ASTM A387 Grade 12 Class 2 is a high-performance chromium-molybdenum alloy steel plate specified by the ASTM A387/A387M standard, engineered for more demanding high-temperature and high-pressure service scenarios than its Class 1 counterpart, it undergoes a quenching and tempering heat treatment process that significantly boosts its tensile and yield strength while retaining good ductility, toughness and weldability, and it features excellent creep resistance, oxidation resistance and sour service corrosion resistance, making it an ideal material for fabricating heavy-duty pressure-containing components like high-pressure refinery reactors, thick-walled boiler headers, large-diameter sour oil and gas pipelines, and high-stress chemical reaction vessels across the petrochemical, oil and gas, and power generation industries.
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 Requirements for ASTM A387 Grade 12 Alloy Steel Plates
| Element | Chemical Composition (%) | |
| ASTM A387 Grade 12 | ||
| Carbon: | Heat Analysis: | 0.05 - 0.17 |
| Product Analysis: | 0.04 - 0.17 | |
| Manganese: | Heat Analysis: | 0.40 - 0.65 |
| Product Analysis: | 0.35 - 0.73 | |
| Phosphorus: | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Sulphur (max): | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Silicon: | Heat Analysis: | 0.15 - 0.40 |
| Product Analysis: | 0.13 - 0.45 | |
| Chromium: | Heat Analysis: | 0.80 - 1.15 |
| Product Analysis: | 0.74 - 1.21 | |
| Molybdenum: | Heat Analysis: | 0.45 - 0.60 |
| Product Analysis: | 0.40 - 0.65 |
Key Applications & Industries
Pressure Vessels
Ideal for manufacturing heavy-duty vessels dedicated to the safe storage and continuous processing of high-temperature liquids and gases, delivering exceptional structural integrity to withstand extreme pressure fluctuations and long-term thermal stress in harsh industrial settings.
Boilers & Heat Exchangers
Serves as a core material for critical components in power plants and large-scale industrial facilities, including boiler drums, header pipes and shell-and-tube heat exchangers, with its outstanding heat resistance ensuring stable operation even under prolonged exposure to high-temperature steam and thermal cycling conditions.
Oil & Gas Industry
Widely utilized in refineries, petrochemical plants and onshore/offshore extraction systems, especially engineered for sour service environments containing hydrogen sulfide. It provides reliable corrosion resistance and mechanical strength to fabricate wellhead equipment, process manifolds and transportation pipelines that handle aggressive, high-temperature oil and gas media.
Power Generation
Applied to fabricate key components in thermal power stations, gas/steam turbines and Heat Recovery Steam Generators (HRSGs), effectively withstanding the high-pressure, high-temperature operating conditions of power generation systems and contributing to improved energy conversion efficiency and equipment service life.
Piping & Ducting
Suited for manufacturing high-temperature piping systems, robust pipe supports and industrial ductwork, offering excellent creep resistance and structural stability to maintain integrity when conveying hot fluids, gases or exhaust in heavy-industry processes.
Chemical Industry
A preferred material for critical processing equipment exposed to corrosive substances and high temperatures, such as reactors, fractionation towers and storage tanks, effectively resisting erosion from acidic, alkaline and organic chemical media to ensure safe and efficient chemical production operations.
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What is the basic attribute and design orientation of ASTM A387 Grade 12 Class 2?
It is a chromium-molybdenum (Cr-Mo) alloy steel plate specified in the ASTM A387/A387M standard, developed for more demanding high-temperature and high-pressure service scenarios compared with Class 1. It is tailored for pressure-containing equipment that requires higher mechanical strength and structural stability.
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.