Metalman
Hi - New member - always in a learning mode.  I understand general heat treating, but I have never come across a clue on one thing.  Generally in heat treating steel we can anneal, work, harden and then temper to desired hardness...a tried and true system, fine.  I don't have a Rockwell C tester and I can get various results with another system but can not find anything definitive about it.  It is simple anneal, work...and then heat to some temperature and quench with of course a hardness increasing with a temperature used...I think.  Am I completely wrong on this? It sure sounds simple to me.

Another thing, I quite often see reference to annealing copper type metals by heating and then quenching.  I have a couple of Brinell  Hardness Testers and have been annealing copper all of my life and have never seen any difference between annealing copper by just heating and letting air cool and heating and quenching.  As I wrote in my registration for every one thing I may think I know, there would be a thousand and more things that I don't know.

Are there any of you guys that can tell me more about these things?

Now I have to find a 'Send' button. 
Quote 0 0


Skarzs the Cave Troll
Hello, Metalman, and welcome to the forum family! Hopefully you stick around; there's some good info to be gotten on here.

With the copper, annealing by air cooling is somewhat softer, but both work.

Now, about the steel, it really depends on the steel type. The temperature you quench at is the critical temperature, often tested when a magnet no longer sticks to the steel, but some steels need to be a bit hotter for a good harden. Some alloys with .40% carbon can be quenched in both oil and water, but need a higher temperature for the oil quench; these alloys can be very forgiving with the hardening. 5160 hardens well at a bright red- Only quench in oil. 1084 (a very easy steel) can be quenched at a cherry red with very good results- also an oil quench steel. 
What the critical temperature is is the point at which the carbon molecules, when cooled, will align in a crystalline orientation, giving the material its hardness, much like a diamond. Lower alloys can need a fast quench like water in order to harden, and anything around .3% (the bare minimum carbon for hardening) will need to not only be quenched in water, but done so at a hotter temperature. But it's not only the carbon that dictates that temperature range. Metals like chromium, vanadium, manganese, nickel, and others, will change the way it reacts to the temperature, as well as the medium it is quenched in. For example, W1 can have a whole 1% carbon, but can be quenched at high temperatures in in water without cracking (though some blade smiths will say to harden in oil anyways, and I can agree). This is because of how simple an alloy it is. Compare that to 5160, which is a rather rich alloy, and, if hardened in water, can have disastrous results- I'm talking from experience.


So. . . Sorry about the wall of text. Hope that gave you some answers and doesn't scare you away. XD
Quote 0 0
Metalmelt
Welcome Metalman. I haven't had the need to harden anything other than a punch to this point, and that took me several times to get it right. I do mostly casting Bronze and Aluminum and have gotten into forging to combine with my castings. Plus, the forge I belong to has some great tools to make all kinds of things.
What do you use the annealed copper for? I would like to do some engraving, like I need another hobby.
Quote 0 0
Metalman
Well thanks Skarzs and I gather that you are talking about the regular and general heat treating methods.  I have a general gist of that...but I was wondering about my unorthodox method of heat treating where only 'partial' hardening is done 'after' the 'working' part is done.  I realize the conventional methods that you are talking about are more predictable and controllable and is usually the method for most steel metal heat treating.

I have not gotten around to making a Rockwell Hardness Tester.  I think that I can make one for just the cost of the indentor.  And since I have a faceting machine and a lathe I could even make that.

On the copper, where you say, "With the copper, annealing by air cooling is somewhat softer, but both work".  Do you happen to know 'WHY' with the air cooling method it is softer.  With my limited experience with this I can't confirm this.

I understand with carbon steel the slower cooling will allow more carbon crystals to escape from being caught in the iron crystals that cause internal stress and subsequent hardness of the steel.  But with copper I don't think this is an issue.  At least I can not visualize it.

I wish Victor would provide a 'send button' for postings that may be easier to find.
Quote 0 0
jmccustomknives
Howdy. To start lets look at what's going on inside that steel.  As the iron heats the molecules begin vibrating and expand.  Since the iron molecule is basically a box at a certain point (the austinitic state) the box becomes large enough for carbon atoms to move inside.  This is when the iron becomes non magnetic.  When the steel cools slowly the carbon atom is pushed out of the iron molecule, but if cooling is rapid enough the box snaps shut and the structure is put under a load making is very hard.  The more of these you have (raising carbon content) the more wear resistance and harder the steel can be (there is a limit to how much carbon the iron can hold).  A good example of this concept is a katana, they are forged strait but when quenched using the clay baked heat treat the blade curves because the unhardened steel shrinks back more.
There are a lot of mitigating factors, but for the most part on a simple carbon steel there is a peak temperature that you must quench.  It works out to be just past the non magnetic state.  If you come in just under that temp you wont get enough carbon in solution to get full hardening.  If you go over that temp crystal growth (called grain) becomes in issue.  Large grain structure weakens the steel and reduces wear resistance.  Alloys like chromium, vanadium and molybdenum to name a few can all effect how steel acts and where the austinitic point occurs.  Some of these alloying elements also want to bond with carbon having a synergistic effect increasing the wear risistance

As far as the copper goes, yeah that's been my experience too.  I think most guys quench it just too cool it.  When working copper it work hardens, heating it re-aligns the molecules softening it and allowing it to be worked some more without loosing structural integrity.

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
Metalman
Hi Metalmelt - Hey, I am finding this forum format very hard to get use to.  I can't seem to separate postings so have to apologize for any awkward postings.  But you did ask me, " What do you use the annealed copper for? "
I have been annealing copper for, lets see, when I was in the sixth grade...about 1944 or 1945 and I still do it regularly, but for a different purpose.
When I was kid growing up our next door neighbor worked at a foundry making mining tool bits.  One day he was telling me the basics of heat treating.  And he mentioned how copper was different than steel in heat treating.  And I always being curious went home and heated some copper pennies on my mother's kitchen stove and sure enough after getting then as hot as I could, I could bend them with my fingers.  This did amaze my school mates.  I soon found out that they were very discolored after heating them so I cleaned them with a kitchen cleanser and then reoxidized them in the the kitchen stove oven to look more like back to normal.
Now-a-days I anneal shell cases quite often.  In reloading and accurate shooting one should try to make their reloads as uniform as possible, and this may involve trying to keep the tension of the case neck on the bullet as uniform as possible.  As a shell case is fired and then reformed it is 'work hardened'.  Each time this is done, the tension is typically increased by the case neck on the bullet.  At least two things can be done to try to keep this uniform.  One is to thin the case neck as much as can be dealt with, to have less effect by the reduced tension, and the other is to try to uniformly anneal the cases.  You may have noticed on the typical military small arms ammunition there is a darkened neck on the case (brass) resulting from the annealing process.  This is to try for a more uniform tension between the case and bullet.  This is also done to regular commercial ammunition but this discoloration is typically polished off.
Oh I think that copper and brass annealing will be around for a while.  You said that you are into Aluminum melting.  Aluminum annealing is a very big thing especially in aircraft manufacturing.
Quote 0 0
Metalman
Welcome Metalman.
What do you use the annealed copper for? 

Hi Metalmelt - I forgot, you asked...I still have some copper rivets that I was playing with and using 70 years ago and they have age hardened so If i want to make them more friendly to use these days I will anneal them because they will upset more easily and pretty.  Also I have a bunch of brass from Italy dated 1939 and it has really 'age hardened.
You said that you were into aluminum.  Have you noticed having trouble with 'age hardened' aluminum and aluminum rivets? 
My first job out of the Air Force in 1956 was with Douglas Aircraft and I noticed regular chest type freezers along the assembly lines that was used for the aluminum rivets.  Newly annealed aluminum will age harden very fast.  Those aluminum rivets will spoil faster than food out of the freezers.  And they will still go bad in the freezers.  As they do they can go back to the maker for reannealing-sometimes.
You may experiment with some of your aluminum and see how fast it may age harden.  It is surprising how fast some of it does. 
Quote 0 0
Metalmelt
I used to reload some ammo, I don't do it anymore. I had a few casings crack and I'd throw them away. I didn't know that they could be annealed. I was just wanting cheap ammo.
I haven't notice the aluminum hardening. I usually just cast artsy stuff. Rivets oxidize so bad that they won't even melt. They just dirty up the melt. 
Quote 0 0