The act of bending the tube will achieve a significant amount of work hardening. Beyond that, you might try hammering the resulting bend slightly flat for more rigidity, but there is no heat treatment method that you can use to achieve more than a trivial increase in hardness (I vaguely recollect hearing of some heat-hardening treatments for certain brass alloys but they are very subtle in their effect if I recall correctly).
Bill
Unlike silver, which softens by heating and quenching in water, brass will get harder after reaching annealing temperatures if immediately quenched in cold water. If, (and I know it’s off topic) you want to soften brass, it should be slowly cooled preferably in hot sand. As said before, quenching will lock a hard crystal pattern in the brass. Heat it to a dull rose color, quench immediately and you shouldn’t have to do any further work hardening.
Marc
Ah, that’s it Marc, thanks, I was probably thinking of silver when I mentioned heat treatment regimens… I think you can make silver a bit harder by post-treating it, if the quench has softened it.
The brass quenching trick is good to know. All the same, the amount of hardness difference for brass (between fast and cold quench) is very modest compared with steel, no? And it’s still a lot less hard than work-hardened brass…
regards
Bill
I really don’t know too much about steel. There’s also a trick you can do to harden silver a bit by heating it to 1200F and letting it air cool. You’ll have to polish it, but it can make springy cathes and pins a bit harder without hammering. Back to brass, though, once you’ve got your bend in a tube, I wouln’t think you would have to harden it. It should be strong enough on its own.
The above statement might be a bit misleading to some. If I may:
Annealing a non-ferrous material is accomplished by heating to somewhere just below the melting point and cooling in air or quenching in water. Quenching in water is a matter of convenience.
Alpha brasses (64-99% copper and less than 37% zinc) are annealed by heating to 700 to 1400F (mo hotta mo softa) and can then be air cooled or quenched.
Alpha-beta brasses (55 to 64% copper and 37%-45% zinc) anneal at the same temp and can be hardened slightly from dead soft by quenching at the annealing temperature.
Note the word “slightly” above. For the purposes of forging brass for a chanter key I seriously doubt you would notice an appreciable difference between air cooled or quenched Alpha-beta brass, particularly at the lower end of the annealing temperature range. Cold working produces a much greater degree of hardness.
For copper alloys in general you see quench hardening and tempering employed on aluminum bronzes with 9 to 11.5% Al and nickel aluminum bronzes with 8.5 to 11.5% Al, which respond to quench hardening with a martensitic type reaction. Quench cracking is generally an issue if aluminum content is higher whereas alloys with lower aluminum content don’t contain enough high-temperature beta phase to respond to quench treatments. Relatively far removed from brass of course…just being pedantic.
Kevin
I think there’s a noticable difference between cooling slowly and quenching. I notice it anyway! Perhaps it’s all in my mind. This would be from red hot. Bends don’t need hardening, especially not when a crown has been hammered onto it. My bass drone fell out of my stock and landed 8ft down a stone staircase, you can hardly tell it happened!
These days I carry my pipes with the drones sticking up . . . .
Be careful not to overheat your brass. It can liberate zinc from the alloy and compromise some of the appearance and working properties of the metal. Volatized zing vapors aren’t too much fun either, though they are much less harmfull than other metals like mercury, antimony, lead etc.
Most brasses I’ve worked with don’t seem to like silver solder all too much. 10k easy flow gold solder should work if you have access to a jewelry supply place. It melts and flows somewhere around 1100-1200F. It should be plenty strong enough and will beter match the color of the brass. You need strong enough to hold, but you(I hope) won’t be hammering things with your bass drone anyway.
You mentioned a burned appearance on the brass when you finish soldering. Do you use paste flux before and an acid pickling solution after? That should prevent and remove most scorching. If you have copper stain that isn’t easily removed by pickling, add some hydrogen peroxide to your pickle solution. It only works for about 15 minutes, but it will remove the copper stain. If you can get Sparex, that works well for pickling. If you can’t get that, powdered pool acid will do the trick. Sodium hydrosulphate?
Marc
Battern’s flux will be a real problem for you. It really is only for silver gold and platinum. Use white paste flux on copper, nickle, bronze and brass. You might try tinning your pieces by melting small squares(paillons) of braze to the contact points of the work to be joined together. Once you’ve done this, you can reflux, fit the pieces together and hold them with iron binding wire until you’ve done your heating.
The Complete Metalsmith by Tim McCreight and Robert Von Neuman’s jewelry tech. book are both available at Borders and have great advice for basic metalsmithing. If you want to splurge, Oppi Untracht has a huge informative text for metalsmiths($90.00).
Marc