Copper Annealing

[Guest]

I am restoring an early Cadillac engine. Before re-assembling the cylinder-head units, I want to anneal the copper water jacket (which are already removed). I have read that the annealing temperature is about 700 degrees, but I have read conflicting information about cooling. Should I allow the water jackets to cool slowly, or immerse in water, or no difference?

[Guest]

You don't need to quench copper or brass when annealing. Most people seem to believe quenching is necessary, but I have many years of experience to the contrary. I can't tell you the exact temperature, but in a shop with low light, you only need to see the slightest red glow (dark cherry red) and it's done. This can't be seen in the sunlight, until it's much hotter. Be very careful not to overheat. Pure copper takes on hydrogen at high temperatures and becomes brittle.<P>I would suggest getting feedback from other Cadilac owners about whether it is necessary to anneal these, and is there a problem with over hardened jackets. Copper gets very soft when annealed. I can picture them deforming when bolted in place and leaking.

[Guest]

Copper annealing (making soft)occurrs at temps about 900d F. If annealed in "air" it will form an oxidation layer and be dark. If annealed in an inert gas medium (nitrogen) it will be bright. Quenching in water is ok but, not necessary. All it does is make it cooler sooner. I don't think that annealing the copper water jackets soft is a good idea... They will deform.