17-7PH questions 4

[hbean]

I have an application that is currently using Half Hard 304. This grade is not stiff enough for my application and I'd like to use 17-7PH to get a stiffer part.
The application uses very thin sheet (0.2mm to 0.7mm thick) that is formed then laser welded together.
My questions are:
(1) Is 17-7PH available in thin sheet in this range?
(2) I have read that 17-7PH when transformed to condition C at the mill is magnetic. It there a heat treatment process that does not result in a magnetic part?

 

[TVP]

Since the elastic modulus does not meaningfully change with alloying, stiffness becomes a function of geometry. The properties that change are strength, fracture toughness, corrosion resistance, etc. The answers to your questions are as follows:

(a) Yes, it is possible to obtain 17-7PH in that thickness. Suppliers include Somers Thin Strip and Ulbrich:

http://www.olinbrass.com/companies/somers/Products/Pages/StainlessSteel.aspx

http://www.ulbrich.com/index.php/design/design/page/strip_coil.html

(b) The stip can be annealed after cold rolling, which changes the microstructure back to an austenitic form, which is not magnetic. However, this removes the strain hardening and thus the increased strength.

 

[EdStainless]

As the man said, stiffness will not change.
How far you deflect it before it takes a bend will change as you change strength.

Your half hard 304 is magnetic, is this a problem?
The annealed 17-7 is not much stronger than any annealed SS.
If you want maximum strength you anneal at 1725F, cold roll, hold at -100F, age at 900F.

If you need strength and non-magnetic have some 21-6-9 (S21904) cold rolled. It is still fully non-magnetic at 160ksi UTS.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[mighoser]

If you want to stick with PH stainless, A286 is an option which is non magnetic.

 

[jagad5]

How much stiffer do you need to make it? Stainless steels are all in the 28 msi range. Some of the Nickel-based superalloys are 5-10% stiffer (31-33 msi range). My materials selector (Machine Design, 1993 edition) lists some Cobalt-based superalloys in the 34-35 msi range). Beyond that you have to start getting unusual. Composites, Beryllium, Ceramics.

Doug

 

[mfgenggear]

why not heat treat 17-7 after welding, sub critical anneal & then solution harden?
it has very little dimensional changes.

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.