JP4038368B2

JP4038368B2 - Aluminum alloy welded joint

Info

Publication number: JP4038368B2
Application number: JP2001364552A
Authority: JP
Inventors: 正敏吉田; 光弘江間
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2001-11-29
Filing date: 2001-11-29
Publication date: 2008-01-23
Anticipated expiration: 2021-11-29
Also published as: JP2003164990A

Description

【０００１】
【発明の属する技術分野】
本発明はアルミニウム合金溶接接合材であって、溶接接合部 (溶接継手部とも言う) の強度と伸びとが優れたアルミニウム合金溶接接合材 (以下、アルミニウムを単にAlと言う) に関するものである。
【０００２】
【従来の技術】
自動車などの輸送機のパネル類、フレーム類、メンバー類などの部材には、Al合金展伸材 (圧延板材、押出形材、鍛造材などの総称）やAl合金鋳造材（以下、展伸材や鋳造材を総称してAl合金材と言う) を種々組み合わせて溶接接合した構造材が用いられるようになっている。
【０００３】
これら溶接継手乃至溶接継手部を有するAl合金溶接接合材においては、部材の形状や要求特性、あるいは要求製作コストなどに応じて、Al合金材同士の組み合わせ方が適宜選択される。即ち、同じ板材、形材、鍛造材、鋳造材の同士の組み合わせや、違うAl合金材同士の組み合わせが、溶接接合されるAl合金材同士の形状や厚みが違う場合を含めて、適宜選択される。
【０００４】
前記Al合金溶接接合材の中でも、厚みの違う板材同士が接合された接合板材であるテーラードブランク材は、パネル、フレームなどの他の部材の製造過程で発生した種々の端材を再使用できる点や、要求強度や成形性などが部位により異なる部材を、素材の厚みや材質の調整で製作できる点などで利点が大きい。このため、鋼板のテーラードブランク材などは既に自動車などの輸送機で利用されている。
【０００５】
これら成形される接合板材用Al合金としては、従来から溶接構造用Al合金として汎用されるAA乃至JIS 規格に規定される(AA 乃至JIS 規格を満足する)5000 系や、6063、6N01、6061などの6000系 (以下、AA乃至JIS は省略) 、7N01、7003などの7000系などのAl合金材がある。
【０００６】
ただ、この接合板材用Al合金の中でも、熱処理型Al合金である6000系や7000系などのAl合金材は、溶体化処理および焼き入れ処理 (質別記号T4) と、その後の人工時効処理 (質別記号T6) や過時効処理 (質別記号T7) 、あるいは、熱間加工から冷却後の人工時効処理 (質別記号T5) などの調質処理によって、所定の強度を得る。一方、非熱処理型Al合金である5000系Al合金などは、冷間加工などの加工硬化によって所定の強度を得る。
【０００７】
熱処理型Al合金は、前記T4〜T7などの調質処理によって優れた時効硬化性が得られる反面、逆に溶接時には、その接合性（接合強度）が低下するという問題がある。即ち、少なくともいずれかのAl合金材を熱処理型Al合金として溶接接合した場合、溶接時の加熱によって、溶接接合部の近傍乃至周囲に熱影響部 (以下、HAZ とも言う) が必然的に生成する。そして、このHAZ では前記熱影響によって材料が軟化し、他の定常部に比して硬度が著しく低くなる。
【０００８】
溶接継手を有するAl合金接合材の場合、Al合金接合材としての強度は、この熱影響部によって律せられる。このため、熱影響部の硬度低下が生じると、Al合金溶接接合材の強度は大幅に低下することなる。
【０００９】
図6 は、板厚の違う熱処理型の過剰Si型6000系Al合金板同士の溶接接合材を示す。図6 において、溶接接合材1 は、板厚t₂の薄板2 と板厚t₁の厚板3 とを、例えば溶接施工部5 からCO₂レーザーで突き合わせ溶接したものであり、差厚テーラードブランク材でもある。また、図6 において、4 は接合部、6 は薄板2 のHAZ 、7 は厚板3 のHAZ である。
【００１０】
この溶接接合材1 の接合部4 を中心とするビッカース硬度(HV)分布硬度を図7 に示す。図7 において、溶接接合材1 の接合部4 や他の定常部に比して、薄板2 のHAZ6や厚板3 のHAZ7の硬度は、著しく低くなっている。
【００１１】
また、この溶接接合材1 の薄板2 の母材 (定常部) とHAZ6の変形特性 (応力- ひずみ関係) を図8 に示す。この図8 において、前記図7 に示したHAZ の硬度分布低下からも分かる通り、薄板2 のHAZ6の継手強度σ_B-HAZ(MPa) は、定常部の継手強度σ_B(MPa) に比して、著しく低くなっている。したがって、溶接継手を有するAl合金溶接接合材の強度は、最も強度の低い薄板2 のHAZ6の継手強度σ_B-HAZによって律せられる。また、薄板2 のHAZ6が破断する応力が加わった時点での、定常部に生じる伸びδ' は素材の伸びδに大きく劣る。このため、溶接継手を有するAl合金溶接接合材の伸びも、HAZ6の存在により、著しく低下することとなる。
【００１２】
更に、本発明者が知見したところによれば、厚板3 と薄板2 との板厚比(t₁/t₂) が大きくなるほど、継手強度と継手伸びの低下率が大きい。熱処理型Al合金板同士の溶接接合材1 の厚板3 と薄板2 との板厚比(t₁/t₂) が異なる素材を試験片中央部で溶接したJIS5号引張試験片 (標点間距離50mm) の溶接接合材1 の全伸び (εf 、%)の変化を図9 に斜線範囲で示す。この図9 の通り、横軸の厚板3 と薄板2 との板厚比(t₁/t₂) が大きくなるほど全伸びの低下率が大きい。そして、この傾向は、比較のために記載した、5000系などの非熱処理型Al合金板同士の溶接接合材の傾向に比較しても、低下率が著しい。また、この傾向は、全伸びと相関する継手強度においても同様である。
【００１３】
したがって、これらの事実から、熱処理型Al合金を含むAl合金溶接接合材では、HAZ の硬度低下によって、継手強度と継手伸びの低下が著しく、この傾向は継手の厚みの差が大きいほど強くなることが分かる。
【００１４】
この傾向は、特に溶接線が比較的長いか溶接点が連続する、アークなどの熱源を用いる溶融溶接方法、即ち、ティグ(TIG) 、ミグ(MIG) などの高速アーク溶接や、レーザー溶接、電子ビーム溶接、抵抗シーム溶接などで、溶接して継手を形成する際に顕著となる。
【００１５】
更に、本発明者らが知見したところによれば、この傾向は、溶接接合部が比較的高温にならない接合方法である、摩擦攪拌接合(FSW) 方法においても生じる。非熱処理型の5000系のAl合金の場合には、FSW や溶融溶接方法において、前記溶接継手効率の著しい低下は生じない。
【００１６】
このように、熱処理型のAl合金溶接接合材では、溶接の熱影響による強度の低下と伸び (破断伸び) の低下が生じる。このような場合、特にテーラードブランク材として、溶接継手部を含む板材をプレス成形などの成形加工する場合には、その伸びの低下により、成形時に加わった引張などの応力によって、前記HAZ で破断し、成形および製品化ができない。また、溶接後に成形加工を受けないAl合金溶接接合材でも、例えば、衝突などの応力負荷時の大きな変形を考慮すれば、前記破断伸びの低下を原因として、構造部材としての耐久性あるいはクラッシャブル性などの機能が発揮できないことにつながる。
【００１７】
一方、従来から、Al合金溶接接合材のHAZ の軟化に対しては、溶接施工方法の側から、下記溶接条件などの種々の改善が行なわれてきた。
▲１▼特開平11-104860 号公報などに例示される通り、極力低入熱で溶接する、あるいは冷却しながら溶接接合する方法。
▲２▼溶接後の継手を焼き入れ焼き戻し処理する、あるいは特開平5-222498号公報軽金属溶接Vol37(1999)No.9 の397 〜405 頁などのように、時効硬化処理前の材料(T1 、T4材) を溶接後、時効硬化処理する、などの熱処理によって軟化を回復させる方法。
▲３▼溶接後にAl合金溶接接合材のHAZ の部分を含めて補強材を設置する方法。
▲４▼特開平11-104860 号公報などに開示された、溶接接合部が比較的高温にならない接合方法である、摩擦攪拌接合(FSW) で溶接する方法。
【００１８】
【発明が解決しようとする課題】
しかし、前記▲１▼の低入熱で溶接する、あるいは冷却しながら溶接接合する方法では、溶接効率が著しく低下し、実用的ではない。また、低入熱化した場合、接合強度自体が低下する問題もある。
【００１９】
また、前記▲２▼の溶接後の継手を熱処理する方法では、熱処理の付加に手間やコストがかかり生産性を阻害するとともに、他の継手定常部分の強度が高くなり、前記溶接接合材の成形加工性が低下したり、構造部材としての耐久性あるいはクラッシャブル性などの他の機能を却って低下させることにもつながる。
【００２０】
前記▲３▼の補強材を設置する方法は、補強材をAl合金溶接接合材へ溶接する場合には、同じHAZ 軟化の問題を引き起こすため、接合方法や接合強度の確保という別の問題を生じる。また、接合強度の確保やHAZ 軟化によるAl合金溶接接合材の強度や伸びの低下を補う、などのためには、補強材が相当量必要となり、重量増加や部材点数の増加によるコストアップなどの問題を生じる。
【００２１】
更に、前記▲４▼の摩擦攪拌接合(FSW) で溶接する方法でも、本発明者らが知見したところによれば、前記した通り、Si過剰型の6000系Al合金材などの熱処理型のAl合金材を用いた溶接接合材の場合には、溶接継手効率は、強度、伸び共にいずれも著しく低くなる傾向がある。
【００２２】
したがい、前記溶接施工方法の側からの改善には限界があり、この熱処理型のAl合金材の溶接接合材において、薄肉側のHAZ における継手強度や伸びの低下が必然的に生じても、溶接接合材に引張などの応力が負荷された場合に、薄肉側のHAZ で破断しない技術が求められていた。
【００２３】
本発明はこの様な事情に着目してなされたものであって、その目的は、継手強度と継手伸びとが優れた熱処理型Al合金の溶接接合材を提供しようとするものである。
【００２４】
【課題を解決するための手段】
この目的を達成するために、本発明Al合金溶接接合材の請求項1 の要旨は、熱処理型アルミニウム合金材同士、または熱処理型アルミニウム合金材と非熱処理型アルミニウム合金材との、厚みの違うアルミニウム合金材同士が溶接接合され、少なくとも薄肉側の前記熱処理型アルミニウム合金材側の溶接熱影響部に、厚肉部が溶接前に予め設けられていることである。
【００２５】
本発明者らは、熱処理型のAl合金溶接接合材において、溶接継手の引張強さと伸びを律する前記溶接熱影響部(HAZ) を、溶接前に予め部分的に厚肉化しておけば、溶接接合材に引張などの応力が負荷された場合に、この肉厚効果により、継手強度や破断伸びが保証されることを知見した。即ち、HAZ の厚肉化によって、溶接接合材に引張応力が負荷された場合に、HAZ に発生する応力を定常継手領域に比して小さくできる。この結果、溶接時に、HAZ における強度や伸びの低下が必然的に生じても、HAZ での破断を防止し、定常継手域で破断するようにでき、継手強度や破断伸びを大きくできる。
【００２６】
また、HAZ の厚肉化によって、より薄い元の肉厚に比して、溶接時の薄肉側のHAZ における継手強度や伸びの低下自体を抑制できる効果があることも知見した。
【００２７】
これらの効果達成のために、好ましくは、前記厚肉部を前記Al合金材の製造時にAl合金材と一体に設ける。また、同じく効果達成のために、 Al合金溶接接合材の厚肉部の厚みが (定常部の厚み×定常部の引張強さ)/熱影響部の引張強さ以上とすることが好ましい。
【００２８】
なお、本発明において、前記HAZ とは、HAZ の内で、少なくとも最も硬度が低下するHAZ 部分を含み、その硬度低下が溶接接合材の継手引張強さと伸びの低下に大きな影響を与えるHAZ 部分のことである。したがって、継手引張強さと伸びの低下に大きな影響を与えるHAZ の硬度低下の状況に応じて、最も硬度が低下するHAZ のみを厚肉化する場合から、その周辺のHAZ や母材部分を含めて厚肉化する場合まで、本発明では適宜選択される。
【００２９】
また、溶接接合前の熱処理型Al合金材での溶接熱影響部とは、溶接された後で継手強度と伸びを律するHAZ となる、あるいは、該HAZ となることが想定される、溶接前のAl合金材の部位乃至領域のことである。
【００３０】
本発明は以上のような効果を有するため、薄肉側のHAZ における継手強度や伸びの低下の問題が大きい、厚みの違うAl合金材同士が溶接接合されてなり、前記厚肉部を薄肉側の熱処理型アルミニウム合金材の溶接熱影響部分に少なくとも設けることが好ましい。また、例えばテーラードブランク材などのように、 Al合金溶接接合材がプレス成形されて使用される用途に適用することが好ましい。
【００３１】
更に、溶接後に成形加工を受けないAl合金継手構造体でも、例えば、衝突などの大きな変形を考慮した構造部材としての耐久性あるいはクラッシャブル性などの機能を発揮することが重要な、バンパー補強材、サイドシル、センターピラー、ルーフサイドレール、ドアビームなどの、フレーム類に適用することが好ましい。また、薄肉側のHAZ における継手強度や伸びの低下の問題が大きい、AA乃至JIS 規格に規定される6000系乃至7000系のアルミニウム合金継手に適用することが好ましい。
【００３２】
【発明の実施の形態】
本発明溶接接合材で用いるAl合金材 (母材Al合金) は、溶接接合材のいずれか一方のAl合金材が熱処理型Al合金材であるものとする。したがって、本発明溶接接合材の組み合わせとしては、熱処理型Al合金材同士の溶接接合材、熱処理型Al合金材と非熱処理型Al合金材との溶接接合材などがある。
【００３３】
これらAl合金溶接接合材においては、前記した通り、部材の形状や要求特性、あるいは要求製作コストなどに応じて、Al合金材同士の組み合わせ方が適宜選択される。即ち、同じ板材、形材、鍛造材、鋳造材の同士の組み合わせや、違うAl合金材同士の組み合わせが、溶接接合されるAl合金材同士の形状や厚みが違う場合を含めて、適宜選択される。
【００３４】
例えば、板材同士あるいは板材と他のAl合金材同士を溶接接合したAl合金構造材（接合板材）は、板材の部分を更に部材形状にプレス成形などで成形加工してフード、ドア、ルーフなどのパネル類に用いられる。また、前記フレーム類は、形材同士あるいは形材と他のAl合金材同士を溶接接合したAl合金構造材からなりバンパー補強材、サイドシル、センターピラー、ルーフサイドレール、ドアビームなどとして用いられる。また、サブフレームなどは、板材、形材、鍛造材、鋳造材などを適宜組み合わせて溶接接合したAl合金構造材からなる。
【００３５】
以下に、図面を用いて、溶接熱影響部分(HAZ) に、溶接前に予め厚肉部を設けた実施態様を説明する。先ず、図1(a)、(b) 、(c) 、(d) はAl合金構造材であって、Al合金板同士の溶接接合材の側面図を示す。図1(a)の態様の溶接接合材1aは、板厚の違う薄板2aと厚板3aとを、溶接施工部5 で突き合わせ溶接したプレス成形用の差厚テーラードブランク材である。図1(a)において、薄板2aの、接合部4aの近傍で、溶接接合材の引張強さと伸びを律する (硬度が低くなる)HAZ6aに、断面矩形状の厚肉部8aをHAZ6a に沿って設けている。
【００３６】
本発明では、溶接接合材の引張強さと伸びを律するHAZ を溶接前に予め厚肉化し、前記した通り、溶接接合材に引張などの応力が負荷された場合に、HAZ に発生する応力を定常継手領域に比して小さくできる。この結果、HAZ における強度や伸びの低下が必然的に生じても、HAZ での破断を防止し、定常継手域や構造材部分で破断するようにでき、継手強度や破断伸びを大きくできる。
【００３７】
この主旨のためには、少なくとも、最も硬度が低くなるHAZ の部分に厚肉部を溶接前に予め設けること必須である。言い換えると、熱処理型Al合金材の溶接接合材の引張強さと伸びを律するHAZ に厚肉部を溶接前に予め設けることが必須である。なお、以下にHAZ として示す部分は溶接接合後、HAZ の最も硬度が低くなる部分であり、HAZ の部分全てを示すものでは、必ずしもない。
【００３８】
ただ、本発明の溶接前に予め厚肉部を設ける範囲としては、最も硬度が低くなるHAZ 以外のHAZ 部分や、その他の構造材部分に渡って厚肉部を設けても良い。本発明の厚肉部は、前記した従来技術のように、溶接後に補強材を設置するのではなく、溶接前に予め、最も硬度が低くなるHAZ の部分にのみ最低厚肉部を設ける。このため、前記した通り、溶接時のHAZ における継手強度や伸びの低下自体を抑制できる効果がある。したがって、HAZ 軟化による強度低下を補うために、前記した補強材方式のような多量の補強材使用は必要ない。この結果、厚肉化部の範囲、大きさの選択や設計は、重量増加しない範囲で、比較的自由に選択できる利点もある。
【００３９】
また、本発明では、差厚継手の場合に、薄肉側 (薄板側) のHAZ だけでなく、厚肉側 (厚板側) のHAZ に厚肉部を設けても良い。前記した図6 において、熱処理型Al合金材溶接接合材のHAZ における継手強度や伸びの低下は、薄板2 のみならず、厚板3 のHAZ7でも生じている。ただ、厚板3 のように肉厚が大きい場合、この肉厚効果により、溶接接合材に引張応力が負荷されても、HAZ7に発生する応力を定常継手領域に比して小さくできる。また、肉厚効果により、溶接時の薄肉側のHAZ における継手強度や伸びの低下自体を抑制できる。この結果、溶接接合材に引張応力が負荷された場合に破断するのは、主として、前記肉厚効果が発揮されない薄板2 側のHAZ6となる。したがって、厚肉側 (厚板側) のHAZ に厚肉部を設けて意味があるのは、この肉厚効果が発揮されにくい、接合するAl合金材同士の肉圧差が少ない場合の、厚肉側のHAZ である。
【００４０】
図1(b)の態様の溶接接合材1bのみは参考例であり、同じ板厚の薄板2bと薄板3bとを、溶接施工部5 で突き合わせ溶接したプレス成形用の等厚テーラードブランク材である。図1(b)において、薄板2bと薄板3bの両方の、接合部4bの近傍である、HAZ6a 、6bに、断面矩形状の厚肉部8a、8bを、HAZ6a 、6bに沿って設けている。
【００４１】
図1(c)の態様の溶接接合材1cは、板厚の違う薄板2cと厚板3cとを、溶接施工部5a、5bの2 箇所で重ね合わせ溶接した、プレス成形用の差厚テーラードブランク材である。図1(c)において、接合部4cの近傍である薄板2cのHAZ6c に断面矩形状の厚肉部8cをHAZ6c に沿って設けている。
【００４２】
図1(d)の態様の溶接接合材1dは、板厚が違い、かつ端部をL 字状に折り曲げた薄板2dと厚板3dとを、薄板2dの前記折り曲げ部において、溶接施工部5a、5bの2 箇所で重ね合わせ溶接した溶接接合材である。図1(d)において、接合部4dの近傍である薄板2dのHAZ6d に断面矩形状の厚肉部8dをHAZ6d に沿って設けている。
【００４３】
次に、図2(a)、(b) 、(c) 、(d) は、Al合金構造材における、Al合金板とAl合金形材同士の溶接接合材の側面図を示す。これらAl合金構造材がプレス成形される場合には、Al合金板側がプレス成形される。
【００４４】
図2(a)の態様の溶接接合材1eは、肉厚の薄い矩形中空形材2eと、厚板3eとを、溶接施工部5a、5bの2 箇所で重ね合わせ溶接した接合材である。図2(a)の溶接接合材1eでは、矩形中空形材2e側の接合部4eの近傍である、HAZ6e 、6eの、中空形材2eの内側に、断面矩形状の厚肉部8e、8eをHAZ6e 、6eに沿って設けている。なお、厚肉部8e、8eはHAZ6e 、6eの中空形材2eの外側に設けても良い。
【００４５】
図2(b)の態様の溶接接合材1fは、肉厚の薄い矩形中空形材2fと厚板3fとを、中空形材2fのフランジ部9 において、溶接施工部5a、5bの2 箇所で重ね合わせ溶接した溶接接合材である。図2(b)の溶接接合材1fでは、肉厚の薄い矩形中空形材2f側の接合部4fの近傍であるフランジ部9 のHAZ6f の上部に、断面矩形状の厚肉部8fをHAZ6f に沿って設けている。なお、厚肉部8fはフランジ部9 のHAZ6f の下部に設けても良い。
【００４６】
図2(c)の態様の溶接接合材1gは、逆に肉厚の厚い矩形中空形材3gと薄板2gとを、中空形材3gの上部において、溶接施工部5a、5bの2 箇所で重ね合わせ溶接した溶接接合材である。図2(c)の溶接接合材1gでは、薄板2g側の接合部4gの近傍であるHAZ6g の上部に、断面矩形状の厚肉部8gをHAZ6g に沿って設けている。なお、厚肉部8gは薄板2gのHAZ6g の下部に設けても良い。
【００４７】
図2(d)の態様の溶接接合材1hは、逆に肉厚の薄い矩形中空形材3hと、同じく板厚の薄い薄板2hとを、中空形材3hのフランジ部9 において、溶接施工部5a、5bの2 箇所で重ね合わせ溶接した溶接接合材である。図2(d)の溶接接合材1hでは、各々接合部4hの近傍である、中空形材3h側のHAZ6h 、6hの中空形材の内側に、薄板2h側のHAZ6i の上部に、それぞれ断面矩形状の厚肉部8h、8h、8iを、HAZ6h 、6h、HAZ6i に沿って設けている。なお、厚肉部8h、8hはHAZ6h 、6hの中空形材3hの外側に設けても良い。また、厚肉部8hは薄板2hのHAZ6i の下部に設けても良い。
【００４８】
図3 に、プレス成形されずに用いられるAl合金構造材に厚肉部を設けた、他の本発明の態様を示す。前記図1 、2 の例では、プレス成形されるパネル用途であるため、軽量化の要求を満足するために、できるだけ厚肉部も小さくした例を示した。しかし、この図3 の例では、それなりの応力を負担する構造材の例を示し、厚肉部を比較的大きくしている。
【００４９】
即ち、図3 の態様の溶接接合材1i自体は、前記図1(a)と同様、肉厚の薄い板材2iと厚板3iとを、溶接施工部5 で突き合わせ溶接した溶接接合材である。ただ、この図3 の態様の溶接接合材1iでは、継手強度を高めるため、溶接施工部5 の両材の板厚差による段差も埋めるように、肉厚の薄い板材2i側のHAZ6i を厚肉化している。このため、図3 の厚肉部8iは、板材2iに向かって傾斜する斜辺9 を有する、比較的大きな矩形形状 (台形断面形状) をしている。
【００５０】
これら厚肉部は、厚肉部の肉厚効果によりAl合金材の伸びや肉厚減少を保証して、溶接接合材の引張応力負荷時の、HAZ での破断を防止する。したがって、厚肉部の設ける位置と厚みなどが重要となり、厚肉部の断面形状などは、設け易い形状を適宜選択すれば良い。また、厚肉部の長手方向は、前記した通り、HAZ に沿って設けるが、その効果を達成できるのであれば、長手方向に連続せずとも、断続的に設けても良い。更に、厚肉部を長手方向に分割して設けても良い。また、それなりの応力を負担する構造材用途では、継手強度を高めるために、前記図3 のように厚肉部を比較的大きくしても良い。
【００５１】
以下に、本発明厚肉部の好ましい設け方を説明する。
図4 に図1(a)と同じ溶接接合材を示すように、溶接接合材への引張応力P が負荷された際の、HAZ での破断を防止するためには、好ましくは、薄板2 側のHAZ6の厚肉部8 の肉厚効果を、薄板2 の定常部と同じ肉厚効果以上とする。即ち、薄板2 側のHAZ6の厚肉部8 の板厚(t4)と引張強さ (σ_B4) との積、t4×σ_B4を、薄板2 の定常部の板厚(t1)と引張強さ (σ_B1) との積、t1×σ_B1以上とする。
言い換えると、本発明溶接接合材において、薄肉側のHAZ の厚肉部の厚みは (薄肉部の厚みt1×定常部の引張強さσ_B1)/熱影響部の引張強さσ_B4以上とすることが好ましい。
【００５２】
なお、HAZ 部分の厚肉部は、1 個でなくとも、溶接接合材の長手方向や溶接接合 (溶接線) 方向に、2 個以上分割して設けても良い。また、HAZ 部分の前記長手方向や溶接接合方向を全て網羅せずとも、これらの方向で、継手強度や成形性が特に要求されるHAZ 部分のみに、部分的に厚肉部を設けても良い。
【００５３】
このHAZ の厚肉部の厚みを、問題となる薄肉側の熱処理型Al合金材の調質状態 (引張強さと伸び) を考慮して、決定することが好ましい。前記薄肉側の熱処理型Al合金材がT4調質材の場合には、T5またはT6調質材と比較して、溶接熱影響による引張強さと伸びの低下が比較的小さいので、薄肉側の熱処理型Al合金材に設ける厚肉部の厚みを定常部の1/0.95以上で1/0.8 以下とするのが好ましい。
【００５４】
一方、前記熱処理型Al合金材がT5またはT6調質材の場合には、溶接熱影響による引張強さと伸びの低下が比較的大きく、上記厚肉部の厚みを定常部の1/0.75以上で1/0.55以下と比較的大きくとるのが好ましい。
【００５５】
更に、引張強さと伸びが最も低下するHAZ の位置は、図5 に前記図4 と同じ継手で示すように、通常の溶接施工条件の場合、概ね、溶接接合部中心から20〜25mm以内の範囲の領域に納まる。また、そのHAZ の幅も、概ね幅2 〜5mm の範囲に納まる。ただ、前記熱処理型Al合金材がT4調質材の場合には、溶接接合部中心から25mm以内の領域が部分的に強度低下する。また、前記熱処理型Al合金材がT5またはT6調質材の場合には、前記厚肉部を溶接接合部中心から20mm以内の領域が全体的に強度低下する。
【００５６】
したがって、厚肉部を設ける位置については、前記熱処理型Al合金材がT4調質材の場合には、好ましくは、前記厚肉部を溶接接合部中心から25mm以内の領域( 部位) に幅2 〜5mm の範囲で、1 箇所以上設けることによって、引張強さと伸びを律するHAZ の位置を概ねカバーできる。
【００５７】
また、前記熱処理型Al合金材がT5またはT6調質材の場合には、好ましくは、前記厚肉部を、溶接接合部中心から20mm以内の領域に全体的に設けることによって、引張強さと伸びを律するHAZ の位置を概ねカバーできる。
【００５８】
厚肉部の設け方は、熱処理型Al合金材 (母材) に溶接前に予め設ける。溶接後に設けた場合、前記した通り、設け方によらず、溶接時のHAZ における継手強度や伸びの低下自体を抑制できる厚肉効果が発揮されない。
【００５９】
板材において厚肉部を予め設ける場合、前記した溶接接合材の厚肉部設置位置 (部位) に対応した母材の部位が厚肉部となるよう、板材の圧延製造の際に異形圧延等して一体的に設けるか、機械加工等により厚肉部以外の (薄肉相当) 部分を研削するなどして一体的に設けることが好ましい。この他、圧延後の板材の所定位置に所定条件の厚肉部材を接着して設けることも可能であるが、板材と厚肉部材との接着強度を高める必要がある。
【００６０】
形材、鋳鍛材、鋳造材の場合には、板材と同様に接着等で予め設けることも可能であるが、予め、厚肉部形状を含めた母材形状として設計し、押出、鍛造、鋳造の際に、簡便に一体的に形成することができる。
【００６１】
本発明溶接接合材で用いる熱処理型Al合金材 (展伸材) は、AA乃至JIS 規格に規定され(AA 乃至JIS 規格を満足し) 、溶接構造用Al合金として汎用される、前記6000系、7000系などのAl合金材である。なお、熱処理型Al合金鋳造材としては、AA乃至JIS 規格に規定された(AA 乃至JIS 規格を満足する)Al-Cu-Si 系、Al-Cu-Mg-Si 系、Al-Mg-Si系などのAl合金である。また、前記6000系Al合金材の中でも、薄肉側のHAZ における継手強度や伸びの低下の問題が大きい、Si/Mg が1 以上の(Mg 含有量に対しSiが過剰に含有されている) 、6N01、6016、6111、6022などの、Si過剰型の6000系(Al-Mg-Si 系) Al合金に適用されて好ましい。
【００６２】
本発明溶接接合材で用いる熱処理型、あるいは非熱処理型Al合金材自体は、溶解、鋳造、均質化熱処理、熱間加工 (圧延、押出、鍛造) 、必要により中間焼鈍、冷間加工 (圧延、鍛造) 等の常法工程により、板材や形材 (中空断面など断面形状が長さ方向のどの位置でも本質的に同一である形材) 、鍛造材、更には鋳造材として製造される。
【００６３】
製造後の熱処理型Al合金材は、前記したT4、T5、T6などの調質処理によって、所定の強度などの特性を得、溶接接合材としての母材として用いられる。また、非熱処理型Al合金材は, 製造まま、あるいは焼鈍(O材) などの調質処理によって、所定の強度などの特性を得、溶接接合材としての母材として用いられる。
【００６４】
本発明溶接接合材の溶接接合方法は、前記した溶接接合材HAZ の強度と伸びの低下が著しい、溶接線が長い、アークなどの熱源を用いる溶融溶接方法である、ティグ(TIG) 、ミグ(MIG) などの高速アーク溶接やレーザー溶接、電子ビーム溶接、抵抗シーム溶接などの溶接方法、あるいは摩擦攪拌接合(FSW) 方法を対象とする。
【００６５】
また、これらの溶接接合方法における施工条件は常法の範囲で行う。但し、溶融溶接の場合には、5356などの5000系Al合金溶加材 (棒) や4047などの4000系Al合金溶加材を適用することが好ましい。この点、より低温の摩擦攪拌接合方法では、溶加材を用いずとも、差厚接合部の段差近傍の、HAZ を含む肉厚増加が容易である。
【００６６】
本発明Al合金溶接接合材は、溶接接合後、具体的な構造材用途に応じて、曲げ加工やプレス成形などの成形加工され、または成形加工されずに、他の部材と組み合わされて、構造材として適宜設置され使用される。
【００６７】
【実施例】
次に、本発明の実施例を説明する。
(実施例1)
表1 に示すような合金組成の過剰Si型6022Al合金板のT4調質材同士を各々用いて、前記図1(a)に示す形状で、厚肉部を有する溶接接合材 (テーラードブランク材) 1aを製作した。溶接接合材には、厚肉部以外の部分を薄肉化する機械加工により表3 に示す条件で、薄板側HAZ6a に厚肉部8aを予め一体的に設けた。接合部の溶接長さは700mm とし、表2 に示す各溶接方法および溶接条件で接合した。比較のために、前記厚肉部が無い以外は発明例と同じ条件とした6022Al合金T4調質板材同士の溶接接合材および5182Al合金O 調質板材同士の溶接接合材を製作した。
【００６８】
なお、表3 には (後述する実施例2 の表5 にも) 各例が、薄肉側のHAZ の厚肉部の、前記したT4調質材の好ましい条件として、▲１▼厚肉部の厚みを (薄肉部の厚みt1×定常部の引張強さσ_B1)/熱影響部の引張強さσ_B4以上とする、▲２▼厚肉部の厚みを定常部の薄肉側Al合金材のT4調質に対応して定常部の1/0.95以上で1/0.8 以下とする、▲３▼溶接接合部中心から25mm以内の領域( 部位) に幅2 〜5mm の範囲で設ける、を満足する場合を〇、満足しない場合をーで示す。
【００６９】
また、溶接接合材の接合部分の断面を100 倍の光学顕微鏡により観察し、目視できる溶接割れの他に、ミクロ的な溶接割れの有無を調査した。その結果、発明例、比較例ともに接合部の溶接割れは認められなかった。
【００７０】
更に、溶接接合材の (溶接後の) 6022Al合金薄板2a側のHAZ6a と定常部の硬度を測定した。また、溶接接合材の継手強度 (σ_B) と継手伸び (δ) をJIS Z 2241に従い測定した。更に、このようにして得た溶接接合材を自動車パネル材に適用することを想定してプレス成形試験し、成形性を評価した。これらの結果を表4 に示す。
【００７１】
プレス成形品の条件は、製品部高さ35mm、長さ550mm 、幅450mm 、隅角部の曲率R100〜150mm の略角筒型形状とし、金型のドロービードやダイフェースの長さは前記成形品形状条件に適応させて設けた。そして、しわ押さえ力50tonf、使用潤滑油R-303 、成形速度20mm/ 分の条件でプレス成形を行った。
【００７２】
そして、プレス成形品が溶接接合部を含めいずれの箇所も破断しておらず、良好に成形できた場合を〇とし、HAZ や溶接接合部は破断せずHAZ や溶接接合部の強度は良好であるものの定常部で破断したものを△、HAZ が破断した場合を×と評価した。
【００７３】
表3 、4 から明らかな通り、前記▲１▼〜▲３▼の好ましい条件を全て満足する発明例No.1、2 、3 、8 、9 の溶接接合材は、溶接後の溶接接合材の薄板2a側のHAZ6a の硬度が、定常部の硬度に比して大きく低下しているにも関わらず、溶接接合材自体の継手引張強度 (σ_B) と継手伸び (δ) および溶接接合材効率も100%と比較的高い。そして、プレス成形品がHAZ の割れを含めいずれの箇所も破断しておらず、プレス成形性が良好である。しかも、これらの結果は、溶接方法や溶加材条件の違いによらず得られている。
【００７４】
また、HAZ の厚肉部の厚みが比較的薄く、前記▲１▼の好ましい条件を下限に満足していない (前記▲２▼、▲３▼の好ましい条件は満足している) 発明例No.4、5 の溶接接合材は、継手引張強度 (σ_B) と溶接接合材効率は比較的高い。しかし、継手伸び (δ) が比較的低く、プレス成形品の定常部が破断しており、前記各発明例に比して、プレス成形性が劣る。したがって、プレス成形性向上の点で、HAZ の厚肉部の厚みを必要量厚くすること、および前記▲１▼厚肉部の厚みを (薄肉部の厚みt1×定常部の引張強さσ_B1)/熱影響部の引張強さσ_B4以上とする好ましい条件の重要性が分かる。
【００７５】
一方、厚肉部の肉厚が比較的厚く、前記▲２▼の好ましい条件を上限に満足していない( ▲１▼、▲３▼の好ましい条件は満足している) 発明例No.6の溶接接合材も、前記発明例No.1、2 、3 、8 、9 と同様に、継手引張強度 (σ_B) と継手伸び (δ) および溶接接合材効率も100%と比較的高く、プレス成形性が良好である。ただ、厚肉部の肉厚が比較的薄い前記発明例No.1、2 、3 、8 、9 でも、プレス成形性は良好であり、軽量化の観点からは、この発明例No.6ほどに厚肉部の肉厚を厚くせずとも、目的が達成できることが分かる。したがって、前記▲２▼の厚肉部の厚みを定常部の1/0.95以上で1/0.8 以下とする好ましい条件が、軽量化を損なわずにプレス成形性を向上させるために重要であることが分かる。
【００７６】
更に、厚肉部の肉厚は比較的厚いものの、厚肉部の幅が比較的狭く、前記▲３▼の好ましい条件を下限に満足していない (前記▲１▼、▲２▼の好ましい条件は満足している) 発明例No.7の溶接接合材は、継手引張強度 (σ_B) と継手伸び (δ) および溶接接合材効率が比較的低い。このため、プレス成形品の定常部が破断しており、前記各発明例に比して、プレス成形性が劣る。したがって、プレス成形性向上の点で、HAZ の厚肉部の幅を必要量厚くすること、および前記▲３▼の厚肉部を溶接接合部中心から25mm以内の領域( 部位) に幅2 〜5mm の範囲で設ける好ましい条件の下限の重要性が分かる。
【００７７】
ただ、厚肉部の幅が比較的広く、前記▲３▼の好ましい条件を上限に満足していない (前記▲１▼、▲２▼の好ましい条件は満足している) 発明例No.10 の溶接接合材は、前記発明例No.1、2 、3 、8 、9 と同様に、継手引張強度 (σ_B) と継手伸び (δ) および溶接接合材効率も100%と比較的高く、プレス成形性が良好である。ただ、軽量化の観点からは、この発明例No.10 ほどに厚肉部の幅を広くせずとも、目的が達成できることが分かる。したがって、前記▲３▼の好ましい条件の上限が、軽量化を損なわずに、プレス成形性を向上させるために重要であることが分かる。
【００７８】
これに対し、厚肉部を設けていない比較例No.1〜4 では、非熱処理型の5182合金同士を用いた比較例No.4を除いて、溶接接合材自体の継手引張強度 (σ_B) と継手伸び (δ) および溶接継手効率も発明例に比して低く、プレス成形でもHAZ の割れが生じ、発明例に比してプレス成形が劣っている。
【００７９】
非熱処理型の5182合金同士を用いた比較例No.4の溶接接合材は、溶接後の溶接接合材の薄板2a側のHAZ6a の硬度や、溶接接合材自体の継手引張強度 (σ_B) と継手伸び (δ) および溶接継手効率もあまり低下せず、HAZ での割れも生じずプレス成形性も良好である。
【００８０】
これら実施例の結果から、熱処理型Al合金溶接接合材において、HAZ における強度や伸びの低下が必然的に生じても、HAZ の厚肉化によって、HAZ での破断を防止でき、継手強度や破断伸びおよび成形性を向上できる、本発明厚肉部やその好ましい条件の臨界的な意義が裏付けられる。また、前記非熱処理型の5182Al合金溶接接合材である比較例4 との比較において、前記HAZ における強度や伸びの低下の問題が、熱処理型Al合金溶接接合材特有の問題であることが分かる。
【００８１】
【表１】

【００８２】
【表２】

【００８３】
【表３】

【００８４】
【表４】

【００８５】
(実施例2)
次に、実施例1 と同じ表1 に示した合金組成の過剰Si型6022Al合金板のT6調質材同士を各々用いて、前記図3 に示す形状で、傾斜面9 がある厚肉部8iを設けた溶接接合材1iを製作した。表5 に示す条件で、6022Al合金板材の薄板側HAZ に、薄肉部の機械的研削により厚肉部を予め一体的に設けた。なお、厚肉部の幅は、傾斜面9(水平方向の長さが5mm)を除く、平坦部のみの幅としている。また、接合部の溶接長さは30mmとし、表5 に示す各溶接方法および溶接条件で接合した。比較のために、厚肉部が無い以外は同じ条件とした6022Al合金T6調質板材同士の溶接接合材を製作した。
【００８６】
なお、表5 には各例が、薄肉側Al合金材のT5またはT6調質材に対応して、薄肉側のHAZ の厚肉部の、▲１▼厚みを( 薄肉部の厚みt1×定常部の引張強さσ_B1)/熱影響部の引張強さσ_B4以上とする、▲２▼厚みを定常部の1/0.95以上で1/0.8 以下とする、▲３▼溶接接合部中心から20mm以内の領域に全体的に設ける、などの前記好ましい条件を満足する場合を〇、満足しない場合をーで示す。
【００８７】
溶接後の各溶接接合材の接合部分の断面を100 倍の光学顕微鏡により観察し、目視できる溶接割れの他に、ミクロ的な溶接割れの有無を調査した結果、発明例、比較例ともに接合部の溶接割れは認められなかった。
【００８８】
このようにして得た溶接接合材の (溶接後の) Al合金薄板2i側のHAZ6i と定常部の硬度を測定した。また、溶接接合材自体の継手強度 (σ_B) をJIS Z 2241に従い測定した。これらの結果を表6 に示す。
【００８９】
表5 、6 から明らかな通り、前記▲１▼〜▲３▼の好ましい条件を全て満足する発明例No. 11、12、13の溶接接合材は、溶接後の溶接接合材の薄板2i側のHAZ6i の硬度が定常部の硬度に比して大きく低下しているにも関わらず、溶接接合材自体の継手引張強度 (σ_B) が350MPa以上、継手効率は100%と著しく高い。しかも、これらの結果は、溶接方法や溶加材条件の違いによらず得られている。
【００９０】
また、HAZ の厚肉部の厚みが比較的薄く、前記▲１▼の好ましい条件を下限に満足していない (前記▲２▼、▲３▼の好ましい条件は満足している) 発明例No.14 、15の溶接接合材は、継手強度と継手効率が、発明例No. 11、12、13に比して低い。したがって、薄肉側Al合金材がT5またはT6調質材の場合に、継手強度と継手効率とを向上させる点で、HAZ の厚肉部の厚みを必要量厚くすること、および前記▲１▼厚肉部の厚みを( 薄肉部の厚みt1×定常部の引張強さσ_B1)/熱影響部の引張強さσ_B4以上とする好ましい条件の重要性が分かる。
【００９１】
一方、厚肉部の肉厚が比較的厚く、前記▲２▼の好ましい条件を上限に満足していない( ▲１▼、▲３▼の好ましい条件は満足している) 発明例No.16 の溶接接合材も、前記発明例No.11 、12、13と同等に、継手強度と継手効率が高い。ただ、厚肉部の肉厚が比較的薄い前記発明例No.11 、12、13と性能が同等であるということは、軽量化の観点からは、この発明例No.6ほどに厚肉部の肉厚を厚くせずとも、目的が達成できることが分かる。したがって、前記▲２▼の厚肉部の厚みを定常部の1/0.95以上で1/0.8 以下とする好ましい条件が、軽量化を損なわずに継手強度と継手効率を向上させるために重要であることが分かる。
【００９２】
更に、厚肉部の肉厚は比較的厚いものの、厚肉部の幅が比較的狭い (前記▲１▼、▲２▼の好ましい条件は満足している) 発明例No.17 の溶接接合材は、継手強度と継手効率が比較的低い。したがって、継手強度と継手効率向上の点で、HAZ の厚肉部の幅を必要量広くすることが分かる。
【００９３】
ただ、厚肉部の幅が比較的広く、前記▲３▼の好ましい条件を上限に満足していない発明例No.18 は、前記発明例No.11 、12、13と同等に、継手強度と継手効率が高い。ただ、厚肉部の幅が比較的狭い前記発明例No.11 、12、13と性能が同等であるということは、軽量化の観点からは、この発明例No.18 ほどに厚肉部の幅を広くせずとも、目的が達成できることが分かる。したがって、軽量化の観点からは、前記▲３▼の厚肉部を溶接接合部中心から20mm以内の領域に全体的に設ける好ましい条件の重要性が分かる。
【００９４】
これに対し、厚肉部を設けていない比較例No.5〜7 では、溶接接合材自体の継手引張強度 (σ_B) と継手効率も発明例に比して著しく低い。
【００９５】
これら実施例の結果から、熱処理型Al合金溶接接合材において、HAZ における強度や伸びの低下が必然的に生じても、HAZ の厚肉化によって、継手強度を向上できる、本発明厚肉部やその好ましい条件の意義が裏付けられる。
【００９６】
【表５】

【００９７】
【表６】

【００９８】
【発明の効果】
本発明によれば、HAZ における硬度低下が生じても、溶接接合材の継手強度と伸びや、成形性に優れた熱処理型Al合金溶接接合材を提供することができる。したがって、熱処理型Al合金溶接接合材の自動車用途などへの拡大を図れる点で、工業的な価値が大きい。
【図面の簡単な説明】
【図１】図1(a)、(b) 、(c) 、(d) は、各々本発明Al合金溶接接合材の1 実施態様を示す側面図である。
【図２】図2(a)、(b) 、(c) 、(d) は、各々本発明Al合金溶接接合材の他の実施態様を示す側面図である。
【図３】本発明Al合金溶接接合材の他の実施態様を示す側面図である。
【図４】本発明Al合金溶接接合材の厚肉部の設け方を示す側面図である。
【図５】本発明Al合金溶接接合材の厚肉部の設け方を示す側面図である。
【図６】 Al合金溶接接合材の熱影響部を示す側面図である。
【図７】 Al合金溶接接合材の熱影響部を含めたビッカース硬度(HV)分布を示す説明図である。
【図８】 Al合金溶接接合材の継手強度と継手伸びを示す説明図である。
【図９】 Al合金溶接接合材の継手伸びと肉厚との関係を示す説明図である。
【符号の説明】
1:Al合金溶接接合材、2:Al合金材、3:Al合金材、4:接合部、5:溶接施工方向、6:熱影響部（HAZ)、7:熱影響部（HAZ)、8:厚肉部、9:フランジ部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aluminum alloy welded joint material, which relates to an aluminum alloy welded joint material (hereinafter, aluminum is simply referred to as Al) having excellent strength and elongation of a weld joint (also referred to as a weld joint).
[0002]
[Prior art]
For members such as panels, frames, members, etc. of transport equipment such as automobiles, Al alloy wrought material (generic name for rolled plate material, extruded profile, forged material, etc.) and Al alloy cast material (hereinafter referred to as wrought material) And cast materials are collectively referred to as Al alloy materials), and structural materials welded and joined in various combinations have come to be used.
[0003]
In the Al alloy welded joint material having these welded joints or welded joint portions, the combination method of Al alloy materials is appropriately selected according to the shape and required characteristics of the member, the required production cost, or the like. In other words, combinations of the same plate, shape, forging, and casting, and combinations of different Al alloy materials are selected as appropriate, including cases where the shape and thickness of the Al alloy materials that are welded are different. The
[0004]
Among the Al alloy welded joint materials, tailored blank materials, which are joint plate materials in which plate materials having different thicknesses are joined, can reuse various end materials generated in the manufacturing process of other members such as panels and frames. In addition, there is a great advantage in that a member having different required strength, formability, and the like can be manufactured by adjusting the thickness and material of the material. For this reason, steel plate tailored blanks and the like have already been used in transportation equipment such as automobiles.
[0005]
As these Al alloys for joining plate materials to be formed, 5000 series (satisfying AA to JIS standards), 6063, 6N01, 6061, etc., which are stipulated in the conventional AA to JIS standards as Al alloys for welded structures. 6000 series (hereinafter abbreviated AA to JIS), 7N01, 7003 and other 7000 series Al alloy materials.
[0006]
However, among these Al alloys for bonding plate materials, heat treatment type Al alloys such as 6000 series and 7000 series are solution treatment and quenching treatment (classification symbol T4), followed by artificial aging treatment ( A predetermined strength is obtained by a tempering treatment such as a quality symbol T6), an overaging treatment (quality symbol T7), or an artificial aging treatment after cooling from hot working (quality symbol T5). On the other hand, a 5000 series Al alloy, which is a non-heat-treatable Al alloy, obtains a predetermined strength by work hardening such as cold work.
[0007]
The heat-treatable Al alloy can obtain excellent age-hardening properties by the tempering treatment such as T4 to T7, but conversely has a problem that its weldability (joining strength) is lowered during welding. That is, when at least one of the Al alloy materials is welded as a heat-treatable Al alloy, a heat-affected zone (hereinafter also referred to as HAZ) is inevitably generated near or around the welded joint due to heating during welding. . In this HAZ, the material is softened by the heat effect, and the hardness is remarkably lowered as compared with other stationary parts.
[0008]
In the case of an Al alloy bonding material having a welded joint, the strength as the Al alloy bonding material is determined by this heat-affected zone. For this reason, when the hardness reduction of a heat affected zone arises, the intensity | strength of Al alloy welding joining material will fall significantly.
[0009]
FIG. 6 shows a welded joint between heat-treatable excess Si type 6000 series Al alloy plates having different thicknesses. In FIG. 6, welded joint material 1 has a thickness t₂Thin plate 2 and thickness t₁For example, from the welding section 5 to the CO₂It is butt welded with a laser and is also a differential thickness tailored blank material. In FIG. 6, 4 is a joint, 6 is the HAZ of the

thin plate

2, and 7 is the HAZ of the thick plate 3.
[0010]
FIG. 7 shows the Vickers hardness (HV) distribution hardness around the joint 4 of the welded joint material 1. In FIG. 7, the hardness of HAZ6 of the thin plate 2 and HAZ7 of the thick plate 3 are significantly lower than those of the welded portion 4 of the welded joint material 1 and other stationary portions.
[0011]
In addition, FIG. 8 shows the deformation characteristics (stress-strain relationship) of the base metal (stationary part) of the thin plate 2 and the HAZ 6 of the welded joint material 1. In FIG. 8, the joint strength σ of HAZ6 of the thin plate 2 can be seen from the decrease in the hardness distribution of HAZ shown in FIG._B-HAZ (MPa) is the joint strength σ of the steady part_BIt is significantly lower than (MPa). Therefore, the strength of Al alloy welded joints with welded joints is the HAZ6 joint strength σ_B-Rated by HAZ. Further, the elongation δ ′ generated in the steady portion at the time when the stress at which the HAZ 6 of the thin plate 2 breaks is applied is greatly inferior to the elongation δ of the material. For this reason, the elongation of the Al alloy welded joint having a welded joint is also significantly reduced due to the presence of HAZ6.
[0012]
Furthermore, according to the findings of the present inventor, the thickness ratio of the thick plate 3 and the thin plate 2 (t₁/ t₂) Increases, the decrease rate of joint strength and joint elongation increases. Thickness ratio between thick plate 3 and thin plate 2 of welded joint 1 between heat-treatable Al alloy plates (t₁/ t₂Figure 9 shows the change in the total elongation (εf,%) of the welded joint material 1 of JIS No. 5 tensile test specimen (distance between gauge points 50 mm) welded at the center of the specimen with different materials. As shown in Fig. 9, the thickness ratio of thick plate 3 and thin plate 2 on the horizontal axis (t₁/ t₂) Increases, the rate of decrease in total elongation increases. And this tendency has a remarkable reduction rate even if it compares with the tendency of the welding joining material of non-heat processing type Al alloy plates, such as 5000 series, described for the comparison. This tendency is the same in the joint strength correlated with the total elongation.
[0013]
Therefore, from these facts, in Al alloy welded joints containing heat-treatable Al alloys, joint strength and joint elongation decrease significantly due to HAZ hardness reduction, and this tendency becomes stronger as the difference in joint thickness increases. I understand.
[0014]
This tendency is especially true for fusion welding methods using a heat source such as arc, where the weld line is relatively long or the welding point is continuous, that is, high-speed arc welding such as TIG (MIG), laser welding, electronic This becomes noticeable when a joint is formed by welding, such as beam welding or resistance seam welding.
[0015]
Furthermore, according to the findings of the present inventors, this tendency also occurs in the friction stir welding (FSW) method, which is a joining method in which the weld joint does not reach a relatively high temperature. In the case of a non-heat treatment type 5000 series Al alloy, the weld joint efficiency is not significantly reduced in FSW and the fusion welding method.
[0016]
As described above, in heat-treatable Al alloy welded joints, the strength and elongation (breaking elongation) decrease due to the heat effect of welding. In such a case, particularly when a plate material including a welded joint is formed by press molding or the like as a tailored blank material, the HAZ breaks due to a decrease in elongation due to a stress such as tension applied at the time of molding. Can not be molded and commercialized. In addition, even in the case of Al alloy welded joints that are not subjected to forming after welding, for example, considering a large deformation at the time of stress load such as a collision, the durability as a structural member or crushable due to the decrease in the elongation at break. This leads to the inability to perform functions such as sex.
[0017]
On the other hand, conventionally, various improvements such as the following welding conditions have been made for the softening of the HAZ of the Al alloy weld joint material from the side of the welding method.
(1) As exemplified in Japanese Patent Application Laid-Open No. 11-104860, etc., a method of welding with low heat input as much as possible or welding with cooling.
(2) Quenching and tempering the joint after welding, or materials before age hardening (T1), as disclosed in JP-A-5-222498, Light Metal Welding Vol. 37 (1999) No. 9, pages 397 to 405. , T4 material) is softened by heat treatment such as age hardening after welding.
(3) A method of installing a reinforcing material including the HAZ part of the Al alloy weld joint after welding.
(4) A method of welding by friction stir welding (FSW), which is a joining method disclosed in Japanese Patent Application Laid-Open No. 11-104860 and the like, in which the weld joint does not reach a relatively high temperature.
[0018]
[Problems to be solved by the invention]
However, the method of welding with the low heat input of the above (1), or welding and joining while cooling is not practical because the welding efficiency is remarkably lowered. Further, when the heat input is lowered, there is a problem that the bonding strength itself is lowered.
[0019]
In addition, in the method (2) for heat-treating the welded joint, the heat treatment is troublesome and costly, and the productivity is hindered, and the strength of the other joint steady portion is increased, and the welding joint material is formed. It also leads to a decrease in workability and other functions such as durability as a structural member or crushability.
[0020]
The method of installing the reinforcing material of the above (3) causes another problem of securing the bonding method and the bonding strength because it causes the same HAZ softening problem when the reinforcing material is welded to the Al alloy welded bonding material. . In addition, a considerable amount of reinforcing material is required to secure the bonding strength and compensate for the decrease in strength and elongation of the Al alloy welded joint due to HAZ softening. Cause problems.
[0021]
Further, in the method of welding by friction stir welding (FSW) described in (4), according to the findings of the present inventors, as described above, heat treatment type Al such as Si-rich 6000 series Al alloy material is used. In the case of a welded joint material using an alloy material, the weld joint efficiency tends to be remarkably low in both strength and elongation.
[0022]
Therefore, there is a limit to the improvement from the side of the welding method described above, and in this heat-treatable Al alloy material welded joint, even if the joint strength and elongation of the thin-walled HAZ inevitably decrease, welding There has been a demand for a technique that does not break at the thin-walled HAZ when stress such as tension is applied to the bonding material.
[0023]
The present invention has been made paying attention to such circumstances, and an object of the present invention is to provide a heat-treatable Al alloy welded joint material excellent in joint strength and joint elongation.
[0024]
[Means for Solving the Problems]
  In order to achieve this object, the gist of claim 1 of the Al alloy welded joint material of the present invention is that heat treated aluminum alloy materials or heat treated aluminum alloy materials and non-heat treated aluminum alloy materialsAluminum alloy materials of different thicknessAre welded,At least on the thin sideA thick-walled portion is previously provided in the heat-affected zone on the heat-treatable aluminum alloy material side before welding.
[0025]
In the heat-treatable Al alloy welded joint, the present inventors can weld the weld heat-affected zone (HAZ), which regulates the tensile strength and elongation of the welded joint, by partially thickening in advance before welding. It has been found that when a stress such as tension is applied to the bonding material, the joint strength and elongation at break are guaranteed by this thickness effect. That is, by increasing the thickness of the HAZ, when tensile stress is applied to the welded joint, the stress generated in the HAZ can be reduced compared to the steady joint region. As a result, even when the strength and elongation of the HAZ are inevitably lowered during welding, the HAZ can be prevented from breaking and can be broken in the steady joint region, and the joint strength and breaking elongation can be increased.
[0026]
In addition, we found that increasing the thickness of the HAZ has the effect of suppressing the reduction in joint strength and elongation of the HAZ on the thin wall side during welding, compared to the thinner original thickness.
[0027]
  In order to achieve these effects, preferably,in frontThe thick portion is provided integrally with the Al alloy material when the Al alloy material is manufactured. Also, to achieve the same effect, AlIt is preferable that the thickness of the thick part of the alloy welded material is equal to or greater than (the thickness of the steady part × the tensile strength of the steady part) / the tensile strength of the heat affected zone.
[0028]
In the present invention, the HAZ includes at least the HAZ portion where the hardness is most reduced in the HAZ, and the reduction in the hardness greatly affects the reduction in joint tensile strength and elongation of the welded joint material. That is. Therefore, depending on the HAZ hardness reduction, which has a major impact on joint tensile strength and elongation reduction, from the case of thickening only the HAZ with the lowest hardness, including the surrounding HAZ and base metal parts. In the present invention, the thickness is appropriately selected until the thickness is increased.
[0029]
In addition, the heat affected zone of the heat-treatable Al alloy material before welding is the HAZ that regulates joint strength and elongation after welding, or is assumed to be the HAZ before welding. It is a part or region of an Al alloy material.
[0030]
  Since the present invention has the above effects, ThinAl alloy materials with different thicknesses, which have a large problem of joint strength and elongation reduction in the HAZ on the meat side, are welded together, and the thick wall portion is at least part of the heat affected aluminum alloy material on the heat treatment type aluminum alloy material on the thin wall side. It is preferable to provide it. Also, compareIf-Lard blank material, AlIt is preferable to apply to an application in which an alloy weld joint material is press-formed.
[0031]
  In addition, it is important for aluminum alloy joint structures that are not subjected to forming after welding to exhibit functions such as durability or crushability as structural members that take into account large deformations such as collisions. , Side sill, center pillar, roof side rail, door beam, etc.Of theIt is preferable to apply to lams. Also, ThinIt is preferable to apply to aluminum alloy joints of 6000 series to 7000 series specified in AA to JIS standards, which have a large problem of joint strength and elongation reduction in the HAZ on the meat side.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
In the Al alloy material (base material Al alloy) used in the welded joint material of the present invention, any one of the welded joint material Al alloy materials is a heat-treatable Al alloy material. Therefore, as a combination of the present invention weld joint material, there are a weld joint material between heat treated Al alloy materials, a weld joint material between a heat treated Al alloy material and a non-heat treated Al alloy material, and the like.
[0033]
In these Al alloy welded joint materials, as described above, a combination method of Al alloy materials is appropriately selected according to the shape, required characteristics, required production cost, and the like of the members. In other words, combinations of the same plate, shape, forging, and casting, and combinations of different Al alloy materials are selected as appropriate, including cases where the shape and thickness of the Al alloy materials that are welded are different. The
[0034]
For example, an Al alloy structural material (joint plate material) in which plate materials or plate materials and other Al alloy materials are welded to each other is formed into a member shape by press molding or the like to form a hood, door, roof, etc. Used for panels. The frames are made of Al alloy structural material in which the shape members or shape materials and other Al alloy materials are welded together, and are used as bumper reinforcements, side sills, center pillars, roof side rails, door beams and the like. In addition, the subframe or the like is made of an Al alloy structural material that is welded and joined by appropriately combining plate materials, profiles, forging materials, casting materials, and the like.
[0035]
Hereinafter, an embodiment in which a thick-walled portion is provided in advance in the welding heat-affected zone (HAZ) before welding will be described with reference to the drawings. First, FIGS. 1 (a), (b), (c) and (d) are side views of an Al alloy structural material and a welded joint material between Al alloy plates. The welded joint material 1a in the mode of FIG. 1 (a) is a press-formed differential thickness tailored blank material in which a thin plate 2a and a thick plate 3a having different plate thicknesses are butt-welded at a welding construction part 5. In FIG. 1 (a), in the vicinity of the joint 4a of the thin plate 2a, a thick section 8a having a rectangular cross section is formed along the HAZ 6a along the HAZ 6a that regulates the tensile strength and elongation of the welded joint (the hardness decreases). Provided.
[0036]
In the present invention, the HAZ that regulates the tensile strength and elongation of the welded joint is thickened in advance before welding, and as described above, when stress such as tension is applied to the welded joint, the stress generated in the HAZ is steady. It can be made smaller than the joint area. As a result, even if the strength and elongation of the HAZ are inevitably lowered, the HAZ can be prevented from breaking, and the joint can be broken at the steady joint region or the structural material portion, so that the joint strength and elongation at break can be increased.
[0037]
For this purpose, it is indispensable to provide a thick part in advance at least in the HAZ part where the hardness is the lowest before welding. In other words, it is essential to provide a thick-walled portion in advance on the HAZ that regulates the tensile strength and elongation of the heat-treated Al alloy material welded joint. The part indicated as HAZ below is the part where the hardness of HAZ becomes the lowest after welding and does not necessarily show all the part of HAZ.
[0038]
However, as a range in which the thick portion is provided in advance before welding according to the present invention, the thick portion may be provided over the HAZ portion other than the HAZ having the lowest hardness, or over other structural material portions. The thick wall portion of the present invention is not provided with a reinforcing material after welding as in the prior art described above, but the minimum thick wall portion is provided in advance only in the HAZ portion having the lowest hardness before welding. For this reason, as described above, there is an effect that it is possible to suppress a decrease in joint strength and elongation itself in the HAZ during welding. Therefore, it is not necessary to use a large amount of reinforcing material as in the above-described reinforcing material method in order to compensate for the strength reduction due to HAZ softening. As a result, there is an advantage that the selection and design of the range and size of the thickened portion can be relatively freely selected without increasing the weight.
[0039]
In the present invention, in the case of the differential thickness joint, a thick portion may be provided not only on the thin wall side (thin plate side) HAZ but also on the thick wall side (thick plate side) HAZ. In FIG. 6, the reduction in joint strength and elongation in the HAZ of the heat treatment type Al alloy material welded joint material occurs not only in the thin plate 2 but also in the HAZ 7 of the thick plate 3. However, when the wall thickness is large as in the case of the thick plate 3, even if a tensile stress is applied to the welded joint material, the stress generated in the HAZ 7 can be reduced compared to the steady joint region. In addition, due to the wall thickness effect, it is possible to suppress a decrease in joint strength and elongation of the HAZ on the thin wall side during welding. As a result, when the tensile stress is applied to the welded joint, the fracture mainly occurs in the HAZ 6 on the thin plate 2 side where the thickness effect is not exhibited. Therefore, it is meaningful to provide a thick part on the thick-walled (thick plate-side) HAZ so that this thickening effect is difficult to achieve, and when the difference in wall pressure between the Al alloy materials to be joined is small. HAZ on the side.
[0040]
  Welded joint material 1b in the mode of FIG.1 (b)Is only a reference example,This is an equal thickness tailored blank material for press forming in which the thin plate 2b and the thin plate 3b having the same thickness are butt welded at the welding portion 5. In FIG. 1 (b), both the thin plate 2b and the thin plate 3b are provided in the

HAZ

6a, 6b, which are in the vicinity of the joint portion 4b, with

thick portions

8a, 8b having a rectangular cross section along the

HAZ

6a, 6b. .
[0041]
The welded joint material 1c in the embodiment shown in FIG. 1 (c) is a differential thickness tailored blank for press forming, in which a thin plate 2c and a thick plate 3c having different thicknesses are overlapped and welded at two locations of the welded

portions

5a and 5b. It is a material. In FIG. 1 (c), a thick portion 8c having a rectangular cross section is provided along the HAZ 6c in the HAZ 6c of the thin plate 2c in the vicinity of the joint 4c.
[0042]
The welding joint material 1d in the embodiment of FIG. 1 (d) has a plate thickness of 2d and a thick plate 3d whose end portions are bent in an L shape, and the welded portion 5a in the bent portion of the thin plate 2d. This is a welded joint material that is superposed and welded at two locations of 5b. In FIG. 1 (d), a thick section 8d having a rectangular cross section is provided along the HAZ 6d in the HAZ 6d of the thin plate 2d in the vicinity of the joint section 4d.
[0043]
Next, FIGS. 2 (a), (b), (c), and (d) are side views of a welded joint between an Al alloy plate and an Al alloy profile in an Al alloy structural material. When these Al alloy structural materials are press-molded, the Al alloy plate side is press-molded.
[0044]
The welded joint material 1e in the embodiment of FIG. 2 (a) is a joint material obtained by laminating and welding a thin rectangular hollow shape material 2e and a thick plate 3e at two locations of the welded

portions

5a and 5b. In the welded joint material 1e in FIG. 2 (a), the thick section 8e, 8e having a rectangular cross section is formed inside the hollow section 2e of the

HAZ

6e, 6e, which is in the vicinity of the joint section 4e on the rectangular hollow section 2e side. HAZ6e and 6e are provided. The thick portions 8e and 8e may be provided outside the hollow shape member 2e of the

HAZ

6e and 6e.
[0045]
The welded joint material 1f in the embodiment shown in FIG. 2 (b) includes a thin rectangular hollow member 2f and a thick plate 3f, which are welded at the flange portion 9 of the hollow member 2f at two locations, welded

portions

5a and 5b. It is a welded joint material welded by lap welding. In the welded joint material 1f shown in Fig. 2 (b), the thick section 8f having a rectangular cross section is formed on the HAZ6f at the top of the HAZ6f of the flange section 9 near the joint section 4f on the thin rectangular hollow section 2f side. It is provided along. The thick part 8f may be provided below the HAZ 6f of the flange part 9.
[0046]
The welding joint material 1g in the embodiment of FIG. 2 (c), conversely, has a thick rectangular hollow material 3g and a thin plate 2g, which are overlapped at the upper part of the hollow material 3g at two locations, welded

parts

5a and 5b. It is a welded joint material welded together. In the welded joint material 1g of FIG. 2 (c), a thick section 8g having a rectangular cross section is provided along the HAZ 6g on the top of the HAZ 6g, which is in the vicinity of the joint 4g on the thin plate 2g side. The thick part 8g may be provided below the HAZ 6g of the thin plate 2g.
[0047]
The welding joint material 1h in the embodiment of FIG. 2 (d), conversely, has a rectangular hollow shape member 3h having a thin wall thickness and a thin plate 2h having a thin plate thickness in the flange portion 9 of the hollow shape member 3h. It is a welded joint material that is overlap welded at 5a and 5b. In the welded joint material 1h in FIG. 2 (d), the rectangular cross section is formed in the vicinity of the joint 4h, inside the hollow section 3h side HAZ6h, inside the hollow section 6h, and above the thin plate 2h side HAZ6i. The

thick wall portions

8h, 8h, and 8i having a shape are provided along the HAZ6h, 6h, and HAZ6i. The

thick wall portions

8h, 8h may be provided outside the

HAZ

6h, 6h hollow profile 3h. The thick part 8h may be provided below the HAZ 6i of the thin plate 2h.
[0048]
FIG. 3 shows another embodiment of the present invention in which a thick part is provided in an Al alloy structural material used without being press-formed. In the examples shown in FIGS. 1 and 2, the thick wall portion is made as small as possible in order to satisfy the demand for weight reduction because it is used for press-molded panels. However, in the example of FIG. 3, an example of a structural material that bears a certain amount of stress is shown, and the thick portion is made relatively large.
[0049]
That is, the welded joint material 1i itself in the embodiment of FIG. 3 is a welded joint material obtained by butt welding the thin plate material 2i and the thick plate 3i at the welding construction part 5, as in FIG. However, in the welded joint material 1i of this embodiment shown in Fig. 3, in order to increase the joint strength, the HAZ6i on the thin plate material 2i side is thickened so as to fill in the step due to the difference in the plate thickness between the two materials in the welded part 5. It has become. For this reason, the thick portion 8i in FIG. 3 has a relatively large rectangular shape (trapezoidal cross-sectional shape) having a hypotenuse 9 inclined toward the plate 2i.
[0050]
These thick parts guarantee the elongation and thickness reduction of the Al alloy material by the thickness effect of the thick part, and prevent fracture at the HAZ when the weld joint is loaded with tensile stress. Therefore, the position and thickness of the thick portion are important, and the cross-sectional shape of the thick portion may be appropriately selected as a shape that is easy to provide. The longitudinal direction of the thick portion is provided along the HAZ as described above, but may be provided intermittently without being continuous in the longitudinal direction as long as the effect can be achieved. Furthermore, the thick portion may be provided by being divided in the longitudinal direction. Further, in structural material applications that bear a certain amount of stress, the thick portion may be made relatively large as shown in FIG. 3 in order to increase the joint strength.
[0051]
Below, the preferable provision method of this invention thick part is demonstrated.
As shown in Fig. 4 which shows the same welded joint as in Fig. 1 (a), in order to prevent fracture at HAZ when a tensile stress P is applied to the welded joint, it is preferable that the thin plate 2 side The thickness effect of the thick portion 8 of the HAZ 6 is equal to or greater than the same thickness effect as the steady portion of the thin plate 2. That is, the thickness (t4) and tensile strength (σ of the thick part 8 of the HAZ6 on the thin plate 2 side_B4) Product, t4 × σ_B4The thickness (t1) and tensile strength (σ_B1) Product, t1 × σ_B1That's it.
In other words, in the welded joint material of the present invention, the thickness of the thick part of the thin HAZ is (thickness t1 of the thin part x tensile strength σ of the steady part)_B1) / Tensile strength σ of heat affected zone_B4The above is preferable.
[0052]
Note that the thick portion of the HAZ portion may be divided into two or more in the longitudinal direction of the welded joint material or in the weld joint (weld line) direction, instead of one. Also, it is not necessary to cover all the longitudinal directions and weld joint directions of the HAZ part, and in these directions, a thick part may be provided only in the HAZ part where joint strength and formability are particularly required. .
[0053]
The thickness of the thick part of the HAZ is preferably determined in consideration of the tempered state (tensile strength and elongation) of the heat-treatable Al alloy material on the thin wall side in question. When the heat treatment type Al alloy material on the thin wall side is a T4 tempered material, the decrease in tensile strength and elongation due to the influence of welding heat is relatively small compared to the T5 or T6 tempered material. The thickness of the thick portion provided in the type Al alloy material is preferably 1 / 0.95 or more and 1 / 0.8 or less of the steady portion.
[0054]
On the other hand, when the heat-treatable Al alloy material is a T5 or T6 tempered material, the decrease in tensile strength and elongation due to the effect of welding heat is relatively large, and the thickness of the thick part is 1 / 0.75 or more of the steady part. It is preferable to take a relatively large value of 1 / 0.55 or less.
[0055]
Furthermore, the position of the HAZ where the tensile strength and elongation decrease most is generally within a range of 20 to 25 mm from the center of the welded joint under normal welding conditions, as shown by the same joint in FIG. It fits in the area. Also, the width of the HAZ is generally within the range of 2 to 5 mm. However, when the heat-treatable Al alloy material is a T4 tempered material, the region within 25 mm from the center of the welded joint part is partially reduced in strength. Further, when the heat-treatable Al alloy material is a T5 or T6 tempered material, the strength of the thick portion in the region within 20 mm from the center of the welded joint is lowered overall.
[0056]
Therefore, with regard to the position where the thick part is provided, when the heat-treatable Al alloy material is a T4 tempered material, preferably, the thick part is set to a width (region) within 25 mm from the center of the welded joint. By providing one or more locations within the range of ~ 5mm, the HAZ position that regulates tensile strength and elongation can be covered generally.
[0057]
Further, when the heat-treatable Al alloy material is a T5 or T6 tempered material, preferably, the thick-walled portion is provided entirely in a region within 20 mm from the center of the welded joint, thereby increasing the tensile strength and elongation. The position of the HAZ that regulates
[0058]
The thick part is provided in advance on the heat-treatable Al alloy material (base material) before welding. When it is provided after welding, as described above, the thick-wall effect that can suppress the decrease in joint strength and elongation itself in the HAZ during welding is not exhibited regardless of the way of providing.
[0059]
When a thick portion is provided in advance in the plate material, profile rolling or the like is performed during the rolling production of the plate material so that the base material portion corresponding to the thick portion installation position (region) of the welded joint material becomes the thick portion. It is preferable to provide them integrally, or to grind parts other than the thick part (equivalent to a thin part) by machining or the like. In addition, a thick member having a predetermined condition can be bonded to a predetermined position of the rolled plate material, but it is necessary to increase the bonding strength between the plate material and the thick member.
[0060]
In the case of a shape material, cast forging material, cast material, it is also possible to provide it in advance by bonding or the like as with the plate material, but it is designed in advance as a base material shape including a thick part shape, extruded, forged, In casting, it can be easily and integrally formed.
[0061]
The heat-treatable Al alloy material (stretched material) used in the welded joint material of the present invention is specified in AA to JIS standards (satisfying AA to JIS standards), and is widely used as an Al alloy for welded structures, 6000 series, Al alloy material such as 7000 series. The heat-treatable Al alloy castings are Al-Cu-Si, Al-Cu-Mg-Si, and Al-Mg-Si based on AA or JIS standards (satisfying AA to JIS standards) Al alloy such as. In addition, among the 6000 series Al alloy materials, there is a large problem of joint strength and elongation reduction in the thin-walled HAZ, Si / Mg is 1 or more (Si is excessively contained with respect to Mg content), It is preferably applied to Si-rich 6000 series (Al-Mg-Si series) Al alloys such as 6N01, 6016, 6111 and 6022.
[0062]
The heat treatment type or non-heat treatment type Al alloy material itself used in the present invention welded material is melted, cast, homogenized heat treatment, hot working (rolling, extrusion, forging), if necessary, intermediate annealing, cold working (rolling, By a conventional process such as forging, a plate material or a profile (a profile whose cross-sectional shape is essentially the same at any position in the length direction, such as a hollow cross section), a forged material, or a cast material is manufactured.
[0063]
The heat-treated Al alloy material after manufacture obtains characteristics such as predetermined strength by the tempering treatment such as T4, T5, T6 and the like, and is used as a base material as a welding joint material. Further, the non-heat-treatable Al alloy material is used as a base material as a welded joint by obtaining characteristics such as predetermined strength as it is manufactured or by tempering treatment such as annealing (O material).
[0064]
The weld joint method of the present invention weld joint material is a fusion welding method using a heat source such as an arc such as TIG (TIG), MIG ( It covers welding methods such as high-speed arc welding such as MIG), laser welding, electron beam welding, resistance seam welding, and friction stir welding (FSW).
[0065]
Moreover, the construction conditions in these welding joining methods are performed within the range of ordinary methods. However, in the case of fusion welding, it is preferable to apply a 5000 series Al alloy filler (rod) such as 5356 or a 4000 series Al alloy filler such as 4047. In this regard, in the lower temperature friction stir welding method, it is easy to increase the thickness including HAZ in the vicinity of the step of the differential thickness joint portion without using a filler material.
[0066]
The Al alloy welded joint material of the present invention has a structure in which it is combined with other members after being welded and jointed with other members without being subjected to a molding process such as bending or press molding, depending on a specific structural material application. It is properly installed and used as a material.
[0067]
【Example】
Next, examples of the present invention will be described.
(Example 1)
Using each of the T4 tempered materials of the excess Si type 6022Al alloy plate having an alloy composition as shown in Table 1, a welded joint material having a thick part in the shape shown in FIG. 1 (a) (tailored blank material) Made 1a. In the welded joint material, a thick portion 8a was integrally provided in advance on the thin plate side HAZ 6a under the conditions shown in Table 3 by machining to thin the portion other than the thick portion. The weld length of the joint was 700 mm, and the joints were joined by the welding methods and welding conditions shown in Table 2. For comparison, a welded joint material between 6022Al alloy T4 tempered plate materials and a welded material between 5182Al alloy O tempered plate materials were manufactured under the same conditions as in the invention examples except that the thick part was not present.
[0068]
Table 3 (also in Table 5 of Example 2 to be described later) shows that each example shows the preferable conditions for the above-mentioned T4 tempered material of the thick part of the HAZ on the thin wall side. Thickness (Thickness of thin part t1 × Tensile strength of steady part σ_B1) / Tensile strength σ of heat affected zone_B4(2) The thickness of the thick part is 1 / 0.95 or more and 1 / 0.8 or less of the steady part corresponding to the T4 tempering of the thin part Al alloy material of the steady part. (3) Welded joint ○ indicates that it is satisfied that it is provided within an area (part) within 25 mm from the center with a width of 2 to 5 mm.
[0069]
In addition, the cross section of the welded joint was observed with a 100 × optical microscope, and the presence or absence of microscopic weld cracks was investigated in addition to the visible weld cracks. As a result, no weld cracks in the joints were observed in the invention examples and comparative examples.
[0070]
Further, the hardness of the HAZ 6a and the steady part on the 6022Al alloy thin plate 2a side (after welding) of the welded joint material was measured. Also, the joint strength (σ_B) And joint elongation (δ) were measured according to JIS Z 2241. Furthermore, a press molding test was conducted on the assumption that the welded joint material thus obtained was applied to an automobile panel material, and the moldability was evaluated. These results are shown in Table 4.
[0071]
The conditions of the press-molded product are as follows: product part height 35mm, length 550mm, width 450mm, corner radius of curvature R100-150mm, and the shape of the draw bead and die face of the mold It was provided to adapt to the shape conditions. Then, press molding was performed under the conditions of a wrinkle holding force of 50 tonf, a used lubricating oil R-303, and a molding speed of 20 mm / min.
[0072]
In addition, when the press-formed product is not broken at any point including the welded joint and can be molded well, it is marked as ◯. The HAZ and welded joints are not broken, and the strength of the HAZ and welded joints is good. Some were broken at the stationary part, and Δ when HAZ was broken.
[0073]
As is apparent from Tables 3 and 4, the welded joints of Invention Examples Nos. 1, 2, 3, 8, and 9 that satisfy all of the preferred conditions (1) to (3) are the weld joints after welding. Despite the fact that the hardness of HAZ6a on the thin plate 2a side is significantly lower than the hardness of the steady part, the joint tensile strength (σ_B), Joint elongation (δ) and weld joint efficiency are also relatively high at 100%. In addition, the press-formed product is not broken at any place including the crack of HAZ, and the press formability is good. Moreover, these results are obtained regardless of differences in welding methods and filler material conditions.
[0074]
Further, the thickness of the thick part of the HAZ is relatively thin, and the preferable conditions of the above (1) are not satisfied at the lower limit (the preferable conditions of the above (2) and (3) are satisfied). Welded

joints

4 and 5 have joint tensile strength (σ_B) And welding joint material efficiency is relatively high. However, the joint elongation (δ) is relatively low, the steady portion of the press-formed product is broken, and the press formability is inferior to those of the above-described invention examples. Therefore, from the viewpoint of improving press formability, the thickness of the thick part of the HAZ should be increased by the required amount, and the thickness of the above-mentioned (1) thick part (the thickness t1 of the thin part × the tensile strength σ of the steady part)_B1) / Tensile strength σ of heat affected zone_B4The importance of the preferable conditions mentioned above is understood.
[0075]
On the other hand, the thickness of the thick part is relatively thick and does not satisfy the upper limit of the preferable condition (2) (the preferable conditions (1) and (3) are satisfied). The welded joint material was also subjected to joint tensile strength (σ) in the same manner as in Invention Examples Nos. 1, 2, 3, 8, and 9._B), Joint elongation (δ) and weld joint efficiency are relatively high at 100%, and press formability is good. However, even in the invention examples No. 1, 2, 3, 8, and 9 where the thickness of the thick part is relatively thin, the press formability is good, and from the viewpoint of weight reduction, the invention example No. 6 In addition, it can be seen that the object can be achieved without increasing the thickness of the thick portion. Therefore, the preferable condition that the thickness of the thick part of the above (2) is 1 / 0.95 or more and 1 / 0.8 or less of the steady part is important for improving the press formability without impairing the weight reduction. I understand.
[0076]
Further, although the thickness of the thick part is relatively large, the width of the thick part is relatively narrow, and the preferable condition of the above (3) is not satisfied with the lower limit (the preferable conditions of the above (1) and (2) The weld joint material of Invention Example No. 7 has a joint tensile strength (σ_B) And joint elongation (δ) and weld joint efficiency are relatively low. For this reason, the stationary part of the press-formed product is broken, and the press formability is inferior to each of the above invention examples. Therefore, in order to improve press formability, the width of the thick part of the HAZ should be increased by the required amount, and the thick part of the above (3) should be placed within a region (part) within 25 mm from the center of the welded joint. The importance of the lower limit of preferable conditions provided in the range of 5 mm can be seen.
[0077]
However, the width of the thick part is comparatively wide and does not satisfy the upper limit of the preferable condition (3) (the preferable conditions (1) and (2) are satisfied). The welded joint material has a joint tensile strength (σ as in the case of the invention examples No. 1, 2, 3, 8, 9)._B), Joint elongation (δ) and weld joint efficiency are relatively high at 100%, and press formability is good. However, from the viewpoint of weight reduction, it can be seen that the object can be achieved without increasing the width of the thick portion as much as in Invention Example No. 10. Therefore, it can be seen that the upper limit of the preferable condition (3) is important for improving the press formability without impairing the weight reduction.
[0078]
On the other hand, in Comparative Examples No. 1 to 4 where no thick part is provided, except for Comparative Example No. 4 using non-heat treated type 5182 alloys, the joint tensile strength (σ_B), Joint elongation (δ), and welded joint efficiency are also lower than those of the inventive examples, and HAZ cracking occurs even in the press forming, and the press forming is inferior to the inventive examples.
[0079]
The welded joint material of Comparative Example No. 4 using non-heat treatment type 5182 alloy is the hardness of HAZ6a on the thin plate 2a side of the welded joint material after welding, and the joint tensile strength (σ_B), Joint elongation (δ) and weld joint efficiency do not decrease so much, cracks do not occur in HAZ, and press formability is good.
[0080]
From the results of these examples, in heat treated Al alloy welded joints, even if the strength and elongation of HAZ are inevitably decreased, the HAZ can be prevented from breaking by increasing the thickness of the HAZ, and the joint strength and fracture can be prevented. The critical significance of the thick part of the present invention and its preferred conditions, which can improve the elongation and formability, is supported. Further, in comparison with Comparative Example 4 which is the non-heat treatment type 5182Al alloy welded joint material, it can be seen that the problems of the strength and elongation decrease in the HAZ are problems specific to the heat treatable Al alloy welded joint material.
[0081]
[Table 1]

[0082]
[Table 2]

[0083]
[Table 3]

[0084]
[Table 4]

[0085]
(Example 2)
Next, using each of the T6 tempered materials of the excess Si type 6022Al alloy plate having the alloy composition shown in Table 1 as in Example 1, the thick portion 8i having the inclined surface 9 in the shape shown in FIG. Welded joint material 1i provided with Under the conditions shown in Table 5, on the thin plate side HAZ of the 6022Al alloy plate material, a thick portion was provided integrally in advance by mechanical grinding of the thin portion. The width of the thick portion is the width of only the flat portion excluding the inclined surface 9 (the horizontal length is 5 mm). The weld length of the joint was 30 mm, and the joints were joined according to the welding methods and welding conditions shown in Table 5. For comparison, a welded joint material between 6022Al alloy T6 tempered plate materials was manufactured under the same conditions except that there was no thick part.
[0086]
In Table 5, each example corresponds to the T5 or T6 tempered material of the thin-walled Al alloy material, and the thickness (1) of the thick-walled portion of the thin-walled HAZ (thickness of thin-walled portion t1 × steady-state) Tensile strength σ_B1) / Tensile strength σ of heat affected zone_B4The above-mentioned preferable conditions such as (2) The thickness is set to 1 / 0.95 or more and 1 / 0.8 or less of the steady portion, and (3) is generally provided in a region within 20 mm from the center of the welded joint are satisfied. The case is marked with ◯, and the case where it is not satisfactory is marked with-.
[0087]
The cross-section of each welded joint after welding was observed with a 100x optical microscope, and in addition to visible weld cracks, the presence of microscopic weld cracks was investigated. No weld cracking was observed.
[0088]
The hardness of the HAZ6i and the steady part on the Al alloy thin plate 2i side (after welding) of the welded joint material thus obtained was measured. Also, the joint strength (σ_B) Was measured according to JIS Z 2241. These results are shown in Table 6.
[0089]
As is apparent from Tables 5 and 6, the welded joints of Invention Examples Nos. 11, 12, and 13 that satisfy all of the preferred conditions (1) to (3) described above are on the thin plate 2i side of the welded joints after welding. Although the HAZ6i hardness is significantly lower than the hardness of the steady-state part, the joint tensile strength (σ_B) Is 350MPa or more, and the joint efficiency is remarkably high at 100%. Moreover, these results are obtained regardless of differences in welding methods and filler material conditions.
[0090]
Further, the thickness of the thick part of the HAZ is relatively thin, and the preferable conditions of the above (1) are not satisfied at the lower limit (the preferable conditions of the above (2) and (3) are satisfied). The welded joint materials 14 and 15 have lower joint strength and joint efficiency than those of Invention Examples Nos. 11, 12, and 13. Therefore, when the thin-walled Al alloy material is T5 or T6 tempered material, in order to improve the joint strength and joint efficiency, increase the thickness of the thick part of the HAZ to the required amount, and the above (1) thickness The thickness of the meat part ((thickness t1 of the thin part x tensile strength σ of the steady part)_B1) / Tensile strength σ of heat affected zone_B4The importance of the preferable conditions mentioned above is understood.
[0091]
On the other hand, the thickness of the thick part is comparatively thick and does not satisfy the upper limit of the preferable condition (2) (the preferable conditions (1) and (3) are satisfied). The weld joint material also has high joint strength and joint efficiency, similar to the invention examples Nos. 11, 12, and 13. However, the performance of the invention part Nos. 11, 12, and 13 is relatively small in the thickness of the thick part. From the viewpoint of weight reduction, the thick part is as thick as the invention example No. 6. It can be seen that the object can be achieved without increasing the thickness of the film. Therefore, the preferable condition that the thickness of the thick part of (2) is 1 / 0.95 or more and 1 / 0.8 or less of the steady part is important for improving joint strength and joint efficiency without impairing weight reduction. I understand that.
[0092]
Furthermore, although the thickness of the thick part is relatively large, the width of the thick part is relatively narrow (the above preferable conditions (1) and (2) are satisfied). Has relatively low joint strength and joint efficiency. Therefore, it can be seen that the width of the thick part of the HAZ is increased by the required amount in terms of improving joint strength and joint efficiency.
[0093]
However, Invention Example No. 18 in which the width of the thick portion is relatively wide and does not satisfy the upper limit of the preferable condition of (3) is equivalent to the joint strength and the invention example No. 11, 12, and 13. High joint efficiency. However, the performance of the invention part Nos. 11, 12, 13 having a relatively narrow width is equal to that of the invention part No. 18, from the viewpoint of weight reduction. It can be seen that the objective can be achieved without increasing the width. Therefore, from the viewpoint of weight reduction, it is understood that the preferable condition of providing the thick part (3) in the entire region within 20 mm from the center of the welded joint is important.
[0094]
On the other hand, in Comparative Examples No. 5 to 7 where no thick part is provided, the joint tensile strength (σ_B) And the joint efficiency are also significantly lower than the invention example.
[0095]
From the results of these examples, in the heat treatment type Al alloy welded joint material, even when the strength and elongation of the HAZ are inevitably lowered, the joint strength can be improved by increasing the thickness of the HAZ. The significance of the preferable conditions is supported.
[0096]
[Table 5]

[0097]
[Table 6]

[0098]
【The invention's effect】
According to the present invention, it is possible to provide a heat-treatable Al alloy welded joint material excellent in joint strength and elongation of the welded joint material and formability even when the hardness decreases in HAZ. Therefore, the industrial value is great in that the heat-treatable Al alloy welded joint can be expanded to automotive applications.
[Brief description of the drawings]
1 (a), (b), (c), and (d) are side views showing one embodiment of an Al alloy welded joint material of the present invention.
FIGS. 2 (a), (b), (c), and (d) are side views showing other embodiments of the Al alloy welded joint material of the present invention.
FIG. 3 is a side view showing another embodiment of the Al alloy welded joint material of the present invention.
FIG. 4 is a side view showing how to provide a thick portion of the Al alloy welded joint material of the present invention.
FIG. 5 is a side view showing how to provide a thick portion of the Al alloy welded joint material of the present invention.
FIG. 6 is a side view showing a heat affected zone of an Al alloy welded joint material.
FIG. 7 is an explanatory diagram showing a Vickers hardness (HV) distribution including a heat-affected zone of an Al alloy weld joint.
FIG. 8 is an explanatory view showing joint strength and joint elongation of an Al alloy welded joint material.
FIG. 9 is an explanatory view showing a relationship between joint elongation and wall thickness of an Al alloy welded joint material.
[Explanation of symbols]
1: Al alloy welded material, 2: Al alloy material, 3: Al alloy material, 4: Joint, 5: Welding direction, 6: Heat affected zone (HAZ), 7: Heat affected zone (HAZ), 8 : Thick part, 9: Flange part

Claims

Heat-treatable aluminum alloy materials, or heat-treatable aluminum alloy materials and non-heat-treatable aluminum alloy materials with different thicknesses are welded together , and at least the heat effect of the heat-treatable aluminum alloy material on the thin wall side A thick-walled part is provided in advance in the part before welding, and an aluminum alloy welded joint material is provided.

2. The aluminum alloy welded joint material according to claim 1 , wherein the thickness of the thick portion is equal to or greater than ( thickness of the steady portion × tensile strength of the steady portion ) / tensile strength of the heat affected zone .