Stress Relief Annealing cartridge brass

[Alantoo]

Interesting read - What it boils down to is using plain soap as your temperature indicator (400c) instead of using exactly the same routine using the more usual (and more expensive) 750F Templiaq.

Another factor to consider is that the annealing process in brass is a factor of time AND temperature.

I use these machines:

Well yes and no. As you can see from the video it is a lot quicker and simpler than painting tempilaq onto each case. Most people use the Tempilaq to set the length of time and then try and repeat exactly the same position in the flame for that specific length of time. The advantage of the soap is the speed of application which makes it possible to use on each and every case rather than just the initial set-up few, so you do not run the risk of "efficiency creep" as you go through the batch.

The other factor of time and temperature is dealt with by the soap...on material of this thickness @ 400˚C I do not believe time is really an issue...but much more of an issue when doing the heating by hand is maintaining the case in the same place in the variable temperatures of the flame cone and then still trying to gauge your annealing temperature by timing.

The soap goes from straw through brown to black so you can be fairly precise regarding repetition of temperature regardless of where you hold it in the flame and how long it takes to achieve the heat.

It just seems more direct to try and gauge your temperature by a temperature indicator, rather than by time to me.

Lovely machines...mesmerising, better than watching telly! I am most envious.

Alan

 

[Cloudhopper]

Alan,
This is my take and I have only a rudimentary knowledge, I'm not an expert in heat treatment.

Stresses exist within the material at levels up to the yield point. As the stress level exceeds yield, plastic deformation occurs, i.e strain causes dislocations to move thorough the lattice and pile up at the grain boundaries - the material work hardens.
A stress relieve anneal will reduce the yield point locally within the material allowing regions of high stress to "do work". By this I mean the lattice will be able to accommodate the plastic deformation due to the elevated temperature. The lower residual stress levels will show as a reduction in measured hardness but the material is still in the work hardened state; the lattice is highly strained/deformed and the dislocation density is high.

I home-load but I don't anneal; I'm not happy that I could develop an effective and reliable process; perhaps I'm overcomplicating. As far as I'm aware the point of annealing cartridge cases is to soften the neck region after working due to repeated firings/resizings and avoid the risk of the neck splitting. I think I'd prefer to recrystallise and reset to the baseline.
CH

 

[Ray7756]

Ray, induction coils don't get hot, they're water cooled.
CH

Ok point taken , more research required by me ,but the case still gets hot enough to glow red for the annealing process to work, ie you still have glowing metal in the process
this is in no way meant to take away from a well written and researched post by the OP but merely a safety observation
BTW i dont bother annealing as I renew my cases as required, but i am interested in the process
Cheers
Ray

 

[Sauer90]

Ok point taken , more research required by me ,but the case still gets hot enough to glow red for the annealing process to work, ie you still have glowing metal in the process
this is in no way meant to take away from a well written and researched post by the OP but merely a safety observation
BTW i dont bother annealing as I renew my cases as required, but i am interested in the process
Cheers
Ray

Seeing that you do not bother to anneal your brass therefore having no experience, it is a little rich that you try and tell me how to anneal mine.
There is no need for the case to glow in the process. As for your safety observation it misses the mark, as you said you need to do much more research.
It appears that you conflate hot metal with a naked flame or sparks - the hot (not glowing at any time) metal does not get near powders or primers and is not in itself hot enough to ignite powder.
The previous posted videos of the old fashioned flame annealers would be totally unsafe in a reloading room.
In fact no exposed flame in a reloading room is my practise.

I personally think that the op is trying to fix something that is not broken.
Process control does take care of the annealing operation without the need to inspect every case that gets put through. Once I have a setting for a particular headstamp batch, I'm good to go.
Fully anneal the case necks and there is little point in chasing stress relieving.

 

[Alantoo]

snip...

I personally think that the op is trying to fix something that is not broken.
Process control does take care of the annealing operation without the need to inspect every case that gets put through. Once I have a setting for a particular headstamp batch, I'm good to go.
Fully anneal the case necks and there is little point in chasing stress relieving.

The problem that I was trying to fix was largely one of my ignorance. I was wary of the unsubstantiated sweeping statements about the annealing process that were made by reloaders and those supplying annealing machines on YouTube and on the various shooting fora. They conflicted with my experience of working with brass in the workshop on various projects both hot-forged and cold-formed / fabricated.

I hoped the thread would be seen as a work in progress and shared my findings to date by way of opening the debate. And hopefully learning more from others, such as yourself.

Until I started to read up on stress relief and found the paper by Hartmann I did not even know whether the widely quoted 400'C Tempilaq derived temperature had any particular value.

From the paper by Hartmann (and others I have found) I am now confident that 400'C will stress relieve the brass, and that there is a danger of huge variation of resulting hardness if you under heat it in the 250-350'C range…. but I have no idea whether that 400’C produces the optimum condition for case necks...just a load of pundits saying it does.

I put 2 and 2 together to use the well-established aluminium annealing soap colour change system to achieve that 400'C regularly and to avoid under heating.

I do think the soap colour change system is an improvement over counting to seven while holding the case somewhere in the flame cone. So that is possibly a problem fixed.

I do appreciate that the induction heater with its fine adjustment of heat and time is by far the best and most controllable system.

But the mensuration system used, and how you establish the settings you have mentioned are crucial to the process…do you reckon to replicate the condition of the brass that the cartridge case manufacturers supply, or have you established a personal preferred variation? How do you test to see whether the machine or settings are actually producing the condition you require? Rockwell gauge?

Alan

 

[Yorric]

If one gets a case red hot during annealing it will already be burning off the zinc in the brass. - Not a good thing to change the composition of the brass!
With gas annealers it is advisable to heat cases to just below the point where the flame turns yellow (zinc burn off). The time will vary with case size & flame intensity. - It is IMHO the best practical way to control the process.
Also you cannot use the change of case colour as a guide - different levels of case surface oxydization/cleanliness give varied colouration when heated both by gas or induction heaters.

Ian

 

[Alantoo]

If one gets a case red hot during annealing it will already be burning off the zinc in the brass. - Not a good thing to change the composition of the brass!
With gas annealers it is advisable to heat cases to just below the point where the flame turns yellow (zinc burn off). The time will vary with case size & flame intensity. - It is IMHO the best practical way to control the process.
Also you cannot use the change of case colour as a guide - different levels of case surface oxydization/cleanliness give varied colouration when heated both by gas or induction heaters.

Ian

IMHO this is one of the sweeping statements that is oft repeated but I do not think stands up...Burning off maybe right, but not burning out. It is an alloy. The most you would be doing is burning the zinc molecules on the surface...you would not be changing the composition deeper in than a molecule...the thickness of any tarnish...unless you were melting the metal. Or can the zinc molecules become un-alloyed and migrate through the copper to the surface somehow?

Think about the temperature you silver solder brass at...red/orange heat around 800˚C. Think of casting brass...neither process burns out the zinc throughout the metal enough to change its composition.

Give it a wipe with metal polish and you are back to yellow brass.

Alan

 

[Cloudhopper]

IMHO this is one of the sweeping statements that is oft repeated but I do not think stands up...Burning off maybe right, but not burning out. It is an alloy. The most you would be doing is burning the zinc molecules on the surface...you would not be changing the composition deeper in than a molecule...the thickness of any tarnish...unless you were melting the metal. Or can the zinc molecules become un-alloyed and migrate through the copper to the surface somehow?

Think about the temperature you silver solder brass at...red/orange heat around 800˚C. Think of casting brass...neither process burns out the zinc throughout the metal enough to change its composition.

Give it a wipe with metal polish and you are back to yellow brass.

Alan

When in doubt look at the binary phase diagram. At 30wt% Zinc up to a temperature of about 900 degrees C it's the alpha phase - a single phase solid solution. Atoms (not molecules) of zinc existing either substitutionally or interstitially within the copper lattice. I don't know what causes the change in flame colour, I doubt it has anything to do with the zinc.
CH

 

[JockStalk]

You know, there can't be many stalking forums where you can get mention of both binary phase diagrams and interstitially (spelt correctly as well) in a single post.

Keep up the good work.

 

[Alantoo]

snip...
Atoms (not molecules) of zinc snip...

Oops! I should have stuck with Phys. and Chem. instead of Geog. and Hist.

I always got my best marks in the metalwork shop though...

Alan

 

[Middlebridge]

I thought the burning off as temp rises was lead, giving a tinned like surface to the annealed brass.

A very interesting write up that I'm following closely. Having recently bought all the bits to build an annealer, but being too tight to fork out on the tempilac, it would be good to get acceptable results with a bar of soap and lower temps, and save myself a lot of effort.

BTW, Any particular soap? I've knicked a bar of the Wife's palmolive.

 

[Alantoo]

I thought the burning off as temp rises was lead, giving a tinned like surface to the annealed brass.

A very interesting write up that I'm following closely. Having recently bought all the bits to build an annealer, but being too tight to fork out on the tempilac, it would be good to get acceptable results with a bar of soap and lower temps, and save myself a lot of effort.

BTW, Any particular soap? I've knicked a bar of the Wife's palmolive.

I have always used Fairy laundry soap...no moisturiser and little or no perfume...I pinched a bar from my mum 30 years ago and it is still in the drawer in the forge, pulled out every time I needed to anneal aluminium...sadly I have recently discovered they stopped making it a few years ago...but any basic soap would do...Palmolive is probably a bit too impure!

I was going to buy some of the basic laundry soap on Amazon and compare it with the Fairy...I will post the result.

Alan

p.s. In the interests of balance, having been a tad scathing of unsubstantiated statements in this thread...I should add that the need for plain soap is also unsubstantiated...I was taught it, have read it, and have always used it as it made sense, but I will do some tests against Tempilaq 400˚C with a few soaps to confirm or deny....Alan

 

[Alantoo]

I thought the burning off as temp rises was lead, giving a tinned like surface to the annealed brass.

snip...

I don't think cartridge brass has any lead in it...that is usually put into the 60/40 brasses to aid machinability.

cuzn30 which is the commercial cartridge brass spec is 70/30 and the only additive is sometimes 0.03% Arsenic to prevent dezincification when it is used for heat exchanger tubes...according to the Copper Development Association spec sheet.

But I suppose it depends on what the individual cartridge case manufacturers specify, they may have a proprietary mix.

Alan

 

[Sauer90]

When in doubt look at the binary phase diagram. At 30wt% Zinc up to a temperature of about 900 degrees C it's the alpha phase - a single phase solid solution. Atoms (not molecules) of zinc existing either substitutionally or interstitially within the copper lattice. I don't know what causes the change in flame colour, I doubt it has anything to do with the zinc.
CH

The yellow orange flame is zinc 'burning'.

 

[Middlebridge]

I don't think cartridge brass has any lead in it...that is usually put into the 60/40 brasses to aid machinability.

I seem to remember reading that they put 2% lead in cartridge brass, and the EPA forced manufacturers to cut it to 1.4% on environmental grounds, but I may well be mistaken.

Edit; I was mistaken, it's less than .07%, so barely a trace.

 

[Alantoo]

I seem to remember reading that they put 2% lead in cartridge brass, and the EPA forced manufacturers to cut it to 1.4% on environmental grounds, but I may well be mistaken.

Edit; I was mistaken, it's less than .07%, so barely a trace.

I got the impression from the spec sheets I have looked at that if there was any lead in cartridge brass, it was because they hadn't refined it out from the bit of scrap they recycled rather than that they had added any in.
Alan

 

[Alantoo]

Herewith the promised trial of soap and Tempilaq 399˚C 750˚F.

The top line on both before and after images is currently available from Amazon and is called Falcon Household soap

The middle line is Tempilaq 399˚C 750˚F

The bottom line is the no longer made Fairy laundry soap.

This was done on a bit of 1.25" x 0.25" Aluminium (30x6mm).

The top end soap colour change temperatures I gave in post one are confirmed...and also the advantage of the soap going from straw to brown and then black which gives a bit of warning and a range of temperatures.

Alan

 

[Alantoo]

Induction annealing is the way to go, no flames, no hit and miss.
No need for nice and clean brass any more. Once I have my settings for the particular brass I'm good to go dirty or not!
The other nicety is that I can anneal while I'm reloading, it's no longer a faff and the annealer is in my loading room - no danger of naked flame.

Snip...
I personally think that the op is trying to fix something that is not broken.
Process control does take care of the annealing operation without the need to inspect every case that gets put through. Once I have a setting for a particular headstamp batch, I'm good to go.
Fully anneal the case necks and there is little point in chasing stress relieving.

snip...
But the mensuration system used, and how you establish the settings you have mentioned are crucial to the process…do you reckon to replicate the condition of the brass that the cartridge case manufacturers supply, or have you established a personal preferred variation? How do you test to see whether the machine or settings are actually producing the condition you require? Rockwell gauge?

Alan

I am still hoping you will add to the thread by sharing and describing the system and criteria you use for arriving at your settings...and the temperature you then fully anneal your case necks at.

Alan

 

[Alantoo]

Deafening silence...

I agree, positively earsplitting...

Alan

 

[ChesterP]

Herewith the promised trial of soap and Tempilaq 399˚C 750˚F.

The top line on both before and after images is currently available from Amazon and is called Falcon Household soap

The middle line is Tempilaq 399˚C 750˚F

The bottom line is the no longer made Fairy laundry soap.

This was done on a bit of 1.25" x 0.25" Aluminium (30x6mm).

The top end soap colour change temperatures I gave in post one are confirmed...and also the advantage of the soap going from straw to brown and then black which gives a bit of warning and a range of temperatures.

Alan



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Very interesting and informative post Alan. Can you please qualify whether you heated the aluminium from the back (ie placed into a holder and heated the back face to ensure temperature indication relates to the aluminium temperature throughout) or whether you the flame was direct to each sample onto the face with the soap)?

A genuine question here, but unless you're applying the soap via a thin brush to the inside of the necks, how do you know that you are consistently achieving the stress relieving consistently through the thickness of the case neck?

Must admit that I use 750F tempilaq on the inside of the case necks and watch for the flame colour as the brass is heated until the tempilaq indicates 750F has been reached. Rather than paint every case to be annealed I then set the annealer timer to this setting but appreciate that varying case neck thickness then becomes an issue. There's greater chance though of inconsistent results playing with the machine timer for every case so unless I just anneal by hand again as I used to like you do, it seems there's little else to be done with machine annealers. Proof of the pudding though is that ES figures from the chrono plus very tight group sizes would seem to indicate consistent neck tension and perhaps this is the only reliable method of measuring whether our stress relieving has been achieved with sufficient consistency?