It is best to bring your onshore training welding certificate when you board the ship, but it is not needed at ordinary times; Of course, you should also bring your CCS operation certificate, just in case.
The coppersmith on board is mainly engaged in electric welding. Nothing is very demanding, at least within your own scope. Usually I don't participate in the maintenance of engine room equipment, and sometimes I need to go to the deck to do some welding work.
Nothing else, I hope I can help you.