Steel A387 Gr 11 Q&T Cl.2
Heat-treated state
ASTM A387 Gr 11 · UNS K11789
Q&T Cl.2 = 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.
Values for the Q&T Cl.2 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 + 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 Cl.2This page 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 Q&T Cl.2?
A387 Gr 11 Q&T Cl.2 is A387 Gr 11 heat treated to Q&T Cl.2 — used on heavy-wall plate where liquid quenching plus temper is needed to meet Class 2 strength and low-temperature CVN through thickness. A387 Gr 11 Q&T Cl.2 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi). A387 Gr 11 Q&T Cl.2 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; Q&T Cl.2 is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 135 MPa·√m (122.9 ksi·√in), better than 93% of steel grades
- High service temperature — 540°C (1,004 °F), better than 93% of steel grades
A387 Gr 11 Q&T Cl.2 properties
Typical room-temperature values for A387 Gr 11 Q&T Cl.2; 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 Q&T Cl.2 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 Q&T Cl.2 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A387 Gr 11 Q&T Cl.2 is rated for continuous service to 540°C (1,004 °F). It conducts heat at 37 W/m·K (21.4 BTU/hr·ft·°F), worse than 71% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
A387 Gr 11 Q&T Cl.2 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 Q&T Cl.2 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 Q&T Cl.2's machinability is fair (46/100, worse than 59% of steel grades); weldability fair (52/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A387 Gr 11 Q&T Cl.2
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 Q&T Cl.2 — frequently asked
What is A387 Gr 11 Q&T Cl.2 used for?
A387 Gr 11 Q&T Cl.2 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 Q&T Cl.2?
A387 Gr 11 Q&T Cl.2 has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is A387 Gr 11 Q&T Cl.2 easy to machine?
Reasonably — machinability is rated fair (46/100, worse than 59% 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 Q&T Cl.2 be welded?
With care — weldability is rated fair (52/100). 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 Q&T Cl.2?
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 Q&T Cl.2 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 Q&T Cl.2?
A387 Gr 11 Q&T Cl.2 is rated for continuous use to about 540°C (1,004 °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 Q&T Cl.2?
Yes — A387 Gr 11 Q&T Cl.2 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.