Advice for tempering steel

[Cark]

I'm pretty new to knife-making, have only made about 2-3. Well, I've got a blade that's 1080 that I forged, hardened, and tempered. Problem is, I was a big dummy and when I was researching the temperatures required for tempering I was looking at them in Celcius. I ended up tempering my blade at only 250 F. I did 2 two hour cycles. Problem number 2 is that this was about a year ago, I haven't had the time until recently to get back into it. Blade shows no cracks or anything concerning, would I be okay re-tempering the blade at a proper temp? Or would I need to normalize, and re-harden? Or is it a lost cause altogether? Thanks in advance for any words of wisdom

 

[scdub]

Hello and welcome to the forum!

I’m not an expert but I have some thoughts.

First off, the fact that a couple of years has passed shouldn’t matter - the crystalline composition of the steel won’t have changed.

Secondly, I don’t think that a 250F temper will have softened the steel much if at all.

Personally, I’d go ahead and re-run the tempering cycles at the proper temperature. I might cut down the time slightly if I wanted to err on the side of a harder edge, knowing that I could re-temper again to further reduce hardness.

Good luck and please let us know how it goes.

 

[me2]

For that steel and that temperature just temper again at the desired temperature. I’d say 350-400 F should do it.

 

[Stacy E. Apelt - Bladesmith]

Agreed, re-temper at 400°F for at least an hour. No need for a second temper cycle after that.

My guess on the first hardening a year ago is it was not fully hardened. Most likely not the right temperature at the quench and not enough or the right type quenchant. That is why it hasn't been chipping or broken.