The latest specification of national welding standard
1, welding materials should comply with the design requirements and the provisions of the relevant standards, should check the quality certificate and baking records.
2, the welder must pass the exam, check the welding conditions of the welder's corresponding certificate and the date of the exam.
3. Class I and II welds must be inspected by flaw detection, and shall meet the design requirements and construction and acceptance specifications. Check the flaw detection report of the weld.
4. There shall be no defects such as cracks, flash, burn-through and arc pits. On the weld surface of Class I and Class II welds. There shall be no surface porosity, slag inclusion, arc pit, crack, arc scratch and other defects in the secondary weld, and there shall be no undercut, incomplete penetration and other defects in the primary weld.
Two. Basic project
1. weld appearance: uniform weld appearance, smooth transition from weld bead to weld bead, weld bead to base metal, and removal of welding slag and spatter.
2. Surface porosity: primary weld and secondary weld are not allowed; The allowable diameter of Class III weld is ≤ 0.4t; Or less per 50 mm length; Two air holes are less than or equal to 3 mm; Pore spacing ≤6 times pore diameter.
3. Edge undercut: No first-class weld is allowed.
Secondary weld: undercut depth ≤0.05t and ≤0.5mm, continuous length ≤ 100mm, and total undercut length on both sides ≤ 10% of weld length.
Tertiary weld: undercut depth ≤0.lt and ≤1mm.
Note: T is the thinner plate thickness at the joint.
4. See Table 5- 1 for allowable deviation items.
Three. Finished product protection
1, joints are not allowed after welding, and the newly welded steel bars are not allowed to be watered. Slow cooling measures should be taken at low temperature.
2. It is not allowed to strike an arc on the parent metal outside the weld at will.
3, all kinds of components can be welded after correction, and the shim and fixture shall not be moved at will to prevent component size deviation. The hidden part of the weld must go through the concealment acceptance procedures before the next concealment process can be carried out.
4, low-temperature welding is not allowed to clear slag immediately, should wait for the weld to cool.
Fourth, the quality problems that should be paid attention to
1. The dimension exceeds the allowable deviation: insufficient weld length, width and thickness, centerline deviation, bending and other deviations. The relative position and size of the welding parts shall be strictly controlled, and welding shall be allowed only after it is qualified, and care shall be taken during welding.
2. Weld cracks: In order to prevent cracks, appropriate welding process parameters and welding procedures should be selected to avoid large current and sudden flameout. The weld length should be 10 ~ 15mm, and the weldment can be moved or knocked during welding.
3. Surface porosity: covered electrode should be baked at the specified temperature and time, and the welding area must be cleaned. In the welding process, appropriate welding current should be selected to reduce the welding speed and make the gas in the molten pool escape completely.
4. Welding slag inclusion: Welding slag should be removed layer by layer during multi-layer welding. When operating, the welding slag should be correct and the arc length should be appropriate. Pay attention to the flow direction of slag. When alkaline covered electrode is used, slag should be left.
Verb (abbreviation of verb) quality record
This process standard should have the following quality records:
1, welding material quality certificate.
2, welder certificate and number.
3. Welding procedure test report.
4. Welding quality inspection report and flaw detection report.
5. Records of design changes and negotiations.
6, take cover engineering acceptance record.
7. Other technical documents.
Requirements of weld grade classification and nondestructive testing
According to the importance of the structure, load characteristics, weld form, working environment and stress state, different quality grades should be selected according to the following principles.
1. All butt welds of parts requiring fatigue calculation shall be fully welded, and their quality grades are as follows.
1) Transverse butt weld or T-butt weld and fillet weld with stress perpendicular to the weld length direction, with tensile grade I and compressive grade II;
2) The longitudinal butt weld with stress parallel to the weld length direction shall be Grade II.
2. For members that don't need to calculate fatigue, the butt weld with the same strength as the base metal should be fully penetrated, and its quality grade should not be lower than Grade II in tension and Grade II in compression.
3. For the heavy-duty working system, the T-shaped weld between the web and L flange of the crane beam with lifting weight Q≥50t, and the T-shaped weld between the chord on the crane leg and the joint plate shall be fully welded. Weld is generally a combination of butt welding and fillet welding, and its quality grade should not be lower than Grade II.
4.I &； # 39; The quality grades of fillet welds and incomplete fillet welds used in I-joints or butt joints and fillet welds used in lap joints are as follows
1) For structures directly subjected to dynamic load and crane beams with crane lifting capacity equal to or greater than 50t, the quality standard of weld appearance shall reach Grade II;
2) For other structures, the weld appearance quality standard can be Grade II.
Visual inspection is generally used for appearance inspection, and crack inspection should be carried out with a 5-fold magnifying glass under suitable lighting conditions. Magnetic particle inspection or penetrant inspection can be used when necessary, and measuring tools and calipers should be used for size measurement.
The appearance quality of weld shall meet the following requirements
There shall be no defects such as incomplete penetration, root shrinkage, undercut and poor joint. The primary weld and the secondary weld shall not have defects such as surface porosity, slag inclusion, cracks, arc abrasion, etc.
The appearance quality of the secondary weld shall meet the requirements in the first paragraph of this article and the relevant provisions in the following table.
The appearance quality of tertiary weld shall comply with the relevant provisions in the table below.
Welding quality grade
test item
assistant
Three levels
Incomplete welding
≤ 0.2+0.02t and ≤ 1mm, and the cumulative length of incomplete penetration of each 100mm weld is ≤25mm.
≤ 0.2+0.04t and ≤2mm, and the cumulative length of incomplete penetration per 100mm weld is ≤25mm.
Root contraction
≤0.2+0.02t≤ 1mm, with unlimited length.
≤0.2+0.04t≤2mm, with unlimited length.
Undercut
≤0.05t≤0.5mm, continuous length ≤ 100mm, total undercut length on both sides of weld ≤65438+ 00% of total weld length.
≤ 0. 1t and ≤ 1mm, with unlimited length.
dotted line
not allow
There are pits and cracks with allowable length ≤ 5 mm
Arc scratch
not allow
Individual arc scratches are allowed.
Bad joints
The notch depth is ≤ 0.05t and ≤ 0.5mm, and the length of each 1000mm weld should not exceed one notch.
The notch depth shall be ≤ 0. 1t and ≤ 1mm, and the length of each 1000mm weld shall not exceed one notch.
Surface porosity
not allow
Every 50mm long weld is allowed to have two blowholes with diameters of ≤ 0.4t and ≤3mm; The hole spacing should be ≥6 times the hole diameter.
Surface slag inclusion
not allow
Depth ≤ 0.2t, length ≤ 0.5t and ≤ 20mm.
Inspection of internal defects of full penetration weld in design shall meet the following requirements:
1 grade welds shall be inspected according to 100%, and the qualified grade shall be Grade II or above of Grade B inspection in the current national standard Manual Ultrasonic Inspection Method and Quality Grading Method for Steel Welds (GB 1 1345);
Grade 2 welds shall be sampled, with a sampling ratio of not less than 20%, and the qualified grade shall be Grade B or above in the current national standard Manual Ultrasonic Inspection Method and Quality Grading Method for Steel Welds (GB 1 1345);
3. Non-destructive testing is not required for full penetration tertiary welds.
4. The ultrasonic flaw detection method and defect classification of welded ball joint grid joints shall conform to the current national standard JG/T203-2007 Ultrasonic flaw detection and quality classification method for steel structures.
5 The ultrasonic inspection method and defect classification of welded joints of bolted ball joints shall conform to the current national standard JG/T203-2007 Ultrasonic Inspection and Quality Classification of Steel Structures.
6. The NDT results of the electroslag welding seam of the box-shaped member partition shall not only meet the relevant provisions of Article 7.3.3 of GB50205-200 1 standard, but also detect the weld penetration width and weld offset according to the provisions of Appendix C. ..
Ultrasonic flaw detection method and defect classification of T, K and Y joints of circular tubes shall comply with the provisions in Appendix D of GB50205-200 1 standard.
If the design documents stipulate that the nature of defects cannot be determined by radiographic inspection or ultrasonic inspection, radiographic inspection can be used for inspection and verification.
X-ray flaw detection shall conform to the current national standard "Radiography and Quality Classification of Butt Joints of Steel Fusion Welding" (GB 3323), and the radiographic quality grade shall conform to Class AB requirements. The first-level welding evaluation shall be Grade II or above in Radiography and Quality Classification of Butt Joints of Steel Fusion Welding (GB 3323), and Grade III or above in Radiography and Quality Classification of Butt Joints of Steel Fusion Welding (GB 3323).
10 shall be subjected to surface inspection under any of the following circumstances:
1) When cracks are found by visual inspection, 100% surface inspection shall be conducted for this batch of similar welds;
2) When there is a crack by visual inspection, the surface of the suspicious part shall be inspected;
3) When surface flaw detection is stipulated in the design drawings;
4) When the inspector thinks it is necessary.
Surface defects of magnetic materials should be detected by magnetic particle testing. When magnetic particle testing cannot be used due to structural or material reasons, penetrant testing can be used. Magnetic particle inspection shall conform to the current national standard "Magnetic particle inspection method and defect mark classification of welds" (JB/T 606 1), and penetrant inspection shall conform to the current national standard "Weld penetrant inspection method and defect mark classification" (JB/T 6062). The qualified standards of magnetic particle inspection and penetrant inspection shall conform to the relevant provisions of visual inspection.
The internal defects of the primary weld and the secondary weld requiring full penetration should be inspected by ultrasonic flaw detection. If ultrasonic flaw detection can't judge the defect, radiographic flaw detection should be adopted. The classification and inspection methods of internal defects shall conform to the current national standards GB 1 1345 Manual Ultrasonic Inspection Methods and Classification of Inspection Results for Steel Welds or GB3323 Inspection and Quality Classification for Butt Joints of Steel Fusion Welding.
The classification and inspection methods of internal defects of welded ball grid joints, bolted ball grid joints and intersecting lines of T, K and Y points of circular tubes shall respectively conform to the provisions of the current national standard JG/T203-2007 Ultrasonic Inspection and Quality Classification Method for Steel Structures and Technical Specification for Welding of Building Steel Structures JGJ8 1.