How do you avoid scaling when using an oven for hardening springs and frizzens?

[Rolf]

I have paragon oven. I can harden springs and frizzens with it, but I get a ton of scaling.
I have tried dipping the parts in Brownell's antiscaling liquid, but that seems to leave the parts softer after quenching in oil.

At moment, I get the best results using an oxy/acetylen torch for hardening and using the oven only for annealing.

How do you harden in a oven?

Best regards

Rolf

[smart dog]

Hi Rolf,
I believe anything that prevents the part from being exposed to O2 will do the trick.  Packing in charcoal like case hardening would likely help although you will change the carbon content of the surface of the steel part. I have an oven but when I harden springs I just use my oxy/acetylene torch with the O2 set low to heat the spring red hot.  I usually quench in brine but some maker's springs, like Chambers, need an oil quench.  I prefer using the torch because it is so much faster and don't worry about scale.  My answer to scale is a Dremel tool with a white 3M bristle disc that takes off all the scaling in a few minutes.   I do that before tempering the spring in my oven. 

dave

[Jim Kibler]

Yes, it's not a good idea to try to harden in an air furnace for the parts we do.  As you said, scaling and decarb is a problem.  Using a torch is the best solution.  We have a molten salt pot which is the best choice in my view, but expensive and in some ways nasty to use.  Use your furnace for tempering, stress relieving, annealing and pack hardening.

[bnewberry]

Have you tried the foil wrap knifmakers use?

[Jim Kibler]

It helps but causes difficulty with quenching.

[hudson]

I have tried the stainless foil rap so far even with the best designs by the time I get it out it has cooled much more than I liked. I have read some were that placing the part in sand works. Know the numbers and have the furnace I rebuilt but just a beginner here also.