JP2017013102A - Manufacturing method of seamless steel pipe - Google Patents
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- JP2017013102A JP2017013102A JP2015134182A JP2015134182A JP2017013102A JP 2017013102 A JP2017013102 A JP 2017013102A JP 2015134182 A JP2015134182 A JP 2015134182A JP 2015134182 A JP2015134182 A JP 2015134182A JP 2017013102 A JP2017013102 A JP 2017013102A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 67
- 239000010959 steel Substances 0.000 title claims abstract description 67
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 25
- 238000005096 rolling process Methods 0.000 claims abstract description 63
- 239000002826 coolant Substances 0.000 claims abstract description 42
- 238000005507 spraying Methods 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims abstract description 10
- 239000007787 solid Substances 0.000 claims abstract description 5
- 238000002347 injection Methods 0.000 claims description 31
- 239000007924 injection Substances 0.000 claims description 31
- 239000000498 cooling water Substances 0.000 claims description 12
- 238000009826 distribution Methods 0.000 abstract description 14
- 238000010791 quenching Methods 0.000 description 13
- 230000000171 quenching effect Effects 0.000 description 11
- 238000001816 cooling Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 4
- 239000007921 spray Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 238000012545 processing Methods 0.000 description 2
- 239000002436 steel type Substances 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000003491 array Methods 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
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Abstract
Description
本発明は、熱間で中空素管を延伸圧延して継目無鋼管を製造するにあたって、均一な組織を有する継目無鋼管の製造方法に関するものである。 The present invention relates to a method for producing a seamless steel pipe having a uniform structure when a hollow shell is drawn and rolled hot to produce a seamless steel pipe.
従来から、継目無鋼管を製造するにあたって、中実のビレットを加熱して穿孔圧延を行ない、得られた中空素管を延伸圧延機で延伸圧延して継目無鋼管を製造する技術が実用化されている。延伸圧延機は、中空素管の内部にプラグを挿入して、中空素管の外側の圧延ロールと内側のプラグとの間で圧下を加えて、所定の外径、肉厚を有する継目無鋼管を製造、あるいはプラグに代えて長尺のバーを用いて所望の継目無鋼管を製造するものである。 Conventionally, when manufacturing seamless steel pipes, a technology has been put into practical use in which a solid billet is heated to perform piercing and rolling, and the obtained hollow shell is drawn and rolled with a drawing mill. ing. A drawing mill is a seamless steel pipe having a predetermined outer diameter and thickness by inserting a plug into the hollow shell and applying a reduction between the outer roll and the inner plug of the hollow shell. Or a desired seamless steel pipe is produced using a long bar instead of a plug.
一般的な継目無鋼管の製造ラインは、延伸圧延機（たとえばエロンゲータ、プラグミル、あるいはマンドレルミル等）から継目無鋼管をサイザー、ストレッチレデューサに送給して、外径や肉厚の寸法精度を高めるように構成されているが、サイザー等ではプラグ等の内面工具を使用しない。以下では、たとえばエロンゲータやプラグミル、あるいはマンドレルミルのように、プラグ等の内面工具を用いて中空素管の延伸を行なう圧延機を延伸圧延機と記す。 In general seamless steel pipe production lines, seamless steel pipes are fed to sizers and stretch reducers from stretch rolling mills (eg, elongator, plug mill, mandrel mill, etc.) to improve the dimensional accuracy of outer diameter and wall thickness. However, a sizer or the like does not use an internal tool such as a plug. Hereinafter, a rolling mill that stretches a hollow shell using an internal tool such as a plug, such as an elongator, a plug mill, or a mandrel mill, will be referred to as a stretching mill.
そして、様々な用途に応じて規定される特性（たとえば機械的特性等）を満足するために、成分を好適な範囲に調整したビレットを素材として用いて、継目無鋼管を製造している。しかし近年、厳しい環境で使用できる継目無鋼管の必要性が高まっており、ビレットの成分を調整しても得ることができないほどの高強度の継目無鋼管が求められている。そのような高強度の継目無鋼管を製造するために、製造ラインの出側で熱処理（たとえば焼入れ、焼戻し等）を行なう技術が検討されている。 And in order to satisfy the characteristic (for example, mechanical characteristic etc.) prescribed | regulated according to various uses, the seamless steel pipe is manufactured using the billet which adjusted the component to the suitable range as a raw material. However, in recent years, there is an increasing need for seamless steel pipes that can be used in harsh environments, and there is a demand for seamless steel pipes that are so strong that they cannot be obtained by adjusting billet components. In order to manufacture such a high-strength seamless steel pipe, a technique of performing a heat treatment (for example, quenching, tempering, etc.) on the exit side of the production line has been studied.
継目無鋼管の焼入れを行なう際には、継目無鋼管をオーステナイト域まで加熱し、引き続き急冷（たとえば冷却水槽に浸漬）する。あるいは、熱間で製造する継目無鋼管は、製造ラインから排出される時には高温であることから、製造ラインの出側で直ちに急冷する技術も開発されている。その後、所望の強度を得るために焼戻しを行なう。いずれの焼入れにおいても、ビレットの穿孔圧延および中空素管の延伸圧延によって継目無鋼管に形成された圧延方向に展伸した組織が、焼入れ後の組織の均一化に寄与することが知られている。焼入れで形成された組織が均一であれば、焼戻し後も均一な組織を有する継目無鋼管が得られる。 When quenching the seamless steel pipe, the seamless steel pipe is heated to the austenite region and then rapidly cooled (for example, immersed in a cooling water bath). Or since the seamless steel pipe manufactured hot is high temperature when discharged | emitted from a production line, the technique of quenching immediately on the exit side of a production line is also developed. Thereafter, tempering is performed to obtain a desired strength. In any quenching, it is known that the structure expanded in the rolling direction formed in the seamless steel pipe by the piercing and rolling of the billet and the drawing and rolling of the hollow shell contributes to the homogenization of the structure after quenching. . If the structure formed by quenching is uniform, a seamless steel pipe having a uniform structure even after tempering can be obtained.
しかし、焼入れ前の継目無鋼管の組織が圧延方向に展伸した組織であっても、継目無鋼管の温度が不均一であれば、焼入れ後に必ずしも均一な組織は得られない。 However, even if the structure of the seamless steel pipe before quenching is a structure expanded in the rolling direction, if the temperature of the seamless steel pipe is non-uniform, a uniform structure is not necessarily obtained after quenching.
たとえば特許文献１〜３に、加熱された継目無鋼管を冷却水槽に浸漬して焼入れを行なう技術が開示されている。これらの技術は、いずれも、温度が室温まで低下した継目無鋼管を加熱して急冷する場合のみならず、製造ラインから排出された高温の継目無鋼管を直ちに急冷（以下、直接焼入れという）する場合にも適用できる。しかも、圧延方向に展伸した組織を有する継目無鋼管の焼入れが可能である。 For example, Patent Documents 1 to 3 disclose techniques for quenching by immersing a heated seamless steel pipe in a cooling water tank. Both of these technologies not only heat and rapidly cool a seamless steel pipe whose temperature has dropped to room temperature, but also immediately quench (hereinafter referred to as direct quenching) a high-temperature seamless steel pipe discharged from the production line. It can also be applied to cases. Moreover, it is possible to quench the seamless steel pipe having a structure expanded in the rolling direction.
しかし従来の継目無鋼管の製造技術では、穿孔圧延機（いわゆるピアサー）から延伸圧延機を経てサイザーに至る工程で、継目無鋼管の温度にバラツキが生じるのは避けられない。 However, in the conventional seamless steel pipe manufacturing technology, it is inevitable that the temperature of the seamless steel pipe varies in the process from the piercing and rolling mill (so-called piercer) through the drawing mill to the sizer.
そこで継目無鋼管の温度差を解消して、均一な温度分布を有する継目無鋼管を製造ライン（とりわけ延伸圧延機）から排出する技術が検討されている。 Therefore, a technique for eliminating the temperature difference of the seamless steel pipe and discharging the seamless steel pipe having a uniform temperature distribution from the production line (particularly, a drawing mill) has been studied.
たとえば特許文献４には、中実のビレットを穿孔する際に、穿孔された側の内面に冷却水を噴射して、穿孔圧延機から排出される中空素管の温度を均一に分布させる技術が開示されている。穿孔圧延機から排出された中空素管は、延伸圧延機にてプラグを挿入して、延伸圧延を行なう場合、そのプラグは冷材であるから、延伸圧延の開始時にはプラグの温度は低いが、延伸圧延中に中空素管からの伝熱効果によってプラグの温度が上昇する。一方で、中空素管は、延伸圧延の開始時には温度が高いが、延伸圧延中に放熱効果によって温度が低下する。つまり、延伸圧延の開始から終了の間にプラグと中空素管の温度が変化し、その結果、製造ラインから排出される継目無鋼管の長手方向の温度分布が不均一になる。
For example,
温度分布が不均一な継目無鋼管に直接焼入れを行なうと、均一な組織が得られず、その結果、継目無鋼管の特性にバラツキが生じる。 If a seamless steel pipe with a non-uniform temperature distribution is directly quenched, a uniform structure cannot be obtained, and as a result, the characteristics of the seamless steel pipe vary.
温度分布が不均一であっても、継目無鋼管を一旦室温まで冷却した後に、加熱炉等で加熱して焼入れを行なうと、焼入れに起因する特性のバラツキは抑制できる。しかし、継目無鋼管の生産性の低下や製造コストの上昇を招くばかりでなく、冷却過程で継目無鋼管の曲がりが発生するという問題が生じる。 Even if the temperature distribution is not uniform, if the seamless steel pipe is once cooled to room temperature and then quenched by heating in a heating furnace or the like, variations in characteristics due to quenching can be suppressed. However, there is a problem that not only the productivity of the seamless steel pipe is lowered and the manufacturing cost is increased, but also the bending of the seamless steel pipe occurs in the cooling process.
本発明は、従来の技術の問題点を解消し、延伸圧延によって均一な温度分布を有する継目無鋼管を得て、ひいては均一な組織を有する継目無鋼管を製造する方法を提供することを目的とする。 An object of the present invention is to provide a method for solving the problems of the prior art, obtaining a seamless steel pipe having a uniform temperature distribution by drawing and rolling, and thus producing a seamless steel pipe having a uniform structure. To do.
本発明者は、プラグを用いる延伸圧延機で実験を行ない、延伸圧延された継目無鋼管の温度を測定して、その温度分布を調査した。そして、
(a)測定された温度の最大値と最小値の差（以下、温度偏差という）は、継目無鋼管の外面よりも、内面の方が大きい、
(b)継目無鋼管の内面の温度偏差は、延伸圧延におけるプラグと中空素管の温度変化が主要な原因である
ということを見出した。
The inventor conducted an experiment with a drawing mill using a plug, measured the temperature of the drawn seamless steel pipe, and investigated the temperature distribution. And
(a) The difference between the maximum and minimum measured temperatures (hereinafter referred to as temperature deviation) is greater on the inner surface than on the outer surface of the seamless steel pipe.
(b) The temperature deviation of the inner surface of the seamless steel pipe was found to be mainly caused by temperature changes of the plug and the hollow shell in the drawing rolling.
そこで本発明者は、延伸圧延における中空素管の温度変化、およびその内部に挿入されるプラグの温度変化が、延伸圧延機から排出される継目無鋼管の内面の温度偏差に及ぼす影響について、詳細に検討した。その結果、
(A)中空素管の先端を延伸圧延するときは、中空素管の温度は高いが、プラグの温度は低い、
(B)中空素管の後端を延伸圧延するときは、中空素管は放熱して温度が低下する一方で、プラグは中空素管からの伝熱で温度が上昇する、
(C)中空素管とプラグの温度の変化は、穿孔圧延においても同様の現象が認められる、
(D)穿孔圧延にて中空素管の内面に生じた温度偏差が、延伸圧延によって、さらに大きくなる
ということが判明した。
Therefore, the present inventor details the influence of the temperature change of the hollow shell in the drawing rolling and the temperature change of the plug inserted therein on the temperature deviation of the inner surface of the seamless steel pipe discharged from the drawing mill. It was examined. as a result,
(A) When the end of the hollow shell is drawn and rolled, the temperature of the hollow shell is high, but the temperature of the plug is low,
(B) When the rear end of the hollow shell is stretch-rolled, the hollow shell is dissipated to lower the temperature, while the plug rises due to heat transfer from the hollow shell,
(C) The change in the temperature of the hollow shell and plug is also observed in piercing and rolling,
(D) It has been found that the temperature deviation generated on the inner surface of the hollow shell by piercing and rolling is further increased by drawing and rolling.
次に、延伸圧延機から排出される継目無鋼管の内面の温度偏差を防止する技術について検討を重ねて、
(E)延伸圧延にてプラグの温度を一定に保つのは困難である、
(F)延伸圧延にて、プラグを支持するプラグバーから冷却媒体（たとえば冷却水等）を延伸圧延直後、中空素管の内面に吹付けて、温度の高い部位を冷却すれば、中空素管の温度偏差を解消できる、
(G)穿孔圧延で得られた中空素管の内面の温度を、その寸法や鋼種に応じて予め測定しておき、その測定結果に基づいて延伸圧延直後、冷却媒体の吹付けを調整しながら延伸圧延を行なうことによって、継目無鋼管の温度分布の均一性がさらに向上する、
(H)延伸圧延で得られた継目無鋼管の内面の温度分布は、上記(G)の温度分布と同様の傾向を示す
という知見を得た。
Next, repeated examination on the technology to prevent the temperature deviation of the inner surface of the seamless steel pipe discharged from the drawing mill,
(E) It is difficult to keep the plug temperature constant by drawing and rolling.
(F) If the cooling medium (for example, cooling water) is blown from the plug bar that supports the plug to the inner surface of the hollow shell immediately after stretching and the hot part is cooled, The temperature deviation of
(G) The temperature of the inner surface of the hollow shell obtained by piercing and rolling is measured in advance according to its dimensions and steel type, and after adjusting the spraying of the cooling medium immediately after stretching rolling based on the measurement result By drawing and rolling, the uniformity of the temperature distribution of the seamless steel pipe is further improved.
(H) It was found that the temperature distribution on the inner surface of the seamless steel pipe obtained by drawing rolling shows the same tendency as the temperature distribution in (G) above.
本発明は、このような知見に基づいてなされたものである。 The present invention has been made based on such knowledge.
すなわち本発明は、加熱された中実のビレットを穿孔して中空素管とした後、プラグを用いる延伸圧延機で中空素管を延伸して継目無鋼管を製造する継目無鋼管の製造方法において、中空素管の内部にプラグを挿入して延伸圧延し、かつ延伸圧延直後の中空素管の内面に冷却媒体を吹付けながら延伸を行なう継目無鋼管の製造方法である。 That is, the present invention relates to a method for producing a seamless steel pipe, in which a heated solid billet is punched to form a hollow shell, and then the hollow shell is drawn by a drawing mill using a plug to produce a seamless steel pipe. This is a method for producing a seamless steel pipe, in which a plug is inserted into the hollow shell and drawn and rolled, and the drawing is performed while spraying a cooling medium onto the inner surface of the hollow shell immediately after the drawing and rolling.
本発明の製造方法においては、延伸圧延機のプラグバーの内部に冷却媒体の流路を設けて、プラグバーの側面に設けた噴射口から延伸圧延直後の中空素管に冷却媒体を吹付けることが好ましい。また、その流路を介して供給される冷却媒体を、プラグバーの先端に装着される穿孔プラグの底部に設けた噴射溝から吹付けても良い。 In the production method of the present invention, a cooling medium flow path is provided inside the plug bar of the drawing mill, and the cooling medium is sprayed from the injection port provided on the side surface of the plug bar to the hollow shell immediately after the drawing and rolling. Is preferred. Further, the cooling medium supplied through the flow path may be sprayed from an injection groove provided at the bottom of a perforated plug attached to the tip of the plug bar.
冷却媒体を吹付けについては、穿孔圧延機の出側で中空素管の内面温度を予め測定しておき、内面温度の測定値に基づいて冷却媒体の吹付け開始と吹付け停止、および流量、圧力を調整することが好ましい。冷却媒体は、冷却水を使用することが好ましい。 For spraying the cooling medium, the inner surface temperature of the hollow shell is measured in advance on the exit side of the piercing mill, and the cooling medium spraying start and stop, and the flow rate based on the measured value of the inner surface temperature, It is preferable to adjust the pressure. It is preferable to use cooling water as the cooling medium.
本発明によれば、延伸圧延によって均一な温度分布を有する継目無鋼管を得ることができ、ひいては均一な組織を有する継目無鋼管を製造できるので、産業上格段の効果を奏する。 According to the present invention, a seamless steel pipe having a uniform temperature distribution can be obtained by drawing and rolling, and as a result, a seamless steel pipe having a uniform structure can be manufactured.
本発明は延伸圧延後の中空素管の温度を均一化することが目的であるため、冷却媒体は延伸圧延中ではなく、延伸圧延の直後から、それ以上加工熱が入らない状態で吹き付ける必要がある。延伸圧延の加工熱が加わり続けている延伸圧延中では、十分かつ安定した冷却ができないからである。なお、延伸圧延の直後とは、中空素管がプラグから離れた直後を意味する。 The purpose of the present invention is to equalize the temperature of the hollow shell after drawing and rolling, so the cooling medium is not being drawn and must be blown immediately after drawing and in a state where no further processing heat is applied. is there. This is because sufficient and stable cooling cannot be performed during the drawing and rolling in which the processing heat of the drawing and rolling is continuously applied. The term “immediately after drawing and rolling” means immediately after the hollow shell is separated from the plug.
図１は、本発明を適用する延伸圧延機の例を模式的に示す説明図であり、中空素管１を断面図として示す。中空素管１の外側の圧延ロールは、図示を省略する。図１中の矢印Ａは、中空素管１の進行方向を示す。 FIG. 1 is an explanatory view schematically showing an example of a drawing mill to which the present invention is applied, and shows a hollow shell 1 as a cross-sectional view. Illustration of the rolling roll outside the hollow shell 1 is omitted. An arrow A in FIG. 1 indicates the traveling direction of the hollow shell 1.
図１(a)は、プラグバー２の側面に設けた噴射口３から、延伸圧延直後の中空素管１の内面に冷却媒体４（たとえば冷却水等）を吹付ける例である。プラグバー２の内部には冷却媒体４の流路が設けられており、その流路を介して供給される冷却媒体４を噴射口３から吹付ける。なお、冷却媒体４の流路については後述する。
FIG. 1A shows an example in which a cooling medium 4 (for example, cooling water) is sprayed from the
図１(a)には２個の噴射口３を設ける例を示したが、噴射口３の個数は特に限定しない。ただし、噴射口３の個数が少なすぎると、延伸圧延機から排出される継目無鋼管の内面の温度偏差を防止する効果が得られない。一方で、噴射口の個数が多すぎると、プラグバー２の強度が低下して、延伸圧延に支障を来す。したがって噴射口３の個数は、円周方向（すなわちプラグバー２の軸芯に垂直な断面内）に２〜４個の範囲内が好ましい。
Although FIG. 1 (a) shows an example in which two
そして、その円周方向に配置された噴射口３の列を、プラグバー２の軸芯に平行な方向に２列以上配列しても良い。その場合は、プラグバーや中空素管の寸法等に応じて、噴射口３の列数を設定する。
Then, two or more rows of the
複数個の噴射口３を設ける場合は、線状に配列（たとえば長手方向に配列、円周方向に配列、螺旋状に配列）するのが好ましい。あるいは、その線状の配列を２列以上設けても良い。いずれの配列においても、噴射口３を等間隔で線状に設けることが好ましい。
When a plurality of
図１(b)は、プラグ５の底部に設けた噴射溝６から中空素管１の内面に冷却媒体４を吹付ける例である。図１(b)には２個の噴射溝６を設ける例を示したが、噴射溝６の個数は特に限定しない。ただし、噴射溝６の個数が少なすぎると、延伸圧延を終了して延伸圧延機から排出される継目無鋼管の内面の温度偏差を防止する効果が得られない。一方で、噴射溝６の個数が多すぎると、プラグ５の強度が低下して、延伸圧延に支障を来す。したがって、噴射溝６の個数は２〜５個の範囲内が好ましい。
FIG. 1B shows an example in which the
複数個の噴射溝６を設ける場合は、プラグ５の軸芯から放射状に、かつ等間隔（すなわちプラグ円周方向に等しい角度）で設けることが好ましい。
When a plurality of
また、プラグバー２の側面に設けた噴射口３と、プラグ５の底部に設けた噴射溝６との両方から冷却媒体４を吹付けても良い（図示せず）。
Further, the cooling medium 4 may be sprayed from both the
冷却媒体４は、空気等の気体を使用しても良いが、液体を使用すれば冷却能力が高まるので好ましい。特に、冷却水を使用すれば安価であるから、継目無鋼管の製造コストの削減および品質の向上（すなわち組織の均一性）を両立することが可能となる。
As the
延伸圧延を行なうにあたって、中空素管の寸法や鋼種等に応じて、予め内面の温度を測定しておく。使用する温度計は、中空素管の内面あるいは継目無鋼管の内面の温度を測定できるものであれば良く、特に限定しない。ただし、延伸圧延機の稼働中に温度を測定する必要があることから、非接触式の測定技術（たとえば放射温度計、画像解析等）を採用することが好ましい。 In performing the drawing and rolling, the inner surface temperature is measured in advance according to the dimensions of the hollow shell, the steel type, and the like. The thermometer to be used is not particularly limited as long as it can measure the temperature of the inner surface of the hollow shell or the inner surface of the seamless steel tube. However, since it is necessary to measure the temperature during operation of the drawing mill, it is preferable to employ a non-contact measurement technique (for example, a radiation thermometer, image analysis, etc.).
そして、その温度が高い部位に冷却媒体を吹付けるように、吹付け開始と吹付け停止のタイミングを設定し、さらに、冷却媒体の吹付け量や吹付け圧力を設定して、延伸圧延を行なう。 And the timing of spraying start and spraying stop is set so that the cooling medium is sprayed to the part where the temperature is high, and further, the amount of cooling medium spraying and the spraying pressure are set, and the stretch rolling is performed. .
このようにして延伸圧延を行なうことによって、延伸圧延機から排出される継目無鋼管の内面の温度偏差を防止できる。とりわけ、樽型の圧延ロールを用いて傾斜式圧延を行なう延伸圧延機（たとえばエロンゲータ等）では、中空素管１が管軸を回転軸として回転するので、内面の温度分布の均一性がさらに向上する。 By performing the drawing and rolling in this way, it is possible to prevent temperature deviation of the inner surface of the seamless steel pipe discharged from the drawing and rolling mill. In particular, in a drawing mill (e.g., an elongator) that performs inclined rolling using a barrel-type rolling roll, the hollow shell 1 rotates with the tube axis as the rotation axis, so the uniformity of the temperature distribution on the inner surface is further improved. To do.
図２は、冷却媒体の流路を備えたプラグバーの例を模式的に示す断面図である。冷却媒体４の流路22は、プラグバー本体21の外周（図２(a)参照）に設けても良いし、プラグバー本体21の内部（図２(b)参照）に設けても良い。いずれも、噴射口３から冷却媒体４を吹付けることができ、かつプラグバー本体21を冷却する効果が得られ、さらにプラグ５を冷却する効果も得られる。また、プラグ５の底部に設けた噴射溝から冷却媒体４を吹付ける場合（図示せず）においても、流路22から噴射溝を通って、冷却媒体４を吹付けることは可能である。
FIG. 2 is a cross-sectional view schematically showing an example of a plug bar having a cooling medium flow path. The
このようにして噴射口３および／または噴射溝６から冷却媒体４を中空素管１の内面に吹付けながら、延伸圧延を行なう。
In this way, stretching and rolling are performed while spraying the cooling medium 4 from the
＜実施例１＞
ピアサーを用いて、SUS420J1相当のビレット（いわゆる13Cr鋼、長さ350mm、温度1250℃）の穿孔圧延を行ない、長さ875mmの中空素管とした。得られた中空素管の内面の温度を、ピアサーの出側で数秒以内に、進行方向の先端と後端、および長さ方向に１／４、１／２、３／４の位置で測定した。中空素管の内面の温度は、非接触式で撮影した熱画像を解析して求めた。その結果、中空素管の中央部（すなわち長さ方向に１／２の位置）以降にて内面の温度が急激に上昇しており、温度偏差は32℃であった。
<Example 1>
Using a piercer, a billet (so-called 13Cr steel, length 350 mm, temperature 1250 ° C.) equivalent to SUS420J1 was pierced and rolled to obtain a hollow tube having a length of 875 mm. The temperature of the inner surface of the obtained hollow shell was measured within a few seconds on the exit side of the piercer at the front and rear ends in the traveling direction, and at 1/4, 1/2, and 3/4 positions in the length direction. . The temperature of the inner surface of the hollow shell was obtained by analyzing a thermal image taken in a non-contact manner. As a result, the temperature of the inner surface increased rapidly after the central portion of the hollow shell (that is, a half position in the length direction), and the temperature deviation was 32 ° C.
続いて、噴射溝から冷却媒体を吹付ける構成のプラグとプラグバー（図１(b)参照）を使用して、上記の長さ875mmの中空素管の延伸圧延を行なった。その際、冷却媒体である冷却水をプラグの後面から噴射して中空素管の中央部以降の内面に吹付けるようにした（総吹付け量５Ｌ、吹付け圧力１MPa）。これを発明例１とする。 Subsequently, using the plug and the plug bar (see FIG. 1 (b)) configured to spray the cooling medium from the injection groove, the above hollow tube having a length of 875 mm was stretch-rolled. At that time, cooling water as a cooling medium was sprayed from the rear surface of the plug and sprayed to the inner surface after the central portion of the hollow shell (total spray amount 5 L, spray pressure 1 MPa). This is referred to as Invention Example 1.
発明例１においても、得られた中空素管の内面の温度を測定した結果、温度偏差は５℃であった。 Also in Invention Example 1, as a result of measuring the temperature of the inner surface of the obtained hollow shell, the temperature deviation was 5 ° C.
一方、従来例としてプラグの後面から冷却水を噴射せず、空冷のまま延伸圧延したところ、温度偏差は40℃に拡大した。 On the other hand, as a conventional example, when the rolling water was stretched and rolled with air cooling without spraying the cooling water from the rear surface of the plug, the temperature deviation expanded to 40 ° C.
つまり本発明を適用することによって、冷却媒体を使用しない従来の延伸圧延と比べて、中空素管の温度偏差が大幅に減少することが確かめられて、均一な温度分布を有する継目無鋼管が得られることが分かった。 In other words, by applying the present invention, it has been confirmed that the temperature deviation of the hollow shell tube is greatly reduced as compared with the conventional stretch rolling without using a cooling medium, and a seamless steel tube having a uniform temperature distribution is obtained. I found out that
＜実施例２＞
非調質一般鋼のビレットの穿孔圧延を行なった後、中空素管をさらに延伸圧延した。その際、噴射口から冷却媒体を吹付ける構成のプラグとプラグバー（図１(a)参照）を使用し、冷却媒体である冷却水をプラグバーから中空素管の中央部以降の内面に吹付けるように調整した。これを発明例２とする。
<Example 2>
After piercing and rolling a billet of non-tempered general steel, the hollow shell was further drawn and rolled. At that time, a plug and a plug bar (see FIG. 1 (a)) configured to blow a cooling medium from the injection port are used, and cooling water as a cooling medium is blown from the plug bar to the inner surface of the hollow shell after the center. Adjusted to attach. This is referred to as Invention Example 2.
発明例２においても、得られた中空素管の内面の温度を測定した結果、温度偏差は10℃であった。 Also in Invention Example 2, as a result of measuring the temperature of the inner surface of the obtained hollow shell, the temperature deviation was 10 ° C.
一方、従来例としてプラグバーから冷却水を噴射せず、空冷のまま延伸圧延したところ、温度偏差は38℃に拡大した。 On the other hand, as a conventional example, when the rolling water was drawn and rolled without cooling water being injected from the plug bar, the temperature deviation expanded to 38 ° C.
つまり本発明を適用することによって、冷却媒体を使用しない従来の延伸圧延と比べて、中空素管の温度偏差が大幅に減少することが確かめられて、均一な温度分布を有する継目無鋼管が得られることが分かった。 In other words, by applying the present invention, it has been confirmed that the temperature deviation of the hollow shell tube is greatly reduced as compared with the conventional stretch rolling without using a cooling medium, and a seamless steel tube having a uniform temperature distribution is obtained. I found out that
さらに、発明例２の中空素管から圧延方向の先端側から２個、後端側から２個（合計４個）の試験片を採取して引張試験を行なったところ、引張強度の最大値と最小値の差（以下、強度偏差という）は15MPaであった。 Further, when two tensile specimens were collected from the hollow shell of Invention Example 2 from the front end side in the rolling direction and two specimens from the rear end side (total of four specimens) were subjected to a tensile test, the maximum tensile strength was obtained. The difference between the minimum values (hereinafter referred to as intensity deviation) was 15 MPa.
一方で、従来の冷却媒体の吹付けを行なわない場合の引張試験のデータを解析したところ、非調質一般鋼の中空素管の強度偏差は70MPa程度であった。 On the other hand, when analyzing the data of the tensile test in the case where the conventional cooling medium was not sprayed, the strength deviation of the hollow shell of the non-heat treated general steel was about 70 MPa.
つまり、発明例２の中空素管の強度偏差は従来よりも大幅に減少しており、本発明を適用することによって、均一な組織を有する中空素管が得られることが確かめられた。 That is, the strength deviation of the hollow shell of Inventive Example 2 is greatly reduced as compared with the conventional case, and it was confirmed that a hollow shell having a uniform structure can be obtained by applying the present invention.
１ 中空素管
２ プラグバー
21 プラグバー本体
22 冷却媒体の流路
３ 噴射口
４ 冷却媒体
５ プラグ
６ 噴射溝
1
21 Plug bar body
22
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Cited By (3)
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| WO2019107443A1 (en) | 2017-11-29 | 2019-06-06 | 日本製鉄株式会社 | Piercing machine, mandrel bar, and method for manufacturing seamless metallic tube using same |
| WO2019107418A1 (en) | 2017-11-29 | 2019-06-06 | 日本製鉄株式会社 | Piercing machine and method for manufacturing seamless metallic tube using same |
| CN110153190A (en) * | 2019-06-13 | 2019-08-23 | 南通市嘉业机械制造有限公司 | A kind of high stable piercing plug for seamless steel tubes |
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| JP2012139697A (en) * | 2010-12-28 | 2012-07-26 | Jfe Steel Corp | Seamless steel pipe rolling device and rolling method |
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| JPH0523711A (en) * | 1991-07-22 | 1993-02-02 | Sumitomo Metal Ind Ltd | Manufacture of hot seamless steel tube |
| JPH1043804A (en) * | 1996-08-05 | 1998-02-17 | Nkk Corp | Forced cooling type plug and its cooling method |
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Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2019107443A1 (en) | 2017-11-29 | 2019-06-06 | 日本製鉄株式会社 | Piercing machine, mandrel bar, and method for manufacturing seamless metallic tube using same |
| WO2019107418A1 (en) | 2017-11-29 | 2019-06-06 | 日本製鉄株式会社 | Piercing machine and method for manufacturing seamless metallic tube using same |
| CN111432948A (en) * | 2017-11-29 | 2020-07-17 | 日本制铁株式会社 | Piercing machine, mandrel bar, and method for producing seamless metal pipe using same |
| RU2738291C1 (en) * | 2017-11-29 | 2020-12-11 | Ниппон Стил Корпорейшн | Piercing installation, mandrel bar and method for manufacturing seamless metal pipe using them |
| EP3718655A4 (en) * | 2017-11-29 | 2021-09-15 | Nippon Steel Corporation | Piercing machine, mandrel bar, and method for manufacturing seamless metallic tube using same |
| CN111432948B (en) * | 2017-11-29 | 2021-11-30 | 日本制铁株式会社 | Piercing machine, mandrel bar, and method for producing seamless metal pipe using same |
| US11344935B2 (en) | 2017-11-29 | 2022-05-31 | Nippon Steel Corporation | Piercing machine, mandrel bar, and method for producing seamless metal pipe using the same |
| US11511326B2 (en) | 2017-11-29 | 2022-11-29 | Nippon Steel Corporation | Piercing machine, and method for producing seamless metal pipe using the same |
| CN110153190A (en) * | 2019-06-13 | 2019-08-23 | 南通市嘉业机械制造有限公司 | A kind of high stable piercing plug for seamless steel tubes |
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