ASTM A387 Grade 12 Class 2 (A387GR12CL2) Boiler And Pressure Vessel Steel Plate

ASTM A387 Grade 12 Class 2 (A387GR12CL2) is a chromium-molybdenum alloy boiler plate specifically designed for welded boilers and pressure vessels in high-temperature and high-pressure service environments.

Due to its excellent high-temperature strength, resistance to hydrogen corrosion, and good weldability, ASTM A387 Grade 12 Class 2 (A387GR12CL2) boiler and pressure vessel steel plate is an ideal material for manufacturing boilers and pressure vessels operating in high-temperature, high-pressure, and mildly corrosive environments.

Key Features and Advantages

Excellent High-Temperature Strength: Maintains good strength within the temperature range of 400°C to 550°C, with low susceptibility to creep.

Good Oxidation Resistance: The chromium content enables resistance to corrosion from water vapor, air, and other oxidizing atmospheres.

Strong Resistance to Hydrogen Corrosion: Suitable for petrochemical applications, it resists hydrogen attack in high-temperature, high-pressure hydrogen environments.

Good Weldability: As a low-alloy steel with well-controlled carbon content, it offers favorable weldability. However, strict welding procedures must be followed, typically requiring preheating and post-weld heat treatment.

Yuxin Steel supplies steel plates within the following specification ranges: thickness 6-300mm, width 1500-4050mm, length 3000-15000mm, with support for custom cutting and bevel processing.

Typical Applications of ASTM A387 Grade 12 Class 2 (A387GR12CL2) Boiler And Pressure Vessel Steel Plate in Oil & Gas:

Energy Sector:

High-temperature and high-pressure equipment used in petrochemical and coal chemical industries, such as hydroreactors, ammonia synthesis towers, coal gasifiers, heat exchangers, etc.

Power Sector:

Manufacturing of steam drums for power plant boilers, superheater pipes, and high-temperature pressure vessels.

Other Fields:

Nuclear energy equipment, catalytic cracking units in refineries, and pipeline systems requiring resistance to hydrogen corrosion.

Welding Precautions

Welding ASTM A387 Grade 12 Class 2 (A387GR12CL2) steel plate requires special care to prevent hydrogen-induced cracking (cold cracking):

Electrode selection: Typically, matching low-hydrogen welding consumables such as AWS A5.5 E8018-B2 (electrode) or AWS A5.28 ER80S-B2 (wire) are selected.

Preheating: Preheating is mandatory, with a temperature generally recommended between 150°C and 200°C, depending on the plate thickness.

Interpass temperature: The interpass temperature must be controlled during welding, approximately within the same range as the preheating temperature.

Post-weld heat treatment: Mandatory requirement. Hydrogen removal treatment must be performed immediately after welding, followed by a full normalizing + tempering or stress relief annealing to restore the properties of the heat-affected zone and eliminate residual stress. The typical PWHT temperature ranges from 620°C to 680°C.

Usage Precautions

Temperature Limits: The recommended long-term service temperature should be ≤500°C, with a short-term peak temperature not exceeding 530°C. If higher temperatures are required, upgrade to Grade 22 (2.25Cr-1Mo).

Stress Control: Avoid the formation of high residual stresses in welds and heat-affected zones. It is recommended to employ vibratory stress relief or furnace-based overall tempering to eliminate stresses.

Corrosion Protection: In environments containing Cl⁻, control the surface roughness to Ra ≤ 3.2μm and conduct regular penetrant testing (PT) to prevent stress corrosion cracking.

Comparison with Other Similar Materials

Comparison with ASTM A387 Gr 11:

Gr 11 (1.25Cr-0.5Mo) contains higher amounts of chromium and molybdenum, resulting in greater high-temperature strength and hydrogen resistance. However, it also comes with higher costs and a greater tendency to harden. Gr 12 can be considered an economical alternative to Gr 11, suitable for less demanding applications.

Comparison with ASTM A387 Gr 22 (2.25Cr-1Mo):

Gr 22 is a higher-grade chromium-molybdenum steel with superior high-temperature performance, often used in more demanding environments.

Comparison with Carbon Steel (e.g., SA516):

Ordinary carbon steel experiences a significant drop in strength when temperatures exceed approximately 400°C and lacks oxidation and hydrogen corrosion resistance. Gr 12 is specifically designed to address these issues.