Schaeffler Coordinate Helper

Source & assumptions

IWE Module 2 – Materials and Their Behavior during Welding, Chapter 15, Sections 5, 6 and 7 (Cr- and Ni-Equivalents; Schaeffler, DeLong and Other Structure-Diagram; Measuring the Ferrite Content) and Chapter 22, Sections 2, 4 and 6 (Use of Schaeffler-Diagram; Effect of Dilution; Typical Applications)

Assumptions

• Creq and Nieq are empirical coordinate indices used as Schaeffler-diagram coordinates — not weight percentages, even though the composition inputs used to derive them are weight percent.
• The standard Cr/Ni equivalent formulas (Creq = Cr + 1.4×Mo + 1.5×Si + 0.5×Nb + 2×Ti; Nieq = Ni + 30×C + 0.5×Mn + 30×N) are used as the Schaeffler-coordinate basis, reusing the same formulas already implemented and registered as FR-004's standard equivalents — never the modified duplex (SINTEF/Sandvik) formulas, which are a different thing for a different purpose.
• Direct coordinates (Path A) are accepted as already-calculated values entered by the user — this calculator does not verify, and cannot verify, what formula produced them.
• Composition inputs (Path B) are entered as weight percent (wt%), using the standard 9-element set (C, Mn, Si, Cr, Ni, Mo, Nb, Ti, N) — not the duplex-only elements (Co, Cu, V, Al, W).
• An element absent from the composition is treated as 0 (not reported / negligible), matching the convention already used by Carbon Equivalent, Cr/Ni Equivalent, Material Certificate Check, and Estimated Mixed Composition.
• A composition supplied with inputBasis = "estimatedMixedComposition" requires extra caution, since it rests on an estimate (e.g. from a dilution calculation) rather than a measured chemical analysis.
• Manual diagram and metallurgical review is required — this calculator prepares a coordinate; it does not read the diagram for the user.
• Source worked example (hard-facing electrode, Ch. 15 §6): composition C=0.6, Mn=16, Si=0.5, Ni=1, Cr=4 wt% (P=0.035 wt% is also stated but has no term in either standard formula). Via the standard formulas above this computes Nieq=27 (exact match to the source) and Creq=4.75 (the source prints 4.8 — 4.75 rounds to 4.8 at one decimal place under round-half-up; this reconciliation is this project's own independent verification, not a source statement). The source states this composition's structure as Austenite. That structure label is recorded here only as the source's own worked-example reference for manual review — it is never produced as this calculator's output, and is not a general classifier.

Limitations

• This is a coordinate helper only.
• It does not perform automatic Schaeffler region classification.
• It does not implement DeLong or WRC calculation.
• It does not predict a ferrite number.
• It does not measure ferrite content — the source's own practical methods (a grid technique on a micro-etched picture, or a magnetic field measuring instrument) are physical measurements, not calculations this app can perform.
• It does not predict phase fractions.
• It does not predict martensite.
• It does not make a cracking decision.
• It does not make a cold-brittleness decision.
• It does not make a corrosion decision.
• It does not approve material selection.
• It does not approve a WPS or PQR.
• It does not recommend a filler metal.
• It does not assess service suitability.
• It does not replace metallurgical review, procedure qualification, ferrite measurement, material certificate review, or engineering judgement.
• The 'unusually high' per-element sanity-check warnings (reused from Cr/Ni Equivalent's thresholds, surfaced automatically when Path B delegates to calculateCrNiEquivalent) are implementation-level heuristics, not sourced from IWE Module 2 as compositional limits.
• Results require technical review before production use.