Welded Al Alloy, annealing question 2

[Alfonzo]

Hi Guys,

I have a welded structure that comprises of a 12mm thick 6082 Al Alloy plate welded to a 2" dia. x 16swg tube. Because of the large difference in sectional thickness, our guys had to put a lot of heat into the plate prior to getting a decent TIG weld. The plate forms a lifting eye by which the structure is suspended by, so we are worried that the now annealed softer al alloy may not be quite man enough for the job (the 2" tube). We've decided to add some additional welded gusset plates (prob. 3mm thick) to help share the lifting loads along the 2" tube, and in order to get some welds in shear. TBH, the design could have been a lot better, but too late now. Question - having heated the al alloy once during the intial welding procedure, will the strength degrade further from another bout of heating and welding, or is it (as I believe) a case of the damage was done first time round, and it will stay the same through repeated heating?

 

[TVP]

It is unlikely that the microstructure could be made any weaker with additional welding, provided that aren't any fusion defects (porosity, crater cracks, etc.).

 

[metengr]

Agree with TVP. One question based on your quote below;
The plate forms a lifting eye by which the structure is suspended by, so we are worried that the now annealed softer al alloy may not be quite man enough for the job (the 2" tube). We've decided to add some additional welded gusset plates (prob. 3mm thick) to help share the lifting loads along the 2" tube, and in order to get some welds in shear

Are you intending to perform any nondestructive testing (NDT) of the structural welds? Namely, Liquid Penetrant testing?

 

[Alfonzo]

Cheers guys. I must admit, I hadn't thought of carrying out any NDT, but maybe we will. This has been one of those projects where the lack of time has forced some crappy decisions. I guess we've all been there eh?

 

[metengr]

Alfonzo;
When it comes to lifting lugs that are attached by welding, I always want to be sure nothing has been missed (cracks), which is the reason for conducting NDT. I like to sleep well at night.