Effects of spherodizing on 44xxx steel 4

[QAFitz]

I've seen a few posts on heat treating various versions of AISI 4xxx steel (4142, 4340 etc.) to achieve very specific tensile and charpy properties. Most of the time we address the quench and temper operations. What about the pre-Q & T ops like process annealing, normalizing, spherodizing?
Does anybody have a feel for what these will do to enhance the mechanical property outcome of a Q & T ?
Thanks in advance for your time.

 

[metengr]

I have seen a normalizing treatment performed prior to quench and tempering for the 41XX alloy steels as conditioning treatment before final heat treatment. I don't see any benefit of annealing or spheroidizing before Q&T. The conditioning treatment aids in grain refinement and removes prior hot working effects in the material before final heat treatment.

 

[swall]

I did an experiment a while back on H-11, as the supplier literature reported that normalizing prior to Q&T was beneficial in preventing grain growth. It didn't make much difference. Also used to perform a high temperature normalize on 5120 warm forgings for grain refinement to prevent grain growth during subsequent carburizing. This worked, but was not necessarily cost effective. If you are looking at induction hardening, a spheroidized structure is the last thing you want. The best starting structure for the money is normalized.

 

[redpicker]

Agreeing with swall, but just adding that for just about any hardening operation, you want to avoid a spheroidized structure. Even with conventional furnace Q & T operations, starting with a spheroidized structure can result in inconsistant results. The spheroidized structure can be very difficult to austenitize and, once austenitized, it can take varying amounts of time to fully dissolve the carbides.

Normalizing can produce improved results from a subsequent Q & T operation, particularly if the prior thermal/mechanical processing has resulted in a coarse-grained, shperodized, or highly distorted structure. The other processes you mentioned would either be detrimental or have a negligable effect.

rp

 

[Robertmet]

If the spheroidized comes from a Q and 1200 F temper the carbides are fine and don't create problems.Typically a speroidized structure offers nothing as far as properties go.