Salt Bath Annealing Doesn't Work! by AMP

[ntsqd]

This whole thing reminds me of the quote: "I only trust the Statistics that I made up myself."

I didn't read their full report as I inherently do not trust articles of this nature. Had it come from a source without an oar in this particular pond I'd be more inclined to thoroughly read it.
That said, annealing is a time at temperature process. The closer the heat source is to the ideal annealing temperature the longer the saturation time will have to be. And the longer the saturation time the more likely you are to see heat where it is not wanted.

A slight annealing, i.e. removing some but not all work ha3rdening, case hardening, etc. is called "Tempering". The process removes some of the hardening, restoring some ductility, while not removing ALL of the hardening and rendering the metal dead soft.

Given some of the comments made here I suspect that a full annealing of the neck is not desirable. Rather, a case neck Tempered to some as yet undefined hardness may well be the most desired outcome. I'd like to see someone independent of all annealing vendors test ES & SD vs. case neck hardness in multiple calibers.

 

[Korhil78]

Haha....people were just fine doing with what they were doing before this article came out and had good groups and nice brass and POOF! Now it's sour grapes and peeing into the wind bad. I have an AMP and like it a lot but that doesn't mean it's the only way to do it and still get long lasting, consistent brass.

 

[Rex Tharp]

Haha....people were just fine doing with what they were doing before this article came out and had good groups and nice brass and POOF! Now it's sour grapes and peeing into the wind bad. I have an AMP and like it a lot but that doesn't mean it's the only way to do it and still get long lasting accurate brass.

Now I know where all this rain in Okla. came from today. LOL. No one has mentioned that chamber dimensions are a variable in all of this, and the most likely culprit for the work hardened case necks. Most of poor boys are stuck shooting factory chambered barrels and can't afford some of the equipment we really want. The salt bath setup is an affordable way to extend the usable life of brass cases, which is for some just as important as tiny groups.

 

[redleg1013]

My question is why salt bath annealing seems to be annealing the shoulder area MORE than the neck. It is easily visible in the graphs. AMP does not discern the reason for this phenomenon. Is it because the temp is not consistent through out the depth of the molten salts? Almost seems the salts the neck portion of the cartridge is submerged in, is not heated a much as the shoulder which is submerged much higher in the salts. Heat rises. Also the shoulder this thicker than the neck, so all being equal, seems the neck would heat quicker and anneal quicker.

Convection flow. Yes, heat rises and as it raises from the source it cools, and thusly descends.
As to the phenomenon they describe, Occam's Razor would indicate that AMP cooked their numbers (pun intended) since they obviously have skin in the game and don't want the potential for lost sales.

 

[J E Custom]

Has there been any study of just stress relief in the brass depending on the type of case preparation? Tumbling with metal media, soft media, no tumbling? Aging? Low temp baking? All these things can be factors in other metals.

This is not based on any study because brass cartridge cases don't need to be stress relieved, only annealed. The alloy is such that cartridge cases need to be malleable in order to be shaped/sized to fit your chamber. They don't have or need the tinsel strength to withstand the chamber pressures. Basically, they are containers with a low yield strength. If you changed the alloy the yield strength could go up or down rendering the case unusable.

Normally tumbling, polishing does not effect hardness, only sizing, firing or reshaping (Wildcatting) the reason for annealing is to keep the case in a malleable state in certain areas. If it becomes to hard, it will fail because it is no longer malleable and will crack in most cases.

If you tried to bake the brass, it would not change unless you reached annealing temperatures, then you would anneal the entire case rendering it useless. The neck and shoulder area are the normal areas that need annealing, and the rest of the case can remain stronger and
support the rest of the case and the pressure to a point.

J E CUSTOM

 

[Wedgy]

Quenching it doesnt have the same effect on brass as it does other metals.

Agreed, but the quenching in this case(literally) is to stop the annealing from spreading farther down the shoulder.
For the record I flame anneal with no quench and have been looking into the salt bath, AMP seem a bit pricey for me.

 

[redleg1013]

Another thing to consider with the AMP report... for any and all contemplating that the orientation of the brass in the salt bath creates the condition that AMP alleges; just kick back and open up one of your favorite beverages, and remember the cases are oriented the same way in the AMP... unless they are saying that the laws of thermodynamics are different in their lab. It doesn't matter one whit to the material how it is heated, once the heat source is removed, it will IMMEDIATELY begin to cool, in this case, at a rate of 70 BTU/sq ft/ft/hr/°F @ 68°F assuming that cooling isn't expedited by quenching... but that is another story.

 

[Rudolph Ferdinand]

Reading through the posts I noticed that brian b, Mikecr, Kyron and possibly others suggested that AMP have done this testing because the Salt Bath Annealing has put a dent in their sales.
If this were true why would AMP have suggested this in the second to last paragraph of their report,
"For those reloaders considering getting started on annealing, and who are on a budget, we would recommend a gas flame-based option." ?

Thank you for your input in this matter of Annealing brass cases. I'm not on a budget, but I don't want to put out $1300 for an annealing machine, there is cheaper, machines than the $1300 unit.

 

[Gcan]

My question is why salt bath annealing seems to be annealing the shoulder area MORE than the neck. It is easily visible in the graphs. AMP does not discern the reason for this phenomenon. Is it because the temp is not consistent through out the depth of the molten salts? Almost seems the salts the neck portion of the cartridge is submerged in, is not heated a much as the shoulder which is submerged much higher in the salts. Heat rises. Also the shoulder this thicker than the neck, so all being equal, seems the neck would heat quicker and anneal quicker.

If I had to guess it's because the shoulder is a larger mass/larger heat sink. Takes longer to cool and cycle out of annealing temp.
Just a guess.

 

[HobieH3]

Ok...the first thing that pops into my mind is something that I've thought was improper to do regardless the method used...quenching the brass.

I'm no engineer so I've never study any on how metal works technically. But I have heat treated and tempered steel while build a AK receiver. It seems to have worked as there is no wear in the areas I did.

Any way...I wonder if they had let the brass cool naturally, if it would have improved there results. I do mine with a torch and let them cool naturally. The brass fairly hot to touch for long time.

I have read like many of you I'm sure, that the job is done as soon as the heat leaves the piece so it doesn't matter how you cool the brass. But that has never seemed correct in my little brain.

I AM an Engineer. Quenching is used when you're hardening. The whole point of annealing is a slow cool.

Quenching will create stresses by locking in the crystalline structure.

 

[Barrelnut]

Always found this clip interesting on how Remington makes ammo. Have a look at 1:20 in the video. You can seed the brass cases being annealed. They use a flame and just let it cool.

 

[ntsqd]

I AM an Engineer. Quenching is used when you're hardening. The whole point of annealing is a slow cool.

Quenching will create stresses by locking in the crystalline structure.

True when dealing with steel and other ferrous metals. Not (always?) true when dealing with non-ferrous metals. For instance, the surest way to end up with gummy, super soft aluminum IS to quench it from a high heat.

I'm an Engineer now, but I was a race car fabricator prior to and while going through college.

 

[redleg1013]

I AM an Engineer. Quenching is used when you're hardening. The whole point of annealing is a slow cool.

Quenching will create stresses by locking in the crystalline structure.

THANK YOU!

 

[raider1v1]

in for this thread and the info. really looking for the results from everyone here.

also.

seems that AMP is a bit salty....


sorry. cant turn the dad jokes off.