2 step quench ???

[Bo T]

I've just read a recent post about the best quench medium for 1095. A member on that thread mentioned salts and I think it was in regard to avoiding the pearlite nose. So quenching to 600 degrees F using a quick medium then finishing up with a slower medium to room temperature to avoid microcracking seems to be a better strategy than a rapid cool to room temperature.

What are the techniques used to do this? Would rapidly pressing the blade between 2 larger metal plates at 500 degrees F work?

 

[mete]

Commercial quenchants are designed to cool rapidly to get past the pearlite nose then slower below that . There's also marquenching - quenching to the Ms temperature [better done in salt] then it can be air cooled from there.
If you have a problem with warping you could ,once past the pearlite nose , examine and straighten in the time it takes to get below the Ms. In that area it's still austenite which is fairly soft.

 

[Bo T]

Thanks. I searched marquenching and got a lot of the information that I was looking for. It appears that a low temperature salt bath is not that useful for the types of steel I am interested in at this time. I also read about high temperature oils that would get the steel below the pearlite nose but above martensitic start temperature although at the temperatures used tend to be somewhat dangerous.

So would pressing the knife between two copper plates at or a little above Ms conduct the heat out of 1095 steel rapidly enough?

 

[me2]

Plate quenching at room temperature is just a step below open air quenching. Quenching between 2 heated plates would be slower. If the heated salt or oil baths cool too slowly to miss the pearlite region, then the heated plates will be slower still.

 

[Bo T]

Plate quenching at room temperature is just a step below open air quenching. Quenching between 2 heated plates would be slower. If the heated salt or oil baths cool too slowly to miss the pearlite region, then the heated plates will be slower still.

So then an interrupted quench after a set time to a temperature below the pearlite nose but above Ms, followed by placing the blade in an oven just above Ms to equalize, followed by gradual cooling to below Mf seems to be the best strategy??

 

[mete]

Once you get below the pearlite nose you can air cool if you like .Large complex shapes need equalizing normally in salt .Blades are thin enough not to need anything complex.

 

[Bo T]

Thanks again. This really helps with my understanding of the TTT diagrams and their application towards optimizing the quenching process.