Salt (Brine) 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... ;-)

Edited January 30, 2009 by mod07

[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...

[Golden_eagle]

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?

10% by mass OR IN OTHER WORDS: use a one gallon bucket, ten gallons water to one- one gallon bucket full of salt

[blksmth]

Golden eagle, I do not think it makes much difference if you are over or under with the salt. I have read that you should be able to float a potato if the salt is at the right proportion. I have not tried it myself. I'm sure you know that the salt is more severe than still water alone and works by helping to eliminate the air bubbles that tend to surround the hot iron being quenched.

Dick Nietfeld, Shady Grove Blacksmith Shop, Shady Grove Blacksmith Shop

[mark stephen]

Many steels cant be salt quenched.You would have to have the ITT chart for the steel your quenching to determine if you can use low temp salt as a quench medium.Most scrap steels need a faster quench (5160,1095,)Use a vegatable oil.

[Mills]

veg oil is faster than brine? I had thought it was the other way. I seek enlightenment.

[markb]

[ThomasPowers]

Hmm, I'm going to have to look into getting some cottonseed oil....

[mark stephen]

Yes veg.oil is faster.If you look at, say1095s itt chart ,the nose of the curve will tell you if you need water ,oil,or if you can use salts.1095 needs to be quenched fast to harden.I use salts for 0-1 and l-6 only.I use commercial quench oils for everything else.Hope this helps.

[blksmth]

Salt is a faster (hardens quicker) quench than water. Water is a faster quench than oil. That is a good chart posted by Marcb.

Typically a salt quench is only used on larger pieces of steel, primarily plain carbon water hardening steels. It could break small pieces as it would be too quick.

1095 is a water quench steel with a shallow hardening depth. If thin pieces (under 1/4") of 1095 are quenched they might break in water therefore oil might be a more prudent and slower quench for the thin pieces.

If you were making a hammer head out of 1095, you would want to quench in water to get as deep a hardness as possible and temper the eye and faces to an appropriate hardness (RC50 to RC55).

Note that in Marb's chart, moving fluid is a quicker quench that still water.

[mark stephen]

Salt is faster than water?Sorry, but its the other way around.Im taking about heat treatment salts.These are low temp salts used by the steel industry for quenching and tempering certain steels.Quench a piece(i dont care how thin)of 1095 in these salts and you wont harden it because its a slower quench medium than oils(true heat treat oils or veg.oil).Water hardening 1095 is to risky and will most likley cause cracking.Id choose a deep hardening steel for a hammer head.

[Quenchcrack]

May I suggest using the term "Brine quench" when referring to a solution of water and Sodium Chloride? A true "Salt quench" is a pot of molten salt, typically in the 600F-900F range. It is used to bring the steel down to the martensite start temperature whereupon, it is removed from the salt and allowed to slowly air cool. This will fully harden the appropriate steel with very little distortion. And a brine quench IS faster than a water quench in most cases.

[blksmth]

Don Fogg Custom Knives has a good article on Heat Treating @ http://www.dfoggknives.com/hardening.htm. Also see Heat Treatments: Direct Hardening a portion follows:

"Quench Media

Quenching is the act of rapidly cooling the hot steel to harden the steel.

Water: Quenching can be done by plunging the hot steel in water. The water adjacent to the hot steel vaporizes, and there is no direct contact of the water with the steel. This slows down cooling until the bubbles break and allow water contact with the hot steel. As the water contacts and boils, a great amount of heat is removed from the steel. With good agitation, bubbles can be prevented from sticking to the steel, and thereby prevent soft spots.

Water is a good rapid quenching medium, provided good agitation is done. However, water is corrosive with steel, and the rapid cooling can sometimes cause distortion or cracking.

Salt Water: Salt water is a more rapid quench medium than plain water because the bubbles are broken easily and allow for rapid cooling of the part. However, salt water is even more corrosive than plain water, and hence must be rinsed off immediately.

Oil: Oil is used when a slower cooling rate is desired. Since oil has a very high boiling point, the transition from start of Martensite formation to the finish is slow and this reduces the likelihood of cracking. Oil quenching results in fumes, spills, and sometimes a fire hazard."

[bbehnke]

Should distilled water be used (in the brine mix)?

[blksmth]

bbehnke, distilled water would be excellent as would be rainwater. Tap water could have minerals in it which could be detrimental. That said, I use tap water because it is easy, cheap, and plentiful. My slack tub/quench tank holds about 24 gallons. Tap water has not been a problem that I know of. My tap water is generally considered hard by most folks around here, and most have water softeners. Would the results be better if I used distilled water? Probably, but I like quick, easy, simple and it works for me.

[bill83]

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...

Get an egg from a free range bird. Also, if it's healthier for us to eat such an egg, mebbe it would be better for the quench water too!:rolleyes:

[Francis Trez Cole]

adding salt to water raises the boiling point it also lowers the freezing temp (ice cream making). I use the gunther super quench. I use a misture of Used motor oil 2/3and diesel fuel 1/3. I have seem molten salt bath to bring the steel up to an even temp Albion swords ltd use this method. egg or potato when brineing a ham I use a potato