Pouring of Metal
Pouring of Metal
the process whereby molten metal is introduced into molds, where the metal then crystallizes to form ingots. Distinguished from casting, in which the metal hardens to give shaped castings, pouring is an important step in the technological cycle for the production of metal because it is during the pouring and crystallization of the ingot that many of the metal’s physicomechanical properties are formed. The quantity, as well as the quality, of acceptable ingots depends on the organization of the pouring process.
Molten metal from the smelting furnace is usually poured into a ladle, from which the metal is then poured from the lip at the top of the ladle when the ladle is of small capacity. When the ladle is larger, the metal is poured through a refractory nozzle at the bottom of the ladle. The nozzle can be closed from inside the ladle by a refractory stopper. Devices without stoppers are also widely used. Here, the ladle’s nozzle is closed from the outside by a refractory plate. The plate, which has an orifice, can be moved so that the orifice coincides with the nozzle, thus allowing the metal to flow out.
In the steel industry, molten steel is poured from a ladle into molds, or a process of continuous steel casting is used. The metal can be poured into the mold either from the top of the mold or from the bottom through a connecting channel. In the first case, the steel is poured from the ladle directly into the mold (Figure 1, a). After the mold is filled, the ladle opening is closed and the ladle is moved by crane to the next mold, where the process is repeated. In bottom pouring, several molds (from two to 60) can be filled with steel simultaneously. Here, the molds are mounted on a stool having channels lined with refractory brick. The steel from the ladle descends through the fountain into the channels of the stool and then enters the mold from the bottom (Figure 1, b). The pouring method used depends on such factors as the steel’s grade and weight and the intended use of the ingots.
In order to improve the quality, steel is sometimes subjected to various types of treatment during the pouring process, for example, treatment with synthetic slags. In this case, slag of known composition is charged into the ladle after being smelted in a special furnace. When metal from the smelting furnace also enters the ladle, the slag and metal mix and reactions occur at a significantly higher rate than in a furnace. The result is a lowering of the content of sulfur, oxygen, and nonmetallic inclusions. Vacuum treatment is also an efficient method for improving the quality of steel during the pouring process.
Pouring of nonferrous metals and alloys can be carried out, either directly from smelting furnaces or through ladles into molds, or ingot stools, as well as by means of continuous casting machines. Special pouring machines are widely used for pouring cast iron, nonferrous metals, and ferroalloys.
IA. D. ROZENTSVEIG