Fractured Chain Link
A chain link which was part of the hoisting mechanism of a drop hammer broke after three or four months of service. It was reportedly manufactured of the heat resistant steel 30 Cr-Mo-V 9 (Material No. 1.7707). The fracture of the chain link had a conchoidal structure and ran along the austenitic grain boundaries. Such fractures are characteristic results of strong overheating. The coarse-grained, coarse acicular heat-treated structure of the chain link confirmed overheating. Because temperatures in excess of 1150 deg C are required for the solution of impurities, it is more probable that the real damage was done during the heat-up forging (drop-forging) and could not be removed during heat-treatment.
Friedrich Karl Naumann, Ferdinand Spies, Fractured Chain Link, ASM Failure Analysis Case Histories: Material Handling Equipment, ASM International, 2019, https://doi.org/10.31399/asm.fach.matlhand.c9001262
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