Lost mold casting process runner design principles
In order to prevent the type cavity gas backinjection during pouring, the transverse pouring channel should have enough space to do the gas chamber, and the cross-sectional area of the transverse pouring channel should be designed larger.
Design principle of inner pouring: width and short thickness. The function of the inner pouring gate is to inject metal liquid into the type cavity.
The design of disappearing die casting should pay attention to four links:
1) The cutting position of the inner pouring mouth should be reasonable;
2) Less heat loss in the inner pouring mouth;
3) The cutting direction of the inner pouring gate should be straight along with the negative pressure field;
4) The cross-sectional area of the inner channel cannot be blocked. So the requirement of inner pouring way: width and short thickness.
The traditional sand cast liquid metal filling cavity can achieve smooth filling without turbulence. Because the appearance is mostly flat (horizontal classification), the rise distance is not high, and the temperature difference between the bottom note is not big.
The disappearing die casting is completely different from the traditional sand casting. The cavity is occupied by foam, and the design of the inner gate must consider the objective existence of foam die. While studying the influence of foam mode gasification characteristics on liquid metal filling, it is also necessary to study the influence of liquid metal filling on the disappearance of foam mold gasification —— These are two specific process conditions that cannot be separated by binding together. The endothermal decomposition of foam mold will affect the change of limited heat and temperature carried by liquid metal, affect the flow form in the process of liquid metal filling, and then affect the thermal field distribution and solidification process. Therefore, accurately predicting the flow field and thermal field of liquid metal filling type and effectively guidance and control are the key to prevent and eliminate the defects of shrinkage, shrinkage and cold separation.
The loss and consumption of temperature and heat in the process of liquid metal filling directly affect the shape, speed and disappearance of the foam die. Therefore, it is the key to prevent and eliminate the defects of porosity, carbon precipitation and carbon enhancement to correctly understand the disappearance characteristics of foam mold and effectively guide and regulate the disappearance of gas mold, including pores, carbon precipitation and carbon enhancement caused by the gasification process of foam mold.
