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为改善超细晶粒钢焊缝热影响区(HAZ)组织软化问题,对不同Al含量的Fe-Mn-Si超细晶粒钢进行了热模拟研究。结果表明,在一定冷速条件下,此类钢随Al元素添加量的变化,组织从上贝氏体转变为无碳化物贝氏体,且随Al含量的不同,无碳化物贝氏体中残留奥氏体含量及其形态存在明显变化。另一方面,适当Al含量可增加此类钢种焊接条件下贝氏铁素体的形核数量,造成晶粒细化。残留奥氏体相数量与形态变化及晶粒细化是含Al超细晶粒钢HAZ区韧性提高的根本原因。
In order to improve the tissue softening of heat-affected zone (HAZ) of ultrafine grained steel, the thermal simulation of Fe-Mn-Si ultrafine grained steel with different Al contents was carried out. The results show that under a certain cooling rate, the microstructure changes from upper bainite to carbide-free bainite with the addition of Al, and with the content of Al, carbide-free bainite The retained austenite content and its morphology change significantly. On the other hand, proper Al content can increase the amount of bainitic ferrite nucleation under such welding conditions, resulting in grain refinement. Residual austenite phase morphology and grain refinement is the fundamental reason for the increase of HAZ toughness of Al-containing ultra-fine grain steel.