CN1255242C - In-situ fast method of eliminating residual stress in welded joint of small-diameter pipe - Google Patents
In-situ fast method of eliminating residual stress in welded joint of small-diameter pipe Download PDFInfo
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- CN1255242C CN1255242C CN 03133348 CN03133348A CN1255242C CN 1255242 C CN1255242 C CN 1255242C CN 03133348 CN03133348 CN 03133348 CN 03133348 A CN03133348 A CN 03133348A CN 1255242 C CN1255242 C CN 1255242C
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- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000011065 in-situ storage Methods 0.000 title 1
- 238000010438 heat treatment Methods 0.000 claims abstract description 25
- 238000003466 welding Methods 0.000 claims abstract description 19
- 238000007669 thermal treatment Methods 0.000 claims description 23
- 229910000831 Steel Inorganic materials 0.000 claims description 10
- 230000006835 compression Effects 0.000 claims description 10
- 238000007906 compression Methods 0.000 claims description 10
- 239000010959 steel Substances 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 9
- 239000010935 stainless steel Substances 0.000 claims description 7
- 229910001220 stainless steel Inorganic materials 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 5
- 238000005516 engineering process Methods 0.000 claims description 4
- 239000012467 final product Substances 0.000 claims description 4
- 229910000746 Structural steel Inorganic materials 0.000 claims description 3
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 239000000956 alloy Substances 0.000 claims description 3
- 229910001209 Low-carbon steel Inorganic materials 0.000 claims description 2
- 238000005265 energy consumption Methods 0.000 abstract description 3
- 238000010276 construction Methods 0.000 abstract description 2
- 239000002184 metal Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 3
- 230000008030 elimination Effects 0.000 description 3
- 238000003379 elimination reaction Methods 0.000 description 3
- 238000005336 cracking Methods 0.000 description 2
- 238000005272 metallurgy Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000005674 electromagnetic induction Effects 0.000 description 1
- QFXZANXYUCUTQH-UHFFFAOYSA-N ethynol Chemical group OC#C QFXZANXYUCUTQH-UHFFFAOYSA-N 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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Abstract
The present invention relates to the technical field of prolonging the service life of a welded structure, particularly to a method for fast eliminating the residual stress of welding joints of pipelines with small diameter. Particularly, the present invention is deformed by temperature difference, and pressure stress areas at two sides of the annular welding seams of the joints of the pipelines with small diameter are fast heated, and temperature difference between a heating area and the welding seam part is made. The method comprises the following steps: 1) the heating area is symmetrically distributed using the welding seams as the center, and the distance between the heating area and the annular seams is from 20mm to 40mm; the heating width is from 10 to 30mm; 2) the heating area is fast heated, and the temperature difference between the heating area and the annular seams can reach 150 DEG C to 550 DEG C; then, the heating area is naturally cooled. The pulling stress of the welding joints can be reduced by 80% to 100% through the present invention; the present invention not only can eliminate most part of the stress but also can completely eliminate SCC harm. The present invention has the characteristics of simple and convenient construction, and high efficiency; the present invention has the advantages of high speed, short time and low energy consumption; the present invention is especially suitable for the popularization on sites.
Description
Technical field
The present invention relates to the Welding Structure processing technology field of lengthening the life, specifically a kind of method of quick elimination small diameter pipeline welding point residual stress.
Technical background
In industries such as petrochemical industry, metallurgy, small diameter pipeline (φ＜300mm) in the transport pipeline system, occupy important function.The corrosivity of transportation of substances and the synergy that partly there is residual-tensile stress in pipeline welded joint in the pipeline; run, drip, leak etc. even accident such as cracking fully usually can take place at the pipeline welded joint position; this phenomenon that causes ftractureing owing to effect corrosive medium and tensile stress on certain material is called stress corrosion cracking, is called for short SCC.Because thoroughly eliminate the difficulty of small diameter pipeline welding residual stress, this phenomenon perplexs industries such as chemical industry, metallurgy, has potential safety hazard, causes very big waste and loss always, therefore be necessary to solve the SCC problem of pipe joint.
The tradition local heat treatmet generally adopts heat tape to be entangled on the material, heat, reduce stress by creep, can reduce stress level to about 2/3rds of material yield point, but require that cooling velocity is can not be too fast, temperature retention time is longer, still there is higher residual stress, thereby can not eliminates the harm of SCC fully.And traditional local heat treatmet has a fatal weakness, is exactly that treatment effeciency is low, energy consumption is high, the incompatibility field popularization application.
Summary of the invention
The method that the purpose of this invention is to provide the more excellent quick elimination small diameter pipeline welding point residual stress of a kind of effect.
Purpose technical scheme of the present invention is: adopt temperature difference deformation process, utilize firing equipment, carry out Fast Heating in the compression district on small diameter pipeline joint ring weld seam both sides, make the temperature difference at the thermal treatment zone and weld seam position reach a certain size; Concrete technology is:
1) thermal treatment zone is that the center is symmetrically distributed with the weld seam, leaves the circumferential weld distance and is 20mm～40mm; Its width of heating is 10～30mm;
2) heating rapidly makes the thermal treatment zone and circumferential weld reach 150 ℃～550 ℃ temperature difference; Naturally cooling gets final product then.
Wherein: heat the outer surface that the distance of leaving weld seam in the position is chosen in inner surface axial compression district correspondence; For the 20 steel temperature difference is 150～550 ℃, is 200～550 ℃ for the 16Mn steel temperature difference, is 150～550 ℃ for the stainless steel temperature difference; Small diameter pipeline can be conveyance conduit, caliber diameter range: 50～300mm; Material can be various steel for pipe such as mild steel, low-alloy structural steel, stainless steel; Described heating can be adopted flame, far infrared or electromagnetic-induction heating method, and as talking about easily, available at the scene oxy-acetylene flame is realized heating rapidly.
The present invention has following beneficial effect:
1. the effect that eliminates stress is more excellent.It is suitable that the temperature difference of the thermal treatment zone and the non-thermal treatment zone should be selected, and can not effectively eliminate the weld metal zone tension too for a short time, can form new high tensile stress district in the thermal treatment zone again too greatly, will be extremely harmful to stainless steel material.Because the temperature difference at the thermal treatment zone of the present invention and weld seam position is reasonable, not only can eliminate most stress so adopt this method, even can near joint, cause compression stress, can only reduce 1/3～1/4 of welding point welding residual stress with local heat treatmet in the prior art compares, the present invention can reduce welding point tension 80%～100%, even cause a certain size compression at welding point, eliminate the harm of SCC fully.
2. the present invention has easy construction, the high characteristics of efficient, and speed is fast, the time is short, and energy consumption is low, particularly is fit to field popularization application.
The specific embodiment
Embodiment 1
Adopt temperature difference deformation process, carry out Fast Heating, make the temperature difference at the thermal treatment zone and weld seam position reach a certain size in the compression district on small diameter pipeline joint ring weld seam both sides; Concrete technology is:
20 steel pipes of cut-off footpath 100mm, wall thickness 4.5mm, the thermal treatment zone is that the center is symmetrically distributed with the weld seam, use the annular flame heater, heat the outer surface that the distance of leaving weld seam is chosen in inner surface axial compression district correspondence, the effective width of heating 10mm of flame, heat time heating time is (present embodiment is 35s) between 30～40s, and flame kernel point is apart from axis of a weld 25～30mm (present embodiment is 25mm).Inwall and flame kernel over against point, its maximum temperature reaches 400～500 ℃.In the time of 500 ℃, the highest temperature difference of putting on it and the axis of a weld reaches 200 ℃, and cooling gets final product naturally then.The decline situation of residual stress is as follows after tested:
Original residual-stress value (MPa)
| With axis of a weld distance (mm) | 5 | 10 | 20 | 30 | 40 | |
| Outer surface | Axially | -143 | -105 | 112 | 215 | 209 |
| Hoop | -25 | 13 | 32 | 143 | 175 | |
| Inner surface | Axially | 258 | 254 | 19 | -118 | -139 |
| Hoop | 150 | 206 | -159 | -212 | -145 | |
Handle back residual-stress value (MPa)
| With axis of a weld distance (mm) | 5 | 10 | 20 | 30 | 40 | |
| Outer surface | Axially | -180 | -203 | -48 | -118 | 5 |
| Hoop | -105 | -184 | 47 | 157 | 134 | |
| Inner surface | Axially | -134 | -46 | 117 | 234 | 48 |
| Hoop | -93 | -222 | -238 | 103 | -252 | |
As seen, present embodiment can make the welding point inner surface become compression by the tension near material yield point, can eliminate the harm of SCC fully.
The principle of the invention is as follows:
Cause inside pipe wall to have axial tension stress because the small diameter pipeline girth joint shortens, this is the principal element that causes SCC.Make the thermal treatment zone and the thermal treatment zone-weld metal zone, center not produce the temperature difference in the heating of the compression district on weld seam both sides, the temperature difference causes the expanded by heating of the thermal treatment zone on weld seam both sides to be subjected to the restriction of the adjacent with it non-thermal treatment zone-weld metal zone, center.When the temperature difference reaches sizable numerical value, just can make the thermal treatment zone produce compressive plastic deformation, after the temperature balance, the thermal treatment zone, weld seam both sides is shortened like this, coordinate mutually with the weld metal zone, center, thereby weld metal zone stress is reduced and even elimination.
It is suitable that the temperature difference of the thermal treatment zone of the present invention and the non-thermal treatment zone should be selected, and can not effectively eliminate the weld metal zone tension too for a short time, can form new high tensile stress district in the thermal treatment zone again too greatly, will be extremely harmful to stainless steel material.
Embodiment 2
Difference from Example 1 is:
Get stainless-steel pipe, diameter: 300mm, wall thickness 4.5mm, the thermal treatment zone is left the circumferential weld distance and is 30mm; Its width of heating is 20mm, is heated to be 40s, makes the thermal treatment zone and circumferential weld reach 600 ℃, and the temperature difference is 400 ℃, and cooling gets final product naturally then.
Its result:
Original residual-stress value (MPa)
| With axis of a weld distance (mm) | 5 | 10 | 20 | 30 | 40 | |
| Outer surface | Axially | 1 | 1 | 22 | 247 | 166 |
| Hoop | 76 | 42 | -11 | 18 | 80 | |
| Inner surface | Axially | 250 | -31 | -88 | -190 | -134 |
| Hoop | 169 | 61 | -63 | -78 | -14 | |
Handle back residual-stress value (MPa)
| With axis of a weld distance (mm) | 5 | 10 | 20 | 30 | 40 | |
| Outer surface | Axially | 127 | 16 | -156 | -134 | 6 |
| Hoop | -100 | 30 | 23 | 47 | 33 | |
| Inner surface | Axially | 29 | -39 | 53 | 72 | -11 |
| Hoop | -17 | 10 | -15 | 28 | -21 | |
The present invention can also get various steel for pipe such as low-alloy structural steel.
Adopt the present invention to determine the treatment process parameter, comprise the selected of the selection of heater, the distance of leaving weld seam and heat time heating time according to material, diameter and the wall thickness of concrete pipeline.Wherein the selection of heater can be decided according to the concrete condition at scene, in general adopts flame heat more convenient and practical at the scene; Can determine in advance by test its heat time heating time.Definite principle of the required temperature difference of various steel for pipe is according to the thermal coefficient of expansion of steel and handles the stress value that will reach and determine.
Claims (4)
1. the method for small diameter pipeline welding point residual stress is eliminated at a scene fast, it is characterized in that: adopt temperature difference deformation process, carry out Fast Heating in the compression district on small diameter pipeline joint ring weld seam both sides, cause the temperature difference at the thermal treatment zone and weld seam position; Concrete technology is:
1) thermal treatment zone is that the center is symmetrically distributed with the weld seam, leaves the circumferential weld distance and is 20mm～40mm; Its width of heating is 10～30mm;
2) heating rapidly makes the thermal treatment zone and circumferential weld reach 150 ℃～550 ℃ temperature difference; Naturally cooling gets final product then;
Wherein heat time heating time is between 30～40s; Diameter range: 50～300mm.
2. eliminate the method for small diameter pipeline welding point residual stress according to the described scene of claim 1 fast, it is characterized in that: heat the outer surface that the distance of leaving weld seam is chosen in inner surface axial compression district correspondence.
3. eliminate the method for small diameter pipeline welding point residual stress according to the described scene of claim 1 fast, it is characterized in that: small diameter pipeline can be conveyance conduit, and material can be mild steel, low-alloy structural steel, the various steel for pipe of stainless steel.
4. eliminate the method for small diameter pipeline welding point residual stress according to the described scene of claim 1 fast, it is characterized in that: for the 20 steel temperature difference is 150～550 ℃, is 200～550 ℃ for the 16Mn steel temperature difference, is 150～550 ℃ for the stainless steel temperature difference.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 03133348 CN1255242C (en) | 2003-05-22 | 2003-05-22 | In-situ fast method of eliminating residual stress in welded joint of small-diameter pipe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 03133348 CN1255242C (en) | 2003-05-22 | 2003-05-22 | In-situ fast method of eliminating residual stress in welded joint of small-diameter pipe |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1548265A CN1548265A (en) | 2004-11-24 |
| CN1255242C true CN1255242C (en) | 2006-05-10 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN 03133348 Expired - Fee Related CN1255242C (en) | 2003-05-22 | 2003-05-22 | In-situ fast method of eliminating residual stress in welded joint of small-diameter pipe |
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Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102409153B (en) * | 2011-11-14 | 2013-04-10 | 苏州热工研究院有限公司 | Postweld heat treatment method of welded joint of pipelines with different specifications |
| CN102839270B (en) * | 2012-09-05 | 2013-09-04 | 中国化学工程第十四建设有限公司 | Postwelding stress-releasing heat treatment technology for pressure bearing equipment |
| CN106884086B (en) * | 2017-02-17 | 2018-04-03 | 燕山大学 | A kind of bilateral flame heating removes the device and technique of submerged arc pipe weld residual stress |
| CN114182088B (en) * | 2021-12-08 | 2023-10-13 | 中国石油大学(华东) | Local heat treatment method for reducing stress corrosion cracking risk of welded joint of heat exchange tube and tube plate of shell-and-tube heat exchanger |
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| Publication number | Publication date |
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| CN1548265A (en) | 2004-11-24 |
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