Chromoly is a commonly used alloy in the high-end fabrication world. You will see it most frequently applied in chassis or structural environments.
The alloy is very strong, and can endure a workload overtime without tempering or changing molecularly.
Now, as any material- there is a shelf life- in the motorsports world you will find that chassis will "relax" over time- losing some of its stiffness.
As far as weldability, this is my setup- generically speaking. Susceptible to change depending on material thickness, or weld joint.
- #14 Weld Cup
- 30 CFH Argon
- 1.2 Pre-Flow
- 12 Post Flow
- 3/32" 2% Ceriated Tungsten
- 1/16" ER70 or ER80 Filler
- 4 Rips per Joint (Connect Tacks at 90 degree Increments)