What causes a weld crack?

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Overheating the unit will crack the welds
 
Cracks can be caused by crappy design or crappy fabrication. Poor surface prep and bad welding technique are usually the fab issues. Square Corners tend to be a weak point in design. Overheating can exceed the metallurgical rating of the steel but usually is just revealing design and fabrication issues. Various alloys can make the steel more temperature resistant at a big increase in material cost. Wire feeding welding techniques like MIG are particularly prone to poor technique (crappy penetration) and can hide poor surface prep by leaving contaminants under the weld which can turn into cracks. Stoves are not pressure parts so welding certifications are frequently not required. A good welder can reweld a bad joint as long as the metal was not overheated above its temperature rating. Once its overheated, new cracks can form along the new welds.
 
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Please post a series of detailed pics of your cracked stove. This way the members can analyze and contribute there valuable time to a planned fix for you. Thanks
 
Please post a series of detailed pics of your cracked stove. This way the members can analyze and contribute there valuable time to a planned fix for you. Thanks
It's a new stove. There shouldn't be any cracks.
 
Methinks this was instigated by thr user with a crack in a BK princess.
 
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Cracks can be caused by crappy design or crappy fabrication. Poor surface prep and bad welding technique are usually the fab issues. Square Corners tend to be a weak point in design. Overheating can exceed the metallurgical rating of the steel but usually is just revealing design and fabrication issues. Various alloys can make the steel more temperature resistant at a big increase in material cost. Wire feeding welding techniques like MIG are particularly prone to poor technique (crappy penetration) and can hide poor surface prep by leaving contaminants under the weld which can turn into cracks. Stoves are not pressure parts so welding certifications are frequently not required. A good welder can reweld a bad joint as long as the metal was not overheated above its temperature rating. Once its overheated, new cracks can form along the new welds.
It's a generic question and this excellent answer that applies to all steel stoves.
 
It's a generic question and this excellent answer that applies to all steel stoves.
Manufacturers make basic service requirements and recommendations, as noted in the Owners & Operators Manual of wood heaters. Cracks inside or adjacent to a weld can be caused by failure to observe these requirements/recommendations. We recommend that doors be installed and adjusted at the time of installation. We then recommend the fitment be check after a brief period of time as new gaskets will become "seated". Failure to keep a door seal tight can result is excessive localized temperatures to various surfaces. Several years ago, on this site, a member posted the image below. You can see that as a result of the air leak by the door handle, the materials are exposed to higher than desirable temperatures.

IMG_0013.JPG
 
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