High-Carbon Titanium-Stabilized Austenitic Stainless for Creep Service

What is Stainless Steel 321H?

321H takes the titanium-stabilized 18/10 base and tightens carbon to a 0.04–0.10% band (with a minimum grain size), giving it certified creep and stress-rupture strength in the 525–816°C range. The titanium still ties up carbon as TiC, so it avoids the sensitization that would otherwise affect a high-carbon grade.

This is the stabilized high-temperature grade for welded hot-service systems — headers, transfer lines, and refinery piping. The trade-off versus niobium-stabilized 347H is that TiC is slightly less stable than NbC above ~1000°C, so for the most extreme creep duty 347H is preferred. For chloride-bearing hot streams, 316H (with molybdenum) is the better choice.

Chemical Composition (Weight %)

★ Carbon 0.04–0.10% with a minimum grain size underwrites creep strength, while titanium (≥5×(C+N)) keeps the steel sensitization-immune. Carbon stays at the 304 level (up to 0.08%).

Mechanical Properties

Values are for the solution-annealed condition per ASTM A240, A182 (F321H), and A312 (TP321H). The advantage appears in ASME time-dependent allowable stresses above 525°C.

Modulus of Elasticity 193 GPa. 321H carries code-listed creep/rupture allowable stresses from about 525°C to ~816°C. Titanium stabilization gives slightly lower creep ductility than 347H.

Physical Properties

Corrosion Resistance

High-Temperature Strength

The controlled carbon and coarse grain give 321H certified creep and stress-rupture strength from about 525°C to ~816°C, carrying ASME allowable stresses where plain 321/304 drop out.

Weld Sensitization Immunity

Titanium ties up carbon as TiC, so 321H does not sensitize in the 425–815°C range after welding — the key advantage over non-stabilized high-carbon grades.

Pitting in Chlorides

No molybdenum (PREN ~18) means limited pitting resistance in chlorides. For hot chloride streams, use 316H (with molybdenum).

321H vs 347H

TiC is slightly less stable than NbC above ~1000°C, so 347H has better very-high-temperature creep stability. 321H is the more common, lower-cost stabilized option for the 525–816°C band.

Stainless Steel 321H vs Similar Grades — Selection Guide

Applicable Standards

HT PIPE Supply — Stainless Steel 321H Product Forms

HT PIPE supplies 321H with controlled carbon, coarse-grain practice, and titanium stabilization, with MTRs showing high-temperature properties.

Project Experience — Stainless Steel 321H

HT PIPE supplies 321H for welded high-temperature process, header, and refinery piping.

We verify grain size and provide ASME high-temperature allowable-stress data for 321H creep design.

FAQ — Stainless Steel 321H