Overview
ISO 23692:2021 specifies procedures for the quantitative analysis of Mn dendritic segregation in continuously cast steel products using electron probe microanalysis (EPMA). The standard covers mapping and line-analysis methods to convert EPMA X‑ray counts into Mn concentration maps, enabling calculation of a segregation ratio (SR) for quality control and process optimization. It applies to billets, blooms and slabs (and can be used for ingots, cast iron and cast steel) with Mn > 0.01 % by mass. The minimum analysable dendrite size depends on EPMA microscope resolution and beam size.
Key topics and requirements
- Principle: Use EPMA mapping or line analysis to obtain X‑ray count distributions, apply a calibration curve from matched reference materials, export quantitative Mn concentration data and compute the dendritic segregation ratio (SR = C_high / C_low).
- Reference materials & calibration: Select certified reference materials with the same matrix and composition range (per ISO 14595, ISO 11938). Establish calibration curves (per ISO 22489) to convert counts to concentration.
- Sampling & specimen preparation:
- Prefer transversal sections; ensure representative sampling (recommend two or more sections).
- Metallographic preparation: careful sectioning, sequential grinding/polishing to ≤1 µm finish, cleaning and drying. Use conductive mounting or provide a conductive path to ground to prevent charging.
- Instrument calibration & stability: Regular checks of beam current, magnification, stage stability and X‑ray intensity; monitor stability over the mapping time (ISO 11938).
- Recommended EPMA parameters (examples from ISO 23692):
- WDS crystal: LIF, Mn Kα
- Accelerating voltage: 15–20 kV
- Beam current: 100–300 nA
- Beam/pixel size: 1–10 µm (pixel size = beam size)
- Mapping dwell: 5 ms–5 s; mapping area ≥1 mm2 including ≥10 dendrites; >10 000 pixels
- Line analysis: dwell 0.1–5 s; pixel number >1 000; line length >1 mm; multiple lines across X/Y
- Data processing: Remove zeros/negatives and MnS inclusion outliers, sort concentrations, compute low/high averages (P recommended 0.15), then compute SR.
- Uncertainty & reporting: Consider specimen prep, calibration, reference material selection and correction methods (see ISO 22309). Reports must reference ISO 23692:2021 and include specimen ID, sampling locations, test conditions, reference materials and SR.
Applications and users
- Primary users: steel producers, metallurgical labs, EPMA laboratories, materials characterization and failure-analysis teams.
- Practical uses: quantify Mn microsegregation to control banded structure, support process optimization in continuous casting, production quality control, R&D into solidification and alloy homogeneity.
Related standards
Keywords: ISO 23692:2021, EPMA, electron probe microanalysis, Mn dendritic segregation, continuously cast steel, quantitative analysis, mapping analysis, line analysis, calibration curve, reference materials.