Originally Posted by maddog34

2040 steel is a European Designation, and long outdated now...it was known for stiffness (which is pretty much the same as other steel alloys as steel's Young's Modulus doesn't change between alloys, don't confuse strength with stiffness) due to the high carbon content (which is usually what harden able steels have, higher carbon content), and it also resisted heat hardening when brazed (when brazing if one were to quench the hot joint only then would the steel potentially become hardened. For a brazed joint and the usual slow cool down no hardening will happen) or welded, negating the need to anneal the frame after joining

most other high carbon steel alloys readily harden when heated to a glow, then cooled (as in very quickly cooled. The crystallin structure has to be "frozen" and not allowed to slowly revert back to the non hardened state during cooling).... hardened steel becomes BRITTLE steel... Brittle steel likes to Crack at high stress junctions