Welding Basis.
Welding Metallurgy.
Welding Processes (SMAW-GTAW-GMAW-FCAW-SAW) etc.
Welding Procedure Specifications - WPS.
Welding Procedure Qualification Testing - WPQT
Post Weld Heat Treatment - PWHT.
Procedure Qualification Record - PQR.
Destructive Testing.
NDE - NonDestructive Examination
Norms and standards related to welding and inspection.
API
ASTM
ASME
AWS
EN
ISO etc.