Impact fracture energies of cold-formed steel square hollow section in and after fire

Abstract Charpy impact tests were performed on a cold-formed steel square hollow section at high temperatures and the ambient temperature after heating and cooling processes. The specimens were quarried from the flat and corner parts of the cross-section, respectively. High-temperature tests were conducted at 100–600 °C to verify the Charpy impact energies, including the blue-brittleness temperatures region (100–300 °C). In the ambient-temperature tests after the heating and cooling processes, the specimens were subjected to three heating and cooling methods: air cooling in a furnace from 600 to 900 °C (slow cooling process from the high temperature), quenching with water from 600 to 900 °C (fast cooling process from the high temperature), and air cooling outside of the furnace from 200 to 400 °C (slow cooling process from the medium temperature). The test results confirmed that the Charpy impact energy was not reduced after the slow cooling from the high temperature. However, the specimens subjected to either the quenching process from the high temperature or the slow cooling process from the medium temperature exhibited low Charpy impact energies.