JP3604120B2

JP3604120B2 - Method and apparatus for lateral multi-layer welding of steel pipe

Info

Publication number: JP3604120B2
Application number: JP16731498A
Authority: JP
Inventors: 藤清一佐; 上善孝川; 山修志丸; 戸誠一郎平; 健治堀
Original assignee: Tetra Co Ltd
Current assignee: Tetra Co Ltd
Priority date: 1998-06-15
Filing date: 1998-06-15
Publication date: 2004-12-22
Anticipated expiration: 2018-06-15
Also published as: JP2000000664A

Description

【０００１】
【発明の属する技術分野】
本発明は、端面を突合せて立てた上，下鋼管の間の開先を、自動溶接ロボットにて鋼管を中心に溶接ト−チを旋回させて横向き多層盛り溶接する方法および該自動溶接ロボットに関する。
【０００２】
【従来の技術】
従来、鋼管の横向き多層盛り溶接に於いて、自動溶接ロボットにより形成する溶接ビードの始端と終端との会合部を、パス毎に周方向に一定距離づつ移動させることが行なわれている。各パスの始端では、溶接スタート時にアークの発生に対して溶接台車の溶接速度への昇速にタイムラグがあり、溶接ビード始端では溶接ワイヤの溶融が先行し溶接ビードが膨らむ。アークが発生する前に、溶接台車を動かして所定の位置に達したときに溶接を開始する方法もあるが、この方法では、溶接トーチのチップと母材間（エクステンション）のワイヤ（溶材）の長さにより溶接アークの発生位置が違ってくるので母材に対する溶接開始位置のばらつきが大きく、溶接ビ−ド会合部に溶接欠陥を生じ易い。
【０００３】
したがって溶接ア−ク発生に合せて溶接台車の走行を開始することが一般的であり、溶接ト−チが鋼管を一廻りして該始端の溶接ビ−ドに達すると、そこでクレ−タ処理に移り、所定時間のクレ−タ処理を終えるとそこで１パスの溶接を終える。この始端と後端処理の重なり部を会合部というが、上述のように会合部ではビ−ドが膨らむので、この膨らみを周方向に分散させるために、上述のように、会合部を、パス毎に周方向に一定距離づつ移動させることが行なわれている。
【０００４】
これにより、厚肉鋼管の場合にはパス数が多く、各パスの会合部が、開先内で螺旋状に分布することになる。すなわち、鋼管の周方向に溶接ビード会合部が広く散らばることになる。
【０００５】
【発明が解決しようとする課題】
溶接ビード会合部は、溶接ビードが高く、それに接する次パスの溶接でメタル垂れが生じやすく、溶接欠陥を生じ易い。したがって、溶接ビード会合部は、特別に品質検査，後加工又は後処理をする可能性が高いが、会合部が周方向に薄く広く分散することは、これらに手間を要することになる。
【０００６】
本発明は溶接ビード会合部のビードの高さを低くすることを第１の目的とし、溶接ビード会合部近辺でのメタル垂れを防止することを第２の目的とする。
【０００７】
【課題を解決するための手段】
（１）本発明は、送給される溶接ワイヤをチップから突き出してワイヤ先端と鋼管との間に溶接アークを発生して鋼管を溶接する溶接トーチを用いる、自動溶接ロボットによる鋼管の横向き多層盛り溶接に於いて、
溶接スタート時、低い初期電流・電圧で溶接アークを発生させ、次にそれよりも高く本電流・電圧よりも低い中間電流・電圧で溶接を行い、一定距離だけ進行後本電流・電圧で溶接を行い、パス終端部は、本電流より低いエンド電流・電圧で、又、本電流・電圧域よりも遅い一定の速度で該パスの始端部と一定距離ラップさせ、該パスの溶接を終了する、ことを特徴とする。
【０００８】
溶接スタート時の電流・電圧を、本電流・電圧より低くすることにより、溶接ビード会合部のビードの膨らみが小さくなる。パス溶接の始端と終端が重なるが、始端溶接時は低い初期電流・電圧および中間電流・電圧であるので始端ビ−ドが低く、該始端ビ−ドに重なる後端溶接時は、低いエンド電流・電圧であるので、溶接ビード会合部のビードの膨らみは小さい。後端溶接は、低速度のクレ−タ処理で終えるので、終端処理が確実かつ安定したものとなり、終端欠陥を生じない。
【０００９】
（２）各パスの始端ビ−ドと終端ビ−ドとの会合部を１パス毎に、設定範囲内で周方向にずらす。これにより会合部が設定範囲内となり、会合部が周方向に薄く広く分散することがなく、溶接ビード会合部の、品質検査，後加工又は後処理の手間が節約になる。
【００１０】
（３）会合部を１パス毎に小さい設定パス毎減少量ΔＬｏ分周方向にずらし、パス毎のずらし移動量Ｌａの積算値がずらし移動量初期値Ｌｏを越えるとき、ずらし移動量初期値Ｌｏのずらしを行なって、その後また１パス毎にパス毎減少量ΔＬｏ分周方向にずらす。これによれば、例えば会合部のラップ距離Ｄ＝０における図９および図１０に示すように、会合部（Ｓ，Ｅ）が逆三角形の２辺に交互に飛ぶように分布し、会合部の分布に重なりがなく、しかも比較的に限られた領域に集中するので、メタル垂れを生ずることがなく、しかも溶接ビード会合部の、品質検査，後加工又は後処理の手間が節約になる。
【００１１】
（４）第２パスは、第１パスの会合部に対してずらし移動量初期値Ｌｏ分周方向に会合部をずらして第１パスとは逆方向に溶接ヘッドを駆動して溶接を行ない、第３パスは、第２パスの会合部に対してずらし移動量初期値Ｌｏ−パス毎減少量ΔＬｏ分周方向に会合部をずらして第１パスと同方向に溶接ヘッドを駆動して溶接を行ない、第４パスは、第３パスの会合部に対してずらし移動量初期値Ｌｏ−パス毎減少量ΔＬｏ×２分周方向に会合部をずらして第１パスと逆方向に溶接ヘッドを駆動して溶接を行ない、ずらし移動量Ｌａ＝Ｌｏ−ΔＬｏ×ｎが０以下かつｎが奇数となるパスでずらし移動量初期値Ｌｏ分周方向に会合部をずらし、次のパス以降ではまた順次にずらし移動量初期値をパス毎減少量ΔＬｏ分づつ減らす。
【００１２】
すなわち、会合部のラップ距離Ｄ＝０における図９および図１０に示すように、会合部（Ｓ，Ｅ）が逆三角形の２辺に交互に飛ぶように分布し、会合部の分布に重なりがなくしかも比較的に限られた領域に集中するので、メタル垂れを生ずることがなく、しかも溶接ビード会合部の、品質検査，後加工又は後処理の手間が節約になる。
【００１３】
（５）鋼管(14)を周回するリング状のレ−ル(10)；
該レ−ル(10)に装着されレ−ル(10)に沿って鋼管(14)を周回移動する溶接台車(11)；
溶接台車(11)に搭載された溶接ト−チ(12)；
溶接台車(11)に搭載された走行駆動機構(2L,RL,ML)；
該走行駆動機構を正，逆走行駆動する駆動手段(4,3,1L)；
鋼管(13,14)に対する始終端での、溶接電流・電圧，ラップ距離Ｄ，ずらし移動量初期値Ｌｏ，パス毎減少量ΔＬｏ，外形Ｐ，管厚Ｔ，開先底面幅Ｇ，開先角度αおよびレール外径Ｒを入力するための入力手段(8)；
入力された値に基づいて鋼管(13,14)に対する各パス(i)の会合部の位置(r,z)，パス毎のずらし移動量(La)およびト−チ(12)の周方向移動量(L)に対応した溶接条件(電流・電圧,速度)に切替える手段(4,9)；および、
生成された各パス(i)の会合部の位置(r,z)，パス毎のずらし移動量(La)およびト−チ(12)の周方向移動量(L)対応の溶接条件(電流・電圧,速度)に従って、溶接台車(11)の走行および溶接条件を制御する溶接制御手段(4,3,1w)；
を備える鋼管の横向き多層盛り溶接装置。なお、理解を容易にするためにカッコ内には、図面に示し後述する実施例の対応要素の符号もしくは対応事項又はその記号を、参考までに付記した。
【００１４】
これによれば、オペレ−タが、鋼管(13,14)に対する各溶接パス(i)の位置(r,z)，溶接電流・電圧，ラップ距離Ｄ，ずらし移動量初期値Ｌｏおよびパス毎減少量ΔＬｏを入力することによって、各パスの、上記（１）〜（５）の多層盛り溶接を行なう各パスの溶接制御スケジュ−ルが自動生成され、溶接装置に対する各パラメ−タの設定が容易である。
【００１５】
（６）更に、生成されたパススケジュ−ルを記憶する手段；を含む鋼管の横向き多層盛り溶接装置。これによれば、同一の始終端条件，鋼管サイズおよびレール外径となる、同一仕様の上下鋼管対の複数のそれぞれに対して、入力は一度でよく、作業能率が高い。
【００１６】
本発明の他の目的および特徴は、図面を参照した以下の実施例の説明より明らかになろう。
【００１７】
【実施例】
図１に本発明の一実施例の機構の外観を示す。高さ方向ｚに端面を合せて上下に配置された下鋼管１３と上鋼管１４の合せ端面には、レ型開先（図６）が形成されている。上鋼管１４には、それと同軸にリング状のレ−ル１０が固定されており、このレ−ル１０に溶接台車１１が装着されている。溶接台車１１には、レ−ル１０をその周方向には移動自在に、上下方向ｚおよび半径方向ｒには移動不可に保持するガイドロ−ラおよびレ−ルと噛み合う車輪があり、該車輪は、図示しない減速機を介して、周回駆動用の電気モ−タＭＬで、正，逆回転駆動され、正回転駆動されると溶接台車１１の基台は時計方向に、逆回転駆動されると反時計方向に回動する。すなわちレ−ル１０に沿って円運動する。電気モ−タＭＬにはロータリエンコーダＲＬが結合しておりこれが、キヤリッジ１１の所定短距離の移動につき１パルスの電気パルスを発生する。
【００１８】
溶接台車１１の、車輪を支持する基台には昇降機構が結合されており、昇降駆動用の電気モ−タＭｚにて該機構が駆動され、電気モ−タＭｚの正回転により、溶接台車１１の基台に対して昇降台１９が上昇し、逆回転により降下する。電気モ−タＭｚにはロータリエンコーダＲｚが結合しておりこれが、昇降台１９の所定短距離の移動につき１パルスの電気パルスを発生する。
【００１９】
昇降台１９には進退機構が結合されており、進退駆動用の電気モ−タＭｒにて該機構が駆動され、電気モ−タＭｒの正回転により、進退台２０が鋼管１４の中心に近付く方向に移動し、逆回転により中心より離れる方向に移動する。電気モ−タＭｒにはロータリエンコーダＲｒが結合しておりこれが、進退台２０の所定短距離の移動につき１パルスの電気パルスを発生する。
【００２０】
進退台２０には傾動機構が結合されており、傾動用の電気モ−タＭθにて該機構が駆動され、電気モ−タＭθの正回転によりト−チホルダ２１の、水平面に対する傾斜θが小さくなり、逆回転により大きくなる。電気モ−タＭθにはロータリエンコーダＲθが結合しておりこれが、ト−チホルダ２１の所定小角度の回転につき１パルスの電気パルスを発生する。
【００２１】
溶接ト−チ１２はト−チホルダ２１で支持され、水平面に対して角度θをなす。溶接ト−チ１２には、図示しないワイヤ送給装置より溶接ワイヤが供給される。
【００２２】
溶接台車１１には、電気ケ−ブルおよび流体ホ−スが接続されており、それらならびにワイヤ送給装置の配設上の制約から、多層盛り溶接のときには、大略で言うと、奇数番パスの溶接は例えば溶接台車１１を時計廻りに回動駆動して行なわれ、偶数番パスの溶接は反時計廻りに回動駆動して行なわれる。その逆であってもよい。なお後述するように、先行パスの溶接を終了すると、先行パスでの台車１１の移動方向と同方向に、次パスの会合部のずらし移動量分台車１１が回動駆動されて停止し、そして台車を先行パスでの回動方向と逆方向に駆動して次パスの溶接が開始される。
【００２３】
図２に、図１に示す溶接装置の電気要素の概要を示す。上述の昇降機構，進退機構および傾動機構には、それぞれに運動範囲を定める始端リミットスイッチＬｚｏ，Ｌｒｏ，Ｌθｏおよび終端リミットスイッチＬｚｅ，Ｌｒｅ，Ｌθｅが備わっており、ト−チ１２が各機構の始端相当位置にあるときに始端リミットスイッチが開、終端リミットスイッチは閉であり、ト−チ１２が始端相当位置と終端端相当位置の間にあるときには両スイッチ共に閉、ト−チ１２が各機構の終端相当位置にあるときに始端リミットスイッチは閉、終端リミットスイッチは開である。
【００２４】
上述の昇降機構，進退機構および傾動機構それぞれの電気モ−タＭｚ，Ｍｒ，およびＭθの回転軸には、ロータリエンコーダＲｚ，ＲｒおよびＲθが結合されており、これらは電気モ−タの所定小角度の回転につき１個の電気パルスを発生する。ト−チ１２を駆動しているとき、マイクロプロセッサを含むコントロ−ラ１ｚ，１ｒおよび１θが、電気モ−タＭｚ，ＭｒおよびＭθを正転付勢しているときにはロータリエンコーダが発生する電気パルスをカウントアップし、逆転付勢しているときにはロータリエンコーダが発生する電気パルスをカウントダウンし、始端リミットスイッチＬｚｏ，ＬｒｏおよびＬθｏが開のときにはカウント値をクリアする（カウントデ−タを０を示すものにする）。
【００２５】
例えば、コントロ−ラ１ｚは、それ自身に電源が投入されると、始端リミットスイッチＬｚｏが開（ト−チ１２の回転位置が始端位置）であるかをチェックし、それが閉（始端位置にない）であると、モ−タドライバ２ｚにモ−タ逆転付勢を指示し、モ−タドライバ２ｚが逆転通電回路を閉じる。この逆転通電回路に始端リミットスイッチＬｚｏが含まれておりそれが閉であるので、電気モ−タＭｚに逆転電流が流れ電気モ−タＭｚが逆回転する。この逆回転で始端リミットスイッチＬｚｏが開になると、逆転通電回路が開となって電気モ−タＭｚへの逆転電流が遮断されて電気モ−タＭｚが停止する。一方コントロ−ラ１ｚは、始端リミットスイッチＬｚｏが閉から開に切換わると、モ−タドライバ２ｚへの逆転指示を解除し、昇降位置レジスタ（マイクロプロセッサの内部ＲＡＭの１領域）をクリアする。ここでト−チ１２の昇降位置が昇降範囲の始端にあり、昇降位置レジスタのデ−タは０（基点）を示すものになっていることになる。
【００２６】
コントローラ１ｒおよび１θの動作も１ｚのものと同様であり、モータドライバ２ｒおよび２θの動作も２ｚのものと同様である。マイクロプロセッサ（以下ＣＰＵと記す）４は、オペレータの１番目の教示指令（図１１に示す開先底コーナー部Ｏの位置記憶）に応じてコントローラ１Ｌに走行距離レジスタのクリアを指示する。この走行位置が、走行範囲の始端となり、走行位置レジスタのデータは０（基点）を示すものになっていることになる。
【００２７】
コントローラ１ｗはＣＰＵ４の指示に応じて、トーチ１２が接続される溶接電源１６には、溶接電流・電圧およびオン（通電）／オフ（通電停止）を指定する信号を与え、流体供給装置１７にはオン（ガス供給）／オフ（供給停止）を指示する信号を与え、ワイヤ送給装置１８には供給速度およびオン（供給）／オフ（供給停止）を指示する信号を与える。ＣＰＵ４には、入出力（Ｉ／Ｏ）ポート３を介してコントローラ１Ｌ，１ｚ，１ｒ，１θおよび１ｗ、ならびに操作／表示ボード８および不揮発メモリ９が選択的に接続される。この接続は、システムコントローラ５を介してＣＰＵ４が指定する。ＣＰＵ４のアドレスバス，データバスにはＲＯＭ６およびＲＡＭ７が接続されている。システムコントローラ５は、ＣＰＵ４が指示する制御信号をＲＯＭ６，ＲＡＭ７および操作／表示ボード８に与える。
【００２８】
図３に、図１および図２に示す本発明の実施例を使用するオペレータの作業概要を示し、図４に、ＣＰＵ４の制御動作を示す。オペレータは図１に示すようにレール１０および溶接台車１１を鋼板１４に装着し溶接台車１１は中心位置に位置決めする。そして始終端条件を、操作表示ボード８で入力し（図３のＡ）、鋼管外径等、鋼管の寸法およびレール外径を入力し（図３のＢ）、開先形状に対する開先底面幅Ｇ，開先角度α，鋼管の管厚Ｔを入力する。そして、図１１に示す開先底部のコーナー部Ｏにワイヤの先端を移動させ、教示位置Ｋ（Ｌ，ｒ，ｚ，θ）として各軸の位置を記憶させる。そして、ＣＰＵ４は、オペレータが、１番目の教示位置Ｋ１の指令に応じて、コントローラ１Ｌに走行距離レジスタのクリアを指示する。この位置が、走行範囲の始端となり、走行位置レジスタのデータは０（基点）を示すものになっていることになる。
【００２９】
この操作を鋼管１周に対し、ｎ個行う。この１番目の教示位置Ｋ１の（ｒ１，ｚ１，θ１）とｎ番目の教示位置Ｋｎの（ｒｎ，ｚｎ，θ１）は同じ位置とする。次に、ＣＰＵ４は、教示位置ＫｎのＬｎを０とし、教示位置Ｋ１からＫｎ−１のＬ１（＝０），Ｌ２，Ｌ３，・・・・，Ｌｎ−１を、Ｌｎ，Ｌｎ−Ｌ２，Ｌｎ−Ｌ３，・・・・，Ｌｎ−Ｌｎ−１に書替える。ここで、Ｌｎ−Ｌ１は、ずらし移動量Ｌａ＝０およびラップ距離Ｄ＝０のときレール上での１パスの溶接距離となる。これらのデータを図４のステップ２で読取り、使用するワイヤ径φ１．２ｍｍと、予めプログラムに固定値として書込んでいる、本溶接電流値のワイヤ送給量Ｖｆｗ，電圧値Ｖｗ，１層当たりの層高さＨ，１パス当たりのパス断面積Ｓから、「溶接条件生成」（ステップ３）で、データに対応したパススケジュールの生成を行い、各パスの溶接条件および溶接位置を演算生成する。
【００３０】
なお、溶接速度については、第１パスの溶接位置（ｒｓ１，ｚｓ１）、特に半径方向の位置ｒｓ１による速度ずれ分、溶接速度を補正している。例えば、同一の周速度で溶接台車１１を施回駆動した場合、トーチ先端（ワイヤ）が開先の底（裏当材１５（図６）に近い、パスＮｏ．ｉが小さいパスでは、トーチ先端の周速度が遅く、レールに近い、パスＮｏ．ｉが大きいパスでは、トーチ先端の周速度が速く、これらの速い，遅いが、溶接速度ずれとなり、レール取付け位置を基準とし、第ｉパスの溶接速度（台車移動速度）Ｖｗｉを、Ｖｗｉ×Ｒ／（Ｐ−（Ｔ−ｒｓｉ）×２）に書替える。ここで、Ｒはレール径，Ｐは外径，Ｔは管厚，ｒｓｉは第ｉパスのｒ位置である。
【００３１】
以下において、上記パス毎のデータ群をパススケジュールと称す。ここで、パスＮｏ．は、図６に示すように、一周１回の溶接を１パスとして実行順に番号を付けたものである。
【００３２】
又、溶接位置は、教示位置との相対距離で表示しているため、例えば、ＣＰＵ４がコントローラ１ｚに、パスＮｏ．ｉの高さｚｉのデータを与えると、コントローラ１ｚは、パスＮｏ．ｉの溶接位置（ｚｅ（ｅ番目の教示位置の昇降方向位置）＋ｚｉ）と昇降位置レジスタのデータが示す前パスの溶接位置（実高さ）ｚａ＝ｚｅ＋ｚｉ−１の偏差（ｚｉ−ｚｉ−１）の極性をチェックして、それが正であればモータドライバ２ｚに正転指示し、負であれば逆転を指示する。モータドライバ２ｚがこれに応答して、電気モータＭｚを正転通電又は逆転通電する。この通電により電気モータＭｚが回転し、ロータリエンコーダＲｚが１パルスを発生する毎に、コントローラ１ｚは、正転通電のときには昇降位置レジスタのデータを前の値より１大きい数値を示すものに更新し、逆転通電のときには前の値より１小さい数値を示すものに更新して、昇降位置レジスタのデータがパスＮｏ．ｉの溶接位置を示すものになったときに、モータドライバ２ｚへの正転指示又は逆転指示を解除（モータ停止指示）する。モータドライバ２ｚがこれに応答してモータＭｚの通電を遮断する。このようにして、ＣＰＵ４が指示する高さｚｉにトーチ１２の高さｚａが設定される。更に、各教示位置間は直線補完を行っている。
【００３３】
次に、オペレータが溶接スタートを入力すると、ＣＰＵ４は教示位置ＫｎからＫ１に向かって第１パスから溶接を開始する。第１パスの溶接が終了すると、順次パススケジュールに基づいて、第２パス以降の溶接を行う。第２パスは、第１パスとは逆方向に溶接台車１１を駆動して溶接を行う。第３パスは、第１パスと同方向に溶接台車１１を駆動して溶接を行う。第４パスは、第２パスと同方向に溶接台車１１を駆動して溶接を行う。このように溶接方向は、パス毎に溶接方向を逆転する往復溶接で行う。パススケジュールの最終パスの溶接を終了すると、溶接終了を報知する。オペレータは、溶接終了の報知があると、レール１０を鋼管１４から外し、次の溶接対象鋼管に装着する。次の溶接も同一仕様であるときには、ＣＰＵ４が不揮発メモリ９に書込んだ前回の始終端条件（図３のＡ）を利用することができる。
【００３４】
オペレ−タ入力の始終端条件は、次の通りである。
【００３５】

なお、上記データは、オペレータの図３の「始終端条件初期設定」（Ａ）での入力を、ＣＰＵ４が図４の「入力読取り」（ステップ２）で読込んでセーブしているものである。ここで、（１），（２），（４），（５）のデータは、図７および図８に示すように、１パスの溶接の始終端部の溶接電流，電圧であり、このデータは全パス共通である。図７および図８に示す（３）のデータは、予めプログラム上に固定値として設定している。
【００３６】
なお、図７は溶接トーチ１２の円周移動を直線展開して示し、図８は管軸を中心にした円周移動をそのまま示す。
【００３７】
オペレータ入力の鋼管サイズおよびレール外形としては、外形Ｐ，管厚Ｔ，開先底面幅Ｇ（開先の底幅），開先角度αおよびレール外形Ｒである。
【００３８】
再度図５を参照する。ＣＰＵ４は「溶接条件生成」を行うと（図４のステップ３）、パスＮｏ．ｉを１に設定し、パス毎減少回数ｎを０に初期化して（ステップ２１）、教示データを読込む（ステップ２２）。そして、「溶接条件生成」で生成したパススケジュールに基づいて、各パスの溶接軌跡（周方向開始位置Ｌｓｉ，周方向終了位置Ｌｃｉ）を設定する。溶接軌跡、すなわち溶接台車１１の駆動範囲は、パスＮｏ．ｉが１であると、ずらし移動量Ｌａを０とする（ステップ２３〜２６）。そして、ｎ番目の教示位置ＫｎのＬｎ（＝０）と、ずらし移動量Ｌａ１（＝０）に基づいて、第１パスの周方向開始位置Ｌｓ１をＬｎ（＝０）に設定する。次に、溶接速度の補正と同様に、第１パスの溶接位置（ｒｓ１，ｚｓ１）、特に半径方向の位置ｒｓ１による距離ずれ分、ラップ距離Ｄを補正する（ステップ２８）。例えば、ある一定速度で溶接台車１１を旋回駆動した場合、ト−チ先端（ワイヤ）が開先の底（裏当材１５（図６））に近い、パスＮｏ．ｉが小さいパスでは、トーチ先端の移動距離が溶接台車１１の移動距離より短く、これが距離ずれとなる。ステップ２８では、レール取付け位置を基準とし、第ｉパスのラップ距離Ｄｉを、Ｄ×Ｒ／（Ｐ−（Ｔ−ｒｓｉ）×２）に書替える。ここで、Ｄはラップ距離，Ｒはレール径，Ｐは半径，Ｔは管厚，ｒｓｉは第１パスのｒ位置である。そして、１パスの溶接長Ｌｎ−Ｌ１と、ラップ距離Ｄｉに基づいて、周方向終了位置Ｌｃ１をＬｎ−Ｌ１＋Ｄｉに設定する。第２パスは、ＣＰＵ４が、ずらし移動量Ｌａ（第２パスのものはＬａ２）に、ずらし移動量初期値Ｌ０を設定し（ステップ２２，２３，３１）、第１パスの周方向終了位置Ｌｃ１にずらし移動量Ｌａ２＝Ｌ０を加えた和を算出して、それを周方向開始位置Ｌｓ２とする。次に、第２パスの半径方向位置ｒｓ２による距離ずれ分、ラップ距離Ｄ２を、Ｄ×Ｒ／（Ｐ−（Ｔ−ｒｓ２）×２）に書替え、第２パスの周方向開始位置Ｌｓ２にパスの溶接長Ｌｎ−Ｌ１と、ラップ距離Ｄ２の和を減算したＬａ２−（Ｌｎ−Ｌ１＋Ｄ）を周方向終了位置Ｌｃ２とする。
【００３９】
第３パスは、ＣＰＵ４が、パス毎減少回数ｎを１インクリメントして（ステップ２２，２３，３１）、ずらし移動量
Ｌａ３＝Ｌ０−１×ΔＬ０
を算出する（ステップ３２）。そしてＬａ３が負値（１パス毎にパス毎減少量のΔＬ０分のずらしをした積算値ｎ×ΔＬ０が、ずらし移動量初期値Ｌ０以上になった：再度Ｌ０分のずらし要）かをチェックして（ステップ３３）、正値であると、前パスである第２パスの終了位置Ｌｃ２より、算出したずらし移動量Ｌａ３を減算した差（Ｌａ３が負値であると実際には和）を算出して、それを周方向開始位置Ｌｓ３とする（ステップ２６）。次に、第３パスの半径方向位置ｒｓ３による距離ずれ分、ラップ距離Ｄ３を、Ｄ×Ｒ／（Ｐ−（Ｔ−ｒｓ３）×２）に書替え、第３パスの周方向開始位置Ｌｓ３に１パスの溶接長Ｌｎ−Ｌ１と、ラップ距離Ｄ３の和を算出して、それを周方向終了位置Ｌｃ３とする。
【００４０】
第４パスは、ＣＰＵ４が、パス毎減少回数ｎを１インクリメントして（ステップ２２，２３，３１）、ずらし移動量
Ｌａ４＝Ｌ０−２×ΔＬ０
を算出する（ステップ３２）。そしてＬａ４が負値かをチェックして（ステップ３３）、正値であると、前パスである第３パスの終了位置Ｌｃ３より、算出したずらし移動量Ｌａ４を加算した和（Ｌａ４が負値であると実際には差）を算出して、それを周方向開始位置Ｌｓ４とする（ステップ２６）。次に、第４パスの半径方向の位置ｒｓ４による距離ずれ分、ラップ距離Ｄ４を、Ｄ×Ｒ／（Ｐ−（Ｔ−ｒｓ３）×２）に書替え、第４パスの周方向開始位置Ｌｓ４に１パスの溶接長Ｌｎ−Ｌ１と、ラップ距離Ｄ４の和を算出して、それを周方向終了位置Ｌｃ４とする。
【００４１】
以下、第５パス以降の奇数番パスのパススケジュ−ルは、上記の第３パスと同様に生成し、第６パス以降の偶数番パスのパススケジュ−ルは、上記の第４パスと同様に生成する。
【００４２】
その過程で、算出したずらし移動量
Ｌａｉ＝Ｌ０−ｎ×ΔＬ０
が０以下の値となったときは、ｎが奇数であるかをチェックし（ステップ３４）、奇数であるとずらし移動量Ｌａｉにずらし移動量初期値Ｌ０を設定する（ステップ３０）。奇数でなかったら、次の奇数パスでこれを行なう。
【００４３】
オペレ−タが、溶接スタ−トを入力すると、ＣＰＵ４は図４のステップ３，ステップ４で生成したパススケジュールをディスプレイに表示して、パスＮｏ．レジスタｉに１を設定して（第１パスを指定して）、第ｉパスのパススケジュールに基づいて、第ｉパスの溶接を、図７および図８に示すように行なう。第１パスの溶接は、ト−チ位置および姿勢を（ｒｓ１，ｚｓ１，θｓ１）にして第１パスの周方向開始位置Ｌｓ１から開始するが、第２パスは、第１パスの終点Ｌｃ１でト−チ位置および姿勢を（ｒｓ２，ｚｓ２，θｓ２）にしそして第２パスの周方向開始位置Ｌｓ２にト−チを駆動してから開始する。第３パスは、第２パスの終点Ｌｃ２でト−チ位置および姿勢を（ｒｓ３，ｚｒｓ３，θｓ３）にし、そして第３パスの周方向開始位置Ｌｓ３にト−チを駆動してから開始する。以下同様である。いずれのパスにおいても、溶接速度，方向，溶接電流，電圧および電流，電圧の切換タイミングは、パススケジュールのデータに対応して定める（図４のステップ９〜１６）。
【００４４】
以上に説明した実施例によれば、溶接スタート時、（１）低い初期電流，電圧で溶接アークを発生させ、次にそれよりも高く本電流・電圧よりも低い（２）中間電流，電圧で行い、一定距離だけ進行後（３）本電流・電圧で溶接を行うことによりスタ−ト時のト−チ移動の遅れによる初期ビ−ドの膨らみが少く、各パスのビ−ド会合部の膨らみが少く、メタル垂れを生じない。
【００４５】
溶接ビード会合部（１パスの溶接始端と終端とのラップ部）は、本電流より低い（４）低電流，電圧で、又、本電流，電圧域よりも遅い一定の速度で一定距離Ｄラップさせ、その位置でクレータ溶接条件で終了するので、会合部に溶接欠陥を生じない。
【００４６】
溶接ビード会合部を１パス毎に移動させ、一定の距離範囲内で繰り返している。すなわち、ずらし移動量初期値Ｌｏを設定し、１パス毎のパス毎減少量ΔＬｏだけずらし移動量を減少して行きずらし移動量Ｌａ≦０になるときは、Ｌａ＝Ｌｏとする。減少回数ｎ＝Ｌｏ÷ΔＬｏ＝偶数、の場合は、もう一回継続する。これを繰り返すことにより、一定の距離範囲内に会合部が繰り返し現われる。このことにより特に欠陥が生じやすい溶接ビード会合部を一定の距離範囲内に納めることが出来る。図９および図１０に、パス間の溶接開始位置のずらし移動量を実線で示す。横軸が溶接ト−チ１２の周方向位置であり、０点が、第１パスの溶接開始時の周方向溶接位置（狙い位置）である。数値の単位はｍｍである。
【図面の簡単な説明】
【図１】本発明の一実施例の機構外観を示す斜視図である。
【図２】図１に示す溶接装置の電気系システム構成を示すブロック図である。
【図３】図１に示す溶接装置を使用するオペレ−タの作業手順を示すフローチャートである。
【図４】図２に示すＣＰＵ４が行なう処理の概要を示すフローチャートである。
【図５】図４に示す「溶接軌跡生成」（４）の内容の一部を示すフローチャートである。
【図６】図１に示す溶接対象の鋼管１３，１４の一部分の拡大縦断面図であり、多層盛り溶接を行なった開先の横断面を示す。
【図７】図１に示す溶接装置による１パスの溶接の間の溶接電流，電圧の変化と溶接速度の変化を示すグラフであり、横軸は、溶接ト−チ１２の周方向移動を直線展開した移動距離である。
【図８】図１に示す溶接装置による１パスの溶接の間の溶接電流，電圧の変更点を示す平面図である。
【図９】図１に示す溶接装置による多層盛り溶接の場合の、パス毎の溶接開始位置ずらし移動量の一例を実線で示すグラフであり、横軸は、溶接ト−チ１２の周方向移動を直線展開した移動距離である。
【図１０】図１に示す溶接装置による多層盛り溶接の場合の、パス毎の溶接開始位置ずらし移動量のもう１つの例を実線で示すグラフであり、横軸は、溶接ト−チ１２の周方向移動を直線展開した移動距離である。
【図１１】図１に示す溶接対象の鋼管１３，１４の一部の拡大縦断面であり、ワイヤ先端での教示位置を示す開先の横断面を示す。
【符号の説明】
１０：レ−ル１１：溶接台車
１２：溶接ト−チ１３，１４：鋼管
１９：昇降基台２０：進退基台
２１：ト−ルホルダＭＬ，Ｍｚ，Ｍｒ，Ｍθ：電気モ−タ
ＲＬ，Ｒｚ，Ｒｒ，Ｒθ：ロータリエンコーダ[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a groove between upper and lower steel pipes with their end faces abutting each other by turning a welding torch around a steel pipe by means of an automatic welding robot and performing multi-layer laterally-welded welding and the automatic welding robot. .
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in horizontal multi-layer welding of steel pipes, a joint portion between a starting end and a terminating end of a weld bead formed by an automatic welding robot is moved by a constant distance in a circumferential direction for each pass. At the beginning of each pass, there is a time lag in increasing the welding bogie to the welding speed with respect to the occurrence of arc at the start of welding, and at the beginning of the welding bead, the welding wire precedes and the welding bead expands. There is also a method of starting welding when the welding bogie is moved to a predetermined position before an arc is generated. However, in this method, a wire (fused material) between a tip of a welding torch and a base material (extension) is formed. Since the position where the welding arc is generated differs depending on the length, the variation in the welding start position with respect to the base metal is large, and welding defects are likely to occur at the weld bead junction.
[0003]
Therefore, it is common to start the running of the welding bogie in accordance with the occurrence of welding arc. When the welding torch goes around the steel pipe and reaches the welding bead at the start end, the crater processing is performed there. When the crater processing for a predetermined time is completed, one-pass welding is completed there. The overlapping portion of the start end and rear end treatments is referred to as a meeting portion. Since the bead swells at the meeting portion as described above, in order to disperse the swelling in the circumferential direction, the meeting portion is connected to the path as described above. Each time, a constant distance is moved in the circumferential direction.
[0004]
As a result, in the case of a thick steel pipe, the number of passes is large, and the meeting portion of each pass is distributed spirally within the groove. That is, the weld bead joints are widely scattered in the circumferential direction of the steel pipe.
[0005]
[Problems to be solved by the invention]
The weld bead joint portion has a high weld bead, and the next pass welding in contact with the weld bead tends to cause metal sagging, which tends to cause welding defects. Therefore, it is highly likely that the weld bead joint portion is specifically subjected to quality inspection, post-processing, or post-treatment. However, if the joint portion is thin and widely dispersed in the circumferential direction, it takes time and effort.
[0006]
A first object of the present invention is to reduce the height of a bead at a weld bead meeting portion, and a second object is to prevent metal sagging near a weld bead meeting portion.
[0007]
[Means for Solving the Problems]
(1) The present invention Using a welding torch to project the welding wire to be fed from the tip and generate a welding arc between the wire tip and the steel pipe to weld the steel pipe, In the horizontal multi-layer welding of steel pipe by automatic welding robot,
At the start of welding, a welding arc is generated with a low initial current and voltage, then welding is performed with an intermediate current and voltage higher than this and lower than the main current and voltage, and after a certain distance, welding is performed with this current and voltage. line The end of the path is wrapped at a constant distance lower than the main current at an end current / voltage lower than the main current and at a constant speed lower than the main current / voltage range, and ends welding of the path. It is characterized by the following.
[0008]
By making the current / voltage at the start of welding lower than this current / voltage, the bulge of the bead at the weld bead junction is reduced. Become. path The beginning and end of welding overlap, but the starting end bead is low because the initial current and voltage are low and the intermediate current and voltage are low during starting end welding, and the low end current and current are low during rear end welding that overlaps the starting end. Because of the voltage, the bulge of the bead at the weld bead junction is small. Since the rear end welding is completed by a low-speed crater process, the terminal process is assured and stable, and no terminal defects occur.
[0009]
( 2 ) The junction between the start bead and the end bead of each pass is shifted in the circumferential direction within the set range for each pass. As a result, the meeting portion is within the set range, the meeting portion is not thinly and widely dispersed in the circumferential direction, and the labor of quality inspection, post-processing, or post-processing of the welding bead meeting portion is saved.
[0010]
( 3 ) The meeting unit is shifted in the direction of dividing the set path decreasing amount ΔLo by a small amount for each pass, and when the integrated value of the shifting amount La for each path exceeds the initial value Lo, the shifting amount Lo is shifted. After that, the shift amount ΔLo is shifted in the frequency dividing direction for each pass again for each pass. According to this, for example, as shown in FIG. 9 and FIG. 10 when the lap distance D of the meeting portion is 0, the meeting portions (S, E) are distributed so as to alternately fly on two sides of an inverted triangle. Since the distribution is non-overlapping and concentrated in a relatively limited area, metal sagging does not occur and the quality inspection, post-processing or post-processing of the weld bead joint is saved.
[0011]
( 4 In the second pass, welding is performed by driving the welding head in the direction opposite to the first pass by shifting the meeting portion in the direction of dividing the shift amount initial value Lo with respect to the meeting portion of the first pass, and performing the welding in the third pass. In the pass, the welding is performed by driving the welding head in the same direction as the first pass by shifting the meeting portion in the direction of dividing by the shift amount initial value Lo-decrease amount ΔLo for each pass with respect to the meeting portion of the second pass, In the fourth pass, the welding head is driven in the direction opposite to the first pass by shifting the meeting portion in the direction of dividing by the shift amount initial value Lo-decrease amount per path ΔLo × 2 with respect to the meeting portion of the third pass. Welding is performed, and the shift portion La is shifted in a direction where the shift amount La = Lo−ΔLo × n is 0 or less and n is an odd number, and the associated portion is shifted in the direction of dividing the initial value Lo, and the shift portion is sequentially shifted after the next pass. The amount initial value is decreased by the amount of decrease ΔLo for each pass.
[0012]
That is, as shown in FIG. 9 and FIG. 10 when the lap distance D of the meeting portion is 0, the meeting portions (S, E) are distributed so as to alternately fly on two sides of the inverted triangle, and the distribution of the meeting portion is overlapped. In addition, since it is concentrated in a relatively limited area, metal sagging does not occur, and the quality inspection, post-processing or post-processing of the weld bead joint is saved.
[0013]
( 5 ) A ring-shaped rail (10) orbiting a steel pipe (14);
A welding bogie (11) mounted on the rail (10) and moving around the steel pipe (14) along the rail (10);
Welding torch (12) mounted on welding trolley (11);
Traveling drive mechanism (2L, RL, ML) mounted on the welding trolley (11);
Drive means (4,3,1L) for driving the traveling drive mechanism forward and backward;
Welding current / voltage, lap distance D, displacement amount initial value Lo, reduction amount per pass ΔLo, outer shape P, pipe thickness T, groove bottom width G, groove angle at start and end of steel pipes (13, 14) input means (8) for inputting α and rail outer diameter R;
Based on the input values, the position (r, z) of the joint of each path (i) with respect to the steel pipe (13, 14), the amount of displacement (La) for each path, and the circumferential movement of the torch (12) Means (4, 9) for switching to welding conditions (current, voltage, speed) corresponding to the amount (L); and
Welding conditions (current and current) corresponding to the position (r, z) of the meeting part of each generated path (i), the amount of shift (La) for each path, and the amount of circumferential movement (L) of the torch (12) Welding control means (4, 3, 1w) for controlling running and welding conditions of the welding cart (11) according to the voltage and speed);
A horizontal multi-layer welding apparatus for steel pipes comprising: In addition, in order to facilitate understanding, in the parentheses, reference numerals or corresponding items of corresponding elements of the embodiment shown in the drawings and described below or symbols thereof are added for reference.
[0014]
According to this, the operator can reduce the position (r, z) of each welding path (i) with respect to the steel pipes (13, 14), the welding current / voltage, the lap distance D, the initial value Lo of the shift movement, and decrease for each path. By inputting the amount ΔLo, a welding control schedule of each pass for performing the above multi-pass welding (1) to (5) of each pass is automatically generated, so that setting of each parameter for the welding apparatus is easy. It is.
[0015]
( 6 ) Generated pass schedule Means for storing laterally multi-layered welding of steel pipes. According to this, the same Beginning For each of a plurality of pairs of upper and lower steel pipes having the same specifications, which are the termination condition, the steel pipe size, and the outer diameter of the rail, only one input is required and the work efficiency is high.
[0016]
Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.
[0017]
【Example】
FIG. 1 shows the appearance of a mechanism according to an embodiment of the present invention. At the mating end face of the lower steel pipe 13 and the upper steel pipe 14 arranged vertically with the end faces in the height direction z, a die groove (FIG. 6) is formed. A ring-shaped rail 10 is fixed to the upper steel pipe 14 coaxially with the upper steel pipe 14, and a welding carriage 11 is mounted on the rail 10. The welding cart 11 includes a guide roller and a wheel that meshes with the rail, which holds the rail 10 so as to be movable in the circumferential direction and not movable in the vertical direction z and the radial direction r. The motor ML is driven forward and backward by a circular drive electric motor ML via a speed reducer (not shown). When the forward rotation is performed, the base of the welding carriage 11 is driven clockwise and reversely driven. Rotates counterclockwise. That is, a circular motion is made along the rail 10. A rotary encoder RL is coupled to the electric motor ML, and generates one electric pulse for a predetermined short distance movement of the carriage 11.
[0018]
An elevating mechanism is connected to a base supporting the wheels of the welding bogie 11, and the mechanism is driven by an electric motor Mz for driving up and down, and the welding bogie is driven by the forward rotation of the electric motor Mz. The elevator 19 rises with respect to the base 11 and descends by reverse rotation. A rotary encoder Rz is coupled to the electric motor Mz, and generates one electric pulse per movement of the elevator 19 over a predetermined short distance.
[0019]
An elevating mechanism is coupled to the elevating table 19, and the mechanism is driven by an electric motor Mr for driving the elevating means, and the forward / retreat table 20 approaches the center of the steel pipe 14 by the forward rotation of the electric motor Mr. Move in the direction, and move in the direction away from the center by reverse rotation. A rotary encoder Rr is connected to the electric motor Mr, and generates a single electric pulse for a predetermined short distance of movement of the slide 20.
[0020]
A tilting mechanism is connected to the reciprocating table 20. The mechanism is driven by the tilting electric motor Mθ, and the forward rotation of the electric motor Mθ reduces the tilt θ of the torch holder 21 with respect to the horizontal plane. And becomes larger due to reverse rotation. A rotary encoder R.theta. Is coupled to the electric motor M.sub..theta., Which generates one electric pulse per rotation of the torch holder 21 at a predetermined small angle.
[0021]
The welding torch 12 is supported by a torch holder 21 and forms an angle θ with respect to a horizontal plane. The welding torch 12 is supplied with a welding wire from a wire feeding device (not shown).
[0022]
An electric cable and a fluid hose are connected to the welding trolley 11, and due to restrictions on the arrangement of the wire feeding device and the electric cable, in the case of multi-layer welding, generally, an odd-numbered pass is used. Welding is performed, for example, by rotating the welding cart 11 clockwise, and welding of even-numbered passes is performed by rotating counterclockwise. The reverse is also possible. As will be described later, when the welding of the preceding pass is completed, the bogie 11 is rotated and driven to stop in the same direction as the moving direction of the bogie 11 in the preceding pass by the shift amount of the meeting portion of the next pass, and The bogie is driven in the direction opposite to the rotation direction in the preceding pass, and welding in the next pass is started.
[0023]
FIG. 2 shows an outline of electric components of the welding apparatus shown in FIG. The above-described lifting / lowering mechanism, advance / retreat mechanism, and tilting mechanism are provided with start limit switches Lzo, Lro, Lθo and end limit switches Lze, Lre, Lθe respectively defining a movement range, and the torch 12 is connected to the start end of each mechanism. The start limit switch is open and the end limit switch is closed when the torch 12 is at the corresponding position. When the torch 12 is between the start position and the end position, both switches are closed, and the torch 12 is closed. The start limit switch is closed and the end limit switch is open when the switch is at the position corresponding to the end of.
[0024]
Rotary encoders Rz, Rr, and Rθ are coupled to the rotating shafts of the electric motors Mz, Mr, and Mθ of the above-described lifting / lowering mechanism, the forward / backward mechanism, and the tilting mechanism, respectively. One electrical pulse is generated for each rotation of the angle. When the torch 12 is being driven, the electric pulses generated by the rotary encoder when the controllers 1z, 1r and 1θ including the microprocessor are energizing the electric motors Mz, Mr and Mθ in the forward direction. When the reverse rotation is energized, the electric pulse generated by the rotary encoder is counted down, and when the start end limit switches Lzo, Lro and Lθo are open, the count value is cleared (the count data is set to 0). Do).
[0025]
For example, when the power is supplied to the controller 1z, the controller 1z checks whether the start limit switch Lzo is open (the rotational position of the torch 12 is at the start position), and closes (at the start position). If not, the motor driver 2z is instructed to energize the motor in the reverse direction, and the motor driver 2z closes the reverse rotation energizing circuit. Since the reverse rotation energizing circuit includes the start limit switch Lzo and is closed, a reverse current flows through the electric motor Mz, and the electric motor Mz rotates in the reverse direction. When the start end limit switch Lzo is opened by this reverse rotation, the reverse rotation energizing circuit is opened, the reverse rotation current to the electric motor Mz is cut off, and the electric motor Mz stops. On the other hand, when the start end limit switch Lzo switches from the closed state to the open state, the controller 1z cancels the reverse rotation instruction to the motor driver 2z and clears the elevation position register (one area of the internal RAM of the microprocessor). Here, the ascending / descending position of the torch 12 is at the beginning of the ascending / descending range, and the data in the ascending / descending position register indicates 0 (base point).
[0026]
The operations of the controllers 1r and 1θ are the same as those of the 1z, and the operations of the motor drivers 2r and 2θ are the same as those of the 2z. The microprocessor (hereinafter abbreviated as CPU) 4 instructs the controller 1L to clear the mileage register in response to the first instruction command (storage of the groove bottom corner O shown in FIG. 11) by the operator. This travel position is the start end of the travel range, and the data in the travel position register indicates 0 (base point).
[0027]
In response to an instruction from the CPU 4, the controller 1 w supplies a welding power source 16 to which the torch 12 is connected with a signal for designating welding current / voltage and ON (energization) / OFF (energization stop). A signal instructing ON (gas supply) / OFF (supply stop) is given, and a signal instructing the supply speed and ON (supply) / OFF (supply stop) is given to the wire feeding device 18. Controllers 1L, 1z, 1r, 1θ and 1w, an operation / display board 8 and a nonvolatile memory 9 are selectively connected to the CPU 4 via an input / output (I / O) port 3. This connection is specified by the CPU 4 via the system controller 5. The ROM 6 and the RAM 7 are connected to an address bus and a data bus of the CPU 4. The system controller 5 supplies a control signal specified by the CPU 4 to the ROM 6, the RAM 7, and the operation / display board 8.
[0028]
FIG. 3 shows an outline of an operation of an operator using the embodiment of the present invention shown in FIGS. 1 and 2, and FIG. 4 shows a control operation of the CPU 4. The operator mounts the rail 10 and the welding cart 11 on the steel plate 14 as shown in FIG. 1, and positions the welding cart 11 at the center position. Then, the start and end conditions are input on the operation display board 8 (A in FIG. 3), the dimensions of the steel pipe and the rail outer diameter such as the outer diameter of the steel pipe are input (B in FIG. 3), and the groove bottom width with respect to the groove shape. G, groove angle α, and thickness T of the steel pipe are input. Then, the tip of the wire is moved to the corner O at the bottom of the groove shown in FIG. 11, and the position of each axis is stored as the teaching position K (L, r, z, θ). Then, the CPU 4 instructs the controller 1L to clear the travel distance register in accordance with the instruction of the first teaching position K1. This position is the start end of the travel range, and the data in the travel position register indicates 0 (base point).
[0029]
This operation is performed n times for one round of the steel pipe. (R1, z1, θ1) of the first teaching position K1 and (rn, zn, θ1) of the nth teaching position Kn are the same position. Next, the CPU 4 sets Ln of the teaching position Kn to 0, and converts L1 (= 0), L2, L3,..., Ln-1 of Kn-1 from the teaching position K1 into Ln, Ln-L2, Ln. .., Ln−Ln−1. Here, Ln-L1 is a welding distance of one pass on the rail when the shift amount La = 0 and the lap distance D = 0. These data are read in step 2 in FIG. 4, and the wire diameter φ1.2 mm to be used and the wire feed amount Vfw, voltage value Vw of the actual welding current value, which has been previously written as a fixed value in the program, per layer In step 3, a pass schedule corresponding to the data is generated from the layer height H and the pass cross-sectional area S per pass, and the welding condition and welding position of each pass are calculated and generated. .
[0030]
In addition, as for the welding speed, the welding position (rs1, zs1) of the first pass, particularly the speed deviation by the radial position rs1, and the welding speed are corrected. For example, when the welding bogie 11 is driven to rotate at the same peripheral speed, the torch tip (wire) is close to the bottom of the groove (the backing material 15 (FIG. 6), and in a path with a small pass No. i, the torch tip). In the pass where the peripheral speed of the torch tip is large and the peripheral speed of the torch tip is large, the peripheral speed at the tip of the torch is high, and these are high and low. Rewrite the welding speed (trolley moving speed) Vwi to Vwi × R / (P− (T−rsi) × 2), where R is the rail diameter, P is the outer diameter, T is the pipe thickness, and rs is the rs i This is the r position of the path.
[0031]
Hereinafter, the data group for each pass will be referred to as a pass schedule. Here, the path No. As shown in FIG. 6, the numbers are assigned in the order of execution, with one round of welding as one pass.
[0032]
Further, since the welding position is displayed as a relative distance from the teaching position, for example, the CPU 4 sends the pass No. to the controller 1z. When the data of the height zi of the i.i. Deviation (zi-zi-1) of welding position (ze (elevation direction position of e-th teaching position) + zi) and welding position (actual height) za = ze + zi-1 of the previous pass indicated by the data of the elevation position register ) Is checked, and if the polarity is positive, a forward rotation instruction is given to the motor driver 2z, and if negative, a reverse rotation instruction is given. In response to this, the motor driver 2z energizes the electric motor Mz in forward rotation or reverse rotation. Each time the electric motor Mz rotates due to this energization and the rotary encoder Rz generates one pulse, the controller 1z updates the data of the elevation position register to a value which is larger than the previous value by one at the time of forward energization. , When the reverse rotation is energized, the data is updated to a value that is smaller than the previous value by one, and the data of the elevation position register is changed to the pass No. When the position i indicates the welding position, the normal rotation instruction or the reverse rotation instruction to the motor driver 2z is released (motor stop instruction). In response to this, the motor driver 2z shuts off the current supply to the motor Mz. Thus, the height za of the torch 12 is set to the height zi specified by the CPU 4. Further, linear interpolation is performed between the teaching positions.
[0033]
Next, when the operator inputs welding start, the CPU 4 starts welding from the first pass from the teaching position Kn to K1. When the welding of the first pass is completed, welding of the second and subsequent passes is sequentially performed based on the pass schedule. In the second pass, welding is performed by driving the welding cart 11 in a direction opposite to the first pass. The third pass drives the welding cart 11 in the same direction as the first pass to perform welding. The fourth pass drives the welding cart 11 in the same direction as the second pass to perform welding. Thus, the welding direction is performed by reciprocating welding in which the welding direction is reversed for each pass. When the welding of the last pass in the pass schedule is completed, the completion of welding is notified. When notified of the end of welding, the operator removes the rail 10 from the steel pipe 14 and mounts it on the next steel pipe to be welded. When the next welding has the same specification, the previous start / end condition (A in FIG. 3) written by the CPU 4 in the nonvolatile memory 9 can be used.
[0034]
The starting and ending conditions of the operator input are as follows.
[0035]

The above data is obtained by the CPU 4 reading and saving the input by the operator in the "initial setting of the start and end conditions" (A) in FIG. 3 by "input read" (step 2) in FIG. Here, the data of (1), (2), (4) and (5) are, as shown in FIGS. 7 and 8, the welding current and voltage at the start and end of one-pass welding. Is common to all paths. The data of (3) shown in FIG. 7 and FIG. 8 is set as a fixed value in a program in advance.
[0036]
7 shows the circumferential movement of the welding torch 12 in a linearly developed manner, and FIG. 8 shows the circumferential movement about the pipe axis as it is.
[0037]
The steel pipe size and the rail outer shape input by the operator include the outer shape P, the pipe thickness T, the groove bottom width G (the bottom width of the groove), the groove angle α, and the rail outer shape R.
[0038]
FIG. 5 is referred to again. When the CPU 4 performs “welding condition generation” (step 3 in FIG. 4), the pass No. i is set to 1, the number of reductions n per pass is initialized to 0 (step 21), and the teaching data is read (step 22). Then, based on the path schedule generated in "Generation of welding conditions", the welding locus (circumferential start position Lsi, circumferential end position Lci) of each pass is set. The welding locus, that is, the driving range of the welding bogie 11 is determined by the pass No. If i is 1, the shift amount La is set to 0 (steps 23 to 26). Then, the circumferential start position Ls1 of the first pass is set to Ln (= 0) based on Ln (= 0) of the n-th teaching position Kn and the shift amount La1 (= 0). Next, similarly to the correction of the welding speed, the welding position (rs1, zs1) of the first pass, particularly the distance deviation due to the radial position rs1, and the lap distance D are corrected (step 28). For example, when the welding bogie 11 is turned at a certain speed, the torch tip (wire) is close to the bottom of the groove (backing material 15 (FIG. 6)). In a path where i is small, the moving distance of the tip of the torch is shorter than the moving distance of the welding bogie 11, which is a distance shift. In step 28, the lap distance Di of the i-th pass is rewritten to D × R / (P− (T−rsi) × 2) based on the rail attachment position. Here, D is the lap distance, R is the rail diameter, P is the radius, T is the pipe thickness, and rsi is the r position of the first pass. Then, the circumferential end position Lc1 is set to Ln-L1 + Di based on the welding length Ln-L1 of one pass and the lap distance Di. In the second pass, the CPU 4 sets the initial value L0 of the displacement amount for the displacement amount La (La2 for the second path) (steps 22, 23, 31), and the circumferential end position Lc1 of the first path. Is calculated by adding the shift amount La2 = L0, and the sum is defined as the circumferential start position Ls2. Next, the lap distance D2 and the lap distance D2 are rewritten to D × R / (P− (T−rs2) × 2), and the path is shifted to the circumferential start position Ls2 of the second pass. La2- (Ln-L1 + D) obtained by subtracting the sum of the welding length Ln-L1 and the lap distance D2 is defined as a circumferential end position Lc2.
[0039]
In the third pass, the CPU 4 increments the number of reductions n for each pass by 1 (steps 22, 23, 31) and shifts the shift amount.
La3 = L0-1 × ΔL0
Is calculated (step 32). Then, it is checked whether or not La3 is a negative value (the integrated value n × ΔL0 obtained by shifting the decrease amount by ΔL0 for each pass is equal to or more than the initial shift amount L0: it is necessary to shift L0 again). If it is a positive value (step 33), a difference (actually, if La3 is a negative value, a sum) is calculated by subtracting the calculated shift amount La3 from the end position Lc2 of the second pass which is the previous pass. Then, it is set as the circumferential start position Ls3 (step 26). Next, the lap distance D3 and the lap distance D3 are rewritten to D × R / (P− (T−rs3) × 2) by the distance deviation due to the radial position rs3 of the third pass, and 1 is set as the circumferential start position Ls3 of the third pass. The sum of the welding length Ln-L1 of the path and the lap distance D3 is calculated, and is set as the circumferential end position Lc3.
[0040]
In the fourth pass, the CPU 4 increments the number of reductions n for each pass by 1 (steps 22, 23, 31), and shifts the shift amount.
La4 = L0−2 × ΔL0
Is calculated (step 32). Then, it is checked whether La4 is a negative value (step 33). If it is a positive value, the sum of the calculated shift amounts La4 is added from the end position Lc3 of the third pass which is the previous pass (La4 is a negative value). If there is, the difference is actually calculated, and the calculated difference is set as the circumferential start position Ls4 (step 26). Next, the lap distance D4 and the lap distance D4 are rewritten to D × R / (P− (T−rs3) × 2) by the distance shift due to the radial position rs4 of the fourth pass, and the lap distance D4 is set to the circumferential start position Ls4 of the fourth pass. The sum of the welding length Ln-L1 of one pass and the lap distance D4 is calculated and defined as the circumferential end position Lc4.
[0041]
Hereinafter, the path schedule of the odd-numbered pass after the fifth pass is generated in the same manner as in the above-described third pass, and the pass schedule of the even-numbered pass after the sixth pass is generated in the same manner as the above-described fourth pass. I do.
[0042]
In the process, the calculated shift amount
Lai = L0−n × ΔL0
Is less than or equal to 0, it is checked whether n is an odd number (step 34). If it is an odd number, the shift movement amount Lai is set to the shift movement initial value L0 (step 30). If not, do this in the next odd pass.
[0043]
When the operator inputs the welding start, the CPU 4 displays the pass schedule generated in steps 3 and 4 of FIG. The register i is set to 1 (designating the first pass), and the welding of the i-th pass is performed as shown in FIGS. 7 and 8 based on the pass schedule of the i-th pass. The welding of the first pass starts from the circumferential start position Ls1 of the first pass with the torch position and posture set to (rs1, zs1, θs1), while the second pass welds at the end point Lc1 of the first pass. -Set the torch position and posture to (rs2, zs2, θs2) and drive the torch to the circumferential start position Ls2 of the second pass before starting. The third pass is started after the torch position and posture are set to (rs3, zrs3, θs3) at the end point Lc2 of the second pass, and the torch is driven to the circumferential start position Ls3 of the third pass. The same applies hereinafter. In any of the passes, the welding speed, direction, welding current, voltage and switching timing of the current and voltage are determined in accordance with the data of the pass schedule (steps 9 to 16 in FIG. 4).
[0044]
According to the embodiment described above, at the start of welding, (1) a welding arc is generated with a low initial current and voltage, and then higher and lower than the main current and voltage (2) with an intermediate current and voltage. (3) Welding with this current and voltage reduces the swelling of the initial bead due to the delay of the torch movement at the start, and the bead joint of each pass is reduced. Little swelling and no metal sagging.
[0045]
The weld bead junction (lap portion between the welding start and end of one pass) is lower than the main current (4) at a low current and voltage, and at a constant speed D lap at a constant speed lower than the main current and voltage range. Then, the welding is completed at the position under the crater welding conditions, so that no welding defect occurs at the associated portion.
[0046]
The weld bead joint is moved for each pass and repeated within a certain distance range. In other words, the initial value of the shift amount Lo is set, and when the shift amount is reduced by the decrease amount ΔLo for each pass and the shift amount La ≦ 0 is satisfied, La = Lo. If the number of reductions n = Lo ÷ ΔLo = even number, it continues once more. By repeating this, the meeting part repeatedly appears within a certain distance range. This makes it possible to keep the weld bead joint where a defect is particularly likely to occur within a certain distance range. 9 and 10 show the amount of shift of the welding start position between passes by a solid line. The horizontal axis is the circumferential position of the welding torch 12, and the zero point is the circumferential welding position (target position) at the start of the first pass welding. The unit of the numerical value is mm.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an external appearance of a mechanism according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an electric system configuration of the welding device shown in FIG.
FIG. 3 is a flowchart showing an operation procedure of an operator using the welding device shown in FIG.
FIG. 4 is a flowchart showing an outline of a process performed by CPU 4 shown in FIG. 2;
FIG. 5 is a flowchart showing a part of the contents of “generating welding locus” (4) shown in FIG. 4;
FIG. 6 is an enlarged longitudinal sectional view of a part of the

steel pipes

13 and 14 to be welded shown in FIG. 1 and shows a transverse section of a groove subjected to multi-layer welding.
7 is a graph showing a change in welding current and voltage and a change in welding speed during one-pass welding by the welding apparatus shown in FIG. 1, and a horizontal axis indicates a linear movement of the welding torch 12 in a circumferential direction. This is the distance of movement that has been deployed.
FIG. 8 is a plan view showing changes in welding current and voltage during one-pass welding by the welding apparatus shown in FIG. 1;
9 is a graph showing, by a solid line, an example of the amount of shift of the welding start position for each pass in the case of multi-layer welding by the welding apparatus shown in FIG. 1, and the horizontal axis indicates the circumferential movement of the welding torch 12. Is a moving distance obtained by linearly developing.
10 is a solid line graph showing another example of the shift amount of the welding start position shift for each pass in the case of multi-layer welding by the welding apparatus shown in FIG. 1, and the horizontal axis represents the welding torch 12; This is the movement distance obtained by linearly developing the circumferential movement.
11 is an enlarged vertical cross-sectional view of a part of the

steel pipes

13 and 14 to be welded shown in FIG. 1, showing a cross-section of a groove indicating a teaching position at a wire tip.
[Explanation of symbols]
10: Rail 11: Welding trolley
12: welding torch 13, 14: steel pipe
19: Elevating platform 20: Moving platform
21: Toll holder ML, Mz, Mr, Mθ: Electric motor
RL, Rz, Rr, Rθ: Rotary encoder

Claims

In the horizontal multi-layer welding of a steel pipe by an automatic welding robot using a welding torch that projects a welding wire to be fed from a tip to generate a welding arc between the wire tip and the steel pipe and welds the steel pipe,
At the start of welding, a welding arc is generated with a low initial current and voltage, then welding is performed with an intermediate current and voltage higher than the current and lower than the main current and voltage. There line path termination part is lower than the current end current-voltage, also by a predetermined distance wrap start end of the path at a slow constant rate than the current-voltage region, and terminates the welding of the path sideways multi-layer welding process of the steel pipe, characterized in that.

2. The method according to claim 1, wherein the joining portion between the start bead and the end bead of each pass is shifted in the circumferential direction within a set range for each pass.

The meeting unit is shifted in the direction of frequency division by the amount of decrease ΔLo for each path, and when the integrated value of the amount of shift for each path exceeds the initial value of the shift movement amount Lo, a shift of about the initial amount of shift movement Lo is performed. 3. The method of claim 2 , further comprising shifting the reduced amount ΔLo in the circumferential direction in each pass.

In the second pass, welding is performed by driving the welding head in the direction opposite to the first pass by shifting the associated portion in the direction of dividing the shift amount initial value Lo by the displacement amount relative to the associated portion of the first pass, and performing the third pass. The welding is performed by driving the welding head in the same direction as the first pass by shifting the joining portion in the direction of dividing by the shift amount initial value Lo-decrease amount ΔLo per pass with respect to the joining portion of the second pass, and performing the welding. In the 4th pass, welding is performed by driving the welding head in the direction opposite to the 1st pass by shifting the meeting portion in the direction of dividing by a shift amount initial value Lo-decrease amount per path ΔLo × 2 with respect to the joining portion of the 3rd pass. Is performed, and the shift portion La is shifted in the direction of dividing the shift amount La = Lo−ΔLo × n is equal to or less than 0 and n is an odd number in the direction of the shift amount initial value Lo, and the shift amount is sequentially shifted after the next pass. 3. The side of the steel pipe according to claim 2, wherein the initial value Lo is reduced by a reduction amount ΔLo for each pass. Multi-layer welding methods can.

Ring-shaped rail that goes around the steel pipe;
A welding bogie mounted on the rail and moving around the steel pipe along the rail;
Welding torch mounted on the welding trolley;
Traveling drive mechanism mounted on the welding trolley;
Driving means for driving the traveling drive mechanism forward and backward;
Welding current / voltage, lap distance D, initial displacement amount Lo, reduction amount per pass ΔLo, outer shape P, pipe thickness T, groove bottom width G, groove angle α, and rail outer diameter at the start and end of the steel pipe Input means for inputting R;
Means for switching to welding conditions corresponding to the position of the junction of each pass with respect to the steel pipe, the displacement La for each pass, and the displacement of the torch in the circumferential direction based on the input values;
A welding control means for controlling the running and welding conditions of the welding bogie according to the generated position of the joint portion of each pass, the displacement La for each pass and the welding conditions corresponding to the circumferential displacement of the torch. Horizontal multi-layer welding equipment.

6. The apparatus according to claim 5 , further comprising: means for storing the generated pass schedule.