Explain to me how annealing the brass helps? Does it somewhat soften the brass, making it easier to conform to the chamber for less blow-back?
My Good Froogal....
Thanks for Asking!
It a long and invovled story, but one that needs telling!
First we must hearken back to our early days in the Chemistry and Metallurgy class...
Iron and steel ( ie "ferrous") when engaged in their native state are almost invariabley starting out as "soft" , or "annealed".
This means that the atomic structure of the metal is not aligned, and the metal is basically "soft.
Both Iron and steel will "work harden" and become brittle.
If one heats them to approximately red (the crystal structure loses alignement) and cools them slowly ( heheheh define "slowly)
they become "annealed" or soft again.
Steel can be heat treated to be "hardened" .... ie - heated to red , the crystal structure becomes fluid, then quenchened quickly
(hehehe define "quickly") and the crystal structure stays aligned... ie "hard"
I will now deferr to Mr Wikipedia for a few detailed, precise an succint sentences:
snip --------------------
Depending on the temperature, it (steel) can take two crystalline forms (allotropic forms): body centred cubic and face centred cubic.
The interaction of the allotropes of iron with the alloying elements, primarily carbon, gives steel and cast iron their range of unique properties.
In pure iron, the crystal structure has relatively little resistance to the iron atoms slipping past one another, and so pure iron is quite ductile,
or soft and easily formed. In steel, small amounts of carbon, other elements, and inclusions within the iron act as hardening agents that prevent the movement of dislocations.
The carbon in typical steel alloys may contribute up to 2.14% of its weight. Varying the amount of carbon and many other alloying elements,
as well as controlling their chemical and physical makeup in the final steel (either as solute elements, or as precipitated phases), slows
the movement of those dislocations that make pure iron ductile, and thus controls and enhances its qualities. These qualities include the
hardness, quenching behaviour, need for annealing, tempering behaviour, yield strength, and tensile strength of the resulting steel.
The increase in steel's strength compared to pure iron is possible only by reducing iron's ductility.
endsnip----------------------
and
snip----------------------
In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material
to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature,
maintaining a suitable temperature for an appropriate amount of time and then cooling.
In annealing, atoms
migrate in the crystal lattice and the number of dislocations decreases, leading to a change in ductility and hardness.
As the material cools it
recrystallizes. For many alloys, including carbon steel, the crystal grain size and phase composition, which ultimately
determine the material properties, are dependent on the heating rate and cooling rate. Hot working or cold working after the annealing
process alters the metal structure, so further heat treatments may be used to achieve the properties required. With knowledge of the
composition and phase diagram, heat treatment can be used to adjust from harder and more brittle to softer and more ductile.
In the case of ferrous metals, such as steel, annealing is performed by heating the material (generally until glowing) for a while and then
slowly letting it cool to room temperature in still air. Copper, silver and brass can be either cooled slowly in air, or quickly by quenching in
water.[1] In this fashion, the metal is softened and prepared for further work such as shaping, stamping, or forming.
endsnip------------------------------
Brass and other Copper alloys are a bit contrary. They cannot be hardened by heat, but they do work harden.
Once work hardened, brass and bronze are brittle, and more likely to split.
However, one Can anneal or soften brass by heating it past magic "phase point" and letting it cool. Unlike steel, one
can cool brass quickly in a quench and it weill still remain soft.
So to summarize.
brass got brittle by work hardening
anneal only the case mouth by heating the case mouth to about red, then dumping in water.
make sure to not anneal the case head ( the part near the rim ) - that leads to a less harmonious outcome....
hope this helps
prf mumbles
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