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Major Melt—Crucible Systems
Published in Nagaiyar Krishnamurthy, Metal–Crucible Interactions, 2023
The primary steel-making process largely follows the blast furnace–LD process/basic oxygen furnace (BF–LD/BOF) route and to a lesser extent, the directly reduced iron–electric arc furnace (DRI–EAF) route. Secondary steel making covers the refining of primary steel with respect to composition and cleanliness before casting. Secondary steel making involves deoxidation or killing with Al/Si additives, vacuum degassing, desulphurization, homogenization, alloying, and control of inclusion chemistry and content. These operations are commonly performed using ladle furnaces (Fruehan 1998).
Phase Diagrams
Published in Yip-Wah Chung, Monica Kapoor, Introduction to Materials Science and Engineering, 2022
Iron ores are mainly in the form of oxides. The first step in steelmaking is to reduce iron oxide to metallic iron by heating a mixture of coke (mostly carbon) and the iron ore. The resulting iron is known as pig iron, which contains up to 4 w/o carbon and other impurities such as sulfur and phosphorus derived from coke. Plain carbon steels contain up to 1.0 w/o C, and most other steels contain less than 0.5 w/o C. While having some carbon helps to increase strength, having too much carbon reduces the toughness and makes it difficult to weld. Sulfur and phosphorus tend to segregate to grain boundaries and reduce the strength and toughness of these alloys. Therefore, it is critical to reduce the content of these impurities to achieve a favorable balance of properties.
Nuclear Renaissance
Published in William J. Nuttall, Nuclear Renaissance, 2022
Steel making generates harmful carbon dioxide emissions for two main reasons. First, there is a need to provide very high temperatures sufficient to melt iron and steel. Second, there is a need to provide carbon as a reducing agent. This latter aspect relates to the fact that the CO2 emitted is a direct consequence of the process chemistry. The good news is that both aspects of the problem can be mitigated, and hydrogen is key to improved iron ore smelting. Rather than using coking coal and yielding carbon dioxide, smelting can be performed using hydrogen such that the process yields harmless water vapour, not CO2. Linking to the use of a low-carbon heat source, such as might be supplied via nuclear energy would further reduce the emissions associated with steel making.
Utilization of accelerated carbonation to enhance the application of steel slag: a review
Published in Journal of Sustainable Cement-Based Materials, 2023
Yue Wang, Jianhui Liu, Xiang Hu, Jun Chang, Tingting Zhang, Caijun Shi
Steel slag is the main co-product during the steel manufacturing process which adds lime, dolomite, and other supplementary materials into blast furnace to remove carbon, phosphorus, sulfur, and other elements in pig iron [14]. It can be divided into three categories according to the main production processes of steel. The basic-oxygen furnace (BOF) is employed during the primary steel refinement process which uses molten iron, steel scraps with lime or dolomite as the main raw materials [15]. The electric-arc furnace (EAF) has a similar steelmaking process to BOF except using high-power electric arcs to produce high quality steel mainly from recycled steel scrap. The EAF process requires much less capital than the BOF process and involves using a combination of steel scrap that will be purified in the EAF process [3, 16]. The ladle furnace (LF) process is the final operation of steel refinement which is generally called as the secondary metallurgy process. After the primary steel refinement process in the BOF or EAF, both carbon and stainless steel are poured into a LF and are deoxidized, desulfurized and suitably alloyed under the protection of a basic slag. The chemical composition and properties of LF slags are quite different from that of BOF and EAF slags because of the use of various fluxes [17].
Subgrade stabilisation mixtures with EAF steel slag: an experimental study followed by field implementation
Published in International Journal of Pavement Engineering, 2022
Irem Zeynep Yildirim, Monica Prezzi
Steel slags take their name from the steelmaking process that generate them. In the last decade, the electric-arc-furnace (EAF) steelmaking process has become more prevalent than the basic-oxygen-furnace (BOF) steelmaking process in most countries, as well as in the U.S. The main feed of EAF–consisting of pig iron (∼20–30%) and recycled steel scraps (∼70–80%)–are molten in the furnace with the help of an electric arc. Burnt lime (CaO) or dolomite CaMg(CO3)2 are also added to the furnace as fluxing agents. In primary steelmaking operations, some of the oxidised iron and impurities in the hot metal combine with lime (CaO) to form slag. After cooling, metal recovery and crushing operations, this by-product of the primary steelmaking processes is referred to as EAF steel slag (EAF SS). The chemical composition of EAF SS is, in general, similar to that of BOF steel slag (BOF SS) (Shi 2004, Yildirim and Prezzi 2015). The chemical composition of steel produced in EAFs are fine tuned in ladle furnaces to produce high-grade steels. The by-product that is referred as ladle steel slag (LF SS) is generated during these ladle refining operations at EAF Plants.
Red Mud: Fundamentals and New Avenues for Utilization
Published in Mineral Processing and Extractive Metallurgy Review, 2021
After a neutralization cycle, from the table, an XRD of red mud showed an increase in calcium carbonate content by 2%. Calcium carbonate or limestone is a material used in iron and steelmaking as a flux material in order to enhance separation of impure slags from the iron. This newly formed material can be utilized as a fluxing material in pyrometallurgical processes for the removal of iron (Archambo, Valluri and Kawatra 2020). For leaching techniques to extract minerals for red mud, a neutralizing step with CO2 can reduce the pH of red mud prior to acid leaching to reduce the amount of acid required for leaching (Rivera et al. 2017). The CO2 seemed to hinder the iron leach efficiency due to compounds such as calcite and cancrinite forming and depleting available acid that could have been used for iron dissolution.