Causes of strip defects in flange weld of 2219 aluminum alloy box bottom

In the radiographic testing of a certain type of box bottom flange weld, it was found that there were strip crack defects in the weld area. The causes of the crack defects were analyzed by means of macroscopic observation, chemical composition analysis, mechanical property test, metallographic examination, scanning electron microscope and energy spectrum analysis. The results show that in the process of flange welding, the local welding line energy input was too large, which made the low melting point eutectic phase located in the fusion line and adjacent to the base metal near the weld zone appeared intergranular liquefaction. Under the combined action of structural stress and thermal stress, strip defects were produced in the weld.