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Welding quality inspection, weld grade classification and NDT requirements

Date:2022-07-29 14:14:01 Views:109

(1) Guarantee project

1. Welding materials shall meet the design requirements and relevant standards, and quality certificates and baking records shall be checked.

2. The welder must pass the examination, and check the certificate and examination date of the welder's corresponding welding conditions.

3. Grade I and II welds must be subject to flaw detection and meet the design requirements and the provisions of construction and acceptance specifications. Check the weld flaw detection report.

4. Grade I and II welds on the weld surface shall be free of cracks, weld beading, burn through, craters and other defects. Grade II welds shall be free of surface pores, slag inclusions, craters, cracks, arc scratches and other defects, and grade I welds shall be free of undercut, incomplete welding and other defects.

焊接质量检测 焊缝等级分类及无损检测要求

(2) Basic items

1. Weld appearance: the weld appearance is uniform, the transition between weld bead and weld bead, between weld bead and base metal is smooth, and the welding slag and spatter are removed.

2. Surface porosity: Grade I and II welds are not allowed; The allowable diameter of grade III weld is ≤ 0.4t per 50mm length of weld; And 2 pores ≤ 3mm; Pore spacing ≤ 6 times of pore diameter.

3. Undercut: Grade I weld is not allowed.

Grade II weld: undercut depth ≤ 0.05T, and ≤ 0.5mm, continuous length ≤ 100mm, and total undercut length on both sides ≤ 10% weld length.

Grade III weld: undercut depth ≤ 0.lt and ≤ 1mm.

Note: t is the thickness of the thinner plate at the connection.

(3) Weld grade classification and NDT requirements

According to the importance of the structure, load characteristics, weld form, working environment and stress state, different quality grades shall be selected for the welds according to the following principles:

1. In the components requiring fatigue calculation, all butt welds shall be fully welded, and their quality grade is:

1) The transverse butt weld or T-shaped butt and fillet combined weld with the force perpendicular to the length of the weld shall be grade I in tension and grade II in compression;

2) The longitudinal butt weld with the force parallel to the weld length direction shall be class II.

2. In the members that do not need to calculate fatigue, the butt weld with the same strength as the base metal shall be fully welded, and its quality grade shall not be lower than grade II when in tension and grade II when in compression.

3. Heavy duty working system and lifting capacity Q ≥ 50t. The T-joint welds between the web and l-flange of the crane beam and between the chord and the gusset plate on the crane frame are required to be fully welded. The weld form is generally the combined weld of butt and fillet, and its quality grade should not be lower than grade II.

4. The quality grade of fillet weld or partially penetrated butt and fillet combined weld used for 'I' joints that do not require penetration, and fillet weld used for lap connection is:

1) For structures that directly bear dynamic loads and need to check fatigue, and intermediate working crane beams with crane lifting capacity equal to or greater than 50t, the appearance quality standard of welds shall meet grade II;

2) For other structures, the appearance quality standard of welds can be grade II.

Visual inspection is generally used for appearance inspection. Crack inspection should be supplemented by 5-fold magnifying glass and carried out under appropriate lighting conditions. Magnetic particle flaw detection or penetrant flaw detection can be used when necessary. Measuring tools and caliper should be used for size measurement.

The appearance quality of welds shall meet the following requirements:

1. The primary weld shall not have defects such as incomplete welding, root shrinkage, undercut and poor joint, and the primary weld and secondary weld shall not have defects such as surface pores, slag inclusions, cracks and arc scratches;

2. The appearance quality of secondary welds shall not only meet the requirements of paragraph 1 of this article, but also meet the relevant provisions of the following table;

3. The appearance quality of grade III welds shall comply with the relevant provisions in the table below.

The inspection of internal defects of full penetration welds shall meet the following requirements:

1. 100% inspection shall be carried out for grade I welds, and the qualification grade shall be grade II and above of grade B inspection in the current national standard "manual ultrasonic flaw detection methods and quality classification methods for steel welds" (GB 11345);

2. Spot check shall be carried out for grade II welds, and the proportion of spot check shall not be less than 20%. Its qualification grade shall be grade III and above of grade B inspection in the current national standard "manual ultrasonic flaw detection methods and quality classification methods for steel welds" (GB 11345);

3. Non destructive testing is not required for grade III welds with full penetration;

4. The ultrasonic flaw detection method and defect classification of welded spherical joint grid welds shall comply with the provisions of the current national standard jg/t203-2007 "ultrasonic flaw detection and quality classification method of steel structures";

5. The ultrasonic flaw detection method and defect classification of bolt ball joint grid frame welds shall comply with the provisions of the current national standard jg/t203-2007 "ultrasonic flaw detection and quality classification method of steel structures";

6. In addition to the relevant provisions of article 7.3.3 of GB50205-2001 standard, the nondestructive testing results of electroslag welding welds of box member diaphragms shall also be tested for weld penetration width and weld offset according to Appendix C;

7. The ultrasonic flaw detection method and defect classification of the welds of T, K and Y nodes of circular tubes shall comply with the provisions of Appendix D of GB50205-2001 standard;

8. When the design documents specify that radiographic inspection or ultrasonic inspection cannot judge the nature of defects, radiographic inspection can be used for inspection and verification;

9. Radiographic inspection shall comply with the provisions of the current national standard "radiography and quality classification of steel fusion welded butt joints" (GB 3323), and the quality grade of radiography shall meet the requirements of grade ab. The qualification grade of grade I weld shall be grade II and above in the radiographic and quality classification of fusion welded butt joints in steel (GB 3323), and the qualification grade of grade II weld shall be grade III and above in the radiographic and quality classification of fusion welded butt joints in steel (GB 3323).

10. Surface inspection shall be carried out under one of the following conditions:

1) When cracks are found in the appearance inspection, 100% of the surface of the same kind of welds in this batch shall be tested;

2) When cracks are suspected in the appearance inspection, the suspected parts shall be subject to surface flaw detection;

3) When surface flaw detection is specified in the design drawing;

4) When the inspector deems it necessary.

Ferromagnetic materials shall be tested for surface defects by magnetic particle inspection. If magnetic particle testing cannot be used due to structural or material reasons, penetrant testing can be used. The magnetic particle inspection shall comply with the provisions of the current national standard "magnetic particle inspection method of welds and classification of defective magnetic traces" (jb/t 6061), and the penetrant inspection shall comply with the provisions of the current national standard "penetrant inspection method of welds and classification of defective magnetic traces" (jb/t 6062). The qualification standard of magnetic particle inspection and penetrant inspection shall comply with the relevant provisions of visual inspection.

The grade I and II welds with full penetration required by the design shall be inspected for internal defects by ultrasonic flaw detection. When ultrasonic flaw detection cannot judge the defects, radiographic flaw detection shall be used. The classification and flaw detection method of internal defects shall comply with the provisions of the current national standard "manual ultrasonic wave flaw detection methods and classification of flaw detection results for steel welds" gb11345 or "radiography and quality classification of steel fusion welded butt joints" gb3323.

The internal defect classification and flaw detection methods of welded ball joint grid welds, bolt ball joint grid welds and circular tube T, K and Y-point intersection line welds shall comply with the current national standards jg/t203-2007 ultrasonic flaw detection and quality classification method of steel structures and jgj81 technical specification for welding of building steel structures.