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Heat treating annealed 1095 spring steel -- recommendations wanted

W_Higgins

Hot Rolled
Joined
Mar 13, 2009
Location
Realville, Penna.
I've searched my books and the forum for heat treating annealed 1095 spring steel and have come up empty. There is a little bit on the blade forums, but it involves a lot of voo doo with no standards.

My pieces are strips 1/2" wide, 2-3/4" long, and 0.032 in. thick and I have an oven. Does anybody know a proven process for this?


Thanks!


-Walter
 
Hi Walter, This is what I did on some springs I made out of 1095.
1. anneal @ 1400 in a closed pipe full of ashes. I had done some hot forming and just wanted to even out the grain. The ashes/closed pipe was to minimize decarb. I let them come up with the oven and shut it off and left them in over night to cool.
2. preheat oven to 1500 with a small piece of 1/2" plate. The 10 minute was to minimize decarb, the 1/2' plate I grabbed with a tong and used to dump the in the quench
3. set the springs (mine were .062 x .5) on the plate, gave them 10 minutes. 10 minute was to minimize decarb, the 1/2 plate I grabbed with a tong and used to dump them in the quench. Plate to help hold heat between oven and quench
4. quenched in 100 degree oil, I used some DTE 25 drained from a tool spindle at work.
5. tempered at 780, let the springs come up with the oven, shut it off and let them come down with it.
This was hotter tempering than I anticipated, I tried several steps about 20 degrees apart trying to get the tension down. I think the original springs were probably lower in carbon, maybe 1070
I am not a professional at this but it works for me. It may be more complicated than necessary but did the job.
 
Thanks Ray. I found a very economical copy on Abe Books and it is already on its way.

Thanks also to Kootne. I will weigh your procedure against what is in the book. I like your bit about the 1/2" plate because one of my concerns was the rapid cooling of such a thin piece.

If I can remember to do so, I'll report back with the results once I finally get it sorted out.
 
If you found an economical copy of that book you won the lottery for the year. I have been looking for quite some time and the used copies I have found are listed for more than the new copies on Amazon.

I would find the difference in the recommendation between 1095 and W1 interesting. I expect the difficult part of heat treating a thin piece such as yours is preventing decarb in the heating cycle. .005/side is a significant part of the total thickness, and is on the highest stressed surface. It will be interesting to hear your methods and results.
 
I think I've had pretty good success with this. Since the parts are thin and the and heat time short, I didn't bother wrapping in stainless.

Preheat oven to 1,500F (oven is small and loses heat fast when door is open).

Set spring on heavy stainless plate, put in oven, and dial back to 1,475F.

From that point, cooked for 15 minutes including time for oven to come back up (about three minutes).

Pull plate and spring together, tilt the plate, and let it fall into the quench oil.

I let the oven cool back down on its own, then put the plate back into the oven with a heavy steel slug I had laying around to slow down the cool time of my little oven.

To temper, put the spring back in the cold oven, let it come up to 800F with the oven, soak for 30 minutes, then shut off oven and left everything overnight.

I tried a few variations on that. Cooking for ten minutes left the end product a little softer than I wanted. Cooking it for 20 made it extremely brittle prior to tempering such that my Rockwell tester shattered it. I tried a slower temper cool-down and that also made the end product much softer.

These numbers aren't quite right, but will give you some sense of the process. I just left my usual C-scale diamond in the Rockwell tester and I also don't have the right one for thin material.

In annealed form, it measured -25Rc, after 1,475 heat-and-quench it registered 35Rc, and after tempering about 30Rc. To contrast that with what five minutes +/- will do (without tempering), it was about 15Rc after ten minutes. After 20 minutes I couldn't even check it without the part shattering.

At any rate, I'm going to put the spring in service and see what happens. I think it's tough enough to handle the wear it will see and deflection is minimal, so I expect it to run a good long time given some of the torture I put my test pieces through.

If I can remember, after the spring has been in service for awhile I will report back with the results. It's a simple ignition component for a timer opened by a two-lobed cam.
 
If you found an economical copy of that book you won the lottery for the year. I have been looking for quite some time and the used copies I have found are listed for more than the new copies on Amazon.

The first one I bought and bitched about the price for years. The second one I got for free so I consider it a wash. :)
 
You should NEVER hardness test a piece of steel that can be expected to be full hard before tempering. Locked in stresses can cause the part to shatter with the penetration of the braile. When properly quenched, a 1095 steel will be full hard.

As for properly hardness testing your spring after tempering, a Rockwell N (superficial) hardness would be appropriate. This uses your existing C scale braile, but you remove some of the weight from the lever arm. How much weight you remove depends on which superficial scale you wish to use.
 
Point taken on the hardness testing bit. I didn't know what the expectation should have been as I still couldn't find much to go on with thin material. Nevertheless, for such things I always wear safety glasses regardless because you never know when an issue can arise, such as this.

Check Abe Books for a copy of that Heat Treater's Guide. Amazon has a lot of unrealistically priced books like that for some reason. I paid about $60 bucks for this one. It's a 30 year old copy, but in near perfect condition. Newer versions probably have some updated stuff, but that kind of information doesn't change much and it's fine for my occasional use here.
 
Slave's blood is the only proper quenchant :D

Personally i have had better luck with fresh - still warm from the teat Unicron milk.

IMHO a lot of the sucess in heat treating small parts is fast heat and quench times, small bits lose heat fast and gain it fast, being thin they can also lose carbon real fast if soaked for too long. Am not a fan of soaking in a case hardening type ash compound either, seen it cause issues - springs to then crack in use due to the increased surface carbon. Just foil wrap with a bit of paper to create a pretty inert atmosphere, no need to bury them in a potentially carbon rich material.

99% of heat treat is in the temper though, not the initial hardening.
 








 
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