JP3743609B2 - Seamless pipe rolling apparatus and rolling control method - Google Patents

Description

【００２５】
上記式（１）における関数ｆ₁の一例として、次式を選択した場合について、さらに詳細に説明する。
【数６】

【００２６】
本究明者らは、さらに鋭意試験研究を行った結果、前記式（２）のように、ΔＷＴ＿Ｓ／ＷＴ−ＳをΔＷＴ＿Ｍ／ＷＴ＿Ｍに対して線形に、ａ及びｂをρに対して線形に定式化した場合、定数ｃ及びｄの値は、それぞれ次の範囲内であること、
−０．０２≦ｃ（ｊ）≦０ ・・・（３）
０．９≦ｄ（ｊ）≦１．１ ・・・（４）
定数ｅ及びｆの値は、ミルの設置状況、管の寸法、材質などにより異なるが、
−０．００２≦ｅ（ｊ）≦０．００２ ・・・（５）
−０．０３≦ｆ（ｊ）≦０．０３ ・・・（６）
の範囲内であることを見出した。
【００２７】
従って、絞り圧延機上流側（マンドレルミル下流側）の肉厚測定結果に基づいて、マンドレルミル最終２スタンド若しくは３スタンドのロールギャップ又は絞り圧延機の圧下位置を調整する場合には、前記式（２）のΔＷＴ＿Ｓを０にすることを目標として調整すればよく、このとき、ΔＷＴ＿Ｍの目標値は、式（２）においてΔＷＴ＿Ｓ＝０とすることにより、−ｂ／ａ×ＷＴ＿Ｍとなる。よって、以下の式に従って、マンドレルミル最終２スタンド若しくは３スタンドのロールギャップ又は絞り圧延機の圧下位置を調整すればよい。
【数７】

【００２８】
また、絞り圧延機下流側の肉厚測定結果に基づいて、マンドレルミル最終２スタンド若しくは３スタンドのロールギャップ又は絞り圧延機の圧下位置を調整する場合にも、式（２）のΔＷＴ＿Ｓを０にすることを目標として調整すればよく、以下の式に従えばよい。
【数８】

【００２９】
以上では、ΔＷＴ＿Ｓ／ＷＴ−ＳをΔＷＴ＿Ｍ／ＷＴ＿Ｍに対して線形に、ａ及びｂをρに対して線形に定式化した場合について詳細に説明したが、もちろん他の一般的な関数を選んでもよく、さらに、関数の値は管材質にも影響を受けることを考慮すれば、前記肉厚測定結果に基づく圧下位置調整法は、次のように表すことができる。
【００３０】
（１）絞り圧延機上流側（マンドレルミル下流側）の肉厚測定結果に基づいて、マンドレルミル最終２スタンド若しくは３スタンドのロールギャップ又は絞り圧延機の圧下位置を調整する場合
【数９】

ここで、前述した式（７）のようなケースでｂ（ｊ）≒０とみなせることを考慮すれば、上記式（９）は、近似的に以下の式で表すことができる。
【数１０】

【００３１】
（２）絞り圧延機下流側の肉厚測定結果に基づいて、マンドレルミル最終２スタンド若しくは３スタンドのロールギャップ又は絞り圧延機の圧下位置を調整する場合
【数１１】

ここで、前述した式（８）のようなケースで、ＷＴ＿Ｓ≒ＷＴ＿Ｍとなる場合が多いことを考慮すれば、上記式（１１）は、近似的に以下の式で表すことができる。
【数１２】

【００３２】
本発明は、本発明者らが見出した前述の新しい知見に基づき案出されたものであり、絞り圧延機の出側において偏肉の小さい管を製造し得る、継ぎ目無し管の圧延装置および圧延制御方法を提供するものである。
【００３５】
本願の第１発明は、複数の孔型ロールスタンドを具備し、該孔型ロールスタンドが形成するロール孔型配列内にマンドレルバーが配置され、管を圧延するリトラクト方式のマンドレルミルと、該マンドレルミルの下流側に直列配置され、前記マンドレルバーから前記管を引き抜くエキストラクタ又は前記管の外径を調整する圧延機と、前記エキストラクタ又は前記圧延機の下流側に配置され、前記マンドレルミルの圧下方向の前記管の肉厚を測定する、又は前記管の周方向５箇所以上の前記管の肉厚を測定して前記マンドレルミルの圧下方向の前記管の肉厚を推定する熱間肉厚測定装置とを備えることを特徴とする継ぎ目無し管の圧延装置である。
【００３６】
本願の第２発明は、複数の孔型ロールスタンドを具備し、該孔型ロールスタンドが形成するロール孔型配列内にマンドレルバーが配置され、管を圧延するリトラクト方式のマンドレルミルと、該マンドレルミルの下流側に直列配置され、前記マンドレルバーから前記管を引き抜くエキストラクタ又は前記管の外径を調整する圧延機と、前記マンドレルミルと、前記エキストラクタ又は前記圧延機との間に配置され、前記管の周方向５箇所以上の前記管の肉厚を測定して前記マンドレルミルの圧下方向の前記管の肉厚を推定する熱間肉厚測定装置とを備えることを特徴とする継ぎ目無し管の圧延装置である。
【００３７】
本願の第３発明は、複数の孔型ロールスタンドを具備し、内面工具を用いずに管の外径を調整する圧延機と、該圧延機の下流側に配置され、該圧延機の圧下方向の前記管の肉厚を測定する、又は前記管の周方向５箇所以上の前記管の肉厚を測定して前記圧延機の圧下方向の前記管の肉厚を推定する熱間肉厚測定装置と、前記熱間肉厚測定装置で測定した前記圧延機の圧下方向の前記管の肉厚、又は前記熱間肉厚測定装置で測定した前記管の周方向５箇所以上の前記管の肉厚によって推定した前記圧延機の圧下方向の前記管の肉厚に基づき、前記圧延機の圧下位置を調整する圧延制御装置を備えることを特徴とする継ぎ目無し管の圧延装置である。
【００３８】
本願の第４発明は、複数の孔型ロールスタンドを具備し、内面工具を用いずに管の外径を調整する圧延機と、該圧延機の上流側に配置され、該圧延機の圧下方向の前記管の肉厚を測定する、又は前記管の周方向５箇所以上の前記管の肉厚を測定して前記圧延機の圧下方向の前記管の肉厚を推定する熱間肉厚測定装置と、前記熱間肉厚測定装置で測定した前記圧延機の圧下方向の前記管の肉厚、又は前記熱間肉厚測定装置で測定した前記管の周方向５箇所以上の前記管の肉厚によって推定した前記圧延機の圧下方向の前記管の肉厚に基づき、前記圧延機の圧下位置を調整する圧延制御装置を備えることを特徴とする継ぎ目無し管の圧延装置である。
【００３９】
本願の第５発明は、前記第１発明において、前記熱間肉厚測定装置で測定した前記マンドレルミルの圧下方向の前記管の肉厚、又は前記熱間肉厚測定装置で測定した前記管の周方向５箇所以上の前記管の肉厚によって推定した前記マンドレルミルの圧下方向の前記管の肉厚に基づき、前記マンドレルミルのロールギャップを調整する圧延制御装置を備えることを特徴とする継ぎ目無し管の圧延装置である。
【００４０】
本願の第６発明は、前記第２発明において、前記熱間肉厚測定装置で測定した前記管の周方向５箇所以上の前記管の肉厚によって推定した前記マンドレルミルの圧下方向の前記管の肉厚に基づき、前記マンドレルミルのロールギャップを調整する圧延制御装置を備えることを特徴とする継ぎ目無し管の圧延装置である。
【００４１】
本願の第７発明は、複数の孔型ロールスタンドを具備し、内面工具を用いずに管の外径を調整する圧延機と、該圧延機の下流側に配置され、該圧延機の圧下方向の前記管の肉厚を測定する、又は前記管の周方向５箇所以上の前記管の肉厚を測定して前記圧延機の圧下方向の前記管の肉厚を推定する熱間肉厚測定装置とを備える継ぎ目無し管の圧延装置において、前記熱間肉厚測定装置で測定した前記圧延機の圧下方向の前記管の肉厚、又は前記熱間肉厚測定装置で測定した前記管の周方向５箇所以上の前記管の肉厚によって推定した前記圧延機の圧下方向の前記管の肉厚に基づき、前記圧延機の圧下位置を調整することを特徴とする継ぎ目無し管の圧延制御方法である。
【００４２】
本願の第８発明は、複数の孔型ロールスタンドを具備し、内面工具を用いずに管の外径を調整する圧延機と、該圧延機の上流側に配置され、該圧延機の圧下方向の前記管の肉厚を測定する、又は前記管の周方向５箇所以上の前記管の肉厚を測定して前記圧延機の圧下方向の前記管の肉厚を推定する熱間肉厚測定装置とを備える継ぎ目無し管の圧延装置において、前記熱間肉厚測定装置で測定した前記圧延機の圧下方向の前記管の肉厚、又は前記熱間肉厚測定装置で測定した前記管の周方向５箇所以上の前記管の肉厚によって推定した前記圧延機の圧下方向の前記管の肉厚に基づき、前記圧延機の圧下位置を調整することを特徴とする継ぎ目無し管の圧延制御方法である。
【００４３】
本願の第９発明は、前記第１発明に係る圧延装置において、前記熱間肉厚測定装置で測定した前記マンドレルミルの圧下方向の前記管の肉厚、又は前記熱間肉厚測定装置で測定した前記管の周方向５箇所以上の前記管の肉厚によって推定した前記マンドレルミルの圧下方向の前記管の肉厚に基づき、前記マンドレルミルのロールギャップを調整することを特徴とする継ぎ目無し管の圧延制御方法である。
【００４４】
本願の第１０発明は、前記第２発明に係る圧延装置において、前記熱間肉厚測定装置で測定した前記管の周方向５箇所以上の前記管の肉厚によって推定した前記マンドレルミルの圧下方向の前記管の肉厚に基づき、前記マンドレルミルのロールギャップを調整することを特徴とする継ぎ目無し管の圧延制御方法である。
【００４５】
本願の第１１発明は、前記第３発明又は第５発明において、前記圧延制御装置が、前記圧延機の圧下位置又は前記マンドレルミルの仕上スタンドのロールギャップを次式に基づいて調整することを特徴とする継ぎ目無し管の圧延装置である。
【数１３】

なお、前記「仕上スタンド」の語は、マンドレルミルの各スタンドのうち、管材の各部位を圧延する最終のスタンド、つまり、当該スタンドの孔型の溝底部で圧延された管材の部位が、それ以降のマンドレルミルのどのスタンドでも圧延されない場合を意味するものとして使用する。特許請求の範囲及び以下の記載において、全て同様である。
【００４６】
本願の第１２発明は、前記第４発明又は第６発明において、前記圧延制御装置が、前記圧延機の圧下位置又は前記マンドレルミルの仕上スタンドのロールギャップを次式に基づいて調整することを特徴とする継ぎ目無し管の圧延装置である。
【数１４】

【００４７】
本願の第１３発明は、前記第７発明又は第９発明において、前記圧延機の圧下位置又は前記マンドレルミルのロールギャップを次式に基づいて調整することを特徴とする継ぎ目無し管の圧延制御方法である。
【数１５】

【００４８】
本願の第１４発明は、前記第８発明又は第１０発明において、前記圧延機の圧下位置又は前記マンドレルミルのロールギャップを次式に基づいて調整することを特徴とする継ぎ目無し管の圧延制御方法である。
【数１６】

【００４９】
【発明の実施の形態】
以下、本発明の実施の形態について、添付図面を参照して説明する。
図１は、前述した本願の第３発明、第７発明、第１１発明及び第１３発明の一実施形態を示す構成図である。
【００５０】
図１において、１１は複数個のスタンド＃１，…，＃Ｎからなる３ロールの絞り圧延機、１２はマンドレルミルで圧延された母管、１３は絞り圧延機１１の圧延ロールをそれぞれ示す。３ロールの絞り圧延機１１の各スタンドにおけるロールは、３個の孔型口一ル１３が１２０°間隔で組み込まれたものである。さらに、絞り圧延機１１の上流側からみて、例えば、奇数スタンドは図７（ａ）のように、偶数スタンドは図７（ｂ）のように、隣接するスタンドでロールの圧下方向が６０°交差するように配置されている。母管１２は、絞り圧延機１１のスタンド＃１から順に、圧延ロール１３によって外径が絞り加工され、所定の管外径に仕上げられる。
【００５１】
また、図１において、１４は絞り圧延機１１の下流側に設置された熱間肉厚測定装置、１５は演算装置、１６は絞り圧延機１１の各ロール圧下装置をそれぞれ示す。演算装置１５及びロール圧下装置１６によって圧延制御装置が構成されている。演算装置１５は、管肉厚、材質、絞り圧延機１１における外径加工率、及び熱間肉厚測定装置１４により測定された絞り圧延機１１の圧下方向の肉厚から、予め与えられた式に基づいて絞り圧延機１１の＃１、＃２スタンドにおける適切な母管偏肉量を計算する。さらに、前記適切な母管偏肉量を与えるために必要な絞り圧延機１１の♯１、＃２スタンドの圧下位置の変更量を算出する。
【００５２】
絞り圧延機１１の下流側に設置された熱間肉厚測定装置１４は、絞り圧延機１１の奇数スタンド圧下方向（３方向）及び偶数スタンド圧下方向（３方向）の合計６方向の管肉厚を測定する。図９に示すように、熱間肉厚測定装置１４は、絞り圧延機１１の圧下方向に沿って、γ線発光器９１とγ線受光器９２とが対向配置された構成であり、斯かる構成により管肉厚を測定するものである。
【００５３】
演算装置１５に組み込まれている絞り圧延機１１の♯１、＃２スタンドにおける適切な母管偏肉量を計算する式と、前記適切な母管偏肉量を与えるために必要な＃１、♯２スタンドの圧下位置の変更量を求める式とは、例えば以下のような試験によって定式化することができる。
【００５４】
図５に示すマンドレルミル５６において、まず通常の製造方法により、中空素管５４を圧延する。このとき、マンドレルミル圧延中に、マンドレルミル５６の下流側で管５４の上部管端部の外表面に人工疵を付し、管５４のどの方向をマンドレルミル５６で圧下したかが識別できるようにしておく。次に、マンドレルミル５６で圧延した母管を、図１の絞り圧延機１１で絞り加工し、絞り加工された管について、マンドレルミル最終２スタンドの圧下方向に対応する肉厚Ｔ１、Ｔ１’、Ｔ２及びＴ２’（図１０（ａ））を計測する。ここで肉厚計測された管を以降管Ａという。
【００５５】
次に、前記管Ａを圧延したときに使用した中空素管と同一の寸法、材質からなる中空素管５４を、マンドレルミル５６において、前記管Ａを圧延したときと同一のマンドレルバー５５を用い、次の点を除いて前記管Ａを圧延したときと同一の条件で圧延する。すなわち、前記管Ａを圧延したときと条件が異なるのは、マンドレルミル５６のスタンド数をＮとしたときに、＃Ｎ−１スタンドでは、圧延ロール５８とマンドレルバー５５との間隙が０．５ｍｍ大きくなるように、逆に♯Ｎスタンドでは、圧延ロール５８とマンドレルバー５５の間隙が０．５ｍｍ小さくなるように、最終２スタンドのロール圧下位置を調整する点である。なお、前記管Ａを圧延したときと同様に、マンドレルミル圧延中に、マンドレルミル５６の下流側で管５４の上部管端部の外表面に人工疵を付し、管５４のどの方向をマンドレルミル５６で圧下したかを識別し得るようにしておく。次に、マンドレルミル５６で圧延した母管を、絞り圧延機１１で絞り加工し、絞り加工された管について、マンドレルミル最終２スタンドの圧下方向に対応する肉厚Ｔ３、Ｔ３’、Ｔ４及びＴ４’（図１０（ｂ））を計測する。
【００５６】
以上の試験により、絞り圧延機１１で発生する偏肉量と、絞り圧延機１１の前で付与された１．Ｏｍｍの偏肉量が絞り圧延機１１の出側でどの程度減少するかを以下の式で知ることができる。
【数１７】

【００５７】
さらに、絞り圧延機１１での外径加工率を変えて同様の実験をすることにより、絞り圧延機１１の前で付与された１．Ｏｍｍの偏肉量の絞り圧延機１１の出側での減少量（式(17)のａ）及び絞り圧延機１１の出側の偏肉量（式(17)のｂ）を、外径加工量の関数で求めることができる。また、管の肉厚、材質毎に絞り加工された管の絞り圧延機１１圧下方向の肉厚を測定することにより、管の肉厚、材質毎の偏肉量を求めることができる。このようにして得られた以下の式（１８）が、絞り圧延機１１の♯１、♯２スタンドにおける適切な母管偏肉量を計算する式として、予め演算装置１５に組み込まれている。
【数１８】

【００５８】
なお、ΔＷＴ＿Ｓ／ＷＴ＿ＳはΔＷＴ＿Ｍ／ＷＴ＿Ｍの関数であり、ａ及びｂはρの関数であるが、式(18)では簡易的に、ΔＷＴ＿Ｓ／ＷＴ＿ＳをΔＷＴ＿Ｍ／ＷＴ＿Ｍに対して線形とし、ａ及びｂをρに対して線形とした。本発明はこれに限るものではなく、前記試験結果に基づき、例えば、以下の式(19)のような、より厳密な式を演算装置１５に組み込んでもよい。
【数１９】

【００５９】
さらに、絞り圧延機１１の＃１スタンドの圧下位置を変更して圧延する試験により、＃１スタンドの圧下位置を１ｍｍ変更したときの絞り圧延後の偏肉量ΔＷＴ＿Ｓの変化量δ（＃１）を測定し、＃２スタンド以降の絞り圧延機１１での外径圧下率ρを用いて式(18)を逆算すれば、＃１スタンドの圧下位置を１ｍｍ変更した場合の絞り圧延機１１の＃１スタンドでの偏肉量変化量ｐ＿Ｓ（♯１）を次式のように求めることができる。
【数２０】

【００６０】
＃２スタンドについても同様に、絞り圧延機１１の＃２スタンドの圧下位置を変更して圧延する試験により、＃２スタンドの圧下位置を１ｍｍ変更したときの絞り圧延後の偏肉量ΔＷＴ＿Ｓの変化量δ（＃２）を測定し、＃３スタンド以降の絞り圧延機１１での外径圧下率ρを用いて式(18)を逆算すれば、＃２スタンドの圧下位置を１ｍｍ変更した場合の絞り圧延機１１の♯２スタンドでの偏肉量変化量ｐ＿Ｓ（＃２）を次式のように求めることができる。
【数２１】

【００６１】
絞り圧延機１１の＃１、＃２スタンドにおける適切な母管偏肉量を与えるために必要な＃１、＃２スタンドの圧下位置の変更量を求めるため、例えば上記試験で得られた式(20)及び式(21)が予め演算装置１５に組み込まれている。
【００６２】
演算装置１５は、熱間肉厚測定装置１４で測定した絞り圧延機１１の♯１、＃２スタンドの圧下方向（６方向）それぞれの偏肉量ΔＷＴ＿Ｓから、式(18)に基づき＃１、＃２スタンドで与えるべきそれぞれの偏肉量ΔＷＴ＿Ｍを計算する。さらに、前記偏肉量ΔＷＴ＿Ｍを得るために必要な＃１、＃２スタンドの圧下位置の変更量を式(20)及び式(21)に基づき計算し、計算された＃１、＃２スタンドの圧下位置の変更量を絞り圧延機１１の各ロール圧下装置１６に指令し、圧下位置が調整される。
【００６３】
以上に説明した構成を整理すると、以下の式(22)となる。
【数２２】

【００６４】
上記のように構成されたことによって、絞り圧延機１１で絞り加工された管１２の周方向の肉厚分布に発生した偏肉は、管１２の円周６方向に設置されたγ線発光器９１とγ線受光器９２とからなる熱間肉厚測定装置１４によって測定され、演算装置１５に出力される。演算装置１５は、熱間肉厚測定装置１４から入力される所定圧下位置時の溝底部の肉厚と６方向の肉厚の平均値との差として得られる偏肉量ΔＷＴ＿Ｓが０となる♯１、＃２スタンドでの偏肉量ΔＷＴ＿Ｍを式(18)に基づき演算する。さらに、前記偏肉量ΔＷＴ＿Ｍを得るために必要な、＃１、♯２スタンドの圧下位置の変更量を式(20)及び式(21)に基づき演算し、算出された圧下位置の変更量を＃１、＃２スタンドの各ロール圧下装置１６に指令し、圧下位置を調整する。よって、圧下位置を調整した後に圧延した管材の、絞り圧延機１１の＃１、＃２スタンドの各ロール圧下方向の肉厚分布は均一化され、管１２の周方向における偏肉を抑制することができる。
【００６５】
次に、本願の第４発明、第８発明、第１２発明及び第１４発明の一実施の形態を図２を参照して説明する。
【００６６】
図２において、２１は複数個のスタンド＃１，…，＃Ｎからなる３ロールの絞り圧延機、２２はマンドレルミルで圧延された母管、２３は絞り圧延機２１の圧延ロールをそれぞれ示す。３ロールの絞り圧延機２１の各スタンドにおけるロールは、３個の孔型ロール２３が１２０°間隔で組み込まれたものである。さらに、絞り圧延機２１の上流側からみて、例えば、奇数スタンドは図７（ａ）のように、偶数スタンドは図７（ｂ）のように、隣接するスタンドでロールの圧下方向が６０°交差するように配置されている。母管２２は、絞り圧延機２１のスタンド＃１から順に、圧延ロール２３によって外径が絞り加工され、所定の管外径に仕上げられる。
【００６７】
また、図２において、２４は絞り圧延機２１の上流側に設置された熱間肉厚測定装置、２５は演算装置、２６は絞り圧延機２１の各ロール圧下装置をそれぞれ示す。演算装置２５及びロール圧下装置２６によって圧延制御装置が構成されている。演算装置２５は、管肉厚、材質、絞り圧延機２１における外径加工率、及び熱間肉厚測定装置２４により測定された絞り圧延機２１の圧下方向の肉厚から、予め与えられた式(18)に基づいて絞り圧延機２１の＃１、♯２スタンドにおける適切な母管偏肉量を計算する。さらに、前記適切な母管偏肉量を与えるために必要な＃１、＃２スタンドの圧下位置の変更量を式(20)及び式(21)に基づいて算出する。
【００６８】
絞り圧延機２１の下流側に設置された熱間肉厚測定装置２４は、絞り圧延機２１の奇数スタンド圧下方向（３方向）及び偶数スタンド圧下方向（３方向）の合計６方向の管肉厚を測定する。図９に示すように、熱間肉厚測定装置１４は、絞り圧延機２１の圧下方向に沿って、γ線発光器９１とγ線受光器９２とが対向配置された構成であり、斯かる構成により管肉厚を測定するものである。
【００６９】
演算装置２５には、式(18)、式(20)及び式(21)が予め組み込まれている。演算装置２５では、式(18)に基づき、絞り圧延機２１の＃１、＃２スタンドで与えるべきそれぞれの偏肉量ΔＷＴ＿Ｍが計算される。図２の熱間肉厚測定装置２４で測定した絞り圧延機２１の♯１、＃２スタンドの圧下方向（６方向）それぞれの偏肉量ΔＷＴ＿Ｍ’が前記偏肉量ΔＷＴ＿Ｍと異なる場合には、＃１、＃２スタンドの圧下方向（６方向）それぞれの偏肉量ΔＷＴ＿Ｍ’を前記偏肉量ΔＷＴ＿Ｍに等しくするために必要な♯１、＃２スタンドの圧下位置の変更量を式(20)及び式(21)に基づき計算する。さらに、前記計算された＃１、＃２スタンドの圧下位置の変更量を絞り圧延機２１の各ロール圧下装置２６に指令し、圧下位置を調整する。
【００７０】
以上に説明した構成を整理すると、以下の式（２３）となる。
【数２３】

【００７１】
上記のように構成されたことによって、絞り圧延機２１に供給された母管２２の周方向の肉厚分布に発生した偏肉は、母管２２の円周６方向に設置されたγ線発光器９１とγ線受光器９２とからなる熱間肉厚測定装置２４によって測定され、演算装置２５に出力される。演算装置２５は、式(18)に基づき、絞り圧延機２１の出側の絞り圧延機２１の圧下方向（６方向）の偏肉量が０となる絞り圧延機＃１、♯２スタンドでの偏肉量ΔＷＴ＿Ｍを演算する。さらに、熱間肉厚測定装置２４から入力される絞り圧延機２１の＃１、＃２スタンドの圧下方向（６方向）それぞれの偏肉量ΔＷＴ＿Ｍ’と前記＃１，＃２スタンドでの必要な偏肉量ΔＷＴ＿Ｍとの差から、絞り圧延機２１の出側の絞り圧延機２１の圧下方向（６方向）の偏肉量を０とするために必要な＃１、＃２スタンドの圧下位置の変更量を式(20)及び式(21)に基づき演算し、算出された圧下位置の変更量を＃１、＃２スタンドの各口一ル圧下装置２６に指令し、圧下位置を調整する。よって、絞り圧延機２１の＃１、＃２スタンドの各ロール圧下方向の肉厚分布は均一化され、管２２の周方向における偏肉を抑制することができる。
【００７２】
次に、本願の第１発明、第５発明、第９発明、第１１発明及び第１３発明の一実施の形態を図３を参照して説明する。
【００７３】
図３において、３１は複数個のスタンド＃１，…，＃Ｎからなるマンドレルミル、３２はピアサーで穿孔された中空素管（素管）、３３はマンドレルバー、３４はマンドレルミル３１の圧延ロール、３５は複数個のスタンド＃１，・・・，＃Ｎからなる３ロールのエキストラクタ又は絞り圧延機である。ピアサーで穿孔された素管３２は、内部にマンドレルバー３３が挿入され、マンドレルバー３３の後端が保持装置（図示せず）により一定速度に保持された状態で、マンドレルミル３１においてマンドレルバー３３と複数の孔型圧延ロール３４とにより延伸圧延される。マンドレルミル３１での圧延が完了した後、マンドレルバー３３が停止し、母管３２は、エキストラクタ又は絞り圧延機３５によってマンドレルバー３３から引き抜かれる。３ロールのエキストラクタ又は絞り圧延機３５の各スタンドにおけるロールは、３個の孔型ロール３６が１２０°間隔で組み込まれたものである。さらに、エキストラクタ又は絞り圧延機３５の上流側からみて、例えば、奇数スタンドは図７（ａ）のように、偶数スタンドは図７（ｂ）のように、隣接するスタンドでロールの圧下方向が６０°交差するように配置されている。マンドレルミル３１で圧延され、マンドレルバー３３から引き抜かれた母管３２は、エキストラクタ又は絞り圧延機３５のスタンド＃１から順に、圧延ロール３６によって外径が絞り加工され、所定の管外径に仕上げられる。
【００７４】
また、図３において、３７はエキストラクタ又は絞り圧延機３５の下流側に設置された熱間肉厚測定装置、３８は演算装置、３９はマンドレルミル３１の仕上げスタンドの各ロール圧下装置をそれぞれ示す。演算装置３８及びロール圧下装置３９によって圧延制御装置が構成されている。演算装置３８は、管肉厚、材質、エキストラクタ又は絞り圧延機３５における外径加工率、及び熱間肉厚測定装置３７により測定されたマンドレルミル３１の圧下方向の肉厚から、予め与えられた式(18)に基づいてマンドレルミル３１出側における母管３２の適切な偏肉量を計算する。さらに、前記適切な母管偏肉量を与えるために必要なマンドレルミル３１仕上げスタンドの圧下位置の変更量を求める。
【００７５】
エキストラクタ又は絞り圧延機３５の下流側に設置された熱間肉厚測定装置３７は、マンドレルミル３１の仕上げ２又は３スタンドの圧下方向の管肉厚を測定する。図９に示すように、熱間肉厚測定装置３７は、マンドレルミル３１仕上げスタンドの圧下方向に沿って、γ線発光器９１とγ線受光器９２とが対向配置された構成であり、斯かる構成により管肉厚を測定するものである。
【００７６】
演算装置３８には、式(18)が予め組み込まれている。図３の熱間肉厚測定装置３７で測定したマンドレルミル３１仕上げ２又は３スタンドの圧下方向それぞれの偏肉量ΔＷＴ＿Ｓから、演算装置３８において、式(18)に基づきマンドレルミル３１出側で与えるべきそれぞれの方向の偏肉量ΔＷＴ＿Ｍが計算される。さらに、演算装置３８は、前記偏肉量ΔＷＴ＿Ｍを得るために必要な仕上げ２又は３スタンドの圧下位置の変更量を計算し、該計算された圧下位置の変更量をマンドレルミル３１仕上げスタンドの各ロール圧下装置３９に指令し、圧下位置を調整する。
【００７７】
以上に説明した構成を整理すると、以下の式(24)となる。
【数２４】

【００７８】
上記のように構成されたことによって、エキストラクタ又は絞り圧延機３５で絞り加工された管３２の周方向の肉厚分布に発生した偏肉は、管３２の円周方向に設置されたγ線発光器９１とγ線受光器９２とからなる熱間肉厚測定装置３７によって測定され、演算装置３８に出力される。演算装置３８は、熱間肉厚測定装置３７から入力される所定圧下位置時のマンドレルミル３１溝底方向の肉厚と円周方向の肉厚の平均値との差として得られる偏肉量ΔＷＴ＿Ｓが０となるマンドレルミル３１出側での偏肉量ΔＷＴ＿Ｍを式(18)に基づき演算する。さらに、前記偏肉量ΔＷＴ＿Ｍを得るために必要なマンドレルミル３１の仕上げ２又は３スタンドの圧下位置の変更量を演算し、算出された圧下位置の変更量を仕上げ２又は３スタンドの各ロール圧下装置３９に指令し、圧下位置を調整する。よって、圧下位置を調整した後に圧延した管材において、マンドレルミル３１の仕上げ２又は３スタンドの各ロール圧下方向の肉厚分布は均一化され、管３２の周方向における偏肉を抑制することができる。
【００７９】
次に、本願の第２発明、第６発明、第１０発明、第１２発明及び第１４発明の一実施の形態を図４を参照して説明する。
【００８０】
図４において、４１は複数個のスタンド＃１，…，＃Ｎからなるマンドレルミル、４２はピアサーで穿孔された中空素管（素管）、４３はマンドレルバー、４４はマンドレルミル４１の圧延ロール、４５は複数個のスタンド＃１，…，＃Ｎからなる３ロールのエキストラクタ又は絞り圧延機である。ピアサーで穿孔された素管４２は、内部にマンドレルバー４３が挿入され、マンドレルバー４３の後端が保持装置（図示せず）により一定速度に保持された状態で、マンドレルミル４１においてマンドレルバー４３と複数の孔型圧延ロール４４とにより延伸圧延される。マンドレルミル４１での圧延が完了した後、マンドレルバー４３が停止し、母管４２は、エキストラクタ又は絞り圧延機４５によってマンドレルバー４３から引き抜かれる。３ロールのエキストラクタ又は絞り圧延機４５の各スタンドにおけるロールは、３個の孔型ロール４６が１２０°間隔で組み込まれたものである。さらに、エキストラクタ又は絞り圧延機４５の上流側からみて、例えば、奇数スタンドは図７（ａ）のように、偶数スタンドは図７（ｂ）のように、隣接するスタンドでロールの圧下方向が６０°交差するように配置されている。マンドレルミル４１で圧延され、マンドレルバー４３から引き抜かれた母管４２は、エキストラクタ又は絞り圧延機４５のスタンド＃１から順に、圧延ロール４６により外径が絞り加工され、所定の管外径に仕上げられる。
【００８１】
また、図４において、４７はマンドレルミル４１とエキストラクタ又は絞り圧延機４５との問に設置された熱間肉厚測定装置、４８は演算装置、４９はマンドレルミル４１の仕上げスタンドの各ロール圧下装置をそれぞれ示す。演算装置４８及びロール圧下装置４９によって圧延制御装置が構成されている。演算装置４８は、管肉厚、材質、エキストラクタ又は絞り圧延機４５における外径加工率、及び熱間肉厚測定装置４７により測定されたマンドレルミル４１の圧下方向の肉厚から、予め与えられた式(18)に基づいてマンドレルミル４１出側における適切な母管４２の偏肉量を計算する。さらに、前記適切な母管偏肉量を与えるために必要なマンドレルミル４１仕上げスタンドの圧下位置の変更量を求める。
【００８２】
マンドレルミル４１とエキストラクタ又は絞り圧延機４５との間に設置された熱間肉厚測定装置４７は、マンドレルミル４１の仕上げ２又は３スタンドの圧下方向の管肉厚を測定する。図９に示すように、熱間肉厚測定装置４７は、マンドレルミル４１仕上げスタンドの圧下方向に沿って、γ線発光器９１とγ線受光器９２とが対向配置された構成であり、斯かる構成により管肉厚を測定するものである。
【００８３】
演算装置４８には、式(18)が予め組み込まれている。演算装置４８は、式(18)に基づきマンドレルミル４１仕上げスタンドで与えるべきそれぞれの偏肉量ΔＷＴ＿Ｍを計算し、熱間肉厚測定装置４７で測定したマンドレルミル４１仕上げ２又は３スタンドの圧下方向それぞれの偏肉量ΔＷＴ＿Ｍ’が、前記偏肉量ΔＷＴ＿Ｍと異なる場合には、仕上げ２又は３スタンドの圧下方向それぞれの偏肉量ΔＷＴ＿Ｍ’を前記偏肉量ΔＷＴ＿Ｍに等しくするために必要なマンドレルミル４１仕上げスタンドの圧下位置の変更量を計算する。さらに、計算された圧下位置の変更量をマンドレルミル４１仕上げスタンドの各ロール圧下装置４９に指令し、圧下位置を調整する。
【００８４】
以上に説明した構成を整理すると、以下の式(25)となる。
【数２５】

【００８５】
上記のように構成されたことによって、エキストラクタ又は絞り圧延機４５に供給された母管４２の周方向の肉厚分布に発生した偏肉は、母管４２の円周方向に設置されたγ線発光器９１とγ線受光器９２とからなる熱間肉厚測定装置４７によって測定され、演算装置４８に出力される。演算装置４８は、式(18)に基づき、エキストラクタ又は絞り圧延機４５の出側のマンドレルミル４１仕上げ２又は３スタンドの圧下方向の偏肉量が０となるマンドレルミル４１出側での偏肉量ΔＷＴ＿Ｍを演算する。さらに、熱間肉厚測定装置４７から入力されるマンドレルミル４１仕上げ２又は３スタンドの圧下方向それぞれの偏肉量ΔＷＴ＿Ｍ’と前記マンドレルミル４１出側での必要な偏肉量ΔＷＴ＿Ｍとの差から、エキストラクタ又は絞り圧延機４５の出側のマンドレルミル４１仕上げ２又は３スタンドの圧下方向の偏肉量を０とするために必要なマンドレルミル４１仕上げ２又は３スタンドの圧下位置の変更量を演算する。算出された圧下位置の変更量をマンドレルミル４１の仕上２又は３スタンドの各ロール圧下装置２６に指令し、圧下位置を調整する。よって、圧下位置を調整した後に圧延した管材において、マンドレルミル４１の仕上げ２又は３スタンドの各ロール圧下方向の肉厚分布は均一化され、管４２の周方向における偏肉を抑制することができる。
【００８６】
なお、本願の第１〜第１４発明において、熱間肉厚測定装置の測定方向は、測定方向が十分多い（５方向以上）場合には、マンドレルミル又は絞り圧延機の圧下方向に合致していなくてもよい。つまり、補間やフーリエ変換等を利用することにより、マンドレルミル又は絞り圧延機の圧下方向の肉厚を推定し、該推定値を使用することも可能である。
【００８７】
例えば、熱間肉厚測定装置の測定方向が、図１１における０°、４０°、８０°、１２０°、１６０°、２００°、２４０°、２８０°及び３２０°の９方向であり、マンドレルミル又は絞り圧延機の圧下方向の１つが図１１の４５°の場合、斯かる４５°方向の肉厚は、次の式で推測できる。
45°方向の肉厚＝（40°方向の肉厚×35＋80°方向の肉厚×5）／40・・・(26)
【００８８】
ここで、補間又はフーリエ変換により圧下方向の肉厚を推定する際に、５方向以上の肉厚を測定する必要があるのは、以下の理由による。すなわち、サンプリング定理によると、フーリエ変換を用いてｎ次の偏肉量（周方向肉厚分布のうち、管断面を一周するときに、一定周期で肉厚がｎ回の最大値をもつ肉厚分布成分）を抽出するには、周方向２ｎ＋１箇所の肉厚の値が必要となる。ここで、マンドレルミルの圧下量変更により制御できる偏肉量の次数は、２ロールの場合には２次であり、２×２＋１＝５方向の肉厚があれば、マンドレルミル圧下方向の肉厚を推定することができる。つまり、補間又はフーリエ変換により２ロールマンドレルミルの圧下方向の肉厚を推定するには、５方向以上の肉厚を測定すればよいことになる。
【００８９】
また、説明を簡単にするために、本願の第３、第４、第７、第８、第１１〜第１４発明に対応する上記実施形態においては、絞り圧延機の圧下位置調整スタンドを＃１、♯２に限定したが、本発明はこれに限るものではなく、＃１、＃２以外の外径加工を行うスタンドで圧下位置を調整してもよいし、＃１、＃２と＃１、＃２以外のスタンドとの両方の圧下位置を調整してもよい。絞り圧延機の複数のスタンドで圧下位置を調整する場合は、以下の式(27)又は式(28)のように、各スタンドで付与する偏肉量の和が修正すべき偏肉量となるようにすればよい。
【数２６】

【００９０】
また、本願の第１〜第１４発明において、肉厚測定結果を反映させるタイミングは、測定された管が圧延されるときであってもよく、前記測定された管が圧延された後に供給される管材を圧延するときであってもよく、また、圧下位置の調整量は、長手方向に亘って変更してもよい。
【００９１】
さらに、以上の説明では、絞り圧延機は３ロールとしたが、絞り圧延機が２ロール又は４ロール以上であっても、同様の方法で偏肉を抑制することが可能である。また、マンドレルミルは２ロール又は２ロールの下流側に４ロールスタンドを１つだけ併設したミルとしたが、３ロールマンドレルミルや、２スタンド以上の４ロールマンドレルミル等であっても、同様の方法で偏肉を抑制することができる。
【００９２】
また、本願の第３、第４、第７、第８、第１１〜第１４発明については、マンドレルミルラインのみならず、プラグミルラインにおいても適用可能である。
【００９３】
以下、実施例を説明することにより、本発明の特徴をより一層明らかにする。外径３２０．Ｏｍｍ、肉厚３０．Ｏｍｍの素管を、圧下方向を交互に９０°交差させて連続配置された５スタンドの２ロールミルで圧延し、次いで、前記２ロールミルの圧下方向に対して４５°傾斜させた４方向からロールミルで圧延するマンドレルミルで、外径２７６．Ｏｍｍ、肉厚１５．Ｏｍｍに延伸圧延した後、８スタンドからなる３ロール絞り圧延機により外径２１９．Ｏｍｍ、肉厚１６．２ｍｍに圧延した。
【００９４】
（実施例１：本発明法Ａ）対象材が圧延される前に、対象材が圧延されるのと同様の条件の下にマンドレルミルで延伸圧延し、絞り圧延機で定径圧延した後、絞り圧延機の下流側の熱間肉厚測定装置で測定した絞り圧延機＃１、＃２スタンドの圧下方向（６方向）それぞれの偏肉量ΔＷＴ＿Ｓから、式(18)に基づき絞り圧延機＃１、＃２スタンドで与えるべきそれぞれの偏肉量ΔＷＴ＿Ｍを計算した。次に、前記偏肉量ΔＷＴ＿Ｍを得るために必要な前記絞り圧延機＃１、♯２スタンドの圧下位置の変更量を式(20)及び式(21)に基づき計算し、計算された圧下位置の変更量により前記絞り圧延機＃１、＃２スタンドの圧下位置を調整した。この状態で対象材をマンドレルミルで延伸圧延し、絞り圧延機で定径圧延した。
【００９５】
（実施例２：本発明法Ｂ）マンドレルミルで延伸圧延した後、式(18)に基づき、絞り圧延機＃１、＃２スタンドで与えるべきそれぞれの偏肉量ΔＷＴ＿Ｍを計算した。次に、絞り圧延機の上流側の熱間肉厚測定装置で測定した絞り圧延機＃１、＃２スタンドの圧下方向（６方向）それぞれの偏肉量ΔＷＴ＿Ｍ’が、前記偏肉量ΔＷＴ＿Ｍと異なる場合には、絞り圧延機♯１、＃２スタンドの圧下方向（６方向）それぞれの偏肉量ΔＷＴ＿Ｍ’を前記偏肉量ΔＷＴ＿Ｍに等しくするために必要な＃１、♯２スタンドの圧下位置の変更量を式(20)及び式(21)に基づき計算した。計算された絞り圧延機＃１、＃２スタンドの圧下位置の変更量により、絞り圧延機の各ロール圧下位置を調整し、絞り圧延機で定径圧延した。
【００９６】
（実施例３：本発明法Ｃ）対象材が圧延される前に、対象材が圧延されるのと同様の条件の下にマンドレルミルで延伸圧延し、絞り圧延機で定径圧延した後、絞り圧延機の下流側の熱間肉厚測定装置で測定したマンドレルミル仕上げ３スタンドの圧下方向（８方向）それぞれの偏肉量ΔＷＴ＿Ｓから、式(18)に基づきマンドレルミル出側で与えるべきそれぞれの方向の偏肉量ΔＷＴ＿Ｍを計算した。次に、前記偏肉量ΔＷＴ＿Ｍを得るために必要な前記マンドレルミル仕上げ３スタンドの圧下位置の変更量を計算し、計算された圧下位置の変更量によりマンドレルミル仕上げスタンドの各ロール圧下位置を調整した。この状態で対象材をマンドレルミルで延伸圧延し、絞り圧延機で定径圧延した。
【００９７】
（実施例４：本発明法Ｄ）マンドレルミルで延伸圧延した後、式(18)に基づき、マンドレルミル仕上げスタンドで与えるべきそれぞれの偏肉量ΔＷＴ＿Ｍを計算した。次に、マンドレルミル下流側の熱間肉厚測定装置で測定したマンドレルミル仕上げ３スタンドの圧下方向（８方向）それぞれの偏肉量ΔＷＴ＿Ｍ’が、前記偏肉量ΔＷＴ＿Ｍと異なる場合には、マンドレルミル仕上げ３スタンドの圧下方向（８方向）それぞれの偏肉量ΔＷＴ＿Ｍ’を前記偏肉量ΔＷＴ＿Ｍに等しくするために必要な仕上げスタンドの圧下位置の変更量を計算した。計算されたマンドレルミル仕上げスタンドの圧下位置の変更量により、マンドレルミル仕上げスタンドの各ロール圧下位置を調整し、絞り圧延機で定径圧延した。
【００９８】
（実施例５：本発明法Ｅ）対象材が圧延される前に、対象材が圧延されるのと同様の条件の下にマンドレルミルで延伸圧延し、絞り圧延機で定径圧延した後、絞り圧延機の下流側の熱間肉厚測定装置で測定した絞り圧延機＃１、＃２スタンドの圧下方向（６方向）及びマンドレルミル仕上げ３スタンドの圧下方向（８方向）それぞれの偏肉量ΔＷＴ＿Ｓから、式(18)に基づき絞り圧延機＃１、＃２スタンド及びマンドレルミル仕上げ３スタンドで与えるべきそれぞれの方向の偏肉量ΔＷＴ＿Ｍを計算した。次に、前記偏肉量ΔＷＴ＿Ｍを得るために必要な前記絞り圧延機♯１、♯２スタンドの圧下位置の変更量を式(20)及び式(21)に基づき計算し、さらに前記偏肉量ΔＷＴ＿Ｍを得るために必要な前記マンドレルミル仕上げ３スタンドの圧下位置の変更量を計算した。計算された絞り圧延機＃１、＃２スタンドの圧下位置の変更量及びマンドレルミル仕上げ３スタンドの圧下位置の変更量により、前記＃１、＃２スタンドの圧下位置及び前記仕上げスタンドの各ロール圧下位置を調整した。この状態で対象材をマンドレルミルで延伸圧延し、絞り圧延機で定径圧延した。
【００９９】
（比較例１：従来法）比較例として、マンドレルミルの下流側で肉厚測定を行い、マンドレルミル仕上げスタンドの各ロール圧下位置を、マンドレルミルの出側で管が真円に近くなるように調整する特開平８−７１６１６号に示された従来法で圧延した。
【０１００】
上記本発明法Ａ、本発明法Ｂ、本発明法Ｃ、本発明法Ｄ、本発明法Ｅ、及び従来法のそれぞれについて肉厚分布を比較した結果を表１に示す。
【表１】

【０１０１】
表１に示すように、マンドレルミルの下流側又は絞り圧延機の上流側の肉厚測定結果によりマンドレルミル又は絞り圧延機の圧下位置を調整した本発明法Ｂ及びＤは、従来法と比較して、偏肉率は３％程度改善された。また、絞り圧延機の下流側の肉厚測定結果によりマンドレルミル又は絞り圧延機の圧下位置を調整した本発明法Ａ及びＣは、従来法と比較して、偏肉率は４％程度改善された。さらに、絞り圧延機の下流側の肉厚測定結果によりマンドレルミル及び絞り圧延機の圧下位置を調整した本発明法Ｅは、従来法と比較して、偏肉率は５％程度改善された。
【発明の効果】
以上に述べたように、本発明によれば、マンドレルミルの下流側又は内面工具を用いずに管の外径を調整する圧延機の上流側若しくは下流側に、前記マンドレルミルの圧下方向又は前記圧延機の圧下方向の肉厚を測定する熱間肉厚測定装置を備えるため、その測定結果に基づき，圧延機の圧下位置又はマンドレルミルの各ロール圧下位置を調整することにより、円周方向の肉厚分布の均一な管が得られるという優れた効果を奏する。
【図面の簡単な説明】
【図１】 図１は、本発明（第３発明、第７発明、第１１発明及び第１３発明）の一実施形態に係る圧延装置を示す概略構成図である。
【図２】 図２は、本発明（第４発明、第８発明、第１２発明及び第１４発明）の一実施形態に係る圧延装置を示す概略構成図である。
【図３】 図３は、本発明（第１発明、第５発明、第９発明、第１１発明及び第１３発明）の一実施形態に係る圧延装置を示す概略構成図である。
【図４】 図４は、本発明（第２発明、第６発明、第１０発明、第１２発明及び第１４発明）の一実施形態に係る圧延装置を示す概略構成図である。
【図５】 図５は、マンネスマンーマンドレルミル方式による継ぎ目無し鋼管の製造工程の説明図である。
【図６】 図６は、真円孔型ロールでのロールギャップと孔型形状との関係を示し、（ａ）は孔型ロールとマンドレルバーの間隔が円周方向で均一の場合、（ｂ）はロールギャップを締めた場合をそれぞれ表す。
【図７】 図７は、３ロール絞り圧延機の隣接スタンドのロール配置の説明図であり、（ａ）は奇数スタンド（ｂ）は偶数スタンドをそれぞれ表す。
【図８】 図８は、角張り位相の説明図であり、（ａ）は負の角張り位相を示す周方向角度と増肉率との関係、（ｂ）は正の角張り位相を示す周方向角度と増肉率との関係を表す。
【図９】 図９は、γ線による熱間肉厚測定の原理を示す説明図である。
【図１０】 図１０は、γ線による熱間肉厚測定の方向を示す説明図である。
【図１１】 図１１は、角度方向の呼称の説明図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a seamless pipe rolling apparatus and a rolling control method capable of reducing uneven thickness in a pipe circumferential direction in a mandrel mill line or a plug mill line.
[0002]
[Prior art]
FIG. 5 is an explanatory view showing a method of manufacturing a seamless steel pipe by a Mannesmann-mandrel mill method. As shown in FIG. 5, when manufacturing a seamless steel pipe, the billet 51 is first heated to 1200 to 1300 ° C. in a heating furnace 52. Next, the heated billet 51 is pierced and rolled by a piercer 53 to form a hollow shell 54. A mandrel bar 55 is inserted into the hollow shell 54 and stretched and rolled by a mandrel mill 56 to adjust the tube thickness. Thereafter, the mandrel bar 55 is extracted, and the tube is formed into a predetermined diameter by an outer diameter adjusting rolling machine 57 such as a sizer or a stretch reducer (hereinafter, the outer diameter adjusting rolling mill is referred to as a drawing mill for convenience), and finished to a product size. In the mandrel mill 56, in the plurality of stands # 1,..., #N, the hollow shell 54 is constrained by the perforated roll 58 from the outside and the mandrel bar 55 from the inside, respectively, and 90 in the plane perpendicular to the rolling direction. Roll the wall thickness at the intersections alternately.
[0003]
In the mandrel mill 56, the wall thickness is determined by a geometrically determined interval by the hole diameter of the hole roll 58 and the outer diameter of the mandrel bar 55 to be used. Therefore, when the finished wall thickness of the seamless steel pipe is different, it is necessary to change the interval between the hole roll 58 and the mandrel bar 55 according to the thickness. There is a change in the roll gap (gap between the mandrel bar 55 and the hole roll 58) by changing to another different mandrel bar 55, replacing the hole roll 58, and adjusting the position of the hole roll 58.
[0004]
However, the replacement of the hole-type roll 58 takes more time than the replacement of the mandrel bar 55 and is not realistic.
[0005]
Further, when the roll gap of the mandrel mill 56 is changed, uneven thickness occurs in the circumferential direction. This is because the wall thickness is determined by an interval determined geometrically by the hole diameter of the hole roll 58 and the outer diameter of the mandrel bar 55 to be used, and therefore a pair of hole rolls 58 other than the predetermined roll gap. This is because the diameter (shape) of the hole formed by the above changes, and the interval also changes in the circumferential direction.
[0006]
FIG. 6 schematically shows the above phenomenon, taking a finishing stand roll of a perfect circular hole type roll as an example. Hereinafter, the deepest part of the roll hole type in FIG. 6 is referred to as a groove bottom part 63 of the roll, and the opening part of the roll hole type that is sandwiched between two rolls and is not subjected to thickness reduction is referred to as a flange part 64. FIG. 6A shows a case where the distance formed between the pair of perforated rolls 61 and the mandrel bar 62 is uniform in the circumferential direction, that is, the thickness is uniform in the circumferential direction. FIG. 6B shows a case where the wall thickness is nonuniform in the circumferential direction when the roll gap is tightened. In the case of FIG. 6B, the gap between the hole roll 61 and the mandrel bar 62 is the smallest at the portion corresponding to the groove bottom 63 of the hole roll 61, and the flange 64 side of the hole roll 61 is closer to the flange 64. As the process proceeds, the distance between the hole roll 61 and the mandrel bar 62 increases. Therefore, the rolled tube is minimized at the groove bottom 63 of the perforated roll 61 and becomes thicker toward the flange 64.
[0007]
Further, the finishing stand of the mandrel mill 56 is usually composed of two stands, and a general method is to use a hole-type roll 61 having the same curvature and set the same roll gap. Since the adjacent stands of the mandrel mill 56 are alternately crossed by 90 ° in the rolling direction, the thickness of the pipe after the finishing 2 stand is the smallest at the portion corresponding to the hole roll groove bottom 63 of the finishing 2 stand. Thickness and a thickness distribution where the position deviated by 45 ° is the maximum thickness.
[0008]
For the reasons as described above, the mandrel bar 62 is exchanged for the change of the finished wall thickness. However, in order to prevent uneven thickness in the circumferential direction by the mandrel mill 56, it is necessary to have a large number of mandrel bars 62 having an outer diameter corresponding to the pitch of the finished wall thickness. Therefore, there is a problem that the manufacturing cost becomes high.
[0009]
In order to solve this problem, various methods for preventing circumferential unevenness due to the roll gap change have been proposed in order to change the finished wall thickness by changing the roll gap using the mandrel bar 62 having a limited size. ing. As a countermeasure against uneven thickness in the circumferential direction in the mandrel mill, the raw tube is rolled by two or more two-roll mills continuously arranged with the rolling direction alternately intersecting by 90 °, and then the rolling direction of the two-roll mill is A method of changing the finished wall thickness of a steel pipe by rolling with a roll mill from four directions inclined at 45 ° to shape the pipe shape and changing the roll rolling amount of each lump mill (JP-A-6-87008) Publication). Further, in order to make the gap accuracy of the 2-roll mill and the 4-roll mill less than ± 0.1 mm, a hot thickness measuring device is arranged downstream of the 4-roll mill, and the final 3 measured by the hot thickness measuring device. A method (Japanese Patent Laid-Open No. 8-71616) for adjusting the roll gap of the last three stands based on the thickness measurement result of the stand in the rolling direction has been proposed.
[0010]
On the other hand, as shown in FIGS. 7A and 7B, a drawing mill such as a 3-roll sizer or a 3-roll stretch reducer has an angle formed by the rolling direction of each roll in a plane perpendicular to the rolling direction. A stand arranged to be 120 ° is used. Further, between adjacent stands so that the drive shaft is horizontal, the rolling direction of the hole roll 75 is alternately shifted by 60 °, and 4 to 28 stands (the number of stands is determined by the outside diameter processing degree). ), The mother pipe 76 is continuously drawn and rolled to reduce the outer diameter and slightly reduce the thickness, thereby finishing the product to a predetermined product size.
[0011]
Here, in the single stand rolling of the drawing mill, the rolling groove extends at the bottom of the roll groove as compared with the edge portion (flange portion), and the circumferential thickness of the pipe undergoes uneven deformation. In rolling with a continuous stand, the roll groove bottom part and the edge part have almost the same thickness because the plastic deformation is repeated alternately for each stand, but as shown in FIG. The point is a negative phase (Fig. 8 (a)) or a thick phase (Fig. 8 (b)) where the thickness is thinner than the thickness of the roll groove bottom and edge, and the hexagonal squares with different phases. Is produced. This squareness phenomenon tends to increase as the drawing ratio in the longitudinal direction of the pipe in drawing rolling increases and as the diameter becomes thicker and smaller. Further, the six-direction thick portion generated in the drawing mill overlaps with the four-direction thick portion generated in the mandrel mill at a position shifted by 45 ° from the reduction direction of the mandrel mill. There is a known problem that uneven thickness (uneven thickness) in the circumferential direction is promoted.
[0012]
As a measure against the uneven thickness promoted by the drawing mill, the mandrel mill and the drawing mill are arranged in tandem so that thick portions do not overlap, and any of the rolling directions of the mandrel mill and the drawing mill There has been proposed a method (Japanese Patent Laid-Open No. Hei 8-19806) for arranging so that any one of the reduction directions is within a range of ± 5 °.
[0013]
[Problems to be solved by the invention]
The inventors of the present invention simultaneously trial-rolled using the method disclosed in the above-mentioned JP-A-8-71616 and the method disclosed in JP-A-8-19806. The rolling direction of the mandrel mill on the outlet side of the mandrel mill is as follows. Although the uneven thickness in the mandrel mill on the outlet side of the rolling mill and the rolling direction in the rolling mill on the outlet side of the rolling mill should be suppressed to ± 0.1 mm or less. I could not.
[0014]
In the trial rolling, different uneven thicknesses are generated for each rolling direction of each roll of a three-roll drawing mill. In the method shown in JP-A-8-19806, each of the three-roll drawing mills Although the hexagonal tension that occurs evenly in the roll reduction direction can be suppressed, there is a disadvantage that uneven thicknesses that differ for each roll reduction direction cannot be suppressed.
[0015]
In the trial rolling, uneven thickness is generated in the drawing mill, and the method disclosed in Japanese Patent Laid-Open No. 8-71616 includes uneven thickness of the main pipe of the reduced rolling mill, that is, an unevenness generated in the mandrel mill. Although meat can be suppressed, there is a disadvantage that uneven thickness generated in the drawing mill cannot be suppressed.
[0016]
The present invention has been made to solve the problems in the mandrel mill and the drawing mill, and has a small uneven thickness on the outlet side of the drawing mill or the like that adjusts the outer diameter of the pipe without using an inner surface tool. It is an object of the present invention to provide a seamless pipe rolling apparatus and a rolling control method.
[0017]
[Means for Solving the Problems]
The inventors of the present invention conducted intensive test research to achieve the above-described object. As a result, (1) the uneven thickness larger than ± 0.1 mm occurs in the rolling process of both the mandrel mill and the drawing mill, and (2) the cause of the uneven thickness in the mandrel mill is In addition to the roll gap setting error shown in Kaihei No. 8-71616, it is also because the positions of the two opposing rolls are displaced in the direction of the rotation axis. (3) There is uneven thickness in the drawing mill. The cause of the occurrence is that there is a shift in the stand roll installation position of the drawing mill, and due to this shift, the outer diameter reduction amount of the pipe becomes uneven for each roll reduction direction, and the outer diameter reduction amount increases. It has been found that the compressive force is applied in the pipe circumferential direction and the amount of increase in the thickness of the pipe is increased.
[0018]
From the above knowledge, depending on the mill that generates uneven thickness, the mandrel mill or the reduction mill is reduced on the downstream side of the mandrel mill where the uneven thickness occurs, or on the upstream side or downstream side of the reduced rolling mill where the uneven thickness occurs. A thickness measuring device was installed so that the thickness in the direction could be measured, and based on the thickness measurement result by the device, the necessity of adjusting the rolling position of the mill in the direction to suppress uneven thickness was found.
[0019]
Further, (4) the amount of uneven thickness generated in the mandrel mill is almost uniquely determined for each wall thickness and material of the tube rolled by the mandrel mill, unless each roll of the mandrel mill is installed again, (5) The amount of uneven thickness generated in the drawing mill increases substantially in proportion to the outer diameter processing rate in the reduction rolling mill. (6) The amount of uneven thickness given before the drawing mill is the reduction rolling mill. It has been found that the amount of decrease in uneven thickness increases in proportion to the outer diameter processing rate in the drawing mill.
[0020]
From the above knowledge, (7) (a) The amount of uneven thickness generated in the mandrel mill and the amount of uneven thickness generated in the drawing mill are formulated using the thickness of the pipe, the material and the outside diameter processing rate in the drawing mill. (B) Based on such a formula, the thickness deviation in the rolling direction of the mandrel mill on the exit side of the drawing mill is minimized, and the amount of deviation in the main pipe of the drawing mill is back-calculated, (c) Based on the wall thickness measurement result downstream of the mandrel mill in the rolling direction of the last 2 mandrels or 3 stands, the final 2 mandrels or 3 stands Uneven wall thickness by adjusting the roll gap
We have found that a small tube can be obtained.
[0021]
Alternatively, (8) (a) Based on the above formula, the amount of uneven thickness of the main pipe of the drawing mill that minimizes the amount of uneven thickness in the rolling direction of the drawing mill on the outlet side of the drawing mill. (B) Based on the wall thickness measurement result on the upstream side of the drawing mill (downstream side of the mandrel mill) in the reduction direction of the drawing mill so as to obtain a mother pipe of the above-mentioned back-calculated uneven thickness amount, It was clarified that a tube with a small unevenness can be obtained by adjusting the rolling position of the rolling mill.
[0022]
Alternatively, (9) (a) Based on the thickness measurement result on the downstream side of the drawing mill, the above formula is set so that the amount of deviation in the mandrel mill reduction direction or the reduction direction of the reduction mill on the outlet side of the reduction mill is minimized. By adjusting the roll gap of the last 2 or 3 stands of the mandrel mill or the reduction position of the drawing mill according to the formula obtained, it has been found that a tube with a small unevenness can be obtained.
[0023]
The timing for reflecting the wall thickness measurement result may be when the measured pipe is rolled, or may be when the pipe material supplied after the measured pipe is rolled is rolled. . Further, the adjustment amount of the reduction position may be changed over the longitudinal direction.
[0024]
From the facts found by the present inventors described above, generally, (1) the amount of uneven thickness on the drawing side of the drawing mill varies depending on the outside diameter processing rate (outside diameter reduction rate) of the drawing mill, 2) Although it can be said that the amount of unevenness on the drawing side of the drawing mill changes by adjusting the amount of unevenness on the entrance side of the drawing mill, this is expressed as follows.
[Equation 5]

[0025]
Function f in the above equation (1) ₁ As an example, the case where the following expression is selected will be described in more detail.
[Formula 6]

[0026]
As a result of further diligent test research, the present inventors have formulated ΔWT_S / WT-S linearly with respect to ΔWT_M / WT_M and a and b linearly with respect to ρ, as shown in Equation (2). The values of the constants c and d are within the following ranges,
−0.02 ≦ c (j) ≦ 0 (3)
0.9 ≦ d (j) ≦ 1.1 (4)
The values of constants e and f vary depending on the mill installation status, pipe dimensions, material, etc.
−0.002 ≦ e (j) ≦ 0.002 (5)
−0.03 ≦ f (j) ≦ 0.03 (6)
It was found to be within the range of.
[0027]
Therefore, when adjusting the roll gap of the last 2 or 3 stands of the mandrel mill or the reduction position of the drawing mill based on the thickness measurement result on the upstream side of the rolling mill (downstream side of the mandrel mill), the above formula ( The target value of ΔWT_S in 2) may be adjusted to 0. At this time, the target value of ΔWT_M is −b / a × WT_M by setting ΔWT_S = 0 in Equation (2). Therefore, what is necessary is just to adjust the roll gap of the last 2 mandrel mills or 3 stands, or the reduction position of a drawing mill according to the following formula | equation.
[Expression 7]

[0028]
Also, when adjusting the roll gap of the last 2 or 3 stands of the mandrel mill or the reduction position of the drawing mill based on the thickness measurement result on the downstream side of the drawing mill, ΔWT_S in Expression (2) is set to 0. It may be adjusted with the goal of doing, and the following equation may be followed.
[Equation 8]

[0029]
In the above, the case where ΔWT_S / WT-S is formulated linearly with respect to ΔWT_M / WT_M and a and b are linearly defined with respect to ρ has been described in detail. Of course, other general functions may be selected. Further, considering that the value of the function is also affected by the tube material, the reduction position adjustment method based on the wall thickness measurement result can be expressed as follows.
[0030]
(1) When adjusting the roll gap of the last 2 or 3 stands of the mandrel mill or the reduction position of the drawing mill based on the wall thickness measurement result upstream (downstream of the mandrel mill)
[Equation 9]

Here, considering that b (j) ≈0 in the case of the above-described equation (7), the above equation (9) can be approximately expressed by the following equation.
[Expression 10]

[0031]
(2) When adjusting the roll gap of the last 2 or 3 stand mandrel mills or the reduction position of the drawing mill based on the thickness measurement result downstream of the drawing mill
## EQU11 ##

Here, considering that there are many cases where WT_S≈WT_M in the case of Equation (8) described above, Equation (11) can be approximately expressed by the following equation.
[Expression 12]

[0032]
The present invention has been devised based on the above-mentioned new findings found by the present inventors, and can produce a tube with a small unevenness on the exit side of a drawing mill, and a seamless tube rolling apparatus and a rolling machine A control method is provided.
[0035]
No. of this application 1 The present invention includes a retract type mandrel mill that includes a plurality of hole type roll stands, a mandrel bar is arranged in a roll hole type array formed by the hole type roll stand, and rolls a tube, and a downstream side of the mandrel mill Arranged in series, an extractor that pulls out the tube from the mandrel bar, or a rolling mill that adjusts the outer diameter of the tube, and arranged on the downstream side of the extractor or the rolling mill, and in the reduction direction of the mandrel mill A hot wall thickness measuring device for measuring the wall thickness of the pipe or measuring the wall thickness of the pipe at five or more circumferential directions of the pipe to estimate the wall thickness of the pipe in the rolling direction of the mandrel mill; A rolling device for seamless pipes, comprising:
[0036]
No. of this application 2 The present invention includes a retract type mandrel mill that includes a plurality of hole type roll stands, a mandrel bar is arranged in a roll hole type array formed by the hole type roll stand, and rolls a tube, and a downstream side of the mandrel mill Are arranged in series, and are arranged between an extractor that pulls out the tube from the mandrel bar or a rolling mill that adjusts the outer diameter of the tube, the mandrel mill, and the extractor or the rolling mill. A seamless tube rolling apparatus comprising: a hot wall thickness measuring device for measuring the wall thickness of the tube at five or more circumferential directions to estimate the wall thickness of the tube in the reduction direction of the mandrel mill It is.
[0037]
No. of this application 3 The invention A rolling mill having a plurality of perforated roll stands and adjusting the outer diameter of the pipe without using an inner surface tool, and disposed on the downstream side of the rolling mill, and reducing the wall thickness of the pipe in the rolling direction of the rolling mill A hot wall thickness measuring device for measuring or measuring the wall thickness of the pipe at five or more circumferential directions of the pipe to estimate the wall thickness of the pipe in the rolling direction of the rolling mill; Estimated by the wall thickness of the tube in the rolling direction of the rolling mill measured by the hot wall thickness measuring device or the wall thickness of the tube at five or more circumferential directions of the tube measured by the hot wall thickness measuring device. A seamless pipe rolling apparatus comprising a rolling control device that adjusts a rolling position of the rolling mill based on a thickness of the pipe in a rolling direction of the rolling mill.
[0038]
No. of this application 4 The invention A rolling mill provided with a plurality of perforated roll stands and adjusting the outer diameter of the pipe without using an inner surface tool, and disposed on the upstream side of the rolling mill, the thickness of the pipe in the rolling direction of the rolling mill A hot wall thickness measuring device for measuring or measuring the wall thickness of the pipe at five or more circumferential directions of the pipe to estimate the wall thickness of the pipe in the rolling direction of the rolling mill; Estimated by the wall thickness of the tube in the rolling direction of the rolling mill measured by the hot wall thickness measuring device or the wall thickness of the tube at five or more circumferential directions of the tube measured by the hot wall thickness measuring device. A seamless pipe rolling apparatus comprising a rolling control device that adjusts a rolling position of the rolling mill based on a thickness of the pipe in a rolling direction of the rolling mill.
[0039]
No. of this application 5 The invention is the first 1 In the invention, the thickness of the tube in the rolling direction of the mandrel mill measured by the hot thickness measuring device, or the thickness of the tube at five or more circumferential directions of the tube measured by the hot thickness measuring device. A seamless tube rolling device comprising a rolling control device that adjusts a roll gap of the mandrel mill based on a thickness of the tube in a rolling direction of the mandrel mill estimated by a thickness.
[0040]
No. of this application 6 The invention is the first 2 In the invention, the roll of the mandrel mill is based on the thickness of the tube in the rolling direction of the mandrel mill estimated by the thickness of the tube at five or more circumferential directions of the tube measured by the hot thickness measuring device. A rolling device for seamless pipes, comprising a rolling control device for adjusting a gap.
[0041]
No. of this application 7 The invention A rolling mill having a plurality of perforated roll stands and adjusting the outer diameter of the pipe without using an inner surface tool, and disposed on the downstream side of the rolling mill, and reducing the wall thickness of the pipe in the rolling direction of the rolling mill A seamless pipe comprising a hot wall thickness measuring device for measuring or measuring the wall thickness of the pipe at five or more circumferential directions of the pipe to estimate the wall thickness of the pipe in the rolling direction of the rolling mill In the rolling apparatus, the thickness of the pipe in the rolling direction of the rolling mill measured by the hot wall thickness measuring apparatus, or the pipes at five or more circumferential directions of the pipe measured by the hot wall thickness measuring apparatus. A rolling control method for a seamless pipe, wherein the rolling position of the rolling mill is adjusted based on the thickness of the pipe in the rolling direction of the rolling mill estimated by the thickness.
[0042]
No. of this application 8 The invention A rolling mill provided with a plurality of perforated roll stands and adjusting the outer diameter of the pipe without using an inner surface tool, and disposed on the upstream side of the rolling mill, the thickness of the pipe in the rolling direction of the rolling mill A seamless pipe comprising a hot wall thickness measuring device for measuring or measuring the wall thickness of the pipe at five or more circumferential directions of the pipe to estimate the wall thickness of the pipe in the rolling direction of the rolling mill In the rolling apparatus, the thickness of the pipe in the rolling direction of the rolling mill measured by the hot wall thickness measuring apparatus, or the pipes at five or more circumferential directions of the pipe measured by the hot wall thickness measuring apparatus. A rolling control method for a seamless pipe, wherein the rolling position of the rolling mill is adjusted based on the thickness of the pipe in the rolling direction of the rolling mill estimated by the thickness.
[0043]
No. of this application 9 The invention is the first 1 In the rolling apparatus according to the invention, the thickness of the pipe in the rolling direction of the mandrel mill measured by the hot thickness measuring apparatus, or five or more circumferential directions of the pipe measured by the hot thickness measuring apparatus. A seamless pipe rolling control method comprising adjusting a roll gap of the mandrel mill based on a thickness of the pipe in a rolling direction of the mandrel mill estimated from a thickness of the pipe.
[0044]
No. of this application 10 The invention is the first 2 In the rolling apparatus according to the invention, based on the thickness of the pipe in the rolling direction of the mandrel mill estimated by the thickness of the pipe at five or more circumferential directions of the pipe measured by the hot thickness measuring apparatus, A rolling control method for a seamless pipe characterized by adjusting a roll gap of a mandrel mill.
[0045]
No. of this application 11 The invention is the first 3 Invention or No. 5 In the invention, the rolling control device adjusts a rolling position of the rolling mill or a roll gap of a finishing stand of the mandrel mill on the basis of the following formula, and is a seamless tube rolling device.
[Formula 13]

The term “finishing stand” refers to the final stand for rolling each part of the pipe material among the stands of the mandrel mill, that is, the part of the pipe material rolled at the hole-shaped groove bottom of the stand. It is used to mean the case where it is not rolled on any of the subsequent mandrel mills. The same applies to the claims and the following description.
[0046]
No. of this application 12 The invention is the first 4 Invention or No. 6 In the invention, the rolling control device adjusts a rolling position of the rolling mill or a roll gap of a finishing stand of the mandrel mill on the basis of the following formula, and is a seamless tube rolling device.
[Expression 14]

[0047]
No. of this application 13 The invention is the first 7 Invention or No. 9 In the invention, the rolling control method of the seamless pipe is characterized in that the rolling position of the rolling mill or the roll gap of the mandrel mill is adjusted based on the following equation.
[Expression 15]

[0048]
No. of this application 14 The invention is the first 8 Invention or No. 10 In the invention, the rolling control method of the seamless pipe is characterized in that the rolling position of the rolling mill or the roll gap of the mandrel mill is adjusted based on the following equation.
[Expression 16]

[0049]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 illustrates the above-described application. 3rd invention, 7th invention, 11th invention, and 13th invention It is a block diagram which shows one Embodiment.
[0050]
In FIG. 1, 11 is a three-roll drawing mill comprising a plurality of stands # 1,..., #N, 12 is a mother pipe rolled by a mandrel mill, and 13 is a rolling roll of the drawing mill 11. The roll in each stand of the three-roll drawing mill 11 is one in which three perforations 13 are incorporated at 120 ° intervals. Further, when viewed from the upstream side of the drawing mill 11, for example, the odd-numbered stands are as shown in FIG. 7A, and the even-numbered stands are as shown in FIG. 7B. Are arranged to be. The outer diameter of the mother pipe 12 is drawn by a rolling roll 13 in order from the stand # 1 of the drawing mill 11, and finished to a predetermined pipe outer diameter.
[0051]
In FIG. 1, reference numeral 14 denotes a hot thickness measuring device installed on the downstream side of the drawing mill 11, 15 denotes an arithmetic unit, and 16 denotes each roll reduction device of the drawing mill 11. The calculation device 15 and the roll reduction device 16 constitute a rolling control device. The calculation device 15 is a formula given in advance from the tube thickness, material, outer diameter processing rate in the drawing mill 11 and the thickness in the rolling direction of the drawing mill 11 measured by the hot thickness measuring device 14. Based on the above, an appropriate thickness deviation of the main pipe in the # 1 and # 2 stands of the drawing mill 11 is calculated. Further, the amount of change in the reduction position of the # 1 and # 2 stands of the drawing mill 11 necessary to give the appropriate thickness deviation of the main pipe is calculated.
[0052]
The hot wall thickness measuring device 14 installed on the downstream side of the drawing mill 11 has a total of six tube thicknesses in the odd stand reduction direction (three directions) and the even stand reduction direction (three directions). Measure. As shown in FIG. 9, the hot thickness measuring device 14 has a configuration in which a γ-ray emitter 91 and a γ-ray receiver 92 are arranged to face each other along the reduction direction of the drawing mill 11. Tube thickness is measured by configuration.
[0053]
An expression for calculating an appropriate thickness deviation of the main pipe in the # 1 and # 2 stands of the drawing mill 11 incorporated in the arithmetic unit 15, and # 1 necessary for giving the appropriate thickness deviation of the main pipe, The formula for determining the amount of change in the # 2 stand reduction position can be formulated by the following test, for example.
[0054]
In the mandrel mill 56 shown in FIG. 5, the hollow shell 54 is first rolled by a normal manufacturing method. At this time, during mandrel mill rolling, an artificial ridge is attached to the outer surface of the upper pipe end of the pipe 54 on the downstream side of the mandrel mill 56, so that it can be identified which direction of the pipe 54 has been reduced by the mandrel mill 56. Keep it. Next, the mother pipe rolled by the mandrel mill 56 is drawn by the drawing mill 11 of FIG. 1, and the drawn pipes have thicknesses T1 and T1 ′ corresponding to the rolling direction of the last two stands of the mandrel mill. T2 and T2 ′ (FIG. 10A) are measured. The tube whose thickness is measured is hereinafter referred to as tube A.
[0055]
Next, in the mandrel mill 56, the same mandrel bar 55 as that used for rolling the tube A is used in the mandrel mill 56 for the hollow shell 54 made of the same size and material as the hollow tube used when the tube A is rolled. The tube A is rolled under the same conditions as when the tube A is rolled except for the following points. That is, the condition is different from that when the tube A is rolled. When the number of stands of the mandrel mill 56 is N, in the # N-1 stand, the gap between the rolling roll 58 and the mandrel bar 55 is 0.5 mm. Conversely, in the #N stand, the roll reduction position of the final two stands is adjusted so that the gap between the rolling roll 58 and the mandrel bar 55 is reduced by 0.5 mm so as to increase. As in the case of rolling the tube A, during mandrel mill rolling, an artificial rod is attached to the outer surface of the upper tube end portion of the tube 54 on the downstream side of the mandrel mill 56, and in which direction of the tube 54 the mandrel It is possible to identify whether the mill 56 has been reduced. Next, the mother pipe rolled by the mandrel mill 56 is drawn by the drawing mill 11, and the drawn pipes have thicknesses T3, T3 ′, T4 and T4 corresponding to the rolling direction of the final two stands of the mandrel mill. '(Fig. 10 (b)) is measured.
[0056]
By the above test, the amount of uneven thickness generated in the drawing mill 11, and 1. given in front of the drawing mill 11. It can be known from the following equation how much the thickness deviation of Omm decreases on the exit side of the drawing mill 11.
[Expression 17]

[0057]
Furthermore, by changing the outer diameter processing rate in the drawing mill 11 and performing the same experiment, 1. given in front of the drawing mill 11. The outer diameter processing is performed for the amount of decrease in Omm uneven thickness on the exit side of the drawing mill 11 (a in equation (17)) and the uneven thickness on the exit side of the drawing mill 11 (b in equation (17)). It can be obtained as a function of quantity. Further, by measuring the thickness of the pipe drawn by the rolling mill 11 in the rolling direction of the pipe and the thickness of each pipe, the thickness of the pipe and the thickness deviation for each material can be obtained. The following equation (18) obtained in this way is incorporated in advance in the arithmetic unit 15 as an equation for calculating an appropriate thickness deviation of the main pipe at the # 1 and # 2 stands of the drawing mill 11.
[Formula 18]

[0058]
Note that ΔWT_S / WT_S is a function of ΔWT_M / WT_M, and a and b are functions of ρ. In Equation (18), ΔWT_S / WT_S is simply made linear with respect to ΔWT_M / WT_M, and a and b Was linear with respect to ρ. The present invention is not limited to this, and based on the test result, for example, a stricter expression such as the following expression (19) may be incorporated in the arithmetic unit 15.
[Equation 19]

[0059]
Furthermore, the amount of change δ (# 1) in the uneven thickness amount ΔWT_S after the drawing rolling when the rolling position of the # 1 stand is changed by 1 mm by a test of changing the rolling position of the # 1 stand of the drawing mill 11. And the equation (18) is calculated back using the outer diameter reduction ratio ρ in the drawing mill 11 after the # 2 stand, and the # of the drawing mill 11 when the reduction position of the # 1 stand is changed by 1 mm. The thickness variation amount p_S (# 1) in one stand can be obtained as follows.
[Expression 20]

[0060]
Similarly, for the # 2 stand, the change in the thickness deviation ΔWT_S after the drawing rolling when the # 2 stand reduction position is changed by 1 mm in the rolling test by changing the reduction position of the # 2 stand of the drawing mill 11. When the amount δ (# 2) is measured and equation (18) is calculated back using the outer diameter reduction ratio ρ of the drawing mill 11 after the # 3 stand, the reduction position of the # 2 stand is changed by 1 mm. An uneven thickness variation amount p_S (# 2) at the # 2 stand of the drawing mill 11 can be obtained as follows.
[Expression 21]

[0061]
In order to obtain the amount of change in the reduction position of the # 1 and # 2 stands necessary for giving an appropriate amount of deviation of the main pipe in the # 1 and # 2 stands of the drawing mill 11, for example, the formula ( 20) and Equation (21) are incorporated in the arithmetic unit 15 in advance.
[0062]
The arithmetic unit 15 calculates # 1 and # 2 based on the equation (18) from the amount of deviation ΔWT_S in the rolling direction (six directions) of the # 1 and # 2 stands of the drawing mill 11 measured by the hot wall thickness measuring device 14. # 2 Each thickness deviation amount ΔWT_M to be given by the stand is calculated. Further, the amount of change in the reduction position of the # 1 and # 2 stands required to obtain the uneven thickness ΔWT_M is calculated based on the equations (20) and (21), and the calculated # 1 and # 2 stand The change amount of the reduction position is commanded to each roll reduction device 16 of the drawing mill 11, and the reduction position is adjusted.
[0063]
To summarize the configuration described above, the following equation (22) is obtained.
[Expression 22]

[0064]
Due to the above configuration, the uneven thickness generated in the circumferential thickness distribution of the pipe 12 drawn by the drawing mill 11 is a γ-ray emitter installed in the circumferential direction of the pipe 12. It is measured by a hot wall thickness measuring device 14 composed of 91 and a γ-ray receiver 92 and output to the arithmetic unit 15. In the arithmetic unit 15, the deviation amount ΔWT_S obtained as the difference between the thickness at the bottom of the groove at the predetermined reduction position inputted from the hot thickness measuring device 14 and the average value of the thicknesses in the six directions becomes 0 # 1. The thickness deviation amount ΔWT_M at the # 2 stand is calculated based on the equation (18). Further, the amount of change in the reduction position of the # 1 and # 2 stands required to obtain the uneven thickness amount ΔWT_M is calculated based on the equations (20) and (21), and the calculated amount of change in the reduction position is calculated. Commands are sent to the roll reduction devices 16 of the # 1 and # 2 stands to adjust the reduction position. Therefore, the thickness distribution in the roll reduction direction of each roll of the # 1 and # 2 stands of the drawing mill 11 of the pipe rolled after adjusting the reduction position is made uniform, and uneven thickness in the circumferential direction of the pipe 12 is suppressed. Can do.
[0065]
Next, this application 4th invention, 8th invention, 12th invention and 14th invention One embodiment will be described with reference to FIG.
[0066]
In FIG. 2, 21 is a three-roll drawing mill comprising a plurality of stands # 1,..., #N, 22 is a mother pipe rolled by a mandrel mill, and 23 is a rolling roll of the drawing mill 21. The roll in each stand of the three-roll drawing mill 21 has three perforated rolls 23 incorporated at 120 ° intervals. Further, when viewed from the upstream side of the drawing mill 21, for example, the odd-numbered stands are as shown in FIG. 7 (a), and the even-numbered stands are as shown in FIG. 7 (b). Are arranged to be. The outer diameter of the mother pipe 22 is drawn by a rolling roll 23 in order from the stand # 1 of the drawing mill 21 and finished to a predetermined pipe outer diameter.
[0067]
In FIG. 2, reference numeral 24 denotes a hot thickness measuring device installed on the upstream side of the drawing mill 21, 25 denotes an arithmetic unit, and 26 denotes each roll reduction device of the drawing mill 21. The arithmetic device 25 and the roll reduction device 26 constitute a rolling control device. The arithmetic unit 25 calculates a formula given in advance from the tube thickness, the material, the outer diameter processing rate in the drawing mill 21, and the thickness in the rolling direction of the drawing mill 21 measured by the hot thickness measuring device 24. Based on (18), an appropriate thickness deviation of the main pipe in the # 1 and # 2 stands of the drawing mill 21 is calculated. Further, the amount of change in the reduction position of the # 1 and # 2 stands required to give the appropriate thickness deviation of the mother pipe is calculated based on the equations (20) and (21).
[0068]
The hot wall thickness measuring device 24 installed on the downstream side of the drawing mill 21 has a total of six pipe thicknesses in the odd-numbered stand reduction direction (three directions) and the even-numbered stand reduction direction (three directions). Measure. As shown in FIG. 9, the hot thickness measuring device 14 has a configuration in which a γ-ray emitter 91 and a γ-ray receiver 92 are arranged to face each other along the rolling direction of the drawing mill 21. Tube thickness is measured by configuration.
[0069]
Expression (18), Expression (20), and Expression (21) are incorporated in the arithmetic device 25 in advance. In the arithmetic unit 25, the uneven thickness amount ΔWT_M to be given by the # 1 and # 2 stands of the drawing mill 21 is calculated based on the equation (18). When the uneven thickness amount ΔWT_M ′ in the rolling direction (six directions) of the # 1 and # 2 stands of the drawing mill 21 measured by the hot thickness measuring device 24 in FIG. 2 is different from the uneven thickness amount ΔWT_M, The amount of change in the reduction position of the # 1 and # 2 stands required to make the uneven thickness amount ΔWT_M ′ of the # 1 and # 2 stands in the rolling direction (six directions) equal to the uneven thickness amount ΔWT_M is expressed by the equation (20). And calculation based on equation (21). Further, the calculated amount of change in the reduction position of the # 1 and # 2 stands is commanded to each roll reduction device 26 of the drawing mill 21 to adjust the reduction position.
[0070]
To summarize the configuration described above, the following equation (23) is obtained.
[Expression 23]

[0071]
Due to the above configuration, the uneven thickness generated in the thickness distribution in the circumferential direction of the mother tube 22 supplied to the drawing mill 21 is γ-ray emission installed in the six circumferential directions of the mother tube 22. Measured by a hot thickness measuring device 24 comprising a measuring device 91 and a γ-ray receiver 92, and output to the computing device 25. Based on the equation (18), the arithmetic unit 25 is based on the drawing mills # 1 and # 2 stands where the amount of deviation in the rolling direction (six directions) of the drawing mill 21 on the exit side of the drawing mill 21 is zero. The thickness deviation amount ΔWT_M is calculated. Further, the amount of deviation ΔWT_M ′ in the reduction direction (six directions) of the # 1 and # 2 stands of the drawing mill 21 input from the hot wall thickness measuring device 24 and the necessary for the # 1 and # 2 stands. From the difference from the amount of uneven thickness ΔWT_M, the reduction positions of # 1 and # 2 stands required to make the amount of uneven thickness in the reduction direction (six directions) of the drawing mill 21 on the exit side of the drawing mill 21 zero. The amount of change is calculated based on Equation (20) and Equation (21), and the calculated amount of change in the reduction position is commanded to each of the # 1 and # 2 stand-down devices 26 to adjust the reduction position. Therefore, the thickness distribution in the roll reduction direction of the # 1 and # 2 stands of the drawing mill 21 is made uniform, and uneven thickness in the circumferential direction of the tube 22 can be suppressed.
[0072]
Next, this application 1st invention, 5th invention, 9th invention, 11th invention and 13th invention One embodiment will be described with reference to FIG.
[0073]
In FIG. 3, 31 is a mandrel mill composed of a plurality of stands # 1,..., #N, 32 is a hollow element tube (element tube) perforated by a piercer, 33 is a mandrel bar, 34 is a rolling roll of the mandrel mill 31 , 35 is a three-roll extractor or drawing mill comprising a plurality of stands # 1,..., #N. The mandrel bar 33 pierced by the piercer has a mandrel bar 33 inserted therein, and the mandrel bar 33 is held at a constant speed by a holding device (not shown) in the mandrel mill 31 while the mandrel bar 33 is held at a constant speed. And a plurality of perforated rolling rolls 34. After the rolling in the mandrel mill 31 is completed, the mandrel bar 33 is stopped, and the mother pipe 32 is pulled out from the mandrel bar 33 by the extractor or the drawing mill 35. The roll in each stand of the three-roll extractor or the drawing mill 35 is one in which three perforated rolls 36 are incorporated at intervals of 120 °. Further, when viewed from the upstream side of the extractor or the drawing mill 35, for example, the odd-numbered stand is as shown in FIG. 7A, and the even-numbered stand is as shown in FIG. 7B. It is arranged so as to cross 60 °. The outer diameter of the mother pipe 32 rolled by the mandrel mill 31 and drawn from the mandrel bar 33 is drawn by the rolling roll 36 in order from the stand # 1 of the extractor or the drawing mill 35 to obtain a predetermined pipe outer diameter. Finished.
[0074]
In FIG. 3, reference numeral 37 denotes a hot thickness measuring device installed on the downstream side of the extractor or the drawing mill 35, 38 denotes an arithmetic device, and 39 denotes each roll reduction device of the finishing stand of the mandrel mill 31. . The calculation device 38 and the roll reduction device 39 constitute a rolling control device. The calculation device 38 is given in advance from the tube thickness, the material, the outer diameter processing rate in the extractor or the drawing mill 35, and the thickness of the mandrel mill 31 in the rolling direction measured by the hot thickness measurement device 37. Based on the equation (18), an appropriate thickness deviation of the mother pipe 32 on the outlet side of the mandrel mill 31 is calculated. Further, a change amount of the reduction position of the mandrel mill 31 finishing stand necessary for giving the appropriate thickness deviation of the mother pipe is obtained.
[0075]
The hot wall thickness measuring device 37 installed on the downstream side of the extractor or the drawing mill 35 measures the tube wall thickness in the rolling direction of the finishing 2 or 3 stand of the mandrel mill 31. As shown in FIG. 9, the hot wall thickness measuring device 37 has a configuration in which a γ-ray emitter 91 and a γ-ray receiver 92 are arranged to face each other along the rolling direction of the mandrel mill 31 finishing stand. The tube thickness is measured by this configuration.
[0076]
Expression (18) is incorporated in the arithmetic device 38 in advance. From the thickness deviation ΔWT_S in the rolling direction of the finish 2 or 3 stand of the mandrel mill 31 measured by the hot thickness measuring device 37 in FIG. 3, the calculation device 38 gives the mandrel mill 31 on the outlet side based on the equation (18). The thickness deviation amount ΔWT_M in each of the power directions is calculated. Further, the calculation device 38 calculates the change amount of the reduction position of the finishing 2 or 3 stand necessary for obtaining the uneven thickness amount ΔWT_M, and calculates the change amount of the reduction position of each of the mandrel mill 31 finishing stands. The roll reduction device 39 is commanded to adjust the reduction position.
[0077]
To summarize the configuration described above, the following equation (24) is obtained.
[Expression 24]

[0078]
Due to the above configuration, uneven thickness generated in the thickness distribution in the circumferential direction of the pipe 32 drawn by the extractor or the drawing mill 35 is γ-rays installed in the circumferential direction of the pipe 32. It is measured by a hot wall thickness measuring device 37 composed of a light emitter 91 and a γ-ray light receiver 92, and is output to the arithmetic device 38. The arithmetic unit 38 receives the thickness deviation amount ΔWT_S obtained as the difference between the thickness of the mandrel mill 31 in the groove bottom direction and the average thickness in the circumferential direction at the predetermined reduction position input from the hot thickness measuring device 37. The thickness deviation amount ΔWT_M on the outlet side of the mandrel mill 31 where becomes 0 is calculated based on the equation (18). Further, the amount of change in the reduction position of the finishing 2 or 3 stand of the mandrel mill 31 necessary for obtaining the uneven thickness amount ΔWT_M is calculated, and the calculated amount of change in the reduction position is reduced in each roll of the finishing 2 or 3 stand. Command the device 39 to adjust the reduction position. Therefore, in the pipe rolled after adjusting the reduction position, the thickness distribution in the roll reduction direction of the finish 2 or 3 stand of the mandrel mill 31 is made uniform, and uneven thickness in the circumferential direction of the pipe 32 can be suppressed. .
[0079]
Next, this application 2nd invention, 6th invention, 10th invention, 12th invention and 14th invention One embodiment will be described with reference to FIG.
[0080]
In FIG. 4, 41 is a mandrel mill composed of a plurality of stands # 1,..., #N, 42 is a hollow element tube (element tube) perforated by a piercer, 43 is a mandrel bar, 44 is a rolling roll of the mandrel mill 41 , 45 is a three-roll extractor or drawing mill comprising a plurality of stands # 1,..., #N. The mandrel bar 43 is inserted into the raw pipe 42 pierced by the piercer, and the mandrel bar 43 is held in the mandrel mill 41 in a state where the rear end of the mandrel bar 43 is held at a constant speed by a holding device (not shown). And a plurality of perforated rolling rolls 44. After the rolling in the mandrel mill 41 is completed, the mandrel bar 43 is stopped, and the mother pipe 42 is pulled out from the mandrel bar 43 by the extractor or the drawing mill 45. The roll in each stand of the 3-roll extractor or the drawing mill 45 is one in which three perforated rolls 46 are incorporated at intervals of 120 °. Further, when viewed from the upstream side of the extractor or the drawing mill 45, for example, the odd-numbered stand is as shown in FIG. 7A, and the even-numbered stand is as shown in FIG. It is arranged so as to cross 60 °. The outer diameter of the mother pipe 42 rolled by the mandrel mill 41 and drawn from the mandrel bar 43 is drawn by the rolling roll 46 in order from the stand or the stand # 1 of the extractor or the drawing mill 45 to obtain a predetermined pipe outer diameter. Finished.
[0081]
In FIG. 4, 47 is a hot wall thickness measuring device installed between the mandrel mill 41 and the extractor or drawing mill 45, 48 is an arithmetic unit, and 49 is a roll reduction of each finishing stand of the mandrel mill 41. Each device is shown. The calculation device 48 and the roll reduction device 49 constitute a rolling control device. The calculation device 48 is given in advance from the tube thickness, the material, the outer diameter processing rate in the extractor or the drawing mill 45, and the thickness in the reduction direction of the mandrel mill 41 measured by the hot thickness measurement device 47. Based on the equation (18), an appropriate thickness deviation of the mother pipe 42 on the outlet side of the mandrel mill 41 is calculated. Further, a change amount of the reduction position of the mandrel mill 41 finishing stand necessary to give the appropriate thickness deviation of the mother pipe is obtained.
[0082]
A hot wall thickness measuring device 47 installed between the mandrel mill 41 and the extractor or the drawing mill 45 measures the tube wall thickness in the rolling direction of the finishing 2 or 3 stand of the mandrel mill 41. As shown in FIG. 9, the hot wall thickness measuring device 47 has a configuration in which a γ-ray emitter 91 and a γ-ray receiver 92 are arranged to face each other along the rolling direction of the mandrel mill 41 finishing stand. The tube thickness is measured by this configuration.
[0083]
Expression (18) is incorporated in the arithmetic device 48 in advance. The computing device 48 calculates the uneven thickness ΔWT_M to be given to the mandrel mill 41 finishing stand based on the equation (18), and the mandrel mill 41 finishing 2 or 3 stand down direction measured by the hot wall thickness measuring device 47. When the thickness deviation amount ΔWT_M ′ is different from the thickness deviation amount ΔWT_M, the mandrel mill necessary for making the thickness deviation amount ΔWT_M ′ in the rolling direction of finishing 2 or 3 stands equal to the thickness deviation amount ΔWT_M. 41 Calculate the amount of change in the reduction position of the finishing stand. Further, the calculated change amount of the reduction position is commanded to each roll reduction device 49 of the finishing stand of the mandrel mill 41 to adjust the reduction position.
[0084]
To summarize the configuration described above, the following equation (25) is obtained.
[Expression 25]

[0085]
Due to the above configuration, the uneven thickness generated in the thickness distribution in the circumferential direction of the mother pipe 42 supplied to the extractor or the drawing mill 45 is a γ installed in the circumferential direction of the mother pipe 42. It is measured by a hot wall thickness measuring device 47 including a line light emitter 91 and a γ-ray light receiver 92, and is output to the arithmetic device 48. Based on the equation (18), the computing device 48 calculates the deviation on the outlet side of the mandrel mill 41 where the thickness deviation in the rolling direction of the mandrel mill 41 finish 2 or 3 stand on the outlet side of the extractor or the drawing mill 45 becomes zero. The meat amount ΔWT_M is calculated. Further, from the difference between the thickness deviation ΔWT_M ′ in the rolling direction of the mandrel mill 41 finish 2 or 3 stand input from the hot thickness measuring device 47 and the required thickness deviation ΔWT_M on the outlet side of the mandrel mill 41. The amount of change in the reduction position of the mandrel mill 41 finishing 2 or 3 stand required to make the amount of deviation in the reduction direction of the mandrel mill 41 finishing 2 or 3 stand on the exit side of the extractor or drawing mill 45 zero. Calculate. The calculated change amount of the reduction position is commanded to each roll reduction device 26 of the finishing 2 or 3 stand of the mandrel mill 41 to adjust the reduction position. Therefore, in the pipe rolled after adjusting the reduction position, the thickness distribution in the roll reduction direction of the finish 2 or 3 stand of the mandrel mill 41 is made uniform, and uneven thickness in the circumferential direction of the pipe 42 can be suppressed. .
[0086]
In addition, the 1st-1st of this application 14 In the invention, the measurement direction of the hot wall thickness measuring device may not coincide with the reduction direction of the mandrel mill or the drawing mill when the measurement direction is sufficiently large (more than five directions). That is, it is possible to estimate the thickness of the mandrel mill or the drawing mill in the rolling direction by using interpolation, Fourier transform, or the like, and use the estimated value.
[0087]
For example, the measurement direction of the hot thickness measuring device is 9 directions of 0 °, 40 °, 80 °, 120 °, 160 °, 200 °, 240 °, 280 ° and 320 ° in FIG. Alternatively, when one of the rolling directions of the drawing mill is 45 ° in FIG. 11, the thickness in the 45 ° direction can be estimated by the following equation.
Thickness in the 45 ° direction = (Thickness in the 40 ° direction × 35 + Thickness in the 80 ° direction × 5) / 40 (26)
[0088]
Here, when estimating the thickness in the reduction direction by interpolation or Fourier transform, it is necessary to measure the thickness in five directions or more for the following reason. That is, according to the sampling theorem, the n-th order uneven thickness amount using the Fourier transform (thickness having a maximum thickness of n times in a constant cycle when the tube crosses the tube cross section of the circumferential thickness distribution). In order to extract (distribution component), the value of the wall thickness in 2n + 1 locations in the circumferential direction is required. Here, the order of the amount of uneven thickness that can be controlled by changing the reduction amount of the mandrel mill is second order in the case of two rolls, and if there is a thickness of 2 × 2 + 1 = 5 directions, the thickness in the mandrel mill reduction direction Can be estimated. That is, in order to estimate the thickness in the rolling direction of the two-roll mandrel mill by interpolation or Fourier transform, it is only necessary to measure the thickness in five or more directions.
[0089]
In addition, for simplicity of explanation, Third, fourth, seventh, eighth, eleventh to fourteenth inventions In the above embodiment corresponding to the above, the reduction position adjusting stand of the drawing mill is limited to # 1 and # 2, but the present invention is not limited to this, and outer diameter machining other than # 1 and # 2 is performed. The reduction position may be adjusted by a stand, or the reduction positions of both # 1, # 2 and a stand other than # 1, # 2 may be adjusted. When adjusting the reduction position with multiple stands of a drawing mill, as shown in the following formula (27) or formula (28), the sum of the thickness deviation given by each stand is the thickness deviation to be corrected. What should I do?
[Equation 26]

[0090]
In addition, the first to the first of the present application 14 In the invention, the timing of reflecting the wall thickness measurement result may be when the measured pipe is rolled, or when the pipe material supplied after the measured pipe is rolled is rolled. In addition, the adjustment amount of the reduction position may be changed over the longitudinal direction.
[0091]
Furthermore, in the above description, the drawing mill has three rolls, but even if the drawing mill has two rolls or four rolls or more, uneven thickness can be suppressed by the same method. Moreover, although the mandrel mill is a mill having only one 4-roll stand on the downstream side of two rolls or two rolls, the same applies to a three-roll mandrel mill or a four-roll mandrel mill having two or more stands. Uneven thickness can be suppressed by the method.
[0092]
In addition, Third, fourth, seventh, eighth, eleventh to fourteenth inventions Is applicable not only to mandrel mill lines but also to plug mill lines.
[0093]
Hereinafter, the features of the present invention will be further clarified by describing examples. Outer diameter 320. Omm, wall thickness 30. The Omm blank tube was rolled by a 5-stand 2-roll mill continuously arranged with the rolling direction alternately intersecting by 90 °, and then rolled from 4 directions inclined by 45 ° with respect to the rolling direction of the 2-roll mill. Rolling mandrel mill with outer diameter 276. Omm, wall thickness 15. After drawing and rolling to Omm, the outer diameter 219. It rolled to Omm and wall thickness 16.2mm.
[0094]
(Example 1: Method A of the present invention) Before the target material is rolled, it is stretch-rolled with a mandrel mill under the same conditions as the target material is rolled, and after constant diameter rolling with a drawing mill, From the uneven thickness amount ΔWT_S of each of the rolling mills # 1 and # 2 in the rolling direction (six directions) measured by the hot wall thickness measuring device on the downstream side of the rolling mill, the rolling mill # 1 based on the formula (18) 1 and # 2 The thickness deviation amount ΔWT_M to be given by the stand # 2 was calculated. Next, the amount of change in the reduction position of the drawing mills # 1 and # 2 stands necessary to obtain the uneven thickness amount ΔWT_M is calculated based on the equations (20) and (21), and the calculated reduction position The reduction position of the drawing mill # 1, # 2 stand was adjusted according to the amount of change. In this state, the target material was stretch-rolled with a mandrel mill and fixed-diameter rolled with a drawing mill.
[0095]
(Example 2: Invention Method B) After drawing and rolling with a mandrel mill, the amount of uneven thickness ΔWT_M to be given by the drawing mills # 1 and # 2 stands was calculated based on the equation (18). Next, the thickness deviation amount ΔWT_M ′ of each of the rolling mills # 1 and # 2 stands in the rolling direction (six directions) measured by the hot wall thickness measuring device on the upstream side of the rolling mill is the thickness deviation amount ΔWT_M. If they are different, the reduction positions of the # 1 and # 2 stands required to make the deviation amount ΔWT_M ′ in the rolling direction (six directions) of the drawing mills # 1 and # 2 stands equal to the deviation amount ΔWT_M. The amount of change was calculated based on Equation (20) and Equation (21). Each roll rolling position of the drawing mill was adjusted according to the calculated amount of change in the rolling position of the drawing mills # 1 and # 2, and constant diameter rolling was performed with the drawing mill.
[0096]
(Example 3: Method C of the present invention) Before the target material is rolled, it is stretch-rolled with a mandrel mill under the same conditions as the target material is rolled, and after constant diameter rolling with a drawing mill, From the thickness deviation ΔWT_S in the rolling direction (8 directions) of the three mandrel mill finishing stands measured by the hot wall thickness measurement device downstream of the drawing mill, each to be given on the mandrel mill exit side based on equation (18) The thickness deviation amount ΔWT_M in the direction was calculated. Next, the amount of change in the reduction position of the three mandrel mill finishing stands required to obtain the uneven thickness amount ΔWT_M is calculated, and each roll reduction position of the mandrel mill finishing stand is adjusted by the calculated amount of change in the reduction position. did. In this state, the target material was stretch-rolled with a mandrel mill and fixed-diameter rolled with a drawing mill.
[0097]
(Example 4: Invention Method D) After stretching and rolling with a mandrel mill, the amount of uneven thickness ΔWT_M to be given by the mandrel mill finishing stand was calculated based on the formula (18). Next, when the uneven thickness amount ΔWT_M ′ of each of the three mandrel mill finishing three stands in the rolling direction (8 directions) measured by the hot thickness measuring device on the downstream side of the mandrel mill is different from the uneven thickness amount ΔWT_M, the mandrel The amount of change in the reduction position of the finishing stand required to make the uneven thickness amount ΔWT_M ′ of each of the mill finishing 3 stands in the rolling direction (8 directions) equal to the uneven thickness amount ΔWT_M was calculated. Each roll reduction position of the mandrel mill finishing stand was adjusted according to the calculated change amount of the reduction position of the mandrel mill finishing stand, and constant diameter rolling was performed with a drawing mill.
[0098]
(Example 5: Invention method E) Before the target material is rolled, it is stretch-rolled with a mandrel mill under the same conditions as the target material is rolled, and after constant diameter rolling with a drawing mill, The amount of uneven thickness in the rolling direction of the rolling mills # 1 and # 2 (6 directions) and in the rolling direction (8 directions) of the 3 stands of mandrel mill finishing measured by the hot wall thickness measuring device downstream of the drawing mill. From ΔWT_S, the thickness deviation amount ΔWT_M in each direction to be given by the drawing mill # 1, # 2 stand and the mandrel mill finishing 3 stand was calculated based on the equation (18). Next, the amount of change in the reduction position of the drawing mills # 1 and # 2 stands necessary for obtaining the uneven thickness amount ΔWT_M is calculated based on the equations (20) and (21), and the uneven thickness amount is further calculated. The amount of change in the reduction position of the three mandrel mill finished 3 stands required to obtain ΔWT_M was calculated. Depending on the calculated change amount of the reduction position of the drawing mills # 1 and # 2 and the change amount of the reduction position of the 3 mandrel mill finishing stand, the reduction position of the # 1 and # 2 stand and each roll reduction of the finishing stand The position was adjusted. In this state, the target material was stretch-rolled with a mandrel mill and fixed-diameter rolled with a drawing mill.
[0099]
(Comparative example 1: conventional method) As a comparative example, the wall thickness measurement is performed on the downstream side of the mandrel mill, and the roll reduction position of the mandrel mill finishing stand is set so that the pipe is close to a perfect circle on the exit side of the mandrel mill. Rolling was performed by the conventional method shown in JP-A-8-71616 to be adjusted.
[0100]
Table 1 shows the results of comparing the wall thickness distribution for each of the present invention method A, the present invention method B, the present invention method C, the present invention method D, the present invention method E, and the conventional method.
[Table 1]

[0101]
As shown in Table 1, the methods B and D of the present invention in which the reduction position of the mandrel mill or the drawing mill is adjusted based on the wall thickness measurement result on the downstream side of the mandrel mill or the upstream side of the drawing mill are compared with the conventional method. Thus, the uneven thickness ratio was improved by about 3%. In addition, the method A and C of the present invention in which the reduction position of the mandrel mill or the drawing mill is adjusted based on the thickness measurement result on the downstream side of the drawing mill is improved by about 4% compared to the conventional method. It was. Furthermore, the present invention method E in which the reduction positions of the mandrel mill and the drawing mill were adjusted based on the thickness measurement results on the downstream side of the drawing mill improved the thickness deviation rate by about 5% compared to the conventional method.
【The invention's effect】
As described above, according to the present invention, on the downstream side of the mandrel mill or on the upstream side or downstream side of the rolling mill that adjusts the outer diameter of the pipe without using an inner surface tool, Since it is equipped with a hot wall thickness measuring device that measures the wall thickness in the rolling direction of the rolling mill, by adjusting the rolling position of the rolling mill or each roll rolling position of the mandrel mill based on the measurement results, An excellent effect is obtained in that a tube having a uniform wall thickness distribution can be obtained.
[Brief description of the drawings]
FIG. 1 illustrates the present invention ( 3rd invention, 7th invention, 11th invention, and 13th invention It is a schematic block diagram which shows the rolling apparatus which concerns on one Embodiment.
FIG. 2 illustrates the present invention ( 4th invention, 8th invention, 12th invention and 14th invention It is a schematic block diagram which shows the rolling apparatus which concerns on one Embodiment.
FIG. 3 illustrates the present invention ( 1st invention, 5th invention, 9th invention, 11th invention and 13th invention It is a schematic block diagram which shows the rolling apparatus which concerns on one Embodiment.
FIG. 4 shows the present invention ( 2nd invention, 6th invention, 10th invention, 12th invention and 14th invention It is a schematic block diagram which shows the rolling apparatus which concerns on one Embodiment.
FIG. 5 is an explanatory view of a manufacturing process of a seamless steel pipe by a Mannes-Mandrel mill method.
FIG. 6 shows a relationship between a roll gap and a hole shape in a perfectly circular roll, and (a) shows a case where the distance between the hole roll and the mandrel bar is uniform in the circumferential direction (b) ) Represents the case where the roll gap is tightened.
FIG. 7 is an explanatory diagram of roll arrangement of adjacent stands of a three-roll drawing mill, in which (a) represents an odd-numbered stand (b) represents an even-numbered stand.
FIGS. 8A and 8B are explanatory diagrams of a squared phase, where FIG. 8A is a relationship between a circumferential angle showing a negative squared phase and a thickness increase rate, and FIG. 8B is a positive squared phase. This represents the relationship between the circumferential angle and the rate of wall thickness increase.
FIG. 9 is an explanatory diagram showing the principle of hot wall thickness measurement using γ rays.
FIG. 10 is an explanatory diagram showing the direction of hot thickness measurement using γ rays.
FIG. 11 is an explanatory diagram of naming in the angular direction.

Claims (14)

A retract type mandrel mill comprising a plurality of perforated roll stands, a mandrel bar arranged in a roll perforated array formed by the perforated roll stands, and rolling the tube;
A rolling mill which is arranged in series on the downstream side of the mandrel mill and extracts the tube from the mandrel bar or adjusts the outer diameter of the tube;
It is arranged on the downstream side of the extractor or the rolling mill, and measures the wall thickness of the pipe in the rolling direction of the mandrel mill, or measures the wall thickness of the pipe at five or more circumferential directions of the pipe. A seamless pipe rolling apparatus, comprising: a hot wall thickness measuring device that estimates a wall thickness of the pipe in a rolling direction of a mandrel mill. A retract type mandrel mill comprising a plurality of perforated roll stands, a mandrel bar arranged in a roll perforated array formed by the perforated roll stands, and rolling the tube;
A rolling mill which is arranged in series on the downstream side of the mandrel mill and extracts the tube from the mandrel bar or adjusts the outer diameter of the tube;
It is arranged between the mandrel mill and the extractor or the rolling mill, and measures the wall thickness of the pipe at five or more locations in the circumferential direction of the pipe to determine the wall thickness of the pipe in the reduction direction of the mandrel mill. A seamless pipe rolling device comprising a hot wall thickness measuring device for estimation. A rolling mill comprising a plurality of perforated roll stands and adjusting the outer diameter of the pipe without using an inner surface tool;
It is arranged on the downstream side of the rolling mill and measures the thickness of the pipe in the rolling direction of the rolling mill, or measures the thickness of the pipe at five or more circumferential directions of the rolling mill to reduce the rolling mill. A hot wall thickness measuring device for estimating the wall thickness of the tube in the direction;
Estimated by the wall thickness of the tube in the rolling direction of the rolling mill measured by the hot wall thickness measuring device or the wall thickness of the tube at five or more circumferential directions of the tube measured by the hot wall thickness measuring device. was based on said thickness of said tube rolling direction of the rolling mill, the rolling mill rolling apparatus of seamless pipe you anda rolling control device for adjusting the rolling positions of the. A rolling mill comprising a plurality of perforated roll stands and adjusting the outer diameter of the pipe without using an inner surface tool;
It is arranged on the upstream side of the rolling mill and measures the thickness of the pipe in the rolling direction of the rolling mill, or measures the thickness of the pipe at five or more circumferential directions of the rolling mill to reduce the rolling mill. A hot wall thickness measuring device for estimating the wall thickness of the tube in the direction;
Estimated by the wall thickness of the tube in the rolling direction of the rolling mill measured by the hot wall thickness measuring device or the wall thickness of the tube at five or more circumferential directions of the tube measured by the hot wall thickness measuring device. was based on said thickness of said tube rolling direction of the rolling mill, the rolling mill rolling apparatus of seamless pipe you anda rolling control device for adjusting the rolling positions of the. Estimated by the wall thickness of the tube in the rolling direction of the mandrel mill measured by the hot wall thickness measuring device, or by the wall thickness of the tube at five or more circumferential directions of the tube measured by the hot wall thickness measuring device. It was based on the wall thickness of the tube pressing direction of the mandrel mill, rolling mill for seamless tube according to claim 1, characterized in that it comprises a rolling control apparatus for adjusting the roll gap of the mandrel mill. The roll gap of the mandrel mill is adjusted based on the wall thickness of the pipe in the rolling direction of the mandrel mill estimated by the wall thickness of the pipe at five or more circumferential directions of the pipe measured by the hot wall thickness measuring device. The rolling device for a seamless pipe according to claim 2 , further comprising a rolling control device that performs the rolling control. A rolling mill provided with a plurality of perforated roll stands and adjusting the outer diameter of the pipe without using an inner surface tool, and disposed on the downstream side of the rolling mill, the thickness of the pipe in the rolling direction of the rolling mill A seamless pipe comprising a hot wall thickness measuring device for measuring or measuring the wall thickness of the pipe at five or more circumferential directions of the pipe to estimate the wall thickness of the pipe in the rolling direction of the rolling mill In rolling equipment,
Estimated by the wall thickness of the tube in the rolling direction of the rolling mill measured by the hot wall thickness measuring device or the wall thickness of the tube at five or more circumferential directions of the tube measured by the hot wall thickness measuring device. A rolling control method for a seamless pipe, wherein the rolling position of the rolling mill is adjusted based on the thickness of the pipe in the rolling direction of the rolling mill. A rolling mill provided with a plurality of perforated roll stands and adjusting the outer diameter of the pipe without using an inner surface tool, and disposed on the upstream side of the rolling mill, the thickness of the pipe in the rolling direction of the rolling mill A seamless pipe comprising a hot wall thickness measuring device for measuring or measuring the wall thickness of the pipe at five or more circumferential directions of the pipe to estimate the wall thickness of the pipe in the rolling direction of the rolling mill In rolling equipment,
Estimated by the wall thickness of the tube in the rolling direction of the rolling mill measured by the hot wall thickness measuring device or the wall thickness of the tube at five or more circumferential directions of the tube measured by the hot wall thickness measuring device. A rolling control method for a seamless pipe, wherein the rolling position of the rolling mill is adjusted based on the thickness of the pipe in the rolling direction of the rolling mill. In the rolling apparatus according to claim 1 ,
Estimated by the wall thickness of the tube in the rolling direction of the mandrel mill measured by the hot wall thickness measuring device, or by the wall thickness of the tube at five or more circumferential directions of the tube measured by the hot wall thickness measuring device. A rolling control method for a seamless pipe, wherein the roll gap of the mandrel mill is adjusted based on the thickness of the pipe in the rolling direction of the mandrel mill. In the rolling apparatus according to claim 2 ,
The roll gap of the mandrel mill is adjusted based on the wall thickness of the pipe in the rolling direction of the mandrel mill estimated by the wall thickness of the pipe at five or more circumferential directions of the pipe measured by the hot wall thickness measuring device. A rolling control method for a seamless pipe, characterized by: The seamless rolling apparatus according to claim 3 or 5 , wherein the rolling control device adjusts a rolling position of the rolling mill or a roll gap of a finishing stand of the mandrel mill based on the following equation.

7. The seamless pipe rolling device according to claim 4 or 6 , wherein the rolling control device adjusts a rolling position of the rolling mill or a roll gap of a finishing stand of the mandrel mill based on the following equation.

The rolling control method for a seamless pipe according to claim 7 or 9 , wherein a rolling position of the rolling mill or a roll gap of the mandrel mill is adjusted based on the following equation.

The rolling control method for a seamless pipe according to claim 8 or 10 , wherein a rolling position of the rolling mill or a roll gap of the mandrel mill is adjusted based on the following equation.

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