1. Core Definition & Standard Relationship

ASTM A335/ASME SA335 define requirements for seamless Cr-Mo alloy steel products, with distinct but complementary roles:

• ASTM A335: A general industrial standard specifying seamless Cr-Mo alloy steel pipes and plates for high-temperature service, covering chemical composition, mechanical properties, and manufacturing tolerances.

• ASME SA335: A certification-focused variant of ASTM A335, approved by the American Society of Mechanical Engineers (ASME) for use in boilers, pressure vessels, and nuclear components (compliant with ASME Section I, III, and VIII).

• Core Scope: Designed for service temperatures ranging from -29°C to 650°C+ and pressures up to 345 MPa (50,000 psi), where resistance to creep, thermal fatigue, and oxidation is non-negotiable.

• Material Category: Single-phase or multi-phase Cr-Mo alloys, with varying chromium (1.25–9%) and molybdenum (0.5–1.8%) content, often enhanced with vanadium (V), niobium (Nb), or tungsten (W) for superior high-temperature performance.

2. Popular Grades & Chemical Composition

ASTM A335/ASME SA335 encompasses multiple grades, with three variants dominating industrial use due to their balanced performance and cost-effectiveness: P5, P11, and P92. Each grade is distinguished by its alloy formulation, which directly dictates its temperature and pressure capabilities.

Core Alloy Functions

• Chromium (Cr): Forms a dense protective oxide layer (Cr₂O₃) to resist oxidation and corrosion at elevated temperatures.

• Molybdenum (Mo): Enhances creep strength and thermal stability by slowing atomic diffusion in the alloy matrix.

• Tungsten (W): (Unique to P92) Boosts high-temperature strength and creep resistance, enabling service at 650°C+.

• Vanadium (V)/Niobium (Nb): Refines grain structure and forms carbides (VC, NbC) to further improve creep resistance and toughness.

3. Key Technical Parameters

3.1 Dimensional Range (Steel Plates)

ASTM A335/ASME SA335 steel plates are supplied in flexible dimensions to suit diverse equipment requirements:

• Thickness: 6 mm to 200 mm (standard); customized up to 300 mm for heavy-duty pressure vessels.

• Width: 1000 mm to 3200 mm (standard); customizable up to 4000 mm.

• Length: 2000 mm to 12000 mm (standard); cut-to-length available for project-specific needs.

• Dimensional Tolerance: Thickness tolerance ±5% (standard) or ±3% (precision); width/length tolerance ±3 mm (for plates ≤1000 mm) or ±5 mm (for larger plates).

3.2 Mechanical Properties (Typical Values for Plates ≥12 mm, Post Heat Treatment)

3.3 High-Temperature Performance

• Creep Resistance: Critical for HTHP service – P92 exhibits <0.1% creep deformation after 100,000 hours at 600°C; P5/P11 maintain integrity for 100,000 hours at 550°C.

• Oxidation Resistance: All grades form a stable Cr₂O₃ layer; P92’s higher Cr content ensures minimal oxide spallation even at 650°C.

• Thermal Fatigue Resistance: Resists cracking from repeated heating/cooling cycles, a key requirement for boiler and reactor components.

4. Production Process & Quality Control

ASTM A335/ASME SA335 steel plates undergo rigorous manufacturing and testing to meet the standards’ strict safety requirements:

1. Raw Material Selection: High-purity billets produced via electric arc furnace (EAF) + vacuum degassing (VD) or electroslag remelting (ESR) to minimize impurities (P≤0.035%, S≤0.035%).

2. Hot Rolling: Billets heated to 1150–1250°C and hot-rolled to target thickness using thermo-mechanical control processing (TMCP) to optimize grain structure.

3. Heat Treatment:

• P5/P11: Normalization (900–950°C) + tempering (650–700°C) to achieve a tempered martensite/ferrite microstructure.

• P92: Normalization (1040–1080°C) + tempering (730–780°C) to form a fine-grained tempered martensite structure with dispersed carbides.

4. Surface Treatment: Shot blasting to remove oxide scale; pickling and passivation optional for enhanced corrosion resistance in aggressive environments.

5. Non-Destructive Testing (NDT):

• Ultrasonic Testing (UT): 100% volumetric inspection for internal defects (per ASTM A609).

• Magnetic Particle Testing (MT)/Liquid Penetrant Testing (PT): 100% surface inspection for cracks (per ASTM A609).

• Radiographic Testing (RT): Optional for critical pressure vessel components (per ASME Section V).

6. Mechanical & Chemical Testing: Tensile, bend, and impact tests; spectrometric analysis for alloy composition verification; creep testing for high-temperature grade validation (P92).

7. Pressure Testing: For plate-based components (e.g., vessel shells), hydrostatic testing at 1.5× design pressure to ensure leak tightness.

Certifications

All ASTM A335/ASME SA335 steel plates come with EN 10204 3.1/3.2 certification. ASME SA335 plates include additional ASME certification (Section I/III/VIII) for boiler and pressure vessel use. Manufacturers typically hold ISO 9001, ISO 14001, and API Q1 certifications.

5. Core Applications

ASTM A335/ASME SA335 steel plates are engineered for critical HTHP components where failure is catastrophic, making them essential in:

• Power Generation: Boiler drums, superheater/reheater headers, steam turbine casings, and heat recovery steam generator (HRSG) shells (P5, P11, P92).

• Petrochemical & Refining: Hydrocracker reactors, reformer tubes, catalytic converter shells, and high-temperature process pipelines (P5, P11).

• Nuclear Energy: Secondary coolant system components, pressure vessel liners, and steam generators (ASME SA335 P92, compliant with ASME Section III).

• Industrial Processing: Furnace shells, thermal oxidizers, and high-pressure heat exchanger tubesheets (P5, P11).

• Oil & Gas: Offshore platform process equipment, downhole wellheads, and refinery heater tubes (P11, P92).

6. Selection Guide: Choosing the Right Grade

7. Supply Chain & Value-Added Services

• Minimum Order Quantity (MOQ): 1 ton (standard grades, standard dimensions); 5 tons (custom thickness/grades).

• Delivery Lead Time: 10–15 days for stock grades; 35–50 days for custom orders (including heat treatment and certification).

• Packaging: Seaworthy export packaging (waterproof plastic film + kraft paper + steel strips) with anti-rust oil coating; wooden crates optional for large plates.

• Value-Added Services: Cut-to-length, beveling, drilling, welding preparation, and custom heat treatment; third-party testing (SGS, BV, TÜV) for independent validation.

• Global Reach: Supplied to over 70 countries, with key loading ports in Shanghai, Tianjin (China), Houston (USA), and Antwerp (Belgium).

8. Conclusion

ASTM A335/ASME SA335 steel plates represent the gold standard for Cr-Mo alloy steel in HTHP applications, offering unmatched reliability, thermal stability, and safety. Their graded alloy formulations (P5, P11, P92) enable precise alignment with project requirements—from cost-effective moderate-temperature service (P5/P11) to ultra-high-temperature critical components (P92). Backed by strict manufacturing controls, comprehensive NDT, and globally recognized certifications, these plates are indispensable for industries where performance under extreme conditions directly impacts safety and operational efficiency. When selecting a grade, prioritize service temperature, pressure, and corrosion environment to ensure optimal performance, minimize lifecycle costs, and maintain compliance with industry safety standards. For boiler and pressure vessel applications, ASME SA335 remains the mandatory choice to meet regulatory requirements.