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Cinerion Eremita Montanus
cine@cawfee.club
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Snacks
snacks
@cine @whirly so, you know how diamonds and graphite are just different crystal structures for carbon? Steels can do that better
Iron and simple low carbon steels are just ferrite crystals and turn into austenite at higher temperatures. Austenite is a non magnetic crystal that is more elastic, very corrosion resistant and i think also harder, it also dissolves carbon better, we use a bunch of different metals to keep the crystals as austenite at lower temperatures, mostly nickel.
Then there's also i think cementite which isn't even a metal alloy, it's a metal ceramic and the proper name would be iron carbide. It's hard and also helps with elasticity somehow? Spring steel is here afaik. Basically the original steels all had a bunch of that in them iirc. You get it by just putting too much iron to dissolve in the ferrite crystals, but the fun part is actually high carbon steels that have way too much carbon. You can quench them and get martensite which is again mostly ferrite with cementite but also carbon stuck in ferrite, causing a bunch of weirdness causing it to become stupid hard, at this point austenite is actually what's making your steel soft and if you go overboard with the carbon content crystals get stuck as austenite unless you cool everything down further with like liquid nitrogen.
Uhh, just some stuff from the top of my head, can't promise everything's correct
Iron and simple low carbon steels are just ferrite crystals and turn into austenite at higher temperatures. Austenite is a non magnetic crystal that is more elastic, very corrosion resistant and i think also harder, it also dissolves carbon better, we use a bunch of different metals to keep the crystals as austenite at lower temperatures, mostly nickel.
Then there's also i think cementite which isn't even a metal alloy, it's a metal ceramic and the proper name would be iron carbide. It's hard and also helps with elasticity somehow? Spring steel is here afaik. Basically the original steels all had a bunch of that in them iirc. You get it by just putting too much iron to dissolve in the ferrite crystals, but the fun part is actually high carbon steels that have way too much carbon. You can quench them and get martensite which is again mostly ferrite with cementite but also carbon stuck in ferrite, causing a bunch of weirdness causing it to become stupid hard, at this point austenite is actually what's making your steel soft and if you go overboard with the carbon content crystals get stuck as austenite unless you cool everything down further with like liquid nitrogen.
Uhh, just some stuff from the top of my head, can't promise everything's correct
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Cinerion Eremita Montanus
cine@cawfee.club
@snacks @whirly Well, I tried to understand this, but ended up in a rabbithole of ferrite materials used for inductor cores. Very interesting stuff.
I like the way you say the other metals in steel are used to keep the martensite crystals at lower temperatures. Sounds like adding alcohol to water to keep it from freezing at lower temperatures. Which is probably what's happening, just plotting the phase diagrams for that many compounds is non trivial.
Also, this also explains why some stainless steels which are austenitic aren't as mechanically resistant as the other non-stainless variants. Trade mechanical resistance for chemical resistance. Which makes me curious about the design considerations of using austenitic steels for vessels for high pressure processes that are also corrosive.
I like the way you say the other metals in steel are used to keep the martensite crystals at lower temperatures. Sounds like adding alcohol to water to keep it from freezing at lower temperatures. Which is probably what's happening, just plotting the phase diagrams for that many compounds is non trivial.
Also, this also explains why some stainless steels which are austenitic aren't as mechanically resistant as the other non-stainless variants. Trade mechanical resistance for chemical resistance. Which makes me curious about the design considerations of using austenitic steels for vessels for high pressure processes that are also corrosive.
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Snacks
snacks
@cine @whirly never really looked into electric steels, afaik itcs mostly just about adding silicone and some other elements to keep the crystals as small as possible? Just shows how dizzingly much you can do to manipulate iron crystals, i think the only other metal we go to such lengths with is titanium. Adding salt or alcohol to water is a decent analogy i think yeah, relatedly, did you know ice has a bunch of different crystal phases too?
usually you use austenite steel for anything corrosive afaik, if that's not an option you prob just use a liner.
usually you use austenite steel for anything corrosive afaik, if that's not an option you prob just use a liner.
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Cinerion Eremita Montanus
cine@cawfee.club
@snacks @whirly Very cool all the stuff that can be done to iron, yeah. The ferrites I saw are mostly of the form Metal-Fe2O3 or Metal Oxide-Fe2O3 for choke inductors, so ceramics, for filtering of high frequencies. Probably for switching mode power supplies and RF. And EMC. Whereas electrical steel, silicon iron, uses a SiFe alloy of varying Si %, and it's used in power transformers. Either for the utilities or for linear power supplies.
I assume the material choice has to do with the AC frequency of the application, but I'm not clear on it. And cost ofc.
Also yeah I was aware there's lots of ice crystals, I'm just no familiar with crystal phases and their processes. I've mostly dealt with fluid phase equilibria, so that's what I use as a reference.
Austenite is indeed the way to go for e.g. Foods. But even that falls short when dealing with high saline concentrations i.e above 2000 ppm. Pretty good for strong acidic conditions, though. Also, liners my beloved. A shame they are not always appropriate.
I assume the material choice has to do with the AC frequency of the application, but I'm not clear on it. And cost ofc.
Also yeah I was aware there's lots of ice crystals, I'm just no familiar with crystal phases and their processes. I've mostly dealt with fluid phase equilibria, so that's what I use as a reference.
Austenite is indeed the way to go for e.g. Foods. But even that falls short when dealing with high saline concentrations i.e above 2000 ppm. Pretty good for strong acidic conditions, though. Also, liners my beloved. A shame they are not always appropriate.
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