Material Family

Nickel-Iron-Chromium Austenitic Alloy (High-Temperature Optimized)

Premium grades for high-temperature, load-bearing piping applications.

Primary Distinction

Guaranteed Enhanced Creep Rupture Strength at temperatures above 540°C (1000°F).

This is the primary reason to specify 800H/HT over standard 800 pipe for high-temperature designs.

Common Forms

Seamless Pipe (SMLS) is the standard and required form for critical service. Welded pipe may be used for non-critical, large-diameter applications.

Seamless construction ensures the integrity of the mandatory coarse grain structure.

Chemical Composition (Typical wt.%)

Common: Ni 30.0-35.0, Cr 19.0-23.0, Fe ≥39.5
C: 0.05 - 0.10
Al: 0.15 - 0.60
Ti: 0.15 - 0.60
800HT Specific: (Al + Ti) must be 0.85 - 1.20

Controlled Carbon (C) is key for strength. 800HT's required (Al+Ti) sum ensures optimal precipitation strengthening for the best creep performance.

Mechanical Properties (Annealed, Room Temp)

Tensile Strength (Rm): 450 - 600 MPa (min yield varies by spec)
Yield Strength (Rp0.2): 170 - 240 MPa (min)
Elongation (A): 30% min

Room temperature properties are similar to standard 800. The critical properties are elevated temperature strength and creep data.

Physical Properties

Density: 7.94 g/cm³
Melting Range: 1350 - 1400 °C
Primary Service Range: 600°C - 950°C (1110°F - 1740°F) for maximum benefit of enhanced creep strength.

Optimized for long-term exposure in this high-temperature window.

Mandatory Thermal-Mechanical Processing

Pipe must be annealed at a minimum of 1121°C (2050°F) to achieve an ASTM grain size of 5 or coarser (typically ASTM 3-5). This is a non-negotiable requirement per ASTM B407.

This controlled coarse grain structure is essential to develop the specified high-temperature creep strength. It is verified via metallographic examination.

Key Standards (Pipe)

Primary Pipe Spec: ASTM B163 / ASME SB-163 (Seamless Pipe and Tube)
MANDATORY Supplementary Spec: ASTM B407 (Covers grain size and heat treatment requirements for UNS N08810 & N08811)

Purchasing to ASTM B163 alone is insufficient. Orders must specify compliance with ASTM B407 to guarantee the high-temperature properties.

Common Sizes & Schedules

OD Range: 1/8" NPS to 12"+ NPS (Seamless)
Wall Thickness: Heavy walls are common (Sch 80, 160, XXS), especially for reformer furnace tubes.
Length: Random, Double Random, Cut to Length.

Often used as heavy-walled reformer tubes or high-pressure superheater tubes.

Typical Applications

• Petrochemical: Steam Methane Reformer (SMR) furnace tubes, ethylene cracking furnace tubes, transfer line exchangers.
• Power Generation: High-temperature superheater/reheater tubes, header piping.
• Industrial Heating: Radiant tubes, retorts, muffles for high-temperature heat treating.

The dominant material for pressurized high-temperature tubing in the petrochemical industry, especially in reforming and cracking furnaces.