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| Neubert1975:
--- Quote from: vtsteam on July 15, 2018, 09:37:30 AM ---btw, sorry just one more a humorous thought, I have a 20 year old garbage can (dustbin, Br.) that lives by the road, outdoors in all Vermont weather. It is hot dip galvanized steel (zinc coated). It's in fine shape -- no deterioration, despite its rough use, exposure to rain, corrosive contents, and proximity to road salt. If it had been plain steel of the same thickness, treated this way for twenty years, it would indeed now be a small pile of rust flakes. My 20 year old house roof is also made of galvanized steel sheeting. In fact the very roof that protects my ferrous machine tools from the elements is also zinc coated. I know some rake is going to point out the galvanic series now, and trot out old saws about anodic protection, but I would ask that he or she then consider all-zinc roofs. No steel couple. Why in the world choose a metal that will turn to white fluff to protect against the elements? Tell me when my zinc headstock will be powder, so I can switch off the lathe in time, boys! :lol: Lets just say, that i wouldent save materials for that day, i dont think it will come for the first 20+ years :beer: /quote] --- End quote --- |
| Fergus OMore:
Perhaps -a salt and battery? :scratch: Somewhat whimsically Norm |
| vtsteam:
Okay, off the jokes, here's some simple data re. casting. Zamak 2 Ultimate tensile strength is 52,000 PSI (apologies to metric folks, but just for relative comparison) Zamak 12 is 58,000 PSI SAE1008 steel is 42,000-52,000 PSI Named aluminum casting alloys ~ 45,000 PSI For yield strength: Zamak 2 = 41,000 PSI Zamak 12 = 46,000 PSI SAE1008 steel = 20,000-40,000 PSI Named aluminum casting alloys ~ 22,000 PSI |
| vtsteam:
So what are the implications of the above? Well yes, cast parts can be cheapened by a manufacturer, because it is so strong, you can design a part to use very little material, by forcing it into webs and hollow shapes. They feel cheap, too because they are relatively light in weight. And they are brittle because the thin webs have ironically, the tremendous yield strength of the material. Now suppose you don't want to cheapen a part. But are looking to endow a lathe (for example) with high strength and stiffness. So you build parts with equivalent thickness in ZA-12 to cast iron or steel. In this case the yield strength of the part will be enormous. Greater than any other metal you could cast. The parts won't be brittle in any practical sense, because the application can never come close to generating yield forces. The strength of the part will exceed most everything you could build out of except hardened tool steel. The mass will be substantial, because Zamak weighs almost as much as iron. It won't feel or seem cheap or insubstantial. When painted, one casting looks the same as another.Iron is also painted for resistance to rust. Zamak does have the advantage of bearing slipperiness, so it will be better than steel for slides, and stronger there than cast iron, which is also a good bearing. In other words, for me, it was the material of choice. |
| WeldingRod:
I think y'all are worrying about zinc pest: https://en.m.wikipedia.org/wiki/Zinc_pest Modern lead free alloys don't suffer from this. Fascinating reading! Sent from my SAMSUNG-SM-G891A using Tapatalk |
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