View Full Version : Magnetic 304 stainless steel stock

PT Doc
10-26-2013, 06:12 PM
McMaster Carr states that 304 stainless stock can become slightly magnetic when worked. I Want the stock that I have to be magnetic, so what is the best way to magnetize 304. Thanksfor the help.

10-26-2013, 06:20 PM
I've machined linear MILES of this stuff back in the day. Never once experienced even SLIGHT magnetism. In fact, we used it for tooling that was being used near the work envelope of resistance welding applications for just this property.

10-26-2013, 06:23 PM
I believe what they mean is that 304 will be attracted by a magnet where as 316 will not.
I may be wrong but I don't think you can actually magnetize 304 stainless.

10-26-2013, 06:53 PM
I think you may have to switch to one of the 400 series of stainless steels if you need magnetic properties.
As a bonus it is much more receptive to machining, drilling, tapping etc.

PT Doc
10-26-2013, 09:13 PM
Thanks for the helps. The item has been finished so I guess to bad. We'll see how strong the magnet is that I intended to attach.

Oh well. This is not critical just would have been convenient.

Thanks again.

10-27-2013, 05:00 AM
When they say "SLIGHTLY magnetic" they mean what they say. You will not notice any appreciable change in the magnetic properties of the 304.

There are very sensitive instruments such as mass spectrometers whose spectrographic results can be influenced by even the slightest bit of magnetism and it is for this reason that the disclaimer is made by the distributor. For all practical purposes the 304 will not become noticeably magnetic. At work we use 316 when magnetism must be kept to an absolute minimum.

I think Willy is correct when he says you need to look at 400 series stainless, and also correct when he says the machining properties are better, but the trade-off is in loss of corrosion resistance.

10-27-2013, 05:48 AM
"Standard" 304 has a percentage Carbon content which promotes slight magnetism. 304L is the low Carbon lower magnetic grade.

Regards Ian

The Artful Bodger
10-27-2013, 06:10 AM
I Want the stock that I have to be magnetic, so what is the best way to magnetize 304. Thanksfor the help.

Some alloys, even though attracted by a magnet, are not able to retain magnetism and 304 sounds like that. One way to make a piece of such material appear as a permanent magnet is to attach a strong magnet to it, in this video..
... you can see a small "solenoid engine" I made where the two bars sliding through the coils are magnetised in this way, in this instance I stuck a magnet on each end.

10-27-2013, 10:23 AM
Not sure the metallurgical details (flunked that course and had to take it twice) but austenitic (3xx series) becomes magnetic as it is cold worked. An example of this is cold-headed stainless (18-8 is common composition) fasteners with roll-formed threads. A magnet will stick to these at roughly 1/4 the pull that you find in regular fasteners. The amount of magnet pull is related to degree of cold work. You don't observe magnetism in 304 bar stock because the amount of cold work is small.

Alan Douglas
10-27-2013, 09:24 PM
That explains why it's so variable. We tried to distinguish 18-8 from 316 bolts in the stock drawers at work by checking with a magnet, but with erratic results.

10-28-2013, 05:49 AM
I've found that even stock describing itself as 316 is weakly attracted to Nedimium magnets.

10-28-2013, 07:23 AM
L application also for 316. ie. 316L

Regards Ian.