Search results
Results from the WOW.Com Content Network
Shrinkage and Contraction can again be classified into liquid shrinkage and solid contraction. Liquid shrinkage is the reduction in volume during the process of solidification (liquid to solid), the liquid shrinkage is accounted for by risers. Solid contraction is the reduction in dimensions during the cooling of the (solid) cast metal.
A bronze casting showing the sprue and risers. A riser, also known as a feeder, [1] is a reservoir built into a metal casting mold to prevent cavities due to shrinkage.Most metals are less dense as a liquid than as a solid so castings shrink upon cooling, which can leave a void at the last point to solidify.
Directional solidification can be used as a purification process. Since most impurities will be more soluble in the liquid than in the solid phase during solidification, impurities will be "pushed" by the solidification front, causing much of the finished casting to have a lower concentration of impurities than the feedstock material, while the ...
The wax patterns require extreme care for they are not strong enough to withstand forces encountered during the mold making. One advantage of investment casting is that the wax can be reused. [5] The process is suitable for repeatable production of net shape components from a variety of different metals and high performance alloys.
As a result, xerogels cannot achieve the high porosities and instead peak at lower porosities and exhibit large amounts of shrinkage after drying. [39] To avoid the collapse of fibers during slow solvent evaporation and reduce surface tensions of the liquid-solid interfaces, aerogels can be formed by lyophilization (freeze-drying). Depending on ...
To increase the rate of solidification, the strand is sprayed with large amounts of water as it passes through the spray-chamber; this is the secondary cooling process. Final solidification of the strand may take place after the strand has exited the spray-chamber. It is here that the design of continuous casting machines may vary.
Crystallization of polymers is a process associated with partial alignment of their molecular chains. These chains fold together and form ordered regions called lamellae, which compose larger spheroidal structures named spherulites. [1] [2] Polymers can crystallize upon cooling from melting, mechanical stretching or solvent evaporation ...
In both types of extrusion the raw material must be plasticized to allow and induce the flow of the material in the process. Complex technical ceramic parts are commonly formed using either the injection moulding process or "hot wax moulding." Both rely on heat sensitive plasticizers to allow material flow into a die.