EN 10253-1 is the standard specification for butt welding fittings of wrought carbon steel. For general use and without specific requirements. Generally the material may be S235 or its alternative S265.
EN 10253-2 is the standard specification for butt welding pipe fittings of non-alloy and ferritic alloy steels. With specific inspection requirements. Typical materials include P235GH, P265GH, 16Mo3, 13CrMo4-5, P355NH, and L450QB, etc.