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Iron ore sintering is a type of powder metallurgy used to pre-treat iron before using it in manufacturing applications. Sintering involves heating iron powder to partially, but not completely, melt the iron particles. The exact process used and additional elements involved vary, with some methods using gas or electricity in addition to heat. Through the process of iron ore sintering, iron is reduced through diffusion, thus removing non-iron particles prior to further application-specific processing.
To understand iron ore sintering, it is necessary to first understand certain aspects of raw iron ore. Raw iron ore is found throughout the world and is, in fact, one of the most prevalent elements on earth. Mining operations pull raw ore from the earth’s crust, separating it into high-grade and low-grade, based on how much raw iron is present. High-grade iron ore has a higher concentration of iron that low-grade iron ore. Typically, the concentration of iron is somewhere between 65 and 72 percent.
Different processing methods, such as sintering and pelleting, require different grades of iron ore. Specifically, iron ore sintering requires the use of fine ore, produced by crushing high-grade iron ore into particles only a few millimeters in diameter. Depending on the specific machine and iron ore sintering process used, substances such as coke breeze and burnt limestone are used to ignite and heat the iron ore particles until the particles congeal. Once congealed into an agglomerate, the ore is again crushed. Screening ensures non-iron particles are removed and the remaining iron particles average between 15 and 30 millimeters in diameter.
Other iron ore sintering processes use machines that take crushed iron ore and mix it with water and other substances, known as fluxes, prior to igniting the mixture. Electricity is conducted through the mixture, and its surface is ignited to help form an agglomerate. Dust from the iron ore, as well as iron particles that do not meet size requirements, are recirculated through the machine with each batch of iron ore processed.
Primarily, the goals of iron ore sintering are to produce consistent chemical composition, to increase the strength of iron particles, and to create a uniform particle size. As such, how iron ore is sintered depends on the intended purpose of the finished product. Certain manufacturing applications require smaller particle sizes, while others require differences in particle strength. For example, metal-ceramic composites require a much finer particle size than the sintered iron used in some clutch plates. Similarly, some applications require the highest iron purity possible and thus require a different sintering process.