(12-12-2017, 10:08 AM)ike Brubacher Wrote: It looks as if there are already a couple of good questions on the table for you Mark so I'll throw mine on the pile as well. I've managed to accumulate a fair collection of old metal files myself. As you know, they can be picked up at little expense at auction. I'd guess that most of mine date from the 20's to the 50's. What would be your best guess on the type and quality of the steel they are made from? Is it possible to detemper them and then harden/temper again? Seems as if something useful should be made from them. They harken back to an era when men were men you know.
Mike, if your files where manufactured before summer 1945 than it is so called low-background steel which is not contaminated by radioactive isotopes. Some very sensitive instruments require such a low-background steel.
The first atomic test, the Trinity test conducted on July 1945 and following nuclear explosions, released radioactive dust which was globally embedded into the steel giving it very weak radioactive signature.
Since 1963 the background radiation level is decreasing, but radioactive cobalt still contaminates current steel production because of recycling contaminated scarp steel.
The main source of low-background steel, besides your file collection, is ships that were constructed before the Trinity test, most of them the scuttled German World War I battleships.
Jan