On Thu, 21 Nov 2013, Robert Watzlavick wrote: > I hadn't thought about the screws on the outside of the tank becoming > brittle. I assumed they would just get stronger as they're the normal > alloy cap screws (180 ksi typ)... The two are not incompatible, alas. Metals *do* generally get stronger at cryo temperatures; the reason why some get brittle is that their yield strength increases faster than their ultimate strength does, and when the two curves cross over, the ductility is gone. My understanding is that there is no substitute for test data on the exact alloy used, but non-stainless steels generally should be viewed with some suspicion. (For that matter, not all stainless steels are immune to the problem, although the odds are much better.) You could always dunk a few in LN2 for a minute, and then apply a hammer and see what happens! Henry Spencer henry@xxxxxxxxxxxxxxx (hspencer@xxxxxxxxxxxxx) (regexpguy@xxxxxxxxx)