I always thought annealing meant softening metal (so you could bend it easier, etc.) and the way you did that was to heat the metal cherry red and let it cool SLOWLY at ambient temperature. Hardening was done by heating to cherry red and IMMEDIATELY QUENCHING in water OR oil. Is this correct? And does it make a difference if you quench in oil or water? I'm guessing, but does heating to dull read, bright red, dull orange, white-orange control the temper (hardness)? Finally, can you harden music wire without making it brittle, or is it already optimally hardened? Guess I need to attend metallurgy 101... jd
Annealing, tempering, hardening, etc...
Stuka Stunt Main Forum · 7 of 7 known posts recovered
I do believe you have it correct but it depends alot upon the material. For example, if you heat copper tubing and quench it, that makes it soft. heating and slow cooling copper or working it makes it hard.
Most ferrous metals however are the way you described. I'll check for some more specific material in my library.
Tempering or drawing removes the brittleness from a rapid quenched part.
The actual hardness value achieved will depend upon the carbon content and alloy of the material.
You can also tell alot about the material and the hardness by observing the colors of sparks from grinding.
For stainless steels, like 304, 316 , they are work hardenable--bending them, rolling it, or trying to machine it will cause it to harden.
I also recall that the pupose of the oil when oil hardening is to provide high carbon infusion to the surface of the material providing carbon hardening to a shallow depth in normally low carbon or mild steel. this is called case hardening and provides good wear resistance and strong ductile core.
Some of the engine folks like Leonard or GMA will know alot more and be able to verify this.
Curt
I can't give you all of the answers, but your are correct on the annealing, hardening issue. Music wire is probably optimally hardened as-is. If you heat it, then quench it to try to harden it further it could, indeed, fracture and break. I tried that with a landing gear once in my "less brilliant" days (which my wife says I never grew out of). I heated it in order to bend it, then decided to quench it in water since I didn't want it "soft" where it would bend on landing. It didn't. It broke, instead. I think oil quenching is a little less violent (and gives that nice blued surface, too) but I will leave it to the engineers in the crowd to tell you how much to heat and with what to quench (if at all).
Leonard Neumann
Bingo! The light just came on! Actually, I think I read Leonard's advice on annealing copper (or brass?) tubing to bush the bellcrank holes and I think he said to quench it immediately.
That threw me because I was thinking about the ferrous materials. Thanks guys - I think I understand now.
That threw me because I was thinking about the ferrous materials. Thanks guys - I think I understand now.
LAST EDITED ON Dec-14-00 AT 06:00 PM (EST)
Annealing of steel is when you heat it to its currie point (where it loses it ferro magnetic properties) usually a dull red hot or hotter And then GRADUALLY reduce the oven temperature 50 degrees at a time, holding at each temp for approximately one hour before lowering to the next lower 50 degree step until room temperature is reached. This will make the steel as soft as it can ever be. Heating the steel to its currie point and just letting it air cool is called normalizing and is some harder than annealed metal. Normalizing is most commonly used as it doesn't take controled oven manipulation. As to heating and cooling brass or copper, Most brass tubing you get at the hobby shop is drawn and hardened. You try to bend it and it will flatten or kink. You can heat it red hot and let it air cool slowly and you can bend it easily with your fingers. As for copper, I cannot give you any help.
Brass, when it is extruded or drawn often gets very small particles of oxided material pushed into the metal and drawn out into long stringers in the walls of the tubing and these are often attacked by the alcohol and nitro in our fuels and then under vibration crack. That is why many experienced modelers replace the brass tubing in their fuel tanks with copper which doesn't exhibit that tendency.
Generally speaking, when you grind steel: lots of bright red-yellow sparks= high carbon content in the metal. Fewer more orangish sparks = low carbon content Fewer yet very bright white sparks = high chrome content.
The higher the carbon content in steel means you can actually get it harder.
There is a LOT more to this process than what is covered here, but I have covered enough for a good start. If anyone is interested in more, I suggest you look up a heat-treating facility in your area and go there and get the straight poop for the metal and the job you wish it to do from the professionals.
Bigiron (ex materials and processes engineer)Ret.
Wow! Great write-up for us country boys! We can actually understand it!
Larry F
As far as brass goes, the heating and letting it cool slowly is NOT correct. If you want to render it dead soft, you quench immediately in cool water. This is the standard method used to anneal rifle and pistol cartridge cases and prevent cracking of the necks from working of the brass during reloading (which hardens it).
Music wire, or any type of spring steel is pretty much a one shot deal, once it's tempered, heating it again (above a certain level) will destroy that, and render it useless.
Music wire, or any type of spring steel is pretty much a one shot deal, once it's tempered, heating it again (above a certain level) will destroy that, and render it useless.
J.