ENTC 207 Exam 3 question n answers 2023 passed

ENTC 207 Exam 3Types of cast irons: - correct answer Gray Iron Malleable Iron White Iron Ductile Iron Alloy Irons Malleable iron is ____ - correct answer heat treated for ductility White iron is ____ - correct answer hard and wear resistant Ductile iron has ____ - correct answer some ductility as cast Cast irons are located where on the iron-iron carbide diagram? - correct answer Above 2% C Casting methods: - correct answer sand casting permanent mold die casting investment casting centrifugal casting shell molding Gray iron can be considered a ____ with ____ in it. - correct answer steel; graphite Chemical composition of gray iron: - correct answer 2-4% carbon 1%+ silicon Microstructure of gray iron: - correct answer ferrite, pearlite, or martensite with graphite flakes Strength of gray iron depending on microstructure: - correct answer Ferrite yields low strength Pearlite yields higher strength Martensite yields high strength when high-carbon matrix is quench hardened Designation of gray iron: - correct answer ASTM A 48 Class 20 Class number indicates minimum tensile strength in ksi Physical and mechanical properties of gray cast iron: - correct answer High damping capacity Growth at elevated temps High resistivity compared to carbon steel; higher for coarse graphite structure over fine structure Ferromagnetic (except for austenitic gray iron) Good corrosion resistance compared to carbon steels Very brittle; do not obey Hooke's law well since there is little strain before fracture Great compressive strength (3-5x that of tensile strength) Hardness increases as class number does Low ductility and poor toughness GREAT WEAR RESISTANCE (due to graphite) Gray irons are ternary, secondary, or primary alloys? - correct answer Ternary Heat treatments for gray irons: - correct answer Normalizing (remove internal stresses and increases strength) Annealing (provide optimal machinability) Stress Relieving Quench hardening (.5-.7% C, 100% pearlite with fine graphite is best for hardening