Which Makes for a Better Stove? Cast Iron or Steel?

 
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dlj
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Post by dlj » Sat. Feb. 06, 2010 6:28 am

BigBarney wrote:Coalrunner:

If you need to cut cast iron a modern factory would use an abrasive
water cutter which will slice through even 6-8" cast iron like a hot
knife through butter.Cast iron has a large cost disadvantage to
steel fabrications in modern industry,so is used for very limited
uses in special applications.Steel is available today in the proper
formulations to be used for stove or furnace applications.

BigBarney
BigBarney,

Water cutters are really amazing what they can cut! You mention steels "in proper formulations" for stoves, whats the specfication? I'm not aware of it.

The one for grey castings for the firebox areas is ASTM A319. Here's a link to ASTM's web page if anyone's interested:

http://www.astm.org/Standards/A319.htm

dj

 
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Post by japar » Sat. Feb. 06, 2010 9:02 pm

It basiclly comes down to experience and opinions. I asked 2 of the local heavyweights . Slim bought a cast iron Franklin and hates it. Tiny bought a cast iron Chubby and loves it. I bought a steel Hearthmate and love it. If one material is better but the stove was poorly made or designed it has no advantage. You can get a cheap thin steel stove thats junk. You can buy a poorly designed cast stove that cracks . Do some homework on the stove be fore you buy.

 
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coaledsweat
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Post by coaledsweat » Sun. Feb. 07, 2010 9:04 am

japar wrote:If one material is better but the stove was poorly made or designed it has no advantage. You can get a cheap thin steel stove thats junk. You can buy a poorly designed cast stove that cracks . Do some homework on the stove be fore you buy.
This is true of any product but doesn't really relate to the question of which material is a better one to use for this particular product.


 
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BigBarney
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Post by BigBarney » Mon. Feb. 08, 2010 4:12 pm

DLJ:

The steel that is available in very low carbon like the A-36 grade is

a very good steel because it has the ability to resist heat induced

stress cracks.Many companies in the heating industry try to use

stainless steel to resist corrosion but at the sacrifice of useful

life because of the work hardening which causes cracks.

In a solid fuel appliance, especially in coal combustion, the

fire introduces carbon into the steel and that makes the

surface hard and vulnerable to heat cracks on the heat and

cooling cycles.The more cycles the more the chance of

failure. In some other applications that don't operate at

elevated temperatures the stainless is excellant, like auto

exhaust systems.

BigBarney

 
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Post by samhill » Mon. Feb. 08, 2010 5:07 pm

If you want a smaller radiant heat type stove cast is probably the better choice, holds heat better without distortion. If your looking for a larger add on furnace type then steel, easier to design with separate heat chambers but most likely will still have some cast. The early stoves were cast because it was better & cheaper then, steel before modern welding was mostly rivets, therefore large & bulky.

 
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Post by endinmaine » Mon. Feb. 08, 2010 7:46 pm

I have been burning wood for 40+ years and now coal for 5 years and have experience with cast iron, steel and sheet metal stoves. The stoves I have now are the best,,, a Harman Mark III , a steel stove that does very well burning coal and wood. My other stove, that is used 24/7 is a Margin Gem Cookstove that is made out of cast iron and sheet metal. It burns wood for 8 hours on one load and coal for 12 hours on one load. You get what you pay for so buy quality and you won't be sorry.


 
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dlj
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Post by dlj » Mon. Feb. 08, 2010 10:08 pm

BigBarney wrote:DLJ:
The steel that is available in very low carbon like the A-36 grade is a very good steel because it has the ability to resist heat induced stress cracks.Many companies in the heating industry try to use stainless steel to resist corrosion but at the sacrifice of useful life because of the work hardening which causes cracks.

In a solid fuel appliance, especially in coal combustion, the fire introduces carbon into the steel and that makes the surface hard and vulnerable to heat cracks on the heat and cooling cycles.The more cycles the more the chance of failure. In some other applications that don't operate at elevated temperatures the stainless is excellant, like auto exhaust systems.
BigBarney

BigBarney, Thanks for the reply. Structural grade A36 should work well in areas of a stove outside the firebox. I'm interested in what you are mentioning about "heat induced stress cracks". Do you find these mainly in the welds, or quite close to them? ASME boiler code is about the best guide you can get for understanding steels, where and how to use them. It's kind of a tough read, but is one of the major standards used for high temperature alloy use.

One of the advantages of using the appropriate cast iron in stoves is that they are completely saturated with carbon and do not take on more carbon as the steels do in this application. They do take up some, but a lot less and over longer time periods than the steels. Another big advantage of the cast irons is how strong they remain at higher temperatures. An A36 will have lost a lot of it's rigidity by about 800 degrees F where as cast iron keeps its rigidity to much higher temperatures. (I'd have to go look up the temps they are rated for)...

I'm surprised a bit about your comments regarding stainless and cracks. 304, for example, is rated up to 1500 f service in boilers, whereas most of your lower garde carbon steels, like the A36, get cut off at 800F as their highest usable temp.. I'd have to know what kind of service these are being used in to understand that better...

dj

 
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dlj
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Post by dlj » Mon. Feb. 08, 2010 10:26 pm

endinmaine wrote:I have been burning wood for 40+ years and now coal for 5 years and have experience with cast iron, steel and sheet metal stoves. The stoves I have now are the best,,, a Harman Mark III , a steel stove that does very well burning coal and wood. My other stove, that is used 24/7 is a Margin Gem Cookstove that is made out of cast iron and sheet metal. It burns wood for 8 hours on one load and coal for 12 hours on one load. You get what you pay for so buy quality and you won't be sorry.
endinmaine, I've heard good things about the Harman MarkIII but have never used one. It does use cast iron grates, front door and legs... They also use firebrick to line the firebox, what Greg L. mentioned before. That's a good way to go, easy to replace when needed, simple construction. One thing that's always bothered me is the fact that firebrick conducts heat less than ferrous materials by an order of magnitude. I've always wondered if you could take an identical stove design, one with the firebrick and one made of cast iron in that same area and be able to tell a difference or not in how much heat the stove gives out.

I am also a big fan of buying good quality rather than cheap.. It pays out in the long run...

dj

 
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Post by Kenbod » Mon. Feb. 08, 2010 11:26 pm

The science nerd in me loves this discussion. And there's a lot of great information here. As far as the technical aspects of the metallurgy go, I'm afraid there is no "correct" answer. Good companies with smart engineers are actively producing both quality steel and cast products. Either can last a lifetime.

The alloys of iron, including steel, mixed with common (and not so common) elements can yield impressive properties. The applications are just as important. Design is probably even more important. Good companies tend to make good products and earn good reputations. Stick with them. This site is full of recommendations.

That said, discussions of the stability of the crystalline matrixes of iron infused with various alloying atoms under various temperatures can be fascinating...

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