I have a chance to get a hay fork...(it's a 3-pt hay fork if that makes any difference in possible steel type).  Anyone have an idea of what type of steel the hay forks are generally made of?  Would it be good for making a 2 to 3 pound rounding hammer, for example?

I assume you're talking about the kind for moving round bales.  Not sure if the 3 point hitch version is the same, but I have seen the main tine break off one made for a skid steer. There was no noticeable set either side of the break, so I would guess that one was at least a medium carbon steel that had been hardened.  The diameter would seem about right for a hammer head, and you can check to make sure it is hard or will harden before you spend a bunch of time heating and beating.

Yeah, the hay fork is for round bales.  Since it is a single fork, I was thinking it might be a tougher steel than doubles for buckets, skid steers, the bolt-on kinds that might carry lighter loads per fork.

I asked once about the steel type for a hay fork which was a skid loader attachment. Frosty said it might be 4140. 

The one I saw that broke was a single main tine for lifting the bale and two much smaller and shorter tines on the corners of the frame - probably for stabilizing only.  The tine didn't snap because of lifting bales.  The guy who snapped it was moving junk cars around with it and got one stuck on it near the end of the tine.  You can do the math from there.

arkie, if your spear is a C2-49 then;

All spears are made of silicon manganese spring steel. Each spear is roll forged, heat-treated, hardened and tempered with a nominal hardness of 45/49HRC. Each spear is straightened and strength tested.

 

http://www.metzproseries.com/C2-49-Bale-Spear-C2-49.htm

1 hour ago, coldironkilz said:

arkie, if your spear is a C2-49 then;

All spears are made of silicon manganese spring steel. Each spear is roll forged, heat-treated, hardened and tempered with a nominal hardness of 45/49HRC. Each spear is straightened and strength tested.

 

http://www.metzproseries.com/C2-49-Bale-Spear-C2-49.htm

I doubt if the farmer knows what it is.  He's going to put it in a farm auction and I may have a crack at it early.  I wonder if they are 4140, as Frosty and tonyw above mentioned.  Sounds like the single spears might be higher quality than the doubles.  At least those Metz spears aren't made in China!!!

Depends on the age and make, many older ones are simply 2" round or square 1018 or A36 (those that are welded together) those that look forged, particularly the taperd and fullerd ones (they are either bolted or pined into sockets) are medium carbon. Esentualy forklift tines. 

Thanks, guys, for the info on the forks.  Unfortunately, I got sick and never got to look at the fork before it went to auction and didn't get to attend the auction....bummer.  At least I know more about the spears should another come available.