多元低合金化对蠕墨铸铁组织与性能的影响

Effect of Multi-Component Micro-Alloying on Microstructure and Properties of Compacted Graphite Cast Iron

采用光学金相、扫描电镜、力学性能测试等手段研究了普通蠕墨铸铁、Cu-Mo-Sn蠕墨铸铁、Cu-Mo-Sn-Cr蠕墨铸铁的铸态显微组织和不同温度下的拉伸性能,分析了多元低合金化对蠕墨铸铁蠕化率、屈强比(σ0.2/σb)、高温强度保持率(高温强度/室温强度)的影响。结果表明:多元合金元素的复合加入对其蠕化效果无明显影响,但可促进珠光体的形成并强化基体组织;多元低合金化处理可以提高蠕墨铸铁的屈强比,降低合金的伸长率。并且多元合金化对中低温(350℃)强度保持率影响不明显,但可以大大提高高温(500℃)强度保持率,其500℃抗拉强度保持率由56%提高到71%以上;断口分析表明,室温下其微观断裂呈现为以解理为主的解理-韧窝混合断裂,随着多元低合金元素的加入,韧窝、撕裂棱减少,塑性降低。

Microstructure and tensile properties of three kinds of compacted graphite cast irons, no-alloyed, Cu-Mo-Sn alloyed and Cu-Mo-Sn-Cr alloyed, were studied by using optical microscopy, scanning electron microscopy and mechanical properties testing in the paper. The effects of multi-component micro-alloying on vermicularizing, the ratio of yield strength and ultimate tensile strength （σ0.2/σb）, retention rate of strength at elevated temperatures were analyzed. The results showed that the obvious effects of multi-component micro-alloying elements on vermicularizing was not observed, but the improving formation of pearlite and strengthening the microstructure of matrix took place when elements Cu, Mo, Sn and Cr were added. Meanwhile, the ratio of σ0.2/σb of Cu-Mo-Sn and Cu-Mo-Sn-Cr alloyed compacted graphite cast iron at room temperature was increased, and the elongation was decreased compared to the normal compacted graphite cast iron. The strength retention rate of three kinds of compacted graphite cast irons at 350℃ kept almost the same lever, however, it was improved greatly, increased from 56% to over 71%, at 500 ℃ compared to compacted graphite cast iron. Fracture analysis of test material showed that cleavage-dimples mixed fracture mechanism, but cleavage was the dominant fracture mechanism at room temperature. With addition of multi-alloying elements, the number of dimples and tear edges on fracture surface of compacted graphite cast iron reduced and toughness decreased.