Defects in Casting Flashcards Preview

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Flashcards in Defects in Casting Deck (13):
1

Metallic Projections

1) Fins & Flash
- Material squeezes out between 2 halves
2) Swells
- enlargement of mold cavity localized by pressure

Solution: increase strength of mold

2

Defective Surface Causes

-Wall Erosion
-Pouring too fast
-overheating

3

Defective Surface Solutions

-Slow down pour
-Reduce temp of liquid
-Add additives to sand

4

Porosity Causes

-Thick regions of cast solidify slower
-Thin regions block thick regions if solidified faster

5

Porosity solution

Design cast to have runners go to thick parts of the mold
-Shorten sprue/add well
-Purge metal with inert gas

6

3 types of Cavities

-Porosity (Trapped Gases)
-Blowholes
-Pin Holes

7

3 types of Discontinuities

-Cracks
-Cold/Hot tears
-Cold Shuts

Causes: (stress concentration)
Solution: (avoid sharp corners)

8

Cold Shuts Solutions

-Increase pouring temps
-Increase pour velocity

9

Incomplete casting (2 Types)

Metal doesn't fill the cavity completely

- Mis-runs
- Runouts

10

Mis runs

Causes:
-Premature solidification
-insufficient volume of metal

Solution:
-increase pouring temp to increase fluidity

11

Run outs

Causes:
-Loss of metal after pouring

Solution:
-Modify parting line or gating system

12

Incorrect Dimensions

Causes:
-Shrinkage
-Uneven contraction
-Uneven flow

Solutions:
-Break up flat surfaces with staggered ribs

13

Inclusions

Causes:
-oxidation reaction
-Foreign material trapped in metal

Solutions:
-Decrease x-sec area to trap 'dross'
-filters