Investigation Of High Strain And Low Cycle Fatigue Behaviors Of Hot Rolled And High Strength H-beam Steels

The hot rolled H-beam steel structure which had a lot of advantages, such as the structure is scientific,the processing and installation is simple,the plasticity, ductility and anti-seismic capability are good, is widely used for all fields of the economic construction .When H-beam is used in seismic building, the high strain low cycle fatigue performance is very important for architectural structure.Based on the purpose of testing and researching high strain low cycle fatigue performance of H-beam,the rolling process is controlled .Choosing the best altematives parameters and using quadrature design.The results show that the influence of three factors on high strain and low cycle fatigue behaviors,which are heating temperature,deformation under 950℃and final rolled temperature, are declined in turn.With the purpose of acquiring high cyclic toughness and fine performance of high strain low cycle fatigue,the technological parameters of rolling process are designed as the billet heating temperature is 1250 , the deformation under 950 is 50%, the final rolling temperature is during 820～880 .According to the parameters of rolling process, 30mm steel was rolled,and the steel behave a good performance of high strain low cycle fatigue.The strain ageing effect exhibits a slight decreasing of cyclic toughness than the hot rolled one,while still keeping a very high level(35.3J·cm^-3).Using two kinds of methods,which are manual arc welding and CO₂ arc welding ,to weld the 30mm steel.The results show that the cyclic toughness as welded H-beam is 60% of that as hot-rolled.The extent of the decline is obvious. The welded materials show cyclic softening followed by fracture..The SEM micrographs of the manual arc welding materials revealed that the micro-cracks nucleation occurred at HAZ(heat affected zone).Tiny compartments and inclusion exist in the welding joint. And with the propagation of the micro-cracks,the materials crack under low fatigue life.The results of the cantilever beam experiment,which on condition that with high strain repeatedly,show that the hot rolled H-beam in this issue with good seismic performance.