Heat Treating W2 and C70 (1075)

[Alarion]

Here what I do, with a coal forge burning coke:

I use old nicholson files (which should be W-2), or C70 steel.
I put them in the forge, heat them to non mag, and let cool in the forge.
This anneal is done before starting forging them
This should give a nice annealing to the steel.
I forge them, then bring them to non-mag, leave them at non mag for about 1 min, and let air cool, looking for warpage.
If there's any, I straighten the blade while still at least at cherry red.
After this, I bring again at non-mag, let it there for 1-2 minutes, and let air cool, looking again for warpage. usually, at this point, there isn't any.

1) From what Kevin and Mete told me, I suspect I should keep the blade at non-mag for at least 5 minutes, and quench the blade to avoid the formation of inter-boundary carbides that can compromise the resilience of the blade.

After this, I bring to non-mag, and quench in hydraulic fluid.
I then clean the blade, and temper it immediately on the forge.
I use the hot air of the forge, with a gentle blow, to slowly bring the blade to temp. I usually take about 20 minutes to bring the blade to straw color.
In about half an hour it will go to dark straw, and then brown-purplish. Given the amount of carbon in the steel, I set for this color with W-2, while I go for straw with C70. I know color is surface only, and heat must soak well into steel I work with 3-5 mm thickness.
I let the color come out in the face OPPOSITE to the one facing the fire, going up very slowly so to let the heat soak THROUGH the blade, instead of just blasting the surface.
I then put the blade on the firebrick that stands beside the fire, cranck up to a full blast and, keeping the tip and edge shielded from it by the brick, I heat up the spine until it gets pale blue with W-2 files, and deep purplish to blue with C70.
I then quench in hydraulic fluid again.

I know I'm not doing the best way, which would be in an oven, but unfortunately I can't use one, for various reasons.
So: any advice here is welcome.
My main doubts are about the time at non mag. I keep it short to avoid grain growth, but I fear I'm not getting all the austenite I could get. I feel I should get better control of the forge temp and let the blade in the fire much longer than I do.
Moreover, I think the second normalizing should be at non-mag, kept there for enough time to convert all austenite (how long?), and then quench instead of air cooling with W-2.
Any suggestion on any of the various steps is welcome.

 

[mete]

There is no need and no benefit to quench after temper , just air cool.Your tempering process is good for the method you have to use....Too high a temperature is much more responsible for grain growth than time...Conversion to austenite will occur quickly with 1075 as the pearlite converts completely to austenite. W-2 will take longer as excess carbides need to be dissolved. 5 minutes will work for both.

 

[Alarion]

Thanks Mete.
I quench only with the second part of the differential heat treating, when I heat up the spine a lot, to avoid that the higher heat in the spine can bleed into the edge and tip, if I let the blade Air cool.