Cr/Ni Equivalent (Standard & Duplex)
Calculates standard stainless-steel Creq/Nieq and modified duplex Creq/Nieq from chemical composition. These are empirical equivalents only — this calculator does not plot a Schaeffler/DeLong diagram or predict final weld metal structure.
Engineering calculator — results require technical review before production use.
Source & assumptions
IWE Module 2 – Materials and Their Behavior during Welding, Chapter 15, Section 5 (Cr- and Ni-Equivalents)
Assumptions
- Some alloying elements promote a ferritic structure and others promote an austenitic structure; empirical Cr- and Ni-equivalents are a useful way to summarize this balance, per the source.
- Standard Creq = Cr + 1.4*Mo + 1.5*Si + 0.5*Nb + 2*Ti, all elements in weight percent.
- Standard Nieq = Ni + 30*C + 0.5*Mn + 30*N, all elements in weight percent.
- Modified duplex Creq = Cr + 2*Si + 1.5*Mo + 5*V + 5.5*Al + 1.75*Nb + 1.5*Ti + 0.75*W (SINTEF/Sandvik), all elements in weight percent.
- Modified duplex Nieq = Ni + Co + 30*C + 25*N + 0.5*Mn + 0.3*Cu (SINTEF/Sandvik), all elements in weight percent.
- An element absent from the input is treated as 0 (not reported / negligible).
- The standard and duplex equivalents are computed from the same shared composition; `mode` only controls which results are returned, not how they are calculated — computing both is unambiguous, with no conflicting element handling between the two formula sets.
Limitations
- This calculator only computes empirical Cr/Ni equivalents — it does not by itself determine final weld metal structure.
- It does not plot a Schaeffler or DeLong diagram, and does not implement WRC or ferrite-number structure prediction — the equivalents computed here are commonly used as inputs to such diagrams, but no diagram, region lookup, or structure classification is implemented in this calculator.
- It does not approve a WPS, filler metal selection, or welding procedure.
- Results require technical review before production use.
- The 'unusually high' composition warnings are an implementation-level input sanity check for likely data-entry errors — they are not sourced from IWE Module 2 and are not a compositional specification limit.