S35000 is a chromium-nickel-molybdenum semi-austenitic precipitation-hardening (PH) stainless steel. This datasheet presents the material within the American (ASTM / ASME / AMS / UNS) standard system.
With about 16.5% chromium, 4.3% nickel, 2.75% molybdenum and a controlled nitrogen addition, AM-350 combines high strength and excellent weldability with corrosion resistance comparable to type 316 — superior to the other PH and the hardenable 400-series grades. It is supplied in the soft austenitic condition (Condition A), formed, then transformed to martensite and precipitation-hardened by a multi-step heat treatment. The low-temperature hardening gives minimum distortion. It is widely used in edge-welded bellows and other applications combining high strength with formability.
Typical applications include aerospace structural and bellows components, edge-welded bellows, precision seals, semiconductor-equipment couplings and high-vacuum-system hardware.
Typical values, SCT1000 condition.
| Property | Value | Unit |
|---|---|---|
| Density | 7.91 | g/cm³ |
| Melting range | 1400–1440 | °C |
| Elastic modulus | 200 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 11.7 | µm/m·°C |
| Thermal conductivity (20 °C) | 14.2 | W/m·K |
| Specific heat (20 °C) | 480 | J/kg·K |
| Structure | Semi-austenitic (precipitation-hardening) | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Iron | Fe | Balance | — | Base element |
| Chromium | Cr | 16.0 | 17.0 | Corrosion resistance |
| Nickel | Ni | 4.0 | 5.0 | Austenite stability |
| Molybdenum | Mo | 2.50 | 3.25 | Strength; pitting resistance |
| Nitrogen | N | 0.07 | 0.13 | Strengthening element |
| Manganese | Mn | 0.50 | 1.25 | Deoxidiser; austenite former |
| Silicon | Si | — | 0.50 | Deoxidiser |
| Carbon | C | 0.07 | 0.11 | Strengthening element |
| Phosphorus | P | — | 0.040 | Residual impurity |
| Sulphur | S | — | 0.030 | Residual impurity |
Typical values by heat-treatment condition, per ASTM A693 / AMS 5548 for UNS S35000.
| Condition | Tensile strength | 0.2% Yield | Hardness |
|---|---|---|---|
| SCT850 | ≥1410 MPa (205 ksi) | ≥1170 MPa (170 ksi) | ~48 HRC |
| SCT1000 | ≥1210 MPa (175 ksi) | ≥1050 MPa (152 ksi) | ~42 HRC |
| DA (double-aged) | ≥1140 MPa (165 ksi) | ≥1000 MPa (145 ksi) | ~40 HRC |
| Condition A (annealed) | ~1100 MPa (160 ksi) | ~380 MPa (55 ksi) | ~B95 HRB |
Confirm against the mill test report. Elongation typically ≥8–13% depending on condition.
| Environment | Performance | Notes |
|---|---|---|
| Atmospheric / general | Very Good | Comparable to type 316 |
| Mild acids | Good | Molybdenum addition aids resistance |
| Chloride pitting | Good | Better than other PH grades (Mo) |
| Oxidation | Good | At elevated temperature |
| Seawater | Limited | Not recommended for prolonged exposure |
Corrosion resistance is comparable to type 316 in most media and superior to the other precipitation-hardening and the hardenable 400-series grades.
A semi-austenitic precipitation-hardening alloy; supplied in Condition A (soft, austenitic) and hardened by a multi-step transformation-plus-ageing sequence.
Solution Treatment (Condition A) Supplied solution-treated (~1040 °C) in the soft austenitic condition for forming.
Transformation and Precipitation Hardening SCT (sub-zero cooling and tempering): condition at ~930 °C, refrigerate (~−75 °C) to transform austenite to martensite, then temper — SCT850 (~455 °C) for maximum strength, SCT1000 (~540 °C) for higher toughness. DA (double ageing): age at ~735 °C then ~455 °C for components where refrigeration is impractical. Air cool after tempering.
Excellent weldability — a particular advantage of this alloy, especially for edge-welded bellows. Matching filler is used; heat treatment after welding develops full properties.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Excellent | Matching AM-350-type filler |
| Resistance / seam | Excellent | — (edge-welded bellows) |
| GMAW / MIG | Good | Matching filler |
Weld in Condition A; heat-treat after welding to develop strength.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Preferred condition | Condition A for best formability and machinability |
| Work hardening | Moderate-to-high rate; positive feeds, rigid setup |
| Coolant | Ample flood coolant |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | Good in Condition A (formable semi-austenitic PH) |
| Hot forming | ~1150–950 °C; solution treat + harden afterward |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Aerospace | Bellows, structural parts, fittings | High strength + weldability |
| Bellows / seals | Edge-welded bellows, precision seals | Formability + fatigue resistance |
| Semiconductor | Couplings, high-vacuum hardware | Cleanliness + corrosion resistance |
| General industrial | High-strength welded components | Strength + corrosion resistance |
| Product Form | ASTM Standard | ASME / AMS |
|---|---|---|
| Plate, sheet and strip | ASTM A693 grade 633 | ASME SA-693 / AMS 5548 |
| Bar and wire | ASTM A564 (633) | AMS 5745 |
| Welded bellows stock | — | AMS 5548 |
| Welding consumables | Matching AM-350-type filler | — |
Chromium-nickel-molybdenum semi-austenitic precipitation-hardening stainless steel. UNS S35000.
| UNS | Cr % | Ni % | Mo % | Other | Best Used For |
|---|---|---|---|---|---|
| S35000 | 16–17 | 4–5 | 2.5–3.25 | N | Semi-austenitic PH; bellows, weldability, 316-like corrosion |
| S35500 | 15–16 | 4–5 | 2.5–3.25 | N | Semi-austenitic PH; highest strength |
| S17700 | 16–18 | 6.5–7.75 | — | Al | Semi-austenitic PH; springs, formability |
| S15700 | 14–16 | 6.5–7.75 | 2.0–3.0 | Al | Semi-austenitic PH; high strength at temperature |
| S17400 | 15–17.5 | 3–5 | — | Cu, Nb | Martensitic PH; general high strength |




