February 2024 Volume 6

MAINTENANCE

MATERIALS

In the absence of such inclusions, clean steel exhibits superior performance, excelling in high-stress applications like mobile, energy, construction and beyond. To ship clean steel, suppliers need to implement processes aimed at preventing the development of these detrimental inclusions, and then through statistical process control, detect and reject material that does not meet clean steel targets. Charter Steel is dedicated to doing just that by providing high-quality steel solutions and value-added processing. Through proactive troubleshooting and process controls, steel manufacturers can ensure the highest-quality steel is delivered to their customers each and every time—without fail. The Process Behind Clean Steel To effectively prioritize clean steel within their supply chain, OEMs aiming to address lightweighting requirements should possess a nuanced understanding of the intricate steelmaking process. This comprehension is crucial for identifying a supplier with a proactive approach, ensuring the steel utilized aligns seamlessly with the OEM’s business needs and commitment to high-quality materials. When evaluating clean steel suppliers, a comprehensive approach that emphasizes well-defined process targets during the melting phase is indispensable. Factors such as the melting process should be considered. Although blast furnace sourced steels were historically considered to provide the cleanest steel, modern electric arc furnaces (EAFs) coupled with advanced process controls can now compete in the same markets while being much more sustainable. Leveraging

an electric arc furnace (EAF) which uses electrical currents to melt scrap steel and other recycled materials results in 75% less CO2 emissions compared to other steelmaking processes, according to a study released by the Steel Manufacturers Association (Source: https://steelnet.org/steelmaking-emissions-report-2022/) . This more sustainable practice, which can help meet OEM sustainability goals, coupled with defined process controls can provide a very clean material. To maintain optimal cleanliness, key process benchmarks for a supplier include maintaining full slag coverage when there is risk of atmospheric exposure, strict adherence to rinsing time guidelines and avoiding over deoxidizing when incorporating aluminum, among other crucial considerations. Additionally, synthetic slag is one of the most important components for controlling steel cleanliness. Performing a wide array of functions, synthetic slag can act as a collector of nonmetallic inclusions, help prevent atmospheric reoxidation, safeguard insulating refractories and insulate electrode arcing. Clean steel requires a highly engineered and controlled process design to address the diverse range of possible inclusions across varying steel formulations. Argon rinsing and vacuum degassing are two key factors in clean steel practices that promote inclusion removal. Argon rinsing accelerates the floatation of non-metallic inclusions to the surface of the ladle. Vacuum degassing aims to reduce unwanted dissolved gases but also prevents the reintroduction of oxygen during stirring.

A degasser at Charter Steel’s mill in Cleveland, Ohio.

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