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Weld cracking

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Re: Weld cracking

Postby cj737 » Wed Mar 15, 2017 7:00 am

Why not use a Nickel 99 or 55 rod with your Stick welder to join them? But if TIG welding it, cast iron needs a preheat as mentioned.
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Re: Weld cracking

Postby Olivero » Wed Mar 15, 2017 5:01 pm

Sounds an awful lot like cast with the bubbling and everything.

I never preheat cast when I weld it and I never had it crack either.

Gotta be the alloy, can't think of any other reason its acting up so much, shouldn't be THAT difficult to weld together.
if there's a welder, there's a way
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Re: Weld cracking

Postby Keith_J » Fri Mar 17, 2017 2:55 pm

Ductile or nodular iron? Cast steel IS weldable, welds are just cast metal without a mold. Filler metals are much higher quality than most casting alloys. I know CF8 castings and CF8M (304 and 316 stainless resp) are repaired with similar filler as the primary differences are in silicon which adds fluidity.

Cast iron relies on excess carbon for fluidity and this comes out of solution before solidification which is why the tacks break. Also, the cooling rate is high from self quench so it takes only a trifle base metal dilution to make carbon in the weld to jump over 1%. Remember, without other carbon equivalents, all it takes is 0.30% carbon to make welding sporty. Cast iron can have over 4% carbon.
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Re: Weld cracking

Postby Keith_J » Fri Mar 17, 2017 3:02 pm

How does this mystery metal drill/grind or spark? Without XRF PMI, ferrous metal ID by grinding sparks is subjective yet informative. If sparks end in a poof like a big firework, welding is going to be difficult.

Drill press with a known good bit..cast iron makes tiny chips or powder. No ductility.Still drills good, especially gray iron as the excess carbon is graphite. Swarf from gray iron stains fingers graphite gray.
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