Annealing and elasticity

[precision.riflecraft]

Suffice it to say that I'm not a metallurgist, but I had been fairly confident that annealing increases elasticity. I understand the term "elasticity" to mean the degree to which a metal is ductile. Then I read the article at the bottom of this post, which states "Freshly annealed brass will have less elasticity. Brass that has been fired many times will have more elasticity." (Page 3, Para 4)

Doesn't firing and sizing brass (without annealing) cause work hardening, in other words, the inverse of ductility? Doesn't annealing increase elasticity? If someone could educate me, I would appreciate it!

https://www.uniquetek.com/store/696296/uploaded/Expander_Ball_Tips_and_Information.pdf

 

[Metal God]

Yes , or it could be called spring back or any number of phrases we use in reloading .

Example

Lets say you have 2 cases one that is fully annealed and one that has been work hardened . Ok now lets size them both to have .005 neck tension/bullet hold . The work hardened neck will resist being forced to enlarge as you seat the bullet resulting in more bullet hold do to it trying to spring back and clamping harder onto the bullet . While the fully annealed neck will actually be resized larger by the bullet as it's seated because it can't resist the bullet stretching it out like the work hardened neck can . You see this same thing happening when bumping the shoulders of a fully anneal cases compared to ones that are work hardened . You can size both cases with the same die setting and the work hardened case will spring back (elasticity) resulting in it measuring longer then the fully annealed cases ( head to datum ) because the annealed shoulder can't resist the sizing like the work hardened case can .

 

[precision.riflecraft]

Yes , or it could be called spring back or any number of phrases we use in reloading .

Example

Lets say you have 2 cases one that is fully annealed and one that has been work hardened . Ok now lets size them both to have .005 neck tension/bullet hold . The work hardened neck will resist being forced to enlarge as you seat the bullet resulting in more bullet hold do to it trying to spring back and clamping harder onto the bullet . While the fully annealed neck will actually be resized larger by the bullet as it's seated because it can't resist the bullet stretching it out like the work hardened neck can . You see this same thing happening when bumping the shoulders of a fully anneal cases compared to ones that are work hardened . You can size both cases with the same die setting and the work hardened case will spring back (elasticity) resulting in it measuring longer then the fully anneal cases ( head to datum ) because the annealed shoulder can't resist the sizing like the work hardened case can .

Interesting! I appreciate the explanation. It sounds like they are using the term "elasticity" quite literally, which sort of went over my head. Thanks for clarifying that.

 

[JFrank]

From the other side of the coin, Perhaps that non annealed brass gets stronger while annealing makes brass soft yet each time we fire the annealed case it wants to return to the pre annealed state so we repeat the process of (work hardening.)

 

[JimSC]

this subject has pretty much been beaten to death but annealing does not affect the elasticity in the least. Elasticity is determined by the atomic structure of a material. The attraction of the protons and electrons.

Damon Cali does a great job of explaining what happens when a metal cold is worked and how annealing benefits the reloder in this article

The Science of Cartridge Brass Annealing​

 

[mikecr]

This is my understanding of it,, please correct me if wrong.

- The linear elongation of brass represents it's elastic property. That is, it's region of spring back to original form when tensile force is removed.
- The curving portion represents plastic deformation, with the dropping dotted lines representing ultimate tensile strength (point of cracking/failure). Once plastic, brass does not spring back to original form.
- 'Ductility' of brass describes it's ability to deform more or less distance without failure. And fully annealed brass provides the highest ductility as graphed.
- Cartridge brass is best used as partially work hardened/process annealed. Neither fully annealed, nor fully work hardened.

 

[RustyInBend]

That article from the OP seems to represent that "annealing" state is synonymous with "number of firings". I find this part of the article confusing and not entirely accurate ... but that's just me. There is the characteristics of the metal based upon number of firings, and the elasticity of the brass based upon how it's been annealed after those firings ... but those are not the same thing.

 

[JimSC]

T

That article from the OP seems to represent that "annealing" state is synonymous with "number of firings". I find this part of the article confusing and not entirely accurate ... but that's just me. There is the characteristics of the metal based upon number of firings, and the elasticity of the brass based upon how it's been annealed after those firings ... but those are not the same thing.

The article linked in the OP demonstrates the author has absolutely no clue as to how anealing affects the brass. Mikecr's post 6 and the article by Damon Cali Iinked in post 5 explains it

 

[mikecr]

So if I have it right so far then you can see on the graph that ELASTICITY (ability to fully recover with spring back), goes UP as brass is work hardened. That softer annealed brass elongates beyond elastic limit with lower forces.

IMO, the primary function of process annealing(not full annealing) is to reasonably restore DUCTILITY, or undo our work hardening, to prevent brass FAILURE. Important, is the reasonable part.
We would normally want 1.0-1.5 Y-PSi of bullet gripping force (as depicted on this graph).

So let's say load is developed well with 1.5 Y-PSI of Tension.
Consistency as managed would take perfect annealing, at just the right rate, for any sized interference greater than elastic limit. This, to overcome a bit of work hardening with each reload cycle.
I don't like that precarious balance. Seems too much to juggle.
Instead, I strive to stay within the elastic limit[or very close] with sizing, so that my brass does not work harden[or much]. I do a dip process anneal with initial preps, and after fully fire formed to stable I'll develop a load with adjustment of neck sizing LENGTH to manage tension. Very rarely, if ever, needing annealing.
I watch this with friction normalized necks and an instrumented pre-seating mandrel.

 

[divingin]

Interesting! I appreciate the explanation. It sounds like they are using the term "elasticity" quite literally, which sort of went over my head. Thanks for clarifying that.

Definitions. You can probably use the term "elasticity" to mean "the property that allows a material to stretch" or you can use it to mean "the property that allows a material to stretch and return to its original size". Related (sort of) but different. Context is important.

I'd assume the latter is more important (and less desirable) in terms of case forming and annealing. You're actually trying to increase ductility (the former statement above) and decrease elasticity (the latter statement.) Along with reducing the brittleness of the brass.

 

[precision.riflecraft]

Definitions. You can probably use the term "elasticity" to mean "the property that allows a material to stretch" or you can use it to mean "the property that allows a material to stretch and return to its original size". Related (sort of) but different. Context is important.

I'd assume the latter is more important (and less desirable) in terms of case forming and annealing. You're actually trying to increase ductility (the former statement above) and decrease elasticity (the latter statement.) Along with reducing the brittleness of the brass.

Well said - specificity is important.

 

[mikecr]

What allows brass forming without destruction is ductility and malleability. This is provided with full annealing, and needed for manufacturing of brass cases.
Modulus of elasticity represents a linear region of stress to strain where brass recovers fully on stress removal. This provides our strength and spring back for firing/sizing cycles. We balance work hardening and process annealing to manage practical elasticity.

 

[Metal God]

Definitions. You can probably use the term "elasticity" to mean "the property that allows a material to stretch" or you can use it to mean "the property that allows a material to stretch and return to its original size". Related (sort of) but different. Context is important.

Correct I considered defining that but thought I'd let it lie . I've always considered a rubber band to be elastic while something that does not return to it's original size or close to it was simply stretching . I'd also say there is an area ( bell curve ) if you will that both annealed and work hardened can work inside of but take either to the extreme and the case either stretches or cracks .

 

[Doom]

Try this

What is Ductility - Definition | Material Properties

In materials science, ductility is the ability of a material to undergo large plastic deformations prior to failure and it is one of very important characteristics that engineers consider during design.

material-properties.org

 

[Metal God]

Oh boy a new word , I’m very excited

 

[RegionRat]

See if these tables help visualize the properties of the brass a little.

This one shows the relationship between the amount of cold work versus the other properties.


Notice the elongation at break numbers and how fast they change with cold work, as well as the yield strengths. Those elongation at break values basically illustrate the ductility.

This next table also shows what happens as we anneal that brass. This isn't a perfect representation of the values of a thin neck, but come close.



Again, you will notice that as the hardness changes with the annealing temper, so does the grain size and several other properties. Note the yield strengths how much more they change compared to the ultimate.
Cartridge brass is almost perfect for our purposes.

 

[Webster]

Suffice it to say that I'm not a metallurgist, but I had been fairly confident that annealing increases elasticity. I understand the term "elasticity" to mean the degree to which a metal is ductile. Then I read the article at the bottom of this post, which states "Freshly annealed brass will have less elasticity. Brass that has been fired many times will have more elasticity." (Page 3, Para 4)

Doesn't firing and sizing brass (without annealing) cause work hardening, in other words, the inverse of ductility? Doesn't annealing increase elasticity? If someone could educate me, I would appreciate it!

https://www.uniquetek.com/store/696296/uploaded/Expander_Ball_Tips_and_Information.pdf

To many articles written by people that think they are experts. I would read the the tech articles on the AMPS website. They are very competent. You don't need to be a scientist to anneal brass. Just heat it up for a few seconds and your done. Keep it simple.

 

[mikecr]

To many articles written by people that think they are experts. I would read the the tech articles on the AMPS website. They are very competent. You don't need to be a scientist to anneal brass. Just heat it up for a few seconds and your done. Keep it simple.

JUST HEAT IT UP FOR A FEW SECONDS AND YOUR DONE...
Is that what you got out of an expert's tech articles?

Cartridge brass is almost perfect for our purposes.

Where on your tables was Cartridge Brass?
I don't see the alloy identified, and all the numbers change from C24000 to C28000.
That said, I agree with you.

 

[RegionRat]

Where on your tables was Cartridge Brass?

UNS C26000

 

[JFrank]

To many articles written by people that think they are experts. I would read the the tech articles on the AMPS website. They are very competent. You don't need to be a scientist to anneal brass. Just heat it up for a few seconds and your done. Keep it simple.

Or skip the process entirely and get better dies.