Casting

Question 1

Reynolds # formula

Answer 1

(density * Velocity * Flow Length)/Dynamic Viscosity
or
(rhoVL)/mu

Question 2

Where does flow transition from laminar to turbulent?

Answer 2

Re = 500,000

Question 3

What are disadvantages for low filling speeds?

Answer 3

Filling takes more time (lower productivity)
Chance of solidifying portions before mold is filled: “Cold Running”

Question 4

What are advantages of low filling speeds?

Answer 4

Minimizes free surface area
Minimizes Oxidation & loss of material properties

Question 5

Phases of heat dissipation(3)

Answer 5

1.T_pouring to T_liquidus
2.T_liquidus to T_solidus 3.T_solidus to RT

Question 6

E_dissipation =

Answer 6

(change in temp) * (Specific Heat) * (Mass in kg)

Question 7

What can be done about shrinkage?

Answer 7

Add extra Material during filling
Make the mold bigger

Question 8

What does Chvorinov’s Rule Calculate?

Answer 8

Cooling time

Question 9

t_Chvor =

Answer 9

C*(V/A)^2
C: Chvorinov’s coefficient
V: Volume
A: Surface Area

Question 10

Defects of Casting? (3)

Answer 10

1. Porosity
2. Internal stresses
3. Distortion

Question 11

Porosity Causes

Answer 11

“Shrinkage porosity”: not enough extra material is fed into the casting to compensate for the shrinkage
Gas bubbles released during solidification

Question 12

Thermal Strain (e_th)=

Answer 12

CLTE*(delta T)
CLTE: coefficient of thermal expansion
delta T: Temperature difference

Question 13

Why are alloying elements used?(3)

Answer 13

1.Improve Processability (lower viscosity or T_melting)
2.Improve material properties(strength)
3.Minimize effects of impurities

Question 14

Shape Casting methods(5)

Answer 14

1.Sand Casting
2.Gravity Die Casting
3.Low Pressure Die Casting
4.High Pressure Die Casting
5.Investment Casting