What are the mechanical properties of SA387 Grade 5 Class 1?
SA387 Grade 5 Class 1 refers to a specific type of weldable, chromium-molybdenum alloy steel plate (ASME SA-387 standard) used for high-temperature pressure vessels, offering enhanced corrosion resistance and strength, with "Grade 5" indicating its ~5% chromium content and "Class 1" defining its lower tensile strength range compared to Class 2. This material is crucial in the oil, gas, chemical, and petrochemical industries for components like boilers and heat exchangers.
The mechanical properties of SA387 Grade 5 Class 1 are defined by the ASTM/ASME SA-387 standard for this specific 5% chromium, 0.5% molybdenum alloy steel plate in the annealed condition.
Guaranteed Mechanical Properties (SA-387)
| Property | Requirement |
|---|---|
| Tensile Strength | 415 - 585 MPa (60 - 85 ksi) |
| Yield Strength (0.2% Offset) | ≥ 205 MPa (≥ 30 ksi) |
| Elongation (in 50 mm / 2 in.) | ≥ 18% (typical for annealed plates) |
| Hardness (Brinell) | ≤ 201 HBW (annealed condition ensures softness for fabrication) |
Key Characteristics & Context
Annealed Condition (Class 1):
The "Class 1" designation means the plate is supplied in a soft, annealed state. This results in:
Lower strength but higher ductility compared to normalized & tempered (Class 2) conditions.
Better machinability and cold formability, making it suitable for complex fabrication before final heat treatment.
A uniform, stress-relieved microstructure ideal for subsequent welding and forming.
High-Temperature Performance:
Grade 5 is selected for elevated temperature and corrosion-resistant service (e.g., in refinery heaters or hydrogen service). Its key design properties-creep strength and allowable stress values at high temperatures-are tabulated in codes like ASME BPVC Section II, Part D. These values are developed after the final post-weld heat treatment (PWHT) in service.
Impact Toughness:
The standard does not mandate impact testing unless specified by the purchaser (via Supplementary Requirement S8). If required, test temperature and absorbed energy (e.g., Charpy V-notch) would be agreed upon in the order.
Important Notes
Actual vs. Minimum: Mill Test Certificates (MTRs) will report actual tested values, which typically meet or exceed the minimums above. Actual yield strength often exceeds 205 MPa.
Comparison with Class 2: Grade 5 Class 2 (normalized & tempered) would have higher strength (e.g., yield ≥ 275 MPa/40 ksi) but lower as-supplied ductility.
Final Use: Components made from Class 1 material must undergo a final PWHT after fabrication to achieve the required service properties (including stress relief and tempering).
Summary
SA387 Grade 5 Class 1 provides moderate strength (min. yield 205 MPa) with high ductility and softness in its as-supplied state, optimizing it for severe forming and welding operations. Its true engineering value lies in its elevated-temperature corrosion resistance and strength, which are realized after the final manufacturing heat treatment. For design, engineers rely on ASME code allowable stress values at operating temperatures, not just the room-temperature properties.
What is SA387 Grade 5 Class 1?
SA387 Grade 5 Class 1 is a specification for chromium-molybdenum alloy steel plates designed for service in welded pressure vessels where enhanced resistance to oxidation and high-temperature strength are required.
What is the chemical composition of SA387 Gr5 Cl1?
Its typical composition includes Chromium (4.00-6.00%) and Molybdenum (0.45-0.65%), along with controlled amounts of Carbon, Manganese, Silicon, Phosphorus, and Sulfur.
What are the mechanical properties of SA387 Grade 5 Class 1?
Key mechanical properties include a minimum tensile strength of 515-690 MPa (75-100 ksi) and a minimum yield strength of 310 MPa (45 ksi).
Is SA387 Grade 5 Class 1 equivalent to 5Cr-0.5Mo steel?
Yes, SA387 Grade 5 is the standard specification for 5% Chromium - 0.5% Molybdenum alloy steel plates, commonly referred to as 5Cr-0.5Mo.
What is the primary application of SA387 Grade 5 steel?
It is primarily used in petroleum refinery equipment, such as hydroprocessing reactors, hydrocrackers, and other pressure vessels exposed to high-temperature hydrogen service and sulfidic corrosion.
What is the maximum service temperature for SA387 Gr5 Cl1?
It is suitable for continuous service at metal temperatures up to approximately 1200°F (649°C), depending on the specific environment and stress conditions.
How do you heat treat SA387 Grade 5 Class 1?
Class 1 material can be supplied in the annealed or normalized and tempered condition. Post-weld heat treatment (PWHT) is almost always required, typically in the range of 1250-1350°F (677-732°C).
What welding rod is used for SA387 Grade 5?
Welding typically requires preheat and PWHT. Common filler metals include AWS E502-16 (for matching composition) or high-chromium nickel-based alloys for dissimilar welds or severe service.
What is the difference between Grade 5 and Grade 22 in SA387?
The main difference is chromium content. Grade 5 has 5% Cr for better oxidation and sulfidation resistance, while Grade 22 has about 2.25% Cr and higher molybdenum, offering different strength and corrosion properties.
Does SA387 Grade 5 require impact testing?
Impact testing (Charpy V-Notch) is not a mandatory requirement of the base SA387 specification. However, it is often specified as an additional requirement by the vessel designer or applicable construction code for low-temperature service.
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.
