Dear Friends
The variability of rebars in terms of carbon content is because they are usually made from scrap which varies a lot. The carbon content is a reasonable predictor of their life in a fire. The high tensile deformed (lumpy) bars are going to last longer than the mild steel round bars because they have more carbon, though it is not a heck of a lot more. Cast iron has a great deal. In a high carbon environment like a fire, the steel absorbs carbon and gives it off (strangely enough) depending on the temperature. Cast iron has enough carbon in it so that it pretty much maintains its crystal structure at high temperature. The difference between mild steel and cast iron can be shown by looking at what happens to a thin plate of each when exposed to high temperature. The mild steel peels off in thin layers over time. Cast iron does not. The only difference between them is the amount of carbon in it. When it is over 900 C (yellow) mild steel opens its pores, so to speak, and allows carbon to penetrate at a rate of about 0.1 mm per hour. That is how case hardening is done. Exposed to air at the same time, the iron is easily corroded. If it already has a back-up supply of carbon the iron can resist this corrosion for longer. Cast iron still corrodes if it is kept really hot - it is not magic, it is just better. Kept hot in an oxidising environment, cast iron also disappears. Regards Crispin From: Stoves [mailto:[email protected]] On Behalf Of Frans Peeters Sent: Monday, August 26, 2013 7:34 PM To: Stoves Subject: [Stoves] Stove grates Dear Stovers Rebars 12x12x700 mm x15 p. I used 40 years ago . Later 4mm iron sheet with 5x5 mm holes and 5x5 mm closed spaces .. Now I prefer stainles steel 6 mm woven round wires with 10x10 mm spaces . 350x700 mm . It supports the load 6-20 Kg wood . It last for ever if covered with stainless seeve made of 1 mm thick stainless cut in windows 3x6 mm quenced .The later , It last 1 year and gives white ash protecting partly the grates due it smal size and its isolation !! The smal mass dont rob heat as rebars do . Rebars have no protection by ash isolation . Rebars gives carbon loss, no white ash . Alumine ceramic plate Al2O3 must be the ideal grate if 10 mm thick and conical holes and 3X6 mm .open on the top . 4x8 mm under . Spaces 4 mm . It can be mouldes as perles for electric heaters have . Regards Frans.
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