Casting Defects

Castings

FaultPossible Cause
aLappingPouring too slow
Metal not hot enough
bTube outer dia. roughProtrusion of pouring bucket
spout in bore beyond the end plate of mould
cSlag/oxide bands producedInadequate deoxidizing agent in ladle
dBore tube oxidizationTemperature of metal too low
Mould temperature too low
Crucible/pouring bucket temperature too low
Furnace and casting pouring into mould delayed
eRough tube surface at spray endMould not cool enough
Spinning time of mould insufficient to cool mould
fTube surface dimpled often at centerLow spin speed
Pressure of spray tank too high
Low metal temperature
Consistency of mould wash too smooth
gTube length incomplete or tapered tube wallMould contains refractory material, possibly from pouring bucket or furnace
Pouring bucket or spout requires maintenance
hSpray end showing isolated patches of slagBelling at either or both ends of tube.
Check dimensions of mould
Check coating
Check mould temperature
iCasting difficult to removeBelling at either or both ends of tube.
Check dimensions of mould
Check coating Check mould temperature
jTube surface inconsistent (a spiral appearance may be produced)Inadequate mould coating in tank
Spray cone nozzle worn or restricted
Coating Slurry too thin
kLarge diameter tubes longitudinal cracks in castingTube run on at high speed for too long after casting
lSurface of tube covered with pin holes, especially pronounced at spray endLow metal temperature
Oil traces in airline (faulty filter)
mCracking/tearing fracture around circumferenceContraction of tube restricted
Mould wash left in mould, inadequate cleaning
Belling - refer to item (i).
nPatches of slag deposits on spray end of tube Metal deposits requires cleaning at furnace and/or ladle
oPin-holing in patches and/or condensationLance dripping with spray or craters at spray end
Lance sloping downwards
pMolten metal raining in mouldMolten metal temperature too high
Speed to slow