Hints and Tips - Annealing Solid Copper Headgaskets

From: Stuart
Sent: 14 April 2002
To: british-cars-pre-war
Subject: soft in the head

Dear All, Soon I will have to anneal the rather thick solid copper head gasket on my blown Ulster A7 engine. I remember this as quite exciting as the red hot gasket hits the water, especially if one forgets to lower the gasket into the water end on, as it were. Not that I object to a little innocent fun, but I wonder if heating the copper to dull red then allowing it to return to ambient temp. in air might be sufficient? I have a faint recollection that I have read something to this effect in the past. No doubt the team will put me straight!

Thanks in anticipation, Stuart.


From: mike tebbett
Sent: 14 April 2002
To: British-Cars-Pre-War
Subject: Re: soft in the head

As I understand it, it is the heating process that anneals the copper, not the cooling. So let it cool in air. If unsure then why not try it on a scrap bit of copper?

Mike


From: Bob Rich
Sent: 15 April 2002
To: Stuart; british-cars-pre-war
Subject: Re: soft in the head

Stuart et al,

Copper has a cubic crystal structure and is very ductile, but it work hardens. That's why it needs to be annealed when used as a head gasket.

Work hardening introduces defects known as 'dislocations' into the structure and these defects make the copper hard. Annealing the metal loosens everything up and softens it by eliminating the dislocations so that it is once again composed of nice perfect crystals.

Annealing is normally done at greater than 50% of the melting point on the absolute temperature scale. Copper melts at 1083:C = 1356:K so annealing is done at greater than 678:K = 405:C = 761:F. However, it will take rather a long time at the lower end of the range so it is more common to anneal at around 700 to 800:c.

Copper will maintain its soft crystal structure after annealing at any realistic cooling rate (from very slow like letting fire die down to fast like dumping it in a bucket of water). Heat the head gasket to a dull red with a propane torch and either hang it on a nail to cool slowly or dunk it in a tub of water - either way will work as well as the other.

Cheers, "Bob".


From: Stuart
Sent: 16 April 2002
To: Bob Rich
cc: british-cars-pre-war
Subject: Re: soft in the head

Thank you Bob, Mike and Barry for the advice. Annealing will now become the least terrifying part of the process - a nice change!

Regards, Stuart


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