50% welded. 50% of the metal is the heat affected zone. As shown in Fig. 2 (b), the Charpy specimen at the root is taken so that the position where the inner and outer weld metals meet is aligned with the center of the Charpy specimen, and the notch position is 50% welded. 50% of the metal is the heat affected zone. The Charpy test is performed three times each, and shows each measured value and its average value.

表2,3中のLは、母材表面とコンタクトチップ先端との距離(mm)を指す。   L in Tables 2 and 3 indicates the distance (mm) between the surface of the base material and the tip of the contact chip.

Figure 0004998353
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記号1〜4は発明例であり、いずれも良好な溶接が得られ、かつ熱影響部の靭性も優れている。
記号5は比較例であり、外面溶接金属の溶接入熱が高くなりすぎ、熱影響部の靭性が劣化し、−30℃のシャルピー試験において、3本中の1本は吸収エネルギーが50J以下であった。記号6は比較例であり、内面溶接入熱と外面溶接入熱の比が1.1を下回り、溶け込み不足が生じた。記号7は比較例であり、内面溶接の入熱が高くなりすぎ、ルート部のシャルピー試験片3本中の1本は吸収エネルギーが50J以下であった。
Symbols 1 to 4 are examples of the invention, all of which provide good welding and are excellent in toughness of the heat affected zone.
Symbol 5 is a comparative example, where the heat input of the outer surface weld metal becomes too high and the toughness of the heat affected zone deteriorates. In the Charpy test at −30 ° C., one of the three has an absorbed energy of 50 J or less. there were. Symbol 6 is a comparative example, and the ratio of inner surface welding heat input to outer surface welding heat input was less than 1.1, resulting in insufficient penetration. Symbol 7 is a comparative example, in which heat input by internal welding becomes too high, and one of the three Charpy test pieces in the root portion has an absorbed energy of 50 J or less.

記号8は発明例であり、熱影響部の靭性が優れている。ただし第2電極と第3電極の位相差が60°であるから、溶接欠陥(すなわちスラグ巻き込み)が発生した。
記号9は発明例であり、良好な靭性が得られている。ただし第1電極のワイヤ径が4.0mmであるから、溶接欠陥(すなわちアンダーフィル,溶け込み不足)が発生した。
Symbol 8 is an invention example, and the toughness of the heat affected zone is excellent. However, since the phase difference between the second electrode and the third electrode was 60 °, welding defects (that is, slag entrainment) occurred.
Symbol 9 is an invention example, and good toughness is obtained. However, since the wire diameter of the first electrode was 4.0 mm, a welding defect (that is, underfill, insufficient penetration) occurred.

溶接鋼管と電極の配置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 arrangement | positioning of a welded steel pipe and an electrode. シャルピー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 test piece.

符号の説明Explanation of symbols

1 溶接鋼管
2a 第1電極のコンタクトチップ
2b 第2電極のコンタクトチップ
2c 第3電極のコンタクトチップ
3 溶接用ワイヤ
1 Welded steel pipe
2a Contact tip of the first electrode
2b Second electrode contact tip
2c 3rd electrode contact tip 3 Welding wire

Claims (3)

溶接鋼管のシームの外面側と内面側をサブマージアーク溶接にてそれぞれ1層ずつ溶接する溶接鋼管の製造方法において、前記内面側の溶接における溶接入熱HIIN(J/cm)と前記外面側の溶接における溶接入熱HIOUT(J/cm)の比が下記の(1)式を満足し、かつ前記HIIN(J/cm)と前記溶接鋼管の厚みt(mm)が下記の(2)式を満足することを特徴とする溶接鋼管の製造方法。
1.1≦HIOUT/HIIN≦1.5 ・・・(1)
HIIN≦231×t1.56 ・・・(2)
HIIN:内面側の溶接における溶接入熱(J/cm)
HIOUT:外面側の溶接における溶接入熱(J/cm)
t:溶接鋼管の厚み(mm)
In a method for manufacturing a welded steel pipe in which the outer surface side and the inner surface side of a seam of the welded steel pipe are welded one layer at a time by submerged arc welding, the welding heat input HI IN (J / cm) in the inner surface side welding and the outer surface side The ratio of the welding heat input HI OUT (J / cm) in welding satisfies the following formula (1), and the HI IN (J / cm) and the thickness t (mm) of the welded steel pipe are the following (2) The manufacturing method of the welded steel pipe characterized by satisfy | filling Formula.
1.1 ≦ HI OUT / HI IN ≦ 1.5 (1)
HI IN ≦ 231 × t 1.56 (2)
HI IN : Weld heat input (J / cm) in inner side welding
HI OUT : Weld heat input (J / cm) for welding on the outer surface side
t: thickness of welded steel pipe (mm)
前記シームの外面側の溶接と内面側の溶接を行なうにあたって3電極以上の溶接機を用い、前記溶接機の進行方向の先頭に位置する第1電極に直径3.2mm以下の溶接用ワイヤを供給するとともに、その他の第2電極以降の少なくとも1個の電極に直径3.2mm以下の溶接用ワイヤを供給し、前記溶接鋼管の表面と前記溶接機のコンタクトチップ先端との距離をいずれも30mm以上とし、前記溶接機の全電極に交流電流を供給し、互いに隣り合う電極に供給される前記交流電流の位相差を90〜120°の範囲内とすることを特徴とする請求項1に記載の溶接鋼管の製造方法。   When welding the outer surface side and the inner surface side of the seam, a welding machine having three or more electrodes is used, and a welding wire having a diameter of 3.2 mm or less is supplied to the first electrode located at the head in the traveling direction of the welding machine. In addition, a welding wire having a diameter of 3.2 mm or less is supplied to at least one of the other electrodes after the second electrode, and the distance between the surface of the welded steel pipe and the tip of the contact tip of the welder is 30 mm or more, 2. The welded steel pipe according to claim 1, wherein an alternating current is supplied to all electrodes of the welding machine, and a phase difference between the alternating currents supplied to adjacent electrodes is within a range of 90 to 120 °. Manufacturing method. 前記シームの外面側の溶接と内面側の溶接を行なうにあたって3電極以上の溶接機を用い、前記溶接機の進行方向の先頭に位置する第1電極に直径3.2mm以下の溶接用ワイヤを供給するとともに、その他の第2電極以降の少なくとも1個の電極に直径3.2mm以下の溶接用ワイヤを供給し、前記溶接鋼管の表面と前記溶接機のコンタクトチップ先端との距離をいずれも30mm以上とし、前記溶接機の第1電極に直流電流を供給するとともに、その他の第2電極以降に交流電流を供給し、前記第2電極以降の互いに隣り合う電極に供給される前記交流電流の位相差を90〜120°の範囲内とすることを特徴とする請求項1に記載の溶接鋼管の製造方法。
When welding the outer surface side and the inner surface side of the seam, a welding machine having three or more electrodes is used, and a welding wire having a diameter of 3.2 mm or less is supplied to the first electrode located at the head in the traveling direction of the welding machine. In addition, a welding wire having a diameter of 3.2 mm or less is supplied to at least one of the other electrodes after the second electrode, and the distance between the surface of the welded steel pipe and the tip of the contact tip of the welder is 30 mm or more, A direct current is supplied to the first electrode of the welding machine, an alternating current is supplied to the second and subsequent electrodes, and the phase difference of the alternating current supplied to the adjacent electrodes after the second electrode is set to 90. The method for producing a welded steel pipe according to claim 1, wherein the method is within a range of ˜120 °.
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