AWS B2.1-4-221 : 2021 Title: Standard Welding Procedure Specification (SWPS) for Gas Tungsten Arc Welding (Consumable Insert Root) followed by Shielded Metal Arc Welding of Chromium-Molybdenum Steel (M-4/P-4, Group 1 or 2) Year: 2021 Publisher: American Welding Society Availability: Within 1-2 working days