Tempering question

[Burton Harruff]

Morning all, I have a question. I fell asleep last night with knives in the oven on a tempering cycle. My wife came and woke me up after midnight and asked if the oven should still be on The steel is 1080/1084/15n20 damascus. I tempered at 400 degrees for what ended up being 4 hours. I usually do 2 cycles of 2 hours each at 400. Do I need to do another cycle or am I alright where they are now? Thanks for the help. -Burton

 

[Nathan the Machinist]

It is possible to temper too long, but I think you'll be fine. Four hours at 400 might give a similar effect as two hours at something like 425 (WAG). If you had let it go all night, that might be a problem.

Yes, you still need to do a second temper. The purpose of the second temper is to temper any new martensite that may have formed after cooling from the 1st temper. There shouldn't be much, but that is the purpose and the long temper probably won't change that much.

 

[Burton Harruff]

Thanks Nathan I wondered if I would have to do another cycle but wasn't for sure. I am glad my wife caught it because I probably would have slept all night