ASTM A203 Grade B low temperature pressure vessel steel
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.
Key Characteristics of ASTM A203 Grade B:
1. Chemical Composition (Defining Feature):
Nominal Nickel Content: 2.25%. This is the key alloying element that significantly improves low-temperature toughness.
Low carbon content (max 0.17%) and controlled manganese/silicon levels ensure good weldability and formability.
2. Mechanical Properties (for plates ≤ 2.5 in / 63.5 mm):
Tensile Strength: 65 – 85 ksi (450 – 585 MPa) [Range]
Yield Strength (Minimum): 37.5 ksi (260 MPa)
Elongation (Minimum): 22% (Longitudinal), 18% (Transverse)
Impact Toughness (Mandatory): Charpy V-Notch tested at -75°F (-60°C). Minimum average absorbed energy is 15 ft-lbf (20 J) for full-size specimens. This is its core performance guarantee.
3. Heat Treatment:
Supplied in the normalized or normalized and tempered condition to achieve the required microstructure for toughness.
Why It's Used for Low-Temperature Pressure Vessels:
Proven Toughness: The standardized -75°F impact test provides a verifiable safety margin against brittle fracture, which is the primary failure mode of concern in low-temperature vessels.
Cost-Effective Nickel Alloy: With 2.25% Ni, it offers a significant toughness improvement over carbon steels (like A516) at a lower cost than higher-nickel steels (like A553 for LNG).
Good Weldability: Its chemistry and heat treatment make it relatively straightforward to weld using low-hydrogen practices, a crucial factor for pressure vessel fabrication.
A203 Grade B mechanical properties
Tensile Requirements |
ASTM A 203 |
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Grade B |
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ksi |
[MPa] |
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Tensile strength |
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2 in. (50 mm) & under |
70-90 |
[485-620] |
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over 2 in. (50 mm) |
70-90 |
[485-620] |
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Yield strength, min. |
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2 in. (50 mm) & under |
40 |
[275] |
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over 2 in. (50 mm) |
40 |
[275] |
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Elongation in 8 in. (200 mm), min, % |
17 |
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Elongation in 2 in. (50 mm), min, % |
21 |
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Steelmaking process:
ASTM A203 Grade B low temperature pressure vessel steel should be killed steel and should meet the fine-grained material requirements z in the A20/A20M standard.
The ASTM A203 standard specifies the size, shape, technical requirements, inspection methods, inspection rules, packaging, markings and quality certificates of A203 Grade B steel plates for low-temperature pressure vessels. The maximum thickness of 100mm of A203 Grade B steel plate is restricted by chemical composition regulations and mechanical performance requirements. The small thickness of the steel plate is limited to 0.25in (6.5mm).
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.
