From Table 3.1 - ASTM A572 gr 50 is a Group II base metal.
From Table 4.8 - Any Group II to Any Group II qualifies the WPS for Any Group II to any Group II, Any Group I to Any Group II and it qualifies for any Group I to any Group I
ASTM A36 less than or equal to 3/4 inch thick is a Group I, any ASTM A36 greater than 3/4 inch is a Group II base metal. Thus pre the previous paragraph, your WPS is qualified for ASTM A36 to A36 for all thicknesses.
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