Reasons for cracks in stamping of composite plate heads
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Material: Q345R+316L; Thickness: (28+3) mm; Inner diameter after head forming: 4200 mm. After hot stamping of the head, inspections on site revealed cracks in the composite layer. The mechanical properties and adhesion level specified on the material certificate meet the standards, and the retesting was also successful. What is the cause of the cracks in this end cap? How should the rework process be determined? I would appreciate it if an expert could give some advice. Thank you~~~
Are there welds at the location where cracks appear in the laminated layer you mentioned? If it is a laminated joint, it may crack during the stamping process. Only by grinding away the multi-layered cracks, preferably through cold working, followed by surface inspection, and only after no cracks are detected should resurfacing be carried out.
There are no welds at the locations where cracks occur; rather, they are on the surface of the clad base material~~~ The methods for dealing with these visible cracks include carbon arc gas gouging or grinding with a grinder, followed by welding repairs, further grinding, and PT testing. However, the workshop did not inspect the areas where no cracks were present, and now I’m worried that there might be some cracks that are invisible to the naked eye. To test these areas, does one need to add a PT test?
Reply 3# Tjumagic is necessary
At the very least, a surface inspection PT should be carried out; if possible, it is better to conduct a PT or UT.
Hmm~~~ It seems I still need to suggest that the workshop conduct a full-surface PT
Usually, only PT is performed to locate cracks; however, the most reliable approach is to use UT + PT
Is it a problem with the temperature control during hot stamping? Then why do cracks appear even though the material passes the re-inspection? It’s probably because the temperature wasn’t controlled properly
Half a year has passed – what was the final outcome of how it was handled back then? Can the quality of the composite panel head be ensured after processing? The moderator should give a final decision, haha.
This is probably a problem with the sheet material. We encountered this situation before as well; we negotiated with the manufacturer and asked them to send welders to carry out the repairs. It is recommended to perform all PT tests on the clad layer, all RT tests on the butt welds, grind away all defects, and then carry out surfacing. During welding, the interlayer temperature should be controlled; if the defects are deep, PT testing should be conducted after each layer is welded, and PT testing should be performed again after the entire welding is completed.
What is the hot stamping temperature? Due to the different thermal expansion coefficients of the base layer and the overlay layer, cracks are more likely to occur during stress stamping; therefore, the overlay layer must undergo overall PT treatment~