[TheForge] oil temps (one more time)

[Geoff]

Hi Steve

If you have oil at above the boiling pint of water and the blade you are 
tempering has just come out of a water quench and still has wet clay on 
it you may end up with a steam explosion.

I am sure that you thought about this but just in case you did not I 
would be very unhappy if by not reminding you you did burn down your 
shop or worse.

Geoff
Warragul
Australia

On 19/11/2010 2:32 AM, Steve Bloom wrote:
> At 09:14 AM 11/18/2010, Mark wrote:
>>   Great info, thanks Steve....Just curious as to why you are using
>> oil for Japanese style work? Doesn't that have an ill effect on the
>> hamon activity? I was always under the impression that using water
>> would produce the most pleaseing hamon activity? I could be worn,
>> and usually am!! Ha ha
> The quench will be in heated water but the stress relief / tempering
> will be in oil.  I've discovered that if there is much hesitation
> between the quench and the stress relief (read that as a few seconds
> to admire the curve), there is a decided chance that I will hear
> 'CRACK' ....so there is a need for quick acting stress
> relief.  Typically, I use salt baths for austempering (1550 F high -
> the lava pool) with a quench and soak in low-temp salt (475 F).  My
> gear can handle a blade up to 18" long, so tanto length pieces are
> doable with my usual setup but anything longer requires new gear.
>
>    I've just completed one of the Don Fogg drum forges and have lined
> up a quench bath (a 40" long gun-blueing tank with a propane burner
> from a cheap $20 grill that can run the water up to 180 F), but I
> need a tempering facility.
>
> The options appear to be air, salt, glass beads, and oil.
>
> (1) Air won't be quick and doesn't have much thermal mass (but it
> doesn't burn or corrode);
> (2) Salt won't burn but the melt is at 350-400 F ,is very corrosive,
> and for a 4"x4"x36" bath, the cost is ~ $240;
> (3) Glass beads will need stirring and I have my doubts about the
> speed of heat transfer to the metal; and
> (4) Oil will burn but is inexpensive, is fluid at the right
> temperature, and ought to have the right degree of heat transfer and
> thermal mass
>
>    - so it looks like oil is the way to go (as long as I don't burn
> down the shop).  Since I'll be submerging a quenched blade in oil
> that is below the flash point, I don't see any real danger with the
> oil (and the bath will have a snuff lid anyway).  My low-temp salt
> pot runs off a 110V water heater element and maintains 475F with
> about the same total volume of fluid, so I don't expect any problems
> with getting the oil up to the temp I need.
>
> Steve
>
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