JPH073330A - Production of high tensile strength and high toughness bent tube excellent in corrosion resistance - Google Patents
Production of high tensile strength and high toughness bent tube excellent in corrosion resistanceInfo
- Publication number
- JPH073330A JPH073330A JP14802393A JP14802393A JPH073330A JP H073330 A JPH073330 A JP H073330A JP 14802393 A JP14802393 A JP 14802393A JP 14802393 A JP14802393 A JP 14802393A JP H073330 A JPH073330 A JP H073330A
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- Japan
- Prior art keywords
- toughness
- less
- corrosion resistance
- strength
- tempering
- 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.)
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- Bending Of Plates, Rods, And Pipes (AREA)
- 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、水素誘起割れ(HI
C)や硫化物応力腐食割れ(SSCC)の生じにくい耐
蝕性に優れた高張力高靱性曲がり管の製造方法に関す
る。The present invention relates to hydrogen-induced cracking (HI
The present invention relates to a method for producing a high-strength, high-toughness bent pipe excellent in corrosion resistance in which C) and sulfide stress corrosion cracking (SSCC) hardly occur.
【0002】[0002]
【従来の技術】石油や天然ガスを輸送する手段としてパ
イプラインが用いられている。パイプライン用鋼材とし
ては、通常API規格に規定されているX80グレード
までの強度と、−10℃以下でのDWTT特性が要求さ
れるため、シャルピー衝撃試験における破面遷移温度v
Trsで−60℃以下の低温靭性を確保する必要があ
る。また、輸送流体である原油や天然ガス中に硫化水素
を含む場合には、上記強度及び靭性のみならず、HIC
やSSCCの生じにくい耐食性をも考慮した鋼材が要求
される。2. Description of the Related Art Pipelines are used as means for transporting oil and natural gas. As a steel material for pipelines, strength up to X80 grade, which is usually specified in API standards, and DWTT characteristics at −10 ° C. or lower are required, so the fracture surface transition temperature v in the Charpy impact test
It is necessary to secure a low temperature toughness of -60 ° C or lower in Trs. In addition, when hydrogen sulfide is contained in crude oil or natural gas as a transport fluid, not only the strength and toughness described above but also HIC
Steel materials that take into account the corrosion resistance that does not easily cause SSCC or SSCC are required.
【0003】パイプラインには、直管部分のほか輸送方
向を変化させたり、直管部分の温度変化による膨張収縮
を吸収するための曲がり管の部分もあり、直管部分のみ
ならず曲がり管部分に対しても強度及び靭性、並びに耐
食性に優れた鋼材が要求されている。In addition to the straight pipe portion, the pipeline also has a bent pipe portion for changing the transportation direction and absorbing expansion and contraction due to temperature change of the straight pipe portion, and not only the straight pipe portion but also the bent pipe portion. However, a steel material excellent in strength, toughness, and corrosion resistance is required.
【0004】従来、これらの曲がり管は、直管を連続的
に誘導加熱曲げ加工装置に押し入れ、加熱コイル内を通
して加熱しながら曲げる方法、又は、軸方向に沿って曲
がった半円筒形状の鋼板2つを溶接により接合する方法
等により製造されている。Conventionally, these bent pipes are formed by continuously pushing a straight pipe into an induction heating bending apparatus and bending it while heating it through a heating coil, or by bending it in the axial direction into a semi-cylindrical steel plate 2. It is manufactured by a method of joining two by welding.
【0005】これらの場合、加工後の熱処理として、A
PI 5L規格X52以上の鋼種については特開昭62
−15154号公報、特開平4−154913号公報に
記載されているように、曲げ加工後焼入れ処理(Q)と
450〜650℃の温度で焼戻し処理(T)を行なう
か、又は、特公昭63−76525号公報に記載されて
いるように、焼入れのままで製造されている。In these cases, as a heat treatment after processing, A
For steel grades of PI 5L standard X52 or higher, see JP-A-62
As described in JP-A-15154 and JP-A-4-154913, quenching treatment (Q) after bending and tempering treatment (T) at a temperature of 450 to 650 ° C. are performed, or JP-B-63 As described in Japanese Patent Publication No. -76525, it is manufactured by quenching.
【0006】ところが、特開昭62−15154号公報
に記載されているように、焼き入れ後、550〜650
℃の温度で焼戻し処理を行なうと、耐食性は優れるもの
の、矯正試験片において高い降伏応力(YS)が得られ
ず、さらにYSが低い割にDWTT特性を含めた低温靭
性が劣るという問題がある。また、特開平4−1549
13号公報に記載されているように、焼入れ処理及び4
50〜600℃の温度での焼戻し処理によってBを含有
した鋼からなる曲がり管を得ると、強度及び耐食性は優
れるものの、低温靭性及び溶接性が劣るといった問題が
ある。However, as described in Japanese Patent Application Laid-Open No. 62-15154, 550 to 650 after quenching.
When the tempering treatment is performed at a temperature of ° C, although the corrosion resistance is excellent, a high yield stress (YS) cannot be obtained in the straightened test piece, and further, the low temperature toughness including DWTT characteristics is inferior despite the low YS. In addition, JP-A-4-1549
As described in Japanese Patent No. 13, a quenching treatment and 4
When a bent pipe made of steel containing B is obtained by a tempering treatment at a temperature of 50 to 600 ° C., the strength and corrosion resistance are excellent, but the low temperature toughness and weldability are inferior.
【0007】一方、特公昭63−76525号公報に記
載されているように、焼入れ処理のままで製造されてい
る曲がり管は、低炭素量、低炭素当量で高い引張強度
(TS)が得られるが、降伏点が現れないため、降伏応
力(YS)が低い。従って、所望のYSを得るためには
TSを高くしなければならず、その場合には硬さが上昇
して耐食性が劣る場合があるという問題がある。以上の
ように、従来の方法では、耐食性、強度、低温靭性の要
求を全て満たす曲がり管を製造することは困難であっ
た。On the other hand, as described in Japanese Patent Publication No. Sho 63-76525, the bent pipe manufactured by the quenching treatment has a low carbon content and a high tensile strength (TS) at a low carbon equivalent. However, since the yield point does not appear, the yield stress (YS) is low. Therefore, in order to obtain the desired YS, it is necessary to increase the TS, and in that case, there is a problem in that the hardness increases and the corrosion resistance may deteriorate. As described above, according to the conventional method, it is difficult to manufacture a bent pipe that satisfies all the requirements of corrosion resistance, strength, and low temperature toughness.
【0008】[0008]
【発明が解決しようとする課題】本発明はかかる事情に
鑑みてなされたものであって、低炭素量、低炭素当量で
耐食性に優れた高張力高靭性曲がり管の製造方法を提供
することを目的とする。具体的には、API 5L規格
X60〜X70グレードを満たす強度、及びvTrs≦
−60℃、DWTTの85%SATT≦−10℃なる低
温靭性を示しつつ、耐HIC性、耐SSCC性に優れた
曲がり管の製造方法を提供することを目的とするもので
ある。SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for producing a high-strength, high-toughness bent pipe having a low carbon content, a low carbon equivalent and excellent corrosion resistance. To aim. Specifically, strength satisfying API 5L standard X60 to X70 grade, and vTrs ≤
It is an object of the present invention to provide a method for producing a bent pipe having excellent HIC resistance and SSCC resistance while exhibiting low temperature toughness of -60 ° C and 85% SATT ≤ -10 ° C of DWTT.
【0009】[0009]
【課題を解決するための手段及び作用】本願発明者ら
は、上述した従来の問題点を解決すべく鋭意研究を重ね
た結果、炭素当量を低くした特定組成の低合金鋼を、原
則としてAc3 以上に加熱して曲げ加工を行ない直ちに
焼入れし、その後250〜500℃という従来よりも低
い温度で焼き戻すことによって、耐食性に優れた高張力
高靭性を有する曲がり管を得ることができることを見出
した。本発明は本願発明者らのこのような知見に基づい
て完成されたものであって、第1に、重量%で、C:
0.02〜0.08%、Si:0.05〜0.5%、M
n:0.8〜2.0%、Nb:0.01〜0.06%、
Ti:0.005〜0.05%、Al:0.01〜0.
06%、N:0.002〜0.01%、Ca:0.00
1〜0.005%を含有し、不純物としてのP、Sを夫
々、P:0.015%以下、S:0.002%以下に制
限し、残部鉄及びその他の不可避的不純物からなる低合
金鋼で形成された直管を、Ac3 点以上、1050℃以
下の温度範囲に加熱して曲げ加工を行い、その直後に焼
き入れ処理を施し、次いで、250〜500℃の温度範
囲で焼き戻すことを特徴とする耐食性に優れた高張力高
靭性曲がり管の製造方法であり、第2に、重量%で、
C:0.02〜0.08%、Si:0.05〜0.5
%、Mn:0.8〜2.0%、Nb:0.01〜0.0
6%、Ti:0.005〜0.05%、Al:0.01
〜0.06%、N:0.002〜0.01%、Ca:
0.001〜0.005%を含有し、さらに、Cu:
0.5%以下、Ni:1.0%以下、Cr:0.3%以
下、Mo:0.3%以下、V:0.1%以下のうち少な
くとも1種を含有し、不純物としてのP、Sを夫々、
P:0.015%以下、S:0.002%以下に制限
し、残部鉄及びその他の不可避的不純物からなる低合金
鋼で形成された直管を、Ac3 点以上、1050℃以下
の温度範囲に加熱して曲げ加工を行い、その直後に焼き
入れ処理を施し、次いで、250〜500℃の温度範囲
で焼き戻すことを特徴とする耐食性に優れた高張力高靭
性曲がり管の製造方法である。As a result of intensive studies to solve the above-mentioned conventional problems, the inventors of the present invention have found that a low alloy steel of a specific composition with a low carbon equivalent is, in principle, Ac. It was found that a bent pipe having high tensile strength and high toughness with excellent corrosion resistance can be obtained by heating to 3 or more, bending, quenching immediately, and then tempering at a lower temperature of 250 to 500 ° C than before. It was The present invention has been completed based on such findings of the inventors of the present application. Firstly, C:
0.02-0.08%, Si: 0.05-0.5%, M
n: 0.8 to 2.0%, Nb: 0.01 to 0.06%,
Ti: 0.005-0.05%, Al: 0.01-0.
06%, N: 0.002-0.01%, Ca: 0.00
1 to 0.005%, P and S as impurities are limited to P: 0.015% or less and S: 0.002% or less, respectively, and a low alloy containing the balance iron and other unavoidable impurities. A straight pipe made of steel is heated to a temperature range of Ac 3 points or higher and 1050 ° C or lower to be bent, immediately after that, a quenching treatment is performed, and then tempered in a temperature range of 250 to 500 ° C. A second aspect of the present invention is a method for producing a high-strength, high-toughness bent pipe having excellent corrosion resistance, which is characterized by:
C: 0.02 to 0.08%, Si: 0.05 to 0.5
%, Mn: 0.8 to 2.0%, Nb: 0.01 to 0.0
6%, Ti: 0.005 to 0.05%, Al: 0.01
~ 0.06%, N: 0.002-0.01%, Ca:
0.001 to 0.005%, and further Cu:
0.5% or less, Ni: 1.0% or less, Cr: 0.3% or less, Mo: 0.3% or less, V: 0.1% or less, and P as an impurity. , S respectively
P: 0.015% or less, S: 0.002% or less, and a straight pipe formed of a low alloy steel consisting of the balance iron and other unavoidable impurities, at a temperature of Ac 3 points or more and 1050 ° C or less. A method for producing a high-strength, high-toughness bent pipe excellent in corrosion resistance, which is characterized in that heating is performed in a range to perform bending, quenching is performed immediately after that, and then tempering is performed in a temperature range of 250 to 500 ° C. is there.
【0010】本発明においてこのような構成をとる理由
は以下のとおりである。なお、以下の説明において元素
の量を示す%表示は全て重量%である。 (1)低合金鋼のC量を0.08%以下にし、かつNb
等を添加することにより、焼入れ組織を細粒のベイナイ
トもしくはベイナイトとフェライトの混合組織とする。
なお、C量の低下による強度の低下はMnまたは前述の
合金成分の増加により補う。また、C量を0.08%以
下とするのは、後述する図1から明らかな通り、vTr
sを−60℃以下とするためであり、また、0.08%
を超えると、後述する焼戻し処理を施しても島状マルテ
ンサイトなどの硬化組織が消失しない場合があり、その
硬化組織がHICの起点となるためである。The reason why such a configuration is adopted in the present invention is as follows. In the following description, all percentages indicating the amounts of elements are% by weight. (1) C content of low alloy steel is 0.08% or less, and Nb
And the like make the quenching structure a fine grain bainite or a mixed structure of bainite and ferrite.
Note that the decrease in strength due to the decrease in the amount of C is compensated by the increase in Mn or the above alloy components. In addition, the amount of C is set to 0.08% or less as shown in FIG.
This is because s is set to -60 ° C or less, and 0.08%
If it exceeds, the hardened structure such as island martensite may not disappear even if the tempering treatment described later is performed, and the hardened structure becomes a starting point of HIC.
【0011】(2)直管として用いる低合金鋼のAc3
点以上の温度に加熱し、その温度において管を曲げ加工
し、直ちに急冷してその強度を向上させる。 (3)最後に、250〜500℃の温度で焼き戻すと、
ベイナイト中の島状マルテンサイトが分解して硬さが低
下し、耐HIC性、耐SSCC性が向上すると共に、Y
Sび低温靱性が向上する。(2) Ac 3 which is a low alloy steel used as a straight pipe
Heat to a temperature above the point, bend the tube at that temperature and immediately quench to improve its strength. (3) Finally, when tempering at a temperature of 250 to 500 ° C.,
Island-like martensite in bainite is decomposed to reduce hardness, improve HIC resistance and SSCC resistance, and Y
S and low temperature toughness are improved.
【0012】以下、具体的に説明する。図1は、C−M
n−Nb−V−Ti系の厚さ25mmの鋼材における焼
入れ処理と焼入れ焼戻し処理後のYS、TS、vTrs
に及ぼすC量の影響を示した。なお、焼入れ焼戻し処理
後のものについては、耐HIC性、耐SSCC性につい
ても示した。A detailed description will be given below. Figure 1 shows CM
YS, TS, vTrs after quenching treatment and quenching and tempering treatment on an n-Nb-V-Ti-based steel material having a thickness of 25 mm
The effect of the amount of C on C. The HIC resistance and SSCC resistance after the quenching and tempering treatment are also shown.
【0013】焼入れ処理条件は、加熱温度を1030℃
とし、その後800℃から400℃までの平均冷却速度
10℃/secとし、焼戻し処理条件は、加熱温度40
0℃で30分間保持し、その後空冷とした。The quenching condition is that the heating temperature is 1030 ° C.
Then, the average cooling rate from 800 ° C. to 400 ° C. was 10 ° C./sec, and the tempering treatment condition was a heating temperature of 40 ° C.
It was kept at 0 ° C. for 30 minutes and then air-cooled.
【0014】HIC試験は、2種類の溶液で行った。一
つはNACE TM02−84に準拠したpH4.8〜
5.4のいわゆるBP溶液であり、他はNACE TM
01−77に準拠したpH3.0〜4.0のいわゆるN
ACE溶液である。試験条件は、いずれの溶液において
もNACE TM02−84に従った。また、SSCC
試験については、NACE TM01−77に準拠し、
X60グレードの規格下限降伏応力(SMYS)の80
%に相当する応力33.8kgf /mm2 を負荷して720
時間浸漬し、破断の有無を調査した。The HIC test was carried out with two types of solutions. One is pH 4.8 based on NACE TM02-84.
5.4 so-called BP solution, others NACE ™
So-called N having a pH of 3.0 to 4.0 according to 01-77
It is an ACE solution. The test conditions were in accordance with NACE TM02-84 in all the solutions. Also, SSCC
Regarding the test, according to NACE TM01-77,
X60 grade standard lower limit yield stress (SMYS) of 80
720 by applying a stress equivalent to 33.8 kgf / mm 2
It was immersed for a period of time and examined for breakage.
【0015】図1から明らかなように、400℃の焼戻
処理を行なうことにより、焼入れ処理のままよりもYS
とvTrsが向上している。また、C量を下げることに
より400℃という低温での焼戻し処理後に優れた低温
靱性、耐HIC性、耐SSCC性を得ることができる。As is apparent from FIG. 1, by performing the tempering treatment at 400.degree.
And vTrs have improved. Further, by reducing the C content, excellent low temperature toughness, HIC resistance, and SSCC resistance can be obtained after tempering at a low temperature of 400 ° C.
【0016】図2は、図1に示したC0.05%鋼につ
いて、焼き入れ後種々の温度で焼戻したときの強度、靱
性、耐HIC性、耐SSCC性を示す。なお、鋼成分は
0.33%Si−1.5%Mn−0.036%Nb−
0.065%V−0.012%Ti−0.028%Al
−0.0035%Nである。熱処理として、1030℃
に加熱後、800℃から400℃間の平均冷却速度10
℃/secで焼入れ処理を行ない、焼戻し処理は200
℃から650℃までの種々の温度で30分間保持し、そ
の後空冷した。FIG. 2 shows the strength, toughness, HIC resistance, and SSCC resistance of the C0.05% steel shown in FIG. 1 when tempered at various temperatures after quenching. The steel composition is 0.33% Si-1.5% Mn-0.036% Nb-.
0.065% V-0.012% Ti-0.028% Al
-0.0035% N. As heat treatment, 1030 ℃
After heating to 80 ℃, the average cooling rate between 800 ℃ and 400 ℃ is 10
Quenching at ℃ / sec, tempering at 200
The temperature was kept at various temperatures from 0 ° C to 650 ° C for 30 minutes, followed by air cooling.
【0017】図2から明らかなとおり、YS、耐SSC
C性は250℃以上の焼戻し温度で向上し、YSは55
0℃以上でNb,Vの炭窒化物の析出によって大幅に上
昇している。As is clear from FIG. 2, YS and SSC resistant
C property improves at tempering temperature of 250 ° C or higher, and YS is 55
At 0 ° C. or higher, the precipitation of Nb and V carbonitrides significantly increases.
【0018】一方、靱性は、500℃までは温度の上昇
とともに向上するが、500℃を超えると炭窒化物の析
出により劣化する。特に、DWTTの85%SATT特
性はその傾向が著しく、550℃以上では焼入れのまま
と同等か、もしくはさらに高温側となる。On the other hand, the toughness improves as the temperature rises up to 500 ° C., but if it exceeds 500 ° C., it deteriorates due to the precipitation of carbonitrides. In particular, the tendency of the 85% SATT characteristic of DWTT is remarkable, and at 550 ° C. or higher, it is equivalent to the as-quenched state, or becomes higher temperature side.
【0019】以上のように、低C量の低合金鋼において
は、焼戻し温度を500℃以下とすることによって、耐
食性に優れ、かつ、従来の焼入れ処理のままや、焼入れ
後600℃付近の温度で焼戻す場合よりも良好な強度と
低温靱性のバランスが得られる。As described above, in a low alloy steel with a low C content, by setting the tempering temperature to 500 ° C. or less, the corrosion resistance is excellent, and the temperature is about 600 ° C. after the quenching process or after the conventional quenching treatment. A good balance between strength and low temperature toughness can be obtained as compared with the case of tempering.
【0020】しかし、図1に示すようにC量を低下させ
ることにより靱性及び耐食性は向上するものの、強度は
低下する。そこで、本発明では、強度を向上させるため
Mn,Cr,Mo,Vなどの元素を必要な量添加する。However, as shown in FIG. 1, although the toughness and corrosion resistance are improved by reducing the C content, the strength is reduced. Therefore, in the present invention, necessary amounts of elements such as Mn, Cr, Mo and V are added to improve the strength.
【0021】図3はC量が0.08%以下で厚さ25m
mの鋼板について、焼入れままと焼き入れ後400℃で
焼戻したときの炭素当量CeqとTS,vTrsとの関
係を示した図である。ここで、Ceqは以下の式で表わ
される。FIG. 3 shows that the amount of C is 0.08% or less and the thickness is 25 m.
It is a figure showing the relation between carbon equivalent Ceq and TS, vTrs when tempering at 400 ° C after quenching about the steel plate of m. Here, Ceq is represented by the following formula.
【0022】Ceq=C+Mn/6+(Cu+Ni)/
15+(Cr+Mo+V)/5 この図3から、C量が低下しても他の元素を添加するこ
とによりCeqを一定以上にすれば必要な強度を維持す
ることができることがわかる。Ceq = C + Mn / 6 + (Cu + Ni) /
15+ (Cr + Mo + V) / 5 From this FIG. 3, it can be seen that the required strength can be maintained if the Ceq is kept above a certain level by adding other elements even if the C content decreases.
【0023】次に、本発明の鋼の成分範囲を上述のよう
に規定した理由について説明する。C量は0.02〜
0.08%の範囲に規定される。Cは、図1に示す通
り、0.08%を超えると、(1)400℃で焼戻をし
てもvTrs−60℃以上となり、600℃で焼戻しさ
れる従来の曲がり管よりも高い低温靱性が得られないこ
と、(2)焼戻し処理を施しても島状マルテンサイトな
どの硬化組織が消失しない場合があり、その硬化組織が
HICの起点となること、などの不都合がある。従っ
て、C量の上限を0.08%とした。Next, the reason why the composition range of the steel of the present invention is defined as described above will be explained. C amount is 0.02-
It is specified in the range of 0.08%. As shown in FIG. 1, when C exceeds 0.08%, (1) it becomes vTrs−60 ° C. or higher even if tempered at 400 ° C., which is higher than the conventional bent pipe tempered at 600 ° C. There are inconveniences such as the lack of toughness, and (2) the hardening structure such as island martensite may not disappear even after the tempering treatment, and the hardening structure serves as the starting point of HIC. Therefore, the upper limit of the amount of C is set to 0.08%.
【0024】一方、下限については、C量が低いほど強
度が下がるので、その分他の元素を補充しなければなら
なくなるので、経済的な観点から0.02%とした。S
i量は0.05〜0.5%の範囲に規定される。On the other hand, the lower limit is 0.02% from an economical point of view because the lower the amount of C is, the lower the strength is, so that other elements must be supplemented accordingly. S
The i amount is specified in the range of 0.05 to 0.5%.
【0025】Siは脱酸効果を有する元素であり、その
効果を得るために0.05%以上であることが必要であ
る。しかし、その量が0.5%を超えると、焼戻し処理
後も島状マルテンサイトが残存し、耐HIC性及び靭性
の向上が望めない。従って、その上限を0.5%とし
た。Si is an element having a deoxidizing effect, and it is necessary that the Si content be 0.05% or more in order to obtain the effect. However, if the amount exceeds 0.5%, island martensite remains after the tempering treatment, and improvement in HIC resistance and toughness cannot be expected. Therefore, the upper limit is set to 0.5%.
【0026】Mn量は0.8〜2%の範囲に規定され
る。Mnは、Cに次いで有効な強化元素であり、所望の
強度を確保するためには少なくとも0.8%以上添加す
る必要がある。しかし、過度に添加すると靱性と溶接性
に悪影響をあたえると共に、ミクロ偏析が顕著となり、
耐HIC性を害するので、その上限をこれらの悪影響を
及ぼさない限界である2.0%に規定した。The amount of Mn is specified in the range of 0.8 to 2%. Mn is an effective strengthening element next to C, and it is necessary to add at least 0.8% or more in order to secure desired strength. However, if added excessively, the toughness and weldability are adversely affected, and the microsegregation becomes remarkable,
Since the HIC resistance is impaired, its upper limit is set to 2.0%, which is the limit at which these adverse effects are not exerted.
【0027】Nb量は0.01〜0.06%の範囲に規
定される。Nbは炭窒化物を形成し、焼入れ加熱時の粒
成長を抑制し、靱性の向上をもたらすとともに、オース
テナイト粒に適度に固溶すると焼入れ性を向上させ、強
度を確保する。従って、強度確保の観点から0.01%
以上は必要であるが、0.06%を超えると溶接性を低
下させるだけでなく、固溶Nb量の増加によって靱性を
劣化させるため、上限を0.06%とした。The amount of Nb is specified in the range of 0.01 to 0.06%. Nb forms carbonitrides, suppresses grain growth during quenching and heating, and improves toughness. When it forms an appropriate solid solution with austenite grains, Nb improves quenchability and secures strength. Therefore, from the viewpoint of securing strength, 0.01%
The above is necessary, but if it exceeds 0.06%, not only the weldability is deteriorated, but also the toughness is deteriorated due to an increase in the amount of solute Nb, so the upper limit was made 0.06%.
【0028】Ti量は0.005〜0.05%に規定さ
れる。Tiは、窒化物として焼入れ加熱時の粒成長を抑
制し、靭性向上に寄与するが、0.005%未満ではそ
の効果が小さい。一方、0.05%を超えるとその効果
が飽和するとともに、靱性及び溶接性を害するので、上
限を0.05%とした。The amount of Ti is specified to be 0.005 to 0.05%. Ti suppresses grain growth during quenching and heating as a nitride and contributes to improvement of toughness, but if less than 0.005%, its effect is small. On the other hand, if it exceeds 0.05%, the effect is saturated and the toughness and weldability are impaired, so the upper limit was made 0.05%.
【0029】Al量は0.01〜0.06%の範囲に規
定される。Alは脱酸材として有効な元素であり、ま
た、AlNとして析出して焼入れ加熱時に粒成長を抑制
し、靭性向上に寄与するが、これらの効果を得るために
は0.01%以上添加する必要がある。しかし、0.0
6%を超えると靭性を害するだけでなく、鋳塊の表面疵
を多発させるので、上限を0.06%とした。The amount of Al is specified in the range of 0.01 to 0.06%. Al is an element effective as a deoxidizing agent, and is precipitated as AlN to suppress grain growth during quenching and heating and contributes to the improvement of toughness. To obtain these effects, 0.01% or more is added. There is a need. But 0.0
If it exceeds 6%, not only the toughness is impaired but also surface defects of the ingot occur frequently, so the upper limit was made 0.06%.
【0030】N量は0.002〜0.01%の範囲に規
定される。Nは、TiN、AlNとして析出して、焼入
れ加熱時に粒成長を抑制し、もって靭性向上に寄与する
が、その効果を発揮するためには0.002%以上は必
要である。しかし、その量が0.01%を超えると、特
に溶接部の靱性が損なわれるため、上限を0.01%と
した。The amount of N is specified in the range of 0.002 to 0.01%. N precipitates as TiN and AlN and suppresses grain growth during quenching and heating, thus contributing to improvement of toughness, but 0.002% or more is necessary to exert the effect. However, if the amount exceeds 0.01%, the toughness of the welded part is particularly impaired, so the upper limit was made 0.01%.
【0031】Ca量は0.001〜0.005%の範囲
に規定される。Caは、MnSを球状化して耐HIC
性、耐SSCC性及び靭性に寄与する元素であるが、こ
れらの効果を発揮するためにはその量が0.001%以
上であることが必要である。一方、その量が0.005
%を超えると、Ca系介在物を形成して耐食性を劣化さ
せるばかりでなく、靭性及び溶接性をも劣化させるの
で、上限を0.005%とした。The amount of Ca is specified in the range of 0.001 to 0.005%. Ca makes MnS spherical and HIC resistant
Element, which contributes to the toughness, SSCC resistance, and toughness, but its amount must be 0.001% or more to exert these effects. On the other hand, the amount is 0.005
%, The Ca-based inclusions are formed to deteriorate not only corrosion resistance but also toughness and weldability, so the upper limit was made 0.005%.
【0032】本発明における鋼の成分は、上記組成を基
本とするが、より管厚が厚い場合や、強度の高いグレー
ドの鋼成分は、上記組成にCu、Ni、Cr、Mo、V
のうち少なくとも1種を以下の範囲の量で含有させるこ
とにより得ることができる。The steel composition in the present invention is basically based on the above composition. However, when the pipe thickness is thicker or the steel composition of the grade having high strength is Cu, Ni, Cr, Mo, V in the above composition.
It can be obtained by containing at least one of these in an amount within the following range.
【0033】Cu量は0.5%以下の範囲とする。Cu
は、強度、靭性、耐HIC性の向上に効果があるが、
0.5%を超えると熱間加工性を害するので上限を0.
5%とした。The amount of Cu is set to 0.5% or less. Cu
Has the effect of improving strength, toughness, and HIC resistance,
If it exceeds 0.5%, the hot workability is impaired, so the upper limit is set to 0.
It was set to 5%.
【0034】Ni量は1.0%以下の範囲とする。Ni
は良好な強度靭性バランスを得るための有効な元素であ
り、Cu疵の発生を防止する作用もあるが、多量の添加
は溶接性を損なうとともに経済的にも不利となるため、
上限を1.0%とした。The Ni content is in the range of 1.0% or less. Ni
Is an effective element for obtaining a good balance of strength and toughness, and also has an effect of preventing the generation of Cu flaws, but addition of a large amount impairs weldability and is economically disadvantageous.
The upper limit was 1.0%.
【0035】Cr量は0.3%以下の範囲とする。Cr
は強度向上に効果があるが、多過ぎると靱性及び溶接性
を害するので、上限を0.3%とした。The Cr content is within the range of 0.3% or less. Cr
Has the effect of improving strength, but if it is too large, it impairs toughness and weldability, so the upper limit was made 0.3%.
【0036】Mo量は0.3%以下の範囲とする。Mo
は、鋼の強度を向上と組織のベイナイト化に寄与する
が、多過ぎると靱性及び溶接性を害するので、上限を
0.3%とした。The Mo content is in the range of 0.3% or less. Mo
Contributes to improving the strength of the steel and making the structure bainite, but if it is too large, it impairs the toughness and weldability, so the upper limit was made 0.3%.
【0037】V量は0.1%以下の範囲とする。Vは、
鋼の強度向上に有効な元素であるが、多過ぎると靱性や
溶接性を害するので、上限を0.1%とした。The amount of V is set in the range of 0.1% or less. V is
It is an element effective for improving the strength of steel, but if it is too much, it impairs toughness and weldability, so the upper limit was made 0.1%.
【0038】本発明における鋼は、上記添加元素の他、
残部の鉄及び不可避的不純物からなる。これら不純物の
うち、特にP及びSについては、以下のように規定され
る。P量は0.015%以下の範囲とする。In the steel according to the present invention, in addition to the above-mentioned additional elements,
The balance consists of iron and inevitable impurities. Of these impurities, P and S in particular are defined as follows. The amount of P shall be 0.015% or less.
【0039】Pはミクロ偏析することにより耐HICに
有害な元素であり、さらに靭性にも影響を与えるため、
上限をこのような悪影響を及ぼさない限界である0.0
15%とした。P is an element harmful to HIC resistance due to micro-segregation and further affects toughness.
The upper limit is 0.0, which is a limit that does not have such an adverse effect.
It was set to 15%.
【0040】S量は0.002%以下の範囲とする。S
はMnSを形成し、耐HIC性及び靭性に有害な元素で
あるため、上限をこのような悪影響を及ぼさない限界で
ある0.002%とした。The amount of S is set to 0.002% or less. S
Forms MnS and is an element harmful to HIC resistance and toughness, so the upper limit was made 0.002%, which is the limit that does not have such an adverse effect.
【0041】その他の不可避的不純物は、製造される曲
がり管の特性を損なわせない範囲で許容される。次に、
曲げ加工条件の限定理由を説明する。Other unavoidable impurities are acceptable as long as they do not impair the characteristics of the bent pipe manufactured. next,
The reasons for limiting the bending conditions will be described.
【0042】曲げ加工時の加熱温度は、鋼のAc3 点以
上1050℃以下とする。これにより、オーステナイト
組織とし、その後の処理によって所望の組織を得ること
ができる。適度なNbの固溶とオーステナイト粒の成長
抑制の観点から、加熱温度の上限を1050℃とした。
これは、1050℃を超えるとオーステナイト粒が粗大
化して焼入れ性が増加し、過度に強度が上昇して靭性及
び耐食性が劣化するためである。上記温度範囲であれば
耐食性が優れているが、強度靭性のバランスを最良とす
るためには900〜1050℃の範囲とすることが望ま
しい。The heating temperature during bending is set to the Ac 3 point of the steel or more and 1050 ° C. or less. Thereby, an austenite structure can be obtained, and a desired structure can be obtained by the subsequent treatment. The upper limit of the heating temperature was set to 1050 ° C. from the viewpoint of moderate solid solution of Nb and suppression of growth of austenite grains.
This is because when the temperature exceeds 1050 ° C., the austenite grains are coarsened and the hardenability is increased, the strength is excessively increased and the toughness and the corrosion resistance are deteriorated. Although the corrosion resistance is excellent in the above temperature range, it is desirable to set it in the range of 900 to 1050 ° C. in order to obtain the best balance of strength and toughness.
【0043】この加熱の際の保持時間は、オーステナイ
ト粒の粗大化を防止する点から短時間であることが望ま
しい。所望の短時間加熱は誘導加熱により達成すること
ができるが、誘導加熱に限定されるものではない。The holding time during this heating is preferably short in order to prevent coarsening of austenite grains. The desired short-time heating can be achieved by induction heating, but is not limited to induction heating.
【0044】また、加熱時における加熱速度は3℃/s
ec以上、保持時間は10分以内とすることが望まし
い。焼入れの際の冷却速度は、800℃から400℃間
の平均冷却速度で8℃/秒以上とすることが望ましい。The heating rate during heating is 3 ° C./s.
ec or more and the holding time is preferably 10 minutes or less. The cooling rate during quenching is preferably 8 ° C./sec or more at an average cooling rate between 800 ° C. and 400 ° C.
【0045】次に、焼戻し処理条件の限定理由について
説明する。まず、その温度については図2に示すとお
り、YSが焼入れのままより上昇し、耐食性が向上する
250℃を下限とし、Nb,Vなどの炭窒化物による析
出硬化によって靱性が劣化しない500℃を上限とす
る。Next, the reason for limiting the tempering condition will be described. First, as shown in FIG. 2, the lower limit of the temperature is 250 ° C. at which YS rises further as it is quenched and the corrosion resistance is improved, and 500 ° C. at which the toughness does not deteriorate due to precipitation hardening by carbonitrides such as Nb and V. The upper limit.
【0046】また、保持時間については、特に限定され
るものではないが、30分間の保持でもYS、靱性、耐
食性の向上が認められるので、従来のように管厚1イン
チ当り1時間といった長時間の保持は必要ない。一般的
に長時間に亘って焼戻し温度に保持することは軟化を招
くので、30分間程度とすることが望ましい。The holding time is not particularly limited, but since YS, toughness, and corrosion resistance are improved even after holding for 30 minutes, a long time such as 1 hour per 1 inch of pipe thickness as in the conventional case. Need not be retained. Generally, holding the tempering temperature for a long time causes softening, so it is desirable to set the tempering temperature to about 30 minutes.
【0047】なお、焼戻処理は一般的には加熱炉におい
て実施されるが、これに限定されるものではない。な
お、本発明における曲がり管には、継目無し鋼管のみで
なく溶接鋼管をも含まれる。この場合、溶接金属を母材
と同一組成、すなわち上記組成と同一にしておけば、上
記熱処理によって、耐食性、強度、靭性に優れた溶接部
及び溶接熱影響部が得られる。The tempering treatment is generally carried out in a heating furnace, but is not limited to this. The bent pipe in the present invention includes not only seamless steel pipe but also welded steel pipe. In this case, if the weld metal has the same composition as the base metal, that is, the same composition as the above, the heat treatment provides a welded portion and a weld heat affected zone having excellent corrosion resistance, strength, and toughness.
【0048】[0048]
【実施例】次に、本発明の具体的な実施例について説明
する。表1に示す寸法及び化学成分を有する直管を、表
2に示す曲げ加工条件にて曲がり管に製造した。なお、
焼き入れ時の冷却速度は10〜50℃/秒であり、焼戻
し処理における保持時間は30分間とした。EXAMPLES Next, specific examples of the present invention will be described. Straight pipes having the dimensions and chemical components shown in Table 1 were manufactured into bent pipes under the bending conditions shown in Table 2. In addition,
The cooling rate during quenching was 10 to 50 ° C./sec, and the holding time in the tempering treatment was 30 minutes.
【0049】表2には、従来の曲がり管と本発明による
曲がり管の引張試験、シャルピー試験、DWTT、HI
C試験、SSCC試験の結果を併せて示した。なお、試
験片は、曲がり管の曲げ内周側(コンプレッション側)
から採取した。引張試験片については、未矯正のまま採
取する丸棒試験片と、矯正して採取する全厚試験片のう
ちYSが低く現れる試験片を用いた。すなわち、焼入れ
ままの曲がり管については未矯正のまま採取する丸棒試
験片で評価し、焼き戻し処理をほどこした曲がり管につ
いては矯正して採取する全厚試験片で評価した。また、
HIC試験については、前述のBP溶液とNACE溶液
の2種類の溶液で行った、SSCC試験についてはNA
CE TM01−77に準拠し、規格下限降伏応力(S
MYS)の80%に相当する負荷応力のもとで720時
間浸漬し、破断の有無を調査した。Table 2 shows the tensile test, Charpy test, DWTT, and HI of the conventional bent pipe and the bent pipe according to the present invention.
The results of the C test and SSCC test are also shown. In addition, the test piece is the bending inner circumference side of the bent pipe (compression side).
Collected from. As the tensile test piece, a round bar test piece that was sampled without correction and a test piece that showed a low YS among all the thickness-corrected test pieces that were sampled were used. That is, a bent bar as-quenched was evaluated by a round bar test piece that was taken uncorrected, and a bent tube that had been tempered was evaluated by a full-thickness test piece that was straightened and collected. Also,
The HIC test was carried out with two kinds of solutions, the BP solution and the NACE solution, and the SSCC test was NA.
In conformity with CE TM01-77, the standard lower limit yield stress (S
It was immersed for 720 hours under a load stress corresponding to 80% of MYS), and the presence or absence of breakage was investigated.
【0050】[0050]
【表1】 [Table 1]
【0051】[0051]
【表2】 [Table 2]
【0052】表1、表2に示す比較曲がり管は、鋼の化
学成分及び曲げ加工条件のいずれかが本発明の範囲から
外れており(表1及び2中白抜き三角で示す)、表2に
示すように強度、靭性、耐食性の少なくとも1つが劣っ
ていた(黒塗り三角で示す)。In the comparative bent pipes shown in Tables 1 and 2, either the chemical composition of steel or the bending conditions are out of the scope of the present invention (shown by white triangles in Tables 1 and 2). As shown in, at least one of strength, toughness, and corrosion resistance was inferior (indicated by black triangles).
【0053】これに対して、化学成分及び曲げ加工条件
がいずれも本発明に規定する範囲内の本発明曲がり管
は、vTrs≦−60℃、85%SATT≦−10℃と
いう優れた低温靭性、及び優れた耐食性が得られること
が確認され、本発明の効果が明らかとなった。On the other hand, the bent pipe of the present invention, in which both the chemical composition and the bending condition are within the range specified in the present invention, has excellent low temperature toughness of vTrs ≦ -60 ° C. and 85% SATT ≦ -10 ° C. It was also confirmed that excellent corrosion resistance was obtained, and the effect of the present invention was clarified.
【0054】[0054]
【発明の効果】以上説明したとおり、本発明によれば、
低炭素量、低炭素当量で耐食性に優れた高張力高靭性曲
がり管の製造方法が提供される。具体的には、API
5L規格X60〜X70グレードを満たす強度、及びv
Trs≦−60℃、DWTTの85%SATT≦−10
℃なる低温靭性を示しつつ、耐HIC性、耐SSCC性
に優れた曲がり管を製造することができ、工業的価値は
大である。As described above, according to the present invention,
Provided is a method for producing a high tensile strength and high toughness bent pipe having a low carbon content, a low carbon equivalent and excellent corrosion resistance. Specifically, API
Strength that satisfies 5L standard X60 to X70 grade, and v
Trs ≦ −60 ° C., DWTT 85% SATT ≦ −10
It is possible to manufacture a bent pipe excellent in HIC resistance and SSCC resistance while exhibiting a low temperature toughness of ℃, and its industrial value is great.
【図面の簡単な説明】[Brief description of drawings]
【図1】強度、靭性、耐食性に及ぼすC量の影響を示す
図。FIG. 1 is a diagram showing the influence of C content on strength, toughness, and corrosion resistance.
【図2】焼戻し温度による材質変化を要約して示す図。FIG. 2 is a diagram summarizing a change in material depending on a tempering temperature.
【図3】炭素当量CeqとTSおよびvTrsとの関係
を示す図。FIG. 3 is a diagram showing a relationship between carbon equivalent Ceq and TS and vTrs.
フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 FI 技術表示箇所 C22C 38/14 (72)発明者 高岸 正章 東京都中央区築地一丁目13番10号 第一高 周波工業株式会社内 (72)発明者 木原 惣一 東京都中央区築地一丁目13番10号 第一高 周波工業株式会社内Continuation of the front page (51) Int.Cl. 6 Identification number Reference number in the agency FI Technical indication C22C 38/14 (72) Inventor Masaaki Takagishi 1-13-10 Tsukiji, Chuo-ku, Tokyo Dai-ichi High Frequency Industrial Co., Ltd. In-house (72) Inventor Souichi Kihara 1-13-10 Tsukiji, Chuo-ku, Tokyo Inside Daiichi High Frequency Industry Co., Ltd.
Claims (2)
Si:0.05〜0.5%、Mn:0.8〜2.0%、
Nb:0.01〜0.06%、Ti:0.005〜0.
05%、Al:0.01〜0.06%、N :0.00
2〜0.01%、Ca:0.001〜0.005%を含
有し、不純物としてのP、Sを夫々、P :0.015
%以下、S :0.002%以下に制限し、残部鉄及び
その他の不可避的不純物からなる低合金鋼で形成された
直管を、Ac3 点以上、1050℃以下の温度範囲に加
熱して曲げ加工を行い、その直後に焼き入れ処理を施
し、次いで、250〜500℃の温度範囲で焼き戻すこ
とを特徴とする耐食性に優れた高張力高靭性曲がり管の
製造方法。1. C .: 0.02 to 0.08% by weight,
Si: 0.05-0.5%, Mn: 0.8-2.0%,
Nb: 0.01 to 0.06%, Ti: 0.005 to 0.
05%, Al: 0.01 to 0.06%, N: 0.00
2 to 0.01%, Ca: 0.001 to 0.005%, and P and S as impurities, respectively, P: 0.015
% Or less, S: 0.002% or less, and a straight pipe formed of a low alloy steel consisting of the balance iron and other unavoidable impurities is heated to a temperature range of Ac 3 points or more and 1050 ° C. or less. A method for producing a high-strength, high-toughness bent tube excellent in corrosion resistance, which comprises bending, immediately followed by quenching, and then tempering in a temperature range of 250 to 500 ° C.
Si:0.05〜0.5%、Mn:0.8〜2.0%、
Nb:0.01〜0.06%、Ti:0.005〜0.
05%、Al:0.01〜0.06%、N :0.00
2〜0.01%、Ca:0.001〜0.005%を含
有し、さらに、Cu:0.5%以下、Ni:1.0%以
下、Cr:0.3%以下、Mo:0.3%以下、V :
0.1%以下のうち少なくとも1種を含有し、不純物と
してのP、Sを夫々、P :0.015%以下、S :
0.002%以下に制限し、残部鉄及びその他の不可避
的不純物からなる低合金鋼で形成された直管を、Ac3
点以上、1050℃以下の温度範囲に加熱して曲げ加工
を行い、その直後に焼き入れ処理を施し、次いで、25
0〜500℃の温度範囲で焼き戻すことを特徴とする耐
食性に優れた高張力高靭性曲がり管の製造方法。2. By weight%, C: 0.02-0.08%,
Si: 0.05-0.5%, Mn: 0.8-2.0%,
Nb: 0.01 to 0.06%, Ti: 0.005 to 0.
05%, Al: 0.01 to 0.06%, N: 0.00
2 to 0.01%, Ca: 0.001 to 0.005%, and further Cu: 0.5% or less, Ni: 1.0% or less, Cr: 0.3% or less, Mo: 0. 0.3% or less, V:
At least one of 0.1% or less is contained, and P and S as impurities are respectively P: 0.015% or less and S:
A straight pipe formed of a low alloy steel containing the balance iron and other unavoidable impurities is restricted to Ac 3
Bending is performed by heating in a temperature range of 1050 ° C. or higher and 1050 ° C. or lower, followed by quenching treatment, and then 25
A method of manufacturing a bent pipe having high tensile strength and high toughness, which is excellent in corrosion resistance, characterized by tempering in a temperature range of 0 to 500 ° C.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14802393A JP3290247B2 (en) | 1993-06-18 | 1993-06-18 | Method for manufacturing high tensile strength and high toughness bent pipe with excellent corrosion resistance |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14802393A JP3290247B2 (en) | 1993-06-18 | 1993-06-18 | Method for manufacturing high tensile strength and high toughness bent pipe with excellent corrosion resistance |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH073330A true JPH073330A (en) | 1995-01-06 |
JP3290247B2 JP3290247B2 (en) | 2002-06-10 |
Family
ID=15443384
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP14802393A Expired - Lifetime JP3290247B2 (en) | 1993-06-18 | 1993-06-18 | Method for manufacturing high tensile strength and high toughness bent pipe with excellent corrosion resistance |
Country Status (1)
Country | Link |
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JP (1) | JP3290247B2 (en) |
Cited By (11)
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JPH08204096A (en) * | 1995-01-30 | 1996-08-09 | Nec Corp | Method of lead visual inspection of semiconductor device and inspector |
WO2008007737A1 (en) * | 2006-07-13 | 2008-01-17 | Sumitomo Metal Industries, Ltd. | Bend pipe and process for producing the same |
WO2008139639A1 (en) | 2007-05-16 | 2008-11-20 | Sumitomo Metal Industries, Ltd. | Bend pipe and process for manufacturing the same |
CN103352106A (en) * | 2013-06-28 | 2013-10-16 | 安徽呈合科技有限责任公司 | Surface-hardening treatment method for inner wall of low-carbon steel long cylinder |
US9644248B2 (en) | 2013-04-08 | 2017-05-09 | Dalmine S.P.A. | Heavy wall quenched and tempered seamless steel pipes and related method for manufacturing said steel pipes |
US9657365B2 (en) | 2013-04-08 | 2017-05-23 | Dalmine S.P.A. | High strength medium wall quenched and tempered seamless steel pipes and related method for manufacturing said steel pipes |
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WO2018216638A1 (en) | 2017-05-22 | 2018-11-29 | 新日鐵住金株式会社 | Bent steel pipe and method for producing same |
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US11124852B2 (en) | 2016-08-12 | 2021-09-21 | Tenaris Coiled Tubes, Llc | Method and system for manufacturing coiled tubing |
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-
1993
- 1993-06-18 JP JP14802393A patent/JP3290247B2/en not_active Expired - Lifetime
Cited By (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH08204096A (en) * | 1995-01-30 | 1996-08-09 | Nec Corp | Method of lead visual inspection of semiconductor device and inspector |
WO2008007737A1 (en) * | 2006-07-13 | 2008-01-17 | Sumitomo Metal Industries, Ltd. | Bend pipe and process for producing the same |
US7770428B2 (en) | 2006-07-13 | 2010-08-10 | Sumitomo Metal Industries, Ltd. | Hot bend pipe and a process for its manufacture |
JP5200932B2 (en) * | 2006-07-13 | 2013-06-05 | 新日鐵住金株式会社 | Bend pipe and manufacturing method thereof |
WO2008139639A1 (en) | 2007-05-16 | 2008-11-20 | Sumitomo Metal Industries, Ltd. | Bend pipe and process for manufacturing the same |
US7780800B2 (en) | 2007-05-16 | 2010-08-24 | Sumitomo Metal Industries, Ltd. | Method of manufacturing a bent pipe |
US11952648B2 (en) | 2011-01-25 | 2024-04-09 | Tenaris Coiled Tubes, Llc | Method of forming and heat treating coiled tubing |
US10378074B2 (en) | 2013-03-14 | 2019-08-13 | Tenaris Coiled Tubes, Llc | High performance material for coiled tubing applications and the method of producing the same |
US9803256B2 (en) | 2013-03-14 | 2017-10-31 | Tenaris Coiled Tubes, Llc | High performance material for coiled tubing applications and the method of producing the same |
US10378075B2 (en) | 2013-03-14 | 2019-08-13 | Tenaris Coiled Tubes, Llc | High performance material for coiled tubing applications and the method of producing the same |
US11377704B2 (en) | 2013-03-14 | 2022-07-05 | Tenaris Coiled Tubes, Llc | High performance material for coiled tubing applications and the method of producing the same |
US9657365B2 (en) | 2013-04-08 | 2017-05-23 | Dalmine S.P.A. | High strength medium wall quenched and tempered seamless steel pipes and related method for manufacturing said steel pipes |
US9644248B2 (en) | 2013-04-08 | 2017-05-09 | Dalmine S.P.A. | Heavy wall quenched and tempered seamless steel pipes and related method for manufacturing said steel pipes |
US11105501B2 (en) | 2013-06-25 | 2021-08-31 | Tenaris Connections B.V. | High-chromium heat-resistant steel |
CN103352106A (en) * | 2013-06-28 | 2013-10-16 | 安徽呈合科技有限责任公司 | Surface-hardening treatment method for inner wall of low-carbon steel long cylinder |
US11124852B2 (en) | 2016-08-12 | 2021-09-21 | Tenaris Coiled Tubes, Llc | Method and system for manufacturing coiled tubing |
WO2018216638A1 (en) | 2017-05-22 | 2018-11-29 | 新日鐵住金株式会社 | Bent steel pipe and method for producing same |
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