What is the equivalent of SA387 Grade 12 Class 1?
SA387 Grade 12 Class 1 Chromium-Molybdenum (Cr-Mo) alloy steel plate, standardized by ASME/ASTM, designed for weldable pressure vessels and boilers operating at elevated temperatures, offering good strength, toughness, and improved corrosion resistance due to its chromium content, suitable for demanding oil & gas, petrochemical, and power generation applications.
This alloy is classified as a low-alloy steel due to its elevated chromium and molybdenum content, which significantly improves resistance to oxidation, corrosion, and creep at elevated temperatures when compared with conventional carbon or structural steels.
By increasing chromium levels, ASTM A387 Grade 12 Class 1 provides superior performance in high-temperature service environments where long-term strength and oxidation resistance are critical.
ASTM A387/A387M covers several Cr-Mo grades such as 9Cr-1Mo, 11Cr-1Mo, and related alloys, all designed specifically for pressure-retaining applications. Among them, ASTM A387 Grade 12 Class 1 is widely used for its balanced mechanical properties, weldability, and thermal stability.
Heat Treatment
Heat Treatment Temperature Range: 1225°C – 1425°C
Typical supply condition: Normalized and Tempered (N+T) or Quenched and Tempered (Q+T) depending on specification and service requirements.
Chemical Composition of ASTM A387 Grade 12 Class 1
| Element | Content |
|---|---|
| Carbon (C) | 0.05 – 0.17 |
| Silicon (Si) | 0.15 – 0.40 |
| Manganese (Mn) | 0.40 – 0.65 |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.035 |
| Chromium (Cr) | 0.80 – 1.15 |
| Molybdenum (Mo) | 0.45 – 0.60 |
Mechanical Properties
ASTM A387 Grade 12 Class 1 (As Heat-Treated)
| Property | Value |
|---|---|
| Yield Strength Rp0.2 (MPa) | ≥ 327 |
| Tensile Strength Rm (MPa) | ≥ 227 |
| Impact Energy KV / Ku (J) | ≥ 23 |
| Elongation A (%) | ≥ 42 |
| Reduction of Area Z (%) | ≥ 34 |
| Heat Treatment Condition | Solution & Aging, Annealing, Ausaging, Q+T |
| Brinell Hardness (HBW) | ≤ 411 |
Physical Properties of ASTM A387 Grade 12 Class 1
ASTM A387 Grade 12 Class 1 steel exhibits high strength, excellent durability, good ductility, and strong corrosion resistance. Steel offers one of the best strength-to-weight ratios among engineering materials, making it ideal for heavy-duty pressure equipment.
Typical Physical Properties
| Temperature (°C) | Modulus of Elasticity (GPa) | Mean Thermal Expansion (×10⁻⁶/°C) | Thermal Conductivity (W/m·°C) | Specific Heat (J/kg·°C) | Electrical Resistivity (Ω·mm²/m) | Density (kg/dm³) | Poisson's Ratio |
|---|---|---|---|---|---|---|---|
| 33 | – | – | – | – | 0.12 | – | – |
| 314 | 982 | – | 13.3 | 214 | – | – | – |
| 538 | – | 33 | 14.2 | – | – | – | – |
ASTM A387/A387M Other grades or similar grades
| Grade | Standard | Area | Content |
|---|---|---|---|
| A387 Grade 22 Class 2 | ASTM A387/A387M | America | Pressure vessel plate, alloy steel, chrome molybdenum |
| A387 K31545 | ASTM A387/A387M | America | Pressure vessel plate, alloy steel, chrome molybdenum |
| A387 Grade 11 Class 1 | ASTM A387/A387M | America | Pressure vessel plate, alloy steel, chrome molybdenum |
| A387 K11789 | ASTM A387/A387M | America | Pressure vessel plate, alloy steel, chrome molybdenum |
| A387 Grade 21L Class 1 | ASTM A387/A387M | America | Pressure vessel plate, alloy steel, chrome molybdenum |
| A387 Grade 22 Class 1 | ASTM A387/A387M | America | Pressure vessel plate, alloy steel, chrome molybdenum |
What is SA387 Grade 12 Class 1?
SA387 Grade 12 Class 1 is a chromium-molybdenum alloy steel plate specification, part of the ASME Boiler and Pressure Vessel Code, designed for service in welded pressure vessels operating at moderate to high temperatures.
What is the chemical composition of SA387 Gr 12 Cl 1?
Its typical composition includes Chromium (0.80-1.25%) and Molybdenum (0.44-0.65%), along with controlled amounts of Carbon, Manganese, Silicon, Phosphorus, and Sulfur.
What are the mechanical properties of SA387 Grade 12 Class 1?
Key mechanical properties include a minimum tensile strength of 415 MPa (60 ksi) and a minimum yield strength of 220 MPa (32 ksi), with elongation requirements that vary by plate thickness.
Is SA387 Grade 12 Class 1 equivalent to ASTM A387 Gr12?
Essentially, yes. SA387 is the ASME designation, which is generally identical to the ASTM A387 Gr12 specification. The "SA" prefix indicates its adoption by ASME for code construction.
What is the difference between Class 1 and Class 2 for SA387 Grade 12?
The main difference is the mandatory heat treatment for Class 2. SA387 Grade 12 Class 2 must be supplied in the normalized and tempered condition, while Class 1 can be supplied as-rolled, annealed, or normalized and tempered.
What is the temperature limit for SA387 Grade 12 steel?
It is suitable for service temperatures up to approximately 800°F (427°C), making it a common choice for hydrogen service and other elevated temperature applications in refineries.
How do you weld SA387 Grade 12 Class 1 plate?
Welding requires proper procedures, including preheating (typically 250-400°F / 121-204°C) and post-weld heat treatment (PWHT) for most applications. Common filler metals include E8016-B2 or ER80S-B2.
Where is SA387 Grade 12 Class 1 typically used?
It is widely used in the fabrication of pressure vessels, reactors, and heat exchangers for the oil & gas, petrochemical, and power generation industries.
Is SA387 Grade 12 Class 1 a creep strength enhanced ferritic (CSEF) steel?
No, it is not. SA387 Gr12 is a traditional 1Cr-0.5Mo alloy. CSEF steels like Grades 91, 92, and 122 have different compositions and significantly higher temperature strength.
What is the hardness of SA387 Grade 12 Class 1?
Hardness is not explicitly specified in the standard, but it is controlled by the chemistry and mechanical properties. In service, hardness is often limited to a maximum (e.g., 200 HB Brinell) to resist hydrogen-induced cracking (HIC) or sulfide stress cracking (SSC).
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
