During the casting process, a manufacturer pours molten plastic or metal into a mold. As the material cools, it hardens into a new form determined by the shape of the cavity. The continuous casting process, a specialized form of casting, has become an important commercial technology in steel mills. It sometimes occurs at the point immediately prior to the production of steel extrusions.
Continuous Casting Process
The process of continuous casting developed during the 1950s. This sophisticated casting system has increased efficiency at many steel mills by eliminating several steps involved in the casting of steel ingots using discrete stationary molds. It permits high-volume steel billet production.
Continuing casting relies on four important steps:
1. First, a manufacturer heats ferrous metal alloys to high temperatures in a blast furnace in order to produce molten steel. This process occurs on a nearly continuous basis.
2. Next, the manufacturer uses automated machinery to ladle the molten steel into a tundish. The tundish consists of a broad funnel-shaped bath serving as a mold opening. A wide hole at the bottom functions as the gate for a continuous casting mold located beneath it. Some manufacturers treat molten steel in the tundish to facilitate the removal of impurities. The use of the tundish helps control the speed of the continuous flow of molten metal into the mold.
3. The molds used in continuous casting sit at the top of a slope. Unlike most traditional molds, these structures permit the flow of hot metal through openings at the bottom of the molds as a result of gravity. Continuous casting machines vary somewhat; in some models a single tundish sends molten metal into a single mold, while in other machines a large tundish contains multiple openings connecting to multiple molds. The manufacturer continuously lubricates the molds and causes these structures to oscillate slightly. A body of water surrounds the molds. It helps to cool the exterior edges of the steel to cause the development of a partially solidified skin. Some manufacturers also run the hot metal between adjoining lubricated metal rollers as the steel leaves the mold cavity to help maintain its shape. As steel passes out of the mold flowing downwards, the manufacturer applies jets of cooling water to the metal to lower the surface temperature even further. The steel flows downhill, and continues solidifying during this journey.
4. At the bottom of the slope the manufacturer will cut the hot metal into sections to form discrete billets of steel. These strips provide the raw material for rolling or extruding the metal into other shapes.
Materials And Applications
Performing continuous casting generally requires a substantial capital investment.
Continuous casting typically utilizes molten steel. However, copper, aluminum, and even some types of cast irons can also serve as raw materials. This casting process requires an investment in high volume production facilities: a blast furnace, automated metal ladles, a tundish, water sprays, and graphite molds. Manufacturers must supply mold lubricating and cooling capabilities.
Applications for this casting process exist within the steel mill industry. It facilitates high volume production.
Advantages of The Continuous Casting Process
Continuous casting offers several advantages.
- It permits manufacturers to generate high volumes of steel billets efficiently. This process occurs on an ongoing 24/7 basis in some production environments. Workers do not need to interrupt casting to remove metal from molds.
- Manufacturers can automate continuous casting environments extensively. This step enhances worker safety and reduces labor costs.
- Continuous casting permits the generation of large quantities of raw steel.
- In many production facilities, this process enables the casting of high quality steels. Manufacturers may use one (or more) tundish baths to help remove impurities from molten steel.
Semi-continuous casting also utilizes a tundish. However, the molten material flows, not along a slope, but directly downwards into a pit between jets of water to form a vertical metal column or block. Removing the vertical billet after solidification requires an interruption of the continuity of the casting process. Some manufacturers use this technology to create copper castings.