JP2008062277A - Multi-layered welding method of stainless steel tube, and multi-layered weldment - Google Patents
Multi-layered welding method of stainless steel tube, and multi-layered weldment Download PDFInfo
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- JP2008062277A JP2008062277A JP2006244186A JP2006244186A JP2008062277A JP 2008062277 A JP2008062277 A JP 2008062277A JP 2006244186 A JP2006244186 A JP 2006244186A JP 2006244186 A JP2006244186 A JP 2006244186A JP 2008062277 A JP2008062277 A JP 2008062277A
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- 238000003466 welding Methods 0.000 title claims abstract description 155
- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 80
- 239000010935 stainless steel Substances 0.000 title claims abstract description 80
- 238000000034 method Methods 0.000 title claims abstract description 31
- 229910052751 metal Inorganic materials 0.000 claims description 15
- 239000002184 metal Substances 0.000 claims description 15
- 229910000831 Steel Inorganic materials 0.000 claims description 10
- 239000010959 steel Substances 0.000 claims description 10
- 238000001816 cooling Methods 0.000 description 15
- 238000012360 testing method Methods 0.000 description 15
- 230000007797 corrosion Effects 0.000 description 9
- 238000005260 corrosion Methods 0.000 description 9
- 238000005336 cracking Methods 0.000 description 8
- 239000000463 material Substances 0.000 description 5
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 4
- 238000013142 basic testing Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000004907 flux Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 3
- 229910052721 tungsten Inorganic materials 0.000 description 3
- 239000010937 tungsten Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
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Abstract
Description
本発明は、ステンレス鋼管同士を突き合わせ円周方向に沿って開先溶接する溶接パスを複数回行う該ステンレス鋼管の多層溶接方法及び多層溶接物に関する。 The present invention relates to a method for multilayer welding of stainless steel pipes and a multilayer weldment in which a stainless steel pipe is welded a plurality of times in a circumferential direction in which stainless steel pipes are butted together and welded along the circumferential direction.
ステンレス鋼管同士を多層溶接した場合、溶接されたステンレス鋼管の内表面の熱影響部に発生する応力腐食割れが問題となる。この応力腐食割れは、ステンレス鋼管の材質と、溶接したステンレス鋼管が設置される環境と、ステンレス鋼管にかかる引張応力という３因子のうち、いずれかの因子が所定の条件を満たさない場合、発生しない。 When stainless steel pipes are welded in multiple layers, stress corrosion cracking that occurs in the heat-affected zone on the inner surface of the welded stainless steel pipes becomes a problem. This stress corrosion crack does not occur if any of the three factors of the material of the stainless steel pipe, the environment in which the welded stainless steel pipe is installed, and the tensile stress applied to the stainless steel pipe does not satisfy the predetermined condition. .
応力因子の改善方法として、従来、水***接方法、高周波誘導加熱方法、外面バタリング工法又はピーニング方法が提案されている。 Conventionally, a water-cooling welding method, a high-frequency induction heating method, an outer surface buttering method, or a peening method has been proposed as a method for improving the stress factor.
また、特許文献１には、ステンレス鋼管の材質、詳細には、溶接熱影響部の組織を改善する方法として、所定の溶接パス以降、溶接時のピーク温度を低くして、Ｃｒ炭化物やＣｒ欠乏層の発生を防止する方法が提案されている。 Further, in Patent Document 1, as a method for improving the material of the stainless steel pipe, specifically, the structure of the heat affected zone, the peak temperature during welding is lowered after a predetermined welding pass, and Cr carbide or Cr deficiency A method for preventing the generation of layers has been proposed.
しかしながら、上述した応力因子の改善方法によれば、通常の溶接設備に加えて多大な付帯設備が必要であり、コスト高を招くという問題がある。 However, according to the stress factor improving method described above, there is a problem in that a large amount of incidental equipment is required in addition to normal welding equipment, resulting in high costs.
また、上記特許文献１の方法は、ステンレス鋼管の材質ないし組織の改善であって、溶接後のステンレス鋼管の内表面に残留する応力を改善しようとするものではない。 Further, the method of Patent Document 1 described above is an improvement in the material or structure of the stainless steel pipe, and does not attempt to improve the stress remaining on the inner surface of the stainless steel pipe after welding.
本発明は、溶接後のステンレス鋼管の内表面に残留する応力を、簡便な設備かつ簡単な方法で、圧縮応力にすることができるステンレス鋼管の多層溶接方法及び多層溶接物を提供することを目的とする。 It is an object of the present invention to provide a multi-layer welding method for a stainless steel pipe and a multi-layer welded product capable of converting the stress remaining on the inner surface of the stainless steel pipe after welding into a compressive stress using simple equipment and a simple method. And
ステンレス鋼管の多層溶接時、各溶接パスにおいて、入熱量を互いに一定かつ大入熱量とした場合、ステンレス鋼管の内表面の熱影響部において、溶接パス毎の残留応力値は、中間層の溶接パス（管肉厚の中ごろ）で最大の圧縮応力値を示し、その後の溶接パスで引張応力値に転換して、これが応力腐食割れの因子となっていると言われている。 In multi-layer welding of stainless steel pipes, if the heat inputs are constant and large in each weld pass, the residual stress value for each weld pass is the intermediate layer weld pass in the heat-affected zone of the inner surface of the stainless steel pipe. It is said that the maximum compressive stress value is shown at the middle of the pipe wall thickness, which is converted into a tensile stress value in the subsequent welding pass, which is a factor of stress corrosion cracking.
また、中間層以降の溶接パスでステンレス鋼管の溶接部に横曲がり変形が顕著に発生し、これが、ステンレス鋼管の内表面の熱影響部における引張残留応力発生の原因となっていると言われている。 In addition, it is said that lateral bending deformation is noticeably generated in the welded part of the stainless steel pipe in the welding pass after the intermediate layer, and this is said to be the cause of the generation of tensile residual stress in the heat affected zone of the inner surface of the stainless steel pipe. Yes.
本発明者らは、上記事項に基づき鋭意研究を進めた結果、中間層の溶接パス以降の溶接時入熱量を低くすることにより、ステンレス鋼管の内表面の熱影響部において、残留応力が圧縮応力から引張応力に転換することを防止できることを見出し、本発明を完成するに至ったものである。 As a result of conducting earnest research based on the above matters, the present inventors have reduced the heat input at the time of welding after the intermediate layer welding pass, so that the residual stress is compressive stress in the heat affected zone of the inner surface of the stainless steel pipe. The present inventors have found that it is possible to prevent the transition from tensile stress to tensile stress and have completed the present invention.
本発明は、第１の視点において、ステンレス鋼管の端面同士を突き合わせ、円周方向に沿って開先溶接する溶接パスを複数回行い、該端面同士を溶接するステンレス鋼管の多層溶接方法であって、溶接前、前記ステンレス鋼管の端面同士の間に形成する開先を狭開先とし、溶接開始後、前記ステンレス鋼管の肉厚の３８％〜４５％まで溶接する溶接パスにおいては大入熱溶接を行い、以降の溶接パスにおいては、前記大入熱溶接時よりも低い入熱量で低入熱溶接を行い、多層溶接終了時、前記ステンレス鋼管の内表面の熱影響部に残留する応力を圧縮応力とすることを特徴とするステンレス鋼管の多層溶接方法を提供する。本発明は、第２の視点において、ステンレス鋼管の端面同士が突き合わせられ、円周方向に沿って開先溶接する溶接パスが複数回行われ、該端面同士が溶接されたステンレス鋼管の多層溶接物であって、溶接金属が、内表面側から鋼管の肉厚の３８％〜４５％までは軸方向に沿って幅広に形成され、それから外表面側に向って軸方向に沿って一定幅に形成されていることを特徴とするステンレス鋼管の多層溶接物を提供する。 In the first aspect, the present invention is a multi-layer welding method for stainless steel pipes in which end faces of stainless steel pipes are butted together and a welding pass for performing groove welding along the circumferential direction is performed a plurality of times, and the end faces are welded together. Before welding, the groove formed between the end faces of the stainless steel pipe is a narrow groove, and after welding starts, welding is performed to 38% to 45% of the wall thickness of the stainless steel pipe. In the subsequent welding passes, low heat input welding is performed with a lower heat input than during the large heat input welding, and at the end of multi-layer welding, the residual stress in the heat affected zone of the inner surface of the stainless steel pipe is compressed. A multi-layer welding method for stainless steel pipes characterized by stress. In the second aspect, the present invention provides a multi-layer welded product of stainless steel pipes in which end faces of stainless steel pipes are butted together and a welding pass for groove welding is performed a plurality of times along the circumferential direction. The weld metal is formed to be wide along the axial direction from the inner surface side to 38% to 45% of the wall thickness of the steel pipe, and then formed with a constant width along the axial direction toward the outer surface side. A multilayer weldment of stainless steel pipes is provided.
本発明によれば、溶接が肉厚の所定割合まで到達した溶接パス以降、溶接時入熱量をそれ以前よりも低くすることによって、ステンレス鋼管の内表面の熱影響部に、最終的に、圧縮残留応力が作用するようにする。これによって、ステンレス鋼管の内表面の熱影響部における応力腐食割れが高度に防止される。なお、初期の溶接パスまでは、大入熱溶接を行うことによって、かえって、応力腐食割れの原因となっている引張残留応力の発生が抑制される傾向がある。 According to the present invention, after the welding pass in which the welding reaches a predetermined ratio of the wall thickness, the heat input during welding is made lower than before, thereby finally compressing the heat affected zone on the inner surface of the stainless steel pipe. Residual stress is applied. This highly prevents stress corrosion cracking in the heat affected zone of the inner surface of the stainless steel pipe. Note that, until the initial welding pass, by performing high heat input welding, the generation of tensile residual stress that causes stress corrosion cracking tends to be suppressed.
本発明の好ましい実施の形態において、大入熱溶接を行う溶接パスでは入熱量を１００００Ｊ／ｃｍ以上とし、低入熱溶接を行う溶接パスでは入熱量を５０００Ｊ／ｃｍ以下とする。大入熱溶接において、好ましくは、入熱量を１００００〜２５０００Ｊ／ｃｍの範囲、より好ましくは１００００〜２００００Ｊ／ｃｍの範囲、さらに好ましくは１３０００〜２００００Ｊ／ｃｍの範囲とする。低入熱溶接において、好ましくは入熱量を２０００〜５０００Ｊ／ｃｍの範囲、さらに好ましくは２０００〜３５００Ｊ／ｃｍの範囲とする。 In a preferred embodiment of the present invention, the heat input is set to 10,000 J / cm or more in a welding pass for performing high heat input welding, and the heat input is set to 5000 J / cm or less in a welding pass for performing low heat input welding. In the high heat input welding, the heat input amount is preferably in the range of 10,000 to 25000 J / cm, more preferably in the range of 10,000 to 20000 J / cm, and still more preferably in the range of 13,000 to 20000 J / cm. In the low heat input welding, the heat input amount is preferably in the range of 2000 to 5000 J / cm, more preferably 2000 to 3500 J / cm.
本発明の好ましい実施の形態においては、前記大入熱溶接時の半分以下の入熱量で低入熱溶接を行う。好ましくは、前記大入熱溶接時の入熱量（これを「大入熱量」と称する）と、前記低入熱溶接時の入熱量（これを「低入熱量」と称する）の比（＝大入熱量／低入熱量）を、３〜７の範囲にする。 In a preferred embodiment of the present invention, low heat input welding is performed with a heat input amount that is less than half that of the large heat input welding. Preferably, a ratio (= high) of heat input during the high heat input welding (referred to as “high heat input”) and heat input during the low heat input welding (referred to as “low heat input”). (Heat input / low heat input) is set in the range of 3-7.
本発明の好ましい実施の形態において、前記ステンレス鋼管同士の間に形成する開先は、Ｉ形又はそれに近いすきま、すなわち、Ｕ形等の狭い開先で行う狭開先を採用する（ＪＩＳＺ３００１ 用語番号２７０８参照）。狭開先の場合、管の肉厚と開先幅の関係を例示すると、肉厚１０ｍｍ−開先幅５ｍｍ、肉厚２０ｍｍ−開先幅７ｍｍ、肉厚３０ｍｍ−開先幅９〜１０ｍｍ、肉厚４０ｍｍ−開先幅１３〜１４ｍｍである。狭開先溶接を行うことによって、さらに、上記熱影響部における引張残留応力の発生を高度に防止することができる。 In a preferred embodiment of the present invention, the groove formed between the stainless steel pipes adopts a narrow groove formed by a narrow groove such as an I shape or a gap close thereto, that is, a U shape (JISZ3001 terminology number). 2708). In the case of a narrow groove, the relationship between the thickness of the tube and the groove width is exemplified. The wall thickness is 10 mm—the groove width is 5 mm, the wall thickness is 20 mm—the groove width is 7 mm, the wall thickness is 30 mm—the groove width is 9 to 10 mm, The thickness is 40 mm and the groove width is 13 to 14 mm. By performing narrow groove welding, it is possible to highly prevent the occurrence of tensile residual stress in the heat affected zone.
本発明の好ましい実施の形態に係る溶接物においては、溶接金属が、内表面側から鋼管の肉厚の３８％〜４５％までは軸方向に沿って幅広（鋼管の内表面側の溶接金属が同外表面側の溶接金属よりも幅広）に形成され、それから外表面側に向って軸方向に沿って一定幅に形成されている（図２参照）。 In the weldment according to a preferred embodiment of the present invention, the weld metal is wide along the axial direction from the inner surface side to 38% to 45% of the wall thickness of the steel pipe (the weld metal on the inner surface side of the steel pipe is It is formed wider than the weld metal on the outer surface side, and then is formed with a constant width along the axial direction toward the outer surface side (see FIG. 2).
以下、図面を参照して本発明の一実施例を説明する。まず、ステンレス鋼管の多層溶接方法の概要を説明する。 An embodiment of the present invention will be described below with reference to the drawings. First, an outline of a multilayer welding method for stainless steel pipes will be described.
溶接機は、高速自動ＴＩＧ溶接装置（商品名「ＤＳＰ ＴＩＧ−５００」愛知産業株式会社製）を用いた。溶接ヘッドには、ダブルフラックス・ガスシールド法用のヘッドを用いた。この溶接ヘッドには、通常の電極の他に、回転偏芯電極を適用可能である。 A high-speed automatic TIG welding apparatus (trade name “DSP TIG-500” manufactured by Aichi Sangyo Co., Ltd.) was used as the welding machine. A double flux / gas shield head was used as the welding head. In addition to the normal electrode, a rotating eccentric electrode can be applied to this welding head.
なお、「ダブルフラックス・ガスシールド法」とは、タングステン電極を２層の不活性ガスで覆いながら溶接を行う方法であって、エネルギー密度が高くなるため低入熱での溶接を可能とする。「回転偏芯電極」とは、開先中心に対してタングステン電極が偏芯しながら回転するものである。 The “double flux / gas shield method” is a method of welding while covering the tungsten electrode with two layers of inert gas, and the energy density becomes high, so that welding with low heat input is possible. The “rotary eccentric electrode” is one in which the tungsten electrode rotates while being eccentric with respect to the groove center.
この溶接機により、タングステン電極と母材（ステンレス鋼管）との間にアークを発生させ，そのアーク熱によって溶加材および母材を溶融して溶接する。溶接時の入熱量は、電極に与える電気的エネルギー量によって調整することができる。すなわち、溶接時の入熱量（ｊ／ｃｍ）は、溶接電流×溶接電圧×６０／溶接速度で表される。 With this welding machine, an arc is generated between the tungsten electrode and the base material (stainless steel pipe), and the filler metal and the base material are melted and welded by the arc heat. The amount of heat input during welding can be adjusted by the amount of electrical energy given to the electrodes. That is, the heat input (j / cm) during welding is expressed by welding current × welding voltage × 60 / welding speed.
溶接工程を説明すると、溶接するステンレス鋼管の端面同士を突き合わし、初層溶接を行う。各溶接パスにおいては、開先内に円周方向に沿って金属を溶着させる。この溶接パスを複数回繰り返すことにより、溶着金属を鋼管内面から鋼管表面方向に向って積層していき、鋼管同士を溶接する。 Explaining the welding process, the end surfaces of the stainless steel pipes to be welded are brought into contact with each other, and the first layer welding is performed. In each welding pass, metal is deposited along the circumferential direction in the groove. By repeating this welding pass a plurality of times, the weld metal is laminated from the inner surface of the steel pipe toward the surface of the steel pipe, and the steel pipes are welded together.
［基礎試験１］
開先を狭くすることによって、ステンレス鋼管の内表面の熱影響部の残留応力が低減するかを検討する基礎試験を行った。試験体には、４００Ａ×ｔ２１．４ｍｍのＳＵＳ３１６Ｌのオーステナイト系ステンレス鋼管を用い、一方の試験体は、開先幅７ｍｍのＵ形開先とし、比較のため他方の試験体は開先幅１４ｍｍのＶ形狭開先とした。溶接後、ステンレス鋼管の内表面の熱影響部の残留応力を歪ゲージを用いて測定したところ、一方の試験体、すなわち、狭開先溶接の方が、約１００〜１５０ＭＰａ程度、残留応力が低減し、開先を狭くする効果があることがわかった。
[Basic test 1]
A basic test was conducted to examine whether the residual stress in the heat-affected zone on the inner surface of the stainless steel pipe is reduced by narrowing the groove. A 400 A × t 21.4 mm SUS316L austenitic stainless steel pipe is used as a test body, and one test body is a U-shaped groove with a groove width of 7 mm, and the other test body has a groove width of 14 mm for comparison. A V-shaped narrow groove was used. After welding, when the residual stress of the heat-affected zone on the inner surface of the stainless steel pipe was measured using a strain gauge, one of the specimens, that is, narrow groove welding, reduced the residual stress by about 100 to 150 MPa. And it was found that there is an effect of narrowing the groove.
［基礎試験２］
上記狭開先溶接に、冷却ワイヤを導入して低入熱溶接を行い、溶接残留応力が低減するかどうかを確認した。冷却ワイヤとは、溶接時、溶接ワイヤとは別に溶融プール中に挿入され、溶融プールを強制的に冷却・凝固させるために使用されるものである。試験体には、４００Ａ×ｔ２１．４ｍｍのＳＵＳ３１６Ｌのオーステナイト系ステンレス鋼管を用い、開先は開先幅７ｍｍのＵ形狭開先とし、２５００〜３０００Ｊ／ｃｍの低入熱溶接を行った。比較のため、冷却ワイヤを用いない以外は、前記と同様に溶接を行った。
[Basic test 2]
A cooling wire was introduced into the narrow groove welding to perform low heat input welding, and it was confirmed whether or not the welding residual stress was reduced. The cooling wire is inserted into the molten pool separately from the welding wire during welding, and is used to forcibly cool and solidify the molten pool. A 400 A × t 21.4 mm SUS316L austenitic stainless steel pipe was used as the test body, the groove was a U-shaped narrow groove with a groove width of 7 mm, and low heat input welding at 2500 to 3000 J / cm was performed. For comparison, welding was performed in the same manner as described above except that no cooling wire was used.
溶接後、ステンレス鋼管の内表面の熱影響部の残留応力を歪ゲージを用いて測定したところ、冷却ワイヤを用いることにより、溶接後の残留応力が５０〜１００ＭＰａ緩和されることがわかった。なお、冷却ワイヤを用いなくても低入熱溶接が可能ではあるが、それを用いることにより、溶融金属を強制凝固させる効果が発揮されるため、希釈量及び熱影響部が減少し、溶接効率も改善される。 After welding, when the residual stress in the heat-affected zone on the inner surface of the stainless steel pipe was measured using a strain gauge, it was found that the residual stress after welding was relaxed by 50 to 100 MPa by using a cooling wire. Although low heat input welding is possible without using a cooling wire, the effect of forcibly solidifying the molten metal is exhibited by using it, so the dilution amount and heat affected zone are reduced, and the welding efficiency is reduced. Will be improved.
［試験１］
上記基礎試験の結果に基づいて、開先を７ｍｍのＵ形狭開先とし、冷却ワイヤを用い、
ステンレス鋼管の肉厚の何％で、大入熱溶接と低入熱溶接を切替えたらよいかを検討した。
[Test 1]
Based on the result of the basic test, the groove is a U-shaped narrow groove of 7 mm, and a cooling wire is used.
We examined what percentage of the wall thickness of stainless steel pipes should be switched between large heat input welding and low heat input welding.
図１は、本発明の一実施例に係る試験１で用いた試験体Ａ〜Ｈの形状を示す図である。図１を参照すると、試験体には、３００Ａ×ｔ２１．４ｍｍのＳＵＳ３１６Ｌのオーステナイト系ステンレス鋼管を用い、開先は開先幅７ｍｍのＵ形狭開先とし、各設定したステンレス鋼管の肉厚まで大入熱溶接を行い、その後低入熱溶接を行った。溶接後、ステンレス鋼管の内表面の熱影響部の横収縮量を測定した。また。ステンレス鋼管の内表面の熱影響部の残留応力を歪ゲージを用いて測定した。 FIG. 1 is a diagram showing the shapes of specimens A to H used in Test 1 according to an example of the present invention. Referring to FIG. 1, a 300 A × t 21.4 mm SUS316L austenitic stainless steel pipe is used as a test body, and the groove is a U-shaped narrow groove with a groove width of 7 mm, up to the thickness of each set stainless steel pipe. Large heat input welding was performed, and then low heat input welding was performed. After welding, the amount of lateral shrinkage of the heat affected zone on the inner surface of the stainless steel pipe was measured. Also. The residual stress in the heat affected zone on the inner surface of the stainless steel pipe was measured using a strain gauge.
詳細には、ステンレス鋼管の内表面の熱影響部において、溶接開始箇所から溶接時の鋼管回転方向に沿って９０度の点をＢ点、−９０度の点をＤ点とし、それぞれの点で残留応力を軸方向及び周方向に関して測定し、最大残留応力値を求めた。 Specifically, in the heat-affected zone on the inner surface of the stainless steel pipe, a point at 90 degrees is B point and a point at -90 degrees is D point from the welding start position along the steel pipe rotation direction at the time of welding. Residual stress was measured in the axial and circumferential directions to determine the maximum residual stress value.
表１は、本発明の一実施例に係る試験１の結果を示す表である。 Table 1 is a table | surface which shows the result of the test 1 which concerns on one Example of this invention.
表１中、積層方法の欄においては、上段が大入熱溶接を行ったステンレス鋼管の肉厚の割合を百分率で示し、下段が低入熱溶接を行ったステンレス鋼管の肉厚の割合を百分率で示す。 In Table 1, in the column of the lamination method, the upper part indicates the percentage of the thickness of the stainless steel pipe subjected to the high heat input welding, and the lower part indicates the percentage of the thickness of the stainless steel pipe subjected to the low heat input welding. It shows with.
入熱量の欄においては、上段が大入熱溶接時の入熱量、下段が低入熱溶接時の入熱量を示す。溶接方法の欄においては、大入熱溶接時にホットワイヤを用いたかどうか、低入熱溶接時に冷却ワイヤないし偏芯電極を用いたどうかを示す。なお、ホットワイヤとは、溶接ワイヤとは別に、溶融プール中に挿入されて、溶接金属の積層高さを高度に制御し易くするためのものである。 In the column of heat input, the upper row shows the heat input amount during high heat input welding, and the lower row shows the heat input amount during low heat input welding. In the column of the welding method, whether a hot wire is used at the time of high heat input welding or whether a cooling wire or an eccentric electrode is used at the time of low heat input welding is shown. The hot wire is inserted into the molten pool separately from the welding wire so as to make it easy to highly control the stacking height of the weld metal.
溶接パス数の欄においては、左上段に大入熱溶接を行った溶接パス数、左下段に前記大入熱溶接を行った溶接パスの後に低入熱溶接を行った溶接パス数、右段に総パス数を示す。 In the column of the number of welding passes, the number of welding passes in which large heat input welding was performed in the upper left stage, the number of welding passes in which low heat input welding was performed after the welding path in which the large heat input welding was performed in the lower left stage, and the right stage Shows the total number of paths.
表１を参照すると、大入熱溶接をステンレス鋼管の肉厚の３５％以下まで行い、以降は低入熱溶接を行った場合（試験体Ａ〜Ｃ）、溶接終了後、ステンレス鋼管の内表面の熱影響部の最大残留応力値はプラスになり、すなわち、熱影響部に応力腐食割れの因子となる引張応力が残留した。 Referring to Table 1, when high heat input welding is performed to 35% or less of the thickness of the stainless steel pipe, and after that, when low heat input welding is performed (specimens A to C), after the welding is finished, the inner surface of the stainless steel pipe The maximum residual stress value of the heat-affected zone was positive, that is, tensile stress that was a factor of stress corrosion cracking remained in the heat-affected zone.
一方、大入熱溶接をステンレス鋼管の肉厚の３８％まで行い、以降は低入熱溶接を行った場合（試験体Ｆ）、溶接終了後、ステンレス鋼管の内表面の熱影響部の最大残留応力値はマイナスになり、すなわち、熱影響部には圧縮応力が残留した。 On the other hand, when high heat input welding is performed up to 38% of the wall thickness of the stainless steel pipe, and after that, when low heat input welding is performed (specimen F), the maximum residual heat affected zone on the inner surface of the stainless steel pipe after welding is completed. The stress value became negative, that is, compressive stress remained in the heat affected zone.
大入熱溶接をステンレス鋼管の肉厚の４３％まで行い、以降は低入熱溶接を行った場合も（試験体Ｄ，Ｇ）、溶接終了後、ステンレス鋼管の内表面の熱影響部の最大残留応力値はマイナスになり、すなわち、熱影響部には圧縮応力が残留した。 Even when high heat input welding is performed up to 43% of the wall thickness of the stainless steel pipe, and thereafter low heat input welding is performed (specimens D and G), the maximum heat-affected zone on the inner surface of the stainless steel pipe after welding is completed. The residual stress value became negative, that is, compressive stress remained in the heat affected zone.
大入熱溶接をステンレス鋼管の肉厚の４６％以上行い、以降は低入熱溶接を行った場合も（試験体Ｅ，Ｈ）、溶接終了後、ステンレス鋼管の内表面の熱影響部の最大残留応力値はプラスになり、すなわち、熱影響部に応力腐食割れの因子となる引張応力が残留した。 Even if high heat input welding is performed for 46% or more of the wall thickness of the stainless steel pipe and then low heat input welding is performed (specimens E and H), the maximum heat-affected zone on the inner surface of the stainless steel pipe after welding is completed. The residual stress value was positive, that is, tensile stress that was a factor of stress corrosion cracking remained in the heat affected zone.
ホットワイヤを用いた場合と用いない場合を比較すると（試験体Ｄ，Ｇ）、ホットワイヤを用いた方が、溶接終了後、ステンレス鋼管の内表面の熱影響部の最大残留応力値がよりマイナス側になり、良好であった。 Comparing the case where hot wire is used and the case where hot wire is not used (test bodies D and G), the maximum residual stress value of the heat affected zone on the inner surface of the stainless steel pipe is more negative after using the hot wire when the hot wire is used. The side was good.
冷却ワイヤを用いた場合と用いない場合を比較すると（試験体Ｄ，Ｇ）、冷却ワイヤを用いた方が、溶接終了後、ステンレス鋼管の内表面の熱影響部の最大残留応力値がよりマイナス側になり、良好であった。 When the case where the cooling wire is used and the case where the cooling wire is not used are compared (test bodies D and G), the maximum residual stress value of the heat-affected zone on the inner surface of the stainless steel pipe is more negative after using the cooling wire. The side was good.
図２は、表１中の試験体Ｇの熱影響部のマクロ組織を示す写真である。図２を参照すると、溶接終了後、ステンレス鋼管の内表面の熱影響部に好ましい圧縮応力が得られた試験体Ｇにおいて、ブローホールや融合不良等の溶接欠陥は認められなかった。また、試験体Ｇの熱影響部においては、内表面側に幅広の溶接金属が形成され、それより外表面に向って一定幅の溶接金属が形成されている。よって図２及び表１から、溶接金属が、内表面側から鋼管の肉厚の３８％〜４５％までは軸方向に沿って幅広（鋼管の内表面側の溶接金属が同外表面側の溶接金属よりも幅広）に形成され、それから外表面側に向って軸方向に沿って一定幅に形成されていることにより、多層溶接終了時、前記ステンレス鋼管の内表面の熱影響部に残留する応力を圧縮応力とすることが可能となると考えられる。 FIG. 2 is a photograph showing the macro structure of the heat-affected zone of the specimen G in Table 1. Referring to FIG. 2, no weld defects such as blow holes and poor fusion were observed in the specimen G in which a preferable compressive stress was obtained in the heat-affected zone on the inner surface of the stainless steel pipe after the end of welding. Moreover, in the heat affected zone of the test body G, a wide weld metal is formed on the inner surface side, and a weld metal having a constant width is formed toward the outer surface. Therefore, from FIG. 2 and Table 1, the weld metal is wide along the axial direction from the inner surface side to 38% to 45% of the wall thickness of the steel pipe (the weld metal on the inner surface side of the steel pipe is welded on the outer surface side). The stress remaining in the heat-affected zone on the inner surface of the stainless steel pipe at the end of multi-layer welding by being formed with a constant width along the axial direction toward the outer surface side. It is considered that can be made a compressive stress.
以上の試験結果より、ステンレス鋼管の内表面の熱影響部の応力腐食割れを防止する残留応力圧縮法においては、以下の手段を用いることが好ましい。 From the above test results, it is preferable to use the following means in the residual stress compression method for preventing the stress corrosion cracking of the heat-affected zone on the inner surface of the stainless steel pipe.
（１）溶接機
・ダブルフラックス・ガスシールドによる低入熱溶接
・冷却ワイヤの導入（溶接ワイヤと冷却ワイヤの２本同時送給）
（２）開先形状
・狭開先、例えば、開先幅６．５〜７ｍｍのＵ型狭開先
（３）溶接施工法
・肉厚（板厚）３８％〜４５％まで大入熱溶接
・それ以降から最終層（最終パス）までは低入熱溶接
・上記大入熱溶接においてはホットワイヤ併用が好ましい
・上記低入熱溶接においては冷却ワイヤ併用が好ましい
・上記大入熱溶接においては入熱量１３０００Ｊ／ｃｍ以上が好ましい
・上記低入熱溶接においては入熱量３５００Ｊ／ｃｍ以下が好ましい
・大入熱量／低入熱量＝３〜７、さらには４〜６が好ましい
(1) Welding machine, double flux, low heat input welding with gas shield, introduction of cooling wire (simultaneous feeding of welding wire and cooling wire)
(2) Groove shape / narrow groove, for example, U-shaped narrow groove with groove width of 6.5 to 7 mm (3) Welding method / wall thickness (sheet thickness) 38% to 45% high heat input welding -Low heat input welding from that to the final layer (final pass)-Hot wire combination is preferable in the above high heat input welding-Cooling wire combination is preferable in the above low heat input welding-In the above high heat input welding A heat input of 13000 J / cm or more is preferable. In the low heat input welding, a heat input of 3500 J / cm or less is preferable. A large heat input / low heat input = 3 to 7, more preferably 4 to 6.
最後に、本発明によって、ステンレス鋼管の溶接部内表面の残留応力が圧縮応力に転換された理由を図示する。図３は、本発明の原理を説明するための模式図である。 Finally, the reason why the residual stress on the inner surface of the welded portion of the stainless steel pipe is converted into the compressive stress by the present invention will be illustrated. FIG. 3 is a schematic diagram for explaining the principle of the present invention.
図３を参照すると、本発明の場合、初層の溶接パスでは、溶着金属の収縮により、ステンレス鋼管の内表面の熱影響部に引張残留応力が作用し、中間層までの溶接パスにおいて、大入熱溶接（好ましくはホットワイヤ併用）により更なる広幅溶接が実現でき、それ以降の溶接パスでは、低入熱溶接（好ましくは冷却ワイヤ併用）を行うことにより、落込みによる回転変形が最小限に抑制され、最終的にはステンレス鋼管の内表面の熱影響部に残留応力が圧縮応力として残る。 Referring to FIG. 3, in the case of the present invention, in the first layer welding pass, tensile residual stress acts on the heat-affected zone of the inner surface of the stainless steel pipe due to shrinkage of the weld metal, and in the welding pass up to the intermediate layer, Further wide welding can be realized by heat input welding (preferably combined with hot wire), and in subsequent welding passes, rotational deformation due to drop is minimized by performing low heat input welding (preferably combined with cooling wire). In the end, residual stress remains as compressive stress in the heat affected zone of the inner surface of the stainless steel pipe.
本発明は、応力腐食割れが発生し易い環境で使用されるステンレス鋼管、特に、オーステナイト系ステンレス鋼管の溶接方法に好適に適用される。本発明は、配管径３００〜６００Ａのステンレス鋼管の溶接に好適に適用される。 The present invention is suitably applied to a stainless steel pipe used in an environment where stress corrosion cracking is likely to occur, in particular, a method for welding an austenitic stainless steel pipe. The present invention is suitably applied to welding of a stainless steel pipe having a pipe diameter of 300 to 600A.
Claims (4)
溶接前、前記ステンレス鋼管の端面同士の間に形成する開先を狭開先とし、
溶接開始後、前記ステンレス鋼管の肉厚の３８％〜４５％まで溶接する溶接パスにおいては大入熱溶接を行い、以降の溶接パスにおいては、前記大入熱溶接時よりも低い入熱量で低入熱溶接を行い、
多層溶接終了時、前記ステンレス鋼管の内表面の熱影響部に残留する応力を圧縮応力とすることを特徴とするステンレス鋼管の多層溶接方法。 A multi-layer welding method for stainless steel pipes, in which the end faces of the stainless steel pipes are butted together and the welding passes are welded multiple times along the circumferential direction, and the end faces are welded together.
Before welding, the groove formed between the end faces of the stainless steel pipe is a narrow groove,
After the start of welding, large heat input welding is performed in a welding pass for welding up to 38% to 45% of the wall thickness of the stainless steel pipe, and in subsequent welding passes, the heat input amount is lower than that during the large heat input welding. Heat input welding,
A multi-layer welding method for stainless steel pipes, characterized in that, at the end of multi-layer welding, the stress remaining in the heat-affected zone of the inner surface of the stainless steel pipe is a compressive stress.
溶接金属が、内表面側から鋼管の肉厚の３８％〜４５％までは軸方向に沿って幅広に形成され、それから外表面側に向って軸方向に沿って一定幅に形成されていることを特徴とするステンレス鋼管の多層溶接物。 The end faces of the stainless steel pipes are butted together, a welding pass for groove welding along the circumferential direction is performed a plurality of times, and the end faces are welded multi-layered stainless steel pipes,
The weld metal is formed to be wide along the axial direction from 38% to 45% of the wall thickness of the steel pipe from the inner surface side, and then formed with a constant width along the axial direction toward the outer surface side. Multi-layer welded stainless steel pipe characterized by
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| CN106271172A (en) * | 2016-08-13 | 2017-01-04 | 江苏标新工业有限公司 | The method controlling fire check for the welding of heat resisting steel furnace roller |
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