Steel A387 Gr 11 N&T+PWHT
Heat-treated state
ASTM A387 Gr 11 · UNS K11789
N&T+PWHT = n&T + simulated PWHT / stress relief
Order this when the vessel sees long or multiple PWHT cycles — properties are certified after simulated post-weld heat treatment, at somewhat lower strength.
Values for the N&T+PWHT condition
Other A387 Gr 11 tempers and conditions
A387 Gr 11 is listed in 5 conditions; see the grade overview at A387 Gr 11.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
N&T Class 1 | Pick Class 1 when maximum ductility/toughness and easier forming and welding matter more than strength (415–585 MPa band). | 275 | 480 | 27 | 150 HB | — |
N&T+PWHTThis page N&T + simulated PWHT / stress relief | Order this when the vessel sees long or multiple PWHT cycles — properties are certified after simulated post-weld heat treatment, at somewhat lower strength. | 330 | 530 | 25 | 165 HB | 8 % IACS |
N&TDefault Normalized and tempered | Default stocked condition: N&T Class 2 plate for pressure vessels needing the higher 515–690 MPa tensile band. | 355 | 560 | 23 | 175 HB | 8 % IACS |
N&T Class 2 | Explicit Class 2 order for reactor shells and hot piping designed to the higher ASME allowable stresses. | 355 | 560 | 23 | 175 HB | 8 % IACS |
Q&T Class 2 | Used on heavy-wall plate where liquid quenching plus temper is needed to meet Class 2 strength and low-temperature CVN through thickness. | 400 | 585 | 22 | 185 HB | 8 % IACS |
What is A387 Gr 11 N&T+PWHT?
A387 Gr 11 N&T+PWHT is A387 Gr 11 heat treated to N&T+PWHT — order this when the vessel sees long or multiple PWHT cycles — properties are certified after simulated post-weld heat treatment, at somewhat lower strength. A387 Gr 11 N&T+PWHT has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 78% of steel grades. Elongation at break is 25% and the elastic modulus is 207 GPa (30 Msi). A387 Gr 11 N&T+PWHT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,450°C (2,642 °F). N&T is the default condition FabDigit quotes; N&T+PWHT is available on request or by drawing note.
Advantages
- High service temperature — 550°C (1,022 °F), better than 95% of steel grades
- Tough — resists crack growth — 125 MPa·√m (113.8 ksi·√in), better than 85% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
Limitations
- Low strength — 330 MPa (47.9 ksi), worse than 78% of steel grades
A387 Gr 11 N&T+PWHT properties
Typical room-temperature values for A387 Gr 11 N&T+PWHT; 22 are specific to this condition. Other listed values are A387 Gr 11 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A387 Gr 11 N&T+PWHT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,450°C (2,642 °F).
Mechanical16
A387 Gr 11 N&T+PWHT has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 78% of steel grades. Elongation at break is 25% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A387 Gr 11 N&T+PWHT is rated for continuous service to 550°C (1,022 °F). It conducts heat at 38 W/m·K (22 BTU/hr·ft·°F), worse than 69% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
A387 Gr 11 N&T+PWHT conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (20/100), better than 87% of steel grades.
Sustainability4
Producing a kilogram of A387 Gr 11 N&T+PWHT takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 25%.
Manufacturability7
A387 Gr 11 N&T+PWHT's machinability is fair (53/100, better than 53% of steel grades); weldability good (58/100); formability fair (54/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A387 Gr 11 N&T+PWHT
Is A387 Gr 11 easy to machine?
Machines like normalized 4130 at roughly 55 % of AISI 1212 — rigid setups, carbide tooling and moderate speeds; the 0.5–0.8 % Si makes chips slightly abrasive.
Can A387 Gr 11 be welded?
P-No.4 material: preheat 150–250 °C, low-hydrogen B2/CM filler (E8018-B2, ER80S-B2), interpass control, and PWHT at 690–730 °C to avoid hard HAZ and hydrogen cracking.
Can A387 Gr 11 be formed, bent or molded?
Cold-form only with generous radii; heavy heads and shells are hot-formed 900–1000 °C and then re-normalized and tempered.
What surface finishes work on A387 Gr 11?
Not anodizable — blast and paint, aluminize/thermal-spray for hot service, or weld-overlay/clad with 347SS or Inconel 625 where corrosive process fluids contact the surface.
A387 Gr 11 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 |
|---|---|---|
| Cheat analysis | 0.05 – 0.17 | 0.12 |
| Sihigh-Si is characteristic of Gr 11 | 0.5 – 0.8 | 0.65 |
| Mn | 0.4 – 0.65 | 0.52 |
| P | ≤ 0.04 | 0.02 |
| Smax; often restricted to ≤0.010 for clean-steel reactor plate | ≤ 0.04 | 0.01 |
| Cr | 1 – 1.5 | 1.25 |
| Mo | 0.45 – 0.65 | 0.55 |
| Fe | balance | — |
A387 Gr 11 N&T+PWHT — frequently asked
What is A387 Gr 11 N&T+PWHT used for?
A387 Gr 11 N&T+PWHT is typically used for boilers, pressure vessels and cracking tower. In short: chrome-moly pressure plate.
What is the yield strength of A387 Gr 11 N&T+PWHT?
A387 Gr 11 N&T+PWHT has a typical yield strength of 330 MPa (47.9 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 78% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is A387 Gr 11 N&T+PWHT easy to machine?
Reasonably — machinability is rated fair (53/100, better than 53% of steel grades). Machines like normalized 4130 at roughly 55 % of AISI 1212 — rigid setups, carbide tooling and moderate speeds; the 0.5–0.8 % Si makes chips slightly abrasive.
Can A387 Gr 11 N&T+PWHT be welded?
Yes — weldability is rated good (58/100). P-No.4 material: preheat 150–250 °C, low-hydrogen B2/CM filler (E8018-B2, ER80S-B2), interpass control, and PWHT at 690–730 °C to avoid hard HAZ and hydrogen cracking.
What surface finishes work on A387 Gr 11 N&T+PWHT?
Not anodizable — blast and paint, aluminize/thermal-spray for hot service, or weld-overlay/clad with 347SS or Inconel 625 where corrosive process fluids contact the surface.
Can A387 Gr 11 N&T+PWHT be formed, bent or molded?
Cold-form only with generous radii; heavy heads and shells are hot-formed 900–1000 °C and then re-normalized and tempered.
What is the maximum service temperature of A387 Gr 11 N&T+PWHT?
A387 Gr 11 N&T+PWHT is rated for continuous use to about 550°C (1,022 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in A387 Gr 11 N&T+PWHT?
Yes — A387 Gr 11 N&T+PWHT is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A387/A387M — Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum — ASTM International (2021)
- ASME BPVC Section II Part A (SA-387) and Part D (allowable stresses, physical properties) — ASME (2023)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- API RP 941 — Steels for Hydrogen Service at Elevated Temperatures — API (2016)
- GB/T 713 (15CrMoR ) — SAC (2014)
- Mysteel / 1688 (2026)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.