Headgasket problems

[Bort62]

Copper is different than ferrous metals in that it anneals by heating to a dull red color and then dropping it edge-on into water.

Terry

I beg to differ.

This is frankly a very complicated subject so I will spare all of the details.

However, annealing copper can be successfully done by heating it to its annealing temperature (which is much below the dull red glow temp) and letting it cool slowly, in air.

We used to do this all the time at my last job. Because copper does not heat treat, heating it dull red and then dropping it in water would probably anneal it as well - but it is not the industry standard (as far as I know)

Annealing most metals is a fairly similar process, but heat treatable alloys can be tricky because you can accidentally end up partially re-heat treating them (making them harder) if you don't cool them right.

To truley attain an "O" (annealed) condition with any metal, there is a specific process that needs to be followed. However, for the home user, heating the metal past it's annealing point and allowing it to cool slowly typically does 90% of the job.

From Wikipedia:

"A full anneal typically results in the softest state a metal can assume. To perform a full anneal, a metal is heated to its annealing point and held for some time to allow the material to fully austenitize. The material is then allowed to cool slowly so that the equilibrium microstructure is obtained.
"

Naturally, the time you hold the material at it's annealing temperature (or above) is a significant factor. Grain growth takes a finite amount of time.

 

[MustangSix]

The ancient machinist that I learned a lot from taught me to "clean it up good, heat to a dull red with that little propane torch, then hang it on that nail until it cools."

 

[Bort62]

The Annealing temperature for C101 is between 700 and 1200 F. Melting point is 1981 F.

Copper starts to "glow" at 1300 F.

So heating it until it glows is actually taking it past the annealing temperature, and that means you are probably doing other things to it that you don't realize, like promoting grain growth which is actually going to make it MORE brittle and overall degrade the mechanical properties of the material.

 

[MustangSix]

Dunno. Never measured the temps, but it always seemed to work. But "glow" is too hot, for sure. That's why he would stop me when I tried to use the acetylene rig. Too much heat. I'd have to do it with the little propane job and it took longer. No glow, just red.

 

[Bort62]

All that great theory aside, If I had to anneal some copper in my garage I would heat it w/ a MAP torch until it was good and hot and then let it sit.

I might use some temp sticks to check the temp as they are cheap and easy.

 

[Jmonty]

The Annealing temperature for C101 is between 700 and 1200 F. Melting point is 1981 F.

Copper starts to "glow" at 1300 F.

So heating it until it glows is actually taking it past the annealing temperature, and that means you are probably doing other things to it that you don't realize, like promoting grain growth which is actually going to make it MORE brittle and overall degrade the mechanical properties of the material.

Makes me glad that the machine shop I work in has it's own heat treat oven good for up to 2200*F We make medical instruments from stainless & aluminum so we do our own heat treat in house. Digital programming on the oven is my friend :!:

Bort62 is correct though, once you go past the annealing temps you are actually doing another type of heat treatment. Given that this is not severe duty for the metal it should be no real problem. A few heat sticks (we call them crayons 'cause they melt like wax when you are at/above the temp they are rated for) around the temp that you are looking for will help you get the temps correct. I don't recommend an IR thermometer because they are not all they are cracked up to be (found that out the hard way flame hardening some 440 stainless steel) something to do with reflectivity of the surface or some such...

MSC has them for about $12 each here... http://www1.mscdirect.com/CGI/NNPDF...321005&PMITEM=93312023&PMCTLG=00&PMT4TP=*LTIP

McMaster-Carr has them on pg 545 for about $10 each @ http://www.mcmaster.com/

Search temperature crayons & you will find them.

Happy annealing!