01 defect name: Blowhole

Welding method, cause of occurrence, prevent measure shielded metal arc welding welding rod bad or damp. (2) weldment with moisture, grease or rust. The welding speed is too fast. The current is too strong. (5) arc length is not suitable. (6) the thickness of the weldment is large, and the cooling speed of metal is too fast. (1) select proper electrode and pay attention to drying. (2) clean the parts to be welded before welding. (3) reduce the welding speed, so that the internal gas easy to escape. (4) use manufacturer’s recommended current. (5) adjust the proper arc length. (6) perform proper warming-up. The CO2 Gas metal arc welding is dirty. (2) the wire is rusty or the flux is wet. (3) poor spot welding and improper selection of welding wire. (4) the dry extension length is too long and the CO2 gas protection is not perfect. (5) the wind speed is big, does not have the windscreen device. (6) welding speed is too fast, cooling fast. (7) sparks fly and stick to the NOZZLE, causing turbulence. (8) The gas is of poor purity and contains a lot of impurities (especially moisture) . (1) before welding, pay attention to clean the place to be welded. (2) select suitable welding wire and keep it dry. (3) spot welds shall be free of defects, clean and clean, and shall be of suitable wire size. (4) reduce the length of dry extension, adjust the appropriate gas flow. (5) installation of windscreen equipment. (6) slow down to allow the internal gas to escape. (7) pay attention to the removal of welding slag at the nozzle, and coated with spatter inhibitor to extend the life of the nozzle. (8) the purity of CO2 is above 99.98% and the moisture is below 0.005% .

02 defect name: Undercut

02 defect name: Undercut welding method, cause, preventive measure shielded metal arc welding current is too strong. (2) the electrode is not suitable. The ARC is too long. (4) improper operation. (5) unclean base material. Overheat of base material. (1) use lower current. (2) select the appropriate type and size of electrode. (3) maintain an appropriate arc length. (4) use the correct angle, slower speed, shorter arc and narrower running method. (5) remove grease or rust from base metal. (6) use a smaller diameter electrode. CO2 Gas shielded arc welding (1) is too long, welding speed is too fast. (2) when fillet welding, the electrode alignment is not correct. (3) vertical welding swing or poor operation, so that the two sides of the weld bead to fill the lack of undercut. (1) reduce the ARC length and speed. (2) in horizontal fillet welding, the position of welding wire should be 1 ~ 2mm away from the intersection point. (3) correct the operation method.

03 defect name: Slag Inclusion

Welding method, cause of occurrence, preventive measure, shielded metal arc welding slag is not completely removed. The welding current is too low. The welding speed is too slow. (4) too wide swing of electrode. (5) poor weld combination and design. (1) remove the front welding slag completely. (2) use higher current. (3) improve the welding speed. (4) reduce electrode swing width. (e) correction of proper slope angles and clearances. CO2 GAS ARC welding (1) the base metal inclines (descends) to lead the slag. (2) after the previous welding, the slag is not clean. (3) the current is too small, the speed is slow, welding quantity is much. (4) with the forward welding method, the slag in the groove is much ahead of time. (1) place the weldment as far as possible in a horizontal position. (2) pay attention to the cleanliness of each weld bead. (3) increase the current and welding speed, so that the slag is easy to float. (4) improve the welding speed

04 Defect Name: Incomplete Penetration

Welding methods, causes, prevention measures shielded metal arc welding welding rod selection is inappropriate. The current is too low. (3) the welding speed is too fast and the temperature rise is not enough, and the welding speed is too slow. The ARC impulse is blocked by the welding slag and can not be given to the base metal. (4) incorrect Weld Design and assembly. (1) use a more permeable electrode. (2) use appropriate electric current. (3) switch to appropriate welding speed. (4) increase the number of notches, increase the clearance, and reduce the root depth. CO2 GAS SHIELDED ARC welding (1) is too small, the welding speed is too low. The ARC is too long. (3) poor slotting design. (1) increase the welding current and speed. (2) reduce the ARC length. (3) increase the number of notches. Increasing clearance reduces root depth. Self-shielded flux-cored wire (1) current is too low. The welding speed is too slow. The voltage is too high. (4) improper arcing. (5) improper slope angle. (1) increase the current. (2) increase the welding speed. (3) lower voltage. Practice more. (5) slotting at a greater angle.

05 defect name: Crack

Welding method, cause of occurrence, preventive measures shielded metal arc welding welding parts containing excessive carbon, manganese and other alloy elements. (2) The electrode is of poor quality or damp. (3) excessive weld restraint stress. (4) the parent bar material is too high in sulfur to be suitable for welding. (5) inadequate preparation for construction. (6) the thickness of base metal is large and the cooling speed is too fast. The current is too strong. (8) insufficient first pass resistance to shrinkage stress. (1) use low hydrogen electrode. (2) use suitable electrode, and pay attention to dry. (3) improve the structure design, pay attention to the welding sequence, heat treatment after welding. (4) avoid using defective steel. (5) pre-heating or post-heating should be considered when welding. (6) preheat the base metal and cool it after welding. (7) use appropriate electric current. (8) The weld metal of the first pass shall be fully resistant to shrinkage stresses. The angle of the CO2 Gas metal arc welding is too small, resulting in pear-shaped and bead cracks during high current welding. (2) High Carbon content of base metal and other alloys (weld bead and heat-affected zone). (3) when multi-layer Welding, the first layer weld bead is too small. (4) improper welding sequence, resulting in excessive binding force. (5) the wire is wet and hydrogen enters the weld bead. (6) the sleeve plate is not closely connected, resulting in uneven height and stress concentration. (7) slow cooling due to excessive welding of the first layer (stainless steel, aluminum alloy, etc.) .

06 defect name: Deformation

Welding method, cause of occurrence, preventive measures manual welding CO2 Gas metal arc welding self-shielded flux-cored wire welding automatic submerged arc welding (1) too many welding layers. (2) improper welding sequence. (3) inadequate preparation for construction. Overcooling of base metal. (5) overheat of base metal. (sheet metal)(6) improper weld design. Too much welded metal. (8) imprecise manner of restraint. (1) use electrode with larger diameter and higher current. (2) correct the welding sequence (3) fix the weldment with fixture before welding to avoid warping. (4) avoid cooling too quickly or preheating the base metal. (5) select welding materials with low penetration. (6) reduce the weld clearance, reduce the number of slotting degrees. (7) pay attention to the welding size, do not make the bead too large. (8) pay attention to the fixing measures to prevent deformation.

08 other welding defects

Welding mode, cause of occurrence, prevent measure overlap (1) current is too low. The welding speed is too slow. (1) use an appropriate current. (2) use the right speed. Bad Appearance Of Weld Bead (1) bad electrode. (2) improper operation. (3) the welding current is too high and the diameter of electrode is too coarse. (4) overheating of weldment. (5) bad melting and filling method in weld bead. (6) Abrasion of conductive nozzle. (7) the extension length of the welding wire is not changed. (1) use a properly sized dry electrode. (2) adopt uniform and proper speed and welding sequence. (3) welding with appropriate current and diameter. (4) lower the current. Practice more. (6) replacement of conductive nozzle. (7) maintain a fixed length and proficiency. Pit (1) improper use of electrode. (2) wet electrode. (3) excessive cooling of base metal. (4) unclean electrode and segregation of welding parts. (5) the welding parts contain too much carbon and manganese. (1) use a suitable electrode, if it can not be eliminated, use a low hydrogen type electrode. (2) use a dry electrode. (3) reduce the welding speed, avoid rapid cooling, it is best to apply pre-heating or post-heating. (4) use good low hydrogen electrode. (5) use high base electrode. Partial Arc (1) in DC welding, the magnetic field produced by the welding piece is uneven, so that the ARC is biased. (2) poor position of ground wire. Too Large trailing angle of welding torch. (4) the length of the wire is too short. The voltage is too high and the ARC is too long. Too much current. The welding speed is too fast.

Source: Caitong

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