4.5 APPLYING SQUEEZE CASTING
57
Feature CDC Squeeze Metal temperature
Cycle time Number of cavities
Alloy flexibility Shrink porosity
Oxide entrapment Equipment cost
Automation Metal cost
Recycling Mechanical properties
Heat treatable Metal heating
Metal loss
+ = indicates favorable rating -
+ +
+ -
- ++
++ +
+ -
- +
+ -
- +
+ +
+ +
+ +
+ +
+ +
+
Figure 4.5 Comparisons of conventional die casting and squeeze casting.
fill of the die cavity and longer intensification times. Key process characteristics of squeeze casting include metal temperature, melt
cleanliness, cavity pressure, and gate velocities.
2
4.5 APPLYING SQUEEZE CASTING
Squeeze casting is a high integrity die casting process that builds upon conventional die casting practices and is compatible with
aluminum, magnesium, zinc, and copper alloy systems. Cycle times are longer in comparison to conventional die casting due to
longer metal injection durations. Component integrity is improved by minimizing entrapped air and reducing solidification shrinkage.
Most squeeze casting components can be heat treated without blis- tering defects to improve mechanical properties.
Squeeze cast components have many advantages over conven- tional die castings. A qualitative comparison of these two pro-
cesses is shown in Figure 4.5.
3
Conventional die casting is lower
58
CASE STUDIES: SQUEEZE CASTING
cost in the areas of capital equipment. Squeeze casting has addi- tional costs associated with automated sawing for separating the
runner system from squeeze cast components. A saw must be purchased, operated, and maintained along with fixturing.
These additional costs, however, are often offset with benefits in the areas of porosity reduction related to solidification shrink-
age, which improves mechanical properties. Moreover, the reduc- tion in entrapped gas results in a heat-treatable casting.
In converting conventional die castings to squeeze castings, one must consider the benefits sought. If porosity from gas entrapment
and solidification is a problem, squeeze casting can offer improve- ments. If only entrapped gas is an issue, vacuum die casting may
be sufficient. Moreover, squeeze casting can be combined with vacuum die casting. The use of a vacuum system during squeeze
casting can further reduce entrapped gas beyond that normally achieved when squeeze casting. Components currently produced
using higher cost manufacturing methods can be converted to squeeze casting while maintaining functional requirements. Ex-
amples of conversions are presented next.
REFERENCES
1. Dorcic, J., and S. Verma, ‘‘Squeeze Casting,’’ in Stefanescu, D. editor, Met- als Handbook,
9th ed. Vol. 15, Casting, ASM International, Materials Park, OH, 1988, p. 323.
2. Corbit, S., and R. DasGupta, ‘‘Squeeze Cast Automotive Applications and Squeeze Cast Aluminum Alloy Properties,’’ Paper Number 1999-01-0343,
Society of Automotive Engineers, Warrendale, PA, 1999. 3. DasGupta, R., and D. Killingsworth. ‘‘Automotive Applications Using Ad-
vanced Aluminum Die Casting Processes,’’ Paper Number 2000-01-0678, So- ciety of Automotive Engineers, Warrendale, PA, 2000.
CASE STUDIES: SQUEEZE CASTING INTRODUCTION
In 1997, only nine component producers were identified with squeeze casting capabilities in North America.
1
Regardless of the limited number of producers, squeeze casting process capacity has
Kategori