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Vacuum arc remelting (VAR) is a secondary melting process for production of metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. [1] The VAR process has revolutionized the specialty traditional metallurgical techniques industry, and has made possible tightly controlled materials used in biomedical ...
Vitallium is an alloy of 65% cobalt, 30% chromium, 5% molybdenum, and other substances.The alloy is used in dentistry and artificial joints, because of its resistance to corrosion.
Like other nickel/iron compositions, Invar is a solid solution; that is, it is a single-phase alloy.In one commercial grade called Invar 36 it consists of approximately 36% nickel and 64% iron, [4] has a melting point of 1427C, a density of 8.05 g/cm3 and a resistivity of 8.2 x 10-5 Ω·cm. [5] The invar range was described by Westinghouse scientists in 1961 as "30–45 atom per cent nickel".
The new ingot is covered in an engineered slag that is superheated by the electric current. The electrode tip is slowly melted from contact with the slag. These metal droplets travel through the slag to the bottom of the water-cooled mold and slowly freeze as the ingot is directionally solidified upwards from the bottom of the mold.
The name is a contraction of the French élasticité invariable ('invariable elasticity'). It was invented by Charles Édouard Guillaume, a Swiss physicist who also invented Invar, another alloy of nickel and iron with very low thermal expansion.
Ingot molds are tapered to prevent the formation of cracks due to uneven cooling. A crack or void formation occurs as the liquid to solid transition has an associated volume change for a constant mass of material. The formation of these ingot defects may render the cast ingot useless and may need to be re-melted, recycled, or discarded.
In the era of commercial wrought iron, blooms were slag-riddled iron castings poured in a bloomery before being worked into wrought iron. In the era of commercial steel, blooms are intermediate-stage pieces of steel produced by a first pass of rolling (in a blooming mill) that works the ingots down to a smaller cross-sectional area, but still greater than 36 in 2 (230 cm 2). [1]
When the metal had cooled and hardened, the smaller ingots (the "pigs") were simply broken from the runner (the "sow"), hence the name "pig iron". [4] As pig iron is intended for remelting, the uneven size of the ingots and the inclusion of small amounts of sand are insignificant issues when compared to the ease of casting and handling.