JPH0925518A - Production of seamless steel tube with high strength and high corrosion resistance - Google Patents
Production of seamless steel tube with high strength and high corrosion resistanceInfo
- Publication number
- JPH0925518A JPH0925518A JP17187295A JP17187295A JPH0925518A JP H0925518 A JPH0925518 A JP H0925518A JP 17187295 A JP17187295 A JP 17187295A JP 17187295 A JP17187295 A JP 17187295A JP H0925518 A JPH0925518 A JP H0925518A
- Authority
- JP
- Japan
- Prior art keywords
- rolling
- tempering
- quenching
- stress cracking
- sulfide stress
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
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- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、組成上の改良を施した
鋼に補熱を伴う直接焼入れ法を適用することにより、強
度、靭性および耐硫化物応力割れ性の全てに優れた性能
を備えた継目無鋼管を製造する方法に関するものであ
る。BACKGROUND OF THE INVENTION The present invention applies the direct quenching method with supplementary heat to a steel having a compositional improvement to obtain excellent performance in all of strength, toughness and sulfide stress cracking resistance. The present invention relates to a method for producing a provided seamless steel pipe.
【０００２】[0002]
【従来の技術】継目無鋼管の熱間加工は、ビレットをピ
アサ−で穿孔した後、プラグミル、またはマンドレルミ
ルで展伸し、その後サイザ−、またはレデュ−サ−等に
て仕上げ加工を施すことによっておこなわれる。穿孔に
プレスが用いられる場合もある。その後、鋼管は再加熱
され焼入れ焼戻しを施され、必要な強度、靭性および耐
硫化物応力割れ性を付与された後、使用者に提供され
る。この焼入れを直接焼入れに置き換えることができれ
ば、製造コストを下げることができる。ここで直接焼入
れとは、圧延後、圧延ライン上で、Ａｒ3 点以上のオ−
ステナイト状態から焼入れることによってマルテンサイ
トやベイナイトからなる硬化組織を得る焼入れ方法をい
う。2. Description of the Related Art In the hot working of a seamless steel pipe, a billet is pierced by a piercer, expanded by a plug mill or a mandrel mill, and then finished by a sizer or a reducer. It is done by. A press may be used for drilling. The steel pipe is then reheated, quenched and tempered to provide the required strength, toughness and resistance to sulfide stress cracking before being provided to the user. If this quenching can be directly replaced by quenching, the manufacturing cost can be reduced. Here, direct quenching means that after rolling, on the rolling line, an Ar point of 3 or more is applied.
It is a quenching method for obtaining a hardened structure composed of martensite and bainite by quenching from a stenite state.
【０００３】直接焼入れ法は従来の焼入れ法に比べて、
製品の結晶粒を粗大にする場合が多い。粗大な結晶粒で
は、継目無鋼管で最も重要視される靭性および耐硫化物
応力割れ性が劣るので、直接焼入れ法は高強度高耐食継
目無鋼管の製造法には採用することができない。Compared with the conventional quenching method, the direct quenching method is
In many cases, the crystal grains of the product are coarsened. Since coarse crystal grains are inferior in toughness and sulfide stress cracking resistance, which are most important in seamless steel pipes, the direct quenching method cannot be used in the production method of high strength and high corrosion resistance seamless steel pipes.
【０００４】直接焼入れ法の採用に伴う鋼管の性能劣化
を防止する改良方法はこれまでにも数多く提案されてき
た。A number of improved methods for preventing the performance deterioration of the steel pipe due to the adoption of the direct quenching method have been proposed so far.
【０００５】その一つに、圧延中または圧延を終了した
製造ライン上の鋼管に、冷却と再加熱の熱サイクルを付
与して結晶粒の微細化をはかる提案がある。例えば、粗
圧延と仕上げ圧延の中間に、冷却と再加熱のプロセスを
組み込む方法を開示する特開昭５６−３６２６号公報
や、最終仕上げ圧延後に冷却と再加熱を組み合わせた方
法を開示する特開平４−３５８０２３号公報がある。さ
らに、特開昭５８−１１７８３２号公報に記載されるよ
うに圧延途中および圧延後の２回、冷却および再加熱す
ることによって結晶粒を微細化する方法が提案されてい
る。しかしながら、製造ライン上での強制冷却と迅速な
加熱は、エネルギ−消費が著しく大きくかつ高価な大型
設備を必要とする。このため、オフラインの焼入れ設備
と比較して、それほど大きな設備コストや運転コストの
削減効果は得られない。従ってこれらの提案は、本発明
の目的とする、安価な設備により、高い生産性で、性能
の優れた鋼管を製造するという思想とは遠く隔たったも
のである。As one of them, there is a proposal for refining crystal grains by applying a thermal cycle of cooling and reheating to a steel pipe on a manufacturing line during or after rolling. For example, Japanese Laid-Open Patent Publication No. 56-3626 discloses a method of incorporating a cooling and reheating process between rough rolling and finish rolling, and Japanese Patent Laid-Open Publication No. H06-26326 discloses a method of combining cooling and reheating after final finishing rolling. There is a publication of 4-358023. Further, as described in JP-A-58-117832, a method of refining crystal grains by cooling and reheating during rolling and twice after rolling has been proposed. However, forced cooling and rapid heating on the production line require large equipment, which consumes a lot of energy and is expensive. Therefore, compared to the off-line quenching equipment, the effect of reducing the equipment cost and the operating cost is not so large. Therefore, these proposals are far from the idea of manufacturing a steel pipe with high productivity and excellent performance by using inexpensive equipment, which is the object of the present invention.
【０００６】これら以外に結晶粒を微細化する工夫とし
て、厚鋼板の直接焼入れ法において、未再結晶域で圧延
加工を行い、自然放冷中に再結晶をさせ、微細な結晶粒
とした後に直接焼入れするという方法が提案されてい
る。特開昭６４−５５３３５号公報等に、この方法が示
されている。ここでは未再結晶域での圧延の定義はなさ
れていない。以下の説明において未再結晶域圧延とは、
圧延加工によって導入された転位密度の１／２以上が約
１５秒間残っている温度域での圧延をいうものとする。
このような圧延は鋼板のように未再結晶温度域すなわち
比較的低温での大圧下圧延が可能な場合には有効な方法
である。しかしこれら鋼板の圧延方法を複雑な鋼管の圧
延に適用することは通常の継目無鋼管の圧延設備では不
可能である。例えば、マンドレルミルによる圧延を未再
結晶温度域である１０００℃以下で実施した場合、ミル
の圧延能力を超えるか、もしくは表面疵や欠陥が発生す
るか、またはマンドレルバ−の引き抜きが著しく困難に
なるといった問題が直ちに発生する。したがって、実用
的にはこのような圧延は不可能である。In addition to these, as a device for refining crystal grains, in the direct quenching method for thick steel plates, rolling is performed in the non-recrystallized region, recrystallization is performed during spontaneous cooling, and fine crystal grains are formed. A method of directly quenching has been proposed. This method is disclosed in JP-A-64-55335. Here, the definition of rolling in the non-recrystallized region is not made. In the following description, the unrecrystallized region rolling,
It means rolling in a temperature range in which ½ or more of the dislocation density introduced by rolling remains for about 15 seconds.
Such rolling is an effective method when large reduction rolling can be performed in a non-recrystallization temperature range, that is, a relatively low temperature, like a steel sheet. However, it is not possible to apply the rolling method for these steel sheets to the rolling of complicated steel pipes with a normal rolling mill for seamless steel pipes. For example, when rolling with a mandrel mill is carried out at a temperature of 1000 ° C. or less, which is a non-recrystallization temperature range, the rolling capability of the mill is exceeded, surface defects or defects occur, or it becomes extremely difficult to pull out the mandrel bar. Such problems occur immediately. Therefore, such rolling is practically impossible.
【０００７】特開昭６１−２３８９１７号公報に、継目
無鋼管の製造法において製管後の再結晶を利用して結晶
粒の微細化を図る技術が開示されている。しかし、ここ
では熱間加工条件によって継目無鋼管の靭性改善を行う
ことは実用的でないとして、熱間加工条件が全く特定さ
れていない。このような方法を実際のミルラインに適用
して再結晶温度域で圧延を終了した場合、粒成長を促進
してかえって粗粒となる可能性が大きい。Japanese Unexamined Patent Publication No. 61-238917 discloses a technique for refining crystal grains by utilizing recrystallization after pipe production in a method for producing a seamless steel pipe. However, here, it is not practical to improve the toughness of the seamless steel pipe by the hot working condition, and the hot working condition is not specified at all. When such a method is applied to an actual mill line and rolling is completed in the recrystallization temperature range, there is a high possibility that grain growth will be promoted and rather coarse grains will be formed.
【０００８】耐硫化物応力割れ性を改良するために、組
織と耐硫化物割れ性との関係についても膨大な研究がな
されてきた。耐硫化物応力割れ性の向上には焼戻マルテ
ンサイトからなる組織が利くことおよび細粒組織が望ま
しいことは、周知の事実である。それ以外に特開昭６３
−９３８２２号公報にはベイナイト組織とすることによ
って性能向上を図る方法、および特開昭６２−３０８４
９号公報には圧延加工により展伸した形状の粒により改
善する方法が示されている。細粒組織とする熱処理方法
としては、特開昭６１−９５１９号公報には誘導加熱等
の急速加熱を適用する方法、また特開昭５９−２３２２
２０号公報には鋼を２回焼入れする方法が開示されてい
る。これらの方法は効果は認められるものの、従来のオ
フラインでの焼入れ処理と同等の再加熱をおこなう処理
であるので、製造コストの低減をもたらさない。In order to improve the resistance to sulfide stress cracking, a great deal of research has been conducted on the relationship between the structure and the resistance to sulfide cracking. It is a well-known fact that a structure composed of tempered martensite and a fine grain structure are desirable for improving sulfide stress cracking resistance. Other than that, JP-A-63
No. 93822 discloses a method for improving performance by forming a bainite structure, and JP-A-62-3084.
No. 9 discloses a method of improving by the grain of the shape expanded by rolling. As a heat treatment method for forming a fine grain structure, JP-A 61-9519 discloses a method of applying rapid heating such as induction heating, and JP-A-59-2322.
Japanese Patent Publication No. 20 discloses a method of quenching steel twice. Although these methods are effective, they do not reduce the manufacturing cost because they are reheating processes equivalent to the conventional offline quenching process.
【０００９】耐硫化物応力割れ性を向上する技術には、
前記の結晶粒および組織を改良する方法の他に、その理
由は完全に明らかにされていないが化学組成の最適範囲
を選択する方法がある。特開昭６２−２５３７２０号公
報にはＳｉ、ＭｎおよびＰ量等の化学組成と同時に降伏
応力を制限する方法が、特開昭６３−２７４７１７号公
報には高炭素鋼を選定する方法が、また特開昭６３−２
３８２４２号公報にはＺｒを添加する方法が示されてい
る。Techniques for improving sulfide stress crack resistance include:
In addition to the above-mentioned method of improving the grain and structure, there is a method of selecting the optimum range of the chemical composition, although the reason is not completely clear. Japanese Unexamined Patent Publication (Kokai) No. 62-253720 discloses a method of limiting yield stress at the same time as chemical compositions such as Si, Mn and P contents, and Japanese Unexamined Patent Publication (Kokai) No. 63-274717 discloses a method of selecting high carbon steel. JP-A-63-2
Japanese Patent No. 38242 discloses a method of adding Zr.
【００１０】ＷはＭｏと同族の元素であり、化学的性質
が類似しているので、これまでにもＭｏに複合添加する
合金元素として使用されてきた。例えば、直接焼入れ焼
戻し鋼において不純物の粒界偏析を抑制して耐硫化物応
力割れ性を向上させるのにＭｏ＋１／２Ｗで０．０５〜
０．８０％を含有させる方法が特開昭６０−５２５２０
号公報に提案されている。しかし、これらはいずれも従
来の直接焼入れ法を前提にしたものである。本発明のよ
うに改良した直接焼入れ法に適用したものではないの
で、本発明が対象とする高強度レベルの鋼の耐硫化物応
力割れを抑制することは不可能であった。W is an element of the same group as Mo and has similar chemical properties, so that it has been used as an alloying element to be added to Mo in a complex manner. For example, in the case of direct quenching and tempering steel, in order to suppress the grain boundary segregation of impurities and improve the sulfide stress cracking resistance, Mo + 1 / 2W is 0.05 to 0.05-
A method of containing 0.80% is disclosed in JP-A-60-52520.
No. 1993. However, these are all based on the conventional direct quenching method. Since it was not applied to the improved direct quenching method as in the present invention, it was impossible to suppress the sulfide stress cracking resistance of high strength steel targeted by the present invention.
【００１１】[0011]
【発明が解決しようとする課題】本発明の目的は、直接
焼入れ法に改良を施すことおよびそれに組成上の改善を
組み合わせることによって前記の粗大組織を克服し、従
来法では不可能とされていた高性能の高強度継目無鋼管
を安価に製造する方法を提供することにある。具体的に
は、ＡＰＩ規格Ｃ１２５級（ＹＳ＝１２５〜１４０ｋｓ
ｉ (87.9〜98.4kgf/mm2 ) ）の強度レベルで、割れ発生
下限界応力σth：１００ｋｓｉ以上（１００ｋｓｉはＣ
１２５級のＳＭＹＳ（規格最小降伏応力）の８０％に対
応）の耐硫化物応力割れ性を有する高強度継目無鋼管を
安価に大量生産する方法を提供することにある。SUMMARY OF THE INVENTION The object of the present invention is to overcome the above-mentioned coarse structure by improving the direct quenching method and by combining it with the compositional improvement, which has been made impossible by the conventional methods. An object of the present invention is to provide a method for inexpensively manufacturing a high-performance, high-strength seamless steel pipe. Specifically, API standard C125 grade (YS = 125-140ks
i (87.9-98.4 kgf / mm 2 )) at a strength level of crack initiation lower limit stress σ th : 100 ksi or more (100 ksi is C
It is an object of the present invention to provide a method for inexpensively mass-producing a high-strength seamless steel pipe having sulfide stress cracking resistance of 125 grade SMYS (corresponding to 80% of standard minimum yield stress).
【００１２】[0012]
【課題を解決するための手段】本発明者らは、前記した
問題を改善するために研究を重ねた結果、下記の改良を
施した直接焼入れ法を、下記の組成を有する鋼に適用す
ることにより靭性と耐硫化物応力割れ性の著しい向上が
得られることを確認した。DISCLOSURE OF THE INVENTION As a result of repeated studies to improve the above-mentioned problems, the inventors of the present invention have applied the following direct quenching method to steel having the following composition. It was confirmed that the toughness and the sulfide stress cracking resistance were remarkably improved.
【００１３】最終圧延を行う仕上げ圧延機において４
０％以上の加工を８００〜１０５０℃でおこなった後
に、８５０〜１１００℃で１０秒〜３０分間補熱する
と、その間に再結晶を生じ、オ−ステナイト結晶粒が著
しく細粒になる。本明細書において圧延後、直接焼入れ
するまでの間、再結晶を進行させるためにオンライン中
に加熱することを「補熱」という。4 in the finishing mill for the final rolling
When 0% or more processing is performed at 800 to 1050 ° C. and then supplementary heating is performed at 850 to 1100 ° C. for 10 seconds to 30 minutes, recrystallization occurs during that time, and the austenite crystal grains become remarkably fine grains. In the present specification, heating during on-line in order to promote recrystallization after rolling until direct quenching is referred to as “supplementary heat”.
【００１４】この細粒は単に補熱のみをおこなっただ
けでは得られず、鋼が微量のＮｂまたはＴｉを含有する
場合にのみ得られる。前記したように鋼管の圧延は厚鋼
板のように１パスあたりの圧下を大きくとることができ
ない。そのため再結晶温度域である高温で大きな圧下を
加えなければならない。これらの加工歪は直ちに再結晶
により消失してしまい、結晶粒の微細化に有効に働かな
い。 (a)加工歪が蓄積した状態で、 (b)低温で再結晶し
た場合にのみ細粒が得られる。しかし、鋼管の圧延設備
では低温での圧下を大きくとり加工歪を累積しにくい。
しかし微量のＮｂもしくはＴｉを含有すれば高温での再
結晶が抑制されるので、加工歪を部分的であるが累積し
て蓄積することができる。この加工歪が補熱中に再結晶
の駆動力として働くので補熱温度を低く設定して、一定
時間かければ、微細な再結晶粒を得ることが可能とな
る。補熱がなく、微量のＮｂもしくはＴｉのみが含まれ
ている場合には、低温では再結晶が生じにくいので未再
結晶のまま変態することになる。未再結晶オ−ステナイ
トからの変態組織では耐硫化物応力割れ性は優れたもの
が得られない。加工歪を蓄積した状態で低温域に補熱さ
れ再結晶することにより、はじめて微細なオ−ステナイ
ト粒が得られるのである。The fine grains cannot be obtained only by supplementing heat, but only when the steel contains a trace amount of Nb or Ti. As described above, the rolling of the steel pipe cannot take a large reduction per pass unlike the thick steel plate. Therefore, a large reduction must be applied at a high temperature which is a recrystallization temperature range. These processing strains are immediately lost by recrystallization and do not work effectively for refining the crystal grains. Fine grains are obtained only when (a) processing strain is accumulated and (b) recrystallized at a low temperature. However, in rolling equipment for steel pipes, it is difficult to accumulate processing strain by taking large reduction at low temperatures.
However, if a small amount of Nb or Ti is contained, recrystallization at a high temperature is suppressed, so that the processing strain can be partially accumulated but accumulated. Since this processing strain acts as a driving force for recrystallization during supplementary heat, it is possible to obtain fine recrystallized grains if the supplementary heat temperature is set low and a certain period of time elapses. When there is no supplementary heat and only a small amount of Nb or Ti is contained, recrystallization is difficult to occur at low temperatures, so that transformation occurs without recrystallization. With the transformation structure from unrecrystallized austenite, excellent sulfide stress cracking resistance cannot be obtained. Fine austenite grains can be obtained for the first time by supplementing heat in the low temperature range and recrystallizing in the state where the working strain is accumulated.
【００１５】しかしながら、上記の方法による細粒化
は、そのままでは耐硫化物応力割れの向上には結びつか
ない。耐硫化物応力割れ性の向上には、当面の実用化目
標である前記のＣ１２５級の高強度鋼においても６００
℃以上の高温焼戻しが不可欠である。しかし、高温焼戻
しによる強度低下をＭｏ含有量の増加のみで保証しよう
とするとＭｏ含有量が増えすぎ、粗大な針状Ｍｏ炭化物
が析出するため、前記の方法によって細粒化しても、耐
硫化物応力割れ性は劣化してしまうのである。ＷはＭｏ
と同様な効果をもつので、Ｍｏ含有量を１．５％以下に
抑制してＷをＭｏとともに複合添加して高温焼戻しを保
証することにより前記の方法による細粒化の効果が生か
せ、高レベルの耐硫化物応力割れ性を得ることができ
る。However, the grain refining by the above method does not directly lead to the improvement of sulfide stress cracking resistance. In order to improve the resistance to sulfide stress cracking, 600 is also applied to the above-mentioned C125-grade high-strength steel, which is a target for practical use for the time being.
High temperature tempering above ℃ is indispensable. However, if it is attempted to guarantee the strength reduction due to high temperature tempering only by increasing the Mo content, the Mo content will increase too much, and coarse needle-like Mo carbide will precipitate. The stress cracking property deteriorates. W is Mo
Since it has the same effect as the above, by suppressing the Mo content to 1.5% or less and adding W together with Mo to ensure high temperature tempering, the effect of grain refining by the above method can be utilized, and a high level is achieved. The sulfide stress cracking resistance can be obtained.
【００１６】直接焼入れした鋼管をさらに再焼入れ、
もしくは２回焼入れ処理を行うことによって、直接焼入
れままよりもさらに細粒化が可能である。これは従来の
粗大な結晶粒となる直接焼入れ法の組織を改良する再焼
入れと異なり、前記の細粒組織をもたらす直接焼入れ法
に加える再焼入れなので、結晶粒はより微細化し、その
効果の到達レベルは一層高いものとなる。Further quenching the steel tube directly quenched,
Alternatively, by performing the quenching treatment twice, it is possible to make the particles finer than when directly quenching. This is different from the re-quenching that improves the structure of the conventional direct quenching method that produces coarse crystal grains, because it is the re-quenching that is added to the direct quenching method that produces the above-mentioned fine grain structure, the crystal grains become finer, and the effect is reached. The level will be higher.
【００１７】ここに本発明は、これらの結果に基づき、
以下に示す高強度高耐食性継目無鋼管の製造方法を要旨
とする。The present invention is based on these results.
The gist of the method for producing a high-strength, high-corrosion-resistant seamless steel pipe is as follows.
【００１８】（１）重量％で、Ｃ：０．１５〜０．５０
％、Ｓｉ：０．１〜１．５％、Ｍｎ：０．１〜１．５
％、Ｐ：０．０５％以下、Ｓ：０．０１％以下、Ｃｒ：
０．１〜１．５％、Ｎｉ：０．１％以下、 Ｍｏ：０．
１〜１．５％、Ｗ：０．１〜２．０％、sol Ａｌ：０．
００５〜０．５０％、Ｔｉ：０．００５〜０．５０％、
Ｎｂ：０．００５〜０．５０％、Ｖ：０〜０．５％、Ｚ
ｒ：０〜０．５％、Ｂ：０．０００１〜０．０１０％、
Ｃａ：０〜０．０１％、Ｎ：０．０１％以下およびＯ：
０．０１％以下を含み他はＦｅおよび不可避的不純物か
らなる組成を有するビレットを、熱間で穿孔し圧延する
際、最終圧延において断面圧縮率４０％以上の加工を８
００〜１１００℃にて施した後、８５０〜１１００℃に
１０秒〜３０分間加熱しそのまま焼入れをおこない、そ
の後に焼戻しすることを特徴とする高強度高耐食継目無
鋼管の製造方法。(1) C: 0.15 to 0.50 in% by weight
%, Si: 0.1 to 1.5%, Mn: 0.1 to 1.5
%, P: 0.05% or less, S: 0.01% or less, Cr:
0.1 to 1.5%, Ni: 0.1% or less, Mo: 0.
1 to 1.5%, W: 0.1 to 2.0%, sol Al: 0.
005 to 0.50%, Ti: 0.005 to 0.50%,
Nb: 0.005 to 0.50%, V: 0 to 0.5%, Z
r: 0 to 0.5%, B: 0.0001 to 0.010%,
Ca: 0 to 0.01%, N: 0.01% or less and O:
When a billet having a composition of 0.01% or less and Fe and unavoidable impurities other than the above is hot-pierced and rolled, in the final rolling, processing with a sectional compression rate of 40% or more is performed.
A method for producing a high-strength, highly corrosion-resistant seamless steel pipe, which comprises performing heating at 850 to 1100 ° C., heating at 850 to 1100 ° C. for 10 seconds to 30 minutes, quenching as it is, and then tempering.
【００１９】（２）上記（１）に記載の製造方法におい
て、焼入れと焼戻しの間に再焼入れを１回もしくは２回
おこなうことを特徴とする高強度高耐食継目無鋼管の製
造方法。(2) A method for producing a high-strength, highly corrosion-resistant seamless steel pipe, characterized in that in the production method described in (1) above, re-quenching is performed once or twice between quenching and tempering.
【００２０】[0020]
【作用】以下にビレットの化学組成およびそれを素材と
する鋼管の製造条件の限定理由について説明する。FUNCTION The reasons for limiting the chemical composition of the billet and the manufacturing conditions of the steel pipe using the same will be described below.
【００２１】１．ビレットの化学組成 Ｃ：０．１５〜０．５０％ Ｃは焼入れ性を高め、強度を向上させるために必要な元
素である。０．１５％未満では焼入れ性が不足して高強
度が得られない。０．５０％を超えると焼き割れや遅れ
破壊が起こり易くなり継目無鋼管の製造が困難になるの
で、０．１５〜０．５０％とした。1. Billet Chemical Composition C: 0.15 to 0.50% C is an element necessary to enhance hardenability and strength. If it is less than 0.15%, the hardenability is insufficient and high strength cannot be obtained. If it exceeds 0.50%, quench cracking and delayed fracture are likely to occur, making it difficult to manufacture a seamless steel pipe, so the content was made 0.15 to 0.50%.
【００２２】Ｓｉ：０．１０〜１．５％ Ｓｉは鋼の脱酸に必要であり、焼戻し軟化抵抗を高め耐
硫化物応力割れ性を向上させる元素であるが、過剰に含
有すると鋼を脆化させる。脱酸と耐硫化物応力割れ性の
向上の目的からは０．１０％以上が必要であるが、１．
５％を超えると靭性が低下するので、０．１０〜１．５
％とした。Si: 0.10 to 1.5% Si is an element necessary for deoxidation of steel and increases tempering softening resistance and sulfide stress cracking resistance. Turn into For the purpose of deoxidation and improvement of sulfide stress cracking resistance, 0.10% or more is necessary.
If it exceeds 5%, the toughness decreases, so 0.10 to 1.5
%.
【００２３】Ｍｎ：０．１０〜１．５％ Ｍｎは鋼の脱酸のために必要である。脱酸の目的のため
には０．１０％以上が必要である。一方、添加量が１．
５％を超えると靭性および耐硫化物応力割れ性が低下す
るので、０．１０〜１．５％とした。Mn: 0.10 to 1.5% Mn is necessary for deoxidation of steel. For the purpose of deoxidation, 0.10% or more is necessary. On the other hand, the addition amount is 1.
If it exceeds 5%, the toughness and the resistance to sulfide stress cracking will deteriorate, so it was made 0.10 to 1.5%.
【００２４】Ｐ：０．０５％以下 Ｐは不純物として鋼中に不可避的に存在するが、０．０
５％を超えると、粒界に偏析して靭性および耐硫化物応
力割れ性を低下させるので、不純物として混入するとし
ても０．０５％以下にしなければならない。その含有量
は低ければ低いほど好ましい。P: 0.05% or less P is unavoidably present in steel as an impurity, but 0.0
If it exceeds 5%, it segregates at the grain boundaries to reduce toughness and sulfide stress cracking resistance, so even if it is mixed as an impurity, it must be 0.05% or less. The lower the content, the better.
【００２５】Ｓ：０．０１％以下 ＳもＰと同様不純物として鋼に混入し、０．０１％を超
えると粗大な介在物を生成して靭性および耐硫化物応力
割れ性を低下させるので、０．０１％以下とした。その
含有量は低いほど好ましい。S: 0.01% or less S, like P, is mixed in the steel as an impurity, and if it exceeds 0.01%, coarse inclusions are formed to reduce toughness and sulfide stress cracking resistance. It was set to 0.01% or less. The lower the content, the better.
【００２６】Ｃｒ：０．１〜１．５％ Ｃｒは焼入れ性を確保し、強度を向上させるとともに耐
硫化物応力割れ性を向上させる。０．１％未満ではその
効果が得られず、１．５％を超えると靭性および耐硫化
物応力割れ性がかえって低下するので、０．１〜１．５
％とした。Cr: 0.1 to 1.5% Cr secures hardenability, improves strength, and improves resistance to sulfide stress cracking. If it is less than 0.1%, the effect cannot be obtained, and if it exceeds 1.5%, the toughness and sulfide stress cracking resistance are rather deteriorated.
%.
【００２７】Ｎｉ：０．１％以下 Ｎｉは耐硫化物応力割れ性を低下するので、０．１％以
下に制限する。Ni: 0.1% or less Ni limits the sulfide stress cracking resistance, so it is limited to 0.1% or less.
【００２８】Ｍｏ：０．１〜１．５％ Ｍｏは焼入れ性を向上し高強度を確保するとともに、焼
戻軟化抵抗を高めて耐硫化物応力割れ性を向上する元素
である。０．１％未満ではその効果が十分でない。１．
５％を超えると針状のＭｏ炭化物を析出させて、耐硫化
物応力割れ性を劣化させ、前記の改善された直接焼入れ
法の効果を生かすことができない。そこでＭｏ含有量は
０．１〜１．５％とした。Mo: 0.1 to 1.5% Mo is an element that improves hardenability and secures high strength, and also increases temper softening resistance to improve sulfide stress cracking resistance. If it is less than 0.1%, the effect is not sufficient. 1.
If it exceeds 5%, needle-like Mo carbides are precipitated to deteriorate the sulfide stress cracking resistance, and the effect of the improved direct quenching method cannot be utilized. Therefore, the Mo content is set to 0.1 to 1.5%.
【００２９】Ｗ：０．１〜２％ Ｗは焼入れ性を向上し高強度を確保するとともに、焼戻
軟化抵抗を高めて耐硫化物応力割れ性を向上する元素で
ある。そこで耐硫化物応力割れ性を損なわない範囲にＭ
ｏ添加量をとどめ、焼戻軟化抵抗の向上にＷを利用する
ことができる。W: 0.1 to 2% W is an element that improves hardenability and secures high strength, and also increases temper softening resistance and sulfide stress cracking resistance. Therefore, in the range that does not impair sulfide stress cracking resistance, M
It is possible to use W to improve the temper softening resistance by limiting the addition amount of o.
【００３０】Ｗ原子はＭｏの約２倍の原子量なので拡散
速度が遅く、焼戻時に粗大な炭化物を形成し難いという
利点がある。このためＭｏの役割を分担させるべくＭｏ
と複合添加することにより、過剰Ｍｏ量とすることなく
高温焼戻しが可能となる。この結果、前記の改良された
直接焼入れ法による細粒化の効果をそのまま受けること
ができる。高温焼戻しにより同一強度を確保できた場
合、内部歪は減少しセメンタイト等の炭化物は球状化す
るので耐硫化物応力割れ性を高められる。０．１％未満
ではその効果が十分でなく、２％を超えると効果が飽和
するだけでなく、偏析を起こしかえって耐硫化物応力割
れ性を低下させるので、０．１〜２．０％とした。Since the W atom has an atomic weight about twice that of Mo, the diffusion rate is slow and there is an advantage that it is difficult to form a coarse carbide during tempering. Therefore, to share the role of Mo, Mo
By adding together with, it becomes possible to perform high temperature tempering without increasing the amount of Mo. As a result, the effect of grain refinement by the improved direct quenching method can be directly obtained. When the same strength can be secured by high temperature tempering, internal strain is reduced and carbides such as cementite are spheroidized, so that sulfide stress cracking resistance can be improved. If it is less than 0.1%, the effect is not sufficient, and if it exceeds 2%, the effect is not only saturated, but also segregation occurs and the sulfide stress cracking resistance is deteriorated. did.
【００３１】sol Ａｌ：０．００５〜０．５０％ Ａｌは鋼の脱酸に必要な元素である。sol Ａｌとして
０．００５％未満ではその効果が得られず、０．５０％
を超えると介在物が多くなって靭性が低下する。Sol Al: 0.005 to 0.50% Al is an element necessary for deoxidizing steel. If less than 0.005% as sol Al, the effect cannot be obtained, and 0.50%
If it exceeds, the inclusions increase and the toughness decreases.
【００３２】なお、油性管用継目無鋼管はその管端に接
続用のネジを切ることが多いが、Ａｌが多いとネジ切り
部に欠陥が発生し易くなる。以上の理由によりsol Ａｌ
の含有量は０．００５〜０．５０％とした。A seamless steel pipe for an oily pipe is often provided with a connecting screw at its pipe end. However, if a large amount of Al is contained, a defect is likely to occur in the threaded portion. Sol Al for the above reasons
Was 0.005 to 0.50%.
【００３３】Ｔｉ：０．００５〜０．５０％ Ｔｉは鋼中の不純物であるＮをＴｉＮとして固定する。
鋼中にＴｉが含まれていれば、直接焼入れする際、窒素
はＴｉＮとして固定されているので直接焼入れ時にＢは
ＢＮとして析出することはない。このためＢは焼入れ性
に有効な固溶状態で存在し、直接焼入れ時の焼入れ性を
向上する。ＮをＴｉＮとして固定する以上のＴｉは、未
再結晶温度域を高温まで拡げて高温での加工歪を部分的
に蓄積する作用を持つ。補熱温度を低温に設定し一定時
間かけると、微細な再結晶粒を得ることができる。一定
時間とは、後記するように、補熱温度を８５０〜１１０
０℃とした場合、１０秒〜３０分間である。また固溶状
態のＴｉは直接焼入れ後の焼戻し時に微細に析出して焼
戻し軟化抵抗を向上させるので、ＭｏおよびＷとともに
より高温での焼戻しを可能とする。０．００５％未満で
はその効果が小さく、０．５０％を超えると靭性を低下
させるので、０．００５〜０．５０％とした。Ti: 0.005 to 0.50% Ti fixes N which is an impurity in steel as TiN.
If Ti is contained in the steel, nitrogen is fixed as TiN during direct quenching, so B does not precipitate as BN during direct quenching. Therefore, B exists in a solid solution state effective for hardenability and improves hardenability during direct quenching. The above Ti that fixes N as TiN has the effect of expanding the non-recrystallization temperature region to high temperatures and partially accumulating processing strain at high temperatures. Fine recrystallized grains can be obtained by setting the supplementary heat temperature to a low temperature and applying it for a certain period of time. As will be described later, the fixed time means a supplementary heat temperature of 850 to 110.
When the temperature is 0 ° C., it is 10 seconds to 30 minutes. Further, since Ti in a solid solution state is finely precipitated during the tempering after the direct quenching and improves the tempering softening resistance, it is possible to temper at a higher temperature together with Mo and W. If it is less than 0.005%, the effect is small, and if it exceeds 0.50%, the toughness decreases, so the content was made 0.005 to 0.50%.
【００３４】Ｎｂ：０．００５〜０．５０％ Ｎｂは加工歪を蓄積する温度域を高温まで拡げることが
できるので、低い補熱温度で保持して微細な再結晶粒を
得るのに不可欠の元素である。その効果はＴｉよりも強
い。また固溶したまま直接焼入れされたＮｂはその後の
焼戻し時に微細に析出する。このためＭｏ、ＷおよびＴ
ｉとともに鋼の焼戻し軟化抵抗を増大させ耐硫化物応力
割れ性を向上させる。含有量が０．００５％未満ではそ
の効果が得られず、０．５０％を超えると靭性が低下す
るので、０．００５〜０．５０％とした。Nb: 0.005 to 0.50% Nb is capable of expanding the temperature range in which working strain is accumulated to a high temperature, so it is indispensable for keeping fine recrystallized grains by holding at a low supplementary heating temperature. It is an element. The effect is stronger than Ti. Further, Nb directly quenched as a solid solution is finely precipitated during the subsequent tempering. Therefore, Mo, W and T
Along with i, the temper softening resistance of steel is increased to improve sulfide stress cracking resistance. If the content is less than 0.005%, the effect cannot be obtained, and if it exceeds 0.50%, the toughness decreases, so the content was made 0.005 to 0.50%.
【００３５】Ｖ：０〜０．５％ Ｖも焼戻し時に微細な炭化物として析出して耐硫化物応
力割れ性を向上させる効果を有する。Ｎｂ含有材ではＶ
を添加しなくても十分な焼戻し軟化抵抗を有するが、Ｎ
ｂとともにＶを添加することで一層の耐硫化物応力割れ
性の向上を得ることができる。含有量が０．５％を超え
ると靭性が低下するので、０〜０．５％以下とした。V: 0 to 0.5% V also has the effect of precipitating as fine carbide during tempering and improving sulfide stress cracking resistance. V for Nb-containing materials
Has sufficient temper softening resistance without the addition of
By adding V together with b, further improvement in sulfide stress cracking resistance can be obtained. If the content exceeds 0.5%, the toughness decreases, so the content was made 0 to 0.5% or less.
【００３６】Ｚｒ：０〜０．５％ Ｚｒを含有すると引張試験時の降伏点伸びが増加し、結
果として耐硫化物応力割れ性が向上する。Ｚｒは高価な
元素でもあり添加しなくても十分な耐硫化物応力割れ性
を有するが、添加するとさらに耐硫化物応力割れ性を向
上させる。一方、０．５％を超えて含有すると介在物が
多くなって靭性が低下するので、０〜０．５％以下とし
た。Zr: 0 to 0.5% When Zr is contained, the yield point elongation in the tensile test is increased, and as a result, the sulfide stress cracking resistance is improved. Zr is an expensive element and has sufficient resistance to sulfide stress cracking even if it is not added. However, Zr further improves resistance to sulfide stress cracking. On the other hand, if the content exceeds 0.5%, the inclusions increase and the toughness decreases, so the content was made 0 to 0.5% or less.
【００３７】Ｂ：０．０００１〜０．０１０％ Ｂは微量で焼入れ性を向上させ、特に厚肉材の耐硫化物
応力割れ性を改善する。０．０００１％以下ではその効
果が得られず、０．０１０％を超えると、靭性および耐
硫化物応力割れ性が低下するので、０．０００１〜０．
０１０％とした。B: 0.0001 to 0.010% A small amount of B improves the hardenability, and particularly improves the sulfide stress cracking resistance of thick-walled materials. If it is 0.0001% or less, the effect cannot be obtained, and if it exceeds 0.010%, toughness and sulfide stress cracking resistance decrease, so 0.0001 to 0.
It was set to 010%.
【００３８】Ｃａ：０〜０．０１％ Ｃａは鋼中のＳと反応して硫化物を形成することによっ
て介在物の形状を改善し、耐硫化物応力割れ性を向上さ
せる。Ｓの含有量によってその効果の度合いが異なり、
また脱酸が十分でないとかえって耐硫化物応力割れ性が
低下することもある。したがって、添加するかしないか
を適宜選択できる元素である。添加する場合はその含有
量は０．０００１〜０．０１％とすることが好ましい。
０．０００１％未満では効果が現れないからであり、ま
た過剰の含有は靭性および耐硫化物応力割れ性を低下
し、鋼管表面に欠陥をもたらすので０．０１％以下とし
た。Ca: 0 to 0.01% Ca reacts with S in steel to form sulfides, thereby improving the shape of inclusions and improving sulfide stress cracking resistance. The degree of the effect depends on the content of S,
If the deoxidation is not sufficient, the resistance to sulfide stress cracking may decrease. Therefore, it is an element that can be appropriately selected whether to add or not. When it is added, its content is preferably 0.0001 to 0.01%.
This is because if the content is less than 0.0001%, the effect is not exhibited, and if the content is excessive, the toughness and the resistance to sulfide stress cracking are lowered and defects are caused on the surface of the steel pipe.
【００３９】Ｎ：０．０１％以下 Ｎは不純物として鋼に存在し、靭性および耐硫化物応力
割れ性を低下させるので０．０１％以下とした。０にす
ることはできないが、できるだけ少ないほうがよい。N: 0.01% or less N is present in steel as an impurity and reduces toughness and sulfide stress cracking resistance, so the content is made 0.01% or less. It cannot be set to 0, but it should be as small as possible.
【００４０】Ｏ（酸素）：０．０１％以下 酸素は不純物として鋼に存在し、靭性および耐硫化物応
力割れ性を低下させるので０．０１％以下とした。下限
は分析精度上ゼロとみなせるものまでを含む。O (oxygen): 0.01% or less Oxygen is present as an impurity in steel and reduces toughness and sulfide stress cracking resistance, so 0.01% or less. The lower limit includes those that can be regarded as zero in terms of analytical accuracy.
【００４１】２．製造条件 ビレット加熱条件：図１はビレット加熱から直接焼入れ
に至るまでの継目無鋼管の製造方法を示す図面である。
加熱温度は、図１に示すように、次に配置された穿孔機
２にて熱間穿孔できる温度であれば良い。最適温度は材
質によって異なり、高温延性と高温強度を考慮して決め
る。通常は１１００℃から１３００℃の間に加熱する。
加熱法はガス加熱炉または誘導加熱などいずれでもよ
い。しかし、酸化スケ−ルが厚くなると表面キズの原因
となるので無酸化雰囲気とすることが必要である。高能
率のビレット加熱を実現するためには、ビレット長さは
なるべく長尺とした方がよく、加熱炉１の出口に切断機
を設置して切断した後に穿孔機に導入してもよい。2. Manufacturing conditions Billet heating conditions: Fig. 1 is a drawing showing a method for manufacturing a seamless steel pipe from billet heating to direct quenching.
As shown in FIG. 1, the heating temperature may be a temperature at which hot punching can be performed by the punching machine 2 arranged next. The optimum temperature depends on the material, and is determined by taking hot ductility and high temperature strength into consideration. Usually, heating is performed between 1100 ° C and 1300 ° C.
The heating method may be either a gas heating furnace or induction heating. However, if the oxide scale becomes thick, it may cause surface scratches, so it is necessary to make the atmosphere non-oxidizing. In order to realize highly efficient billet heating, it is preferable that the billet length be as long as possible, and a cutting machine may be installed at the exit of the heating furnace 1 to cut the billet and then introduced into the punching machine.
【００４２】穿孔条件：穿孔は中実のビレットに熱間で
貫通穴を開け鋼管の基本形状を製造する工程である。穿
孔方法は傾斜圧延やプレス穿孔等、その方法は特に限定
しない。なお、ビレットの表面温度が低下すると、穿孔
時に疵が発生し易くなるので、穿孔機２の直前に補助加
熱装置、例えば誘導加熱装置等を設置してもよい。Punching condition: Punching is a process in which a solid billet is hot-punched to produce a basic shape of a steel pipe. The method of piercing is not particularly limited, such as inclined rolling and press piercing. Note that when the surface temperature of the billet decreases, flaws are likely to occur during punching, so an auxiliary heating device, such as an induction heating device, may be installed immediately before the punching machine 2.
【００４３】最終圧延条件：ここでいう最終圧延あるい
は最終仕上げ圧延とは、マンドレルミルによる加工とサ
イザ−による加工を合わせたものを指す。鋼管の最終仕
上げ圧延は、図１に示すように、穿孔機２の後段に配置
された最終圧延機（マンドレルミル３およびサイザ−
４）によっておこなわれる。この段階の圧延は穿孔機２
での加工に比べると低温域での加工となるので、加工熱
処理にとって重要である。最終圧延は加工度を大きくと
れる条件が好ましい。このため、従来、マンドレルミル
３とサイザ−４は分離した圧延装置であったが、これを
分離せずに一体型の連続配置とすると、製造するすべて
のサイズに対して圧下量を分離させずに一続きの圧延で
断面圧縮率４０％以上の加工が実現できる。マンドレル
ミル３で付与された加工歪が大きく回復する前に、直ち
にエキストラクティングサイザ−４にてさらに加工を加
えることによって、その後の再結晶粒を微細化できる。
このとき最終圧延の加工度としてマンドレルミル３とエ
キストラクティングサイザ−４による両者を合算したも
のが採用できる。加工度が断面圧縮率で４０％未満では
再結晶がスムーズに進行せず、細粒化効果が得られない
ので、最終圧延の加工度は断面圧縮率で４０％以上とす
る。細粒化のためには加工度だけでなく最終圧延の仕上
げ温度が大切であり、低温ほど補熱過程で微細な再結晶
粒が短時間で得られる傾向がある。しかし、あまり仕上
げ温度を低温にすると、補熱における温度回復に時間が
かかり生産能率が低下するので８００℃以上とした。ま
た、１０５０℃を超える仕上げ温度では再結晶粒が粗大
となるので上限は１０５０℃とした。Final rolling conditions: The final rolling or final rolling as referred to herein means a combination of processing by a mandrel mill and processing by a sizer. As shown in FIG. 1, the final finish rolling of the steel pipe is performed by a final rolling mill (mandrel mill 3 and sizer) arranged at the subsequent stage of the punching machine 2.
4). Rolling at this stage is performed by the piercing machine 2
This is important for thermomechanical processing because it requires a lower temperature range than that of. It is preferable that the final rolling is performed under the condition that the workability can be increased. For this reason, conventionally, the mandrel mill 3 and the sizer-4 were separated rolling devices, but if they are not separated but integrated and continuously arranged, the reduction amount is not separated for all sizes to be manufactured. With a series of rolling, it is possible to achieve processing with a sectional compression rate of 40% or more. Immediately before further processing strain applied by the mandrel mill 3 is recovered, further processing is performed by the extracting sizer-4, whereby the recrystallized grains thereafter can be made fine.
At this time, the sum of the mandrel mill 3 and the extractor sizer-4 can be adopted as the final rolling workability. If the workability is less than 40% in cross-section compression rate, recrystallization does not proceed smoothly and the grain refining effect cannot be obtained. Therefore, the workability of final rolling is set to 40% or more in cross-section compression rate. Not only the workability but also the finishing temperature of the final rolling are important for making the grains fine, and the lower the temperature, the more likely it is that fine recrystallized grains will be obtained in a short time during the supplementary heating process. However, if the finishing temperature is too low, it takes time to recover the temperature in the supplementary heat, and the production efficiency is lowered. Further, since the recrystallized grains become coarse at a finishing temperature exceeding 1050 ° C, the upper limit was made 1050 ° C.
【００４４】補熱条件：本発明では最終圧延と直接焼入
れの間の加熱炉５で再結晶を進行させることが大きな特
徴である。これによって、結晶粒の微細化が可能とな
る。補熱の加熱条件として、８５０℃未満、１０秒間未
満では再結晶が進行せず細粒組織とならず、１０５０℃
を超え、また３０分間を超えては結晶粒が大きく成長し
て粗粒化するので、加熱温度を８５０〜１０５０℃と
し、時間は１０秒〜３０分間とした。Supplementary heating conditions: The present invention is characterized in that recrystallization is advanced in the heating furnace 5 between the final rolling and the direct quenching. This makes it possible to reduce the size of crystal grains. If the heating condition for supplementary heat is less than 850 ° C. and less than 10 seconds, recrystallization does not proceed and a fine grain structure does not occur, and 1050 ° C.
Since the crystal grains grow large and coarsen for more than 30 minutes and over 30 minutes, the heating temperature was set to 850 to 1050 ° C. and the time was set to 10 seconds to 30 minutes.
【００４５】補熱を実施することによって、靭性が向上
するだけでなく、焼入れ温度の確保が容易となり、鋼管
の長手方向の均熱度、およびロット間の均一性が保証さ
れ性能ばらつきが大幅に小さくなる。さらに前記の組成
上の改善を前提として細粒化の効果をそのまま受けて耐
硫化物応力割れ性が飛躍的に向上する。By performing the supplementary heat, not only the toughness is improved, but also the quenching temperature can be easily secured, the uniform temperature distribution in the longitudinal direction of the steel pipe and the uniformity between lots are guaranteed, and the variation in performance is greatly reduced. Become. Further, on the premise of the above compositional improvement, the effect of grain refining is directly received, and the sulfide stress cracking resistance is dramatically improved.
【００４６】直接焼入れ条件：仕上げ圧延の後直接焼入
れまでの間、Ａｒ3 点温度以上を維持することが必要で
ある。圧延後８５０℃以上に補熱され再結晶を終了した
後に、冷却装置６により直接焼入れをおこなう。本発明
の組成範囲にある鋼は、８５０℃より低いＡｒ3 点をも
つので、補熱によりＡｒ3 点以上を維持することは保証
される。Direct quenching conditions: It is necessary to maintain the Ar 3 point temperature or higher between the finish rolling and the direct quenching. After rolling, after supplementing heat to 850 ° C. or higher and ending recrystallization, direct quenching is performed by the cooling device 6. Steels in the compositional range of the present invention have an Ar 3 point below 850 ° C., so that supplementary heat ensures that the Ar 3 point or higher is maintained.
【００４７】直接焼入れ後の再焼入れ：本発明は、直接
焼入れ直前のオ−ステナイト粒径が再結晶によって微細
となっているので、前記の組成上の工夫を行った鋼を直
接焼入れ後Ａｃ1 点直下に焼戻すだけで、優れた靭性と
耐硫化物応力割れ性が実現できる。この状態で十分使用
に耐え得るが、さらに再焼入れ処理を実施することによ
って、もう一段上位の靭性と耐硫化物応力割れ性が得ら
れ、さらに強度を高めても問題を生じることなく使用す
ることができる。この再焼入れ処理は繰り返すと結晶粒
が細かくなるので靭性および耐硫化物応力割れ性が向上
するが、３回以上繰り返してもコストアップに見合うだ
けの性能向上が得られないので、直接焼入れ後に再焼入
れ処理を行う場合は１回または２回の焼入れ処理が好ま
しい。なお、２回目の再焼入れ温度は１回目の再焼入れ
温度に比べて低くする方が靭性および耐硫化物応力割れ
性とも好ましい結果となる。Re-quenching after direct quenching: In the present invention, since the austenite grain size immediately before direct quenching is fine by recrystallization, the steel having the above-mentioned compositional measures is directly quenched after Ac 1 Excellent toughness and sulfide stress cracking resistance can be achieved simply by tempering just below the point. Although it can withstand sufficient use in this state, by further performing re-quenching treatment, it is possible to obtain toughness and sulfide stress cracking resistance that are one step higher, and even if the strength is increased, use without causing problems. You can Repeating this re-quenching treatment improves the toughness and sulfide stress cracking resistance because the crystal grains become finer, but even if it is repeated three times or more, the performance improvement commensurate with the cost increase cannot be obtained. When the quenching treatment is performed, it is preferable to perform the quenching treatment once or twice. It should be noted that lowering the second re-quenching temperature as compared to the first re-quenching temperature leads to preferable results in terms of toughness and sulfide stress cracking resistance.
【００４８】中間焼戻し条件：前記の直接焼入れまたは
再焼入れの後に、置き割れなどと呼ばれる遅れ破壊を防
ぐ目的で中間焼戻しを行うことにより水素の放出促進お
よび強度低下を図る。Intermediate tempering conditions: After the above direct quenching or re-quenching, an intermediate tempering is carried out for the purpose of preventing delayed fracture called so-called cracking in order to promote the release of hydrogen and reduce the strength.
【００４９】焼入れ処理の後、次の再焼入れまたは最終
の焼戻しまでの時間が５時間を越える時は中間焼戻し処
理を実施した方が好ましく、効果的に遅れ破壊を防止で
きる。After the quenching treatment, when the time until the next re-quenching or the final tempering exceeds 5 hours, it is preferable to carry out the intermediate tempering treatment, and the delayed fracture can be effectively prevented.
【００５０】後に再焼入れがおこなわれる場合には、中
間焼戻しの上限温度はＡｃ1 点以下でありさえすればよ
い。後に再焼入れがなく焼戻しのみがおこなわれる場合
には、中間焼戻しの効果が焼戻しに加算されるので焼戻
し温度より２０℃以上低温で加熱時間は２時間以内とす
る。また、温度の下限は焼戻し効果が見込める５５０℃
とする。When re-quenching is carried out later, the upper limit temperature of the intermediate tempering need only be the Ac 1 point or lower. When tempering is only performed without subsequent re-quenching, the effect of intermediate tempering is added to tempering, so the temperature is 20 ° C or more lower than the tempering temperature and the heating time is within 2 hours. The lower limit of the temperature is 550 ° C, which is expected to have a tempering effect.
And
【００５１】焼戻し条件：焼戻しは製品の性能を決定す
る重要な処理であるので十分な均熱性が要求される。温
度はＡｃ1 点以下で、ばらつきは±１０℃とし、好まし
くは±５℃とする。これによって、ＹＳおよびＴＳの変
動を±５kgf/mm2 以下に抑えられる。焼戻し温度は、Ａ
ｃ1 点以下でありさえすればよく、特に制限しない。し
かし、通常は、６００℃以上で行い、靭性と耐硫化物応
力割れ性を確保する。ただし、Ｃ１２５級として必要な
耐硫化物応力割れ性を得るには、６５０℃以上で焼戻す
ことが望ましい。Tempering conditions: Since tempering is an important process that determines the performance of products, sufficient soaking property is required. The temperature is Ac 1 point or less and the variation is ± 10 ° C., preferably ± 5 ° C. As a result, fluctuations in YS and TS can be suppressed to ± 5 kgf / mm 2 or less. The tempering temperature is A
There is no particular limitation as long as it is 1 or less. However, it is usually performed at 600 ° C. or higher to ensure toughness and sulfide stress cracking resistance. However, in order to obtain the sulfide stress cracking resistance required for C125 grade, it is desirable to temper at 650 ° C or higher.
【００５２】直接焼入れをＤＱ、再焼入れをＲＱ、中間
焼戻しをＩＴまた焼戻しをＴとすると、本発明の対象と
なる典型的な方法は、以下の７方法およびそれらの焼戻
しの前に中間焼戻しＩＴを加える方法の計１４通りであ
る。Assuming that direct quenching is DQ, re-quenching is RQ, intermediate tempering is IT, and tempering is T, typical methods of the present invention include the following seven methods and intermediate tempering IT before the tempering. There are a total of 14 ways to add.
【００５３】（１）ＤＱ−Ｔ （２）ＤＱ−ＲＱ−Ｔ （３）ＤＱ−ＩＴ−ＲＱ−Ｔ （４）ＤＱ−ＲＱ−ＲＱ−Ｔ （５）ＤＱ−ＲＱ−ＩＴ−ＲＱ−Ｔ （６）ＤＱ−ＩＴ−ＲＱ−ＲＱ−Ｔ （７）ＤＱ−ＩＴ−ＲＱ−ＩＴ−ＲＱ−Ｔ(1) DQ-T (2) DQ-RQ-T (3) DQ-IT-RQ-T (4) DQ-RQ-RQ-T (5) DQ-RQ-IT-RQ-T ( 6) DQ-IT-RQ-RQ-T (7) DQ-IT-RQ-IT-RQ-T
【００５４】[0054]
【実施例】本発明を実施した結果を比較例と併せて以下
にしめす。表１および２は、実験に用いた本発明の組成
の範囲内にある鋼ａ〜ｆおよび比較鋼ｇ〜ｏの組成の一
覧表である。いずれも１５０ｋｇ真空炉にて溶製をおこ
なった。（ａ，ｇ）、（ｂ，ｈ，ｍ，ｎ）、（ｃ，
ｉ）、（ｄ，ｊ，ｏ）、（ｅ，ｋ）および（ｆ，ｌ）は
それぞれの括弧内で互いに分湯して溶製した鋼であり、
それぞれの括弧内でＷ以外の組成は同じである。EXAMPLES The results of carrying out the present invention are shown below together with comparative examples. Tables 1 and 2 are a list of the compositions of the steels a to f and the comparative steels g to o within the composition range of the present invention used in the experiment. All were melted in a 150 kg vacuum furnace. (A, g), (b, h, m, n), (c,
i), (d, j, o), (e, k) and (f, l) are steels melted from each other in the respective parentheses,
The composition other than W is the same in each bracket.
【００５５】[0055]
【表１】 [Table 1]
【００５６】[0056]
【表２】 [Table 2]
【００５７】それらを鍛造して２０ｍｍ厚×８０ｍｍ幅
×２５０ｍｍ長のブロックを作製した。表３から６まで
は、上記の鋼に対して圧延から最終の焼戻しにいたる各
製造条件を変化させて検討した試験を試験毎に番号づけ
した一覧表である。これらの表において本発明例を番号
１〜１２、および３１〜３５に、また比較例を番号１３
〜３０、および３６〜４１に示す。番号１〜１２は、Ｗ
量を適正量含む鋼ａ〜ｆに対して前記の方法の効果を調
査したものである。各鋼に対して前記の（１）ＤＱ−Ｔ
および（２）ＤＱ−ＲＱ−Ｔの２種類の方法を適用し
た。These were forged to form a block having a thickness of 20 mm, a width of 80 mm, and a length of 250 mm. Tables 3 to 6 are tables in which the tests examined by changing the respective manufacturing conditions from rolling to final tempering of the above steels are numbered for each test. In these tables, the invention examples are numbered 1 to 12, and 31 to 35, and the comparative example is numbered 13.
˜30, and 36 to 41. Numbers 1 to 12 are W
The effect of the above method was investigated on steels a to f containing appropriate amounts. (1) DQ-T for each steel
And (2) two types of methods, DQ-RQ-T, were applied.
【００５８】比較例１３〜３０は、従来の直接焼入れ法
を本発明の範囲外の組成の鋼に適用したものである。発
明例３１〜３５は、本発明の範囲内の組成の鋼に対し
て、本発明に係る直接焼入れを施した後焼戻しまでの間
に、１回もしくは２回の再焼入れを挿入したものであ
る。比較例３６〜４１は、従来のオフラインでの焼入れ
焼戻しもしくは焼入れ再焼入れ焼戻しを行った方法を示
す。熱間圧延条件は、表３および４にしめす厚鋼板の圧
延条件により穿孔から仕上げ圧延に至る圧延加工を模擬
した。断面圧縮率は鋼管の圧延と鋼板の圧延でほぼ同等
であり、表３および表４の仕上げ圧延加工度は断面圧縮
率にほぼ等しいと判断できる。その後、表５および６に
しめすように、鋼種および熱処理条件に応じて焼戻し条
件を変化させて強度をほぼＣ１２５級（ＹＳ＝１２５〜
１４０ｋｓｉ（８７．９〜９８．４ｋｇｆ／ｍｍ2 ））
に調整した。In Comparative Examples 13 to 30, the conventional direct quenching method was applied to steels having compositions outside the scope of the present invention. Inventive Examples 31 to 35 are steels having a composition within the scope of the present invention, in which one or two re-quenchings are inserted between the direct quenching according to the present invention and the tempering. . Comparative Examples 36 to 41 show methods of performing conventional quenching and tempering or quenching and requenching and tempering off-line. As the hot rolling conditions, rolling processes from piercing to finish rolling were simulated according to the rolling conditions of thick steel plates shown in Tables 3 and 4. The cross-section compressibility is almost the same for steel tube rolling and steel plate rolling, and it can be judged that the finish rolling workability in Tables 3 and 4 is almost equal to the cross-section compressibility. After that, as shown in Tables 5 and 6, the tempering conditions are changed according to the steel type and the heat treatment conditions, and the strength is almost C125 grade (YS = 125-125).
140 ksi (87.9-98.4 kgf / mm 2 ))
Was adjusted.
【００５９】[0059]
【表３】 [Table 3]
【００６０】[0060]
【表４】 [Table 4]
【００６１】[0061]
【表５】 [Table 5]
【００６２】[0062]
【表６】 [Table 6]
【００６３】表７および８は、各試験に対して、強度、
オ−ステナイト結晶粒度番号、靭性（ｖＴｒｓ）および
耐硫化物応力割れ性の結果を示す一覧表である。耐硫化
物応力割れ性はＮＡＣＥ（National Association of Co
rrosion Engineers ）ＴＭ０１７７ ＭＥＴＨＯＤ−Ｂ
（３点曲げ法）によりＳｃ値を、またＭＥＴＨＯＤ−Ａ
（単軸引張り試験法）にて付加応力１００ｋｓｉ（Ｃ１
２５のＳＭＹＳの８０％）における破断有無を評価し
た。Tables 7 and 8 show for each test the strength,
3 is a list showing the results of austenite grain size number, toughness (vTrs) and sulfide stress cracking resistance. Sulfide stress crack resistance is NACE (National Association of Co
rrosion Engineers) TM0177 METHOD-B
Sc value by (3-point bending method), METHOD-A
Additional stress of 100 ksi (C1
The presence or absence of breakage in 80% of 25 SMYS) was evaluated.
【００６４】[0064]
【表７】 [Table 7]
【００６５】[0065]
【表８】 [Table 8]
【００６６】本発明例はいずれもＮＡＣＥ ＴＭ０１７
７ ＭＥＴＨＯＤ−Ａにて応力を１００ｋｓｉ付加して
も破断を生じずＣ１２５級として十分な耐硫化物応力割
れ性を有している。試番１３〜３０は、Ｗを含まない
か、あるいはその含有量が請求範囲外のものであり、付
加応力１００ｋｓｉでは破断を生じており、また破断応
力Ｓｃ値も発明例に比べれば劣る。The examples of the present invention are all NACE TM017.
7 Even if a stress of 100 ksi was applied by METHOD-A, no fracture occurred and it had sufficient sulfide stress cracking resistance as C125 grade. Test Nos. 13 to 30 do not contain W or the content thereof is out of the claimed range, fracture occurs at an applied stress of 100 ksi, and the fracture stress Sc value is also inferior to the invention examples.
【００６７】鋼ｂに対しては、前記の（１）〜（７）の
すべての製造方法が適用され、番号３、４、３１〜３５
として表示されている。これらもいずれもＣ１２５級と
して優れた耐硫化物応力割れ性を示すことが確認され
た。For steel b, all the manufacturing methods (1) to (7) described above are applied, and the numbers 3, 4, 31 to 35 are applied.
Is displayed as. It was confirmed that all of them exhibited excellent sulfide stress cracking resistance as C125 grade.
【００６８】番号３６〜４１は従来製法である焼入れ焼
戻し法による鋼の諸性能とを比較したものである。試番
３６、３９および４０は、本発明例のいずれの方法によ
るものよりも結晶粒径が大きく、耐硫化物応力割れ性お
よび靭性の両方で劣っている。番号３８、３９および４
１のオフラインでの２回焼入れ処理によるものは粒径は
小さく、靭性は良好なものの耐硫化物応力割れ性はＣ１
２５級を満足しない。Nos. 36 to 41 are comparisons of various performances of steel by the conventional quenching and tempering method. Sample Nos. 36, 39 and 40 have a larger crystal grain size than any of the methods of the present invention examples, and are inferior in both sulfide stress cracking resistance and toughness. Numbers 38, 39 and 4
In the case of No. 1 with the offline quenching treatment, the grain size is small and the toughness is good, but the sulfide stress cracking resistance is C1.
Not satisfied with 25th grade.
【００６９】[0069]
【発明の効果】補熱を加えた直接焼入れ法を、改良した
組成の鋼に適用することにより、細粒組織を得ることが
できる。そのような組織に高温焼戻しを適用することに
より、従来法では製造できなかったＣ１２５級の高強度
高耐食継目無鋼管を安価にかつ高い生産性のもとに提供
することができる。By applying the direct quenching method with supplementary heat to steel having an improved composition, a fine grain structure can be obtained. By applying high temperature tempering to such a structure, it is possible to provide a high-strength, high-corrosion, corrosion-resistant seamless steel pipe of C125 grade, which could not be manufactured by the conventional method, at low cost and with high productivity.
【図１】図１はビレット加熱から直接焼入れに至るまで
の継目無鋼管の製造方法を示す図面である。FIG. 1 is a drawing showing a method for producing a seamless steel pipe from billet heating to direct quenching.
１…加熱炉、２…穿孔機、３…マンドレルミル、４…サ
イザ−（エキストラクテインク゛サイサ゛-）、５…加熱炉、６…冷却装
置DESCRIPTION OF SYMBOLS 1 ... Heating furnace, 2 ... Punching machine, 3 ... Mandrel mill, 4 ... Sizer (extra-inking sizer), 5 ... Heating furnace, 6 ... Cooling device
Claims (2)
ｉ：０．１〜１．５％、Ｍｎ：０．１〜１．５％、Ｐ：
０．０５％以下、Ｓ：０．０１％以下、Ｃｒ：０．１〜
１．５％、Ｎｉ：０．１％以下、 Ｍｏ：０．１〜１．
５％、Ｗ：０．１〜２．０％、sol Ａｌ：０．００５〜
０．５０％、Ｔｉ：０．００５〜０．５０％、Ｎｂ：
０．００５〜０．５０％、Ｖ：０〜０．５％、Ｚｒ：０
〜０．５％、Ｂ：０．０００１〜０．０１０％、Ｃａ：
０〜０．０１％、Ｎ：０．０１％以下およびＯ（酸
素）：０．０１％以下を含み残部はＦｅおよび不可避的
不純物からなる組成を有するビレットを、熱間で穿孔し
圧延する際、最終圧延において断面圧縮率４０％以上の
加工を８００〜１１００℃で施した後、８５０〜１１０
０℃に１０秒〜３０分間補熱し、そのまま直接焼入れを
おこない、その後に焼戻しすることを特徴とする高強度
高耐食継目無鋼管の製造方法。C .: 0.15 to 0.50% by weight, S
i: 0.1-1.5%, Mn: 0.1-1.5%, P:
0.05% or less, S: 0.01% or less, Cr: 0.1
1.5%, Ni: 0.1% or less, Mo: 0.1 to 1.
5%, W: 0.1-2.0%, sol Al: 0.005-
0.50%, Ti: 0.005 to 0.50%, Nb:
0.005-0.50%, V: 0-0.5%, Zr: 0
~ 0.5%, B: 0.0001 to 0.010%, Ca:
When a billet having a composition of 0 to 0.01%, N: 0.01% or less and O (oxygen): 0.01% or less and the balance of Fe and unavoidable impurities is hot-punched and rolled. 850 to 110 after processing at a compression rate of 40% or more in the final rolling at 800 to 1100 ° C.
A method for producing a high-strength, high-corrosion-resistant seamless steel pipe, which comprises supplementing heat to 0 ° C for 10 seconds to 30 minutes, performing direct quenching as it is, and then tempering.
焼入れと焼戻しの間で再焼入れを１回もしくは２回おこ
なうことを特徴とする高強度高耐食継目無鋼管の製造方
法。2. The method for producing a high-strength, highly corrosion-resistant seamless steel pipe according to claim 1, wherein re-quenching is performed once or twice between direct quenching and tempering.
Priority Applications (9)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17187295A JP3362565B2 (en) | 1995-07-07 | 1995-07-07 | Manufacturing method of high strength and high corrosion resistant seamless steel pipe |
| DE69617002A DE69617002D1 (en) | 1995-05-15 | 1996-05-15 | METHOD FOR THE PRODUCTION OF HIGH-STRENGTH SEAMLESS STEEL TUBES WITH EXCELLENT SULFUR INDUCED TENSION crack cracking resistance |
| DE69617002T DE69617002T4 (en) | 1995-05-15 | 1996-05-15 | METHOD FOR PRODUCING HIGH-STRENGTH SEAMLESS STEEL TUBES WITH EXCELLENT SULFUR-INDUCED TENSION crack cracking resistance |
| DK96915150T DK0828007T3 (en) | 1995-05-15 | 1996-05-15 | Process for Manufacturing High Strength Seamless Steel Pipe and Excellent Sulfide Stress Crack Resistance |
| MX9708775A MX9708775A (en) | 1995-05-15 | 1996-05-15 | Process for producing high-strength seamless steel pipe having excellent sulfide stress cracking resistance. |
| US08/952,222 US5938865A (en) | 1995-05-15 | 1996-05-15 | Process for producing high-strength seamless steel pipe having excellent sulfide stress cracking resistance |
| EP96915150A EP0828007B1 (en) | 1995-05-15 | 1996-05-15 | Process for producing high-strength seamless steel pipe having excellent sulfide stress cracking resistance |
| PCT/JP1996/001274 WO1996036742A1 (en) | 1995-05-15 | 1996-05-15 | Process for producing high-strength seamless steel pipe having excellent sulfide stress cracking resistance |
| NO19975237A NO321325B1 (en) | 1995-05-15 | 1997-11-14 | Process for Producing High Strength Seamless Stalrups with Excellent Sulfide Stress Crack Resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17187295A JP3362565B2 (en) | 1995-07-07 | 1995-07-07 | Manufacturing method of high strength and high corrosion resistant seamless steel pipe |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0925518A true JPH0925518A (en) | 1997-01-28 |
| JP3362565B2 JP3362565B2 (en) | 2003-01-07 |
Family
ID=15931362
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17187295A Expired - Fee Related JP3362565B2 (en) | 1995-05-15 | 1995-07-07 | Manufacturing method of high strength and high corrosion resistant seamless steel pipe |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3362565B2 (en) |
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| WO2010061882A1 (en) * | 2008-11-26 | 2010-06-03 | 住友金属工業株式会社 | Seamless steel pipe and method for manufacturing same |
| JP2011246798A (en) * | 2009-06-24 | 2011-12-08 | Jfe Steel Corp | High-strength seamless steel tube for oil well with excellent resistance to sulfide stress cracking, and method for producing the same |
| JP2012519238A (en) * | 2009-03-03 | 2012-08-23 | バローレック・マネスマン・オイル・アンド・ガス・フランス | Low alloy steel with high yield stress and high sulfide stress cracking resistance |
| JP2012197507A (en) * | 2011-02-07 | 2012-10-18 | Dalmine Spa | High-strength steel pipe having excellent toughness at low temperature and sulfide stress corrosion cracking resistance |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AR075976A1 (en) * | 2009-03-30 | 2011-05-11 | Sumitomo Metal Ind | METHOD FOR THE MANUFACTURE OF PIPE WITHOUT SEWING |
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| JP2012197507A (en) * | 2011-02-07 | 2012-10-18 | Dalmine Spa | High-strength steel pipe having excellent toughness at low temperature and sulfide stress corrosion cracking resistance |
| JP2016079426A (en) * | 2014-10-10 | 2016-05-16 | 新日鐵住金株式会社 | Steel sheet excellent in high temperature strength and toughness and manufacturing method therefor |
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