Turning 304 / 316 magnetic

[pharmequip]

Hi,

I have an application where we utilise mild steel, 304 and 316(L) stainless steel components. The s/s 316 component has been running on a 316L shaft and has been damaged quite considerably. Swarf (relatively large particles) has entered the product however these particulates are magnetic. The mild steel seal housing shows no visible signs of wear so it's unlike that this is the source of the these particulates.

Is it possible that the heat generated by the stainless steel components has caused the swarf to become magnetic? I would have thought that this was unlikely however I would welcome a second opinion.

Thanks in advance.

Andy

 

[jet1749]

I have found 304 stainless steel components to be magnetic, 316 isn't

 

[kenvlach]

316 becomes slightly magnetic when cold worked; sufficient heating will remove the magnetism.

"The s/s 316 component has been running on a 316L shaft and has been damaged quite considerably."
This is due to galling, a kind of cold-welding of the materials together under stress. 316/316L is very, very well-known for this.

Many previous threads on austenitic SS magnetism & galling.

 

[pharmequip]

Thanks for the info. I clearly wasn't searching with the right options (i.e. Keywords!!!).

I think I need to do a lot more research into this!!!

Cheers,



Andy Wilkinson

http://www.pharmequip.co.za

http://www.manufacturingnet.co.za

http://www.lotsofpixels.co.za

 

[TEV]

304 and 316 will become slightly magnetic when deformed due to a martensite transformation. The martensite is magnetic. The leaner the alloys are in austenite stabilizing alloying elements (Nickel, Carbon, Nitrogen) the more susceptable it is to this transformation. We have even observed minute areas of martensite on machined surfaces of 316.

 

[Ashereng]

Thanks everyone for all the posts.

I didn't realise that 316 could turn magnetic, I always thought of magnetism as a physical property, and not variable due to stress (physical or heat wise).

 

[EdStainless]

When you cold draw wire or tubing this is a real issue. Even when the level of martensite can not be seen there will be some ferromagnetism in the leaner alloys.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[CoryPad]

Ashereng,

Ferromagnetism is a physical property, but it is a function of crystal structure in steels. Ferrite (body-centered cubic) and martensite (body-centered tetragonal) are ferromagnetic, while austenite (face-centered cubic) is not ferromagnetic.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Ashereng]

Thanks Cory. Didn't know that either.