THE Materials Oracle
Join Date: Feb 2006
Location: Finally... home :-)
Bikes: Univega Alpina 5.1 that became a 5.9, that became a road bike... DMR TrailStar custom build
4130 is the AISI, not ANSI (American Iron and Steel Institute, not American National Standards Institute) for a 0.3% carbon, 1% chromium, 0.25% molybdenum steel. Nothing more. It has become synonimous with 'chomoly' and vice versa the same way hook-and-loop fatsener and the tradename Velcro did. Because people are lazy :-p
Almost all the chromium molybdenum steel used in bicycle frames is, however, 4130 or an equivalent international standard because of its prevalence in tubular aircraft structures. Lots of 4130 gets drawn to a variety of tubing sizes in plain guage - it wasn't too much work to have it redrawn or reshaped into bicycle frames.