A537 Class 3 refers to a high-strength, quenched and tempered (Q&T) carbon-manganese-silicon steel plate, primarily used for fusion-welded pressure vessels, boilers, and storage tanks in moderate-pressure applications, offering a minimum yield strength of 380 MPa (55 ksi) and superior strength and hardness through heat treatment. It's a specific grade under the ASTM A537 standard, distinct from Class 1 (normalized) and Class 2 (also Q&T but lower tempering temp).
ASTM boiler grade A537 class 3 pressure vessel steel plate chemical composition:
| Grade | C | Mn | P | S | Si | Cu | Ni | Cr | Mo |
| A537 class 3 | 0.24 | 0.92-1.72 | 0.035 | 0.035 | 0.13-0.55 | 0.38 | 0.28 | 0.29 | 0.09 |
The mechanical properties of A537 class 3 steel plate at ambient temperature:
| Grade | Thickness(mm) | Min Yield (Mpa) | Tensile(MPa) | Elongation(%) |
| A537 class 3 | 8mm-65mm | Min 380Mpa | 550-690Mpa | 22% |
| 66mm-100mm | Min 345Mpa | 515-655Mpa | 22% | |
| 101mm-150mm | Min 275Mpa | 485-620Mpa | 20% |
Other trade names of A537 class 3 plate:
A537 plate
A537 steel
A537 class 3 steel
ASTM A537 steel
A537 carbon steel
A537 steel plate
ASTM A537 plate
A537 grade plate
The following A537 grades are also available:
ASTM A537 / ASME SA537 class 1 / A537CL1
ASTM A537 / ASME SA537 class 2 / A537CL2
A537 class 3 steel plate thickness is under 150 mm [6 inch]. A537CL3 steel is mainly used in the oil, gas and petrochemical industry.
Key Applications
Pressure Vessels & Boilers: Its primary use is in building equipment that holds liquids or gases under pressure, requiring good toughness.
Oil & Gas Industry: Used in separators, storage tanks, and processing equipment.
Chemical Industry: Suitable for tanks and reactors storing chemicals.
Power Plants: For steam components and other critical systems.
Storage Tanks: For various industrial liquids and gases (like LPG).
Key Characteristics
Heat Treatment: Typically quenched and tempered (Q&T) for strength and toughness.
Weldability: Good weldability, crucial for pressure vessel construction.
Toughness: Offers improved notch toughness, important for cyclic loads and lower temperatures.
Corrosion Resistance: Can be specified with Hydrogen Induced Cracking (HIC) testing for corrosive environments.
Why Class 3?
Class 3 offers a balance of strength and toughness, making it a versatile choice for demanding conditions, often selected when higher strength or specific toughness properties are needed compared to Class 1 or 2. It's a heat-treated carbon-manganese-silicon steel designed for reliable performance in elevated temperatures and moderate pressure services, meeting standards like ASME SA537 Class 3.
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.
At what temperature is impact testing performed for ASTM A537 Class 3?
Impact testing for ASTM A537 Class 3 is conducted at -46°C. This low-temperature test ensures the material maintains sufficient toughness to resist brittle fracture in cold environments. The results help verify the effectiveness of the normalization and tempering heat treatment.
What is the purpose of normalizing ASTM A537 Class 3?
Normalizing ASTM A537 Class 3 refines the grain structure, improves toughness, and reduces segregation. The steel is heated to 870–925°C and air-cooled, which produces a uniform ferrite-pearlite microstructure. This step is essential for achieving consistent mechanical properties across thick plates.
Why is tempering required after normalization for ASTM A537 Class 3?
Tempering after normalization reduces hardness, relieves residual stresses, and improves toughness. The steel is heated to at least 595°C, which allows carbon to diffuse and form more stable carbides. This results in a balance of strength and ductility necessary for pressure vessel service.
What is the maximum carbon content allowed in ASTM A537 Class 3?
ASTM A537 Class 3 limits carbon to a maximum of 0.23 percent. This restriction ensures good weldability by preventing excessive hardness in the heat-affected zone. Lower carbon content also helps improve toughness and reduce the risk of hydrogen-induced cracking.
What role does manganese play in ASTM A537 Class 3?
Manganese in ASTM A537 Class 3, ranging from 1.00 to 1.60 percent, enhances strength and hardenability. It also improves toughness by refining the grain structure during heat treatment. Proper manganese content ensures the steel meets the required yield and tensile strength levels.
Why are phosphorus and sulfur kept low in ASTM A537 Class 3?
Phosphorus and sulfur are limited to reduce embrittlement and improve toughness. Phosphorus can cause cold shortness, while sulfur forms brittle sulfide inclusions. Controlling these elements ensures better weldability and resistance to cracking in pressure vessel applications.
What are the typical dimensions of ASTM A537 Class 3 plates?
ASTM A537 Class 3 plates are produced in various thicknesses, commonly up to 150 mm. Widths and lengths depend on manufacturing capabilities but typically range from 1500 to 4000 mm and 6000 to 12000 mm, respectively. Thicker plates require special heat treatment to maintain properties.
What standards should be referenced when fabricating with ASTM A537 Class 3?
Fabrication of ASTM A537 Class 3 typically references ASME Section II for material acceptance and ASME Section VIII for pressure vessel construction. Welding procedures follow AWS D1.1 or ASME Section IX. Testing standards include ASTM A370 for mechanical tests and ASTM A609 for ultrasonic inspection.
What welding consumables are suitable for ASTM A537 Class 3?
Suitable consumables for ASTM A537 Class 3 include low-hydrogen electrodes such as E7018 for SMAW. For GMAW, ER70S-6 is commonly used, while FCAW may use E71T-1. SAW typically employs EL8 electrodes with matching fluxes. Consumables should provide good toughness and strength matching.
What are the advantages of ASTM A537 Class 3 over A516 grades?
ASTM A537 Class 3 offers higher strength than A516 grades, allowing thinner plates and weight reduction. It also provides better low-temperature toughness due to normalization and tempering. These benefits make it suitable for more demanding pressure vessel and storage tank applications.
What are the limitations of ASTM A537 Class 3?
ASTM A537 Class 3 may have higher material and processing costs compared to lower-strength carbon steels. It also requires careful welding procedures and may need PWHT for thick sections. Additionally, its availability in very thick plates can be limited, requiring special production arrangements.