This article is about metal foundries. Unsourced material may be challenged and removed. Metals are cast into shapes by melting them into a liquid, foundry casting process pdf the metal in a mold, and removing the mold material or casting after the metal has solidified as it cools.
In this process, parts of desired shapes and sizes can be formed. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods. Virgin material, external scrap, internal scrap, and alloying elements are used to charge the furnace. The process includes melting the charge, refining the melt, adjusting the melt chemistry and tapping into a transport vessel. During the tap, final chemistry adjustments are made. Several specialised furnaces are used to heat the metal.
Furnaces are refractory-lined vessels that contain the material to be melted and provide the energy to melt it. Furnace choice is dependent on the alloy system quantities produced. For ferrous materials EAFs, cupolas, and induction furnaces are commonly used. Reverberatory and crucible furnaces are common for producing aluminium, bronze, and brass castings. Furnaces in foundries can be any size, ranging from small ones used to melt precious metals to furnaces weighing several tons, designed to melt hundreds of pounds of scrap at one time. They are designed according to the type of metals that are to be melted.
Furnaces must also be designed based on the fuel being used to produce the desired temperature. Electricity, propane, or natural gas are usually used to achieve these temperatures. The majority of foundries specialize in a particular metal and have furnaces dedicated to these metals. EAF, while a steel foundry will use an EAF or induction furnace. Degassing is a process that may be required to reduce the amount of hydrogen present in a batch of molten metal. Hydrogen is a common contaminant for most cast metals.
It forms as a result of material reactions or from water vapor or machine lubricants. Porosity often seriously deteriorates the mechanical properties of the metal. An efficient way of removing hydrogen from the melt is to bubble a dry, insoluble gas through the melt by purging or agitation. When the bubbles go up in the melt, they catch the dissolved hydrogen and bring it to the surface. Chlorine, nitrogen, helium and argon are often used to degas non-ferrous metals.