Chapter 10 Manufacturing
10.4 What is the difference between open mold and closed mold
Open- liquid is poured till fills open cavity, closed- permit molten metal to flow from outside into cavity
10.11 What are some of the factors that affect the fluidity of a molten metal during pouring into a mold cavity
Pouring temp relative to melting point, metal comp, viscosity, heat transfer to surroundings
10.13 How does solidification of alloys differ from solidification of pure metals
Pure at constant temp equal to freezing point alloys freeze over a temperature range
10.6 which casting process is the most important commercially
Sand casting
Which of the following riser types are completely enclosed within the sand mold and connected to the main cavity by a channel to feed the molten metal (two correct answers): (a) blind riser, (b) open riser, (c) side riser, and (d) top riser?
(a) blind riser, (c) side riser
In foundry work, a runner is which one of the following: (a) channel in the mold leading from the downsprue to the main mold cavity, (b) foundryman who moves the molten metal to the mold, or (c) vertical channel into which molten metal is poured into the mold?
(a) channel in the mold leading from the downsprue to the main mold cavity
The upper half of a sand-casting mold is called which of the following: (a) cope or (b) drag?
(a) cope
Sand casting is which of the following types: (a) expendable mold or (b) permanent mold?
(a) expendable mold
Total solidification time is defined as which one of the following: (a) time between pouring and complete solidification, (b) time between pouring and cooling to room temperature, (c) time between solidification and cooling to room temperature, or (d) time to give up the heat of fusion?
(a) time between pouring and complete solidification
In casting, a flask is which one of the following: (a) beverage bottle for foundrymen, (b) box which holds the cope and drag, (c) container for holding liquid metal, or (d) metal which extrudes between the mold halves?
(b) box which holds the cope and drag
In a sand-casting mold, the V/A ratio of the riser should be (a) equal to, (b) greater than, or (c) smaller than the V/A ratio of the casting itself?
(b) greater than
Turbulence during pouring of the molten metal is undesirable for which of the following reasons (two best answers): (a) it causes discoloration of the mold surfaces, (b) it dissolves the binder used to hold together the sand mold, (c) it increases erosion of the mold surfaces, (d) it increases the formation of metallic oxides that can become entrapped during solidification, (e) it increases the mold filling time, and (f) it increases total solidification time?
(c) it increases erosion of the mold surfaces, (d) it increases the formation of metallic oxides that can become entrapped during solidification
A riser in casting is described by which of the following (three correct answers): (a) an insert in the casting that inhibits buoyancy of the core, (b) gating system in which the sprue feeds directly into the cavity, (c) metal that is not part of the casting, (d) source of molten metal to feed the casting and compensate for shrinkage during solidification, and (e) waste metal that is usually recycled?
(c) metal that is not part of the casting, (d) source of molten metal to feed the casting and compensate for shrinkage during solidification, and (e) waste metal that is usually recycled?
During solidification of an alloy when a mixture of solid and liquid metals is present, the solid-liquid mixture is referred to as which one of the following: (a) eutectic composition, (b) ingot segregation, (c) liquidus, (d) mushy zone, or (e) solidus?
(d) mushy zone
Chvorinov's rule states that total solidification time is proportional to which one of the following quantities: (a) (A/V)n, (b) Hf, (c) Tm, (d) V, (e) V/A, or (f) (V/A)2; where A = surface area of casting, Hf = heat of fusion, Tm = melting temperature, and V = volume of casting?
(f) (V/A)2
10.3 What is a factory that performs casting operations usually called
A foundry
10.14 what is a eutectic alloy?
A particular composition in an alloy system for qhich the solidus and liquidus are at the same temperature
10.9 Why should turbulent flow of molten metal into the mold be avoided
Accelerates formation of metal oxides, aggravates mold erosion
10.1 Identify some of the important advantages of shape-casting processes
Complex internal and external shapes, capable of producing net shape parts, very large parts, performed on any liquid metal, mass production
10.5 Name the two basic mold types that distinguish casting processes
Expendable mold and permanent mold
10.17 What is a chill in casting?
Internal or external heat sinks that cause rapid freezing in certain regions of the casting
10.7 What is the difference between a pattern and a core in sand molding
Pattern made of wood metal plastic and has the shape of the part to be cast, core determines the interior geometry of the part
10.2 What are some of the limitations and disadvantages of casting
Porosity, poor dimensional accuracy, poor surface finish, safety hazards, environment
10.8 What is meant by the term superheat
Superheat is the temperature difference above the melting point at which the molten metal is poured. The term also refers to the amount of heat that is removed from the molten metal between pouring and solidification
10.15 What is the reolationship known as Chvorivov's rule in casting?
T= Cm(V/A)^2 value depends on the particular conditions of the casting operation
10.12 What does the heat of fusion mean in casting
The amount of heat required to solidify the metal from the liquid state
10.16 Identify the three sources of contraction in a metal casting after pouring
The three contractions occur due to (1) contraction of the molten metal after pouring, (2) solidification shrinkage during transformation of state from liquid to solid, and (3) thermal contraction in the solid state.
10.10 What is the continuity law as it applies to the flow of molten metal casting
Volume flow rate remains the same at the top and bottom of the sprue