Hobart SDX S2Si-EM12K description: SDX S2Si-EM12K is a copper-coated carbon-steel solid wire for submerged arc welding. SDX S2Si-EM12K is a versatile, general purpose product suitable for joining a wide range of non-alloyed steels with a wide variety of flux(es). Hobart recommends using this wire with the following flux(es): SWX 110, SWX 120, SWX 130, SWX 135, SWX 140, and SWX 150.