AWS B2.1-5A-225 : 2022, Standard Welding Procedure Specification for Gas Tungsten Arc Welding of Chromium- Molybdenum Steel , IN521 and ER90S-B3, 1/8 Inch [3 Mm] Through 1/2 Inch [13 Mm] Thick, As-Welded Condition; 1/8 Inch [3 Mm] Through 3/4 Inch [19 Mm] Thick, PWHT Condition, Primarily Pipe Applications : AWS B2.1-5A-225