CPM 3V stress relief decarb

Robber58

Robber58

Joined
Oct 9, 2008
Messages
478
I am getting ready to make some hard use blades from CPM 3V. Over the last few years, I have developed a habit of stress relieving all of my blanks before grinding by soaking at 1200 F for a couple of hours and furnace cooling. That process has reduced the amount of warping I get during heat treat with material that I had to straighten before use (most of it lately). I have almost exclusively used stainless alloys such as ATS 34, CPM 154, CPM S30V and have not bothered to protect the blanks with foil. At 1200 F they come out clean and ready to go. I did a small piece of A2 recently and it came out with a lot of decarb. Can I expect the CPM 3V with its low chromium content to decarb at 1200 F like the A2? I would like to know because it will affect my sequence for cleaning the blanks.

I can run a test on a small sample to find the answer but I am hoping someone can give me the benefit of their experience to save some time and power cost. I will appreciate any insights.

Thanks,
Randy
 
Heating your steel before HT, at 1200 F is fine for minimizing warping .
However at 1200 F, which is below the critical , there will be very little scale forming and there should be NO decarburization. Are you confusing scale with decarburization ?
I' f you are HT'ing stainless without foil you will certainly get high amounts of scale and decarburization and a very poor blade .
 
when i was doing my 3v tempers at 1000f i was foil wrapping to keep them nice and clean and i would do that also to any steel at 1200f (but hey thats just me )
it is another reason that i have changed my HT of 3v to the lower tempering temp
 
mete said:
I' f you are HT'ing stainless without foil you will certainly get high amounts of scale and decarburization and a very poor blade .
Click to expand...

Robert, if you leave a lot of "sacrificial steel" and grind down good you will be fine.
- Mitch

YES, foil is the best way. I'm just saying that there's ways around not using it and still getting a great blade.
 
Last edited:
yep i jsut hate grinding away was could have been good steel (or leaving thick and then having more post HT steel to remover to clean up
for me its clean in and clean out tho if you are just doing this to barstock then the loss would be minimal
 
I am not sue I did a good job stating my question. I always use foil for austenizing. I have not used foil for the stress relief at 1200 F on the stainless and have always had a clean surface after. I got concerned about the 3V when I did a 1200 F stress relief on a piece of A2 and had fairly significant coating of what I believe to be decarb, not scale. It took a lot of grinding on an already thin piece to get back to sound metal. Since the 3V has relatively low chromium, I have guessed that I will have some decarb at 1200 F based solely on my experience with the A2. I will just run a test each way to see what happens.
Thanks for your inputs all.
Randy
 
You're confusing decarb and scale .Scale [iron oxide ] is a coating and easily seen. Decarb is IN the steel and not easily seen . There is little scale or decarb at 1200 F .A thin layer of oxide [like temper colors] is all you expect from 1100-1200 F and less with stainless. This is why much of preheat preheat is done at 1200 F.

Once you get above critical temperature then things start to happen . Both scale and decarb form and become problems. Decarb must be removed by grinding down into the steel. To prevent decarb and scale we protect the steel with vacuum or inert gas or anti-oxidant coatings or foil.
 
I accept your view about what I have seen. What I do know is that when I did a 1200 degree soak with the A2 I had a black coating that had to be ground off, scale it is. I have never seen that on the stainless, only the light coloring from oxides you mentioned. I did not expect the coating so I double checked my furnace temps and all was as it should be. That one event is the basis for my question.
Randy
 
over 1000f any steel i have put in the kiln gets black (ok not sure on SS cause i never temper that hot ) i also have never done any of the pre work stress relief
 
You must log in or register to reply here.
Back
Top