Howdy All,
I got in some political trouble a number of years ago when I was writing a column for SuperStock and I made some comments about welding 4130CrMo tubing. Seems that one of the big advertisers had chassis parts and pieces and took great exception to what I stated about 4130.
Well, I cited the AWS (American Welding Society), ASME (American Society of Mechanical Engineers), and the FAA procedures for welding the stuff as a rebuttal.
Being an engineer conditioned me to write the rebuttal in a report format and the "problem" went away but it spoke volumes of the amount of poor info that is abundant in the motorsports ranks "because everybody tig welds CrMo..."
Simply put is that CrMo is very problematic and prone to cracking just outside the welded zone (martensitic failure) UNLESS it is post heated and cooled at a slow enough rate to return the parent material and the weldment back to a "normalized" condition (CrMo is normally supplied in a condition N).
Additionally, the use of low carbon steel is much more safe in the relationship of being able to absorb the energy of a crash without failure. Although NASCAR is not the mecca of all things mechanical, they very sensibly REQUIRE that the roll cage structures and the vehicles are constructed of low carbon steel. Note that this is in racing that has huge budgets.
Also be wary of the "if it is heavy it is safe" syndrome. Any structure can be made to endure tremendous loads and still be survivable under most conditions. Exotic materials do not ensure anything other than the use of different materials. One should look at material selection in a "truth tree" type approach so that one has opportunity to look at all the positive and the negatives for each.
OK, I am done ranting for the moment because I have to get back to my carbon fiber body reinforced with 2.7absolutelyunobtanium that I am welding together in a perfect vacuum using cast off outerspace technology!
Best Regards to All,
HB2