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Best Stainless Steel for Mirror like Surface.
- Thread starter zj4041
- Start date
btrueblood
Mechanical
The hardest alloys will polish best. Hard-drawn 301 or 302 sheet, or 440...
Alloys with more chrome will hold that polish longer (not oxidize as rapidly). 309, 310...
Alloys with more chrome will hold that polish longer (not oxidize as rapidly). 309, 310...
- Thread starter
- #3
No, 321 is not harder than 304.
"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein
"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein
Compositepro
Chemical
Polishing will have more effect on the type of reflection (specular versus scattering) that on the absorbtivity of the surface.
I just measured a group of stainless steels for reflectivity and emittance for this purpose. Austenitics are distinctly better than ferritics. Just choose one based on the environment it will face. 304 is good except near sea spray. In that case use 316.
Don't spend too much on a pretty finish. That only affects the specularity of the reflection, not the percentage of light reflected.
304 bright anneal will be very hard to improve upon. This can be purchased from service center stock. Anything more will be diminishing returns.
Michael McGuire
Don't spend too much on a pretty finish. That only affects the specularity of the reflection, not the percentage of light reflected.
304 bright anneal will be very hard to improve upon. This can be purchased from service center stock. Anything more will be diminishing returns.
Michael McGuire
btrueblood
Mechanical
Hard-drawn or hard-rolled products are harder (have higher y.s.) than others. They will deform less, and tend to embed less abrasives during the act of polishing. 302 and 301 are more typically supplied in sheet with 1/4-hard or higher ratings.
CPro, there are published values for s.s. in most heat transfer textbooks that are much lower for "polished" than "mill" finish. Yes, specularity plays a role in lowering emissivity, but I think the ability to clean, and keep clean (i.e. free of heavy oxidation) is also part of it. It's easier to see the dullness of oxidation build-up on a previously polished surface.
CPro, there are published values for s.s. in most heat transfer textbooks that are much lower for "polished" than "mill" finish. Yes, specularity plays a role in lowering emissivity, but I think the ability to clean, and keep clean (i.e. free of heavy oxidation) is also part of it. It's easier to see the dullness of oxidation build-up on a previously polished surface.
- Thread starter
- #8
- Thread starter
- #9
Be careful of data generated with reflectometers which use only selected wavelengths. Stainless has poor reflectivity for blue light which is specified in ASTM 1549. This procedure gives falsely low values for stainless.
Michael McGuire
Michael McGuire
mcquire,
In your vat repertoire of SS information do you have any information on the emissivity and reflectance of from a preoxidized surfaace on SS?
the reason for asking is that I was asked to do this on some 316 SS panels by using steam air + an organic for essentially the same purpose as the OP. I oxidized about 20 2'x 2' panels and shipped the off and never heard anything back.
In your vat repertoire of SS information do you have any information on the emissivity and reflectance of from a preoxidized surfaace on SS?
the reason for asking is that I was asked to do this on some 316 SS panels by using steam air + an organic for essentially the same purpose as the OP. I oxidized about 20 2'x 2' panels and shipped the off and never heard anything back.
- Thread starter
- #12
ive been using the data sheet from omega-
no worries, im going to calculate the emissivity based on wall temperature.
no worries, im going to calculate the emissivity based on wall temperature.
EdStainless
Materials
321 will contain many TiC inclusions by design. If you can't stand many tiny surface flaws then stick with 316.
A cold rolled sheet to high hardness will help.
The final surface will need to be electropolished to remove any smeared material.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
A cold rolled sheet to high hardness will help.
The final surface will need to be electropolished to remove any smeared material.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
In answer to unclesyd, the emissivity will jump to that of the oxide, or about 0.85. The reflectance will be 1 minus 0.85, or 0.15.
Mirror-like stainless have emissivity of 0.05 to 0.10 with reflectivity of 0.90 to 0.95.
Michael McGuire
Mirror-like stainless have emissivity of 0.05 to 0.10 with reflectivity of 0.90 to 0.95.
Michael McGuire
mcquire
Thanks, they weren't doing what I thinking they were doing. Your information has got my curosity up. inquiring minds have got to know and the problem is that this group always worked behind closed doors and probably didn't leave any record.
Thanks, they weren't doing what I thinking they were doing. Your information has got my curosity up. inquiring minds have got to know and the problem is that this group always worked behind closed doors and probably didn't leave any record.
Chromium is odd for a metal. It has high emissivity, 0.64, and therefore absorbs much of the solar energy instead of reflecting it.
Michael McGuire
Michael McGuire
I retract my statement on chromium, having found tables listing its emissivity at less than 0.10 in the polished condition. The same for nickel. The key is that polished, un-oxidized metals, in general, are highly reflective and have very low emissivity. The issue is how low they stay un-oxidized.
Michael McGuire
Michael McGuire
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