Is round CD 4340 easier to machine annealed or normalized? I am talking about turning, drilling, milling, etc. in a lathe. I suppose it comes down to tool life...is annealed 'nice and soft' or 'gummy and burns up inserts'????
Thanks!
From my experience, Fully annealed material is just like you said 'gummy'. but i ususally only turn mild steel (1026).
'normalized' and 'annealed' are basically the same, but annealed take it a bit further as in cook and cool down time.
I prefer to turn something with at least some hardness for finish quality and easy chip breaking.
Both are processes that relieve stresses(and soften) in the mat'l.
maybe someone with excess knowledge on the subject can correct me if need be.
For alloys where there's a significant difference, normalizing usually gives you better machinability than annealing. Not all alloys respond to normalizing differently from a basic annealing, but those that do get a grain structure refinement that annealing doesn't provide.
Machinability-wise they're similar, though you're right that annealed material can be gummier. Both are heated up past critical temperature, but annealed steel is furnace cooled while normalized steel is air cooled.
Both are considered readily machinable. Normalized material can help with process reliability but IMO is marginal. 4340 is usually selected for its properties after hardening, and part of the hardening process involves normalizing first.
If you're planning to harden the part after machining, you could probably just use the cheaper material (annealed). It will make no difference after hardening.
4340 ann is not going to be gummy. Insert life shouldn't be a problem with coolant. Feed pretty heavy, .05 to .2 doc, .02 ipr at 450sfm, and it will chip nicely.