JP2014166649A - Method for manufacturing seamless steel pipe - Google Patents
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本発明は継目無鋼管の製造方法に関し、特に円柱状鋼片をマンネスマン穿孔等にて中空素管とし、これをプラグミルにて圧延する継目無鋼管の製造方法に関する。 The present invention relates to a method of manufacturing a seamless steel pipe, and more particularly to a method of manufacturing a seamless steel pipe in which a cylindrical steel slab is formed into a hollow shell by Mannesmann drilling or the like, and this is rolled by a plug mill.
一般に継目無鋼管は、円柱状鋼片を素材とし、マンネスマン穿孔等にて中空素管とし、これを適宜エロンゲータと呼ばれる中間圧延工程を経て肉厚および外径を調整したのち、プラグミルあるいはマンドレルミル等にて延伸圧延し、更に中間加熱を行う等し、最終的にサイザーやストレッチレデューサにより定径圧延して最終製品とされる。継目無鋼管は管全長に亘り一定の材質、強度が得られるため、使用環境の厳しい油井等で用いられ、あるいは機械構造用等の構造用鋼管に適用される。 In general, a seamless steel pipe is made of a cylindrical steel slab and is made into a hollow shell by Mannesmann drilling or the like, and after appropriately adjusting the thickness and outer diameter through an intermediate rolling process called an elongator, a plug mill or a mandrel mill, etc. The film is stretched and rolled at, and further subjected to intermediate heating, and finally is subjected to constant diameter rolling with a sizer or stretch reducer to obtain a final product. Since seamless steel pipes have a certain material and strength over the entire length of the pipe, they are used in oil wells and the like where the usage environment is severe, or are applied to structural steel pipes for mechanical structures.
構造用鋼管や一部の油井用鋼管は施工上、高寸法精度が要求されるが、継目無鋼管は製造技術上、肉厚精度を飛躍的に高めるのが難しい。例えば電縫溶接鋼管では素材が薄板圧延により得られたものであるため電縫溶接部を除けばその肉厚はミクロンオーダーの精度であるが、継目無鋼管では加熱した素材を穿孔するため中心孔となるべきものが偏芯しやすい。更に、プラグミルでは、1対の孔型ロールと内面工具(プラグ)を用い、通常2パスあるいはそれ以上で圧延が行われ、各パスとその次のパスとで、カリバー底に接触させる被圧延管の円周方向位置を90度ずらして圧延する(これを、圧下位置90度変更という)必要があるため、その対向部で均一な肉厚にはなりにくく、管断面内で偏肉を生ずる可能性がある。 Structural steel pipes and some oil well steel pipes require high dimensional accuracy in construction, but seamless steel pipes are difficult to dramatically increase in wall thickness accuracy due to manufacturing technology. For example, in ERW welded pipes, the material is obtained by rolling thin plates, so the thickness of the wall is accurate to the micron order except for ERW welds. Things that should be easy to eccentric. Furthermore, in a plug mill, a pair of perforated rolls and an internal tool (plug) are used, and rolling is usually performed in two or more passes, and the rolled tube is brought into contact with the caliber bottom in each pass and subsequent passes. Since it is necessary to perform rolling by shifting the circumferential direction position of 90 degrees (this is referred to as changing the rolling position to 90 degrees), it is difficult to achieve a uniform thickness at the opposite portion, and uneven thickness may occur within the tube cross section. There is sex.
加熱起因の偏芯偏肉は炉加熱パターンの制御等により軽減可能であるが、プラグミル圧延での偏肉は、前記圧下位置90度変更が最終目標肉厚を達成するために必要であることから、軽減するのが難しい。
一方、例えば2以上のロールから構成される圧下スタンドを連続かつ奇数スタンドと偶数スタンドを対向配置して延伸圧延するマンドレルミルにおいては、多スタンドであることから、前段スタンドで比較的主圧下部の円弧形状範囲が狭い、いわゆるオープンカリバーとしたロールを使用し、肉厚や形状を決定する後段スタンドではその範囲を大きくするクローズドカリバーとしたロールを用いて偏肉を抑制している(非特許文献1)。
Eccentric eccentric thickness due to heating can be reduced by controlling the furnace heating pattern, etc. However, the uneven thickness in plug mill rolling is necessary to achieve the final target thickness by changing the reduction position by 90 degrees. Difficult to mitigate.
On the other hand, for example, in a mandrel mill in which a rolling stand composed of two or more rolls is continuously stretched and rolled with an odd-numbered stand and an even-numbered stand facing each other, it is a multi-stand, so the lower part of the main pressure is relatively lower than the previous stand A roll with a narrow arc shape range, a so-called open caliber, is used, and the rear stand that determines the wall thickness and shape uses a roll with a closed caliber that increases the range to suppress uneven thickness (non-patent literature) 1).
しかしながら、肉厚を減ずる圧延装置として大径鋼管の製造で適用されているプラグミル圧延方式では、通常、一対のカリバーロールと1個の内面工具(プラグ)にて圧延するため、前段の圧延装置であるエロンゲータなどにより製造された中空素管を所定の工具の組み合わせでしか圧延できない。加えてプラグとロールカリバーの位置関係から、管断面内において局部的に圧下の強い領域ができ、そこで疵を発生させることもある。このような偏肉や疵を防止する観点から、一部のプラグミルでは孔型を胴長の長いロールに複数個作製し、これをもって多スタンド圧延であるかのような延伸圧延も可能であるとされている(非特許文献2)。 However, the plug mill rolling method applied in the production of large-diameter steel pipes as a rolling device for reducing the wall thickness usually rolls with a pair of caliber rolls and a single inner surface tool (plug). A hollow shell manufactured by an elongator or the like can be rolled only with a predetermined combination of tools. In addition, due to the positional relationship between the plug and the roll caliber, a region of strong local reduction is formed in the cross section of the tube, and wrinkles may be generated there. From the viewpoint of preventing such uneven thickness and wrinkles, some plug mills produce a plurality of hole molds in a roll having a long trunk length, and with this, it is possible to perform extension rolling as if it were multi-stand rolling. (Non-Patent Document 2).
また、プラグミルによる圧下設定については、プラグ径が1種類であることを前提として幾何学的な影響を考慮し、相対的位置関係を示す特性値により圧下設定を行うという方法が提案されている(特許文献1)。さらに、この設定方法ではロールやプラグの熱膨張等により変化が考慮されておらず、最適設定に成りえないとして、被圧延材のサイズ等のロット変更にあたり、前材のロールギャップ値を基準として、圧延工具径と目標肉厚とで決まる幾何学的寸法差によって修正するとともに、さらに、前材と次材の材質変更に伴う変形抵抗差、前材と次材の温度差、または前材と次材の圧延工具径差による補正を加味して、被圧延材のロット替わり一本目の肉厚または長さが目標値となる初期圧下値を、前材の圧延情報を用いて決定する方法が提案されている(特許文献2)。 In addition, regarding the reduction setting by the plug mill, a method has been proposed in which the reduction setting is performed based on the characteristic value indicating the relative positional relationship in consideration of the geometrical effect on the assumption that there is only one type of plug diameter ( Patent Document 1). Furthermore, in this setting method, changes due to the thermal expansion of rolls and plugs are not considered, and it cannot be set optimally.When changing the lot such as the size of the material to be rolled, the roll gap value of the previous material is used as a reference. In addition to correction by the geometric dimension difference determined by the rolling tool diameter and the target wall thickness, the deformation resistance difference due to the material change between the previous and next materials, the temperature difference between the previous and next materials, or the previous material In consideration of correction due to the difference in rolling tool diameter of the next material, there is a method for determining the initial rolling reduction value at which the first thickness or length of the material to be rolled becomes the target value using the rolling information of the previous material. It has been proposed (Patent Document 2).
また、ピアサーミルで穿孔された鋼鋳片を、エロンゲータで拡管し、引き続き上下一対の主ロールおよび戻しロールからなるプラグミルで延伸圧延するに際して、延伸圧延中に、プラグミルの主ロールの上下間隔を、エロンゲータで使用するプラグの外径、エロンゲータを通過した管の外径および温度に基づき予め定めた速度で変更することにより、管長手方向での肉厚偏差を小さくする継目無鋼管の製造方法が提案されている(特許文献3)。 In addition, when the steel slab drilled by the Piercer mill is expanded with an elongator and subsequently stretch-rolled with a plug mill consisting of a pair of upper and lower main rolls and a return roll, A method of manufacturing a seamless steel pipe is proposed in which the thickness deviation in the longitudinal direction of the pipe is reduced by changing at a predetermined speed based on the outer diameter of the plug used in the pipe, the outer diameter of the pipe that has passed through the elongator, and the temperature. (Patent Document 3).
また、マンドレルミルにおいては内面工具であるバーに黒鉛系などの潤滑剤を付着させて圧延することにより内面性状を確保する技術が一般に使用されている(特許文献4)。マンドレルミルでは制御の有無に関わらずバーが一定ないしは圧延材に近い速度で圧延方向へ移動するため、内面工具(バー)と被圧延管との相対速度差が大きくなることは少なく、潤滑による内面疵の防止効果が得られる。 Further, in a mandrel mill, a technique is generally used in which inner surface properties are ensured by attaching and rolling a graphite-based lubricant to a bar which is an inner surface tool (Patent Document 4). In the mandrel mill, the bar moves in the rolling direction at a constant speed or close to that of the rolled material, regardless of the presence or absence of control, so there is little increase in the relative speed difference between the inner surface tool (bar) and the tube to be rolled. The effect of preventing wrinkles is obtained.
しかしながら、前記プラグミルのロールに複数個の孔型を作製して圧延する方法は、大径鋼管を製造するためには大径かつ胴長の長い巨大なロールが必要となり、また寸法(特に外径)が多岐に亘る鋼管を製造するためには大きなロールを数多く保有する必要があるため現実的でなく、採用することができない。
加えて、特許文献1または特許文献2に示されるような圧下設定法は、全長を設定値に近くして平均肉厚を合わせることが可能であるとしても、圧延方向に対し垂直な横断面の肉厚分布、特に孔型形状とプラグ形状との関係に基づく圧下分布については改善が期待できない。また、特許文献3に示されている継目無鋼管の製造方法では、管長手方向での肉厚偏差を抑制することは可能であるが、プラグミルでは、通常、複数回の圧延が一回の圧延ごとに被圧延管を周方向に90度回転して行われるため、管長手方向に垂直な断面内の偏肉を抑制することは困難である。
However, the method of producing and rolling a plurality of perforations in the roll of the plug mill requires a large roll having a large diameter and a long trunk length in order to produce a large diameter steel pipe, and also has dimensions (especially outer diameter). However, in order to manufacture a wide range of steel pipes, a large number of large rolls must be held, which is not realistic and cannot be employed.
In addition, the reduction setting method as shown in
また、前記潤滑による内面疵防止対策も、プラグミルでは内面工具(プラグ)が固定されて内面工具と被圧延管との相対速度差が大きい上に、1パス圧延後すぐに出側から入側へ被圧延管を戻して間髪をおかず2パス目の圧延を行うという特異な圧延方式であることと、圧延前のプラグ温度が一般に低いことから強固な潤滑膜を形成させることが難しく、潤滑の効果が限定される。特に、焼付き疵などを低減させる酸化スケールが生じにくい鋼管材料の圧延や低温条件での圧延の場合は、内面疵の発生を防止することが非常に難しい状況にある。 In addition, the inner surface tool (plug) is fixed in the plug mill, and the relative speed difference between the inner surface tool and the pipe to be rolled is large in the plug mill, and from the outlet side to the inlet side immediately after one pass rolling. It is difficult to form a strong lubricating film because it is a unique rolling method in which the tube to be rolled is returned and the second pass rolling is performed without any gaps, and the plug temperature before rolling is generally low. Is limited. In particular, in the case of rolling a steel pipe material in which an oxide scale that reduces seizure flaws or the like hardly occurs, or rolling under low temperature conditions, it is very difficult to prevent the occurrence of flaws on the inner surface.
上述のように、プラグミルを用いた継目無鋼管延伸圧延では、孔型形状変更、潤滑剤の利用のいずれの手段も適用困難であって、管断面内の偏肉および内面疵の発生を完全には防止できないという課題があった。 As described above, in seamless steel pipe drawing and rolling using a plug mill, it is difficult to apply any means for changing the shape of the hole or using a lubricant. There was a problem that could not be prevented.
発明者らは、上記の課題を解決するために、プラグミルでの延伸圧延中の被圧延管と、孔型ロールおよびプラグとの接触関係に着目し、FEA(有限要素解析)および圧延実験により検討した結果、以下の要旨からなる発明を完成した。
〔1〕断面が円形ないしは楕円形である中空素管を出発素材とし、被圧延管の外面側を加工するカリバー形状が略円弧形状である一対の孔型ロールと、内面側を加工する断面が円形状のプラグとを有するプラグミルにて熱間で複数パスの延伸圧延を行い、その際、各パスとその次パスとで被圧延管のカリバー底当接位置を90度ずらす圧下位置90度変更を行う、継目無鋼管の製造方法において、各パスで、下記式(1)を満たすように延伸圧延を行うことを特徴とする継目無鋼管の製造方法。
Dp≦2×R1−2×t+0.05×t (1)
ここで、Dp:ロールバイト下死点におけるプラグ径〔mm〕、R1:カリバー底部孔半径〔mm〕、t:出側目標肉厚〔mm〕
In order to solve the above-mentioned problems, the inventors focused on the contact relationship between a rolled tube during drawing and rolling with a plug mill, a hole roll, and a plug, and examined them by FEA (finite element analysis) and rolling experiments. As a result, the invention having the following gist was completed.
[1] A hollow raw tube having a circular or elliptical cross section as a starting material, a pair of perforated rolls whose caliber shape for processing the outer surface side of the rolled tube is a substantially arc shape, and a cross section for processing the inner surface side Multiple passes are hot-rolled in a plug mill having a circular plug, and at that time, the reduction position 90 degrees is changed by shifting the caliber bottom contact position of the rolled tube by 90 degrees between each pass and the next pass. In the method for producing a seamless steel pipe, a method for producing a seamless steel pipe is characterized in that in each pass, stretching and rolling are performed so as to satisfy the following formula (1).
Dp ≦ 2 × R1-2 × t + 0.05 × t (1)
Here, Dp: plug diameter [mm] at the bottom dead center of roll bite, R1: caliber bottom hole radius [mm], t: outlet side target thickness [mm]
〔2〕1基のプラグミルを用い、前記圧下位置90度変更は各パスとその次パスとの間で被圧延管を管周方向に90度回転させて行い、且つ前記次パス用のプラグを前記式(1)を満たすものに交換することを特徴とする〔1〕に記載の継目無鋼管の製造方法。 [2] Using a single plug mill, the reduction position is changed by 90 degrees by rotating the rolled pipe 90 degrees in the circumferential direction between each pass and the next pass, and the plug for the next pass is used. It replaces | exchanges for what satisfy | fills said Formula (1), The manufacturing method of the seamless steel pipe as described in [1] characterized by the above-mentioned.
本発明によれば、プラグミルを用いた鋼管の延伸圧延において被圧延管の内面疵および偏肉を大幅に低減することができる。 ADVANTAGE OF THE INVENTION According to this invention, the internal surface flaw and uneven thickness of a to-be-rolled pipe can be reduced significantly in the extending | stretching rolling of the steel pipe using a plug mill.
プラグミルを用いた継目無鋼管の延伸圧延においては前述の通り、孔型の変更は困難である。そこで、発明者らは、プラグミルでの延伸圧延中に被圧延管が孔型ロールおよびプラグと最適な条件で接して圧延される圧延条件について、FEA(有限要素解析)および圧延実験により検討した。
プラグミル圧延は、通常、これに先立つエロンゲータ圧延により減肉された略円形断面の中空素管を出発素材とし、1パス目の圧延後、再度入側へ戻して2パス目の圧延を行う。この際、各パスの圧延で管断面形状は略楕円形状となるが、発明者らは、FEAおよび圧延実験により、被圧延管とプラグおよびロールとの接触に特徴があることを見出した。
In the drawing and rolling of seamless steel pipes using a plug mill, as described above, it is difficult to change the hole shape. Therefore, the inventors studied FEA (finite element analysis) and rolling experiments on rolling conditions in which the rolled tube is rolled in contact with the hole-type roll and the plug under the optimum conditions during the drawing and rolling in the plug mill.
In the plug mill rolling, usually, a hollow shell having a substantially circular cross-section reduced by the elongator rolling prior to this is used as a starting material, after the first pass rolling, it is returned to the entry side and the second pass rolling is performed. At this time, the tube cross-sectional shape becomes substantially elliptical by rolling in each pass, but the inventors have found that the contact between the rolled tube and the plug and roll is characteristic by FEA and rolling experiments.
図1は、本発明の実施の形態を示す断面図(詳しくは圧延方向に垂直で且つロールバイト下死点を通る断面図)である。1は一対の孔型ロール、2はプラグである。
プラグミルの孔型ロール1のカリバーは、一般に、カリバー底点Zとパスライン中心点0(詳しくはパスライン中心線内のいずれか2点)を通る平面に対して左右対称であり、カリバー底点Zを孤長中心とする曲率半径R1の円弧CDをなすカリバー底部の両側に夫々曲率半径がR2(R2>R1)の円弧BC,DEをなすカリバー側面部が連接し、その外側に夫々逆曲がりの曲率半径R3(R3≪R2)の円弧AB、EFをなすフランジ部が連接する形状とされる。
FIG. 1 is a cross-sectional view showing an embodiment of the present invention (specifically, a cross-sectional view perpendicular to the rolling direction and passing through the bottom dead center of a roll bite). 1 is a pair of perforated rolls, and 2 is a plug.
The caliber of the plug
本発明に用いるカリバー形状が略円弧形状の孔型ロールとは、図1において、カリバー底部の曲率半径R1(即ちカリバー底部孔半径R1)の円弧CDの角度範囲θが90度〜150度のものをいう。
一方、プラグ2は、断面形状が円形状である。
上記プラグミルで、径が異なるプラグを用いて、前記略円形断面の中空素管に対し、1パス目の圧延およびこれに続き圧下位置90度変更して行う2パス目の圧延を行った場合の、各圧延における被圧延材とロール、プラグとの接触状態をFEAで求めた結果の例を図2〜5に示す。図2と図4は夫々プラグ径が適正で疵の発生がなく偏肉も小さい場合の1パス目と2パス目の例であり、図3と図5は夫々プラグ径が過大で内面疵が多く発生し偏肉も大きい場合の1パス目と2パス目の例である。これらの図において、10は被圧延管(但し管全周の1/4の部分)、K1は管外面のロール接触開始線、K2は同接触終了線、P1は管内面のプラグ接触開始線、P2は同接触終了線である。ロール接触開始線K1からロール接触終了線K2までの管外面領域がロールとの接触部であり、プラグ接触開始線P1からプラグ接触終了線P2までの管内面領域がプラグとの接触部である。
The caliber shape used in the present invention has a substantially arc-shaped hole-shaped roll in FIG. 1 in which the angle range θ of the arc CD of the radius of curvature R1 of the caliber bottom (that is, the caliber bottom hole radius R1) is 90 to 150 degrees. Say.
On the other hand, the plug 2 has a circular cross-sectional shape.
In the above plug mill, when the plugs having different diameters are used, the first round of rolling and the second round of rolling performed by changing the rolling position by 90 degrees are performed on the hollow shell having a substantially circular cross section. FIGS. 2 to 5 show examples of results obtained by FEA for the contact state between the material to be rolled, the roll, and the plug in each rolling. 2 and 4 are examples of the first pass and the second pass when the plug diameter is appropriate, wrinkles are not generated, and the uneven thickness is small. FIGS. 3 and 5 are respectively the plug diameters being excessive and the inner surface wrinkles. This is an example of the first pass and the second pass when many occurrences and uneven thickness are large. In these figures, 10 is a rolled pipe (however, 1/4 part of the entire circumference of the pipe), K1 is a roll contact start line on the outer surface of the pipe, K2 is a contact end line, P1 is a plug contact start line on the inner surface of the pipe, P2 is the contact end line. The tube outer surface region from the roll contact start line K1 to the roll contact end line K2 is a contact portion with the roll, and the tube inner surface region from the plug contact start line P1 to the plug contact end line P2 is a contact portion with the plug.
図2と図3を比較すると、プラグ径が大きい場合(図3)にはフランジ側近くでロールとの接触が早く始まり、接触長さも長くなっていることがわかる。この現象は、接触開始点付近で局所的に圧下が大きくなっていることを示しており、1パス目の圧延で偏肉や内面疵を誘発することに繋がる。さらに、図4と図5に示すように、2パス目の圧延ではプラグ径によって接触状態が大きく異なってくる。すなわち、プラグ径が小さく適正な場合(図4)には1パス目で未圧延部となるカリバー底部を集中的に接触しているのに対し、プラグ径が過大な場合(図5)にはカリバー底部に加えフランジ側の部分でも大きく接触している。したがって、プラグ径が過大な場合には、1パス目で強圧下された近傍に加え、1パス目の圧延でカリバー底部であった部分も再度圧下されることになり、偏肉や内面疵を誘発することになる。 When FIG. 2 and FIG. 3 are compared, when the plug diameter is large (FIG. 3), it can be seen that the contact with the roll starts early near the flange side, and the contact length is also long. This phenomenon indicates that the reduction is locally increased in the vicinity of the contact start point, which leads to inducing uneven thickness and inner surface flaws in the first pass rolling. Furthermore, as shown in FIG. 4 and FIG. 5, in the second pass rolling, the contact state varies greatly depending on the plug diameter. That is, when the plug diameter is small and appropriate (FIG. 4), the bottom of the caliber that will be the unrolled part is intensively contacted in the first pass, whereas when the plug diameter is excessive (FIG. 5). In addition to the caliber bottom, the flange side is also in great contact. Therefore, in the case where the plug diameter is excessive, in addition to the vicinity that was strongly reduced in the first pass, the portion that was the bottom of the caliber in the first pass rolling will be reduced again, and uneven thickness and inner surface flaws will be reduced. Will trigger.
上記のことから、被圧延管とロールおよびプラグとの接触状態を適正化することで偏肉や内面疵の発生を抑制することが可能であると考え、そのための圧延条件を、実験乃至FEAにより鋭意検討した。その結果、プラグ径Dpがロールカリバー底部孔半径R1および出側目標肉厚tと下記式(1)を満たすプラグを用いて圧延すると、偏肉や内面疵の発生を抑制することができることを見出した。
Dp≦2×R1−2×t+0.05×t (1)
From the above, it is considered that it is possible to suppress the occurrence of uneven thickness and inner surface flaws by optimizing the contact state between the rolled tube and the rolls and plugs, and the rolling conditions therefor are determined through experiments or FEA. We studied diligently. As a result, it is found that when the plug diameter Dp is rolled using a plug satisfying the roll caliber bottom hole radius R1, the outlet side target thickness t and the following formula (1), the occurrence of uneven thickness and inner surface flaws can be suppressed. It was.
Dp ≦ 2 × R1-2 × t + 0.05 × t (1)
なお、幾何学的に適正な範囲は、Dp≦2×R1−2×tであるが、更に付与されている項(+0.05×t)は、実際の管圧延における被圧延管の変形挙動を考慮して補正したものである。すなわち、被圧延管の肉厚が薄い場合には、被圧延管の変形が圧延機外でも生じ、管断面内のフランジ側で被圧延管とプラグとの接触が緩くなってフランジ側での肉厚圧下が小さくなるのに対し、厚肉管の場合には、管の剛性が高いため被圧延管が圧延機外で変形することなく、圧延前の形状を維持した状態でロールバイト内で圧延されるため、全周に亘って適正に圧下され易い、という傾向を考慮して補正したものである。 The geometrically appropriate range is Dp ≦ 2 × R1-2 × t, but the further added term (+ 0.05 × t) is the deformation behavior of the rolled tube in actual tube rolling. Is corrected in consideration of the above. That is, when the thickness of the tube to be rolled is thin, deformation of the tube to be rolled occurs outside the rolling mill, and the contact between the tube to be rolled and the plug becomes loose on the flange side in the tube cross section, and the wall on the flange side is reduced. In contrast to the reduced thickness reduction, in the case of a thick-walled tube, the tube is rolled in a roll bite while maintaining the shape before rolling without deforming the rolled tube outside the rolling mill because of the high rigidity of the tube. Therefore, the correction is made in consideration of the tendency that the entire circumference is easily reduced.
これにより、図2と図4に示したように、被圧延管とロールおよびプラグとの接触が適性となり、偏肉や内面疵の発生を抑制できる。
なお、プラグ径が小さすぎると管断面円周方向の肉厚分布が極端に不均一となる。この弊害は、使用するプラグ径を常に計算上適正な径とすることで回避できるが、そのためには微妙に径の異なる多数のプラグを備えておく必要がある。しかしながら、保有するプラグ径のピッチを細分化し過ぎることはコスト上昇などの観点からも現実的でない。したがって、工業的に保有し得るプラグ径のピッチを考慮すると、上記式(1)の右辺から0.2×tを引き去った値を下限値とするのが好ましい。
Thereby, as shown in FIG. 2 and FIG. 4, the contact between the tube to be rolled, the roll, and the plug becomes appropriate, and the occurrence of uneven thickness and inner surface flaws can be suppressed.
If the plug diameter is too small, the wall thickness distribution in the circumferential direction of the pipe cross section becomes extremely non-uniform. This adverse effect can be avoided by always setting the plug diameter to be used as a suitable diameter for calculation, but in order to do so, it is necessary to provide a large number of plugs having slightly different diameters. However, it is not realistic from the standpoint of cost increase to excessively subdivide the pitch of the plug diameter possessed. Therefore, in consideration of the plug diameter pitch that can be industrially held, it is preferable to set the lower limit value to a value obtained by subtracting 0.2 × t from the right side of the formula (1).
また、1基のプラグミルを用いて複数パスの延伸圧延を行う場合、前記圧下位置90度変更は、各パスとその次パスの間で被圧延管を管周方向に90度回転させることで行う。これの代わりに孔型ロールをパスライン中心線周りに90度回転させるのは設備が複雑となって不利である。また、圧延スケジューリングの段階で、前記次パスが式(1)を満たさないことがわかった場合、孔型ロール交換にて対応するのは時間がかかって圧延能率が低下するので、プラグ交換によって対応する。すなわち、当該次パス用のプラグを式(1)を満たすものに交換するのが良い。 Further, in the case where a plurality of passes are stretched and rolled using one plug mill, the reduction of the rolling position by 90 degrees is performed by rotating the rolled tube by 90 degrees in the pipe circumferential direction between each pass and the next pass. . Instead of this, it is disadvantageous to rotate the perforated roll 90 degrees around the center line of the pass line because the equipment becomes complicated. Also, if it is found at the rolling scheduling stage that the next pass does not satisfy the formula (1), it is time consuming to replace the hole-type roll and the rolling efficiency is reduced. To do. That is, it is preferable to replace the plug for the next path with one that satisfies the formula (1).
一般炭素鋼(JIS G3101 SS400該当鋼)の継目無鋼管を、プラグミル1基を用いた2パスの延伸圧延(1パス目と2パス目の間で被圧延管を管周方向に90度回転)により、次の圧延スケジュールで製造した。
・ビレット径:170mm、加熱温度:1250℃→穿孔(ピアサ)→エロンゲータ出側目標寸法:外径198mm×肉厚17.0mm(=プラグミル圧延の出発素材)
・プラグミル圧延:1パス目出側目標寸法(肉厚14.5mm)→2パス目出側目標寸法(外径193mm×肉厚13.0mm)
・プラグミル孔型ロールのR1=95.5mm
・プラグミルのプラグは、本発明例ではDp=162mmのプラグを使用し、比較例ではDp=164mmのプラグを使用した。
・圧延本数N:本発明例、比較例とも30本
偏肉の抑制効果は、長手中央での断面内偏肉率(周方向を16点に分割マークし、該測定点を超音波肉厚計で実測して、その(最大肉厚−最小肉厚)/平均肉厚を求めた)にて評価した。また、内面疵の発生防止効果は、管長手先後端の非定常部各0.5mを除く全長での0.3mm深さを超える疵の発生有無によって評価した。
A seamless steel pipe of general carbon steel (JIS G3101 SS400 applicable steel) is drawn and rolled in two passes using one plug mill (the rolled tube is rotated 90 degrees in the pipe circumferential direction between the first pass and the second pass). According to the following rolling schedule.
Billet diameter: 170 mm, heating temperature: 1250 ° C. → drilling (piercer) → elongator outlet side target dimensions: outer diameter 198 mm × thickness 17.0 mm (= starting material for plug mill rolling)
-Plug mill rolling: target dimension on the first pass (wall thickness 14.5 mm) → target dimension on the second pass (side diameter 193 mm x wall thickness 13.0 mm)
・ R1 = 95.5mm of plug mill hole type roll
The plug mill plug used was a Dp = 162 mm plug in the present invention, and a Dp = 164 mm plug was used in the comparative example.
-Number of rolling N: 30 in both the present invention example and the comparative example The effect of suppressing the thickness deviation is the thickness deviation ratio in the cross section at the longitudinal center (divided marks in the circumferential direction into 16 points, and the measurement point is an ultrasonic thickness gauge) And (the maximum thickness−minimum thickness) / average thickness was determined). Further, the effect of preventing the generation of inner surface flaws was evaluated by the presence or absence of wrinkles exceeding a depth of 0.3 mm in the entire length excluding 0.5 m each of the unsteady portion at the longitudinal end of the tube.
上記圧延スケジュールにおいて、プラグミル圧延1パス目で本発明に適合したプラグ径Dpは
Dp≦2×R1−2×t+0.05×t
=2×95.5−2×14.5+0.05×14.5=162.725
であり、プラグ径は162.725mm以下であれば本発明範囲であるが、プラグ径があまりに小さすぎると管断面円周方向の肉厚分布が極端に不均一になるため、上記式右辺から0.2×tを引き去った値を下限値とする。したがって、プラグ径162mmが本発明範囲であり、プラグ径164mmは径が過大である。一方、2パス目は、プラグ径164mmが適性範囲となる。
In the above rolling schedule, the plug diameter Dp suitable for the present invention in the first pass of the plug mill rolling is Dp ≦ 2 × R1-2 × t + 0.05 × t
= 2 x 95.5-2 x 14.5 + 0.05 x 14.5 = 162.725
However, if the plug diameter is 162.725 mm or less, it is within the scope of the present invention. However, if the plug diameter is too small, the wall thickness distribution in the circumferential direction of the tube cross section becomes extremely nonuniform. The value obtained by subtracting 2 × t is set as the lower limit. Therefore, the plug diameter of 162 mm is within the scope of the present invention, and the plug diameter of 164 mm is excessive. On the other hand, in the second pass, a plug diameter of 164 mm is an appropriate range.
圧延の結果、比較例では全数の偏肉率が10.7%であったのに対し、本発明例では8.2%と大幅に改善した。また、比較例では30本中13本で内面疵が発生したが、本発明例では全く発生しなかった。 As a result of rolling, the uneven thickness ratio of the total number in the comparative example was 10.7%, whereas in the example of the present invention, it was greatly improved to 8.2%. Further, in the comparative example, internal flaws occurred in 13 out of 30, but in the inventive example, no internal flaws occurred.
一般炭素鋼(JIS G4053 SCM435該当鋼)の継目無鋼管を、プラグミル1基を用いた2パスの延伸圧延(1パス目と2パス目の間で被圧延管を管周方向に90度回転)により、次の圧延スケジュールで製造した。
・ビレット径:300mm、加熱温度:1250℃→穿孔(ピアサ)→エロンゲータ出側目標寸法:外径329mm×肉厚11.5mm(=プラグミル圧延の出発素材)
・プラグミル圧延:1パス目出側目標寸法(肉厚9.3mm)→2パス目出側目標寸法(肉厚8.5mm)
・プラグミル孔型ロールのR1=160mm
・プラグミルのプラグは、比較例では1パス目と2パス目とで同じものを使用し、本発明例では1パス目と2パス目とでDpの異なるプラグを使用した。
(本発明例)1パス目用プラグのDp=300mm(≦2×R1−2×t+0.05×t=2×160−2×9.3+0.05×9.3=301.865)、2パス目用プラグのDp=302mm(≦2×R1−2×t+0.05×t=2×160−2×8.5+0.05×8.5=303.425)
(比較例)1パス目用プラグのDp=302mm(>2×R1−2×t+0.05×t=2×160−2×9.3+0.05×9.3=301.865)、2パス目用プラグのDp=302mm(≦2×R1−2×t+0.05×t=2×160−2×8.5+0.05×8.5=303.425)
・圧延本数N:本発明例、比較例とも30本
圧延後、前記と同じ方法で偏肉と内面疵の評価を行った結果、径302mmのプラグを連続使用した比較例では、30本中11本で疵が発生し、偏肉率が9.7%であったが、本発明例では疵の発生はなく、偏肉率も8.3%と大幅に改善した。
A seamless steel pipe made of general carbon steel (JIS G4053 SCM435 applicable steel) is drawn and rolled in two passes using one plug mill (the rolled tube is rotated 90 degrees in the pipe circumferential direction between the first pass and the second pass). According to the following rolling schedule.
Billet diameter: 300 mm, heating temperature: 1250 ° C. → drilling (piercer) → elongator outlet side target dimensions: outer diameter 329 mm × thickness 11.5 mm (= starting material for plug mill rolling)
・ Plug mill rolling: Target dimension on the first pass (thickness 9.3 mm) → Target dimension on the second pass (thickness 8.5 mm)
・ R1 = 160mm for plug mill hole type roll
In the comparative example, the same plug mill plug was used in the first pass and the second pass, and in the present invention example, plugs having different Dp were used in the first pass and the second pass.
(Example of the present invention) Dp of plug for the first pass = 300 mm (≦ 2 × R1-2 × t + 0.05 × t = 2 × 160-2 × 9.3 + 0.05 × 9.3 = 301.865), 2 Dp of the plug for the pass = 302 mm (≦ 2 × R1-2 × t + 0.05 × t = 2 × 160-2 × 8.5 + 0.05 × 8.5 = 303.425)
(Comparative example) Dp of plug for first pass = 302 mm (> 2 × R1-2 × t + 0.05 × t = 2 × 160-2 × 9.3 + 0.05 × 9.3 = 301.865), 2 passes Eye plug Dp = 302 mm (≦ 2 × R1-2 × t + 0.05 × t = 2 × 160-2 × 8.5 + 0.05 × 8.5 = 303.425)
-Rolling number N: 30 for both the inventive example and the comparative example After rolling, the uneven thickness and the inner surface flaw were evaluated in the same manner as described above. As a result, in the comparative example in which a plug having a diameter of 302 mm was continuously used, 11 out of 30 Although wrinkles were generated in the books and the uneven thickness ratio was 9.7%, no wrinkles were generated in the examples of the present invention, and the uneven thickness ratio was greatly improved to 8.3%.
1 孔型ロール
2 プラグ
10 被圧延管
K1: ロール接触開始線
K2: ロール接触終了線
P1: プラグ接触開始線
P2: プラグ接触終了線
1 Hole type roll 2
Claims (2)
Dp≦2×R1−2×t+0.05×t (1)
ここで、Dp:ロールバイト下死点におけるプラグ径〔mm〕、
R1:カリバー底部孔半径〔mm〕、t:出側目標板厚〔mm〕 A hollow blank tube having a circular or elliptical cross section is used as a starting material, a pair of perforated rolls whose caliber shape for processing the outer surface side between the rolled parts is a substantially arc shape, and a cross section for processing the inner surface side is circular. A plurality of passes are hot-rolled in a plug mill having a plug, and at that time, the rolling position is changed by 90 degrees to shift the caliber bottom contact position of the rolled tube by 90 degrees between each pass and the next pass. In the manufacturing method of a seamless steel pipe, the rolling process is performed so that it may satisfy | fill following formula (1) by each pass, The manufacturing method of the seamless steel pipe characterized by the above-mentioned.
Dp ≦ 2 × R1-2 × t + 0.05 × t (1)
Here, Dp: plug diameter [mm] at the bottom dead center of the roll bite,
R1: Caliber bottom hole radius [mm], t: Delivery side target plate thickness [mm]
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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KR101680805B1 (en) * | 2015-05-21 | 2016-11-29 | 한국생산기술연구원 | Drawing method for seamless tube |
CN113909305A (en) * | 2021-09-22 | 2022-01-11 | 江苏天淮钢管有限公司 | Hot continuous rolling production method of 530 mm large-caliber seamless steel pipe |
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JPS54102270A (en) * | 1978-01-30 | 1979-08-11 | Sumitomo Metal Ind Ltd | Controlling method for rolling reduction in pipe forming mill |
JPS5794409A (en) * | 1980-12-04 | 1982-06-11 | Kawasaki Steel Corp | Method for removing thickness deviation of seamless steel pipe |
US5412974A (en) * | 1992-04-16 | 1995-05-09 | Mannesmann Aktiengesellschaft | Method of producing seamless pipes utilizing a plug rolling procedure |
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JPS54102270A (en) * | 1978-01-30 | 1979-08-11 | Sumitomo Metal Ind Ltd | Controlling method for rolling reduction in pipe forming mill |
JPS5794409A (en) * | 1980-12-04 | 1982-06-11 | Kawasaki Steel Corp | Method for removing thickness deviation of seamless steel pipe |
US5412974A (en) * | 1992-04-16 | 1995-05-09 | Mannesmann Aktiengesellschaft | Method of producing seamless pipes utilizing a plug rolling procedure |
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Publication number | Priority date | Publication date | Assignee | Title |
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KR101680805B1 (en) * | 2015-05-21 | 2016-11-29 | 한국생산기술연구원 | Drawing method for seamless tube |
CN113909305A (en) * | 2021-09-22 | 2022-01-11 | 江苏天淮钢管有限公司 | Hot continuous rolling production method of 530 mm large-caliber seamless steel pipe |
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