Microstructural analysis and mechanical properties of simulated heat affected zone in A572 Gr.65steel plates
|Keywords:||銲接熱模擬;銲接入熱量;高強度低合金剛;變韌鐵;heat input;welding simulation;HSLA;bainite||Issue Date:||2006||Abstract:||
For the purpose of investigating the phase transformation of ASTM A572 grade 65 steel plates during the welding process, simulated heat affected zone (HAZ) experiments with heat inputs of 10, 20 and 30kJ/cm have been carried out by dilatometer. Furthermore, the evolutions of microstructure after post heat (at 300℃) and post weld heat (at 590℃) treatment within different soak time were also be concerned as well. The results indicate that the phase transformation temperature (Bainite starting temperature, Bs) of the steel plate would change with different heat inputs, and that the simulated HAZ microstructure gives large amount of lower bainite. Under the TEM (Transmission electron microscope) observation, it was found that with heat input of 10kJ/cm the significant amounts of auto-tempered martensite were obtained in the bainite matrix. Upper bainite became dominant while the simulated welding condition was changed to be 30kJ/cm. In order to investigate the tend of toughness versus variation of microstructual constituent for A572Gr.65, the thermal simulation for charpy impact test samples was carried out on a Gleeble machine. The result shows that specimens, which were experienced the heat input of 20kJ/cm, then held at 300℃ for 30min postheat treatment and at 590℃ for 180 min post-weld heat treatment, have higher toughness than those obtained from other heat treatment processes.
|Appears in Collections:||材料科學與工程學系|
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