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, 0.010 % S.

2 · Method

Cr_eq = %Cr + %Mo + 0.7·%Nb

Ni_eq = %Ni + 35·%C + 20·%N + 0.25·%Cu

BN2 qualifier: Cr_eq − 0.91·Ni_eq ≤ limit

The calculator evaluates the two WRC-1992 equivalents from the certified chemistry, then two independent screens on them. The equivalents themselves are the constitution-diagram coordinates: 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 discriminant is the linear low-ferrite qualifier: subtract 0.91 times the nickel equivalent from the chromium equivalent and compare against the qualifying limit, which arrives as a defaulted input. Separately, and only when a sulfur content is supplied, the autogenous-weld window is applied — a lower and an upper bound, both defaulted inputs, 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: the FN is read from the WRC-1992 diagram, which is copyrighted plate content and is not embedded here. What this card gives you are the two coordinates you carry onto your own licensed copy of that diagram, plus the linear qualifiers that do not require it.

3 · Calculation

1. Cr_eq = 17 + 2.1 + 0.7 × 0 = 19.1.
2. Ni_eq = 12 + 35 × 0.02 + 20 × 0.05 + 0.25 × 0 = 12 + 0.7 + 1.0 = 13.7.
3. BN2 = 19.1 − 0.91 × 13.7 = 19.1 − 12.467 = 6.633 → 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; the diagram plate itself is not embedded. · ASME BPE — App. G (ferrite determination) and MM-5.2.1.1(a), autogenous-weld sulfur window (bounds are defaulted inputs).