JPH0138851B2 - - Google Patents
Info
- Publication number
- JPH0138851B2 JPH0138851B2 JP60149467A JP14946785A JPH0138851B2 JP H0138851 B2 JPH0138851 B2 JP H0138851B2 JP 60149467 A JP60149467 A JP 60149467A JP 14946785 A JP14946785 A JP 14946785A JP H0138851 B2 JPH0138851 B2 JP H0138851B2
- Authority
- JP
- Japan
- Prior art keywords
- tempered
- toughness
- content
- weld metal
- quenched
- 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.)
- Expired
Links
- 229910052751 metal Inorganic materials 0.000 claims description 36
- 239000002184 metal Substances 0.000 claims description 36
- 238000005496 tempering Methods 0.000 claims description 26
- 238000010438 heat treatment Methods 0.000 claims description 25
- 238000000034 method Methods 0.000 claims description 13
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 229910052710 silicon Inorganic materials 0.000 claims description 3
- 229910052796 boron Inorganic materials 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 229910052719 titanium Inorganic materials 0.000 claims description 2
- 238000003466 welding Methods 0.000 description 19
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 17
- 229910000831 Steel Inorganic materials 0.000 description 14
- 230000000171 quenching effect Effects 0.000 description 14
- 239000010959 steel Substances 0.000 description 14
- 238000010791 quenching Methods 0.000 description 13
- 230000007423 decrease Effects 0.000 description 12
- 239000010955 niobium Substances 0.000 description 11
- 230000000694 effects Effects 0.000 description 10
- 239000000203 mixture Substances 0.000 description 10
- 239000010936 titanium Substances 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 8
- 239000010949 copper Substances 0.000 description 8
- 239000011572 manganese Substances 0.000 description 8
- 230000006698 induction Effects 0.000 description 5
- 239000010953 base metal Substances 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000004907 flux Effects 0.000 description 3
- 238000009863 impact test Methods 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 238000004881 precipitation hardening Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 229910001563 bainite Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000010790 dilution Methods 0.000 description 2
- 239000012895 dilution Substances 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Bending Of Plates, Rods, And Pipes (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Articles (AREA)
Description
[産業上の利用分野]
この発明は、サブマージアーク溶接法により溶
接し、誘導加熱により曲げられる大径溶接鋼管等
の製造方法に関し、特に、溶接部の低温靭性及び
強度に優れたベンド管の製造方法に関する。
[従来の技術]
第3図に示すように、従来、サブマージアーク
溶接法により溶接して得た大径溶接鋼管を誘導加
熱しつつ曲げ加工した後、鋼管全体を焼入れし、
次いで鋼管を焼戻すことにより、ベンド管が製造
されている。
[発明が解決しようとする問題点]
しかしながら、この方法の場合は、鋼管の全長
に亘り高周波誘導加熱して焼入れるため、熱処理
時間が長く、しかも熱処理に際してダミー管を取
付ける必要があるため作業能率が悪い。このた
め、従来方法においては、ベンド管を製造するた
めに多大の時間及び工数が必要であるという問題
点がある。
[問題点を解決するための手段]
この発明は斯かる事情に鑑みてなされたもので
あつて、素管の曲部のみを焼入れし、次いで素管
全体を焼戻しすることにより、熱処理時間を短縮
し、作業能率を向上させると共に、溶接部におけ
る低温靭性が優れた高強度のベンド管を製造する
ことができるベンド管の製造方法を提供すること
を目的とする。
この発明に係るベンド管の製造方法は、重量%
で、Cが0.05乃至0.15%、Siが0.5%以下、Mnが
1.0乃至2.0%、Niが0.5乃至3.0%、Cuが0.02乃至
1.0%、Oが0.03%以下、Nbが0.01乃至0.10%、
Tiが0.005乃至0.05%であり、更に、0.1%以下の
V、1.0%以下のMo、及び0.0005乃至0.005%のB
のうち一種類以上の成分を含有し、残部がFe及
び不可避的不純物よりなる溶接金属で溶接された
素管を、加熱しつつ曲げ加工し、曲部を900乃至
1100℃の温度で焼入れし、その後、素管全体を
550乃至700℃の温度で5分以上加熱して焼き戻し
することを特徴とする。
第2図に示すように、サブマージアーク溶接法
によつて溶接して得た大径溶接素管を、誘導加熱
によつて曲げ加工した後、曲部QTのみを焼入れ
し、次いで素管全体をガス炉等で焼戻しする方法
においては、直線部Tの焼入れを省略することが
できるため、熱処理時間が短縮し、ダミー管を取
付ける必要がないため、作業能率が高い。しか
し、この曲部QTのみを焼入れし、全体を焼戻す
方法においては、焼入れ焼戻しの熱覆歴を受ける
溶接金属部分QTと焼戻しの熱覆歴のみを受ける
溶接金属部分Tとが共存するため、両部分の低温
靭性及び強度を満足させる必要がある。特に、ベ
ンド管をアラスカ等の寒冷地で使用する場合に、
溶接金属の低温靭性が問題となる。
本願発明者等は、上記方法において低温靭性及
び強度を向上させるべく種々検討を重ねた結果、
溶接金属の組成及び熱処理条件を適切に選択する
ことにより、曲部及び直線部の低温靭性及び強度
を向上させ得ることを見出した。この発明は、こ
のような知見に基いてなされたものであつて、溶
接金属の組成及び熱処理条件を、本発明にて規定
した範囲に調整することにより、−50℃における
シヤルピー衝撃試験において10Kgf・m以上の吸
収エネルギが得られ、50乃至70Kgf/mm2の強度が
得られる。従つて、この発明により、低温靭性が
優れた高強度のベンド管を製造することができ
る。
以下、この発明について具体的に説明する。
誘導加熱による焼入れでは、通常、加熱速度が
100乃至500℃/分、最高加熱温度における保持時
間が1分以内、冷却速度が10乃至50℃/秒であ
り、炉内焼戻しにおいては、焼戻温度の保持時間
が5乃至120分であり、このようなベンド管の熱
覆歴は通常の熱処理方法によるものとは異なる。
このような熱覆歴を受ける溶接金属において、
焼入れ焼戻し処理を受けた部分(以下、焼入焼戻
部という)と焼戻しのみを受けた部分(以下、焼
戻部という)との双方について、低温靭性を満足
させるためには、溶接金属の組成は以下の如く規
定される。
先ず、ニツケルNi、銅Cu、チタンTi、ボロン
B等の添加が、焼入焼戻部と焼戻部との双方の低
温靭性を向上させる上で有効である。
Ni含有量は0.5乃至3.0重量%である。Niは、焼
入れ時のオーステナイトを安定化して焼入れ性を
増し、焼戻し時には析出硬化を生じないため、焼
入焼戻部の低温靭性を向上させるために有効な成
分である。一方、焼戻し部においては、Niはフ
エライト地を強化すると共に、焼戻しによつても
析出硬化しないため、その低温靭性を向上させる
作用を有する。しかしながら、サブマージアーク
溶接の場合は、溶接金属にNiを3%を超えて含
有すると高温割れが発生するため、Ni含有量は
3%以下に制限する必要がある。一方、Ni含有
量が0.5%より少ないと前述の低温靭性を高める
という効果が得られない。第1図は、横軸にNi
の含有量をとり、縦軸にシヤルピー衝撃試験(−
50℃)における吸収エネルギをとつて、Niの含
有量と、焼入焼戻部及び焼戻部におけるシヤルピ
ー吸収エネルギとの関係を示すグラフである。こ
れによると、溶接金属の焼入焼戻部と焼戻部との
双方とも、Niが増加するに従い低温靭性が増加
していることがわかる。この第1図から明らかな
ように、焼入焼戻部及び焼戻部の双方について十
分な低温靭性を確保するためには、Niの含有量
を0.5%以上にする必要がある。
Cu含有量は0.02乃至1.0重量%である。Cuの含
有量が1%以下であると、焼入焼戻部及び焼戻部
の双方の低温靭性が向上する。しかし、Cu含有
量が0.02%より低いとその効果が少ない。このた
め、Cu含有量を0.02乃至1.0%に規定する。
Ti含有量は0.005乃至0.05重量%である。Tiは
溶接金属の組織を微細化し、溶接金属の焼戻部の
靭性を向上させる。しかし、溶接金属中にTiが
0.05%を超えて含有すると、析出硬化によつて靭
性が低下する一方、0.005%以下では組織の細粒
化が十分ではない。
B含有量は0.0005乃至0.005重量%である。B
はTiと共に複合添加することにより、溶接金属
の組織を微細化する効果があり、溶接金属の焼戻
部の靭性を増加させる。また、ベンド管曲部の焼
入焼戻部のように急速加熱及び急速冷却を受ける
部分では、微量のBにより靭性が向上する。しか
し、B含有量が0.005%を超えると溶接金属の焼
入焼戻部の靭性が低下し、
0.0005%より少ないと前記効果を得ることがで
きない。このため、B含有量を0.0005乃至0.005
重量%に設定する。
次に、炭素C及びマンガンMnは、焼入焼戻部
及び焼戻部の双方について、その低温靭性及び強
度に大きな影響を及ぼす。
C含有量は0.05乃至0.15重量%である。溶接金
属の焼入焼戻部において、Cが0.05%より少ない
と、十分な焼入れ効果を得ることができず、0.15
%を超えると、焼戻しマルテンサイト組織を有す
るが硬化してしまい、また溶接高温割れ等が発生
する。焼戻部では、Cが0.10%程度の場合に微細
な炭化物が析出して最も高靭性となるが、0.05乃
至0.15%の範囲においても低温靭性が良好であ
る。このため、C含有量は0.05乃至0.15%に設定
する。
Mn含有量は1.0乃至2.0重量%である。Mn含有
量が1.0%より低い場合は、焼入れ性が低下する
ため焼入焼戻部において十分な靭性を得ることが
できない。また、焼戻部においては、粗大なフエ
ライトが粒界に析出するため、低温靭性が劣化す
る。一方、Mnが2.0%を超えると、強度は高くな
るが、焼入れ焼戻部の焼戻脆化感受性が高くなつ
てしまう。また、焼戻部においては、Mn含有量
が2.0%を超えると、上部ベイナイトが晶出する
ため、靭性が劣化する。従つて、焼入焼戻部及び
焼戻部の双方について、十分な靭性を確保するた
めに、Mn含有量は1.0乃至2.0%であることが必
要である。
珪素Si含有量は0.5重量%以下にする必要があ
る。Siは母材、溶接ワイヤ及びフラツクスから溶
接金属中に入るが、Siが0.5%を超えると、焼入
焼戻部及び焼戻部いずれにおいても溶接金属の靭
性が低下するからである。
酸素O含有量は0.03重量%以下である。Oは溶
接金属の切欠靭性に影響を及ぼす。つまり、溶接
金属中のOはその殆んどが介在物としてに存在し
ているが、Oが減少するとそれに伴い介在物が減
少する。そして、介在物が減少するとノツチ効果
が低減するため、Oの減少により、焼入焼戻部及
び焼戻部の双方について切欠靭性が向上する。ま
た、特に、焼入焼戻部では、Oを含有する介在物
がフエライトの核生成サイトとなり、これが焼入
れ性を阻害する。このため、焼入れ性を確保する
ためにもOの減少は有効である。以上の理由か
ら、焼入焼戻部及び焼戻部の双方の低温靭性が優
れたベンド管を得るために、O含有量を0.03%以
下にすることが必要である。
一方、ニオブNb、バナジウムV、モリブデン
Mo等の成分は鋼材からの希釈によつて溶接金属
に入る。サブマージアーク溶接では母材の希釈率
が60乃至70%であるから、母材のNb,V,Mo等
の含有量も溶接金属の焼入焼戻部及び焼戻部の靭
性に対して影響を与える。
Nb含有量は0.10重量%以下である。Nbが0.10
%を超えると溶接金属で焼戻しによる析出硬化を
起こして靭性が低下する。このため、Nb含有量
は0.10%以下であることが必要である。しかし、
鋼材の強度及び靭性の確保のため、鋼材にはNb
が添加されており、このため溶接金属中にNbが
0.01%以上混入してくる。このような理由で、
Nb含有量は、通常、0.01乃至0.10%になる。
V含有量は0.1重量%以下である。VはNbと同
様の作用を有し、その含有量が0.10%を超えると
靭性が低下するからである。
Mo含有量は1.0重量%以下である。Moは焼入
焼戻部の溶接金属の強度を高める成分であり、少
量添加により高強度の溶接金属を得ることができ
る。しかし、Mo含有量が増加すると、靭性が低
下するため、焼入焼戻部の低温靭性を確保するた
めに、Mo含有量を1.0%以下にする必要がある。
また、焼戻部においては、Moの添加によつて組
織が微細化されて低温靭性が向上するが、過剰に
添加すると上部ベイナイト組織が混在するように
なつて靭性が低下する。従つて、Moが高価であ
ることも考慮し、Mo含有量は1.0%以下にする。
燐P及びイオウSは、母材及び溶接材料から不
純物として入つてくる成分であり、溶接高温割れ
等の溶接欠陥を生じやすくするため、できるだけ
少ないほうがよい。
次に、熱処理条件の限定理由について説明す
る。この発明においては、ベンド管曲部の焼入温
度を900乃至1100℃の温度範囲にする。これは、
焼入温度が900℃より低い場合は、十分に焼きが
入らないため溶接金属の強度が低下し、1100℃を
超えると溶接金属の強度は十分であるが靭性が劣
化するからである。
曲部及び直線部の焼戻温度は550乃至700℃であ
る。これは、焼戻温度が550℃より低い場合は、
焼戻し効果が十分でなく低靭性となり、700℃を
超えると、2相域に入るため靭性が急激に低下す
るからである。
上記焼戻温度における保持時間は5分以上であ
ることが必要である。これは、焼戻し保持時間が
5分未満であると、十分な焼戻し効果を得ること
ができないからである。なお、焼戻し保持時間の
上限は、処理能率及びエネルギ消費量の観点から
120分以下とすることが望ましい。
[実施例]
以下、この発明の実施例について説明する。
試験例 1
いずれも管厚が20mmの0.09C−1.50Mn−0.02Nb
−0.25Mo系UOE鋼管Aと、0.10C−1.50Mn−
0.02Nb−0.03V系UOE鋼管Bとをサブマージア
ーク溶接により両面一層溶接した。溶接条件は、
内面側については、先行が940A−36V、後行が
740A−40V、溶接速度が80cm/分、溶接入熱が
47KJ/cmであり、外面側については、先行が
960A−38V、後行が700A−44V、溶接速度が75
cm/分、溶接入熱が54KJ/cmである。また、サ
ブマージアーク溶接の溶接棒のワイヤとしては、
以下の第1表に示すW−1乃至W−5に示す組成
のものを用い、フラツクスとしては、以下の第2
表に示すF−1乃至F−3に示す組成のものを用
いた。
[Industrial Application Field] The present invention relates to a method for producing large-diameter welded steel pipes, etc., which are welded by submerged arc welding and bent by induction heating, and in particular, relates to a method for producing bent pipes with excellent low-temperature toughness and strength at welded parts. Regarding the method. [Prior Art] As shown in Fig. 3, conventionally, a large-diameter welded steel pipe obtained by welding by submerged arc welding is bent while being induction heated, and then the entire steel pipe is quenched.
A bent pipe is then manufactured by tempering the steel pipe. [Problems to be Solved by the Invention] However, in this method, the entire length of the steel pipe is quenched by high-frequency induction heating, so the heat treatment time is long, and it is necessary to attach a dummy pipe during heat treatment, which reduces work efficiency. It's bad. Therefore, the conventional method has a problem in that a large amount of time and man-hours are required to manufacture the bent pipe. [Means for Solving the Problems] This invention was made in view of the above circumstances, and it shortens the heat treatment time by hardening only the curved portion of the raw tube and then tempering the entire raw tube. Another object of the present invention is to provide a method for manufacturing a bent pipe that can improve work efficiency and produce a high-strength bent pipe with excellent low-temperature toughness at the welded part. The method for manufacturing a bent pipe according to the present invention includes:
So, C is 0.05 to 0.15%, Si is 0.5% or less, and Mn is
1.0 to 2.0%, Ni 0.5 to 3.0%, Cu 0.02 to 2.0%
1.0%, O 0.03% or less, Nb 0.01 to 0.10%,
Ti is 0.005 to 0.05%, and further V is 0.1% or less, Mo is 1.0% or less, and B is 0.0005 to 0.005%.
A raw pipe welded with a weld metal containing one or more of these components, with the remainder consisting of Fe and unavoidable impurities, is bent while heating, and the bent portion is
Hardened at a temperature of 1100℃, then the entire raw tube is
It is characterized by being tempered by heating at a temperature of 550 to 700°C for 5 minutes or more. As shown in Figure 2, a large-diameter welded raw pipe obtained by welding by submerged arc welding is bent by induction heating, then only the bent part QT is quenched, and then the entire raw pipe is In the method of tempering in a gas furnace or the like, since the hardening of the straight portion T can be omitted, the heat treatment time is shortened, and there is no need to attach a dummy tube, so the work efficiency is high. However, in this method of quenching only the curved part QT and tempering the entire part, the weld metal part QT, which undergoes the heat coverage history of quenching and tempering, coexists with the weld metal part T, which receives only the heat coverage history of tempering. It is necessary to satisfy the low temperature toughness and strength of both parts. Especially when using bent pipes in cold regions such as Alaska,
The low-temperature toughness of weld metal becomes a problem. As a result of various studies to improve low-temperature toughness and strength in the above method, the inventors of the present application found that
It has been found that by appropriately selecting the composition of weld metal and heat treatment conditions, it is possible to improve the low-temperature toughness and strength of curved parts and straight parts. This invention was made based on such knowledge, and by adjusting the composition of weld metal and heat treatment conditions within the range specified in the present invention, 10 kgf · Absorbed energy of 50 to 70 Kgf/mm 2 can be obtained. Therefore, according to the present invention, a high-strength bent pipe with excellent low-temperature toughness can be manufactured. This invention will be explained in detail below. In induction quenching, the heating rate is usually
100 to 500°C/min, the holding time at the highest heating temperature is within 1 minute, the cooling rate is 10 to 50°C/sec, and in furnace tempering, the holding time at the tempering temperature is 5 to 120 minutes, The thermal history of such bent pipes is different from that obtained by ordinary heat treatment methods. In weld metal that undergoes such a thermal history,
In order to satisfy the low-temperature toughness of both the part that has undergone quenching and tempering treatment (hereinafter referred to as the quenched and tempered part) and the part that has undergone only tempering (hereinafter referred to as the tempered part), it is necessary to change the composition of the weld metal. is defined as follows. First, addition of nickel Ni, copper Cu, titanium Ti, boron B, etc. is effective in improving the low-temperature toughness of both the quenched and tempered part and the tempered part. Ni content is 0.5 to 3.0% by weight. Ni stabilizes austenite during quenching to increase hardenability, and does not cause precipitation hardening during tempering, so it is an effective component for improving the low-temperature toughness of the quenched and tempered part. On the other hand, in the tempered part, Ni has the effect of strengthening the ferrite base and improving its low-temperature toughness because it does not harden by precipitation even during tempering. However, in the case of submerged arc welding, if the weld metal contains more than 3% of Ni, hot cracking will occur, so the Ni content must be limited to 3% or less. On the other hand, if the Ni content is less than 0.5%, the aforementioned effect of increasing low-temperature toughness cannot be obtained. In Figure 1, the horizontal axis shows Ni
The content of
50° C.), and is a graph showing the relationship between the Ni content and the Charpy absorbed energy in the quenched and tempered portion and the tempered portion. According to this, it can be seen that the low-temperature toughness increases as the Ni content increases in both the quenched and tempered part and the tempered part of the weld metal. As is clear from FIG. 1, in order to ensure sufficient low-temperature toughness in both the quenched and tempered portion and the tempered portion, the Ni content must be 0.5% or more. Cu content is 0.02 to 1.0% by weight. When the Cu content is 1% or less, the low-temperature toughness of both the quenched and tempered portion and the tempered portion is improved. However, the effect is small when the Cu content is lower than 0.02%. For this reason, the Cu content is defined as 0.02 to 1.0%. The Ti content is 0.005 to 0.05% by weight. Ti refines the structure of the weld metal and improves the toughness of the tempered part of the weld metal. However, Ti in the weld metal
If the content exceeds 0.05%, the toughness will decrease due to precipitation hardening, while if it is less than 0.005%, the grain size of the structure will not be sufficiently refined. B content is 0.0005 to 0.005% by weight. B
When added in combination with Ti, it has the effect of refining the structure of the weld metal and increases the toughness of the tempered part of the weld metal. In addition, in a portion that undergoes rapid heating and rapid cooling, such as the quenched and tempered portion of a bent pipe bend, the toughness is improved by a small amount of B. However, if the B content exceeds 0.005%, the toughness of the quenched and tempered part of the weld metal decreases, and if it is less than 0.0005%, the above effects cannot be obtained. For this reason, the B content is 0.0005 to 0.005.
Set to weight%. Next, carbon C and manganese Mn greatly influence the low temperature toughness and strength of both the quenched and tempered parts and the tempered parts. The C content is 0.05 to 0.15% by weight. In the quenched and tempered part of the weld metal, if C is less than 0.05%, sufficient quenching effect cannot be obtained;
If it exceeds %, the tempered martensitic structure will be hardened, and hot welding cracks will occur. In the tempered part, fine carbides precipitate when the C content is about 0.10%, resulting in the highest toughness, but low-temperature toughness is also good in the range of 0.05 to 0.15%. Therefore, the C content is set at 0.05 to 0.15%. The Mn content is 1.0 to 2.0% by weight. If the Mn content is lower than 1.0%, hardenability decreases, making it impossible to obtain sufficient toughness in the quenched and tempered part. Furthermore, in the tempered portion, coarse ferrite precipitates at grain boundaries, resulting in poor low-temperature toughness. On the other hand, when Mn exceeds 2.0%, the strength increases, but the susceptibility to temper embrittlement of the quenched and tempered portion increases. Moreover, in the tempered part, when the Mn content exceeds 2.0%, upper bainite crystallizes, resulting in deterioration of toughness. Therefore, in order to ensure sufficient toughness in both the quenched and tempered part and the tempered part, the Mn content needs to be 1.0 to 2.0%. The silicon content must be 0.5% by weight or less. This is because Si enters the weld metal from the base metal, welding wire, and flux, but if Si exceeds 0.5%, the toughness of the weld metal decreases in both the quenched and tempered portion and the tempered portion. The oxygen O content is 0.03% by weight or less. O affects the notch toughness of weld metal. In other words, most of the O in the weld metal exists as inclusions, but as O decreases, the number of inclusions decreases accordingly. Since the notch effect is reduced when the inclusions are reduced, the notch toughness of both the quenched and tempered portion and the tempered portion is improved due to the reduction of O. Further, particularly in the quenched and tempered portion, inclusions containing O become nucleation sites for ferrite, which inhibits hardenability. Therefore, reducing O is effective to ensure hardenability. For the above reasons, in order to obtain a bent pipe with excellent low-temperature toughness in both the quenched and tempered portion and the tempered portion, it is necessary to reduce the O content to 0.03% or less. On the other hand, niobium Nb, vanadium V, molybdenum
Components such as Mo enter the weld metal by dilution from the steel material. In submerged arc welding, the dilution rate of the base metal is 60 to 70%, so the content of Nb, V, Mo, etc. in the base metal also affects the toughness of the quenched and tempered parts of the weld metal. give. Nb content is 0.10% by weight or less. Nb is 0.10
%, precipitation hardening occurs in the weld metal due to tempering, resulting in a decrease in toughness. Therefore, the Nb content needs to be 0.10% or less. but,
In order to ensure the strength and toughness of steel materials, Nb is added to steel materials.
is added, which causes Nb to be added to the weld metal.
Contains more than 0.01%. For this reason,
The Nb content will typically be between 0.01 and 0.10%. The V content is 0.1% by weight or less. This is because V has the same effect as Nb, and if its content exceeds 0.10%, the toughness decreases. Mo content is 1.0% by weight or less. Mo is a component that increases the strength of the weld metal in the quenched and tempered part, and by adding a small amount, a high-strength weld metal can be obtained. However, as the Mo content increases, the toughness decreases, so in order to ensure the low temperature toughness of the quenched and tempered part, the Mo content needs to be 1.0% or less.
Furthermore, in the tempered part, the addition of Mo refines the structure and improves the low-temperature toughness, but if it is added in excess, the upper bainite structure becomes mixed and the toughness decreases. Therefore, taking into account that Mo is expensive, the Mo content is set to 1.0% or less. Phosphorus P and sulfur S are components that enter as impurities from the base metal and the welding material, and since they tend to cause welding defects such as weld hot cracking, it is better to reduce them as much as possible. Next, the reason for limiting the heat treatment conditions will be explained. In this invention, the quenching temperature of the bent pipe portion is set in a temperature range of 900 to 1100°C. this is,
If the quenching temperature is lower than 900°C, the strength of the weld metal will decrease because the quenching will not be done sufficiently, and if it exceeds 1100°C, the strength of the weld metal will be sufficient, but the toughness will deteriorate. The tempering temperature of the curved portion and the straight portion is 550 to 700°C. This means that if the tempering temperature is lower than 550℃,
This is because the tempering effect is insufficient, resulting in low toughness, and when the temperature exceeds 700°C, the toughness rapidly decreases as it enters a two-phase region. The holding time at the above tempering temperature needs to be 5 minutes or more. This is because if the tempering retention time is less than 5 minutes, a sufficient tempering effect cannot be obtained. The upper limit of the tempering retention time is determined from the viewpoint of processing efficiency and energy consumption.
It is desirable that the duration be 120 minutes or less. [Examples] Examples of the present invention will be described below. Test example 1 0.09C−1.50Mn−0.02Nb with pipe thickness of 20 mm
−0.25Mo UOE steel pipe A and 0.10C−1.50Mn−
Both sides of the 0.02Nb-0.03V UOE steel pipe B were welded in a single layer by submerged arc welding. The welding conditions are
Regarding the inner side, the leading one is 940A−36V, and the trailing one is 940A−36V.
740A−40V, welding speed 80cm/min, welding heat input
47KJ/cm, and for the outer surface, the leading
960A-38V, trailing 700A-44V, welding speed 75
cm/min, welding heat input is 54KJ/cm. In addition, as a welding rod wire for submerged arc welding,
The compositions shown in W-1 to W-5 shown in Table 1 below were used, and the fluxes were as follows:
The compositions shown in F-1 to F-3 shown in the table were used.
【表】【table】
【表】【table】
【表】【table】
【表】
第3表は、鋼管A,Bを溶接するときの溶接金
属の化学組成と熱処理後の溶接金属の機械的性質
を示す。熱処理条件については、鋼管曲部を加熱
し950℃に5秒保持した後、20℃/秒(800℃から
400℃までの速度)の冷却速度で焼入れし、鋼管
の全体を加熱し650℃に30分保持して焼戻した。
表中QTとあるのは焼入焼戻部を、Tとあるのは
焼戻部を示す。
第3表中、実施例1〜4は本願発明にて規定し
た組成範囲内のもの、比較例1〜4はその範囲か
ら外れるものである。なお、実施例1〜4及び比
較例1〜4のワイヤ及びフラツクスの組成の組合
せを第4表に示す。[Table] Table 3 shows the chemical composition of the weld metal when steel pipes A and B are welded and the mechanical properties of the weld metal after heat treatment. Regarding the heat treatment conditions, the bent part of the steel pipe was heated and held at 950℃ for 5 seconds, and then heated at 20℃/second (from 800℃
The tube was quenched at a cooling rate of 400℃ (up to 400℃), and the entire steel tube was heated and held at 650℃ for 30 minutes to temper it.
In the table, QT indicates the quenched and tempered part, and T indicates the tempered part. In Table 3, Examples 1 to 4 are within the composition range defined by the present invention, and Comparative Examples 1 to 4 are outside of that range. Table 4 shows the combinations of wire and flux compositions of Examples 1 to 4 and Comparative Examples 1 to 4.
【表】【table】
【表】
実施例1〜4はいずれも、溶接金属の焼入焼戻
部と焼戻部との双方とも−50℃においてシヤルピ
ー吸収エネルギが10Kgf・m以上である。また、
各実施例では十分な引張強度を有している。これ
に対し、比較例1はNiが0.5%未満であり、比較
例2,4はTiが0.05%を超えており、比較例3は
Niが0.5%未満で且つCuが1.0%を超えており、い
ずれもこの発明にて規定した組成の範囲外である
ため、−50℃において、シヤルピー衝撃試験にお
ける吸収エネルギが、焼入焼戻部又は焼戻部で10
Kgf・mより低い値となつている。
試験例 2
第5表は、第3表の実施例1及び4に示す組成
の溶接金属で溶接したUOE鋼管において、熱処
理条件を変化させた場合の焼入れ焼戻部QT及び
焼戻部Tの機械的特性を示す。[Table] In all of Examples 1 to 4, the shear py absorbed energy of both the quenched and tempered part and the tempered part of the weld metal is 10 Kgf·m or more at -50°C. Also,
Each example has sufficient tensile strength. On the other hand, in Comparative Example 1, Ni is less than 0.5%, in Comparative Examples 2 and 4, Ti is more than 0.05%, and in Comparative Example 3, Ti is more than 0.05%.
Since Ni is less than 0.5% and Cu is more than 1.0%, both of which are outside the composition range specified in this invention, the absorbed energy in the Charpy impact test at -50°C is or 10 in the tempering section
The value is lower than Kgf・m. Test Example 2 Table 5 shows the mechanical properties of the quenched and tempered part QT and the tempered part T when the heat treatment conditions were changed for UOE steel pipes welded with weld metals having the compositions shown in Examples 1 and 4 in Table 3. It shows the characteristics of
【表】
熱処理条件としては、焼入れ温度Qを850乃至
1150℃の範囲で変化させ、焼戻し温度Tを550乃
至650℃の範囲で変化させた。なお、焼入れ処理
における冷却速度は20℃/秒(800℃から400℃ま
での速度)、焼戻し処理の保持時間は30分である。
第5表中、実施例5〜7は本願発明にて規定した
範囲内の熱処理条件のもの、比較例5〜6はその
範囲から外れるものである。実施例5〜7におい
ては、いずれも焼入れ温度が900乃至1100℃、焼
戻し温度が550乃至700℃の範囲内である。溶接金
属の焼入焼戻部と焼戻部のいずれも、−50℃にお
けるシヤルピー衝撃試験における吸収エネルギが
10Kgf・m以上となり靭性が高い。これに対し、
比較例5は焼入れ温度が850℃、比較例6は焼入
れ温度が1150℃であるから、いずれもこの発明に
規定した熱処理条件の範囲外であるため、焼入焼
戻部における−50℃のシヤルピー衝撃試験の吸収
エネルギが10Kgf・m未満となり、靭性が低い。
[発明の効果]
この発明によると、ベンド管の製造工程が極め
て簡略化され、ベンド管の生産性が著しく向上す
ると共に、優れた低温靭性及び強度を有するベン
ド管を得ることができる。このため、この発明は
工業的価値が極めて高い。[Table] As heat treatment conditions, the quenching temperature Q is 850 to 850.
The tempering temperature T was varied within a range of 1150°C, and the tempering temperature T was varied within a range of 550 to 650°C. The cooling rate in the quenching process was 20°C/sec (speed from 800°C to 400°C), and the holding time in the tempering process was 30 minutes.
In Table 5, Examples 5 to 7 were heat treatment conditions within the range defined by the present invention, and Comparative Examples 5 to 6 were outside the range. In Examples 5 to 7, the quenching temperature is in the range of 900 to 1100°C, and the tempering temperature is in the range of 550 to 700°C. The absorbed energy of both the quenched and tempered parts of the weld metal in the Sharpie impact test at -50°C was
It has a high toughness of 10Kgf・m or more. On the other hand,
Comparative Example 5 has a quenching temperature of 850°C, and Comparative Example 6 has a quenching temperature of 1150°C, both of which are outside the range of heat treatment conditions specified in this invention. The absorbed energy in the impact test was less than 10 kgf・m, and the toughness was low. [Effects of the Invention] According to the present invention, the manufacturing process of a bent pipe is extremely simplified, the productivity of the bent pipe is significantly improved, and a bent pipe having excellent low-temperature toughness and strength can be obtained. Therefore, this invention has extremely high industrial value.
第1図は溶接金属の靭性に対するNi含有量の
影響を示すグラフ図、第2図はこの発明における
ベンド管の熱処理方法を示す模式図、第3図は従
来のベンド管の熱処理方法を示す模式図である。
QT:曲部、T:直線部。
Figure 1 is a graph showing the influence of Ni content on the toughness of weld metal, Figure 2 is a schematic diagram showing the heat treatment method for bent pipes in this invention, and Figure 3 is a schematic diagram showing the conventional heat treatment method for bent pipes. It is a diagram. QT: curved section, T: straight section.
Claims (1)
下、Mnが1.0乃至2.0%、Niが0.5乃至3.0%、Cu
が0.02乃至1.0%、Oが0.03%以下、Nbが0.01乃至
0.10%、Tiが0.005乃至0.05%であり、更に、0.1
%以下のV、1.0%以下のMo、及び0.0005乃至
0.005%のBのうち一種類以上の成分を含有し、
残部がFe及び下可避的不純物よりなる溶接金属
で溶接された素管を、加熱しつつ曲げ加工し、曲
部を900乃至1100℃の温度で焼入れし、その後、
素管全体を550乃至700℃の温度で5分以上加熱し
て焼き戻しすることを特徴とするベンド管の製造
方法。1% by weight, C 0.05 to 0.15%, Si 0.5% or less, Mn 1.0 to 2.0%, Ni 0.5 to 3.0%, Cu
0.02 to 1.0%, O 0.03% or less, Nb 0.01 to 1.0%
0.10%, Ti is 0.005 to 0.05%, and furthermore, 0.1
% or less V, 1.0% or less Mo, and 0.0005 to
Contains one or more components of 0.005% B,
A raw pipe welded with weld metal with the balance consisting of Fe and unavoidable impurities is bent while being heated, the bent portion is quenched at a temperature of 900 to 1100°C, and then,
A method for manufacturing a bent pipe, which comprises heating and tempering the entire raw pipe at a temperature of 550 to 700°C for 5 minutes or more.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14946785A JPS6210212A (en) | 1985-07-08 | 1985-07-08 | Production of bend pipe |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14946785A JPS6210212A (en) | 1985-07-08 | 1985-07-08 | Production of bend pipe |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS6210212A JPS6210212A (en) | 1987-01-19 |
JPH0138851B2 true JPH0138851B2 (en) | 1989-08-16 |
Family
ID=15475773
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP14946785A Granted JPS6210212A (en) | 1985-07-08 | 1985-07-08 | Production of bend pipe |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS6210212A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1993016823A1 (en) * | 1992-02-21 | 1993-09-02 | Nkk Corporation | Method of manufacturing bent pipe of high tensile steel |
WO2021153559A1 (en) | 2020-01-29 | 2021-08-05 | Jfeスチール株式会社 | Welded steel pipe and method for manufacturing same |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2827839B2 (en) * | 1993-09-28 | 1998-11-25 | 住友金属工業株式会社 | Method of manufacturing high strength, thick wall, high toughness bend steel pipe |
JP4649753B2 (en) * | 2000-03-31 | 2011-03-16 | Jfeスチール株式会社 | Elementary pipe for high strength thick welded bend steel pipe with excellent weld toughness and method for manufacturing the same |
JP5229300B2 (en) * | 2000-03-31 | 2013-07-03 | Jfeスチール株式会社 | Elementary pipe for high-strength thick-walled welded bend steel pipe with excellent weld toughness and method for producing the same |
JP4581275B2 (en) * | 2000-03-31 | 2010-11-17 | Jfeスチール株式会社 | Elementary pipe for high-strength welded bend steel pipe with excellent weld toughness and manufacturing method thereof |
CN102284569B (en) * | 2011-06-15 | 2014-06-04 | 中国石油天然气股份有限公司 | Hot bending process method |
JP6191393B2 (en) * | 2013-10-28 | 2017-09-06 | 新日鐵住金株式会社 | Submerged arc welding metal with excellent cryogenic toughness, and wire and flux for forming submerged arc welding |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5629627A (en) * | 1979-08-20 | 1981-03-25 | Kawasaki Steel Corp | Manufacture of high strength steel pipe having good weldability for use at ordinary and medium temperature zone |
JPS5834133A (en) * | 1981-08-22 | 1983-02-28 | Kawasaki Steel Corp | Production of api standard class x80 steel pipe having excellent low temperature toughness |
JPS5834132A (en) * | 1981-08-22 | 1983-02-28 | Kawasaki Steel Corp | Production of api standard class x80 steel pipe having excellent low-temperature toughness |
-
1985
- 1985-07-08 JP JP14946785A patent/JPS6210212A/en active Granted
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5629627A (en) * | 1979-08-20 | 1981-03-25 | Kawasaki Steel Corp | Manufacture of high strength steel pipe having good weldability for use at ordinary and medium temperature zone |
JPS5834133A (en) * | 1981-08-22 | 1983-02-28 | Kawasaki Steel Corp | Production of api standard class x80 steel pipe having excellent low temperature toughness |
JPS5834132A (en) * | 1981-08-22 | 1983-02-28 | Kawasaki Steel Corp | Production of api standard class x80 steel pipe having excellent low-temperature toughness |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1993016823A1 (en) * | 1992-02-21 | 1993-09-02 | Nkk Corporation | Method of manufacturing bent pipe of high tensile steel |
WO2021153559A1 (en) | 2020-01-29 | 2021-08-05 | Jfeスチール株式会社 | Welded steel pipe and method for manufacturing same |
Also Published As
Publication number | Publication date |
---|---|
JPS6210212A (en) | 1987-01-19 |
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