A friend of mine called me this evening wanting to know about welding ductile iron. It seems his ductile iron backhoe boom has cracked. It has a "do not weld" tag on it. Somewhere I seem to recall that it could be welded with the proper technique. Is that the case? Or did I dream it up??
He uses the hoe in his septic business. It gets some tough usage. Hard digging and lots of hammering. The replacement cost is around $7k. If it can be welded, that'll be the way he'll go. What y'all think?
Of course all those "do not weld" stickers are there for warranty purposes. They would just love to have you tack on some bracket or other just to let them off the hook on warranty. But once a machine is off the warranty, broke down and out of service, you do what ya gotta do.
If nothing else, maybe it can be put back into service long enough to work on getting a new boom at a more convenient time. Make sure it is out of warranty first I guess. For the older steel booms that would crack they would always plate the darn thing after welding the crack. On cast I don't know if that would help or hurt.
I have welded Ductile Iron fire hydrant extensions using Ni55 rod, but it was not a stress-critical operation. The Lincoln "Metals and How to Weld Them" book recommends similar procedures to cast iron, i.e. preheat to 500-600F and weld with about 60% Ni rod.
i have repaired cracks in ductile iron pipe.[emergency only].it is a bear.preheat ,7018 rods on low amps, post heat.and it will still crack on you. i would not repair anything ductile that was going to have much of a load on it.
I'm a big fan of brazing when I can heat the entire part up, I like to vee the joint and then I grind grooves into the joint to make it look like the face of the old meat tenderizing hammers, it gives the braze something to grab onto, and as soon as I'm done I post heat the part and take my chipping hammer and start tapping on the joint to stress relieve it. I forgot to note I also pre heat the part.
On parts that are to big to pre heat I use a nickle rod, slightly preheat and weld an inch at a time and peen with the chipping hammer between each 1" of weld.