I know that supposedly multiple tempers in the oven can make grain structure finer (am I right?) Also am I right that doing multiple quenches with cooling down to room temp in between can also tighten the grain? Anyways what does each of the above statements have for an advantage over each other? Is it better to do multiple quenches or single quench and multiple tempers or both? The last knife I built I did 2 quenches just because I felt that while doing the file test after the first quench the test was a little shaky so I redid the heat and quench process to assure I got it right for proper hardness. Then I followed by my standard single 1 hour temper in the oven. And in the back of my head I am wondering if I didn't inadvertantly do myself and my knife a favor by doing that.
-
The BladeForums.com 2024 Traditional Knife is ready to order! See this thread for details: https://www.bladeforums.com/threads/bladeforums-2024-traditional-knife.2003187/
Price is$300$250 ea (shipped within CONUS). If you live outside the US, I will contact you after your order for extra shipping charges.
Order here: https://www.bladeforums.com/help/2024-traditional/ - Order as many as you like, we have plenty.
advanced heat treat questions
- Thread starter cory
- Start date
- Joined
- Jul 21, 2001
- Messages
- 2,869
Cory: You can evaluate everything you do by experimenting in your shop. You don't have to take anyone's word for it. The knife is very easy to test. You have everything you need right in your shop. A steel rod to test for chip, rope to test for cut and a vice to flex blades. If you don't have my book, or get Wayne's book and read about testing. This is the only way you will know for sure when it comes to your steel and your methods.
DaQo'tah Forge
Banned
- Joined
- Aug 26, 2002
- Messages
- 1,333
Hi this is DaQo'tah
and this is a Question dealing with this topic and 52100 steel.
In Ed Fowler's Book "KNIFE TALK" there is a photo of a blade that has been etched to show us the temper lines. The photos shows that sometimes the heat treating can get messed up, and that the temper lines can run down too close to the sharp edge...
so..okay,,,how would a guy fix this knife?
What steps could you do to a messed up temper line before you put the handle on?
if you have done a 3 time heat treating, then a 3 time tempering in a oven,,,can you just fix the knife with just one more heat treating,then one more oven tempering, then etch it again Fixed!...?
or
do you need to start all over and do 3 new heat treatings, then 3 more temperings on the 52100 steel?
and this is a Question dealing with this topic and 52100 steel.
In Ed Fowler's Book "KNIFE TALK" there is a photo of a blade that has been etched to show us the temper lines. The photos shows that sometimes the heat treating can get messed up, and that the temper lines can run down too close to the sharp edge...
so..okay,,,how would a guy fix this knife?
What steps could you do to a messed up temper line before you put the handle on?
if you have done a 3 time heat treating, then a 3 time tempering in a oven,,,can you just fix the knife with just one more heat treating,then one more oven tempering, then etch it again Fixed!...?
or
do you need to start all over and do 3 new heat treatings, then 3 more temperings on the 52100 steel?
- Joined
- Jul 21, 2001
- Messages
- 2,869
Back in the days when I was using ball bearings, it was too much to go back to fix after the third heat. Too many variables came from the ball bearings from different times and places. I tried to figure it out, and at times had lots of answers, at one time went up to over 11 heats. But results made no sense due to inconsistent steel. I simply used the blades with mistakes for testing or discarded them.
3 is deffinately a number of high influence with 52100 and 5160. You would think that multibles of 3 would remain significant, but on one batch 7 really worked actually as good as 3, almost.
Remember, the martensite cone inside of the blade will extend further (higher) than the temper line. Also the matrix of each zone is influenced by the adjacient composition. this is probably the most significant variable we have to explore, both the chemistry and structure enjoy a recipical influence. It gets kind of complicated but as soon as the science is abvailable to evaluate what I beleive happens, fasten your seat belts!
Today the question could be answered with Rex's steel. I believe a fourth heat would result in a blade with slightly diminished cutting ability and possibly a change in toughness. I haven't messed up a blade for a long time, but when I do I will experiment, then I will know.
3 is deffinately a number of high influence with 52100 and 5160. You would think that multibles of 3 would remain significant, but on one batch 7 really worked actually as good as 3, almost.
Remember, the martensite cone inside of the blade will extend further (higher) than the temper line. Also the matrix of each zone is influenced by the adjacient composition. this is probably the most significant variable we have to explore, both the chemistry and structure enjoy a recipical influence. It gets kind of complicated but as soon as the science is abvailable to evaluate what I beleive happens, fasten your seat belts!
Today the question could be answered with Rex's steel. I believe a fourth heat would result in a blade with slightly diminished cutting ability and possibly a change in toughness. I haven't messed up a blade for a long time, but when I do I will experiment, then I will know.
- Joined
- Oct 16, 2001
- Messages
- 1,917
Cory,
Good questions. And thanks to Ed for taking his valuable time to participate here.
As to your question about multiple tempers (as opposed to multiple quenches), these are a good thing. They do not, however, refine grain size. That will be done in your forging, normalizing, and quenching (and sometimes annealing). When you harden a blade you have gone from austenite to martensite. This leaves you with two "problems"--untempered martensite, which is brittle, and retained austenite. When you temper once, you not only temper martensite, but also covert some of the retained austenite into new, untemplered (read brittle) martensite. When you temper a second time, the same thing occurs. It seems a third time is both good and sufficient both to transform the great majority of retained austenite and to temper most all of the martensite.
I don't know why 3 is such a magic number when working with steel, but it seems to be the optimum number for many different heat treating operations (normalizing/thermal cycling and tempering almost all high carbon steels, and hardening such steels as 52100 and 5160).
Good luck,
John
Good questions. And thanks to Ed for taking his valuable time to participate here.
As to your question about multiple tempers (as opposed to multiple quenches), these are a good thing. They do not, however, refine grain size. That will be done in your forging, normalizing, and quenching (and sometimes annealing). When you harden a blade you have gone from austenite to martensite. This leaves you with two "problems"--untempered martensite, which is brittle, and retained austenite. When you temper once, you not only temper martensite, but also covert some of the retained austenite into new, untemplered (read brittle) martensite. When you temper a second time, the same thing occurs. It seems a third time is both good and sufficient both to transform the great majority of retained austenite and to temper most all of the martensite.
I don't know why 3 is such a magic number when working with steel, but it seems to be the optimum number for many different heat treating operations (normalizing/thermal cycling and tempering almost all high carbon steels, and hardening such steels as 52100 and 5160).
Good luck,
John
I can say that the best (I think) edge rententive blade I have done so far was double quenched. I did not set out to do so but, like you, I doubted my first austinization and after grinding off the de-carb decided to austinitize again.
I have not tryed double heating since but often wonder about it.
As for tempering; I like to 'snap temper' followed by three tempers.
Roger
I have not tryed double heating since but often wonder about it.
As for tempering; I like to 'snap temper' followed by three tempers.
Roger