Machining 17-4 SS, H1150 vs. H900 vs. "A"
I am looking to make a couple of small home use parts on my SB10L lathe, and am considering using 17-4 stainless steel. The parts are 5/16" to 3/8" OD, and involve some tapered ID turning, and both internal and external threading.
Any of the 17-4 options would be quite a bit higher yield than the 316 that I used before, so strength is not my prime consideration when shopping for the right heat treatment. But any practical advice on the differences in machining H1150, H900, or Annealed 17-4 would be very much appreciated.
The selling literature makes a flat statement:
Do Not Use In The Annealed Condition
H1100(or H1150) machines nicely and you can actually buy it
H900 is hard - like 44 Rockwell C, and I have never heard of it being for sale, but only getting to that condition by heat treat. I don't think I would try to machine H900 on a 10L.
Ordinarily with 17-4, you make something from A and then send it off to get it to H900, or whatever other hardness you need and can't readily buy like that.
McMaster has it available in all three conditions (H900, H1150, and annealed). I didn't see a caution on their site against using it in the annealed condition, though I did later see that warning elsewhere. Why?
Real simple - annealed does not have near the properties the heat treated stuff has. It is after all a high strength alloy - but only when heat treated.
Definitely an H1150, cuts much much easier than annealed(solution treated), not as gummy and a higher machinability rating. Even though an H900 is up in the mid 40's C scale, its pretty darn easy to machine also.
On the never use in the annealed condition, I hadn't heard that until recently either. In fact we do a lot of 17-4 castings and do the assemblies also. Annealed condition, no heat treat. Ground support equipment, not critical, I'm just saying... I prefer it heat treated myself.
By far and away my favorite stainless, well maybe its a tie with 303, but 17-4 is so much more functional.
I thought not using 17-4 in condition A had something to do with susceptibility to stress corrosion cracking. Or maybe that was another alloy.