Lecture 1

Question 1

What is casting?

Answer 1

Transforming liquids into solid form

Question 2

What is forming?

Answer 2

Transfoming solids into other solid form

Question 3

What is finishing?

Answer 3

Changing properties of the surface

Question 4

How does casting work?

Answer 4

1 - pour molten metal into a mould
2 - allow it to solidify
3- remove part from mould

Question 5

Disadvantages of casting

Answer 5

Dangerous
skill intensive
prone to errors

Question 6

advantages of casting

Answer 6

Capable of complex shapes

capable of making large parts in one piece

Question 7

The mould

Answer 7

Flask: outer container
Upper half: cope
Lower half: drag

Question 8

Mould features

Answer 8

Designed to allow for escape of gas and material shrinkage

Question 9

what is a sprue

Answer 9

in a mould: molten metal poured through this

Question 10

What is a gate

Answer 10

in a mould: after sprue; ensures uniform metal flow into mould

Question 11

what is a riser

Answer 11

in a mould: allows air to escape, indicates a full mould

Question 12

How can dissolved gases be removed from mould

Answer 12

flushed with inert gas or melted and poured under vacuum

Question 13

how does mould take into account material shrinkage

Answer 13

• usually oversized use risers to supply extra metal (avoiding porosity)

Question 14

describe pure metal cast structure

Answer 14

columnar areas (grains nucleate at cool mould walls)

Question 15

what is the mush zone

Answer 15

in alloy solidification: dendrites surrounded by liquid

Question 16

Which cools faster sand or chill??

Answer 16

Chill (metal mould)

Question 17

What happens to properties as grain size decreases?

Answer 17

• Increased strength and ductility

- Tendency to crack decreases

Question 18

What does an inoculant do?

Answer 18

provides a nucleation site to promote grain isotropy

Question 19

Why are hot tears formed

Answer 19

because casting cannot shrink freely during cooling

Question 20

What are chills

Answer 20

increase cooling rate at critical points to avoid porosity - internal or external

Question 21

What does time to solidify depend on

Answer 21

volume and surface area

Question 22

what equation is used to measure time to solidify

Answer 22

Chvorinov’s rule - T = C(V/A)^n

C = constant for process V = volume A = surface area n = constant between 1.5 and 2.5

Question 23

Sphere, Cube, Cylinder - what solidifies fastest and slowest?

Answer 23

Sphere - slowest

Cube - fastest