What are the mechanical properties of SA203 Grade B?
SA203 Grade B is a nickel-alloy steel plate standardized under the ASME Boiler and Pressure Vessel Code (Section II, Part A). It is specifically designed for low-temperature and cryogenic service in welded pressure vessels and other critical structures where good notch toughness at sub-zero temperatures is required
The mechanical properties for SA203 Grade B are defined by the ASME SA-203/SA-203M specification. Below are the key properties for the most common plate thickness ranges.
Key Mechanical Properties (ASME SA-203/SA-203M)
1. Tensile Properties (for plates ≤ 2.5 in / 63.5 mm thick):
Tensile Strength: 65 – 85 ksi (450 – 585 MPa)
Yield Strength (Minimum): 37.5 ksi (260 MPa)
Elongation (Minimum in 2 in / 50 mm):
22% for longitudinal specimens
18% for transverse specimens
2. Tensile Properties for Thicker Plates:
Properties decrease with increasing thickness per the standard's tables.
For plates > 2.5 to 4 in (63.5 to 100 mm):
Tensile Strength: 65 – 85 ksi (450 – 585 MPa)
Yield Strength (Min): 35.5 ksi (245 MPa)
For plates > 4 to 8 in (100 to 200 mm):
Tensile Strength: 63 – 83 ksi (435 – 570 MPa)
Yield Strength (Min): 33 ksi (230 MPa)
3. Impact Toughness (Charpy V-Notch):
Impact testing is a fundamental requirement for SA203 materials.
The standard test temperature for Grade B is -75°F (-60°C).
Minimum Acceptance Criteria (for full-size specimens, 10mm x 10mm):
Average of 3 specimens: 15 ft-lbf (20 J) minimum.
Single specimen minimum: 12 ft-lbf (16 J).
Note: Purchasers can specify lower test temperatures (e.g., -100°F / -73°C) or higher energy values, which will be reflected in the material certification.
Summary Table (for plates ≤ 2.5 in / 63.5 mm)
Important Application Notes:
Heat Treatment: SA203 Grade B is supplied in the normalized or normalized and tempered condition to achieve these properties.
Primary Design Driver: Its primary selection criterion is not high strength, but verified low-temperature toughness. The relatively moderate yield strength (37.5 ksi) is offset by its excellent impact resistance at -75°F, making it a classic choice for low-temperature pressure vessels.
Thickness Effect: Always use the property values corresponding to the actual plate thickness from the ASME SA-203M table when designing.
Certification: The Mill Test Report (MTR) must certify both the tensile properties and the Charpy impact results at the specified temperature.
In essence, the mechanical profile of SA203 Grade B is characterized by moderate strength combined with standardized, guaranteed toughness at -75°F, making it a reliable and widely used material for cryogenic applications.
1.What is SA203 Grade B?
SA203 Grade B is a nickel-alloy steel plate designed for low-temperature pressure vessel service, with a nominal nickel content of 2.25%, offering good notch toughness for applications down to approximately -75°F (-60°C).
2.What is the chemical composition of SA203 Grade B?
Its composition includes approximately 2.25% Nickel, along with controlled amounts of Carbon (max 0.17%), Manganese (max 0.70%), Silicon (0.15-0.40%), Phosphorus, and Sulfur.
3.What are the mechanical properties of SA203 Grade B?
Key mechanical properties include a minimum tensile strength of 65-85 ksi (450-585 MPa) and a minimum yield strength of 37.5 ksi (260 MPa) for plates up to 2.5 inches thick.
4.Is SA203 Grade B a carbon steel or alloy steel?
It is classified as a nickel-alloy steel due to its intentional and significant (2.25%) nickel content, which differentiates it from carbon steels and gives it enhanced low-temperature properties.
5.What is the impact toughness of SA203 Grade B?
SA203 Grade B is known for good notch toughness, typically requiring Charpy V-Notch impact testing at -75°F (-60°C) with minimum absorbed energy values specified.
6.How does SA203 Grade B differ from Grade A, D, and E?
The primary difference is nickel content. Grade B has 2.25% Ni, while Grade A has 2.25% Ni but lower strength, Grade D has 3.25% Ni, and Grade E has 3.50% Ni, offering progressively better low-temperature toughness.
7.What is SA203 Grade B used for?
It is commonly used in low-temperature pressure vessels, storage tanks, and structural components for applications such as propane tanks, ethylene storage, and other services down to -75°F (-60°C).
8.Can SA203 Grade B be welded?
Yes, it has good weldability. However, welding procedures should use low-hydrogen practices, and matching or suitable nickel-alloy filler metals are often recommended for critical applications.
9.What is the heat treatment for SA203 Grade B?
SA203 Grade B is typically supplied in the normalized or normalized and tempered condition to achieve the required mechanical properties and toughness.
10.Is SA203 Grade B suitable for cryogenic service?
Yes, it is a standard material for moderately low-temperature (cryogenic) service, commonly used for applications in the -50°F to -150°F (-46°C to -101°C) range, making it suitable for many liquefied gas storage applications.
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.
