This program to investigate the validity of conventional carbon equivalent formulas applicable to the weldability of nine low-carbon micro-alloyed steels for marine structures included in its scope the determination of CGHAZ hardness as a function of cooling time from 800 to 500C, measurement of cooling times/cooling rate as a function of welding conditions, validation of calculation methods, the categorization of HAZ microstructures and hydrogen assisted cracking by three different methods namely: the Battelle Underbead Cracking, UT-Modified Hydrogen Sensitivity and Implant Cracking tests.The steels tested were: HSLA-80-1, HSLA-80-2, HSLA-80M, HSLA-100, HSLA-130, HY-130, DQ-125, DQ-8O, and AC-50.