Metal Composition:

• Low CEV for section thickness causing chill
• Lead>0.0004% can affect graphite and reduce strength
• Tin>0.1% embrittles the iron
• Insufficient manganese to balance sulphur (Mn%=1.7S%+0.3)
  Sulphur is a potent chill forming element
• Presence of carbide-promoting elements such as chromium
• Presence of antimony, boron and lead from enamelled scrap in the charge

Production conditions leading to high stress

• Faults in running and gating system
• Restraint of strong cores surrounded by thin metal sections
• Fins of sand on cores producing notch effect
• Differential cooling of thick and thin wall sections producing high stresses
  Rapid cooling
• Sharp corners and re-entrant angles between sections and at ingate to casting connection

• Sand, slag, laps and shrinkage acting as stress raisers
• Cracks in flash propagating into the casting
• Imperfect surface on chills and denseners causing restriction on contraction
• Rapid or uneven heating in stress-relief heat treatment
• Crossed joint causing cracking in thin sections
• Excessive shot-blasting

Knockout, felting & handling

• Hammering to remove sand, runners, risers or flash
• Throwing castings into stillages
• Stacking castings in piles
• Inadequate care in handling stressed castings

Machining practice

• Bad handing
• Excessive or uneven clamping
• Heavy cut and high machining speeds
• Poor condition of cutting tools
• Heat generation during rapid deep grinding, or insufficient flow of cooling lubricant
• Interrupted cut