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本文研究了微量铋在球墨铸铁焊缝和熔合区中对球化、石墨化和铁素体化的影响规律。结果果指出,微铋强烈增加石墨球数、稳定球化、促进铁素体形成、有效地减少或消除焊缝和半熔化区的渗碳体,从而大大提高冷焊接头的切削加工性和抗裂性能。如果焊缝含铋量为100～120ppm 时,冷焊后焊缝可达到球化1～2级,含80%～95%铁素体,没有渗碳体,抗拉强度σ_b=540MPa 和延伸率δ=5.7%。由此,研究了一种新型含Bi 球铁焊条“铸238F”,具有较高的抗裂性和良好的切削加工性,已成功地用于生产。
In this paper, the effects of micro-bismuth on the nodularity, graphitization and ferrite in the weld and fusion zone of ductile iron were studied. The results indicate that micro-bismuth strongly increases the number of graphite balls, stabilizes the spheroidization and promotes the formation of ferrite, effectively reducing or eliminating the cementite in the weld and semi-molten zone, thereby greatly improving the machinability and resistance of the cold welded joint Cracking performance. If the amount of bismuth in the weld is 100 ~ 120ppm, the weld after cold welding can reach 1 ~ 2 grades of spheroidization, containing 80% ~ 95% ferrite, without cementite, tensile strength σ_b = 540MPa and elongation δ = 5.7%. Thus, a new type of Bi-containing ductile iron “Cast 238F” was studied, which has high crack resistance and good machinability and has been successfully used in the production.