Salt Quench

[Feukair]

I want to try quenching in a 10% salt solution. I've found a website where someone likes to use a 10% salt solution and i'd like to give it a try.

But what exactly does a 10% solution mean? 10% by weight or 10% by volume?

One pound of salt for every 10 pounds of water? Or one gallon of salt for every 10 gallons of water?

I dont know which, i'm not a chemist or a baker... ;-)

[HWooldridge]

Excerpted from Robb Gunter

Robb Gunter's "Super Quench"

5 gal water

5 lb Salt

32 oz Dawn (blue) dishwashing liquid (28 oz if it says "concentrated" on the label)

8oz Shaklee Basic I* or 7oz UNSCENTED Jet-Dry or other surfactant (like Simple Green) of appropriate quantity for 5 gal mix (wetting agents)

The Jet-Dry (or whatever you use for a rinse agent) does something chemically to the surface of the steel. It allows the salt in the mix to start attacking it as soon as it hits the air - make sure you have a LOT of clear water to rinse in ready at hand. These surfacants are wetting agents. They break down the surface tension of water allowing it to make contact with a material. We've all dipped a cold piece of metal in water and seen a bubble-like "skin" form with dry metal under it. This is surface tension trapping a layer of air, it makes a fair heat shield. In a quench, steam will form a similar surface "skin" and prevent full contact with the water, insulating the steel from a proper chill. Wetting agents prevent the "skin" from forming.
Detergents do a somewhat similar job, they're emulsifiers allowing oils and water to mix. This prevents any oily residues from the fire from forming a "heat shield" surface layer. The salt in the water raises the specific heat of the water and draws the heat from the steel faster.

Stir it up to get it moving before you quench. Don't quench anything with more than 45- 50 points of carbon. Will harden mild steel to Rockwell 42-45 (in spite of common wisdom that says you can't harden mild steel). It's color coded - when you've exhausted the usefulness of the quench, it'll shift color from blue to green.


This will get you started...looks like pounds/gallons to me.

[Hillbillysmith]

HW is correct. But for the recipe that you have, a 10% salt solution would be that 10% of the total solution is salt and the other 90% is water (which you know). But you can't do this in the way of gallons b/c a solid (salt) can't be properly measured in liquid (water) measurements. I, personally, would do this in the matter of weight. just figure that one gallon of water weighs approximately 8 pounds. So, lets just say you want five gallons of this salt quench. 5 gallons=40lbs. (roughly). and 10% salt would be 4lbs. Now, in true mathematical terms, this will not yield you 5 gallons. It would be more b/c you are adding to the already 5 gallons. But since the salt dissolves into the water, the volume will be the same (at least 99% the same) but the density will change. Now, the 5 gallons of water weighs approximately 44 pounds.

I know its a little too drawn out, but I hope this helps.
-Tony

[jimmy seale]

water weights 8.34 ppg if your around brine water its 9.5 - 10.0 ppg and sea water is appx, 9.4 ppg, total saturation is 14 ppg

[Hillbillysmith]

Thank you jimmy. I was curious about the exact measurements.

[philip in china]

I am in China. Would Mono Sodium Glutomate work in place of salt? That is what everybody here uses in food.

[rusty_iron]

Oh I expect that it would just make you want to quench your work again after 10 minutes and then again 10 minutes later....

I guess that would just be the Chinese forging effect

Rusty_iron,
Brisbane, Oz.

[ThomasPowers]

Traditional version was that you added salt until it "would float an egg". Don't know how the density of modern eggs would compare to those 120 years ago though...

Note also that Rob's Super Quench will generally shatter high carbon steels that might be ok in a straight brine quench.

[habu68]

I seem to remember reading in an old blacksmith text of an "uneducated" smith who was snookered into to buying Hydrated Sodium Chloride from the local pharmacist to use as a quench. It was $.10 a gallon. The man swore by it as the best ever. Seems cheap enough now.

[ThomasPowers]

I read that story too and as I recall it the smith with the secret receipe was in cahoots with the pharmacist and the receipe read "An Aqueous Solution of Sodium Chloride".

Theophilus in "Divers Arts" written around 1120 A.D. suggested the urine of a red headed boy or that of a goat fed ferns for three days. Both of them work but have such an amusing smell when the hot steel hits them...