JPH09170019A - Production of seamless martensitic stailess steel pipe excellent in ssc resistance - Google Patents
Production of seamless martensitic stailess steel pipe excellent in ssc resistanceInfo
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- JPH09170019A JPH09170019A JP32774595A JP32774595A JPH09170019A JP H09170019 A JPH09170019 A JP H09170019A JP 32774595 A JP32774595 A JP 32774595A JP 32774595 A JP32774595 A JP 32774595A JP H09170019 A JPH09170019 A JP H09170019A
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Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は、耐SSC性に優れ
たマルテンサイト系ステンレス継目無鋼管の製造方法に
関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a martensitic stainless seamless steel pipe having excellent SSC resistance.
【0002】[0002]
【従来の技術】マルテンサイト系ステンレス鋼は、AI
SI 420鋼に代表されるように、強度、耐CO2 腐
食特性に優れることから1980年頃より油井管として
適用されてきている。最近では420鋼より優れた耐C
O2 腐食特性、さらには耐H2S性に対する市場要求が
高まり、特開平3−120337号公報などに見られる
ような、低CおよびNi−Mo添加鋼、あるいは、特開
平2−247360号公報などに見られるような、低C
およびNi−Cu−Mo添加鋼といった鋼種(いわゆる
Modified 13Cr鋼と称される鋼種)が開発されてき
ている。かかる鋼は、特開平3−120337号公報な
どに見られるように、熱間加工後にAc3 点以上の温
度に再度加熱・保定した後Ms点以下まで冷却する焼入
処理(もしくは焼準処理)を施すか、Ac1 点〜Ac
3 点の温度域に再度加熱・保定した後にMs点以下まで
冷却する二相域処理を施すか、Ac1 点以下の温度に
再度加熱・保定した後にMs点以下まで冷却する焼戻処
理を施すか、あるいは,,を適宜組み合わせるこ
とによって熱処理が施されて製造される。2. Description of the Related Art Martensitic stainless steel has been developed using AI.
As represented by SI 420 steel, it has been used as an oil country tubular good since around 1980 due to its excellent strength and CO 2 corrosion resistance. Recently, it has better C resistance than 420 steel.
Market demand for O 2 corrosion characteristics, and further H 2 S resistance has increased, and low C and Ni—Mo added steels such as those found in JP-A-3-120337 or JP-A-2-247360. Low C as seen in
And steel types such as Ni-Cu-Mo added steel (so-called
A steel type called Modified 13Cr steel) has been developed. Such steel is, as seen in Japanese Patent Laid-Open No. 3-120337, a quenching treatment (or normalizing treatment) in which after hot working, it is heated and held again at a temperature of Ac 3 point or higher and then cooled to Ms point or lower. Or Ac 1 point to Ac
A two-phase region treatment is performed in which the material is heated and held again at a temperature of 3 points and then cooled to the Ms point or lower, or a tempering treatment is performed where it is heated and held again to a temperature of Ac 1 point or lower and then cooled to the Ms point or lower. It is manufactured by performing heat treatment by appropriately combining or.
【0003】[0003]
【発明が解決しようとする課題】しかしながら、かかる
熱処理方法は鋼本来が有する機能を最大限に引き出すに
十分な条件を与えておらず、その結果、鋼としては優れ
ていても油井管としては必ずしも満足すべきものとはな
っていなかった。たとえば、上記の方法では焼入マル
テンサイト組織であるため降伏強度(YS)は異常に低
く引張強度(TS)が異常に高い材料となり構造物形成
には全く実用的でない。また、上記あるいは+で
は焼入マルテンサイトと焼戻マルテンサイトの混合組織
となるため、YSは僅かな熱処理条件の変動によって大
きく影響され安定的に所定範囲内のYSに造り込むこと
が困難である。上記の方法を用いれば鋼は焼戻マルテ
ンサイトとなるため降伏強度と引張強度のバランスはほ
ど良いものとなり、必要なYSを安定的に得ることがで
きる。このことから、+,+,++の熱
処理が実用的である。しかしながら、これら焼戻処理
を必須とした熱処理を施してもその条件を十分に規定し
なければ、耐食性油井管として満足すべき特性、すなわ
ち、十分な耐硫化物応力割れ(SSC)特性が得られな
いという問題がある。However, such a heat treatment method does not give sufficient conditions for maximizing the functions of the steel itself, and as a result, even if it is excellent as a steel, it is not always suitable for an oil country tubular good. It was not satisfactory. For example, the above method is a material having an extremely low yield strength (YS) and an abnormally high tensile strength (TS) because it has a quenched martensite structure, and is not practical at all for forming a structure. Further, in the above or +, since a mixed structure of quenched martensite and tempered martensite is obtained, YS is greatly affected by slight changes in heat treatment conditions, and it is difficult to stably build YS within a predetermined range. . When the above method is used, the steel becomes tempered martensite, so that the yield strength and tensile strength are well balanced, and necessary YS can be stably obtained. From this fact, the heat treatment of +, +, ++ is practical. However, even if these heat treatments that require tempering treatment are performed, if the conditions are not sufficiently specified, sufficient properties as a corrosion resistant oil country tubular good, that is, sufficient sulfide stress cracking (SSC) properties can be obtained. There is a problem that there is no.
【0004】本発明は、かかる問題を解決するものであ
って、焼戻処理における条件を規制することにより耐食
性油井管として必要な耐SSC性を確保するマルテンサ
イト系ステンレス鋼油井管の製造方法を提供することを
目的とする。The present invention solves the above problem and provides a method for producing a martensitic stainless steel oil country tubular goods which secures the SSC resistance required as a corrosion resistant oil country tubular goods by regulating the conditions in tempering treatment. The purpose is to provide.
【0005】[0005]
【課題を解決するための手段】本発明者らは、種々成分
系の素材に対しマンネスマン方式の継目無鋼管圧延を施
し、室温まで放冷した後、種々の前履歴を有する素材に
対し温度・昇温速度を変化させて焼戻処理を実施し、得
られた材料の特性(YS/TSバランスおよび耐SSC
性)を評価した。その結果、耐SSC性はYS/TS比
(YR)に依存し、同一YSでもYRが高い方が良好な
耐SSC性を示すことを知見した。さらに、高いYRを
得るための焼戻処理の条件(焼戻温度、昇温速度)を解
明した。[Means for Solving the Problems] The inventors of the present invention have performed a Mannesmann system seamless steel pipe rolling on materials of various components and allowed to cool to room temperature. The characteristics of the obtained material (YS / TS balance and SSC resistance
Sex) was evaluated. As a result, it was found that the SSC resistance depends on the YS / TS ratio (YR), and the higher the YR is, the better the SSC resistance is even in the same YS. Furthermore, the conditions of the tempering treatment (tempering temperature, temperature rising rate) for obtaining high YR were clarified.
【0006】本発明はこの知見に基づいて構成したもの
であり、その要旨は、(1)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A
c1 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ことを特徴とするマル
テンサイト系ステンレス継目無鋼管の製造方法であり、
(2)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、 Ca:0.001〜0.020、 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A
c1 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ことを特徴とするマル
テンサイト系ステンレス継目無鋼管の製造方法であり、
(3)熱間加工の後にMs点以下の温度まで冷却し、そ
の後Ac3 点以上の温度に再加熱した後Ms点以下の温
度まで冷却し、さらに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
熱処理を施すことを特徴とする前記(1)または(2)
項に記載のマルテンサイト系ステンレス継目無鋼管の製
造方法であり、(4)熱間加工の後にMs点以下の温度
まで冷却し、その後Ac1 点以上Ac3 点以下の温度に
再加熱した後Ms点以下の温度まで冷却し、さらに55
0℃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M
s点以下の温度まで冷却する熱処理を施すことを特徴と
する前記(1)または(2)項に記載のマルテンサイト
系ステンレス継目無鋼管の製造方法であり、(5)熱間
加工の後にMs点以下の温度まで冷却し、その後Ac3
点以上の温度に再加熱した後Ms点以下の温度まで冷却
し、引き続きAc1 点以上Ac3 点以下の温度に再加熱
した後Ms点以下の温度まで冷却し、さらに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ことを特徴とする前
記(1)または(2)項に記載のマルテンサイト系ステ
ンレス継目無鋼管の製造方法であり、(6)熱処理を施
した鋼管材の降伏強度と引張強度の比が0.77以上で
あることを特徴とする前記(1)〜(5)項の何れかに
記載のマルテンサイト系ステンレス継目無鋼管の製造方
法である。The present invention is constructed on the basis of this finding, and the gist thereof is (1)% 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 0.10, and the balance of Fe and inevitable impurities having a composition of martensitic stainless steel having a composition of Ms point or less after hot working. Cool to temperature, then 550 ° C or higher A
Martensite, characterized in that a temperature T of c 1 or lower is subjected to a heat treatment in which the temperature is raised to an average heating rate of 500 to T ° C. of 1.0 ° C./sec or higher and then cooled to a temperature of the Ms point or lower. Is a method for producing stainless steel seamless steel pipe,
(2) In% by weight, 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, Ca : 0.001 to 0.020, with the balance being Fe and inevitable impurities, the martensitic stainless steel is hot-worked and then cooled to a temperature not higher than the Ms point, and then 550 ° C. or higher A
Martensite, characterized in that a temperature T of c 1 or lower is subjected to a heat treatment in which the temperature is raised to an average heating rate of 500 to T ° C. of 1.0 ° C./sec or higher and then cooled to a temperature of the Ms point or lower. Is a method for producing stainless steel seamless steel pipe,
(3) After hot working, it is cooled to a temperature of Ms point or lower, then reheated to a temperature of Ac 3 point or higher and then cooled to a temperature of Ms point or lower, and a temperature T of 550 ° C. or higher and Ac 1 or lower.
(1) or (2) above, which is subjected to a heat treatment in which the temperature is raised to an average heating rate of 500 to T ° C. of 1.0 ° C./sec or more and then cooled to a temperature of the Ms point or less.
The method for producing a martensitic stainless seamless steel pipe according to item (4), after cooling to a temperature of Ms point or less after hot working, and then reheating to a temperature of Ac 1 point or more and Ac 3 point or less Cool to a temperature below the Ms point, and then cool to 55
After heating to a temperature T of 0 ° C. or more and Ac 1 or less so that the average heating rate of 500 to T ° C. is 1.0 ° C./sec or more, M
The method for producing a martensitic stainless seamless steel pipe according to the above (1) or (2), characterized by performing a heat treatment of cooling to a temperature of s point or lower, and (5) Ms after hot working. Cool to below the point, then Ac 3
After being reheated to a temperature not lower than the point, it is cooled to a temperature not higher than the Ms point, subsequently reheated to a temperature not lower than Ac 1 point and not higher than Ac 3 point, and then cooled to a temperature lower than the Ms point, and further not lower than 550 ° C and not higher than Ac 1 point. The temperature T of 500 to T ° C. is subjected to a heat treatment of raising the temperature to an average heating rate of 1.0 ° C./sec or more and then cooling to a temperature below the Ms point (1) or The method for producing a martensitic stainless seamless steel pipe according to the item (2), wherein the ratio of the yield strength to the tensile strength of the heat-treated steel pipe material is 0.77 or more. A method for producing a martensitic stainless seamless steel pipe according to any one of items (1) to (5).
【0007】[0007]
【発明の実施の形態】以下、本発明について詳細に説明
する。本発明におけるマルテンサイト系ステンレス鋼の
成分限定理由は以下の通りである。 C:CはCr炭化物などを形成し耐食性を劣化させる元
素であるため可及的低レベルが好ましい。現時点での工
業的精錬技術の到達レベルを考慮して最大値を0.05
%とした。 Si:Siは製鋼工程において脱酸剤として添加され残
留されるもので、敢えて添加する元素ではなく、0.5
%を超えて含有されると靭性や耐SSC性が劣化するこ
とから上限を0.5%とした。BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The reasons for limiting the components of the martensitic stainless steel in the present invention are as follows. C: C is an element that forms Cr carbide or the like and deteriorates corrosion resistance, so that the lowest possible level is preferable. The maximum value is 0.05 in consideration of the achievement level of the current industrial refining technology.
%. Si: Si is added and remains as a deoxidizer in the steelmaking process, and is not an element to be intentionally added, but 0.5
%, The toughness and SSC resistance deteriorate, so the upper limit was made 0.5%.
【0008】Mn:Mnはオーステナイト安定化元素で
あり熱間加工時にδ相の析出を抑制することにより圧延
疵防止に有効であるが、1.5%を超えて添加すると粒
界強度を低下させSSC抵抗性が劣化するので、1.5
%を上限とした。 P:粒界に偏析して粒界強度を低下させ耐SSC性を劣
化させるため、上限を0.03%とした。Mn: Mn is an austenite stabilizing element and is effective in preventing rolling flaws by suppressing precipitation of the δ phase during hot working, but if added in excess of 1.5%, the grain boundary strength decreases. Since SSC resistance deteriorates, 1.5
% As the upper limit. P: The upper limit was set to 0.03% because it segregates at the grain boundaries to lower the grain boundary strength and deteriorate the SSC resistance.
【0009】S:熱間加工性を劣化させる上耐CO2 腐
食性、耐SSC性を減じるため、上限を0.005%と
した。 Cr:耐食性向上の基本元素であり、十分な耐CO2 腐
食性を得るには11%以上の添加が必要であるが、フェ
ライト安定化元素でもあり、多すぎると熱間加工時にδ
相が析出して熱間加工性劣化を起こすと共に、製品とし
てもマルテンサイト単相とならず耐SSC性を劣化する
ことになるため、上限を14%とした。S: In order to deteriorate hot workability and reduce CO 2 corrosion resistance and SSC resistance, the upper limit was made 0.005%. Cr: A basic element for improving corrosion resistance, and 11% or more is required to obtain sufficient CO 2 corrosion resistance, but it is also a ferrite stabilizing element, and if too much, δ during hot working.
The upper limit was set to 14% because the phases precipitate and the hot workability deteriorates, and the product does not become a martensite single phase and the SSC resistance deteriorates.
【0010】Ni:耐CO2 腐食性向上および靭性向上
に有効である。また、オーステナイト安定化元素であり
圧延疵につながるδ相の形成を抑制する。これら効果は
添加量4.0%未満では不十分であり7.0%を超えて
添加しても効果が飽和することから、最適添加範囲を
4.0〜7.0%とした。 Al:脱酸の目的で添加されるが、0.05%以下の添
加で十分な効果が得られる。Ni: Effective for improving CO 2 corrosion resistance and toughness. Further, it is an austenite stabilizing element and suppresses the formation of a δ phase which leads to rolling defects. These effects are insufficient if the addition amount is less than 4.0%, and the effects are saturated even if the addition amount exceeds 7.0%. Therefore, the optimum addition range is set to 4.0 to 7.0%. Al: It is added for the purpose of deoxidation, but a sufficient effect can be obtained with addition of 0.05% or less.
【0011】N:強力なオーステナイト安定化元素であ
るので高価なNiの代替元素として添加される。しかし
ながら、添加し過ぎるとマルテンサイト状態での硬さが
高くなり遅れ破壊感受性が増大するため最適添加量とし
て0.01〜0.10%とした。 Mo:Crと同様、耐食性向上元素であると共にフェラ
イト形成元素である。耐CO2 腐食性、耐SSC性、熱
間加工性の観点から最適添加範囲を1.0〜2.5%と
した。N: Since it is a strong austenite stabilizing element, it is added as an alternative element to expensive Ni. However, if added too much, the hardness in the martensitic state becomes high and the delayed fracture susceptibility increases, so the optimum addition amount was made 0.01 to 0.10%. Similar to Mo: Cr, it is an element for improving corrosion resistance and an element for forming ferrite. From the viewpoint of CO 2 corrosion resistance, SSC resistance, and hot workability, the optimum addition range was 1.0 to 2.5%.
【0012】Cu:Niと同様に耐CO2 腐食性向上に
有効な元素であると共にオーステナイト安定化元素であ
り圧延疵防止にも有効であるが、1.0%未満ではこれ
らの効果が十分に得られず2.5%を超えて添加すると
熱間加工性が著しく劣化するため最適範囲を1.0〜
2.5%とした。 Ca:Sによる熱間加工性劣化を抑制するものであり必
要に応じて添加するが、0.001%未満では効果が発
現されず0.02%を超えて添加してもその効果は飽和
するため、最適添加量を0.001〜0.02%とし
た。Similar to Cu: Ni, it is an element effective in improving the CO 2 corrosion resistance and an austenite stabilizing element, and is also effective in preventing rolling flaws. However, if it is less than 1.0%, these effects are sufficient. If not added and added in excess of 2.5%, the hot workability deteriorates significantly, so the optimum range is 1.0-
It was set to 2.5%. It suppresses the deterioration of hot workability due to Ca: S, and is added as necessary, but if it is less than 0.001%, the effect is not exhibited, and if it exceeds 0.02%, the effect is saturated. Therefore, the optimum addition amount is set to 0.001 to 0.02%.
【0013】次に、かかる組成の鋼の熱処理方法につい
て述べる。かかる組成の鋼は、その利用目的からして主
に耐食性向上のためCを低減すると共に、それによって
生じる耐SSC性に有害なδフェライトの析出を防止す
るためNiやCuなどの添加を行ったものであるが、か
かるγ形成元素の添加はAc1 変態点を大幅に低下させ
ることになる。したがって、必然的にかかる組成の鋼で
は低温焼戻を余儀なくされるが、低温焼戻を行えば強度
が高くなり、結果として十分な耐SSC性が得られな
い。Next, a heat treatment method for steel having such a composition will be described. The steel having such a composition is mainly added with Ni and Cu for the purpose of use in order to reduce C mainly for improving the corrosion resistance and to prevent the precipitation of δ ferrite which is harmful to the SSC resistance. However, the addition of such a γ-forming element significantly lowers the Ac 1 transformation point. Therefore, although steel having such a composition is inevitably subjected to low temperature tempering, low temperature tempering increases strength, resulting in insufficient SSC resistance.
【0014】しかしながら、本発明者らが鋭意研究した
結果、かかる組成鋼のAc1 変態点は昇温速度に依存す
ることが明らかとなった。すなわち、図1に示すよう
に、Ac1 変態点は昇温速度が速い程高くなる。この理
由は、析出物が高昇温速度ほど析出、凝集、固溶の進行
が遅れることによりα→γ変態が遅れるためと考えられ
る。ここでいう昇温速度とは、析出物の状態変化に関係
する550℃からAc1点以下の焼戻温度Tの温度域で
の平均昇温速度である。However, as a result of diligent research conducted by the present inventors, it became clear that the Ac 1 transformation point of such a composition steel depends on the heating rate. That is, as shown in FIG. 1, the Ac 1 transformation point becomes higher as the heating rate increases. It is considered that the reason for this is that the higher the heating rate of the precipitate, the later the progress of precipitation, aggregation, and solid solution, which delays the α → γ transformation. The heating rate here is the average heating rate in the temperature range of 550 ° C. to the tempering temperature T of Ac 1 point or less related to the change in the state of the precipitate.
【0015】上記の挙動は、前履歴が異なっても同様で
あり、圧延ままで常温まで冷却したもの(符号:R)、
その後Ac3 点以上に再加熱した後常温まで冷却したも
の(符号:R−N)、符号Rの処理に引き続きAc1 点
以上Ac3 点以下に再加熱した後常温まで冷却したもの
(符号:R−L)、符号R−Nの処理に引き続きAc1
点以上Ac3 点以下に再加熱した後常温まで冷却したも
の(符号:R−N−L)の4種の供試材(図3)で類似
の結果が得られた。通常の炉加熱方式では0.3℃/sec
程度の昇温速度しか得られないためAc1 点は630℃
程度であるが、1.0℃/sec以上の高速昇温ではAc1
点は650℃以上となる。このことから、高速昇温を行
えばAc1 変態点を高め、結果として高温焼戻が可能と
なり耐SSC性に有害な高強度化を防止することが可能
となる。かかる高速昇温を可能とする熱処理方法として
は、例えば誘導加熱法、塩浴加熱法などが挙げられる。
焼戻保定時間については、長時間保定するとAc1 変態
点が低下するため1分以内が望ましい。The above behavior is the same even if the previous history is different, that is, as-rolled and cooled to room temperature (reference: R),
After that, it was reheated to Ac 3 points or more and then cooled to room temperature (code: RN), and subsequently, after the treatment of code R, it was reheated to Ac 1 point or more and Ac 3 points or less and then cooled to room temperature (code: RN). R-L), subsequently Ac 1 to the processing of the code R-N
Similar results were obtained with the four types of test materials (FIG. 3) that were reheated to a temperature not lower than the Ac 3 and lower than the Ac 3 and then cooled to room temperature (symbol: RN-L). 0.3 ° C / sec with normal furnace heating method
Ac 1 point is 630 ° C because only a moderate heating rate can be obtained
Although it is about the level, Ac 1
The point is 650 ° C or higher. From this, it is possible to raise the Ac 1 transformation point by performing high-speed temperature rise, and as a result, it becomes possible to perform high temperature tempering and prevent the strengthening which is detrimental to the SSC resistance. Examples of the heat treatment method that enables the rapid temperature rise include an induction heating method and a salt bath heating method.
It is desirable that the tempering retention time be within 1 minute because the Ac 1 transformation point decreases when retained for a long time.
【0016】次に上記の熱処理方法によって得られた鋼
材のSSC特性について説明する。上述の熱処理方法に
よって得られた鋼材を用いてSSC試験を行い、その結
果を昇温速度との関係で整理し、図2に示す。SSC試
験は、t3.0×10×65mmサイズの短冊状試験片に
4点支持法によりYSの100%となる曲げ応力を加え
た状態で、H2 Sを分圧0.3atm で飽和させた5%酢
酸の溶液中に常温で浸漬して割れ有無を評価した。図2
から明らかなように、焼戻前の履歴(符号:R,R−
N,R−L,R−N−L、図3参照)によらず、昇温速
度1℃/sec以上で優れた耐SSC性が得られる。この理
由は、高昇温速度で焼戻すことによりYRが高くなるた
め同一YSにおいても高昇温速度材ほどTSが低くなる
ことによる。Next, the SSC characteristics of the steel material obtained by the above heat treatment method will be described. An SSC test was conducted using the steel material obtained by the heat treatment method described above, and the results are summarized in relation to the temperature rising rate and shown in FIG. The SSC test was performed by saturating H 2 S at a partial pressure of 0.3 atm while applying a bending stress of 100% of YS to a strip-shaped test piece of size t3.0 × 10 × 65 mm by a four-point supporting method. It was immersed in a 5% acetic acid solution at room temperature and evaluated for cracks. FIG.
As is apparent from the history before tempering (code: R, R-
It is possible to obtain excellent SSC resistance at a temperature rising rate of 1 ° C./sec or more regardless of N, RL, RN, and FIG. 3). The reason for this is that, since tempering at a high temperature rising rate increases the YR, the higher the temperature rising rate, the lower the TS in the same YS.
【0017】次に、かかる高速昇温による焼戻処理を施
した鋼材が満たすべき機械的特性としてYS/TS比
(YR)≧0.77を規定すれば望ましい理由について
述べる。上述の熱処理方法によって鋼材のYSを69.
1〜75.1kg/mm2 (油井管としての95ksi 級に相
当)に調質した材料を用いSSC試験を行い、その結果
をYRとの関係で整理した。SSC試験は、t3.0×
10×65mmサイズの短冊状試験片に4点支持法により
YSの100%となる曲げ応力を加えた状態で、H2 S
を分圧0.3atm で飽和させた5%酢酸の溶液中に常温
で浸漬して割れ有無を評価した。その結果、焼戻前の履
歴(符号;R,R−N,R−L,R−N−L、図3参
照)によらず、YRが0.77を下回ると耐SSC性が
やや低下する。したがって、上述の熱処理方法によって
得られる鋼材にYR≧0.77の条件を付加すれば、よ
り優れた耐SSC性が得られる。Next, the reason why it is desirable to define YS / TS ratio (YR) ≧ 0.77 as the mechanical properties to be satisfied by the steel material subjected to the tempering treatment by the high-speed temperature rise will be described. The YS of the steel material was changed to 69.
An SSC test was performed using a material that had a quality of 1 to 75.1 kg / mm 2 (corresponding to 95 ksi class as an oil country tubular good), and the results were summarized in relation to YR. SSC test is t3.0 ×
H 2 S was applied to a 10 × 65 mm strip test piece under a bending stress of 100% of YS by a four-point support method.
Was immersed in a solution of 5% acetic acid saturated with a partial pressure of 0.3 atm at room temperature, and the presence or absence of cracks was evaluated. As a result, regardless of the history before tempering (signs: R, RN, RL, RN, see FIG. 3), if YR is less than 0.77, the SSC resistance is slightly reduced. . Therefore, if the condition of YR ≧ 0.77 is added to the steel material obtained by the above heat treatment method, more excellent SSC resistance can be obtained.
【0018】[0018]
【実施例】以下、本発明の実施例について説明する。表
1に示す鋼を用いて試験を行った。矩形断面のブルーム
を素材としプレスロール穿孔−エロンゲータ圧延方式の
継目無鋼管圧延を行い、常温まで冷却した鋼管を素材と
して表2に示す条件で焼戻処理前の履歴を与え、さらに
表3に示す条件で焼戻処理を施した。焼戻保定時間は1
分以内とした。この供試材より試験片を採取して引張試
験およびSSC試験を行った。SSC特性は、t3.0
×10×65mmサイズの短冊状試験片に4点支持法によ
り降伏強度の100%となる曲げ応力を加えた状態で、
H2 Sを分圧0.3atm で飽和させた0.5%酢酸の溶
液中に常温で浸漬して割れ有無を求めることにより評価
した。Embodiments of the present invention will be described below. The test was conducted using the steels shown in Table 1. A seamless steel tube is rolled using a press roll piercing-elongator rolling method using a rectangular cross-section bloom as a raw material, and a steel pipe cooled to room temperature is used as a raw material to give a history before tempering under the conditions shown in Table 2, and further shown in Table 3. A tempering process was performed under the conditions. Temporary retention time is 1
Within minutes A test piece was sampled from this test material and subjected to a tensile test and an SSC test. SSC characteristic is t3.0
In a state in which a bending stress of 100% of the yield strength is applied to a strip-shaped test piece of a size of × 10 × 65 mm by a four-point supporting method,
It was evaluated by immersing H 2 S in a 0.5% acetic acid solution saturated with a partial pressure of 0.3 atm at room temperature and determining the presence or absence of cracks.
【0019】両試験の結果を表3に併せて示す。表3に
おいて、本発明No.1〜13は高いYRが得られ優れた
耐SSC性を示す。一方、比較例について言えば、No.
22,23は供試材の化学成分が本発明の範囲を外れる
ため耐SSC性は不十分であり、No.15,17,1
8,19,20,21,22は昇温速度が本発明の範囲
を外れるため十分な耐SSC性が得られない。また、N
o.14は焼戻温度がAc1 を超えるため耐SSC性は
不十分であり、No.16,23は、昇温速度、焼戻温度
共に本発明の範囲を外れ耐SSC性が劣化する。The results of both tests are also shown in Table 3. In Table 3, the present invention No. 1 to 13 have high YR and show excellent SSC resistance. On the other hand, regarding comparative examples, No.
Nos. 22 and 23 have insufficient SSC resistance because the chemical composition of the sample material is out of the range of the present invention. 15, 17, 1
No. 8,19,20,21,22 cannot obtain sufficient SSC resistance because the heating rate is out of the range of the present invention. Also, N
o. No. 14 has an insufficient SSC resistance because the tempering temperature exceeds Ac 1 , and No. 14 In Nos. 16 and 23, both the heating rate and the tempering temperature are out of the range of the present invention, and the SSC resistance deteriorates.
【0020】[0020]
【表1】 [Table 1]
【0021】[0021]
【表2】 [Table 2]
【0022】[0022]
【表3】 [Table 3]
【0023】[0023]
【発明の効果】以上のように、本発明によれば、耐SS
C性に優れたマルテンサイト系ステンレス鋼油井管を得
ることが可能となる。As described above, according to the present invention, SS resistance
It is possible to obtain a martensitic stainless steel oil country tubular good having excellent C property.
【図1】昇温速度とAc1 変態点の関係を示す。FIG. 1 shows the relationship between the temperature rising rate and the Ac 1 transformation point.
【図2】焼戻の昇温速度と耐SSC性の関係を示す。な
お、プロット横数値は表3におけるNo.を意味する。FIG. 2 shows the relationship between the temperature rising rate of tempering and SSC resistance. The plot lateral values are shown in Table 3. Means
【図3】本発明の対象となる焼戻前の熱履歴の概要を示
す。FIG. 3 shows an outline of a thermal history before tempering which is a target of the present invention.
R :圧延まま R−N :圧延まま材をAc3 点以上に再加熱して常
温まで冷却 R−L :圧延まま材をAc1 〜Ac3 点の温度域に
再加熱して常温まで冷却 R−N−L:R−N材をAc1 〜Ac3 点の温度域に再
加熱して常温まで冷却R: As-rolled RN: As-rolled material is reheated to Ac 3 points or higher and cooled to room temperature RL: As-rolled material is reheated to Ac 1 to Ac 3 points temperature range and cooled to room temperature R -N-L: cooling the R-N material to room temperature and re-heated to a temperature range of Ac 1 to Ac 3 point
Claims (6)
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A
c1 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ことを特徴とするマル
テンサイト系ステンレス継目無鋼管の製造方法。1. 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 0.10. , And the balance is Fe and unavoidable impurities, and a martensitic stainless steel having a composition consisting of inevitable impurities is cooled to a temperature not higher than the Ms point after hot working, and then 550 ° C. or higher A
Martensite, characterized in that a temperature T of c 1 or lower is subjected to a heat treatment in which the temperature is raised to an average heating rate of 500 to T ° C. of 1.0 ° C./sec or higher and then cooled to a temperature of the Ms point or lower. Of stainless steel seamless steel pipe.
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A
c1 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ことを特徴とするマル
テンサイト系ステンレス継目無鋼管の製造方法。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 0.10. , Ca: 0.001 to 0.020, with the balance being Fe and inevitable impurities, the martensitic stainless steel is cooled to a temperature not higher than the Ms point after hot working, and then 550 ° C. or higher. A
Martensite, characterized in that a temperature T of c 1 or lower is subjected to a heat treatment in which the temperature is raised to an average heating rate of 500 to T ° C. of 1.0 ° C./sec or higher and then cooled to a temperature of the Ms point or lower. Of stainless steel seamless steel pipe.
却し、その後Ac3点以上の温度に再加熱した後Ms点
以下の温度まで冷却し、さらに550℃以上Ac1 以下
の温度Tに、500〜T℃の平均加熱速度が1.0℃/s
ec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ことを特徴とする請求項1または
請求項2に記載のマルテンサイト系ステンレス継目無鋼
管の製造方法。3. After hot working, the material is cooled to a temperature below the Ms point, then reheated to a temperature above the Ac 3 point and then cooled to a temperature below the Ms point, and further to a temperature T above 550 ° C. and below Ac 1. In addition, the average heating rate from 500 to T ° C is 1.0 ° C / s.
The method for producing a martensitic stainless seamless steel pipe according to claim 1 or 2, wherein the heat treatment is performed such that the temperature is raised to ec or higher and then cooled to a temperature equal to or lower than the Ms point.
却し、その後Ac1点以上Ac3 点以下の温度に再加熱
した後Ms点以下の温度まで冷却し、さらに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ことを特徴とする請
求項1または請求項2に記載のマルテンサイト系ステン
レス継目無鋼管の製造方法。4. After hot working, it is cooled to a temperature below the Ms point, then reheated to a temperature below the Ac 1 point and below the Ac 3 point, then cooled to a temperature below the Ms point, and further above 550 ° C. to Ac 1 The temperature T below is subjected to a heat treatment in which the temperature is raised to an average heating rate of 500 to T ° C. of 1.0 ° C./sec or more and then cooled to a temperature below the Ms point. The method for producing a martensitic stainless seamless steel pipe according to claim 2.
却し、その後Ac3点以上の温度に再加熱した後Ms点
以下の温度まで冷却し、引き続きAc1 点以上Ac3 点
以下の温度に再加熱した後Ms点以下の温度まで冷却
し、さらに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
すことを特徴とする請求項1または請求項2に記載のマ
ルテンサイト系ステンレス継目無鋼管の製造方法。5. After hot working, it is cooled to a temperature of Ms point or lower, then reheated to a temperature of Ac 3 point or higher and then cooled to a temperature of Ms point or lower, and subsequently to a temperature of Ac 1 point or higher and Ac 3 point or lower. After being reheated to a temperature, it is cooled to a temperature not higher than the Ms point, and further heated to a temperature T of 550 ° C. or higher and Ac 1 or lower, 500
3. The martense according to claim 1 or 2, wherein the heat treatment is performed such that the temperature is raised to an average heating rate of 1.0 to T ° C or more to 1.0 ° C / sec or more and then cooled to a temperature equal to or lower than the Ms point. Site-based stainless steel seamless steel pipe manufacturing method.
強度の比が0.77以上であることを特徴とする請求項
1,2,3,4または5のそれぞれに記載のマルテンサ
イト系ステンレス継目無鋼管の製造方法。6. The martensite system according to claim 1, wherein the yield strength and the tensile strength of the heat-treated steel pipe material are 0.77 or more. Manufacturing method of stainless steel seamless steel pipe.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP32774595A JP4010017B2 (en) | 1995-12-15 | 1995-12-15 | Method for producing martensitic stainless steel pipe with excellent SSC resistance |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP32774595A JP4010017B2 (en) | 1995-12-15 | 1995-12-15 | Method for producing martensitic stainless steel pipe with excellent SSC resistance |
Publications (2)
Publication Number | Publication Date |
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JPH09170019A true JPH09170019A (en) | 1997-06-30 |
JP4010017B2 JP4010017B2 (en) | 2007-11-21 |
Family
ID=18202513
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JP32774595A Expired - Lifetime JP4010017B2 (en) | 1995-12-15 | 1995-12-15 | Method for producing martensitic stainless steel pipe with excellent SSC resistance |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2010014269A1 (en) * | 2008-07-28 | 2010-02-04 | Ati Properties, Inc. | Thermal mechanical treatment of ferrous alloys, and related alloys and articles |
JP2012149317A (en) * | 2011-01-20 | 2012-08-09 | Jfe Steel Corp | High strength martensitic stainless steel seamless pipe for oil well |
-
1995
- 1995-12-15 JP JP32774595A patent/JP4010017B2/en not_active Expired - Lifetime
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2010014269A1 (en) * | 2008-07-28 | 2010-02-04 | Ati Properties, Inc. | Thermal mechanical treatment of ferrous alloys, and related alloys and articles |
US7931758B2 (en) | 2008-07-28 | 2011-04-26 | Ati Properties, Inc. | Thermal mechanical treatment of ferrous alloys, and related alloys and articles |
US8313592B2 (en) | 2008-07-28 | 2012-11-20 | Ati Properties, Inc. | Thermal mechanical treatment of martensitic stainless steel |
JP2012149317A (en) * | 2011-01-20 | 2012-08-09 | Jfe Steel Corp | High strength martensitic stainless steel seamless pipe for oil well |
Also Published As
Publication number | Publication date |
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JP4010017B2 (en) | 2007-11-21 |
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