Question & Answer

The volume rate of flow of molten metal into the downsprue from the pouring cup is 50 in3 /sec. At the top where the pouring cup leads into the downsprue, the cross-sectional area = 1.0 in2 . Determine what the area should be at the bottom of the sprue if its length = 8.0 in. It is desired to maintain a constant flow rate, top and bottom, in order to avoid aspiration of the liquid metal

The flow rate of liquid metal into the downsprue of a mold = 1 liter/sec. The cross-sectional area at the top of the sprue = 800 mm² , and its length = 175 mm. What area should be used at the base of the sprue to avoid aspiration of the molten metal?

A mold has a downsprue of length = 6.0 in. The cross-sectional area at the bottom of the sprue is 0.5 in2 . The sprue leads into a horizontal runner which feeds the mold cavity, whose volume = 75 in3 . Determine (a) the velocity of the molten metal flowing through the base of the downsprue, (b) the volume rate of flow, and (c) the time required to fill the mold cavity

The downsprue leading into the runner of a certain mold has a length = 175 mm. The cross-sectional area at the base of the sprue is 400 mm² . The mold cavity has a volume = 0.001 m³ . Determine (a) the velocity of the molten metal flowing through the base of the downsprue, (b) the volume rate of flow, and (c) the time required to fill the mold cavity

A sufficient amount of pure copper is to be heated for casting a large plate in an open mold. The plate has dimensions: length = 20 in, width = 10 i_n, and thickness = 3 in. Compute the amount of heat that must be added to the metal to heat it to a temperature of 2150°F for pouring. Assume that the amount of metal heated will be 10% more than what is needed to fill the mold cavity. Properties of the metal are: density = 0.324 lb_m/in³ , melting point = 1981°F, specific heat of the metal = 0.093 Btu/lb_m-F in the solid state and 0.090 Btu/lb_m-F in the liquid state, and heat of fusion = 80 Btu/lb_m.

A disk 40 cm in diameter and 5 cm thick is to be cast of pure aluminum in an open mold casting operation. The melting temperature of aluminum = 660°C, and the pouring temperature will be 800°C. Assume that the amount of aluminum heated will be 5% more than what is needed to fill the mold cavity. Compute the amount of heat that must be added to the metal to heat it to the pouring temperature, starting from a room temperature of 25°C. The heat of fusion of aluminum = 389.3 J/g. Other properties can be obtained from Tables 4.1 and 4.2 in the text. Assume the specific heat has the same value for solid and molten aluminum

There are 15 correct answers in the following multiple choice questions (some questions have multiple answers that are correct). To attain a perfect score on the quiz, all correct answers must be given. Each correct answer is worth 1 point. Each omitted answer or wrong answer reduces the score by 1 point, and each additional answer beyond the correct number of answers reduces the score by 1 point. Percentage score on the quiz is based on the total number of correct answers.

10.1 Sand casting is which of the following types: (a) expendable mold or (b) permanent mold?

10.2 The upper half of a sand-casting mold is called which of the following: (a) cope or (b) drag?

10.3 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?

10.4 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?

10.5 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?

10.6 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?

10.7 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?

10.8 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?

10.9 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?

10.10 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?

10.11 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?

What is a chill in casting?

Identify the three sources of contraction in a metal casting after pouring

What is the relationship known as Chvorinov's rule in casting?

What is a eutectic alloy?

How does solidification of alloys differ from solidification of pure metals?

What does heat of fusion mean in casting?

What are some of the factors that affect the fluidity of a molten metal during pouring into a mold cavity?

What is the continuity law as it applies to the flow of molten metal in casting?

Why should turbulent flow of molten metal into the mold be avoided?

What is meant by the term superheat?

What is the difference between a pattern and a core in sand molding?

Which casting process is the most important commercially?

Name the two basic mold types that distinguish casting processes.

What is the difference between an open mold and a closed mold?

What is a factory that performs casting operations usually called?

What are some of the limitations and disadvantages of casting?

Identify some of the important advantages of shape-casting processes

A composite has a matrix of polyester with Kevlar-29 fibers. The volume fractions of polyester and Kevlar are 60% and 40%, respectively. The Kevlar fibers have a modulus of elasticity of 60 GPa in the longitudinal direction and 3 GPa in the transverse direction. The polyester matrix has a modulus of elasticity of 5.6 GPa in both directions. (a) Determine the modulus of elasticity for the composite in the longitudinal direction. (b) Determine the modulus of elasticity in the transverse direction