A Fresh Look at Slag Analysis – From Granular Material to Result

Introduction

Chemical analysis of slag is a crucial component of process optimization in steelmaking. But how reliable are analytical results when samples are not homogenized or pulverized beforehand? That’s the central question we at QuantoLux are investigating in a focused round robin test involving over ten steel plants — with a spotlight on granular ladle slag.

The goal is to evaluate the impact of sample preparation and analysis procedures across different laboratories. In other words: How much do results vary when identical slag material is prepared and analyzed independently by different labs using their own standard routines?

multiple subsets of 1 LF slag sample prepared for shipping in the round-robin test

Traditional Round Robin Tests – Efficient, but not made for "real-life" comparison

Most round robin tests involving slag samples use pre-homogenized and pulverized material to ensure comparability. The aim is typically to benchmark X-ray fluorescence (XRF) performance under controlled lab conditions. While useful for evaluating instruments, these protocols deliberately minimize the influence of sample preparation — and in doing so, they fail to reflect real-world challenges.

However, Steelmaking Slag is inherently heterogeneous. Minor differences in grinding, homogenization, or pellet pressing can lead to significant measurement variations — with direct consequences for melt shop decision-making and process control.

A New Approach – Closer to Real-World Practice

Our round robin takes a realistic and practice-oriented approach. Instead of sending pre-pulverized powders, we distribute granular ladle slag material from a single batch — exactly as it appears thousands of times per day in routine steel plant operations.

Each participating plant analyzes the material using its standard preparation and measurement procedures, capturing the real-life variability that naturally arises in daily sample handling and analysis.

To ensure transparency and provide reference data on sample homogeneity and baseline composition:

• Each sample is additionally analyzed using a QuantoLux Laser OES slag analyzer (QLX9). This system performs quasi-nondestructive, rapid measurements directly on the granular material, offering a fast and consistent reference point for comparison.

• A selected subset of the samples is also analyzed by an accredited laboratory using fused bead preparation and XRF, delivering high-precision certified reference values for benchmarking.

What We're Investigating

This test setup enables us to finally quantify the influence of sample preparation under realistic conditions:

• How much do analytical results vary across different labs?

• What is the estimated contribution of sample splitting, preparation, and sampling technique to total measurement error?

These are essential insights for any steel producer aiming to optimize not only the slag analysis process, but also the broader operational workflow surrounding slag utilization and process feedback.

Laser OES – A Potential Gamechanger?

Modern technologies such as Laser Optical Emission Spectroscopy (Laser OES) offer the potential to dramatically reduce sample preparation time while preserving analytical precision.

With Laser OES, heterogeneous materials like slag can be analyzed in under one minute — without grinding, pressing, or fusing — and directly on the shop floor. This opens the door for real-time, process-integrated slag monitoring that supports more agile and efficient steelmaking operations.

Conclusion

This round robin test is the first to place slag analysis into a real-world context, evaluating how much of the total analytical variation stems from sample handling and preparation rather than instrumentation alone. We’re excited to work with our steel industry partners on this journey — because understanding your sample better means controlling your process smarter.