Brownell's NitreBlue salts, suggestions....

J

John Frankl

Joined
Oct 16, 2001
Messages
1,917
Hello All,

My wife is so sick of the smell of steel tempering in her oven that she started asking about my buying an oven for the garage. Then it came to me, low temp salts would be cheaper than buying a second oven, and be useful not only for tempering but also for marquenching, martempering, and heat coloring.

I am going to go with Brownell's NitreBlue but am wondering what sorts of containers and burners/temp. controls all of you are using on your low temp salts.

Thanks,

John
 
John, you can use any old stainless pans. I say panS because the salts creep like no tomorrow, and you'll soon have a little "crystal garden" growing over the inner container.

Guys use plain carbon tanks, too, but they will corrode in time. You can use cheapo hotplates or the standard gunsmith burners and a good thermometer to regulate. Nitre salts blue carbon steels at temps above those for tempering, so you can't really blue blades with it.

Hope all is well out in CA, and the shop and other ventures are coming along well...
 
The Nitre Blue cools to a nice solid brick when not in use. Its the Oxynate #7 that grows into the neighbors yard.

I use a coleman propane double cook stove with good results. Be sure the use a good thermometer. A tempering oven is still handier for its intended purpose of just tempering.
 
ah, sorry i had it wrong. i knew some salts crept like mad.
 
I see IG's salts yesterday and it is creepy, he uses the other type like bruce is talking about. it's a lower temp salt I believe also.
like under 300 deg's I think?
 
Thanks to all of you.

Fitzo, CA is good, and pretty warm too. I'm all set up for stock removal/finishing, and well on my way to forging.

Bruce, What makes the salts less convenient for tempering? I have no experience with salts, but figured/heard they were great for tempering due to the better thermal conductivity, etc.

John
 
John, heating and maintaining the correct heat of the salt is the troublesome part. The electric oven is "set it and come back in an hour" but salts require constant monitoring and small adjustments constantly. Im not saying they have no place in a knife shop but I wouldnt sell my oven. I use high heat and low heat salts and have allot of fun but it is time consuming for sure. Advanced heat treating methods include martempering and marquenching. Nitre blue salts are great for this but need a flame to rapidly bring them to temp. Elecricity is slow.
 
Originally posted by John Frankl
Thanks to all of you.
I have no experience with salts, but figured/heard they were great for tempering due to the better thermal conductivity, etc...

John
Click to expand...

Hi John

Looks like you have been keeping yourself pretty busy with all the new equipment construction. I have never worked with nitre bule salts so I cannot give much help there, and Bruce is probably right about the temperature control due to the fact that if one is working with bluing salts they probably have a hot bluing heater set up.

On the other hand I have been working with Park Metallurgicals Thermo-Quench salts for quite a few years now, and would absolutely refuse to temper in anything else, if given the choice. If heated with the proper equipment, monitored by good digital controllers and thermocouplers, the heat is incredibly even and very quick, conductively speaking. (though it does take a bit to melt the salts at the start of the day). I simply get the salts melted and then set my desired temperature and forget about it for the rest of the day, this is usually good to within 5 degrees on a bad day and + or - 1 degree when things are really cooking. Introduction of blades will drop it by 20 degrees or so and the controller will have them back to set temp in 5 to 10 minutes whether I am in the shop or not.

You are correct that it is very efficient to have your quench tank double for your tempering. The down side to all this includes the quantity of purchase that Park requires and the cost of the equipment to heat things accurately. If you are using a vertical tube, keep the moisture out of the salts (this means keeping them sealed when not it use), with horizontal troughs this is not as critical.
 
And everyone else again. I'm not sure I'll have the $$ for anything too high tech right off the bat. For now I'll just do the labor intensive thing with a good analog thermometer from Brownell's and a lot of watching and tweaking. Which is what I wind up doing with the kitchen oven anyway, just can't leave it unwatched.

And Kevin, thanks for all the help with the burner and forge. I build a burnder essentially per our discussions/Tim Zowada's plans. For the forge I wound up casting 2" of insulating castable (IRC 25), followed by 1" of high alumina. This was in a 12" diameter well casing, giving me 3" of refractory and a 6" chamber. I believe it is 18" long and I also cut some 2" lengths off of a 10" well casing to cast doors. These have angle iron legs and sit dead center in the front and back of the 12" pipe. I used fire brick as the mold to cast the holes in the doors. Now I can plug the back simply by sliding a fire brick into the perfectly corresponding hole. And I can 1/2 plug the front by laying a firebrick flat in that hole (thanks to Tom Ferry for the idea).

John
 
John, I was planning on trying the exact same thing. I'm watching ebay for a lab hot plate. Those have (I hope) a very accurate temp holder. They use a heavy ceramic top to keep the heat consistent. Max temperatures range from 200 to 1,000 degrees.

Again, I'm hoping that I can get a nice constant temp for low temp salts this way. Give, the length of time to come up to temp Kevin and Bruce mention I'm going to add 'high wattage' to my requirements.

Steve
 
You must log in or register to reply here.
Back
Top