Revolutionizing Steel Production

Grinding vs. Scarfing in the Fight Against Carbon Emissions

Published May 14, 2024

In 2023, the steel industry discharged 2.8 billion tons of CO2, constituting 8% of global direct CO2 emissions (source: IEA, 2023, Emissions Measurement and Data Collection for a Net Zero Steel Industry). As we propel toward a net-zero future by 2050, the imperative to decarbonize steel production becomes paramount.

This is where Saint-Gobain Abrasives steps in, offering a diverse array of more sustainable solutions to facilitate the decarbonization of our customers’ operations. One such solution involves the surface conditioning of semi-finished steel products like slabs. Surface conditioning, performed prior to rolling, is essential for eliminating surface defects such as inclusions, pits, cracks, and seams, to ensure that the final product meets quality standards. Typically, a thin layer of material must be removed from the surface of the product.
 

Traditionally, this task was accomplished using manual or automated flame scarfers on carbon steel. Flame scarfers work by melting and oxidizing the metal with an oxyfuel torch, while a separate oxygen stream removes the oxidized metal scales from the surface. However, in recent years, grinding has emerged as a viable alternative due to advancements in both the productivity of grinding machines and the performance of grinding wheels. An additional benefit of grinding is the production of swarfs, which can be directly recycled in converters and electrical furnaces, unlike the scarfing slag. Swarfs, being metallic iron, do not require reduction. This results in potential cost savings of approximately €18 per ton of ground steel, based on a scrap cost of €350 per ton.

Saint-Gobain Abrasives initially partnered with a conditioning service provider to gain insights into scarfing and grinding operations. Leveraging our own expertise and collaborating with a leading global manufacturer of grinding machines renowned for their cutting-edge innovations, we delved into grinding operations. Drawing from real-world cases, Saint-Gobain Abrasives developed scenarios and conducted a thorough comparative Life Cycle Assessment (LCA) study. This study underwent rigorous scrutiny by a committee comprising four independent experts with extensive experience in pertinent fields, including steel manufacturing, abrasives, and specifically the grinding of semi-finished products, as well as LCA applied to steel manufacturing.

The study conclusively demonstrates that grinding on flat carbon steel (vs. automated flame scarfing) reduces the CO2 footprint of the conditioning process by approximately 80% in France (with reductions of at least 40% in other regions, depending on their electricity mix's carbon intensity). Additionally, grinding facilitates further steel and CO2 savings of at least 25%, owing to the superior control over the thickness of material removed afforded by grinding machines. Furthermore, grinding enables significant Scope 1 decarbonization, as it requires no fuel.

Transitioning from scarfing to grinding alone could potentially decrease the carbon footprint of a slab by up to 5% in an electrical steelmaking plant!

For further insights into the benefits of grinding versus scarfing, don't hesitate to reach out to Andre Collin, Product Manager & Market Director Primary Steel, Saint-Gobain Abrasives EMEA. For more details on the external verification process, you can access the report issued by the committee of experts. The report confirms the study’s compliance to the standards that apply to LCA, namely ISO 14040 and ISO 14044. 
 

NB. Analysis was conducted on the scenario involving the removal of a 3mm layer of material from the wide sides of a carbon steel slab. Our findings indicate that the abrasiveness of scarfing often results in the removal of more material than necessary. Actual measurements from numerous cases show that, on average, scarfing removes approximately 4.6mm of material. However, for the purposes of this study, a conservative estimate of 4mm was adopted.

Data collection for this study involved collaboration with operators, machine manufacturers, and steelmakers. The information gathered reflects real-world operations in steelmaking plants.

Life Cycle Assessment (LCA) results were obtained using the EF 3.1 characterization method, focusing on the "Climate Change, Total" indicator.