Effect of the Nonuniform Distribution of the Mechanical Properties of Rolled Sheets on the Shape of a Round Billet after Forming in Making Large-Diameter Pipes

The influence of a nonuniform distribution of the mechanical properties of rolled sheet steel on the shape of a pipe billet in making large-diameter pipes in the 1420 pipe-electric welding unit line is studied. The technique and results of measuring the hardness along the perimeter of the initial 25.8 × 4340 × 12 200 mm rolled sheet of strength class K60 are presented. The hardness of the sheet is maximal in the longitudinal direction at the tail end and is minimal at the center. The height and radius of the crimped edge are measured after crimping. The geometric discrepancy in the billet edges along the length is larger than that across the width by 6%. The horizontal and vertical diameters, the gap width, the edge displacement in height, and the diameters at l = 100 mm from the edge end are measured after step-by-step forming. The dependence of the gap width of the pipe billet after forming on the yield strength of the rolled sheet is determined.