TubaForum.net

So I was nosing around online and came across a thread discussing differences between yellow brass and "gold" brass (I think of rose brass when I see this) and the discussion centered as usual on audible differences between materials that are hard to quantify. What made me curious though, was a claim by a horn sales person about "bell hardening" reducing their perceived differences between the two materials. There's also fair amounts of discussion about annealing but some conflicting talk about the effect of annealing and, frankly, I decided to make this post to this here maudlin group 'cause somethin is just not clicking in my head. Maybe reading some informed replies will quiet the confusion in my head (I know, good luck with that!)
Anyways, I understand annealing a heat treatment, heating of a local spot or uniformly heating the whole piece to relieve stress in the material (usually metal or glass) to make it softer & easier to work with. When I read the term "harden" in conjunction with annealing the process I think of is called quenching, basically heating a material like brass close to red hot and then plunging it into water oil or some other liquid. This does make the material "harder" (like for say, bullet casings) but also brittle. Working with various materials in space applications my entire career I "get" why quenched material is seldom used there (no one wants brittle in the thermal dynamics of space.)
Back to the claim of bell-hardening. I'm not familiar with a controlled way or hardening brass apart from annealing followed by quenching. I do know that working brass (shaping, de-denting, drawing, etc) hardens brass but I don't see it as a controlled process that yields a uniformly-hardened end product. In other words, the hardening would not be the goal of shaping drawing or de-denting but a side-effect. And not uniform either.
SO...when I read about a "hardening" process on tuba bells, what are they doing? Oven-treating? If hot enough its annealing which softens the metal. Is it practical to heat bells to red-hot and then quench them? When you repair people are heating pipes or flanges or braces or other bits, do you quench them after you're done? How would one get a pretty finish on something as large as a quenched bell? Is my concern about embrittlement just over-thinking? Damn I wish it wasn't Monday all the good BBQ places here are closed Mondays.

dp wrote: ↑Mon Jul 15, 2024 9:43 am I'm not familiar with a controlled way or hardening brass apart from annealing followed by quenching.

That works with ferrous metals, but not with brass. Quenched annealed brass stays soft.

mouthpipes:

It's difficult enough for (me, since I've only done a few dozen in my lifetime, and don't possess a whole bunch of cool tools) to make really nice mouthpipes, so - once I have them shaped just as they need to be - I'm not going back (likely: hard-here/soft-there) heating the entire thing red-hot, and then dropping it in (likely not water, but) acid (as acid will instantly clean off the oxidation, in that temperature range).

I'm (simply) going to say to myself, "Thank God...This mouthpipe turned out (regarding the shape, and no oval areas) just fine", and stick it on the instrument.

bell hardening:
I obviously haven't read as much as you, and having head of this (fad...?? something old is new again...??) thing.

Most makers' old bells (from way back) are relatively soft.

Work-hardened bells end up with specific work-hardened areas that behave like aluminum beer cans (push it in - it pops back out).
If those areas have a pretty finish, I shrug my shoulders and do the best I can with them. If NO finish (yes) I might anneal (cool SLOWLY) a work-hardened area, so that I can soften it and smooth it out properly.

Even in the modern era (a few decades ago) I recall that annealed (soft) bells were a fad - particularly with french horn bells (which tend to be detachable/swappable, and - thus - end up being custom/aftermarket, if not gimmicky/gimmickry.

...I didn't answer any of your questions per typical with these types of discussions on this site.

Also, I'm not going to get into any discussions (particularly if I'm not willing to be more than 20 cents that I'm right), but - when I anneal brass, I don't quench it - if I want it to stay soft. Also (and it may be my imagination), I'm not sure that annealing nickel-brass does all that much good.

I don’t know if this clears or muddies the waters but here is an excerpt from a story about Edwards Instruments. The author interviewed Christian Griego and the complete article is here. It doesn’t explain exactly how they do the annealing, but it does indicate that it is part of the process.

https://www.thefabricator.com/thefabric ... akes-music

Tempering plays a role too. Every time you work-harden and anneal with ovens or hand torches, the process can affect the sound. "On a pro-level bell, we might anneal it between seven and 11 times," Griego explained. "So we study the hardening and softening processes to achieve the outcomes we want."

Quenching won't hardening brass alloys. The hardening during quenching of steels, titanium, some aluminum alloys etc comes from a phase transformation (I teach an entire semester long course on Phase Transformations in Metals). Brass is a single phase metal, the zinc is in a solid solution and simply replaces the copper on the lattice.

The only way to effective harden brass is by work hardening or by changing chemistry (easy in steels - case hardening, nitriding etc but difficult and expensive in brass). Unlike what the bullet reloading community believes, brass does not age harden like some aluminum or magnesium alloys either. To harden brass uniformly you would need to do something like shot peening or blasting then burnish the surface smooth again or by more modern methods like laser shock peening (time consuming and expensive).

I always sigh when someone hands me a RM tuba bell to repair...

...Push oh-so-carefully on a crease...another one forms "over there".

That employee of that maker likely absolutely knows what they're talking about, but I'd prefer to hear "whatever" truth from a maker other than that particular one.

Being redundant, I DO remember (not all that long ago) when SOFT-metal bells were the big-@$$ deal...

Also: thick/thin
thick - fewer dents
thin - easier to carry, and to balance when playing

People missed notes, played out-of-tune, and phrased poorly then - just as now.

bloke wrote: ↑Mon Jul 15, 2024 11:12 am I always sigh when someone hands me a RM tuba bell to repair...

...Push oh-so-carefully on a crease...another one forms "over there".

That employee of that maker likely absolutely knows what they're talking about, but I'd prefer to hear "whatever" truth from a maker other than that particular one.

Being redundant, I DO remember (not all that long ago) when SOFT-metal bells were the big-@$$ deal...

Also: thick/thin
thick - fewer dents
thin - easier to carry, and to balance when playing

People missed notes, played out-of-tune, and phrased poorly then - just as now.

As fine as RM tubas are, this aspect, because events requiring repair do eventuate, even to the most careful of players, is probably the reason I don't own an RM tuba.

Quenching...

I'm ready to admit that I was misinformed.

The next time I anneal some brass alloy (whereby I WOULD HAVE avoided quenching it in cleaning acid, as that WOULD HAVE removed all the heat-caused oxidation) I will GO AHEAD and quench, to determine if the softening characteristic remains.

...I'll report back...

UncleBeer wrote: ↑Mon Jul 15, 2024 9:57 am

dp wrote: ↑Mon Jul 15, 2024 9:43 am I'm not familiar with a controlled way or hardening brass apart from annealing followed by quenching.

That works with ferrous metals, but not with brass. Quenched annealed brass stays soft.

So how ARE bullet casings "hardened"?

I tend to wonder if (simply) the act of mashing bullet casings into shape hardens them.



bloke "making no statements"

bloke wrote: ↑Mon Jul 15, 2024 12:59 pm I tend to wonder if (simply) the act of mashing bullet casings into shape hardens them.

Yup. Large amount of deformation and brass work hardens faster than many other metals. You are venturing into one of my research areas, deformation physics of metals (one of my recent papers https://www.sciencedirect.com/science/a ... 5424002660). Sir Alan Cottrell was a famous (in metallurgy circles) physicist and he made the following statement in 2012 not long before his death:

"It is sometimes said that the turbulent flow of fluids is the most difficult remaining problem in classical physics. Not so. Work hardening is worse"

So we are in good company with our discussion here.

Regarding RM bells…

I understood them, as many others know, to have been work hardened and left more in that state on purpose than typically is done by other makers. They are springy and behave differently when repairs are attempted as a result.

Side/main note: There was a place that distributed them near here. When they closed up shop, along with a bunch of other stuff, there was a big pile of used RM bells with some pretty minimal damage. The procedure back in the day was to not repair even modest damage on RM tuba bells (the thought was that doing so would negatively affect the bell and the tuba over all, not to mention cost and results factors), but rather replace them, hence the pile. Those bells were sold off, repaired, and ended up on everything under the sun. Some really weird combinations were born. If you ever see an out of place RM bell on some random tuba, chances are it came from that pile.

Interesting on those bells but weird, and to me seems dumb but to your benefit.

Some know that I had a 5 valve C with the second trigger - a tuba that I additionally tricked out and played for maybe two or three years at the most. It's now in a suburb of Atlanta. Its bell had issues, and I had to approach it more cautiously than any other bell when straightening it out. Over months of time, I got out all the little bitty places and eventually sold the thing to a friend of mine in darn good condition. The lacquer they put on those things was ridiculous. In other words: thick... and scratch resistant as well.

It never actually benefited me other than amusement from a distance. I could describe some of them, but I don’t want to cast any shadows. I saw some crazy matches done. (I actually typed one out, but deleted it before posting. Think twice, post once…)

I think the lacquer situation has improved. Those old ones had all sorts of dirt and runs in them. I was told… that the view was that the lacquer didn’t matter. It was an after thought that was done in the basement.