UV 420 TTR is an agglomerated fluoride-basic flux for Submerged Arc Welding of un- and low-alloyed steel grades. It is characterized by its neutral metallurgical behaviour and has been designed mainly for multi-pass welding. Very good slag detachability in narrow gap weld preparations. UV 420 TTR has been optimised for welding operations in combination with wire electrodes Union S 1 CrMo 2 and Union S 2 CrMo to maintain high strength levels after long PWHT-durations with good toughness. The pick-up of Phosphorus is limited to +0.004 % and makes the flux suited for step-cooling requirements.