JP2004132437A - Manufacturing method for steel pipe for boiler having superior steam oxidation resistance property - Google Patents
Manufacturing method for steel pipe for boiler having superior steam oxidation resistance property Download PDFInfo
- Publication number
- JP2004132437A JP2004132437A JP2002296339A JP2002296339A JP2004132437A JP 2004132437 A JP2004132437 A JP 2004132437A JP 2002296339 A JP2002296339 A JP 2002296339A JP 2002296339 A JP2002296339 A JP 2002296339A JP 2004132437 A JP2004132437 A JP 2004132437A
- Authority
- JP
- Japan
- Prior art keywords
- steam oxidation
- steel pipe
- oxidation resistance
- boiler
- resistant steel
- 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.)
- Granted
Links
Landscapes
- Rigid Pipes And Flexible Pipes (AREA)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、火力発電設備に用いられるボイラ・配管用鋼管に関し、鋼管内面において優れた耐水蒸気酸化特性を有するフェライト系およびオーステナイト系耐熱鋼管の製造方法に関するものである。
【０００２】
【従来の技術】
近年、火力発電プラントにおいては、経済性の向上、炭酸ガス排出抑制の関点から、発電効率を向上させるために蒸気条件を従来以上に高温高圧化することが検討されている。そのためには、従来材以上の高い高温強度と耐食性を有する鋼管材料が必要であり、例えば、２２Ｃｒ−２５Ｎｉの新しい高強度高耐食のオーステナイト系耐熱鋼が既に開発されている（例えば、非特許文献１参照）。
【０００３】
オーステナイト系耐熱鋼は熱膨張係数が大きいことから、ボイラ用鋼管内面に生成する水蒸気酸化スケールが剥離しやすく、剥離したスケールによる管の閉塞や、タービンブレードのエロージョンといった問題が頻繁に生じた。また、熱膨張係数が大きく熱伝導率が低いという欠点を解決すべく９〜１２Ｃｒの高強度フェライト系耐熱鋼の開発が現在も盛んに行われている。しかし、フェライト系耐熱鋼はオーステナイト系耐熱鋼に比べてＣｒ添加量が少ないために耐食性が劣るという欠点がある。特に、管内面に生じる水蒸気酸化に対しては、６００℃を越えるような蒸気温度の場合には十分な耐性があるとは言えない。
【０００４】
管内面の水蒸気酸化性を劇的に向上させる手法としては、例えば、内面にショットブラストや研磨等の冷間加工を施す方法が考案され、既に実用化されている（例えば、非特許文献２参照）。
【０００５】
しかしこの方法ではフェライト系耐熱鋼では、Ｃｒ量含有量が概ね１３％を越える場合から効果が現れ、さらに確実な効果を得るためには少なくとも１６％を越える量のＣｒを添加する必要があり、Ｃｒ量が１６％以下であるフェライト系耐熱鋼には適用することができないのが現状である。また、オーステナイト系耐熱鋼においては、７００℃までは劇的な水蒸気酸化抑制効果を示すものの、７００℃を越える温度域ではその効果が小さくなるという欠点を有しており、蒸気温度のさらなる高温高圧化のためには、７００℃を越える温度域でも効果を発揮する水蒸気酸化抑制方法が必要であった。
【０００６】
【非特許文献１】
「火力原子力発電」昭和６１年１月１５日、第３８巻、第１号、Ｐ．７５
【非特許文献２】
「日本鋼管技報」昭和５３年５月１５日、第７７巻、Ｐ．２０
【０００７】
【発明が解決しようとする課題】
本発明は、上記の従来技術の問題点に鑑みて、従来に比べて格段に耐水蒸気酸化性に優れたボイラ用フェライト系耐熱鋼管および７００℃を越える温度域でも安定して優れた耐水蒸気酸化特性を発揮するボイラ用オーステナイト系耐熱鋼管を製造する方法を提供するものである。
【０００８】
【課題を解決するための手段】
本発明者らは、上記課題を解決するために、管内表面に施す冷間加工の方法を種々検討した結果、超音波衝撃処理により、耐水蒸気酸化性が向上するＣｒ量をショット加工よりも低減させることができることを見いだした。
【０００９】
本発明はこれらの知見に基づいてなされたものであり、その要旨とするところは、以下のとおりである。
【００１０】
（１） 質量％で５〜３０％のＣｒを含有するフェライト系耐熱鋼管の内表面に超音波衝撃処理を施すことを特徴とする、耐水蒸気酸化性の優れたボイラ用鋼管の製造方法。
【００１１】
（２） 質量％で５〜３０％のＣｒを含有するオーステナイト系耐熱鋼管の内表面に超音波衝撃処理を施すことを特徴とする、耐水蒸気酸化性の優れたボイラ用鋼管の製造方法。
【００１２】
（３） 超音波衝撃処理による表面への加工層の厚さが２０μｍ以上であることを特徴とする前記（１）または（２）に記載の耐水蒸気酸化性の優れたボイラ用鋼管の製造方法。
【００１３】
（４） 振幅１０〜５０μｍ、振動数５〜５０ｋＨｚの条件下で超音波衝撃処理を施すことを特徴とする前記（１）〜（３）のいずれか１項に記載の耐水蒸気酸化性の優れたボイラ用鋼管の製造方法。
【００１４】
【発明の実施の形態】
本発明者は、表面近傍に圧縮の残留応力を導入する技術である超音波衝撃処理（ＵＳＰ６，１７１，４１５号公報参照）に着目し、その耐水蒸気酸化性向上効果について鋭意検討を行った。その結果、ＪＩＳ ＳＴＢＡ２５（５Ｃｒ−０．５Ｍｏ）に対して６００℃での耐水蒸気酸化性向上効果を確認することができた。さらに、ＪＩＳ ＳＵＳ３０４ＨＴＢ（１８Ｃｒ−８Ｎｉ）に対して７５０℃での耐水蒸気酸化性向上効果を確認することができた。
【００１５】
冷間加工による耐水蒸気酸化性向上効果は、冷間加工により表面近傍に導入された高密度の欠陥を通じての表面へのＣｒの拡散が容易になり、保護性の高いＣｒ２Ｏ３層が酸化初期に表面に均一に生成することに起因すると考えられている。超音波衝撃処理法は従来のショット加工に比べて、大幅に加工度の高い冷間加工を表面近傍に集中的に付与することができるために、それによって形成される表面加工層の冶金学的形態は従来のショット加工の場合と大きく異なる。超音波衝撃処理法による著しい耐水蒸気酸化性の向上は、現時点で詳細な理由は明らかではないが、Ｃｒの内部から表面への拡散が通常のショット加工では到底得ることのできないほどに格段に容易になったために表面でのＣｒ２Ｏ３層形成が促進され、より低いＣｒ量でも耐水蒸気酸化性向上効果が発揮されるようになったものと考えられる。
【００１６】
次に本発明鋼の化学成分の限定理由について説明する。なお、以下に示す「％」は、特段の説明がない限りは、「質量％」を意味するものとする。上記のように本発明では酸化に対して保護性の高いＣｒ２Ｏ３皮膜による効果を利用しているために、Ｃｒ含有鋼が前提となる。しかし、Ｃｒ含有量が５％未満の場合には、耐酸化性を大幅に向上させるのに十分なだけＣｒ２Ｏ３層が生成しないために、本発明では５％以上のＣｒを含有する鋼に限定した。また、Ｃｒ含有量が３０％を越えると従来通りのショット加工を施しても十分に耐水蒸気酸化性向上効果が得られるために、本発明ではＣｒ含有量の上限を３０％に限定した。なお、オーステナイト系耐熱鋼においては、Ｃｒ含有量が１６％以下の場合には、７００℃を越える温度域で耐酸化性を大幅に向上させるのに十分なＣｒ２Ｏ３層が生成しないために、１６％超のＣｒを含有することが好ましい。
【００１７】
本発明の効果に影響をおよぼす化学成分はＣｒだけであるため、本発明では他の化学成分は特に規定しない。Ｃｒ以外の化学成分の適正な添加量は、本発明で対象としているボイラ用フェライト系耐熱鋼管またはオーステナイト系耐熱鋼管で一般的に添加されている化学成分量の範囲内である。
【００１８】
次に、加工層の厚さの限定理由について説明する。ここで、加工層厚さを次のように定義する。超音波衝撃処理を施した表面に垂直な断面に対して、最表面位置から内部に向けて適当な間隔でビッカース硬さを測定していくと、最表面に近いほど加工硬化が大きく、内部に向かって順に硬さが減少していき、やがて肉厚中央部の硬さまで飽和するのであるが、最表面から５μｍ内部側の位置での硬さと、肉厚中央部の硬さとの平均値と等しい硬さを示す位置の、最表面からの距離を加工層厚さと定義する。
【００１９】
加工層厚さが２０μｍ未満の場合には加工度が低すぎて、内部から表面に拡散して来るＣｒが十分な量でないために、耐水蒸気酸化性向上効果が得られない。
【００２０】
そのため、加工層厚さの下限を２０μｍとした。加工層厚さは極端に厚すぎると母材の機械的性質を損なう可能性も考えられるが、超音波衝撃処理によってそのような厚さの加工層が形成されることはないので、特に上限は定めない。望ましい加工層厚さは５０〜１５０μｍである。
【００２１】
次に、超音波衝撃処理条件の限定理由について説明する。本発明では振幅を１０〜５０μｍの範囲に限定した。その理由は、振幅は１０μｍ未満では十分な加工を加えることができず、一方５０μｍを越えると管内面に入る塑性変形か大きくなりすぎて、肉厚の変化が無視できなくなるためである。また、振動数は５〜５０ｋＨｚの範囲に限定した。その理由は、超音波衝撃処理によって管に与えられる衝撃エネルギーがこの周波数の領域で最も効率が良くなるためである。
【００２２】
なお、本発明でのボイラ用鋼管とは、ボイラ本体内部で用いられる鋼管のみならず、そこで作られた高温高圧の蒸気をタービン等に輸送するための蒸気配管も含まれる。
【００２３】
【実施例】
以下に、本発明の効果を実施例によって具体的に説明する。
（実施例１）
表１に、供試鋼管の種類とそのＣｒ含有量を示す。表１において、鋼番ａは実験室で溶解し、熱間押出により製造した本発明範囲内の１６％Ｃｒ鋼管である。また、鋼番ｂ〜ｄは、ＪＩＳ Ｇ３４６２に記載のフェライト系ボイラ用鋼管であるＳＵＳ４１０ＴＢ，ＳＴＢＡ２６およびＳＴＢＡ２５である。これらの鋼管のＣｒ含有量も本発明範囲内である。また、鋼番ｅは、同じくＪＩＳ Ｇ３４６２に記載のＳＴＢＡ２４であり、そのＣｒ含有量は、本発明範囲から外れている。なお、鋼番ｂ〜ｅはマンネスマン法により製造した鋼管である。
【００２４】
これらの鋼管に対して、表２に示す条件で管内面に超音波衝撃処理を施した。
【００２５】
なお、超音波振動の超音波発生装置は、５００ｗ〜１ｋｗの電源を用いて、発振機により超音波を発振後、トランスデューサーによりその周波数を１〜６０ｋＨｚに変換し、さらに、ウェーブガイドにてその振幅を増幅させて、直径２ｍｍ〜２０ｍｍφのピンからなる超音波振動端子を５〜６０μｍの振幅で機械的に振動させる装置である。これによって、打撃部の表面において、平滑性を維持しつつ打撃前の表面に対して深さ数百μｍ程度の圧痕を形成することができる。
【００２６】
超音波衝撃処理材および比較のための未処理材から、その内表面が試験片表面の一部になるように試験片を切り出し、６００℃で５００時間保持する水蒸気酸化試験を実施した。水蒸気酸化試験は「鉄と鋼」第７４巻第１２７頁に記載の方法に準じて行った。試験後、試料を樹脂に埋め込み、断面を切断して鏡面研磨し、水蒸気酸化スケール断面を光学顕微鏡でミクロ観察した。スケール厚さは、５００倍の倍率で任意の５視野を写真撮影し、スケール部の面積を画像処理により求め、それをスケール厚さに換算し、５視野の平均値を求めた。
【００２７】
【表１】
【表２】
この表２に示した試験Ｎｏ．１〜４は、本発明範囲内の化学成分および製造条件で製造した本発明例である。表２に示されているように、超音波衝撃処理を施すことにより水蒸気酸化スケールはほとんど観察されず、超音波衝撃処理およびショット加工を施さない試験Ｎｏ．１４〜１８と比較して、耐水蒸気酸化特性は極めて良好であった。
【００３０】
一方、試験Ｎｏ．１３はＣｒ含有量が２．３％と少なすぎて、超音波衝撃処理を施すことによる耐水蒸気酸化性向上効果が小さかった例である。試験Ｎｏ．１９〜２２はいずれも化学成分は本発明範囲内であるが、超音波衝撃処理ではなく、０．５ｍｍのＳＵＳ３０４カットワイヤーを用いて投射圧４ｋｇｆ／ｃｍ２で従来のショット加工を施した比較例であるが、耐水蒸気酸化特性向上効果が小さかった。
【００３１】
また、試験Ｎｏ．５〜８はいずれも化学成分は本発明範囲内であるが、超音波衝撃処理後の加工層厚さが小さく、超音波衝撃処理による耐水蒸気酸化性向上効果が得られたが、やや不十分であった。また、試験Ｎｏ．９〜１２はいずれも化学成分は本発明範囲内であるが、超音波衝撃処理時の振幅が小さく、耐水蒸気酸化性向上効果が得られたが、やや不十分であった。
（実施例２）
表３に、供試鋼管の種類とそのＣｒ含有量を示す。表３において、鋼番ｆは実験室で溶解し、熱間押出により製造した本発明範囲内の３０％Ｃｒ鋼管である。また、鋼番ｇ〜ｊは熱間押出により製造したＪＩＳ Ｇ３４６３に記載のオーステナイト系ボイラ用鋼管ＳＵＳ３１０ＴＢ，ＳＵＳ３０４ＨＴＢ，およびＳＵＳ３１６ＨＴＢである。これらの鋼管のＣｒ含有量も本発明範囲内である。また、鋼番ｅは実験室で溶解し、熱間押出により製造した１３％Ｃｒ鋼管であり、そのＣｒ含有量は本発明範囲内ではあるが望ましい範囲からは外れている。
【００３２】
これらの鋼管に対して、実施例１と同じ超音波発生装置を用いて、表４に示す条件で管内面に超音波衝撃処理を施した。超音波衝撃処理材および比較のための未処理材から、その内表面が試験片表面の一部になるように試験片を切り出し、７５０℃で５００時間保持する水蒸気酸化試験を実施した。水蒸気酸化試験およびスケール厚の測定は実施例１と同様にして行った。
【００３３】
【表３】
【表４】
表４に示した試験Ｎｏ．２３〜２６は、本発明範囲内の化学成分および製造条件で製造した本発明例である。表２に示されているように、超音波衝撃処理を施すことにより水蒸気酸化スケール厚さは大幅に減少し、超音波衝撃処理およびショット加工を施さない試験Ｎｏ．３６〜３９と比較して、耐水蒸気酸化特性は極めて良好であった。試験Ｎｏ．２７は、超音波衝撃処理およびショット加工を施さない試験Ｎｏ．４０と比較して耐水蒸気酸化性はかなり向上したものの、Ｃｒ量が望ましい範囲から外れているため、超音波衝撃処理を施すことによっても７５０℃で生成される水蒸気酸化性スケール厚さは厚かった例である。
【００３６】
一方、試験Ｎｏ．４１〜４５は、超音波衝撃処理ではなく、０．５ｍｍのＳＵＳ３０４カットワイヤーを用いて投射圧４ｋｇｆ／ｃｍ２で従来のショット加工を施した比較例であり、７５０℃では耐水蒸気酸化特性向上効果が小さい。なお、試験Ｎｏ．４５は、Ｃｒ量が望ましい化学成分範囲からは外れており、同一材料で超音波衝撃処理を施した試験Ｎｏ．２７と比較すると、耐水蒸気酸化性が格段に劣る。
【００３７】
また、試験Ｎｏ．２８〜３１はいずれも化学成分は本発明範囲内であるが、超音波衝撃処理後の加工層厚さが小さく、超音波衝撃処理による耐水蒸気酸化性向上効果が得られたが、やや不十分であった。また、試験Ｎｏ．３２〜３５はいずれも化学成分は本発明範囲内であるが、超音波衝撃処理時の振幅が小さく、耐水蒸気酸化性向上効果が得られたが、やや不十分であった。
【００３８】
【発明の効果】
本発明の適用により、従来に比べて格段に耐水蒸気酸化性に優れたボイラ用フェライト系耐熱鋼管およびボイラ用オーステナイト系耐熱鋼管を製造する方法を提供することが可能となる。したがって、本発明においては、産業の発展に寄与するところ極めて大なるものがある。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a boiler / pipe steel pipe used in a thermal power plant, and more particularly to a method for producing a ferritic and austenitic heat-resistant steel pipe having excellent steam oxidation resistance on the inner surface of the steel pipe.
[0002]
[Prior art]
In recent years, in a thermal power plant, it has been studied to increase the steam condition to a higher temperature and a higher pressure than ever before in order to improve power generation efficiency from the viewpoint of improving economic efficiency and suppressing carbon dioxide emission. For that purpose, a steel pipe material having higher high-temperature strength and corrosion resistance than conventional materials is required. For example, a new high-strength and high-corrosion austenitic heat-resistant steel of 22Cr-25Ni has already been developed (for example, Non-Patent Documents) 1).
[0003]
Since austenitic heat-resistant steel has a large coefficient of thermal expansion, steam oxidation scale generated on the inner surface of a steel pipe for boiler tends to peel off, and problems such as blockage of the pipe by the peeled scale and erosion of turbine blades frequently occur. Further, development of 9-12 Cr high-strength ferritic heat-resistant steel has been actively pursued in order to solve the drawback that the thermal expansion coefficient is large and the thermal conductivity is low. However, ferritic heat-resistant steel has a drawback that corrosion resistance is inferior due to the small amount of Cr added as compared with austenitic heat-resistant steel. In particular, it cannot be said that the steam oxidation generated on the inner surface of the tube has sufficient resistance at a steam temperature exceeding 600 ° C.
[0004]
As a method of dramatically improving the steam oxidation property of the inner surface of the tube, for example, a method of performing cold working such as shot blasting or polishing on the inner surface has been devised and has already been put to practical use (for example, see Non-Patent Document 2). ).
[0005]
However, in this method, the effect is exhibited when the content of Cr exceeds approximately 13% in ferritic heat-resistant steel, and it is necessary to add at least 16% of Cr in order to obtain a more reliable effect. At present, it cannot be applied to ferritic heat-resistant steel having a Cr content of 16% or less. Further, austenitic heat-resistant steel has a dramatic effect of suppressing steam oxidation up to 700 ° C, but has a disadvantage that its effect is reduced in a temperature range exceeding 700 ° C. For this purpose, a method for suppressing steam oxidation that is effective even in a temperature range exceeding 700 ° C. is required.
[0006]
[Non-patent document 1]
"Thermal Nuclear Power", Vol. 38, No. 1, January 15, 1986 75
[Non-patent document 2]
"Nihon Kokan Giho," Vol. 77, May 15, 1978, p. 20
[0007]
[Problems to be solved by the invention]
In view of the above-mentioned problems of the prior art, the present invention provides a ferritic heat-resistant steel tube for a boiler that has much more excellent steam oxidation resistance than the conventional one, and a steam oxidation resistance that is stably excellent even in a temperature range exceeding 700 ° C. An object of the present invention is to provide a method for producing an austenitic heat-resistant steel pipe for a boiler exhibiting characteristics.
[0008]
[Means for Solving the Problems]
The present inventors have studied various methods of cold working applied to the inner surface of the pipe in order to solve the above-described problems, and as a result, the amount of Cr that improves steam oxidation resistance is reduced by the ultrasonic shock treatment compared to the shot processing. I found something that could be done.
[0009]
The present invention has been made based on these findings, and the gist thereof is as follows.
[0010]
(1) A method for producing a steel pipe for a boiler having excellent steam oxidation resistance, which comprises subjecting an inner surface of a ferritic heat-resistant steel pipe containing 5 to 30% by mass of Cr to ultrasonic shock treatment.
[0011]
(2) A method for producing a boiler steel tube having excellent steam oxidation resistance, wherein an ultrasonic impact treatment is performed on the inner surface of an austenitic heat-resistant steel tube containing 5 to 30% by mass of Cr.
[0012]
(3) The method for producing a steel pipe for a boiler having excellent steam oxidation resistance according to the above (1) or (2), wherein a thickness of a processed layer on a surface by the ultrasonic impact treatment is 20 μm or more. .
[0013]
(4) The steam oxidation resistance according to any one of (1) to (3), wherein the ultrasonic impact treatment is performed under the conditions of an amplitude of 10 to 50 μm and a frequency of 5 to 50 kHz. Of boiler steel tubes.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventor paid attention to ultrasonic impact treatment (see US Pat. No. 6,171,415) which is a technique for introducing a compressive residual stress in the vicinity of the surface, and intensively studied the effect of improving steam oxidation resistance. As a result, the effect of improving steam oxidation resistance at 600 ° C. with respect to JIS STBA25 (5Cr-0.5Mo) was confirmed. Furthermore, the effect of improving steam oxidation resistance at 750 ° C. with respect to JIS SUS304HTB (18Cr-8Ni) could be confirmed.
[0015]
The effect of improving the steam oxidation resistance by cold working is that diffusion of Cr to the surface through high-density defects introduced near the surface by cold working becomes easy, and the highly protective Cr 2 O 3 layer is oxidized. It is thought to be due to the uniform formation on the surface at the beginning. Compared to conventional shot processing, the ultrasonic impact treatment method can apply cold work, which is significantly higher in processing rate, to the vicinity of the surface in a concentrated manner. The form is significantly different from the case of conventional shot processing. The remarkable improvement in steam oxidation resistance by the ultrasonic impact treatment method is not clear at this time, but the diffusion of Cr from the inside to the surface is much easier than ordinary shot processing can achieve. It is considered that the formation of a Cr 2 O 3 layer on the surface was promoted due to the formation of the Cr, and the effect of improving the steam oxidation resistance was exhibited even with a lower Cr content.
[0016]
Next, the reasons for limiting the chemical components of the steel of the present invention will be described. Note that “%” shown below means “% by mass” unless otherwise specified. As described above, in the present invention, a Cr-containing steel is premised because the effect of the Cr 2 O 3 film having high protection against oxidation is used. However, when the Cr content is less than 5%, a Cr 2 O 3 layer is not generated only enough to greatly improve oxidation resistance. Limited to. If the Cr content exceeds 30%, the effect of improving the steam oxidation resistance can be sufficiently obtained even when the conventional shot processing is performed. Therefore, the upper limit of the Cr content is limited to 30% in the present invention. In the austenitic heat-resistant steel, when the Cr content is 16% or less, a Cr 2 O 3 layer sufficient to greatly improve oxidation resistance in a temperature range exceeding 700 ° C. is not generated. , More than 16% Cr.
[0017]
Since the only chemical component that affects the effects of the present invention is Cr, other chemical components are not particularly defined in the present invention. The appropriate amount of addition of the chemical components other than Cr is within the range of the amount of the chemical component generally added in the heat-resistant ferritic steel pipe for a boiler or the heat-resistant austenitic steel pipe used in the present invention.
[0018]
Next, the reason for limiting the thickness of the processed layer will be described. Here, the working layer thickness is defined as follows. Measure the Vickers hardness at appropriate intervals from the outermost surface position to the inside of the section perpendicular to the surface subjected to the ultrasonic impact treatment. The hardness gradually decreases toward the center, and eventually saturates to the hardness at the center of the thickness, but is equal to the average value of the hardness at the position inside 5 μm from the outermost surface and the hardness at the center of the thickness. The distance from the outermost surface at the position indicating the hardness is defined as the thickness of the processed layer.
[0019]
When the thickness of the processed layer is less than 20 μm, the degree of processing is too low, and the amount of Cr diffused from the inside to the surface is not sufficient, so that the effect of improving steam oxidation resistance cannot be obtained.
[0020]
Therefore, the lower limit of the thickness of the processed layer is set to 20 μm. If the thickness of the working layer is extremely large, the mechanical properties of the base material may be impaired.However, since the working layer having such a thickness is not formed by the ultrasonic impact treatment, the upper limit is particularly limited. Not determined. Desirable working layer thickness is 50 to 150 μm.
[0021]
Next, the reason for limiting the ultrasonic impact processing conditions will be described. In the present invention, the amplitude is limited to the range of 10 to 50 μm. The reason is that if the amplitude is less than 10 μm, sufficient processing cannot be performed, while if it exceeds 50 μm, the plastic deformation entering the inner surface of the pipe becomes too large, and the change in wall thickness cannot be ignored. The frequency was limited to the range of 5 to 50 kHz. The reason for this is that the impact energy given to the tube by the ultrasonic impact treatment is most efficient in this frequency range.
[0022]
The boiler steel pipe in the present invention includes not only a steel pipe used inside the boiler main body but also a steam pipe for transporting high-temperature and high-pressure steam produced there to a turbine or the like.
[0023]
【Example】
Hereinafter, the effects of the present invention will be specifically described with reference to examples.
(Example 1)
Table 1 shows the types of the test steel pipes and their Cr contents. In Table 1, steel number a is a 16% Cr steel pipe within the scope of the present invention that was melted in a laboratory and manufactured by hot extrusion. Steel numbers b to d are SUS410TB, STBA26, and STBA25, which are ferrite-based boiler steel pipes described in JIS G3462. The Cr content of these steel tubes is also within the scope of the present invention. The steel number e is STBA24 described in JIS G3462, and its Cr content is out of the range of the present invention. Steel numbers be are steel pipes manufactured by the Mannesmann method.
[0024]
These steel pipes were subjected to ultrasonic impact treatment on the inner surfaces of the pipes under the conditions shown in Table 2.
[0025]
In addition, the ultrasonic generator for ultrasonic vibration uses a power supply of 500 w to 1 kw, oscillates ultrasonic waves by an oscillator, converts the frequency to 1 to 60 kHz by a transducer, and further converts the frequency to 1 to 60 kHz by a waveguide. This is a device that amplifies the amplitude and mechanically vibrates an ultrasonic vibration terminal composed of a pin having a diameter of 2 mm to 20 mm with an amplitude of 5 to 60 μm. This makes it possible to form indentations having a depth of about several hundred μm with respect to the surface before hitting while maintaining smoothness on the surface of the hitting portion.
[0026]
From the ultrasonic impact treated material and the untreated material for comparison, a test piece was cut out so that its inner surface became a part of the test piece surface, and a steam oxidation test was performed at 600 ° C. for 500 hours. The steam oxidation test was performed according to the method described in “Iron and Steel”, vol. 74, p. 127. After the test, the sample was embedded in resin, the cross section was cut and mirror-polished, and the cross section of the steam oxidation scale was microscopically observed with an optical microscope. The scale thickness was obtained by photographing five arbitrary visual fields at a magnification of 500 times, determining the area of the scale part by image processing, converting the area to the scale thickness, and determining the average value of the five visual fields.
[0027]
[Table 1]
[Table 2]
Test No. shown in Table 2 Examples 1 to 4 are examples of the present invention manufactured under the chemical components and manufacturing conditions within the scope of the present invention. As shown in Table 2, almost no steam oxidation scale was observed by performing the ultrasonic impact treatment, and Test No. 14 to 18, the steam oxidation resistance was extremely good.
[0030]
On the other hand, Test No. No. 13 is an example in which the Cr content was too small as 2.3%, and the effect of improving the steam oxidation resistance by performing the ultrasonic impact treatment was small. Test No. Comparative Examples 19 to 22 in which the chemical components were within the scope of the present invention, but were not subjected to ultrasonic impact treatment, but were subjected to conventional shot processing at a projection pressure of 4 kgf / cm 2 using a 0.5 mm SUS304 cut wire. However, the effect of improving the steam oxidation resistance was small.
[0031]
Test No. 5 to 8 all have chemical components within the range of the present invention, but the processed layer thickness after the ultrasonic impact treatment was small, and the effect of improving the steam oxidation resistance by the ultrasonic impact treatment was obtained, but somewhat insufficient. Met. Test No. Nos. 9 to 12 all have chemical components within the range of the present invention, but the amplitude during ultrasonic impact treatment was small, and the effect of improving steam oxidation resistance was obtained, but was somewhat insufficient.
(Example 2)
Table 3 shows the types of test steel pipes and their Cr contents. In Table 3, steel number f is a 30% Cr steel pipe within the scope of the present invention that was melted in a laboratory and manufactured by hot extrusion. Steel numbers g to j are austenitic boiler steel pipes SUS310TB, SUS304HTB, and SUS316HTB described in JIS G3463 manufactured by hot extrusion. The Cr content of these steel tubes is also within the scope of the present invention. Steel No. e is a 13% Cr steel pipe melted in a laboratory and manufactured by hot extrusion, and its Cr content is within the range of the present invention but outside the desirable range.
[0032]
These steel pipes were subjected to ultrasonic impact treatment on the inner surfaces of the pipes under the conditions shown in Table 4 using the same ultrasonic generator as in Example 1. A test piece was cut out from the ultrasonic impact treated material and an untreated material for comparison so that the inner surface became a part of the test piece surface, and a steam oxidation test was performed at 750 ° C. for 500 hours. The steam oxidation test and the measurement of the scale thickness were performed in the same manner as in Example 1.
[0033]
[Table 3]
[Table 4]
Test No. shown in Table 4 23 to 26 are examples of the present invention manufactured under the chemical components and manufacturing conditions within the scope of the present invention. As shown in Table 2, the thickness of the steam-oxidized scale was significantly reduced by performing the ultrasonic impact treatment, and Test No. As compared with Nos. 36 to 39, the steam oxidation resistance was extremely good. Test No. Test No. 27 which does not perform ultrasonic impact treatment and shot processing is No. 27. Although the steam oxidation resistance was considerably improved as compared with 40, the amount of Cr was out of the desired range, and thus the thickness of the steam oxidation scale produced at 750 ° C. by the ultrasonic impact treatment was large. It is an example.
[0036]
On the other hand, Test No. Nos. 41 to 45 are comparative examples in which conventional shot processing was performed at a projection pressure of 4 kgf / cm 2 using a SUS304 cut wire of 0.5 mm instead of the ultrasonic impact treatment, and the effect of improving steam oxidation resistance at 750 ° C. Is small. In addition, the test No. In Test No. 45, the amount of Cr was out of the desirable range of the chemical composition, and Test No. 45 in which the same material was subjected to ultrasonic impact treatment. Compared with No. 27, the steam oxidation resistance is remarkably inferior.
[0037]
Test No. Although the chemical components of all of Nos. 28 to 31 are within the range of the present invention, the processed layer thickness after the ultrasonic impact treatment was small, and the effect of improving the steam oxidation resistance by the ultrasonic impact treatment was obtained, but was somewhat insufficient. Met. Test No. Although the chemical components of Nos. 32 to 35 are all within the range of the present invention, the amplitude at the time of the ultrasonic impact treatment was small, and the effect of improving the steam oxidation resistance was obtained, but was somewhat insufficient.
[0038]
【The invention's effect】
ADVANTAGE OF THE INVENTION By applying this invention, it becomes possible to provide the method of manufacturing the ferritic heat-resistant steel pipe for boilers and the austenitic heat-resistant steel pipe for boilers which is much more excellent in steam oxidation resistance than before. Therefore, in the present invention, there is an extremely large portion that contributes to the development of industry.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002296339A JP4205921B2 (en) | 2002-10-09 | 2002-10-09 | Manufacturing method of steel pipe for boilers with excellent steam oxidation resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002296339A JP4205921B2 (en) | 2002-10-09 | 2002-10-09 | Manufacturing method of steel pipe for boilers with excellent steam oxidation resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2004132437A true JP2004132437A (en) | 2004-04-30 |
| JP4205921B2 JP4205921B2 (en) | 2009-01-07 |
Family
ID=32286356
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2002296339A Expired - Fee Related JP4205921B2 (en) | 2002-10-09 | 2002-10-09 | Manufacturing method of steel pipe for boilers with excellent steam oxidation resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4205921B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009068079A (en) * | 2007-09-14 | 2009-04-02 | Sumitomo Metal Ind Ltd | Steel tube with excellent steam oxidation resistance |
| WO2011155296A1 (en) * | 2010-06-09 | 2011-12-15 | 住友金属工業株式会社 | Austenitic stainless steel tube having excellent steam oxidation resistance, and method for producing same |
| CN102510909A (en) * | 2011-11-18 | 2012-06-20 | 住友金属工业株式会社 | Austenitic stainless steel |
| RU2610096C1 (en) * | 2015-07-27 | 2017-02-07 | Общество с ограниченной ответственностью "Аквамодуль" | Austenitic and austenitic-ferritic steel processing method |
| US9612008B2 (en) | 2011-06-28 | 2017-04-04 | Nippon Steel & Sumitomo Metal Corporation | Austenitic stainless steel tube |
-
2002
- 2002-10-09 JP JP2002296339A patent/JP4205921B2/en not_active Expired - Fee Related
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009068079A (en) * | 2007-09-14 | 2009-04-02 | Sumitomo Metal Ind Ltd | Steel tube with excellent steam oxidation resistance |
| WO2011155296A1 (en) * | 2010-06-09 | 2011-12-15 | 住友金属工業株式会社 | Austenitic stainless steel tube having excellent steam oxidation resistance, and method for producing same |
| EP2581464A1 (en) * | 2010-06-09 | 2013-04-17 | Nippon Steel & Sumitomo Metal Corporation | Austenitic stainless steel tube having excellent steam oxidation resistance, and method for producing same |
| EP2581464A4 (en) * | 2010-06-09 | 2013-07-31 | Nippon Steel & Sumitomo Metal Corp | Austenitic stainless steel tube having excellent steam oxidation resistance, and method for producing same |
| US8852362B2 (en) | 2010-06-09 | 2014-10-07 | Nippon Steel & Sumitomo Metal Corporation | Austenitic stainless steel pipe excellent in steam oxidation resistance and manufacturing method therefor |
| US9612008B2 (en) | 2011-06-28 | 2017-04-04 | Nippon Steel & Sumitomo Metal Corporation | Austenitic stainless steel tube |
| CN102510909A (en) * | 2011-11-18 | 2012-06-20 | 住友金属工业株式会社 | Austenitic stainless steel |
| JP5029788B1 (en) * | 2011-11-18 | 2012-09-19 | 住友金属工業株式会社 | Austenitic stainless steel |
| WO2013073055A1 (en) * | 2011-11-18 | 2013-05-23 | 住友金属工業株式会社 | Austenitic stainless steel |
| RU2507294C2 (en) * | 2011-11-18 | 2014-02-20 | Сумитомо Метал Индастриз, Лтд. | Austenitic stainless steel |
| KR101393784B1 (en) * | 2011-11-18 | 2014-05-12 | 신닛테츠스미킨 카부시키카이샤 | Austenitic stainless steel |
| RU2610096C1 (en) * | 2015-07-27 | 2017-02-07 | Общество с ограниченной ответственностью "Аквамодуль" | Austenitic and austenitic-ferritic steel processing method |
Also Published As
| Publication number | Publication date |
|---|---|
| JP4205921B2 (en) | 2009-01-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| RU2507294C2 (en) | Austenitic stainless steel | |
| Lim et al. | Enhancement of abrasion and corrosion resistance of duplex stainless steel by laser shock peening | |
| JP5187461B2 (en) | Austenitic stainless steel pipe | |
| JP4952862B2 (en) | Austenitic stainless steel pipe excellent in steam oxidation resistance and manufacturing method thereof | |
| CA2510987C (en) | Steel tube excellent in exfoliation resistance of scale on inner surface | |
| Pellizzari et al. | Thermal fatigue resistance of gas and plasma nitrided 41CrAlMo7 steel | |
| US20090246064A1 (en) | Austenitic Stainless Steel Tube for Boiler with Excellent Resistance to High Temperature Steam Oxidation | |
| RU2706257C1 (en) | Seamless steel pipe and method of its production | |
| JP2009068079A (en) | Steel tube with excellent steam oxidation resistance | |
| Kim et al. | C-ring stress corrosion test for Inconel 600 and Inconel 690 sleeve joint welded by Nd: YAG laser | |
| Kishor et al. | Cavitation erosion of thermomechanically processed 13/4 martensitic stainless steel | |
| Li et al. | Fatigue crack growth law of API X80 pipeline steel under various stress ratios based on J‐integral | |
| Soyama et al. | Comparison of the effects of submerged laser peening, cavitation peening and shot peening on the improvement of the fatigue strength of magnesium alloy AZ31 | |
| JP2004132437A (en) | Manufacturing method for steel pipe for boiler having superior steam oxidation resistance property | |
| Hong et al. | Evaluation of the effects of thermal aging of austenitic stainless steel welds using small punch test | |
| JP2011068919A (en) | Fe-ni based alloy with high-strength hydrogen embrittlement resistant | |
| JP2007039745A (en) | Method for improving water vapor oxidation resistance of ferritic heat resistant steel, ferritic heat resistant steel having excellent water vapor oxidation resistance, and heat resistant steel for boiler | |
| JP2003342639A (en) | Process for manufacturing uoe steel pipe showing excellent crushing strength | |
| Gomez et al. | Microstructure and mechanical properties of low alloy steel T11–austenitic stainless steel 347H bimetallic tubes | |
| JP4196755B2 (en) | Pipe welded joint of low carbon stainless steel pipe and its manufacturing method | |
| JP3503560B2 (en) | Low yield ratio martensitic stainless steel with excellent corrosion resistance and method for producing the same | |
| JPH0559168B2 (en) | ||
| Yang et al. | Modeling of corrosion fatigue life of stainless steel joints welded by laser-metal active gas hybrid welding | |
| JPS60211053A (en) | High strength alloy for industrial container | |
| Wang et al. | Microscopic residual stresses beneath a scratch and their effects on scratch-related crack initiation of thermally treated uns n06690 in high-temperature pressurized water |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20041217 |
|
| A977 | Report on retrieval |
Effective date: 20070727 Free format text: JAPANESE INTERMEDIATE CODE: A971007 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20070807 |
|
| A521 | Written amendment |
Effective date: 20070918 Free format text: JAPANESE INTERMEDIATE CODE: A523 |
|
| A131 | Notification of reasons for refusal |
Effective date: 20080122 Free format text: JAPANESE INTERMEDIATE CODE: A131 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20080318 |
|
| A131 | Notification of reasons for refusal |
Effective date: 20080805 Free format text: JAPANESE INTERMEDIATE CODE: A131 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20080903 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Effective date: 20081007 Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20081017 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Year of fee payment: 3 Free format text: PAYMENT UNTIL: 20111024 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Year of fee payment: 3 Free format text: PAYMENT UNTIL: 20111024 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111024 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121024 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121024 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20131024 Year of fee payment: 5 |
|
| S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313531 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Year of fee payment: 5 Free format text: PAYMENT UNTIL: 20131024 |
|
| S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20131024 Year of fee payment: 5 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| LAPS | Cancellation because of no payment of annual fees |