JPH0524985B2 - - Google Patents
Info
- Publication number
- JPH0524985B2 JPH0524985B2 JP21156587A JP21156587A JPH0524985B2 JP H0524985 B2 JPH0524985 B2 JP H0524985B2 JP 21156587 A JP21156587 A JP 21156587A JP 21156587 A JP21156587 A JP 21156587A JP H0524985 B2 JPH0524985 B2 JP H0524985B2
- Authority
- JP
- Japan
- Prior art keywords
- heat treatment
- oxide film
- grain boundary
- boundary strengthening
- heat exchanger
- 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.)
- Expired - Lifetime
Links
- 238000010438 heat treatment Methods 0.000 claims description 66
- 238000005728 strengthening Methods 0.000 claims description 35
- 238000000034 method Methods 0.000 claims description 25
- 229910045601 alloy Inorganic materials 0.000 claims description 22
- 239000000956 alloy Substances 0.000 claims description 22
- 239000011651 chromium Substances 0.000 claims description 15
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims description 9
- 229910000423 chromium oxide Inorganic materials 0.000 claims description 9
- 229910052759 nickel Inorganic materials 0.000 claims description 9
- 238000005260 corrosion Methods 0.000 description 34
- 230000007797 corrosion Effects 0.000 description 32
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 21
- 150000002500 ions Chemical class 0.000 description 15
- 238000010828 elution Methods 0.000 description 11
- 230000000694 effects Effects 0.000 description 6
- 229910052742 iron Inorganic materials 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000000137 annealing Methods 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 239000000523 sample Substances 0.000 description 4
- 230000001771 impaired effect Effects 0.000 description 3
- 238000009616 inductively coupled plasma Methods 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- UFGZSIPAQKLCGR-UHFFFAOYSA-N chromium carbide Chemical compound [Cr]#C[Cr]C#[Cr] UFGZSIPAQKLCGR-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000007872 degassing Methods 0.000 description 2
- 229910001055 inconels 600 Inorganic materials 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 229910052596 spinel Inorganic materials 0.000 description 2
- 239000011029 spinel Substances 0.000 description 2
- 229910003470 tongbaite Inorganic materials 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000005802 health problem Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000000399 optical microscopy Methods 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 238000001637 plasma atomic emission spectroscopy Methods 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
Description
（産業上の利用分野）
本発明は、高温高圧水環境下で用いられるNi
基合金伝熱管、例えば加圧水型電子炉（PWR）
の蒸気発生器用伝熱管の耐食性、特に、耐全面腐
食性を向上させる熱処理方法に関するものであ
る。
（従来の技術）
例えば、加圧水型原子炉の蒸気発生器用伝熱管
のような高温高圧水環境下で用いられる伝熱管の
素材には、現在、アロイ600（75％Ni−15％Cr−
10％Fe）等のNi基合金が用いられている。Ni基
合金は耐食性や高温強度に優れるが、かかるNi
基合金からなる伝熱管を、例えば加圧水型原子炉
の蒸気発生器に使用した場合、１次系水には、溶
存酸素のない脱気処理された高温高圧水が使用さ
れているにもかかわらず、１次系水と接している
伝熱管表面は、わずかながらも次第に腐食され、
腐食により放出されたNiイオンやCoイオンが炉
心で放射化された後、１次系配管等に沈着し、定
期検査等において作業者の安全衛生上の問題が生
じる。
そこで、本発明者は先に、高温高圧水中での耐
食性が、前述のアロイ600よりも遥かに優れた、
Crを30％と多く含有させたアロイ690（60％Ni−
30％Cr−10％Fe）のNi基合金を開発し、特許出
願した（特開昭59−85850号公報）。これにより、
高温高圧水中における伝熱管の腐食は大きく軽減
された。
（発明が解決しようとする問題点）
しかし、伝熱管の使用環境は今後益々厳しくな
ることが予想され、安全衛生面からの要請も高ま
る一方である。このようなことから、更に耐食性
に優れた、特にその中でも耐全面腐食性がより優
れた伝熱管の開発が望まれている。
ここに、耐全面腐食性とは高温高圧水中で材料
表面からの合金成分の均一腐食に対する抵抗性の
ことをいい、耐全面腐食性が悪いと材料表面から
Fe、Ni、Cr等の合金成分の溶出が大きくなり、
例えば加圧水型原子炉の蒸気発生器用伝熱管とし
て使用した場合には、１次系配管に放射化された
腐食生成物の堆積が起こる。
本発明の目的は、高温高圧水環境下で用いられ
るNi基合金伝熱管、例えば加圧水型原子炉の蒸
気発生器用伝熱管の耐食性、特に、その中でも耐
全面腐食性をさらに改善することにある。
（問題点を解決するための手段）
本発明者は、高温高圧水環境下で使用される
Ni基合金製の伝熱管について、機械的性質を損
なうことなく、耐全面腐食性をさらに向上させる
方法について種々検討を行つた。
通常、伝熱管は、特別の防食処理をせぶ裸管の
まま使用されている。そのため、元来耐食性のよ
いNi基合金であつてもわずかながらも次第に腐
食が進行する。このような腐食を抑制するには伝
熱管表面を防食及膜処理して使用することが考え
られる。一般に金属製品の防食皮膜処理には、め
つき、塗装等をはじめとして種々の方法がある。
しかし、これらの方法はいずれも製造工程が増
え、製造コストが嵩むだけでなく、Ni基合金の
伝熱管という特殊な製品に適用するうえで好まし
い方法とは言い難い。
そこで、本発明者はこのような方法を採ること
なく、伝熱管表面に何らかの防食皮膜を付与する
方法についてさらに検討を行つた結果、下記の知
見を得た。
Ni基合金からなる伝熱管は、その最終製造工
程で高温高圧水中での粒界応力腐食割れ（SCC）
を防止するために、900℃以上の温度で焼鈍処理
され、次いで焼鈍で生じたCr欠乏層を修復する
ために、その後粒界強化熱処理が施される。この
粒界強化熱処理は、焼鈍後の粒界にクロム炭化物
を析出させて粒界を強化し、耐食性を向上させる
ものであつて、一般に、550〜750℃の温度範囲
で、且つ加熱中の着色を防止するために
10-5Torr以上の高真空下で行われる。
本発明者は、この粒界強化熱処理工程中の一部
で真空度を下げて熱処理したところ、粒界強化の
効果が何ら損なわれず、逆に伝熱管表面に耐食性
に優れるクロム酸化物を主体とする薄い酸化皮膜
が形成され、その結果、耐全面腐食性や耐SCC等
の耐食性が大幅に向上することを見出し、本発明
を完成した。
ここに、本発明の要旨とするところは、重量％
で、Cr：20〜35％、Ni：40〜70％を含有するNi
基合金伝熱管を高真空下で加熱保持する粒界強化
熱処理に際し、その熱処理工程の一部を10-2〜
10-4Torrの真空度で、添付第１図の点ＡとＢ、
ＢとＣ、ＣとＤ、ＤとＥ、ＥとＦおよびＦとＡを
それぞれ結ぶ直線によつて囲まれる領域内の条件
で熱処理し、表面にクロム酸化物を主体とする酸
化皮膜を形成させることを特徴とする伝熱管の熱
処理方法、にある。
第１図は、粒界強化熱処理工程の一部で採用す
る本発明にかかる熱処理の加熱温度と加熱時間の
関係を示したものである。
なお、破線で示す領域内の条件は、焼鈍後、通
常一般に採られている粒界強化熱処理の加熱温度
と時間を示したものであつて、10-5Torr以上の
高真空下で概ね550〜750℃の温度範囲で１〜100
時間保持する。
本発明は、この粒界強化熱処理工程の一部を、
10-2〜10-4Torrの範囲内の真空度に調整し、そ
の真空雰囲気下で第１図の点Ａ（1h、750℃）、Ｂ
（1H、650℃）、Ｃ（10h、550℃）、Ｄ（50h、550
℃）、Ｅ（5h、650℃）およびＦ（5h、750℃）の６
点を結ぶ直線によつて囲まれる領域内の加熱温度
と加熱時間で熱処理し、伝熱管表面にNiイオン
やCoイオンの溶出抑制に効果のあるクロム酸化
物を主体とする酸化皮膜を形成する。
（作用）
次ぎに各条件の限定理由を説明する。
加熱時間がAB線で示される１時間およびBC
線で示される１〜10時間より少ないと、形成され
る酸化皮膜は薄くNiイオンやCoイオンの溶出抑
制に有効な厚さの酸化皮膜が得られない。又DE
線で示される５〜50時間およびEF線で示される
５時間より長くなると、形成される酸化皮膜が厚
くなりすぎ、ひび割れや剥離が発生しやすくなつ
て逆に耐食性を悪化させることになる。
一方、加熱温度はAF線で示される750℃より高
い温度およびCD線で示される550℃より低い温度
では、粒界強化熱処理自体の目的が達成されな
い。即ち、75℃を超える温度ではクロム炭化物が
粒界に析出する量が少なく、粒界強化が得られな
いとともに、生成する酸化皮膜は（Ni、Fe）
Ｏ・Cr2O3のスピネル構造のものが主体となり、
Cr2O3のクロム酸化物を主体とする酸化皮膜の生
成量が少なくなつて耐食性に劣る。又、550℃よ
り低い温度でも長時間加熱すれば、Cr2O3主体の
酸化皮膜を生成させることができるが、有効な厚
さの酸化皮膜形成に長時間かかるとともに、粒界
強化熱処理の時間も長くなり、製造面から不利と
なり実用的ではない。
本発明は、前述のように粒界強化熱処理を活用
して伝熱管表面にクロム酸化物を主体とする酸化
皮膜を形成させるわけであるが、この時、加熱温
度と加熱時間の外に真空度を10-2〜10-4Torrの
範囲に調整して熱処理することが重要である。真
空度が10-2Torr未満の低真空では、耐蝕性に劣
る（Ni、Fe）Ｏ・Cr2O3のスピネル構造主体の
酸化皮膜となり好ましくない。一方10-4Torrを
超える高真空では、実用範囲内で長時間熱処理し
ても金属溶出抑制に有効な酸化皮膜が確保しにく
くなる。
粒界強化熱処理工程の一部で、前述した条件の
真空度、加熱温度および加熱時間で熱処理するこ
とでNi基合金伝熱管表面には、Cr2O3のクロム酸
化物を主体とした厚さがおよそ500〜5000Åの酸
化皮膜が形成される。
この酸化皮膜を形成させる処理は、粒界強化熱
処理工程の処理時間内のどこかで実施すればよ
い。例えば粒界強化熱処理工程の前半段階で行つ
てもよく、中間段階で行つてもよくあるいは後半
段階で行つてもよい。工程的には後半段階で実施
する方が真空度制御の点から望ましい。後半段階
で実施する場合、後述する実施例でとつたヒート
パターンに示すように、前半は粒界強化を目的と
した熱処理を行い、次いで後半で真空度を10-2〜
10-4Torrの範囲に下げて、その真空下で一定時
間加熱保持して酸化皮膜処理と粒界強化処理とを
兼ねて行う方法（第２ａ）。或いは後半の粒界強
化熱処理を一旦中断し、室温まで冷却したのち次
いで再加熱して所定の真空度の下で一定時間加熱
保持して酸化皮膜処理と粒界強化処理とを兼ねて
行う方法（第２図ｂ）がある。
なお、本発明の方法では、粒界強化熱処理工程
の一部で加熱温度を変更することなく真空度を
10-2〜10-4Torrの範囲に低下すれば容易に実施
することができるが、粒界強化処理時の加熱温度
と酸化皮膜処理時の加熱温度を変えて実施しても
よい。温度変更は高温側から段階的に下げてもよ
く、逆の方法でもよい。更に真空雰囲気としては
真空以外に10-2〜10-4Torr相当の酸素分圧を有
するアルゴンガス等の不活性ガスを使用してもよ
い。
本発明の熱処理方法は、重量％でCrを20〜35
％、Niを40〜70％含有したNi基合金伝熱管を対
象とするものである。
その理由は、前述した耐食性に優れるCr2O3の
クロム酸化物を主体とする酸化皮膜を得るには、
重量％で、20〜35％のCrを必要とするからであ
る。Ni量が40〜70％の範囲内であればNi基合金
の優れた耐食性を損なうことはない。
又、本発明が対象とするNi基合金伝熱管は、
CrとNiの外にＣとTi、Mn或いはMg等の１種以
上含んだものであつてもよい。Ｃは通常この種
Ni基合金には0.005〜0.07％含有されているが、
本発明においては、粒界強化と強度の観点から
0.015〜0.03％のものが好ましい。又、Ti、Mn、
Mgは加工性を改善するために添加されるもので
あり、それぞれTi：0.5％以下、Mn：0.5％以下
及びMg：0.1％以下の１種以上を含有させても本
発明の効果を何ら損なうものではない。
以下、実施例によつて本発明の効果を具体的に
説明する。
（実施例）
真空溶解炉を用いて第１表に示すＡ、B2種の
Ni基合金を溶製し、熱間鍛造、熱間圧延して７
mm厚の板材とし、次いで、冷間圧延によつて4.9
mm厚の供試材を製造した。
この供試材を1050℃の温度で0.24時間加熱して
水冷する焼鈍を施した後、第２表に示す加熱温
度、保持時間および真空度で粒界強化熱処理と酸
化皮膜処理を行つた。粒界強化熱処理と酸化皮膜
処理は、第２図のヒートパターンに示すように、
粒界強化熱処理の後半で真空度を下げて酸化皮膜
処理と粒界強化熱処理とを兼ねて行つたものと、
後半で粒界強化熱処理を一旦中断し、次いで再加
熱して酸化皮膜処理と粒界強化熱処理とを兼ねて
行つたものの２タイプ実施した。
このようにして得た供試材に対して、酸化皮膜
圧、高温水中のNiイオン溶出量および耐脱気高
温水SCC性を調べた結果を同じく第２表に示す。
なお、酸化皮膜量はIMMA（Ion Micro Mass
Anal yser）により分析した。高温水中のNiイオ
の溶出量はPWR一次模擬水（500ppmB3+＋
1ppmLi+、325℃脱気）中で容量500mlの白金容器
を用い、第３図に示した静止型オートクレーブ中
で200h浸漬し、溶液中の溶出Niイオン量をICP
（Inductively Coup led Plasma：高周波誘導プ
ラズマ発光分光法）により分光し、耐全面腐食性
を評価した。また、耐脱気高温水SCC試験は、上
述の一次模擬水（360℃）中で、Ｕ曲げ試験を
1000h行い、試験後の割れ深さを断面光学顕微鏡
観察により行つた。
(Industrial Application Field) The present invention is directed to Ni
Base alloy heat transfer tubes, e.g. pressurized water furnace (PWR)
The present invention relates to a heat treatment method for improving the corrosion resistance, particularly the general corrosion resistance, of heat exchanger tubes for steam generators. (Prior art) For example, the material for heat transfer tubes used in high-temperature, high-pressure water environments, such as heat transfer tubes for steam generators in pressurized water nuclear reactors, is currently made of alloy 600 (75% Ni-15% Cr-
Ni-based alloys such as 10% Fe) are used. Although Ni-based alloys have excellent corrosion resistance and high-temperature strength,
When heat transfer tubes made of base alloys are used, for example, in the steam generator of a pressurized water reactor, even though the primary system water is high-temperature, high-pressure water that has been degassed and has no dissolved oxygen, , the surface of the heat exchanger tube in contact with the primary water is slightly but gradually corroded,
Ni and Co ions released due to corrosion are activated in the reactor core and then deposited in the primary system piping, etc., causing safety and health problems for workers during periodic inspections. Therefore, the present inventor first developed a alloy that has far superior corrosion resistance in high-temperature, high-pressure water than the aforementioned Alloy 600.
Alloy 690 (60%Ni−) containing as much as 30% Cr
We developed a Ni-based alloy (30% Cr - 10% Fe) and filed a patent application (Japanese Patent Laid-Open No. 85850/1985). This results in
Corrosion of heat transfer tubes in high-temperature, high-pressure water was greatly reduced. (Problems to be Solved by the Invention) However, the environment in which heat exchanger tubes are used is expected to become increasingly severe in the future, and demands from the safety and health perspective are also increasing. For these reasons, there is a desire to develop heat exchanger tubes that have even better corrosion resistance, especially better overall corrosion resistance. Here, general corrosion resistance refers to the resistance to uniform corrosion of alloy components from the material surface in high-temperature, high-pressure water.
Elution of alloy components such as Fe, Ni, and Cr increases,
For example, when used as a heat exchanger tube for a steam generator in a pressurized water reactor, activated corrosion products accumulate in the primary system piping. An object of the present invention is to further improve the corrosion resistance of Ni-based alloy heat exchanger tubes used in high-temperature, high-pressure water environments, such as heat exchanger tubes for steam generators in pressurized water nuclear reactors, particularly the overall corrosion resistance. (Means for Solving the Problems) The present inventor has discovered that
We investigated various ways to further improve the general corrosion resistance of Ni-based alloy heat exchanger tubes without impairing their mechanical properties. Normally, heat transfer tubes are used as bare tubes after special anti-corrosion treatment. Therefore, even if the Ni-based alloy has good corrosion resistance, corrosion gradually progresses, albeit slightly. In order to suppress such corrosion, it is considered that the surface of the heat exchanger tube is subjected to anti-corrosion treatment and film treatment before use. Generally, there are various methods for treating metal products with anticorrosion coatings, including plating, painting, etc.
However, all of these methods not only increase the number of manufacturing steps and manufacturing costs, but are also not suitable for application to special products such as Ni-based alloy heat exchanger tubes. Therefore, the inventors of the present invention conducted further studies on a method of applying some kind of anticorrosive film to the surface of a heat exchanger tube without adopting such a method, and as a result, the following findings were obtained. Heat exchanger tubes made of Ni-based alloys suffer from intergranular stress corrosion cracking (SCC) in high-temperature, high-pressure water during the final manufacturing process.
In order to prevent this, the steel is annealed at a temperature of 900°C or higher, and then grain boundary strengthening heat treatment is performed to repair the Cr-depleted layer caused by the annealing. This grain boundary strengthening heat treatment is a process in which chromium carbide is precipitated at the grain boundaries after annealing to strengthen the grain boundaries and improve corrosion resistance. to prevent
It is carried out under high vacuum of 10 -5 Torr or higher. The inventor of the present invention found that when the heat treatment was carried out by lowering the degree of vacuum during part of the grain boundary strengthening heat treatment process, the grain boundary strengthening effect was not impaired at all, and on the contrary, chromium oxide, which has excellent corrosion resistance, was mainly formed on the surface of the heat exchanger tube. The present invention was completed based on the discovery that a thin oxide film is formed, resulting in significantly improved corrosion resistance such as general corrosion resistance and SCC resistance. Here, the gist of the present invention is that the weight%
and Ni containing Cr: 20-35%, Ni: 40-70%
When grain boundary strengthening heat treatment is performed to heat and hold base alloy heat exchanger tubes under high vacuum, a part of the heat treatment process is performed at 10 -2 ~
At a vacuum level of 10 -4 Torr, points A and B in the attached figure 1,
Heat treatment is performed under conditions within the area surrounded by straight lines connecting B and C, C and D, D and E, E and F, and F and A, respectively, to form an oxide film mainly composed of chromium oxide on the surface. A heat treatment method for a heat exchanger tube, characterized in that: FIG. 1 shows the relationship between the heating temperature and heating time of the heat treatment according to the present invention, which is employed in a part of the grain boundary strengthening heat treatment step. The conditions in the region indicated by the broken line indicate the heating temperature and time of the commonly used grain boundary strengthening heat treatment after annealing. 1-100 in the temperature range of 750℃
Hold time. The present invention includes a part of this grain boundary strengthening heat treatment process,
The degree of vacuum was adjusted to within the range of 10 -2 to 10 -4 Torr, and points A (1 hour, 750°C) and B in Figure 1 were measured in the vacuum atmosphere.
(1H, 650℃), C (10h, 550℃), D (50h, 550℃)
℃), E (5h, 650℃) and F (5h, 750℃) 6
Heat treatment is performed at the heating temperature and heating time within the area surrounded by the straight line connecting the points, to form an oxide film mainly composed of chromium oxide, which is effective in suppressing the elution of Ni ions and Co ions, on the surface of the heat exchanger tube. (Operation) Next, the reason for limiting each condition will be explained. Heating time is 1 hour indicated by line AB and BC
If the time is shorter than 1 to 10 hours as indicated by the line, the oxide film formed will be too thin to form an oxide film with a thickness effective for suppressing the elution of Ni ions and Co ions. Also DE
If the time is longer than the 5 to 50 hours shown by the line and the 5 hours shown by the EF line, the oxide film formed becomes too thick, making cracking and peeling more likely to occur, conversely worsening the corrosion resistance. On the other hand, if the heating temperature is higher than 750°C as shown by the AF line or lower than 550°C as shown by the CD line, the purpose of grain boundary strengthening heat treatment itself cannot be achieved. In other words, at temperatures exceeding 75°C, the amount of chromium carbide precipitated at grain boundaries is small, grain boundary strengthening cannot be obtained, and the oxide film that is formed is (Ni, Fe)
Mainly has a spinel structure of O.Cr 2 O 3 ,
The amount of oxide film mainly composed of chromium oxide of Cr 2 O 3 is reduced, resulting in poor corrosion resistance. Furthermore, if heated for a long time at a temperature lower than 550°C, an oxide film mainly composed of Cr 2 O 3 can be formed, but it takes a long time to form an oxide film with an effective thickness, and the grain boundary strengthening heat treatment takes a long time. It is also long, which is disadvantageous in terms of manufacturing and is not practical. As mentioned above, the present invention utilizes grain boundary strengthening heat treatment to form an oxide film mainly composed of chromium oxide on the surface of the heat transfer tube, but at this time, in addition to the heating temperature and heating time, the degree of vacuum It is important to adjust the heat treatment to a range of 10 -2 to 10 -4 Torr. A low vacuum of less than 10 -2 Torr is undesirable because it forms an oxide film mainly having a spinel structure of (Ni, Fe)O.Cr 2 O 3 which has poor corrosion resistance. On the other hand, in a high vacuum exceeding 10 -4 Torr, it becomes difficult to secure an oxide film that is effective in suppressing metal elution even if heat treatment is performed for a long time within a practical range. As part of the grain boundary strengthening heat treatment process, heat treatment is performed under the vacuum degree, heating temperature, and heating time conditions described above to create a thickness mainly composed of chromium oxide of Cr 2 O 3 on the surface of the Ni-based alloy heat transfer tube. An oxide film with a thickness of approximately 500 to 5000 Å is formed. The treatment for forming this oxide film may be carried out at some point within the treatment time of the grain boundary strengthening heat treatment step. For example, it may be carried out in the first half of the grain boundary strengthening heat treatment process, in the middle, or in the latter half. From the viewpoint of vacuum degree control, it is preferable to carry out the process in the latter half of the process. When carrying out the process in the latter half of the process, as shown in the heat pattern obtained in the examples described below, heat treatment is performed in the first half for the purpose of strengthening grain boundaries, and then in the second half, the degree of vacuum is reduced to 10 -2 ~
A method in which the temperature is lowered to a range of 10 -4 Torr and heated and held for a certain period of time in a vacuum to perform both oxide film treatment and grain boundary strengthening treatment (Step 2a). Alternatively, the grain boundary strengthening heat treatment in the latter half is temporarily interrupted, the material is cooled to room temperature, and then reheated and kept heated for a certain period of time under a predetermined degree of vacuum to perform both the oxide film treatment and the grain boundary strengthening treatment ( Figure 2b) is shown. In addition, in the method of the present invention, the degree of vacuum can be increased without changing the heating temperature in a part of the grain boundary strengthening heat treatment process.
This can be easily carried out if the temperature is reduced to a range of 10 -2 to 10 -4 Torr, but it may be carried out by changing the heating temperature during the grain boundary strengthening treatment and the heating temperature during the oxide film treatment. The temperature may be changed stepwise from the high temperature side, or vice versa. Further, as the vacuum atmosphere, in addition to vacuum, an inert gas such as argon gas having an oxygen partial pressure equivalent to 10 -2 to 10 -4 Torr may be used. The heat treatment method of the present invention has a Cr content of 20 to 35% by weight.
%, and Ni-based alloy heat exchanger tubes containing 40 to 70% Ni. The reason is that in order to obtain the oxide film mainly composed of chromium oxide of Cr 2 O 3 , which has excellent corrosion resistance, it is necessary to
This is because Cr of 20 to 35% by weight is required. If the Ni content is within the range of 40 to 70%, the excellent corrosion resistance of the Ni-based alloy will not be impaired. In addition, the Ni-based alloy heat exchanger tube targeted by the present invention is
It may contain one or more of C, Ti, Mn, Mg, etc. in addition to Cr and Ni. C is usually this type
Ni-based alloys contain 0.005 to 0.07%,
In the present invention, from the viewpoint of grain boundary strengthening and strength,
0.015-0.03% is preferred. Also, Ti, Mn,
Mg is added to improve workability, and even if one or more of Ti: 0.5% or less, Mn: 0.5% or less, and Mg: 0.1% or less are included, the effects of the present invention will not be impaired in any way. It's not a thing. Hereinafter, the effects of the present invention will be specifically explained with reference to Examples. (Example) Two types A and B shown in Table 1 were prepared using a vacuum melting furnace.
By melting Ni-based alloy, hot forging, and hot rolling, 7
It is made into a plate material with a thickness of 4.9 mm and then cold rolled to
A sample material with a thickness of mm was manufactured. This sample material was annealed by heating it at a temperature of 1050° C. for 0.24 hours and cooling with water, and then subjected to grain boundary strengthening heat treatment and oxide film treatment at the heating temperature, holding time, and degree of vacuum shown in Table 2. The grain boundary strengthening heat treatment and oxide film treatment are as shown in the heat pattern in Figure 2.
In the second half of the grain boundary strengthening heat treatment, the degree of vacuum is lowered and the oxide film treatment and grain boundary strengthening heat treatment are performed at the same time.
Two types of heat treatment were carried out, in which the grain boundary strengthening heat treatment was once interrupted in the second half, and then reheated to serve as both the oxide film treatment and the grain boundary strengthening heat treatment. The test materials thus obtained were examined for oxide film pressure, amount of Ni ion elution in high temperature water, and degassing high temperature water SCC properties, and the results are also shown in Table 2. The amount of oxide film is IMMA (Ion Micro Mass
Analyzed by anal yser). The elution amount of Ni ions in high-temperature water is calculated using PWR primary simulated water (500ppmB 3+ +
Using a platinum container with a capacity of 500 ml in 1ppmLi + 325℃ degassing), the solution was immersed for 200 hours in the stationary autoclave shown in Figure 3, and the amount of eluted Ni ions in the solution was measured by ICP.
(Inductively Coupled Plasma: High Frequency Induced Plasma Emission Spectroscopy) to evaluate general corrosion resistance. In addition, the deaeration resistance high temperature water SCC test is performed by performing a U-bending test in the above-mentioned primary simulated water (360℃).
The test was carried out for 1000 hours, and the crack depth after the test was observed by cross-sectional optical microscopy.
【表】【table】
【表】
＊１ 分折できず、＊２ 孔食発生。
第２表より明らかなように、酸化皮膜処理の加
熱時間が本発明で規定する時間より短い比較例に
あたる試料No.11、12、15および16は、形成される
酸化皮膜が薄いためにNiイオン溶出量が多く、
金属溶出抑制効果が小さい。一方加熱時間の長い
比較例にあたる試料No.13及び14は、厚い酸化皮膜
が得られるが、その皮膜が厚すぎるため所々でヒ
ビ割れが発生しており、そのために金属溶出抑制
効果は低い。また、酸化皮膜処理のない従来法の
粒界強化熱処理のみ行つた試料No.17は、酸化皮膜
がほとんど形成されないためNiイオン溶出量が
著しく多い。これに対して本発明例にあたる試料
No.１〜10のものは、適度の酸化皮膜が形成され
て、Niイオン溶出量が少なく且つ耐SCC性も従
来の熱処理によるものと何ら変わりない。
なお、Coイオン量もICPで分析したが、本発明
例のものはいずれも検出限界以下であつた。
（発明の効果）
以上説明したように、本発明方法によれば焼鈍
後の粒界強化熱処理工程で耐食性に優れたクロム
酸化物を主体とする酸化皮膜を伝熱管の表面に形
成することができて、伝熱管の耐食性、特に耐全
面腐食性が大きく向上する。また、その方法は新
たな工程を付加することなく粒界強化熱処理工程
内で行えるから製造コストの増加を招くこともな
い。[Table] *1 Unable to separate, *2 Pitting corrosion occurred.
As is clear from Table 2, samples Nos. 11, 12, 15, and 16, which are comparative examples whose heating time for oxide film treatment is shorter than the time specified in the present invention, have Ni ions because the oxide film formed is thin. The amount of elution is large;
The effect of suppressing metal elution is small. On the other hand, samples Nos. 13 and 14, which are comparative examples having a long heating time, yield thick oxide films, but the films are so thick that cracks occur in some places, and therefore the effect of suppressing metal elution is low. In addition, in sample No. 17, which was subjected to only the conventional grain boundary strengthening heat treatment without oxide film treatment, the amount of Ni ion elution was significantly large because almost no oxide film was formed. In contrast, a sample corresponding to an example of the present invention
In Nos. 1 to 10, an appropriate oxide film was formed, the amount of Ni ions eluted was small, and the SCC resistance was no different from that obtained by conventional heat treatment. Incidentally, the amount of Co ions was also analyzed by ICP, and the amounts in all of the examples of the present invention were below the detection limit. (Effects of the Invention) As explained above, according to the method of the present invention, an oxide film mainly composed of chromium oxide with excellent corrosion resistance can be formed on the surface of the heat exchanger tube in the grain boundary strengthening heat treatment step after annealing. Therefore, the corrosion resistance of the heat exchanger tube, especially the general corrosion resistance, is greatly improved. Further, since this method can be performed within the grain boundary strengthening heat treatment process without adding any new process, it does not increase manufacturing costs.
第１図は、粒界強化熱処理の加熱温度と加熱時
間の関係を示すグラフであつて、破線で囲まれ範
囲が粒界強化熱処理の条件、実線で囲まれる範囲
が本発明にかかる酸化皮膜を形成するめの熱処理
条件である。第２図ａ及びｂは、本発明の実施例
で採用した粒界強化と酸化皮膜熱処理のヒートパ
ターンである。第３図は、実施例でNiイオン、
Coイオン溶出量の測定に用いた静止型オートク
レーブを示す一部断面概略図、である。
FIG. 1 is a graph showing the relationship between heating temperature and heating time for grain boundary strengthening heat treatment, in which the range surrounded by a broken line is the condition of the grain boundary strengthening heat treatment, and the range surrounded by a solid line is the oxide film according to the present invention. These are the heat treatment conditions for forming. FIGS. 2a and 2b show heat patterns for grain boundary strengthening and oxide film heat treatment employed in the examples of the present invention. Figure 3 shows Ni ions and
FIG. 2 is a partially cross-sectional schematic diagram showing a stationary autoclave used for measuring the amount of Co ion elution.
Claims (1)
合金伝熱管を高真空下で加熱保持する粒界強化熱
処理に際し、その熱処理工程の一部を10-2〜
10-4Torrの真空度で、添付第１図の点ＡとＢ，
ＢとＣ，ＣとＤ，ＤとＥ，ＥとＦおよびＦとＡを
それぞれ結ぶ直線によつて囲まれる領域内の条件
で熱処理し、表面にクロム酸化物を主体とする酸
化皮膜を形成させることを特徴とする伝熱管の熱
処理方法。[Claims] In grain boundary strengthening heat treatment in which a Ni-based alloy heat exchanger tube containing 1% by weight of Cr: 20-35% and Ni: 40-70% is heated and held under high vacuum, the heat treatment step 10 -2 ~
At a vacuum level of 10 -4 Torr, points A and B in the attached figure 1,
Heat treatment is performed under conditions within the area surrounded by straight lines connecting B and C, C and D, D and E, E and F, and F and A, respectively, to form an oxide film mainly composed of chromium oxide on the surface. A heat treatment method for heat exchanger tubes, characterized by:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21156587A JPS6455366A (en) | 1987-08-26 | 1987-08-26 | Heat treatment for heat-transfer pipe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21156587A JPS6455366A (en) | 1987-08-26 | 1987-08-26 | Heat treatment for heat-transfer pipe |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6455366A JPS6455366A (en) | 1989-03-02 |
| JPH0524985B2 true JPH0524985B2 (en) | 1993-04-09 |
Family
ID=16607892
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21156587A Granted JPS6455366A (en) | 1987-08-26 | 1987-08-26 | Heat treatment for heat-transfer pipe |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6455366A (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4042362B2 (en) | 2000-08-11 | 2008-02-06 | 住友金属工業株式会社 | Ni-base alloy product and manufacturing method thereof |
| JP3960069B2 (en) | 2002-02-13 | 2007-08-15 | 住友金属工業株式会社 | Heat treatment method for Ni-base alloy tube |
| JP3979281B2 (en) * | 2002-12-04 | 2007-09-19 | 株式会社日立製作所 | Manufacturing method of valve stem, valve stem manufactured by the manufacturing method, and steam valve using the same |
| JP4720590B2 (en) * | 2006-04-12 | 2011-07-13 | 住友金属工業株式会社 | Method for producing Cr-containing nickel-base alloy tube |
| EP2275583B1 (en) | 2008-05-16 | 2017-11-15 | Nippon Steel & Sumitomo Metal Corporation | Ni-cr alloy material |
| JP2010270400A (en) * | 2010-07-21 | 2010-12-02 | Sumitomo Metal Ind Ltd | Steam generator tubing for nuclear power plant |
| JP4978755B2 (en) | 2010-08-26 | 2012-07-18 | 住友金属工業株式会社 | Cr-containing austenitic alloy tube and manufacturing method thereof |
| ES2706182T3 (en) | 2012-03-28 | 2019-03-27 | Nippon Steel & Sumitomo Metal Corp | Austenitic alloy containing Cr |
| CN104271790B (en) | 2012-04-04 | 2017-06-09 | 新日铁住金株式会社 | Alloy containing chromium austenite |
| JP5459633B1 (en) | 2012-06-20 | 2014-04-02 | 新日鐵住金株式会社 | Austenitic alloy tube |
| EP3202932B1 (en) | 2014-09-29 | 2019-03-20 | Nippon Steel & Sumitomo Metal Corporation | Ni-BASED ALLOY PIPE |
-
1987
- 1987-08-26 JP JP21156587A patent/JPS6455366A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6455366A (en) | 1989-03-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP5268942B2 (en) | Process for reducing the susceptibility of nickel-based alloys primarily for nuclear reactor nuclear assemblies and reactors to environmentally assisted cracking, and products made from the processed alloys | |
| US6576068B2 (en) | Method of producing stainless steels having improved corrosion resistance | |
| JP2002121630A (en) | Ni BASED ALLOY PRODUCT AND ITS PRODUCTION METHOD | |
| JPH0524985B2 (en) | ||
| AU2002256261A1 (en) | Method of producing stainless steels having improved corrosion resistance | |
| JP2001512785A (en) | Metallurgical method of treating nickel and iron based superalloys | |
| JP2758590B2 (en) | Heat treatment method for nickel-base alloy tubular body | |
| WO2000012268A1 (en) | Abrasion, corrosion, and gall resistant overlay alloys | |
| White et al. | Influence of surface treatment on the metal dusting behavior of alloy 699 XA | |
| US4408709A (en) | Method of making titanium-stabilized ferritic stainless steel for preheater and reheater equipment applications | |
| JPH0645866B2 (en) | Heat treatment method for stainless steel for heater tubes | |
| JPH01159362A (en) | Heat treatment of heat exchanger tube made of ni alloy | |
| US4374666A (en) | Stabilized ferritic stainless steel for preheater and reheater equipment applications | |
| JPS58177444A (en) | Heat treatment of ni-cr alloy | |
| Webb et al. | Stress corrosion cracking behavior of Alloy 600 in high temperature water | |
| JPS60211053A (en) | High strength alloy for industrial container | |
| JPH0233781B2 (en) | ||
| JPS5817823B2 (en) | Heat treatment method for Ni-based alloy containing Cr | |
| JPH06128671A (en) | Alloy excellent in resistance to stress corrosion cracking | |
| WO2021250968A1 (en) | Creep life evaluation method for nickel alloy component | |
| JPH0153340B2 (en) | ||
| JPS5952699B2 (en) | Method for producing Ni-based alloy containing Cr | |
| JPS60245773A (en) | Manufacture of highly corrosion resistant ni base alloy | |
| JPH0545664B2 (en) | ||
| JPH05112842A (en) | Ni-cr alloy low in exposing property and good in alkali corrosion resistance |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term | ||
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080409 Year of fee payment: 15 |