“salt bath” to soften metal

[jason udallParticipant @jasonudall57142]

I believe saltpeter is Potassium nitrate. ..and thats the stuff on blackpowder

[Sub MandrelParticipant @submandrel]

It was when I was an errant schoolboy

Neil

[FMESParticipant @fmes]

Sure, at 800 deg C Al would be very soft….. you could pour it in any form you like!

Regards, Frank

Soz, got me F's and C's confused

Lofty

[Ian S CParticipant @iansc]

Salt baths can be, depending on the salt used, between about 300*C and 1400*C, so they can be used to heat treat aluminium alloy, and case harden steel. To stretch a point, stripping paint to restore funiture in hot caustic soda might be counted in. Ian S C

[John BurridgeParticipant @johnburridge26484]

If you look at the first book in the workshop pratice series it explains the use of salt baths for hardening and tempering.

As an apprentice i used cyanide salt baths for tempering materials,now because of health and safety most heat traetment is done in vacuum or gas filled furnesses taking away ythe dangers of materials and processe we are no longer aload to use.

[Mark CParticipant @markc]

Ian,

On the grounds that it is a salt and is hot then you are probably right, especially as water is sometimes added to a heat treatment salt bath.

Mark
ps. Don't be tempted to try adding water to your home made molten salt bath – it will explode!

[maurice bennieParticipant @mauricebennie99556]

Hi Re salt (sodium chloride) bath ,tried adding same to boiling water and it does raise temp,the amount I managed to get away with (some one elses salt) it raised the temp by 4c, not much but adding a kilo of sugar the temp rises much higher ,the temp of jam.I only managed about a table spoonful of salt in a pint of water.

Takes me back to Beery my chemistry master many eons ago.

Maurice

[Gordon WParticipant @gordonw]

I think we are getting mixed up with molten salts and salt solutions. Molten cyanide salt was used for case hardening, and yes if water got in it caused an almighty bang. Adding just about anything to water will raise the boiling point, I keep trying to explain this to my wife when I want the tatties to cook quicker, but she won't believe me. There used to be lots of alloys for heat treating, tin, zinc and lead in various combinations, etc. etc. maybe still used for all I know. Just remembered;- years ago was talking to a factory manager when a man in overalls rushed in, shouting " the cyanide bath's blowen up, its all over ". Manager took some white tablets out of his desk drawer and said "take this , this is the antidote" Later he showed them to me :- Polo mints.

[Mark CParticipant @markc]

Gordon,

I think that Ian was probably stretching the definition generally used but strictly (and I stand to be corrected) any salt bath or water bath that has salt and water dissolved together would be a solution and it is possible to add water to the molten salt baths involved in quenching to modify the quench rate. The proportions would be quite small but the effects would be significant, as you mentioned in the example of the spuds!

Mark

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