Working Roll with Shell-Shaped Fractures
A working roll of 210 mm diam and 500 mm face length was examined because of shell-shaped fractures. The roll consisted of Fe-0.83C-1.6Cr steel. The chromium content was low for a roll of this diam. The crack origin was located about 10 mm under the roil face. Surface hardness (HV1) of 900 kp/sq mm was exceptionally high corresponding to the martensitic peripheral structure. An untempered piece with such a thick cross section and a hardened peripheral zone with such high hardness must have high residual stresses that culminate in the transition zone. Therefore it must be very sensitive against additional stresses, be these of a mechanical or thermal nature. This contributed to the fragmenting of the roll face.
Friedrich Karl Naumann, Ferdinand Spies, Working Roll with Shell-Shaped Fractures, ASM Failure Analysis Case Histories: Steelmaking and Thermal Processing Equipment, ASM International, 2019, https://doi.org/10.31399/asm.fach.steel.c9001245
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