CASTING IN SAND MOLD.
The process of casting in sand mold includes 3 steps as follow :
1) Production preparation:
+ Design preparation: Technical department based on drawings of machine part created casting drawings, calculations, processing the technical requirements.
+ Technology preparation: manufacture the model (castings, cores, pouring system ..), making mold ( groove, center of pouring system, head metal and risering/whistler), making cores.
2) Casting production:
+ Conducting assemblemold; testing cores; smelting and pouring liquid metal into the mold after solidification are formed in the casting mold; dismantling of mold, breaking cores ...
3) Mixture for molding and coring :
+ Flexibility : The ability to permanent deformation of the mixture after shaping of groove..
+ The settlement: The ability to reduce the volume when load bearing, allowing elastic while metal freezes, reducing volume (to avoid cracking, break molds, cores). As settlement increased as large-grained, little plastic adhesive, additive increases.
+ The ventilation: The ability to escape through the gas mixture out, avoid pitting gas .The ventilation will increase when the grain of sand are big and steady, porosity of additives increase, clay, adhesives, little amount of water .
+ The heat resistance: The ability to keep durability, no melting, burn at high temperatures. Grain of sand need to be big and rounded, little additives.
+ Moisture: The amount of water contained in the mixture, moisture up to 8% making durability and ductility of the mixture increase. if it exceeds too limited, will have bad effects.
+ The long-lasting: The ability to use mixture many times but still ensuring about technical requirements, increasing economic efficiency.
+ Sand: the major component SiO2
+ The clay: mAl2O3+nSiO2+qH2O
+ The adhesives are substances which put into the mixture to increase the ductility, increase durability, adhesive particles together.. Normally using: vegetable oil, asphalt, cement, mixed with sand, adhesives, additives, additives increase porosity (sawdust, straw ..).
+ Substances to paint mold: increasing surface gloss, heat durability and heat resistance.
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