JP6516247B2 - One side spot welding method - Google Patents

One side spot welding method Download PDF

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JP6516247B2
JP6516247B2 JP2014240010A JP2014240010A JP6516247B2 JP 6516247 B2 JP6516247 B2 JP 6516247B2 JP 2014240010 A JP2014240010 A JP 2014240010A JP 2014240010 A JP2014240010 A JP 2014240010A JP 6516247 B2 JP6516247 B2 JP 6516247B2
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metal plate
nugget
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JP2016101591A (en
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雅裕 石出
雅裕 石出
吉野 鋭
鋭 吉野
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Daihatsu Motor Co Ltd
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本発明は、片側スポット溶接方法に関する。   The present invention relates to a one-sided spot welding method.

片側スポット溶接は、金属板の両側に電極を挟み込むように配置する必要がなく、従来に比べて溶接箇所の制限が緩和され、設計の自由度が高まる等の利点を有することから、例えば複雑な三次元形状の板組みを有する自動車ボデー用鋼板の接合に適用されている。   One-sided spot welding does not have to be arranged so as to sandwich the electrode on both sides of the metal plate, and has the advantages of being less restricted in the welding position and more freedom of design compared to the prior art. It is applied to the joining of the steel plate for motor vehicles body which has a plate assembly of three-dimensional shape.

片側スポット溶接は、ダイレクトスポット溶接のように重ね合わせた複数の金属板を一対の電極で挟み込むわけではないため、溶接作業中に溶接電極と金属板との接触状態が変化し、通電状態も変化するのが一般的である。そのため、この種のスポット溶接においては、溶接電極による金属板への加圧力、通電量(電流値)を多段階で変化させて、所定サイズのナゲットを得るべく最適な溶接条件を設定することが検討されている(例えば、特許文献1を参照)。   In one-side spot welding, a plurality of stacked metal plates are not sandwiched between a pair of electrodes as in direct spot welding, so the contact state between the welding electrode and the metal plate changes during the welding operation, and the electrification state also changes It is common to do. Therefore, in this type of spot welding, it is necessary to set optimum welding conditions to obtain a nugget of a predetermined size by changing the pressure applied to the metal plate by the welding electrode and the amount of current flow (current value) in multiple steps. It is examined (for example, refer patent document 1).

その一方で、ナゲット形成を目的した片側スポット溶接は、非常に大きな入熱量及び加圧力を必要とする場合が少なくない。そのため、ナゲットを形成する場合と比べて低い電流値及び加圧力で済む、固相接合を利用した片側スポット溶接が提案されている(例えば、特許文献2)。   On the other hand, single-sided spot welding aimed at nugget formation often requires very large heat input and pressure. Therefore, one-side spot welding using solid phase bonding has been proposed which requires a lower current value and pressure than that in the case of forming a nugget (for example, Patent Document 2).

特開2013−193095号公報JP, 2013-193095, A 特開2011−31266号公報JP 2011-31266 A

片側スポット溶接における溶接条件は、通常、重ね合わせた金属板同士が密着している、あるいは加圧により密着することを前提としたものであるから、溶接箇所に相応の大きさの板隙(金属板間に生じる板厚方向の隙間)が存在した状態では溶接電極の直下にナゲットを形成することが難しい。片側スポット溶接では、溶接に用いられる電極(例えば溶接電極と給電用電極)が互いに金属板の平面方向に離隔した位置に配置されるので、板隙がある場合、溶接電極と接触する側の金属板を平面方向に沿って流れ易くなるためである。   The welding conditions in one-sided spot welding are usually based on the premise that the stacked metal plates are in close contact with each other or in close contact with pressure. It is difficult to form a nugget immediately below the welding electrode in a state where there is a gap in the plate thickness direction that occurs between the plates. In one-side spot welding, the electrodes used for welding (for example, the welding electrode and the feeding electrode) are arranged at positions separated from each other in the planar direction of the metal plate, so if there is a plate gap, the metal on the side that contacts the welding electrode It is because it becomes easy to flow a board along a plane direction.

例えば特許文献1のように、第一段階(通電初期段階)で加圧力を高めて金属板同士を密着させるようにすれば板隙は解消するようにも思われるが、片側スポット溶接では、金属板の一方側からのみ加圧力を付与することになるため当該板がたわみ易く、またあまりに大きくたわむと形状精度の低下の原因となる。以上の理由から、加圧力を高めるのにも限界がある。   For example, as in Patent Document 1, if the pressure is increased in the first stage (the initial stage of energization) to cause the metal plates to adhere to each other, it seems that the plate gap is eliminated. Since the pressing force is applied only from one side of the plate, the plate is easily bent, and when it is bent too much, it causes a decrease in shape accuracy. For the above reasons, there is a limit to increasing the pressure.

例えば通電量(電流値の大きさ)を大きくして、溶接電極に接触する金属板を加熱により軟化させて板隙を詰める方法も考えられるが、単に電流値を大きくするだけでは、金属板と溶接電極との接触部が過剰に加熱されて、溶け落ちや溶着の原因となるため、板隙を詰めるための方法として適切とはいえない。   For example, it is conceivable to increase the amount of current (magnitude of the current value) and soften the metal plate in contact with the welding electrode by heating to close the gap, but simply increasing the current value Since the contact portion with the welding electrode is excessively heated, which causes melting and welding, it is not suitable as a method for filling the gap.

例えば特許文献2に記載の如き接合態様とすれば、金属板間に溶融凝固部となるナゲットを形成せずに済むため、それほど高い電流値を必要とせずに済むメリットがある。しかしながら、この場合でも、電極を金属板に押込んで金属板同士を密着変形させる必要があるため、板隙に対するロバスト性を確保することは難しい。また、固相拡散接合の良否は当然に被接合材(金属板)の表面状態にも左右されるため、強度の安定性をより重視するのであれば、ナゲットを形成することによる接合が望ましい。   For example, if it is set as a joining aspect as described in patent document 2, since it is not necessary to form the nugget which becomes a fusion | melting solidification part between metal plates, there exists a merit which does not need a very high electric current value. However, even in this case, since it is necessary to press the electrodes into the metal plate to closely deform the metal plates, it is difficult to secure robustness to the plate gap. In addition, since the quality of solid phase diffusion bonding naturally depends on the surface condition of the material to be bonded (metal plate), if strength stability is more important, bonding by forming nuggets is desirable.

以上の事情に鑑み、本発明により解決すべき課題は、溶接電極の直下に板隙が存在する場合であっても、有効な大きさのナゲットを安定的に形成することのできる片側スポット溶接方法を提供することにある。   In view of the above circumstances, the problem to be solved by the present invention is a single-side spot welding method capable of stably forming an nugget of effective size even when a plate gap exists immediately below a welding electrode. To provide.

前記課題の解決は、本発明に係る片側スポット溶接方法によって達成される。すなわち、この溶接方法は、重ね合わせた2枚の金属板のうち一方の金属板の側にのみ溶接電極を配置して行う片側スポット溶接方法であって、一方の金属板の溶接電極との接触部の周囲における電気抵抗が、接触部の直下で一方の金属板から他方の金属板に跨って電流が流れる際の電気抵抗よりも大きくなるよう、通電により一方の金属板を加熱する加熱ステップと、加熱ステップの時よりも大きな電流で通電することで、接触部の直下に他方の金属板に跨って形成されるナゲットを形成するナゲット形成ステップとを備えた点をもって特徴付けられる。   The solution to the above problems is achieved by the one-sided spot welding method according to the present invention. That is, this welding method is a one-side spot welding method performed by arranging the welding electrode only on the side of one of the two stacked metal plates, and the one metal plate is in contact with the welding electrode Heating the one metal plate by energization so that the electric resistance in the periphery of the part becomes larger than the electric resistance when current flows from one metal plate to the other metal plate directly under the contact part The method is characterized by including a nugget forming step of forming a nugget formed across the other metal plate immediately below the contact portion by energizing with a current larger than that of the heating step.

このように、本発明によれば、ナゲットの形成に先立って、一方の金属板の溶接電極との接触部の周囲における電気抵抗よりも、接触部の直下で他方の金属板に跨って電流が流れる際の電気低抗を相対的に小さくすることができる。これにより、溶接電極から他の電極(例えば給電用電極)までの通電経路を、溶接電極の直下で一方の金属板から他方の金属板を跨ぐ方向に誘導して、ナゲット形成に有効な通電状態を作り出すことができる。よって、電流値を過度に高めることなくナゲットを形成することができ、これにより溶け落ち等を生じることなく有効なサイズのナゲットを安定的に得ることが可能となる。   As described above, according to the present invention, prior to the formation of the nugget, the electric current across the other metal plate immediately below the contact portion is greater than the electric resistance around the contact portion of one metal plate with the welding electrode. The electrical resistance when flowing can be made relatively small. As a result, the conduction path from the welding electrode to the other electrode (for example, a feeding electrode) is induced in a direction straddling the other metal plate from the one metal plate directly below the welding electrode, and the conduction state effective for nugget formation Can be produced. Therefore, the nuggets can be formed without excessively increasing the current value, which makes it possible to stably obtain nuggets of effective size without causing burn-out and the like.

また、本発明では、ナゲット形成に先立って溶接電極と接触する側(一方)の金属板を優先的に加熱するようにしたので、一方の金属板のみを軟化させることができる。これにより、例えば溶接電極の直下に板隙が存在する場合であっても、主に一方の金属板を溶接電極の先端形状に倣って変形させて、他方の金属板との板隙を詰めることができる。よって、溶接電極による一方の金属板への加圧力をそれほど高めずとも金属板同士を密着させて、比較的容易にナゲットを形成することができる。従って、板隙に起因するロバスト性の向上を図って、安定した接合強度を得ることが可能となる。   Further, in the present invention, since the metal plate on the side (one side) in contact with the welding electrode is preferentially heated prior to nugget formation, only one metal plate can be softened. Thus, for example, even when there is a space just below the welding electrode, mainly one metal plate is deformed according to the tip shape of the welding electrode to close the space with the other metal plate. Can. Thus, the nuggets can be formed relatively easily by bringing the metal plates into close contact with each other without significantly increasing the pressure applied to the one metal plate by the welding electrode. Therefore, it is possible to obtain stable bond strength by improving robustness due to the plate gap.

また、本発明によれば、上述の如く、加圧力をそれほど高めずとも金属板同士を確実に密着させることができるので、片側からの加圧による金属板(板組み)の形状精度の低下を軽減することが可能となる。   Further, according to the present invention, as described above, the metal plates can be reliably adhered to each other without increasing the pressure so much, so that the shape accuracy of the metal plate (plate assembly) due to the pressure from one side is reduced. It is possible to reduce.

以上のように、本発明によれば、溶接電極の直下に板隙が存在する場合であっても、有効な大きさのナゲットを安定的に形成することができる。   As described above, according to the present invention, it is possible to stably form a nugget having an effective size even when a plate gap exists immediately below a welding electrode.

本発明の一実施形態に係る片側スポット溶接方法の概要を説明するための金属板の要部断面図であって、通電開始前の状態を示す要部断面図である。It is principal part sectional drawing of the metal plate for demonstrating the outline | summary of the one side spot welding method which concerns on one Embodiment of this invention, Comprising: It is principal part sectional drawing which shows the state before an electricity supply start. 図1に示す金属板に通電を開始した直後の状態を示す要部断面図である。It is principal part sectional drawing which shows the state immediately after starting electricity supply to the metal plate shown in FIG. 図1に示す金属板同士が接触した際の状態を示す要部断面図である。It is principal part sectional drawing which shows the state at the time of metal plates shown in FIG. 1 contacting. 図1に示す金属板にナゲットが形成された直後の状態を示す要部断面図である。It is principal part sectional drawing which shows the state immediately after nugget is formed in the metal plate shown in FIG. 図4に示すナゲットが成長した際の状態を示す要部断面図である。It is principal part sectional drawing which shows the state at the time of the nugget shown in FIG. 4 having grown. 図1〜図5に係る通電期間中の電流値の変動を示すグラフである。It is a graph which shows the fluctuation | variation of the electric current value in the electricity supply period which concerns on FIGS. 1-5.

以下、本発明の一実施形態に係る片側スポット溶接方法を図面に基づき説明する。     Hereinafter, the one side spot welding method concerning one embodiment of the present invention is explained based on a drawing.

この溶接方法は、図1に示すように、相互に重ね合わせた2枚の金属板1,2のうち一方(図1でいえば上側)の金属板1の側に溶接電極3を配置して行う片側スポット溶接方法である。本実施形態では、1個の溶接電極3を一方の金属板1の側に配置すると共に、給電用電極4を、他方の金属板2の側でかつ溶接電極3と各金属板1,2の平面方向に離隔した位置に配置した状態で、溶接電極3を一方の金属板1に押し当てながら通電することで、金属板1,2間に後述するナゲット5(図5等を参照)を形成するものである。なお、図1に示すように、先にナゲット5が形成されている箇所がある場合、このナゲット5が直下に位置するように、給電用電極4を配置するようにしてもよい。   In this welding method, as shown in FIG. 1, the welding electrode 3 is disposed on the side of the metal plate 1 of one (the upper side in FIG. 1) of the two metal plates 1 and 2 stacked on each other. It is the one side spot welding method to carry out. In the present embodiment, one welding electrode 3 is disposed on the side of one metal plate 1, and the feeding electrode 4 is disposed on the other metal plate 2 side of the welding electrode 3 and each of the metal plates 1 and 2. With the welding electrodes 3 being pressed against one of the metal plates 1 while being arranged at positions separated in the planar direction, a nugget 5 (see FIG. 5 etc.) described later is formed between the metal plates 1 and 2 It is Note that, as shown in FIG. 1, when there is a portion where the nugget 5 is formed first, the power supply electrode 4 may be arranged such that the nugget 5 is positioned immediately below.

ここで、溶接電極3はその先端(図1でいえば下側)に向かうにつれて縮径する形状をなすもので、本実施形態では、テーパ状に縮径するテーパ面3aと、テーパ面3aとその小径側で連続し、略平坦な形状をなす先端面3bとを一体的に有する。   Here, the welding electrode 3 has a shape in which the diameter decreases toward the tip (in FIG. 1, the lower side in FIG. 1). In the present embodiment, the tapered surface 3a having a tapered diameter and the tapered surface 3a It has a tip surface 3b which is continuous on its small diameter side and has a substantially flat shape.

本発明に係る片側スポット溶接方法は、上記形状の溶接電極3で一方の金属板1を加圧しながら給電用電極4との間で通電することで、一方の金属板1を加熱する加熱ステップ(S1)と、加熱ステップ(S1)の時よりも大きな電流で通電することで、金属板1,2間にナゲット5を形成するナゲット形成ステップ(S2)と、ナゲット形成ステップ(S2)の時よりも小さな電流で通電することで、ナゲット5を成長させるナゲット成長ステップ(S3)とを備える。以下、各ステップの詳細を説明する。   In the one-sided spot welding method according to the present invention, a heating step of heating one metal plate 1 by energizing one of the metal plates 1 with the feeding electrode 4 while pressing the one metal plate 1 with the welding electrode 3 of the above shape By applying a current larger than that in the heating step (S1) and the heating step (S1), the nugget forming step (S2) for forming the nugget 5 between the metal plates 1 and 2 and the nugget forming step (S2) A nugget growth step (S3) for growing the nugget 5 by energizing with a small current. The details of each step will be described below.

(S1)加熱ステップ
まず、図1に示す状態から、溶接電極3を一方の金属板1に押し当てると共に、他方の金属板2に当接させた状態の給電用電極4との間で通電を開始する(図2)。なお、本実施形態において、通電を開始した時点では、一方の金属板1と溶接電極3との接触部1aの直下に、板厚方向の隙間、いわゆる板隙6が存在している。
(S1) Heating Step First, from the state shown in FIG. 1, while pressing welding electrode 3 against one metal plate 1 and supplying electricity to the feeding electrode 4 in a state of being in contact with the other metal plate 2 Start (Figure 2). In the present embodiment, at the time when the energization is started, a gap in the thickness direction, that is, a so-called plate gap 6 is present immediately below the contact portion 1 a between the one metal plate 1 and the welding electrode 3.

この通電による一方の金属板1の加熱は、一方の金属板1の溶接電極3との接触部1aの周囲における電気抵抗が、接触部1aの直下で一方の金属板1から他方の金属板2に跨って電流が流れる際の電気抵抗よりも大きくなるまで継続される。すなわち、上記加熱により、接触部1aの周囲には、発光している状態が視認できる程度の加熱領域7が発生し(図2)、通電を継続することで、加熱領域7が一方の金属板1の平面方向に拡大する(図3)。   The heating of the one metal plate 1 by this energization is such that the electric resistance around the contact portion 1a of the one metal plate 1 with the welding electrode 3 is lower than the one metal plate 1 directly below the contact portion 1a. It continues until it becomes larger than the electrical resistance at the time of the current flowing across. That is, the heating generates a heating area 7 around the contact portion 1a such that the light emitting state can be visually recognized (FIG. 2), and the heating area 7 is one metal plate by continuing the energization. Expand in the plane direction of 1 (Fig. 3).

ここで、金属は、通常、温度上昇に伴ってその電気抵抗(固有抵抗ともいう)が上昇する特性を有し、特に自動車用ボデーに用いられることの多い鋼は、アルミニウムや銅などの金属に比べて温度上昇に伴う電気抵抗の上昇度合いが高い。よって、上述のように加熱領域7においては、加熱領域7の更に外径側の領域(いわば一方の金属板1の加熱領域7以外の領域)よりも電気抵抗が高まる。その一方で、溶接電極3から離れた側の金属板(他方の金属板2)は、板隙6が存在する場合には特に顕著であるが、一方の金属板1ほど加熱されることはない。通電は主に一方の金属板1の平面方向に沿って生じるためである。これにより溶接電極3の直下においては、一方の金属板1と他方の金属板2との間で明確な温度差、ひいては電気抵抗の差が生じる。以上の理由より、一方の金属板1の溶接電極3との接触部1aの周囲における電気抵抗が、接触部1aの直下で一方の金属板1から他方の金属板2に跨って電流が流れる際の電気抵抗よりも大きくなる。言い換えると、金属板1,2間に跨って電流が流れる際の電気抵抗が、接触部1aの周囲における電気抵抗よりも相対的に小さくなる。これにより、通電開始初期においては、一方の金属板1を平面方向に沿って流れていた電流が、接触部1aの直下に向けて流れ易い状態に変化する。   Here, the metal usually has a characteristic that its electrical resistance (also called specific resistance) increases with the temperature rise, and in particular, steels often used for automobile bodies are metals such as aluminum and copper. In comparison, the degree of increase in electrical resistance with temperature rise is high. Therefore, as described above, in the heating area 7, the electrical resistance is higher than the area on the further outer diameter side of the heating area 7 (in other words, the area other than the heating area 7 of one metal plate 1). On the other hand, the metal plate on the side away from the welding electrode 3 (the other metal plate 2) is particularly remarkable when the plate gap 6 exists, but it is not heated as much as one metal plate 1 . The energization is mainly generated along the planar direction of one metal plate 1. As a result, immediately below the welding electrode 3, a clear temperature difference, and hence a difference in electric resistance, occurs between one metal plate 1 and the other metal plate 2. From the above reasons, when the electric resistance in the vicinity of the contact portion 1a of the one metal plate 1 with the welding electrode 3 flows from one metal plate 1 to the other metal plate 2 directly below the contact portion 1a. Higher than the electrical resistance of the In other words, the electrical resistance when current flows across the metal plates 1 and 2 is relatively smaller than the electrical resistance around the contact portion 1a. As a result, in the initial stage of the start of energization, the current flowing through the one metal plate 1 along the planar direction changes to a state in which it easily flows directly under the contact portion 1a.

また、この際、主に一方の金属板1が通電により加熱されることにより、その加熱領域7が軟化し、溶接電極3の先端形状に倣って変形する。これにより、他方の金属板1との間の板隙6が詰められ、接触部1aの直下において、一方の金属板1と他方の金属板2とが当接する(図3)。これにより、接触部1aの直下において一方の金属板1から他方の金属板2に跨って流れるための電流経路が確立される。   At this time, the heating area 7 is softened mainly by heating one of the metal plates 1 by energization, so that the shape is deformed according to the shape of the tip of the welding electrode 3. As a result, the space 6 between the other metal plate 1 is filled, and one metal plate 1 and the other metal plate 2 come into contact with each other immediately below the contact portion 1a (FIG. 3). Thereby, a current path for flowing across one metal plate 1 to the other metal plate 2 immediately below the contact portion 1a is established.

上述の如き電気抵抗の変動をもたらすための手段として、通電条件の調整がある。ここで、加熱ステップ(S1)時の電流値C1は、従来の片側ステップ溶接時の電流値と比べて小さく設定され、かつ、その通電時間T1は、従来の片側ステップ溶接時の通電時間、ここでは通電開始時からナゲット形成時までの時間に比べて長い。定性的に述べるとすれば、少なくとも上述した電流経路の変化が生じるような電気抵抗の差を作り出し得る程度の加熱量が得られ、かつ溶け落ちや溶着が生じない程度に加熱ステップ(S1)中の電流値C1や総加熱量を調整することが肝要である。具体的な電流値C1の大きさ及び通電時間T1は、板組み、特に一方の金属板1の板厚や材質によっても変動するので一概に特定することは難しいが、例を挙げるとすれば、一方の金属板1の板厚が0.5mm以上でかつ1.5mm以下であり、材質が軟鋼である場合、電流値C1を1.5kA以上でかつ3.5kA以下、好ましくは2.0kA以上でかつ3.0kA以下に設定するのがよい。また、通電時間T1に関しては、0.2sec以上でかつ0.5sec以下、好ましくは0.3sec以上でかつ0.4secに設定するのがよい。なお、上述の例であれば、加熱領域7の温度は凡そ700度以上でかつ溶け落ちを確実に防ぐことができる温度(例えば1000度程度)以下となる。   As a means to bring about the above-mentioned change of electric resistance, there is adjustment of energization conditions. Here, the current value C1 at the heating step (S1) is set smaller than the current value at the conventional one-side step welding, and the conduction time T1 thereof is the conduction time at the conventional one-side step welding, In this case, it is longer than the time from the start of energization to the time of nugget formation. Qualitatively speaking, at least a heating amount sufficient to create the difference in electric resistance that causes the change in the current path mentioned above is obtained, and during the heating step (S1) to the extent that melting or welding does not occur. It is important to adjust the current value C1 and the total heating amount of the Although the specific magnitude of the current value C1 and the current application time T1 vary depending on the plate assembly, particularly the thickness and material of one of the metal plates 1, it is difficult to specify uniquely, but to give an example, When the thickness of one metal plate 1 is 0.5 mm or more and 1.5 mm or less and the material is mild steel, the current value C1 is 1.5 kA or more and 3.5 kA or less, preferably 2.0 kA or more And should be set to 3.0 kA or less. Further, with regard to the energization time T1, it is preferable to set to 0.2 sec or more and 0.5 sec or less, preferably 0.3 sec or more and 0.4 sec. In the above example, the temperature of the heating area 7 is about 700 ° C. or more and not more than the temperature (for example, about 1000 ° C.) that can reliably prevent the burnout.

(S2)ナゲット形成ステップ
上述のように一方の金属板1を加熱した後、電流値C2を加熱ステップ(S1)時の電流値C1よりも高めて、一方の金属板1から他方の金属板2に向けて板厚方向に電流を流す。これにより、一方の金属板1の溶接電極3との接触部1aの直下であって、一方の金属板1と他方の金属板2とに跨るようにナゲット5(あるいはナゲット5の核となる部分)が形成される(図4)。
(S2) Nugget formation step After heating one metal plate 1 as described above, the current value C2 is made higher than the current value C1 at the heating step (S1), and from one metal plate 1 to the other metal plate 2 Pass current in the direction of the plate thickness. Thereby, the nugget 5 (or a portion which becomes the nucleus of the nugget 5 so as to straddle the one metal plate 1 and the other metal plate 2 immediately under the contact portion 1 a of the one metal plate 1 with the welding electrode 3. ) Is formed (FIG. 4).

なお、この際の通電条件に関しても、定性的に述べるとすれば、少なくとも金属板1,2間にナゲット5を形成可能な程度の加熱量が得られ、かつ溶け落ちや溶着が生じない程度にナゲット形成ステップ(S2)中の電流値C2や総加熱量を調整することが肝要である。また、具体的な電流値C2は、板組みに関する上述の例でいえば、3.5kA以上でかつ10kA以下に設定するのがよく、好ましくは5.0kA以上でかつ7.0kA以下に設定するのがよい。また、通電時間T2は、0.1sec以上でかつ溶け落ちや板切れの誘発を確実に回避することができる時間(例えば0.2〜0.3sec)以下に設定するのがよい。   In addition, also regarding the current-carrying conditions at this time, if qualitatively stated, a heating amount sufficient to form nugget 5 between at least metal plates 1 and 2 is obtained, and burn-off and welding do not occur. It is important to adjust the current value C2 and the total heating amount during the nugget formation step (S2). Further, in the above-mentioned example of the plate assembly, the specific current value C2 is preferably set to 3.5 kA or more and 10 kA or less, preferably 5.0 kA or more and 7.0 kA or less That's good. In addition, it is preferable to set the current application time T2 to 0.1 sec or more and a time (for example, 0.2 to 0.3 sec) or less at which induction of burn-out and plate breakage can be reliably avoided.

(S3)ナゲット成長ステップ
上述のようにナゲット5を形成した後、電流値C3を加熱ステップ(S1)時の電流値C1よりも高く、かつナゲット形成ステップ(S2)時の電流値C2よりも低くして(図6)、引き続き通電を行う。これにより、一方の金属板1の溶接電極3との接触部1aの直下に形成されたナゲット5を成長させる。これにより所定サイズのナゲット径を有するナゲット5が得られる(図5)。
(S3) Nugget growth step After forming the nugget 5 as described above, the current value C3 is higher than the current value C1 at the heating step (S1) and lower than the current value C2 at the nugget formation step (S2) Then (Fig. 6), the power is continued. Thereby, the nugget 5 formed immediately below the contact portion 1 a of the one metal plate 1 with the welding electrode 3 is grown. As a result, a nugget 5 having a nugget diameter of a predetermined size is obtained (FIG. 5).

このように、本発明では、加熱ステップ(S1)において、一方の金属板1の溶接電極3との接触部1aの周囲(加熱領域7)における電気抵抗が、接触部1aの直下で一方の金属板1から他方の金属板2に跨って電流が流れる際の電気抵抗よりも大きくなるよう、通電により一方の金属板1を加熱するようにした。これによれば、ナゲット5の形成に先立って、一方の金属板1の溶接電極3との接触部1aの周囲における電気抵抗よりも、接触部1aの直下で他方の金属板2に跨って電流が流れる際の電気低抗を相対的に小さくすることができる。これにより、溶接電極3から給電用電極4への通電経路を、一方の金属板1から他方の金属板2を跨ぐ方向に誘導して(図3)、ナゲット5の形成に有効な通電状態を作り出すことができる。よって、電流値C1を過度に高めることなくナゲット5を形成することができ、これにより溶け落ち等を生じることなく有効なサイズのナゲット5を安定的に得ることが可能となる。   Thus, in the present invention, in the heating step (S1), the electric resistance in the periphery (heating area 7) of the contact portion 1a of the one metal plate 1 with the welding electrode 3 is one metal immediately below the contact portion 1a. One metal plate 1 was heated by energization so as to be larger than the electric resistance when current flows across the plate 1 and the other metal plate 2. According to this, prior to the formation of the nugget 5, the electric current immediately under the contact portion 1a and straddling the other metal plate 2 is higher than the electric resistance around the contact portion 1a with the welding electrode 3 of one metal plate 1 When the current flows, the electrical resistance can be made relatively small. As a result, the conduction path from the welding electrode 3 to the feeding electrode 4 is induced in the direction crossing the one metal plate 1 to the other metal plate 2 (FIG. 3), and the conduction state effective for forming the nugget 5 is Can be produced. Therefore, the nugget 5 can be formed without excessively increasing the current value C1, and it is possible to stably obtain the nugget 5 of an effective size without causing burn-out and the like.

また、本発明では、ナゲット5の形成に先立って溶接電極3と接触する側(一方)の金属板1を優先的に加熱するようにしたので、一方の金属板1のみを軟化させることができる。これにより、例えば溶接電極3の直下に板隙6が存在する場合であっても、主に一方の金属板1を溶接電極3の先端形状に倣って変形させて、他方の金属板2との板隙6を詰めることができる。よって、溶接電極3による一方の金属板1への加圧力をそれほど高めずとも金属板1,2同士を密着させて、比較的容易にナゲット5を形成することができる。従って、板隙6に起因するロバスト性の向上を図ることができる。言い換えると、板隙6の有無に関係なく、さらにいえば板隙6の大小に関係なく、安定した接合強度を得ることが可能となる。なお、板組みに係る上述の例でいえば、溶接電極3による一方の金属板1への加圧力Fを98N以上でかつ245N以下に設定した場合であっても、有効なサイズのナゲット5を形成することができる。   Further, in the present invention, since the metal plate 1 on the side (one side) in contact with the welding electrode 3 is preferentially heated prior to the formation of the nugget 5, only one metal plate 1 can be softened. . Thereby, even if, for example, the plate gap 6 exists immediately below the welding electrode 3, mainly one metal plate 1 is deformed according to the tip shape of the welding electrode 3, and the other metal plate 2 The gap 6 can be packed. Thus, the nuggets 5 can be formed relatively easily by bringing the metal plates 1 and 2 into close contact without increasing the pressure applied to the one metal plate 1 by the welding electrode 3 so much. Therefore, the robustness due to the plate gap 6 can be improved. In other words, it is possible to obtain a stable bonding strength regardless of the presence or absence of the plate gap 6, and more specifically, regardless of the size of the plate gap 6. In the above example of the plate assembly, the nugget 5 having an effective size is obtained even when the pressure F applied to one metal plate 1 by the welding electrode 3 is set to 98 N or more and 245 N or less. It can be formed.

特に、本実施形態によれば、先端に向けてテーパ状に縮径した形状をなす溶接電極3で一方の金属板1を加圧しながら通電するようにしたので、加熱に伴う軟化により溶接電極3の先端形状に倣って変形した一方の金属板1の加熱領域7を、比較的容易に点接触あるいはこれに準じた態様で他方の金属板2と接触させることができる(図3)。これにより、金属板1,2間を流れる電流密度を高めて、さらに低い電流値でもってナゲット5を形成することが可能となる。一例として、上述した溶接条件下で発明者らが行った実験によれば、溶接電極3直下における一方の金属板1と他方の金属板2との界面相当位置を中心にナゲット5が形成され、かつ成長していることが試験片断面の観察より確認された。   In particular, according to the present embodiment, since one metal plate 1 is energized while being pressed by the welding electrode 3 having a tapered diameter toward the tip, the welding electrode 3 is softened by heating. The heating area 7 of one of the metal plates 1 deformed according to the tip shape of can be brought into contact with the other metal plate 2 relatively easily in a point contact manner or a similar manner (FIG. 3). As a result, the current density flowing between the metal plates 1 and 2 can be increased, and the nugget 5 can be formed with a lower current value. As an example, according to the experiment conducted by the inventors under the above-described welding conditions, the nugget 5 is formed around the position corresponding to the interface between one metal plate 1 and the other metal plate 2 directly below the welding electrode 3 And it was confirmed from the observation of the cross section of the test piece that it was growing.

また、本発明によれば、上述の如く、加圧力をそれほど高めずとも金属板1,2同士を確実に密着させることができるので、片側からの加圧による金属板1,2(板組み)の形状精度の低下を軽減することが可能となる。   Further, according to the present invention, as described above, since the metal plates 1 and 2 can be reliably adhered without increasing the pressing force so much, the metal plates 1 and 2 (plate assembly) by pressure from one side It is possible to reduce the decrease in the shape accuracy of the

以上、本発明の一実施形態を説明したが、本発明に係る片側スポット溶接方法は上記例示の形態に限定されることなく、本発明の範囲内において任意の形態を採り得ることはもちろんである。   As mentioned above, although one Embodiment of this invention was described, it is needless to say that the one side spot welding method which concerns on this invention can take arbitrary forms within the scope of the present invention, without being limited to the form of the said illustration. .

例えば上記実施形態では、一方の金属板1の側に溶接電極3を配置し、他方の金属板2の側に給電用電極4を配置して通電を行う場合を例示したが、もちろん、これ以外の構成を採ることも可能である。例えば図示は省略するが、一方の金属板1の側に2個の溶接電極を当該金属板1の平面方向に離隔して配置し、これらの電極間で通電を行う場合など、溶接電極3と接触する側からのみ加圧し、その反対側では支持のない状態(中空状態)で通電を行うスポット溶接である限りにおいて、本発明を適用することが可能である。   For example, in the above embodiment, the welding electrode 3 is disposed on the side of one metal plate 1 and the feeding electrode 4 is disposed on the side of the other metal plate 2 to conduct electricity. Of course, other than this It is also possible to adopt the structure of For example, although not shown, two welding electrodes are arranged on the side of one metal plate 1 separately in the plane direction of the metal plate 1, and when conducting electricity between these electrodes, etc. The present invention can be applied as long as spot welding is performed by applying pressure only from the side that contacts and the other side with no support (hollow state).

また上記実施形態では、溶接電極3の例として、テーパ状に縮径した形状をなすものを使用した場合を挙げたが、もちろんこれ以外の形状をなす溶接電極3を使用することも可能である。例えば先端をR形状としたものなど、先端に向かうにつれて縮径する形状の電極を溶接電極3として使用することがかのうである。   Moreover, in the said embodiment, although the case where the thing which made the shape which carried out the diameter reduction in taper shape was used was mentioned as an example of the welding electrode 3, of course, it is also possible to use the welding electrode 3 which makes shapes other than this. . For example, it is possible to use, as the welding electrode 3, an electrode whose diameter decreases toward the tip, such as the tip having an R-shape.

また、以上の説明では、溶接対象となる金属板の例として軟鋼を挙げたが、もちろん、これ以外の鋼、例えばハイテン材(340MPa以上)や超ハイテン材(980MPa以上)を含む板組みに対しても本発明を適用可能である。   Also, in the above description, mild steel was mentioned as an example of a metal plate to be welded, but of course, other plate steels, such as high tensile materials (340 MPa or more) and super high tension materials (980 MPa or more) Even the present invention is applicable.

また、以上の説明では、2枚の金属板を重ね合わせてなる板組みに対して片側スポット溶接を施す場合を例示したが、もちろん、3枚以上の金属板を重ね合わせてなる板組みに対して本発明に係る片側スポット溶接を施すことも可能である。この場合、厚み方向一端側に位置する第一の金属板の側に溶接電極を配置し、この溶接電極との間で通電を行う他の電極(給電用電極又はもう一方の溶接電極)を厚み方向他端側に位置する第二の金属板の側に配置して本発明に係る片側スポット溶接を施すことが可能である。ここで、第一の金属板を本発明における一方の金属板とした場合、この第一の金属板と隣り合う金属板が本発明における他方の金属板となる。もちろん、3枚以上の金属板に跨ってナゲット5を形成できるのであれば、ナゲット5が形成される最も厚み方向他端側に位置する金属板が他方の金属板となる。   Moreover, although the case where one-side spot welding is performed with respect to the plate assembly formed by superposing two metal plates was illustrated in the above description, of course, with respect to the plate assembly formed by superposing three or more metal plates. It is also possible to apply one-sided spot welding according to the invention. In this case, the welding electrode is disposed on the side of the first metal plate located at one end side in the thickness direction, and the other electrode (the feeding electrode or the other welding electrode) to be energized with the welding electrode is thick It is possible to arrange on the side of the second metal plate located on the other end side of the direction to perform one-side spot welding according to the present invention. Here, when the first metal plate is one metal plate in the present invention, the metal plate adjacent to the first metal plate is the other metal plate in the present invention. Of course, if the nugget 5 can be formed across three or more metal plates, the metal plate located at the other end in the thickness direction where the nugget 5 is formed is the other metal plate.

1,2 金属板
1a 接触部
3 溶接電極
4 給電用電極
5 ナゲット
6 板隙
7 加熱領域
C1 加熱ステップにおける電流値
C2 ナゲット形成ステップにおける電流値
C3 ナゲット成長ステップにおける電流値
T1 加熱ステップにおける通電時間
T2 ナゲット形成ステップにおける通電時間
T3 ナゲット成長ステップにおける通電時間
1, 2 metal plate 1a contact portion 3 welding electrode 4 feeding electrode 5 nugget 6 plate gap 7 heating area C1 current value C2 in the heating step current value C3 in the nugget forming step current value C3 in the nugget growth step current value T1 in the heating step conduction time T2 in the heating step Energization time in nugget formation step T3 Energization time in nugget growth step

Claims (1)

重ね合わせた2枚の金属板のうち一方の金属板の側に1個の溶接電極を配置し、他方の金属板の側に1個の給電用電極を配置して行う片側スポット溶接方法であって、
一方の金属板の溶接電極との接触部の直下に板隙があり、板隙から一方の金属板の平面方向に離れた位置に一方の金属板と他方の金属板との密着部がある状態で、一方の金属板の平面方向に沿って溶接電極と給電用電極との間で電流が流れるように通電を開始して、一方の金属板の溶接電極との接触部の周囲における電気抵抗が、接触部の直下で一方の金属板から他方の金属板に跨って電流が流れる際の電気抵抗よりも大きくなるよう、通電により一方の金属板を加熱する加熱ステップと、
加熱ステップの時よりも大きな電流で通電することで、接触部の直下に他方の金属板に跨って形成されるナゲットを形成するナゲット形成ステップとを備えた、
加熱ステップにおける通電時間をナゲット形成ステップにおける通電時間よりも長くして、一方の金属板の溶接電極との接触部の周囲における電気抵抗が、接触部の直下で一方の金属板から他方の金属板に跨って電流が流れる際の電気抵抗よりも大きくなるまで通電を継続することを特徴とする、片側スポット溶接方法。
This is a one-side spot welding method in which one welding electrode is disposed on the side of one of the two stacked metal plates and one of the feeding electrodes is disposed on the other side of the metal plate. ,
There is a plate gap directly below the contact portion of one metal plate with the welding electrode, and a contact portion of one metal plate and the other metal plate at a position away from the plate gap in the planar direction of one metal plate. Then, energization is started so that current flows between the welding electrode and the feeding electrode along the planar direction of one metal plate, and the electric resistance around the contact portion of one metal plate with the welding electrode is A heating step of heating one of the metal plates by energization so as to be larger than the electric resistance when a current flows from one metal plate to the other metal plate directly under the contact portion;
A nugget forming step of forming a nugget formed straddling the other metal plate immediately below the contact portion by energizing with a current larger than that of the heating step.
The electrical resistance time in the heating step is longer than the electrical conduction time in the nugget forming step, and the electrical resistance at the periphery of the contact portion of one metal plate with the welding electrode is determined from the one metal plate to the other metal plate directly below the contact portion. A method of one-side spot welding method , characterized in that energization is continued until it becomes larger than the electric resistance at the time of current flow .
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