ASTM A387 Grade 12 Class 2 is a chrome-molybdenum alloy steel plate designed for elevated temperature applications, primarily for weldable pressure vessels and boilers, offering excellent corrosion/oxidation resistance, especially in "sour" (sulfide-rich) environments, with Class 2 indicating higher mechanical strength properties (like tensile and yield strength) compared to Class 1. It's known for good high-temperature performance and toughness, making it ideal for oil & gas, petrochemicals, and other heavy industrial uses.
Specifications for ASTM A387 Grade 12 Alloy Steel Plates
| Designation | Nominal Chromium Content (%) |
Nominal Molybdenum Content (%) |
| A387 Grade 12 | 1.00% | 0.50% |
Tensile Requirements for ASTM A387 Grade 12 Alloy Steel Plates Class 2 Plates
| Designation: | Requirement: | Grade 12 |
| A387 Grade 12 | Tensile strength, ksi [MPA] | 65 to 85 [450 to 585] |
| Yield strength, min, ksi [MPa]/(0.2% offset) | 40 [275] | |
| Elongation in 8 in. [200mm], min % | 19 | |
| Elongation in 2 in. [50mm], min, % | 22 | |
| Reduction of area, min % | ––– |
Chemical Composition
| C | Mn | P | S | Si | Cr | Mo |
| 0.04 - 0.17 | 0.35 - 0.73 | 0.035 | 0.035 | 0.13 - 0.45 | 0.74 - 1.21 | 0.4 - 0.65 |
Key Applications & Industries
Pressure Vessels: Manufacturing vessels for storing and processing hot liquids and gases.
Boilers & Heat Exchangers: Components in power plants and industrial facilities requiring high heat resistance.
Oil & Gas Industry: Used in refineries, petrochemical plants, and for sour service (hydrogen sulfide environments).
Power Generation: Components in thermal power stations, gas/steam turbines, and HRSGs (Heat Recovery Steam Generators).
Piping & Ducting: High-temperature piping, pipe supports, and ductwork.
Chemical Industry: Equipment for chemical processing where corrosion and heat are concerns.
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How does the heat treatment process of ASTM A387 Grade 12 Class 2 differ from that of Class 1?
Unlike Class 1 which is supplied in the normalized condition, ASTM A387 Grade 12 Class 2 adopts a quenching and tempering heat treatment process. This process significantly improves the steel's tensile strength and hardness while maintaining good ductility and toughness, making it suitable for heavier load-bearing applications.
What are the core performance advantages of ASTM A387 Grade 12 Class 2?
It has higher tensile and yield strength than Class 1, along with excellent high-temperature creep resistance and oxidation resistance. It also maintains reliable corrosion resistance in sour service environments containing hydrogen sulfide, and its weldability meets the requirements of on-site fabrication of large pressure vessels.