No. 13011. Argued March 8, 1960. Decided April 13, 1960. Supplemental Opinion May 17, 1960. Duane Beeson, Washington, D.C. (Stuart Rothman, Gen. Counsel, Thomas J. McDermott, Associate Gen. Counsel, Marcel Mallet-Prevost, Asst. Gen. Counsel, Standau E. Weinbrecht, Atty., N.L.R.B., Washington, D.C., on the brief), for petitioner. W.D. Armour, Pittsburgh, Pa. (John C. Bane, Jr., John G. Wayman, Reed, Smith, Shaw McClay, Robert Molinar, Pittsburgh, Pa., on the brief), for United States Steel Corp. J