It had been known for some time that higher carbon alloy 800 had higher creep and rupture properties than
low-carbon material. For that reason, Special Metals had melted to a carbon range of 0.05 to 0.10% except
for special orders where customers specified a lower carbon content. The carbon range of 0.05 to 0.10% is
within the ASTM and ASME specification limits for alloy 800 and is in the upper portion of that range.
Special Metals generated data for this material and presented them to the ASME Code. The Code approved
higher design stresses for Section I and Divisions 1 and 2 of Section VIII, which appeared in Code Case 1325-
7. Note that alloy 800H required not only a carbonrange of 0.05 to 0.10% but also an average grain size of
ASTM 5, or coarser.
With the issuance of Code Case 1325-7 and the common use of the term "800H", there was no longer a
need to refer to "Grade 2" because it was replaced by 800H, and the material that had been called Grade 1
became, simply, INCOLOY alloy 800.
Limiting Chemical Compositions , %, for INCOLOY ALLOY 800, and 800HT
|Iron||39.5 min.||39.5 min.||39.5 min.|
|Aluminum + Titanium||0.30-1.20||0.30-1.20||0.85-1.20|
|ASTM grain size||Not Specificated||5 or coarser||5 or coarser|
| || || || |