3 ms·

Oh hey snap! I’m from Adelaide, currently living in Launceston. Tiny aside, and because I like dreaming about actually building these structures: I work with

Oh hey snap! I’m from Adelaide, currently living in Launceston. Tiny aside, and because I like dreaming about actually building these structures: I work with metal everyday and hold a trade certificate in metal fabrication / engineering. You don’t need to go to stainless steels to achieve great strength. There are a range of carbon steels available that have up to four times the tensile strength of regular Grade 250 steel used in most structural steel applications. The 250 refers to 250 mega pascal tensile yield strength. Ultimate tensile strength increases after yield as the steel work-hardens, but that’s what makes steel such a great building material: it yields and increases in strength before failing. Anyway, I digress. See for example Bisalloy’s range of high tensile structural steels: https://www.bisalloy.com.au/product/bisalloy-structural/ https://www.bisalloy.com.au/product/bisalloy-structural/ The strength of these steels comes from the addiction of higher amounts of carbon, manganese, chromium, and molybdenum, but in far smaller quantities than required to make stainless steels. You might want stainless steels for some exposed parts for corrosion and radiation resistance, but these are unlikely to be the main structural components due to the relative rarity and cost of the main alloying elements.

cletus 6y ago
So I'm not metallurgist but my impression is that stainless steel is used as an example because it's readily available, relatively cheap to produce and sufficiently effective. A number of megastructures require much greater tensile strength than that (eg space elevator). Sometimes those materials are theoretical, sometimes not and even when not, often we've yet to produce them in sufficient quantities for such a large engineering effrot. But stainless steel cylinders? There's no in our technology to produce those (although producing them in space or on an airless world like the Moon or Mercury might be a challenge given our reliance on oxygen refining steel). I don't know if there are any issues with having different alloys (eg carbon steel and stainless steel) in contact with each other. I know with other metals this can be an issue. But again, I'm no expert.
- TheSpiceIsLife 6y ago
  I’m saying I don’t believe there’s any real strength benefits from adding large amounts of chromium and nickel. 316 (marine / medics grade) stainless has a yield stength if about 600Mpa, whereas high tensile carbon steels exceed that, and adding enough chromium to make corrosion resistant stainless steel makes it a pain in the bottom to work with. You don’t need to add all that expensive chromium (11%+) to obtain high strength steels. Dissimilar metals in contact with each other are a problem because they form a battery due to moisture and solutes, thereby causing electrolysis. This would be much less of an issue in the vacuum of space.

cletus 6y ago

So I'm not metallurgist but my impression is that stainless steel is used as an example because it's readily available, relatively cheap to produce and sufficiently effective. A number of megastructures require much greater tensile strength than that (eg space elevator). Sometimes those materials are theoretical, sometimes not and even when not, often we've yet to produce them in sufficient quantities for such a large engineering effrot. But stainless steel cylinders? There's no in our technology to produce those (although producing them in space or on an airless world like the Moon or Mercury might be a challenge given our reliance on oxygen refining steel). I don't know if there are any issues with having different alloys (eg carbon steel and stainless steel) in contact with each other. I know with other metals this can be an issue. But again, I'm no expert.

TheSpiceIsLife 6y ago
I’m saying I don’t believe there’s any real strength benefits from adding large amounts of chromium and nickel. 316 (marine / medics grade) stainless has a yield stength if about 600Mpa, whereas high tensile carbon steels exceed that, and adding enough chromium to make corrosion resistant stainless steel makes it a pain in the bottom to work with. You don’t need to add all that expensive chromium (11%+) to obtain high strength steels. Dissimilar metals in contact with each other are a problem because they form a battery due to moisture and solutes, thereby causing electrolysis. This would be much less of an issue in the vacuum of space.