In another recent thread - Heat treat ovens - a question was raised about the TIME in getting the blade from the oven To the quench.
There is this misconception that this needs to be done in UNDER one second, or something like that.
Below is what I wrote on that thread, but thought it deserved its own thread so maybe those who didn't go there might see this one.
I hope it may as well, open up some dialogue that might allow for clearing up any other misconceptions, too.
"That facet of knife making is one of the most important, yet most misunderstood, parts of knife making there is.
This is why I and Lin repeatedly profess using the CORRECT quenching oil for knife making.
It's two in the morning here, so I hope this comes across right - it's NOT the time in getting TO the quench.
You could probably walk across the room if your blade is hot and thick enough. It'll hold the heat just fine.
The important factor is the SPEED of the OIL!!
To avoid what is called the PEARLITE NOSE, (which looks like a "nose" when drawn on a graph of time/temperature) once you have quenched the blade and the oil BEGINS extracting heat from the, say 1500 degree blade, the QUENCHANT needs to be able to extract the heat from the steel down to about 950-1000 degress in around 1 second!! But, of course, that is only for simple carbon steels like 1084/1095/W1/W2.
If the steel does NOT get below this temp, (950 in UNDER one second!) the steel will REVERT TO PEARLITE, and NOT make the transformation to MARTENSITE.
When using deep hardening steels like O1, L6, 5160 or 52100, because of the higher alloy content, this Pearlite nose is the same temperatures, but you will have about 4-5 seconds instead of one second to get the steel below 950.
So, you use a SLOWER oil!!
Get it? It's once the steel has BEGUN its radical downward decline in temperature, as a result of the quench, that it needs to CONTINUE in that direction to UNDER 950 in a few seconds, or it will revert to a condition OTHER than what you want.
It's the SPEED OF THE OIL not THE SPEED OF THE MAKER!
The relatively few degrees of temp you lose on the way from the heat source to the quench is UTTERLY IRRELEVANT.
I really hope a LOT of people on this forum read what I just wrote.
It was a really great question/topic and one that needed to be asked.
Maybe in the way it was asked, and in light of my answer, more guys will understand this basic aspect of making.
There is an EXTREME importance upon using the CORRECT QUENCHANT for the steel type being used. Goofy stuff like peanut oil and mineral oil and strange combinations of this and that, just do NOT have the correct additives to extract heat at the proper rate to avoid the Pearlite nose.
That's why so many new makers have such fits and failures in the beginning. Their oil doesn't get the heat out fast enough, and in all due honesty, the heat source itself is often insufficient as well. The combination of those two factors results in many, many failures and frustrations. In actual fact, the steel reverted to pearlite before the quenchant could get the heat out and FORCE the transformation to martensite.
Then, instead of blaming the heat and the oil, they blame TIME in getting to the quench as the problem.
Hardening a blade is a piece of cake if the maker will only be humble enough to admit he has an insufficient heat source and the wrong quenchant.
Good question!!"
Topic: Maybe this will help some folks (Read 608 times)
