JP3740031B2 - Liquid phase diffusion bonding method using groove filler and its joint - Google Patents
Liquid phase diffusion bonding method using groove filler and its joint Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
本発明は金属材料の液相拡散接合に関し、詳しくは炭素鋼、ステンレス鋼、Ｎｉ基合金、超合金ないしは耐熱合金鋼等の液相拡散接合に用いられる開先充填材及びそれを用いた溶接継手に関する。
【０００２】
【従来の技術】
従来、鋼材、ステンレス鋼、Ｎｉ基合金、超合金ないしは耐熱合金鋼等の金属材料の接合は、主として溶接にて実施されており、母材と同等以上の特性を確保するためにその溶接条件を制御していた。一般に金属材料の溶接方法は、被溶接材料の接合面を機械加工で仕上げた、いわゆる開先形状を形成し、種々の溶接材料で開先部間を融合することにより溶接継手を形成する。
【０００３】
この溶接継手の機械的特性は、溶接後の溶融金属の冷却に伴って生じる凝固組織の制御が技術的に重要となる。特に、溶接においては、一般的に溶接後の溶融金属の冷却速度が急速なため、溶接部の大きな熱膨張、収縮に伴う残留歪みを生じることが知られており、また、被溶接材料（母材）と溶接金属の化学成分が通常異なることから、構造用材料の継手形状及び特性を制御する上で問題となることが多い。また、溶接時には、溶接金属を一旦溶融するため局部的に大きなエネルギーを投入し、溶融金属の局部的な温度は３０００℃にも達する。このため、溶接金属の周囲の被溶接材料（母材）の特性に与える影響は大きく、その溶接熱影響部の組織の不均一化及び強度、靱性等の機械的特性の低下が溶接継手特性劣化の一要因となる。これらの問題に加え、溶接による金属材料の接合では、基本的に、溶接継手の品質は、その接合開先への良好な溶接金属形成のための溶接作業者の熟練度に負うところが大きい。したがって、信頼性を有する構造材料を溶接により接合する場合は、多額の費用と時間を要するのが常であった。
【０００４】
一方、これらの溶接技術を代替する金属材料の接合技術として、溶接のように溶融金属の高温状態からの急激な冷却による凝固現象を伴わず、溶融金属から開先面を経て被接合材料中へ原子を拡散させ、溶融金属の組成変質による凝固で継手を形成する液相拡散接合法が検討されている。
この液相拡散接合法については、例えば、特開昭５３−８１４５８号公報、特開昭６２−３４６８５号公報、特開昭６２−２２７５９５号公報等では、真空または不活性雰囲気における液相拡散接合方法が開示され、特許第１８９１６１８号公報、特許第１８９１６１９号公報、特許第１８３７５７２号公報等では、酸化雰囲気で接合可能な接合用合金箔（インサートメタル）に関して開示されている。
【０００５】
一般に液相拡散接合においては、接合部の溶融金属の凝固は等温状態で生じるため、溶接のような歪みは残留し難く、また、溶融金属の最高加熱温度も接合材の非晶質合金箔（インサートメタル）を溶融するに必要な比較的低い温度、かつ被接合材料の融点以下の温度であるため、溶接法に比べて熱影響部への組織や機械的影響が少なく、その結果、継手特性への影響も少ない。さらに、溶融金属の被接合材料中への拡散現象を決定する接合条件は、非晶質合金箔（インサートメタル）の化学成分と被接合材料特性等からほぼ規定させるため、予め入熱量、接合時間などを計算機などにより厳密に制御可能であり、開先付き合わせ工程と接合工程を連結して統括的に制御することにより接合工程をほぼ自動化することが可能である。したがって、液相拡散接合のシステムは、溶接のロボットのシステム制御のような熟練した溶接技術者を基に人間の感覚器官及び溶接ノウハウ等のデータを蓄積し利用する等の複雑なシステムの必要はなく、極めてその操作が容易になる。
【０００６】
しかしながら、液相拡散接合は、一般に急冷凝固法等によって工業的に製造される厚さ数十ミクロンの薄い非晶質合金箔（インサートメタル）を用いて接合するため、被接合材の開先形状や付き合わせ精度が悪いと接合面に溶融金属に均一に充填されずに接合部に欠陥を生じる場合があり、そのために被接合材開先形状の極めて高精度な機械加工及び良好な付き合わせ精度が要求される。また、被接合材の付き合わせ精度を維持するために、２つの被接合材の付き合わせ時における軸心の不整合、目違い、開先面の加工精度等を厳密に管理し、自動接合工程のシステムに組み入れる必要があった。
【０００７】
図２に従来の液相拡散接合における被接合材の突き合わせ工程を模式図として示す。従来の液相拡散接合において、例えば、被接合材として、肉厚：１０ｍｍ、外径：１００ｍｍの２つの鋼管同士を端面接合する際は、両者の軸心不整による開先の開き７を１ｍｍ以下、目違い量８を鋼管肉厚の１０％以下（この場合、１ｍｍ以下）、鋼管開先面の加工精度を表面粗さ（Ｒｍａｘ）で１０μm 以下にするように管理されていた。ここで、開先の開き７は、両被接合材（鋼管）同士の接触点５の反対側に位置する両鋼管端面外縁間の距離とする。また、目違い量８は、接触点５で接している両被接合材（鋼管）の内の端面で接する方の被接合材（鋼管）端面における接触点５と端面外縁間の距離とする。
【０００８】
【発明が解決しようとする課題】
本発明は、上記従来技術の問題点に鑑みて、従来の液相拡散接合の被接合材の付き合わせ工程における両被接合材の軸心の不整合、目違い等の突き合わせ精度や被接合材開先面の加工精度等の条件のばらつきによる接合部特性の劣化を防止し、安定して良好な接合継手特性が得られる液相拡散接合方法を提供するものである。
【０００９】
具体的には、本発明は、液相拡散接合において、被接合材開先面間に所定の形状および成分及び特性を有する開先充填材（スペーサ）を非晶質合金箔（インサートメタル）を介して挿入して接合することにより、付き合わせ精度及び加工精度による接合不良を防止可能な液相拡散接合方法およびその接合継手を提供することを目的とする。
【００１０】
【課題を解決するための手段】
本発明は、上記の課題を解決するものであり、その要旨とするところは、以下の通りである。
（１）被接合材開先面同士を非晶質合金箔の液相拡散により接合する液相拡散接合方法において、両被接合材の開先面の間に、室温から接合温度までにおける引張強度が、下記（１）式の関係を満たす開先充填材を該開先充填材の接合面が前記両被接合材の開先面を包含するように挿入するとともに、該開先充填材の接合面と前記被接合材の開先面の少なくとも１方に非晶質合金箔を貼付し、その後、加圧・昇温することにより液相拡散接合を行うことを特徴とする液相拡散接合方法。
（開先充填材の引張強度）／（被接合材の引張強度）≦０．７ ・ ・（１）
【００１１】
（２）前記開先充填材が、質量％で、Ｃ：０．１５％以下を含有することを特徴とする上記（１）に記載の液相拡散接合方法。
（３）前記開先充填材が、質量％で、Ｃ：０．１５％以下、Ｃｒ：０．１〜３５％、Ｎｉ：０．１〜４０％を含有することを特徴とする上記（１）に記載の液相拡散接合方法。
（４）前記開先充填材の接合面の表面粗さ（Ｒｍａｘ）が１００μm 以下であることを特徴とする上記（１）から（３）の内の何れか１項に記載の液相拡散接合方法。
（５）前記開先充填材の形状として、突き合わせ方向の長さが０．１〜２０ｍｍ、２つの接合面がなす角度が４５度以下であることを特徴とする上記（１）から（４）の内の何れか１項に記載の液相拡散接合方法。
（６）前記（１）から（５）の内の何れか１項に記載の液相拡散接合方法によって接合され、前記開先充填材及び５００℃以上に１秒以上加熱させた被接合材の接合熱影響部の肉厚の増肉量が接合前の被接合材肉厚の１〜２０％であることを特徴とする液相拡散接合継手。
【００１２】
【発明の実施の形態】
以下、本発明の内容について詳細に説明する。
通常の液相拡散接合方法では、２つの被接合材の開先面の何れか１方に非晶質合金箔（以下インサートメタルと称する。）を貼付し、その後、２つの被接合材の内の１方から突き合わせ方向に所定応力を負荷し、且つ接合部をインサートメタルの融点以上の温度に加熱し、接合温度における被接合材の引張強度以上の所定応力を負荷したままで接合温度に液相拡散接合の等温凝固に必要な所定時間だけ保持することにより接合を終了させ、接合継ぎ手特性に応じて所定冷却速度あるいは、さらに熱処理を施すことで行われる。このような従来の液相拡散接合方法では、前述の通り、突き合わせ制御の精度および被接合材の開先面の機械加工精度（表面粗さ）の低下により、接合部に欠陥が生じて接合継手特性が劣化すると言う問題があり、これを防止するために、従来は、被接合材の突き合わせ時の両者の軸心不整による開先の開きを１ｍｍ以下、目違い量を鋼管肉厚の１０％以下、鋼管開先面の加工精度を表面粗さ（Ｒｍａｘ）で１０μm 以下に厳しく管理されていた。
【００１３】
本発明者らは、これらの従来の突き合わせ制御の精度および被接合材の開先面の機械加工精度（表面粗さ）の低下が生じた場合にも接合部の欠陥がなく良好な接合継手特性が得られる方法について鋭意検討を行った。
その結果、液相拡散接合する際に、突き合わせ接合する両被接合材の開先面の間に、所定の熱間塑性変形特性を有する開先充填材（以下、スペーサと称する）を挿入し液相拡散接合することにより、被接合材の開先面の表面粗さに起因する接合不良を防止することができることがわかった。また、さらに、上記の開先充填材の形状を所定範囲に規定することにより、被接合材の突き合わせ制御不良時の接合継手特性の劣化を防止できることがわかった。
【００１４】
本発明は、これらの知見を基になされたものであり、本発明により被接合材の突き合わせ時の両者の軸心不整による開先の開きを２０ｍｍ以下（従来：１ｍｍ以下）、目違い量を鋼管肉厚の２０％以下（従来：１０％以下）、被接合材の開先面の加工精度を表面粗さ（Ｒｍａｘ）で１００μm 以下（従来：１０μm 以下）まで緩和した条件においても、良好な接合継手特性が得られる方法である。
【００１５】
以下に本発明を詳細に説明する。
最初に本発明のスペーサの強度特性について説明する。
図７に、室温から１２００℃（接合温度近傍）までのスペーサの引張強度と被接合材の引張強度の比（強度比）の最大値と、接合で得られた接合継手の引張強度と被接合材の引張強度との比（強度比）の関係を示す。
【００１６】
前述の通り、従来の液相拡散接合では、被接合材の接合に用いられるインサートメタルの厚みが数十ミクロンと非常に薄いため、被接合材開先面の機械加工精度（表面粗さ）が悪い場合、その開先面の凹凸部に溶融金属が均一に充填されないため良好な液相拡散接合ができず、接合継手の必要強度、靱性等の特性を得られないことがあった。
【００１７】
これに対して、本発明者らの実験によれば、被接合材の開先間にインサートメタルを介して充填されたスペーサは、接合部の加圧・加熱時に自ら熱間塑性変形することによって開先面の凹凸形状に順応し、開先面表面にインサートメタルを均一に充填させることができ、その結果、良好な液相拡散接合部を形成できることがわかった。
【００１８】
本発明者らの実験によれば、図７から明らかなように室温から接合温度近傍に至るあらゆる温度において、スペーサと被接合材の強度比が以下の関係にあれば、被接合材に大きな塑性変形を誘起せずに、スペーサのみが塑性変形し開先面の凹凸形状に対応するよう柔軟に変形し、接合部に欠陥がなく良好な接合継ぎ手（接合継手と被接合材との強度比で０．９以上）が得られることが判った。
（スペーサの引張強度）／（被接合材の引張強度）≦０．７ ・ ・ （１）
このため、本発明では、スペーサの引張強度と被接合材の引張強度の比（強度比）を上記（１）式のように規定する。
【００１９】
従来の液相拡散接合では、接合部に欠陥がなく良好な接合継手特性を得るために、被接合材の開先面の機械加工精度（表面粗さ）を表面粗さ（Ｒｍａｘ）で１０μm 以下に厳しく管理されていたが、上記（１）式を満足する強度特性を有する本発明のスペーサを用いて液相拡散接合することにより、被接合材の開先面の機械加工精度（表面粗さ）を表面粗さ（Ｒｍａｘ）で１００μm 以下にまで緩和しても良好な接合継手特性を得ることが可能である。
【００２０】
次に本発明のスペーサに含有する化学成分（含有量は全て質量％）の限定理由について説明する。
一般に被接合材を液相拡散接合する際に用いるインサートメタルは、液相拡散接合部の組織の均質性の観点から被接合材の化学組成に応じて使い分けられる。この際、被接合材とインサートメタルは化学的に溶融混合し、それらの中間的な組成を有する接合相を生成するため、接合に用いるインサートメタルの化学成分は継ぎ手特性に影響を与える。したがって、本発明で使用するスペーサの化学成分もインサートメタルとの接合部の組織及び特性の均一性の観点から用いる被接合材の種類によって以下のように規定することが好ましい。
（鉄基系スペーサ）
本発明において、炭素鋼等の鉄基被接合材をスペーサを用いて液相拡散接合する場合には、その接合部の組織及び特性の均質性の観点から鉄基系スペーサを使用することが好ましい。特に、炭素鋼等の鉄基被接合材の場合には、スペーサ中の炭素量が液相拡散接合部の靱性に大きな影響を与えるため、本発明のスペーサでは、Ｃの含有量を以下のように規定する。
【００２１】
Ｃ：Ｃは、母材強度を向上させる基本的な元素として欠かせない元素であるが、本発明は、液相拡散接合部の靱性の極度の劣化が生じないようにその含有量の上限を０．１５％に規定する。本発明者らの実験の結果、Ｃ含有量が０．００１％から０．１５％の範囲で液相拡散接合部の靱性が良好であった。本発明では、Ｃ含有量の下限については、特に規定する必要がないが、液相拡散接合部に強度を必要する場合には、その所要強度に応じてＣ含有量を調整できる。
【００２２】
図５には、スペーサの炭素含有量と接合で得られた接合継手の引張強度と被接合材の引張強度との比（強度比）の関係を示す。なお、この際のスペーサのＭｎ含有量：１％、Ｓｉ：０．０５％であるが、本発明者らの実験の結果、Ｃ以外の成分は、接合特性に大きな影響は与えなかった。図７からスペーサのＣ含有量が０．１５％以下で接合継ぎ手の必要強度（接合継手と被接合材との強度比で０．９以上）が得られることが判る。
（Ｃｒ−Ｎｉ系スペーサ）
本発明において、Ｃｒ、Ｎｉを含有する被接合材、例えば、耐食ステンレス鋼、耐熱ステンレス鋼、工具鋼、Ｎｉ基合金鋼または超合金鋼を液相拡散接合する場合には、液相拡散接合部の組織及び特性の均質性の観点からＣｒ−Ｎｉ系スペーサを使用することが好ましい。特に、Ｃｒ、Ｎｉを含有する被接合材の場合には、鉄基系スペーサに比べて液相拡散接合部の熱間強度を要求されることが多いため、その相をγ単相あるいはα−γ２相に調整し、オーステナイト、あるいはマルテンサイトの組織に均質化する必要があり、このために、上記の鉄基系スペーサのＣ含有量を同様な理由で０．１５％以下に規定するとともに、さらにＣｒ、Ｎｉの含有量を以下のように規定する。
【００２３】
Ｃｒ：Ｃｒは耐食性を向上させる元素であり、例えば、雨水や水道水等のような非常にマイルドな腐食環境から溶融塩あるいは高温燃焼灰が付着するボイラ等の厳しい腐食環境に耐えられる耐食性を発揮するためには、０．１％以上含有する必要があるが、３５％を超える多量な添加は、靱性低下等の悪影響を及ぼすため、その含有量を０．１〜３５％とする。
【００２４】
Ｎｉ：Ｎｉは、金属格子構造を変化させて高温強度を向上させる元素であり、オーステナイト鋼にとって重要な元素である。この効果を充分に得るために、０．１質量％以上、Ｃｒ含有量とのバランスのもとで含有し、靱性低下等の悪影響のないように上限を４０％とし、０．１％〜４０％の範囲で添加する。
図６には、Ｃｒ：２０％及びＮｉ：２５％を含有するスペーサ中の炭素含有量と接合で得られた接合継手の引張強度と被接合材の引張強度との比（強度比）の関係を示す。図５と同様にスペーサ中のＣ含有量が０．１５％以下で接合継ぎ手の必要強度（接合継手と被接合材との強度比で０．９以上）が得られることが判る。これは、炭化物生成による継ぎ手特性劣化によるものである。
【００２５】
次に本発明のスペーサの表面加工精度（表面粗さ）及び形状の限定理由について説明する。
（表面加工精度（表面粗さ））
スペーサの表面加工精度は、上述の強度特性とともに被接合材の開先面との間で良好な液相拡散接合部を形成するために重要となる。特に、インサートメタルが薄い場合には、表面加工精度、つまり表面粗さが粗くなると、被接合材の開先面及びスペーサ面の凹凸形状により、開先面とスペーサ間に間隙が生じ、良好な液相拡散接合部を形成し難い。
【００２６】
本発明のスペーサーは、上述のスペーサ強度特性を有する軟質材であり、被接合材の開先面の凹凸形状に対応するように塑性変形可能なため、その表面加工精度は、従来の被接合材の開先面に要求される表面加工精度（表面粗さ（Ｒｍａｘ）：１０μm 以下、インサートメタル厚みが約３０μm の場合）よりも粗くできるが、表面加工粗さが１００μm を超えると、被接合材の開先面とスペーサ間に間隙が生じ、良好な液相拡散接合部を形成できないため、その表面加工精度（表面粗さ（Ｒｍａｘ））の上限を１００μm に規定する必要がある。
【００２７】
図４に、スペーサー表面の加工精度（表面粗さ（Ｒｍａｘ））と接合で得られた接合継手の引張強度と被接合材の引張強度との比（強度比）の関係を示す。工業的に使用可能な接合継手の引張強度の目安である接合継手と被接合材との強度比：０．９以上を達成できるためには、スペーサーの表面加工粗さが１００μm以下とする必要がある。
（スペーサ形状）
本発明の液相拡散接合で使用するスペーサは、被接合材開先面にインサートメタルを介して挿入する際に、その後の液相拡散接合に必要な溶融インサートメタルを開先面全体に均一に覆わせるために、少なくとも開先面を充分に包含する形状とする必要がある。被接合材開先面に対してスペーサの一部に欠損領域がある場合は、液相拡散接合時に溶融インサートメタルがその欠損領域に滞留し被接合材の開先面全体を均一に覆わせることができなくなり、特にインサートメタルの厚みが１０μｍ以下のように薄くなる程、その傾向が大きく、所望の品質を確保できない。
【００２８】
また、本発明のスペーサは、被接合材同士の突き合わせ精度が充分でない場合に、その開先間を補完して液相拡散接合を良好に行い、所望の品質を確保するための役割を担う。
以上の理由から本発明のスペーサーの形状を以下のように限定することが好ましい。
（スペーサ厚み）
図１に本発明のスペーサと被接合材の配置図を示す。
【００２９】
本発明では、図１に示すスペーサ厚み（突き合わせ方向に平行な長さの最大長さ）を０．１〜２０ｍｍに規定する。スペーサ厚み（突き合わせ方向に平行な長さの最大長さ）は、突き合わせ精度が充分でない場合に、その開先間を充分に補完して良好な液相拡散接合を形成させるために作用するが、０．１ｍｍ未満では、液相拡散接合に溶融インサートメタルを開先面全体に均一に覆わせることができなく、また、２０ｍｍを超えると、接合面での均一かつ充分な押付け力が得られなくなるため、スペーサ厚み（突き合わせ方向に平行な長さの最大長さ）を０．１〜２０ｍｍとした。
【００３０】
従来の液相拡散接合では、接合部に欠陥がなく良好な接合継手特性を得るために、被接合材の突き合わせ時の両者の軸心不整による開先の開きを１ｍｍ以下に厳しく管理されていたが、上記の厚みを有する本発明のスペーサを用いて液相拡散接合することにより、軸心不整による開先の開きを２０ｍm 以下にまで緩和しても良好な接合継手特性を得ることが可能である。
（スペーサ接合面の角度）
一般に、２つの被接合材の開先面を互いに突き合わせる際に、両被接合材の軸心が一致することは少なく、突き合わせ精度のばらつきにより、両被接合材の軸心がずれたり傾くことが多い。本発明のスペーサは、このような突き合わせ時の被接合材同士の軸心の不整合が生じた場合に、それを補完、修正する作用がある。本発明では、被接合材同士の軸心の不整合が生じて、それぞれの開先面が非平行になった場合にも補完、修正する機能が充分えられるように、予めその突き合わせ不整合に応じて、スペーサの２つの接合面がなす角度（図１中の４）を０〜４５度の範囲に調整することが好ましい。
（接合継ぎ手部の増肉量）
従来、２つの被接合材の開先面形状が同一であっても、突き合わせ精度が充分でない場合に、図２に示されるような目違い（図２中の８）が生じる。この目違いは、溶接継手にとって実質的に接合面積が低減することを意味するため、接合継手の強度に影響する。通常、接合継手の引張強度は、引張り測定時に母材破断に至らない強度が必要となる。
【００３１】
本発明のスペーサは、上述ように突き合わせから溶接時にかけての引張強度が被接合材より低いため、被接合材の開先間にインサートメタルを介して充填されたスペーサは、軸心方向の接合応力によって熱影響部を含む接合部位を塑性変形して目違いを補完するように増肉することが可能となる。本発明によれば、従来、被接合材突き合わせ時の目違い量をその肉厚の１０％以下に管理する必要があったが、本発明によりそれを肉厚の２０％まで許容できることができ、突き合わせ精度を緩和することが可能となる。
【００３２】
図８は、接合継手部の増肉量（接合前の被接合材の肉厚に対する比率、５点測定の平均値）と、接合で得られた接合継手の引張強度と被接合材の引張強度との比（強度比）の関係を示す。接合継手部の増肉量が２０％まで接合時のスペーサの熱間塑性変形により接合面積の増大し、接合継手の必要強度（接合継手と被接合材との強度比で０．９以上）が得られることが判った。
【００３３】
本発明では、上記の接合部の増肉による接合面積の増大効果を得るために、接合継手部の増肉量を被接合材の肉厚の比率で１％以上にする必要があるが、増肉量が２０％を超えると、継ぎ手形状が著しく変化し、得られた溶接部材を使用する際に制約を受けるため、その上限を２０％とする。
【００３４】
【実施例】
次に、本発明の実施例について述べる。
３００ｋｇの真空溶解炉あるいは１００Ｔｏｎ電気炉を用いて表１に示す炭素鋼とステンレス鋼をそれぞれ溶製し、その後、炭素鋼は１２００℃から熱間鋳造して５０ｍｍの丸棒とし、ステンレス鋼も同様に１０５０℃から熱間鋳造にて５０ｍｍの丸棒に成形した。ステンレス鋼は１０５０℃で１５分間の溶体化処理を施した後、水中で急冷して試験に用いた。接合実験は、接合前に表面を研磨して酸化皮膜を除去し、外皮の影響を除いた。続いて、長さを１５０ｍｍに切断して各端面は側面が完全に９０度になるように加工し、開先面側の端面は、１０〜３００μm の精度で機械研削で仕上げた。
【００３５】
スペーサについては、１０ｋｇ、５０ｋｇ、１００ｋｇの真空溶解炉で溶製し、１２００℃で１時間予備加熱した後に２０ｍｍの厚みに熱間圧延で仕上げ、４００〜８００℃で１０分から５時間、歪み除去および脱水素焼鈍を実施した。ここから、最大２０ｍｍの厚みを有する５０ｍｍの直径の円盤を何種類か切り出し宇、スペーサとした。その化学成分を表２に示す。Ａ，Ｂ，Ｃは何れも炭素鋼を接合する場合、Ｄ，Ｅは高強度ステンレス鋼を接合する場合にそれぞれ使用した。液相拡散接合は、３００ｋｗの加熱電源を使用し、高周波誘導コイルで、５０ｍｍの直径の丸棒を突き合わせて接合した。接合温度は、一律１２００℃とし、保持時間は１０分で、昇温時間は６０秒とし、冷却は放冷とした。接合応力は１０ＭＰａで一定とし、加熱前から、接合、冷却終了後まで負荷し続けた。使用したインサートメタルの化学成分を表３に示す。ＢＮｉ−２，ＢＮｉ−３，ＢＮｉ−６は何れもＪＩＳ規格に準拠したＮｉ基液相拡散接合用合金箔（Ｃｒ−Ｎｉ系スペーサ）であり、これらを用いた接合では、誘導加熱装置全体を真空チャンバー内に設置し、真空度を１０−６ｔｏｒｒに制御して行った。ＩＭＡ−１，２に記載のインサートメタルは特許第１８９１６１８号公報、特許第１８９１６１９号公報で開示されている化学成分の酸化雰囲気中での接合が可能なインサートメタルを使用し、チャンバーを使用せずに大気中で接合を行った。接合に際しては、開先面とそれに対向するスペーサ表面の加工精度（加工表面粗さ（Ｒｍａｘ）の変化、および接合突き合わせ方向から被接合材の軸心を意図的に傾斜させて２つの被接合材の軸心を不整合にさせ、さらには、被接合材の接合端面に目違いを発生させて、スペーサの形状及び強度特性、接合条件の変化による接合で得られた継手特性の変化を調査した。
【００３６】
図３は接合実験における被接合材である丸棒試験片の設置の様子を模式的に図示したものである。被接合材である２つの丸棒試験片のうち、一方の丸棒試験片２４を油圧サーボ機構にて上下動可能なクロスヘッドを有する加圧台１９上に丸棒試験片２４の軸心方向１５が鉛直方向になるように設置し、他方の丸棒試験片２５をその軸心方向１６が前記丸棒試験片２４の軸心方向１５と不整合となるように角度調整可能な傾斜台２１を介して水平台２０上にセットする。この結果、各丸棒試験片２４、２５のそれぞれの軸心１５、１６は角度１８をなし、丸棒試験片２４は、丸棒試験片２５の端面上の一つの接触点２２で接触し、その接点から丸棒試験片２５の外縁までの距離である所定量の目違い２３が発生する。両丸棒試験片２４、２５のそれぞれの開先面１２は、予め所定の粗さに切削加工しているが、接合試験ではそれぞれの開先面１２にスポット溶接で２５μm のインサートメタル２７を添付し、所定の開先間距離１４を有する両丸棒試験片２４、２５開先の間隙にスペーサ２６を１３の方向から挿入し開先間隙を充填した。スペーサの各開先面と接触する表面も所定の切削加工精度で研削した。スペーサ２６の各開先面と接触する２つの面がなす角度９は、原則として各丸棒試験片２４、２５のそれぞれの軸心１５、１６がなす角度１８以下とした。また、スペーサ２６の最大長さ１０は、各開先面１２がなす開先間隙１４の値以下とする。
【００３７】
接合試験は、各丸棒試験片２４、２５の開先間隙にスペーサ２６を挿入した段階で、誘導加熱コイル２８を所定の位置にセットし、加圧台１９のクロスヘッドで加圧したまま、１分間昇温して接合温度１２００℃にし、その後その温度で１０分間保持し、その後放冷により冷却した。この際、接合雰囲気はインサートメタルがＢＮｉ−２，ＢＮｉ−３，ＢＮｉ−６の場合は、真空中で、ＩＭＡ−１，２の場合は大気中とした。接合後、各丸棒試験片２４、２５の軸心１５、１６がなす角度１８は、加熱、加圧による熱間塑性変形により接合前よりも小さくなり、接合部の増肉が生じる。接合部の増肉量は、接合継手部の最大外径をノギスで５点測定してその平均値を代表値とした。また、接合継手の評価はすべて、接合後、丸棒ままの引張試験と、丸棒中心付近から、ＪＩＳ４号衝撃試験片を切り出して、両丸棒試験片２４、２５の接触点２２側からスペーサの中心相当位置にノッチを入れて、シャルピー衝撃値を測定して接合継手の靱性を評価した。
【００３８】
表４には被接合材である丸棒試験片２４、２５の接合前の各軸心がなす傾き角度（図３中の１８）を種々変化させ、これに応じた角度９を有するスペーサ２６を用意し、それを両丸棒試験片２４、２５の開先間隙に挿入して接合した場合の継手破断強度（引張強さ）を示す。試験片表面加工精度（表面粗さ）は、Ｒｍａｘ＝５０μm 、スペーサ表面加工精度（表面粗さ）は、Ｒｍａｘ＝２０μm の例であり、被接合材とスペーサの種類も表中に示している。
【００３９】
接合条件は、接合初期から５ＭＰａの接合応力を負荷し、昇温時間は６０秒、接合温度１２００℃での保持時間は６００秒とし、その後、放冷して冷却し、インサートメタルがＢＮｉ−２，３，６の場合は、真空度を１０−６ｔｏｒｒで、ＩＭＡ，ＩＭＢの場合は、大気中で接合した。
接合強度は、継手の引張強度と被接合材の引張強度との比で示した。また、接合部のシャルピーも同様に２０℃での継手の吸収エネルギーと被接合材の吸収エネルギーとの比で示した。表４に本発明の条件を満たした発明例の評価結果を接合条件とともにスペーサ形状を付して示した。発明例Ｎｏ．１〜１９は全て、被接合材の母材以上の強度及び靱性が得られ、良好な品質の接合継手が得られることが判る。
【００４０】
また、表５には、同様に本発明の条件から外れた比較例の評価結果を接合条件とともにスペーサ形状を付して示した。Ｎｏ．２０の溶接継手は、スペーサの開先面に接触する面がなす角度が５０度と本発明範囲より大きかった例、Ｎｏ．２１、２２の溶接継手は、被接合材の開先面加工精度（表面粗さ（Ｒｍａｘ））がそれぞれ１２１μm 、１０７μm と本発明範囲より粗く、インサートメタルが接合材の開先面の凹凸形状に充分対応できずに接合部に欠陥が生じ、接合継手の強度・靱性が低下した例、Ｎｏ．２３の溶接継手は、鉄基（炭素鋼）系スペーサ中のＣ含有量が０．１５質量％を超えたために、接合継手の強度・靱性が低下した例、Ｎｏ．２４の溶接継手は、Ｃｒ−Ｎｉ（ステンレス）系スペーサ中のＣ含有量が０．１５質量％を超えたために、接合継手の強度・靱性が低下した例、Ｎｏ．２５、２６の溶接継手は、被接合材に対してスペーサの引張強度が本発明範囲（（スペーサの引張強度）／（被接合材の引張強度）＜０．７）より高いため、スペーサの充分な塑性変形がなく、開先面の凹凸形状に対応できずに接合継手の強度・靱性が低下した例、Ｎｏ．２７の溶接継手は、目違い量が２８と本発明範囲をより高いため、スペーサの熱間塑性変形による増肉作用でも充分な接合面積が得られず、接合継手の強度・靱性が低下した例である。
【００４１】
以上の実施例から、本発明のスペーサを用いるにより、従来の液相拡散接合の接合条件に比べて、緩和した接合条件において良好な接合継ぎ手を得ることが可能となる。
【００４２】
【表１】
【表２】
【表３】
【表４】
【表５】
【発明の効果】
本発明によれば、従来に比べての化学成分および製造方法に限定し、Ｔｉ添加後にＭｇを適切に添加、あるいはＴｉとＭｇの同時添加後にＭｇを適切に添加することで、溶接入熱に関わらずＨＡＺの旧γ粒の粒成長を抑制することができ、この効果によりHAZ 靱性を広い入熱範囲で向上させることが可能である。その結果、ラインパイプに対する安全性が大幅に向上する。
【図面の簡単な説明】
【図１】本発明のスペーサと被接合材の配置図である。
【図２】従来の液相拡散接合方法における被接合材の突き合わせ工程の模式図である。
【図３】本発明のスペーサを用いた液相拡散接合方法における被接合材の突き合わせ工程の模式図である。
【図４】スペーサー接合面の表面加工精度（表面粗さ（Ｒｍａｘ））と接合継手の引張強度と被接合材の引張強度との比（強度比）の関係を示す図である。
【図５】炭素鋼スペーサ中の炭素含有量と接合継手の引張強度と被接合材の引張強度との比（強度比）の関係を示す図である。
【図６】２０Ｃｒ−２５Ｎｉ鋼スペーサ中の炭素含有量と接合継手の引張強度と被接合材の引張強度との比（強度比）の関係を示す図である。
【図７】室温から１２００℃（接合温度近傍）までのスペーサの引張強度と被接合材の引張強度の比（強度比）の最大値と、接合継手の引張強度と被接合材の引張強度との比（強度比）の関係を示す図である。
【図８】接合継手部の増肉量と接合継手の引張強度と被接合材の引張強度との比（強度比）の関係を示す図である。
【符号の説明】
１…被接合材の軸心
２…スペーサの接合面
３…スペーサの接合面
４…スペーサの接合面がなす角度
５…接触点
６…被接合材（鋼管）の軸心
７…軸心不整合による開先の開き
８…目違い量
９…スペーサの接合面がなす角度
１０…スペーサ厚み
１１…スペーサ接合面
１２…被接合材開先面
１３…スペーサ挿入方向
１４…開先距離
１５…被接合材２４の（丸棒試験片）軸心方向
１６…被接合材２５の（丸棒試験片）軸心方向
１７…水平台の垂線
１８…被接合材２５の（丸棒試験片）軸心と水平台の垂線１７との角度
１９…加圧台
２０…水平台
２１…傾斜台
２２…接触点
２３…目違い量
２４…被接合材（丸棒試験片）
２５…被接合材（丸棒試験片）
２６…スペーサ
２７…インサートメタル
２８…誘導加熱コイル[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to liquid phase diffusion bonding of metal materials, and in particular, groove fillers used for liquid phase diffusion bonding of carbon steel, stainless steel, Ni-base alloy, superalloy or heat-resistant alloy steel, and welded joints using the same. About.
[0002]
[Prior art]
Conventionally, joining of metal materials such as steel, stainless steel, Ni-base alloy, superalloy, or heat-resistant alloy steel has been performed mainly by welding, and the welding conditions are set in order to secure the same or better characteristics as the base material. I was in control. In general, a welding method of a metal material forms a so-called groove shape in which a joint surface of a material to be welded is finished by machining, and forms a weld joint by fusing the groove portions with various welding materials.
[0003]
As for the mechanical characteristics of this welded joint, it is technically important to control the solidified structure that occurs as the molten metal is cooled after welding. In particular, in welding, since the cooling rate of the molten metal after welding is generally rapid, it is known that residual strain is generated due to large thermal expansion and contraction of the welded part. Since the chemical composition of the material is usually different from that of the weld metal, there are many problems in controlling the joint shape and characteristics of the structural material. Further, at the time of welding, a large amount of energy is locally applied to melt the weld metal once, and the local temperature of the molten metal reaches 3000 ° C. For this reason, the effect on the properties of the material to be welded (base metal) around the weld metal is large, and the structure of the weld heat affected zone becomes uneven and the mechanical properties such as strength and toughness deteriorate. It becomes one factor. In addition to these problems, in joining metal materials by welding, basically, the quality of the welded joint is largely dependent on the skill of the welding operator for forming a good weld metal on the joint groove. Therefore, in the case of joining structural materials having reliability by welding, a large amount of cost and time are usually required.
[0004]
On the other hand, as a joining technique for metal materials that replaces these welding techniques, the molten metal does not undergo solidification due to rapid cooling from a high temperature state of the molten metal as in welding, and enters the material to be joined through the groove surface from the molten metal. A liquid phase diffusion bonding method has been studied in which atoms are diffused and a joint is formed by solidification by compositional change of molten metal.
As for this liquid phase diffusion bonding method, for example, in Japanese Patent Application Laid-Open Nos. 53-81458, 62-34685, and 62-227595, liquid phase diffusion bonding in a vacuum or an inert atmosphere is used. A method is disclosed, and in Patent No. 1891618, Patent No. 1891619, Patent No. 1837572, etc., it is disclosed regarding a bonding alloy foil (insert metal) that can be joined in an oxidizing atmosphere.
[0005]
In general, in liquid phase diffusion bonding, solidification of the molten metal in the joint occurs in an isothermal state, so that distortion such as welding hardly remains, and the maximum heating temperature of the molten metal is also the amorphous alloy foil ( This is a relatively low temperature required to melt the insert metal) and is below the melting point of the material to be joined, so there is less structure and mechanical influence on the heat affected zone compared to the welding method, resulting in joint characteristics. There is little influence on. Furthermore, since the joining conditions that determine the diffusion phenomenon of molten metal into the material to be joined are substantially defined by the chemical composition of the amorphous alloy foil (insert metal) and the properties of the material to be joined, the amount of heat input, the joining time in advance. And the like can be strictly controlled by a computer or the like, and the joining process can be substantially automated by connecting and controlling the groove attaching process and the joining process. Therefore, the liquid phase diffusion bonding system needs a complicated system that accumulates and uses human sensory organs and welding know-how data based on skilled welding engineers such as system control of welding robots. The operation is extremely easy.
[0006]
However, since liquid phase diffusion bonding is generally performed using a thin amorphous alloy foil (insert metal) with a thickness of several tens of microns that is industrially manufactured by a rapid solidification method or the like, the groove shape of the material to be bonded is If the bonding accuracy is poor, the weld surface may not be uniformly filled with molten metal and defects may occur in the joint. Therefore, extremely precise machining of the groove shape of the material to be bonded and good bonding accuracy are possible. Is required. In addition, in order to maintain the accuracy of joining of the materials to be joined, the automatic centering process is performed by strictly managing the misalignment of the shaft center, the misalignment, the processing accuracy of the groove surface, etc. when the two materials to be joined are attached. Needed to be integrated into the system.
[0007]
FIG. 2 is a schematic diagram showing a joining process of the materials to be joined in the conventional liquid phase diffusion bonding. In conventional liquid phase diffusion bonding, for example, when joining two steel pipes having a wall thickness of 10 mm and an outer diameter of 100 mm as end members, the groove opening 7 due to the misalignment of both axes is 1 mm or less. The
[0008]
[Problems to be solved by the invention]
In view of the above-described problems of the prior art, the present invention is a conventional liquid phase diffusion bonding process for joining materials to be joined. It is an object of the present invention to provide a liquid phase diffusion bonding method capable of preventing deterioration of joint properties due to variations in conditions such as processing accuracy of a groove surface and stably obtaining good joint properties.
[0009]
Specifically, according to the present invention, in liquid phase diffusion bonding, a groove filler (spacer) having a predetermined shape, composition, and characteristics is bonded between the groove surfaces to be bonded by using an amorphous alloy foil (insert metal). It is an object of the present invention to provide a liquid phase diffusion bonding method capable of preventing a bonding failure due to an attachment accuracy and a processing accuracy and a joint joint thereof.
[0010]
[Means for Solving the Problems]
This invention solves said subject and the place made into the summary is as follows.
(1) In a liquid phase diffusion bonding method in which the groove surfaces to be bonded are bonded to each other by liquid phase diffusion of an amorphous alloy foil, the tensile strength from room temperature to the bonding temperature between the groove surfaces of both bonded materials. However, a groove filler satisfying the relationship of the following formula (1) is inserted so that the joint surface of the groove filler includes the groove surfaces of the two materials to be joined, and the groove filler is joined. A liquid phase diffusion bonding method comprising: bonding an amorphous alloy foil to at least one of a surface and a groove surface of the material to be bonded, and then performing liquid phase diffusion bonding by pressurization and temperature rise .
(Tensile strength of groove filler) / (Tensile strength of material to be joined) ≦ 0.7 (1)
[0011]
(2) The liquid phase diffusion bonding method according to the above (1), wherein the groove filler contains, by mass%, C: 0.15% or less.
(3) The above-mentioned groove filling material is characterized by containing, in mass%, C: 0.15% or less, Cr: 0.1-35%, Ni: 0.1-40% (1) ) Liquid phase diffusion bonding method.
(4) The liquid phase diffusion bonding according to any one of (1) to (3) above, wherein the surface roughness (Rmax) of the bonding surface of the groove filler is 100 μm or less. Method.
(5) The shape of the groove filler is 0.1 to 20 mm in the length in the abutting direction, and the angle formed by the two joint surfaces is 45 degrees or less. (1) to (4) The liquid phase diffusion bonding method according to any one of the above.
(6) The bonding material bonded by the liquid phase diffusion bonding method according to any one of (1) to (5) and heated to 500 ° C. or more for 1 second or more. A liquid phase diffusion bonding joint characterized in that the thickness increase of the thickness of the joining heat affected zone is 1 to 20% of the thickness of the material to be joined before joining.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the contents of the present invention will be described in detail.
In a normal liquid phase diffusion bonding method, an amorphous alloy foil (hereinafter referred to as an insert metal) is pasted on either one of the groove surfaces of two materials to be joined, and then, of the two materials to be joined. A predetermined stress is applied from one side to the butting direction, the joint is heated to a temperature equal to or higher than the melting point of the insert metal, and the predetermined temperature equal to or higher than the tensile strength of the material to be bonded at the bonding temperature is applied. The bonding is terminated by holding for a predetermined time required for isothermal solidification of phase diffusion bonding, and a predetermined cooling rate or further heat treatment is performed according to the bonding joint characteristics. In such a conventional liquid phase diffusion bonding method, as described above, due to a decrease in the accuracy of the butting control and the machining accuracy (surface roughness) of the groove surface of the material to be bonded, a defect occurs in the bonded portion, and the bonded joint There is a problem that the characteristics deteriorate, and in order to prevent this, conventionally, the opening of the groove due to the misalignment of both axes at the time of abutting the materials to be joined is 1 mm or less, and the misalignment amount is 10% of the steel pipe wall thickness. Hereinafter, the processing accuracy of the groove surface of the steel pipe was strictly controlled to 10 μm or less in terms of surface roughness (Rmax).
[0013]
The present inventors have found that there is no defect in the joint part even when the accuracy of the conventional butt control and the machining accuracy (surface roughness) of the groove surface of the material to be joined are deteriorated, and good joint joint characteristics. We have intensively studied how to obtain.
As a result, when performing liquid phase diffusion bonding, a groove filling material (hereinafter referred to as a spacer) having a predetermined hot plastic deformation characteristic is inserted between the groove surfaces of both materials to be bonded to each other. It was found that poor bonding due to the surface roughness of the groove surface of the material to be joined can be prevented by phase diffusion bonding. Furthermore, it has been found that by defining the shape of the groove filler in a predetermined range, it is possible to prevent deterioration of the joint characteristics when the butt control of the materials to be joined is poor.
[0014]
The present invention has been made on the basis of these findings, and according to the present invention, the opening of the groove due to the misalignment of both axes at the time of abutting the materials to be joined is 20 mm or less (conventional: 1 mm or less), Good even under conditions where the steel pipe wall thickness is 20% or less (conventional: 10% or less) and the processing accuracy of the groove surface of the material to be joined is relaxed to 100 μm or less (conventional: 10 μm or less) in terms of surface roughness (Rmax). This is a method of obtaining the joint characteristics.
[0015]
The present invention is described in detail below.
First, the strength characteristics of the spacer of the present invention will be described.
FIG. 7 shows the maximum value of the ratio (strength ratio) between the tensile strength of the spacer and the tensile strength of the material to be joined from room temperature to 1200 ° C. (near the joining temperature), the tensile strength of the joint joint obtained by joining, and the joining target. The relationship of the ratio (strength ratio) with the tensile strength of the material is shown.
[0016]
As described above, in conventional liquid phase diffusion bonding, the thickness of the insert metal used for joining the materials to be joined is very thin, tens of microns, so the machining accuracy (surface roughness) of the groove surface of the materials to be joined is low. In a bad case, the melted metal is not uniformly filled in the concave and convex portions of the groove surface, so that good liquid phase diffusion bonding cannot be performed, and characteristics such as required strength and toughness of the joint joint may not be obtained.
[0017]
On the other hand, according to the experiments by the present inventors, the spacer filled through the insert metal between the gaps of the material to be joined is deformed by hot plastic deformation during pressurization / heating of the joint. It was found that the groove surface could be adapted to the irregular shape and the groove surface could be uniformly filled with insert metal, and as a result, a good liquid phase diffusion bonded portion could be formed.
[0018]
According to the experiments by the present inventors, as is clear from FIG. 7, if the strength ratio between the spacer and the material to be joined is in the following relationship at any temperature from room temperature to the vicinity of the joining temperature, the material to be joined has a large plasticity. Without inducing deformation, only the spacer is plastically deformed and deformed flexibly so as to correspond to the concave and convex shape of the groove surface, and there is no defect in the joint, and a good joint (with the strength ratio between the joint and the material to be joined) 0.9 or more) was obtained.
(Tensile strength of spacer) / (Tensile strength of material to be joined) ≦ 0.7 (1)
For this reason, in this invention, ratio (strength ratio) of the tensile strength of a spacer and the tensile strength of a to-be-joined material is prescribed | regulated as said (1) Formula.
[0019]
In conventional liquid phase diffusion bonding, in order to obtain good joint characteristics without defects in the joint, the machining accuracy (surface roughness) of the groove surface of the material to be joined is 10 μm or less in terms of surface roughness (Rmax). However, by performing liquid phase diffusion bonding using the spacer of the present invention having strength characteristics satisfying the above equation (1), the machining accuracy (surface roughness) of the groove surface of the material to be joined ) Can be relaxed to a surface roughness (Rmax) of 100 μm or less, it is possible to obtain good joint properties.
[0020]
Next, the reason for limiting the chemical components (all contents are mass%) contained in the spacer of the present invention will be described.
In general, an insert metal used for liquid phase diffusion bonding of a material to be bonded is properly used depending on the chemical composition of the material to be bonded from the viewpoint of the homogeneity of the structure of the liquid phase diffusion bonded portion. At this time, since the material to be joined and the insert metal are chemically melted and mixed to generate a joining phase having an intermediate composition between them, the chemical component of the insert metal used for joining affects the joint characteristics. Therefore, it is preferable to define the chemical components of the spacer used in the present invention as follows according to the type of the material to be joined used from the viewpoint of the structure of the joint portion with the insert metal and the uniformity of characteristics.
(Iron-based spacer)
In the present invention, when an iron base material to be joined such as carbon steel is subjected to liquid phase diffusion bonding using a spacer, it is preferable to use an iron base spacer from the viewpoint of the homogeneity of the structure and characteristics of the joint. . In particular, in the case of an iron-base bonded material such as carbon steel, the amount of carbon in the spacer has a great influence on the toughness of the liquid phase diffusion bonding portion. Therefore, in the spacer of the present invention, the C content is as follows: Stipulate.
[0021]
C: C is an indispensable element as a basic element for improving the strength of the base metal. However, the present invention limits the upper limit of the content so that extreme deterioration of the toughness of the liquid phase diffusion joint does not occur. It is specified to 0.15%. As a result of experiments by the present inventors, the toughness of the liquid phase diffusion bonded portion was good when the C content was in the range of 0.001% to 0.15%. In the present invention, the lower limit of the C content need not be specified, but when the liquid phase diffusion bonding portion requires strength, the C content can be adjusted according to the required strength.
[0022]
FIG. 5 shows the relationship between the carbon content of the spacer and the ratio (strength ratio) between the tensile strength of the bonded joint obtained by bonding and the tensile strength of the material to be bonded. In addition, although Mn content of the spacer in this case is 1% and Si: 0.05%, as a result of experiments by the present inventors, components other than C did not significantly affect the bonding characteristics. It can be seen from FIG. 7 that the required strength of the joint joint (0.9 or more in terms of the strength ratio between the joint joint and the material to be joined) is obtained when the C content of the spacer is 0.15% or less.
(Cr-Ni spacer)
In the present invention, when liquid phase diffusion bonding is performed on materials to be bonded containing Cr and Ni, for example, corrosion resistant stainless steel, heat resistant stainless steel, tool steel, Ni-base alloy steel or superalloy steel, It is preferable to use a Cr—Ni-based spacer from the viewpoint of the homogeneity of the structure and characteristics. In particular, in the case of a material to be bonded containing Cr and Ni, the hot strength of the liquid phase diffusion bonding portion is often required as compared with an iron-based spacer. It is necessary to adjust to the γ2 phase and homogenize the structure of austenite or martensite. For this reason, the C content of the iron-based spacer is regulated to 0.15% or less for the same reason, Further, the contents of Cr and Ni are defined as follows.
[0023]
Cr: Cr is an element that improves corrosion resistance. For example, it exhibits corrosion resistance that can withstand severe corrosion environments such as boilers to which molten salt or high-temperature combustion ash adheres from extremely mild corrosive environments such as rainwater and tap water. In order to do this, it is necessary to contain 0.1% or more, but a large amount of addition exceeding 35% has an adverse effect such as a decrease in toughness, so the content is made 0.1 to 35%.
[0024]
Ni: Ni is an element that improves the high-temperature strength by changing the metal lattice structure, and is an important element for austenitic steel. In order to sufficiently obtain this effect, the content is 0.1% by mass or more and in balance with the Cr content, and the upper limit is set to 40% so that there is no adverse effect such as a decrease in toughness. Add in the range of%.
FIG. 6 shows the relationship between the carbon content in the spacer containing Cr: 20% and Ni: 25% and the ratio (strength ratio) between the tensile strength of the joint joint obtained by joining and the tensile strength of the material to be joined. Indicates. As in FIG. 5, it can be seen that when the C content in the spacer is 0.15% or less, the required strength of the joint joint (0.9 or more in terms of the strength ratio between the joint joint and the material to be joined) can be obtained. This is due to the deterioration of the joint characteristics due to the formation of carbides.
[0025]
Next, the reason for limiting the surface processing accuracy (surface roughness) and shape of the spacer of the present invention will be described.
(Surface processing accuracy (surface roughness))
The surface processing accuracy of the spacer is important in order to form a good liquid phase diffusion bonded portion with the groove surface of the material to be bonded together with the above-described strength characteristics. In particular, when the insert metal is thin, if the surface processing accuracy, that is, the surface roughness becomes rough, a gap is generated between the groove surface and the spacer due to the concave and convex shapes of the groove surface and the spacer surface of the material to be joined. It is difficult to form a liquid phase diffusion bonding portion.
[0026]
The spacer of the present invention is a soft material having the above-described spacer strength characteristics, and can be plastically deformed so as to correspond to the concave and convex shape of the groove surface of the material to be joined. The surface processing accuracy required for the groove surface (surface roughness (Rmax): 10 μm or less, when the insert metal thickness is about 30 μm) can be made rougher, but if the surface processing roughness exceeds 100 μm, Since a gap is formed between the groove surface and the spacer and a good liquid phase diffusion bonded portion cannot be formed, the upper limit of the surface processing accuracy (surface roughness (Rmax)) must be regulated to 100 μm.
[0027]
FIG. 4 shows the relationship between the processing accuracy of the spacer surface (surface roughness (Rmax)) and the ratio (strength ratio) between the tensile strength of the joint joint obtained by joining and the tensile strength of the material to be joined. In order to achieve a strength ratio of the joint joint to the material to be joined, which is a measure of the tensile strength of the joint joint that can be used industrially: 0.9 or more, the surface processing roughness of the spacer needs to be 100 μm or less. is there.
(Spacer shape)
The spacer used in the liquid phase diffusion bonding of the present invention uniformly inserts the molten insert metal necessary for the subsequent liquid phase diffusion bonding over the entire groove surface when the spacer is inserted into the workpiece groove surface through the insert metal. In order to cover, it is necessary to make it a shape that sufficiently includes at least the groove surface. If there is a deficient region in the spacer with respect to the grooved surface of the material to be joined, the molten insert metal stays in the deficient region during liquid phase diffusion bonding, and the entire grooved surface of the material to be bonded is uniformly covered. In particular, the thinner the insert metal is as thin as 10 μm or less, the greater the tendency, and the desired quality cannot be ensured.
[0028]
In addition, the spacer of the present invention plays a role of ensuring the desired quality by complementing the gaps and performing the liquid phase diffusion bonding well when the joining accuracy of the materials to be bonded is not sufficient.
For the above reasons, the shape of the spacer of the present invention is preferably limited as follows.
(Spacer thickness)
FIG. 1 shows a layout of spacers and materials to be joined according to the present invention.
[0029]
In the present invention, the spacer thickness (maximum length parallel to the butting direction) shown in FIG. 1 is defined as 0.1 to 20 mm. The spacer thickness (the maximum length parallel to the butting direction) acts to form a good liquid phase diffusion bonding by sufficiently complementing the gap when the butting accuracy is not sufficient. If it is less than 0.1 mm, the molten insert metal cannot be uniformly covered over the entire groove surface in the liquid phase diffusion bonding, and if it exceeds 20 mm, a uniform and sufficient pressing force on the joining surface cannot be obtained. Therefore, the spacer thickness (the maximum length parallel to the butting direction) was set to 0.1 to 20 mm.
[0030]
In the conventional liquid phase diffusion bonding, in order to obtain good bonded joint characteristics with no defects in the bonded portion, the opening of the groove due to the misalignment of both axes at the time of abutting the materials to be bonded was strictly controlled to 1 mm or less. However, by performing liquid phase diffusion bonding using the spacer of the present invention having the above-mentioned thickness, it is possible to obtain good joint characteristics even if the groove opening due to the misalignment of the axis is reduced to 20 mm or less. is there.
(Spacer joint angle)
In general, when the groove surfaces of two materials to be joined are brought into contact with each other, the axes of the materials to be joined rarely coincide with each other, and the shaft centers of the materials to be joined are shifted or inclined due to variations in the accuracy of matching. There are many. The spacer of this invention has the effect | action which complements and corrects it, when the mismatching of the axial center of the to-be-joined materials at the time of abutting arises. In the present invention, in order to obtain sufficient functions for complementation and correction even when the misalignment of the axial centers of the materials to be joined occurs and the respective groove faces become non-parallel, the matching mismatch is made in advance. Accordingly, it is preferable to adjust the angle (4 in FIG. 1) formed by the two joint surfaces of the spacer to a range of 0 to 45 degrees.
(Thickening of joint joints)
Conventionally, even when the groove face shapes of the two materials to be joined are the same, a difference (8 in FIG. 2) as shown in FIG. This difference means that the joint area is substantially reduced for the welded joint, and thus affects the strength of the joint. Usually, the tensile strength of the joint joint needs to be strong enough not to break the base material at the time of tensile measurement.
[0031]
As described above, the spacer of the present invention has lower tensile strength from butt to welding than the material to be joined. Therefore, the spacer filled through the insert metal between the grooves of the material to be joined has a joint stress in the axial direction. As a result, it is possible to increase the thickness of the joint part including the heat-affected zone by plastic deformation to compensate for the difference. According to the present invention, conventionally, it was necessary to manage the amount of misalignment at the time of butting the materials to be joined to 10% or less of the wall thickness, but according to the present invention, it can be allowed up to 20% of the wall thickness, The matching accuracy can be relaxed.
[0032]
FIG. 8 shows the amount of increase in the thickness of the bonded joint (ratio to the thickness of the material to be bonded before bonding, average value of 5-point measurement), the tensile strength of the bonded joint obtained by bonding, and the tensile strength of the bonded material The ratio (strength ratio) is shown. The joining area increases due to the hot plastic deformation of the spacer during joining, and the required strength of the joining joint (the strength ratio of the joining joint to the material to be joined is 0.9 or more) up to 20% thickening of the joint joint. It turns out that it is obtained.
[0033]
In the present invention, in order to obtain the effect of increasing the joint area by increasing the thickness of the above-mentioned joint, it is necessary to increase the thickness of the joint joint by 1% or more as a ratio of the thickness of the material to be joined. If the amount of meat exceeds 20%, the joint shape is remarkably changed, and restrictions are imposed when the obtained welded member is used, so the upper limit is made 20%.
[0034]
【Example】
Next, examples of the present invention will be described.
Carbon steel and stainless steel shown in Table 1 are melted using a 300 kg vacuum melting furnace or a 100 Ton electric furnace, respectively, and then the carbon steel is hot cast from 1200 ° C. to form a 50 mm round bar. A 50 mm round bar was molded from 1050 ° C. by hot casting. The stainless steel was subjected to a solution treatment at 1050 ° C. for 15 minutes, and then quenched in water and used for the test. In the joining experiment, the surface was polished before joining to remove the oxide film, and the influence of the outer skin was removed. Subsequently, the length was cut to 150 mm and each end face was processed so that the side face was completely 90 degrees, and the end face on the groove face side was finished by mechanical grinding with an accuracy of 10 to 300 μm.
[0035]
The spacers were melted in a 10 kg, 50 kg, and 100 kg vacuum melting furnace, preheated at 1200 ° C. for 1 hour, and then hot-rolled to a thickness of 20 mm, and subjected to strain removal at 400 to 800 ° C. for 10 minutes to 5 hours. Dehydrogenation annealing was performed. From this, several types of discs with a diameter of 50 mm having a maximum thickness of 20 mm were cut out and used as spacers. The chemical components are shown in Table 2. A, B, and C were used when carbon steel was joined, and D and E were used when high-strength stainless steel was joined. In the liquid phase diffusion bonding, a heating power source of 300 kw was used, and a round bar having a diameter of 50 mm was abutted and bonded with a high frequency induction coil. The bonding temperature was uniformly 1200 ° C., the holding time was 10 minutes, the temperature raising time was 60 seconds, and the cooling was allowed to cool. The joining stress was kept constant at 10 MPa, and the load was continued from before heating until after finishing joining and cooling. Table 3 shows the chemical composition of the insert metal used. BNi-2, BNi-3, and BNi-6 are all Ni-based liquid phase diffusion bonding alloy foils (Cr-Ni spacers) compliant with JIS standards. It was installed in a vacuum chamber and the degree of vacuum was controlled to 10-6 torr. The insert metal described in IMA-1 and 2 uses an insert metal that can be bonded in an oxidizing atmosphere of a chemical component disclosed in Japanese Patent No. 1891618 and Japanese Patent No. 1891619, and does not use a chamber. Bonding was performed in the atmosphere. When joining, two workpieces are produced by intentionally tilting the axis of the workpiece from the machining accuracy (change in machining surface roughness (Rmax) of the groove surface and the spacer surface facing the groove surface, and the joining butting direction. Inconsistency was caused to the misalignment of the shaft center of the joint, and further, the joint end face of the material to be joined was misunderstood, and changes in the joint characteristics obtained by joining due to changes in the shape and strength characteristics of the spacer and joining conditions were investigated. .
[0036]
FIG. 3 schematically shows how a round bar test piece, which is a material to be joined, is installed in a joining experiment. Of the two round bar test pieces to be joined, one of the round
[0037]
In the joining test, at the stage where the spacers 26 are inserted into the groove gaps of the respective round
[0038]
In Table 4, the inclination angle (18 in FIG. 3) formed by the respective axes before joining the round
[0039]
The joining conditions were 5 MPa from the beginning of joining, a heating time of 60 seconds, a holding time of 1200 ° C. holding time of 600 seconds, and then cooled by cooling, and the insert metal was BNi-2. , 3 and 6, the degree of vacuum was 10-6 torr, and IMA and IMB were bonded in the atmosphere.
The bonding strength is indicated by the ratio between the tensile strength of the joint and the tensile strength of the material to be joined. Similarly, the Charpy of the joint was also expressed as a ratio of the absorbed energy of the joint at 20 ° C. to the absorbed energy of the material to be joined. Table 4 shows the evaluation results of the invention examples satisfying the conditions of the present invention, together with the joining conditions and the spacer shape. Invention Example No. It can be seen that all of Nos. 1 to 19 have a strength and toughness that are equal to or higher than the base material of the material to be joined, and a good quality joint is obtained.
[0040]
Table 5 also shows the evaluation results of comparative examples that deviate from the conditions of the present invention, together with the bonding conditions and the spacer shape. No. In the case of the welded joint of No. 20, the angle formed by the surface contacting the groove surface of the spacer is 50 degrees, which is larger than the range of the present invention, No. In the welded
[0041]
From the above embodiments, by using the spacer of the present invention, it is possible to obtain a good joint at a relaxed joining condition as compared with the joining condition of the conventional liquid phase diffusion joining.
[0042]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
[Table 5]
【The invention's effect】
According to the present invention, it is limited to chemical components and manufacturing methods as compared with conventional ones, and Mg is appropriately added after Ti addition, or Mg is appropriately added after simultaneous addition of Ti and Mg. Regardless, it is possible to suppress the growth of old γ grains of HAZ, and this effect can improve HAZ toughness in a wide heat input range. As a result, the safety for the line pipe is greatly improved.
[Brief description of the drawings]
FIG. 1 is a layout view of spacers and materials to be joined according to the present invention.
FIG. 2 is a schematic view of a joining process of materials to be joined in a conventional liquid phase diffusion bonding method.
FIG. 3 is a schematic view of a joining process of materials to be joined in a liquid phase diffusion bonding method using the spacer of the present invention.
FIG. 4 is a diagram showing the relationship between the surface processing accuracy (surface roughness (Rmax)) of the spacer joint surface, the ratio (strength ratio) between the tensile strength of the joint joint and the tensile strength of the material to be joined.
FIG. 5 is a graph showing the relationship between the carbon content in the carbon steel spacer, the tensile strength of the joint joint, and the tensile strength of the material to be joined (strength ratio).
FIG. 6 is a graph showing the relationship between the carbon content in a 20Cr-25Ni steel spacer, the tensile strength of a joint joint, and the tensile strength of a material to be joined (strength ratio).
FIG. 7 shows the maximum value of the ratio (strength ratio) between the tensile strength of the spacer and the tensile strength of the material to be joined from room temperature to 1200 ° C. (near the joining temperature), the tensile strength of the joint joint, and the tensile strength of the material to be joined. It is a figure which shows the relationship of ratio (intensity ratio).
FIG. 8 is a diagram showing the relationship between the amount of increase in the thickness of the joint joint, the ratio of the tensile strength of the joint joint and the tensile strength of the material to be joined (strength ratio).
[Explanation of symbols]
1 ... The axis of the material to be joined
2 ... Spacer interface
3 ... Spacer interface
4 ... An angle formed by the joint surface of the spacer
5 ... Contact point
6 ... Center axis of the material to be joined (steel pipe)
7 ... Opening of groove due to misalignment of shaft center
8 ... Mistake amount
9 ... An angle formed by the joint surface of the spacer
10 ... Spacer thickness
11 ... Spacer interface
12 ... groove face to be joined
13 ... Spacer insertion direction
14 ... groove distance
15 ... (Round bar specimen) axial direction of the material to be joined 24
16 ... (round bar test piece) axial direction of the material to be joined 25
17 ... Horizontal vertical line
18: Angle between the axis of the (round bar specimen) of the material to be joined 25 and the
19 ... Pressure table
20 ... Horizontal stand
21 ... Tilting table
22 ... Contact point
23 ... Mistake amount
24 ... Material to be joined (round bar specimen)
25 ... Material to be joined (round bar test piece)
26 ... Spacer
27 ... Insert metal
28 ... induction heating coil
Claims (6)
（開先充填材の引張強度）／（被接合材の引張強度）≦０．７ ・ ・（１）In the liquid phase diffusion bonding method in which the groove surfaces to be bonded are bonded to each other by liquid phase diffusion of an amorphous alloy foil, the tensile strength from room temperature to the bonding temperature between the groove surfaces of both bonded materials is as follows. (1) Inserting a groove filler satisfying the relationship of the formula so that the joint surface of the groove filler includes the groove surfaces of the two materials to be joined, and the joint surface of the groove filler and the A liquid phase diffusion bonding method, comprising: bonding an amorphous alloy foil to at least one of the groove surfaces of a material to be bonded, and then performing liquid phase diffusion bonding by pressurizing and heating.
(Tensile strength of groove filler) / (Tensile strength of material to be joined) ≦ 0.7 (1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001114438A JP3740031B2 (en) | 2000-04-13 | 2001-04-12 | Liquid phase diffusion bonding method using groove filler and its joint |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000112223 | 2000-04-13 | ||
| JP2000-112223 | 2000-04-13 | ||
| JP2001114438A JP3740031B2 (en) | 2000-04-13 | 2001-04-12 | Liquid phase diffusion bonding method using groove filler and its joint |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2001353582A JP2001353582A (en) | 2001-12-25 |
| JP3740031B2 true JP3740031B2 (en) | 2006-01-25 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2001114438A Expired - Fee Related JP3740031B2 (en) | 2000-04-13 | 2001-04-12 | Liquid phase diffusion bonding method using groove filler and its joint |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110666328A (en) * | 2019-11-01 | 2020-01-10 | 西安西工大超晶科技发展有限责任公司 | Diffusion welding method for cast high-temperature alloy and martensitic stainless steel |
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2001
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110666328A (en) * | 2019-11-01 | 2020-01-10 | 西安西工大超晶科技发展有限责任公司 | Diffusion welding method for cast high-temperature alloy and martensitic stainless steel |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2001353582A (en) | 2001-12-25 |
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