Welding characteristics Welding quality evaluation depends on the detection of a series of typical welding quality parameters. The following parameters can be comprehensively evaluated by visual and mechanical tests.
A Fusion welding joint FUSION ACROSS THE WELD
B lap amount before welding PRE-WELD OVERLAP
C Welds after welding POST-WELD OVERLAP
D Fusion EXPULSION
E Overall Weld Shape GENERAL WELD SHAPE
F Weld thickness WELD THICKNESS
G weld parallelism PARALLELISM
H weld color COLOUR
I Weld defects DEFECTS
The fusion of the welding cross-section can be observed and evaluated using a microscope. Good bonding means that the two interfaces of the welding seam overlap completely into a single unit structure. This indicates that the current from the welding wheel (welding electrode) passes through the overlap. At the interface, under the effect of welding pressure, the metal itself generates heat, softens and recrystallizes, so that the original two overlapping interfaces disappear and a good welding structure is formed.
If the supplied heat is not enough, cold welding will be caused, and if the amount of heat is too high, the weld will be brittle. Improper adjustment of the welder under certain conditions will cause cold welding and over welding at the same time for the same weld spot. Due to the periodic nature of the welding current, the degree of fusion will periodically change along the longitudinal direction of the can body. At the same time, the indentation of the welding wheel is attached to the plate that is welded to soften, so that the appearance of the welding wire is slightly wavy.
The correct evaluation of the fusion must be performed in the laboratory, but multiple weld appearances and strength tests can also be reliably judged at the work site.
The detection method is as follows:
Head Shot Test BALL TEST
Tear detection RIP TEST
Visual inspection VIISUAL TEST
Weld thickness WELD THICKNESS
Latch (before and after welding) OVERLAP (PRE-AND POST-WELING)
Rewind test REVERSAL TEST
Reverse testing FLANGE TEST
Cone Test CONE TEST
The third type of test, which focuses on detecting the strength of the weld in the opposite side region, is crucial to guarantee the hermeticity of the double-seal.
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