ASME SA302 Gr.B Boiler Steel Plate

ASME SA302 Gr.B Steel Plate

ASME SA302 Gr.B is a manganese‑molybdenum (Mn‑Mo) low‑alloy high‑strength steel plate under ASME/ASTM specifications, engineered for fusion‑welded boilers, steam drums, petrochemical reactors, and medium‑to‑high pressure vessels operating under continuous high temperatures up to 480°C.

Distinct from general ASTM A302 plate, the "SA" prefix denotes full compliance with ASME Section VIII Boiler and Pressure Vessel Code, making it eligible for bidding on global engineering projects requiring ASME U‑Stamp certification. Free of chromium alloying elements, SA302 Gr.B delivers dependable creep resistance at elevated temperatures, coupled with outstanding resistance to Hydrogen Induced Cracking (HIC) and Sulfide Stress Cracking (SSC) in hydrogen sulfide‑containing service media. It achieves lower material costs compared with Cr‑Mo heat‑resistant steel such as ASTM A387.

Core Characteristics of ASME SA302 Gr.B Plate

 

 

1

High Strength and Superior Toughness

Stable mechanical strength at intermediate temperatures (350~480°C) coupled with satisfactory low-temperature toughness.

2

Excellent Weldability

Moderate carbon equivalent brings low cold cracking susceptibility, perfectly matching welding procedures for pressure vessel fabrication.

3

Hydrogen Corrosion Resistance

Molybdenum (Mo) alloying element greatly enhances resistance to high-temperature hydrogen attack, ideal for hydrogenation unit service conditions.

4

Creep Resistance & Fatigue Resistance

Stable metallurgical microstructure under long-term high-temperature pressure service, delivering strong resistance to permanent deformation and fatigue cracking.

ASME SA302 Boiler Steel Plate Delivery Condition

Heat Treatment: Normalized (N) or Normalized + Tempered (N+T)

Normalizing Temperature: 900–940°C

Tempering Temperature: ≥595°C (optional)

Surface Quality: Free from laminations and cracks; local grinding is permitted.

ASME SA302 Steel Plate Key Application 

• Petrochemical Industry: Hydroprocessing reactors, heat exchangers, separators, spherical tanks, liquefied gas storage tanks
• Power Industry: Boiler drums, steam generators, nuclear power pressure vessels
• Energy Equipment: High-pressure vessels, pipelines, offshore platform structural components

 ASME SA302 Grade B Boiler Steel Plate Specification

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1. Precision Deep Processing Service: Provide one-stop processing including laser cutting, flame cutting, bending, drilling, polishing, surface grinding and plate flattening. Strictly control processing tolerance to ensure the flatness and dimensional accuracy of steel plates, directly supply finished semi-finished products, save customers' secondary processing costs and cycle time.
2. Urgent Order Priority Production Service: Arrange independent production lines and inventory reserves for customer urgent orders, shorten production and delivery cycle, prioritize production and shipment, effectively solve the problem of tight construction cycle of customer projects.

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FAQ

What is the maximum temperature resistance of SA302 Gr.B?
ASME SA302 Grade B (manganese-molybdenum low-alloy steel) is approved for pressure vessel service at temperatures up to approximately 650°F to 700°F (343°C to 371°C), depending on the specific ASME Boiler and Pressure Vessel Code section and allowable stress limits. Beyond roughly 400°C (752°F), the material experiences significant loss of tensile strength and potential creep effects.

Is SA302 Gr.B steel plate good for welding?
Yes, SA302 Gr.B steel plate is explicitly engineered for welding. As a manganese-molybdenum low-alloy steel, it is designed specifically for the fabrication of welded boilers, high-pressure vessels, and nuclear components where strong weld integrity and high tensile strength are critical.

What are the differences between SA302 Gr.B and SA302 Gr.C?
ASME SA302 Grade B and Grade C are both manganese-molybdenum alloy steel plates for welded boilers and pressure vessels. The primary difference is that Grade C contains added nickel (0.40–0.70%) for enhanced toughness, whereas Grade B is a nickel-free manganese-molybdenum steel.