Annealing SS430 to maximize magnetic permeability
Annealing SS430 to maximize magnetic permeability
(OP)
Hi,
I recently bought some SS430 tubes from China, expecting a certain magnetic permeability. However, the magnetic permeability seems very low when I tried using it as a core. Further research shows that the cold working involved in making it into a tube probably reduced its magnetic properties, and annealing it should bring it back. I've tried a few options so far:
- heat to 800C for 10 minutes and then air cool down to room
- Heat to 800C for 10 minutes and water quench (suggested by manufacturer)
- Heat to 800C for 10 minutes, lower temperature to 600C in oven over 2 hours, and then air cool
None of them seem to have improved the magnetic properties significantly. Any thoughts / ideas on what I should do to return it to its expected values (what I found in literature)? Thanks.
Kazi
I recently bought some SS430 tubes from China, expecting a certain magnetic permeability. However, the magnetic permeability seems very low when I tried using it as a core. Further research shows that the cold working involved in making it into a tube probably reduced its magnetic properties, and annealing it should bring it back. I've tried a few options so far:
- heat to 800C for 10 minutes and then air cool down to room
- Heat to 800C for 10 minutes and water quench (suggested by manufacturer)
- Heat to 800C for 10 minutes, lower temperature to 600C in oven over 2 hours, and then air cool
None of them seem to have improved the magnetic properties significantly. Any thoughts / ideas on what I should do to return it to its expected values (what I found in literature)? Thanks.
Kazi





RE: Annealing SS430 to maximize magnetic permeability
https://www.cartech.com/en/alloy-techzone/technica...
RE: Annealing SS430 to maximize magnetic permeability
Of the three annealing options you listed, the third one was the best. If that didn't bring you the permeability you want, then you might need to explore other alloys or suppliers that are willing to control/guarantee a particular permeability value.
Just out of curiosity, what level of permeability did you need/require?
RE: Annealing SS430 to maximize magnetic permeability
This should be 430S, low C if you want higher perm.
IF this is high C material (martensitic) then even reaching a value of 1000 could be difficult.
If it is the low C (ferritic) alloy then you should be able to get 1500-2000
Is the saturation OK?
Quenching from 800C is correct, you should be able to verify this by micros.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Annealing SS430 to maximize magnetic permeability
RE: Annealing SS430 to maximize magnetic permeability
All 304L is both 304L and 304, not not the other way around.
And 430 comes as both martensitic (higher C with no minimum) or 430S (for special) that is ferritic (lower C).
What spec did you order to?
What UNS number was called out?
To make it more confusing there are also stabilized versions of 430 with Ti and/or Nb in them.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Annealing SS430 to maximize magnetic permeability
Our recipe is:
anneal at 800-850°C for 1 hour in a dry hydrogen atmosphere
cool at 100°C per hour(max)rate to 500°C, any cooling rate thereafter
RE: Annealing SS430 to maximize magnetic permeability
RE: Annealing SS430 to maximize magnetic permeability
Quantities are dictated by the coil sizes that the mills will sell us.
We deliberately buy the C in the 0.05-0.09% range, it still forms and welds easily but also anneals as ferritic.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Annealing SS430 to maximize magnetic permeability
If I'm looking for material with permeability above a certain amount, what's the best way of specifying that to a supplier? I imagine most manufacturers don't measure permeability? Are there specific codes I should mention? Should I specify some form of treatment? Or would it be normal to specify magnetic permeability? Thanks!
RE: Annealing SS430 to maximize magnetic permeability
RE: Annealing SS430 to maximize magnetic permeability
If someone asked us to work to a perm we would ask them to spec chemistry and validate a heat treatment, we wouldn't guarantee perm.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Annealing SS430 to maximize magnetic permeability
EdStainless, based on that, any thoughts on chemistry / heat treatment that should deliver that or above?
RE: Annealing SS430 to maximize magnetic permeability
I'll defer to EdStainless for a recommendation of heat treatment.
RE: Annealing SS430 to maximize magnetic permeability
For a maximized perm, you should at least get a ferritic structure with an anneal HT slow cool. The max carbon is normally <.065%. The material you got possibly has a high carbon content, fast cool (water, air cool) further helped to get a martensitic structure, otherwise, 600+ perm is not so difficult to get for a ferrite SS.
RE: Annealing SS430 to maximize magnetic permeability
----------------------------------------
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.