laeraor

 Have you used a saline bath for heat treatment? votes

 yes 0 votes
0%
 No 3 votes
100%
Please sign up or log in to vote.
Hello folks,
I've read quite a bit about heat treating using a saline bath.  I've read a lot about the transformation process however I would love information on actually building a saline bath and the best way of heating the mixture up and what is best to make the bath with and where to get the ingredients for said bath.
Any info is most welcome!
Quote 0 0


jmccustomknives
Sorry for not getting to this sooner.  Before we get to you question we need to cover why we quench blades.  That is to form martinsite (hardened steel).  There are a lot of variables from the amount of carbon in the iron to other alloying elements.  A saline (brine) quench is very fast and works for steels that have a relatively low carbon content (.4 - .6%) and no other major alloys.  Some steels with higher carbon (like 1095) can respond to a brine quench but with higher carbon content comes a high failure rate (blades cracking).  Even steels that are listed as water quenched should be quenched in oil as the rating is on a 1" thick section and not a thin knife blade.
With higher carbon steels the proper quenching oil should be used.  A commercial oil like Parks 50 will cool the steel as fast as water down to 350F then slow the rate of cooling down as to not build up to much stress reducing the likely hood of cracking.  With the addition of other alloys the rate of cooling to form hardened steel is further reduced, these are the "oil quenched" steels.  The last group of steels have high chromium and molibnium content along with carbon forms the hardened steel structures at a slow cooling rate without a liquid quench.  These are the air hardening steels.

I said all that to say this, brine quenches should only be used on steels that wont fully harden in a proper oil quench.  By quenching a blade made from 1095 in brine you are accepting at minimum a 50% failure rate. 

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
laeraor
jmccustomknives wrote:
Sorry for not getting to this sooner.  Before we get to you question we need to cover why we quench blades.  


Hello thanks for the reply, I certainly learned a bit, however I was more talking about using a saline bath to bring the piece evenly to temperature, prior to quenching. 
Quote 0 0
jmccustomknives
laeraor wrote:


Hello thanks for the reply, I certainly learned a bit, however I was more talking about using a saline bath to bring the piece evenly to temperature, prior to quenching. 


What are you making?  For knife blades it wouldn't be necessary.  Some steels do need to stage the heat treat by, for example bring and hold at 1200F for an hour before finally bringing to the austinizing temperature.  Those steels are usually high alloy.  None would benefit from a saline bath.

Now if you are speaking of using a salt pot for heat treating, that's another animal all together.  It's not saline (salt water) but other kinds of salts.  These are melted and used to dip the steel in and bring to temperature.  Using this method is superior to ovens and forges because of the density of the fluid and the easier control of the heat.  Normally the hardening temperature using salt pots is 25-50F less than with a forge or kiln. 

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
laeraor
jmccustomknives wrote:


Now if you are speaking of using a salt pot for heat treating, that's another animal all together.  It's not saline (salt water) but other kinds of salts.  These are melted and used to dip the steel in and bring to temperature.  Using this method is superior to ovens and forges because of the density of the fluid and the easier control of the heat.  Normally the hardening temperature using salt pots is 25-50F less than with a forge or kiln. 



Yep.. that was what I was talking about.. oops ^_^;;; I was thinking of using this for large armor pieces since they will be irregularly shaped.  I would like to know what kind of salts to use and where to get them, also any advise or info concerning this in general would be most welcome! thank you!
Quote 0 0
jmccustomknives
What kind of armor?

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
laeraor
jmccustomknives wrote:
What kind of armor?


Anything that is super curved and/or large like a breastplate or a helmet.
Quote 0 0
jmccustomknives
What steel are you using?

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
laeraor
jmccustomknives wrote:
What steel are you using?


This is all theoretical at this point, I simply wish to learn as much as I can for now.  (mainly from the lack of a forge ^_^;;...) How would using different types of metals change the reaction to said metal in a salt bath? 
Quote 0 0
jmccustomknives
It all starts with carbon.  Traditionally, armor was made from wrought iron which had little to no carbon.  It wasn't heat treatable, just forged to shape.  Modern armor plate is normally in the .3-.5 range, these might benefit from that kind of heat treat and would far exceed the earlier wrought armor. 

The real benefit of using a salt pot would be to evenly heat the piece.  It still would have to be quenched, this raises a problem for you.  Steel, when in odd shapes tends to want to warp and move when it's cooled rapidly.  While using hardened steel would be easy for doing a dragon scale armor, doing a full breastplate would be a challenge indeed.

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
laeraor
jmccustomknives wrote:
doing a full breastplate would be a challenge indeed.


Alright so back to the last question then, does using a lower carbon steel, let's say, 35% have a different reaction to the salt bath versus a 55% carbon steel, or a case hardened steel?
Also now that warping has been brought up, would heat treating a poleyn or counter have the same problem of warpage despite being smaller because they're more heavily curved? What's the correct way to avoid this? Mounting bracers onto them to keep them from warping? If so do you have advice on the placement of said bracers?

Now, back onto my original question, how do you make a salt bath? What ingredient do you use to melt, and how to get it? Also any advise on the making of the tub itself or heating it or the type of thermometer to use would all be extremely helpful information.
Quote 0 0
jmccustomknives
Take a look at Heathbath, they make several salts.  They however don't sell to individuals so you'd have to call them and they would point you to a supplier as well as which product would best work for your application. 

As far as your heat treating, probably would need some kind of jig to keep things strait.  That might take some trial and error to work out.  Complex curved surfaces add a whole new element to keeping things in place.

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
Hank Rearden
Thanks for this topic! Great information here.
code[Maglio.gif]  Keep the fires burning hot!
2020 ABANA Conference in Sarasota New York. June 3rd. through June 6th. Plan now!
Quote 0 0
Hammerhand
Let me encourage you to abandon the idea of using liquid salts to heat treat steel.  You need to melt the salt so you need a crucible big enough to handle your work-piece.  Expensive.  Then you need to figure out a way to heat the salt from the top down.  Melt the salt on the bottom first and it will explode.  Then you need to find a way to keep water out of the salt.  Water (even humidity) will collect at the bottom of the crucible and when heated will flash to steam and explode.  Most heat treaters have gone away from salt because it is just too dangerous and expensive.
Quote 0 0
laeraor
Hammerhand wrote:
Let me encourage you to abandon the idea of using liquid salts to heat treat steel.  You need to melt the salt so you need a crucible big enough to handle your work-piece.  Expensive.  Then you need to figure out a way to heat the salt from the top down.  Melt the salt on the bottom first and it will explode.  Then you need to find a way to keep water out of the salt.  Water (even humidity) will collect at the bottom of the crucible and when heated will flash to steam and explode.  Most heat treaters have gone away from salt because it is just too dangerous and expensive.


Hey there! Thank you for all the info!~ This is exactly the type of information I was looking for.  I was reading about it in some metallurgy books however it barely went into any practical detail.  I will take serious caution if I ever attempt this, which will not be in any near future, but any more info or reference material would be most appreciated, as I  want to learn as much as i can.  Thanks!
Quote 0 0
jmccustomknives
Thanks Hammerhead, I might have eventually got there.  The idea intrigued me, and the cost was my greatest concern.  I figured if a man was willing to drop 15G's on the equipment the safety concerns would follow.  lol.  But yeah, the process is dangerous.

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
Skarzs the Cave Troll
I suppose it would prevent scaling, though.
Quote 0 0
Hank Rearden
Laeraor,

I have a book that has a chapter that explains salt baths. You can find a copy of it on eBay for a few bucks. It might be worth the investment. I find it detailed and beyond my needs to do backyard blacksmithing. However, I does provide a good foundation of understanding. I originally wanted to read an comment on it, here on the forum. That proved difficult with out plagiarizing it because of my lack of expertise to explain it in my own words.

Tool Steel Simplified" completely revised world's best-selling Handbook of the modern practice for the man who makes tools and dies, and it's by the carpenter Steel company of Reading Pennsylvania.
code[Maglio.gif]  Keep the fires burning hot!
2020 ABANA Conference in Sarasota New York. June 3rd. through June 6th. Plan now!
Quote 0 0