Investigation of Tensile Properties at Room and Elevated Temperatures of S1100QL Steel and Its Welded Joints

The aim of this paper was to present an experimental study into the influence of elevated temperatures on the tensile properties of the ultra-high-strength steel (UHSS) S1100QL and its welded joints. S1100QL steel belongs to the group of structural steels, and it is mainly used for designing various types of lifts and cranes with the goal of decreasing the mass of structures while increasing their load capacity. Since the structures mentioned are mostly produced as welded structures, tensile tests were also conducted on the specimens prepared from two different types of welded butt joints made of S1100QL steel. One plate was welded with a preheating temperature of approx. 175 °C with a similar undermatching filler material, and the second plate was welded with slight preheating and with two different filler materials. For the root pass, an austenitic filler material was used, and for further passes the same undermatching filler material as in the first case was used. The goal of this study was to determine the highest temperature at which the steel and its welded joints maintain their properties. The first set of tensile tests focused on testing the properties of the base material at room and seven other elevated temperatures (from 100 °C to 700 °C). The results obtained showed that between 400 °C and 500 °C, properties begin to drop. The second set of tests focuses on investigating the tensile properties of S1100QL welded joints, both at room and elevated temperatures. In this paper, details on the welding technologies used and the microstructures obtained are also presented.