Ductile casting manufacturing process
(1) strict with chemical composition of the original requirements of carbon and silicon content in liquid iron is higher than grey cast iron and manganese in lower nodular cast iron,phosphorus,sulfur content
(2) than gray cast iron melt temperature higher than iron,castings than compensation spheroidizing,inoculation in molten iron temperature loss
(3) the spheroidizing treatment,namely the ball a change agent is added to iron
(4) for processing
(5) ductile castings liquidity is poorer,shrinkage is bigger,so need higher pouring temperature and gating system size,more applied riser and chill,in a sequential solidification principle
(6) for heat treatment
Ductile casting for bearing need higher hardness,and often will cast iron quenching and tempering treatment at low temperature. Process is: all kinds of casting temperature,heated to 860-900 ℃ heat preservation to the original matrix all austenitizing after cooling achieve quenching in oil or molten salt,after 250-350 ℃ heat insulation tempering,
The original matrix into tempered martensite and retained austenite,the spheroidal graphite shape unchanged.
After processing of castings with high hardness and a certain toughness,retained the lubrication performance of the graphite,wear-resisting performance is improved.