I ran into this site and just had to answer someone..
Please pass this around to all your associates
I started riding serious bikes in the 1960's (Gitane) and still have a Raliegh Team bike - Reynolds 531 frame.
I have been in the Metals Industry running an Aerospace Division for 27 years working with the largest
manufacturers in the US.
First -
Heat Treating is a genaric phrase and never used by a professional in the metals industry.
Heat treating covers "ALL" thermal processes
You : Anneal * Stress Relieve * Normalize * Normalize & Temper * Quench & Temper *
These are all "Heat Treat " processes with different results for different applications.
Airframe tube *AISI 4130 * EF 4130 * 4130 Alloy steel - whatever you want to call it ..is the bottom end
of the Aircraft alloys.
4100 designates a Chrome-Moly basic alloy structure
4130 designates a Cr-Mo with 30 points of Carbon (actually .27-.32 point range)
No alloy with less than 40 points of carbon (4140) is considered to be a "Thru-Hardening" grade..
30 points is in limbo....the middle ground
Less than 30 points requires Carborizing (having the surface impregnated with additional carbon by imersion while heating and case-hardening) to improve the Surface hardness..but you only get a hard surface and no depth....
Welding weakens the joint..the intergranular structure changes from the heat and impurities in the flux!
My Raliegh 531 frame like my old Gitane's are "LUGGED"..
All the best are lugged..may not be as pretty..but are the best..and the strongest.
If you Normalize after welding (which is recomended)..it is to make it all uniform strength (Normal)
But if you Normalize & Temper..or Quench & Temper (that is drawing down quickly after heating by imersion into an Oil or Salt Water bath)...How do you plan on straightening the frame after..
It could come out looking like a pretzel..