Casting Processes Review Questions

Question 1

Name two basic catagories of casting processes

Answer 1

expendable mold casting - mold sacrificed

permanent mold casting - mold can be used for multiple castin processes

Question 2

There are various types of patterns used in sand casting. What is the difference between a split pattern and a match-plate pattern?

Answer 2

Split Plate Pattern consists of two pieces, dividing the part along a plane coinciding with the parting line of a mold

Match plate pattern - two pieces of the split pattern are attached to opposite sides of a wood or metal plate

Question 3

What is a chaplet?

Answer 3

Supports that to hold a core in place in the mold cavity during pouring

Usually made of metal with a higher melting temperature

Question 4

What properties determine the quality of a sand mold for sand casting?

Answer 4

• strength - ability to maintain shape and resist erosion caused by flow of molten metal
• permeability - capacity of mold to allow hot air and gases to pass through voids
• thermal stability - ability of sand at surface to resist cracking and buckling upon contact with molten metal
• collapsibility - ability of mold to give way and allow casting to shrink without collapsing
• reusability - can sand be broken up and used again

Question 5

What is Antioch process

Answer 5

Involves using about 50% sand mixed with the plaster, heating the mold in an autoclave, and then drying

Soltuon to the disadvantage with plaster mold not being permeable

Question 6

What are most common metals used in die casting

Answer 6

Commonly made of steel or cast iron

Question 7

Which die casting machines have a higher production rate: cold chamber or hot chamber, and why?

Answer 7

Cold-Chamber Machines are not as fast as hot chamber machines due to the need to ladle liquid metal into chamber from external source

Question 8

What is flash in die casting/

Answer 8

When liquid metal under hgih pressure squeezes into small space begween die halves at the parting line or into clearances around the cores and ejector pins

Question 9

What is a cupola

Answer 9

Vertical cylindrical furnace equipped with a tapping spout near its base

Used for melting cast irons

Question 10

What are some of the operations required in sand casting after casting is removed from mold

Answer 10

1. trimming
2. removing the core
3. surface cleaning
4. inspection
5. repair
6. heat treatment

Question 11

What are some general defects encountered in casting processes

Answer 11

• misruns
  
  • casting solidify before completely filling mold cavity
• cold shuts
  
  • two portions of metal flow together but lack fusion between them due to premature freezing
• cold shots
  
  • splattering during pouring, casuing formation of solid globules of metal entrapped in casting
• shrinkage cavity
  
  • depression in surface or internal void
• microporosity
  
  • network of small voids distributed throughout casting
• hot tearing
  
  • casting restrained from contraction by unyielding mold during final stage of solidification
• sand blow
  
  • release of mold gases during pouring, balloon shaped gas cavity
• pinholes
  
  • caused by release of gas during pouring, many small gas cavities
• sand wash
  
  • irregularity in surface of casting that result from erosion of sand mold during pouring
• scabs
  
  • rough areas of surface due to encrustration of sand and metal
• penetration
  
  • fluidity of metal is high, penetrates into sand
• mold shift
  
  • sidewase displacement of mold cope relative to mold drag
• core shift
  
  • core is displaced
• mold crack
  
  • mold strength insufficient, cracks develop