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Electric Power Industry Standard of the People's Republic of China
Technical Specification for Construction and Acceptance of Electric Power
Welding of Thermal Power Plants
DL5007--92
Editor: Technical Committee for Welding Standardization of Power Plants of the Ministry of Energy Approved by: Ministry of Energy of the People's Republic of China Ministry of Energy of the People's Republic of China
Notice on Issuing the Electric Power Industry Standard "Technical Specification for Construction and Acceptance of Electric Power (Welding of Thermal Power Plants)"
Energy Base [1991] 1015 No.
To all power management bureaus, power bureaus of provinces, municipalities directly under the Central Government, and autonomous regions, Electric Power Planning Institute, Huaneng International Power Development Company, Electric Power Construction Institute, and Hydropower Press:
In order to adapt to the development of welding technology in the power industry and ensure the installation quality of thermal power plants, our department has revised the Technical Specification for Construction and Acceptance of Power Construction (Welding of Thermal Power Plants) SDJ51-82 issued in 1982, and its number is DL5007-92. It will be implemented from September 1, 1992, and the original specification will be abolished at the same time. If any units have any problems in implementation, please inform the Infrastructure Department of our department and the main editing unit.
December 31, 1991
1 General Provisions
1.0.1 This specification applies to the welding work of boilers, pressure pipes, pressure vessels and steel structures for the design, manufacture, installation and maintenance of thermal power generation equipment of 600MW and below in the power system of the energy industry. 1.0.2 This specification is applicable to manual arc welding, manual tungsten inert gas welding, oxy-acetylene welding and submerged arc automatic welding of carbon steel (carbon content ≤ 0.35%), low alloy steel and heat-resistant steel. For other materials and welding methods, technical requirements can be formulated with reference to this specification and relevant standards.
1.0.3 The construction and acceptance of imported thermal power generating units shall be carried out in accordance with the provisions of this specification, except for the parts with specific provisions in the construction contract.
1.0.4 The weld quality inspection shall be evaluated according to the working conditions of the components and the classification of quality requirements.
1.0.5 The inspection of metal materials, inspection of equipment welding doors, ball test, welding process evaluation, welding joint quality inspection, welding personnel assessment and other items shall be carried out in accordance with the provisions of relevant regulations. 1.0.6 Welding work (welding, heat treatment and metal inspection) must comply with the relevant provisions of safety, environmental protection, fire prevention and other regulations. 2 Welding personnel
2.0.1 Welding personnel include welding technicians, welding quality inspection personnel, welding inspectors, welders and welding heat treatment personnel. 2.0.2 Each enterprise shall set up welding professional and technical persons in charge and full-time welding quality inspection personnel
2.0.2.1 The welding professional and technical person in charge shall be an engineer (or technician) with a certain professional and technical level and rich practical experience and a welding technician of a certain position, who shall be fully responsible for the engineering welding technology and quality management and the qualification review of welding personnel.
2.0.2.2 Enterprises and their competent departments shall regularly organize professional and technical training for welding personnel to continuously improve their technical level, professional theoretical level and management level.
2.0.3 Basic requirements and work content for welding personnel. 2.0.3.1 Welding technicians
(1) Technicians who are engaged in welding professional and technical management for the first time shall undergo more than one year of production practice and systematic training, and obtain the corresponding qualifications after assessment. (2) Master the project overview, conscientiously implement this specification, prepare welding construction organization design and technical measures in combination with actual conditions, formulate coal I training plans, participate in the inspection of welder technical assessment committee and welder technical assessment work and welding material management. 1424
(3) Provide technical disclosure to relevant personnel based on technical measures, and provide in-depth technical guidance and supervision. (4) Organize welding process assessment and prepare welding operation instructions.
(5) Participate in the quality acceptance of important pipelines and components. (6) Record, check and organize welding data and the handover and technical summary of project completion technical documents. 2.0.3.2 Welding quality inspectors
(1) Personnel engaged in welding quality inspection should have a junior high school education or above, have certain practical experience and technical level, and have obtained a qualification certificate after professional assessment. (2) Welding quality inspectors are responsible for the preparation of welding quality acceptance items, the issuance of inspection documents, and the inspection, supervision and acceptance assessment of welding projects. (3) Participate in the review of technical measures, often conduct in-depth supervision of the implementation of technical measures, and promptly stop and report to relevant departments any illegal operations. (4) Pay attention to the accumulation and summary of quality supervision data, and cooperate with relevant personnel to do a good job in the handover of project completion data. (5) Determine the welds to be inspected, record them carefully, and urge relevant departments to do a good job in quality inspection. (6) Check the welder's qualification certificate, understand his technical status, and have the right to stop the welding work of those who often fail to meet the welding quality standards, and recommend that the welder technical assessment committee revoke their qualification certificates. 2.0.3.3 Welding inspectors (1) Inspectors can only perform corresponding welding inspection work after receiving professional technical training and passing the assessment and obtaining the corresponding professional qualification certificate.
(2) Nondestructive testing of weld quality shall be carried out in accordance with this specification and relevant regulations. The evaluation of the test results must be performed by personnel of level II or above.
(3) Inspection shall be carried out according to the inspected parts determined by the welding quality inspector, and the inspection shall be timely, the conclusion shall be accurate, and the feedback shall be timely.
(4) Welding inspectors shall carefully fill out, sort out and keep all inspection records.
(5) Nondestructive testing shall be refused for welds with unqualified appearance.
2.0.3.4 Welders
(1) They must be trained in basic welding knowledge and practical operation skills, and be assessed in accordance with SD263-88 "Technical Assessment Procedures for Welders" to obtain welder qualification certificates.
(2) All welders who are responsible for welding the following components must pass the technical assessment of the corresponding items.
a. Pressure-bearing steel structure: boiler steel frame (main column, main beam), lifting equipment structure, main factory building frame. b. Boiler heating surface pipes.
C, T. Pressure vessels and pipelines with pressure greater than 0.1MPa. d. Containers for storing flammable and explosive media (gas, liquid) and their delivery pipelines.
Welding of non-pressure-bearing parts on monitored pressure-bearing parts. e.
f. Welding of high-speed rotating parts.
(3) Have good work style, strictly follow the given welding process and welding technical measures to weld, strictly abide by this specification and the welding process details formulated by the enterprise, and conscientiously implement quality self-inspection.
(4) Welding T. Be familiar with the operation instructions before welding. If there is any discrepancy with the requirements of the operation instructions, the welder should refuse to weld. When major quality problems occur, report to the relevant personnel and do not handle them on your own.
(5) If a qualified welder has stopped welding monitored parts for more than six months, he must be re-evaluated when he resumes welding monitored parts.
(6) A qualified welder shall not perform welding work beyond his qualification items.
2.0.3.5 Welding heat treatment personnel
(1) Welding heat treatment personnel must undergo professional training and obtain qualification certificates.
(2) They must comply with the provisions of this specification and welding technical measures and welding operation instructions on heat treatment, and ensure correct operation and accurate records.
(3) After heat treatment, self-inspection must be carried out, and heat treatment data must be accumulated and sorted out.
3 Steel and welding materials
3.0.1 Before welding, the steel grade of the material to be welded must be found out in order to correctly select the corresponding welding materials and determine the appropriate welding process and heat treatment process
3.0.2 Steel must comply with national standards (or ministerial standards, professional technical conditions), and imported steel must comply with the national standards of the country or the technical conditions specified in the contract
The chemical composition, mechanical properties and reference data of steel commonly used in power plants are shown in Appendix A.
3.0.3 The quality of welding materials [welding rods, welding wires, tungsten rods, argon, oxygen, acetylene gas (electricity) and welding flux] should comply with national standards (or relevant standards).
The chemical composition and mechanical properties of welding rods and welding wires commonly used in power plants are shown in Appendix B and Appendix C.
3.0.4 Steel, welding rods, welding wires, etc. should all have quality certificates from the manufacturer. If there is no quality certificate or there is doubt about its quality, it should be sampled and tested according to the batch number, and only qualified ones can be used. 3.0.5 The selection of welding rods and welding wires shall be based on the chemical composition, mechanical properties and crack resistance of the base metal, carbon diffusion, preheating before welding, heat treatment after welding and use conditions. 3.0.5.1 When welding the same type of steel, the selection of welding rods (welding wires) shall generally meet the following requirements:
(1) The properties and chemical composition of the weld metal are equivalent to those of the base metal. (2) The process performance is good.
3.0.5.2 When welding dissimilar steels, the selection of welding rods (welding wires) should generally meet the following requirements:
(1) When both sides of the steel are not austenitic stainless steel, welding rods (welding wires) with a composition between the two or matching the side with a lower alloy content can be selected.
(2) When one of the two sides is austenitic stainless steel, stainless steel welding rods (welding wires) with a higher nickel content can be selected. The recommended values ​​of welding rods (welding wires) and post-weld heat treatment temperatures for welding dissimilar steels are shown in Appendix E.
3.0.6 The electrode used for tungsten inert gas fluorine arc welding should be a tungsten rod, and the purity of the argon gas used should not be less than 99.95%.
3.0.7 The purity of oxygen used for oxy-acetylene welding should be above 98.5%. The purity of acetylene gas should comply with the provisions of GB6819--86 "Dissolved Acetylene". If acetylene gas is prepared with calcium carbide, the calcium carbide shall have a factory certificate. Its quality can be determined by checking the sulfur and phosphorus content in the weld metal (according to the standard of the metal being welded); acetylene gas used for welding shall be filtered. Calcium carbide that has not been checked or whose impurity content exceeds the standard shall not be used for welding the monitored parts. 3.0.8
8 The flux used for submerged arc automatic welding shall comply with the requirements of relevant standards. A brief list of commonly used submerged arc welding fluxes is shown in Appendix D. 4 Preparation before welding
4.0.1 The location of the weld should avoid stress concentration areas and be convenient for welding and heat treatment. Generally, it should meet the following requirements: 4.0.1.1 The center line of the boiler heating surface pipe weld should be at least 70mm away from the pipe bending starting point or the outer wall of the drum, header and the edge of the support and hanger. The distance between two butt welds shall not be less than 150mm
4.0.1.2 The center line of the pipeline butt weld should be at least 100mm away from the pipe bending starting point (except for welded, forged and cast pipe fittings) and at least 50mm away from the edge of the support and hanger. The distance between two butt welds shall not be less than the pipe diameter and shall not be less than 150mm.
4.0.1.3 Pipe joints and instrument sockets shall generally not be set in welds or heat-affected zones.
4.0.1.4 For the butt weld of the cylinder, the distance between the center line and the starting point of the head bend shall not be less than the wall thickness plus 15mm, and shall not be less than 25mm and not more than 50mmlo
4.0.1.5 For the cylinder and the head with longitudinal welds, the distance between two adjacent longitudinal welds shall be greater than 3 times the wall thickness and not less than 100mms
4.0.1.6 The pipe holes of welded pipes shall be avoided as far as possible on the welds, and the overlap of the heat affected zone of the pipe hole welds and the adjacent welds shall be avoided. If it is necessary to open holes on or near the welds, the following conditions shall be met: (1) The welds on both sides of the pipe holes that are larger than the hole diameter and not less than 60mm shall be qualified by non-destructive testing in accordance with the requirements of Table 8.0.3. (2) The hole edge shall not be on the weld defect.
(3) The pipe joints shall be subjected to post-weld heat treatment to eliminate stress. 4.0.1.7 The lap size of the lap weld should be no less than 5 times the thickness of the parent material and no less than 30mm
4.0,2 The groove form of the arm, arm channel, pressure vessel and steel structure should be in accordance with the design drawings. If there is no regulation, the type and size of the groove should be selected according to the principles of ensuring welding quality, less filling metal, improving labor conditions, facilitating operation, reducing welding stress and deformation, and meeting the requirements of flaw detection.
The basic forms and sizes of welded joints are shown in Table 4.0.2. 4.0.3 Cutting of weldments and groove processing shall be carried out in accordance with the following requirements: 4.0.3.1 It is advisable to use mechanical methods for cutting weldments. For alloy steels with a greater tendency to harden, pipes with a nominal diameter of <100mm and steam and water pipes with a nominal diameter of >100mm and a working pressure of >3.9MPa, mechanical methods should be used. 4.0.3.2 If hot working methods (such as gas cutting) are used for cutting, a processing allowance should be left at the cut part to remove the hardened layer and overheated metal. For alloy steel with a high hardening tendency, the cut part should be annealed before processing. 4.0.3.3 The preparation of the groove should be carried out by mechanical processing. If flame cutting is used to cut the groove, the oxides, slag and splashes on the surface of the cut should be cleaned according to the requirements of Article 4.0.5, and the uneven parts should be repaired and leveled.
4.0.4 After cutting and groove processing, the weldment shall be inspected according to the following requirements and can only be assembled after passing the inspection.
(1) If flame cutting is used to cut the groove of steel with high hardenability, the surface flaw detection inspection shall be passed after processing. (2) There shall be no defects such as cracks, heavy skin, groove damage and burrs in the base material at the groove.
(3) The processing size of the groove shall meet the requirements of the drawing. (4) There are no defects such as cracks and interlayers within the cleaning range specified in Article 4.0.5.
4.0.5 Before assembly, the weld surface and the inner and outer walls of the nearby parent material should be cleaned of oil, paint, dirt, rust, etc. until the metallic luster is emitted. The cleaning range is as follows: (1) Manual arc welding butt weld: 10~j5mm on each side
(2) Submerged arc welding weld: 20mm on each side. (3) Fillet joint weld: weld leg K value +10mm. 4.0.6 The end face of the butt pipe joint should be perpendicular to the center line of the pipe. Its deflection Af shall not exceed the provisions of Table 4.0.6. Basic forms and sizes of welding joints
Joint structure dimensions
Sequence joint
Groove form
No. type
Thickness of weldment
Arc welding
Submerged arc welding>1620
Arc welding
30°～35
10°~15°
Scope of application
(mm)(mm)|(mm)
1～3/1～2
Containers and
General steel structures
All kinds of bearing
Pressure pipe pressure
|tt||pressure vessels and
medium and thin bearing
heavy-duty structures
medium and thick
wall steam and water pipes
sequence joint
number type
groove form,
double V-shaped flat
5" pairs
double V-shaped straight
comprehensive
weldment thickness
arc welding>16～60
[arc welding||≥16~60
arc welding
arc welding
buried arc welding
8°~12°
35° -- 40°15°~- 20′
20°~25°
20°~25°
30°～35°
Arc welding pipe diameter is not limited
Arc welding
5°10°
Same thick-walled pipe groove processing requirements
Same thick-walled pipe groove processing requirements
Scope of application
Thick-walled steam
Water pipeline
Thick-walled steam
Water pipeline|| tt||steam pipe
welded
large container
and junction
pipeline or
junction seal
pipeline or
junction plug
sequence joint
groove form
number|type
slope washing door
single V type
thickness of weldment!
arc welding
arc welding
$76 133
Arc welding
Submerged arc welding
Arc welding
Submerged arc welding
Arc welding
Submerged arc welding
Arc welding
Arc welding
Submerged arc welding
Note: ① The weld structure dimensions of tungsten inert gas hydrogen arc welding and arc welding are the same. ② For heating surface pipes with a wall thickness of ≤6mm, argon arc welding can also be used for base and cover. Joint
Applicable scope
(mm)(mm)(mm)
Water, instrument
According to the wall thickness
Sampling table
50°~60°30°~35 2 ~ 3
50~60°30~352~31~2
10~2
50°-60°
50°~60°
50°~~ 60°
③ Pipes with a wall thickness greater than 6mm can be primed with argon arc welding and covered with electric welding. ④ For the head, the value shall be in accordance with the design requirements: the value may be in accordance with the design requirements and shall not be less than 20mm. ③ The overlap size L=58 and shall not be less than 30mm. 1428
1~21~2
1 ～2 12
etc. pipe
steam pipe
duct
or
tube socket
pipe|
container
pipe|||seat
structure
for
structure
for
for
large
and
structure
4.0.7 When aligning weldments, the inner walls should generally be flush. If there is misalignment, the misalignment value should meet the following requirements:
Skewing requirements between the pipe end face and the pipe center
Pipe outer diameter
>60~159
>159-219
4.0.7.1 The local misalignment value of single-sided butt welding should not exceed 10% of the wall thickness and should not be greater than 1mm
4.0.7.2 The local misalignment value of double-sided butt welding should not exceed 10% of the weldment thickness and should not be greater than 3mm.
4.0.8 When weldments of different thicknesses are matched [1, the thickness difference can be handled in the following ways:
(1) When the inner wall dimensions are unequal but the outer wall dimensions are flush, they can be processed into the form of Figure 4.0.8 (u)
(2) When the outer wall dimensions are unequal but the inner wall dimensions are flush, they can be processed into the form of Figure 4.0.8 (b)
(3) When both the inner and outer wall dimensions are unequal, they can be processed into the form of Figure 4.0.8 ().
(4) When the inner dimensions are unequal and the thickness difference is ≤5mm, they can be processed into the form of Figure 4.0.8 (d) without affecting the strength of the weldment.
Figure 4.0.8 Handling methods for weldments of different thicknesses (a) The inner wall dimensions are unequal; (b) The outer wall dimensions are unequal; (c) The inner and outer wall dimensions are unequal Etc.: (d) 82-8≤5mm4.0.9 When the local gap of the weld is too large, it should be trimmed to the specified size. It is strictly forbidden to add fillers in the gap. 4.0.10 Welding rods, welding wires and fluxes should be stored in a dry, well-ventilated warehouse with a temperature greater than 5°C and a monthly relative air humidity less than 60%.
Before use, welding rods and fluxes should be baked according to the requirements of their instructions, and repeated baking should not exceed twice. Before use, rust and oil stains should be removed from the welding wire until the metallic luster is exposed. When welding rods for welding important components, they should be placed in a special insulation box with a temperature maintained at 100-150°C and taken out as needed. When welding rods that have been stored for more than one year are used for welding important components, if there is any doubt about their quality, they should be re-identified and allowed to be used only after they meet the requirements.
4. 0.11 During welding and assembly, the workpiece to be welded should be firmly padded to prevent deformation and additional stress during welding and heat treatment. 4.0.12 Except for the cold-drawn joints specified in the design, it is prohibited to use force to align the other welds, and it is not allowed to use the thermal expansion method to align the joints to prevent additional stress.
4.0.13 Wind, rain, snow and cold protection measures should be taken at the welding site.
4.0.14 The welding construction process includes four important processes: aligning assembly, welding, heat treatment and inspection. The next process can only be carried out after the current process meets the requirements, otherwise the next process is prohibited. 4.0.15 Before welding the boiler heating surface pipes, qualified welders should conduct simulation exercises that are adapted to the actual conditions, and formal welding can only be carried out after the fracture surface inspection meets the requirements. 5 Welding process
5.0.1 The minimum allowable ambient temperature during welding is as follows: Carbon steel: -200.
Low alloy steel, ordinary low alloy steel: -10℃. Medium and high alloy steel: 0℃.
5.0.2 The preheating and temperature distribution of various steel materials before welding are as shown in Table 5.0.2, and the following provisions are made:
5.0.2.1 Preheating requirements are proposed based on the welding process assessment. 5.0.2.2 When alloy steel pipes, pipe fittings (such as elbows, tees, etc.) with a wall thickness of ≥6mm and thick plates are welded at negative temperatures, the preheating temperature can be increased by 20 to 50℃ according to the specified value in Table 5.0.2. 5.0.2.3 Low alloy steel pipes with a wall thickness of <6mm and carbon steel pipes with a wall thickness of >15mm should also be properly preheated when welded at negative temperatures.
5.0.2.4 When welding dissimilar steels, the preheating temperature shall be selected according to the side with poorer welding performance or higher gold content. 5.0.2.5 When welding the pipe socket to the main pipe, the preheating temperature specified in 1429
of the main pipe shall prevail.
5.0.2.6 When welding non-pressure-bearing parts to pressure-bearing parts, the preheating temperature shall be selected according to the pressure-bearing parts.
5.0.3 The preheating width starts from the center of the joint, and each side shall not be less than three times the thickness of the weldment. The heating rate during preheating of welded joints with a thickness greater than 35mm shall comply with the provisions of Section 6.0.5. 5.0.4 During welding, the interlayer temperature shall not be lower than the lower limit of the specified preheating temperature and shall not be higher than 400℃. 5.0.5 When welding pressure-bearing pipelines, in order to ensure the cleanliness of the inner wall of the pipeline (or pipe) and the quality of the root layer of the weld, the welding method used shall comply with the provisions of Table 5.0.5.
5.0.6 For medium and high alloy steel (chromium content ≥3% or total alloy content >5%) pipes and pipeline welds, in order to prevent root layer oxidation or overburning, the inner wall should be inflated with gas or mixed gas for protection during welding. Preheating temperature before welding
(steel grade)
Preheating temperature thickness
(mm）
Carbon steel with carbon content
0.35%
and its castings
C-Mn(16Mn)
Mn-V(15MnV)
(12CrMo)
1Cr--Mo
(15CrMe
ZG20CrMo)
(14MnMoV、
18MnMoNbg)
1CrMoV
(12CriMoV
ZG20CrMo)
1-Cr-1Mo-V
(15Cr,Mo V.www.bzxz.net
ZG1SCr;Mo, V)
(12Cr2MowV)
2—Cr-1Mo-
(12CrzMo)
3Cr-IMoVTi
(12Cr:MoVSi TiB)
Preheating temperature
[100 ~200 ≥34
[150 ~200
150-250
200~30g
250~350
100150
150~200
Steel Type (Steel No.)
9Cr-1Mo
12Cr-1Mo-V
Thick Preheating Temperature Thick
[300 400
Preheating Temperature
Note: 1. When tungsten plate argon arc welding is used for base coating, the lower limit temperature can be reduced by 50r
2. When the outer diameter of the pipe is greater than 219mm or the wall thickness is greater than 20mm (including 20mm), electric heating should be used for preheating. Provisions on welding methods for pressure pipelines
Component name
Heating surface pipes of boilers with p≥10MPa.≤6mm
Pipes and fittings with p≥10MPa, 8>6mm
p=4MPa, t=450t pipelines
Reheat steam cold and hot section pipelines comply with their
Cooling and lubrication system pipelines and fuel pipelines of steam turbines and generators
Obstructed hot surface pipes of medium and low pressure boilers with p<10MPa, ≤6mm
Other pipelines\)
Note: 1) is a non-mandatory requirement.
Root weld
Other welds
TIG/SMAW
TIG/SMAW
TIG/SMAW
5.0.7 It is strictly forbidden to ignite arc, test current or weld temporary supports on the surface of the workpiece to be welded. The surface of high-alloy steel materials shall not be welded with matching fixtures.
5.0.8 When welding pipes, there shall be no draft inside the pipes. 5.0.9 When spot welding, in addition to the welding materials, welding process, welder and preheating temperature being the same as those in formal welding, the following requirements shall also be met:
5.0.9.1 When spot welding the matching root, the quality of each weld shall be checked after spot welding. If there are defects, they shall be removed immediately and spot welded again.
5.0.9.2 If thick-walled large-diameter pipes are spot-fixed by the method of filling, the parent material should not be damaged when the temporary spot fixation is removed, and the residual weld scars should be cleaned and polished.
5.0.10 After the root layer weld of the tungsten inert gas fluorine arc welding is inspected, the secondary layer weld should be welded in time to prevent cracks. When welding multi-layer and multi-pass welds, they should be inspected layer by layer. Only after passing the self-inspection can the secondary layer be welded until completion. 5.0.11 The welding of thick-walled large-diameter pipes should be carried out by multi-layer and multi-pass welding. When the wall thickness is greater than 35mm, it should also comply with the following regulations: 5.0.11.1
The thickness of the arc welding base weld layer shall not be less than
5.0.11.2 The single layer thickness of other welds shall not be greater than the diameter of the welding rod used plus 2mm.
5.0.11.3 The swing width of a single weld pass shall not exceed 5 times the diameter of the electrode used. The requirements for multi-pass arrangement of thick-walled large-diameter pipes are shown in Figure 5.0.11. ≥5g
Figure 5.0.11 Schematic diagram of weld pass arrangement for thick-walled pipes 2 In order to reduce welding deformation and joint defects, butt welding of pipes with a diameter greater than 5.0.12
194mm and boiler dense pipes (tube spacing ≤30mm) should be carried out by two people symmetrically. 5.0.13 The welding of steel structures shall be carried out in accordance with the provisions of the operation instructions. 5.0.14 During welding, special attention shall be paid to the quality of joints and arc closure. When closure, the molten pool shall be filled and the joints of multi-layer multi-pass welding shall be staggered.
5.0.15 The welding process shall be completed continuously except for the requirements of welding in batches in terms of process and inspection. If forced to be interrupted, measures to prevent cracks (such as post-heating, slow cooling, insulation, etc.) shall be taken. When re-welding, a careful inspection should be carried out to confirm that there are no cracks before welding can be continued according to the process requirements.
5.0.16 For butt welds of pipes or containers with a nominal diameter greater than or equal to 1000mm, double-sided welding should be adopted, and root cleaning measures should be taken to ensure the quality of the bottom welding. After root cleaning, the oxides should be cleaned according to the requirements of Article 4.0.5. 5.0.17 For hidden welds that need to be inspected, other processes can only be carried out after passing the inspection.
5.0.18 The weld should be cleaned after welding, and the welder's code stamp or permanent mark should be stamped near the weld after passing the self-inspection.
5.0.19 For steels that are prone to delayed cracking, heat treatment should be carried out immediately after welding, otherwise post-heat treatment should be carried out. The temperature should be 300-350℃, and the constant temperature time should not be less than 2h. The heating range of post-heat treatment is the same as the heat treatment requirements. 5.0.20 When the welded joint has defects exceeding the standard, it can be repaired by digging and patching.
However, the number of digging and patching at the same position shall not exceed three times in general, and medium and high alloy steels shall not exceed two times, and the following regulations shall be observed: 5.0.20.1 Thoroughly remove defects.
5.0.20.2 When repairing welding, specific repair welding measures shall be formulated and carried out in accordance with process requirements.
5.0.20.3 Welded joints that require heat treatment shall be reheated after repair.
5.0.21 The loading tool used to install the cold-drawn pipe mouth shall not be unloaded until the entire butt welding and heat treatment are completed. 5.0.22 The welded joint shall not be heated for correction. 6 Post-weld heat treatment
6.0.1 Heat treatment is to reduce the residual stress of the welded joint and improve the structure and properties of the weld metal. The heat treatment process shall be carried out strictly in accordance with this specification and relevant regulations.
6.0.2 The following welded joints shall be heat treated after welding: 6.0.2.1 Carbon steel pipes and fittings with wall thickness > 30mm. 6.0.2.2 Carbon steel containers with wall thickness > 32mm. 6.0.2.3 Ordinary low alloy steel containers with wall thickness > 28mm. 6.0.2.4 Heat resistant steel pipes and fittings (except for those specified in Article 6.0.3).
6.0.2.5 Welds that require heat treatment after welding procedure assessment. 6.0.3 The following parts that are preheated before welding and properly cooled after welding using arc welding or low-fluorine type electrodes may be exempted from post-weld heat treatment. 6.0.3.1 15CrMo and 12Cr2Mo steel pipes with wall thickness less than or equal to 10mm and pipe diameter less than or equal to 108mm. 6.0.3.2 12CriMoV steel pipes with a wall thickness of less than or equal to 8mm and a diameter of less than or equal to 108mm.
6.0.3.3 12CriMoWVB steel pipes with a wall thickness of less than or equal to 6mm and a diameter of less than or equal to 63mm. 6.0.4 Post-weld heat treatment is generally high-temperature tempering. The post-weld heat treatment temperature and constant temperature time of commonly used steels are shown in Table 6.0.4.
6.0.5 During the heat treatment process, the heating and cooling rates are specified as follows: 6.0.5.1 The heating and cooling rates can generally be calculated as 250×25
C/h, and not more than 300 /h.
6.0.5.2 During the cooling process, the temperature below 300℃ can be uncontrolled.
6.0.6 The post-weld heat treatment of dissimilar steel welded joints shall be considered comprehensively according to the steel materials on both sides and the welding rods (wires) used. The heat treatment temperature shall generally not exceed the lower critical point Acl of the steel material with low alloy steel composition, see Appendix E.
6.0.7 The heating width of the heat treatment, measured from the center of the weld, shall not be less than 3 times the wall thickness of the pipe on each side, and shall not be less than 60mm. 1431
C≤0.35(20, ZG25)
C-Mn(16Mn)
(Steel No.）
1 /2('r-1 2Mo( 12(rMo)
Post-weld heat treatment temperature and constant temperature time
600650
>12.5 ~25>25~37.5>37.5~5d >50 ~75>75 ~100>100~12512.
650~700
1Cr--Mo( 15(rMo.ZG20CrMo)
670700
(12Cr MoV,ZG20CrMoV)
1 Cr-1Mo-V(ZG15Cr,Mo, V)
2Cr-1Mo
2Cr-Mo-VW(12Cr,MoWVB)
3Cr-IMo- Vi(12Cr:MoVSiTiB)
9Cr-1Mo
12Cr-1Mo
720~750
720~750
750-·780
6.0.8 The insulation width during heat treatment, measured from the center of the weld, shall not be less than 5 times the wall thickness of the pipe on each side to reduce the temperature gradient. 6.0.9 The heating method for heat treatment should strive to ensure uniform temperature on both sides of the inner and outer walls and the weld. When the temperature is constant, the temperature can be kept within the heating range at any time. The temperature difference between the two measuring points should be less than 50℃. When the thickness is greater than 10mm, induction heating or resistance heating should be used.
6.0.10 The temperature measurement of heat treatment must be accurate and reliable, and automatic temperature recording should be used. The instruments, thermocouples and their accessories used should be calibrated or verified according to the measurement requirements. 6.0.11 When performing heat treatment, the temperature measurement points should be symmetrically arranged on both sides of the center of the weld, and there should be no less than two points. The measuring points of horizontal pipes should be arranged symmetrically up and down.
6.0.12 After heat treatment of the welded joint, Record and mark, and stamp the heat treatment worker's code steel stamp or permanent mark. 7 Quality Inspection
7.0.1 Attention should be paid to the inspection and testing of welding quality, and a welding quality inspection and acceptance system should be implemented. The method of combining self-inspection with professional inspection should be implemented to do a good job in inspection and evaluation. Welding quality inspection includes three stages of quality inspection before welding, during welding and after welding. It should be carried out strictly according to the inspection items and procedures.
7.0.2 Methods and specifications for classification inspection of welding joints The scope and quantity shall be in accordance with Table 7.0.2 and shall comply with the following provisions: 7.0.2.1 For welds that fail the appearance inspection, other inspection items are not allowed.
7.0.2.2 For welded joints that require heat treatment, non-destructive testing shall be carried out after heat treatment.
7.0.2.3 Radiographic or ultrasonic testing of welded joints shall be selected in accordance with the following provisions:
(1) When ultrasonic testing is used for steam and water pipes with a thickness of ≤20mm, radiographic testing of not less than 20% of the testing amount shall be carried out.
(2) For pipes and weldments with a thickness of >20mm and less than 70mm, either radiographic testing or ultrasonic testing may be selected. (3) For pipes with a thickness of ≥70mm, 100% radiographic testing shall be carried out when the pipe is welded to about 20mm, and 100% ultrasonic testing shall be carried out after welding.
(4) For boiler heating surface tubes with welded joints of type 2, in addition to radiographic inspection of not less than 25%, ultrasonic inspection of 25% shall also be performed.
After welding, the welds of alloy steel parts shall be subjected to spectral analysis and re-inspection, as specified below:
Item scope and quantity of classification inspection of welded joints
Type of welded joints
Heating surface pipes of boilers with working pressure greater than or equal to 9.81MPa
Pipes and pipes within the boiler body with working pressure greater than 9.81MPa with outer diameter greater than 159mm or wall thickness greater than 20mm
Steam pipes with outer diameter greater than 159mm and working temperature greater than 450
Steam, water, oil, pipes with working pressure greater than 8MPa
Steam and water pipes and pipe fittings with working temperature greater than 300℃ and not greater than 450℃
Working pressure is 0.1~1.6MPa pressure vesselHeating surface pipes of boilers with working pressure less than 9.81MPa
Steam pipes and pipe fittings with working temperature higher than 150℃ and not higher than 300℃
Steam, water, oil and gas pipelines with working pressure of 4～8MPa
Steam, water, oil and gas pipelines with working pressure greater than 1.6MPa and less than 4MPa
Steel structures bearing static loads
Working pressure of 0.1～1.6MPa Steam, water, oil, gas pipelines
Smoke, wind, coal, powder, ash and other pipelines and accessories Non-pressure-bearing structures and sealing structures
General supporting structures (equipment support, ladders, platforms, pull rods, etc.)
Drainage, drainage, sewage, sampling pipes within the water pressure range of boilers with an outer diameter less than 76mm
Inspection party
Self-inspection" Special inspection
Ultrasonic hardness1)
Cutting sample2)/substitute sample
Note: 1) Welded joints that have been evaluated by welding process and have heat treatment automatic recording curves that are consistent with the provisions of the operation instructions can be exempted from hardness measurement. 2) Welded joints of boiler heating surface pipes that have been evaluated by welding process and welded according to the operation instructions can be exempted from cutting sample inspection. 3) The non-destructive testing method and proportion of steel structures shall be carried out according to design requirements. 4) Smoke, wind, coal, powder, and ash pipelines should be 100% inspected for oil seepage. (1) No less than 10% for boiler heating surface tubes. (2) 100% for other tubes and pipes.
(3) Spectral analysis review should be conducted according to the daily workload of each welder.
7.0.3 When cutting or replacing samples for boiler heating surface tubes, the number of samples is shown in Table 7.0.3. The cutting position and processing specifications of the samples are shown in Appendix F.
7.0.4 If there are unqualified items in the inspection results of cutting or replacing samples, double re-inspection of the number of unqualified samples for that item should be conducted. 7.0.5 If the results of non-destructive testing are unqualified, in addition to repairing the unqualified welds, double inspection of the number of unqualified joints from the same batch of welded joints of the welder on the same day should be conducted. If there are still unqualified items in the double inspection, the batch of joints will be evaluated as unqualified. Items and test quantity of cutting sample (or substitute sample) for inspection of welding joint of heating surface pipe of boiler
Force cold bending (piece)
(piece)
Surface bending
Root bending
Metallographic (piece)
[Section (piece)
1(Medium and high alloy steel)
7.0.6 For unqualified welding joints, the reasons shall be found out and 1433
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