Quenching/ tempering

D

Drummer

Joined
Aug 20, 2000
Messages
141
I was searching through some old threads and read where somebody reccomended tempering the knife immediately after it had reached about 150 degrees F from the quench. I always let my blades sit in the quenching medium for 24 hours undisturbed before tempering, and have been pleased with the results.

Has anyone done any testing or had better results doing the tempering immediately as opposed to waiting? I had always heard that you didn't want to disturb the quench until the blade got down to room temp. Which way do you think is better?

Thanks,

David
 
Drummer,
There is a common sense saying, "if it ain't broke don't fix it". If you are pleased with the results and the steel is working as you intended it to, then you have the beast by the reigns. Steel doesn't know what it is and what it should be.
As a rule of thumb, tempering immediately is recommended. I have let a blade go months before tempering with no problems, others have cracked in a few hours before tempering. Today I temper immediately, but that is a result of such a large mix of personalized methods, reasons and trial and error that work for myself with my steel, temperatures, tools and skill or lack there of.
As far as disturbing the quench, that depends on what you want. If you move the blade around, it keeps an envelope of heat from forming around the piece. This effect is more noticeable with oil quench as opposed to water quench. Retaining that heat of course means a slower quench and a subsequently lower hardness. In some cases you must avoid this, in some cases you don't and in some it will make no difference at all.
Something to keep in mind, once a lot of carbon or low alloy steels used in knives drops within the 150°-ish range, most transformations are completed. Other steels like stainless must receive and addition drop in temperature (cryogenics) to continue or excel microstructural change if so desired.

Maybe that will help answer some questions.

-Jason
 
Drummer,

Epsilon is exactly right. IF IT AIN'T BROKE DON'T FIX IT.

To answer your other question. Ed Fowler has done many test in this area and has found that when using 52100 or 5160 steels that a twenty four hour interval between quench and tempering results in a blade that will cut significantly better than one tempered immediatly after hardening.
 
I think Bill and Jason have hit on the crux of the matter and that is if it works for you... you get the idea.

That said I'm curious what steel you are using. I let 5160 sit in the quench overnight between quenches when I'm using the triple normalize-triple quench-triple temper technique that works so well for 5160 and 52100.

Most straight carbon steels and low alloy steels are under severe internal strains after quenching and if left untempered can crack or break even if left sitting undisturbed. As mentioned already this may occur quickly or may take years. Steels like L6, from what I've read by those who know the nitty gritty of metallurgy, continue to form martensite after they are quenched making a speady temper a necessity to avoid warping and or cracking. These types of steels I get in the oven as quickly as possible for double or triple tempering cycles.

Interesting stuff, let us know what steel you are using.
 
Thanks for the comments guys. I use 1084 quenched in veggie oil at 140-150 F. Some of it that i've been using has a very small amount of chromium in it, according to spec sheet.

Next time around i'm going to temper the blade after it cools to about to the temp of the quench and see if I can notice any performance differences.

The reason i've been leaving it in the quench is because, to a point anyway, moving the blade while its still cooling can create uneveness in the hardness, or so i've been told. I also heard of some people getting better performance on low-alloy blades when leaving them sit in the quench over night. I wanted to see what your experiences were.

Thanks again,

David
 
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