EMPLOYEE WAS WELDING A D-RING ON A LOWER ROLLER SHAFT ON A 2800 P&H SHOVEL. THE FINISHED VERTICAL WELD LEFT A LAYER OF SLAG OVER THE WELD. EMPLOYEE WIPED THE SLAG OFF WITH HIS LEFT HAND AND UNDER THE SLAG WAS A SHARP BAR, CUTTING THROUGH HIS GLOVED HAND. SUTURES REQUIRED.