Any experts out there on the properties of LM25 casting alloy?

[alan_thomas]

I am going to have a go repairing some damage on my own cylinder heads with 'HTS 2000' and am advised I should preheat them to about 200c because the alloy conducts heat away so quickly. I have used the HTS 2000 rods with great success on smaller alloy bits before but this will be the first time on something so large requiring preheating.
No problems heating the heads as they easily fit inside Mrs T's electric oven but my question is will exposure to say 250c for up to one hour affect the physical properties of the castings. If I was annealing Aluminuim alloy sheet to form it I would heat it to about 400c and allow it to cool after which it would be as soft as putty for forming and then it would work harden as it was being worked.
So what tempering characteristics does LM25 have as I don't want 'putty' cylinder heads! am I safe to heat them to 250c?

- Alan

[martin]

Hi Alan, as your 250c is a long way below the melting point, I would have said you're safe. Not my risk I know. Try a scrap head first. I've used HTS 2000 to repair Mazak, so LM25 should not be a problem. Martin.