JP3922263B2 - Method of manufacturing resistance spot welded joint - Google Patents
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- 238000004519 manufacturing process Methods 0.000 title claims description 11
- 238000003466 welding Methods 0.000 claims description 117
- 239000002184 metal Substances 0.000 claims description 42
- 230000014509 gene expression Effects 0.000 claims 2
- 229910000831 Steel Inorganic materials 0.000 description 23
- 239000010959 steel Substances 0.000 description 23
- 238000000034 method Methods 0.000 description 18
- 230000020169 heat generation Effects 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 4
- 230000002787 reinforcement Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
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- 238000007747 plating Methods 0.000 description 2
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Description
本発明は、重ね抵抗溶接法の一種である抵抗スポット溶接法に係り、とくに複数枚の薄肉の金属板（被溶接材）を重ね合わせた板組みを抵抗スポット溶接法により、散りの発生なく所望サイズのナゲットを形成し、抵抗スポット溶接継手とする、抵抗スポット溶接継手の製造方法に関する。 The present invention relates to a resistance spot welding method which is a kind of lap resistance welding method, and in particular, a plate assembly in which a plurality of thin metal plates (materials to be welded) are overlapped is desired by a resistance spot welding method without causing any scattering. The present invention relates to a resistance spot welded joint manufacturing method in which a size nugget is formed to form a resistance spot welded joint.
一般に、重ね合わせられた金属板同士の接合には、重ね抵抗溶接法の一種である抵抗スポット溶接法が用いられている。例えば、自動車の製造にあたっては１台あたり数千点ものスポット溶接がなされている。この溶接法は、２枚以上の金属板を重ね合わせ、その表面を直接、上下の電極で挟み加圧力を加えながら、上下電極間に大電流の溶接電流を短時間通電して接合する方法である。大電流の溶接電流を流すことで発生する抵抗発熱を利用して、点状の溶接部が得られる。この点状の溶接部は、ナゲットと呼ばれ、両金属板に電流を流した際に両金属板の接触箇所で両金属板が溶融し、凝固した部分であり、これにより両金属板が点状に接合される。 In general, a resistance spot welding method, which is a kind of a lap resistance welding method, is used for joining metal plates that are overlapped. For example, in the manufacture of automobiles, several thousand spots are welded per vehicle. This welding method is a method in which two or more metal plates are overlapped, and the surface is directly sandwiched between the upper and lower electrodes and a large current is applied between the upper and lower electrodes for a short time to join them. is there. A spot-like weld is obtained by utilizing resistance heat generated by passing a large welding current. This spot-like weld is called a nugget and is a part where both metal plates melt and solidify at the contact points of both metal plates when current is passed through both metal plates. Are joined together.
抵抗スポット溶接部の接合強度は、ナゲット径により左右されるため、自動車部品等の高い接合強度を必要とする場合にはとくに、所定の径以上のナゲット径を確保することが重要となってくる。一般に、加圧力、通電時間を一定とした場合には、ナゲット径は、溶接電流の増加にしたがって徐々に増加するが、ある値以上になると金属板間に溶融金属が飛散する散りという現象が生じる。散りの発生は、危険である上に、溶接部周辺に散りが付着し外観を悪化させ、ナゲット径や継手引張強度にばらつきを生じさせ、継手部の品質が不安定になる。 Since the joint strength of resistance spot welds depends on the nugget diameter, it is important to ensure a nugget diameter of a predetermined diameter or greater, especially when high joint strength is required for automobile parts and the like. . In general, when the applied pressure and energization time are constant, the nugget diameter gradually increases as the welding current increases, but when the value exceeds a certain value, a phenomenon of scattering of molten metal between the metal plates occurs. . The occurrence of scatter is dangerous and scatters around the weld and deteriorates the appearance, causing variations in the nugget diameter and joint tensile strength, resulting in unstable joint quality.
このような問題に対し、例えば、特許文献１には、棒状電極間に、２枚以上の薄鋼板を任意の圧力で挟持し一回以上の散りを発生する電流を印加通電する前期通電を行った後、任意の冷却時間を与え、引き続き、散りを発生しない電流を用いて後期通電する薄鋼板重ね抵抗点溶接方法が提案されている。特許文献１に記載された技術では、散り発生を容認し、生成した空洞を後期通電時に圧縮縮小させるとしているが、前記の散り発生による問題点は残されたままである。 In order to deal with such a problem, for example, in Patent Literature 1, two or more thin steel plates are sandwiched between rod-shaped electrodes at an arbitrary pressure, and the previous energization is performed to apply a current that causes one or more scatterings. After that, a thin steel sheet lap resistance spot welding method has been proposed in which an arbitrary cooling time is given and subsequently energized late using a current that does not cause scattering. The technique described in Patent Document 1 accepts the occurrence of scattering and compresses and shrinks the generated cavity during the latter energization, but the problems due to the occurrence of scattering remain.
また、特許文献２には、溶接部外周部にのみナゲットが存在するドーナツ状ナゲットの発生を防止する抵抗スポット溶接方法が提案されている。特許文献２に記載された技術は、溶接後の溶接部最小板厚が、重ね合わされた鋼板の全体板厚の80％を下回らないように加圧力および通電量（溶接電流値×通電時間）を調節して抵抗スポット溶接を行うというものであるが、やはり、前記の散り発生による問題点を解決できない。 Patent Document 2 proposes a resistance spot welding method that prevents the occurrence of a doughnut-shaped nugget in which a nugget exists only on the outer periphery of the weld. In the technique described in Patent Document 2, the applied pressure and energization amount (welding current value x energization time) are set so that the minimum thickness of the welded portion after welding does not fall below 80% of the total thickness of the stacked steel plates. Although resistance spot welding is performed after adjustment, the problem due to the occurrence of scattering cannot be solved.
また、近年、自動車車体の衝突安全性の向上という要求の高まりから、例えば、車両のフロア部を構成する、フロアパネルとメンバーとの間にリインフォースメントを挟み込んだ構造が採用されるようになっている。この構造では、従来の単純な二枚重ねの鋼板をスポット溶接する場合と異なり、３枚以上の鋼板を重ね合わせてスポット溶接することが要求される。 Further, in recent years, due to the increasing demand for improving the collision safety of automobile bodies, for example, a structure in which reinforcement is sandwiched between a floor panel and a member constituting a floor portion of a vehicle has been adopted. Yes. In this structure, unlike the conventional simple two-ply steel plate that is spot-welded, it is required that three or more steel plates be superposed and spot-welded.
さらに、最近では、車体の衝突安全性の更なる向上要求にともない、リインフォースメントなどの高強度化、厚肉化が進み、外側に板厚の薄いフロアパネル（薄板）を配置し、内側に板厚の厚いメンバー、リインフォースメント（厚板）を組み合わせた板組みをスポット溶接することが必要となる場合が多い。なお、ここでは、薄板とは板組みされた金属板のうち、肉厚が相対的に小さいものを薄板と記載し、肉厚の相対的に大きいものを厚板と記載することとし、以下も同様の記載とする。 Furthermore, recently, with the demand for further improvement in the collision safety of the car body, the reinforcement and the thickening of reinforcement etc. have progressed, and a floor panel (thin plate) with a thin plate thickness has been placed on the outside, and the plate on the inside It is often necessary to spot weld a plate assembly that combines thick members and reinforcements (thick plates). In addition, suppose that a thin plate is described as a thin plate, and a relatively large thickness is described as a thick plate among metal plates assembled in a plate, and the following is also used. The same description is used.
このような板厚比（＝総厚（Ａ）／一番薄い板の板厚（Ｂ））の大きな板組みにおいて、従来のような、加圧力、溶接電流を一定の値としたままにするスポット溶接を行った場合には一番外側（電極チップと接触する側）の薄板と厚板の間に必要なサイズのナゲットが形成されにくいことが知られている。とくに板厚比が５を超えるような板組みでは、この傾向が強い。 In such a plate assembly having a large plate thickness ratio (= total thickness (A) / thickness of the thinnest plate (B)), the pressure and welding current are kept constant as in the conventional case. It is known that when spot welding is performed, it is difficult to form a nugget of a necessary size between the thin plate and the thick plate on the outermost side (the side in contact with the electrode tip). This tendency is particularly strong when the plate thickness ratio exceeds 5.
これは、電極チップによる冷却によって一番外側の薄板と厚板の間では温度が上がりにくいことが原因である。ナゲットは、電極間の中央付近から鋼材の固有抵抗により体積抵抗発熱にて形成されるが、ナゲットが薄板にまで成長するまでに、電極間中央部に近い部分に位置する厚板と厚板間でのナゲットの成長が大きく、電極による加圧では抑えきれずに散りが発生するため、散り発生なく必要なサイズのナゲットを薄板・厚板間に得ることが困難となる。 This is because the temperature hardly rises between the outermost thin plate and the thick plate due to cooling by the electrode tip. Nugget is formed by volume resistance heat generation due to the specific resistance of steel material from the center between the electrodes, but before the nugget grows to a thin plate, between the thick plate and the thick plate located near the center between the electrodes The nugget grows at a large distance, and it is difficult to obtain a nugget of a necessary size between the thin plate and the thick plate without the occurrence of scattering, because the nugget grows greatly and cannot be suppressed by pressing with an electrode.
また、一番外側に配置される薄板がフロアパネルの場合には、強度よりも成形性が重要となるため、使用される鋼板は軟鋼となることが多い。一方、板厚の厚い鋼板は強度補強部材であり高張力鋼板が使用される場合が多い。このような板組みでは、発熱する位置は、固有抵抗の高い高張力鋼板側に偏るため、厚板−薄板（軟鋼）間にはさらにナゲットが形成されにくくなる。また、使用される鋼板がめっき鋼板となると、低温で溶融しためっき層が鋼板間の通電経路を拡大するため電流密度が減少し、薄板側でのナゲットの形成がさらに困難となる。 Further, when the thin plate disposed on the outermost side is a floor panel, formability is more important than strength, so that the steel plate used is often mild steel. On the other hand, a thick steel plate is a strength reinforcing member, and a high-tensile steel plate is often used. In such a plate assembly, the position where heat is generated is biased toward the high-tensile steel plate having a high specific resistance, so that nuggets are more difficult to be formed between the thick plate and the thin plate (mild steel). Moreover, when the steel plate used becomes a plated steel plate, the plating layer melted at a low temperature expands the current-carrying path between the steel plates, thereby reducing the current density and making it more difficult to form a nugget on the thin plate side.
このような問題に際し、例えば、特許文献３には、重ね合わされた２枚の厚板の少なくとも一方に薄板をさらに重ね合わせた板厚比の大きな板組みをスポット溶接する方法が提案されている。特許文献３に記載された技術は、薄板の溶接すべき部位に部分的に一般部より一段高い座面を形成するとともに、薄板に対抗する電極を、先端を球面に形成し、溶接初期は低加圧力で、薄板の座面を押しつぶすようにして、薄板とこれと隣り合う厚板とを溶接し、その後、高加圧力で２枚の厚板同士を溶接するスポット溶接方法である。この技術によれば、散りを発生することなく、薄板−厚板間にも必要サイズのナゲットを形成できるとしている。
特許文献３に記載された技術では、薄板−厚板間に必要サイズのナゲットを形成することができるが、しかし、薄板の溶接する部分に予め一般部より一段高い座面をプレスなどで形成する工程が必要となり、工程が複雑になり、生産性が低下するという問題がある。 In the technique described in Patent Document 3, a nugget of a necessary size can be formed between a thin plate and a thick plate. However, a seat surface that is one step higher than a general portion is formed in advance on a portion to be welded by a press or the like. There is a problem that a process is required, the process becomes complicated, and productivity is lowered.
本発明は、上記した従来技術の問題を有利に解決し、板厚比の大きな板組みにおいても余計な工程を付加することなく、また散りを発生することなく、必要サイズのナゲットを形成できる、抵抗スポット溶接継手の製造方法を提案することを目的とする。 The present invention advantageously solves the above-mentioned problems of the prior art, and can form a nugget of a necessary size without adding an extra step even in a plate assembly having a large plate thickness ratio, and without causing scattering. It aims at proposing the manufacturing method of a resistance spot welded joint.
本発明者らは、上記した課題を達成するため、抵抗スポット溶接におけるナゲット形成に及ぼす各種要因について鋭意検討した。その結果、薄板が外側に配置された板厚比の大きな板組み（スポット溶接継手）において、薄板とそれと隣り合う厚板との間、厚板−厚板間ともに必要なサイズのナゲットを形成するには
（１）薄板−厚板間にナゲットを形成するためには、溶接初期に金属板間の接触抵抗発熱を有効に活用すること、
（２）散り発生を抑制するためには、加圧力、電流の条件を溶接の途中で変化させることが肝要であること
を知見した。
In order to achieve the above-described problems, the present inventors diligently studied various factors affecting nugget formation in resistance spot welding. As a result, a nugget of a necessary size is formed between the thin plate and the adjacent thick plate and between the thick plate and the thick plate in a plate assembly (spot weld joint) having a large plate thickness ratio in which the thin plate is disposed on the outside. (1) In order to form a nugget between a thin plate and a thick plate, the contact resistance heat generation between the metal plates should be used effectively in the initial stage of welding.
(2) In order to suppress the occurrence of scattering, it has been found that it is important to change the conditions of applied pressure and current during welding.
本発明は、上記した知見に基づき、さらに検討を加えて完成されたものである。 The present invention has been completed based on the above findings and further studies.
すなわち、本発明の要旨はつぎのとおりである。
（１）複数枚の金属板を重ね合わせた板組みを抵抗スポット溶接により溶接接合し抵抗スポット溶接継手を製造するにあたり、前記板組みを、重ね合わせた２枚以上の厚板の少なくとも一方に薄板を重ね合わせた、板厚比が５以上の板組みとし、前記抵抗スポット溶接を第一段および第二段の二段階からなる溶接とし、該第二段の溶接が前記第一段の溶接に比べ、高加圧力、低電流又は同じ電流、長通電時間又は同じ通電時間の溶接とすることを特徴とする抵抗スポット溶接継手の製造方法。
（２）（１）において、前記第一段の溶接を、該溶接の加圧力ＰI 、溶接電流ＩＩ、通電時間ＴＩが、前記複数枚の金属板のうち最も薄肉の金属板の板厚tmとの関係で、次（１）〜（３）式
0.8tm≦ＰＩ≦５tm ………（１）
２≦ＴＩ≦６ ………（２）
３tm＋５≦ＩＩ ………（３）
（ここで、tm：複数枚の金属板のうち最も薄肉の金属板の板厚（mm）、ＰＩ：加圧力（kＮ）、ＩＩ：溶接電流（kＡ）、ＴＩ：通電時間（cycles/50Ｈz））
を満足する溶接とし、前記第二段の溶接を、該溶接の加圧力ＰII、溶接電流ＩII 、通電時間ＴII が次（４）〜（６）式
1.1ＰＩ≦ＰII≦10ＰＩ ………（４）
0.5ＩＩ≦ＩII≦ＩＩ ………（５）
ＴＩ≦ＴII≦10ＴＩ ………（６）
（ここで、tm：複数枚の金属板のうち最も薄肉の金属板の板厚（mm）、ＰＩ、ＰII ：加圧力（kＮ）、ＩＩ、ＩII ：溶接電流（kＡ）、ＴＩ、ＴII ：通電時間（cycles/50Ｈz））
を満足する溶接とすることを特徴とする抵抗スポット溶接継手の製造方法。
That is, the gist of the present invention is as follows.
(1) In manufacturing a resistance spot welded joint by welding a plate assembly in which a plurality of metal plates are overlapped by resistance spot welding, the plate assembly is thinned on at least one of the two or more thick plates overlapped. And the resistance spot welding is a two-stage welding of the first stage and the second stage, and the second stage welding is the first stage welding. A method of manufacturing a resistance spot welded joint, characterized in that welding is performed with a high applied pressure, a low current or the same current, a long energization time or the same energization time.
(2) In (1), the welding of the first stage is performed with the welding metal pressure P I , welding current I I , and energization time T I of the thinnest metal plate among the plurality of metal plates. The following formulas (1) to (3) in relation to the thickness tm
0.8tm ≦ P I ≦ 5tm (1)
2 ≦ T I ≦ 6 ......... ( 2)
3tm + 5 ≦ I I (3)
(Where tm is the thickness (mm) of the thinnest metal plate among a plurality of metal plates, P I is the applied pressure (kN), I I is the welding current (kA), T I is the energization time (cycles / 50Hz))
The welding in the second stage is the welding pressure P II , welding current I II , energization time T II of the following equations (4) to (6):
1.1 P I ≦ P II ≦ 10 P I (4)
0.5I I ≦ I II ≦ I I (5)
T I ≦ T II ≦ 10T I ......... (6)
(Where tm is the thickness (mm) of the thinnest metal plate among the plurality of metal plates, P I and P II are the applied pressure (kN), I I and I II are the welding current (kA), T I, T II: energizing time (cycles / 50Hz))
A method of manufacturing a resistance spot welded joint, characterized in that the welding satisfies the above .
本発明によれば、重ね合わせた２枚以上の厚板の少なくとも一方に薄板を重ね合わせた、板厚比が５を超えるような大きな板組みにおいても、余計な工程を付加することなく、また散りを発生することなく、必要サイズのナゲットを有するスポット溶接継手を容易に作製でき、産業上格段の効果を奏する。 According to the present invention, even in a large plate assembly in which a thin plate is overlaid on at least one of two or more thick plates that are overlaid and the plate thickness ratio exceeds 5, without adding an extra step, A spot-welded joint having a nugget of a necessary size can be easily produced without generating scatter, and a remarkable industrial effect can be obtained.
本発明では、複数枚の金属板を重ね合わせた板組みを、上下一対の電極チップで挟み、加圧、通電する抵抗スポット溶接により溶接接合し、必要サイズのナゲットを形成して抵抗スポット溶接継手とする。 In the present invention, a plate assembly in which a plurality of metal plates are overlapped is sandwiched between a pair of upper and lower electrode tips and welded and joined by resistance spot welding that is pressurized and energized to form a nugget of a required size to form a resistance spot welded joint And
本発明で好適に使用可能な溶接装置は、上下一対の電極チップを備え、溶接中に加圧力、溶接電流をそれぞれ任意に制御可能であれば、加圧機構（エアシリンダやサーボモータ等）、形式（定置式、ロボットガン等）、電極形状等はとくに限定されない。 A welding apparatus that can be suitably used in the present invention includes a pair of upper and lower electrode tips, and a pressurizing mechanism (such as an air cylinder or a servo motor), as long as the pressurizing force and welding current can be arbitrarily controlled during welding, The type (stationary, robot gun, etc.), electrode shape, etc. are not particularly limited.
本発明では、抵抗スポット溶接を第一段および第二段の二段階からなる溶接とする。 In the present invention, the resistance spot welding is a welding consisting of two stages of a first stage and a second stage.
図１に示すような、重ね合わせた２枚以上の厚板12、13の外側に薄板11を重ね合わせた金属板板組みをスポット溶接する場合を例に、以下、説明する。
An example in which spot welding is performed on a metal plate assembly in which
まず、所望の溶接位置で板組みを上下一対の電極で挟み、加圧を開始する。加圧力がかかり始めてから通電を開始する。第一段の溶接では、接触抵抗発熱が小さくならないように、加圧力、溶接電流を設定し、金属板11、12間にナゲットN1を形成する。第一段の溶接では、低加圧力で大溶接電流を短時間で加えることが好ましい。これにより、金属板11（薄板）と12（厚板）間は通電経路が狭く電流密度が高くなり、めっきの溶融等による通電経路の拡大の影響も少なく、発生する接触抵抗発熱を有効にナゲットN1形成に作用させることができるようになる。
First, the plate assembly is sandwiched between a pair of upper and lower electrodes at a desired welding position, and pressurization is started. Start energization after pressure is applied. In the first stage welding, the nugget N1 is formed between the
第一段の溶接では、加圧力ＰI（kN）は、複数枚の金属板のうち最も薄肉の金属板の板厚tm（図１では金属板11の板厚：mm）との関係で、次（１）式
0.8tm≦ＰＩ≦５tm ………（１）
を満足するように設定することが好ましい。第一段の溶接における加圧力ＰIが５tm（kN）以上では、加圧力が高くなりすぎて、接触抵抗による発熱が小さくなり、金属板11、12間にナゲットが形成されなくなる。一方、加圧力ＰIが0.8tm以下の場合には、電極チップと金属板11との間での接触抵抗が大きくなり、スパークが発生しやすくなるとともに、金属板11、12間からも散りが発生しやすくなる。
In the first stage welding, the pressure P I (kN) is related to the thickness tm of the thinnest metal plate among the plurality of metal plates (in FIG. 1, the thickness of the metal plate 11: mm). Next formula (1)
0.8tm ≦ P I ≦ 5tm ......... ( 1)
It is preferable to set so as to satisfy the above. The pressure P I in the welding of the first stage is 5TM (kN) or more, pressure becomes too high, heat generation due to contact resistance is reduced, not nugget is formed between the
また、第一段の溶接では、通電時間ＴＩ（cycles／50Ｈz）は、次（２）式
２≦ＴＩ≦６ ………（２）
を満足するように設定することが好ましい。通電時間ＴＩが、２cycles以下では通電時間が短かすぎるため、金属板11、12間に所望サイズのナゲットが形成されなくなる。一方６cyclesよりも長くなると、散りが発生する。
Moreover, in the welding of the first stage, the energization time T I (cycles / 50Hz), the following equation (2)
2 ≦ T I ≦ 6 (2)
It is preferable to set so as to satisfy the above. Energization time T I is, for too short energization time is less 2 cycles, the desired size of the nugget is not formed between the
また、第一段の溶接では、溶接電流ＩＩ（kA）は、複数枚の金属板のうち最も薄肉の金属板の板厚tm（図１では金属板11の板厚：mm）との関係で、次（３）式
３tm＋５≦ＩＩ ………（３）
を満足するように設定することが好ましい。第一段の溶接における溶接電流ＩＩが、（３tm＋５）以下の小電流では、接触抵抗発熱を有効に利用できず、金属板11、12間にナゲットが形成されなくなる。第一段の溶接では、初期の数サイクルの間大電流を流すことが好ましい。
In the first stage welding, the welding current I I (kA) is related to the thickness tm of the thinnest metal plate among the plurality of metal plates (the thickness of the
3tm + 5 ≦ I I (3)
It is preferable to set so as to satisfy the above. Welding current I I in the welding of the first stage, the (3tm + 5) following a small current, can not be effectively utilized contact resistance heating, no longer nugget is formed between the
このようなことから、第一段の溶接では、前記した（１）、（２）、（３）式を満足するように加圧力ＰＩ、溶接電流ＩＩ、通電時間ＴＩを設定することが、金属板11、12間に所望サイズのナゲットを形成するために好ましい。
For this reason, in the welding of the first stage, the above-mentioned (1), (2), (3) the pressure P I to satisfy the equation, the welding current I I, setting the energization time T I Is preferable for forming a nugget of a desired size between the
そして、本発明では、上記した第一段の溶接に続いて第二段の溶接を行なう。第二段の溶接は、第一段の溶接に比べ、高加圧力で低電流、長通電時間の溶接とする。本発明の抵抗スポット溶接における加圧パターンを図３に、通電パターンを図４に、模式的に示す。本発明では、溶接途中で（第一段の溶接終了後）、第一段の溶接時に比べて、加圧力を増加させ、溶接電流を減少させ、通電時間を長くする。これにより、散りの発生が抑制されるとともに、体積抵抗発熱による発熱が主体となり、電極間中央部でナゲットが形成され、図２に示すように、金属板12、13間にも所定サイズのナゲットN2を形成することができる。 In the present invention, the second stage welding is performed following the first stage welding described above. The second stage welding is a welding with a high pressure, a low current, and a long energization time as compared with the first stage welding. The pressurization pattern in resistance spot welding of the present invention is schematically shown in FIG. 3, and the energization pattern is schematically shown in FIG. In the present invention, during welding (after the completion of the first stage welding), the pressurizing force is increased, the welding current is decreased, and the energization time is lengthened as compared with the first stage welding. As a result, the occurrence of scattering is suppressed, and heat generation by volume resistance heat generation is mainly performed, and a nugget is formed at the center between the electrodes. As shown in FIG. N2 can be formed.
第二段の溶接では、加圧力ＰIIは、第一段溶接の加圧力ＰＩとの関係で、次（４）式
1.1ＰＩ≦ＰII≦10ＰＩ ………（４）
（ここで、ＰＩ、ＰII ：加圧力（kＮ））
を満足するように設定することが好ましい。また、溶接電流ＩII は、第一段溶接の溶接電流ＩＩとの関係で、次（５）式
0.5ＩＩ≦ＩII≦ＩＩ ………（５）
を満足するように設定することが好ましい。また、通電時間ＴII は、第一段溶接の通電時間ＴＩとの関係で、次（６）式
ＴＩ≦ＴII≦10ＴＩ ………（６）
を満足するように設定することが好ましい。第二段の溶接の条件が上記した範囲から外れると、散りの発生防止や所定サイズのナゲット径を得ることが困難となり、また、加圧力を過大に増加するとヒートマークや浮き上がりが大きくなるという問題も生じる。
In the second stage welding, the pressure P II is related to the pressure P I in the first stage welding.
1.1 P I ≦ P II ≦ 10 P I (4)
(Where P I , P II : pressure (kN))
It is preferable to set so as to satisfy the above. Further, the welding current I II is related to the welding current I I of the first stage welding.
0.5I I ≦ I II ≦ I I (5)
It is preferable to set so as to satisfy the above. Further, the energization time T II, in relation to the energization time T I of the first stage welding, the following equation (6)
T I ≦ T II ≦ 10T I ......... (6)
It is preferable to set so as to satisfy the above. If the conditions of the second stage welding are out of the above range, it will be difficult to prevent the occurrence of scattering and obtain a nugget diameter of a predetermined size, and if the applied pressure is excessively increased, the heat mark and lift will increase. Also occurs.
本発明の抵抗スポット溶接継手の製造方法は、図１に例示した板組みに限定されることはない。また、被溶接材として本発明を適用する金属板には、鋼板が例示できる。鋼板としては、強度レベル（軟鋼、高張力鋼板）や表面処理の有無（表面処理なし、めっき鋼板）に限定されることはない。本発明はいずれの種類の鋼板についても適用可能である。また、本発明は、板厚比（＝総板厚mm／一番薄い板の板厚mm）が５以上の板組みの場合に適用する。 Method for producing a resistance spot welded joint of the present invention is not limited to the illustrated plate assembled in FIG. Moreover, a steel plate can be illustrated as a metal plate which applies this invention as a to-be-welded material. The steel plate is not limited to the strength level (soft steel, high-tensile steel plate) or the presence or absence of surface treatment (no surface treatment, plated steel plate). The present invention is applicable to any type of steel sheet. Further, the present invention is a plate thickness ratio (= SoitaAtsu mm / thickness mm of the thinnest plate) is applied to the case of 5 or more Itakumi.
（実施例１）
表１に示す２〜４枚の薄鋼板を重ね合わせた板組みについて、表２に示す溶接条件で抵抗スポット溶接を行い、抵抗スポット溶接継手を作製した。抵抗スポット溶接は、定置式でサーボモータ加圧方式の単相交流抵抗スポット溶接機を用いて行なった。なお、使用した電極は、ＤＲ型（先端径６mm）の電極チップ（図５）とした。
Example 1
Resistance spot welding was carried out under the welding conditions shown in Table 2 on the plate assembly in which 2 to 4 thin steel sheets shown in Table 1 were overlapped to produce a resistance spot welded joint. Resistance spot welding was performed using a stationary, servo-motor pressurization type single-phase AC resistance spot welding machine. The electrode used was a DR type (tip diameter: 6 mm) electrode tip (FIG. 5).
得られた各溶接継手について、溶接部を切断し、断面（図２参照）をエッチング後、光学顕微鏡により観察し、ナゲット径ｄ（mm）を測定し、ナゲット径ｄが４√ｔ以上（ｔ：隣り合う２枚の鋼板のうち薄い方の鋼板の板厚（mm））である場合を、良好（○）として評価した。ナゲット径ｄが４√ｔ未満を不良（×）とした。得られた結果を表２に併記する。ただし、板組数が３以上の場合は、例えば、ナゲット径は図２のN1およびN2のように複数計測する。この場合、全てのナゲット径が４√ｔ以上を満たす場合を評価○とした。 For each of the obtained welded joints, the welded portion was cut, the cross section (see FIG. 2) was etched, and then observed with an optical microscope, the nugget diameter d (mm) was measured, and the nugget diameter d was 4√t or more (t : The case of the thickness (mm) of the thinner steel plate of two adjacent steel plates was evaluated as good (◯). A nugget diameter d of less than 4√t was regarded as defective (x). The obtained results are also shown in Table 2. However, when the number of plate assemblies is 3 or more, for example, a plurality of nugget diameters are measured as N1 and N2 in FIG. In this case, the case where all nugget diameters satisfy 4√t or more was evaluated as “Good”.
本発明例はいずれも、散りの発生がなく、４√ｔ以上の径を有するナゲットが得られ、良好なスポット溶接継手が得られている。本発明例では、板厚比が５を超えるめっき鋼板の板組みの場合であっても散りを発生させることなく、必要なサイズのナゲットを有するスポット溶接が可能となる。一方、本発明の範囲を外れる比較例では、散りが発生するか、あるいは十分なサイズのナゲットが形成されていない。
（実施例２）
実施例１で評価○となった溶接条件について、適正溶接電流範囲を調査した。適正溶接電流範囲は、第一段あるいは第二段の溶接条件を固定し、第二段あるいは第一段の溶接における溶接電流を変化して、ナゲット径ｄが４√ｔ以上（ｔ：隣り合う２枚の鋼板のうち薄い方の鋼板の板厚（mm））となる限界電流値（下限電流値）、および散り発生限界電流値（上限電流値）を求め、その差を適正溶接電流範囲とした。
In all of the examples of the present invention, there is no occurrence of scattering, a nugget having a diameter of 4√t or more is obtained, and a good spot welded joint is obtained. In the example of the present invention, spot welding having a nugget of a necessary size can be performed without generating scattering even when the plate thickness ratio is 5 or more. On the other hand, in the comparative example outside the scope of the present invention, scattering occurs or a nugget having a sufficient size is not formed.
(Example 2)
About the welding conditions evaluated as ○ in Example 1, the appropriate welding current range was investigated. In the appropriate welding current range, the welding conditions of the first stage or the second stage are fixed, the welding current in the second stage or the first stage is changed, and the nugget diameter d is 4√t or more (t: adjacent) Obtain the limit current value (lower limit current value) and the scatter occurrence limit current value (upper limit current value) that will be the thickness (mm) of the thinner one of the two steel sheets, and calculate the difference between the appropriate welding current range did.
得られた結果を表３（第二段溶接の適正溶接電流範囲）、および表４（第一段溶接の適正溶接電流範囲）に示す。 The obtained results are shown in Table 3 (Appropriate welding current range for second stage welding) and Table 4 (Appropriate welding current range for first stage welding).
実施例１で示した抵抗スポット溶接条件（本発明例）は、いずれも第一段および第二段の溶接においても２kA以上の適正溶接電流範囲を有し、抵抗スポット溶接作業が容易になることがわかる。 The resistance spot welding conditions (examples of the present invention) shown in Example 1 both have an appropriate welding current range of 2 kA or more even in the first stage and second stage welding, and resistance spot welding work is facilitated. I understand.
11、14 金属板(薄板)
12、13 金属板(厚板)
11, 14 Metal plate (thin plate)
12, 13 Metal plate (thick plate)
Claims (2)
記
0.8tm≦ＰＩ≦５tm ………（１）
２≦ＴＩ≦６ ………（２）
３tm＋５≦ＩＩ ………（３）
1.1ＰＩ≦ＰII≦10ＰＩ ………（４）
0.5ＩＩ≦ＩII≦ＩＩ ………（５）
ＴＩ≦ＴII≦10ＴＩ ………（６）
ここで、tm：複数枚の金属板のうち最も薄肉の金属板の板厚（mm）、
ＰＩ、ＰII ：加圧力（kＮ）、
ＩＩ、ＩII ：溶接電流（kＡ）、
ＴII ：通電時間（cycles/50Ｈz） In the first-stage welding, the welding pressure P I , welding current I I , and energization time T I are related to the thickness tm of the thinnest metal plate among the plurality of metal plates. The welding satisfying the expressions (1) to (3), and the welding of the second stage, the welding pressure P II , the welding current I II and the energization time T II are the following expressions (4) to (6) The method of manufacturing a resistance spot welded joint according to claim 1, wherein the welding is satisfactory.
Record
0.8tm ≦ P I ≦ 5tm (1)
2 ≦ T I ≦ 6 (2)
3tm + 5 ≦ I I (3)
1.1P I ≦ P II ≦ 10P I ......... (4)
0.5I I ≦ I II ≦ I I (5)
T I ≦ T II ≦ 10T I ......... (6)
Here, tm: the thickness (mm) of the thinnest metal plate among the plurality of metal plates,
P I , P II : Applied pressure (kN),
I I , I II : welding current (kA),
T II : Energizing time (cycles / 50Hz)
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