Production of Heavy Plates of Pipe Steel with Increased Strength and Cold Resistance on the 5000 Rolling Mill at PJSC MMK

Abstract

Abstract—On the basis of laboratory experiments on an ITs Termodeform-MGTU test system, the production of rolled plates with large thickness from pipe steel of improved strength (R_t 0.5 = 505–610 MPa, R_m = 570–680 MPa) and cold resistance (KV^–48 ≥ 170 J, DWTT^–55 ≥ 90%) is introduced in the 5000 rolling mill at PJSC MMK. To ensure high cold resistance, the formation of predominantly quasi-polygonal and polygonal (polyhedral) ferrite is optimal. It is found that, if the steel microstructure includes a considerable quantity of bainite, the performance of the steel in drop tests is impaired. By means of the Gleeble 3500 test system, the thermokinetic diagram of supercooled-austenite decomposition is plotted for the new low-carbon pipe steel, with up to 1% Ni.