Stainless Steel AM-355
UNS S35500 · also Alloy 355, Alloy 634
AM-355 (UNS S35500, Alloy 355 / Alloy 634) is a higher-carbon version of AM-350 that reaches greater strength through the same semi-austenitic transformation and precipitation hardening route.
Reference datasheet — AM-355 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the SCT850 condition
AM-355 tempers and conditions
AM-355 is supplied in 5 conditions, soft to hard. SCT850 is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Supply condition for forming, machining and welding before the customer runs the SCT hardening cycle. | 450 | 1,000 | 25 | 25 HRC | — |
equalized, sub-zero cooled and tempered at 540 °C | Slightly lower strength than SCT 850 but better ductility, toughness and stress-corrosion behaviour; preferred for thick sections and higher service temperature. | 1,000 | 1,170 | 19 | 37 HRC | 2.2 % IACS |
Double aged | Simplified hardening route for sheet and welded assemblies where sub-zero cooling is impractical; strength somewhat below SCT 850. | 1,030 | 1,240 | 12 | 39 HRC | 2.2 % IACS |
SCT850Default equalized, sub-zero cooled and tempered at 455 °C | Peak-strength aerospace condition — choose when maximum tensile/fatigue strength is the driver and toughness demands are moderate. | 1,070 | 1,275 | 17 | 40 HRC | 2.2 % IACS |
Cold rolled (Condition A strip) and tempered/aged | Highest-strength strip/spring condition; use for thin flat springs, diaphragms and clamps where forming is done before final ageing. | 1,590 | 1,720 | 5 | 48 HRC | — |
What is AM-355?
AM-355 (UNS S35500, Alloy 355 / Alloy 634) is a higher-carbon version of AM-350 that reaches greater strength through the same semi-austenitic transformation and precipitation hardening route. In SCT condition it provides about 1070 MPa yield, 1275 MPa tensile, 17 % elongation and 40 HRC with a 200 GPa modulus and service to 425 °C, which suits aerospace forgings and structural fittings. Density is 7.91 g/cm³, thermal conductivity 16.3 W/m·K, electrical conductivity 2.2 % IACS and melting point 1400 °C. Limits are poor formability (score 10), low machinability (22) and restricted weldability (35); AM-350 is the choice when sheet forming matters more than strength. AM-355 has a density of 7.91 g/cm³ (0.286 lb/in³), heavier than 76% of stainless steel grades. It melts at 1,400°C (2,552 °F). AM-355 has a yield strength of 1,070 MPa (155 ksi) and a tensile strength of 1,275 MPa (185 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 17% and the elastic modulus is 200 GPa (29 Msi).
What is AM-355 used for?
- aircraft forgings
- structural fittings
- fasteners
Advantages
- High strength — 1,070 MPa (155 ksi), better than 98% of stainless steel grades
Limitations
- Difficult to machine — 22/100, worse than 95% of stainless steel grades
- Limited formability — 10/100, worse than 95% of stainless steel grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 91% of stainless steel grades
- Limited ductility — 17%, worse than 86% of stainless steel grades
- Difficult to weld — 35/100, worse than 86% of stainless steel grades
AM-355 properties
Typical room-temperature values for AM-355-SCT850; bars are the position among stainless steel grades.
Physical3
AM-355 has a density of 7.91 g/cm³ (0.286 lb/in³), heavier than 76% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical16
AM-355 has a yield strength of 1,070 MPa (155 ksi) and a tensile strength of 1,275 MPa (185 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 17% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
AM-355 is rated for continuous service to 425°C (797 °F). It conducts heat at 16.3 W/m·K (9.42 BTU/hr·ft·°F), better than 68% of stainless steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
AM-355 conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (55/100), worse than 71% of stainless steel grades.
Sustainability4
Producing a kilogram of AM-355 takes about 57 MJ of energy and emits 4.6 kg of CO₂ — more than 62% of stainless steel grades. Typical recycled content is 40%.
Manufacturability8
AM-355's machinability is poor (22/100, worse than 95% of stainless steel grades); weldability fair (35/100); formability not recommended (10/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. AM-355 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with AM-355
Is AM-355 easy to machine?
Machine in Condition A wherever possible; in SCT 850 use rigid setups, positive-rake carbide or ceramic, heavy feeds and low speeds to cut under the work-hardened layer, with flood coolant.
Can AM-355 be welded?
GTAW/GMAW/EB weld in Condition A with matching or AM-355 filler, low heat input and no preheat, then run the full equalize–refrigerate–temper cycle to restore joint strength; welding after hardening is not recommended.
Can AM-355 be formed, bent or molded?
Cold form only in Condition A (austenitic, work-hardens rapidly — allow generous bend radii and interstage annealing); hot forge 1150–950 °C followed by re-annealing.
AM-355 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Chigher than AM-350 (0.07–0.11) — the main strength difference | 0.1 – 0.15 | 0.13 |
| Mn | 0.5 – 1.25 | 0.9 |
| Si | ≤ 0.5 | 0.3 |
| P | ≤ 0.04 | |
| S | ≤ 0.03 | |
| Cr | 15 – 16 | 15.5 |
| Ni | 4 – 5 | 4.5 |
| Mo | 2.5 – 3.25 | 2.9 |
| Naustenite stabiliser controlling the transformation response | 0.07 – 0.13 | 0.1 |
| Fe | balance |
What surface finishes work on AM-355?
Passivate per AMS 2700/ASTM A967 after machining; electropolishing and fine mechanical polishing work well, and shot peening is common to raise fatigue life in hardened parts.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel AM-355 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S35500
- Trade names
- Alloy 355Alloy 634
How much does AM-355 cost?
AM-355 is a high-cost stainless steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
AM-355 — frequently asked
What is AM-355 used for?
AM-355 is typically used for aircraft forgings, structural fittings and fasteners. In short: stronger than AM-350; forging-grade PH stainless; 40 HRC after SCT.
What is the yield strength of AM-355?
AM-355 has a typical yield strength of 1,070 MPa (155 ksi) and a tensile strength of 1,275 MPa (185 ksi) — stronger than 98% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is AM-355 easy to machine?
Not especially — machinability is rated poor (22/100, worse than 95% of stainless steel grades). Machine in Condition A wherever possible; in SCT 850 use rigid setups, positive-rake carbide or ceramic, heavy feeds and low speeds to cut under the work-hardened layer, with flood coolant.
Can AM-355 be welded?
With care — weldability is rated fair (35/100). GTAW/GMAW/EB weld in Condition A with matching or AM-355 filler, low heat input and no preheat, then run the full equalize–refrigerate–temper cycle to restore joint strength; welding after hardening is not recommended.
What surface finishes work on AM-355?
Passivate per AMS 2700/ASTM A967 after machining; electropolishing and fine mechanical polishing work well, and shot peening is common to raise fatigue life in hardened parts.
Can AM-355 be formed, bent or molded?
Cold form only in Condition A (austenitic, work-hardens rapidly — allow generous bend radii and interstage annealing); hot forge 1150–950 °C followed by re-annealing.
What is the maximum service temperature of AM-355?
AM-355 is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between AM-355 SCT850 and AM-355-A?
SCT850 is the default condition — peak-strength aerospace condition — choose when maximum tensile/fatigue strength is the driver and toughness demands are moderate. A: supply condition for forming, machining and welding before the customer runs the SCT hardening cycle. Yield strength is 1,070 MPa in SCT850 versus 450 MPa in A.
How much does AM-355 cost?
AM-355 is a high-cost stainless steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM A564/A564M — Hot-Rolled and Cold-Finished Age-Hardening Stainless Bars and Shapes (Type 355 / UNS S35500) — ASTM International (2019)
- AMS 5743 — Steel, Corrosion Resistant, Bars and Forgings, 15.5Cr–4.5Ni–2.9Mo, Consumable Electrode Melted, SCT — SAE International (2018)
- AMS 5547 — Steel, Corrosion Resistant, Sheet, Strip and Plate, 15.5Cr–4.5Ni–2.9Mo (AM-355) — SAE International (2017)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels and High-Performance Alloys (semi-austenitic PH stainless) — ASM International (1990)
- MMPDS-16 — Metallic Materials Properties Development and Standardization, AM-355 sections — Battelle/FAA (2021)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.