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Thread: 316L....why is it magnetic?
12-15-2008, 11:06 AM #1
316L....why is it magnetic?
Does anyone know why a magnet is attracted to my 316L, stainless steel sheet stock?
Can it be returned to a non magnetic condition, and how?
the sheet is 3/16" thick
12-15-2008, 11:23 AM #2
The Jorgensen catalog says that 316 is non-magnetic in the anealed condition.
Can it be anealed?
12-15-2008, 11:35 AM #3
Austenitic stainless steels are non-magnetic in the annealed, fully austenitic condition. The magnetic permeability of the Alloys 316 and 317L in the annealed condition is generally less than 1.02 at 200 H (oersteds). Permeability values for cold deformed material vary with composition and the amount of cold deformation but are usually higher than that for annealed material.
Another reference mentioned that annealing 316L should be done by a certified heat treat facility, implying it is not for amateurs.
12-15-2008, 11:36 AM #4
If you in fact have 316L stainless it is very slightly magnetic if it has been work hardened. By slightly I would mean that a magnet hung from a string would show a small amount of attraction but would not stick well enough to support the weight of the magnet. If the material shows more magnetic attraction then this I would question wether you in fact have 316 stainless. The one exception to this is that austenitic stainless steels become magnetic when subjected to extrem cold. I don't of hand remember the transition temperater for 316L but it is well below zero.
12-15-2008, 11:38 AM #5
316L, or any other austenitic stainless steel, will become somewhat magnetic when it is cold worked. Sheet metal is frequently cold worked during the final stages of production, especially if a smooth, shiny surface finish is desired. To eliminate the magnetic properties, the material would have to be annealed after final rolling. However, this would tarnish the surface. It would also reduce the strength.
Try testing some stainless steel fasteners. You will discover the same characteristic.
12-15-2008, 11:42 AM #6
I've had 1.5 and 2" rods of 316 that were quite magnetic, it happens. Just about any other work you do to it afterward will again make it somewhat magnetic, sawing sure does. So maybe anneal last? but who knows what your parts will be like then, warp, etc.
12-15-2008, 11:52 AM #7
To anneal 300 series stainless, you generally have to heat it to a low red heat, then quench immediately in water.
This ought to make it non-magnetic again.
But it is not something you generally want to do to finished parts, especially with a lot of expensive machine work in them.
316 Stainless steel has somewhere around 70% iron in it.
The remarkable thing, to me, is that its not MORE magnetic.
There are other series of stainless that will stay less magnetic, if thats a property you really need. Nitronic, 219, and others. but they may have different machining characteristics, yield strengths, and, most likely, cost a lot more than 300 series.
12-15-2008, 03:29 PM #8
Thanks guys...I tried heating it...but not quenching.....This is something I can bead blast to
12-15-2008, 03:51 PM #9
well... heating and quenching didn't work... I checked the rest oF the material and 316L is on there in blue ink stenciling It was bought from M-Carr. Does someone have the exact heating temperature before quenching? I do have an electric heat treat furnace.
12-15-2008, 04:48 PM #10
Since as you have been told before in this thread, some slight magnetism is normal and unavoidable after any cold working or machining, why are you in such a tizzy about it?
12-15-2008, 04:54 PM #11
If I am going by everything I am told... I should be able to make it non magnetic. Why are you so interested in my emotions? This is a forum for metal working....not feelings
12-15-2008, 05:00 PM #12
The mil-certs I have of SS say from .5 to 2hrs at 1040C, 1960F, water quenched. Must vary with the size I guess. Probably not getting that one done with a torch...
Why go through the trouble?
12-15-2008, 05:14 PM #13
thanks for the constructive answer(s).... I'll try that.
It boils down to trying to make a customer happy. They are using this with an iron oxide paint and don't want it to pull the iron out of the paint.
12-15-2008, 05:36 PM #14
316L....why is it magnetic?
I can tell you why some ss is not magnetic:
Stainless steel becomes Non-magnetic because the added chromium lowers its currie point to that of or below room temperature.
Currie point is when steel no longer has magnetic properties. If you heat carbon steel to a certain point, it becomes non-magnetic. Continue to heat it further, and it becomes magnetic again. This is a small part of what is going on, but perhaps it helps understand some of the properties of steel.
12-15-2008, 05:46 PM #15
Most of the painting world has been searching for years for a paint that would be attracted in such a manner. As you now know the magnetic oull of 316 is very slight. The magnetic potential for hematite is similarly slight. In any case almost all paints using hematite as a pigment are enamel type paints, in which the pigment settles to bottom( surface painted) and the vehicle forms a glossy skin on top. The only exception that comes to mind is the red oxide primers. You probably don't have to worry about the part rusting here.
As for as your emotions, I didn't know you were THAT overwrought about it.
12-16-2008, 05:57 PM #16
I don't know what a magnetic oull is........ but I do know what an annoying troll is.
12-17-2008, 01:16 AM #17