Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: chadley on January 20, 2012, 07:48:06 AM
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Can somebody give me a list of metals OWB's are made of in their order of strength/durability? I can't keep all the different types of metal straight. which is the strongest, weakest etc.?
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There is no set Best worst or anything like that...
Mild steel is good.. Handles heat well ND is generally thicker than let's say a 409 stainless firebox
409 stainless allows companies to use thinner firebox material for better heat transfer, it doesn't have the stress corrosion/cracking problems that's present in 304 grade stainless, 409 is like 88% mild steel
304, it does not rust but can still be affected by a cracking type corrosion, go to central boiler.com and you'll see there steel comparison vs 304. I've seen several hardy stoves have to have fireboxes replaced due to this crows feet type cracking all over it
IMO mild steel and 409 are really good......
But please don't start thinking that a thicker firebox is more efficient because it's not.. 409 boxes are usually a little over 1/8 thick. Most mild boxed are 1/4. Test have shown that for each 1/8" you use that you lose roughly 13% in efficiency
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As a general rule stainless steel doesn't transfer heat as well as mild steel but that doesn't prevent it from making the water hot. What happens with metals that are poor conducters of heat is you get uneven heating and then uneven expansion or buckeling which causes cracks at welds, corners etc. This is why good stainless cookware is always clad in copper or aluminum so the heat will be spread out. Copper and Gold are some of the best conductors of heat but a BIT cost prohibitive. Mild steel makes a good compromise between cost and efficiency.
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The stainless heat shielding is more so on 304 stainless, that's why hardys are like 1/16" thick
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Don't forget Boiler Plate steel folks! The exact alloys and brands used are trade secrets....but there is a reason why industrial companies use this stuff. A516, A387, and A588 are some of the most popular alloys. This product resists the effects of weather and temperature variation. Only a very select few of the higher quality OWB's use boiler plate steel!