Thank you. I am not familiar with reference set. But I have created a new one in the assembly that contains the welding making myself sure that this new reference set includes the weldings. Then I have selected this reference set to be active in the upper level assembly and I still can't see the welding in it.
I can't see it even if I make work part the assembly that contains the welding operation. The only way I can see the welding is by making it displayed part.