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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.
Molten metal before casting Casting iron in a sand mold. In metalworking and jewelry making, casting is a process in which a liquid metal is delivered into a mold (usually by a crucible) that contains a negative impression (i.e., a three-dimensional negative image) of the intended shape.
A micrograph of bronze revealing a cast dendritic structure In some cases, the metallographic structure is large enough to be seen with the unaided eye. Metallography is the study of the physical structure and components of metals, by using microscopy.
Casting bronze ding-tripods, from the Chinese Tiangong Kaiwu encyclopedia of Song Yingxing, published in 1637. Copper was the first metal to be smelted. [10] How the discovery came about is debated. Campfires are about 200 °C short of the temperature needed, so some propose that the first smelting of copper may have occurred in pottery kilns. [11]
Bronze casting showing sprue and risers. A sprue is a large diameter vertical channel through which liquid material is introduced into a mold. It connects the pouring basin to the runner. In many cases it controls the flow of material into the mold.
A mold is a counterpart to a cast. The very common bi-valve molding process uses two molds, one for each half of the object. Articulated molds have multiple pieces that come together to form the complete mold, and then disassemble to release the finished casting; they are expensive, but necessary when the casting shape has complex overhangs. [3 ...
An ingot is a piece of relatively pure material, usually metal, that is cast into a shape suitable for further processing. [1] In steelmaking, it is the first step among semi-finished casting products. Ingots usually require a second procedure of shaping, such as cold/hot working, cutting, or milling to produce a useful final product.
Bronze is widely used for casting bronze sculptures. Common bronze alloys have the unusual and desirable property of expanding slightly just before they set, thus filling the finest details of a mould. Then, as the bronze cools, it shrinks a little, making it easier to separate from the mould. [30]