Adapting XRF Sample Preparation for Green Steel Production

Green steel production promises lower emissions, but it also introduces a more unpredictable analytical environment. Scrap variability, hydrogen reduction chemistry, and evolving slag compositions generate conditions where small material differences can produce large analytical deviations. In many laboratories, this is exposing the limitations of conventional X-ray fluorescence (XRF) sample preparation methods and accelerating the adoption of fusion-based workflows designed to improve repeatability across highly variable sample matrices.

How Green Steel Production Alters Sample Chemistry

Traditional ironmaking relies on relatively stable ore streams with predictable mineralogy and chemistry. Green steel production changes those conditions considerably. Hydrogen-based Direct Reduced Iron (DRI) processes generate porous materials containing varying concentrations of metallic iron alongside residual iron oxides such as FeO and Fe2O3. Even small fluctuations in reduction efficiency can alter the chemistry of the final product, producing inconsistencies between batches that appear similar during production.

Chemical variability and analytical complexity increase further in Electric Arc Furnace (EAF) operations. EAFs process large volumes of recycled scrap, and scrap composition can differ significantly depending on its source. Automotive steel, galvanised scrap, construction materials, and industrial offcuts all introduce different concentrations of tramp elements including copper, zinc, tin, chromium, and nickel. At the same time, slag chemistry shifts continuously as operators modify lime additions and fluxing conditions to maintain furnace performance.

For XRF laboratories, such variability forms a difficult analytical environment for accurate and repeatable compositional measurement. Matrix effects become more pronounced because one element can influence the quantified intensity of another through absorption and enhancement interactions. Changes in oxidation state, density, mineralogy, and particle size add further instability to calibration models. Laboratories supporting green steel operations therefore require XRF sample preparation methods capable of reducing matrix-related interference while preserving calibration stability throughout variable sample streams.

Why Traditional Pressed Pellet Methods Struggle

Pressed pellet preparation has been widely used in mining and metallurgical laboratories for decades because it offers relatively fast processing times and lower consumable costs. However, DRI materials and EAF slags expose several weaknesses. Pressed pellets retain the original crystalline and mineralogical structure of the sample. In DRI materials, metallic iron and oxidised iron phases coexist within the same pressed surface, yet these phases interact differently with incident X-rays during analysis. This generates inconsistent absorption behaviour that can destabilise calibrations, particularly when reduction conditions differ between production campaigns. Particle-size effects produce another complication as metallic iron particles often grind differently from surrounding oxide phases, resulting in uneven particle distribution while being pulverised.

EAF slags present similar challenges because they commonly contain metallic inclusions, refractory fragments, and partially reacted silicates that resist complete homogenisation in a pressed pellet. Since XRF analysis only measures a shallow depth near the sample surface, localised inconsistencies can distort elemental readings significantly. With inconsistent mineralogy and uneven sample homogeneity, high-performance XRF spectrometers can struggle to deliver reliable analytical data. For green steel laboratories, XRF sample preparation quality increasingly influences analytical accuracy more than instrument capability alone.

Borate Fusion as the Preferred Solution

Borate fusion is becoming the preferred XRF sample preparation method for a number of green steel laboratories as it removes the mineralogical and particle-size effects that compromise pressed pellet analysis. In fusion, the sample dissolves completely into a molten borate flux at temperatures typically ranging between 1000°C and 1050°C before cooling into a homogeneous glass disc suitable for XRF analysis. Within this process, crystalline structures and physical inconsistencies present in the original material are eliminated entirely.

The analytical benefits are substantial. Fusion produces a chemically homogeneous glass bead that reduces XRF sensitivity to mineralogy, porosity, and uneven particle distribution. More stable calibration curves, improved matrix corrections, and strong analytical repeatability help laboratories retain reliable results across variable DRI and EAF sample streams.

DRI materials do, however, introduce a significant technical challenge throughout fusion. Metallic iron can alloy directly with platinum crucibles at elevated temperatures, potentially damaging expensive laboratory equipment. To prevent this, laboratories incorporate controlled oxidation stages into the fusion cycle before complete dissolution occurs. Chemical oxidisers such as lithium nitrate convert metallic iron into oxidised forms prior to fusion, protecting platinumware and preserving analytical integrity. Laboratories also adjust lithium tetraborate and lithium metaborate ratios to achieve stable dissolution across varying slag chemistries and maintain consistent bead quality.

Preparing XRF Laboratories for Green Steel Production

Hydrogen reduction technologies and scrap-intensive EAF production are changing the expectations placed on XRF laboratories. To support these evolving requirements, XRF Scientific offers automated fusion instrumentation, custom flux chemistries, oxidiser systems, and platinumware engineered for high-demand metallurgical applications like direct reduced iron processing and recycled scrap analysis. The xrFuse platform enables laboratories to improve repeatability and reduce XRF sample preparation variability across diverse sample types. Speak to XRF Scientific to find out more about how our fusion technology can enhance analytical performance in green steel operations.