Blue Color during tempering

[Inthewind]

I did a two hour temper at 450 (1080 high carbon) and it came out with this blueish color. Did i ruin the heat treatment? Is there a way to fix it? Should i just start over?

 

[Stacy E. Apelt - Bladesmith]

The colors on the blade after temper are caused by the oils and such on the blade, and usually have nothing to do with the actual temper. If you are worried, test the edge with a brass rod to see if it flexes or rolls.




Moved to the proper forum- Shop Talk.
Around the Grinder is for non-knife chit chat.

 

[Mudbug007]

Did you sand the blade before tempering? I sand down to bare metal in a few places on the blade before tempering. It's not unusual to have different colors on the blade due to oils and scale, but the areas I sanded bare is where I check my color. Straw color is what I'm looking for in those places.

 

[Leethal Cutlery]

Did you sand the blade before tempering? I sand down to bare metal in a few places on the blade before tempering. It's not unusual to have different colors on the blade due to oils and scale, but the areas I sanded bare is where I check my color. Straw color is what I'm looking for in those places.

+1 After I quench I hit the blade up on the KMG to get clean metal so I can see the steel easily when tempering.

 

[Don Hanson III]

When you heat steel its changes color...

 

[Inthewind]

Did you sand the blade before tempering?

No, after i quenched it i cleaned it up with a wire wheel on my 4 inch grinder but that was it.

 

[Justin King]

If you didn't clean it with solvent before taking it to the wire wheel then the blade was probably still contaminated with quench oil residue when you put it in the oven. The wire wheel is now contaminated also, as well as any blade you use it on in the near future. Oil will make blue oxide at 400 degrees or less, which throws any useful judgements from the color out the window.
I don't put much faith in oxide colors as temperature indicators, but if you are going to I suggest cleaning the blade thoroughly with solvent as well as sanding, immediately before doing the temper.