Manufacturing Processes and Surface Engineering Flashcards
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Read the first 6 Manufacturing Processes and Surface Engineering flashcards as text
In forging, closed-die (impression die) forging differs from open-die forging because it:
Answer: Confines the metal in shaped die cavities to produce precise near-net-shape parts, with excess material forming flash
Closed-die forging uses mated dies with a cavity that shapes the metal precisely, with excess material squeezed into a flash gutter; flash is later trimmed off.
The purpose of a flux in soldering and brazing operations is to:
Answer: Remove oxides from the base metal and filler to ensure wetting and bonding
Flux chemically reduces or dissolves metal oxides on the base metal and filler surfaces, enabling the molten filler to wet and flow across the joint for a sound bond.
Additive manufacturing (3D printing) of metal parts using selective laser melting (SLM) produces parts that often require post-processing because:
Answer: Rapid solidification creates residual stresses and may leave unmelted powder requiring stress relief and HIP
SLM's rapid heating and cooling cycles generate large residual stresses and may produce some porosity; stress relief annealing and hot isostatic pressing (HIP) are commonly used post-processes.
Galvanizing steel with zinc provides corrosion protection by which mechanism?
Answer: Zinc acts as a sacrificial anode, corroding preferentially to protect the underlying steel cathodically
Zinc is more anodic than steel in the galvanic series; it corrodes preferentially (sacrificial anode), providing cathodic protection to the steel even where the coating is scratched.
The purpose of normalizing steel after hot rolling or forging is to:
Answer: Refine the grain structure and homogenize the microstructure for improved and uniform mechanical properties
Normalizing austenitizes the steel and air cools it to refine the coarse, non-uniform microstructure produced by hot working, giving a more uniform, fine-grained structure.
In metal injection molding (MIM), the debinding step removes:
Answer: The polymer binder (feedstock binder) from the green part before sintering
In MIM, the molded green part contains metal powder plus a polymer binder; debinding (thermal or solvent) removes the binder, leaving a porous brown part ready for sintering.