JP2005144504A

JP2005144504A - Lap laser welding method for galvanized steel sheet and welded joint of lap welded galvanized steel sheet

Info

Publication number: JP2005144504A
Application number: JP2003386358A
Authority: JP
Inventors: Koji Hirano; 弘二平野; Atsushi Sugibashi; 敦史杉橋; Naoya Hamada; 直也浜田; Akihiro Miyasaka; 明博宮坂
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2003-11-17
Filing date: 2003-11-17
Publication date: 2005-06-09
Anticipated expiration: 2023-11-17
Also published as: JP4344221B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lap laser welding method for galvanized steel sheets having excellent weld bead shape and quality, with which the explosion of a weld metal and the occurrence of a weld defect due to the occurrence of a zinc vapor can be reduced, in lap laser welding of two galvanized steel sheets, and a defect-free lap welded joint of the galvanized steel sheets. <P>SOLUTION: A gap is obtained between the two galvanized steel sheets when performing lap welding by preliminarily bending the one steel sheet by irradiation with a laser beam prior to welding of the two galvanized steel sheets. Both ends of the two steel sheets are restrained and the welding is performed while the stable gap is obtained. By such method, the explosion of the weld metal and the occurrence of the weld defect due to the occurrence of the zinc vapor can be reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は自動車外板などに用いられる亜鉛めっき鋼板を、レーザ光の照射により重ね溶接する技術に関する。 The present invention relates to a technique for lap welding a galvanized steel sheet used for an automobile outer sheet or the like by laser light irradiation.

自動車ボデーの製造ラインなどでは、２枚の亜鉛めっき鋼板を重ね溶接する工程がある。この溶接工程では従来スポット溶接が多用されていたが、スポット溶接では２枚の亜鉛めっき鋼板の溶接部であるスポット部の強度的信頼性が低いという問題があった。そのため、上記スポット部の数を増加させたり、補強部材を入れるなどの対策がなされていたが、生産性やコストの点で問題があった。近年、レーザ溶接などの高速溶接装置を用いた連続溶接への移行が図られつつある。 In the production line of an automobile body, there is a step of lap welding two galvanized steel sheets. Conventionally, spot welding has been frequently used in this welding process, but spot welding has a problem that the strength reliability of the spot portion, which is a welded portion of two galvanized steel sheets, is low. For this reason, measures such as increasing the number of the spot portions or inserting a reinforcing member have been taken, but there are problems in terms of productivity and cost. In recent years, a shift to continuous welding using a high-speed welding apparatus such as laser welding is being attempted.

一般に、レーザ溶接は、高速溶接ができ、また、溶接品質も良好であるという点で優れた方法とされている。ところが、亜鉛めっき鋼板の重ね溶接においては、鋼板表面にめっきされた亜鉛の沸点が母材に比べて低いため、鋼板溶融直前あるいは溶融中に２枚の鋼板にはさまれた部分で亜鉛が蒸気となり、溶融部に取り残されて気泡（ブローホールやピット）となったり、圧力によって周りの溶融金属を吹き飛ばす爆飛現象を生じることがある。いずれも溶接ビード形状、継手の強度特性などの溶接品質を劣化させる要因となるため、安定して良好な連続ビードを得ることが困難である。 Generally, laser welding is an excellent method in that high-speed welding can be performed and welding quality is also good. However, in the lap welding of galvanized steel sheets, the boiling point of zinc plated on the surface of the steel sheet is lower than that of the base metal, so that zinc is vaporized immediately before or during melting between the two steel sheets. In some cases, bubbles are left behind in the melted part to form bubbles (blow holes or pits), or a blow-off phenomenon occurs in which the surrounding molten metal is blown away by pressure. Any of them becomes a factor that degrades the welding quality such as the weld bead shape and the strength characteristics of the joint, and thus it is difficult to stably obtain a good continuous bead.

この問題を解決するために、種々の検討がなされてきた。その一つに、溶接前に被溶接部の亜鉛を除去する方法がある。例えば（特許文献１）には、レーザ光をエネルギー密度の低い集光レーザ光とエネルギー密度の高い集光レーザ光に分割し、前者で鋼板の重ね合せ部位を照射して亜鉛めっきを蒸発・離散させ、後者で鋼板を溶接・接合する方法が開示されている。また、（特許文献２）には、鋼板に照射するレーザ光の出力を制御して、ピークの低いパルスのレーザ光と、ピークの高いパルスのレーザ光とを溶接部位に交互に照射し、前者により亜鉛めっき層を除去し、後者により鋼板の溶接を行なう方法が開示されている。 Various studies have been made to solve this problem. One of them is a method of removing zinc from the welded part before welding. For example, in (Patent Document 1), the laser beam is divided into a focused laser beam having a low energy density and a focused laser beam having a high energy density, and the former is irradiated with overlapping portions of steel sheets to evaporate / discrete galvanizing. In the latter, a method for welding and joining steel sheets is disclosed. Further, in (Patent Document 2), by controlling the output of the laser beam applied to the steel plate, the laser beam having a low peak pulse and the laser beam having a high peak pulse are alternately irradiated to the welding portion, and the former Discloses a method of removing the galvanized layer and welding the steel plate by the latter.

また、パルスレーザを利用する方法としては、パルス動作の周波数およびデューティを所定の範囲に設定することによって、レーザ光照射による鋼板の溶融部である溶融池を連続保持して、良好な溶接ビードを得ようとする方法が例えば（特許文献３）に開示されている。 In addition, as a method using a pulse laser, by setting the frequency and duty of the pulse operation within a predetermined range, a molten pool that is a molten portion of the steel sheet by laser light irradiation is continuously held, and a good weld bead is obtained. A method to be obtained is disclosed in, for example, (Patent Document 3).

一方、亜鉛めっき鋼板間に適当な隙間を形成し、溶接時に発生する亜鉛蒸気を溶接部から逃がすことを可能にすることにより、良好な重ね溶接が行なえることは良く知られているところであり、隙間を形成する方法として、さまざまな検討がなされている。例えば（特許文献４）には、亜鉛めっき鋼板間に適当な隙間を形成できるように、予め塑性加工を施す方法が開示されている。また、亜鉛めっき鋼板間に別の部材を挿入して隙間を得る方法も検討されており、例えば（特許文献５）には鋼板間に紙を挟みこむ溶接方法が、（特許文献６）には鋼板間に多孔質のスペーサを挿入して溶接する方法が開示されている。さらに（特許文献７）には、レーザ光照射側の亜鉛めっき鋼板のみを重ね溶接位置より所定の距離離れた位置において溶融させて、２枚の亜鉛めっき鋼板の間に隙間を形成し、その後重ね溶接する方法が開示されている。
特開平０４−２３１１９０号公報特開平０４−２５１６８４号公報特開平０９−１０８８７２号公報特開昭６１−２７１８９号公報特開平０５−２７９２９１号公報特開平０６−２８８９８６号公報特許第３１１５４５６号公報 On the other hand, it is well known that good lap welding can be performed by forming an appropriate gap between galvanized steel sheets and allowing zinc vapor generated during welding to escape from the welded part. Various studies have been made as methods for forming the gap. For example, (Patent Document 4) discloses a method of performing plastic working in advance so that an appropriate gap can be formed between galvanized steel sheets. In addition, a method of obtaining a gap by inserting another member between galvanized steel sheets has been studied. For example, (Patent Document 5) discloses a welding method in which paper is sandwiched between steel sheets, (Patent Document 6). A method of welding by inserting a porous spacer between steel plates is disclosed. Furthermore, in (Patent Document 7), only the galvanized steel sheet on the laser beam irradiation side is melted at a position a predetermined distance away from the lap welding position to form a gap between the two galvanized steel sheets, and then overlapped A method of welding is disclosed.
JP 04-231190 A Japanese Patent Laid-Open No. 04-251684 Japanese Patent Laid-Open No. 09-108772 JP-A 61-27189 JP 05-279291 A Japanese Patent Laid-Open No. 06-288986 Japanese Patent No. 3115456

しかしながら、上述した従来の方法にはそれぞれに問題点があった。すなわち、（特許文献１）、（特許文献２）にて開示された方法では、２枚の亜鉛めっき鋼板間に十分な隙間がない場合には、亜鉛の蒸発・離散を安定性良く行なうことは難しく、亜鉛蒸気起因の溶接部欠陥および溶融金属の爆飛の発生を実用レベルで十分に無くすことは不可能であった。また（特許文献３）に開示された方法は、高いパワー密度を有するパルスレーザ光を溶接部に照射するときに、母材金属の瞬間的蒸発圧力により形成される空洞（キーホール）をパルス制御により安定に保持しようとするものである。しかしながら、キーホールの時間挙動は未だよく解明されていない不確定な部分があるため、溶接する鋼板性状の微妙な変化などによりパルス光照射条件の狙いが外れ易く、生産現場で長時間安定して重ね溶接することが難しかった。 However, each of the conventional methods described above has problems. That is, in the methods disclosed in (Patent Document 1) and (Patent Document 2), when there is no sufficient gap between two galvanized steel sheets, it is possible to stably evaporate and separate zinc. It was difficult, and it was impossible to sufficiently eliminate the occurrence of weld defects and molten metal explosions due to zinc vapor at a practical level. In addition, the method disclosed in (Patent Document 3) uses a pulse control of a cavity (keyhole) formed by an instantaneous evaporation pressure of a base metal when irradiating a welded portion with a pulsed laser beam having a high power density. It tries to keep it more stable. However, the time behavior of keyholes is still unclear and there is an uncertain part, so the target of pulsed light irradiation conditions is likely to deviate due to subtle changes in the properties of the steel sheet to be welded, and stable at production sites for a long time. It was difficult to lap weld.

また（特許文献４）にて開示された方法のように、被溶接材である亜鉛めっき鋼板に予め塑性加工を施し、亜鉛めっき鋼板間に適当な隙間を形成する方法は、プレス加工など溶接前の加工工程が１つ増えてしまう。また（特許文献５）や（特許文献６）に開示された方法のような亜鉛めっき鋼板間に紙や多孔質材などを挿入する方法では、鋼板間に挟み込んだ部材が保水材となって、亜鉛めっきが損傷を受けた溶接部近傍の腐食が加速されることがある。一方、（特許文献７）の方法では、溶接時にレーザ光照射側の鋼板を拘束しないため、鋼板の熱変形が生じ爆飛抑制に必要な隙間高さを維持することが困難である。また溶接時に隙間高さが変動すると、最適入熱条件が変化することでハンピングが発生し、安定した溶接ビードを得ることができないという問題がある。 In addition, as in the method disclosed in (Patent Document 4), a method of forming a suitable gap between galvanized steel sheets in advance by subjecting a galvanized steel sheet as a material to be welded to plastic working is performed before welding. The number of processing steps increases by one. Moreover, in the method of inserting paper, a porous material, etc. between the galvanized steel plates like the method disclosed in (Patent Document 5) and (Patent Document 6), the member sandwiched between the steel plates becomes a water retaining material, Corrosion near the weld where the galvanizing is damaged may be accelerated. On the other hand, in the method of (Patent Document 7), the steel plate on the laser beam irradiation side is not restrained at the time of welding, so that it is difficult to maintain the gap height required for explosion suppression because of the thermal deformation of the steel plate. Further, when the gap height fluctuates during welding, there is a problem that humping occurs due to a change in optimum heat input conditions, and a stable weld bead cannot be obtained.

本発明は、上記の従来技術の問題点に鑑みてなされたものであり、亜鉛めっき鋼板の重ねレーザ溶接において、亜鉛蒸気の発生による溶融金属の爆飛や溶接部欠陥の発生を低減し、かつ、溶接ビード形状および品質に優れた、亜鉛めっき鋼板の重ねレーザ溶接方法および重ね溶接した亜鉛めっき鋼板の溶接継手を提供することを目的とする。 The present invention has been made in view of the above-described problems of the prior art, and in lap laser welding of galvanized steel sheets, reduces the explosion of molten metal due to the generation of zinc vapor and the occurrence of weld defects, and An object of the present invention is to provide a lap laser welding method for galvanized steel sheets and a weld joint for lap-welded galvanized steel sheets, which are excellent in weld bead shape and quality.

本発明者らは、上記目的を達成するために、重ねレーザ溶接のレーザ照射方法および被溶接材の亜鉛めっき鋼板の保持方法を鋭意検討した結果本発明に至った。すなわち、本発明は、
（１）レーザを用いて２枚の亜鉛めっき鋼板を重ね溶接する溶接方法において、予め一方の前記亜鉛めっき鋼板１の溶接部近傍に１本または複数本の溶接ビードに略平行な線に沿って予備成形用レーザ光を照射して、該予備成形用レーザ光照射側に該亜鉛めっき鋼板１を屈曲させた後、該亜鉛めっき鋼板１の予備成形用レーザ光照射側に亜鉛めっき鋼板２を重ね合せ、これら２枚の鋼板の溶接部の両側を拘束したうえで、亜鉛めっき鋼板１を屈曲させたことで生じる２枚の鋼板の間の隙間発生部分に亜鉛めっき鋼板２側から溶接用レーザ光を照射して、前記２枚の亜鉛めっき鋼板を重ね溶接することを特徴とする亜鉛めっき鋼板の重ね溶接方法。
（２）レーザを用いて２枚の亜鉛めっき鋼板を重ね溶接する溶接方法において、予め一方の前記亜鉛めっき鋼板２上の溶接部近傍に複数本の溶接ビードに略平行な線に沿って予備成形用レーザ光を照射して、該亜鉛めっき鋼板２を該複数の線に沿って該予備成形用レーザ光照射側に屈曲させた後、該亜鉛めっき鋼板２の予備成形レーザ光照射側の反対側に亜鉛めっき鋼板１を重ね合せ、これら２枚の鋼板の溶接部の両側を拘束し、亜鉛めっき鋼板２を屈曲させたことで生じる２枚の鋼板の隙間発生部分に亜鉛めっき鋼板２側から溶接用レーザ光を照射して、前記２枚の亜鉛めっき鋼板を重ね溶接することを特徴とする亜鉛めっき鋼板の重ね溶接方法。
（３）２枚の亜鉛めっき鋼板の重ね溶接継手において、少なくとも一方の鋼板の重ね合せ面または外表面でかつ重ねレーザ溶接ビードを挟んでその両側に、該重ねレーザ溶接ビードに略平行で、その幅が溶接ビード幅未満のレーザ光照射痕を複数本有することを特徴とする亜鉛めっき鋼板の重ね溶接継手。
である。 In order to achieve the above-mentioned object, the present inventors have intensively studied a laser irradiation method of lap laser welding and a method of holding a galvanized steel sheet as a material to be welded, and have reached the present invention. That is, the present invention
(1) In a welding method in which two galvanized steel plates are lap welded using a laser, in the vicinity of the welded portion of one of the galvanized steel plates 1 in advance, along a line substantially parallel to one or a plurality of weld beads. After irradiating the preforming laser beam and bending the galvanized steel sheet 1 on the preforming laser beam irradiation side, the galvanized steel sheet 2 is overlapped on the preforming laser beam irradiation side of the galvanized steel sheet 1. In addition, the laser beam for welding is applied from the galvanized steel plate 2 side to the gap generation portion between the two steel plates generated by bending the galvanized steel plate 1 after restraining both sides of the welded portions of these two steel plates. Is applied, and the two galvanized steel sheets are lap welded together.
(2) In a welding method in which two galvanized steel sheets are lap welded using a laser, preforming is performed in advance in the vicinity of a welded portion on one of the galvanized steel sheets 2 along a line substantially parallel to a plurality of weld beads. The galvanized steel sheet 2 is bent along the plurality of lines toward the preforming laser light irradiation side, and then the opposite side of the galvanized steel sheet 2 to the preformed laser light irradiation side. The galvanized steel sheet 1 is overlapped with each other, both sides of the welded part of these two steel sheets are restrained, and the gap between the two steel sheets generated by bending the galvanized steel sheet 2 is welded from the galvanized steel sheet 2 side. A method for lap welding of galvanized steel sheets, wherein the two galvanized steel sheets are lap welded by irradiating a laser beam for use.
(3) In the lap welded joint of two galvanized steel sheets, the overlap surface or outer surface of at least one steel sheet and on both sides of the lap laser weld bead are substantially parallel to the lap laser weld bead, A lap-welded joint for galvanized steel sheets, having a plurality of laser beam irradiation traces having a width less than the weld bead width.
It is.

本発明の方法では、亜鉛めっき鋼板の重ねレーザ溶接において、２枚の鋼板を溶接する前に、一方の鋼板に予備成形用レーザ光を１回または複数回照射して、該亜鉛めっき鋼板を該レーザ光照射側に屈曲させる。一方の鋼板を屈曲させることで、２枚の亜鉛めっき鋼板を重ね合せた際に、２枚の鋼板の間に隙間が得られる。また、２枚の鋼板の溶接部の両側を拘束するため、安定して十分な大きさの隙間が得られる。このため、溶接用レーザ光を照射し溶接を行なう際に、亜鉛蒸気の発生による溶融金属の爆飛や溶接部欠陥の発生を低減することができる。したがって、溶接ビード形状および品質に優れた亜鉛めっき鋼板の重ね溶接継手を得ることができる。 In the method of the present invention, in the lap laser welding of galvanized steel sheets, before welding the two steel sheets, one of the steel sheets is irradiated with a preforming laser beam once or a plurality of times so that the galvanized steel sheets are Bend toward the laser beam irradiation side. By bending one steel plate, a gap is obtained between the two steel plates when the two galvanized steel plates are overlapped. Moreover, since both sides of the welded portion of the two steel plates are constrained, a sufficiently large gap can be obtained stably. For this reason, when performing welding by irradiating the laser beam for welding, it is possible to reduce the explosion of molten metal and the occurrence of defects in the weld due to the generation of zinc vapor. Therefore, a lap welded joint of galvanized steel sheets excellent in weld bead shape and quality can be obtained.

本発明の本旨とするところをより詳らかとするため、以下、添付の図面に基づき説明を行なう。
図１（ａ）および図１（ｂ）は本発明を用いて亜鉛めっき鋼板をレーザ溶接する場合の断面図である。まず、亜鉛めっき鋼板１上の溶接する部分７に予備成形用レーザ光を照射走査する。図１（ａ）および図１（ｂ）においてレーザ光の走査方向は紙面に垂直な向きである。この照射によって鋼板１は、照射位置７を中心に予備成型用レーザ光が照射される側に屈曲する。 In order to make the gist of the present invention more detailed, the following description will be given with reference to the accompanying drawings.
1 (a) and 1 (b) are cross-sectional views when laser welding a galvanized steel sheet using the present invention. First, the laser beam for preforming is irradiated and scanned on the portion 7 to be welded on the galvanized steel sheet 1. In FIGS. 1A and 1B, the scanning direction of the laser light is perpendicular to the paper surface. By this irradiation, the steel plate 1 is bent around the irradiation position 7 to the side irradiated with the laser beam for preforming.

このメカニズムは以下のように説明される。レーザ光照射により、照射位置７付近の板の温度が上昇するが、その上昇幅は鋼板の表面に近いほど大きい。したがって、板厚方向に温度差が生じる。このため、図１（ａ）に示すように鋼板１の一端をのみを拘束具３ａ、３ｂを用いて拘束し、端部５は自由に変位できるようにしておくと、レーザ光照射側の表面には圧縮応力がはたらき、裏面には引張応力がはたらく。この結果、鋼板１に塑性変形が生じる。レーザ光照射後、板厚方向の温度差がなくなっても、レーザ光照射側の表面には圧縮ひずみが、裏面には引張ひずみが残留する。このようにして、照射位置７にレーザ光が照射された鋼板１は、図１（ａ）に破線で示すように、照射位置７を中心にレーザ光６が照射される側に屈曲する。 This mechanism is explained as follows. The temperature of the plate in the vicinity of the irradiation position 7 is increased by the laser beam irradiation, but the increase width is larger as the surface is closer to the surface of the steel plate. Therefore, a temperature difference occurs in the plate thickness direction. For this reason, as shown in FIG. 1 (a), if only one end of the steel plate 1 is restrained by the restraining tools 3a and 3b and the end portion 5 can be freely displaced, the surface on the laser light irradiation side Compressive stress acts on the back surface, and tensile stress acts on the back surface. As a result, plastic deformation occurs in the steel plate 1. Even after the laser beam irradiation, even if the temperature difference in the plate thickness direction disappears, compressive strain remains on the surface on the laser beam irradiation side, and tensile strain remains on the back surface. In this way, the steel sheet 1 irradiated with the laser beam at the irradiation position 7 is bent toward the side irradiated with the laser beam 6 around the irradiation position 7 as indicated by a broken line in FIG.

ところで、レーザ光６を照射した側に鋼板１を屈曲させることは、レーザ光照射により鋼板を溶融させることによっても実現できる。このメカニズムは以下のように説明される。レーザ光を鋼板に照射することにより生じる溶融部の大きさは、図４に示すようにレーザ光を照射した側ほど大きくなる。このとき、溶融金属の凝固、冷却過程で溶融金属に体積収縮が生じるが、上記のような溶融部１１の構造からレーザ光照射側の収縮が大きく、反対側にいくほど収縮は小さくなる。したがって、鋼板は溶融部のビードを中心にレーザ光照射側に屈曲する。また、溶融部はレーザ光照射側の溶融幅を広くするほど、また反対側の溶融幅を狭くするほどこの屈曲角を大きくすることができる。ただし、レーザ光のパワーおよび走査速度は、鋼板の溶融が貫通しない程度に設定しなければならない。一般的に、鋼板を溶融させる方法は、前記した溶融させずに温度差を利用して屈曲させる方法よりも大きな屈曲角を得ることができ、２枚の鋼板を重ね合せた際に大きな隙間を得るのに有利である。 By the way, bending the steel plate 1 to the side irradiated with the laser beam 6 can also be realized by melting the steel plate by laser beam irradiation. This mechanism is explained as follows. As shown in FIG. 4, the size of the melted portion generated by irradiating the steel plate with the laser beam becomes larger as the side irradiated with the laser beam. At this time, volume shrinkage occurs in the molten metal during the solidification and cooling process of the molten metal, but the shrinkage on the laser beam irradiation side is large due to the structure of the molten portion 11 as described above, and the shrinkage is smaller toward the opposite side. Therefore, the steel plate is bent toward the laser beam irradiation side around the bead of the melted part. In addition, the bending angle of the melting portion can be increased as the melting width on the laser beam irradiation side is increased and the melting width on the opposite side is decreased. However, the power and scanning speed of the laser beam must be set to such an extent that the steel sheet does not penetrate. In general, the method of melting a steel plate can obtain a larger bending angle than the above-described method of bending using a temperature difference without melting, and a large gap is formed when two steel plates are overlapped. It is advantageous to obtain.

前記の予備成形用レーザ光照射によって鋼板１を該レーザ光照射側に屈曲させた後、図１（ｂ）に示すように、亜鉛めっき鋼板２を予備成形用レーザ光照射側から重ね合せ、２枚の亜鉛めっき鋼板を拘束具３、４によって拘束し、亜鉛めっき鋼板２側から溶接用レーザ光を照射することで重ね溶接を行なう。予備成形用レーザ光を照射し鋼板１を屈曲させたことにより、２枚の亜鉛めっき鋼板の間には図１（ｂ）に示すような三角形状の断面をもつ隙間９が生じる。また２枚の鋼板の溶接部の両側を拘束するために安定した高さの隙間を得ることができる。２枚の鋼板の重ね部分から溶接時に発生する亜鉛蒸気は、この隙間９から逃げることが可能なため、溶融金属の爆飛を抑制し、良好な溶接を行なうことができる。 After bending the steel plate 1 to the laser beam irradiation side by the laser beam irradiation for preforming, as shown in FIG. 1 (b), the galvanized steel plate 2 is overlapped from the laser beam irradiation side for preforming. The galvanized steel sheets are constrained by the restraining tools 3 and 4, and lap welding is performed by irradiating welding laser light from the galvanized steel sheet 2 side. By bending the steel plate 1 by irradiating the preforming laser beam, a gap 9 having a triangular cross section as shown in FIG. 1B is formed between the two galvanized steel plates. Moreover, since the both sides of the welding part of two steel plates are restrained, the clearance gap with the stable height can be obtained. Since zinc vapor generated at the time of welding from the overlapped portion of the two steel plates can escape from the gap 9, it is possible to suppress the explosion of the molten metal and perform good welding.

また、図２（ａ）、図２（ｂ）に一例を示すように、亜鉛めっき鋼板１に複数本の予備成型用レーザ光６ａ、６ｂを照射し、鋼板１を該複数本の線に沿って屈曲させた後、鋼板２を該レーザ光照射側から重ねて拘束することで生じる隙間部分に、鋼板２側から溶接用レーザ光６を照射することにより溶接を行なうこともできる。この方法は、図１（ａ）および図１（ｂ）に示した方法と比べると、次の点で優れている。すなわち、亜鉛めっき鋼板１の屈曲角に加えて複数の曲げ位置の間隔を変えられるため、隙間９の高さおよび体積を、より広範囲にかつ安定した状態で制御することが可能となり、亜鉛蒸気による爆飛の低減を確実に行なうことができる。 Further, as shown in FIG. 2 (a) and FIG. 2 (b), the galvanized steel sheet 1 is irradiated with a plurality of preforming laser beams 6a and 6b, and the steel sheet 1 is moved along the plurality of lines. After being bent, welding can be performed by irradiating the laser beam 6 for welding from the steel plate 2 side to the gap portion formed by overlapping and restraining the steel plate 2 from the laser light irradiation side. This method is superior to the method shown in FIGS. 1A and 1B in the following points. That is, since the intervals of a plurality of bending positions can be changed in addition to the bending angle of the galvanized steel sheet 1, the height and volume of the gap 9 can be controlled in a wider range and in a stable state. It is possible to reliably reduce explosion.

上述段落［００１６］の方法によると、片側の亜鉛めっき鋼板１の重ね合せ面において、重ねレーザ溶接ビードを挟んだ両側に、該ビードにほぼ平行な複数の予備成形レーザ光照射痕を有する重ね溶接継手が得られる。 According to the method of the above paragraph [0016], lap welding having a plurality of preformed laser beam irradiation traces substantially parallel to the bead on both sides of the lap laser welding bead on the overlapping surface of the galvanized steel sheet 1 on one side. A joint is obtained.

また、一方の亜鉛めっき鋼板に予備成形用レーザ光を照射し、該亜鉛めっき鋼板を屈曲させたのち、該鋼板側から溶接用レーザ光を照射することにより重ね溶接を行なうことも可能である。図３（ａ）および図３（ｂ）は２本の予備成形用レーザ光を用いる場合の例を示す断面図である。まず図３（ａ）に示すように、溶接する２枚の亜鉛めっき鋼板を重ね、亜鉛めっき鋼板２の端部１０が自由に変位できる状態で２本の予備成形用レーザ光を照射する。尚、図１の方法と同様に、レーザ光の走査方向は図３においても紙面に垂直な向きである。段落［００１３］および［００１４］に記したメカニズムにより、予備成形用レーザ光を照射した亜鉛めっき鋼板２は、図３（ａ）に示すようにレーザ光照射位置の２ヵ所で屈曲する。その後２枚の亜鉛めっき鋼板を拘束すると、図３（ｂ）に示すように、亜鉛めっき鋼板２の予備成形用レーザ光照射位置間が予備成形用レーザ光を照射した２ヵ所を支点として湾曲し、２枚の鋼板の間に隙間９が生じる。この部分に亜鉛めっき鋼板２側から溶接用レーザ光を照射することで重ね溶接を行なう。隙間９に亜鉛蒸気が逃げることが可能なため、溶融金属の爆飛を抑制し、良好な溶接を行なうことができる。 It is also possible to perform lap welding by irradiating one of the galvanized steel sheets with a laser beam for preforming, bending the galvanized steel sheet, and then irradiating the laser beam for welding from the steel sheet side. FIG. 3A and FIG. 3B are cross-sectional views illustrating an example in which two preforming laser beams are used. First, as shown in FIG. 3A, two galvanized steel sheets to be welded are stacked, and two pre-forming laser beams are irradiated in a state where the end portion 10 of the galvanized steel sheet 2 can be freely displaced. As in the method of FIG. 1, the scanning direction of the laser beam is also perpendicular to the paper surface in FIG. By the mechanism described in paragraphs [0013] and [0014], the galvanized steel sheet 2 irradiated with the preforming laser beam is bent at two positions of the laser beam irradiation position as shown in FIG. Thereafter, when the two galvanized steel plates are constrained, as shown in FIG. 3 (b), between the pre-forming laser beam irradiation positions of the galvanized steel plate 2 is bent with the two points irradiated with the pre-forming laser beam as fulcrums. A gap 9 is generated between the two steel plates. Lap welding is performed by irradiating this portion with a laser beam for welding from the galvanized steel sheet 2 side. Since zinc vapor can escape into the gap 9, it is possible to suppress the explosion of the molten metal and perform good welding.

上述段落［００１８］の方法によると、片側の亜鉛めっき鋼板２の外表面において、重ねレーザ溶接ビードを挟んだ両側に、該ビードにほぼ平行な複数の予備成形レーザ光照射痕を有する重ね溶接継手が得られる。 According to the method of the above paragraph [0018], a lap weld joint having a plurality of preformed laser beam irradiation traces substantially parallel to the bead on both sides of the lap laser weld bead on the outer surface of the galvanized steel sheet 2 on one side. Is obtained.

この方法は、図１および図２に示した方法と比べると、次の点で優れている。すなわち、予備成型用レーザ光を照射し屈曲させる処理から２枚の鋼板を重ね溶接する処理に移る際に、図１および図２に示した方法では、亜鉛めっき鋼板２を別の場所から持ってきて重ねる処理が必要になるのに対して、図３に示した方法では、２枚の鋼板を拘束するだけでよく、屈曲させる処理と溶接処理の間の時間をより短くすることが可能である。 This method is superior to the method shown in FIGS. 1 and 2 in the following points. That is, when moving from the process of irradiating and bending the preforming laser beam to the process of lap welding two steel sheets, the method shown in FIGS. 1 and 2 brings the galvanized steel sheet 2 from another location. 3 is required, the method shown in FIG. 3 only needs to restrain the two steel plates, and can shorten the time between the bending process and the welding process. .

前記の図１、図２、図３に示した方法はいずれも、予備成形用レーザ光、溶接用レーザ光の２種類のレーザ光照射走査が必要になる。いずれの照射についても、（Ａ）片方の亜鉛めっき鋼板を屈曲させる、もしくは（Ｂ）２枚の亜鉛めっき鋼板を溶接する、という目的が達成されるようなパワーおよび走査速度に設定して行なう。この２種類の目的のためには、必ずしも異なる種類のレーザ光を用いる必要はなく、１種類のレーザ光をパワーまたは走査速度を変えて用いてもよい。さらに、１本のレーザ光を２つのビームに分割して用いてもよい。例えば、図２、図３に示した方法では、１本のレーザ光を２つのビームに分割して用いれば、２ヵ所の予備成型用レーザ光照射を同時に行なうことが可能である。 Each of the methods shown in FIGS. 1, 2, and 3 requires two types of laser beam irradiation scans of a preforming laser beam and a welding laser beam. In any irradiation, the power and the scanning speed are set so as to achieve the purpose of (A) bending one galvanized steel sheet or (B) welding two galvanized steel sheets. For these two types of purposes, it is not always necessary to use different types of laser light, and one type of laser light may be used with varying power or scanning speed. Further, one laser beam may be divided into two beams. For example, in the method shown in FIGS. 2 and 3, if one laser beam is divided into two beams and used, it is possible to simultaneously perform two pre-forming laser beam irradiations.

また、予備成形用レーザ光、溶接用レーザ光の照射はいずれも、必ずしも走査方向に連続的に行なう必要はない。例えば図５に示すように、一定の間隔を空けながら破線状にレーザ光を照射することによっても前記（Ａ）や（Ｂ）の目的は達せられる。 Further, it is not always necessary to continuously perform the irradiation with the laser beam for preforming and the laser beam for welding in the scanning direction. For example, as shown in FIG. 5, the objects (A) and (B) can also be achieved by irradiating the laser beam in a broken line shape with a certain interval.

なお、２枚の亜鉛めっき鋼板をレーザ重ね溶接する際に必要な２枚の鋼板間の隙間高さは、５０μｍ〜２００μｍ程度といわれている。この隙間高さを確保するためには一定の屈曲角が必要となる。屈曲角を大きくするためには段落［００１４］に記したように、溶融を伴うレーザ光照射が有利である。さらに、同じ場所を複数回照射することによっても屈曲角を大きくすることができる。また、十分な隙間高さが得られている場合は、溶接用レーザ光を照射する際に、隙間の中心位置、すなわち隙間高さが最大となる位置を走査する必要はない。ただし、溶接用レーザ光照射中に、亜鉛蒸気が逃げることが可能な隙間を確保するためには、隙間の端の方を照射することは避けるべきである。 In addition, it is said that the gap height between two steel plates required for laser lap welding of two galvanized steel plates is about 50 μm to 200 μm. In order to secure this gap height, a certain bending angle is required. In order to increase the bending angle, as described in paragraph [0014], laser beam irradiation with melting is advantageous. Furthermore, the bending angle can be increased by irradiating the same place multiple times. Further, when a sufficient gap height is obtained, it is not necessary to scan the center position of the gap, that is, the position where the gap height is maximized when the laser beam for welding is irradiated. However, in order to secure a gap through which zinc vapor can escape during irradiation of the laser beam for welding, irradiation at the end of the gap should be avoided.

以下、本発明を実施例で説明する。
図６（ａ）および図６（ｂ）は本発明の一実施例を示す平面図である。それぞれの図は、図１（ａ）および図１（ｂ）と対応した平面図である。各図中１、２は厚さ１ｍｍ、亜鉛目付け量３０ｇ／ｍ^２の亜鉛めっき鋼板である。まず、図１（ａ）および図６（ａ）に示すように予備成型用レーザ光を照射する鋼板１の一端を拘束具３に固定した。この状態で、点線で示した位置７に沿って炭酸ガスレーザ光を照射した。レーザ光のパワーは２ｋＷ、走査速度は１０ｍ／分としたところ、鋼板１は照射位置７に沿って１°屈曲した。このとき、照射位置７上に溶融は見られなかった。次に、鋼板１上に鋼板２を予備成型用レーザ光照射側から重ね合せ、図１（ｂ）および図６（ｂ）に示すように拘束した。このとき、２枚の鋼板間の隙間高さは８の鎖線の下で測定したところ５０μｍであった。その後、鋼板２側から鎖線８に沿って、前記の炭酸ガスレーザ光を溶接用レーザ光として再び照射し、２枚の鋼板を溶接した。このとき、パワーは６ｋＷ、走査速度は５ｍ／分であった。この結果、溶接後の鋼板表裏面７の位置に１本のレーザ光照射による溶融ビードが形成された溶接欠陥のない良好な重ね継手鋼板が得られた（図７）。 Hereinafter, the present invention will be described with reference to examples.
6 (a) and 6 (b) are plan views showing an embodiment of the present invention. Each figure is a plan view corresponding to FIGS. 1 (a) and 1 (b). In each figure, 1 and 2 are galvanized steel sheets having a thickness of 1 mm and a zinc basis weight of 30 g / m ² . First, as shown in FIGS. 1 (a) and 6 (a), one end of a steel plate 1 that was irradiated with laser light for preforming was fixed to the restraining tool 3. In this state, the carbon dioxide laser beam was irradiated along the position 7 indicated by the dotted line. When the power of the laser beam was 2 kW and the scanning speed was 10 m / min, the steel plate 1 was bent by 1 ° along the irradiation position 7. At this time, no melting was observed on the irradiation position 7. Next, the steel plate 2 was superposed on the steel plate 1 from the side of the preforming laser light irradiation and restrained as shown in FIGS. 1 (b) and 6 (b). At this time, the gap height between the two steel plates was 50 μm when measured under the chain line of 8. Then, the said carbon dioxide laser beam was again irradiated as a laser beam for welding along the chain line 8 from the steel plate 2 side, and the two steel plates were welded. At this time, the power was 6 kW and the scanning speed was 5 m / min. As a result, a good lap joint steel plate without welding defects in which a melt bead was formed by irradiation of one laser beam at the position of the steel plate front and back surfaces 7 after welding was obtained (FIG. 7).

段落［００２４］で述べたのと同様の方法で、厚さ１ｍｍ、亜鉛目付け量６０ｇ／ｍ^２の亜鉛めっき鋼板に対して溶接を実施した。しかし、この場合は前記１°の屈曲では、亜鉛蒸気蒸発による爆飛を完全に抑えることはできず溶接欠陥が発生した。これは、亜鉛目付け量６０ｇ／ｍ^２に対し、２枚の鋼板間の隙間が狭すぎたためである。そこで鋼板１の屈曲角を増大させるために、点線で示した位置７に沿って予備成型用レーザ光を照射する条件のみをパワー２ｋＷ、走査速度５ｍ／分に変更して溶接を実施した。その結果、予備成型用レーザ光照射後、鋼板１は照射位置７に沿って２°屈曲した。このとき照射位置７上には溶融が見られた（この時、裏面は非溶融のハーフペネ状態であった）。また２枚の鋼板を重ね合せた後の隙間は、鎖線８の下で測定したところ１００μｍであった。その後、鎖線８に沿ってパワー６ｋＷ、走査速度５ｍ／分の条件で溶接を行なったところ、鋼板表裏面７の位置に１本のレーザ光照射による溶融ビードが形成された溶接欠陥のない良好な重ね継手鋼板が得られた。このように亜鉛目付け量が多い場合には、亜鉛蒸気を逃がす空間を大きくするために、予備成型用レーザ光照射走査部分に溶融を生じさせて大きな屈曲角を得ることで良好な溶接をすることが可能である。 Welding was performed on a galvanized steel sheet having a thickness of 1 mm and a zinc basis weight of 60 g / m ^{2 in} the same manner as described in paragraph [0024]. However, in this case, with the 1 ° bend, explosion by zinc vapor evaporation could not be completely suppressed, resulting in welding defects. This is because the gap between the two steel sheets was too narrow with respect to the zinc basis weight of 60 g / m ² . Therefore, in order to increase the bending angle of the steel plate 1, welding was carried out by changing only the conditions for irradiating the preforming laser beam along the position 7 indicated by the dotted line to a power of 2 kW and a scanning speed of 5 m / min. As a result, the steel plate 1 was bent by 2 ° along the irradiation position 7 after the laser beam for preforming was irradiated. At this time, melting was observed on the irradiation position 7 (at this time, the back surface was in an unmelted half-penetration state). The gap after the two steel plates were overlapped was 100 μm when measured under the chain line 8. Then, welding was performed along the chain line 8 under the conditions of power 6 kW and scanning speed 5 m / min. As a result, a weld bead was formed on the front and back surfaces 7 of the steel sheet by a single laser beam irradiation. A lap joint steel sheet was obtained. In this way, when the amount of zinc is large, in order to increase the space for escaping zinc vapor, good welding is performed by obtaining a large bending angle by causing melting in the laser beam irradiation scanning portion for preforming Is possible.

図８（ａ）および図８（ｂ）は本発明の別の実施例を示す平面図である。それぞれの図は、図２（ａ）および図２（ｂ）と対応した平面図である。各図中１、２は厚さ１ｍｍ、亜鉛目付け量６０ｇ／ｍ^２の亜鉛めっき鋼板である。まず、図２（ａ）および図８（ａ）に示すように鋼板１の一端を拘束具３を用いて固定した。この状態で鋼板１の７ａ、次いで７ｂに沿って炭酸ガスレーザ光を予備成型用レーザ光として照射した。パワーは２ｋＷ、走査速度は１０ｍ／分としたところ、鋼板１は照射位置７ａ、７ｂに沿ってそれぞれ１°ずつ屈曲した。尚、本実施例では、照射位置７ａと７ｂの間隔は６ｍｍとした。次に鋼板１、２を、図２（ｂ）および図８（ｂ）に示すように拘束した。このとき、２枚の鋼板間の隙間は、鎖線８の下で測定したところ５０μｍであった。その後、鋼板２側から鎖線８に沿って、前記の炭酸ガスレーザ光を溶接用レーザ光として再び照射し、２枚の鋼板を溶接した。このとき、パワーは６ｋＷ、走査速度は５ｍ／分であった。この結果、溶接欠陥のない良好な溶接重ね継手鋼板が得られた。図９に示すように、この溶接継手の表面には８の位置に１本の貫通溶融ビードが形成され、片方の鋼板２の外表面には、８の位置にある溶融ビードの両側にある７ａ、７ｂの位置に予備成形用レーザ光照射痕が残っていた。段落［００２５］に記したように、亜鉛目付け量６０ｇ／ｍ^２の亜鉛めっき鋼板の重ね溶接について、鋼板１の位置７に沿って１°屈曲させるだけでは溶接欠陥が発生した。しかし、本方法のように予備成型用レーザ光照射位置を２ヵ所にすると、それぞれの屈曲角は変化しなくても亜鉛蒸気が逃げる隙間体積が増加するため、爆飛を抑え溶接欠陥をなくすことができる。 FIG. 8A and FIG. 8B are plan views showing another embodiment of the present invention. Each figure is a plan view corresponding to FIG. 2 (a) and FIG. 2 (b). In the drawings, 1 and 2 are galvanized steel sheets having a thickness of 1 mm and a zinc basis weight of 60 g / m ² . First, as shown in FIG. 2A and FIG. 8A, one end of the steel plate 1 was fixed using a restraining tool 3. In this state, carbon dioxide laser light was irradiated as laser light for preforming along 7a and then 7b of the steel sheet 1. When the power was 2 kW and the scanning speed was 10 m / min, the steel plate 1 was bent by 1 ° along the irradiation positions 7a and 7b. In this embodiment, the distance between the irradiation positions 7a and 7b is 6 mm. Next, the steel plates 1 and 2 were restrained as shown in FIGS. 2 (b) and 8 (b). At this time, the gap between the two steel plates was 50 μm when measured under the chain line 8. Then, the said carbon dioxide laser beam was again irradiated as a laser beam for welding along the chain line 8 from the steel plate 2 side, and the two steel plates were welded. At this time, the power was 6 kW and the scanning speed was 5 m / min. As a result, a good weld lap joint steel plate without weld defects was obtained. As shown in FIG. 9, one through-melt bead is formed at the position 8 on the surface of the welded joint, and the outer surface of the one steel plate 2 has 7a on both sides of the melt bead at the position 8. , 7b, a laser beam irradiation mark for preforming remained. As described in paragraph [0025], a welding defect was generated only by bending the galvanized steel sheet having a zinc basis weight of 60 g / m ² by bending 1 ° along the position 7 of the steel sheet 1. However, if there are two laser beam irradiation positions for preforming as in this method, the gap volume through which the zinc vapor escapes increases even if the bending angle does not change, thus preventing explosions and eliminating welding defects. Can do.

図１０（ａ）および図１０（ｂ）は本発明の別の実施例を示す溶接部の平面図である。それぞれの図は断面図、図３（ａ）および図３（ｂ）と対応している。各図中１、２は厚さ１ｍｍ、亜鉛目付け量１００ｇ／ｍ^２の亜鉛めっき鋼板であり、段落［００２５］、［００２６］で述べた例よりもさらに亜鉛目付け量が多くなっている。まず、図３（ａ）および図１０（ａ）に示すように鋼板１、２のそれぞれの一端を拘束具３を用いて固定した。この状態で鋼板２の７ａ、次いで７ｂに沿って炭酸ガスレーザ光を予備成型用レーザ光として照射した。パワーは２ｋＷ、走査速度は５ｍ／分としたところ、鋼板２は照射位置７ａ、７ｂに沿ってそれぞれ２°ずつ屈曲した。このとき照射位置７ａ、７ｂ上に溶融が見られた。尚、本実施例では、照射位置７ａと７ｂの間隔は６ｍｍとした。次に鋼板１、２を、図３（ｂ）および図１０（ｂ）に示すように拘束した。このとき、２枚の鋼板間の隙間は、鎖線８の下で測定したところ１００μｍであった。その後、鋼板２側から鎖線８に沿って、前記の炭酸ガスレーザ光を溶接用レーザ光として再び照射し、２枚の鋼板を溶接した。このとき、パワーは６ｋＷ、走査速度は５ｍ／分であった。この結果、溶接欠陥のない良好な溶接重ね継手鋼板が得られた。図１１に示すように、この溶接継手の表面には８の位置に１本の貫通溶融ビードが形成され、片方の鋼板２の外表面には、８の位置にある溶融ビードの両側にある７ａ、７ｂの位置に溶融を伴う予備成形用レーザ光照射痕が残っていた。尚、この厚さ１ｍｍ、亜鉛目付け量１００ｇ／ｍ^２の亜鉛めっき鋼板の重ね溶接を段落［００２５］で述べた方法で行なったが、爆飛が原因の溶接欠陥が発生した。段落［００２５］に述べた１ヵ所で屈曲させる方法で得られた隙間高さ１００μｍは、照射位置７ａ、７ｂの２ヵ所で屈曲させることを特徴とする本方法で得られた高さと同じであったが、本方法の方が２枚の鋼板間にできる隙間９の体積は大きくなる。この点が爆飛を抑え溶接欠陥をなくすのに有効に働いたといえる。 10 (a) and 10 (b) are plan views of a welded portion showing another embodiment of the present invention. Each figure corresponds to a cross-sectional view, FIG. 3 (a) and FIG. 3 (b). In the drawings, 1 and 2 are galvanized steel sheets having a thickness of 1 mm and a zinc basis weight of 100 g / m ² , and the zinc basis weight is larger than the examples described in paragraphs [0025] and [0026]. First, as shown in FIG. 3A and FIG. 10A, one end of each of the steel plates 1 and 2 was fixed using a restraining tool 3. In this state, carbon dioxide laser light was irradiated as laser light for preforming along 7a and then 7b of the steel plate 2. When the power was 2 kW and the scanning speed was 5 m / min, the steel plate 2 was bent by 2 ° along the irradiation positions 7a and 7b. At this time, melting was observed on the irradiation positions 7a and 7b. In this embodiment, the distance between the irradiation positions 7a and 7b is 6 mm. Next, the steel plates 1 and 2 were restrained as shown in FIGS. 3 (b) and 10 (b). At this time, the gap between the two steel plates was 100 μm when measured under the chain line 8. Then, the said carbon dioxide laser beam was again irradiated as a laser beam for welding along the chain line 8 from the steel plate 2 side, and the two steel plates were welded. At this time, the power was 6 kW and the scanning speed was 5 m / min. As a result, a good weld lap joint steel plate without weld defects was obtained. As shown in FIG. 11, one through-melting bead is formed at the position of 8 on the surface of this welded joint, and the outer surface of one steel plate 2 has 7a on both sides of the molten bead at the position of 8. , 7b, a laser beam irradiation mark for preforming with melting remained. Note that lap welding of the galvanized steel sheet having a thickness of 1 mm and a zinc basis weight of 100 g / m ² was performed by the method described in paragraph [0025], but a welding defect caused by explosion was generated. The gap height of 100 μm obtained by the method of bending at one place described in paragraph [0025] is the same as the height obtained by this method characterized by bending at the irradiation positions 7a and 7b. However, the volume of the gap 9 formed between the two steel plates is larger in this method. It can be said that this point worked effectively to suppress explosions and eliminate welding defects.

尚、段落［００２６］、［００２７］に記した実施例では照射位置７ａと８、８と７ｂの間隔はそれぞれ３ｍｍとした。一般的に、レーザ光照射部・溶接部は表面の亜鉛が蒸発し防錆・防食効果が失われる。ただし１ヵ所のレーザ光照射で亜鉛の蒸発する幅は１ｍｍ程度であり、この程度の幅であれば周辺の亜鉛によって防錆・防食効果は維持される。本方法でこの効果を維持するためには、鋼板２上の７ａ、７ｂおよび８にレーザ光照射後も各照射部分の間に適当な量の亜鉛が存在するようにすればよい。したがって照射位置７ａと８、８と７ｂの間隔はそれぞれ２ｍｍ以上とするのが好ましい。 In the examples described in paragraphs [0026] and [0027], the intervals between the irradiation positions 7a and 8, and 8 and 7b were 3 mm, respectively. In general, the zinc on the surface of the laser beam irradiated part / welded part evaporates and the rust prevention / corrosion prevention effect is lost. However, the width of evaporation of zinc by laser light irradiation at one place is about 1 mm, and if it is this width, the antirust and anticorrosive effect is maintained by the surrounding zinc. In order to maintain this effect in this method, an appropriate amount of zinc may be present between the irradiated portions of the laser beam 7a, 7b and 8 on the steel plate 2 even after the laser beam irradiation. Therefore, the distance between the irradiation positions 7a and 8, and 8 and 7b is preferably 2 mm or more.

ところで、段落［００２６］、［００２７］で述べた方法では、６ａ、６ｂの順に予備成型用レーザ光を照射した。照射点７ｂにレーザ光を照射する際には、すでに７ａに沿った屈曲が生じているため、レーザ光照射点７ｂは元の位置より上方にΔｈの位置ずれを生じた。しかし、２本のレーザ光照射位置７ａ、７ｂの間隔は前述のように６ｍｍであり、したがってΔｈは０．２ｍｍ程度であった。段落［００２６］、［００２７］のいずれの実施例においても、レーザ光６ｂは焦点距離１００ｍｍ程度のレンズで集光したので、焦点深度は±０．３ｍｍ程度あり、Δｈの位置ずれが問題になることはなかった。もちろん、図２（ａ）、図３（ａ）に示すように予め焦点位置をΔｈだけずらしてレーザ光６ｂを照射すると、より安定した加工結果を得ることができる。また本実施例のように、照射位置７ａ、７ｂの順に照射する際のΔｈの位置ずれが問題にならない場合は、照射位置７ａ、７ｂへの照射を２つのレーザ光を用いて同時に行なうことも可能となる。 By the way, in the method described in paragraphs [0026] and [0027], the laser beam for preforming was irradiated in the order of 6a and 6b. When the irradiation point 7b is irradiated with the laser beam, the bending along the line 7a has already occurred, so that the laser beam irradiation point 7b is displaced by Δh above the original position. However, the distance between the two laser light irradiation positions 7a and 7b was 6 mm as described above, and therefore Δh was about 0.2 mm. In both the embodiments of paragraphs [0026] and [0027], the laser beam 6b is collected by a lens having a focal length of about 100 mm, so that the focal depth is about ± 0.3 mm, and a positional deviation of Δh becomes a problem. It never happened. Of course, as shown in FIGS. 2 (a) and 3 (a), when the laser beam 6b is irradiated with the focal position shifted in advance by Δh, a more stable processing result can be obtained. In addition, as in the present embodiment, when the positional deviation of Δh when irradiating in the order of the irradiation positions 7a and 7b is not a problem, irradiation to the irradiation positions 7a and 7b may be performed simultaneously using two laser beams. It becomes possible.

（ａ）は本発明の予備成形レーザ光照射の一例を示す断面図、（ｂ）は（ａ）に引き続いて行う本発明の溶接用レーザ光照射を示す断面図である。(A) is sectional drawing which shows an example of the preforming laser beam irradiation of this invention, (b) is sectional drawing which shows the laser beam irradiation for welding of this invention performed following (a). （ａ）は本発明の予備成形レーザ光照射の他の例を示す断面図、（ｂ）は（ａ）に引き続いて行う本発明の溶接用レーザ光照射を示す断面図である。(A) is sectional drawing which shows the other example of the preforming laser beam irradiation of this invention, (b) is sectional drawing which shows the laser beam irradiation for welding of this invention performed following (a). （ａ）は本発明の予備成形レーザ光照射の更に別の例を示す断面図、（ｂ）は（ａ）に引き続いて行う本発明の溶接用レーザ光照射を示す断面図である。(A) is sectional drawing which shows another example of the preforming laser beam irradiation of this invention, (b) is sectional drawing which shows the laser beam irradiation for welding of this invention performed following (a). レーザ光を鋼板に照射したときの溶融部の断面図である。It is sectional drawing of a fusion | melting part when a laser beam is irradiated to a steel plate. レーザ光照射部の平面図である。It is a top view of a laser beam irradiation part. 図１に基づき行った本発明の実施例を示すもので、（ａ）は予備成形レーザ光照射時の平面図、（ｂ）は溶接用レーザ光照射時の平面図である。FIG. 2 shows an embodiment of the present invention performed based on FIG. 1, (a) is a plan view when irradiated with a preforming laser beam, and (b) is a plan view when irradiated with a laser beam for welding. 図６の本発明の実施例により得られた重ね溶接継手を示す図である。It is a figure which shows the lap weld joint obtained by the Example of this invention of FIG. 図２に基づき行った本発明の実施例を示すもので、（ａ）は予備成形レーザ光照射時の平面図、（ｂ）は溶接用レーザ光照射時の平面図である。FIGS. 2A and 2B show an embodiment of the present invention performed based on FIG. 2, in which FIG. 2A is a plan view when a preforming laser beam is irradiated, and FIG. 図８の本発明の実施例により得られた重ね溶接継手を示す図である。It is a figure which shows the lap weld joint obtained by the Example of this invention of FIG. 図３に基づき行った本発明の実施例を示すもので、（ａ）は予備成形レーザ光照射時の平面図、（ｂ）は溶接用レーザ光照射時の平面図である。FIGS. 3A and 3B show an embodiment of the present invention based on FIG. 3, wherein FIG. 3A is a plan view when irradiated with a preforming laser beam, and FIG. 図１０の本発明の実施例により得られた重ね溶接継手を示す図である。It is a figure which shows the lap weld joint obtained by the Example of this invention of FIG.

Explanation of symbols

１、２…亜鉛めっき鋼板
３、４…拘束具
５、１０…端部
６…レーザ光
７、８…レーザ光の照射位置
９…隙間
１１…溶融部 DESCRIPTION OF SYMBOLS 1, 2 ... Galvanized steel plate 3, 4 ... Restraint tool 5, 10 ... End part 6 ... Laser beam 7, 8 ... Irradiation position of laser beam 9 ... Gap 11 ... Melting part

Claims

In a welding method in which two galvanized steel sheets are overlap-welded using a laser, preliminarily formed along a line substantially parallel to one or a plurality of weld beads in the vicinity of the welded portion of one of the galvanized steel sheets 1 After irradiating a laser beam to bend the galvanized steel sheet 1 on the laser beam irradiation side for preforming, the galvanized steel sheet 2 is superimposed on the laser beam irradiation side for preforming the galvanized steel sheet 1, A laser beam for welding is irradiated from the galvanized steel sheet 2 side to a gap generating portion between the two steel sheets generated by bending the galvanized steel sheet 1 after restraining both sides of the welded portion of the two steel sheets. A lap welding method for galvanized steel sheets, wherein the two galvanized steel sheets are lap welded.

In a welding method in which two galvanized steel sheets are overlap-welded using a laser, preliminarily forming laser light along a line substantially parallel to a plurality of weld beads in the vicinity of a welded portion on one of the galvanized steel sheets 2 in advance. The galvanized steel sheet 2 is bent along the plurality of lines to the preforming laser beam irradiation side, and then galvanized on the opposite side of the galvanized steel sheet 2 from the preformed laser beam irradiation side. Laser beam for welding from the galvanized steel plate 2 side to the gap generation part of the two steel plates generated by overlapping the steel plates 1, restraining both sides of the welded part of these two steel plates and bending the galvanized steel plate 2 Is applied, and the two galvanized steel sheets are lap welded together.

In a lap welded joint of two galvanized steel sheets, the overlapping surface or outer surface of at least one steel sheet and on both sides of the lap laser weld bead are substantially parallel to the lap laser weld bead and the width is welded. A lap-welded joint for galvanized steel sheets having a plurality of laser beam irradiation traces less than the bead width.