JP2004074194A

JP2004074194A - Method for ultrasonically joining aluminum material with steel and ultrasonically joined body

Info

Publication number: JP2004074194A
Application number: JP2002235648A
Authority: JP
Inventors: Satoru Iwase; 岩瀬　哲; Shigetomi Morita; 森田　重富; Seiji Sasabe; 笹部　誠二; Tatsuya Asai; 浅井　達也; Yoshihiro Miyake; 三宅　義浩
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2002-08-13
Filing date: 2002-08-13
Publication date: 2004-03-11

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of ultrasonically joining aluminum or aluminum alloy with steel for obtaining stable joining strength without generating any Al-Fe intermetallic compounds on a joining interface and to obtain an ultrasonically joined body. <P>SOLUTION: A galvanized layer 2 of the thickness of 0.3 to 50 μm and the Vickers hardness of ≤190 Hv is formed on a joined surface portion of at least an aluminum alloy 1 on the surface of a steel 3. The joining condition in the ultrasonic joining is set so that the pressure P is 294 to 3,430 N, the amplitude is 20 to 80 μm, the frequency is 10 to 50 kHz, and the joining energy is 200 to 800 J. A zinc diffusion layer is generated on the joining interface thereby. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、アルミニウム又はアルミニウム合金材（以下、総称してアルミニウム合金材という）と、鋼材との異種金属間の超音波接合方法及び超音波接合体に関する。
【０００２】
【従来の技術】
アルミニウム合金材は軽量で美観に優れており、輸送機等の軽量化のための材料として使用されている。なかでも、アルミニウム合金材を強度及び成形性が優れた鋼材とを組合せたハイブリッド構造のものが注目されている。
【０００３】
しかし、アルミニウム合金材と鋼材とを接合する場合、鋼材同士の接合において従来から使用されている各種の溶接技術をそのまま適用することは困難である。例えば、抵抗スポット溶接をアルミニウム合金材と鋼材との接合に適用した場合、アルミニウム合金材は導電性が良いので、加圧、通電後の両材の接合界面に、脆弱な金属間化合物が形成されてしまう。このため、アルミニウム合金材と鋼材との接合部分は界面剥離しやすく、十分な接合品質が得られない。
【０００４】
この抵抗スポット溶接に代わり、超音波接合によりこれらの異種金属を接合する方法が提案されている。超音波接合は、固相接合の一種であり、接合界面に対して、接合界面に垂直の方向の加圧による応力と、接合界面に平行な方向の高い振動加速度による繰返し応力とを与えて接合界面に摩擦発熱を生じさせ、被溶接材の原子の移動を促し、これを拡散させて接合するという接合方法である。例えば、特開２０００―２０２６４３号公報には、鋼材とアルミニウム合金材との接合部に、その接合強度を損なうことなく十分な防錆処理を施すために、鋼材の接合箇所にフラックスを塗布した後、溶融亜鉛メッキを施し、この亜鉛メッキ膜にアルミニウム合金材の接合箇所を当接させて超音波接合するという方法が開示されている。
【０００５】
【発明が解決しようとする課題】
しかしながら、単に、亜鉛メッキ鋼材とアルミニウム合金材とを超音波接合により接合しても、接合界面にＡｌ―Ｆｅ系の金属間化合物が生じてしまうため、接合強度が極めて弱いという問題点がある。
【０００６】
本発明はかかる問題点に鑑みてなされたものであって、接合界面にＡｌ―Ｆｅ系の金属間化合物が生成せず、安定して高い接合強度が得られるアルミニウム系（アルミニウム又はアルミニウム合金）材と鋼材との超音波接合方法及び超音波接合体を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明に係るアルミニウム系材と鋼材との超音波接合方法は、アルミニウム又はアルミニウム合金材と鋼材とを超音波接合する方法において、予め前記鋼材の表面における少なくとも前記アルミニウム又はアルミニウム合金材との接合部に、厚さが０．３乃至５０μｍ、ビッカース硬さが１９０Ｈｖ以下である亜鉛メッキ層を形成した後、加圧力が２９４乃至３４３０Ｎ、振幅が２０乃至８０μｍ、周波数が１０乃至５０ｋＨｚ、接合エネルギが２００乃至８００Ｊの接合条件で超音波接合することを特徴とする。
【０００８】
本発明に係る他のアルミニウム系材と鋼材との超音波接合方法は、アルミニウム又はアルミニウム合金材と鋼材とを超音波接合する方法において、予め前記鋼材の表面における少なくとも前記アルミニウム又はアルミニウム合金材との接合部に、厚さが０．３乃至５０μｍ、ビッカース硬さが１９０Ｈｖ以下である亜鉛箔を配置した後、加圧力が２９４乃至３４３０Ｎ、振幅が２０乃至８０μｍ、周波数が１０乃至５０ｋＨｚ、接合エネルギが２００乃至８００Ｊの接合条件で超音波接合することを特徴とする。
【０００９】
また、本発明に係るアルミニウム系材と鋼材との超音波接合体は、亜鉛メッキ層を形成した鋼材とアルミニウム又はアルミニウム合金材とが前記亜鉛メッキ層を間に挟んで超音波接合により接合された超音波接合体において、前記アルミニウム又はアルミニウム合金材と鋼材との接合部界面に、前記アルミニウム又はアルミニウム合金材側に向けて亜鉛が拡散して形成された亜鉛拡散層が介在していることを特徴とする。
【００１０】
【発明の実施の形態】
以下、本発明の実施の形態について添付の図面を参照して具体的に説明する。本発明者等は、アルミニウム合金材と鋼材とを超音波接合する際に、予めこの鋼材の表面における少なくとも前記アルミニウム合金材との接合部に、亜鉛メッキを施しておき、このときに鋼材の表面に形成させておく亜鉛メッキ層の性状が極めて重要であり、具体的には、メッキ層の厚さを０．３乃至５０μｍに限定し、且つメッキ層の硬さをビツカース硬さで１９０Ｈｖ以下となるようにメッキ処理条件を調節することが、課題解決に必要であることを見出した。これにより、接合界面に脆弱なＦｅ−Ａｌ系金属間化合物が生成されず、しかも接合強度を向上させることができる。
【００１１】
また、超音波接合条件として、被接合材に対する加圧力、超音波の振幅及び周波数並びに接合エネルギの全てについて、適切な範囲に限定した条件下で行うことにより、一層安定した良好な接合強度が得られる。即ち、超音波接合条件の適正な具体的諸元は、加圧力を２９４乃至３４３０Ｎ、振幅を２０乃至８０μｍ、周波数を１０乃至５０ｋＨｚ、そして接合エネルギを２００乃至８００Ｊに設定することが必要である。
【００１２】
図１は、本発明によりアルミニウム合金材と鋼材とを超音波接合するときの超音波接合装置を示す縦断面図である。なお、本発明では、この図１に示すものに限らず、種々の超音波接合装置を使用することができる。図１に示すように、アルミニウム合金材１と、少なくとも接合部の表面に亜鉛メッキ層２が形成されている鋼材３とを、亜鉛メッキ層２を間に挟んで重ね、この積層体４を、水平姿勢に固定して設置されたアンビル６と、水平方向に超音波振動（Ｓ）するホーン５との間に配置する。そして、ホーン５を介して、積層体５に接合面に垂直の加圧力Ｐを印加し、この状態で、ホーン５を水平方向に超音波振動（Ｓ）させて、ホーン５と共に鋼材３を高い振動加速度で超音波振動させる。そうすると、超音波振動する鋼材３と、固定されたアルミニウム合金材１との間に摩擦力による発熱が生じ、接合界面にて、原子の移動が促進され、Ｚｎ原子のアルミニウム合金材１への拡散が生じる。これにより、図２に示すように、鋼材３とアルミニウム合金材１との接合界面にて、亜鉛メッキ層２からアルミニウム合金材１内に向けて亜鉛拡散層８が形成され、アルミニウム合金材１と鋼材３とが固相接合される。
【００１３】
このとき、本発明においては、亜鉛メッキ層２の厚さ及び硬さを所定範囲にすると共に、超音波接合条件を所定条件にしたので、アルミニウム合金材１と鋼材３との接合部において、亜鉛拡散層８が形成するが、脆弱なＦｅ−Ａｌ系の金属間化合物は生成せず、接合強度が高く、安定した異種金属の接合構造となる。
【００１４】
以下に、上述した鋼材３の亜鉛メッキ層２の性状及び超音波接合条件の諸元の限定理由を説明する。
【００１５】
「亜鉛メッキ層２の厚さ：０．３〜５０μｍ」
図１に示したように、予め鋼材３には亜鉛メッキ２を施したうえで、これとアルミニウム合金材１とを超音波接合する。この亜鉛メッキ層を設けないまま超音波接合を施すと、接合時にＡｌ原子又はＡｌとＦｅとの両原子が相互に拡散し、接合界面７でＡｌ−Ｆｅ系の金属間化合物が生成するため、接合強度は極めて低下する。ところが、本発明においては、鋼材３の表面に亜鉛メッキ層２が介在しているので、接合時に亜鉛メッキ層２中のＺｎ原子がアルミニウム合金材１側に拡散し、亜鉛拡散層２を形成する。
【００１６】
このように、亜鉛メッキ層２によって、Ａｌ原子がＦｅ原子側に拡散するのを抑制するため、Ａｌ−Ｆｅ系の脆弱な金属間化合物の生成が抑制される。ところが、この亜鉛メッキ層の厚さが、０．３μｍよりも薄い場合には、上記Ａｌ原子のＦｅ原子側への拡散抑制効果が十分でなく、Ａｌ原子が鋼材３側に拡散してしまうためにＡｌ−Ｆｅ系の金属間化合物が生成してしまう。よって、亜鉛メッキ層の厚さは、０．３μｍ以上を必要とする。しかしながら、亜鉛メッキ層の厚さが、５０μｍよりも厚くなると、接合後にも亜鉛メッキ層２が単体で残存するため、接合部の強度を下げてしまう。従って、亜鉛メッキ層の厚さは０．３〜５０μｍとする。
【００１７】
「亜鉛メッキ層のビツカース硬さ：１９０Ｈｖ以下」
亜鉛メッキ層の硬さは、硬過ぎると塑性変形し難いため、超音波接合時にアルミニウム合金材１との接合界面７における接触馴染みが得られなくなるため、超音波接合ができなくなってしまう。従って、メッキ層の硬度はビツカース硬さで１９０Ｈｖ以下とする。
【００１８】
なお、亜鉛メッキ層２を設ける方法は特に限定する必要はなく、溶融亜鉛メッキ及び電気メッキのいずれの方法でもよい。また、亜鉛メッキ層２は、亜鉛メッキが主要構成成分となっていれば、ニッケル等の金属元素を含んでいてもよい。
【００１９】
「超音波接合の加圧力：２９４乃至３４３０Ｎ」、
「振幅：２０乃至８０μｍ」、
「周波数１０〜５０ｋＨｚ」、且つ、
「接合エネルギ２００〜８００Ｊ」
超音波接合の条件は、接合部の強さを決定する要因であり、上記４要因のうち１つの要因についてであっても、その数値を上記数値よりも低く設定して接合を行うと、接合が十分に行われないために接合強度が十分でない。しかしながら、上記４要因のうち１つの要因についてであっても、その数値を上記数値よりも高く設定して接合を行うと、超音波振動が過大になるため、被接合界面７でアルミニウム系接合材料１側が著しくえぐられて変形してしまう。従って、超音波接合時の超音波接合の加圧力は２９４乃至３４３０Ｎ、超音波の振幅は２０乃至８０μｍ、周波数は１０乃至５０ｋＨｚ、接合エネルギは２００乃至８００Ｊに設定して接合する必要がある。
【００２０】
アルミニウム系被溶接材料１と鋼系被溶接材料３との超音波接合において、鋼系接合材料３の亜鉛メッキ層２の性状及び超音波接合条件の諸元について、上述した条件が全て満たされて接合されたときの接合部断面は、図２に示したように、鋼系被溶接材料３とアルミニウム系接合材料１との被接合界面７からアルミニウム系接合材料１側へのＺｎ原子の拡散層が存在し、強度を低下させるＡｌ−Ｆｅ系の脆弱で粗大な金属間化合物又は金属間化合物層は存在せず、極めて健全な接合部の界面構造が得られる。
【００２１】
【実施例】
次に、本発明の実施例の効果について、本発明の範囲から外れる比較例と比較して説明する。
【００２２】
「試験１」
下記表１に示す亜鉛メッキ層が形成された板厚０．６ｍｍの亜鉛メッキ鋼板及び板厚１．０ｍｍのアルミニウム合金板を、図１に示したと同様に重ねて超音波接合機のホーン５とアンビルとの間にセットし、超音波接合条件は、加圧力を６８６Ｎ、振幅を５０μｍ、周波数を３０ｋＨｚ、そして接合エネルギを５００Ｊに設定して超音波接合を行った。超音波接合後、試験片を採取して引張剪断試験を行い、接合強度を測定すると共に、破断形態を目視で観察した。更に、ＥＰＭＡ（Ｅｌｅｃｔｒｏｎ　Ｐｒｏｖｅ　Ｍｉｃｒｏ　Ａｎａｌｙｚｅｒ）により、接合界面における縦断面のミクロ的界面構造を観察した。下記表２に、この試験結果を示す。
【００２３】
【表１】

【００２４】
【表２】

【００２５】
以上の試験結果より、比較例１は、亜鉛メッキ鋼板のメッキ層の厚さが本発明の下限値０．３μｍより薄かったので、アルミニウム合金板から亜鉛メッキ鋼板側へのＡｌの拡散を抑制することができず、Ａｌ−Ｆｅ系の金属間化合物が接合界面に生成したために、接合界面で破断し、接合強度が小さかった。比較例２は、亜鉛メッキ鋼板のメッキ層の厚さが本発明の上限値５０μｍより厚かったので、接合後にも亜鉛メッキ層が単体で残存したため、接合界面で破断し、接合強度が小さかった。比較例３は、亜鉛メッキ鋼板のメッキ層の硬さが本発明の上限値１９０Ｈｚより硬かったので、超音波接合時に亜鉛メッキ層とアルミニウム合金板とのなじみが悪く、接合が不十分であった。そのために接合界面で破断し、接合強度が小さかった。
【００２６】
これに対して、実施例１乃至６は全て、亜鉛メッキ鋼板のメッキ層の厚さ及び硬さが本発明の条件を満たしていたので、良好な超音波接合が行われ、接合部の強度は大きく、アルミニウム合金材の母材で破断した。
【００２７】
「試験２」
厚さが１０μｍ、硬さが３５Ｈｖの亜鉛メッキ層が形成された板厚０．６ｍｍの亜鉛メッキ鋼板及び板厚１．０ｍｍのアルミニウム合金板を、図１に示したように重ねて、超音波接合機のホーン５とアンビルとの間にセットし、超音波接合条件として、下記表３に示す加圧力、振幅、周波数、及び接合エネルギに設定して超音波接合を行った。超音波接合後、試験片を採取して引張剪断試験を行い、接合強度を測定すると共に、破断形態を目視で観察した。下記表４に、この試験結果を示す。
【００２８】
【表３】

【００２９】
【表４】

【００３０】
以上の試験結果より、実施例７は亜鉛メッキ層の厚さ及び硬さが本発明の条件を満たしていると共に、接合条件が本発明の範囲内で適正であったために、接合部の強度が高く、母材で破断した。これに対し、比較例４は、加圧力が不足しているため、比較例５は加圧力が強すぎたため、比較例６は振幅が小さすぎるため、比較例７は振幅が大きすぎるため、比較例８は振動周波数が小さすぎるため、比較例９は振動周波数が大きすぎるため、比較例１０は接合エネルギが小さすぎるため、比較例１１は接合エネルギが大きすぎるため、いずれも、接合部の強度が低く、接合界面で破断した。また、亜鉛拡散が希薄であったり、工具との摩擦が激しく、アルミニウム材が溶融、排除されて板厚が減少していたり（アルミニウム材排除）、亜鉛メッキ層が残留していた。
【００３１】
【発明の効果】
以上詳述したように、本発明によれば、アルミニウム系材と鋼材との超音波接合において、接合界面にＡｌ―Ｆｅ系の金属間化合物が生成せず、安定した接合強度が得られる。よって、アルミニウム又はアルミニウム合金材料と鋼系材との異種金属同士の接合を、溶接フラックス等の特別な消耗品を使用せずに低コストで行うことができる。
【図面の簡単な説明】
【図１】本発明法によりアルミニウム系材と鋼系材とを超音波接合するときの超音波接合装置を示す縦断面図である。
【図２】亜鉛拡散層がアルミニウム合金材と鋼材との接合界面に形成された界面構造を示す模式的断面図を示す。
【符号の説明】
１：アルミニウム合金材
２：亜鉛メッキ層
３：鋼材
４：積層体
５：ホーン
６：アンビル
８：亜鉛拡散層
Ｐ：加圧力
Ｓ：超音波振動[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic bonding method and an ultrasonic bonded body between aluminum or an aluminum alloy material (hereinafter, collectively referred to as an aluminum alloy material) and a steel, and a dissimilar metal.
[0002]
[Prior art]
Aluminum alloy materials are lightweight and excellent in appearance, and are used as materials for reducing the weight of transport aircraft and the like. Above all, a hybrid structure combining an aluminum alloy material with a steel material having excellent strength and formability has attracted attention.
[0003]
However, when joining an aluminum alloy material and a steel material, it is difficult to directly apply various welding techniques conventionally used in joining steel materials. For example, when resistance spot welding is applied to the joining of an aluminum alloy material and a steel material, since the aluminum alloy material has good conductivity, a fragile intermetallic compound is formed at the joint interface between the two materials after pressing and energizing. Would. For this reason, the joint between the aluminum alloy material and the steel material is easily separated at the interface, and sufficient joining quality cannot be obtained.
[0004]
Instead of the resistance spot welding, a method of joining these dissimilar metals by ultrasonic joining has been proposed. Ultrasonic welding is a type of solid-state welding, in which a stress is applied to a bonding interface in a direction perpendicular to the bonding interface and a repetitive stress is applied to the bonding interface in a direction parallel to the bonding interface due to high vibration acceleration. This is a joining method in which frictional heat is generated at the interface to promote the movement of atoms of the material to be welded, and this is diffused for joining. For example, in Japanese Patent Application Laid-Open No. 2000-202643, after applying a flux to a joint portion of a steel material in order to perform a sufficient rust prevention treatment on a joint portion between a steel material and an aluminum alloy material without impairing the joint strength. A method is disclosed in which hot-dip galvanizing is performed, and a bonding portion of an aluminum alloy material is brought into contact with the galvanized film to perform ultrasonic bonding.
[0005]
[Problems to be solved by the invention]
However, even if the galvanized steel material and the aluminum alloy material are simply joined by ultrasonic joining, there is a problem that the joining strength is extremely weak because an Al—Fe-based intermetallic compound is generated at the joining interface.
[0006]
The present invention has been made in view of such a problem, and does not generate an Al—Fe intermetallic compound at a bonding interface, and an aluminum (aluminum or aluminum alloy) material that can stably obtain a high bonding strength. It is an object of the present invention to provide an ultrasonic bonding method and an ultrasonic bonded body between steel and a steel material.
[0007]
[Means for Solving the Problems]
An ultrasonic bonding method for an aluminum-based material and a steel material according to the present invention is a method for ultrasonically bonding an aluminum or aluminum alloy material and a steel material, wherein a bonding portion between at least the aluminum or aluminum alloy material on a surface of the steel material in advance After forming a galvanized layer having a thickness of 0.3 to 50 μm and a Vickers hardness of 190 Hv or less, a pressing force of 294 to 3430 N, an amplitude of 20 to 80 μm, a frequency of 10 to 50 kHz, and a bonding energy of 200 It is characterized in that ultrasonic bonding is performed under a bonding condition of 800 J to 800 J.
[0008]
Another ultrasonic bonding method between an aluminum-based material and a steel material according to the present invention is a method for ultrasonically bonding an aluminum or aluminum alloy material and a steel material, wherein at least the aluminum or aluminum alloy material on a surface of the steel material is used in advance. After arranging a zinc foil having a thickness of 0.3 to 50 μm and a Vickers hardness of 190 Hv or less on the joining portion, the pressing force is 294 to 3430 N, the amplitude is 20 to 80 μm, the frequency is 10 to 50 kHz, and the joining energy is Ultrasonic bonding is performed under a bonding condition of 200 to 800 J.
[0009]
Further, in the ultrasonic bonded body of the aluminum-based material and the steel material according to the present invention, the steel material having the galvanized layer and the aluminum or aluminum alloy material are bonded by ultrasonic bonding with the galvanized layer interposed therebetween. In the ultrasonic bonded body, a zinc diffusion layer formed by diffusion of zinc toward the aluminum or aluminum alloy material side is interposed at an interface between the aluminum or aluminum alloy material and the steel material. And
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. The present inventors, when ultrasonically joining an aluminum alloy material and a steel material, at least a joint portion of the surface of the steel material with the aluminum alloy material is galvanized, and at this time, the surface of the steel material The properties of the galvanized layer to be formed are extremely important. Specifically, the thickness of the galvanized layer is limited to 0.3 to 50 μm, and the hardness of the plated layer is 190 Hv or less in Vickers hardness. It has been found that it is necessary to adjust the plating treatment conditions so as to achieve the object. Thereby, a fragile Fe-Al-based intermetallic compound is not generated at the bonding interface, and the bonding strength can be improved.
[0011]
Further, as the ultrasonic bonding conditions, the welding force to the material to be bonded, the amplitude and frequency of the ultrasonic wave, and the bonding energy are all performed under conditions limited to appropriate ranges, so that a more stable and good bonding strength can be obtained. Can be That is, appropriate specifics of the ultrasonic bonding conditions include setting the pressing force to 294 to 3430 N, the amplitude to 20 to 80 μm, the frequency to 10 to 50 kHz, and the bonding energy to 200 to 800 J.
[0012]
FIG. 1 is a longitudinal sectional view showing an ultrasonic bonding apparatus when ultrasonic bonding an aluminum alloy material and a steel material according to the present invention. In the present invention, not only the one shown in FIG. 1 but also various ultrasonic bonding apparatuses can be used. As shown in FIG. 1, an aluminum alloy material 1 and a steel material 3 having a galvanized layer 2 formed on at least the surface of a joint are overlapped with the galvanized layer 2 interposed therebetween. It is disposed between an anvil 6 fixedly installed in a horizontal posture and a horn 5 that performs ultrasonic vibration (S) in a horizontal direction. Then, a pressing force P perpendicular to the joint surface is applied to the laminated body 5 through the horn 5, and in this state, the horn 5 is ultrasonically vibrated (S) in the horizontal direction, and the steel material 3 is raised together with the horn 5. Ultrasonic vibration with vibration acceleration. Then, heat is generated by frictional force between the ultrasonically vibrating steel material 3 and the fixed aluminum alloy material 1, and the movement of atoms is promoted at the joint interface, and Zn atoms diffuse into the aluminum alloy material 1. Occurs. Thereby, as shown in FIG. 2, a zinc diffusion layer 8 is formed from the galvanized layer 2 toward the inside of the aluminum alloy material 1 at the joining interface between the steel material 3 and the aluminum alloy material 1, and The steel material 3 is solid-phase bonded.
[0013]
At this time, in the present invention, the thickness and hardness of the galvanized layer 2 are set to predetermined ranges, and the ultrasonic bonding conditions are set to predetermined conditions. Although the diffusion layer 8 is formed, a brittle Fe-Al-based intermetallic compound is not generated, and the bonding strength is high and a stable bonding structure of different metals is obtained.
[0014]
Hereinafter, the reason for limiting the properties of the galvanized layer 2 of the steel material 3 and the specifications of the ultrasonic bonding conditions will be described.
[0015]
"Thickness of zinc plating layer 2: 0.3 to 50 m"
As shown in FIG. 1, after galvanizing 2 is applied to the steel material 3 in advance, the steel material 3 is ultrasonically bonded to the aluminum alloy material 1. If ultrasonic bonding is performed without providing the zinc plating layer, Al atoms or both atoms of Al and Fe are diffused at the time of bonding, and an Al-Fe based intermetallic compound is generated at the bonding interface 7. The joining strength is extremely reduced. However, in the present invention, since the zinc plating layer 2 is interposed on the surface of the steel material 3, Zn atoms in the zinc plating layer 2 diffuse to the aluminum alloy material 1 at the time of joining to form the zinc diffusion layer 2. .
[0016]
As described above, since the zinc plating layer 2 suppresses the diffusion of Al atoms to the Fe atoms, the generation of Al-Fe-based fragile intermetallic compounds is suppressed. However, when the thickness of the galvanized layer is smaller than 0.3 μm, the effect of suppressing the diffusion of the Al atoms to the Fe atoms is not sufficient, and the Al atoms diffuse to the steel material 3 side. Al-Fe-based intermetallic compounds are formed. Therefore, the thickness of the galvanized layer needs to be 0.3 μm or more. However, if the thickness of the galvanized layer is greater than 50 μm, the galvanized layer 2 remains alone after the bonding, and the strength of the bonded portion is reduced. Therefore, the thickness of the galvanized layer is set to 0.3 to 50 μm.
[0017]
"Vickers hardness of galvanized layer: 190Hv or less"
If the hardness of the galvanized layer is too hard, it is difficult to plastically deform, so that contact fitting at the joining interface 7 with the aluminum alloy material 1 at the time of ultrasonic joining cannot be obtained, so that ultrasonic joining cannot be performed. Therefore, the hardness of the plating layer is set to 190 Hv or less in Vickers hardness.
[0018]
The method of providing the galvanized layer 2 is not particularly limited, and may be any of hot-dip galvanizing and electroplating. The zinc plating layer 2 may include a metal element such as nickel if zinc plating is a main component.
[0019]
"Pressing force of ultrasonic bonding: 294 to 3430N",
“Amplitude: 20 to 80 μm”,
"Frequency 10 to 50 kHz" and
"Joint energy 200-800J"
The ultrasonic bonding condition is a factor that determines the strength of the bonded portion. Even if one of the above four factors is set, the value is set lower than the above value and the bonding is performed. Bonding is not performed sufficiently, so that the bonding strength is not sufficient. However, even if one of the above four factors is set and the value is set to be higher than the above value, the ultrasonic vibration becomes excessively large. One side is severely caught and deformed. Therefore, it is necessary to set the welding pressure at 294 to 3430 N, the amplitude of the ultrasonic wave at 20 to 80 μm, the frequency at 10 to 50 kHz, and the bonding energy at 200 to 800 J during the ultrasonic bonding.
[0020]
In the ultrasonic welding of the aluminum-based material 1 and the steel-based material 3, all of the above-mentioned conditions are satisfied for the properties of the galvanized layer 2 of the steel-based material 3 and the ultrasonic bonding conditions. As shown in FIG. 2, the cross section of the joint when joined is a diffusion layer of Zn atoms from an interface 7 to be joined between the steel-based material 3 and the aluminum-based material 1 to the aluminum-based material 1. Is present, and there is no Al-Fe-based brittle and coarse intermetallic compound or intermetallic compound layer that reduces the strength, and an extremely sound interface structure of the joint can be obtained.
[0021]
【Example】
Next, the effect of the embodiment of the present invention will be described in comparison with a comparative example out of the scope of the present invention.
[0022]
"Test 1"
A galvanized steel sheet having a thickness of 0.6 mm and an aluminum alloy sheet having a thickness of 1.0 mm on which a galvanized layer shown in Table 1 below was formed and stacked in the same manner as shown in FIG. Ultrasonic welding was performed by setting the pressure to 686 N, the amplitude to 50 μm, the frequency to 30 kHz, and the welding energy to 500 J. After ultrasonic bonding, a test piece was sampled and subjected to a tensile shear test to measure the bonding strength and visually observe the fracture form. Furthermore, the micro interface structure of the longitudinal section at the joining interface was observed by EPMA (Electron Probe Micro Analyzer). Table 2 below shows the test results.
[0023]
[Table 1]

[0024]
[Table 2]

[0025]
From the above test results, Comparative Example 1 suppresses the diffusion of Al from the aluminum alloy plate to the galvanized steel sheet side because the thickness of the plated layer of the galvanized steel sheet was smaller than the lower limit of 0.3 μm of the present invention. As a result, Al-Fe-based intermetallic compounds were formed at the bonding interface, and were broken at the bonding interface, resulting in low bonding strength. In Comparative Example 2, since the thickness of the plated layer of the galvanized steel sheet was thicker than the upper limit of 50 μm of the present invention, the galvanized layer remained alone even after joining, and was broken at the joining interface, resulting in low joining strength. In Comparative Example 3, since the hardness of the plating layer of the galvanized steel sheet was higher than the upper limit value of 190 Hz of the present invention, the penetration between the galvanized layer and the aluminum alloy plate during ultrasonic bonding was poor, and the bonding was insufficient. . For this reason, it was broken at the bonding interface, and the bonding strength was low.
[0026]
On the other hand, in all of Examples 1 to 6, since the thickness and hardness of the plating layer of the galvanized steel sheet satisfied the conditions of the present invention, good ultrasonic bonding was performed, and the strength of the bonded portion was reduced. Large, fractured in the base material of aluminum alloy material.
[0027]
"Test 2"
As shown in FIG. 1, a zinc-plated steel sheet having a thickness of 10 mm and a galvanized steel sheet having a hardness of 35 Hv and a thickness of 0.6 mm and an aluminum alloy plate having a thickness of 1.0 mm were superposed on each other as shown in FIG. It was set between the horn 5 of the welding machine and the anvil, and the ultrasonic welding was performed by setting the welding force, amplitude, frequency, and welding energy shown in Table 3 below as the ultrasonic welding conditions. After ultrasonic bonding, a test piece was sampled and subjected to a tensile shear test to measure the bonding strength and visually observe the fracture form. Table 4 below shows the test results.
[0028]
[Table 3]

[0029]
[Table 4]

[0030]
From the above test results, in Example 7, the thickness and hardness of the galvanized layer satisfied the conditions of the present invention, and the bonding conditions were appropriate within the scope of the present invention. High and fractured in the base metal. On the other hand, in Comparative Example 4, the pressing force was insufficient, and in Comparative Example 5, the pressing force was too strong. In Comparative Example 6, the amplitude was too small. In Comparative Example 7, the amplitude was too large. The vibration frequency of Example 8 is too low, the vibration frequency of Comparative Example 9 is too high, the bonding energy of Comparative Example 10 is too low, and the bonding energy of Comparative Example 11 is too high. And was broken at the joint interface. In addition, zinc diffusion was low, friction with the tool was severe, and the aluminum material was melted and eliminated to reduce the plate thickness (aluminum material was excluded), or the zinc plating layer remained.
[0031]
【The invention's effect】
As described above in detail, according to the present invention, in the ultrasonic bonding of an aluminum-based material and a steel material, an Al-Fe-based intermetallic compound is not generated at a bonding interface, and a stable bonding strength can be obtained. Therefore, the joining of dissimilar metals between the aluminum or aluminum alloy material and the steel-based material can be performed at low cost without using special consumables such as welding flux.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an ultrasonic bonding apparatus when ultrasonically bonding an aluminum-based material and a steel-based material according to the method of the present invention.
FIG. 2 is a schematic cross-sectional view showing an interface structure in which a zinc diffusion layer is formed at a joint interface between an aluminum alloy material and a steel material.
[Explanation of symbols]
1: Aluminum alloy material 2: Galvanized layer 3: Steel material 4: Laminated body 5: Horn 6: Anvil 8: Zinc diffusion layer P: Pressure S: Ultrasonic vibration

Claims

In the method of ultrasonically bonding an aluminum or aluminum alloy material and a steel material, a thickness of 0.3 to 50 μm and a Vickers hardness of 190 Hv or less are at least previously bonded to the aluminum or aluminum alloy material on the surface of the steel material. After forming a zinc plating layer, an ultrasonic bonding is performed under the bonding conditions of a pressing force of 294 to 3430 N, an amplitude of 20 to 80 μm, a frequency of 10 to 50 kHz, and a bonding energy of 200 to 800 J. Method of ultrasonic bonding between steel and steel.

In the method of ultrasonically bonding an aluminum or aluminum alloy material and a steel material, a thickness of 0.3 to 50 μm and a Vickers hardness of 190 Hv or less are at least previously bonded to the aluminum or aluminum alloy material on the surface of the steel material. After the zinc foil is placed, the aluminum-based material is subjected to ultrasonic bonding under the bonding conditions of a pressing force of 294 to 3430 N, an amplitude of 20 to 80 μm, a frequency of 10 to 50 kHz, and a bonding energy of 200 to 800 J. Ultrasonic bonding method between steel and steel.

In an ultrasonic bonded body in which a steel material having a galvanized layer formed thereon and aluminum or an aluminum alloy material are bonded by ultrasonic bonding with the galvanized layer interposed therebetween, a bonding interface between the aluminum or aluminum alloy material and the steel material And a zinc diffusion layer formed by diffusing zinc toward the aluminum or aluminum alloy material side.