Crack in wood stove

[Hilbilly]

My 15 year old wood stove has a hairline crack radiating out from the upper right hand corner of the door frame. It is about 3" long and barely visible. The metal is 1/8" thick steel. I have previously welded this crack a few years ago when it was shorter. I am wondering if this will just keep happening or is there a permanent fix.

As I recall, I ground the old crack out before welding it using GMAW but that did not end up being a permanent fix.

 

[HawkinsHollow]

In plastic welding they drill a hole at either end of the crack to keep it from going further. Not sure if this applies in metal. I am sure someone more knowledgable will chime in soon.

 

[yomax4]

Did you drill a hole at both ends of the crack before welding? Expansion and contraction will keep the crack alive if not. If the Mig process isn't working you may need something more ductile that can expand and contract better. Simple brazing rod like Bronze, Silicon bronze or Nickel Silver will all work but if you can stop that crack you should be ok with standard Mig or Tig repair.

 

[MAX-24-Dean]

Did you drill a hole at both ends of the crack before welding? Expansion and contraction will keep the crack alive if not. If the Mig process isn't working you may need something more ductile that can expand and contract better. Simple brazing rod like Bronze, Silicon bronze or Nickel Silver will all work but if you can stop that crack you should be ok with standard Mig or Tig repair.

I took my stove to the local weld shop after drilling a hole at the end of the crack where the door cam lock kept it closed. They Mig welded the 3/16" steel plate.
Ran the stove for another 6 years before replacement this last November.

 

[Hilbilly]

Thanks! I think I will wait until the heating season is over and then drill a small hole at the end of the crack, open up the crack to get good penetration, preheat the steel and then weld it again.

 

[CliffordK]

If you keep using the stove, it may not be bad to make sure you have a carbon monoxide detector nearby.

Is this stove a "modern" stove with some type of low smoke system like either a catalytic converter, or top of stove air injection system? If not, it may be beneficial to upgrade.

 

[rScotty]

In plastic welding they drill a hole at either end of the crack to keep it from going further. Not sure if this applies in metal. I am sure someone more knowledgable will chime in soon.

"Stop drilling" absolutely does apply to metal - or any material that can crack. This is all normal crack growth. Cracks progress faster and easier when the tip is narrow. To stop cracks, go slightly but completely past the end of the crack and drill a hole there. You want the crack to extend into the hole and stop there. Drill it right thru using a drill diameter at least the same or larger than the thickness of the meal. For 1/8" steel i would use a 5/32 drill. Don't weld it, just leave the hole.

If you want, you can loosely plug the hole it with something that has lots of clearance and is NOT tightened down. Or a blob of something elastic like high temperature silicone muffler sealer.

I would do it now, why wait? If you are drilling cast steel or cast iron, practice first. For stoves made of rolled steel products drill as normal.

Stop drilling works because the same thermal force that was concentrated before into the thin point of the crack is now dissipated over the much larger area of the hole. Same force, but larger area.
Luck,
rScotty

 

[Hilbilly]

This is a modern Blaze King wood stove with a catalytic converter it was bought new 15 years ago. Plus we have CO detectors in the house.

I understand the idea of the stop drilling but can't leave a hole in my wood stove. I will try drilling then welding the hole afterwards. Worst thing that will happen is it will crack again and I will weld it again, maybe with a different method or material.

 

[rScotty]

This is a modern Blaze King wood stove with a catalytic converter it was bought new 15 years ago. Plus we have CO detectors in the house.

I understand the idea of the stop drilling but can't leave a hole in my wood stove. I will try drilling then welding the hole afterwards. Worst thing that will happen is it will crack again and I will weld it again, maybe with a different method or material.

I'm familiar with wood stoves. We've had quite a few different ones through the years. Yes, a catalytic converter can cause cracking. Stop drilling applies to all brittle materials that have stess cracks. It works mainly because the radius of the drilled hole is larger than the radius of the tip of a crack.

If you still plan to weld the hole, you may want to first think some more on why stop drilling works and what it does. If you want to learn more about cracking, search for articles on "fracture mechanics". The tip of a crack is like a sharpened chisel. It doesn't take much energy to cause it to advance. The trick is to dull the advancing edge.

I'll bet you can figure out how to seal a hole without welding it. Might even be some innovative examples online.
rScotty

 

[Rockbadchild]

if it be mine i would use a cut off wheel and cut half way through and past the crack then weld it.