At present , greensand casting is the most widely used and the most convenient molding method , about account for 60~70% of the all sand mold usage .
The sand mold ( core ) no need drying and hardening process is non-existent by greensand casting .
The main advantages of greensand casting are highly production flexible ; high productivity ; short production cycle ; easy to organize current production ; be apt to implement automation and mechanization in productive process ; low material cost ; save drying plant , fuel , electric power and the workshop production area ; prolong the working life of sand box ; etc .
But , the greensand casting also has some flaws by greensand casting :
Air hole : that is a common ticklish problem , if the air permeability of sand mold is bad , gas is too late to be transmitted , air hole will be formed , the reject because of air hole account for more than 50% of all rejects .
Sand inclusion : at the surface of casting , there are a layer of metal tablets or nodules , a bed of sand is in them .
Slag inclusion : it not only reduces casting quality ,but also increases labor to clean casting .