Permanentis also called and it is a kind of to acquire castings through pouring liquid metals into metal mold . The mold is made of metal , so it can be used repeatedly ( hundreds to thousands times ) .
Compared with, there are many advantages of in technically and economically , as follows :
The mechanical properties of permanent mold casting is higher than it of sand casting : the same alloy , the tensile strength average increase of about 25% , the yield strength average increase of about 20% , the anticorrosion and hardness both are significantly improved .
The precision and surface finish of permanent mold casting is higher than them of sand casting , and quality & size are steady .
The yield of casting is high , the consumption of liquid metals decreased , normally can save 15%~30% .
No need sand or need little sand , the molding material can be saved 80%~100% .
In addition , the production rate of permanent mold casting is high , the reason that make casting produce defect reduce , the process is simple , easy to realize mechanize and automation .
But , there are also shortcomings :
Metal mold manufacturing costs .
Metal mold is airtight and has no deformability , easily cause casting misrun , crack and other defects .
Working temperature of casting mold , pouring temperature and speed of alloy and needed coating also need strict controls .