Thermo cycle question???

[David Loukides]

Hi Guys,
This is my first winter I have been forging blades. Right now I am using 5160. The temperature in the garage is usually around 25 to 35 deg F. This means that the sand box is also that cold. The forth time I bring the blade up to non magnetic It goes into the sand box. When the blade comes out of the sand box it is still hard in most area's. Does the sand temperature matter? I would like to forge when I have a the time and not have to look at the thermometer.
Thanks For Your Answers!!!!

 

[Stacy E. Apelt - Bladesmith]

Get rid of the sand and fill the box with vermiculite. It is a good insulator. Even rolling the blade in a piece of insuwool will work better than sand.
Stacy

 

[Karl B. Andersen]

I used vermiculite for a long time until I was given a better insulation in lime. Vermiculite has many small air spaces between the particulates which allow for heat escape. The lime holds it in better.
use the stuff from your yard and garden center, not the agricultural type.
As well, do this:
Get two pieces of heavy steel as long as your blade. Do you have a horizontal box? Dig a pit in the middle. heat up the two heavy pieces to red hot and palce them in the lime about 3 inches apart. Cover to insulate.
Then, heat up your blade and place between the two hot bars.
Cover with an inch or so of lime.
I live in Northern Illinois - cold is cold.
I've gone out the next morning and NOT been able to pick up the blade without heavy leather gloves!
Sorry that's out of focus - I use my oven now.