To successfully transition to a carbon-neutral society, it is essential to decarbonize the industrial sector, which emits large amounts of greenhouse gases and is heavily reliant on carbon and energy. In particular, the steel industry is a highly carbon-intensive industry that emits significant amounts of greenhouse gases during its production process. Globally, the steel industry accounts for 7% of total greenhouse gas emissions and 25% of industrial emissions. In South Korea, the steel industry's greenhouse gas emissions constitute 13% of the nation's total emissions and 39% of industrial emissions, which is higher than the global average. Considering the steel industry's status as a key driver of South Korea's industrial development and the steady increase in demand for steel due to industrial advancement (1-2% annual growth, with global demand expected to reach approximately 2.747 billion tons by 2050), decarbonizing the steel industry is seen as an essential task.

   The high greenhouse gas emissions from the steel industry primarily stem from the blast furnace-based manufacturing process, where coke is used as a reducing agent and reacts with iron ore to produce steel (for example, producing 1 ton of steel emits approximately 2 tons of CO2). As a solution to this problem, hydrogen reduction steelmaking has been proposed, which uses hydrogen as a reducing agent and emits no greenhouse gases. However, commercializing reduction furnaces to replace blast furnaces and producing green hydrogen as a coke substitute are expected to take considerable time and involve numerous trials and errors. In the meantime, the "Electric Arc Furnace Process Based on Steel Scrap Recycling," which can reduce greenhouse gas emissions by over a quarter compared to the blast furnace-based process, is gaining recognition as the most viable decarbonization alternative.

   However, even apart from the burden of electricity costs in the manufacturing process, electric arc furnaces have several critical disadvantages compared to blast furnaces. Firstly, the blast furnace process allows for easy control of alloying elements, enabling the production of various high-value steel products for different uses. In contrast, the electric arc furnace process, which recycles steel scrap of varying compositions, struggles to adjust alloying elements, resulting in a limited range of products and lower profit margins (e.g., bars, rebar). Furthermore, tramp elements, which are difficult to remove during the scrap refining process, accumulate within the steel through repeated recycling cycles, degrading its mechanical properties and making it challenging to produce high-quality steel. Thus, overcoming these challenges is essential for successfully establishing an electric arc furnace production system based on steel scrap recycling.

  In light of this, the current research project aims to develop a recycling-oriented, sustainable, environmentally-friendly variable-property steel material (REUSES: REcycling-oriented Uni-Steel for Environment and Sustainability) to support the establishment of an electric arc furnace production system.

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1. Single-Composition Steel: The developed material has a single composition, yielding a uniform scrap composition, making it highly conducive to recycling and reproduction.

 

2. Variable-Property Steel Based on Microstructure Design: Through extreme control technologies for the microstructure, such as Thermo Mechanical Process (TMP) that influences element redistribution and phase transformations, the developed material can exhibit diverse properties despite its single composition. This allows it to be applied to various high-value steel products and components with opposing properties, using a single material. In contrast to conventional steel materials, which achieve the desired properties through changes in the alloy's chemical composition via a Chemistry-dominated Alloy Design, this research pursues a Microstructure-dominated Alloy Design, where the steel's broad range of properties relies more on microstructure control than on the alloy's chemical composition.

 

3. Damage-Tolerant Microstructure: Through extreme microstructure control technologies based on TMP, the developed material has a microstructure resistant to damage (Damage-Tolerant Microstructure), enabling excellent performance even in extreme environments such as cryogenic and hydrogen embrittlement conditions.

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4. Tramp Element Resistance: Through a physical metallurgical study of tramp elements that negatively impact the properties of recycled steel (e.g., Cu, Sn, P), we aim to develop a material that exhibits minimal mechanical degradation even with high concentrations of these elements.