Hello R. Mitchell, the use of a Young boom indicates to me that the machine is not being used as it was originally intended, thus you will generally make some concessions on the life of the machine and how well it will hold up. Many years ago I had access to some Catepillar documents for the repair of their booms and other weldments, I would venture to say these are still available in a revised format, even though this is a Young boom the repair and reinforcement practices from Cat will likely also apply to your application. Try to procure one of these publications. In the meantime, since Young has somewhat indicated the material and wire that they use I would follow the preheat, interpass, and postheat recommendations for the A572 gr 50 materials and the wire manufacturers parameters. I don't have the specifics for the A 572, but it is readily available through Google on the net, consider your material thicknesses as well when looking at the procedures. If the boom is in two pieces pay close attention to the joint prep. and getting it clean and then use some form of backing to ensure 100% joint penetration, also pay attention to the weld out progression to limit the stresses that are induced from the welding. The Cat publications would definitely help with this and also with designing and implementing any fish-plating and reinforcement pieces. If the boom is still in one piece you may need to be a little creative with the crack excavation and preparation, but try hard to end up with complete joint penetration in this case also. If you don't completely get to the root of any cracks they will likely reappear in short order.
You may also wish to re-evaluate the use of this machine and ensure that it is truly suited to the service that it is being used for. There are also some other individuals that frequent the forum that have a lot of experience in the area that you are questioning, hopefully they will chime in here and have some suggestions for you also. Best regards, aevald
I wanted to add a couple of addtional items for your consideration, there is an author by the name of John Lancaster who has many publications that deal with distortion control in welding and other welding related topics. You may want to consider getting your hands on some of his books. I have a couple, one of them is titled " Handbook of Structural Welding". I just located another good publication, this one is by Caterpillar and is titled "Techniques of Structural Repair" it isn't the one that covers reinforcement but it has a number of good topics and items in it. The copy that I have lists: Form JEG03717 3/72.