I can't answer your question. Cranes are made of many different types of steel and require different filler metals for welding. Using the wrong one could lead to serious trouble.
You mention your "old crane". Is this one a pre-manufactured unit? Or are you building a new one?
If it's a maufactured crane, I suggest contacting the crane manufacturer for advice on what you wish to do. They should know the materials to use and will problably have a repair procedure to follow.
If you are building a new crane, I suggest checking with the designing engineer. He/she should be able to collect the right information.
I would not make assumptions on what is OK or not OK. With a crane, it is best to find out for certain.
Chet Guilford