JPH0333071B2 - - Google Patents
Info
- Publication number
- JPH0333071B2 JPH0333071B2 JP60055103A JP5510385A JPH0333071B2 JP H0333071 B2 JPH0333071 B2 JP H0333071B2 JP 60055103 A JP60055103 A JP 60055103A JP 5510385 A JP5510385 A JP 5510385A JP H0333071 B2 JPH0333071 B2 JP H0333071B2
- Authority
- JP
- Japan
- Prior art keywords
- welding
- welded
- stainless steel
- weld
- duplex stainless
- 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 - Lifetime
Links
- 230000007797 corrosion Effects 0.000 claims description 10
- 238000005260 corrosion Methods 0.000 claims description 10
- 229910001039 duplex stainless steel Inorganic materials 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 8
- 230000001590 oxidative effect Effects 0.000 claims description 7
- 229910000859 α-Fe Inorganic materials 0.000 claims description 6
- 239000000945 filler Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 229910001566 austenite Inorganic materials 0.000 claims description 4
- 238000003466 welding Methods 0.000 description 22
- 239000010953 base metal Substances 0.000 description 12
- 239000000243 solution Substances 0.000 description 11
- 239000013078 crystal Substances 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 238000010897 surface acoustic wave method Methods 0.000 description 6
- 230000007547 defect Effects 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 231100000989 no adverse effect Toxicity 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
Landscapes
- Heat Treatment Of Articles (AREA)
Description
（産業上の利用分野）
本発明は石油または天然ガス用ラインパイプ、
油井管、原子力用、地熱用、化学プラント用、一
般配管用などに使用する二相ステンレス溶接管の
製造法に関するものである。
（従来の技術）
近年、上記の各種用途に二相ステンレス溶接管
が使用されるようになり、その溶接方法として
は、TIG、SAW法が用いられている。TIG溶接
方法は比較的薄板の溶接に用いられ、溶接速度が
遅く、生産性が劣る。
一方、SAW溶接方法は、中、厚板に用いられ
溶加材を用いた大入熱による比較的高能率溶接法
である。
TIG、SAW法で溶接された溶接部組織を観察
すると、熱影響部は粗大結晶粒の凝固組織であ
り、母材部に比べフエライト量が多くなる傾向に
ある。溶接後、高温熱処理（以下溶体化処理と呼
ぶ）を行つても溶接部は再結晶が行われず粗大結
晶粒のままである。そのため、耐食性、延性、靭
性を損うという問題点がある。
なお、フエライト系ステンレス鋼の溶接鋼管で
は、この他にアツプセツト溶接も行われ、特公昭
53−28014号公報で開示された製造法がある。し
かし、この製造法は、アツプセツト溶接部の結晶
粒の細粒化の考えはなく、素材成分であるＣ、
Ｎ、Ｓ、Ｏを極力低下させることにより耐食性、
冷間加工性の改善を狙つたものである。
（発明が解決しようとする問題点）
本発明は衝合部の成分調整することなく溶接後
の溶接部組織を母材部と同等またはそれ以上の細
粒の結晶粒組織となすことによつて溶接部の耐食
性、延性、靭性を改善したフエライト相とオース
テナイト相の二相ステンレス溶接管を提供するこ
とを目的とするものである。
（問題点を解決するための手段）
本発明はフエライト相とオーステナイト相から
なる二相ステンレス鋼を非酸化性ガス雰囲気中に
て溶加材を使用せずにアツプセツト量を肉厚×1/
４以上としてアツプセツト溶接し、その後、溶体
化処理することを特徴とする耐食性の優れた二相
ステンレス溶接管の製造方法である。
本発明の構成要件の限定理由は次の通りであ
る。
二相ステンレス鋼のアツプセツト溶接を非酸化
性ガス雰囲気中で行わない場合には、アツプセツ
ト溶接の加熱の際に接合面が酸化して緻密な酸化
物が発生し、これが接接衝合部に残存して溶接欠
陥となり耐食性、延性、靭性を低下させる因子と
なる。そのため、溶接欠陥発生防止のためには溶
接雰囲気を非酸化性ガス雰囲気にする必要があ
る。そして該雰囲気中の酸素濃度は0.2％以下と
することが好ましく、更に好ましい酸素濃度は
0.05％以下である。
二相ステンレス鋼板を不活性ガス、還元性ガス
等の非酸化性ガス雰囲気中で高周波誘導加熱、高
周波抵抗加熱、アーク加熱により接合表面を加
熱、溶融後、アツプセツトし、溶接衝合部を形成
する際、アツプセツト量が肉厚×1/4以下では溶
融金属が十分にアツプセツトされずビードが形成
されないため、成形時に生じた応力により溶接溶
融部の外、内表面に微細なクラツク状欠陥が発生
するので、アツプセツト量の下限は肉厚×1/4と
した。好ましいアツプセツト量の範囲は肉厚×
（1/3〜2/3）である。
アツプセツト溶接時に溶加棒を用いると、高速
溶接を阻害し、生産性を低下させるので溶加棒は
使用しない。
アツプセツト溶接後、溶体化処理により溶接部
の組織は母材部と同等な細粒の結晶粒組織に再結
晶するが、溶体化処理温度が、950℃未満では析
出物が固溶しなく、また、1150℃を越えるとフエ
ライト量が多くなること及び結晶粒が大きくなる
ことより好ましい溶体化処理温度は950〜1150℃
である。
（作用）
本発明の上記の如く構成したことによる特有の
作用は次の通りである。
二相ステンレス鋼を非酸化性ガス雰囲気中にて
アツプセツト溶接するので、溶接衝合部にCr、
Mn、Si等の酸化物が発生せず、溶接欠陥がなく
溶接部の耐食性、延性、靭性に悪影響を及ぼすこ
とがない。このようにして、酸化物のない溶融鋼
を生成した後、溶接部をアツプセツトした際、溶
接部は大きな歪エネルギーを受ける。この状態の
溶接部組織は結晶粒界、格子欠陥等の結晶の不連
続部に濃縮したＣ、Ｎ、Cr等の偏析が生じてい
る。その後、溶体化処理による熱エネルギーとア
ツプセツトの際に生じた歪エネルギーにより、溶
接部は整粒で、かつ、偏析のない細粒の結晶粒に
再結晶する。その際、溶体化処理温度を950〜
1150℃に設定すれば、フエライト量とオーステナ
イト量の比は母材部と同等に保たれる。
このように、非酸化性雰囲気中でのアツプセツ
ト溶接とその後の溶体化処理の組合せにより溶接
部の耐食性、延性、靭性は母材部と同等な特性を
具備した二相ステンレス溶接管が得られる。
（実施例）
表１に示すように本発明例の溶接部の耐食性、
延性、低温靭性は従来例に比較し、優れた特性を
示す。特に本発明例は従来例の高周波抵抗溶接材
に比し、その効果は顕著である。更に、本発明例
の溶接速度は従来例のTIG、SAW法に比し数十
倍であり生産性からも優れている。
本発明例（No.３）の全体像、溶接部、および母
材部の顕微鏡金属組織写真を夫々第１図、第２
図、第３図で示し、従来例（No.８）の全体像、溶
接部、および母材部の顕微鏡金属組織写真を夫々
第４図、第５図、第６図に示す。本発明例の溶体
化処理後の溶接部組織は母材部と同等な細粒組織
を呈する。これに対し、SAW法による溶接部組
織は粗粒組織である。
(Industrial Application Field) The present invention relates to oil or natural gas line pipes,
This invention relates to a method for manufacturing two-phase stainless steel welded pipes used for oil country tubular goods, nuclear power, geothermal, chemical plants, general piping, etc. (Prior Art) In recent years, duplex stainless steel welded pipes have come to be used for the various purposes mentioned above, and TIG and SAW methods are used as welding methods. The TIG welding method is used for welding relatively thin plates, has a slow welding speed, and has poor productivity. On the other hand, the SAW welding method is a relatively high-efficiency welding method that uses a filler metal and uses a large heat input, and is used for medium to thick plates. When observing the structure of welds welded by TIG and SAW methods, the heat-affected zone is a solidified structure of coarse crystal grains, and the amount of ferrite tends to be larger than that of the base metal. After welding, even if high-temperature heat treatment (hereinafter referred to as solution treatment) is performed, recrystallization is not performed in the welded area and coarse crystal grains remain. Therefore, there is a problem that corrosion resistance, ductility, and toughness are impaired. In addition, for welded ferritic stainless steel pipes, upset welding is also performed, and
There is a manufacturing method disclosed in Publication No. 53-28014. However, this manufacturing method does not consider refining the crystal grains in the upset weld, and the material components C,
Corrosion resistance by reducing N, S, and O as much as possible.
The aim is to improve cold workability. (Problems to be Solved by the Invention) The present invention is capable of solving the problem by making the welded part structure after welding into a fine-grained crystal grain structure that is equal to or larger than that of the base metal part, without adjusting the composition of the abutting part. The object of the present invention is to provide a two-phase stainless steel welded pipe with improved corrosion resistance, ductility, and toughness of the welded part, consisting of a ferrite phase and an austenite phase. (Means for Solving the Problems) The present invention improves the upset amount of duplex stainless steel consisting of a ferrite phase and an austenite phase in a non-oxidizing gas atmosphere by increasing wall thickness x 1/without using a filler metal.
This is a method for manufacturing a duplex stainless steel welded pipe with excellent corrosion resistance, which is characterized in that it is upset welded as 4 or more, and then subjected to solution treatment. The reasons for limiting the constituent elements of the present invention are as follows. If upset welding of duplex stainless steel is not performed in a non-oxidizing gas atmosphere, the joint surface will oxidize during the heating of upset welding, producing dense oxides, which will remain in the weld abutment. This becomes a welding defect and becomes a factor that reduces corrosion resistance, ductility, and toughness. Therefore, in order to prevent the occurrence of welding defects, it is necessary to make the welding atmosphere a non-oxidizing gas atmosphere. The oxygen concentration in the atmosphere is preferably 0.2% or less, and the more preferable oxygen concentration is
Less than 0.05%. The joining surfaces of duplex stainless steel plates are heated by high-frequency induction heating, high-frequency resistance heating, and arc heating in an atmosphere of non-oxidizing gas such as inert gas or reducing gas, and after melting, they are set up to form welded abutments. If the offset amount is less than 1/4 of the wall thickness, the molten metal will not be sufficiently offset and a bead will not be formed, and the stress generated during forming will cause minute crack-like defects on the outside and inside surfaces of the weld fusion zone. Therefore, the lower limit of the offset amount was set to 1/4 of the wall thickness. The preferred range of offset amount is wall thickness x
(1/3 to 2/3). If a filler rod is used during upset welding, it will impede high-speed welding and reduce productivity, so a filler rod is not used. After upset welding, the structure of the weld zone recrystallizes to a fine-grained structure equivalent to that of the base metal through solution treatment, but if the solution treatment temperature is lower than 950℃, the precipitates will not dissolve into solid solution. If the temperature exceeds 1150°C, the amount of ferrite increases and the crystal grains become large, so the preferred solution treatment temperature is 950 to 1150°C.
It is. (Function) The unique effects of the above-described configuration of the present invention are as follows. Since duplex stainless steel is upset welded in a non-oxidizing gas atmosphere, there is no Cr or
Oxides such as Mn and Si are not generated, there are no weld defects, and there is no adverse effect on the corrosion resistance, ductility, and toughness of the weld. After producing oxide-free molten steel in this manner, the weld is subjected to large strain energies when it is upset. In the weld structure in this state, segregation of concentrated C, N, Cr, etc. occurs at crystal discontinuities such as grain boundaries and lattice defects. Thereafter, due to the thermal energy from the solution treatment and the strain energy generated during upsetting, the weld zone recrystallizes into fine grains with regular grain size and no segregation. At that time, the solution treatment temperature should be set to 950~
If the temperature is set at 1150°C, the ratio of ferrite content to austenite content will be maintained at the same level as the base metal. As described above, by combining upset welding in a non-oxidizing atmosphere and subsequent solution treatment, a duplex stainless steel welded pipe with corrosion resistance, ductility, and toughness of the welded part equivalent to that of the base metal can be obtained. (Example) As shown in Table 1, the corrosion resistance of the welded part of the example of the present invention,
It exhibits superior ductility and low-temperature toughness compared to conventional examples. In particular, the effects of the present invention are remarkable compared to conventional high-frequency resistance welding materials. Furthermore, the welding speed of the example of the present invention is several tens of times higher than that of the conventional TIG and SAW methods, and it is also superior in terms of productivity. Figures 1 and 2 show the overall image, welded area, and microscopic metallographic photographs of the base metal of the invention example (No. 3).
3, and microscopic metallographic photographs of the overall image, welded area, and base material of the conventional example (No. 8) are shown in FIGS. 4, 5, and 6, respectively. The structure of the weld zone after solution treatment in the example of the present invention exhibits a fine grain structure equivalent to that of the base metal. On the other hand, the weld structure obtained by the SAW method is a coarse-grained structure.
【表】【table】
【表】【table】
【表】
（発明の効果）
本発明の効果は以下の通りである。
(1) 溶体化処理後の溶接部組織は母材部と同等な
細粒の再結晶組織となり、耐食性、延性、低温
靭性の品質特性が母材部と同等となる。これに
より溶接部と母材部間で品質特性の均一化がは
かられる。
(2) 溶接速度が従来例のTIG、SAW法に比較し
速く、かつ、上記(1)の理由から溶接部品質の優
れた二相ステンレス溶接管を安価に製造でき
る。[Table] (Effects of the invention) The effects of the invention are as follows. (1) The weld zone structure after solution treatment becomes a fine-grained recrystallized structure equivalent to that of the base metal, and the quality characteristics of corrosion resistance, ductility, and low-temperature toughness are equivalent to those of the base metal. This ensures uniformity of quality characteristics between the welded part and the base metal part. (2) The welding speed is faster than the conventional TIG and SAW methods, and for the reason mentioned in (1) above, duplex stainless steel welded pipes with excellent weld quality can be manufactured at low cost.
第１図乃至第６図は、本発明実施例（No.３）の
高周波抵抗溶接法、および従来例（No.８）の
SAW法で製造し、その後、溶体化処理したもの
の顕微鏡金属組織を示す写真であり、第１図、第
２図、第３図は本発明実施例の全体像、溶接部、
母材部を示し、第４図、第５図、第６図は従来例
（No.８）の全体像、溶接部、母材部を示す。
Figures 1 to 6 show the high frequency resistance welding method of the embodiment of the present invention (No. 3) and the conventional example (No. 8).
These are photographs showing microscopic metal structures of products manufactured by the SAW method and then subjected to solution treatment.
The base metal part is shown, and FIGS. 4, 5, and 6 show the overall image, welded part, and base metal part of the conventional example (No. 8).
Claims (1)
相ステンレス鋼を非酸化性ガス雰囲気中にて溶加
材を使用せずに、アツプセツト量を肉厚×1/4以
上としてアツプセツト溶接し、その後、溶体化処
理することを特徴とする耐食性の優れた二相ステ
ンレス溶接管の製造方法。1 Duplex stainless steel consisting of a ferrite phase and an austenite phase is offset welded in a non-oxidizing gas atmosphere without the use of filler metal, with an offset amount of at least 1/4 of the wall thickness, and then solution treated. A method for manufacturing a duplex stainless steel welded pipe with excellent corrosion resistance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5510385A JPS61212483A (en) | 1985-03-19 | 1985-03-19 | Production of two phase stainless welding pipe having excellent corrosion resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5510385A JPS61212483A (en) | 1985-03-19 | 1985-03-19 | Production of two phase stainless welding pipe having excellent corrosion resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61212483A JPS61212483A (en) | 1986-09-20 |
| JPH0333071B2 true JPH0333071B2 (en) | 1991-05-15 |
Family
ID=12989410
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5510385A Granted JPS61212483A (en) | 1985-03-19 | 1985-03-19 | Production of two phase stainless welding pipe having excellent corrosion resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61212483A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS51145454A (en) * | 1975-06-10 | 1976-12-14 | Nippon Steel Corp | Method for manufacture of electriccweld steel pipe |
| JPS5550757A (en) * | 1978-10-06 | 1980-04-12 | Hitachi Denshi Ltd | Signal change-over control device |
-
1985
- 1985-03-19 JP JP5510385A patent/JPS61212483A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS51145454A (en) * | 1975-06-10 | 1976-12-14 | Nippon Steel Corp | Method for manufacture of electriccweld steel pipe |
| JPS5550757A (en) * | 1978-10-06 | 1980-04-12 | Hitachi Denshi Ltd | Signal change-over control device |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61212483A (en) | 1986-09-20 |
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