A stamping tool, which includes a separable die holder and set of interchangeable inserts (Fig. 1), is presently used at the Chelyabinsk Tube Rolling Mill (ChTPZ) for final forming of single-seam tubes with a diameter from 530 to 820mm on a P-753 press. Reductions of 0.2-0.6 percent are achieved when using U-shaped stock. The 200-MN force of the press forms stock with a maximum wall thickness of 16mm from steel 17G1SU (sigma_y=470 MPa) and up to 30mm from steels St2 and St3 (sigma_y=225-260 MPa). However, already when forming tubes with a 10-mm wall thickness a limited life of the stamping tool, not exceeding 10,000 formings in a number of cases, is noted. Destruction of the interchangeable tool made of high-strength cast iron, occurs as a consequence of the formation and rapid development of cracks in characteristic zones of the bottom part off the forming surface. The structural complexity, high labor intensity of manufacture, and large material expenditures, as well as the little amount of information about calculating and designing an interchangeable tool for forming large-diameter tubes determine the urgency of investigating the stress-strain state (SSS) of the stamping tool.
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