crankshaft steel & rusting

[petertha]

Ive read a few posts recommending 1144 for crank shafts for its strength, good machining qualities & reduced likelyhood to post-machining stress relief? warpage. Ive also read where people complain about 12L14, that despite its nice machining qualities, will show rust after a while.

My question is, what is in 1144 that would make it much different that 12L14 from the corrosion standpoint?
Is it the Manganese? The contents appear similar. 1144 has 1.35-1.65%, 12L14 has 0.85 - 1.15% according to this link. Are their other ingredients in either steel that influence this?

http://www.onlinemetals.com/steelguide.cfm

Also (not that I'm advocating 12L14 for crankshafts) what makes it 'ok' and not have rust problems when its used for cylinders & liners as it appears to be called for in various designs?

 

[rake60]

The only real difference between 1144 stressproof steel and 12L14 steel is the "L".

That "L" signifies the addition of lead to the alloy.
Lead make the steel more easily machinable, but should not make it more likely to rust.

Manganese is a toughness additive. The more you have the stronger the steel. Too much
makes the alloy brittle.

I have machined cone rock crusher bowl liners that were very high manganese steel.
It's like cutting flint with a glass insert.

Rick

 

[steamer]

1144 has more carbon in it and will provide for a better crankshaft from the perspective of abrasive wear. As far as rust is concerned, if the alloy has less stress in it, it will probably rust less all things being equal.

For a crankshaft, in a high stress application of the two I would go with 1144. 1144 has better properties in the neighborhood of 4130 and 4340 but is much nicer to machine.

If the crank is well oiled...it won't rust much...unless it's in the bilge of a boat. I made my crank from 303 stainless to avoid that problem. Works fine.

Here's a link to references from MATWEB dot com. Great resource for all kinds of materials....don't leave home without it! ;D

1144

http://www.matweb.com/search/DataSheet.aspx?MatGUID=ea7aa091dcb947769b4f34f00c27062e&ckck=1

4340

http://www.matweb.com/search/DataSheet.aspx?MatGUID=fd1b43a97a8a44129b32b9de0d7d6c1a

12L14

http://www.matweb.com/search/DataSheet.aspx?MatGUID=fa62760bdedd40c79c2a2dc2416fb4ab

Dave

 

[petertha]

1144 has better properties in the neighborhood of 4130 and 4340 but is much nicer to machine. Dave

according to the link website, 4340 has a machinability index of 50% & 4130 shows 70%. Higher is better right? (12L14 = 160% so kind of makes sense). Not quite sure what 1144 index is for comparison, I didnt see it referenced, maybe it's alloy specific but I didnt find one.

 

[steamer]

I'd put it in the "in between range" somewhere better than 4340....but not much.

It's not bad at all, but if your going to hog agressively...you'll need carbide to keep your tool wear down.

But for normal machining like most of us do HSS works just fine.

Dave