Steel A387 Gr 12
ASTM A387 Gr 12 · UNS K11757
A387 Grade 12 (K11757, 13CrMo4-5, 1.7335, SCMV3, 12CrMo) is a 1 % Cr–0.5 % Mo low-alloy pressure vessel plate steel supplied annealed or normalized-and-tempered in Class 1 and Class 2, with a quenched-and-tempered Class 2 option.
Reference datasheet — A387 Gr 12 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 CL2-NT condition
A387 Gr 12 tempers and conditions
A387 Gr 12 is supplied in 4 conditions, soft to hard. CL2-NT is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Class 1, Annealed | Softest, most formable and weld-friendly condition; pick for heavy cold forming or when only Class 1 minimum strength is required. | 270 | 430 | 28 | 137 HB | — |
Class 1, Normalized and Tempered | Class 1 strength with a refined normalized structure — better toughness than the annealed plate at the same strength level. | 290 | 460 | 27 | 145 HB | — |
CL2-NTDefault Class 2, Normalized and Tempered | The standard stocked condition for refinery and boiler pressure vessels — higher allowable stress than Class 1 with good toughness. | 330 | 500 | 24 | 160 HB | — |
Class 2, Quenched and Tempered | Accelerated-cooled (liquid quenched) and tempered heavy plate — used when Class 2 properties must be met through thick sections or when low-temperature Charpy values are specified. | 370 | 530 | 23 | 175 HB | — |
What is A387 Gr 12?
A387 Grade 12 (K11757, 13CrMo4-5, 1.7335, SCMV3, 12CrMo) is a 1 % Cr–0.5 % Mo low-alloy pressure vessel plate steel supplied annealed or normalized-and-tempered in Class 1 and Class 2, with a quenched-and-tempered Class 2 option. It offers good elevated-temperature strength for boilers and refinery vessels, with 330 MPa yield, 500 MPa tensile, 24 % elongation, 160 HB (84 HRB) and service to 540 °C. Weldability (60) and formability (60) are the best in the A387 family, though preheat and PWHT are still required. It is slightly leaner in chromium than Grade 11. A387 Gr 12 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). A387 Gr 12 has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 78% of steel grades. Elongation at break is 24% and the elastic modulus is 205 GPa (29.7 Msi).
What is A387 Gr 12 used for?
- boiler drums
- steam piping flanges
- refinery reactor plate
- heat exchanger shells
Advantages
- Tough — resists crack growth — 150 MPa·√m (136.5 ksi·√in), better than 96% of steel grades
- High service temperature — 540°C (1,004 °F), better than 93% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
- Low strength — 330 MPa (47.9 ksi), worse than 78% of steel grades
A387 Gr 12 properties
Typical room-temperature values for A387 Gr 12-CL2-NT; bars are the position among steel grades.
Physical3
A387 Gr 12 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
A387 Gr 12 has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 78% of steel grades. Elongation at break is 24% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A387 Gr 12 is rated for continuous service to 540°C (1,004 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
A387 Gr 12 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of A387 Gr 12 takes about 29 MJ of energy and emits 2.3 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 25%.
Manufacturability7
A387 Gr 12's machinability is good (55/100, better than 62% of steel grades); weldability good (60/100); formability good (60/100).
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 steel family
Yield strength against density for every steel grade FabDigit runs. A387 Gr 12 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A387 Gr 12
Is A387 Gr 12 easy to machine?
Machines like a medium-carbon low-alloy steel at ~60% of 1212; use rigid setups, carbide tooling and moderate speeds — the bainitic Class 2 plate work-hardens the cut surface if feeds are too light.
Can A387 Gr 12 be welded?
Readily weldable with matching B2/E8018-B2 (or low-carbon B2L) consumables, but requires 150–250 °C preheat/interpass and PWHT at ~690–730 °C; keep hydrogen low to avoid delayed cracking.
Can A387 Gr 12 be formed, bent or molded?
Cold-form with generous bend radii (≥3t) in the annealed condition; hot forming at 900–1000 °C is preferred for heads and thick shells, followed by re-normalizing and tempering.
A387 Gr 12 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, ASTM A387 | 0.05 – 0.17 | 0.12 |
| Mn | 0.4 – 0.65 | 0.52 |
| Si | 0.15 – 0.4 | 0.27 |
| P | ≤ 0.03 | 0.01 |
| S | ≤ 0.03 | 0.01 |
| Cr | 0.8 – 1.15 | 1 |
| Mo | 0.45 – 0.6 | 0.52 |
| Fe | balance |
What surface finishes work on A387 Gr 12?
No anodizing; shot-blast and paint, metallize or alonize for oxidation and atmospheric protection — bare plate rusts quickly in humid storage.
Surface treatments FabDigit runs on 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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel A387 Gr 12 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does A387 Gr 12 cost?
A387 Gr 12 is a budget-cost steel ($), cheaper than about 90% 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.
A387 Gr 12 — frequently asked
What is A387 Gr 12 used for?
A387 Gr 12 is typically used for boiler drums, steam piping flanges, refinery reactor plate and heat exchanger shells. In short: leanest Cr-Mo A387 plate; best weldability in A387; 540 °C service temperature.
What is the yield strength of A387 Gr 12?
A387 Gr 12 has a typical yield strength of 330 MPa (47.9 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 78% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A387 Gr 12 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like a medium-carbon low-alloy steel at ~60% of 1212; use rigid setups, carbide tooling and moderate speeds — the bainitic Class 2 plate work-hardens the cut surface if feeds are too light.
Can A387 Gr 12 be welded?
Yes — weldability is rated good (60/100). Readily weldable with matching B2/E8018-B2 (or low-carbon B2L) consumables, but requires 150–250 °C preheat/interpass and PWHT at ~690–730 °C; keep hydrogen low to avoid delayed cracking.
What surface finishes work on A387 Gr 12?
No anodizing; shot-blast and paint, metallize or alonize for oxidation and atmospheric protection — bare plate rusts quickly in humid storage.
Can A387 Gr 12 be formed, bent or molded?
Cold-form with generous bend radii (≥3t) in the annealed condition; hot forming at 900–1000 °C is preferred for heads and thick shells, followed by re-normalizing and tempering.
What is the maximum service temperature of A387 Gr 12?
A387 Gr 12 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.
What is the difference between A387 Gr 12 CL2-NT and A387 Gr 12 CL1-ANN?
CL2-NT is the default condition — the standard stocked condition for refinery and boiler pressure vessels — higher allowable stress than Class 1 with good toughness. CL1-ANN: softest, most formable and weld-friendly condition; pick for heavy cold forming or when only Class 1 minimum strength is required. Yield strength is 330 MPa in CL2-NT versus 270 MPa in CL1-ANN.
How much does A387 Gr 12 cost?
A387 Gr 12 is a budget-cost steel ($), cheaper than about 90% 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 A387/A387M — Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum — ASTM International (2021)
- EN 10028-2 (13CrMo4-5, 1.7335) — CEN (2017)
- ASME BPVC Section II Part D — Materials 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 713 / GB/T 3077 (12CrMo, 15CrMo ) — SAC (2014)
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.