Excessive noise and high vibration are inherently associated with
equipment used in the mining, extraction, and processing of mineral
resources. High vibration degrades structural components, often leading
to catastrophic failure and loss of productivity, and excessive noise
can result in permanent hearing loss.
In order to foster efficient utilization of the Nation’s mineral
resources and minimize occupational hazards associated with mineral
processing, the Bureau of Mines investigated the relationship between
the microstructures of carbon and alloy steels and cast irons and their
damping capacities (ability to absorb vibration). Researchers measured
damping capacity and other properties and investigated the effects of
carburizing, spheroidizing, and annealing.
The investigators found that in carbon and alloy steels, rounded colonies
of fine-grained pearlite in a ferrite matrix correlate well with
low damping capacity. Steel microstructures that exhibit sharp-faceted
pearlite in ferrite matrix and partially or fully spheroidized cementite
in ferrite show considerably higher damping. In cast irons, the lowest
damping capacity is associated with nodular graphite microstructure, and
the specific damping capacity (SDC) increases as the graphite microstructure
progresses from nodular to compacted to flake. Predominant
ferrite in cast irons is also associated with good damping. SDC data
are presented for selected carbon and alloy steels and cast irons.