JP4552268B2 - How to connect high strength martensitic stainless steel pipes for oil wells - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、原油あるいは天然ガスの油井、ガス井に使用される油井管用の鋼材に関し、とくに炭酸ガス（CO2 ）、塩素（Cl- ）等を含む極めて腐食環境の厳しい油井、ガス井で使用するに適した、優れた低温靱性、耐食性を有し、かつ溶接可能な高強度マルテンサイト系ステンレス油井用鋼管の接続方法に関するものである。
【０００２】
【従来の技術】
近年に至り、原油価格の高騰や近い将来に予想される石油資源の枯渇化を目前にして、従来は省みられなかったような深層油田や、開発が一旦は放棄されていた腐食性の強い油田等に対する開発が、世界的規模で盛んになっている。このような油田、ガス田は一般に深度が極めて深く、またその雰囲気は高温でかつ、CO2 、Cl- 等を含む厳しい腐食環境となっている。したがってこのような油田、ガス田の採掘に使用される油井鋼管としては高温条件においても高強度で、しかも耐食性を兼ね備えた材質が要求される。
【０００３】
一般に、CO2 、Cl- を含む環境下では耐CO2 腐食性、耐孔食性の優れた13％Crマルテンサイト系ステンレス鋼管が多く使用されている。
また、これらの油井管はネジにて接続されている。最近の油田は掘削環境が厳しくなっているため、ネジに対する要求が厳しくなり、種々のPremium Joint が開発されている。しかしながら、ネジに対する要求は年々厳しくなり、Premium Joint によっても必要な特性が得られないような掘削条件も出てきている。鋼管の接続方法としては溶接が一般的であり、ラインパイプでは一般的に行われているが、油井用鋼管は強度が高いために溶接性が劣ることから、通常、溶接では接続されない。
【０００４】
最近、油井管を拡散接合にて接続しようという試みがあるが、溶接部が硬化するために、溶接部の機械的性質、耐腐食われ性が著しく劣化するという問題点があった。
【０００５】
【発明が解決しようとする課題】
この発明は以上の事情を背景としてなされたもので、前述のようにCO2 、Cl- 等を含む苛酷な腐食環境下において優れた耐食性に加え、機械的性質にも優れる高強度油井鋼管を溶接により接続できる方法を提供することを目的とするものである。
【０００６】
【課題を解決するための手段】
本発明者らは前記目的を達成するべく、代表的なマルテンサイト系ステンレス鋼である13％Cr鋼をベースとして、高強度化と溶接部の特性の両立を検討した結果、Ｃ、Ｎを従来より著しく低減し、必要に応じて合金元素を添加した13％Cr鋼において、溶接部の硬さを規制することによって、機械的性質、耐腐食われ性を確保できることを見出し、本発明をなすに至った。
【０００７】
すなわち、本発明は、質量％で、
Ｃ：0.03％以下、 Si：0.70％以下、
Mn：0.30〜2.00％、 Ｐ：0.03％以下、
Ｓ：0.005 ％以下、 Cr：10.5〜15.0％、
Ni：7.0 ％以下、 Al：0.05％以下、
Ｎ：0.2 ％以下、 Ｏ：0.01％以下
を含有し、さらに必要に応じて
Nb：0.20％以下、 Ｖ：0.20％以下、
Mo：0.1 〜3.0 ％、 Cu：3.5 ％以下、
Ti：0.3 ％以下、 Zr：0.2 ％以下、
Ｗ：3.0 ％以下、 Ｂ：0.0005〜0.01％、
Ca：0.0005〜0.01％
のうち１種または２種以上を含有し、残部がFeおよび不可避的不純物からなる油井用高強度マルテンサイト系ステンレス鋼管を接続する方法であって、溶接継手部の最高硬さがＨV 380 以下でかつ溶接金属の平均硬さと溶接熱影響部の最高硬さの差がＨV 100 以下となるように溶接接続することにより溶接部において-20℃でのシャルピー吸収エネルギーが100Ｊ以上になる靭性及び下記ＳＳＣ試験でわれの発生がない耐硫化物応力腐食割れ性を確保することを特徴とする油井用高強度マルテンサイト系ステンレス鋼管の接続方法である。
記
ＳＳＣ試験：継手溶接部から採取した板厚５mm、幅15mm、長さ115 mmの４点曲げ試験片を用い、100 ％ＳＭＹＳの応力を付加し、試験液に720 時間浸漬後、われの有無をチェックする試験であり、試験液は、５％NaCl水溶液に酢酸と酢酸ナトリウムを添加してｐＨを4.5 に調整し、５％硫化水素＋95％二酸化炭素の混合ガスを流したものを用いる。
【０００８】
【発明の実施の形態】
まず、本発明に係る鋼の組成（化学組成）の限定理由について説明する。
Ｃ：0.03％以下
Ｃは、マルテンサイト系ステンレス鋼の強度に関係する重要な元素であるが、溶接熱影響部の硬さを上げ、溶接われを引き起こす危険性がある。そこで溶接われを引き起こさないため、0.03％以下とした。また、Ｃは、耐食性からみても少ないほうが良く、好ましくは0.02％以下の範囲である。なお、本発明では、後述するようにＣの低減による強度低下をNi、あるいはさらにNb、Ｖの添加によって補うこととした。
【０００９】
Si：0.70％以下
Siは、通常の製鋼過程において脱酸剤として必要な元素であるが、0.70％を超えると耐CO2 腐食性を低下させ、さらに熱間加工性も低下させることから、0.70％以下とした。
Mn：0.30〜2.00％
Mnは、油井管用マルテンサイト系ステンレス鋼としての強度を確保するために0.30％以上必要であるが、2.00％を超えると靱性に悪影響を及ぼすことから、0.30〜2.00％とした。
【００１０】
Ｐ：0.03％以下
Ｐは、耐CO2 腐食性、耐CO2 応力腐食われ性、耐孔食性および耐硫化物応力腐食われ性をともに劣化させる元素であり、その含有量は可及的に少ないことが望ましいが、極端な低減は製造コストの上昇を招く。そこで、工業的に比較的安価に実施可能でかつ耐CO2 耐食性、耐CO2 応力腐食われ性、耐孔食性および耐硫化物応力腐食われ性を劣化させない範囲として、Ｐは0.03％以下とした。
【００１１】
Ｓ：0.005 ％以下
Ｓは、パイプ製造過程においてその熱間加工性を著しく劣化させる元素であり、可及的に少ないことが望ましいが、0.005 ％以下に制限すれば通常の工程でのパイプ製造が可能となることから、0.005 ％以下とした。なお、好ましくは、0.003 ％以下である。
【００１２】
Cr：10.5〜15.0％
Crは、耐CO2 腐食性、耐CO2 応力腐食割れ性を保持するために主要な元素であり、耐食性の観点からは10.5％以上必要であるが、15.0％を超えると熱間加工性が劣化することから、10.5〜15.0％とした。なお、好ましくは10.5〜13.5％である。
【００１３】
Ni：7.0 ％以下
Niは、保護皮膜を強固にして、耐CO2 腐食性、耐CO2 応力腐食われ性、耐孔食性を高めるとともに、Ｃを低減した13％Cr鋼の強度を上昇させるために添加されるが、7.0 ％を超えるとマルテンサイト組織の安定性を損なうことから、7.0 ％以下とした。なお、好ましくは1.0 〜6.5 ％である。
【００１４】
Al：0.05％以下
Alは、強力な脱酸作用を有するが、0.05％を超えると靱性に悪影響を及ぼすことから、0.05％以下とした。
Ｎ：0.2 ％以下
Ｎは、耐孔食性を著しく向上させる元素であるが、0.2 ％を超えるとその効果が飽和してしまい、かつ溶接性を低下させるので、0.2 ％以下とした。なお、好ましくは0.08％以下である。
【００１５】
Ｏ：0.01％以下
Ｏは、本発明鋼の性能を十分に発揮させるために可及的に低減すべき元素である。すなわち、Ｏ含有量が多いと各種の酸化物を形成して熱間加工性、耐CO2 腐食性、耐CO2 応力腐食割れ性、耐孔食性および靱性を著しく低下させる。ただし0.01％以下は許容しうるので、Ｏは0.01％以下とした。なお、好ましくは0.006 ％以下である。
【００１６】
Nb：0.02％以下、Ｖ：0.20％以下
Nb、Ｖは、いずれも靱性を劣化させずに常温、および高温における強度を上昇させる効果があるが、0.20％超えて添加すると靱性を劣化させるため、夫々0.20％以下とした。
Mo：0.1 〜3.0 ％
Moは、Cl- による孔食に対して抵抗性を与える元素であるが、0.1 ％未満ではその効果は認められず、一方、3.0 ％を超えるとδフェライトの発生を招き、耐CO2 腐食性、耐CO2 応力腐食割れ性および熱間加工性が低下することから、0.1 〜3.0 ％とした。なお、好ましくは0.8 〜2.5 ％である。
【００１７】
Cu：3.5 ％以下
Cuは、保護皮膜を強固にして鋼中への水素の侵入を抑制し、耐硫化物応力腐食われ性を高める元素であるが、3.5 ％を超えると高温でCuS が粒界析出し、熱間加工性が低下することから、3.5 ％以下とした。なお、好ましくは0.2 〜2.5 ％である。
【００１８】
Ti：3.0 ％以下、Zr：0.2 ％以下、Ｗ：3.0 ％以下、Ｂ：0.0005〜0.01％以下 Ti、Zr、Ｗ、Ｂは、いずれも強度を上昇させる効果、および耐応力腐食割れ性を改善する効果があるが、Tiは0.3 ％を超えて、Zrは0.2 ％を超えて、Ｗは3.0 ％を超えて添加すると靱性を劣化させるため、また、Ｂは0.0005％未満では効果がなく、0.01％を超えた添加は靱性を劣化させるため、Ti：0.3 ％以下、Zr：0.2 ％以下、Ｗ：3.0 ％以下、Ｂ：0.0005〜0.01％とした。
【００１９】
Ca：0.0005〜0.01％
Caは、ＳをCaS として固定しＳ系介在物を球状化することにより、介在物の周囲のマトリックスの格子歪を小さくして、水素のトラップ能を下げる作用がある。その効果は0.0005％未満では顕著ではなく、一方、0.01％を超えるとCaO の増加を招き、耐CO2 腐食性、耐孔食性が低下することから、Caは、0.0005〜0.01％、好ましくは0.001 〜0.005 ％とした。
【００２０】
上記組成を有するマルテンサイト系ステンレス鋼管は、これを溶接継手部の最高硬さがＨV 380 以下、溶接金属と溶接熱影響部の硬さの差がＨV 100 以下になる溶接にて接続することにより、上記溶接部の靱性、上記耐硫化物応力腐食割れ性を確保することができる。かかる溶接継手硬さ条件を満足するためには、母材組成に応じて溶接材料の選択および／または溶接入熱の制御を適切に行うことが重要であるが、これら以外に、溶接後熱処理を加えることによって、硬さを調節してもよい。
【００２１】
本発明の接続方法に供する油井用鋼管を製造するにあたっては、通常の製造工程に何ら手を加えることを要しない。すなわち、鋼素材を継目無鋼管あるいは電縫鋼管に成形後、成形のまま、または900 〜1100℃の温度範囲に加熱して水冷または空冷により冷却し、その後、油井用鋼管として必要な強度を得るべく500 〜650 ℃の温度範囲で焼戻すという常法で製造できる。
【００２２】
また、溶接による接続方法としては、アーク溶接が好ましいが、これのみならず、拡散接合、抵抗溶接、レーザ溶接等、他の溶接方法を用いることも可能である。
【００２３】
【実施例】
表１に示す組成になる鋼を溶製して直径600 mmのビレットを鋳造し、これを小型圧延ミルにて板厚10mm、外径62mmの継目無鋼管となし、引き続き、焼入れ、焼戻しの熱処理を施し、降伏強度を95grade のレベルに調整した。
これらの継目無鋼管をＴＩＧ溶接法にて表１に示す条件で溶接接続し、継手を作製した。溶接材料としては、表２に組成を示す25％Cr系溶接材料（Ｎo.１）および２種類の共金系溶接材料（Ｎo.２，３）を用いた。
【００２４】
前記継手に対してシャルピー試験および硫化物応力腐食われ性試験（ＳＳＣ試験）を行った。
シャルピー試験は、溶接金属（ＷＭ）と溶接熱影響部（ＨＡＺ）とから採取したフルサイズ試験片を用いて−20℃で行った。
ＳＳＣ試験は、継手溶接部から採取した板厚５mm、幅15mm、長さ115 mmの４点曲げ試験片を用い、100 ％ＳＭＹＳ（Specified yield Strength,95ksi＝655MPa) の応力を付加し、試験液に720 時間浸漬後、われの有無をチェックした。試験液は、５％NaCl水溶液に酢酸と酢酸ナトリウムを添加してｐＨを4.5 に調整し、５％硫化水素＋95％二酸化炭素の混合ガスを流したものを用いた。
【００２５】
これらの試験結果を表１に併せて示す。ＳＳＣ試験結果についてはわれの発生したものを×、発生しなかったものを○で示した。
【００２６】
【表１】
【表２】
表１より、本発明の組成要件を満たす鋼管を本発明の溶接継手硬さ条件を満たすように溶接接続して作製した継手は、ＷＭおよびＨＡＺの−20℃での吸収エネルギーが100J以上という優れた靱性を示し、さらに、ＳＳＣ試験においてわれの発生は認められず、優れた耐硫化物応力腐食われ性を示した。
【００２９】
【発明の効果】
本発明によれば、13％Cr鋼においてＣ含有量を従来よりも著しく低減し、Si、Mn、Ｐ、Ｓ、Cr、Ni、Al、Ｎ、Ｏの各含有量を所定の範囲に規制するとともに溶接継手部の硬さを規制することにより、優れた低温靱性とH2S 、Cl- を含む厳しい腐食環境下でも十分な耐応力腐食われ性を示す油井用高強度マルテンサイト系ステンレス鋼管の溶接接続が可能となるという優れた効果を奏する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to oil well pipe steel used for oil or gas wells for crude oil or natural gas, and particularly used in oil wells and gas wells that have extremely corrosive environments including carbon dioxide (CO 2 ), chlorine (Cl − ), etc. The present invention relates to a method for connecting a high-strength martensitic stainless steel well steel pipe that has excellent low-temperature toughness and corrosion resistance and is weldable.
[0002]
[Prior art]
In recent years, deep oil fields that have not been excluded in the past and the highly corrosive properties that were once abandoned in the near future due to soaring crude oil prices and the depletion of oil resources expected in the near future Developments in oil fields etc. are flourishing on a global scale. Such oil, gas fields are generally the depth is very deep, and its atmosphere and a high temperature, CO 2, Cl - has a severe corrosive environment and the like. Therefore, oil well steel pipes used for mining such oil and gas fields are required to be made of a material having high strength and high corrosion resistance even under high temperature conditions.
[0003]
In general, 13% Cr martensitic stainless steel pipes having excellent resistance to CO 2 corrosion and pitting corrosion are often used in an environment containing CO 2 and Cl − .
These oil well pipes are connected by screws. Since the recent oil field has a severe drilling environment, the demand for screws has become strict, and various premium joints have been developed. However, the demand for screws has become stricter year by year, and excavation conditions have emerged where the necessary characteristics cannot be obtained even with Premium Joint. As a method for connecting steel pipes, welding is generally used, and is generally performed for line pipes. However, oil well steel pipes are not generally connected by welding because of their high strength and poor weldability.
[0004]
Recently, attempts have been made to connect oil well pipes by diffusion bonding. However, since the welded portion is hardened, there has been a problem that the mechanical properties and corrosion resistance of the welded portion are significantly deteriorated.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the background art described above, CO 2, Cl as described above - in addition to the excellent corrosion resistance in such harsh corrosive environments including, welding high strength oil country tubular goods having excellent mechanical properties It is an object of the present invention to provide a method that allows connection.
[0006]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present inventors have studied 13% Cr steel, which is a typical martensitic stainless steel, as a base, and as a result of studying both high strength and welded properties, C and N are conventionally used. In 13% Cr steel, which is significantly reduced and added with alloying elements as necessary, it has been found that the mechanical properties and corrosion resistance can be secured by regulating the hardness of the welded portion, and the present invention is made. It came.
[0007]
That is, the present invention is mass%,
C: 0.03% or less, Si: 0.70% or less,
Mn: 0.30 to 2.00%, P: 0.03% or less,
S: 0.005% or less, Cr: 10.5 to 15.0%,
Ni: 7.0% or less, Al: 0.05% or less,
Contains N: 0.2% or less, O: 0.01% or less, and if necessary
Nb: 0.20% or less, V: 0.20% or less,
Mo: 0.1-3.0%, Cu: 3.5% or less,
Ti: 0.3% or less, Zr: 0.2% or less,
W: 3.0% or less, B: 0.0005 to 0.01%,
Ca: 0.0005 to 0.01%
Contain one or two or more of the balance to a method of connecting the oil well high strength martensitic stainless steel consisting of Fe and unavoidable impurities, maximum hardness of the weld joint portion H V 380 or less toughness and Charpy absorbed energy is equal to or greater than 100J of in and at -20 ° C. at the welded portion by the difference between the maximum hardness of the average hardness and HAZ of the weld metal is welded connection so that H V 100 or less it is a method of connecting the oil wells for high strength martensitic stainless steel you, characterized in that to ensure the crack generation is no resistance to sulfide stress corrosion cracking by the following SSC test.
Record
SSC test: Using a 4-point bending test specimen with a thickness of 5mm, width of 15mm, and length of 115mm taken from the joint weld, applying 100% SMYS stress and immersing it in the test solution for 720 hours. In this test, a test solution is prepared by adding acetic acid and sodium acetate to a 5% NaCl aqueous solution to adjust the pH to 4.5 and flowing a mixed gas of 5% hydrogen sulfide + 95% carbon dioxide.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
First, the reason for limiting the composition (chemical composition) of the steel according to the present invention will be described.
C: 0.03% or less C is an important element related to the strength of martensitic stainless steel, but there is a risk of increasing the hardness of the heat affected zone and causing weld cracking. Therefore, in order not to cause welding, 0.03% or less was set. Further, C is preferably as small as possible in view of corrosion resistance, and is preferably in the range of 0.02% or less. In the present invention, as will be described later, the strength reduction due to the reduction of C is compensated for by adding Ni, or further Nb and V.
[0009]
Si: 0.70% or less
Si is an element necessary as a deoxidizing agent in a normal steelmaking process. However, if it exceeds 0.70%, the CO 2 corrosion resistance is lowered and further hot workability is lowered.
Mn: 0.30 to 2.00%
Mn is required to be 0.30% or more in order to ensure the strength as a martensitic stainless steel for oil well pipes. However, if it exceeds 2.00%, the toughness is adversely affected, so 0.30 to 2.00% was set.
[0010]
P: 0.03% or less P is an element that deteriorates both CO 2 corrosion resistance, CO 2 stress corrosion resistance, pitting corrosion resistance and sulfide stress corrosion resistance, and its content is as low as possible. Although desirable, extreme reduction leads to increased manufacturing costs. Therefore, P is set to 0.03% or less as a range that can be implemented industrially at a relatively low cost and does not deteriorate the CO 2 corrosion resistance, the CO 2 stress corrosion resistance, the pitting corrosion resistance, and the sulfide stress corrosion resistance. .
[0011]
S: 0.005% or less S is an element that significantly deteriorates the hot workability in the pipe manufacturing process, and is preferably as small as possible. However, if it is limited to 0.005% or less, pipe manufacturing in a normal process is possible. Because it becomes possible, it was made 0.005% or less. In addition, Preferably, it is 0.003% or less.
[0012]
Cr: 10.5 to 15.0%
Cr is resistant CO 2 corrosion is a major element in order to hold the anti-CO 2 stress corrosion cracking resistance, but from the viewpoint of corrosion resistance is required than 10.5%, the hot workability exceeds 15.0 percent Since it deteriorates, it was made into 10.5 to 15.0%. In addition, Preferably it is 10.5 to 13.5%.
[0013]
Ni: 7.0% or less
Ni is to strengthen the protective coating, resistant CO 2 corrosion resistance and CO 2 stress corrosion cracking resistance, to increase the pitting resistance, but is added as to increase the strength of 13% Cr steel with reduced C If the content exceeds 7.0%, the stability of the martensite structure is impaired. In addition, Preferably it is 1.0 to 6.5%.
[0014]
Al: 0.05% or less
Al has a strong deoxidizing action, but if it exceeds 0.05%, it adversely affects toughness, so 0.05% or less was set.
N: 0.2% or less N is an element that remarkably improves pitting corrosion resistance. However, if it exceeds 0.2%, the effect is saturated and weldability is lowered. In addition, Preferably it is 0.08% or less.
[0015]
O: 0.01% or less O is an element that should be reduced as much as possible in order to sufficiently exhibit the performance of the steel of the present invention. That is, when the O content is large, various oxides are formed, and hot workability, CO 2 corrosion resistance, CO 2 stress corrosion cracking resistance, pitting corrosion resistance and toughness are significantly reduced. However, since 0.01% or less is acceptable, O is set to 0.01% or less. In addition, Preferably it is 0.006% or less.
[0016]
Nb: 0.02% or less, V: 0.20% or less
Nb and V both have the effect of increasing the strength at normal temperature and high temperature without degrading the toughness, but if added over 0.20%, the toughness is degraded, so each was made 0.20% or less.
Mo: 0.1-3.0%
Mo is, Cl - but by an element providing a resistance to pitting, that effect is not observed in less than 0.1%, while more than 3.0%, the lead to the occurrence of δ ferrite, resistance CO 2 corrosion Further, since the resistance to CO 2 stress corrosion cracking and hot workability deteriorated, the content was set to 0.1 to 3.0%. In addition, Preferably it is 0.8 to 2.5%.
[0017]
Cu: 3.5% or less
Cu is an element that strengthens the protective film and suppresses the penetration of hydrogen into the steel and improves the resistance to sulfide stress corrosion. However, if it exceeds 3.5%, CuS precipitates at grain boundaries at high temperatures, Since workability deteriorates, the content is set to 3.5% or less. In addition, Preferably it is 0.2 to 2.5%.
[0018]
Ti: 3.0% or less, Zr: 0.2% or less, W: 3.0% or less, B: 0.0005 to 0.01% or less Ti, Zr, W, and B all improve strength and improve stress corrosion cracking resistance However, when Ti exceeds 0.3%, Zr exceeds 0.2%, and W exceeds 3.0%, the toughness deteriorates, and when B is less than 0.0005%, there is no effect. Since addition exceeding 1% deteriorates toughness, Ti: 0.3% or less, Zr: 0.2% or less, W: 3.0% or less, B: 0.0005 to 0.01%.
[0019]
Ca: 0.0005 to 0.01%
Ca fixes S as CaS and spheroidizes S-based inclusions, thereby reducing the lattice strain of the matrix around the inclusions and lowering the hydrogen trapping ability. The effect is not significant when the content is less than 0.0005%. On the other hand, if the content exceeds 0.01%, CaO increases, and the resistance to CO 2 corrosion and pitting corrosion decreases. Therefore, Ca is 0.0005 to 0.01%, preferably 0.001. It was set to -0.005%.
[0020]
Martensitic stainless steel pipe having the above composition, maximum hardness of the weld joint part which H V 380 or less, the difference in hardness of the weld heat affected zone and the weld metal is connected by welding to become H V 100 or less it makes it possible to ensure the toughness of the weld, the sulfide stress corrosion cracking resistance. In order to satisfy such weld joint hardness conditions, it is important to appropriately select the welding material and / or control the welding heat input in accordance with the base material composition. The hardness may be adjusted by adding.
[0021]
In manufacturing the oil well steel pipe to be used in the connection method of the present invention, it is not necessary to modify the normal manufacturing process. That is, after forming the steel material into a seamless steel pipe or ERW steel pipe, it is cooled as it is, or heated to a temperature range of 900 to 1100 ° C and cooled by water cooling or air cooling, and then the necessary strength as an oil well steel pipe is obtained. Therefore, it can be produced by a conventional method of tempering in a temperature range of 500 to 650 ° C.
[0022]
As a connection method by welding, arc welding is preferable, but not only this but other welding methods such as diffusion bonding, resistance welding, and laser welding can also be used.
[0023]
【Example】
Steel with the composition shown in Table 1 is melted and a billet with a diameter of 600 mm is cast into a seamless steel pipe with a thickness of 10 mm and an outer diameter of 62 mm in a small rolling mill, followed by heat treatment for quenching and tempering. The yield strength was adjusted to 95 grade.
These seamless steel pipes were welded and connected by the TIG welding method under the conditions shown in Table 1 to produce joints. As the welding material, 25% Cr-based welding material (No. 1) and two kinds of commingling-type welding materials (No. 2, 3) whose compositions are shown in Table 2 were used.
[0024]
A Charpy test and a sulfide stress corrosion resistance test (SSC test) were performed on the joint.
The Charpy test was performed at −20 ° C. using a full-size test piece collected from the weld metal (WM) and the weld heat affected zone (HAZ).
The SSC test uses a 4-point bend specimen with a plate thickness of 5mm, width of 15mm, and length of 115mm taken from the joint weld, applying a stress of 100% SMYS (Specified Yield Strength, 95ksi = 655MPa) After 720 hours of immersion, the presence or absence of cracks was checked. The test solution was prepared by adding acetic acid and sodium acetate to a 5% NaCl aqueous solution to adjust the pH to 4.5 and flowing a mixed gas of 5% hydrogen sulfide + 95% carbon dioxide.
[0025]
These test results are also shown in Table 1. As for the SSC test results, those in which cracks occurred were indicated by ×, and those in which cracks did not occur were indicated by ○.
[0026]
[Table 1]
[Table 2]
From Table 1, a joint produced by welding a steel pipe satisfying the composition requirements of the present invention so as to satisfy the hardness condition of the welded joint of the present invention has an excellent absorption energy of WM and HAZ at −20 ° C. of 100 J or more. Furthermore, no cracks were observed in the SSC test, and excellent resistance to sulfide stress corrosion resistance was exhibited.
[0029]
【The invention's effect】
According to the present invention, the C content in the 13% Cr steel is significantly reduced as compared with the prior art, and the contents of Si, Mn, P, S, Cr, Ni, Al, N, and O are regulated within a predetermined range. together by regulating the hardness of the welded joint portion, excellent low-temperature toughness and H 2 S, Cl - oil well for high strength martensitic stainless steel exhibits sufficient stress corrosion cracking resistance even under a severe corrosive environment containing There is an excellent effect that welding connection is possible.
Claims (2)
Ｃ：0.03％以下、 Si：0.70％以下、
Mn：0.30〜2.00％、 Ｐ：0.03％以下、
Ｓ：0.005 ％以下、 Cr：10.5〜15.0％、
Ni：7.0 ％以下、 Al：0.05％以下、
Ｎ：0.2 ％以下、 Ｏ：0.01％以下
を含有し、残部がFeおよび不可避的不純物からなる油井用高強度マルテンサイト系ステンレス鋼管を接続する方法であって、溶接継手部の最高硬さがＨV 380 以下でかつ溶接金属の平均硬さと溶接熱影響部の最高硬さの差がＨV 100 以下となるように溶接接続することにより溶接部において-20℃でのシャルピー吸収エネルギーが100Ｊ以上になる靭性及び下記ＳＳＣ試験でわれの発生がない耐硫化物応力腐食割れ性を確保することを特徴とする油井用高強度マルテンサイト系ステンレス鋼管の接続方法。
記
ＳＳＣ試験：継手溶接部から採取した板厚５mm、幅15mm、長さ115 mmの４点曲げ試験片を用い、100 ％ＳＭＹＳの応力を付加し、試験液に720 時間浸漬後、われの有無をチェックする試験であり、試験液は、５％NaCl水溶液に酢酸と酢酸ナトリウムを添加してｐＨを4.5 に調整し、５％硫化水素＋95％二酸化炭素の混合ガスを流したものを用いる。 % By mass
C: 0.03% or less, Si: 0.70% or less,
Mn: 0.30 to 2.00%, P: 0.03% or less,
S: 0.005% or less, Cr: 10.5 to 15.0%,
Ni: 7.0% or less, Al: 0.05% or less,
N: 0.2% or less, O: 0.01% or less, the balance is a method of connecting high strength martensitic stainless steel pipes for oil wells consisting of Fe and inevitable impurities, where the maximum hardness of the welded joint is H the Charpy absorbed energy at -20 ° C. at the welded portion or 100J by the difference between the maximum hardness of the average hardness and HAZ of the V 380 or less and the weld metal is welded connection so that H V 100 or less toughness and a method of connecting the oil wells for high strength martensitic stainless steel you, characterized in that to ensure the crack generation is no resistance to sulfide stress corrosion cracking by the following SSC test becomes.
Record
SSC test: Using a 4-point bending test specimen with a thickness of 5mm, width of 15mm, and length of 115mm taken from the joint weld, applying 100% SMYS stress and immersing it in the test solution for 720 hours. In this test, a test solution is prepared by adding acetic acid and sodium acetate to a 5% NaCl aqueous solution to adjust the pH to 4.5 and flowing a mixed gas of 5% hydrogen sulfide + 95% carbon dioxide.
Ｃ：0.03％以下、 Si：0.70％以下、
Mn：0.30〜2.00％、 Ｐ：0.03％以下、
Ｓ：0.005 ％以下、 Cr：10.5〜15.0％、
Ni：7.0 ％以下、 Al：0.05％以下、
Ｎ：0.2 ％以下、 Ｏ：0.01％以下
を含有し、さらに
Nb：0.20％以下、 Ｖ：0.20％以下、
Mo：0.1 〜3.0 ％、 Cu：3.5 ％以下、
Ti：0.3 ％以下、 Zr：0.2 ％以下、
Ｗ：3.0 ％以下、 Ｂ：0.0005〜0.01％、
Ca：0.0005〜0.01％
のうち１種または２種以上を含有し、残部がFeおよび不可避的不純物からなる油井用高強度マルテンサイト系ステンレス鋼管を接続する方法であって、溶接継手部の最高硬さがＨV 380 以下でかつ溶接金属の平均硬さと溶接熱影響部の最高硬さの差がＨV 100 以下となるように溶接接続することにより溶接部において-20℃でのシャルピー吸収エネルギーが100Ｊ以上になる靭性及び下記ＳＳＣ試験でわれの発生がない耐硫化物応力腐食割れ性を確保することを特徴とする油井用高強度マルテンサイト系ステンレス鋼管の接続方法。
記
ＳＳＣ試験：継手溶接部から採取した板厚５mm、幅15mm、長さ115 mmの４点曲げ試験片を用い、100 ％ＳＭＹＳの応力を付加し、試験液に720 時間浸漬後、われの有無をチェックする試験であり、試験液は、５％NaCl水溶液に酢酸と酢酸ナトリウムを添加してｐＨを4.5 に調整し、５％硫化水素＋95％二酸化炭素の混合ガスを流したものを用いる。 % By mass
C: 0.03% or less, Si: 0.70% or less,
Mn: 0.30 to 2.00%, P: 0.03% or less,
S: 0.005% or less, Cr: 10.5 to 15.0%,
Ni: 7.0% or less, Al: 0.05% or less,
N: 0.2% or less, O: 0.01% or less,
Nb: 0.20% or less, V: 0.20% or less,
Mo: 0.1-3.0%, Cu: 3.5% or less,
Ti: 0.3% or less, Zr: 0.2% or less,
W: 3.0% or less, B: 0.0005 to 0.01%,
Ca: 0.0005 to 0.01%
Contain one or two or more of the balance to a method of connecting the oil well high strength martensitic stainless steel consisting of Fe and unavoidable impurities, maximum hardness of the weld joint portion H V 380 or less toughness and Charpy absorption energy is equal to or greater than 100J of in and at -20 ° C. at the welded portion by the difference between the maximum hardness of the average hardness and HAZ of the weld metal is welded connection so that H V 100 or less connection of oil wells for the high strength martensitic stainless steel you, characterized in that to ensure the crack generation is no resistance to sulfide stress corrosion cracking by the following SSC test.
Record
SSC test: Using a 4-point bending test specimen with a thickness of 5mm, width of 15mm, and length of 115mm taken from the joint weld, applying 100% SMYS stress and immersing it in the test solution for 720 hours. In this test, a test solution is prepared by adding acetic acid and sodium acetate to a 5% NaCl aqueous solution to adjust the pH to 4.5 and flowing a mixed gas of 5% hydrogen sulfide + 95% carbon dioxide.
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| JP4774588B2 (en) * | 2000-10-26 | 2011-09-14 | Ｊｆｅスチール株式会社 | Manufacturing method of high strength oil well steel pipe joint with excellent corrosion resistance and high strength oil well steel pipe joint |
| JP4765283B2 (en) * | 2004-08-31 | 2011-09-07 | Ｊｆｅスチール株式会社 | Method for producing martensitic stainless steel pipe circumferential welded joint |
| JP5162820B2 (en) * | 2005-11-28 | 2013-03-13 | Ｊｆｅスチール株式会社 | Stainless steel pipe for oil well pipes with excellent pipe expandability |
| JP2007321181A (en) * | 2006-05-31 | 2007-12-13 | Jfe Steel Kk | Method for forming martenstic stainless steel material welded part |
| JP4797953B2 (en) * | 2006-11-30 | 2011-10-19 | Ｊｆｅスチール株式会社 | Welded joint with excellent fatigue strength |
| WO2010026672A1 (en) * | 2008-09-04 | 2010-03-11 | Ｊｆｅスチール株式会社 | Seamless pipe of martensitic stainless steel for oil well pipe and process for producing the same |
| JP5499575B2 (en) * | 2008-09-04 | 2014-05-21 | Ｊｆｅスチール株式会社 | Martensitic stainless steel seamless pipe for oil well pipe and method for producing the same |
| JP5401931B2 (en) * | 2008-11-07 | 2014-01-29 | Ｊｆｅスチール株式会社 | Member for high pressure carbon dioxide injection |
| JP5040973B2 (en) * | 2009-08-24 | 2012-10-03 | Ｊｆｅスチール株式会社 | Method for producing martensitic stainless steel pipe circumferential welded joint |
| JP5408031B2 (en) * | 2010-05-17 | 2014-02-05 | 新日鐵住金株式会社 | Circumferential welded joint of high-strength steel pipe with excellent low cycle fatigue resistance and its manufacturing method |
| CN106041265B (en) * | 2016-06-07 | 2018-10-02 | 西安向阳航天材料股份有限公司 | A kind of welding method of control petroleum pipeline low-alloy steel weld affected zone hardness |
| CN114160930B (en) * | 2021-12-27 | 2023-05-02 | 西安西材三川智能制造有限公司 | Argon arc welding process for molybdenum-lanthanum alloy pipeline |
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| JPH0641679A (en) * | 1992-07-27 | 1994-02-15 | Nippon Steel Corp | Electric-resistance-welded steel tube excellent in sulphide stress corrosion cracking resistance |
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| JPH03268877A (en) * | 1990-03-16 | 1991-11-29 | Sumitomo Metal Ind Ltd | Manufacture of sulfide stress cracking resistant welded steel pipe for oil well |
| JPH0857683A (en) * | 1994-08-16 | 1996-03-05 | Nippon Steel Corp | Method for welding high-cr steel |
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