Machining Stainless-Speeds and Feeds

[SPEC]

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[Boostinjdm]

I'm not worried, she doesn't like old fookers.  Ya smell funny.

[Doug Heim]

I know it to be leaded. Stainless has no carbon as the carbon would be magnetic, right?. Carbon is present in some magnetic stainless steels like 400 series stainless and 17-4 where it can be hardened.

Oh and another note on stainless machining... DO NOT try to cut it too fast as it may work harden and you will piss trying to punch through it!

My wife loves the stickey!

[Boostinjdm]

I'd have to look it up, but I don't believe carbon is magnetic.  Iron is though.  I also believe that stainless does have carbon in it.

[Doug Heim]

Actually I believe you are correct as carbide (carbon) inserts are not very magnetic although they do draw slightly.

[Boostinjdm]

#9  The L stands for low carbon.

http://www.ssina.com/faq/index.html

[Doug Heim]

Thanks, I learned somthing new myself!

What I was refereing to, because I see it more, is materials like12L14 (mild steel) where the L is within the grade number and does mean leaded stock. I have Stainless with the L after it and always avoided using it in welding applications. Now I know different. It is easier to cut though which was my inital statment.

[hemi43]

Here's another tip that I use !!
To tell the difference between 304 stainless and 316, I use a rare earth magnet (those realy strong ones ).
304 will have no attraction, but the 316 will attract the magnet slightly.

Here's another confusing thing about stainless.
 I use 304 "J" bends for doing exhaust. A rare earth magnet won't stick to the straight part, but will where the tubing has been bent. I still have not figured out why this happens. Would love the answer to this !!

Here's the chemistry makeup of 316 stainless;


Chemistry % by Weight
Fe 62.045-72%
Cr 16-18%
Ni 10-14%
Mo 2-3%
Mn 2%
N 0.1%
S 0.03%
C 0.03%
Si 0.75%
P 0.045%



As you can see, there's no lead (pb) present.

[fabr]

Yeah I'm still trying to figure out where the lead is that doug talks about. Maybe on the surface for some purpose during rolling it to thickness? ?? ?Lube maybe? Hell I don't know. I've never heard of it IN SS.

[Doug Heim]

The lead I know to be present is certianly in steels. We use 12L14 and 41L40 for specific jobs and the presence of the lead is to increase machining speeds for high production. the material is slightly more expensive. It is way easier to machine than non leaded.

Since this thread, I thought tha 316L, The L stoof or ead as well. I guess I just thought the same for streel was the same for stainless. Obviously not. If anyone wants me to send a small sample piece of 12L14 for the fun of seeing how easy to machine it is. Let me know.

[Boostinjdm]

I've got a theory there Hemi.  This is just shooting from the hip, but Fe is iron which is magnetic and makes up the largest part of 304.  The chromium and nickle "shield" the magnetic properties in the straight section, but in the curve the material is stretched.  The chromium and nickle is spread thinner allowing more of the iron's magnetic properties to surface.  I'm no expert though, I just watched somebody play one on an infomercial once.

EDIT    My bad, I see that was the chemistry for 316.  Oh well, Imma gonna stick to my theory anyway.

[Boostinjdm]

The lead I know to be present is certainly in steels. We use 12L14 and 41L40 for specific jobs and the presence of the lead is to increase machining speeds for high production. the material is slightly more expensive. It is way easier to machine than non leaded.

IIRC the lead is for lubrication and also aides in chip separation.

[Grimm Reaper Racing]

Here's another tip that I use !!
To tell the difference between 304 stainless and 316, I use a rare earth magnet (those realy strong ones ).
304 will have no attraction, but the 316 will attract the magnet slightly.

Here's another confusing thing about stainless.
 I use 304 "J" bends for doing exhaust. A rare earth magnet won't stick to the straight part, but will where the tubing has been bent. I still have not figured out why this happens. Would love the answer to this !!

Here's the chemistry makeup of 316 stainless;


Chemistry % by Weight
Fe 62.045-72%
Cr 16-18%
Ni 10-14%
Mo 2-3%
Mn 2%
N 0.1%
S 0.03%
C 0.03%
Si 0.75%
P 0.045%



As you can see, there's no lead (pb) present.

     As for why the Stainless is magnetic on the bends?  The answer is that it depends.  Your 316 SS is 'austenitic' and has a face center cubic crystal structure.  It is the nickel which modifies the physical structure of the steel and makes it non-magnetic. 

     Now when you make a tight bend in your material you're going through the materials elastic modulus and into it's deformation modulus.  By doing so you have pulled apart many of the bonds and there for have physical changed the crystal structure just enough to make it resemble a more 'martensitic' or body centered tetragonal crystal structure state.  So depending on how much and how tight your bend is will effect it's magnetic properties.

[fabr]

N0w that's interesting. Thanks for the info.

[Doug Heim]

Too many big words for me!