Ferrite / Weldability Calculator (WRC-1992, ASME BPE) — Sample Report

1 · Design inputs

A 316L hygienic tube heat offered for autogenous orbital welding. Certificate: 17.0 % Cr, 12.0 % Ni, 0.020 % C, 0.050 % N, 2.10 % Mo, 0.50 % Si, 1.50 % Mn, 0.010 % S.

2 · Method

WRC-1992: Cr_eq = %Cr + %Mo + 0.7·%Nb · Ni_eq = %Ni + 35·%C + 20·%N + 0.25·%Cu

BN2: Cr(eq) = %Cr + 1.5·%Si + %Mo + 2·%Ti · Ni(eq) = %Ni + 0.5·%Mn + 30·%C + 30·(%N − 0.02)

BN2 criterion: Cr(eq) − 0.91·Ni(eq) ≤ limit

ASME BPE Appendix G uses two different pairs of equivalents for two different jobs, and the calculator keeps them apart. The WRC-1992 pair (G-1) places a heat on the constitution diagram: chromium equivalent gathers the ferrite-forming elements, nickel equivalent the austenite-formers, with carbon and nitrogen weighted at 35 and 20 because interstitials are overwhelmingly the strongest austenite stabilisers per unit mass — 0.02 % carbon carries the same weight in the nickel equivalent as 0.7 % nickel does. The BN2 criterion (G-3(d) and its footnote, citing Basler Norm BN2) is a heat-selection limit for low-ferrite material such as grade 1.4435, and it is written on its own equivalents: silicon and titanium join the chromium term, manganese joins the nickel term, carbon counts 30 and nitrogen counts 30 above a 0.02 % offset. The 0.91 coefficient and the limit belong to that pair only — applied to the WRC-1992 pair they give a different number, which is why BN2 needs the certified silicon and manganese and is not evaluated without them. Separately, and only when a sulfur content is supplied, the autogenous-weld window is applied — a lower and an upper bound, both taken from MM-5.2.1.1(a) unless your specification sets its own, with the verdict reported as in-range, low or high and a PASS only for in-range. A heat below the window draws the erratic-penetration warning; above it, the hot-cracking and corrosion-resistance warning. The Ferrite Number itself is deliberately not returned: it is read from the WRC-1992 diagram, which is published plate content and is not embedded here. What this card gives you are the two coordinates you carry onto your own copy of that diagram, plus the criteria that do not require it.

3 · Calculation

1. WRC-1992: Cr_eq = 17 + 2.1 + 0.7 × 0 = 19.1; Ni_eq = 12 + 35 × 0.02 + 20 × 0.05 + 0.25 × 0 = 12 + 0.7 + 1.0 = 13.7.
2. BN2 equivalents: Cr(eq) = 17 + 1.5 × 0.5 + 2.1 + 2 × 0 = 19.85; Ni(eq) = 12 + 0.5 × 1.5 + 30 × 0.02 + 30 × (0.05 − 0.02) = 12 + 0.75 + 0.6 + 0.9 = 14.25.
3. BN2 = 19.85 − 0.91 × 14.25 = 19.85 − 12.9675 = 6.883 → within the qualifying limit.
4. Sulfur 0.010 % sits inside the autogenous window → verdict in-range: PASS.

4 · Results PASS

5 · Verification statement

The result values above are locked as fixture ferrite-number.json, case “316L, S in window -> pass”, tolerance 0.001, in the calc-core continuous verification gate (see https://pipingtoolset.com/trust/validation.html). Allowable-stress and factor data are user-supplied inputs; citations: WRC-1992 (Kotecki–Siewert) constitution diagram — Cr/Ni equivalent forms as given in ASME BPE-2026 App. G-1; the diagram plate itself is not embedded. · ASME BPE-2026 — App. G, G-3(d) and its footnote: the BN2 low-ferrite criterion and its own Cr(eq)/Ni(eq) (Basler Norm BN2). · ASME BPE-2026 — MM-5.2.1.1(a), autogenous-weld sulfur window (bounds are defaulted inputs).