Time between heattreat and temper?

C

canyonman

Joined
Jul 22, 2001
Messages
12
Can someone please explain to me how much time can pass between the HT and the Temper? What happens if you exceed that amount of time?
Thank-you in advance
Larry
 
First get your terms correct ." Heat treat" includes all the hardening and tempering steps. Then you are asking how long between hardening and tempering. When you harden you are forming martensite which in the untempered state is very brittle and unstable. I have seen martensite crack when not tempered immediately.So temper immediately after hardening, with a minimum of 400F ,and temper at least 1 hour . Tempering "to color" is not satisfactory.
 
Larry you will find people HT and Temper so may different ways till it will make your head spin. I just went down this road
myself. I bought a HT over and got all kind of different viewpoints how to HT 440C.But anyway I was told after the hardeing to put them back in for the temper while they are still hot. I do not understand what mete is talking about the mimimum of 400F hope he will explain.All the data I see on 440C. Here is a example of how I HT 440C. Bring over up to 1880 put blades and springs in for 15 minutes.Take out air quench fast.When I can handle the blades they are still pretty warm I put the blades in a Toaster over at 225 for 2 hours. I let the Big oven come down to 1100 degrees and put the
springs in for 1 hour. I was so confused I called makers like Wally Watts and AT Barr when I started but my knives have been coming out fine.Goodluck !
 
Thats a loaded question. Lots of varibles. Type of steel. Type of quenchant and others play a big part in temper time versus after quench. Example, if your quenching a 10 serie steel in water with a interrupted quench you better have your oven heated up and relieve some stress pretty quick. That holds true with some oils too, but theres some quench oils that will cool slow enough that you get good hardening without a great deal of stress, of course that depends on the steel make up also.
Another example, I can quench 52100 in my quench oil,edge quench and then totally submerge and not worry about it until the next day. Then do it again. So sense we all do things differently in each and every shop, you need to work out your times for your procedures.
As for draw temps that also depends on quenchant and steel. I was quenching in ATF for years and in order to get some steels to pass the brass rod test I would have to draw 20 - 40 degrees higher then with this quench oil I use now, some will say I'm not getting the hardness with this oil that I was getting with ATF and this could be possibly true, I think I'm getting the hardness but not the stress. But after drawing at a lower temp the blades will out perform any ATF quenched blade, in my shop anyway.

Good luck,

Bill
 
Thank-you for the quick replies, yes I should have mentioned the type of steel, it's carbon steel, not stainless, 1095 in particular. I'm using a torch to normalize and harden and quench in Hydralic Fluid warmed to 120 degrees.
So if I understand, as long as I'm not getting any stress cracks and the blade is harder than a file, I'm close to on my way? Or is there the possibility that there are very small stress cracks, that don't become apparent, until a most in-appropriate time?
 
Heatride, you can get info on the proper heat treating of the steel you use from the steel maker or supplier. First you should quench down to the temperature where transformation to martensite is complete. Second significant tempering of martensite starts at 400F. I can't see that anything happens at 225F. Those that wait till the next day to temper are getting away with it, like those that temper to color.They are not using proper heat treating procedures.
 
Originally posted by heatride
Larry you will find people HT and Temper so may different ways till it will make your head spin. I just went down this road
myself. I bought a HT over and got all kind of different viewpoints how to HT 440C.But anyway I was told after the hardeing to put them back in for the temper while they are still hot. I do not understand what mete is talking about the mimimum of 400F hope he will explain.All the data I see on 440C. Here is a example of how I HT 440C. Bring over up to 1880 put blades and springs in for 15 minutes.Take out air quench fast.When I can handle the blades they are still pretty warm I put the blades in a Toaster over at 225 for 2 hours. I let the Big oven come down to 1100 degrees and put the
springs in for 1 hour. I was so confused I called makers like Wally Watts and AT Barr when I started but my knives have been coming out fine.Goodluck !
Click to expand...


http://www.admiralsteel.com/reference/sstltech.html

:eek: :eek:
 
mete, I'd say heatride is holding his steel at temp. while the oven is cooling to the temper range he wants. Therefore the 225 F.

RL
 
Guys, heatride is using what is called a PQSR (Post Quench Stress Relief). Whether intentional or not in that effect, it works perfect for his situation. Its an effective way to simply avoid cracking, before the primary tempering procedures that otherwise, cannot be performed right away. I use it all the time. :cool:
 
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