RESEARCH ON IMPACT TOUGHNESS OF Q460C HIGH-STRENGTH STEEL AT LOW TEMPERATURE

摘要

In order to obtain the influence degree for toughness of high strength steel,impact toughness tests of Q460C steel with 14 mm thickness as a new type of high strength structural steel at low temperature were conducted in this paper.SANS type pendulum impact testing machine as well as a low temperature incubator were employed for the experimental study.What's more,the paper reported the results to identify the effects of low-temperature flexibility,plate thickness and material strength on the plastic deformation capacity governed by brittle fracture.Moreover,analyze the scanning electronic microscope of fracture surfaces of the specimen at different temperature points.In addition,the charpy impact power level was compared with that of Q345 steel with 60 mm,90 mm,120 mm and 150 mm thickness respectively.And the results demonstrated that:the impact toughness of Q460C steel declined with the descending temperature; The influence of steel strength on low temperature brittleness of Q460C steel was less apparent than that of plate thickness on that of Q345 steel.The fracture surfaces of impact test specimens of Q460C steel,which impact broke at-20°C had already finished the transition form ductile to brittle,with a large of notable brittle characteristics.Meanwhile,Boltzmann function fit analysis got-11.1 °C as the brittle ductile transition temperature for Q460C steel.Test results showed that low temperature brittleness of Q460C steel were obvious,which should be paid sufficient attention to.