hypothetical heat treating question

[Nebulae]

So If I wanted to heat treat this steel (it doesn't matter what steel it is this is just a decent picture to illustrate my point) to a final hardness of 62 you can see I have several options. I can austenize at a higher temp & temper higher, or I could Austenize lower and temper lower.
Austenizing higher should dissolve the carbides more, and tempering higher would mean more stress relief, but the higher temp may promote grain growth, or other maladies. Which one is better? specifically which one would yield better toughness?


[edit]: dont look at this picture, I screwed up. this is the closest thing I can find to what I am trying to describe, but I didn't read carefully enough

 

[mete]

You have to look at the properties of the individual steel. The steel shown obviously has good amounts of elements like Mo, V, W because of the secondary hardening.
While higher hardening temperatures dissolve more carbides there is a trade off as it will give larger amounts of retained austenite .That would require cryo for the lower tempering temperature.High tempering temperatures should yield higher toughness.
However if the information is gotten from typical 1" samples it may be different for knives .Of course the whole HT procedure depends also on the application and your personal choices..

 

[Nebulae]

oh shoot I got the wrong picture those are all different steels:foot:

well the line with the red circle should be some steel say 1095 austenize at 1600 F the black circle should be 1095 at 1550 F the triangle should be 1095 at1500, square 1450 F etc. as you can guess I made these numbers up, but just humor me

sorry mete

 

[mete]

http://www.titussteel.com/dc53.htm

Here's the whole story on DC53 steel. It's similar to CPM3V.

Now you've changed the story sustantially !! 1095 has more chance of grain growth than DC53 .1095 doesn't have secondary hardening !! Now do you see we have to discuss a particular steel ?

 

[Dmitry.M]

Just my 2 cents. The HT for the knife or long blade could be quite different from the datasheet...
I was tought to heat to the upper limit and than temper to desirable hardness\toughness. But as Mete said, it's a traidoff. It is always a traidoff.

 

[Nebulae]

yeah sorry about the picture I had one picked out but it was in a pdf, so I couldn't link it here and this one is blurry, and it looked the same... oh well. what I am trying to say is forget what steel it is just in general what's the difference. or is it completely specific to each steel? I am coming to think it must be


edited to add secondary hardening would make a huge difference, because obviously you would want to temper at the temp that yields the best secondary hardening, and then adjust the austenizing temp to get toughness, or at least put as much priority on obtaining the secondary hardening benefits as on the austenizing I had not realy though about that!

edited again. Oh Crap! my question only makes since if there is secondary hardening, in which case there would be very little doubt what to do. jeese I feel like an idiot! its even worse, because i understood, and resolved it myself. Well mostly, thanks mete, I had completely forgotten about secondary hardening, as an actual reason, not only for the shape of the graph, but for the selection of tempering temperature.

sorry about this