HAZ characteristics of grain-refined ferrite-pearlite steels(I) (Variation of HAZ microstructures with welding conditions)

摘要

The effect of ferrite grain refinement on the heat-affected zone microstructural evolution was investigated usinggrain-refined ferrite-pearlite steel with ferrite grain size of4#mu#m. HAZ austenite grain size and microstructure volumefractions were measured and compared them with normal steels.An established theoretical model for the prediction of HAZmicrostructures of normal steels was modified for grain-refinedsteels. Ferrite grain refinement resulted in smaller HAZ austenitesize. Compared to 320 #mu#m of normal steels, grain-refinedsteels showed only 104 #mu#m at the welding condition of T_p1350 deg C-triangle open 20s for example. Variation of austenitesize with welding conditions can be predicted reasonably wellwhen the initial austenite size of grain-refined steels is 9 #mu#m.It was shown that the established Johnson-Mehl type model wasalso applicable to grain-refined steel when correctional factor dueto grain refinement was incorporated in it. Measured andcalculated values showed a good agreement when the correctional factor was 0.5.