Abstract The present study investigates the combined effect of cooling-rate during solidification and hot deformation on the microstructure and mechanical properties of low-carbon steel, especially considering the beneficial effect of acicular ferrite. Low-carbon steel was cast in two different moulds to vary the cooling-rate during solidification. The cast ingots were soaked and hot forged at different temperatures. Relatively slower cooling-rate during solidification and deformation at relatively lower temperature were found to be beneficial for the acicular ferrite formation, which increased the hardness and strength without hampering the ductility. The difference in solute contents at the dendrite center and the interdendritic regions of the cast-ingots, as a result of microsegregation, and the compositional homogenization during soaking were predicted. Based on the predicted compositions, the microstructures of the cast and hot forged ingots were explained considering the effect of prior-austenite grain size, austenite conditioning during deformation, fraction of non-metallic inclusions and the segregation of Nb along the prior-austenite grain boundaries on the phase transformation.

中文翻译：

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凝固冷却速度对低碳钢热变形组织性能关系的影响

摘要 本研究研究了凝固和热变形过程中冷却速度对低碳钢组织和力学性能的综合影响，特别是考虑了针状铁素体的有益影响。低碳钢被浇铸在两个不同的模具中，以改变凝固过程中的冷却速度。铸锭在不同温度下进行均热和热锻。发现在相对较低的温度下凝固和变形过程中相对较慢的冷却速度有利于针状铁素体的形成，从而在不影响延展性的情况下增加硬度和强度。由于微观偏析，铸锭枝晶中心和枝晶间区域溶质含量的差异，并预测了浸泡过程中的成分均匀化。基于预测的成分，考虑了原奥氏体晶粒尺寸、变形过程中的奥氏体调质、非金属夹杂物的比例和 Nb 沿原奥氏体晶界的偏析的影响，解释了铸造和热锻铸锭的显微组织关于相变。