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A nickel-iron-chromium alloy, 800H/AT is designed for high temperature structural applications

Alloy 800H/AT is an austenitic heat resistant alloy designed for high temperature structural applications. The strength of 800H/AT is achieved by controlled levels of carbon, aluminum and titanium along with a 1148°C minimum anneal to achieve a grain size of ASTM 5 or coarser.


Product form Size range from Size range to
800H/AT round bar 12.7 mm 203.2 mm
800H/AT sheet & plate 0.6 mm 25.4 mm
800H/AT pipe 0.5 in 8 in
800H/AT flanges 0.5 in 8 in
800H/AT pipe fittings 0.5 in 8 in

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    Pipe Fittings

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    Sheet & Plate

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    Round Bar

Chemical Analysis

% Cr Ni Si C Mn P S Cu Fe Al Al+Ti
Min 19 30 0.06 39.5 0.15 0.85
Max 23 35 1 0.1 1.5 0.045 0.015 0.75 0.6 1.2


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Perfect for applications in the Petrochemical & Refinery sector

800H/AT can be used in a variety of applications including:

  • Super-heaters and re-heater tubing
  • Reformer outlet pigtails and manifolds
  • Heat exchangers
  • Pressure vessels
  • Dampers
  • Industrial furnaces

About 800H/AT

With close control of the carbon, aluminium and titanium contents combined with the high temperature anneal, 800H/AT has significantly higher creep-stress rupture strength than Alloy 800.

This alloy is commonly welded using RA82 (ERNiCr-3) bare wire for applications under 788°C. RA330-04 (UNS N08334) bare filler wire offers a closer match than RA82 based on the thermal expansion coefficient and higher strength. For maximum strength alloy 617 (ERNiCrCoMo-1) bare wire or 117 (ENiCrCoMo-1) covered electrodes are suggested.

To avoid possible stress relaxation grain boundary cracking in applications above 538°C the welded fabrication may be heat treated at 899°C for approximately one hour per inch of thickness or 30 minutes minimum followed by air cooling.



7.94 g/cm³
Melting Range:
1357 – 1385°C
Specific Heat Capacity:
460 J/kg°C (0-100°C)
Curie Temperature:


UNS Number:
N08810, N08811
Werkstoff Number:
1.4958, 1.4959
ASME SB 407 Code Case 1325, ASME SB 408, ASME SB 409, ASTM B 407, ASTM B 408, ASTM B 409
Download the 800H/AT Data Sheet Download

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