Effect of rare earths on impact toughness of a low-carbon steel
Effect of rare earths on impact toughness of a low-carbon steel
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DOI：
10.1016/j.matdes.2011.06.042
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发表时间：
2012
影响因子：
8.4
通讯作者：
Hongling Liu;Chengjun Liu;M. Jiang
中科院分区：
文献类型：
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作者：
Hongling Liu;Chengjun Liu;M. Jiang
对一种工业用低碳钢（B450 NbRE）的研究表明，其冲击韧性在实际使用中出乎意料地低，这可能是由于在炼钢过程中稀土（RE）的回收不稳定所致。研究了稀土对低碳钢冲击韧性的影响。B450 NbRE钢的含量为0.0012-0.0180wt.%，采用真空感应炉冶炼稀土。研究了热轧后的冲击韧性和显微组织。采用Gleeble-1500热模拟试验机验证了稀土对合金组织的影响。结果表明，热轧钢的显微组织由多边形铁素体、准多边形铁素体、贝氏体和珠光体组成。冲击韧性随稀土含量的增加而增加，在稀土含量为0.0047wt.%时达到峰值RE时，这种变化表现出与铁素体量的情况相同的规律。然而，这种冲击韧性的改善不仅是由于铁素体量的增加，而且是由于细晶组织和更清洁的晶界。含量为0.0180wt.% RE太多了。稀土的加入导致晶界处马氏体析出，这对冲击韧性极为不利。
Studies of an industrial low-carbon steel (B450NbRE) suggest that the impact toughness is unexpectedly low under its practical service, probably resulting from the unstable recovery of rare earths (RE) in steelmaking. The purpose of this work is to investigate the effect of RE on the impact toughness in low-carbon steel. The B450NbRE steels with content of 0.0012–0.0180wt.% RE were produced by vacuum induction furnace. The impact toughness and microstructure were investigated after hot rolled. The Gleeble-1500 thermal simulator was used to validate the effect of RE on the microstructure. The results indicate that the microstructure of hot-rolled steels is characterized by polygonal ferrite, quasi-polygonal ferrite, bainite and pearlite. The impact toughness increases with RE contents reaching the peak with content of 0.0047wt.% RE, such a change exhibits the same rule as the case of the ferrite amount. However, this improvement in impact toughness is not only due to an increase in ferrite amount, but also the fine grained structure and the cleaner grain boundaries. And content of 0.0180wt.% RE is excessive. Such an addition of the RE resulted in the martensite precipitates at the grain boundaries, which are extremely detrimental to impact toughness.