Stainless - changing thickness and measuring hardness
Stainless - changing thickness and measuring hardness
(OP)
How would I best change the thickness of stainless steel? For example, if I bought some with a thickness of 0.25mm how would I best change this to 0.23mm. I would like to test 0.21mm, 0.22mm, 0.23mm and 0.24mm but it is only available in 0.20mm or 0.25mm.
How do I test the hardness of stainless steel? For example if I bought some that was 0.25mm, how would I know it was half hard, full hard etc. with more accuracy than bending it by hand.
Ultimately the purpose of this is to make a stainless steel disc with a resonant frequency of 50KHz for a piezo buzzer. Changing the diameter is relatively easy but i'm constrained with the diameter so I must alter the thickness and hardness of the disc. I may need for example a thickness of 0.22mm and a hardness of "xyz". The stainless grade is 304/316.
How do I test the hardness of stainless steel? For example if I bought some that was 0.25mm, how would I know it was half hard, full hard etc. with more accuracy than bending it by hand.
Ultimately the purpose of this is to make a stainless steel disc with a resonant frequency of 50KHz for a piezo buzzer. Changing the diameter is relatively easy but i'm constrained with the diameter so I must alter the thickness and hardness of the disc. I may need for example a thickness of 0.22mm and a hardness of "xyz". The stainless grade is 304/316.





RE: Stainless - changing thickness and measuring hardness
For thinning samples the only thing that comes to mind is lapping them. You have to keep them flat and minimize cold work. This should work.
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Plymouth Tube
RE: Stainless - changing thickness and measuring hardness
Antknee.
RE: Stainless - changing thickness and measuring hardness
Lapping involves rubbing the work article against a reference surface with loose abrasive grains interposed. Sort of like grinding, without the heat, and without the speed. It's possible to do it by hand, but it's very time-consuming, for which reason lapping machines exist.
Mike Halloran
Pembroke Pines, FL, USA
RE: Stainless - changing thickness and measuring hardness
Meanwhile cold rolling will reduce thickness and increase hardness.
Pressing will at a guess not be effective although it'll make the part flatter.
RE: Stainless - changing thickness and measuring hardness
Pressing can reduce the thickness also, but it requires a huge and stiff press to achieve the necessary pressures, that are achieved with much less force in a rolling mill. I.e. stressing a line to yield is much easier than stressing an area to yield.
Mike Halloran
Pembroke Pines, FL, USA
RE: Stainless - changing thickness and measuring hardness
RE: Stainless - changing thickness and measuring hardness
RE: Stainless - changing thickness and measuring hardness
I don't think hardness will have any effect on your resonant frequency. It will affect strength.
The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Stainless - changing thickness and measuring hardness
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Plymouth Tube
RE: Stainless - changing thickness and measuring hardness
The thing that occurs to me is that the critical factor effecting the resonant frequency is the stiffness of the stainless, the 0.2mm stainless might be as stiff as the 0.3mm despite being thinner - I have no accuarate way of checking. It appears I need the stainless rolled stronger or harder but I don't know the difference between hardness and strength.
Does that sound sensible?
What is the difference between hardness and strength?
Regards,
Antknee.
RE: Stainless - changing thickness and measuring hardness
How are these mounted?
Is the edge tightly clamped?
It might be that the diaphragm stiffness outweighs the change in thickness.
You may need to try and figure out how to cut some shallow concentric grooves into these to make them more flexible.
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Plymouth Tube
RE: Stainless - changing thickness and measuring hardness
The pzt resonates at 40KHz. Attached to the 0.2mm stainless the combined mechanical resonant frequency is 45KHz. So I can guess the stainless on its own would resonate mechanically at say 55KHz. So I need the stainless to be stiffer and pull the combined frequency up a bit more to 50KHz.
PZT = 40KHz
Stainless = 55KHz?
PZT + Stainless = 45KHz
How do I order stainless with a different stiffness? I mean do I ask for some stainless 0.2mm at 3/4 hard and full hard? Or do I ask for specific shore hardness values?
Is it possible to buy a cheap hardness tester? I don't need huge accuracy and couldn't justify the large cost for an industrial one.
I might be able to get away with some off the shelf stainless for this purpose but the next buzzer is 100KHz which I'd say will have to be cold rolled much stiffer/stronger
RE: Stainless - changing thickness and measuring hardness
There are some SS alloys that are a little stiffer, such as 439.
This might be enough to help you.
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Plymouth Tube
RE: Stainless - changing thickness and measuring hardness
PZT = 40KHz
Stainless = 30KHz?
PZT + stainless = 35KHz
RE: Stainless - changing thickness and measuring hardness
Mike Halloran
Pembroke Pines, FL, USA