Slow cool, or quick cool when tempering

T

Tom Lewis

Well-Known Member
I have heard this discussed before, but wanted to get some more input. When tempering, is it best to let the blade cool off slowly as the oven cools off, or is it better to take it out of the oven and quench it in say, water. Or, does it make any difference.
 
it was recommended to me to quench in cold water between tempers and quench in cold water after last temper. i have made that part of my process and have had good results. i also use the quench in water as a good time to clean off scale and oil.
 
Tom, out of curiosity, what negative effects have you been told could result from quenching? It is correct that it makes no difference (with the small possibility of benefits to quenching) but I am always curious to know the explanations to any popular ideas in the knifemaking field, it helps me better address misinformation and at the very least can have entertainment value.
 
Kevin, I don't know that I have been told any negative effects that would come from quenching. I have heard some say to do it, and others that it is not needed. I just wanted to get more information on which way was best. Thanks for the information.
 
wow, this thread could possibly save someone a whole lotta tempering time. I can't image cooking something for 2 hours, letting it cool for and hour, cooking it for 2 hours, letting it cool for an hour before I can work on it again. That's a whole days worth of letting it sit. I dunk it every time, dry it and stick it right back in.
 
N.N said:
wow, this thread could possibly save someone a whole lotta tempering time. I can't image cooking something for 2 hours, letting it cool for and hour, cooking it for 2 hours, letting it cool for an hour before I can work on it again. That's a whole days worth of letting it sit. I dunk it every time, dry it and stick it right back in.
Click to expand...
That is exactly what I did when I first started making and heat treating knives.....quench them in water between tempering cycles. Why? Time!!!
 
There was some discussion that quick cooling (water quenching) after tempering could improve toughness for blades used in cold conditions. I'm pretty sure it was a general statement in the following context. It might help some steels in some applications, it won't hurt other steels, and it saves a lot of time, so go ahead and quickly cool your blades after tempering.
 
N.N said:
wow, this thread could possibly save someone a whole lotta tempering time. I can't image cooking something for 2 hours, letting it cool for and hour, cooking it for 2 hours, letting it cool for an hour before I can work on it again. That's a whole days worth of letting it sit. I dunk it every time, dry it and stick it right back in.
Click to expand...
hi,
another thing to consider is that 2 one hour tempers is usually all you need for thin(1/8" or less) carbon steels. that would cut your time in half again.
 
Last edited:
There are three possible issues that could be affected by quenching- TE, TME and RA. TE, or "Tempering Embrittlement" occurs in richer alloy steels at much higher tempering temperatures, higher than say 650F. In these alloys the slow cooling from these temperatures will allow precipitation of embrittling phases, quenching avoids this by cooling at a rate which exceeds the precipitation. TME, or "Tempered Martensite Embrittlement" can occur in simple alloys that have certain elements (like Mn or Mo) in the range from 450F to 550F, and is the result of inter-lathe or inter-plate precipitates, for the most part just heating to this range can cause it but quenching, rather than slow cooling, may limit it. RA, or retained austenite, if you have it, will begin to destabilize at temperatures exceeding 400F, since you already have it on the matt quenching is an excellent way of finishing it off. All of these effects will be very slight at best if your initial heat treatment was good, but the time savings is so great that why not go for it and if there is a little gain that is even better. Either way it isn't hurting anything.
 
I always wondered about the warnings to never quench after tempering. I read them jn a couple ofknifemaking books. It made me wonder why such a moderate quench would crack something that just survived much greater temperature swings, rapid cooling, and at least one phase change.
 
i just bought my oven, this thread probably saved me a lot of heartache :D
but i', about to start learning HTing so i'll have abundance of that anyway lol
 
RA, or retained austenite, if you have it, will begin to destabilize at temperatures exceeding 400F, since you already have it on the matt quenching is an excellent way of finishing it off.
Click to expand...
This was the reasoning I was given for possible benefits for a post-temper quench, and the reason I do it (other than the time factor).
 
You must log in or register to reply here.
Back
Top