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本文对国产中Ni—Cr球墨复合铸铁轧辊发生早期失效碎裂件,应用光学和电子显微镜等手段,对材质化学成分、低倍酸蚀、夹杂物、残余应力等进行了测定分析。结果表明:造成轧辊早期断裂的主要原因是由于基体中含有反球化元素Sn、Sb和超标Cu,产生畸形片状、蠕虫状石墨及超标冶金缺陷,白口层超厚,残余应力集中,致使基体组织结合能力、机械性能降低而发生。文中重点探讨了冶金缺陷、畸形片状、蠕虫状石墨的成因及引起内部微裂纹萌生、扩展断裂机制。提出了防止冶金缺陷和球化不良的预防措施,并在工业生产中获得验证。
In this paper, the early failure fragments of Ni-Cr ductile iron composite cast iron roll were made in China. The chemical composition, low acid corrosion, inclusions and residual stress were measured and analyzed by optical and electron microscope. The results show that the main reason of the early fracture of the roll is that the matrix contains anti-nodular elements Sn, Sb and excessive Cu, resulting in deformed flaky, vermicular graphite and excessive metallurgical defects. The white stratum is thick and the residual stress is concentrated. Substrate tissue binding ability, reduced mechanical properties occur. This paper focuses on the metallurgical defects, deformity flake, vermicular graphite causes and causes the internal microcracking initiation, expansion fracture mechanism. Preventive measures against metallurgical defects and spheroidisation were proposed and validated in industrial production.