Smelting not only melts raw materials to a temperature suitable for pouring, but it also has important implications for producing high-quality, low-cost casting products. The smelting operation must be capable of serving the foundry workshop by supplying a certain amount of molten iron with a specific composition, in a timely manner, at a sufficient temperature, and at the lowest operating costs. Iron liquid, on the other hand, must meet the terms and conditions in order to guarantee the production of cast objects of acceptable quality.
Terms and conditions of cast iron liquid to guarantee product quality
Metallurgically clean (devoid of impurities)
These impurities are oxides and slags, with other elements with a high affinity for O2 present in trace amounts only. This type of iron liquid can only be identified by its clear surface and does not exhibit immediate changes when solidified. A metallurgically dirty iron liquid will immediately form an oxidation skin, which colors the liquid’s surface and shows specific changes. This impurity is caused primarily by raw materials, specifically rust, impurities, and easily oxidized elements.
Pollution caused by dirt during smelting can be avoided with careful smelting supervision, which includes:
- accurate melting temperature control.
- keep an eye out for changes in chemical composition.
- slag composition accomplishments.
Stacked slag, porous, gases around the surface, pinholes, and defects caused by unexpected freezing are all defects that are very likely to appear as a result of dirty liquids. These flaws are hazardous because the majority of them will not be discovered until the castings are machined.
Have planned sprouts
Molten iron must have the properties of planned freezing. These properties are:
- Formation of the basic structure
- Sprout formation for graphite crystallization
- And Graphite Formation
The formation of the basic structure, in addition to the thickness of the casting products, is also determined by several elements it contains (for example Mn, Cu, or other foreign elements). By controlling the number of these elements, the basic structure of perlite, ferrite, bainite, or even white freezing will be produced.
Graphite crystallization occurs mainly due to the presence of foreign elements that are deliberately spread in the liquid through inoculation, the absence of this foreign element will result in carbon that cannot become graphite and is bound as cementite (Fe3C) to the structure and cause defects that are generally indicated by the presence of hard parts.
This form of graphite growth is mainly strongly influenced by O2 and S, where too much quantity will give rise to flake graphite. With strong desulfurization and deoxidation (e.g. using Mg) spherical graphite can be produced. Keep in mind, however, that there are many other elements that prevent the formation of spherical graphite (e.g. Ti).
Good temperature and homogenization of liquids
The storage of the two things above will certainly directly affect the service life of the casting, due to the difference in hardness in the parts or cold joints.
Cheap
The selling price of castings, of course, will be greatly influenced by the cost of smelting (including energy and raw materials). Energy savings can be achieved through accurate calculation of the design as well as the discipline of furnace operation. However, cheap raw materials do not necessarily guarantee low costs.
In recent years there have been many facts that prove that cheap raw materials (in the sense of the word uncertain quality) will only give rise to various problems that thus increase production costs.
Smelting costs can be reduced through the accuracy of loading techniques and smelting processes as well as supervision of the procurement/storage of raw materials. Starting from accurate processing, and loading discipline (weighing) to completeness of smelting data and supervision of recycled materials.