JP2007130659A - Spot welding method, and electrode for spot welding - Google Patents

Spot welding method, and electrode for spot welding Download PDF

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JP2007130659A
JP2007130659A JP2005325185A JP2005325185A JP2007130659A JP 2007130659 A JP2007130659 A JP 2007130659A JP 2005325185 A JP2005325185 A JP 2005325185A JP 2005325185 A JP2005325185 A JP 2005325185A JP 2007130659 A JP2007130659 A JP 2007130659A
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spot welding
electrode
welding
mark
recess
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JP4919317B2 (en
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Hiroshi Abe
博司 阿部
Takashi Shinmyo
高史 新明
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Daihatsu Motor Co Ltd
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Daihatsu Motor Co Ltd
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Priority to MYPI20080141A priority patent/MY164289A/en
Priority to CNA2006800343433A priority patent/CN101267908A/en
Priority to PCT/JP2006/321841 priority patent/WO2007055130A1/en
Priority to US11/920,634 priority patent/US20090218323A1/en
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for determining the quality of the spot welding by a non-destructive inspection. <P>SOLUTION: An electrode having a recess in which the depth of a weld trace formed on a surface of a metal body and reaching a deepest part is set to be a predetermined value when an electrode surface is a substantially projecting curved surface and a nugget is excellently formed in a center of an electrode surface by the spot welding is used for at least one electrode to perform the spot welding. The quality of the spot welding is determined based on the shape of the weld trace formed on the surface of the metal body corresponding to the recess by the spot welding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明はスポット溶接方法およびスポット溶接用電極に関するものである。   The present invention relates to a spot welding method and a spot welding electrode.

スポット溶接は、ナゲット径でスポット溶接の強度を評価することが知られている。具体的手法としては、スポット溶接された２枚の鋼板の間にタガネを圧入してスポット溶接部を剥がし、ナゲット径を直接計測するいわゆるタガネ検査や、スポット溶接部を切断してナゲット径を直接計測する切断検査などの個別破壊計測が行なわれている。   It is known that spot welding evaluates the strength of spot welding by the nugget diameter. Specific methods include press fitting between two spot-welded steel plates, peeling off the spot welded part, so-called flare inspection to directly measure the nugget diameter, and cutting the spot welded part to directly determine the nugget diameter. Individual destruction measurement such as cutting inspection to be measured is performed.

また、スポット溶接に関する非破壊計測技術としては超音波を利用したもの（特開昭６２−１１９４５３号、特開平４−２６５８５４号）、振動を利用したもの（特開平９−１７１００７号）、断続光照射に伴う音波を検出するもの（特開平３−２６５９号）、溶接電極から発した弾性波の反射波を検出するもの（特開平４−４０３５９号）などが各種提案されている。また、特開２００１−１６５９１１号公報には、スポット溶接部に磁力線を貫通させたときに測定されるスポット溶接部のナゲット周縁での環状高インダクタンス部分の直径と、前記高インダクタンス部分とナゲット中央部における低インダクタンス部分とのインダクタンス高低落差の２つの変数を用いて、ナゲット直径の予測値としての各変数を判別式で表し、ナゲット直径の良否を区別する閾値を設定するものが開示されている。
特開２００１−１６５９１１号公報 Nondestructive measurement techniques relating to spot welding are those using ultrasonic waves (Japanese Patent Laid-Open Nos. 62-119453 and 4-265854), those using vibration (Japanese Patent Laid-Open No. 9-171007), and intermittent light. Various proposals have been made for detecting a sound wave accompanying irradiation (Japanese Patent Laid-Open No. 3-2659), detecting a reflected wave of an elastic wave emitted from a welding electrode (Japanese Patent Laid-Open No. 4-40359), and the like. Japanese Patent Laid-Open No. 2001-165911 discloses a diameter of an annular high inductance portion at the periphery of a nugget of a spot welded portion measured when a magnetic field line is passed through the spot welded portion, and the high inductance portion and the nugget central portion. Are used to express each variable as a predicted value of the nugget diameter with a discriminant and set a threshold value for discriminating whether the nugget diameter is good or bad.
JP 2001-165911 A

タガネ検査は、破壊計測したものについて、スポット溶接の強度を評価することができるが、破壊計測していないものはスポット溶接の強度を直接評価することができない。また、近年、自動車のボディー等には軽量化を図るためハイテン（高張力鋼）材が多く用いられつつあるが、ハイテン材をスポット溶接した部位は通常の鋼板を溶接した部位に比べて硬いため、製造ラインで抜き打ちによるタガネ検査を行うには不向きであった。   The chisel inspection can evaluate the strength of spot welding for those subjected to fracture measurement, but cannot directly evaluate the strength of spot welding for those not subjected to fracture measurement. In recent years, high-tensile (high-tensile steel) materials are often used to reduce the weight of automobile bodies, but the spot-welded part of high-tensile material is harder than the part welded with normal steel plates. It was unsuitable for performing an inspection by punching on the production line.

従って、非破壊検査によるスポット溶接の良否評価を行えるスポット溶接方法を確立することが望まれている。非破壊検査は特開２００１−１６５９１１号公報などに開示されているが、設備コストや作業性の面を考慮すれば、より簡単な設備でより簡単に検査でき、信頼性が高い検査方法が望ましい。   Therefore, it is desired to establish a spot welding method capable of evaluating the quality of spot welding by nondestructive inspection. Non-destructive inspection is disclosed in Japanese Patent Application Laid-Open No. 2001-165911. However, in view of equipment cost and workability, an inspection method that can be easily inspected with simple equipment and has high reliability is desirable. .

図１に示すように、スポット溶接を行う一対の電極１、２のうち、一方の電極２に、電極面に窪み３を形成したものを用いてスポット溶接を行うと、図１、図２に示すように、電極２の電極面に形成した窪み３に対応して鋼板４、５（金属体）の表面に凸状の溶接痕６が形成される。本発明者らは、この凸状の溶接痕６に着目し、凸状の溶接痕６の高さと、ナゲット７の直径（ナゲット径）と、引張せん断強度（ＴＳＳ）のそれぞれの相関関係を調べた。   As shown in FIG. 1, when spot welding is performed using one of the electrodes 1 and 2 to be spot welded and one electrode 2 having a depression 3 formed on the electrode surface, FIG. 1 and FIG. As shown, convex welding marks 6 are formed on the surfaces of the steel plates 4 and 5 (metal bodies) corresponding to the depressions 3 formed on the electrode surface of the electrode 2. The present inventors pay attention to the convex welding trace 6 and examine the correlation between the height of the convex welding trace 6, the diameter of the nugget 7 (nugget diameter), and the tensile shear strength (TSS). It was.

図３は、凸部の高さとナゲット径との相関関係を示すデータの一例を、図４は凸部の高さと引張せん断強度（ＴＳＳ）との相関関係を示すデータの一例を、図５はナゲット径と引張せん断強度（ＴＳＳ）との相関関係を示すデータの一例をそれぞれ示している。   FIG. 3 shows an example of data showing the correlation between the height of the convex portion and the nugget diameter, FIG. 4 shows an example of data showing the correlation between the height of the convex portion and the tensile shear strength (TSS), and FIG. One example of data indicating the correlation between the nugget diameter and the tensile shear strength (TSS) is shown.

この実施形態では、図２に示すように、上下一対の電極３，４のうち、上側の電極３の表面に凹部５として、所定直径（３ｍｍと５ｍｍ）の円筒形状の窪みを形成した電極を用いている。図３〜図５の相関関係図は、電極３の表面に凹部５として形成した円筒形状の窪みの直径が３ｍｍのものと、５ｍｍのもので２種類の電極でデータを取った。それぞれ加圧力は２５０ｋｇｆ（約２．４５ｋＮ）と１５０ｋｇｆ（約１．４７ｋＮ）の２通り、また電流値は５ｋＡ〜１３ｋＡの間で変え、通電時間は４cycle〜１０cycleの間で変えてスポット溶接のエネルギーを変え、凸部の高さやナゲット径、引張せん断強度（TSS）が異なる試料を作成した。また異なる条件毎に複数個ずつ試料を作成した。なお、この実施形態では、周波数６０Hzの交流でスポット溶接を行っており、cycleは通電時間を設定する単位であり、１cycleは１/６０secである。   In this embodiment, as shown in FIG. 2, an electrode in which a cylindrical recess having a predetermined diameter (3 mm and 5 mm) is formed as a recess 5 on the surface of the upper electrode 3 of the pair of upper and lower electrodes 3 and 4. Used. In the correlation diagrams of FIGS. 3 to 5, data was taken with two types of electrodes, with the diameter of the cylindrical recess formed as the recess 5 on the surface of the electrode 3 being 3 mm and 5 mm. Each of the applied pressure is 250 kgf (about 2.45 kN) and 150 kgf (about 1.47 kN), the current value is changed between 5 kA and 13 kA, the energization time is changed between 4 cycles and 10 cycles and the energy of spot welding is changed. Samples with different heights, nugget diameters, and tensile shear strength (TSS) were prepared. A plurality of samples were prepared for each different condition. In this embodiment, spot welding is performed with an alternating current with a frequency of 60 Hz, cycle is a unit for setting the energization time, and 1 cycle is 1/60 sec.

その結果、図３〜図５に示すように、これらには相関関係が見られ、凸状の溶接痕６の高さからナゲット径及び引張せん断強度（ＴＳＳ）が推定できるとの知見を得た。そして、斯かる知見を基に、非破壊検査により、スポット溶接の良否判定が行える方法について以下のような発明をした。   As a result, as shown in FIGS. 3 to 5, there is a correlation between them, and the knowledge that the nugget diameter and the tensile shear strength (TSS) can be estimated from the height of the convex welding mark 6 was obtained. . And based on such knowledge, the following invention was invented about the method which can judge the quality of spot welding by nondestructive inspection.

すなわち、本発明に係るスポット溶接方法は、スポット溶接を行う少なくとも一方の電極に、電極面が略凸曲面で、かつ、電極面中心部に、スポット溶接により良好にナゲットが形成された場合に、金属体表面に形成される溶接痕が最深部に到達する所定深さに設定した窪みを形成した電極を用い、スポット溶接を行い、スポット溶接により前記窪みに対応して金属体表面に形成された溶接痕の形状に基づいてスポット溶接の良否を判定することを特徴としている。また、本発明に係るスポット溶接用電極は、電極面が略凸曲面で、かつ、電極面中心部に、スポット溶接により良好にナゲットが形成された場合に、金属体表面に形成される溶接痕が最深部に到達する所定深さに設定した窪みを形成したことを特徴としている。   That is, in the spot welding method according to the present invention, when at least one electrode for spot welding, the electrode surface is a substantially convex curved surface, and the nugget is favorably formed by spot welding at the center of the electrode surface, Spot welding was performed using an electrode in which a depression set to a predetermined depth at which a welding mark formed on the surface of the metal body reaches the deepest portion, and spot welding was performed on the surface of the metal body corresponding to the depression. The quality of spot welding is determined based on the shape of the welding mark. Further, the spot welding electrode according to the present invention is a welding mark formed on the surface of a metal body when the electrode surface is a substantially convex curved surface and a nugget is favorably formed by spot welding at the center of the electrode surface. Is characterized in that a depression set at a predetermined depth reaching the deepest part is formed.

このスポット溶接方法によれば、スポット溶接を行う少なくとも一方の電極に、電極面が略凸曲面で、かつ、電極面中心部に、スポット溶接により良好にナゲットが形成された場合に、金属体表面に形成される溶接痕が最深部に到達する所定深さに設定した窪みを形成した電極を用いて、スポット溶接を行っている。このため、スポット溶接の良否は溶接痕の外形形状で、溶接痕が窪みの最深部に到達したか否かを判定でき、これにより、溶接痕の外形形状でスポット溶接の良否判定が可能であり、非破壊検査によりスポット溶接の良否が判定できる。   According to this spot welding method, when at least one electrode to be spot welded has a substantially convex curved surface and a nugget is favorably formed by spot welding at the center of the electrode surface, the surface of the metal body Spot welding is performed using an electrode in which a depression is set at a predetermined depth at which a welding mark formed on the innermost part reaches the deepest part. For this reason, the quality of spot welding is the outer shape of the welding mark, and it can be determined whether or not the welding mark has reached the deepest part of the depression, and thereby the quality of the spot welding can be determined by the outer shape of the welding mark. The quality of spot welding can be determined by nondestructive inspection.

以下、本発明の一実施形態に係るスポット溶接方法およびスポット溶接用電極を図面に基づいて説明する。   Hereinafter, a spot welding method and a spot welding electrode according to an embodiment of the present invention will be described with reference to the drawings.

このスポット溶接方法では、スポット溶接を行う少なくとも一方の電極に、図６（ａ）（ｂ）に示すように、電極面１１が略凸曲面で、かつ、電極面１１の中心部に窪み１２を形成したスポット溶接の良否判定用電極１０（以下、「マーク電極」という。）を用いてスポット溶接を行う。マーク電極１０の電極面１１に形成した窪み１２は、図７に示すように、スポット溶接により良好にナゲット１３が形成された場合に、金属体としての鋼板１４の表面に形成される溶接痕１５が最深部１６に到達する所定深さに設定している。なお、図７に図示する例では、スポット溶接は、一方の電極にマーク電極１０を用い、他方に通常のスポット溶接用電極２０を用いている。   In this spot welding method, as shown in FIGS. 6 (a) and 6 (b), at least one electrode to be spot welded, the electrode surface 11 is a substantially convex curved surface, and a depression 12 is formed at the center of the electrode surface 11. Spot welding is performed using the formed spot welding quality determination electrode 10 (hereinafter referred to as “mark electrode”). As shown in FIG. 7, the depression 12 formed on the electrode surface 11 of the mark electrode 10 has a welding mark 15 formed on the surface of the steel plate 14 as a metal body when the nugget 13 is favorably formed by spot welding. Is set to a predetermined depth that reaches the deepest portion 16. In the example illustrated in FIG. 7, the spot welding uses the mark electrode 10 for one electrode and the normal spot welding electrode 20 for the other.

すなわち、斯かるマーク電極１０を用いてスポット溶接を行うと、図７に示すように、鋼板１４の表面には、マーク電極１０に対応した凸状の溶接痕１５が形成される。マーク電極１０の電極面１１に形成した窪み１２は、図７に示すように、スポット溶接により良好にナゲット１３が形成された場合に、鋼板１４の表面に形成される溶接痕１５が最深部１６に到達する所定深さに設定している。このため、スポット溶接により形成されるナゲット１３が不十分な場合には、鋼板１４の表面に形成される溶接痕１５が最深部に到達せず、スポット溶接により良好にナゲット１３が形成された場合には、鋼板１４の表面に形成される溶接痕１５が最深部に到達する。斯かる窪み１２の深さは、予め基礎実験を行うことにより、斯かる機能を奏するのに適切な深さを見出して設定するとよい。   That is, when spot welding is performed using such a mark electrode 10, convex welding marks 15 corresponding to the mark electrode 10 are formed on the surface of the steel plate 14 as shown in FIG. 7. As shown in FIG. 7, the depression 12 formed on the electrode surface 11 of the mark electrode 10 has a weld mark 15 formed on the surface of the steel plate 14 when the nugget 13 is satisfactorily formed by spot welding. Is set to a predetermined depth to reach. For this reason, when the nugget 13 formed by spot welding is insufficient, the welding mark 15 formed on the surface of the steel plate 14 does not reach the deepest portion, and the nugget 13 is formed favorably by spot welding. The welding mark 15 formed on the surface of the steel plate 14 reaches the deepest part. The depth of the recess 12 may be set by finding a suitable depth for performing such a function by conducting a basic experiment in advance.

ナゲット１３の形成は、重ね合わせる金属体の材質や厚さ、重ね合わせる数、電極の形状、電流、通電時間、加圧力などの条件により変わる。基礎実験では、例えば、これらの条件を変えながら、スポット溶接を行い、タガネ検査等の個別破壊計測により良好にナゲット７が形成される場合の溶接痕１５の高さを見出し、マーク電極１０の電極面１１の中心部に形成する窪み１２について適切な深さを見出すとよい。   The formation of the nugget 13 varies depending on conditions such as the material and thickness of the metal body to be overlaid, the number to be overlaid, the shape of the electrode, the current, the energization time, and the applied pressure. In the basic experiment, for example, spot welding is performed while changing these conditions, and the height of the weld mark 15 is found when the nugget 7 is formed satisfactorily by individual fracture measurement such as chisel inspection. An appropriate depth may be found for the recess 12 formed in the center of the surface 11.

また、この実施形態では、マーク電極１０の電極面１１に形成する窪み１２は、図６（ａ）に示すように、窪み１２の周縁部にＲを付けて、電極面１１から滑らかに窪ませている。これにより、スポット溶接の際、マーク電極１０の窪みに沿って、鋼板１４の表面が滑らかに隆起していき、通電面積（電極の接触面積）が急激に変化した場合に生じる散り（溶融金属が飛び散る現象）を防止することができる。このように散りが生じにくい構造を採用することにより、通電する電流値を大きくすることが可能になり、スポット溶接を良好に行うことができる。   In this embodiment, the recess 12 formed on the electrode surface 11 of the mark electrode 10 is smoothly recessed from the electrode surface 11 by adding an R to the peripheral edge of the recess 12 as shown in FIG. ing. As a result, during spot welding, the surface of the steel plate 14 rises smoothly along the depressions of the mark electrode 10, and scattering (molten metal is generated when the current-carrying area (electrode contact area) changes abruptly. (Spattering phenomenon) can be prevented. By adopting such a structure in which scattering does not easily occur, it is possible to increase the current value to be energized and to perform spot welding satisfactorily.

また、マーク電極１０は窪み１２の最深部１６にマーカーを設けてもよい。マーク電極１０は窪み１２の最深部にマーカーを設けることにより、溶接痕１５の頂部に、マーカーに対応したマークが形成されたか否かで、スポット溶接の良否を判定することができるので、スポット溶接の良否判定が容易になる。   The mark electrode 10 may be provided with a marker at the deepest portion 16 of the recess 12. Since the mark electrode 10 is provided with a marker at the deepest portion of the depression 12, the quality of spot welding can be determined based on whether or not a mark corresponding to the marker is formed on the top of the welding mark 15. It becomes easy to determine whether the product is good or bad.

例えば、図６（ａ）（ｂ）に示すマーク電極１０は、窪み１２の最深部１６にマーカーとして平坦面１７を形成している。この場合、図７に示すように、溶接痕１５の頂部に、マーク電極１０の窪み１２に形成したマーカーとしての平坦面１７に対応した平坦面１８が形成されたか否かで、スポット溶接の良否を判定することができる。   For example, the mark electrode 10 shown in FIGS. 6A and 6B has a flat surface 17 as a marker at the deepest portion 16 of the recess 12. In this case, as shown in FIG. 7, whether or not the spot welding is good depends on whether or not the flat surface 18 corresponding to the flat surface 17 as the marker formed in the depression 12 of the mark electrode 10 is formed on the top of the welding mark 15. Can be determined.

また、マーカーは、図８に示すように、凸起２１で形成してもよい。この場合、図９に示すように、溶接痕１５の頂部に、マーカーとしての凸起２１に対応した凹み２２が形成されたか否かで、スポット溶接の良否を判定することできる。   Moreover, you may form a marker by the protrusion 21, as shown in FIG. In this case, as shown in FIG. 9, whether or not the spot welding is good can be determined based on whether or not the recess 22 corresponding to the protrusion 21 as the marker is formed on the top of the welding mark 15.

また、マーカーは、図１０に示すように、凹み２３で形成してもよい。この場合、図１１に示すように、溶接痕１５の頂部に、マーカーとしての凹み２３に対応した凸起２４が形成されたか否かで、スポット溶接の良否を判定することができる。   Moreover, you may form a marker by the dent 23, as shown in FIG. In this case, as shown in FIG. 11, whether or not the spot welding is good can be determined based on whether or not the protrusion 24 corresponding to the recess 23 as the marker is formed on the top of the welding mark 15.

図６（ａ）、図８、図１０に示すようにマーク電極１０の窪み１２にマーカー１７、２１、２３を設けることにより、図７、図９、図１１に示すように溶接痕１５の頂部に対応するマーク１８、２２、２４が形成されるので、スポット溶接の良否判定が容易になる。スポット溶接の良否判定は、作業者の目視で行ってもよいが、溶接痕の形状をＣＣＤカメラなどの撮影装置で撮影し、コンピュータによる画像処理により、形状マッチングを行って判定するようにしてもよい。この際、図６、図８、図１０に示すようなマーカー１７、２１、２３を設けることにより、図７、図９、図１１に示すように溶接痕１５の頂部に対応するマーク１８、２２、２４が形成されるので、コンピュータによる画像処理により、形状マッチングを行って判定をする場合においても、画像処理においてマーク１８、２２、２４を識別すればよく、画像処理が比較的容易になり、スポット溶接の良否判定の精度を向上させることができる。   By providing the markers 17, 21, and 23 in the recess 12 of the mark electrode 10 as shown in FIGS. 6 (a), 8 and 10, the top of the weld mark 15 as shown in FIGS. Since marks 18, 22, and 24 corresponding to are formed, it is easy to determine whether or not spot welding is good. The quality of spot welding may be judged visually by the operator, but the shape of the welding mark is photographed with a photographing device such as a CCD camera, and shape matching is performed by image processing by a computer. Good. At this time, by providing markers 17, 21, and 23 as shown in FIGS. 6, 8, and 10, marks 18 and 22 corresponding to the top of the weld mark 15 as shown in FIGS. , 24 are formed, it is sufficient to identify the marks 18, 22, and 24 in image processing even when shape matching is performed by image processing by a computer, and image processing becomes relatively easy. The accuracy of the spot welding quality determination can be improved.

以下、本発明者らが行った一実施例を説明する。本発明者らは、図７に示すように、ＳＰＣ５９０、厚さ１．２ｍｍの鋼板１４ａ、１４ｂを２枚重ね、これを上下一対の電極１０、２０で挟み、４００ｋｇｆで加圧し、１６cycleで通電した場合に、溶接電流値と、ナゲット径の関係を調べた。上下一対の電極１０、２０は、一方にマーク電極１０を用い、他方に通常の電極２０を用いている。   Hereinafter, an embodiment performed by the present inventors will be described. As shown in FIG. 7, the present inventors stacked two sheets of SPC590 and 1.2 mm thick steel plates 14a and 14b, sandwiched between a pair of upper and lower electrodes 10 and 20, pressurized with 400 kgf, and energized with 16 cycles. In this case, the relationship between the welding current value and the nugget diameter was examined. The pair of upper and lower electrodes 10 and 20 uses the mark electrode 10 on one side and the normal electrode 20 on the other side.

通常の電極２０には、図１２（ｂ）に示すように、直径が１６ｍｍの電極で、先端の周縁部をＲ８の曲面とし、先端の中央部を直径１０ｍｍの領域をＲ１５の曲面として電極面２１を形成したものを用いた。マーク電極１０は、図１２（ａ）に示すように、直径が１６ｍｍの電極で、先端の周縁部をＲ８の曲面とし、先端の中央部を直径１０ｍｍの領域をＲ１５の曲面として電極面１１を形成している。マーク電極１０の電極面１１の中央部には、直径６．２ｍｍの領域に窪み１２を形成している。窪み１２の中央部に形成される最深部１６は、マーカーとして、深さを１．４ｍｍ、直径２．０ｍｍの平坦面１７を形成している。窪み１２は、窪み１２の周縁部および最深部１６の平坦面１７に掛けて、Ｒを付けて電極面１１から全体として滑らかに窪ませている。   As shown in FIG. 12B, the normal electrode 20 is an electrode having a diameter of 16 mm, a peripheral edge portion of the tip having an R8 curved surface, and a central portion of the tip having a diameter of 10 mm having an R15 curved surface. 21 was used. As shown in FIG. 12A, the mark electrode 10 is an electrode having a diameter of 16 mm, the peripheral edge portion of the tip is a curved surface of R8, the central portion of the tip is a curved surface of R15, and the electrode surface 11 is a curved surface of R15. Forming. In the center of the electrode surface 11 of the mark electrode 10, a recess 12 is formed in a region having a diameter of 6.2 mm. The deepest portion 16 formed at the center of the depression 12 forms a flat surface 17 having a depth of 1.4 mm and a diameter of 2.0 mm as a marker. The recess 12 is hung on the peripheral surface of the recess 12 and the flat surface 17 of the deepest portion 16, and is smoothly recessed as a whole from the electrode surface 11 with an R.

試験は、上記の条件で、溶接電流値を変えて、スポット溶接を行い、切断検査などの個別破壊計測によりナゲット径を調べた。斯かる試験による溶接電流値とナゲット径との関係を図１３に示す。図１３中、黒抜きのプロット点ａは溶接痕の頂部にマーカー１７に対応したマークが形成できなかったものであり、白抜きのプロット点ｂは溶接痕の頂部にマーカー１７に対応したマークが形成されたものである。黒抜きプロット点ａではナゲット径も小さく、良好なスポット溶接とは言えない程度であるが、白抜きプロット点ｂでは、ナゲット径も十分に大きく良好なスポット溶接と言える。なお、白抜き星印のプロット点ｃは、溶接中にチリが発生したものであり、溶接電流値が高過ぎたものと考えられる。   In the test, spot welding was performed by changing the welding current value under the above conditions, and the nugget diameter was examined by individual fracture measurement such as cutting inspection. FIG. 13 shows the relationship between the welding current value and the nugget diameter according to such a test. In FIG. 13, a black plot point a is a mark corresponding to the marker 17 on the top of the welding trace, and a white plot point b is a mark corresponding to the marker 17 on the top of the welding trace. It is formed. The black plot point a has a small nugget diameter and cannot be said to be good spot welding, but the white plot point b has a sufficiently large nugget diameter and can be said to be good spot welding. In addition, it is thought that the plot point c of a white star is a thing which dust generate | occur | produced during welding and the welding current value was too high.

また、この試験では、上下一対の電極にそれぞれ通常の電極２０を用いる場合に比べて、少なくとも一方の電極に上記のマーク電極１０を用いてスポット溶接を行う場合には、チリやスパッタが発生する条件が緩和されることがわかった。すなわち、マーク電極１０は、電極面１１の中央部に電極面１１から滑らかに窪んだ窪み１２が形成されているので、通電初期の接触面積が円形で接触面積が稼げる点、および、通電が開始され、鋼板１４が加熱されて表面が軟化されるとそれに応じて接触面積が増えていく。このためスポット溶接における散りやスパッタの発生も極めて低いレベルに抑えることができると考えられる。このように上記のマーク電極１０を用いると、チリやスパッタが発生しにくくなるので、溶接電流値を高く設定でき、溶接電流値を高く設定することにより良好なナゲットが形成され、良好なスポット溶接が行える。   Also, in this test, dust and spatter are generated when spot welding is performed using the mark electrode 10 on at least one of the electrodes as compared with the case where the normal electrode 20 is used for each of the pair of upper and lower electrodes. It was found that the conditions were relaxed. That is, since the mark electrode 10 has a recess 12 that is smoothly recessed from the electrode surface 11 at the center of the electrode surface 11, the contact area at the initial stage of energization is circular and the contact area can be increased, and energization is started. When the steel plate 14 is heated and the surface is softened, the contact area increases accordingly. For this reason, it is considered that the occurrence of scattering and spatter in spot welding can be suppressed to an extremely low level. When the mark electrode 10 is used in this way, dust and spatter are less likely to occur, so that the welding current value can be set high, and by setting the welding current value high, a good nugget is formed and good spot welding is performed. Can be done.

以上、本発明の一実施形態に係るスポット溶接方法およびスポット溶接の良否判定用電極を説明したが、本発明に係るスポット溶接方法およびスポット溶接の良否判定用電極は上記の実施形態に限定されない。   The spot welding method and spot welding quality determination electrode according to an embodiment of the present invention have been described above, but the spot welding method and spot welding quality determination electrode according to the present invention are not limited to the above-described embodiment.

例えば、マーク電極の窪みの最深部に形成するマーカーは上述した実施形態で例示したものに限定されず、他の形態を採用することができる。また、本発明に係るスポット溶接方法およびスポット溶接の良否判定用電極は、ダイレクトスポット溶接、インダイレクトスポット溶接、シリーズスポット溶接など、種々のスポット溶接に適用することができる。   For example, the marker formed in the deepest part of the depression of the mark electrode is not limited to those exemplified in the above-described embodiment, and other forms can be adopted. In addition, the spot welding method and the spot welding quality determination electrode according to the present invention can be applied to various spot weldings such as direct spot welding, indirect spot welding, and series spot welding.

電極面に窪みを形成した電極を用いてスポット溶接を行う基礎実験を示す概略図。Schematic which shows the basic experiment which performs spot welding using the electrode which formed the hollow in the electrode surface. 凸状の溶接痕の縦断面図。The longitudinal cross-sectional view of a convex welding trace. スポット溶接により形成される凸部の高さとナゲット径との相関関係の一例を示す図である。It is a figure which shows an example of the correlation with the height of the convex part formed by spot welding, and a nugget diameter. スポット溶接により形成される凸部の高さと引張せん断強度（ＴＳＳ）との相関関係の一例を示す図である。It is a figure which shows an example of the correlation of the height of the convex part formed by spot welding, and tensile shear strength (TSS). ナゲット径と引張せん断強度（ＴＳＳ）との相関関係の一例を示す図である。It is a figure which shows an example of correlation with a nugget diameter and tensile shear strength (TSS). （ａ）は本発明の一実施形態に係るスポット溶接の良否判定用電極を示す部分縦断面図。（ｂ）は本発明の一実施形態に係るスポット溶接の良否判定用電極の底面図。(A) is a fragmentary longitudinal cross-section which shows the electrode for quality determination of the spot welding which concerns on one Embodiment of this invention. (B) is a bottom view of the electrode for quality determination of spot welding according to an embodiment of the present invention. スポット溶接において凸状の溶接痕が形成される状態を示す図。The figure which shows the state in which a convex welding trace is formed in spot welding. 本発明の他の実施形態に係るスポット溶接の良否判定用電極を示す部分縦断面図。The fragmentary longitudinal cross-section which shows the electrode for quality determination of spot welding which concerns on other embodiment of this invention. 図８に示すスポット溶接の良否判定用電極を用いて形成された凸状の溶接痕を示す縦断面図。The longitudinal cross-sectional view which shows the convex welding trace formed using the electrode for quality determination of the spot welding shown in FIG. 本発明の他の実施形態に係るスポット溶接の良否判定用電極を示す部分縦断面図。The fragmentary longitudinal cross-section which shows the electrode for quality determination of spot welding which concerns on other embodiment of this invention. 図１０に示すスポット溶接の良否判定用電極を用いて形成された凸状の溶接痕を示す縦断面図。The longitudinal cross-sectional view which shows the convex-shaped welding trace formed using the electrode for quality determination of the spot welding shown in FIG. 一実施例の試験で用いた上下一対の電極を示す縦断面図であり、（ａ）はマーク電極を示し、（ｂ）は通常の電極を示す。It is a longitudinal cross-sectional view which shows a pair of upper and lower electrodes used by the test of one Example, (a) shows a mark electrode, (b) shows a normal electrode. 一実施例の試験で得られた溶接電流値とナゲット径との関係を示す図。The figure which shows the relationship between the welding current value obtained by the test of one Example, and the nugget diameter.

符号の説明Explanation of symbols

１０ マーク電極（スポット溶接の良否判定用電極）
１１ 電極面
１３ ナゲット
１４ 鋼板（金属体）
１５ 溶接痕
１６ 最深部
１７ 平坦面（マーカー）
１８ 平坦面（マーク）
２０ スポット溶接用電極
２１ 凸起（マーカー）
２２ 窪み（マーク）
２３ 窪み（マーカー）
２４ 凸起（マーク）

10 Mark electrode (spot welding quality determination electrode)
11 Electrode surface 13 Nugget 14 Steel sheet (metal body)
15 Weld mark 16 Deepest part 17 Flat surface (marker)
18 Flat surface (mark)
20 Spot welding electrode 21 Protrusion (marker)
22 depression (mark)
23 depression (marker)
24 Projection (mark)

Claims (6)

スポット溶接を行う少なくとも一方の電極に、電極面が略凸曲面で、かつ、電極面中心部に、スポット溶接により良好にナゲットが形成された場合に、金属体表面に形成される溶接痕が最深部に到達する所定深さに設定した窪みを形成した電極を用い、
スポット溶接を行い、スポット溶接により前記窪みに対応して金属体表面に形成された溶接痕の形状に基づいてスポット溶接の良否を判定することを特徴とするスポット溶接方法。 When at least one of the electrodes to be spot welded has a substantially convex curved electrode surface and a good nugget is formed by spot welding at the center of the electrode surface, the weld mark formed on the surface of the metal body is the deepest. Using an electrode formed with a recess set to a predetermined depth to reach the part,
A spot welding method characterized in that spot welding is performed, and whether or not the spot welding is good or bad is determined based on the shape of a welding mark formed on the surface of the metal body corresponding to the depression by spot welding. 前記少なくとも一方の電極の電極面中心部に形成される窪みは最深部にマーカーが形成されており、前記溶接痕の頂部に前記マーカーに対応したマークが形成されたか否かで、スポット溶接の良否を判定することを特徴とする請求項１に記載のスポット溶接方法。   The depression formed at the center of the electrode surface of the at least one electrode has a marker formed at the deepest portion, and whether or not the mark corresponding to the marker is formed at the top of the welding mark, whether or not spot welding is good The spot welding method according to claim 1, wherein: 電極面が略凸曲面で、かつ、電極面中心部に、スポット溶接により良好にナゲットが形成された場合に、金属体表面に形成される溶接痕が最深部に到達する所定深さに設定した窪みを形成したことを特徴とするスポット溶接用電極。   When the electrode surface is a substantially convex curved surface and the nugget is well formed by spot welding at the center of the electrode surface, the welding mark formed on the surface of the metal body is set to a predetermined depth that reaches the deepest part. An electrode for spot welding, wherein a recess is formed. 前記窪みの最深部にマーカーを設けたことを特徴とする請求項３に記載のスポット溶接の良否判定電極。   The spot welding quality determination electrode according to claim 3, wherein a marker is provided at a deepest portion of the recess. 前記マーカーは、平坦面で形成したことを特徴とする請求項４に記載のスポット溶接用電極。   The spot welding electrode according to claim 4, wherein the marker is a flat surface. 前記電極面に形成する窪みは、窪みの周縁部にＲを付けて、電極面から滑らかに窪ませたことを特徴とする請求項３に記載のスポット溶接用電極。

4. The spot welding electrode according to claim 3, wherein the recess formed in the electrode surface is smoothly recessed from the electrode surface by adding an R to the peripheral edge of the recess.

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