casting failure

Question 1

too large casting caused by what

Answer 1

too high burn out temp

wrong type of investment material used

excessive setting expansion or hygroscopic expanson

Question 2

distortion of casting caused by

Answer 2

distorted wax pattern, pattern not placed in central position of ring

Question 3

what could cause rough surface

Answer 3

rough wax pattern, too low water powder ration, applying too much wetting agent taht dilutes investment, too great casting force

Question 4

what could cause air bubbles

Answer 4

inadequate use of wetting agent

air not eliminated from investment

too thick an investment mix

Question 5

what can voids be caused by

Answer 5

underheating, wax not completely eliminated

Question 6

what can fins be caused by

Answer 6

heated too rapidly, ring placed too near heating element, differential expansion of investment mould if mould built up from 2 or more mixes of different water powder ratio

Question 7

what are some porosity that is caused by cooling and solidification

Answer 7

localised shrinkage porosity, microporosity, subsurface porosity

Question 8

what is localised shrinkage porosity caused by

Answer 8

caused by lack of molten metal during solidification which occurs when too small sprue diameter, investment not sufficiently heated

Question 9

what can microporosity be caused by

Answer 9

too rapid a solidfiication from metal, which occurs when temperature of mould too low, temperature of molten metal near its liquidus temperature

Question 10

what is sub surface porosity caused by

Answer 10

molten meteal fed into mould too rapidly at high temp

Question 11

pin hole porosity caused by what

Answer 11

oxygen being dissolved in metal alloy