Low Temp Salt Quench for O1

Deering Knives

Deering Knives

Joined
Jun 9, 2014
Messages
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So I wanted to get peoples input on quenching low temp salts. From what I've read the benefits are great by avoiding stresses and allowing for correction of warps as the blade slowly cools to martensite if I am correct. I have been having lots of problems with warping O1 and have decided that I will give an interrupted quench a try, but I think that this type of thing takes skill to develop good timing to do it with consistency. I wouldn't want to have a batch of soft blades without a rockwell tester around.

So here is my idea. On craigslist you can find a number for vertical pottery type kilns for a great price (found an even heat for $150). I was thinking that a tank of low temp salts could easily be loaded into one of these kilns and used for quenching. Actually, thinking about it now you could probably use high temp salts for heating as well. I would just need to make a tank that could handle high/low temps to place in the kiln.

I thought this might be a great option for someone who isn't good with wiring things to make my own tank.

Anyone try this method? if so, results? things I should know before I take a leap?
 
IIRC, Kevin Cashen has said in the past that using just low temp pots do not really give you much benefit by themselves other than perhaps giving you an easy way to temper. It is the high temp ones that do the trick.
 
I have a small kiln that has a 16" low temp salt pot sticking out the lid. The low temp salts and niter bluing salts work well in it. The "advantage" is the ability to stop the quench at Ms and do any straightening as needed before removing the blade and letting air cool to ambient.
The tank is heavy wall stainless welded to a bottom plate. There is a hole in the lid that closely fits the tube. Satanite was used to seal the joint. A piece of ins-wool was wrapped around the exposed neck and laid over the top to help maintain temperature.

Since I have so little warp issues, and now 95% of all blades go to Peter's, I don't use the setup currently. In the future, I will probably set it up for niter bluing damascus and knife fittings.


High temp salts are a different animal, and a kiln conversion would have to be very well done to be safe. I will not go into detail beyond saying that hot salt ions and high voltage coils do not mix well at all. High temp salt pots are something only for the large professional shop in my opinion.
 
A good medium speed oil and proper HT regime should take care of most warp issues in O-1.

In some specific situations, marquenching and holding in molten salt at 400F has uses, but for most knives, it isn't really much (or any) better than oil.

O-1 and the other eutectoid steels have a much slower cooling curve than most folks think. You have plenty of time to straighten any warp. Pull it out after a count of 5, straighten, and put back in the oil to cool down below 200F.

The TTT of eutectoid steels gives you lots of time:
1 second to clear the nose at 1000F,
5 seconds to get to 800F,
1 minute to get to 600F,
2+ minutes to reach 450F ( Ms)
1/2 hour before it stiffens too much to straighten (50% martensite)
You have several hours before it has to get to 200F(Mf)

Eutectoid TTT chart : http://blog.ub.ac.id/okkyardiansyah...mation-Diagram-for-a-1080-Eutectoid-Steel.jpg

During the two minute time between 800F and 400F, you can twist, bend, hammer, etc. with no fear. A wooden mallet and a wooden plank on the anvil will keep cooling rate down when whacking out twist and warp. Even with taking all that time, the as quenched should be around Rc64.

To see how long two minutes is, go to a football field. Start at one goal post and walk to the other. Turn around and walk back. That took about two minutes at a leisurely stroll. Math is 3-4MPH walking speed = 100 yards per minute.
 
Once i started doing a stress relief cycle, my warping issues pretty much disappeared.
 
JDM - did one. Didn't help

Stacey - thanks!!! Really great info there. Parks AAA is shipped. Hope this solves the issue.

First time doing a stress relief and I honestly don't think it is necessary since I am doing stock removal, cutting out blank, drill three holes, and punch logo.

The results were exactly the same with and without it so I might as well skip it.

Thanks everyone!
 
As I always say when I find that someone want to use Salt pot...
Do you have a bunker to put this there ? ( because if you let a DROP of water into a hot salts, you will end up badly...)
 
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