JP3864585B2 - Method of oxidizing the inner surface of stainless steel pipe - Google Patents
Method of oxidizing the inner surface of stainless steel pipe Download PDFInfo
- Publication number
- JP3864585B2 JP3864585B2 JP31276898A JP31276898A JP3864585B2 JP 3864585 B2 JP3864585 B2 JP 3864585B2 JP 31276898 A JP31276898 A JP 31276898A JP 31276898 A JP31276898 A JP 31276898A JP 3864585 B2 JP3864585 B2 JP 3864585B2
- Authority
- JP
- Japan
- Prior art keywords
- stainless steel
- heating furnace
- steel pipe
- steel tube
- water vapor
- 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 - Fee Related
Links
Images
Landscapes
- Heat Treatment Of Articles (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、半導体や医薬品、食品の製造に使用されるオゾン含有水等の流体を搬送するために使用されるステンレス鋼管の内面を酸化処理する方法に関する。
【０００２】
【従来の技術】
近年の半導体素子の製造においては、素子の高集積化に伴い微細な加工がなされる。特に超ＬＳＩと称されるデバイスには、１μｍ以下の微細なパターンの加工が施されている。超ＬＳＩ製造プロセスでは、使用されるガスや水の微量の不純物が配線パターンに付着して回路不良の原因となる。したがって、超ＬＳＩのような半導体を製造するプロセスで使用するガスや水などの流体は、高純度なものでなければならない。
【０００３】
これらの流体を供給する配管や部材に対しても、流体に接触する面からの微粒子や不純物の放出が極力少ないことが要求される。
【０００４】
最近、半導体製造工程等におけるシリコンウエハ等の洗浄には、オゾンを含有する洗浄水（オゾン含有水）が用いられるようになってきた。オゾンは漂白剤、殺菌剤として使用されていることからもわかるように、強い酸化力を持っているので、金属をイオン化し、有機物を分解する作用がある。そのため、オゾン含有超純水でシリコンウエハ等を洗浄すると、それに付着している金属はイオン化されることにより、また有機物は分解されることにより除去される。さらにオゾンは、洗浄後自己分解するため、シリコンウエハ上に汚染物として残留することがない。このようにオゾン含有水はシリコンウェハの洗浄に極めて有効である。
【０００５】
従来から使用されてきたステンレス鋼は、半導体製造プロセスで使用される超純水の配管用および装置部材として必要な強度を持っており、加工性にも優れている。しかし、オゾンを含む水に対する耐食性に劣るという欠点がある。すなわち、ステンレス鋼材がオゾン含有超純水によって腐食され、鋼材からＦｅ、Ｃｒ、Ｎｉなどの金属イオンが溶出し、オゾン含有水が汚染されるという問題がある。本発明者らは、ステンレス鋼からオゾン含有水中へ金属イオンが溶出するのを防止する対策として、ステンレス鋼の鋼材表面にＡｌ酸化物の皮膜を設けることを提案した（特開平１０−７２６４５号公報）。
【０００６】
Ａｌ酸化物皮膜を備えた鋼材として、特開平７−６００９９号公報に１０〜１５０オングストロームのＡｌ酸化物皮膜を備えた超真空環境で使用されるステンレス鋼、および特開平６−２７１９９３号公報に自動車排気ガス用部材等の高温用部品に適したＡｌ酸化物皮膜を備えた耐酸化性に優れたオーステナイト系ステンレス鋼が開示されている。
【０００７】
また、ステンレス鋼管の内面に酸化皮膜を形成させる装置が、特開平２−４３３５３号公報、および特開平３−１１１５５２号公報に開示されている。
【０００８】
これらの酸化処理装置は、所定の雰囲気、温度の加熱炉内に鋼管全体を挿入して固定し、鋼管内に所定の組成のガスを流しながら、鋼管を外面から加熱する装置で、いわゆるバッチ方式の酸化処理方法である。
【０００９】
しかしながら、従来のバッチ方式で、最も多用されている外径が６．３５ｍｍで、長さが４ｍもある長いステンレス鋼管を酸化処理する場合、次の２つの問題がある。
【００１０】
１つは、酸化処理の能率が悪いことである。すなわち、被処理鋼管の炉への取り付け、不活性ガスの流入による鋼管内に残留する空気のパージ、鋼管内面に付着している水分を除去するためのベーキング、酸化処理ガスへの切り替え、加熱処理、冷却および被処理鋼管の取り外し、といった多工程をバッチ処理毎に繰り返す必要がある。また、処理能率の改善を目的として、１回で処理可能な鋼管本数を増やした場合には、装置が複雑で高価になる。
【００１１】
もう一つの問題は、酸化物皮膜を鋼管全長に渡って被膜厚を均一に形成させることができないこと、および被膜中のＡｌ含有量も均一にならないことである。前述したオゾン含有水用配管として要求される性能を確保するためには、この問題が解消されねばならない。
【００１２】
従来のバッチ式処理方法では、鋼管の全長にわたって同時に酸化反応が起こるので、酸化性ガスが導入される管端近傍が最も酸化されるのに対し、酸化性ガスの出口となる管端近傍では酸化されにくくなり、鋼管の長さ方向に不均一なＡｌ酸化物皮膜が生成されてしまう。酸化性ガスの出口側の管端近傍が酸化されにくいのは、酸化性ガスが導入される側の管端近傍部と比較して、ガス中の酸化性成分である水蒸気や酸素の濃度が低くなっているからである。
【００１３】
また、被膜中のＡｌ含有量が鋼管の長さ方向に不均一となるのは次の理由による。
【００１４】
管内に導入された酸化性ガスは消費されながら導入側から出側へと移動する。したがって、出側管端の近傍部の酸素分圧は、導入側の管端近傍部よりも低くなるため、導入側と出側では形成される皮膜の組成が異なる。すなわち、酸素分圧が低いと鋼中のＡｌのみが酸化されるが、酸素分圧が高いとＣｒやＦｅも酸化される。そのため、ガス入り側管端部では酸化被膜中にＣｒやＦｅが混在してＡｌの含有量が低くなるが、ガス出側管端に近づくに従いＡｌ含有量が高くなるといった現象が生じる。
【００１５】
【発明が解決しようとする課題】
本発明の課題は、半導体、医薬品や食品の製造においてオゾン含有水等の流体を搬送するために使用されるステンレス鋼管の内面に、能率良く、しかもＡｌ含有量と膜厚が均一なＡｌ酸化物皮膜を鋼管全長に形成する酸化処理方法を提供することである。
【００１６】
【課題を解決するための手段】
本発明の要旨は以下の通りである。
【００１７】
（１）水素：１０〜９９．９９９９体積％、水蒸気：０．５〜３０体積ｐｐｍを含み、残部が不活性ガスからなる酸化性混合ガスを、重量％でＡｌを１〜６％含有するステンレス鋼管内に流しつつ、加熱炉内に前記ステンレス鋼管を挿入し、その長手方向に移動させながら８００〜１２００℃に加熱して、ステンレス鋼管の内面にＡｌ酸化物被膜を形成させるステンレス鋼管内面の酸化処理方法であって、加熱炉の入り口近傍、加熱炉内および加熱炉出口近傍においてステンレス鋼管の外面が酸化しないように、酸素濃度３体積ｐｐｍ以下で且つ水蒸気濃度３０体積ｐｐｍ以下である不活性ガスからなる雰囲気のチャンバ内に加熱炉を設けることにより、ステンレス鋼管のパスライン周辺雰囲気を調整することを特徴とするステンレス鋼管内面の酸化処理方法。
【００１８】
（２）水素：１０〜９９．９９９９体積％、水蒸気：０．５〜３０体積ｐｐｍを含み、残部が不活性ガスからなる酸化性混合ガスを、重量％でＡｌを１〜６％含有するステンレス鋼管内に流しつつ、加熱炉内に前記ステンレス鋼管を挿入し、その長手方向に移動させながら８００〜１２００℃に加熱して、ステンレス鋼管の内面にＡｌ酸化物被膜を形成させるステンレス鋼管内面の酸化処理方法であって、ステンレス鋼管内に流す酸化性混合ガスの流量が下記式を満足する量であることを特徴とするステンレス鋼管内面の酸化処理方法。
酸化性混合ガスの流量（リットル／分）≧８．２６×Ｒ×（Ｌ／Ｔ）／Ｃ、
ここで、Ｒ：ステンレス鋼管の内径（ｍｍ）、
Ｌ：加熱炉均熱帯長さ（ｃｍ）、
Ｔ：ステンレス鋼管の均熱帯での酸化処理時間（分）、
Ｃ：酸化性ガス中の水蒸気濃度（体積ｐｐｍ）。
【００１９】
（３）水素：１０〜９９．９９９９体積％、水蒸気：０．５〜３０体積ｐｐｍを含み、残部が不活性ガスからなる酸化性混合ガスを、重量％でＡｌを１〜６％含有するステンレス鋼管内に流しつつ、加熱炉内に前記ステンレス鋼管を挿入し、その長手方向に移動させながら８００〜１２００℃に加熱して、ステンレス鋼管の内面にＡｌ酸化物被膜を形成させるステンレス鋼管内面の酸化処理方法であって、加熱炉の入り口近傍、加熱炉内および加熱炉出口近傍においてステンレス鋼管の外面が酸化しないように、ステンレス鋼管のパスライン周辺を酸素濃度３体積ｐｐｍ以下で且つ水蒸気濃度３０体積ｐｐｍ以下である不活性ガスからなる雰囲気とし、かつ、ステンレス鋼管内に流す酸化性混合ガスの流量が下記式を満足する量であることを特徴とするステンレス鋼管内面の酸化処理方法。
酸化性混合ガスの流量（リットル／分）≧８．２６×Ｒ×（Ｌ／Ｔ）／Ｃ、
ここで、Ｒ：ステンレス鋼管の内径（ｍｍ）、
Ｌ：加熱炉均熱帯長さ（ｃｍ）、
Ｔ：ステンレス鋼管の均熱帯での酸化処理時間（分）、
Ｃ：酸化性ガス中の水蒸気濃度（体積ｐｐｍ）。
【００２０】
（４）水素：１０〜９９．９９９９体積％、水蒸気：０．５〜３０体積ｐｐｍを含み、残部が不活性ガスからなる酸化性混合ガスを、重量％でＡｌを１〜６％含有するステンレス鋼管内に流しつつ、加熱炉内に前記ステンレス鋼管を挿入し、その長手方向に移動させながら８００〜１２００℃に加熱して、ステンレス鋼管の内面にＡｌ酸化物被膜を形成させるステンレス鋼管内面の酸化処理方法であって、加熱炉の入り口近傍、加熱炉内および加熱炉出口近傍においてステンレス鋼管の外面が酸化しないように、酸素濃度３体積ｐｐｍ以下で且つ水蒸気濃度３０体積ｐｐｍ以下である不活性ガスからなる雰囲気のチャンバ内に加熱炉を設けることにより、ステンレス鋼管のパスライン周辺雰囲気を調整し、かつ、ステンレス鋼管内に流す酸化性混合ガスの流量が下記式を満足する量であることを特徴とするステンレス鋼管内面の酸化処理方法。
酸化性混合ガスの流量（リットル／分）≧８．２６×Ｒ×（Ｌ／Ｔ）／Ｃ、
ここで、Ｒ：ステンレス鋼管の内径（ｍｍ）、
Ｌ：加熱炉均熱帯長さ（ｃｍ）、
Ｔ：ステンレス鋼管の均熱帯での酸化処理時間（分）、
Ｃ：酸化性ガス中の水蒸気濃度（体積ｐｐｍ）。
【００２１】
（５）水素：１０〜９９．９９９９体積％、水蒸気：０．５〜３０体積ｐｐｍを含み、残部が不活性ガスからなる酸化性混合ガスを、重量％でＡｌを１〜６％含有するステンレス鋼管内に流しつつ、加熱炉内に前記ステンレス鋼管を挿入し、その長手方向に移動させながら８００〜１２００℃に加熱して、ステンレス鋼管の内面にＡｌ酸化物被膜を形成させるステンレス鋼管内面の酸化処理方法であって、加熱炉の入り口近傍、加熱炉内および加熱炉出口近傍においてステンレス鋼管の外面が酸化しないように、加熱炉よりも長いマッフルを備えた加熱炉を用い、マッフル内を酸素濃度３体積ｐｐｍ以下で且つ水蒸気濃度３０体積ｐｐｍ以下である不活性ガスからなる雰囲気としてステンレス鋼管のパスライン周辺雰囲気を調整し、かつ、ステンレス鋼管内に流す酸化性混合ガスの流量が下記式を満足する量であることを特徴とするステンレス鋼管内面の酸化処理方法。
【００２２】
酸化性混合ガスの流量（リットル／分）≧８．２６×Ｒ×（Ｌ／Ｔ）／Ｃ
ここで、 Ｒ：ステンレス鋼管の内径（ｍｍ）
Ｌ：加熱炉均熱帯長さ（ｃｍ）
Ｔ：ステンレス鋼管の均熱帯での酸化処理時間（分）
Ｃ：酸化性ガス中の水蒸気濃度（体積ｐｐｍ）
本発明者らは、従来のバッチ式の酸化処理方法の欠点を解消すべく種々実験、検討した結果以下の知見を得て本発明を完成するに至った。
【００２３】
ａ）ステンレス鋼管内面にオゾンを含有する超純水に対する耐食性を付与して金属イオンの溶出を防止するには、Ａｌの含有率が９０原子％以上で、厚さが１０〜２００ｎｍのＡｌ酸化物皮膜をステンレス鋼管内面に形成するのが好ましい。 ｂ）そのようなＡｌ酸化物被膜を形成するのに用いる酸化性ガスとして好適なのは、水素：１０〜９９．９９９９体積％、水蒸気：０．５〜３０体積ｐｐｍを含み残部が不活性ガスからなる酸化性混合ガスであり、８００〜１２００℃の温度範囲内で酸化処理するのがよい。
【００２４】
ｃ）鋼管の長手方向に厚さが均一になるようにＡｌ酸化物皮膜を生成させ、しかも酸化物被膜中のＡｌ量を均一にするには、酸化性混合ガスを鋼管内に流しつつ、加熱炉内で鋼管をその長手方向に移動させながら酸化処理するのがよい。
【００２５】
【発明の実施の形態】
以下、本発明の酸化処理方法を具体的に説明する。
【００２６】
図１は、本発明の酸化処理方法を実施するのに使用する酸化処理装置の一例を示す概略縦断面図である。
【００２７】
チャンバ３の中に加熱炉５が設けられており、管継ぎ手９により接続されたステンレス鋼管１ａ、１ｂが図示しない鋼管移動装置により所定の速度でチャンバ、加熱炉内に挿入され、その長手方向に移動される。ステンレス鋼管内には管の後端に取り付けられた酸化性ガス供給口８から酸化性ガス２が供給される。また、チャンバ内には酸素濃度３体積ｐｐｍ以下で且つ水蒸気濃度３０体積ｐｐｍ以下である不活性ガス４がチャンバの供給口７ａから供給され、必要により７ｂから排出される。
【００２８】
図１に示した例では、ステンレス鋼管を長手方向に２本接続した例であるが、多数の鋼管を接続してもよく、また接続した鋼管を複数本同時に炉内で処理すればより効率がよくなる。
【００２９】
複数の鋼管を長手方向に接続する場合、管の継ぎ手部からの管外雰囲気ガスの混入を避けるため、気密性のある接続法が必要である。具体的には、溶接や金属ガスケット式機械継ぎ手、食い込み式機械継ぎ手等が例示される。
【００３０】
加熱炉で加熱された管の内面で酸化反応が起こり始める。加熱炉３に搬入される前の管の温度は、酸化性ガスが反応しない温度にしておく、通常は常温であればよい。また、加熱炉５内で酸化処理が終了して炉外へ排出された管の外面が大気によって酸化されるのを防止するために、加熱炉５からチャンバ外へ出るまでの距離を約２ｍ以上にして、酸化反応が起こらない程度の温度まで管を徐冷した後にチャンバ外へ排出するのが望ましい。
【００３１】
以下、本発明の酸化処理方法で規定した各条件について説明する。
【００３２】
１）ステンレス鋼管、Ａｌ含有量
ステンレス鋼管は鋼種に限定されるものでなく、オーステナイト系ステンレス鋼管、フェライト系ステンレス鋼管および２相系ステンレス鋼管が対象となる。
【００３３】
しかし、Ａｌ酸化物被膜を生成させるので、Ａｌ含有量は、重量％で１〜６％含有させる必要がある。１％未満では、本発明の方法で酸化処理してもオゾン含有超純水に金属イオンを溶出させないＡｌ酸化物被膜が得られない。一方、６％を超えると金属間化合物が析出して熱間加工性および靭性が劣化する。したがって、Ａｌ含有量は、１〜６％とした。
【００３４】
対象とするステンレス鋼の好ましい化学組成は以下の通りである。
【００３５】
重量％で、Ｃｒ：１２〜３０％、Ｎｉ：０〜３５％、Ａｌ：１〜６％、Ｓｉ：０．３％以下、Ｍｏ：０〜３％、Ｂ＋Ｌａ＋Ｃｅ：０〜０．０１％、Ｃｕ：０．１％以下、Ｎｂ＋Ｔｉ＋Ｚｒ：０．１％以下、Ｃ：０．０３％以下、Ｍｎ：０．２％以下、Ｐ：０．０３％以下、Ｓ：０．０１％以下、Ｎ：０．０５％以下、Ｏ：０．０１％以下、残部：Ｆｅおよび不可避的不純物。
【００３６】
上記のステンレス鋼のなかでも、Ｎｉ含有率が重量％で０〜５％のフェライト系ステンレス鋼、Ｃｒ、ＮｉおよびＳｉ含有率が重量％でＣｒ：１２〜２５％、Ｎｉ：１４〜３５％、Ｓｉ：０．２％以下であるオーステナイト系ステンレス鋼材などが実用上もっとも好適である。
【００３７】
２）酸化性混合ガス
（ａ）水素含有量
水素含有率が１０体積％未満では、酸化反応がおきている際の管内の水蒸気含有率のわずかな変化で酸化挙動が大きく変化し、Ａｌ含有率が高くて均一な厚さのＡｌ酸化物皮膜を安定して形成することができない。一方、９９．９９９９体積％を超えると高価になり経済的でないため、上限を９９．９９９９体積％とした。
（ｂ）水蒸気
水蒸気の含有量が０．５体積ｐｐｍ未満では、Ａｌ酸化物皮膜を十分に形成することができない。３０体積ｐｐｍを超えて含有させると、Ａｌ酸化物皮膜厚が２００ｎｍを超える程に成長し、管内面が粗くなる。均一な厚さを保ち、かつＡｌ含有量が高いＡｌ酸化物皮膜を形成するためには、水蒸気の含有量を０．５〜２０体積ｐｐｍとするのがよい。さらに好ましくは、１〜１０体積ｐｐｍである。
【００３８】
（ｃ）不活性ガス
水蒸気および水素以外の混合ガスは不活性ガスとする。不活性ガスとしては、ヘリウムガス、アルゴンガス、ネオンガス等を用いることができる。これらのガスのうち、安価なアルゴンガスを使用するのが好ましい。水素ガスおよび不活性ガスの含有量は流量制御器により、水蒸気は露点計測と水蒸気添加器により調整することができる。
【００３９】
３）ステンレス鋼管の加熱温度
ステンレス鋼管の加熱温度は、８００〜１２００℃とする。８００℃未満ではＡｌ含有率が９０％以下の薄い酸化物被膜しか形成できない。一方、１２００℃を超えると酸化の進行が速いために皮膜が過度に厚くなる。好ましい加熱温度は８５０〜１１００℃である。
【００４０】
４）酸化性ガスの流量
Ａｌの含有率が９０原子％以上で、厚さが１０〜２００ｎｍのＡｌ酸化物皮膜をステンレス鋼管内面に形成するためには、上述した加熱温度および酸化性ガスの組成に加え、酸化性ガスの流量を下記の式を満足する量とするのが好ましい。酸化物皮膜の酸素源となるのに十分な量の酸素を含有する酸化性ガスを管内に供給する必要がある。管内面にＡｌ酸化物（Ａｌ2Ｏ3、分子量１０１．９３、密度 ３．９９ｇ／ｃｍ3）を最低１０ｎｍ生成させるためには、皮膜中とガス中の酸素量を比較する計算から、酸化性ガス流量の必要下限は次式で表される。
【００４１】
酸化性混合ガスの流量（リットル／分）≧８．２６×Ｒ×（Ｌ／Ｔ）／Ｃ、
ここで、Ｒ：ステンレス鋼管の内径（ｍｍ）、
Ｌ：加熱炉均熱帯長さ（ｃｍ）、
Ｔ：ステンレス鋼管の均熱帯での酸化処理時間（分）、
Ｃ：酸化性ガス中の水蒸気濃度（体積ｐｐｍ）。
加熱炉均帯長さ（Ｌ）とは、加熱炉内で加熱目標温度になっている部分の長さである。加熱炉の均熱帯の長さ（Ｌ）は、例えば、複数の加熱ゾーンを持つヒーターを使用して、加熱ゾーンの長さを変えることにより変更することができる。 鋼管の均熱帯での処理時間（Ｔ）は、鋼管の任意の点が加熱炉均熱帯を通過する時間である。
【００４２】
処理時間（Ｔ）は、１〜６０分の範囲に設定するのが好ましい。１分未満では膜厚が不足することがあり、また６０分を超えると皮膜が過度に厚くなるとともに酸化処理の能率が低下する。
【００４３】
酸化性ガスの水蒸気濃度（Ｃ）は、管内面にＡｌ酸化物皮膜を必要最低限である１０ｎｍ以上の厚さに生成させることを目標とし、酸化反応に必要な酸素は全て酸化性ガス中の水蒸気から供給されると見なして設定する値である。
【００４４】
管の移動速度は、処理時間Ｔと加熱炉均熱帯長さＬから、Ｌ／Ｔにより得られた値となる。
【００４５】
上記の式から分かるように、酸化性ガスの流量は、鋼管内径、加熱炉中の均熱長さが長いほど、また処理時間と水蒸気濃度が小さいほど多くなる。上記の式で求められる値に満たない流量では、反応に使用される酸化性ガスが不足するため、鋼管内面の微視的凹凸を考慮した場合に、前述した機能を発揮するのに必要な最低膜厚１０ｎｍ以上のＡｌ酸化物皮膜が鋼管全長にわたって形成されないことがある。一方、酸化性ガスを必要以上に供給することは、ガスのコストを上昇させるので好ましくない。流量の上限値は、下限値の３倍以内とするのが好ましい。
【００４６】
また、ガス圧力に関しては、鋼管の継ぎ手部分あるいは鋼管前方先端からの空気あるいは非酸化性ガスの混入を防ぐために、鋼管内ガスの圧力を大気圧および加熱炉内圧より高めにしておく。具体的には、０．２ｋｇｆ／ｃｍ2 以上、好ましくは０．５ｋｇｆ／ｃｍ2 以上とする。鋼管の内圧は、鋼管が細径の場合は、
鋼管内抵抗により上昇するので、特に昇圧の手段は必要ない。しかし、鋼管径が大きな、具体的には外径１２．７ｍｍ（１／２インチ）以上の場合には、鋼管先端を小径化するためのオリフィス（図１の６）を取り付けて昇圧するのがよい。
【００４７】
５）Ａｌ酸化物皮膜
ステンレス鋼管の内面にＡｌ酸化物皮膜（Ａｌ2Ｏ3）を生成させるのは、前記したようにオゾンを含有する超純水に対する耐食性を付与し、オゾン含有超純水への金属イオンの溶出を防止するためである。Ａｌ酸化物被膜は、Ａｌの含有率が９０原子％以上、厚さが１０〜２００ｎｍとするのが好ましい。なお、Ａｌ酸化物被膜は、全てがＡｌ酸化物からなっているのが好ましいが、そのような酸化物被膜を生成させることは困難であり、ＣｒおよびＦｅ等の酸化物を含むものとするが、それらはできるだけ少ないのが好ましい。
【００４８】
６）酸化性ガスをステンレス鋼管内に流しつつ、鋼管を加熱炉内を移動させながらの酸化処理
ステンレス鋼管の長手方向に厚さが均一になるようにＡｌ酸化物皮膜を生成させること、および酸化物被膜中のＡｌ量を均一にするために酸化性混合ガスを鋼管内に流しつつ、加熱炉内で鋼管をその長手方向に移動させながら酸化処理する。
【００４９】
このような方法により酸化処理をおこなうと、鋼管の長手方向のどの位置でも加熱炉内での酸化処理条件が同じになるため、酸化物被膜厚および被膜中のＡｌ含有量が均一となる。
【００５０】
７）雰囲気
外表面が酸化したステンレス鋼管は、酸化皮膜の剥離による不純物が発生するため、清浄度が要求される半導体や医薬品、食品の製造に使用される配管には適さない。したがって、酸化処理中にステンレス鋼管の外面が酸化するのを防止するために、加熱炉の入り口近傍、加熱炉内および加熱炉出口近傍のステンレス鋼管のパスライン周辺を酸素濃度３体積ｐｐｍ以下で且つ水蒸気濃度３０体積ｐｐｍ以下である不活性ガスからなる雰囲気にするのが好ましい。上記雰囲気にするには図１に示した手段がある。
【００５１】
図２は、ステンレス鋼管のパスライン周辺を酸素濃度３体積ｐｐｍ以下で且つ水蒸気濃度３０体積ｐｐｍ以下である不活性ガスからなる雰囲気にする他の方法を示す図である。すなわち、加熱炉５内に加熱炉よりも長いマッフル１０を挿入してマッフル内を酸素濃度３体積ｐｐｍ以下で且つ水蒸気濃度３０体積ｐｐｍ以下である不活性ガスからなる雰囲気とする方法で、上記チャンバを用いるより簡単な装置となる利点がある。
【００５２】
なお、上記の雰囲気は、さらに好ましくは酸素濃度１体積ｐｐｍ以下且つ水蒸気濃度１０体積ｐｐｍ以下の不活性ガスとするのがよい。
【００５３】
【実施例】
表１に示す化学組成を有するオーステナイト系ステンレス鋼から表２に示す３種類の寸法のステンレス鋼管を通常の方法で製造した。これらの鋼管に表３に示す諸条件で酸化処理を施した。酸化処理は図１に示した装置を用いておこなった。
【００５４】
【表１】
【表２】
【表３】
チャンバ内の雰囲気は、水分を含まない水素とした。
【００５８】
表３のNo.１〜１３は、本発明の方法による酸化処理を施したものである。No.１４〜１９は本発明で規定する条件から外れている方法で酸化処理を施したものである。また、No.１９は、加熱炉内で鋼管を移動させないで固定したまま酸化処理したもので、バッチ方法に類似している（従来のバッチ方法では、鋼管全体が同時に加熱されて酸化処理される）。
【００５９】
加熱炉雰囲気が鋼管内へ混入することを防止するために、酸化性ガスの出側には口径３ｍｍのオリフィス６を取り付けた。
【００６０】
酸化処理後の鋼管内面のＡｌ酸化物皮膜の性状は次のようにして評価した。
【００６１】
鋼管の端部から長さ１００ｃｍ毎の計５ヶ所をマークし、酸化性ガスを導入した鋼管の入口部を位置１とし、酸化性ガスの出口である鋼管の端部を位置５とし、中間部を順に位置２、３、４とした。それぞれの位置の鋼管の部分を縦半割りにして試験片を切り出し、鋼管の内面に形成されているＡｌ酸化物皮膜を膜厚方向に窒素イオンスパッタリングによる２次イオン質量分析をおこなって、Ａｌ含有量と膜厚を測定した。
【００６２】
酸化処理後の鋼管内面の耐オゾン含有水性は以下の方法で評価した。
【００６３】
鋼管内部に、オゾン１１０ｇ／ｍ3を含む８０℃の酸素と比抵抗１６ＭΩｃｍの超純水を封入し１００時間保持した。この場合、超純水は約７ｍｇ／ｌ（リットル）のオゾンを含むオゾン含有水となる。次に、このオゾン含有水を誘導結合プラズマイオン質量分析法により定量分析し、オゾン含有水中に溶出した金属イオン量（Ｆｅイオン、Ｃｒイオン、Ｎｉイオン、Ａｌイオンの総和）を求めた。この結果をもとに、鋼管内面の表面積当たりの金属イオン溶出量を換算し、耐オゾン水性を評価した。溶出量が０．５ｍｇ／ｍ2未満の場合は良好、０．５ｍｇ／ｍ2以上２．０ｍｇ／ｍ2未満の場合は普通、２．０ｍｇ／ｍ2以上の場合は不良とした。結果を表４に示す。
【００６４】
なお、表４には上記の溶出量を、それぞれ、○、△、×で表示した。
【００６５】
【表４】
本発明例である No.１〜１３は、鋼管の径および長さ方向の位置によらず、Ａｌ含有量が９０％を超え、膜厚１０ｎｍ〜２００ｎｍのＡｌ酸化物皮膜が生成していた。また、耐オゾン含有水性も良好であった。
【００６７】
これに対し、水蒸気含有率、水素含有率、鋼管の加熱温度のいずれかが本発明の範囲外の比較例である No.１４〜１８では、Ａｌ含有率９０％未満のものや膜厚が１０ｎｍ〜２００ｎｍの範囲にならないものがあり、鋼管の位置によってＡｌ含有量や膜厚が異なっていた。 No.１９で生成したＡｌ酸化物皮膜は、Ａｌ含有率が低く膜厚も不足していた。さらに No.１４〜１８では、オゾン含有水中での金属溶出量が多く、耐オゾン含有水性は不芳であった。
【００６８】
【発明の効果】
本発明の酸化処理方法によれば、半導体や医薬品、食品の製造に使用されるオゾン含有水等の流体を搬送するために使用するステンレス鋼管の内面に、能率良くしかもＡｌ含有量と膜厚が均一なＡｌ酸化物皮膜を形成することができる。
【図面の簡単な説明】
【図１】本発明の酸化処理方法を実施するのに用いる酸化処理装置の１例を示す概略断面図である。
【図２】本発明の酸化処理方法を実施するのに用いる酸化処理装置の他の例を示す概略断面図である。
【符号の説明】
１ａ、１ｂ：ステンレス鋼管
２：酸化性ガス
３：チャンバ
４：酸素濃度３体積ｐｐｍ以下で且つ水蒸気濃度３０体積ｐｐｍ以下である不活性ガスからなる雰囲気
５：加熱炉
６：オリフィス
７ａ、７ｂ：酸素濃度３体積ｐｐｍ以下で且つ水蒸気濃度３０体積ｐｐｍ以下である不活性ガス供給、排出口
９：管継ぎ手
10：マッフル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for oxidizing an inner surface of a stainless steel pipe used for transporting fluids such as ozone-containing water used for manufacturing semiconductors, pharmaceuticals, and foods.
[0002]
[Prior art]
In the manufacture of semiconductor devices in recent years, fine processing is performed with the high integration of devices. In particular, a device called a VLSI is processed with a fine pattern of 1 μm or less. In the VLSI manufacturing process, a trace amount of impurities such as gas and water used adheres to the wiring pattern and causes a circuit failure. Therefore, a fluid such as gas or water used in a process for manufacturing a semiconductor such as a VLSI must have a high purity.
[0003]
The pipes and members that supply these fluids are also required to emit as little particulates and impurities as possible from the surface in contact with the fluid.
[0004]
Recently, cleaning water containing ozone (ozone-containing water) has been used for cleaning silicon wafers and the like in semiconductor manufacturing processes and the like. As can be seen from the fact that ozone is used as a bleaching agent and disinfectant, it has a strong oxidizing power, so it has the effect of ionizing metals and decomposing organic substances. Therefore, when a silicon wafer or the like is washed with ozone-containing ultrapure water, the metal adhering thereto is ionized and the organic matter is removed by being decomposed. Furthermore, since ozone is self-decomposed after cleaning, it does not remain as a contaminant on the silicon wafer. Thus, ozone-containing water is extremely effective for cleaning silicon wafers.
[0005]
Conventionally used stainless steel has the necessary strength for piping and equipment of ultrapure water used in semiconductor manufacturing processes, and is excellent in workability. However, there is a disadvantage that the corrosion resistance to water containing ozone is poor. That is, there is a problem that the stainless steel material is corroded by the ozone-containing ultrapure water, and metal ions such as Fe, Cr, Ni are eluted from the steel material, and the ozone-containing water is contaminated. The inventors of the present invention elute metal ions from stainless steel into ozone-containing water.PreventAs a countermeasure to stop, it has been proposed to provide an Al oxide film on the surface of stainless steel (Japanese Patent Laid-Open No. 10-72645).
[0006]
As a steel material having an Al oxide film, Japanese Patent Laid-Open No. 7-60099 discloses stainless steel used in an ultra-vacuum environment having an Al oxide film of 10 to 150 angstrom, and Japanese Patent Laid-Open No. 6-271993 discloses an automobile. An austenitic stainless steel excellent in oxidation resistance having an Al oxide film suitable for high-temperature parts such as exhaust gas members is disclosed.
[0007]
An apparatus for forming an oxide film on the inner surface of a stainless steel pipe is disclosed in Japanese Patent Application Laid-Open Nos. 2-43353 and 3-111552.
[0008]
These oxidation treatment apparatuses are apparatuses that insert and fix the entire steel pipe in a heating furnace having a predetermined atmosphere and temperature, and heat the steel pipe from the outer surface while flowing a gas of a predetermined composition in the steel pipe, so-called batch system. This is an oxidation treatment method.
[0009]
However, when a long stainless steel pipe having an outer diameter of 6.35 mm and a length of 4 m, which is most frequently used in the conventional batch system, is oxidized, there are the following two problems.
[0010]
One is that the efficiency of the oxidation treatment is poor. That is, the steel pipe to be treated is attached to the furnace, the air remaining in the steel pipe is purged by the inflow of the inert gas, the baking is performed to remove the moisture adhering to the inner surface of the steel pipe, the switching to the oxidizing gas, and the heat treatment It is necessary to repeat multiple processes such as cooling and removal of the steel pipe to be processed for each batch process. Further, when the number of steel pipes that can be processed at one time is increased for the purpose of improving the processing efficiency, the apparatus becomes complicated and expensive.
[0011]
Another problem is that the oxide film cannot be uniformly formed over the entire length of the steel pipe, and the Al content in the film is not uniform. In order to ensure the performance required for the above-mentioned ozone-containing water piping, this problem must be solved.
[0012]
In the conventional batch processing method, an oxidation reaction occurs simultaneously over the entire length of the steel pipe, so that the vicinity of the pipe end where the oxidizing gas is introduced is most oxidized, whereas the oxidation near the pipe end where the oxidizing gas exits. This makes it difficult to form a non-uniform Al oxide film in the length direction of the steel pipe. The reason why the vicinity of the pipe end on the outlet side of the oxidizing gas is difficult to oxidize is that the concentration of water vapor and oxygen, which are oxidizing components in the gas, is lower than the vicinity of the pipe end on the side where the oxidizing gas is introduced. Because it is.
[0013]
Moreover, the reason why the Al content in the coating is not uniform in the length direction of the steel pipe is as follows.
[0014]
The oxidizing gas introduced into the pipe moves from the introduction side to the exit side while being consumed. Therefore, since the oxygen partial pressure in the vicinity of the outlet side pipe end is lower than that in the vicinity of the inlet side pipe end, the composition of the coating formed on the inlet side and the outlet side is different. That is, when the oxygen partial pressure is low, only Al in the steel is oxidized, but when the oxygen partial pressure is high, Cr and Fe are also oxidized. For this reason, Cr and Fe are mixed in the oxide film at the gas inlet side tube end portion, and the Al content is lowered. However, as the gas outlet side pipe end is approached, the Al content is increased.
[0015]
[Problems to be solved by the invention]
An object of the present invention is to provide an Al oxide with an efficient Al content and a uniform film thickness on the inner surface of a stainless steel pipe used for transporting fluids such as ozone-containing water in the manufacture of semiconductors, pharmaceuticals and foods. An object of the present invention is to provide an oxidation method for forming a coating on the entire length of a steel pipe.
[0016]
[Means for Solving the Problems]
The gist of the present invention is as follows.
[0017]
(1) Stainless steel containing 10% to 99.9999% by volume of hydrogen, 0.5% to 30% by volume of water vapor, and 1% to 6% of Al by weight% of an oxidizing mixed gas composed of an inert gas as the balance While flowing into the steel pipe, the stainless steel pipe is inserted into the heating furnace and heated to 800 to 1200 ° C. while moving in the longitudinal direction to form an Al oxide film on the inner surface of the stainless steel pipe.A method for oxidizing an inner surface of a stainless steel pipe, wherein an oxygen concentration is 3 volume ppm or less and a water vapor concentration is 30 volume ppm or less so that the outer surface of the stainless steel pipe is not oxidized in the vicinity of the entrance of the heating furnace, in the heating furnace, or in the vicinity of the heating furnace outlet. The atmosphere around the pass line of the stainless steel pipe is adjusted by providing a heating furnace in a chamber of an inert gas atmosphere.An oxidation treatment method for an inner surface of a stainless steel pipe.
[0018]
(2)In a stainless steel tube containing hydrogen: 10 to 99.9999 vol%, water vapor: 0.5 to 30 volppm, the balance of an oxidizing mixed gas consisting of an inert gas containing 1 to 6% by weight of Al In the oxidation method of the inner surface of the stainless steel tube, the stainless steel tube is inserted into the heating furnace while flowing, heated to 800-1200 ° C. while moving in the longitudinal direction, and an Al oxide film is formed on the inner surface of the stainless steel tube. The flow rate of the oxidative mixed gas flowing in the stainless steel pipe is an amount satisfying the following formula:A method for oxidizing the inner surface of stainless steel pipes.
Flow rate of oxidizing mixed gas (liter / minute) ≧ 8.26 × R × (L / T) / C,
Here, R: inner diameter (mm) of stainless steel pipe,
L: heating furnace soaking length (cm),
T: oxidation time of the stainless steel pipe in the soaking zone (min),
C: Water vapor concentration (volume ppm) in the oxidizing gas.
[0019]
(3)In a stainless steel tube containing hydrogen: 10 to 99.9999 vol%, water vapor: 0.5 to 30 volppm, the balance of an oxidizing mixed gas consisting of an inert gas containing 1 to 6% by weight of Al In the oxidation method of the inner surface of the stainless steel tube, the stainless steel tube is inserted into the heating furnace while flowing, heated to 800-1200 ° C. while moving in the longitudinal direction, and an Al oxide film is formed on the inner surface of the stainless steel tube. In order to prevent oxidation of the outer surface of the stainless steel pipe in the vicinity of the inlet of the heating furnace, in the heating furnace and in the vicinity of the outlet of the heating furnace, the oxygen concentration around the pass line of the stainless steel pipe is 3 volume ppm or less and the water vapor concentration is 30 volume ppm or less. Made of some inert gasAtmosphere andAnd the flow rate of the oxidizing mixed gas flowing in the stainless steel pipe is an amount satisfying the following formula:A method for oxidizing the inner surface of stainless steel pipes.
Flow rate of oxidizing mixed gas (liter / minute) ≧ 8.26 × R × (L / T) / C,
Here, R: inner diameter (mm) of stainless steel pipe,
L: heating furnace soaking length (cm),
T: oxidation time of the stainless steel pipe in the soaking zone (min),
C: Water vapor concentration (volume ppm) in the oxidizing gas.
[0020]
(4)In a stainless steel tube containing hydrogen: 10 to 99.9999 vol%, water vapor: 0.5 to 30 volppm, the balance of an oxidizing mixed gas consisting of an inert gas containing 1 to 6% by weight of Al In the oxidation method of the inner surface of the stainless steel tube, the stainless steel tube is inserted into the heating furnace while flowing, heated to 800 to 1200 ° C. while moving in the longitudinal direction, and an Al oxide film is formed on the inner surface of the stainless steel tube. An atmosphere composed of an inert gas having an oxygen concentration of 3 volume ppm or less and a water vapor concentration of 30 volume ppm or less so that the outer surface of the stainless steel pipe is not oxidized in the vicinity of the entrance of the heating furnace, in the heating furnace, or in the vicinity of the exit of the heating furnace. By installing a heating furnace in the chamber, the atmosphere around the pass line of the stainless steel pipe is adjusted, and the oxidative mixing that flows in the stainless steel pipe Flow rate of the scan is equal to or is an amount which satisfies the following formulaA method for oxidizing the inner surface of stainless steel pipes.
Flow rate of oxidizing mixed gas (liter / minute) ≧ 8.26 × R × (L / T) / C,
Here, R: inner diameter (mm) of stainless steel pipe,
L: heating furnace soaking length (cm),
T: oxidation time of the stainless steel pipe in the soaking zone (min),
C: Water vapor concentration (volume ppm) in the oxidizing gas.
[0021]
(5)In a stainless steel tube containing hydrogen: 10 to 99.9999 vol%, water vapor: 0.5 to 30 volppm, the balance of an oxidizing mixed gas consisting of an inert gas containing 1 to 6% by weight of Al In the oxidation method of the inner surface of the stainless steel tube, the stainless steel tube is inserted into the heating furnace while flowing, heated to 800-1200 ° C. while moving in the longitudinal direction, and an Al oxide film is formed on the inner surface of the stainless steel tube. In order to prevent oxidation of the outer surface of the stainless steel pipe in the vicinity of the entrance of the heating furnace, in the heating furnace and in the vicinity of the heating furnace outlet, a heating furnace having a muffle longer than the heating furnace is used, and the oxygen concentration in the muffle is 3 volume ppm. Adjust the atmosphere around the pass line of the stainless steel pipe as an atmosphere consisting of an inert gas having a water vapor concentration of 30 ppm by volume or less, andThe flow rate of the oxidizing gas mixture flowing in the stainless steel pipe is an amount that satisfies the following formula:It is characterized byA method for oxidizing the inner surface of stainless steel pipes.
[0022]
Flow rate of oxidizing gas mixture (liter / min) ≧ 8.26 × R × (L / T) / C
Where R: inner diameter of stainless steel pipe (mm)
L: heating furnace soaking length (cm)
T: Oxidation time of stainless steel pipe in soaking zone (min)
C: Water vapor concentration in the oxidizing gas (volume ppm)
As a result of various experiments and studies to solve the drawbacks of the conventional batch type oxidation treatment method, the present inventors have obtained the following knowledge and completed the present invention.
[0023]
a) To prevent corrosion of ultra pure water containing ozone and prevent elution of metal ions on the inner surface of a stainless steel tube, an Al oxide having an Al content of 90 atomic% or more and a thickness of 10 to 200 nm The coating is preferably formed on the inner surface of the stainless steel pipe. b) As an oxidizing gas used for forming such an Al oxide film, hydrogen: 10 to 99.9999 vol%, water vapor: 0.5 to 30 volppm, with the balance being an inert gas It is an oxidative mixed gas, and it is good to oxidize within the temperature range of 800-1200 degreeC.
[0024]
c) In order to produce an Al oxide film so that the thickness is uniform in the longitudinal direction of the steel pipe, and to make the amount of Al in the oxide film uniform, heating is performed while flowing an oxidizing mixed gas into the steel pipe. It is preferable to oxidize the steel pipe while moving it in the longitudinal direction in the furnace.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the oxidation treatment method of the present invention will be specifically described.
[0026]
FIG. 1 is a schematic longitudinal sectional view showing an example of an oxidation treatment apparatus used to carry out the oxidation treatment method of the present invention.
[0027]
A
[0028]
The example shown in FIG. 1 is an example in which two stainless steel pipes are connected in the longitudinal direction. However, a large number of steel pipes may be connected, and more efficiency can be obtained if a plurality of connected steel pipes are processed in the furnace at the same time. Get better.
[0029]
When connecting a plurality of steel pipes in the longitudinal direction, an airtight connection method is required in order to avoid mixing of atmospheric gas outside the pipe from the joint portion of the pipe. Specific examples include welding, metal gasket type mechanical joints, bite type mechanical joints, and the like.
[0030]
An oxidation reaction starts to occur on the inner surface of the tube heated in the heating furnace. The temperature of the tube before being carried into the heating furnace 3 is set to a temperature at which the oxidizing gas does not react. Further, in order to prevent the outer surface of the pipe discharged outside the furnace after being oxidized in the
[0031]
Hereinafter, each condition prescribed | regulated with the oxidation treatment method of this invention is demonstrated.
[0032]
1) Stainless steel pipe, Al content
Stainless steel pipes are not limited to steel types, and austenitic stainless steel pipes, ferritic stainless steel pipes, and duplex stainless steel pipes are targeted.
[0033]
However, since an Al oxide film is generated, the Al content needs to be 1 to 6% by weight. If it is less than 1%, an Al oxide film that does not elute metal ions into ozone-containing ultrapure water cannot be obtained even if oxidation treatment is performed by the method of the present invention. On the other hand, when it exceeds 6%, an intermetallic compound precipitates, and hot workability and toughness deteriorate. Therefore, the Al content is set to 1 to 6%.
[0034]
The preferable chemical composition of the target stainless steel is as follows.
[0035]
% By weight, Cr: 12-30%, Ni: 0-35%, Al: 1-6%, Si: 0.3% or less, Mo: 0-3%, B + La + Ce: 0-0.01%, Cu : 0.1% or less, Nb + Ti + Zr: 0.1% or less, C: 0.03% or less, Mn: 0.2% or less, P: 0.03% or less, S: 0.01% or less, N: 0 .05% or less, O: 0.01% or less, balance: Fe and inevitable impurities.
[0036]
Among the above stainless steels, ferritic stainless steel having a Ni content of 0 to 5% by weight, Cr, Ni and Si contents of Cr: 12 to 25%, Ni: 14 to 35%, An austenitic stainless steel material having Si: 0.2% or less is most suitable for practical use.
[0037]
2) Oxidizing gas mixture
(A) Hydrogen content
When the hydrogen content is less than 10% by volume, the oxidation behavior changes greatly due to a slight change in the water vapor content in the tube during the oxidation reaction, and the Al oxide film has a high Al content and a uniform thickness. Cannot be formed stably. On the other hand, if it exceeds 99.9999% by volume, it becomes expensive and not economical, so the upper limit was made 99.9999% by volume.
(B) Water vapor
When the water vapor content is less than 0.5 ppm by volume, an Al oxide film cannot be sufficiently formed. When it contains more than 30 volume ppm, it will grow so that Al oxide membrane | film | coat thickness exceeds 200 nm, and a pipe | tube inner surface will become rough. To form an Al oxide film having a uniform thickness and a high Al content, the water vapor content is preferably 0.5 to 20 ppm by volume. More preferably, it is 1-10 volume ppm.
[0038]
(C) Inert gas
A mixed gas other than water vapor and hydrogen is an inert gas. As the inert gas, helium gas, argon gas, neon gas, or the like can be used. Of these gases, it is preferable to use an inexpensive argon gas. The contents of hydrogen gas and inert gas can be adjusted by a flow controller, and the water vapor can be adjusted by dew point measurement and a water vapor adder.
[0039]
3) Heating temperature of stainless steel pipe
The heating temperature of the stainless steel pipe is 800 to 1200 ° C. Below 800 ° C., only a thin oxide film having an Al content of 90% or less can be formed. On the other hand, when the temperature exceeds 1200 ° C., the film is excessively thick because the oxidation proceeds rapidly. A preferable heating temperature is 850 to 1100 ° C.
[0040]
4) Flow rate of oxidizing gas
In order to form an Al oxide film having an Al content of 90 atomic% or more and a thickness of 10 to 200 nm on the inner surface of the stainless steel pipe, in addition to the heating temperature and the composition of the oxidizing gas described above, The flow rate is preferably set to an amount that satisfies the following formula. An oxidizing gas containing a sufficient amount of oxygen to serve as an oxygen source for the oxide film must be supplied into the tube. Al oxide (Al2OThree, Molecular weight 101.93, density 3.99 g / cmThree) Is generated at least 10 nm, the required lower limit of the oxidizing gas flow rate is expressed by the following equation based on a calculation comparing the amounts of oxygen in the film and the gas.
[0041]
Flow rate of oxidizing gas mixture (liter / min) ≧ 8.26 × R × (L / T) / C,
Where R: inner diameter of stainless steel pipe (mm),
L: heating furnace soaking length (cm),
T: Oxidation time of stainless steel pipe in soaking zone (min),
C: Water vapor concentration in the oxidizing gas (volume ppm).
The heating furnace uniform zone length (L) is the length of the portion at the heating target temperature in the heating furnace. The soaking zone length (L) of the heating furnace can be changed, for example, by changing the length of the heating zone using a heater having a plurality of heating zones. The treatment time (T) in the soaking zone of the steel pipe is the time for any point of the steel pipe to pass through the heating furnace soaking zone.
[0042]
The treatment time (T) is preferably set in the range of 1 to 60 minutes. If it is less than 1 minute, the film thickness may be insufficient. If it exceeds 60 minutes, the film becomes excessively thick and the efficiency of the oxidation treatment decreases.
[0043]
The water vapor concentration (C) of the oxidizing gas is aimed at generating an Al oxide film on the inner surface of the tube to a minimum thickness of 10 nm or more, and all the oxygen necessary for the oxidation reaction is in the oxidizing gas. This value is set assuming that it is supplied from water vapor.
[0044]
The moving speed of the tube is a value obtained by L / T from the processing time T and the heating furnace soaking length L.
[0045]
As can be seen from the above equation, the flow rate of the oxidizing gas increases as the inner diameter of the steel pipe and the soaking length in the heating furnace are longer, and as the treatment time and the water vapor concentration are smaller. If the flow rate is less than the value obtained by the above formula, the oxidizing gas used for the reaction is insufficient, so that the minimum necessary for performing the above-mentioned functions is taken into account when considering microscopic irregularities on the inner surface of the steel pipe. An Al oxide film having a thickness of 10 nm or more may not be formed over the entire length of the steel pipe. On the other hand, supplying an oxidizing gas more than necessary is not preferable because it increases the cost of the gas. The upper limit value of the flow rate is preferably within 3 times the lower limit value.
[0046]
Regarding the gas pressure, the pressure of the gas in the steel pipe is set higher than the atmospheric pressure and the pressure in the heating furnace in order to prevent air or non-oxidizing gas from entering from the joint portion of the steel pipe or the front end of the steel pipe. Specifically, 0.2 kgf / cm2Or more, preferably 0.5 kgf / cm2That's it. The internal pressure of the steel pipe is
Since it rises due to the resistance in the steel pipe, no means for boosting is required. However, when the steel pipe diameter is large, specifically, when the outer diameter is 12.7 mm (1/2 inch) or more, it is possible to increase the pressure by attaching an orifice (6 in FIG. 1) for reducing the diameter of the steel pipe tip. Good.
[0047]
5) Al oxide film
Al oxide film (Al2OThree) Is generated in order to impart corrosion resistance to ultrapure water containing ozone as described above, and to prevent elution of metal ions into the ozone-containing ultrapure water. The Al oxide film preferably has an Al content of 90 atomic% or more and a thickness of 10 to 200 nm. In addition, although it is preferable that the Al oxide film is entirely made of Al oxide, it is difficult to form such an oxide film and includes oxides such as Cr and Fe. Is preferably as small as possible.
[0048]
6) Oxidation treatment while moving the steel pipe in the heating furnace while flowing oxidizing gas into the stainless steel pipe
In order to produce an Al oxide film so that the thickness is uniform in the longitudinal direction of the stainless steel pipe, and in order to make the amount of Al in the oxide film uniform, flowing an oxidizing mixed gas into the steel pipe, a heating furnace The steel pipe is oxidized while moving in the longitudinal direction.
[0049]
When the oxidation treatment is performed by such a method, the oxidation treatment conditions in the heating furnace are the same at any position in the longitudinal direction of the steel pipe, so that the oxide film thickness and the Al content in the coating become uniform.
[0050]
7) AtmosphereAtmosphere
Stainless steel pipes with oxidized outer surfaces are not suitable for piping used in the manufacture of semiconductors, pharmaceuticals, and foods that require cleanliness because impurities are generated due to peeling of the oxide film. Therefore, in order to prevent the outer surface of the stainless steel pipe from being oxidized during the oxidation treatment, the vicinity of the stainless steel pipe pass line in the vicinity of the entrance of the heating furnace, in the heating furnace and in the vicinity of the outlet of the heating furnace is used.It consists of an inert gas having an oxygen concentration of 3 volume ppm or less and a water vapor concentration of 30 volume ppm or less.An atmosphere is preferred.the aboveThere are means shown in FIG.
[0051]
Figure 2 shows the area around the stainless steel pipe pass line.It consists of an inert gas having an oxygen concentration of 3 volume ppm or less and a water vapor concentration of 30 volume ppm or less.It is a figure which shows the other method of making atmosphere. That is, a
[0052]
Note that the aboveatmosphereHahaMore preferably, the oxygen concentration is 1 volume ppm or less and the water vapor concentration is 10 volume ppm or less.IncongruityActive gasToIt is good.
[0053]
【Example】
Shown in Table 1SukerStainless steel pipes having three kinds of dimensions shown in Table 2 were produced by a conventional method from austenitic stainless steel having a chemical composition. These steel pipes were oxidized under various conditions shown in Table 3. The oxidation treatment was performed using the apparatus shown in FIG.
[0054]
[Table 1]
[Table 2]
[Table 3]
In chamberAtmosphereThe atmosphere was hydrogen containing no water.
[0058]
Nos. 1 to 13 in Table 3 are subjected to oxidation treatment by the method of the present invention. No.14 ~19Is subjected to oxidation treatment by a method deviating from the conditions specified in the present invention. In addition, No. 19 was oxidized without fixing the steel pipe in the heating furnace, and is similar to the batch method (in the conventional batch method, the entire steel pipe is simultaneously heated and oxidized. ).
[0059]
In order to prevent the heating furnace atmosphere from being mixed into the steel pipe, an
[0060]
The properties of the Al oxide film on the inner surface of the steel pipe after the oxidation treatment were evaluated as follows.
[0061]
Mark a total of 5 points every 100cm in length from the end of the steel pipe, the inlet part of the steel pipe into which the oxidizing gas is introduced is
[0062]
The ozone-containing water content on the inner surface of the steel pipe after the oxidation treatment was evaluated by the following method.
[0063]
110 g / m of ozone inside the steel pipeThreeOxygen containing 80 ° C. and ultrapure water having a specific resistance of 16 MΩcm were sealed and held for 100 hours. In this case, ultrapure water is about 7 mg / l.(liter)It becomes ozone-containing water containing ozone. Next, this ozone-containing water was quantitatively analyzed by inductively coupled plasma ion mass spectrometry, and the amount of metal ions eluted into the ozone-containing water (total of Fe ions, Cr ions, Ni ions, and Al ions) was determined. Based on this result, the metal ion elution amount per surface area of the steel pipe inner surface was converted to evaluate the ozone water resistance. Elution amount is 0.5mg / m2Less than 0.5, good, 0.5 mg / m22.0 mg / m or more2If it is less than 2.0mg / m2In the above cases, it was regarded as defective.The results are shown in Table 4.
[0064]
In addition,Table 4Indicates the above elution amounts as ◯, Δ, and X, respectively.
[0065]
[Table 4]
In Nos. 1 to 13, which are examples of the present invention, an Al oxide film having an Al content exceeding 90% and a film thickness of 10 nm to 200 nm was generated regardless of the diameter and the position in the length direction of the steel pipe. Moreover, the ozone-containing aqueous solution was also good.
[0067]
On the other hand, in No. 14 to 18, which are comparative examples in which any one of the water vapor content, the hydrogen content, and the heating temperature of the steel pipe is outside the scope of the present invention, the Al content is less than 90% and the film thickness is 10 nm. There were some which did not become the range of -200 nm, and Al content and film thickness differed with the position of the steel pipe. The Al oxide film produced in No. 19 had a low Al content and a lack of film thickness. Furthermore, in Nos. 14 to 18, the amount of metal elution in the ozone-containing water was large, and the ozone-resistant aqueous solution was poor.
[0068]
【The invention's effect】
According to the oxidation treatment method of the present invention, the inner surface of a stainless steel pipe used for transporting fluids such as ozone-containing water used in the manufacture of semiconductors, pharmaceuticals, and foods has an efficient Al content and film thickness. A uniform Al oxide film can be formed.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of an oxidation treatment apparatus used for carrying out an oxidation treatment method of the present invention.
FIG. 2 is a schematic cross-sectional view showing another example of an oxidation treatment apparatus used for carrying out the oxidation treatment method of the present invention.
[Explanation of symbols]
1a, 1b:Stainless steel pipe
2:Oxidizing gas
3:Chamber
4: Consisting of an inert gas having an oxygen concentration of 3 vol ppm or less and a water vapor concentration of 30 vol ppm or lessatmosphere
5:heating furnace
6:Orifice
7a, 7b: An inert gas having an oxygen concentration of 3 vol ppm or less and a water vapor concentration of 30 vol ppm or lessSupply and discharge port
9:Pipe joint
Ten:Muffle
Claims (5)
酸化性混合ガスの流量（リットル／分）≧８．２６×Ｒ×（Ｌ／Ｔ）／Ｃ
ここで、Ｒ：ステンレス鋼管の内径（ｍｍ）
Ｌ：加熱炉均熱帯長さ（ｃｍ）
Ｔ：ステンレス鋼管の均熱帯での酸化処理時間（分）
Ｃ：酸化性ガス中の水蒸気濃度（体積ｐｐｍ） In a stainless steel pipe containing 1 to 6% by weight of an oxidizing mixed gas containing hydrogen: 10 to 99.9999% by volume, water vapor: 0.5 to 30% by volume, and the balance being an inert gas. In the oxidation method of the inner surface of the stainless steel tube, the stainless steel tube is inserted into the heating furnace while flowing, heated to 800 to 1200 ° C. while moving in the longitudinal direction, and an Al oxide film is formed on the inner surface of the stainless steel tube. A method for oxidizing an inner surface of a stainless steel pipe, wherein the flow rate of the oxidizing mixed gas flowing in the stainless steel pipe is an amount satisfying the following formula :
Flow rate of oxidizing gas mixture (liter / min) ≧ 8.26 × R × (L / T) / C
Where R: inner diameter of stainless steel pipe (mm)
L: heating furnace soaking length (cm)
T: Oxidation time of stainless steel pipe in soaking zone (min)
C: Water vapor concentration in the oxidizing gas (volume ppm)
酸化性混合ガスの流量（リットル／分）≧８．２６×Ｒ×（Ｌ／Ｔ）／Ｃ
ここで、Ｒ：ステンレス鋼管の内径（ｍｍ）
Ｌ：加熱炉均熱帯長さ（ｃｍ）
Ｔ：ステンレス鋼管の均熱帯での酸化処理時間（分）
Ｃ：酸化性ガス中の水蒸気濃度（体積ｐｐｍ） In a stainless steel pipe containing 1 to 6% by weight of an oxidizing mixed gas containing hydrogen: 10 to 99.9999% by volume, water vapor: 0.5 to 30% by volume, and the balance being an inert gas. In the oxidation method of the inner surface of the stainless steel tube, the stainless steel tube is inserted into the heating furnace while flowing, heated to 800-1200 ° C. while moving in the longitudinal direction, and an Al oxide film is formed on the inner surface of the stainless steel tube. In order to prevent oxidation of the outer surface of the stainless steel pipe in the vicinity of the inlet of the heating furnace, in the heating furnace, and in the vicinity of the outlet of the heating furnace, the oxygen concentration around the pass line of the stainless steel pipe is 3 ppm by volume or less and the water vapor concentration is 30 ppm by volume or less. and wherein the certain the atmosphere of an inert gas, and an amount that the flow rate of the oxidizing gas mixture satisfies the following formulas to flow into the stainless steel tube Oxidation method stainless steel inner surfaces that.
Flow rate of oxidizing gas mixture (liter / min) ≧ 8.26 × R × (L / T) / C
Where R: inner diameter of stainless steel pipe (mm)
L: heating furnace soaking length (cm)
T: Oxidation time of stainless steel pipe in soaking zone (min)
C: Water vapor concentration in the oxidizing gas (volume ppm)
酸化性混合ガスの流量（リットル／分）≧８．２６×Ｒ×（Ｌ／Ｔ）／Ｃ
ここで、Ｒ：ステンレス鋼管の内径（ｍｍ）
Ｌ：加熱炉均熱帯長さ（ｃｍ）
Ｔ：ステンレス鋼管の均熱帯での酸化処理時間（分）
Ｃ：酸化性ガス中の水蒸気濃度（体積ｐｐｍ） In a stainless steel tube containing hydrogen: 10 to 99.9999 vol%, water vapor: 0.5 to 30 volppm, the balance of an oxidizing mixed gas consisting of an inert gas containing 1 to 6% by weight of Al In the oxidation method of the inner surface of the stainless steel tube, the stainless steel tube is inserted into the heating furnace while flowing, heated to 800 to 1200 ° C. while moving in the longitudinal direction, and an Al oxide film is formed on the inner surface of the stainless steel tube. An atmosphere composed of an inert gas having an oxygen concentration of 3 volume ppm or less and a water vapor concentration of 30 volume ppm or less so that the outer surface of the stainless steel pipe is not oxidized in the vicinity of the entrance of the heating furnace, in the heating furnace, or in the vicinity of the exit of the heating furnace. By installing a heating furnace in the chamber, the atmosphere around the pass line of the stainless steel pipe is adjusted, and the oxidative mixing that flows in the stainless steel pipe Oxidation method stainless steel tube inner surface, wherein the flow rate of the scan is an amount that satisfies the following equation.
Flow rate of oxidizing gas mixture (liter / min) ≧ 8.26 × R × (L / T) / C
Where R: inner diameter of stainless steel pipe (mm)
L: heating furnace soaking length (cm)
T: Oxidation time of stainless steel pipe in soaking zone (min)
C: Water vapor concentration in the oxidizing gas (volume ppm)
酸化性混合ガスの流量（リットル／分）≧８．２６×Ｒ×（Ｌ／Ｔ）／Ｃ
ここで、Ｒ：ステンレス鋼管の内径（ｍｍ）
Ｌ：加熱炉均熱帯長さ（ｃｍ）
Ｔ：ステンレス鋼管の均熱帯での酸化処理時間（分）
Ｃ：酸化性ガス中の水蒸気濃度（体積ｐｐｍ） In a stainless steel tube containing hydrogen: 10 to 99.9999 vol%, water vapor: 0.5 to 30 volppm, the balance of an oxidizing mixed gas consisting of an inert gas containing 1 to 6% by weight of Al In the oxidation method of the inner surface of the stainless steel tube, the stainless steel tube is inserted into the heating furnace while flowing, heated to 800 to 1200 ° C. while moving in the longitudinal direction, and an Al oxide film is formed on the inner surface of the stainless steel tube. In order to prevent oxidation of the outer surface of the stainless steel pipe in the vicinity of the entrance of the heating furnace, in the heating furnace and in the vicinity of the heating furnace outlet, a heating furnace having a muffle longer than the heating furnace is used, and the oxygen concentration in the muffle is 3 volume ppm. adjust the pass line atmosphere around stainless steel tube as an atmosphere consisting of inert gas or less and a water vapor concentration of 30 ppm by volume or less, and stainless Oxidation method stainless steel tube inner surface, wherein the flow rate of the oxidizing gas mixture flowing into the steel pipe is an amount that satisfies the following equation.
Flow rate of oxidizing gas mixture (liter / min) ≧ 8.26 × R × (L / T) / C
Where R: inner diameter of stainless steel pipe (mm)
L: heating furnace soaking length (cm)
T: Oxidation time of stainless steel pipe in soaking zone (min)
C: Water vapor concentration in the oxidizing gas (volume ppm)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31276898A JP3864585B2 (en) | 1998-11-04 | 1998-11-04 | Method of oxidizing the inner surface of stainless steel pipe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31276898A JP3864585B2 (en) | 1998-11-04 | 1998-11-04 | Method of oxidizing the inner surface of stainless steel pipe |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000144369A JP2000144369A (en) | 2000-05-26 |
| JP3864585B2 true JP3864585B2 (en) | 2007-01-10 |
Family
ID=18033194
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP31276898A Expired - Fee Related JP3864585B2 (en) | 1998-11-04 | 1998-11-04 | Method of oxidizing the inner surface of stainless steel pipe |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3864585B2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| JP5401964B2 (en) * | 2008-12-15 | 2014-01-29 | 新日鐵住金株式会社 | Metal tube manufacturing method |
| JP5827499B2 (en) * | 2010-06-11 | 2015-12-02 | 株式会社半導体エネルギー研究所 | Surface treatment method for equipment |
| CN103484829B (en) * | 2013-09-29 | 2016-04-20 | 西安超码科技有限公司 | In a kind of pipe, the method for film is prepared in chemical vapour deposition |
| JP7486925B2 (en) * | 2019-04-02 | 2024-05-20 | 日本製鉄株式会社 | Alloy Tube |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5531001Y2 (en) * | 1974-05-28 | 1980-07-24 | ||
| JP2768952B2 (en) * | 1988-08-04 | 1998-06-25 | 忠弘 大見 | Metal oxidation treatment apparatus and metal oxidation treatment method |
| JPH04350180A (en) * | 1991-05-27 | 1992-12-04 | Sumikin Stainless Kokan Kk | Production of pipe having extra-clean inner face and pipe for ultrapure gas |
| JP3379070B2 (en) * | 1992-10-05 | 2003-02-17 | 忠弘 大見 | Method of forming oxidation passivation film having chromium oxide layer on surface |
| JPH06257950A (en) * | 1993-03-02 | 1994-09-16 | Daido Steel Co Ltd | Continuous atmospheric furnace and its operation |
| JP3434857B2 (en) * | 1993-08-23 | 2003-08-11 | 日新製鋼株式会社 | Ultra-vacuum material and manufacturing method thereof |
| JP2783128B2 (en) * | 1993-08-24 | 1998-08-06 | 住友金属工業株式会社 | Stainless steel member for clean room and method of manufacturing the same |
| JPH07103867A (en) * | 1993-10-05 | 1995-04-21 | Mitsubishi Chem Corp | Method for supplying sample to moisture measuring equipment |
| JP3596234B2 (en) * | 1996-05-29 | 2004-12-02 | 住友金属工業株式会社 | Ozone-containing stainless steel for water and method for producing the same |
| JP3566069B2 (en) * | 1998-03-12 | 2004-09-15 | 住金ステンレス鋼管株式会社 | Method of forming a coating on the inner surface of stainless steel pipe |
-
1998
- 1998-11-04 JP JP31276898A patent/JP3864585B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2000144369A (en) | 2000-05-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0427853B1 (en) | Metal oxidation apparatus and method | |
| JP3433452B2 (en) | Internal oxidation treatment method for ferritic stainless steel pipe | |
| EP0612580B1 (en) | Corrosion resistant welding of stainless steel | |
| JP3960069B2 (en) | Heat treatment method for Ni-base alloy tube | |
| Ohmi et al. | Formation of chromium oxide on 316L austenitic stainless steel | |
| US5951787A (en) | Method of forming oxide-passivated film, ferrite system stainless steel, fluid feed system and fluid contact component | |
| KR20080109925A (en) | Method for producing cr-containing nickel-based alloy pipe and cr-containing nickel-based alloy pipe | |
| JP3864585B2 (en) | Method of oxidizing the inner surface of stainless steel pipe | |
| EP0386257A1 (en) | Metal oxidation apparatus | |
| JP3596234B2 (en) | Ozone-containing stainless steel for water and method for producing the same | |
| JP3566069B2 (en) | Method of forming a coating on the inner surface of stainless steel pipe | |
| JPH0639543A (en) | Method and process device for forming oxide passive state film in weld zone | |
| JP2783128B2 (en) | Stainless steel member for clean room and method of manufacturing the same | |
| JPH10280123A (en) | Stainless steel member for ozone-containing ultrapure water and its production | |
| JP2000176643A (en) | Method for forming oxidized passive state film in weld zone | |
| JPH0633264A (en) | Austenitic stainless steel for high purity gas excellent in corrosion resistance and its manufacture | |
| JP2925876B2 (en) | Metal surface oxidation treatment method | |
| JPH07268669A (en) | Surface treatment of stainless steel | |
| JP2001140044A (en) | Low dust generation and high corrosion resistant stainless steel pipe for piping | |
| JP3257492B2 (en) | Method for producing stainless steel with excellent resistance to ozone-containing water | |
| JP2007224371A (en) | METHOD FOR PRODUCING Cr-CONTAINING NICKEL-BASED ALLOY TUBE | |
| JP2932966B2 (en) | Ferritic stainless steel for high purity gas | |
| JP3119165B2 (en) | Manufacturing method of stainless steel for high purity gas | |
| JP2992977B2 (en) | High Cr stainless steel for high purity gas | |
| EP4282994A1 (en) | Method for producing annealed and pickled steel sheet |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20050620 |
|
| RD02 | Notification of acceptance of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7422 Effective date: 20050623 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20060131 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20060613 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20060811 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20060912 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20060925 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20091013 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20101013 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111013 Year of fee payment: 5 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121013 Year of fee payment: 6 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20131013 Year of fee payment: 7 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20131013 Year of fee payment: 7 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313111 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20131013 Year of fee payment: 7 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| LAPS | Cancellation because of no payment of annual fees |