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本文对早期失效的ZG25钢桩帽和长寿命失效的进口桩帽进行了全面的失效分析对比,证实:强度和韧性都较高的进口桩帽的失效断口由多冲疲劳亚稳扩展区和偶然的直接锤击的快速扩展区构成,而强度和韧性都较低的ZG25钢桩帽的失效断口几乎没有多冲疲劳扩展区,直接锤击的迅速扩展区占据了整个断口。由此表明,欲提高桩帽的使用寿命必须提高桩帽用钢的强度和韧性和改善铸钢的冶金质量。 在本文指导下新研制成的ZG22铬硅钼稀土桩帽用钢,经适当的热处理后桩帽的使用寿命比原ZG25钢桩帽提高8～12倍,达到2000～2800小时,超过了进口桩帽的寿命。
In this paper, a comprehensive failure analysis and comparison of the early failed ZG25 steel pile cap and the long-life failed imported pile cap is carried out. It is verified that the failure fracture of the imported pile cap with high strength and toughness is caused by the multi-impact fatigue metastable expansion zone and accidental Of the rapid expansion of the direct expansion of the composition, and the strength and toughness of the lower failure of the ZG25 steel pile cap almost no fatigue extension of the fatigue zone, the rapid expansion of direct impact area occupied the entire fracture. This shows that to improve the service life of pile caps must increase the strength and toughness of the pile cap steel and improve the metallurgical quality of the cast steel. Under the guidance of this paper, the newly developed ZG22 chrome silicon-molybdenum rare earth pile cap steel, after appropriate heat treatment, the service life of pile cap is 8 to 12 times higher than the original ZG25 steel pile cap, reaching 2000 to 2800 hours, Cap life.