JP6927304B2 - Gas shield arc welding method for steel sheets - Google Patents
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- 238000003466 welding Methods 0.000 title claims description 88
- 229910000831 Steel Inorganic materials 0.000 title claims description 49
- 239000010959 steel Substances 0.000 title claims description 49
- 238000000034 method Methods 0.000 title claims description 12
- 239000007789 gas Substances 0.000 description 33
- 238000005336 cracking Methods 0.000 description 17
- 229910052751 metal Inorganic materials 0.000 description 16
- 239000002184 metal Substances 0.000 description 16
- 238000010276 construction Methods 0.000 description 11
- 229910052761 rare earth metal Inorganic materials 0.000 description 10
- 150000002910 rare earth metals Chemical class 0.000 description 9
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 6
- 229910052739 hydrogen Inorganic materials 0.000 description 6
- 239000001257 hydrogen Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
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- 238000005516 engineering process Methods 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
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- 239000000463 material Substances 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 239000011324 bead Substances 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
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- 230000002950 deficient Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000006249 magnetic particle Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
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- 238000004544 sputter deposition Methods 0.000 description 1
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- 238000009628 steelmaking Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/16—Arc welding or cutting making use of shielding gas
- B23K9/173—Arc welding or cutting making use of shielding gas and of a consumable electrode
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/23—Arc welding or cutting taking account of the properties of the materials to be welded
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Description
本発明は、鋼板を突き合わせて多層溶接によって接合するガスシールドアーク溶接方法に関するものである。 The present invention relates to a gas shielded arc welding method in which steel plates are butted and joined by multi-layer welding.
ガスシールドアーク溶接は、溶接によって鋼板を接合する部位とその周辺(以下、接合部位という)をシールドガス(たとえば、CO2単独ガス、あるいはArとCO2との混合ガス等)で覆いながら、溶接ワイヤ(いわゆる消耗電極)を使用して鋼板を接合する技術であり、自動車、建築、橋梁、および電気機器等の工事現場や製造現場で普及している。なかでも建築や橋梁の分野では、近年、鋼構造物の大型化が著しく進展し、その鋼構造物の強度を確保するために高強度厚鋼板が使用されるようになり、それに適した溶接技術が開発されている。In gas shielded arc welding, welding is performed while covering the part where the steel sheets are joined by welding and the surrounding area (hereinafter referred to as the joining part) with a shield gas (for example, CO 2 single gas or a mixed gas of Ar and CO 2). It is a technology for joining steel plates using wires (so-called consumable electrodes), and is widely used at construction sites and manufacturing sites for automobiles, construction, bridges, and electrical equipment. Especially in the fields of construction and bridges, the size of steel structures has increased remarkably in recent years, and high-strength thick steel plates have come to be used to secure the strength of the steel structures, and welding technology suitable for them has come to be used. Has been developed.
建築や橋梁を構築するための構造物の製造現場、あるいは、それを施工する工事現場にて、鋼板を突き合わせてガスシールドアーク溶接で接合するにあたって、溶接ワイヤを複数本使用する、あるいは、溶接ワイヤを同じ接合部位に複数回通過させることによって、多数の層状の溶接金属を積み重ねる溶接技術(以下、多層溶接という)が、一般に広く採用される。ところがガスシールドアーク溶接による鋼板の多層溶接では、溶接によって鋼板に生じる溶接金属と熱影響部からなる部位(以下、溶接部という)が冷却された後に、低温割れが発生し易いという問題がある。 When joining steel plates by gas shield arc welding at the manufacturing site of a structure for building or building a bridge, or at the construction site where it is constructed, multiple welding wires are used, or welding wires are used. A welding technique (hereinafter referred to as multi-layer welding) in which a large number of layers of weld metal are stacked by passing the weld metal through the same joint site a plurality of times is generally widely adopted. However, in multi-layer welding of a steel sheet by gas shield arc welding, there is a problem that low-temperature cracks are likely to occur after a portion (hereinafter, referred to as a welded zone) consisting of a weld metal and a heat-affected zone generated in the steel sheet by welding is cooled.
溶接部の低温割れは、溶接が終了した後、つまり溶接部が室温程度まで冷却された後に発生する割れ(いわゆる遅れ割れ)であり、溶接部に関わる3要素(すなわち溶接部の残留応力や硬さ、溶接部に内在する水素)の重畳的な相互作用が原因であることが判明している。そして、引張強さが590MPa以上の鋼板では、このような低温割れの発生頻度が増加する傾向がある。 Low-temperature cracks in the weld are cracks that occur after the weld is completed, that is, after the weld has been cooled to about room temperature (so-called delayed cracks), and are the three elements related to the weld (that is, the residual stress and hardness of the weld). Now, it has been found that the cause is the overlapping interaction of hydrogen) inherent in the weld. Then, in a steel sheet having a tensile strength of 590 MPa or more, the frequency of occurrence of such low temperature cracks tends to increase.
そこで、引張強さが590MPa以上の鋼板については、このような低温割れを防止するための技術が種々検討されている。 Therefore, various techniques for preventing such low-temperature cracking have been studied for steel sheets having a tensile strength of 590 MPa or more.
たとえば、引張強さが590MPa以上の鋼板の多層溶接を行なう前に予め接合部位を加熱して、鋼板およびその付着物(たとえば水滴等)の水素を大気中へ放散させる予熱処理が、低温割れの防止に有効であることが知られている。しかし接合部位の予熱処理は多大な時間と労力を必要とし、その結果、ガスシールドアーク溶接の施工コストの増大を招く。 For example, preheat treatment that heats the joint site in advance before performing multi-layer welding of a steel sheet with a tensile strength of 590 MPa or more to dissipate hydrogen from the steel sheet and its deposits (for example, water droplets) into the atmosphere is a low-temperature cracking process. It is known to be effective in prevention. However, preheat treatment of the joint portion requires a great deal of time and labor, resulting in an increase in the construction cost of gas shielded arc welding.
また特許文献1には、引張強さが780MPa以上の鋼板の多層溶接において、予熱処理を必要とせず、低温割れを抑制することが可能なレーザ・アークハイブリッド溶接の技術が開示されている。この技術は、ハイブリッド溶接を行なうために大型の治具やレーザ発信装置等を使用するので、狭い場所では施工できないという制約がある。特に建築や橋梁の分野では、鋼板からなる鋼構造物を組み立てる際に、現場溶接と呼ばれる現地での溶接施工が必ず必要となる。 Further, Patent Document 1 discloses a laser-arc hybrid welding technique capable of suppressing low-temperature cracking without requiring preheat treatment in multi-layer welding of steel sheets having a tensile strength of 780 MPa or more. Since this technique uses a large jig, a laser transmitter, or the like for performing hybrid welding, there is a restriction that it cannot be applied in a narrow space. Especially in the fields of construction and bridges, when assembling a steel structure made of steel plate, on-site welding called on-site welding is indispensable.
現場溶接は、鋼構造物である柱と梁(あるいは柱と柱)を工事現場で接合する作業であり、作業員が安全に作業できる十分な広さの空間を確保するのは難しい。つまり、現場溶接にて大型の治具や装置を使用することが困難であるという問題点が、レーザ・アークハイブリッド溶接の現場溶接における普及を妨げている。 On-site welding is the work of joining columns and beams (or columns and columns), which are steel structures, at the construction site, and it is difficult to secure a sufficient space for workers to work safely. That is, the problem that it is difficult to use a large jig or device in on-site welding hinders the spread of laser-arc hybrid welding in on-site welding.
これに対して、レーザ・アークハイブリッド溶接よりも簡便な手段で施工できるガスシールドアーク溶接による多層溶接を採用する場合は、既に説明した通り、低温割れを防止する必要があるので、接合部位の予熱処理を工事現場で実施せざるを得ない。その結果、建築や橋梁を構築するのに要する工事費用の増大、工期の延長を招く。 On the other hand, when multi-layer welding by gas shielded arc welding, which can be performed by a simpler means than laser / arc hybrid welding, is adopted, it is necessary to prevent low temperature cracking as described above. There is no choice but to carry out heat treatment at the construction site. As a result, the construction cost required to construct the building and the bridge will increase, and the construction period will be extended.
本発明は、従来の技術の問題点を解消し、鋼板を突き合わせて多層溶接によって接合する際に、接合部位の予熱処理を行なうことなくガスシールドアーク溶接を施工し、冷却した後に発生する溶接部の低温割れを効果的に防止することが可能なガスシールドアーク溶接方法を提供することを目的とする。 The present invention solves the problems of the prior art, and when the steel plates are butted and joined by multi-layer welding, gas shielded arc welding is performed without preheat treatment of the joint portion, and the welded portion generated after cooling is performed. It is an object of the present invention to provide a gas shielded arc welding method capable of effectively preventing low temperature cracking.
なお本発明のガスシールドアーク溶接方法が適用される鋼板は、引張強さが590MPa以上かつ板厚が22mm以上である鋼板を意味する。 The steel sheet to which the gas shielded arc welding method of the present invention is applied means a steel sheet having a tensile strength of 590 MPa or more and a plate thickness of 22 mm or more.
本発明者は、上記した課題を解決するために、引張強さが590MPa以上かつ板厚が22mm以上である2枚の鋼板を突き合わせて、その開先形状および溶接ワイヤの成分を種々変化させてガスシールドアーク溶接を行ない、溶接部の低温割れの発生状況を調査した。その結果、
(a)開先角度と開先ギャップを適正な範囲に調整する、
(b)溶接ワイヤに含有される希土類元素(以下、REMという)の含有量を適正な範囲に調整することによって、接合部位の予熱処理を行なうことなく溶接部の低温割れを効果的に防止できることを見出した。In order to solve the above-mentioned problems, the present inventor abuts two steel plates having a tensile strength of 590 MPa or more and a plate thickness of 22 mm or more, and variously changes the groove shape and the composition of the welding wire. Gas shield arc welding was performed to investigate the occurrence of low temperature cracks in the weld. resulting in,
(a) Adjust the groove angle and groove gap to an appropriate range,
(b) By adjusting the content of rare earth elements (hereinafter referred to as REM) contained in the weld wire to an appropriate range, low-temperature cracking of the weld can be effectively prevented without preheat treatment of the joint. I found.
さらに、溶接電流や溶接電圧、溶接速度等の溶接条件を変化させてガスシールドアーク溶接を行なったところ、溶接条件に関わらず上記(a)(b)を適正な範囲に調整することによって、低温割れを防止できることが判明した。 Furthermore, when gas shielded arc welding was performed by changing the welding conditions such as welding current, welding voltage, and welding speed, the temperature was lowered by adjusting the above (a) and (b) to an appropriate range regardless of the welding conditions. It turned out that cracking can be prevented.
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。 The present invention has been made based on such findings.
すなわち本発明は、引張強さが590MPa以上かつ板厚が22mm以上である2枚の鋼板を突き合わせて、開先角度を10°以下かつ開先ギャップを7〜15mmとし、REMを0.015〜0.100質量%含有する溶接ワイヤを用いて、溶接ワイヤをマイナスとした下向きガスシールドアーク溶接を行ない、突き合わせ多層溶接によって鋼板を接合するガスシールドアーク溶接方法である。 That is, in the present invention, two steel plates having a tensile strength of 590 MPa or more and a plate thickness of 22 mm or more are butted together, the groove angle is 10 ° or less, the groove gap is 7 to 15 mm, and the REM is 0.015 to 0.100 mass. This is a gas shielded arc welding method in which downward gas shielded arc welding is performed using a welding wire containing%, with the welding wire as a minus, and steel sheets are joined by butt multi-layer welding.
本発明によれば、鋼板(引張強さ:590MPa以上、板厚:22mm以上)を突き合わせて多層溶接によって接合する際に、接合部位の予熱処理を行なうことなくガスシールドアーク溶接を施工し、冷却した後に発生する溶接部の低温割れを効果的に防止することが可能となる。そして、溶接施工の時間と労力を大幅に低減できるので、産業上格段の効果を奏する。 According to the present invention, when steel plates (tensile strength: 590 MPa or more, plate thickness: 22 mm or more) are butted and joined by multi-layer welding, gas shielded arc welding is performed and cooling is performed without preheat treatment of the joint portion. It is possible to effectively prevent low-temperature cracking of the welded portion that occurs after the heat treatment. Moreover, since the time and labor of welding work can be significantly reduced, it is extremely effective in industry.
本発明を適用する鋼板について、図1を参照して説明する。本発明は、板厚22mm以上であり、かつ、引張強さ590MPa以上の2枚の鋼板を突き合わせてガスシールドアーク溶接を行う際に適用するガスシールドアーク溶接方法である。 The steel sheet to which the present invention is applied will be described with reference to FIG. The present invention is a gas shielded arc welding method applied when two steel plates having a plate thickness of 22 mm or more and a tensile strength of 590 MPa or more are butted against each other to perform gas shielded arc welding.
板厚:22mm以上
鋼板の板厚tが22mm未満であれば、V形開先において開先角度を大きくし、かつ開先ギャップを小さくしなければならない。その結果、開先2の形状によってはその断面積が縮小するので、溶着金属の少ない高能率な溶接が要求され、施工コストの上昇を招く。Plate thickness: 22 mm or more If the plate thickness t of the steel plate is less than 22 mm, the groove angle must be increased and the groove gap must be reduced in the V-shaped groove. As a result, the cross-sectional area of the groove 2 is reduced depending on the shape of the groove 2, so that high-efficiency welding with a small amount of weld metal is required, which leads to an increase in construction cost.
つまり、板厚t:20mmの鋼板1を、開先角度θ:0°、開先ギャップG:7mmのI形開先で溶接する場合、開先2の断面積は140mm2である。これに対して板厚t:20mmの鋼板1を、開先角度θ:25°、開先ギャップG:2mmのレ形開先(bevel groove)で溶接する場合、開先2の断面積は133mm2に縮小するから、溶着金属の体積が少なくても十分な接合強度を得るための対応(たとえば、高価な成分を多量に含有する溶接ワイヤを使用する等)が求められる。That is, when the steel plate 1 having a plate thickness t: 20 mm is welded with an I-shaped groove having a groove angle θ: 0 ° and a groove gap G: 7 mm, the cross-sectional area of the groove 2 is 140 mm 2 . On the other hand, when a steel plate 1 having a plate thickness t: 20 mm is welded with a bevel groove having a groove angle θ: 25 ° and a groove gap G: 2 mm, the cross-sectional area of the groove 2 is 133 mm. Since it is reduced to 2, it is necessary to take measures to obtain sufficient bonding strength even if the volume of the weld metal is small (for example, use a welding wire containing a large amount of expensive components).
したがって本発明を適用する鋼板1の板厚tは、22mm以上とする。 Therefore, the plate thickness t of the steel plate 1 to which the present invention is applied is 22 mm or more.
なお板厚tの上限は、鋼板1の製造工場にて圧延可能な上限値である。具体的には、板厚tは22〜120mmが好ましい。 The upper limit of the plate thickness t is an upper limit value that can be rolled at the manufacturing plant of the steel plate 1. Specifically, the plate thickness t is preferably 22 to 120 mm.
引張強さ:590MPa以上
ガスシールドアーク溶接による鋼板1の多層溶接を従来の技術で行なった場合は、溶接部の低温割れが発生し易いという問題があり、特に引張強さが590MPa以上の鋼板1において、低温割れの発生頻度が著しく増加する。Tensile strength: 590MPa or more When multi-layer welding of steel sheet 1 by gas shield arc welding is performed by conventional technology, there is a problem that low temperature cracks are likely to occur in the welded part, and in particular, steel sheet 1 having a tensile strength of 590MPa or more. In, the frequency of low-temperature cracking increases remarkably.
これに対して本発明は、引張強さが590MPa以上の鋼板1であっても、接合部位の予熱処理を行なうことなくガスシールドアーク溶接を施工でき、しかも溶接部の低温割れを防止することが可能となる。つまり、引張強さが590MPa以上の鋼板1のガスシールドアーク溶接による多層溶接に本発明を適用することによって、低温割れを防止するという顕著な効果が発揮される。
また、開先ギャップGが小さいほど、溶接中に発生したスパッタが開先の表面に付着しやすく、スパッタが、コンタクトチップやシールドノズルと干渉してアークストップが発生し易い。On the other hand, according to the present invention, even if the steel sheet 1 has a tensile strength of 590 MPa or more, gas shielded arc welding can be performed without preheat treatment of the joint portion, and low temperature cracking of the welded portion can be prevented. It will be possible. That is, by applying the present invention to multi-layer welding by gas shielded arc welding of a steel sheet 1 having a tensile strength of 590 MPa or more, a remarkable effect of preventing low temperature cracking is exhibited.
Further, the smaller the groove gap G, the more easily the spatter generated during welding adheres to the surface of the groove, and the spatter easily interferes with the contact tip and the shield nozzle to generate an arc stop.
したがって本発明を適用する鋼板1の引張強さは、590MPa以上とする。したがって、本発明は、板厚22mm以上であり、かつ、引張強さ590MPa以上の2枚の鋼板を突き合わせてガスシールドアーク溶接を行う際に適用することがより好ましい。低温割れは、さらに高強度の780MPa以上の鋼板において発生頻度がより高くなる傾向にある。そのため、本発明は、780MPa以上の鋼板の突き合わせガスシールドアーク溶接に適用すると、より効果が顕著となるため、鋼板の引張強度は780MPa以上とすることが好ましい。 Therefore, the tensile strength of the steel sheet 1 to which the present invention is applied shall be 590 MPa or more. Therefore, the present invention is more preferably applied when two steel plates having a plate thickness of 22 mm or more and a tensile strength of 590 MPa or more are butted against each other to perform gas shielded arc welding. Low temperature cracking tends to occur more frequently in steel sheets with higher strength of 780 MPa or higher. Therefore, when the present invention is applied to butt gas shielded arc welding of a steel sheet of 780 MPa or more, the effect becomes more remarkable, so that the tensile strength of the steel sheet is preferably 780 MPa or more.
次に、本発明を適用する鋼板1を突き合わせて形成される開先2の形状について、図1、2を参照して説明する。 Next, the shape of the groove 2 formed by abutting the steel plates 1 to which the present invention is applied will be described with reference to FIGS. 1 and 2.
開先角度:10°以下
開先角度θが10°を超えると、開先2の断面積が増加し、ひいては溶着金属の体積が増加するので、低温割れが発生し易くなる。Groove angle: 10 ° or less When the groove angle θ exceeds 10 °, the cross-sectional area of the groove 2 increases, and the volume of the weld metal increases, so that low-temperature cracking is likely to occur.
つまり、既に説明した溶接部を構成する溶接金属3は、溶接によって開先に付着した溶着金属が冷却されたものであるから、溶着金属に水素が混入すれば、溶接金属3にも水素が残留し、その水素が主要な原因となって低温割れを引き起こす。溶着金属の体積が多くなると、混入する水素も増加し易くなり、その結果、低温割れが発生し易くなる。 That is, since the weld metal 3 constituting the welded portion described above is obtained by cooling the weld metal adhering to the groove by welding, if hydrogen is mixed in the weld metal, hydrogen remains in the weld metal 3 as well. However, the hydrogen is the main cause of low temperature cracking. As the volume of the weld metal increases, the amount of hydrogen mixed in tends to increase, and as a result, low-temperature cracking tends to occur.
したがって開先角度θは、10°以下とする。 Therefore, the groove angle θ is set to 10 ° or less.
なお、開先角度θの下限は0°(すなわちI形開先)であっても良いが、I形開先では溶接中の角変更によって開先角度が負となり、健全な溶接ができないという問題が生じる場合がある。そこで、開先角度θを2〜10°として、下向きガスシールドアーク溶接を行なうことが好ましい。より好ましくは、開先角度θは、5〜8°である。 The lower limit of the groove angle θ may be 0 ° (that is, the I-shaped groove), but in the I-shaped groove, the groove angle becomes negative due to the angle change during welding, and sound welding cannot be performed. May occur. Therefore, it is preferable to perform downward gas shielded arc welding with the groove angle θ set to 2 to 10 °. More preferably, the groove angle θ is 5 to 8 °.
開先ギャップ:7〜15mm
開先ギャップGが小さいほど、溶接金属3の体積が小さくなり、低温割れの発生が抑制されるが、接合不良等の欠陥が生じ易い。一方で開先ギャップGが大きいほど、溶接金属3の体積が大きくなり、低温割れが発生し易い。Groove gap: 7 to 15 mm
The smaller the groove gap G is, the smaller the volume of the weld metal 3 is, and the occurrence of low-temperature cracks is suppressed, but defects such as poor joining are likely to occur. On the other hand, the larger the groove gap G, the larger the volume of the weld metal 3, and the lower temperature cracks are likely to occur.
したがって開先ギャップGは、7〜15mmとする。好ましくは、8〜12mmである。 Therefore, the groove gap G is set to 7 to 15 mm. It is preferably 8 to 12 mm.
次に、ガスシールドアーク溶接で使用する溶接ワイヤのREM(Rare Earth Metal)含有量について説明する。 Next, the REM (Rare Earth Metal) content of the welding wire used in gas shielded arc welding will be described.
REM:0.015〜0.100質量%
REMは、製鋼工程および鋳造工程の介在物の微細化や、溶接金属の靭性改善に有効な元素である。また、ガスシールドアーク溶接において、溶接ワイヤをマイナス(いわゆる正極性)とした場合や、溶接電流を大きくした場合に、溶滴の微細化および溶滴移行の安定化を達成し、さらに開先面方向へのアークの発生を抑制する効果も有する。ガスシールドアーク溶接における溶滴の微細化と溶滴移行の安定化は、スパッタの発生を抑制して、安定した円滑な溶接施工に寄与する。REM: 0.015 to 0.100% by mass
REM is an element effective for miniaturizing inclusions in the steelmaking process and casting process and improving the toughness of weld metal. Further, in gas shielded arc welding, when the welding wire is negative (so-called positive electrode property) or when the welding current is increased, the droplets are made finer and the droplet migration is stabilized, and the groove surface is further formed. It also has the effect of suppressing the generation of arcs in the direction. The miniaturization of droplets and the stabilization of droplet migration in gas shielded arc welding suppress the generation of spatter and contribute to stable and smooth welding.
REM含有量が0.015質量%未満では、その溶滴の微細化と溶滴移行の安定化の効果が得られなくなり、多量のスパッタが発生してアークストップが発生し易い。一方、0.100質量%を超えると、溶接ワイヤの製造工程で割れが生じ易くなるばかりでなく、溶接施工による溶接金属の靭性低下を招くと同時に、スパッタの発生による溶接不安定を招く。 If the REM content is less than 0.015% by mass, the effect of refining the droplets and stabilizing the droplet migration cannot be obtained, and a large amount of sputtering is likely to occur and arc stop is likely to occur. On the other hand, if it exceeds 0.100% by mass, not only cracks are likely to occur in the welding wire manufacturing process, but also the toughness of the weld metal due to welding work is lowered, and at the same time, welding instability is caused by the generation of spatter.
したがって溶接ワイヤのREM含有量は、0.015〜0.100質量%とする。好ましくは0.025〜0.050質量%である。 Therefore, the REM content of the welding wire is 0.015 to 0.100% by mass. It is preferably 0.025 to 0.050% by mass.
また溶接施工における溶接ワイヤの極性は、REMの添加による溶滴の微細化と溶滴移行の安定化という効果を十分に発揮するという観点から、溶接ワイヤをマイナス(正極性)とすることが好ましい。 Further, the polarity of the welding wire in the welding work is preferably negative (positive electrode property) from the viewpoint of sufficiently exerting the effects of miniaturizing the droplets and stabilizing the droplet migration by adding REM. ..
表1に示す条件で、ガスシールドアーク溶接による鋼板の突き合わせ多層溶接を行なった。接合部位の予熱は行なっていない。 Under the conditions shown in Table 1, butt welding of steel sheets by gas shielded arc welding was performed. The joint site was not preheated.
使用した鋼板の成分は、いずれもS:0.005質量%以下、O:0.003質量%以下、N:0.004質量%以下である。開先の加工にはガス切断を採用し、開先面には研削等の手入れを施していない。 The components of the steel sheet used were S: 0.005% by mass or less, O: 0.003% by mass or less, and N: 0.004% by mass or less. Gas cutting is used for groove processing, and the groove surface is not maintained by grinding.
使用した溶接ワイヤは、いずれも溶接対象の鋼材強度用またはそれより1ランク上用の強度グレードのソリッドワイヤ(ワイヤ径1.2mm)であり、その成分はS:0.005質量%以下、O:0.003質量%以下、N:0.005質量%以下、Si:0.6〜0.8質量%、Al:0.005〜0.030質量%である。 The welding wires used are all strength grade solid wires (wire diameter 1.2 mm) for the strength of the steel material to be welded or one rank higher than that, and the components are S: 0.005% by mass or less, O: 0.003 mass. % Or less, N: 0.005% by mass or less, Si: 0.6 to 0.8% by mass, Al: 0.005 to 0.030% by mass.
シールドガスには100%CO2ガスを使用し、100%CO2ガスを流量20L/minでシールドノズルに供給した。The shielding gas using 100% CO 2 gas was fed into the shield nozzle 100% CO 2 gas at a flow rate 20L / min.
表1中のNo.1〜13は狭開先の例、No.14〜16は従来から標準的に用いられる開先形状の例である。なお、本発明において、「狭開先」とは、25°以下を示す。 Nos. 1 to 13 in Table 1 are examples of narrow grooves, and Nos. 14 to 16 are examples of groove shapes that have been used as standard in the past. In the present invention, the “narrow groove” means 25 ° or less.
そして、溶接を行ないながら1パス毎に溶接性について調査し、1パス中に1回以上のアークストップが発生したものを不良(×)、アークストップが発生しなかったものを良好(〇)として評価した。その結果を表1に示す。 Then, while performing welding, the weldability was investigated for each pass, and those in which arc stop occurred more than once in one pass were regarded as defective (x), and those in which arc stop did not occur were regarded as good (〇). evaluated. The results are shown in Table 1.
さらに、溶接が終了した後、ビードの表面を浸透探傷試験と磁粉探傷試験で検査し、1ケ所以上の低温割れが認められたものを割れ有(×)、低温割れが発生しなかったものを割れ無(〇)として評価した。その結果を表1に示す。 Furthermore, after welding is completed, the surface of the bead is inspected by a penetrant inspection test and a magnetic particle inspection test. It was evaluated as no crack (〇). The results are shown in Table 1.
表1から明らかなように、発明例は、溶接性および低温割れの評価が全て〇であった。比較例は、溶接性および/または低温割れの評価が×であった。 As is clear from Table 1, in the examples of the invention, the evaluation of weldability and low temperature cracking was all 0. In the comparative example, the evaluation of weldability and / or low temperature cracking was x.
1 鋼板
2 開先
3 溶接金属
4 裏当て材1 Steel plate 2 Groove 3 Welded metal 4 Backing material
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