Thread: Temper Colors?

I've just hardened and tempered a new file razor, but I'm concerned & confused about the color of the steel after tempering.
The blade was in the toaster oven for 2 x 1 hour cycles at around 395-400 F.
I was expecting a straw/yellow color, but there is definitely shades of blue/purple in there.
It never went over 400F during the tempering. It is however an unknown steel.
It was an old Wilthshire file.
Can anybody shed any light on the coulors here, have I over cooked it?







Thanks
Grant

I think you found something important about toaster ovens. They don't have the finest control around a set point.

I see some of the right sort of bronzish in there. Other color oxides appear depending on cleaning chemicals if you wiped down the blade.

Does it still skate a file?

I hate to admit it but the file does seem to be scratching more than it should.
I dont think my temperature was out though. The dial on the toaster oven and the extra thermometer thats in the above picture both said 200 deg C.
Can some steels blue turn at lower temperatures, and if so does the colour still represent the hardness in the same way?

I just went and rubbed this razor and an old broken Fredrick Reynolds razor on a good file and a worn one also.
It's a hard thing to judge, but they seemed similar in hardness.
Obvoiusly If I need to re harden and temper it I will have to do it before grinding.
Wish I had a hardness tester.
I did clean it with dish washing liquid and a scouring pad before putting it in the oven wrapped in foil. Dont know if that would make any difference.
Maybe I should just re do the whole process and temper at a little lower temp.
At least if its too hard to hone after grinding I can always put it back in the oven until I get it right.
Grant

I'm no expert, but I'd say that it probably needs to be re-hardened. In my limited metallurgical experiences, I've heard that the blue shade usually represents the steel having been spring tempered and will probably be too soft to hold a razor's edge.

Originally Posted by Mike Blue

I think you found something important about toaster ovens. They don't have the finest control around a set point.

What Mike said.

Additionally, the positioning of the heating element is also very important. It looks as if the edge was closest to the heating element, and the spine furthest away.

Originally Posted by baldy

I did clean it with dish washing liquid and a scouring pad before putting it in the oven wrapped in foil. Dont know if that would make any difference.

Not really. You're seeing the effects of heat.

Yep, as expected you guys were right.
I figured out the problem though, so thats the main thing.
Just a stupid novice mistake.
I left a tray in the oven with the razor sitting on that, while the thermometer was hanging from that shelf.
The tray essentially made 2 sections to the oven, with the razor in the top section and the thermometer in the bottom. Giving me a false reading



I just turned everything back on just like last night, and the thermometer sat on 400F, I then moved it up to the top shelf where the razor was sitting last night, and sure enough it began to climb. So obviously the top is much hotter than the bottom section.
So when the kids go to bed tonight I'll be firing up the forge again and repeating the whole process. Tempering on a wire rack with the thermometer sitting right next to the blade, like I successfully did it last time.
Would you guys recommend going back to the start of my routine, which is 3 thermal cycles to normalize before the quench?

Thanks guys
Grant

Although i dont have anything to add here with regard to metalurgy, I just wanted to tell you how much i like your razor here.
Great shape Grant !
I started a file razor well over a year ago and kinda dropped it so I'm really interested in how this gets done.
Thanks for posting.
Mike

Good show Grant, I look forward to seeing it finished. That point would scare the crap out of me after I tried to take my ear off the other day with a simple spike! It shows that you took your time on it.