Re: Arc weld a cracked block with nikel rods?
Faber,
I mig the exhaust manifold water passages closed with 1/2" steel rod ground to fit so I'm filling a 1/4"-3/8" V. I didn't have a torch to pre-heat and no oven. You could hear the cast 'tinking' away as it cracked and cooled. I tried to keep the heat down so I kept the bead about 1/2-3/4".
Would cutting out a section of old manifold to fill the water passages instead of the steel rod helped reduce the cracking?
I plan to go to the aluminum exhaust manifold next time around. Never welded aluminum before. I get to do a lot of practicing.
How important is knowing what type aluminum you're welding?
How is welding cast aluminum? More difficult?
The cracking was because it wasn't preheated and peened.
I wouldn't say you need to cut out a new piece... Grind it out, and get your hands on a torch, preheat it to at least 450*, weld, peen.
1/2" rod is pretty beefy. I like to use more weld then filler rod. Anything over 1/8"-3/16" is over killer unless you have a big gap. With a filler rod that thick you have a big cold spot in the middle of the welds.
You want just enough filler to keep you from burning through... the rest should be weld. If you lay your filler rod over the crack then your not really welding the crack which is weaker. If at all possible you don't want to use filler rod unless you have a decent sized gap between materials or the material is so thin that you have to use a filler rod.
If you have any pics I could tell you exactly what you need to do... not quite sure what you mean by welding the water passages closed.
As far as aluminum goes:
Cast aluminum is pretty much all the same except for the amount of sand it has in it but it needs to be tigged...
Run one or two passes without rod(fusion weld). That'll burn all the peroscity/sand out... Because of all the sand in cast you need to keep fusion welding it until you don't see any air bubbles in your weld. Then you can start using filler rod and weld it permantly.
