Chapter 1 and Intro to casting

Question 1

Definition of Manufacturing

Answer 1

A well organized method of converting raw material to an end product that has value and utility

Question 2

Casting

Answer 2

liquid material is poured into a mold allowing for solidification of the desired shape

Question 3

Forming and Shaping

Answer 3

Uses stresses (like compression, tension, shear) to plastically deform the material to the desired shape

Question 4

Machining

Answer 4

process of removing material from a workpiece using power-driven machine tools

Question 5

Joining

Answer 5

welding two or more parts are melted and forced together

Question 6

Finishing

Answer 6

performed after the part is formed

-Alters the surface of the part to achieve certain properties

Question 7

Fundamentals of High Quality Production with:

• Good surface finish
• Dimensionally accurate
• Good Strength
• Lack of defects

Answer 7

1) Solidification of metal and accompanying shrinkage
2) Flow of the molten metal into the mold cavity
3) Heat transfer during solidification and cooling of the metal in the mold
4) Mold Material and its influence on the casting operations

Question 8

Solidification of Pure Metals

Answer 8

Pure metals have clearly defined melting and freezing points

Solidification takes place at constant temperature

Contracts when it cools changing the density

Question 9

Solidification of Alloys

Answer 9

Alloys solidify over a range of temperatures (mushy/paste state)

Phase diagrams graphically illustrate the relationship between phase and temperature and composition of material

Question 10

Purpose of the Riser

Answer 10

• “Cavity is full” verified
• gases escape
• reinforcement for metal shrinkage

Question 11

What are hot spots?

Answer 11

Sections of the casting that will solidify last

Question 12

Proper Fluid flow will minimize these three variables

Answer 12

• premature cooling
• turbulence
• gas entrapment

Question 13

Sprue Geometry

Answer 13

Tapers in to prevent aspirations (gap between fluid and wall allowing for air to get into the fluid)

Question 14

Critical Reynolds number

Answer 14

Over 20,000 represents severe turbulence resulting in air entrapment

Question 15

What is Fluidity

Answer 15

The ability of the molten metal to fill mold cavities

Question 16

Characteristics that Influence Fluidity

Answer 16

• Viscosity (decreases fluidity)
• Surface tension (reduces fluidity)
• Inclusions
• Shorter solidification range of pure metals give higher fluidity
• Alloys with longer freezing ranges have lower fluidity

Question 17

Casting parameters that effect fluidity

Answer 17

• Mold design (sprue runners etc..)
• Mold material (higher thermal conductivity of mold lowers fluidity)
• Rate of Pouring (lower rate of pouring the lower the fluidity)
• Heat transfer affects viscosity and therefore affects fluidity

Question 18

Chvorinov’s Rule

Solidification time

Answer 18

solidification time = C *(volume/Surface Area)^(n)

• C is a constant related to material properties
• n is usually 2

Question 19

Shrinkage

Answer 19

Caused by:

• Contraction of molten metal as it cools
• Contraction during phase change (largest potential amount of shrinkage)
• Contraction as metal cools to room temperature