U ovom radu ispitana je zavarljivost čelika gradacije API 5L X80. čelik je bio isporučen u obliku ploče, proizveden je kontroliranim termo-mehaničkim postupkom valjanja (TMCP Thermo Mechanical Controlled Process). Za tehnologiju zavarivanja odabrano je zavarivanje praškom punjenom žicom (FCAW – Flux Cored Arc Welding) s tri različite praškom punjene žice. Prašak u žicama bio je rutilnog i bazičnog karaktera i žice su dobavljene od 2 različita proizvođača (A i B). Prema odabranom planu pokusa utvrđeno je 14 stanja pokusa, od čega je 6 ponavljanja u centru. Kao utjecajne nezavisne varijable odabrani su: unos topline (E, kJ/cm) i temperatura predgrijavanja (Tp, ⁰C). Cilj je bio utvrditi njihovo djelovanje na količinu difundiranog vodika u materijalu odabranim postupkom zavarivanja i kritično Implant naprezanje u jednakim uvjetima zavarivanja. Eksperimentalni dio proveden je na Fakultetu strojarstva i brodogradnje, u Laboratoriju za zavarivanje. Za potrebe istraživanja izrađene su epruvete za mjerenje količine difundiranog vodika i za Implant ispitivanje. Epruvete za Implant ispitivanje korištene su nakon utvrđivanja kritičnog Implant naprezanja (RIK) za makro i mikroanalizu, za mjerenje tvrdoće HV10, za analizu na SEM uređaju i za EDS analizu. Dobiveni rezultati podvrgnuti su detaljnoj analizi i statističkoj obradi koja je utvrdila predviđanje djelovanja pojedinih nezavisnih varijabli te je izrađen matematički model za predviđanje količine difundiranog vodika i kritičnog Implant naprezanja. \Na osnovi svih eksperimentalnih podataka utvrđena je kritična količina difundiranog vodika u ml H2 / 100 g zavara, te optimalni parametri zavarivanja kod kojih je manja vjerojatnost nastanka hladnih pukotina kao posljedica djelovanja vodika. This paper reflects on the weldability of steel API 5L X80. The steel was delivered in a plate form, and was produced by the TMCP (Thermo Mechanical Controlled Process). FCAW (Flux Cored Arc Welding) was applied as a welding technology using three different filled wires. The flux in the wires was of rutile and basic character and the wires were delivered by two different manufacturers (A and B). According to the DOE (Design of Experiments) there were 14 different experimental states, by which 6 of them were in the center. Heat input (E, kJ/cm) and preheat temperature (Tp, ⁰C) were chosen as independent variables. The goal was to determine how each of the chosen variables affects the content of the diffusible hydrogen in the material after welding and the critical Implant stress through all experimental states. The experimental work was carried out at the Faculty of Mechanical Engineering and Naval Architecture in Zagreb, in the Laboratory of Welded Structures. Test pieces were made for experimental purposes to investigate the content of diffusible hydrogen and Implant test. Of all test pieces used for Implant tests, the ones that were declared as critical Implant stresses were used for macro and microanalysis, for hardness measurements (HV 10), and for SEM (Scanning Electron Microscope) and EDS (Energy Dispersive Spectrometer) analysis. Results were analyzed and statistically processed. According to the results and the design of experiment model it was possible to determine a mathematical model for prediction of the diffusible hydrogen content and critical Implant stress. Based on all collected results it was possible to determine the critical hydrogen concentration in ml H2/100g weld metal, and the optimal welding parameters for which the risk of HIC (Hydrogen Induced cracking) is minimized.