ingot
ingot
[′iŋ·gət]ingot
silicon ingot
A salami-shaped bar of silicon, which is a single crystal, technically known as a "boule." The ingot is the first step in chip making. High-speed saws slice the ingot into "wafers" about the thickness of a dime, which are then ground and polished mirror smooth. The surfaces of the wafer are etched to form all the transistors on all the chips at the same time. The final step is to cut apart the chips and place them into their packages. See wafer, chip package and transistor. |
| Drawing the Silicon Ingot |
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| An ingot is being drawn from a furnace containing molten silicon. (Image courtesy of Texas Instruments, Inc.) |
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| An Ingot Plant |
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| At a Silicon Valley Microelectronics plant, the ingots are "grown" in these cylinders. SVM makes the ingots and slices them into wafers for their customers. (Image courtesy of Silicon Valley Microelectronics, Inc., www.svmi.com) |
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| The Pulled Ingot |
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| This is a finished ingot ready for slicing into wafers. (Image courtesy of Silicon Valley Microelectronics, Inc., www.svmi.com) |
Ingot
a cast metal blank intended for further processing by some method of plastic deformation (rolling, forging, or extrusion), by remelting (molding or alloying), or by electrolysis (in which the anodes are of blister copper or nickel). Ingots are obtained by pouring molten metal into molds with comparatively simple shapes, by continuous casting, and by filling water-cooled crystallizers (electroslag remelting and remelting in arc vacuum furnaces).
Ingots cast in molds and intended for subsequent pressure shaping usually have the form of a truncated pyramid or truncated cone. If a metal crystallizes with a shrinkage, as is the case with killed steel, the ingot will contain a head, which usually contains a contraction cavity. During subsequent conversion, the head is cut off and routed for remelting. Rimmed steel solidifies without forming a contraction cavity, and the ingots thus do not have a head.
Ingots cast by continuous casting methods have the shape of a prism with a square, rectangular, or polygonal cross section or the shape of a cylinder. Ingots are sometimes cast in more complex shapes, for example, hollow shapes. A comparatively small contraction cavity is located in the upper part of continuously cast ingots. This part is separated when the blanks are cut to measured lengths. In ingots obtained by electroslag and arc vacuum remelting, the contraction cavity is much smaller. This is caused by the lowering of the filling speed during the final stage of ingot formation.
The weight of ingots destined for pressure shaping ranges from several kilograms to more than 250 tons. The most widely used ingots weigh 0.5 to 20 tons.
Pig iron ingots and ingots of certain nonferrous metals destined for remelting are usually in the shape of small, strongly tapered, truncated pyramids called pigs, whose weight, as a rule, does not exceed 30–40 kg. Other ingot shapes include bars (copper) and billets of various shapes.
Since the conditions for crystallization of a metal change substantially during solidification, the structure and chemical composition of ingots are nonhomogeneous. The larger the ingot, the more pronounced is the chemical and structural nonho-mogeneity. Ingots obtained by continuous casting or by filling a crystallizer are much more homogeneous than ingots cast in molds.
REFERENCES
Metallurgiia stali. Edited by V. I. Iavoiskii and G. N. Oiks. Moscow, 1973.Kurdiumov, A. V., M. V. Pikunov, and V. M. Chursin. Liteinoe proizvodstvo tsvetnykh i redkikh metallov. Moscow, 1972.
A. IA. STOMAKHIN