Join Date: Apr 2014
Location: Bulls, Rangatikie, New Zealand
With the small quantites that I have of the tubes it would be impossible to use weight as a definitive way of working out what is and is not Chromolly steel. I have used a series of crude tests to come to the conclussion along with the NZ Ducati agents verifying our conclussions as well, though they could not tell me exactly what grade of Cromoly steel they were manufactured from. I have the actual material spec listed down some where but at the moment I seem to have miss placed it.
For the purpose of this repair I am going to proceed with the belief that it is Chromemolly 4130 (or an equivalent there of. To that end and having spoken to our Aeronautical metal workers and welders in the Royal New Zealand Airforce they have recomended that i use MESSER MG600 tig welding rods. This rod is designed for maxmium strength and is the best rod to use for joining disimilar metals if you are not 100% sure what the metals actually are. Apparently the RNZAF use alot of this for various welding jobs for some of the historic aircraft that we still fly.
As far as not MIG welding Chromemolly steel - have a look at the robitic welding of the KTM frames - manufactured useing Chromemolly steel and MIG welded.