What caused this

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For any experienced welders on the forum this is the side of a Quadrafire 5700 wood stove. The other side also has a crack like this in the same location. This is a weld seam on the inside of the stove where they welded the air tube manifold so it is cracked right through. Obviously heat created the crack but my question refers to what can do this on 1/4" steel at a weld joint such as a deep weld or something to that effect? The manifold is made with tube iron with one end capped off and drilled for the lateral secondary burn heat tubes running across the top. The other end is open to an air inlet flap. The next question is what is the proper way to fix this?

[Reyer Farms]

Is the crack beside that little weld were the red is?

[Rustyiron]

I'd shoot them an email. & pics. I'd say it's due to expansion issues with heating/cooling cycles, but that is a guess. They may have issues with this model. Post this over at hearth.com, that link I sent you the other day.

[Shield Arc]

I don't really know what caused it. Most likely too much stress in that location when hot.

I'd drill a hole at each end of the cracks, grind a groove in the cracks. Punch a key hole in the groove with some 6010 for the root pass, and cap it off with some 3/32-inch 7018.

[CNC Dan]

Weld it up like SA said, but do it when is at half the normal running temperature. That way it will see only half as much stress when hot.
And only half as much stress when cold.

[Mark @ Everlast]

Ditto, especially grinding a hole at the end of the crack on both ends. I'd probably use MIG though for heat and speed control. It would not hurt to weld it when the stove is hot.

[ghenges]

Ditto, especially grinding a hole at the end of the crack on both ends. I'd probably use MIG though for heat and speed control. It would not hurt to weld it when the stove is hot.

A shallow penetrating Mig weld is likely what facilitated the crack in the first place.

To fix it,
do what Shield Arc suggested above,

or take it to someone that has something more substantial than the "toy" Mig solder placers most folks mistakenly call welding machines.

In welding and sex, there is no substitute for maximum penetration. Know how to use your rod.

[Mark @ Everlast]

A mig weld is not shallow penetrating unless you make it so. That is a myth. And it's more of an issue with a technique. If you try to "paint" on a weld over the seam, nothing is going to work. The metal in that unit is not all that thick...maybe a 1/4". A little grinding out a groove and fill it up. In fact, that is the method of choice it appears to weld the stove from the manufacturer. It's likely from a creation of a large HAZ combined with shrink swell issues as it is. Stick would likely increase the HAZ. Stick would work. But it's not necessary.

[cdaigle430]

A shallow penetrating Mig weld is likely what facilitated the crack in the first place.

To fix it,
do what Shield Arc suggested above,

or take it to someone that has something more substantial than the "toy" Mig solder placers most folks mistakenly call welding machines.

In welding and sex, there is no substitute for maximum penetration. Know how to use your rod.

MIG welders are not toys They build the world just as much as STICK, TIG, Brazing and Spot Welders. No they certainly are not anymore a "toy" as is the rest of them. No mistake-MIGs are here to stay commercially and residentially.

And as for ghenges's opinion-the same thing can happen with either STICK or TIG as well. Its all about the person who did the welding and the conditions. I think thats what the person actually meant-the person not the method I think.


CJ

[Gary Fowler]

A mig weld is not shallow penetrating unless you make it so. That is a myth. And it's more of an issue with a technique. If you try to "paint" on a weld over the seam, nothing is going to work. The metal in that unit is not all that thick...maybe a 1/4". A little grinding out a groove and fill it up. In fact, that is the method of choice it appears to weld the stove from the manufacturer. It's likely from a creation of a large HAZ combined with shrink swell issues as it is. Stick would likely increase the HAZ. Stick would work. But it's not necessary.

I agree that a big high amperage MIG will penetrate, but as Ghenges said, those little 110V MIG machines just lay the metal on top and aren't much better bonded than Bondo.