table salt as temperature indicator

scott.livesey

scott.livesey

Dealer - Purveyor
hi,
heat treating some small blades made of Aldo's1084. if i placed some table salt on the spine edge, would i be at the right temperature if i waited until it melted? was thinking, see salt melt, 2 minutes by clock, quench in oil. Am i on the right track?
scott

"OLD SAILORS NEVER DIE, THEY JUST BECOME GRUMPY OLD MEN."
 
I have heard of the trick. I'd have to look up the melting temperature which may or may not be in the ball part. You might also want to look into temperature crayons, I think Tempistiks might be a brand name. They come in 50 degree increments if I remember right. I keep meaning to run out to one of the welding supply shops to check on them, though I guess that I could order them on line like most of the rest of my equipment.

Doug
 
This is where I bought mine. It was the cheapest place I could find them and the shipped them really quick. I had them in like 3 days.

Tempilstiks

I've heard about salt melting, but to be honest, I can't remember at what temp it melts. Off the top of my head, I'd say between 1450 and 1500 but hopefully someone more knowledgeable will check in and give a firm answer.
 
Sodium Chloride melts at 801 degC/ 1474 degF.

Potassium Chloride, as used in "low Sodium" salt, melts at 770 degC/ 1418 degF.

One of the problems I have found whilst playing with salt pots on the cheap, is that, although it's nominally Sodium Chloride, table salt tends to have "other stuff" (Potassium Chloride and anti-caking agents) added, making the melting point less clear-cut than we'd like. Tempilstiks are probably better.

I use a thermocouple.
 
Thanks for the link, Don. I did some looking around and that's about the best price that I saw. One other place had prices at that level but it was hard to navigate their list to tell what you were ordering. No order to it at all. This place looks like it wants to do business and it will probably get some.

Doug
 
What all temperatures of the temp sticks would you need to heat treat 1084, 5160, 1095, and 01.

D. Adams
JOhn 3:16
 
I would approach it from what I wanted to heat to do for normalization I would start with a 1600 degree, followed by a 1500 degree, then for a sub-critical third cycle 1400 degree. To austinize hypoeutectic, the 5160, or eutectic steel, which would be something like 1075/1080, 1500 or even 1550. To austinize and soak a hypereutectic steel, such as 1084, 1095, or O1 then 1450. From what people who have used O1 have said you might need to do a sub-critical pre-soak to get the best performance out of the steel but, if you want to go that route, you should be using a regulated heat treating kiln.

Doug
 
I would leave 01 out of that group unless one has an oven. It really needs two presoaks before austenitizing. One as a stress relief, and another as a preheat. Although one can get a usable blade with a simpler heat treat, it will be far from it's potential.
 
To the OP,

I'm curious as to your heat source with this method.

My main concern would be difference in temp between the spine and edge/tip of the blade reguarless of how accurate the melting point of the salt would be.

My big fear would be that you ended up with grain growth in the thinner sections of the blade due to overheating and as a result ended up with poor performance, chipping, and loss of toughness in the areas where it's needed most.

-Josh
 
A valid point Josh. That fact is a drawback to the salt trick. It may work fine in a baffled forge arrangement, but maybe not so well in an open forge.
 
Josh Dabney said:
To the OP,

I'm curious as to your heat source with this method.

My main concern would be difference in temp between the spine and edge/tip of the blade reguarless of how accurate the melting point of the salt would be.

My big fear would be that you ended up with grain growth in the thinner sections of the blade due to overheating and as a result ended up with poor performance, chipping, and loss of toughness in the areas where it's needed most.

-Josh
Click to expand...
heat source would be charcoal/wood fire. looking for something more accurate than "Magnet won't stick". NaCl (table salt) melts about 1480, hardening temp for 1084 is 1475 to 1500. getting impatient with lack of $$$ to buy electric or propane furnace and have several small knives in 1084 ready to heat treat.
scott
 
Scott,

IMHO, The magnet is great indicator for 1084 and is accurate as magnatism will be lost at 1414 degrees IIRC. My opinion is that this is plenty of info for hardening 1084 and many folks have been using magnatism as an indicator of temp for years.

FOR 1084 !- Knowing the EXACT temp of the steel is less important than getting a nice even heat on the blade (supposing you want to fully harden and not shoot for a differential ht) It needs to be hot enough to harden and overshooting the temp a little isn't going to hurt.

For example- 1084 will harden at 1425 but it's no big deal if it's 1500 and maybe even a little higher than that. (keep in mind we're talking SPECIFICALLY about 1084)

IMHO, the ability to use a primitve heat source and pull your blade out exactly as it loses magnetism is fairly non-existant. The exception would be a smith with years of experience. The thinner sections of the blade are going to lose magnatism first and as you bring the temp up and get your whole blade non magnetic the chances of not being hot enough to harden are slim. From my own experience if you get it non-magnetic and quench it's going to harden just fine for ya.

Using any primitive method for hardening takes some time and patience. Bring your steel up slow and sneek up on non-magnetic being mindful not to overheat the thin sections and you'll have a great blade. It does help a great deal to see someone who knows what they're doing harden a blade with the methods you intend to use so if you have any oppertunity to do that I'd highly recommend it !

As newbies we tend to over-think it ALOT ! I'm more guilty of this than anyone and it's ok. As we learn and gain hands-on experience our fears subside and we move on to worrying about other things, LOL.

Fire up the charcoal and harden your blade.

If you don't like what you get then harden it again.

If you still dont like it seek assistance and try another blade. We try to save'em all but inevitably some will end up in "The Bucket" LOL.

Be sure to let us know how it goes !

-Josh
 
thanks josh.
hope to work on hardening soon. in the middle of 12hr on /12 hr off maintenance shutdown with temperatures in the 100's. you are right, i tend to overthink, part of my ADD. makes sense though, when the spine(1/8") has gone non magnetic, the edge should be right. will post results when i get them.
scott
 
It is a fact that the thinner edge will heat up faster than the spine. It doesn't matter what the heat source is, solid fuel, gas, molten solids, induction, or whatever. Keeping your heat low and heating slowly will reduce this problem, not eliminate it. On thing that you can do with a solid fuel forge is to heat the blade with the edge up and the spine down in a hotter section of the the fire. Also remember that it is not sufficient to heat the steel to non-magnetic. That will happen just a little before the phase change occurs. You need to get it just a tad hotter. In most cases, this will happen anyway just because it's hard to catch the temperature right at or just very little above this point but it can be done leaving you to wonder what went wrong-a magnet doesn't lie after all.

Remember also that grain growth is a function of time and temperature with temperature being the most critical. That mean that a short soak at around 1500° won't cause much grain growth; a short soak at 1900° will may cause problems. I say may because the alloy of the steel being treated also comes into play. Some of the more complex steels actually require and austinizing temperature in this range and a soak of 30-60 minutes. Know your steel and do your heat treating according to it's requirement. Even whether the steel was deoxidized with aluminum or silicon will influence grain growth. Heat and time are just two factors.

Doug
 
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