JP3783676B2 - Drawing method of Ni-base alloy tube - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、Ｎｉ基合金管の冷間引抜加工方法に関し、より詳しくは、被加工材表面に化成処理潤滑皮膜、または油潤滑皮膜を形成させた冷間加工において、被加工材に発生するびびり振動を有効に防止することができるＮｉ基合金管の引抜加工方法に関するものである。
【０００２】
【従来技術】
原子力発電設備における蒸気発生器や、各種機器の給水ヒータなどの熱交換器に組み込んで使用される管は、外径が４０mm以下の小径で、長さが１５ｍ以上の長尺管として製造される。通常、このような原子力発電設備等に用いられる小径長尺管は、熱間製管法によって製造された継目無鋼管または溶接によって製造された溶接管を素管として冷間加工によって製造される。この冷間加工では、引抜加工方法が行われる。
【０００３】
一般に、管の冷間引抜加工では、素管の内外表面に化成処理潤滑皮膜を形成する方法が用いられている。しかし、化成処理潤滑皮膜を形成する場合には、小径長尺管を引抜加工する素管も長尺であるため、化成処理時に素管の内面まで充分に処理することに留意しなければならない。このため、その処理に多大の工数を要するとともに、使用する薬品が比較的高価であり、作業コストが高くなるという面があるものの、化成処理された素管の引抜加工は比較的安定するという有利な面も多くある。
【０００４】
最近では、化成処理潤滑皮膜を形成するのに必要な薬品に比べて安価であり、その後の処理も比較的容易であることから、素管の表面に油潤滑皮膜を形成する引抜加工が行われている。この油潤滑皮膜を形成する方法は、化成処理潤滑皮膜を形成する方法に比べ、潤滑皮膜の厚さが薄く、かつ強度が低いので油切れを生じ易い。このため、油潤滑皮膜を形成する方法では、加工部への導入油量が少なくなり、引抜加工中に焼き付きやびびり振動を発生し易くなる。
【０００５】
ところが、油潤滑皮膜を形成する方法であっても、特許文献１で提案されるように、被加工材の表面に予め強固な乾燥樹脂皮膜を形成し、この乾燥樹脂皮膜によって加工部における被加工材の表面と工具表面とが直接接触しないようにした上で、乾燥樹脂皮膜上に油潤滑皮膜を形成させて冷間加工を行うことによって、安定した引抜状況に改善することができる。
【０００６】
具体的には、特許文献１で提案された方法は、表面を清浄にした素管の内外面のいずれか一方または両方に、苛性ソーダまたはアンモニアで中和した水溶性アクリル樹脂からなる乾燥樹脂皮膜を形成し、その後に不乾性潤滑油を内外面に塗布して引抜加工するものである。
【０００７】
さらに、油潤滑皮膜を用いた冷間引抜加工の一種として、冷間引抜加工の安定化を図るとともに、管製品の品質向上に大きな効果を発揮する高圧潤滑引抜法（高圧抽伸法）が開発されている。この方法は、内部に素管を装入した高圧容器内に潤滑油を充満させ、高圧潤滑油を供給しつつ冷間加工を行いながら、素管を高圧容器外へ引き抜く、管の加工方法である。
【０００８】
図１は、高圧潤滑油を供給しつつ冷間加工を行う高圧潤滑引抜法を説明する模式図である。図１において、素管１をダイス２およびプラグ３によって冷間加工する際に、一方端が閉鎖され、開放端がテレスコピック構造４ａとされた筒状の容器４は、閉鎖端側を支点に開放端側を引き抜きパスラインと素管挿入ラインとの間に位置可変なように揺動自在に設けられている。
【０００９】
容器４内には、引き抜きパスラインに固定配置されたダイス２内にプラグ３を位置させて、プラグ３を保持するプラグ支持桿５が貫通配置されている。
【００１０】
上記の容器４内には、必要であればデスケール処理などして内外面を清浄化し、例えば、処理が容易な外面のみに乾燥樹脂皮膜を形成させた素管１が装入され、図１に示すように、ダイス２とプラグ３とで画成される環状空間に素管１の口絞り部を通した状態にセットされる。
【００１１】
そして、この状態でポンプＰにより容器４内に高圧潤滑油を供給充填し、素管１を上記環状空間より容器４外へ引抜いて所定の寸法の管製品に仕上げる。この引抜加工の全工程において、素管１の内外面には容器４内に供給充填した高圧潤滑油が連続的に供給される。
【００１２】
このとき、容器４の開放端とダイス２との間の気密保持は、容器４の開放端側に設けられたテレスコピック構造部４ａが高圧の潤滑油によって図中の左方に押されてその先端がダイス２の入側面に圧接することで自動的に行われる。また、ダイス２とプラグ３のと環状空間の気密は、引抜加工中の素管１によって維持される。
【００１３】
【特許文献１】
特開平１０−７１４１８号公報
【特許文献２】
特許２５２２３９７号公報（特公平３−１８４１９号公報）
【特許文献３】
特開平１０−３２３７１１号公報
【００１４】
【発明が解決しようとする課題】
管の引抜加工においては、通常、素管の熱処理後、デスケール処理等を行って内外面を清浄化したのち、潤滑処理が施されていたが、小径長尺管が対象となるとその処理に多大の工数を要するとともに、使用する薬品が高価であり、その後の廃液処理も煩雑になる。このため、熱処理後のデスケール処理が不要になるように、還元雰囲気中で光輝熱処理を施した素管を用いて、引抜加工を行うことがある。
【００１５】
この場合には、光輝熱処理を施した素管表面に、直接、化成処理潤滑皮膜、または油潤滑皮膜が形成される。特に、油潤滑皮膜を形成する場合には、前述の通り、処理が容易な外面のみにアクリル樹脂などの合成樹脂を主成分とする乾燥樹脂皮膜を形成させたのち、その皮膜上に油潤滑皮膜を形成させて冷間加工を行うのが望ましい。
【００１６】
潤滑処理して冷間引抜加工する場合には、加工中に発生する焼き付き、およびびびり振動に留意する必要がある。焼き付きは、小径長尺管の内面の潤滑不良に基因して発生するものであり、この焼き付きの多発はプラグ原単位を低下させるとともに、管製品の表面品質を悪化させ、歩留まり低下を招き、管製品の製造コストを上昇させる。
【００１７】
このような焼き付きは、上述した高圧潤滑引抜法を採用することによって、常時、高圧潤滑油が供給、充填されることからほぼ防止することができる。しかしながら、高圧潤滑引抜法を採用する場合であっても、びびり振動に関しては、その発生防止が充分でない場合がある。
【００１８】
このびびり振動は、被加工材と工具（ダイス、プラグ）との間に生じる摩擦係数の変動に起因した自励振動として一般に知られ、スティック状態とスリップ状態を繰り返すスティックスリップ現象の一種とされている。
【００１９】
びびり振動を発生させた引抜加工によって得られた管製品は、その内径が極めて微少ではあるが軸長方向に変動する。その管製品が原子力発電設備に使用される場合に、安全上極めて厳しい品質管理が要求されることから、このような軸長方向の内径変動に関しては、その外観検査や内面渦流探傷検査において厳しい検査基準が設けられる。特に、内面渦流探傷検査では、軸長方向の内径変動はノイズの発生原因になって、探傷のＳ／Ｎ比を著しく低下させ、不合格製品の発生要因となっている。
【００２０】
本発明は、上記の冷間引抜加工の実情に鑑みなされたものであり、光輝熱処理を施した素管表面に化成処理潤滑皮膜、または油潤滑皮膜を形成させて冷間加工を行う場合に、被加工材に発生するびびり振動を有効に防止することができる、Ｎｉ基合金管の引抜加工方法を提供することを目的としている。
【００２１】
【課題を解決するための手段】
本発明者らは、上記の課題を解決するため、種々の被加工材を用いて、各種の潤滑条件、さらに高圧潤滑引抜法も採用して引抜加工を行い、びびり振動が発生する要因調査を行った。
【００２２】
その結果、例えば、光輝熱処理を施したＮｉ基合金素管を用いて冷間引抜加工を行う場合に、びびり振動が多発することがある。そのときに使用した工具、特にプラグの表面にはアルミナ酸化物（Ａｌ2Ｏ3）の微粉が多く付着しており、引抜方向に筋模様が観察された。このことから、素管の表面に残留するアルミナ酸化物の微粉がびびり振動の発生原因と推定できた。
【００２３】
Ｎｉ基合金素管の表面に存在する酸化物は、引抜加工前に施される熱処理において生成されるものであり、還元雰囲気中で光輝熱処理を行う場合に、雰囲気条件を調整、管理することにより、素管の内外表面に残留する酸化物、例えば、クロム酸化物（Ｃｒ2Ｏ3）、アルミナ酸化物（Ａｌ2Ｏ3）等の生成を抑制することができる。これにより、引抜加工中の素管と工具との摩擦係数の変動を抑え、冷間加工中の管に発生するびびり振動を防止することができる。
【００２４】
本発明は、上記の知見に基づいて完成されたものであり、下記（１）および（２）のＮｉ基合金管の引抜加工方法を要旨としている。
（１）光輝熱処理を施した素管を用いて冷間工程で引抜加工する方法であって、前記光輝熱処理は露点が−５０℃以下の水素雰囲気中で行われることを特徴とするＮｉ基合金管の引抜加工方法である。
（２）上記（１）の引抜加工方法では、引抜加工される管製品が小径長尺管であって、素管の内外表面に油潤滑皮膜を形成し、さらには、引抜加工に高圧潤滑引抜法を採用するのが望ましい。
【００２５】
本発明で規定する小径長尺管とは、原子力発電設備に用いられる蒸気発生管や、給水ヒータチューブ等を想定しており、外径が４０ｍｍ以下で長さが１５ｍ以上のＮｉ基合金管が該当する。
【００２６】
さらに、これらの小径長尺管は、薄肉であって肉厚／外径比率が１０％以下の寸法特性を具備することが多い。また、管製品が小径薄肉の特性を具備するものであれば、冷間引抜加工の仕上げ工程における断面減少率Ｒｄは、３０％を超える高加工度になりやすい。
【００２７】
【発明の実施の形態】
本発明の引抜加工方法では、還元性である水素雰囲気中で光輝熱処理を施した素管を用いることとしている。これは、大気雰囲気または酸化性雰囲気中で熱処理を行うと、素管の熱処理後、デスケール処理が必要になる。上述の通り、被加工材の主体が小径長尺管になると、その処理に多大の工数を要するとともに、使用する薬品が高価となる。このようなデスケール処理を回避するため、素管を熱処理する際に、殆ど表面にスケールの発生がない、水素還元雰囲気による光輝熱処理を施すこととした。
【００２８】
前述の通り、びびり振動の発生要因として、引抜加工前の管表面に存在する酸化物が挙げられる。この素管表面に存在する酸化物は、引抜加工前に施される光輝熱処理において生成されるものであるから、その還元雰囲気として用いられる水素の露点を変化させて、素管の表面に生成される酸化物について検討した。
【００２９】
通常、水素雰囲気の露点調整は、露点調整器によって水素雰囲気中の含有水分量を調整して行われる。
【００３０】
素管材質としてＮｉ基合金（Ｎｉ≧５８％）を用いて、水素雰囲気の露点を−２０℃超え〜−５６℃の範囲で変化させ、素管表面に形成される酸化物を調査した。その調査結果によると、水素雰囲気の露点が−２０℃以上の条件では、素管表面にクロム酸化物が形成されるが、露点が−２０℃〜−５６℃の範囲ではアルミナ酸化物が素管表面に析出する。水素雰囲気の露点を低くすることによって、素管表面に析出するアルミナ酸化物は減少する。そして、水素雰囲気の露点が−５６℃以下になると、酸化物の析出は見られなくなる。
【００３１】
水素雰囲気の露点が−５０℃になると、若干のアルミナ酸化物の析出があるが（面積率で１．４％程度）、冷間引抜加工に及ぼす影響は無視することができ、びびり振動の発生は低率に留まる。そのため、本発明では、水素雰囲気の露点を−５０℃以下で管理することとした。さらに、びびり振動を完全に防止するには、水素雰囲気の露点を−６０℃以下で管理するのが望ましい。
【００３２】
【実施例】
外径２３．００mm、肉厚１．４６０mmおよび長さ１００００mmのＮｉ基合金の素管を対象とし、図１に示す高圧潤滑引抜法によって、外径１６．０２mm、肉厚１．００５mmおよび長さ２１０００mmの管製品に、断面減少率５２％で引抜加工した。素管材質のＮｉ基合金は、ASME SB-163 UNS NO66690 に規定するものである。
【００３３】
引抜加工前の光輝熱処理は、水素雰囲気中で電気抵抗加熱方式として、水素雰囲気の露点を−５０℃と−４３℃の２通りとした。光輝熱処理を施した素管を引抜加工して、びびり振動の発生状況を調査した。このとき、塩素化油脂、塩素化エステルおよび硫化油脂との混合組成物１００重量部に対し、極圧添加剤としてのＣｌを１５重量％、およびＳを５重量％含有させた潤滑油を用いて、１１８MPaの圧力を付与し、引抜き速度２５ｍ／分で引抜いた。
【００３４】
図２および図３は、光輝熱処理の前後における素管の内表面のＳＥＭ観察（×２０００）結果を示す図である。図２は熱処理前の観察結果である。図３は熱処理後の観察結果であり、同(a)は水素雰囲気の露点を−５０℃とした場合の観察結果、同(b)は水素雰囲気の露点を−４３℃とした場合の観察結果を、それぞれ示している。
【００３５】
図２に示すように、熱処理前には、素管の表面にアルミナ等の酸化物の析出は見られなかったが、図３(a)、(b)に示すように、熱処理後はアルミナ酸化物の析出が観察された。図３(a)、(b)に示す観察結果において、白点部がアルミナ酸化物を示している。
【００３６】
図３(a)は水素雰囲気の露点を−５０℃とした場合であり、アルミナ酸化物の面積率は１．４％に抑制されているのに対し、同(b)は水素雰囲気の露点を−４３℃とした場合であり、アルミナの面積率は５０．６％と著しく増加している。
【００３７】
このため、引抜加工でのびびり振動の発生率は、水素雰囲気の露点を−５０℃とした場合に１％であったのに対し、水素雰囲気の露点を−４３℃とした場合には４％と増加している。ただし、びびり振動の発生率は、引抜本数の比率で示している。
【００３８】
さらに、管製品の渦流探傷時のＳ／Ｎ比に関して、水素雰囲気の露点を−５０℃とした場合に、びびり振動が発生していない全数の管製品を内面渦流探傷して、Ｓ／Ｎ比が良好であることを確認している。
【００３９】
【発明の効果】
本発明の引抜加工方法によれば、特殊な防止装置を有する冷間加工設備を用いることなく、小径長尺管であっても、化成処理潤滑皮膜、または油潤滑皮膜のいずれを形成する場合であっても、びびり振動の発生を有効に防止し、安定して冷間加工を行うことができる。
【００４０】
特に、高圧潤滑引抜法を採用する場合には、びびり振動の発生をなくし、冷間引抜の安定化を図るとともに、表面性状の優れた管製品を低コストで製造することができる。
【図面の簡単な説明】
【図１】高圧潤滑油を供給しつつ冷間加工を行う高圧潤滑引抜法を説明する模式図である。
【図２】光輝熱処理前における素管の内表面のＳＥＭ観察（×２０００）結果を示す図である。
【図３】光輝熱処理後における素管の内表面のＳＥＭ観察（×２０００）結果を示す図であり、(a)は水素雰囲気の露点を−５０℃とした場合の観察結果、(b)は水素雰囲気の露点を−４３℃とした場合の観察結果を示す。
【符号の説明】
１：素管、 ２：ダイス、 ３：プラグ
４：容器、 ４ａ：テレスコピック構造
５：プラグ支持桿[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for cold drawing of a Ni-based alloy tube, and more particularly, chatter generated in a work material in cold work in which a chemical conversion treatment lubricating film or an oil lubrication film is formed on the surface of the work material. The present invention relates to a method for drawing a Ni-based alloy tube that can effectively prevent vibration.
[0002]
[Prior art]
Tubes used in heat exchangers such as steam generators in nuclear power generation facilities and water heaters for various equipment are manufactured as long tubes with a small outer diameter of 40 mm or less and a length of 15 m or more. . Usually, a small-diameter long tube used in such a nuclear power generation facility or the like is manufactured by cold working using a seamless steel tube manufactured by a hot pipe manufacturing method or a welded tube manufactured by welding as a base tube. In this cold working, a drawing method is performed.
[0003]
Generally, in the cold drawing of a pipe, a method of forming a chemical conversion treatment lubricating film on the inner and outer surfaces of the raw pipe is used. However, when forming a chemical conversion treatment lubricating film, it must be noted that the inner tube of the raw tube is sufficiently processed during the chemical conversion treatment because the raw tube for drawing a small diameter long tube is also long. For this reason, the process requires a lot of man-hours, and the chemicals to be used are relatively expensive and the work cost is high, but the drawing process of the chemical conversion-treated raw tube is relatively stable. There are many important aspects.
[0004]
Recently, since it is cheaper than chemicals necessary for forming a chemical conversion treatment lubricating film, and subsequent processing is relatively easy, drawing processing is performed to form an oil lubricating film on the surface of the raw tube. ing. This method of forming an oil lubrication film tends to cause oil shortage because the thickness of the lubricant film is thin and the strength is low, compared to the method of forming a chemical conversion treatment lubrication film. For this reason, in the method of forming the oil lubrication film, the amount of oil introduced into the processed portion is reduced, and seizure and chatter vibration are likely to occur during the drawing process.
[0005]
However, even in the method of forming the oil lubrication film, as proposed in Patent Document 1, a strong dry resin film is formed in advance on the surface of the workpiece, and the dry resin film is used to process the processed part. A stable drawing condition can be improved by forming an oil-lubricated film on the dry resin film and performing cold working after preventing the material surface and the tool surface from directly contacting each other.
[0006]
Specifically, in the method proposed in Patent Document 1, a dry resin film made of a water-soluble acrylic resin neutralized with caustic soda or ammonia is applied to either or both of the inner and outer surfaces of a raw pipe whose surface is cleaned. Then, non-drying lubricating oil is applied to the inner and outer surfaces and drawn.
[0007]
Furthermore, as a kind of cold drawing using an oil lubricant film, a high pressure lubrication drawing method (high pressure drawing method) has been developed that stabilizes the cold drawing process and has a great effect on improving the quality of pipe products. ing. This method is a tube processing method in which a high-pressure vessel filled with a raw pipe is filled with lubricating oil, and cold processing is performed while supplying high-pressure lubricating oil, and the raw pipe is pulled out of the high-pressure vessel. is there.
[0008]
FIG. 1 is a schematic diagram for explaining a high-pressure lubrication drawing method in which cold working is performed while supplying high-pressure lubricating oil. In FIG. 1, when cold-working the tube 1 with a die 2 and a plug 3, a cylindrical container 4 whose one end is closed and whose open end is a
[0009]
In the container 4, a plug support rod 5 for holding the plug 3 is disposed so as to be positioned in the die 2 fixedly arranged on the extraction pass line.
[0010]
In the container 4, if necessary, the inner and outer surfaces are cleaned by descaling or the like, and, for example, a raw tube 1 in which a dry resin film is formed only on the outer surface that can be easily processed is inserted in FIG. As shown in the figure, the annular space defined by the die 2 and the plug 3 is set in a state in which the mouth restrictor of the raw tube 1 is passed.
[0011]
In this state, the pump 4 is supplied and filled with high-pressure lubricating oil into the container 4, and the raw pipe 1 is pulled out of the annular space from the container 4 to finish a pipe product having a predetermined size. In all the drawing processes, the high pressure lubricating oil supplied and filled in the container 4 is continuously supplied to the inner and outer surfaces of the raw tube 1.
[0012]
At this time, the airtight maintenance between the open end of the container 4 and the die 2 is such that the
[0013]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-71418 [Patent Document 2]
Japanese Patent No. 2522397 (Japanese Patent Publication No. 3-18419)
[Patent Document 3]
Japanese Patent Laid-Open No. 10-323711
[Problems to be solved by the invention]
In pipe drawing processing, after the inner and outer surfaces have been cleaned by performing a descaling process after heat treatment of the raw pipe, lubrication has been applied. In addition, the chemicals to be used are expensive, and the subsequent waste liquid treatment becomes complicated. For this reason, drawing processing may be performed using a raw tube that has been subjected to bright heat treatment in a reducing atmosphere so that descaling after heat treatment is not necessary.
[0015]
In this case, a chemical conversion treatment lubricating film or an oil lubricating film is directly formed on the surface of the raw tube subjected to the bright heat treatment. In particular, when forming an oil lubrication film, as described above, after forming a dry resin film mainly composed of a synthetic resin such as an acrylic resin on only the outer surface that can be easily treated, the oil lubrication film is formed on the film. It is desirable to perform cold working after forming the film.
[0016]
When cold drawing is performed after lubrication, it is necessary to pay attention to seizure and chatter vibration that occur during processing. The seizure occurs due to poor lubrication of the inner surface of the small-diameter long tube, and this frequent seizure reduces the basic unit of the plug, deteriorates the surface quality of the pipe product, and decreases the yield. Increase product manufacturing costs.
[0017]
Such seizure can be substantially prevented from being constantly supplied and filled with the high-pressure lubricating oil by employing the above-described high-pressure lubricating drawing method. However, even when the high-pressure lubrication drawing method is adopted, the occurrence of chatter vibration may not be sufficiently prevented.
[0018]
This chatter vibration is generally known as self-excited vibration caused by fluctuations in the coefficient of friction that occurs between the workpiece and the tool (die, plug), and is considered a kind of stick-slip phenomenon that repeats the stick state and the slip state. Yes.
[0019]
The pipe product obtained by the drawing process that generates chatter vibrations varies in the axial direction although its inner diameter is very small. When such pipe products are used in nuclear power generation facilities, extremely strict quality control is required for safety, so with regard to such inner diameter fluctuations in the axial direction, strict inspection is required in the appearance inspection and inner eddy current inspection. Standards are established. In particular, in the internal eddy current flaw detection, the fluctuation in the inner diameter in the axial length direction causes noise, which significantly reduces the S / N ratio of flaw detection, and causes the generation of rejected products.
[0020]
The present invention was made in view of the above-mentioned cold drawing process, and when performing cold working by forming a chemical conversion treatment lubricating film or an oil lubricating film on the surface of the raw tube subjected to the bright heat treatment, It is an object of the present invention to provide a method for drawing a Ni-based alloy pipe, which can effectively prevent chatter vibration generated in a workpiece.
[0021]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have conducted a drawing process using various work materials, employing various lubrication conditions and also using a high-pressure lubrication drawing method, and investigated the cause of chatter vibration. went.
[0022]
As a result, for example, chatter vibration may frequently occur when cold drawing is performed using a Ni-based alloy element tube subjected to bright heat treatment. A lot of fine powder of alumina oxide (Al 2 O 3 ) adhered to the surface of the tool used at that time, particularly the plug, and a streak pattern was observed in the drawing direction. From this, it was estimated that the fine powder of alumina oxide remaining on the surface of the raw tube was the cause of chatter vibration.
[0023]
The oxide present on the surface of the Ni-based alloy element tube is generated in the heat treatment performed before the drawing process, and when performing the bright heat treatment in the reducing atmosphere, the atmospheric conditions are adjusted and managed. The generation of oxides remaining on the inner and outer surfaces of the raw tube, such as chromium oxide (Cr 2 O 3 ) and alumina oxide (Al 2 O 3 ), can be suppressed. Thereby, the fluctuation | variation of the friction coefficient of the raw pipe | tube and tool during a drawing process can be suppressed, and the chatter vibration which generate | occur | produces in the pipe | tube during a cold working can be prevented.
[0024]
The present invention has been completed on the basis of the above findings, and the gist of the following (1) and (2) Ni-based alloy pipe drawing methods.
(1) A Ni-based alloy characterized by a method of drawing in a cold process using a base tube subjected to bright heat treatment, wherein the bright heat treatment is performed in a hydrogen atmosphere having a dew point of -50 ° C or lower. This is a pipe drawing method.
(2) In the drawing method of (1) above, the pipe product to be drawn is a small-diameter long pipe, and an oil lubrication film is formed on the inner and outer surfaces of the raw pipe. It is desirable to adopt the law.
[0025]
The small-diameter long pipe defined in the present invention is assumed to be a steam generation pipe used in nuclear power generation facilities, a feed water heater tube, or the like, and an Ni-based alloy pipe having an outer diameter of 40 mm or less and a length of 15 m or more. Applicable.
[0026]
Further, these small diameter long tubes are often thin and have dimensional characteristics with a thickness / outer diameter ratio of 10% or less. Further, if the pipe product has a small diameter and thin wall characteristic, the cross-section reduction rate Rd in the finishing process of the cold drawing process tends to be a high workability exceeding 30%.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
In the drawing method of the present invention, an elementary tube that has been subjected to a bright heat treatment in a reducing hydrogen atmosphere is used. When heat treatment is performed in an air atmosphere or an oxidizing atmosphere, a descaling process is required after the heat treatment of the raw tube. As described above, when the main body of the workpiece is a small-diameter long tube, a large amount of man-hours are required for the processing, and the chemicals used are expensive. In order to avoid such a descaling treatment, a bright heat treatment in a hydrogen reduction atmosphere in which almost no scale is generated on the surface is performed when the base tube is heat-treated.
[0028]
As described above, the occurrence factor of chatter vibration includes oxides present on the surface of the tube before drawing. Since the oxide present on the surface of the tube is generated in the bright heat treatment performed before the drawing process, it is generated on the surface of the tube by changing the dew point of hydrogen used as the reducing atmosphere. Oxides were investigated.
[0029]
Usually, the dew point of the hydrogen atmosphere is adjusted by adjusting the water content in the hydrogen atmosphere with a dew point adjuster.
[0030]
Using a Ni-based alloy (Ni ≧ 58%) as a raw material, the dew point of the hydrogen atmosphere was changed in a range of −20 ° C. to −56 ° C., and oxides formed on the surface of the raw tube were investigated. According to the results of the investigation, chromium oxide is formed on the surface of the raw tube when the dew point of the hydrogen atmosphere is -20 ° C or higher, but when the dew point is in the range of -20 ° C to -56 ° C, the alumina oxide is the raw tube. Precipitate on the surface. By reducing the dew point of the hydrogen atmosphere, the alumina oxide deposited on the raw tube surface is reduced. When the dew point of the hydrogen atmosphere is −56 ° C. or lower, oxide deposition is not observed.
[0031]
When the dew point of the hydrogen atmosphere reaches -50 ° C, there is some precipitation of alumina oxide (area ratio is about 1.4%), but the influence on cold drawing can be ignored, and chatter vibration occurs. Remains low. Therefore, in the present invention, the dew point of the hydrogen atmosphere is managed at -50 ° C. or lower. Furthermore, in order to completely prevent chatter vibration, it is desirable to manage the dew point of the hydrogen atmosphere at −60 ° C. or lower.
[0032]
【Example】
For an Ni-based alloy element tube having an outer diameter of 23.00 mm, a wall thickness of 1.460 mm, and a length of 10,000 mm, the outer diameter is 16.02 mm, the wall thickness is 1.005 mm and the length is measured by the high-pressure lubrication drawing method shown in FIG. The tube product of 21000 mm was drawn with a cross-section reduction rate of 52%. The Ni-based alloy of the raw material is specified in ASME SB-163 UNS NO66690.
[0033]
The bright heat treatment before the drawing process is an electric resistance heating method in a hydrogen atmosphere, and the dew point of the hydrogen atmosphere is set to two types of −50 ° C. and −43 ° C. The raw tube subjected to bright heat treatment was drawn to investigate the occurrence of chatter vibration. At this time, a lubricating oil containing 15% by weight of Cl as an extreme pressure additive and 5% by weight of S with respect to 100 parts by weight of a mixed composition of chlorinated oil / fat, chlorinated ester and sulfurized oil / fat was used. A pressure of 118 MPa was applied, and drawing was performed at a drawing speed of 25 m / min.
[0034]
2 and 3 are diagrams showing SEM observation (× 2000) results of the inner surface of the blank tube before and after the bright heat treatment. FIG. 2 shows the observation results before the heat treatment. Fig. 3 shows the observation results after heat treatment. Fig. 3 (a) shows the observation results when the dew point of the hydrogen atmosphere is -50 ° C, and Fig. 3 (b) shows the observation results when the dew point of the hydrogen atmosphere is -43 ° C. Respectively.
[0035]
As shown in FIG. 2, no oxide such as alumina was deposited on the surface of the raw tube before the heat treatment. However, as shown in FIGS. 3 (a) and 3 (b), the alumina was oxidized after the heat treatment. Precipitation of the product was observed. In the observation results shown in FIGS. 3 (a) and 3 (b), the white spots indicate alumina oxide.
[0036]
Fig. 3 (a) shows the case where the dew point of the hydrogen atmosphere is -50 ° C, while the area ratio of alumina oxide is suppressed to 1.4%, while Fig. 3 (b) shows the dew point of the hydrogen atmosphere. In this case, the area ratio of alumina is significantly increased to 50.6%.
[0037]
Therefore, the occurrence rate of chatter vibration in the drawing process was 1% when the dew point of the hydrogen atmosphere was −50 ° C., whereas it was 4% when the dew point of the hydrogen atmosphere was −43 ° C. And increasing. However, the occurrence rate of chatter vibration is indicated by the ratio of the number of drawn wires.
[0038]
Furthermore, regarding the S / N ratio at the time of eddy current flaw detection of pipe products, when the dew point of the hydrogen atmosphere is -50 ° C., all the pipe products in which chatter vibration does not occur are subjected to eddy current flaw detection, and the S / N ratio. Is confirmed to be good.
[0039]
【The invention's effect】
According to the drawing method of the present invention, it is possible to form either a chemical conversion treatment lubricating film or an oil lubricating film even with a small-diameter long pipe without using a cold working facility having a special prevention device. Even if it exists, generation | occurrence | production of chatter vibration can be prevented effectively and cold work can be performed stably.
[0040]
In particular, when the high-pressure lubrication drawing method is adopted, chatter vibration is eliminated, and the cold drawing is stabilized, and a pipe product having excellent surface properties can be manufactured at a low cost.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining a high-pressure lubrication drawing method in which cold working is performed while high-pressure lubricating oil is supplied.
FIG. 2 is a diagram showing a result of SEM observation (× 2000) of an inner surface of a raw tube before bright heat treatment.
FIG. 3 is a diagram showing the SEM observation (× 2000) result of the inner surface of the blank tube after the bright heat treatment, (a) is the observation result when the dew point of the hydrogen atmosphere is −50 ° C., (b) The observation result when the dew point of hydrogen atmosphere is -43 degreeC is shown.
[Explanation of symbols]
1: Raw tube, 2: Die, 3: Plug 4: Container, 4a: Telescopic structure 5: Plug support rod
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002295353A JP3783676B2 (en) | 2002-10-08 | 2002-10-08 | Drawing method of Ni-base alloy tube |
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| JP2002295353A JP3783676B2 (en) | 2002-10-08 | 2002-10-08 | Drawing method of Ni-base alloy tube |
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| JP3783676B2 true JP3783676B2 (en) | 2006-06-07 |
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| EP2517801B1 (en) | 2009-12-21 | 2019-07-24 | Nippon Steel Corporation | Base tube for cold-drawing, manufacturing method for same, and manufacturing method for cold-drawn tube |
| CN112275813A (en) * | 2020-09-14 | 2021-01-29 | 江苏华程工业制管股份有限公司 | Three-wire drawing machine for steel pipe |
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