SY/T 0452-2002 Welding procedure qualification for metal pipelines for petroleum and natural gas
Some standard content:
1 General Principles
Petroleum and Natural Gas Industry Standard of the People's Republic of China Welding Procedure Qualification for Metal Pipelines for Petroleum and Natural Gas Approval Department: National Economic and Trade Commission Approval Date: 2002-05-28
Implementation Date: 2002-08-01
SY/T0452-—2002
Agency Police SY4052-1992
1.0.1 This standard is formulated to unify the methods and contents of welding procedure qualification for metal pipelines in the construction of petroleum and natural gas projects, to formulate correct welding procedures and to ensure the welding quality of the projects. 1.0.2 This standard specifies the rules, test methods and qualified indicators for welding procedure qualification for metal pipelines in the construction of petroleum and natural gas projects. 1.0.3 This standard applies to the welding procedure qualification of various metal pipelines in onshore petroleum and natural gas projects (excluding oil refining projects) by gas welding, arc welding, gas tungsten arc welding, gas metal arc welding, automatic and semi-automatic welding of self-shielded tubular flux-cored wire, automatic submerged arc welding and their combination.
1.0.4 The welding procedure qualification of coal slurry transportation pipelines and on-site equipment can refer to this standard and implement 1.0.5 for welding procedure qualification. In addition to implementing this standard, it should also comply with the provisions of design drawings and technical documents and relevant national standards in force.
2 Basic provisions
2.0.1 The welding procedure qualification should be based on reliable material welding performance and should be carried out before engineering welding. 2.0.2 The general process of welding procedure qualification is: drafting welding procedure instructions, welding test pieces and preparing samples, inspecting test pieces and samples, determining whether the welded joints have the required performance, proposing welding procedure qualification reports, and formulating welding procedure specifications (instructions). 2.0.3 The parent materials and welding materials (electrodes, welding wires, fluxes and gases, etc.) used in welding procedure qualification shall have factory quality certificates or re-inspection reports, and shall comply with the design requirements and relevant standards. 2.0.4 The groove form and size of the welding procedure qualification test piece (hereinafter referred to as the qualification test piece) shall comply with the design requirements and relevant regulations; if there are no regulations, they shall be implemented in accordance with the provisions of "Basic Forms and Dimensions of Weld Grooves for Gas Welding, Manual Arc Welding and Gas Shielded Welding" GB/T985 or "Basic Forms and Dimensions of Weld Grooves for Submerged Arc Welding" GB/T986, or designed and determined in the welding procedure qualification. 2.0.5 The welding equipment, test and inspection equipment used in welding procedure qualification shall be in good condition, and the instruments and measuring tools shall be qualified by metrological verification. 2.0.6 The personnel engaged in welding procedure qualification mainly include technical personnel of relevant majors and skilled welders. 2.0.7 The number of qualification test pieces shall be able to meet the requirements of test piece inspection and qualification. When using tubular butt weld specimens, when the outer diameter of the pipe is greater than or equal to 711mm, a 1/2 circumference welding specimen may be used, but it must include all positions from 6 to 12 o'clock. 2.0.8 With the consent of the owner, units with the same pressure pipeline construction qualifications may use each other's welding process assessments that have been assessed as qualified according to this standard as the basis for compiling welding process regulations (instructions), but they must be authorized and approved by the assessment unit and the welding responsible engineer of the unit in advance.
2.0.9 Any welding process assessment that complies with this standard and has complete original data and specimens can be considered valid. 3 Assessment rules
3.0.1 The welding process assessment should use butt weld specimens or fillet weld specimens. The welding process that has been assessed as qualified for butt specimens is also applicable to fillet weld specimens. The commonly used welding procedure qualification test piece forms are shown in Figure 3.0.1. 3.0.2 The welding of tubular or plate test pieces can be carried out by any welding method specified in Article 1.0.3 of this standard or their combined welding methods.
SY/T0452—2002
3.0.3 The qualified welding procedure of tubular butt weld test pieces can be applied to plate butt welds, and vice versa. Plate butt weld test piece
Tube-plate fillet weld test piece
(a) Butt weld test piece
Socket-tube fillet weld test piece
(b) Pipe fillet weld test piece
Tubular butt weld test piece
Tee-tube fillet weld test piece
Figure 3.0.1 Common welding procedure qualification test piece forms 3.0.4 The qualified welding procedure for the seat-type fillet weld is applicable to the socket-type fillet weld. 3.0.5 If the welding method is changed, the welding procedure qualification should be re-conducted. 3.0.6 Welding process factors are divided into important factors, supplementary factors and minor factors. Important factors refer to welding process factors that affect the tensile strength and bending properties of welded joints; supplementary factors refer to welding process factors that affect the impact properties of welded joints; minor factors refer to welding process factors that have no obvious effect on the mechanical properties required to be measured. Important factors, supplementary factors and minor factors in welding procedure assessment shall be determined in accordance with the provisions of Table 3.0.6. 1 When any important factor is changed, the welding procedure assessment shall be re-conducted. 2 When the design has requirements for impact performance, any supplementary factor shall be added or changed, and the impact performance test piece shall be welded according to the added or changed supplementary factor for testing.
3 When a minor factor is changed, the welding procedure assessment does not need to be re-conducted, but the welding procedure instruction book shall be re-compiled. 3.0.7 When two or more welding methods or welding processes with different important factors and supplementary factors are used for the same weld, each welding method or welding process may be assessed separately; it is also possible to use two or more welding methods and welding processes to weld test pieces for assessment. When the combination is qualified and used for weldments, one or several welding methods and welding processes may be used, but the important factors and supplementary factors shall remain unchanged, and the effective range of each welding method or welding process applicable to the weldment thickness or weld metal thickness shall be determined in accordance with the provisions of Articles 3.0.10 and 3.0.11 of this standard. 3.0.8 In order to reduce the number of welding process assessments, the parent materials shall be classified and grouped according to Table 3.0.8 based on the chemical composition, mechanical properties and welding properties of each parent material. For parent materials that cannot be classified and grouped according to the provisions of Table 3.0.8, welding process assessments shall be conducted separately. A welding process that has been qualified for a parent material can be used for other materials of the same group number when the important factors and supplementary factors remain unchanged. 2 The assessment of the parent material with group number VI-2 is applicable to the parent material with group number Ⅱ-1. 3 In the same category number, the assessment of the parent material with a higher group number is applicable to the welded joint composed of the parent material with the lower group number. 4 Except as provided in paragraphs 2 and 3 of this article, when the parent material group number is changed, it shall be re-evaluated. 600
SY/T 0452—2002
5 When the parent materials of different categories form a welded joint, even if the parent materials have been individually evaluated as qualified, the welded joint still needs to be re-evaluated. However, the evaluation of the parent material of the same steel grade with category number Ⅱ (or group number VI-1, VI-2) is applicable to the welded joint composed of the parent material of the category number (or group number) and the parent material of category number I. Table 3.0.6
Welding position
Welding conditions
[1. Groove form
2. Add or remove steel pad
3. Group gap
4. Add or remove non-metallic or non-melting metal welding backing
1. 1. Welding rod brand (only consider the first two digits after the category code)
2. Use non-low-hydrogen coated welding rod instead of low-hydrogen coated welding rod
3. Use low-hydrogen coated welding rod instead of non-low-hydrogen coated welding rod
4. Welding rod diameter
Important factors for welding process assessment of various welding methods
5. Flux-cored wire brand (only consider the first two digits after the category code), welding wire steel grade
6. Replace the flux-cored wire with a flux-cored wire with a higher impact absorption energy with a flux-cored wire with a lower impact absorption energy 7. Replace the flux-cored wire with a flux-cored wire with a higher impact absorption energy 8. Wire diameter
9. Flux brand, mixed flux ratio nitrogen 10. Add or remove filler metal
11. Change solid wire to flux-cored wire or vice versa Change from qualified welding position to upward vertical welding Electrode arc welding
Arc welding
Metal arc welding
Self-shielded tubular flux-cored wire welding
Gas tungsten arc welding
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Supplementary factors
Submerged arc welding
Metallic arc welding
Gas tungsten arc welding
Self-shielded tubular flux-cored wire welding
Mass arc welding
Secondary factors
Submerged arc welding
Self-shielded tubular flux-cored wire welding
Metallic arc welding
Gas tungsten arc welding
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SY/T0452-—2002
Welding conditions
1. The preheating temperature is reduced by more than 50℃ compared with the qualified value that has been evaluated. 2.The interlayer temperature deviation from the assessed recorded value is more than ±50°C 3. From the end of welding to post-weld heat treatment, change the post-heating temperature range and insulation time
1. Type of combustible gas
2. Type of shielding gas; the ratio of mixed shielding gas changes greatly
3. When the category number is IV, the back shielding gas is cancelled or replaced with a mixed gas including inert gas
4. When the group number is IV-2 and the category number is the base material, the gas flow rate is reduced by 10% or more 5. Add or cancel the tail shielding gas or change the tail shielding gas composition
6. Shielding gas flow
7. Add or cancel the back shielding gas, change the back shielding gas flow and composition
1. Type or polarity of current
2. Increase the line energy or the molten metal volume per unit length of weld exceeds the assessed qualified value
3. The current value or voltage value changes slightly
4. Superimpose or cancel the pulse current on the DC power supply [5. Type or diameter of tungsten electrode
1. 1. From oxidizing flame to reducing flame, or vice versa 2. Left-hand welding or right-hand welding
3. Non-oscillating welding or oscillating welding
4. Cleaning before welding and cleaning between layers
5. Root cleaning method
6. Wire oscillation amplitude, frequency and dwelling time at both ends 7. Distance from conductive nozzle to workpiece
8. From multi-pass welding to single-pass welding
9. Single-wire welding to multi-wire welding, or vice versa
10. Non-melting electrode oscillation amplitude, frequency and dwelling time at both ends
11. Wire (electrode) spacing
12. Nozzle size
Important factors
Electrode
Submerged arc welding
Self-shielded tubular flux-cored wire welding||tt| |Metallic arc welding
Rust-arc gas shielded welding
Supplementary factors
Metallic arc welding
Stick arc welding
Submerged arc welding
Self-shielded tubular flux-cored welding
Tungsten plate gas shielded welding
0/010010
Secondary factors
Hemp stick battery
Submerged arc welding
Japanese shielded tubular flux-cored welding
Metallic arc welding
Gas shielded arc welding
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Note: "○\ indicates that the welding method is an assessment factor, SY/T 0452--2002
* It is not considered as an additional factor when the material undergoes post-weld heat treatment above the upper transformation temperature or when the austenitic base material undergoes solid solution treatment after welding. 6 Materials that have been included in national standards and industry standards shall be classified into corresponding categories and groups, or divided into other categories and groups based on their chemical composition, mechanical properties and welding performance; materials that are not included in national standards and industry standards shall be subject to welding process assessment separately. 7 When foreign materials are used for the first time, welding process assessment shall be carried out for each material (named according to the standards of that country). When the welding performance of the material is mastered, and its chemical composition and mechanical properties are equivalent to a material in Table 3.0.8, and a material has undergone welding process assessment, the imported material can be exempted from welding process assessment. This foreign material can be classified into a certain category or group in the technical documents of this unit. Table 3.0.8 Classification and grouping of base materials||t t||Category No.
Group No.
Example of Brand
Q235-A·F,Q235-A,BC,10,20,20R,20G,20g,20HP,25,1.175,L210,L245,L29016Mn,16MnR,16Mng,L320,L360
15MnVR,15MnNbR,20 MnMo,10MoWVNb.L390,L41515MnVN,15MnVNR,L450,L485
13MnNiMoNbR,18MnMoNb R,20MnMoNb07MnCrMoVR
15CrMo, 15CrMoG, 15CrMoR, 14Cr1Mo, 14CrlMoR, 12CrMo, 12CrMoG,
12CrMoV,12CrMoVG
12Cr2Mo, 12Cr2MoG, 12Cr2Mo1, 12Cr2Mo1R1Cr5Mo
09MnD, 09MnNiD, 09MnNiDR | 0Cr18Ni12Mo2Ti,00Cr17Ni14Mo2,0Cr19Ni13Mo3, 00Cr19Nil3Mo30Cr13
1Cr13，2Cr13
L1, L2, L3, L4, L5, L6, LF21LF2,LF3
LF4.LF5, LF6, LF11
T1, T2,T3, TP1, TP2
H62,H68,HFe59 -1-1
When the post-weld heat treatment type is changed, the welding procedure should be re-qualified. 3.0.9
3.0.10 For qualified welding procedures, the applicable range of base metal thickness and weld metal thickness should comply with the provisions of Table 3.0.10. 3.0.11 When the test piece meets the welding conditions listed in Table 3.0.11, after the test piece is qualified, the maximum thickness applicable to the weldment shall be implemented in accordance with the provisions of Table 3.0.11, and the minimum thickness shall still be implemented in accordance with the provisions of Table 3.0.10. 3.0.12 The qualified welding process is used for weld repair and repair welding, and the thickness of the weldment parent material and the weld metal thickness shall comply with the provisions of Articles 3.0.10 and 3.0.11 of this standard. When the thickness of the parent material is not less than 38mm, the maximum thickness of the weldment parent material for the repair weld applicable to the qualified welding process may not be limited. 603
SY/T 0452--2002
3.0.13 The qualified welding process can be used for butt welds of unequal thickness, but the thickness of the parent material on both sides of the weldment should be within the applicable range of the qualified thickness.
3.0.14 When the welding process qualified by the butt weld specimen is used for fillet weld, the applicable range of the fillet weld parent material thickness is not limited; when the welding process qualified by the fillet weld specimen is used for non-pressure fillet weld, the applicable range of weldment thickness is not limited. Table 3.0.10 Applicable range of thickness of qualified welding process Applicable range of weldment parent material thickness
1.5≤T<8
Applicable range of weldment parent material thickness
Minimum value
Maximum value
2T, and not more than 12
Note: "t\ refers to the thickness of the weld metal deposited on the specimen by the same welding method (or welding process). Applicable range of weld metal thickness
Minimum value
Table 3.0. 11 Specimen thickness and weldment thickness regulations under special welding conditions Serial number
Specimen welding conditions
Except for gas welding, the specimen shall be subjected to post-weld heat treatment exceeding the upper transformation temperature Gas welding
Short-circuit transition metal arc welding, when the specimen thickness is less than 13mm Short-circuit transition metal arc welding, when the weld metal thickness is less than 13mm Note: ① Follow the corresponding provisions in Table 3.0.10. 4 Test and evaluation
4.1 Specimen inspection
Maximum value
2t, and not more than 12
Applicable to the maximum thickness of the weldment
Weld metal
4.1.1 After welding or heat treatment, the specimen shall be cooled to room temperature before inspection and testing. For delayed cracking of welds For welded joints with a large tendency to cracks, the appearance inspection should be carried out 48 hours after welding. 4.1.2 The inspection items for butt weld specimens and test pieces are: appearance inspection, notch hammer test, X-ray flaw detection and mechanical property test. Mechanical property test items include tensile test, impact test (when specified) and bending test. 4.1.3 The inspection items for fillet weld specimens and test pieces are: appearance inspection, metallographic inspection (macroscopic) or notch hammer test. 4.1.4 When the design documents require other inspection items for welded joints, the corresponding items should be added. 4.1.5 The appearance inspection of the specimens shall comply with the requirements of the design documents or relevant standards. 4.1.6 The X-ray flaw detection inspection and qualified indicators of butt welds shall be carried out in accordance with the design requirements or relevant standards. 4.2 Specimen preparation and testing
4.2.1 For test pieces that require heat treatment, all performance tests shall be conducted after heat treatment. 4.2.2 For test pieces that have passed the appearance inspection and non-destructive testing, test specimens shall be prepared by mechanical methods. The types and quantities of test specimens shall comply with the provisions of Table 4.2.2.
When the test piece adopts two or more welding methods: 4.2.3
1 The tensile surface of the bending test specimen shall include the weld metal of each welding method (or welding process). 2 When the impact test is required, three impact test specimens shall be taken for the weld zone and heat-affected zone of each welding method (or welding process); for welds with different base materials on both sides, three impact test specimens shall be taken for each heat-affected zone. 4.2.4 The sampling of the evaluation test piece should be mechanically cut, and cold leveling can be carried out before cutting and removing the weld excess height. When flame cutting is used for sampling, processing allowance shall be reserved. The sampling order and position of the evaluation test piece shall comply with the provisions of Figures 4.2.4-1 and 4.2.4-2. When sampling with 1/2 circumference welded specimens, the specimens shall be cut twice at the approximate positions according to the sequence shown in Figure 4.2.4-2, and 20 mm shall be cut off at the start and end positions of welding.
Table 4.2.2 Specimen Test Items and Sampling Quantity Specimen Base Material Thickness T
1. 5≤T<10
10≤T<20
T≥20
Tensile?
Notched Hammer Fracture?
Face Bending?
Note: ① In tensile test, one full-section specimen of tubular specimen can replace two plate specimens. Back Bending?
② Plate-shaped butt weld specimens are not required to undergo notched hammer fracture test. For pipes with an outer diameter of >323.9mm, four specimens shall be taken from notched hammer fracture. Side bend
③ During the bending test, when there is a significant difference in the bending properties between the base metals on both sides of the weld of the specimen or between the weld metal and the base metal, a longitudinal bend specimen may be used instead. During longitudinal bending, only two face bends and two back bends are taken. ① Four transverse side bend specimens may be used instead of two face bends and two back bends. Discard
(a) When side bend specimens are not taken
Longitudinal| Tension
Face bend: Extension:
Longitudinal! Longitudinal pulling|Impact
: God: Back bending
(c) When taking longitudinal bending test specimen
Note: The specimen width is 20mm
Sampling position of plate test specimen
Figure 4.2.4-1
(b) When taking lateral bending test specimen
SY/T0452--2002
(a) When the tensile test specimen is a whole tube, what is the position of the bending test specimen?
(b) When impact test is not required|| tt||（c）When impact test is required
1 Tensile test specimen, 2 Face bend test specimen; 3 Back bend test specimen; 4 One side bend test specimen; 5 Impact test specimen; 6 Notched hammer-break test specimen; ③③? Positioning mark when horizontal fixed position Figure 4.2.4-2 Sampling position of tubular test specimens
4.2.5 Tensile test specimens shall be machined to remove the weld excess height, and the test specimens shall comply with the following provisions: 1 For test specimens with a thickness less than or equal to 30mm, full-thickness test specimens shall be used. 2 For test specimens with a thickness greater than 30mm, full-thickness test specimens may be used according to the conditions of the testing machine, or the full-thickness test specimens may be mechanically cut into sub-test specimens with the same thickness and the least number of sub-test specimens. All qualified sub-test specimens may replace one qualified full-thickness test specimen. 3 For plate test specimens and tubular test specimens with an outer diameter greater than 76mm, shoulder-plate tensile test specimens shall be used, and their form and size shall comply with the provisions of Figure 4.2.5-1.
4 For tubular test pieces with an outer diameter less than or equal to 76mm, a pipe joint shoulder tensile test piece shall be used, and its form and size shall comply with the provisions of Figure 4.2.5-2.
5 For tubular test pieces with an outer diameter less than or equal to 76mm, a full-section tensile test piece may also be used, and the form and size of the full-section tensile test of the pipe joint shall comply with the provisions of Figure 4.2.5-3. 4.2.6 The notched hammer-broken test piece (as shown in Figure 4.2.6-1) is about 230mm long and 25mm wide. The sample can be prepared by mechanical cutting or flame cutting 606
. Use a hacksaw to saw a groove in the center of the weld end face on both sides of the sample (based on the weld). SY/T 0452—2002
When using this method to prepare some notched hammer-broken test pieces for automatic welding or semi-automatic welding, it may sometimes break on the parent material instead of on the weld. When the previous test shows that the parent material may break, in order to ensure that the fracture is on the weld, a groove can be cut on the outer surface of the weld excess height, but the depth shall not exceed 1.6mm from the weld surface.
The specimen can be tightened on a tensile machine, supported at both ends, and hit in the middle with a hammer, or supported at one end and hit at the other end with a hammer. The exposed area of the fracture should be at least 19mm wide.
T-test piece thickness; t-test piece thickness; w-test piece tensile plane width, greater than or equal to 25 mm; HK-width of the widest part of the weld; h-clamping part length, according to the requirements of the testing machine fixture; L-test piece length, R-corner radius
Tensile test piece for plate and tubular test piece with outer diameter greater than 76 mm Figure 4.2.5-1
R≥25
Tensile test piece for tubular test piece with outer diameter less than or equal to 76 mm Figure 4.2.5-2
V-shaped clamp of testing machinewww.bzxz.net
Tensile test piece for full section of pipe joint
Figure 4.2.5-3
SY/T 0452-—2002
About 3. 2 mm
Minimum 19am
No weld thickening
Grooved specimen with hacksaw, can be mechanically cut or oxygen cut/Both sides must be smooth and parallel to each other
About 230mm
The groove depth on the weld surface is not more than 1. 6 mm
Specimens that need to be grooved on the weld surface
Figure 4.2.6-1 Grooved hammer fracture test specimen
4.2.7 The weld excess height of the bending specimen shall be removed mechanically. The tensile surface of the face bending and back bending specimens shall retain the original surface of at least one side of the parent material. The machining marks shall be slight and parallel to the longitudinal axis of the specimen. The form and size of the bending specimen shall comply with the following provisions: 1 Transverse face bending and back bending specimens shall comply with the provisions of Figure 4, 2.7-1 and Table 4.2.7. When the specimen thickness is greater than 10mm, the excess thickness shall be removed from the pressure surface of the specimen. 2 Transverse side bending specimens shall comply with the provisions of Figure 4.2.7-2. When the specimen thickness is less than 38mm, a full-thickness side bend specimen shall be used, and the specimen width shall be equal to the specimen thickness; when the specimen thickness is greater than or equal to 38mm, multiple specimens with a width of 20mm to 38mm may be cut along the specimen thickness direction to replace a full-thickness specimen. 3 Longitudinal bend specimens shall comply with the provisions of Figure 4.2.7-3, and the longitudinal axis of the specimen shall be parallel to the weld. 4.2.7 Dimensions of bending specimens
Test specimen thickness T
1.5≤T<10
T≥10
Test specimen thickness
≥150
(a) Tubular and plate face bend
(b) Tubular and plate back bend
Figure 4.2.7-1
≥150
Transverse face and back bend specimens
Figure 4.2.7-2
≥150
Note: B—specimen width, plate specimen B=30mm; transverse side bend specimen
SY/T 0452--2002
Tubular specimen B=t+t/20 mm, and 10≤B≤38mm (where: Φ pipe outer diameter t—specimen thickness). Figure 4.2.7-3 Longitudinal bending specimen
4.2.8 Impact specimens shall be machined, and their form and test methods shall comply with the provisions of GB/T229. The longitudinal axis of the specimen shall be perpendicular to the weld axis, the notch axis shall be perpendicular to the surface of the parent material, the notch axis of the weld zone specimen shall be located on the center line of the weld, and the intersection of the notch axis and the specimen axis of the heat affected zone specimen shall be located in the heat affected zone (see Figure 4.2.8). The impact specimen is a standard specimen of 10mm×10mm×55mm. If it is impossible to prepare a standard specimen, a small-sized specimen with a thickness of 7.5mm or 5mm may also be used.
SY/T 0452—2002
4.2.9 The cutting positions and methods of the macroscopic metallographic structure of fillet weld specimens and the notched hammer-broken specimens are shown in Figures 4.2.9-1 and 4.2.9-2. 4.2.10 The macroscopic metallographic inspection of fillet welds shall comply with the following provisions: 1 The specimens shall be cut mechanically; if flame cutting is used, sufficient processing allowance shall be left. 2 Each specimen shall be 50mm long and not less than 25mm wide. The pipe-to-pipe or pipe-to-plate fillet weld specimen shall be cut into 4 equal parts. The starting and ending positions of the weld shall be located in the middle of the specimen. 3 For each specimen, one surface in the same direction shall be processed. Any two inspection surfaces shall not be the two side surfaces of the same cut. If necessary, corrosion shall be carried out first to reveal a clear weld outline for macroscopic inspection. 4.2.11 Various test methods shall comply with the current national standards: 1 Tensile test shall be carried out in accordance with the provisions of GB/T228 "Metal Tensile Test Method". (a) Heat affected zone
(b) Weld metal
1-Weld metal; 2-Heat affected zone, 3-Impact specimen; 4-Center line of specimen t-Distance from specimen to edge of parent material, t≥1mm; t-Distance from center line of specimen to edge of parent material Figure 4.2.8 Cutting position of impact specimen
Note: ① For tube-sheet fillet weld specimen, the thickness of the base plate parent material shall not be less than the thickness of the tube wall, and the maximum weld leg shall be equal to the thickness of the tube wall; ② For socket fillet weld specimen, the thickness of the outer tube wall shall not be less than the thickness of the inner tube wall, and the maximum weld leg shall be equal to the thickness of the inner tube wall; ③ The dotted line in the figure is a schematic line for cutting the specimen. Figure 4.2.9-1 Form of fillet weld macroscopic metallographic inspection specimen 610
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