Analysis on the Impact Resistance of Q460FRW for Building Structure at Low Temperature

In order to verify the design requirements of low temperature impact resistance of Q460FRW steel, its impact toughness at low temperature was tested with SANS pendulum impact testing machine, and the fracture morphology of samples was analyzed. According to GB/T 229—2007 Metallic Materials Charpy Pendulum Impact Test Method, low temperature impact test was carried out on Q460FRW steel specimens of 10 mm and 28 mm at - 20, - 40, - 60 ℃ ambient temperature. The impact energy value A_kV was obtained, and the experimental curve of impact strength with temperature was plotted from two series of Q460FRW steel specimens at each low temperature point. The tensile strength, yield strength and elongation of FRW steel at room temperature and low temperature were tested. Scanning electron microscope (SEM, at 1 000 magnification) was used to analyze the fracture morphology of Q460FRW steel specimens in two standard sizes after impact fracture. The results shown that Q460FRW steel can maintain high impact energy and good impact toughness at low temperature. At the same time, the impact toughness increases slightly with the decrease of temperature at -20, - 40, - 60 ℃. The longitudinal impact energy values of the two series Q460FRW were greater than 34 J, according with the requirements of GB/T 19879—2005 Steel Plates for Building Structures, and meeting the design requirements of impact resistance at low temperature. SEM observation and analysis shown that the crack propagates outward from the fiber area in the center of the specimen during impact tension, and a large plastic deformation occurs near the crack area, forming a large shear notch, which indicated that were ductile. There is no significant difference in the size and depth of the fracture dimple from SEM.