JP4016911B2 - Laser welding method of high strength steel - Google Patents

Laser welding method of high strength steel Download PDF

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JP4016911B2
JP4016911B2 JP2003300415A JP2003300415A JP4016911B2 JP 4016911 B2 JP4016911 B2 JP 4016911B2 JP 2003300415 A JP2003300415 A JP 2003300415A JP 2003300415 A JP2003300415 A JP 2003300415A JP 4016911 B2 JP4016911 B2 JP 4016911B2
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忠紀 岡田
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Toyota Motor Corp
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Description

本発明は、レーザビームによって所定厚さの高張力鋼板同士を重ね合わせ溶接する高張力鋼のレーザ溶接方法に関する。特に、自動車用の衝撃吸収部材などのフランジ部の溶接に好適なレーザ溶接方法に関する。   The present invention relates to a laser welding method for high-strength steel in which high-tensile steel sheets having a predetermined thickness are overlapped and welded with each other by a laser beam. In particular, the present invention relates to a laser welding method suitable for welding a flange portion such as a shock absorbing member for automobiles.

一般に、自動車の車体前部の両サイドには、フロントサイドメンバと呼ばれる閉断面構造の衝撃吸収部材が設けられ、正面からの衝突時に効率よく潰れて衝突のエネルギを吸収し乗員の安全を確保する構造となっている。従来、このような衝撃吸収部材の衝突時のエネルギ吸収特性を高めることを目的に、衝突時の圧潰モードのコントロールや溶接位置の適正化、あるいは溶接部強度の向上に必要な溶接部形状の検討など多くの提案がなされている。例えば、閉断面構造の衝撃吸収部材を構成するハット断面形状の鋼板とフラット形状の鋼板とをフランジにおいてレーザ溶接する方法において、レーザ溶接の溶融幅をある範囲に限定して溶接する方法が提案されている（特許文献１参照）。この方法によりスポット溶接時のような軸衝撃時の溶接部からの破断による圧潰モードの不良などの問題がなく、優れた衝撃吸収特性が得られるとしている。そして、５９０ＭＰａ以上の鋼板を用いて衝撃吸収部材を製造することにより、更に衝撃吸収特性を向上させることができるとしている。   In general, on both sides of the front part of a car body, a shock absorbing member having a closed cross-sectional structure called a front side member is provided, which is efficiently crushed at the time of a collision from the front and absorbs the energy of the collision to ensure the safety of the passenger. It has a structure. Conventionally, in order to enhance the energy absorption characteristics at the time of collision of such shock absorbing members, investigation of the weld shape required for controlling the crush mode at the time of collision, optimizing the welding position, or improving the weld strength Many proposals have been made. For example, in a method of laser welding a steel plate having a hat cross-sectional shape and a flat steel plate constituting a shock-absorbing member having a closed cross-sectional structure at a flange, a method of welding by limiting the melting width of laser welding to a certain range has been proposed. (See Patent Document 1). According to this method, there is no problem such as a failure of the crushing mode due to fracture from the welded part at the time of axial impact such as spot welding, and it is said that excellent shock absorption characteristics can be obtained. And it is supposed that an impact-absorbing characteristic can be improved further by manufacturing an impact-absorbing member using a steel plate of 590 MPa or more.

しかし、４４０Ｍｐａ以上の高張力鋼板の重ね合わせレーザ溶接部の剥離方向の強度は、材料強度が上昇するにつれて低下するために、例えば衝撃吸収部材の圧潰時に溶接部から破断が生じ、十分な衝撃吸収特性を発揮できない可能性がある。図７に材料強度と重ね合わせレーザ溶接部の剥離強度との関係を示す。図７は、厚さ１．２ｍｍの鋼板を２枚重ねてその上面からレーザ光を照射して形成した溶接試験片を、後述する試験方法で剥離試験を行い試験片が破断した強度を剥離強度としてプロットしたものである。引張強度が２７０ＭＰａ程度の軟鋼（ＳＰＣＤ）（○）では、単位長さ当たりの剥離強度は２７０Ｎ／ｍｍ（２２５ＭＰａ）とほぼ母材強度に近い値が得られるが、例えば、引張強度が５９０ＭＰａの高張力鋼（ＳＰＦＣ５９０Ｙ）（◆）では、剥離強度は５５〜７５Ｎ／ｍｍ（４６〜６３ＭＰａ）と母材強度に比べて極めて低い値しか得られな。   However, the strength in the peeling direction of the superposed laser welded portion of a high-tensile steel plate of 440 Mpa or more decreases as the material strength increases. For example, when the impact absorbing member is crushed, the welded portion breaks, and sufficient impact absorption is achieved. There is a possibility that the characteristics cannot be exhibited. FIG. 7 shows the relationship between the material strength and the peel strength of the overlapping laser weld. FIG. 7 shows the peel strength of a welded test piece formed by stacking two 1.2 mm-thick steel plates and irradiating a laser beam from the upper surface, and performing a peel test by a test method described later. As plotted. With mild steel (SPCD) (◯) having a tensile strength of about 270 MPa, the peel strength per unit length is 270 N / mm (225 MPa), which is a value close to the base material strength. For example, the tensile strength is as high as 590 MPa. In tensile steel (SPFC590Y) (♦), the peel strength is 55 to 75 N / mm (46 to 63 MPa), which is only a very low value compared to the base material strength.

これは、高強度材料ほど変形し難いために、低強度材料に比べて溶接ビード部により大きな曲げ応力が作用するためである。図８に引張強度の低い、例えば軟鋼などの低強度材料（ａ）と、高張力鋼のような高強度材料（ｂ）とについて、各々重ね合わせレーザ溶接して、同一荷重Ｆで剥離試験を行った場合の剥離試験片の変形の様子を模式的に示した。Ｂは溶接ビード部であり、Ｃは剥離試験するために溶接試験片を９０゜曲げした曲げ部である。つまり、同じ荷重条件では溶接ビードＢを支点とするモーメントアームの長さが、低強度材料（ａ）ではＬ1と短いが、高強度材料（ｂ）ではＬ2と長くなり、高強度材料の場合には溶接ビード部Ｂに低強度材料（ａ）よりも大きな曲げ応力が作用するためである。また、レーザ溶接した溶接ビードＢの近傍は急冷されて焼き入れ硬化しているために母材よりも硬さが上昇し延性は低下している。従って、剥離変形時に最も大きく変形する溶接ビード境界部Ａでは変形に対する許容度は低下している。さらに、図９に示すように、溶接ビード部Ｂが冷却による収縮などによってビードの母材近傍部にアンダーカットＤが生じる。このためアンダーカットＤ部の厚さｔは、母材の厚さｔ0よりも減少するので、この部分が剥離荷重を受けた場合の最弱部Ｅとなる場合が多い。このため、剥離試験で試験片を両側へ引っ張ると、試験片は板厚の薄い最弱部Ｅで破断し（図１０参照）、この荷重が剥離強度となる。以上のように従来の高張力鋼の重ね合わせレーザ溶接方法においては、材料強度よりも遙かに低い剥離強度しか得ることができなかった。
特開２００２−７９３８８号公報 This is because a higher bending strength is applied to the weld bead portion than a low-strength material because the higher-strength material is less likely to be deformed. In FIG. 8, a low strength material (a) having a low tensile strength, such as mild steel, and a high strength material (b), such as a high strength steel, are overlapped and laser welded, and a peel test is performed with the same load F. The state of deformation of the peel test piece when performed is schematically shown. B is a weld bead portion, and C is a bent portion obtained by bending a weld test piece by 90 ° for a peel test. That is, under the same load condition, the length of the moment arm with the weld bead B as a fulcrum is as short as L 1 in the low-strength material (a) but as long as L 2 in the high-strength material (b). This is because a bending stress larger than that of the low-strength material (a) acts on the weld bead portion B in some cases. Further, since the vicinity of the laser-welded weld bead B is quenched and quenched and hardened, the hardness is higher than the base material and the ductility is reduced. Therefore, the tolerance for deformation is reduced at the weld bead boundary portion A that is most greatly deformed at the time of peeling deformation. Further, as shown in FIG. 9, undercut D occurs in the vicinity of the base material of the bead due to the shrinkage of the weld bead B due to cooling. For this reason, since the thickness t of the undercut D portion is smaller than the thickness t 0 of the base material, this portion often becomes the weakest portion E when subjected to a peeling load. For this reason, when the test piece is pulled to both sides in the peel test, the test piece is broken at the weakest portion E having a thin plate thickness (see FIG. 10), and this load becomes the peel strength. As described above, in the conventional high-strength steel superposition laser welding method, only a peel strength much lower than the material strength could be obtained.
JP 2002-79388 A

本発明は、上記の従来技術の問題点に鑑み、高張力鋼の重ね合わせレーザ溶接において、その溶接部の剥離強度を向上させるレーザ溶接方法を提供することを目的とする。   An object of the present invention is to provide a laser welding method for improving the peel strength of a welded portion in superposition laser welding of high-strength steel in view of the above-described problems of the prior art.

発明者らは高張力鋼の重ね合わせレーザ溶接において、溶接ビード部に形成されるアンダーカットを解消して、剥離変形時に最も大きく変形する溶接ビード境界部の板厚を増肉することにより高張力鋼の剥離強度を向上させることに着目した。   In superposition laser welding of high-tensile steel, the inventors eliminated the undercut formed in the weld bead and increased the thickness of the weld bead boundary, which is the most deformed at the time of delamination deformation. We focused on improving the peel strength of steel.

すなわち、本発明の高張力鋼のレーザ溶接方法は、等しい厚さの２枚の高張力鋼をレーザビームによって重ね合わせ溶接する高張力鋼のレーザ溶接方法において、重ね合わせ溶接部にフィラーを供給して溶接ビード断面の余盛り高さが、前記高張力鋼の厚さの２０〜１２０％となるように溶接ビード部に余盛りを形成することを特徴とする。ここで、余盛高さは、重ね合わせた上板と下板とを融合しているビード部の上板の上面から突出しているビードの最高点までの高さと、下板の下面から突出しているビードの最高点までの高さとの和である。 That is, the high-strength steel laser welding method of the present invention is a high-tensile steel laser welding method in which two high-strength steels of equal thickness are overlap welded with a laser beam, and a filler is supplied to the overlap weld. The surplus height of the weld bead cross section is 20 to 120% of the thickness of the high-tensile steel, and the surplus height is formed in the weld bead portion. Here, the height of the surplus is determined by the height up to the highest point of the bead protruding from the upper surface of the upper plate of the bead unit where the upper plate and the lower plate overlapped with each other and the lower surface of the lower plate. It is the sum of the height to the highest point of the bead.

溶接ビード部に余盛を形成することにより、ビード部に冷却によるアンダーカットといった形状不良を発生することがなく、剥離変形時に最も大きく変形する溶接ビード境界部の板厚を増肉することができるので高張力鋼の剥離強度を向上させることができる。そして、溶接ビード部の余盛高さがこの範囲にあれば、軟鋼（ＳＰＣＤ）の引張強度、つまり２７０ＭＰａ以上の剥離強度を得ることができる。 By forming a surplus in the weld bead portion, it is possible to increase the thickness of the weld bead boundary portion that is deformed the most at the time of peeling deformation without causing a shape defect such as an undercut due to cooling in the bead portion. Therefore, the peel strength of high-strength steel can be improved. And if the extra height of a weld bead part exists in this range, the tensile strength of mild steel (SPCD), ie, the peel strength of 270 MPa or more, can be obtained.

また、本発明の高張力鋼のレーザ溶接方法においては、高張力鋼は引張強度が４４０ＭＰａ以上の高張力鋼であることが望ましい。   In the laser welding method for high strength steel of the present invention, the high strength steel is preferably a high strength steel having a tensile strength of 440 MPa or more.

引張強度が４４０ＭＰａ以上の高張力鋼を用いることにより、例えば、衝撃吸収部材の衝撃吸収エネルギを増大させ、自動車の軽量化とともに衝突安全性を一層向上させることができる。図１１に衝撃吸収部材を高速で軸圧潰するときに測定される荷重−変位曲線を模式的に示す。図１１では、同一形状の衝撃吸収部材を実線で示す高張力鋼で形成した場合と、点線で示す軟鋼を用いた場合とを併記して比較した。衝撃吸収エネルギは、荷重を変位で積分して得られ、この値が大きいほど衝撃吸収部材の衝撃吸収能は高く、軟鋼に代えて高張力鋼を使用することにより衝撃吸収エネルギを増大させることが分かる。   By using high-tensile steel having a tensile strength of 440 MPa or more, for example, the impact absorbing energy of the impact absorbing member can be increased, and the collision safety can be further improved along with the weight reduction of the automobile. FIG. 11 schematically shows a load-displacement curve measured when the impact absorbing member is axially crushed at high speed. In FIG. 11, the case where the impact-absorbing member having the same shape is formed of high-strength steel indicated by a solid line and the case where mild steel indicated by a dotted line is used are written and compared. The shock absorption energy is obtained by integrating the load with the displacement. The larger the value, the higher the shock absorption capacity of the shock absorption member, and it is possible to increase the shock absorption energy by using high strength steel instead of mild steel. I understand.

本発明の高張力鋼のレーザ溶接方法は、レーザビームによって重ね合わせ溶接する高張力鋼のレーザ溶接方法において、重ね合わせ溶接部にフィラーを供給して溶接ビード部に余盛りを形成することを特徴とする。   The laser welding method for high-strength steel according to the present invention is a laser welding method for high-strength steel that is lap welded by a laser beam, wherein filler is supplied to the lap weld to form a surplus in the weld bead. And

本発明のレーザ溶接方法は、図１に示すように一般の鋼板を溶接するレーザ溶接装置を使用して実施することができる。高張力鋼板イとロとを重ね合わせ溶接するレーザ溶接装置１０において、１１はレーザ発振器Ｒのレーザ溶接トーチであり、このレーザ溶接トーチ１１の先端には、レーザビームを集光させる集光レンズ１２が設けられている。また、レーザ溶接トーチ１１の先端部付近には巻回収納されている収納部１３より導出される線状のフィラーワイヤ１４の導出端が集光レンズ１２の先端に供給されるようにブラケット１５を介して挿通自在に支持されている。ここで、フィラーワイヤ１４は、溶接ビードの断面形状に余盛を形成することができればよいから、母材よりも極端に弱い材料でなければフィラーの材質には特に制約はない。例えば、ＪＩＳに規定されているＹＧＷ１７やＹＧＷ２３などを好適に使用することができる。   The laser welding method of the present invention can be carried out using a laser welding apparatus for welding a general steel plate as shown in FIG. In a laser welding apparatus 10 for superposing and welding high-tensile steel plates A and B, 11 is a laser welding torch of a laser oscillator R, and a condensing lens 12 for condensing a laser beam at the tip of the laser welding torch 11. Is provided. Further, the bracket 15 is provided so that the lead-out end of the linear filler wire 14 led out from the storage part 13 wound around and stored in the vicinity of the tip of the laser welding torch 11 is supplied to the tip of the condenser lens 12. It is supported so that it can be inserted through. Here, since the filler wire 14 is only required to be able to form a surplus in the cross-sectional shape of the weld bead, the filler material is not particularly limited as long as it is not extremely weaker than the base material. For example, YGW17, YGW23, etc. prescribed | regulated to JIS can be used conveniently.

図２は、レーザ溶接装置１０を用いて高張力鋼（ＳＰＣ４４０）に余盛を形成した溶接ビード部の断面をスケッチしたものである。板厚ｔ0の高張力鋼板イとロとが溶接ビードＢで融合されている。そして、フィラーを供給することによりビード部Ｂの上面には高さｈ1の余盛が、また下面には高さｈ2の余盛が形成されている。この余盛の大きさ（以下、余盛高さという。）は溶接条件、例えば溶接速度やフィラーワイヤの供給速度などを調節することにより所望の高さとすることができる。ここで、溶接ビード部Ｂの合計の余盛高さＨを各余盛高さの合計、すなわち、Ｈ＝ｈ1＋ｈ2とすると、合計余盛高さＨは、溶接された高張力鋼の板厚ｔ0の２０〜１２０％であることが望ましい。合計余盛高さＨが２０％未満では余盛による十分な剥離強度の向上を得ることができない。また、１２０％を越えるとレーザ溶接時に溶融金属が垂れ落ちる危険性が高くなるので好ましくない。より好ましくは７５〜１２０％である。 FIG. 2 is a sketch of a cross section of a weld bead portion in which a surplus is formed on high-tensile steel (SPC440) using the laser welding apparatus 10. The high-tension steel plates A and B having a plate thickness t 0 are fused with the weld bead B. By supplying the filler, a surplus of height h 1 is formed on the upper surface of the bead portion B, and a surplus of height h 2 is formed on the lower surface. The size of the surplus (hereinafter referred to as surplus height) can be set to a desired height by adjusting the welding conditions such as the welding speed and the filler wire supply speed. Here, when the total surplus height H of the weld bead portion B is the sum of the surplus heights, that is, H = h 1 + h 2 , the total surplus height H is obtained from the welded high-tensile steel. It is desirable that it is 20 to 120% of the plate thickness t 0 . When the total surplus height H is less than 20%, it is not possible to obtain a sufficient improvement in peel strength due to surplus. On the other hand, if it exceeds 120%, the risk of dripping of the molten metal during laser welding increases, which is not preferable. More preferably, it is 75 to 120%.

図３は図２に示した溶接部を剥離試験によって引っ張り破断させた溶接ビード部の断面をスケッチしたものである。ビード部Ｂには変形がなく高張力鋼板ロの母材部分で延性破壊していることが分かる。   FIG. 3 is a sketch of a cross section of a weld bead portion in which the weld portion shown in FIG. 2 is pulled and broken by a peel test. It can be seen that the bead portion B is not deformed and is ductile fractured at the base material portion of the high-tensile steel plate B.

以下、実施例により本発明をさらに詳しく説明する。   Hereinafter, the present invention will be described in more detail with reference to examples.

供試材の高張力鋼として、厚さが１．２ｍｍで引張強度が４４０ＭＰａ以上のＳＰＦＣ４４０，ＳＰＦＣ５９０Ｙ、ＳＰＦＣ９８０Ｙとを準備した。   SPFC440, SPFC590Y, and SPFC980Y having a thickness of 1.2 mm and a tensile strength of 440 MPa or more were prepared as high-tensile steels as test materials.

レーザ溶接は、ＹＡＧレーザを用い、レーザ発振出力を４ｋＷ、溶接速度を１ｍ／ｍｉｎとし、直径１．２ｍｍのフィラーワイヤ（ＹＧＷ１７）を集光レンズ先端へ供給した。ここで、フィラーワイヤの供給速度を０．５〜２．０ｍ／ｍｉｎの範囲で変化させ、各供試材のビードの余盛高さＨが所望の高さとなるように調節した。また、レーザビームは、鋼板上に集光し、集光スポットは直径２．３５ｍｍとした。   For laser welding, a YAG laser was used, the laser oscillation output was 4 kW, the welding speed was 1 m / min, and a filler wire (YGW17) having a diameter of 1.2 mm was supplied to the tip of the condenser lens. Here, the supply speed of the filler wire was changed within a range of 0.5 to 2.0 m / min, and the extra height H of the beads of each test material was adjusted to a desired height. The laser beam was focused on the steel plate and the focused spot was 2.35 mm in diameter.

まず、各鋼板から図４に示す形状（厚さ１．２ｍｍ×１００ｍｍ×６０ｍｍ、チャック幅４０ｍｍ）の試験片２枚を切り出した。次に、これら２枚の試験片をギャップが生じないように重ね合わせ、６０ｍｍ幅の端辺Ｋから１５ｍｍ隔てた位置に端辺Ｋに平行に上記の条件でレーザ溶接してビードＢを形成し溶接試験片ＴＰ1とした。なお、レーザ溶接長さは５０ｍｍとした。 First, two test pieces having the shape shown in FIG. 4 (thickness 1.2 mm × 100 mm × 60 mm, chuck width 40 mm) were cut out from each steel plate. Next, these two test pieces are overlapped so as not to cause a gap, and a bead B is formed by laser welding in parallel to the end K at a position 15 mm away from the end K having a width of 60 mm under the above conditions. A weld specimen TP 1 was obtained. The laser welding length was 50 mm.

得られた各溶接試験片ＴＰ1を図５に示す剥離試験片ＴＰ2に形成した。剥離試験片ＴＰ2は、溶接試験片ＴＰ1の接合された２枚の各鋼板を、溶接ビード部Ｂから２１ｍｍの位置で曲げ半径３ｍｍで各々９０゜に外側に曲げ、引張り可能なＴ字型の試験片としたものである。この剥離試験片ＴＰ2を引張試験機で剥離方向に引っ張り破断荷重を求めた。この破断荷重を溶接部の長さ（５０ｍｍ）で除して剥離強度Ｆ（Ｎ／ｍｍ）とした。剥離試験の引張速度は６ｍｍ／ｍｉｎ一定とした。なお、同一条件による繰り返し数は３としてその平均値で評価した。結果を図６に示す。 Each welded test piece TP 1 obtained was formed into a peel test piece TP 2 shown in FIG. The peel test piece TP 2 is a T-shape that can be pulled by bending two steel plates joined to the weld test piece TP 1 outward at 90 ° with a bend radius of 3 mm at a position 21 mm from the weld bead B. This is a test piece. It was determined tensile fracture load peeling direction at the peeling test piece TP 2 tensile tester. The breaking load was divided by the length of the welded part (50 mm) to obtain peel strength F (N / mm). The tensile speed of the peel test was constant at 6 mm / min. Note that the number of repetitions under the same conditions was 3, and the average value was evaluated. The results are shown in FIG.

図６では、横軸を各溶接試験片の余盛高さＨとし、縦軸は溶接部の単位当たりの剥離強度Ｆ（Ｎ／ｍｍ）とした。なお、図６の記号は鋼板の種類を表し、ａ（■）は実施例であるＳＰＦＣ４４０（引張強度、４４０ＭＰａ）、ｂ（◆）は同様にＳＰＦＣ５９０Ｙ（同５９０ＭＰａ）、ｃ（△）は参考例であるＳＰＦＣ９８０Ｙ（同９８０ＭＰａ）の測定結果である。ここで、剥離強度Ｆが２５９Ｎ／ｍｍの点線ｆはフィラーによる余盛を実施しない場合の軟鋼（ＳＰＣＤ）の剥離強度である。   In FIG. 6, the horizontal axis is the extra height H of each weld specimen, and the vertical axis is the peel strength F (N / mm) per unit of the weld. 6 represents the type of steel sheet, a (■) is SPFC 440 (tensile strength 440 MPa), b (♦) is SPFC 590Y (590 MPa), and c (Δ) is a reference example. It is a measurement result of SPFC980Y (980 MPa). Here, a dotted line f having a peel strength F of 259 N / mm is a peel strength of mild steel (SPCD) when no surfacing with a filler is performed.

いずれの鋼板についても、余盛高さの増加に比例して剥離強度が向上することが分かる。特にａのＳＰＦＣ４４０とｂのＳＰＦＣ５９０Ｙについては余盛高さＨの増加による剥離強度Ｆの向上は顕著である。ａのＳＰＦＣ４４０では余盛高さＨが０．３ｍｍ（鋼板板厚の２５％）を越すと軟鋼の剥離強度よりも高い剥離強度が得られるようになり、ｂのＳＰＦＣ５９０Ｙでは０．９ｍｍ（同７５％）を越えると軟鋼の剥離強度よりも高い剥離強度を得ることができる。   It can be seen that the peel strength is improved in proportion to the increase in surplus height for any steel plate. In particular, with respect to SPFC440 of a and SPFC590Y of b, the improvement in peel strength F due to the increase in the height H is remarkable. In SPFC440 of a, when the surplus height H exceeds 0.3 mm (25% of the steel plate thickness), a peel strength higher than that of mild steel can be obtained, and in SPFC590Y of b, 0.9 mm (75 %), A peel strength higher than that of mild steel can be obtained.

本発明のレーザ溶接方法を用いることにより、例えば、軟鋼（ＳＰＣＤ）で形成された衝撃吸収部材を板厚の薄い高張力鋼を用いて軽量化しても、溶接部の剥離強度を軽量化前の軟鋼材の剥離強度よりも高くすることができ衝撃吸収特性をより向上することができる。   By using the laser welding method of the present invention, for example, even if the impact absorbing member formed of mild steel (SPCD) is reduced in weight using thin high-strength steel, the peel strength of the welded portion is reduced. The peel strength of the mild steel material can be made higher, and the impact absorption characteristics can be further improved.

本発明の高張力鋼のレーザ溶接方法によれば、レーザ溶接部の剥離強度を向上させることができるので、自動車ボディーのフロントサイドパネルなどの衝撃吸収部材の軽量化とともに、衝撃吸収特性をも向上させることができる。   According to the laser welding method of the high strength steel of the present invention, the peel strength of the laser welded portion can be improved, so that the weight of the shock absorbing member such as the front side panel of the automobile body is reduced and the shock absorbing characteristics are also improved. Can be made.

重ね合わせレーザ溶接の溶接装置を説明する要部構成図である。It is a principal part block diagram explaining the welding apparatus of superposition laser welding. 溶接ビード部に余盛を形成した重ね合わせレーザ溶接の溶接ビード部の断面スケッチである。It is a cross-sectional sketch of the welding bead part of the superposition laser welding which formed the surplus in the welding bead part. 剥離試験により破断した図２の溶接ビード部を示す断面スケッチである。It is a cross-sectional sketch which shows the weld bead part of FIG. 2 fractured | ruptured by the peeling test. 重ね合わせレーザ溶接の溶接試験片の形状を示す図である。It is a figure which shows the shape of the welding test piece of superposition laser welding. 剥離試験片の形状を示す図である。It is a figure which shows the shape of a peeling test piece. 各高張力鋼の余盛高さと剥離強度との関係を示す図である。It is a figure which shows the relationship between the surplus height and peeling strength of each high-tensile steel. 各鋼材の引張強度と剥離強度との関係を示す図である。It is a figure which shows the relationship between the tensile strength and peeling strength of each steel material. 剥離試験時の試験片の変形の様子を示す図である。（ａ）は低強度材料の場合、（ｂ）は高強度材料の場合を示す。It is a figure which shows the mode of a deformation | transformation of the test piece at the time of a peeling test. (A) shows the case of a low-strength material, and (b) shows the case of a high-strength material. フィラーを用いない従来技術になる重ね合わせレーザ溶接の溶接ビード部の断面スケッチである。It is a cross-sectional sketch of the weld bead part of the superposition laser welding used as the prior art which does not use a filler. 剥離試験により破断した図９の溶接ビード部を示す断面スケッチである。10 is a cross-sectional sketch showing the weld bead portion of FIG. 9 broken by a peel test. 衝撃吸収部材の荷重−変位曲線の模式図である。It is a schematic diagram of the load-displacement curve of an impact-absorbing member.

符号の説明Explanation of symbols

１０：レーザ溶接装置 １１：レーザ溶接トーチ １２：集光レンズ １４：フィラーワイヤ Ａ：溶接ビード境界部 Ｂ：溶接ビード Ｃ：曲げ部 Ｄ：アンダーカット Ｅ：最弱部 ｈ1，ｈ2：余盛高さ Ｒ：レーザ発振器 10: laser welding apparatus 11: laser welding torch 12: condenser lens 14: filler wire A: weld bead boundary B: weld bead C: bend D: undercut E: weakest portion h 1, h 2: excess weld Height R: Laser oscillator

Claims (2)

等しい厚さの２枚の高張力鋼をレーザビームによって重ね合わせ溶接する高張力鋼のレーザ溶接方法において、
前記重ね合わせ溶接部にフィラーを供給して、溶接ビード断面の余盛り高さが、前記高張力鋼の厚さの２０〜１２０％となるように溶接ビード部に余盛りを形成することを特徴とする高張力鋼のレーザ溶接方法。
ここで、前記余盛高さは、重ね合わせた上板と下板とを融合しているビード部の該上板の上面から突出している該ビードの最高点までの高さと該下板の下面から突出している該ビードの最高点までの高さとの和である。 In a high-strength steel laser welding method in which two high-strength steels of equal thickness are overlap-welded with a laser beam,
A filler is supplied to the overlap welded portion, and the surplus height is formed in the weld bead portion so that the surplus height of the weld bead cross section is 20 to 120% of the thickness of the high-tensile steel. Laser welding method for high strength steel.
Here, the height of the surplus is the height from the upper surface of the upper plate of the bead portion where the upper plate and the lower plate that are overlapped are fused to the highest point of the bead and the lower surface of the lower plate. Is the sum of the height of the bead protruding from the height to the highest point. 前記高張力鋼は引張強度が４４０ＭＰａ以上の高張力鋼である請求項１に記載の高張力鋼のレーザ溶接方法。   The high-strength steel laser welding method according to claim 1, wherein the high-tensile steel is a high-tensile steel having a tensile strength of 440 MPa or more.
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