CN115436597A - Method for testing spatial spiral bent pipe - Google Patents
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- 238000012546 transfer Methods 0.000 claims abstract description 48
- 238000001514 detection method Methods 0.000 claims abstract description 31
- 230000007797 corrosion Effects 0.000 claims abstract description 29
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- 238000005452 bending Methods 0.000 claims abstract description 28
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- 238000009659 non-destructive testing Methods 0.000 claims abstract description 10
- 238000009662 stress testing Methods 0.000 claims abstract description 7
- 230000035882 stress Effects 0.000 claims description 40
- 238000009864 tensile test Methods 0.000 claims description 15
- 238000009826 distribution Methods 0.000 claims description 13
- 230000032683 aging Effects 0.000 claims description 11
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- 238000003723 Smelting Methods 0.000 description 1
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- 230000033228 biological regulation Effects 0.000 description 1
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- 239000012530 fluid Substances 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
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Abstract
The invention discloses a method for inspecting a spatial spiral bent pipe, which comprises the following steps: selecting a plurality of straight tube heat transfer tubes, and carrying out butt welding to form a plurality of welded tubes, wherein each welded tube is provided with the same or different number of welded joints; carrying out nondestructive testing and physicochemical inspection on the welding joint; manufacturing to obtain spatial spiral bent pipes, wherein the welding joints are positioned in the bent pipe units, and at least two spatial spiral bent pipes are provided with at least 2 bent pipe units with the smallest spiral diameters; nondestructive testing, X-ray residual stress testing and MgCl of welding joint 2 Stress corrosion and microcrack inspection; x-ray residual stress detection and MgCl detection are carried out on non-welded parts 2 Stress corrosion and micro-crack inspection; the whole coil of the spatial spiral elbow comprises a starting bending point, a final bending point, a part with a welding joint, a part without a welding joint, straight pipe sections positioned at two ends, an elbow unit and a transition section between the straight pipe sections and the elbow unit.
Description
The application is a divisional application of an invention patent application with the application date of 2019, 20.11 months and the application number of 201911140266.5, and the invention name of "inspection method of space spiral bent pipe for heat exchanger".
Technical Field
The invention relates to the technical field of pipe fitting detection, in particular to a method for detecting a space spiral bent pipe for a heat exchanger.
Background
The space spiral coil heat exchanger is a special shell-and-tube heat exchanger, has compact structure, large heat transfer coefficient and wide application, and is mainly used in the fields of electric power, machinery, ocean engineering and the like. When the design space is limited and the U-shaped heat exchange tube cannot be placed or the pressure drop of the fluid in the heat transfer tube is required to be small, the unique structure and the flowing advantage of the spatial spiral coil are highlighted.
Although the space spiral coil heat exchanger has unique advantages, certain manufacturing and inspection difficulties exist. For a heat transfer pipe with a larger spiral diameter, a straight pipe with enough length is required to be bent, but the straight pipe with the required length cannot be produced due to the influence of straight pipe equipment in a manufacturing plant, so that the length requirement is met by butt welding two or more straight pipes. The welded joint of the spiral coil pipe becomes the weakest part of the whole branch pipe, and the main difficulty is how to fully inspect the welded area and the whole spiral coil pipe to meet the requirements of design and regulation. In addition, the space spiral coil heat exchanger usually has high safety level requirements and belongs to key components. Before the official products are manufactured, the spiral coil process evaluation work needs to be carried out to verify that the overall quality of the spiral coil manufactured by the supplier can meet the design requirements.
The spiral coil is made of UNS N06690 (American trademark, NC30Fe corresponding to French trademark) which is an austenite high nickel chromium iron (Ni-Cr-Fe) alloy. The alloy has remarkable oxidation resistance and stress corrosion resistance, and has high strength, excellent metallurgical stability and processing characteristics.
The general manufacturing process flow of the spiral coil in the prior art is as follows: vacuum induction smelting → electroslag remelting → forging cogging → hot extrusion → rolling annealing → aging treatment → butt welding → space bending → nondestructive testing → cleanliness inspection → packaging.
The spiral coil process assessment means that a manufacturer manufactures and inspects a certain number of heat transfer tubes according to expected requirements before the official batch production, and the manufacturing conditions are the same as those in the official batch production. The bent pipe process evaluation is also a verification method generally adopted before the mass production of the heat transfer tubes of the heat exchanger.
The prior art and the standard only refer to the basic requirements of the bent pipe process evaluation, and only have the minimum requirements for the whole bent pipe process evaluation, and the integral quality and the manufacturing stability of the pipe are not enough to be verified before batch production.
Disclosure of Invention
In view of this, in order to overcome the defects of the prior art and achieve the above object, the present invention aims to provide a method for inspecting a spatial spiral bend for a heat exchanger, so as to improve the accuracy of the inspection result and reduce the inspection cost.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for testing a space spiral elbow for a heat exchanger comprises the following steps:
step 1): selecting a plurality of straight tube heat transfer tubes, wherein the length of each straight tube heat transfer tube meets the requirement of bending at least one bent tube unit with the minimum spiral diameter, and after rolling annealing and aging treatment of the straight tube heat transfer tubes, carrying out butt welding on the selected straight tube heat transfer tubes to form a plurality of welded tubes, wherein each welded tube is provided with the same or different number of welded joints;
step 2): carrying out nondestructive testing and physicochemical inspection on all welding joints in the welded pipe obtained in the step 1);
and step 3): bending the welded pipe prepared in the step 1) to obtain a space spiral bent pipe with the minimum spiral diameter, wherein the space spiral bent pipe is provided with a plurality of bent pipe units and welding joints, and the welding joints are positioned in the bent pipe units. The control welding joint is positioned at the bending section of the elbow unit and cannot be positioned at the transition section or the straight pipe section of the spatial spiral elbow;
step 4): performing nondestructive testing, X-ray residual stress testing and MgCl testing on the welding joint in the spatial spiral bent pipe in the step 3) 2 Stress corrosion and micro-crack inspection; carrying out X-ray residual stress detection and MgCl on the non-welding position of the space spiral bent pipe in the step 3) 2 Stress corrosion and microcrack inspection.
Preferably, the straight pipe heat transfer pipes in the step 1) at least comprise straight pipe heat transfer pipes with the highest temperature and straight pipe heat transfer pipes with the lowest temperature in the furnace in the rolling annealing or aging treatment. Wherein the highest and lowest temperature points are determined based on furnace temperature uniformity measurements, furnace structure, and heat treatment furnace active area, which is common knowledge of those skilled in the art.
Preferably, each welded pipe in the step 1) is formed by welding not less than 2 straight pipe heat transfer pipes.
Preferably, the inspection items of the non-destructive inspection in step 2) and step 4) include penetration inspection and radiation inspection.
More preferably, the physicochemical inspection in step 2) comprises the steps of:
a. selecting a welded pipe with at least 2 welded joints for a tensile test, wherein the test items comprise room-temperature tensile test and high-temperature tensile test; the room temperature here is 18-28 ℃ and the elevated temperature is based on the values given by the purchasing or design side, generally greater than 50 ℃.
b. Selecting a welded pipe with at least 2 welded joints to carry out an intercrystalline corrosion test;
c. selecting a welded pipe with at least 2 welding joints for hardness inspection, wherein the inspection part comprises a welding seam area, a heat affected zone and a base body area; the hardness test adopts a Vickers hardness test method for measurement;
d. a welded pipe with at least 1 welded joint is selected for metallographic examination, and the examination items comprise a microstructure test (500X on the inner surface and the outer surface), a grain size determination test and a carbide distribution examination test (500X and 1000X on the inner surface and the outer surface and the middle part). Both 500X and 1000X represent multiples.
More preferably, the length of the sample used for the room temperature tensile test in the step a is at least 300mm, the length of the sample used for the high temperature tensile test is at least 800mm, and the length of the sample used for the intergranular corrosion test, the hardness test, the microstructure test, the grain size determination test and the carbide distribution test in the steps b, c and d is at least 20mm.
More preferably, the sample for the intergranular corrosion test in the step b is transversely detected; and d, respectively detecting the longitudinal direction and the transverse direction of the sample for the grain size determination test in the step d, and detecting the longitudinal direction of the sample for the carbide distribution test. For testing, longitudinal and/or transverse sampling is generally specified for grain size, carbide distribution, or inclusions, while axial and/or circumferential sampling is generally specified for residual stress testing.
Preferably, in the spatial spiral elbow bent in the step 3), at least two spatial spiral elbows contain no less than 2 elbow units with the smallest spiral diameter.
More preferably, the welding joint part of the spatial spiral elbow with the minimum spiral diameter elbow unit in the step 4) is subjected to penetration detection, radiation detection, X-ray residual stress detection, mgCl 2 Stress corrosion and micro-crack inspection; performing X-ray residual stress detection and MgCl on the non-welding position of the space spiral bent pipe in the step 4) 2 Stress corrosion and micro-crack inspection.
Further preferably, the X-ray residual stress detection test in step 4) includes two directions, namely an axial direction and an annular direction, the selected sample for X-ray residual stress detection should be a complete bent pipe with an elbow and a transition section, and the free ends of the straight pipe sections at two ends need to be kept at least 200mm in length. The elbow refers to the position with the maximum bending, namely the position with the maximum residual stress; the straight tube is the initial tube without any deformation; the portion between the straight tube and the bent tube is called a transition section, i.e. a portion slightly deformed, and can be understood as a region near a starting bending point or a final bending point.
The minimum spiral diameter is the minimum diameter of the tube bundle determined during the design of the heat exchanger, and the definition of the tube bundle is as follows: a group of pipes with the same diameter and size, which are orderly arranged according to a certain rule, can be understood as a batch or a bundle of pipes with the same specification.
Manufacturing factors and using conditions are fully considered in the sampling process, the overall quality of the heat exchanger welding space elbow can be comprehensively checked through carrying out a room temperature tensile test, a high temperature tensile test, a hardness detection test, a carbide distribution inspection test, a grain size determination test, an intercrystalline corrosion test, a surface residual stress detection test and the like on a welded pipe, the manufacturing capability and the management capability of a manufacturer are verified, whether the quality of a heat transfer pipe meets design and safety requirements or not is judged, the repeatability of the manufacturing quality is ensured, inspection items are effectively reduced, and the inspection cost is reduced to the greatest extent.
Compared with the prior art, the invention has the advantages that: the method for testing the space spiral bent pipe for the heat exchanger carries out nondestructive testing and physicochemical testing on the welded pipe before bending and the space spiral bent pipe after bending, verifies the uniformity of the internal quality of the spiral bent pipe and the representativeness of an acceptance test by using a limited testing part and testing means through a reasonable evaluating, sampling and quality testing method, can completely test the overall quality of the heat transfer pipe, can reduce the testing cost to the greatest extent, is economical and applicable, and is suitable for popularization.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic view of the manufacturing and inspection process of a spatial spiral bend pipe according to a preferred embodiment of the present invention;
FIG. 2 is a schematic illustration of butt welding of straight tube heat transfer tubes after as-rolled annealing and aging treatment of the sampling tubes in accordance with a preferred embodiment of the present invention;
FIG. 3 is a schematic view of a room temperature tensile sampling position of a straight tube heat transfer tube on a butt welded sampling tube according to a preferred embodiment of the present invention;
FIG. 4 is a schematic diagram illustrating a high temperature tensile sampling position of a straight tube heat transfer tube after butt welding on a sampling tube according to a preferred embodiment of the present invention;
FIG. 5 is a schematic diagram illustrating an intergranular corrosion sampling position on a straight tube heat transfer tube after butt welding of the sampling tube according to a preferred embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating a hardness testing sampling position of a straight tube heat transfer tube on a butt welded sampling tube according to a preferred embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating the microstructure, grain size and carbide inspection sampling locations of a straight tube heat transfer tube after butt welding;
FIG. 8 is a schematic view of a spatial spiral bend in accordance with a preferred embodiment of the present invention;
FIG. 9 is a schematic view of a spatial spiral bend in a preferred embodiment of the invention in a sample position with and without weld joints.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not a whole embodiment. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the process flow of the manufacturing process of the spatial spiral elbow in this embodiment at least includes: rolling → rolling annealing → aging → butt welding → nondestructive test (penetration test and ray detection) → physical and chemical inspection → space bending → nondestructive test (penetration test and ray detection) → physical and chemical inspection. The rolling annealing process is used for improving the performance of the heat transfer pipe in the aspects of strength, toughness and the like, and the aging treatment process is mainly used for improving the carbide distribution and the corrosion resistance of the heat transfer pipe.
The method for testing the space spiral bent pipe for the heat exchanger comprises the following steps:
step 1): selecting a plurality of straight tube heat transfer tubes, wherein the length of each straight tube heat transfer tube meets the requirement of bending at least one bent tube unit with the minimum spiral diameter, and after rolling annealing and aging treatment of the straight tube heat transfer tubes, carrying out butt welding on the selected straight tube heat transfer tubes to form a plurality of welded tubes, wherein each welded tube is provided with the same or different number of welded joints.
Wherein the straight tube heat transfer tubes at least include the straight tube heat transfer tube with the highest temperature point in the furnace and the straight tube heat transfer tube with the lowest temperature point in the rolling annealing or aging treatment. Wherein the highest and lowest temperature points are determined based on furnace temperature uniformity measurements, furnace structure, and heat treatment furnace active area, which is common knowledge of those skilled in the art.
Each welded pipe is formed by welding at least 2 straight pipe heat transfer pipes.
The minimum spiral diameter is the minimum diameter of the tube bundle determined during the design of the heat exchanger, and the definition of the tube bundle is as follows: a group of pipes with the same diameter and size arranged according to a certain rule and order can be understood as a batch or a bundle of pipes with the same specification. This is common knowledge to a person skilled in the art.
As shown in fig. 2, which is a schematic diagram of the sampling tube 10 butt-welded after the rolling-state annealing and aging treatment of the straight tube heat transfer tube of the present invention, the sampling tube 10 is obtained by butt-welding two straight tube heat transfer tubes, and the whole welded heat transfer tube is composed of a weld zone, a heat-affected zone, and a base material zone.
Step 2): performing nondestructive testing and physicochemical inspection on all welding joints in the welded pipe obtained in the step 1). The inspection items of the nondestructive inspection include penetration inspection and radiation inspection.
The physical and chemical inspection comprises the following steps:
a. and selecting a welded pipe with at least 2 welded joints for a tensile test, wherein the test items comprise room-temperature tensile and high-temperature tensile. The room temperature here is 18-28 ℃ and the elevated temperature is based on the values given by the purchasing or design side, generally greater than 50 ℃.
As shown in fig. 3, a room temperature tensile sample A1 was taken from a straight tube heat transfer tube on a sample tube 10 after butt welding, and a length of A1 in the axial direction of the sample tube 10 was 300mm and spanned a base material region, a heat affected zone, and a butt weld region.
As shown in fig. 4, a high-temperature tensile sample A2 was taken of a straight tube heat transfer tube on a butt-welded sampling tube 20, where A2 had a length of 800mm in the axial direction of the sampling tube 20 and spanned a base material region, a heat affected zone, and a butt-weld region.
In other embodiments, the length of the specimen used to perform the room temperature tensile test is at least 300mm and the length of the specimen used to perform the high temperature tensile test is at least 800mm.
b. A welded tube having at least 2 welded joints was selected for intergranular corrosion testing.
As shown in fig. 5, an intercrystalline corrosion sample A3 was cut out of a straight tube heat transfer tube on a sample tube 30 after butt welding, and A3 was at least 30mm long in the axial direction of the sample tube 30 and spanned the heat affected zone and the butt weld zone.
c. Selecting a welded pipe with at least 2 welding joints for hardness inspection, wherein the inspection part comprises a welding seam area, a heat affected zone and a base body area; the hardness test adopts a Vickers hardness test method for measurement.
As shown in fig. 6, a hardness test sample A4 was cut out of the straight tube heat transfer tube on the sampling tube 40 after butt welding, and A4 was 70mm in axial length of the sampling tube 40 and spanned over the base material region, the heat affected zone, and the butt weld region.
d. Selecting a welded pipe with at least 1 welding joint for metallographic examination, wherein examination items comprise a microstructure test (500X on the inner surface and the outer surface), a grain size determination test and a carbide distribution examination test (500X and 1000X on the inner surface and the outer surface and the middle part). Wherein 500X and 1000X both represent multiples.
As shown in fig. 7, a microstructure, grain size and carbide test sample A5 was taken from a straight tube heat transfer tube on a sample tube 50 after butt welding, and a length of A5 in the axial direction of the sample tube 50 was 50mm and extended across a base material region, a heat affected zone and a butt weld region.
In other embodiments, the length of the sample used to perform the intergranular corrosion test, the hardness test, the microstructure test, the granulometry test, and the carbide distribution test is at least 20mm. B, transversely detecting the sample for the intergranular corrosion test in the step b; in the step d, the longitudinal direction and the transverse direction of the sample for the grain size measurement test are respectively detected, and the longitudinal direction of the sample for the carbide distribution test is detected. For the examination, longitudinal and/or transverse sampling is generally prescribed for grain size, carbide distribution or inclusions, while axial and/or circumferential sampling is generally prescribed for residual stress examination, which is common knowledge of those skilled in the art.
Step 3): bending the welded pipe prepared in the step 1) to obtain a space spiral bent pipe with the minimum spiral diameter, wherein the space spiral bent pipe is provided with a plurality of bent pipe units and welding joints, and the welding joints are positioned in the bent pipe units. The control weld joint is located at the bend section of the elbow unit and cannot be located at the transition or free section of the spatial spiral elbow. As shown in fig. 8 and 9.
And step 4): performing nondestructive testing, X-ray residual stress testing and MgCl on the welding joint in the space spiral bent pipe in the step 3) 2 Stress corrosion and micro-crack inspection; carrying out X-ray residual stress detection and MgCl on the non-welding position of the space spiral bent pipe in the step 3) 2 Stress corrosion and microcrack inspection. The items of inspection for nondestructive inspection include penetration inspection and radiation inspection.
In the step, penetration detection, ray detection, X-ray residual stress detection and MgCl detection are carried out on the welding joint part of the space spiral elbow with the minimum spiral diameter elbow unit 2 Stress corrosion and micro-crack inspection; detecting the X-ray residual stress and MgCl on the non-welding seam part of the spatial spiral bent pipe in the step 4) 2 Stress corrosion and micro-crack inspection. The X-ray residual stress detection test comprises an axial direction and an annular direction, the selected sample for X-ray residual stress detection is a complete bent pipe with an elbow and a transition section, and the free ends of the straight pipe sections at two ends are required to be kept at least 200mm in length.
Fig. 8 shows a schematic view of a spatial spiral bend. The whole coil comprises a starting bending point, a final bending point, a part with a welding joint, a part without the welding joint, straight tube sections positioned at two ends, a bent tube unit, a transition section between the straight tube sections and the bent tube unit and other characteristic points. Wherein, the elbow refers to the position with the maximum bending, namely the position with the maximum residual stress; the straight tube is an initial tube without any deformation; the portion between the straight and curved tubes is called the transition section, i.e. there is little deformation, which can be understood as the area around the starting or final bending point.
As shown in FIG. 9, the elbow unit without welded joint is tested for surface residual stress, sample A6 selected for X-ray residual stress testing should be a complete elbow with elbow and transition, the same elbow unit with welded joint is tested for surface residual stress, and sample A7 selected for X-ray residual stress testing should be a complete elbow with elbow and transition, i.e., A6 has no welded joint and A7 has a welded joint, but the sampling locations of both are elbow and transition. The starting bending point sample A8 and the final bending point sample A9 are integral bent pipes with elbows and transition sections, and the free ends of the straight pipe sections need to be kept at least 200mm in length.
Manufacturing factors and using conditions are fully considered in the sampling process, the overall quality of the heat exchanger welding space bent pipe can be comprehensively checked through carrying out room temperature tensile test, high temperature tensile test, hardness detection test, carbide distribution inspection test, grain size determination test, intercrystalline corrosion test, surface residual stress detection test and the like on the welded pipe, the manufacturing capability and management capability of a manufacturer are verified, whether the quality of the heat transfer pipe meets design and safety requirements or not is judged, the repeatability of the manufacturing quality is ensured, inspection items are effectively reduced, and the inspection cost is reduced to the maximum extent.
The above embodiments are merely illustrative of the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the content of the present invention and implement the invention, and not to limit the scope of the invention, and all equivalent changes or modifications made according to the spirit of the present invention should be covered by the scope of the present invention.
Claims (15)
1. A method for inspecting a space spiral bent pipe is characterized by comprising the following steps: the method comprises the following steps:
step 1): selecting a plurality of straight tube heat transfer tubes, carrying out rolling annealing and aging treatment on the selected straight tube heat transfer tubes, and then carrying out butt welding to form a plurality of welded tubes, wherein each welded tube has the same or different number of welded joints, and the distance between every two adjacent welded joints can be used for bending at least one bent tube unit with the minimum spiral diameter;
step 2): carrying out nondestructive testing and physicochemical inspection on the welding joint in the welded pipe obtained in the step 1);
step 3): bending the welded pipe prepared in the step 1) to obtain a space spiral bent pipe with the minimum spiral diameter, wherein the space spiral bent pipe is provided with a plurality of bent pipe units and welding joints, and the welding joints are positioned in the bent pipe units;
step 4): performing nondestructive testing, X-ray residual stress testing and MgCl on the welding joint in the space spiral bent pipe in the step 3) 2 Stress corrosion and microcrack inspection; detecting the X-ray residual stress and MgCl on the non-welding seam part of the space spiral bent pipe in the step 3) 2 Stress corrosion and micro-crack inspection;
the whole coil of the spatial spiral elbow comprises a starting bending point, a final bending point, a part with a welding joint, a part without a welding joint, straight pipe sections positioned at two ends, an elbow unit and a transition section between the straight pipe sections and the elbow unit.
2. The method for inspecting a spatial helical bend according to claim 1, wherein: and (3) carrying out surface residual stress detection on the elbow unit without the welding joint, wherein the selected sample for carrying out X-ray residual stress detection has no welding joint and is a complete elbow with an elbow and a transition section.
3. A method of inspecting a spatial helical bend according to claim 2, wherein: the elbow is the position with the maximum bending, namely the position with the maximum residual stress; the straight pipe is an initial pipe which is not deformed at all; the transition section is a part between the straight pipe and the bent pipe.
4. The method for inspecting a spatial helical bend according to claim 1, wherein: and the bent pipe unit with the welding joint is used for detecting the surface residual stress, and the selected sample for detecting the X-ray residual stress is a complete bent pipe with an elbow and a transition section and is provided with the welding joint.
5. The method for inspecting a spatial helical bend according to claim 1, wherein: the starting bending point sample and the final bending point sample are complete bent pipes with elbows and transition sections, and the length of the free end of the straight pipe section needs to be at least 200mm.
6. The method for inspecting a spatial helical bend according to claim 1, wherein: the minimum spiral diameter is the minimum diameter of a tube bundle determined in the design of the heat exchanger, and the tube bundle is a batch of tubes with the same specification.
7. The method for inspecting a spatial helical bend according to claim 1, wherein: each welding pipe in the step 1) is formed by welding at least 2 straight pipe heat transfer pipes; the welded heat transfer tube comprises a weld joint area, a heat affected area and a base body base material area.
8. The method for inspecting a spatial helical bend according to claim 1, wherein: the straight pipe heat transfer pipes in the step 1) at least comprise the straight pipe heat transfer pipe with the highest temperature point in the furnace and the straight pipe heat transfer pipe with the lowest temperature point in rolling annealing or aging treatment.
9. The method according to claim 8, wherein the method comprises the steps of: the highest temperature point and the lowest temperature point are determined based on furnace temperature uniformity measurement, a furnace structure and an effective area of a heat treatment furnace.
10. The method for inspecting a spatial helical bend according to claim 1, wherein: the physicochemical inspection in the step 2) comprises the following steps:
a. selecting a welded pipe with at least 2 welding joints for a tensile test, wherein the test items comprise room-temperature tensile and high-temperature tensile;
b. selecting a welded pipe with at least 2 welding joints to carry out an intercrystalline corrosion test;
c. selecting a welding pipe with at least 2 welding joints for hardness test;
d. selecting a welded pipe with at least 1 welded joint for metallographic examination, wherein examination items comprise a microstructure test, a grain size determination test and a carbide distribution examination test.
11. A method of inspecting a spatial helical bend according to claim 10, wherein: the length of a sample used for carrying out a room temperature tensile test in the step a is at least 300mm, and the sample spans a base material area, a heat affected zone and a butt weld area; the length of a sample for carrying out a high-temperature tensile test is at least 800mm, and the sample stretches across a base material area, a heat affected zone and a butt weld area;
the length of the sample for performing the intergranular corrosion test in the step b is at least 30mm, and the sample spans the heat affected zone and the butt weld zone;
the length of the sample used for the intergranular corrosion test, the hardness test, the microstructure test, the grain size determination test and the carbide distribution test in the steps c and d is at least 50mm, and the sample spans the base material area, the heat affected zone and the butt weld area.
12. A method of inspecting a spatial helical bend according to any one of claims 1 to 11, wherein: in the spatial spiral bent pipes obtained by bending in the step 3), at least two spatial spiral bent pipes comprise at least 2 bent pipe units with the minimum spiral diameter.
13. A method of inspecting a spatial helical bend according to claim 12, wherein: performing penetration detection, ray detection, X-ray residual stress detection, mgCl and MgCl on the welding joint part of the spatial spiral elbow with the minimum spiral diameter elbow unit in the step 4) 2 Stress corrosion and micro-crack inspection; performing X-ray residual stress detection and MgCl on the non-welding position of the space spiral bent pipe in the step 4) 2 Stress corrosion and micro-crack inspection.
14. A method of inspecting a spatial helical bend according to claim 13, wherein: the X-ray residual stress detection test in the step 4) comprises an axial direction and an annular direction, the selected sample for X-ray residual stress detection is a complete elbow with an elbow and a transition section, and the free ends of the straight pipe sections at two ends are required to be kept at least 200mm in length.
15. The method for inspecting a spatial helical bend according to claim 1, wherein: the material of the space spiral bent pipe is austenite high nickel chromium iron alloy.
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