Originally Posted by
Scooper
Essentially, yes. 725 and AISI 4130 alloys have the same chemistry. 725 is heat treated for greater strength.
Right, but the specs on the Reynolds 725 is just a mid range temper for the alloy that could certainly be procured (or achieved by subsequent heat treat) in 4130 as well.
I am new to this forum but not cycling in general. While I don't post much (pretty much never) I do lurk on a few threads including the framebuilder section as I have an interest in fabrication and have an extensive background in metallurgical testing. It seams to me a lot of people get caught up here with certain materials and suppliers. While Reynolds supplies good materials and has a niche in the cycling industry, in reality, any premium alloy for cycling is also very likely good for use in other applications as well (motorsports, aerospace, etc.) and is therefore, likely readily available. My point, is these are not "magic metals"-don't get caught up so much on one material supplier and the special alloy designation but focus on the alloy equivalent. You may find other viable options in terms of choice, availability and cost.
While I am not ready to go out build myself a frame yet, if I do it will be made from 17-4. While a little heavier, it is easy to fabricate, age harden to a broad range of tensile properties, dimensionally stable, decent corrosion resistance, and I have access to lots of material.
Just sayin'
'bob