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Ti-Mg船板钢铸态组织中发现大量晶内针状铁素体(IGF),IGF大幅提高铸坯强韧性的同时,也给连铸弯曲矫直工艺和连铸机寿命带来影响。为探明连铸坯中IGF的诱发机制,进行了冷却速率、钢中夹杂物尺寸及分布等因素对铸态组织中IGF诱发的影响研究。结果表明:对试验钢种而言,夹杂物的尺寸和分布是该类钢种铸态组织的决定性因素。与钢板焊接热影响区中能够诱发IGF的夹杂物尺寸多为3μm以下相比,在铸坯中能够诱发IGF的夹杂物多为5~15μm。因此为保证连铸机的寿命和拉矫工艺的稳定,最好将夹杂物尺寸控制在5μm以下,以降低IGF含量。
A large amount of intragranular acicular ferrite (IGF) was found in the as-cast structure of Ti-Mg steel, and IGF significantly enhanced the strength and toughness of slab, meanwhile, it affected the bending and straightening process of continuous casting and the life of continuous casting machine. In order to investigate the induction mechanism of IGF in billet, the effect of cooling rate, the size and distribution of inclusions in steel on the IGF induction in as-cast microstructure was studied. The results show that the size and distribution of inclusions are the decisive factor for the as-cast microstructure of the steels. Compared with the case where the size of the IGF-capable inclusions in the heat-affected zone of the steel plate is mostly 3 μm or less, the inclusions capable of inducing IGF in the slab are mostly 5 to 15 μm. Therefore, in order to ensure the life of the caster and the straightening process, it is best to control the inclusion size below 5μm to reduce the IGF content.