Proper temperature for salt water annealing....

[mikecr]

Metal God, good questions.
With a dip you can set the temp to ~800deg, as measured with an RTD or thermocouple, and take your sweet time. In prepping for improvement of 6.5wssm cases I dipped to mid bodies, holding caseheads with my fingers. This was slow insertion/retraction, taking ~30sec total. Seemed to me that you could hold a dip that deep all day and never reach 450deg at the webs.
This was lead dip, which requires slow insertion. Otherwise it solidifies for a bit at the brass surface. I haven't tried salt yet.
But we do not need higher temperatures, and relatively long dwell times, to get what we want (normal spring back).
AMP shows this,, dipping is doing the same thing, except there is no rocket science needed for dipping.

Timing for dipping isn't needed (like it is for inductive heating). So you can't get it wrong provided you measure the medium temp.

 

[MN50Shooter]

Only anecdotal results: So far, I've only annealed 50 BMG brass. Cases have turned necks @ .020". I ran the salt batch at 550°C. and tested dipping at different times. We did not use Tempilaq, but compared the annealed color of the brass (down the body, below the shoulder) and found that at 8 seconds, it matched factory annealed brass. The head/web never got hot, according to my fingers picking up the case from the annealer, and dropping into the water bucket to cool.

I plan to try testing using a laser temp reader, but I believe that will only measure surface temp's. I feel it beats my turning case with a small motor, and annealing with a handheld torch. I'll be happy if it prevents from splitting necks in my match prepped brass. Especially, in the middle of a match.

I will say that these large cases can drop the temp as they are dipped, one after the other. I stopped, and allowed temps to rise back to 550C, when it dropped too 545C. It only took a couple of minutes to return to preferred temp.

 

[Grimstod]

WRONG............. Zinc melts at 787.2 degrees............. Yellow brass is composed of about 60% or 70% copper; 30%-40% zinc, and trace amounts of tin and lead....... you will end up throwing away all your casing at that temperature.

Not really. Alloy metals have different melting temperatures then their indavidual parts.

 

[jds holler]

Not really. Alloy metals have different melting temperatures then their indavidual parts.

And as I recall, most alloys melt at a lower temp than their base metals. Correct me if i'm wrong. jd

 

[smokinghole]

When it concerns whether salt bath softens the necks, I dinged some necks dropping them into the water. I ran them through my expander mandrel again just to straighten them again. The same cases were previously sized and neck turned before I had the annealing setup finished, I can tell it made a difference. I'm convinced it works and its very effective for very little money. Now I have a bunch of nicely prepped RP brass that should last me a good while.

 

[Grimstod]

And as I recall, most alloys melt at a lower temp than their base metals. Correct me if i'm wrong. jd

O

Could be true for most alloys. You are right about Zink on its own. However for Yellow brass its melting temperature is 1710 degrese F
Brings up an interesting note. Flame from a tourch is 2000 so i can see why repeated anealing from a tourch does eventually polute the brass on the serface.

 

[dcali]

And as I recall, most alloys melt at a lower temp than their base metals. Correct me if i'm wrong. jd

It's complicated:

https://www.engineeringtoolbox.com/melting-points-mixtures-metals-d_1269.html

 

[mikecr]

Only anecdotal results: So far, I've only annealed 50 BMG brass. Cases have turned necks @ .020". I ran the salt batch at 550°C. and tested dipping at different times. We did not use Tempilaq, but compared the annealed color of the brass (down the body, below the shoulder) and found that at 8 seconds, it matched factory annealed brass. The head/web never got hot, according to my fingers picking up the case from the annealer, and dropping into the water bucket to cool.

I think 550C/1,022F is too hot. And well process annealed is not really 'darkened' but more like slightly 'tanned'.
A factory may very well fully anneal (torched), before and at various forming stages. This can burn off some zinc at the surface. That's not what we do or need with dipping. It's what we don't have to do.

I plan to try testing using a laser temp reader, but I believe that will only measure surface temp's.

This is not so simple, given emissivity of brass.
http://blog.thermoworks.com/2012/03/infrared-thermometry/

I will say that these large cases can drop the temp as they are dipped, one after the other. I stopped, and allowed temps to rise back to 550C, when it dropped too 545C. It only took a couple of minutes to return to preferred temp.

This is interesting. I see it with lead dip as well but way less change, and recovery is faster.

 

[smokinghole]

I ran another 25 cases of 300 SAUM for future neck down. They were highly polished 1x fired RP brass. The color change on the neck was noticeable but less drastic than my unpolished brass. Anyhow I ran the salt at 530c. I'll judge how they neck down and fire form for my 7saum.

 

[done111]

I ran another 25 cases of 300 SAUM for future neck down. They were highly polished 1x fired RP brass. The color change on the neck was noticeable but less drastic than my unpolished brass. Anyhow I ran the salt at 530c. I'll judge how they neck down and fire form for my 7saum.

Keep us posted!

 

[divingin]

And as I recall, most alloys melt at a lower temp than their base metals. Correct me if i'm wrong. jd

Copper melt temp 1984F (1085C)
Zinc melt temp 787F (419.5C)

Cartridge Brass melt temp 1750F (954C) (as near as I can tell. Most reference melt temp of generic brass, rather than temps of specific named alloys. They all seem to list the temp as between 1640 to 1750 though.)

Most sites state that zinc will not leave the alloy below the melt temp (so the burning off of zinc from overheating is incorrect, unless you factor in other gasses etching/reacting with the brass.)