Quenching temperature?

[stabman]

Wondering for when quenching, does it really matter that much what temperature the oil is?
I recall something about heating the oil for optimal results, but I'm wondering if I'm forging 1070 steel with the ambient temperature being 31 degrees Celcius, would it cause any issues?
Just a dumb noob question.

 

[Stacy E. Apelt - Bladesmith]

Quenching ( for knife making purposes) is a process of bringing the steel down to the martensitic start range. For simple steels, that means getting lower than 900 in about one second. The things that happen in the quench medium ( oil) are how that happens. If the oil boils too much, or the vapor jacket stays too long, or the oil is too viscous.....these things will slow down the process.
Now, when the vapor jacket collapses, and the steel starts cooling rapidly, the opposite needs to occur. The cooling rate needs to slow down a bit.

All this happens by choosing the right oil for the job....and having it at the right temperature to do the job.

For 90% of the oils we use 130F/55C is a good temp to use. Too cold and things don't start fast enough, too hot and they don't go right.

 

[Nathan the Machinist]

Stacy is, as usual, spot on. But just for clarification I'll add: Oil that is too cold quenches slower because it is thick, reducing circulation.

 

[stabman]

Cool.
I'll see how it goes tomorrow.