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