Zeron 100 SA is the standard supply state for super duplex stainless steel: bar, plate, forgings, and finished fasteners delivered in the solution-annealed condition straight from the mill. The thermal cycle, 1100-1140°C soak followed by rapid water quench, dissolves any sigma-phase, chi-phase, or other intermetallic precipitates that might have formed during prior hot-working, then locks in the equilibrium 50/50 austenite-ferrite microstructure. SA is the metallurgical baseline; every other Zeron 100 supply state (FG, FLT, AFP) starts here and adds a downstream operation.
Solution-anneal 1100-1140°C, water quench · Yield ≥ 550 MPa · PREN ≥ 40 · Ferrite 35-55%
Use SA for: heavy hex nuts (which can only be hot-forged then SA, cold-work routes don't work for nuts), large forgings to ASTM A182 F55, plate to A240, pipe to A790, fittings to A815, and stud bolts / hex bolts where the buyer spec doesn't reference A193 B7-equivalent yield. SA is also the only correct supply state for any heat-treated or welded sub-assembly, once you weld or stress-relieve cold-worked FG, you've thermally restored it to SA properties anyway, so start with SA from the outset.
Super duplex stainless steel is a high-alloy stainless grade with a 50/50 austenite-ferrite microstructure and PREN (Pitting Resistance Equivalent Number) of 40 or higher. The "super" prefix distinguishes it from standard duplex grades like SAF 2205 (S31803/S32205, PREN ~35). Zeron 100 (UNS S32760) is the Rolled Alloys super duplex grade; equivalent mill grades include SAF 2507 (UNS S32750) from Sandvik and Ferralium 255 (UNS S32550) from Langley Alloys. All three share the 25Cr-7Ni-3.5Mo backbone and clear NORSOK M-650 + NACE MR0175 sour-service qualification.
Super duplex steels exist in a metastable phase balance: heat them to 600-1000°C and the ferrite phase decomposes into Cr-rich sigma-phase plus chi, M23C6 carbides, and Cr2N nitrides, a brittle, corrosion-vulnerable microstructure that drops Charpy from 100 J to under 5 J. The solution-anneal cycle puts everything back: 1100-1140°C dissolves the brittle phases, and the water quench passes through the sigma-precipitation window (around 850°C) fast enough to retain the dissolved state at room temperature. Without SA, you have a duplex that fails its own purpose. Every shipment of Zeron 100 in any other supply state has been SA at some point in its mill history.
| Property | SA (typical) | SA (minimum) | Test method |
|---|---|---|---|
| 0.2% Yield Strength | 620-720 MPa | 550 MPa | ASTM A370 |
| Ultimate Tensile | 800-870 MPa | 750 MPa | ASTM A370 |
| Elongation (4D) | 30-38 % | 25 % | ASTM A370 |
| Reduction of Area | 50-65 % | 40 % | ASTM A370 |
| Hardness (body) | 22-27 HRC | 200-270 HBW | ASTM E18 / E10 |
| Hardness (rolled-thread root) | 25-28 HRC | ≤ 28 HRC (NACE) | HV converted per E140 |
| Charpy V-notch @ -46°C | 60-110 J | 45 J avg / 35 J min | ASTM E23 |
| Ferrite content | 40-52 % | 35-55 % | ASTM E562 / EN ISO 8249 |
| CPT (G48 Method E, 50°C / 24 hr) | ≥ 50°C | 50°C | ASTM G48-E |
| CCT (G48 Method F) | ≥ 35°C | 30°C | ASTM G48-F |
| Sigma-phase (A923 Method C) | Pass | 60 J at RT | ASTM A923 Method C |
| Standard | What it covers |
|---|---|
| ASTM A479 | Stainless steel bars and shapes, the home spec for SA bar; chemistry, ferrite, mechanical, IGC test |
| ASTM A276 | Stainless bars and shapes (alt), SA bar from this spec for headed fastener stock |
| ASTM A182 F55 | Forged piping components, flanges, fittings, valves; F55 is the super-duplex code |
| ASTM A240 | Stainless plate / sheet / strip, for membrane vessels, scrubber plate, tank linings |
| ASTM A789 | Seamless / welded super duplex tube |
| ASTM A790 | Seamless / welded super duplex pipe |
| ASTM A815 | Wrought super duplex pipe fittings (WP-S grade) |
| ASTM A1082 | Stainless stud, bolt, screw, threaded rod, SA finished fasteners |
| ASTM A988 | HIP'd stainless flanges and fittings |
| NORSOK M-630 MDS 055 | Material data sheet for super duplex SS, SA acceptance criteria |
| NACE MR0175 / ISO 15156-3 | Sour-service hardness limit ≤ 28 HRC |
| EN 10088-3 / EN 10222-5 / EN 10272 | European stainless steel bars / forgings / pressure-equipment |
The solution-anneal window is narrow: below 1050°C, residual sigma-phase doesn't fully dissolve; above 1180°C, the ferrite-to-austenite ratio shifts past the 55% ferrite ceiling. The 1100-1140°C window is 40 K wide, we run our furnaces at 1120°C±10°C with a 40-min soak at section size to ensure full dissolution. Water quench (not air, not oil) is required: cooling rate from 1000°C to 600°C must exceed ~30 K/sec to skip the sigma-nucleation nose of the TTT diagram. Plate up to 50 mm and bar up to 75 mm OD water-quench fast enough; thicker sections (heavy A182 F55 forgings) need closer monitoring, we instrument the part with a thermocouple during the test cycle.
| Form / application | Why SA |
|---|---|
| Heavy hex nuts (all sizes) | Nuts must be hot-forged; cold-work FG impossible; SA is the only path |
| ASTM A182 F55 forgings, flanges, fittings, valve bodies | Large-section forgings can't be cold-worked; SA after final forge |
| Plate & sheet (A240), vessels, scrubbers, tanks | Mill-finish plate is SA; cold-rolling for FG would distort vessel geometry |
| Pipe & tube (A789 / A790), process piping, heat exchangers | Welded / seamless pipe is SA from mill; FG would not be weldable downstream |
| Headed fasteners (low / medium load) | Hot-headed in SA; cheaper than CNC-machined FG when load class allows |
| Equipment frame / bracket fasteners | SA yield (550 MPa) is plenty; no need for B7-equivalent uplift |
| Seawater service, pumps, manifolds, RO membrane vessels | SA performs identically to FG on corrosion; pick by load class only |
| Pulp & paper bleach plant components | Same corrosion as seawater; no high-strength load path |
| Welded sub-assemblies of any kind | Welding restores SA at HAZ regardless, start SA, save the cold-work cost |
| Factor | SA | FG |
|---|---|---|
| Yield strength | 620-720 MPa typ | 700-800 MPa typ (matches A193 B7) |
| Hot-headable (forged bolt heads, nuts) | Yes | No (hot work erases cold-work) |
| Weldable without re-anneal | Yes | HAZ reverts to SA, mismatch in joint |
| Manufacturing cost | Baseline | +25-40% |
| NORSOK M-650 topside flange bolting (high-load) | Below buyer-spec yield | Standard supply state |
| API 6A PSL3 wellhead studs | Below load envelope | Standard supply state |
| Heavy hex nuts (regardless of stud spec) | Only path | Cannot be made |
| Charpy reserve (-46°C) | 60-110 J | 50-90 J (cold-work raises DBTT slightly) |
| Galling resistance (uncoated) | Lower hardness, less prone | Higher hardness, more prone (consider AFP) |
Nuts are hot-forged from bar (heated to ~1100°C, upset-forged into the hex blank, then drilled and tapped). The forging step is hot work. If you forged from cold-drawn FG bar, the heat cycle would re-anneal the cold work back to SA properties everywhere except the part-thickness gradient might leave inconsistent residual cold work. The clean engineering answer is: forge hot, then SA the finished blank to a uniform microstructure, then tap. So nuts are always SA. This is not a limitation; it's metallurgically the right choice.
Yes for low-load applications, SA Zeron 100 has yield (550-720 MPa) above A193 B8M class 2 (240 MPa). For high-load applications stay with FG. The corrosion envelope of SA Zeron 100 is dramatically better than B8M (316 stainless): PREN 40 vs 26, CPT ≥ 50°C vs 25-30°C. Cost is 3-4× higher than B8M, justified by the corrosion case.
Yes, SA Zeron 100 is the canonical NACE MR0175 super duplex condition for sour-service piping, valves, and lower-load fasteners. The 22-27 HRC SA hardness sits well below the 28 HRC NACE ceiling. For sour-service stud bolts and high-load flange bolting, FG is preferred (yield reserve), but SA is acceptable when load class permits.
Continuous service to 250°C is fine. From 250-300°C, periodic inspection for 475°C-embrittlement onset is recommended (Cr-rich α' precipitation in ferrite). Above 300°C continuous, super duplex (any supply state) loses Charpy reserve and is the wrong alloy choice, consider Inconel 625 or 718 instead. Short excursions to 400°C (process upsets) are tolerable provided cumulative time-at-temperature is tracked.
Yes, flanges (weld-neck, slip-on, blind, threaded, lap-joint), fittings (elbows, tees, reducers, caps), and valve bodies up to 600 mm OD / 200 mm cross-section. F55 is the super-duplex grade designation in A182. Every forging ships with full SA cert + ferrite check + Charpy + sigma-phase test + UT + visual / dimensional. Lead time 4-8 weeks depending on size and stock heat availability.
Send the spec (form, bar / plate / pipe / tube / forging / bolt / nut, size, length, standards / MDS to comply with, quantity, destination port) to info@torqbolt.com or +91-22-66157017 / WhatsApp. We reply with stock availability, mill route, lead time, MTC tier, and price within one business day (Mumbai IST).
