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采用金相、扫描电镜对409L连铸坯的夹杂物数量、分布、类型进行实验研究,热力学分析连铸坯中夹杂物形成机理。结果表明:连铸坯上表面夹杂物数量较多,连铸坯边部三角区域的堆状复合夹杂物数量较多;夹杂物类型以TiN、TiN包裹MgO·Al2O3的复合夹杂物为主;当钢中[N]质量分数0.01%、钢液温度1 580~1 600℃,生成TiN夹杂所需要平衡[Ti]质量分数为0.124%~0.154%;钢中[Al]质量分数为0.01%,若钢中[Mg]质量分数不小于7.5×10-5%,则钢液中易生成MgO·A12O3,当[Mg]质量分数不小于0.000 7%后,MgO·A12O3转变为MgO。
The number, distribution and types of inclusions in 409L slab were investigated by metallography and scanning electron microscopy. The formation mechanism of inclusions in slab was analyzed thermodynamically. The results show that there are many inclusions in the upper surface of continuous casting slab, and there are more heap-like composite inclusions in the triangular region of the slab. The inclusion types mainly include composite inclusions of MgO · Al2O3 and TiN, TiN. The mass fraction of [N] in steel is 0.01%, and the temperature of molten steel is in the range of 1 580 ~ 1 600 ℃. The mass fraction of [Ti] needed to form TiN inclusions is 0.124% ~ 0.154% When the mass fraction of [Mg] in steel is not less than 7.5 × 10-5%, MgO · A12O3 is easily formed in the molten steel. When the mass fraction of [Mg] is not less than 0.000 7%, MgO · A12O3 is transformed into MgO.