AWS B2.1-4-220 : 2021 Title: STANDARD WELDING PROCEDURE SPECIFICATION(SWPS) FOR GAS TUNGSTEN ARC WELDING (CONSUMABLE INSER ROOT) OF CHROMIUM-MOLYBDENUM STEEL (M-4?P-4, GROUP 1 OR 2), 1/8 THROUGH 1/2IN. THICK Year: 2021 Publisher: American Welding Society Availability: Within 1-2 working days