INFLUENCE OF TEMPERATURE AND STRUCTURE ON THE FORMABILITY OF STEELS FOR THE PRODUCTION OF SEAMLESS TUBES

Abstract

The aim of the paper was to determine the temperature dependence of formability of investigated steels by uniaxial tensile fracture tests under thermomechanical conditions corresponding to punching (1340–1395 °C) and pilger rolling (800–1050 °C) in The Tube Mill TŘINECKÉ ŽELEZÁRNY a.s. The deformation behavior of N1 and 42CrMo4 steels was investigated. In both cases, the effect of the structure on formability was taken into account. In the case of high-temperature examination corresponding to the punching process, the tests were performed on samples taken from the area of the column crystals (i.e. closer to the outer surface of the continuously cast semi-finished product) and also from the area below the column crystals closer to the center. In the case of low-temperature tests corresponding to pilger rolling, the strength-plastic properties were evaluated from an area closer to the inner or closer to the outer surface of the roll after punching. Uniaxial tensile tests to the fracture were performed on the HDS-20 simulator.