A302 Grade D is a manganese-molybdenum-nickel alloy steel plate designed specifically for welded boilers and pressure vessels. It is valued for its high strength and durability in high-pressure environments.
Chemical Composition( %):
|
Grade/ Material |
Element |
Composition( Max-A, Min-I) |
|
A302 Grade D/ A302 GrD |
C |
A:0.20 |
|
Mn |
1.15-1.50 |
|
|
Si |
0.15-0.40 |
|
|
P |
0.035 |
|
|
S |
0.035 |
Mechanical Properties( Mpa)
|
Grade/ Material |
Tensile Test |
Ksi/MPa |
|
A302 Grade D/ A302 GrD |
Tensile Strength |
80-100/550-690 |
|
Yield Strengh |
I:50/345 |
|
|
Elongation |
I:17% |
|
|
Impact Test( if any) |
|
Core Processing Links & Requirements
Heat Treatment (Core Step):
Mandatory normalizing + tempering process. Normalizing temperature is controlled at 890-950℃, with sufficient holding time (1.5-2.5 hours per 25mm thickness) to ensure uniform heating of the steel plate. Tempering is performed immediately after normalizing, with temperature set at 590-650℃, followed by air cooling or furnace cooling to room temperature, which enhances toughness and reduces internal stress.
Cutting & Forming:
Adopt mechanical cutting (plasma cutting, flame cutting) or shearing. Flame cutting requires preheating to 80-150℃ to avoid cold cracking. Forming operations (bending, rolling) should be conducted at room temperature or low preheating (≤200℃), and the minimum bending radius shall not be less than 1.5 times the plate thickness to prevent material damage.
Welding Operation:
Use low-hydrogen electrodes (such as E7018) or submerged arc welding wires matching the material. Preheat the base metal to 100-150℃ before welding, and perform post-weld heat treatment (tempering at 580-620℃) to eliminate welding stress and avoid weld brittleness. Welding current and voltage should be stable to ensure weld quality.
Post-Processing & Inspection:
Remove welding spatter and burrs after processing, and conduct surface cleaning (derusting, degreasing). Carry out non-destructive testing (UT, MT) on key parts to check for internal defects. Ensure the processed workpiece meets dimensional accuracy requirements and no visible cracks or deformations exist.
advantages
1. Superior Mechanical Strength
Compared to other common pressure vessel steels, A302 Grade D offers some of the highest yield strength (minimum 345 MPa) and tensile strength (550–690 MPa) in its class. This allows engineers to design lighter and more efficient structures without compromising safety.
2. Enhanced Toughness via Nickel
The defining advantage of Grade D over Grades A and B is the addition of nickel (0.67% – 1.03%).
Impact Resistance: Nickel significantly improves the material's toughness, particularly at lower temperatures.
Ductility: It allows the steel to reach high strength levels without becoming brittle, which is vital for preventing catastrophic failures in pressure vessels.
3. Excellent Weldability
Despite its high alloy content, A302 Grade D is designed to be readily welded using standard industrial methods. This makes it a preferred choice for the fabrication of complex boilers and large-scale storage tanks.
4. Resistance to Harsh Environments
Heat Resistance: The inclusion of molybdenum increases the steel's resistance to softening at elevated temperatures and improves its creep resistance.
Hydrogen Resistance: It offers excellent resistance to hydrogen-induced cracking (HIC), making it ideal for hydrogenation units and reactors in refineries.
5. Versatility in Treatment
The material responds well to various heat treatments. While typically supplied as-rolled, it can be normalized or stress-relieved to further refine its grain structure and improve dimensional stability for critical applications.
Supply & Manufacturing Details
Delivery State: Typically supplied in the as-rolled condition, but plates thicker than 50mm usually require normalizing.
Typical Dimensions: Suppliers like TJC Steel provide thicknesses from 4mm up to 400mm.
Supplementary Tests: Frequently undergoes Ultrasonic Testing (UT), Charpy V-Notch Impact Testing, or Simulated Post-Weld Heat Treatment (PWHT) for mission-critical projects.
Contact us at beam@gneesteelgroup.com for pricing, technical support, or customized solutions. We are always ready to support your project.
What is the impact toughness of A302 Grade D at room temperature?
At room temperature, its Charpy V-notch impact toughness is at least 27 J (20 ft-lb). This ensures the steel can resist sudden impact loads without brittle fracture, enhancing equipment operational safety.
Can A302 Grade D be used in low-temperature environments? What is the minimum service temperature?
It is not ideal for ultra-low temperatures but can be used down to -20°C (-4°F) with proper heat treatment. Below this temperature, its impact toughness may decrease, so low-temperature testing is recommended for such applications.
What is the standard specification that A302 Grade D complies with?
It complies with ASTM A302/A302M, a standard issued by the American Society for Testing and Materials (ASTM) for low-alloy steel plates for pressure vessels, specifying chemical composition, mechanical properties, and testing requirements.
What is the typical thickness range of A302 Grade D plates?
The typical thickness range is 6 mm to 200 mm. Thicker plates may require special heat treatment to ensure uniform mechanical properties across the entire cross-section, meeting different equipment design needs.
How does A302 Grade D perform in terms of corrosion resistance?
It has moderate corrosion resistance to atmospheric and mild corrosive media. For harsh corrosive environments (e.g., acidic or alkaline media), additional anti-corrosion treatments (such as painting or galvanizing) are recommended.
What testing methods are used to verify the quality of A302 Grade D?
Common testing methods include tensile testing, yield strength testing, impact testing (Charpy V-notch), hardness testing, chemical composition analysis (spectroscopy), and non-destructive testing (ultrasonic, radiographic).
What is the difference between A302 Grade D and A302 Grade B?
The main difference lies in carbon content and mechanical properties: Grade D has higher C (0.20-0.28% vs 0.15-0.23% for B) and higher tensile/yield strength, making it more suitable for high-pressure, high-load applications.
Can A302 Grade D be cold-formed? What precautions are needed?
It can be cold-formed, but with precautions: avoid excessive deformation to prevent cracks, perform intermediate annealing if needed to restore ductility, and check for surface defects after forming to ensure structural integrity.
What is the hardness range of A302 Grade D after heat treatment?
After normalizing and tempering, its Brinell hardness (HB) ranges from 137 to 187. This hardness balance ensures good machinability and wear resistance, suitable for subsequent processing and long-term service.
Is A302 Grade D suitable for boiler drum manufacturing?
Yes, it is widely used for boiler drum manufacturing. Its high-temperature resistance, high tensile strength, and good weldability meet the strict requirements of boiler drums operating under high pressure and continuous heat.