CN110834177A - Method for reducing welding residual stress of large pressure vessel - Google Patents
Method for reducing welding residual stress of large pressure vessel Download PDFInfo
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- CN110834177A CN110834177A CN201911027600.6A CN201911027600A CN110834177A CN 110834177 A CN110834177 A CN 110834177A CN 201911027600 A CN201911027600 A CN 201911027600A CN 110834177 A CN110834177 A CN 110834177A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
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- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
Abstract
The invention provides a method for reducing welding residual stress of a large pressure vessel, which comprises the following steps: 1) processing an X-shaped groove on two parts to be welded, wherein the angle of the groove is 50-60 degrees, and if the thicknesses of the two parts are different, performing tapered transition pretreatment on the thicker side to ensure that the thickness of the tail end of the thicker side is consistent with that of the thinner side; 2) filling welding is carried out, an inner side and an outer side are welded alternately, 2-4 layers of welding operation is continued to the outer side after 2-4 layers of welding operation are carried out on the inner side, and the operation is repeated until the welding operation of the filling weld bead is finished; 3) performing cover welding, namely horizontally placing the pressure container to perform cover welding operation, wherein the welding sequence of the cover welding is that the welding sequence from two sides to the middle is adopted to respectively perform inner and outer cover welding operation; 4) polishing the weld reinforcement at the joint to be flat, and taking no obvious discontinuous protrusion as a standard; 5) and (4) carrying out full-coverage impact operation on the weld bead and the area nearby the weld bead by adopting a mechanical method, namely finishing the elimination of residual stress.
Description
Technical Field
The invention relates to the technical field of processing and manufacturing of steel containers, in particular to a method for reducing welding residual stress of a large-sized pressure container.
Background
The pressure vessel is used as a pressure-bearing device and is widely applied to the fields of petrifaction, nuclear power, aerospace and the like. The large-scale pressure-bearing equipment is the necessary way to improve the economic benefit. However, the large size of the equipment can pose significant manufacturing challenges. Due to the fact that the diameter and the wall thickness are overlarge, the number of welding beads is large, and the restraint is strong, large welding residual stress can be generated, and stress corrosion, fatigue and creep cracking are caused. Especially, the joint weld between the end socket and the cylinder introduces the problem of stress concentration due to the difference of design thickness, which aggravates the failure risk of the equipment. Therefore, the effective reduction of the welding residual stress at the two welded joints is of great significance to the manufacture of large pressure vessels.
The method for reducing welding residual stress widely used at present mainly comprises postweld heat treatment, including integral and local heat treatment: the whole heat treatment after welding is obviously not suitable for large pressure vessels, and the local heat treatment operation is improper, but additional heat stress is introduced, so that the method is suitable for the contrary. Moreover, the heat treatment process requires a large amount of energy and time, and a large amount of manpower and material resources are invested, which is not suitable for high-efficiency production. In addition, there are often instances where the weld seam location cracks prior to the post-weld heat treatment. Therefore, in the design and manufacturing stage of the pressure vessel, the reduction of the welding residual stress through the improvement of the manufacturing process has important significance for improving the structural integrity of the pressure vessel.
Disclosure of Invention
Aiming at the problem that the welding residual stress of a welding joint of a large pressure vessel (the wall thickness is more than or equal to 50mm) is too large to easily cause cracking, the invention provides a method which is convenient to operate, has high efficiency and can reduce the welding residual stress of the pressure vessel in the design and manufacturing process.
The invention adopts the following technical scheme:
a method for reducing welding residual stress of a large-sized pressure vessel comprises the following steps:
(1) processing an X-shaped groove on two parts to be welded, wherein the angle of the groove is 50-60 degrees, and if the thicknesses of the two parts are different, performing tapered transition pretreatment on the thicker side to ensure that the thickness of the tail end of the thicker side is consistent with that of the thinner side;
(2) performing filling welding
Adopting an inner-outer alternate welding mode, welding 2-4 layers on the inner side, then turning to the outer side to continue 2-4 layers of welding operation, and so on until the welding of the filling weld bead is finished;
(3) performing cover welding
Horizontally placing the pressure container for facing welding operation, wherein the welding sequence of facing welding is to respectively perform inner and outer facing welding operation by adopting a welding sequence from two sides to the middle;
(4) polishing the weld reinforcement at the joint to be flat, and taking no obvious discontinuous protrusion as a standard;
(5) and (4) carrying out full-coverage impact operation on the weld bead and the area nearby the weld bead by adopting a mechanical method, namely finishing the elimination of residual stress.
Further, in the step (1), when the thicknesses of the two parts are inconsistent, the thicker side is subjected to conical transition pre-cutting treatment.
Further, the thicker side in the step (1) is a cylinder body; the thinner side is a seal head.
Further, the method also comprises the step of carrying out flame heating and preheating treatment before butt welding, wherein the preheating temperature is 100-200 ℃.
Further, the flame heating is oxyacetylene flame heating.
Further, in the step (2), the total alternating times of the internal and external alternate welding is not less than 3 times.
Further, the temperature between all the solder layers is below 150 ℃.
Further, the mechanical method in the step (5) is ultrasonic impact or shot blasting.
Further, after the steps (2) and (3), the harmful welding residual stress of the obtained large-sized pressure container is within 5mm of the surface layer.
The invention has the beneficial effects that:
the internal and external alternate welding scheme provided by the invention is beneficial to reducing the axial residual stress, particularly the residual tensile stress on the inner side surface, and can improve the structural strength and the pressure bearing capacity of the pressure container, particularly the internal pressure container; the capping welding sequence can obviously reduce the circumferential residual stress of a welding toe area, and a large amount of practice proves that the welding toe area is the frequent position of the crack of the welding seam, and the crack resistance of the welding seam can be improved by adopting the method; the problem of stress concentration can be solved by polishing the weld reinforcement; the ultrasonic impact treatment after welding can basically eliminate harmful residual tensile stress and form a compressive stress layer on the surface, thereby improving the tensile strength of the structure and improving the stress corrosion cracking resistance; the method reduces the welding residual stress in the manufacturing process of the pressure vessel, and has important significance for improving the structural integrity of the pressure vessel and enhancing the stress corrosion cracking resistance of the welding joint of the pressure vessel.
Drawings
FIG. 1 is a schematic diagram of the tapered transition and groove form of the end socket and the cylinder (wherein 1 is the end socket and 2 is the cylinder);
FIG. 2 is a schematic view showing the effect of eliminating axial residual stress;
FIG. 3 is a schematic view of a face welding sequence;
fig. 4 is a schematic diagram of the effect of eliminating the hoop residual stress.
Detailed Description
The invention is described in detail below with reference to the accompanying drawings:
a method for reducing welding residual stress of a large-sized pressure vessel comprises the following steps:
(1) processing X-shaped bevels on two parts to be welded, wherein the bevel angle is 50-60 degrees. If the thicknesses of the two parts are not consistent, firstly carrying out tapered transition pretreatment on the thicker side (which can be a cylinder) to ensure that the thickness of the tail end of the thicker side is consistent with that of the thinner side (which can be a seal head); before welding, flame heating and preheating treatment is carried out, and the preheating temperature is 100-200 ℃.
(2) Performing filling welding
Adopting an inner-outer alternate welding mode, welding 2-4 layers on the inner side, then turning to the outer side to continue 2-4 layers of welding operation, and so on until the welding of the filling weld bead is finished; the total number of alternations is not less than 3 (one from one side to the other).
(3) Performing cover welding
Horizontally placing the pressure container for facing welding operation, wherein the welding sequence of facing welding is to respectively perform inner and outer facing welding operation by adopting a welding sequence from two sides to the middle;
the temperature between all solder layers is below 150 ℃.
(4) Polishing the weld reinforcement at the two joints to be flat, and taking no obvious discontinuous bulges as a standard;
(5) the harmful residual stress can be controlled within 5mm of the surface layer by the welding method; and the residual stress can be basically eliminated by adopting mechanical methods such as ultrasonic impact, shot blasting and the like to carry out full-coverage impact operation on the weld bead and the nearby area.
Example 1
Taking the welding of the end socket and the cylinder of the large-sized pressure vessel as an example:
referring to fig. 1, the cylinder is first tapered to reduce the thickness of the joint between the end socket and the cylinder. The taper transition length of the inner side is 70mm, and the taper transition is carried out after a straight edge section of 10mm is reserved on the outer side. And (3) forming an X-shaped groove at the joint, wherein the truncated edge is 2mm, the gap is 2mm, and the angle theta of the groove is controlled to be 50-60 degrees.
Cleaning a groove before welding, polishing the end socket and the cylinder body, polishing 20mm of oil stain, rust, moisture, burrs and other stains on two sides of the welding groove, and heating by oxyacetylene flame, wherein the preheating temperature is not lower than 100 ℃. And performing back gouging treatment after the tack welding.
Filling welding is firstly carried out on the inner side, and the inner side and the outer side are alternately welded, and every 2-4 layers are changed to the other side until the filling welding is finished.
The axial residual stress relief effect is shown in fig. 2, in which the ordinate is the residual stress (MPa), which represents the axial residual stress of the inner side surface; the abscissa represents the distance distribution along the path of the weld surface. The solid square point curve in the figure represents the distribution of the welding residual stress processed by the common welding method, and the hollow circular point curve represents the distribution of the welding residual stress processed by the method of the present invention. Compared with the common method, the method for connecting the end socket and the cylinder of the pressure vessel has the advantages that the integral residual stress is greatly reduced, and the residual stress in a welding seam area, particularly a welding toe area, is reduced by about 170 MPa. Compared with the common welding method, the internal and external alternate welding sequence adopted by the invention can obviously reduce the axial welding residual stress of the end socket cylinder.
Referring to fig. 3, the cover welding sequence is schematically shown, after the completion of the filling weld bead, the equipment is horizontally placed, and the cover welding operation is performed on the inner side and the outer side. The welding pass sequence is from two sides to the middle.
The hoop residual stress relief effect is shown in fig. 4, the ordinate is residual stress (MPa), which represents hoop residual stress along the weld line, and the abscissa represents distance distribution along the weld line path of the head and the barrel. The solid square point curve in the figure represents the distribution of the welding residual stress processed by the common welding method, and the hollow circular point curve represents the distribution of the welding residual stress processed by the method of the present invention. Compared with the common method, the method for connecting the end socket and the cylinder of the pressure vessel has the advantages that the residual stress is reduced by about 160MPa to the maximum extent in the near-surface region near the fusion line, and the overall distribution is more uniform compared with the common method.
Compared with the common welding method, the invention adopts the cover surface welding sequence from two sides to the middle, which can obviously reduce the circumferential welding residual stress of the end socket cylinder.
And after welding, primarily polishing and flattening the weld reinforcement on the basis of no obvious discontinuous bulges.
Finally, the surface of the welding seam can be impacted by mechanical actions such as ultrasonic impact, shot blasting and the like, so that the surface appearance of the welding seam is further improved, the residual tensile stress is eliminated, and the residual tensile stress is converted into beneficial compressive stress.
It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, alterations, additions or substitutions within the spirit and scope of the present invention.
Claims (9)
1. A method for reducing the welding residual stress of a large-sized pressure vessel is characterized by comprising the following steps:
(1) processing an X-shaped groove on two parts to be welded, wherein the angle of the groove is 50-60 degrees, and if the thicknesses of the two parts are different, performing tapered transition pretreatment on the thicker side to ensure that the thickness of the tail end of the thicker side is consistent with that of the thinner side;
(2) performing filling welding
Adopting an inner-outer alternate welding mode, welding 2-4 layers on the inner side, then turning to the outer side to continue 2-4 layers of welding operation, and so on until the welding of the filling weld bead is finished;
(3) performing cover welding
Horizontally placing the pressure container for facing welding operation, wherein the welding sequence of facing welding is to respectively perform inner and outer facing welding operation by adopting a welding sequence from two sides to the middle;
(4) polishing the weld reinforcement at the joint to be flat, and taking no obvious discontinuous protrusion as a standard;
(5) and (4) carrying out full-coverage impact operation on the weld bead and the area nearby the weld bead by adopting a mechanical method, namely finishing the elimination of residual stress.
2. The method for reducing the welding residual stress of the large-sized pressure vessel according to the claim 1, wherein in the step (1), when the thicknesses of the two parts are not consistent, the tapered transition pretreatment is carried out on the thicker side, and the tapered transition pretreatment is carried out.
3. The method for reducing the welding residual stress of the large-scale pressure vessel according to the claim 1, wherein the thicker side in the step (1) is a cylinder body; the thinner side is a seal head.
4. The method for reducing the welding residual stress of the large-sized pressure vessel according to claim 1, further comprising a flame heating preheating treatment before the butt welding, wherein the preheating temperature is 100-200 ℃.
5. The method for reducing the welding residual stress of the large-scale pressure vessel according to claim 4, wherein the flame heating is oxyacetylene flame heating.
6. The method for reducing the welding residual stress of the large-sized pressure vessel according to the claim 1, wherein in the step (2), the total number of times of the inner and outer alternate welding is not less than 3 times.
7. The method for reducing the welding residual stress of the large-scale pressure vessel according to the claim 1, wherein the temperature between all welding layers is lower than 150 ℃.
8. The method for reducing the welding residual stress of the large-scale pressure vessel according to the claim 1, wherein the mechanical method in the step (5) is ultrasonic impact or shot blasting.
9. The method for reducing the welding residual stress of the large pressure vessel as claimed in claim 1, wherein the harmful welding residual stress near the welding seam of the large pressure vessel obtained through the steps (2) and (3) is within 5mm of the surface layer.
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| CN201911027600.6A CN110834177A (en) | 2019-10-28 | 2019-10-28 | Method for reducing welding residual stress of large pressure vessel |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111069856A (en) * | 2019-12-28 | 2020-04-28 | 天津航天长征火箭制造有限公司 | Assembling welding and shape and position size control method for 5-meter-diameter cylinder section flange |
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| CN104002023A (en) * | 2014-05-29 | 2014-08-27 | 南通中远重工有限公司 | Welding process special for thick dissimilar material plate |
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2019
- 2019-10-28 CN CN201911027600.6A patent/CN110834177A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10128534A (en) * | 1996-10-31 | 1998-05-19 | Toshiba Corp | Method for welding device of furnace |
| CN101648310A (en) * | 2008-08-15 | 2010-02-17 | 中国海洋石油总公司 | Method for welding circular casings with large-thickness casing walls |
| CN102233500A (en) * | 2010-04-22 | 2011-11-09 | 上海华谊集团装备工程有限公司 | Process for controlling deformation in split welding and heat treatment of large pipe plate |
| CN104002023A (en) * | 2014-05-29 | 2014-08-27 | 南通中远重工有限公司 | Welding process special for thick dissimilar material plate |
| CN106112225A (en) * | 2016-08-02 | 2016-11-16 | 中国石油大学(华东) | A kind of Nozzle Zone of Vessels reducing welding residual stress and end socket method of attachment |
| CN107803630A (en) * | 2017-10-30 | 2018-03-16 | 上海振华重工启东海洋工程股份有限公司 | A kind of cutter suction dredger trunnion base steel-casting welding procedure |
| CN107876942A (en) * | 2017-12-07 | 2018-04-06 | 江苏省沙钢钢铁研究院有限公司 | A kind of normalized steel buried arc welding method for improving welding point low-temperature impact toughness |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111069856A (en) * | 2019-12-28 | 2020-04-28 | 天津航天长征火箭制造有限公司 | Assembling welding and shape and position size control method for 5-meter-diameter cylinder section flange |
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Application publication date: 20200225 |
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