Abstract This work aimed to investigate the segregation sequence of impurity elements in the weld metal of carbon steel with various solidification sequences, such as δ single-phase, hypo-peritectic, hyper-peritectic, and γ-single-phase solidification. Moreover, the relationship between the solidification sequence and toughness of the weld metal of carbon steel was studied. The solidification sequence was controlled by the nickel content of the base metals. Various amounts of sulfur and phosphorous were added to the base metals as impurity elements, and the segregation amount of the impurity elements in the weld metals increased in the order of δ-single-phase, hypo-peritectic, hyper-peritectic, and γ-single-phase. The amount of sulfur was higher than that of phosphorous in each solidification sequence. In δ-single-phase solidification, sulfur segregated during solidification and relaxed during cooling after solidification. In contrast, in γ-single-phase solidification, sulfur continued to segregate during and after solidification. The segregated sulfur was in the grain boundaries of the prior austenite at low temperatures. Charpy impact test results revealed that the ductile-brittle transition temperature (DBTT) increased, and the upper shelf energy decreased with an increase in the nickel content, specifically, only for the specimen of γ-single-phase solidification with S addition. In particular, the tendency in the specimens containing sulfur was more significant compared to the specimens containing phosphorous. Moreover, the intergranular fracture surface was only observed in the γ-single-phase solidification specimen, and sulfur was concentrated on the surface. Therefore, the superposition of segregation during and after solidification induced intergranular embrittlement and deterioration of toughness.

中文翻译：

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碳钢焊缝金属凝固顺序与韧性的关系

摘要 本研究旨在研究δ单相、亚包晶、超包晶和γ单相凝固等不同凝固顺序的碳钢焊缝金属中杂质元素的偏析顺序。此外，研究了碳钢焊缝金属的凝固顺序与韧性之间的关系。凝固顺序由贱金属的镍含量控制。在母材中添加不同量的硫、磷作为杂质元素，焊缝金属中杂质元素的偏析量按δ-单相、亚包晶、超包晶、γ-的顺序增加。单相。在每个凝固顺序中，硫的量高于磷的量。在δ-单相凝固中，硫在凝固过程中偏析，凝固后冷却过程中松弛。相反，在γ-单相凝固中，硫在凝固过程中和凝固后继续偏析。偏析的硫在低温下位于原奥氏体的晶界中。夏比冲击试验结果表明，随着镍含量的增加，韧性-脆性转变温度（DBTT）升高，上架能降低，特别是仅适用于添加S的γ-单相凝固试样。特别是，与含磷样品相比，含硫样品的趋势更显着。此外，仅在γ-单相凝固试样中观察到晶间断面，硫在表面富集。所以，