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<正> 低碳铁素体加马氏体双相钢的强度和塑性取决于马氏体的数量和分布,这与亚温区加热过程中奥氏体形成的特点有关。由于奥氏体的形成是在高温下进行,速度快,难于直接获得有关形核的信息。本文研究低碳钢中奥氏体形成的部位,以及预先冷轧的影响。 试验用低碳1.5Mn钢,其化学成分为(wt-％):C 0.08,Mn 1.45,si 0.21,Al 0.045,N 0.005。经高频感应电炉熔炼成45kg的钢锭后,热轧成2.5mm厚的板材。在真空炉中经过1200℃均匀化退火24h。然后,在盐炉中900℃加热15min后空冷,获得铁素体加珠光体型的正火原始组织。另将一部分正火的坯料进行厚度压下量

The normalized and normalized plus cold-rolled structures and their effects on the formation of austenite in 0.08C-1.5Mn steel were examined by TEM. It was shown that during intercritical annealing, the austenite formation was accompanied by spheroidization of cementite in the initially normalized structure, a result attributed to the existence of more dislocation in ferrite and degenerated pearlite containing many changes in spacing and interruption in lamellar morphology in the normalized condition. The austenite nucleated not only at the cementite particles located at the triple points and faces of ferrite grain boundaries, but also at the interfaces of ferrite and cementite which was within ferrite matrix. Due to the effect of cold rolling, the lamellar cementite in the cold-rolled structure was distorted severely and even fragmented. Also, a great amount of dislocations were introduced into the ferrite matrix. These effects of the cold rolling accelerated the spheroidization of cementire and enhanced the possibility that the austenite formed within ferrite grains during intercritical annealing. The relationship between austenite formation and cementite spheroidization and the possible sites of austenite nucleation were discussed.