ASTM A387 Grade 5 Class 1 is a chromium-molybdenum alloy steel plate specified in the ASTM A387/A387M standard, designed primarily for the welded fabrication of pressure vessels and related equipment operating under high-temperature conditions. It features a carefully calibrated chemical composition centered on chromium and molybdenum additions, which endow it with excellent high-temperature strength, creep resistance and corrosion resistance for harsh industrial service. Supplied in the normalized heat treatment condition, it balances reliable mechanical performance with good weldability, making it suitable for on-site fabrication of large-scale components. This steel grade is widely applied across the oil and gas, petrochemical and power generation industries, typically used to manufacture pressure vessels, heat exchangers, industrial boiler components and pipelines that handle high-temperature fluids and resist acidic or alkaline corrosive media, maintaining stable structural integrity even during prolonged thermal cycling.
Chemical Composition
| Grades | C | Mn | P | S | Si | Cr | Mo |
| ASTM A387 Gr. 5 | 0.15 max | 0.25 – 0.66 | 0.035 | 0.030 | 0.55 max | 3.9 – 6.1 | 0.40 – 0.7 |
Mechanical Properties
|
Grade |
Tensile Strength(MPa) |
Yield Strength(MPa) min |
% Elongation in 2 in.(50mm) min |
Impacting Test Temperature(°C) |
|
A387 Grade 5 |
415-585 |
205 |
18 |
-20,40,-60 |
Key Characteristics & Applications
High-Temperature Service
Engineered for sustained performance at elevated temperatures, with retained mechanical strength and thermal stability. Critical for core equipment in power plants, refineries, and chemical processing facilities.
Corrosion Resistance
Chromium content forms a protective passive film, delivering reliable resistance to atmospheric, acidic, alkaline, and oxidizing corrosive environments (per Alpha Overseas and Gnee Steels technical data). Extends component service life and cuts maintenance costs.
Welded Components Compatibility
Excellent weldability with low crack sensitivity; weld joints match base metal properties post heat treatment. Ideal for fabricating large welded structures like industrial boilers and pressure vessels, meeting strict industry safety standards.
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What is the ASTM A387 equivalent to?
Among the ASTM A387 Grade 22 equivalent steel grades, SA387 Grade 22, 10CrMo9-10 is more popular than other equivalents. SA387 Grade 22 steel is under ASME SA387/ SA387M standard. The chemical performance and technical requirements of SA387 Grade 22 steel is almost same with ASTM A387 Grade 22 steel.
What is the difference between ASTM A387 GRADE 5 CLASS 1 and Class 2?
The main difference between ASTM A387 Grade 5 Class 1 and Class 2 lies in their mechanical properties, specifically tensile strength and yield strength, with Class 2 offering higher strength but potentially lower ductility (elongation) compared to Class 1, though both share the same chemical composition and are used for high-temperature pressure vessels. Class 2 provides higher stress resistance, while Class 1 is slightly more ductile, though for Grade 5, elongation values can be similar.