Researchers Unveil Carbon-Free Heat Treatment for Steel Industry

Researchers at the Korea Institute of Energy Research (KIER), led by Dr. Hookyung Lee, have developed an innovative electrification technology that transforms the conventional metal heat treatment process, widely used in the production of galvanized steel strips, into a carbon-free method. This breakthrough is expected to significantly aid the transition towards decarbonizing energy-intensive industries, particularly steelmaking, which has faced increasing pressure to reduce its greenhouse gas emissions.

As the South Korean government intensifies its efforts to meet national greenhouse gas reduction targets for 2035, industries such as steel are under scrutiny to adopt cleaner technologies. The aim is to achieve a reduction of up to 31% in industrial sector emissions from 2018 levels through various means, including electrifying industrial processes and scaling up the production of low-carbon products, as outlined during the 5th Plenary Meeting of the Presidential Committee on Carbon Neutrality and Green Growth in November 2025.

Decarbonizing Steel Production

The production of galvanized steel strips typically involves a continuous galvanizing line (CGL) process, where steel plates are coated with molten zinc. During this process, the steel undergoes annealing, a heat treatment that enhances its ductility and formability. Traditionally, heat for this annealing process is derived from burning fossil fuels, resulting in substantial emissions of greenhouse gases, including carbon dioxide and nitrogen oxides. In fact, emissions from the steel industry, particularly those associated with zinc manufacturing, account for approximately 15% of South Korea’s total national emissions.

To combat this environmental challenge, the research team has created a “carbon-free annealing system” that utilizes electricity rather than fossil fuels. By replacing traditional burners in combustion-based annealing furnaces with electric heating elements, the new system demonstrated a remarkable reduction in emissions. Tests conducted under conditions simulating commercial production revealed a decrease of more than 98% in the concentrations of carbon dioxide and nitrogen oxides in exhaust gases.

The design of the new system retains the refractory structure and steel-strip conveying mechanisms of conventional furnaces. Electric heating elements are strategically installed in both the upper and lower sections of the furnace, allowing for rapid and uniform heating while minimizing heat loss. In experiments with steel strips measuring 0.49 millimeters in thickness at temperatures of 750°C, the annealed strips exhibited color, microstructure, and mechanical properties comparable to those produced by traditional methods, but with significantly lower emissions.

Implications for the Future

This innovative electric annealing furnace eliminates the need for fuel and air supply systems, burners, and exhaust systems required by conventional combustion-based furnaces, leading to a reduction in capital investment costs and installation footprint by approximately 40%. Furthermore, when powered by renewable energy sources such as wind and solar, the system could facilitate a truly carbon-free heat treatment process, aligning with global environmental regulations, including the Carbon Border Adjustment Mechanism (CBAM).

“This demonstration is the world’s first case to show that carbon-free heating can be achieved simply by replacing burners with electric heating elements,” stated Dr. Hookyung Lee.

Looking ahead, the research team plans to expand this technology into an artificial intelligence-based design and operation system. This system is intended to automatically recommend optimal heating configurations based on factors such as steel-strip width, thickness, and conveying speed. The ultimate goal is to develop an export-ready carbon-free heating solution in collaboration with domestic steelmakers and international markets.

The findings of this study were published in September 2025 in the journal Applied Thermal Engineering, a notable publication in the field of energy and thermal engineering. This research was supported by South Korea’s Ministry of Trade, Industry and Energy, with practical demonstrations conducted at the facilities of Samwoo Eco Co., Ltd., illustrating a collaborative effort between academia and industry.