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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.
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. Contraction allowance takes into account only the solid contraction.
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.
Two-part silicones use moisture in the second component as well as a cross-linker such as active alkoxy to cure the silicone in a process called condensation curing. Two-part silicones can also be platinum catylized in a "addition" reaction. [3] Other reactive species to facilitate cross-linking include acetoxy, amine, octoate, and ketoxime. [4]
Casting process simulation is a computational technique used in industry and metallurgy to model and analyze the metal-casting process. This technology allows engineers to predict and visualize the flow of molten metal, crystallization patterns, and potential defects in the casting before the start of the actual production process .
The thermal method involves changing the temperature of the entire part uniformly, either through heating or cooling. When parts are heated for stress relief, the process may also be known as stress relief bake. [13] Cooling parts for stress relief is known as cryogenic stress relief and is relatively uncommon. [citation needed]
Austempering is defined by both the process and the resultant microstructure. Typical austempering process parameters applied to an unsuitable material will not result in the formation of bainite or ausferrite and thus the final product will not be called austempered. Both microstructures may also be produced via other methods.