Abstract Mechanical properties of recently supplied ASTM A-420 WPL6 yr. 1996 (rev. a) fittings are discussed. Impact test results showing the detrimental effects of post weld heat treatment (PWHT) on the base material and weld heat affected zone toughness of quenched and tempered vanadium micro-alloyed fittings are presented. Micro-hardness test results from using the low heat input shielded metal arc welding (SMAW) process are also presented. Other chemical element differences between the ASTM / ASME A-420 yr. 1995 and the micro-alloyed ASTM A-420 yr. 1996 (rev. a) standards are discussed. The status of recent ASME Code committee activities to evaluate micro-alloyed steels for P number, fabrication and PWHT rules separate from standard P No. 1 materials is shared.