Steel woodburner developed a crack in the back...can I weld it?

As much as I would love to build a RMH or masonry heater in our house, it's going to be a long-term project and I'm already not looking forward to the bureaucratic process involved. And we have a situation: heating season will be here soon (we actually lit the fire twice last week when a vicious southerly came through and left snow on the nearby mountains) but I was doing routine checks on the thing and I just noticed a crack in the rear wall of the firebox, about 15 cm long and 1-2 mm wide. I'll try and get photos tomorrow.

The metal has deformed and bulged outward, and shows obvious signs of overheating and fatigue. Can I weld it as a quick fix to get us through the winter? The main thing I want to do is prevent it from opening further and messing up the airflow.

It looks to me like a poor design...there probably ought to be some refractory material there. CFB would probably not withstand having logs shoved into it, so firebrick splits, perhaps? This will mean some sort of brackets to hold the bricks in place. More welding.

I need to get in the habit of inspecting this thing at the *end* of fire season instead of just before the beginning. We might get lucky and not need it for another month, or there might be a cold snap next week when my mother-in-law is visiting.

You can probably weld it. I have welded many wood stoves.

Is it cast iron or steel?

Either can be welded and a trick I use for cast iron is to use 6011 welding rod for either. The latter will draw in enough cast iron into the pool to make it fused. I find it is easier to weld and saves you from buying special cast iron rod.

To keep cast iron from re cracking, make sure you use preheat and pot heat to bring the part welded from going or losing heat too rapidly.

It's hard to tell without photos.

Is it mild steel or cast iron?

Offhand, as an emergency fix, I would put a bead of stove gasket glue in the crack for an airtight seal, and set a piece of heavy sheet metal inside to take some of the direct heat from the fire.

That's a great idea, Doug. Certainly beats what I had in mind (getting a nice hot fire going, waiting for the metal to glow, and filling it in with the torch).



The material is mild steel plate, 6mm thick. I'm guessing it's suffered a lot of reduction embrittlement and trying to weld on it is very likely to make things worse. Those plugs are for a wetback loop and are 350mm apart...that might be a good way to fix a sacrificial plate to the back.