52100 temper colors

[Coutel]

I crossed over to 52100 steel sometime ago...previously I was always using 10xx and 5160.

I have noticed that 52100 doesnt seem to want to stay in the mid to dark brown temper color very long, and it can easily be missed and go staight to a patchy purple color. I never had this problem with other steels.

..yet my testing on my blades shows that the purple (patchy) seems to be just the right hardness I want.

Has anyone else noticed this?

I was thinking that maybe its the alloys in the steel affecting the color?

[mete]

Tempering by color is not an exact science. The color is affected by condition of the surface , how clean etc and also the alloy .After all the 'color' is a layer of oxide ,nothing else.In addition tempering should be done in an oven and held at temperature for at least 1 hour. For 52100 and other higher carbon and the more complex steels I would double temper , two hours each time.

[Coutel]

Originally Posted by mete

Tempering by color is not an exact science. The color is affected by condition of the surface , how clean etc and also the alloy .After all the 'color' is a layer of oxide ,nothing else.In addition tempering should be done in an oven and held at temperature for at least 1 hour. For 52100 and other higher carbon and the more complex steels I would double temper , two hours each time.

Thanks.

The steel is ground and cleaned to shiny steel before tempering and triple tempered in an oven..2 hrs each.........or stops when the color changes as I explained.

[cactusforge]

I have found that the Brown color is very hard to nail, you need a very accurate temperature control and a oven with a steady heat, no spikes or dips. Gib