A Scale-up Study on Chemical Segregation and the Effects on Tensile Properties in Two Medium Mn Steel Castings
A Scale-up Study on Chemical Segregation and the Effects on Tensile Properties in Two Medium Mn Steel Castings
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DOI：
10.1007/s11661-021-06533-w
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发表时间：
2021-10
期刊：
影响因子：
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通讯作者：
T. Kwok;C. Slater;X. Xu;C. Davis;D. Dye
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文献类型：
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作者：
T. Kwok;C. Slater;X. Xu;C. Davis;D. Dye
生产了两块分别重 400 克和 5 公斤、标称成分为 Fe-8Mn-4Al-2Si-0.5C-0.07V-0.05Sn 的铸锭，以研究加工变量对微观结构发展的影响。较大的铸件具有更能代表商业生产的冷却速率，并且可以了解在扩大中锰钢规模的过程中与铸造相关的偏析所带来的潜在挑战，而较小的铸件具有较高的冷却速率和不同的偏析模式。两块铸锭的切片在 1250°C 下均质化不同时间，以研究化学均匀性和铁素体溶解程度。在 2 小时内，Mn 偏析范围（最大 - 最小）在 400 g 铸锭中从 8.0 wt% 下降到 1.7 wt%，在 5 kg 铸锭中从 6.2 wt% 下降到 1.5 wt%。 2 小时后，两个铸锭中的一些铁素体也仍未发生转变，但 5 千克铸锭的铁素体含量几乎是 400 克铸锭的三倍。进行了 Microress 建模，预测和测量的偏析水平和分布之间具有良好的一致性。热机械加工后发现，5公斤铸锭中粗大的未相变铁素体转变为成品中的粗大铁素体纵梁，导致屈服强度略有下降。然而，与完全均质化的样品相比，两种锭轧制的带材均表现出 MPa 屈服强度、MPa 拉伸强度和 PCT 伸长率，且强度存在 PCT 差异，并且延展性没有变化。
Two ingots weighing 400 g and 5 kg with nominal compositions of Fe–8Mn–4Al–2Si–0.5C–0.07V–0.05Sn were produced to investigate the effect of processing variables on microstructure development. The larger casting has a cooling rate more representative of commercial production and provides an understanding of the potential challenges arising from casting-related segregation during efforts to scale up medium Mn steels, while the smaller casting has a high cooling rate and different segregation pattern. Sections from both ingots were homogenized at 1250C for various times to study the degree of chemical homogeneity and-ferrite dissolution. Within 2 hours, the Mn segregation range (max–min) decreased from 8.0 to 1.7 wt pct in the 400 g ingot and from 6.2 to 1.5 wt pct in the 5 kg ingot. Some-ferrite also remained untransformed after 2 hours in both ingots but with the 5 kg ingot showing nearly three times more than the 400 g ingot. Micress modeling was carried out, and good agreement was seen between predicted and measured segregation levels and distribution. After thermomechanical processing, it was found that the coarse untransformed-ferrite in the 5 kg ingot turned into coarse-ferrite stringers in the finished product, resulting in a slight decrease in yield strength. Nevertheless, rolled strips from both ingots showedMPa yield strength,MPa tensile strength, andpct elongation withpct difference in strength and no change in ductility when compared to a fully homogenized sample.