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Cast Repair HELP

boozer

Aluminum
Joined
Jun 22, 2006
Location
Pennsylvania
Im not new to welding, Certified in just about everything, but one thing has alway got me stumpped.
Doing repair welding on Cast iron where redrilling or rethreading is needed in the weld area, Its get super hard, impossable to drill or retap. any suggestions. ive tried cast rods, SS rods, 6011s, 7018s, hard wire, just about anything and everything, i can drill the weld, the cast beside the weld, but cannot drill where the weld and cast meet, (plug welds).
 
This may sound silly but if you locate where the thread goes, open the repair hole much larger than the thread, then plug, weld, tap drill, tap. The thread is now completely within new steel.
 
I agree with Fran, i always hog out the hole area then fill it with good machinable rod. I never brazed cast but i know its done, my dad said he would break my arm if i ever put brass on a casting. Well 30 years later i still haven't done it...Bob
 
i weld the cast with ni rod. and drill it with no problems. build up a lot of ears on old carbs. i use an esob rod. i would never braze cast iron.
 
That hard spot is coming from the weld chilling right at the transition point so you get carbide precipitation. That's why the weld and the parent stock can be drilled but not the bonding point.

After welding, you might want to try a secondary post heat followed by slow cooling in vermiculite or ashes to soften the area. This should change the structure so machining is possible. I've welded a lot of cast iron and it can be done with good results but a few special techniques are needed that are different from steel.
 
I have in the past made Brass dowles, that i put into bolt holes, where the castings are thin, that prevented any weld from getting into the holes, but this doesn't help when welded a threaded hole. I never tried reheating and slowly cooling to lower the hardness.
The project im about to start on is changing a 4 bolt pattern brake drum to a 5 lug, and one of the new holes cuts one of the old holes in half, ill probabby just end up plugging the threaded hole with a stud, and maching threw it.
 
We used to do it where i worked, it was welding a cast flange to a Mild steel pipe, the first weld would alway crack, (hairlines) but the second pass help up. it wasn't a critical area, i personnally wouldn't do it for any repairs, This was with hardwire, im not sure if flux core would be any better or worse,
 
As per Mike W's post above, anybody considering cast iron repair should read every thing here.

The Straight Skinny

John
 
My dad has used Lincoln 92k2h for mig welding cast. Pein or use a pneumatic descaler between passes. He welded up an old bell support with it and it came out great. Using the descaler it actully blended the weld in with the old metal by leaving a stipled pattern on the weld similar to the original cast.
 
i've used nickel-99 and nickel-55 with great
success.remove a little more c.i. where you
need to machine.
stitch and move ....tack , wait for the craze to
form
in the center of the weld , then tack again an
inch or two away... then go back and clean slag
from the welds, and reweld the spots only..repeat as
needed...
once i have enough tags , i'll weld ...starting with
3-4 at a time, then making a full pass when the
whole shebang is good and hot.

not cheap, though...at $30/lb , big c.i. jobs
are pricey.

i've had good success w/ lincoln's "ferroweld"
cast iron rod. cheap as 7018 , it works when you
can use a lot of filler, but forget drilling
or tapping it.... an angle grinder's the only
tool it understands. i'd only use that rod for
non-critical ornamental jobs and such
good luck.
 
NI 55 rod will do the trick with no problem! You must preheat the cast iron previous and subsequent to welding. If you have a gas grill turn it to preheat and that should get you up aroun 600-700 farenheit. Make your welds and then put it back in the grill and turn the temperature down slowly so that it cools over a period of about four hours to a temperature that is below 170 degree farenheit. There is a lot of carbon in cast iron so if you ignore the preheat and the postheat you will definitely heat treat the welded area which will make it very difficult to machine with anything other than carbide tooling and it will be much more likely to crack.

Joe
 








 
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