60's era Metallurgy

[NV Stig]

Has anyone heard that the late 60's era Porsches were made out of Italian steel that is prone to becoming brittle over time? I haven't seen this happening to my car, but I heard it is an issue that exists beyond the rust from a guy in Reno. I was trolling the threads, and it doesn't look like it has come up as an issue. Any tribal knowledge on the subject?

[Flieger]

That sounds like the punch line of a joke...

The steel is certainly not precipitation-hardening steel, as that has only become widespread recently. So it won't get brittle over time unless you are stressing it too much and causing it to work harden.

Now if you want to talk about rust over time, that is a different matter.

911s must be German steel.

[moito]

yes i have expierienced that the steel gets brittle on early 911...this also happened to some nos parts i have here in my shop....so i also think that the steel is ageing...
sheet metal used for stamping car body parts is a special steel(sondertiefziehgüte--thats the german word) and it can not be stored for long time cause it looses its positive charactaristics for forming within weeks after production. i assume this process slows down but never ends...im not a metallurgy geek ....so just dangerous half knowledge.

but i doubt that this is a safety issue .....so far

[sithot]

Buy a Corvette.

[moito]

or a A110

[M_deJong]

I always heard Karmann invented rust and licensed it to the Italians...

[Flieger]

yes i have expierienced that the steel gets brittle on early 911...this also happened to some nos parts i have here in my shop....so i also think that the steel is ageing...
sheet metal used for stamping car body parts is a special steel(sondertiefziehgüte--thats the german word) and it can not be stored for long time cause it looses its positive charactaristics for forming within weeks after production. i assume this process slows down but never ends...im not a metallurgy geek ....so just dangerous half knowledge.

but i doubt that this is a safety issue .....so far

Were those parts plated?

I agree that nowadays steels are designed to harden over time (but only at elevated temperatures) or to have retained metastable phases that convert after cold-working or heat treatment, but I believe that in the 1960's it was mostly just plain steel.

[304065]

My car is made of German steel and I prove it here: http://www.early911sregistry.org/for...ts+restoration

[Bullethead]

Aside from the various forms of oxidation, metals don't "age". The only thing that makes steel brittle is excessive cold... we're talking double digit
negative Kelvin numbers here, not winter temperatures. If of the same metallurgical composition, old steel or new will have the same tensile and
compressive strength. Excessive heat is the killer, altering the molecular alignment of most metals... any car that's been in a fire should be scrapped.

Sitting for 50 years in a dry barn? No problem.

[moito]

Aside from the various forms of oxidation, metals don't "age". The only thing that makes steel brittle is excessive cold... we're talking double digit
negative Kelvin numbers here, not winter temperatures. If of the same metallurgical composition, old steel or new will have the same tensile and
compressive strength. Excessive heat is the killer, altering the molecular alignment of most metals... any car that's been in a fire should be scrapped.

Sitting for 50 years in a dry barn? No problem.

o.k. metals dont age...but metal used for a 86 is different from the one a 67 is made out of..it is easier to form and softer. and is not cracking as fast...

what about magnesium alloy? i would not go for a hot ride with my 917 even on nos rims.... what is this process called that makes magnesium brittle?