非晶变质处理对超高碳钢组织结构及力学性能的影响

发布时间：2018-04-18 16:21

本文选题：超高碳钢 + 非晶态变质剂　；参考：《天津理工大学》2017年硕士论文

【摘要】：超高碳钢作为一类含碳量在1.0-2.1wt.%之间的铁基合金材料,在常规铸造凝固状态下组织中极易存在粗大的网状碳化物,导致塑、韧性很差,致使其的应用受到限制。本文针对成分为Fe-1.81C-0.32Si-1.52Cr-0.40Al-0.62Mn的超高碳钢,采用热力学结构状态完全不同的晶态与非晶态稀土-硅铁-钠/钾变质剂对其进行变质处理,借助研究不同变质处理条件下实验用钢的显微组织形态与力学性能的特征,探究非晶变质处理对超高碳钢碳化物析出形态的影响规律。实验结果发现:相比于直接凝固处理,实验用钢经晶态稀土-硅铁-钠/钾变质处理,骨骼状凝固组织形态得以抑制,但仍然存在碳化物的网状析出。相比之下,经同成分非晶稀土-硅铁-钠/钾变质处理,实验用钢凝固组织中碳化物以细小的颗粒状形态出现,网状析出现象得到有效克服,且变质剂的加入量为0.2wt.%时,颗粒状碳化物的形貌以及均匀分布的状态均较佳,对应材料的抗拉强度与冲击韧性值分别达到具有较高工程应用价值的1182MPa和11 J/cm2。值得注意的是,虽然本文所设计实验用钢的含碳量已经超出一般超高碳钢碳含量的上限,但经历非晶稀土-硅铁-钠/钾变质处理,碳化物的析出形态仍能得到有效改善。通过比较分析实验用钢凝固试棒的横、纵向显微组织结构发现,非晶稀土-硅铁-钠/钾变质处理改善碳化物析出形态的整体效果优于同成分晶态变质剂的变质处理。
[Abstract]:As a kind of Fe-base alloy material with carbon content between 1.0-2.1 wt.%, ultra-high carbon steel is prone to exist coarse reticular carbide in the microstructure of conventional casting solidification, which leads to poor plasticity and toughness, which limits its application.In this paper, ultrahigh carbon steel with Fe-1.81C-0.32Si-1.52Cr-0.40Al-0.62Mn composition was modified with crystalline and amorphous rare-earth ferrosilicon-sodium / potassium modifiers with completely different thermodynamic structure.By studying the microstructure and mechanical properties of experimental steel under different modification conditions, the effect of amorphous modification on carbide precipitation morphology of ultra-high carbon steel was investigated.The experimental results show that compared with direct solidification treatment, the microstructure of skeleton solidified steel can be inhibited by the modification of crystalline rare-earth, ferrosilicon-sodium / potassium, but there still exists the network precipitation of carbides.By contrast, after the modification of amorphous rare earths, ferrosilicon, sodium and potassium, the carbide in solidified microstructure of the experimental steel appeared in fine granular form, and the phenomenon of network precipitation was effectively overcome, and when the amount of modifier was 0.2wt.%,The morphology and uniform distribution of granular carbides were better, and the tensile strength and impact toughness of the corresponding materials reached 1182MPa and 11J / cm ~ (2), respectively, which had higher engineering application value.It is worth noting that although the carbon content of the experimental steels designed in this paper has already exceeded the upper limit of the carbon content of general ultra-high carbon steels, the precipitation morphology of carbides can still be improved effectively after the modification of amorphous rare earths, ferrosilicon, sodium and potassium.By comparing and analyzing the transverse and longitudinal microstructure of solidified steel bars, it is found that the modification of amorphous rare earths, ferrosilicon, sodium / potassium can improve the morphology of carbide precipitation better than that of the same composition crystalline modifier.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1;TG260

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