THE MANUFACTURE OF STEEL

Metallurgist, 2007

Modern oxygen-converter steelmaking is a combination of a technology that has proven itself over many years and modern equipment that controls the steelmaking operation and protects the environment. When used together with out-of-furnace treatment units, this steelmaking method makes it possible to produce steel for high-technology applications in accordance with the most stringent existing standards on the cleanliness of the metal. The method is flexible, is characterized by extremely high productivity, and can be incorporated in a very wide range of manufacturing processes. As a high technology, oxygen-converter steelmaking will remain in demand for decades to come.

Steelmaking is the method of developing steel from iron ore (usually haematite) and scrap. The impurities such as nitrogen, sulphur, silicon, phosphorus and excess carbon are separated out from the raw iron and alloying elements such as nickel, manganese, vanadium, molybdenum and chromium are added to impart different properties to steel. The technology of steelmaking has made great advancements with time. This paper describes the modern technologies used in a steel plant while reviewing the conventional processes as well.

Revue de Métallurgie, 2004

2017

The basic technologies for modern iron and steel production were developed about half a century ago. Then and thereafter, raw materials pretreatments, coke making and blast furnace process itself were strongly improved, energy consumption and emissions were decreased as well as productivity and product quality were raised. Modern top, bottom and combined blowing converter processes were developed, which revolutionized steel production based on iron ore concentrates. Today, oxygen converter process is the main primary steelmaking technology with a share of about two thirds of the world steel production. Another mainstream of steelmaking is based on recycled steel as raw material. Smaller share of the scrap is used in converters as cooling material, but most of it is melted in ultra-high power electric furnaces. The progresses in these primary steelmaking technologies have been solidly associated with the emergence and developments of secondary steelmaking processes in ladles as well ...

The industrial development program of any country, by and large, is based on its natural resources. Depleting resources of coking coal, the world over, is posing a threat to the conventional (blast furnace [BF]-basic oxygen furnace [BOF]) route of iron and steelmaking. During the last four decades, a new route of ironmaking has rapidly developed for direct reduction (DR) of iron ore to metallic iron by using noncoking coal/natural gas. This product is known as direct reduced iron (DRI) or sponge iron. Processes that produce iron by reduction of iron ore (in solid state) below the melting point are generally classified as DR processes. Based on the types of reductant used, DR processes can be broadly classified into two groups: (1) coal-based DR process and (2) gas-based DR process. Details of DR processes, reoxidation, storage, transportation, and application of DRI are discussed in this section.

IntechOpen eBooks, 2023

The blast furnace and direct reduction processes have been the major iron production routes for various iron ores (i.e. goethite, hematite, magnetite, maghemite, siderite, etc.) in the past few decades, but the challenges of maintaining the iron and steel-making processes are enormous. The challenges, such as cumbersome production routes, scarcity of metallurgical coke, high energy demands, and high cost of production, cannot be overemphasized. This study provides a systematic overview of the different ironmaking routes, their operational limitations and proper sound future perspectives to mitigate the challenges involve based on iron production demands in the modern-day metallurgical process. Subsequently, strategic ways toward improving the production efficiency and product quality of metallic iron produced in the recent iron processing routes were suggested. The study reiterated that the non-contact direct reduction and reduction-smelting routes are the faster ironmaking and steelmaking processes that can utilize alternative energy sources efficiently with little or no carbon deposition. Both processes also have promising features based on their requirements in terms of fewer energy demands, time-saving, cost-effectiveness, and operational efficiency. Thus, in today's iron and steelmaking processes, non-contact direct reduction and reduction-smelting processes remain viable alternative iron production routes.

Metalurgija, 2004

2005

Current blast furnace technology is a two-stage ironmaking process that requires that iron ore concentrate first be formed into pellets, fired at 1260°C, cooled, transported to the blast furnace, and then reheated to approximately 1500°C to produce pig iron. This heating, cooling, and then reheating wastes a great deal of energy, which would be saved if the ironmaking process had only a single heating step. Kobe Steel's ITmk3 process is intended as a replacement for blast furnace processing that produces "pig iron nuggets" directly from cold-pelletized iron ore concentrate in a single stage of heating. It is therefore more energy-efficient than the current technology. Iron nuggets are produced by combining iron ore concentrate with a reducing agent (finely ground low-sulfur coal), a binder, and a flux to form pellets. These pellets are then heated to approximately 1400-1500°C in a rotary-hearth furnace. Upon heating, the pellets self-reduce to molten iron and molten slag, which separate from each other to form a metallic pig iron nugget and a slag drop. Upon cooling, the slag separates cleanly from the metal nugget. The objective of this project was to determine how the transformation from powdered iron oxide to metal+slag occurs, to examine how the transformation is affected by temperature and processing time, and to determine the optimum conditions for producing iron nuggets as a function of temperature. This project determined that, contrary to what had been believed by the developers of the ITmk3 process, the iron oxides did not directly react with the coal to produce pig iron in a single step. Instead, the transition consisted of the following stages: 1. Coal volatiles reacted with the iron oxides to produce "Direct Reduced Iron" (DRI) 2. Silicate gangue, coal ash, flux, and FeO melted to produce a slag, while the direct reduced iron began to melt due to dissolving excess carbon from the coal. This produced a mixed slag/metal product, "Transition Direct Reduced Iron" (TDRI) 3. The TDRI then fully separated into a liquid pig iron drop and a liquid slag drop. Upon cooling, this produced a pig iron nugget and a cleanly-separated slag nodule. The time needed for this transformation was a strong function of temperature, with times ranging from over 40 minutes at 1400°C, to approximately 10 minutes at 1500°C. It was determined that industrialscale rotary-hearth furnaces were producing nuggets with highly variable quality due to some pellets being heated more than others, with the cooler pellets having insufficient time to complete the transformation to iron nuggets. Uniform heating in the furnace is therefore key to maintaining satisfactory nugget quality.

ISIJ International

In this study, a thermodynamics model was developed for the basic oxygen steelmaking (BOS) process (combined top & bottom blown), which was used to calculate the transient carbon, silicon, manganese, and phosphorus contents, as well as their slag composition, for different input hot metal-carbon contents. The model considered three different zones, and the volume of different phases was calculated using the Equip module of the FactSage macro processing code. The results of the model showed that manganese, phosphorus, and iron oxidation rates were high for input hot metal with low carbon content (3%). Additionally, the model predicted transient metal composition, and metal bath temperature, which were similar to plant observations for input carbon percentages ranging from 4 to 4.5.