JP3802642B2 - Arc welding method for galvanized steel sheet - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、亜鉛めっき鋼板のパルスアーク溶接方法に関するものであり、特に、ブローホールやピット等の溶接欠陥の発生防止に有効な亜鉛めっき鋼板のパルスアーク溶接方法に関するものである。
【０００２】
【従来の技術】
亜鉛めっき鋼板などの薄鋼板の接合方法としては従来から消耗電極式アーク溶接方法が実施されており、なかでも高速溶接が可能なＭＡＧ溶接法やＭＩＧ溶接法が広く採用されている。しかし、これらのアーク溶接法で亜鉛めっき鋼板を接合（例えば重ね合わせ溶接）すると、ブローホールやピット等の溶接欠陥が発生して継手強度を低下させる問題が生じる。これは、ビード形成部分に予め存在するめっき層中の亜鉛がビード形成過程でビード内に溶け込み、蒸気化して残留するためである。
【０００３】
そこで、このような問題を解決するために、特開昭６３−１０８９９５号公報や特開昭６３−５６３９５号公報の提案がある。
特開昭６３−１０８９９５号公報は、亜鉛めっき鋼板の接合界面となる表面に特殊塗料を塗布し、塗料中に存在するＰによって亜鉛よりも高融点の合金（Ｆｅ−Ｐ−Ｚｎ）を形成し、溶接時の亜鉛ガスの発生を防止して、ブローホール等の溶接欠陥を低減させる技術である。
また、特開昭６３−５６３９５号公報は、Ｔｅ，Ｓｅ，ＲＥＭ，Ｓｂの単体または酸化物を亜鉛めっき鋼板の接合界面に塗布し、溶融時の溶鋼の粘性を低下させて発生した亜鉛ガスの排出を促進する方法である。
【０００４】
【発明が解決しようとする課題】
これらの方法の提案によって、亜鉛めっき鋼板のアーク溶接時のブローホールやピット等の溶接欠陥の発生は低減したが、以下の問題が残った。
すなわち、上記の方法はいずれも溶接に先立って亜鉛めっき鋼板の接合界面に塗料を塗布しておく必要があり溶接作業負荷が増加すること、また、塗料等を使用するため接合界面上に限定して塗布することが困難なため、溶接後、残存した塗布物を除去するためにランニングコストがかかり溶接部品のコスト上昇を招く課題がある。
【０００５】
従って本発明では、上記した従来の問題点を解決して、従来のような塗料の塗布を必要とせず、ブローホールやピット等の溶接欠陥の発生を低減し、溶接品質の向上した溶接部が得られる亜鉛めっき鋼板のアーク溶接方法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明は上記目的を達成するため、アーク溶接時に溶融池内に侵入する亜鉛蒸気をシールドガス中に添加した酸素によって亜鉛よりも高融点の酸化亜鉛（ＺｎＯ）とすることで、溶接ビード中に固体として存在させること、また、溶接対象とする亜鉛めっき鋼板の板厚に対して、溶接入熱を最適化させることで亜鉛の蒸発量と溶融池の凝固速度を制御し、溶融池中に侵入した亜鉛蒸気を溶融池が凝固する前に排出させる効果を利用して、亜鉛めっき鋼板のアーク溶接時のブローホールを低減させるものである。
【０００７】
すなわち、本発明の要旨とするところは次の通りである。
亜鉛めっき鋼板のガスシールドアーク溶接において、シールドガスとして酸素を体積％で１０％以上含有し、残部Ａｒ及びＣＯ2 の１種または２種からなる混合ガスを使用するとともに、溶接電流をパルス電流とし、式（Ａ），（Ｂ）で表される溶接入熱（ＨＩ）が、被溶接材の板厚に応じて求められる条件式（Ｃ）を満足し、かつピーク電流時間（ｔｐ）を０．１〜１．３ｍｓの範囲とすることを特徴とする亜鉛めっき鋼板の溶接方法。
ＨＩ＝（Ｉａ×Ｖ）×６０／ｖ ‥‥‥‥‥（Ａ）
ここで、
ＨＩ；溶接入熱（J/cm）
Ｉａ；平均電流（Ａ）
Ｖ ；電極チップ−亜鉛めっき鋼板間電圧（Ｖ）
ｖ ；溶接速度（cm/min）
Ｉａ＝（（Ｉｐ×ｔｐ）＋（Ｉｂ×ｔｂ））／（ｔｐ＋ｔｂ）‥‥‥（Ｂ）
ここで、
Ｉｐ；ピーク電流（Ａ）
ｔｐ；ピーク電流時間（ms）
Ｉｂ；ベース電流（Ａ）
ｔｂ；ベース電流時間（ms）
1.0×103 ×exp(0.35×ｔ) ≦ＨＩ≦ 1.2×103 ×exp(0.35×ｔ) ‥‥（Ｃ）
ここで、
ｔ；亜鉛めっき鋼板板厚（mm）
【０００８】
【発明の実施の形態】
以下本発明に従う亜鉛めっき鋼板のアーク溶接方法について詳細に説明する。
亜鉛めっき鋼板のアーク溶接で発生するブローホール等の溶接欠陥は、一般に接合界面近傍に存在する低融点、低沸点の亜鉛が蒸気となって溶融池内に侵入し、溶融池の外壁部が凝固した後も気泡として残留するため、ビード内に無数のブローホールを形成するとされている。当然のことながら、接合部に低沸点成分が存在しない非めっき鋼板においては、ブローホールはほとんど存在しない。このため、亜鉛めっき鋼板のアーク溶接時に発生するブローホールの低減対策としては、１）溶融池内に侵入する亜鉛蒸気を低減させる、あるいは、２）侵入した亜鉛蒸気を溶融池が凝固する前に溶融池内より排出させる、さらに３）侵入した亜鉛を融点の高い反応生成物に置換させる３つの方法が考えられる。
【０００９】
溶融池内に侵入した亜鉛蒸気の存在状態について、詳細な解析を行ったところ、ビード中の亜鉛はブローホールの内壁（ブローホールの内側界面）に付着した状態にあるものの、大部分の亜鉛はブローホールの外のビード中にＺｎＯとして固溶していること、溶鋼中の固溶酸素量の増加とともにＺｎＯ化が促進されブローホール欠陥の抑制が進行するという知見が得られた。
【００１０】
溶鋼中に酸素を含有させる技術としては、特開昭６４−３１５９６号公報があるが、この方法はワイヤー成分に酸素を含有させるものであって、酸素の投入方法としてワイヤー外皮中の酸素量を変えたり、また、フラックス中にＦｅＯ，ＭｎＯ，Ａｌ2 Ｏ3 等の金属酸化物を添加する方法があるとしているが、これらの金属酸化物は溶鋼中で容易に解離されることはなく固溶酸素としての機能は発揮されない。酸素は溶鋼中に固溶酸素として存在することで亜鉛との結合が可能であり、フラックス中にＦｅＯ，ＭｎＯ，Ａｌ2 Ｏ3 等の金属酸化物を添加する場合、溶鋼中に存在する亜鉛より酸化性の高い金属との結合が進行するため亜鉛のＺｎＯ化効率は大きく阻害され、ブローホール発生の抑制は困難なものとなる。上述の結果から、亜鉛めっき鋼板のアーク溶接時のブローホールの低減には、溶融池の溶鋼中にいかに効率よく酸素を継続的に添加するかが重要となる。溶鋼中への固溶酸素の添加方法として、シールドガス中に酸素を添加することで、効率よく溶鋼中へ酸素を添加することが可能となる。シールドガス中の酸素量を１０％以上にすると後述の溶接入熱条件式（Ｃ）の範囲内で安定的にブローホール低減の効果が現れる。また、酸素濃度の上限は特に規定しないが、シールドガス中の酸素濃度が極端に高くなるとスパッタの多発やビード形状の悪化を招くため酸素濃度は１０〜２０％が望ましい。
【００１１】
また、酸素の添加によってスパッタ発生の増大が懸念されるが、パルス状電流の使用により、酸素を添加していないシールドガスと同様の程度までスパッタの発生を防止することができる。これは、パルス状電流の使用により溶接中の溶滴の移行が確実になりアーク放電が安定化するものと本発明者らは考えている。望ましいパルス条件としては、パルスピーク電流Ｉｐが３００Ａ以上、５００Ａ以下、かつ該ピーク電流時間ｔｐ（すなわちパルス幅）が０．１msec以上、１．３msec以下である。さらに、アーク放電が安定化し、ブローホールが著しく低減するので、パルス幅は０．１〜０．７msecの範囲が更に望ましい。パルス状電流の使用により、スパッタの発生を防止することが可能になるとともに、パルス幅を小さくすることで、溶接後のブローホールの発生率も低減した。
【００１２】
パルス状電流のパルス幅を小さくすると、ブローホールの発生率が低減する理由は、今のところ必ずしも定かではないが、パルス幅を小さくすると溶接中の溶滴の移行時間が長くなり、すなわち、移行する溶滴の径が大きくなる現象が確認されたことから、径の大きな溶滴が溶融池に落下するときに溶融池を攪拌あるいは、揺らす（振動させる）ために、Ｚｎガスの流動性が高まり溶融池中に存在するＺｎのガスがより排出しやすくなったものと本発明者らは考えている。
【００１３】
シールドガスへの酸素の添加により溶接ビード中のブローホール欠陥は低減するが、同一の酸素濃度でも溶接条件によって、ブローホールの発生量が大幅に異なることが判明した（例えば図１）。
【００１４】
このため、さらなるブローホールの低減方法を検討した。前述のように、アーク溶接時のブローホールの低減対策としては、溶接時のＺｎの蒸発量は少なくして溶融池の凝固速度を遅くすることが望ましい。溶接時のＺｎの蒸発量は、投入される熱量すなわち溶接入熱が大きくなると多くなるので、Ｚｎの蒸発量を少なくさせるには、溶接入熱を小さくすればよい。しかし、溶接入熱を小さくすると溶融池の凝固速度は速くなるので、Ｚｎ蒸気は排出しにくくなるため単純に溶接入熱を小さくすることはできない。すなわち、Ｚｎの蒸発排出と溶融池の凝固によるＺｎ蒸気トラップとの相反する反応が良好となる溶接入熱値でブローホールは最も少なくなる可能性がある。さらに、シールドガス中の酸素が１０体積％以上のガスシールドアーク溶接で形成された溶融池の凝固速度は、同一の溶接入熱でも板厚が大きくなると速くなる。このため、ブローホールが低減可能な溶接入熱値は板厚によっても変化すると本発明者らは考えた。
【００１５】
このような観点から、シールドガス中の酸素が１０体積％以上のもので、ガスシールドアーク溶接用の溶接入熱を種々変化させて、亜鉛めっき鋼板の重ね隅肉溶接を実施した。図１は板厚と溶接入熱を変化させたときのブローホールの発生率の変化を示している。ブローホールの評価は、溶接ビード全線をＸ線透過試験して全ブローホールを検出し、ブローホールの総長が占める割合（％）を測定して行った。溶接ビード中のブローホールの量は溶接入熱によって変化し、ブローホールの量が著しく低下する溶接入熱領域が存在することが判明した。そして、ブローホールが極小となる溶接入熱は、板厚によって変化し、ブローホールの極小値は板厚が小さいものほど低くなる。これは、板厚の異なる鋼板の溶接後の冷却速度を等しくするためには、板厚が大きくなると溶接入熱を高くする必要がある。そして、溶接入熱が高くなると鋼板表面のＺｎ蒸発量が多くなるため、結果として板厚の大きいものほどブローホールの極小値が高くなることになると本発明者らは考えている。
【００１６】
そして、これらの結果から板厚の異なる亜鉛めっき鋼板のアーク溶接において、ブローホールが著しく低減する溶接入熱条件として（Ｃ）式を得た。（Ｃ）式で示される溶接入熱が１．０×１０3 ×ｅｘｐ（０．３５×ｔ）よりも小さくなると溶融池の冷却速度が速くなりＺｎ蒸気が十分に排出される前に溶融池が凝固してしまう。また、溶接入熱が１．２×１０3 ×ｅｘｐ（０．３５×ｔ）よりも大きくなるとＺｎ蒸気の発生量が多くなりＺｎ蒸気の十分な排出が達成されなくなる。
【００１７】
なお、本発明の効果は特定の亜鉛めっき鋼板に限定されることはなく、溶融めっき法、電気めっき法、蒸着めっき法、溶射法など各種の製造方法によるものがあり、めっき組成としては純Ｚｎの他、ＺｎとＦｅ、ＺｎとＮｉ、ＺｎとＡｌ、ＺｎとＭｎなどＺｎを主成分として、耐食性など諸特性向上のため１種ないし２種以上の合金元素および不純物元素を含み、また、ＳｉＯ2 ，Ａｌ2 Ｏ3 などのセラミックス粉末や有機高分子をめっき層中に分散させたものがあり、めっき層の厚さ方向で単一組成のもの、連続的あるいは層状に組成が変化するものがあり、めっき層の厚み方向で単一組成のもの、連続的あるいは層状に組成が変化するものがあり、さらに複層めっき鋼板では最上層がＦｅやＮｉを主成分としてＺｎやＰ等各種合金元素を含むものがある。例えば、溶融亜鉛めっき鋼板、鉄−亜鉛合金化溶融亜鉛めっき鋼板、亜鉛を主体とするアルミニウム、鉄などの合金溶融亜鉛めっき鋼板、めっき層断面方法で下層のみが合金化されている合金化溶融亜鉛めっき鋼板、片面−合金化溶融亜鉛めっき層、他面溶融亜鉛めっき層からなるめっき鋼板、これらのめっき層上に電気めっき、蒸着めっき等により亜鉛、鉄、ニッケルを主成分とする金属をめっきした鋼板、あるいは、電気亜鉛めっき鋼板、亜鉛、ニッケル、クロム等合金電気めっき鋼板等、さらに単一合金層または複層亜鉛および亜鉛含有金属の蒸着めっき鋼板等がある。
【００１８】
【実施例】
図２に示すように、板厚とめっき目付量を変化させた各種亜鉛めっき鋼板１に２を重ね押え材３で押えて重ね隅肉溶接を実施した。溶接条件は、シールドガス組成、溶接入熱を変化させている。ワイヤは１．２mm径で日鐵溶接工業（株）製のＹＭ−２２Ｚを使用し、溶接速度は１２０cm/minで行った。溶接姿勢は水平で、図２に示したトーチ４の傾斜角度（θ）が６０゜、トーチ４の前進角度（β）が０゜、チップ−母材間距離（ｄ）が１５mmの自動溶接とした。
ブローホールの評価は、溶接ビード全線（３０cm）をＸ線透過試験して全ブローホールを検出し、ブローホールの総長が占める割合（％）を測定して行った。
【００１９】
表１（表１−１，表１−２）に溶接条件とともにブローホール欠陥面積率を示した。また、図３は表１のＧＡ材の２．３mmt の結果について溶接入熱と欠陥面積率との関係を示したものである。表１および図３より、めっき種によらず、本発明の範囲内であればブローホール欠陥の発生が大幅に低減し、シールドガスへの酸素添加だけではなく、溶接入熱を最適化すること、さらにパルス幅を小さくすることがブローホールを低減させることがわかる。
【００２０】
【表１】
【表２】
【発明の効果】
以上の結果から明らかなように、本発明によって亜鉛めっき鋼板のアーク溶接で問題となるブローホール欠陥の発生を大幅に低減することができ、溶接品質の向上に効果を発揮することが明らかとなった。
【図面の簡単な説明】
【図１】ブローホールの発生率に及ぼす板厚と溶接入熱の影響を示したものである。
【図２】実施例である亜鉛めっき鋼板の溶接方法の説明図で（Ａ）は正面図、（Ｂ）は側面図である。
【図３】本発明の範囲内と範囲外の溶接条件でのブローホールの欠陥率と溶接入熱の関係を示したものである。
【符号の説明】
１：被溶接材（亜鉛めっき鋼板）
２：被溶接材（亜鉛めっき鋼板）
３：押え材
４：溶接トーチ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pulse arc welding method for a galvanized steel sheet, and more particularly to a pulse arc welding method for a galvanized steel sheet that is effective in preventing the occurrence of welding defects such as blow holes and pits.
[0002]
[Prior art]
Conventionally, consumable electrode arc welding methods have been used as methods for joining thin steel plates such as galvanized steel plates, and among them, MAG welding methods and MIG welding methods capable of high-speed welding are widely used. However, when galvanized steel sheets are joined (for example, lap welding) by these arc welding methods, welding defects such as blow holes and pits are generated, resulting in a problem of reducing joint strength. This is because zinc in the plating layer preliminarily present in the bead forming portion dissolves in the bead during the bead forming process, and remains in a vaporized state.
[0003]
In order to solve such a problem, there are proposals of Japanese Patent Laid-Open Nos. 63-108995 and 63-56395.
Japanese Patent Laid-Open No. 63-108995 discloses that a special paint is applied to the surface which becomes a bonding interface of a galvanized steel sheet, and an alloy (Fe-P-Zn) having a melting point higher than that of zinc is formed by P present in the paint. This is a technology that prevents the generation of zinc gas during welding and reduces welding defects such as blow holes.
JP-A-63-56395 discloses that zinc gas generated by applying Te, Se, REM, Sb alone or an oxide to the joint interface of a galvanized steel sheet to lower the viscosity of the molten steel at the time of melting. It is a way to promote emissions.
[0004]
[Problems to be solved by the invention]
Although these methods have reduced the occurrence of welding defects such as blow holes and pits during arc welding of galvanized steel sheets, the following problems remain.
That is, all of the above methods require that paint be applied to the joint interface of the galvanized steel sheet prior to welding, which increases the welding work load, and is limited to the joint interface because paint is used. Therefore, there is a problem that a running cost is required to remove the remaining applied material after welding, and the cost of the welded parts is increased.
[0005]
Accordingly, the present invention solves the above-described conventional problems, does not require the application of paint as in the prior art, reduces the occurrence of welding defects such as blow holes and pits, and has a welded portion with improved welding quality. It aims at providing the arc welding method of the galvanized steel plate obtained.
[0006]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention provides a zinc oxide having a melting point higher than that of zinc (ZnO) by means of oxygen added to the shield gas, which is a zinc oxide that penetrates into the molten pool during arc welding. In addition, by optimizing the welding heat input with respect to the thickness of the galvanized steel sheet to be welded, the amount of zinc evaporation and the solidification rate of the molten pool were controlled, and entered the molten pool. By utilizing the effect of discharging zinc vapor before the molten pool solidifies, blow holes during arc welding of the galvanized steel sheet are reduced.
[0007]
That is, the gist of the present invention is as follows.
In gas shielded arc welding of galvanized steel sheets, oxygen is contained as a shielding gas in a volume percentage of 10% or more, and a mixed gas consisting of one or two of Ar and CO 2 is used, and the welding current is a pulse current. The welding heat input (HI) represented by the formulas (A) and (B) satisfies the conditional formula (C) determined according to the thickness of the material to be welded , and the peak current time (tp) is 0. A method for welding a galvanized steel sheet, characterized by being in the range of 1 to 1.3 ms .
HI = (Ia × V) × 60 / v (A)
here,
HI: Weld heat input (J / cm)
Ia: Average current (A)
V: Voltage between electrode tip and galvanized steel sheet (V)
v: Welding speed (cm / min)
Ia = ((Ip × tp) + (Ib × tb)) / (tp + tb) (B)
here,
Ip: Peak current (A)
tp: Peak current time (ms)
Ib: Base current (A)
tb: Base current time (ms)
1.0 × 10 3 × exp (0.35 × t) ≦ HI ≦ 1.2 × 10 3 × exp (0.35 × t) (C)
here,
t: Galvanized steel sheet thickness (mm)
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the arc welding method of the galvanized steel sheet according to the present invention will be described in detail.
Weld defects such as blowholes that occur during arc welding of galvanized steel sheets are generally caused by the low melting point and low boiling point zinc present in the vicinity of the joint interface entering the molten pool and solidifying the outer wall of the molten pool. Since it remains as bubbles afterwards, it is said that innumerable blow holes are formed in the bead. As a matter of course, in the non-plated steel sheet in which the low boiling point component does not exist in the joint, there is almost no blowhole. Therefore, measures to reduce blowholes that occur during arc welding of galvanized steel sheets include 1) reducing zinc vapor that enters the molten pool, or 2) melting the zinc vapor that has entered before the molten pool solidifies. There are three possible methods of discharging from the pond, and 3) replacing the invading zinc with a reaction product having a high melting point.
[0009]
A detailed analysis of the state of zinc vapor that entered the molten pool revealed that zinc in the bead was attached to the inner wall of the blowhole (inner interface of the blowhole), but most zinc was blown. The knowledge that ZnO was dissolved as a solid solution in the bead outside the hole, and that the formation of ZnO was promoted as the amount of dissolved oxygen in the molten steel increased, and the suppression of blowhole defects progressed.
[0010]
As a technique for containing oxygen in molten steel, there is JP-A-64-31596, but this method is to contain oxygen in the wire component. There is a method of changing or adding metal oxides such as FeO, MnO, and Al 2 O 3 in the flux, but these metal oxides are not easily dissociated in molten steel but are dissolved. The function as oxygen is not demonstrated. Oxygen can be combined with zinc because it exists as solute oxygen in the molten steel. When adding metal oxides such as FeO, MnO, and Al 2 O 3 to the flux, oxygen can be combined with zinc present in the molten steel. Since the bonding with a highly oxidizable metal proceeds, the ZnO conversion efficiency of zinc is greatly hindered, making it difficult to suppress the generation of blowholes. From the above results, it is important how efficiently oxygen is continuously added to the molten steel in the molten pool to reduce blowholes during arc welding of the galvanized steel sheet. As a method for adding solute oxygen into the molten steel, it is possible to efficiently add oxygen into the molten steel by adding oxygen into the shield gas. When the amount of oxygen in the shield gas is 10% or more, the effect of reducing blowholes appears stably within the range of the welding heat input conditional expression (C) described later. The upper limit of the oxygen concentration is not particularly defined. However, if the oxygen concentration in the shield gas is extremely high, it causes frequent spattering and deterioration of the bead shape, so that the oxygen concentration is preferably 10 to 20%.
[0011]
Moreover, although there is a concern about the increase in spatter generation due to the addition of oxygen, the use of a pulsed current can prevent the occurrence of spatter to the same extent as the shield gas to which oxygen is not added. The present inventors consider that the use of a pulsed current ensures the transfer of droplets during welding and stabilizes arc discharge. Desirable pulse conditions are a pulse peak current Ip of 300 A or more and 500 A or less, and a peak current time tp (that is, a pulse width) of 0.1 msec or more and 1.3 msec or less. Moreover, the arc discharge is stabilized, because the blow holes are significantly reduced, the pulse width is more preferably in the range of 0.1～0.7Msec. The use of a pulsed current made it possible to prevent the occurrence of spatter, and by reducing the pulse width, the incidence of blowholes after welding was also reduced.
[0012]
The reason why the occurrence rate of blowholes decreases when the pulse width of the pulse current is reduced is not necessarily clear at present, but if the pulse width is decreased, the transition time of the droplets during welding becomes longer, that is, the transition As a result, it was confirmed that the diameter of the droplets increased, and when the large droplets dropped into the molten pool, the molten pool was stirred or shaken (vibrated). The present inventors consider that Zn gas existing in the molten pool is more easily discharged.
[0013]
Although the addition of oxygen to the shield gas reduces blowhole defects in the weld bead, it has been found that the amount of blowholes generated varies greatly depending on the welding conditions even at the same oxygen concentration (for example, FIG. 1).
[0014]
For this reason, further methods for reducing blowholes were studied. As described above, as a measure for reducing blowholes during arc welding, it is desirable to reduce the amount of Zn evaporated during welding to slow the solidification rate of the molten pool. The amount of Zn evaporation during welding increases as the amount of heat input, that is, the welding heat input increases, so that the welding heat input can be reduced in order to reduce the amount of Zn evaporation. However, if the welding heat input is reduced, the solidification rate of the molten pool increases, so that it is difficult to discharge Zn vapor, so the welding heat input cannot simply be reduced. That is, there is a possibility that blowholes may be minimized at a welding heat input value at which the opposite reaction between Zn vaporization and Zn vapor trap due to solidification of the molten pool is good. Furthermore, the solidification rate of the molten pool formed by gas shielded arc welding in which oxygen in the shielding gas is 10% by volume or more increases as the plate thickness increases even with the same welding heat input. For this reason, the present inventors considered that the welding heat input value at which blowholes can be reduced also changes depending on the plate thickness.
[0015]
From such a point of view, lap fillet welding of galvanized steel sheets was performed with oxygen in the shielding gas of 10% by volume or more and various changes in welding heat input for gas shielded arc welding. FIG. 1 shows the change in blow hole occurrence rate when the plate thickness and welding heat input are changed. The blowhole was evaluated by measuring the ratio (%) of the total length of the blowhole by detecting the entire blowhole by performing an X-ray transmission test on the entire weld bead. It has been found that the amount of blowholes in the weld bead varies with welding heat input, and there exists a welding heat input region in which the amount of blowholes significantly decreases. The welding heat input at which the blowhole is minimized varies depending on the plate thickness, and the minimum value of the blowhole becomes lower as the plate thickness is smaller. In order to equalize the cooling rate after welding of steel plates having different plate thicknesses, it is necessary to increase the welding heat input as the plate thickness increases. The inventors believe that, as the welding heat input increases, the amount of Zn evaporation on the steel sheet surface increases, and as a result, the smaller the plate thickness, the higher the minimum value of the blowhole.
[0016]
Then, from these results, in arc welding of galvanized steel sheets having different plate thicknesses, Equation (C) was obtained as a welding heat input condition for significantly reducing blowholes. When the welding heat input represented by the formula (C) becomes smaller than 1.0 × 10 3 × exp (0.35 × t), the cooling rate of the molten pool is increased and the molten pool is sufficiently discharged before Zn vapor is sufficiently discharged. Will solidify. In addition, when the welding heat input is greater than 1.2 × 10 3 × exp (0.35 × t), the amount of Zn vapor generated increases, and sufficient discharge of Zn vapor cannot be achieved.
[0017]
The effect of the present invention is not limited to a specific galvanized steel sheet, and there are various manufacturing methods such as a hot dipping method, an electroplating method, a vapor deposition plating method, and a thermal spraying method. In addition to Zn and Fe, Zn and Ni, Zn and Al, Zn and Mn, etc., containing Zn or one or more alloy elements and impurity elements for improving various properties such as corrosion resistance, and SiO. 2. There are ceramic powders such as Al 2 O 3 and organic polymers dispersed in the plating layer, which have a single composition in the thickness direction of the plating layer, and those whose composition changes continuously or in layers. Yes, there are those with a single composition in the thickness direction of the plating layer, those whose composition changes continuously or in layers, and in multilayer plated steel sheets, the uppermost layer is Fe or Ni as the main component and various alloying elements such as Zn and P The There is Dressings. For example, hot-dip galvanized steel sheet, iron-zinc alloyed hot-dip galvanized steel sheet, alloy hot-dip galvanized steel sheet such as aluminum and iron mainly composed of zinc, and alloyed hot-dip zinc in which only the lower layer is alloyed by the plating layer cross-section method Plated steel sheet, one side-alloyed hot dip galvanized layer, other side hot dip galvanized layer, plated steel sheet, plated with metal containing zinc, iron, nickel as main components by electroplating, vapor deposition, etc. There are steel sheets, electrogalvanized steel sheets, zinc, nickel, chromium and other alloy electroplated steel sheets, and further, single alloy layers or multi-layer zinc and zinc-containing metal vapor-deposited steel sheets.
[0018]
【Example】
As shown in FIG. 2, two fillets were pressed on various galvanized
The blowhole was evaluated by measuring the ratio (%) of the total length of the blowhole by detecting the entire blowhole by performing an X-ray transmission test on the entire weld bead (30 cm).
[0019]
Table 1 (Tables 1-1 and 1-2) shows the blowhole defect area ratio together with the welding conditions. FIG. 3 shows the relationship between the welding heat input and the defect area ratio for the 2.3 mmt results for the GA material in Table 1. From Table 1 and FIG. 3, regardless of the plating type, the occurrence of blowhole defects is greatly reduced within the scope of the present invention, and not only the addition of oxygen to the shielding gas but also the optimization of welding heat input. Further, it can be seen that further reducing the pulse width reduces blowholes.
[0020]
[Table 1]
[Table 2]
【The invention's effect】
As is clear from the above results, it has become clear that the present invention can greatly reduce the occurrence of blowhole defects, which is a problem in arc welding of galvanized steel sheets, and is effective in improving welding quality. It was.
[Brief description of the drawings]
FIG. 1 shows the influence of plate thickness and welding heat input on the occurrence rate of blowholes.
FIG. 2 is an explanatory view of a welding method for a galvanized steel sheet as an example, in which (A) is a front view and (B) is a side view.
FIG. 3 shows the relationship between blow hole defect rate and welding heat input under welding conditions within and outside the scope of the present invention.
[Explanation of symbols]
1: Welded material (galvanized steel sheet)
2: Material to be welded (galvanized steel sheet)
3: Presser material 4: Welding torch
Claims (1)
ＨＩ＝（Ｉａ×Ｖ）×６０／ｖ ‥‥‥‥‥（Ａ）
ここで、
ＨＩ；溶接入熱（J/cm）
Ｉａ；平均電流（Ａ）
Ｖ ；電極チップ−亜鉛めっき鋼板間電圧（Ｖ）
ｖ ；溶接速度（cm/min）
Ｉａ＝（（Ｉｐ×ｔｐ）＋（Ｉｂ×ｔｂ））／（ｔｐ＋ｔｂ）‥‥‥（Ｂ）
ここで、
Ｉｐ；ピーク電流（Ａ）
ｔｐ；ピーク電流時間（ms）
Ｉｂ；ベース電流（Ａ）
ｔｂ；ベース電流時間（ms）
1.0×103 ×exp(0.35×ｔ) ≦ＨＩ≦ 1.2×103 ×exp(0.35×ｔ) ‥‥（Ｃ）
ここで、
ｔ；亜鉛めっき鋼板板厚（mm）In gas shielded arc welding of galvanized steel sheets, oxygen is contained as a shielding gas in a volume percentage of 10% or more, and a mixed gas consisting of one or two of Ar and CO 2 is used, and the welding current is a pulse current. The welding heat input (HI) represented by the formulas (A) and (B) satisfies the conditional formula (C) determined according to the thickness of the material to be welded , and the peak current time (tp) is 0. An arc welding method for a galvanized steel sheet, characterized by being in the range of 1 to 1.3 ms .
HI = (Ia × V) × 60 / v (A)
here,
HI: Weld heat input (J / cm)
Ia: Average current (A)
V: Voltage between electrode tip and galvanized steel sheet (V)
v: Welding speed (cm / min)
Ia = ((Ip × tp) + (Ib × tb)) / (tp + tb) (B)
here,
Ip: Peak current (A)
tp: Peak current time (ms)
Ib: Base current (A)
tb: Base current time (ms)
1.0 × 10 3 × exp (0.35 × t) ≦ HI ≦ 1.2 × 10 3 × exp (0.35 × t) (C)
here,
t: Galvanized steel sheet thickness (mm)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06359897A JP3802642B2 (en) | 1997-03-17 | 1997-03-17 | Arc welding method for galvanized steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06359897A JP3802642B2 (en) | 1997-03-17 | 1997-03-17 | Arc welding method for galvanized steel sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10258367A JPH10258367A (en) | 1998-09-29 |
| JP3802642B2 true JP3802642B2 (en) | 2006-07-26 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP06359897A Expired - Fee Related JP3802642B2 (en) | 1997-03-17 | 1997-03-17 | Arc welding method for galvanized steel sheet |
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| US10518350B2 (en) | 2013-06-07 | 2019-12-31 | Kabushiki Kaisha Yaskawa Denki | Arc welding apparatus, arc welding system, and arc welding method |
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| JP5968934B2 (en) * | 2014-03-07 | 2016-08-10 | 大陽日酸株式会社 | Welding method of galvanized steel sheet |
| CN104588851A (en) * | 2014-11-27 | 2015-05-06 | 芜湖中集瑞江汽车有限公司 | Consumable electrode mixed gas shielded arc welding process for steel plate with thickness below 3 mm |
| JP6023156B2 (en) * | 2014-11-27 | 2016-11-09 | 日新製鋼株式会社 | Arc welding method for Zn-plated steel sheet |
| CN104588850A (en) * | 2014-11-27 | 2015-05-06 | 芜湖中集瑞江汽车有限公司 | Welding technology for steel plates |
| CN104842047A (en) * | 2015-05-05 | 2015-08-19 | 柳州金茂机械有限公司 | Iron plate welding process |
| JP6114785B2 (en) | 2015-05-29 | 2017-04-12 | 日新製鋼株式会社 | Arc welding method for hot-dip Zn-based plated steel sheet with excellent weld appearance and weld strength, and method for producing welded member |
| JP6518160B2 (en) * | 2015-07-27 | 2019-05-22 | 株式会社神戸製鋼所 | Welding method of galvanized steel sheet |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US10518350B2 (en) | 2013-06-07 | 2019-12-31 | Kabushiki Kaisha Yaskawa Denki | Arc welding apparatus, arc welding system, and arc welding method |
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| JPH10258367A (en) | 1998-09-29 |
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