JP6950851B1 - High-strength stainless steel seamless steel pipe for oil wells - Google Patents
High-strength stainless steel seamless steel pipe for oil wells Download PDFInfo
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Abstract
高強度で熱間加工性に優れるとともに、優れた耐炭酸ガス腐食性を備え、低温の環境における耐SSC性に優れた、油井用高強度ステンレス継目無鋼管を提供することを目的とする。特定の成分組成を含有し、かつ下記(1)式および下記(2)式を満足し、残部Feおよび不可避的不純物からなる組成を有し、長径が5μm以上で、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である介在物の数密度が0.5個/mm2以上3個/mm2以下である、降伏強さが655MPa以上である油井用高強度ステンレス継目無鋼管。(ここで、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0における、Ti、Al、Mg、Ca:介在物中の各元素の含有量(質量%)であり、含有しない元素はゼロとする。)記Cr+0.65Ni+0.6Mo+0.55Cu−20C ≧ 15.0 ‥‥(1)Cr+Mo+0.3Si−43.3C−0.4Mn−Ni−0.3Cu−9N ≦ 11.0 ‥‥(2)ここで、Cr、Ni、Mo、Cu、C、Si、Mn、N:各元素の含有量(質量%)であり、含有しない元素はゼロとする。It is an object of the present invention to provide a high-strength stainless seamless steel pipe for oil wells, which has high strength and excellent hot workability, excellent carbon dioxide gas corrosion resistance, and excellent SSC resistance in a low temperature environment. It contains a specific component composition, satisfies the following equations (1) and (2), has a composition consisting of the balance Fe and unavoidable impurities, has a major axis of 5 μm or more, and 0.5 <Ti / (Ti +). Al + Mg + Ca) <1.0 High-strength stainless seamless steel pipe for oil wells with a density of 0.5 inclusions / mm2 or more and 3 pieces / mm2 or less and a yield strength of 655 MPa or more. (Here, in 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0, Ti, Al, Mg, Ca: the content (mass%) of each element in the inclusions, and the elements not contained are zero. (1) Cr + 0.65Ni + 0.6Mo + 0.55Cu-20C ≥ 15.0 (1) Cr + Mo + 0.3Si-43.3C-0.4Mn-Ni-0.3Cu-9N ≤ 11.0 (2) Here, Cr, Ni , Mo, Cu, C, Si, Mn, N: The content (mass%) of each element, and the element not contained is zero.
Description
本発明は、原油あるいは天然ガスの油井、ガス井(以下、単に油井と称する。)等に好適に用いられるステンレス継目無鋼管に関する。特に、炭酸ガス(CO2)、塩素イオン(Cl−)を含み、150℃以上の高温の極めて厳しい腐食環境下での耐炭酸ガス腐食性と低温の環境における耐SSC性に優れたステンレス継目無鋼管に関する。The present invention relates to stainless seamless steel pipes that are suitably used for oil wells of crude oil or natural gas, gas wells (hereinafter, simply referred to as oil wells) and the like. In particular, stainless steel seamless, which contains carbon dioxide (CO 2 ) and chlorine ion (Cl − ) and has excellent carbon dioxide corrosion resistance in an extremely severe corrosion environment at a high temperature of 150 ° C or higher and SSC resistance in a low temperature environment. Regarding steel pipes.
近年、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という観点から、従来、省みられなかったような、高深度の油田や、硫化水素等を含む、いわゆるサワー環境下にある厳しい腐食環境の油田やガス田等の開発が盛んになっている。このような油田、ガス田は一般に深度が極めて深く、またその雰囲気も高温でかつCO2、Cl−、さらにH2Sを含む厳しい腐食環境となっている。このような環境下で使用される油井用鋼管には、所望の高強度でかつ優れた耐食性を兼ね備えた材質を有することが要求される。In recent years, from the viewpoint of soaring crude oil prices and the expected depletion of petroleum resources in the near future, it is in a so-called sour environment that includes deep oil fields and hydrogen sulfide, which have not been omitted in the past. The development of oil fields and gas fields in severely corroded environments is active. Such oil and gas fields are generally extremely deep, and their atmosphere is high, and they are in a severe corrosive environment containing CO 2 , Cl − , and H 2 S. Steel pipes for oil wells used in such an environment are required to have a material having desired high strength and excellent corrosion resistance.
従来、炭酸ガス(CO2)、塩素イオン(Cl−)等を含む環境の油田、ガス田では、採掘に使用する油井管として13Cr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。さらに、最近では13Crマルテンサイト系ステンレス鋼のCを低減し、Ni、Mo等を増加させた成分系の改良型13Crマルテンサイト系ステンレス鋼の使用も拡大している。Conventionally, 13Cr martensitic stainless steel pipes are often used as oil well pipes used for mining in oil and gas fields in environments containing carbon dioxide (CO 2 ), chloride ions (Cl −), and the like. Furthermore, recently, the use of improved 13Cr martensitic stainless steel, which has a reduced C content and increased Ni, Mo, etc., of 13Cr martensitic stainless steel, is expanding.
例えば、特許文献1には、質量%で、C:0.010〜0.030%、Mn:0.30〜0.60%、P:0.040%以下、S:0.0100%以下、Cr:10.00〜15.00%、Ni:2.50〜8.00%、Mo:1.00〜5.00%、Ti:0.050〜0.250%、V:0.25%以下、N:0.07%以下と、Si:0.50%以下、Al:0.10%以下のうちの1種以上とを含有し、残部はFe及び不純物からなり、式(1)として6.0≦Ti/C≦10.1を満たし、758〜862MPaの降伏強度を有するマルテンサイト系ステンレス鋼が開示されている。 For example, Patent Document 1 describes, in terms of mass%, C: 0.010 to 0.030%, Mn: 0.30 to 0.60%, P: 0.040% or less, S: 0.0100% or less. Cr: 10.00 to 15.00%, Ni: 2.50 to 8.00%, Mo: 1.00 to 5.00%, Ti: 0.050 to 0.250%, V: 0.25% Hereinafter, N: 0.07% or less, Si: 0.50% or less, Al: 0.10% or less, one or more of them are contained, and the balance is composed of Fe and impurities as the formula (1). Martensite-based stainless steels satisfying 6.0 ≦ Ti / C ≦ 10.1 and having a yield strength of 758 to 862 MPa are disclosed.
また、特許文献2には、重量%で、C:≦0.050、Si:≦0.5、Mn:≦1.5、P:≦0.03、S:≦0.005、Cr:11.0〜14.0、Ni:4.0〜7.0、Mo:1.0〜2.5、Cu:1.0〜2.5、Al:≦0.05、N:0.01〜0.10、を含み、残部がFeおよび不可避的不純物からなる組成を有するマルテンサイト系ステンレス鋼を熱間加工の後にMs点以下の温度まで冷却し、その後550℃以上Ac1以下の温度Tに、500〜T℃の平均加熱速度が1.0℃/sec以上となるように昇温したのちMs点以下の温度まで冷却する熱処理を施すマルテンサイト系ステンレス継目無鋼管の製造方法が開示されている。Further, in Patent Document 2, in% by weight, C: ≤0.050, Si: ≤0.5, Mn: ≤1.5, P: ≤0.03, S: ≤0.005, Cr: 11 .0 to 14.0, Ni: 4.0 to 7.0, Mo: 1.0 to 2.5, Cu: 1.0 to 2.5, Al: ≤0.05, N: 0.01 to A martensitic stainless steel containing 0.10, which has a composition of Fe and unavoidable impurities as a balance, is cooled to a temperature below the Ms point after hot working, and then cooled to a temperature T of 550 ° C or higher and Ac 1 or lower. Disclosed is a method for manufacturing a martensitic stainless seamless steel tube, which is subjected to a heat treatment of raising the temperature so that the average heating rate of 500 to T ° C. is 1.0 ° C./sec or more and then cooling it to a temperature of Ms point or less. There is.
また、特許文献3には、重量%で、C:0.06%以下、Cr:12〜16%、Si:1.0%以下、Mn:2.0%以下、Ni:0.5〜8.0%、Mo:0.1〜2.5%、Cu:0.3〜4.0%、N:0.05%以下を含み、δ−フェライト相の面積率が10%以下で、かつCuの微細な析出物が基地に分散している耐応力腐食割れ性に優れた高強度マルテンサイト系ステンレス鋼が開示されている。 Further, in Patent Document 3, in% by weight, C: 0.06% or less, Cr: 12-16%, Si: 1.0% or less, Mn: 2.0% or less, Ni: 0.5 to 8 It contains 0.0%, Mo: 0.1 to 2.5%, Cu: 0.3 to 4.0%, N: 0.05% or less, and the area ratio of the δ-ferrite phase is 10% or less. A high-strength martensitic stainless steel having excellent stress corrosion cracking resistance in which fine precipitates of Cu are dispersed in a matrix is disclosed.
最近の、厳しい腐食環境の油田やガス田等の開発に伴い、油井用鋼管には、高強度と、150℃以上の高温で、かつ、CO2、Cl−を含む厳しい腐食環境下においても、優れた耐炭酸ガス腐食性とを兼備することが求められてきた。加えて、開発環境の過酷化に伴い、深海のような低温の環境においても優れた耐SSC性を有することが求められてきた。With the recent development of oil fields and gas fields in severe corrosive environments, steel pipes for oil wells have high strength, high temperatures of 150 ° C or higher, and even in severe corrosive environments containing CO 2 and Cl −. It has been required to have excellent carbon dioxide gas corrosion resistance. In addition, with the harsh development environment, it has been required to have excellent SSC resistance even in a low temperature environment such as the deep sea.
しかしながら、特許文献1〜3に記載された技術では、高強度と優れた耐炭酸ガス腐食性は有するものの、低温の環境における耐SSC性が十分ではなかった。 However, although the techniques described in Patent Documents 1 to 3 have high strength and excellent carbon dioxide corrosion resistance, the SSC resistance in a low temperature environment is not sufficient.
そこで、本発明は、かかる従来技術の問題を解決し、高強度で熱間加工性に優れるとともに、優れた耐炭酸ガス腐食性を備え、低温の環境における耐SSC性に優れた、油井用高強度ステンレス継目無鋼管を提供することを目的とする。 Therefore, the present invention solves the problems of the prior art, has high strength and excellent hot workability, has excellent carbon dioxide corrosion resistance, and has excellent SSC resistance in a low temperature environment. It is an object of the present invention to provide a strong stainless seamless steel pipe.
なお、ここでいう「高強度」とは、降伏強さYS:95ksi(655MPa)以上を有する場合をいうものとする。 The term "high strength" as used herein means a case where the yield strength is YS: 95 ksi (655 MPa) or more.
また、耐炭酸ガス腐食性に優れていることとは、オートクレーブ中に保持された試験液:20質量%NaCl水溶液(液温:150℃、10気圧のCO2ガス雰囲気)中に、試験片を浸漬し、浸漬期間を14日間として実施した場合の腐食速度が0.125mm/y以下の場合をいうものとする。In addition, excellent carbon dioxide corrosion resistance means that the test piece is placed in a test solution held in an autoclave: a 20 mass% NaCl aqueous solution (liquid temperature: 150 ° C., CO 2 gas atmosphere at 10 atm). It means the case where the corrosion rate is 0.125 mm / y or less when the immersion is carried out with the immersion period set to 14 days.
また、「低温の環境における耐SSC性が優れる」とは、試験液:25質量%NaCl水溶液(液温:4℃、H2S:0.1 bar、CO2:0.9 bar)に、酢酸Na+塩酸を加えてpH:4.5に調整した水溶液中に、試験片を浸漬させ、浸漬時間を720時間として、降伏応力の90%を負荷応力として付加して試験を行い、試験後の試験片に割れが発生しない場合をいうものとする。In addition, "excellent SSC resistance in a low temperature environment" means that sodium acetate + hydrochloric acid is added to a test solution: 25 mass% NaCl aqueous solution (liquid temperature: 4 ° C, H 2 S: 0.1 bar, CO 2: 0.9 bar). In addition, the test piece was immersed in an aqueous solution adjusted to pH: 4.5, the immersion time was set to 720 hours, and 90% of the yield stress was added as the load stress to perform the test, and the test piece after the test cracked. It shall mean the case of not doing so.
本発明者らは、上記した目的を達成するために、各種組成のステンレス鋼管について、低温の耐SSC性への影響について鋭意検討した。その結果、ステンレス鋼のSSCはいずれも孔食を起点としていることがわかった。つぎに孔食の発生について検討したところ、低温の環境においては、種々の介在物のうち、Al、Ca、Mg等を主成分とする酸化物または硫化物が最も孔食の起点となりやすくことが分かった。したがって、低温の環境における耐SSC性を向上させるためには、Al、Ca、Mg等を主成分とする酸化物系または硫化物系の介在物をできるだけ低減することが重要である。しかしながら、酸化物系の介在物や硫化物系の介在物は、鋼中に不純物として含有される酸素や硫黄により生成されることから、工業的にゼロにすることは不可能である。そこで、酸化物系の介在物や硫化物系の介在物の構造を変化させることで無害化する発想に至った。具体的には、上述した孔食となりやすい介在物をTiNによって被覆することにより、孔食の起点となりにくくし、低温の環境における耐SSC性を向上できることを見出した。この理由は、介在物をTiNで覆うことにより、介在物が溶解した際、溶液中にNイオンが放出され、これがNH3+に変化することで介在物周辺のpHを局所的に上昇させ、孔食の発生・成長が阻害されるためと考えられる。In order to achieve the above-mentioned object, the present inventors have diligently studied the influence on the low temperature SSC resistance of stainless steel pipes having various compositions. As a result, it was found that all stainless steel SSCs originated from pitting corrosion. Next, when the occurrence of pitting corrosion was examined, it was found that oxides or sulfides containing Al, Ca, Mg, etc. as the main components are most likely to be the starting point of pitting corrosion among various inclusions in a low temperature environment. Do you get it. Therefore, in order to improve the SSC resistance in a low temperature environment, it is important to reduce oxide-based or sulfide-based inclusions containing Al, Ca, Mg, etc. as main components as much as possible. However, oxide-based inclusions and sulfide-based inclusions are produced by oxygen and sulfur contained as impurities in steel, and therefore cannot be industrially reduced to zero. Therefore, we came up with the idea of detoxifying by changing the structure of oxide-based inclusions and sulfide-based inclusions. Specifically, it has been found that by coating the above-mentioned inclusions that are prone to pitting corrosion with TiN, it is difficult to become the starting point of pitting corrosion and the SSC resistance in a low temperature environment can be improved. The reason for this is that by covering the inclusions with TiN, when the inclusions dissolve, N ions are released into the solution, which changes to NH 3+ , which locally raises the pH around the inclusions. This is thought to be due to the inhibition of pitting corrosion.
本発明者らは、低温の耐SSC性への組織の影響についても検討した。その結果、低温の環境においては、旧オーステナイト粒径を小さくした方が、孔食の成長や割れの発生が抑制され、耐SSC性が向上することが分かった。これは、旧オーステナイト粒界に偏析するPやSが、(1)孔食成長時の旧オーステナイト粒界の選択溶解を助長すること、(2)水素が鋼中に侵入した際の、粒界の脆化を助長したためであると考えられる。旧オーステナイト粒径が小さい方が、単位体積当たりの粒界面積は広くなるため、旧オーステナイト粒界に偏析するPやSの濃度が低下し、耐SSC性が向上すると考えられる。なお、低温の環境において耐SSC性に及ぼす旧オーステナイト粒界の影響が顕著である理由は、鋼中への水素の侵入を助長する硫化水素の試験液中への溶解度が増加すること、温度の低下により、水素のガス化が抑制されることが原因であると考えられる。 We also investigated the effect of tissue on cold SSC resistance. As a result, it was found that in a low temperature environment, reducing the particle size of the old austenite suppresses the growth of pitting corrosion and the occurrence of cracks, and improves the SSC resistance. This is because P and S segregated at the old austenite grain boundaries (1) promote the selective dissolution of the old austenite grain boundaries during pitting corrosion growth, and (2) the grain boundaries when hydrogen invades the steel. It is considered that this is because it promoted the embrittlement of. It is considered that the smaller the grain size of the old austenite, the wider the grain boundary area per unit volume, so that the concentration of P and S segregated at the grain boundary of the old austenite decreases, and the SSC resistance is improved. The reason why the influence of the old austenite grain boundaries on the SSC resistance in a low temperature environment is remarkable is that the solubility of hydrogen sulfide in the test solution, which promotes the invasion of hydrogen into steel, increases, and the temperature It is considered that the cause is that the gasification of hydrogen is suppressed due to the decrease.
本発明は、かかる知見に基づき、さらに検討を加えて完成されたものである。すなわち、本発明の要旨はつぎのとおりである。
[1]質量%で、
C:0.002〜0.05%、 Si:0.05〜0.50%、
Mn:0.04〜1.80%、 P :0.030%以下、
S:0.002%以下、 Cr:11.0〜14.0%、
Ni:3.0〜6.5%、 Mo:0.5〜3.0%、
Al:0.005〜0.10%、 V :0.005〜0.20%、
Ti:0.01〜0.20%、 Co:0.01〜1.0%、
N:0.002〜0.15%、 O :0.010%以下
を含有し、かつ下記(1)式および下記(2)式を満足し、残部Feおよび不可避的不純物からなる組成を有し、
長径が5μm以上で、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である介在物の数密度が0.5個/mm2以上3個/mm2以下である、降伏強さが655MPa以上である油井用高強度ステンレス継目無鋼管。
(ここで、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0における、Ti、Al、Mg、Ca:介在物中の各元素の含有量(質量%)であり、含有しない元素はゼロとする。)
記
Cr+0.65Ni+0.6Mo+0.55Cu−20C ≧ 15.0 ‥‥(1)
Cr+Mo+0.3Si−43.3C−0.4Mn−Ni−0.3Cu−9N ≦ 11.0 ‥‥(2)
ここで、Cr、Ni、Mo、Cu、C、Si、Mn、N:各元素の含有量(質量%)であり、含有しない元素はゼロとする。
[2]前記組成に加えてさらに、質量%で、Cu:0.05〜3.0%、W:0.05〜3.0%のうちから選ばれた1種または2種を含有する[1]に記載の油井用高強度ステンレス継目無鋼管。
[3]前記組成に加えてさらに、質量%で、Nb:0.01〜0.20%、Zr:0.01〜0.20%、B:0.0005〜0.01%、REM:0.0005〜0.01%、Ca:0.0005〜0.0025%、Sn:0.02〜0.20%、Ta:0.01〜0.1%、Mg:0.002〜0.01%のうちから選ばれた1種または2種以上を含有する[1]または[2]に記載の油井用高強度ステンレス継目無鋼管。
[4]平均旧オーステナイト粒径が40μm以下である [1]〜[3]のいずれかに記載の油井用高強度ステンレス継目無鋼管。The present invention has been completed with further studies based on such findings. That is, the gist of the present invention is as follows.
[1] By mass%,
C: 0.002-0.05%, Si: 0.05-0.50%,
Mn: 0.04 to 1.80%, P: 0.030% or less,
S: 0.002% or less, Cr: 11.0 to 14.0%,
Ni: 3.0-6.5%, Mo: 0.5-3.0%,
Al: 0.005 to 0.10%, V: 0.005 to 0.20%,
Ti: 0.01-0.20%, Co: 0.01-1.0%,
It contains N: 0.002 to 0.15%, O: 0.010% or less, satisfies the following formulas (1) and (2), and has a composition consisting of the balance Fe and unavoidable impurities.
The major axis is 5 μm or more, 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0, the number density of inclusions is 0.5 / mm 2 or more and 3 / mm 2 or less, and the yield strength is 655 MPa or more. High-strength stainless seamless steel pipe for oil wells.
(Here, in 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0, Ti, Al, Mg, Ca: the content (mass%) of each element in the inclusions, and the elements not contained are zero. )
Record
Cr + 0.65Ni + 0.6Mo + 0.55Cu-20C ≧ 15.0 ‥‥ (1)
Cr + Mo + 0.3Si-43.3C-0.4Mn-Ni-0.3Cu-9N ≤ 11.0 ... (2)
Here, Cr, Ni, Mo, Cu, C, Si, Mn, N: the content (mass%) of each element, and the element not contained is zero.
[2] The height for oil wells according to [1], which further contains one or two selected from Cu: 0.05 to 3.0% and W: 0.05 to 3.0% in mass% in addition to the above composition. Strong stainless seamless steel pipe.
[3] In addition to the above composition, in mass%, Nb: 0.01 to 0.20%, Zr: 0.01 to 0.20%, B: 0.0005 to 0.01%, REM: 0.0005 to 0.01%, Ca: 0.0005 to 0.0025%, Sn. The high-strength stainless steel seam for oil wells according to [1] or [2], which contains one or more selected from 0.02 to 0.20%, Ta: 0.01 to 0.1%, and Mg: 0.002 to 0.01%. Steelless pipe.
[4] The high-strength stainless seamless steel pipe for oil wells according to any one of [1] to [3], wherein the average old austenite particle size is 40 μm or less.
本発明によれば、熱間加工性に優れるとともに、優れた耐炭酸ガス腐食性を有し、低温環境での耐SSC性に優れ、かつ降伏強さYS:655MPa以上の高強度を有する油井用高強度ステンレス継目無鋼管が得られる。 According to the present invention, for oil wells having excellent hot workability, excellent carbon dioxide corrosion resistance, excellent SSC resistance in a low temperature environment, and high yield strength of YS: 655 MPa or more. A high-strength stainless seamless steel pipe can be obtained.
まず、本発明の油井用高強度継目無鋼管の組成限定理由について説明する。以下、とくに断わらない限り、質量%は単に%と記す。 First, the reason for limiting the composition of the high-strength seamless steel pipe for oil wells of the present invention will be described. Hereinafter, unless otherwise specified, mass% is simply referred to as%.
C:0.002〜0.05%
Cは、マルテンサイト系ステンレス鋼の強度を増加させる重要な元素である。本発明では、所望の強度を確保するために0.002%以上のCを含有することが必要である。一方、0.05%を超えてCを含有すると、強度がかえって低下する。また、低温の環境における耐SSC性も悪化する。このため、本発明では、C含有量は0.002〜0.05%とする。なお、耐炭酸ガス腐食性の観点から、C含有量は0.03%以下とすることが好ましい。より好ましくは、0.002%以上であり、より好ましくは0.015%以下である。さらに好ましくは、0.002%以上であり、さらに好ましくは0.010%以下である。C: 0.002-0.05%
C is an important element that increases the strength of martensitic stainless steel. In the present invention, it is necessary to contain 0.002% or more of C in order to secure the desired strength. On the other hand, if C is contained in excess of 0.05%, the strength is rather lowered. In addition, SSC resistance in a low temperature environment also deteriorates. Therefore, in the present invention, the C content is 0.002 to 0.05%. From the viewpoint of carbon dioxide corrosion resistance, the C content is preferably 0.03% or less. More preferably, it is 0.002% or more, and more preferably 0.015% or less. More preferably, it is 0.002% or more, and further preferably 0.010% or less.
Si:0.05〜0.50%
Siは、脱酸剤として作用する元素である。この効果は0.05%以上のSi含有で得られる。一方、0.50%を超えるSiの含有は、熱間加工性が低下するとともに、耐炭酸ガス腐食性が低下する。このため、Si含有量は0.05〜0.50%とする。好ましくは、Si含有量は0.10%以上であり、好ましくは0.40%以下である。より好ましくは、0.10%以上であり、より好ましくは0.30%以下である。Si: 0.05-0.50%
Si is an element that acts as an antacid. This effect is obtained with a Si content of 0.05% or more. On the other hand, if the Si content exceeds 0.50%, the hot workability is lowered and the carbon dioxide corrosion resistance is lowered. Therefore, the Si content is set to 0.05 to 0.50%. Preferably, the Si content is 0.10% or more, preferably 0.40% or less. More preferably, it is 0.10% or more, and more preferably 0.30% or less.
Mn:0.04〜1.80%
Mnは、熱間加工時のδフェライト生成を抑制し、熱間加工性を向上させる元素であり、本発明では0.04%以上のMnの含有を必要とする。一方、過剰に含有すると、靭性や低温の環境における耐SSC性に悪影響を及ぼす。このため、Mn含有量は0.04〜1.80%の範囲とする。好ましくは、Mn含有量は0.04%以上であり、好ましくは0.80%以下である。より好ましくは0.05%以上であり、より好ましくは0.50%以下であり、さらに好ましくは0.05%以上であり、さらに好ましくは0.26%以下である。Mn: 0.04 to 1.80%
Mn is an element that suppresses the formation of δ ferrite during hot working and improves hot workability, and the present invention requires the content of Mn to be 0.04% or more. On the other hand, excessive content adversely affects toughness and SSC resistance in low temperature environments. Therefore, the Mn content is in the range of 0.04 to 1.80%. Preferably, the Mn content is 0.04% or more, preferably 0.80% or less. It is more preferably 0.05% or more, more preferably 0.50% or less, still more preferably 0.05% or more, still more preferably 0.26% or less.
P:0.030%以下
Pは、耐炭酸ガス腐食性、耐孔食性、耐SSC性をともに低下させる元素であり、本発明ではできるだけ低減することが好ましいが、極端な低減は製造コストの高騰を招く。このため、特性の極端な低下を招くことなく、工業的に比較的安価に実施可能な範囲として、P含有量は0.030%以下とする。好ましくは、P含有量は0.020%以下である。P: 0.030% or less
P is an element that lowers carbon dioxide corrosion resistance, pitting corrosion resistance, and SSC resistance, and it is preferable to reduce it as much as possible in the present invention, but an extreme reduction causes an increase in manufacturing cost. Therefore, the P content is set to 0.030% or less as a range that can be industrially carried out at a relatively low cost without causing an extreme deterioration in characteristics. Preferably, the P content is 0.020% or less.
S:0.002%以下
Sは、熱間加工性を著しく低下させ、また、Sは旧オーステナイト粒界への偏析やCa系介在物の生成により、低温の環境における耐SSC性を悪化させるためできるだけ低減することが好ましい。S含有量は0.002%以下であればCa系介在物の数密度を低減し、旧オーステナイト粒界へのSの偏析を抑制し、所望の耐SSC性を得ることができる。このようなことから、S含有量は0.002%以下とする。好ましくは、S含有量は0.0015%以下である。S: 0.002% or less
S is preferably reduced as much as possible because it significantly reduces hot workability, and S deteriorates SSC resistance in a low temperature environment due to segregation to the old austenite grain boundaries and formation of Ca-based inclusions. When the S content is 0.002% or less, the number density of Ca-based inclusions can be reduced, the segregation of S into the former austenite grain boundaries can be suppressed, and the desired SSC resistance can be obtained. Therefore, the S content is set to 0.002% or less. Preferably, the S content is 0.0015% or less.
Cr:11.0〜14.0%
Crは、保護皮膜を形成して耐食性向上に寄与する元素であり、高温での耐食性を確保するために、本発明では11.0%以上のCrの含有を必要とする。一方、14.0%を超えるCrの含有は、マルテンサイト変態させずに、残留オーステイトを生じやすくすることで、マルテンサイト相の安定性が低下し、所望の強度が得られなくなる。このため、Cr含有量は11.0〜14.0%とする。好ましくは、Cr含有量は11.5%以上であり、好ましくは13.5%以下であり、より好ましくは、12.0%以上であり、より好ましくは13.0%以下である。Cr: 11.0 to 14.0%
Cr is an element that forms a protective film and contributes to the improvement of corrosion resistance, and in order to secure the corrosion resistance at high temperatures, the content of Cr of 11.0% or more is required in the present invention. On the other hand, if the content of Cr exceeds 14.0%, the stability of the martensite phase is lowered and the desired strength cannot be obtained by facilitating the formation of residual autostate without transforming the martensite. Therefore, the Cr content is set to 11.0 to 14.0%. Preferably, the Cr content is 11.5% or more, preferably 13.5% or less, more preferably 12.0% or more, and more preferably 13.0% or less.
Ni:3.0〜6.5%
Niは、保護皮膜を強固にして耐食性を向上させる作用を有する元素である。また、Niは、固溶して鋼の強度を増加させる。このような効果は3.0%以上のNiの含有で得られる。一方、6.5%を超えるNiの含有は、マルテンサイト変態させずに、残留オーステイトを生じやすくすることで、マルテンサイト相の安定性が低下し、強度が低下する。このため、Ni含有量は3.0〜6.5%とする。好ましくは、Ni含有量は5.0%以上であり、好ましくは6.0%以下である。Ni: 3.0-6.5%
Ni is an element that has the effect of strengthening the protective film and improving corrosion resistance. In addition, Ni dissolves in solid solution to increase the strength of steel. Such an effect can be obtained with a Ni content of 3.0% or more. On the other hand, if the content of Ni exceeds 6.5%, the stability of the martensite phase is lowered and the strength is lowered by facilitating the formation of residual austate without transforming the martensite. Therefore, the Ni content is set to 3.0 to 6.5%. Preferably, the Ni content is 5.0% or more, preferably 6.0% or less.
Mo:0.5〜3.0%
Moは、Cl−や低pHによる孔食に対する抵抗性を増加させる元素であり、本発明では0.5%以上のMoの含有を必要とする。0.5%未満のMoの含有では、苛酷な腐食環境下での耐食性を低下させる。一方、3.0%を超えるMoの含有は、δフェライトを発生させて、熱間加工性および耐食性の低下を招く。このため、Mo含有量は0.5〜3.0%とする。好ましくは、Mo含有量は0.5%以上であり、好ましくは2.5%以下である。より好ましくは、1.5%以上であり、より好ましくは2.3%以下である。Mo: 0.5-3.0%
Mo is an element that increases resistance to pitting corrosion due to Cl − and low pH, and the present invention requires a content of Mo of 0.5% or more. A Mo content of less than 0.5% reduces corrosion resistance in harsh corrosive environments. On the other hand, if the Mo content exceeds 3.0%, δ ferrite is generated, which causes deterioration of hot workability and corrosion resistance. Therefore, the Mo content is set to 0.5 to 3.0%. Preferably, the Mo content is 0.5% or more, preferably 2.5% or less. More preferably, it is 1.5% or more, and more preferably 2.3% or less.
Al:0.005〜0.10%
Alは、脱酸剤として作用する元素である。この効果は、Alを0.005%以上含有することで得られる。一方、0.10%を超えてAlを含有すると、酸化物量が多くなりすぎて、靭性に悪影響を及ぼす。このため、Al含有量は0.005〜0.10%とする。好ましくは、Al含有量は0.01%以上であり、好ましくは0.03%以下である。Al: 0.005 to 0.10%
Al is an element that acts as an antacid. This effect is obtained by containing 0.005% or more of Al. On the other hand, if Al is contained in excess of 0.10%, the amount of oxide becomes too large and the toughness is adversely affected. Therefore, the Al content is set to 0.005 to 0.10%. Preferably, the Al content is 0.01% or more, preferably 0.03% or less.
V:0.005〜0.20%
Vは、析出強化により鋼の強度を向上させる元素である。この効果は、Vを0.005%以上含有することで得られる。一方、0.20%を超えてVを含有しても、低温靭性が低下する。このため、V含有量は0.005〜0.20%とする。好ましくは、V含有量は0.03%以上であり、好ましくは0.08%以下である。V: 0.005 to 0.20%
V is an element that improves the strength of steel by strengthening precipitation. This effect is obtained by containing 0.005% or more of V. On the other hand, even if V is contained in excess of 0.20%, the low temperature toughness is lowered. Therefore, the V content is set to 0.005 to 0.20%. Preferably, the V content is 0.03% or more, preferably 0.08% or less.
Ti:0.01〜0.20%
Tiは、TiNを形成し、このTiNが酸化物系または硫化物系の介在物を覆うことで低温の環境における耐SSC性を向上させる元素である。このような効果は、Tiを0.01%以上含有することが必要である。一方、0.20%を超えてTiを含有しても、効果は飽和する。このため、Ti含有量は0.01〜0.20%とする。好ましくは、Ti含有量は0.03%以上であり、好ましくは0.20%以下である。より好ましくは、0.05%以上であり、より好ましくは0.15%以下である。Ti: 0.01-0.20%
Ti is an element that forms TiN, which improves SSC resistance in low temperature environments by covering oxide-based or sulfide-based inclusions. For such an effect, it is necessary to contain 0.01% or more of Ti. On the other hand, even if Ti is contained in excess of 0.20%, the effect is saturated. Therefore, the Ti content is set to 0.01 to 0.20%. Preferably, the Ti content is 0.03% or more, preferably 0.20% or less. More preferably, it is 0.05% or more, and more preferably 0.15% or less.
Co:0.01〜1.0%
Coは、Ms点を上昇させることで残留オーステナイト分率を低減し、強度および耐SSC性を向上させる元素である。このような効果は0.01%以上のCoを含有することで得られる。一方、1.0%を超えてCoを含有しても熱間加工性が低下する。このため、Co含有量は0.01〜1.0%とする。好ましくは、Co含有量は0.05%以上であり、好ましくは0.15%以下である。より好ましくは、Co含有量は0.05%以上であり、より好ましくは0.09%以下である。Co: 0.01-1.0%
Co is an element that increases the Ms point to reduce the retained austenite fraction and improve strength and SSC resistance. Such an effect can be obtained by containing 0.01% or more of Co. On the other hand, even if Co is contained in excess of 1.0%, the hot workability is lowered. Therefore, the Co content is set to 0.01 to 1.0%. Preferably, the Co content is 0.05% or more, preferably 0.15% or less. More preferably, the Co content is 0.05% or more, and more preferably 0.09% or less.
N:0.002〜0.15%
Nは、耐孔食性を著しく向上させる元素である。この効果は、0.002%以上のNの含有で得られる。一方、0.15%を超えてNを含有すると、低温靭性が低下する。このため、N含有量は0.002〜0.15%とする。好ましくは、N含有量は0.002%以上であり、好ましくは0.015%以下であり、より好ましくは、N含有量は0.003%以上であり、より好ましくは0.008%以下である。N: 0.002 to 0.15%
N is an element that significantly improves pitting corrosion resistance. This effect is obtained with an N content of 0.002% or more. On the other hand, if N is contained in excess of 0.15%, the low temperature toughness decreases. Therefore, the N content is set to 0.002 to 0.15%. Preferably, the N content is 0.002% or more, preferably 0.015% or less, more preferably the N content is 0.003% or more, and more preferably 0.008% or less.
O(酸素):0.010%以下
O(酸素)は、鋼中では酸化物として存在し、各種特性に悪影響を及ぼす。このため、Oはできるだけ低減することが望ましい。特に、O含有量が0.010%を超えると、熱間加工性、低温における耐SSC性がともに著しく低下する。このため、O含有量は0.010%以下とする。好ましくは、O含有量は0.006%以下である。より好ましくは、O含有量は0.004%以下である。O (oxygen): 0.010% or less
O (oxygen) exists as an oxide in steel and adversely affects various properties. Therefore, it is desirable to reduce O as much as possible. In particular, when the O content exceeds 0.010%, both hot workability and SSC resistance at low temperatures are significantly reduced. Therefore, the O content should be 0.010% or less. Preferably, the O content is 0.006% or less. More preferably, the O content is 0.004% or less.
また、本発明では、Cr、Ni、Mo、Cu、Cを、上記した範囲内でかつ下記(1)式を満足するように含有する。
Cr+0.65Ni+0.6Mo+0.55Cu−20C ≧ 15.0 ‥‥(1)
(ここで、Cr、Ni、Mo、Cu、C:各元素の含有量(質量%)であり、含有しない元素はゼロとする。)
(1)式の左辺値が15.0未満であると、150℃以上の高温でCO2、Cl−を含む高温腐食環境下における耐炭酸ガス腐食性が低下する。このため、本発明では、Cr、Ni、Mo、Cu、Cについて、(1)式を満足するように含有する。Further, in the present invention, Cr, Ni, Mo, Cu and C are contained within the above range and so as to satisfy the following equation (1).
Cr + 0.65Ni + 0.6Mo + 0.55Cu-20C ≧ 15.0 ‥‥ (1)
(Here, Cr, Ni, Mo, Cu, C: the content (mass%) of each element, and the element not contained is zero.)
When the lvalue of Eq. (1) is less than 15.0, the carbon dioxide gas corrosiveness in a high temperature corrosive environment containing CO 2 and Cl − decreases at a high temperature of 150 ° C. or higher. Therefore, in the present invention, Cr, Ni, Mo, Cu, and C are contained so as to satisfy the equation (1).
さらに、本発明では、Cr、Mo、Si、C、Mn、Ni、Cu、Nを、下記(2)式を満足するように含有する。
Cr+Mo+0.3Si−43.3C−0.4Mn−Ni−0.3Cu−9N ≦ 11.0 ‥‥(2)
(ここで、Cr、Mo、Si、C、Mn、Ni、Cu、N:各元素の含有量(質量%)であり、含有しない元素はゼロとする。)
(2)式の左辺値が11.0超えであると、ステンレス継目無鋼管を造管するうえでの必要十分な熱間加工性を得ることができず、鋼管の製造性が低下する。このため、本発明では、Cr、Mo、Si、C、Mn、Ni、Cu、Nについて、(2)式を満足するように含有する。Further, in the present invention, Cr, Mo, Si, C, Mn, Ni, Cu and N are contained so as to satisfy the following equation (2).
Cr + Mo + 0.3Si-43.3C-0.4Mn-Ni-0.3Cu-9N ≤ 11.0 ... (2)
(Here, Cr, Mo, Si, C, Mn, Ni, Cu, N: the content (mass%) of each element, and the element not contained is zero.)
If the lvalue of Eq. (2) exceeds 11.0, the hot workability necessary and sufficient for forming a stainless seamless steel pipe cannot be obtained, and the manufacturability of the steel pipe is lowered. Therefore, in the present invention, Cr, Mo, Si, C, Mn, Ni, Cu, and N are contained so as to satisfy the equation (2).
また、本発明では、長径が5μm以上で、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である介在物の数密度が0.5個/mm2以上3個/mm2以下とする。長径が5μm以上で、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である介在物の数密度が0.5個/mm2未満となると、TiNに覆われていない介在物の量が増え、SSCの起点である孔食となるため、低温の環境における所望の耐SSC性を得ることができない。一方で、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である介在物の数密度が3個/mm2よりも多くなると、介在物の数密度の増加と共に介在物の大きさも増加し、逆に孔食の起点となり、低温の環境における所望の耐SSC性を得ることができない。なお、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0における、Ti、Al、Mg、Ca:介在物中の各元素の含有量(質量%)であり、含有しない元素はゼロとする。Further, in the present invention, the number density of inclusions having a major axis of 5 μm or more and 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0 is 0.5 pieces / mm 2 or more and 3 pieces / mm 2 or less. When the major axis is 5 μm or more and the number density of inclusions with 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0 is less than 0.5 pieces / mm 2 , the amount of inclusions not covered by TiN increases and SSC Since it becomes pitting corrosion, which is the starting point of the above, it is not possible to obtain the desired SSC resistance in a low temperature environment. On the other hand, when the number density of inclusions with 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0 is higher than 3 pieces / mm 2 , the size of inclusions increases as the number density of inclusions increases, and conversely. It becomes the starting point of pitting corrosion, and the desired SSC resistance in a low temperature environment cannot be obtained. In addition, in 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0, Ti, Al, Mg, Ca: the content (mass%) of each element in the inclusions, and the elements not contained are set to zero. ..
また、長径5μm以上の介在物を対象とするのは、長径5μm以上の介在物が孔食の起点となりやすいためである。 In addition, inclusions having a major axis of 5 μm or more are targeted because inclusions having a major axis of 5 μm or more are likely to be the starting points of pitting corrosion.
本発明では、上記した成分以外の残部は、Feおよび不可避的不純物からなる。 In the present invention, the balance other than the above-mentioned components consists of Fe and unavoidable impurities.
上記した成分が基本の成分であるが、これら基本の組成に加えてさらに、必要に応じて選択元素として、Cu:0.05〜3.0%、W:0.05〜3.0%のうちから選ばれた1種または2種を含有することができる。さらに、Nb:0.01〜0.20%、Zr:0.01〜0.20%、B:0.0005〜0.01%、REM:0.0005〜0.01%、Ca:0.0005〜0.0025%、Sn:0.02〜0.20%、Ta:0.01〜0.1%、Mg:0.002〜0.01%のうちから選ばれた1種または2種以上を含有することもできる。 The above-mentioned components are the basic components, but in addition to these basic compositions, one or more selected from Cu: 0.05 to 3.0% and W: 0.05 to 3.0% as a selection element, if necessary, or Two kinds can be contained. Furthermore, Nb: 0.01 to 0.20%, Zr: 0.01 to 0.20%, B: 0.0005 to 0.01%, REM: 0.0005 to 0.01%, Ca: 0.0005 to 0.0025%, Sn: 0.02 to 0.20%, Ta: 0.01 to 0.1% , Mg: One or more selected from 0.002 to 0.01% may be contained.
Cu:0.05〜3.0%
Cuは、保護皮膜を強固にして、耐食性を高める元素であり、必要に応じて含有できる。このような効果は、0.05%以上のCuを含有することで得られる。一方、3.0%を超えるCuの含有は、CuSの粒界析出を招き熱間加工性が低下する。このため、Cuを含有する場合には、Cu含有量は0.05〜3.0%とする。好ましくは、Cu含有量は0.5%以上であり、好ましくは2.5%以下である。より好ましくは、Cu含有量は0.5%以上であり、より好ましくは1.1%以下である。Cu: 0.05-3.0%
Cu is an element that strengthens the protective film and enhances corrosion resistance, and can be contained as needed. Such an effect can be obtained by containing 0.05% or more of Cu. On the other hand, if the content of Cu exceeds 3.0%, the grain boundary of CuS is precipitated and the hot workability is lowered. Therefore, when Cu is contained, the Cu content is set to 0.05 to 3.0%. Preferably, the Cu content is 0.5% or more, preferably 2.5% or less. More preferably, the Cu content is 0.5% or more, and more preferably 1.1% or less.
W:0.05〜3.0%
Wは、強度増加に寄与する元素であり、必要に応じて含有できる。このような効果は、0.05%以上のWを含有することで得られる。一方、3.0%を超えてWを含有しても、効果は飽和する。このため、Wを含有する場合には、W含有量は0.05〜3.0%とする。好ましくは、W含有量は0.5%以上であり、好ましくは1.5%以下である。W: 0.05-3.0%
W is an element that contributes to increasing the strength and can be contained as needed. Such an effect can be obtained by containing 0.05% or more of W. On the other hand, even if W is contained in excess of 3.0%, the effect is saturated. Therefore, when W is contained, the W content is set to 0.05 to 3.0%. Preferably, the W content is 0.5% or more, preferably 1.5% or less.
Nb:0.01〜0.20%
Nbは、強度を高める元素であり、必要に応じて含有できる。このような効果は、0.01%以上のNbを含有することで得られる。一方、0.20%を超えてNbを含有しても、効果は飽和する。このため、Nbを含有する場合には、Nb含有量は0.01〜0.20%とする。好ましくは、Nb含有量は0.05%以上であり、好ましくは0.15%以下である。より好ましくは、0.07%以上であり、より好ましくは0.13%以下である。Nb: 0.01 to 0.20%
Nb is an element that enhances strength and can be contained as needed. Such an effect can be obtained by containing 0.01% or more of Nb. On the other hand, even if Nb is contained in excess of 0.20%, the effect is saturated. Therefore, when Nb is contained, the Nb content is set to 0.01 to 0.20%. Preferably, the Nb content is 0.05% or more, preferably 0.15% or less. More preferably, it is 0.07% or more, and more preferably 0.13% or less.
Zr:0.01〜0.20%
Zrは、強度増加に寄与する元素であり、必要に応じて含有できる。このような効果は、0.01%以上のZrを含有することで得られる。一方、0.20%を超えてZrを含有しても、効果は飽和する。このため、Zrを含有する場合には、Zr含有量は0.01〜0.20%とする。Zr: 0.01-0.20%
Zr is an element that contributes to increasing strength and can be contained as needed. Such an effect can be obtained by containing 0.01% or more of Zr. On the other hand, even if Zr is contained in excess of 0.20%, the effect is saturated. Therefore, when Zr is contained, the Zr content is set to 0.01 to 0.20%.
B:0.0005〜0.01%
Bは、強度増加に寄与する元素であり、必要に応じて含有できる。このような効果は、0.0005%以上のBを含有することで得られる。一方、0.01%を超えてBを含有すると、熱間加工性が低下する。このため、Bを含有する場合には、B含有量は0.0005〜0.01%とする。B: 0.0005-0.01%
B is an element that contributes to increasing the strength and can be contained as needed. Such an effect can be obtained by containing 0.0005% or more of B. On the other hand, if B is contained in excess of 0.01%, the hot workability is lowered. Therefore, when B is contained, the B content is set to 0.0005 to 0.01%.
REM:0.0005〜0.01%
REMは、耐食性改善に寄与する元素であり、必要に応じて含有できる。このような効果は、0.0005%以上のREMを含有することで得られる。一方、0.01%を超えてREMを含有しても、効果が飽和し、含有量に見合う効果が期待できなくなり、経済的に不利となる。このため、REMを含有する場合には、REM含有量は0.0005〜0.01%とする。REM: 0.0005-0.01%
REM is an element that contributes to the improvement of corrosion resistance and can be contained as needed. Such an effect can be obtained by containing 0.0005% or more of REM. On the other hand, even if REM is contained in excess of 0.01%, the effect is saturated and the effect commensurate with the content cannot be expected, which is economically disadvantageous. Therefore, when REM is contained, the REM content is set to 0.0005 to 0.01%.
Ca:0.0005〜0.0025%
Caは、熱間加工性改善に寄与する元素であり、必要に応じて含有できる。このような効果は、0.0005%以上のCaを含有することで得られる。一方、0.0025%を超えてCaを含有すると、粗大なCa系介在物の数密度が増加し、低温の環境における所望の耐SSC性を得ることができなくなる。このため、Caを含有する場合には、Ca含有量は0.0005〜0.0025%とする。Ca: 0.0005-0.0025%
Ca is an element that contributes to the improvement of hot workability and can be contained as needed. Such an effect can be obtained by containing 0.0005% or more of Ca. On the other hand, if Ca is contained in an amount of more than 0.0025%, the number density of coarse Ca-based inclusions increases, and the desired SSC resistance in a low temperature environment cannot be obtained. Therefore, when Ca is contained, the Ca content is set to 0.0005 to 0.0025%.
Sn:0.02〜0.20%
Snは、耐食性改善に寄与する元素であり、必要に応じて含有できる。このような効果は、0.02%以上のSnを含有することで得られる。一方、0.20%を超えてSnを含有しても、効果が飽和し、含有量に見合う効果が期待できなくなり、経済的に不利となる。このため、Snを含有する場合には、Sn含有量は0.02〜0.20%とする。Sn: 0.02 to 0.20%
Sn is an element that contributes to the improvement of corrosion resistance and can be contained as needed. Such an effect can be obtained by containing 0.02% or more of Sn. On the other hand, even if Sn is contained in excess of 0.20%, the effect is saturated and the effect commensurate with the content cannot be expected, which is economically disadvantageous. Therefore, when Sn is contained, the Sn content is set to 0.02 to 0.20%.
Ta:0.01〜0.1%
Taは、強度を増加させる元素であり、耐硫化物応力割れ性を改善する効果も有する。また、TaはNbと同様の効果をもたらす元素であり、Nbの一部をTaに置き換えることができる。このような効果は、0.01%以上のTaを含有することで得られる。一方、0.1%を超えてTaを含有すると、靭性が低下する。このため、Taを含有する場合には、Ta含有量は0.01〜0.1%とする。Ta: 0.01-0.1%
Ta is an element that increases strength and also has the effect of improving sulfide stress cracking resistance. In addition, Ta is an element that has the same effect as Nb, and a part of Nb can be replaced with Ta. Such an effect can be obtained by containing 0.01% or more of Ta. On the other hand, if Ta is contained in excess of 0.1%, the toughness decreases. Therefore, when Ta is contained, the Ta content is set to 0.01 to 0.1%.
Mg:0.002〜0.01%
Mgは、耐食性を向上させる元素であり、必要に応じて含有できる。このような効果は、0.002%以上のMgを含有することで得られる。一方、0.01%を超えてMgを含有しても、効果が飽和し、含有量に見合う効果が期待できなくなる。このため、Mgを含有する場合には、Mg含有量は0.002〜0.01%とする。Mg: 0.002 to 0.01%
Mg is an element that improves corrosion resistance and can be contained as needed. Such an effect can be obtained by containing 0.002% or more of Mg. On the other hand, even if Mg is contained in excess of 0.01%, the effect is saturated and the effect commensurate with the content cannot be expected. Therefore, when Mg is contained, the Mg content is set to 0.002 to 0.01%.
本発明の油井用高強度ステンレス継目無鋼管では、所望の強度を確保するために、マルテンサイト相(焼戻マルテンサイト相)を主相とする。主相以外の残部は、残留オーステナイト相、フェライト相の少なくとも1種を含む。ここで、主相とは、体積率(面積率)で45%以上のことを指す。 In the high-strength stainless seamless steel pipe for oil wells of the present invention, the martensite phase (tempered martensite phase) is used as the main phase in order to secure the desired strength. The remainder other than the main phase contains at least one of a retained austenite phase and a ferrite phase. Here, the main phase means a volume ratio (area ratio) of 45% or more.
また、本発明では、平均の旧オーステナイト粒径が40μm以下であることが低温の環境における所望の耐SSC性を得る観点から、好ましい。 Further, in the present invention, it is preferable that the average austenite particle size is 40 μm or less from the viewpoint of obtaining the desired SSC resistance in a low temperature environment.
なお、本発明における長径が5μm以上で、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である介在物の数密度、および、平均の旧オーステナイト粒径については、後述する実施例に記載した方法で測定することができる。 The number densities of inclusions having a major axis of 5 μm or more and 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0 in the present invention and the average austenite particle size are described in Examples described later. It can be measured by the method.
次に、本発明の油井用高強度ステンレス継目無鋼管の好ましい製造方法について、説明する。 Next, a preferable manufacturing method of the high-strength stainless seamless steel pipe for oil wells of the present invention will be described.
本発明では、上記した組成を有する鋼管素材を出発素材とする。出発素材である鋼管素材の製造方法は、特に限定する必要なく、通常公知の継目無鋼管の製造方法がいずれも適用できる。上記した組成の溶鋼を、転炉等の常用の溶製方法で溶製し、連続鋳造法、造塊−分塊圧延法等、通常の方法でビレット等の鋼管素材とすることが好ましい。上記した0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である介在物の個数は、例えば、製鋼工程において酸素量をオンラインで測定し、その値に応じてTi、Nの添加量を変えることで所望の値に制御することができる。 In the present invention, a steel pipe material having the above composition is used as a starting material. The method for producing the steel pipe material as the starting material does not need to be particularly limited, and any of the generally known methods for producing the seamless steel pipe can be applied. It is preferable that the molten steel having the above composition is melted by a common melting method such as a converter and used as a steel pipe material such as a billet by a usual method such as a continuous casting method, an ingot-incubation rolling method or the like. The number of inclusions with 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0 described above is, for example, the amount of oxygen measured online in the steelmaking process, and the amount of Ti and N added according to the value. It can be controlled to a desired value by changing it.
ついで、これら鋼管素材を加熱し、通常公知の造管方法である、マンネスマン−プラグミル方式、あるいはマンネスマン−マンドレルミル方式の造管工程を用いて、熱間加工し造管して、所望寸法の上記した組成を有する継目無鋼管とする。なお、プレス方式による熱間押出で継目無鋼管としてもよい。造管後の継目無鋼管は、空冷以上の冷却速度で室温まで冷却することが好ましい。これにより、マルテンサイト相を主相とする鋼管組織を確保できる。平均の旧オーステナイト粒径を小さくするために、(造管後の鋼管の断面積)/(鋼管素材の断面積)は、0.20以下となるような条件で造管することが好ましい。また、(造管後の鋼管の断面積)/(穿孔後の鋼管の断面積)は、0.40以下となるような条件で造管することが好ましい。 Then, these steel pipe materials are heated and hot-processed by using a pipe-making process of a Mannesmann-plug mill method or a Mannesmann-mandrel mill method, which is a generally known pipe-making method, and the above-mentioned desired dimensions are obtained. A seamless steel pipe having the above composition. In addition, a seamless steel pipe may be obtained by hot extrusion by a press method. The seamless steel pipe after pipe formation is preferably cooled to room temperature at a cooling rate equal to or higher than air cooling. As a result, a steel pipe structure having the martensite phase as the main phase can be secured. In order to reduce the average old austenite grain size, it is preferable to make the pipe under the condition that (cross-sectional area of steel pipe after pipe making) / (cross-sectional area of steel pipe material) is 0.20 or less. Further, it is preferable to make the pipe under the condition that (cross-sectional area of the steel pipe after pipe making) / (cross-sectional area of the steel pipe after drilling) is 0.40 or less.
造管後の空冷以上の冷却速度で室温まで冷却する冷却に引続き、本発明では、さらに鋼管に、Ac3変態点以上、好ましくは800℃以上の温度へ再加熱し、好ましくは5分間以上保持し、続いて空冷以上の冷却速度で100℃以下の温度まで冷却する焼入れ処理を施す。これにより、マルテンサイト相の微細化と高強度化が達成できる。なお、焼入れ処理の加熱温度は、組織の粗大化を防止する観点から800〜950℃とすることが好ましい。Following cooling to cool to room temperature at a cooling rate equal to or higher than air cooling after pipe formation, in the present invention, the steel pipe is further reheated to a temperature of Ac 3 transformation point or higher, preferably 800 ° C. or higher, and held for 5 minutes or longer. Then, a quenching process is performed in which the temperature is cooled to 100 ° C. or lower at a cooling rate equal to or higher than air cooling. As a result, the martensite phase can be made finer and stronger. The heating temperature of the quenching treatment is preferably 800 to 950 ° C. from the viewpoint of preventing the coarsening of the structure.
また、ここで、「空冷以上の冷却速度」とは、0.01℃/s以上である。 Further, here, the "cooling rate of air cooling or higher" is 0.01 ° C./s or higher.
焼入れ処理を施された鋼管は、ついで、焼戻処理を施される。焼戻処理は、500℃以上Ac1変態点未満の温度(焼戻温度)に加熱し、所定時間、好ましくは10分間以上保持した後空冷する処理とする。焼戻温度がAc1変態点以上となると、焼戻後に、フレッシュマルテンサイト相が析出し、所望の高強度を確保できなくなる。このため、焼戻温度は500℃以上Ac1変態点未満とすることがより好ましい。これにより、組織が、焼戻マルテンサイト相を主相とする組織となり、所望の強度と、所望の耐食性を有する継目無鋼管となる。The hardened steel pipe is then tempered. The tempering treatment is a treatment of heating to a temperature of 500 ° C. or higher and lower than the Ac 1 transformation point (tempering temperature), holding for a predetermined time, preferably 10 minutes or longer, and then air-cooling. When the tempering temperature becomes equal to or higher than the Ac 1 transformation point, the fresh martensite phase is precipitated after the tempering, and the desired high strength cannot be secured. Therefore, it is more preferable that the tempering temperature is 500 ° C. or higher and lower than the Ac 1 transformation point. As a result, the structure becomes a structure having the tempered martensite phase as the main phase, and becomes a seamless steel pipe having a desired strength and a desired corrosion resistance.
また、平均の旧オーステナイト粒径を小さくする観点からは、焼入れ−焼戻しを二回以上繰り返すことが望ましい。 Further, from the viewpoint of reducing the average austenite particle size, it is desirable to repeat quenching and tempering twice or more.
なお、上記のAc3変態点およびAc1変態点は、15℃/minの速度で試験片(φ3mm×L10mm)を昇温、冷却した場合の膨張率(線膨張率)の変化から読み取った実測値とする。The above Ac 3 transformation point and Ac 1 transformation point are actually measured from the change in expansion coefficient (linear expansion coefficient) when the test piece (φ3 mm × L10 mm) is heated and cooled at a speed of 15 ° C / min. Let it be a value.
ここまでは継目無鋼管を例にして説明したが、本発明はこれに限定されるものではない。上記した組成の鋼管素材を用いて、通常の工程に従い、電縫鋼管、UOE鋼管を製造し油井用鋼管とすることも可能である。 Up to this point, the seamless steel pipe has been described as an example, but the present invention is not limited thereto. Using the steel pipe material having the above composition, it is also possible to manufacture an electrosewn steel pipe and a UOE steel pipe according to a normal process to obtain a steel pipe for an oil well.
以下、さらに実施例に基づき、本発明を説明する。 Hereinafter, the present invention will be described further based on Examples.
表1に示す組成の溶鋼を溶製し、鋼管素材に鋳造し、モデルシームレス圧延機を用いる熱間加工により造管し、造管後空冷し、外径83.8mm×肉厚12.7mmの継目無鋼管とした。なお、鋼管No.13については、長径が5μm以上で、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である介在物の個数が3個/mm2超えとなるように、製鋼工程において酸素量をオンラインで測定し、その値に応じてTi、Nの添加量を変えることで制御した。また、鋼管No.14については、長径が5μm以上で、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である介在物の個数が0.5個/mm2未満となるように、製鋼工程において酸素量をオンラインで測定し、その値に応じてTi、Nの添加量を変えることで制御した。The molten steel with the composition shown in Table 1 is melted, cast into a steel pipe material, piped by hot working using a model seamless rolling mill, air-cooled after pipe making, and seamless with an outer diameter of 83.8 mm and a wall thickness of 12.7 mm. It was a steel pipe. In addition, steel pipe No. For No. 13, the amount of oxygen is adjusted online in the steelmaking process so that the number of inclusions with a major axis of 5 μm or more and 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0 exceeds 3 / mm 2. It was controlled by changing the amount of Ti and N added according to the value. In addition, the steel pipe No. For 14, the amount of oxygen is online in the steelmaking process so that the major axis is 5 μm or more and the number of inclusions with 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0 is less than 0.5 / mm 2. It was controlled by changing the amount of Ti and N added according to the value.
次いで、得られた継目無鋼管から、試験片素材を切り出し、表2に示す加熱温度(再加熱温度)、均熱時間で加熱したのち、表2に示す冷却停止温度で空冷する焼入れ処理を施した。そして、さらに表2に示す焼戻温度、均熱時間で加熱し空冷する焼戻処理を施した。 Next, the test piece material was cut out from the obtained seamless steel pipe, heated at the heating temperature (reheating temperature) and soaking time shown in Table 2, and then air-cooled at the cooling stop temperature shown in Table 2. bottom. Then, a tempering process of heating at the tempering temperature and soaking time shown in Table 2 and air-cooling was performed.
また、焼入れ−焼戻処理を施された試験片素材から、API(American Petroleum Institute)弧状引張試験片を採取し、APIの規定に準拠して引張試験を実施し引張特性(降伏強さYS、引張強さTS)を求めた。降伏強さYSが655MPa以上のものを合格とし、655MPa未満のものを不合格とした。 In addition, API (American Petroleum Institute) arc-shaped tensile test pieces are collected from the hardened-tempered test piece material, and a tensile test is conducted in accordance with the API regulations. Tensile characteristics (yield strength YS, Tensile strength TS) was determined. Those with a yield strength of YS of 655 MPa or more were accepted, and those with a yield strength of less than 655 MPa were rejected.
さらに、焼入れ−焼戻処理を施された試験片素材から、厚さ3mm×幅30mm×長さ40mmの腐食試験片を機械加工によって作製し、腐食試験を実施した。 Further, a corrosion test piece having a thickness of 3 mm, a width of 30 mm, and a length of 40 mm was prepared by machining from the material of the test piece subjected to the quenching-tempering treatment, and the corrosion test was carried out.
腐食試験は、オートクレーブ中に保持された試験液:20質量%NaCl水溶液(液温:150℃、10気圧のCO2ガス雰囲気)中に、試験片を浸漬し、浸漬期間を14日間として実施した。試験後の試験片について、重量を測定し、腐食試験前後の重量減から計算した腐食速度を求めた。腐食速度が0.125mm/y以下のものを合格とし、0.125mm/y超えのものを不合格とした。The corrosion test was carried out by immersing the test piece in a test solution held in an autoclave: a 20 mass% NaCl aqueous solution (liquid temperature: 150 ° C., CO 2 gas atmosphere at 10 atm), and the immersion period was 14 days. .. The weight of the test piece after the test was measured, and the corrosion rate calculated from the weight loss before and after the corrosion test was determined. Those with a corrosion rate of 0.125 mm / y or less were accepted, and those with a corrosion rate of more than 0.125 mm / y were rejected.
また、腐食試験後の試験片について倍率:10倍のルーペを用いて試験片表面の孔食発生の有無を観察した。なお、孔食有りは、直径:0.2mm以上の場合をいう。孔食発生無のものを合格とし、孔食発生有のものを不合格とした。 In addition, the presence or absence of pitting corrosion on the surface of the test piece was observed using a loupe with a magnification of 10 times for the test piece after the corrosion test. Note that pitting corrosion refers to the case where the diameter is 0.2 mm or more. Those without pitting corrosion were accepted, and those with pitting corrosion were rejected.
SSC試験は、NACE TM0177 Method Aに準拠して実施した。試験環境は、25質量%NaCl水溶液(液温:4℃、H2S:0.1bar、CO2:0.9bar)に、酢酸Na+塩酸を加えてpH:4.5に調整した水溶液を用いた。浸漬時間を720時間として、降伏応力の90%を負荷応力として試験を実施した。試験後の試験片に割れが発生しない場合を合格(表3中:無し)とし、割れが発生した場合を不合格(表3中:有り)とした。The SSC test was conducted in accordance with NACE TM0177 Method A. The test environment used was an aqueous solution adjusted to pH: 4.5 by adding sodium acetate + hydrochloric acid to a 25 mass% NaCl aqueous solution (liquid temperature: 4 ° C, H 2 S: 0.1 bar, CO 2: 0.9 bar). The test was carried out with the immersion time as 720 hours and 90% of the yield stress as the load stress. The case where no cracks occurred in the test piece after the test was regarded as acceptable (in Table 3: none), and the case where cracks occurred was regarded as unacceptable (in Table 3: yes).
熱間加工性の評価には、平行部径10mmの丸棒形状の平滑試験片を用い、グリーブル試験機にて1250℃に加熱し、100秒間保持後、1℃/secで1000℃まで冷却し、10秒間保持した後、破断するまで引っ張り、断面減少率を測定した。断面減少率が70%以上の場合を、優れた熱間加工性を有するとみなし合格とした。断面減少率が70%未満の場合を不合格とした。 To evaluate hot workability, a round bar-shaped smoothing test piece with a parallel part diameter of 10 mm was used, heated to 1250 ° C with a gleeble tester, held for 100 seconds, and then cooled to 1000 ° C at 1 ° C / sec. After holding for 10 seconds, it was pulled until it broke, and the cross-sectional reduction rate was measured. When the cross-sectional reduction rate was 70% or more, it was considered to have excellent hot workability and passed. If the cross-section reduction rate was less than 70%, it was rejected.
介在物の個数は、鋼管管端の周方向任意1箇所より管肉厚方向に直交する断面の走査型電子顕微鏡(SEM)用試料として、管外面から肉厚の1/4の位置、3/4の位置から500mm2の領域を採取した。採取したそれぞれの試料について、SEM観察により介在物をそれぞれ同定するとともに、SEMに付随する特性X線分析装置で化学組成を分析した。0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である介在物を算出し、単位面積あたりの介在物の個数を算出した。また、長径が5μm以上である介在物の判別は、走査型電子顕微鏡の反射電子像によるコントラストを二値化して介在物の外周部を定義し、介在物の外周部から長径を測定することにより行った。The number of inclusions is 1/4 of the wall thickness from the outer surface of the pipe, 3/ An area of 500 mm 2 was sampled from position 4. For each sample collected, inclusions were identified by SEM observation, and the chemical composition was analyzed by the characteristic X-ray analyzer attached to the SEM. The inclusions with 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0 were calculated, and the number of inclusions per unit area was calculated. In addition, inclusions having a major axis of 5 μm or more are determined by binarizing the contrast of the reflected electron image of the scanning electron microscope to define the outer peripheral portion of the inclusions and measuring the major axis from the outer peripheral portion of the inclusions. went.
平均の旧オーステナイト粒径の測定試料は、鋼管管端の周方向任意1箇所より管長手方向に直交する断面の管外面から肉厚の1/2の位置から採取した。採取した試料について、EBSD観察をおこなったのち、旧オーステナイト粒の逆解析ソフトウェアを使用し、当該EBSDの観察データから旧オーステナイト粒の再構築を行った。得られた旧オーステナイト粒再構築像について、管円周方向に300μmの直線を500μm間隔で3本引き、切断法により、平均の旧オーステナイト粒径を測定した。 The measurement sample of the average austenite particle size was taken from an arbitrary position in the circumferential direction of the steel pipe end at a position of 1/2 of the wall thickness from the outer surface of the pipe having a cross section orthogonal to the longitudinal direction of the pipe. After observing the collected samples with EBSD, the old austenite grains were reconstructed from the observation data of the EBSD using the inverse analysis software of the old austenite grains. With respect to the obtained reconstructed image of austenite grains, three straight lines of 300 μm were drawn in the circumferential direction of the tube at intervals of 500 μm, and the average austenite particle size was measured by a cutting method.
得られた結果を表3に示す。 The results obtained are shown in Table 3.
本発明例はいずれも、降伏強さYS:655MPa以上で熱間加工性に優れるとともに、CO2、Cl−を含む150℃以上の高温の腐食環境下における耐食性(耐炭酸ガス腐食性)に優れ、さらに低温の環境における耐SSC性に優れ、断面減少率が70%以上であった。一方、本発明の範囲を外れる比較例は、降伏強さYS、熱間加工性、低温環境での耐SSC性、腐食速度、断面減少率の少なくとも1つが所望の値を得られなかった。All of the examples of the present invention have a yield strength of YS: 655 MPa or more and are excellent in hot workability, and also have excellent corrosion resistance (carbon dioxide corrosion resistance) in a high temperature corrosive environment of 150 ° C. or more including CO 2 and Cl −. Furthermore, it was excellent in SSC resistance in a low temperature environment, and the cross-sectional reduction rate was 70% or more. On the other hand, in the comparative example outside the scope of the present invention, at least one of yield strength YS, hot workability, SSC resistance in a low temperature environment, corrosion rate, and cross-sectional reduction rate could not be obtained.
Claims (4)
C :0.002〜0.05%、 Si:0.05〜0.50%、
Mn:0.04〜1.80%、 P :0.030%以下、
S :0.002%以下、 Cr:11.0〜14.0%、
Ni:3.0〜6.5%、 Mo:0.5〜3.0%、
Al:0.005〜0.10%、 V :0.005〜0.20%、
Ti:0.01〜0.20%、 Co:0.01〜1.0%、
N :0.002〜0.15%、 O :0.010%以下
を含有し、かつ下記(1)式および下記(2)式を満足し、残部Feおよび不可避的不純物からなる組成を有し、
長径が5μm以上で、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0である全ての介在物の数密度が0.5個/mm2以上3個/mm2以下である、降伏強さが655MPa以上である油井用高強度ステンレス継目無鋼管。
(ここで、0.5 < Ti/(Ti+Al+Mg+Ca)<1.0における、Ti、Al、Mg、Ca:介在物中の各元素の含有量(質量%)であり、含有しない元素はゼロとする。)
記
Cr+0.65Ni+0.6Mo+0.55Cu−20C ≧ 15.0 ‥‥(1)
Cr+Mo+0.3Si−43.3C−0.4Mn−Ni−0.3Cu−9N ≦ 11.0 ‥‥(2)
ここで、Cr、Ni、Mo、Cu、C、Si、Mn、N:各元素の含有量(質量%)であり、含有しない元素はゼロとする。 By mass%
C: 0.002 to 0.05%, Si: 0.05 to 0.50%,
Mn: 0.04 to 1.80%, P: 0.030% or less,
S: 0.002% or less, Cr: 11.0 to 14.0%,
Ni: 3.0-6.5%, Mo: 0.5-3.0%,
Al: 0.005 to 0.10%, V: 0.005 to 0.20%,
Ti: 0.01-0.20%, Co: 0.01-1.0%,
N: 0.002 to 0.15%, O: 0.010% or less, satisfy the following formulas (1) and (2), and have a composition consisting of the balance Fe and unavoidable impurities.
The major axis is 5 μm or more, 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0, the number density of all inclusions is 0.5 / mm 2 or more and 3 / mm 2 or less, and the yield strength is 655 MPa or more. High-strength stainless seamless steel pipe for oil wells.
(Here, in 0.5 <Ti / (Ti + Al + Mg + Ca) <1.0, Ti, Al, Mg, Ca: the content (mass%) of each element in the inclusions, and the elements not contained are zero. )
Record
Cr + 0.65Ni + 0.6Mo + 0.55Cu-20C ≧ 15.0 ‥‥ (1)
Cr + Mo + 0.3Si-43.3C-0.4Mn-Ni-0.3Cu-9N ≤ 11.0 ... (2)
Here, Cr, Ni, Mo, Cu, C, Si, Mn, N: the content (mass%) of each element, and the element not contained is zero.
Zr:0.01〜0.20%、
B:0.0005〜0.01%、
REM:0.0005〜0.01%、
Ca:0.0005〜0.0025%、
Sn:0.02〜0.20%、
Ta:0.01〜0.1%、
Mg:0.002〜0.01%のうちから選ばれた1種または2種以上を含有する請求項1または2に記載の油井用高強度ステンレス継目無鋼管。 In addition to the above composition, in mass%, Nb: 0.01 to 0.20%,
Zr: 0.01-0.20%,
B: 0.0005-0.01%,
REM: 0.0005-0.01%,
Ca: 0.0005-0.0025%,
Sn: 0.02 to 0.20%,
Ta: 0.01-0.1%,
The high-strength stainless seamless steel pipe for oil wells according to claim 1 or 2, which contains one or more selected from 0.002 to 0.01% of Mg.
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Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2001131698A (en) * | 1999-10-28 | 2001-05-15 | Sumitomo Metal Ind Ltd | Steel tube excellent in sulfide stress cracking resistance |
WO2018181404A1 (en) * | 2017-03-28 | 2018-10-04 | 新日鐵住金株式会社 | Martensitic stainless steel material |
WO2019065114A1 (en) * | 2017-09-29 | 2019-04-04 | Jfeスチール株式会社 | Oil well pipe martensitic stainless seamless steel pipe and production method for same |
WO2019225280A1 (en) * | 2018-05-25 | 2019-11-28 | Jfeスチール株式会社 | Martensitic stainless steel seamless steel tube for oil well pipes, and method for producing same |
WO2019225281A1 (en) * | 2018-05-25 | 2019-11-28 | Jfeスチール株式会社 | Martensitic stainless steel seamless steel tube for oil well pipes, and method for producing same |
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JP5487689B2 (en) * | 2009-04-06 | 2014-05-07 | Jfeスチール株式会社 | Manufacturing method of martensitic stainless steel seamless pipe for oil well pipe |
BR112018068914B1 (en) * | 2016-03-29 | 2022-02-15 | Jfe Steel Corporation | HIGH STRENGTH SEAMLESS STAINLESS STEEL PIPE FOR OIL WELL |
RU2710808C1 (en) * | 2016-05-20 | 2020-01-14 | Ниппон Стил Корпорейшн | Steel long products for well element and well element |
BR112020004808B1 (en) * | 2017-09-29 | 2024-02-20 | Jfe Steel Corporation | MARTENSITIC STAINLESS STEEL SEAMLESS TUBE FOR PETROLEUM TUBULAR PRODUCTS AND METHOD FOR MANUFACTURE THEREOF |
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Publication number | Priority date | Publication date | Assignee | Title |
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JP2001131698A (en) * | 1999-10-28 | 2001-05-15 | Sumitomo Metal Ind Ltd | Steel tube excellent in sulfide stress cracking resistance |
WO2018181404A1 (en) * | 2017-03-28 | 2018-10-04 | 新日鐵住金株式会社 | Martensitic stainless steel material |
WO2019065114A1 (en) * | 2017-09-29 | 2019-04-04 | Jfeスチール株式会社 | Oil well pipe martensitic stainless seamless steel pipe and production method for same |
WO2019225280A1 (en) * | 2018-05-25 | 2019-11-28 | Jfeスチール株式会社 | Martensitic stainless steel seamless steel tube for oil well pipes, and method for producing same |
WO2019225281A1 (en) * | 2018-05-25 | 2019-11-28 | Jfeスチール株式会社 | Martensitic stainless steel seamless steel tube for oil well pipes, and method for producing same |
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US20230033540A1 (en) | 2023-02-02 |
EP4043591A1 (en) | 2022-08-17 |
MX2022007286A (en) | 2022-07-12 |
EP4043591A4 (en) | 2022-10-12 |
WO2021131445A1 (en) | 2021-07-01 |
AR120872A1 (en) | 2022-03-23 |
CN114829647A (en) | 2022-07-29 |
BR112022011761A2 (en) | 2022-08-30 |
JPWO2021131445A1 (en) | 2021-12-23 |
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