Exhaust studs are notorious for freezing up and breaking. Thats when people go to youtube searching for things like "how to remove a broken bolt" or "exhaust stud removal".
Well, next time someone searches, hopefully this video will show up and help someone in a jam.
If you have a tig welder, you are in luck. One of the side benefits of having a tig welder is being able to pinpoint heat accurately enough to puddle a broken stud or bolt and add enough weld metal to get a nut welded on. Sometimes you get lucky and the heat from the tig welder breaks the stud loose. But most of the time, 2 or 3 tries is the ticket.
In this video, I was working on another project when someone walked in with this exhaust manifold with a broken stud. It had already been drilled and had an ez out stuck in it.
So I tried at first to remove the broken ez-out thinking that would allow the hollow drilled out stud to shrink with heat and come out easily.
It did wiggle just a bit but it broke off.
Oh well. No surprise. Most of the time, it takes a few tries .... I just puddled the stud again and this time fused it all together ez-out and stud using er309 ss tig rod.
1. because it has enough nickel and chromium to prevent it from becoming brittle from the high carbon in the ez out.
2. I had some nearby and handy
3. its much cheaper than nickel rods like hastelloy W.
4. its usually strong enough to remove a broken bolt or stud.
The second try was a charm and with the help of a oxyfuel torch and then some wd 40 after it had cooled to about 200f, the broken stud came out pretty easily without galling the threads.
REMEMBER... cast iron will become brittle if you cool it quickly from a high heat ( in theory, cast iron has to be at least pink from heat in order to harden but that varies with the type and who knows the type on odd jobs like this)
IF you dont have an ez out to contend with, often times, plain old er70s-2 tig rod will work ok but with the contamination, rust, oil, etc, 309 works better for me.
I have never tried removing a broken stud or bolt without a foot pedal but I know it would be more difficult than with one. It takes some fairly precise amperage control and a steady torch.
I dont remember exactly but I think I had the machine set on about 80 amps and did not use nearly all of that...I feathered the foot pedal to get the size puddle I needed to weld to the broken stud but not fuse the cast iron exhaust manifold.
I used a 2% lanthanated electrode sharpened to a point 3/32" diameter but 1/16" would have also worked. The main thing is to have it sharp enough to direct the heat where you want it.