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What's in an Engine &
Why? Pistons form a combustion
seal and transmit forces from combustion to the connecting rods. Pistons are made
from either a low carbon steels or aluminum
alloys. The piston is subjected to high heat, inertia, vibration, and
friction. Carbon steels minimize the effects of differential thermal
expansion between the piston and cylinder walls. The lowered weight of
aluminum compared to cast iron is lost due to thicker sections needed for
strength. Carbon steel piston are
made from SAE G2500 grade gray iron. Gray
iron has good fluidity at elevated temperatures. This is a valuable property
since most pistons are formed from squeeze casting. Aluminum pistons are made from alloy with a relatively high concentration of silicon. Aluminum high in silicon improves wear resistance, compared to low concentrations of alloying element. Thermodynamic properties allow a more uniform distribution of silicon, and less segregation. Other aluminum alloys include 356 and 390 grades, containing low compositions of silicon (3% to 8%). |
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Last Updated: |
Contact the professor at: stoebe@u.washington.edu
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