JP6037018B2 - Resistance spot welding method - Google Patents

Resistance spot welding method Download PDF

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JP6037018B2
JP6037018B2 JP2015529734A JP2015529734A JP6037018B2 JP 6037018 B2 JP6037018 B2 JP 6037018B2 JP 2015529734 A JP2015529734 A JP 2015529734A JP 2015529734 A JP2015529734 A JP 2015529734A JP 6037018 B2 JP6037018 B2 JP 6037018B2
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electrode
tip
plate
aluminum plate
resistance spot
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JPWO2015133096A1 (en
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松田　広志
広志 松田
央海 澤西
央海 澤西
池田　倫正
倫正 池田
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JFE Steel Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/16—Resistance welding; Severing by resistance heating taking account of the properties of the material to be welded
    • B23K11/20—Resistance welding; Severing by resistance heating taking account of the properties of the material to be welded of different metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/10—Spot welding; Stitch welding
    • B23K11/11—Spot welding
    • B23K11/115—Spot welding by means of two electrodes placed opposite one another on both sides of the welded parts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/30—Features relating to electrodes
    • B23K11/3009—Pressure electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
    • B23K35/0205—Non-consumable electrodes; C-electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
    • B23K35/0255—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
    • B23K35/0255—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in welding
    • B23K35/0261—Rods, electrodes, wires
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • B23K35/28—Selection of soldering or welding materials proper with the principal constituent melting at less than 950 degrees C
    • B23K35/286—Al as the principal constituent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
    • B23K35/3053—Fe as the principal constituent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/18—Dissimilar materials
    • B23K2103/20—Ferrous alloys and aluminium or alloys thereof

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Resistance Welding (AREA)

Description

本発明は、抵抗スポット溶接方法に関し、具体的には、鋼板とアルミニウム板を重ね合わせた板組みの抵抗スポット溶接方法に関する。なお、本発明において、アルミニウム板とは、純アルミニウム板とアルミニウム合金板を総称したものである。   The present invention relates to a resistance spot welding method, and specifically to a resistance spot welding method for a plate assembly in which steel plates and aluminum plates are overlapped. In the present invention, the aluminum plate is a general term for a pure aluminum plate and an aluminum alloy plate.

近年の自動車産業では、車体軽量化による燃費向上を目的として、高強度鋼板の適用による鋼板の薄肉化や、車体へのアルミニウム合金板等の軽金属材の適用が進められている。   In recent years, in the automobile industry, for the purpose of improving the fuel efficiency by reducing the weight of the vehicle body, the thinning of the steel plate by the application of a high-strength steel plate and the application of a light metal material such as an aluminum alloy plate to the vehicle body are being promoted.

現在、車体における鋼板同士の接合には、他の溶接方法に比べてコストや効率面で優位にある抵抗スポット溶接方法が最も多く用いられており、１台あたりの打点数は３０００点から６０００点に及ぶ。これは重ね合わせた２枚以上の鋼板を挟んでその上下から一対の電極で加圧しつつ、上下電極間に高電流の溶接電流を短時間通電して抵抗発熱により接合する方法である。   Currently, the resistance spot welding method, which is superior in cost and efficiency compared to other welding methods, is most often used for joining steel plates in a vehicle body, and the number of hit points per unit is 3000 to 6000 points. It extends to. In this method, two or more stacked steel plates are sandwiched and pressed with a pair of electrodes from above and below, and a high-current welding current is passed between the upper and lower electrodes for a short time to join them by resistance heating.

車体の生産工程のコストと効率の維持という観点からは、鋼板同士の場合と同様、アルミニウム板が混在する場合の接合においても抵抗スポット溶接方法を用いることが有効である。しかし、鋼板とアルミニウム板の異種材料接合においては、電極の加圧と通電時の発熱により軟質なアルミニウム板が溶接中に大きく減厚したり、接合界面に脆弱な金属間化合物が形成したりすることで継手強度が確保できないという問題がある。   From the viewpoint of maintaining the cost and efficiency of the production process of the vehicle body, it is effective to use the resistance spot welding method also in joining when aluminum plates are mixed, as in the case of steel plates. However, in dissimilar material joining of steel plate and aluminum plate, the soft aluminum plate is greatly reduced in thickness during welding due to the pressurization of the electrode and the heat generated during energization, and fragile intermetallic compounds are formed at the joint interface. Therefore, there is a problem that the joint strength cannot be secured.

上記の問題に対応するため、以下に述べるような技術が提案されている。   In order to deal with the above problems, the following techniques have been proposed.

例えば、特許文献１には、溶接を極短時間化し、高電流を付与することで溶融部を周囲に飛散させて、正常な金属面同士の接触と原子の拡散による接合を達成させる抵抗スポット溶接方法が記載されている。   For example, Patent Document 1 discloses resistance spot welding in which welding is performed in an extremely short time and a high current is applied to disperse the melted part to the surroundings, thereby achieving normal contact between metal surfaces and joining by atomic diffusion. A method is described.

また、特許文献２には、鋼板とアルミニウム板の間に鉄／アルミニウムクラッド薄板を同種材同士が向かい合うようにインサートさせることで、電極へのアルミニウムの溶着量を最小限に抑えながら、低電流でも高強度の継手が得られる抵抗スポット溶接方法が記載されている。   Further, Patent Document 2 discloses that an iron / aluminum clad thin plate is inserted between a steel plate and an aluminum plate so that the same kind of materials face each other, thereby minimizing the amount of aluminum deposited on the electrode while maintaining high strength even at a low current. A resistance spot welding method is described which provides a joint of

また、特許文献３には、鋼板とアルミニウム板の両側に当て板を１枚以上添えて溶接を行うことで、当て板と被接合材料の界面が抵抗発熱し、鋼とアルミニウムが抵抗拡散接合されて高強度の継手が得られる抵抗スポット溶接方法が記載されている。   Further, Patent Document 3 discloses that welding is performed by attaching one or more contact plates on both sides of a steel plate and an aluminum plate, so that the interface between the contact plate and the material to be bonded generates resistance heat, and the steel and aluminum are resistance diffusion bonded. In addition, a resistance spot welding method capable of obtaining a high-strength joint is described.

また、特許文献４では、鋼板および鋼板表面酸化皮膜におけるＭｎおよびＳｉの各量を適正化することで、大きいナゲット径を得つつ散り発生を抑制する事ができると記載されている。   Patent Document 4 describes that the occurrence of scattering can be suppressed while obtaining a large nugget diameter by optimizing the amounts of Mn and Si in the steel sheet and the steel sheet surface oxide film.

また、特許文献５では、融点の異なる複数の金属体の溶接において、融点の低い金属体に接する電極として先端面中央に凹部を設けた電極で溶接することにより、中散りによるバリの形成を防止して、高い生産性と高品質の溶接部を得る溶接方法が提案されている。   Moreover, in patent document 5, in the welding of the several metal body from which melting | fusing point differs, by forming with the electrode which provided the recessed part in the front-end | tip surface as an electrode which contact | connects a metal body with low melting | fusing point, formation of the burr | flash by scattering is prevented. A welding method for obtaining a high-productivity and high-quality weld has been proposed.

また、特許文献６では、ＧＡ鋼板とアルミニウム材とのスポット溶接時にアルミニウム材側に使用する凸型電極の先端曲率半径を鋼板側よりも２倍〜６倍大きくすることにより、アルミニウムの溶融部の排除を起こりにくくし、溶融プールを接合面に形成しやすくし、かつ溶融亜鉛めっきを比較的容易に接合面から溶融除去することにより、接合強度を確保する方法が提案されている。   Moreover, in patent document 6, by making the tip curvature radius of the convex electrode used for the aluminum material side at the time of spot welding of GA steel plate and aluminum material 2-6 times larger than a steel plate side, the fusion | melting part of an aluminum is carried out. There has been proposed a method of ensuring bonding strength by making it difficult to eliminate, facilitating formation of a molten pool on a bonded surface, and relatively easily removing molten galvanized plating from the bonded surface.

特開２００４−１７１４８号公報JP 2004-17148 A 特開平７−１３６７７４号公報JP-A-7-136774 特開平９−１５５５６１号公報JP-A-9-155561 特開２００５−１５２９５８号公報JP 2005-152958 A 特開平１１−３４２４７７号公報JP-A-11-342477 特開２００８−２００６８７号公報JP 2008-200747 A

しかしながら、特許文献１に記載の抵抗スポット溶接方法では、鋼板同士の抵抗スポット溶接方法と比較して大電流を付与する必要があるため、自動車生産ラインで一般的に用いられている溶接トランスの電源容量では電流値が不足するという問題点がある。   However, in the resistance spot welding method described in Patent Document 1, it is necessary to apply a large current compared to the resistance spot welding method between steel plates, and therefore a power source for a welding transformer generally used in an automobile production line There is a problem that the current value is insufficient in the capacity.

また、特許文献２および３に記載の抵抗スポット溶接方法では、車体の構造上不要である当て板やクラッド薄板の使用、さらには車体の生産ラインの工程変更が必要となるため、大幅なコスト増や重量低減が十分に図れないなどの問題がある。   In addition, the resistance spot welding methods described in Patent Documents 2 and 3 require the use of a backing plate or a clad thin plate that is not necessary for the structure of the vehicle body, and further the process change of the production line of the vehicle body. And there is a problem that weight cannot be reduced sufficiently.

また、特許文献４では、鋼板および酸化皮膜中の合金元素量および分布を限定する必要があるため、要求性能を満たす鋼板の使用が制限されるなどの課題があり、特に最近の鋼板では高強度化にともなって高合金化が進んでいる状況下では、その適用は極めて制限される。   Moreover, in patent document 4, since it is necessary to limit the amount and distribution of the alloy element in a steel plate and an oxide film, there exists a subject that the use of the steel plate which satisfy | fills a required performance is restrict | limited, especially in recent steel plates, it is high strength. Under the circumstances where high alloying is progressing with the progress of application, its application is extremely limited.

また、特許文献５、６の場合、溶接点数の増加に伴って低融点材もしくはアルミニウム材と接する側の電極先端の損耗が進むが、その時の低融点材もしくはアルミニウム材側電極の先端損耗が著しく進んでいくために、溶接自体が不安定になる。その結果電極を極めて高頻度に交換する必要が生じるなどの問題がある。   Further, in Patent Documents 5 and 6, as the number of welding points increases, the wear of the electrode tip on the side in contact with the low melting point material or the aluminum material proceeds, but the tip wear of the low melting point material or the aluminum material side electrode at that time is remarkably increased. As it progresses, the welding itself becomes unstable. As a result, there is a problem that the electrode needs to be replaced very frequently.

本発明は、上記の問題を有利に解決するもので、鋼板とアルミニウム板を重ね合わせた板組みを抵抗スポット溶接するに際して、自動車生産ラインで一般的に用いられている溶接トランスで出力可能な電流範囲で、かつ鋼板同士の接合と同じ生産工程により、鋼板とアルミニウム板の継手特性が確保でき、かつ連続溶接時の電極損耗時においても溶接の安定性を確保し得る抵抗スポット溶接方法を提供することを目的とする。   The present invention advantageously solves the above-described problem. When resistance plate welding is performed on a plate assembly in which a steel plate and an aluminum plate are overlapped, a current that can be output by a welding transformer generally used in an automobile production line. Provided is a resistance spot welding method that can secure the joint characteristics of a steel plate and an aluminum plate in the range and the same production process as the joining of steel plates, and can ensure the stability of welding even at the time of electrode wear during continuous welding For the purpose.

上記の課題を解決すべく、本発明者らは電極先端形状と溶接後の鋼板およびアルミニウム板のインデンテーション（減厚）の状態ならびに継手強度の関係について研究を行った。その結果、鋼板に接する電極とアルミニウム板に接する電極を適切に選択して、溶接後の溶接部のインデンテーション量（減厚量）を適正化することにより健全な溶接部が得られることを知見した。   In order to solve the above-mentioned problems, the present inventors have studied the relationship between the electrode tip shape, the state of indentation (thinning) of the steel plate and aluminum plate after welding, and the joint strength. As a result, it is found that a sound weld can be obtained by appropriately selecting the electrode in contact with the steel plate and the electrode in contact with the aluminum plate and optimizing the amount of indentation (thickness reduction) of the weld after welding. did.

本発明は、上記の知見に基づき、さらに検討を重ねて完成されたもので、その要旨構成は次のとおりである。   The present invention has been completed through further studies based on the above findings, and the gist of the present invention is as follows.

［１］鋼板とアルミニウム板を複数枚重ねて、最外側に配置される板の一方が鋼板で、他方がアルミニウム板とした板組みを抵抗スポット溶接するに際して、
鋼板と接する電極の先端径ＤＦｅと、アルミニウム板と接する電極の先端径ＤＡｌとの関係が、
ＤＦｅ＜ＤＡｌ
を満たし、
かつ、アルミニウム板と接する電極の先端形状が、フラット形状か、先端曲率半径が１７０ｍｍ以上の凸型形状か、先端曲率半径が１０ｍｍ以上の凹型形状かのいずれかとすることを特徴とする抵抗スポット溶接方法。[1] When performing resistance spot welding on a plate assembly in which a plurality of steel plates and aluminum plates are stacked and one of the plates arranged on the outermost side is a steel plate and the other is an aluminum plate,
The relationship between the tip diameter DFe of the electrode in contact with the steel plate and the tip diameter DAl of the electrode in contact with the aluminum plate is
DFe <DAl
The filling,
The resistance spot welding is characterized in that the tip shape of the electrode in contact with the aluminum plate is either a flat shape, a convex shape having a tip curvature radius of 170 mm or more, or a concave shape having a tip curvature radius of 10 mm or more. Method.

［２］アルミニウム板と接する電極の先端形状が、先端曲率半径が１７０ｍｍ以上１５００ｍｍ以下の凸型形状か、先端曲率半径が１０ｍｍ以上１０００ｍｍ以下の凹型形状かのいずれかとすることを特徴とする前記［１］に記載の抵抗スポット溶接方法。   [2] The tip shape of the electrode in contact with the aluminum plate is either a convex shape having a tip curvature radius of 170 mm or more and 1500 mm or less, or a concave shape having a tip curvature radius of 10 mm or more and 1000 mm or less. 1] The resistance spot welding method according to item 1.

［３］アルミニウム板と接する電極の先端径ＤＡｌと、当該アルミニウム板の板厚ｔＡｌの関係が、
ＤＡｌ≧３ｔＡｌ
を満たすことを特徴とする前記［１］または［２］に記載の抵抗スポット溶接方法。[3] The relationship between the tip diameter DAl of the electrode in contact with the aluminum plate and the thickness tAl of the aluminum plate is
DAl ≧ 3tAl
The resistance spot welding method according to [1] or [2], wherein:

［４］接合部中心におけるアルミニウム板のインデンテーション量が減厚率（接合部中央の板厚／元板厚）で０．８以上の溶接部を形成させることを特徴とする前記［１］乃至［３］に記載の抵抗スポット溶接方法。   [4] The above-described [1] to [1], wherein a welded portion having an aluminum plate indentation amount of 0.8 or more in thickness reduction ratio (plate thickness at the center of the joint / original plate thickness) is formed. The resistance spot welding method according to [3].

本発明においては、鋼板とアルミニウム板を重ね合わせた板組みを抵抗スポット溶接するに際して、自動車生産ラインで一般的に用いられている溶接トランスで出力可能な電流範囲で、かつ鋼板同士の接合と同じ生産工程により、鋼板とアルミニウム板の継手特性が確保でき、かつ連続溶接時の電極損耗時においても溶接の安定性を確保することができる。   In the present invention, when resistance spot welding is performed on a plate assembly in which a steel plate and an aluminum plate are overlapped, a current range that can be output by a welding transformer generally used in an automobile production line and the same as the joining of steel plates By the production process, the joint characteristics between the steel plate and the aluminum plate can be secured, and the welding stability can be secured even when the electrode is worn during continuous welding.

すなわち、本発明によれば、鋼板同士を抵抗スポット溶接している一般的な自動車のアセンブリラインで、新たな設備導入によるコスト増加などを引き起こすことなく、鋼板とアルミニウム板を安定して接合することが可能となる。   That is, according to the present invention, in a general automobile assembly line in which steel plates are resistance spot welded together, the steel plate and the aluminum plate can be stably joined without causing an increase in cost due to the introduction of new equipment. Is possible.

本発明の一実施形態における抵抗スポット溶接方法を説明する図である。It is a figure explaining the resistance spot welding method in one Embodiment of this invention. 本発明の一実施形態において用いる電極の先端径Ｄと先端曲率半径Ｒを説明する図である。It is a figure explaining the tip diameter D and the tip curvature radius R of the electrode used in one Embodiment of this invention.

本発明をその実施形態によって詳細に説明する。   The present invention will be described in detail by its embodiments.

図１は、本発明の一実施形態における抵抗スポット溶接方法を説明する図である。板厚ｔＦｅの鋼板１と板厚ｔＡｌのアルミニウム板２を直接重ね合わせた板組み３を一対の電極（上電極４、下電極５）で挟んで加圧しつつ、上下電極４、５間に高電流の溶接電流を短時間通電して抵抗発熱により接合して、鋼板１とアルミニウム板２の抵抗スポット溶接継手を得るようにしている。   FIG. 1 is a diagram illustrating a resistance spot welding method according to an embodiment of the present invention. A plate assembly 3 in which a steel plate 1 having a plate thickness tFe and an aluminum plate 2 having a plate thickness tAl are directly overlapped is pressed between a pair of electrodes (upper electrode 4 and lower electrode 5) and pressed between the upper and lower electrodes 4 and 5. A current welding current is applied for a short time and joined by resistance heating to obtain a resistance spot welded joint between the steel plate 1 and the aluminum plate 2.

そして、上記で得られた、鋼板１とアルミニウム板２の抵抗スポット溶接継手を変形させた場合、より軟質なアルミニウム板２側、もしくは鋼板１とアルミニウム板２との接合界面で破壊が生じる。このため、十分な継手強度を確保するには、溶接部（接合部）でのアルミニウム板２の減厚を抑制することと、接合界面での脆弱な金属間化合物の生成を極力抑制することが必要となり、特に、溶接部でのアルミニウム板２の減厚を抑制することが重要である。これは、接合界面での金属間化合物の生成を抑制しつつ十分な接合面積を得られるような条件を見出して、接合界面の強度を十分に確保できた場合においても、アルミニウム板２が減厚してアルミニウム板２の減厚部から破断し、結果的に十分な強度が確保できなくなることが問題であるからである。   When the resistance spot welded joint between the steel plate 1 and the aluminum plate 2 obtained as described above is deformed, the fracture occurs at the softer aluminum plate 2 side or at the joint interface between the steel plate 1 and the aluminum plate 2. For this reason, in order to ensure sufficient joint strength, it is necessary to suppress the thickness reduction of the aluminum plate 2 at the welded portion (joined portion) and to suppress the generation of fragile intermetallic compounds at the joining interface as much as possible. In particular, it is important to suppress the thickness reduction of the aluminum plate 2 at the weld. This is because the aluminum plate 2 is reduced in thickness even when a sufficient bonding area can be obtained while suppressing the formation of intermetallic compounds at the bonding interface and sufficient strength of the bonding interface can be secured. This is because the aluminum plate 2 is broken from the reduced thickness portion, and as a result, sufficient strength cannot be secured.

そこで、この実施形態においては、電極の先端径と先端形状を以下に述べるように限定することによって、上記の問題を解決するようにしている。   Therefore, in this embodiment, the above-mentioned problem is solved by limiting the tip diameter and tip shape of the electrode as described below.

すなわち、鋼板１と接する電極（上電極）４の先端径ＤＦｅとアルミニウム板２と接触する電極（下電極）５の先端径ＤＡｌの関係を、ＤＦｅ＜ＤＡｌを満足させることにより、アルミニウム板２を溶接部より広い領域で加圧・支持し、かつアルミニウム板２側での電極（下電極５）からの抜熱を十分に安定して確保することにより、アルミニウム板２の表面および内部の極端な軟質化を抑えて、溶接部のアルミニウム２側の減厚を抑制することが可能となる。   That is, the relationship between the tip diameter DFe of the electrode (upper electrode) 4 in contact with the steel plate 1 and the tip diameter DAl of the electrode (lower electrode) 5 in contact with the aluminum plate 2 satisfies the condition DFe <DAl. By pressing and supporting in a wider area than the welded portion and sufficiently stably removing heat from the electrode (lower electrode 5) on the aluminum plate 2 side, the surface of the aluminum plate 2 and the extreme inside It becomes possible to suppress softening and to suppress the thickness reduction of the welded portion on the aluminum 2 side.

さらに、アルミニウム板２側の電極５の先端形状をフラット形状（先端曲率半径Ｒは無限大）とするか、もしくは凸型形状の場合は先端曲率半径Ｒを１７０ｍｍ以上とするか、凹型形状の場合は先端曲率半径Ｒを１０ｍｍ以上とするかのいずれかとすることにより、上記効果を安定して得られると同時に、電極損耗時においても、溶接時、特に通電初期におけるアルミニウム板２側の通電を接合部よりかなり広い範囲でリング状にすることができ、アルミニウム板２の減厚を安定して抑制でき、安定した溶接部を確保しやすくなる。   Furthermore, the tip shape of the electrode 5 on the aluminum plate 2 side is a flat shape (tip radius of curvature R is infinite), or the tip radius of curvature R is 170 mm or more in the case of a convex shape, or in the case of a concave shape. The above-mentioned effect can be obtained stably by setting the radius of curvature R of the tip to 10 mm or more. At the same time, even when the electrode is worn, the energization on the aluminum plate 2 side at the time of welding, particularly at the initial stage of energization is joined. It can be made into a ring shape in a considerably wider range than the part, the thickness reduction of the aluminum plate 2 can be stably suppressed, and it becomes easy to secure a stable welded part.

そして、上記の効果は、アルミニウム板２側の電極５の先端形状を先端曲率半径が１７０ｍｍ以上１５００ｍｍ以下の凸型形状か、先端曲率半径が１０ｍｍ以上１０００ｍｍ以下の凹型形状かのいずれかとすることにより、より一層発揮される。これにより、組立てラインなどの実工程で必ずしも面直（溶接面に対して電極の中心軸が直交）が精度よく得られていない状態でも、安定した溶接が可能となる。   The above effect is achieved by making the tip shape of the electrode 5 on the aluminum plate 2 side either a convex shape with a tip curvature radius of 170 mm or more and 1500 mm or less, or a concave shape with a tip curvature radius of 10 mm or more and 1000 mm or less. , Even more. Thereby, stable welding is possible even in a state in which the straightness (the center axis of the electrode is orthogonal to the welding surface) is not necessarily obtained with high accuracy in an actual process such as an assembly line.

これは以下の理由による。すなわち、アルミニウム板２側の電極５の先端形状を先端曲率半径が１５００ｍｍ超えの凸型形状とした場合、電極５が新品の時やドレッシング直後の時には、溶接時の面直精度（溶接面と電極の中心軸との直交度合）を高精度に調整しないと、電極５の先端がアルミニウム板２の表面に片当りして、想定した効果が得られない可能性がある。これに対して、電極５の先端形状を先端曲率半径が１７０ｍｍ以上１５００ｍｍ以下の凸型形状とした場合は、電極５の先端が比較的尖った形状となるため、上記のような電極５が初期状態の時（新品の時やドレッシング直後の時）に生じる片当りを的確に抑制することができる。好ましくは２００ｍｍ以上１０００ｍｍ以下の範囲である。また、電極５の先端形状を先端曲率半径が１０ｍｍ以上１０００ｍｍ以下の凹型形状とした場合は、電極５の先端がアルミニウム板２の表面に片当りしても、溶融したアルミニウムが電極５の内側（中心軸側）へ押されるために、溶接が安定する。好ましくは４０ｍｍ以上５００ｍｍ以下の範囲である。   This is due to the following reason. That is, when the tip shape of the electrode 5 on the aluminum plate 2 side is a convex shape with a tip radius of curvature exceeding 1500 mm, when the electrode 5 is new or just after dressing, the surface straightness accuracy during welding (weld surface and electrode) If the degree of orthogonality with respect to the central axis of the electrode 5 is not adjusted with high accuracy, the tip of the electrode 5 may hit the surface of the aluminum plate 2 and the expected effect may not be obtained. On the other hand, when the tip shape of the electrode 5 is a convex shape having a tip curvature radius of 170 mm or more and 1500 mm or less, the tip of the electrode 5 has a relatively sharp shape. It is possible to accurately suppress the one-piece contact that occurs in a state (when it is new or immediately after dressing). Preferably it is the range of 200 mm or more and 1000 mm or less. Further, when the tip shape of the electrode 5 is a concave shape with a tip curvature radius of 10 mm or more and 1000 mm or less, even if the tip of the electrode 5 hits the surface of the aluminum plate 2, the molten aluminum remains inside the electrode 5 ( The welding is stabilized because it is pushed to the center axis side). Preferably it is the range of 40 mm or more and 500 mm or less.

なお、電極の先端径Ｄと先端曲率半径Ｒについては、図２において、（ａ−１）と（ａ−２）がフラット形状（先端曲率半径Ｒは無限大）の場合の例、（ｂ−１）と（ｂ−２）が凸型形状の場合の例、（ｃ−１）と（ｃ−２）が凹型形状の場合の例をそれぞれ示している（ＪＩＳ Ｃ ９３０４）。ちなみに、（ｃ−１）は凹型部分の周囲がフラットになっている凹型形状である。   As for the tip diameter D and the tip curvature radius R of the electrode, in FIG. 2, (a-1) and (a-2) are flat shapes (tip curvature radius R is infinite), (b- Examples where 1) and (b-2) are convex shapes and examples where (c-1) and (c-2) are concave shapes are shown (JIS C 9304), respectively. Incidentally, (c-1) is a concave shape in which the periphery of the concave portion is flat.

したがって、アルミニウム板と接する電極の先端曲率半径をＲＡｌ、鋼板と接する電極の先端曲率半径をＲＦｅとした場合、鋼板１に接触する電極４として、図２に示した電極を使用する場合は、図２中に示している先端径Ｄが電極４の先端径ＤＦｅとなり、図２中に示している先端曲率半径Ｒが電極４の先端曲率半径ＲＦｅとなる。同様に、アルミニウム板２に接触する電極５として、図２に示した電極を使用する場合は、図２中に示している先端径Ｄが電極５の先端径ＤＡｌとなり、図２中に示している先端曲率半径Ｒが電極５の先端曲率半径ＲＡｌとなる。   Therefore, when the tip radius of curvature of the electrode in contact with the aluminum plate is RAl and the tip radius of curvature of the electrode in contact with the steel plate is RFe, the electrode shown in FIG. 2 is the tip diameter DFe of the electrode 4, and the tip radius of curvature R shown in FIG. 2 is the tip radius of curvature RFe of the electrode 4. Similarly, when the electrode shown in FIG. 2 is used as the electrode 5 in contact with the aluminum plate 2, the tip diameter D shown in FIG. 2 becomes the tip diameter DAl of the electrode 5, and is shown in FIG. The tip radius of curvature R is the tip radius of curvature RAl of the electrode 5.

なお、この効果については、アルミニウム板２と接する電極５の先端径ＤＡｌと、そのアルミニウム板２の板厚ｔＡｌの関係をＤＡｌ≧３ｔＡｌとすることにより、アルミニウム板２の板厚に対して十分な強度を安定して得ることができる。   For this effect, the relationship between the tip diameter DAl of the electrode 5 in contact with the aluminum plate 2 and the thickness tAl of the aluminum plate 2 is DAl ≧ 3tAl, which is sufficient for the thickness of the aluminum plate 2. The strength can be obtained stably.

上述した状態で溶接した場合、接合部中心におけるアルミニウム板２側のインデンテーション量が減厚率（接合部中央の板厚／元板厚）で０．８以上となる溶接部を形成させることが可能となり、継手強度の確保に極めて有効である。   When welding is performed in the above-described state, it is possible to form a welded portion in which the indentation amount on the aluminum plate 2 side at the joint center is 0.8 or more in thickness reduction ratio (plate thickness at the center of the joint / original plate thickness). This is possible and is extremely effective in securing joint strength.

なお、この実施形態では、鋼板１とアルミニウム板２の２枚重ねの板組み（溶接継手）を例として説明したが、その２枚の板間にさらにもう１枚以上の鋼板あるいはアルミニウム板を順不同で挟んだ３枚重ね以上の板組み（溶接継手）についても適用可能である。   In this embodiment, a two-layer plate assembly (welded joint) of the steel plate 1 and the aluminum plate 2 has been described as an example, but one or more other steel plates or aluminum plates are arranged in any order between the two plates. It can also be applied to a plate assembly (welded joint) of three or more layers sandwiched between two.

また、本発明の規定を満たしていれば、溶接中の電流値・通電時間・加圧力は一定である必要はなく、電流値や加圧力を２段階以上に変化させても問題はない。   Moreover, as long as the provisions of the present invention are satisfied, the current value, energization time, and applied pressure during welding need not be constant, and there is no problem even if the current value and applied pressure are changed in two or more stages.

また、溶接中の抵抗値・電圧値といったパラメータを監視し、その変動に応じて電流値や通電時間を変化させる制御方法を用いてもよい。   Also, a control method may be used in which parameters such as resistance value and voltage value during welding are monitored, and the current value and energization time are changed according to the fluctuation.

なお、本発明の接合方法で対象とする鋼板は、軟質鋼から高強度鋼、またステンレスや高合金鋼など鋼板であれば特段の限定はされない。さらに、その表面にＺｎやＡｌ、Ｍｇおよびその合金の溶融めっき、合金化溶融めっき、電気めっきを施したもの、加えて、さらに表面にクロメート処理を施したものや、樹脂皮膜を形成させたものも含まれる。また、アルミニウム板に関しても同様で、特に限定されない。   In addition, the steel plate made into the object by the joining method of this invention will not be specifically limited if it is steel plates, such as soft steel to high strength steel, stainless steel, and high alloy steel. Furthermore, Zn, Al, Mg and its alloys are hot-plated, alloyed hot-plated, electroplated on the surface, and the surface is further chromated, or a resin film is formed. Is also included. The same applies to the aluminum plate and is not particularly limited.

本発明を実施例によってさらに詳細に説明する。なお、下記実施例は本発明を限定する性質のものではなく、本発明の要旨を満足する限りいずれも本発明の技術的範囲に含まれるものである。   The invention is explained in more detail by means of examples. The following examples are not intended to limit the present invention, and are all included in the technical scope of the present invention as long as the gist of the present invention is satisfied.

供試材として、鋼板に軟鋼を用い、アルミニウム板に５０００系アルミニウム合金板を用いた。そして、これらを直接重ね合わせた板組みとした。溶接機はインバータ直流式抵抗スポット溶接機を用い、加圧力２．５ｋＮとし、電極形状と溶接電流、通電時間を変化させて溶接を行った。   As test materials, mild steel was used for the steel plate, and a 5000 series aluminum alloy plate was used for the aluminum plate. And it was set as the board assembly which piled up these directly. As the welding machine, an inverter DC resistance spot welding machine was used. The welding pressure was 2.5 kN, and welding was performed while changing the electrode shape, welding current, and energization time.

溶接後は継手を溶接部中央で切断して断面観察を行い、アルミニウム板の接合部中央の厚みを測定し、元板厚との比から減厚率（接合部中央の板厚／元板厚）を求めた。また、継手品質は、ＪＩＳ Ｚ ３１４４に規定のピール試験によりピール径（ｍｍ）を測定して判断した。ピール時に円状に剥離しなかった場合は、プラグ状に残った面積の円相当直径をピール径と判断した。   After welding, cut the joint at the center of the weld and observe the cross section, measure the thickness at the center of the joint of the aluminum plate, and reduce the thickness from the ratio of the original plate thickness (plate thickness at the center of the joint / original plate thickness). ) The joint quality was judged by measuring the peel diameter (mm) by a peel test specified in JIS Z 3144. When peeling did not occur in a circular shape at the time of peeling, the equivalent circle diameter of the area remaining in the plug shape was determined as the peel diameter.

継手特性の評価基準としては、アルミニウム板の溶接前の板厚を基準板厚ｔ（ｍｍ）として、ピール径が４√ｔ以上でかつ減厚率が０．８以上であるものを◎、ピール径が４√ｔ以上でかつ減厚率が０．７以上０．８未満であるものを○、ピール径が４√ｔ未満であるかまたは減厚率が０．７未満であるものを×とした。   As the evaluation criteria for joint characteristics, the thickness of the aluminum plate before welding is defined as the reference thickness t (mm), and the peel diameter is 4√t or more and the thickness reduction rate is 0.8 or more. A circle having a diameter of 4√t or more and a thickness reduction ratio of 0.7 or more and less than 0.8, and a peel diameter of less than 4√t or a thickness reduction ratio of less than 0.7. It was.

表１に面直誤差０％の場合における結果を示し、表２に面直誤差５％の場合における結果を示す。表１、表２に示すように、本発明例においては、全てのケースで評価は○ないし◎であった。   Table 1 shows the results when the surface perpendicularity error is 0%, and Table 2 shows the results when the surface perpendicularity error is 5%. As shown in Tables 1 and 2, in the examples of the present invention, the evaluations were ○ to ◎ in all cases.

Figure 0006037018
Figure 0006037018

Figure 0006037018
Figure 0006037018

１ 鋼板
２ アルミニウム板
３ 板組み
４ 鋼板と接する電極（上電極）
５ アルミニウム板と接触する電極（下電極）
1 Steel plate 2 Aluminum plate 3 Board assembly 4 Electrode in contact with steel plate (upper electrode)
5 Electrode in contact with aluminum plate (lower electrode)

Claims (4)

鋼板とアルミニウム板を複数枚重ねて、最外側に配置される板の一方が鋼板で、他方がアルミニウム板とした板組みを抵抗スポット溶接する（ただし、溶接中の通電時間が２００ｍｓｅｃ以上を除く）に際して、
鋼板と接する電極の先端径ＤＦｅと、アルミニウム板と接する電極の先端径ＤＡｌとの関係が、
ＤＦｅ＜ＤＡｌ
を満たし、
かつ、アルミニウム板と接する電極の先端形状が、フラット形状か、先端曲率半径が１７０ｍｍ以上の凸型形状か、先端曲率半径が１０ｍｍ以上の凹型形状かのいずれかとすることを特徴とする抵抗スポット溶接方法。 A plurality of steel plates and aluminum plates are stacked, and resistance spot welding is performed on a plate assembly in which one of the outermost plates is a steel plate and the other is an aluminum plate (except for energization time of 200 msec or more during welding). On the occasion
The relationship between the tip diameter DFe of the electrode in contact with the steel plate and the tip diameter DAl of the electrode in contact with the aluminum plate is
DFe <DAl
The filling,
The resistance spot welding is characterized in that the tip shape of the electrode in contact with the aluminum plate is either a flat shape, a convex shape having a tip curvature radius of 170 mm or more, or a concave shape having a tip curvature radius of 10 mm or more. Method. アルミニウム板と接する電極の先端形状が、先端曲率半径が１７０ｍｍ以上１５００ｍｍ以下の凸型形状か、先端曲率半径が１０ｍｍ以上１０００ｍｍ以下の凹型形状かのいずれかとすることを特徴とする請求項１に記載の抵抗スポット溶接方法。   The tip shape of the electrode in contact with the aluminum plate is either a convex shape having a tip radius of curvature of 170 mm to 1500 mm, or a concave shape having a tip radius of curvature of 10 mm to 1000 mm. Resistance spot welding method. アルミニウム板と接する電極の先端径ＤＡｌと、当該アルミニウム板の板厚ｔＡｌの関係が、
ＤＡｌ≧３ｔＡｌ
を満たすことを特徴とする請求項１または２に記載の抵抗スポット溶接方法。 The relationship between the tip diameter DAl of the electrode in contact with the aluminum plate and the thickness tAl of the aluminum plate is
DAl ≧ 3tAl
The resistance spot welding method according to claim 1, wherein: 接合部中心におけるアルミニウム板のインデンテーション量が減厚率（接合部中央の板厚／元板厚）で０．８以上の溶接部を形成させることを特徴とする請求項１乃至３に記載の抵抗スポット溶接方法。   4. The welded portion according to claim 1, wherein an indentation amount of the aluminum plate in the center of the joint is formed by a thickness reduction ratio (plate thickness in the center of the joint / original plate thickness) of 0.8 or more. Resistance spot welding method.
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JP2006224148A (en) * 2005-02-17 2006-08-31 Kobe Steel Ltd Resistance spot welding method for different materials
JP2008200687A (en) * 2007-02-16 2008-09-04 Kobe Steel Ltd Different material joining method of steel and aluminum material
US20090050608A1 (en) * 2004-10-26 2009-02-26 Noboru Hayashi Method for joining iron member and aluminum member

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JP2006224148A (en) * 2005-02-17 2006-08-31 Kobe Steel Ltd Resistance spot welding method for different materials
JP2008200687A (en) * 2007-02-16 2008-09-04 Kobe Steel Ltd Different material joining method of steel and aluminum material

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