JPH02160179A - Slit coil for butt welding - Google Patents

Abstract

PURPOSE:To prevent a crack by a third lip and a fracture at the time of forming by coating specific % coil width per one end toward the central part from both ends in the cross direction of a coil in the longitudinal direction of one side at least of the coil with electrically conductive material with specific thickness. CONSTITUTION:Three to twenty % coil width per one end of the coil is coated with the electrically conductive material 1 with 1-100mum thickness. Steel sheets obtained by cutting the coil in the prescribed length are used to manufacture a wheel rim for an automobile. When the steel sheets are clamped by welding electrodes and subjected to butt welding, since contact resistance is reduced on both ends coated with the electrically conductive material as compared with on the central part, electric current density thereon increases. Since a temperature rise in the cross direction of the steel sheets can be uniformized, the generation of the third lip and a defective shape of the ends are prevented. There are gold plating, silver plating, copper plating, silver powder coating application, etc., as coating of the electrically conductive material. By this method, the shape of a welded zone is uniformized and the crack and fracture are prevented.

Description

【発明の詳細な説明】[Detailed description of the invention]

〔産業上の利用分野Ｊ 本発明は、パット溶接に供される熱延鋼板スリットコイ
ルに関し、さらに詳しくは、パット溶接を行うに際して
溶接部にサードリップや溶接端部の形状不良の発生を防
止するスリットコイルに関する。 〔従来の技術Ｊ 最近、スリットコイルを用いて自動車用ホイールリムを
製造する工程において、従来のフラッシュパット溶接方
法に代わり、パット溶接方法が多用されるようになって
きた。このパット溶接方法は、被溶接材を各々電極でク
ランプし、被溶接材端面同士を突合せ、予め所定の加圧
力（以下アブセット力という）を加えたまま画電極に電
圧を印加して所定の電流を流し被溶接材の固有抵抗と突
合せ面の接触抵抗によるジュール熱によって突合せ面を
加熱軟化させ、軟化部を板厚方向へ押出して溶接する方
法である。パット溶接方法はフラッシュパット溶接方法
に比較すると、処理時間が短時間であり、またフラッシ
ュを生じることもなく安全性が高くまた省エネルギー効
果もあるという利点がある。[Industrial Application Field J] The present invention relates to a hot-rolled steel plate slit coil to be used for pad welding, and more specifically, it is used to prevent the occurrence of third rip in the welded part or defective shape of the welded end when performing pad welding. Regarding slit coils. [Prior Art J] Recently, in the process of manufacturing automobile wheel rims using slit coils, a pad welding method has been frequently used instead of the conventional flash pad welding method. In this pad welding method, each material to be welded is clamped with an electrode, the end surfaces of the materials to be welded are butted together, and a voltage is applied to the picture electrode while applying a predetermined pressure (hereinafter referred to as "abset force") in advance to generate a predetermined current. In this method, the abutting surfaces are heated and softened by Joule heat generated by the specific resistance of the welded material and the contact resistance of the abutting surfaces, and the softened portion is extruded in the thickness direction to perform welding. Compared to the flash pad welding method, the pad welding method has the advantage of short processing time, no flash, high safety, and energy saving effect.

【発明が解決しようとする課題】[Problem to be solved by the invention]

スリットコイルにパット溶接方法を適用すると上述のよ
うな利点がある反面、次のような欠点がある。すなわち
、溶接部の板幅方向の端部から数ｃｍ内側に第２図（第
２図（ａ）は平面図、第２図（ｂ）は第２図（ａ）のＡ
−Ａ断面図である）に示すようなサードリップ２と呼ば
れる非定常部が発生し、ホイールリムに成形される際こ
のサードリップ部が丁度リム断面のコーナ一部付近なる
ことが多く、ヘアクラックと称される溶接面に沿った割
れ目となり、タイヤを装着するときエア漏れを生じるこ
とがある。 また、溶接条件によってはサードリップは生じないもの
の第３図（第３図（ａ）は平面図、第３図（ｂ）は第３
図（ａ）の端°部の断面図である）に示すように溶接端
部が不規則な座屈変形をすることがある。この場合には
リム成形ラインでのサイドカット後の形状不良となりフ
レア加工時にクラックを生じ不良品となる。 ホイールメーカーでは電極の形状の変更、或はｉｌｌ板
の溶接端面形状を変化させるなどの工夫をこらしてこれ
らの防止を試みているが、未だ完全に防止できるパット
溶接用スリットコイルは開発されていない。 本発明は上述の問題点を解決するために提案されたもの
であり、パット溶接を適用しても溶接部にサードリップ
の発生はなく、かつ、溶接端部の形状不良が生じないパ
ット溶接用スリットコイルを提供することを課題とする
ものである。 〔課題を解決するための手段１ 本発明者等はパット溶接方法に右ける溶接条件を種々変
更してサードリップの発生状況および溶接端部形状を詳
細に調査し、以下の新知見を得た。 （１）サードリップの発生位置は薄鋼板の電極クランプ
力によって変化し、クランプ力が大きい時は中央部付近
に発生し、クランプ力が小さい時は端部付近に発生する
。また、電極と薄鋼板の幅方向の接触程度の差によって
も発生する。これは薄鋼板端部がスリットされる際、剪
断変形で押し潰された形状となっており中央部に比較す
ると加圧力で５〜１３％程度低い値となっている。しか
し、電極と薄鋼板はこの端部においても接触を保ってい
る。 （２）サードリップの発生は溶接端面のアブセット力に
依存し、アブセット力が大きい程発生しにくくなる。 （３）アプセット力が大きいとサードリップの発生は抑
制されるが溶接端部で座屈を生じ端部の形状不良が発生
する。 （４）溶接端部のアブセット力は一般に中央部より低い
。 （５）（１）の状態で溶接端面間の接触抵抗の分布と、
電極と１１１ｍ板間の接触抵抗の分布をそれぞれ測定し
た結果、溶接端面間の接触抵抗の不均一さは電極と薄鋼
板間のそれの５％以下であった。 以上の知見に基き更に調査研究の結果、次の結論が得ら
れた。 ■薄鋼板幅方向のクランプ力が不均一な分布により電流
密度が不均一になり僅かにクランプ圧力の高い部分は電
流密度が高（従って、高温部となり、僅かにクランプ圧
力の低い部分は低温部となる。 ■相対的に温度の低い部分と高い部分が隣り合う領域の
高温部にサードリップが発生する。これは、高温部はア
プセット圧力により変形し得るが、低温部は変形抵抗が
高いために変形し難く、従って、低温部の隣り合う領域
の高温部は変形しようとして低温部の高変形抵抗に抑止
され、さらに温度が上昇してしまい遂にサードリップが
発生するものである。 Ｏｉ８接部端部が低温部となる時には両端部は板幅方向
に対しては拘束力のない状態であが、アプセット圧力は
全溶接面に均一に印加されるので。 低温で変形抵抗が高いにも拘らず変形する。ただし、こ
の変形は薄鋼板本来のその温度に右ける変形抵抗以下の
応力下での変形であるので座屈変形となり、不規則な形
状を呈する。 以上の結論から、本発明のスリットコイルは。 次の技術手段を採った。すなわち、 コイルの少くとも片面の長手方向に、コイルの幅方向両
端部から中心部に向けて片端部当りコイル幅の３〜２０
％にわたり導電材を１〜１ｏ。 μｍの厚さで？１ｌＥｆｌＬだ、。 【作用Ｊ 本発明は、上述のように構成したので、このコイルを所
定の長さに切断した薄鋼板を用いて自動車用ホイールリ
ムを製造する工程で、薄鋼板を溶接電極でクランプして
パット溶接すると、導電材で被覆した両端部は中央部に
比べ接触抵抗が減少するので電流密度が上昇し、板幅方
向の温度上昇を均一にすることができるので、サードリ
ップや端部の形状不良の発生は防止できる。 なお、被覆幅を片端部当り板幅の３〜２０％としたのは
、片端部当り３％未満では、端部の温度上昇は不十分で
あり、片端部当り２０％を超えると端部の温度は上昇し
過ぎるからである。また、波層厚さは、１μｍ未満では
根面の凹凸のために接触抵抗は変化せず、また、１００
μｍを超えると板中央部は電極に接触しなくなることが
ある。 従って、１１層厚さは１〜１１００ｕとした。 なお、本発明で使用した導電材は当然のことながら何れ
も電気抵抗は鉄よりも低いものである。 ［実施例］ 本発明の実施例を図面により説明する。第１図は斜視説
明図であり、板厚２．６　ｍ　ｍ　、板幅２００ｍｍの
スリットコイルの表面長手方向に、コイルの幅方向両端
部から中心部に向けて片端部当りコイル幅の３〜２０％
にわたり導電材ｌを１〜１００μｍの厚さで被覆したも
のである。 このスリットコイルを所定の長さに切断した薄鋼板を第
２表のパット溶接条件で溶接した。第１表は、本発明の
スリットコイルの導電材塗布状況および溶接結果（番号
２〜番号２３（内、番号５と番号１０は限定条件を超え
て導電材ｌを塗布した比較例である））と従来例（番号
ｌ）のスリットコイルの溶接結果を示したものである。 第１表の従来例では、端部は温度が低いために中央部に
比べて変形抵抗が高く、座屈を生じた上にサードリップ
も発生している。 も端部形状は良好でありサードリップも発生しでいない
。 【発明の効果１ 本発明のパット溶接用スリットコイルを使用することに
より、溶接部の形状は均一となり、サードリップによる
クラックや端部形状不良による成形時の割れを防止する
ことが可能となるので、ホイールのエア漏れ防止、ホイ
ールリムの品質向上に優れた効果を奏する。Applying the pad welding method to slit coils has the above-mentioned advantages, but it also has the following disadvantages. In other words, a few centimeters inward from the edge of the welded part in the plate width direction as shown in Fig. 2 (Fig. 2 (a) is a plan view, Fig. 2 (b) is a
- An unsteady part called the third lip 2 as shown in A sectional view) occurs, and when it is formed into a wheel rim, this third lip part is often located just near a corner of the rim cross section, causing hair cracks. This creates cracks along the welded surface, called ``crack'', which can cause air leakage when installing the tire. Also, depending on the welding conditions, third drip may not occur, but as shown in Figure 3 (Figure 3 (a) is a plan view, Figure 3 (b) is a third
As shown in Figure (a), which is a sectional view of the end portion, the welded end portion may undergo irregular buckling deformation. In this case, the shape becomes defective after side cutting on the rim forming line, and cracks occur during flaring, resulting in a defective product. Wheel manufacturers are trying to prevent these problems by changing the shape of the electrode or the shape of the welding end surface of the ill plate, but a slit coil for pad welding that can completely prevent them has not yet been developed. . The present invention was proposed in order to solve the above-mentioned problems, and is a pad welding method that does not cause a third rip in the welded part even when pad welding is applied, and does not cause shape defects at the welded end. An object of the present invention is to provide a slit coil. [Means for Solving the Problem 1 The inventors of the present invention made various changes to the welding conditions that depend on the pad welding method, and investigated in detail the occurrence of third drip and the shape of the weld end, and obtained the following new findings. . (1) The position where the third rip occurs changes depending on the electrode clamping force of the thin steel plate; when the clamping force is large, it occurs near the center, and when the clamping force is small, it occurs near the end. It also occurs due to a difference in the degree of contact between the electrode and the thin steel plate in the width direction. When the end portions of the thin steel plate are slit, they are crushed by shear deformation, and the pressing force is about 5 to 13% lower than that at the center. However, the electrode and the thin steel plate maintain contact even at this end. (2) The occurrence of third rip depends on the offset force on the weld end face, and the greater the offset force, the less likely it is to occur. (3) If the upsetting force is large, the occurrence of third rip is suppressed, but buckling occurs at the welded end, resulting in poor shape of the end. (4) Abset force at the welded end is generally lower than at the center. (5) Distribution of contact resistance between welded end surfaces in the state of (1),
As a result of measuring the distribution of contact resistance between the electrode and the 111m plate, the non-uniformity of the contact resistance between the welded end faces was 5% or less of that between the electrode and the thin steel plate. Based on the above findings, further investigation and research resulted in the following conclusions. ■The current density becomes uneven due to the uneven distribution of clamping force in the width direction of the thin steel plate, and the current density is high in areas where the clamping pressure is slightly high (thus, the areas where the clamping pressure is slightly low are high temperature areas, and the areas where the clamping pressure is slightly low are low temperature areas. ■Third drip occurs in the high temperature area where relatively low and high temperature areas are adjacent.This is because the high temperature area can be deformed by upset pressure, but the low temperature area has high deformation resistance. Therefore, the high-temperature portion in the area adjacent to the low-temperature portion attempts to deform but is restrained by the high deformation resistance of the low-temperature portion, causing the temperature to rise further and finally causing third drip. When the edge becomes a low-temperature part, there is no restraining force in the width direction of the plate at both ends, but the upset pressure is applied uniformly to the entire welding surface. Despite the high deformation resistance at low temperatures. However, since this deformation occurs under stress that is lower than the original deformation resistance of the thin steel sheet depending on its temperature, it becomes buckling deformation and takes on an irregular shape.From the above conclusion, it is clear that the present invention For the slit coil, the following technical measures were adopted: In the longitudinal direction of at least one side of the coil, from both ends in the width direction of the coil toward the center, 3 to 20 mm of the coil width per one end was used.
% of conductive material from 1 to 1o. With a thickness of μm? It's 1lEflL. [Function J] Since the present invention is configured as described above, in the process of manufacturing an automobile wheel rim using a thin steel plate obtained by cutting this coil into a predetermined length, the thin steel plate is clamped with a welding electrode and put on a pad. When welding, the contact resistance at both ends coated with a conductive material decreases compared to the center, increasing the current density and making the temperature rise uniform in the width direction of the plate, which eliminates third lips and poor shape at the ends. can be prevented from occurring. The reason why the covering width is set to 3 to 20% of the board width per one end is because if it is less than 3% per one end, the temperature rise at the end is insufficient, and if it exceeds 20% per one end, the temperature at the end will increase. This is because the temperature will rise too much. Furthermore, when the wave layer thickness is less than 1 μm, the contact resistance does not change due to the unevenness of the root surface;
If it exceeds μm, the central part of the plate may not come into contact with the electrode. Therefore, the thickness of the 11 layers was set to 1 to 1100 u. Note that, as a matter of course, all of the conductive materials used in the present invention have electrical resistance lower than that of iron. [Example] An example of the present invention will be described with reference to the drawings. FIG. 1 is a perspective explanatory view, in which the surface of a slit coil with a plate thickness of 2.6 mm and a plate width of 200 mm is measured in the longitudinal direction from both ends of the coil in the width direction toward the center. 20%
The conductive material 1 is coated with a thickness of 1 to 100 μm. A thin steel plate obtained by cutting this slit coil into a predetermined length was welded under the pad welding conditions shown in Table 2. Table 1 shows the conductive material application status and welding results of the slit coil of the present invention (numbers 2 to 23 (of which, numbers 5 and 10 are comparative examples in which the conductive material l was applied beyond the limiting conditions)) This figure shows the welding results of the slit coil of the conventional example (number 1). In the conventional example shown in Table 1, the end portions have a higher deformation resistance than the center portion due to the lower temperature, causing buckling and third lip. The end shape is also good and no third drip occurs. [Effect of the invention 1] By using the slit coil for pad welding of the present invention, the shape of the welded part becomes uniform, and it is possible to prevent cracks due to third lip and cracks during forming due to poor end shape. , has excellent effects on preventing wheel air leaks and improving the quality of wheel rims.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明の一実施例の斜視説明図、第２図はサー
ドリップの説明図であり、第２図（ａ）は平面図、第２
図（ｂ）は第２図（ａ）のＡ−Ａ断面図、第３図は端部
座屈の説明図であり、第３図（ａ）は平面図、第３図（
ｂ）は第３図（ａ）の端部の断面図である。FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is an explanatory view of a third lip, and FIG. 2(a) is a plan view, and FIG.
Figure (b) is a sectional view taken along the line A-A in Figure 2 (a), Figure 3 is an explanatory diagram of end buckling, Figure 3 (a) is a plan view, Figure 3 (
b) is a sectional view of the end of FIG. 3(a).

Claims (1)

【特許請求の範囲】[Claims] １　コイルの少くとも片面の長手方向に、コイルの幅方
向両端部から中心部に向けて片端部当りコイル幅の３〜
２０％にわたり導電材を１〜１００μｍの厚さで被覆し
たことを特徴とするパット溶接用スリットコイル。1. In the longitudinal direction of at least one side of the coil, from both ends in the width direction of the coil toward the center, 3 to 3 of the coil width per one end.
A slit coil for pad welding, characterized in that 20% of the coil is coated with a conductive material at a thickness of 1 to 100 μm.