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A Nickel-Iron-Chromium alloy, 800H/HT® is designed for high temperature structural applications

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


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800H/HT® round bar12.7 mm203.2 mm GET A QUOTE
800H/HT® sheet & plate0.6 mm3 mm GET A QUOTE
800H/HT® pipe0.5 in8 in GET A QUOTE
800H/HT® flanges0.5 in8 in GET A QUOTE
800H/HT® pipe fittings0.5 in8 in GET A QUOTE

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Pipe Fittings

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Sheet & Plate

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Chemical Analysis



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Perfect for applications in the Petrochemical & Refinery sector

800H/HT® can be used in a variety of applications, here are just a few examples:

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

About 800H/HT®

With close control of the Carbon, Aluminium and Titanium contents combined with the high temperature anneal, 800H/HT® 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:
UNS N08810, UNS N08811
ASME SB 407 Code Case 1325, ASME SB 408, ASME SB 409, ASTM B 407, ASTM B 408, ASTM B 409
W. Nr./EN 1.4958, W. Nr./EN 1.4959
Download the 800H/HT® Data Sheet Download

FAQs & Resources

Alloy 321, 316Ti, 309, 310S, 800 H/AT, 253 MA®, RA330®, RA333®, 600, 601, 602 CA® are generally referred to as heat resisting alloys and used in various high temperature applications.

Grain size and grain geometry can have a significant impact on physical and mechanical properties of an alloy such as its yield strength, ultimate tensile strength (UTS), formability, hardness, creep strength etc. Some alloy grades require the grain size to be more refined while some undergo heat treatment process to make the grains coarser to suit their final applications. The grain size requirements are specified in the ASTM standard for certain grades i.e. 625 (DDQ) to ensure adequate manufacturing controls are in place. It is thus important to bear in mind any possible effect of various grain sizes on your production and final application when purchasing a material.

a. Elongation (El) is usually used to describe the ductility of a material in terms of percentage elongation (%El).
%El = [(Lf – L0)/L0] x 100 where Lf – Final gage length at fracture and L0 – Initial gage length of the specimen.

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