Characteristics of Embrittlement in Weather Resistant Steel in Austenite and γ-Ferrite Temperature Range

Abstract

The embrittlement of particular weather resistant steel has been investigated by thermal tensile tests using a Gleeble-1500D system at temperatures range from 600 to 1300°C and at a strain rate of 10-3/s. The specimen was reheated and cooled to the test temperature before the tensile deformation in order to get the mechanical properties subject to the continuous casting process. To make clear the plastic flow behavior in Austenite and γ-Ferrite temperature range of the weather resistant steel, the tensile tests were performed and the results indicate that the stress-strain curves as a function of temperature and with the temperature increased the stress became less, while the hot ductility changed significantly due to the work hardening and recrystallization. All of the strength indices (including yield strength, tensile strength and fracture strength) of the steel increased gradually with decreasing temperature, except for small fluctuations during the γ→α transformation occurred. Special emphases were placed on the hot ductility to clarify the sensitivity of surface cracking during unbending operation and the embrittlement zone occurred in the temperature range between 750 and 1050°C, in which the minimum %R of A was around 22% at 850°C. In the embrittlement zone, the specimens were fractured with little plastic deformation by either grain boundary sliding or by localization of strain in the film proeutectoid ferrite produced by the γ→α transformation. Keywords: Weather Resistant Steel, Embrittlement Zone, Stress-Strain Analysis, Hot Ductility, Fracture Surface.