JP3033446B2 - Eccentric solidification continuous casting method of seamless steel pipe material and method of manufacturing seamless steel pipe - Google Patents

Eccentric solidification continuous casting method of seamless steel pipe material and method of manufacturing seamless steel pipe

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Publication number
JP3033446B2
JP3033446B2 JP6212184A JP21218494A JP3033446B2 JP 3033446 B2 JP3033446 B2 JP 3033446B2 JP 6212184 A JP6212184 A JP 6212184A JP 21218494 A JP21218494 A JP 21218494A JP 3033446 B2 JP3033446 B2 JP 3033446B2
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JP
Japan
Prior art keywords
slab
steel pipe
seamless steel
round billet
solidification
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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JP6212184A
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Japanese (ja)
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JPH0852555A (en
Inventor
章裕 山中
忠男 渡部
豊 永瀬
雅義 秋山
Original Assignee
住友金属工業株式会社
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Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION
【0001】[0001]
【産業上の利用分野】本発明は、炭素鋼、低合金鋼、高
合金鋼及びステンレス鋼等より継目無鋼管素材として最
の丸ビレットを得るための偏心凝固連続鋳造方法及び
その鋳片を素材とした内面疵のない継目無鋼管の製造方
法に関する。
BACKGROUND OF THE INVENTION The present invention, carbon steel, low alloy steel, the eccentric solidification continuous casting method and slab for optimum round billet as seamless steel pipe material from high alloy steel and stainless steel The present invention relates to a method of manufacturing a seamless steel pipe having no inner surface flaws as a material.
【0002】[0002]
【従来の技術】継目無鋼管の製造方法の一つとして、
面の連続鋳造鋳片をマンネスマン・マンドレルミル方
式やマンネスマン・プラグミル方式等の穿孔機を使って
製造する方法が行なわれている。これらのマンネスマン
方式による継目無鋼管の製造方法は、加熱炉で所定の圧
延温度に加熱した素材(丸ビレット)を穿孔機で穿孔圧延
した後、その中空素管をマンドレルミルやプラグミル等
の延伸圧延機で拡管して肉厚を減じた後、ストレッチレ
デューサやサイザ等の絞り圧延機で外径を絞り製品鋼管
に仕上げるのである。
2. Description of the Related Art As one method of manufacturing a seamless steel pipe, a round steel pipe is used.
Method of producing a continuous casting slab of cross-section with a drilling machine such as a Mannesmann mandrel mill method or Mannesmann plug mill method is performed. The method of manufacturing a seamless steel pipe by the Mannesmann method is that a material (round billet) heated to a predetermined rolling temperature in a heating furnace is pierced and rolled by a piercing machine, and then the hollow shell is drawn and rolled by a mandrel mill, a plug mill, or the like. After reducing the wall thickness with a mill, the outer diameter is reduced with a rolling mill such as a stretch reducer or a sizer to finish the product steel pipe.
【0003】継目無鋼管は、使用する素材の内質部が管
の内表面となるため、素材の外表面のみならず内質部で
の健全性が要求される。
[0003] In a seamless steel pipe, since the inner part of the material used is the inner surface of the pipe, soundness is required not only on the outer surface of the material but also on the inner part.
【0004】ところで、連続鋳造された鋳片は、鋳造時
の最終凝固位置に相当する鋳片の横断面(引抜き方向に
対し直角方向の断面)中心部に、軸方向に不連続の内部
空隙(センターポロシティ)が存在する。この内部空隙
が穿孔圧延時に十分に圧着されないで、管内面に露出し
て管内面疵となる場合がある。
Meanwhile, a continuously cast slab has an axially discontinuous internal void (a cross section perpendicular to the drawing direction) at the center of the slab corresponding to the final solidification position during casting. Center porosity). This internal void may not be sufficiently pressed during piercing and rolling, and may be exposed on the inner surface of the pipe to become a flaw on the inner surface of the pipe.
【0005】また、内部空隙を圧着させようとして分塊
工程を経たものを丸ビレットとして使用した場合でも、
内部空隙が十分に圧着されないで、穿孔圧延時に管内面
疵となることがあり、完全には管内面疵の発生を防止で
きない。
[0005] In addition, even if a round billet is used as a round billet after the sizing step in order to press the internal space,
If the internal gap is not sufficiently press-bonded, the inner surface may be flawed at the time of piercing and rolling, and the generation of flaws on the inner surface of the tube cannot be completely prevented.
【0006】この内部空隙を排除するための対策とし
て、「内部品質に優れた連続鋳造鋳片の製造方法」(特
開平3−124352号公報)が提案されている。この
技術は、鋳片の厚さの2〜5倍の直径を有するロールを
用いて鋳片内部の未凝固部を圧下することにより、凝固
した鋳片に対する圧下に比べ弱い圧下力で内部空隙を低
減させるものであり、それなりの低減効果が期待でき
る。
As a countermeasure for eliminating the internal voids, there has been proposed a "method for producing a continuous cast slab having excellent internal quality" (Japanese Patent Laid-Open No. 3-124352). This technology uses a roll having a diameter of 2 to 5 times the thickness of the slab to reduce the unsolidified portion inside the slab, thereby reducing the internal gap with a lower rolling force than the reduction on the solidified slab. Therefore, a reasonable reduction effect can be expected.
【0007】[0007]
【発明が解決しようとする課題】前記特開平3−124
352号公報に開示された連続鋳造鋳片の製造方法は、
鋳片のサイズや温度によっては、圧下力の内部への浸透
が不十分で内部空隙を完全に圧着できない場合があり、
更に圧下力を増し大きな圧下を施すと凝固界面に割れが
生じ、いわゆる「内部割れ」が問題となる。
SUMMARY OF THE INVENTION The above-mentioned JP-A-3-124
No. 352, the method for producing a continuous cast slab is disclosed in
Depending on the size and temperature of the slab, the penetration of the rolling force may be insufficient and the internal voids may not be completely pressed.
When the rolling force is further increased and a large rolling is applied, cracks occur at the solidification interface, and so-called "internal cracking" becomes a problem.
【0008】また、丸ビレットの場合、圧下により真円
度を損なうことは避けられず、丸ビレット鋳片としての
本来のねらいであるネァーネット・シェイプ・キャステ
ィングの意義を失うことになる。
Further, in the case of a round billet, it is inevitable that the roundness is impaired due to the reduction, and the original purpose of the net billet casting as the round billet cast piece is lost.
【0009】本発明は、前記従来技術に見られる問題点
を解決し、穿孔圧延時に管内面疵が発生しない継目無鋼
管素材用連続鋳造鋳片の製造方法及び継目無鋼管の製造
方法を提供するものである。
The present invention solves the above-mentioned problems in the prior art, and provides a method for producing a continuous cast slab for a seamless steel pipe material which does not cause any flaws on the inner surface of the pipe during piercing and rolling, and production of a seamless steel pipe.
It provides a method .
【0010】[0010]
【課題を解決するための手段】本発明者らは、前記目的
を達成するため、種々の実験・研究を重ねた。その結
果、連続鋳造鋳片内に存在する内部空隙の表面は、鋳造
時にほとんど酸化されないので、鋳片に十分な加工変形
を与えれば内部空隙は圧着し、管内面疵の発生原因を除
くことができる。
Means for Solving the Problems The present inventors have conducted various experiments and studies to achieve the above object. As a result, the surface of the internal voids present in the continuous cast slab is hardly oxidized during casting, so if sufficient deformation is given to the slab, the internal voids will be compressed and the cause of tube inner surface flaws will be eliminated. it can.
【0011】また、マンネスマン方式の製管方法での穿
孔工程における加工変形は、分塊工程における加工変形
に比べて加工度が高く、鋳片内の内部空隙を圧着させる
のに十分である。
Further, the working deformation in the drilling step in the Mannesmann-type pipe making method is higher than the working deformation in the lumping step, and is sufficient to press the internal voids in the slab.
【0012】以上の事柄から勘案して、管内面疵のない
高品質の継目無鋼管を作るには、鋳片中心から外れた位
置に内部空隙が存在する鋳片を素材に使用すればよいこ
とを見い出した。本発明は、この知見に基づいて完成さ
れたものである。
In view of the above, in order to produce a high-quality seamless steel pipe having no flaws on the inner surface of the pipe, it is necessary to use a slab having an internal void at a position off the center of the slab. I found The present invention has been completed based on this finding.
【0013】[0013]
【0014】すなわち、本発明は、継目無鋼管素材の丸
ビレットの連続鋳造において、鋳片が鋳型直下から長さ
3m以上15m以下の二次冷却帯で、鋳片周方向の半周と残
り半周の水量密度を違えて冷却し、鋳片の最終凝固位置
を鋳片中心より鋳片径の1%以上3%以下ずらせることを特
徴とする。
That is, according to the present invention, in a continuous casting of a round billet of a seamless steel pipe material, a slab has a length from immediately below a mold.
In the secondary cooling zone of 3 m or more and 15 m or less, cooling is performed with the water density of the half circumference and the remaining half circumference in the slab circumferential direction different, and the final solidification position of the slab is 1% or more and 3% or less of the slab diameter from the center of the slab It is characterized by shifting.
【0015】本発明の継目無鋼管の製造方法は、鋳片の
最終凝固位置を鋳片中心より鋳片径の1%以上3%以下ずら
せた丸ビレットを、圧延温度に加熱し、丸ビレット中心
をセンターとして穿孔圧延し、中空素管を製造すること
を特徴とする。
The method of manufacturing a seamless steel pipe of the present invention, 3% or less displaced round billet was more than 1% of the slab diameter than the slab around the final solidification position of the slab, heated to rolling temperature, the round billet It is characterized in that a hollow shell is manufactured by piercing and rolling around the center.
【0016】[0016]
【作用】一般に、連続鋳造鋳片の内部空隙は、溶鋼の流
動が低下した最終凝固段階において発生する。したがっ
て、この内部空隙は、鋳片周方向の冷却が均等であれ
ば、最終凝固段階の位置は鋳片の中心部(引抜き方向に
対し直角方向の横断面の中心部)に発生する。
Generally, the internal voids of a continuous cast slab are generated in the final solidification stage where the flow of molten steel is reduced. Therefore, if the cooling in the circumferential direction of the slab is uniform, the internal void is formed at the final solidification stage at the center of the slab (the center of the cross section perpendicular to the drawing direction).
【0017】通常、鋳型を出た鋳片は、水スプレーによ
る二次冷却または放冷により冷却され、表面から熱が奪
われて凝固シェルを発達させながら順次凝固してゆく。
このようにして、溶鋼が凝固する際には、凝固潜熱に相
当する熱が凝固シェルを介して外部へ抜熱される。この
際、周囲からの冷却が均等であれば、単位時間当たりの
凝固シェルの発達は、全周にわたりほぼ同等であり、最
終凝固位置は鋳片横断面のほぼ中心となるのである。
Normally, the slab that has left the mold is cooled by secondary cooling or cooling by water spray, and heat is removed from the surface to solidify sequentially while developing a solidified shell.
In this way, when the molten steel is solidified, heat corresponding to the latent heat of solidification is removed to the outside through the solidified shell. At this time, if the cooling from the surroundings is uniform, the development of the solidified shell per unit time is almost the same over the entire circumference, and the final solidified position is substantially at the center of the cross section of the slab.
【0018】本発明は、連続鋳造鋳片の最終凝固位置に
発生する内部空隙を鋳片横断面の中心部からずらすこと
を目的に、二次冷却帯での冷却強度を周方向で違えて冷
却・凝固させることにある。
According to the present invention, the cooling strength in the secondary cooling zone is varied in the circumferential direction to shift the internal void generated at the final solidification position of the continuous cast slab from the center of the slab cross section.・ To coagulate.
【0019】すなわち、鋳型直下から完全凝固の間に、
鋳片の引抜き方向に二次冷却帯を設置し、鋳片の周方向
の二次冷却水量の分布を変えることにより、周方向の冷
却強度を変化させる。これにより冷却強度の大きな部分
の凝固シェルの成長速度が増大し優先的に発達する。そ
のため、鋳片の周囲から内部へ向けて凝固速度の異なる
凝固シェルが成長して最終凝固部が鋳片中心より偏寄
し、その結果内部空隙も鋳片中心から外れた位置に形成
されることになる。
That is, during the period from immediately below the mold to complete solidification,
A secondary cooling zone is provided in the slab withdrawal direction, and the distribution of the amount of secondary cooling water in the circumferential direction of the slab is changed to change the circumferential cooling strength. As a result, the growth rate of the solidified shell in a portion having a large cooling strength is increased and the shell is preferentially developed. Therefore, solidification shells with different solidification rates grow from the periphery of the slab toward the inside, and the final solidified part is deviated from the center of the slab, and as a result, the internal voids are also formed at positions off the center of the slab become.
【0020】本発明において、二次冷却帯の長さを3m以
15m以下とした理由について説明する。通常、鋳型を
出た鋳片が鋳型直下から完全凝固に至るまでの距離は通
常十数mから40m程度あり、二次冷却帯は鋳型直下に近い
上流側に設置することが望ましい。これは、凝固末期に
鋳片を冷却しても、凝固シェルの発達が大きく、凝固シ
ェルの熱抵抗が大きいため、拔熱が効果的に行なわれな
いためである。
In the present invention, the reason why the length of the secondary cooling zone is set to 3 m or more and 15 m or less will be described. Normally, the distance from the point immediately below the mold to the complete solidification of the slab that has exited the mold is usually about ten to several meters to about 40 m, and the secondary cooling zone is desirably installed on the upstream side near immediately below the mold. This is because even if the slab is cooled at the end of solidification, the solidified shell develops greatly and the heat resistance of the solidified shell is large, so that heat is not effectively removed.
【0021】このような二次冷却帯が3m未満で短い場
合には、二次冷却中に生じた凝固シェルの成長速度の差
が、冷却終了時点から完全凝固に至るまでの期間に均等
化され、最終凝固部の偏寄効果がなくなるためである。
When such a secondary cooling zone is shorter than 3 m and short, the difference in the growth rate of the solidified shell generated during the secondary cooling is equalized in the period from the end of cooling to the time of complete solidification. This is because the bias effect of the final solidified portion is eliminated.
【0022】また、凝固末期に至るまでの余りに長い二
次冷却は、前記のように凝固シェルの大きな部分での効
果を期待できないこと、強冷却部と弱冷却部の温度差が
大きくなり、鋳片の熱変形を招くので、最大で15m程
度に留めることが望ましい。
In addition, the secondary cooling which is too long until the end of solidification cannot expect the effect in the large portion of the solidified shell as described above, and the temperature difference between the strong cooling portion and the weak cooling portion becomes large. It is desirable to keep the length to about 15 m at the maximum because thermal deformation of the piece is caused.
【0023】次に、丸ビレットの内部空隙の発生する位
置を鋳片中心から鋳片径の1%以上3%以下ずらせる理由に
ついて説明する。本発明が対象とする鋼管素材の穿孔圧
延においては、理論上ビレットの半径部分が穿孔圧延
後に得られる中空素管の肉厚となり、ビレットの中心
が素管の内表面となるので、内部空隙はビレツトの中
心上に存在しない限り、中空素管の肉厚内にあって、穿
孔圧延時に圧着され、素管の内表面に現れないから、内
面疵が発生することはない。
Next, the reason why the position where the internal void of the round billet is generated is shifted from the center of the slab by 1% or more and 3% or less of the slab diameter will be described. In piercing the steel pipe material to which the present invention is directed, it is the wall thickness of the hollow shell radius portion of the theoretically round billet is obtained after piercing, since the center of the round billet becomes the inner surface of the base pipe, the internal As long as the gap does not exist on the center of the round billet, it exists within the thickness of the hollow shell, is pressed during piercing and rolling, and does not appear on the inner surface of the shell, so that no inner surface flaw is generated.
【0024】しかし、真円の中実丸ビレットを得ること
は工業的に事実上不可能であり、また穿孔圧延において
プラグ中心と中実丸ビレット中心を完全に一致させた状
態で圧延することも事実上不可能であることから、数多
くの実験を行ない、中実丸ビレットの横断面中心から、
その直径の1%以上、最終凝固位置をずらした場合に限
り、管内面疵が発生しないか、あるいは著しく低減する
という事実を見出した。
However, it is practically industrially impossible to obtain a solid round billet of a perfect circle, and it is also possible to perform rolling in a state where the center of the plug and the center of the solid round billet are completely aligned in piercing and rolling. Since it is practically impossible, we conducted many experiments, and from the center of the cross section of the solid round billet,
It has been found that only when the final solidification position is shifted by 1% or more of the diameter, the inner surface flaw does not occur or is significantly reduced.
【0025】前記のごとく、丸ビレットの最終凝固位置
を鋳片直径の1%以上ずらせることにより、内部空隙の全
部あるいはその大部分が中心上には存在しないようにし
た中実丸ビレットを使用して、穿孔圧延時に内部空隙の
全部あるいはその大部分が管内表面に露出しないように
したものである。この内部空隙の全部あるいはその大部
分は、マンドレルミルやプラグミル等による穿孔圧延時
に管内表面に露出することなく圧着される。また、鋳片
の最終凝固位置が鋳片直径の3%を超えると、内面疵の低
減効果が飽和するばかりでなく、不均一冷却が大きくな
ってがり発生などの問題が懸念される。
As described above, a solid round billet is used in which the final solidification position of the round billet is shifted by 1% or more of the slab diameter so that all or most of the internal voids do not exist on the center. Thus, all or most of the internal voids are not exposed to the inner surface of the pipe during piercing and rolling. All or most of the internal space is pressed without being exposed to the inner surface of the pipe during piercing and rolling by a mandrel mill, a plug mill, or the like. Also, the final solidification position of the slab is more than 3% of the slab diameter, not only the effect of reducing the internal surface flaws is saturated, problems such as song rising generation nonuniform cooling increases is concerned.
【0026】前記したように、鋳片の内部空隙は最終凝
固位置に発生し、一般的に横断面の径方向に空隙で分布
する。そして、最終凝固位置の中心には、粗大かつ連続
的な空隙が存在しており、径方向の外側になるにつれて
空隙は小さく、かつ散発的に存在するようになってく
る。したがって、最終凝固位置を鋳片中心より鋳片径の
1%以上3%以下ずらせることにより、穿孔圧延時に前記粗
大な空隙が管内表面に露出するのを防止することができ
る。
As described above, the internal voids in the slab occur at the final solidification position and are generally distributed in the voids in the radial direction of the cross section. At the center of the final solidification position, there is a large and continuous gap, and the gap becomes smaller and sporadically exists toward the outside in the radial direction . Therefore, the final solidification position is
By shifting by 1% or more and 3% or less, it is possible to prevent the coarse voids from being exposed on the inner surface of the pipe during piercing and rolling.
【0027】[0027]
【実施例】図1に示す丸ビレット製造用の湾曲型連続鋳
造機により、鋳造鋼種として内部空隙が問題となりやす
い5%Cr鋼を使って直径190mmの丸ビレットを連
続鋳造した。ここで、取鍋1からタンディッシュ2を経
て鋳型3に注入された溶鋼は、鋳型3を出て二次冷却帯
4で二次冷却して凝固が進み、ピンチロール13により
引き出される。この際、鋳型直下から二次冷却されるこ
とにより鋳片5の凝固シェル6は次第に成長しながら引
き出されピンチロール13を出た後完全に凝固が終了す
る。
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A round billet having a diameter of 190 mm was continuously cast using a curved type continuous casting machine for producing a round billet shown in FIG. Here, the molten steel injected into the mold 3 from the ladle 1 via the tundish 2 exits the mold 3, undergoes secondary cooling in the secondary cooling zone 4, solidifies, and is drawn out by the pinch roll 13. At this time, the solidified shell 6 of the slab 5 is drawn out while being gradually grown by being secondarily cooled just below the mold, and is completely solidified after exiting the pinch roll 13.
【0028】前記二次冷却帯4は、鋳型直下より17m
の位置まで設けた。この二次冷却帯4におけるスプレー
7はミストスプレーとし、図1(B)に示すように、鋳
片5を取り囲んで12個のノズルを円周配置したリング
状からなり、鋳造方向に500mm間隔で30個のスプ
レー7を配設した。各スプレー7は、上面側と下面側で
それぞれ1/3周範囲で、スプレー水量とエアー量共に
変更可能に設けた。
The secondary cooling zone 4 is 17 m below the mold.
To the position of. The spray 7 in the secondary cooling zone 4 is a mist spray, as shown in FIG. 1 (B), and has a ring shape in which twelve nozzles are arranged around the slab 5 at intervals of 500 mm in the casting direction. Thirty sprays 7 were provided. Each spray 7 was provided so as to be able to change both the amount of spray water and the amount of air in the range of 1/3 circumference on the upper surface side and the lower surface side, respectively.
【0029】この実施例においては、前記二次冷却帯4
の鋳型直下より2m位置までの範囲は、上下の全スプレ
ーのスプレー水量とエアー量を同じにして全周均等冷却
とした。その理由は、鋳型直下の凝固シェルの薄い部分
で不均一に冷却すると、鋳片周方向に引張り応力が生
じ、凝固シェルの破断を招く恐れがあるからである。
In this embodiment, the secondary cooling zone 4
In the range from immediately below the mold to the position of 2 m, the spray water amount and the air amount of all the upper and lower sprays were the same, and the entire circumference was uniformly cooled. The reason is that if the solidified shell is cooled unevenly in the thin portion of the solidified shell directly below the mold, a tensile stress is generated in the circumferential direction of the slab, which may cause the solidified shell to break.
【0030】前記鋳型直下より2m位置までの範囲の冷
却は、水量密度600 l/m2・min、気水比30
で行なった。このように、鋳型直下より2m位置までの
範囲を比較的強く全周均等冷却することにより、以降の
強弱不均等冷却において凝固シェルの破断を生じないよ
うに、凝固シェル厚と温度低下による凝固シェル強度を
確保した。なお、前記鋳型直下の均等冷却長さは、鋳片
の断面大きさにより多少変化させることができる。
The cooling in the range from immediately below the mold to a position 2 m below is performed at a water density of 600 l / m 2 · min and a water / water ratio of 30
Performed in As described above, the solidified shell by the solidified shell thickness and the temperature drop is formed so that the solidified shell can be relatively uniformly cooled in a range from immediately below the mold to a position of 2 m so that the solidified shell does not break in the subsequent uneven cooling. Strength was secured. The uniform cooling length immediately below the mold can be changed slightly depending on the cross-sectional size of the slab.
【0031】前記鋳型直下の均等冷却後の2m〜17m
位置までの範囲では、鋳片周方向の上半部と下半部の水
量密度を違えて冷却した。この場合、下半部の水量密度
は20 l/m2・min、気水比は40で一定とし、
上半部の水量密度は70 l/m2・min、120
l/m2・min、及び170 l/m2・minの3種
類に変更し、かつ気水比はいずれも40とした。また、
同時に冷却の不均等スプレー帯の長さを2〜17mの範
囲で変更し、その影響を調べた。
2 to 17 m after uniform cooling just below the mold
In the range up to the position, the upper half part and the lower half part in the slab circumferential direction were cooled with different water density. In this case, the water density in the lower half is 20 l / m 2 · min, and the air / water ratio is constant at 40.
The water density in the upper half is 70 l / m 2 · min, 120
1 / m 2 · min and 170 l / m 2 · min, and the air / water ratio was set to 40. Also,
At the same time, the length of the non-uniform cooling spray zone was changed in the range of 2 to 17 m, and the effect was examined.
【0032】なお、前記実施例と同時に、比較例とし
て全周の水量密度を均一にし均等冷却して鋳片を製造し
た。この場合、鋳型直下より2m位置までの冷却は前記
本発明の実施例と同一のスプレー条件で均等冷却し、鋳
型直下の均等冷却後の2m〜17m位置までの範囲で
は、上半部と下半部の水量密度に差を付けることなく、
全周を水量密度70 l/m2・min、気水比40の
条件で均等冷却を施した。また、比較例として、比較
例と同じ条件で、更に凝固末期にピンチロールを利用
して鋳片の圧下を実施した。この際の圧下量は10mm
とした。
At the same time as the above example, as a comparative example, a cast piece was produced by uniformizing the water density over the entire circumference and uniformly cooling. In this case, the cooling from the position directly below the mold to the position 2 m is uniformly cooled under the same spraying conditions as in the embodiment of the present invention, and the upper half and the lower half in the range from 2 m to 17 m after the uniform cooling immediately below the mold. Without making any difference in the water density of the part
The entire circumference was uniformly cooled under the conditions of a water density of 70 l / m 2 · min and a gas-water ratio of 40. Further, as a comparative example, under the same conditions as in the comparative example, the slab was further reduced by using a pinch roll at the end of solidification. The amount of reduction at this time is 10 mm
And
【0033】前記実施例において、上半部の水量密度を
120 l/m2・min、下半部の水量密度を20
l/m2・min、不均等スプレー帯の長さを4mとし
た実施例と比較例、による鋳片横断面でみた内部空
隙の発生状況を図2に示す。本発明の実施例と比較例
の内部空隙12は同等の大きさであるが、その発生位置
は比較例では鋳片中心であるに対し、本願発明の実施
例は鋳片の下半部側へ2.8mm外れた位置にある。比
較例では、内部空隙12は圧下により小さくはなって
いるが、完全には消滅しておらず、その上内部割れが見
られた。また、圧下により上下の圧下位置で円弧面が平
坦化しており、断面が真円ではなくなっている。
In the above embodiment, the water density of the upper half is 120 l / m 2 · min, and the water density of the lower half is 20
l / m 2 · min, the examples and comparative examples in which the length of the uneven spray zone was 4m, the occurrence of internal voids as seen in slab cross-section according to FIG. 2. The internal voids 12 of the example of the present invention and the comparative example have the same size, but the position of occurrence is the center of the slab in the comparative example, whereas the example of the present invention is directed to the lower half side of the slab. It is located 2.8mm off. In the comparative example, the internal voids 12 became smaller due to the reduction, but did not completely disappear, and internal cracks were observed. Further, the arc surface is flattened at the upper and lower rolling positions by the rolling, and the cross section is not a perfect circle.
【0034】前記本発明の実施例において、不均等スプ
レー帯の長さと冷気水の水量密度を変化させたときの鋳
片横断面で見た内部空隙の発生位置の鋳片中心からのず
れ(偏心率と称す)を図3に示す。図中の○印付き曲線
は上半部の水量密度70 l/m2・min、下半部の
水量密度20 l/m2・minの場合、□印付き曲線
は上半部水量密度を120 l/m2・min、下半部
の水量密度20 l/m2・minの場合、△印付き曲
線は上半部水量密度を170 l/m2・min、下半
部の水量密度20 l/m2・minの場合である。こ
の結果、水量密度とスプレー帯の長さを変化させること
により、内部空隙の発生位置の偏心率を1%以上とする
ことが可能であり、下半部の水量密度に対する上半部水
量密度の比が大きいほど偏心率が高いことがわかる。ま
た、上半部水量密度の高低にかかわらず不均等スプレー
帯長さが約10mを超えると偏心率効果は飽和する。し
たがって、不均等スプレー帯長さを必要以上に長くする
ことは、鋳片に温度差を与えるだけで好ましくない。
In the embodiment of the present invention, when the length of the non-uniform spray zone and the water density of the cold air are changed, the position of occurrence of the internal void as viewed from the cross section of the slab is shifted from the center of the slab (eccentricity). FIG. 3). The curve with a circle in the figure indicates a water density of 70 l / m 2 · min in the upper half and a water density of 20 l / m 2 · min in the lower half, and a curve with a square indicates a water density of 120 in the upper half. In the case of l / m 2 · min and the water density of the lower half of 20 l / m 2 · min, the curve with a triangle indicates the water density of the upper half of 170 l / m 2 · min and the water density of the lower half of 20 l. / M 2 · min. As a result, by changing the water density and the length of the spray zone, it is possible to make the eccentricity of the position where the internal void is generated 1% or more, and the upper half water density with respect to the lower half water density. It can be seen that the larger the ratio, the higher the eccentricity. In addition, the eccentricity effect is saturated when the uneven spray zone length exceeds about 10 m regardless of the upper half water density. Therefore, it is not preferable to make the length of the uneven spray zone longer than necessary, because it only gives a temperature difference to the slab.
【0035】前記により作られたビレットを加熱炉で1
200℃に加熱した後、穿孔機により穿孔圧延し、外径
63mm、肉厚5mmの中空素管を製造した。その製管
加工状態を図4に示す。図面において、8は上下に傾斜
配置された2個対をなす鼓型ロールで、この上下ロール
とその上下ロール間に配置したプラグ9とにより、スパ
イラル状に回転前進する中実丸ビレット10を穿孔圧延
して中空素管11に仕上げる。このとき、中実丸ビレッ
ト10の中心から外方へずれて存在する内部空隙12
は、中空素管11の内表面に露出することなく、管の肉
厚内にあって圧延時の圧下により圧着し空隙は排除され
る。
The billet prepared above was heated in a heating furnace for 1 hour.
After heating to 200 ° C., piercing and rolling was performed using a piercing machine to produce a hollow shell having an outer diameter of 63 mm and a wall thickness of 5 mm. FIG. 4 shows the state of the pipe making process. In the drawing, reference numeral 8 denotes a pair of drum-shaped rolls, which are vertically inclined and arranged in pairs. The upper and lower rolls and a plug 9 disposed between the upper and lower rolls pierce a solid round billet 10 which rotates and advances in a spiral shape. It is rolled to finish the hollow shell 11. At this time, the internal space 12 existing outside the center of the solid round billet 10 is shifted outward.
Is within the wall thickness of the tube without being exposed on the inner surface of the hollow shell 11, and is pressed under pressure during rolling to eliminate voids.
【0036】得られた中空素管について、超音波探傷装
置を用い管肉厚中間部の割れ及び管内面疵を調べた。そ
の結果を、ビレットごとの疵発生総個数として図5に示
す。比較例の場合は、疵は36個発生しており、また
圧下により内部空隙を減らした比較例の場合は、疵の
発生は比較例に比べ約40%低減できるが、内部割れ
に起因する疵が見られた。一方、本発明の比較例として
あげた内部空隙の偏心率が0.8%の場合には疵軽減の
効果は見られず疵発生個数は比較例とほとんど変わり
ない。これに対し本発明の実施により内部空隙の偏心率
を1%以上とした場合(図には偏心率1.1%、2.8
%、6.5%の3例を示す)には、いずれも疵の発生は
ほとんど見られず、低減効果の著しいことがわかる。な
お、図からわかるように、偏心率2.8%と6.5%で
は疵の低減効果には差が見られず約3%程度で飽和して
いることがわかる。また、偏心率を大きくするため鋳造
時の不均一冷却を大きくすると鋳片のまがり発生などの
問題が懸念されるため、偏心率は1〜3%程度にとどめ
ることが望ましい。
With respect to the obtained hollow shell, cracks in the middle part of the pipe thickness and flaws on the inner surface of the pipe were examined using an ultrasonic flaw detector. The results are shown in FIG. 5 as the total number of flaws generated for each billet. In the case of the comparative example, 36 flaws were generated. In the case of the comparative example in which the internal voids were reduced by reduction, the generation of flaws could be reduced by about 40% as compared with the comparative example. It was observed. On the other hand, when the eccentricity of the internal void is 0.8%, which is given as a comparative example of the present invention, the effect of flaw reduction is not seen, and the number of flaws generated is almost the same as the comparative example. On the other hand, when the eccentricity of the internal gap is set to 1% or more by the implementation of the present invention (the eccentricity of 1.1%, 2.8 in the figure).
% And 6.5%) show almost no flaws, indicating a remarkable reduction effect. As can be seen from the figure, there is no difference in the flaw reduction effect between the eccentricity ratios of 2.8% and 6.5%, and it is understood that the eccentricity is saturated at about 3%. In addition, if non-uniform cooling during casting is increased to increase the eccentricity, problems such as the occurrence of cast slabs may be caused. Therefore, the eccentricity is desirably limited to about 1 to 3%.
【0037】[0037]
【発明の効果】本発明により、連続鋳造鋳片の最終凝固
位置に発生する内部空隙を鋳片横断面の中心から鋳片径
の1%以上3%以下ずらすことにより、穿孔圧延時に管内面
疵が発生しない継目無鋼管素材用の連続鋳造鋳片を提供
することができる。また、鋳片の最終凝固位置を鋳片中
心より鋳片径の1%以上3%以下ずらせた丸ビレットを、圧
延温度に加熱し、丸ビレット中心をセンターとして穿孔
圧延し、中空素管を製造することにより、管内面疵のな
い継目無鋼管を製造することができる。
According to the present invention, the internal void generated at the final solidification position of the continuous cast slab is shifted from the center of the slab cross-section by 1% or more and 3% or less of the slab diameter, so that the inner surface flaw of the pipe during piercing and rolling is improved. It is possible to provide a continuous cast slab for a seamless steel pipe material in which no cracks occur. Further, a round billet in which the final solidification position of the slab is shifted from 1% to 3% of the slab diameter from the slab center is heated to the rolling temperature, and piercing-rolling is performed with the round billet center as a center, By manufacturing the hollow shell, a seamless steel pipe having no inner surface flaws can be manufactured.
【図面の簡単な説明】[Brief description of the drawings]
【図1】図1(A)は本発明の実施例における丸ビレッ
ト製造用の湾曲型連続鋳造機の概要を示す説明図、図1
(B)はその二次冷却帯のスプレー装置の詳細を示す斜
視図である。
FIG. 1A is an explanatory view showing an outline of a curved continuous casting machine for producing a round billet according to an embodiment of the present invention;
(B) is a perspective view showing the details of the spray device for the secondary cooling zone.
【図2】本発明の実施例と比較例により鋳造された鋳片
の内部空隙を比較して示す説明図である。
FIG. 2 is an explanatory diagram showing a comparison between internal voids of cast pieces cast according to an example of the present invention and a comparative example.
【図3】本発明の実施による不均等スプレー帯長さと内
部空隙の偏心率との関係を示すグラフである。
FIG. 3 is a graph showing the relationship between the uneven spray zone length and the eccentricity of the internal void according to the embodiment of the present invention.
【図4】本発明の実施により偏心凝固連続鋳造した丸ビ
レットを穿孔圧延する際の加工状態を示す説明図であ
る。
FIG. 4 is an explanatory view showing a processing state when piercing and rolling a round billet continuously cast by eccentric solidification according to an embodiment of the present invention.
【図5】本発明の実施例及び比較例により作られた中空
素管の疵発生状況を比較して示すグラフである。
FIG. 5 is a graph showing a comparison of the occurrence of flaws in a hollow shell made according to an example of the present invention and a comparative example.
【符号の説明】[Explanation of symbols]
1 取鍋 2 タンディッシュ 3 鋳型 4 二次冷却帯 5 鋳片 6 凝固シェル 7 スプレー 8 鼓型ロール 9 プラグ 10 中実丸ビレット 11 中空素管 12 内部空隙 13 ピンチロール DESCRIPTION OF SYMBOLS 1 Ladle 2 Tundish 3 Mold 4 Secondary cooling zone 5 Cast piece 6 Solidified shell 7 Spray 8 Hour roll 9 Plug 10 Solid round billet 11 Hollow shell 12 Internal gap 13 Pinch roll
───────────────────────────────────────────────────── フロントページの続き (72)発明者 秋山 雅義 大阪府大阪市中央区北浜4丁目5番33号 住友金属工業株式会社内 (56)参考文献 特開 平2−182347(JP,A) (58)調査した分野(Int.Cl.7,DB名) B22D 11/22 B22D 11/124 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masayoshi Akiyama 4-5-33 Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd. (56) References JP-A-2-182347 (JP, A) ( 58) Field surveyed (Int. Cl. 7 , DB name) B22D 11/22 B22D 11/124

Claims (2)

    (57)【特許請求の範囲】(57) [Claims]
  1. 【請求項1】 継目無鋼管素材の丸ビレットの連続鋳造
    において、鋳片を鋳型直下から長さ3m以上15m以下の二
    次冷却帯で、鋳片周方向の半周と残り半周の水量密度を
    違えて冷却し、鋳片の最終凝固位置を鋳片中心より鋳片
    径の1%以上3%以下ずらせることを特徴とする継目無鋼管
    素材の偏心凝固連続鋳造方法。
    In a continuous casting of a round billet made of a seamless steel pipe material, a slab is provided in a secondary cooling zone having a length of 3 m or more and 15 m or less immediately below a mold. A method for continuously casting eccentric solidification of seamless steel pipe material, wherein the slab is cooled and the final solidification position of the slab is shifted from the slab center by 1% or more and 3% or less of the slab diameter.
  2. 【請求項2】 連続鋳造した丸ビレットからの継目無鋼
    管の製造方法において、鋳片の最終凝固位置を鋳片中心
    より鋳片径の1%以上3%以下ずらせた丸ビレットを、圧
    温度に加熱し、丸ビレット中心をセンターとして穿孔圧
    延し、中空素管を製造することを特徴とする継目無鋼管
    の製造方法。
    2. A method of producing a seamless steel pipe from a continuous cast round billet, 3% or less displaced round billet was more than 1% of the slab diameter than the slab around the final solidification position of the cast slab, rolling A method for producing a seamless steel pipe, comprising heating to a temperature, piercing and rolling around a center of a round billet to produce a hollow shell.
JP6212184A 1994-08-12 1994-08-12 Eccentric solidification continuous casting method of seamless steel pipe material and method of manufacturing seamless steel pipe Expired - Fee Related JP3033446B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP6212184A JP3033446B2 (en) 1994-08-12 1994-08-12 Eccentric solidification continuous casting method of seamless steel pipe material and method of manufacturing seamless steel pipe

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP6212184A JP3033446B2 (en) 1994-08-12 1994-08-12 Eccentric solidification continuous casting method of seamless steel pipe material and method of manufacturing seamless steel pipe

Publications (2)

Publication Number Publication Date
JPH0852555A JPH0852555A (en) 1996-02-27
JP3033446B2 true JP3033446B2 (en) 2000-04-17

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Country Link
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JP3367332B2 (en) * 1996-05-15 2003-01-14 日本鋼管株式会社 Manufacturing method of difficult-to-work seamless steel pipe
JP4045813B2 (en) * 2001-03-27 2008-02-13 Jfeスチール株式会社 Seamless steel pipe manufacturing method
CN112340826A (en) * 2020-11-23 2021-02-09 同济大学 Pipeline coagulation method for rapidly reducing river discharge pollution

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