ASTM B409/B409M is the standard specification by ASTM International covering rolled nickel-iron-chromium alloy plate, sheet, and strip — primarily Alloy 800 (UNS N08800), Alloy 800H (UNS N08810), and Alloy 800HT (UNS N08811). These alloys deliver exceptional high-temperature strength, oxidation resistance, and carburization resistance up to approximately 1100°C (2000°F), making them the workhorse materials for ethylene cracking furnaces, steam methane reformers, and nuclear steam generator tubing. The companion specification ASME SB409 adopts identical requirements for ASME Code-stamped pressure equipment.

Zhengzhou Huitong (HT Pipe) supplies ASTM B409 / ASME SB409 compliant plate, sheet & strip with full Mill Test Certificates (MTC) per EN 10204 3.1. 

1. Standard Scope & Designation

ASTM B409/B409M covers rolled nickel-iron-chromium alloy (Alloy 800/800H/800HT) plate, sheet, and strip for general corrosion-resisting and high-temperature applications. The specification defines UNS N08800 (Alloy 800), UNS N08810 (Alloy 800H), and UNS N08811 (Alloy 800HT) with controlled carbon and Al+Ti content optimized for elevated-temperature creep resistance.

2. Grades Covered by ASTM B409

ASTM B409 covers the following grades. Each grade is defined by its UNS number and specific chemistry targeted at different service environments.

3. Chemical Composition

Values are weight percent maximum unless shown as a range. Heat analysis. Per ASTM B409 Table 1.

4. Mechanical Property Requirements

All values are minimum requirements. Tensile testing per ASTM E8/E8M.

5. Heat Treatment Requirements

6. Testing & Inspection Requirements

7. Dimensions & Dimensional Tolerances

ASTM B409 covers plate, sheet, and strip in standard mill dimensions. Thickness ranges from thin strip (≥ 0.005 in / 0.13 mm) to heavy plate (up to 4 in / 100 mm). Widths and lengths per mill capability and purchaser agreement.

8. Industries & Applications

9. ASTM B409 vs ASTM B407 (Ni-Fe-Cr Alloy Seamless Pipe & Tube) — Comparison

10. Related Standards

11. How to Order — Required Information

12. Frequently Asked Questions

Q: What is the difference between Alloy 800, 800H, and 800HT?

The key difference lies in carbon and Al+Ti content for creep strength. Alloy 800 (UNS N08800, C ≤ 0.10%, Al+Ti 0.30–1.20%) is for general corrosion and moderate-temperature service. Alloy 800H (UNS N08810, C 0.05–0.10%, Al+Ti 0.30–1.20%) has a controlled carbon range and requires grain size ASTM 5 or coarser, designed for high-temperature creep service up to ~815°C. Alloy 800HT (UNS N08811, C 0.06–0.10%, Al+Ti 0.85–1.20%) has the highest creep-rupture strength at temperatures above 700°C, with tighter Al+Ti control to optimize gamma-prime precipitation strengthening. All grades share the same base Ni-Fe-Cr chemistry.

Q: What is the maximum service temperature for ASTM B409 Alloy 800H/800HT?

Alloy 800H is typically specified for continuous service up to approximately 870°C (1600°F) and short-term exposure to 980°C (1800°F). Alloy 800HT extends this capability to approximately 925°C (1700°F) continuous with improved creep-rupture properties. Both grades maintain good oxidation and carburization resistance up to 1100°C (2000°F). The 100,000-hour rupture strength at 760°C (1400°F) is approximately 34 MPa (5 ksi) for 800H and 45 MPa (6.5 ksi) for 800HT, giving 800HT a ~30% advantage at these temperatures.

Q: Why is grain size ASTM No. 5 mandatory for 800H and 800HT?

Coarse grain size (ASTM No. 5 or coarser, corresponding to average grain diameter ~64 µm) is essential for creep-rupture performance. Fine-grained 800H/800HT exhibits significantly lower creep resistance at elevated temperatures. The solution-annealing temperature (≥ 1100°C for 800H, ≥ 1150°C for 800HT) is specified specifically to achieve this coarse grain structure through grain growth during heat treatment. Grain size must be verified per ASTM E112 on each lot.

Q: Can ASTM B409 plate be welded?

Yes. Alloy 800/800H/800HT plate is readily weldable using GTAW (TIG), GMAW (MIG), SMAW (stick), and SAW processes. Recommended filler metals: ERNiCr-3 (AWS A5.14 / ENiCrFe-2) or ERNiCrCoMo-1 for high-temperature applications. Pre-heating is not required. The welding procedure should address the risk of hot cracking (solidification cracking) by ensuring proper joint design and filler metal selection. Post-weld heat treatment (PWHT) may be applied at 980°C (1800°F) followed by rapid cooling for stress relief, but is not mandatory for all applications.

Q: What are the main applications of ASTM B409 in the petrochemical industry?

ASTM B409 Alloy 800H/800HT is the primary material for ethylene furnace tubes (radiant coils and outlet pigtails), steam methane reformer (SMR) catalyst tubes, transfer line exchangers (TLEs), quench boiler tube sheets, and methanol reformer tubes. The alloy's exceptional resistance to carburization, oxidation, and sigma-phase embrittlement at temperatures up to 1100°C makes it superior to 300-series stainless steels in these critical pyrometallurgical furnace applications. Alloy 800HT is specifically preferred for extended creep life in modern high-severity ethylene furnaces.

Request a Quote — ASTM B409 Alloy 800H / 800HT Plate, Sheet & Strip

Zhengzhou Huitong (HT Pipe) supplies ASTM B409 / SB409 Alloy 800, 800H (UNS N08810), and 800HT (UNS N08811) rolled plate, sheet, and strip in standard and custom dimensions. All products supplied with full EN 10204 3.1 CMTRs, grain size certification per ASTM E112, and tensile reports from qualified mills.