Sherodized annealed steel
Sherodized annealed steel
(OP)
When you heat treat ( hardening & tempering)a steel which was spherodized annealed before cold working,
do you follow the same heat treatment cycle as you would do in case of non-spherodized annealed steel of
the same grade of steel , or is it different?
do you follow the same heat treatment cycle as you would do in case of non-spherodized annealed steel of
the same grade of steel , or is it different?





RE: Sherodized annealed steel
RE: Sherodized annealed steel
RE: Sherodized annealed steel
The spheroidized steel will be difficult to austenitize. A lot depends on the chemistry, but if you have Cr and Mo (as in 41XX, 43XX etc...), and you end up with a structure of ferrite and speheroidized carbides, the ferrite isn't going to want to change to austenite until it gets above 1725F, or it absorbs enough carbon from the carbides. But, the carbides are M23C6 with all of the Chrome and Moly being tied up in the carbides, so they aren't going to dissolve very quickly.
The short version is, yes you can harden a spehrodized structure just by austentitizing as, say 1500F, but you will need a much longer holding time than you would with either a normalized or as-rolled structure. Much longer. If you don't hold it long enough, you will not get all of the carbon and alloy into solution with the austenite and, while you will harden, you be effectively be hardening an alloy with a lower carbon content and lower Cr and Mo (since these will still exist in the undissolved carbides). You can avoid this by either an normalizing treatment prior to hardening, or by austenitizing at 1700F and cooling to 1500F prior to quenching (assuming 0.35-0.45C).
RE: Sherodized annealed steel
Could you please suggest an appropriate cycle.
RE: Sherodized annealed steel
However, for a staring point, you can try heating to 1550F for one hour plus an extra hour per inch of thickness, oil quenching, and tempering for 1.5 times your hardening time at a suitable temperature for your desired hardness, followed by air cooling from tempering.
RE: Sherodized annealed steel
Maui
RE: Sherodized annealed steel
Cycle followed now is 1600 F -20 min- Mar quenching @ 240 -40 minutes.
Tried 1550 F -5 min-Mar quenching @ 240 -40 minutes, But did not find any improvement.
I will try cycles suggested by you & let you know.
RE: Sherodized annealed steel
Are you tempering once or twice? At what temperature, and for what length of time?
Why are you marquenching?
Maui
RE: Sherodized annealed steel
For smaller rings with less distortion potential, we quenched in conventional 150F oil
You did not mention the atmosphere conditions, i.e. dewpoint, carbon potential. Have you looked at a microstructure? Have you seen any evidence of decarburization, or the opposite, saturated carbon at the surface? Either condition can contribute to brittleness.